基于频率线性映射的海上风电-低频输电系统的调频控制方法

Frequency support control method for offshore wind farm integrated with low frequency transmission system based on frequency linear mapping

随着海上风电场高占比接入电网,迫切需要海上风电主动支撑电网频率以缓解系统的频率稳定问题。然而,背靠背式变换器作为低频输电技术的核心元件,将海上风电系统和陆上交流系统之间解耦,使得海上风电场无法直接响应陆上系统的频率变化。为此,该文针对海上风电经低频输电并网系统提出一种频率协调控制策略。首先提出一种下垂控制策略将陆上交流系统的频率变化映射为低频输电系统的频率变化,背靠背式变换器采用双环控制策略以响应频率的调整。接着,使用下垂系数对风电机组功率进行协调控制,为大电网的频率提供支撑。仿真结果表明,海上风电场采用该文提出的方法能够很好地响应陆上电力系统的频率变化,从而加快陆上电网频率的恢复。

The flexible low-frequency AC transmission technology has received extensive attention in the grid connection of offshore wind farm because it has the advantages of traditional AC transmission and flexible DC transmission.With the increasing penetration of offshore wind farm connected to the grid,it is necessary that the offshore wind farm can provide frequency support for the bulk power system to alleviate its frequency stability issue.However,the offshore wind power system is decoupled from the onshore bulk power system by the back-to-back converter,which is the core component of the low frequency power transmission technology.As a result,the offshore wind farm cannot respond to the frequency change of the onshore bulk power system.Therefore,this paper proposes a frequency support control strategy for offshore wind farm integrated with low frequency transmission system.First,a droop control strategy is developed to map the frequency change of the onshore bulk power system to the frequency change of the low frequency transmission system,and the back-to-back converter uses a dual-loop control strategy in response to the frequency adjustment.Finally,the droop factor is used to control the active power output of the wind turbine to provide frequency support for the bulk power system.The simulation results show that the offshore wind farm can provide effective frequency support in response to the frequency change of the onshore bulk power system using the method proposed in this paper.