Research On Power Quality Control Method Of AC/DC Hybrid Power Supply Microgrid

Traditional fossil energy has become increasingly tense,and distributed power generation technology has achieved rapid development in recent years.Micro-grid technology that integrates distributed generation,power electronics,and power system control technologies has received increasing attention.Among them,AC/DC hybrid microgrid technology has broad application prospects,which can improve the flexibility of grid-connected power supply,power supply efficiency and economy.Therefore,the research on power quality control method of AC/DC hybrid microgrid has considerable research value.Power Electronic Transformer(PET)is a new type of intelligent transformer that combines power electronic conversion technology with power conversion technology.Not only voltage conversion,electrical isolation and power transfer functions,but also power factor correction,output voltage regulation and harmonic suppression.The power electronic transformer itself has both DC and AC links,which facilitates the integration of new energy power generation.This paper first analyzes the topology and working principle of power electronic transformers.In order to reduce the adjustment time of the system parameters,the steady-state voltage output is realized more quickly,the overshoot of the control system is better optimized,the DC bus voltage is more stable,the system robustness is improved,and the entire AC-DC microgrid is improved.Power Quality.The input stage adopts an improved sliding mode variable structure double closed-loop control mode to improve the current inner loop,and adopts a fuzzy control strategy to adjust the approach rate.For the isolation stage,a single-phaseshifted DC-DC converter is used,and the output stage adopts a voltage closed loop and a current closed loop control strategy.Then establish the photovoltaic grid-connected system on the DC bus of the power electronic transformer.Combined with the working principle of the photovoltaic system,the supercapacitor is introduced as the energy storage system to provide a certain degree of support for the good power quality of the whole system,and improve the stability and anti-interference of the photovoltaic system.Finally,based on the Matlab/simulink simulation platform,a power electronic transformer and an AC/DC microgrid including a photovoltaic power generation system,a micro gas turbine and an energy storage system were built.Firstly,the simulation analysis is carried out on all aspects of the power electronic transformer,including the input stage,the isolation stage and the output stage.Then the whole AC/DC microgrid system is simulated.Through the analysis of the output voltage frequency and harmonics,it shows that the improved PET based on fuzzy sliding mode variable structure control can improve the voltage drop,three-phase unbalance and harmonics of the grid.The power quality of the AC bus and the DC bus under a large content ensures the stability of the output voltage and reduces the adverse effects on the electrical equipment.