JP2024011347A - Power conversion device and method of controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device capable of deciding a duty ratio by simple calculation to reduce a loss.

SOLUTION: A power conversion device comprises: a transformer with a primary coil and a secondary coil; a primary side bridge circuit in which the primary coil is provided at a bridge portion for connecting a connection point between a first arm and a second arm and a connection point between a third arm and a fourth arm; and a secondary side bridge circuit in which the secondary coil is provided at a bridge portion for connecting a connection point between a fifth arm and a sixth arm and a connection point between a seventh arm and an eighth arm. In a case where a DC voltage of the primary side bridge circuit and that of the secondary side bridge circuit are different from each other, a ratio of a duty ratio of the primary side bridge circuit and that of the secondary side bridge circuit is adjusted depending on a ratio of these DC voltages.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure relates to a power conversion device and a control method thereof.

A bidirectional isolated DC/DC converter called DAB (Dual Active Bridge) in which two single-phase bridge circuits are connected via a high-frequency isolation transformer is known (for example, see Non-Patent Document 1). This converter is suitable for high-power applications because ZVS (Zero-Voltage Switching), which can reduce switching loss, can be applied when power control is adopted to adjust the phase difference between bridges.

In applications such as battery charging and discharging systems, buck-boost operation of the DAB converter may be essential. It is known that the power conversion efficiency in this case is lower than when the DC voltages of the primary bridge circuit and the secondary bridge circuit are equal. This is because the switching current increases when the switching element on the high voltage side turns off, leading to an increase in switching loss.

Therefore, if the voltage difference between the DC voltages of the primary bridge circuit and the secondary bridge circuit is large, in addition to controlling the phase difference between the bridges, it is possible to control the duty ratio of the AC voltage on one side or both sides. It is known that low loss can be achieved. For example, in Patent Document 1, the duty ratio of the primary side AC voltage and the secondary side AC voltage is increased or decreased so that the absolute value of the AC current becomes the minimum.

Patent No. 6559362

R.W.A.A. De Doncker, D.M. Divan, and M.H. Kheraluwala, "A Three-Phase Soft-Switched High-Power-Density dc/dc Converter for High-Power Applications", IEEE Transactions on Industry Applications, Volume 27, Issue 1, Pages 63- 73, January/February 1991.

However, the duty ratio calculation method proposed in Patent Document 1 is complicated, takes time to calculate, and may be difficult to implement on a computer.

The present disclosure provides a power conversion device and a control method thereof that can determine a duty ratio through simple calculation and achieve low loss.

In one aspect of the present disclosure,
A transformer having a primary winding and a secondary winding;
It has a first leg in which a first arm on the high side and a second arm on the low side are connected in series, and a second leg in which a third arm on the high side and a fourth arm on the low side are connected in series. , a primary side bridge circuit in which the primary winding is provided in a bridge portion connecting a connection point between the first arm and the second arm and a connection point between the third arm and the fourth arm;
It has a third leg in which a fifth arm on the high side and a sixth arm on the low side are connected in series, and a fourth leg in which a seventh arm on the high side and an eighth arm on the low side are connected in series. , a secondary side bridge circuit in which the secondary winding is provided in a bridge portion connecting a connection point between the fifth arm and the sixth arm and a connection point between the seventh arm and the eighth arm; ,
a control device that controls a switching phase difference between the primary bridge circuit and the secondary bridge circuit so that power is transmitted between the primary bridge circuit and the secondary bridge circuit; , comprising;
The control device includes:
When the DC voltage of the primary side bridge circuit and the DC voltage of the secondary side bridge circuit are different, the DC voltage of the primary side bridge circuit is A power conversion device is provided that adjusts a ratio between a duty ratio of an alternating current voltage of a side bridge circuit and a duty ratio of an alternating current voltage of the secondary side bridge circuit.

In another aspect of the present disclosure,
A transformer having a primary winding and a secondary winding;
It has a first leg in which a first arm on the high side and a second arm on the low side are connected in series, and a second leg in which a third arm on the high side and a fourth arm on the low side are connected in series. , a primary side bridge circuit in which the primary winding is provided in a bridge portion connecting a connection point between the first arm and the second arm and a connection point between the third arm and the fourth arm;
It has a third leg in which a fifth arm on the high side and a sixth arm on the low side are connected in series, and a fourth leg in which a seventh arm on the high side and an eighth arm on the low side are connected in series. , a secondary side bridge circuit in which the secondary winding is provided in a bridge portion connecting a connection point between the fifth arm and the sixth arm and a connection point between the seventh arm and the eighth arm; A method for controlling a power conversion device, comprising:
controlling a switching phase difference between the primary bridge circuit and the secondary bridge circuit so that power is transmitted between the primary bridge circuit and the secondary bridge circuit;
When the DC voltage of the primary side bridge circuit and the DC voltage of the secondary side bridge circuit are different, the voltage of the primary side bridge circuit is A control method for a power conversion device is provided, which adjusts a ratio between a duty ratio of an AC voltage of a side bridge circuit and a duty ratio of an AC voltage of the secondary side bridge circuit.

According to one aspect of the present disclosure, the duty ratio can be determined by simple calculation, and loss can be reduced.

FIG. 1 is a diagram illustrating a configuration example of a power conversion device according to an embodiment. FIG. 2 is a block diagram showing an example of a configuration of a control device. FIG. 6 is a diagram for explaining an example of a method of calculating a duty ratio when the DC voltages E1 and E2 of the primary side bridge circuit and the secondary side bridge circuit are equal. FIG. 6 is a diagram for explaining an example of a method of calculating a duty ratio when the DC voltage E1 of the primary side bridge circuit is lower than the DC voltage E2 of the secondary side bridge circuit. FIG. 6 is a diagram for explaining an example of a method of calculating a duty ratio when the DC voltage E1 of the primary side bridge circuit is higher than the DC voltage E2 of the secondary side bridge circuit. The simulation operation waveform of a comparative example is shown. 3 shows simulation operation waveforms of an example.

Embodiments of the present disclosure will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of a power conversion device according to the present embodiment. Power converter 100 shown in FIG. 1 is a bidirectional isolated DC/DC converter that includes bridge circuits on both sides of transformer 30. The power conversion device 100 can bidirectionally supply power between the primary bridge circuit 130 and the secondary bridge circuit 140.

Power conversion device 100 includes a transformer 30, a primary bridge circuit 130, a secondary bridge circuit 140, and a control device 150.

The transformer 30 has a primary winding 31 and a secondary winding 32, and the primary winding 31 and the secondary winding 32 are magnetically coupled. The winding ratio of the primary winding 31 and the secondary winding 32 is set as appropriate. In this specification, for convenience of explanation, a case will be exemplified in which the winding ratio of the primary winding 31 and the secondary winding 32 is 1:1.

The primary side bridge circuit 130 is connected to a primary side DC terminal (a positive side terminal and a negative side terminal), and exchanges power with an external device connected to the primary side DC terminal. Further, the primary side bridge circuit 130 is connected to the primary side of the transformer 30 and exchanges power with the primary winding 31 of the transformer 30.

The primary side bridge circuit 130 has a primary side DC bus bar pair P1, N1, the positive side terminal of the primary side DC terminal is connected to the positive side DC bus line P1, and the negative side terminal of the primary side DC terminal is connected to the negative side DC bus line P1. Connected to bus line N1. The primary side bridge circuit 130 switches the polarity of the voltage applied to the primary winding 31 of the transformer 30 by the primary side DC bus pair P1, N1.

The primary side bridge circuit 130 is a full bridge circuit having a plurality of legs 11 and 12.

The primary side bridge circuit 130 includes, for example, a U1 phase leg 11 in which a high side arm Q1 and a low side arm Q2 are connected in series, and a high side arm Q3 and a low side arm Q4 are connected in series. It has a V1 phase leg 12. Arm Q1 is an example of a first arm, arm Q2 is an example of a second arm, arm Q3 is an example of a third arm, and arm Q4 is an example of a fourth arm. The U1 phase leg 11 is an example of a first leg, and the V1 phase leg 12 is an example of a second leg.

In the primary bridge circuit 130, a primary winding 31 of a transformer 30 is provided at a bridge portion connecting an intermediate connection point a1 between arms Q1 and Q2 and an intermediate connection point b1 between arms Q3 and Q4. It is a full bridge circuit. The primary bridge circuit 130 may include a reactor connected in series to the primary winding 31 of the transformer 30 in the bridge portion.

In the example shown in FIG. 1, the primary side bridge circuit 130 includes a capacitor C1 and arms Q1 to Q4.

The capacitor C1 is connected between the DC bus pair P1 and N1 on the primary side, and smoothes the voltage between the DC bus pair P1 and N1 (voltage of the capacitor C1).

Arms Q1 to Q4 are switching elements on the primary side. Specific examples include semiconductor switching elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors).

The leg 11 includes an arm Q1 and an arm Q2 connected in series between the DC bus pair P1 and N1, and the leg 12 includes an arm Q3 and an arm Q4 connected in series between the DC bus pair P1 and N1. Contains configurations connected to. Arms Q1 to Q4 each have a first main terminal, a second main terminal, and a control terminal. For example, the first main terminal corresponds to a drain or collector, the second main terminal corresponds to a source or emitter, and the control terminal corresponds to a gate. Arms Q1-Q4 may include reverse-connected diodes between their main terminals. If arms Q1-Q4 are MOSFETs, this diode may be a parasitic diode. FIG. 1 illustrates freewheeling diodes D1, D2, D3, and D4.

With this configuration, when arm Q1 and arm Q4 are turned on and arm Q2 and arm Q3 are turned off, primary side bridge circuit 130 electrically connects intermediate connection point a1 to DC bus P1, and connects intermediate connection point b1 to DC bus P1. is electrically connected to the DC bus N1, and the voltage V1 between the intermediate connection point a1 and the intermediate connection point b1 is set to a positive voltage "E1". E1 is a voltage value between the DC bus pair P1 and N1. Further, when arm Q1 and arm Q4 are turned off and arm Q2 and arm Q3 are turned on, primary side bridge circuit 130 electrically connects intermediate connection point a1 to DC bus N1, and connects intermediate connection point b1 to DC bus P1. is electrically connected to make the voltage V1 a negative voltage "-E1". In this way, the primary side bridge circuit 130 switches the polarity of the voltage applied to the primary winding 31 of the transformer 30 by the primary side DC bus pair P1, N1.

Furthermore, when arm Q1 and arm Q3 are turned on and arm Q2 and arm Q4 are turned off, primary side bridge circuit 130 electrically connects both intermediate connection point a1 and intermediate connection point b1 to DC bus P1, The voltage V1 is made substantially zero. Alternatively, when arm Q1 and arm Q3 are turned off and arm Q2 and arm Q4 are turned on, primary side bridge circuit 130 electrically connects both intermediate connection point a1 and intermediate connection point b1 to DC bus N1, The voltage V1 is made substantially zero.

The secondary side bridge circuit 140 is connected to secondary side DC terminals (positive side terminal and negative side terminal), and exchanges power with an external device connected to the secondary side DC terminal. Further, the secondary side bridge circuit 140 is connected to the secondary side of the transformer 30 and exchanges power with the secondary winding 32 of the transformer 30.

The secondary side bridge circuit 140 has a secondary side DC bus bar pair P2, N2, in which the positive side terminal of the secondary side DC terminal is connected to the positive side DC bus line P2, and the negative side terminal of the secondary side DC terminal is connected to the positive side DC bus line P2. It is connected to the negative side DC bus N2. The secondary side bridge circuit 140 switches the polarity of the voltage applied to the secondary winding 32 of the transformer 30 by the secondary side DC bus pair P2, N2.

The secondary side bridge circuit 140 is a full bridge circuit having a plurality of legs 13 and 14.

The secondary side bridge circuit 140 includes, for example, a U2 phase leg 13 in which a high side arm Q5 and a low side arm Q6 are connected in series, and a high side arm Q7 and a low side arm Q8 are connected in series. It has a V2 phase leg 14. Arm Q5 is an example of the fifth arm, arm Q6 is an example of the sixth arm, arm Q7 is an example of the seventh arm, and arm Q8 is an example of the eighth arm. The U2 phase leg 13 is an example of the third leg, and the V2 phase leg 14 is an example of the fourth leg.

In the secondary bridge circuit 140, the secondary winding 32 of the transformer 30 is provided at a bridge portion connecting an intermediate connection point a2 between arm Q5 and arm Q6 and an intermediate connection point b2 between arm Q7 and arm Q8. This is a fully bridged circuit. The secondary bridge circuit 140 may include a reactor connected in series to the secondary winding 32 of the transformer 30 in the bridge portion.

In the example shown in FIG. 1, the secondary bridge circuit 140 includes a capacitor C2 and arms Q5 to Q8.

The capacitor C2 is connected between the DC bus pair P2 and N2 on the secondary side, and smoothes the voltage between the DC bus pair P2 and N2 (voltage of the capacitor C2).

Arms Q5 to Q8 are switching elements on the secondary side. Specific examples thereof include semiconductor switching elements such as MOSFETs and IGBTs, similar to the arms Q1 to Q4.

Leg 13 includes an arm Q5 and an arm Q6 connected in series between the DC bus pair P2 and N2, and leg 14 includes an arm Q7 and an arm Q8 connected in series between the DC bus pair P2 and N2. Contains configurations connected to. Like arms Q1 to Q4, arms Q5 to Q8 each have a first main terminal, a second main terminal, a control terminal, and a diode. FIG. 1 illustrates freewheeling diodes D5, D6, D7, and D8.

With such a configuration, when arm Q5 and arm Q8 are turned on and arm Q6 and arm Q7 are turned off, secondary side bridge circuit 140 electrically connects intermediate connection point a2 to DC bus P2, and connects intermediate connection point a2 to DC bus P2. b2 is electrically connected to the DC bus N2, and the voltage V2 between the intermediate connection point a2 and the intermediate connection point b2 is set to a positive voltage "E2". E2 is a voltage value between the DC bus pair P2 and N2. Further, when arm Q5 and arm Q8 are turned off and arm Q6 and arm Q7 are turned on, secondary side bridge circuit 140 electrically connects intermediate connection point a2 to DC bus N2, and connects intermediate connection point b2 to DC bus. It is electrically connected to P2 to make the voltage V2 a negative voltage "-E2". In this way, the secondary side bridge circuit 140 switches the polarity of the voltage applied to the secondary winding 32 of the transformer 30 by the secondary side DC bus pair P2, N2.

Furthermore, when arm Q5 and arm Q7 are turned on and arm Q6 and arm Q8 are turned off, secondary side bridge circuit 140 electrically connects both intermediate connection point a2 and intermediate connection point b2 to DC bus P2. , the voltage V2 is made substantially zero. Alternatively, when arm Q5 and arm Q7 are turned off and arm Q6 and arm Q8 are turned on, secondary side bridge circuit 140 electrically connects both intermediate connection point a2 and intermediate connection point b2 to DC bus N2. , the voltage V2 is made substantially zero.

The control device 150 adjusts the switching phase difference between the primary bridge circuit 130 and the secondary bridge circuit 140 ( (hereinafter also referred to as phase difference δ). The control device 150 adjusts the power transmitted between the primary bridge circuit 130 and the secondary bridge circuit 140 by controlling the phase difference δ between the voltage V1 and the voltage V2. The control device 150 generates gate signals g1 to g4 for controlling ON or OFF of the control terminals of the arms Q1 to Q4 of the primary side bridge circuit 130, and ON or OFF of the control terminals of the arms Q5 to Q8 of the secondary side bridge circuit 140. Alternatively, gate signals g5 to g8 for controlling off are output.

Power conversion device 100 includes a primary GDU 160 and a secondary GDU 170. The primary side GDU 160 is a primary side drive circuit that controls switching on or off of the arms Q1 to Q4 of the primary side bridge circuit 130 according to gate signals g1 to g4. The secondary GDU 170 is a secondary drive circuit that controls switching on or off of the arms Q5 to Q8 of the secondary bridge circuit 140 according to gate signals g5 to g8.

The control device 150 acquires the DC voltage detection values of each of the primary side bridge circuit 130 and the secondary side bridge circuit 140, and the DC current detection value of one side of the bridge circuit (in this example, the secondary side bridge circuit 140). do. Control device 150 generates control signals g1 to g8 for controlling transmission power between bridges based on these detected values and current or power command values, and controls arms Q1 to Q8. In this embodiment, the control device 150 acquires the detected voltage value E1, the detected voltage value E2, and the detected current value I2, and controls the transmission power between the bridges based on these detected values and the current command value I2*. Control signals g1 to g8 are generated to control the arms Q1 to Q8.

The voltage detection value E1 is a detection value of the DC voltage of the primary side bridge circuit 130, and more specifically, a detection value of the voltage E1 between the DC bus pair P1 and N1. The voltage detection value E2 is a detection value of the DC voltage of the secondary side bridge circuit 140, and more specifically, a detection value of the voltage E2 between the DC bus pair P2 and N2. The current detection value I2 is a detection value of the DC current of the secondary side bridge circuit 140, and more specifically, a detection value of the current I2 flowing through the DC bus P2. The current command value I2* is a command value for the DC current of the secondary bridge circuit 140, and more specifically, it is a command value for the current I2 flowing through the DC bus P2. The command value is also called a target value.

The functions of the control device 150 are realized by a processor such as a CPU (Central Processing Unit) operating according to a program stored in a memory. The functions of the control device 150 may be realized by an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

FIG. 2 is a block diagram showing the main parts of the control device. The control device 150 includes a current control section 51, a duty ratio calculation section 52, and a gate signal generation section 53.

The current control unit 51 calculates the switching phase difference δ between the primary bridge circuit 130 and the secondary bridge circuit 140 based on the current detection value I2 and the current command value I2*. Current control section 51 includes a subtracter 54 and a PI adjuster 55. The subtractor 54 calculates the difference (current difference ΔI) between the current command value I2* and the current detected value I2. The PI controller 55 calculates a phase difference δ such that the current difference ΔI calculated by the subtractor 54 converges to zero by PI control or PID control (P: proportional control, I: integral control, D: differential control). ).

The duty ratio calculation unit 52 calculates the duty ratio D1 of the AC voltage V1 of the primary side bridge circuit 130 and the duty ratio D2 of the AC voltage V2 of the secondary side bridge circuit 140 based on the voltage detection value E1 and the voltage detection value E2. do. When the voltage detection value E1 and the voltage detection value E2 are different, the duty ratio calculation unit 52 adjusts the duty ratio D1 and the duty ratio D2 so that D1/D2=E1/E2 is satisfied.

The gate signal generation section 53 generates gate signals g1 to g8 based on the phase difference δ outputted from the current control section 51 and the duty ratios D1 and D2 outputted from the duty ratio calculation section 52. A well-known method may be used to generate the gate signals g1 to g8 based on the phase difference δ and the duty ratios D1 and D2.

FIG. 3 is a diagram for explaining an example of a method of calculating the duty ratio when the DC voltages E1 and E2 of the primary side bridge circuit and the secondary side bridge circuit are equal. ωt on the horizontal axis represents the phase. When the voltage detection value E1 and the voltage detection value E2 are equal, the duty ratio calculation unit 52 (FIG. 2) calculates the duty ratio D1 of the AC voltage V1 of the primary bridge circuit 130 and the duty of the AC voltage V2 of the secondary bridge circuit 140. The ratio D2 is fixed to 1 (pulse width=π).

FIG. 4 is a diagram for explaining an example of a method of calculating the duty ratio when the DC voltage E1 of the primary bridge circuit is lower than the DC voltage E2 of the secondary bridge circuit. ωt on the horizontal axis represents the phase. When the detected voltage value E1 is lower than the detected voltage value E2, the duty ratio calculation unit 52 (FIG. 2) fixes the duty ratio D1 of the AC voltage V1 to 1 (pulse width = π), and sets the duty ratio of the AC voltage V2 to 1 (pulse width = π). D2 is adjusted to satisfy D2=E2/E1 (pulse width=E2/E1×π).

FIG. 5 is a diagram for explaining an example of a method of calculating the duty ratio when the DC voltage E1 of the primary side bridge circuit is higher than the DC voltage E2 of the secondary side bridge circuit. ωt on the horizontal axis represents the phase. When the detected voltage value E1 is higher than the detected voltage value E2, the duty ratio calculation unit 52 (FIG. 2) fixes the duty ratio D2 of the AC voltage V2 to 1 (pulse width = π), and sets the duty ratio of the AC voltage V1 to 1 (pulse width = π). D1 is adjusted to satisfy D1=E1/E2 (pulse width=E1/E2×π).

FIG. 6 shows simulation operation waveforms in the case of the conventional method. FIG. 7 shows simulation operation waveforms when using the power conversion device and its control method according to the present embodiment. The simulation conditions in FIGS. 6 and 7 are as follows:
・E1<E2
・Transmission direction: Transmission from the primary side to the secondary side.

FIG. 6 shows the AC voltages V1 and V2 of the primary bridge circuit 130 and the secondary bridge circuit 140 and the AC current Iac1 (primary FIG. I _A , I _B , I _C , and I _D represent the switching currents of legs 11, 12, 13, and 14, respectively. Note that the symbols shown in FIG. 1 are used for convenience.

Referring to FIG. 6, the switching currents I _C and I _D of the legs 13 and 14 of the bridge circuit on the high voltage side (secondary side) are equal to the switching current I _A of the legs 11 and 12 of the bridge circuit on the low voltage side (primary side). , higher than I _B. As a result, the loss during turn-off of the arms Q5 to Q8 included in the legs 13 and 14 on the high voltage side increases, and the efficiency of the power converter 100 decreases.

FIG. 7 shows the AC voltages V1 and V2 of the primary bridge circuit 130 and the secondary bridge circuit 140 and the AC current Iac1 of the primary bridge circuit 130 (in the primary winding 31) when the method of this embodiment is applied. FIG.

Referring to FIG. 7, when focusing on the switching current _IC of the leg 13 of the bridge circuit on the high voltage side (secondary side), it is lower than in the case of FIG. As a result, the loss during turn-off of the arms Q5 and Q6 included in the high voltage side leg 13 is reduced, and the efficiency of the power converter 100 is increased compared to when the conventional method is applied.

In this way, according to the present embodiment, it is possible to provide a power conversion device that can determine the duty ratio through simple calculations and achieve low loss.

Although the embodiments have been described as above, the embodiments are presented as examples, and the present invention is not limited to the embodiments described above. The embodiments described above can be implemented in various other forms, and various combinations, omissions, substitutions, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

100 Power conversion device 11, 12, 13, 14 Leg 30 Transformer 31 Primary winding 32 Secondary winding 51 Current control section 52 Duty ratio calculation section 53 Gate signal generation section 54 Subtractor 55 PI regulator 130 Primary side bridge circuit 140 Secondary side bridge circuit 150 Control device C1, C2 Capacitor D1~D8 Free wheel diode Q1~Q8 Arm

Claims (5)

A transformer having a primary winding and a secondary winding;
It has a first leg in which a first arm on the high side and a second arm on the low side are connected in series, and a second leg in which a third arm on the high side and a fourth arm on the low side are connected in series. , a primary side bridge circuit in which the primary winding is provided in a bridge portion connecting a connection point between the first arm and the second arm and a connection point between the third arm and the fourth arm;
It has a third leg in which a fifth arm on the high side and a sixth arm on the low side are connected in series, and a fourth leg in which a seventh arm on the high side and an eighth arm on the low side are connected in series. , a secondary side bridge circuit in which the secondary winding is provided in a bridge portion connecting a connection point between the fifth arm and the sixth arm and a connection point between the seventh arm and the eighth arm; ,
a control device that controls a switching phase difference between the primary bridge circuit and the secondary bridge circuit so that power is transmitted between the primary bridge circuit and the secondary bridge circuit; , comprising;
The control device includes:
When the DC voltage of the primary side bridge circuit and the DC voltage of the secondary side bridge circuit are different, the voltage of the primary side bridge circuit is A power conversion device that adjusts a ratio between a duty ratio of an alternating current voltage of a side bridge circuit and a duty ratio of an alternating current voltage of the secondary side bridge circuit. The control device includes:
The duty ratio of the AC voltage of the primary side bridge circuit is D1, the duty ratio of the AC voltage of the secondary side bridge circuit is D2, the DC voltage of the primary side bridge circuit is E1, the DC voltage of the secondary side bridge circuit is When E2,
D1/D2=E1/E2
The power conversion device according to claim 1, wherein D1 and D2 are adjusted so as to satisfy the following. The control device includes:
The power conversion device according to claim 2, wherein when E1<E2, D1 is fixed to 1 and D2 is adjusted so as to satisfy D2=E2/E1. The control device includes:
The power conversion device according to claim 3, wherein when E1>E2, D2 is fixed to 1 and D1 is adjusted so as to satisfy D1=E1/E2. A transformer having a primary winding and a secondary winding;
It has a first leg in which a first arm on the high side and a second arm on the low side are connected in series, and a second leg in which a third arm on the high side and a fourth arm on the low side are connected in series. , a primary side bridge circuit in which the primary winding is provided in a bridge portion connecting a connection point between the first arm and the second arm and a connection point between the third arm and the fourth arm;
It has a third leg in which a fifth arm on the high side and a sixth arm on the low side are connected in series, and a fourth leg in which a seventh arm on the high side and an eighth arm on the low side are connected in series. , a secondary side bridge circuit in which the secondary winding is provided in a bridge portion connecting a connection point between the fifth arm and the sixth arm and a connection point between the seventh arm and the eighth arm; A method for controlling a power conversion device, comprising:
controlling a switching phase difference between the primary bridge circuit and the secondary bridge circuit so that power is transmitted between the primary bridge circuit and the secondary bridge circuit;
When the DC voltage of the primary side bridge circuit and the DC voltage of the secondary side bridge circuit are different, the voltage of the primary side bridge circuit is A method for controlling a power conversion device, comprising adjusting a ratio between a duty ratio of an alternating current voltage of a side bridge circuit and a duty ratio of an alternating current voltage of the secondary side bridge circuit.

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