JP7450504B2 - Grid stabilization system and grid stabilization method - Google Patents

Description

The present disclosure relates to a grid stabilization system and a grid stabilization method that stabilize the frequency of a power grid.

When a power trip or a drop in power output occurs within a power system, the frequency of the power system decreases. If the frequency drops significantly, a chain reaction of power outages may occur, leading to a major power outage. Therefore, when an accident such as a power supply trip or a drop in power supply output occurs, it is necessary to perform control such as a necessary amount of load shedding (hereinafter also referred to as negative control) or system separation. The grid stabilization system is a system that prevents major power outages in the event of an accident such as the one described above.

One of the calculation methods applied in the grid stabilization system is a pre-calculation method. In the pre-calculation method, simulation calculations are performed using a power system model assuming accident patterns and power flow patterns in advance so that various accidents can be handled. When the grid stabilization system detects the occurrence of an accident, it executes control such as generator cutoff (also referred to as electric control) or negative control by referring to the results of simulation calculations.

Pre-computation methods are classified into online pre-computation type and offline pre-computation type, depending on the data used for the calculation. In the online pre-calculation type, online information such as system configuration and power flow status is collected and reflected in the calculation. In the offline pre-calculation type, simulations are performed for various assumed system states and power flow states.

In the case of the online pre-calculation type, it is necessary to construct a system that has the computing power to run simulations using online information for the expected number of accident cases within a certain period of time. Therefore, there is a problem in that the system introduction cost and the maintenance cost after the start of operation increase.

In the case of the off-line pre-calculation type, there is no need to perform simulation in the system stabilization system, so the required calculation capacity is limited. Therefore, it is possible to construct a maintenance-free system using the same hardware as the protective relay device, and the cost at the time of system installation and maintenance cost after the start of operation is lower than that of the online pre-calculation type. However, on the other hand, if an accident occurs in a power flow state that was not anticipated during the preliminary calculation, there is a risk that appropriate control may not be implemented.

Japanese Unexamined Patent Publication No. 2011-19362 (Patent Document 1) discloses an example of an online pre-computation type system stabilization system. The system stabilization system in this document uses online simulation to calculate the amount of output increase (spinning reserve) possible through governor-free control of the generator when the frequency drops after an accident, and uses this to stabilize the frequency. The required control amount is calculated.

Japanese Patent Application Publication No. 2011-19362

The system stabilization system described in the above-mentioned Japanese Patent Application Publication No. 2011-19362 (Patent Document 1) takes into account the dynamic characteristics of the generator control system by using online simulation results in calculating the required control amount. This does not take into account uncertain factors based on the dynamic characteristics of the load. Examples of load uncertainties include load shedding due to an under frequency relay (UFR). Furthermore, in the case of power systems that include renewable energy power sources, uncertain factors due to their omissions are not taken into account. Furthermore, since online simulation results are not taken into account in determining whether control is necessary, control by the grid stabilization system may be performed even though it is not originally necessary.

The present disclosure has been made in consideration of the above background and issues, and in one aspect, the purpose is to provide system stabilization that realizes appropriate frequency stabilization control that takes into account the dynamic characteristics of the power system with less computational resources. The goal is to provide a system.

In one embodiment, a grid stabilization system is provided that stabilizes the frequency of a power grid. The central processing unit includes a pre-calculation section and a control execution section. The pre-calculation unit performs simulations based on online data representing the state of the power system and a simulation model that simulates the power system, in response to multiple accident cases in which at least one generator included in the power system is assumed to fall off. Execute. The simulation model consists of an inertial model that simulates the rotor dynamic characteristics of a synchronous generator included in the power system using one mass point and calculates frequency deviation based on the imbalance between supply and demand, and an inertial model that simulates the rotor dynamic characteristics of a synchronous generator included in the power system using one mass point and calculates frequency deviation based on the imbalance between supply and demand. It includes a load model simulated by , and a synchronous machine model that simulates a synchronous generator in a power system. When an accident occurs in the power system, the control execution unit should shut down the power system so that the frequency does not fall below the first threshold frequency, based on a comparison between the actual phenomenon of the power system and the simulation results for each accident case. Determine at least one load or transmission line.

According to the grid stabilization system of the above embodiment, dynamic characteristics of the power grid are taken into account by performing preliminary calculations based on online data and a simple simulation model including a synchronous machine model, a load model, and an inertial model. Appropriate frequency stabilization control can be achieved with less computational resources.

1 is a diagram conceptually illustrating a configuration of a power system envisioned according to the present disclosure. 2 is a block diagram showing an example of the hardware configuration of each terminal device and central processing unit in FIG. 1. FIG. FIG. 2 is a block diagram showing an example of the functional configuration of the central processing unit in FIG. 1. FIG. FIG. 2 is a block diagram showing an example of the configuration of a simulation model. FIG. 2 is a block diagram showing an example of the configuration of a synchronous machine model. FIG. 2 is a block diagram showing an example of the configuration of a DC interconnection model. FIG. 2 is a block diagram illustrating an example of a renewable energy power source model. FIG. 2 is a block diagram showing an example of a load model. It is a flowchart which shows an example of the procedure of frequency control of an electric power system by a system stabilization system. 10 is a flowchart showing the procedure of step S10 in FIG. 9 in detail. 10 is a flowchart showing the procedure of step S20 in FIG. 9 in detail. It is a figure which shows an example of a control table. 12 is a flowchart illustrating an example of a procedure for frequency control of an electric power system by the system stabilizing system according to the second embodiment.

Each embodiment will be described in detail below with reference to the drawings. In addition, the same reference numerals are given to the same or corresponding parts, and the description thereof will not be repeated.

Embodiment 1.
[Conceptual diagram of power system]
FIG. 1 is a diagram conceptually showing the configuration of a power system envisioned by the present disclosure. Referring to FIG. 1, a power system 10 (10A, 10B) includes a plurality of generators 21, one or more power converters 22 connected to a DC system, a plurality of loads 23, and a power transmission line 25. , 26, 29, 34, and a distribution line 35. Power system 10 includes two power systems 10A and 10B connected via power transmission line 38. A circuit breaker 39 is provided on the power transmission line 38 .

In the case of FIG. 1, the power transmission line 25 connects each generator 21 and the interconnection line 27 (27A, 27B), and the power transmission line 34 connects between the power conversion device 22 and the interconnection line 27A. Further, the power transmission line 26 connects the interconnection line 27 and the primary substation 14, and the power transmission line 29 connects the interconnection line 27 and the secondary substation 15. Distribution line 35 connects between secondary substation 15 and load 23 . Each load 23 includes a renewable energy power source along with the individual load.

The power system 10 further includes a transformer 30 and a circuit breaker 32 provided between the generator 21 and the power transmission line 25, and a transformer 36 and circuit breaker provided between the power converter 22 and the power transmission line 34. 37, a plurality of bus bars 28, a plurality of transformers 31, and a plurality of circuit breakers 33 provided in each of the primary substation 14 and the secondary substation 15.

The central power supply control center 59 controls the output of each generator 21 by outputting a command value to each generator 21 . The frequency control of the power system 10 performed by the central power dispatch center 59 includes economic load dispatching control (EDC) to cope with slow load changes such as daily load fluctuations, and relatively short period control. Load Frequency Control (LFC) is used to deal with unpredictable load changes that occur. In EDC, the generator 21 with high fuel efficiency is preferentially operated based on predictions of load changes. In LFC, there is a delay of several tens of seconds until the output of the generator changes.

The grid stabilization system 1 stabilizes the frequency of the power grid 10 in response to a frequency drop when an accident occurs such as the generator 21 of the power grid 10 falling off or a decrease in output. Such a frequency drop can be dealt with to some extent by the governor free control provided for each generator 21 and the UFRs 18_1 to 18_3 provided at the substation. However, these methods have limitations because they are controlled using only local information. The grid stabilization system 1 realizes optimal control that reflects the overall state of the power grid 10.

Specifically, as shown in FIG. 1, the grid stabilization system 1 includes a plurality of terminal devices 40 (40_1 to 40_7) and a central processing unit 50. Each terminal device 40 and the central processing unit 50 are connected via a wired or wireless communication path 58.

Each terminal device 40 detects voltage and current (hereinafter collectively referred to as electrical quantity) via a voltage transformer VT and a current transformer CT provided in the power system 10. Each terminal device 40 further detects the occurrence of an accident based on the detected amount of electricity or the open/closed state of the circuit breaker. Each terminal device 40 further outputs a trip signal to the corresponding circuit breaker 32, 33, or 37 according to a command from the central processing unit 50.

Specifically, in the case of FIG. 1, terminal devices 40_1, 40_2 corresponding to each generator 21, terminal device 40_3 corresponding to the power conversion device 22, terminal devices 40_4 to 40_6 corresponding to each primary substation 14, A terminal device 40_7 corresponding to the circuit breaker 39 provided on the power transmission line 38 between the systems 10A and 10B is provided.

Each of the terminal devices 40_1, 40_2 detects the output voltage and output current of the corresponding generator 21, and outputs a trip signal to the corresponding circuit breaker 32 to connect the corresponding generator 21 to the power system 10 (10A , 10B).

The terminal device 40_3 detects the voltage and current input to or output from the power conversion device 22, and outputs a trip signal to the corresponding circuit breaker 37 to connect the power system 10A to the DC interconnection equipment. A certain power conversion device 22 is separated.

Each of the terminal devices 40_4 to 40_6 detects voltage and current via a voltage transformer VT and a current transformer CT provided in the corresponding primary substation 14. Furthermore, each of the terminal devices 40_4 to 40_6 disconnects the corresponding power transmission line 29 by outputting a trip signal to the corresponding circuit breaker 33.

The terminal device 40_7 separates the power system 10A and the power system 10B by outputting a trip signal to the corresponding circuit breaker 39.

Each of the UFRs 38_1 to UFR_3 detects voltage via a voltage transformer VT provided in the corresponding secondary substation 15, and calculates the system frequency from time series data of the detected voltage. Further, each of the UFRs 38_1 to UFR_3 isolates the corresponding load 23 from the power system 10 by outputting a trip signal to the corresponding circuit breaker 33 when the calculated frequency is lower than the threshold frequency. Note that when the load 23 includes the renewable energy power source 24, the renewable energy power source 24 is also separated from the power system 10.

The central processing unit 50 performs frequency stabilization control of the power system 10 using an online pre-calculation method based on online data acquired from the central power dispatch center 59. The central processing unit 50 monitors the state of the power grid 10 based on the amount of electricity in the power grid 10 detected by each terminal device 40, and determines whether to start stabilization control. When performing stabilization control, the central processing unit 50 determines whether at least one load 23, power transmission line 29, or power system 10A should be cut off, based on a comparison between a prior simulation result and an actual phenomenon in the power system 10. , 10B, and the like is determined.

[Example of hardware configuration of terminal device and central processing unit]
FIG. 2 is a block diagram showing an example of the hardware configuration of each terminal device and central processing unit in FIG. 1.

(1. Example of hardware configuration of terminal device)
Referring to FIG. 2, the terminal device 40 includes input conversion auxiliary transformers 41_1, 41_2, ... (generally referred to as auxiliary transformers 41), and analog filters (AF) 42_1, 42_2. , ... (generally referred to as analog filter 42), A/D converter 43, processing circuit 44, communication circuit 45, digital output (DO) circuit 46, digital input (DI: (Digital Input) circuit 47. The auxiliary transformer 41 is also referred to as an input transformer.

The terminal device 40 is provided with a plurality of channels in order to receive the current signal of each phase output from the corresponding current transformer CT and the voltage signal of each phase output from the corresponding voltage transformer VT. There is. A current signal of each phase and a current signal of each phase are respectively inputted to each channel from the corresponding current transformer CT. In FIG. 2, only two channels are typically shown.

Auxiliary transformers 41 (41_1, 41_2, . . . ) are provided for each channel. Each auxiliary transformer 41 receives a current signal from a current transformer CT or a voltage signal from a voltage transformer VT, and processes the received voltage signal or current signal in an A/D converter 43 and a processing circuit 44. Converts the signal to a voltage level suitable for the

The analog filters 42 (42_1, 42_2, . . . ) are provided for each channel, corresponding to the plurality of auxiliary transformers 41, respectively. Each analog filter 42 is, for example, a low-pass filter that cuts high frequencies of the current signal or voltage signal of the corresponding channel. Analog filter 42 is provided to remove aliasing errors during A/D conversion.

The A/D converter 43 converts the analog current signal or voltage signal output from each analog filter 42 into a digital value. The A/D converter 43 may include a sample and hold circuit (not shown) and a multiplexer (not shown) for each channel. In this case, the multiplexer sequentially selects the electrical quantity signals held in the sample and hold circuit, and the A/D converter 43 A/D converts the signals selected by the multiplexer.

In this embodiment, the processing circuit 44 is configured as a microcomputer including at least one CPU (Central Processing Unit), at least one RAM (Random Access Memory), and at least one nonvolatile memory. . In this case, the CPU implements the desired functions according to the control program stored in the nonvolatile memory. The control program may be provided as a non-temporary storage medium or via a network.

Note that the processing circuit 44 may be configured as at least one FPGA (Field Programmable Gate Array), or may be configured as a dedicated circuit such as at least one ASIC (Application Specific Integrated Circuit). Alternatively, the processing circuit 44 may be configured by any combination of a CPU, FGPA, and ASIC.

The communication circuit 45 transmits and receives data to and from the communication circuit 51 of the central processing unit 50 via the communication path 58 .

The digital output circuit 46 is an interface circuit for outputting digital signals to external equipment. For example, the digital output circuit 46 outputs a trip signal to the corresponding circuit breaker 32 or 33 according to instructions from the processing circuit 44 .

The digital input circuit 47 is an interface circuit for receiving digital signal input from external equipment. For example, the digital input circuit 47 receives information from the circuit breaker 32 or 33 or 39 regarding the open/closed state of the contacts of the circuit breaker.

The processing circuit 44 further outputs a digital output so as to output a trip signal to the circuit breaker 32 or 33 when receiving a command to open the circuit breaker 32 or 33 from the central processing unit 50 via the communication circuit 45. command circuit 46. The digital output circuit 46 outputs a trip signal to the corresponding circuit breaker 32 or 33 according to a command from the processing circuit 44 .

(2. Example of hardware configuration of central processing unit)
Referring to FIG. 2, central processing unit 50 includes communication circuits 51 and 52, a processing circuit 53, and a storage device 54.

The communication circuit 51 transmits and receives data to and from the communication circuit 45 of the terminal device 40 via the communication path 58 . The communication circuit 52 receives information regarding the state of the power system 10 as online data from the central power dispatch center 59 .

In this embodiment, the processing circuit 53 is configured as a microcomputer including at least one CPU, at least one RAM, and at least one nonvolatile memory. In this case, the CPU executes processing according to the control program and simulation program stored in the nonvolatile memory and/or storage device 54. The control program and simulation program may be provided as a non-temporary storage medium or via a network.

Note that the processing circuit 53 may be configured as at least one FPGA or may be configured as at least one ASIC. Alternatively, the processing circuit 44 may be configured by any combination of a CPU, FGPA, and ASIC.

The processing circuit 53 performs a preliminary simulation based on online data representing the state of the power system 10 received from the central power dispatch center 59. The processing circuit 53 stores the simulation results in the storage device 54. Furthermore, the processing circuit 53 creates a control table that defines the objects to be controlled when an accident occurs based on the simulation results, and stores it in the storage device 54. When an accident occurs, the processing circuit 53 executes control for frequency stabilization according to the control table.

The storage device 54 is, for example, a hard disk, SSD (Solid State Drive), or other non-temporary non-volatile storage device.

[Functional configuration of central processing unit]
FIG. 3 is a block diagram showing an example of the functional configuration of the central processing unit shown in FIG. Referring to FIG. 3, the processing circuit 53 of the central processing unit 50 functions as a pre-computation section 60 that performs online pre-computation, and a control execution section 61 that executes frequency stabilization control based on the computation results of the pre-computation section 60. Function.

Specifically, the pre-calculation unit 60 determines whether at least one synchronized generator 21 included in the power system 10 has fallen off, based on online data 64 representing the state of the power system 10 and a simulation model 70 simulating the power system 10. Run simulations for multiple accident cases assuming When an accident occurs in the power system 10, the control execution unit 61 determines whether the frequency of the power system 10 is a first threshold frequency (hereinafter referred to as an allowable minimum frequency) based on a comparison between the actual phenomenon of the power system 10 and the simulation results for each accident case. At least one load 23 or transmission line 29 to be disconnected is determined such that the frequency does not fall below the frequency (referred to as frequency).

Here, the simulation model 70 includes an inertial model that simulates the rotor dynamic characteristics of the plurality of synchronous generators 21 included in the power system 10 using one mass point and calculates a frequency deviation based on the imbalance between supply and demand, and The feature is that it is a simple model that includes a load model that simulates a plurality of loads 23 included in one load, and a synchronous machine model that simulates the plant dynamic characteristics of a plurality of synchronous generators 21. The simulation model 70 further includes a renewable energy power source model that simulates a plurality of renewable energy power sources included in an electric power system using one power source, and a DC power source model that simulates a plurality of facilities interconnected with at least one DC system. It may also include a grid interconnection model.

Analysis of synchronization stability to prevent synchronization of multiple synchronous generators requires consideration of system voltage behavior and uneven distribution of loads. Therefore, it is necessary to perform simulations using a detailed electric circuit model that takes into account the network configuration of the power system. In contrast, in the case of the central processing unit 50 of the present disclosure, the function is limited to analysis of frequency stability, particularly analysis of frequency drop due to disconnection of the generator or reduction in output. Therefore, sufficient accuracy can be obtained by simulation using a simple model that simulates only the frequency response. As a result, computational resources can be reduced. Details of the simulation model 70 will be described later with reference to FIGS. 4 to 8.

Hereinafter, an outline of the frequency stabilization control procedure by the pre-calculation unit 60 and the control execution unit 61 will be explained. Details will be described later with reference to FIGS. 9 to 12.

First, the online data 64 includes the total output of the synchronous generators 21 included in the power system 10 , the total demand of the loads 23 included in the power system 10 , and the total demand of the multiple renewable energy power sources 24 included in the power system 10 . It includes the total output and the total output of a plurality of DC interconnection equipment (such as the power converter 22) interconnected with at least one DC system. The preliminary calculation unit 60 acquires these online data 64 from the central power dispatch center 59. The central processing unit 50 may obtain the online data 64 directly from the central power dispatch center 59, or may obtain the online data 64 through another device. Alternatively, the central processing unit 50 may calculate the above-mentioned total output and total demand based on information acquired from each terminal device 40 individually.

The pre-calculation unit 60 calculates the frequency change rate when the frequency of the power system decreases to a second threshold frequency (hereinafter also referred to as start-up determination frequency) higher than the above-mentioned minimum allowable frequency, the minimum frequency of the power system 10, etc. , are stored in the storage device 54 as simulation results 62. Then, for a plurality of specific accident cases in which the lowest frequency is lower than the allowable minimum frequency among the plurality of accident cases, the pre-calculation unit 60 determines the amount of load that should be reduced so that the frequency of the power system does not fall below the allowable minimum frequency. Determine. For this purpose, the pre-calculation unit 60 executes a new simulation multiple times using the load amount to be reduced as a variable for each specific accident case. In this disclosure, a specific accident case is referred to as a startup accident case, and the amount of load to be reduced is referred to as a control amount.

The pre-calculation unit 60 determines at least one load or power transmission line to be cut off as a control target based on the control amount determined for each startup accident case. Then, the pre-calculation unit 60 stores the correspondence between the plurality of startup accident cases and at least one controlled object in the storage device 54 as a control table 63.

When the frequency of the power system reaches the activation determination frequency due to the occurrence of an accident, the control execution unit 61 controls at least one terminal device corresponding to at least one control target based on the comparison with the simulation result 62 and the control table 63. A shutoff command is output to 40.

[Simulation model]
The configuration of the simulation model used in the present disclosure will be described in detail below with reference to FIGS. 4 to 8.

(1. Overall composition)
FIG. 4 is a block diagram showing an example of the configuration of a simulation model. The simulation model 70 in FIG. 4 is a simple model for use in analyzing the frequency dynamic characteristics of the power system.

Referring to FIG. 4, the simulation model 70 includes a synchronous machine model 100, a DC interconnection model 110, a renewable energy power source model 120, a load model 130, an inertia model 80, an adder 71, and a multiplier. 72, a subtracter 73, a threshold determination section 74, and a load frequency characteristic model 75. Since the simulation time is a maximum of several tens of seconds, the LFC model and EDC model, which have a small influence, are not included in the simulation model 70, but they may be included in the simulation model 70.

The synchronous machine model 100 simulates the plant dynamic characteristics of a synchronous generator such as a thermal power plant, a nuclear power plant, a hydroelectric power plant, and the like. A more detailed configuration of the synchronous machine model 100 will be described later with reference to FIG.

The DC interconnection model 110 simulates the dynamic characteristics of DC interconnection equipment provided in the target power system 10. Examples of DC interconnection equipment include frequency conversion stations (FC), HVDC (High Voltage Direct Current), and BTB (Back-To-Back). A more detailed configuration of the DC interconnection model 110 will be described later with reference to FIG. 6.

The renewable energy power source model 120 simulates the dynamic characteristics of renewable energy power sources such as solar power generation, wind power generation, and biomass power generation. A more detailed configuration of the renewable energy power source model 120 will be described later with reference to FIG. 7.

The load model 130 simulates the dynamic characteristics of a general load. A more detailed configuration of the load model 130 will be described later with reference to FIG. 8.

Adder 71 adds each output of synchronous machine model 100, DC interconnection model 110, and renewable energy power source model 120. Thereby, the adder 71 outputs the total power supplied to the power system 10.

The load frequency characteristic model 75 multiplies the frequency deviation u by a constant K _L representing the frequency characteristic of the load, thereby outputting a rate of change in load consumption (1+K _L ×u) according to frequency fluctuation. Note that the load frequency characteristic model 75 may not be included in the simulation model 70.

The multiplier 72 multiplies the output of the load model 130 by a rate of change (1+K _L ×u) according to the frequency fluctuation output from the load frequency characteristic model 75. As a result, the load power consumption is calculated in consideration of the self-controllability of the load according to frequency fluctuations.

The subtracter 73 calculates the supply-demand imbalance ΔP by subtracting the output of the multiplier 72 from the output of the adder 71.

The inertia model 80 simulates the inertia of the power system 10 based on the sum M of unit inertia constants of the generators. The total of unit inertia constants M takes into account the fall of the generator due to an accident. Specifically, the inertial model 80 includes dividers 81 and 82, an integrator 83, an adder 84, and a constant multiplier 85.

The divider 81 calculates the torque deviation ΔT by dividing the supply and demand imbalance ΔP by the angular velocity ω. The angular velocity ω is a value expressed in unit system. The adder 84 calculates each velocity ω by adding 1 to the angular velocity deviation Δω.

The divider 82 divides the torque deviation ΔT by the sum M of unit inertia constants, and the integrator 83 integrates the result of the division by the divider 82. As a result, the angular velocity deviation Δω is calculated. Note that the angular velocity deviation Δω expressed in the unit method is equal to the frequency deviation ΔF expressed in the unit method. The constant multiplier 85 calculates the frequency deviation u at the rated frequency of 50 Hz by multiplying the frequency deviation ΔF expressed in the unit method by 50.

The threshold determination unit 74 determines whether the estimated frequency (50-u) is smaller than the lowest allowable frequency.

(2. Synchronous machine model)
FIG. 5 is a block diagram showing an example of the configuration of a synchronous machine model. In the synchronous machine model 100 of FIG. 5, only governor free control is modeled. Specifically, in the example of FIG. 5, the synchronous machine model 100 includes a subtracter 103, an adder 104, and a governor free model 105.

A subtracter 103 subtracts the amount of power lost 102 in a hypothetical accident case from the total output 101 of the synchronous generator acquired as online data. Thereby, the subtractor 103 calculates the total power supplied from the synchronous generator to the power system 10 in the hypothetical accident case.

The governor free model 105 adjusts the output of the synchronous generator according to the frequency deviation u so that the rotational speed of the synchronous generator is kept constant. The governor free model may be a first-order lag model, a more detailed model, or a more simplified model.

The adder 104 calculates the output 107 of the synchronous machine model 100 by adding the control amount by the governor free control to the total power supplied from the synchronous generator to the power system 10 in a hypothetical accident case.

Note that a plant model that closely simulates the dynamic characteristics of a power generation plant may be used as the synchronous machine model.

(3. DC interconnection model)
FIG. 6 is a block diagram showing an example of the configuration of a DC interconnection model. The DC interconnection model 110 in FIG. 6 incorporates a frequency response model 112 of the DC interconnection equipment. The frequency response model 112 calculates the amount of change in the output of the DC interconnection equipment according to the frequency deviation u. The DC interconnection model 110 may be a model that models the dynamic characteristics of the DC interconnection equipment in more detail, or may be a more simplified model.

Specifically, in the example of FIG. 6, the DC interconnection model 110 includes the frequency response model 112 described above and an adder 113. The adder 113 calculates the output 114 of the DC interconnection model 110 according to the frequency deviation u by adding the output change amount by the frequency response model 112 to the total output 111 of the DC interconnection equipment acquired as online data. do.

(4. Renewable energy power source model)
FIG. 7 is a block diagram illustrating an example of a renewable energy power source model. The renewable energy power source model 120 in FIG. 7 incorporates a trip model 122 due to frequency drop. Trip model 122 separates some renewable energy power sources from power system 10 depending on frequency deviation u. The renewable energy power source model 120 may be a model that models the dynamic characteristics of the renewable energy power source in more detail, or may be a more simplified model.

Specifically, in the example of FIG. 7, the renewable energy power source model 120 includes the above-described trip model 122 and a subtractor 123. The subtractor 123 calculates the output 124 of the renewable energy power source model 120 according to the frequency deviation u by subtracting the amount of output reduction due to the trip model 122 from the total output 121 of the renewable energy power source acquired as online data. do.

(5. Load model)
FIG. 8 is a block diagram showing an example of a load model. The load model 130 in FIG. 8 incorporates a UFR model & load drop model 132 and a stabilization control model 133. The UFR model simulates each UFR element, and when the system frequency decreases, the load amount corresponding to the UFR element that operates according to the frequency deviation u is separated from the power system 10. In the load drop model, when the system frequency decreases, part of the load is dropped according to the frequency deviation u. The stabilization control model 133 simulates the dynamic characteristics of the grid stabilization system 1, and calculates the amount of reduction in power consumption of the load according to the frequency deviation u.

The load model 130 may be a more detailed model of the dynamic characteristics of the load, or may be a more simplified model. Furthermore, the characteristics of the UFR and the dynamic characteristics of the system stabilization system 1 may not be simulated by the load model 130, but may be incorporated into the simulation model 70 as separate models.

Specifically, in the example of FIG. 8, the load model 130 includes the above-mentioned UFR model & load drop model 132, a stabilization control model 133, and a subtracter 134. The subtractor 134 subtracts the amount of decrease in power consumption of the load by the UFR model & load drop model 132 and the amount of decrease in the power consumption of the load by the stabilization control model 133 from the total load amount 131 acquired as online data. , calculate the output 135 of the load model 130 according to the frequency deviation u.

Note that since the operation of the URF model and the operation of the load drop model are similar, the URF model will be treated as a representative in the following explanation.

[Operation of central processing unit]
Next, the control operation by the central processing unit 50 will be explained in detail with reference to FIGS. 9 to 12.

FIG. 9 is a flowchart illustrating an example of a procedure for frequency control of the power system by the central processing unit. In FIG. 9, steps S10 to S30 indicate procedures that are periodically executed before an accident occurs by the preliminary calculation unit 60 in FIG. The procedure executed in the case of YES in step S40 is shown below.

Referring to FIG. 9, in step S10, pre-calculation unit 60 executes a simulation for a plurality of assumed accident cases using simulation model 70 described in FIGS. 4 to 8. Note that the preliminary calculation unit 60 acquires online the total output amount and total load amount (also referred to as total demand amount) of all the generators 21 necessary for the simulation. The pre-calculation unit 60 stores the simulation result 62 in the storage device 54, and selects a plurality of startup accident cases requiring frequency stabilization control from among the plurality of assumed accident cases based on the simulation result 62.

Here, one or more generators 21 falling off is set in advance as each of the above assumed accident cases. It does not take into account that a plurality of power supplies are disconnected at different times, but only the case that negative power supplies are disconnected at the same time is considered.

FIG. 10 is a flowchart showing the procedure of step S10 in FIG. 9 in detail. Referring to FIG. 10, first in step S200, pre-calculation unit 60 sets parameters N and i. Specifically, the pre-calculation unit 60 assigns the total number of accident cases set in advance to the parameter N. The pre-calculation unit 60 assigns 1 as the initial value of the accident case number i.

In the next step S210, the preliminary calculation unit 60 executes a simulation using the simulation model 70 described in FIGS. 4 to 8 in the i-th accident case.

In the next step S220, the pre-calculation unit 60 records the simulation result 62. Specifically, the pre-calculation unit 60 records the operated UFR elements, the rate of change of the system frequency at the start-up determination frequency, the lowest frequency, and the like. Here, the start-up determination frequency refers to a threshold frequency for determining whether or not it is necessary to start frequency stabilization control by cutting off the load or separating the system when an accident such as a fall of the generator 21 occurs. If the frequency of power system 10 does not decrease to this threshold frequency, central processing unit 50 does not perform frequency stabilization control.

In the next step S230, the pre-calculation unit 60 determines whether the lowest frequency obtained as the simulation result 62 is lower than the allowable lowest frequency. Here, the allowable lowest frequency refers to a threshold frequency at which the power system 10 can maintain a stable state. If the frequency of the electric power system 10 falls below this threshold frequency, the power supply may fail in a chain reaction, leading to a major power outage.

If the lowest frequency is less than the allowable lowest frequency (YES in step S230), the pre-calculation unit 60 advances the process to step S240. In step S240, the preliminary calculation unit 60 stores the i-th accident case in the table as a case in which frequency stabilization control should be activated. On the other hand, if the lowest frequency is equal to or higher than the allowable lowest frequency (NO in step S230), the pre-calculation unit 60 does not execute step S240.

In the next step S250, if the accident case number i is smaller than the total number N of accident cases (YES in step S250), the pre-calculation unit 60 increments the accident case number i by 1 in the next step S258. Thereafter, the preliminary calculation unit 60 returns the process to step S210 and repeats steps S210 to S240 for the next accident case number i. On the other hand, if the accident case number i is equal to the total number N of accident cases (NO in step S250), the pre-calculation unit 60 ends the process.

Referring again to FIG. 9, in the next step S20, the pre-calculation unit 60 executes a simulation for various variables using the control amount, which is the amount of load reduction, as a variable for each of the selected startup accident cases. This determines the control amount necessary for the frequency of the power system 10 to exceed the allowable minimum frequency.

FIG. 11 is a flowchart showing the procedure of step S20 in FIG. 9 in detail. Referring to FIG. 11, first in step S300, pre-calculation unit 60 initializes each parameter.

Specifically, the pre-calculation unit 60 calculates the control amount step PLs [MW], the activation determination frequency FL [Hz], the minimum allowable frequency FBO [Hz], the control time TPL [s], and the ratio of the UFR introduction amount to the total demand amount. RUFR and the total number of startup accident cases Ntg are set. Furthermore, the preliminary calculation unit 60 sets the initial value of the start accident case number j to 1, and sets the initial value of the control amount change flag Flg to 0. Here, the control amount change flag Flg is set to 0 when executing the first simulation to try the initial value of the control amount PL, and is set to 1 when the control amount PL is increasing. Set to 2 if PL is decreasing.

In the next step S310, the preliminary calculation unit 60 sets the initial value of the control amount PL. Specifically, the initial value of the control amount PL is set to a value obtained by subtracting a value obtained by multiplying the total demand amount by the introduction ratio of UFR from the amount of power supply failure in the j-th startup accident case.

In the next step S320, the pre-calculation unit 60 executes a simulation for the j-th startup accident case. In this simulation, the pre-calculation unit 60 further reduces the control amount PL from the output 135 of the load model 130 when the control time TPL has elapsed since the frequency of the power system 10 fell below the threshold frequency FL.

In the next step S330, the pre-calculation unit 60 determines whether the lowest frequency of the power system 10 obtained by the simulation is lower than the allowable lowest frequency FBO.

As a result of this determination, if the lowest frequency is lower than the allowable lowest frequency FBO (YES in step S330), in the first simulation for the j-th startup accident case (controlled variable change flag Flg = 0, in step S340) (YES), the pre-calculation unit 60 advances the process to step S350. In step S350, the preliminary calculation unit 60 increases the control amount PL by the control amount step PLs, and sets the control amount change flag Flg to 1 (that is, the control amount PL is increasing).

After that, the preliminary calculation unit 60 executes a simulation using the new control amount PL (step S320). As a result of the simulation, if the state in which the lowest frequency continues to be lower than the allowable lowest frequency FBO (YES in step S330, YES in step S340), the pre-calculation unit 60 advances the process to step S350 and sets the control amount. PL is further increased by the control amount step PLs. Note that the control amount change flag Flg remains at 1 (control amount PL is increasing).

As a result of executing the simulation with the new control amount PL (step S320), if the lowest frequency changes from less than the allowable minimum frequency FBO (YES in step S330) to more than the allowable minimum frequency FBO (NO in step S330), the control Since the amount change flag Flg is 1 (NO in step S370, YES in step S360), the pre-calculation unit 60 advances the process to step S390. In step S390, the preliminary calculation unit 60 determines the final control amount for the j-th startup accident case to be the currently set control amount PL.

After that, if the number j of the startup accident case has not reached the total number Ntg of startup accident cases (YES in step S410), in the next step S420, the pre-calculation unit 60 increments the number j of the startup accident case by 1. Increment. Thereafter, steps S320 to S400 are repeated for a new start-up accident case with number j. If the starting accident case number j reaches the total number Ntg of starting accident cases (NO in step S410), the pre-calculation unit 60 ends the process.

On the other hand, if the lowest frequency is equal to or higher than the allowable lowest frequency FBO as a result of the determination in step S330 (NO in step S330), in the first simulation for the j-th starting accident case (controlled variable change flag Flg=0, step (YES in S370), the pre-calculation unit 60 advances the process to step S380. In step S380, the preliminary calculation unit 60 decreases the control amount PL by the control amount step PLs, and sets the control amount change flag Flg to 2 (that is, the control amount PL is decreasing).

After that, the pre-calculation unit 60 executes the simulation using the new control amount PL (step S320). As a result of the simulation, if the state in which the lowest frequency continues to be equal to or higher than the allowable lowest frequency FBO (NO in step S330, YES in step S370), the pre-calculation unit 60 advances the process to step S380, and sets the control amount PL. is further decreased by the control amount step PLs. Note that the control amount change flag Flg remains at 2 (control amount PL is decreasing).

As a result of executing the simulation with the new control amount PL (step S320), if the lowest frequency changes from more than the allowable minimum frequency FBO (NO in step S330) to less than the allowable minimum frequency FBO (YES in step S330), the control Since the amount change flag Flg is 2 (NO in step S340, NO in step S360), the pre-calculation unit 60 advances the process to step S400. In step S400, the preliminary calculation unit 60 determines the final control amount for the j-th startup accident case to be the value obtained by adding the control amount step PLs to the currently set control amount PL.

After that, if the number j of the startup accident case has not reached the total number Ntg of startup accident cases (YES in step S410), in the next step S420, the pre-calculation unit 60 increments the number j of the startup accident case by 1. Increment. Thereafter, the procedures of steps S320 to S400 are repeated for a new start-up accident case with number j. If the starting accident case number j reaches the total number Ntg of starting accident cases (NO in step S410), the pre-calculation unit 60 ends the process.

Referring again to FIG. 9, in the next step S30, the pre-calculation unit 60 determines the combination of control objects, that is, the load to be cut off and the load to be separated, so as to satisfy the necessary control amount determined in step S20 for each startup accident case. Determine the appropriate lineage. The pre-calculation unit 60 stores the determined combination of control objects in the storage device 54 as a control table 63.

FIG. 12 is a diagram showing an example of a control table. Referring to FIG. 12, the control table 63 determines, for each of the total number Ntg startup accident cases, one or more loads to be interrupted among the total number N1 loads and one or more loads to be interrupted among the total number N2 power transmission lines. Indicates a combination with one or more power transmission lines that should be shut down. It may be set to shut off only one of the load or the transmission line.

Referring again to FIG. 9, in the next step S40, if notification of accident occurrence is not received from any of the terminal devices 40 (NO in step S40), the pre-calculation unit 60 updates the latest online information. The above steps S10 to S30 are repeated based on the data.

On the other hand, when receiving a notification from one of the terminal devices 40 that an accident has occurred, that is, that the generator 21 has fallen off or that the output has decreased (YES in step S40), the control execution unit 61 controls the power output due to the occurrence of the accident. Changes in the frequency of the system 10 are monitored (step S50). Here, in order to further distribute the calculation load in order to reduce the amount of data to be communicated, the frequency is calculated on the terminal device 40 side, and the calculated frequency is transmitted from the terminal device 40 to the central processing unit 50. However, the central processing unit 50 may calculate the frequency of the system based on the voltage data received from the terminal device 40.

After that, if the control execution unit 61 further receives information on the occurrence of an accident from another terminal device 40, it treats the information as if a plurality of accidents have occurred at the same time (step S60).

In the next step S70, the control execution unit 61 determines whether the system frequency has reached the startup determination frequency for starting frequency stabilization control. If the system frequency has decreased to the start-up determination frequency (YES in step S70), the control execution unit 61 determines whether the actual phenomenon matches the prior simulation result 62 in the next step S80. Specifically, the control execution unit 61 determines whether the frequency change rate at the activated UFR element and the activation determination frequency matches the simulation result 62.

As a result of the determination in step S80, if the actual phenomenon matches the simulation result 62 (YES in step S80), the control execution unit 61 advances the process to step S100.

As a result of the determination in step S80, if the actual phenomenon does not match the simulation result 62 (NO in step S80), the control execution unit 61 advances the process to step S90. In step S90, the control execution unit 61 interprets that a severe accident case closest to the actual phenomenon has occurred. Specifically, the control execution unit 61 selects an accident case that has a calculation result close to the frequency change rate at the operated UFR element and the threshold frequency for operation determination. Note that if there are multiple accident cases with calculation results close to actual phenomena, the accident case with a larger control amount is selected.

In step S100, the control execution unit 61 determines whether the accident case that has occurred is an accident case for which activation is determined to be necessary in the preliminary calculation. If the accident case is determined to require activation (YES in step S100), the control execution unit 61 advances the process to step S110. If the accident case is determined to require no activation (NO in step S100), the control execution unit 61 ends the process.

In step S110, the control execution unit 61 determines a control target, that is, at least one load or power transmission line to be cut off, according to the control table 63.

In the next step S120, the control execution unit 61 transmits a control command, that is, a command to shut off the corresponding circuit breaker 33, to the terminal device 40 corresponding to the control target determined in step S110.

[Effects of Embodiment 1]
As described above, according to the grid stabilization system of Embodiment 1, frequency stabilization simulation is executed using the online pre-calculation method using a simple model of the power system, so the amount of calculations that are regularly executed can be suppressed. . Furthermore, since the online data required for the simulation includes the total output amount of the synchronous generator and the total demand amount of the load, the types of online data that need to be collected can be reduced compared to the past. Furthermore, since a simple model is used, there is no need to change the simulation model even if the network configuration of the power system is changed.

Even if there is a difference between the actual phenomenon and the preliminary simulation result, such as a difference in the operating UFR elements, the control amount and the controlled object can be appropriately determined by using the simulation result that is close to the actual phenomenon.

Embodiment 2.
The central processing unit 50 of Embodiment 2 executes correction control for correcting the excess or deficiency of the frequency stabilization control that has already been performed, based on the detected value of the amount of electricity in the power system 10 at the time of occurrence of the accident. For example, the central processing unit 50 acquires an instantaneous change in the active power of the generator 21 at the time of occurrence of an accident. If the difference between the obtained instantaneous change amount of active power and the amount estimated by the preliminary calculation exceeds a threshold value, the central processing unit 50 determines the amount of drop of the load 23 or the amount of drop of the renewable energy power source 24, etc. is estimated to be large, and performs correction control for the excess or deficiency of the control amount that has already been implemented.

FIG. 13 is a flowchart illustrating an example of a procedure for frequency control of an electric power system by the system stabilizing system according to the second embodiment. The flowchart in FIG. 13 differs from the flowchart in FIG. 9 of the first embodiment in that step S50 is changed to step S50A and steps S130 and S140 are added. Steps in the flowchart of FIG. 13 that are common to those in FIG. 9 are given the same reference numerals and descriptions will not be repeated.

Referring to FIG. 13, in step S50A, control execution unit 61 monitors changes in the frequency of power system 10 due to the occurrence of an accident, and also monitors instantaneous changes in active power output from generators 21 that are not in failure. do.

In step S130, the control execution unit 61 determines whether the instantaneous change in active power detected in step S50A exceeds a threshold value. If the instantaneous change in active power exceeds the threshold and the grid frequency is below the threshold frequency (YES in steps S130 and S140), in the next step S150, the control execution unit 61 detects an excess of the control amount that has already been carried out. Execute correction control for the shortfall.

As described above, according to the central processing unit 50 of the second embodiment, the modeling error included in the online preliminary calculation can be corrected based on the detected value of the amount of electricity in the power system 10 at the time of occurrence of the accident.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of this application is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

1 Grid stabilization system, 10 Power system, 21 Power generator, 22 Power converter, 23 Load, 24 Renewable energy power source, 25, 26, 29, 34 Power transmission line, 30, 31, 36 Transformer, 32, 33 , 37 circuit breaker, 35 distribution line, 14 primary substation, 15 secondary substation, 40 terminal device, 44, 53 processing circuit, 50 central processing unit, 54 storage device, 58 communication path, 59 central dispatch center, 60 Pre-calculation unit, 61 Control execution unit, 62 Simulation results, 63 Control table, 64 Online data, 70 Simulation model, 75 Load frequency characteristic model, 80 Inertia model, 91 Thermal power plant model, 100 Synchronous machine model, 105 Governor free model, 110 DC interconnection model, 112 Frequency response model, 120 Renewable energy power source model, 130 Load model, FBO first threshold frequency (minimum allowable frequency), FL second threshold frequency (startup determination frequency), Flg control amount change Flag, PL control amount, PLs control amount step, TPL control time.

Claims (12)

A grid stabilization system that stabilizes the frequency of a power grid,
Based on online data representing the state of the power system and a simulation model simulating the power system, simulations are performed according to a plurality of accident cases in which at least one generator included in the power system is assumed to fall off. Equipped with a pre-calculation section to
The simulation model includes an inertial model that simulates the rotor dynamic characteristics of a plurality of synchronous generators included in the power system at one mass point and calculates a frequency deviation based on the imbalance between supply and demand, and a A load model that simulates a load with one load, and a synchronous machine model that simulates a synchronous generator of the power system,
Furthermore, when an accident occurs in the power system, based on a comparison between the actual phenomenon of the power system and the simulation result for each accident case, the frequency of the power system is prevented from falling below a first threshold frequency; A grid stabilization system comprising a control executive that determines at least one load or transmission line to be disconnected. The grid stabilization system according to claim 1, wherein the online data includes a total output of synchronous generators included in the power system and a total demand amount of loads included in the power system. The grid stabilization system according to claim 2, wherein the synchronous machine model simulates governor control that changes the total output of the generator according to the frequency deviation. The simulation model simulates a frequency drop relay based on the frequency deviation,
The grid stabilization system according to claim 2 or 3, wherein the load model subtracts the load amount dropped by the frequency reduction relay from the total demand amount. The simulation model includes a renewable energy power source model that simulates a plurality of renewable energy power sources included in the power system with one power source,
The online data includes the total output of a plurality of renewable energy power sources included in the power system,
The grid stabilization system according to claim 4, wherein the output of the renewable energy power source model changes according to the frequency deviation. The simulation model includes a DC interconnection model that simulates a plurality of equipment interconnected with at least one DC system,
The online data includes the total output of the plurality of equipment,
The grid stabilization system according to claim 4 or 5, wherein the output of the DC interconnection model changes according to the frequency deviation. The pre-calculation unit calculates a frequency change rate when the frequency of the power system decreases to a second threshold frequency higher than the first threshold frequency, an element of the frequency reduction relay that is activated, and the frequency change rate of the power system when the frequency decreases to a second threshold frequency higher than the first threshold frequency. The system stabilizing system according to any one of claims 4 to 6, wherein the lowest frequency is recorded as a result of the simulation. The pre-calculation unit is configured to calculate, for a plurality of specific accident cases among the plurality of accident cases in which the lowest frequency is lower than the first threshold frequency, the frequency of the power system does not fall below the first threshold frequency. 8. The grid stabilization system according to claim 7, wherein a new simulation is executed a plurality of times using the load amount to be reduced as a variable in order to determine the load amount to be reduced so that the load amount to be reduced does not occur. The pre-calculation unit determines the at least one load or power transmission line to be cut off based on the determined load amount to be reduced for each specific accident case, and storing a correspondence relationship with at least one load or power transmission line to be cut off as a control table in a storage device;
The control execution unit is configured to control at least one terminal device corresponding to the at least one load or power transmission line to be cut off based on the control table when the frequency of the power system reaches the second threshold frequency. The grid stabilization system according to claim 8, which outputs a shutdown command to. The control execution unit corrects the excess or deficiency of the control amount due to the interruption of at least one load or transmission line for frequency stabilization, based on the detected value of the electricity amount of the power system at the time of occurrence of the accident. The grid stabilization system according to any one of claims 1 to 9. The system stabilization system according to claim 1, wherein the simulation model includes a plant model that simulates dynamic characteristics of a power generation plant instead of the synchronous machine model. A system stabilization method for stabilizing the frequency of a power system, the method comprising:
A processing circuit responds to a plurality of accident cases in which at least one generator included in the power system is assumed to fall off, based on online data representing the state of the power system and a simulation model simulating the power system. and a step to run the simulation.
The simulation model includes an inertial model that simulates the rotor dynamic characteristics of a plurality of synchronous generators included in the power system at one mass point and calculates a frequency deviation based on the imbalance between supply and demand, and a A load model that simulates a load with one load, and a synchronous machine model that simulates a synchronous generator included in the power system,
Further, the processing circuit is configured to prevent the frequency of the power system from falling below a first threshold frequency based on a comparison between an actual phenomenon of the power system and a result of the simulation for each accident case when an accident occurs in the power system. A system stabilization method comprising the step of determining at least one load or transmission line to be disconnected to ensure that the load or transmission line is not affected.

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