| With the rapid development of the economy,the development and research of renewable energy has become a hot spot.Solar power generation is gradually evolving and adopted in many fields.Factors such as light and temperature in solar power have a great impact on photovoltaic cells,which would affect the stability and continuity of the power generation system.Research adopts energy storage system to solve this problem.In this paper,batteries and super capacitors are employed as energy storage system,and an independent photovoltaic DC-microgrid system with the energy storage system is designed.In this paper,the working principle and working characteristics of photovoltaic cells are analyzed.Based on the principle of Maximum Power Point Tracking(MPPT),the duty cycle perturbation method is adopted as the control algorithm of MPPT,and the photovoltaic cell power generation system based on MPPT control is designed.The MATLAB/SIMULINK simulation model has been built and verified the output power of the photovoltaic system can quickly reach the maximum value under the corresponding conditions with the change of light intensity and temperature.The independent photovoltaic DC-microgrid with solely battery or super capacitor as storage component has been studied separately.Both energy storage systems adopt bidirectional half-bridge DC converter as charging and discharging controller.The control strategy adopted by the energy storage system in this paper is double closed-loop control,that is,voltage outer loop and current inner loop.This control method is easily realized and reliable,and also can keep the bus voltage stable.Considering the problem that overcharge or overdischarge will seriously affect the battery life,this paper also focuses on the battery overcharge and overdischarge protection control,adopting the fuzzy control algorithm to make the detection of the state of charge more accurate.The simulation results prove that the battery energy storage system designed in this paper can charge and discharge stably for a long time and keep system coltage stable,and supercapacitor energy storage system can achieve fast charge and discharge of high power,and restrain the impact power.Consideringcomplementarity of batteries and super capacitors,this paper designs a hybrid energy storage system of 20 kWh,and makes research on capacity allocation.The simplex algorithm is adopted to optimize the number of batteries and supercapacitors.Then the working mode of mixed energy storage was determined and the energy management strategy is designed.Energy storage control strategy designed in this paper is applied to the hybrid energy storage system.The simulation results show that the hybrid energy storage system designed in this paper is superior to single energy storage system in both work efficiency and system stability.At the same time,the adoption of super capacitors can restrain the impact power,and can reduce the impact current of adoption battery,thereby protecting the battery. |
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