Research On Control Strategy Of Photovoltaic/Hybrid Energy Storage Micro-grid

With the large consumption of disposable energy and the impact on the environment,finding clean energy to instead of the traditional fossil energy is very urgent,and the distributed generation as the use of clean energy,one of the most effective way,has been widely concerned.For the distributed power generation problems,many scholars put forward the concept of micro-grid.As an important part of the energy conversion in the micro-grid,the control strategy of inverter is of great significance for micro-grid's security and stable operation.In this paper,the micro-grid containing photovoltaic and hybrid energy storage is studied.And two kinds of distributed power sources are analyzed.Firstly,the working principle of photovoltaic cell is briefly introduced,and the corresponding mathematical model is established,and the output characteristic analysis is carried out.The maximum power point tracking of PV power generation unit is determined by the combination of constant voltage method and variable step perturbation observation method,and the effectiveness of this method is verified through simulation.Afterwards according to the equivalent circuit of battery and supercapacitor,the corresponding mathematical model is established.The second-order low-pass filter power fractional frequency control strategy is adopted to compensate the power fluctuation in the micro-grid.The simulation results show the effectiveness of the strategy.Then,the control strategy of micro-grid is studied.The master-slave control and peer-to-peer control strategy is analyzed,and both advantages and disadvantages are explained.According to the difficulties of traditional master-slave control and peer-to-peer control,such as automatic power distribution problem,switching controller problem and so on.In this paper an improved master-slave control strategy is proposed which based on traditional constant voltage/constant frequency control strategy.It isn't need to change the inverter's control strategy when the micro-grid's mode is switching.And the strategy can realize the automatic adjustment and distribution of power.And then the mathematical model control of the improved type is established.Finally,based on the Matlab/Simulink platform,the simulation results show that the photovoltaic / hybrid energy storage micro-grid with the control strategy has the stability in steady state or transient switching state by setting different simulation conditions.