Power conversion device, power conversion method, and program

Abstract

The power conversion device (1) includes a matrix conversion circuit (10) having a plurality of switching elements and performing bidirectional power conversion between primary-side AC power and secondary-side AC power, a power conversion control unit (114) that switches on / off of the plurality of switching elements in association with a carrier in such a manner that the secondary-side AC power follows a control command, and a carrier change unit (116) that changes a frequency of the carrier based on a level of proximity between a frequency of the primary side and a frequency of the secondary side.

Description

Technical Field

[0001] This disclosure relates to a power conversion device, a power conversion method, and a procedure. Background Technology

[0002] Patent document 1 discloses a matrix converter having multiple bidirectional switches that connect each phase of an AC power source to each phase of an AC device, which outputs power generated by the AC device to the AC power source and controls the AC device based on the power supplied from the AC power source.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-67169 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] This disclosure provides a power conversion device that effectively suppresses heat generation in switching elements.

[0008] Technical solution

[0009] One aspect of the power conversion apparatus disclosed herein includes: a matrix converter circuit having multiple switching elements and performing bidirectional power conversion between primary-side AC power and secondary-side AC power; a power conversion control unit that switches the multiple switching elements on / off in conjunction with a carrier wave such that the secondary-side AC power follows a control command; and a carrier wave changing unit that changes the frequency of the carrier wave based on the proximity level between the primary-side frequency and the secondary-side frequency.

[0010] Another aspect of the power conversion method disclosed herein includes: switching the on / off state of the multiple switching elements in conjunction with a carrier wave in a manner that causes the AC on the secondary side of a matrix conversion circuit having multiple switching elements and performing bidirectional power conversion between AC on the primary side and AC on the secondary side to follow control commands; and changing the frequency of the carrier wave based on the proximity level between the frequency on the primary side and the frequency on the secondary side.

[0011] Another aspect of the procedure of this disclosure enables the power conversion device to perform: switching the multiple switching elements on / off in conjunction with a carrier wave in a manner that causes the AC on the secondary side of a matrix conversion circuit having multiple switching elements and performing bidirectional power conversion between AC on the primary side and AC on the secondary side to follow control commands; and changing the frequency of the carrier wave based on the proximity level between the frequency on the primary side and the frequency on the secondary side.

[0012] Invention Effects

[0013] According to this disclosure, a power conversion device that effectively suppresses heat generation in switching elements can be provided. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the configuration of a power conversion device.

[0015] Figure 2 This is a schematic diagram illustrating a specific example of a two-way switch.

[0016] Figure 3 This is a graph illustrating the relationship between the carrier frequency and the rated current.

[0017] Figure 4 It is a graph showing the setting examples of frequency band and current band.

[0018] Figure 5 This is a block diagram illustrating the hardware configuration of a control circuit.

[0019] Figure 6 This is a flowchart illustrating the control process of a matrix transformation circuit.

[0020] Figure 7 This is an example illustrating the following: Figure 4 The flowchart shows the process of setting the frequency of the carrier wave.

[0021] Figure 8 This is an example illustrating the following: Figure 4 The flowchart shows the process of setting the frequency of the carrier wave.

[0022] Figure 9 This is an example illustrating the following: Figure 4 The flowchart shows the process of setting the frequency of the carrier wave.

[0023] Figure 10 It is a graph showing a variation of the frequency band and current band settings.

[0024] Figure 11 This is an example illustrating the following: Figure 10 The flowchart shows the process of setting the frequency of the carrier wave.

[0025] Figure 12 This is an example illustrating the following: Figure 10 The flowchart shows the process of setting the frequency of the carrier wave.

[0026] Figure 13 This is an example illustrating the following: Figure 10 The flowchart shows the process of setting the frequency of the carrier wave.

[0027] Figure 14 This is an example illustrating the following: Figure 10 The flowchart shows the process of setting the frequency of the carrier wave. Detailed Implementation

[0028] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used to refer to the same elements or elements having the same function, and repeated descriptions are omitted.

[0029] [Power conversion device]

[0030] Figure 1 The power conversion device 1 shown is a device that performs bidirectional power conversion between primary-side AC power and secondary-side AC power. For example, the power conversion device 1 converts the primary-side AC power supplied from the power source 91 into secondary-side AC power and supplies it to the motor 92. In addition, the power conversion device 1 converts the secondary-side AC power (regenerated power) generated by the motor 92 into primary-side AC power and supplies it to the power source 91.

[0031] The alternating current (AC) on both the primary and secondary sides can be either single-phase or three-phase. The following explanation addresses the case where both the primary and secondary AC sides are three-phase. For example, the primary AC side may consist of phases R, S, and T, while the secondary AC side may consist of phases U, V, and W.

[0032] The power conversion device 1 includes a matrix conversion circuit 10, a filter 30, a voltage detection circuit 40, a current sensor 50, and a control circuit 100.

[0033] The matrix converter circuit 10 has multiple switching elements, enabling bidirectional power conversion between primary and secondary AC power without DC conversion. For example, the matrix converter circuit 10 includes: primary power lines 11R, 11S, and 11T; secondary power lines 12U, 12V, and 12W; and nine sets of bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW. Power line 11R is the R-phase transmission line, power line 11S is the S-phase transmission line, and power line 11T is the T-phase transmission line. Power line 12U is the U-phase transmission line, power line 12V is the V-phase transmission line, and power line 12W is the W-phase transmission line.

[0034] Each of the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW switches between three states: a state allowing current to flow from the primary side to the secondary side, a state allowing current to flow from the secondary side to the primary side, and a state where no current flows. Bidirectional switch 2RU, located between power line 11R and power line 12U, switches between three states: a first closed state allowing current to flow from power line 11R to power line 12U, a second closed state allowing current to flow from power line 12U to power line 11R, and a bidirectional open state where no current flows. Bidirectional switch 2SU, located between power line 11S and power line 12U, switches between three states: a first closed state allowing current to flow from power line 11S to power line 12U, a second closed state allowing current to flow from power line 12U to power line 11S, and a bidirectional open state where no current flows. The bidirectional switch 2TU is located between power line 11T and power line 12U, and switches between the following states: a first closed state that allows current to flow from power line 11T to power line 12U, a second closed state that allows current to flow from power line 12U to power line 11T, and a bidirectional open state that prevents current from flowing.

[0035] Bidirectional switch 2RV is located between power line 11R and power line 12V, and switches between the following states: a first ON state allowing current to flow from power line 11R to power line 12V, a second ON state allowing current to flow from power line 12V to power line 11R, and a bidirectional OFF state where no current flows. Bidirectional switch 2SV is located between power line 11S and power line 12V, and switches between the following states: a first ON state allowing current to flow from power line 11S to power line 12V, a second ON state allowing current to flow from power line 12V to power line 11S, and a bidirectional OFF state where no current flows. Bidirectional switch 2TV is located between power line 11T and power line 12V, and switches between the following states: a first ON state allowing current to flow from power line 11T to power line 12V, a second ON state allowing current to flow from power line 12V to power line 11T, and a bidirectional OFF state where no current flows.

[0036] Bidirectional switch 2RW is located between power lines 11R and 12W, and switches between the following states: a first closed state allowing current to flow from power line 11R to power line 12W; a second closed state allowing current to flow from power line 12W to power line 11R; and a bidirectional open state where no current flows. Bidirectional switch 2SW is located between power lines 11S and 12W, and switches between the following states: a first closed state allowing current to flow from power line 11S to power line 12W; a second closed state allowing current to flow from power line 12W to power line 11S; and a bidirectional open state where no current flows. Bidirectional switch 2TW is located between power lines 11T and 12W, and switches between the following states: a first closed state allowing current to flow from power line 11T to power line 12W; a second closed state allowing current to flow from power line 12W to power line 11T; and a bidirectional open state where no current flows.

[0037] like Figure 2 As illustrated in the examples, the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW each have two switches 21 and 22. When switch 21 is in the ON state, it allows current to flow from the primary side to the secondary side but prevents current from flowing from the secondary side to the primary side. When switch 22 is in the ON state, it allows current to flow from the secondary side to the primary side but prevents current from flowing from the primary side to the secondary side. The bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW are changed to the first ON state by setting switch 21 to the ON state and switch 22 to the OFF state; they are changed to the second ON state by setting switch 21 to the OFF state and switch 22 to the ON state; and they are changed to the bidirectional OFF state by setting both switches 21 and 22 to the OFF state.

[0038] Return to Figure 1The filter 30 reduces high-order harmonics of the primary-side alternating current. For example, the filter 30 includes inductors 31R, 31S, and 31T, and capacitors 34R, 34S, and 34T. Inductors 31R, 31S, and 31T are respectively located on power lines 11R, 11S, and 11T. Capacitor 34R is located between power line 11R and neutral point 35, on the secondary side of inductor 31R (between inductor 31R and bidirectional switches 2RU, 2RV, and 2RW). Capacitor 34S is located between power line 11S and neutral point 35, on the secondary side of inductor 31S (between inductor 31S and bidirectional switches 2SU, 2SV, and 2SW). Capacitor 34T is located between power line 11T and neutral point 35, on the secondary side of inductor 31T (between inductor 31T and bidirectional switches 2TU, 2TV, and 2TW). The voltage detection circuit 40 detects the AC voltage on the primary side. For example, the voltage detection circuit 40 detects the phase voltage of each of the power lines 11R, 11S, and 11T.

[0039] The current sensor 50 detects the magnitude of the current on the secondary side (the current flowing between the matrix converter circuit 10 and the motor 92). For example, the current sensor 50 detects the magnitude of the current in the power lines 12U, 12V, and 12W. The current sensor 50 can be configured to detect the magnitude of the current in all phases of the power lines 12U, 12V, and 12W, or it can be configured to detect the magnitude of the current in any two phases of the power lines 12U, 12V, and 12W. Unless a zero-phase current is generated, the sum of the magnitudes of the currents in phases U, V, and W is zero. Therefore, even when detecting the magnitudes of two-phase currents, information about the magnitude of the current in all phases can be obtained.

[0040] The control circuit 100 executes the following actions: switching the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW on / off in conjunction with the carrier wave, such that the secondary-side AC follows the control command; and changing the carrier wave frequency based on the proximity level between the primary-side frequency (the frequency of the primary-side AC) and the secondary-side frequency (the frequency of the secondary-side AC). It should be noted that "making the secondary-side AC follow the control command" means making the physical quantities related to the electrical state of the AC power on the secondary side follow the control command. Examples of physical quantities related to the electrical state include electrical power, voltage, and current. Furthermore, "AC frequency" refers to the frequency of the AC voltage or the frequency of the AC current.

[0041] As a specific example of a control command, a voltage command can be cited. When the control command is a voltage command, the control circuit 100 switches the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW on / off in such a way that the AC voltage on the secondary side follows the voltage command.

[0042] For example, the control circuit 100 has a functional configuration including a current information acquisition unit 111, a command generation unit 112, a phase / amplitude calculation unit 113, a power conversion control unit 114, a rated current changing unit 115, and a carrier wave changing unit 116 (hereinafter referred to as "functional blocks"). The current information acquisition unit 111 acquires current information of the power lines 12U, 12V, and 12W from the current sensor 50.

[0043] The instruction generation unit 112 generates a voltage instruction based on a frequency instruction and the secondary-side current information acquired by the current information acquisition unit 111. The instruction generation unit 112 acquires the frequency instruction from, for example, a host controller 200. A specific example of the host controller 200 could be a programmable logic controller (PLC). For example, the instruction generation unit 112 calculates the voltage instruction in such a way that the operating speed (e.g., rotational speed) of the motor 92 follows the frequency instruction.

[0044] The phase / amplitude calculation unit 113 calculates the phase, amplitude, and frequency of the primary-side AC voltage based on the phase voltages of the power lines 11R, 11S, and 11T obtained from the voltage detection circuit 40. Hereinafter, the calculation results of the phase, amplitude, and frequency will be referred to as "primary-side voltage information." The power conversion control unit 114 switches the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW on / off in a manner that causes the secondary-side AC voltage to follow the control command in conjunction with the carrier wave. For example, the power conversion control unit 114 switches the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW on / off in a manner that causes the secondary-side AC voltage to follow the voltage command in conjunction with the carrier wave.

[0045] Alternatively, the power conversion control unit 114 may switch the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW on / off in a manner that limits the magnitude of the secondary side current based on the rated current of the secondary side. For example, the command generation unit 112 generates a voltage command in a manner that limits the magnitude of the secondary side current to below a current limit value specified based on the rated current. By generating the voltage command in this manner, the power conversion control unit 114 switches the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW on / off to limit the magnitude of the secondary side current to below the current limit value. At this time, the power conversion control unit 114 switches the on / off state of the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW by keeping the current magnitude of the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW continuously at a current limit value for the on-time.

[0046] When the carrier frequency is greater than a predetermined threshold (hereinafter referred to as the "current adjustment threshold"), the rated current changing unit 115 reduces the rated current on the secondary side according to the increase in carrier frequency; when the carrier frequency is less than the current adjustment threshold, it keeps the rated current on the secondary side constant. Figure 3 As shown, for example, when the carrier frequency is greater than the current adjustment threshold CT1, the rated current changing unit 115 calculates the rated current of the secondary side corresponding to the carrier frequency based on the adjustment curve CP1, which represents the relationship between the carrier frequency and the rated current of the secondary side. The adjustment curve CP1 is determined to be such that the rated current of the secondary side decreases as the carrier frequency increases. As an example, the adjustment curve CP1 may be determined to be such that the rated current decreases as a linear function of the increase in carrier frequency.

[0047] Here, the power loss in each of the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW includes switching loss and steady-state loss. Switching loss is the loss that occurs during the on / off switching process. Steady-state loss is the loss caused by the current flowing steadily in the on state.

[0048] As the carrier frequency increases, the switching frequency of the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW increases, thus increasing switching losses. Therefore, with steady-state losses remaining constant, power losses increase with increasing carrier frequency. Conversely, if the rated current on the secondary side is reduced according to the increased carrier frequency, the steady-state losses will decrease. Therefore, it is possible to suppress the increase in power losses due to increased carrier frequency.

[0049] As described above, the rated current changing unit 115 keeps the rated current constant when the carrier frequency is lower than the current adjustment threshold. For example, the rated current changing unit 115 sets the rated current to a predetermined fixed current value when the carrier frequency is lower than the current adjustment threshold. The fixed current value may be the rated current value corresponding to the current adjustment threshold on the adjustment curve CP1.

[0050] Return to Figure 1 The carrier frequency change unit 116 changes the carrier frequency based on the proximity level between the primary side frequency and the secondary side frequency. For example, the carrier frequency change unit 116 may change the carrier frequency based on the proximity level between the primary side frequency (included in the primary side voltage information) and the voltage command frequency. There are no particular limitations on the evaluation method for the proximity level, which represents the proximity level between the primary side frequency and the voltage command frequency. For example, the carrier frequency change unit 116 may evaluate the proximity level based on the absolute value of the difference between the primary side frequency and the voltage command frequency.

[0051] As an example, the variable range of the secondary side frequency implemented by the power conversion control unit 114 includes: a first frequency band, including the same frequency as the primary side; a second frequency band, which is lower than the first frequency band; and a third frequency band, which is higher than the first frequency band. Here, "the frequency band" means that the maximum value of the frequency band is lower than the minimum value of the other frequency bands. "The frequency band" means that the minimum value of the frequency band is higher than the maximum value of the other frequency bands. The same applies below.

[0052] When the frequency on the secondary side is within the second frequency band and when the frequency on the secondary side is within the third frequency band, the carrier change unit 116 sets the carrier frequency to the first carrier frequency. When the frequency on the secondary side is within the first frequency band, the carrier frequency is set to the second carrier frequency, which is lower than the first carrier frequency.

[0053] The carrier frequency changing unit 116 can set the first carrier frequency to a value higher than or equal to the current adjustment threshold, and set the second carrier frequency to a value lower than or equal to the current adjustment threshold. The carrier frequency changing unit 116 can also set the second carrier frequency to a value higher than the cutoff frequency of the filter 30.

[0054] The variable range of the secondary side frequency implemented by the power conversion control unit 114 may also include a fourth frequency band that is lower than the second frequency band. When the frequency of the secondary side is within the fourth frequency band, the carrier change unit 116 may also set the carrier frequency to the second carrier frequency.

[0055] The carrier frequency can be further changed based on the magnitude of the secondary current. As an example, the variable range of the secondary current magnitude implemented by the power conversion control unit 114 may include a first current band and a second current band that is lower than the first current band.

[0056] It is possible that when the magnitude of the secondary-side current is within the second current band, the carrier frequency change unit 116 does not change the carrier frequency based on a near-horizontal level; however, when the magnitude of the secondary-side current is within the first current band, it changes the carrier frequency based on a near-horizontal level. For example, when the magnitude of the secondary-side current is within the second current band, the carrier frequency is set to the first carrier frequency. Furthermore, when the magnitude of the secondary-side current is within the first current band, the carrier frequency change unit 116 changes the carrier frequency based on whether the secondary-side frequency belongs to a first, second, third, or fourth frequency band. For example, when the secondary-side frequency is within the second and third frequency bands, the carrier frequency is set to the first carrier frequency; when the secondary-side frequency is within the first and fourth frequency bands, the carrier frequency is set to the second carrier frequency.

[0057] Figure 4 This is a graph showing the setting examples of frequency band and current band. The vertical axis represents the magnitude of the secondary current, and the horizontal axis represents the frequency of the secondary side. Figure 4 In this circuit, the variable range of the secondary side current, implemented by the power conversion control unit 114, includes a current band AR1 and a current band AR2 that is lower than current band AR1. The minimum value of current band AR1 is, for example, the rated current. The minimum value of current band AR2 is zero, and the maximum value of current band AR2 is below the rated current. For example, the maximum value of current band AR2 is smaller than the minimum value of current band AR1, and a buffer band AR3 is sandwiched between current band AR1 and current band AR2.

[0058] The variable range of the secondary side frequency implemented by the power conversion control unit 114 includes: frequency band FR1 (first frequency band), which includes the same frequency F1 as the primary side frequency; frequency band FR2 (second frequency band), which is lower than frequency band FR1; frequency band FR3 (third frequency band), which is higher than frequency band FR1; and frequency band FR4 (fourth frequency band), which is lower than frequency band FR2.

[0059] For example, the minimum value of frequency band FR1 is 85%–95% of frequency F1, and the maximum value of frequency band FR1 is 105%–110% of frequency F1. The minimum value of frequency band FR4 is zero, and the maximum value of frequency band FR4 is 5%–15% of frequency F1. The minimum value of frequency band FR2 is greater than the maximum value of frequency band FR4. For example, the minimum value of frequency band FR2 is greater than the maximum value of frequency band FR4, and a buffer band FR5 exists between frequency bands FR4 and FR2. The maximum value of frequency band FR2 is less than the minimum value of frequency band FR1. For example, the maximum value of frequency band FR2 is less than the minimum value of frequency band FR1, and a buffer band FR6 exists between frequency bands FR2 and FR1. The minimum value of frequency band FR3 is greater than the maximum value of frequency band FR1. For example, the minimum value of frequency band FR3 is greater than the maximum value of frequency band FR1, and a buffer band FR7 exists between frequency bands FR1 and FR3.

[0060] exist Figure 4 In the example, when the secondary side current is within current band AR2, the carrier conversion unit 116 sets the carrier frequency to the first carrier frequency. When the secondary side current is within current band AR1, the carrier conversion unit 116 changes the carrier frequency based on which frequency band FR1, FR2, FR3, or FR4 the secondary side frequency belongs to. For example, when the secondary side frequency is within frequency band FR2 and frequency band FR3, the carrier conversion unit 116 sets the carrier frequency to the first carrier frequency; when the secondary side frequency is within frequency band FR1 and frequency band FR4, the carrier frequency is set to the second carrier frequency. When the secondary side frequency is within buffer band FR5, buffer band FR6, or buffer band FR7, the carrier conversion unit 116 does not change the carrier frequency.

[0061] In this way, when the magnitude of the current on the secondary side is within the current band AR1, the frequency of the carrier will be changed depending on which of the frequency bands FR1, FR2, FR3, and FR4 the secondary side frequency belongs to. Therefore, the current band AR1 is equivalent to an example of the first current band mentioned above.

[0062] When the secondary side current is within buffer band AR3, the carrier conversion unit 116 sets the carrier frequency to the first carrier frequency when the secondary side frequency is within band FR2 and when the secondary side frequency is within band FR3. When the secondary side current is within buffer band AR3, the carrier conversion unit 116 does not perform carrier frequency conversion when the secondary side frequency is outside band FR2 and outside band FR3. Although no frequency conversion is performed when the secondary side frequency is within band FR1 or band FR4, when the secondary side current is within buffer band AR3, no change in carrier frequency from the first carrier frequency to the second carrier frequency occurs. On the other hand, when the secondary side frequency is within band FR2 or band FR3, the carrier frequency changes from the second carrier frequency to the first carrier frequency. For example, in band FR4, the secondary side current changes from within current band AR1 to within buffer band AR3 and maintains the second carrier frequency. In this state, the secondary side frequency changes, passing through buffer band FR5 and becoming within band FR2. Therefore, buffer band AR3 is also an example of the first current band mentioned above.

[0063] It should be noted that since the functional blocks described above are components of the control circuit 100, the processing performed by each functional block is equivalent to the processing performed by the control circuit 100.

[0064] Figure 5 This is a block diagram illustrating the hardware configuration of the control circuit 100. For example... Figure 5As shown, the control circuit 100 includes one or more processors 191, memory 192, storage 193, communication port 194, input / output port 195, and switch control circuit 196. Memory 193 is, for example, a non-volatile semiconductor memory or other computer-readable storage medium. Memory 193 stores a program that causes the power conversion device to perform: switching the AC on / off of multiple switching elements in conjunction with a carrier wave in a manner that causes the AC on the secondary side of a matrix converter circuit having multiple switching elements and performing bidirectional power conversion between primary and secondary AC power, in accordance with control commands; and changing the carrier wave frequency based on the proximity level between the primary and secondary frequencies. Memory 192 temporarily stores the program loaded from the storage medium of memory 193 and the calculation results implemented by processor 191. The processor 191 and memory 192 cooperate in executing the above-mentioned programs to constitute the functional blocks of the control circuit 100. Input / output port 195 performs electrical signal input / output between voltage detection circuit 40 and current sensor 50 according to instructions from processor 191. Communication port 194 communicates with the host controller 200 according to instructions from processor 191. Switch control circuit 196 outputs drive signals to matrix conversion circuit 10 to switch the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW on / off according to instructions from processor 191.

[0065] It should be noted that the control circuit 100 is not necessarily limited to having its functions configured by a program. For example, the control circuit 100 may also have at least a portion of its functions configured by a dedicated logic circuit or an ASIC (Application Specific Integrated Circuit) that integrates dedicated logic circuits.

[0066] [Electricity conversion process]

[0067] Next, as an example of a power conversion method, the control process of the matrix converter circuit 10 executed by the control circuit 100 is illustrated. This process includes: switching the AC on / off of the secondary side of the matrix converter circuit, which has multiple switching elements and performs bidirectional power conversion between primary and secondary AC, in a manner that follows control commands and is linked to a carrier wave; and changing the frequency of the carrier wave based on the proximity level between the primary and secondary frequencies.

[0068] like Figure 6As shown, the control circuit 100 sequentially executes steps S01, S02, S03, S04, S05, S06, and S07. In step S01, the current information acquisition unit 111 acquires the current information of the power lines 12U, 12V, and 12W from the current sensor 50. In step S02, the command generation unit 112 generates a voltage command based on the frequency command and the secondary-side current information acquired by the current information acquisition unit 111.

[0069] In step S03, based on the phase voltages of the power lines 11R, 11S, and 11T obtained by the voltage detection circuit 40, the phase / amplitude calculation unit 113 calculates the phase, amplitude, and frequency of the AC voltage on the primary side (the aforementioned primary side voltage information). In step S04, the carrier frequency change unit 116 sets the carrier frequency based on the magnitude of the current on the secondary side and the frequency of the secondary side. The process of setting the carrier frequency will be described later.

[0070] In step S05, the rated current changing unit 115 sets the rated current of the secondary side based on the carrier frequency set in step S04. For example, if the carrier frequency is lower than the current adjustment threshold, the rated current changing unit 115 sets the rated current of the secondary side to the fixed current value. If the carrier frequency is higher than the current adjustment threshold, the rated current changing unit 115 sets the rated current of the secondary side based on the adjustment curve CP1 and the carrier frequency. In step S06, the command generation unit 112 corrects the voltage command to limit the magnitude of the secondary side current to below the rated current. In step S07, the power conversion control unit 114 starts switching the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, and 2TW on / off in conjunction with the carrier to make the AC on the secondary side follow the control command. The control circuit 100 repeats the above process at a predetermined control cycle.

[0071] Figure 7 This is a flowchart illustrating the process of setting the carrier frequency in step S04. For example... Figure 7 As shown, the control circuit 100 first executes step S11. In step S11, the carrier changing unit 116 checks whether the magnitude of the current on the secondary side is within the current band AR2. If it is determined in step S11 that the magnitude of the current on the secondary side is within the current band AR2, the control circuit 100 executes step S12. In step S12, the carrier changing unit 116 sets the frequency of the carrier to the aforementioned first carrier frequency.

[0072] If, in step S11, it is determined that the magnitude of the current on the secondary side is not within the current band AR2, the control circuit 100 executes step S13. In step S13, the carrier conversion unit 116 confirms whether the magnitude of the current on the secondary side is within the current band AR1.

[0073] In step S13, if the magnitude of the secondary current is determined to be within current band AR1, then... Figure 8 As shown, the control circuit 100 executes step S21. In step S21, the carrier changing unit 116 checks whether the frequency of the secondary side is within frequency band FR2. If it is determined in step S21 that the frequency of the secondary side is not within frequency band FR2, the control circuit 100 executes step S22. In step S22, the carrier changing unit 116 checks whether the frequency of the secondary side is within frequency band FR3. If it is determined in step S21 that the frequency of the secondary side is within frequency band FR2 and in step S22 that the frequency of the secondary side is within frequency band FR3, the control circuit 100 executes step S23. In step S23, the carrier changing unit 116 sets the frequency of the carrier to the aforementioned first carrier frequency.

[0074] If, in step S22, it is determined that the frequency of the secondary side is not within frequency band FR3, the control circuit 100 executes step S24. In step S24, the carrier change unit 116 confirms whether the frequency of the secondary side is within frequency band FR1. If, in step S24, it is determined that the frequency of the secondary side is not within frequency band FR1, the control circuit 100 executes step S25. In step S25, the carrier change unit 116 confirms whether the frequency of the secondary side is within frequency band FR4. If, in step S24, it is determined that the frequency of the secondary side is within frequency band FR1, and in step S25, it is determined that the frequency of the secondary side is within frequency band FR4, the control circuit 100 executes step S26. In step S26, the carrier change unit 116 sets the carrier frequency to the aforementioned second carrier frequency.

[0075] If it is determined in step S25 that the frequency of the secondary side is not within the frequency band FR4, the carrier change unit 116 does not change the frequency of the carrier corresponding to the frequency of the secondary side.

[0076] In step S13 (refer to) Figure 7 If the magnitude of the secondary current is not within the current band AR1 as determined in the calculation, then... Figure 9 As shown, the control circuit 100 executes step S31. In step S31, the carrier changing unit 116 checks whether the frequency of the secondary side is within frequency band FR2. If it is determined in step S31 that the frequency of the secondary side is not within frequency band FR2, the control circuit 100 executes step S32. In step S32, the carrier changing unit 116 checks whether the frequency of the secondary side is within frequency band FR3. If it is determined in step S31 that the frequency of the secondary side is within frequency band FR2 and in step S32 that the frequency of the secondary side is within frequency band FR3, the control circuit 100 executes step S33. In step S33, the carrier changing unit 116 sets the frequency of the carrier to the aforementioned first carrier frequency.

[0077] If, in step S32, it is determined that the frequency of the secondary side is not within frequency band FR3, the carrier change unit 116 does not change the frequency of the carrier corresponding to the frequency of the secondary side. Thus, the setting of the carrier frequency is complete.

[0078] [Variation Example]

[0079] Figure 10 This is a graph showing a variation of the frequency and current band settings. The vertical axis represents the magnitude of the secondary current, and the horizontal axis represents the secondary frequency. Figure 10 In this process, the variable range of the secondary side current implemented by the power conversion control unit 114 includes: current band AR11; current band AR12, which is lower than current band AR11; and current band AR13, which is higher than current band AR11.

[0080] The minimum value of current band AR11 is, for example, the rated current. The minimum value of current band AR12 is zero, and the maximum value of current band AR12 is below the rated current. For example, the maximum value of current band AR12 is smaller than the minimum value of current band AR11, and a buffer band AR14 is sandwiched between current band AR11 and current band AR12.

[0081] The maximum value of current band AR11 is, for example, 100% to 120% of the rated current. The minimum value of current band AR13 is greater than the maximum value of current band AR11. For example, the minimum value of current band AR13 is greater than the maximum value of current band AR11, and a buffer band AR15 is sandwiched between current band AR11 and current band AR13.

[0082] The variable frequency range of the secondary side, implemented by the power conversion control unit 114, includes: frequency band FR11 (first frequency band), which includes frequency F1, the same as the primary side frequency; frequency band FR12 (second frequency band), which is lower than frequency band FR11; frequency band FR13 (third frequency band), which is higher than frequency band FR11; and frequency band FR14 (fourth frequency band), which is lower than frequency band FR12. For example, the minimum value of frequency band FR11 is 85% to 95% of frequency F1, and the maximum value of frequency band FR11 is 105% to 110% of frequency F1. The minimum value of frequency band FR14 is zero, and the maximum value of frequency band FR14 is 5% to 15% of frequency F1.

[0083] The minimum value of band FR12 is greater than the maximum value of band FR14. For example, if the minimum value of band FR12 is greater than the maximum value of band FR14, a buffer band FR15 exists between bands FR14 and FR12. The maximum value of band FR12 is less than the minimum value of band FR11. For example, if the maximum value of band FR12 is less than the minimum value of band FR11, a buffer band FR16 exists between bands FR12 and FR11. The minimum value of band FR13 is greater than the maximum value of band FR11. For example, if the minimum value of band FR13 is greater than the maximum value of band FR11, a buffer band FR17 ​​exists between bands FR11 and FR13.

[0084] The bandwidths of frequency bands FR11, FR12, FR13, and FR14 vary depending on the magnitude of the secondary current. For example, in Figure 10 In the middle, the bandwidth of frequency bands FR11 and FR14 increases as the secondary current increases, while the bandwidth of frequency bands FR12 and FR13 decreases as the secondary current increases.

[0085] exist Figure 10 In the example, when the magnitude of the current on the secondary side is within the current band AR12, the carrier conversion unit 116 sets the carrier frequency to a first carrier frequency. When the magnitude of the current on the secondary side is within the current band AR13, the carrier conversion unit 116 sets the carrier frequency to a second carrier frequency.

[0086] When the current on the secondary side is within current band AR11, the carrier frequency is changed by the carrier conversion unit 116 according to which of the frequency bands FR11, FR12, FR13, and FR14 the secondary side frequency belongs to. For example, when the secondary side frequency is within frequency band FR12 and when the secondary side frequency is within frequency band FR13, the carrier frequency is set to a first carrier frequency; when the secondary side frequency is within frequency band FR11 and when the secondary side frequency is within frequency band FR14, the carrier frequency is set to a second carrier frequency.

[0087] When the secondary side frequency is within buffer band FR15, buffer band FR16, or buffer band FR17, the carrier frequency changing unit 116 does not change the carrier frequency. Therefore, when the secondary side current is within current band AR11, the carrier frequency will be changed depending on which of the frequency bands FR11, FR12, FR13, or FR14 the secondary side frequency belongs to. Thus, current band AR11 corresponds to an example of the first current band described above.

[0088] When the secondary-side current is within the buffer band AR14, the carrier conversion unit 116 sets the carrier frequency to the first carrier frequency when the secondary-side frequency is within the frequency band FR12 and when the secondary-side frequency is within the frequency band FR13. When the secondary-side current is within the buffer band AR14, the carrier conversion unit 116 does not perform carrier frequency conversion when the secondary-side frequency is outside both the frequency band FR12 and the frequency band FR13. Although no frequency conversion is performed when the secondary-side frequency is within the frequency band FR11 or FR14, therefore, when the secondary-side current is within the buffer band AR14, no change in carrier frequency from the first carrier frequency to the second carrier frequency occurs. On the other hand, when the secondary-side frequency belongs to the frequency band FR12 or FR13, the carrier frequency changes from the second carrier frequency to the first carrier frequency. For example, consider the following scenario: Within frequency band FR14, the magnitude of the secondary current changes from current band AR11 to buffer band AR14 while maintaining the second carrier frequency. In this state, the secondary frequency changes, passing through buffer band FR15 and becoming frequency band FR12. Therefore, buffer band AR14 is also an example of the first current band described above.

[0089] When the secondary-side current is within the buffer band AR15, the carrier frequency is set to the second carrier frequency by the carrier change unit 116 when the secondary-side frequency is within the frequency band FR11 and when the secondary-side frequency is within the frequency band FR14. When the secondary-side current is within the buffer band AR15, the carrier change unit 116 does not change the carrier frequency when the secondary-side frequency is outside both the frequency band FR11 and the frequency band FR14. Even when the secondary-side frequency is within the frequency band FR12 or FR13, no frequency change occurs; therefore, when the secondary-side current is within the buffer band AR15, no change in carrier frequency from the second carrier frequency to the first carrier frequency occurs. On the other hand, when the secondary-side frequency belongs to the frequency band FR11 or FR14, the carrier frequency may sometimes change from the first carrier frequency to the second carrier frequency. Therefore, the buffer band AR15 is also an example of the first current band described above.

[0090] Figure 11 This is an example illustrating the following: Figure 10 The example is a flowchart of the process for setting the carrier frequency. For example... Figure 11As shown, the control circuit 100 first executes step S41. In step S41, the carrier conversion unit 116 checks whether the magnitude of the current on the secondary side is within the current band AR12. If it is determined in step S41 that the magnitude of the current on the secondary side is within the current band AR12, the control circuit 100 executes step S42. In step S42, the carrier conversion unit 116 sets the carrier frequency to the aforementioned first carrier frequency.

[0091] If, in step S41, it is determined that the magnitude of the secondary side current is not within current band AR12, the control circuit 100 executes step S43. In step S43, the carrier conversion unit 116 confirms whether the magnitude of the secondary side current is within current band AR13. If, in step S43, it is determined that the magnitude of the secondary side current is within current band AR13, the control circuit 100 executes step S44. In step S44, the carrier conversion unit 116 sets the carrier frequency to the aforementioned second carrier frequency.

[0092] If, in step S43, it is determined that the magnitude of the secondary side current is not within the current band AR13, the control circuit 100 executes step S45. In step S45, the carrier conversion unit 116 confirms whether the magnitude of the secondary side current is within the current band AR11.

[0093] If, in step S45, it is determined that the magnitude of the secondary side current is within current band AR11, then... Figure 12 As shown, the control circuit 100 executes step S51. In step S51, the carrier changing unit 116 confirms whether the frequency of the secondary side is within frequency band FR12. If it is determined in step S51 that the frequency of the secondary side is not within frequency band FR12, the control circuit 100 executes step S52. In step S52, the carrier changing unit 116 confirms whether the frequency of the secondary side is within frequency band FR13. If it is determined in step S51 that the frequency of the secondary side is within frequency band FR12 and in step S52 that the frequency of the secondary side is within frequency band FR13, the control circuit 100 executes step S53. In step S53, the carrier changing unit 116 sets the frequency of the carrier to the aforementioned first carrier frequency.

[0094] If, in step S52, it is determined that the frequency of the secondary side is not within frequency band FR13, the control circuit 100 executes step S54. In step S54, the carrier change unit 116 confirms whether the frequency of the secondary side is within frequency band FR11. If, in step S54, it is determined that the frequency of the secondary side is not within frequency band FR11, the control circuit 100 executes step S55. In step S55, the carrier change unit 116 confirms whether the frequency of the secondary side is within frequency band FR14. If, in step S54, the frequency of the secondary side is determined to be within frequency band FR11, and in step S55, the frequency of the secondary side is determined to be within frequency band FR14, the control circuit 100 executes step S56. In step S56, the carrier change unit 116 sets the carrier frequency to the aforementioned second carrier frequency.

[0095] If it is determined in step S55 that the frequency of the secondary side is not within the frequency band FR14, the carrier change unit 116 does not change the frequency of the carrier corresponding to the frequency of the secondary side.

[0096] Return to Figure 11 If, in step S45, it is determined that the magnitude of the current on the secondary side is not within the current band AR11, the control circuit 100 executes step S46. In step S46, the carrier conversion unit 116 confirms whether the magnitude of the current on the secondary side is within the buffer band AR14.

[0097] If, in step S46, it is determined that the magnitude of the secondary-side current is within the buffer band AR14, then... Figure 13 As shown, the control circuit 100 executes step S61. In step S61, the carrier changing unit 116 checks whether the frequency of the secondary side is within frequency band FR12. If it is determined in step S61 that the frequency of the secondary side is not within frequency band FR12, the control circuit 100 executes step S62. In step S62, the carrier changing unit 116 checks whether the frequency of the secondary side is within frequency band FR13. If it is determined in step S61 that the frequency of the secondary side is within frequency band FR12 and in step S62 that the frequency of the secondary side is within frequency band FR13, the control circuit 100 executes step S63. In step S63, the carrier changing unit 116 sets the frequency of the carrier to the aforementioned first carrier frequency.

[0098] If it is determined in step S62 that the frequency of the secondary side is not within the frequency band FR13, the carrier change unit 116 does not change the frequency of the carrier corresponding to the frequency of the secondary side.

[0099] In step S46 (refer to) Figure 11 If the magnitude of the secondary current is not within the buffer band AR14, as determined in the following case... Figure 14As shown, the control circuit 100 executes step S71. In step S71, the carrier changing unit 116 confirms whether the frequency of the secondary side is within frequency band FR11. If it is determined in step S71 that the frequency of the secondary side is not within frequency band FR11, the control circuit 100 executes step S72. In step S72, the carrier changing unit 116 confirms whether the frequency of the secondary side is within frequency band FR14. If it is determined in step S71 that the frequency of the secondary side is within frequency band FR11 and in step S72 that the frequency of the secondary side is within frequency band FR14, the control circuit 100 executes step S73. In step S73, the carrier changing unit 116 sets the frequency of the carrier to the aforementioned second carrier frequency.

[0100] If, in step S72, it is determined that the frequency of the secondary side is not within frequency band FR14, the carrier changing unit 116 does not change the frequency of the carrier corresponding to the frequency of the secondary side. Thus, the setting of the carrier frequency is complete.

[0101] [Effects of this implementation method]

[0102] As described above, the power conversion device 1 includes: a matrix conversion circuit 10 having multiple switching elements and performing bidirectional power conversion between primary-side AC and secondary-side AC; a power conversion control unit 114 that switches the multiple switching elements on / off in conjunction with a carrier wave so that the secondary-side AC follows a control command; and a carrier wave changing unit 116 that changes the frequency of the carrier wave based on the proximity level between the primary-side frequency and the secondary-side frequency.

[0103] The power loss in the switching elements (the power consumed by the switching elements) includes switching losses caused by on / off switching and steady-state losses caused by the steady-state current flowing in the on state. In the matrix converter circuit 10, the steady-state loss of each of the plurality of switching elements changes depending on the relationship between the phase of the AC current on the primary side and the phase of the AC current on the secondary side when the switching element is turned on.

[0104] When the frequency of the primary side becomes increasingly similar to that of the secondary side, the phase relationship between the AC current on the primary side and the AC current on the secondary side becomes difficult to change. Consequently, the steady-state losses of each of the multiple switching elements also become difficult to change. Therefore, in switching elements with high steady-state losses, the high steady-state loss state may persist, and heat generation may increase.

[0105] In contrast, by changing the carrier frequency based on the proximity level, the carrier frequency can be reduced, for example, if the proximity level becomes higher than the specified level. When the carrier frequency is reduced, switching losses decrease, thus reducing switching losses, suppressing power losses, and suppressing heat generation even in switching elements with high steady-state losses. Therefore, this power conversion device 1 is effective in suppressing heat generation in switching elements.

[0106] The carrier frequency change unit 116 can further change the carrier frequency based on the magnitude of the secondary current. In this case, even in the aforementioned near-high level state, heat generation in the switching element can be suppressed when the magnitude of the secondary current is small. Therefore, by further changing the carrier frequency based on the magnitude of the secondary current, useless changes to the carrier frequency can be eliminated.

[0107] The variable range of the secondary-side current, implemented by the power conversion control unit 114, may include a first current band and a second current band lower than the first current band. When the secondary-side current is within the second current band, the carrier frequency change unit 116 does not change the carrier frequency based on a near-level value; when the secondary-side current is within the first current band, it changes the carrier frequency based on a near-level value. In this case, the carrier frequency is changed based on a near-level value in a limited manner according to the secondary-side current, thereby eliminating unnecessary changes to the carrier frequency.

[0108] Alternatively, the variable range of the secondary side frequency implemented by the power conversion control unit 114 may include: a first frequency band, including frequencies the same as the primary side frequency; a second frequency band, lower than the first frequency band; and a third frequency band, higher than the first frequency band. The carrier changing unit 116 sets the carrier frequency to the first carrier frequency when the secondary side frequency is within the second frequency band and when the secondary side frequency is within the third frequency band; and sets the carrier frequency to the second carrier frequency, lower than the first carrier frequency, when the secondary side frequency is within the first frequency band. In this case, changing the carrier frequency based on proximity to the primary side can be implemented with simple logic.

[0109] Alternatively, the variable range of the secondary side frequency implemented by the power conversion control unit 114 may also include a fourth frequency band lower than the second frequency band. When the secondary side frequency is within the fourth frequency band, the carrier frequency of the carrier conversion unit 116 may also be set to the second carrier frequency. It is possible that between zero and the tuning frequency (the same frequency as the primary side), as the secondary side frequency approaches zero, the duration of the continuous on / off state of each switching element becomes longer, leading to increased heat generation in each switching element. In contrast, in the above situation, by reducing the carrier frequency when the secondary side frequency is within the fourth frequency band, which is closer to zero than the second frequency band, the switching losses of each switching element are suppressed. This suppresses power losses and heat generation in each switching element. Therefore, this power conversion device 1 is more effective at suppressing heat generation in the switching elements.

[0110] Alternatively, the power conversion device 1 may also include a filter 30 for reducing high-order harmonics on the primary side, and the carrier frequency conversion unit 116 may set the second carrier frequency to a value greater than the cutoff frequency of the filter 30. In this case, the increase in high-frequency components due to the reduction of the carrier frequency can be suppressed.

[0111] Alternatively, the power conversion device 1 may also include a rated current changing unit 115. When the carrier frequency is higher than a predetermined threshold, the rated current changing unit 115 reduces the rated current on the secondary side based on the increased carrier frequency; when the carrier frequency is lower than the threshold, it keeps the rated current on the secondary side constant. The power conversion control unit 114 switches the on / off states of multiple switching elements by limiting the magnitude of the secondary side current based on the rated current on the secondary side. The carrier frequency changing unit 116 sets the second carrier frequency to a value lower than the threshold. In this case, the rated current changing unit 115 reduces the carrier frequency to a frequency band that constantly maintains the rated current on the secondary side, thereby more reliably suppressing power loss.

[0112] The implementation methods have been described above, but this disclosure is not necessarily limited to the above-described implementation methods, and various changes can be made without departing from its spirit.

[0113] Explanation of reference numerals in the attached figures

[0114] 1: Power conversion device

[0115] 10: Matrix Transformation Circuit

[0116] 30: Filter

[0117] 114: Power Conversion Control Department

[0118] 115: Rated Current Change Section

[0119] 116: Carrier Change Department

Claims

1. A power conversion device comprising: A matrix converter circuit has multiple switching elements and performs bidirectional power conversion between primary and secondary AC power. The calculation unit calculates the voltage information of the primary side, which includes the AC voltage of the primary side detected by the voltage detection circuit. A power conversion control unit, in conjunction with a carrier wave, switches the on / off states of the plurality of switching elements such that the AC current on the secondary side follows a control command, which is a voltage command; and The carrier frequency change unit changes the carrier frequency based on the proximity level between the primary side frequency included in the primary side voltage information calculated by the calculation unit and the secondary side frequency indicated by the voltage command. in, The carrier frequency is further changed based on the magnitude of the current on the secondary side. The variable range of the secondary side current, implemented by the power conversion control unit, includes a first current band and a second current band that is lower than the first current band. When the magnitude of the current on the secondary side is within the second current band, the carrier frequency change unit does not change the carrier frequency based on the near level; when the magnitude of the current on the secondary side is within the first current band, it changes the carrier frequency based on the near level.

2. The power conversion device according to claim 1, wherein, The variable range of the secondary side frequency implemented by the power conversion control unit includes: a first frequency band, including the same frequency as the primary side frequency; a second frequency band, lower than the first frequency band; and a third frequency band, higher than the first frequency band. The carrier modulation unit sets the carrier frequency to a first carrier frequency when the frequency on the secondary side is within the second frequency band and when the frequency on the secondary side is within the third frequency band; and sets the carrier frequency to a second carrier frequency that is lower than the first carrier frequency when the frequency on the secondary side is within the first frequency band.

3. The power conversion device according to claim 2, wherein, The variable frequency range of the secondary side, implemented by the power conversion control unit, also includes a fourth frequency band that is lower than the second frequency band. When the frequency on the secondary side is within the fourth frequency band, the carrier change unit also sets the frequency of the carrier to the second carrier frequency.

4. The power conversion device according to claim 3, further comprising: A filter that reduces higher harmonics on the first side. The carrier modulation unit sets the second carrier frequency to a value greater than the cutoff frequency of the filter.

5. The power conversion device according to claim 3 or 4, further comprising: The rated current changing unit reduces the rated current on the secondary side when the carrier frequency is higher than a predetermined threshold, and keeps the rated current on the secondary side constant when the carrier frequency is lower than the threshold. The power conversion control unit switches the multiple switching elements on / off in a manner that limits the magnitude of the current on the secondary side based on the rated current on the secondary side. The carrier frequency change unit sets the second carrier frequency to a value smaller than the threshold.

6. A power conversion method, comprising: A matrix converter circuit with multiple switching elements is used to perform bidirectional power conversion between the primary and secondary AC power. The calculation unit calculates the voltage information of the primary side, which includes the AC voltage of the primary side detected by the voltage detection circuit. The power conversion control unit switches the multiple switching elements on / off in a manner that coordinates with the carrier wave, causing the AC power on the secondary side to follow a control command, which is a voltage command; and The carrier frequency is changed by the carrier changing unit based on the proximity level between the primary side frequency included in the primary side voltage information calculated by the calculation unit and the secondary side frequency indicated by the voltage command. The carrier frequency is further changed based on the magnitude of the current on the secondary side. The variable range of the secondary side current, implemented by the power conversion control unit, includes a first current band and a second current band that is lower than the first current band. When the magnitude of the current on the secondary side is within the second current band, the carrier frequency change unit does not change the carrier frequency based on the near level; when the magnitude of the current on the secondary side is within the first current band, it changes the carrier frequency based on the near level.

7. A computer program product comprising a computer program that, when executed by a processor, causes a power conversion device to perform: A matrix converter circuit with multiple switching elements is used to perform bidirectional power conversion between the primary and secondary AC power. The calculation unit calculates the voltage information of the primary side, which includes the AC voltage of the primary side detected by the voltage detection circuit. The power conversion control unit switches the multiple switching elements on / off in a manner that coordinates with the carrier wave, causing the AC power on the secondary side to follow a control command, which is a voltage command; and The carrier frequency is changed by the carrier changing unit based on the proximity level between the primary side frequency included in the primary side voltage information calculated by the calculation unit and the secondary side frequency indicated by the voltage command. in, The carrier frequency is further changed based on the magnitude of the current on the secondary side. The variable range of the secondary side current, implemented by the power conversion control unit, includes a first current band and a second current band that is lower than the first current band. When the magnitude of the current on the secondary side is within the second current band, the carrier frequency change unit does not change the carrier frequency based on the near level; when the magnitude of the current on the secondary side is within the first current band, it changes the carrier frequency based on the near level.

Images