为防控类似2018年"3·21"巴西大停电事故,针对特高压直流开展整流侧阀组未连交流母线失压风险分析,分别分析了送端换流站全部交流线路跳开、 换流变间隔所在串开关跳开、 交流系统故障等导致的失压或无交流滤波器运行情况,进而提出了增加阀组未连接交流母线跳闸功能.经过仿真验证,该功能可以在换流阀未连接交流母线时快速跳闸停运直流并发出闭锁信号,避免安稳装置因未及时收到闭锁信号而延迟动作.新增逻辑经现场验证并实施,增强了南方电网系统安全可靠运行能力.

直流在孤岛运行方式下送端为弱交流系统,安全稳定控制对电网的稳定运行十分重要.分析了新东直流输电处于孤岛方式运行下的控制策略,结合新东直流安稳控制策略的验证,开展了RTDS仿真试验,并针对试验中暴露出的现有稳控系统对小孤岛状态判别的缺陷,深入分析了稳控系统中电厂稳控装置动作的原理,提出了优化的小孤岛判别方法,并验证了该方法的有效性.所提方法对于稳控系统测试标准化具有重要的借鉴意义.

Due to the difference between MMC-HVDC and LCC-HVDC control characteristics and the mutual influence of parallel connection, its power modulation strategy is different from that of LCC-HVDC. Coordinated control strategy of parallel system of MMC-HVDC and LCC-HVDC is analyzed. The methods of power distribution, rate distribution and reactive power control of power limit function are described. Combined with RTDS simulation research of modulation function of Luxi back-to-back HVDC system, the control characteristics of power limitation function of the parallel system under the condition of AC fault at the rectifier side are analyzed in view of the exposed defects. The coordination method of the power limit function, the high voltage crossing control function and the rate distribution optimization is proposed. The simulation results show that the optimized parallel system can perform the power limiting function according to the correct timing and rate.

在某些检修方式下,当直流送端交流系统发生严重故障时,整流站交流母线可能存在电压过低或过高的问题,极大限制了直流运行方式。为提高直流输送能力和系统安全稳定性,建立了基于数字实时仿真器的实时数字物理混合仿真试验平台,研究了直流送端弱联网方式下使用无功控制模式、电压控制模式的系统稳定性。仿真结果表明,采用电压控制模式可提高整流站母线电压稳定性。