MMC－MTDC输电系统频率协调控制策略

Frequency Coordinated Control Strategy for MMC－MTDC Transmission System

摘要:

针对交流系统通过 MMC － MTDC 实现异步联网后无法实现区域间频率支撑的问题，参照交流系统功 － 频特 性和柔性直流输电系统直流电压下垂特性设计了 3 种频率协调控制策略: 固定频率控制、频率偏差 PI 控制和功率估 算频率控制。固定频率控制将频率参考值设定为常数来获得功率支撑量; 频率偏差 PI 控制是将频率事故换流站的频 率与参与协调控制换流站的频率平均值之差作为 PI 控制器的输入量来获取功率支撑量; 功率估算频率控制根据事故 换流站交流侧频率的实时变化，利用功 － 频静特性系数估算功率变化量来决定换流站的功率支撑量。在 PSCAD 仿真 软件中搭建了异步联网交直流系统进行仿真验证，仿真结果表明了所提 3 种利用 MMC － MTDC 实现区域间频率协调 的可行性和有效性。

关键词:MMC－MTDC; 频率协调控制; 电压下垂控制; 固定频率控制; 频率偏差控制; 功率估算; 功频静特性系数

Abstract:

The problem of inter － area frequency support can not be achieved after asynchronous networking is realized through MMC － MTDC． Ｒeferring to the power － frequency characteristics of AC system and the DC voltage droop characteristics of flexible HVDC system，3 frequency coordinated control strategies are designed: fixed frequency control，frequency deviation PI control and power estimation frequency control． Fixed frequency control sets frequency reference value as the constant to obtain power support． The frequency deviation PI control obtains the power support by taking the frequency of converter station with frequency accident and the difference of the average frequency of the coordinated control converter station as the input of PI controller． The power estimation frequency control is based on the instantaneous change of the frequency of AC side of the accident converter station． And the power － frequency characteristic coefficient is used to estimate the power variation to determine the power support of the converter station． In PSCAD simulation software，an asynchronous networking system is set up for simulation verification，and the simulation results show the feasibility and effectiveness of the proposed 3 methods to achieve inter － area frequency coordinated control．

Key words:MMC － MTDC; frequency coordinated control; voltage droop control; fixed frequency control; frequency deviation control; power estimation; power － frequency characteristic coefficient