Power conversion device and power conversion method

Abstract

The present disclosure relates to a power conversion device and a power conversion method. The power conversion device 1 includes: a matrix converter circuit 10 configured to perform bidirectional power conversion between primary side power and secondary side power; a degradation level calculation unit 154 configured to calculate the degradation level based on the secondary side current of the matrix converter circuit 10, the carrier frequency, and the difference between the primary side frequency and the secondary side frequency of the matrix converter circuit 10; and a notification unit 158 ​​configured to notify that the degradation level exceeds a predetermined level.

Description

Technical Field

[0001] The present disclosure relates to a power conversion device and a power conversion method. Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2016-67169 discloses a matrix converter including a plurality of bidirectional switches connecting each phase of an AC power source and each phase of an AC device, outputting power generated by the AC device to the AC power source, and controlling the AC device based on power supplied from the AC power source. Summary of the invention

[0003] [Problems to be Solved by the Invention]

[0004] The present disclosure provides a power converter that is effective for timely maintenance of a matrix converter circuit.

[0005] [Solution to the problem]

[0006] A power conversion device according to one aspect of the present disclosure includes: a matrix converter circuit configured to perform bidirectional power conversion between a primary side and a secondary side; and a control circuit configured to: calculate a degradation level based on a secondary side current of the matrix converter circuit, a carrier frequency, and a primary-secondary frequency difference between a primary side frequency and a secondary side frequency of the matrix converter circuit; and output a degradation notification in response to determining that the degradation level exceeds a predetermined level.

[0007] A power conversion method according to another aspect of the present disclosure includes: calculating a degradation level based on a secondary-side current of a matrix converter circuit that performs bidirectional power conversion between primary-side power and secondary-side power, a carrier frequency, and a primary-secondary frequency difference between a primary-side frequency and a secondary-side frequency of the matrix converter circuit; and outputting a degradation notification in response to determining that the degradation level exceeds a predetermined level.

[0008] [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a power converter that is effective for timely maintenance of a matrix converter circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram illustrating the configuration of a power conversion device.

[0011] Figure 2 is a schematic diagram showing a specific example of a bidirectional switch.

[0012] Figure 3 is a graph illustrating transitions of the primary side voltage and the secondary side current.

[0013] Figure 4 is a block diagram illustrating the configuration of a first mode control unit.

[0014] Figure 5 is a block diagram illustrating the configuration of the second mode control unit.

[0015] Figure 6 is a block diagram illustrating the configuration of a degradation detection unit.

[0016] Figure 7 is a graph illustrating a coefficient profile.

[0017] Figure 8 is a graph illustrating a degradation profile.

[0018] Fig. 9 is a block diagram illustrating the hardware configuration of the control circuit.

[0019] Fig.10 is a flow chart illustrating a control mode switching process.

[0020] Fig.11 is a flow chart illustrating a first mode control process.

[0021] Fig.12 is a flow chart illustrating the second mode control process.

[0022] Fig.13 is a flow chart illustrating the phase tracking control process.

[0023] Fig.14 is a flow chart illustrating a degradation detection process. DETAILED DESCRIPTION

[0024] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In the specification, the same elements or elements having the same functions are denoted by the same reference numerals, and repeated descriptions are omitted.

[0025] Power conversion device

[0026] Figure 1 The power conversion device 1 shown in is a device that performs bidirectional power conversion between the primary side and the secondary side. For example, the power conversion device 1 converts the primary side power supplied from the power supply 91 into the secondary side power and supplies the secondary side power to the electric device 92. The power conversion device 1 converts the secondary side power (regenerative power) generated by the electric device 92 into the primary side power and supplies the primary side power to the power supply 91.

[0027] The primary side power and the secondary side power may be single-phase AC power or three-phase AC power. The primary side power and the secondary side power may be DC power. Hereinafter, the case where both the primary side power and the secondary side power are three-phase AC power will be described. For example, the primary side power includes three phases of R phase, S phase and T phase, and the secondary side power includes three phases of U phase, V phase and W phase.

[0028] The power conversion device 1 includes a matrix converter circuit 10, a filter 30, a voltage detection circuit 40, a current sensor 50, and a control circuit 100. Hereinafter, the configuration of each element will be exemplified in detail.

[0029] Matrix converter circuit

[0030] The matrix converter circuit 10 has a plurality of switching elements and performs bidirectional power conversion between the primary side power and the secondary side power without going through a DC conversion process. For example, the matrix converter circuit 10 has power lines 11R, 11S, 11T on the primary side, power lines 12U, 12V, 12W on the secondary side, and nine sets of bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, 2TW. The power line 11R is an R-phase power transmission line, the power line 11S is an S-phase power transmission line, and the power line 11T is a T-phase power transmission line. The power line 12U is a U-phase power transmission line, the power line 12V is a V-phase power transmission line, and the power line 12W is a W-phase power transmission line.

[0031] Each of the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, 2TW switches between three states: a state in which current flows from the primary side to the secondary side, a state in which current flows from the secondary side to the primary side, and a state in which no current flows.

[0032] The bidirectional switch 2RU is inserted between the power line 11R and the power line 12U, and switches between a first on-state in which current flows from the power line 11R to the power line 12U, a second on-state in which current flows from the power line 12U to the power line 11R, and a bidirectional off-state in which no current flows. The bidirectional switch 2SU is inserted between the power line 11S and the power line 12U, and switches between a first on-state in which current flows from the power line 11S to the power line 12U, a second on-state in which current flows from the power line 12U to the power line 11S, and a bidirectional off-state in which no current flows. The bidirectional switch 2TU is inserted between the power line 11T and the power line 12U, and switches between a first on-state in which current flows from the power line 11T to the power line 12U, a second on-state in which current flows from the power line 12U to the power line 11T, and a bidirectional off-state in which no current flows.

[0033] The bidirectional switch 2RV is inserted between the power line 11R and the power line 12V, and switches between a first on-state in which current flows from the power line 11R to the power line 12V, a second on-state in which current flows from the power line 12V to the power line 11R, and a bidirectional off-state in which no current flows. The bidirectional switch 2SV is inserted between the power line 11S and the power line 12V, and switches between a first on-state in which current flows from the power line 11S to the power line 12V, a second on-state in which current flows from the power line 12V to the power line 11S, and a bidirectional off-state in which no current flows. The bidirectional switch 2TV is inserted between the power line 11T and the power line 12V, and switches between a first on-state in which current flows from the power line 11T to the power line 12V, a second on-state in which current flows from the power line 12V to the power line 11T, and a bidirectional off-state in which no current flows.

[0034] The bidirectional switch 2RW is inserted between the power line 11R and the power line 12W, and switches between a first on-state in which current flows from the power line 11R to the power line 12W, a second on-state in which current flows from the power line 12W to the power line 11R, and a bidirectional off-state in which no current flows. The bidirectional switch 2SW is inserted between the power line 11S and the power line 12W, and switches between a first on-state in which current flows from the power line 11S to the power line 12W, a second on-state in which current flows from the power line 12W to the power line 11S, and a bidirectional off-state in which no current flows. The bidirectional switch 2TW is inserted between the power line 11T and the power line 12W, and switches between a first on-state in which current flows from the power line 11T to the power line 12W, a second on-state in which current flows from the power line 12W to the power line 11T, and a bidirectional off-state in which no current flows.

[0035] like Figure 2 As shown, each of the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, 2TW includes two switches 21 and 22. In the on state, the switch 21 transfers the current from the primary side to the secondary side, and does not transfer the current from the secondary side to the primary side. In the on state, the switch 22 transfers the current from the secondary side to the primary side, and does not transfer the current from the primary side to the secondary side. In addition, the switches 21 and 22 are switches with reverse blocking capability, and can maintain the off state in the off state relative to the voltage application in the direction opposite to the flow direction of the on state.

[0036] The bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, 2TW are in a first on state by, for example, turning on switch 21 and turning off switch 22, in a second on state by turning off switch 21 and turning on switch 22, and in a bidirectional off state by turning off switches 21 and 22. Figure 2 In the embodiment, the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, 2TW may include diodes, each of which is connected in series with each of the switches 21 and 22 having no reverse blocking capability. In this case, the connection point between the switch 21 and the diode may be connected to the connection point between the switch 22 and the diode.

[0037] Return to Figure 1 , the filter 30 reduces the harmonic components of the voltage or current on its primary side. For example, the filter 30 includes inductors 31R, 31S, 31T and capacitors 34R, 34S, 34T. The inductors 31R, 31S, 31R are respectively arranged in the power lines 11R, 11S, 11T. The capacitor 34R is arranged between the power line 11R and the neutral point 35 on the secondary side of the inductor 31R (between the inductor 31R and the bidirectional switches 2RU, 2RV, 2RW). The capacitor 34S is arranged between the power line 11S and the neutral point 35 on the secondary side of the inductor 31S (between the inductor 31S and the bidirectional switches 2SU, 2SV, 2SW). The capacitor 34T is arranged between the power line 11T and the neutral point 35 on the secondary side of the inductor 31T (between the inductor 31T and the bidirectional switches 2TU, 2TV, 2TW). As described above, since the filter 30 is provided between the power source 91 and the matrix converter circuit 10 , the harmonic components of the voltage or current of the power source 91 are reduced by the filter 30 .

[0038] The voltage detection circuit 40 (voltage sensor) detects the instantaneous value of the voltage on the primary side of the matrix converter circuit 10. For example, the voltage detection circuit 40 detects the instantaneous value of the phase voltage on each primary side of the filter 30. The voltage detection circuit 40 can detect the instantaneous value of the phase voltage on the secondary side of the filter 30. Hereinafter, the voltage on the primary side of the matrix converter circuit 10 is referred to as "primary side voltage". The current on the primary side of the matrix converter circuit 10 is referred to as "primary side current".

[0039] The current sensor 50 detects the instantaneous value of the current on the secondary side of the matrix converter circuit 10 (the current flowing between the matrix converter circuit 10 and the electrical device 92). For example, the current sensor 50 detects the instantaneous value of the current of the power lines 12U, 12V, 12W. Hereinafter, the current on the secondary side of the matrix converter circuit 10 is referred to as the "secondary side current". The voltage on the secondary side of the matrix converter circuit 10 is referred to as the "secondary side voltage". The current sensor 50 may be configured to detect the secondary side current values ​​of all phases of the power lines 12U, 12V, 12W, or may be configured to detect the secondary side current values ​​of any two phases of the power lines 12U, 12V, 12W. As long as zero-phase current is not generated, the sum of the current values ​​of the U phase, the V phase, and the W phase is zero, so that even when the secondary side current values ​​of two phases are detected, information on the secondary side current values ​​of all phases is obtained.

[0040] Control Circuit

[0041] The control circuit 100 controls the matrix converter circuit 10 to perform power conversion between the primary side power and the secondary side power. If the state in which the secondary side phase and the primary side phase are aligned is maintained in the matrix converter circuit 10, the current is concentrated on any one of the switching elements of the matrix converter circuit 10, and the heat generation in the switching element increases. The state in which the secondary side phase and the primary side phase are aligned corresponds to a state in which there is no difference between the primary side phase and the secondary side phase. In addition, as the secondary side frequency approaches the primary side frequency, this phenomenon occurs repeatedly at the frequency of the difference between the secondary side frequency and the primary side frequency.

[0042] On the other hand, the control circuit 100 is configured to: select a first control mode in response to determining that a command-primary frequency difference between the command frequency and the primary side frequency of the matrix converter circuit 10 is above a predetermined threshold, wherein the first control mode includes causing the secondary side frequency of the matrix converter circuit 10 to follow the command frequency; select a second control mode in response to determining that the command-primary frequency difference is below the threshold, wherein the second control mode includes maintaining a primary-secondary phase difference between the secondary side phase and the primary side phase of the matrix converter circuit 10 within a predetermined target range; and control the matrix converter circuit 10 according to the selection of the first control mode or the second control mode. For example, the control circuit 100 is configured to perform: a first mode control, including performing bidirectional power conversion between primary side power and secondary side power by the matrix converter circuit 10, so that the secondary side frequency of the matrix converter circuit 10 follows the command frequency; a second mode control, including maintaining the difference between the secondary side phase and the primary side phase of the matrix converter circuit 10 at an odd multiple of 60°±30° by the matrix converter circuit 10; and a mode switching, including switching the first mode control and the second mode control, so that if the command-primary frequency difference is higher than a threshold value, the first mode control is performed, and if the command-primary frequency difference is lower than the threshold value, the second mode control is performed. Therefore, the state in which the secondary side phase and the primary side phase are aligned is avoided, thereby suppressing the heating of the switching element. It should be noted that the difference falling below the predetermined threshold means that the amplitude (absolute value) of the difference falls below the predetermined threshold, regardless of whether the difference is positive or negative. Similarly, the difference exceeding the predetermined threshold means that the amplitude of the difference exceeds the predetermined threshold. The same applies to the following description.

[0043] For example, the control circuit 100 has a phase / amplitude calculation unit 111, a power conversion control unit 112, a current information acquisition unit 113, a first mode control unit 114, a second mode control unit 115, a mode switching unit 116, and a degradation detection unit 117 as a functional configuration (hereinafter referred to as a "functional block").

[0044] Phase / amplitude calculation unit 111 calculates the phase, oscillation amplitude and frequency of the primary voltage based on the phase voltage of power lines 11R, 11S, 11T obtained by voltage detection circuit 40. Hereinafter, the calculation results of the phase, oscillation amplitude and frequency are referred to as "primary voltage information".

[0045] The power conversion control unit 112 switches the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, 2TW on / off in conjunction with the carrier wave so as to output an AC voltage or AC current corresponding to the control command to the secondary side of the matrix converter circuit 10. For example, based on the primary side voltage information and the voltage command, the power conversion control unit 112 switches the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SW, 2TW on / off in conjunction with the carrier wave so as to output a secondary side voltage corresponding to the voltage command.

[0046] More specifically, the power conversion control unit 112 sequentially selects each of the R phase, the S phase, and the T phase as the reference phase based on the primary side voltage information, and controls the matrix converter circuit 10 to output the secondary side voltage corresponding to the voltage command according to the potential difference between the reference phase and the other two phases. For example, the power conversion control unit 112 repeats at the frequency of the primary side voltage: setting the R phase to the positive reference phase in the first part where the voltage of the R phase is the maximum value, setting the T phase to the negative reference phase in the second part where the voltage of the T phase is the minimum value, setting the S phase to the positive reference phase in the third part where the voltage of the S phase is the maximum value, setting the R phase to the negative reference phase in the fourth part where the voltage of the R phase is the minimum value, setting the T phase to the positive reference phase in the fifth part, and setting the S phase to the negative reference phase in the sixth part.

[0047] The power conversion control unit 112 maintains the state in which the reference phase is connected to the secondary side, and at the same time, switches on / off between the other two phases and the secondary side. For example, in the first part, the power conversion control unit 112 switches the bidirectional switches 2SU, 2TU, 2SV, 2TV, 2SW, 2TW on and off while keeping any one of the bidirectional switches 2RU, 2RV, 2RW on. In the second part, the power conversion control unit 112 switches the bidirectional switches 2RU, 2TU, 2RV, 2TV, 2RW, 2TW on and off while keeping any one of the bidirectional switches 2SU, 2SV, 2SW on. In the third part, the power conversion control unit 112 switches the bidirectional switches 2RU, 2SU, 2RV, 2SV, 2RW, 2SW on and off while keeping any one of the bidirectional switches 2TU, 2TV, 2TW on. In the fourth part, the power conversion control unit 112 switches the bidirectional switches 2SU, 2TU, 2SV, 2TV, 2SW, 2TW on and off while keeping any one of the bidirectional switches 2RU, 2RV, 2RW on. In the fifth part, the power conversion control unit 112 switches the bidirectional switches 2RU, 2TU, 2RV, 2TV, 2RW, 2TW on and off while keeping any one of the bidirectional switches 2SU, 2SV, 2SW on. In the sixth part, the power conversion control unit 112 switches the bidirectional switches 2RU, 2SU, 2RV, 2SV, 2RW, 2SW on and off while keeping any one of the bidirectional switches 2TU, 2TV, 2TW on. The length (phase angle) of each of the first to sixth parts is 1 / 6 (60°) of one cycle. Hereinafter, the period (the first part, the third part and the fifth part) when any one of the R phase, the S phase and the T phase is the positive reference phase is referred to as the positive reference period, and the period (the second part, the fourth part and the sixth part) when any one of the R phase, the S phase and the T phase is the negative reference phase is referred to as the negative reference period.

[0048] The power conversion control unit 112 generally controls the phase of the primary side current so that the primary side power factor is one, so as to maximize the use of the primary side voltage to the secondary side voltage. The power conversion control unit 112 can adjust the power factor of the primary side by moving the first part to the sixth part within the following range: in this range, the voltage of the R phase becomes a positive peak in the first part, the voltage of the T phase becomes a negative peak in the second part, the voltage of the S phase becomes a positive peak in the third part, the voltage of the R phase becomes a negative peak in the fourth part, and the voltage of the S phase becomes a negative peak in the sixth part. For example, the power conversion control unit 112 moves the center phases of the first part, the third part, and the fifth part within a range greater than -30° and less than 30° relative to the phase where the voltages of the R phase, the S phase, and the T phase become positive peaks. In addition, the power conversion control unit 112 moves the center phases of the second part, the fourth part, and the sixth part within a range greater than -30° and less than 30° relative to the negative peak of the voltages of the R phase, the S phase, and the T phase. Below, the center phases of the first part, the third part, and the fifth part are referred to as positive reference phases. The center phase of the second, fourth, and sixth parts is called the negative reference phase. The phase where the voltage of the R phase, S phase, and T phase becomes a positive peak is called the "primary side positive peak phase". The phase where the voltage of the R phase, S phase, and T phase becomes a negative peak is called the "primary side negative peak phase".

[0049] The voltage command includes an amplitude command value and a phase command value. The amplitude command value is a command value of the oscillation amplitude of the secondary side voltage. The phase command value is a command value of the phase of the secondary side voltage. As an example, the amplitude command value corresponds to the amplitude of the voltage command vector in the fixed coordinate system, and the phase command value corresponds to the rotation angle of the voltage command vector in the fixed coordinate system. The fixed coordinate system is a coordinate system fixed to the stator of the electric device 92. A specific example of the fixed coordinate system includes an αβ coordinate system having an α axis and a β axis orthogonal to each other as coordinate axes.

[0050] The power conversion control unit 112 obtains the amplitude command value and the phase command value, and controls the matrix converter circuit 10 to output the secondary side voltage having the oscillation amplitude and phase corresponding to the amplitude command value and the phase command value. The current information acquisition unit 113 acquires the information of the secondary side current. For example, the current information acquisition unit 113 obtains the current value of the power line 12U, 12V, 12W from the current sensor 50.

[0051] The first mode control unit 114 is configured to make the secondary side frequency of the matrix converter circuit 10 follow the command frequency. The secondary side frequency refers to the frequency of the secondary side voltage or the secondary side current. For example, the first mode control unit 114 controls the matrix converter circuit 10 so that the frequency of the secondary side voltage follows the command frequency. The frequency of the secondary side current follows the frequency of the secondary side voltage. Therefore, making the frequency of the secondary side voltage follow the command frequency is synonymous with making the frequency of the secondary side current follow the command frequency. Hereinafter, the control performed by the first mode control unit 114 is referred to as "first mode control".

[0052] The second mode control unit 115 is configured to control the matrix converter circuit 10 according to the second control mode. For example, the second mode control unit 115 is configured to maintain the primary-secondary phase difference within a predetermined target range. The primary side may include a primary side phase and a primary side adjacent phase. An example of a combination of the primary side phase and the secondary side phase is a voltage phase of the R phase and a voltage phase of the S phase. Another example of a combination of the primary side phase and the secondary side phase is a voltage phase of the S phase and a voltage phase of the T phase. Another example of a combination of the primary side phase and the secondary side phase is a voltage phase of the T phase and a voltage phase of the R phase. The second mode control unit 115 may also be configured to maintain the primary-secondary phase difference within a target range and maintain the secondary side phase between the primary side phase and the primary side adjacent phase. In three-phase AC power, the primary intra-phase difference between the primary side phase and the primary side adjacent phase is 120°. For example, the primary internal phase difference between the R phase and the S phase is 120°, the primary internal phase difference between the S phase and the T phase is also 120°, and the primary internal phase difference between the T phase and the R phase is also 120°. In this case, the second mode control unit 115 can also be configured to maintain the primary-secondary phase difference within a target range, which is ±30° of an odd multiple of 60°. Odd multiples of 60° can be positive or negative. Maintaining the primary-secondary phase difference within the target range means maintaining the absolute value of the primary-secondary phase difference within the target range. For example, the second mode control unit 115 can maintain the difference between the secondary side phase and the primary side phase at 45° to 75°, the difference between the secondary side phase and the primary side phase at 55° to 65°, and the difference between the secondary side phase and the primary side phase at approximately 60°.

[0053] The secondary side phase is the phase of the secondary side voltage or the secondary side current. The primary side phase is the phase of the primary side voltage or the primary side current. The primary side phase may be the phase of the primary side voltage of the matrix converter circuit 10 (the primary side voltage phase of the matrix converter circuit 10), and the secondary side phase may be the phase of the primary side current of the matrix converter circuit 10 (the secondary side current phase of the matrix converter circuit 10). For example, the second mode control unit 115 may also be configured to control the matrix converter circuit 10 so as to maintain the primary-secondary phase difference between the secondary side current phase acquired by the current information acquisition unit 113 and the primary side voltage phase calculated by the phase / amplitude calculation unit 111 within ±30° of an odd multiple of 60°. For example, the second mode control unit 115 may also be configured to: calculate the deviation between the target difference predetermined within the target range and the primary-secondary phase difference; calculate the voltage command to reduce the deviation; and make the secondary side voltage of the matrix converter circuit 10 follow the voltage command. Hereinafter, the control performed by the second mode control unit 115 is referred to as "second mode control".

[0054] The mode switching unit 116 is configured to select the first control mode in response to determining that the command-primary frequency difference is higher than a predetermined threshold value, and to select the second control mode in response to determining that the command-primary frequency difference is lower than the threshold value. The first mode control unit 114 or the second mode control unit 115 controls the matrix converter circuit 10 according to the selection of the first control mode or the second control mode. For example, if the mode switching unit 116 selects the first control mode, the first mode control unit 114 controls the matrix converter circuit. If the mode switching unit 116 selects the second control mode, the second mode control unit 115 controls the matrix converter circuit. For example, the mode switching unit 116 is configured to switch the control mode of the matrix converter circuit 10 based on the command-primary difference between the command frequency and the primary side frequency, so that when the command-primary difference exceeds the predetermined threshold value, the control performed by the first mode control unit 114 is performed, and when the command-primary difference is lower than the threshold value, the control performed by the second mode control unit 115 is performed. For example, when the difference between the command frequency and the primary side frequency becomes equal to or less than a predetermined first threshold, the mode switching unit 116 transfers the control performed by the first mode control unit 114 to the control performed by the second mode control unit 115. The mode switching unit 116 may transfer the control performed by the second mode control unit 115 to the control performed by the first mode control unit 114 in response to the difference between the command frequency and the primary side frequency exceeding a predetermined second threshold. The primary side frequency refers to the frequency of the primary side voltage or the primary side current.

[0055] For example, when the difference between the command frequency and the frequency of the primary side voltage drops below a first threshold, the mode switching unit 116 transfers the control performed by the first mode control unit 114 to the control performed by the second mode control unit 115, and when the difference between the command frequency and the frequency of the primary side voltage exceeds a second threshold, the control performed by the second mode control unit 115 is transferred to the control performed by the first mode control unit 114. The first threshold and the second threshold may be equal to or different from each other. For example, the second threshold may be greater than the first threshold.

[0056] The frequency of the primary voltage is substantially equal to the frequency of the primary current. Therefore, the difference between the command frequency and the frequency of the primary voltage falls below the first threshold, which is synonymous with the difference between the command frequency and the frequency of the primary current falling below the first threshold. The difference between the command frequency and the frequency of the primary voltage exceeds the second threshold, which is synonymous with the difference between the command frequency and the frequency of the primary current exceeding the second threshold.

[0057] After the mode switching unit 116 transfers the control performed by the first mode control unit 114 to the control performed by the second mode control unit 115, the second mode control unit 115 can gradually change the difference between the secondary side phase and the primary side phase from outside the range of ±30° of odd multiples of 60° to within the range, and then maintain the difference between the secondary side phase and the primary side phase within ±30° of odd multiples of 60°.

[0058] Figure 3 : is a graph illustrating transitions of the primary side voltage and the secondary side current before and after the mode switching unit 116 transfers the control performed by the first mode control unit 114 to the control performed by the second mode control unit 115. In the graph, the horizontal axis represents the elapsed time, the vertical axis represents the amplitude of the primary side voltage or the secondary side current, the solid line graph represents the transition of the primary side voltage, and the dotted line graph represents the transition of the secondary side current.

[0059] From time t0 corresponding to the origin of the graph to time t1, control is performed by the first mode control unit 114. In this control, the command frequency gradually increases, and in time t1, the difference between the command frequency and the frequency of the primary side voltage drops below the first threshold. The mode switching unit 116 now transfers the control performed by the first mode control unit 114 to the control performed by the second mode control unit 115.

[0060] The second mode control unit 115 gradually changes the difference between the phase of the secondary side current and the phase of the primary side voltage up to 60° from time t1 to time t2. Then, the second mode control unit 115 maintains the difference between the phase of the secondary side current and the phase of the primary side voltage at substantially 60°. By maintaining the difference between the phase of the secondary side current and the phase of the primary side voltage at 60°, the secondary side frequency becomes equal to the primary side frequency, but a state in which the phase of the secondary side current and the phase of the primary side voltage are aligned is avoided.

[0061] The degradation detection unit 117 is configured to calculate the degradation level based on the secondary side current, the carrier frequency, and the primary-secondary frequency difference between the primary side frequency and the secondary side frequency of the matrix converter circuit; and output a degradation notification in response to determining that the degradation level exceeds a predetermined level. For example, the degradation detection unit 117 evaluates the degradation level of the switching element based on the information of the primary side voltage calculated by the phase / amplitude calculation unit 111, the command frequency, the information of the secondary side current acquired by the current information acquisition unit 113, and the carrier frequency in the power conversion control unit 112. Below, the configurations of the first mode control unit 114, the second mode control unit 115, and the degradation detection unit 117 will be explained in more detail by way of example.

[0062] First mode control unit

[0063] When the first mode control is selected by the mode switching unit 116, the first mode control unit 114 obtains the command frequency from the host controller 200 and controls the matrix converter circuit 10 so that the secondary side frequency follows the command frequency. Figure 4 As shown, the first mode control unit 114 includes a voltage command generating unit 121, an amplitude command value calculating unit 122, and a phase command value calculating unit 123, and a series of control cycles are repeated by these units.

[0064] The voltage command generating unit 121 calculates the voltage command of the secondary side voltage based on the command frequency ω*. For example, the voltage command generating unit 121 calculates the voltage command vector in the rotating coordinate system by the V / f method. The rotating coordinate system is a coordinate system that rotates synchronously with the command frequency. Specific examples of the rotating coordinate system include a γδ coordinate system, in which the γ axis with the magnetic pole direction of the rotor as the target direction and the δ axis perpendicular to the γ axis are coordinate axes. The voltage command generating unit 121 can calculate the voltage command vector based on the detection value of the secondary side current, the torque command, and the like.

[0065] The amplitude command value calculation unit 122 calculates the command value of the oscillation amplitude of the secondary side voltage. Hereinafter, the command value of the oscillation amplitude of the secondary side voltage is referred to as the “amplitude command value.” For example, the amplitude command value calculation unit 122 calculates the amplitude of the voltage command vector as the amplitude command value |V|.

[0066] The phase command value calculation unit 123 calculates the command value of the phase of the secondary side voltage. Hereinafter, the command value of the phase of the secondary side voltage is referred to as the "phase command value". For example, the phase command value calculation unit 123 calculates the phase command value θ based on the rotation angle of the rotating coordinate system relative to the fixed coordinate system and the phase angle of the voltage command vector in the rotating coordinate system. PWM .

[0067] The amplitude command value calculation unit 122 outputs the amplitude command value |V| to the power conversion control unit 112, and the phase command value calculation unit 123 outputs the phase command value θ to the power conversion control unit 112. PWM The power conversion control unit 112 controls the matrix converter circuit 10 to output a signal having an oscillation amplitude corresponding to the amplitude command value |V| and a phase command value θ PWM The secondary side voltage of the corresponding phase.

[0068] Second mode control unit

[0069] The second mode control unit 115 may also be configured to: generate a target phase of the secondary side voltage phase to maintain the primary-secondary phase difference within a target range; and calculate the deviation based on the comparison between the target phase and the secondary side voltage phase. The second mode control unit 115 may also be configured to: detect the current-voltage phase difference between the secondary side voltage phase and the secondary side current phase; and generate the target phase based on the current-voltage phase difference. The second mode control unit 115 may also be configured to: generate a target phase so that the target-primary phase difference between the target phase and the primary side voltage phase is within a target range; and calculate the deviation based on the comparison between the target phase and the secondary side current phase. For example, when the second control mode is selected by the mode switching unit 116, the second mode control unit 115 may generate a target phase of the secondary side voltage phase to maintain the primary-secondary phase difference within ±30° of an odd multiple of 60°, and control the matrix converter circuit 10 so as to reduce the deviation between the target phase and the phase of the secondary side voltage. For example, the second mode control unit 115 may also be configured so that the amplitude of the secondary side voltage (the secondary side voltage amplitude of the matrix converter circuit 10) follows an amplitude command value that is different from the amplitude of the primary side voltage (the primary side voltage amplitude of the matrix converter circuit 10). The second mode control unit 115 may generate a phase command value based on the deviation, and control the matrix converter circuit 10 to output a secondary side voltage having an oscillation amplitude corresponding to the amplitude command value and a phase corresponding to the phase command value. The second mode control unit 115 may set the amplitude command value to a value different from the oscillation amplitude of the primary side voltage.

[0070] As an example, Figure 5 As shown, the second mode control unit 115 includes a voltage command generating unit 136, an amplitude command value calculating unit 131, a current-voltage phase difference detecting unit 133, a target phase calculating unit 132, and a phase command value calculating unit 134, and a series of control cycles are repeated by these units.

[0071] Like the voltage command generating unit 121, the voltage command generating unit 136 calculates the voltage command of the secondary side voltage based on the command frequency ω*. For example, the voltage command generating unit 136 calculates the voltage command vector in the rotating coordinate system by the V / f method. The voltage command generating unit 136 can calculate the voltage command vector based on the detection value of the secondary side current, the torque command, and the like.

[0072] The amplitude command value calculation unit 131 calculates the amplitude command value similarly to the amplitude command value calculation unit 122. For example, the amplitude command value calculation unit 131 calculates the amplitude of the voltage command vector as the amplitude command value |V|. The amplitude command value |V| may be different from the oscillation amplitude of the primary side voltage. The current-voltage phase difference detection unit 133 calculates the phase difference of the secondary side voltage relative to the phase of the secondary side current. Hereinafter, the difference calculated by the current-voltage phase difference detection unit 133 is referred to as "current-voltage phase difference".

[0073] For example, the current-voltage phase difference detection unit 133 acquires the phase command value output to the power conversion control unit 112 in the previous control cycle as information indicating the phase of the secondary side voltage. Hereinafter, the phase command value is referred to as the "phase command value of the previous cycle". In addition, the current-voltage phase difference detection unit 133 calculates the phase of the secondary side current based on the current values ​​Iu, Iv, Iw of the power lines 12U, 12V, 12W acquired by the current information acquisition unit 113. Then, the current-voltage phase difference detection unit 133 calculates the current-voltage phase difference based on the phase command value of the previous cycle and the calculated phase of the secondary side current.

[0074] The target phase calculation unit 132 generates a target phase of the secondary side voltage so that the difference between the phase of the secondary side current and the phase of the primary side voltage has a value of ±30° of an odd multiple of 60°. For example, the target phase calculation unit 132 calculates a current target phase whose difference from the phase of the primary side voltage is ±30° of an odd multiple of 60°. If the phase of the secondary side current leads the phase of the primary side voltage, the target phase calculation unit 132 can calculate the current target phase by adding ±30° of an odd multiple of 60° to the phase of the primary side voltage. If the phase of the secondary side current lags behind the phase of the primary side voltage, the target phase calculation unit 132 can calculate the current target phase by subtracting ±30° of an odd multiple of 60° from the phase of the primary side voltage. The target phase calculation unit 132 generates the target phase of the secondary side voltage based on the current-voltage phase difference calculated by the current-voltage phase difference detection unit 133 and the current target phase. For example, the current-voltage phase difference may be calculated by subtracting the secondary side current phase from the secondary side voltage phase. In this case, the target phase calculation unit 132 may generate the target phase of the secondary side voltage by adding the current-voltage phase difference to the current target phase.

[0075] The phase command value calculation unit 134 calculates the phase command value based on the deviation between the target phase and the phase of the secondary side voltage. For example, the phase command value calculation unit 134 calculates the deviation between the target phase and the phase command value of the previous cycle, and calculates the phase command value so as to reduce the deviation. For example, the phase command value calculation unit 134 calculates the deviation between the target phase and the phase command value of the previous cycle, as shown in the addition point 141. The phase command value calculation unit 134 performs a proportional-integral operation on the deviation, as shown in block 142. In addition, the phase command value calculation unit 134 multiplies the result of the proportional-integral operation by the period Ts of one control cycle to calculate the phase change amount, as shown in block 143. In addition, the phase command value calculation unit 134 calculates the phase command value θ by adding the phase change amount to the phase command value of the previous cycle. PWM2 , as shown in addition point 144.

[0076] The amplitude command value calculation unit 131 outputs the amplitude command value |V| to the power conversion control unit 112, and the phase command value calculation unit 134 outputs the phase command value θ to the power conversion control unit 112. PWM2 The power conversion control unit 112 controls the matrix converter circuit 10 to output a signal having an oscillation amplitude corresponding to the amplitude command value |V| and a phase command value θ PWM2 The secondary side voltage of the corresponding phase.

[0077] As described above, since the current-voltage phase difference detection unit 133 adds the phase change amount to the phase command value of the previous cycle, the phase command value θ PWM2The delay of one cycle is included in the control cycle, and the reduction of the deviation is delayed accordingly. Therefore, the second mode control unit 115 may also be configured to: calculate the delay compensation value based on the primary side frequency; modify the phase command value based on the delay compensation value to compensate for the delay of the deviation reduction; and make the secondary side voltage phase follow the modified phase command value. The second mode control unit 115 may also be configured to repeat a control cycle, which includes: calculating the deviation; calculating the phase command value based on the previous phase command value and the deviation calculated in the previous control cycle; calculating the delay compensation value based on the primary side frequency; modifying the phase command value based on the delay compensation value; and making the secondary side voltage phase follow the modified phase command value. The second mode control unit 115 may also be configured to calculate the delay compensation value based on the deviation and the cycle time of the control cycle. For example, the second mode control unit 115 may calculate the delay compensation value based on the primary side frequency, and add the delay compensation value to the phase command value to compensate for the delay of the deviation reduction. The second mode control unit 115 may also be configured to: calculate the delay compensation value according to the weighted average of the command frequency and the primary side frequency; and gradually increase the weight of the primary side frequency in the delay compensation value after transferring from the first control mode to the second control mode. The second mode control unit 115 may also be configured to gradually increase the weight of the command frequency in the delay compensation value before transferring from the second control mode to the first control mode. For example, the second mode control unit 115 also includes a compensation value calculation unit 135.

[0078] The compensation value calculation unit 135 calculates the delay compensation value based on the primary side frequency ωin. For example, the compensation value calculation unit 135 calculates the delay compensation value by multiplying the primary side frequency ωin by the period Ts. As shown in the addition point 147, the phase command value calculation unit 134 adds the delay compensation value to the phase command value of the previous cycle to calculate the phase estimation value of the current secondary side voltage, and inputs the phase estimation value to the addition point 144. Accordingly, the phase command value θ is calculated by adding the phase change amount to the current phase estimation value of the secondary side voltage. PWM2 .

[0079] As the command frequency ω* approaches the primary side frequency ωin when the first mode control is transferred to the second mode control, the compensation value calculation unit 135 can calculate the delay compensation value based on the weighted average of the command frequency ω* and the primary side frequency ωin. For example, the compensation value calculation unit 135 calculates the delay compensation value by multiplying the weighted average by the time period Ts. After the mode switching unit 116 transfers the first mode control to the second mode control, the compensation value calculation unit 135 gradually increases the weight of the primary side frequency ωin in the delay compensation value and gradually reduces the weight of the command frequency ω*. As a result, the secondary side frequency is transferred from the command frequency ω* to the primary side frequency ωin, the transfer from the first mode control to the second mode control becomes smoother, and more stable control in the second mode becomes possible.

[0080] In addition, the compensation value calculation unit 135 can gradually increase the weight of the command frequency ω* and gradually reduce the weight of the primary side frequency ωin in the delay compensation value before the mode switching unit 116 transfers the second mode control to the first mode control. For example, when the difference between the command frequency and the frequency of the primary side voltage exceeds the second threshold, the mode switching unit 116 outputs a transfer preparation command to the second mode control unit 115. Accordingly, the compensation value calculation unit 135 gradually increases the weight of the command frequency ω* in the delay compensation value and gradually reduces the weight of the primary side frequency ωin. During this period, the second mode control continues. When the weight of the primary side frequency ωin in the delay compensation value becomes zero, the second mode control unit 115 outputs a preparation completion notification to the mode switching unit 116. Accordingly, the mode switching unit 116 transfers the second mode control to the first mode control.

[0081] The second mode control unit 115 may generate a target phase of the secondary side current instead of a target phase of the secondary side voltage, and control the matrix converter circuit 10 to reduce the deviation between the target phase and the phase of the secondary side current. For example, the second mode control unit 115 may calculate the phase command value θ by performing a proportional-integral operation or the like on the deviation between the target phase and the phase of the secondary side current, and adding the phase change amount to the phase estimation value of the secondary side voltage. PWM2 .

[0082] Degradation detection unit

[0083] The degradation detection unit 117 can be configured to: estimate an average heating value (average heating level) based on the secondary side current and the carrier frequency; calculate a concentration coefficient based on the primary-secondary frequency difference between the primary side frequency and the secondary side frequency; estimate a local heating level based on the average heating value and the concentration coefficient; calculate a degradation level based on the local heating level; and notify that the degradation level exceeds a predetermined level.

[0084] For example, Figure 6 As shown, the degradation detection unit 117 includes an average temperature rise estimation unit 151, a coefficient calculation unit 152, a local temperature rise estimation unit 153, a degradation level calculation unit 154, a comparison unit 157, and a notification unit 158. The average temperature rise estimation unit 151 is configured to estimate an average heating value based on the secondary side current and the carrier frequency. For example, the average temperature rise estimation unit 151 calculates the average heating value based on the following expression.

[0085] ΔT=A·I2+(B+C·fc+D)·I (1)

[0086] ΔT: Average heating value

[0087] I: Oscillation amplitude of secondary side current

[0088] fc: carrier frequency

[0089] A, B, C, D: coefficients

[0090] The coefficients A, B, C, and D are obtained in advance through actual machine testing or simulation. The average heating value calculated by expression (1) includes a steady loss caused by conduction of the secondary side current and a switching loss caused by turning on / off the switching element.

[0091] The coefficient calculation unit 152 is configured to calculate the concentration coefficient based on the primary-secondary frequency difference. For example, the coefficient calculation unit 152 obtains information about the difference between the primary side frequency and the command frequency from the mode switching unit 116, and calculates the concentration coefficient based on the information. In detail, the coefficient calculation unit 152 increases the concentration coefficient as the absolute difference between the primary side frequency and the command frequency decreases. For example, the degradation detection unit 117 also includes a coefficient profile storage unit 161.

[0092] The coefficient profile storage unit 161 (profile storage device) stores a coefficient profile representing the relationship between the absolute value of the primary-secondary phase difference and the concentration coefficient so that the concentration coefficient increases as the absolute value of the primary-secondary frequency difference decreases. The primary-secondary frequency difference may be the difference between the primary side frequency and the command frequency (command-primary frequency difference). The coefficient profile stored in the coefficient profile storage unit 161 may be a discrete data sequence or a function.

[0093] The coefficient calculation unit 152 may also be configured to calculate the concentration coefficient based on the absolute value of the primary-secondary frequency difference and the coefficient profile. For example, the coefficient calculation unit 152 derives the concentration coefficient corresponding to the absolute difference between the primary side frequency and the command frequency in the coefficient profile.

[0094] Figure 7 is a graph illustrating a coefficient profile, wherein the horizontal axis represents the magnitude of the absolute value of the difference, and the vertical axis represents the concentration coefficient. The coefficient profile is determined such that when the absolute difference value is equal to or greater than a predetermined threshold value f1, the concentration coefficient is zero, and when the absolute difference value is less than the threshold value f1, the concentration coefficient gradually increases as the absolute difference value decreases.

[0095] The local temperature rise estimation unit 153 is configured to estimate the local heating level based on the average heating value (average heating level) and the concentration coefficient. For example, the local temperature rise estimation unit 153 calculates the local heating level by multiplying the average heating value by the concentration coefficient. Figure 7 In the case of the determination coefficient profile shown, when the absolute value of the difference is equal to or greater than the threshold value f1, the local heating level is set to zero and the progress of degradation due to the temperature rise is ignored.

[0096] The degradation level calculation unit 154 is configured to calculate the degradation level of the switching element based on the local heating level. For example, the degradation level calculation unit 154 may also be configured to: calculate the degradation progress based on the local heating level; and integrate the degradation progress to update the degradation level. The degradation level calculation unit 154 may calculate the degradation level by repeatedly calculating the degradation progress based on the local heating level in the control cycle and integrating the degradation progress.

[0097] One of the reasons for the degradation of the switching element due to temperature rise is the contraction of the conductive part caused by the temperature rise and temperature drop, so the degradation level of the switching element is also affected by the repetition frequency of the temperature rise and temperature drop. Therefore, the degradation level calculation unit 154 can also be configured to: calculate the temperature rise frequency based on the primary-secondary frequency difference; and integrate the degradation progress by the temperature rise frequency to update the degradation level. For example, the degradation level calculation unit 154 can also be configured to: calculate the degradation level by repeatedly calculating the degradation progress based on the local heating level, calculating the temperature rise frequency based on the primary-secondary frequency difference, and integrating the result of multiplying the degradation progress by the temperature rise frequency. For example, the degradation level calculation unit 154 includes a degradation profile storage unit 162, a degradation progress calculation unit 155, a frequency calculation unit 156, and an integration unit 159, and the degradation progress is repeatedly integrated by these units.

[0098] The degradation profile storage unit 162 (degradation profile storage device) stores a degradation profile indicating the relationship between the local heating level and the progress of degradation. Figure 8is a graph illustrating a degradation profile, wherein the horizontal axis represents the local heating level and the vertical axis represents the degradation progress. The degradation profile indicates that the degradation progress increases as the local heating level increases. For example, the degradation profile may be defined such that when the local heating level is equal to or less than a predetermined threshold value T1, the degradation progress is zero, and when the local heating level exceeds the threshold value T1, the degradation progress increases as the local heating level increases. In addition, the degradation profile may be defined such that when the local heating level is equal to or greater than a threshold value T2, the degradation progress is constant, wherein the threshold value T2 is greater than T1.

[0099] The degradation progress may be a numerical value obtained by converting the degradation of the switching element into the number of repetitions of temperature increase and temperature decrease. Since the life (allowable degradation level) of the switching element can be determined by the number of repetitions of temperature increase / decrease, when the degradation progress is represented by the number of repetitions of temperature increase / decrease, the degradation level and life can be easily compared.

[0100] The degradation progress calculation unit 155 is configured to calculate the degradation progress based on the local heating level and the degradation profile. For example, the degradation progress calculation unit 155 obtains the degradation progress corresponding to the local heating level in the degradation profile.

[0101] The frequency calculation unit 156 calculates the frequency of the local temperature rise that occurs per unit time (for example, every second). The temperature of the switching element increases locally during the period in which the phase of the primary side voltage and the phase of the secondary side current are aligned, and gradually decreases as the phase difference between the phase of the primary side voltage and the phase of the secondary side current increases. Therefore, it can be said that the frequency of the phase alignment of the primary side voltage and the phase of the secondary side current per unit time is substantially proportional to the frequency of the local temperature rise. Therefore, the frequency calculation unit 156 calculates the difference between the primary side frequency and the secondary side frequency as the frequency of the local temperature rise. For example, the frequency calculation unit 156 calculates the absolute difference between the primary side frequency and the command frequency as the frequency of the local temperature rise.

[0102] The integration unit 159 integrates the degradation progress calculated by the degradation progress calculation unit 155 according to the frequency calculated by the frequency calculation unit 156. For example, the integration unit 159 multiplies the degradation progress by the frequency to calculate the degradation progress per unit time, and also multiplies the degradation progress by the period Ts of the control cycle to calculate the degradation progress of each cycle. Then, the degradation progress of each cycle is added to the degradation level calculated in the previous control cycle.

[0103] The comparison unit 157 compares the degradation level calculated by the degradation level calculation unit 154 with a predetermined level. The notification unit 158 ​​notifies that the degradation level exceeds the predetermined level. For example, the notification unit 158 ​​displays that the degradation level has exceeded the predetermined level on a display screen such as a liquid crystal display. The notification unit 158 ​​may output a notification signal to the host controller 200 indicating that the degradation level has exceeded the predetermined level.

[0104] As described above, as the difference between the primary side frequency and the secondary side frequency decreases, the time that the phase of the primary side voltage is aligned with the phase of the secondary side current continues increases. Therefore, as the difference between the primary side frequency and the secondary side frequency becomes smaller, the local temperature rise value of any one of the switching elements of the matrix converter circuit 10 becomes larger, and the fluctuation width of the temperature due to this also becomes larger. According to the degradation detection unit 117, it is possible to evaluate the degradation level of the switching element in consideration of the temperature fluctuation, and notify the degradation of the switching element at an appropriate timing.

[0105] In the first control mode, the difference between the secondary side phase and the primary side phase of the matrix converter circuit 10 can be changed without limit. On the other hand, in the second control mode, the difference between the secondary side phase and the primary side phase is maintained within the target range. When the mode switching unit 116 transfers the first mode control to the second mode control, the state in which the primary side voltage phase and the secondary side current phase are aligned is forcibly avoided, thereby suppressing the occurrence of local temperature rise. Accordingly, the coefficient calculation unit 152 can also be configured to reduce the concentration coefficient in response to the transfer from the first control mode to the second control mode. For example, the coefficient calculation unit 152 can set the concentration coefficient to zero when the first mode control is transferred to the second mode control.

[0106] The mode switching unit 116 corresponds to a state transition unit configured to transition a state in the matrix converter circuit from a first state to a second state having a smaller switching loss than the first state in response to the primary-secondary frequency difference falling below a predetermined threshold. Transitioning the first control mode to the second control mode is an example of transitioning a state in the matrix converter circuit 10 from a first state to a second state having a smaller switching loss than the first state in response to the primary-secondary frequency difference falling below a predetermined threshold. The second state may be a state in which the total loss (power loss) of the switching loss and the stability loss is less than that of the first state.

[0107] In the second state, switching of the connection between the primary side and the secondary side of the matrix converter circuit 10 is performed less frequently than in the first state. For example, the first state may be a state in which switching of the connection between the primary side and the secondary side of the matrix converter circuit 10 is performed, and the second state may be a state in which the switching of the connection is performed less frequently than in the first state. For example, the second state may be a state in which the carrier frequency is lower than in the first state. For example, in the first state, switching of the connection state is repeatedly performed at a first carrier frequency, and in the second state, switching of the connection is repeatedly performed at a second carrier frequency lower than the first carrier frequency.

[0108] The primary line of the primary side and the secondary line of the secondary side may be repeatedly connected and disconnected in the first state, and the electrical connection between the primary line and the secondary line may be maintained in the second state. For example, the second state may be a state in which the primary side and the secondary side are directly connected by the matrix converter circuit 10. For example, the second state may be a state in which the power lines 11R, 11S, 11T (primary lines) and the power lines 12U, 12V, 12W (secondary lines) are directly connected by the matrix converter circuit 10.

[0109] Hardware configuration of control circuit

[0110] Fig. 9 1 is a block diagram illustrating the hardware configuration of the control circuit 100. Fig. 9 As shown in , the control circuit 100 includes a processor 191, a memory 192, a storage section 193, a communication port 194, an input / output port 195, and a switch control circuit 196. The processor 191 may include a plurality of processing devices, the memory 192 may include a plurality of memory devices, and the storage section 193 may include a plurality of storage devices.

[0111] The storage unit 193 includes a computer-readable storage medium, such as a non-volatile semiconductor memory. The storage unit 193 stores a program to cause the control circuit 100 to perform a power conversion method, including: a first mode control, including performing bidirectional power conversion between primary-side power and secondary-side power by the matrix converter circuit 10, so that the secondary-side frequency of the matrix converter circuit 10 follows the command frequency; a second mode control, including maintaining the difference between the secondary-side phase and the primary-side phase of the matrix converter circuit 10 within ±30° of an odd multiple of 60° by the matrix converter circuit 10; and a mode switching, including switching the control mode of the matrix converter circuit 10 based on the difference between the command frequency and the primary-side frequency of the matrix converter circuit 10 and a predetermined threshold value, so that if the difference is higher than the threshold value, the control performed by the first mode control unit 114 is performed, and if the difference is lower than the threshold value, the control performed by the second mode control unit 115 is performed. The storage section 193 may store a program to cause the control circuit 100 to perform a power conversion method, including estimating an average heating value (average heating level) based on a secondary-side current of a matrix converter circuit 10 that performs bidirectional power conversion between primary-side power and secondary-side power, calculating a concentration coefficient based on a difference between a primary-side frequency and a secondary-side frequency of the matrix converter circuit 10, estimating a local heating level based on the average heating value and the concentration coefficient, calculating a degradation level based on the local heating level, and notifying that the degradation level has exceeded a predetermined level. For example, the storage section 193 stores a program for configuring each functional block in the control circuit 100.

[0112] The memory 192 temporarily stores the program loaded from the storage medium of the storage section 193 and the operation result of the processor 191. The processor 191 configures each functional block of the control circuit 100 by executing the program in cooperation with the memory 192. The input / output port 195 inputs and outputs electrical signals between the voltage detection circuit 40 and the current sensor 50 according to the command from the processor 191. The communication port 194 performs information communication with the host controller 200 according to the command from the processor 191. The switch control circuit 196 outputs a drive signal for turning on and off the bidirectional switches 2RU, 2SU, 2TU, 2RV, 2SV, 2TV, 2RW, 2SV, 2TW to the matrix converter circuit 10 according to the command from the processor 191.

[0113] It should be noted that the control circuit 100 is not necessarily limited to a circuit in which each function is configured by a program. For example, at least a part of the functions of the control circuit 100 may be configured by a dedicated logic circuit or an application specific integrated circuit (ASIC) in which the dedicated logic circuit is integrated.

[0114] Power conversion process

[0115] Next, a control process of the matrix converter circuit 10 performed by the control circuit 100 will be described as an example of a power conversion method. The control process includes: a first mode control including performing bidirectional power conversion between primary side power and secondary side power by the matrix converter circuit 10 so that the secondary side frequency of the matrix converter circuit 10 follows the command frequency; a second mode control including maintaining the difference between the secondary side phase and the primary side phase of the matrix converter circuit 10 within ±30° of an odd multiple of 60° by the matrix converter circuit 10; and a mode switching including switching the control mode of the matrix converter circuit 10 based on the difference between the command frequency and the primary side frequency of the matrix converter circuit 10 and a predetermined threshold value, so that if the difference is higher than the threshold value, the control performed by the first mode control unit 114 is performed, and if the difference is lower than the threshold value, the control performed by the second mode control unit 115 is performed. The control process may also include estimating an average heating level based on a secondary-side current of a matrix converter circuit 10 that performs bidirectional power conversion between primary-side power and secondary-side power, calculating a concentration coefficient based on a difference between a primary-side frequency and a secondary-side frequency of the matrix converter circuit 10, estimating a local heating value (local heating level) based on the average heating value and the concentration coefficient, calculating a degradation level based on the local heating level, and notifying that the degradation level exceeds a predetermined level.

[0116] For example, the control circuit 100 performs the control mode switching process, the first mode control process, the second mode control process, and the degradation detection process in parallel. In the following, each process will be described in detail by way of example.

[0117] Control mode switching process

[0118] like Fig.10 As shown, the control circuit 100 sequentially performs steps S01, S02, S03, S04, S05, and S06. In step S01, the mode switching unit 116 outputs a first mode command to the first mode control unit 114. In response, the first mode control unit 114 initiates a first mode control process. In step S02, the mode switching unit 116 waits for the difference between the command frequency and the primary side frequency to drop below a first threshold. In step S03, the mode switching unit 116 outputs a second mode command to the second mode control unit 115. In response, the second mode control unit 115 initiates a second mode control process. In step S04, the mode switching unit 116 waits for the difference between the command frequency and the primary side frequency to exceed a second threshold.

[0119] In step S05, the mode switching unit 116 outputs a transfer preparation command to the first mode control to the second mode control unit 115. In response, the second mode control unit 115 initiates transfer preparation to the first mode control, as described below. In step S06, the mode switching unit 116 waits for the second mode control unit 115 to complete the transfer preparation. The control circuit 100 then returns the process to step S01. Thus, the first mode control process performed by the first mode control unit 114 is resumed again. The control circuit 100 repeats the above process.

[0120] First mode control process

[0121] like Fig.11 As shown, the control circuit 100 sequentially performs steps S11 to S16. In step S11, the first mode control unit 114 waits for the output of the first mode command from the mode switching unit 116. In step S12, the voltage command generating unit 121 calculates the voltage command vector of the secondary side voltage based on the command frequency ω*. In step S13, the amplitude command value calculating unit 122 calculates the amplitude of the voltage command vector as the amplitude command value. In step S14, the phase command value calculating unit 123 calculates the phase command value based on the rotation angle of the rotating coordinate system relative to the fixed coordinate system and the phase angle of the voltage command vector in the rotating coordinate system. In step S15, the amplitude command value calculating unit 122 outputs the amplitude command value to the power conversion control unit 112, and the phase command value calculating unit 123 outputs the phase command value to the power conversion control unit 112. The power conversion control unit 112 controls the matrix converter circuit 10 to output a secondary side voltage having an oscillation amplitude corresponding to the oscillation amplitude of the secondary side voltage and a phase corresponding to the phase command value.

[0122] In operation S16, the first mode control unit 114 checks whether the second mode command is output from the mode switching unit 116. If it is determined in operation S16 that the second mode command is not output, the control circuit 100 returns the process to operation S12. Thereafter, the first mode control process is repeated until the mode switching unit 116 outputs the second mode command. If it is determined in operation S16 that the second mode command is output, the control circuit 100 completes the first mode control process.

[0123] Second mode control process

[0124] like Fig.12As shown, the control circuit 100 first executes steps S21, S22, S23, and S24. In step S21, the second mode control unit 115 waits for the output of the second mode command from the mode switching unit 116. In step S22, the compensation value calculation unit 135 begins to gradually increase the weight of the primary side frequency and gradually reduce the weight of the command frequency in the delay compensation value. In step S23, the second mode control unit 115 performs phase tracking control to maintain the difference between the phase of the secondary side current and the phase of the primary side voltage within ±30° of an odd multiple of 60°. The specific content of step S23 will be described later. In step S24, the second mode control unit 115 confirms whether a transfer preparation command to the first mode control is output from the mode switching unit 116.

[0125] If it is determined in step S24 that the transfer preparation command is not output, the control circuit 100 returns the process to step S23. Thereafter, the phase tracking control is continued until the transfer preparation command is output.

[0126] If it is determined in step S24 that the transfer preparation command is output, the control circuit 100 executes steps S25, S26, and S27. In step S25, the compensation value calculation unit 135 starts to gradually increase the weight of the command frequency in the delay compensation value and gradually decrease the weight of the primary side frequency. In step S26, the second mode control unit 115 performs phase tracking control. In step S27, the second mode control unit 115 checks whether the weight of the primary side frequency in the delay compensation value has reached zero.

[0127] If it is determined in step S27 that the weight of the primary side frequency in the delay compensation value has not reached zero, the control circuit 100 returns the process to step S26. Thereafter, the phase tracking control is continued until the weight of the primary side frequency in the delay compensation value reaches zero. If it is determined in step S27 that the weight of the primary side frequency in the delay compensation value reaches zero, the control circuit 100 completes the second mode control process.

[0128] Fig.13 FIG. 2 is a flow chart illustrating the phase tracking control process in steps S23 and S26. Fig.13 As shown, the control circuit 100 sequentially executes steps S31, S32, S33, S34, S35, S36, S37, S38, and S39. In step S31, the voltage command generating unit 136 calculates the voltage command vector of the secondary side voltage based on the command frequency ω*. In step S32, the amplitude command value calculating unit 131 calculates the amplitude of the voltage command vector as the amplitude command value.

[0129] In step S33, the current information acquisition unit 113 acquires information on the secondary side current. For example, the current information acquisition unit 113 obtains the current value of the power lines 12U, 12V, 12W from the current sensor 50. In step S34, the current-voltage phase difference detection unit 133 calculates the phase difference (current-voltage phase difference) of the secondary side voltage relative to the phase of the secondary side current.

[0130] In step S35, the target phase calculation unit 132 generates a target phase of the secondary side voltage so that the difference between the phase of the secondary side current and the phase of the primary side voltage is ±30° of an odd multiple of 60°. For example, the target phase calculation unit 132 calculates a current target phase whose difference from the phase of the primary side voltage is ±30° of an odd multiple of 60°, and generates the target phase of the secondary side voltage by adding the current-voltage phase difference to the current target phase. In step S36, the phase command value calculation unit 134 calculates the deviation between the target phase and the phase command value of the previous cycle, and calculates the phase change amount for reducing the deviation.

[0131] In step S37, the compensation value calculation unit 135 calculates the delay compensation value. In step S38, the phase command value calculation unit 134 adds the delay compensation value to the phase command value of the previous cycle to calculate the phase estimation value of the current secondary side voltage, and adds the phase change amount to the phase estimation value to calculate the phase command value.

[0132] In step S39, the amplitude command value calculation unit 131 outputs the amplitude command value to the power conversion control unit 112, and the phase command value calculation unit 134 outputs the phase command value to the power conversion control unit 112. The power conversion control unit 112 controls the matrix converter circuit 10 to output a secondary side voltage having an oscillation amplitude corresponding to the amplitude command value and a phase corresponding to the phase command value. Thus, one cycle of the phase following control process is completed. It should be noted that the execution order of the steps can be changed as appropriate.

[0133] Degradation Detection Process

[0134] like Fig.14 As shown, the control circuit 100 first performs steps S41, S42, S43, S44, S45, S46, and S47. In step S41, the average temperature rise estimation unit 151 estimates the average heating value based on the secondary side current and the carrier frequency. In step S42, the coefficient calculation unit 152 calculates the concentration coefficient based on the difference between the primary side frequency and the secondary side frequency. In step S43, the local temperature rise estimation unit 153 estimates the local heating level based on the average heating value and the concentration coefficient. In step S44, the degradation progress calculation unit 155 calculates the degradation progress based on the local heating level and the degradation profile.

[0135] In step S45, the frequency calculation unit 156 calculates the difference between the primary side frequency and the secondary side frequency as the frequency of the local temperature rise. In step S46, the integration unit 159 calculates the degradation level by integrating the degradation progress calculated by the degradation progress calculation unit 155 and the frequency calculated by the frequency calculation unit 156. In step S47, the comparison unit 157 checks whether the degradation level calculated by the degradation level calculation unit 154 exceeds a predetermined level.

[0136] If step S47 determines that the degradation level does not exceed the predetermined level, the control circuit 100 returns the process to step S41. Thereafter, until the degradation level exceeds the predetermined level, the calculation of the degradation progress and the frequency and the integration of the degradation progress by the calculation result of the frequency are repeated.

[0137] If step S47 determines that the degradation level exceeds the predetermined level, the control circuit 100 performs step S48. In step S48, the notification unit 158 ​​notifies that the degradation level exceeds the predetermined level. This completes the degradation detection process.

[0138] Effects of the Current Embodiment

[0139] As described above, the power conversion device 1 includes: a matrix converter circuit 10, which is configured to perform bidirectional power conversion between primary-side power and secondary-side power; a degradation level calculation unit 154, which is configured to calculate the degradation level based on the secondary-side current of the matrix converter circuit 10, the carrier frequency, and the difference between the primary-side frequency and the secondary-side frequency of the matrix converter circuit; and a notification unit 158, which is configured to notify that the degradation level exceeds a predetermined level.

[0140] The matrix converter circuit that performs bidirectional power conversion between the primary side AC and the secondary side AC has more switching elements than the inverter circuit that performs power conversion between DC and the secondary side AC. Therefore, the heat generated in each switching element is small. This has a favorable effect on the life of the device.

[0141] However, in the matrix converter circuit, when the difference between the frequency of the primary side voltage and the frequency of the secondary side current becomes small, heat is concentrated on a specific switching element, and degradation of the switching element may be promoted. Therefore, if degradation progresses unexpectedly, there is a possibility that timely maintenance may not be performed before failure.

[0142] On the contrary, according to the power conversion device 1, in addition to the secondary side current and the carrier frequency, the degradation level is calculated based on the difference between the primary side frequency and the secondary side frequency. Therefore, the degradation level can be evaluated in consideration of the promotion of degradation caused by the reduction of the difference between the primary side frequency and the secondary side frequency. When the degradation level exceeds a predetermined level, it will be reported. Therefore, it is effective for timely maintenance of the matrix converter circuit 10.

[0143] The power conversion device 1 may further include: an average temperature rise estimation unit 151 configured to estimate an average heating level based on the secondary side current and the carrier frequency; a coefficient calculation unit 152 configured to calculate a concentration coefficient based on the difference between the primary side frequency and the secondary side frequency; and a local temperature rise estimation unit 153 configured to estimate a local heating level based on the average heating level and the concentration coefficient, and wherein the degradation level calculation unit 154 is further configured to calculate the degradation level based on the local heating level. In this case, it is possible to more appropriately evaluate the degradation level in consideration of the promotion of degradation caused by the reduction of the difference between the primary side frequency and the secondary side frequency.

[0144] The degradation level calculation unit 154 may also be configured to calculate the degradation level by repeatedly calculating the degradation progress based on the local heating level and integrating the result multiplied by the degradation progress. In this case, the degradation level can be more appropriately evaluated.

[0145] The degradation level calculation unit 154 may also be configured to calculate the degradation level by repeatedly calculating the degradation progress based on the local heating level, calculating the temperature rise frequency based on the difference between the primary side frequency and the secondary side frequency, and integrating the result of multiplying the degradation progress by the temperature rise frequency. In this case, the degradation level can be more appropriately evaluated.

[0146] The power conversion device 1 may further include a profile storage unit 161 that stores a coefficient profile representing a relationship between an absolute value of a difference between a primary side frequency and a secondary side frequency and a concentration coefficient, such that the concentration coefficient increases as the absolute value of the difference decreases, and wherein the coefficient calculation unit 152 is further configured to calculate the concentration coefficient based on the absolute value of the difference and the coefficient profile. In this case, an appropriate concentration coefficient can be easily calculated.

[0147] The power conversion device 1 may further include a state transition unit 116 configured to transition the switch state in the matrix converter circuit 10 from a first state to a second state having a smaller switching loss than the first state in response to the difference between the primary side frequency and the secondary side frequency falling below a predetermined level, and wherein the coefficient calculation unit 152 is further configured to reduce the concentration coefficient in response to the state transition unit 116 transitioning the first state to the second state. In this case, overestimation of the degradation level can be suppressed. Therefore, timely maintenance of the matrix converter circuit 10 is more effective.

[0148] In the second state, the switching of the connection between the primary side and the secondary side of the matrix converter circuit 10 is performed less frequently than in the first state. For example, the first state may be a state in which the switching of the connection between the primary side and the secondary side of the matrix converter circuit 10 is performed, and the second state may be a state in which the switching of the connection is performed less frequently than in the first state. In this case, by shifting the first state to the second state, the heat generation in each switching element is sufficiently suppressed. Therefore, even if the concentration coefficient is reduced as the first state shifts to the second state, the degradation level is less likely to be underestimated. Therefore, timely maintenance of the matrix converter circuit 10 is more effective.

[0149] The first state may be a state in which the difference between the secondary side phase and the primary side phase of the matrix converter circuit 10 changes without limit, and the second state may be a state in which the difference between the secondary side phase and the primary side phase is maintained within ±30° of an odd multiple of 60°. In this case, by shifting the first state to the second state, the heat generation in each switching element is sufficiently suppressed. Therefore, even if the concentration coefficient is reduced as the first state shifts to the second state, the degradation level is less likely to be underestimated. Therefore, timely maintenance of the matrix converter circuit 10 is more effective.

[0150] The power conversion device 1 may also include: a frequency control unit 114, which is configured by the matrix converter circuit 10 so that the secondary side frequency follows the command frequency; and a phase tracking control unit 115, which is configured by the matrix converter circuit 10 to maintain the difference between the secondary side phase and the primary side phase within ±30° of an odd multiple of 60°, and wherein the state transition unit 116 is also configured to transfer the first state to the second state by transferring the control performed by the frequency control unit 114 to the control performed by the phase tracking control unit 115. In this case, based on the switching of the control method, the transition from the first state to the second state can be quickly detected, and the concentration coefficient can be quickly reduced. This makes it possible to more reliably suppress the overestimation of the degradation level.

[0151] Although the embodiments have been described above, the present invention is not necessarily limited to the embodiments described above, but various modifications may be made without departing from the scope of the present invention.

Claims

1. A power conversion device, comprising: a matrix converter circuit configured to perform bidirectional power conversion between a primary side and a secondary side; an average temperature rise estimation unit configured to estimate an average heating level based on a secondary side current and a carrier frequency of the matrix converter circuit; a coefficient calculation unit configured to calculate a concentration coefficient based on a primary-secondary frequency difference between a primary-side frequency and a secondary-side frequency of the matrix converter circuit; a local temperature rise estimation unit configured to estimate a local heating level based on the average heating level and the concentration coefficient; a degradation level calculation unit configured to calculate a degradation level based on the local heating level; as well as The notification unit is configured to output a degradation notification in response to determining that the degradation level exceeds a predetermined level.

2. The power conversion device according to claim 1, wherein the degradation level calculation unit is further configured to: calculating a degradation progress based on the local heating level; and The degradation progress is integrated to update the degradation level.

3. The power conversion device according to claim 2, further comprising a degradation profile storage device storing a degradation profile between the local heating level and the degradation progress, The degradation level calculation unit is further configured to calculate the degradation progress based on the degradation profile and the local heating level. 4 . The power conversion device according to claim 3 , wherein the degradation profile indicates that the degradation progress increases as the local heating level increases.

5. The power conversion device according to any one of claims 2 to 4, wherein the degradation level calculation unit is further configured to: calculating a temperature rise frequency based on the primary-secondary frequency difference; and The degradation progress is integrated according to the temperature increase frequency to update the degradation level.

6. The power conversion device according to any one of claims 1 to 4, further comprising a coefficient profile storage device storing a coefficient profile between the absolute value of the primary-secondary frequency difference and the concentration coefficient, The coefficient calculation unit is further configured to calculate the concentration coefficient based on the coefficient profile and an absolute value of the primary-secondary frequency difference. 7 . The power conversion device according to claim 6 , wherein the coefficient profile shows that the concentration coefficient increases as the absolute value of the primary-secondary frequency difference decreases.

8. The power conversion device according to any one of claims 1 to 4, further comprising a state transition unit configured to transition a state in the matrix converter circuit from a first state to a second state having a smaller power loss than the first state in response to the primary-secondary frequency difference falling below a predetermined threshold value, The coefficient calculation unit is further configured to decrease the concentration coefficient in response to a transition from the first state to the second state.

9. The power conversion device according to claim 8, wherein: Switching of the connection between the primary side and the secondary side of the matrix converter circuit in the second state is performed less frequently than in the first state.

10. The power conversion device according to claim 9, wherein the switching of the connection is repeatedly performed at a first carrier frequency in the first state, and In the second state, switching of the connection is repeatedly performed at a second carrier frequency which is lower than the first carrier frequency.

11. The power conversion device according to claim 8, wherein the primary side includes a primary line and the secondary side includes a secondary line, wherein the primary line and the secondary line are repeatedly connected and disconnected in the first state, and Wherein in the second state the electrical connection between the primary line and the secondary line is maintained.

12. The power conversion device according to claim 8, wherein a primary-secondary phase difference between a secondary side phase and a primary side phase of the matrix converter circuit changes in the first state, and Wherein the primary-secondary phase difference is maintained within a predetermined target range in the second state.

13. The power conversion device according to claim 12, further comprising: a frequency control unit configured by the matrix converter circuit to make the secondary side frequency follow a command frequency in the first state; as well as A phase tracking control unit is configured to maintain the primary-secondary phase difference within the target range in the second state.

14. The power conversion device according to claim 13, wherein the primary side includes the primary side phase and a primary side adjacent phase adjacent to the primary side phase, in, The primary side phase is the primary side voltage phase, Wherein, the secondary side phase is the secondary side current phase, wherein the primary-secondary phase difference is the difference between the secondary side current phase and the primary side voltage phase, and The phase tracking control unit is further configured to maintain the primary-secondary phase difference within the target range to maintain the secondary side phase between the primary side phase and the primary side adjacent phase.

15. The power conversion device according to claim 14, wherein the primary intra-phase difference between the primary side phase and the primary side adjacent phase is 120°, and The phase tracking control unit is further configured to maintain the primary-secondary phase difference within the target range, which is ±30° which is an odd multiple of 60°.

16. A method for converting electric power, comprising: estimating an average heating level based on a secondary-side current and a carrier frequency of a matrix converter circuit that performs bidirectional power conversion between primary-side power and secondary-side power; calculating a concentration coefficient based on a primary-secondary frequency difference between a primary side frequency and a secondary side frequency of the matrix converter circuit; estimating a local heating level based on the average heating level and the concentration coefficient; calculating a degradation level based on the local heating level; and In response to determining that the degradation level exceeds a predetermined level, a degradation notification is output.

17. The power conversion method of claim 16, wherein calculating the degradation level based on the local heating level comprises: calculating a degradation progress based on the local heating level; and The degradation progress is integrated to update the degradation level.

18. A non-transitory memory device having instructions stored thereon, wherein the instructions, in response to being executed by a processing device, cause the processing device to perform an operation, the operation comprising: estimating an average heating level based on a secondary-side current and a carrier frequency of a matrix converter circuit that performs bidirectional power conversion between primary-side power and secondary-side power; calculating a concentration coefficient based on a primary-secondary frequency difference between a primary side frequency and a secondary side frequency of the matrix converter circuit; estimating a local heating level based on the average heating level and the concentration coefficient; calculating a degradation level based on the local heating level; and In response to determining that the degradation level exceeds a predetermined level, a degradation notification is output.

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