Control device for power conversion device and power conversion system

Abstract

Provided is a control device of a power conversion device that can appropriately supply power from a plurality of power conversion devices to a load without requiring a common control device for the plurality of power conversion devices in a state in which the plurality of power conversion devices are connected in parallel. The control device of the power conversion device includes a voltage recognition unit that detects a voltage at a grid point of the plurality of power conversion devices, and a control unit that, in a case in which a control target power conversion device autonomously operates as a voltage source, controls an amplitude and a frequency of a voltage output by the control target power conversion device based on active power and reactive power output by the control target power conversion device, and in a case in which the control target power conversion device grid-connected operates as a current source, controls the active power and the reactive power output by the control target power conversion device based on the amplitude and the frequency of the voltage detected by the voltage recognition unit to compensate for an excess or a deficiency of the active power and the reactive power at the grid point.

Description

Technical Field

[0001] This disclosure relates to control devices and power conversion systems for power conversion devices. Background Technology

[0002] Patent document 1 discloses a power conversion system. According to this power conversion system, when multiple power converters connected in parallel are operated through a shared control device, operation control information can be transmitted without laying dedicated signal lines.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 10-201105 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, the power conversion system described in Patent Document 1 requires a control device shared by multiple power converters. Therefore, the power conversion system becomes complex.

[0008] This invention was made to solve the aforementioned problems. The object of this invention is to provide a control device and a power conversion system for a power conversion device, which can appropriately supply power from multiple power converters to a load without requiring a shared control device for all power converters when multiple power converters are connected in parallel.

[0009] Methods used to solve problems

[0010] The control device for the power conversion apparatus of the present invention includes: a voltage identification unit that detects the voltage at the grid connection point of the plurality of power converters when multiple power converters that convert DC power from a DC power source to AC power are connected in parallel with a load; and a control unit that, when the power converter of the controlled object is operated autonomously as a voltage source while the plurality of power converters are connected in parallel, controls the amplitude and frequency of the voltage output by the power converter of the controlled object based on the active power and reactive power output by the power converter of the controlled object; and when the power converter of the controlled object is operated grid-connected as a current source while the plurality of power converters are connected in parallel, controls the active power and reactive power output by the power converter of the controlled object based on the amplitude and frequency of the voltage detected by the voltage identification unit, so as to compensate for excess or insufficient active power and reactive power at the grid connection point.

[0011] The power conversion system of the present invention comprises: a plurality of power converters connected in parallel with respect to a load, which convert DC power from a DC power source into AC power; and a voltage detector that detects the voltage at the grid connection point of the plurality of power converters; a portion of the plurality of power converters operating autonomously as a voltage source, controlling the amplitude and frequency of their output voltage based on their own output active power and reactive power; and another portion of the plurality of power converters operating grid-connected as a current source, controlling their own output active power and reactive power based on the amplitude and frequency of the voltage detected by the voltage detector, in order to compensate for excess or insufficient active power and reactive power at the grid connection point.

[0012] Invention Effects

[0013] According to the present invention, when multiple power converters are connected in parallel, power can be appropriately supplied to the load from multiple power converters without the need for a shared control device for the multiple power converters. Attached Figure Description

[0014] Figure 1 This is a structural diagram of the power conversion system according to Implementation Method 1.

[0015] Figure 2 It is an autonomous operation control block that is implemented as a voltage source by the control device of the power conversion device of the power conversion system of embodiment 1.

[0016] Figure 3 It is a grid-connected operation control block that is implemented by the control device of the power conversion device of the power conversion system in Embodiment 1 as a voltage source.

[0017] Figure 4 This is a flowchart illustrating a method for determining the amplitude of the output voltage, which is a voltage source, implemented by the control device of the power conversion apparatus of the power conversion system of Embodiment 1.

[0018] Figure 5 This is a flowchart illustrating the method for determining the operating frequency of a voltage source implemented by the control device of the power conversion device of the power conversion system of Embodiment 1.

[0019] Figure 6 This is a flowchart illustrating the method for determining the output active power as a voltage source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 1.

[0020] Figure 7 This is a flowchart illustrating the method for determining the output reactive power as a voltage source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 1.

[0021] Figure 8This is a hardware structure diagram of the control device of the power conversion device in the power conversion system of embodiment 1.

[0022] Figure 9 It is an autonomous operation control block that is implemented as a voltage source by the control device of the power conversion device of the power conversion system of embodiment 2.

[0023] Figure 10 It is a grid-connected operation control block that is implemented by the control device of the power conversion device of the power conversion system in Embodiment 2 as a current source.

[0024] Figure 11 This is a flowchart illustrating the method for determining the amplitude of the output voltage as a voltage source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 2.

[0025] Figure 12 This is a flowchart illustrating the method for determining the operating frequency of a voltage source implemented by the control device of the power conversion device of the power conversion system of Embodiment 2.

[0026] Figure 13 This is a flowchart illustrating the method for determining the output active power as a current source implemented by the control device 14 of the power conversion device 6 of the power conversion system in Embodiment 2.

[0027] Figure 14 This is a flowchart illustrating the method for determining the output reactive power as a current source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 1. Detailed Implementation

[0028] The embodiments will be described with reference to the accompanying drawings. Furthermore, in each drawing, the same or corresponding parts are given the same reference numerals. Repeated descriptions of these parts are appropriately simplified or omitted.

[0029] Implementation method 1.

[0030] Figure 1 This is a structural diagram of the power conversion system according to Implementation Method 1.

[0031] exist Figure 1 In this system, multiple DC power sources 1 are configured to output DC power. For example, the multiple DC power sources 1 may be wind power generation devices, solar power generation devices, or energy storage devices. System 2 is operated by a power company, etc. System 2 is configured to output AC power. A transformer 3 is connected between the DC power sources 1 and system 2. A load 4 is located between system 2 and transformer 3. A switching device 5 is connected between system 2 and load 4.

[0032] Multiple power conversion devices 6 are respectively provided corresponding to multiple DC power supplies 1. The multiple power conversion devices 6 are respectively connected between the corresponding DC power supply 1 and the transformer 3. The multiple power conversion devices 6 are connected in parallel with respect to the load 4. For example, the power conversion device 6 includes a power converter 7, a harmonic filter 8, a switch 9, a first current detector 10, a second current detector 11, a first voltage detector 12, a second voltage detector 13, and a control device 14.

[0033] The power converter 7 is configured to convert DC power from the DC power source 1 into AC power. For example, the power converter 7 is configured to convert DC power into three-phase AC power. The harmonic filter 8 is configured to absorb harmonics from the AC power from the power converter 7. The switch 9 is configured to open or close the wiring between the transformer and the harmonic filter 8.

[0034] The first current detector 10 is configured to detect the current flowing between the power converter 7 and the harmonic filter 8 as the inverter output current. The second current detector 11 is configured to detect the current flowing between the harmonic filter 8 and the switch 9 as the system 2 current. The first voltage detector 12 is configured to detect the voltage between the harmonic filter 8 and the switch 9 as the inverter voltage. The second voltage detector 13 is configured to detect the voltage between the transformer and the switch 9 as the system voltage at the grid connection point.

[0035] The control device 14 controls the operation of the power converter 7 based on the first current detector 10, the second current detector 11, the first voltage detector 12, and the second voltage detector 13. The control device 14 controls the operation of the power converter 7 by outputting gate pulse information. For example, the control device 14 includes a voltage recognition unit 15 and a control unit 16.

[0036] The voltage identification unit 15 identifies the voltage value detected by the second voltage detector 13. The control unit 16 controls the power converter 7 based on the voltage identified by the voltage identification unit 15.

[0037] For example, if the switching device 5 opens when system 2 is de-energized, a portion of the multiple power converters 7 functions as a voltage source. Another portion of the multiple power converters 7 functions as a current source.

[0038] At this time, in the control device 14, when the power converter 7 of the controlled object is operated autonomously as a voltage source, the control unit 16 controls the amplitude and frequency of the voltage output by the power converter 7 based on the active power and reactive power output by the power converter 7. For example, when the power converter 7 of the controlled object is operated in grid-connected mode as a current source, the control unit 16 controls the active power and reactive power output by the power converter 7 based on the amplitude and frequency of the voltage detected by the voltage recognition unit 15, so as to compensate for the excess or deficiency of active power and reactive power at the grid connection point.

[0039] Next, use Figure 2 This describes the method for controlling the power converter 7 as a voltage source.

[0040] Figure 2 It is an autonomous operation control block that serves as a voltage source, consisting of the control device of the power conversion device of the power conversion system in Embodiment 1.

[0041] like Figure 2 As shown, the control device 14 includes a first amplifier 17, a second amplifier 18, a first adder 19, a first integrator 20, a first UVW / dq converter 21, a first subtractor 22, a second subtractor 23, a first d-axis voltage controller 24, a third subtractor 25, a first q-axis voltage controller 26, and a first dq / UVW converter 27.

[0042] Amplifier 17 receives input information about the value of the active power feedback. Amplifier 17 outputs information about the value obtained by multiplying the active power feedback by the gain k1.

[0043] The second amplifier 18 receives input information about the value of the reactive power feedback. The second amplifier 18 outputs information about the value obtained by multiplying the reactive power feedback by the gain k2.

[0044] The first adder 19 receives input information about the value (fixed value) of the rated frequency f0. The first adder 19 also receives input information about the output value of the second amplifier 18. The first adder 19 outputs information about the value obtained by adding the value of the rated frequency f0 to the output value of the second amplifier 18.

[0045] The first integrator 20 receives input information about the output value of the first adder 19. The first integrator 20 outputs phase information based on the output value of the first adder 19.

[0046] The first UVW / dq converter 21 receives input information about the inverter output voltage value. The first UVW / dq converter 21 also receives input phase information from the first integrator 20. The first UVW / dq converter 21 outputs information based on the inverter output voltage value, the phase information, the d-axis current feedback value, and the q-axis voltage feedback value.

[0047] The first subtractor 22 accepts input information about the value of the output voltage reference V0 (rated voltage, fixed value). The first subtractor 22 also accepts input information about the output value of the first amplifier 17. The first subtractor outputs information about the value obtained by subtracting the output value of the first amplifier 17 from the value of the output voltage reference V0.

[0048] The second subtractor 23 receives input information about the d-axis voltage feedback value from the first UVW / dq converter 21. The second subtractor 23 also receives input information about the output value of the first subtractor 22. The second subtractor 23 outputs information about the value obtained by subtracting the d-axis voltage feedback value from the output value of the first subtractor 22.

[0049] The first d-axis voltage controller 24 receives input information about the output value of the second subtractor 23. The first d-axis voltage controller 24 outputs information about the d-axis voltage command value based on the output value of the second subtractor 23.

[0050] The third subtractor 25 accepts an input of a value of 0. The third subtractor 25 also accepts an input of the q-axis voltage feedback value from the first UVW / dq converter 21. The third subtractor 25 outputs the value obtained by subtracting the q-axis voltage feedback value from the value of 0.

[0051] The first q-axis voltage controller 26 receives input information about the output value of the third subtractor 25. The first q-axis voltage controller 26 outputs information about the q-axis voltage command value based on the output value of the third subtractor 25.

[0052] The first dq / UVW converter 27 receives input information about the d-axis voltage command value from the first d-axis voltage controller 24. The first dq / UVW converter 27 receives input information about the q-axis voltage command value from the first q-axis voltage controller 26. The first dq / UVW converter 27 receives input phase information from the first integrator 20. The first dq / UVW converter 27 generates three-phase voltage command values ​​based on the d-axis voltage command value, the q-axis voltage command value, and the phase information, and transmits them to the gate pulse generation circuit.

[0053] Next, use Figure 3 This describes the method for controlling the power converter 7 as a current source.

[0054] Figure 3It is a grid-connected operation control block that is implemented by the control device of the power conversion device of the power conversion system in Embodiment 1 as a current source.

[0055] like Figure 3 As shown, the control device 14 includes a fourth subtractor 28, a first low-pass filter 29, a fifth subtractor 30, a first active power controller 31, a second d-axis current controller 32, a sixth subtractor 33, a second low-pass filter 34, a seventh subtractor 35, a first reactive power controller 36, a second q-axis current controller 37, and a second dq / UVW converter 38.

[0056] The fourth subtractor 28 accepts input information about the value (fixed value) of the rated voltage V0. The fourth subtractor 28 accepts input information about the system voltage V. s The input is the value of the input. The output of the fourth subtractor 28 is the system voltage V0 minus the value of the rated voltage V0. s The information obtained from the value.

[0057] The first low-pass filter 29 receives the input information of the output value of the fourth subtractor 28. The first low-pass filter 29 outputs the information of the value obtained by multiplying the value corresponding to the low-frequency region in the output value of the fourth subtractor 28 by the gain k3.

[0058] The fifth subtractor 30 receives input information about the output value of the first low-pass filter 29. The fifth subtractor 30 also receives input information about the active power feedback value. The fifth subtractor 30 outputs information about the value obtained by subtracting the active power feedback value from the output value of the first low-pass filter 29.

[0059] The first active power controller 31 receives input information about the output value of the fifth subtractor 30. The first active power controller 31 outputs information about the active current reference based on the output value of the fifth subtractor 30.

[0060] The second d-axis current controller 32 receives input information of the value obtained by subtracting the active power feedback value from the active current reference value from the first active power controller 31. The second d-axis current controller 32 outputs information of the d-axis voltage command value based on the active current reference.

[0061] The 6th subtractor 33 is affected by the system frequency f detected by the PLL. s The input is the value (fixed value). The 6th subtractor 33 accepts the input of the value of the rated frequency f0. The 6th subtractor 33 outputs the value from the system frequency f0. s The information is obtained by subtracting the value of the rated frequency f0 from the value of the given frequency.

[0062] The second low-pass filter 34 receives the input information of the output value of the sixth subtractor 33. The second low-pass filter 34 outputs the information of the value obtained by multiplying the value corresponding to the low-frequency region in the output value of the sixth subtractor 33 by the gain k4.

[0063] The 7th subtractor 35 receives input information about the output value of the 2nd low-pass filter 34. The 7th subtractor 35 also receives input information about the reactive power feedback value. The 7th subtractor 35 outputs information about the value obtained by subtracting the reactive power feedback value from the output value of the 2nd low-pass filter 34.

[0064] The first reactive power controller 36 receives input information about the output value of the seventh subtractor 35. The first reactive power controller 36 outputs reactive current reference information based on the output value of the seventh subtractor 35.

[0065] The second q-axis current controller 37 receives input information of the value obtained by subtracting the reactive power feedback value from the reactive power reference value from the first reactive power controller 36. The second q-axis current controller 37 outputs information of the q-axis voltage command value based on the reactive current reference.

[0066] The second dq / UVW converter 38 receives input information about the d-axis voltage command value from the second d-axis current controller 32. The second dq / UVW converter 38 receives input information about the q-axis voltage command value from the second q-axis current controller 37. The second dq / UVW converter 38 receives input information about the phase information detected by the PLL. The second dq / UVW converter 38 generates three-phase voltage command values ​​based on the d-axis voltage command value, the q-axis voltage command value, and the phase information, and transmits them to the gate pulse generation circuit.

[0067] Next, use Figure 4 This section explains the method for determining the amplitude of the output voltage when the power converter 7 is controlled as a voltage source. This process is performed by the control unit 16 of the control device 14.

[0068] Figure 4 This is a flowchart illustrating a method for determining the amplitude of the output voltage, which is a voltage source, implemented by the control device of the power conversion apparatus of the power conversion system of Embodiment 1.

[0069] In step S1, the control device 14 starts operating with voltage reference V0. Then, the control device 14 performs step S2. In step S2, the control device 14 detects the active power P. out Then, the control device 14 performs step S3. In step S3, the control device 14 determines the active power P. out The value of .

[0070] In step S3, the active power P out When the value is 0, the control device 14 performs step S4. In step S4, the control device 14 operates with V0 as the voltage reference. Then, the control device 14 performs step S2.

[0071] In step S3, the active power P out If the value is not 0, the control device 14 performs step S5. In step S5, the control device 14 controls the active power P. out Multiply by the gain k1 and subtract from V0. Then, control device 14 performs step S6. In step S6, control device 14 calculates V0 - k1 × P. out It operates as a voltage reference. Then, the control device 14 performs the operation of step S2.

[0072] Next, use Figure 5 This section explains the method for determining the operating frequency when the power converter 7 is controlled as a voltage source. This process is performed by the control unit 16 of the control device 14.

[0073] Figure 5 This is a flowchart illustrating the method for determining the operating frequency of a voltage source implemented by the control device of the power conversion device of the power conversion system of Embodiment 1.

[0074] In step S11, the control device 14 starts operating at the operating frequency f0. Then, the control device 14 performs the action in step S12. In step S12, the control device 14 detects the reactive power Q. out Then, the control device 14 performs step S13. In step S13, the control device 14 determines the reactive power Q. out The value of .

[0075] In step S13, the reactive power Q out When the value is 0, the control device 14 performs step S14. In step S14, the control device 14 operates with f0 as the operating frequency. Then, the control device 14 performs step S12.

[0076] In step S13, the reactive power Q out If the value is not 0, the control device 14 performs step S15. In step S15, the control device 14 controls the reactive power Q. out Multiply by the gain k2 and add to f0. Then, control device 14 performs step S16. In step S16, f0 + k2 × Q is added. out It operates at the specified operating frequency. Then, the control device 14 performs the action of step S12.

[0077] Next, use Figure 6 This section explains the method for determining the output active power when the power converter 7 is controlled as a current source. This process is performed by the control unit 16 of the control device 14.

[0078] Figure 6 This is a flowchart illustrating the method for determining the output active power as a current source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 1.

[0079] In step S21, the control device 14 uses 0 as the active power reference P. ref Then, operation begins. Next, control device 14 performs step S22. In step S22, control device 14 detects the system voltage V. s Then, the control device 14 performs step S23. In step S23, the control device 14 determines the system voltage V. s The value of .

[0080] In step S23, the system voltage V s If the value of the active power reference P is the same as the value of the rated voltage V0, the control device 14 performs step S24. In step S24, the control device 14 sets the active power reference P... ref It is set to 0 and then operates. Then, the control device 14 performs the action of step S22.

[0081] In step S23, the system voltage V s If the value of the voltage is different from the value of the rated voltage V0, the control device 14 performs step S25. In step S25, the control device 14 subtracts the system voltage V from the rated voltage V0. s And multiply by the gain k3. Then, the control device 14 performs the action of step S26. In step S26, (V0-V s )×k3 is set as the active power reference P ref Then, the control device 14 performs the action of step S22.

[0082] Next, use Figure 7 This section explains the method for determining the output reactive power when the power converter 7 is controlled as a current source. This process is performed by the control unit 16 of the control device 14.

[0083] Figure 7 This is a flowchart illustrating the method for determining the output reactive power as a current source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 1.

[0084] In step S31, the control device 14 sets 0 as the reactive power reference Q. refThen it begins operation. Next, control device 14 performs step S32. In step S32, control device 14 detects the system frequency f. s Then, the control device 14 performs step S33. In step S33, the control device 14 determines the system frequency f. s The value of .

[0085] In step S33, the system frequency f s If the value is the same as the rated frequency f0, the control device 14 performs step S34. In step S34, the control device 14 sets 0 as the reactive power reference Q. ref Then, the control device 14 performs the action of step S32.

[0086] In step S33, the system frequency f s If the value of f0 is different from the rated frequency f0, the control device 14 performs step S35. In step S35, the control device 14 selects the system frequency f0 from the rated frequency f0. s Subtract the rated frequency f0 and multiply by the gain k4. Then, control device 14 performs step S36. In step S36, (f s -f0)×k4 is set as the reactive power reference Q ref Then, the control device 14 performs the action of step S22.

[0087] According to Embodiment 1 described above, when the control device 14 operates the controlled power converter 7 autonomously as a voltage source in a state where multiple power converters 7 are connected in parallel, it controls the amplitude and frequency of the voltage output by the controlled power converter 7 based on the active and reactive power output by the controlled power converter 7. When the control device 14 operates the controlled power converter 7 as a current source connected to the grid in a state where multiple power converters 7 are connected in parallel, it controls the active and reactive power output by the controlled power converter 7 based on the amplitude and frequency of the voltage at the grid connection point of the multiple power converters 7, in order to compensate for the excess or deficiency of active and reactive power at the grid connection point. Therefore, in a state where multiple power converters are connected in parallel, it is not necessary to use a shared control device for multiple power converters 7, exchange information between each control device 14, or detect the power consumption of the load 4, to appropriately supply power to the load 4 from multiple power converters 7.

[0088] Specifically, when multiple power converters 7 are connected in parallel and the controlled power converter 7 operates autonomously as a voltage source, the control device 14 controls the amplitude of the voltage output by the controlled power converter 7 based on the active power output, and controls the frequency of the voltage output by the controlled power converter 7 based on the reactive power output. When multiple power converters 7 are connected in parallel and the controlled power converter 7 operates grid-connected as a current source, the control device 14 controls the active power output by the controlled power converter 7 based on the amplitude of the voltage at the grid connection point of the multiple power converters 7, and controls the reactive power output by the controlled power converter 7 based on the frequency of the voltage at the grid connection point of the multiple power converters 7. Therefore, a shared control device for multiple power converters is not required, and a shared control device for multiple power converters 7 is not required, enabling more appropriate power supply to the load 4 from multiple power converters 7.

[0089] Next, use Figure 8 An example illustrating control device 14.

[0090] Figure 8 This is a hardware structure diagram of the control device of the power conversion device in the power conversion system of embodiment 1.

[0091] The functions of the control device 14 can be implemented by a processing circuit. For example, the processing circuit has at least one processor 100a and at least one memory 100b. For example, the processing circuit has at least one dedicated hardware 200.

[0092] When the processing circuit has at least one processor 100a and at least one memory 100b, the functions of the control device 14 are implemented by software, firmware, or a combination of software and firmware. At least one of the software and firmware is described as a program. At least one of the software and firmware is stored in at least one memory 100b. The program stored in at least one memory 100b is read from and executed by at least one processor 100a to implement the functions of the control device 14. At least one processor 100a is also referred to as a central processing unit, processing device, arithmetic unit, microprocessor, microcomputer, or DSP. For example, at least one memory 100b is RAM, ROM, flash memory, EPROM, EEPROM, non-volatile or volatile semiconductor memory, disk, floppy disk, optical disk, CD, MD, DVD, etc.

[0093] When the processing circuit has at least one dedicated hardware 200, the processing circuit is implemented, for example, by a single circuit, a composite circuit, a programmable processor, a parallel programmable processor, an ASIC, an FPGA, or a combination thereof. For example, each function of the control device 14 is implemented by the processing circuit. For example, each function of the control device 14 is implemented centrally by the processing circuit.

[0094] Regarding the various functions of the control device 14, some can be implemented using dedicated hardware 200, while others can be implemented using software or firmware. For example, the functions of the control unit 16 can be implemented by a processing circuit that is a dedicated hardware 200, while functions other than those of the control unit 16 can be implemented by at least one processor 100a reading out and executing a program stored in at least one memory 100b.

[0095] In this way, the processing circuit implements the various functions of the control device 14 through hardware 200, software, firmware, or a combination thereof.

[0096] Implementation method 2.

[0097] Figure 9 It is an autonomous operation control block that is implemented as a voltage source by the control device of the power conversion device of the power conversion system of embodiment 2. Figure 10 This is a grid-connected operation control block that functions as a voltage source, implemented by the control device of the power conversion unit in the power conversion system of Embodiment 2. Furthermore, parts that are identical or corresponding to those in Embodiment 1 are assigned the same reference numerals. Descriptions of these parts are omitted.

[0098] Figure 9 This diagram illustrates the method of controlling the power converter 7 as a voltage source. (For example...) Figure 9 As shown, the control device 14 includes a third amplifier 39, a fourth amplifier 40, an eighth subtractor 41, a second integrator 42, a second UVW / dq converter 43, a second adder 44, a ninth subtractor 45, a fifth d-axis voltage controller 46, a tenth subtractor 47, a fifth q-axis voltage controller 48, and a third dq / UVW converter 49.

[0099] The third amplifier 39 receives input information about the value of the reactive power feedback. The third amplifier 39 outputs information about the value obtained by multiplying the active power feedback by the gain k1.

[0100] The fourth amplifier 40 receives input information about the value of the active power feedback. The fourth amplifier 40 outputs information about the value obtained by multiplying the active power feedback by the gain k2.

[0101] The 8th subtractor 41 receives input information about the value of the rated frequency f0 (a fixed value). The 8th subtractor 41 also receives input information about the output value of the 4th amplifier 40. The 8th subtractor 41 outputs information about the value obtained by subtracting the output value of the 4th amplifier 40 from the value of the rated frequency f0.

[0102] The second integrator 42 receives input information about the output value of the eighth subtractor 41. The second integrator 42 outputs phase information based on the output value of the eighth subtractor 41.

[0103] The second UVW / dq converter 4 receives input information about the inverter output voltage value. The second UVW / dq converter 43 receives input information about the phase from the second integrator 42. The second UVW / dq converter 43 outputs information based on the inverter output voltage value, phase information, d-axis current feedback value, and q-axis voltage feedback value.

[0104] The second adder 44 receives input information about the output value of the third amplifier 39. The second adder 44 also receives input information about the value of the output voltage reference V0 (rated voltage, fixed value). The second adder 44 outputs information about the value obtained by adding the output value of the third amplifier 39 and the value of the output voltage reference V0.

[0105] The 9th subtractor 45 receives input information about the output value of the 2nd adder 44. The 9th subtractor 45 also receives input information about the d-axis voltage feedback value from the 2nd UVW / dq converter 43. The 9th subtractor 45 outputs information about the value obtained by subtracting the d-axis voltage feedback value from the output value of the 2nd adder 44.

[0106] The 5th d-axis voltage controller 46 receives input information about the output value of the 9th subtractor 45. The 5th d-axis voltage controller 46 outputs information about the d-axis voltage command value based on the output value of the 9th subtractor 45.

[0107] The 10th subtractor 47 accepts an input of a value of 0. The 10th subtractor 47 also accepts an input of the q-axis voltage feedback value from the 2nd UVW / dq converter 43. The 10th subtractor 47 outputs the value obtained by subtracting the q-axis voltage feedback value from the value of 0.

[0108] The 5th q-axis voltage controller 48 receives input information about the output value of the 10th subtractor 47. The 5th q-axis voltage controller 48 outputs information about the q-axis voltage command value based on the output value of the 10th subtractor 47.

[0109] The 3dq / UVW converter 49 receives input information about the d-axis voltage command value from the 5d-axis voltage controller 46. The 3dq / UVW converter 49 receives input information about the q-axis voltage command value from the 5q-axis voltage controller 48. The 3dq / UVW converter 49 receives input phase information from the 2nd integrator 42. The 3dq / UVW converter 49 generates three-phase voltage command values ​​based on the d-axis voltage command value, the q-axis voltage command value, and the phase information, and transmits them to the gate pulse generation circuit.

[0110] Figure 10 This diagram illustrates the method of controlling the power converter 7 as a current source. (For example...) Figure 10 As shown, the control device 14 includes an 11th subtractor 50, a 3rd low-pass filter 51, a 12th subtractor 52, a 2nd active power controller 53, a 6th d-axis current controller 54, a 13th subtractor 55, a 4th low-pass filter 56, a 14th subtractor 57, a 2nd reactive power controller 58, a 6th q-axis current controller 59, and a 4th dq / UVW converter 60.

[0111] Subtractor 50 of the 11th type receives input information about the value (fixed value) of the rated frequency f0. Subtractor 50 of the 11th type receives input information about the system frequency f0 detected by the PLL. s The input is the value of the subtractor 50. The output of the 11th subtractor is the value of the rated frequency f0 minus the system frequency f. s The information obtained from the value.

[0112] The third low-pass filter 51 receives the input information of the output value of the eleventh subtractor 50. The third low-pass filter 51 outputs the information of the value obtained by multiplying the value corresponding to the low-frequency region in the output value of the eleventh subtractor 50 by the gain k3.

[0113] The 12th subtractor 52 receives input information about the output value of the 3rd low-pass filter 51. The 12th subtractor 52 also receives input information about the active power feedback value. The 12th subtractor 52 outputs information about the value obtained by subtracting the active power feedback value from the output value of the 3rd low-pass filter 51.

[0114] The second active power controller receives input information about the output value of the 12th subtractor 52. The second active power controller outputs information about the active current reference based on the output value of the 12th subtractor 52.

[0115] The 6th d-axis current controller 54 receives input information of the value obtained by subtracting the active power feedback value from the active current reference value from the 2nd active power controller. The 6th d-axis current controller 54 outputs information of the d-axis voltage command value based on the active current reference.

[0116] Subtractor 13, Receiver 55, System Voltage V s The input of the value information. The 13th subtractor 55 accepts the input information of the rated voltage V0 (fixed value). The output of the 13th subtractor 55 is from the system voltage V. s The information is obtained by subtracting the value of the rated voltage V0 from the value of the voltage.

[0117] The fourth low-pass filter 56 receives information about the output value of the 13th subtractor 55 as input. The fourth low-pass filter 56 outputs information about the value obtained by multiplying the value corresponding to the low-frequency region in the output value of the 13th subtractor 55 by the gain k4.

[0118] Subtractor 57 14 receives input information about the output value of low-pass filter 56. Subtractor 57 14 receives input information about the reactive power feedback value. Subtractor 57 14 outputs information about the value obtained by subtracting the reactive power feedback value from the output value of low-pass filter 56.

[0119] The second reactive power controller 58 receives input information about the output value of the fourteenth subtractor 57. The second reactive power controller 58 outputs reactive current reference information based on the output value of the fourteenth subtractor 57.

[0120] The 6th q-axis current controller 59 receives input information of the value obtained by subtracting the reactive power feedback value from the reactive current reference value from the 2nd reactive power controller 58. The 6th q-axis current controller 59 outputs information of the q-axis voltage command value based on the reactive current reference.

[0121] The 4th dq / UVW converter 60 receives input information about the d-axis voltage command value from the 6th d-axis current controller 54. The 4th dq / UVW converter 60 receives input information about the q-axis voltage command value from the 6th q-axis current controller 59. The 4th dq / UVW converter 60 receives input information about the phase information detected by the PLL. The 4th dq / UVW converter 60 generates three-phase voltage command values ​​based on the d-axis voltage command value, the q-axis voltage command value, and the phase information, and transmits them to the gate pulse generation circuit.

[0122] Next, use Figure 11 This section explains the method for determining the amplitude of the output voltage when the power converter 7 is controlled as a voltage source. This process is performed by the control unit 16 of the control device 14.

[0123] Figure 11 This is a flowchart illustrating the method for determining the amplitude of the output voltage as a voltage source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 2.

[0124] In step S41, the control device 14 starts operating with voltage reference V0. Then, the control device 14 performs the operation in step S42. In step S42, the control device 14 detects the reactive power Q. out Then, the control device 14 performs step S43. In step S43, the control device 14 determines the reactive power Q. out The value of .

[0125] In step S43, the reactive power Q out When the value is 0, the control device 14 performs step S44. In step S44, the control device 14 operates with V0 as the voltage reference. Then, the control device 14 performs step S42.

[0126] In step S43, the reactive power Q out If the value is not 0, the control device 14 performs step S45. In step S45, the control device 14 controls the reactive power Q. out Multiply by the gain k1 and add to V0. Then, control device 14 performs step S46. In step S46, V0 + k1 × Q is... out It operates as a voltage reference. Then, the control device 14 performs the action of step S42.

[0127] Next, use Figure 12 This section explains the method for determining the operating frequency when the power converter 7 is controlled as a voltage source. This process is performed by the control unit 16 of the control device 14.

[0128] Figure 12 This is a flowchart illustrating the method for determining the operating frequency of a voltage source implemented by the control device of the power conversion device of the power conversion system of Embodiment 2.

[0129] In step S51, the control device 14 starts operating at the operating frequency f0. Then, the control device 14 performs the action in step S52. In step S52, the control device 14 detects the active power P. out Then, the control device 14 performs step S53. In step S53, the control device 14 determines the active power P. out The value of .

[0130] In step S53, the active power P out When the value is 0, the control device 14 performs step S54. In step S54, the control device 14 operates with f0 as the operating frequency. Then, the control device 14 performs step S52.

[0131] In step S53, the active power P outIf the value is not 0, the control device 14 performs step S55. In step S55, the control device 14 controls the active power P. out Multiply by the gain k2 and subtract from f0. Then, control device 14 performs step S56. In step S56, f0 - k2 × P out It operates at the specified operating frequency. Then, the control device 14 performs the action in step S52.

[0132] Next, use Figure 13 This section explains the method for determining the output active power when the power converter 7 is controlled as a current source. This process is performed by the control unit 16 of the control device 14.

[0133] Figure 13 This is a flowchart illustrating the method for determining the output active power as a current source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 2.

[0134] In step S61, the control device 14 sets 0 as the active power reference P. ref Then it begins operation. Next, control device 14 performs step S62. In step S62, control device 14 detects the system frequency f. s Then, the control device 14 performs step S63. In step S63, the control device 14 determines the system frequency f. s The value of .

[0135] In step S63, the system frequency f s If the value is the same as the rated frequency f0, the control device 14 performs step S64. In step S64, the control device 14 sets the active power reference P... ref It is set to 0 and then operates. Then, the control device 14 performs the action of step S62.

[0136] In step S63, the system frequency f s If the value of the frequency f0 differs from the value of the rated frequency f0, the control device 14 performs step S65. In step S65, the control device 14 subtracts the system frequency f from the rated frequency f0. s And multiply by the gain k3. Then, the control device 14 performs the action of step S66. In step S66, the control device 14 multiplies (f0 - f) by the gain k3. s )×k3 is set as the active power reference P ref Then, the control device 14 performs the action of step S62.

[0137] Next, use Figure 14This section explains the method for determining the output reactive power when the power converter 7 is controlled as a current source. This process is performed by the control unit 16 of the control device 14.

[0138] Figure 14 This is a flowchart illustrating the method for determining the output reactive power as a current source, implemented by the control device of the power conversion device of the power conversion system of Embodiment 1.

[0139] In step S71, the control device 14 sets 0 as the reactive power reference Q. ref Then, operation begins. Next, control device 14 performs step S72. In step S72, control device 14 detects the system voltage V. s Then, the control device 14 performs step S73. In step S73, the control device 14 determines the system voltage V. s The value of .

[0140] In step S73, the system voltage V s If the value is the same as the rated voltage V0, the control device 14 performs step S74. In step S74, the control device 14 sets 0 as the reactive power reference Q. ref Then, the control device 14 performs the action of step S72.

[0141] In step S73, the system voltage V s If the value of the voltage is different from the rated voltage V0, the control device 14 performs step S75. In step S75, the control device 14 obtains the system voltage V0 value from the rated voltage V0. s Subtract the rated voltage V0 and multiply by the gain k4. Then, control device 14 performs step S76. In step S76, (V s -V0)×k4 is set as the reactive power reference Q ref Then, the control device 14 performs the action of step S72.

[0142] According to Embodiment 2 described above, when the control device 14 operates the controlled power converter 7 as a voltage source autonomously with multiple power converters 7 connected in parallel, it controls the amplitude of the voltage output by the controlled power converter 7 based on the reactive power output by the controlled power converter 7, and controls the frequency of the voltage output by the controlled power converter 7 based on the active power output by the controlled power converter 7. When the control device 14 operates the controlled power converter 7 as a current source connected to the grid with multiple power converters 7 connected in parallel, it controls the active power output by the controlled power converter 7 based on the frequency of the voltage at the grid connection point of the multiple power converters 7, and controls the reactive power output by the controlled power converter 7 based on the amplitude of the voltage at the grid connection point of the multiple power converters 7. Therefore, a shared control device for multiple power converters 7 is not required, and power can be supplied to the load 4 more appropriately from multiple power converters 7.

[0143] Furthermore, in the control unit 16 of the control device 14 in Embodiments 1 and 2, when the power converter 7 of the controlled object is operated in grid-connected mode as a current source, the response time of controlling the active and reactive power output of the power converter 7 of the controlled object based on the amplitude and frequency of the voltage at the grid connection point of the multiple power converters 7 can be adjusted within the required response range. In this case, it is possible to suppress the situation where some power converters 7 excessively supply power and other power converters 7 absorb the power due to small detection errors of the detector or small deviations in the operation timing of the control device 14. Therefore, it is possible to suppress the transmission and reception of power among the multiple power converters 7 that function as current sources.

[0144] For example, in the control unit 16 of the control device 14 corresponding to the multiple power converters 7 that function as current sources, it can be configured to make the difference in response time between the active power and reactive power output by each power converter 7 equal when controlling the voltage amplitude and frequency of the grid connection point of the multiple power converters 7. In this case, it is possible to suppress the transmission and reception of power between the multiple power converters 7 that function as current sources.

[0145] For example, in the control unit 16 of the control device 14 corresponding to the multiple power converters 7 that function as current sources, it can be configured to make the ratio of the response time when controlling the active power and reactive power output by each power converter 7 based on the amplitude and frequency of the voltage at the grid connection point of the multiple power converters 7 equal. In this case, it is possible to suppress the transmission and reception of power between the multiple power converters 7 that function as current sources.

[0146] For example, in the control unit 16 of the control device 14 corresponding to the multiple power converters 7 that function as current sources, the response time when controlling the active and reactive power output of each power converter 7 based on the amplitude and frequency of the voltage at the grid connection point of the multiple power converters 7 can be set by random numbers. In this case, the transmission and reception of power between the multiple power converters 7 that function as current sources can be suppressed.

[0147] For example, in the control unit 16 of the control device 14 corresponding to the multiple power converters 7 that function as current sources, the response time variation when controlling the active and reactive power output of each power converter 7 based on the amplitude and frequency of the voltage at the grid connection point of the multiple power converters 7 can be adjusted according to preset conditions. For example, the response time can be varied at regular intervals. In this case, by having the power converter 7 with a faster response time respond first and the power converter 7 with a slower response time respond later, deviations in the power consumption of the DC power supply 1 can be suppressed. Therefore, the operating rate of the multiple power converters 7 can be made more uniform. As a result, the power conversion system can be operated stably.

[0148] Furthermore, the type of power converter 7 is not limited. For example, it can be a single-phase power converter 7. For example, it can be a two-level power converter 7. For example, it can be a neutral-point clamped multi-level power converter. For example, it can be a neutral-point switching multi-level power converter 7. For example, it can be a parallel multi-level power converter 7. For example, it can be a series multi-level power converter 7. In these cases, it is also possible to appropriately supply power to the load 4 from multiple power converters 7.

[0149] Industrial availability

[0150] As described above, the control device 14 and power conversion system of the power conversion device 6 of the present invention can be used in a system that converts power.

[0151] Label Explanation

[0152] 1 DC power supply; 2 System; 3 Transformer; 4 Load; 5 Switching device; 6 Power conversion device; 7 Power converter; 8 Harmonic filter; 9 Switch; 10 First current detector; 11 Second current detector; 12 First voltage detector; 13 Second voltage detector; 14 Control device; 15 Voltage identification unit; 16 Control unit; 17 First amplifier; 18 Second amplifier; 19 First adder; 20 First integrator; 21 First UVW / dq converter; 22 First subtractor; 23 Second subtractor; 24 First d-axis voltage controller; 25 Third subtractor; 26 First q-axis voltage controller; 27 First dq / UVW converter; 28 Fourth subtractor; 29 First low-pass filter; 30 Fifth subtractor; 31 First active power controller; 32 Second d-axis current controller; 33 Sixth subtractor; 34 Second low-pass filter; 35 7th Subtractor; 36th First Reactive Power Controller; 37th Second q-Axis Current Controller; 38th Second dq / UVW Converter; 39th Third Amplifier; 40th Fourth Amplifier; 41st Eighth Subtractor; 42nd Second Integrator; 43rd Second UVW / dq Converter; 44th Second Adder; 45th Ninth Subtractor; 46th Fifth d-Axis Voltage Controller; 47th Tenth Subtractor; 48th Fifth q-Axis Voltage Controller; 49th Third dq / UVW converter; 50 11th subtractor; 51 3rd low-pass filter; 52 12th subtractor; 53 2nd active power controller; 54 6th d-axis current controller; 55 13th subtractor; 56 4th low-pass filter; 57 14th subtractor; 58 2nd reactive power controller; 59 6th q-axis current controller; 60 4th dq / UVW converter; 100a processor; 100b memory; 200 hardware.

Claims

1. A control device of a power conversion device, characterized by comprising: a voltage recognition section that detects a voltage at a point of interconnection of a plurality of power converters that convert direct-current electric power from a direct-current power source into alternating-current electric power, when the plurality of power converters are connected in parallel with respect to a load; and a control section that controls an amplitude and a frequency of a voltage output from a control target power converter, in a case where the control target power converter is autonomously operated as a voltage source in a state where the plurality of power converters are connected in parallel, on the basis of active power and reactive power output from the control target power converter, and controls the active power and the reactive power output from the control target power converter, in a case where the control target power converter is grid-connected operated as a current source in the state where the plurality of power converters are connected in parallel, on the basis of the amplitude and the frequency of the voltage detected by the voltage recognition section, to compensate for excess or deficiency of the active power and the reactive power at the point of interconnection.

2. The control device of a power conversion device according to claim 1, characterized in that the control section controls the amplitude of the voltage output from the control target power converter on the basis of the active power output from the control target power converter, and controls the frequency of the voltage output from the control target power converter on the basis of the reactive power output from the control target power converter, in the case where the control target power converter is autonomously operated as the voltage source in the state where the plurality of power converters are connected in parallel, and controls the active power output from the control target power converter on the basis of the amplitude of the voltage detected by the voltage recognition section, and controls the reactive power output from the control target power converter on the basis of the frequency of the voltage detected by the voltage recognition section, in the case where the control target power converter is grid-connected operated as the current source in the state where the plurality of power converters are connected in parallel.

3. The control device of a power conversion device according to claim 1, characterized in that the control section controls the frequency of the voltage output from the control target power converter on the basis of the active power output from the control target power converter, and controls the amplitude of the voltage output from the control target power converter on the basis of the reactive power output from the control target power converter, in the case where the control target power converter is autonomously operated as the voltage source in the state where the plurality of power converters are connected in parallel, and controls the active power output from the control target power converter on the basis of the frequency of the voltage detected by the voltage recognition section, and controls the reactive power output from the control target power converter on the basis of the amplitude of the voltage detected by the voltage recognition section, in the case where the control target power converter is grid-connected operated as the current source in the state where the plurality of power converters are connected in parallel.

4. The control device of a power conversion device according to any one of claims 1 to 3, characterized in that ​ ​ ​ ​ ​ The control section is configured to, in a case where the control target power converter is caused to operate as a current source in parallel with the plurality of power converters, be able to adjust a response time when controlling active power and reactive power output from the control target power converter based on the amplitude and frequency of the voltage detected by the voltage identification section.

5. A power conversion system characterized by comprising: a plurality of power converters connected in parallel with respect to a load, which convert direct-current power from a direct-current power source into alternating-current power; a voltage detector that detects a voltage at a point of interconnection of the plurality of power converters; a part of the plurality of power converters autonomously operates as a voltage source, controlling the amplitude and frequency of a voltage output from the part based on active power and reactive power output from the part; another part of the plurality of power converters operates in parallel as a current source, controlling active power and reactive power output from the other part based on the amplitude and frequency of the voltage detected by the voltage detector, to compensate for excess or deficiency of active power and reactive power at the point of interconnection.

6. The power conversion system according to claim 5, characterized in that the part of the plurality of power converters controls the amplitude of the voltage output from the part based on active power output from the part, and controls the frequency of the voltage output from the part based on reactive power output from the part; the other part of the plurality of power converters controls active power output from the other part based on the amplitude of the voltage detected by the voltage detector, and controls reactive power output from the other part based on the frequency of the voltage detected by the voltage detector.

7. The power conversion system according to claim 5, characterized in that the part of the plurality of power converters controls the amplitude of the voltage output from the part based on reactive power output from the part, and controls the frequency of the voltage output from the part based on active power output from the part; the other part of the plurality of power converters controls active power output from the other part based on the frequency of the voltage detected by the voltage detector, and controls reactive power output from the other part based on the amplitude of the voltage detected by the voltage detector.

8. The power conversion system according to any one of claims 5 to 7, characterized in that the other part of the plurality of power converters is configured to be able to adjust a response time when controlling active power and reactive power output from each of the plurality of power converters based on the amplitude and frequency of the voltage detected by the voltage detector.

9. The power conversion system according to claim 8, characterized in that the other part of the plurality of power converters is configured so that differences in response time when controlling active power and reactive power output from each of the plurality of power converters based on the amplitude and frequency of the voltage detected by the voltage detector are equalized.

10. The power conversion system according to claim 8, characterized in that the other part of the plurality of power converters is configured so that ratios of response time when controlling active power and reactive power output from each of the plurality of power converters based on the amplitude and frequency of the voltage detected by the voltage detector are equalized.

11. The power conversion system according to claim 8, characterized in that ​ ​ Another part of the plurality of power converters changes the response time when controlling the active power and the reactive power output from each power converter based on the amplitude and the frequency of the voltage detected by the voltage detector, by a random number.

12. The power conversion system of claim 8, wherein, Another part of the plurality of power converters changes the response time when controlling the active power and the reactive power output from each power converter based on the amplitude and the frequency of the voltage detected by the voltage detector, by a predetermined condition.

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