The Control Strategies And Implementation Methods For Cascaded Multilevel Inverters

At present,there are two puzzles for human beings,one is scanty of energy sources,the other is environment pollution.It is extremely important to economize energy sources before new ones are developed.High voltage multilevel inverters have the following advantages :high realiability,high input power factor,high efficiency,low cost,low input&output harmonic,low common mode voltage and low dv/dt.Hence,it is significant to develop and popularize high voltage inverters to reduce industry energy waste.By reasons of its uncomparable advantages, such as low harmonic pollution, high input power factor and perfect output waves, the cascaded multilevel inverter is reseached in this paper as follows:1. Several tipical topologies of multilevel inverters are compared and analyzed,including their principles,their advantages and disadvantages. More-over,the mathematical mode of cascaded multilevel inverter is proposed. Finally,the reason to choose cascaded multilevel inverter is given.2.Carrier PWM and SPWM control strategies are compared and analyzed.Their sorts,principles,and essential relation between them are discussed in details.And then,on the basis of 3-cell cascaded multilevel inverter and phase shifted carrier PWM control strategy,the simulation is carried out.3.Based on the theory analyse above,the main circuit(based on IPM) of 3-cell cascaded multilevel inverter is designed,so are the control circuit(composed of CPLD&DSP) and data collection circuit.What is more, the function and sofeware design of control circuit are presented in details.At last,phase shifted carrier control strategy is performed on the experiment equipment of cascaded multilevel inverter. The design of main circuit is correct and the controller developed in this paper is suitable for cascaded multilevel inverter,which are proved by the experiment results.