计及等效电阻的无刷直流电机换相转矩脉动的分析与抑制

为便于分析无刷直流电机转矩脉动的形式，通常采用忽略等效电阻的简化电机模型，这会得出转矩存在上升脉动的错误结论，进而使一些方法出现正反馈补偿，导致系统性能更加恶劣的情况。针对这种情况，首先在考虑等效电阻的情况下，推导出无刷直流电机在120°自然换相模式下三相电流在传导区和换相区内的数学表达式；然后给出换相转矩脉动的表达式，并结合表达式证明了自然换相下换相转矩必然跌落的事实。同时，为抑制换相转矩脉动，在全面分析各种重叠换策略的优劣的基础上，选择了ON-PWM-PWM重叠换相策略。仿真和实验验证了对转矩脉动分析的准确性和对转矩脉动抑制的有效性。

Analysis and reduction of torque ripple in brushless DC machine considering the equivalent resistance

To facilitate the analysis of the torque ripple form of BLDCM, the simplified model is used by most researchers, which will lead to the wrong conclusion that the torque could increase in some situations. This may cause the positive feedback in some systems and degenerate the control effect. Aimed at this problem, the mathematical formulas of the three-phase current in conducting and commutation period are derived in the case of 120 degree natural commutation mode. Then, the torque ripple formula is presented, and the fact that the commutation torque is bound to fall under the natural commutation is proved by the formula. To reduce torque ripple, the overlap commutation strategy is widely used. This paper analyzes and compares the advantages and disadvantages of all the overlap commutation strategies and selects the ON-PWM-PWM mode to reduce torque ripple. The accuracy of the torque ripple analysis and effectiveness of the torque ripple reduction of the proposed method are verified through the simulation and experimental results. This work is supported by National Natural Science Foundation of China (No. 51607083) and High-level Introduction of the Scientific Research Foundation Personnel of Nanjing Institute of Technology (No.YKJ201412).