Research On Integrated Simulation And Coordinated Control Strategy Of PV-Storage Microgrid System

Solar energy is a typical clean and renewable energy source.It has the advantages of abundant,clean and pollution-free,etc,has been widely developed and applied in recent years.However,solar power generation has the problems of output power fluctuation and mismatch to the time requirements of the loads.Generally,the photovoltaic(PV)systems equipped with energy storage devices to form PV-Storage microgrid to solve this problems.The energy storage devices smooth the fluctuation of the output power of PV systems and regulate the relationship of the PV power generation and loads.The operation state of PV-Storage microgrid is changeable and its inertia is small,so it is very important to study a flexible and reliable control strategy of PV-Storage microgrid.The simulation model is one of the most direct and effective methods to verify the correctness of control strategies.Therefore,this paper focuses on the simulation models and control strategies of the PV-Storage micro grid.The input or output power of Power conversion system(PCS)for energy storage mutation when the load is suddenly changed,which may deteriorate the reliability of the islanded PV-Storage microgrid.In this paper,a coordinated control strategy for PV inverter and PCS based on PV-Storage microgrid is proposed.The differentials of output active power of PCS is calculated and used to compensate the d axis current of'PV inverter.In this way,the PV system is controlled to respond the change of load with PCS simultaneously,thus the transient power fluctuation of PCS is suppressed.The simulation model of PV-Storage microgrid is built in MATLAB/Simulink,and a parallel experimental platform of PV-Storage inverters is built in the laboratory.The effectiveness of the proposed coordinated control strategy is verified by the comparison simulation and experimental results under different working conditions.In order to verify the stability of PV-Storage microgrid using the coordinated control strategy of PV inverter and PCS,a complete small-signal model of microgrid including PCS,PV inverter,coordination control system,network and loads is established in this paper.The rootlocus method is used to analyze the stability of the microgrid and the time domain simulation in MATLAB/Simulink is used to verify the results of the stability analysis.When the microgrid has non-linear loads,the harmonic current generated by it will distort the common point voltage and the grid-connected current,which will seriously affect the power quality.A compensation of the common point harmonics voltage using quasi-proportional multi-resonant controllers is added to the voltage loop control of the voltage source inverter in this paper,making the common point voltage meets the power quality requirements.When the microgrid is connected to the grid,it can also make the grid-connected current meets the power quality requirements.The effectiveness of the harmonic compensation strategy is verified by simulation results of microgrid in off-grid and in-grid operation.