The Research Of Cell Series Multi-level High Voltage Frequency Inverter

With the development of electric drive technologies, the research on high voltage drive systems gets more and more attention. The advanced development of the high-voltage frequency control technology has crucial importance, not only for China’s energy conservation but also for the significant improvement of the dynamic and static performance of motor. As one of the main topology of high voltage frequency converter, the cell series multi-level high voltage inverter has the following advantages:input side has less harmonic pollution to the power grid; output voltage approaches to sine wave, structure is simple and easy to be modularized and so on. These advantages make the cell series multi-level high voltage frequency inverter to be widely used in the electric drive field, especially for blower fan and water pump which require lower timing capability. Specifically speaking, the main contents in this paper are as follows:(1) Firstly, the topologic structure of main circuit and the theory of cell circuit in the cascaded inverter are analyzed. Parameters of lOkV high voltage inverter are designed. Carrier phase-shifted SPWM modulation method is used on power unit in this paper, and the carrier phase-shifted SPWM control principles are analyzed in detail.(2) While electric traction and other fields increasingly high demand for high-voltage electrical system, vector control plays an increasingly important position in the high-voltage inverter system.This paper studies the high-voltage inverter system based on vector control. The rotor field oriented vector control strategy is introduced into the cascaded multilevel high-voltage inverter system and the system of rotor field oriented control is analyzed.(3) Various parts of the cell series high voltage frequency inverter are modeled and simulated. The feasibility of a carrier phase-shifted SPWM control method is verified by simulation and analysis. The influences of carrier phase shift angle and modulation ratio to the output voltage are analyzed in detail. Provide a theoretical basis for practical application.(4) The open-loop system model and the closed-loop system model are built by MATLAB. Modeling and simulation of open-loop system proves that it is suitable for the field which requires lower timing capability. This paper designs a high voltage inverter vector control system based on rotor flux field-oriented. Simulation of the system is performed and the result is presented. The simulation results show that:the output voltage waveform of the inverter is correct, the dynamic and static performance of the motor are perfect. This verifies the correctness and feasibility of the system control strategy.