Improved Dynamic Control Method For Energy Storage Units In PV Dominated Microgrids

With the development of science and technology,more and more new energy equipment uses DC power as their power source.Because the DC microgrid can directly provide a stable DC voltage,compared to the AC microgrid,voltage conversion is not required and can be directly utilized.Moreover,there is no need to consider the reactive power,frequency and phase problems in the AC microgrid,and it has higher stability.Therefore,DC microgrid has gradually become one of the research hotspots in the field of new energy.In the PV dominated DC microgrid studied in this paper,due to the intermittent and unstable problems of photovoltaic power generation units,it is usually used in combination with energy storage in practical applications.In many energy storage methods,the battery is usually selected as its energy storage device.Since different battery energy storage units have different parameters when the system is running.The conventional control method is simple and easy to implement.However,it is also prone to problems such as overcharging and overdischarging of the battery,insufficient control accuracy,and voltage drop,which seriously affect the stability of the system.Aiming at the problems in the energy storage control technology in the PV dominated DC microgrid.In this paper,a load power allocation weighting calculation method based on three parameters of the state of charge,capacity and maximum input(output)power of the battery is proposed to obtain the current correction coefficient.And the weighted distribution method of the proposed load power is realized by introducing an improved control method with the reference current correction coefficient.Since the DC microgrid has no reactive power flow,system operating frequency and voltage phase,the DC voltage becomes the only indicator reflecting the power balance of the DC microgrid system.In the control system of the DC microgrid,the fluctuation of the DC bus voltage is mainly considered.A sudden change in load in a DC microgrid often occurs.Considering the sudden change of the load,the bus voltage will fluctuate,and the amplitude of the fluctuation will affect the stable operation of the system.Therefore,in the control system of the energy storage unit of this paper,the secondary control link of voltage is added to realize the dynamic adjustment of DC bus voltage fluctuation.The stability of the system is further enhanced.Finally,the simulation results based on MATLAB/Simulink verify the effectiveness and stability of the proposed control strategy.