A Study On Key Techniques Of Cascaded Inverter

The study of this paper concentrates on cascaded inverter. The main content and innovation include:1. Simple model of cascaded inverter is given and all redundant states are analyzed. Concept of cascaded differ inverter and differ SHPWM are founded.2. Multilevel select harmonic elimination technique is summarized. When Newton's method is applied to solve nonlinear equations, an algorithm adopting discriminate genes is proposed, which is more convergence and can provide better solution for harmonic eliminate equations. Walsh function can be applied to build linear equations, which is valid in selected area. Switch angle difference is analyzed. Robust coefficient of switch angle is defined, which is useful in switch angle selection.3. A novel balance control method based on random distribution is proposed. It can be concluded from the distribute procedure based on random function that the active probability of each cell is same. So, with the device working longer, the utilization of each cell inverter is going to be the same. Random function can be realized by random number generator. The fixed section method suits simple random number generator, while varied section method can assure each random number is valid. Linear congruent method and chaos mapping method can be applied to generate random number. It is easy to embedded random distribution in control algorithm. Result of simulation and experiment is also given.4. Reliability analysis of cascaded inverter is carried out. Fault diagnosis based on analyze of output waveform is proposed. BP neural network is applied to realize fault pattern isolation. Multiple fault diagnosis can provide precise fault accommodation. For more fault information contained in cascaded differ inverter, it is possible to isolate fault quickly. Build in test design of cascaded inverter and test procedure are also provided.5. Concept of independent cell is proposed. Function and structure design of independent cell are also provided. Phase control, including output phase, amplitude phase and carrier phase control, can be applied to regular output waveform. Run procedure based on independent cell is also given.