The Research Of Opration Control Strategy For Islanded Microgrids

With the influence of environmental problems being more and more prominent and energy crisis deepening in recent years, the distributed generation technology mainly based on renewable energy has developed very quickly. As a new network structure of power system, the micro-grid can solve the problem that distributed generation operated in parallel with the grid,it provide a solution to solve the low utilization of renewable energy, it has an important signification to implement energy-saving reduction task emission for our country. Research on micro-grid technology is the hot spot at present, the basic question is the control strategy of micro-grid, as a supplement for the main power grid, micro-grid in islanded operation has a reliable power supply and be safety for user, therefore, to solve the control problem of islanded micro-grid is very important to the micro net development.In this paper, the micro-grid control simulation and analysis is made based on the model with the photovoltaic and battery. First, established a typical model based on typical photovoltaic(PV) cells system with battery, it include three-phase inverter, photovoltaic cells, Boost converters, battery storage unit, battery charge and discharge Buck/Boost converter and analyze its related control circuit model.The simulation model of photovoltaic cells is established based on the photovoltaic and battery model and the related mathematical model of converter. and made a simulation and analysis for its maximum power point tracking. Made a simulation and analysis for charge and discharge model.The droop control based P/V control has significant advantages, its load power following characteristics is good. But when the load power fluctuates frequently, resulting in DG power frequent changes, this brings frequent charging and discharging of the battery lead, it reduces the battery life. To solve the above problem, Vg/Vdc control method is used in this paper to improve the P/V control strategy, with this strategy,when the load power changes in a small scale, the system power can be balanced by change the amplitude of the output voltage.At last, establish a simulation model for micro-grid of PV with energy storage in Matlab/Simulink. Simulation for Vg/Vdc droop control, P/Vdroop control based on Vg/Vdc droop control is verificated. Simulation results shows that power balance is achieved quickly with Vg/Vdc droop control, while the load or distributed power has a small fluctuations, it’s no need to charge and discharge the energy storage unit, thus increasing the life of the energy storage unit; P/Vdroop control based on Vg/Vdc droop control make up the combination P/V droop control problem of frequent power change, the method can achieve better load power sharing.The micro-grid simulation model provides the basis for further research, it has some practical value for the verification of micro-grid control scheme and the development of micro-grid technology.