JP3418503B2 - Power system frequency stabilizer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system maintenance and frequency maintenance method for an electric power system, and in particular, in the case where a system separation occurs, online information is taken in and adaptively operated and controlled to maintain the system maintenance and frequency. The present invention relates to a frequency stabilizing device for maintaining.

[0002]

2. Description of the Related Art In the operation of a power system, when a power line route disconnection occurs due to a transmission line accident or the like, a frequency deviation occurs in a separated system due to supply and demand imbalance. In order to eliminate this and stabilize the frequency fluctuations in the isolated system, it is necessary to promptly correct the imbalance between supply and demand in the isolated system. The means for that is to forcibly cut off the power supply or the load. For this purpose, a frequency stabilizing device has been installed in the isolated system for urgently cutting off the power (electrical control) and cutting off the load (negative control).

Since it is difficult to grasp the supply and demand imbalance by observation, the current system makes some estimation of the supply and demand imbalance. For example, consider the load drop due to the interconnection flow and the voltage drop at the separation occurrence point. The tidal current of the interconnection line is grasped by observation, and the load drop amount is estimated and calculated from the past statistics of the voltage drop rate as a rough estimation method.

The estimated load drop amount and the interconnection line flow rate are summed up, and it is considered that there is a supply-demand imbalance that should be eliminated. This supply-demand imbalance is used as the first-stage control amount for control to maintain the supply-demand balance. Stabilizes the frequency.

As a known example of this type, Japanese Patent Publication No. 7-108
No. 063, Japanese Patent Publication No. 7-184324 and the like.

[0006]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 7-108
Japanese Patent Laid-Open No. 063 discloses a method of performing control so as to eliminate most of the estimated supply and demand balance immediately after separation. In this case, excessive control may be performed due to the influence of an error in the statistical load drop amount estimation processing and an error in the observation processing. In particular, in the case of eliminating the supply-demand imbalance for the separated system in the excessive supply state by the electric control, the excessive electric control puts the separated system in the insufficient supply state. This causes a significant deterioration in the frequency characteristics of the isolated system, which increases the risk of maintaining the isolated system.

[0007] To prevent this problem, in order to prevent excessive electric control, the control amount in the control immediately after the occurrence of separation is made small and the remaining supply / demand imbalance is observed by making the control amount too small. There is an idea to solve it by. However, in this case, a transient frequency peak may become a problem by making the control amount short after the separation occurs.

This idea is based on the latter Japanese Patent Publication No. 7-18432.
In this case, the main means is to check the threshold value of the peak frequency obtained from the pre-settled coefficient, and the calculation of the control amount adapted to the characteristics of the separated system is required. I haven't arrived. In the current situation where power system components are diversifying, it is an important issue to adapt to the characteristics of the isolated system online.

An object of the present invention is to provide a frequency stabilizing device capable of maintaining the system and maintaining the frequency by adapting to the characteristics of the on-line separated system.

[0010]

SUMMARY OF THE INVENTION The above-mentioned object is that the characteristics of the frequency of the isolated system largely depend on the configuration of the generators in parallel with the isolated system and their operating states, and therefore the output of the generator and the power generation. An observation device for observing the state quantity of the machine control system online is installed, and a storage device for storing the constants of the generator and the generator control system that do not depend on the operation state is installed. This is achieved by providing the control signal output device with an estimating and calculating means for the characteristics of the separated system and a frequency peak predicting calculating means, or a control amount calculating means for considering the frequency peak.

If the above-mentioned means is used, the characteristics related to the frequency response of the isolated system are estimated by the on-line observing device of the generator output and the state quantity of the generator control system, whereby the peak frequency is predicted. It is possible to determine that it is necessary to immediately perform the control in order to suppress the frequency response after separation within the allowable frequency range.

Further, when the frequency response exceeds the allowable frequency range, it is possible to calculate the minimum control capable of suppressing the predicted peak frequency within the allowable frequency and to execute only the minimum control immediately after the separation occurs. become. The allowed control residue can be reliably eliminated based on observation.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which the present invention is applied to a frequency stabilizing device for stabilizing the frequency of a separated system.

First, in the electric power system, an online database 16 is provided, and a plurality of potential grid accident points 1
1. The tidal flow rate 12 of 1 and each output amount 15 of the plurality of generators 14 in the separation system 13 generated by the system separation of the assumed point 11 are periodically sampled online and stored in the online database 16. To do. Further, a database 17 for accumulating the offline data of the plurality of generators 14 included in the separation system 13 is prepared. This database 17 stores parameters that do not depend on operation for each generator i. In the first embodiment,
The inertia constant M _i and the governor adjustment rate δ _i are stored.

From the grid online database 16, it is recognized that the generators 14 having an effective generator output P _Gi are connected in parallel in the separated grid 13, and the database 17 of the generators 14 of each generator 14 is recognized. The characteristics are input to the electric control determining means 18, an appropriate electric control amount in consideration of the maximum frequency is immediately calculated, and the electric control command 19 is output immediately after the separation, thereby maintaining the separation system 13 and stabilizing the frequency. To realize.

The calculation contents of the electronic control determining means 18 will be described below. First, the pre-computation is performed by the process shown in FIG. The pre-calculation unit cyclically processes all the monitoring point cyclic calculations 21 for the assumed separation point that is the target of stabilization.

Next, the generator configuration in the separated system is grasped from the above-mentioned observation mechanism and the separated system parallel generator recognition means 22. Based on the resulting generator set of the separated system, the separated system characteristic calculation means 23 calculates the characteristics of the entire separated system. In the first embodiment, the number 1, the number 2, and the number 3
Calculate.

[0019]

[Equation 1]

[0020]

[Equation 2]

[0021]

[Equation 3]

Here, P _G represents the total output in the separation system, and M _G corresponds to the inertia constant of the entire separation system. K _G corresponds to the frequency characteristic coefficient of the isolated system.

Using these calculated values of the isolated system characteristic calculating means 23 and the interconnection line power flow ΔP _o , the maximum frequency Δfmax in the uncontrolled state is predicted as shown in equation (4).

[0024]

[Equation 4]

Here, the constant A is a coefficient that correlates with the time constant of the generator governor. This value can be calculated from the design time constant of the control block of the generator governor, or settled by an offline or online simulation.

By the above pre-processing, when the value of Δfmax obtained by the above equation 4 exceeds the value of the maximum allowable frequency deviation Δf _LIMIT determined by another means, proper electric control is performed as shown in FIG. Will be needed.

At the time of system separation detection, proper electric control is carried out by the processing of FIG. When the system separation detecting means 31 detects the system separation, the electric quantity calculating means 32 immediately obtains the electric quantity P _c . P _c is calculated by Equation 5.

[0028]

[Equation 5]

Here, K _S is the ratio (constant) of the in-house load to the amount of power generation, and α is a constant that is uniquely determined with respect to the system state, and is expressed by Equation 6.

[0030]

[Equation 6]

When the calculated amount of electric control has a positive value, electric control is required corresponding to the case where the value of Δfmax exceeds the value of Δf _LIMIT . The control target determining unit 33 selects an electric control machine corresponding to the electric control amount as a control target, and executes the control commanding unit 34. The above is the calculation contents of the electronic control determining means 18.

By installing the frequency stabilizing device shown above in the electric power system, it is expected that the maximum frequency after control will be suppressed to the allowable maximum frequency deviation Δf _LIMIT or less and excessive electric control will be prevented as much as possible. it can. This improves the certainty of control in maintaining the separated system. Also,
By reducing the control amount, economic loss can be expected to be suppressed.

In the above embodiment, an example is shown in which the electric control is carried out when the supply and demand balance in the separated system is excessive.

As a second embodiment, as shown in FIG. 5, the tidal flow rate 41 of insufficient supply to the separation system side at the separation occurrence point.
The frequency stabilizing device in such a case will be described.

The same principle is applied to the case where the negative control is carried out in the state of insufficient supply. The same as in the case of the first embodiment, the negative decision command 42 is calculated by the negative decision command 42.
Is output, the frequency is stabilized by performing an appropriate emergency cutoff of the load 44 to be cut off in consideration of the peak frequency.

In the isolated system characteristic calculation means 23 of the first embodiment, the constant A which is a coefficient correlating with the governor time constant.
Was set in advance. However, the constant A can be adaptively calculated when the configuration of the system is changed or the operating state is drastically changed.

As a third embodiment, in addition to the first embodiment, a frequency stabilizing device for adaptively calculating the constant A by the isolated system characteristic calculating means 23 in the pre-calculation will be described.

Separated system characteristic calculation means 2 of the first embodiment
In calculating the constant A in 3, first, the generator is roughly divided into a thermal boiler machine and a combined cycle machine offline, and the constant A is prepared in the offline database 17 for each. Here, the value Ac for the combined cycle governor and the value Ab of the thermal power boiler are used. Then, the separation system characteristic calculation means 23 weights and averages the values of Ac and Ab by the output ratio of the thermal boiler machine and the combined cycle machine. In the third embodiment, the total output of the thermal power boiler is Pb and the total output of the combined cycle is Pc.
The constant A will be calculated by a calculation formula such as Equation 7.

[0039]

[Equation 7]

By the above processing, the isolated system characteristic calculation means 2
In the third embodiment, in addition to the first embodiment, it is possible to add a process that adapts to the operation status of the generator online.

By installing the frequency stabilizing device shown in the third embodiment in the electric power system, in addition to the effects of the first embodiment, except for the case of a new generator, settling work and the like can be performed. Maintenance can be further reduced.

Further, in addition to the first to third embodiments, it is possible to more accurately calculate the control amount by observing the state amount of the control system of the generator.

In other words, as the fourth embodiment, by observing the state quantity of the control system of the generator, the power generation output adjustment amount, which was treated as a simple model for the observed frequency deviation in the first embodiment, is accurately grasped. Therefore, the control amount can be calculated more accurately. FIG. 6 shows a device configuration diagram.

First, in the electric power system, the interconnection flow tides 12 at a plurality of assumed grid separation accident points 11 and the output amounts 15 of a plurality of generators 14 in the separated grid 13 caused by the separation accidents at the assumed grid points, In addition, the governor main valve opening control signal 51 of the control system 50 of each generator is periodically sampled online, and the online database 1
Accumulate in 6.

Further, a database 17 for accumulating offline data of a plurality of generators 14 which can be included in the separated system is prepared. The database 17 stores parameters that do not depend on the operation, such as the inertia constant M _i and the governor adjustment rate δ _i , for each generator i.

It is recognized from the grid online database 16 that the generators having an effective generator output P _Gi are connected in parallel in the separated grid, and the characteristics of each generator are controlled from the database 17 for those generators. After inputting to the determining means 52 and estimating the response of the output control of the generator by the governor based on the observation, an appropriate electric control considering the maximum frequency is immediately calculated and the electric control command 19 is output immediately after the separation. By doing so, it is possible to realize the maintenance of the separated system and the stabilization of the frequency.

By installing the frequency stabilizing device shown in the fourth embodiment in the power system, the control amount is calculated including the suppression amount of the control system. Therefore, the accuracy of the control according to the first embodiment is improved. In addition to being able to further increase the number, it is possible to reduce the work for setting and maintaining the parameters used in the estimation means that is an alternative to observation in the first embodiment.

Finally, the grounds for deriving the operation contents used in the first embodiment will be described. First, the number of simple prediction equations 4 for the maximum frequency is derived as follows.

As can be derived from the equation of motion of the rotating system, the oscillation equations of the generator are summarized with respect to frequency and expressed by the differential equation number 8.

[0050]

[Equation 8]

M represents the inertia constant of the generator, and the unbalanced amount in the separated system is given by the initial unbalanced amount ΔP _o and the governor output suppression amount ΔP _G (t).

The response of ΔP _G (t) is the time constant τ and the adjustment rate δ.
The frequency response equation (9) is obtained by solving the equation of simple free vibration obtained by combining with the equation (8) by appropriately simplifying from the temporary delay model of. Therefore, the maximum frequency is given by Equation 10.

[0053]

[Equation 9]

[0054]

[Equation 10]

When this is applied to a multi-machine system, the following equation 11 is obtained. Here, the subscript i represents the generator number.

[0056]

[Equation 11]

According to the equations 1, 2, and 3, M _G , P _G , and K _G
When is obtained, the equation 11 can be expressed as the equation 12.

[0058]

[Equation 12]

However, the average value of τi is τ '. Equation 4 is derived from this.

Next, Formula 5 is derived. Maximum frequency is Δf
_It is assumed that the power is disconnected for the control amount Pc such that the limit is reached. In the state after control, the supply and demand imbalance is ΔP ′ _O , the total output is P ′ _G , the system inertia constant is M ′ _G , the system frequency characteristic coefficient is K ′ _G , and the parallel load power station load is P Represented by _S. In this case, it suffices to obtain the power supply limitation amount P _C that satisfies the expression 13.

[0061]

[Equation 13]

However, the combination of inertia constants,
It is not practical to solve the problem by considering the combination in the adjustment rate and the combination for the in-house load because complicated processing is required. Therefore, the combination problem is simplified and summarized as shown in Expression 14.

[0063]

[Equation 14]

Here, if the constant term that is uniquely determined for the system is represented by α by the equation 6, an equation that further simplifies the equation 14 can be obtained. From this, the control amount P _C is solved, and Equation 5 is derived.

[0065]

According to the present invention, it becomes possible to carry out the minimum control immediately after the occurrence of separation so that the peak frequency falls within an appropriate range. The allowed control residue can be reliably eliminated based on observation.

As a result, since excessive control can be prevented, the reliability of control is improved in terms of maintaining the separated system. Further, it is possible to expect economical loss control by surely reducing the control amount.

Further, by adapting the operating condition of the generator online, the accuracy of the above technique can be improved, and maintenance such as settling work can be reduced except when a new generator is installed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a frequency stabilizing device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a pre-calculation unit in FIG.

FIG. 3 is a schematic diagram of the post-computation means of FIG.

FIG. 4 is an explanatory view of a maximum frequency suppression state.

FIG. 5 is a configuration diagram of a frequency stabilizing device according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of a frequency stabilizing device according to another embodiment of the present invention.

[Explanation of symbols]

11 ... Assumed point, 12 ... Interconnection tidal flow rate, 13 ... Separation system, 14 ... Generator, 15 ... Output amount, 16 ... Online database, 17 ... Parameter database, 18 ... Electricity control determining means, 19 ... Control command, 21 ... Cyclic calculation of all monitoring points, 22 ... Separation system parallel generator recognition means, 23 ...
Separation system characteristic calculation means, 31 ... System separation detection means, 32
... electric control amount calculation means, 33 ... controlled object determination means, 34 ... control command means, 41 ... tidal flow rate, 42 ... negative control determination means, 43
... negative control command, 44 ... load, 50 ... control system, 51 ... main valve opening control signal, 52 ... electronic control determining means.

─────────────────────────────────────────────────── ─── Continued front page (72) Tomoji Nakamura Inventor Tomoji Nakamura 1-1-1, Kokubuncho, Hitachi City, Ibaraki Hitachi Co., Ltd. Kokubun Factory (72) Inventor Masuo Tsukada 1 Higashishinmachi, Higashi-ku, Nagoya-shi, Aichi Chubu Electric Power Co., Inc. (72) Inventor Masamichi Kojima 1 Higashishinmachi, Higashi-ku, Nagoya, Aichi Chubu Electric Power Co., Ltd. (56) Reference JP-A-7-184324 (JP, A) JP-A-7-241035 (JP , A) Japanese Patent Publication 7-108063 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02J 3/00-5/00

Claims (8)

(57) [Claims] 1. In a frequency stabilizer for a power system supplying electric power from a plurality of generators, a plurality of grid separation assumed points in the power system are connected to each other from normal times and the tidal flow rate from the grid is assumed. , A monitoring device that periodically observes the generator output and the state quantity of the control system of the generator that occurs due to the system separation at the assumed point, and a storage device that stores the constants of each generator When an occurrence occurs, the supply and demand imbalance in the separation system is based on the observed tidal flow rate, the observed generator output amount, the observed generator control system state quantity, and various constants of each generator in the storage device. A frequency stabilizing device for a power system, which is provided with means for determining whether a frequency peak is within a certain range by predicting a transient change in frequency caused by the frequency stabilizing device. 2. In a frequency stabilizer for a power system that supplies electric power from a plurality of generators, for a plurality of assumed grid separation points in the power system, the tidal flow rate from normal to the assumed grid , The observation device that periodically observes the generator output and the state quantity of the generator control system in the separation system caused by the system separation at the assumed point, and the storage device that stores the constants of each generator are provided. When it occurs, based on the observed tidal flow, the observed generator output, the observed generator control system state quantity, and the constants of each generator in the storage device, the supply and demand imbalance in the isolated system causes By predicting the transient change in the frequency that occurs, when the frequency peak exceeds a certain range, calculate the amount of supply and demand imbalance elimination necessary to suppress the frequency peak within the certain range, including the control system suppression amount. What to do ,
A frequency stabilizing device for a power system, characterized by being provided with a means for performing a control for limiting a power source or a load immediately after a system isolation, or a limit corresponding thereto. 3. The frequency stabilizing device for an electric power system according to claim 1, wherein the prediction determining unit includes each of the observed tidal flow rate, the observed generator output amount, and the storage device. Based on the constants of the generator, by combining them according to the share of the amount of power generated by multiple generators, the characteristics of multiple generators are reduced to the characteristics of one generator, A frequency stabilizing device for a power system, which is characterized by predicting a transient change in frequency caused by an imbalance between supply and demand in a separated system. 4. The frequency stabilizing device for a power system according to claim 1, wherein the prediction determining means includes the observed tidal flow rate, the observed generator output amount, and each of the storage devices. Based on the constants of the generator, by combining them according to the share of the amount of power generated by multiple generators, the characteristics of multiple generators are reduced to the characteristics of one generator, A frequency stabilizing device for a power system, which is characterized by predicting a transient change in frequency caused by supply and demand imbalance in a separated system from the equation of motion. 5. The frequency stabilizing device for a power system according to claim 4, wherein the prediction determining unit predicts a transient change in frequency caused by supply and demand imbalance from a motion equation of a generator. A frequency stabilizer for electric power systems, which is characterized by roughly estimating the frequency peak from the secondary vibration component of. 6. The frequency stabilizer for the electric power system according to claim 1, wherein the generator constant storage device classifies the generator and control system into types in advance, A storage device for storing the settling power generator and various constants of the control system is provided, and the prediction determination unit is configured to store the observed tidal flow rate, the observed generator output amount, and a corresponding type of advance in the storage device. Based on the settling constants, the characteristics of multiple generators can be reduced to the characteristics of a single generator by combining them according to the share of the power generation amount of multiple generators. A frequency stabilization device for a power system, which is characterized by predicting a transient change in frequency caused by an imbalance between supply and demand in the system. 7. The frequency stabilizing device for a power system according to any one of claims 1, 2, wherein the generator various constant storage device performs classification of the type for the generator and a control system in advance, A storage device for storing the settling power generator and various constants of the control system is provided, and the prediction determination unit is configured to store the observed tidal flow rate, the observed generator output amount, and a corresponding type of advance in the storage device. Based on the selection constants, the characteristics of multiple generators are reduced to the characteristics of one generator by combining them according to the share of the power generation amount of multiple generators. A frequency stabilizer for a power system characterized by predicting a transient change in frequency caused by a supply-demand imbalance in a separated system using a motion equation. 8. The power system frequency stabilizing apparatus according to claim 2, wherein the control means performs power supply limitation or load limitation in order to suppress a frequency peak within the certain range, or a limitation corresponding thereto. When calculating the unbalance elimination control amount, the calculation formula obtained by treating the change in the combinational influence by the selection of discrete control targets with a continuous mathematical expression regarding the influence of the assumed control amount on the system characteristics. A power system frequency stabilizer characterized by using