LCC-MMC混合级联型直流输电系统受端接线和控制方式

基于某规划直流工程，分析了基于电网换相换流器（line commutated converter, LCC）和模块化多电平换流器（modular multileve converter, MMC）的混合级联型输电系统受端接线和控制方式。具体考虑因素包括接入受端交流系统的形式（集中接入或分散接入），逆变侧并联MMC的控制方式（定直流电压或定有功功率），以及多端接入条件下LCC和MMC换流站建设形式（合站建设或分站建设）。结果显示：分散接入有助于减小逆变侧交流故障下LCC和MMC在直流侧的交互影响；并联MMC均采用定直流电压控制有助于MMC交流侧故障后系统快速恢复稳定，且利用电流均衡控制策略能够消除潜在器件参数偏差导致的电流分配不对称现象；合站建设有助于减小直流故障风险，提高系统可靠性并降低投资成本。

Inverter Station Connection Modes and Control Strategies of LCC-MMC Hybrid HVDC Systems

In this paper, the inverter connection modes and control strategies of LCC-MMC hybrid HVDC systems are analyzed, on the basis of a planned HVDC project. The considered factors include the form of access to the receiving-end AC system （concentrated access or distributed access）, the control mode of parallel-connected MMCs （fixed DC voltage or fixed active power） and the form of converter construction under the condition of multi-terminal access （joint station construction or separate station construction）. The analysis results show that the distributed access to AC system helps reduce the DC-side interaction of LCC and MMC under AC faults. Fixed DC voltage control on parallel MMCs contributes to system fast recovery after MMC AC-side faults, and the DC current balance control is able to eliminate the potential unbalance of DC current caused by possible parameter deviation. The joint station construction helps reduce the risk of DC faults and decrease investment cost as well as improve system reliability.