A method and system for wind turbines and energy storage to collaboratively participate in system frequency regulation

Abstract

The application provides a method and system for frequency regulation of a wind turbine generator set and energy storage cooperation system, comprising: acquiring data of energy storage battery capacity, system frequency and generator set converter bus voltage during frequency regulation; determining a system frequency deviation amount according to the system frequency; determining charging / discharging of the energy storage battery and controlling the working state of the wind turbine generator set based on the system frequency deviation amount, the energy storage battery capacity and the generator set converter bus voltage. Through the method, it is determined whether the wind turbine generator set is pitched according to the charging / discharging state to achieve secondary load reduction to achieve regulation. The pitch regulation depth of the generator set is fully utilized, the charging and discharging process of the energy storage battery is optimized, the converter direct current side is monitored and protected, the safety and response capability of the wind storage combined frequency regulation are improved, the power generation efficiency of the energy storage battery energy is improved, and the availability of the wind storage combined frequency regulation scheme is improved.

Description

Technical Field

[0001] The present invention belongs to the field of new energy access and control, and specifically relates to a method and system for wind turbines and energy storage to collaboratively participate in system frequency regulation. Background Art

[0002] As traditional thermal power plants are replaced by wind power, the system's regulation capabilities are gradually weakening, posing significant challenges to system stability. Active wind power participation in system frequency regulation has become a key focus. However, due to the intermittent nature of wind power, the power source for wind power participation in system frequency regulation is uncontrollable. Relying on wind turbines to participate in system frequency regulation has certain limitations. For example, load shedding and standby frequency regulation reduces wind energy utilization, while inertia response frequency regulation can cause secondary drops in system frequency. Energy storage batteries offer stable energy and rapid response, and combined wind power and energy storage frequency regulation solutions are attracting widespread attention. However, current wind-storage combined frequency regulation focuses primarily on energy storage discharge methods, with less attention paid to energy storage charging and its impact on wind turbines. Summary of the Invention

[0003] To overcome the above-mentioned deficiencies of the prior art, the present invention proposes a method for wind turbines and energy storage to collaboratively participate in system frequency regulation, comprising:

[0004] Obtain data on energy storage battery capacity, system frequency, and unit converter bus voltage during frequency regulation;

[0005] determining a system frequency deviation amount according to the system frequency;

[0006] Based on the system frequency deviation, the energy storage battery capacity and the unit converter bus voltage, it is determined whether to charge / discharge the energy storage battery and control the working state of the wind turbine unit.

[0007] Preferably, charging / discharging the energy storage battery based on the system frequency deviation, the energy storage battery capacity and the unit converter bus voltage includes:

[0008] When the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within the specified capacity range:

[0009] It is determined whether the system frequency deviation is less than zero. If so, the energy storage battery is discharged based on the unit converter bus voltage; otherwise, the energy storage battery is charged based on the unit converter bus voltage.

[0010] Preferably, the charging / discharging of the energy storage battery based on the unit converter bus voltage includes:

[0011] Determine the charge / discharge power of the energy storage battery during frequency modulation based on the system frequency and the capacity of the energy storage battery, and charge / discharge the energy storage battery;

[0012] When the energy storage battery is in the discharge process: determine whether the unit converter bus voltage is greater than or equal to the maximum value of the unit converter bus voltage, if so, stop discharging, otherwise continue discharging;

[0013] When the energy storage battery is in the charging process, it is determined whether the unit converter bus voltage is less than or equal to the minimum value of the unit converter bus voltage. If so, charging is stopped; otherwise, charging is continued.

[0014] Preferably, the calculation formula for the charge / discharge power of the energy storage battery is as follows:

[0015]

[0016] Where, P B is the charging power or discharging power of the energy storage battery, Δf represents the system frequency deviation, f d represents the dead zone of grid frequency regulation, k1 is the coefficient related to the frequency change rate, k2 is the coefficient related to the frequency change amount, and k3 is the coefficient that constrains the charging and discharging process based on the characteristics of the energy storage battery. It is the physical quantity that changes with time during the system frequency change process.

[0017] Preferably, the calculation formula of the coefficient k1 related to the frequency change rate is as follows:

[0018]

[0019] Where J0 is the initial value of k1, C1 is a constant, and sign is the sign function.

[0020] Preferably, the value of the coefficient k3 constraining the charging and discharging process based on the characteristics of the energy storage battery is as follows:

[0021]

[0022] Where soc is the capacity of the battery and n is the power function exponent.

[0023] Preferably, controlling the working state of the wind turbine generator set based on the system frequency deviation and the energy storage battery capacity includes:

[0024] When the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within the specified capacity range:

[0025] It is determined whether the system frequency deviation is less than zero. If so, the wind turbine is controlled to operate normally. If not, pitch control of the wind turbine is performed based on the capacity of the energy storage battery.

[0026] Preferably, the pitch control of the wind turbine generator set based on the capacity of the energy storage battery includes:

[0027] When the energy storage battery capacity reaches its maximum value and the wind turbine output power is greater than the preset ratio of the rated power, the active power adjustment value is obtained based on the system frequency deviation through the set droop curve;

[0028] Subtracting the current output active power from the active adjustment value to obtain an active reference value;

[0029] Obtaining a unit speed reference value based on the active power reference value via a speed-power curve;

[0030] The pitch reference value is obtained by subtracting the actual wind turbine speed from the speed reference value through PI;

[0031] The variable pitch system performs load reduction control on the wind turbine generator set according to the pitch reference value, and participates in system frequency regulation.

[0032] Based on the same inventive concept, the present application also provides a system for wind turbines and energy storage to collaboratively participate in system frequency regulation, comprising: an acquisition module, a deviation determination module, and a status module;

[0033] The acquisition module is used to obtain data on the energy storage battery capacity, system frequency and unit converter bus voltage during frequency modulation;

[0034] The deviation determination module is configured to determine the system frequency deviation according to the system frequency;

[0035] The state module is used to determine the charging / discharging of the energy storage battery and control the working state of the wind turbine based on the system frequency deviation, the capacity of the energy storage battery and the bus voltage of the unit converter.

[0036] Preferably, the state module includes a charge / discharge state submodule and a working state submodule;

[0037] The charge / discharge state submodule is configured to, when the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within a specified capacity range, determine whether the system frequency deviation is less than zero; if so, discharge the energy storage battery based on the unit converter bus voltage; otherwise, charge the energy storage battery based on the unit converter bus voltage;

[0038] The working status submodule is used to determine whether the system frequency deviation is less than zero when the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within the specified capacity range. If so, the wind turbine is controlled to operate normally; if not, the wind turbine is pitch-controlled based on the energy storage battery capacity.

[0039] Compared with the closest prior art, the present invention has the following beneficial effects:

[0040] 1. The present invention provides a method and system for wind turbines and energy storage to collaboratively participate in system frequency regulation, including: obtaining data on energy storage battery capacity, system frequency, and unit converter bus voltage during frequency regulation; determining a system frequency deviation based on the system frequency; and determining charging / discharging of the energy storage battery and controlling the wind turbine operating state based on the system frequency deviation, energy storage battery capacity, and unit converter bus voltage. This method improves the safety and responsiveness of wind-storage combined frequency regulation, enhances the power generation efficiency of energy storage batteries, and improves the availability of wind power and energy storage combined frequency regulation solutions.

[0041] 2. The present invention provides an optimization method for the charge and discharge process of the energy storage battery, reduces the charge and discharge depth of the energy storage battery, and simulates the inertia response and primary frequency regulation process of the traditional synchronous unit, which can take into account the rapidity of the system frequency regulation, stability requirements and SOC characteristics;

[0042] 3. The present invention provides a wind turbine pitch control system that works in conjunction with an energy storage battery. At low frequencies, the wind turbine operates at maximum power, reducing wind energy loss. At high frequencies, the two are jointly adjusted, resulting in a fast response and greater adjustment capability.

[0043] 4. The present invention provides a monitoring and protection system for the bus voltage of the unit converter to ensure the safety of wind-storage combined frequency regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic flow chart of a method for wind turbines and energy storage to collaboratively participate in system frequency regulation provided by the present invention;

[0045] Figure 2 A schematic diagram of a typical power grid low-frequency accident curve in a method provided by the present invention for wind turbines and energy storage to collaboratively participate in system frequency regulation;

[0046] Figure 3 A method for wind turbines and energy storage to collaboratively participate in system frequency regulation provided by the present invention. A schematic diagram of wind turbine pitch control when the grid frequency increases and exceeds the dead zone.

[0047] Figure 4 A schematic diagram of the control framework of wind-storage joint frequency regulation, a method for wind turbines and energy storage to collaboratively participate in system frequency regulation, provided by the present invention;

[0048] Figure 5 A schematic diagram of the system framework in which a wind turbine and energy storage cooperate to regulate system frequency provided by the present invention. DETAILED DESCRIPTION

[0049] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present invention and are not intended to limit the present invention.

[0051] Example 1:

[0052] The application principle of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Figure 1 As shown, a method for wind turbines and energy storage to collaboratively participate in system frequency regulation in an embodiment of the present invention includes:

[0053] Step 1: Obtain data on energy storage battery capacity, system frequency, and unit converter bus voltage during frequency regulation;

[0054] Step 2: determining a system frequency deviation according to the system frequency;

[0055] Step 3: Determine charging / discharging of the energy storage battery and control of the wind turbine operating state based on the system frequency deviation, the energy storage battery capacity and the unit converter bus voltage.

[0056] The energy storage battery is connected in parallel with the DC side of the wind turbine converter through a DC / DC buck-boost converter, and the DC / DC converter communicates with the wind turbine converter through optical fiber. The wind turbine side converter controls the active and reactive power of the generator, and the grid side converter controls the DC bus voltage and grid side reactive power. When the grid frequency disturbance is within the dead zone, the unit operates normally (maximum power tracking state) and the energy storage is locked; when the grid frequency decreases and exceeds the frequency regulation dead zone, the wind turbine operates in the maximum power tracking state, and the energy storage battery participates in the grid frequency regulation; when the grid frequency increases and exceeds the frequency regulation dead zone, the energy storage battery is charged first, and then the wind turbine pitch is changed to achieve secondary load reduction and deep regulation. The specific steps are as follows: Figure 4 shown.

[0057] (1) Energy storage battery charging and discharging control

[0058] The energy storage battery responds to the grid frequency change rate (system frequency change) and frequency deviation adjustment, and at the same time constrains the charging and discharging process according to the battery characteristics. B It is composed of frequency change rate related quantities and frequency deviation related quantities, and is regulated and constrained by three key coefficients k1, k2, and k3.

[0059]

[0060] Where Δf is the grid frequency deviation (system frequency deviation), i.e. the difference between the actual grid frequency (actual system frequency) and the rated frequency Δf = ff n , fd is the dead zone of grid frequency regulation, k1 is the coefficient related to the frequency change rate, i.e. the simulated inertia coefficient, k2 is the coefficient related to the frequency change amount, i.e. the simulated primary frequency regulation coefficient, and k3 is the coefficient related to the charging and discharging characteristics of the energy storage battery.

[0061] k1 is the simulated inertia response, which can achieve a rapid response to the trend of grid frequency changes. Its size is determined by the grid frequency changes. Considering that in actual grid frequency events, the frequency change is a deep "V" characteristic (such as Figure 2 As shown). During the frequency drop process, df / dt < 0, Δf < 0. At this time, k1 should be increased to slow down the frequency drop rate and raise the lowest frequency point. During the frequency recovery process, df / dt > 0, Δf < 0. At this time, k1 should be smaller to avoid overshoot during recovery. The frequency increase situation is similar and will not be repeated here. The value of k1 is as follows:

[0062]

[0063] Where J0 is the initial value of k1, C1 is a constant, and sign is the sign function.

[0064] k2 is the simulated primary frequency modulation coefficient, which can achieve stable support of frequency deviation and keep its size constant, that is,

[0065] k2=C2

[0066] Where C2 is a constant.

[0067] k3 is a coefficient that constrains the charge and discharge process based on the characteristics of the energy storage battery. The SOC curve of the energy storage battery is similar to a power function. Dynamically adjusting k3 based on the power function can take into account both frequency modulation requirements and SOC characteristics, achieving frequency response optimization. The values ​​of k3 are as follows:

[0068]

[0069] In the formula, SOC reflects the remaining capacity of the battery, and its value range is 0 to 1. N is the power function exponent, and its value should be between 2 and 5. The specific value can be selected according to the SOC characteristics.

[0070] To prevent the energy storage battery from being damaged due to over-discharge (over-charge), the energy storage battery SOC should meet the following requirements:

[0071] soc min ≤soc≤soc max

[0072] Where, soc min 、soc max They are the lower and upper limits of the energy storage battery SOC respectively.

[0073] In addition, when the energy storage battery is connected to the DC side of the wind turbine converter, the rapid release or absorption of power during frequency modulation may cause a sudden rise or fall in the DC bus voltage. If the grid-side converter is sluggish in regulation, it may cause the DC voltage to cross the line, posing a threat to the safety of the unit. Therefore, the DC voltage U dc Monitor when U dc Close to the minimum DC voltage U dcmin Or the maximum value U dcmax When , the charging and discharging process stops.

[0074] (2) Wind turbine pitch control

[0075] As mentioned above, when the frequency decreases, the energy storage parameters are adjusted and the wind turbines maintain normal operation; when the frequency increases, the energy storage battery and the wind turbines need to cooperate in the adjustment, such as Figure 3 shown.

[0076] The grid frequency (system frequency) increases and exceeds the dead zone, the energy storage battery is charged first, and when the soc reaches soc max If the wind turbine output power P0 is greater than 20% of the rated power (20% P n ), the wind turbine participates in the system frequency regulation by changing the pitch and reducing the load, specifically as follows: the grid frequency deviation is obtained by the set droop curve to obtain the active adjustment value ΔP, and the current output active power P0 is obtained by the difference between ΔP to obtain the active reference value P ref , P ref The speed reference value ω of the unit is obtained through the speed-power curve ref , actual unit speed ω r With ω ref The pitch reference value β is obtained by subtracting it from PI ref , and finally the load reduction control is achieved by the pitch system.

[0077] Example 2:

[0078] Based on the same inventive concept, the present invention also provides a system in which wind turbines and energy storage cooperate to participate in system frequency regulation. Since the principles of these systems in solving technical problems are similar to the method in which wind turbines and energy storage cooperate to participate in system frequency regulation, the repeated parts will not be repeated.

[0079] A system in which wind turbines and energy storage cooperate to regulate system frequency, such as Figure 5 Shown, including:

[0080] Acquisition module, deviation determination module and status module;

[0081] The acquisition module is used to obtain data on the energy storage battery capacity, system frequency and unit converter bus voltage during frequency modulation;

[0082] The deviation determination module is configured to determine the system frequency deviation according to the system frequency;

[0083] The state module is used to determine the charging / discharging of the energy storage battery and control the working state of the wind turbine based on the system frequency deviation, the capacity of the energy storage battery and the bus voltage of the unit converter.

[0084] The state module includes a charge / discharge state submodule and a working state submodule;

[0085] The charge / discharge state submodule is configured to, when the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within a specified capacity range, determine whether the system frequency deviation is less than zero; if so, discharge the energy storage battery based on the unit converter bus voltage; otherwise, charge the energy storage battery based on the unit converter bus voltage;

[0086] The working status submodule is used to determine whether the system frequency deviation is less than zero when the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within the specified capacity range. If so, the wind turbine operates normally; if not, the wind turbine is pitch-controlled based on the energy storage battery capacity.

[0087] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0088] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0089] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0090] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit its scope of protection. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading this application, those skilled in the art may still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the application.

Claims

1. A method for wind turbines and energy storage to collaboratively participate in system frequency regulation, characterized in that: include: Obtain data on energy storage battery capacity, system frequency, and unit converter bus voltage during frequency regulation; determining a system frequency deviation amount according to the system frequency; Determine charging / discharging of the energy storage battery and control of the wind turbine operating state based on the system frequency deviation, the energy storage battery capacity and the unit converter bus voltage; The charging / discharging of the energy storage battery based on the system frequency deviation, the energy storage battery capacity, and the unit converter bus voltage includes: When the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within the specified capacity range: Determine whether the system frequency deviation is less than zero, and if so, discharge the energy storage battery based on the unit converter bus voltage; otherwise, charge the energy storage battery based on the unit converter bus voltage; The charging / discharging of the energy storage battery based on the unit converter bus voltage includes: Determine the charge / discharge power of the energy storage battery during frequency modulation based on the system frequency and the capacity of the energy storage battery, and charge / discharge the energy storage battery; When the energy storage battery is in the process of discharging: determining whether the unit converter bus voltage is greater than or equal to the maximum value of the unit converter bus voltage, if so, stopping discharging, otherwise continuing discharging; When the energy storage battery is in the charging process: determining whether the unit converter bus voltage is less than or equal to the minimum value of the unit converter bus voltage, if so, stopping charging, otherwise continuing charging; The calculation formula for the charge / discharge power of the energy storage battery is as follows: Where, P B is the charging power or discharging power of the energy storage battery, Vf represents the system frequency deviation, f d represents the dead zone of grid frequency regulation, k1 is the coefficient related to the frequency change rate, k2 is the coefficient related to the frequency change amount, and k3 is the coefficient that constrains the charging and discharging process based on the characteristics of the energy storage battery. It is the physical quantity that changes with time during the system frequency change process; The value of the coefficient k3 constraining the charging and discharging process based on the characteristics of the energy storage battery is as follows: Where soc is the capacity of the battery and n is the power function exponent.

2. The method according to claim 1, characterized in that The calculation formula of the coefficient k1 related to the frequency change rate is as follows: Where J0 is the initial value of k1, C1 is a constant, and sign is the sign function.

3. The method according to claim 1, characterized in that Controlling the working state of the wind turbine generator set based on the system frequency deviation and the energy storage battery capacity includes: When the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within the specified capacity range: It is determined whether the system frequency deviation is less than zero. If so, the wind turbine is controlled to operate normally. If not, pitch control of the wind turbine is performed based on the capacity of the energy storage battery.

4. The method according to claim 3, characterized in that The pitch control of the wind turbine generator system based on the energy storage battery capacity includes: When the energy storage battery capacity reaches its maximum value and the wind turbine output power is greater than the preset ratio of the rated power, the active power adjustment value is obtained based on the system frequency deviation through the set droop curve; Subtracting the current output active power from the active adjustment value to obtain an active reference value; Obtaining a unit speed reference value based on the active power reference value via a speed-power curve; The pitch reference value is obtained by subtracting the actual wind turbine speed from the speed reference value through PI; The variable pitch system performs load reduction control on the wind turbine generator set according to the pitch reference value, and participates in system frequency regulation.

5. A system in which wind turbines and energy storage cooperate to regulate system frequency, characterized in that: include: Acquisition module, deviation determination module and status module; The acquisition module is used to obtain data on the energy storage battery capacity, system frequency and unit converter bus voltage during frequency modulation; The deviation determination module is configured to determine a system frequency deviation according to the system frequency; The state module is used to determine the charging / discharging of the energy storage battery and control the working state of the wind turbine generator set based on the system frequency deviation, the energy storage battery capacity and the unit converter bus voltage; The charging / discharging of the energy storage battery based on the system frequency deviation, the energy storage battery capacity, and the unit converter bus voltage includes: When the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within the specified capacity range: Determine whether the system frequency deviation is less than zero, and if so, discharge the energy storage battery based on the unit converter bus voltage; otherwise, charge the energy storage battery based on the unit converter bus voltage; The charging / discharging of the energy storage battery based on the unit converter bus voltage includes: Determine the charge / discharge power of the energy storage battery during frequency modulation based on the system frequency and the capacity of the energy storage battery, and charge / discharge the energy storage battery; When the energy storage battery is in the process of discharging: determining whether the unit converter bus voltage is greater than or equal to the maximum value of the unit converter bus voltage, if so, stopping discharging, otherwise continuing discharging; When the energy storage battery is in the charging process: determining whether the unit converter bus voltage is less than or equal to the minimum value of the unit converter bus voltage, if so, stopping charging, otherwise continuing charging; The calculation formula for the charge / discharge power of the energy storage battery is as follows: Where, P B is the charging power or discharging power of the energy storage battery, Vf represents the system frequency deviation, f d represents the dead zone of grid frequency regulation, k1 is the coefficient related to the frequency change rate, k2 is the coefficient related to the frequency change amount, and k3 is the coefficient that constrains the charging and discharging process based on the characteristics of the energy storage battery. It is the physical quantity that changes with time during the system frequency change process; The value of the coefficient k3 constraining the charging and discharging process based on the characteristics of the energy storage battery is as follows: Where soc is the capacity of the battery and n is the power function exponent.

6. The system according to claim 5, characterized in that The state module includes a charge / discharge state submodule and a working state submodule; The charge / discharge state submodule is configured to, when the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within a specified capacity range, determine whether the system frequency deviation is less than zero; if so, discharge the energy storage battery based on the unit converter bus voltage; otherwise, charge the energy storage battery based on the unit converter bus voltage; The working status submodule is used to determine whether the system frequency deviation is less than zero when the absolute value of the system frequency deviation is greater than the grid frequency regulation dead zone and the energy storage battery capacity is within the specified capacity range. If so, the wind turbine is controlled to operate normally; if not, the wind turbine is pitch-controlled based on the energy storage battery capacity.

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