Topology Study Of Permanent Magnet Synchronous Generator And Its Power Converter

In recent years, permanent magnet synchronous generators (PMSG) have been applied in many industrial fields, such as wind power generation, electric vehicles, and energy storage, etc. The PMSG AC output can be converted to DC power with a PWM rectifier. The PWM rectifier has excellent control performance, such as small short-circuit current, wide voltage control range, low voltage adjustment rate and so on. In many applications, the generator speed is very high, reaching 10000r/min or even higher. And the fundamental frequency of the PMSG output will be high, too. The traditional power devices have limited switching frequency, so when the fundamental frequency is high, the switching frequency of the PWM rectifier is relatively slow. In this situation, the current harmonics of the generator will be increasing and the rectifier system even can’t work. In order to solve this problem and improve the control performance of the PWM rectifier, the switching frequency of the rectifier should be increased.In this paper, topology of the PMSG rectification system, principle of the PWM rectifier and the vector control method are analyzed in detail. Solutions of the hardware architecture and software algorithms are proposed to increase the switching frequency of the rectifier. In terms of hardware architecture, the equivalent switching frequency can be increased by increasing the number of the power switches. The series or parallel switches undertake the chopping together, so each single switch just has half of the burden. When the neutral point of PMSG windings is opened, the topology of generator becomes open-winding connected. It needs two normal three-phase PWM rectifiers to control the open-winding PMSG, and it achieves the performance of the normal three-level control. But, when the dual-rectifier uses a common DC bus, a zero-sequence current path is formed. In order to suppress the zero-sequence current in the stator wingdings, a zero-sequence current regulator is proposed in this paper, which makes the phase current more sinusoidal, and stabilizes the rectified DC bus voltage with less ripple. In terms of the control algorithm, the traditional SVPWM control uses the typical seven-segment switching sequence. In order to increase the equivalent switching frequency, actually, to decrease the demand of switching frequency, SVPWM control can be achieved by using the five-segment switching sequence, too.In this paper, the mathematical model of the open-winding permanent magnet synchronous generators is established. In order to satisfy the requirements of the PWM rectifier system, modular hardware circuit and experiment platform are designed. Both simulation and experimental results preliminarily validate the effectiveness of the proposed system.