Research On Micro-grid Control Strategy Based On Virtual Synchronous Generator

Micro-grid is an important supplement of large power grid. But the conventional control strategy cannot be satisfied of no difference control of micro-grid voltage and frequency, especially when the load fluctuation will seriously affect the safe and stable operation of micro grid. When generation power of the micro power is greater than the load power, the micro grid energy contra-flow will also cause adverse effect on large power grid. In this paper, the micro grid based on virtual synchronous generator control is the object of study. At the same time stable micro-grid voltage and frequency, and achieve micro grid of zero contra-flow.Firstly, the paper introduces the concept and structure of micro-grid, and the domestic and foreign development status of micro-grid. It also analyzes the methods of micro-grid connected and isolated control. Then the paper in-depth analyzes the coordinated control and different strategies for interface. Secondly, considering micro power in micro-grid lacks the physical inertia, that no moment of inertia of the synchronous generator. In this paper, the virtual synchronous generator control is used in the micro-grid. Through in-depth analysis of the mechanical properties of the rotor and electrical characteristics of the stator of the synchronous generator, the control strategy of synchronous generator is applied to control the micro-power, which makes micro-power to overcome the above weaknesses, and to maintain a stable frequency and voltage of the system under the adjustment of power frequency controller and excitation controller. In order to prevent excess energy of micro-grid reflux into the large grid, which results a large harmonics increase and harm to the load of electrical safety, the paper designs that use storage battery as energy storage device of micro-grid. When the micro-power generation is greater than the micro-grid load power, by the power frequency controller of zero contra-flow control the battery charges and discharges in accordance with directive, The excess energy is stored which meets the requirements of micro-grid zero contra-flow. Thirdly, the paper theoretically analyzes and calculates the parameter of LC filter and connection inductance in main circuit of micro-grid, and then determines the range of parameters in the practical application. Finally, the paper builds a simulation model using MATLAB/Simulink software. The simulation results show that the methods satisfy the performance requirements of the micro-grid. The control strategy of virtual synchronous generator is applied to the micro-grid, not only can solve no difference control of the voltage and frequency, and can realize the zero contra-flow of micro-grid. From the performance point of view, this method has a good application prospect.