Research On The Power Control Of Interlinking Converter In AC/DC Hybrid Microgrid

With the development of economy,the national electricity demand increased rapidly,the power generation system which use fossil fuel had bring serious energy crisis and environmental problems.In order to achieve sustainable development,protect human survival environment,such as wind,solar,and energy which environmental pollution-free and inexhaustible clean has got great development and utilization now,led to the rise of distributed power supply and the distributed power generation technology development.Europe,United States,Japan and other developed countries take the lead in microgrid,which use clean energy and can provide personalized power supply,and now distributed generation and microgrid technology began to get the close attention of scholars both at our country and abroad.This article is selected based on the national 863 project “key technology of AC/DC hybrid power distribution network”,has carried out several works in the following.This paper analyzes the power balance relationship in the grid-connected mode and off-grid mode in AC/DC hybrid microgrid,introduced the control method of micro source,the control strategy of microgrid and working principle of the bidirectional DC/DC converter.In order to ensure the power balance between microgrid,mathematical relationship has established in DC voltage,AC frequency and exchange power between DC microgrid and AC microgrid,the droop control of unitized AC/DC hybrid microgrid is proposed in the paper;Segment the AC,DC droop characteristic curves,achieve partition control to avoid frequency action of the converters and the direction of exchange power switch back and forth,improve the stability of the system operation and the power quality.The simulation model of AC/DC hybrid microgrid built in PSCAD/EMTDC shows that,in both the grid-connected mode and the off-grid mode,the interlinking converter can quickly and accurately regulate the exchange power between DC microgrid and AC microgrid,which guarantees the stable operation of AC/DC hybrid microgrid,hence verifies the feasibility of the control strategy.With the capacity and the scale of the hybrid AC/DC microgrid continuous expand,the conditions of multi-interlinking converter operate in parallel become possible.In this paper,a hierarchical power control system is designed for hybrid AC/DC microgrid with multi-interlinking converters.The micro source interface converter is the basic unit of hybrid microgrid,with fast response and low control level,achieve real-time tracking of load;The power exchange between AC and DC microgrid is used as the intermediate control layer to realize power balance between microgrid;As the top-level control,the response of the power coordination layer is slow,but the control level is high,achieve optimal operation of the system.In order to achieve the optimal power allocation among the interlinking converters,this paper designs an optimal control algorithm by maximizing the integra ted transmission efficiency of multiple interlinking converters.The simulation results on the PSCAD/EMTDC show that the power exchanging layer can adjust the power exchange value between the AC microgrid and the DC microgrid quickly and accurately under both grid-connected operation mode and islanding operation mode,and the power coordination layer can achieve the optimal allocation of the exchanging power,which verifies the feasibility of the hierarchical control strategy.