多端柔性直流输电系统协调控制策略

为兼顾系统动态响应速度和换流站精确控制有功功率的能力,并保证系统直流电压控制具有一定刚性,本文提出将直流电压偏差控制特性曲线中定功率特性改为斜率特性,并将其作为辅助站的控制特性,而主导站采用定直流电压控制,其余换流站采用定功率和斜率混合控制。为实现该控制策略,根据各换流站的控制特性设计相应的控制器结构和参数,并在控制器中引入滞环以避免控制模式频繁切换。最后,在PSCAD/EMTDC中搭建5端柔性直流输电系统,对系统处在不同的运行状态分别进行仿真,仿真结果表明,该协调控制策略能够满足系统在不同运行状态下的运行要求。

A Coordinated Control Strategy for VSC-MTDC System

In order to balance the system dynamic response speed and the ability to precisely control the active power of converter, and to ensure a certain rigidity of DC voltage control, the control strategy that the constant power characteristics in characteristic curve of DC voltage margin control is converted into characteristic of slope control is proposed, which is also taken as the control characteristic of assistant station. The constant DC voltage control is used in master station, and the combination of constant DC current control and DC voltage droop control is applied in other stations. The corresponding structure and parameters of the controller are designed according to the control characteristic of converter station. In the end, a five terminal VSC MTDC model is developed in PSCAD/EMTDC, and simulations are carried out under different operating conditions. The results show that the coordinated control strategy can meet the requirements when the system operates under different conditions.