Research On Coordinated Operation Control Of AC/DC Hybrid Microgrid With Multiple Distributed Micro Sources

In order to satisfy the increasing energy demand in the new era and achieve the ambitious goal of carbon neutral,it is imperative to vigorously develop the renewable energy power generation technology.Microgrid technology has become a hot research topic,owing to being an effective way to utilize the local distributed renewable energy.The AC/DC hybrid microgrid integrates the advantages of both AC microgrid and DC microgrid,and meets the requirement of various types of distributed generators and loads,which is an important part of smart grid in the future and has broad application prospect and practical value.In this dissertation,the AC/DC hybrid microgrid with peer-to-peer control architecture is researched,around the AC/DC hybrid microgrid modeling and coordinated operation control strategy.The coordinated control strategies of the microgrid system under different operation modes are proposed,and the operation modes can switch between each other with smooth transition.The typical topological structure of AC/DC hybrid microgrid,the basic control strategies for DC micro source interface converter and AC micro source interface converter,and the system control strategies of microgrid are anlyzed and studied.Based on the study of the basic working principle and control strategy of common distributed generators in detail,the simulation models of these are established,including photovoltagic power generation system,wind power generation system,micro gas turbine,fuel cell,battery and super capacitor.Based on the anlysis of the power distribution principle for parallel operation of DC micro sources and AC micro sources with traditional droop control strategies,the improved droop control strategies are proposed to improve the accuracy of AC subgrid reactive power sharing and DC subgrid active power sharing.By dynamically adjusting the virtual resistance in the traditional droop equation from the perspective of frequency domain,the power integral droop control of supercapacitor is proposed,which realizes the reasonable power distribution about the hybrid energy storage system.With the virtual synchronous generator concept,the virtual capacitance equation on the DC side and the virtual inertia equation on the AC side are established,and then the virtual inertia control strategy of interlinking converter is proposed futher with the power balance relationship between subgrids.Based on the above research,a simulation model of the AC/DC hybrid microgrid is established.As for the islanding operation mode,a hierarchical control strategy is proposed,which divides the islanding operation state into independent operation mode and mutual assistance operation mode,by means of the secondary compensation link and the principle of hysteresis control.In the independent operation mode,the AC/DC hybrid microgrid with light loads can realize none-error operation of DC voltage and AC frequency.In the mutual assistance operation mode,the subgrids can achieve reasonable power change,and the interlinking converter can not switch frequently between start and stop.After the operation mode switching process between islanding mode and grid-connected is analyzed,the presynchronization control strategy is proposed,which can realize the smooth grid connection and off-grid in the AC side or DC side.