Abstract：In high-performance control of AC motors, a dual closed-loop vector control strategy is commonly employed to drive the machine, offering strong anti-interference capability, fast response speed, and stable operation. It is necessary to acquire real-time information about the three-phase currents of the motor stator windings by installing at least two current sensors to detect phase currents. Multiple sensors increase the system cost and equipment volume, which is not conducive to the development of control equipment miniaturization. Based on the DC-link current sensor sampling principle, this paper proposes active zero state pulse width modulation (AZSPWM) as a replacement for controlling the motor after analyzing the issues of phase current reconstruction blind zones caused by space vector pulse width modulation (SVPWM). Firstly, based on the switching states of the three-phase voltage source inverter, six active voltage vectors and two zero voltage vectors are defined, establishing the relationship between DC-bus current and phase currents under different switching states. By analyzing the actual switching process and the variation of DC-bus current, the minimum duration of the switch state Tmin=DTs is determined for current sampling. The voltage vector hexagon under SVPWM control is divided into low modulation region, sector boundary region, and measurable region. A method using AZSPWM is proposed to reduce the phase current reconstruction blind zone. The operational interval of AZSPWM and its phase current reconstruction blind zones are analyzed, and a vector insertion method is employed to address blind zone issues at low modulation regions. This approach allows for a $\frac{2}{\sqrt{3}}(1-2 D)$ voltage utilization rate, and 100% voltage utilization rate can be achieved when $D \leqslant \frac{2-\sqrt{3}}{4}$. The entire voltage vector region is divided into 12 sub-zones, with different voltage combinations selected for different sub-zones. By arranging the switching sequence reasonably, no additional switching is required under AZSPWM control. In the experiments, with a PWM carrier frequency of 10 kHz, Tmin of 10 ?s, and D=0.1, the voltage utilization ratio is $\frac{2}{\sqrt{3}}(1-2 D) \approx 92.4 \%$ . Steady-state operation experiments are conducted in low and high modulation ratio intervals, as well as transient experiments on the transition between vector-inserted and non-vector-inserted AZSPWM control methods. The reconstructed currents closely followed the actual currents, with a reconstruction error smaller than the fluctuation of the actual current within one PWM cycle. As torque increases and speed rises, the current variation within a single PWM cycle increases, leading to a larger standard deviation in the reconstructed current error. Smooth switching between different PWM control methods is achieved. The experiments concluded that (1) the proposed method achieves stable operation in low and high modulation ratio intervals. A 92.4% voltage utilization rate can be achieved without phase current reconstruction blind zones. (2) The error between reconstructed and actual currents is less than the fluctuation of the current within one PWM cycle, with the feedback current lagging behind the actual current by one PWM cycle. (3) The actual current harmonics are mainly distributed near the switching sub-frequency. Different loads almost have no impact on the accuracy of the reconstructed current, although speed changes slightly affect the accuracy.
房钰超, 王博, 王元奎, 王云冲, 沈建新. 基于动态零矢量脉宽调制的永磁同步电机相电流重构方法[J]. 电工技术学报, 2025, 40(14): 4483-4493.
Fang Yuchao, Wang Bo, Wang Yuankui, Wang Yunchong, Shen Jianxin. Phase Current Reconstruction Method for Permanent Magnet Synchronous Motors Based on Active Zero State Pulse Width Modulation. Transactions of China Electrotechnical Society, 2025, 40(14): 4483-4493.
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