Power conversion device

Abstract

The purpose of the present invention is to provide a power conversion device that suppresses voltage fluctuation of an AC power distribution network while securing inertia of the AC power distribution network and suppressing variation in frequency. This power conversion device is provided with a main circuit for performing power conversion and a control unit for controlling the main circuit, and is provided with a function for imparting inertia to an AC power distribution network to be connected. The control unit receives, from a control device that controls the AC power distribution network, an excess / deficiency amount of inertia of the AC power distribution network or a command value corresponding to the excess / deficiency amount, and the control unit adjusts the response speed of the main circuit on the basis of the excess / deficiency amount of inertia of the AC power distribution network or the command value corresponding to the excess / deficiency amount.

Description

Power Conversion Device

[0001] The present invention relates to a power conversion device that contributes to stabilizing the frequency and voltage of an AC power grid.

[0002] In AC power distribution networks such as electric power systems, when a power source trips or the like, changes in the power system frequency are suppressed by inertia supplied by synchronous generators such as thermal power plants. In the future, if renewable energy generation such as solar power generation increases and becomes the main power source, the number of synchronous generators will decrease, and the inertia provided by the synchronous generators will decrease, causing the frequency of the AC power distribution network to become unstable. In order to maintain the stability of the frequency of the AC power distribution network, a grid forming inverter (GFI), which is a power conversion device with a function to supply inertia, is being considered.

[0003] Patent Literature 1 discloses a power supply device that controls operation by changing parameters such as the inertia constant of a power conversion device that has a function of supplying inertia to quickly stabilize the system frequency when a disturbance such as a sudden load change occurs. The document shows an example in which parameters are changed depending on whether the device is on-grid or off-grid. Since inertia is large when on-grid and small when off-grid, the document can be said to show a power conversion device with a function of supplying inertia that changes parameters depending on the magnitude of inertia.

[0004] Patent Document 2 discloses a distributed power system that adjusts the output change rate of a distributed power source to a predetermined value by controlling a power converter according to the inertia of the power grid so that the frequency of the AC power grid falls within an acceptable range when renewable energy power generation suddenly changes. In this system, the magnitude of the inertia of the AC power grid is determined depending on whether it is connected to the power grid or in islanding operation. Furthermore, there is no description of a function for supplying inertia to the power converter.

[0005] One method for quantitatively grasping the inertia of an AC power distribution network is to use a phasor measurement unit (PMU) to acquire data such as voltage, current, and phase time-synchronized with a GPS (Global Positioning System) at multiple points in the network and use that data to estimate the inertia of the network. Another method is to estimate the inertia of an AC power distribution network by integrating the individual inertias shared by devices such as synchronous generators and synchronous motors connected to the AC power distribution network.

[0006] JP 2024-016572 A JP 2024-017513 A

[0007] Quantitative understanding of inertia is important to ensure frequency stability in AC power distribution networks. In the future, when renewable energy generation becomes the primary power source, it is predicted that the inertia of power systems will be quantitatively understood every hour of every day. Furthermore, as GFIs powered by renewable energy generation become more widespread, it is predicted that the inertia of AC power distribution networks will fluctuate more greatly depending on the time of day. When the inertia of AC power distribution networks fluctuates more, there is a greater risk of the inertia falling below the required level, resulting in greater frequency fluctuations. At the same time, it is thought that there will be times when the inertia is unnecessarily large.

[0008] While GFIs mitigate frequency changes in AC power grids, they suffer from the problem of slow response speeds in power output and voltage control due to their function of mitigate frequency changes. Generally, the greater the inertia provided by a power conversion device, the slower the response speed. A slow response speed means that the GFI is slow to restore voltage to the AC power grid in the event of an accident. Increasing the response speed of the GFI speeds up the restoration of voltage in the AC power grid, but the inertia provided to the grid by the GFI decreases, resulting in greater fluctuations in the grid frequency.

[0009] An object of the present invention is to provide a power conversion device that suppresses voltage fluctuations in an AC power distribution network while ensuring the inertia of the AC power distribution network and suppressing frequency fluctuations.

[0010] The present application includes a number of means for solving the above problems. Representative means are as follows:

[0011] 1. A power conversion device comprising: a main circuit for converting DC power and AC power; and a control unit for controlling the main circuit; and having a function of imparting inertia to a connected AC power distribution network, wherein the control unit receives a command value corresponding to an excess or deficiency of the inertia of the AC power distribution network from a control device that controls the AC power distribution network, and the control unit adjusts the response speed of the main circuit based on the command value corresponding to the excess or deficiency of the inertia of the AC power distribution network.

[0012] According to the present invention, it is possible to provide a power conversion device that suppresses voltage fluctuations in an AC power distribution network while ensuring the inertia of the AC power distribution network and suppressing frequency fluctuations.

[0013] FIG. 1 is a block diagram showing the configuration of a power conversion device connected to an AC wiring network and an inertia control device in an embodiment of the present invention. FIG. 2 is a flowchart showing the processing of the inertia control device in an embodiment of the present invention. FIG. 3 is a graph showing an example of changes in estimated inertia, required inertia, and adjusted inertia of an AC distribution network over three days in an embodiment of the present invention. FIG. 4 is a diagram showing the recovery speed of voltage at each point in an AC distribution network in an embodiment of the present invention. FIG. 5 is a diagram showing the control block of a control unit of a power conversion device in an embodiment of the present invention. FIG. 6 is a diagram showing the control block of an inertia conversion unit of a control unit of a power conversion device in an embodiment of the present invention.

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, with reference to the drawings, a detailed description will be given of an embodiment of a power conversion device according to the present invention.

[0015] FIG. 1 is a block diagram showing the configuration of a power conversion device connected to an AC power distribution network and an inertia control device for controlling the inertia of the power conversion device according to an embodiment of the present invention.

[0016] A power conversion device (GFI) 101 is connected to an AC power distribution network 111. The power conversion device 101 includes a main circuit 102 that converts DC power to AC power and a control unit 103 that controls the main circuit. A solar power generator (PV) 104, a storage battery (BAT) 105, or a renewable energy power source such as a wind power generator (not shown) is connected to the power conversion device 101. One or more power conversion devices (GFI) 101 are connected to the AC power distribution network 111. The power conversion device 101 is a grid-forming inverter that can supply inertia to the AC power distribution network 111. The AC power distribution network 111 is a power distribution network within a power system or a microgrid. The power distribution network within a microgrid also includes a power distribution network within a business or factory.

[0017] An inertia control device 106 that controls an AC power distribution network 111 is connected to the control unit 103 of the power conversion device 101 via a control signal line 110. The control signal line 110 may be either wired or wireless. The inertia control device 106 includes an inertia estimation unit 107, an utilized inertia surplus / deficiency determination unit 108, and an utilized inertia surplus / deficiency transmission unit 109. The inertia control device 106 is realized by a computer equipped with a CPU (Central Processing Unit), a main memory device, an external memory device, and an input / output unit. In this embodiment, an example is described in which the inertia control device 106 is realized by a standalone computer, but it may also be realized as a server on the cloud. The inertia control device 106 may be incorporated into a power utility's grid command device or a microgrid's EMS (Energy Management System). Furthermore, when the AC power distribution network 111 is small-scale, or when only one power conversion device is connected to the AC power distribution network 111, the inertia control device 106 may be incorporated into the power conversion device 101. In this case, the control signal line 110 is not required, and the system configuration can be simplified.

[0018] 2 shows a flow of processing executed by the inertia estimation unit 107, the utilized inertia surplus / deficiency determination unit 108, and the utilized inertia surplus / deficiency transmission unit 109 of the inertia control device 106. The inertia estimation unit 107 executes step S1, the utilized inertia surplus / deficiency determination unit 108 executes steps S1 to S6, and the utilized inertia surplus / deficiency transmission unit 109 executes step S7.

[0019] In step S1, the inertia of the AC power distribution network 111 is estimated. One of the following two methods is used to estimate the inertia. One method is to use a phasor measurement unit (PMU) to acquire data on voltage, current, phase, etc. time-synchronized by a GPS (Global Positioning System) at multiple locations on the AC power distribution network 111, and estimate the inertia using that data. The other method is to estimate the inertia of the AC power distribution network 111 by understanding the operating status of synchronous generators, synchronous motors, etc. connected to the AC power distribution network 111, integrating the inertia supplied by each of them. The former method is more suitable for large-scale power systems in which it is easy to install PMUs at multiple locations and there are many devices that supply inertia. The latter method is more suitable for small-scale microgrid power distribution networks in which it is difficult to install PMUs at multiple locations and there are few devices that supply inertia. In the former method, the operating status is collected in real time every 30 minutes or every hour to estimate the inertia, while in the latter method, the operating plans for synchronous generators, synchronous motors, etc. are obtained in advance to estimate the inertia on a daily basis, and information on changes to the plans is received as needed to correct the estimated inertia.

[0020] Figure 3 shows an example of estimated inertia (hereafter referred to as estimated inertia) in the case where GFI, photovoltaic power generation (PV), and storage batteries (BAT) are widely used. The solid line in the figure is the estimated inertia, showing the change over three days. This inertia is inertial energy, and its unit is pu·s. The dashed line in the figure also represents the inertia (hereafter referred to as required inertia) required to keep the grid frequency within a predetermined tolerance range in the event of a predicted accident such as a power source failure. The required inertia includes a margin for error in the estimated inertia.

[0021] Day 1 in Figure 3 is a sunny weekday. During the day, PV power generation increases, and the inertia supplied from the GFI connected to the PV also increases, causing the estimated inertia to significantly exceed the required inertia. Even after sunset, because it is a weekday and power demand is high, many synchronous generators, such as thermal and hydroelectric power plants, are operating, so the estimated inertia continues to exceed the required inertia. Day 2 is a cloudy weekday. During the day, PV power generation is low, and the estimated inertia supplied from the GFI connected to the PV does not increase. Because it is a weekday, power demand increases, and the inertia from the synchronous generators operating to meet that demand increases, causing the estimated inertia to exceed the required inertia. Day 3 is a sunny holiday. During the day, PV power generation increases, and the inertia supplied from the GFI connected to the PV also increases, causing the estimated inertia to exceed the required inertia. However, because power demand is low on the holiday, the inertia supplied by synchronous generators and synchronous motors is low, and after sunset, the estimated inertia falls below the required inertia. There is a method of operating a synchronous generator to supply inertia when the estimated inertia falls below the required inertia, thereby ensuring the required inertia, but operating a synchronous generator requires a large cost.

[0022] In steps S2 and S3, the inertia estimation is judged to be excessive or insufficient. In step S2, the inertia estimation is compared with the required estimation. If the inertia estimation is smaller, i.e., if the inertia is insufficient, proceed to step S5. If not, proceed to step S2. This corresponds to the case where inertia is insufficient after sunset on the third day in Figure 3. In step S3, the inertia estimation is compared with the required estimation + α. If the inertia estimation is larger, i.e., if the inertia is excessive, proceed to step 4. If not excessive, the inertia excess or deficiency is not utilized and the processing of the flow in Figure 2 is terminated. α is a preset inertia width that does not utilize inertia excess or deficiency. This sets an inertia range that does not utilize inertia excess or deficiency, preventing frequent control changes of the power conversion device 101 due to inertia utilization. If frequent control changes are not a problem, there is no need to set α.

[0023] In step S4, the voltage recovery rate of the AC distribution network 111 is calculated to confirm the voltage stability of the AC distribution network 111. Specifically, a simulation of the AC distribution network 111 is performed using the substation (SS) 112, the GFI response rate, and the impedance of the distribution line, and the like, to calculate the voltage recovery rate in the event of an accident. Since the voltage recovery rate varies depending on the location of the AC distribution network 111, it is calculated at multiple locations if the AC distribution network 111 is not small. FIG. 4 shows an example of the results of calculating the voltage recovery rate. The numbers in the figure (1.24 pu / s, 1.42 pu / s, 0.92 pu / s, 0.86 pu / s) are the voltage recovery rates at those locations. The voltage recovery rate is measured in units of pu / s, which represent the amount of voltage recovery per unit time. The power recovery rate may be used instead of the voltage recovery rate. A required range of the voltage recovery rate is determined in advance. Here, the required range is 1.00 pu / s or more.

[0024] In step S5, a power conversion device that utilizes the inertia excess / deficiency is selected using the voltage recovery speed calculated in step S4. If the voltage recovery speed at all points meets the required range, the voltage stability of the AC power distribution network 111 is sufficient and the inertia excess / deficiency is not utilized. If there is a point where the voltage recovery speed does not meet the required range, the voltage stability of the AC power distribution network 111 is insufficient, and a power conversion device 101 connected near the point where the voltage recovery speed does not meet the required range is selected. Power conversion devices that are not operating, such as power conversion devices connected to PV at night, are excluded.

[0025] In step S6, the inertia surplus / deficiency to be allocated to each power electronics device selected in step S4 is determined. To determine the inertia surplus / deficiency to be allocated, the inertia control device 106 stores data on the maximum usable inertia for each power electronics device 101. Because inertia cannot be reduced beyond the inertia supplied by the power electronics device 101, the maximum usable excess inertia for the power electronics device 101 is equal to the inertia supplied by the power electronics device 101. Because inertia cannot be increased beyond the increment of power that the power electronics device 101 can output, the maximum usable inertia deficiency for the power electronics device 101 is a value determined by the increment of power that the power electronics device 101 can output. The inertia surplus / deficiency calculated in step S1 from the estimated inertia of the AC power distribution network and the required inertia is allocated to each power electronics device 101 selected in step S4 so that the inertia surplus / deficiency falls within the maximum usable inertia. If the inertia surplus or deficiency is smaller than the sum of the maximum usable inertia values ​​of the target, the power is preferentially allocated to the power conversion device 101 that has the greatest effect of increasing the voltage recovery speed due to inertia, or allocated equally to the power conversion devices.

[0026] In step S7, a signal indicating the inertia surplus or deficiency allocated to the power electronics device 101 determined in step S6 is transmitted to each power electronics device 101 via the control signal line 110.

[0027] Next, the control unit 103 of the power conversion device 101 will be described.

[0028] 5 shows a control block of the control unit 103 of the power conversion device 101. There are many types of control methods for the GFI, and the control block shown here employs a droop control type that uses an angular frequency droop.

[0029] The main circuit 102 includes a power conversion module 2 that converts DC power and AC power, an AC filter 4 located on the AC distribution network 111 side of the power conversion module 2, a current sensor located between the power conversion module 2 and the AC filter 4, and a voltage sensor located on the AC distribution network 111 side of the AC filter 4.

[0030] The control unit 103 receives AC voltage measurement values ​​and AC current measurement values ​​from the sensors of the main circuit 102, and sends PWM (Pulse Width Modulation) signals to the power conversion module 2 of the main circuit 102 to control the switching elements of the power conversion module 2. The control unit 103 also receives a signal indicating the allocated inertia surplus or deficiency from the inertia control device 106.

[0031] The control unit 103 includes a measurement unit 301, a power calculation unit 302, an active power command unit 303, an inertia conversion unit 304, an angular frequency command generation unit 305, a phase command generation unit 306, a reactive power command unit 307, a first voltage command generation unit 308, a current command generation unit 309, a current command constraint unit 310, a second voltage command generation unit 311, and a main circuit control unit 312.

[0032] The measurement unit 301 converts the AC voltage measurement value and AC current measurement value received from the sensor of the main circuit into V ｏｕｔ , I ｏｕｔ When outputting, measurement noise can be removed using a low-pass filter or the like.

[0033] The power calculation unit 302 calculates the V output from the measurement unit 301. ｏｕｔ , I ｏｕｔ The active power P output from ｏｕｔ and reactive power Q ｏｕｔ For example, calculate the three-phase voltage and current V ｏｕｔ , I ｏｕｔ can be calculated from the voltage and current values ​​in the α-β coordinate system obtained by three-phase to two-phase conversion.

[0034] The active power command unit 303 receives an active power command P ０ Based on the active power command P ０ The active power command P ０ ′ can be received via wired or wireless communication from a higher-level command device for the power conversion device (for example, an energy management system) that is external to the power conversion device 1.

[0035] The inertia conversion unit 304 converts the inertia surplus / deficiency ΔI given from the utilized inertia surplus / deficiency transmission unit 109 of the inertia control device 106. ｎｅｒ０The delay time constant of the filter is the manipulated variable ΔT ｄｏ FIG. 6 shows the control block of the inertia conversion unit 304. First, the inertia I ｎｅｒ , each rated frequency ω ０ , moment of inertia J ｏ The following equation shows the relationship between

[0036]

[0037] Using this, the inertia excess or shortage amount ΔI ｎｅｒ The moment of inertia operation amount ΔJ ｏ Next, the droop coefficient Kp of the active power-angular frequency change command, and the rated frequency ω ０ Using the moment of inertia operation amount ΔJ ｏ The delay time constant is the manipulated variable ΔT ｄｏ The angular frequency command generator 305 converts the active power command P ０ and the effective power P ｏｕｔ The angular frequency command ω is calculated by droop control from the deviation of ＊ FIG. 7 shows a control block of the angular frequency command generator 305. The angular frequency command generator 305 generates an active power command P ０ and the effective power P ｏｕｔ The deviation is multiplied by the droop coefficient Kp of the active power-angular frequency change command, and passed through a first-order lag-lead filter to obtain the angular frequency command ω ＊ The first-order lag-lead filter has a lead time constant T α０ and delay time constant T ｄｏ The delay time constant operation amount ΔT is used from the inertia conversion unit 304. ｄｏ When is given, the original delay time constant T ｄｏ Delay time constant operation amount ΔT ｄｏ The value obtained by subtracting is used as the delay time constant.

[0038] The phase command generator 306 generates the angular frequency command ω ＊ is integrated to obtain the phase command θ ＊ The reactive power command unit 307 generates an external reactive power command Q ０１ and V, which is the output of the measurement unit 301 ｏｕｔ Enter the reactive power command Q ０２ Generate and output reactive power command Q ０２is the rated voltage V ０ (for example, 200 V) and the output of the measuring unit 301, V ｏｕｔ Deviation V ０ -V ｏｕｔ The reactive power command unit 307 generates the reactive power by multiplying the proportional gain Kq (Kq>0) by the droop control. The reactive power command unit 307 receives the external reactive power command Q given from outside the power conversion device 101, instead of the output of this droop control. ０１ is used as the reactive power command Q ０２ The reactive power command Q ０２ is given from the outside of the power conversion device 101 as an active power command P ０ The reactive power command unit 307 determines the active power command P' from the rated power and the desired power factor of the power conversion device 101, thereby enabling behavior conforming to power factor control. ０ and the reactive power command Q from the rated power of the power conversion device 1 and the desired power factor. ０ may be determined.

[0039] The first voltage command generator 308 generates a reactive power command Q ０ and reactive power Q ｏｕｔ The first voltage command V １ Calculate the following.

[0040] The current command generator 309 generates a first voltage command V １ and AC voltage measurement value V ＯＵＴ and impedance Z, the AC terminal voltage of the power conversion module 2 is the first voltage command V １ When the AC current is calculated, the current command I ＊ The current command I ＊ is the d-axis component I in the dq transformation ｄ ＊ and the q-axis component I ｑ ＊ Calculate each.

[0041] The current command constraint unit 310 constrains the current command I generated by the current command generation unit 309. ＊ For example, the d-axis component I ｄ ＊ and the q-axis component I ｑ ＊For each, limiters are set so that the upper and lower threshold currents are the upper and lower limits.

[0042] The second voltage command generator 311 generates the current command I constrained by the current command constraining unit 310 for each of the d-axis component and the q-axis component. ＊ and the AC current measurement value I ｏｕｔ The deviation of the proportional gain K ｖｐ , integral gain K ｖｉ PI control is performed to obtain the second voltage command V ＊ Calculate the following.

[0043] The main circuit control unit 312 outputs a second voltage command V ＊ Phase command θ ＊ Then, an inverse dq transform is performed, and an inverse three-phase to two-phase transform is performed to generate voltage commands for each of the three phases. Based on this, gate waveforms for the switching elements of the power conversion module 2 are generated, and the power conversion module 2 of the main circuit 102 is driven.

[0044] As a result of the above, the control unit 103 of the power conversion device 101 calculates the inertia surplus / deficiency ΔI ｎｅｒｏ The delay time constant T of the filter related to the response speed is calculated by using ｄｏ and changes the control of the power conversion device 101. When the inertia of the AC power distribution network 111 is excessive, the inertia excess / deficiency amount ΔI ｎｅｒｏ When is positive, the delay time constant T ｄｏ As a result, the voltage recovery speed by the power conversion device 101 increases, and the stability of the voltage of the AC power distribution network 111 improves. ｎｅｒｏ When is negative, the delay time constant T ｄｏ As a result, the inertia provided by the power converter 101 increases, improving the frequency stability of the AC power grid 111.

[0045] The inertia after applying the present invention is shown by the dashed line in Figure 3. Compared to the estimated inertia, the excess inertia has been reduced and the insufficiency of inertia has been eliminated.

[0046] In the above embodiment, the utilized inertia surplus / deficiency transmission unit 109 of the inertia control device 106 transmits the inertia surplus / deficiency I ｎｅｒｏThe signal is sent through the control signal line 110, but the inertia surplus / deficiency ΔI ｎｅｒｏ Instead of this, the delay time constant T of the filter according to the inertial excess or deficiency is ｄｏ The control unit 103 of the power conversion device 101 receives the parameter according to the inertia surplus / deficiency and calculates the inertia surplus / deficiency ΔI ｎｅｒｏ Change the response speed in the same way as in

[0047] In the above embodiment, a droop control type using an angular frequency droop is adopted as the control method of the control unit 103, but other droop control types may be adopted, or a synchronous machine simulation control type such as a VSM (Virtual Synchronous Machine) or other control types may be adopted. If another method is adopted and a delay time constant is not used, the same effect as in the above embodiment can be obtained by controlling parameters related to both the response speed and inertia instead of the delay time constant.

[0048] Furthermore, one example of the invention disclosed in the above-mentioned specification of the present application can also be expressed as follows.

[0049] <No. 1> A power conversion device comprising a main circuit that performs power conversion and a control unit that controls the main circuit, and having a function of imparting inertia to an AC power distribution network connected thereto, wherein the control unit receives a command value corresponding to an excess or deficiency of the inertia of the AC power distribution network from an inertia control device that controls the AC power distribution network, and the control unit adjusts the response speed of the main circuit based on the command value corresponding to the excess or deficiency of the inertia of the AC power distribution network.

[0050] <Item 2> The power conversion device according to <Item 1>, characterized in that when the inertia of the AC power distribution network is excessive, the response speed of the main circuit is adjusted by increasing the response speed.

[0051] <Item 3> The power conversion device according to <Item 1>, characterized in that when the inertia of the AC power distribution network is insufficient, the response speed of the main circuit is adjusted by slowing down the response speed.

[0052] <Item 4> The power conversion device according to <Item 1>, wherein the excess or deficiency of inertia is a difference between the inertia of the AC power distribution network and the inertia required to keep the frequency of the AC power distribution network within a predetermined range.

[0053] <Item 5> The power conversion device according to <Item 4>, wherein the inertia of the AC power distribution network is estimated by integrating the inertia of a device that supplies inertia to the AC power distribution network.

[0054] <Item 6> The power conversion device according to <Item 1>, wherein the command value according to the excess or deficiency is a time constant of a filter.

[0055] <Item 7> The power conversion device according to <Item 1>, wherein the inertia control device has a function of allocating the excess or deficiency of the inertia to the plurality of power conversion devices.

[0056] <No. 8> The power conversion device according to <No. 7>, characterized in that the function of allocating the excess or deficiency of inertia to the plurality of power conversion devices allocates the excess or deficiency of inertia based on a recovery speed of the voltage of the AC power distribution network.

[0057] <Item 9> The power conversion device according to <Item 1>, wherein the AC power distribution network is a power system or a microgrid AC power distribution network.

[0058] <Item 10> The power conversion device according to <Item 1>, wherein the inertia control device is provided in a system command system or an EMS.

[0059] <Item 11> The power conversion device according to <Item 1>, wherein the inertia control device is provided in the power conversion device.

[0060] <Item 12> The power conversion device according to <Item 7>, wherein the inertia control device estimates the inertia of the AC power distribution network from data obtained from a phasor information measurement device.

[0061] 101: Power conversion device (GFI) 102: Main circuit 103: Control unit 104: Photovoltaic generator (PV) 105: Storage battery 106: Inertia control device 107: Inertia estimation unit 108: Utilized inertia surplus / deficiency determination unit 109: Utilized inertia surplus / deficiency transmission unit 110: Control signal line 111: AC power distribution network 112: Substation 301: Measurement unit 302: Power calculation unit 303: Active power command unit 304: Inertia conversion unit 305: Angular frequency command generation unit 306: Phase command generation unit 307: Reactive power command unit 308: First voltage command generation unit 309: Current command generation unit 310: Current command constraint unit 311: Second voltage command generation unit 312: Main circuit control unit

Claims

1. A power conversion device comprising a main circuit that performs power conversion and a control unit that controls the main circuit, and having a function of imparting inertia to an AC power distribution network connected thereto, wherein the control unit receives a command value corresponding to the excess or deficiency of the inertia of the AC power distribution network from an inertia control device that controls the AC power distribution network, and the control unit adjusts the response speed of the main circuit based on the command value corresponding to the excess or deficiency of the inertia of the AC power distribution network.

2. The power conversion device according to claim 1, wherein when the inertia of the AC power distribution network is excessive, the response speed of the main circuit is adjusted by increasing the response speed.

3. The power conversion device according to claim 1, wherein when the inertia of the AC power distribution network is insufficient, the response speed of the main circuit is adjusted by slowing down the response speed.

4. The power conversion device according to claim 1, wherein the excess or deficiency of inertia is the difference between the inertia of the AC power distribution network and the inertia required to keep the frequency of the AC power distribution network within a predetermined range.

5. The power conversion device according to claim 4, wherein the inertia of said AC power distribution network is estimated by integrating the inertia of devices that supply inertia to said AC power distribution network.

6. The power conversion device according to claim 1, wherein the command value according to the excess or deficiency is a time constant of a filter.

7. The power conversion device according to claim 1, wherein said inertia control device has a function of allocating the excess or deficiency of inertia to a plurality of said power conversion devices.

8. The power conversion device according to claim 7, characterized in that the function of allocating the excess or deficiency of inertia to the plurality of power conversion devices allocates the excess or deficiency of inertia based on the recovery speed of the voltage of the AC power distribution network.

9. The power conversion device according to claim 1, wherein the AC power distribution network is a power system or a microgrid AC power distribution network.

10. The power conversion device according to claim 1, wherein the inertia control device is provided in a power system command system or an EMS.

11. The power conversion device according to claim 1, wherein the inertia control device is provided in the power conversion device.

12. The power conversion device according to claim 7, wherein the inertia control device estimates the inertia of the AC power distribution network from data obtained from a phasor information measurement device.

Images