JP4827656B2 - Motor control circuit - Google Patents

Description

  The present invention realizes miniaturization in an electromechanical system that operates under the restrictions of existing DC voltage conditions, such as a battery power supply in an automobile and an overhead wire power supply in a railway vehicle, and is more suitable for the operation of the electromechanical system. The present invention relates to a motor control circuit using a DC / DC converter capable of converting a voltage in order to obtain a voltage.

  In recent years, there is a tendency for batteries to be used in various fields as the battery technology advances and becomes larger. For example, an electric drive system that uses a battery of an automobile as a power source, a hybrid drive system that uses an engine and a battery, an electric drive system that does not use an overhead wire that uses a battery in a railway vehicle, or an overhead wire section that is driven from an overhead line using the overhead line as a power source There is a hybrid drive system that obtains power and charges the battery at the same time and uses the battery as a power source in the non-overhead section. In addition, when considering a general automobile, the in-vehicle power source is only a 12V battery, and the electrical equipment used in the in-car is used as it is as a power source, or it is used as a power source by stepping up and down with a DC / DC converter. Either. Thus, DC / DC converters are used for various applications using a battery as a power source. Also in the railway vehicle, when the battery is used as the power source as described above, when the power supply voltage of the overhead line is 1500V, the battery is required to have a high voltage of 1500V, and the DC / DC converter corresponds to 1500V. Is used.

  As described above, when an electric device such as a battery is mounted on a vehicle, it is strongly required to reduce the weight and size of the device including the battery. In addition, voltage adjustment is an important factor, and when a DC / DC converter is used, light weight and downsizing are required.

  Here, consider a DC / DC converter that uses a transformer to set the output voltage to a power supply voltage, for example, twice the battery voltage. FIG. 26 to FIG. 32 show three types of connection methods of center tap type DC / DC converters having the same capacity and the same output voltage, and the output voltage being twice the battery voltage. In these figures, Ba is a battery, TRa and TRb are transistors, Tr is a transformer, Dda and Ddb are diodes, LR is a load, and Sw is a switch. As the transistors TRa to TRb, insulated gate bipolar transistors (IGBT) are used. As shown in FIG. 29, a commonly used IGBT has a diode in reverse parallel between the collector and the emitter, that is, in reverse parallel so that the cathode is connected to the collector side of the diode and the anode is connected to the emitter side. A diode is connected. In the following description, unless otherwise specified, it is assumed that a diode is connected in reverse parallel to the IGBT, and the illustration of this diode is omitted.

  FIG. 26 is a circuit diagram of an example of a center tap connection type DC / DC converter as described in Non-Patent Document 1. The voltage of the battery Ba is E, the (+) terminal of the battery Ba is connected to the terminal C at the midpoint of the primary winding of the transformer Tr, and the transistors TRa and TRb are respectively connected to the terminals AB of the primary winding. And the emitter of the transistors TRa and TRb are connected to the (−) terminal of the battery Ba, and the transistors TRa and TRb are alternately turned on and off at regular intervals. The battery voltage is applied to the upper half of the primary winding of the transformer Tr when the transistor TRa is ON, and to the lower half of the primary winding Tr of the transformer when the transistor TRb is ON. The primary and secondary of the transformer are insulated from each other, and the primary / secondary winding ratio of the transformer is 1: 2, and the terminal C 'at the intermediate point on the secondary side is grounded.

  The anodes of the diodes Dda and Ddb are connected to the terminals A ′ and B ′ of the secondary winding, respectively, and the cathodes of the diodes Dda and Ddb are connected to each other at the (+) terminal of the load LR. The −) side is connected to the terminal C ′ at the midpoint. An AC rectangular wave voltage is induced in the secondary winding by ON / OFF of the transistors TRa and TRb. The secondary winding voltage is rectified by the diodes Dda and Ddb, and the winding ratio is 1: 2 across the load LR, so that a DC output voltage 2E that is twice the battery voltage E appears. In FIG. 26, the switch Sw is provided to turn on and off the load current.

  In FIG. 27, the terminal C ′ at the midpoint of the secondary winding that is grounded in FIG. 26 is the (+) terminal of the battery Ba, and the (−) terminal of the load LR is the secondary winding of the transformer Tr. The connection is changed from the terminal C ′ at the intermediate point to the (−) terminal of the battery Ba. That is, the battery Ba and the secondary side of the DC / DC converter are connected in series. Since the battery voltage is E, the DC / DC converter only has to share the voltage E in order to make the voltage of the load LR 2E. Since the condition is that the output capacities are equal, the current flowing through the load LR is equal to that in FIG. Therefore, in the DC / DC converter, since the current is equal and the voltage is ½ compared to the case of FIG. 26, the capacity of the DC / DC converter may be ½, which is significantly lighter and smaller. Can be realized.

  FIG. 28 is obtained by replacing the transformer Tr in FIG. 27 with a single-winding transformer from a two-winding transformer having primary and secondary windings. is there. There is an effect that the transformer occupying the largest part in weight in the DC / DC converter can be further downsized. Even if the transformer Tr is replaced with a self-winding transformer, it is functionally the same as FIG. However, in this circuit, there is a battery voltage E at the base, and only a voltage higher than E can be obtained.

  The relationship between the two-winding transformer and the single-winding transformer will be described with reference to FIG.

  FIG. 30A shows a two-winding transformer having a winding ratio of 2: 1. Assuming that the primary voltage 2E and the current I are the secondary voltage E and the current 2I, the capacity is 2EI (kVA).

  FIG. 30B shows a single winding transformer having a winding ratio of 2: 1. Assuming that the primary voltage 2E and the current I are the secondary voltage E and the current 2I, the capacity is 2EI (kVA). Except that the primary and secondary windings are not separated, the function is the same as that of the two-winding transformer of FIG. In FIG. 30B, the current flowing between the terminals AC of the winding is I (upward) of the difference between the primary current I and the secondary current 2I. The current flowing between the terminals CB of the winding is I because it is only the primary current. Therefore, since it is equivalent to the two-winding transformer in FIG. 30C in which the winding is divided into two, if expressed as a two-winding transformer, the primary voltage E and current I are the secondary voltage E. , Current I, and the capacity is EI (kVA). This means that a transformer with a winding ratio of 2: 1 means that the capacity, weight, and dimensions are reduced to about 1/2 if a single-turn transformer is used. I understand.

  Conventionally, the output voltage of the DC / DC converter is controlled by changing the conduction width (ON width) of the transistors TRa and TRb. FIG. 31 is a configuration diagram for explaining a basic DC / DC converter. In the figure, Ba is a battery, TRa and TRb are transistors, Tr is a transformer, Dda and Ddb are diodes, L is an inductance, Ca is a capacitor, and LR is a load. The transistors TRa and TRb operate as switching transistors, the inductance L operates as an energy storage inductance, and the capacitor Ca operates as an energy storage capacitor. Similarly to the transistors TRa and TRb in FIGS. 26 to 28, the transistors TRa and TRb are alternately controlled to be opened and closed so that there is no period of conduction.

The output voltage waveform is shown in FIG. The upper waveform is an AC voltage waveform between the terminals A ′ and B ′ and shows a waveform when the conduction width of the transistors TRa and TRb is t. The waveforms shown in the lower two stages are DC waveforms between the outputs DG of the DC / DC converter in the upper stage and between the ends FG of the load LR after the lower stage is smoothed by a filter. The average value of the output voltage is given by
e = (t / T) · E
Therefore, the output voltage can be controlled by controlling the conduction width t.

In such a voltage control method on the primary side of the transformer, the secondary side voltage includes many harmonic components, and the harmonic components do not adversely affect the device (load) to be connected later. In order to remove harmonic components and smooth the voltage, it is necessary to insert a low-pass filter comprising an inductance L and a capacitor Ca between the output of the DC / DC converter and the load. Since this filter uses a reactor with an iron core, it is inevitable that the size and mass of the filter will inevitably increase, and this is not preferable for in-vehicle use. Moreover, in the conventional DC / DC converter, the regenerative braking operation cannot be performed with the circuit as it is.
JP 2003-61354 A "Practical Electronic Circuit Handbook (1)" (January 20, 1989, CQ Publishing Co., Ltd., 31st edition), page 389

  The present invention has been made in view of the above-described circumstances, and as a DC / DC converter, it has substantially the same function as a conventional type, can perform voltage control, has a good output waveform, and is lightweight and downsized. Another object is to provide an electric motor drive circuit using a DC / DC converter. It is another object of the present invention to provide an electric motor drive circuit that has been developed to perform regenerative braking by employing an additional circuit.

  According to the first aspect of the present invention, one pole of a DC power supply is connected to a terminal at the midpoint of the autotransformer, and the other end of the DC power supply is connected to terminals at both ends of the autotransformer via switching elements, respectively. And a plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends and the terminals at both ends of the autotransformer and with respect to the terminal at the intermediate point are respectively selected. It is connected to one terminal of the electric motor through a circuit, the other pole of the DC power supply is connected to the other terminal of the electric motor, and the switching elements are alternately arranged so that there is no period of conduction. Each of the selection circuits is capable of opening / closing control, and includes a unidirectional element that allows current to flow in a direction of driving the electric motor, and at least one selection circuit includes the switching circuit. Characterized in that it is intended to be opened and closed controlled in synchronization with the opening and closing control of the child.

  According to the second aspect of the present invention, one pole of a DC power source is connected to a terminal at the midpoint of the autotransformer, and is located inside the terminals at both ends of the autotransformer and to the terminal at the midpoint. The other poles of the DC power supply are connected to terminals provided at symmetrical positions with respect to each other via switching elements, and the intermediate point is between the terminals at both ends of the autotransformer and the terminals at both ends. A plurality of tap terminals provided at one or more positions symmetrical with respect to the terminal of the motor are respectively connected to one terminal of the motor via a selection circuit, and the other pole of the DC power source is the other terminal of the motor The switching elements are alternately controlled to be opened / closed so that there is no conduction period, and each of the selection circuits is capable of opening / closing control and drives the electric motor. To current Flow has a unidirectional element, wherein the one in which connected the selection circuit to the tap terminal provided at positions symmetrical are synchronized to switching control to the switching control of the switching element.

  According to a third aspect of the present invention, one pole of a DC power supply is connected to a terminal at the midpoint of the autotransformer, and the other end of the DC power supply is connected to terminals at both ends of the autotransformer via switching elements, respectively. And a plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends and the terminals at both ends of the autotransformer and with respect to the terminal at the intermediate point are respectively selected. It is connected to one terminal of the electric motor through a circuit, the other pole of the DC power supply is connected to the other terminal of the electric motor, and the switching elements are alternately arranged so that there is no period of conduction. Each of the selection circuits has a unidirectional element that can be controlled to open and close and that allows a current to flow in the direction of driving the electric motor, and is provided at the symmetrical position. Connect to The selection circuit is controlled to be opened and closed in synchronization with the switching control of the switching element, and at least one selection circuit can be controlled to open and close in parallel to the unidirectional element. A unidirectional element that allows a current to flow in a direction opposite to the direction is connected, and the motor is driven and regenerative braking is performed by opening and closing the unidirectional element.

  According to a fourth aspect of the present invention, one pole of a direct current power source is connected to a terminal at the midpoint of the autotransformer, inside the terminals at both ends of the autotransformer and to the terminal at the midpoint The other poles of the DC power supply are connected to terminals provided at symmetrical positions with respect to each other via switching elements, and the intermediate point is between the terminals at both ends of the autotransformer and the terminals at both ends. A plurality of tap terminals provided at one or more positions symmetrical with respect to the terminal of the motor are respectively connected to one terminal of the motor via a selection circuit, and the other pole of the DC power source is the other terminal of the motor The switching elements are alternately controlled to be opened / closed so that there is no conduction period, and each of the selection circuits is capable of opening / closing control and drives the electric motor. To current A selection circuit having a unidirectional element to flow and connected to a tap terminal provided at the symmetrical position is controlled to be opened and closed in synchronization with the opening and closing control of the switching element, and at least one selected In the circuit, open / close control is possible in parallel with the unidirectional element, and unidirectional elements that flow current in the direction opposite to the direction are connected. It is characterized by driving and regenerative braking.

  According to the fifth aspect of the present invention, one pole of a DC power supply is connected to a terminal at the midpoint of the autotransformer, and the other end of the DC power supply is connected to terminals at both ends of the autotransformer via switching elements, respectively. And a plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends and the terminals at both ends of the autotransformer and with respect to the terminal at the intermediate point are respectively selected. It is connected to one terminal of the electric motor through a circuit, the other pole of the DC power supply is connected to the other terminal of the electric motor, and the switching elements are alternately arranged so that there is no period of conduction. Each of the selection circuits has a unidirectional element that can be controlled to open and close and that allows a current to flow in the direction of driving the electric motor, and is provided at the symmetrical position. Connect to The selected circuit is controlled to be opened and closed in synchronization with the switching control of the switching element, and can be controlled between one or more tap terminals different from the tap terminal and the one terminal. A unidirectional element for supplying a current in a direction opposite to the direction is connected, and the motor is driven and regenerative braking is performed by opening / closing control of the unidirectional element.

  According to the sixth aspect of the present invention, one pole of a DC power source is connected to a terminal at the midpoint of the autotransformer, and is located inside the terminals at both ends of the autotransformer and to the terminal at the midpoint. The other poles of the DC power supply are connected to terminals provided at symmetrical positions with respect to each other via switching elements, and the intermediate point is between the terminals at both ends of the autotransformer and the terminals at both ends. A plurality of tap terminals provided at one or more positions symmetrical with respect to the terminal of the motor are respectively connected to one terminal of the motor via a selection circuit, and the other pole of the DC power source is the other terminal of the motor The switching elements are alternately controlled to be opened / closed so that there is no conduction period, and each of the selection circuits is capable of opening / closing control and drives the electric motor. To current The selection circuit connected to the tap terminal provided at the symmetrical position has a unidirectional element to flow and is controlled to be opened and closed in synchronization with the opening and closing control of the switching element, and the tap terminal Between the one or more different tap terminals and the one terminal, a unidirectional element that allows current to flow in the direction opposite to the direction is connected between the one terminal and the switching control of these unidirectional elements. Thus, the motor is driven and regenerative braking is performed.

  The invention according to claim 7 is the electric motor drive circuit according to any one of claims 3 to 6, wherein the electric motor is mounted on a railway vehicle, and the DC power source is mounted on the railway vehicle. A regenerative current at the time of the regenerative braking is absorbed by the battery.

  According to an eighth aspect of the present invention, in the motor drive circuit according to any one of the first to seventh aspects, a terminal at an intermediate point of the autotransformer is also a tap terminal. In this case, since the terminal at the intermediate point is on the axis of symmetry, in this specification, it is assumed that it is included in the symmetrical position.

  According to the present invention, when the electric motor is driven, a battery in which a direct current power source connected to the intermediate point terminal on the input side of the autotransformer is caused to alternately flow current to the windings on both sides of the intermediate point terminal. The output voltage can be controlled by synchronously opening and closing the selection circuit connected to the output side of the autotransformer with respect to the transistor on the side, and it is also possible to combine conductivity control, Smooth output voltage control is possible. Furthermore, regenerative braking is also possible by combining switching elements that allow current to flow in the direction opposite to the driving direction of the motor as the selection circuit.

  The conventional output voltage control method that changes the conductivity of the transistor on the battery side did not like the large size of the LC filter in order to remove the harmonic component of the output voltage. In the voltage step switching method in which a semiconductor switch is connected to each tap provided in the winding and these are sequentially switched, a DC voltage with less harmonics can be obtained, and the filter becomes small or unnecessary. Although the number of semiconductor switches increases, the cooling fins can be shared, and the overall weight can be reduced.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in each figure, the same code | symbol is attached | subjected to the member or element which has the same function, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a diagram for explaining a configuration corresponding to a basic configuration at the time of driving a load in a DC / DC converter used in the present invention. In the figure, the same parts as those in FIGS. THa and THb are semiconductor switching elements. As an example of the semiconductor switching element, the above-described IGBT or a rectifying element having a valve action, such as a thyristor, is used. In the circuit of FIG. 28, when the DC / DC converter is not operated, if the switch Sw is not provided, a current always flows from the battery Ba to the load LR through the diodes Dda and Ddb, which is not preferable in terms of circuit operation. As shown in FIG. 28, there is no problem if the switch Sw is inserted between the diodes Dda and Ddb and the load LR. It is not preferable. By replacing the diodes Dda and Ddb connected to both terminals of the winding of the autotransformer Tr with semiconductor switching elements THa and THb, not only can this problem be solved, but the semiconductor switching elements THa and THb can be replaced with the transistor TRa. , TRb and control, that is, a new method that can be called a “synchronous ignition method” is provided, and a wide range of applications are possible. However, even if the synchronous call system is adopted in the circuit of FIG. 1, the output voltage is 2E, which is the same as the circuit of FIG. 28 in which the semiconductor switching elements THa and THb are diodes.

  FIG. 2 is a block diagram for explaining the first embodiment of the present invention, and FIG. 3 is a diagram for explaining the operation thereof. In the figure, Ba is a battery, TRa and TRb are transistors, Tr is a transformer, LR is a load, THa1 to THa3, THb1 to THb3, and THn are semiconductor switching elements. As the transistors TRa and TRb, insulated gate bipolar transistors (IGBTs) can be used as described above. In the description of the embodiment of the present invention, unless otherwise specified, the IGBT is described as having a diode connected in antiparallel, and the diode is not shown. As an example of the semiconductor switching elements THa1 to THa3, THb1 to THb3, THn, the above-described IGBT or a rectifying element having a valve action, such as a thyristor, can be used. The load LR is not limited to a direct current motor, but includes an inverter motor and the like. In short, it is sufficient that the load LR can be driven by a direct current output of a DC / DC converter and can output a direct current voltage during regenerative braking.

  The circuit operation of the first embodiment will be described. In addition to the both side terminals of the winding of the autotransformer Tr of the DC / DC converter shown in FIG. 1, this circuit has several tap terminals (in this example, the point C and P, Q , R and S points, but the number and position of the tap terminals are not limited to this, and may be more or less than this example, and the tap terminals at the intermediate points are not necessarily provided. The semiconductor switching elements THa1 to THa3, THb1 to THb3, and THn are connected to the winding end terminals A, P, R, C, B, Q, and S, respectively. The transistors TRa and TRb connected between the winding end terminals A and B of the autotransformer Tr and the battery (−) terminal are associated with each other and turned on and off. The output voltage of the DC / DC converter can be controlled without increasing the harmonic component.

  In this example, the tap terminals are provided so that the number of windings between the tap terminals is equal. However, it does not necessarily have to be equal, and tap terminals may be provided with an appropriate number of windings. In addition, since the ground side is set to the (−) potential, the semiconductor switching elements THa1 to THa3, THb1 to THb3, and THn are connected so that a positive voltage is applied to the load LR. Of course, the reverse direction is also acceptable. The tap terminals P and Q, and R and S are in symmetrical positions with respect to the tap terminal C at the intermediate point.

  First, the operation when the transistors TRa and TRb and the semiconductor switching elements THa1 and THb1 are opened and closed in synchronization will be described. This mode of operation is the same as that of the DC / DC converter shown in FIG. 1, and both ends of the autotransformer Tr are connected to a load (through a selection circuit, in this embodiment, semiconductor switching elements THa1 and THb1). Connected to the motor). The transistors TRa and TRb are alternately conducted for a predetermined time T, and induce a rectangular wave AC voltage in the autotransformer Tr. As shown in the uppermost stage of FIG. 3, if the semiconductor switching element THb1 is closed in synchronization with the transistor TRa and the semiconductor switching element THa1 is closed in synchronization with the transistor TRb in the next half cycle, the load LR A voltage of 2E is applied. That is, a voltage of 2E is output as in the operation of FIG.

  Next, in synchronization with the transistor TRa, the semiconductor switching element THb2 is closed instead of the semiconductor switching element THb1, and the semiconductor switching element THa2 is closed instead of the semiconductor switching element THa1 in synchronization with the transistor TRb. As shown in the second stage from the top in FIG. 3, a voltage of 5E / 3 is applied to the load LR.

  Similarly, if control is performed so that the semiconductor switching element THb3 is closed in synchronization with the transistor TRa and the semiconductor switching element THa3 is closed in synchronization with the transistor TRb, as shown in the third stage from the top of FIG. A voltage of 4E / 3 is applied to.

  Further, if the semiconductor switching element THn is closed in synchronization with the transistor TRa and the semiconductor switching element THn is closed in synchronization with the transistor TRb, as shown in the fourth stage from the top in FIG. E voltage is applied. In order to obtain the output voltage E, the transistors TRa and TRb may be left open and the semiconductor switching element THn may be closed.

  Furthermore, if the semiconductor switching element THa3 is closed in synchronization with the transistor TRa and the semiconductor switching element THb3 is closed in synchronization with the transistor TRb, the load LR has a load LR as shown in the fifth row from the top in FIG. A voltage of 2E / 3 is applied.

  Further, if control is performed so that the semiconductor switching element THa2 is closed in synchronization with the transistor TRa and the semiconductor switching element THb2 is closed in synchronization with the transistor TRb, as shown in the lowermost stage of FIG. Voltage is applied.

  This voltage control method is referred to as “step voltage control”. In step voltage control, the output voltage waveform is almost direct current, and the voltage cuts out at the switching point of the cycle, but it can be absorbed by connecting a few capacitors, and does not require a large filter as in the conductivity control. . Furthermore, although the number of semiconductor switches used for output voltage control increases, since only one element is energized at any moment, the loss is reduced compared to the case of two simple rectifier circuits. There is no increase, and therefore, it is possible to adopt a method in which all semiconductor switches are attached to one cooling fin in terms of structure.

In the above-described step voltage control, the voltage cannot be changed continuously, but continuous voltage control is also possible if continuity control is used in combination with step voltage control. FIG. 4 shows an intermediate process in one embodiment of voltage control. In the case where the semiconductor switching element THa3 is turned on in synchronization with the transistor TRa and the semiconductor switching element THb3 is turned on in synchronization with the transistor TRb to output the voltage 2E / 3, the voltage is raised to the upper step. First, the semiconductor switching element THa3 is turned on in synchronization with the transistor TRa, and then the semiconductor switching element THn is turned on with a conductivity t after a certain time. In the next half cycle, the semiconductor switching element THb3 is first conducted in synchronization with the transistor TRb, and then the semiconductor switching element THn is conducted with the conductivity t. The output voltage e at this time is given by the following equation.
e = (E / 3) · (t / T) + (2E / 3)
By sequentially changing the conductivity t from 0 to 100%, the voltage can be continuously controlled from 2E / 3 to E. The same applies to the other steps. In the method for controlling the continuity in this way, a harmonic component is included in the output voltage, but the magnitude is small (1 / number of steps), and therefore the filter can be small.

  FIG. 5 is a configuration diagram for explaining another example of the first embodiment. In the figure, THa0 and THb0 are semiconductor switching elements. In this embodiment, transistors TRa and TRb are connected to terminals provided inside the both ends of the autotransformer Tr and symmetrically with respect to the intermediate terminal. In other words, the terminals F and G on the output side are provided with the same number of windings on the outer sides of both ends A and B of the autotransformer described in FIG. 2 (that is, tap terminals F, G is in a symmetrical position with the terminal C as a symmetry point.) In this embodiment, since a voltage corresponding to the turn ratio of the outer winding can be added, an output voltage higher than the voltage of 2E can be obtained. Since the operation is the same as that of the embodiment described with reference to FIG.

  An application example of the above-described motor drive circuit will be described below.

  The number of revolutions of the induction motor is determined by the power supply frequency and the number of poles of the motor. However, if the voltage applied to the motor is left as it is just by changing the frequency, it is necessary to generate the torque that is the original purpose of the motor. As the magnetic flux decreases with increasing frequency, the torque that can be generated also decreases. Therefore, if the generated torque of the motor is kept constant with respect to the frequency, it is necessary not only to change the frequency, but also to change the voltage applied to the motor in proportion to the frequency. The area of the half-wave of the AC voltage generated is constant). A VVVF (Variable Voltage Variable Frequency) inverter has been developed for this purpose. If there is no restriction on the power supply voltage and the voltage can be increased in proportion to the frequency, the generated torque can be kept constant as much as possible. However, considering the actual application, the power supply voltage is limited. The voltage applied to the motor cannot be increased in proportion to the frequency.

  In general, a description will be given according to FIG. First, in the region A in which the frequency (substantially proportional to the motor rotation speed) and the voltage can be changed in proportion, the frequency and the voltage are increased proportionally (V) so that the torque is constant (substantially the motor current is constant). / F constant) Accelerate the motor. Since the voltage cannot be increased beyond this, only the frequency is changed at a constant voltage thereafter.

  In the region B, the frequency applied to the electric motor that changes the frequency so that the output power becomes constant cannot be changed. Therefore, the torque that can be generated by the electric motor decreases as the frequency increases. Therefore, with constant power control, the torque that can be generated by the electric motor will eventually become smaller than the required torque, and the electric motor will stall.

  In the region C, in order to avoid this, the power control that makes the output constant before the stall is switched to the control that suppresses the torque within the torque that can be output within the range where the motor does not stall, that is, the control that considers the characteristics of the motor. (The motor torque is reduced in proportion to the square of the frequency). When the acceleration of the motor is completed, the acceleration torque is no longer necessary, and the VVVF inverter controls the motor to rotate at a constant frequency and a constant voltage balanced with the load torque.

  FIG. 7 shows the relationship between the rotational speed and torque of the induction motor when the VVVF inverter is controlled at a constant V / F. The frequency shown in each curve means the frequency of the VVVF inverter for each curve. The intersection of the curve and the horizontal axis (axis of torque 0) indicates the synchronous speed corresponding to each frequency, and the torque is zero at the synchronous speed. The curve to the left of the synchronous speed shows the drive torque. As the difference between the synchronous speed and the motor speed (ie, the slip frequency) increases, the torque increases, reaches a maximum at a certain slip frequency, and then increases the slip frequency. As the torque decreases. This maximum torque is called stationary torque, and the right side of the maximum torque is the range of use as an electric motor in the stable region. The curve to the right of the synchronous speed shows the regenerative braking torque, and the torque increases as the difference between the synchronous speed and the motor speed (in this case, the absolute value of the negative slip frequency) increases, just like the drive torque. It becomes maximum at a certain slip frequency, and then decreases. The left side of the maximum torque is the stable range and the range of use as a brake.

  In order to start and accelerate a stopped induction motor, not only the load torque but also the acceleration torque that can be accelerated by overcoming the inertia of the driven body is required, and it is necessary to give the frequency and voltage that can generate this torque. is there. For example, in the example of FIG. 7, since the necessary slip frequency is about 10 Hz, it can be understood that the necessary torque can be produced by applying a voltage satisfying a frequency equal to the slip frequency of 10 Hz and a constant V / F at the time of startup. . As a result, if the motor starts rotating and the frequency and voltage of the VVVF inverter do not change, the operating point slides on the torque curve in the direction of decreasing frequency (toward the right), and the generated torque decreases with increasing rotation. To do. On the other hand, if the generated frequency of the VVVF inverter is increased so that the slip frequency is always constant, it can be moved to the right on the constant torque line and constant torque acceleration can be performed.

  For example, in order to generate the brake deceleration torque shown in FIG. 7 in the motor rotating at high speed, the frequency and voltage corresponding to the torque curve for generating the brake deceleration torque shown in FIG. Need to give from. The electric motor is decelerated by this brake torque. Assuming that the frequency and voltage of the VVVF inverter do not change, the operating point on the torque curve moves to the left, and the generated torque decreases as the rotation decreases. On the other hand, if the generated frequency of the VVVF inverter is lowered so that the negative slip frequency is always constant, the regenerative braking at a constant torque can be operated by moving to the left on the constant torque line. In order to stably operate the regenerative brake, the DC side of the VVVF inverter is required to have the ability to absorb regenerative energy.

  Generally, when controlling the speed of an electric motor, the relationship between voltage and frequency is controlled so as to keep V / F constant. Voltage control can be broadly classified into two types: PWM (Pulse width modulation) and PAM (Pulse amplitude modulation).

  Description will be made of what control is performed when an AC motor such as an induction motor is driven by a PWM VVVF inverter according to FIGS. The waveform diagram of FIG. 9 collectively shows the waveforms of the respective parts. Waveforms of three sine waves corresponding to the output phase voltages of the three-phase U, V, and W-phase VVVF inverters having a phase difference of 120 ° from the triangular wave are shown in the uppermost stage. The triangular wave is also called a modulated wave, and the three sine waves are also called modulated waves. The triangular wave has a constant amplitude and a frequency of 1 kHz or more (asynchronous), or a waveform having a constant ratio with the sine wave frequency and synchronized with the modulation wave. When the motor M is started, three sine waves having a phase difference of 120 ° corresponding to the slip frequency and voltage (amplitude) for generating the necessary acceleration torque are given as modulated waves. Thereafter, the electric motor M is kept until the amplitude of the sine wave becomes substantially equal to the amplitude of the triangular wave while keeping the ratio of the voltage (amplitude) and frequency of the three modulated sine waves constant so that the slip frequency of the electric motor M becomes constant. It controls to change according to the acceleration of M. FIG. 9 shows a case where the number of triangular waves is 9 (the number of pulses means the number of ± crests of triangular waves included in the half of the sine wave of the modulated wave) 9 and is synchronized with the sine wave. It is a thing.

  As for point A in FIG. 9, only the instantaneous value of the U-phase sine wave is larger than the triangular wave, and the instantaneous value of the V-phase and W-phase sine waves is smaller than the triangular wave. The conduction state of each component of the VVVF inverter at this moment is shown in FIG. Since (U-phase sine wave> triangular wave), the transistor TRu is ON and the transistor TRx is OFF. The U-phase terminal of the electric motor M is connected to the (+) side. Since (V-phase sine wave <triangular wave) and (W-phase sine wave <triangular wave), the transistors TRy and TRz are ON, the transistors TRv and TRw are OFF, and the V-phase and W-phase terminals of the motor M are at zero potential. Is dropped. As a result, in the thick line circuit shown in FIG. 8A, a current flows from the power source Ba to the motor M, and torque is generated in the motor M.

  When the point B in FIG. 9 is reached, all the sine waves of the U, V, and W phases are smaller than the triangular wave, and at point A, the transistor TRu that was turned on is also turned off, and the transistor TRx is turned on. The current that has been disconnected from the power supply and has flown into the U phase of the electric motor M through the transistor TRu until now does not immediately become zero because the inductance of the electric motor M is present even when the transistor TRu is turned off. A closed loop is formed in the circuit shown by a thick line in FIG. 8B through the parallel diode, and the current gradually attenuates as the current flows. On the other hand, the energy stored in the inductance pushes up the voltage of the capacitor Ca in a thick line circuit. When the time elapses and the U-phase sine wave becomes higher than the triangular wave again, the state returns to the state of FIG.

  At the intersection point C between the triangular wave and the V-phase sine wave, the transistor TRy, which has been in the ON state until now, is turned OFF. The current that has flowed through the transistor TRy to the V-phase winding of the motor M until now flows upward through the inductance of the motor M and the antiparallel diode of TRv, as shown in FIG. A closed loop is created and decays with time. On the other hand, the current flowing from the power source into the motor M is reduced by the amount flowing in the V phase.

  After this point, the V-phase sine wave becomes larger than the triangular wave, and at point D, the transistors TRu and TRv are respectively turned on and connected to the power supply (+) side. The transistors TRx and TRy are OFF. Since the transistor TRz continues to be in the ON state, a current flows through the electric motor M in the circuit indicated by the thick line in FIG. This state continues for a period of time until the W-phase sine wave and the triangular wave intersect and the U, V, and W-phase sine waves become larger than the triangular wave.

  When the operating point moves to the right side from this intersection after a lapse of time, for example, at point E, the U, V, and W phase sine waves are larger than the triangular wave, so the transistor TRz that has been turned on until now. Is also OFF. Until now, the current flowing through the transistor TRz does not immediately become zero due to the inductance of the motor M, and the current forming the closed loop indicated by the bold line through the antiparallel diode of the transistor TRw gradually attenuates. This state continues until the intersection of the W-phase sine wave and the triangular wave. When the intersection is exceeded, the state returns to the state of FIG.

  Thereafter, each time the intersection of the U, V, W phase sine wave and the triangular wave comes, the transistor that operates is switched. This relationship is collectively shown in the second to fourth waveforms from the top in FIG. 9, and shows temporal changes in the potentials of the U, V, and W phase terminals of the electric motor M. Three rectangular dense waves with a phase shift of 120 °. For example, regarding the U-phase waveform, the upper line of the rectangular dense wave indicates the state in which the transistor TRu is ON, and the U-phase terminal of the motor M is connected to the power source (+) side. The lower line indicates a state in which the transistor TRx is ON, and the U-phase terminal of the electric motor M is connected to the power source (−) side and thus indicates a zero potential.

  The three waveforms on the lower side of FIG. 9 indicate the inter-terminal voltages of UV, VW, and WU from the top. It is given by a square wave with a dense center and coarse ends. Approximately, it can be seen as a sine wave.

Returning to FIG. 6 again, the relationship between the modulation wave and the VVVF output frequency will be described. In the region A of FIG. 6, the constant torque acceleration region, the induction motor M is accelerated at a constant V / F by the VVVF inverter. In general, in the low speed region, the modulation wave is asynchronous and a relatively high frequency on the order of kHz is used. According to the acceleration, the modulation wave is switched to synchronization, becomes 9 pulses and 3 pulses, and enters the region B as 1 pulse at the end of the region A. In the constant power acceleration region of the region B, only the voltage is constant and only the frequency is changed. The modulation wave is a single pulse of a synchronous system. In the area C, one-pulse modulation is performed by the motor characteristic area control, and the torque is reduced in proportion to 1 / F ² so that the torque does not exceed the stationary torque of the motor.

The waveform of each part of 9 pulses, 3 pulses and 1 pulse is shown in FIGS.
Similarly to FIG. 9, a cut-off between a triangular wave that is a modulated wave and a sine wave having a phase difference of 120 degrees corresponding to the modulated waves U, V, and W phase voltages is shown. The next three waveforms up to the second to fourth stages are rectangular close-packed waves indicating changes in the potentials of the U, V, and W terminals of the motor M in FIG. 8 as in FIG. The upper transistor corresponding to each phase arm of the VVVF motor is ON when the sine wave> triangular wave and the (+) potential of the battery, the sine wave <triangular wave, and the lower phase corresponding to each phase arm of the VVVF motor. When the transistor on the side is ON, it becomes the G potential of the battery. The next three waveforms up to the fifth to seventh stages are waveforms showing changes in voltage between the U-V, V-W, and W-U terminals of the electric motor M in FIG. The voltage between the −V terminals is the difference between the waveform indicating the potential of the U terminal at the second stage and the waveform indicating the potential of the V terminal at the third stage. The same applies hereinafter. The last three stages indicate the phase voltage of the motor by the voltage between the motor terminal and the neutral point of the three-phase winding.

  The greatest merit of PWM control is that the circuit configuration is simplified because voltage control and frequency control can be performed simultaneously with one PWM converter. The voltage waveform cut out by PWM includes many harmonic components in addition to the fundamental wave component as described above, and causes an increase in internal loss of the motor. In general applications using a general-purpose machine, a method of increasing the frame number of the electric motor is used, but such a method cannot be taken from the viewpoint of weight and dimensions when mounted on a vehicle. Moreover, in a general electric motor, the inductance of the winding acts as a filter, and the flowing current is shaped to be close to a sine wave. However, in the case of a high-speed motor used at a low voltage of about 12 V, the number of turns of the winding is very small and the inductance is also small. In a low region (low frequency region), a smoothing effect due to winding inductance cannot be expected. For this reason, the harmonic component included in the voltage waveform includes a harmonic component in the flowing current and also in the gap magnetic flux, and the rotor generates a reaction magnetic flux for canceling out this harmonic magnetic flux. The harmonic current flows, causing resistance loss in the rotor, which causes heat generation of the rotor.

  On the other hand, in the case of PAM control, voltage control and frequency control are performed by separate converters, and the circuit configuration becomes complicated. The voltage control converter uses a chopper or a DC / DC converter, and the frequency control converter uses a 180 ° rectangular wave, a 120 ° rectangular wave, or a fifth, seventh, etc. low-order harmonic having a high content ratio. An inverter using a modulation scheme that eliminates waves is used. The harmonic content of the inverter output voltage relative to the fundamental wave is determined by the modulation method and is not related to the voltage, but in the low frequency range, the voltage applied to the inverter by the voltage controlled converter is kept low, so the absolute value of the harmonics Is kept low, and the loss generated in the rotor is small. As the rotation increases, the voltage rises, the absolute value of the harmonics increases, and the loss tends to increase, but as the frequency approaches the rated frequency, the inductance decreases, but the higher frequency component harmonics. A filter effect can be expected for wave current. Therefore, if a modulation method that removes low-order harmonics with a high content ratio is used, a control method can be realized in which the loss of the rotor can be kept low over the entire speed range, but no matter how good the performance is. However, it is difficult to mount large-sized ones on automobiles. Therefore, the point is how small the voltage controlled converter can be. From this point of view, the motor drive circuit using the above-described autotransformer type DC / DC converter is advantageous for use in automobiles.

  FIG. 13 shows a motor of the present invention when a PAM-type VF inverter and a DC / DC converter proposed here are used as a variable voltage (VV) power source of a high-speed AC motor using a vehicle battery as a power source. It is an example of a control circuit. The reference numerals in the figure are the same as those in FIG. 2, and THc1 and THd1 are also the same as the semiconductor switching elements THa1 and THb1 in FIG. Further, TRu to TRz constituting the VF inverter are switching transistors. FIG. 14 shows the voltage current waveform of each part of the DC / DC converter. The uppermost AC voltage in FIG. 14 indicates the voltage at point A with reference to terminal C at the midpoint of the autotransformer. If the battery voltage is E, the potential at point A when the transistor TRa is ON is -E, and the potential at point A when the transistor TRb is ON is + E. The position of the tap terminal X of the autotransformer is the intermediate point between the terminal A and the intermediate tap terminal C, and the position of the tap terminal Y is the intermediate point between the terminal B and the intermediate tap terminal C (but the tap terminal The position and number of are not limited to this embodiment.) Further, as described in FIG. 5, the autotransformer Tr may be provided with terminals F and G outside the input side. The same applies to the following embodiments.

  In the first mode, an ignition signal is applied to the semiconductor switching element THa2 in synchronization with the transistor TRa and to the semiconductor switching element THb2 in synchronization with the transistor TRb. The potential at point D is E / 2. Assuming that the current flowing through the semiconductor switching elements THa2 and THb2 is I, the current I and the ampere turn between Y and B are upward I between the windings Y and B of the autotransformer and downward between the windings CB. Current I / 2 flows, and as a result, I / 2 is turned upward between the windings Y-B and I / 2 is turned downward between the windings CY, that is, the transistors TRb and TRa are reversed. A current of I / 2 flows through the diode parts connected in parallel, and a current of I / 2 flows through the battery. Although the current changes as the motor accelerates, it is shown as constant in FIG. The PAM inverter is frequency-controlled so that the torque becomes constant according to acceleration.

  In the second mode, an ignition signal is given to the semiconductor switching element THn, the point D is directly connected to the battery, and its potential is E. Assuming that the current flowing through the semiconductor switching element THn is I, since the current flows directly from the battery to the load, only the exciting current flows between the windings CB and CA of the autotransformer. Since it is smaller than the load current, it is not shown in FIG. A current of I flows through the battery.

  In the third mode, ignition signals are given to the semiconductor switching elements THa2 and THb2. Here, as in the first mode, the ignition signals of the semiconductor switching elements THa2 and THb2 are not necessarily synchronized with the transistors TRb and TRa. It is unnecessary and can be given freely, or may be given simultaneously to the semiconductor switching elements THa2 and THb2. When the transistor TRa is turned on, the semiconductor switching element THb2 is turned on. Even if an ignition signal is given to the semiconductor switching element THa2, the reverse potential is applied to the lower potential, so that only the higher potential is turned on. . The potential at point D is 3E / 2, current I flows downward between windings A and Y, and 3I / 2 flows upward between windings C-A. As a result, I is between windings C-A. / 2, I flows between CY.

  In the fourth mode, an ignition signal is given to the semiconductor switching elements THa1 and THb1. When the transistor TRa is turned on, the semiconductor switching element THb1 is turned on, the potential at the point D is 2E, the current I flows downward between the windings A and B, and 2I flows upward between the windings C-A. I flows between the lines C-A and I flows between the windings C-B.

  The reverse conversion mode, that is, the regenerative braking mode in the motor control circuit of FIG. 13 will be described with reference to FIG. 15 which is a waveform diagram. It is assumed that the ignition signals are given to the transistors TRa and TRb of the DC / DC converter, which are alternately turned on and in an operating state. The motor is rotating at high speed and the capacitor Ca is charged with the maximum voltage. When a deceleration command is given, the VF inverter is controlled to decrease its frequency, and the potential of the capacitor Ca is pushed up. Assuming that the transistor TRb is conducting, when the semiconductor switching element THd1 connected in antiparallel with the semiconductor switching element THb1 is fired, the capacitor Ca (+) → the inductance L → the semiconductor switching element THd1 → the transistor TRb → the capacitor Ca A current flows through the circuit (−), and energy is stored in the inductance L (TRb current in FIG. 15). When the ignition signal of the transistor TRb is turned off and the current that has been flowing is cut off, a voltage is generated that tries to keep the current of L · dI / dt flowing through the inductance L. Current flows in the circuit of capacitor Ca (+) → semiconductor switching element THd1 → terminal B → winding BC → battery → capacitor Ca (−), and at the same time, between the windings AC and BC. The current I equal to the ampere turn flows in the direction of A → C in the circuit of terminal A → winding AC → battery → diode portion of transistor TRa → terminal A, and the battery has a current of 2I as a result. Charged. A current flows only on the diode side of the transistor TRa, but an ignition signal is given to the transistor TRa. Since the voltage L · dI / dt generated in the inductance L attenuates with time, the charging current to the battery also decreases with time. FIG. 15 shows a constant value.

  When an ignition signal is given to the semiconductor switching element THa1 when the current has decreased to a specified value, a reverse voltage is applied to the semiconductor switching element THd1 that has been conducted so far, and the semiconductor switching element THd1 is turned OFF. At the same time, the charging current to the battery becomes zero. This time, current flows through the circuit of capacitor Ca (+) → inductance L → semiconductor switching element THa1 → transistor TRa → capacitor Ca (−), and energy is stored in inductance L. The ignition signal of the transistor TRa is turned off, and the current that has been flowing is cut off. Therefore, a voltage is generated to keep the current of L · dI / dt flowing through the inductance L. Current flows in the circuit of capacitor Ca (+) → semiconductor switching element THa1 → winding A−C → battery → capacitor Ca (−), and at the same time, the current and ampere flowing between A and C between windings B and C. The current I having the same turn flows in the direction of B → C in the circuit of winding BC → battery → diode portion of transistor TRb → winding BC, and the battery is eventually charged with a current of 2I. Thereafter, the same process is repeated alternately, and regenerative braking is performed by charging the battery.

  As the rotational speed decreases, the induced voltage of the motor decreases, so the voltage of the capacitor Ca also decreases. Therefore, the charging power to the inductance L also decreases. For this reason, in order to ensure the amount of energy, it is necessary to take long charge time. However, since the absolute amount of stored energy decreases as the speed decreases, the attenuation gradient of L · dI / dt increases, and the charging of the battery decreases as the motor speed decreases.

  FIG. 16 shows an embodiment in which the electric motor control circuit of the present invention is applied to an electric railway vehicle. In FIG. 16, illustration of a circuit composed of a tap terminal and a semiconductor switching element used when driving the electric motor is omitted, but these are provided in appropriate numbers and positions as in FIG. 2 and FIG. 13. Is. In FIG. 16, PT is a pantograph for receiving power from an overhead wire, and FilL is a filter reactor for preventing harmonic current that causes EMI (electromagnetic interference) from flowing out to the outside (the overhead wire side). An EMI filter is configured in pairs. A recent DC train drive system includes an induction motor as an inverter motor. In order to simplify the explanation of the relationship between the VVVF inverter and the induction motor, assuming that the induction motor has two poles, the relationship between the frequency f generated by the VVVF inverter and the rotation frequency fm of the induction motor is f> fm. The power flows from the VVVF inverter toward the induction motor, the induction motor operates as a motor, and the train accelerates. Conversely, if f <fm, the induction motor becomes a generator, the power flows from the induction motor in the direction of the VVVF inverter, a braking force acts on the induction motor, and the train decelerates. This is so-called regenerative braking.

  In order for the braking force to work on the induction motor and the train to decelerate smoothly, there is a saucer that absorbs the power generated by the induction motor. The regenerative braking system in the current DC overhead line power supply system expects this regenerative power tray to train that takes acceleration from the overhead line and happens to accelerate in the same overhead line power supply system via the pantograph PT. . The state where a train is running with power from an overhead line is called power running in railway terms. From now on, the term “powering” will be used. Therefore, it is good if there is a train that is lucky and powering and absorbs the regenerative power. However, if there is no such train, the voltage of the capacitor Ca is raised, the overvoltage detection is activated, and the regenerative brake is given up. It can be switched to a dynamic brake using a resistor mounted on the vehicle as a saucer or a friction brake. This is called regenerative revocation, and it occurs at a fairly high frequency in reality.

  Proposals have been made to mount a battery on the vehicle in order to recover wasteful heat energy due to regenerative expiration and reduce maintenance costs for wear of friction brake parts due to heavy use of friction brakes. In order to simplify the configuration, it is desirable to make the battery voltage equal to the voltage of the overhead power supply system, but when applied to the most common 1500V DC overhead power supply system, the high voltage battery is difficult to handle and the battery is very Because of its large back power, there is also a danger in terms of safety. For this reason, the proposals made in various places set the battery voltage relatively low. The motor control circuit using the DC / DC converter using the autotransformer described above matches this requirement.

  In the regenerative braking by the VVVF inverter, the VVVF inverter itself has a control capability, and in general, the motor current is actually controlled to be constant so that the braking force is constant from the start to the stop of the brake. The regenerative current is the maximum at the brake start point and decreases linearly with a decrease in speed, and at zero speed, the regenerative current becomes zero. On the other hand, the control of the DC / DC converter does not require any correspondence such as the continuity control, and the transistors TRa and TRb are alternately turned on and off alternately, and the semiconductor switching elements THa1 and THa1 are synchronized with this. If a signal is given to the gate of THb1 and a voltage antagonizing the voltage of the capacitor Ca is generated at the terminal D point, the regenerative current is supplied to the battery, the winding A via the winding BC in accordance with the control of the VVVF inverter. Automatically flows into the battery via -C and is absorbed by the battery.

  The amount of energy absorbed by the battery is reused as the acceleration energy of the train during the next driving. In the case of urban traffic, the amount of energy recovered by the battery during braking is equivalent to 30-40% of the total energy required for acceleration, taking into account the charge / discharge efficiency of the battery. Too much to consume. Therefore, the most preferable solution is to use the charged portion as part of the acceleration energy at the next powering. As a discharge method from the battery, there is a method of supplying power in parallel from the overhead wire and the battery at the same time. The sharing of power from the overhead line and the battery can be changed by controlling the output voltage of the DC / DC converter with respect to the overhead line voltage. As for the voltage of the DC / DC converter, there are a method for controlling the conduction ratios of the transistors TRa and TRb generally performed in the DC / DC converter, and a method for controlling the firing positions of the semiconductor switching elements THc1 and THd1 with respect to the transistors TRa and TRb. However, in both cases, the pulsation of the output voltage of the DC / DC converter is large, and it is necessary to keep the pulsation of the current small for stable control, so that the filter inductance becomes large.

  In the motor control circuit of FIG. 16, the anode side of the semiconductor switching element THn is connected to the (+) terminal of the battery, and the cathode side is connected to point D together with the cathodes of the motor control circuits THa1 and THb1. As a result, if the semiconductor switching element THn is in a conducting state during powering, a battery voltage is always applied to the point D, and the ignition positions of the semiconductor switching elements THa1 and THb1 are controlled with respect to the transistors TRa and TRb. Any voltage intermediate between the battery voltage E and twice that of 2E can be obtained. Since the pulsation of the output voltage of the DC / DC converter is ½ compared to the above-described method, there is an advantage that the filter inductance can be reduced.

  The operation during powering of the motor control circuit of FIG. 16 will be described. FIG. 17 shows a voltage waveform at the time of 100% power running. In the DC / DC converter, the transistors TRa and TRb repeat conduction alternately, and the potential at the point A is 2E when the transistor TRb is ON, and the G potential when the transistor TRa is ON. At the time of powering, for example, the semiconductor switching element THn is supplied with an ignition signal and is in a conductive state, so that the battery voltage E is applied as a base. The semiconductor switching elements THa1 and THb1 are turned on in synchronization with the transistors TRb and TRa, or an ignition signal is simultaneously applied to the semiconductor switching elements THa1 and THb1, whereby an output voltage 2E of 100% is obtained.

  In FIG. 18, the semiconductor switching elements THa1 and THb1 are made conductive with a phase angle of α without being synchronized with the transistors TRb and TRa. By changing the phase angle α, the D point voltage can be freely changed between E and 2E.

  FIG. 19 shows an electric motor control circuit of an embodiment in which a semiconductor switching element for regenerative braking is connected to a tap terminal. Also in FIG. 19, illustration of the circuit which consists of a tap terminal and a semiconductor switching element used at the time of the drive of an electric motor is abbreviate | omitted. Semiconductor switching element THc1 for causing tap terminals X and Y provided between winding terminals A and C, and B and C of autotransformer Tr to perform the reverse conversion operation of the DC / DC converter described in FIG. , THd1 is changed from the winding end terminals A and B to the tap terminals X and Y. Similarly to FIG. 13, semiconductor switching elements THa2 and THb2 may be connected in parallel to the tap terminals X and Y. The battery has a relatively large voltage difference between the charge voltage and the discharge voltage. If the output voltage of the DC / DC converter at the time of battery discharge is selected near the upper limit of the normal feeder voltage fluctuation range, the battery is regeneratively charged. It is also necessary to consider the possibility that the output terminal voltage of the DC / DC converter at the time exceeds the limit voltage at the time of regenerative braking and causes the overvoltage detection circuit to operate, resulting in regenerative termination. In the motor control circuit of FIG. 19, by providing intermediate taps of X and Y, it is possible to compensate for fluctuations in the discharge charge voltage of the battery and make the output voltage of the DC / DC converter substantially constant when viewed from the load motor side. It is what. Thereby, stable operation is possible for both power running and regeneration.

  FIG. 20 is a waveform diagram illustrating the reverse conversion operation of the motor control circuit of FIG. 19. The winding ratio between winding AC and winding XC (winding BC and winding YC) is shown in FIG. Let r. The potential of the terminal X is E + rE when the transistor TRb is ON, and E−rE when the transistor TRa is ON. At the time of reverse conversion, the semiconductor switching element THn is turned off. If the semiconductor switching elements THc1 and THd1 are turned on in synchronization with the transistors TRb and TRa, the terminal D faces the voltage E + rE. Here, if the VVVF inverter for driving the motor enters the regenerative braking operation, the voltage of the capacitor Ca is pushed up. When the voltage exceeds E + rE, the transistor TRa is turned on through the inductance L, and an ignition signal is applied to the semiconductor switching element THd1. Assuming that the current is flowing in the circuit of capacitor Ca (+) → inductance L → semiconductor switching element THd1 → terminal Y → winding YC → terminal C → battery → capacitor Ca (−), winding A In -C, a current rI having an ampere-turn equal to the current I flowing in the winding Y-C flows in the direction of AC, and a current I + Ir flows into the battery. When the semiconductor switching element THc1 is fired before switching to the next half cycle, the current flowing through the semiconductor switching element THd1 moves to THc1, and the capacitor Ca (+) → inductance L → semiconductor switching element THc1 → terminal X → winding. A current I flows in a circuit of line X-A → terminal A → transistor TRa → capacitor Ca (−). Battery charging current is also zero. In the next cycle, the transistor TRa is turned off, L · di / dt is induced in the inductance, and added to the voltage of the capacitor Ca, and the capacitor Ca (+) → inductance L → semiconductor switching element THc1 → terminal X → winding. The current I flows in the circuit of the line X-C → terminal C → battery-capacitor Ca (−). In the winding BC, a current rI having an ampere-turn equal to the current I flowing in the winding X-C is obtained. It flows in the direction of B-C, and a current of I + Ir flows into the battery. The same process is followed below.

  FIG. 21 shows another embodiment for providing the same effect as FIG. In order to select the output voltage of the DC / DC converter when charging the battery near the upper limit of the normal feeder voltage fluctuation range during normal operation, and to compensate for the voltage drop during power running, both winding terminals A and B of the autotransformer Windings AX ′ and BY ′ are added to the outside of the DC / DC converter, respectively, so that the output voltage of the DC / DC converter is substantially constant when viewed from the load motor side.

  FIG. 22 shows an embodiment in which the motor control circuit of the present invention is used for speed control of a DC series motor. The DC series motor includes an armature M as a rotor and a field winding MF as a stator. A magnetic field is created by passing a current through the field winding MF, and a rotational force is generated between the magnetic field and the armature current, so that the motor rotates. In order to reverse the motor, the reverser RV is switched, the contact that has been closed is opened, and the contact that has been opened is closed. This changes the direction of the current flowing through the field winding MF. Furthermore, when the direction of current flow is reversed, the direction of the magnetic field is also reversed, causing the rotor to generate a rotational force in the reverse rotation direction. Further, at the time of braking, since it is necessary to reverse the direction of the current without changing the direction of the induced voltage of the motor, the field connection by the reverser RV is also switched.

  In order to control the speed of the DC series motor, the applied voltage needs to be gradually increased according to the acceleration of the motor. In FIG. 22, in order to perform the acceleration operation, the semiconductor switching element THa1 connected to each winding terminal. , THa2, THb1, THb2, and THn are selected and used. The transistors TRa and TRb are alternately turned on every 1/2 cycle to operate the inverter, and the semiconductor switching element THa2 is turned on in synchronization with the transistor TRa and the semiconductor switching element THb2 is turned on alternately in synchronization with the transistor TRb. Thus, the DC motor has the lowest step voltage E / 2 directly (FIG. 23), or the conduction rate control of the transistor TRa and the semiconductor switching elements THa1 and THa2, and the conduction rate of the transistor TRb and the semiconductor switching elements THb1 and THb2. By alternately performing the control, a voltage from zero to the lowest step voltage E / 2 is gradually applied (FIG. 24).

  Since the current decreases in accordance with the acceleration of the motor, the next step, that is, the transistor TRa, the semiconductor switching element THn, and the transistor TRb, the semiconductor switching element THn are alternated with reference to the decrease to the reference current value. To the DC motor, the next step voltage E is applied directly to the DC motor or the conduction ratio control of the transistor TRa, the semiconductor switching element THa2 and the semiconductor switching element THn, and the transistor TRb, the semiconductor switching element THb2 and the semiconductor switching element. The conduction rate control of THn is alternately performed, and the voltage up to the next step voltage E is gradually applied. Similarly, the transistor TRa, the semiconductor switching element THb2, the transistor TRb, and the semiconductor switching element THa2 are alternately switched. By allowing the DC motor to pass, the next step voltage 3E / 2 is directly applied to the DC motor or the conductivity control of the transistor TRa, the semiconductor switching element THn and the semiconductor switching element THb2, and the transistor TRb, the semiconductor switching element THn and the semiconductor switching. The conductivity control of the element THa2 is alternately performed, and a voltage up to a further step voltage 3E / 2 is gradually applied. Lastly, the transistor TRa, the semiconductor switching element THb1, and the transistor TRb, the semiconductor switching element THa1 are alternately conducted directly, or the transistor TRa, the conduction control of the semiconductor switching element THb2 and the semiconductor switching element THb1, and the transistor TRb The continuity control of the semiconductor switching element THa2 and the semiconductor switching element THa1 is alternately performed, the maximum voltage 2E is applied, the motor is further accelerated by the voltage 2E, and continues to rotate at a speed and current balanced with the load.

  In switching to regenerative braking, the semiconductor switching elements THa and THb are turned off once to make the current zero, however, the DC / DC converter continues to operate with no load. The connection of the field windings is switched, and then the semiconductor switching element THc1 is turned on synchronously when the transistor TRa is turned on, and the semiconductor switching element TRd1 is turned on synchronously when the transistor TRb is turned on. Armature M (+) terminal → Series winding field MF → Current interruption preventing inductor L → Semiconductor switching element THc1 → Transistor TRa (or semiconductor switching element THd1 → Transistor TRb alternately every half cycle) → Point G → DC motor A current is raised in a circuit (−) terminal (FIG. 25). The current I flowing through the current interrupt prevention inductance L gradually increases, and energy is stored in the inductance L. When the current I increases to a specified value, in FIG. Correspondingly, at the point X, the semiconductor switching element THc1 is not turned on in synchronization with the conduction of the transistor TRa, and the semiconductor switching element THd1 is kept turned on.

  The B terminal voltage of the autotransformer is pushed up by the energy stored in the inductance L, and the voltage of the capacitor Ca + L · dI / dt is added between the windings B-A, and the capacitor Ca (+) terminal. → Current interrupt prevention inductor L → Semiconductor switching element THd1 → Single-turn transformer Tr winding BA → Transistor TRa → Point G → Capacitor Ca (−) terminal A current I flows through the path. On the other hand, in the autotransformer, in the direction of A-C, the current I in the B-A direction is equal to the ampere turn, and the point C is an intermediate point of the autotransformer, so the number of turns is B-A. As a result, a current of 1/2, 2I, flows between the autotransformers B-C, and a current of I flows in the B-C direction between the autotransformers B-C. Current 2I flows into the battery Ba as a charging current. In this current, since L · dI / dt decreases with time, the current flowing through L tends to decrease.

  At the end of the half cycle of the conduction of the transistor TRa, the Y point in FIG. 25, the semiconductor switching element THc1 is turned on, and a reverse voltage is applied to the semiconductor switching element THd1, so the current is zero immediately and the battery charging current is also zero. Current flows through a path of capacitor Ca (+) terminal → current interrupt prevention inductor L → semiconductor switching element THc1 → transistor TRa → point G → capacitor Ca (−) terminal, energy is stored in L, and current increases.

  When the conduction signal of TRa is turned OFF, a voltage difference between the voltage of the capacitor Ca + L · dI / dt and the voltage of the battery Ba is added in the direction C−A between the windings AC of the autotransformer Tr. A voltage in the B-C direction is generated between the windings B-C, a current flows in the direction of the winding B-C, the battery Ba, the point G, the diode portion of the transistor TRb, and the winding B-C. Between the windings A and C of the autotransformer Tr, a current having an equal ampere flow flows in the direction of canceling out the magnetic field generated in the autotransformer due to the current flowing between B and C. The sum of both currents flows as the charging current. In this current, since L · dI / dt decreases with time, the current flowing through L tends to decrease.

  Thereafter, the same process is followed every half cycle. From the viewpoint of the electric motor, since regenerative braking operates, the speed gradually decreases, and the induced electromotive force also decreases as the speed decreases. Since the braking force of the motor needs to be kept constant regardless of the decrease in speed, it is necessary to control the motor current to be constant. On the other hand, since the battery voltage is substantially constant, it is necessary to increase the push-up voltage due to the inductance L. Therefore, it is necessary to perform control so as to increase the energy storage time in L so that the electric current of the motor becomes constant. As the motor speed decreases, the time width of the charging current to the battery narrows and the charging current decreases.

  The semiconductor switching elements used for regenerative braking (THc1, THd1 in the above-described embodiment) are semiconductor switching elements for obtaining the drive voltage of the motor (THa0-THa3, THb0-THb3, THn, etc. in the above-described embodiments). ) May be selected and used in parallel. Of course, it may be selected and used in parallel with semiconductor switching elements for obtaining drive voltages of all electric motors. In these cases, a semiconductor switching element connected to a tap symmetrical to the intermediate tap C is selected. Further, as described in FIG. 19, the semiconductor switching element used for regenerative braking may be connected to a tap terminal different from the tap terminal to which the semiconductor switching element for obtaining the driving voltage of the electric motor is connected. Good.

  In the present invention, as described above, by using the auto-transformer having a tap terminal and adopting the synchronous ignition method, the operation voltage can be controlled, and when regenerative braking is performed, Stable regenerative braking is possible, and it is effective for automobiles or electric railway vehicles.

It is explanatory drawing of the structure corresponding to the basic structure at the time of the drive of the load in the DC / DC converter used for this invention. It is a block diagram for demonstrating the 1st Embodiment of this invention. It is operation | movement explanatory drawing of FIG. It is explanatory drawing at the time of using together continuity control to step voltage control. It is a block diagram for demonstrating the other Example in 1st Embodiment. It is operation | movement explanatory drawing of an electric motor. It is explanatory drawing of the torque versus rotation speed characteristic of an induction motor. It is operation | movement explanatory drawing of an induction motor with a VVVF inverter. FIG. 9 is a waveform diagram of each part of the circuit of FIG. 8. It is each part waveform diagram in the case of 9 pulse modulation. It is each part waveform diagram in the case of 3 pulse modulation. It is each part waveform diagram in the case of 1 pulse modulation. It is an example of the motor control circuit for motor vehicles of this invention. FIG. 14 is a waveform diagram of each part when the circuit of FIG. 13 is driven by an electric motor. FIG. 14 is a waveform diagram of each part in the case of regenerative braking of the circuit of FIG. 13. It is a circuit diagram of one Example which applied the electric motor control circuit of the present invention to an electric railway vehicle. It is explanatory drawing in the case of 100% power running of the circuit of FIG. It is explanatory drawing in the case of the power running guidance angle | corner (alpha) of the circuit of FIG. It is a motor control circuit diagram of other examples for regenerative braking. FIG. 20 is a waveform diagram of each part of the circuit of FIG. 19. It is a motor control circuit diagram of other examples for regenerative braking. 1 is a circuit diagram of an embodiment in which an electric motor control circuit of the present invention is used for speed control of a DC series motor. FIG. It is operation | movement explanatory drawing of the circuit of FIG. It is operation | movement explanatory drawing of the circuit of FIG. FIG. 23 is a waveform diagram of each part of the circuit of FIG. 22. It is a circuit diagram of an example of a conventional center tap connection type DC / DC converter. FIG. 28 is a circuit diagram in which intermediate points of the primary and secondary windings are connected in the circuit of FIG. 27. It is a circuit diagram of an example of the DC / DC converter using the conventional autotransformer. It is explanatory drawing of IGBT used generally. It is a block diagram for demonstrating the relationship between a 2 coil | winding transformer and a single volume transformer. It is a block diagram for demonstrating the conventional basic DC / DC converter. FIG. 33 is an output voltage waveform diagram of the DC / DC converter of FIG. 32.

Explanation of symbols

  Ba: battery, TRa, TRb ... transistor, THa0 to THa3, THb0 to THb3, THn: semiconductor switching element, Tr: autotransformer, LR: load, L: inductance, Ca: capacitor, M: electric motor, TRu to TRz : Transistor.

Claims (8)

One pole of the DC power supply is connected to the terminal of the midpoint of the autotransformer, and the other pole of the DC power supply is connected to the terminals at both ends of the autotransformer via switching elements, respectively.
A plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends of the autotransformer and the terminals at both ends and symmetrical with respect to the terminal at the intermediate point are respectively connected to the motor via a selection circuit. Connected to one terminal, the other pole of the DC power supply is connected to the other terminal of the motor,
The switching elements are alternately controlled to be opened and closed so that there is no conduction period.
Each of the selection circuits has a unidirectional element that can be controlled to open and close and that allows current to flow in the direction of driving the electric motor,
An electric motor driving circuit, wherein at least one selection circuit is controlled to be opened and closed in synchronization with the switching control of the switching element. One pole of a DC power supply is connected to the terminal of the midpoint of the autotransformer, and is provided at a position symmetrical to the terminals of the midpoint inside the terminals at both ends of the autotransformer. The other pole of the DC power supply is connected to each terminal via a switching element,
A plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends of the autotransformer and the terminals at both ends and symmetrical with respect to the terminal at the intermediate point are respectively connected to the motor via a selection circuit. Connected to one terminal, the other pole of the DC power supply is connected to the other terminal of the motor,
The switching elements are alternately controlled to be opened and closed so that there is no conduction period.
Each of the selection circuits has a unidirectional element that can be controlled to open and close and that allows current to flow in the direction of driving the electric motor.
An electric motor driving circuit, wherein a selection circuit connected to a tap terminal provided at the symmetrical position is controlled to be opened and closed in synchronization with the switching control of the switching element. One pole of the DC power supply is connected to the terminal of the midpoint of the autotransformer, and the other pole of the DC power supply is connected to the terminals at both ends of the autotransformer via switching elements, respectively.
A plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends of the autotransformer and the terminals at both ends and symmetrical with respect to the terminal at the intermediate point are respectively connected to the motor via a selection circuit. Connected to one terminal, the other pole of the DC power supply is connected to the other terminal of the motor,
The switching elements are alternately controlled to be opened and closed so that there is no conduction period.
Each of the selection circuits has a unidirectional element that can be controlled to open and close and that allows current to flow in the direction of driving the electric motor,
The selection circuit connected to the tap terminal provided at the symmetrical position is controlled to be opened and closed in synchronization with the switching control of the switching element,
In addition, in the at least one selection circuit, a unidirectional element that can be controlled to open and close and flows a current in a direction opposite to the direction is connected in parallel to the unidirectional element. An electric motor drive circuit characterized in that the electric motor is driven and regeneratively braked by opening and closing control. One pole of a DC power supply is connected to the terminal of the midpoint of the autotransformer, and is provided at a position symmetrical to the terminals of the midpoint inside the terminals at both ends of the autotransformer. The other pole of the DC power supply is connected to each terminal via a switching element,
A plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends of the autotransformer and the terminals at both ends and symmetrical with respect to the terminal at the intermediate point are respectively connected to the motor via a selection circuit. Connected to one terminal, the other pole of the DC power supply is connected to the other terminal of the motor,
The switching elements are alternately controlled to be opened and closed so that there is no conduction period.
Each of the selection circuits has a unidirectional element that can be controlled to open and close and that allows current to flow in the direction of driving the electric motor.
The selection circuit connected to the tap terminal provided at the symmetrical position is controlled to be opened and closed in synchronization with the switching control of the switching element,
In addition, in the at least one selection circuit, a unidirectional element that can be controlled to open and close and flows a current in a direction opposite to the direction is connected in parallel to the unidirectional element. An electric motor drive circuit characterized in that the electric motor is driven and regeneratively braked by opening and closing control. One pole of the DC power supply is connected to the terminal of the midpoint of the autotransformer, and the other pole of the DC power supply is connected to the terminals at both ends of the autotransformer via switching elements, respectively.
A plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends of the autotransformer and the terminals at both ends and symmetrical with respect to the terminal at the intermediate point are respectively connected to the motor via a selection circuit. Connected to one terminal, the other pole of the DC power supply is connected to the other terminal of the motor,
The switching elements are alternately controlled to be opened and closed so that there is no conduction period.
Each of the selection circuits has a unidirectional element that can be controlled to open and close and that allows current to flow in the direction of driving the electric motor,
The selection circuit connected to the tap terminal provided at the symmetrical position is controlled to be opened and closed in synchronization with the switching control of the switching element,
In addition, one or more tap terminals different from the tap terminal and the one terminal are connected with a unidirectional element capable of opening / closing control and flowing a current in a direction opposite to the direction. An electric motor drive circuit for driving an electric motor and performing regenerative braking by controlling opening and closing of a directional element. One pole of a DC power supply is connected to the terminal of the midpoint of the autotransformer, and is provided at a position symmetrical to the terminals of the midpoint inside the terminals at both ends of the autotransformer. The other pole of the DC power supply is connected to each terminal via a switching element,
A plurality of tap terminals provided at one or more positions symmetrical between the terminals at both ends of the autotransformer and the terminals at both ends and symmetrical with respect to the terminal at the intermediate point are respectively connected to the motor via a selection circuit. Connected to one terminal, the other pole of the DC power supply is connected to the other terminal of the motor,
The switching elements are alternately controlled to be opened and closed so that there is no conduction period.
Each of the selection circuits has a unidirectional element that can be controlled to open and close and that allows current to flow in the direction of driving the electric motor.
The selection circuit connected to the tap terminal provided at the symmetrical position is controlled to be opened and closed in synchronization with the switching control of the switching element,
In addition, one or more tap terminals different from the tap terminal and the one terminal are connected with a unidirectional element capable of opening / closing control and flowing a current in a direction opposite to the direction. An electric motor drive circuit for driving an electric motor and performing regenerative braking by controlling opening and closing of a directional element.   The electric motor is an electric motor mounted on a railway vehicle, and the DC power source is a battery mounted on the rail vehicle, and the battery absorbs a regenerative current during the regenerative braking. 7. The electric motor drive circuit according to any one of items 6 to 6.   The electric motor drive circuit according to any one of claims 1 to 7, wherein a terminal at an intermediate point of the autotransformer is also a tap terminal.

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