Research On Modeling And Control Strategy Of Hybrid AC/DC Microgrid

Microgrid is a distribution subnet which has a certain degree of control capabilities and self-regulation, including local power plant, energy storage device and local loads. Hybrid AC/DC microgrid combines the respective advantages of AC microgrid and DC microgrid. Hybrid AC/DC microgrid reduces the processes of multiple dc-ac-dc or ac-ac-ac conversions in an individual AC or DC microgrid. Therefore reducing energy loss multistage transformation; it can be used for both AC and DC load, reducing user frequency devices inside the device, reducing the manufacturing cost of the device. However, the research on the hybrid AC/DC microgrid is still in the exploratory stage, control strategies of converter under different operating modes and the mode switch e is the key technologies of the stable operation of the microgrid system.This paper mainly studies the integrated control strategy based on the master-slave configuration of hybrid AC/DC microgrid. The main work is as follows:Firstly, on the basis of analyzing bi-directional AC/DC converter structure, it establish the mathematical model of bi-directional AC/DC converter. based on it,this analysis control strategy of bidirectional AC/DC converter under different operating modes:PQ control and Vf control.it indtroduces the design method of the inner loop current controller and outer ring PQ controller,Vf controller.Then it introduces the principle and implementation steps of SVPWM.Secondly, the theoretical analysis of photovoltaic cells working principle and output characteristics is introducesd, building a simple model of photovoltaic cells. the control strategy of photovoltaic cells areMPPT mode and limited power mode under the different operating modes; the working principle and the charge and discharge characteristics of battery is describesed, establishing its model. the control strategy of battery s are constant current charge-discharge mode and voltage closed-loop mode. under the different operating modes.Finally this paper sets up the hybrid AC/DC microgrid simulation model and its control system in Matlab/Simulink, it analysis the various working conditions of hybrid AC/DC microgrid in the grid andthe island mode.changing external environment or load conditions, this paper researchs the switching between work status, verify its correctness by analyzing the simulation results.