适用于混合多端直流输电系统的非线性下垂控制策略

针对混合多端直流输电系统功率协调控制问题，提出了一种非线性下垂控制策略。该策略考虑了各换流站的电流裕度，由多个换流站共同维持直流电压的稳定，使电流裕度大的换流站承担较大的功率变化量，电流裕度小的换流站承担较小的功率变化量，避免出现部分换流站满载而失去对功率变化响应能力的情况。该控制策略可以协调分配各换流站有功功率，有效降低各换流站直流电压的静态偏差，且提高了系统的响应速度。用根轨迹法对所提控制策略进行了稳定性分析。仿真结果验证了所提控制策略的可行性和有效性。

Nonlinear Droop Control Strategy for Hybrid Multi-terminal HVDC Transmission System

Aiming at the problem of power coordinated control of hybrid multi-terminal high voltage direct current(HVDC)transmission system, a nonlinear droop control strategy is proposed. This strategy takes into account the current margin of every converter station. The stability of the DC voltage is maintained by multiple converter stations. The converter stations with more current margin share more power variation, and the stations with less current margin share less power variation. The condition that some converter stations with full load lose response capability to power change is avoided. This control strategy can harmoniously allocate active power for every converter station and effectively reduce the DC voltage static bias. The response speed of the system is improved. The stability analysis of the proposed control strategy is carried out by the root locus method. The simulation results have validated the feasibility and effectiveness of the proposed control strategy.