Primary frequency regulation and virtual inertia control method for wind farms

Abstract

The present invention relates to a primary frequency regulation and virtual inertia control method for a wind farm station, wherein the wind farm station is connected to an energy storage facility, and comprises the following steps: obtaining the voltage, current and grid frequency at the grid connection point of the wind farm station in real time; judging whether the frequency change rate corresponding to the grid frequency is ≤ the rotor kinetic energy control frequency change rate threshold, if so, using the rotor kinetic energy control mode to control the wind turbine generator set, if not, judging whether the frequency change rate corresponding to the grid frequency is ≤ the power standby control frequency change rate threshold, if so, using the power standby control mode to control the wind turbine generator set, if not, using the power compensation control mode to control the output compensation power of the energy storage facility. It can improve the frequency rapid response capability of a wind farm station equipped with an energy storage facility.

Description

Technical Field

[0001] The present invention relates to the field of primary frequency regulation and virtual inertia response control of a wind farm, and in particular to a primary frequency regulation and virtual inertia control method for a wind farm. Background Art

[0002] Configuring energy storage is an ideal way to achieve active power and frequency control of renewable energy stations. Compared with control methods such as pitch angle control and speed control that require sacrificing the maximum power tracking of the unit during frequency response, it can avoid the loss of renewable energy electricity.

[0003] In terms of rapid frequency control technology for new energy stations, the paper Control for the Provision of Virtual Inertia by Wind Turbines with PMSG considering Wind Fluctuations proposes a virtual inertia control technology that supports frequency modulation by enabling the wind turbine to release rotor kinetic energy. However, after the wind turbine rotor is decelerated, due to the action of the maximum power tracking module, the rotor will absorb active power to restore to the original speed, which is easy to cause a secondary drop in frequency. To address this problem, the paper Active Speed ​​Protection Control Strategy for Doubly-Fed Wind Turbines Considering Inertial Frequency Modulation adds a rotor speed protection module on the basis of inertial control to prevent the speed from exceeding the limit, thereby suppressing the secondary drop in frequency; the paper A New Wind Farm Virtual Inertia Cooperative Control Strategy introduces a rotor kinetic energy evaluation factor to quantify the frequency modulation capability of each unit, and coordinates and controls each unit to participate in system frequency modulation according to the frequency modulation capability of each unit, thereby avoiding a secondary drop in system frequency. Affected by the fluctuation of wind speed, the operating state of the wind turbine is prone to change, and the droop control with fixed parameters cannot give full play to the frequency modulation capability of the wind turbine. To address this problem, the literature proposes to use different methods to adjust the droop control parameters according to the wind turbine operation in low, medium and high wind speed zones based on the variable droop coefficient control strategy of the doubly fed wind turbine. The literature combines the variable droop control strategy with load reduction control to better coordinate the differences in wind turbines participating in system frequency regulation at different wind speeds. In order to enable the wind turbine to have a certain power reserve at high wind speeds, the literature improves the frequency control strategy of the variable speed constant frequency doubly fed wind turbine by using variable pitch control to reserve a certain pitch angle in advance to reduce the wind turbine output and reserve active reserve to participate in system frequency regulation. Under most working conditions, the pitch angle of the wind turbine can be controlled to achieve load reduction, so the adjustment range is very wide. The literature combines the frequency control strategy of the doubly fed wind turbine with overspeed reserve and simulated inertia to combine overspeed control with rotor kinetic energy control, while improving the system inertia response capability and primary frequency regulation capability. In terms of fast frequency control technology of energy storage systems, the literature proposes a wind farm virtual inertia compensation strategy based on energy storage technology, which uses fuzzy logic control strategy to control the energy storage system to achieve frequency support for the wind power system.

[0004] In summary, new energy units have certain frequency response capabilities, but there are many types of control technologies and the coordination is complex. In view of the basic development status of large-scale new energy access to the power grid in my country and the relative lack of relevant research on fast frequency control technology for new energy stations and energy storage, it is necessary to study the control method of configuring energy storage new energy stations to participate in fast frequency response. Summary of the invention

[0005] The object of the present invention is to provide a primary frequency regulation and virtual inertia control method for a wind farm station, so as to improve the rapid frequency response capability of a wind farm station equipped with energy storage facilities.

[0006] The technical solution of the present invention is:

[0007] A primary frequency regulation and virtual inertia control method for a wind farm station, wherein the wind farm station is connected to an energy storage facility, comprising the following steps:

[0008] Real-time acquisition of the voltage, current and grid frequency at the wind farm station grid connection point;

[0009] Determine whether the frequency change rate corresponding to the grid frequency is ≤ the rotor kinetic energy control frequency change rate threshold. If the frequency change rate corresponding to the grid frequency is ≤ the rotor kinetic energy control frequency change rate threshold, use the rotor kinetic energy control mode to control the wind turbine set. If the frequency change rate corresponding to the grid frequency is greater than the rotor kinetic energy control frequency change rate threshold, determine whether the frequency change rate corresponding to the grid frequency is ≤ the power standby control frequency change rate threshold. If the frequency change rate corresponding to the grid frequency is ≤ the power standby control frequency change rate threshold, use the power standby control mode to control the wind turbine set. If the frequency change rate corresponding to the grid frequency is greater than the power standby control frequency change rate threshold, use the power compensation control mode to control the energy storage facility to output the compensation power.

[0010] Preferably, the rotor kinetic energy control mode includes virtual inertia control and droop control.

[0011] Further preferably, the virtual inertia control is to introduce an active reference signal related to the frequency change rate into the active power control part of the wind turbine, so that the wind turbine output can respond to the frequency change.

[0012] Further preferably, the droop control is to introduce a change value proportional to the frequency deviation into the active power reference value, thereby realizing frequency deviation proportional control of the active power of the wind turbine.

[0013] Preferably, the power standby control mode includes wind turbine overspeed control and wind turbine pitch control.

[0014] Further preferably, the wind turbine overspeed control is to reduce the fan speed according to the MPPT curve of the fan output, so that the working point moves leftward to approach the optimal operating point.

[0015] Further preferably, the wind turbine pitch control is based on the inverse relationship between wind turbine power and pitch angle when the rotation speed is constant, and the wind turbine output power is brought close to the optimal power by reducing the pitch angle.

[0016] The beneficial effects of the present invention are:

[0017] 1. By comparing the frequency change rate corresponding to the grid frequency with the rotor kinetic energy control frequency change rate threshold and the power reserve control frequency change rate threshold, a suitable control mode is selected to control the wind turbine, thereby stabilizing the grid frequency at the wind farm connection point and reducing grid frequency fluctuations. DETAILED DESCRIPTION

[0018] The present invention is described below in the form of embodiments to assist those skilled in the art in understanding and implementing the present invention. Unless otherwise specified, the following embodiments and the technical terms therein should not be understood without departing from the technical knowledge background of the technical field.

[0019] The energy storage system of new energy stations can increase the inertia of the entire system. Assuming that the mechanical power of the synchronous generator remains unchanged, the inertia constant of the generator can be obtained according to the synchronous generator rotor motion equation in the per-unit system:

[0020]

[0021] According to the above formula, the average generalized inertia constant in a short period of time Δt (the system frequency change rate does not change the sign) can be obtained as:

[0022]

[0023] From the perspective of the units, the participation of new energy stations in the active support control of the power grid is mostly to improve the active control links in the units so that their active output can respond to the frequency changes of the system in real time.

[0024] A primary frequency regulation and virtual inertia control method for a wind farm station, wherein the wind farm station is connected to an energy storage facility and a plurality of wind turbines are arranged in the wind farm station, comprising the following steps:

[0025] Real-time acquisition of the voltage, current and grid frequency at the wind farm station grid connection point;

[0026] Determine whether the frequency change rate corresponding to the grid frequency is less than or equal to the rotor kinetic energy control frequency change rate threshold. If the frequency change rate corresponding to the grid frequency is less than or equal to the rotor kinetic energy control frequency change rate threshold, use the rotor kinetic energy control mode to control the wind turbine generator set. If the frequency change rate corresponding to the grid frequency is greater than or equal to the rotor kinetic energy control frequency change rate threshold;

[0027] Determine whether the frequency change rate corresponding to the grid frequency is ≤ the power standby control frequency change rate threshold. If the frequency change rate corresponding to the grid frequency is ≤ the power standby control frequency change rate threshold, use the power standby control mode to control the wind turbine set. If the frequency change rate corresponding to the grid frequency is > the power standby control frequency change rate threshold, use the power compensation control mode to control the energy storage facility to output the compensation power.

[0028] Among them, the rotor kinetic energy control mode includes virtual inertia control and droop control. Virtual inertia control is to introduce an active reference signal related to the frequency change rate into the active control part of the fan, so that the fan output can respond to the frequency change. Droop control is to introduce a change value proportional to the frequency deviation into the active reference value, so as to realize the frequency deviation proportional control of the active power of the fan.

[0029] Among them, the power standby control mode includes wind turbine overspeed control and wind turbine pitch control. Wind turbine overspeed control is to reduce the wind turbine speed based on the MPPT curve of wind turbine output, so that the working point moves left to the optimal operating point. Wind turbine pitch control is based on the inverse relationship between wind turbine power and pitch angle when the speed is constant, and the wind turbine output power is close to the optimal power by reducing the pitch angle. Overspeed control responds quickly, while pitch control has a wide range of applications. The coordinated control of the two can give full play to the advantages of all parties, thereby effectively improving the active support capacity of wind turbines.

[0030] The present invention has been described in detail above with reference to the embodiments. It should be understood that it is impossible to describe all possible implementation methods in practice, and the inventive concept of the present invention is described as much as possible by way of example. Without departing from the inventive concept of the present invention and without creative work, the technical personnel in this technical field make selections and combinations of the technical features in the above embodiments, make experimental changes to the specific parameters, or use the prior art in this technical field to conventionally replace the technical means disclosed in the present invention to form specific embodiments, which should all belong to the implicit disclosure of the present invention.

Claims

1. A primary frequency regulation and virtual inertia control method for a wind farm station, wherein the wind farm station is connected to an energy storage facility, characterized in that: The following steps are involved: Receive command information issued by the automatic power generation control system, and obtain the voltage, current and grid frequency at the wind farm station grid connection point in real time; Determine whether the frequency change rate corresponding to the grid frequency is less than or equal to the rotor kinetic energy control frequency change rate threshold, If the frequency change rate corresponding to the grid frequency is less than or equal to the rotor kinetic energy control frequency change rate threshold, the rotor kinetic energy control mode is used to control the wind turbine generator set. If the frequency change rate corresponding to the grid frequency is greater than the rotor kinetic energy control frequency change rate threshold; Determine whether the frequency change rate corresponding to the power grid frequency is less than or equal to the power standby control frequency change rate threshold, If the frequency change rate corresponding to the grid frequency is less than or equal to the power standby control frequency change rate threshold, the power standby control mode is used to control the wind turbine generator set. If the frequency change rate corresponding to the grid frequency is greater than the power standby control frequency change rate threshold, the power compensation control mode is used to control the energy storage facility to output compensation power; The rotor kinetic energy control mode includes virtual inertia control and droop control; the virtual inertia control is to introduce an active reference signal related to the frequency change rate into the active power control part of the wind turbine, so that the wind turbine output can respond to the frequency change; the droop control is to introduce a change value proportional to the frequency deviation into the active power reference value, so as to realize the frequency deviation proportional control of the active power of the wind turbine. The power standby control mode includes wind turbine overspeed control and wind turbine pitch control; The wind turbine overspeed control is based on the MPPT curve of the wind turbine output, reducing the wind turbine speed so that the working point moves leftward to approach the optimal operating point; the wind turbine variable pitch control is based on the inverse relationship between the wind turbine power and the pitch angle when the speed is constant, and the wind turbine output power is brought close to the optimal power by reducing the pitch angle.

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