Balanced Control Of Multi Energy Storage DC Microgrid Based On SOC

With the rapid development of today’s era,energy as a necessary condition for the development of production,more and more attention to people,and the development and utilization of renewable energy is the most important part of energy reform.The development of microgrid technology has brought a stage leap for the new energy generation field.In the early stage of the development of microgrid technology,the research of AC microgrid is the main one,and in recent years,DC microgrid has been widely used because of its simple structure and small loss.The energy storage system can be used to reduce the influence of distributed power fluctuation and uncertainty on the stable operation of micro grid,and ensure the safety and stability of the system operation.However,there are many operational problems in the energy storage system with multiple energy storage units,such as different state of charge,different rated capacity and outlet power error.These factors will affect the reasonable output of the energy storage unit,cause the output of the energy storage unit to exceed its rated value,reduce its operation life,part of the energy storage unit out of operation ahead of time,increase the operation pressure of other energy storage units,and affect the system operation.This paper makes the following research:Firstly,taking the photovoltaic storage DC microgrid with multiple energy storage units as the research object,the structure principle is analyzed,the mathematical model and power generation characteristics of photovoltaic power generation and energy storage unit are derived,and the control mode of photovoltaic and energy storage unit export power electronic converter is studied,and the appropriate control mode is selected for in-depth study.Secondly,aiming at the unreasonable distribution of energy storage power in multi energy storage DC microgrid with parallel structure,a balance control strategy based on the state of charge of energy storage unit is proposed.Through the information transmission channel,the central control unit collects the real-time state of charge information of each energy storage unit,introduces the droop control link after the information processing,dynamically controls the output of energy storage units,and realizes the balance of state of charge among energy storage units.At the same time,the variation coefficient factor is introduced to optimize the equilibrium process,which is to restrain the equilibrium speed when the control starts to equalize too fast,and to increase the equilibrium rate when the equilibrium is too slow in the later period of control,so that the equilibrium process is not easy to reach the bottleneck.Considering the influence of different rated capacity of energy storage on output,the capacity weight factor is introduced to ensure the reasonable output of energy storage unit.Finally,the advantages of multi energy storage system with series structure in DC microgrid are introduced,and an adaptive anti droop control is proposed for the energy storage unit with series structure to distribute power reasonably,and the anti droop control link is optimized and accelerated with exponential factor and acceleration factor.The anti droop control has no effect on the total output voltage of the outlet,but for the voltage deviation caused by the droop control in the series structure,this paper proposes a voltage control method to compensate the voltage deviation and make the output voltage of the energy storage unit closer to the reference voltage of the DC bus.In view of the outlet power error caused by different line impedance,zero difference regulation is added in the control to realize the reasonable distribution of power.