Abstract:Brushless direct current (BLDC) motors have become integral components in modern electric drive systems due to their high efficiency, reliability, and ease of control. These motors are widely used in electric vehicles, household appliances, robotics, and industrial automation. However, the common-mode voltage generated by inverters power BLDC motors induces a common-mode current in the motor, which can flow through bearings. Excessive common-mode current can lead to the breakdown of the insulating oil film in the bearings, causing severe corrosion and potential damage to the motor. As a result, managing common-mode voltage is a critical challenge in enhancing the durability and expanding the application of BLDC motors. This paper comprehensively analyzes the common-mode voltage in BLDC motors and introduces an innovative control method. This work discusses six distinct control modes and derives circuit models based on the BLDC motor's basic parameters. These models predict the maximum operating current in six-step communication control for the motor. Furthermore, the switching behavior of the motor current in various switching states is analyzed. Using these models, the common-mode voltage is computed and compared. The simulation and experimental results show excellent agreement with the analytical model, demonstrating the efficiency and accuracy of the proposed calculation method. Secondly, an investigation into the common-mode voltage model reveals three primary components: the back electromotive force (back EMF) component, the freewheeling current component, and the pulse-width modulation (PWM) component. This paper proposes an improved six-step commutation control method to reduce the common-mode voltage. The six-step communication control is enhanced by introducing a zero-voltage signal, which is strategically applied to minimize the common-mode voltage generated by each component. In the new control method, the zero-voltage signal is introduced in the following manner: (1) A three-level inverter injects the zero-voltage signal into the open phases of the two-level inverter under six-step commutation control, effectively suppressing the common-mode voltage caused by the motor's back EMF. (2) The zero-voltage signal is applied to the winding affected by the freewheeling current. This adjustment helps control the phase winding's terminal voltage, mitigating the common-mode voltage induced by freewheeling current. (3) For the PWM component, the improved six-step communication control adds a zero-voltage signal when the switch signal is zero, preventing reverse conduction and reverse voltage in the winding, further reducing the PWM signal's common-mode voltage. The improved six-step communication control achieves over 50% suppression of common-mode voltage compared to conventional two-level inverter systems. Therefore, the enhanced six-step commutation control method suppresses the common-mode voltage and contributes to the broader application of BLDC motors in various industries. By addressing the high common-mode voltage of BLDC motors, this paper paves the way for more efficient, durable, and widely applicable BLDC motor systems, promoting their adoption in industrial manufacturing.
刘晋鹏, 王秀和, 孙玲玲, 谷新伟, 彭一峰. 无刷直流电机六步换相控制下共模电压的快速准确计算与抑制措施[J]. 电工技术学报, 2025, 40(18): 5892-5906.
Liu Jinpeng, Wang Xiuhe, Sun Lingling, Gu Xinwei, Peng Yifeng. Rapid and Accurate Calculation of Common Mode Voltage under Six-Step Communication Control of BLDC Motor and Its Suppression Approach. Transactions of China Electrotechnical Society, 2025, 40(18): 5892-5906.
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