JP3447549B2 - Frequency stabilization method for power system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency stabilizing method in the case where a power source is dropped or a power system is separated in a power system.

[0002]

2. Description of the Related Art A conventional method for stabilizing the frequency of a power system is disclosed in, for example, the literature, "Power System Protection and Control System" by Koji Ota, published by Denki Shoin.
FIG. 6 is a block diagram of the frequency abnormality control device according to this document. In the figure, 1 to 4 are bus lines of the power system, 5 is a power transmission line connecting from the bus line 1 to this system, 6 to 8 are power transmission lines connecting between the bus lines 1 to 4, and 9 is connected to the bus line 1. Load, 10 is the load connected to bus 2,
11 is a generator connected to the bus bar 3, 12 is a generator connected to the bus bar 4, 13 to 16 are connected between each bus bar 1 to 4 and each load 9 and 10, or between the generators 11 and 12. It is a circuit breaker. Reference numeral 17 is a current transformer for detecting the current of the power transmission path 5, 18 is a transformer for detecting the voltage of the power transmission path 5, and 19 is the power flow value of the power transmission path 5 measured by this current and voltage. A measuring terminal for measuring the frequency of the grid, 20 is a central power supply command center that collects information on the grid capacity of the generators 11 and 12, and 21 is based on the power flow value, the frequency of the grid, and the grid capacity (load amount). Calculate the controlled variable,
A central processing unit that outputs and controls a trip signal based on this control amount, and 22 to 25 are control terminals that receive trip signals from the central processing unit 21 and operate the circuit breakers 13 to 16.

In the conventional frequency stabilization method having the above configuration, the measuring terminal 19 is always the current transformer 17 and the transformer 18.
The power flow value of the power transmission line 5 is measured on the basis of the output of the power transmission line 5 and the frequency of the system is measured and transmitted to the central processing unit 21. The central processing unit 21 further constantly acquires information on the system capacity from the central power feeding command station 20, For example, when an accident such as power failure of the electric power system occurs, the load amount to be restricted in order to limit the load amount and control the frequency of the electric power system to an appropriate value is calculated by the following formula. QL: Required load limit amount P: Power flow value before an accident in a power transmission line where power reception is positive WO: System capacity KL: System characteristic constant when load is limited ΔfL: Allowable value for frequency decrease

The central processing unit 21 selects a load amount corresponding to the required load limit amount QL obtained from the equation (1) from each load of the power system when the frequency of the system is abnormally lowered due to an accident such as power loss. However, for example, the load 9 in FIG.
If it is suitable for the system, select it, output a trip signal to the control terminal 22 to activate the circuit breaker 13, and disconnect the load 9 from the system to control the system frequency to an appropriate value. Frequency is the allowable value of frequency decrease Δf
The fluctuation within L can be suppressed.

[0005]

As described above, according to the conventional frequency stabilization method, the power flow value before the accident P of the power transmission line and the system capacity WO are used as input elements for stabilization.
Since the required load limiting amount is determined only by the system characteristic constant KL when the load is limited, it is said that the power system can be stabilized by performing the optimum frequency stabilization control adapted to the state of the system. It was difficult.

The present invention has been made in order to solve such a problem. When the power source of the system is cut off, the instantaneous reserve force is obtained from the governor-free width of the generator remaining in the system. Frequency stabilization to maintain the frequency within the stable operation area of the generator by calculating the required load limit amount considering the instantaneous reserve and performing load limit according to the calculation result, and to stabilize the system more The purpose is to obtain the law.

A frequency stabilizing method for a power system according to the present invention includes a plurality of buses connecting a generator and a load, and a power transmission line that forms a power system by interconnecting the buses or between the buses. enter the operation information of the generator in the system, the frequency stabilization method for a power system and a within central computing device that controls <br/> within allowable minimum frequency of the system at power dropout lines, central the spinning reserve from the rated output and governor-free setpoint generators computing device remained in the system in response to the power dropping with calculated Mel, transient from this spinning reserve supply and demand unbalance index determine the frequency minimum value, the frequency
Calculate the load limit to keep the minimum value within the allowable value
Remember, load control that corresponds to the amount of drop when the power is dropped
The load is controlled by selecting a limit amount .

[0008] obtains the spinning reserve from the central processing unit is the rated output and governor-free setting value of the generator remaining in the system at power dropout, restless destination frequency by the the spinning reserve supply and demand unbalance index Find the value , this calm last week
Calculate the load limit to keep the wave value within the allowable value
Remember, load control that corresponds to the amount of drop when the power is dropped
The load is controlled by selecting a limit amount .

Further, a plurality of buses connecting generators and loads, and a transmission line that connects the buses or the grids to each other to form an electric power system and the operation information of the generators in the grid are input. , the frequency stabilization method for a power system and a within central arithmetic unit that controls the frequency of the self system when the system separation accident within the allowable minimum value, the central processing unit remained in the own system when the system partition generator Machine rated output and governor-free
Set value spinning reserve force with the required Mel from a, a transient frequency minimum value from this spinning reserve force and the supply and demand imbalance rate
Load to keep this frequency minimum value within the allowable value
The limit amount is calculated and stored, and when the power is lost
The load limiting amount corresponding to is selected to perform load control.

Furthermore, when the central processing unit is separated from the system, the rated output of the generator remaining in the system and the governor-free set value are set.
I asked a spinning reserve force from and, asked for calm destination frequency value by and this spinning reserve force and the supply and demand imbalance rate, this fall
Calculates and stores the load limit amount to keep the destination frequency value within the allowable value, and responds to the drop amount when the power source drops.
The load control amount is selected to perform the load control.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 to 4 are for explaining a frequency stabilizing method for a power system according to Embodiment 1 of the present invention. FIG. 1 is a block diagram of the frequency stabilizing method for the power system, and FIG. A flow chart for explaining, FIG. 3 is a frequency change characteristic diagram when the power supply of the system is cut off, FIG. 4 (a) is a characteristic diagram of power variation and frequency deviation, and FIG. 4 (b) is a transient reserve of the generator and supply / demand unbalance. It is a characteristic diagram of the amount of frequency decrease with respect to the product of the balance rate, and in the configuration diagram of FIG. In FIG. 1, 1 to 4 are bus bars of a power system, 5
Is a power transmission line connecting from the bus bar 1 to this system, 6 to 8 are power transmission lines connecting between the bus lines 1 to 4, 9 is a load connected to the bus line 1, 10 is a load connected to the bus line 2, 11 is a generator connected to the bus bar 3, 12 is a generator connected to the bus bar 4, 13 to 16 are each bus bar 1 to 4 and each load 9
And 10, or a circuit breaker connected between the generators 11 and 12, 17 is a current transformer for detecting the current of the power transmission line 5, 18 is a transformer for detecting the voltage of the power transmission line 5, 19
Is a measuring terminal for measuring the power flow value of the power transmission path 5 using this current and voltage and also measuring the frequency of the grid.

Reference numeral 26 denotes a central electric power supply command center for collecting operation information such as the amount of power generation of the electric power generators 11 and 12 connected to the electric power system, and 27 denotes the central electric power supply command office 26 for the generators 11 and 12.
In response to the input of information such as the operating status of the generator, fold the elements such as the generator governor free width and the instantaneous reserve capacity determined by this, and assume the accident such as power loss, the minimum frequency value at the time of the accident is within the allowable value The central processing units 22 and 23 which receive and operate the circuit breakers 13 and 14 to calculate and hold the load limit amount for controlling the control and send out trip signals according to the calculation results. Control terminals 28 and 29 for detecting the power supply are detected and the signals are sent to the central processing unit 27.

FIG. 3 is a frequency change characteristic diagram when the power supply of the system is cut off. When a sudden supply and demand imbalance occurs at time tf and a shortage of generated power occurs, the system frequency is transient as shown in the figure. After the minimum frequency value is shown, the frequency reaches a constant settling frequency after a predetermined time according to the time constant of the speed governor of the generator, and the frequency stabilizes. The frequency minimum value at this time changes depending on the amount of change in power as shown in FIG. 4A, but the amount of frequency decrease up to the instantaneous reserve Pμ of the generator is Δf01, and if it exceeds this, the slope of decrease becomes large. . Further, the frequency decrease amount Δf01 changes depending on the product of the instantaneous reserve capacity Pμ of the generator and the supply and demand imbalance ratio Ru as shown in FIG. 4 (b), and each change is represented by the formulas entered in the figure. It

The frequency stabilization method for the electric power system according to the first embodiment of the present invention uses the transient reserve capacity and the supply / demand imbalance rate obtained from the governor-free width of the generator to determine the transient frequency minimum at the time of power failure. The value is controlled with accuracy within an allowable value, and will be described below with reference to the flowcharts of FIGS. 1 and 2. First, the central processing unit 27 takes in the operation information of the generators 11 and 12 collected by the central power feeding command station 26 in step 1 of the flowchart of FIG. This operation information is information such as the amount of power generation and the governor-free set value.

In step 2, in consideration of the accident of power supply loss, the necessary load limiting amount for controlling the minimum frequency value within the allowable value is determined based on the frequency lowering characteristics of FIGS. 4 (a) and 4 (b). And calculate. The calculation is based on the following formula. PL1: Required load limit amount for controlling the minimum frequency value within the allowable value Pg: Loss of power supply (total of pre-output of the dropped generator) Pμ: Sum of transient reserve of generators remaining in the system = Σ (P
n × GF) Pn: Rated output of the generator remaining in the system GF: Governor-free set value of each generator KL1: System characteristic constant when load is limited ΔfL1: Minimum frequency target value Δf01: Instantaneous reserve and supply / demand Frequency drop value due to imbalance rate = a1 x Ru x Pμ + b1 Ru: Supply and demand imbalance rate = Pg x 100 / W0 a1, b1: Coefficient W0: System capacity (total power generation) Note that the constant KL1 and coefficients a1 and b1 are The value set in advance in the simulation is used.

In step 3, a load limitation pattern is selected from the calculation result of the above equation (2) and registered in the stabilization table as an accident handling pattern when the assumed power failure occurs. The load limitation pattern is selected from the registered loads as the minimum load combination exceeding the required limit load amount. Step 4 repeats the above calculation and registration of the load limitation pattern until all expected power loss accidents are performed, and when all the calculation and registration are completed, the process waits in Step 5 and the power system In order to cope with the state change of the above, the above calculation / registration cycle is executed at predetermined time intervals to update the registered contents.

When the power loss signal from the detection terminal 28 or 29 is received in step 5, the content is specified in step 6, and the load limiting pattern for power loss registered in the stabilization table in step 7. Select the matching pattern from all the assumed values of the
A trip signal is transmitted to the corresponding control terminal on the basis of the load limitation pattern selected in to cut off the required amount of load.

As described above, according to the frequency stabilizing method for the electric power system of the first embodiment of the present invention, the minimum value of the frequency that is lowered due to the supply and demand imbalance at the time of a power loss accident in the electric power system is controlled within an appropriate value. The load limiting amount for this purpose is calculated by using the instantaneous reserve capacity and the supply / demand imbalance ratio obtained from the governor-free set value of the generator, so more precise stabilization control is possible and the state is always maintained. It is possible to maintain the minimum frequency value of the system within an appropriate value while maintaining all the generators stable even in the case of a power system that changes.

Embodiment 2. The frequency stabilization method of the electric power system according to this embodiment is for controlling the settling frequency within the allowable value when the power source of the electric power system is cut off. FIG. 5A is a characteristic diagram showing the deviation Δf2 of the settling frequency with respect to the power change amount P, and FIG. 5B is a characteristic diagram of the frequency decrease amount Δf02 of the settling frequency with respect to the supply and demand imbalance rate Ru. is there. In this embodiment, the central processing unit 27 receives information such as the operating conditions of the generators 11 and 12 from the central power feed command station 26, and determines the instantaneous reserve capacity and the supply / demand imbalance ratio obtained from the governor-free width of the generator. Using the and, the load limiting amount necessary to control the frequency at which to settle down within the allowable range in case of an accident such as power loss is shown in Fig. 5 (a) and Fig. 5 (b). It is calculated and controlled based on the characteristics.

The operation of the central processing unit 27 is the same as that of the first embodiment, but the calculation in step 2 is based on the following equation. Here, PL2: necessary load limit amount for keeping the settling frequency value within the allowable value Pg: power supply dropout amount (total of pre-output of the dropout generator) Pμ: instantaneous reserve power of the generator remaining in the system Total = Σ (P
n × GF) Pn: Rated output of the generator remaining in the grid GF: Governor-free set value of each generator KL2: System characteristic constant when load is limited ΔfL2: Settlement destination frequency target value Δf02: Supply / demand unbalance rate Frequency drop value = a
2 × Ru + b2 Ru: Supply / demand imbalance rate = Pg × 100 / W0 a2, b2: Coefficient W0: System capacity (total power generation) The constant KL2 and the coefficients a2 and b2 are set in advance by simulation as in the first embodiment. It was done.

According to the frequency stabilization method for the electric power system of the second embodiment of the present invention which performs the above-mentioned calculation, when the power supply of the electric power system is lost, the frequency settles down due to the imbalance of the power supply and demand. The required load limit for controlling the frequency value to an appropriate value is calculated and controlled by using the instantaneous reserve capacity and the supply / demand imbalance ratio that are obtained from the governor-free setting value of the generator, so more precise stabilization is possible. It becomes possible to control, and it becomes possible to maintain the settling frequency value of the system at an appropriate value while maintaining all the generators stable even for the power system in which the state changes constantly.

Embodiment 3. The above is the frequency stabilization method against a power loss accident in the system. In this embodiment, however, the interconnection line is broken due to an accident between the systems connected by the transmission lines (interconnection lines), Is calculated, a necessary load limiting amount for controlling the transient minimum frequency value in the separation system within an allowable range is calculated and the load control is performed. As in the first embodiment, the generators 11 and 1
In addition to receiving information such as the operation status of item 2, the power flow status of the interconnection line is input, and the following calculation is performed using the instantaneous reserve capacity and the supply / demand imbalance rate obtained from the governor-free width of the generator.

[0023] PL3: Required load limit amount Pf for controlling the minimum frequency value within the allowable value Pf: Power flow before the accident of the interconnection line where the power reception is positive Pμ: Instantaneous motion of the generator remaining in the separated grid Total reserve capacity = Σ (Pn × GF) Pn: Rated output of the generator remaining in the separated system GF: Governor-free set value of each generator KL1: System characteristic constant when load is limited ΔfL1: Frequency minimum Target value Δf01: Frequency decrease value due to instantaneous reserve and supply / demand imbalance rate = a1 × Ru × Pμ + b1 Ru: Supply / demand imbalance rate = Pg / W0 × 100 a1, b1: Coefficient W1: Capacity of separated system (Total power generation-tidal current)

According to this embodiment, when a power supply / demand unbalance occurs due to the grid separation of the power system, the central processing unit 27 sets the load limiting amount for keeping the minimum value of the transient frequency decrease at an appropriate value. Since it is calculated and controlled using the instantaneous reserve capacity and the supply and demand imbalance rate obtained from the governor-free set value of the generator, more precise stabilization control is possible, and for a power system with constantly changing states. Can suppress the minimum frequency value of the system to an appropriate value while maintaining all generators stable.

Fourth Embodiment In this embodiment, in the case where the interconnection lines are cut off due to an accident between the systems connected by the interconnection lines and the systems are separated, the settling frequency value in the separated system is controlled within an allowable range. The central processing unit 27 receives the information such as the operating conditions of the generators 11 and 12 from the central power feeding command station 26 as in the first embodiment. At the same time, the power flow status of the interconnection line is input, and the following calculation is performed using the instantaneous reserve capacity and the supply and demand imbalance rate obtained from the governor-free width of the generator.

[0026] Here, PL4: Required load limit amount Pg for keeping the settled frequency value within the allowable value Pg: Power flow before the accident of the interconnection line where the power reception is positive Pμ: Instantaneous motion of the generator remaining in the separated grid Total reserve capacity = Σ (Pn × GF) Pn: Rated output of the generator remaining in the separated system GF: Governor-free set value KL2 of each generator: System characteristic constant ΔfL2 when load is limited Frequency target value Δf02: Frequency decrease value due to supply / demand imbalance rate = a
2 × Ru + b2 Ru: Supply and demand imbalance rate = Pg / W0 × 100 a2, b2: Coefficient W0: Separated system capacity (total power generation-connection line flow)

According to this embodiment, the central processing unit 27 calculates and controls as described above, so that when the power system is separated from the power system, the frequency value at which the frequency drop due to the supply and demand imbalance is settled to a proper value. The load limiting amount to be maintained is calculated and controlled using the instantaneous reserve capacity and the supply and demand imbalance ratio obtained from the governor-free set value of the generator, so more precise stabilization control is possible and the state is always maintained. It is possible to maintain the minimum frequency value of the system at an appropriate value while maintaining all the generators stable even in the case of changes in the power system.

[0028]

As described above, according to the present invention, in the case where the power supply accident occurs in the power system or the separation accident occurs between the systems,
Determine the instantaneous reserve from the governor-free width of the generator remaining in the system, and use the instantaneous reserve and the supply-demand imbalance ratio to set the minimum frequency value that transiently decreases when the power generation is insufficient to within the allowable value. Since the required load limit for control is calculated and the required load limit for controlling the frequency at which the frequency drop settles down is within the allowable value, the load is controlled. Can be maintained at an appropriate value for stable operation of the generator with high accuracy, and a frequency stabilization method that can stabilize the power system can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a frequency stabilization method according to a first embodiment of the present invention.

FIG. 2 is a flow chart for explaining the operation of the frequency stabilization method according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram for explaining a frequency change when the power supply is cut off.

FIG. 4 is a characteristic diagram showing Embodiment 1 of the present invention,
(A) is a characteristic diagram for explaining the power variation and frequency deviation,
(B) is a characteristic diagram showing the relationship between the instantaneous reserve capacity of the generator and the frequency reduction amount with respect to the supply and demand imbalance rate.

FIG. 5 is a characteristic diagram showing a second embodiment of the present invention,
(A) is a characteristic diagram for explaining the power variation and frequency deviation,
(B) is a characteristic diagram showing the relationship between the supply and demand imbalance rate and the frequency decrease amount.

FIG. 6 is a configuration diagram illustrating a conventional frequency stabilization method.

[Explanation of symbols]

1-4 busbars, 5-8 power transmission lines, 9, 10 loads, 1
1, 12 generator, 13-16 circuit breaker, 17 current transformer, 18 transformer, 19 measuring terminal, 22, 23 control terminal, 26 central power supply command station, 27 central processing unit,
28, 29 Detection terminal.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 10-32927 (JP, A) JP 7-184324 (JP, A) JP 11-127538 (JP, A) Tsubouchi Mototaka, Kojima Masamichi, Yasuo Sato, et al., Development and verification of control method for next-generation local system SSC, The Institute of Electrical Engineers of Japan Material Power Technology / Power System Technology Joint Study Group, Japan, The Institute of Electrical Engineers of Japan, October 6, 1997 , PE / PSE-97-1 to 10-12 to 15, p. 31-36 Koji Ota, Power System Protection and Control System, Japan, Denki Shoin, May 15, 1975, 1st edition, 1st edition, p. 122-124 (58) Fields investigated (Int.Cl. ⁷ , DB name) H02J 3/00-5/00

Claims (4)

(57) [Claims] 1. A plurality of buses connecting a generator and a load, interconnecting each bus or between grids, and transmitting operation information of each of the above generators in a power transmission line that constitutes an electric power grid and in the grid. , the frequency stabilization method for a power system using a central computing device in that control frequency of the system within the allowed minimum value when the power shedding strains, the central processing unit corresponds to the power supply dropping
The rated output of the remaining power generator to the system Te and the governor-free settings
The spinning reserve force with the required Mel from and, determine the transient frequency minimum value from this spinning reserve force and the supply and demand imbalance rate,
Load limit to keep this frequency minimum value within the allowable value
Is calculated and memorized, and it corresponds to the dropout amount when the power is dropped
A frequency stabilization method for a power system, which is characterized in that load control is performed by selecting a load limiting amount to be applied. 2. A central processing unit obtains the spinning reserve from the rated output and governor-free setting value of the remaining generator system is at power dropout, restless destination frequency by the the spinning reserve supply and demand unbalance index Find the value and set the frequency
It calculates the load shedding amount to a value within the allowable value storage
In addition, when the power is dropped, the load limit amount corresponding to the drop amount.
2. The frequency stabilization method for a power system according to claim 1 , wherein the load control is performed by selecting the . 3. A plurality of buses connecting a generator and a load,
Input the operating information of the above generators in the transmission lines and grids that make up the power grid by connecting each bus or between grids, and keep the frequency of the grid within the allowable minimum value when a grid separation accident occurs. in frequency stabilization of the power system using a central computing device in that control, the rated output and governor-free setting of the generator in which the central processing unit remaining in the own system when the system partition
The spinning reserve force from the value along with the required Mel, seeking a transient frequency minimum value from this spinning reserve force and the supply and demand imbalance rate
Therefore, in order to keep this frequency minimum value within the allowable value,
Calculate and store the limit amount, and use it as the drop amount when the power is dropped.
A frequency stabilization method for a power system, which is characterized by selecting a corresponding load limitation amount to perform load control. 4. The central processing unit obtains the spinning reserve from the rated output and governor-free setting value of the remaining generators in the system when the system partition, restless destination by the the spinning reserve supply and demand unbalance index determine the frequency value, this calmness destination frequency
Serial and calculates the load shedding amount to a number within the allowable value
Remember, load limit corresponding to the amount of power loss when power is lost
The load is controlled by selecting an amount.
A frequency stabilization method for the power system described.