Research And Design Of The Three Phase Inverter Without Dead-zone

With the increasing depletion of fossil fuels and the growing of environmental pollution, the development and use of wind, solar and any other new energy sources have become a top priority. As the connection to the grid and distributed generation systems represented by new energy, grid-connected inverter has a wide range of applications. No dead-zone inverter has no straight leg problem, which will avoid the low-order harmonics introduced by dead-bridge topology and improve power quality. The three-phase dual-buck grid-connected inverter has the advantages of simple structure and optimized design individually of the diodes. The power quality and efficiency can be improved by rational design of filter parameters and improvement of control strategy, which is worth to study.Firstly, the methods to eliminate dead-time effects of three-phase bridge inverter are introduced. Dead-effect compensation can be made by the improvement of control strategies from the control point of view. In another way, the straight leg phenomenon of traditional bridge topology can be eliminated fundamentally by the use of no dead-zone topology.Taking three-phase dual-buck inverter and Z-source inverter for example, the basic mathmatic models and working principle of three-phase dual-buck inverter are presented, the principles of SVPWM modulation and the decoupling control strategy are researched. This paper also analyzes the principle of Z-source inverter and studies the principle of anti-through network design of the two kinds of inverters.Based on analysis of the dead-zone of the bridge circuit, the harmonic calculation models of three-phase bridge inverter with dead-zone and three-phase dual-buck inverter without dead-zone are established. The LCL filter is analyzed, the open-loop and closed-loop correction calculation models of THD are established. With more magnetic components, the volume and weight of three-phase dual-buck inverter is a problem and coupled inductors are used there to solve it. The optimized design of LCL filter parameters is done.Finally, 18 k VA three-phase bridge inverter and three-phase dual-buck inverter based on DSP digital control are built, the hardware and software design are introduced. The experimental results based on the prototype show the correctness of the theoretical analysis and simulation results.