Power Sharing Control And Synchronous Characteristics Research Of Microgrid Inverter

As an effective way by which distributed generators access distribution network system microgrid becomes a focus of research. Most distributed generators in microgrid connect to the grid by inverters, so the research of inverters’control strategies is very important. Power sharing control of parallel multi-inverters, output power decoupling control of an inverter and the synchronous characteristics of inverters with different power control strategies are studied in this paper.In the second chapter, the overall block diagram of an inverter and its control is presented. The controller of the inverter can be divided into two parts:the inner voltage tracker and the outer power controller. The mathematical model of inverter and various control strategies of voltage tracker with different coordinate systems, different control structures, different controller types are presented. In the end, the flexible design of equivalent output impedance of the inverter under the closed-loop control is analyzed.Chapters 3-5 study the specific control methods of the power controller in the realization of different control objectives. In the third chapter, the power controller is proposed to realize accurate power sharing and circulating-current suppression. After analyzing the limitation of traditional droop control, an improved droop control method is put forward. In order to realize the independent control of the active and reactive power of the inverter without the influence of line impedance and achieve better control effect, the relative gain method is used to analyze the coupling characteristics of output active and reactive power and a new decoupling control method is proposed in the fourth chapter. In the fifth chapter, the paper studies the synchronous characteristics of inverters with different active power control methods and compares the synchronous characteristics of droop control and virtual synchronous generator control. At the end of each chapter, corresponding simulation examples are designed to verify the correctness and effectiveness of the proposed control strategies by PSCAD/EMTDC simulation software.