Study On The Control Of Grid Connected Photovoltaic Inverter Based On Virtual Synchronous Generator

In recent years, with the rapid development of global economy and population expanding, energy shortage and environmental pollution become global problems Development and utilization of new energy become imperative. Photovoltaic power generation as the most promising new green energy power generation mode has been extended and supported in recent years.Because of Solar energy’s uneven geographical distribution, the photovoltaic power generation need access to the grid as a distributed power supply. With the high penetration rate of distributed power supply, the capacity of the conventional synchronous generator gradually reduced in the proportion, the spinning reserve capacity of power system and the moment of inertia relative reduced. Due to the primary energy has the uncontrollable and intermittent characteristic, and distributed power generally connecting to the grid with inverter.It has no inherent which the conventional power system has while using this mode parallel in grid.That makes the stability problem of power grid becoming more and more serious. Distributed power supply and load compose microgrid, which has the characteristic of distributed power access and the nearest output. Microgrid gives full play to the advantages of the new energy power generation. In this paper, using the photovoltaic inverter as the research object, the inverter control strategy in microgrid and application are studied.First of all, the structure of grid connected photovoltaic is introduced by this paper briefly, mainly about BOOST converter, the DC/AC inverter and the energy storage unit. Then introduces the control strategy of each part of the system.There are mainly Maximum PowerPoint Tracking control and space vector.Secondly, this paper briefly introduces the general development of micro grid technology, summarizes the micro grid control structure and grid connected strategy. Comparing the property of the synchronous generator with photovoltaic inverter, the result shows photovoltaic inverter with small capacity, small inertia and low capacity of current-carrying.Thirdly, the control principle of a micro grid inverter interface----virtual synchronous generator is introduced by this paper, then this paper describes the basic principle of VSG and its realization method. According to the stator electrical model and rotor mechanical model of synchronous generator, and the technical requirements of grid connected and island operation mode, this paper designs a power frequency controller and excitation controllert.Finally, build simulation model in the MATLAB/SIMULINK environment, virtual synchronous generator’s grid connected characteristics are presented. Then gives a detailed analysis of the simulation results. According to the simulation results, the hardware circuit and software are designed. The simulation and experimental results show that, VSG can meet the requirements both of grid operation and isolated operation mode, and it also can meet requirements of the stability of microgrid to large power grid.