Research On Coordination Control Of A Hybrid AC/DC Microgrid

A hybrid AC/DC microgrid can take advantage of both ac microgrid and dc microgrid, meet the needs of different load, reduce the power conversion device, enhance the efficiency of energy conversion, and improve the economy and reliability of the power supply. The control problem of a hybrid AC/DC microgrid is a research hot topic, this thesis focus on the coordination control of a hybrid AC/DC microgrid, the main contents of this thesis include:Firstly, the working principles and operating characteristics of four kinds of common distributed generators include photovoltaic, wind turbine, micro turbine, battery energy system are studied. And on this basis, the transient simulation models of four kinds of distributed generators are built.Secondly, the simulation model of DC/AC converter and DC/DC converter are built respectively. On this basis, the control methods of these inverter are studied, namely, the constant power control, the constant voltage control, the droop control of DC/DC converter, and the constant power control, the constant voltage/frequency control, the droop control of DC/AC converter; The simulation model of the bidirectional AC/DC converter is built, the operation mode and control method of the bidirectional AC/DC converter in both grid-connected mode and island mode are discussed.Thridly, a finite-time consensus-based distributed cooperative control is proposed for DC microgrids. On the basis of the droop control, a distributed secondary is introduced, which includes a current correct control and a voltage regulate control. Each DG only interchange output current information with neighbors. Proportional power sharing is achieved, through a finite-time consensus protocols. Utilizing the average current, the voltage is regulated. The proposed control scheme is implemented in fully distributed manner, can meet the requirements of the plug and play, and the finite time consensus algorithm has a better convergence performance. To confirm the effectiveness of the scheme, a detailed model of dc microgrid was built in PSCAD/EMTDC. Simulation results indicate that the proposed scheme can effectively achieve the control objectives of voltage regulation and proportional power sharing in dc microgrids.Finally, a coordination control scheme is proposed for the bidirectional AC/DC converter, which connect the dc subgrid with the ac subgrid, to share the power between the dc subgrid and the ac subgrid. The distributed coordination secondry control of the hybrid AC/DC microgrid is studied, a finite-time consensus-based distributed coordination control is proposed for the hybrid AC/DC microgrid to restore the frequency/voltage to rated value. A detailed model of a hybrid AC/DC microgrid was built in PSCAD/EMTDC, the effectiveness of the proposed scheme was demonstrated by the simulation results.