Abstract : Taking a DC750V traction inverter for subway vehicles as an example, this paper designs the inverter main circuit and control system using IGBTs as the main switching elements, and performs simulations using MATLAB/SIMUUNK. Finally, a concept for improving the effect of direct torque control using predictive control is proposed.
Keywords : Metro vehicle; Traction inverter; Direct torque control; Predictive control
0 Introduction
Through more than 30 years of introduction, research, and improvement, my country's subway vehicle technology has achieved a certain level of production capacity and technological foundation in equipment manufacturing. However, a gap still exists compared to international standards. These gaps are mainly reflected in key technologies, such as AC drive systems for traction power systems and safety protection equipment. These are the main technological directions we need to focus on in the localization process of subway equipment. This paper designs the main circuit of the AC traction inverter speed control system for DC750V power supply vehicles in the Beijing and Tianjin subways, describes the selection process of the main switching components, and focuses on the analysis and design of the control system using the direct torque method, and performs MATLAB simulation.
1 System Design
The design of a frequency converter unit is generally divided into three parts: the main circuit, the control system, and the protection circuit. Their relationship is shown in Figure 1. The intermediate circuit of the inverter circuit includes overvoltage chopping, energy feedback, and overvoltage release circuits. The three-phase inverter circuit includes IGBT protection circuits. The control system includes flux linkage, torque observation, and voltage state selection. A filter reactor and supporting capacitor are connected in the input circuit of the frequency converter unit to effectively isolate conducted interference between the frequency converter unit and the power supply system. The cooling method of the system can be selected according to the thermal characteristics requirements of the IGBTs. The main technical parameters of the system are as follows: Rated input voltage: DC750V; Maximum input voltage: DC1000V; Rated output capacity: 2x500kVA; Rated output voltage: 3-phase 0-580V; Rated output current: 2x497.5A; Maximum output current: 2x644A (2min); Maximum regenerative current: 2x589A; Output frequency: 0-140Hz; Maximum switching frequency: 500Hz; Rated efficiency: 98%; Control method: Direct torque control; Maximum peak voltage of switching: ΔU=240V.
For details, please click: Design and Simulation of Variable Frequency Speed Control System for Metro Vehicle Traction
