JP3476630B2 - Frequency stabilization method - 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 for controlling a frequency abnormality, which occurs when a disconnection occurs in an interconnection line of a power system or when a generator falls out, to an appropriate frequency. is there.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of a frequency abnormality control apparatus according to a conventional method shown in, for example, "Protective control system for electric power system-Koji Ohta, Denki Shoin". In the figure,
1 to 4 are bus lines of the power system, 5 is a transmission line (interconnection line) that interconnects the main system and the bus line 1, 6 to 8 are transmission lines that interconnect each of the bus lines 1 to 4, and 9 is a bus line 1. Is a load connected to the bus bar 2, 11 is a generator connected to the bus bar 3, 12 is a generator connected to the bus bar 4, and 13 to 16 are circuit breakers.

Further, 17 is a current transformer for detecting a current I flowing through the power transmission line 5, 18 is a transformer for detecting a voltage V applied to the power transmission line 5, and 19 is a power transmission line based on the current I and the voltage V. A measurement terminal that measures the power flow value P flowing in 5 and the frequency f of the grid, 20 is a central power supply command station that collects the grid capacity W ₀ (load amount) of the generators 11 and 2, 2
1 is a central processing unit that calculates a necessary control amount based on the power flow value P, frequency f, and system capacity W ₀ , and outputs a trip signal based on the control amount. 22 to 25 are trip signals from the central processing unit 21. Circuit breaker 1
It is a control terminal that trips 3 to 16.

Next, the operation will be described. First, the measurement terminal 19 measures the power flow value P flowing through the power transmission line 5 based on the current I detected by the current transformer 17 and the voltage V detected by the transformer 18, and also measures the frequency f of the grid. To do.

As a result, the central processing unit 21 takes in the power flow value P and the frequency f measured by the measuring terminal 19, and also takes in the system capacity W ₀ collected by the central power feeding command station 20 to obtain the frequency of the power system. Is calculated as shown below to control the amount required to control the value.

Q _L = (P−K _L · Δf · W ₀ ) / (1−K _L · Δf _L ) (1) Q _P = −P−K _H · Δf _H · W ₀ (2) Q _L: necessary load shedding amount Q _P: required power restriction rate P: tie-line before the accident trends (the power receiving a positive) W _0: line capacitance K _L: line constants K _H during load limiting: the system when the power limit Constant Δf _L : Settlement destination frequency deviation (when load is limited) Δf _H : Settlement destination frequency deviation (when power source is limited) In addition, the formula (1) is the control amount Q when the frequency is controlled by disconnecting the load from the grid. while showing _L, and the formula (2) shows a control quantity Q _P in the case of controlling the frequency by disconnecting the generator from the system.

That is, the central processing unit 21 needs to raise the frequency f when the frequency f of the system is abnormally lowered. Therefore, the equation (1) is calculated to obtain the controlled variable _QL and the control thereof is controlled. in order to cut off only the load corresponding to the amount Q _L, to select a load commensurate with the load from the load of the power system.

On the other hand, the central processing unit 21 needs to lower the frequency when the frequency f of the system rises abnormally. Therefore, the equation (2) is calculated to obtain the control amount Q _P , and the control value is controlled. In order to cut off only the amount of power generation corresponding to the amount Q _P , the generator that matches the amount of power generation is selected from the generators of the power system.

For example, when the generator 11 is commensurate with the amount of power generation corresponding to the control amount Q _P , this generator 11 is selected and the central processing unit 21 outputs a trip signal to the control terminal 24. Then, the control terminal 24 trips the circuit breaker 15, disconnects the generator 11 from the grid, and controls the frequency of the grid to an appropriate value.

[0010]

Since the conventional frequency stabilizing method is constructed as described above, it is controlled by the system constant at that time with reference to the settling frequency (the frequency settling after the transient frequency fluctuation). Therefore, there is a problem that it is not possible to cope with a transitional frequency change, and therefore it is not possible to appropriately control a sudden frequency increase or decrease observed at the time of a significant supply and demand imbalance.

The present invention has been made to solve the above problems, and uses the characteristics of the supply and demand imbalance rate and the frequency deviation to transiently increase or decrease the frequency,
The objective is to obtain a frequency stabilization method that can maintain the frequency within the stable operation range of the generator by finding the settling frequency and determining the power supply limit amount and load limit amount from the frequency values. .

[0012]

A frequency stabilizing method according to a first aspect of the present invention is based on the amount of power generation in the controlled system and the power flow in the controlled system before the occurrence of the system disconnection and the supply and demand imbalance rate and the frequency deviation in advance. The characteristic is the transitional frequency maximum value, minimum value,
The settling frequency is calculated in advance, and the transient frequency maximum value, minimum value, and settling frequency value at the time of system division are calculated using this characteristic, and the frequency is controlled within the generator stable operation range from each value. It was done like this.

In the frequency stabilizing method according to the second aspect of the present invention, the characteristics of the supply and demand imbalance rate and the frequency deviation are obtained for the plant alone, and the transient frequency of the plant alone at the time of system interruption is calculated using this characteristic. Calculate the maximum value, the minimum value, and the settling frequency value, and weight the average of the operating plants included in the isolated system by the amount of power generation for each frequency to determine the maximum, minimum, and settled transient frequency of the isolated system. The destination frequency is calculated.

In the frequency stabilizing method according to the third aspect of the present invention, the characteristics of the supply and demand imbalance ratio and the frequency deviation of the plant alone are obtained by using the generator output as a parameter, and this characteristic is used to detect the occurrence of system disconnection. It calculates the transient maximum and minimum frequencies and the settling frequency.

In the frequency stabilizing method according to the fourth aspect of the present invention, when the transient maximum frequency value and the settling frequency value exceed the stable operation range of the generator on the frequency rising side, the frequency value is set to the stable range. In order to reduce the power consumption to within the range, the frequency limit value of the plant subject to power restriction is removed from the weighted average to determine the power restriction amount.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. Embodiment 1. FIG. 1 is a frequency change waveform diagram at the time of power system division for explaining the basic principle of the present invention. In the figure, the time point t _f represents the occurrence of grid disconnection, and when the grid grid has excessive power generation, the transient maximum value is recorded as shown in FIG. , Governor) and reach the settled frequency value. Similarly, in the case of insufficient power generation, as shown in FIG. 1 (b), it reaches a settling frequency value through a transient minimum value.

FIG. 2A shows the characteristics of the supply and demand imbalance rate Ru and the frequency deviation Δf _{1 for} the highest and lowest frequency values. 2B shows the characteristics of the supply and demand imbalance rate Ru and the frequency deviation Δf ₂ for the settling frequency.

FIG. 3 is a structural example of a frequency control device based on the frequency stabilizing method according to the first embodiment of the present invention. In the figure, 1 to 4 are bus lines of the power system, 5 is a power transmission line (interconnection line) that interconnects the main system and the bus line 1, 6 to 8 are power transmission lines that interconnect each of the bus lines 1 to 4, and 9 Is a load connected to the busbar 1, 10 is a load connected to the busbar 2, 11 is a generator connected to the busbar 3, 12 is a generator connected to the busbar 4,
13 to 16 are circuit breakers.

Further, 17 is a current transformer for detecting a current I flowing in the power transmission line 5, 18 is a transformer for detecting a voltage V applied to the power transmission line 5, and 19 is a power transmission line based on the current I and the voltage V. A measurement terminal that measures the power flow value P flowing in 5 and measures the frequency f of the grid, and 31 collects operation information of the generators 11 and 12 connected to the power grid (presence or absence of the generator, power generation amount, etc.) The central power feeding command station, 32 is the highest frequency value, the lowest frequency value, and the calm frequency value for an expected accident based on the operation information of the generators 11 and 12 and the power flow value P of the power transmission line 5 collected by the central power feeding command station 31. And a central processing unit for executing the frequency stabilization method of the present invention by an operation based on a flowchart described later.
-25 are control terminals that trip the circuit breakers 13-16, respectively, when a trip signal is output from the central processing unit 32.

Next, the operation will be described with reference to the flowchart of FIG. First, the measurement terminal 19 uses the current I detected by the current transformer 17 and the transformer 18 as in the conventional device.
The power flow value P flowing through the power transmission line 5 is measured based on the voltage V detected by, and the frequency f of the grid is measured.

As a result, the central processing unit 32 takes in the system frequency f measured by the measuring terminal 19, calculates the variation Δf of the frequency f with respect to the reference frequency,
Based on the fluctuation amount, it is determined whether or not an accident to be controlled in the power system has occurred (step ST1).

When it is judged that no accident has occurred in the electric power system, the power flow value P measured by the measuring terminal 19 and the operation of the generators 11, 12 collected by the central power supply command station 31. Import information (step ST
2) The maximum frequency value, the minimum value, and the settling frequency value for the assumed accident are calculated as shown below from the characteristics of FIGS. 2A and 2B (step ST3). Δf _H1 = K _H1 · Ru (3) Δf _L1 = K _L1 · Ru + Δf ₀₁ (4) Δf _H2 = K _H2 · Ru (5) Δf _L2 = K _L2 · Ru + Δf ₀₂ (6) where Δf _H1 : Frequency highest value Δf _L1 : Frequency lowest value Δf _H2 : Ascending side settling frequency value Δf _L2 : Falling side settling frequency value Ru: Supply / demand imbalance rate = -P / P _0G × 100 P: Before interconnection line accident Power flow (Positive power reception is positive) P _0G : Total amount of power generated by the generator in the system K _H1 : System constant at the highest frequency K _L1 : System constant at the lowest frequency K _H2 : System at the rising side settling frequency Constant K _L2 : System constant at the falling side settling frequency Δf ₀₁ : Coefficient of the lowest frequency Δf ₀₂ : Coefficient of the falling side settling frequency where the constants K _H1 , K _L1 , K _H2 , K _L2 and the coefficient Δf ₀₁ ，
Δf ₀₂ is set in advance by simulation.

Then, from the result of the frequency calculation, it is judged whether or not the settling destination frequency and the highest and lowest values of the frequency are within the stable operation region of the generator (step ST4). Arbitrary system control pattern was implemented among a plurality of system control patterns set in advance (combinations of the load to be cut off and the generator, and the output amount of the generator to be controlled are registered in the system control pattern) It is assumed that the settled frequency and the highest and lowest values of the settling frequency are repeatedly calculated and determined until a system control pattern that can transit to the stable operation region is found (steps ST4, ST5, ST6).

[0024] That is, the control amount in the case of carrying out the control pattern Q _L, and Q _P, and calculates the predicted frequency Delta] f 'after controlled as shown below. Δf _H1 '= K _H1 · Ru' (7) Δf _L1 '= K _L1 · Ru' + Δf ₀₁ (8) Δf _H2 '= K _H2 · Ru' (9) Δf _L2 '= K _L2 · Ru' + Δf ₀₂ (10) where Δf _H1 ': maximum frequency value after control Δf _L1 ': minimum frequency value after control Δf _H2 ': rising side settling frequency value after control Δf _L2 ': falling after control Side settling destination frequency value Ru ': Supply and demand imbalance rate after control = (-(P-Q
_L ) -Q _P ) / (P _0G -Q _P ) × 100 P: Power flow before the interconnection line accident (reception is positive) P _0G : Total power generation of generators in the local system K _H1 : At maximum frequency System constant K _L1 : System constant at the lowest frequency K _H2 : System constant at the rising side settling frequency K _L2 : System side constant at the falling side settling frequency Δf ₀₁ : Coefficient of the lowest frequency Δf ₀₂ : Downside settling coefficient of the previous frequency Q _L: required load shedding amount Q _P: required power limit amount

Specifically, since a plurality of system control patterns are set with respective priorities, it is assumed that the system control patterns having higher priorities are sequentially executed, and frequency calculation and stable region determination of the power system are performed. The frequency calculation and the stable region determination are ended at the time when a system control pattern that allows transition of the settling frequency and the maximum and minimum values of the frequency to the stable operation region is found.

Then, when the central processing unit 32 finds a system control pattern capable of transitioning the settling frequency, the maximum frequency value, and the minimum frequency value within the stable operation region, the assumed accident actually occurred in the stabilization control table. The system control pattern is registered as the accident handling pattern at that time (step ST7). However, in step ST4, when it is determined that the settling frequency and the maximum and minimum values of the frequency are within the stable operation range of the generator, and the stable operation range determination based on the system control pattern is not performed, the assumed accident The fact that there is no need to control even if occurs actually is registered in the stabilization control table.

On the other hand, the central processing unit 32 executes the step ST.
When it is determined that an accident has occurred in the power system in 1, the accident point and accident type of the accident are specified based on the power flow value P, active power, voltage V, frequency f, etc. (step ST8). .

Then, when the accident point and the accident type of the accident are specified, it is determined whether or not there is a predicted accident that coincides with the accident among the predicted accidents for which the frequency calculation was performed in step ST3 previously ( In step ST9), if there is a contingency accident that matches the accident, the stabilization control table is referenced and the system control pattern of the concurrence accident is read (step ST10).

Finally, when the central processing unit 32 reads the system control pattern of the coincident expected accident, it outputs a trip signal or a generator control signal to the control terminals 22 to 25 based on the system control pattern. Thereby, the control terminals 22 to 25 cut off the load or the generator,
Alternatively, the output amount of the generator is controlled (step ST1
1).

As described above, according to the first embodiment, when the settled destination frequency and the maximum and minimum values of the frequency are not within the stable operation region of the generator from the result of the frequency calculation of the power system with respect to the expected accident. Selects a system control pattern that can transition the generator into the stable operation range based on the result of frequency calculation performed again assuming that an arbitrary system control pattern has been implemented from among a plurality of preset system control patterns. Therefore, it is possible to control the frequency abnormality to an appropriate frequency while transitioning the generator, which is in an unstable state due to the frequency abnormality, to the stable state. As a result, there is an effect that the power system can be kept stable.

In the registration of the grid control table in steps ST1 to ST7, the state of the power system changes from moment to moment, and if the state of the power system changes, the previously registered system control table will be used for the expected accident. Since it may not be appropriate, the registration of the system control pattern for the expected accident is updated every predetermined period (several seconds to several minutes) so that the appropriate system control table can always be selected. I am trying.

Thus, even if the state of the power system changes momentarily, the frequency abnormality can be controlled to an appropriate frequency while maintaining the state of all the generators stable.

Embodiment 2. In the first embodiment, the frequency maximum value, the minimum value and the settling frequency are predicted and calculated from the characteristics of the supply and demand imbalance rate and the frequency deviation of the separated system,
We have shown the method of determining whether the generator is in the stable operation range from the predicted frequency. From the characteristics of the supply and demand imbalance ratio and frequency deviation of the generator plant alone, the maximum and minimum frequency values of the plant alone, The settling frequency may be predicted and calculated, and the frequency of the separated system may be predicted by weighting and averaging the operating plants in the separated system with the power generation amount, and the same effect as that of the first embodiment is obtained.

That is, the characteristics of the supply and demand imbalance rate and the frequency deviation as shown in FIGS. 2 (a) and 2 (b) are obtained for each generator plant, and the highest and lowest frequency values obtained from the characteristics are obtained. , The frequency of the isolated system from the settling frequency Δ
f is calculated as shown below. Δf = (P _G1 · Δf ₁ + ... ··· + P _G1 · Δf ₁ ) / P _0G (11) where Δf is the highest frequency value, the lowest value, and the settling frequency P _{G1 is} the power generation of each plant. Δf ₁ : Maximum and minimum values of frequency of each plant, settling frequency P _0G : Total amount of power generated by generators in own system

As described above, according to the second embodiment, when the power supply and demand imbalance rate and the frequency characteristics are obtained from the characteristics of the power plant alone included in the power system, the power system changes momentarily. However, it is possible to control the frequency abnormality to an appropriate frequency while maintaining the stable state of all the generators.

Embodiment 3. In the second embodiment, the system constant K and the coefficient Δf ₀ of the characteristics of the supply and demand imbalance rate and frequency deviation of the plant alone are treated as fixed values, and the method for obtaining the system constant K and the coefficient Δf ₀ is not particularly mentioned. However, the system constant K and the coefficient Δf ₀ are determined by the generator output P _G
Therefore, if the system constant K and the coefficient Δf ₀ are appropriately obtained, the frequency can be obtained more accurately than in the second embodiment.

Incidentally, the system constant K is specified by the following equation, and the system constant K and the generator output P _{G have} the relationship shown in FIG.

K _H1 = a _H1 · P _G + b _H1 (12) K _H2 = a _H2 · P _G + b _H2 (13) where a _H1 , b _H1 , a _L1 , b _L1 , a _H2 , b _H2 , A _L2 ,
b _L2 is a predetermined coefficient and is specified from the result of simulation.

The coefficient Δf ₀ is specified by the following equation, and the coefficient Δf ₀ and the generator output P _{G have} the relationship shown in FIG. _{Δf 01 = c 1 · P G} + d 1 ... (14) Δf 02 = c 2 · P G + d 2 ... (15) _{However, c 1, d 1, c} 2, d 2 is a predetermined coefficient,
It is specified from the simulation result.

As described above, according to the third embodiment, the frequency anomaly is accurately controlled to an appropriate frequency by determining the power supply / demand unbalance ratio and the frequency characteristics of the power generation plant by using the generator output as a parameter. it can.

Fourth Embodiment A method of calculating the power supply limitation amount for the stable operation determination frequency of the generator according to the second embodiment will be described. The power supply limit amount to be implemented when the maximum frequency value and the settling frequency determined in the second embodiment exceed the stable operation region of the generator can be calculated by the following equation.

Δf ′ = (P _G1 · Δf ₁ ′ + ··· + P _G1 · Δf ₁ ′ −Q · Δf _Q ^′ ) / (P _0G −Q) (16) where Δf ′: Maximum frequency after control, settling frequency P _G1 : Power generation amount Δf ₁ 'of each plant: Maximum frequency value of each plant after control, settling frequency P _0G : Total power generation amount Δf _Q of generators in its own system ': The maximum frequency value of the power-supply-restricted target plant after control, the settling frequency Q: the power generation amount of the power-supply-restricted target generator In this way, by modifying the equation (11) of the second embodiment as described above, Since the maximum frequency value Δf _H1 and the settling frequency Δf _H2 can be lowered to Δf _H1 ′ and Δf _H2 ′ as shown in FIG. 6, the power supply limit amount Q at that time can be obtained.

As described above, according to the fourth embodiment, by including the arithmetic expression power source limit amount of the predicted frequency, even if the power system changes due to the power source limit, the states of all generators are changed. It is possible to control the frequency abnormality to an appropriate frequency while maintaining stable.

[0044]

As described above, according to the first aspect of the present invention, the characteristics of the supply and demand imbalance rate and the frequency deviation are changed in advance based on the amount of power generation in the controlled system before the occurrence of system disconnection and the interconnection line power flow. The maximum frequency, the minimum value, and the settling frequency are calculated in advance, and the transient frequency maximum value, the minimum value, and the settling frequency value at the time of system division are calculated using these characteristics, and the generator frequency is calculated from each value. Since it is configured to control the frequency within the stable operation range, it is possible to control the frequency anomaly to an appropriate frequency while transitioning the generator that reaches an unstable state due to the frequency anomaly to the stable state. There is an effect that the power system can be stably maintained.

According to the second aspect of the invention, since the characteristics of the supply and demand imbalance rate and the frequency are obtained from the characteristics of the power plant alone included in the own system, even when the power system changes momentarily. There is an effect that the frequency abnormality can be controlled to an appropriate frequency while maintaining the stable states of all the generators.

According to the third aspect of the invention, the power supply / demand unbalance rate and frequency characteristics of the power plant itself are determined by using the generator output as a parameter. Therefore, the frequency abnormality can be accurately controlled to an appropriate frequency. effective.

According to the fourth aspect of the present invention, when the transient maximum frequency value and the settling frequency value exceed the stable operation range of the generator on the frequency increasing side, the frequency value is lowered to within the stable range. In addition, since the power limit amount is calculated by removing the frequency value of the plant subject to power limit from the weighted average, even if the power system changes due to the power limit, the state of all generators can be maintained stable. At the same time, the frequency abnormality can be controlled to an appropriate frequency.

[Brief description of drawings]

FIG. 1 is a frequency waveform diagram when the interconnection line route is broken, showing the basic principle of the present invention.

FIG. 2 is a characteristic diagram of supply and demand imbalance rate and frequency deviation showing the basic principle of the present invention.

FIG. 3 is a configuration diagram showing a frequency abnormality control device according to a first embodiment of the present invention.

FIG. 4 is a flowchart showing processing in the apparatus of FIG.

FIG. 5 is a characteristic diagram showing a supply and demand imbalance rate and a frequency deviation according to the third embodiment of the present invention.

FIG. 6 is a waveform diagram showing waveforms during power supply limitation and power supply non-control according to Embodiment 4 of the present invention.

FIG. 7 is a configuration diagram of a conventional frequency abnormality control device.

[Explanation of symbols]

5 Transmission lines (interconnection lines), 11 and 12 generators.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Kamikubo 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Masuo Tsukada 1 Higashishin-cho, Higashi-ku, Nagoya, Aichi Chubu Electric Power Co., Inc. Company (72) Inventor Masamichi Kojima 1 Higashishinmachi, Higashi-ku, Nagoya, Aichi Chubu Electric Power Co., Inc. (56) Reference JP-A-8-103024 (JP, A) JP-A-62-160038 (JP, A) JP-A-2-276423 (JP, A) JP-A-63-181617 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J 3/00-5/00 H02P 9/10

Claims (4)

(57) [Claims] 1. The characteristics of supply and demand imbalance ratio and frequency deviation are preliminarily determined based on the amount of power generation in the controlled system before the occurrence of system disconnection and the interconnection line power flow with respect to the transient frequency maximum value, minimum value, and destination frequency. In advance, when the power system is divided into grids and an imbalance occurs between the power generation of the generator and the power consumption of the load in the separated grid, the characteristics of the supply and demand imbalance ratio and the frequency deviation are calculated. Use this to find the maximum value of the transient frequency rise when the power generation is excessive, the minimum value of the transient frequency decrease when the power generation is insufficient, and the settling frequency, and the frequency value is outside the stable operation range of the generator. When it is determined that the frequency is stabilized, the frequency is controlled within the generator stable operation region by limiting the power source and the load according to the respective conditions. 2. The characteristics of the supply and demand imbalance ratio and the frequency deviation are obtained for the plant alone, and the transient frequency maximum value, minimum value, and
The frequency of the separation system is calculated by calculating a settling frequency value and performing a weighted average of the respective frequency values with the power generation amount of the operating plant included in the separation system. Stabilization method. 3. The characteristics of the supply and demand imbalance ratio and frequency deviation of the plant alone are obtained by using the generator output as a parameter, and the frequency values of the plant alone obtained by using these characteristics are the operating plants included in the separated system. The frequency stabilizing method according to claim 2, wherein each frequency value of the separated system is calculated by performing weighted averaging with the power generation amount of minutes. 4. When the transient maximum frequency value and the settling frequency value exceed the stable operation range of the generator on the frequency rising side, in order to reduce the frequency value to within the stable range, the power source restricted plant alone The frequency stabilizing method according to claim 2, wherein the power supply limitation amount is obtained by removing the frequency value from the weighted average.