基于电压下垂特性的MMC-MTDC协调控制策略

Coordinated Control Strategy of MMC-MTDC Based on Voltage Droop Characteristic

基于模块化多电平换流器的多端高压直流输电(modular multilevel converter based multi-terminal high voltage direct current,MMC-MTDC)系统中各个换流站的控制对整个系统电压和功率的稳定是至关重要的。基于电压与功率的关系进行设计的传统下垂控制器无法实现受端换流站之间的功率分配。针对这一问题,提出了一种基于电压下垂特性的多端组网协调控制策略。对MMC型换流站数学模型进行了详细地分析并根据多端直流组网结构的特点,推导出各换流站之间电压和电流关系。基于换流站U-I特性曲线,设计了电压外环控制器,通过改变U-I特性曲线的斜率即可实现换流站之间的功率分配。在PSCAD/EMTDC仿真平台上搭建了四端模型,仿真结果显示,通过调整U-I特性曲线斜率即可实现受端换流站功率按既定要求分配,验证了该控制策略的正确性和有效性。

It is crucial for the power and voltage stability to control converters in the system of MMC - MTDC. The traditional droop controller is designed based on the relationship between voltage and power, which makes it incapable of realizing the function of allocating the power among receiving - end converters. In order to solve the above - mentioned problem, a novel multi - terminal network coordinated control strategy based on voltage droop characteristic is proposed. Firstly, the mathemati-cal model is analyzed in detail, and then the relationship between voltage and current among different converters is showed considering the characteristics of network structure of MTDC. A novel voltage droop controller is designed based on the charac-teristic curve （t/-/curve） of converters. The goal of allocating the power among different converters could be easily achieved by changing or adjusting the slope of U -I curve. A four - terminal model is established through PSCAD/EMTDC simulation software. The simulation results show that allocating the power among different receiving - end converters according to the des-ignated goals could be easily realized by changing the slope of U - I curve, which verifies the correctness and feasibility of the proposed control strategy.