基于阀组串联的柔性直流单阀组在线投入/退出控制方案

Research on Control Scheme for Single Converter Online Entry/Exit in Dual-converter Based VSC-HVDC

高压大容量柔性直流系统采用高低阀组串联方案时,单阀组在线投入/退出控制是一项重要环节。首先基于系统主接线方式及直流场开关配置方案,以直流电流连续不中断为要求,研究了阀组在线投退过程中直流场开关的顺控操作。其次分析了开关操作对阀组直流电压、直流电流控制的要求,并提出了MMC定直流电流均压控制策略。之后研究了系统内各站之间的配合关系,基于各站同步投退的方案设计了直流电压调节过程中2种功率调节方案。最后,综合得出了单阀组投退时系统的整体控制方案并进行了仿真,结果验证了所设计的阀组投退方案的有效性和可行性。

For high voltage and high capacity VSC-HVDC adopting dual-converter scheme,online entry/exit control of single converter is an important link.In this paper,based on the system’s main wiring type and DC field switch configuration scheme,for continuous DC current target,sequence operation of DC field switches during the converter online entry/exit is studied firstly.Then,the converter’s DC voltage and DC current control requirements for switch operation is analyzed,and a modular multi-level converter strategy to control DC current while balancing sub-module voltage is proposed.After that,the relationship between stations in the system is studied.Based on the synchronous entry/exit scheme of each station,two power regulation schemes during DC voltage regulation are designed.Finally,the overall control scheme of the system for single converter entry/exit is obtained and simulated.The simulation results verify effectiveness and feasibility of the designed strategy.