| The dc voltage of traction power modules is provided by uncontrolled diode and phase-controlled thyristor rectifiers in the present feeding system of high-speed maglev vehicles, Shanghai. Such rectifiers have the inherent drawbacks of poor power factor and high harmonics in the line current. To reduce the impact to utility, advanced static var generator (ASVG) and fixed capacitor (FC) have to be mounted to filter harmonic current and compensate reactive power. However, there are distinct advantages to replace it with multiple PWM rectifiers. The advantages include low line current harmonics, high power factor, quick dynamic response and bidirectional power flow etc. This paper gave a detail research on operation principle, control scheme, multiple units' harmonic cancellation and applicability of PWM rectifier in the feeding system of maglev vehicles.In this paper, the topology, operation principle and mathematical modeling of PWM rectifier are discussed, and the design of main circuit parameters is given also. According to the operating characteristics of maglev vehicles, the synchronous PI current control scheme and SVPWM are adopted here. The applicability research of PWM rectifier in the feeding system of maglev vehicles is considered in three sections, which are dynamic responses under impact load, power feedback in braking process and control of network voltage. The main circuit, controlling method and harmonic cancellation of the system with four modules in series are analyzed. Based on theoretical analysis and software simulation, a low power PWM rectifier system with four modules in series is setup, and all control performance experiments are carried out on this system.Research shows that PWM rectifier system with multi-module in series meets supply need of high-speed maglev vehicles. The rectifier system have many obvious advantages of simplifying system structure, lowering system cost, enhancing control performance of system and improving power supply quality.
|
PDF Full Text Request