分布式逆变器并网系统谐振机理研究

Resonance Mechanism Analysis of the Power System Involving Distributed Grid-connected Inverters

逆变器诺顿等效电路的等效阻抗与电力系统发生耦合,是逆变器并网系统发生谐振的根源。该文首先对逆变器等效阻抗进行研究,建立逆变器精确数值模型,并与物理实测结果对比,总结提出逆变器阻抗特性。在此基础上,研究并网系统总导纳特性与系统稳定性的关系,得到逆变器并网系统并联谐振的机理：在系统阻抗为阻感特性的情况下,若全部并网逆变器的电导特性均为正值,则并网系统稳定;若存在具有负阻尼特性的逆变器,则并网系统存在谐振风险,并由此给维持系统稳定的并网逆变器应满足的导纳特性条件。仿真与物理实验证明了该分析结果的有效性。

The coupling of the equivalent impedance of theinverters＇ Norton equivalent circuit with the power system is the source of the resonance in the power system involving grid-connected inverters. This paper firstly lucubrated the inverters＇ equivalent impedance, built an accurate numerical model of inverters, which is compared with the real systems＇ results, and summarizes the properties of the inverter＇s impedance. Based on the analysis of the inverters＇ impedance. this paper discussed the relationship of the whole systems＇ admittance properties to the system＇s stability, and acquired the resonance mechanism of the power systems involving grid-connected inverters when power system＇ impedances are resistor-inductance： power systems are stable when all inverters have positive conductivity; power systems have the possibility of resonance when some inverters have the negative damping. According to the mechanism analysis above, admittance properties of the grid-connected inverters were indicated to guarantee the stability of the power systems. Simulation and Experiments verified the correctness of our analysis.