高比例电力电子电力系统过电压(三):直流故障下新能源暂时工频过电压机理

Overvoltage of the Power System Integrated With High Proportion of Power Electronics Equipment(III):Mechanistic Analysis of Temporary Power Frequency Overvoltage Caused by DC Fault

在高比例新能源和大容量直流输电工程大量投运的背景下,电力系统过电压问题日渐凸显,不仅制约直流输电能力,而且可能引发新能源大规模脱网。在新能源占比较高时,与交流设备相比,新能源的工频过电压耐受能力更低,该文针对直流故障引发的送端新能源机端过电压问题进行机理分析。首先,建立直流闭锁和直流多次换相失败后闭锁故障状态下新能源及传统同步机经特高压直流外送系统的等效电路分析模型,基于矢量关系,解析推导直流故障下的暂时工频过电压最大值。然后,分析直流输电功率水平、新能源并网功率、新能源低电压穿越控制参数、同步机至直流换流站电气距离以及新能源至直流换流站电气距离等因素对新能源机端电压最大值的影响。最后,通过PSD-BPA仿真软件在小算例系统和我国西北等值电网中验证理论分析的有效性。

With high share of renewable energy sources and large capacity of DC transmission projects,the problem of overvoltage has drawn more and more attention,which not only restricts the DC transmission capacity,but may also cause large-scale off-grid accidents of renewable energy sources.When the proportion of renewable energy is relatively high,compared with AC equipment,the renewable energy is more likely to face temporary power frequency overvoltage.This paper analyzes the overvoltage of sending end caused by DC fault.First,simplified equivalent circuits of UHVDC for delivery of renewable energy sources and traditional synchronous generators in fault state when HVDC bipolar blocking and HVDC blocks after continuous commutation failures occur are established.Then,based on the phasor relationship,the maximum overvoltage under DC bipolar blocking faults and DC blocking after continuous commutation failure is derived.Further,the influence of the power of HVDC transmission,the active power of renewable energy source,the parameter of low voltage ride through control,the electrical distance from the traditional synchronous generator to the DC converter station,the electrical distance from the renewable energy source to the DC converter station,and other factors on the terminal voltage of the renewable energy source are analyzed.Finally,PSD-BPA simulation software is used for simulation both in minor case and northwest equivalent grid to verify the validity of the theoretical analysis.