Therr-Level Frequency Converteranalysis And Application Of Rolling Procee

AC variable frequency motor has become the core equipment of modern hot-rolled steel production. Control feature of Three-level inverter has direct impact on speed control of rolling line and speed coordination among rolling stands, at the same time, greatly influences the quality and yield of the steel production.In this article, the author studies the working principle of Three-level inverterand analyzes the working process of it. First, the hardware structure of main circuit of three-level inverter and its role in the power supply circuit are carefully studied. Second, the author analyzes the process of how the rectifier achieves power factor to " 1" through voltage vector control and further study how to use space voltage vector graph to work out principle and algorithm inverter control. In other words, according to the needed voltage under load, calculate the modulation rate. Then based on the modulation rate size and angle, find out the exact location o in a space voltage vector diagram, and determines the PWM control signal with the help of the location. Furthermore, control power switch Q1, Q2, Q3, Q4, and the voltage required by the load vector can be obtained.Finally, the author discusses the debugging process of three-level inverter based on rolling practice including:determine the parameters, preparation before transmitting power; zero and gain adjustment of Analog feedback; phase inspection and rectification of the main power supply; Rectifier current loop setting and the voltage loop adjustment process; operation of rectifier with the inverter.