Research On SVG For Three-phase Four-wire Power System

In low-voltage power distribution system In recent years, with non-linear electrical equipment application increasingly widespread, intensified the problem of three-phase load imbalance and a large number of reactive power consumption, which seriously affects the power system reactive power balance and power supply quality. SVG dynamic compensation performance of the flexible, not only can achieve the system reactive power tracking compensation, but also could compensate for unbalanced three-phase system, Static Var Generator has become the indispensable equipment in power systems to improve the power quality.In this paper, the study is reactive power generator that is implicated in stationary low pressure 380 V three-phase four-wire system. Firstly the working principle of the SVG and the topology and mathematical models of the main circuit are described. On the basis of theoretical analysis to find a method of reactive power detection based on ip-iq and dq0 is analyzed by two kinds of reactive current detection method, this paper finally adopted improved dq0 detection methods. In constructing a mathematical model of main circuit, on the basis of the key analysis based on SVPWM no beat control method, and combined with the characteristics of the negative sequence and zero sequence current, build the double closed loop control of SVG control strategy: direct current control of voltage loop control and SVPWM no beat control current inner loop control, so as to realize the system unbalance runtime of positive sequence reactive current, negative sequence current and zero sequence current control at the same time.On the basis of the analysis of compensation current detection and control method, this paper use Matlab software to build simulation models SVG and carried out a detailed simulation analysis, respectively in the three-phase equilibrium and disequilibrium state. The simulation results show that the SVG can well compensation reactive power and current unbalanced current when the system is asymmetrical. The simulation results also show that the methods of detection and control are feasible, when system is imbalance. All this provide a theoretical basis for the subsequent design.For simulation analysis and verification, this paper designed the hardware circuit and software program of SVG, the design of the hardware circuit including main circuit and the TMS320F2812 as main control chip voltage sampling circuit, current sampling circuit, the zero detection circuit, drive circuit design; And A/D conversion, compensation current detection and control algorithm software process.