JP7450505B2 - Grid stabilization system and grid stabilization method - Google Patents

Description

The present disclosure relates to a grid stabilization system and a grid stabilization method for stabilizing a power grid.

If a large-scale power outage occurs in an electric power system for some reason, the system frequency will drop significantly. If this condition is left unaddressed, a chain reaction of power supplies may occur, resulting in a total power outage in the power system. Several countermeasures have been taken to deal with this problem of power outage, but the most effective and widely used of these is the grid stabilization system. In addition to maintaining frequency stability as described above, the grid stabilization system is also used for the purpose of maintaining synchronization stability and voltage stability.

In a system stabilizing system for preventing power supply dropouts, it is necessary to accurately measure the amount of power supply dropouts or output reductions. Generally, some kind of measurement terminal is installed near the power plant or on the power line connecting the power plant and the main power system, and the active power flow before a power failure occurs is grasped. When detecting a power failure, the difference in active power flow before and after the power failure occurs is calculated as the amount of power failure.

Japanese Unexamined Patent Publication No. 2006-333575 (Patent Document 1) discloses a method for calculating the amount of power supply dropout similar to the above. Specifically, the amount of power supply dropout in the own power system is calculated based on the active power flow passing through the interconnection point between the own power system and another power system.

On the other hand, Japanese Unexamined Patent Publication No. 50-92430 (Patent Document 2) discloses a method for estimating the amount of power supply dropout from the amount of frequency drop at an initial point in time when an accident occurs. Specifically, the amount of power supply dropout and The relationship with the amount of frequency reduction is required.

Japanese Patent Application Publication No. 2006-333575 Japanese Patent Application Publication No. 50-92430

Usually, there is a difference between the assumed generator model and the actual generator behavior (hereinafter, this difference is referred to as a modeling error). In the above-mentioned Japanese Patent Laid-Open No. 50-92430 (Patent Document 2), this modeling error is not taken into consideration, and therefore, it is considered that the estimation error of the amount of power supply dropout is still large.

The present disclosure has been made in view of the above background, and an objective in one aspect is to provide a system stabilization system that can accurately estimate the amount of power supply dropout.

A system stabilization system in one aspect includes a calculation unit, a behavior analysis unit, and a stabilization control unit. The calculation unit calculates the electrical output of the generator based on the detected value of the output voltage and the detected value of the output current of the generator provided in the power system, and also calculates the frequency of the output voltage as the measurement frequency. The behavior analysis unit analyzes the behavior of the generator based on the electrical output of the generator and the current mechanical input of the generator. The stabilization control unit performs stabilization control of the power system based on the analysis result of the behavior analysis unit. The behavior analysis section includes a first module that calculates the frequency of the output voltage of the generator as a calculation frequency by integrating the difference between the electrical output and the current mechanical input and dividing it by an inertia constant; A second module that calculates a first correction amount for the mechanical input based on the difference from the rated frequency of the system, and a third module that calculates the second correction amount for the mechanical input based on the difference between the calculated frequency and the measured frequency. module. The current mechanical input is a value obtained by subtracting the first correction amount and the second correction amount from the initial value of the mechanical input.

According to one aspect of the system stabilization system described above, by providing the third module that calculates the second correction amount of mechanical input based on the difference between the calculation frequency and the measurement frequency, it is possible to accurately estimate the amount of power supply dropout. .

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. 2 is a block diagram showing an example of the functional configuration of a terminal device and a central processing unit at the generator end in FIG. 1. FIG. 4 is a block diagram showing the operation of the behavior analysis section of FIG. 3. FIG. It is a flowchart showing the operation of a terminal device and a central processing unit at the generator end. 6 is a flowchart illustrating an example of a procedure for executing frequency stabilization control in step S50 of FIG. 5. FIG. 5 is a block diagram showing a specific example of the governor model and model error correction section of FIG. 4. FIG. 4 is a block diagram showing the operation of the behavior analysis section of FIG. 3 in the system stabilization system of Embodiment 3. FIG. 4 is a block diagram showing the operation of the behavior analysis section of FIG. 3 in the system stabilization system of Embodiment 4. FIG. 6 is a flowchart showing a procedure for executing synchronous stability maintenance control in step S50 of FIG. 5. FIG.

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 , power system 20 includes multiple generators 21 , multiple loads 30 , power transmission lines 23 and 26 , and distribution line 29 . Note that a distributed power source (not shown), interconnection equipment with a DC system, etc. may be further provided.

In the case of FIG. 1, the power transmission line 23 connects each generator 21 and the primary substation 38. Each primary substation 38 is interconnected by interconnection line 24 . Moreover, the power transmission line 26 connects between the primary substation 38 and the secondary substation 39. Distribution line 29 connects between secondary substation 39 and each load 30 .

The power system 20 further includes a busbar 22, a transformer 31, and a circuit breaker 34 provided between the generator 21 and the power transmission line 23, a busbar 25 provided in the primary substation 38, a plurality of transformers 32, and a busbar 25 provided in the primary substation 38. It includes a circuit breaker 35, busbars 27 and 28 provided in a secondary substation 39, a plurality of transformers 33, and a circuit breaker 36.

Governor free control is provided for each generator 21 in order to cope with a frequency drop in the event of an accident such as a generator 21 falling off or a drop in output in the power system 20 . The grid stabilization system 1 realizes frequency stabilization control that reflects the overall state of the power grid 20. The grid stabilization system 1 further performs synchronous stability maintenance control and voltage stabilization control.

Specifically, as shown in FIG. 1, the grid stabilization system 1 includes a plurality of terminal devices 40 (40_1 to 40_6) 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 corresponding voltage transformer VT and current transformer CT provided in the power system 20. Each terminal device 40 further detects the occurrence of an accident based on the detected amount of electricity. Each terminal device 40 further outputs a trip signal to the corresponding circuit breaker 34, 35, or 36 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 devices 40_3, 40_4 corresponding to each primary substation 38, terminal devices 40_5, corresponding to each secondary substation 39, 40_6 is provided.

Each of the terminal devices 40_1, 40_2 detects the output voltage and output current of the corresponding generator 21 via the corresponding voltage transformer VT and current transformer CT. Further, each of the terminal devices 40_1 and 40_2 isolates the corresponding generator 21 from the power system 20 by outputting a trip signal to the corresponding circuit breaker 34.

Each of the terminal devices 40_3, 40_4 detects voltage and current via a voltage transformer VT and a current transformer CT provided in the corresponding primary substation 38. Furthermore, each of the terminal devices 40_3 and 40_4 disconnects the corresponding power transmission line 26 by outputting a trip signal to the corresponding circuit breaker 35.

Each of the terminal devices 40_5, 40_6 detects voltage and current via a voltage transformer VT and a current transformer CT provided in the corresponding secondary substation 39. Furthermore, each of the terminal devices 40_5 and 40_6 isolates the corresponding load 30 from the power system 20 by outputting a trip signal to the corresponding circuit breaker 36.

The central processing unit 50 performs frequency stabilization control and synchronous stability maintenance control of the power system 20 based on the amount of electricity of the power system 20 detected by the terminal device 40 . A more detailed configuration of the central processing unit 50 and frequency stabilization control will be described later with reference to FIGS. 3 to 6.

[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, and 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. . The non-volatile memory is a non-volatile, non-temporary storage device such as a mask ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), a NOR flash memory, and a NAND flash memory. The CPU implements desired functions according to control programs stored in 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 34 or 35 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 34 or 35 or 36 about the open/closed state of the contacts of the circuit breaker.

The processing circuit 44 further outputs a trip signal to the circuit breaker 34, 35, or 36 when receiving a command to open the circuit breaker 34, 35, or 36 from the central processing unit 50 via the communication circuit 45. The digital output circuit 46 is instructed to do so. Digital output circuit 46 outputs a trip signal to the corresponding circuit breaker 34, 35, or 36 according to instructions from processing circuit 44.

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

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 .

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. The CPU executes processes such as frequency stabilization control, synchronous stability maintenance control, and voltage stabilization control of the power system 20 according to programs stored in the nonvolatile memory or storage device 54. The program may be provided as a non-transitory 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 storage device 54 is, for example, a hard disk, SSD (Solid State Drive), or other non-temporary non-volatile storage device. The storage device 54 stores electrical quantity data received from the terminal device 40, calculation results of the processing circuit 53, programs executed by the processing circuit 53, and the like.

[Functional configuration of terminal device and central processing unit]
FIG. 3 is a block diagram showing an example of the functional configuration of the terminal device and central processing unit at the generator end in FIG. 1. In the case of the example shown in FIG. 3, the processing circuit 44 of the terminal devices 40_1 and 40_2 provided at the end of the generator functions as the calculation unit 60, and the processing circuit 53 of the central processing unit 50 functions as the behavior analysis unit 61 and It functions as a stabilization control section 62.

The terminal devices 40_1, 40_2 and the central processing unit 50 may share arithmetic processing in a manner different from the case in FIG. 3. For example, the terminal devices 40_1 and 40_2 may function as the calculation unit 60 and the behavior analysis unit 61 in FIG. 3, and the central processing unit 50 may function as the stabilization control unit 62.

The calculation unit 60 calculates the electrical output P _E [pu] and the frequency deviation ΔF _N [Hz] of the generator based on the output voltage and output current of the corresponding generator 21 detected by the voltage transformer VT and current transformer CT. ] (also referred to as measurement frequency deviation). The frequency deviation ΔF _N is the deviation between the frequency F _N (hereinafter also referred to as "measured frequency") calculated from the output voltage of each generator 21 and the rated frequency F ₀ . pu represents the unit system.

The behavior analysis unit 61 determines _whether the generator ₂₁ to be monitored or a _plurality of Analyze the behavior of an equivalent generator with a single generator. The behavior analysis unit 61 analyzes the behavior of the generator 21 or an equivalent generator by solving simultaneous differential equations including the equation of motion of the generator, a governor model, etc. in real time by numerical integration. Details of the operation of the behavior analysis section 61 will be described later with reference to FIG.

The stabilization control unit 62 executes frequency stabilization control and synchronous stability maintenance control of the power system 20 based on the analysis result of the behavior analysis unit 61. When the stabilization control unit 62 determines that power restriction is necessary, it outputs an opening command to the terminal device 40_1 or 40_2 corresponding to the generator 21 to open the corresponding circuit breaker 34. On the other hand, when the stabilization control unit 62 determines that load limiting is necessary, the stabilization control unit 62 opens the corresponding circuit breaker 35 or 36 for any of the terminal devices 40_3 to 40_6 corresponding to the power transmission line 26 or the load 30. Outputs an open command to do so.

[Operation of behavior analysis section]
FIG. 4 is a block diagram showing the operation of the behavior analysis section of FIG. 3. The block diagram 70 in FIG. 4 shows that there is a difference between the generator model assumed in advance and the actual generator (that is, there is a modeling error), and that the measurement frequency of the bus voltage can be easily measured. It is assumed that _FN and the frequency F calculated by the generator model (hereinafter also referred to as the "calculated frequency") have different movements in a transient manner, and a mechanism is provided to eliminate the error. It has characteristics. Note that the generator may be an individual generator to be monitored, or may be an equivalent generator made up of a plurality of generators.

Specifically, with reference to FIG. 4, the block diagram 70 includes a generator model 71 (first module), a governor model 75 (second module), a model error correction section 76 (third module), It includes a constant multiplier 77 and a subtracter 78.

The generator model 71 calculates mechanical energy given to the generator 21 from a turbine or the like (referred to as mechanical input P _M [pu]) and electrical energy output from the generator 21 (i.e., electrical output The behavior of the rotor of the generator 21 determined by P _E ) is simulated. That is, the generator model 71 expresses the equation of motion of the generator expressed by the following equation (1) in the form of a block diagram.

In the above equation (1), the inertia constant M[s] is a value expressing the weight of the rotating body including the turbine in the generator. The angular velocity deviation Δω [rad/s] represents the deviation between the angular velocity ω [rad/s] and the rated angular velocity ω ₀ [rad/s]. The rated angular velocity ω ₀ is determined by the rated frequency F ₀ [Hz] of the power system 20 to which the generator model 71 is applied, as shown in the following equation (2).

Specifically, as shown in FIG. 4, the generator model 71 includes integrators 72 and 73 and a subtracter 74. A subtractor 74 subtracts the electrical output P _E of the generator from the current mechanical input P _M of the generator.

The integrator 72 performs an integration process (represented by 1/s) on the subtraction result of the subtractor 74, multiplies it by the rated angular velocity ω ₀ , and divides it by the inertia constant M. Thereby, the angular velocity deviation Δω is calculated.

The integrator 73 calculates the phase angle deviation Δδ [rad] by integrating the angular velocity deviation Δω, which is the calculation result of the integrator 72. Further, the constant multiplier 77 calculates the frequency deviation ΔF by multiplying the angular velocity deviation Δω, which is the calculation result of the integrator 72, by 1/2π. The frequency deviation ΔF is the difference between the calculated frequency F and the rated frequency F ₀ .

The governor model 75 calculates a necessary mechanical input correction value ΔX ₁ (first correction amount) according to the frequency deviation ΔF in order to set the rotational speed of the generator rotor to a desired value.

The model error correction unit 76 calculates a mechanical input correction value P GDROP based on the difference between the generator calculation frequency F calculated by the generator model 71 and the measurement frequency F _N based on the actual measured value of the bus voltage _. [pu] (second correction amount) is calculated. That is, it is assumed that the main cause of the difference between the calculation frequency F and the measurement frequency _FN of the generator is a change in mechanical input due to power failure. Therefore, the mechanical input correction value P _GDROP corresponds to the amount of power supply dropout or the amount of decrease in power supply output. By correcting the preset mechanical input value P _M0 of the generator with the mechanical input correction value P _GDROP , errors due to the generator model and the governor model are suppressed.

The subtractor 78 subtracts the mechanical input correction value _ΔX1 by the governor model 75 and the mechanical input correction value P _GDROP by the model error correction unit ₇₆ from the preset value P M0 of the mechanical input of the generator. , generates the current mechanical input P _M of the generator. As a result of repeating the above calculation, the error between the generator calculation frequency F calculated by the generator model 71 and the measured frequency F _N based on the actual measured value of the bus voltage is suppressed during normal conditions before the accident occurs. be done.

The current amount of power failure or the amount of decrease in power output can be determined from the difference between the current value of the mechanical input _PM of the generator and the value of the mechanical input _PM before the power failure occurs. If a single generator is tripped or multiple generators are tripped at the same time, the power dropout amount or output reduction amount is equal to the machine input correction value P _GDROP at the time of the power dropout occurrence.

In FIG. 4, a combination of a generator model 71 and a governor model 75 is a general model that is often used to simulate the behavior of a generator rotor in a system analysis tool. In this general model, when simulating a generator falling off or a drop in output, the initial setting value P _M0 of the mechanical input of the generator is changed. However, it is not possible to directly obtain the value of the mechanical input P _M0 , which takes into account the possibility of the generator falling off.

On the other hand, in the block diagram 70 of FIG. 4, by providing a model error correction unit 76, automatic calculation of the amount of power supply dropout or the amount of decrease in output of the power supply is realized. If the generator does not fall off or the output decreases, there will be no large difference between the measured frequency deviation ΔF _N and the calculated frequency deviation ΔF. On the other hand, when the generator falls off or the output decreases, a large difference occurs between the frequency deviation ΔF _N and the frequency deviation ΔF. By correcting the initial value _PM0 of the mechanical input of the generator so as to eliminate this difference, it becomes possible to calculate the amount of power supply dropout or the amount of decrease in power supply output.

The model shown in FIG. 4 is implemented in a grid stabilization system and operates constantly or when stabilization control is activated based on some information. During the stabilization control operation, the processing _{circuit 53} constructs these models (i.e., simultaneous differential solve the equations one by one. As a result, the values of various variables used in the model are obtained, and the latest values of the amount of power supply dropout or the amount of output reduction are always obtained.

Note that in the above, the frequency _FN of the bus voltage at the generator end is used as the value of the measurement frequency, but if the rotation speed of the generator itself can be directly measured, the measurement frequency can correspond to the rotation speed of the generator. You may also use a frequency that

[Operation of the terminal device and central processing unit at the generator end, especially regarding frequency stabilization control]
FIG. 5 is a flowchart showing the operation of the terminal device and central processing unit at the generator end. Hereinafter, the operations of the terminal devices 40_1, 40_2 and the central processing unit 50 at the generator end will be explained, summarizing the explanation so far, with appropriate reference to FIGS. 1 to 4.

First, the operation of the terminal devices 40_1 and 40_2 provided at the end of the generator will be explained. In step S1 of FIG. 5, the processing circuit 44 of the terminal devices 40_1 and 40_2 measures the electrical output _PE of the generator 21. Specifically, the A/D converter 43 of the terminal device 40_1, 40_2 converts the instantaneous voltage value and instantaneous current value detected by the voltage transformer VT and current transformer CT at the output end of the generator 21 into digital values. By converting, time series data of instantaneous voltage values and instantaneous current values is generated. The processing circuit 44 calculates the electrical output _PE for each calculation cycle based on these time-series data.

In step S2, the processing circuit 44 measures the frequency deviation ΔF _N with respect to the bus voltage. Specifically, the processing circuit 44 calculates the frequency F _N and the frequency deviation ΔF _N based on time series data regarding the instantaneous voltage value of the bus 22 at the output end of the generator 21 .

Thereafter, the processing circuit 44 of the terminal devices 40_1 and 40_2 repeats steps S1 and S2 described above. Note that the above steps S1 and S2 may be executed first or may be executed in parallel.

Next, the operation of the central processing unit 50 will be explained. In step S10 of FIG. 5, the processing circuit 53 of the central processing unit 50 obtains the initial setting value P _M0 of the mechanical input of the generator. This value is stored in the storage device 54, for example.

In the next step S20, the processing circuit 53 of the central processing unit 50 acquires the measured value of the electrical output _PE from the terminal devices 40_1 and 40_2. Furthermore, in step S30, the processing circuit 53 acquires the measured value of the frequency deviation ΔF _N from the terminal devices 40_1 and 40_2. Either of these steps S20 and S30 may be executed first, or they may be executed in parallel.

In the next step S40, the processing circuit 53 calculates the measured value of the electrical output P _E of the generator 21, the measured value of the frequency deviation ΔF _N with respect to the bus voltage, and the value of the initial setting value P _M0 of the mechanical input of the generator. Based on this, the behavior of the generator 21 to be monitored or an equivalent generator that aggregates a plurality of generators 21 is analyzed. Specifically, based on the model explained in FIG. 4, the values of each variable used in the model are calculated in real time.

In the next step S50, the processing circuit 53 executes stabilization control if necessary based on the analysis result in step S40. Thereafter, the processing circuit 53 repeats steps S20 to S50 described above.

FIG. 6 is a flowchart illustrating an example of a procedure for performing frequency stabilization control in step S50 of FIG. Note that the generator model 71, governor model 75, and model error correction unit 76 in FIG. 4 are for an equivalent generator that is a collection of a plurality of generators.

In step S100 of FIG. 6, the processing circuit 53 calculates the difference ΔP _M between the current mechanical input P _M of the generator and the mechanical input P _M of the generator before power failure. This difference ΔP _M corresponds to the amount of falling of the generator or the amount of decrease in the output of the generator. The difference ΔP _M is equal to the mechanical input correction value P _GDROP when a power failure occurs.

In the next step S110, the processing circuit 53 determines whether or not to perform frequency stabilization control based on the above-mentioned difference _ΔPM . As an example, the processing circuit 53 may determine whether the absolute value of the difference ΔP _M is larger than a threshold (first threshold). In this case, if the absolute value of the difference ΔP _M is less than or equal to the threshold (NO in step S110), the processing circuit 53 ends the process without performing frequency stabilization control.

On the other hand, if the absolute value of the difference ΔP _M is larger than the threshold (YES in step S110), the processing circuit 53 advances the process to step S120. In step S120, the processing circuit 53 determines the amount of load restriction corresponding to the amount of power supply dropout.

In the next step S130, the processing circuit 53 determines at least one load 30 or power transmission line 26 to be cut off in order to realize the load restriction amount determined in step S120.

In the next step S140, the processing circuit 53 opens the corresponding circuit breaker 35 or 36 for any one of the terminal devices 40_3 to 40_6 corresponding to the at least one load 30 or the power transmission line 26 determined in step S120. Outputs an open command to do so. With the above steps, the frequency stabilization control ends.

[Effects of Embodiment 1]
As described above, according to the system stabilization system 1 of the first embodiment, the model error correction unit 76 is provided in the analytical model that analyzes the behavior of the generator 21. Thereby, the mechanical input _PM of the generator to be monitored or the equivalent generator can be accurately calculated in real time. Furthermore, the current amount of output reduction of the generator can be calculated with high accuracy from the difference between the current value of the mechanical input PM of the generator and the value of the _mechanical input _PM of the generator before the power failure occurs.

Embodiment 2.
In Embodiment 2, a specific example of the governor model 75 and model error correction unit 76 in FIG. 4 will be described.

FIG. 7 is a block diagram showing a specific example of the governor model and model error correction section of FIG. 4. In the block diagram 70A of FIG. 7, the governor model 75 is represented by a first-order lag element 80, and the model error correction section 76 is represented by proportional-integral control (PI control).

Specifically, the governor model 75 includes a first-order lag element 80 having a gain constant G [pu/Hz] and a time constant T [s]. The model error correction unit 76 includes a proportional element 81 having a gain constant _KP , an integral element 82 having a gain constant _KI , a subtracter 83, and an adder 84.

The subtractor 83 subtracts the measured frequency deviation ΔF _N from the calculated frequency deviation ΔF calculated by the generator model 71. The subtraction results of the subtracter 83 are input to the proportional element 81 and the integral element 82, respectively. The adder 84 generates a mechanical input correction value P _GDROP by adding the output ΔX ₂ of the proportional element 81 and the output ΔX ₃ of the integral element 82 .

According to the system stabilization system 1 of the second embodiment, since the model error correction unit 76 is provided, even if the governor model 75 itself is simulated by a simple first-order lag element 80, the generator output decreases. The accuracy of the amount (power supply drop amount) can be ensured. Furthermore, even if the model error correction section 76 is expressed as PI control having a proportional element 81 and an integral element 82, the difference between the calculation frequency F and the measurement frequency _FN can be appropriately suppressed.

Embodiment 3.
In the third embodiment, the inertia constant M is changed in accordance with the amount of power supply dropout in the first and second embodiments. In addition, in Embodiment 3, the analysis is limited to an equivalent generator that is a collection of a plurality of generators.

FIG. 8 is a block diagram showing the operation of the behavior analysis section of FIG. 3 in the system stabilization system of the third embodiment. The block diagram 70B in FIG. 8 differs from the block diagrams 70 and 70A in FIGS. 4 and 7 in that it further includes an inertia constant calculation section 85.

The inertia constant calculation unit 85 changes the inertia constant M in proportion to the mechanical input after the power supply is disconnected, that is, the value obtained by subtracting the correction value P _GDROP from the initial setting value P _M0 of the mechanical input of the generator. In the case of an equivalent generator that combines multiple generators, the number of operating generators decreases as the power is removed, so calculation accuracy can be improved by reducing the inertia constant M in accordance with the amount of power loss. .

Embodiment 4.
There is a limit to how much generator output can be increased by governor control when the frequency drops. In the fourth embodiment, the output limit of governor control is taken into consideration. Note that Embodiment 4 can be combined with Embodiment 3.

FIG. 9 is a block diagram showing the operation of the behavior analysis section of FIG. 3 in the system stabilization system of the fourth embodiment. The block diagram 70C of FIG. 9 differs from the block diagrams 70, 70A of FIGS. 4 and 7 in that it further includes a limiter 86. The block diagram 70C of FIG. The limiter 86 generates a correction value ΔX ₄ that limits the mechanical input correction value ΔX ₁ outputted from the governor model 75 to within a predetermined upper and lower limit range. A correction value ΔX ₄ is input to the subtracter 78 instead of the correction value ΔX ₁ .

By providing the limiter 86 as described above, the output limit of governor control can be incorporated, so calculation accuracy can be improved.

Embodiment 5.
Many other control calculations in the grid stabilization system require state quantities in the generator model. By using the models described in the first to fourth embodiments for these other control calculations, calculation accuracy can be improved. The case of synchronous stability maintenance control will be described below as an example.

FIG. 10 is a flowchart showing a procedure for executing the synchronous stability maintenance control in step S50 of FIG. Note that the generator model 71, governor model 75, and model error correction unit 76 in FIGS. 4 and 7 to 9 are for one generator 21 to be monitored.

In step S200 of FIG. 10, the processing circuit 53 of the central processing unit 50 determines whether synchronization stability maintenance control is necessary based on the phase angle deviation Δδ. As an example, the processing circuit 53 may determine whether the absolute value of the phase angle deviation Δδ exceeds a threshold (second threshold). In this case, if the absolute value of the phase angle deviation Δδ is less than or equal to the threshold (NO in step S200), the processing circuit 53 ends the process without executing the synchronization stability maintenance control.

On the other hand, if the absolute value of the phase angle deviation Δδ is larger than the threshold (YES in step S200), the processing circuit 53 advances the process to step S210. In step S210, the processing circuit 53 outputs an opening command to the terminal device 40_1 or 40_2 corresponding to the generator 21 to be monitored to open the corresponding circuit breaker 34. As a result, the out-of-step generator 21 is separated from the power system 20, thereby achieving synchronization stabilization.

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, 20 Power system, 21 Generator, 22, 25, 27, 28 Bus bar, 23, 26 Transmission line, 24 Interconnection line, 29 Distribution line, 30 Load, 31, 32, 33 Transformer, 34 , 35, 36 circuit breaker, 40 terminal device, 44, 53 processing circuit, 50 central processing unit, 60 calculation section, 61 behavior analysis section, 62 stabilization control section, 71 generator model (first module), 75 speed governor machine model (second module), 76 model error correction section (third module), 80 first-order lag element, 81 proportional element, 82 integral element, 85 inertia constant calculation section, 86 limiter.

Claims (11)

a calculation unit that calculates the electrical output of the generator and calculates the frequency of the output voltage as a measurement frequency based on the detected value of the output voltage and the detected value of the output current of the generator provided in the power system;
a behavior analysis unit that analyzes the behavior of the generator based on the electrical output of the generator and the current mechanical input of the generator;
and a stabilization control unit that performs stabilization control of the power system based on the analysis result of the behavior analysis unit,
The behavior analysis section includes:
a first module that calculates the frequency of the output voltage of the generator as a calculation frequency by integrating and dividing the difference between the electrical output and the current mechanical input by an inertia constant;
a second module that calculates a first correction amount of the mechanical input based on the difference between the calculated frequency and the rated frequency of the power system;
a third module that calculates a second correction amount of the mechanical input based on the difference between the calculation frequency and the measurement frequency,
The system stabilizing system, wherein the current mechanical input is a value obtained by subtracting the first correction amount and the second correction amount from the initial value of the mechanical input. The system stabilization system according to claim 1, wherein the amount of output reduction when an accident occurs in the generator is a second correction amount when an accident occurs in the generator. The system stabilization system according to claim 2, wherein the stabilization control unit determines whether frequency stabilization control is necessary based on the amount of output decrease. The grid stabilization system according to claim 3, wherein the stabilization control unit executes frequency stabilization control when the output reduction amount exceeds a first threshold. The grid stabilization system according to any one of claims 1 to 4, wherein the second module includes a first-order lag element. The system stabilization system according to any one of claims 1 to 5, wherein the third module executes proportional-integral control. The generator is an equivalent generator that aggregates a plurality of generators,
The system stabilization according to any one of claims 1 to 6, wherein the first module determines the inertia constant to be proportional to a value obtained by subtracting the second correction amount from the initial value of the mechanical input. system. The system stabilizing system according to any one of claims 1 to 7, wherein the behavior analysis section further includes a limiter provided after the second module. the first module calculates a phase difference by integrating the calculation frequency;
The system stabilization according to any one of claims 1 to 8, wherein the stabilization control unit determines whether to execute synchronous stability maintenance control based on the deviation between the phase difference and the initial phase. system. The system stabilization system according to claim 9, wherein the stabilization control unit executes synchronous stability maintenance control when the deviation between the phase difference and the initial phase exceeds a second threshold. Calculating the electrical output of the generator and the frequency of the output voltage as a measurement frequency based on the detected value of the output voltage and the detected value of the output current of a generator provided in the power system;
analyzing the behavior of the generator based on the electrical output of the generator and the current mechanical input of the generator;
and a step of performing stabilization control of the power system based on the analysis result of the analyzing step,
The step of analyzing includes:
calculating the frequency of the output voltage of the generator as a calculation frequency by integrating the difference between the electrical output and the current mechanical input and dividing by an inertia constant;
Calculating a first correction amount for the mechanical input based on the difference between the calculated frequency and the rated frequency of the power system;
Calculating a second correction amount of the mechanical input based on the difference between the calculation frequency and the measurement frequency,
The system stabilization method, wherein the current mechanical input is a value obtained by subtracting the first correction amount and the second correction amount from the initial value of the mechanical input.

Images