Research On Three Phase Grid Connected Inverter Based On Voltage Oriented Control

For global energy crisis and the increasingly serious environmental pollution problems, development and utilization of clean renewable energy is imperative. At present, many studies are carried out on the distributed generation units, including solar photovoltaic cells, wind turbines, and fuel cells. Grid-connected inverter plays an important role between the renewable energy and the grid. The performance of the grid-connected inverter determines whether we can use the renewable energy at a high efficiency. Grid-connected inverter now becomes one of the most popular major topics in the field of renewable energy.Firstly this paper introduces the research status of grid-connected inverter at home and abroad, comparing the current main control Strategy. After a brief introduction to the structure of the system topology and control requirements, this paper focuses on voltage oriented control of three phase grid-connected inverter, described its topology, working principle and mode of operation. Both low and high frequency models are set up in ABC coordinate,αβcoordinate and dq coordinate respectively.Based on the analysis of math model in the dq coordinate reference frame, the grid voltage oriented control strategy is presented, and then current decouple and the grid voltage feed-forward control are introduced. The design principle and control parameter design of the control loop is analyzed in detail.In addition, this paper introduces space vector modulation algorithm which is commonly used in three phase inverter. Then presents coordinate transformation and pre-matrix method for the calculation of the vector time which avoid non-linear operations and improve accuracy. Besides analyze the grid current low frequency harmonics distortion by simulation, and gives a number of suggestions. Then the simulation of dead time compensation is presented, the results show that the compensation strategy is feasible.Finally, a 3KVA grid connected inverter based on DSP is built and the design methods of hardware circuit and software program are presented. The experimental results based on this prototype verify that the analysis is correct.