System stabilization device, system stabilization method, and system stabilization program

Abstract

To provide a system stabilization device, a stabilization method, and a program that appropriately control active power and reactive power of a PCS to improve transient stability and reduce economic loss.SOLUTION: A system stabilization device applied to a power system in which a voltage-controlled PCS and a current-controlled PCS are interconnected as a power conversion device to suppress and stabilize fluctuations of power when a system fault occurs, includes: transient stability calculation means 21A for calculating transient stability by executing a simulation using a measurement value of the power system when a fault point is assumed in the power system; and optimal power flow calculation means 21B for performing an optimal power flow calculation using an objective function with voltage phase angle information determined to be stable by the calculation means 21A being constraint conditions to generate a control correction amount. When an actual fault occurs, the power conversion device is controlled using a control signal based on the control correction amount.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a grid stabilization device, a grid stabilization method, and a grid stabilization program for improving transient stability during normal operation and in the event of a fault in a power grid connected to a PCS (Power Conditioning System), thereby achieving an appropriate power flow state. [Background technology]

[0002] In recent years, numerous distributed power sources, consisting of renewable energy generators such as solar power plants and power conversion devices such as PCSs, have been interconnected to power grids. As a result, the number of synchronous generators is relatively decreasing, and in particular, when grid faults such as ground faults occur, the synchronization force and inertia maintenance function provided by synchronous generators are insufficient, leading to a tendency for power grid stability to decline. To address this, technologies have been developed that equip power conversion devices such as PCSs with a virtual synchronous generator control function (an inertia maintenance function similar to that of a synchronous generator), and control the phase of their output voltage to improve power grid stability. Recently, voltage-controlled PCS (Grid Forming Inverter: GFM), which has the aforementioned inertia maintenance function and also operates as a voltage source like a synchronous generator, has been attracting attention, and it is expected that these GFMs will be newly connected to the power grid in addition to the conventional current-controlled PCS (Grid Following Inverter: GFL).

[0003] Now, in this type of power system, one method for analyzing the transient stability of the power system while considering the dynamic characteristics of the PCS in the event of a system fault is the Time Domain Simulation Method (TDS method), which has no limitations on model description and can faithfully reproduce the dynamic characteristics of actual generators, etc. The simulation method can fully consider the Fault Ride Through (FRT) function of the PCS and is considered an effective method for pre-calculating the power flow states of active power, reactive power, voltage, and phase to stabilize the power system against assumed accidents.

[0004] For example, Patent Document 1 describes a technique for calculating the power transmission capacity of synchronous generators by performing Optimal Power Flow (OPF) incorporating transient stability constraints for assumed accidents in the power system as a so-called preventive control method. Patent Document 2 describes a technique for obtaining the reactive power control amount of each distributed power source by optimal power flow calculation to suppress fluctuations in voltage and the like due to changes in power flow in a power system to which a plurality of distributed power sources are connected. Non-Patent Documents 1 and 2 disclose a method of repeatedly and continuously performing transient stability calculation and optimal power flow calculation in a power system to which a large number of generators are connected to obtain an optimal power flow state.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the optimal power flow calculation described in Patent Document 1, only the continuous dynamic characteristics of synchronous generators are considered, and the dynamic characteristics of power electronics devices such as PCS are not considered. Further, in preventive control, since system accidents with relatively low occurrence probabilities are also targeted, depending on the results of the optimal power flow calculation, the generated power and transmitted power may be restricted more than necessary, resulting in a large economic loss. Furthermore, the prior art described in Patent Document 2 calculates the reactive power control amount from the change in power flow based on the predicted values of load demand and the generated power of distributed power sources, and does not consider the transient stability when an actual system accident occurs. Also, in the technologies described in Non-Patent Documents 1 and 2, since the calculation load of transient stability is large, the overall calculation period including the optimal power flow calculation has to be lengthened, and there is a problem that the error between the assumed accident cross-section (power flow state) at the calculation timing of the optimal power flow calculation and the actual accident occurrence cross-section becomes large, resulting in an overshoot or undershoot in the required control amount.

[0008] Therefore, the problem to be solved by the present invention is to appropriately set the objective function, constraint conditions, calculation period, etc. of the optimal power flow calculation, calculate the active power and reactive power of the PCS that can prevent out-of-step based on the transient stability calculation and the optimal power flow calculation based on a detailed simulation, and when an actual system accident occurs, control the PCS according to the control command based on the above active power and reactive power, thereby providing a system stabilization device, a system stabilization method, and a system stabilization program that improve the transient stabilization of the power system while minimizing the suppression amount of active power.

Means for Solving the Problems

[0009] To solve the above problems, the grid stabilization device of the present invention, as described in claim 1, is a grid stabilization device for suppressing and stabilizing power fluctuations in a power system when a fault occurs in a power system in which voltage-controlled PCS and current-controlled PCS are connected as power conversion devices that convert the output of a power generation device to a predetermined AC power, A transient stability calculation means that calculates transient stability by performing a simulation using measured values ​​from the power system when a fault point is assumed within the power system, The system includes an optimal power flow calculation means that generates a control correction amount by performing an optimal power flow calculation using an objective function that includes the voltage phase angle information of the voltage-controlled PCS as a constraint condition when it is determined to be stable by the transient stability calculation means, When an actual accident occurs at the assumed accident point, the power converter is controlled using a control signal based on the control correction amount.

[0010] Furthermore, as described in claim 2, in claim 1, it is desirable that the transient stability calculation means search for an operating point as a stable operating point in which the voltage phase difference between the grid power supply and the voltage-controlled PCS decreases by increasing the reactive power output of the current-controlled PCS.

[0011] Furthermore, as described in claim 3, in claim 1 or 2, it is desirable that the optimal power flow calculation means generates at least a control correction amount for controlling the reactive power output by the current-controlled PCS.

[0012] Furthermore, as described in claim 4, it is desirable in claim 1 or 2 to set the calculation period by the transient stability calculation means to be longer than the calculation period by the optimal power flow calculation means.

[0013] Furthermore, as described in claim 5, in claim 1 or 2, it is desirable that the optimal power flow calculation means generates the control correction amount using an objective function that includes a penalty to the correction amount of the active power of the power converter.

[0014] Furthermore, as described in claim 6, in claim 1 or 2, it is desirable that the voltage phase angle information is the maximum voltage phase difference of the voltage-controlled PCS.

[0015] Furthermore, the grid stabilization method of the present invention, as described in claim 7, is a grid stabilization method for suppressing and stabilizing power fluctuations in a power system when a fault occurs in a power system in which voltage-controlled PCS and current-controlled PCS are connected as power conversion devices that convert the output of a power generation device to a predetermined AC power, When a fault point is assumed within the aforementioned power system, a simulation is performed using measured values ​​from the aforementioned power system to calculate the transient stability. When the transient stability is determined to be stable, an optimal power flow calculation is performed using an objective function that includes the voltage phase angle information of the voltage-controlled PCS as a constraint to generate a control correction amount. When an actual accident occurs at the assumed accident point, the power converter is controlled using a control signal based on the control correction amount.

[0016] Furthermore, the grid stabilization program of the present invention is a program executed by a computer system as described in claim 8, and includes a power converter that converts the output of a power generator into predetermined AC power. Voltage-controlled PCS and current-controlled PCS are used as examples. A grid stabilization program for suppressing and stabilizing power fluctuations in a power grid when an accident occurs in the interconnected power grid, The process involves performing a simulation using measured values ​​from the power system to calculate transient stability when a fault point is assumed within the power system, and The process involves performing an optimal power flow calculation using an objective function that includes the voltage phase angle information of the voltage-controlled PCS as a constraint when the transient stability is determined to be stable, and generating a control correction amount. The process involves controlling the power converter using a control signal based on the control correction amount when an actual accident occurs at the assumed accident point. [Effects of the Invention]

[0017] According to the present invention, the transient stability of the power system is improved by appropriately controlling reactive power while minimizing the amount of active power suppression output from the PCS during a grid fault, thereby reducing economic losses due to the loss of power generation opportunities. Furthermore, by shortening the calculation period of the optimal power flow calculation relative to the calculation period of the transient stability calculation, the error between the assumed fault cross-section and the actual fault cross-section can be reduced, thereby reducing the excess or deficiency of the required control amount. [Brief explanation of the drawing]

[0018] [Figure 1] This is a diagram showing the configuration of a power system to which a grid stabilization device according to an embodiment of the present invention is applied. [Figure 2] Figure 1 is a functional block diagram showing the main components of the system stabilization device. [Figure 3] This is a flowchart showing the operation of the stabilization calculation means in an embodiment of the present invention. [Figure 4] This is a PQ plan diagram conceptually illustrating the process of searching for an operational point according to an embodiment of the present invention. [Figure 5] This is a PQ plan diagram conceptually illustrating the process of searching for operational points using conventional technology. [Figure 6] This is a diagram illustrating the configuration of a power system using conventional technology. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described below with reference to the figures. Figure 1 shows an example of a power system configuration to which the grid stabilization device 500 of this embodiment is applied. As shown in the figure, the substation 100, which serves as the grid power source, is connected to busbars 301 and 302 via transmission lines 201 and 202.

[0020] A current-controlled PCS (GFL) 400L, which converts the DC output of the solar cell 401 into AC power, is connected to the busbar 301, and a current / voltage detector 402 is provided to detect its output current and output voltage. A load 600 is also connected to the busbar 301, and a current / voltage detector 601 is provided to detect the current and voltage supplied to this load 600. Furthermore, a voltage-controlled PCS (GFM) 400M, which converts the DC output of the solar cell 403 into AC power, is connected to the busbar 302, and a current / voltage detector 404 is provided to detect its output current and output voltage. In addition to solar cells 401 and 402, the power generation device utilizing natural energy may also be a system that converts the AC output of a wind turbine into DC power and inputs it to each PCS 400L and 400M.

[0021] The system stabilization device 500 according to this embodiment receives various measured values ​​such as current, voltage, and active power measurement value P0 detected by current / voltage detectors 402, 404, and 601, as well as the operation signals of protective relays (not shown) installed on the transmission lines 201, 202 and busbars 301, 302, from fault detection terminal devices 101 to 10 described later. n and control terminal devices 301-30 n It receives information from the following devices. Based on this input information, it performs transient stability calculations and optimal power flow calculations to determine the amount of reactive power and active power control corrections necessary to suppress power fluctuations in the power system during a grid fault, and sends control signals based on these control corrections to the above control terminal devices 301-30. n It has the function of transmitting to the GFL 400L and GFM 400M via this to control their operation.

[0022] In Figure 1, the values ​​appended to substation 100, busbar 301, GFL 400L, GFM 400M, and load 600 are, for example, the unit-based "P+Qj" (P: active power, Q: reactive power) and "∠δ,V" (δ: voltage phase angle, V: voltage amplitude) when transient stability and optimal power flow calculations are performed using a simulation that assumes F on transmission line 202 as the fault point, with substation 100 as the reference point. Here, the voltage phase angle δ (∠35.9 or ∠36.2) appended to GFM 400M corresponds to the internal phase difference angle of a synchronous generator. The specific meanings of "P+Qj" and "∠δ,V" in each part will be explained later. Needless to say, the types and number of PCS units connected to the power grid are not limited to the GFL 400L and GFM 400M shown in Figure 1; any number of various PCS units can be connected.

[0023] Next, Figure 2 is a functional block diagram showing the main parts of the system stabilization device 500. In Figure 2, accident detection terminal devices 101-10 n Based on the operation signals of protective relays installed on the transmission lines 201, 202 and busbars 301, 302, and various measured values ​​(detected values) transmitted from the aforementioned current and voltage detectors 402, 404, 601, etc., the system detects system faults such as ground faults and transmits the active power P and reactive power Q of the loads 600, GFL 400L, and GFM 400M at that time to the central processing unit 21 via a wireless or wired communication line 41, along with a fault detection flag.

[0024] Furthermore, this accident detection terminal device 101~10 nAs a preventative control measure based on transient stability analysis using a simulation method when the power system is healthy, as noted in Figure 1 above, for example, assuming that a fault point F occurs on the transmission line 202 with the following parameters: substation 100 parameters set to "(-4+0.9j)" and "∠0.0,1.02", busbar 301 parameters set to "(∠14.8,0.994)", load 600 parameters set to "2.0+0.0j", GFM 400M parameters set to "6.0+2.1j" and "(∠36.2,1.06)", and GFL 400L parameters set to "(0.0+0.0j)", the active power P and reactive power Q of load 600, GFL 400L, and GFM 400M at that time are transmitted to the central processing unit 21 via the communication line 41, along with a fault detection flag. Accident detection terminal devices 101-10 n The above-mentioned features possessed by [this device] may also be present in the GFL 400L and GFM 400M.

[0025] The stabilization calculation means 20 in Figure 2 consists of a computer system such as a personal computer or workstation, and includes a central processing unit 21 such as a CPU that executes programs for transient stability calculation and optimal power flow calculation and comprehensively controls the entire system, as well as memory such as ROM and RAM (not shown), external storage devices such as a hard disk for storing calculation results, input / output devices such as a keyboard, mouse, and display, and a communication interface. Here, the above program is stored in an external storage device or a removable storage medium (CD-ROM, memory card, USB memory, etc.), or is received from a higher-level server and read into the memory for execution.

[0026] The central processing unit 21 includes a transient stability calculation means 21A for analyzing the transient stability of the power system, and an optimal power flow calculation means 21B for performing an optimal power flow calculation under predetermined constraints when the transient stability is determined to be stable, and for calculating the necessary control correction amounts for the active power P and reactive power Q of the GFL 400L and GFM 400M. These transient stability calculation means 21A and optimal power flow calculation means 21B are functions realized by the CPU or the like executing the aforementioned program.

[0027] Here, the configuration of the stabilization calculation means 20 including the central processing unit 21 is not limited to the above-described one, and any configuration may be used as long as it has a function of performing transient stability calculation and optimal power flow calculation based on the state quantities of each part of the power system by a system stabilization program and generating control correction amounts for the GFL 400L and GFM 400M.

[0028] The control correction amount calculated by the optimal power flow calculation means 21B is transmitted via the communication line 42 to the control terminal devices 301 to 30 m (m is an arbitrary plural number). The control terminal devices 301 to 30 m are provided corresponding to PCSs such as the GFL 400L and GFM 400M respectively, and the number m of the control terminal devices 301 to 30 m is equal to the number of PCSs (two in the example of FIG. 1).

[0029] The control terminal devices 301 to 30 m transmit the active power P and reactive power Q corresponding to the received control correction amount to each PCS as control signals, and each PCS controls the active power P and reactive power Q output to the buses 301 and 302 as commands based on these control signals. Also, the control terminal devices 301 to 30 m are configured to transmit the current active power measurement value P0 output by each PCS to the central processing unit 21. These functions of the control terminal devices 301 to 30 m may be provided in the GFL 400L and GFM 400M in the same manner as the accident detection terminal devices 101 to 10 n .

[0030] Next, in this embodiment, a series of operations when the central processing unit 21 performs transient stability calculation and optimal power flow calculation will be described along the flowchart of FIG. 3. First, the central processing unit 21 presets the transient stability calculation period T A and the optimal power flow calculation period (the calculation period of the control correction amount) T B in the memory. Generally, since the transient stability calculation has a larger calculation amount and a longer calculation time than the optimal power flow calculation, TA >T B Far away.

[0031] First, the central processing unit 21 calculates transient stability using a discrete time t A , and discrete time t for performing optimal power flow calculations B Count (Step S1). Discrete time t for optimal tidal flow calculation B is the calculation period T B The discrete time t is reached until it is reached. B Continue counting (step S2N), discrete time t B is the calculation period T B Once it reaches t B Clear it to zero (Step S2Yes). Furthermore, assuming an accident at accident point F, accident detection terminal devices 101-10 n Various measurement values ​​of the power system are input via the control terminal devices 301-30 m Input the current active power measurement value P0 (step S3).

[0032] Next, the optimal power flow calculation means 21B of the central processing unit 21 calculates the discrete time t for transient stability calculation. A is the calculation period T A Until the target is reached (step S4No), the optimal power flow calculation is performed using an objective function that includes constraints on the maximum voltage phase difference L described later, and the control correction amounts for the active power P and reactive power Q required for GFL 400L and GFM 400M are calculated (step S5). Subsequently, the calculated control correction amounts for the active power P and reactive power Q are set by the control terminal devices 301~30 m The system is set to this value (step S6) and controls are generated for the corresponding PCS, namely GFL 400L and GFM 400M. Furthermore, in the optimal power flow calculation, a penalty is added to the correction amount of the active power P output by the PCS as an objective function in order to limit the reallocation of active power to GFL 400L and GFM 400M.

[0033] Here, the objective function, equality constraints, and inequality constraints in conventional optimal power flow calculations are expressed, for example, by Equation 1, with active power P, reactive power Q, voltage amplitude V, and voltage phase angle δ as state variables.

number

[0034] In contrast, in this embodiment, as shown in Equation 2 described later, the objective function is a penalty "ρ ||P0-P||" applied to the correction amount of the active power P output by the PCS. 2 Add the following: Here, ρ is the penalty coefficient, and P0 is the control terminal devices 301-30 controlled by the central processing unit 21. m The current active power measurement value received from the device, P, is the active power as a control signal (command value) given to the PCS.

[0035] Furthermore, in this embodiment, the inequality constraint condition "δ" relates to the maximum voltage phase difference (voltage phase difference threshold) L of the output voltage V of the PCS when the transient stability is judged to be stable. max -δ min Add "≤L". Here, δ max δ is the maximum phase angle of the voltage phase angle δ. min Similarly, the minimum phase angle is used, and for the maximum voltage phase difference L, the latest value that is updated and stored by the process in step S7 described later when performing the optimal power flow calculation is used.

number

[0036] Return to step S4, and use the discrete time t for the transient stability calculation. A is the calculation period T A Once it reaches t AThe value is reset to zero (Step S4 Yes), the transient stability calculation means 21B performs a transient stability calculation, updates the maximum voltage phase difference L at the point when it is determined to be stable, and stores it (Step S7).

[0037] In the transient stability calculation in this embodiment, a detailed time-domain simulation is performed, as described in Non-Patent Documents 1 and 2, for example, to take into account the dynamic characteristics of the PCS. A control signal is generated based on the voltage phase angle δ and voltage amplitude V calculated so that the active power measurement value P0 output from the GFM 400M follows the command value P. When the GFM 400M is operated based on this control signal, it is determined to be "stable" if the fluctuation range of the voltage and frequency of the power system falls within a predetermined range. In more detail, the system explores operating points (combinations of P and Q) that increase the reactive power of the GFL 400L, which has the characteristic of being able to flexibly output reactive power. By controlling the GFL 400L and GFM 400M to reduce the voltage phase angle δ of the GFM 400M (voltage phase difference between substation 100 and GFM 400M) to less than or equal to the maximum voltage phase difference L, transient stability is improved, thereby preventing loss of synchronism.

[0038] Figure 4 is an explanatory diagram of the PQ plane, conceptually illustrating the search process for the operational points described above. In Figure 4, the operational point that is in the unstable region when the hypothetical accident occurs is shown as OP. k The voltage phase angle δ of the GFM 400M at that time is set to "∠36.2", which is equal to the maximum voltage phase difference L. This voltage phase angle δ is the "∠36.2" indicated in parentheses next to the GFM 400M in Figure 1.

[0039] This operational point OP k Starting from this point, the operating point OP is the direction in which the maximum voltage phase difference L (voltage phase angle δ of GFM 400M) decreases with increasing reactive power Q of GFL 400L. k+1 ,……,OP n-1 ...we explored the operational point OP that entered the stable region through sensitivity analysis. nThe maximum voltage phase difference L corresponding to this, for example "∠35.9", is set as the new voltage phase angle δ of the GFM 400M, and at the same time, the maximum voltage phase difference L is updated to "∠35.9" as described in step S7 of Figure 3 and recorded. This maximum voltage phase difference L (voltage phase angle δ) is the bold "∠35.9" appended to the GFM 400M in Figure 1.

[0040] In other words, by increasing the reactive power Q of GFL 400L and decreasing the voltage phase angle δ of GFM 400M, the voltage phase difference between substation 100 and GFM 400M is reduced, thereby preventing loss of synchronism and improving transient stability. Figure 1 shows the case where the reactive power Q of GFL 400L is increased from "0.0" in parentheses to "0.2" in bold, i.e., ΔQ in Figure 4 is set to 0.2. Note that in Figure 4, the operation point is OP. k From the opening n By moving to this position, the reactive power Q of GFL 400L increases by ΔQ, while the active power decreases by ΔP. However, the penalty in the objective function of equation 2 mentioned above, "ρ ||P0-P||", is... 2 As a result of this effect, the reduction amount ΔP is minimized, suppressing economic losses due to the decrease in active power, and also reducing the need for additional load shedding, frequency control, etc.

[0041] In this embodiment, not limited to fault point F in Figure 1, various system faults at various locations are assumed, and transient stability calculations and optimal power flow calculations are performed for these multiple system faults using the state variables of substation 100, GFL 400L, GFM 400M, and load 600. As a result, the reactive power that GFL 400L should output to reduce the voltage phase difference between substation 100 and GFM 400M and stabilize the power system is calculated in advance and stored. Furthermore, when a grid fault actually occurs, the GFL 400L outputs appropriate active and reactive power selected according to the fault location, type of fault, and grid state variables, thereby improving transient stability while reducing the amount of active power suppression.

[0042] Here, Figure 5 conceptually illustrates the process of exploring the operational point for stabilizing the power system by adjusting the active power of two synchronous generators, as described in Non-Patent Document 2. j OP j+1 ,……,OP n-1 OP n This indicates the operating point during the search process. This conventional technique searches for a stable operating point on an active power basis, so for example, the decrease in the active power of one synchronous generator is ΔP g1 As a result, the amount of electricity generated is significantly limited, which restricts opportunities to sell electricity and leads to greater economic losses. In contrast, in this embodiment, a stable operating point is sought on a reactive power basis, increasing the reactive power of the GFL 400L, thus minimizing economic losses due to the suppression of active power.

[0043] Figure 6 shows numerical examples of each part when the transient stability is improved by reducing the active power output of the GFM 400M when a fault occurs, assuming a conventional power system without the grid stabilization device of this embodiment. According to a simulation targeting this power system, if the active power and reactive power when the output voltage and frequency of the GFM 400M were unstable due to a fault were "6.0 + 2.1j", it was confirmed that by reducing the active power to "5.0" (shown in bold), the output voltage and frequency of the GFM 400M transition to a stable state. In other words, with this conventional technology, the reduction in the active power of the GFM 400M leads to economic losses, and in particular, in an isolated grid, additional measures such as load disconnection and frequency control may be required. However, by introducing the grid stabilization device of this embodiment, as mentioned above, there is an advantage in that the amount of active power suppression and thus economic losses can be reduced. [Explanation of Symbols]

[0044] 101,10 n : Accident detection terminal device 20: Stabilization calculation means 21: Central processing unit 21A: Transient stability calculation means 21B: Optimal power flow calculation method 301,30 m : Control terminal device 41,42: Communication lines 100: Substation 201,202: Power transmission lines 301,302: Bus bar 400L: Current-controlled PCS (GFL) 400M: Voltage-controlled PCS (GFM) 401,403: Solar cells 402,404: Current / Voltage Detectors 500: Grid stabilizer 600: Load 601: Current / Voltage Detector F: Accident point

Claims

1. In a power system where voltage-controlled PCS and current-controlled PCS are interconnected as power conversion devices that convert the output of a power generator into predetermined AC power, a power system stabilization device for suppressing and stabilizing power fluctuations in the power system in the event of an accident, A transient stability calculation means that calculates transient stability by performing a simulation using measured values ​​from the power system when a fault point is assumed within the power system, An optimal power flow calculation means generates a control correction amount by performing an optimal power flow calculation using an objective function that includes the voltage phase angle information of the voltage-controlled PCS as a constraint condition when it is determined to be stable by the transient stability calculation means, Equipped with, A grid stabilization device characterized by controlling the power converter using a control signal based on the control correction amount when an actual fault occurs at the assumed fault point.

2. In the system stabilization device described in claim 1, The transient stability calculation means is characterized by searching for an operating point as a stable operating point in which the voltage phase difference between the grid power supply and the voltage-controlled PCS decreases by increasing the reactive power output of the current-controlled PCS.

3. In the system stabilization device described in claim 1 or 2, The power flow calculation means is characterized by generating at least a control correction amount for controlling the reactive power output by the current-controlled PCS.

4. In the system stabilization device described in claim 1 or 2, A power grid stabilization device characterized in that the calculation period of the transient stability calculation means is set to be longer than the calculation period of the optimal power flow calculation means.

5. In the system stabilization device described in claim 1 or 2, The power grid stabilization device is characterized in that the optimal power flow calculation means generates the control correction amount using an objective function that includes a penalty to the correction amount of the active power of the power converter.

6. In the system stabilization device described in claim 1 or 2, The power system stabilization device is characterized in that the voltage phase angle information is the maximum voltage phase difference of the voltage-controlled PCS.

7. In a power system where voltage-controlled PCS and current-controlled PCS are interconnected as power conversion devices that convert the output of a power generator into predetermined AC power, a system stabilization method for suppressing and stabilizing power fluctuations in the power system in the event of an accident, When a fault point is assumed within the aforementioned power system, a simulation is performed using measured values ​​from the aforementioned power system to calculate the transient stability. When the transient stability is determined to be stable, an optimal power flow calculation is performed using an objective function that includes the voltage phase angle information of the voltage-controlled PCS as a constraint to generate a control correction amount. A grid stabilization method characterized by controlling the power converter using a control signal based on the control correction amount when an actual fault occurs at the assumed fault point.

8. A program executed by a computer system, which is a system stabilization program for suppressing and stabilizing power fluctuations in a power system when an accident occurs in a power system in which voltage-controlled PCS and current-controlled PCS are connected as power conversion devices that convert the output of a power generator to predetermined AC power, The process involves performing a simulation using measured values ​​from the power system to calculate transient stability when a fault point is assumed within the power system, and The process involves performing an optimal power flow calculation using an objective function that includes the voltage phase angle information of the voltage-controlled PCS as a constraint when the transient stability is determined to be stable, and generating a control correction amount. The process involves controlling the power converter using a control signal based on the control correction amount when an actual accident occurs at the assumed accident point, A system stabilization program characterized by performing the following actions.

Images