Research On Control Strategy Of Photovoltaic DC Microgrid With Hybrid Energy Storage

The world energy landscape has undergone profound changes,and renewable energy power generation with high penetration characteristics has become a major trend in the energy revolution.However,due to the intermittency,volatility,and randomness of renewable energy,it has brought unprecedented challenges to the safe and stable operation of power grids.Therefore,vigorously developing a DC microgrid dominated by renewable energy and equipping it with corresponding energy storage units has become a feasible solution.This article conducts in-depth research on the control strategies of each unit in the photovoltaic DC microgrid with hybrid energy storage,and proposes a stable and reliable control strategy to provide strong support for the practical application of the DC microgrid.Firstly,a DC microgrid system model is established,and the operating principles and output characteristics of photovoltaic cells,batteries,and supercapacitors are analyzed respectively;In order to solve the problem of multiple peaks in the P-U curve of photovoltaic cells under non-uniform irradiance,this paper proposes a hybrid algorithm based on quantum computation,which combines the cuckoo algorithm(CS)and perturbation observation method,to solve the problem of easily falling into local optimization during maximum power point tracking(MPPT).It can effectively improve the tracking speed of MPPT and greatly reduce the fluctuation of output power.A simulation model was built on the Matlab/Simulink platform to verify the rapidity and stability of the composite algorithm based on CS-P&O for MPPT in the presence of multiple peaks in the P-U curve.Secondly,as a representative of energy based energy storage devices,battery power response control strategies for battery energy storage are discussed in depth.Aiming at the problems that fixed droop coefficients in traditional droop control strategies cannot reasonably allocate power based on the state of charge(SOC)of the battery and the DC bus voltage is offset,this paper introduces a power exponential droop control model based on SOC to achieve dynamic changes in the droop coefficient,And reasonably select the parameters of the model;At the same time,a secondary voltage compensation rule is also added to ensure that the DC bus voltage can be stable near the reference value.Three operating modes of charging,discharging,and charging and discharging are simulated and verified on the Matlab/Simulink platform.Finally,the method of power distribution in a hybrid energy storage system composed of batteries and supercapacitors was studied.As a power type energy storage unit,supercapacitors can respond to high-frequency power fluctuations instantaneously.Combining the characteristics of the capacitors,a droop control strategy based on virtual resistors and capacitors was proposed to achieve reasonable power distribution between energy storage elements with different characteristics,In addition,secondary voltage compensation is added to the virtual capacitor control circuit to achieve terminal voltage recovery of the supercapacitor.The control strategy proposed in this article is applied on the Matlab/Simulink platform to simulate and verify different operating conditions such as uneven irradiance and sudden load changes.The simulation results show that various units in the DC microgrid can coordinate and cooperate under different operating conditions,achieving power balance within the system and stabilizing the DC bus voltage.The feasibility and correctness of the proposed algorithm and control strategy are verified.