Low Frequency Resonance Reduction Method of Induction Motor Used by Electric Vehicle Based on Sixth Harmonic Suppression in dq Coordinate
Feng Wan1,2, Zhang Wenjuan2, Miao Yiru2,3, Huang Shoudao2, Yang Shengbo3
1. College of Electronic Information and Electrical Engineering Changsha University Changsha 410022 China; 2. College of Electrical and Information Engineering Hunan University Changsha 410082 China; 3. State Key Laboratory of Power Transmission Equipment & System Security and New Technology Chongqing University Chongqing 400044 China
Abstract：The development of electric vehicles (EVs) is an effective means to solve energy and environmental problems and achieve the goals of “carbon peaking” and “carbon neutrality”. However, the motor drive system in EVs faces severe vibration and noise issues. If the harmonics in the stator current align with the natural frequency of the motor, motor resonance can occur. In an ideal situation, the inverter line voltage and stator current only have sideband harmonics distributed near the fundamental and switching frequencies and their multiples. However, nonlinear factors such as the conduction voltage drop, snubber capacitance, and dead time are added during the modulation process to prevent bridge arm direct connection in the inverter, causing low harmonic distortion of the stator current. In addition, the inherent frequency of induction motors used in EVs is low, and the motor commonly operates over a wide speed range. The low harmonic generated during the modulation process can coincide with the inherent frequency of the motor, resulting in low-frequency resonance. To suppress the low-order harmonic of the stator current, firstly, the simulation and test method of the natural frequency of the induction motor (IM) is studied, and the natural frequency range of the IM is determined. Then, based on harmonic distortion characteristics caused by dead time and tube voltage drop, a sixth harmonic controller is added to the current inner loop of the vector control system after rotor flux orientation (dq coordinate). Combined with bode plots and pole distribution diagrams, the optimal parameters of the harmonic controller are obtained according to the stability and harmonic suppression characteristics. Finally, the simulation model and experimental platform are established considering current FFT analysis results, power spectral density, and vibration experimental data under four operating conditions (low speed, no load, rated speed, and high speed). Compared with the compensation method of the pulse duration and inverter nonlinearity feedforward, it is proved that suppressing the sixth harmonic in the dq coordinate effectively reduces the fifth and seventh harmonics of the stator current and vibration power of the IM at its natural frequency. The feasibility and correctness of the proposed method can be certified by the simulation and experimental results, and the conclusions are as follows. (1) The dead time and voltage drop between the switch and diode can generate nonlinear errors in the output voltage of the inverter. The current inner loop PI controller based on rotor flux orientation cannot suppress the fifth and seventh harmonic distortion of the stator current caused by nonlinear voltage. (2) The fifth and seventh harmonics in the stator current are transformed into the sixth harmonics in the dq coordinate system. The sixth harmonic controller can effectively suppress the disturbance of nonlinear voltage without generating other harmonic distortion and does not affect the control performance. (3) Compared with the offline feedforward compensation method, the sixth harmonic controller proposed in this paper belongs to a specific frequency harmonic feedback control method. The harmonic controller can adaptively suppress the sixth harmonic component in the stator voltage under the dq coordinate system and has a good control performance.
冯婉, 张文娟, 苗轶如, 黄守道, 杨生博. 基于dq坐标系下6次谐波抑制的车用感应电机低频共振削弱方法[J]. 电工技术学报, 2023, 38(24): 6632-6645.
Feng Wan, Zhang Wenjuan, Miao Yiru, Huang Shoudao, Yang Shengbo. Low Frequency Resonance Reduction Method of Induction Motor Used by Electric Vehicle Based on Sixth Harmonic Suppression in dq Coordinate. Transactions of China Electrotechnical Society, 2023, 38(24): 6632-6645.
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2023, Vol. 38 
