基于余弦函数的无传感器永磁风机IF起动平滑切换方法

采用电流频率比（IF）开环起动方法的永磁无刷风机在切换到采用磁链观测器的无位置传感器闭环算法时，使用传统切换方法如角度平均切换方法易引起电流冲击和转速波动，甚至导致切换失败. 针对此问题，提出切换过程基于余弦函数的IF起动平滑切换方法. 在切换过程中利用平均滤波方法保持最佳转矩电流，磁链角度则利用电机的转矩功角自平衡特性按照余弦函数规律进行切换，以达到电机实际电流平滑过渡的效果，提高电机切换过程中转速的平稳性. 对比角度平均切换和所提平滑切换方法的实验结果，验证切换方法的有效性. 结果表明，该方法对不稳定负载具有较强的适应能力，能提高IF起动切换过程的平滑度和成功率.

IF starting smooth switching method of sensorless permanent magnet fan based on cosine function

It is easy to cause current shock and speed fluctuation, even switching failures for the permanent magnet brushless fan adopting traditional switching method such as angle-average switching, when using current-frequency (IF) open-loop starting method to switch to the position sensorless closed-loop algorithm using flux observer. An IF start smooth switching method based on cosine function in the switching process was proposed for the above problem. The optimal torque current is maintained in the switching process using the average filtering method, and the flux angle switches according to the law of cosine function by motor's torque power angle self-balancing characteristic, which achieves the effect of smooth actual current transition and improves the motor speed stability in switching process. The experimental results of the angle average switching and the proposed smooth switching method were compared to verify the effectiveness of the switching method. Results show that the method has strong adaptability to unstable loads and can improve the smoothness and success rate of the IF startup switching process.