Research On Three-Phase Grid-connected Inverter With LCL Filter

Renewable energy especially solar and wind power is developing rapidly due to the lack of fossil energy and aggravation of environment pollution. At present, grid-connected inverter plays an important role of the interface between renewable energy and the grid whose performances determine the development and application prospects. As a result, research on grid-connected inverter is extremely urgent.Firstly, this paper introduces the research status, trends and applications of grid-connected inverter, brief introduction to topological classification, filtering methods and control strategies. Comparing of different filtering methods, design constraints of LCL filter are given. Accordingly, this paper provides a simple and feasible LCL filter design method. The stability of the LCL filter is also analyzed and passive damping is used to inhibit the resonance.After establishing mathematical models of three-phase grid-connected inverter in abc coordinate,αβcoordinate and dq coordinate respectively and common space vector modulation algorithm, the grid voltage oriented control strategy is used for dq current decouple. The closed-loop control system parameters are analyzed in details. Also the simulation results show the feasibility of the control strategy.In addition, the influence on system stability of the different current feedback controls strategy, the value of damping resistor and equivalent inductance are analyzed, and the simulation results verify it.Finally, a 50kVA three-phase grid-connected engineering prototype inverter based on DSP digital control is built and the hardware and software design are introduced. The experimental results based on the prototype show the correctness the theoretical analysis and simulation results.