逆变型分布式电源并网系统的失步保护研究

Out-of-Step Separation Protection of Inverter-Based Grid-Connecting System for Distributed Generation

针对逆变型分布式电源并网系统中存在的失步问题,分析了逆变型分布式电源并网系统失步和传统旋转型电源电网失步的区别,提出了适用于分布式电源并网系统的失步保护新原理。该保护首先利用公共耦合节点处视在阻抗角偏移量的绝对值构建失步保护启动判据,其次利用视在阻抗角变化的加速度绝对值来判断失步状态。通过MATLAB/SIMULINK搭建三相光伏并网发电系统模型,进行三相短路和失步仿真。仿真结果验证了提出的失步保护原理清晰,可以准确区分逆变型分布式电源并网系统中发生三相短路故障和失步的情况,并且该保护原理不受三相短路故障的影响。

In allusion to the out-of-step fault occurred in inverter-based grid-connecting system for distributed generation,the differences between the out-of-step fault occurred in traditional power grid composed of rotating generators and that occurred in inverter-based grid-connecting system for distributed generation are analyzed,and a new principle for out-of-step separation protection for inverter-based grid-connecting system for distributed generation is proposed.Firstly,the absolute value of apparent impedance angle deviation at the point of common coupling（PCC） is utilized to construct the tripping criterion and out-of-step separation criterion respectively;secondly,the absolute value of variation acceleration of apparent impedance angle is used to judge the out-of-step state.A model of grid-connected three-phase photovoltaic（PV） power system is built by MATLAB/SIMULINK to simulate the three-phase short-circuit fault and out-of-step fault.Simulation results show that the proposed new principle for out-of-step separation protection is correct and the principle is clear,the three-phase short-circuit fault occurred in inverter-based grid-connecting system for distributed generation can be precisely distinguished from the out-of-step fault,and the proposed protection principle is not affected by three-phase short-circuit fault occurred in inverter-based grid-connecting system for distributed generation.