基于转子动能释放的风电并网系统非线性频率控制策略研究

Research on Nonlinear Frequency Control Strategy of Wind Power Grid Connected System Based on Rotor Kinetic Energy Release

近年来风电在电力系统中的渗透率不断提高,导致电力系统惯量降低,电网的频率稳定面临巨大挑战。针对上述问题,该文提出基于转子动能释放的风电并网系统非线性频率控制策略。首先,选择风机功率参考曲线的修正系数作为控制信号,并根据风电机组参与电网频率调节的数学模型建立仿射非线性系统;其次,基于部分线性化最优控制原理将系统变换为一个二阶Brunovsky标准型,求得非线性控制律,从而避免近似线性化产生的问题;最后,引入转子速度函数以及转速恢复函数,避免风机转速的过度下降并完成风机转速的恢复,且不需要控制环节的切换。通过MATLAB/SIMULINK搭建含风电系统进行仿真验证,结果表明,转子动能非线性策略较其他策略在释放更少动能的情况下取得了更优的调频效果,提高了电网的频率稳定性。

In recent years,with the increasing penetration of wind power in power system,the inertia of power system is reduced,and the frequency stability of power grid is facing great challenges.In view of the above problems,this paper proposes a nonlinear frequency control strategy for wind power grid-connected system based on rotor kinetic energy release.First,the correction coefficient of wind turbine power reference curve is selected as the control signal,and the affine nonlinear system is established according to the mathematical model of wind turbine participating in grid frequency regulation.Secondly,based on the optimal control principle of partial linearization,the system is transformed into a second-order Brunovsky standard form to obtain the nonlinear control law,which avoids the problem of approximate linearization.Finally,the rotor speed function and speed recovery function are introduced to avoid the excessive decline of the wind turbine speed and complete the recovery of the wind turbine speed,without switching the control link.MATLAB/SIMULINK is used to build a wind power system for simulation verification.The results show that the nonlinear strategy of rotor kinetic energy has better frequency modulation effect than other strategies under the condition of releasing less kinetic energy,and it also improves the frequency stability of the power grid.