Parameter Design And Research On Optimize Control Strategy In Power Distribution Systems Based On Dissymmetrical Loads

With the development and popularization of Power Electric Technology and Automation Technology in the distribution system.There is incessant new breakthrough in the distribution system research, the three-phase load unbalanced phenomenon of the public distribution transformer was especially serious. It's a contradiction to use various types of loads which influence the power quantity but demand more for power quantity. So this paper invites a new compensator for balancing towards unbalanced load, also capability for harmonic elimination and reactive power compensation.The traditional three-phase three-leg inverters are used widely with three phase balanced loads system, such as APF, STATCOM; three phase voltage outputs can be very symmetrical. But, while the three phase loads are unbalanced or nonlinear, three phase voltage outputs can not be symmetrical. In this paper, the proposed topology of the compensator for balancing be used of three independently phase inverters, can supply a midpoint to the three unbalanced loads and independent compensation. It can control the zero voltages and currents. So this compensator must be used in the three-phase four-line system, outputs three phase symmetrical voltages, can make three loads to attain the balance mutually.A new method is used in this paper , It's symmetry method of the wreath form vector. In unbalanced or nonlinear system , at first, the proposed topology of three independently phase inverters are analyzed, using symmetrical components with two PI, it is verified witch can make the three unbalanced loads to attain the balance. It has high DC voltage utilization ,result in a low distortion of system. The algorithm of the symmetry method of the wreath form vector with double PI will be depict in detail. Moreover, the main electric circuit will inevitably be connect to a great deal of reactor and capcitor, witch will bring about very bad result for electric circuit, so must consider the homologous assistance electric circuit well and the parameter design of the component. At the same time, based on comparison of the inverter control strategies witch were widely used, the mathematic model of the proposed topology of three independently phase inverters is established in two different coordinates.The positive sequence, negative sequence and zero sequence components are controlled indepedently. The control strategy accomplishes the three independently phase inverters. Using MATLAB software, the simulation of the system control strategy validates consistely with theory analysis and the method is feasible.