Distributed Collaborative Control Of DC Microgrid Based On Model Predictive Control

As one of the main ways to achieve the goal of "double carbon",renewable energy power generation technology based on wind power and photovoltaic has received extensive attention.Compared with the AC microgrid whose power supply reliability is greatly affected by the grid connection of distributed generation system,DC microgrid plays a more and more important role in today’s growing demand for DC load because of its low loss.Maintaining bus voltage stability and reasonably distributing load power are the two core control objectives of DC microgrid.In order to achieve these two objectives,many methods are proposed to control each unit of DC microgrid cooperatively.Based on the model predictive control algorithm,this paper studies the distributed cooperative control strategy of multi energy storage DC microgrid.The main work and achievements of this paper are as follows:(1)Firstly,the system composition of DC microgrid is studied,and the mathematical model,working principle and control method of each component unit are analyzed.A multi wind storage DC microgrid simulation model including wind power generation unit,energy storage unit,grid connected inverter unit and AC load unit is built in Matlab / Simulink software.(2)A secondary voltage control strategy based on model predictive control is proposed.Firstly,the widely used voltage secondary control strategy based on distributed consistency algorithm is introduced,and its working principle and limitations are explained in detail.The MPC algorithm is used to optimize the secondary voltage control,which solves the problems of weak instantaneous characteristics of the voltage control strategy under the consistency algorithm,high communication requirements,and the system stability is easily affected when the working conditions of the microgrid system change.(3)A power coordinated control strategy based on model predictive control is proposed.Based on the traditional power exponent droop control,the power exponent is optimized by using the droop coefficient prediction model and objective function.The output power of each battery is distributed according to the state of charge by minimizing the adjacent deviation of intermediate variables,which effectively avoids the overshoot and over discharge of the battery.Compared with the traditional power exponential droop control,this method has faster power response speed and SOC equalization speed.(4)A DC microgrid model with three air storage systems is built in Matlab /Simulink software.The control strategies of(2)and(3)are simulated and analyzed.The results verify the effectiveness of the above methods.