System stabilization device

Abstract

To provide a grid stabilization device with which it is possible to maintain the frequency of a power grid after a grid disturbance within a target frequency range.SOLUTION: The grid stabilization device comprises a frequency prediction unit and a control variable setting unit. The frequency prediction unit predicts a second grid frequency at a second timing after the elapse of a prescribed time from a first timing, on the basis of a first grid frequency at the first timing. The control variable setting unit calculates a first total value of machine input to a plurality of power generators at the first timing, on the basis of the total value of first output of the plurality of power generators at the first timing and the equation of motion of the plurality of power generators, calculates the total value of second output of the plurality of power generators at the second timing, on the basis of the first and second grid frequencies, the total value of first output, and a load frequency response coefficient, and sets the control variable on the basis of the total value of second machine input to the plurality of power generators at the second timing and the total value of second output.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a power grid stabilization device. [Background technology]

[0002] In a power system stabilization system aimed at maintaining frequency, events that cause frequency fluctuations (e.g., power source failure, route cut-off accident on a heavy current line, etc.) are detected, and generators and loads are shut off to maintain frequency (e.g., Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Atsushi Kino, Kenichiro Yamazato, Fuminao Kinjo, Wataru Shima, Yasuyuki Owada, Hiroshi Nishino, Toru Maeda, Shuji Oshida, Development and Application of a Centralized System Stabilization System (SSC) for Small-Scale and Isolated Power Systems, 2011 Electrical Engineering Society Conference, 19-1, 2011 Summary of the Invention [Problem to be solved by the invention]

[0004] Short-term fluctuations and frequency characteristics of load in power systems, as well as short-term output fluctuations and frequency characteristics of renewable energy sources (e.g., solar power generation, wind power generation, etc.), the amount of which has been rapidly increasing in recent years, are uncertain factors in the control performed by power system stabilization systems. Under these circumstances, there is a need for a method to set appropriate control variables (e.g., load control variables, generator control variables) so that the power system frequency does not deviate from the target frequency even when system disturbances occur.

[0005] An object of one aspect of the present disclosure is to provide a power system stabilization device that can maintain the frequency of a power system within a target frequency range after a system disturbance. [Means for solving the problem]

[0006] According to one embodiment, there is provided a power system stabilization device for a power system connected to a plurality of generators and a plurality of loads. The power system stabilization device includes a frequency prediction unit that predicts a system frequency of the power system and a controlled variable setting unit that sets a controlled variable to be disconnected from the power system. The frequency prediction unit predicts a second system frequency at a second timing after a specified time has elapsed from the first timing based on a first system frequency at a first timing. The controlled variable setting unit calculates a first total mechanical input value to the plurality of generators at the first timing based on a first total output value of the plurality of generators at the first timing and an equation of motion for the plurality of generators, calculates a second total output value of the plurality of generators at the second timing based on the first and second system frequencies, the first total output value, and load frequency characteristic coefficients for the plurality of loads, and sets the controlled variable based on a second total mechanical input value to the plurality of generators at the second timing and the second total output value, which is estimated from the first total mechanical input value. [Effects of the Invention]

[0007] According to the present disclosure, the frequency of the power system after a system disturbance can be maintained within a target frequency range. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing an overall configuration of a power grid stabilization system according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of a hardware configuration of an accident detection terminal device. [Figure 3] FIG. 2 is an image diagram for explaining an example of the effect of the first embodiment. [Figure 4] FIG. 10 is an image diagram for explaining another example of the effect according to the first embodiment. [Figure 5] 1 is a block diagram showing an example of a functional configuration of a power system stabilizing device according to a first embodiment. [Figure 6] FIG. 10 is a diagram showing an overall configuration of a power grid stabilization system according to a second embodiment. [Figure 7] FIG. 10 is a diagram for explaining an equivalent load model. [Figure 8] FIG. 10 is a diagram for explaining the frequency characteristics of the total output value of renewable energy power sources. [Figure 9] FIG. 10 is a block diagram showing an example of a functional configuration of a power system stabilizing device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0010] Embodiment 1 <Overall structure> Fig. 1 is a diagram showing the overall configuration of a power system stabilization system 1000 according to a first embodiment. Referring to Fig. 1, the power system stabilization system 1000 includes a fault detection terminal device 10, a power system stabilization device 15, and load control terminal devices 21-2n (hereinafter also referred to as "load control terminal device 20"). When the plant is operating normally, the plant control devices GA1C-GAnC control the input amounts of the generators GA1-GAn in a direction to increase the output of the generators GA1-GAn if the frequency of the power system 120 (hereinafter also referred to as "power system frequency") drops, and to decrease the output of the generators GA1-GAn if the power system frequency rises.

[0011] A plurality of generators GA1 to GAn provided in the power plant 100 are connected to the power system 120 via a bus BA and a power transmission line 80. Electric power from the plurality of generators GA1 to GAn is supplied to the power system 120.

[0012] A plurality of generators GA1 to GAn (hereinafter also collectively referred to as "generators GA") are installed in the power plant 100, and the output of each generator is controlled by a corresponding plant control device. Specifically, the output of the generator GA1 is controlled by a plant control device GA1C, and the output of the generator GAn is controlled by a plant control device GAnC.

[0013] Each of the generators GA1 to GAn is connected to the bus BA via a corresponding transformer and a corresponding circuit breaker. Specifically, the generator GA1 is connected to the bus BA via a transformer MTr1 and a circuit breaker CB1. The generator GAn is connected to the bus BA via a transformer MTrn and a circuit breaker CBn.

[0014] A plurality of loads L1, L2, ... Ln (hereinafter also collectively referred to as "loads L") are connected to the power system 120. Each load L is disconnected from the power system 120 under the control of a corresponding load control terminal device. Specifically, load L1 is disconnected from the power system 120 under the control of load control terminal device 21, load L2 under the control of load control terminal device 22, and load Ln under the control of load control terminal device 2n. Note that each load L may be connected to the power system 120 under the control of a corresponding load control terminal device.

[0015] The power system stabilization device 15 is configured to be able to communicate with each load control terminal device 20, and receives the load amount of the corresponding load L as measurement information from each load control terminal device 20. The power system stabilization device 15 transmits a command signal to the load control terminal device 20 to disconnect the load from the power system 120.

[0016] A current transformer for measuring current is provided at the sending end of each transformer corresponding to generators GA1 to GAn. Specifically, a current transformer CT1 for measuring the sending end output current of generator GA1 is provided at the sending end of transformer MTr1 corresponding to generator GA1. A current transformer CTn for measuring the sending end output current of generator GAn is provided at the sending end of transformer MTrn corresponding to generator GAn. In addition, a voltage transformer PT for measuring the bus voltage is provided at bus BA.

[0017] A power plant 100 is provided with a fault detection terminal device 10. The outputs of the current transformers CT1 to CTn and the output of the voltage transformer PT are individually input to the fault detection terminal device 10. The fault detection terminal device 10 also individually receives signals indicating the open / closed states of the circuit breakers CB1 to CBn (hereinafter also referred to as "open / close signals").

[0018] Each plant control device detects a plant fault (for example, a fault in a boiler, turbine, or a number of valves in the plant control device, or a fault in a generator). When each plant control device detects a plant fault, it outputs a tripping command (i.e., an opening command) to the corresponding circuit breaker.

[0019] Alternatively, a transmission line protection relay (not shown) installed on the transmission line 80 outputs a shutoff command to each circuit breaker when it detects an accident on the transmission line 80 based on the current value detected by the current detector (for example, when the current value is equal to or greater than a specified value).

[0020] When a circuit breaker is opened due to a power transmission line accident, a plant failure, or the like, the corresponding generator is disconnected from the power system 120. In the following description, disconnecting a generator from the power system 120 is also referred to as "the generator dropping out." For example, when the circuit breaker CB1 is opened, the generator GA1 is disconnected from the power system 120 (i.e., the generator GA1 drops out).

[0021] Signals indicating the open / closed states of the circuit breakers CB1 to CBn are transmitted at predetermined intervals from the fault detection terminal device 10 to the power system stabilization device 15. As a result, the power system stabilization device 15 determines whether the generators GA1 to GAn have tripped or not based on the open / close signals of the circuit breakers CB1 to CBn. Specifically, the power system stabilization device 15 determines that the generator GA1 has tripped when the circuit breaker CB1 is open, and determines that the generator GA1 has not tripped when the circuit breaker CB1 is closed.

[0022] The fault detection terminal device 10 calculates the active power value output from each of the generators GA1 to GAn based on the current values ​​from the instrument current transformers CT1 to CTn and the voltage value from the instrument transformer PT. The calculated active power values ​​are transmitted to the system stabilization device 15 at predetermined intervals. This allows the system stabilization device 15 to constantly monitor the active power value output from each generator. The fault detection terminal device 10 may also transmit electrical quantity (e.g., current, voltage) information input from the instrument current transformers CT1 to CTn and the instrument transformer PT to the system stabilization device 15 as measurement information.

[0023] The system stabilization device 15 receives the output active power value of each generator GA1 to GAn as measurement information from the fault detection terminal device 10, and also receives tripping information indicating whether each generator GA has tripped. Note that the mechanical input value to each generator GA1 to GAn corresponds to the output active power value when each generator GA has not tripped and the system is not fluctuating. Typically, the tripping information is an open / close signal of each circuit breaker CB.

[0024] Furthermore, the power system stabilizing device 15 receives, from each of the load control terminal devices 21-2n, the load amount of the corresponding load as measurement information, and drop information indicating whether the corresponding load has dropped. Typically, the drop information is a signal indicating the connection state between each load monitored by each of the load control terminal devices 21-2n and the power system 120. The power system stabilizing device 15 determines whether the loads L1-Ln have dropped based on each drop information. For example, when the power system stabilizing device 15 receives drop information indicating that the load L1 has been disconnected from the load control terminal device 21, it determines that the load L1 has dropped.

[0025] When a system disturbance occurs in the power system 120, the system frequency fluctuates. For example, if a generator trips from the power system 120, the system frequency drops. In this case, the power system stabilization device 15 sets the load control amount to be disconnected (i.e., cut off) from the power system 120 so that the minimum value of the frequency of the power system 120 after the generator trips (hereinafter also referred to as the "bottom frequency") falls within the target frequency range.

[0026] Specifically, the grid stabilization device 15 predicts the grid frequency after the tripping of the generator, and then sets the load control amount so that the predicted grid frequency falls within the target frequency range.

[0027] Typically, the power system stabilization device 15 selects a load corresponding to a load control amount from among the loads L1 to Ln based on a preset priority order, and outputs a command signal to shedding the selected load to the corresponding load control terminal device 21 to 2n. Note that this is an example of a method for setting a load control target in the power system stabilization device 15, and the load may be selected by other methods.

[0028] The grid stabilization device 15 constantly executes grid frequency prediction processing after a generator trips, and can therefore set an appropriate load control amount according to the grid frequency. As a result, when the frequency drops after a grid disturbance, the grid frequency is maintained within the target frequency range. In other words, grid stabilization is performed.

[0029] On the other hand, when a load is dropped from the power grid 120, the system frequency rises. In this case, the power grid stabilization device 15 sets the generator control amount to be disconnected (i.e., shut off) from the power grid 120 so that the maximum value of the frequency of the power grid 120 after the load drop (hereinafter also referred to as the "top frequency") falls within the target frequency range.

[0030] Specifically, the grid stabilization device 15 predicts the grid frequency after the load drop, and then sets the generator control amount so that the predicted grid frequency falls within the target frequency range.

[0031] Typically, the power system stabilizing device 15 selects a generator corresponding to the generator control amount from among the generators GA1 to GAn based on a preset priority order, and outputs a command signal to shut off the selected generator to the fault detection terminal device 10. Note that this is one example of a method for setting the generator control target in the power system stabilizing device 15, and the generator may be selected using other methods. The fault detection terminal device 10 outputs a shutoff command to the circuit breaker CB in accordance with the command signal.

[0032] The grid stabilization device 15 constantly executes grid frequency prediction processing after load drop, and can therefore set appropriate generator control variables according to the grid frequency. As a result, when the frequency increases after a grid disturbance, the grid frequency is maintained within the target frequency range. In other words, grid stabilization is performed.

[0033] <Hardware configuration> (Accident detection terminal device) Fig. 2 is a block diagram showing an example of a hardware configuration of the accident detection terminal device 10. Referring to Fig. 2, the accident detection terminal device 10 includes an auxiliary transformer 32, an A / D conversion unit 35, an arithmetic processing unit 40, a communication circuit 50, a digital output circuit (D / O: Digital Output) 55, and a digital input circuit (D / I: Digital Input) 56.

[0034] The auxiliary transformer 32 receives electrical quantities from the current transformer and voltage transformer, converts them into voltages suitable for signal processing in the relay's internal circuitry, and outputs them. The A / D conversion unit 35 receives the voltages output from the auxiliary transformer 32 and converts them into digital data. Specifically, the A / D conversion unit 35 includes an analog filter, a sample-and-hold circuit, a multiplexer, and an A / D converter.

[0035] The analog filter removes high-frequency noise components from the current waveform signal output from auxiliary transformer 32. The sample-and-hold circuit samples the current waveform signal output from the analog filter at a sampling period. Based on a timing signal input from arithmetic processing unit 40, the multiplexer sequentially switches the waveform signals input from the sample-and-hold circuit in time series and inputs them to the A / D converter. The A / D converter converts the waveform signals input from the multiplexer from analog data to digital data. The A / D converter outputs the digitally converted waveform signals to arithmetic processing unit 40.

[0036] The arithmetic processing unit 40 includes a CPU (Central Processing Unit) 41, a RAM (Random Access Memory) 42, and a ROM (Read Only Memory) 43. These elements are connected to each other via a bus 44. The arithmetic processing unit 40 may include an electrically rewritable non-volatile memory such as a flash memory or hardware.

[0037] The communication circuit 50 communicates with an external device (for example, the power system stabilization device 15). The communication circuit 50 communicates with the external device in accordance with a specified protocol.

[0038] The digital output circuit 55 is an interface circuit for outputting a signal to an external device. For example, the digital output circuit 55 may output a breaker command to a circuit breaker in accordance with a command from the CPU 41. The digital input circuit 56 receives, for example, an open / close signal indicating the open / close state of the circuit breaker from the circuit breaker.

[0039] (System stabilization device, load control terminal device) The hardware configuration of the power system stabilizing device 15 and the load control terminal device 20 may be the same as that of the fault detection terminal device 10. Alternatively, the power system stabilizing device 15 and the load control terminal device 20 may be configured to have hardware equivalent to the arithmetic processing unit 40 and the communication circuit 50 in FIG.

[0040] <Load control amount setting process> A description will now be given of the load control amount setting process executed by the system stabilization device 15. Here, it is assumed that at time t0, the generator trips and the system frequency drops.

[0041] At time t1 after the tripping of the generator, the grid stabilization device 15 executes a process of predicting the grid frequency at time t2, a specified time after time t1. Here, time t1 is the timing at which execution of a control calculation for setting a load control amount starts. Time t2 is the timing at which load control is performed with the set load control amount (i.e., the load corresponding to the load control amount is shedding).

[0042] Typically, the frequency deviation between the reference frequency Fn [Hz] and the system frequency F(t1) [Hz] at time t1 is defined as ΔF(t1), and the system stabilization device 15 calculates ΔF(t2), which is an estimated value of the frequency deviation between the reference frequency Fn and the system frequency F(t2) at time t2, using the following equation (1): EST Calculate (t2).

[0043]

number

[0044] The system frequency F(t1) is calculated from the voltage of the bus BA detected by the potential transformer PT at time t1, for example. F(t1)=Fn+ΔF(t1) holds. The system stabilization device 15 calculates the frequency deviation ΔF EST (t2), the system frequency F(t2) (i.e., F(t2) = Fn + ΔF EST (t2)) can be predicted.

[0045] The rate of change of the frequency deviation used in equation (1) may be simply estimated from the time series data of the grid frequency. Also, in equation (1), the estimated value of the frequency deviation (i.e., ΔF EST(t2)) is calculated as a linear function of time, but by using more time-series data, the estimated value may be calculated as a more complicated function including a quadratic function.

[0046] The total inertia constant of the multiple generators GA1 to GAn connected to the power system 120 is M [s], and the total output value of each generator GA1 to GAn (i.e., the total value of the output active power value) is P E [pu], and the total mechanical input to each generator GA1 to GAn is P M The total inertia constant M is the equivalent inertia constant when the multiple generators GA1 to GAn are considered as one generator. In this case, from the equation of motion of the multiple generators GA1 to GAn (for example, the equation of motion when the multiple generators GA1 to GAn are considered as one generator), the total mechanical input value P M (t1) is the total output value P E The total output value P is calculated using the following formula (2) using (t1). E (t1) is the total value of the active power output from each generator at time t1.

[0047]

number

[0048] If one of the generators GA1 to GAn (for example, generator GAx) trips, the remaining generators will increase their output power due to the characteristics of their governors. However, because the governors have a control system delay, there is a time delay before the output power from the generators changes even when the frequency changes.

[0049] Here, it is assumed that the time from time t1, which is the control calculation timing, to time t2, which is the control execution timing, is short, so that the change due to the governor control of the generator GA can be ignored. In this case, the total mechanical input value P M (t1) is the total mechanical input value P at time t2 M Since it is equal to (t2), the following equation (3) holds.

[0050]

number

[0051] If we ignore losses in the lines, the total output value P E and the total load value P of each load L L In addition, the loss is small enough compared to the total output value, so "P E =P L Furthermore, the frequency deviation between the reference frequency Fn of the power system 120 and the system frequency F (i.e., ΔF=F−Fn) is taken as ΔF, and the total load value P L The initial value of P L0 In this case, the total load value P L ΔF, P L0 and load frequency characteristic coefficient K L Using [pu / Hz], "P L0 (1+K L Therefore, the total output value P E (t1) and the total output value P E The relationship with (t2) is expressed as the following equation (4): Load frequency characteristic coefficient K L is an equivalent frequency characteristic coefficient when a plurality of loads L are regarded as one load, and is stored in advance in the memory of the power system stabilization device 15.

[0052]

number

[0053] Then, the load control amount to resolve the supply-demand imbalance at time t2 is P LCS [pu], the load control amount P LCS is calculated using the following formula (5).

[0054]

number

[0055] kv is an adjustment coefficient for avoiding insufficient control due to voltage changes or the like during load control, and is stored in advance in the memory of the power system stabilization device 15.

[0056] The system stabilization device 15 calculates the load control amount P LCS The load control terminal device 20 outputs a command signal for shedding the load corresponding to the load.

[0057] Fig. 3 is an image diagram for explaining an example of the effect of embodiment 1. Referring to Fig. 3, graph 301 shows the change in frequency over time when control corresponding to the load control amount set based on the series of processes described above is performed (i.e., the load control amount is cut off). Graph 302 shows the change in frequency over time when the control is not performed.

[0058] Referring to graph 301, the generator trips at time t0, causing the system frequency to drop. At time t1 after the generator trips, the system stabilization device 15 predicts the system frequency F(t2) at time t2, which is a specified time after time t1.

[0059] Here, it is assumed that the power system stabilization device 15 determines that the power system frequency F(t2) is less than the threshold value Fth1. In this case, the power system stabilization device 15 calculates the total mechanical input value P M (t1), the output total value P using equation (4) E (t2) and the load control amount P using equation (5) LCS The power system stabilization device 15 executes a process of setting the load control amount P LCS At time t2, a command signal for shedding a load corresponding to the load control amount P LCS A load shedding equivalent to

[0060] From this, it can be seen that the bottom frequency Fsbt after the generator trips is within the target frequency range (i.e., greater than or equal to Fth1 and less than or equal to Fn) in graph 301. Similarly, the finish frequency Fse is also within the target frequency range.

[0061] On the other hand, referring to graph 302 when the load control amount is not cut off, the finished frequency Fce after the generator trips is included in the target frequency range, but the bottom frequency Fcbt is not included in the target frequency range.

[0062] In this way, the system stabilization device 15 according to the first embodiment can keep the system frequency within the target frequency range after the generator trips by shedding the load corresponding to the appropriate load control amount at the appropriate timing.

[0063] <Generator control variable setting process> A description will be given of the process for setting the generator control amount executed by the system stabilization device 15. Here, it is assumed that the load drops at time t0 and the system frequency increases.

[0064] The process flow from equation (1) to equation (4) explained in <Load control amount setting process> is basically the same.

[0065] Specifically, at time t1 after load drop, the system stabilization device 15 executes a process of predicting the system frequency at time t2 after a specified time has elapsed since time t1. Here, time t1 is the timing for executing a control calculation for setting the generator control amount, and time t2 is the timing for performing control with the set generator control amount (i.e., the generator corresponding to the generator control amount is shut off).

[0066] The system stabilization device 15 uses the formula (1) to calculate the estimated value ΔF of the frequency deviation at time t2. EST The power system stabilization device 15 calculates the total mechanical input value P (t2) at time t1 using equation (2). M(t1). Even in the case of load drop, if it is assumed that the change due to the governor control of the generator GA can be ignored, the equation (3) holds. The system stabilization device 15 calculates the total output value P E Calculate (t2).

[0067] Then, the generator control amount to eliminate the supply-demand imbalance at time t2 is P GCS [pu], the generator control amount P GCS is calculated using the following formula (6).

[0068]

number

[0069] Fig. 4 is an image diagram for explaining another example of the effect according to the first embodiment. Referring to Fig. 4, graph 401 shows the change in frequency over time when control corresponding to the generator control amount set based on the series of processes described above is performed (i.e., the generator control amount is shut off). Graph 402 shows the change in frequency over time when the control is not performed.

[0070] Referring to graph 401, the load is dropped at time t0 and the system frequency increases. At time t1 after the load is dropped, the system stabilization device 15 predicts the system frequency F(t2) at time t2, which is a specified time after time t1.

[0071] Here, it is assumed that the power system stabilization device 15 determines that the power system frequency F(t2) is greater than the threshold value Fth2. In this case, the power system stabilization device 15 calculates the total mechanical input value P M (t1), the output total value P using equation (4) E (t2) and the generator control amount P GCS The system stabilization device 15 executes a process of setting the generator control amount P GCS At time t2, a command signal for shutting off the generator corresponding to the generator control variable PGCS A generator shutdown is performed corresponding to

[0072] From this, it can be seen that the top frequency Fstp after load drop is within the target frequency range (i.e., equal to or greater than Fn and equal to or less than Fth2) in the graph 401. Similarly, the finish frequency Fse is also within the target frequency range.

[0073] On the other hand, referring to graph 402 when the generator control variable is not shut off, the finish frequency Fce after load drop is included within the target frequency range, but the top frequency Fctp is not included within the target frequency range.

[0074] In this way, the system stabilization device 15 according to the first embodiment can keep the system frequency after load drop within the target frequency range by shutting off the generator corresponding to the appropriate generator control amount at the appropriate timing.

[0075] <Functional configuration> Fig. 5 is a block diagram showing an example of a functional configuration of the power grid stabilizing device according to the first embodiment. Referring to Fig. 5, the power grid stabilizing device 15 includes an information receiving unit 201, a frequency predicting unit 203, a control amount setting unit 205, and a command transmitting unit 207. Typically, these functions are realized by the CPU of the power grid stabilizing device 15 executing a program, but may also be realized by a dedicated hardware circuit.

[0076] The information receiving unit 201 receives various types of information from the fault detection terminal device 10 and the load control terminal device 20. For example, the information receiving unit 201 receives, from the fault detection terminal device 10, information on the amount of electricity detected by the instrument current transformers CT1 to CTn and the instrument voltage transformer PT, the output active power values ​​of the generators GA1 to GAn, and dropout information. The information receiving unit 201 also receives, from each load control terminal device 20, the load amount and dropout information of the corresponding load L.

[0077] The frequency prediction unit 203 predicts a future system frequency based on a system frequency calculated from the voltage of the bus BA. Specifically, the frequency prediction unit 203 predicts a second system frequency (for example, system frequency F(t2)) at a second timing (for example, time t2) after a specified time has elapsed from a first timing (for example, time t1) based on a first system frequency (for example, system frequency F(t1)) at a first timing (for example, time t1) using equation (1). For example, the frequency prediction unit 203 predicts a system frequency F(t2) (=Fn+ΔF ES Predict (t2).

[0078] The control variable setting unit 205 receives input of measurement information, setting information, and the prediction result of the frequency prediction unit 203, and sets the control variable to be disconnected from the power grid 120. The setting information includes the total inertia constant M of the multiple generators GA, the reference frequency Fn, the load frequency characteristic coefficient K L , adjustment factor k v The setting information is stored in advance in the memory of the power system stabilizing device 15. The controlled variable setting unit 205 may also receive input of dropout information.

[0079] The control amount setting unit 205 calculates the total output value P of the generators GA at time t1. E (t1) and the equations of motion of the multiple generators GA, the total mechanical input value P M For example, the control amount setting unit 205 calculates the total mechanical input value P M Calculate (t1).

[0080] The control variable setting unit 205 determines the system frequency F(t1), the system frequency F(t2), and the total output value P E (t1) and the load frequency characteristic coefficient K L Based on this, the total output value P of the multiple generators GA at time t2 is calculated. E For example, the control amount setting unit 205 calculates the total output value P E Calculate (t2).

[0081] The control amount setting unit 205 sets the total mechanical input value PM The total mechanical input value P at time t2 estimated from (t1) M (t2) and the total output value P E (t2). For example, the control amount setting unit 205 uses the equation (5) to set the load control amount P LCS Alternatively, the control amount setting unit 205 sets the generator control amount P GCS Typically, as shown in equation (3), the total mechanical input value P M (t1) and the total mechanical input value P M It is equal to (t2).

[0082] In one aspect, when the grid frequency F(t2) is less than a first threshold value (for example, a threshold value Fth1), the control amount setting unit 205 sets the total mechanical input value P M The first process calculates (t1) and the output total value P E (t2) and the load control amount P LCS A series of processes including a third process of setting a load control amount is executed. The specified time from the first timing to the second timing is set to be equal to or longer than the time from the start of the series of processes until the load corresponding to the load control amount is disconnected from the power grid 120. As a result, at the second timing, the load corresponding to the load control amount is in a disconnected state.

[0083] In another aspect, when the grid frequency F(t2) is greater than a second threshold value (for example, a threshold value Fth2), the control amount setting unit 205 sets the total mechanical input value P M The first process calculates (t1) and the output total value P E (t2) and the generator control amount P GCS In this case, the specified time is set to be equal to or longer than the time from the start of the series of processes until the generator corresponding to the generator control amount is disconnected from the power grid 120. As a result, at the second timing, the generator corresponding to the generator control amount is in a cut-off state.

[0084] The command transmitting unit 207 transmits a command signal to the load control terminal device 20 to disconnect a load corresponding to the set load control amount from the power system 120. The load control terminal device 20 disconnects the corresponding load L from the power system 120 in accordance with the command signal. In another aspect, the command transmitting unit 207 transmits a command signal to the fault detection terminal device 10 to disconnect a generator corresponding to the set generator control amount from the power system 120. The fault detection terminal device 10 disconnects the corresponding generator GA from the power system 120 in accordance with the command signal.

[0085] Embodiment 2 In the above-described first embodiment, a configuration has been described in which a plurality of generators and a plurality of loads are connected to the power system 120. In the second embodiment, a configuration will be described in which a plurality of renewable energy power sources are further connected to the power system 120.

[0086] Fig. 6 is a diagram showing the overall configuration of a grid stabilization system 1000A according to embodiment 2. Referring to Fig. 6, the grid stabilization system 1000A differs from the grid stabilization system 1000 in Fig. 1 in that renewable energy power sources ER1 to ERn are further connected to the power grid 120. The differences from the grid stabilization system 1000 will be described below.

[0087] A plurality of renewable energy power sources ER1, ER2, ... ERn (hereinafter also collectively referred to as "renewable energy power sources ER") are connected to the power system 120. In the second embodiment, each renewable energy power source ER is disconnected from the power system 120 by control of a corresponding load control terminal device.

[0088] Specifically, the renewable energy power source ERn is disconnected from the power system 120 by the control of the load control terminal device 2n. Furthermore, the power system stabilization device 15 receives the output amount (e.g., active power value) of the corresponding renewable energy power source ER from each load control terminal device 20 as measurement information. Note that each renewable energy power source ER may be connected to the power system 120 by the control of the corresponding load control terminal device. Furthermore, the load control terminal device 20 may be configured to be able to individually control the connection and disconnection between the load L and each of the renewable energy power source ER and the power system 120.

[0089] Furthermore, the power system stabilizing device 15 receives, from each of the load control terminal devices 21 to 2n, disconnection information indicating whether or not the corresponding renewable energy power source ER has disconnected. Based on each piece of disconnection information, the power system stabilizing device 15 determines whether or not the renewable energy power source ER1 to ERn has disconnected.

[0090] Each renewable energy power source ER may be disconnected from or connected to the power grid 120 under the control of a corresponding power control terminal device (not shown). In this case, the power grid stabilization device 15 is configured to be able to communicate with each power control terminal device.

[0091] In the second embodiment, an equivalent load model is considered, which combines a load L and a renewable energy power source ER.

[0092] 7 is a diagram for explaining an equivalent load model. Referring to FIG. 7, the equivalent load amount P of the equivalent load LE, which is a combination of each load L and each renewable energy power source ER, is LE is the total load value P of each load L L The total output value P of renewable energy sources ER ER (i.e., P LE =P L -P ER In the second embodiment, the equivalent load P LE is assumed to be positive. In other words, the total load value P L The total output value P ERshall be greater than

[0093] Referring again to Fig. 6, the power system stabilization device 15 replaces the load in the first embodiment with an "equivalent load" and executes various processes. For example, when a generator trips from the power system 120, the power system frequency drops. Therefore, the power system stabilization device 15 sets a control amount of the equivalent load LE (e.g., equivalent to the load reduction amount of the equivalent load) so that the bottom frequency of the power system 120 after the generator trips falls within the target frequency range.

[0094] The power system stabilization device 15 selects a load corresponding to an equivalent load control amount from among the loads L1 to Ln based on a preset priority order, and outputs a command signal to the corresponding load control terminal device 21 to 2n to shedding the load. Alternatively, the power system stabilization device 15 may select a renewable energy power source corresponding to the equivalent load control amount from among a plurality of renewable energy power sources ER1 to ERn based on a preset priority order, and output a command signal to the renewable energy power source to cause the renewable energy power source to perform a discharge operation (for example, an operation to control power in the discharge direction). Note that the power system stabilization device 15 may be configured to select a load and renewable energy power source corresponding to the equivalent load control amount, and shedding the load and causing the renewable energy power source to perform a discharge operation.

[0095] On the other hand, for example, when a part of the equivalent load LE (for example, the equivalent load LEx) is dropped from the power system 120, the system frequency increases. In the second embodiment, the drop of the equivalent load LEx means that a positive equivalent load P LEX This means that the equivalent load LEx having the equivalent load P LEX is positive when the load amount of the load L at the equivalent load LEx is greater than the output amount of the renewable energy power source ER at the equivalent load LEx.

[0096] The power system stabilization device 15 sets the generator control amount to be disconnected from the power system 120 so that the top frequency of the power system 120 after equivalent load drop falls within the target frequency range. The power system stabilization device 15 selects a generator corresponding to the generator control amount from among the generators GA1 to GAn based on a preset priority order, and outputs a command signal to shut off the selected generator to the fault detection terminal device 10. The fault detection terminal device 10 outputs a shutoff command to the circuit breaker CB in accordance with the command signal.

[0097] <Equivalent load control amount setting process> The flow of the process of setting the equivalent load control amount when a system disturbance occurs (for example, when a generator trips) is basically the same as the process flow described in <Load control amount setting process> in embodiment 1. First, in the process of setting the equivalent load control amount, the process flow of equations (1) to (3) is the same.

[0098] As described above, the equivalent load is a combination of multiple loads L and multiple renewable energy sources ER. Therefore, in the process of setting the equivalent load control amount, the load frequency characteristic coefficient K L is the equivalent load frequency characteristic coefficient K LE [pu / Hz], and the load control amount P in equation (5) LCS is the equivalent load control amount P LECS [pu]. Hereafter, the equivalent load frequency characteristic coefficient K LE The calculation method will be explained below.

[0099] Equivalent load amount P LE The time change of [pu] is P LE (t), equivalent load P LE The initial value of P LE0 [pu], the total load value of each load L (i.e., the total load value P L [pu]) is expressed as P L (t), total load value P L The initial value of P L0 [pu], the total output of each renewable energy source ER (i.e., the total output P ER [pu]) is expressed as PER (t), and the time change of the frequency deviation ΔF [Hz] is ΔF(t). In this case, the following equation (7) holds.

[0100]

number

[0101] P LE0 is calculated based on the load amount of each load L and the output amount of each renewable energy power source ER as measurement information in an initial state (for example, before the occurrence of a system disturbance and when ΔF is 0). The frequency deviation ΔF is the frequency deviation between the reference frequency Fn of the power system 120 and the system frequency F (i.e., ΔF=F-Fn).

[0102] Here, the total output value P ER In this case, the total output value P ER (t) is the total output value P ER The initial value of P ER0 That is, P ER (t)=P ER0 As explained in Figure 7, the equivalent load P LE is the total load value P L to the total output value P ER Since this corresponds to the subtraction of

[0103]

number

[0104] Therefore, “P ER (t)=P ER0 " and equation (8) are used in equation (7), the equivalent load frequency characteristic coefficient K LE is calculated using the following formula (9).

[0105]

number

[0106] Next, the total output value P ER For example, the total output value P ER has the characteristics shown in FIG.

[0107] FIG. 8 is a diagram for explaining the frequency characteristics of the total output value of renewable energy power sources. Referring to FIG. 8, the horizontal axis represents the frequency deviation ΔF, and the vertical axis represents the total output value P ER and its initial value P ER0 Deviation ΔP ER (i.e., ΔP ER =P ER -P ER0 ) is shown.

[0108] The frequency deviation ΔF is within the reference range (for example, -ΔF X ≦ΔF≦ΔF X ), the deviation ΔP ER is 0, so the total output value P ER It is understood that the reference range is the sum of the output values ​​P ER This corresponds to the dead zone where the total output value P ER does not have frequency characteristics when the frequency deviation ΔF is within the reference range, and has frequency characteristics when the frequency deviation ΔF is outside the reference range.

[0109] Therefore, when the frequency deviation ΔF is within the reference range, the total output value P ER does not change (i.e., P ER =P ER0 holds), the equivalent load frequency characteristic coefficient K LE is expressed as the above equation (9).

[0110] On the other hand, the frequency deviation ΔF is “ΔF X If it is greater than P ER (t) is expressed by the following equation (10), and the frequency deviation ΔF is "-ΔF X If it is smaller than P ER (t) is expressed by the following equation (11): K ERis an equivalent frequency characteristic coefficient when a plurality of renewable energy power sources ER are regarded as one renewable energy power source, and is stored in advance in the memory of the power system stabilization device 15.

[0111]

number

[0112] Therefore, when equations (8) and (10) are used in equation (7), the frequency deviation ΔF becomes "ΔF X Equivalent load frequency characteristic coefficient K when it is larger than LE is expressed as the following equation (12).

[0113]

number

[0114] Similarly, when equations (8) and (11) are used in equation (7), the frequency deviation ΔF becomes "-ΔF X Equivalent load frequency characteristic coefficient K when it is smaller than LE is expressed as the following equation (13).

[0115]

number

[0116] Equivalent load frequency characteristic coefficient K calculated using equations (9), (12), and (13) LE By using the following equation (14), which is a transformation of equation (4), the appropriate total output value P E (t2) is calculated. LE (t1) is the K calculated when ΔF in equations (12) and (13) is replaced with "ΔF(t1)". LE In equation (14), K LE (t2) is the K calculated when ΔF in equations (12) and (13) is replaced with "ΔF(t2)".LE is.

[0117]

number

[0118] "P" in equation (5) LCS " to "P LECS " is replaced with the total output value P obtained by equation (14). E By applying (t2), the equivalent load control amount P required to keep the system frequency within the target frequency range after the generator trips is LECS can be obtained.

[0119] <Generator control variable setting process> The flow of the process of setting the generator control amount when a system disturbance occurs (for example, when an equivalent load drops) is basically the same as the process flow described in the <Generator control amount setting process> of the first embodiment. First, in the process of setting the generator control amount, the process flow of equations (1) to (3) is the same. Next, the equivalent load frequency characteristic coefficient K LE Calculation method and total output value P E Similarly, equation (14) is used to calculate (t2).

[0120] Therefore, the total output value P obtained by equation (14) E By applying (t2) to equation (6), the generator control amount P required to keep the system frequency within the target frequency range after the equivalent load drop (for example, after the equivalent load LEx drop) is calculated. GCS can be obtained.

[0121] <Functional configuration> Fig. 9 is a block diagram showing an example of a functional configuration of a power system stabilizing device according to the second embodiment. Referring to Fig. 9, the power system stabilizing device 15 according to the second embodiment corresponds to a configuration in which a coefficient calculation unit 209 is added to the power system stabilizing device 15 according to the first embodiment. The functions of the information receiving unit 201 and the frequency predicting unit 203 are similar to the functions described in Fig. 5.

[0122] The coefficient calculation unit 209 receives input of measurement information and setting information, and calculates an equivalent load frequency characteristic coefficient K LE The setting information is the reference frequency Fn, the frequency characteristic coefficient K G ,K L ,K ER Specifically, the coefficient calculation unit 209 calculates the total load amount P of the plurality of loads L at an initial point in time before the first timing. L0 and the total output value P of multiple renewable energy sources ER ER0 and the load frequency characteristic coefficient K L Based on the equivalent load frequency characteristic coefficient K LE The initial time point is a time point before the system disturbance occurs, for example, a time point before the generator GAx drops out of the power system 120, or a time point before the equivalent load LEx drops out of the power system 120.

[0123] In a certain situation, the total output value P ER does not have a frequency characteristic, the coefficient calculation unit 209 calculates the equivalent load frequency characteristic coefficient K LE Or, the output total value P ER If the frequency deviation ΔF is within the reference range (for example, -ΔF X ≦ΔF≦ΔF X ), the coefficient calculation unit 209 calculates the equivalent load frequency characteristic coefficient K LE Calculate the following.

[0124] In another aspect, the coefficient calculation unit 209 calculates the total load value P L0 and the total output value P ER0 and the load frequency characteristic coefficient K L and the frequency characteristic coefficient K for multiple renewable energy sources ER ER Based on the frequency deviation ΔF and the reference range, the equivalent load frequency characteristic coefficient K LE Calculate the following.

[0125] Specifically, the frequency deviation ΔF is the upper limit of the reference range, ΔF X", the coefficient calculation unit 209 calculates the equivalent load frequency characteristic coefficient K LE The frequency deviation ΔF is calculated when the frequency deviation ΔF is the lower limit of the reference range "-ΔF X ", the coefficient calculation unit 209 calculates the equivalent load frequency characteristic coefficient K LE Calculate the following.

[0126] The control variable setting unit 205 determines the system frequency F(t1), the system frequency F(t2), and the total output value P E (t1) and the equivalent load frequency characteristic coefficient K LE Based on this, the total output value P E For example, the control amount setting unit 205 calculates the total output value P E Calculate (t2).

[0127] The command transmitting unit 207 transmits a command signal to the load control terminal device 20 to disconnect a load corresponding to the set equivalent load control amount from the power grid 120. The command transmitting unit 207 may also transmit a command signal to the load control terminal device 20 to instruct a renewable energy power source corresponding to the set equivalent load control amount to perform a discharge operation. Furthermore, the command transmitting unit 207 may select a load and a renewable energy power source corresponding to the equivalent load control amount, and transmit a command signal to the corresponding load control terminal device 20 to disconnect the load and cause the renewable energy power source to perform a discharge operation.

[0128] In another aspect, the command transmitting unit 207 transmits to the fault detection terminal device 10 a command signal for disconnecting the generator corresponding to the set generator control amount from the power grid 120 .

[0129] Other embodiments. (1) In the above-described embodiment, the power system stabilizing device 15 is configured to receive various pieces of information from the fault detection terminal device 10 and the load control terminal device 20, but is not limited to this configuration. For example, the power system stabilizing device 15 may be configured to store the various pieces of information received from the fault detection terminal device 10 and the load control terminal device 20 in a memory in advance, and to execute the above-described frequency prediction process by using simulation software that can appropriately change the various pieces of information.

[0130] (2) The configurations exemplified as the above-described embodiments are merely examples of the configurations of the present invention, and may be combined with other known technologies, or may be modified, such as by omitting some parts, without departing from the spirit of the present invention. Furthermore, the above-described embodiments may be implemented by appropriately adopting the processes and configurations described in other embodiments.

[0131] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0132] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) 1. A power system stabilization device for a power system to which a plurality of generators and a plurality of loads are connected, the power system stabilization device comprising: a frequency prediction unit that predicts a system frequency of the power system; and a controlled variable setting unit that sets a controlled variable to be disconnected from the power system, wherein the frequency prediction unit predicts a second system frequency at a second timing after a specified time has elapsed from a first timing based on a first system frequency at the first timing; the controlled variable setting unit calculates a first total mechanical input value to the plurality of generators at the first timing based on a first total output value of the plurality of generators at the first timing and an equation of motion of the plurality of generators; calculates a second total output value of the plurality of generators at the second timing based on the first system frequency, the second system frequency, the first total output value, and a load frequency characteristic coefficient for the plurality of loads; and sets the controlled variable based on a second total mechanical input value to the plurality of generators at the second timing that is estimated from the first total mechanical input value and the second total output value.

[0133] (Appendix 2) 2. The power system stabilization device according to claim 1, wherein, when the second power system frequency is less than a first threshold, the controlled variable setting unit executes a series of processes including a first process of calculating the first mechanical input sum value, a second process of calculating the second output sum value, and a third process of setting the controlled variable, and the controlled variable is a load controlled variable to be disconnected from the power system.

[0134] (Appendix 3) 3. The power system stabilization device according to claim 2, wherein the specified time is equal to or longer than the time from the start of the series of processes to the time when the load corresponding to the load control amount is disconnected from the power system.

[0135] (Appendix 4) the control variable setting unit executes a series of processes including a first process of calculating the first mechanical input sum value, a second process of calculating the second mechanical output sum value, and a third process of setting the control variable when the second system frequency is greater than a second threshold value, and the control variable is a generator control variable to be disconnected from the power system.

[0136] (Appendix 5) 5. The power system stabilization device according to claim 4, wherein the specified time is equal to or longer than the time from the start of the series of processes to the time when the generator corresponding to the generator control amount is disconnected from the power system.

[0137] (Appendix 6) 6. The power system stabilizing device according to any one of Supplementary notes 1 to 5, wherein the first mechanical input total value and the second mechanical input total value are equal.

[0138] (Appendix 7) The deviation between the reference frequency of the power system and the first system frequency is ΔF(t1), and the deviation between the reference frequency and the second system frequency is ΔF EST (t2), the load frequency characteristic coefficient is K L , the first output sum value P E (t1), the second output sum is P E 7. The system stabilization device according to any one of Supplementary Note 1 to Supplementary Note 6, wherein when (t2), the controlled variable setting unit calculates the second output total value using the above formula (4).

[0139] (Appendix 8) 8. The power grid stabilization device according to any one of Supplementary note 1 to Supplementary note 7, wherein a plurality of renewable energy power sources are further connected to the power grid, and the system further comprises a coefficient calculation unit that calculates an equivalent load frequency characteristic coefficient for an equivalent load that is a combination of the plurality of loads and the plurality of renewable energy power sources, wherein the coefficient calculation unit calculates the equivalent load frequency characteristic coefficient based on a total load value of the plurality of loads and a total output value of the plurality of renewable energy power sources at an initial point in time before the first timing, and the load frequency characteristic coefficient, and the controlled variable setting unit calculates the second output total value based on the first system frequency and the second system frequency, the first output total value, and the equivalent load frequency characteristic coefficient.

[0140] (Appendix 9) When the total output value of the plurality of renewable energy power sources does not have frequency characteristics, the load frequency characteristic coefficient is set to KL 9. The system stabilization device according to claim 8, wherein, when

[0141] (Appendix 10) The power grid stabilization device according to Appendix 8, wherein the total output value of the plurality of renewable energy power sources does not have frequency characteristics when a frequency deviation between a reference frequency of the power grid and the first system frequency is within a reference range, and has frequency characteristics when the frequency deviation is outside the reference range, and the coefficient calculation unit calculates the equivalent load frequency characteristic coefficient based on the total load value and the total output value at the initial point in time, the load frequency characteristic coefficient, frequency characteristic coefficients for the plurality of renewable energy power sources, the frequency deviation, and the reference range.

[0142] (Appendix 11) The load frequency characteristic coefficient is K L , the frequency characteristic coefficients for the plurality of renewable energy power sources are K ER , the upper limit of the reference range is ΔF X When the frequency deviation is greater than the upper limit of the reference range, the coefficient calculation unit calculates the equivalent load frequency characteristic coefficient using the above formula (12) and sets the lower limit of the reference range to -ΔF X and when the frequency deviation is smaller than a lower limit value of the reference range, the coefficient calculation unit calculates the equivalent load frequency characteristic coefficient by using the above formula (13). [Explanation of symbols]

[0143] 21, 22, 2n load control terminal device, 10 fault detection terminal device, 15 system stabilization device, 32 auxiliary transformer, 35 A / D conversion unit, 40 calculation processing unit, 41 CPU, 44 bus, 50 communication circuit, 55 digital output circuit, 56 digital input circuit, 80 transmission line, 100 power plant, 120 power system, 201 information receiving unit, 203 frequency prediction unit, 205 control quantity setting unit, 207 command transmission unit, 209 coefficient calculation unit, 1000, 1000A system stabilization system.

Claims

1. A system stabilization device for a power system to which a plurality of generators and a plurality of loads are connected, a frequency prediction unit that predicts a system frequency of the power system; a control amount setting unit that sets a control amount to be disconnected from the power grid, the frequency predicting unit predicts a second system frequency at a second timing after a specified time has elapsed from the first timing, based on the first system frequency at the first timing; The control amount setting unit calculating a first total mechanical input value to the plurality of generators at the first timing based on a first total output value of the plurality of generators at the first timing and an equation of motion of the plurality of generators; calculating a second output sum of the plurality of generators at the second timing based on the first system frequency, the second system frequency, the first output sum, and load frequency characteristic coefficients for the plurality of loads; a power system stabilization device that sets the controlled variable based on a second sum of mechanical inputs to the plurality of generators at the second timing, the second sum of outputs being estimated from the first sum of mechanical inputs.

2. when the second system frequency is less than a first threshold value, the controlled variable setting unit executes a series of processes including a first process of calculating the first mechanical input sum value, a second process of calculating the second mechanical output sum value, and a third process of setting the controlled variable; The grid stabilization device according to claim 1 , wherein the controlled variable is a load controlled variable that is disconnected from the power grid.

3. The power system stabilization device according to claim 2 , wherein the specified time is equal to or longer than the time from the start of the series of processes until the load corresponding to the load control amount is disconnected from the power system.

4. when the second system frequency is greater than a second threshold value, the controlled variable setting unit executes a series of processes including a first process of calculating the first mechanical input sum value, a second process of calculating the second mechanical output sum value, and a third process of setting the controlled variable; The grid stabilization device according to claim 1 , wherein the controlled variable is a generator controlled variable for disconnecting from the power grid.

5. 5. The system stabilization device according to claim 4, wherein the specified time is equal to or longer than the time from the start of the series of processes until the generator corresponding to the generator control amount is disconnected from the power system.

6. The power system stabilizing device according to any one of claims 1 to 5, wherein the first mechanical input sum value and the second mechanical input sum value are equal.

7. The deviation between the reference frequency of the power system and the first system frequency is ΔF(t1), and the deviation between the reference frequency and the second system frequency is ΔF ＥＳＴ (t2), the load frequency characteristic coefficient is K Ｌ , the first output sum value P Ｅ (t1), the second output sum value P Ｅ (t2), the control amount setting unit calculates the second output total value using the following equation (1): [Equation 1] The system stabilization device according to any one of claims 1 to 5.

8. a plurality of renewable energy power sources are further connected to the power grid; Further provided is a coefficient calculation unit that calculates an equivalent load frequency characteristic coefficient for an equivalent load that combines the plurality of loads and the plurality of renewable energy power sources, The coefficient calculation unit calculates the equivalent load frequency characteristic coefficient based on a total load amount value of the plurality of loads and a total output value of the plurality of renewable energy power sources at an initial point in time before the first timing, and the load frequency characteristic coefficient; 6. The system stabilization device according to claim 1, wherein the control variable setting unit calculates the second total output value based on the first system frequency, the second system frequency, the first total output value, and the equivalent load frequency characteristic coefficient.

9. When the total output value of the plurality of renewable energy power sources does not have frequency characteristics, the load frequency characteristic coefficient is set to K Ｌ When the above equation is satisfied, the coefficient calculation unit calculates the equivalent load frequency characteristic coefficient using the following equation (2): [Equation 2] The power system stabilization device according to claim 8.

10. The output total value of the plurality of renewable energy power sources does not have frequency characteristics when a frequency deviation between a reference frequency of the power grid and the first system frequency is within a reference range, and has frequency characteristics when the frequency deviation is outside the reference range; The coefficient calculation unit 9. The system stabilization device according to claim 8, wherein the equivalent load frequency characteristic coefficient is calculated based on the load total value and the output total value at the initial point in time, the load frequency characteristic coefficient, frequency characteristic coefficients for the plurality of renewable energy power sources, the frequency deviation, and the reference range.

11. The load frequency characteristic coefficient is K Ｌ , the frequency characteristic coefficients for the plurality of renewable energy power sources are K ＥＲ , the upper limit of the reference range is ΔF Ｘ When the frequency deviation is greater than the upper limit of the reference range, the coefficient calculation unit calculates the equivalent load frequency characteristic coefficient by using the following equation (3): [Equation 3] The lower limit of the reference range is set to -ΔF Ｘ When the frequency deviation is smaller than the lower limit of the reference range, the coefficient calculation unit calculates the equivalent load frequency characteristic coefficient by using the following equation (4): [Equation 4] The power system stabilization device according to claim 10.

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