JP2001037085A - Method and apparatus for frequency controlling power system including secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To instantaneously maintain a demand and supply balance at normal and emergency times in a power system by incorporating a secondary cell for charging or discharging to suppress a change in a frequency based on a detected result of a frequency deviation detector. SOLUTION: A deviation Δf from a reference frequency of a frequency of a system is detected by a frequency detector 31 in an electric circuit 7 of a previously decided measuring ground point. If the deviation Δf exceeds a predetermined deviation range, an output command controller outputs an LFC signal, and controls output of a secondary cell system 30. A power controller 37 applies an output control signal based on a detection signal to a charge/discharge controller 34. The control signal controls the controller 34 to supply a power to the circuit 1 by discharging the cell 36 when the deviation Δf is a negative value. The control signal controls the controller 34 to charge the cell 36 to input the power to the secondary cell system when the deviation Δf is a positive value. Thus, a rapid and efficient operation can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency control method and apparatus for a power system using a secondary battery system.

[0002]

2. Description of the Related Art In a power system of a power business, power sources such as a nuclear power station, a thermal power station, and a hydropower station (including a pumped-storage power station) are used. These power sources fluctuate in frequency when power supply and demand become unbalanced. Of these power sources, nuclear power plants are operated so as to always output constant power. The other power supplies except the nuclear power plant adjust the output based on the output control signal issued from the central power supply dispatching station in response to the fluctuation of the power consumption of the load, that is, the fluctuation of the demand. As a result, the frequency is maintained within a predetermined deviation (for example, control target ± 0.1 Hz) from the reference frequency (50 Hz or 60 Hz) while maintaining a balance between the power supplied from each power supply and the power consumption of the load due to the output adjustment. Has been maintained.

[0003] Control of supply power in a power system (hereinafter, referred to as
Currently, the following two signals are mainly used as control signals for controlling the output of the generator in order to perform supply / demand control). One is an LFC signal (LFC) that controls the output of each generator in response to demand fluctuations in a cycle of several minutes to about 20 minutes.
oad Frequency Control signal, load frequency control signal)
It is. `` LFC '' is an abbreviation of load frequency control, and controls output of the generator so that the frequency does not deviate from a predetermined range of the reference frequency when imbalance occurs in supply and demand due to the demand fluctuation in the cycle. Say. The other is an EDC signal (Economic load Dispatching Control signal) for controlling the output of each generator in response to a large demand fluctuation with a longer cycle (20 minutes or more) than the LFC signal targets. Signal). For demand fluctuations in which the fluctuation width is shorter (less than a few minutes) than the target of the LFC signal, the power is automatically generated according to the frequency fluctuation of the power system by the governor-free function provided in each generator. Controlling the output of the machine. When operating the power system, each of these functions is utilized to appropriately control the output of each generator in response to fluctuations in demand in the power system, so that the frequency of the power system is within a predetermined deviation from the reference frequency. It is controlled to be kept. However, there are cases in which it is not possible to respond to demand fluctuations only by controlling the output of the generator. In such a case, various power storage technologies may be used to store power when demand is low and to release the stored power when demand is high to respond to demand fluctuations.

As a power storage technology, the development of a secondary battery system using a secondary battery such as a sodium-sulfur battery or a redox flow battery is in progress. Since the secondary battery system is linked to the power system via the AC / DC converter using the DC power supply utilizing the chemical reaction, the output responsiveness to the output control signal is higher than the various power supplies. Has features. In addition, as a feature of the secondary battery, overload operation can be performed for a short time of several seconds to several minutes. However, the maximum overload time varies depending on the battery capacity, battery characteristics, and design specifications. Overload operation is charging with power exceeding the rated power of the rechargeable battery (meaning the power when charging and discharging at a constant power for a predetermined time to achieve the highest efficiency in consideration of the capacity of the rechargeable battery). Or discharge. Since the secondary battery has this capability, it can be said that the secondary battery is a more excellent power facility than existing various power sources in terms of supply and demand adjustment capability.

At present, the above two types of secondary batteries are:
The situation is almost technically complete. For example, several hundred kW
Class facilities are actually operated as power storage facilities for the purpose of peak cutting in office buildings and the like. Also,
Studies are also underway on large-capacity facilities of the order of thousands of kW as power storage facilities at the practical stage, and operation in the supply and demand control field in power systems is being studied.

[0006]

Most of the thermal power generators (hereinafter referred to as "thermal power generators") for the electric power industry have their output lower than the rated output during normal operation so as to cope with a sudden increase in demand. The operation is controlled to When demand fluctuations occur, the output of a generator such as a thermal power plant during steady operation is suppressed to below the rating so that the output can be increased or decreased to keep the frequency fluctuation within a predetermined allowable deviation. This is called “securing the LFC adjustment capacity”, and the output with this extra margin is called “LFC adjustment capacity”. In order to secure LFC regulation capacity, even at the time of the day when demand is at its maximum, operation at the rated output with the highest power generation efficiency is not possible, and operation at a lower output than the rating is required. It is in a situation where optimal driving cannot be performed. Therefore, it is necessary to introduce a new technology that does not require as much as possible output suppression operation to secure the LFC adjustment capacity of the thermal power unit, and perform optimal operation of the power system.

[0007] It is known that a thermal power machine has a time delay in response to an output control signal due to its characteristics. This means that if the deviation from the reference frequency becomes large,
Even if output control is performed on a thermal power plant using an LFC signal, in some cases, it may not follow demand fluctuations. Fluctuations in generator output that do not follow demand fluctuations cause frequency disturbances. Therefore, in system operation, a generator with high response to demand fluctuation is desired. That is, if there is a power supply capable of prompt output control,
When a demand fluctuation occurs, an output control corresponding to the fluctuation is immediately performed, and a supply-demand balance can be maintained.

Since there is a time delay in the output control of the generator,
In consideration of the output sharing of the generator corresponding to the demand fluctuation, usually, the LFC adjustment capacity is shared by a plurality of generators. In order to build an efficient system using the supply and demand control technology in the current power system, it is necessary to replace it with a new power supply that can control the output faster than the existing power supply that shares the LFC adjustment capacity. In the normal operation of the power system, if a variable speed pumped generator with higher output responsiveness, that is, easier output control, is connected in parallel to the power system among existing power sources, It is known that the deviation of the frequency can be reduced as compared with the case where it is not performed.

As a change in power supply characteristics in a power system,
A change in output characteristics due to an increase in the size of a thermal power unit is cited. In thermal power plants, drum boilers with output of up to 400 MW (megawatts), which had been the mainstream until the early 1960's, will be replaced by larger boilers with larger output. Became. Drum boilers have a drum in the plant that acts as a buffer for heat capacity. In response to frequency fluctuations due to demand fluctuations, the output can be increased or decreased by this buffer function to maintain a desired output for a certain period of time. On the other hand, in a once-through boiler, water is turned into steam in a steam pipe and sent directly to a superheater and a turbine. Therefore, it does not have a buffer function unlike a drum boiler machine.

FIG. 6A is a graph showing a change from the reference frequency f0 of the frequency due to an increase in power demand accompanied by a small frequency fluctuation such that LFC is not performed. FIG. 6 (b)
Shows the change in the generator output of the drum boiler corresponding to the rapid increase in the power demand, and (c) shows the change in the generator output of the once-through boiler. In the drum boiler machine, as shown in FIG. 6B, when the frequency starts decreasing at time t0, a command to increase the output to Pa1 is issued. By this command, time t0
The generator output increases slightly later, reaches the output command value Pa1 at time t1, and keeps that state thereafter. In the once-through boiler machine, as shown in FIG.
, The generator output reaches the output command value Pb1, but starts decreasing at time t3. The time region in which the output of the once-through boiler machine decreases after time t3 is a region where the output is controlled by the governor-free function (hereinafter referred to as the GF function). In this way, the influence of the output characteristics of the once-through boiler having no heat capacity buffer on the frequency of the power system increases as the ratio of using the once-through boiler in the power system increases, and if the frequency decrease continues for a certain period of time, The output increase corresponding to the LFC adjustment capacity assumed by the grid operator cannot be obtained. Therefore, in recent frequency control, it is necessary to consider an LFC that also targets the GF function, and a power system technology that can cope with this is required.

Although a large number of nuclear power units are operating in Japan, the nuclear power units always operate at a constant output from the viewpoint of economic efficiency even in a light load period such as late at night when the power demand is lowest in a day. are doing. Depending on the configuration of each power supply operated during the light load period, the supplied power may be excessive. In addition, since nuclear power plants do not perform LFC operation, power equipment that controls output to adjust frequency during light load periods is
Some thermal and hydraulic (and possibly variable speed pumps)
It is limited. As a result, the LFC adjustment capacity may be insufficient, and it may be difficult to maintain the frequency at the reference frequency, and frequency fluctuation may increase. There is a demand for a frequency control method by introducing a new technology capable of coping with the suppression of the frequency fluctuation.

In the current operation of the electric power system, for example, there is a case where the LFC adjustment capacity is ensured by operating a low-efficiency thermal power unit that is aging and is not normally used during an increasing demand period. Since such an aging thermal power plant has low energy conversion efficiency, there is room for improvement in operation efficiency from the viewpoint of reducing fuel costs and effectively utilizing fossil fuels. Despite the purpose of ensuring the necessary LFC regulation capacity, the increase in the number of low-efficiency
2) Emissions of nitrogen oxides (NOx), sulfur oxides (SOx), etc. will increase. Therefore, it is necessary to reduce emissions as much as possible in view of social demands for environmental protection and pollution. Therefore, it is desired to introduce a new technology that can secure the necessary LFC adjustment capacity without using such an aging thermal power plant.

As a change in the environment surrounding the operation of the electric power system in the future, there is liberalization of the electric power market. With this liberalization,
It is considered that a large number of power sources using “renewable energy” such as solar and wind power are connected to the power system. Since these power sources use renewable energy in the natural world, they are greatly affected by weather conditions, and it is difficult to always supply constant power during normal operation. When a large number of such power sources with unstable power generation outputs are connected to the grid and their share in the power supply configuration increases, the output fluctuates greatly because it is difficult to obtain a constant power generation output from these power sources at all times. It is considered that a situation occurs in which it becomes difficult to maintain the frequency at the reference frequency. Therefore, it is necessary to construct a new technology capable of instantaneously coping with a large output change caused by an increase in the power source whose power generation output is unstable.

In order to deal with the above-mentioned problem, a prior art concerning frequency control using a secondary battery, which has been disclosed, will be described below. JP-A-5-1681
No. 71 proposes a solar cell power supply system that is connected to a distribution low-voltage system and that is a combination of a solar cell power supply system and a secondary battery. In this conventional technique, a secondary battery is used only as a power storage facility in a normal operation.
Operations that contribute to constant control of the frequency viewed from the power system, such as interpolating output fluctuations of the solar cell power supply system during normal operation due to weather conditions or the like with a secondary battery, are not considered.

Japanese Patent Application Laid-Open No. Hei 8-140285 proposes a power storage / distributed power supply system that uses a sodium-sulfur battery as a secondary battery to minimize fluctuations in system frequency. This system is connected to the distribution system, and does not consider operation in the power supply backbone system. Further, there is no mention of operation in consideration of coordination with other existing power sources by centralized control of the power system (for example, control from a central power supply command center). In addition, no study has been conducted on frequency control including suppression of power line flow fluctuation between interconnected power systems. Therefore, in this system, frequency fluctuations can be suppressed, but interconnection line power flow fluctuations cannot be suppressed. Also, this system does not consider how to handle load fluctuations in the time domain targeted by the LFC.
For example, the correction based on the sequential prediction is a correction one hour to 30 minutes ahead. In addition, LFC that has been shared by existing generators
No consideration is given to the operation of the secondary battery system for substituting for the adjusted capacity.

Japanese Unexamined Patent Publication No. 9-270269 proposes a system using a sodium-sulfur battery, such as a power storage device, a power system peak cut device, and a frequency / voltage stabilization device. This conventional example mainly relates to the specifications of the battery system, and does not relate to system control by operating the system.

The problems to be solved by the present invention are summarized as follows. From the viewpoint of improving operation efficiency, it is irrational from the viewpoint of improving operation efficiency that the thermal power plant's output suppression operation to secure the LFC adjustment capacity necessary for system operation is unreasonable. Was.
Due to a response delay characteristic of the power control of the thermal power unit, the output may not follow the demand fluctuation depending on the demand fluctuation. Due to this response delay, it has been demanded that the LFC adjustment capacity can be ensured without a response delay so that the LFC operation of the thermal power unit itself does not cause a disturbance of the system frequency. In order to secure the LFC adjustment capacity in consideration of the response delay characteristics to the power control of the thermal power unit, the LFC adjustment capacity must be shared by multiple thermal power units, but from the viewpoint of efficient operation of the equipment, the LFC adjustment capacity must be increased. There was a need to provide new means to secure and reduce the number of thermal power plants sharing LFC regulation capacity. When the ratio of the number of operating once-through boilers among the thermal power plants increases, there is a possibility that the power supply becomes insufficient and the LFC adjustment capacity cannot be secured under the situation where the power demand increases and the frequency decreases continuously for several minutes or more. There was a need for a means for securing an LFC adjustment capacity capable of compensating for this shortage of supply power in a short time and suppressing frequency fluctuations.

If the number of power supplies connected to the grid decreases during a time period when the power demand decreases, such as at night, the LFC adjustment capacity may be insufficient and the frequency fluctuation may increase. LFC adjustment capacity securing means for suppressing this was required.
When an aging low-efficiency thermal power plant is operated to secure LFC adjustment capacity when demand increases, operating efficiency and environmental conservation (CO
There is a problem from the viewpoint of (2, suppression of NOx and SOx emissions), and it has been required that the necessary LFC adjustment capacity can be secured without using such an aging thermal power plant. When a large number of renewable energy power sources are connected to a power system, the frequency fluctuation may increase with the output fluctuation. It was necessary to introduce a technology that could secure the LFC adjustment capacity to suppress such output fluctuations at high speed. As is evident from the above, a method and a device for securing the necessary LFC adjustment capacity by maintaining the operation efficiency of a certain power system as a whole and replenishing the insufficient power in a short time without delay in response. The realization has been a problem in the frequency control method and the device of the power system.

[0019]

SUMMARY OF THE INVENTION A frequency control apparatus for a power system according to the present invention is a power system having a power generation unit for generating power, a load for consuming power, and an electric circuit connecting the power generation unit and the load. A frequency deviation detector that measures a frequency that fluctuates in accordance with supply and demand imbalance of the power generation amount and the power consumption amount of the load from the power generation unit, and detects a deviation from a predetermined reference frequency, and the power system. A secondary battery connected via an AC / DC converter and configured to charge or discharge so as to suppress a change in frequency based on the detection result of the frequency deviation detector. Utilizing the high-speed output response of the secondary battery and the overload operation capability allowed in a short time, the secondary battery is charged and discharged according to the fluctuation of the power system to perform output control. Accordingly, it is possible to instantaneously maintain the supply and demand balance in the power system at all times and in an emergency, and to provide a frequency control device for the power system capable of solving the above-described problems.

According to another aspect of the present invention, there is provided a frequency control apparatus for a power system, comprising: a power generation unit configured to generate power; a load consuming power; and a power path connecting the power generation unit and the load. A frequency deviation detector that measures a frequency that fluctuates in accordance with supply and demand imbalance of the power generation amount and the power consumption amount of the load from the unit, and detects a deviation from a predetermined reference frequency, the frequency deviation detector A load frequency control device for receiving a detection signal and providing a load frequency control signal (LFC signal) for controlling the generated power of the power generation unit to the power generation unit when the deviation exceeds a predetermined range, and AC / DC conversion Connected to the power system via a charge / discharge control device having a device, and when the deviation is equal to or less than a predetermined range, the power is discharged to the power system or charged by the power of the power system. Has a battery, the charge and discharge control as the secondary battery of the power generated by the power generation unit by the LFC signal, it suppresses the frequency change of the power system to eliminate the power supply and demand imbalances. For a small supply-demand imbalance in which the deviation is equal to or less than a predetermined range, the power from the power system is stored by charging the secondary battery, or the stored power is supplied by discharging the secondary battery. Due to the high-speed response of the secondary battery, a small supply-demand imbalance can be promptly resolved. When the deviation exceeds a predetermined range, a large supply-demand imbalance has occurred,
By using the LFC signal, the amount of power generated by the power generation unit can be controlled to eliminate a large supply-demand imbalance.

According to the frequency control method for a power system of the present invention, in a power system having a power generation unit for generating power, a load consuming power, and an electric circuit connecting the power generation unit and the load,
Measuring a frequency that fluctuates in accordance with supply and demand imbalance between the power generation amount from the power generation unit and the power consumption amount of the load, and detecting a deviation from a predetermined reference frequency; and The method includes a step of charging or discharging the secondary battery connected via a charge / discharge control device having a conversion device and suppressing a change in frequency based on a detection result of the step of detecting the deviation. Utilizing the high-speed output response of the secondary battery and the overload operation capability allowed in a short time, the secondary battery is charged and discharged according to the fluctuation of the power system to perform output control. This makes it possible to instantaneously maintain the supply and demand balance in the power system at all times and in an emergency, and to provide a power system frequency control method capable of solving the above-described problems.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS. << Embodiment 1 >> Embodiment 1 uses an LFC signal and an EDC signal, which are supply control signals issued to control each power supply from a central power supply command station that controls power generated by a large number of power supplies (generators). The present invention relates to a frequency control method and an apparatus for controlling an input / output of a secondary battery system and maintaining a frequency of a power system within a predetermined deviation of a reference frequency. FIG.
2 is a block diagram of a frequency control device including the secondary battery system 30. FIG. 2 is a block diagram of the secondary battery system 30. In FIG. 1, a power system 1 includes a power generation unit 2
And a customer, that is, a load 8. This system includes a nuclear power generator group 3, a hydroelectric generator group 4, a thermal power generator group 5, and a renewable energy power source group 6 such as a solar cell and a wind generator as the power generation unit 2. The generator group and the power supply group are connected to a load 8 by an electric circuit 7.

A secondary battery system 30 is connected to the electric circuit 7, and a secondary battery 36 provided therein is connected to the electric circuit 7.
To store the power via the power supply or supply the stored power to the electric circuit 7. Among them, the hydraulic power generator group 4, the thermal power generator group 5, and the secondary battery system 30 are LFC target power supplies, and their outputs are controlled according to fluctuations in power demand. The LFC is an output control for responding to a demand fluctuation having a fluctuation period of several minutes to 20 minutes. The nuclear power generator group 3 is always generating a certain amount of electric power, and is a generator not subject to LFC. The renewable energy power source group 6 cannot be controlled because its output constantly fluctuates according to natural conditions, and is a power source not subject to LFC.

The output command control unit 20 provided at the central power supply command station has a frequency detector 21 connected to an input terminal of an LFC device (load frequency control device) 22. The frequency is measured and the reference frequency (50
Hz or 60 Hz) and detects the deviation Δf from the LFC device 22.
Is applied. The output terminal 21 </ b> A of the LFC device 22 is connected to the control input terminals of the hydraulic power generator group 4, the thermal power generator group 5, and the secondary battery system 30 to be LFC-controlled. LFC device 2
The output terminal 21B that outputs the system demand signal from the second 2 is connected to the negative input terminal of the adder 23. The positive input terminal of the adder 23 is connected to the output terminal of the adder 24. Adder 23
Is connected to an input terminal 25A of the EDC device 25. An output terminal 25B of the EDC device 25 is connected to a control input terminal of the power supply to be controlled by the LFC. The other output terminal 25C of the EDC device 25 is connected to the negative input terminal of the adder 24. The actual output value of each generator is input to the positive input terminal of the adder 24.

FIG. 2 is a block diagram showing a detailed configuration of the secondary battery system 30. In the figure, a terminal 29 of the secondary battery system 30 is connected to the electric circuit 7 from the power generation unit 2 to the load 8. Actually, it is connected to the electric circuit 7 at the switchgear 50 (may be a substation) of the power system. The terminal 29 is connected to the frequency detector 3 connected in series with each other.
1, connected via a circuit breaker 32 and a transformer 33 to a charge / discharge control device 34. The charge / discharge control device 34 has an AC / DC converter (not shown), and is connected to a secondary battery 36 via a voltage / current measuring device 35. The secondary battery is, for example, a sodium-sulfur battery. A power control unit 37 including an arithmetic processing unit is provided in the secondary battery system 30, and an LFC signal and an EDC signal output from the output command control unit 20 are input to an input terminal 37A. Power control unit 3
7, a detection output of the frequency detector 31 is input to an input terminal 37B, and a measurement signal of an actual output value measured by an output measurement device built in the charge / discharge control device 34 is input to an input terminal 37C. The actual output value is also input to the output command control unit 20. The measurement signal of the voltage / current value measured by the voltage / current measuring device 35 is input to the charging depth measuring device 38. The charging depth measuring device 38 measures “charging depth” described below, and outputs the measured value to the input terminal 37D of the power control unit 37.
To enter. "Charge depth" refers to the total amount of power (charging capacity) that can be charged to a rechargeable battery starting from a completely discharged state, and the amount of power already charged at a certain point in time. And the ratio. An output terminal 37E of the power control unit 37 is connected to an input terminal of the charge / discharge control device 34.

The secondary battery system 30 uses a secondary battery having a capacity equal to or greater than that of a small-capacity thermal power plant of about 100 MW, and is mainly connected to a power transmission system. In addition, if necessary, a plurality of secondary battery systems may be connected in parallel to the distribution system as a distributed power source having a smaller capacity than the above-mentioned capacity to secure a necessary secondary battery capacity.

Next, the frequency control method of this embodiment will be described. In the electric circuit 7 at a predetermined measuring point, the frequency detectors 21 and 31 detect the deviation “Δf” of the system frequency from the reference frequency. When controlling the interconnection flow indicating the power flow between different power companies, "ΔPt + KΔf" (ΔPt is the deviation of the interconnection line flow frequency from the reference value, K is the system constant, Δf Represents a deviation from the reference frequency). Deviation △ f
Exceeds a predetermined deviation range (for example, ± 0.04 Hz), the output command control unit 20 outputs an LFC signal to control the output of the secondary battery system 30. LF of this embodiment
The control target of C is a demand change having a cycle of about 20 minutes or less, and the demand change in this cycle range is compensated by the LFC.

An output control for a fluctuation in which the cycle of the demand fluctuation is a short cycle of several minutes or less and the fluctuation width is narrow will be described below. The frequency of the system is detected by both the frequency detectors 21 and 31, and for example, the deviation Δf of ± 0.04 Hz or less
Is detected by the frequency detector 31 in the secondary battery system 30. The detection signal indicating the deviation Δf output from the frequency detector 31 is input to the power control unit 37. The power control unit 37 applies an output control signal based on the detection signal to the charge / discharge control device 34. The output control signal controls the charge / discharge control device 34 such that when the deviation Δf is a negative value, the secondary battery 36 is discharged and power is supplied from the terminal 29 to the electric circuit 7. When the deviation Δf is a positive value, the charge / discharge control device 34 is controlled such that power flows into the secondary battery system from the terminal 29 and the secondary battery 36 is charged.

A frequency variation having a frequency deviation exceeding ± 0.04 Hz is detected by a frequency detector 21 in the output command control unit 20, and a deviation detection signal is input to the LFC device 22. The LFC device 22 outputs an LFC signal to the terminal 21A based on the input deviation detection signal. The LFC signal is applied to a control unit (not shown) of the hydroelectric generator group 4 and the thermal power generator group 5 and a power control unit 37 of the secondary battery system 30. LF
The C signal is a pulse code signal and has code information for instructing an increase or decrease in the output of each generator and the secondary battery.
The power control unit 37 receiving the LFC signal supplies an output control signal to the charge / discharge control device 34 to control charging or discharging of the secondary battery 36.

The secondary battery system 30 in the present embodiment
The capacity of the secondary battery 36 is designed on the premise of “overload operation” in which charging and discharging are performed at a current higher than the rated current (hereinafter, referred to as an excessive current) during charging and discharging. Also, the charging depth of the secondary battery 36 is measured by the charging depth measuring device 38,
The measured value is input to a terminal 37D of the power control unit 37.
As a result, the power control unit 37 is controlled by the AC / DC control device 34.
To control the charge and discharge so that the charge depth of the secondary battery 36 is maintained at a predetermined value. In the present embodiment, charging is performed until the charging depth becomes about 70 to 80%, and discharging is performed until the charging depth becomes about 20 to 30%. The charging depth can be about 95% during charging and about 5% during discharging. By keeping the charging depth in the above range, overload operation of about 200 to 250% becomes possible.
The range of the above-mentioned charge depth is determined by individually examining the type, characteristics and intended operation mode of the secondary battery.

The secondary battery system 30 is a DC power supply utilizing a chemical reaction. Since a chemical reaction is used, the response of the output control is remarkably better than that of a conventional thermal power unit or a hydraulic power unit, and a high-speed response is possible. By utilizing this high-speed response, LFC with high speed and high accuracy can be performed. Since the rechargeable battery system 30 can perform overload operation for a short time, the LFC adjustment capacity required for normal operation of the system is controlled by the LFC adjustment that has been secured by conventional thermal power plants and hydraulic power plants. It is possible to secure the necessary LFC adjustment capacity with a secondary battery having a rated capacity smaller than the capacity. However, depending on battery capacity, battery characteristics and design specifications,
The maximum overload time varies. By the way, it is known that the frequency fluctuation from the reference frequency in the power system has a substantially normal distribution. For example, after the state in which the secondary battery 36 needs to be discharged due to the excessive current lasts for not too long, the charging due to the excessive current for the same amount of time often occurs continuously or intermittently. From this, with respect to the transfer of power to and from the system during the overload operation of the secondary battery system 30, the average value is almost 0 if the loss in power conversion is ignored. By utilizing the characteristics of the power system and the overload capacity of the secondary battery, a desired LFC adjusted capacity is secured by using the secondary battery 36 having a rated capacity of two to one third of the LFC adjusted capacity. It becomes possible to perform the operation which performed. As a result, it becomes possible to design a power system while suppressing capital investment costs. When discharged to 20 to 30% of the charging depth of the secondary battery 36, or when charged to 70 to 80%,
Stop charging and discharging. After that, the LFC was hydroelectric generator group 4
And the thermal power generator group 5.

The LFC device 22 receives the signal indicating the frequency deviation Δf input from the frequency detector 21 and calculates the required LFC system data, which is the data indicating the power required to compensate for the power demand fluctuation of the power system 1. Is output to the negative input terminal of the adder 23. On the other hand, from the power generation unit 2 and the battery system 30, an actual output value, which is data indicating their output power, is applied to the positive input terminal of the adder 24. An output command value of data output from the terminal 25C of the EDC device 25 is applied to a negative input terminal of the adder 24, and the actual output value is subtracted from the command value to obtain a difference between the output command value and the actual output value. Can be This difference is applied to the positive input of adder 23. In the adder 23, a control error, which is a difference between the difference and the required system amount, is obtained and applied to the input terminal 25A of the EDC device 25. EDC
The device 25 receives a signal from the terminal 25B based on the control error.
An EDC signal is output and applied to the hydraulic power generator group 4, the thermal power generator group 5, and the secondary battery system 30. The EDC signal has a fluctuation cycle of about 20 minutes or more, and performs control for suppressing a considerably large demand fluctuation. In the EDC, the output is controlled while controlling the individual generators of the hydroelectric generator group 4 and the thermal power generator group 5 so that the preset power generation efficiency is the highest and, therefore, the most economical operation state. Has been increased or decreased.

FIG. 3 (a) is a graph showing fluctuations in power consumption in the power system on one day in the summer week, and FIG. 3 (b) shows fluctuations in the output of the secondary battery on the same day in consideration of frequency fluctuations. It is a graph. The vertical axis of FIG. 3B indicates the ratio of the output of the secondary battery to the rated output, where a positive value indicates discharging and a negative value indicates charging. ± P1 is the percentage of the allowable overload in the design of the secondary battery to be used to the rated load. The operation and effect of the present embodiment are summarized as follows. A short demand cycle with a fluctuation cycle of about 20 minutes or less is first addressed by charging and discharging the secondary battery 36. While the charge depth of the secondary battery 36 is in the range of 20% to 80%, the secondary battery is charged and discharged. When the depth of charge is less than 20% due to discharging, or the depth of charge exceeds 80% due to charging, charging and discharging of the secondary battery 36 is stopped, and the output of the hydroelectric generator group 4 and the thermal power generator group 5 is increased or decreased. Responds to fluctuations in demand.

Since the LFC adjustment capacity is secured by the secondary battery, it is not necessary for the power plant to share the LFC adjustment capacity. Therefore, it is not necessary to perform the output suppression operation of the thermal power unit, and the operation can be performed at the rated output with the highest effect. Rechargeable battery is LFC
Control speed is fast, so that quick and accurate power control is performed, and even if the ratio of the number of once-through boiler
There is no shortage of C adjustment capacity. In addition, since the regulated capacity is secured by the secondary battery, it is not necessary to operate an aging low-efficiency output machine. Even if a large number of renewable energy power sources are systematically interconnected and their output fluctuates rapidly due to sudden changes in weather conditions, the output fluctuation can be compensated for by the fast LFC response of the secondary battery. In addition, as for the frequency fluctuation that is small enough not to be controlled by the LFC signal, the frequency fluctuation (measured by the system) measured by the system in which the secondary battery system is operated is detected, and the conventional hydraulic machine or the like is detected. With a governor-free characteristic that responds in the same manner as a thermal power plant, operation corresponding to a minute frequency can be performed. Further, when the system in which the secondary battery system is operated becomes a single system due to a system accident or the like, output control for maintaining the reference frequency within the single system may be performed.

Embodiment 2 Embodiment 2 is a frequency control device using a redox flow battery 41 as a secondary battery of a secondary battery system 40, and its block diagram is shown in FIG. Other configurations are the same as those in FIG. The redox flow battery 41 is a secondary battery using a redox reaction of vanadium, and includes a battery cell stack portion and electrolyte tanks 42 and 43 for storing an electrolyte of vanadium, and circulation pumps 44 and 45 for circulating the electrolyte. Consists of The redox flow battery is connected to the electrolyte tanks 42 and 43.
Since the capacity of the battery can be increased by increasing the volume of the secondary battery, the secondary battery is suitable for use as a large-scale power supply. FIG. 5 shows an example of the overload operable range (overload time is about several seconds to several tens of seconds) of the redox flow battery.

As can be seen from FIG. 5, depending on the charge depth, in the operation ranges shown in the figures of charge and discharge, respectively.
An overload operation can be performed, and an overload operation of about 300% at the maximum can be performed. When operating in a power system, this depth of charge is measured by the voltage and current of the secondary battery and measured by the depth of charge measuring device 38, and how much overload operation is possible is determined by the secondary battery system 40.
And the output control is performed in accordance with the LFC signal and the EDC signal. Since it is assumed that the overload operation is performed, the operation is performed with a target charging depth of about 70 to 80% at the maximum during charging. Regarding the battery capacity, the volume of the electrolyte tank may be changed according to the purpose of use, and in particular, to secure the power required for system operation, the volume of the electrolyte tank may be increased according to the required amount.

In the redox flow battery, the amount of charge passing through the battery cell per unit time can be increased and the concentration of the electrolyte can be made uniform by changing the flow rate of the electrolyte. Capacity expansion is possible. In the second embodiment, by using a large-capacity redox flow battery, for example, when a large-scale power supply is cut off from the power system due to a system accident, the power supply acts as a power supply having a highly responsive spinning reserve, and the frequency of the system is reduced. It can be used for maintaining operations. In addition, redox flow batteries have significantly better responsiveness than hydropower and thermal power plants, and have better responsiveness to frequency fluctuations, so they have a smaller capacity than the conventional LFC adjustment capacity required for grid operation, and A similar frequency fluctuation suppression effect can be obtained. In addition, by utilizing the overload capacity of the secondary battery, it is possible to maintain the same frequency as before with a secondary battery system with a rated capacity that is smaller than the required LFC adjustment capacity, and to realize a power system with reduced capital investment. Can be configured.

Solar power, wind power, and the like use natural energy and are affected by weather conditions when operating. From the point of view of the system operator, a power supply that always has unstable output fluctuations as a regular power supply. If more of these power sources are connected to the system in the future and their share in the power supply configuration increases, a power source that compensates for the unstable output fluctuation of the power source is required to maintain the reference frequency. If a secondary battery is used as the supplementary power supply equipment, it is possible to use the high-speed response characteristic and a large power capacity to keep the fluctuation of the supply power constant, thereby enabling the operation in which the frequency fluctuation is suppressed.

[0039]

As described in detail in each of the above embodiments, according to the present invention, the regular and emergency frequency control of the power system is performed by using the secondary battery system, so that the existing frequency control method can be implemented. Compared with this, faster and more efficient operation becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of a frequency control device common to Embodiments 1 and 2 of the present invention.

FIG. 2 is a block diagram of a secondary battery system according to the first embodiment.

FIG. 3A is a graph showing an example of a daily change in power consumption in a power system; FIG. 3B is a graph showing an example of a charge / discharge state of a secondary battery;

FIG. 4 is a block diagram of a secondary battery system according to Embodiment 2 of the present invention.

FIG. 5 is a graph showing charging and discharging of the secondary battery of Example 2.

FIG. 6 (a) is a graph showing a change in the frequency of the system, (b) is a graph showing the output of a fired heater having a drum boiler, and (c) is a graph showing a change in output of a thermal plant having a once-through boiler.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 power system 2 power generation unit 3 nuclear power generator group 4 hydroelectric generator group 5 thermal power generator group 6 renewable energy power supply group 7 electric circuit 8 load (consumer) 20 output command control unit 21 frequency detector 22 LFC device 23, 24 Adder 25 EDC device 30 Secondary battery system 31 Frequency detector 32 Circuit breaker 33 Transformer 34 Charge / discharge controller 35 Voltage / ammeter side device 36 Secondary battery 37 Power controller 38 Charge depth measuring device 40 Secondary battery system 41 Redox flow battery 42, 43 Electrolyte tank 44, 45 Circulation pump 46 Power control unit 47, 48 Flow meter 50 Switchyard

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tetsuo Sasaki 3-3-22 Nakanoshima, Kita-ku, Osaka Kansai Electric Power Co., Inc. F term (reference) 5G066 AA05 AE09 JA01 JB03

Claims (9)

[Claims] In a power system having a power generation unit that generates power, a load that consumes power, and an electric circuit that connects the power generation unit and the load, a power generation amount from the power generation unit and a power consumption amount of the load are calculated. Measure the frequency that fluctuates with the supply and demand imbalance,
A frequency deviation detector for detecting a deviation from a predetermined reference frequency, and connected to the power system via a charge / discharge control device having an AC / DC converter, based on a detection result of the frequency deviation detector A frequency control device for an electric power system having a secondary battery that performs charging or discharging so as to suppress frequency fluctuations. 2. In a power system having a power generation unit for generating power, a load consuming power, and an electric circuit connecting the power generation unit and the load, a power generation amount from the power generation unit and a power consumption amount of the load are calculated. Measure the frequency that fluctuates with the supply and demand imbalance,
A frequency deviation detector for detecting a deviation from a predetermined reference frequency, receiving a detection signal of the frequency deviation detector, and controlling the generated power of the power generation unit when the deviation exceeds a predetermined range. When connected to the power system via a load frequency control device that supplies a load frequency control signal (LFC signal) to the power generation unit and a charge / discharge control device having an AC / DC converter, and when the deviation is equal to or less than a predetermined range. A secondary battery that discharges power to the power system or is charged by the power of the power system, and controls power generated by a power generation unit based on the LFC signal and charges and discharges the secondary battery to supply and receive power. A power system frequency control device that eliminates imbalance and suppresses power system frequency fluctuations. 3. The power system frequency control device according to claim 1, wherein the secondary battery is a sodium-sulfur battery. 4. The frequency control device for a power system according to claim 1, wherein the secondary battery is a redox flow battery. 5. The frequency control device for a power system according to claim 1, wherein the secondary battery performs an overload operation in which the secondary battery is charged and discharged with power larger than a rated value. 6. A frequency control device for a power system according to claim 4, further comprising a circulating pump for increasing or decreasing the flow rate of the electrolyte of the redox flow battery in accordance with an increase or decrease in charge / discharge power in order to expand an overload operable range. . 7. A total amount of power that can be charged to the secondary battery by starting charging from a completely discharged state and charging the battery.
A depth-of-charge measuring device that measures a depth of charge defined as a percentage of the amount of power already charged at a certain point in time, and controls charging and discharging of a secondary battery such that the depth of charge is kept within a predetermined range. The frequency control device for a power system according to claim 1, further comprising a control unit that performs the control. 8. The battery according to claim 1, wherein the range of the charging depth is 95% during charging.
8. The frequency control device according to claim 7, wherein the frequency is 5% or more during discharging. 9. In a power system having a power generation unit that generates power, a load that consumes power, and an electric circuit that connects the power generation unit and the load, a power generation amount from the power generation unit and a power consumption amount of the load. Measure the frequency that fluctuates with the supply and demand imbalance,
A step of detecting a deviation from a predetermined reference frequency; and a step of being connected to the electric power system via an AC / DC converter, and suppressing a fluctuation in frequency based on a detection result of the step of detecting the deviation. The method for controlling the frequency of the power system includes the step of charging or discharging the secondary battery as described above.