Power conversion device, control method, and computer readable medium

Abstract

This invention provides a power conversion device capable of efficiently adjusting power transmission. The power conversion device includes: a transformer; a first bridge circuit connected to the primary side of the transformer, capable of switching the polarity of the DC bus pairs on the primary side connected to the transformer; a second bridge circuit connected to the secondary side of the transformer, capable of switching the polarity of the DC bus pairs on the secondary side connected to the transformer; and a control device capable of controlling the switching of the first bridge circuit and the second bridge circuit by creating a phase difference. The control device includes a frequency adjustment unit that adjusts the switching frequency of the first bridge circuit and the second bridge circuit based on the output and target value from either the first or second bridge circuit.

Description

Technical Field

[0001] This invention relates to power conversion devices, control methods, and computer-readable media. Background Technology

[0002] Conventionally, bidirectional DC / DC converters, such as DAB (Dual Active Bridge) converters (see, for example, Patent Document 1), have been used as power conversion devices capable of providing power bidirectionally. Such bidirectional DC / DC converters are connected to bridge circuits on the primary and secondary sides via transformers. In the bidirectional DC / DC converter of Patent Document 1, intermittent operation is performed in regions where the transmitted power is lower than a threshold.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-130997 Summary of the Invention

[0006] Technical problem to be solved by the invention

[0007] When a bidirectional DC / DC converter operates intermittently, it does not transmit power during the rest periods. Furthermore, because the period of power transmission during intermittent operation is shorter in a bidirectional DC / DC converter, the peak current flowing during periods other than the rest periods increases in order to transmit the required power.

[0008] Technical solutions used to solve technical problems

[0009] To address the aforementioned problems, in a first aspect of the present invention, a power conversion device is provided, comprising: a transformer; a first bridge circuit connected to the primary side of the transformer, capable of switching the polarity of the DC bus pair connected to the primary side of the transformer; a second bridge circuit connected to the secondary side of the transformer, capable of switching the polarity of the DC bus pair connected to the secondary side of the transformer; and a control device capable of controlling the switching of the first bridge circuit and the second bridge circuit by creating a phase difference. The control device may include a frequency adjustment unit that adjusts the switching frequency of the first bridge circuit and the second bridge circuit based on the output and target value from either the first bridge circuit or the second bridge circuit.

[0010] The control device may have a phase difference adjustment unit that adjusts the switching phase difference based on the output and target value.

[0011] The frequency adjustment unit can change the switching frequency when the switching phase difference is adjusted to the lower limit phase difference.

[0012] The control device may have a pause period adjustment unit that adjusts the proportion of the pause period that causes the output from the first bridge circuit or the second bridge circuit to pause based on the output and the target value.

[0013] The rest period adjustment unit can change the rest period ratio if the switching frequency is adjusted to the upper limit frequency.

[0014] The control device may include a control arithmetic unit that outputs a control value corresponding to the difference between the output and the target value. A phase difference adjustment unit adjusts the switching phase difference based on the control value. A frequency adjustment unit adjusts the switching frequency based on the value obtained by removing the adjustment amount from the phase difference adjustment unit from the control value. A rest period adjustment unit adjusts the rest period ratio based on the value obtained by removing the adjustment amounts from both the phase difference adjustment unit and the frequency adjustment unit from the control value.

[0015] The control unit can output control values ​​through PI control or PID control corresponding to the difference between the output and the target value.

[0016] The control device may have a selection unit that selects which of the first bridge circuit and the second bridge circuit to be set as the power output side according to the input instruction.

[0017] In a second aspect of the invention, a control method for a power conversion device is provided. The power conversion device may include: a transformer; a first bridge circuit connected to the primary side of the transformer, capable of switching the polarity of the DC bus pair connected to the primary side of the transformer; a second bridge circuit connected to the secondary side of the transformer, capable of switching the polarity of the DC bus pair connected to the secondary side of the transformer; and a control device capable of switching the first bridge circuit and the second bridge circuit by creating a phase difference. The control method may include adjusting the switching frequency of the first bridge circuit and the second bridge circuit based on the output and target value from either the first bridge circuit or the second bridge circuit.

[0018] The control device may include the following: adjusting the switching phase difference based on the output and target values.

[0019] The frequency can be adjusted by changing the switching frequency if the phase difference of the switching is adjusted to the lower limit of the phase difference.

[0020] In a third aspect of the invention, a computer-readable medium is provided that records a control program for controlling a power conversion device. The power conversion device may include: a transformer; a first bridge circuit connected to the primary side of the transformer, capable of switching the polarity of a DC bus pair connected to the primary side of the transformer; a second bridge circuit connected to the secondary side of the transformer, capable of switching the polarity of a DC bus pair connected to the secondary side of the transformer; and a control device capable of switching the first bridge circuit and the second bridge circuit by creating a phase difference. The control program may function as a frequency adjustment unit that adjusts the switching frequency of the first bridge circuit and the second bridge circuit based on the output and target value from either the first or second bridge circuit.

[0021] The control program can function as a phase difference adjustment unit, which adjusts the switching phase difference based on the output and target values.

[0022] The frequency adjustment unit can change the switching frequency when the switching phase difference is adjusted to the lower limit phase difference.

[0023] Furthermore, the above summary of the invention does not list all the essential features of the invention. In addition, sub-combinations of these feature groups can also constitute an invention. Attached Figure Description

[0024] Figure 1 The structure of the power conversion device 100 according to this embodiment is shown together with the primary side device 110 and the secondary side device 120.

[0025] Figure 2 This is an example of the operating waveform of the power conversion device 100 according to this embodiment.

[0026] Figure 3 The structure of the control device 150 according to this embodiment is shown.

[0027] Figure 4 The operation flow of the control device 150 involved in this embodiment is shown.

[0028] Figure 5 This is an example of the operation waveform in the phase difference adjustment operation of the power conversion device 100 according to this embodiment.

[0029] Figure 6 This is an example of the operating waveform during the frequency adjustment operation of the power conversion device 100 according to this embodiment.

[0030] Figure 7This is an example of the operating waveform during the rest period adjustment operation of the power conversion device 100 according to this embodiment. Detailed Implementation

[0031] The present invention will now be described through embodiments thereof, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, the combinations of features described in the embodiments are not necessarily all necessary technical means to solve the technical problems of the present invention.

[0032] Figure 1 The structure of the power conversion device 100 according to this embodiment is shown together with the primary side device 110 and the secondary side device 120. The power conversion device 100 may be an isolated DC / DC converter, capable of providing power bidirectionally between the primary side device 110 connected to the primary side and the secondary side device 120 connected to the secondary side.

[0033] Primary device 110 and secondary device 120 are devices connected to power conversion device 100. Each of primary device 110 and secondary device 120 can have the function of outputting and receiving power. For example, one of the primary device 110 and secondary device 120 (as an example, primary device 110) can be an energy storage device, capable of receiving and charging power transmitted from the other of the primary device 110 and secondary device 120 (as an example, secondary device 120) via power conversion device 100, and providing the charged power to secondary device 120 as needed. Furthermore, for example, one of the primary device 110 and secondary device 120 (as an example, secondary device 120) can be a drive device such as an electric motor, capable of being driven using power provided from the other of the primary device 110 and secondary device 120 (as an example, primary device 110), and providing the regenerated power to primary device 110 during regeneration operations. Furthermore, the primary side device 110 and the secondary side device 120 may each be, for example, a system that combines a solar power generation device and an energy storage device.

[0034] The power conversion device 100 includes a transformer Tr, a primary circuit 130, a secondary circuit 140, and a control device 150. The transformer Tr has a primary winding and a secondary winding. The winding ratio of the primary winding to the secondary winding of the transformer Tr can be determined based on the ratio of the rated voltages of the primary side device 110 and the secondary side device 120. In this specification, for ease of explanation, an example of a 1:1 winding ratio for the transformer Tr is provided.

[0035] The primary circuit 130 is connected to the positive and negative terminals of the primary side device 110, and exchanges power with the primary side device 110. Furthermore, the primary circuit 130 is connected to the primary side of the transformer Tr, and exchanges power with the primary winding of the transformer Tr.

[0036] The primary circuit 130 has primary-side DC bus pairs P1 and N1. The positive terminal of the primary-side device 110 is connected to the positive-side DC bus P1, and the negative terminal of the primary-side device 110 is connected to the negative-side DC bus N1. The primary circuit 130 can be an inverter capable of switching the polarity of the primary-side DC bus pairs connected to the primary winding of a transformer (as an example, a three-level inverter).

[0037] In this embodiment, the primary circuit 130 is a bridge circuit (referred to as "first bridge circuit"), more specifically a full-bridge circuit. Alternatively, the primary circuit 130 may also be implemented by a half-bridge circuit (e.g., a neutral-point clamped three-level inverter) capable of switching the polarity of the DC bus pairs connected to the primary winding of the transformer.

[0038] The primary circuit 130 includes a capacitor C1, switching elements Q1 to Q4, and an inductor L1. The capacitor C1 is connected between the DC bus pairs P1 and N1 on the primary side to filter the voltage and current exchanged between the primary circuit 130 and the primary side device 110.

[0039] Switching elements Q1 to Q4 can be MOSFETs such as power MOSFETs or IGBTs (Insulated Gate Bipolar Transistors), using a full-bridge structure. Switching elements Q1 and Q2 are connected in series between the main terminals (drain-source in MOSFETs, collector-emitter in IGBTs) in this order between the DC bus pairs P1 and N1. Control terminals c1 and c2 (gate) are connected to the control device 150. Switching elements Q1 and Q2 may also include diodes connected in reverse between the main terminals. If switching elements Q1 and Q4 are MOSFETs, these diodes can be parasitic diodes.

[0040] Switching elements Q3 and Q4 are connected in series between the DC bus pairs P1 and N1 in this order between the main terminals, and control terminals c3 and c4 are connected to the control device 150. Switching elements Q3 and Q4 may also include diodes connected in reverse between the main terminals.

[0041] Inductor L1 is connected in series with the primary winding of transformer Tr between the midpoint a1 between switching elements Q1 and Q2 and the midpoint b1 between switching elements Q3 and Q4.

[0042] Using this structure, if in the primary circuit 130, switching elements Q1 and Q4 are turned on and switching elements Q2 and Q3 are turned off, then intermediate point a1 is electrically connected to DC bus P1, intermediate point b1 is electrically connected to DC bus N1, and the voltage V1 between intermediate points a1 and b1 is set to a positive voltage. Furthermore, in the primary circuit 130, if switching elements Q1 and Q4 are turned off and switching elements Q2 and Q3 are turned on, then intermediate point a1 is electrically connected to DC bus N1, intermediate point b1 is electrically connected to DC bus P1, and the voltage V1 is set to a negative voltage. Thus, the primary circuit 130 can switch the polarity of the DC bus pair connected to the primary winding of the transformer. Furthermore, during the rest period adjustment operation described later, the primary circuit 130 can be configured to switch the polarity of the primary winding of the transformer to three or more levels, including positive, negative, and 0. In the primary circuit 130 of this figure, by turning on switching elements Q1 and Q3 and turning off switching elements Q2 and Q4, or by turning off switching elements Q1 and Q3 and turning on switching elements Q2 and Q4, the intermediate points a1 and b1 are electrically connected to the DC bus P1 or the DC bus N1, and the voltage V1 is substantially set to 0.

[0043] Secondary circuit 140 is connected to the positive and negative terminals of secondary side device 120, and exchanges power with secondary side device 120. Furthermore, secondary circuit 140 is connected to the secondary side of transformer Tr, and exchanges power with the secondary winding of transformer Tr. Here, secondary circuit 140, connected to the secondary side of transformer Tr and secondary side device 120, has a structure substantially the same as primary circuit 130, except that its withstand voltage and other characteristics differ depending on the transformation ratio of transformer Tr. Therefore, descriptions of secondary circuit 140 will be omitted except for differences from primary circuit 130.

[0044] The secondary circuit 140 has DC bus pairs P2 and N2 on the secondary side. These DC bus pairs P2 and N2 correspond to the DC bus pairs P1 and N1 in the primary circuit 130. Furthermore, the secondary circuit 140 includes a capacitor C2, switching elements Q5 to Q8, and an inductor L2. The capacitor C2 corresponds to the capacitor C1 in the primary circuit 130, the switching elements Q5 to Q8 correspond to the switching elements Q1 to Q4 in the primary circuit 130, and the inductor L2 corresponds to the inductor L1 in the primary circuit 130.

[0045] In this embodiment, the secondary circuit 140, like the primary circuit 130, is a bridge circuit (referred to as "second bridge circuit"), more specifically, a full-bridge circuit. Alternatively, the secondary circuit 140 can also be implemented by a half-bridge circuit (e.g., a neutral-point clamped three-level inverter) capable of switching the polarity of the connection between the secondary-side DC bus pair and the secondary winding of the transformer. During the rest period adjustment operation described later, the secondary circuit 140 can be configured to switch the polarity of the transformer's secondary winding to three or more levels, including positive, negative, and 0. Furthermore, the primary circuit 130 and the secondary circuit 140 can also be different types of bridge circuits or multi-level inverters.

[0046] The control device 150 is connected to the primary circuit 130 and the secondary circuit 140, and controls the primary circuit 130 and the secondary circuit 140. In this embodiment, the control device 150 receives a direction command value, an E1 command value, an E1 detection value, an E2 command value, and an E2 detection value as inputs, and outputs control signals for controlling the on / off state of the control terminals c1 to c4 of the switching elements Q1 to Q4 in the primary circuit 130, and control signals for controlling the on / off state of the control terminals c5 to c8 of the switching elements Q5 to Q8 in the secondary circuit 140.

[0047] The direction command value is an instruction value indicating whether power is transmitted from the primary side to the secondary side or from the secondary side to the primary side. In the case of power transmission from the secondary side to the primary side, the E1 detection value is an example of an index value indicating the magnitude of the output from the primary circuit 130 to the primary device 110; in this embodiment, it is a value obtained by measuring the voltage E1 supplied to the primary device 110. The E1 command value is an example of a target value for the output from the primary circuit 130 to the primary device 110; in this embodiment, it is a value indicating the target value of the voltage E1 that should be supplied to the primary device 110. The E2 detection value and the E2 command value are index values ​​and target values ​​indicating the magnitude of the output from the secondary circuit 140 to the secondary device 120 in the case of power transmission from the primary side to the secondary side, and are otherwise the same as the E1 detection value and the E1 command value.

[0048] In this embodiment, the control device 150 is input with a voltage value representing the output target, which serves as an index value and a target value. Alternatively, the control device 150 may also input a current value representing the output target, or a power value representing the power supplied to the output target, etc., as index values ​​and target values, and control the switching elements Q1 to Q8 based on these values.

[0049] Figure 2This is an example of the operating waveforms of the power conversion device 100 according to this embodiment. In this figure, the waveforms of the voltage V1 between the midpoints a1 and b1 of the primary circuit 130, the voltage V2 between the midpoints a2 and b2 of the secondary circuit 140, the current I1 flowing through the inductor L1 (in the case of voltage E1 < voltage E2), and the current I1 (in the case of voltage E1 > voltage E2) are shown in order from top to bottom. The time of each waveform is selected as the horizontal axis.

[0050] The control device 150 can control the switching of the primary circuit 130 and the secondary circuit 140 to have a phase difference. Thus, the power conversion device 100 functions as a DAB converter. This illustration shows the case where power is supplied from the primary side to the secondary side.

[0051] In this diagram, the control device 150 switches the voltage V1 between positive and negative voltages at a certain frequency. The control device 150 can set the voltage V1 to a positive voltage E1 by providing a control signal to the primary circuit 130 that turns on switching elements Q1 and Q3 and turns off switching elements Q2 and Q4. Conversely, the control device 150 can set the voltage V1 to a negative voltage -E1 by providing a control signal to the primary circuit 130 that turns off switching elements Q1 and Q3 and turns on switching elements Q2 and Q4.

[0052] Furthermore, the control device 150 switches the polarity of the connection between the midpoints a2 and b2 of the two ends of the secondary winding of the transformer Tr and the positive and negative terminals of the secondary device 120 at the same frequency. The control device 150 sets switching elements Q6 and Q7 to conduct and switching elements Q5 and Q8 to disconnect, thereby connecting midpoint a2 to the negative terminal of the secondary device 120 and midpoint b2 to the positive terminal of the secondary device 120. In this case, the voltage E2 of the secondary device 120 is applied in reverse, and the voltage V2 becomes a negative voltage -E2. Alternatively, the control device 150 can set switching elements Q6 and Q7 to disconnect and switching elements Q5 and Q8 to conduct, thereby setting the voltage V2 to a positive voltage E2.

[0053] The control device 150 has a phase difference, represented in the figure as "primary / secondary phase difference," between the switching of voltage V1 and voltage V2. Here, ideally, the transformer Tr allows the primary current I1 and the secondary current I2 to flow in a ratio corresponding to the reciprocal of the winding ratio. With a winding ratio of 1:1, ideally, current I1 = current I2. Therefore, when considering the current flowing within the power conversion device 100, the transformer Tr can be disregarded.

[0054] In the diagram, if voltage V1 = voltage E1 and voltage V2 = voltage - E2, then the primary side device 110 and the secondary side device 120 are connected in series in the positive direction relative to the series-connected inductors L1 and L2, and voltage (E1 + E2) is applied to the inductors (L1 + L2). Therefore, the current I1 (= I2) flowing through the inductors L1 and L2 rises with a slope of (E1 + E2) / (L1 + L2), and current I1 is positive.

[0055] Next, if after the primary / secondary phase difference, the voltages become V1 = E1 and V2 = E2, then the positive terminals of the primary side device 110 and the secondary side device 120 are connected via inductors L1 and L2, and voltage (E1-E2) is applied to inductors (L1+L2). As a result, current I1 (=I2) changes with a slope of (E1-E2) / (L1+L2).

[0056] Here, when voltage E1 < E2, current I1 decreases. When voltage E1 > E2, current I1 increases further. Furthermore, when voltage E1 = E2, current I1 remains unchanged. However, in actual circuits, there are some losses, so current I1 tends to decrease compared to the ideal situation.

[0057] When the positive terminal of the primary device 110 and the positive terminal of the secondary device 120 are connected via inductors L1 and L2, a positive current I1 (= current I2) flows through, thereby providing a positive current I2 to the positive terminal of the secondary device 120, and the secondary device 120 can perform charging, etc.

[0058] Next, if the voltages V1 = -E1 and V2 = E2, then the primary side device 110 and the secondary side device 120 are connected in series in the opposite direction to the case where V1 = E1 and V2 = -E2, with respect to inductors L1 and L2. In this case, except that the change in current I1 is in the opposite direction, it is the same as the case where V1 = E1 and V2 = -E2.

[0059] Next, if voltage V1 = voltage - E1 and voltage V2 = voltage - E2, then in the same manner as in the case of voltage V1 = voltage E1 and voltage V2 = voltage E2, the secondary side device 120 is charged, etc.

[0060] Furthermore, when power is supplied from the secondary side to the primary side, the control device 150 can delay the switching of voltage V1 relative to the switching of voltage V2. Thus, by performing control that establishes a phase difference between the primary circuit 130 and the secondary circuit 140 and switches them, power can be exchanged between the primary side device 110 and the secondary side device 120. Moreover, when the winding ratio is not 1:1, the same applies as described above, except that the voltage varies according to the winding ratio and the current varies according to the reciprocal of the winding ratio.

[0061] Here, the control device 150 is required to transmit the requested power from the power input side (primary side in this example) to the power output side (secondary side in this example) with the exact amount required. Specifically, in the case where voltage E1 > voltage E2, even if voltages V1 and V2 are positive, current I1 continues to increase. Therefore, the control device 150 according to this embodiment employs a structure for adjusting the amount of power transmitted, as shown below, so that even under the above conditions, excessive power is not output to the power output side.

[0062] Figure 3 The structure of the control device 150 according to this embodiment is shown. The control device 150 can perform phase difference adjustment operations to adjust the phase difference between the switching of the primary circuit 130 and the secondary circuit 140, frequency adjustment operations to adjust the switching frequency, and rest period adjustment operations to adjust the proportion of the rest period that stops power transmission in each switching cycle. As a result, the control device 150 can appropriately control power transmission under various conditions, such as the relationship between the voltage E1 of the primary device 110 and the voltage E2 of the secondary device 120.

[0063] The control device 150 includes a selection unit 310, a subtractor 315, a control calculation unit 320, a phase difference adjustment unit 330, a frequency adjustment unit 350, and a rest period adjustment unit 370. The selection unit 310 selects which of the primary circuit 130 and the secondary circuit 140 to be set as the power output side based on the input instruction. In this embodiment, the selection unit 310 receives a direction command value, an E1 detection value, an E2 detection value, an E1 command value, and an E2 command value as input. Based on the direction command value, it selects which of the E1 and E2 detection values ​​to use as the detection value, and selects which of the E1 and E2 command values ​​to use as the command value (target value). When the direction command value indicates that power should be transferred from the primary side to the secondary side, the selection unit 310 selects the E2 detection value and E2 command value of the secondary side as the output target and outputs them. When the direction command value indicates that power should be transferred from the secondary side to the primary side, the selection unit 310 selects the E1 detection value and E1 command value of the primary side that are the output target and outputs them.

[0064] Subtractor 315 calculates the difference between the instruction value selected by selection unit 310 and the detection value. The subtractor 315 according to this embodiment calculates the difference obtained by subtracting the detection value from the instruction value.

[0065] The control arithmetic unit 320 outputs a control value corresponding to the difference between the output (in this embodiment, the detected value) of the circuits that serve as output sides in the primary circuit 130 and the secondary circuit 140 and the target value (command value). This control value is a value corresponding to the output of the circuits that serve as output sides in the primary circuit 130 and the secondary circuit 140; as an example, it could be a value representing the magnitude of the output at that timing.

[0066] The phase difference adjustment unit 330 adjusts the switching phase difference based on the output and target value of the circuits that become the output side in the primary circuit 130 and the secondary circuit 140. In this embodiment, the phase difference adjustment unit 330 adjusts the switching phase difference based on the control value output by the control calculation unit 320. The phase difference adjustment unit 330 receives the control value output by the control calculation unit 320 as a phase difference command and adjusts the switching phase difference ( Figure 2 The "primary / secondary phase difference" in the command is adjusted to a phase difference corresponding to the phase difference command. Here, when the phase difference command increases, the phase difference adjustment unit 330 adjusts the circuit on the power output side ( Figure 2 The switching of the secondary circuit 140 in the middle is relative to the circuit on the power input side. Figure 2 The phase delay of the switching of the primary circuit 130 increases, and the currents I1 and I2 increase to increase the output. When the phase difference command decreases, the phase delay is reduced, and the currents I1 and I2 are reduced to decrease the output.

[0067] The phase difference adjustment unit 330 includes a phase difference limiter 335 and a phase difference control unit 340. The phase difference limiter 335 restricts the phase difference command so that the switching phase difference does not become smaller than the lower limit phase difference. For example, when the phase difference limiter 335 receives a phase difference command instructing the phase difference to decrease compared to the lower limit phase difference, it limits the phase difference command to the lower limit value so that the phase difference does not decrease further. As an example, the lower limit phase difference can be 0, in which case the phase difference limiter 335 may not set the phase difference between the switching on the output side and the switching on the power input side circuit to be negative. Instead, the lower limit phase difference can also be a positive or negative value.

[0068] The phase difference control unit 340 receives a restricted phase difference command from the phase difference limiter 335 and controls the phase difference between the primary circuit 130 and the secondary circuit 140 according to the phase difference command. The phase difference control unit 340 can set the phase difference between the primary circuit 130 and the secondary circuit 140 to the phase difference specified by the phase difference command. Alternatively, the phase difference control unit 340 can also gradually change the phase difference between the primary circuit 130 and the secondary circuit 140 to approach the phase difference specified by the phase difference command, thereby preventing the phase difference from changing abruptly.

[0069] Then, the phase difference control unit 340 receives the switching waveform from the rest period adjustment unit 370, which is used by the circuits on the input side of the primary circuit 130 and the secondary circuit 140. Figure 2 In the example, the waveform is V1. The switching waveform is delayed by a delay amount corresponding to the set phase difference, thereby generating a switching waveform for the circuit that becomes the output side. Then, the phase difference control unit 340 outputs the corresponding input-side switching waveform and output-side switching waveform for the circuit that becomes the input side and the circuit that becomes the output side in the primary circuit 130 and the secondary circuit 140, respectively, according to the direction command value.

[0070] The frequency adjustment unit 350 adjusts the switching frequency of the primary circuit 130 and the secondary circuit 140 based on the output and target value from either the primary circuit 130 or the secondary circuit 140. Here, the frequency adjustment unit 350 adjusts the switching frequency based on the output and target value from the circuit that serves as the output side in either the primary circuit 130 or the secondary circuit 140. In this embodiment, the frequency adjustment unit 350 changes the switching frequency based on the condition that the phase difference adjustment unit 330 adjusts the switching phase difference to the lower limit phase difference.

[0071] The frequency adjustment unit 350 includes a subtractor 355, a frequency limiter 360, and a frequency control unit 365. The subtractor 355 outputs a frequency increment command corresponding to the difference between the restricted phase difference command output by the phase difference limiter 335 and the phase difference command output by the control calculation unit 320. Thus, the subtractor 355 outputs a value obtained by removing the adjustment amount of the phase difference adjustment unit 330 from the control value output by the control calculation unit 320, and the frequency adjustment unit 350 can adjust the switching frequency based on this value. In this embodiment, the subtractor 355 subtracts the phase difference command output by the control calculation unit 320 from the restricted phase difference command output by the phase difference limiter 335, thereby outputting the inverted value (negative value) of the command value obtained after removing the adjustment amount of the phase difference adjustment unit 330 as a frequency increment command. When the switched phase difference becomes the lower limit phase difference and the phase difference command is limited to the lower limit value, the frequency increment command becomes the following command: the frequency is increased based on the difference obtained by subtracting the actual phase difference command from the phase difference command that is limited to the lower limit value.

[0072] Frequency limiter 360 imposes a restriction on frequency increment commands so that the switching frequency does not exceed the upper limit frequency (also denoted as "fmax"). For example, frequency limiter 360 restricts frequency increment commands so that they are below the upper limit value corresponding to the upper limit frequency.

[0073] The frequency control unit 365 receives a restricted frequency increment command from the frequency limiter 360 and controls the switching frequency of the primary circuit 130 and the secondary circuit 140 according to the frequency increment command. The frequency control unit 365 can set the switching frequency of the primary circuit 130 and the secondary circuit 140 to the frequency specified by the frequency increment command. Alternatively, the frequency control unit 365 can also gradually change the switching frequency to approach the frequency specified by the frequency increment command, thereby preventing abrupt frequency changes. The frequency control unit 365 according to this embodiment generates a basic switching waveform at the frequency specified by the frequency increment command and outputs it to the rest period adjustment unit 370.

[0074] The pause period adjustment unit 370 adjusts the proportion of the pause period that causes the output from the primary circuit 130 or the secondary circuit 140 to pause based on the output and target value from the primary circuit 130 or the secondary circuit 140. Here, the pause period adjustment unit 370 adjusts the proportion of the pause period based on the output and target value from the circuit that becomes the output side of the primary circuit 130 and the secondary circuit 140. In this embodiment, the pause period adjustment unit 370 changes the proportion of the pause period based on the condition that the switching frequency is adjusted to the upper limit frequency by the frequency adjustment unit 350.

[0075] The pause period adjustment unit 370 includes a subtractor 375 and a pulse width control unit 380. The subtractor 375 outputs a pulse width reduction command corresponding to the difference between the restricted frequency increment command output by the frequency limiter 360 and the frequency increment command output by the subtractor 355. Thus, the subtractor 375 outputs a value obtained by removing the adjustment amounts of the phase difference adjustment unit 330 and the frequency adjustment unit 350 from the control value output by the control calculation unit 320. The pause period adjustment unit 370 can adjust the proportion of the pause period based on this value. In this embodiment, the subtractor 375 subtracts the restricted frequency increase command output by the frequency adjustment unit 350 from the frequency increase command output by the subtractor 355, thereby outputting the command value obtained after removing the adjustment amounts of the phase difference adjustment unit 330 and the frequency adjustment unit 350 as the pulse width reduction command. When the switching frequency becomes the upper limit frequency and the frequency increment command is limited to the upper limit value, the pulse width reduction command becomes the following command: the pulse width is reduced based on the difference obtained by subtracting the frequency increment command limited to the upper limit value from the actual frequency increment command.

[0076] The pulse width control unit 380 receives a pulse width reduction command and, within one cycle corresponding to the frequency set by the frequency adjustment unit 350, reduces the pulse width of the specified pulses applied during the switching periods of voltage V1 = E1 and -E1, and voltage V2 = E2 and -E2, respectively, in connection with the switching between the primary circuit 130 and the secondary circuit 140. This allows the pulse width control unit 380 to increase the proportion of the pause period in power transmission between the primary circuit 130 and the secondary circuit 140 within one cycle. In this embodiment, the larger the command value of the pulse width reduction command, the smaller the pulse width is reduced by the pulse width control unit 380. The pulse width control unit 380 can also gradually change the proportion of the pause period during switching to approximate the proportion of the pause period corresponding to the pulse width reduction command, thereby preventing the proportion of the pause period from changing abruptly. Then, the pulse width control unit 380 inputs the basic switching waveform generated by the frequency control unit 365, sets the pulse width of each pulse of the basic switching waveform to the pulse width corresponding to the pulse width reduction command, and outputs it to the phase difference control unit 340.

[0077] According to the control device 150 shown above, the phase difference, frequency, and rest period ratio can be adjusted based on the control value output by the same control arithmetic unit 320. Therefore, if multiple adjustment actions are performed based on the control value output by the same control arithmetic unit 320, control disturbances that may occur when different control arithmetic units are used for each type of adjustment action can be suppressed.

[0078] Figure 4The operation flow of the control device 150 according to this embodiment is shown. In step S400, the control device 150 inputs E1 command value, E2 command value, E1 detection value, E2 detection value and direction command value.

[0079] In S410, the selection unit 310 in the control device 150 selects the direction of power transmission according to the direction command value, selects the command value of the power output side from the E1 command value and the E2 command value and outputs the detection value of the power output side from the E1 detection value and the E2 detection value.

[0080] In S420, the subtractor 315 and the control arithmetic unit 320 within the control device 150 calculate the control value corresponding to the command value and detection value selected in S410. Here, the control arithmetic unit 320 can output the control value through PI control or PID control corresponding to the difference between the output and the target value. Alternatively, it can use any means, including averaging the difference between the output and the target value, to output a control value that reduces the difference between the output and the target value.

[0081] In S430, the phase difference adjustment unit 330 determines the phase difference for switching between the primary circuit 130 and the secondary circuit 140 based on the control value from the control calculation unit 320. In S440, the frequency adjustment unit 350 determines the switching frequency between the primary circuit 130 and the secondary circuit 140 based on the remaining component obtained after removing the amount used for phase difference adjustment by the phase difference adjustment unit 330 from the control value from the control calculation unit 320. In S450, the pause period adjustment unit 370 determines the proportion or length of the pause period for stopping power transmission between the primary circuit 130 and the secondary circuit 140 based on the remaining component obtained after removing the amount used for phase difference adjustment by the phase difference adjustment unit 330 and frequency adjustment by the frequency adjustment unit 350 from the control value from the control calculation unit 320.

[0082] In S460, the phase difference adjustment unit 330, the frequency adjustment unit 350, and the rest period adjustment unit 370 set the frequency, pulse width, and phase of the control signals c1 to c8 for the switching elements Q1 to Q8 according to the direction specified by the direction command value, the phase difference determined in S430, the frequency determined in S440, and the length of the rest period determined in S450, so as to switch the switching elements Q1 to Q4 in the primary circuit 130 and the switching elements Q5 to Q8 in the secondary circuit 140 according to the phase difference determined by them.

[0083] Figure 5This is an example of the operating waveform during the phase difference adjustment operation of the power conversion device 100 according to this embodiment. This figure shows the operating waveform when power is transferred from the primary side to the secondary side when the winding ratio of the transformer Tr is 1:1 and the voltage E1 of the primary side device 110 is higher than the voltage E2 of the secondary side device 120. Furthermore, the operating waveform in this figure is similar to... Figure 2 The V1 waveform, V2 waveform, and I1 waveform (E1 > E2) are the same, therefore, the explanation is omitted except for the following differences.

[0084] In the phase difference adjustment operation, the control device 150 switches the primary circuit 130 and the secondary circuit 140 at a fundamental frequency f1, and switches by maintaining a phase difference between the power output side and the power input side. The control arithmetic unit 320 adjusts the phase difference present during the switching between the primary circuit 130 and the secondary circuit 140 based on the difference between the command value and the detection value. Here, as with Figure 2 As illustrated in relation to this, the larger the phase difference command, the more the phase difference adjustment unit 330 increases the aforementioned phase difference. If the phase difference increases, the rise period of current I1 during the period of voltage V1 = voltage E1 and voltage V2 = voltage - E2 becomes longer, and the power supplied to the secondary-side device 120 increases after voltage V1 = voltage E1 and voltage V2 = voltage E2. Furthermore, if the phase difference increases, the fall period of current I1 during the period of voltage V1 = voltage - E1 and voltage V2 = voltage E2 becomes longer, and the power supplied to the secondary-side device 120 increases during the period of voltage V1 = voltage - E1 and voltage V2 = voltage - E2. Therefore, by increasing the phase difference, the control device 150 can increase the amount of power transmitted to the circuits that become the output side in the primary circuit 130 and the secondary circuit 140. Conversely, the smaller the phase difference command, the more the phase difference adjustment unit 330 reduces the aforementioned phase difference, thus shortening the rise period of current I1 during the voltage V1 = voltage E1 and voltage V2 = voltage - E2, and also shortening the fall period of current I1 during the voltage V1 = voltage - E1 and voltage V2 = voltage E2. Therefore, by reducing the phase difference, the control device 150 can reduce the amount of power transmitted to the output circuits in the primary circuit 130 and secondary circuit 140.

[0085] Here, in applications where the voltage on the power input side (e.g., voltage E1) in the primary-side device 110 and the secondary-side device 120 is significantly larger than the voltage on the power output side (e.g., voltage E2) (e.g., in the case of charging the battery on the power output side), even if... Figure 5Even with the phase difference set to 0 as shown, there is still a possibility that the magnitude of current I1 (≈ current I2) will continue to increase, leading to a larger power transmission amount. As shown below, the power conversion device 100 according to this embodiment suppresses the magnitude of the peak current I1 and the power transmission amount by performing a frequency adjustment operation.

[0086] Figure 6 This is an example of the waveforms during the frequency adjustment operation of the power conversion device 100 according to this embodiment. The figure shows the waveforms of voltage V1, voltage V2, and current I1 during the frequency adjustment operation in top-to-bottom order. Time is selected as the horizontal axis for each waveform.

[0087] The voltage waveforms V1 and V2 in this figure show the case where the voltage on the power input side (e.g., voltage E1) in the primary side device 110 and the secondary side device 120 is greater than the voltage on the power output side (e.g., voltage E2). In this case, as shown by the current waveform I1, the magnitude of the current I1 also increases during periods when the secondary side device 120 is charged with voltages V1 = E1 and V2 = E2, and during periods when the secondary side device 120 is charged with voltages V1 = -E1 and V2 = -E2.

[0088] The power conversion device 100 performs frequency adjustment based on the situation where the power to be transmitted from the primary side to the secondary side decreases and the phase difference is adjusted to the lower limit phase difference during the phase difference adjustment operation. During the frequency adjustment operation, when power should be transmitted from the power output side circuit of the primary circuit 130 and the secondary circuit 140, i.e., the primary side, to the secondary side, the control device 150 adjusts the switching frequency f2 of the primary circuit 130 and the secondary circuit 140 based on the output from the secondary circuit 140 and the target value.

[0089] As with Figure 2 As illustrated in the related diagram, the frequency adjustment unit 350 sets the negative value of the control value obtained by removing the adjustment amount of the phase difference adjustment unit 330 from the control value output by the control calculation unit 320 as the frequency increment command. Based on this frequency increment command, the smaller the phase difference command output by the control calculation unit 320, the more the frequency f2 is increased, thereby reducing the power transmission amount. In this embodiment, the frequency adjustment unit 350 changes the frequency f2 between the frequency f1 (when the phase difference adjustment operation is performed) and the upper limit frequency fmax based on the frequency increment command. If the frequency increases, the switching period 1 / f2 becomes shorter. Therefore, by increasing the frequency, the period during which the control device 150 increases the magnitude of the current I1 is shortened, suppressing the peak value of the current I1, and further reducing the transmitted power.

[0090] During frequency adjustment, the power conversion device 100 can reduce the amount of power transmitted by increasing the frequency without setting a rest period during each switching cycle. Here, if a rest period is set, no power is transmitted during the rest period, and therefore the peak value of the current flowing during the power transmission period becomes larger than the peak value of the current flowing during the same amount of power transmission when the frequency is increased by frequency adjustment. Therefore, when frequency adjustment is used, the amount of power transmitted at the same peak current can be further increased compared to the case where a rest period is set. The power conversion device 100 can perform frequency adjustment under conditions such as increased current outside the rest period and increased periodic current fluctuations when a rest period is set.

[0091] Figure 7 This is an example of the waveforms during the rest period adjustment operation of the power conversion device 100 according to this embodiment. The figure shows the waveforms of voltage V1, voltage V2, and current I1 during the rest period adjustment operation in top-to-bottom order. The period for each waveform is selected as the horizontal axis.

[0092] The voltage waveforms V1 and V2 in this figure show the case where the voltage (e.g., voltage E1) on the power input side of the primary side device 110 and the secondary side device 120 is greater than the voltage (e.g., voltage E2) on the power output side. In this case, as shown by the current waveform I1, the magnitude of the current I1 also increases during periods when the secondary side device 120 is charged with voltages V1 = E1 and V2 = E2, and during periods when the secondary side device 120 is charged with voltages V1 = -E1 and V2 = -E2.

[0093] The power conversion device 100 performs a rest period adjustment operation based on the situation where the power to be transferred from the primary side to the secondary side decreases during the frequency adjustment operation and the frequency is adjusted to the maximum frequency fmax. During the rest period adjustment operation, when power should be transferred from the power output side circuit of the primary circuit 130 and the secondary circuit 140, i.e., the primary side, to the secondary side, the control device 150 adjusts the proportion of the rest period during the switching of the primary circuit 130 and the secondary circuit 140 based on the output from the secondary circuit 140 and the target value.

[0094] As with Figure 2As shown in connection, the rest period adjustment unit 370 removes the adjustment amounts of the phase difference adjustment unit 330 and the frequency adjustment unit 350 from the control value output by the control calculation unit 320 and sets the resulting value as the pulse width reduction command. Based on this pulse width reduction command, the smaller the phase difference command output by the control calculation unit 320, the more the switching pulse width is reduced, thereby reducing the power transmission amount. Here, the control device 150 controls the switching elements Q1 to Q8. Taking the setting of voltage V1 = 0 and voltage V2 = 0 during the rest period as an example, the control device 150 can set the voltage V1 = 0 by setting the switching elements Q1 and Q3 to conduct and Q2 and Q4 to disconnect, thereby connecting the intermediate points a1 and b1 to the positive DC bus P1. Alternatively, it can set the voltage V1 = 0 by setting the switching elements Q1 and Q3 to disconnect and Q2 and Q4 to conduct, thereby connecting the intermediate points a1 and b1 to the negative DC bus N1. Furthermore, the control device 150 can also perform the same control on the switching elements Q5 to Q8 as it does on the switching elements Q1 to Q4, thereby setting the voltage V2 = 0.

[0095] During the rest period when voltage V1 = 0 and voltage V2 = 0, the primary circuit 130 circulates current through inductor L1 and transformer Tr without passing through the primary side device 10, and the secondary circuit 140 circulates current through inductor L2 and transformer Tr via the secondary side device 120. Therefore, the power conversion device 100 maintains currents I1 and I2 during the rest period. However, in reality, currents I1 and I2 may decrease slightly due to factors such as wiring impedance in the current circulation path. After the rest period ends, the power conversion device 100 recovers currents I1 and I2 into capacitors C1 and C2, or uses them in charging the primary side device 110 and secondary side device 120.

[0096] The power conversion device 100 of this embodiment performs control (so-called PWM control) by reducing the time width of power transmission in each switching cycle, thereby setting a rest period during which no power is transmitted. During the rest period adjustment operation, the power conversion device 100 increases the proportion of the rest period within one switching cycle, thus reducing the amount of power transmitted even when the switching frequency is increased. Here, the power conversion device 100 can also set a large portion of one switching cycle as a rest period, thus enabling the installation to handle the lower power transmission amount during the rest period adjustment operation compared to the frequency adjustment operation. On the other hand, during the rest period adjustment operation, the peak current during power transmission is larger than during the frequency adjustment operation, so the installation of the power conversion device 100 can increase the power transmission efficiency of the frequency adjustment operation. Therefore, in such an installation, the power conversion device 100 performs frequency adjustment operation, and when the power transmission amount decreases, it can efficiently transmit power by performing the rest period adjustment operation.

[0097] Instead, the power conversion device 100 can also perform control as described in the so-called burst control: setting a rest period that stops the periodic switching operation and prevents the transmission of circuitry for a certain period (e.g., a period longer than one cycle). Furthermore, the power conversion device 100 can switch between PWM control and burst control during the rest period based on the proportion of the target rest period.

[0098] In the embodiments shown above, the control device 150 switches between phase difference adjustment, frequency adjustment, and rest period adjustment. Alternatively, the control device 150 can adjust the power transmission amount by frequency adjustment without performing phase difference adjustment and rest period adjustment, or by a combination of phase difference adjustment and frequency adjustment, or by a combination of frequency adjustment and rest period adjustment.

[0099] Furthermore, as the requested power transmission amount decreases, the control device 150 can reduce the phase difference and increase the frequency instead of controlling the frequency adjustment operation after reaching the lower limit of the phase difference during the phase difference adjustment operation. Similarly, as the requested power transmission amount decreases, the control device 150 can also increase the frequency and increase the proportion of the rest period. In addition, the control device 150 can also change the phase difference, frequency, and proportion of the rest period all in parallel according to the requested power transmission amount.

[0100] Furthermore, when the frequency reaches the upper limit during frequency adjustment and transitions to a rest period adjustment operation, as the requested power transmission amount decreases, the control device 150 can increase the proportion of the rest period and decrease the frequency to reduce losses caused by switching. In this case, the control device 150 can also lower the switching frequency to a range up to the frequency used in the phase difference adjustment operation, for example, it can lower the switching frequency to a range above a predetermined lower limit frequency outside the audible range (e.g., above 20 kHz).

[0101] Furthermore, in the embodiments shown above, the power conversion device 100 employs a structure capable of bidirectional power transmission. Alternatively, the power conversion device 100 can also be controlled by the control device 150 to transmit power only in one direction, such as from the primary side to the secondary side.

[0102] Various embodiments of the present invention can be described with reference to flowcharts and block diagrams, where a block may represent (1) a stage of a process in which an operation is performed or (2) a portion of a device having the function of performing the operation. Specific stages and portions may be installed using dedicated circuitry, programmable circuitry provided with computer-readable instructions stored on a computer-readable medium, and / or a processor provided with computer-readable instructions stored on a computer-readable medium. Dedicated circuitry may include digital and / or analog hardware circuitry, or integrated circuits (ICs) and / or discrete circuitry. Programmable circuitry may include reconfigurable hardware circuitry including logical AND, logical OR, logical XOR, logical NAND, logical NOR and other logic operations, flip-flops, registers, memory elements such as field-programmable gate arrays (FPGAs), programmable logic arrays (PLAs), etc.

[0103] Computer-readable media can contain any tangible device capable of storing instructions executable by suitable devices. As a result, computer-readable media having instructions stored therein include products containing executable instructions for generating units that perform operations specified by flowcharts or block diagrams. Examples of computer-readable media include electronic storage media, magnetic storage media, optical storage media, electromagnetic storage media, semiconductor storage media, etc. More specific examples of computer-readable media include floppy disks, magnetic disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), electrically erasable programmable memory (EEPROM), static random access memory (SRAM), optical disc read-only memory (CD-ROM), digital versatile disc (DVD), Blu-ray (RTM) discs, memory sticks, integrated circuit cards, etc.

[0104] Computer-readable commands may include any of the following programs: assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code described using any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, Java (registered trademark), C++, and the "C" programming language or existing procedural programming languages ​​containing the same programming language.

[0105] Computer-readable instructions can be provided via a local area network (LAN), a wide area network (WAN) such as the Internet, to the processor or programmable circuit of a general-purpose computer, a special-purpose computer, or other programmable data processing device, in order to create units for performing the operations specified by the flowchart or block diagram, and to execute the computer-readable instructions. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, etc.

[0106] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. Those skilled in the art will recognize that various changes or improvements can be made to the above embodiments. As can be clearly understood from the scope of the claims, such changes or improvements are also included within the technical scope of the present invention.

[0107] It should be noted that the execution order of actions, sequences, steps, and stages in the apparatus, systems, programs, and methods shown in the claims, specification, and drawings can be implemented in any order, unless explicitly indicated as "before," "previously," etc., and unless the output of a previous process is used in a subsequent process. The use of terms such as "firstly," "then," etc., in the action flow of the claims, specification, and drawings for ease of explanation does not imply that the actions must be performed in this order.

[0108] Label Explanation

[0109] 100 Power conversion device, 110 Primary side device, 120 Secondary side device, 130 Primary circuit, 140 Secondary circuit, 150 Control device, 310 Selection unit, 315 Subtractor, 320 Control and calculation unit, 330 Phase difference adjustment unit, 335 Phase difference limiter, 340 Phase difference control unit, 350 Frequency adjustment unit, 355 Subtractor, 360 Frequency limiter, 365 Frequency control unit, 370 Rest period adjustment unit, 375 Subtractor, 380 Pulse width control unit.

Claims

1. A power conversion device, characterized in that, include: transformer; A first bridge circuit is connected to the primary side of the transformer and is capable of changing the polarity of the DC bus pair on the primary side connected to the transformer. A second bridge circuit, which is connected to the secondary side of the transformer, is capable of switching the polarity of the DC bus pair on the secondary side connected to the transformer. as well as The control device is capable of switching the first bridge circuit and the second bridge circuit by creating a phase difference. The control device has: A frequency adjustment unit adjusts the switching frequency of the first bridge circuit and the second bridge circuit based on the output and target value from the first bridge circuit or the second bridge circuit. A phase difference adjustment unit adjusts the switching phase difference based on the output and the target value; A pause period adjustment unit adjusts the ratio of the pause period that causes the output from the first bridge circuit or the second bridge circuit to pause based on the output and the target value. as well as The control calculation unit outputs a control value corresponding to the difference between the output and the target value. The phase difference adjustment unit adjusts the switching phase difference according to the control value. The frequency adjustment unit adjusts the switching frequency based on the value obtained by removing the adjustment amount from the phase difference adjustment unit from the control value. The pause period adjustment unit adjusts the proportion of the pause period based on the value obtained after removing the adjustment amounts of the phase difference adjustment unit and the frequency adjustment unit from the control value.

2. The power conversion device as described in claim 1, characterized in that, The frequency adjustment unit changes the switching frequency based on the condition that the phase difference of the switching is adjusted to the lower limit phase difference.

3. The power conversion device as described in claim 1, characterized in that, The pause adjustment unit changes the proportion of the pause period based on the condition that the switching frequency is adjusted to the upper limit frequency.

4. The power conversion device as described in claim 2, characterized in that, The pause adjustment unit changes the proportion of the pause period based on the condition that the switching frequency is adjusted to the upper limit frequency.

5. The power conversion device as described in claim 1, characterized in that, The control calculation unit outputs the control value through PI control or PID control corresponding to the difference between the output and the target value.

6. The power conversion device as described in claim 2, characterized in that, The control calculation unit outputs the control value through PI control or PID control corresponding to the difference between the output and the target value.

7. The power conversion device as described in claim 3, characterized in that, The control calculation unit outputs the control value through PI control or PID control corresponding to the difference between the output and the target value.

8. The power conversion device as described in claim 4, characterized in that, The control calculation unit outputs the control value through PI control or PID control corresponding to the difference between the output and the target value.

9. The power conversion device according to any one of claims 1 to 8, characterized in that, The control device further includes a selection unit that selects which of the first bridge circuit and the second bridge circuit to be set as the power output side according to the input instruction.

10. A control method, This control method is a control method for a power conversion device, characterized in that... The power conversion device includes: transformer; A first bridge circuit is connected to the primary side of the transformer and is capable of changing the polarity of the DC bus pair on the primary side connected to the transformer. A second bridge circuit, connected to the secondary side of the transformer, is capable of reversing the polarity of the DC bus pair connected to the transformer on the secondary side; and The control device is capable of switching the first bridge circuit and the second bridge circuit by creating a phase difference. The control method includes the following steps: The switching frequency of the first bridge circuit and the second bridge circuit is adjusted based on the output and target value from the first bridge circuit or the second bridge circuit. The phase difference of the switching is adjusted based on the output and the target value; Based on the output and the target value, the proportion of the pause period that causes the output from the first bridge circuit or the second bridge circuit to pause is adjusted; and Output a control value corresponding to the difference between the output and the target value. In the control method, The phase difference of the switching is adjusted according to the control value. The switching frequency is adjusted based on the value obtained after removing the adjustment amount of the phase difference adjustment unit from the control value. The proportion of the rest period is adjusted based on the value obtained after removing the adjustment amounts of the phase difference adjustment unit and the frequency adjustment unit from the control value.

11. The control method as described in claim 10, characterized in that, The frequency is adjusted by changing the switching frequency on the condition that the phase difference of the switching is adjusted to the lower limit phase difference.

12. A computer-readable medium, The computer-readable medium is a computer-readable medium that records a control program for controlling a power conversion device, characterized in that... The power conversion device includes: transformer; A first bridge circuit is connected to the primary side of the transformer and is capable of changing the polarity of the DC bus pair on the primary side connected to the transformer. A second bridge circuit, connected to the secondary side of the transformer, is capable of reversing the polarity of the DC bus pair connected to the transformer on the secondary side; and The control device is capable of switching the first bridge circuit and the second bridge circuit by creating a phase difference. The control program enables the control device It functions as a frequency adjustment unit, which adjusts the switching frequency of the first bridge circuit and the second bridge circuit based on the output and target value from the first bridge circuit or the second bridge circuit. It functions as a phase difference adjustment unit, which adjusts the switching phase difference based on the output and the target value; Functioning as a pause period adjustment unit, this pause period adjustment unit adjusts the proportion of the pause period that causes the output from the first bridge circuit or the second bridge circuit to pause, based on the output and the target value; and This unit functions as a control arithmetic unit, outputting a control value corresponding to the difference between the output and the target value. The phase difference adjustment unit adjusts the switching phase difference according to the control value. The frequency adjustment unit adjusts the switching frequency based on the value obtained by removing the adjustment amount from the phase difference adjustment unit from the control value. The pause period adjustment unit adjusts the proportion of the pause period based on the value obtained after removing the adjustment amounts of the phase difference adjustment unit and the frequency adjustment unit from the control value.

13. The computer-readable medium as claimed in claim 12, characterized in that, The frequency adjustment unit changes the switching frequency based on the condition that the phase difference of the switching is adjusted to the lower limit phase difference.

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