Research On High And Low Frequency Cascaded Inverter

A novel cascaded multilevel inverter consist of high and low frequency unit has been researched in this character. The controll technique and system structure of low-frequency unit and high-frequency unit is analysised in this paper in detail. The adaptive multilevel SHEPWM control method based on neural network is proposed.The high and low frequency cascaded inverter is theoretical analysed in detail. A square wave as the output of the low frequency unit output the active power of the system, The high-frequency unit works in reactive power state, compensate the output waveform of the low-frequency unit to improve the quality of the system output waveform. The simulation proves the proposes control theory is correct. For further improving the quality of the output waveform, multilevel SHEPWM method is used for control. The simulation system based on 9 wave PWM and 5 level PWM is designed. Simulation results has proved the harmonics decreased evidently. In SHEPWM control method, a serial of non linear equations for the switching angle of the low-frequency unit need to be resolved. As a result, the curve fitting process of neural network is proposed to calculate the switching angle offiine. This method has also been verified by simulation.The operating principle of cascaded multilevel inverter system is analyzed in detail. And the program of the control method based on DSP2812 is given. Simulation and experimental research indicate that the inverter has good performance.