双馈电机转子侧变换器死区补偿方法

双馈电机稳定工作时,转子电流频率较低,转子侧变换器所加死区对其影响比较显著.为了改善转子电流波形,分析了死区对变换器输出电压的影响、零电流箝位现象以及死区给输出脉冲带来的不对称性,在此基础上对已有的死区补偿方法进行了改进,将电流矢量所在空间分为6个区域,在每个区域内仅对其中一相输出电压进行补偿,并针对零电流箝位现象进行了补偿.此外,为了避免加入死区给PWM脉冲带来的不对称性,在每个开关周期内对PWM发生器的比较值进行2次修正,以使输出脉冲对称.最后在双馈风力发电实验平台上进行了验证,实验结果表明该补偿策略能够有效地减小双馈电机转子电流谐波且消除了零电流箝位现象.

Dead-time compensation for rotor-side converter of DFIG

When DFIG(Doubly-Fed Induction Generator) works steadily,its rotor current frequency is low,so the influence of dead-time is notable.The influence of dead-time on converter output voltage,the phenomenon of zero-current clamping and the asymmetry caused by dead-time are analyzed,based on which,the existing dead-time compensation strategy is improved.The space of current vector is divided into six regions and only one phase voltage is compensated.The zero-current clamping phenomenon is compensated as well.The comparative value of PWM generator is modified twice in a switching period to avoid the asymmetry caused by dead-time.Tests are carried out on the DFIG experiment platform and the results demonstrate the proposed dead-time compensation method reduces the harmonic components of rotor current effectively and eliminates the zero-current clamping phenomenon.