The Simulation And Experiment Of H Bridge Cascaded High Voltage Converter

Cells cascade multilevel converters has the incomparable advantage for the characteristics of low harmonic current, high power factor and better output waveform. Due to expanding to medium-voltage fields easily, cascaded multilevel power inverters have been utilized in medium-voltage motor drives and reactive power compensations of power system.This paper describes the high-voltage converter and multi-level inverter research status and development trends and technical problems,then introduces the multi-level power converter circuit topologies structure and in-deepth analysises the circuit topologies of the H-bridge cascaded high voltage converter about its circuit topologies structure, working principle, control strategy, implementation theory and design method. It briefly introduces the working principle,its performance and features of the cascaded multilevel inverter control algorithms which commonly used. In order to take depth research on cascade inverter, we adopte Matlab/Simulink software to simulate and analysis VVVF control of the five power units cascaded multilevel high voltage inverter and its carrier phase shift SPWM control algorithm.Base on theoretical analysis, the main circuit and control circuit of power unit cascaded multilevel inverter is designed. The control system bases on Digital Signal Processing (DSP) and Field Programmable Gate Array (FPGA) is also proposed. This paper designs and selectes the inerter control strategy, carrier frequency and the input parameters of transformer reasonable, then uses the FPGA real-time multi pulse power unit to control cascaded high voltage inverter. From scope and transformer, we get the voltage and current experiment results, which show that the method of combining the FPGA and host controller DSP to generate real-time multi pulse is feasible.The experimental results show that the steps'number of output phase voltage and line voltage is very large. The waveform is very close to the sine wave and the changing rate of the voltage is very small. The results show that the main circuit and control system design is correct. And the experiment results also show that level phase-shifting unite cascade high voltage frequency based on carrier phase with excellent output characteristics, like voltage, current, etc.Finally, the paper carried out an experimental on the 6kV high voltage inverter with motor load during startup and steady-state operation performance. The results show that cascade inverter output phase voltage and line voltage with large number of steps, its waveform close to sinusoidal and the change rage of voltage is small. The experiment results improved the correct of main circuit and control system designing.