Voltage Control Of Dc Microgrid Bus Based On Improved Droop Method

As global energy and environmental issues become increasingly prominent,the penetration of renewable clean energy power generation continues to increase.However,renewable energy power generation has strong volatility and randomness,and the load in the DC microgrid system formed by it also has a strong uncertainty,making the source load power in the system prone to unbalance and lead to bus voltage fluctuations.Seriously affect the safe and stable operation of DC microgrid.Therefore,it is of great significance to study the DC microgrid bus voltage control technology and improve the DC microgrid bus voltage stability.In order to improve the stability of the bus voltage of the DC microgrid system,this paper builds a DC microgrid system containing photovoltaic power generation,and studies the DC microgrid bus voltage stabilization method under the coordinated control of each distributed unit.The main contents are as follows:(1)On the basis of understanding the structure of each unit of the DC microgrid system,this paper first analyzes the basic structure of the photovoltaic unit and hybrid energy storage unit and builds the corresponding mathematical model,and performs the output characteristics of the photovoltaic cell in different environments Simulation analysis;secondly,the principle and working mode of DC voltage converters such as photovoltaic Boost and energy storage bidirectional DC/DC are analyzed,and the DC converter control strategy suitable for different working conditions of distributed units is designed;finally,the design of the AC grid part and Rectifier/inverter control method of grid-connected converter.(2)In a DC microgrid system,usually multiple distributed power supplies of the same type work in constant voltage mode at the same time.Due to the difference in output voltage and line impedance,the output power is often uneven,and the droop control is An important solution to achieve reasonable power distribution among distributed power sources.This paper analyzes the disadvantages of power distribution and bus voltage drop in parallel distributed power supplies under traditional droop control,studies the effects of different improved droop control methods on power distribution accuracy and voltage drop,and proposes an improved droop method based on variable virtual resistance and Compensate the bus voltage accordingly.The simulation results show that the improved droop method based on variable virtual resistance can improve the power sharing accuracy of each parallel distributed unit under a given situation and effectively suppress the bus voltage drop(3)In the DC microgrid system,each distributed unit is directly connected in parallel in a decentralized manner to the DC bus.The bus voltage is the only effective and intuitive information that reflects the change in source load power in the DC microgrid system.The voltage is simply stratified within the upper and lower range of the rated bus voltage.According to the bus voltage stratification,a coordinated control strategy for distributed units of DC microgrid system is proposed.Under this control strategy,each distributed unit under each level adopts different operation modes,and its corresponding DC converter automatically switches the control strategy according to the set conditions,so as to realize the stability of the DC micro-grid bus voltage under the coordinated operation of each distributed unit.Finally,the control strategy is applied to the built DC microgrid system under different working conditions for simulation experiments.The simulation results show that the proposed control method can coordinate the power exchange of each unit in the microgrid at different bus voltage levels,achieve bus voltage stability,and ensure the safe and stable operation of the DC microgrid.