Transactions of China Electrotechnical Society  2023, Vol. 38 Issue (6): 1460-1471    DOI: 10.19595/j.cnki.1000-6753.tces.221487
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Random-Frequency Triangular Wave Injection Based Sensorless Control of PMSM Drives for Audible Noise Reduction
Sun Mingyang, He Yang, Qiu Xianqun, Tao Tao, Zhao Wenxiang
School of Electrical and Information Engineering Jiangsu University Zhenjiang 212013 China

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Abstract  High-frequency signal injection is an effective sensorless control method for the permanent magnet synchronous motor (PMSM) at low and zero speeds. However, the injected high-frequency signal will produce severe audible noise. The application of this method in high-end fields such as ship propulsion is limited. Recently, lots of methods were proposed to reduce noise. Random injection methods can effectively reduce noise without other equipment. However, the random objects of these methods are sinusoidal waves or square waves, and their maximum noise at the injection frequency is relatively large. This paper presents the random-frequency triangular wave voltage injection-based sensorless control method to solve this problem.
Firstly, two triangular wave voltage signals with different frequencies are chosen based on the principle of equal volt second area. The random number is generated by the linear congruence method to synthesize triangular wave voltage signals with random frequencies. Secondly, by injecting the signal into the estimated rotor reference system, the maximum noise at injection frequency can be effectively reduced. Meanwhile, the distribution of high-frequency current power spectral density (PSD) is extended. Thus, the audible noise produced by the high-frequency current can be reduced. In addition, a corresponding signal demodulation method is proposed to obtain the rotor position from the induced current. The information of rotor position and speed can be achieved without the demodulation signal. Finally, the sensorless control can be realized with the estimated rotor position and speed.
The feasibility and effectiveness of the proposed method are verified by experimental results. The FFT analysis is used to analyze current. The harmonic components of 312.5 Hz, 625 Hz, and random-frequency trianglar wave at the injection frequency are 1.05 A, 1.33 A, and 0.43 A, respectively. Compared with fixed- frequency triangular wave injection, random triangular wave injection disperses the spectrum and reduces the peak value of the spectrum. Random square wave, random sinusoidal wave, and random triangular wave generate spectrum spikes at the least common multiple of two injection signal frequencies, which are 0.56 A, 0.48 A, and 0.43 A, respectively. The fundamental frequency component of the triangular wave is lower than those of the traditional sinusoidal wave and square wave. In addition, the PSD analysis is also used to evaluate noise. The noise of random triangular wave at 312.5 Hz and 937.5 Hz is lower than that of fixed 312.5 Hz triangular wave injection, and the noise at 625 Hz and 1 875 Hz is lower than that of fixed 625 Hz triangular wave injection. Compared with fixed-frequency triangular wave injection, random-frequency triangular wave injection broadens the current PSD and reduces discrete peaks. Thus, the noise can be reduced. The maximum noise generated by the random square wave, random sinusoidal wave, and random triangular wave at the least common multiple of two injected signal frequencies are -6.6 dB, -8.2 dB, and -10.6 dB, respectively. The maximum noise of the random triangular wave is the lowest. The position errors of sensorless control at medium and full loads are 8 deg and 14 deg, respectively. The speed errors of sensorless control at medium and full loads are 5 r/min and 6 r/min, respectively. When the speed of motor changes from 50 r/min to -50 r/min, and then to 50 r/min, the maximum position error and speed error are 20 deg and 7 r/min, respectively. The results show that the control performance of the motor is good both in the steady state and dynamic state.
A random-frequency triangular wave voltage injection method is proposed. Sensorless control at low speed is then realized. Better noise reduction is also realized. The maximum noise at injection frequency can be reduced by the proposed method. In addition, high-frequency noise caused by fixed-frequency injection can be reduced. The experimental results prove that the proposed method can effectively reduce audible noise with good sensorless control performance of PMSM.
Key wordsPermanent magnet synchronous motor      random-frequency      triangular wave      noise      power spectral density     
Received: 01 August 2022     
PACS: TM315  
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Sun Mingyang
He Yang
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Tao Tao
Zhao Wenxiang
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Sun Mingyang,He Yang,Qiu Xianqun等. Random-Frequency Triangular Wave Injection Based Sensorless Control of PMSM Drives for Audible Noise Reduction[J]. Transactions of China Electrotechnical Society, 2023, 38(6): 1460-1471.
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