Study On Harmonic Source Identification Based On Parameter Identification Method In Power Distributed System

Harmonic becomes an important element of impact for electric quality in power system, harmonic sources identifying and location are necessary for actual detection and management. To detemine whether harmonic soutrces exist in the load is of essitial importance for improving and managing the affect of the harmonics on power system. The major work and conclusion as follows:The paper firstly introduces the existing harmonic sources identification methods in distributed system, and analyzed and summarized these methods advantages and disadvatages. Then, the haomonic source identification based on Parameter Identification method is proposed.The paper in-depth research and analysis the harmonic sources identification based on Parameter Identification method. Based on the non-linear load impedance generating harmonic, the paper establishes the harmonic equivalent load model in time domain. Under the situation of unknown the loads parameters, using SVD algorithm parameter identification method to identify the load impedance according to the physical relationship of voltage and current at the point of common coupling (PCC), then identified the harmonic source. Furthermore, in order to solve the impedance parameters in real time, this paper proposes a load equivalent impedance point by point identification method, that is the sine approximation method.Using the PSCAD / EMTDC software established simulation model which has a good application in harmonic research, to apply the simulation model by MATLAB. SVD algorithm and sine approximation method are simulated by the model programmed with MATLAB, the simulation results demonstrate the effectiveness and feasibility of the proposed method.Combined with the actual situations of three-phase unbalanced system and lager impedance fluctuations in power network, the application of SVD algorithm for evaluating the harmonic impedance is extended from single phase power system to three-phase unbalanced power system. Start from solving the virtual neutral point voltage, the paper analysis the virtual neutral point voltage of the star circuit and triangle circuit. Based on this method, each circuit of the independent phase is analysised. Simulation results show that the idea is reasonable and feasible for the problem of three-phase unbalanced system. Finally, using Loads Non-linearity Factor to evaluate the distortion level of the various nonlinear loads which can judge and divide the responsibility of each harmonic source, simulation results show that the Loads Non-linearity Factor is universal to the loads which under the same voltage level, and can provide some theory for practical use of governing harmonic efficiently.