新能源集群经柔直送出孤岛系统电压优化控制策略

Optimal Voltage Control Strategy for Islanded Aggregated New Energy System Connecting by VSC-HVDC

目前新能源集群电压分层控制研究主要针对接入交流电网的情况,由于孤岛系统的电压控制与交流大电网解耦,其优化控制的目标、对象和方式均与传统电网存在较大差异,故需要结合其特性,制定新的电压控制策略。本文对孤岛方式下新能源集群无功电压控制原理进行论述,设计了送出孤岛系统区域两级电压控制框架,提出了考虑换流站PQ运行区间约束的电压优化策略,在优化目标中综合考虑网损及换流站无功裕度。基于张北柔直示范工程未来规划拓扑的仿真算例表明,该策略可以在保持换流站母线电压在安全运行范围内的前提下,实现电网运行的安全性和经济性的协调。

At present, the study on hierarchical voltage control for aggregated new energy focuses on the AC grid. As the islanded aggregated new energy system connecting by VSCHVDC is decoupling with the AC network, the optimization target and mode of which is quite different from the traditional connection, new voltage control strategies combined with its characteristics are needed to be formulated. This paper discusses the reactive power and voltage control principle for the islanded system and the framework of the two-stage voltage control system is put forward. A new voltage control strategy is presented considering the PQ constraints of the converter station, with both network loss and reactive power margin as its optimization object. Case study is based on the planning topology of the Zhangbei VSC-HVDC demonstration project, which shows that our strategy takes into account the safety and economic operation of the power grid and maintain the bus voltage within the range of safe operation as well.