Power conversion device

Abstract

A power conversion device (1) comprises: a plurality of AC-DC conversion circuits (21, 22, 23) that are connected in parallel between an AC power supply (3) and a DC bus (2) and that perform power conversion between the AC power supply (3) and the DC bus (2); a plurality of AC-DC control units (11, 12, 13) that respectively control the plurality of AC-DC conversion circuits (21, 22, 23); and a main control unit (10) that controls the plurality of AC-DC control units (11, 12, 13). The main control unit (10) transmits an AC command value generated in accordance with the AC power of the AC power supply (3) to each of the plurality of AC-DC control units (11, 12, 13), and the plurality of AC-DC control units (11, 12, 13) respectively control the plurality of AC-DC conversion circuits (21, 22, 23) so that an AC current input from the AC power supply (3) to each of the plurality of AC-DC conversion circuits (21, 22, 23) has a value corresponding to the AC command value. Thus, the number of conversion circuits to be mounted can be arbitrarily selected, and the distortion rate of an AC current waveform can be suppressed.

Description

Power Conversion Device

[0001] The present invention relates to a power conversion device.

[0002] In order to reduce carbon dioxide emissions worldwide, the introduction of solar power generation and electric vehicles, etc., is required, and the development of power conversion equipment such as power conditioners for solar power generation and power conversion devices such as electric vehicle chargers is progressing. However, the desired installation scale, such as the rated power of solar power generation and the number of electric vehicles to be charged, varies depending on the installation site. Therefore, in order to expand the introduction of solar power generation and electric vehicles, etc., it is effective to develop power conversion equipment that can accommodate a wide range of installation scales and increase the number of installation sites. Specifically, it is desirable to realize a power conversion device that can arbitrarily select the number of AC-DC conversion circuits that convert power between an AC power source and a DC bus, or the number of DC-DC conversion circuits that convert power between a solar cell and a DC bus, or between an electric vehicle or a stationary storage battery and a DC bus. Prior art related to such power conversion devices is known, for example, from Patent Documents 1 and 2.

[0003] Patent Document 1 discloses a power combining / distribution device that is connected to the DC power supply devices and combines and distributes the DC power input from each of the DC power supply devices, a plurality of DC / AC converters that are connected to the power combining / distribution device, a plurality of DC / DC converters that are connected to the power combining / distribution device, an AC device connection unit that is connected to the DC / AC converter and to which an AC device that supplies and demands AC power is connected on the other hand, a DC device connection unit that is connected to the DC / DC converter and to which a DC device that supplies and demands DC power is connected on the other hand, and a power combining / distribution device that is connected to the DC / AC converter and to which a DC device that supplies and demands DC power is connected on the other hand. and a control device that controls the combination of DC power and the supply and distribution of power to each of the AC device connection parts and the DC device connection parts by controlling either the AC converter or the DC / DC converter, and when power is exchanged with a power grid, the control device selects at least one master from the plurality of DC / AC converters and stabilizes the DC voltage of the DC bus of the power combining / distribution device by controlling the DC voltage of the master DC / AC converter, and performs active power control on the remaining DC / AC converters and the plurality of DC / DC converters.

[0004] Patent Document 2 discloses a power conversion device that includes multiple power converters connected in parallel to solar cells, in which one of the multiple power converters performs maximum power tracking control of the solar cells as a whole, while the remaining power converters perform current control.

[0005] JP 2020-58161 A JP 2011-141794 A

[0006] The prior art described in Patent Document 1 relates to a power supply and demand system equipped with multiple power supply and demand facilities and aimed at realizing flexible power supply and receipt, in which a master selected from multiple power converters controls DC and AC voltages. However, when multiple power supply and demand facilities are controlled by a single master, voltage fluctuations become large during load changes. While Patent Document 1 discloses the selection of multiple masters to suppress such voltage fluctuations, it does not disclose a method for balancing the currents of each power converter, which is necessary to control a common voltage across multiple power converters.

[0007] Furthermore, the prior art described in Patent Document 2 discloses a power conversion device in which multiple power converters are connected in parallel to configure a larger power conversion device, and describes a method of balancing the currents of the multiple parallel-connected power converters by sending current command values ​​to each power converter and having each power converter perform current control. However, even if this method is applied, as the number of AC-DC conversion circuits and DC-DC conversion circuits connected to the DC bus increases, the time required to calculate the current command value for each conversion circuit increases, and the update interval for the current command value sent to each conversion circuit also becomes longer. This makes it difficult to keep the distortion rate of the AC current waveform, which changes from moment to moment, low in the AC-DC conversion circuit.

[0008] The present invention has been made in view of the above, and has as its object to provide a power conversion device that can arbitrarily select the number of conversion circuits to be mounted and can suppress the distortion rate of the AC current waveform.

[0009] The present application includes a plurality of means for solving the above-described problems. One example is a power conversion device including a plurality of AC-DC conversion circuits connected in parallel between an AC power supply and a DC bus and performing power conversion between the AC power supply and the DC bus, a plurality of AC-DC control units that control the plurality of AC-DC conversion circuits, respectively, and a main control unit that controls the plurality of AC-DC control units, wherein the main control unit transmits AC command values ​​generated according to AC power of the AC power supply to the plurality of AC-DC control units, respectively, and the plurality of AC-DC control units control the plurality of AC-DC conversion circuits so that the AC currents input from the AC power supply to the plurality of AC-DC conversion circuits, respectively, have values ​​according to the AC command values.

[0010] According to the present invention, the number of conversion circuits to be mounted can be selected arbitrarily, and the distortion rate of the AC current waveform can be suppressed.

[0011] FIG. 1 is a diagram showing a power conversion device according to a first embodiment together with related configuration; FIG. 2 is a diagram explaining the calculation principle of an instantaneous phase; FIG. 3 is a diagram explaining the processing principle in an AC current control unit when the amplitude and phase of an AC current are received as AC command values; FIG. 4 is a diagram explaining the processing principle in an AC current control unit when the amplitude and phase of an AC current are received as AC command values; FIG. 5 is a diagram showing a power conversion device according to a second embodiment together with related configuration; FIG. 6 is a diagram showing a power conversion device according to a third embodiment together with related configuration; and FIG. 7 is a diagram showing a power conversion device according to a fourth embodiment together with related configuration.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] First Embodiment A first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG.

[0014] FIG. 1 is a diagram showing a power conversion device according to this embodiment together with related configurations.

[0015] In FIG. 1 , a power conversion device 1 is connected to an AC power source 3, a solar cell 4 (photovoltaic: PV), a storage battery 5, and a load 6. The power generated by the solar cell 4 can be output to the AC power source 3, and power input from the solar cell 4 or the AC power source 3 can be charged into the storage battery 5, supplied to the load 6, or supplied from the storage battery 5 to the load 6. The solar cell 4 functions as a DC power source when generating power, and similarly, the storage battery 5 functions as a DC power source when discharging power. The storage battery 5 may be, for example, a battery mounted on an electric vehicle such as an electric car, or a stationary battery (stationary storage battery). The load 6 may be, for example, a server that receives DC power. In addition to the solar cell 4 and the storage battery 5, other DC power sources that may be connected to the power conversion device 1 include, for example, a fuel cell.

[0016] The power conversion device 1 includes a plurality of AC-DC conversion circuits 21, 22, 23 connected in parallel to perform power conversion between an AC power source 3 and a DC bus 2, a DC-DC conversion circuit 24 to perform power conversion between a solar cell 4, which is a DC power source, and the DC bus 2, a DC-DC conversion circuit 25 to perform power conversion between a storage battery 5, which is a DC power source, and the DC bus 2, AC-DC control units 11, 12, 13 to control the AC-DC conversion circuits 21, 22, 23, DC-DC control units 14, 15 to control the DC-DC conversion circuits 24, 25, and a main control unit 10 to communicate with the AC-DC control units 11, 12, 13 and the DC-DC control units 14, 15.

[0017] The main control unit 10 includes a system control unit 31 , a DC bus voltage control unit 32 , and a power distribution unit 33 .

[0018] The system control unit 31 detects the voltage and current of the AC power supply 3, calculates the effective voltage value, phase, frequency, etc. of the AC power supply 3, and detects system abnormalities such as power outages, voltage rise / drop, and frequency rise / drop. Information on the phase and frequency of the AC power supply 3 calculated by the system control unit 31 is transmitted as a signal 60 to the AC-DC control units 11, 12, and 13. Furthermore, when the values ​​of power and current input and output to and from the AC power supply 3 must be controlled due to system control constraints, an AC power supply target value, which is the target value, is transmitted as a signal 35 to the power distribution unit 33. This AC power supply target value is expressed as the phase and amplitude of the current of the AC power supply, or the active current and reactive current of the AC power supply, or the active power and reactive power of the AC power supply.

[0019] The DC bus voltage control unit 32 detects the voltage of the DC bus 2 and generates a DC bus power command value, which is the power to be input to the DC bus 2 and is required to control the voltage to a target value. Specifically, if the detected voltage of the DC bus 2 is lower than the target value, the DC bus power command value is increased, and if the detected voltage of the DC bus 2 is higher than the target value, the DC bus power command value is decreased, thereby performing feedback control. The DC bus power command value generated by the DC bus voltage control unit 32 is transmitted to the power distribution unit 33 as a signal 34. Note that the above-mentioned DC bus power command value may also be a current to be input to the DC bus 2.

[0020] The power distribution unit 33 uses the AC power supply target value (signal 35) received from the system control unit 31, the DC bus power command value (signal 34) received from the DC bus voltage control unit 32, the power target values ​​of the AC power supply 3, solar cell 4, and storage battery 5 received or generated from outside as signal 36, and the voltages of the solar cell 4 and storage battery 5 received from the DC-DC control units 14 and 15 to generate AC command values ​​to be transmitted as signals 51, 52, and 53 to the AC-DC control units 11, 12, and 13, and DC command values ​​to be transmitted as signals 54 and 55 to the DC-DC control units 14 and 15. Specifically, the power of each of the AC power source 3, the solar cell 4, and the storage battery 5 is set within the power range of the AC power source 3, the solar cell 4, and the storage battery 5, which is restricted by the AC power source target value (signal 35), the power target value (signal 36), and the voltages of the solar cell 4 and the storage battery 5, and the total power input from the AC power source 3, the solar cell 4, and the storage battery 5 is set to be equal to the DC bus power command value (signal 34).

[0021] As described above, the power distribution unit 33 distributes the DC bus power command value to the power input to the DC bus 2 from each of the AC-DC conversion circuits 21, 22, and 23 and the DC-DC conversion circuits 24 and 25. As a result, the main control unit 10 controls the voltage of the DC bus 2 by changing the AC command values ​​(signals 51, 52, and 53) and the DC command values ​​(signals 54 and 55). Here, the AC command values ​​(signals 51, 52, and 53) are expressed as the phase and amplitude of the AC current of the AC-DC conversion circuits 21, 22, and 23, or as the active current and reactive current, or as the active power and reactive power. Furthermore, the DC command values ​​(signals 54 and 55) are expressed as the DC power or DC current of the DC-DC conversion circuits 24 and 25.

[0022] The AC-DC control units 11, 12, and 13 each include an instantaneous phase calculation unit 46, 47, and 48, and an AC current control unit 41, 42, and 43. The instantaneous phase calculation unit 46, 47, and 48 calculates an instantaneous phase using information (signal 60) on the phase and frequency of the AC current of the AC power supply 3 received from the system control unit 31 of the main control unit 10, and transmits the calculated instantaneous phase to the AC current control units 41, 42, and 43 as signals 61, 62, and 63.

[0023] 2 is a diagram for explaining the calculation principle of the instantaneous phase, in which the horizontal axis represents time and the vertical axis represents the instantaneous phase to be calculated.

[0024] As shown in FIG. 2 , at time t1, when the phase θ1 and frequency f1 of the AC current from the AC power supply 3 are received, the instantaneous phase θ is set to phase θ1. Next, until time t2, when the phase and frequency of the AC current from the AC power supply 3 are received, the instantaneous phase θ is calculated using the frequency f1 received at time t1. Specifically, the instantaneous phase θ is calculated by integrating the frequency f1 over time t, multiplying it by 2π, and adding the calculated phase change to the phase θ1. Then, at time t2, when the phase θ2 and frequency f2 of the AC current from the AC power supply 3 are newly received, the instantaneous phase θ is set to phase θ2, and the instantaneous phase θ is calculated using the frequency f2 received at time t2. Thereafter, the instantaneous phase θ is calculated in the same manner, and if the instantaneous phase θ exceeds 2π, 2π is simply subtracted.

[0025] By the processing of the instantaneous phase calculation units 46, 47, 48 described above, the AC-DC control units 11, 12, 13 can relatively accurately calculate and grasp the instantaneous phase of the AC current of the AC power supply 3 even if the time interval at which the phase θ1 of the AC current of the AC power supply 3 is received from the main control unit 10 is long.

[0026] The AC current control units 41, 42, 43 use the instantaneous phases (signals 61, 62, 63) calculated by the instantaneous phase calculation units 46, 47, 48 to control the AC-DC conversion circuits 21 to 23 so that the detected AC power or current of the AC-DC conversion circuits 21, 22, 23 becomes the AC command values ​​(signals 51, 52, 53) received from the main control unit 10.

[0027] 3 and 4 are diagrams for explaining the processing principle in the AC current control unit when the amplitude and phase of the AC current are received as AC command values.

[0028] 3, the horizontal axis represents the sum of the instantaneous phase θ (signals 61, 62, 63) of the AC power supply calculated by the instantaneous phase calculation units 46, 47, 48 and the phase φ of the AC current of the received AC command value (signals 51, 52, 53). The vertical axis represents the AC current I to be flowed through the AC-DC conversion circuits 21, 22, 23, and the current value Ia represents the amplitude of the AC current of the received AC command value (signals 51, 52, 53).

[0029] 3, since the instantaneous phase θ is known, the instantaneous value of the current I to be flowed can be determined from information on the phase φ and amplitude Ia. AC current control units 41, 42, and 43 control the AC currents of the AC-DC conversion circuits 21, 22, and 23 to the above-mentioned current to be flowed.

[0030] In FIG. 4, the horizontal axis represents time t, and the vertical axis represents the waveforms of the voltage V of the AC power supply 3 and the AC current I of the AC-DC conversion circuits 21, 22, and 23.

[0031] 4, the AC current I of the AC-DC conversion circuits 21, 22, 23 leads the phase θ of the AC power supply 3 by the phase φ of the AC current of the AC command values ​​(signals 51, 52, 53), and has an amplitude Ia of the AC current of the AC command values ​​(signals 51, 52, 53). Note that the AC current control units 41, 42, 43 detect the voltage of the DC bus 2, and have a function of correcting the AC power or current of the AC-DC conversion circuits 21, 22, 23 to restore the voltage to its original value when the voltage deviates from a preset value.

[0032] As described above, by controlling the AC power or current of the AC-DC conversion circuits 21, 22, and 23, it is possible to generate a relatively accurate AC waveform even if the update time interval of the AC command values ​​(signals 51, 52, and 53) received from the main control unit 10 is long, and it is possible to keep the distortion rate of the current waveform flowing through the AC power supply 3 low.

[0033] Incidentally, by including frequency components that are integer multiples of the fundamental frequency of the AC power supply 3 in addition to the fundamental frequency of the AC power supply 3 in the AC command values ​​(signals 51, 52, 53), it is possible to further reduce the distortion rate of the waveform of the current flowing through the AC power supply 3. For example, by including third-order harmonic components and fifth-order harmonic components in the AC command values ​​(signals 51, 52, 53), it is possible to reduce the third-order harmonic current and fifth-order harmonic current that flow through the AC power supply 3.

[0034] The DC-DC control units 14, 15 include DC voltage and current control units 44, 45. The DC voltage and current control units 44, 45 control the DC-DC conversion circuits 24, 25 so that the detected DC power or current of the DC-DC conversion circuits 24, 25 becomes the DC command value (signal 54, 55) received from the main control unit 10. Similarly to the AC current control units 41, 42, 43, the DC-DC control units 14, 15 also detect the voltage of the DC bus 2 and have the function of correcting the DC power or current of the DC-DC conversion circuits 24, 25 to restore it to its original value if the voltage deviates from a preset value. The DC-DC control units 14, 15 also transmit the detected voltages of the solar cell 4 and the storage battery 5 to the main control unit 10.

[0035] The effects of the present embodiment configured as above will be described.

[0036] The prior art described in Patent Document 1 relates to a power supply and demand system equipped with multiple power supply and demand facilities and aimed at realizing flexible power supply and receipt, in which a master selected from multiple power converters controls DC and AC voltages. However, when multiple power supply and demand facilities are controlled by a single master, voltage fluctuations become large during load changes. While Patent Document 1 discloses the selection of multiple masters to suppress such voltage fluctuations, it does not disclose a method for balancing the currents of each power converter, which is necessary to control a common voltage across multiple power converters.

[0037] Furthermore, the prior art described in Patent Document 2 discloses a power conversion device in which multiple power converters are connected in parallel to configure a larger power conversion device, and describes a method of balancing the currents of the multiple parallel-connected power converters by sending current command values ​​to each power converter and having each power converter perform current control. However, even if this method is applied, as the number of AC-DC conversion circuits and DC-DC conversion circuits connected to the DC bus increases, the time required to calculate the current command value for each conversion circuit increases, and the update interval for the current command value sent to each conversion circuit also becomes longer. This makes it difficult to keep the distortion rate of the AC current waveform, which changes from moment to moment, low in the AC-DC conversion circuit.

[0038] In contrast to this, in this embodiment, the power conversion device 1 includes a plurality of AC-DC conversion circuits 21, 22, 23 connected in parallel between the AC power supply 3 and the DC bus 2 and performing power conversion between the AC power supply 3 and the DC bus 2, a plurality of AC-DC control units 11, 12, 13 that control the plurality of AC-DC conversion circuits 21, 22, 23, respectively, and a main control unit 10 that controls the plurality of AC-DC control units 11, 12, 13. The main control unit 10 controls an AC command generated in accordance with the AC power of the AC power supply 3. The AC command values ​​(signals 51, 52, 53) are transmitted to the plurality of AC-DC control units 11, 12, 13, respectively, and the plurality of AC-DC control units 11, 12, 13 are configured to control the plurality of AC-DC conversion circuits 21, 22, 23, respectively, so that the AC currents input from the AC power source 3 to the plurality of AC-DC conversion circuits 21, 22, 23, respectively, have values ​​corresponding to the AC command values ​​(signals 51, 52, 53). Therefore, the number of conversion circuits to be installed can be selected arbitrarily, and the distortion rate of the AC current waveform can be suppressed.

[0039] In other words, it is possible to configure a power conversion device with various rated powers by changing the number of AC-DC conversion circuits and DC-DC conversion circuits installed.In addition, it is possible to realize a power conversion device that keeps the distortion rate of the AC current waveform low even when the number of conversion circuits installed increases and the update time interval of the current command value of each conversion circuit becomes longer.

[0040] In this embodiment, the number of DC-DC conversion circuits installed has been described as two, but the number of installed DC-DC conversion circuits may be increased and some or all of them may be connected in parallel. For example, ten DC-DC conversion circuits may be installed, two of which may be connected in parallel to a solar cell, three of which may be connected in parallel to a stationary battery, two of which may be connected in parallel to an electric vehicle, two of which may be connected to separate solar cells, and the remaining one may be connected to another electric vehicle.

[0041] Second Embodiment A second embodiment of the present invention will be described with reference to FIG.

[0042] In this embodiment, the main control unit communicates with other AC-DC control units or DC-DC control units via a specific AC-DC control unit or DC-DC control unit. In this embodiment, the same members and functions as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0043] FIG. 5 is a diagram showing the power conversion device according to this embodiment together with related configurations.

[0044] In FIG. 5 , the power conversion device 100 is connected to an AC power source 3, a solar cell 4 (photovoltaic: PV), a storage battery 5, and a load 6. The power generated by the solar cell 4 can be output to the AC power source 3, and power input from the solar cell 4 or the AC power source 3 can be charged into the storage battery 5, supplied to the load 6, or supplied from the storage battery 5 to the load 6. The solar cell 4 functions as a DC power source when generating power, and similarly, the storage battery 5 functions as a DC power source when discharging power. The storage battery 5 may be, for example, a battery mounted on an electric vehicle such as an electric car, or a stationary battery (stationary storage battery). The load 6 may be, for example, a server that receives DC power. In addition to the solar cell 4 and the storage battery 5, other DC power sources that may be connected to the power conversion device 1 include, for example, a fuel cell.

[0045] The power conversion device 100 includes a plurality of AC-DC conversion circuits 121, 122, and 123 connected in parallel to perform power conversion between an AC power source 3 and a DC bus 120, a DC-DC conversion circuit 124 to perform power conversion between a solar cell 4, which is a DC power source, and the DC bus 120, a DC-DC conversion circuit 125 to perform power conversion between a storage battery 5, which is a DC power source, and the DC bus 120, AC-DC control units 111, 112, and 113 to control the AC-DC conversion circuits 121, 122, and 123, DC-DC control units 114 and 115 to control the DC-DC conversion circuits 124 and 125, and a main control unit 110 to communicate with the AC-DC control units 111, 112, and 113 and the DC-DC control units 114 and 115.

[0046] Here, the AC-DC control units 111, 112, and 113 and the AC-DC conversion circuits 121, 122, and 123 respectively constitute converter units 101, 102, and 103. Similarly, the DC-DC control units 114 and 115 and the DC-DC conversion circuits 124 and 125 respectively constitute converter units 104 and 105.

[0047] When the main control unit 110 communicates with the AC-DC control units 112 and 113 and the DC-DC control unit 114 (specifically, when transmitting signals 52, 53, 54, 60, etc.), the communication is via the AC-DC control unit 111 or the DC-DC control unit 115. For example, when the main control unit 110 communicates with the AC-DC control unit 113, the communication is via communication between the main control unit 110 and the AC-DC control unit 111 (signal 130), communication between the AC-DC control unit 111 and the AC-DC control unit 112 (signal 131), and communication between the AC-DC control unit 112 and the AC-DC control unit 113 (signal 132), or via communication between the main control unit 110 and the DC-DC control unit 115 (signal 140), communication between the DC-DC control unit 115 and the DC-DC control unit 114 (signal 141), and communication between the DC-DC control unit 114 and the AC-DC control unit 113 (signal 150). The order in which the main control unit 110 communicates with each unit is not limited to the above, and various combinations are possible.

[0048] The other configurations are the same as those of the first embodiment.

[0049] The present embodiment configured as above can also achieve the same effects as the first embodiment.

[0050] Furthermore, the number of communication ports required for the main control unit 110 can be reduced while allowing a larger number of converter units to be connected.

[0051] Third Embodiment A third embodiment of the present invention will be described with reference to FIG.

[0052] In this embodiment, each of the converter units is provided with a main control unit, and a specific main control unit functions as a master. Note that in this embodiment, the same components and functions as those in the first and second embodiments are denoted by the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0053] FIG. 6 is a diagram showing the power conversion device according to this embodiment together with related configurations.

[0054] In FIG. 6 , the power conversion device 200 is connected to an AC power source 3, a solar cell 4 (photovoltaic: PV), a storage battery 5, and a load 6. The power generated by the solar cell 4 can be output to the AC power source 3, and power input from the solar cell 4 or the AC power source 3 can be charged into the storage battery 5, supplied to the load 6, or supplied from the storage battery 5 to the load 6. The solar cell 4 functions as a DC power source when generating power, and similarly, the storage battery 5 functions as a DC power source when discharging power. The storage battery 5 may be, for example, a battery mounted on an electric vehicle such as an electric car, or a stationary battery (stationary storage battery). The load 6 may be, for example, a server that receives DC power. In addition to the solar cell 4 and the storage battery 5, other DC power sources that may be connected to the power conversion device 1 include, for example, a fuel cell.

[0055] The power conversion device 200 includes a plurality of AC-DC conversion circuits 221, 222, 223 connected in parallel to perform power conversion between an AC power source 3 and a DC bus 120, a DC-DC conversion circuit 224 to perform power conversion between a solar cell 4, which is a DC power source, and the DC bus 220, a DC-DC conversion circuit 225 to perform power conversion between a storage battery 5, which is a DC power source, and the DC bus 220, AC-DC control units 211, 212, 213 to control the AC-DC conversion circuits 221, 222, 223, DC-DC control units 214, 215 to control the DC-DC conversion circuits 224, 225, and main control units 231, 232, 233, 234, 235 to control the AC-DC control units 211, 212, 213 and the DC-DC control units 214, 215, respectively.

[0056] Here, the AC-DC control units 211, 212, and 213, the AC-DC conversion circuits 221, 222, and 223, and the main control units 231, 232, and 233 respectively constitute converter units 201, 202, and 203. Similarly, the DC-DC control units 214 and 215, the DC-DC conversion circuits 224 and 225, and the main control units 234 and 235 respectively constitute converter units 204 and 205.

[0057] In the power conversion device 200, one of the main control units 231, 232, 233, 234, and 235 serves as a master, and the master main control unit functions as the main control unit for the entire power conversion device 200, while the remaining main control units function as communication devices. When the master main control unit communicates with the AC-DC control units or DC-DC control units of other converter units, the communication is performed via the main control units of the other AC-DC control units or DC-DC control units that are serially connected for communication. For example, when the main control unit 231 acts as a master and communicates with the AC-DC control unit 213, communication is via communication between the main control unit 231 and the main control unit 232 of the converter unit 202 (signal 241), and communication between the main control unit 232 and the main control unit 233 of the converter unit 203 (signal 242), or via communication between the main control unit 231 and the main control unit 235 of the converter unit 205 (signal 245), communication between the main control unit 235 and the main control unit 234 of the converter unit 204 (signal 244), and communication between the main control unit 234 and the main control unit 233 of the converter unit 203 (signal 243).

[0058] The other configurations are the same as those of the first and second embodiments.

[0059] The present embodiment configured as above can also achieve the same effects as the first and second embodiments.

[0060] Furthermore, it is not necessary to provide a housing for the main control unit separately from the converter unit.

[0061] In this embodiment, a configuration has been exemplified in which all of the converter units 201, 202, 203, 204, and 205 are equipped with a main control unit, but it is not necessarily necessary for all of the converter units 201, 202, 203, 204, and 205 to be equipped with a main control unit. For example, it may be configured so that only the converter units 201, 202, and 203 equipped with the AC-DC conversion circuits 221, 222, and 223 are equipped with a main control unit.

[0062] <Fourth Embodiment> A fourth embodiment of the present invention will be described with reference to FIG.

[0063] In this embodiment, devices that are the targets of AC power distribution are connected as loads. In this embodiment, the same members and functions as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0064] FIG. 7 is a diagram showing the power conversion device according to this embodiment together with related configurations.

[0065] In FIG. 7, the power conversion device 301 includes a plurality of AC-DC conversion circuits 21, 22, 23, a DC-DC conversion circuit 24, a DC-AC conversion circuit 325, AC-DC control units 11, 12, 13 that control the AC-DC conversion circuits 21, 22, 23, a DC-DC control unit 14 that controls the DC-DC conversion circuit 24, a DC-AC control unit 315 that controls the DC-AC conversion circuit 325, and a main control unit 10 that communicates with the AC-DC control units 11, 12, 13, the DC-DC control unit 14, and the DC-AC control unit 315.

[0066] The DC-AC conversion circuit 325 converts power between the DC bus 2 and the load 306 that is the target of AC power distribution. The DC-AC control unit 315 includes an AC voltage / current control unit 345. The AC voltage / current control unit 345 detects the AC voltage supplied from the DC-AC conversion circuit 325 to the load 306, and controls the DC-AC conversion circuit 325 so that this AC voltage becomes the AC voltage command value (signal 355) received from the main control unit 10.

[0067] The other configurations are the same as those of the first embodiment.

[0068] The present embodiment configured as above can also achieve the same effects as the first embodiment.

[0069] <Notes> The present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the gist thereof. Furthermore, the present invention is not limited to those including all of the configurations described in the above-described embodiments, and also includes those in which some of the configurations are omitted. Furthermore, the above-described configurations, functions, etc. may be realized in part or in whole by designing them as, for example, integrated circuits. Furthermore, the above-described configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function.

[0070] 1...power conversion device, 2...DC bus, 3...AC power source, 4...solar cell, 5...storage battery, 6...load, 10...main control unit, 11, 12, 13...AC-DC control unit, 14, 15...DC-DC control unit, 21, 22, 23...AC-DC conversion circuit, 24, 25...DC-DC conversion circuit, 31...system control unit, 32...DC bus voltage control unit, 33...power distribution unit, 41, 42, 43...AC current control unit, 44, 45...DC voltage and current control unit, 46, 47, 48...instantaneous phase calculation unit, 100...power conversion device, 101, 102, 103, 104, 105...converter unit, 110...main control unit, 111, 112, 113...AC-DC control unit, 114 , 115...DC-DC control unit, 120...DC bus, 121, 122, 123...AC-DC conversion circuit, 124, 125...DC-DC conversion circuit, 200...power conversion device, 201, 202, 203, 204, 205...converter unit, 211, 212, 213...AC-DC control unit, 214, 215...DC-DC control unit, 220...DC bus, 221, 222, 223...AC-DC conversion circuit, 224, 225...DC-DC conversion circuit, 231, 232, 233, 234, 235...main control unit, 301...power conversion device, 306...load, 315...DC-AC control unit, 325...DC-AC conversion circuit, 345...AC voltage and current control unit

Claims

1. A power conversion device comprising: a plurality of AC-DC conversion circuits connected in parallel between an AC power source and a DC bus and performing power conversion between the AC power source and the DC bus; a plurality of AC-DC control units each controlling the plurality of AC-DC conversion circuits; and a main control unit controlling the plurality of AC-DC control units, wherein the main control unit transmits to each of the plurality of AC-DC control units an AC command value generated according to the AC power of the AC power source, and the plurality of AC-DC control units each control the plurality of AC-DC conversion circuits so that the AC current input from the AC power source to each of the plurality of AC-DC conversion circuits has a value according to the AC command value.

2. A power conversion device as claimed in claim 1, characterized in that the main control unit transmits command values ​​indicating the amplitude and phase of the AC current as the AC command value to each of the multiple AC-DC control units, and the multiple AC-DC control units control each of the multiple AC-DC conversion circuits so that the amplitude and phase of the AC current input from the AC power source to each of the multiple AC-DC conversion circuits become values ​​corresponding to the AC command value.

3. A power conversion device as claimed in claim 1, characterized in that the main control unit transmits command values ​​indicating the active current and reactive current of the AC current as the AC command value to each of the multiple AC-DC control units, and the multiple AC-DC control units control each of the multiple AC-DC conversion circuits so that the active current and reactive current of the AC current input from the AC power source to each of the multiple AC-DC conversion circuits become values ​​corresponding to the AC command value.

4. A power conversion device as described in claim 1, wherein the main control unit transmits command values ​​indicating the active power and reactive power of the AC current as the AC command value to each of the multiple AC-DC control units, and the multiple AC-DC control units control each of the multiple AC-DC conversion circuits so that the active power and reactive power of the AC current input from the AC power source to each of the multiple AC-DC conversion circuits become values ​​corresponding to the AC command value.

5. A power conversion device as claimed in claim 1, characterized in that the AC command value transmitted from the main control unit to each of the plurality of AC-DC control units includes a fundamental wave component of an AC current and a frequency component which is an integer multiple of the fundamental wave frequency.

6. The power conversion device according to claim 1, wherein the main control unit controls the voltage of the DC bus by changing the AC command value.

7. A power conversion device as claimed in claim 1, characterized in that: said main control unit transmits the phase and frequency of said AC power supply to each of said plurality of AC-DC control units; and said plurality of AC-DC control units calculate an instantaneous phase of said AC power supply from the phase and frequency of said AC power supply, and use the calculated instantaneous phase to control each of said plurality of AC-DC conversion circuits so that the AC current input from said AC power supply to each of said plurality of AC-DC conversion circuits has a value corresponding to said AC command value.

8. A power conversion device as claimed in claim 1, comprising: a plurality of DC-DC conversion circuits respectively connected between a plurality of DC power sources and the DC bus, and performing power conversion between the plurality of DC power sources and the DC bus; and a plurality of DC-DC control units respectively controlling the plurality of DC-DC conversion circuits, wherein the main control unit transmits DC command values ​​to the plurality of DC-DC control units, and the plurality of DC-DC control units control the DC-DC conversion circuits so that the DC currents respectively input from the plurality of DC power sources to the plurality of DC-DC conversion circuits have values ​​corresponding to the DC command values.

9. A power conversion device according to claim 8, characterized in that the main control unit controls the voltage of the DC bus by varying the AC command value and the DC command value.

10. A power conversion device as described in claim 8, wherein the main control unit transmits command values ​​indicating DC current power as the DC command values ​​to each of the DC-DC control units, and the multiple DC-DC control units control each of the multiple DC-DC conversion circuits so that the DC current power input from the multiple DC power sources to each of the multiple DC-DC conversion circuits becomes a value corresponding to the DC command value.

11. A power conversion device according to claim 1, further comprising a function of supplying the power of the DC bus to a load.

12. A power conversion device as described in claim 8, wherein the main control unit receives or generates power target values ​​for the AC power source and the DC power source, generates a DC bus current command value required to control the voltage of the DC bus, and distributes the DC bus current command value so that the power of the AC power source and the DC power source becomes a value corresponding to the power target value, thereby generating the AC command value and the DC command value.

13. A power conversion device as described in claim 8, wherein the main control unit receives or generates power target values ​​for the AC power source and the DC power source, generates a DC bus power command value required to control the voltage of the DC bus, and distributes the DC bus power command value so that the power of the AC power source and the DC power source becomes a value corresponding to the power target value, thereby generating the AC command value and the DC command value.

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