Three Phase Unbalanced Responsibility Quantitative Method Research

With the development of economy,the emergence of various kinds load in power grid,three-phase unbalance problem becomes increasingly serious in power system.Determining three-phase unbalance contribution is helpful to improve the initiative of unbalance customers,which is of great significance to improve the power quality of the system.Three phase unbalanced source causing bus voltage asymmetry at the common connection point is one of the main power quality problems by the power supply department,and sing the voltage(current)unbalance degree as the power quality assessment indicators.An unbalanced system mainly caused by non-transposed lines and load imbalance.In order to quantify each three-phase load caused unbalanced voltage size at bus,need to separate the line and load unbalance emission level.By simulation,it is found that the unbalance voltage of the common connection point is mainly caused by the load,so the unbalanced voltage of the line can be ignored.According to the linear and non-linear,load can be divided into linear load and the nonlinear load,the paper firstly research linear load three-phase unbalanced responsibility quantitative method,found that can use conforming and non-conforming method to definite negative sequence current responsibilities,implement reward and punishment measures;then the paper studies the non-linear load three phase unbalanced responsibility quantitative method,this paper presents the definition of three phase unbalanced negative sequence voltage responsibility,second,due to the calculation of negative sequence voltage responsibility is the key to accurate estimation system equivalent negative sequence impedance.This paper presents five point subdivision method in complex field linear regression,in five sampling data into a set of complex linear regression.According to the error limit of screening out the negative sequence impedance parameters in each group,and calculate the average value,then getting the system equivalent negative sequence impedance and the background negative sequence voltage.The simulation verifies feasibility.