Electric power conversion apparatus
Patent Information
- Application Number
- JP2025509448
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-09-25
- Publication Date
- 2025-12-15
- Estimated Expiration
- 2043-03-29
Abstract
Description
Power Conversion Device
[0001] The present disclosure relates to a power conversion device.
[0002] Modular multilevel converters (MMCs) are known as large-capacity power conversion devices installed in power grids. An MMC consists of arms in which multiple unit converters called cells are cascaded. Each cell includes multiple semiconductor switches and a DC capacitor. By turning the semiconductor switches on and off, the MMC outputs either a voltage across the DC capacitor or zero voltage.
[0003] One method of connecting the arms of a three-phase MMC is the delta connection method. A delta-connection cascade three-phase MMC (hereinafter also referred to as a "delta-connection MMC") has a configuration in which multiple cells are cascaded and arms with reactors connected in series are delta-connected.
[0004] In a delta-connected MMC, in order to maintain the voltage of the storage elements within a certain range, a first voltage control is performed to maintain the representative voltage value of the storage elements of all cells constant, and a second voltage control is performed to suppress variation in the representative voltage value of the storage elements of the cells included in each arm between the arms.
[0005] However, when the voltage of the three-phase AC power supply fluctuates or when the three-phase AC voltage is unbalanced, the first voltage control and the second voltage control may interfere with each other, which may hinder stable operation of the delta-connected MMC. Patent Document 1 (WO 2018 / 211624) considers decoupling the first voltage control and the second voltage control by removing the control variable of the first voltage control from the control variable of the second voltage control.
[0006] International Publication No. 2018 / 211624
[0007] However, when the voltage of the three-phase AC power supply fluctuates or when the three-phase AC voltage is unbalanced, there is a problem that interference occurs in the active power output generated by the output current controlled in accordance with the current command values, which are the respective manipulated variables, in the first voltage control and the second voltage control.
[0008] Specifically, the first voltage control (i.e., control that keeps constant the representative voltage values of the storage elements of all cells) outputs active power due to the interaction between the output current according to the three-phase balanced current command value and the three-phase unbalanced voltage. This active power corresponds to the "active power that is not balanced between the arms" that is the control target of the second voltage control, and therefore becomes a disturbance to the second voltage control.
[0009] Furthermore, the second voltage control (i.e., control that suppresses variations between arms in the voltage representative values of the storage elements of the cells included in each arm) outputs active power due to the interaction between the output current according to the three-phase unbalanced current command value and the three-phase unbalanced voltage. This active power corresponds to the "active power common to each arm" that is the control target of the first voltage control, and therefore becomes a disturbance to the first voltage control.
[0010] An object of one aspect of the present disclosure is to stably operate a three-phase MMC in a power conversion device equipped with a delta-connected cascade type three-phase MMC when the voltage of the three-phase AC power supply fluctuates or when the three-phase AC voltage is unbalanced.
[0011] According to one embodiment, there is provided a power conversion device connected to a three-phase AC power source. The power conversion device includes a power converter including three delta-connected arms, and a control device that controls the power converter. Each of the three arms is configured by connecting a plurality of unit converters in series. Each of the plurality of unit converters includes a plurality of switching elements and storage elements connected to the plurality of switching elements. The control device includes a first current command calculation unit that calculates a first current command value for the power converter based on a DC voltage command value and a voltage representative value that represents the voltage values of all storage elements included in the power converter, a power calculation unit that calculates an unbalanced component of the output power of each of the three arms based on an output current representative value and an output voltage representative value of a cell group including each unit converter included in that arm, a first power command calculation unit that calculates an unbalanced component command value for the output power of each arm so that the voltage values of the storage elements are balanced among the three arms, and a second power command calculation unit that calculates an unbalanced component command value for the output power of each arm based on the unbalanced component of the output power of each arm and the DC voltage command value of each arm. the power converter includes a phase current command calculation unit that generates a current command value for each phase based on an unbalanced component command value of the output power; a second current command calculation unit that calculates a second current command value for the power converter based on an output voltage representative value of a cell group included in each arm and the current command value for each phase; a voltage command generation unit that generates an output voltage command value for controlling the output voltage of each unit converter based on the output current of the power converter and a current command value calculated from the first current command value and the second current command value; and a gate signal generation unit that generates a control signal for each switching element included in the power converter based on the output voltage command value.
[0012] According to the present disclosure, in a power conversion device equipped with a delta-connection cascade type three-phase MMC, the three-phase MMC can be operated stably even when the voltage of the three-phase AC power supply fluctuates or when the three-phase AC voltage is unbalanced.
[0013] FIG. 1 is a diagram for explaining an example of the overall configuration of a power conversion device. FIG. 2 is a diagram showing an example of the configuration of an arm. FIG. 3 is a diagram showing an example of the configuration of a cell. FIG. 4 is a block diagram showing an example of the functional configuration of a control device. FIG. 5 is a block diagram showing an example of the configuration of a DC voltage control unit 20 according to a first embodiment. FIG. 6 is a block diagram showing an example of the configuration of an output power calculation unit. FIG. 7 is a block diagram showing an example of the configuration of a total control power command calculation unit. FIG. 8 is a block diagram showing an example of the configuration of a phase control power command calculation unit. FIG. 9 is a block diagram showing an example of the configuration of a phase control current command calculation unit. FIG. 10 is a block diagram showing an example of the configuration of a current command conversion unit. FIG. 11 is a block diagram showing an example of the configuration of a current command calculation unit. FIG. 12 is a block diagram showing an example of the configuration of a current control unit. FIG. 13 is a block diagram showing an example of the configuration of a phase voltage command calculation unit. FIG. 14 is a block diagram showing an example of the configuration of a cell DC voltage control unit. FIG. 15 is a block diagram showing an example of the configuration of a DC voltage control unit according to a second embodiment. FIG. 16 is a block diagram showing an example of the configuration of an output power calculation unit according to the second embodiment. FIG. 17 is a block diagram showing an example of the configuration of a total control current command calculation unit according to the second embodiment. FIG. 18 is a block diagram showing an example of the configuration of a phase control current command calculation unit according to a third embodiment. FIG. 19 is a block diagram showing an example of the configuration of a phase control current command calculation unit according to a modified example of the third embodiment.
[0014] Hereinafter, the present embodiment will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of these components are also the same. Therefore, detailed description thereof will not be repeated.
[0015] [Configuration underlying each embodiment] <Overall configuration> Fig. 1 is a diagram for explaining an example of the overall configuration of a power conversion device 2. The power conversion device 2 is connected to a three-phase AC power supply 1. The power conversion device 2 includes a power converter 3 configured as an MMC and a control device 4 for controlling the power converter 3. The power converter 3 includes a transformer 5a, a voltage detector 5s, current detectors 6uv, 6vw, 6wu, and three arms 7uv, 7vw, 7wu (hereinafter, sometimes collectively referred to as "arm 7"). Each arm 7 is configured by connecting a plurality of unit converters in series.
[0016] One three-phase terminal of the transformer 5a is connected to the three-phase AC power supply 1, and the other three-phase terminal of the transformer 5a is connected to one terminal of each of the power lines L2u, L2v, and L2w.
[0017] The arm 7uv is connected between the other terminal of the power line L2u and the other terminal of the power line L2v. The arm 7vw is connected between the other terminal of the power line L2v and the other terminal of the power line L2w. The arm 7wu is connected between the other terminal of the power line L2w and the other terminal of the power line L2u. As a result, the arms 7uv, 7vw, and 7wu are connected in a delta connection.
[0018] The voltage detector 5s detects the voltages Vuv, Vvw, and Vwu of the three-phase AC power supply 1. The current detector 6uv is arranged on the power line L2u and detects the current flowing in the valve branch 7uv (hereinafter referred to as the "valve current Iuv"). The current detector 6vw is arranged on the power line L2v and detects the current flowing in the valve branch 7vw (hereinafter referred to as the "valve current Ivw"). The current detector 6wu is arranged on the power line L2w and detects the current flowing in the valve branch 7wu (hereinafter referred to as the "valve current Iwu"). The detected voltages Vuv, Vvw, and Vwu and valve branch currents Iuv, Ivw, and Iwu are input to the control device 4.
[0019] In FIG. 1, the power converter 3 is connected to the three-phase AC power supply 1 via a transformer 5a, but it may be configured to be connected to the three-phase AC power supply 1 via an interconnection reactor instead of the transformer 5a.
[0020] 2 is a diagram showing an example of the configuration of the arms. Since the configurations of the arms 7uv, 7vw, and 7wu are similar, the description will be given of one arm as a representative arm.
[0021] Referring to FIG. 2 , arm 7 is connected between two terminals 7a and 7b. Arm 7 has a plurality of cells 9 connected in series. Each of the plurality of cells 9 performs bidirectional power conversion in accordance with a gate signal Sg from control device 4. In this embodiment, n (n is an integer equal to or greater than 2) cells 9 are connected in series in each of three arms 7uv, 7vw, and 7wu. Therefore, the total number of cells 9 included in power converter 3 is 3n. Note that the number of cells 9 included in each of arms 7uv, 7vw, and 7wu does not need to be equal, as long as it is equal to or greater than the minimum number required for operation of power conversion device 2. Therefore, the total number of cells 9 included in power converter 3 is not limited to 3n.
[0022] The arm 7 further includes a reactor 8 connected in series with the plurality of cells 9. The reactor 8 is arranged to suppress circulating current flowing in the delta connection. In this manner, the arm 7 is composed of a cell group including the plurality of cells 9 and the reactor 8.
[0023] 2 shows a configuration in which the reactor 8 is inserted between the output terminal 9a and the terminal 7a, but the configuration is not limited to this. The reactor 8 may be connected in series at any position on the power line connecting the terminals 7a, 7b and the n cells 9. In addition, while the example of FIG. 2 shows a configuration example in which one reactor 8 is included for one arm 7, the reactor 8 may be connected to at least one arm of the arms 7uv, 7vw, and 7wu, and the arm to be connected may be selected arbitrarily.
[0024] 3 is a diagram showing an example of a cell configuration. Referring to FIG. 3, a cell 9 according to a first example configuration has a so-called full-bridge configuration. Specifically, the cell 9 includes a storage element 10, a voltage detector 11, switching elements Q1 to Q4, diodes D1 to D4, and a pair of output terminals 9 a, 9 b.
[0025] One terminal and the other terminal of the storage element 10 are connected to a positive electrode line 10P and a negative electrode line 10N, respectively. The storage element 10 is, for example, a capacitor that stores DC power. The voltage detector 11 detects the DC voltage between the terminals of the storage element 10 (hereinafter also simply referred to as "voltage Vdccell") and outputs a signal indicating the detected voltage Vdccell to the control device 4.
[0026] The switching elements Q1 to Q4 are self-extinguishing power semiconductor elements, and are configured, for example, by insulated gate bipolar transistors (IGBTs). The switching elements Q1 to Q4 are connected to the energy storage element 10 via a positive electrode line 10P and a negative electrode line 10N.
[0027] Switching elements Q1 and Q2 are connected in series between the pair of power lines (i.e., positive electrode line 10P and negative electrode line 10N). Switching elements Q3 and Q4 are connected in series between the pair of power lines. Specifically, one terminal of switching elements Q1 and Q3 is connected to positive electrode line 10P, and the other terminal of switching elements Q1 and Q3 is connected to output terminals 9a and 9b, respectively. One terminal of switching elements Q2 and Q4 is connected to negative electrode line 10N, and the other terminal of switching elements Q2 and Q4 is connected to output terminals 9a and 9b, respectively. Diodes D1 to D4 are connected in anti-parallel to switching elements Q1 to Q4, respectively.
[0028] The cell 9 controls the on and off (i.e., switching operation) of the switching elements Q1 to Q4 based on the gate signal Sg from the control device 4. The cell 9 outputs a voltage of the same polarity as the voltage of the storage element 10, a voltage of the opposite polarity, or zero voltage between the output terminals 9a and 9b in accordance with the switching operation of the switching elements Q1 to Q4 as the cell voltage Vcell.
[0029] The cell 9 according to the second configuration example has a so-called half-bridge configuration, rather than the full-bridge configuration shown in Fig. 3. The cell 9 according to the second configuration example has a configuration in which the switching elements Q3 and Q4 and the diodes D3 and D4 are removed from the cell 9 according to the first configuration example shown in Fig. 3, and the connection position of the output terminal 9b is changed to the negative electrode line 10N. The cell 9 according to the second configuration example controls the on and off (i.e., switching operation) of the switching elements Q1 and Q2 based on the gate signal Sg, thereby outputting a voltage of the same polarity as the voltage of the storage element 10, or zero voltage, between the output terminals 9a and 9b as the cell voltage Vcell.
[0030] The configuration of the cell 9 shown in Fig. 2 is not limited to the first and second configuration examples. The configuration of the cell 9 may be any configuration that includes a series circuit of multiple (e.g., two) switching elements and a capacitor connected in parallel to the series circuit, and that selectively outputs a voltage between the output terminals 9a and 9b in accordance with the switching operations of the multiple switching elements.
[0031] Referring again to Figure 1, the control device 4 controls the operation of the arms 7uv, 7vw, 7wu (i.e., each of the 3n cells 9) using commands from a higher-level device (not shown) and detection signals input from each detector.
[0032] The control device 4 can be configured, for example, by a microcomputer, etc. As an example, the control device 4 has a built-in memory and a CPU (Control Processing Unit) (not shown), and can perform the control operations described below through software processing in which the CPU executes a program stored in advance in the memory.
[0033] At least a part of the control device 4 can be configured using circuits such as an FPGA (Field Programmable Gate Array) and an ASIC (Application Specific Integrated Circuit).
[0034] <Functional Configuration of Control Device> Fig. 4 is a block diagram showing an example of the functional configuration of the control device. The functions of the blocks shown in Fig. 4 can be realized by software processing and / or hardware processing by the control device 4.
[0035] 4, the control device 4 receives inputs of voltages Vuv, Vvw, and Vwu detected by a voltage detector 5s, branch currents Iuv, Ivw, and Iwu detected by current detectors 6uv, 6vw, and 6wu, and a voltage Vdccell of the storage element 10 detected by a voltage detector 11. The control device 4 calculates a gate signal Sg by control calculation configured as shown in FIG. 4 and outputs the signal to the cell 9. Note that there is a voltage Vdccell and a gate signal Sg corresponding to each cell 9, and the number of signals is equal to the number of cells 9 (e.g., 3n). Specifically, the control device 4 includes a DC voltage control unit 20, a current command calculation unit 30, a voltage command generation unit 35, and a gate signal generation unit 70.
[0036] The DC voltage control unit 20 receives inputs of the voltages Vcuv, Vcvw, and Vcwu, the currents Icuv, Icvw, and Icwu, the voltage Vdccell, and the DC voltage command value Vdc*. Based on the input parameters, the DC voltage control unit 20 calculates a first q-axis current command value I1q*, a second d-axis current command value I2d*, a second q-axis current command value I2q*, and a zero-phase current command value Iz*.
[0037] The voltages Vcuv, Vcvw, and Vcwu are representative output voltage values of the cell groups included in the arms 7uv, 7vw, and 7wu, respectively. For example, the voltages Vcuv, Vcvw, and Vcwu are the voltages Vuv, Vvw, and Vwu, respectively. Alternatively, the voltages Vcuv, Vcvw, and Vcwu may be values obtained by adding to the voltages Vuv, Vvw, and Vwu voltages a voltage drop due to components of the power conversion device 2 other than the cell groups, which is calculated from at least a portion of the current command values I0d*, I0q*, I1q*, I2d*, I2q*, and Iz*.
[0038] The currents Icuv, Icvw, and Icwu are representative output current values of the cell groups included in the arms 7uv, 7vw, and 7wu, respectively. For example, the currents Icuv, Icvw, and Icwu are arm currents Iuv, Ivw, and Iwu, respectively. Alternatively, the currents Icuv, Icvw, and Icwu may be values calculated from at least a portion of the current command values I0d*, I0q*, I1q*, I2d*, I2q*, and Iz*.
[0039] The DC voltage command value Vdc* may be input from a higher-level device (not shown), may be predetermined in the control device 4, or may be determined by a specified calculation performed by a DC voltage command calculation unit (not shown).
[0040] The current command calculation unit 30 calculates the d-axis current command value Idr* and the q-axis current command value Iqr* of the power converter 3 based on the reference d-axis current command value I0d*, the reference q-axis current command value I0q*, the first q-axis current command value I1q*, the second d-axis current command value I2d*, and the second q-axis current command value I2q*.
[0041] The reference d-axis current command value I0d* and the reference q-axis current command value I0q* are reference command values for the d-axis current and the q-axis current output from the power converter 3. The reference d-axis current command value I0d* and the reference q-axis current command value I0q* may be input from a higher-level device (not shown) or may be determined in advance in the control device 4. Alternatively, the reference d-axis current command value I0d* and the reference q-axis current command value I0q* may be determined by a specified calculation performed by a d-axis current calculation unit and a q-axis current calculation unit (not shown), respectively. Note that if the purpose of the power conversion device 2 does not include controlling the exchange of active power with the three-phase AC power source 1, other than for the purpose of maintaining the voltage Vdccell of the storage element 10 within a certain range, the reference q-axis current command value I0q* may not be used.
[0042] The voltage command generation unit 35 generates a cell voltage command value Vcell* for controlling the output voltage of each cell 9. Specifically, the voltage command generation unit 35 includes a current control unit 40, a phase voltage command calculation unit 50, and an individual cell DC voltage control unit 60.
[0043] The current control unit 40 calculates a d-axis voltage command value Vd*, a q-axis voltage command value Vq*, and a zero-phase voltage command value Vz* based on the d-axis current command value Idr*, the q-axis current command value Iqr*, the zero-phase current command value Iz*, the voltages Vuv, Vvw, Vwu, and the arm currents Iuv, Ivw, Iwu.
[0044] The phase voltage command calculation unit 50 calculates the phase voltage command values Vuv*, Vvw*, and Vwu* based on the d-axis voltage command value Vd*, the q-axis voltage command value Vq*, and the zero-phase voltage command value Vz*.
[0045] The cell DC voltage control unit 60 calculates the cell voltage command value Vcell* of each cell 9 included in the power converter 3 based on the phase voltage command values Vuv*, Vvw*, Vwu*, the arm currents Iuv, Ivw, Iwu, and the voltage Vdccell of each storage element 10.
[0046] The gate signal generator 70 generates a gate signal Sg based on the cell voltage command value Vcell* of each cell 9. Specifically, the gate signal generator 70 performs PWM control based on each of the 3n cell voltage command values Vcell* calculated by the cell DC voltage controller 60, and generates a gate signal Sg for controlling the on / off of the switching elements Q1 to Q4 of each cell 9 included in the power converter 3.
[0047] The configurations of the DC voltage control unit 20, the current command calculation unit 30, and the voltage command generation unit 35 will be described in more detail below.
[0048] Embodiment 1 <DC voltage control unit> Fig. 5 is a block diagram showing an example of the configuration of DC voltage control unit 20 according to embodiment 1. Referring to Fig. 5, DC voltage control unit 20 includes an output power calculation unit 23, a total control power command calculation unit 24, a phase control power command calculation unit 27, a phase control current command calculation unit 28, and a current command conversion unit 29.
[0049] The output power calculation unit 23 calculates unbalanced components P2uv, P2vw, P2wu of the output power (i.e., active power) of the arms 7uv, 7vw, 7wu based on the currents Icuv, Icvw, Icwu and the voltages Vcuv, Vcvw, Vcwu.
[0050] 6 is a block diagram showing an example of the configuration of the output power calculation unit 23. Referring to Fig. 6, the output power calculation unit 23 includes multipliers 231u, 231v, and 231w, filters 232u, 232v, and 232w, an adder 233, a calculator 233a, and subtractors 234u, 234v, and 234w.
[0051] The multiplier 231u outputs the product of the input voltage Vcuv and current Icuv. The filter 232u outputs a value Pcuv obtained by subtracting a frequency component 2f, which is twice the voltage frequency of the three-phase AC power supply 1, from the output value of the multiplier 231u. The multiplier 231v outputs the product of the input voltage Vcvw and current Icvw. The filter 232v outputs a value Pcvw obtained by subtracting the frequency component 2f from the output value of the multiplier 231v. The multiplier 231w outputs the product of the input voltage Vcwu and current Icwu. The filter 232w outputs a value Pcwu obtained by subtracting the frequency component 2f from the output value of the multiplier 231w. The filters 232u, 232v, and 232w can be moving average filters whose period is half the voltage period of the three-phase AC power supply 1.
[0052] The adder 233 calculates the sum of the values Pcuv, Pcvw, and Pcwu. The calculator 233a multiplies the sum by ⅓ to calculate the average value Pcav of the values Pcuv, Pcvw, and Pcwu.
[0053] The subtractor 234u calculates the unbalanced component P2uv by subtracting the average value Pcav from the value Pcuv. The subtractor 234v calculates the unbalanced component P2vw by subtracting the average value Pcav from the value Pcvw. The subtractor 234w calculates the unbalanced component P2wu by subtracting the average value Pcav from the value Pcwu.
[0054] In this way, the output power calculation unit 23 calculates the unbalanced components (e.g., P2uv, P2vw, P2wu) of the output power of each of the three arms 7uv, 7vw, 7wu based on the output voltage representative values (e.g., voltages Vcuv, Vcvw, Vcwu) and output current representative values (e.g., currents Icuv, Icvw, Icwu) of the cell group included in that arm.
[0055] 5 again, the total control power command calculation unit 24 calculates the all-phase active power command value Pall* based on the voltage Vdccell and the DC voltage command value Vdc*. In the first embodiment, the total control power command calculation unit 24 outputs the all-phase active power command value Pall* as the first q-axis current command value I1q*. The total control power command calculation unit 24 according to the first embodiment functions as a "first current command calculation unit" that calculates the first q-axis current command value I1q*.
[0056] 7 is a block diagram showing an example of the configuration of total control power command calculation unit 24. Referring to FIG. 7, total control power command calculation unit 24 includes a representative value calculation unit 241, a subtractor 242, and a controller 243.
[0057] The representative value calculation unit 241 calculates a voltage representative value that represents the voltage Vdccell of all the cells 9 included in each of the arms 7uv, 7vw, and 7wu (i.e., the 3n cells 9 included in the power converter 3). The voltage representative value can be set to, for example, the average value, maximum value, or minimum value of the voltages Vdccell of all the cells 9.
[0058] The subtractor 242 outputs a value obtained by subtracting the representative voltage value from the DC voltage command value Vdc* (i.e., the deviation between Vdc* and the representative voltage value). The controller 243 executes a control calculation to set the deviation to zero (i.e., so that the representative voltage value follows the DC voltage command value Vdc*), calculates an all-phase active power command value Pall*, and outputs it as a first q-axis current command value I1q*.
[0059] In this way, the total control power command calculation unit 24 executes the first voltage control to keep the representative voltage values of the voltages Vdccell of all the cells 9 constant (for example, to make the representative voltage values follow the DC voltage command value Vdc*), and generates the all-phase active power command value Pall* (here, the first q-axis current command value I1q*). That is, the total control power command calculation unit 24 generates the first q-axis current command value I1q* to keep the representative voltage values constant.
[0060] 5, the phase control power command calculation unit 27 calculates unbalanced component command values P2uv*, P2vw*, and P2wu* of the output power of the arms 7uv, 7vw, and 7wu based on the voltage Vdccell. Specifically, the phase control power command calculation unit 27 calculates the unbalanced component command values P2uv*, P2vw*, and P2wu* so that the voltage Vdccell of the storage elements 10 is balanced among the three arms 7uv, 7vw, and 7wu.
[0061] Fig. 8 is a block diagram showing an example of the configuration of phase control power command calculation unit 27. Referring to Fig. 8, phase control power command calculation unit 27 includes a representative value calculation unit 271, subtractors 272u, 272v, 272w, and controllers 273u, 273v, 273w.
[0062] The representative value calculation unit 271 executes a specified representative value calculation to calculate a representative value Vdcuv of the voltage Vdccell of each cell 9 included in the arm 7uv, a representative value Vdcvw of the voltage Vdccell of each cell 9 included in the arm 7vw, and a representative value Vdcwu of the voltage Vdccell of each cell 9 included in the arm 7wu. As an example, the calculation method of the representative value Vdcuv will be described. The representative value calculation unit 271 calculates the average, maximum, or minimum value of the voltage Vdccell of each cell 9 included in the arm 7uv and calculates the representative value Vdcuv by removing fluctuations from the calculated value. The process of removing fluctuations from the calculated value uses filtering using a moving average filter with a period half the voltage period of the three-phase AC power supply 1. The same applies to the calculation method of the representative values Vdcvw and Vdcwu.
[0063] The representative value calculation unit 271 also calculates a three-phase balanced component Vdcall of the representative values Vdcuv, Vdcvw, and Vdcwu. The three-phase balanced component Vdcall is, for example, an average value of the representative values Vdcuv, Vdcvw, and Vdcwu.
[0064] The subtractor 272u calculates the deviation between the three-phase balanced component Vdcall and the representative value Vdcuv (i.e., Vdcall-Vdcuv). The controller 273u executes a control calculation to set the deviation calculated by the subtractor 272u to zero (i.e., so that the representative value Vdcuv follows the three-phase balanced component Vdcall), and calculates the unbalanced component command value P2uv*.
[0065] The subtractor 272v calculates the deviation between the three-phase balanced component Vdcall and the representative value Vdcvw (i.e., Vdcall-Vdcvw). The controller 273v executes a control calculation to set the deviation calculated by the subtractor 272v to zero, and calculates the unbalanced component command value P2vw*.
[0066] The calculator 272w calculates the deviation between the three-phase balanced component Vdcall and the representative value Vdcwu (i.e., Vdcall-Vdcwu). The controller 273w executes a control calculation to set the deviation calculated by the subtractor 272w to zero, and calculates the unbalanced component command value P2wu*.
[0067] In this way, the phase control power command calculation unit 27 performs a second voltage control to suppress variation between arms in the representative value of the voltage Vdccell of each cell 9 included in each arm 7 (for example, by making the three-phase balanced component Vdcall follow the representative values Vdcuv, Vdcvw, Vdcwu), and generates unbalanced component command values P2uv*, P2vw*, P2wu*.
[0068] 5 again, the phase control current command calculation unit 28 calculates current command values I2uv*, I2vw*, and I2wu* for each phase based on the unbalanced components P2uv, P2vw, and P2wu of the output power of the arms 7uv, 7vw, and 7wu and the unbalanced component command values P2uv*, P2vw*, and P2wu*. Specifically, for each of the three arms 7uv, 7vw, and 7wu, the phase control current command calculation unit 28 calculates a current command value for the phase corresponding to that arm so that the unbalanced component of that arm follows the unbalanced component command value of that arm.
[0069] Fig. 9 is a block diagram showing an example of the configuration of the phase control current command calculation unit 28. Referring to Fig. 9, the phase control current command calculation unit 28 includes subtractors 281u, 281v, and 281w, and controllers 283u, 283v, and 283w.
[0070] The subtractor 281u calculates the deviation between the unbalance component command value P2uv* and the unbalance component P2uv (i.e., P2uv*-P2uv). The controller 283u executes a control calculation to set the deviation calculated by the subtractor 281u to zero (i.e., so that the unbalance component P2uv follows the unbalance component command value P2uv*), and calculates the current command value I2uv*. More specifically, the controller 283u calculates the current command value I2uv* by, for example, feedback control to set the deviation to zero. The feedback control is, for example, P control or PI control. However, the feedback control may be configured by appropriately combining proportional control, integral control, differential control, etc. The same applies to the controllers 283v and 283w.
[0071] The subtractor 281v calculates the deviation between the unbalanced component command value P2vw* and the unbalanced component P2vw (i.e., P2vw*-P2vw). The controller 283v executes a control calculation to set the deviation calculated by the subtractor 281v to zero, and calculates the current command value I2vw*.
[0072] The subtractor 281w calculates the deviation between the unbalance component command value P2wu* and the unbalance component P2wu (i.e., P2wu*-P2wu). The controller 283w executes a control calculation to set the deviation calculated by the subtractor 281w to zero, and calculates the current command value I2wu*.
[0073] In this way, the phase control current command calculation unit 28 performs control calculations to compensate for the deviation between the unbalanced component command values P2uv*, P2vw*, P2wu* generated by the phase control power command calculation unit 27 and the unbalanced components P2uv, P2vw, P2wu.
[0074] 5 , the current command conversion unit 29 calculates a second d-axis current command value I2d*, a second q-axis current command value I2q*, and a zero-phase current command value Iz* for the power converter 3 based on the current command values I2uv*, I2vw*, I2wu* of the respective phases and the voltages Vcuv, Vcvw, Vcwu. The current command conversion unit 29 functions as a “second current command calculation unit” that calculates the second d-axis current command value I2d*, the second q-axis current command value I2q*, and the zero-phase current command value Iz*.
[0075] Fig. 10 is a block diagram showing an example of the configuration of current command conversion unit 29. Referring to Fig. 10, current command conversion unit 29 includes multipliers 291u, 291v, and 291w, a coordinate conversion unit 292, filters 293d and 293q, and subtractors 294d and 294q.
[0076] The multiplier 291u calculates the multiplication value of the current command value I2uv* and the voltage Vcuv. Note that, instead of the voltage Vcuv, a sine wave that is in phase with the voltage Vcuv and has an amplitude of 1 may be input to the multiplier 291u. The multiplier 291v calculates the multiplication value of the current command value I2vw* and the voltage Vcvw. Note that, instead of the voltage Vcvw, a sine wave that is in phase with the voltage Vcvw and has an amplitude of 1 may be input to the multiplier 291v. The multiplier 291w calculates the multiplication value of the current command value I2wu* and the voltage Vcwu. Note that, instead of the voltage Vcwu, a sine wave that is in phase with the voltage Vcwu and has an amplitude of 1 may be input to the multiplier 291w.
[0077] The coordinate conversion unit 292 converts the multiplied values of the multipliers 291u, 291v, and 291w as three-phase inputs into values in the dq0-axis coordinates synchronized with the three-phase AC power supply 1, thereby generating a d-axis output value, a q-axis output value, and a zero-phase output value. The generated zero-phase output value is output as a zero-phase current command value Iz*.
[0078] The filter 293d outputs a value obtained by removing a frequency component 2f, which is twice the voltage frequency of the three-phase AC power supply 1, from the d-axis output value of the coordinate converter 292. The filter 293d is configured, for example, with a notch filter. The subtractor 294d outputs a value obtained by subtracting the output value of the filter 293d from the d-axis output value of the coordinate converter 292 as a second d-axis current command value I2d*. In other words, the second d-axis current command value I2d* is obtained by extracting the frequency component 2f from the d-axis output value of the coordinate converter 292.
[0079] The filter 293q outputs a value obtained by removing the frequency component 2f from the q-axis output value of the coordinate conversion unit 292. The filter 293q is configured, for example, by a notch filter. The subtractor 294q outputs a value obtained by subtracting the output value of the filter 293q from the q-axis output value as a second q-axis current command value I2q*. In other words, the second q-axis current command value I2q* is the frequency component 2f extracted from the q-axis output value.
[0080] <Current Command Calculation Unit> Fig. 11 is a block diagram showing an example of the configuration of current command calculation unit 30. Referring to Fig. 11, current command calculation unit 30 includes adders 31q, 32d, and 32q.
[0081] The adder 31q outputs the sum of the first q-axis current command value I1q* and the second q-axis current command value I2q*. The adder 32d calculates the sum of the reference d-axis current command value I0d* and the second d-axis current command value I2d* as the d-axis current command value Idr*. The adder 32q calculates the sum of the reference q-axis current command value I0q* and the output value of the adder 31q as the q-axis current command value Iqr*.
[0082] 4 , the voltage command generating unit 35 generates a cell voltage command value Vcell* for controlling the output voltage of each cell 9 based on the output current of the power converter 3 (e.g., arm currents Iuv, Ivw, Iwu), the d-axis current command value Idr*, the q-axis current command value Iqr*, and the zero-phase current command value Iz*. Hereinafter, the configurations of the current control unit 40, the phase voltage command calculation unit 50, and the each-cell DC voltage control unit 60 included in the voltage command generating unit 35 will be described in detail.
[0083] <Current Control Unit> Fig. 12 is a block diagram showing a configuration example of current control unit 40. Referring to Fig. 12, current control unit 40 includes coordinate conversion units 41 and 44, subtractors 42d, 42q, and 42z, controllers 43d, 43q, and 43z, and adders 45d and 45q.
[0084] The coordinate converter 41 converts the arm currents Iuv, Ivw, and Iwu as three-phase inputs into values in dq0-axis coordinates synchronized with the three-phase AC power supply 1, thereby generating a d-axis output value, a q-axis output value, and a zero-phase output value. The coordinate converter 44 converts the voltages Vuv, Vvw, and Vwu as three-phase inputs into values in dq-axis coordinates, thereby generating a d-axis output value and a q-axis output value.
[0085] The subtractor 42d calculates the deviation between the d-axis current command value Idr* and the d-axis output of the coordinate conversion unit 41 (i.e., Idr*-d-axis output value). The controller 43d executes a control calculation to set the deviation calculated by the subtractor 42d to zero (i.e., so that the d-axis output value follows the d-axis current command value Idr*), and outputs a control calculation value. The adder 45d calculates the sum of the control calculation value of the controller 43d and the d-axis output value of the coordinate conversion unit 44 as the d-axis voltage command value Vd*.
[0086] The subtractor 42q calculates the deviation between the q-axis current command value Iqr* and the q-axis output of the coordinate transformation unit 41 (i.e., Iqr* - q-axis output value). The controller 43q executes a control calculation to set the deviation calculated by the subtractor 42q to zero (i.e., so that the q-axis output value follows the q-axis current command value Iqr*), and outputs a control calculation value. The adder 45q calculates the sum of the control calculation value of the controller 43q and the q-axis output value of the coordinate transformation unit 44 as the q-axis voltage command value Vq*.
[0087] The subtractor 42z calculates the deviation (i.e., Iz*-zero-phase output value) between the zero-phase current command value Iz* and the zero-phase output value of the coordinate conversion unit 41. The controller 43z executes a control calculation to set the deviation calculated by the subtractor 42z to zero (i.e., so that the zero-phase output value follows the zero-phase current command value Iz*), and calculates the zero-phase voltage command value Vz*.
[0088] <Phase voltage command calculation unit> Fig. 13 is a block diagram showing an example of the configuration of the phase voltage command calculation unit 50. Referring to Fig. 13, the phase voltage command calculation unit 50 includes a coordinate conversion unit 51. The coordinate conversion unit 51 converts the d-axis voltage command value Vd*, the q-axis voltage command value Vq*, and the zero-phase voltage command value Vz* as dq0-axis inputs to calculate the respective phase voltage command values Vuv*, Vvw*, and Vwu*.
[0089] <Cell DC voltage control unit> Fig. 14 is a block diagram showing an example configuration of the cell DC voltage control unit 60. Referring to Fig. 14, each cell DC voltage control unit 60 includes 3n cell control units 600, which corresponds to the total number of cells. Each of the 3n cell control units 600 is configured to generate a cell voltage command value Vcell* for the corresponding cell 9. Since the 3n cell control units 600 have the same configuration, the configuration of the cell control unit 600 corresponding to one cell 9 will be described.
[0090] The cell control unit 600 includes a voltage command selection unit 61 , a representative value calculation unit 62 , a cell voltage extraction unit 63 , a filter 64 , subtractors 65 and 69 , a controller 66 , a valve branch current selection unit 67 , and a multiplier 68 .
[0091] The voltage command selector 61 selects and outputs one of the phase voltage command values Vuv*, Vvw*, and Vwu* according to the phase of the arm 7 that includes the cell 9 to be controlled.
[0092] The representative value calculation unit 62 calculates a representative value Vdccellx of the voltages Vdccell of the n storage elements 10 included in the arm 7 that includes the cell 9 to be controlled. The representative value Vdccellx can be any of the average, maximum, and minimum values of the n voltages Vdccell. The cell voltage extraction unit 63 extracts the voltage Vdccell of the corresponding cell 9 from the 3n voltages Vdccell.
[0093] The filter 64 outputs a value Vdccellf obtained by removing the frequency component that is the same as the frequency of the voltage of the three-phase AC power supply 1 from the voltage Vdccell extracted by the cell voltage extraction unit 63. The filter 64 is, for example, a moving average filter with a period that is the same as the period of the voltage of the three-phase AC power supply 1. The subtractor 65 calculates the deviation between the voltage Vdccellx and the value Vdcccellf (i.e., Vdcccellx - Vdcccellf).
[0094] The controller 66 executes a control calculation to reduce the deviation calculated by the subtractor 65 to zero, and outputs a manipulated variable as a result of the control calculation. The valve branch current selector 67 selects and outputs one of the valve branch currents Iuv, Ivw, and Iwu depending on the phase of the valve branch 7 that includes the cell 9 to be controlled. The multiplier 68 multiplies the manipulated variable output from the controller 66 by the valve branch current selected by the valve branch current selector 67.
[0095] The subtractor 69 calculates the cell voltage command value Vcell* of the cell 9 to be controlled by subtracting the multiplied value output from the multiplier 68 from the voltage command value selected by the voltage command selector 61 .
[0096] <Advantages> When the voltage of the three-phase AC power supply fluctuates or when the three-phase AC voltage is three-phase unbalanced, the output current of the power converter 3 according to the three-phase balanced current command value (i.e., the first q-axis current command value I1q*) generated by the first voltage control by the total control power command calculation unit 24 (i.e., control that keeps constant the representative value of the voltage Vdccell of all cells 9) and the three-phase unbalanced voltage of the three-phase AC power supply 1 result in the output of active power that is not balanced between the arms (i.e., three-phase unbalanced power). This active power can become a disturbance to the second voltage control by the phase control power command calculation unit 27 (i.e., control that suppresses variation between the arms in the representative value of the voltage Vdccell of each cell 9 included in each arm 7).
[0097] However, in the first embodiment, the three-phase unbalanced power is calculated as unbalanced components P2uv, P2vw, and P2wu by the output power calculation unit 23, and the unbalanced components P2uv, P2vw, and P2wu are input to the phase control current command calculation unit 28. Subsequently, the phase control current command calculation unit 28 executes a control calculation to compensate for the deviation between the unbalanced component command values P2uv*, P2vw*, and P2wu* generated by the phase control power command calculation unit 27 and the unbalanced components P2uv, P2vw, and P2wu. The current command values I2uv*, I2vw*, and I2wu* generated by the control calculation are reflected in the second d-axis current command value I2d*, the second q-axis current command value I2q*, and the zero-phase current command value Iz*. The power converter 3 then outputs a current in accordance with the second d-axis current command value I2d*, the second q-axis current command value I2q*, and the zero-phase current command value Iz*.
[0098] With the above configuration, the three-phase unbalanced power, which may be a disturbance to the phase control power command calculation unit 27, is compensated for by the phase control current command calculation unit 28. Therefore, when the three-phase AC power supply 1 is three-phase unbalanced, interference between the total control power command calculation unit 24 and the phase control power command calculation unit 27 can be prevented, and the operational continuity of the power conversion device 2 can be improved.
[0099] Second Embodiment In a second embodiment, a description will be given of another configuration of the DC voltage control unit 20 of the first embodiment described with reference to Fig. 5. The configuration of the second embodiment other than the DC voltage control unit 20 is the same as the configuration of the first embodiment.
[0100] <DC voltage control unit> Fig. 15 is a block diagram showing a configuration example of a DC voltage control unit 20A according to embodiment 2. DC voltage control unit 20A corresponds to DC voltage control unit 20 in Fig. 4, but is denoted by the symbol "A" for convenience in order to distinguish it from DC voltage control unit 20 according to embodiment 1.
[0101] 15, DC voltage control unit 20A includes an output power calculation unit 23A, a total control power command calculation unit 24, a total control current command calculation unit 25, a phase control power command calculation unit 27, a phase control current command calculation unit 28, and a current command conversion unit 29. That is, DC voltage control unit 20A has a configuration in which total control current command calculation unit 25 is added to DC voltage control unit 20 in Fig. 5, and output power calculation unit 23 in Fig. 5 is replaced with output power calculation unit 23A. Detailed description of the configuration similar to that of DC voltage control unit 20 will not be repeated.
[0102] The output power calculation unit 23A calculates the unbalanced components P2uv, P2vw, P2wu and the common component Pall of the output power of the arms 7uv, 7vw, 7wu based on the output current representative values (e.g., currents Icuv, Icvw, Icwu) and output voltage representative values (e.g., voltages Vcuv, Vcvw, Vcwu) of the cell groups included in the arms 7uv, 7vw, 7wu.
[0103] Fig. 16 is a block diagram showing an example of the configuration of output power calculation unit 23A according to embodiment 2. Referring to Fig. 16, output power calculation unit 23A has a configuration in which an adder 235 and a calculator 236 are added to output power calculation unit 23 in Fig. 6. Detailed description of the configuration similar to that of output power calculation unit 23 will not be repeated.
[0104] The adder 235 calculates the sum of the output value of the multiplier 231u (i.e., the output power of the arm 7uv), the output value of the multiplier 231v (i.e., the output power of the arm 7vw), and the output value of the multiplier 231w (i.e., the output power of the arm 7wu). The calculator 236 multiplies the sum by ⅓ to calculate the common component Pall of the output power of each arm 7.
[0105] 15 again, the total control current command calculation unit 25 generates a first q-axis current command value I1q* based on the all-phase active power command value Pall* and the common component Pall. In the second embodiment, the total control power command calculation unit 24 and the total control current command calculation unit 25 function as a "first current command calculation unit" that calculates the first q-axis current command value I1q*.
[0106] 17 is a block diagram showing an example of a configuration of total control current command calculation unit 25 according to embodiment 2. Referring to FIG. 17 , total control current command calculation unit 25 includes a subtractor 251 and a controller 253.
[0107] The subtractor 251 outputs a value obtained by subtracting the common component Pall from the all-phase active power command value Pall* (i.e., the deviation between Pall* and Pall). The controller 253 executes a control calculation to set the deviation to zero (i.e., so that the common component Pall follows the all-phase active power command value Pall*), and generates a first q-axis current command value I1q*.
[0108] <Advantages> A control calculation is executed to compensate for the deviation between the unbalanced components P2uv, P2vw, P2wu and the unbalanced component command values P2uv*, P2vw*, P2wu* generated by the second voltage control by the phase control power command calculation unit 27. The current command values I2uv*, I2vw*, I2wu* generated by the control calculation are reflected in the second d-axis current command value I2d*, the second q-axis current command value I2q*, and the zero-phase current command value Iz*.
[0109] When the voltage of the three-phase AC power supply fluctuates or when the three-phase AC voltage is in a three-phase imbalance, an active power common to each arm (i.e., three-phase unbalanced power) is output by the current output from the power converter 3 in accordance with the second d-axis current command value I2d*, the second q-axis current command value I2q*, and the zero-phase current command value Iz* generated based on the second voltage control, and the three-phase unbalanced voltage of the three-phase AC power supply 1. This active power can become a disturbance to the first voltage control by the total control power command calculation unit 24.
[0110] However, in the second embodiment, the three-phase unbalanced power is calculated as a common component Pall by the output power calculation unit 23A, and the common component Pall is input to the total control current command calculation unit 25. Subsequently, the total control current command calculation unit 25 executes a control calculation to compensate for the deviation between the common component Pall and the all-phase active power command value Pall* generated by the total control power command calculation unit 24, thereby generating a first q-axis current command value I1q*. Then, the power converter 3 outputs a current in accordance with the first q-axis current command value I1q*.
[0111] With the above configuration, the three-phase unbalanced power, which may be a disturbance to the total control power command calculation unit 24, is compensated for by the total control current command calculation unit 25. Therefore, when the three-phase AC power supply 1 is three-phase unbalanced, interference between the total control power command calculation unit 24 and the phase control power command calculation unit 27 can be prevented, and the operational continuity of the power conversion device 2 can be improved.
[0112] Third Embodiment In a third embodiment, another configuration of the phase control current command calculation unit 28 of the first embodiment described with reference to Fig. 9 will be described. The configuration of the third embodiment other than the phase control current command calculation unit 28 is the same as the configuration of the first embodiment.
[0113] Fig. 18 is a diagram showing an example of the configuration of phase control current command calculation unit 28A according to embodiment 3. Note that, in the phase control current command calculation unit 28 shown in Fig. 9, the controllers 283u, 283v, 283w generate the current command values I2uv*, I2vw*, I2wu*, respectively, and the method of generating the current command values I2uv*, I2vw*, I2wu* is the same except for the input and output signals. This is also true for phase control current command calculation unit 28A.
[0114] Therefore, only the method for generating the current command value I2uv* will be described as a representative example in Fig. 18. Phase control current command calculation unit 28A corresponds to phase control current command calculation unit 28 in Fig. 5 or 15, but is denoted by the symbol "A" for convenience in order to distinguish it from phase control current command calculation unit 28 according to the first embodiment. This also applies to Fig. 19 below.
[0115] Referring to FIG. 18, phase control current command calculation unit 28A includes, as components for calculating current command value I2uv*, a subtractor 281u, a controller 283u, a gain circuit 284u, and an adder 285u.
[0116] The subtractor 281u calculates the deviation between the unbalance component command value P2uv* and the unbalance component P2uv. The controller 283u executes a control calculation to set the deviation calculated by the subtractor 281u to zero (i.e., so that the unbalance component P2uv follows the unbalance component command value P2uv*), and calculates a control command value.
[0117] The gain circuit 284u outputs a value obtained by multiplying the unbalanced component command value P2uv* by a constant (for example, by a gain K). The adder 285u calculates the sum of the output value of the gain circuit 284u and the output value (i.e., the control command value) of the controller 283u as the current command value I2uv*. The current command values I2vw* and I2wu* are calculated in a similar manner.
[0118] With the above configuration, the phase control current command calculation unit 28A calculates a control command value for each of the three arms 7uv, 7vw, 7wu so that the unbalance component of that arm follows the unbalance component command value of that arm, and calculates the sum of that control command value and the product of the unbalance component command value multiplied by the gain as the current command value of the phase corresponding to that arm.
[0119] Here, if we ignore the output value of the controller 283u, the gain circuit 284u is a calculation that converts the unbalanced component command value P2uv* into the current command value I2uv*. When the amplitude of the voltage Vcuv is constant and sinusoidal, this conversion is possible by setting the gain K to the reciprocal of the amplitude of the voltage Vcuv. By setting the gain K to the reciprocal of the amplitude of the voltage Vcuv, the path including the controller 283u only needs to operate when the voltage Vcuv deviates from the ideal state in which the amplitude is constant and sinusoidal. Therefore, the response of the controller 283u to changes in the voltage Vcuv is improved. The response of the controller 283v to changes in the voltage Vcvw and the response of the controller 283w to changes in the voltage Vwu are also similarly improved.
[0120] 19 is a diagram showing an example of the configuration of a phase control current command calculation unit 28B according to a modification of the third embodiment. Referring to Fig. 19, the phase control current command calculation unit 28B includes a subtractor 281u, a filter 282u, a controller 283u, a gain circuit 284u, and an adder 285u. The phase control current command calculation unit 28B in Fig. 19 differs from the phase control current command calculation unit 28A in Fig. 18 in that the unbalance component command value P2uv* is not input to the subtractor 281u and in that a filter 282u is added.
[0121] The subtractor 281u subtracts the unbalanced component P2uv from 0 and outputs a value obtained by inverting the polarity of the unbalanced component P2uv. The filter 282u outputs a value obtained by filtering the output value of the subtractor 281u to remove low-frequency components. The filter 282u is, for example, a high-pass filter.
[0122] The controller 283u executes a control calculation to set the output value of the filter 282u to zero and outputs a control command value. The gain circuit 284u outputs a value obtained by multiplying the unbalanced component command value P2uv* by a constant. The adder 285u generates the sum of the output value of the gain circuit 284u and the output value of the controller 283u as the current command value I2uv*. The current command values I2vw* and I2wu* are calculated in a similar manner.
[0123] With the above configuration, the phase control current command calculation unit 28B calculates, for each of the three arms 7uv, 7vw, and 7wu, a control command value for setting to zero the value obtained by inverting the polarity of the unbalanced component of that arm and applying high-pass filtering to that value, and calculates the sum of that control command value and the product of the unbalanced component command value multiplied by the gain as the current command value for the phase corresponding to that arm.
[0124] Here, the unbalance component command value P2uv* is calculated in the phase control power command calculation unit 27 using the voltage Vdccell as an input. The voltage Vdccell is the voltage of the storage element 10, and is proportional to the integrated value of the active power input / output of the cell 9, excluding losses, so its fluctuations are mainly low-frequency components. The unbalance component command value P2uv* calculated using the voltage Vdccell as an input also mainly consists of low-frequency components. On the other hand, the unbalance component P2uv is a value that estimates part of the active power output of the cell 9, so the frequency components of the fluctuations of the unbalance component P2uv are distributed to a higher frequency range than the voltage Vdccell, which is proportional to the integrated value of the active power input / output of the cell 9.
[0125] 19, by inputting the unbalanced component P2uv, from which the low-frequency component has been removed by the filter 282u, to the controller 283u, it becomes easy to raise the control frequency band of the controller 283u, and it is possible to enhance the effect of suppressing fluctuations in the unbalanced component P2uv. The same applies to the other unbalanced components P2vw and P2wu.
[0126] Other Embodiments. The configurations exemplified as the above-described embodiments are examples of the configurations of the present disclosure, and may be combined with other known technologies, or may be modified, such as by omitting some parts, within the scope of the gist of the present disclosure. Furthermore, the above-described embodiments may be implemented by appropriately adopting the processes and configurations described in other embodiments.
[0127] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.
[0128] 1 Three-phase AC power supply, 2 Power conversion device, 3 Power converter, 4 Control device, 5a Transformer, 5s, 11 Voltage detector, 6uv, 6vw, 6wu Current detector, 7uv, 7vw, 7wu Arm, 8 Reactor, 9 Cell, 10 Storage element, 20, 20A DC voltage control unit, 23, 23A Output power calculation unit, 24 Total control power command calculation unit, 25 Total control current command calculation unit, 27 Phase control power command calculation unit, 28, 28A, 28B Phase control current command calculation unit, 29 Current command conversion unit, 30 Current command calculation unit, 35 Voltage command generation unit, 40 Current control unit, 50 Voltage command calculation unit, 60 Each cell DC voltage control unit, 61 Voltage command selection unit, 62, 241, 271 Representative value calculation unit, 63 Cell voltage extraction unit, 67 Arm current selection unit, 70 Gate signal generating unit, 600 cell control unit.
Claims
1. A power conversion device connected to a three-phase AC power supply, a power converter including three delta-connected arms; a control device for controlling the power converter, Each of the three arms is configured by connecting a plurality of unit converters in series, each of the plurality of unit converters includes a plurality of switching elements and a storage element connected to the plurality of switching elements; The control device a first current command calculation unit that calculates a first current command value of the power converter based on a DC voltage command value and a voltage representative value that represents voltage values of all of the storage elements included in the power converter; a power calculation unit that calculates, for each of the three arms, an unbalanced component of the output power of the arm based on a representative output current value and a representative output voltage value of a cell group including each of the unit converters included in the arm; a first power command calculation unit that calculates an unbalanced component command value of the output power of each of the arms so that the voltage values of the storage elements among the three arms are balanced; a phase current command calculation unit that generates a current command value for each phase based on the unbalanced component of the output power of each arm and the unbalanced component command value of the output power of each arm; a second current command calculation unit that calculates a second current command value for the power converter based on the output voltage representative value of the cell group included in each of the arms and the current command value for each phase; a voltage command generation unit that generates an output voltage command value for controlling an output voltage of each of the unit converters based on an output current of the power converter and a current command value calculated from the first current command value and the second current command value; a gate signal generating unit that generates a control signal for each of the switching elements included in the power converter based on the output voltage command value.
2. 2. The power conversion device according to claim 1, wherein the first current command calculation unit calculates a first power command value of the power converter so that the voltage representative value follows the DC voltage command value, and outputs the first power command value as the first current command value.
3. the power calculation unit further calculates a common component of the output power of the three arms based on the output current representative value and the output voltage representative value of the cell group included in each of the three arms; The first current command calculation unit calculating a first power command value for the power converter so that the voltage representative value follows the DC voltage command value; The power conversion device according to claim 1 , wherein the first current command value is calculated so that the common component follows the first power command value.
4. 4. The power conversion device according to claim 1, wherein the phase current command calculation unit calculates a control command value for each of the three arms so that the unbalanced component of that arm follows the unbalanced component command value of that arm, and calculates the control command value as a current command value for a phase corresponding to that arm.
5. 4. The power conversion device according to claim 1, wherein the phase current command calculation unit calculates, for each of the three arms, a control command value such that the unbalanced component of that arm follows the unbalanced component command value of that arm, and calculates, as a current command value for the phase corresponding to that arm, a sum of the control command value and a multiplication value obtained by multiplying the unbalanced component command value of that arm by a gain.
6. the control command value is calculated by feedback control for reducing the deviation between the unbalanced component and the unbalanced component command value to zero; The power conversion device according to claim 4 , wherein the feedback control is P control or PI control.
7. The power conversion device according to any one of claims 1 to 3, wherein the phase current command calculation unit calculates, for each of the three arms, a control command value for setting a value obtained by inverting the polarity of the unbalanced component of that arm and applying high-pass filtering to that value to zero, and calculates an added value of the control command value and a multiplied value obtained by multiplying the unbalanced component command value of that arm by a gain, as a current command value of the phase corresponding to that arm.