混合级联多端直流输电系统的功率协调控制策略

针对一种整流侧采用电网换相换流器（LCC），逆变侧采用LCC与多个模块化多电平换流器（MMC）串联的混合级联多端直流输电系统进行了研究。为解决目前已有的控制策略无法对逆变侧各换流站输送功率进行独立控制的问题，为逆变侧换流器设计了附加功率的协调控制策略，实现了对有功功率的独立灵活控制和MMC之间的功率互相支援，并为系统设计了故障控制策略。最后，在PSCAD/EMTDC中搭建了该直流输电系统模型并对所提出的协调控制策略进行了仿真验证。结果表明，附加功率的协调控制策略能够实现对逆变侧各换流器输送有功功率的独立控制，并且在系统发生故障后具有良好的故障恢复特性。

Power Coordination Control Strategy for Hybrid Cascaded Multi-terminal HVDC System

A hybrid cascaded multi-terminal HVDC system with rectifier side using line commutated converter （LCC） and inverter side using LCC in series with multiple modular multilevel converters （MMC） is studied. In order to solve the problem that the existing control strategies can not control the transmission power of converter stations independently on the inverter side， a coordinated control strategy of additional power is designed for the inverter side converter， which realizes the independent flexible control of active power and the mutual support of power between MMCs， and a fault control strategy is designed for the system. Finally， the model of the HVDC system is built in PSCAD/EMTDC and the proposed coordinated control strategy is verified by simulation. The simulation results show that the coordinated control strategy of additional power can realize the independent control of the active power conveyed by the converters on the inverter side，and the system has a good recovery characteristics after the failure.