H-Bridge Cascade Multi-Levelinverter Circuit And Itsapplication

With the development of the applications of power electronic technology in the newrenewable energy generation and the UHV AC/DC transmission system, multi-level inverter hasbecome more and more popular for the benefits that it could reduce the voltage stress of thepower switches and it could get a high-voltage and high-power output with the devices that cannot withstand very high voltage and it could also reduce the total harmonic distortion (THD) andharmonic content of the output voltage. This paper investigates the implementation andapplication of the cascaded H-bridge multi-level inverter circuit. Based on the CarrierPhase-Shift PWM (Carrier Phase-Shifted PWM, CPS-PWM) technology, a multi-level invertermodulated by SPWM is realized and is used in the wind power grid circuits. The proposedinverter has a low harmonic characteristic because it is easy to be extended and modularized, andhas a huge output voltage under a low voltage condition and can achieve equivalent modulationof high switch frequency under a lower switch frequency condition by eliminating low harmonicmutually. In the MATLAB/Simulink platform, the model of the multi-level inverter and thesimulation model of net-side converter in the wind power storage module are established. Bymeans of the experiment and theoretical analysis, the designed inverter has been proved thevalidity and the feasibility of applying it to the net-side converter in wind power energy storagesystem. In this paper, the research work is in detail as follows:1) The current research status and prospects for multi-level inverter development areanalyzed and its disadvantages are presented, and then the main tasks and significance of worksare illustrated.2) The topology of the conditional multi-level inverter circuit and its control strategy areanalyzed, and the principle of the cascaded H-bridge multilevel inverter and Carrier Phase ShiftPWM control strategy is studied. And then the cascaded H-bridge multilevel inverter based onCarrier Phase Shift PWM strategy is implemented.3) In the MATLAB/Simulink platform, the simulation model of the proposed inverter isestablished. The seven levels cascaded inverter with three phases is studied deeply. Furthermore, theoretical analysis and harmonic analysis of the simulation results is carried out.4) The research status and drawbacks of the existing wind power generation side converteris discussed. The proposed inverter is applied to the network side converter of energy storagemodule for the wind power grid system. The realization and control strategy of grid-connectedcircuit is researched, and then the simulation model is set up. The validity and feasibility of thecircuit is verified.5）On the basis of theoretic analysis and simulation study,the controlling system based onDSP and FPGA was designed and built Preliminary. DSP was completed the main control,andFPGAhas the main feature which is expand the I/O part for DSP.