Research On A Novel Step-up Multi-level Inverter

The main advantages associated with the muti-level converter are high power capacity, good electromagnetic compatibility, less harmonics and less switch stress. These advantages make them popular. CSI(Current Source Inverter) is more suitable for the grid conneted PV system than VSI(Voltage Source Inverter). So we do some researches on the multi-level CSI in this paper.In this paper, a novel step-up five-level CSI based on the Boost converter is proposed by the means of duality principle. Compared with the other five-level CSI, the proposed topology uses less active switches. Also the new topology can be expanded to higher level inverter or even the three phase system. The novel step-up five-level CSI can be evoluted from the step-up DC-DC converter as well. The evolution process and operating principles of the novel inverter are presented. SVPWM(Space Vector Pulse Width Modulation) method and multi-carrier pulse width modulation method are applied to the new topology. Also the ability of step-up and current self-equilibrating of the inverter is evaluated based on theoretical analysis. The open-loop simulation of the system verifies the basic principles and work performces of the inverter. Combained with the different applications and according to the mathematical model of the new topology, this paper presents three kinds of close-loop control strategies: two of them are output current control, and the other is input current control. And then, the simulations of the three close-loop control are finished by Matlab.After the principle analysis and simulation, a prototype of the novel five-level inverter is accomplished. DSP and FPGA compose the digital control system, which generates the inverter’s driving signal. The experimental results verify the correctness of the theoretical analysis and simulation.