JP7572915B2 - Inverter power supply device and control method thereof - Google Patents

Description

The present invention relates to an inverter power supply device and a control method thereof.

Electric railway vehicles powered by AC power are equipped with auxiliary devices such as lighting and lamps, air compressors that drive the brakes and doors, air conditioning equipment, and heating equipment. To power such auxiliary devices, it is common to branch off the AC power supply circuit used for driving the vehicles and use a transformer to step down the voltage to the same level as that of a typical low-voltage distribution line.

Because the power supply for the auxiliary equipment is derived from a branch of the AC power supply used for driving the vehicle, the power supply voltage for the auxiliary equipment fluctuates due to the influence of the current when the vehicle accelerates and decelerates. This voltage fluctuation is particularly noticeable in new transportation systems, where the AC power supply used for driving the vehicle is low voltage. By design, if the auxiliary equipment does not operate normally within the range of voltage fluctuations, a power supply unit is used to supply a stable voltage to the auxiliary equipment.

As such a power supply device, an inverter power supply device equipped with an inverter device is widely used. The inverter power supply device receives a power supply with large voltage fluctuations as input, converts the input voltage to a DC voltage using a rectifier, and pulse-width modulates the DC voltage by switching the switching element of the inverter device, thereby obtaining a stable AC voltage (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2-168867

An inverter device requires a power capacity determined by the product of the voltage at the maximum input voltage and the current at the minimum input voltage. As the range of input voltage fluctuation increases, the power capacity required by the inverter device also increases, leading to an increase in the size and weight of the inverter power supply device. In addition, as the applied voltage and current increase, the switching loss and conduction loss of the switching elements of the inverter device increase, generating heat, and so a cooler with a cooling capacity according to the losses is required.

In particular, in the case of inverter power supplies mounted on electric railway vehicles, in order to reduce failure rates, it may be required not to use power components such as fans and pumps as coolers for the inverter devices. Also, unlike inverter devices for driving main motors that can be expected to be cooled by the wind as the train moves, inverter power supplies that supply power to auxiliary devices are required to operate continuously using only natural air cooling even when the train is stopped, so the dimensions and weight of the coolers tend to increase.

The object of the present invention, which has been made in consideration of the above problems, is to provide an inverter power supply device and a control method thereof that can be made smaller and lighter.

In order to solve the above problems, an inverter power supply device according to the present invention is an inverter power supply device that transforms a single-phase AC voltage input via a pair of a first input terminal and a second input terminal, and outputs the voltage via a pair of a first output terminal and a second output terminal, and includes an inverter device including: a first switching element, a second switching element having one end connected to one end of the first switching element, a third switching element, a fourth switching element having one end connected to one end of the third switching element, a fifth switching element, a sixth switching element having one end connected to one end of the fifth switching element, and a smoothing capacitor having one end connected to the other end of each of the first, third and fifth switching elements and the other end connected to the other end of each of the second, fourth and sixth switching elements; a first transformer; and a second transformer. a first voltage detector detecting a first voltage value which is a secondary side voltage of the first transformer, a second voltage detector detecting a second voltage value which is a voltage of the output capacitor, a third voltage detector detecting a third voltage value which is a voltage of the smoothing capacitor, a current detector detecting a first current value which is a current flowing through a first terminal of the inverter device, and a control unit generating a pulse width signal which controls conduction and cut-off of each of the first to sixth switching elements based on the first to third voltage values and the first current value, wherein one end of a primary winding of the first transformer is connected to the first input terminal, the other end of the primary winding of the first transformer is connected to the second input terminal, and one end of a secondary winding of the first transformer is connected to a connection portion between the first switching element and the second switching element. the first terminal of the inverter device is connected to one end of a secondary winding of the second transformer, the other end of the secondary winding of the second transformer, one end of the output capacitor, and the first output terminal are connected, the other end of the secondary winding of the first transformer is connected to a connection portion between the third switching element and the fourth switching element, one end of a primary winding of the second transformer, the other end of the output capacitor, and the second output terminal are connected to each other, and a third terminal of the inverter device is connected to a connection portion between the fifth switching element and the sixth switching element and the other end of the primary winding of the second transformer is connected, and the control unit includes a PLL calculation unit that calculates a phase of an input voltage waveform based on the first voltage value, and a smoothing capacitor that calculates a proportional value of a difference between the third voltage value and a target voltage of the smoothing capacitor and an integral value of the proportional value. a converter control calculation unit that calculates a current target value of the first terminal based on the current target value of the smoothing capacitor and the phase of the input voltage waveform, and calculates a target value of a line voltage between the first terminal and the second terminal based on the current target value of the first terminal and the first current value; a voltage target calculation unit that calculates a sinusoidal output voltage target value having the phase of the input voltage waveform and a target output voltage amplitude; an inverter control calculation unit that calculates a target value of a line voltage between the third terminal and the second terminal based on the output voltage target value and the first voltage value; and a PWM calculation unit that generates the pulse width signal based on the target value of the line voltage between the first terminal and the second terminal, the target value of the line voltage between the third terminal and the second terminal, and the third voltage value.

In the inverter power supply device according to the present invention, the control unit further includes a feedback calculation unit that calculates a voltage correction value that corrects the difference between the output voltage target value and the first voltage value calculated by the inverter control calculation unit based on the difference between the second voltage value and the output voltage target value, and it is preferable that the inverter control calculation unit calculates the target value of the line voltage between the third terminal and the second terminal by multiplying the sum of the difference between the output voltage target value and the first voltage value and the voltage correction value by the transformation ratio of the second transformer.

In the inverter power supply device according to the present invention, it is preferable that the control unit is realized by software running on a processor or by a combination of hardware.

The control method for an inverter power supply device according to the present invention is a control method for an inverter power supply device that transforms a single-phase AC voltage inputted via a pair of a first input terminal and a second input terminal and outputs the voltage via a pair of a first output terminal and a second output terminal, and the inverter power supply device includes a first switching element, a second switching element having one end connected to one end of the first switching element, a third switching element, a fourth switching element having one end connected to one end of the third switching element, a fifth switching element, a sixth switching element having one end connected to one end of the fifth switching element, and a sixth switching element having one end connected to the other end of each of the first, third and fifth switching elements and the other end connected to the second, fourth and sixth switching elements. the other end of the secondary winding of the first transformer is connected to the first input terminal, the other end of the primary winding of the first transformer is connected to the second input terminal, one end of the secondary winding of the first transformer, a first terminal of the inverter device connected to a connection portion between the first switching element and the second switching element, and one end of the secondary winding of the second transformer are connected to each other, the other end of the secondary winding of the second transformer, one end of the output capacitor, and the first output terminal are connected, a second terminal of the inverter device connected to a connection part, one end of the primary winding of the second transformer, the other end of the output capacitor, and the second output terminal are connected to each other; a third terminal of the inverter device connected to a connection part between the fifth switching element and the sixth switching element is connected to the other end of the primary winding of the second transformer; and a step of calculating a phase of an input voltage waveform based on a first voltage value which is a secondary voltage of the first transformer; a step of calculating a current target value of the smoothing capacitor based on a proportional value of a difference between a third voltage value which is a voltage of the smoothing capacitor and a target voltage of the smoothing capacitor and an integral value of the proportional value; The method includes a step of calculating a target value of the line voltage between the first terminal and the second terminal based on the current target value of the first terminal and a first current value, which is a current flowing through the first terminal of the inverter device; a step of calculating a sinusoidal output voltage target value having the phase of the input voltage waveform and the amplitude of the target output voltage; a step of calculating a target value of the line voltage between the third terminal and the second terminal based on the output voltage target value and the first voltage value; and a step of generating a pulse width signal that controls the conduction and cut-off of each of the first to sixth switching elements based on the target value of the line voltage between the first terminal and the second terminal, the target value of the line voltage between the third terminal and the second terminal, and the third voltage value.

The inverter power supply device and its control method according to the present invention can be made smaller and lighter.

1 is a diagram showing an example of the configuration of an inverter power supply device according to an embodiment of the present invention; FIG. 2 is a diagram illustrating an example of the configuration of a control circuit illustrated in FIG. 1 . 3 is a block diagram showing an example of a functional configuration of a processor shown in FIG. 2 . FIG. 4 is a diagram illustrating an example of the configuration of a PLL calculation unit illustrated in FIG. 3 . 4 is a diagram illustrating an example of the configuration of a capacitor current calculation unit illustrated in FIG. 3 . 4 is a diagram illustrating an example of the configuration of a converter control calculation unit illustrated in FIG. 3 . 4 is a diagram illustrating an example of the configuration of a voltage target calculation unit illustrated in FIG. 3 . FIG. 4 is a diagram illustrating an example of the configuration of a feedback calculation unit illustrated in FIG. 3 . 4 is a diagram illustrating a configuration example of an inverter control calculation unit illustrated in FIG. 3 . FIG. 4 is a diagram illustrating an example of the configuration of a PWM calculation unit illustrated in FIG. 3 . FIG. 1 is a diagram showing an example of the configuration of a conventional inverter power supply device.

The following describes the embodiment of the present invention with reference to the drawings.

Figure 1 is a diagram showing an example of the configuration of an inverter power supply device 1 according to one embodiment of the present invention. The inverter power supply device 1 according to this embodiment transforms a single-phase AC voltage with large fluctuations input via a pair of a first input terminal In1 and a second input terminal In2, converts it into a single-phase AC voltage with stable fluctuations, and outputs it via a pair of a first output terminal Out1 and a second output terminal Out2.

As shown in FIG. 1, the inverter power supply 1 includes a first transformer 2, an inverter device 3, a second transformer 7, and an output capacitor 8. In the following, the maximum rated value of the input voltage is VinMax [Vrms], and the minimum rated value of the input voltage is VinMin [Vrms]. The maximum rated value of the output voltage is VoutMax [Vrms], and the minimum rated value of the output voltage is VoutMin [Vrms]. The standard voltage value of the output voltage is VoutRef [Vrms], and the maximum rated value of the output current is IoutMax [Arms]. When the load capacity is equal to or less than VoutMin×IoutMax [VA], the primary rated voltage of the first transformer 2 is VinMax [Vrms], the secondary rated voltage of the first transformer 2 is VoutMax [Vrms], and the capacity of the first transformer 2 is VoutMax×IoutMax. The primary rated voltage of the second transformer 7 is {VoMin−VinMin×(VoMax/VinMax)} [Vrms], the secondary rated voltage of the second transformer 7 is VoMax [Vrms], and the capacity of the second transformer 7 is {VoMin−VinMin×(VoMax/VinMax)}×IoutMax [VA]. Additionally, the maximum line voltage on the AC side of the inverter device 3 is VoutMax x √2 [Vp-p], and the maximum current is IoutMax x {VoMin - VinMin x (VoMax / VinMax)} ÷ VoMax [Arms].

The inverter device 3 includes an inverter circuit 4, a smoothing capacitor 5, and a smoothing reactor 6.

The inverter circuit 4 includes a first switching element SW1, a second switching element SW2 having one end connected to one end of the first switching element SW1, a third switching element SW3, a fourth switching element SW4 having one end connected to one end of the third switching element SW3, a fifth switching element SW5, and a sixth switching element SW6 having one end connected to one end of the fifth switching element SW5. The other end of the first switching element SW1, the other end of the third switching element SW3, and the other end of the fifth switching element SW5 are connected to each other. The other end of the second switching element SW2, the other end of the fourth switching element SW4, and the other end of the sixth switching element SW6 are connected to each other. Hereinafter, when the first switching element SW1 to the sixth switching element SW6 are not distinguished from each other, they are referred to as switching elements SW.

One end of the smoothing capacitor 5 is connected to the other ends of the first switching element SW1, the third switching element SW3, and the fifth switching element SW5. The other end of the smoothing capacitor 5 is connected to the other ends of the second switching element SW2, the fourth switching element SW4, and the sixth switching element SW6.

The smoothing reactor 6 comprises a first reactor L1, a second reactor L2, and a third reactor L3.

One end of the first reactor L1 is connected to the connection between the first switching element SW1 and the second switching element SW2. The other end of the first reactor L1 constitutes the first terminal T1, which is the terminal of the first phase (U phase) on the AC side of the inverter device 3. One end of the second reactor L2 is connected to the connection between the third switching element SW3 and the fourth switching element SW4. The other end of the second reactor L2 constitutes the second terminal T2, which is the terminal of the second phase (V phase) on the AC side of the inverter device 3. One end of the third reactor L3 is connected to the connection between the fifth switching element SW5 and the sixth switching element SW6. The other end of the third reactor L3 constitutes the third terminal T3, which is the terminal of the third phase (W phase) on the AC side of the inverter device 3.

One end of the primary winding of the first transformer 2 is connected to the first input terminal In1. The other end of the primary winding of the first transformer 2 is connected to the second input terminal In2. One end of the secondary winding of the first transformer 2 is connected to the first terminal T1 (the other end of the first reactor L1) which is connected to the connection between the first switching element SW1 and the second switching element SW2. The other end of the secondary winding of the first transformer 2 is connected to the second terminal T2 (the other end of the second reactor L2) which is connected to the connection between the third switching element SW3 and the fourth switching element SW4.

The wiring connecting one end of the secondary winding of the first transformer 2 and the first terminal T1 branches and is connected to one end of the secondary winding of the second transformer 7. The other end of the secondary winding of the second transformer 7 is connected to one end of the output capacitor 8 and the first output terminal Out1. The wiring connecting the other end of the secondary winding of the first transformer 2 and the second terminal T2 branches and is connected to one end of the primary winding of the second transformer 7, the other end of the output capacitor 8, and the second output terminal Out2. The other end of the primary winding of the second transformer 7 is connected to the third terminal T3 (the other end of the third reactor L3), which is connected to the connection between the fifth switching element SW5 and the sixth switching element SW6. In addition, when the beginning of the secondary winding of the second transformer 7 is connected to the output capacitor 8, the other end of the primary winding of the second transformer 7 connected to the third terminal T3 must be the beginning of the winding.

Thus, in the inverter power supply device 1 according to this embodiment, one end of the primary winding of the first transformer 2 is connected to the first input terminal In1, and the other end of the primary winding of the first transformer 2 is connected to the second input terminal In2. Also, one end of the secondary winding of the first transformer 2, the first terminal T1 of the inverter device 3 connected to the connection between the first switching element SW1 and the second switching element SW2, and one end of the secondary winding of the second transformer 7 are connected to each other. Also, the other end of the secondary winding of the second transformer 7 is connected to one end of the output capacitor 8 and the first output terminal Out1. In addition, the other end of the secondary winding of the first transformer 2, the second terminal T2 of the inverter device 3 connected to the connection between the third switching element SW3 and the fourth switching element SW4, one end of the primary winding of the second transformer 7, the other end of the output capacitor 8, and the second output terminal Out2 are connected to each other. In addition, the third terminal T3 of the inverter device 3 connected to the connection between the fifth switching element SW5 and the sixth switching element SW6 is connected to the other end of the primary winding of the second transformer 7.

With this configuration, a portion of the current from the first transformer 2 flows to the second transformer 7, so the current flowing through the inverter device 3 is reduced. This allows the power capacity of the inverter device 3 to be reduced. In addition, the reduction in the current flowing through the inverter device 3 suppresses an increase in loss in the switching element SW of the inverter device 3, so that an increase in the dimensions and weight of the cooler can also be suppressed. As a result, the inverter power supply device 1 according to this embodiment can be made smaller and lighter.

The inverter power supply device 1 according to this embodiment further includes a first voltage detector VD1, a second voltage detector VD2, a third voltage detector VD3, a current detector CT1, and a control circuit 10.

The first voltage detector VD1 is connected to one end and the other end of the secondary winding of the first transformer 2, and detects a first voltage value, which is the secondary voltage of the first transformer 2.

The second voltage detector VD2 is connected to one end and the other end of the output capacitor 8 and detects a second voltage value, which is the voltage of the output capacitor 8.

The third voltage detector VD3 is connected to one end and the other end of the smoothing capacitor 5 and detects a third voltage value, which is the voltage of the smoothing capacitor 5.

The current detector CT1 is provided between one end of the secondary winding of the first transformer 2 and the first terminal T1 of the inverter device 3, and detects a first current value, which is a current flowing through the first terminal T1.

The control circuit 10 controls the conduction and interruption of the switching element SW based on the first to third voltage values and the first current value.

Figure 2 shows an example configuration of the control circuit 10.

As shown in FIG. 2, the control circuit 10 includes an analog input unit 11, a processor 100 as a control unit, and a switching element drive circuit 12.

The analog input unit 11 acquires the detection results (first to third voltage values and first current value) of the first voltage detector VD1, the second voltage detector VD2, the third voltage detector VD3, and the current detector CT1, and outputs them to the processor 100.

The processor 100 generates a pulse width signal that controls the conduction and cut-off of the switching element SW based on the first to third voltage values and the first current value input from the analog input unit 11, and outputs the signal to the switching element drive circuit 12.

The switching element drive circuit 12 drives the first to sixth switching elements SW1 to SW6 based on the pulse width signal output from the processor 100. The switching element drive circuit 12 insulates the potential of the control circuit 10 from the potential of the main circuit by an isolation circuit using a photocoupler or the like. The switching element drive circuit 12 outputs a gate drive voltage when the switching element SW is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). The power supply of the gate drive circuit that outputs the gate drive voltage is insulated from the control circuit 10 by an isolation type power supply circuit such as a flyback converter. The switching element drive circuit 12 outputs a base current when the switching element SW is a power transistor. The switching element drive circuit 12 outputs an optical signal when the switching element SW is a phototransistor or an optical gate thyristor.

Figure 3 is a block diagram showing an example of the functional configuration of the processor 100. The functions of the processor 100 as a control unit and the control method according to this embodiment described below are realized, for example, by software running on the processor 100, or by a combination of hardware such as an operational amplifier circuit and an oscillator circuit.

As shown in FIG. 3, the processor 100 includes a PLL calculation unit 110, a capacitor current calculation unit 120, a converter control calculation unit 130, a voltage target calculation unit 140, a feedback calculation unit 150, an inverter control calculation unit 160, and a PWM calculation unit 170.

The PLL calculation unit 110 calculates the phase of the input voltage waveform based on the first voltage value detected by the first voltage detector VD1. Figure 4 shows an example of the configuration of the PLL calculation unit 110.

As shown in FIG. 4, the PLL calculation unit 110 includes a PLL (Phase Locked Loop) circuit 111, which determines a first voltage value, i.e., the phase θ of the input voltage waveform, and calculates sin θ corresponding to the phase θ.

Referring again to FIG. 3, the PLL calculation unit 110 outputs the calculated sin θ to the converter control calculation unit 130 and the voltage target calculation unit 140.

The capacitor current calculation unit 120 calculates the current target value of the smoothing capacitor 5 based on the proportional value of the difference between the third voltage value detected by the third voltage detector VD3 and the target voltage of the smoothing capacitor 5 and the integral value of the proportional value. Figure 5 is a diagram showing an example of the configuration of the capacitor current calculation unit 120.

As shown in FIG. 5, the capacitor current calculation unit 120 includes a subtractor 121, an integrator 122, and an adder 123.

The subtractor 121 subtracts the third voltage value from VoutMax × √2. VoutMax is the maximum rated value of the output voltage, and VoutMax × √2 is the target voltage of the smoothing capacitor 5. Therefore, the subtractor 121 outputs the difference between the third voltage value and the target voltage of the smoothing capacitor 5. The proportional value obtained by multiplying the subtraction value by the subtractor 121 with a proportional coefficient K1 is input to the adder 123. In addition, the proportional value is multiplied with an integral coefficient K2 and input to the integrator 122.

The integrator 122 outputs to the adder 123 the integral value obtained by integrating the subtraction value by the subtractor 121 multiplied by the proportional coefficient K1 and the integral coefficient K2.

The adder 123 adds the input proportional value and integral value to calculate the current target value of the smoothing capacitor 5.

Referring again to FIG. 3, the capacitor current calculation unit 120 outputs the calculated current target value of the smoothing capacitor 5 to the converter control calculation unit 130.

The converter control calculation unit 130 calculates the current target value of the first terminal T1 of the inverter device 3 based on the current target value of the smoothing capacitor 5 input from the capacitor current calculation unit 120 and the phase θ of the input voltage waveform (sin θ output from the PLL calculation unit 110). The converter control calculation unit 130 calculates the line voltage command VuvCom, which is the target value of the line voltage between the first terminal T1 and the second terminal T2, based on the calculated current target value of the first terminal T1 and the first current value detected by the current detector CT1. FIG. 6 is a diagram showing an example of the configuration of the converter control calculation unit 130.

As shown in FIG. 6, the converter control calculation unit 130 includes a multiplier 131, a subtractor 132, and an adder 133.

The multiplier 131 multiplies the current target value of the smoothing capacitor 5 by sin θ and outputs the result to the subtractor 132 as the current target value of the first terminal T1.

The subtractor 132 subtracts the first current value from the multiplied value by the multiplier 131 (the current target value of the first terminal T1). The subtracted value by the subtractor 132 is multiplied by a proportionality coefficient K3 and input to the adder 133.

The adder 133 adds the first voltage value to the subtraction value by the subtractor 132 multiplied by the proportionality coefficient K3 to calculate the line voltage command VuvCom.

Referring again to FIG. 3, the converter control calculation unit 130 outputs the calculated line voltage command VuvCom to the PWM calculation unit 170.

The voltage target calculation unit 140 calculates a sinusoidal output voltage target value VoR0 having the phase θ of the input voltage waveform input from the PLL calculation unit 110 and the amplitude of the target output voltage. Figure 7 is a diagram showing an example of the configuration of the voltage target calculation unit 140.

As shown in FIG. 7, the voltage target calculation unit 140 includes a multiplier 141.

The multiplier 141 multiplies sinθ by VoutRef×√2 to calculate the output voltage target value VoR0. Here, VoutRef is the standard voltage value of the output voltage, and VoutRef×√2 indicates the amplitude of the target output voltage. Therefore, the multiplier 141 calculates the sinusoidal output voltage target value VoR0 having the phase θ of the input voltage waveform and the amplitude of the target output voltage.

Referring again to FIG. 3, the voltage target calculation unit 140 outputs the calculated output voltage target value VoR0 to the feedback calculation unit 150 and the inverter control calculation unit 160.

The feedback calculation unit 150 calculates a voltage correction value that corrects the difference between the output voltage target value VoR0 and the first voltage value, which is calculated by the inverter control calculation unit 160 described later, based on the difference between the second voltage value detected by the second voltage detector VD2 and the output voltage target value VoR0 input from the voltage target calculation unit 140. Figure 8 is a diagram showing an example of the configuration of the feedback calculation unit 150.

As shown in FIG. 8, the feedback calculation unit 150 includes a subtractor 151.

The subtractor 151 subtracts the second voltage value from the output voltage target value VoR0. The feedback calculation unit 150 multiplies the subtraction value by the subtractor 151 by a proportionality coefficient K4 to calculate a voltage correction value. Even if the proportionality coefficient K4 is 0, if the stability of the output voltage satisfies the design requirements, the calculation result of the feedback calculation unit 150 may be set to 0. Therefore, the feedback calculation unit 150 is not a required component and can be omitted.

Referring again to FIG. 3, the feedback calculation unit 150 outputs the calculated voltage correction value to the inverter control calculation unit 160.

The inverter control calculation unit 160 calculates the line voltage command VwvCom, which is the target value of the line voltage between the third terminal T3 and the second terminal T2 of the inverter device 3, based on the output voltage target value VoR0 input from the voltage target calculation unit 140 and the first voltage value detected by the first voltage detector VD1. FIG. 9 is a diagram showing an example of the configuration of the inverter control calculation unit 160.

As shown in FIG. 9, the inverter control calculation unit 160 includes a subtractor 161 and an adder 162.

The subtractor 161 subtracts the first voltage value from the output voltage target value VoR0 and outputs the result to the adder 162.

The adder 162 adds the subtraction value by the subtracter 161 and the voltage correction value input from the feedback calculation unit 150. As described above, the feedback calculation unit 150 is not an essential component and may be omitted. If the feedback calculation unit 150 is not provided, the adder 162 does not need to be provided either. The inverter control calculation unit 160 multiplies the addition value by the adder 162 (if the adder 162 is not provided, the subtraction value by the subtracter 161) by the transformation ratio of the second transformer 7, {VoMin-VinMin×(VoMax/VinMax)}/VoMax, to calculate the line voltage command VwvCom.

Referring again to FIG. 3, the inverter control calculation unit 160 outputs the calculated line voltage command VwvCom to the PWM calculation unit 170.

The PWM calculation unit 170 generates a pulse width signal based on the line voltage command VuvCom input from the converter control calculation unit 130, the line voltage command VwvCom input from the inverter control calculation unit 160, and the third voltage value detected by the third voltage detector VD3. FIG. 10 is a diagram showing an example of the configuration of the PWM calculation unit 170.

As shown in FIG. 10, the PWM calculation unit 170 includes a maximum value acquisition unit 171, a minimum value acquisition unit 172, an adder 173, subtractors 174, 175, and 176, and a PWM modulation unit 177.

The maximum value acquisition unit 171 acquires the maximum value from among the line voltage command VuvCom, the line voltage command VwvCom, and 0. The minimum value acquisition unit 172 acquires the minimum value from among the line voltage command VuvCom, the line voltage command VwvCom, and 0.

The adder 173 adds the maximum value acquired by the maximum value acquisition unit 171 and the minimum value acquired by the minimum value acquisition unit 172 from among the line voltage command VuvCom, the line voltage command VwvCom, and 0. The sum of the adder 173 is multiplied by 1/2 to obtain VpAve, which is input to the subtractors 174, 175, and 176.

The subtractor 174 subtracts VpAve output from the adder 173 from the line voltage command VuvCom. The subtracted value by the subtractor 174 is divided by the third voltage value to obtain the conduction ratio αu of the first phase, which is input to the PWM modulation unit 177.

The subtractor 175 subtracts VpAve output from the adder 173 from 0. The subtracted value from the subtractor 175 is divided by the third voltage value to obtain the conduction ratio αv of the second phase, which is input to the PWM modulation unit 177.

The subtractor 176 subtracts VpAve output from the adder 173 from the line voltage command VwvCom. The subtracted value by the subtractor 176 is divided by the third voltage value to obtain the conduction ratio αw of the third phase, which is input to the PWM modulation unit 177.

The PWM modulation unit 177 generates a pulse width signal based on the conduction rates αu, αv, and αw input from the subtractors 174, 175, and 176 and the control data (carrier frequency and dead time value).

By the configuration of the inverter power supply device 1 and the control by the control circuit 10 described above, when a single-phase AC current of VinMin or more and VinMax or less is input via a pair of the first input terminal In1 and the second input terminal In2, a single-phase AC voltage of VoutMin or more and VoutMax or less is output via a pair of the first output terminal Vout1 and the second output terminal Vout2.

The proportionality coefficient K1 is a value of approximately K1≦Cf×Fcal÷2√2, where Cf (F) is the capacitance of the smoothing capacitor 5 and Fcal (Hz) is the PWM carrier frequency. The integral coefficient K2 is a value of approximately K2≦0.25 to 0.1. The proportionality coefficient K3 is a value of approximately K3≦Lf×Fcal÷2, where Lf (H) is the inductance of the smoothing reactor 6 and Fcal (Hz) is the PWM carrier frequency. The proportionality coefficient K4 is a value of approximately K4≦1/2 to 1/4.

The following describes the reduction in power capacity of the inverter device 3 by the inverter power supply device 1 according to this embodiment, in comparison with a conventional inverter power supply device 20 shown in FIG. 11. The inverter power supply device 20, as disclosed in Patent Document 1, converts an input voltage to DC using a rectifier, and outputs an AC voltage by pulse-width modulating the DC voltage using an inverter device.

As shown in FIG. 11, the inverter power supply device 20 includes a transformer 21, an inverter device 22, a smoothing reactor 26, and an output capacitor 27.

One end of the primary winding of the transformer 21 is connected to the first input terminal In1, and the other end of the primary winding is connected to the second input terminal In2. The secondary winding of the transformer 21 is connected to the inverter device 22. The transformer 21 transforms the input voltage and outputs it to the inverter device 22.

The inverter device 22 includes a rectifier 23, a smoothing capacitor 24, and an inverter circuit 25.

The rectifier 23 includes a first diode D1 and a second diode D2 connected in series, and a third diode D3 and a fourth diode D4 connected in series, and converts the secondary voltage (AC voltage) of the transformer 21 into a DC voltage and inputs it to the inverter circuit 25.

The smoothing capacitor 24 smoothes the DC voltage input from the rectifier 23 to the inverter circuit 25.

The inverter circuit 25 includes a first switching element SW1 and a second switching element SW2 connected in series, and a third switching element SW3 and a fourth switching element SW4 connected in series. The inverter circuit 25 converts the DC voltage input from the rectifier 23 into an AC voltage and outputs it by switching the first to fourth switching elements SW1 to SW4.

The smoothing reactor 26 includes a first reactor L1 and a second reactor L2, and smoothes the AC voltage output from the inverter device 22. The AC voltage smoothed by the smoothing reactor 26 is output from the first output terminal Out1 and the second output terminal Out2 via the output capacitor 27.

In the following, the input voltage range is 300 [V] to 600 [V], the output voltage range is 200 [V] ± 5%, and the output capacity is 10 [kVA]. In this case, VinMax = 600 [Vrms], VinMin = 300 [Vrms], VoutMax = 210 [Vrms], VoutMin = 190 [Vrms], VoutRef = 200 [Vrms], IoutMax = 52.6 [Arms].

The primary rated voltage of the first transformer 2 is 600 [V]. The secondary rated voltage of the first transformer 2 is 210 [V]. The maximum current is the current at the minimum voltage, so the primary conversion is 10 [kVA] ÷ 300 [V] = 33.3 [A]. The capacity of a transformer is the product of the maximum voltage and the maximum current, so the capacity of the first transformer 2 is 20 [kVA]. The primary rated voltage of the second transformer 7 is {VoMin - VinMin x (VoMax / VinMax)} = 85 [V]. The secondary rated voltage of the second transformer 7 is 210 [V]. Since all the load current passes through the primary winding, the capacity of the second transformer 7 is 85 [V] x 52.6 [A] = 4.47 [kVA]. Since a current that can obtain power equal to the capacity of the second transformer 7 flows through the first terminal T1 of the inverter device 3 at the lowest input voltage, the maximum current flowing through the first terminal T1 is 4.47 [kVA]÷105 [V]=42.6 [A]. The maximum current flowing through the third terminal T3 of the inverter device 3 is 52.6 [A]×(85/210)=21.3 [A] regardless of the input current. The current flowing through the second terminal T2 of the inverter device 3 is the difference between the current flowing through the first terminal T1 and the third terminal T3, so it is 42.6 [A]-21.3 [A]=21.3 [A]. The voltage of the smoothing capacitor 5 is 210 [V]×√2=296 [V] regardless of the input voltage. The switching capacity of the switching elements SW of the inverter device 3 is 42.6 [Arms] x √2 x 296 [V] = 17.8 [kVA] for the first circuit including the first switching element SW1 and the second switching element SW2, and 21.3 [Arms] x √2 x 296 [V] = 8.9 [kVA] for the second circuit including the third switching element SW3 and the fourth switching element SW4 and the third circuit including the fifth switching element SW5 and the sixth switching element SW6. Therefore, the total switching capacity of all six switching elements SW of the inverter device 3 is 17.8 x 2 + 8.9 x 4 = 71.2 [kVA].

In the inverter power supply device 20 shown in FIG. 11, the inverter device 22 must be able to output the minimum output voltage when the input voltage is at its minimum, so the winding ratio of the transformer 21 is 300:190. Therefore, the secondary voltage of the transformer 21 is 380 [V] for a primary voltage of 600 [V]. The capacity of the transformer 21 is 20 [kVA], the same as the first transformer 2. The output current of the inverter device 22 is equal to the load current, so it is a maximum of 52.6 [A]. Therefore, the switching capacity of the switching element SW of the inverter device 22 is (380 x √2) x (52.6 x √2) = 40.0 [kVA]. Since the inverter device 22 is a single-phase inverter, the sum of the switching capacities of all four switching elements SW provided in the inverter device 22 is 40.0 x 4 = 160 [kVA].

In addition, when a transformer that insulates input and output DC is added to a conventional inverter power supply device as described in Patent Document 1, the inverter device must be able to output the minimum output voltage when the input voltage is at its minimum, so the winding ratio of the input transformer is 300:190. Therefore, the secondary voltage of the input transformer is 380 [V] for a primary voltage of 600 [V]. The capacity of the input transformer is 20 [kVA], the same as the first transformer 2. The output current of the inverter device 22 is equal to the load current, so it is a maximum of 52.6 [A]. In addition, since the voltage of the switching element is doubled by the voltage doubler rectifier circuit, the switching capacity of the switching element of the inverter device is (380 x 2 x √2) [V] x (52.6 x √2) A = 80.0 [kVA]. Since the inverter device is a single-phase inverter with a half-bridge configuration, the inverter device has two switching elements. Therefore, the total switching capacity of all switching elements is 80.0 x 2 = 160 kVA.

As a result, in the inverter power supply device 1 according to this embodiment, instead of adding a second transformer 7 with a capacity of 4.47 kVA, the switching element capacity of the inverter device 3 is reduced by 88.8 kVA, and the power capacity of the inverter device 3 can be reduced. In terms of ratio, when considered together with the first transformer 2, the capacity of the transformer increases by 23.5% and the inverter capacity decreases by 55.5%. In general, the loss per unit capacity is greater in the inverter device than in the transformer, or is approximately the same in the transformer and the inverter device. Therefore, the weight of the cooler, whose size is determined by the loss of the device, can be significantly reduced.

The volume and weight of the smoothing reactor 6 of the inverter device 3 are roughly proportional to ^LI2 (L is inductance, I is peak current). The inductance L of the smoothing reactor 6 is designed by the winding voltage divided by the peak current I, and the peak current I is designed as a ratio to the rated current. As a result, the volume and weight of the smoothing reactor 6 are roughly proportional to the capacity of the inverter device 3. Therefore, it is possible to design the inverter device 3 so that the weight increase of the transformer is offset by the weight decrease of the smoothing reactor 6.

In the inverter power supply device 1 shown in FIG. 1, since VoutMax = 210 [Vrms], the peak voltage is about 297 V (= √2 × VoutMax), so the element voltage of the switching element is set to 300 V. Also, since IoutMax = 52.6 [Arms], the peak current is about 74.3 A (= √2 × IoutMax), so the element current of the switching element is set to 75 A. In this case, the element capacity of the switching element is 300 V × 75 A = 22.5 kVA. In the case of a single-phase configuration, the inverter capacity is 210 Vrms × 52.6 Arms = 11.1 kVA, and in the case of a three-phase configuration, it is 19.1 kVA. Also, the total switching element capacity is 90 kVA in the case of a single-phase configuration and 135 kVA in the case of a three-phase configuration.

Therefore, in the case of a single-phase configuration, the total capacity of the switching elements is about 8 times the inverter capacity, and in the case of a three-phase configuration, the total capacity of the switching elements is about 7 times (≧4√3 times) the inverter capacity. As described above, the switching capacity of the first circuit including the first switching element SW1 and the second switching element SW2 is 17.8 kVA. Therefore, if the first circuit including the first switching element SW1 and the second switching element SW2, which have a switching capacity of 17.8 kVA, is considered to be a circuit in which two switching elements with a switching capacity of 8.9 kVA are connected in parallel, and eight switching elements with a switching capacity of 8.9 kVA are rearranged into a single-phase inverter, the inverter capacity is equivalent to 8.9 kVA. Considering a three-phase inverter device that requires the same cooling performance, the inverter capacity of the inverter device 3 is equivalent to 10.3 kVA when calculated backward from the total capacity of the switching elements of 71.2 kVA. Therefore, in the inverter power supply device 1 according to this embodiment, the power capacity of the inverter device 3 is smaller than the power capacity (20 kVA) of the first transformer 2.

As described above, the power capacity of the first transformer 2 is 20 kVA, and the power capacity of the second transformer 7 is 4.74 kVA. Therefore, in the inverter power supply device 1 according to this embodiment, the power capacity of the second transformer 7 is smaller than the power capacity of the first transformer.

Thus, the inverter power supply device 1 according to this embodiment includes an inverter device 3, a first transformer 2, a second transformer 7, and an output capacitor 8. One end of the primary winding of the first transformer 2 is connected to the first input terminal In1, and the other end of the primary winding of the first transformer 2 is connected to the second input terminal In2. In addition, one end of the secondary winding of the first transformer 2, the first terminal T1 of the inverter device 3 connected to the connection between the first switching element SW1 and the second switching element SW2, and one end of the secondary winding of the second transformer 7 are connected to each other. In addition, the other end of the secondary winding of the second transformer 7, one end of the output capacitor 8, and the first output terminal Out1 are connected. In addition, the other end of the secondary winding of the first transformer 2, the second terminal T2 of the inverter device 3 connected to the connection between the third switching element SW3 and the fourth switching element SW4, one end of the primary winding of the second transformer 7, the other end of the output capacitor 8, and the second output terminal Out2 are connected to each other. In addition, the third terminal T3 of the inverter device 3 connected to the connection between the fifth switching element SW5 and the sixth switching element SW6 is connected to the other end of the primary winding of the second transformer 7.

The inverter power supply device 1 also includes a first voltage detector VD1 that detects a first voltage value, which is the secondary voltage of the first transformer 2, a second voltage detector VD2 that detects a second voltage value, which is the voltage of the output capacitor 8, a third voltage detector VD3 that detects a third voltage value, which is the voltage of the smoothing capacitor 5, a current detector CT1 that detects a first current value, which is the current flowing through the first terminal T1 of the inverter device 3, and a control circuit 10 that generates a pulse width signal that controls the conduction and cut-off of each of the first to sixth switching elements SW1 to SW6 based on the first to third voltage values and the first current value.

The control circuit 10 includes a PLL calculation unit 110 that calculates the phase θ of the input voltage waveform based on the first voltage value, a capacitor current calculation unit 120 that calculates the current target value of the smoothing capacitor 5 based on the proportional value of the difference between the third voltage value and the target voltage of the smoothing capacitor 5 and the integral value of the proportional value, and a converter 130 that calculates the current target value of the first terminal T1 based on the current target value of the smoothing capacitor 5 and the phase of the input voltage waveform, and calculates the target value of the line voltage between the first terminal T1 and the second terminal T2 based on the current target value of the first terminal T1 and the first current value. The inverter control calculation unit 130 includes an inverter control calculation unit 140 that calculates a sine-wave output voltage target value having the phase of the input voltage waveform and the amplitude of the target output voltage, an inverter control calculation unit 160 that calculates a target value of the line voltage between the third terminal T3 and the second terminal T2 based on the output voltage target value and the first voltage value, and a PWM calculation unit 170 that generates a pulse width signal based on the target value of the line voltage between the first terminal T1 and the second terminal T2, the target value of the line voltage between the third terminal T3 and the second terminal T2, and the third voltage value.

With this configuration, part of the current from the first transformer 2 flows to the second transformer 7, so the current flowing to the inverter device 3 is reduced, and the loss in the switching element SW can be reduced. This allows the inverter power supply device 1 to be made smaller and lighter.

The above-described embodiments have been described as representative examples, but it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes are possible without departing from the scope of the claims.

REFERENCE SIGNS LIST 1 Inverter power supply device 2 First transformer 3 Inverter device 4 Inverter circuit 5 Smoothing capacitor 6 Smoothing reactor 7 Second transformer 8 Output capacitor 10 Control circuit 11 Analog input unit 12 Switching element drive circuit 100 Processor (control unit)
REFERENCE SIGNS LIST 110 PLL calculation unit 111 PLL circuit 120 Capacitor current calculation unit 121, 123 Subtractor 122 Integrator 130 Converter control calculation unit 131 Multiplier 132 Subtractor 133 Adder 140 Voltage target calculation unit 141 Multiplier 150 Feedback calculation unit 151 Subtractor 160 Inverter control calculation unit 161 Subtractor 162 Adder 170 PWM calculation unit 171 Maximum value acquisition unit 172 Minimum value acquisition unit 173 Adder 174, 175, 176 Subtractor 177 PWM
In1 First input terminal In2 Second input terminal Out1 First output terminal Out2 Second output terminal SW1 First switching element SW2 Second switching element SW3 Third switching element SW4 Fourth switching element SW5 Fifth switching element SW6 Sixth switching element L1 First reactor L2 Second reactor L3 Third reactor VD1 First voltage detector VD2 Second voltage detector VD3 Third voltage detector CT1 Current detector

Claims (4)

1. An inverter power supply device that transforms a single-phase AC voltage input via a pair of first input terminals and a pair of second input terminals, and outputs the transformed voltage via a pair of first output terminals and a pair of second output terminals,
an inverter device including: a first switching element, a second switching element having one end connected to one end of the first switching element, a third switching element, a fourth switching element having one end connected to one end of the third switching element, a fifth switching element, a sixth switching element having one end connected to one end of the fifth switching element, and a smoothing capacitor having one end connected to the other ends of each of the first, third and fifth switching elements and the other end connected to the other ends of each of the second, fourth and sixth switching elements;
A first transformer; and
A second transformer; and
An output capacitor;
a first voltage detector that detects a first voltage value that is a secondary voltage of the first transformer;
a second voltage detector for detecting a second voltage value, the second voltage value being the voltage of the output capacitor;
a third voltage detector that detects a third voltage value that is the voltage of the smoothing capacitor;
a current detector that detects a first current value that is a current flowing through a first terminal of the inverter device;
a control unit that generates a pulse width signal that controls the conduction and cut-off of each of the first to sixth switching elements based on the first to third voltage values and the first current value,
one end of a primary winding of the first transformer is connected to the first input terminal, and the other end of the primary winding of the first transformer is connected to the second input terminal;
one end of a secondary winding of the first transformer, the first terminal of the inverter device connected to a connection portion between the first switching element and the second switching element, and one end of a secondary winding of the second transformer are connected to each other;
the other end of the secondary winding of the second transformer, one end of the output capacitor, and the first output terminal are connected together;
the other end of the secondary winding of the first transformer, a second terminal of the inverter device connected to a connection portion between the third switching element and the fourth switching element, one end of a primary winding of the second transformer, the other end of the output capacitor, and the second output terminal are connected to each other;
a third terminal of the inverter device connected to a connection portion between the fifth switching element and the sixth switching element and the other end of the primary winding of the second transformer are connected;
The control unit is
a PLL calculation unit that calculates a phase of an input voltage waveform based on the first voltage value;
a capacitor current calculation unit that calculates a current target value of the smoothing capacitor based on a proportional value of a difference between the third voltage value and a target voltage of the smoothing capacitor and an integral value of the proportional value;
a converter control calculation unit that calculates a current target value of the first terminal based on a current target value of the smoothing capacitor and a phase of the input voltage waveform, and calculates a target value of a line voltage between the first terminal and the second terminal based on the current target value of the first terminal and the first current value;
a voltage target calculation unit that calculates a sine wave output voltage target value having a phase of the input voltage waveform and an amplitude of a target output voltage;
an inverter control calculation unit that calculates a target value of a line voltage between the third terminal and the second terminal based on the output voltage target value and the first voltage value;
an inverter power supply device comprising: a PWM calculation unit that generates the pulse width signal based on a target value of a line voltage between the first terminal and the second terminal, a target value of a line voltage between the third terminal and the second terminal, and the third voltage value. 2. The inverter power supply device according to claim 1,
The control unit is
a feedback calculation unit that calculates a voltage correction value that corrects the difference between the output voltage target value and the first voltage value calculated by the inverter control calculation unit based on the difference between the second voltage value and the output voltage target value;
the inverter control calculation unit multiplies a sum obtained by adding the voltage correction value to the difference between the output voltage target value and the first voltage value by a transformation ratio of the second transformer to calculate a target value of the line voltage between the third terminal and the second terminal. 3. The inverter power supply device according to claim 1,
The control unit is realized by software running on a processor or by a combination of hardware. 1. A control method for an inverter power supply device that transforms a single-phase AC voltage input via a pair of first input terminals and a pair of second input terminals and outputs the transformed voltage via a pair of first output terminals and a pair of second output terminals, comprising:
The inverter power supply device includes:
an inverter device including: a first switching element, a second switching element having one end connected to one end of the first switching element, a third switching element, a fourth switching element having one end connected to one end of the third switching element, a fifth switching element, a sixth switching element having one end connected to one end of the fifth switching element, and a smoothing capacitor having one end connected to the other ends of each of the first, third and fifth switching elements and the other end connected to the other ends of each of the second, fourth and sixth switching elements;
A first transformer; and
A second transformer; and
an output capacitor;
one end of a primary winding of the first transformer is connected to the first input terminal, and the other end of the primary winding of the first transformer is connected to the second input terminal;
one end of a secondary winding of the first transformer, a first terminal of the inverter device connected to a connection portion between the first switching element and the second switching element, and one end of a secondary winding of the second transformer are connected to each other;
the other end of the secondary winding of the second transformer, one end of the output capacitor, and the first output terminal are connected together;
the other end of the secondary winding of the first transformer, a second terminal of the inverter device connected to a connection portion between the third switching element and the fourth switching element, one end of a primary winding of the second transformer, the other end of the output capacitor, and the second output terminal are connected to each other;
a third terminal of the inverter device connected to a connection portion between the fifth switching element and the sixth switching element and the other end of the primary winding of the second transformer are connected;
calculating a phase of an input voltage waveform based on a first voltage value which is a secondary voltage of the first transformer;
calculating a current target value of the smoothing capacitor based on a proportional value of a difference between a third voltage value, which is a voltage of the smoothing capacitor, and a target voltage of the smoothing capacitor, and an integral value of the proportional value;
calculating a current target value of the first terminal based on a current target value of the smoothing capacitor and a phase of the input voltage waveform, and calculating a target value of a line voltage between the first terminal and the second terminal based on the current target value of the first terminal and a first current value which is a current flowing through the first terminal of the inverter device;
calculating a sinusoidal output voltage target value having a phase of the input voltage waveform and a target output voltage amplitude;
calculating a target value of a line voltage between the third terminal and the second terminal based on the output voltage target value and the first voltage value;
generating a pulse width signal for controlling the conduction and cut-off of each of the first to sixth switching elements based on a target value of a line voltage between the first terminal and the second terminal, a target value of a line voltage between the third terminal and the second terminal, and the third voltage value;
A control method comprising:

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