Research On Control Strategy Of AC/DC Bidirectional Power Converter In AC/DC Hybrid Microgrid

In order to improve the stability and efficiency of distributed power system and make full use of renewable energy,microgrid has been widely concerned by scholars at home and abroad.AC/DC hybrid micro-grid is not only convenient to accept and organize AC/DC power supplies and loads at the same time,but also can improve the reliability of power supply through mutual support between AC/DC subnetworks,so it has more development advantages.The AC/DC bidirectional power converter is the key link of AC/DC hybrid microgrid.In this paper,based on the current research status of AC/DC bidirectional power converter,the power balance control strategy and harmonic current governance strategy based on AC/DC bidirectional power converter are proposed.Finally,the feasibility and effectiveness of the proposed control strategy is verified through simulation and experiment.The main contents include:First,the research status of AC microgrid,DC microgrid and AC/DC hybrid microgrid is introduced,the topology and filter circuit design of AC/DC bidirectional power converter are analyzed.This paper establishes a mathematical model of AC/DC bidirectional power converter in different coordinate systems.On this basis,the double closed-loop control strategy of AC/DC bidirectional power converter is designed,and the specific design method of current inner loop and voltage outer loop is given.Finally,the model is built in Matlab/Simulink,and the feasibility of the double closed-loop control strategy is verified.Second,The AC/DC bidirectional power converter power balance control strategy and its design method is proposed.That is,AC bus voltage u_a and DC bus voltage U_dc are selected for normalization processing,Then,through active and reactive power control,the AC/DC bidirectional power converter power transmission reference values P_ref?and Q_ref are obtained.Next,the AC/DC bidirectional power converter output current reference values I_drefref and I_qref are calculated.The inner loop closed-loop decoupling control is used to obtain the PWM signal output through the dq0/abc module,and the power balance control of the AC/DC bidirectional power converter is realized.Finally,the feasibility of the control strategy is verified by Matlab/Simulink simulation model.Third,a control strategy of AC/DC bidirectional power converter is proposed,which can suppress the harmonic current of AC bus.Firstly,the definition of FBD power is given,and the harmonic current detection method based on FBD power theory is introduced in detail.On this basis,the control strategy of compensating AC bus harmonic current by controlling AC/DC bidirectional power converter is proposed,and the calculation method of i_refabc,which controls the instruction current of AC/DC bidirectional power converter,is designed.Finally,the feasibility of harmonic current compensation strategy is verified by Matlab/Simulink simulation model.Fourth,an AC/DC hybrid micro-grid experimental platform is designed and built.The main circuit design of the experimental platform includes the determination of ac and dc voltages,the design and selection of parameters of capacitors,diodes and power switches.The auxiliary circuit includes the design of voltage and current sampling circuit and conditioning circuit.The composition and function of logic module and control interface are introduced in the design of experimental software.Finally,the power balance and harmonic current control strategies of AC/DC bidirectional power converter are verified by experiments.