Power converter and control method for power converter

Abstract

An electric power conversion device according to an embodiment of the present invention comprises: a converter circuit that converts direct current power to alternating current power; a circuit breaker having one end to which an external system can be connected, and another end to which the converter circuit is connected via a filter circuit; and a closing unit that, prior to closing the circuit breaker during start-up, sets the converter circuit to an operating state, determines whether or not the voltages at the one end and the other end meet a synchronization condition, and closes the circuit breaker in cases when the synchronization condition has been met.

Description

Technical Field

[0001] Embodiments of the present invention relate to a power conversion device and a control method for the power conversion device.

Background Art

[0002] In recent years, the ratio of inverter power sources has been increasing due to the introduction of renewable energy and the like. In particular, in a system independent of a large-scale power grid in remote islands or isolated areas, a power supply mainly based on renewable energy is desired for the purpose of reducing fuel costs and decarbonization. In such a system, PV, wind power, and a storage battery become the main power supply equipment, so it is expected that the ratio of inverter power sources will become very high.

[0003] On the other hand, a rotating machine type power source such as a diesel generator (DG) plays an important role as a stable power source, and it is expected that a small-capacity DG and a large number of inverter power sources will be used together in an independent power system.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when the inverter power sources are connected, there has been a problem that the leading reactive power of the filter capacitor is supplied from the external power grid. Regarding this problem, a technique has been proposed in which the inverter power source is started in a self-supporting state, the filter capacitor is charged, and then synchronized with the power grid and the connection breaker is closed to switch to the operation in the power grid connection mode. However, in the above technique, when the connected power grid is mainly composed of inverters, there is a risk of control instability when switching to the power grid connection mode.

[0006] The present invention has been made in view of the above, and aims to provide a power converter and a control method for a power converter that enable stable interconnection of an inverter power supply to an external system, particularly a system mainly powered by an inverter power supply, without performing control switching when the interconnection circuit breaker is closed. [Means for solving the problem]

[0007] The power conversion device of this embodiment converts DC power to AC power. Configured as an inverter circuit A converter circuit, a circuit breaker with an external system connectable to one end and the converter circuit connected to the other end via a filter circuit, and a determination of whether the synchronization condition is met for the voltage at one end and the voltage at the other end, and closing the circuit breaker if the synchronization condition is met. It also outputs acceleration / deceleration signals to match the frequency of the voltage at one end and the voltage at the other end. A closing unit, and a control unit that, at startup and before the circuit breaker is closed, activates the converter circuit and uses the acceleration / deceleration signal output by the closing unit to control the frequency of the voltage at one end and the voltage at the other end to match. The control unit comprises a synchronous control unit that calculates and outputs a frequency correction signal based on the acceleration / deceleration signal, a GFM control unit that performs GFM control based on the frequency correction signal input from the synchronous control unit and calculates and outputs the phase of the output voltage, a coordinate system transformation unit that converts the d-axis voltage command value and the q-axis voltage command value based on the phase of the output voltage and outputs them as a reference voltage signal, and a PWM control unit that generates a PWM control signal based on the reference voltage signal and performs PWM control of the converter circuit. It is equipped with. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a block diagram illustrating the schematic configuration of the inverter power supply according to the embodiment. [Figure 2] Figure 2 is a functional block diagram of the control unit of the first embodiment. [Figure 3] Figure 3 is a processing flowchart of the control unit of the embodiment. [Figure 4] Figure 4 is an explanatory diagram of an example of a transfer function for calculating the voltage correction signal Vcorr. [Figure 5] Figure 5 is an explanatory diagram of an example of a transfer function for calculating the frequency correction signal Fcorr. [Figure 6] Figure 6 is an explanatory diagram of an example of a transfer function for calculating the phase θ in the first embodiment. [Figure 7] Figure 7 is an explanatory diagram of an example of a transfer function for calculating the d-axis voltage command value Vdref in the first embodiment. [Figure 8]Figure 8 is an explanatory diagram of an example of a transfer function for calculating the phase θ in the second embodiment. [Figure 9] Figure 9 is an explanatory diagram of an example of a transfer function for calculating the d-axis voltage command value Vdref in the second embodiment. [Figure 10] Figure 10 is a block diagram illustrating the schematic configuration of the power supply system according to the third embodiment. [Figure 11] Figure 11 is an explanatory diagram of an example of a transfer function for calculating the frequency correction signal Fcorr in the third embodiment. [Modes for carrying out the invention]

[0009] Next, embodiments will be described with reference to the drawings. Figure 1 is a block diagram illustrating the schematic configuration of the inverter power supply according to the embodiment. This inverter power supply 10 is controlled by a grid forming type (GFM: Grid Forming control type).

[0010] As shown in FIG. 1, the inverter power supply 10 includes a circuit breaker 11 connected to a bus bar BL that constitutes an external system PW, a filter circuit 12 that functions as a coupling reactor connected in series with the circuit breaker 11, a DC power supply 13 that supplies DC power, a converter circuit 14 configured as an inverter circuit that performs DC / three-phase AC conversion and supplies DC power Pdc to a load, a first voltage sensor 15 that detects the voltage (U-phase voltage, V-phase voltage, W-phase voltage) on the bus bar BL side of the circuit breaker 11 and outputs a first voltage detection signal Vgrid, a first current sensor 16 that detects the current (U-phase current, V-phase current, W-phase current) between the circuit breaker 11 and the filter circuit 12 and outputs a first current detection signal Is, a second voltage sensor 17 that detects the voltage (U-phase voltage, V-phase voltage, W-phase voltage) between the circuit breaker 11 and the filter circuit 12 and outputs a second voltage detection signal Vs, a second current sensor 18 that detects the current (U-phase current, V-phase current, W-phase current) between the filter circuit 12 and the converter circuit 14 and outputs a second current detection signal Is1, and a control unit 19 that performs GFM control of the inverter constituting the converter circuit 14 and controls the entire inverter power supply 10.

[0011] In the above configuration, the external system PW includes a load connected to the bus bar BL, and the inverter power supply 10 is connected in parallel with the load. Also, the inductor shown in the external system PW virtually represents the system-side impedance. Then, the inverter power supply 10 supplies AC power to the load via the bus bar BL in connection with the external system PW. The filter circuit 12 has two coils L1, L2 and a capacitor C, and is configured as a T-type low-pass filter.

[0012] Here, the general operation during normal operation of the inverter power supply 10 according to the embodiment will be described. When the circuit breaker 11 is turned on, three-phase AC power is supplied from the external system PW to the filter circuit 12 via the filter reactor FL.

[0013] The first current sensor 16 of the inverter power supply 10 detects the current (U-phase current, V-phase current, W-phase current) between the circuit breaker 11 and the filter circuit 12, and outputs a first current detection signal Is to the control unit 19. Also, the second voltage sensor 17 detects the voltage (U-phase voltage, V-phase voltage, W-phase voltage) between the circuit breaker 11 and the filter circuit 12, and outputs a second voltage detection signal Vs1 to the control unit 19.

[0014] Thereby, the control unit 19 calculates the power using the values obtained by performing coordinate conversion from the fixed coordinates (abc coordinate system) to the rotating coordinates (dq coordinate system) for the current based on the first current detection signal Is and the voltage based on the second voltage detection signal Vs2.

[0015] Subsequently, the control unit 19 performs droop-type GFM control based on the calculated power value and the voltage value on the rotating coordinate axis, and calculates the phase θ of the output voltage and the d-axis voltage command value Vdref of the output voltage.

[0016] Then, based on the calculated phase θ and d-axis voltage command value Vdref, the voltage command value on the fixed coordinate axis is calculated, PWM modulation is performed, and a PWM control signal Spmw is output to the converter circuit 14.

[0017] As a result, the converter circuit 14 performs DC / three-phase AC conversion on the DC power input from the DC power supply 13 based on the PWM control signal Spmw, converts it into AC power, and supplies it to the external system PW via the filter circuit and the circuit breaker 11.

[0018] As a result of these, it is possible to suppress the influence of voltage fluctuations or current fluctuations of the three-phase AC power supplied by the external system PW and supply stable AC power to the external system PW.

[0019] [1] First Embodiment FIG. 2 is a functional block diagram of the control unit according to the first embodiment. The control unit 19 of the inverter power supply 10 in the first embodiment includes, as shown in Figure 2, a first coordinate system conversion unit 31 that converts the current detection signal Is from abc to dq based on the phase θ and outputs it, a second coordinate system conversion unit 32 that converts the voltage detection signal Vs from the abc coordinate system to the dq coordinate system (abc-dq conversion) based on the phase θ and outputs it, a power calculation unit 33 that performs power calculations based on the abc-dq converted voltage detection signal Vs and the abc-dq converted current detection signal, a synchronization adjustment control unit 34 that calculates and outputs a voltage correction signal Vcorr and a frequency correction signal Fcorr based on the first voltage detection signal Vgrid output by the first voltage sensor 15 and the second voltage detection signal Vs output by the second voltage sensor 17, and the power value calculated by the power calculation unit 33 and the bc-dq converted voltage detection The system includes a GFM control unit 35 that performs droop-type GFM control based on the value of the output signal Vs and calculates the phase θ of the output voltage and the d-axis voltage command value Vdref of the output voltage; a third coordinate system conversion unit 36 ​​that converts the d-axis voltage command value Vdref and the q-axis voltage command value Vqref from the dq coordinate system to the abc coordinate system (dq-abc conversion) based on the phase θ and outputs it as a reference voltage signal Vref; a PWM control unit 37 that generates a PWM control signal Spwm based on the reference voltage signal Vref and performs PWM control of the converter circuit 14 configured as an inverter circuit; and an automatic closing unit 38 that determines that the synchronization condition is met and closes the circuit breaker 11 when the difference in amplitude, frequency, and phase of both voltages becomes less than or equal to a threshold based on the first voltage detection signal Vgrid and the second voltage detection signal Vs.

[0020] In the above configuration, the GFM control unit 35, in this first embodiment, performs droop-type GFM control as voltage-controlled converter control, proportionally decreasing the frequency of the output voltage when the output of the inverter power supply itself increases, and proportionally increasing the frequency of the output voltage when the output of the inverter power supply itself decreases.

[0021] Next, the operation of the first embodiment will be described. Figure 3 is a processing flowchart of the control unit of the embodiment. In the initial state, the circuit breaker 11 is in the open (off) state, and the external system PW is in the operational state. When the operator activates the inverter power supply 10, the control unit 19 outputs a predetermined PWM control signal Spwm corresponding to the activation state, activates (deblocks) the converter circuit 14, puts it into operation (step S11), and supplies DC power from the DC power supply 13.

[0022] As a result, capacitor C in the filter circuit 12 is charged, and then three-phase AC power is supplied, resulting in a voltage being applied to one end of the circuit breaker 11 on the filter circuit 12 side. At this time, the second voltage sensor 17 detects the voltage between the circuit breaker 11 and the filter circuit 12 (U-phase voltage, V-phase voltage, W-phase voltage) and outputs a second voltage detection signal Vs to the control unit 19 (step S12).

[0023] Meanwhile, the first current sensor 16 detects the current (U-phase current, V-phase current, W-phase current) between the circuit breaker 11 and the filter circuit 12, and outputs the first current detection signal Is to the second coordinate system transformation unit 32, the synchronization adjustment control unit 34, and the automatic closing unit 38 of the control unit 19.

[0024] As a result, the control unit 19 calculates the power using the values ​​obtained by transforming the current based on the first current detection signal Is1 and the voltage based on the second voltage detection signal Vs from fixed coordinates (abc coordinate system) to rotating coordinates (dq coordinate system). However, at this point, the circuit breaker 11 is in the open state, so the power is 0.

[0025] In parallel with these operations, if the external power grid PW is operational, three-phase AC power is supplied from the external power grid PW, and a voltage is applied to one end of the busbar BL side of the circuit breaker 11.

[0026] At this time, the first voltage sensor 15 detects the voltage between the circuit breaker 11 and the busbar BL (U-phase voltage, V-phase voltage, W-phase voltage) and outputs the first voltage detection signal Vgrid to the synchronization adjustment control unit 34 and the automatic closing unit 38 of the control unit 19 (step S12).

[0027] Based on these results, the synchronization adjustment control unit 34 calculates a voltage correction signal Vcorr and a frequency correction signal Fcorr based on the first voltage detection signal Vgrid and the second voltage detection signal Vs, and outputs them to the GFM control unit 35.

[0028] Here, we will explain how to calculate the voltage correction signal Vcorr and the frequency correction signal Fcorr. Figure 4 is an explanatory diagram of an example of a transfer function for calculating the voltage correction signal Vcorr. More specifically, the voltage correction signal Vcorr is calculated based on the system voltage RMS value Vgrid [PU: notation using the PU method] and the inverter power supply voltage RMS value [PU], according to the transfer function shown in Figure 4. In this case, when the circuit breaker 11 is closed, the voltage correction signal Vcorr = 0 [PU].

[0029] Figure 5 is an explanatory diagram of an example of a transfer function for calculating the frequency correction signal Fcorr. More specifically, the frequency correction signal Fcorr is calculated according to the transfer function shown in Figure 5, based on the system frequency Fgrid[PU], inverter power supply frequency, and frequency bias Fbias. In this case, if the frequencies on the grid side and the inverter power supply side were to perfectly match, the phase difference would not change and the synchronization condition would never be met. Therefore, a frequency bias Fbias is added to intentionally shift the frequencies. In this case as well, when the circuit breaker 11 is closed, the frequency correction signal Fcorr = 0 [PU].

[0030] As a result, the GFM control unit 35 performs droop-type GFM control based on the calculated power value, the value of the second voltage Vs on the rotating coordinate axis, the voltage correction signal Vcorr, and the frequency correction signal Fcorr. It calculates the phase θ of the output voltage and the d-axis voltage command value Vdref of the output voltage, outputs the phase θ to the first coordinate system transformation unit 31, the second coordinate system transformation unit 32, and the third coordinate system transformation unit 36, and outputs the d-axis voltage command value Vdref to the third coordinate system transformation unit 36.

[0031] Here, we will explain how to calculate the phase θ and the d-axis voltage command value Vdref in the first embodiment. Figure 6 is an explanatory diagram of an example of a transfer function for calculating the phase θ in the first embodiment. More specifically, the phase θ is calculated according to the transfer function shown in Figure 6, based on the active power command value Pref, the inverter power supply active power output Pout, the frequency correction signal Fcorr, and the reference angular velocity ω0.

[0032] Figure 7 is an explanatory diagram of an example of a transfer function for calculating the d-axis voltage command value Vdref in the first embodiment. More specifically, the d-axis voltage command value Vdref is calculated according to the transfer function shown in Figure 7, based on the reactive power command value Qref, the inverter power supply reactive power output Qout, the voltage command value Vset, and the inverter power supply d-axis output voltage Vsd.

[0033] The first coordinate system transformation unit 31 then performs an abc-dq transformation on the current detection signal Is based on the phase θ and outputs it. The second coordinate system transformation unit 32 then performs an abc-dq transformation on the voltage detection signal Vs based on the phase θ and outputs it. Furthermore, the third coordinate system transformation unit 36 ​​performs a dq-abc transformation on the d-axis voltage command value Vdref and the q-axis voltage command value Vqref based on the phase θ and outputs them to the PWM control unit 37 as a reference voltage signal Vref.

[0034] The PWM control unit 37 generates a PWM control signal Spwm based on the reference voltage signal Vref, outputs it to the converter circuit 14, and performs PWM control of the converter circuit 14, which is configured as an inverter circuit. In this case, the droop-type GFM control performed by the GFM control unit 35 of the control unit 19 calculates the deviation Δω of the angular frequency of the output voltage in proportion to the difference between the output active power of the inverter power supply and the active power command value during phase control. The phase θ of the output voltage is calculated and output by integrating the value obtained by adding the reference angular velocity ω0 to the deviation Δω. Furthermore, in voltage control, the GFM control unit 35 calculates a correction amount for the command value of the d-axis component of the output voltage in proportion to the difference between the output reactive power of the inverter power supply 10 and the reactive power command value, and corrects the output voltage amplitude.

[0035] Along with the above operation, the automatic closing unit 38 calculates the voltage amplitude, voltage frequency, and voltage phase of the voltage across the circuit breaker 11 based on the input first voltage signal Vgrid and second voltage signal Vs (step S13). Next, the automatic closing unit 38 determines whether the difference across the circuit breaker 11 for voltage amplitude, voltage frequency, and voltage phase has fallen below a threshold (step S14).

[0036] In the determination in step S14, if the difference across the circuit breaker 11 in any of the voltage amplitude, voltage frequency, or voltage phase exceeds the threshold (step S14; No), the synchronization condition is not met, and the process proceeds to step S12.

[0037] In the determination in step S14, if the difference across the circuit breaker 11 in voltage amplitude, voltage frequency, and voltage phase is less than or equal to the threshold (step S14; Yes), the synchronization condition is determined to be met, and the circuit breaker 11 is closed to the ON state (step S15).

[0038] As described above, according to this first embodiment, while the inverter power supply is performing GFM control to establish a voltage while changing the frequency of the output voltage according to its own output power, the circuit breaker 11 is closed when the synchronization condition is met in which the difference across the circuit breaker 11 in voltage amplitude, voltage frequency, and voltage phase is below a threshold. This eliminates the need to switch the control of the inverter power supply to grid connection control to follow the voltage and frequency of the external grid PW after the circuit breaker 11 is closed.

[0039] Furthermore, even if the frequency or voltage of the external grid fluctuates after grid connection, the inverter power supply can continue to operate stably. Furthermore, it becomes possible to stably start the inverter power supply regardless of the conditions of the connected grid (such as short-circuit capacity and inertia).

[0040] [2] Second embodiment Next, a second embodiment will be described. The inverter power supply of the second embodiment has the same configuration as the inverter power supply of the first embodiment, so it will be explained again with reference to Figure 2.

[0041] The difference between the inverter power supply 10A of the second embodiment and the inverter power supply 10 of the first embodiment is that it uses virtual synchronous generator control (VSG control) to control the GFM control unit 35A. Here, virtual synchronous generator control (VSG control) is a voltage-controlled converter control that simulates the mechanical frequency change characteristics of a synchronous generator.

[0042] Next, the calculation of the phase θ and the d-axis voltage command value Vdref in the second embodiment will be explained. Figure 8 is an explanatory diagram of an example of a transfer function for calculating the phase θ in the second embodiment.

[0043] More specifically, the phase θ is calculated according to the transfer function shown in Figure 8, based on the active power command value Pref, the inverter power supply active power output Pout, the frequency correction signal Fcorr, and the reference angular velocity ω0.

[0044] Here, the difference between the active power command value Pref of the inverter power supply 10 and the active power output Pout of the inverter power supply is input to a transfer function that simulates the motion equation of a synchronous generator of 1 / (Ms+d), and the frequency command value is calculated. In the example in Figure 8, a correction term Kp_VSG is provided in parallel for stabilization. However, for simplicity, it is also possible to configure the system without the correction term Kp_VSG.

[0045] Figure 9 is an explanatory diagram of an example of a transfer function for calculating the d-axis voltage command value Vdref in the second embodiment. More specifically, the d-axis voltage command value Vdref is calculated according to the transfer function shown in Figure 9, based on the reactive power command value Qref, the inverter power supply reactive power output Qout, the voltage command value Vset, and the inverter power supply d-axis output voltage Vsd.

[0046] According to this second embodiment, unlike the first embodiment, if fluctuations in voltage, frequency, etc. occur in the external power grid PW after grid connection, the frequency of the inverter power supply 10 changes in a manner that simulates the characteristics of a synchronous machine, which is a rotating machine type generator.

[0047] As a result, according to this second embodiment, similar to the first embodiment, the voltage difference across the circuit breaker 11 is below a threshold in terms of voltage amplitude, voltage frequency, and voltage phase, and the automatic closing unit 38 does not turn on the circuit breaker 11 until the three-phase AC power from the external power system PW and the three-phase AC power output by the inverter power supply 10 are synchronized.

[0048] Furthermore, according to this second embodiment, even under grid conditions where inverter power supplies similar to the inverter power supply 10 of the present application account for a large proportion of the power supply, grid operators can apply grid stabilization control and frequency control based on the same characteristics as the control of existing synchronous machine power supplies.

[0049] [3] Third embodiment Figure 10 is a block diagram illustrating the schematic configuration of the power supply system according to the third embodiment. In Figure 10, parts similar to those in the first embodiment of Figure 2 are denoted by the same reference numerals. The difference between this third embodiment and the first embodiment is that, as shown in Figure 10, the frequency adjustment of the synchronization control is performed using the acceleration / deceleration signal Ssync generated by the automatic synchronization switching device externally attached to the control unit 19.

[0050] Here, the acceleration / deceleration signal is a signal used to align the frequencies of the voltage corresponding to the first voltage detection signal Vgrid and the voltage corresponding to the second voltage detection signal Vs, which are the voltages across the circuit breaker 11, and is configured as a pulse signal, for example.

[0051] The control unit 19A of the inverter power supply 10A in the third embodiment, as shown in Figure 10, includes a first coordinate system conversion unit 31 that converts the current detection signal Is from abc to dq based on the phase θ and outputs it, a second coordinate system conversion unit 32 that converts the voltage detection signal Vs from the abc coordinate system to the dq coordinate system (abc-dq conversion) based on the phase θ and outputs it, a power calculation unit 33 that performs power calculations based on the abc-dq converted voltage detection signal Vs and the abc-dq converted current detection signal, and calculates a voltage correction signal Vcorr and a frequency correction signal Fcorr based on the first voltage detection signal Vgrid output by the first voltage sensor 15 and the second voltage detection signal Vs output by the second voltage sensor 17. The system includes a synchronization adjustment control unit 34 that outputs a signal, a GFM control unit 35 that performs droop-type GFM control based on the power value calculated by the power calculation unit 33 and the value of the voltage detection signal Vs converted from bc-dq, and calculates the phase θ of the output voltage and the d-axis voltage command value Vdref of the output voltage, a third coordinate system conversion unit 36 ​​that converts the d-axis voltage command value Vdref and the q-axis voltage command value Vqref from the dq coordinate system to the abc coordinate system (dq-abc conversion) based on the phase θ and outputs it as a reference voltage signal Vref, and a PWM control unit 37 that generates a PWM control signal Spwm based on the reference voltage signal Vref and performs PWM control of the converter circuit 14 configured as an inverter circuit.

[0052] Furthermore, the inverter power supply 10A of the third embodiment is equipped with an automatic synchronization switching device 40 that determines that the synchronization condition has been met and switches on the circuit breaker 11 when the difference between the amplitude, frequency, and phase of the first voltage detection signal Vgrid and the second voltage detection signal Vs falls below a threshold.

[0053] Figure 11 is an explanatory diagram of an example of a transfer function for calculating the frequency correction signal Fcorr in the third embodiment. More specifically, the synchronization control unit 34 calculates a frequency correction signal Fcorr based on the acceleration / deceleration signal Ssync, according to the transfer function shown in Figure 11, which includes pulse-to-numerical conversion and integration processing, and outputs it to the GFM control unit 35.

[0054] The GFM control unit 35 then performs GFM control based on the input frequency correction signal Fcorr, calculates the phase θ of the output voltage, and outputs the phase θ to the first coordinate system transformation unit 31, the second coordinate system transformation unit 32, and the third coordinate system transformation unit 36. In this case as well, when the circuit breaker 11 is closed, the frequency correction signal Fcorr is set to 0.

[0055] As a result, by using the acceleration / deceleration signal Ssync, which can be output by an external automatic synchronous switching device, for synchronous adjustment control, it becomes possible to configure the system with a simple mechanism using a synchronous switching device.

[0056] As described above, according to this third embodiment, similar to the first embodiment, the inverter power supply is performing GFM control to establish a voltage while changing the frequency of the output voltage according to its own output power, and the circuit breaker 11 is closed when the synchronization condition is met in which the difference across the circuit breaker 11 in voltage amplitude, voltage frequency, and voltage phase is below a threshold. This eliminates the need to switch the control of the inverter power supply to grid connection control to follow the voltage and frequency of the external grid PW after the circuit breaker 11 is closed.

[0057] Furthermore, even if the frequency or voltage of the external grid fluctuates after grid connection, the inverter power supply can continue to operate stably. Furthermore, it becomes possible to stably start the inverter power supply regardless of the conditions of the connected grid (such as short-circuit capacity and inertia).

[0058] In the above description, an external automatic synchronous switching device 40 was used. However, by giving the automatic switching unit 38 of the first and second embodiments the same functions as the automatic synchronous switching device 40, it is also possible to configure the synchronous control unit 34 of the first and second embodiments to calculate a frequency correction signal Fcorr based on the acceleration / deceleration signal Ssync, according to the transfer function shown in Figure 11, which includes pulse-to-numerical conversion and integration processing, and output it to the GFM control unit 35.

[0059] As a result, in both the first and second embodiments, it is possible to configure the inverter power supply 10 so that its output voltage matches the frequency of the external power system voltage (system voltage).

[0060] The control unit of the power converter in this embodiment has a hardware configuration that utilizes a standard computer.

[0061] The program executed in the control unit of the power converter of this embodiment is provided as an installable or executable file recorded on a computer-readable recording medium such as a USB memory stick, an SSD (Solid State Drive), or a DVD (Digital Versatile Disk).

[0062] Furthermore, the program executed in the control unit of the power converter of this embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Alternatively, the program executed in the control unit or EMS of the power converter of this embodiment may be provided or distributed via a network such as the Internet.

[0063] Furthermore, the program for the control unit or EMS of the power converter of this embodiment may be pre-installed and provided in ROM or the like.

[0064] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

Claims

1. A converter circuit configured as an inverter circuit that converts DC power to AC power, A circuit breaker having an external system connected to one end and the converter circuit connected to the other end via a filter circuit, A closing unit that determines whether the synchronization condition is met for the voltage at one end and the voltage at the other end, closes the circuit breaker if the synchronization condition is met, and outputs an acceleration / deceleration signal to match the frequencies of the voltage at one end and the voltage at the other end, The system includes a control unit that, at startup and before the circuit breaker is closed, activates the converter circuit and uses the acceleration / deceleration signal output by the closing unit to control the frequency of the voltage at one end and the voltage at the other end to match, The control unit, A synchronization control unit calculates and outputs a frequency correction signal based on the acceleration / deceleration signal, A GFM control unit performs GFM control based on a frequency correction signal input from the aforementioned synchronous control unit, calculates the phase of the output voltage, and outputs it. A coordinate system transformation unit that converts the d-axis voltage command value and the q-axis voltage command value based on the phase of the output voltage and outputs them as a reference voltage signal, A PWM control unit generates a PWM control signal based on the aforementioned reference voltage signal and performs PWM control of the converter circuit, A power conversion device equipped with this device.

2. The aforementioned converter circuit is controlled by voltage control. Droop control is used as the control method for the aforementioned voltage-controlled converter. The power conversion device according to claim 1.

3. The aforementioned converter circuit is controlled by voltage control. VSG control is used as the voltage-controlled converter control. The power conversion device according to claim 1.

4. A control method for a power converter comprising a converter circuit configured as an inverter circuit that converts DC power to AC power, and a circuit breaker to which an external system can be connected at one end and to which the converter circuit is connected at the other end via a filter circuit, wherein an acceleration / deceleration signal is input from an automatic synchronous switching device, The steps include: during startup, before the circuit breaker is closed, the converter circuit is put into operation, and the acceleration / deceleration signal is used to control the frequency of the voltage at one end and the voltage at the other end to match; The steps include detecting the voltage at one end and the voltage at the other end, The steps include determining whether the synchronization condition has been met for the voltage at one end and the voltage at the other end, The procedure includes, if the synchronization condition is met in the determination step, closing the circuit breaker and outputting the acceleration / deceleration signal to match the frequencies of the voltage at one end and the voltage at the other end, The step of performing control to match the frequencies of the voltage at one end and the voltage at the other end is: The steps include: calculating and outputting a frequency correction signal based on the acceleration / deceleration signal; The steps include: performing GFM control based on the input frequency correction signal, calculating and outputting the phase of the output voltage; The steps include: converting the d-axis voltage command value and the q-axis voltage command value based on the phase of the output voltage and outputting them as a reference voltage signal; The steps include generating a PWM control signal based on the aforementioned reference voltage signal and performing PWM control of the converter circuit, A method for controlling a power conversion device.

5. The aforementioned determination step involves determining that the synchronization condition is met when the difference between the amplitude, frequency, and phase of the voltage at one end and the voltage at the other end falls below a threshold. A control method for a power converter according to claim 4.

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