JP4095865B2 - Electric motor drive device and electric motor application device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric motor driving device for driving an electric motor and an application device thereof.
[0002]
[Prior art]
For example, Japanese Patent Application Laid-Open No. 11-164526 is known as a conventional motor driving device. This prior art describes the following.
[0003]
The voltage booster circuit includes a reactor connected in series to an AC power source, a first switching element (IGBT) that opens the AC power source through a first rectifier (four diodes connected in a bridge), and a drive thereof. A function that is composed of a circuit, stores the energy in the reactor by turning on the first switching element, and moves the energy stored in the reactor to the voltage dividing capacitor for voltage doubler described below by turning it off to boost the DC voltage have. By performing this ON time for a predetermined time from the zero cross point, the energization angle of the current waveform is widened and the power factor is improved.
[0004]
The voltage doubler rectifier circuit is connected in parallel to the second rectifier (bridge circuit) and the second rectifier, and the connection point is connected to the connection point of one diode series body of the second rectifier. A capacitor and a smoothing capacitor connected in parallel to the voltage dividing capacitor are generated, and a double voltage is generated for full-wave rectification.
[0005]
An inverter circuit that drives an electric motor using a direct current formed by the voltage doubler rectifier circuit as a power source is connected to the subsequent stage of the voltage doubler rectifier circuit, and a switching command is given to the inverter by the inverter control device.
[0006]
[Problems to be solved by the invention]
In the electric motor drive device constituted by the above circuit, when the voltage of the AC power supply is 100 V, the obtained DC voltage is theoretically:
100 × 1.41 × 2 = 282 (V) ◆
It is. However, since there is a voltage drop of the reactor 4 or the like, it is about 230 V in a practical circuit.
[0007]
In the conventional example, the booster circuit is used as a power factor correction circuit. However, if this is applied to the rotation speed control of an electric motor, it will be as follows. When the rotation speed of the electric motor is low, the switching element of the booster circuit is turned off to set the DC voltage to 230 V, and the motor PWM speed is controlled by changing the PWM duty of the inverter. When the PWM duty of the inverter is increased, the speed of the motor increases. However, when the PWM duty of the inverter reaches 100%, the speed of the motor cannot be increased further.
[0008]
At that time, the switching element is turned on with a predetermined duty. When the switching element is turned on, a short-circuit current flows through the AC power supply through the reactor, and electromagnetic energy is accumulated in the reactor. When the switching element is turned off in this state, the electromagnetic energy accumulated in the reactor is released to the output side, and charges are accumulated in the smoothing capacitor. Thus, the DC voltage increases in proportion to the on-duty of the switching element.
[0009]
As the voltage increases, the speed of the motor increases. For example, even a motor with a design point of 250 V can be controlled to a rotational speed higher than the design point.
[0010]
In addition, by controlling the ON timing and on-duty of the switching element according to the phase of the AC power supply, the input current waveform can be approximated to a sine wave shape, and the power source power factor and harmonic current can be set to predetermined values. Yes.
[0011]
In such a conventional circuit, it is usually possible to control up to 7000 rpm by using a motor with a design point of 250 V and 5000 rpm and increasing the voltage to 330 V. At the same time, while controlling the voltage from 250V to 330V, the inverter's PWM duty is set to 100% full duty, thereby increasing the operating efficiency of the motor.
[0012]
However, since the voltage control range is relatively narrow from 250 V to 330 V, the motor speed has to be controlled by PWM duty control of the inverter in the medium speed and low speed regions where the motor is frequently used. When the motor is controlled in such a speed, particularly when the low-speed PWM duty is low, the minimum voltage 230V is not preferable for the following reason.
[0013]
In the state where the minimum voltage is 230 V, the current flowing through the winding coil of the motor is given by the relationship di / dt = V / L, and thus the value of di / dt increases. If the carrier frequency of the PWM signal of the inverter is constant, the current ripple is naturally large. This current ripple becomes an electromagnetic pulsation, causing a current to flow through the core of the stator of the electric motor and increasing the iron loss. That is, the operating efficiency of the electric motor is significantly reduced.
[0014]
An object of the present invention is to provide an electric motor drive device that expands the high-efficiency operation range of an electric motor.
[0015]
[Means for Solving the Problems]
The above purpose is
A second rectifier for converting alternating current to direct current;
A voltage-dividing capacitor connected in parallel to the second rectifier;
A smoothing capacitor connected in parallel to the voltage dividing capacitor;
An inverter connected to the smoothing capacitor and supplying driving power to the motor;
A reactor provided on the AC side of the second rectifier;
A switching element that short-circuits and opens the alternating current through the reactor;
A switch connected between the second rectifier and the voltage dividing capacitor to form a voltage doubler circuit in an on state with a full-wave rectifier circuit in an off state;
A first operation mode in which the switching element is kept off and the switch is kept off;
A second operation mode in which the switch is kept off and the switching element is on / off controlled;
An on-timing in the half cycle of the alternating voltage of the switching element is determined as an input current while keeping the switch on. increase of In response to the To reduce the delay time 3-1 operation mode to change,
When the input current further increases from the 3-1 operation mode, the 3-2 operation mode is switched from the 3-1 operation mode, The on-timing in the half cycle of the AC voltage of the switching element is maintained while keeping the switch on. In the ON timing of the 3-1 operation mode corresponding to the input current at the time of switching Solid Set 3-2 operation mode,
Switching from the 3-1 operation mode to the 3-2 operation mode is achieved by performing when the input current reaches a predetermined value.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail by way of examples. ◆
FIG. 1 is a diagram showing a configuration of an electric motor drive device according to the present invention, which is configured as follows.
[0020]
A reactor 2 connected in series to an AC power source 1 (connected by an outlet or the like to form a power source and a circuit), and a first rectifier 3 connected to a subsequent stage of the reactor 2 and configured by a diode bridge circuit The switching element 4 connected in parallel to the first rectifier 3 and short-circuiting the AC power supply 1 and its drive circuit 11 constitute a first voltage control means.
[0021]
A second rectifier 5 configured by a diode bridge circuit connected to the subsequent stage of the reactor 2, a voltage dividing capacitor 6a, 6b composed of a series body of capacitors connected in parallel to the DC side of the second rectifier 5, and Provided between the smoothing capacitor 7 connected in parallel to the voltage dividing capacitors 6a and 6b, and the connection point (AC side) of one diode series body of the second rectifier 5 and the connection point of the voltage dividing capacitors 6a and 6b. The second voltage control means comprises the switch 8 for switching between the double voltage rectified voltage and the full wave rectified voltage.
[0022]
A three-phase inverter circuit 9 in which six switching elements driven by applying a rotating magnetic field to an electric motor 15 (mainly a DC brushless motor) using a DC voltage generated by the second voltage control means as a power supply, and an inverter The drive circuit 12 is composed of nine drive circuits 12.
[0023]
The microcomputer 10 serving as an arithmetic control means includes an output signal from the zero cross point detection circuit 13 of the AC power supply, an output signal from the current detection circuit 14 that detects an input current of the motor 15 in order to detect the magnetic pole position and the rotation speed of the motor 15, The output signal of the DC voltage detection circuit 16 that detects the voltage across the smoothing capacitor and the motor operation control command from the host controller (not shown) are input, and the scheduled control calculation is performed, so that the first voltage control means An operation signal output to the drive circuit 11 for PWM driving the switching element 4, a switching signal output to the switch 8 of the second voltage control means, and an operation signal output to the inverter 9 for PWM driving the motor 15 are performed.
[0024]
Next, the operation in the above configuration will be described. A first operation mode in which the switch 8 is turned off and the switching element 4 is continuously turned off (opened) in FIG. 1 will be described.
[0025]
In FIG. 1, the state of the first operation mode constitutes a general full-wave rectifier circuit. At this time, the DC voltage output from the rectifier circuit to the inverter 9 is theoretically ◆
100 × 1.41 = 141 (V) ◆
It becomes. However, it is usually about 120V due to a voltage drop of the reactor or the like. Since the motor 15 is a direct current brushless motor, the rotational speed increases or decreases in proportion to the applied direct current voltage. For this reason, when the electric motor 15 is operated in a low rotational speed range (for example, 2000 rpm or less with respect to the maximum rotational speed of 7000 rpm), the efficiency of the entire apparatus is improved by using a low voltage rather than a high DC voltage.
[0026]
If the motor is simply operated at a low rotational speed, the DC voltage supplied to the inverter 9 by a voltage doubler rectifier circuit or the like is set to the DC voltage required by the motor 15 at the maximum rotational speed, and the PWM duty of the inverter 9 is reduced. Thus, the operation of the electric motor 15 can be controlled.
[0027]
However, as described above in the conventional example, the voltage applied to the motor 15 is obtained by chopping a high DC voltage with a small PWM duty. For this reason, since the current change di / dt flowing through the motor 15 increases, the iron loss of the motor increases and the efficiency of the motor drive type deteriorates.
[0028]
Therefore, in this embodiment, the first operation mode described above, that is, the operation mode in which both the first switching element 4 and the second switch 8 are turned off is provided. Thus, when the motor 15 is operated at a low rotational speed, the DC voltage of the smoothing capacitor 7 serving as a voltage source when viewed from the second rectifier 5 and the inverter 9 in the subsequent stage of the voltage dividing capacitor 6 is set to a voltage by full-wave rectification. Thus, by keeping the PWM duty of the inverter 9 relatively large and driving the motor with a small change in current di / dt flowing through the motor, highly efficient operation is possible. Note that the PWM duty of the inverter 9 is calculated so that the voltage applied to the motor 15 becomes the required value even when the input DC voltage varies.
[0029]
Next, in FIG. 1, a second operation mode in which the switch 8 is turned off and the first switching element 4 is controlled to be opened by a predetermined short circuit will be described.
[0030]
In the first operation mode, when the load on the motor is large or when the rotation speed of the motor is increased, the current input from the AC power source 1 increases with the load or rotation speed. At this time, the circuit shown in FIG. 1 basically constitutes a capacitor input circuit in a state where the reactor 2 is connected in series to the AC power supply but the first switching element 4 is not controlled to be shorted and opened. The capacitor input circuit has a characteristic in which the current does not flow because the input current is not a sinusoidal alternating current, and the current peak increases accordingly. Even if the pulsating flow that is the output voltage of the second rectifier 5 rises from the zero crossing point, electric charges are stored in the capacitors 6 and 7 and the voltage of the pulsating flow remains lower than the voltages of the capacitors 6 and 7. In this state, no current flows. When the voltage of the pulsating current is further increased, the voltage of the capacitors 6 and 7 is exceeded, and at this time, current flows from the second rectifier 5 to the capacitors 6 and 7. The period during which the current flows continues until the voltage of the pulsating current becomes lower than the voltages of the capacitors 6 and 7 again. The period during which a current flows during the half cycle of the pulsating flow is referred to as a flow phase angle. Since this current is steeple, the power factor of the input alternating current is deteriorated. Here, the loss caused by the electric resistance is loss P = resistance R × (current I) ² And increases in proportion to the square of the current.
[0031]
Therefore, by providing a second operation mode in which a current is forcibly passed during a period in which no current flows by appropriately short-circuiting the switching element 4, the peak current with a high peak value is reduced, Try to improve the rate. Based on the zero-cross signal of the input AC voltage detected by the zero-cross detection circuit 13, a predetermined delay time until the switching element 4 is short-circuited by the microcomputer 10 and the time for short-circuiting the switching element 4 are calculated, and the switching element 4 is short-circuited. A drive signal to be released is output to the drive circuit 11. As a result, the switching element 4 is controlled to be short-circuited and the input current flows through the reactor 2 and the first rectifier circuit 3, and the time (phase angle) in which the input current flows is expanded depending on the timing at which the switching element 4 is opened. Thus, the peak of the input current can be reduced, and the DC voltage output to the inverter 9 can be controlled by the electromagnetic energy storage effect of the reactor 2. As a result, the peak of the input current is reduced, the loss caused by the fixed resistance of the circuit can be reduced, and a highly efficient motor operation can be achieved.
[0032]
Here, a control method for short-circuiting the switching element 4 will be described. First, the delay time until the switching of the switching element 4 starting from the zero-cross point of the input AC voltage is set to a fixed value because the rotational speed range and load conditions of the motor 15 controlled by the inverter 9 are limited to some extent. . In this case, since the load is not so large, the flow phase angle is small. Therefore, the angle to the zero cross point before and after the flow phase angle is large. For this reason, if the delay time is too short, the current due to turning on the switching element 4 becomes steeper and worsens the current waveform. Therefore, the delay time is experimentally obtained and is set to a fixed value that can improve the power factor without deteriorating the current waveform.
[0033]
In addition, even if it is not set as a fixed value, it is also possible to perform control in which the delay time is changed depending on the rotation speed, load, or input current of the motor 15. Here, the amount to be changed according to the fixed value or the rotation speed of the electric motor can be obtained experimentally, and this result may be used. Of course, the delay time is not set to a fixed value, but table data or an arithmetic expression is prepared, and information such as the rotational speed of the motor, DC voltage, output current, input voltage of the AC power supply 1 and input current is obtained. You may calculate based on.
[0034]
Next, the setting of the short circuit opening time of the switching element 4 will be described. When the electric motor 15 is in a predetermined rotation speed range, the terminal voltage of the smoothing capacitor 7 is controlled to a predetermined predetermined DC voltage (DC voltage command). The microcomputer 10 calculates the increase / decrease width of the short-circuit time from the deviation between the DC voltage information detected by the microcomputer 10 and a predetermined DC voltage, and performs feedback control so that the detected DC voltage information becomes a predetermined DC voltage value. Here, the predetermined DC voltage value determined in advance is larger than the case where the peak value of the input current is continuously opened (off) even if the voltage fluctuation of the input AC power supply 1 is taken into consideration. The voltage value can be realized without any problem. In addition, an upper limit value is set for the short circuit time of the switching element 4 so that the peak value of the input current does not become larger than when the switching element 4 is continuously opened (off). Note that this upper limit value can be simply used as a protection purpose because, if an input voltage detection circuit (not shown) is used, the DC voltage value output to the inverter 9 may be changed in accordance with the detected input voltage value. good.
[0035]
Further, the short-circuit opening time of the switching element 4 in the operation mode 2 and the delay time until the switching element 4 is short-circuited from the zero cross point were experimentally determined depending on the size of the operation region in the operation mode 2 in terms of load. Even with a fixed value, the same effect as described above can be obtained.
[0036]
Next, referring to FIG. 1, the 3-1 and 3-2 operation modes in which the switch 8 is turned on and the switching element 4 is controlled to be short-circuited and opened will be described.
[0037]
First, the operation of the operation mode 3-1 will be described. In the second operation mode, the rotation speed of the motor 15 is determined by the modulation rate of the inverter 9 (the ON ratio of the PWM signal output to the inverter circuit 9 (the DC voltage Vd applied to the inverter circuit 9 and the motor voltage applied to the motor 15). If the ratio to Vm (Vm / Vd))) is increased, the modulation factor will eventually reach almost 100%, and the voltage applied to the motor 15 can no longer be increased. The rotational speed cannot be increased. Since the switch 8 is off in the second operation mode, a full-wave rectifier circuit is basically configured, and the DC voltage is a constant value when there is no fluctuation in the input AC voltage. When the rotational speed of the electric motor 15 is increased in this state, since the DC voltage is insufficient, the rotational speed does not increase more than a certain rotational speed, or the motor becomes inefficient.
[0038]
Therefore, when the rotational speed of the electric motor 15 is increased beyond a certain rotational speed, the voltage doubler rectifier circuit is configured by turning on the switch 8. As a result, the basic voltage becomes 100 V × 2 × 1.41 = 282 V (substantially about 220 to 250 V due to the voltage drop due to the reactor or load) so that the motor 15 can be increased to a higher rotational speed. Become.
[0039]
Here, in the voltage doubler rectifier circuit in which the switch 8 is only turned on, the input current from the AC power supply remains in the capacitor input type, and therefore the peak value of the input current is high and the circuit efficiency is poor as described above. At the same time, harmonic current is generated.
[0040]
Therefore, the switching element 4 is subjected to a predetermined short-circuit opening control to perform an efficient operation for suppressing the peak value of the input current, and to increase the conduction phase angle of the input current (the conduction time during the half cycle of the power supply frequency). Operate with improved power factor.
[0041]
An example of the short circuit opening control of the switching element 4 at this time is shown. In view of the fact that the operation mode 3-1 is a mode immediately after the motor 15 cannot be efficiently operated in the operation mode 2, the operation (rotation speed, load) state of the motor 15 or the input from the AC power source It is considered that the current is a mode performed from an approximately middle region at the maximum when the electric motor driving apparatus of the present embodiment can output (input). Therefore, the input current conduction phase angle (conduction time) is not sufficiently large. Therefore, in the operation mode 3-1, by controlling both the delay time until the switching element 4 is short-circuited from the zero cross point of the AC power supply and the short-circuit time, the operation of the circuit with good efficiency and high power factor is obtained. It is done.
[0042]
First, for example, the operation mode 3-1 is performed in the region from the input current A to the input current B in FIG. Here, FIG. 2 shows the input current on the horizontal axis and the delay time from the zero cross point of the AC power supply to the short circuit of the switching element 4 on the vertical axis, and the delay time is reduced as the input (AC) current increases. ing. The reason why the input current is increased is that the power supplied to the load is increased, which means that the load current is increased. Accordingly, since the current supplied from the capacitors 6 and 7 to the electric motor 15 increases, the voltage of the capacitors 6 and 7 decreases quickly. The period (phase) from when the pulsating current, which is the output of the second rectifier 5, exceeds the zero-cross point until the current starts to flow is shorter when the input current is larger than when the input current is small. That is, the flow phase angle increases.
[0043]
As described above, since the conduction phase angle increases as the input current increases, the period until the current starts to flow from the zero-cross point is shortened, and the delay time is controlled to be small in accordance with this.
[0044]
By reducing the delay time as the input current increases and the conduction phase angle increases in this way, the power factor that keeps the input current conduction phase angle always larger than in the case where the switching element 4 is not controlled to be short-circuited and opened is improved. Operation can be performed and input current can be continuously maintained within a half cycle of the input power supply.
[0045]
Next, short-circuit opening control of the switching element 4 in the operation mode 3-1 will be described. If the short-circuiting time of the switching element 4 is too short, the peak value of the input current cannot be made sufficiently small, and if it is too large, the input current approaches a triangular wave shape and the peak value also becomes larger than the case where the peak value is not short-circuited. Therefore, it has been experimentally found that when the DC voltage output from the second voltage control circuit is controlled to be constant, for example, 250 V as the control parameter of the switching element 4, both the circuit efficiency and the power factor can be controlled satisfactorily. Yes. Thus, the control of the switching element 4 in the operation mode 3-1 calculates the delay time from the zero cross point based on the value of the input current as described above, and after the calculated delay time has elapsed, the switching element 4 Short circuit. Then, the short circuit time during the half cycle of the power supply cycle is calculated from the deviation between a predetermined DC voltage value command (for example, 250 V) and the DC voltage value detected by the DC voltage detection circuit 16, and the switching element 4 after this short circuit time has elapsed. Is released.
[0046]
By performing such control, it is possible to perform an operation with good efficiency and power factor, and further, since the DC voltage output to the inverter circuit 9 is also stabilized, the rotation control of the motor 15 can be performed stably.
[0047]
Next, the operation in the operation mode 3-2 will be described. First, since the operation mode 3-2 is performed when the input current shown in FIG. 2 is B or more, the delay time until the switching element 4 is short-circuited from the zero cross point is set to a fixed value of Td_B. This is because the input current is set in a sufficiently loaded region (region where the input current is greater than or equal to B), and the input current conduction phase angle becomes a sufficiently large value. This is because the power factor is sufficiently improved even when the delay time is set to a fixed value.
[0048]
Moreover, about the short circuit time of the switching element 4, like the operation mode 3-1, the direct current voltage to output is increased / decreased so that it may become predetermined | prescribed DC voltage command value (for example, 250V), operation mode 3-2 The same effect can be obtained.
[0049]
Next, the case where the input power supply voltage fluctuates in the operation modes 3-1 and 3-2 will be described. First, when the input power supply voltage is low, when the operation modes 3-1 and 3-2 are controlled, the DC voltage is increased to a predetermined DC voltage value (for example, 250 V). Increases as the input power supply voltage decreases. If the short-circuit time of the switching element 4 becomes too long, the input current becomes larger than the normal peak value because the switching element 4 is short-circuited, the input current waveform becomes triangular, and the peak value is also high. It is inefficient and has a poor power factor. This means that as shown in FIG. 3, boosting is possible, but efficiency and power factor are reduced.
[0050]
Therefore, a maximum value is provided for the short circuit time of the switching element 4. As a result, when the input power supply voltage is low, boosting is suppressed to some extent, and even if the output DC voltage does not become a predetermined value, an operation with efficient and good power factor is performed. At this time, it is conceivable that the voltage becomes insufficient when the motor 15 is driven at the maximum number of revolutions. In this case, the phase of the rotating magnetic field of the inverter circuit 9 that applies the rotating magnetic field to the motor 15 is adjusted, The electric motor can be driven up to the maximum number of revolutions. This is field weakening control in so-called vector control. As a result, although the motor efficiency of the motor 15 slightly decreases, the degree of the efficiency is lower than the decrease in circuit efficiency when the voltage is increased to a predetermined voltage by the short-circuit opening control of the switching element 4, and overall, efficient motor driving is performed. be able to.
[0051]
Next, when the input power supply voltage is high, the above operation modes 3-1 and 3-2 are controlled. For example, if the input power supply voltage is 115 V, the DC voltage can be taken into account even if the voltage drop is taken into account. Since the voltage rises to about 300 V, the short-circuit control of the switching element 4 is not performed when the predetermined DC voltage value is equal to or lower than this voltage. As a result, if the switching element 4 is not short-circuited and opened, the input current is a capacitor input type as described above, so that the crest value is large and inefficient, and the power factor is deteriorated. Therefore, a minimum value is provided for the short circuit time of the switching element 4. Thus, even when the input power supply voltage is high, the voltage is boosted to some extent, and even if the output DC voltage is equal to or higher than a predetermined value, the operation is performed efficiently and with a good power factor. This will be specifically described with reference to FIG. In FIG. 3, a dotted line represents a short circuit time, power factor, and efficiency graph of the switching element 4, and a solid line represents a relationship between the short circuit time of the switching element 4 and the DC voltage. The standard is to control the DC voltage to about 250 V so that the power factor becomes the maximum value, but even if the input AC voltage fluctuates, the switching element 4 that can maintain the power factor of 95% or more is short-circuited. Select a time. In this case, the power factor is preferentially controlled regardless of whether the DC voltage is slightly increased or decreased. Considering the good power situation in Japan, the above idea is sufficient.
[0052]
Even if the maximum value and minimum value of the switching element 4 are not particularly provided, the input power supply voltage is detected and the DC voltage value to be output is corrected according to the input power supply voltage. When the input power supply voltage is low It goes without saying that the same effect can be obtained by setting the DC voltage to a lower value and setting it to a higher value if it is higher.
[0053]
Next, the control method at the time of transition of each operation mode is demonstrated using FIG.4 and FIG.5. Since the transition from the operation mode 1 to the operation mode 2 is a transition from a state where the short-circuit opening control of the switching element 4 is not performed by full-wave rectification to a state where the short-circuit opening control is performed under a fixed condition, the control is performed in the operation mode 1 The short-circuit opening control of the switching element 4 may be started when the transition condition to the operation mode 2 is established. The transition condition is as indicated by (1) in the figure, and the voltage modulation rate (which may be the rotational speed) of the inverter 9 has reached the switching determination value A of about 100%, or the AC input current is the switching current value. The mode is switched from mode 1 to 2 when either A (average value) is reached. First, the reason for switching depending on whether or not the voltage modulation rate has reached about 100% is that the voltage modulation rate is increasing because the number of revolutions of the motor 15 is increasing, and the modulation rate in the inverter 5 is maximum. This is because the input voltage of the electric motor 15 cannot be increased any more if the value is reached. On the other hand, when the AC input current reaches the switching current value A even if the modulation factor does not reach the maximum value, the mode is switched from 1 to 2. This corresponds to the defrosting operation when the electric motor load is in a low speed and high load state, for example, when an electric motor for driving a compressor such as an air conditioner is considered. In such a case, since the load is high even if the modulation factor does not reach 100%, a reduction in the power factor with respect to the power supply is not preferable. For this reason, when the input current first reaches the switching current value A, ¥ is also switched.
[0054]
Next, the transition from operation mode 2 to operation mode 1 will be described. In this case, it is a transition from a state where the short-circuit opening control of the switching element 4 is performed under a fixed condition by full-wave rectification to a state where the short-circuit opening control is stopped. The short-circuit opening control of the switching element 4 may be stopped when the transition condition is satisfied (the modulation factor is less than 100% and the input current is the switching determination value B (A> B (modulation factor is the same)).
[0055]
Next, the transition from operation mode 2 to operation mode 3-1 will be described. When the transition condition to the operation mode 3-1 is established during the operation in the operation mode 2, the switching element 4 is first short-circuited and opened under a predetermined condition without immediately turning on the switch 8. The predetermined condition is, for example, short-circuit opening control of the switching element 4 in which the short-circuiting time is gradually increased so that the DC voltage output at every zero cross point of the AC power supply voltage, that is, every half cycle of the power supply cycle, gradually increases. The short circuit opening control is performed until the DC voltage reaches about 200V, for example. Thereafter, the switch 8 is turned on to switch to voltage doubler rectification. By so doing, fluctuations in the DC voltage when the switch 8 is turned on can be reduced, and fluctuations in the DC voltage applied to the motor 15 are moderated.
[0056]
In addition, as a method of gradually increasing the DC voltage in the full-wave rectification state, a method of gradually increasing the short-circuit time of the switching element 4 has been described. For example, the number of times of switching with a fixed short-circuit time is gradually increased. However, the same effect can be obtained, and not only the short circuit time but also the delay time from the zero cross point to the short circuit of the switching element 4 may be controlled simultaneously.
[0057]
Further, immediately after the switch 8 is switched, the DC voltage overshoots. In order to quickly converge this overshoot, after the switch 8 is switched, the next zero crossing point or the zero crossing point is not detected until the next zero crossing point or zero crossing point is detected a plurality of times, or the operation mode 3-1 control is performed. Instead of performing the short circuit opening control of the switching element 4 under the above conditions, it is preferable to perform the short circuit opening control under a predetermined fixed condition.
[0058]
The transition condition from the operation mode 2 to 3-1 is determined by whether the modulation rate has reached the switching determination value C or the input current has reached the switching current value C. Since the DC voltage is controlled to be high when the mode 2 is entered, there is a margin in the modulation rate immediately after switching to the mode 2. When this reaches about 100%, the DC voltage cannot be increased any more, so the mode is switched to mode 3-1. The input current is the same as (1).
[0059]
Next, the transition from operation mode 3-1 to operation mode 2 will be described. If the transition condition to the operation mode 2 ((4) in FIG. 5) is satisfied during the operation in the operation mode 3-1, the switch 8 is not turned off immediately, but the switching element 4 is opened to the operation mode 2. After the transition condition is satisfied, the switch 8 is turned off after being continuously turned off until the zero cross point of the AC power source is detected once or a plurality of times. Normally, at this time, the voltage dividing capacitors 6a and 6b and the smoothing capacitor are in a state of being charged, so that the DC voltage that is output even when the switch 8 is turned off is a DC voltage that can be obtained by sudden full-wave rectification. Will not drop. Here, if the switching element 4 is controlled to be shorted and opened in a state in which the DC voltage is not sufficiently lowered after the switch 8 is turned off, the output DC voltage becomes unstable. Until the zero cross point is detected a predetermined number of times, the short circuit opening control of the switching element 4 in the operation mode 2 is not performed.
[0060]
As described above, switching from the operation mode 3-1 in which the behavior of the DC voltage is stable to the operation mode 2 can be performed.
[0061]
Next, the transition time from the operation mode 3-1 to the operation mode 3-2 and from the operation mode 3-2 to the operation mode 3-1 will be described.
[0062]
During operation in the operation mode 3-1, when the transition condition to the operation mode 3-2 is satisfied (when the input current reaches the switching current value E as shown in FIG. 2), that is, the input current is the current in FIG. When the value B is reached, the delay time from the zero cross point of the power supply voltage to the short-circuiting of the switching element 4 is Td_B, which is sufficiently small. Therefore, from the zero cross point of the power supply voltage in the operation mode 3-2. By setting the fixed value of the delay time until the switching element 4 is short-circuited to Td_B, for example, the switching from the operation mode 3-1 to the operation mode 3-2 can be controlled continuously and smoothly.
[0063]
As for the transition from the operation mode 3-2 to the operation mode 3-1, if the control is performed in the opposite direction to the transition from the operation mode 3-1 to the operation mode 3-2, the control is continuously and smoothly switched. It can be carried out.
[0064]
The effect of the present embodiment described above will be described with reference to FIG. The comparison of the applied voltage to the inverter 9 in the electric motor drive apparatus in a present Example and a conventional apparatus is shown. Thus, the voltage applied to the inverter 9 can be reduced in a region where the motor load is small.
[0065]
FIG. 7 shows a comparison of the motor efficiency between the motor drive device of the present embodiment and the conventional device. Thus, in a state where the motor load is low, the motor driving device of the present invention provides a significantly higher motor operating efficiency than the conventional device.
[0066]
If this is applied to a refrigeration apparatus such as an air conditioner or a refrigerator, a refrigeration apparatus with low power consumption, low cost and high commercial value, in particular, an air conditioner, a refrigerator, or the like can be provided.
[0067]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an electric motor drive device that expands the high-efficiency operation range of the electric motor.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an electric motor drive device according to an embodiment of the present invention.
FIG. 2 is a diagram showing a relationship between an input current and a delay time of a switch element in an operation mode 3-1 of an electric motor drive device according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a relationship between a switching element short-circuit time, a DC voltage, and a power factor of an electric motor drive device according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating an example of state transition of an operation mode in the electric motor drive device according to the embodiment of the present invention.
FIG. 5 is a diagram showing conditions at the time of transition of each operation mode in the motor drive device according to one embodiment of the present invention.
FIG. 6 is a diagram illustrating the voltage control effect of the electric motor drive device according to the embodiment of the present invention.
FIG. 7 is a diagram illustrating motor drive efficiency of the motor drive device according to one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... AC power source, 2 ... Reactor, 3 ... 1st rectifier, 4 ... 1st switching element, 5 ... 2nd rectifier, 6 ... Voltage dividing capacitor, 7 ... Smoothing capacitor, 8 ... 2nd switch, 9 DESCRIPTION OF SYMBOLS inverter circuit, 10 ... arithmetic control means (microcomputer), 11, 12 ... drive circuit, 13 ... zero cross detection circuit, 14 ... magnetic pole position detection circuit or current detection circuit, 15 ... electric motor, 16 ... DC voltage detection circuit.

Claims (6)

A second rectifier for converting alternating current to direct current;
A voltage-dividing capacitor connected in parallel to the second rectifier;
A smoothing capacitor connected in parallel to the voltage dividing capacitor;
An inverter connected to the smoothing capacitor and supplying driving power to the motor;
A reactor provided on the AC side of the second rectifier;
A switching element that short-circuits and opens the alternating current through the reactor;
A switch connected between the second rectifier and the voltage dividing capacitor to form a voltage doubler circuit in an on state with a full-wave rectifier circuit in an off state;
A first operation mode in which the switching element is kept off and the switch is kept off;
A second operation mode in which the switch is kept off and the switching element is on / off controlled;
A 3-1 operation mode in which the switch is kept in an on state and an on timing in a half cycle of the alternating voltage of the switching element is changed in a direction of decreasing a delay time according to an increase in input current;
When the input current further increases from the 3-1 operation mode, the 3-2 operation mode is switched from the 3-1 operation mode, the switch is kept on, and the AC of the switching element is switched the on-timing in a half cycle of the voltage, and a third 3-1 3-2 operation mode Ru solid Teisu oN timing of the operation mode corresponding to the input current when the switching said,
Switching from the 3-1 operation mode to the 3-2 operation mode is an electric motor drive device that is performed when an input current reaches a predetermined value. In claim 1,
Switching from the first operation mode to the second operation mode is an electric motor drive device that is performed when the modulation rate of the inverter reaches a predetermined value or the input current reaches a predetermined value. In claim 1,
The motor drive device that performs switching from the second operation mode to the 3-1 operation mode when the modulation rate of the inverter becomes a predetermined value or when the input current becomes a predetermined value. In claim 1,
When stopping the motor 15, the motor drive device that makes a transition to the first operation mode even when operating in any one of the second operation mode, the 3-1 operation mode, and the 3-2 operation mode. . In claim 1,
When switching from the operation mode 2 to the operation mode 3-1, immediately before turning on the switch, the short-circuit time of the switching element is gradually increased several times for each zero-cross signal detection, or the zero-cross detection signal and the next zero-cross An electric motor drive device that performs control to gradually increase the number of times of ON / OFF between detection signals every time a zero-cross signal is detected. In claim 1,
An electric motor driving device that performs control to maintain on / off of the switching element for a plurality of zero-cross signal detection periods immediately before turning off the switch when switching from the operation mode 3-1 to the operation mode 2.

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