载波相移三相单管电路在直驱系统中的应用

为改善传统的直驱型风力发电系统中永磁同步发电机的谐波特性,从功率因数校正(PFC)、升压和提高系统容量的角度出发,将3个三相单管Boost型PFC电路交错运行的方案应用在直驱系统中。结果表明,在支路电流均工作于断续电流模式时,合成电流基本工作于连续电流模式,谐波特性良好。三相单管BoostPFC电路具有开关频率固定、元件数量少、成本低、控制简单、可靠性高等优点,该拓扑能对永磁同步发电机的输出进行功率因数校正,减少发电机电流的谐波含量和发电机损耗,提高发电机的有功功率输出能力和系统效率。采用载波相移技术能在较低的器件开关频率下实现较高开关频率的效果,通过低次谐波的相互抵消提高等效开关频率而不是简单地将谐波向高次推移,能在提高装置容量的同时,有效地减小输出谐波,提高整个装置的信号传输带宽。仿真验证了该方法的可行性和有效性。

Application of Single-switch Three-phase Boost Rectifier to the Direct-drive System

Direct-drive wind power generator has been receiving increasing attention due to their inherent efficiency.In order to allow the variable speed operation of the PMSG,a conventional three-phase bridge rectifier(BR)with a bulky capacitor associated with voltage source current controlled inverter(VS-CSI)is used.This simple scheme introduces a high intensity low frequency current harmonic content into the PMSG and consequently increase the total loss in it,subsequently,decreases the power capability of the system.In this paper,in order to decrease the current harmonic of the PMSG,correct the power factor,boost the voltage and increase the capacity of the system,a single-switch three-phase Boost rectifier(PFC)which interleaved running is applied to the systems.Although each path current is DCM,the complex current is CCM.It can correct the power factor of the PMSG without increasing the system cost,decrease the current harmonic content of the PMSG,subsequently,increase the real power ability and efficiency of system.The system has simple structure and is reliable.The single-switch three-phase Boost PFC circuit has many merits,such as:constant switch frequency,few elements,low cost,simple controller and high reliability.When applying in direct-driven wind generation system,it can correct the power factor of the generator output and increase the system efficiency.Adopting carrier phase shifted modulation can implement the effect of higher equivalent switch frequency when working at the lower switch frequency,increase equivalent switch frequency by counteraction of lower harmonics,but process harmonics to high order simply,so it has good harmonic characteristic and descend the output harmonics with increasing the equipment capacity,increase the signal transmission band of the whole equipment.The validity was verified by simulation.