The Study On Cascaded High-Voltage Inverter Based On Vector Control

The high-voltage inverter for induction motor is a burgeoning technology, which has just been applied in recent years. It has wide applying prospect and capacious developing space for it not only has solved the problems of soft start and variable speed on high power fan or pump but also can save energy remarkably. Facing the increasingly stringent requirements on high-voltage electrical system which is applied in the areas such as electric traction, the research of the theories and technology in Field Oriented Control high-voltage inverter with advanced regulation performance has become hot.Field Oriented Control (FOC) is introduced into a cascaded multilevel high-voltage inverter and the fundamental of Field Oriented Control is analyzed in this paper. Through the coordinate transformation,the mathematical model of an asynchronous motor on a three-phase stationary coordinate is transformed into a model on a two-phase rotating coordinate, and the stator current is decomposed into two DC parts including excitation and torque, which are orientated towards the rotator flux field and controlled respectively, thus the magnetic flux and torque are decoupled, it controls an asynchronous motor in a DC motor way.According to the cascaded multilevel inverter is consisted of several power units in series, the paper adopts carrier Phase-shifted PWM (PS-PWM) technique as the control method. Otherwise, to illustrate the technical characteristics of PS-PWM method in cascade inverter system, the paper gives brief mathematical analysis.The paper presents the Rotor Field Oriented Control algorithm based on speed and current double loop for a cascaded multilevel high-voltage inverter, and the system emulate models are established on Matlab/Simulink. The results prove that the static and dynamic performance of the high-voltage motor is fine and the control algorithm is effective.In the end, the paper completes the system hardware and software design based on TMS320LF2407A DSP and Cyclone FPGA chip, DSP is utilized to detect the position of the flux linkage, speed and circuit for its excellent digital signal processing performance, while FPGA is utilized to produce PS-PWM for its powerful parallel processing performance. The experimental bench is established, and the test results prove that the motor operated smoothly, which is coincided with the simulation results, besides, the results prove that the system control algorithm, hardware and software design are effective.