Research On Three-phase Dual-buck Inverter And Its Magnetic Integration Technology

With the shortage of fossil fuels and the increasment of serious environmental pollution,distributed power generation systems, especially solar and wind power, are playing an important rolein the society. Grid-connected inverter is more critical in the interface between renewable energy andthe grid. Compared to traditional half-bridge inverter, three-phase dual-buck inverter with higherefficiency has the advantage of no straight leg problem. However, more magnetic components requirethe use of integrated magnetic technology to reduce the volume and weight of magnetic components.Therefore three-phase dual-buck inverter and its integrated magnetics technology become one of thehotspots.Firstly, the current research status and trends of three-phase inverter are introduced, including abrief introduction of topology selections, output filter designing and control strategy. Then a furtheranalysis of the research of dual-buck is conducted. After chosen the three-phase dual-buck inverterwith LCL filter as the final option, the basic mathmatic models and working principle of this topologyare presented, the principles of SVPWM modulation, the operation mode of half cycle control areresearched and the current loop has also been designed.On this basis, the hardware architecture and software algorithms of the system are designed,including specific analysis and parametric design of the LCL filter and DC-Bus capacitance. Thesoftware algorithm of slow-start portion is also designed.With more couts of magnetic component, the volume and weight of three-phase dual-buckinverter is a problem. Several possible solutions of integrated magnetics technology are proposed.And it is demonstrated in two modes from the circuit schematic feasibility and impact on waveform ofthe grid current. In the end, a comparison is made about the volume of inductor and the equivalentfilter inductor size in the two possible magnetic integrated solutions, and another comparison with notusing any magnetic integrated solution is also made. Then a better magnetic integrated solution isfound.Finally,15kVA three-phase dual-buck inverter prototype based on DSP digital control is built.The experimental results based on the prototype show the correctness of the theoretical analysis andsimulation results.