Research On The Control Of Interlinking Power Converter In Hybrid AC-DC Microgrids

A distributed control scheme for reliable autonomous operation of a hybrid microgrid including ac/dc/ds is presented by means of power sharing in individual microgrid,power exchange between ac and dc microgrids,and power management among three networks.In the energy exchange process of the above three systems,large variation of active power exchange between AC and DC microgrids will generate a large disturbance in the port voltage,and the nonlinear and a certain amount of asymmetric load in the AC microgrid will give dq component of the AC side of the interlinking power converter in rotating coordinates and DC side voltage Two harmonic oscillation.In order to effectively suppress the above disturbance,feedforward control involtage loop based on an extended state observer(ESO)is developed in this paper to suppress the disturbance.In this paper,the structure and control method of AC/DC hybrid microgrid are analyzed in the following aspects,and we further analyzes the structure model and the improved control method of the interlinking power converter.(1)The system structure and common control strategy of AC/DC hybrid microgrid are briefly summarized.The topology structure and control strategy of the interlinking power converter are mainly studied,the topology structure of interconnected power converter is constructed on the basis of this paper.The average mathematical model of the space state and the small signal model in the vicinity of the steady state point are established.(2)In order to realize the power balance sharing in hybrid AC/DC microgrids,parallel(V-P)droop control and(P-f,Q-V)droop control for multiple DC sources and AC sources is implemented respectively.On the basis of this,the power control is put forward,which is based on the unitization of voltage of DC voltage and frequency of AC microgrid and realizes the energy flow between AC micro grid and DC micro grid by controlling interlinking power converter.In the case of hybrid microgrid with heavy/light loads,the distributed energy storage unit is started in the middle of interlinking power converter,which is based on the SOC droop control in order to maintain the stability of hybrid microgrids.(3)Based on the three power sharing methods described aboved,nevertheless,consistent operation of GPS and SPS under all operation conditions is ont economic,and frequent charge/discharge of distributed stores may leads to obverous degradation of battery life.Under the proposed scheme,the tolerance band of normalized f and Vdc is divided into three region by threshold for scheduling and prioritizing the activation sequences of different operation models.(4)In order to suppress the unbalanced harmonic current of the interconnected power converter and the disturbance caused the large power flow on the bus voltage,the extended state observer(ESO)is designed which observes the disturbance current.Through the feedforward control of voltage link,the design of control compensation circuit is designed to eliminate the disturbance current.(5)Design the simulation parameters of controller system,and build the simulation system of hybrid AC/DC microgrids in Matlab/Simulink simulation environment.The three different operation modes and the transient process mode switching are simulated.In addition,a feedforward control model based on(ESO)extended state observer is developed.The simulation results show that the method is effective and feasible.