JP6474017B2 - Frequency control method and frequency control system in power system - Google Patents

Description

  The present invention relates to a frequency control method and a frequency control system for stably controlling the frequency of an electric power system, and in particular, includes various types of renewable energy power generation equipment, power storage equipment, load equipment, etc. The present invention relates to a control method and a control system that are suitable for application to a small and medium-sized power system such as a microgrid and a smart grid.

In recent years, solar power generation facilities and wind power generation facilities such as power generation facilities using renewable energy, which are difficult to stably control output, have been actively introduced. In Japan, solar power of 28 million [kW] is expected in 2020. Photovoltaic power generation facilities, 4.9 million [kW] wind power generation facilities are planned to be introduced. However, since the amount of power generation using these renewable energies is controlled by the weather, there is a problem that the output is unstable (uncertain).
In the power system, the supply and demand balance between the generated power and the load power must be balanced, but if the above-mentioned renewable energy power generation facilities are connected to the power system, the supply and demand balance between the generated power and the load power will be lost. Therefore, in the worst case, the operation of the power system is stopped due to the fluctuation of the system frequency.

  Normally, control of the system frequency is governed by governor-free operation that is performed by a single generator for frequency fluctuations with a short period, and output from the central power supply command center for frequency fluctuations with a longer period. Control is in charge. As the output control from the central power supply command center, LFC (load frequency control) is performed by constant frequency control, frequency deviation interconnection power control, etc., and this LFC is a large-scale system in one power company jurisdiction. Therefore, it is known as an effective control method when almost no renewable energy-use power generation facilities are introduced.

Here, in patent document 1, in order to ensure LFC capacity | capacitance, trying to utilize an electrical storage installation for the frequency control of an electric power grid | system is tried.
FIG. 6 shows a frequency control device described in Patent Document 1. In FIG. 6, the frequency detection means 203 in the frequency control device 200 detects the frequency f of the power system 100. A plurality of secondary batteries 301 are connected to the electric power system 100 as power storage equipment, and the respective charging depths are detected by the charging depth detection means 201 and input to the charging depth correction means 202.
The frequency deviation calculation means 204 calculates a deviation Δf between the reference frequency and the system frequency f and sends it to the charge depth correction means 202 and the charge / discharge control means 205. The charge / discharge control means 205 is based on the charge depth correction signal generated by the charge depth correction means 202 and the frequency deviation Δf so that the charge depth of the secondary battery 301 is, for example, 50 [%]. The charging / discharging of 301 is controlled, and the system frequency is controlled so as to eliminate the frequency deviation Δf.

  According to this prior art, even when an imbalance occurs in the power supply and demand and the system frequency fluctuates, the charging / discharging of the generator G is controlled by maintaining the charging depth of the secondary battery at a predetermined value. Instead of automatic output control, LFC is implemented to suppress fluctuations in the system frequency.

Further, Patent Document 2 discloses a conventional technique related to LFC and economic load distribution control (EDC) in which frequency stability is improved for a microgrid.
FIG. 7 shows this prior art, in which 400 is a system control device in a microgrid, 500 is a microgrid, 501 is another power system, 601 is an internal combustion power generation facility, and 602 is a power storage such as a secondary battery. equipment, _{G 1} is photovoltaic installations, _{G 2} is a wind power installation, 700 is the load. The grid control device 400 in the microgrid includes a prediction function 401 that performs power supply / demand prediction, a performance database 402, a supply / demand plan 403, an economic load distribution control device 404, and a load frequency control device 405.

In this prior art, the load frequency control unit 405, multiplied by a constant K to the deviation between the reference frequency f ₀ and the power system frequency f as shown in FIG. 8, further areas required by subtraction of the tie-line power flow variation [Delta] P _T The amount (AR) is calculated. Then, the regional requirement amount is distributed to a plurality of power storage facilities 602 and a plurality of internal combustion power generation facilities 601 corresponding to output response speeds (low speed, high speed) by a plurality of distribution means 410 to generate an LFC command. ing.

  In this prior art, after the frequency variation of the regional demand is removed by various filters, a plurality of values are determined according to the ratio calculated by the economic load distribution control device 404 in FIG. 7 or the capacity ratio between the internal combustion power generation facility 601 and the power storage facility 602. By allocating to the equipment, the frequency stability in the microgrid is improved.

JP 2012-16077 A (paragraphs [0024] to [0027], FIG. 1, etc.) Japanese Patent Laying-Open No. 2011-114899 (paragraphs [0015] to [0025], FIG. 1, FIG. 4, etc.)

  However, in power grids such as microgrids and smart grids that generate and consume electricity in a specific small area, where a large amount of power generation equipment using renewable energy is introduced, these power generation systems The reason is that the output fluctuation of the equipment is relatively large, the fluctuation period is relatively short compared to the conventional fluctuation period, and the moment of inertia of the power generation equipment is smaller than that of the large-scale system. Therefore, it is difficult to accurately control the frequency in the target system.

As a method for accurately controlling the frequency in a small and medium-sized power system, for example, it is conceivable to control power storage equipment such as the power storage equipment 602 in Patent Document 2 at high speed. That is, the storage facility itself detects the frequency f in the target system and controls the output of the storage facility at high speed so that the deviation from the reference frequency f ₀ is zero (hereinafter, such frequency control is performed). Called local control).
However, when local control is performed, frequency fluctuation is suppressed only by local control due to its high speed, and cooperation with an existing LFC cannot be achieved. That is, when frequency control is performed only by local control, a very large capacity is required as a power storage facility, and there is a problem that the facility becomes large and expensive.

  Therefore, the problem to be solved by the present invention is to reduce the capacity of power storage equipment by coordinating LFC and local control even when a large amount of power generation equipment using renewable energy is introduced into a small and medium-sized power system. An object of the present invention is to provide a frequency control method and a frequency control apparatus that can stably control the frequency.

In order to solve the above problem, a frequency control method according to claim 1 is a frequency control of a power system that supplies power to a load facility by connecting at least a power generation facility using renewable energy , an internal combustion power generation facility, and a power storage facility. A method,
A supply and demand control system positioned above the power system controls the system frequency by controlling the output of the internal combustion power generation facility and the power storage facility based on the system frequency and information transmitted from each facility. Frequency control,
The power storage facility, local control to control the system frequency by controlling its output based on the system frequency,
In a frequency control method capable of performing
When the system frequency is within a specified range, the system frequency is controlled only by the load frequency control, and when the system frequency deviates from the specified range, the system frequency is controlled by the load frequency control and the local control. To do.

The frequency control system according to claim 2 is a frequency control system of a power system that supplies power to a load facility by connecting at least a power generation facility using renewable energy , an internal combustion power generation facility, and a power storage facility,
A supply and demand control system positioned above the power system controls the system frequency by controlling the output of the internal combustion power generation facility and the power storage facility based on the system frequency and information transmitted from each facility. Frequency control,
The power storage facility, local control to control the system frequency by controlling its output based on the system frequency,
In a frequency control system capable of performing
Means for always enabling the load frequency control regardless of fluctuations in the system frequency;
Means for detecting that the system frequency is within a specified range and disabling the local control, and detecting that the system frequency has deviated from the specified range and enabling the local control. It is.

A frequency control system according to a third aspect is the one according to the second aspect,
Frequency detection means for detecting the system frequency;
Means for calculating a deviation between a detection frequency obtained from the system frequency and a reference frequency;
Means for generating an output command for the power storage facility so that the deviation becomes zero,
The frequency detection means includes
When detecting that the system frequency is within a specified range, the deviation is made zero by outputting the reference frequency as the detection frequency, and when detecting that the system frequency has deviated from the specified range, The system frequency is directly output as a detection frequency, and the deviation is set to a finite value.

  According to the present invention, by utilizing the high-speed responsiveness of local control in a small and medium-sized power system such as a microgrid or a smart grid in which a large amount of power generation facilities using renewable energy are introduced, The system frequency can be stably controlled while reducing the capacity of the power storage facility through cooperation.

It is a lineblock diagram of an electric power system to which an embodiment of the present invention is applied. FIG. 2 is a conceptual diagram of frequency control in the power system of FIG. 1. It is a flowchart which shows the process of local control. It is a block diagram of local control. It is a flowchart which shows the process of LFC. It is a block diagram of the prior art described in patent document 1. FIG. It is a block diagram of the prior art described in patent document 2. FIG. It is a block diagram of the principal part in the load frequency control apparatus of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 shows a system configuration to which this embodiment is applied, and reference numeral 10 denotes a medium-scale power system such as a microgrid or a smart grid. The power system 10, which can be internal power adjusting output power generation facility _{Ga 1, Ga 2, ···,} Ga n, the energy storage equipment _{Ba 1,} Ba 2 such secondary battery, · · ·, _Ba n, renewable energy power generation equipment such as a solar power generation equipment and wind power generation equipment _{Gb 1, Gb 2, ···,} Gb n, and load equipment _{L 1,} L 2 that consume power, ... and _{L n} It is connected.

Here, the renewable energy utilization power generation facilities Gb ₁ , Gb ₂ ,..., Gb are unstable because their outputs depend on the weather, and cause the system frequency to fluctuate. In this embodiment, in order to stabilize the grid frequency, the internal combustion power generation facilities _{Ga 1, Ga 2, ···,} Ga n and storage equipment _{Ba 1,} Ba 2, · · ·, system frequency control targeting the Ba _n It is carried out.

1, internal combustion power generation facilities Ga ₁ , Ga ₂ ,..., G _n , power storage facilities Ba ₁ , Ba ₂ ,..., Ba _n , renewable energy utilization power generation facilities Gb ₁ , Gb ₂ ,. , Gb _n and load facilities L ₁ , L ₂ ,..., L _n are connected to the power system 10 via the power cable 21 and are connected to the communication network 30 via the communication cable 22. .
In addition, a supply and demand control system 40 as a host system is connected to the communication network 30 via a communication cable 22. The demand control system 40, in order to perform the LFC, and detects the frequency f of the power system 10, the internal combustion power generation facilities _{Ga 1,} Ga 2, · · ·, the output power of the current to be transmitted from Ga _n and power storage facilities Ba _1, Ba _{2, ···,} received via the power storage amount of communication network 30 and the current transmitted from the Ba _n, various instructions to control the output of each equipment using these received information Send. At the same time, demand control system 40 is a renewable energy utilization power plant _{Gb 1,} Gb 2, · · ·, output power and load equipment _L 1 of Gb _n, L 2, · · ·, power consumption data, etc. _{L n} To control the supply and demand balance of the entire system.

The supply and demand control system 40 controls the system frequency by executing LFC with a period of about 1 to 3 seconds. In the LFC, demand control system 40 detects the frequency f of the power system 10, the reference frequency (50 [Hz] or 60 [Hz]) _{f 0} and regional demand on the basis of the deviation Δf between the detected frequency (AR) It calculates the internal combustion power generation facilities _Ga 1 by allocating the region demand in accordance with a predetermined distribution _ratio, Ga 2, · · ·, Ga _n and storage equipment _{Ba 1, Ba 2, ···,} Ba n Is output as a command.

Further, power storage equipment _{Ba 1, Ba 2, ···,} Ba n , in addition to the output command from the supply and demand control system 40, energy storage equipment _Ba 1 storage equipment itself detects the power system frequency f, _Ba 2, · ..., and a local control function for controlling the output of the Ba _n. In other words, power storage equipment _{Ba 1,} Ba 2, · · ·, using the fact the output of the Ba _n it is possible to control the output power at high speed is controlled by an inverter, LFC control period due to supply and demand control system 40 (1 shorter time than to 3 seconds), for example, the control period of about several tens to several hundreds [ms], the energy storage equipment _{Ba 1,} Ba 2, · · ·, to local control at high speed output of the Ba _n.

FIG. 2 is a conceptual diagram of frequency control in the electric power system 10 of FIG. 1, and shows the time transition of the system frequency and the contents of the frequency control in association with each other. Here, the system frequency f is controlled by setting the reference frequency f ₀ to 60.0 [Hz] and the frequency regulation range to 59.8 [Hz] (dead band lower limit value) to 60.2 [Hz] (dead band lower limit value). . Note that these reference frequencies and frequency defining ranges are merely examples, and it goes without saying that the present invention is not limited to these examples.

As shown in FIG. 2, in this embodiment, the LFC is always operated (enabled) regardless of the magnitude of the system frequency f, while the local control is performed when the system frequency f is within the frequency regulation range. Stop (invalidate) and operate when it deviates from the specified range (validate). That is, in FIG. 2, the time zone _{T a,} T c, since _{T e} the system frequency f is within the 59.8 [Hz] ~60.2 [Hz] of the specified range, stops the local control, LFC Only the system frequency is controlled. Further, since the time period T _b in the power system frequency f is below the which is the lower limit of the specified range 59.8 [Hz], to operate the local control, the upper limit of the specified range the time zone T _d in the power system frequency f Therefore, the local control is activated.

As described above, when frequency control to correct the frequency deviation Delta] f, the energy storage equipment Ba 1 according to the magnitude of the power system frequency _f, Ba _2, · · ·, be operated / stopped local control by Ba _n , always the energy storage equipment _{Ba 1, Ba 2, ···,} it is possible to avoid a situation such as to control the system frequency f only in Ba _n.
Therefore, it is possible to suppress fluctuations in the grid frequency f while coordinating LFC and local control, and it is not necessary to increase only the capacity of the storage facility in order to absorb fluctuations in the grid frequency f. There is no risk of increasing the size and price.

Next, FIG. 3 is a flowchart showing local control processing.
In the local control, the system frequency f is first detected (step S1), and then it is determined whether or not the system frequency f is within the frequency regulation range (step S2). If the system frequency f is within the specified range, the local control is stopped and terminated (steps S2 Yes, S3). When the system frequency f deviates from the specified range, the local control is operated and terminated (steps S2 No, S4).

As a specific operation of the local control, for example, as shown in FIG. 4, PI control may be performed so that the frequency deviation Δf is zero.
FIG. 4 is a block diagram of local control. In FIG. 4, 51 is a frequency detector that outputs a detection frequency corresponding to the system frequency f, 52 is a subtracting means for obtaining a deviation Δf between the reference frequency f ₀ and the detection frequency, and 53 is a proportional calculation in which the frequency deviation Δf is input. element, integral computing elements that frequency deviation Δf is input 54, 55 energy storage equipment _Ba 1 by adding the outputs of the proportional calculation element 53 and the integral computing element _54, Ba 2, · · ·, the output command to the Ba _n Is an adding means for generating.

The frequency detector 51 operates as follows by determining the magnitude relationship between the system frequency f and its specified range.
When the system frequency f> the dead band upper limit value, the system frequency f is output as the detection frequency.
When the dead band lower limit value ≦ system frequency f ≦ dead band upper limit value, the reference frequency f ₀ is output as the detection frequency.
When the system frequency f <the dead band lower limit value, the system frequency f is output as the detection frequency.

In other words, when the system frequency f deviates from the specified range, the system frequency f is output as it is as the detection frequency, whereby the deviation Δf between the reference frequency f ₀ and the system frequency f becomes a finite value. storage equipment _Ba 1 so that the deviation Δf is _zero, Ba _{2, ···,} the output command for the Ba _n is generated by PI control shown in.
Also, if the system frequency f is within the specified range, the deviation Δf becomes zero by outputting a reference frequency _{f 0} as the detected frequency, power storage equipment _{Ba 1,} Ba 2, · · ·, to the Ba _n The output command becomes zero. This means that the local control function is stopped.

Next, FIG. 5 is a flowchart showing the LFC processing.
In the LFC, the system frequency f is first detected in the same manner as in the local control (step S11), and then the regional deviation (AR) is calculated by obtaining the frequency deviation Δf (step S12). Here, AR is defined as follows.
AR [kW] = − system constant [% kW / Hz] × system capacity [kW] × frequency deviation Δf [Hz]
Finally, on the basis of the regional demand determined, the internal combustion power generation facilities _{Ga 1,} Ga 2 according to a predetermined logic, such as the volume ratio of each facility, · · ·, Ga _n and storage equipment _Ba 1, _Ba 2, · · · , and it generates a command to calculate the output distribution of Ba _n (step S13), and ends the process.

  INDUSTRIAL APPLICABILITY The present invention can be used to stably control the system frequency in various power systems in which the system frequency may fluctuate when a large amount of renewable energy power generation facilities are connected.

10: Power system 21: Power cable 22: Communication cable 30: Communication network 40: Supply and demand control system 51: Frequency detector 52: Subtraction means 53: Proportional calculation element 54: Integration calculation element 55: Addition means G _{a1 to} G _an : Internal power generation facilities B _{a1 to} B _an : Power storage facilities G _{b1 to} G _bn : Renewable energy utilization power generation facilities L _{1 to} L _n : Load facilities

Claims (3)

A frequency control method for a power system that supplies power to a load facility by connecting at least a renewable energy power generation facility , an internal combustion power generation facility, and a power storage facility,
A supply and demand control system positioned above the power system controls the system frequency by controlling the output of the internal combustion power generation facility and the power storage facility based on the system frequency and information transmitted from each facility. Frequency control,
The power storage facility, local control to control the system frequency by controlling its output based on the system frequency,
In a frequency control method capable of performing
When the system frequency is within a specified range, the system frequency is controlled only by the load frequency control, and when the system frequency deviates from the specified range, the system frequency is controlled by the load frequency control and the local control. A frequency control method for an electric power system. A frequency control system for a power system that supplies power to a load facility by connecting at least a power generation facility using renewable energy , an internal power generation facility, and a power storage facility,
A supply and demand control system positioned above the power system controls the system frequency by controlling the output of the internal combustion power generation facility and the power storage facility based on the system frequency and information transmitted from each facility. Frequency control,
The power storage facility, local control to control the system frequency by controlling its output based on the system frequency,
In a frequency control system capable of performing
Means for always enabling the load frequency control regardless of fluctuations in the system frequency;
Means for detecting that the system frequency is within a specified range and invalidating the local control, detecting that the system frequency has deviated from the specified range and enabling the local control;
A frequency control system in an electric power system, comprising: The frequency control system according to claim 2,
Frequency detection means for detecting the system frequency;
Means for calculating a deviation between a detection frequency obtained from the system frequency and a reference frequency;
Means for generating an output command for the power storage facility so that the deviation becomes zero;
With
The frequency detection means includes
When detecting that the system frequency is within a specified range, the deviation is made zero by outputting the reference frequency as the detection frequency, and when detecting that the system frequency has deviated from the specified range, A frequency control system in an electric power system, wherein the system frequency is output as it is as a detection frequency and the deviation is made a finite value.

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