Research On Control Strategy Of Unified Power Quality Regulator

With the rapid development of economy and science,precision instruments have been widely used,so that the users' demand for power quality is getting higher and higher.At the mean while,a large number of current harmonics are injected into the power grid by nonlinear load,which leads to the power quality issues become more severe.Therefore,it has great social and realistic significance to explore effective ways to improve the power quality.UPQC(Unified Power Quality Conditioner)is able to cover the shortcomings of the traditional passive power filter and active power filter.UPQC can compensate the voltage harmonics in the power grid and current harmonics generated by nonlinear loads simultaneously.It is the control strategy which decides the compensation effect of UPQC.In this paper,the passivity-based control(PBC)based on the energy control view is adopted to optimize the compensation effect of UPQC.The voltage and current waveforms in the compensated power grid are maintained to approximate sinusoidal waves,which effectively purify the power grid and improve the power quality of the power grid.The compensation effect can also be maintained when the power grid voltage or load sudden change.In the first part of this paper,we introduce the background and the significance of the topic,then analyze the harmonic detection method and system control strategy which commonly used.In the second chapter,according to the detection error caused by the utilization of phase locked loop based on the instantaneous reactive power theory,a detection method based on the clock in phase with power grid frequency is proposed.In the third chapter,we introduce the hybrid passivity based control strategy of two level UPQC based on EL model and PCHD model respectively.Based on the two level UPQC,in the fourth chapter,TNPC three level inverters are used to construct the power circuit of the three level UPQC.Aiming at the disadvantage caused by the constant parameter in the hybrid passivity based control strategy,in the fifth chapter,a fuzzy hybrid passivity based control strategy is designed to realize the automatic adjustment of the PI controller parameters and injected damping.At the end of each chapter,related simulation results are shown.