Power system frequency control method based on wind storage combined frequency modulation

Abstract

The invention relates to the technical field of power system frequency control, in particular to a power system frequency control method based on wind storage combined frequency modulation. The method comprises the following steps: acquiring frequency data in real time, and quantifying frequency disturbance intensity; calculating an energy storage frequency modulation weight coefficient and a wind power frequency modulation weight coefficient based on the frequency disturbance intensity; the energy storage system performs frequency modulation based on the energy storage frequency modulation weight coefficient to obtain energy storage frequency modulation output power; the wind turbine generator participates in frequency modulation through a rotor inertia frequency modulation channel and a standby channel based on the wind power frequency modulation weight coefficient to obtain wind power inertia frequency modulation output power and response power of the wind power standby channel; and based on the energy storage frequency modulation output power and each frequency modulation power component of the wind power, obtaining total frequency modulation output power, and realizing multi-source collaborative staged frequency control. The problems that in a traditional power system frequency control method, the frequency modulation priority is not clear, the response signal path is fixed, the frequency modulation channel conflicts exist, and a recursive self-stabilization modulation mechanism does not exist are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system frequency control, in particular to a power system frequency control method based on wind storage combined frequency modulation. BACKGROUND

[0002] With the large-scale grid connection of renewable energy such as wind power, the frequency stability of the power system is facing severe challenges. Due to the physical characteristics of the converter interface, wind turbine generators lack natural inertia support capability and are difficult to respond quickly to frequency deviation when the power system is disturbed. At the same time, due to the strong fluctuation of wind power, the participation of wind power in frequency modulation is limited in the conventional frequency modulation strategy. The energy storage system has the advantages of fast response and high regulation accuracy, and has been used in power system primary frequency modulation, secondary frequency modulation and other applications.

[0003] In the traditional power system frequency control method, wind power frequency modulation mainly releases rotor kinetic energy to simulate inertia response and adjusts active power through power reserve formed by load shedding, while the energy storage system usually participates in frequency modulation as a linear response unit. The mainstream method of wind power and energy storage combined frequency modulation is to use a linear superposition model, that is, to model the inertia response, power reserve response and energy storage response of wind power respectively, and then simply add the unified response frequency deviation signal. This method has problems such as unclear frequency modulation priority, fixed response signal path, frequency modulation channel conflict, and no recursive self-stabilizing modulation mechanism, which makes it difficult to meet the dynamic frequency control requirements of high proportion of wind power system; Therefore, there is an urgent need for a wind storage combined frequency modulation control strategy with recursive logic, dynamic weight distribution and frequency modulation feedback function, which can more effectively coordinate different frequency modulation resources, realize the behavior coupling and dynamic dominant right switching between multi-source heterogeneous frequency modulation units, and thus enhance the frequency stability and frequency modulation control accuracy of the power system. SUMMARY

[0004] The present application provides a power system frequency control method based on wind storage combined frequency modulation to solve the problems of unclear frequency modulation priority, fixed response signal path, frequency modulation channel conflict and no recursive self-stabilizing modulation mechanism in the traditional power system frequency control method.

[0005] The present application provides a power system frequency control method based on wind storage combined frequency modulation to solve the problems of unclear frequency modulation priority, fixed response signal path, frequency modulation channel conflict and no recursive self-stabilizing modulation mechanism in the traditional power system frequency control method. A power system frequency control method based on wind storage combined frequency modulation, comprising the following steps: S1, real-time acquisition of frequency data, quantification of frequency disturbance degree, and obtaining frequency disturbance intensity; based on the frequency disturbance intensity, calculating the energy storage frequency modulation weight coefficient and the wind power frequency modulation weight coefficient; S2. The energy storage system performs frequency modulation based on the energy storage frequency modulation weight coefficient to obtain the energy storage frequency modulation output power; the wind turbine participates in frequency modulation through the rotor inertia frequency modulation channel and the backup channel based on the wind power frequency modulation weight coefficient to obtain the wind power inertia frequency modulation output power and the response power of the wind power backup channel; based on the energy storage frequency modulation output power, the wind power inertia frequency modulation output power and the response power of the wind power backup channel, the total frequency modulation output power is obtained to realize multi-source coordinated phased frequency control.

[0006] Preferably, the S1 specifically includes: Based on the frequency data and the rated frequency of the system, the frequency deviation is calculated. Based on the absolute amplitude of the frequency deviation and the frequency deviation change rate, a frequency disturbance intensity function is constructed to obtain the frequency disturbance intensity.

[0007] Preferably, the S1 specifically includes: The frequency disturbance intensity is compared with the preset threshold parameter, and the energy storage frequency regulation weight coefficient is generated through nonlinear mapping, and the wind power frequency regulation weight coefficient is obtained.

[0008] Preferably, the S2 specifically includes: The energy storage system is used as the first execution unit to intervene in the control process. Based on the energy storage frequency regulation weight coefficient, the energy storage frequency regulation gain coefficient and the response time constant of the energy storage system are introduced to compensate for the frequency deviation and obtain the energy storage frequency regulation output power.

[0009] Preferably, the S2 specifically includes: A rotor inertia frequency modulation channel for wind turbines is established. Based on the wind power frequency modulation weight coefficient, the rotor inertia response coefficient and the rotor inertia response time constant of the wind turbine are introduced. Combined with the inertia response suppression function, the frequency deviation is compensated to obtain the wind power inertia frequency modulation output power.

[0010] Preferably, the S2 specifically includes: The inertia response suppression function is constructed based on the energy storage frequency modulation output power and the rated power of the energy storage system.

[0011] Preferably, the S2 specifically includes: Based on the wind power frequency regulation weight coefficient, the wind turbine standby power frequency regulation gain coefficient and the wind turbine pitch response time constant are introduced. Combined with the inertia response suppression function, the frequency deviation is compensated and the response power of the wind power standby channel is calculated.

[0012] Preferably, the S2 specifically includes: The frequency response of the energy storage, the inertia response of the wind power and the response power of the wind power reserve channel are converted from the frequency domain to the time domain, and are weighted and synthesized to obtain total frequency modulation output power; the total frequency modulation output power is used as a final control instruction to jointly modulate the power system.

[0013] The technical scheme of the present application has the following advantages: 1. By constructing a frequency disturbance intensity function, the absolute amplitude and its rate of change of the frequency deviation are comprehensively considered to realize comprehensive quantification of the frequency disturbance degree of the power system, and to provide a scientific basis for subsequent frequency modulation control; according to the frequency disturbance intensity, the frequency modulation weight coefficients of the energy storage system and the wind turbine are dynamically allocated, which not only ensures that the participation proportion of the two is complementary and the sum is constant, but also avoids overlapping or missing of the adjustment, and improves the coordination and system stability.

[0014] 2. The energy storage system responds to the frequency disturbance first, and the wind turbine is supplemented and supported in stages through rotor kinetic energy release and standby capacity adjustment, forming a multi-level and staged frequency suppression and repair mechanism, which significantly enhances the anti-disturbance ability of the power system; by introducing an inertia response suppression function, the wind power inertia frequency modulation intensity is dynamically suppressed according to the energy storage frequency modulation output power, to avoid excessive power superposition leading to secondary frequency fluctuation, and to improve the stability and reliability of the control process.

[0015] 3. All input variables are actual measurable physical quantities, and threshold parameters are obtained based on actual system characteristics, so the structure is clear and easy to implement, and is suitable for dispatching and control application of actual power systems; through the multi-source frequency modulation mechanism of wind and storage cooperation, the energy storage system can be quickly mobilized to respond to the frequency disturbance, and the kinetic energy and standby support of the wind turbine are connected, to realize effective suppression and rapid recovery of frequency fluctuation, and to comprehensively improve the frequency stability and operation safety of the power system. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A flowchart of a power system frequency control method based on wind and storage joint frequency modulation is provided. DETAILED DESCRIPTION

[0017] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0019] The application provides a kind of based on wind storage combined frequency modulation power system frequency control method, and the specific scheme of the method will be specifically described below in conjunction with the drawings.

[0020] Referring to the drawings Figure 1 It shows a kind of based on wind storage combined frequency modulation power system frequency control method flow chart provided by the embodiment of the application, the method comprises the following steps: S1, real-time acquisition frequency data, and quantize the degree of frequency disturbance, to obtain the intensity of frequency disturbance;Based on the intensity of frequency disturbance, the frequency modulation weight coefficient of energy storage and the frequency modulation weight coefficient of wind power are calculated; The frequency data is collected by the frequency measurement unit of the dispatching center of the power system of wind storage combined frequency modulation arranged at the main bus, and the high-precision PLL (phase-locked loop) module is used to extract the frequency data in real time, and the sampling period of frequency data is within 20 ms; The measured value of frequency data is calculated by local controller to obtain frequency deviation, and the rate of change of frequency deviation is obtained by first-order difference method;The first-order difference method is a well-known technical means for those skilled in the art, which will not be described here. The current output power of energy storage system is provided by real-time operation data interface of energy storage converter, which is used to control wind power frequency modulation response threshold and system frequency modulation power synthesis to ensure that the input variables are physical measurable, real-time effective system operation variables; To accurately quantify the frequency deviation of the power system of wind storage combined frequency modulation, the deviation value between the current frequency data of the power system of wind storage combined frequency modulation and the rated frequency of the system is defined, the frequency deviation is obtained, and the frequency deviation is taken as the original input signal of the whole frequency modulation control link;The rated frequency is the reference value required for stable operation of the power system, which is determined by system design parameters and does not change with time or load fluctuation. The expression of frequency deviation can be expressed as: , Wherein, is the frequency deviation at time ; is the rated frequency of the system (such as 50 Hz); is the measured value of frequency data at the current time , which is obtained by the frequency measurement unit at the main bus of the system; To construct a quantitative expression conforming to the frequency disturbance characteristics of power system, the degree of system frequency disturbance needs to be formally defined;The speed of frequency deviation change also affects the real-time judgment and adjustment intensity of frequency modulation control in addition to the absolute amplitude of frequency deviation. Therefore, in order to realize the comprehensive quantification of the degree of frequency disturbance, the frequency disturbance intensity function is defined: , wherein, is the frequency disturbance intensity function at time , representing the comprehensive disturbance degree of the power system at a certain time; is the disturbance rate sensitivity coefficient, used to control the weight of the frequency change rate in the total disturbance perception, with a value range of [0.2, 0.8] and a unit of seconds, which is obtained by regression fitting of the disturbance working condition response process, and is a well-known technical means for those skilled in the art, which will not be repeated here; is the frequency deviation change rate; Based on the frequency disturbance intensity, the frequency modulation priority allocation logic is constructed to obtain the energy storage frequency modulation weight coefficient and the wind power frequency modulation weight coefficient, which are used to describe the participation proportion of the energy storage system and the wind turbine in the overall frequency modulation process under different disturbance intensities. Specifically, the frequency disturbance intensity is compared with the threshold parameter obtained by marking the operating data (i.e. the frequency deviation and its change rate), and the weight coefficient with a value range of 0 to 1 is generated through nonlinear mapping. After determining the energy storage frequency modulation weight coefficient, the wind power frequency modulation weight coefficient needs to maintain a complementary relationship with it to ensure that the participation proportion of the wind turbine and the energy storage system in the system frequency modulation is one, and there is no overlap or vacancy between them. The specific calculation formulas of the energy storage frequency modulation weight coefficient and the wind power frequency modulation weight coefficient are respectively: , , wherein, is the frequency modulation response weight coefficient of the energy storage system at time , that is, the energy storage frequency modulation weight coefficient; is the frequency modulation response weight coefficient of the wind turbine at time , that is, the wind power frequency modulation weight coefficient; is the disturbance response steepness coefficient, used to control the steepness of the function shape, with a value range of [1, 10] and a unit of , which is obtained by simulation fitting, and is a well-known technical means for those skilled in the art, which will not be repeated here; is the energy storage response threshold, and the energy storage system intervenes in frequency modulation quickly after the frequency disturbance intensity exceeds the energy storage response threshold. The energy storage response threshold is set according to the safe operation standard of the power grid, with a unit of .

[0021] S2, the energy storage system performs frequency modulation based on the energy storage frequency modulation weight coefficient to obtain an energy storage frequency modulation output power; the wind turbine participates in frequency modulation through a rotor inertia frequency modulation channel and a standby channel based on a wind power frequency modulation weight coefficient to obtain a wind power inertia frequency modulation output power and a response power of the wind power standby channel; based on the energy storage frequency modulation output power, the wind power inertia frequency modulation output power and the response power of the wind power standby channel, a total frequency modulation output power is obtained to realize multi-source collaborative phased frequency control. After the frequency modulation weight coefficient is calculated, the energy storage system needs to be involved in the control process as the first execution unit; the energy storage system undertakes the function of rapid support in the frequency control of the power system, and the power regulation characteristic thereof can be characterized by a first-order inertia link, and the action mechanism is to realize rapid active power compensation for the frequency deviation with a limited response time constant after detecting the frequency disturbance. The frequency deviation is taken as an input, and after being adjusted by the energy storage frequency modulation weight coefficient, it is transmitted to the power response link of the energy storage system, so that the real-time influence of the frequency disturbance intensity on the participation proportion of the energy storage frequency modulation is reflected in the response process, and the energy storage frequency modulation output power is obtained. The specific formula of the energy storage frequency modulation output power is: , wherein, is the frequency modulation power output of the energy storage system in the Laplace domain , that is, the energy storage frequency modulation output power; is an energy storage frequency modulation gain coefficient, which is derived by the ratio of the rated power of the energy storage system to the maximum frequency response capability, and the unit is ; is a Laplace operator, and the unit is , that is, the reciprocal of seconds; is the response time constant of the energy storage system, which represents the response time from detecting the disturbance to completing the adjustment, and is provided by the energy storage converter controller manufacturer, and the unit is seconds; is the representation of the frequency deviation in the Laplace domain; is a power response function; After the frequency disturbance is partially absorbed by the energy storage system, a rotor inertia frequency modulation channel of the wind turbine is established, the frequency deviation is taken as an input, and at the same time, the limitation of the energy storage frequency modulation power is obtained to obtain the wind power inertia frequency modulation output power; the limitation is characterized by an inertia response suppression function. When the energy storage frequency modulation output power increases, the participation degree of the inertia frequency modulation decreases to avoid excessive superposition between the two to cause frequency regulation conflict; when the energy storage frequency modulation output power decreases, the participation degree of the inertia frequency modulation increases to provide rapid but short kinetic energy support when the energy storage is insufficient. The calculation expression of the wind power inertia frequency modulation output power is: , wherein, is the rotor inertia frequency modulation channel of the wind turbine in the Laplace domain the active power response of the wind power inertia frequency modulation output power; is the rated power of the energy storage system at time ; is the energy storage frequency modulation output power at time ; is obtained by inverse Laplace transform of , which is a well-known technique to those skilled in the art and will not be described here; is an inertia response suppression function for suppressing the inertia frequency modulation channel of the wind turbine, reflecting that the stronger the output of the energy storage system is, the lower the adjustment capability of the inertia frequency modulation channel of the wind turbine should be; is the rotor inertia response coefficient of the wind turbine, which is obtained by wind turbine dynamic characteristic test method, which is a well-known technique to those skilled in the art and will not be described here, and the unit is ; , wherein, is the active power output response function of the wind turbine reserve channel in the Laplace domain , that is, the response power of the wind turbine reserve channel; is the wind turbine reserve power frequency modulation gain coefficient, which represents the power adjustment capability of the wind turbine to the frequency deviation by using the reserved reserve capacity, and is obtained according to the ratio of the active capacity that can be reserved by the wind farm to the frequency deviation target, and the unit is ; is the wind turbine variable pitch response time constant, which represents the response delay of the wind turbine in the reserve channel adjustment due to the mechanical execution mechanism (pitch adjustment), and is set according to the mechanical execution characteristics of the wind turbine electric control system, and the unit is second; The energy storage frequency modulation output power, the wind power inertia frequency modulation output power and the response power of the wind turbine reserve channel are converted from the frequency domain response to the time domain power signal by inverse Laplace transform, and then are uniformly weighted and synthesized to obtain the total frequency modulation output power; the inverse Laplace transform is a well-known technique to those skilled in the art and will not be described here; the specific calculation formula of the total frequency modulation output power is: ​ , wherein, is the total frequency modulation output power at time , as the final control instruction, is directly input to the power system dispatching and control module; , and respectively represent the energy storage frequency modulation output power, the wind power inertia frequency modulation output power and the response power of the wind power reserve channel at time ; In the above scheme, the units of all data related to power are , to eliminate the dimensional problem and ensure that each physical quantity has a consistent numerical scale in subsequent analysis or modeling to maintain dimensional consistency; In practical applications, the power system of wind storage combined frequency modulation will allocate the charge and discharge power of the energy storage system and adjust the output level of the wind turbine according to the final control instruction, so as to realize the combined frequency modulation process under the coordinated action of multiple sources. Therefore, the power system of wind storage combined frequency modulation can quickly mobilize the high-speed response characteristics of the energy storage system when the frequency is disturbed, and at the same time, combine the rotor kinetic energy support and active reserve regulation function of the wind turbine, realize the multi-level suppression and phased repair of frequency fluctuation, and effectively improve the frequency stability and safety of the power system.

[0022] In summary, a power system frequency control method based on wind storage combined frequency modulation is completed.

[0023] The order of the embodiments is only for description, not representing the advantages and disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0024] Each embodiment in the specification is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0025] The above embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for controlling power system frequency based on wind and energy storage combined frequency regulation, characterized in that: The following steps are involved: S1. Collect frequency data in real time and quantify the degree of frequency disturbance to obtain the frequency disturbance intensity; Calculate the energy storage frequency regulation weight coefficient and wind power frequency regulation weight coefficient based on the frequency disturbance intensity; S2. The energy storage system performs frequency modulation based on the energy storage frequency modulation weight coefficient to obtain the energy storage frequency modulation output power. The wind turbine generator system participates in frequency modulation through the rotor inertia frequency modulation channel and the backup channel based on the wind power frequency modulation weight coefficient to obtain the wind power inertia frequency modulation output power and the response power of the wind power backup channel. Based on the energy storage frequency regulation output power, wind power inertia frequency regulation output power and the response power of the wind power backup channel, the total frequency regulation output power is obtained, realizing multi-source coordinated phased frequency control.

2. The method for controlling the frequency of a power system based on wind and energy storage combined frequency regulation according to claim 1, characterized in that: Specifically include: Based on the frequency data and the rated frequency of the system, the frequency deviation is calculated. Based on the absolute amplitude of the frequency deviation and the frequency deviation change rate, a frequency disturbance intensity function is constructed to obtain the frequency disturbance intensity.

3. The method for controlling the frequency of a power system based on wind and energy storage combined frequency regulation according to claim 2, characterized in that: Specifically include: The frequency disturbance intensity is compared with the preset threshold parameter, and the energy storage frequency regulation weight coefficient is generated through nonlinear mapping, and the wind power frequency regulation weight coefficient is obtained.

4. The method for controlling the frequency of a power system based on wind and energy storage combined frequency regulation according to claim 3 is characterized in that: Specifically include: The energy storage system is used as the first execution unit to intervene in the control process. Based on the energy storage frequency regulation weight coefficient, the energy storage frequency regulation gain coefficient and the response time constant of the energy storage system are introduced to compensate for the frequency deviation and obtain the energy storage frequency regulation output power.

5. The method for controlling the frequency of a power system based on wind and energy storage combined frequency regulation according to claim 4, characterized in that: Specifically include: A rotor inertia frequency modulation channel for wind turbines is established. Based on the wind power frequency modulation weight coefficient, the rotor inertia response coefficient and the rotor inertia response time constant of the wind turbine are introduced. Combined with the inertia response suppression function, the frequency deviation is compensated to obtain the wind power inertia frequency modulation output power.

6. The method for controlling the frequency of a power system based on wind and energy storage combined frequency regulation according to claim 5, characterized in that: Specifically include: The inertia response suppression function is constructed based on the energy storage frequency modulation output power and the rated power of the energy storage system.

7. The method for controlling power system frequency based on wind and storage combined frequency regulation according to claim 6, characterized in that: Specifically include: Based on the wind power frequency regulation weight coefficient, the wind turbine standby power frequency regulation gain coefficient and the wind turbine pitch response time constant are introduced. Combined with the inertia response suppression function, the frequency deviation is compensated and the response power of the wind power standby channel is calculated.

8. The method for controlling power system frequency based on wind and energy storage combined frequency regulation according to claim 7, characterized in that: Specifically include: The energy storage frequency modulation output power, wind power inertia frequency modulation output power, and wind power backup channel response power are converted from frequency domain responses back to time domain power signals and weightedly synthesized to obtain the total frequency modulation output power. The total frequency modulation output power is used as the final control instruction to perform joint frequency modulation on the power system.

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