Study On Influencing Factors And Suppression Measures Of Transient Overvoltage In Wind Power Collection Area

China’s wind resources are mainly distributed in the "Three North" areas,which are inversely distributed with the load,and the main development methods are large-scale centralized development and high-pressure long-distance transmission.Due to the weak grid structure and small local load of wind power system,the problem of voltage stability has become the main factor perplexing the safe operation of the system.Considering that all wind farm stations are equipped with dynamic reactive power compensation devices such as static var generator(SVG),some studies show that SVG may worsen transient overvoltage after fault.In order to reduce the risk of fan interlocking disconnection caused by transient overvoltage,it is necessary to study the influencing factors and suppression measures of transient overvoltage of wind power system.Based on the above background,this paper mainly studies the following aspects:(1)Based on the data measured after the semi physical in the loop simulation platform RT-LAB is connected to the fan and SVG respectively,it is converted into a specific data format,and the operating parameters such as maximum capacitive current are obtained after summarizing and processing each working condition;The psd-bpa model of doubly fed wind turbine and each module of SVG is studied;Based on this,the electromechanical transient modeling of doubly fed wind turbine and SVG is completed,which lays the foundation for the follow-up content.(2)The mechanism of the effect of wind power generation control performance on transient overvoltage is studied.It is pointed out that the interlocking process of "low voltage first and high voltage second" is caused by the untimely withdrawal of reactive current and the slow recovery of active current in case of short-circuit fault;The wind turbine and system side are equivalent to a small dual unit system,which can represent the wind turbine terminal voltage under steady-state condition and short-circuit fault respectively;Based on the terminal voltage expression,it is proposed that the transient overvoltage can be suppressed by reducing the reactive power control coefficient of new energy units during low break through,increasing the proportion of active current during low break through and increasing the recovery speed of active power after low break through;Then the correctness of the above conclusions is verified by simulation;(3)At present,most SVG adopt capacitive full generation control strategy after entering low-voltage ride through,which will lead to excess reactive power of the system,especially when the voltage drops slightly.The problem is more obvious,and the excess reactive power will further worsen the transient overvoltage.In order to suppress transient overvoltage,the optimization research of SVG control strategy is proposed from three aspects: SVG provides limited reactive power support during fault,SVG reactive power pullback time advance and SVG fast regulation.Based on the above three aspects,an optimal control strategy based on pre fault reactive current superimposed fault voltage control current is proposed,The effectiveness of the proposed control strategy is verified by simulation.Finally,two key parameters in the proposed control strategy are pointed out:the calculation process of voltage reference value and reactive current coefficient,which are verified by simulation.