直流潮流控制器对直流电网的影响及其选址

Impact and Location Analysis of DC Power Flow Controller on DC Grid

基于电压源型换流器的直流电网,其潮流分布取决于各支路的电阻,其可控支路数遵循N-1准则,故当直流电网支路数较多时,仅由换流器独立控制效果不佳,更难以抑制某些支路的过载。通过直流潮流控制器,可在最大限度保证支路运行在载流限值内的同时,实现与换流站的控保装置的协调配合。综述了典型的直流潮流控制器的拓扑及原理,采用电流灵敏度分析方法研究了其对直流电网的影响,并给出了潮流计算数学模型,推导了电流灵敏度的通用表达式。利用仿真软件和电流灵敏度程序对潮流控制器调整前后支路电流值的变化进行了灵敏度分析,提出了潮流控制器最优安装位置选择方法。以改造后的舟山五端柔性直流工程为例验证了该方法的合理性和有效性。

The power flow in a voltage source converter（VSC） based DC grid is determined by the resistance of each branch and the power flow control capability follows available nodes（N） minus one（N-1） rule. It means that it＇s difficult even impossible to ensure certain branches not overloaded if the number of branches in the DC grid are far more than N-1. The introduction of DC power flow controller can maximally guarantee that the power flows in all branches are within their ratings so as to enhance the power flow control capability of the DC grid. This paper summarized several typical topologies and their working principles of DC power flow controller. Current sensitivity analysis method was used to study the influences of the controller on DC grids. The mathematical models for power flow calculations of DC grids with the voltage source type of DC power flow controller were derived and the general expressions of current sensitivity were presented in detail. The branch currents and their sensitivity with and without the DC power flow controller were studied using the simulation software and the sensitivity analysis methodology. Based on the sensitivity study results, the methods and rules to choose optimal location for DC power flow controller were derived. Finally, a DC grid based on Zhoushan 5-terminal DC project was used to validate the rationality and effectiveness of the current sensitivity analysis method.