随着大量常规机组被直流馈入和新能源发电替代,系统惯量水平下降,调频资源减少,频率稳定性问题日益突出.基于电网换相型换流器的直流输电(line-commutated converter based high-voltage direct-current,LCC-HVDC)应用广泛,利用其功率快速调节能力为系统提供支撑是改善频率稳定性问题的有效手段.该文基于功率阶跃型频率控制的基本框架,考虑 LCC 的出力限制,以出现功率缺额后频率最低点最高为目标建立了LCC-HVDC系统的出力时序优化模型.基于序列二次规划法对优化问题进行求解,确定最佳的LCC附加功率与支撑时间.基于MATLAB/Simulink的仿真验证了所提频率支撑控制策略的有效性.
Power Step Based Frequency Support Control Strategy of LCC-HVDC System
With a large number of synchronous generators being replaced by infeed direct current and new energy gener-ation,the system inertia level has decreased,frequency modulation resources have decreased,and the problem of frequency stability has become increasingly prominent.LCC-HVDC(line-commutated converter based high-voltage di-rect-current)is widely used.It is an effective means to improve frequency stability by using power quick adjustment ability of LCC-HVDC to provide frequency support for the system.In this paper,based on the basic framework of power step frequency control,the output timing optimization model of LCC-HVDC is established when the lowest frequency occurs at the highest as the target after power disturbance considering the output limit of LCC.Based on the sequential quadratic programming method,the optimization problem is solved to determine the best additional power and support time of LCC.Simulations based on MATLAB/Simulink verify the effectiveness of the proposed frequency support control strategy.