含风电特高压直流系统单极接地故障暂态特性研究

When large-scale wind energy transmitted through ultrahigh voltage direct current(UHVDC)projects,its integration made the grid more complicated and versatile, and it is necessary to study the transient characteristics of wind power integrated UHVDC project under monopolar faults.In this paper, the electromagnetic transient simulation model has been built for wind power integrated UHVDC project. Equivalent modulus method is used to analyze the monopolar grounding fault under bipolar mode of the system, and the reason of voltage fluctuations on AC side and wind power connection point is discussed. Multiple factors have been studied to evaluate their influence on the overvoltage, including fault location, terminal resistance, and transmission power etc. Results show that overvoltage on unfaulted pole reaches to maximum when the fault occur at the midpoint of the transmission line. The capacitance of DC filter shows quite influence on the overvoltage. The unbalanced reactive power during fault leads to voltage rise at the connection point of wind energy farm. This overvoltage relates to transmission power and may further cause wind turbine tripping and fault escalation. The transient characteristics and influencing factors of wind power integrated UHVDC and wind turbine are obtained in this paper, which has important reference value for guiding the suppression of overvoltage.