Adaptive Droop Control Of DC Microgrid With Photovoltaic And Storage System

The existence of two major crises of environmental pollution and energy shortage has promoted the development of renewable and clean distributed energy resource?DER?.Due to the volatility of new energy power generation,multiple DERs are usually used to contribute a microgrid.The microgrid is mainly composed of AC,DC and AC/DC hybrids.The DC microgrid doesn't have the problems of reactive power loss and phase synchronization,which has received widespread attention.Focusing on the topic of effective management and control of DC micro-sources,the following research contents are mainly carried out in this paper:Firstly,the concept and research significance of DC microgrid are introduced,and the principle,advantages and disadvantages of the control strategy are analyzed.Then,the DC microgrid composed of micro-source and load such as photovoltaic and energy storage is taken as the research object.The mathematical model of the photovoltaic cell is deduced in detail and the model of the battery is equivalent.The control methods of each micro-source and the topology of the interface converter between the micro-source and the DC bus are given.Therefore,the simulation model is established in the Matlab/Simulink environment according to the derived mathematical formula,and the simulation strategy is combined with the control strategy.Next,in order to ensure the stable operation between parallel energy storage units,an improved droop control strategy based on energy storage battery Soc is proposed.First of all,the principle of traditional droop control and its existing problems are introduced.Later on,the principle and control flow of improved adaptive droop control are introduced,and the control performance of the system under the influence of four different factors is compared and simulated.The results show that the proposed improved droop control is effective for bus voltage stability and the reasonable distribution of micro-source power according to Soc.In addition,the system has the strong resistance to load changes.Finally,the model of the DC microgrid system used in the article is established,which realizes the equalization control of photovoltaic and battery,and maintains the balance of DC bus voltage and battery SOC.The four working modes of the DC microgrid are introduced,and the operation control strategies of the microsources in each mode are analyzed.And,the simulation analysis is carried out with two kinds of power imbalances in the microgrid(i.e.,P_pvindividual changes or P_Lindividual changes).The final results show that under the various modes of DC microgrid operation,the control strategy adopted in this paper can ensure that the system energy in the DC microgrid is in equilibrium,and thus the bus voltage in the microgrid is stable.