改善惯性响应与一次调频的风电全直流系统协调控制策略

Coordinated control strategy for improving inertial response and primary frequency modulation in wind power full DC system

针对风电全直流系统并网给交流电网带来的系统惯量降低、调频能力不足等问题,提出一种改善惯性响应与一次调频的变系数风电全直流系统协调控制策略。在惯量响应方面,网侧换流站采用惯性同步控制,直流升压站采用恒变比控制,实现直流电容对电网的惯量支撑及直流低压侧的直流电压对交流系统频率的感知,在此基础上对直流风电机组(direct current wind turbine,DCWT)附加变虚拟惯性系数的虚拟惯量控制,使风电全直流系统在不同频率响应阶段具备不同的等效惯量。在一次调频方面,DCWT采用超速与变桨相结合的减载运行方式,通过变下垂控制来改变其有功出力,充分利用不同风速下的备用容量,使风电全直流系统更有效地参与一次调频。仿真算例表明,文中所提策略改善了风电全直流系统接入后电力系统的惯性响应及一次调频。

A coordinated control strategy for a variable-coefficient wind power full DC system to address problems such as reduced system inertia and insufficient frequency regulation abilities in the AC grid caused by the integration of wind power full DC systems is proposed.In terms of inertia response,the grid-side converter station adopts inertial synchronization control,while the DC-boost converter station adopts constant variable-ratio control to provide inertia support to the grid through DC capacitor and perceive the AC system frequency through the DC voltage on the low-voltage side.Additionally,a virtual inertia control scheme is introduced by adding a variable virtual inertia coefficient to the DC wind turbine(DCWT),enabling the wind power full DC system to have different equivalent inertia in different frequency response stages.As for frequency regulation,the DCWT operates in a load-reducing mode combining overspeed and variable-pitch control,adjusting its active power output through variable droop control.This approach fully utilizes the available capacity at different wind speeds,allowing the wind power full DC system to participate more effectively in frequency regulation.Simulation results demonstrate that this strategy improves the inertial response and primary frequency modulation of the power system after the integration of the wind-powered full DC system.