含逆变型分布式电源配电网的接地故障中性点电压分析及对策

Analysis on Neutral Point Overvoltage during Grounded Fault in Distribution Network with Inverter-interfaced DGs and Countermeasures

大量逆变型分布式发电(distributed generator,DG)接入导致变压器中性点过电压甚至间隙击穿等事故发生,研究中性点过电压的分析计算以及保护配置迫在眉睫。文章采用序分量理论,推导并简化了故障发生后开关跳开前后变压器中性点过电压理论计算公式。该公式形式简单、计算结果准确,可以广泛应用于规划运行分析中。根据计算公式,分析出了影响过电压的主要因素并提出了保护配置方法。PSCAD仿真算例验证了计算公式的正确性,并讨论了DG输出限流等因素对过电压的影响。

Injection of a large number of inverter-interfaced distributed generators(DGs） has led to neutral point overvoltage and even caused vacuum breakdown,which makes it imminent to analyze neutral point overvoltage in detail,as well as to concern the protection configuration there. In this paper,sequence component theory is used to derivate and simplify theoretical calculation formulas of neutral point overvoltage before and after trip during fault,which is very simple and accurate and can be widely used in system planning and operation. On the basis of these formulas,main factors influencing overvoltage are analyzed and related protection configuration is proposed. Correctness of the formulas is verified by simulation in PSCAD,and the influencing factors of overvoltage such as output current of DGs are analyzed.