Phase Delay Analysis of Current Sampling in Inverter-Fed Induction Machines

For an inverter-fed induction machine, the stator currents are often sampled at the crest or trough of the carrier wave in the inverter. Existing research reveals that this way of current sampling has aliasing that can cause a small delay in the current phase angle. In this paper, the phase delay is proven to considerably degrade the accuracy of inverter active power calculation during no-load tests, making it impossible to tune the machine core-loss parameter with its driving inverter. The time-domain analytical form of this phase delay is derived under space-vector pulse-width modulation (SVPWM) and verified by simulations and experimental tests. The proposed analytical method is further used to evaluate two existing solutions to aliasing. One of the solutions is slightly modified for practical use and proven to be effective for improving the accuracy of inverter active power calculation.

[1]  Thomas A. Lipo,et al.  A high-performance generalized discontinuous PWM algorithm , 1998 .

[2]  Fernando Briz,et al.  Current sampling and measurement in PWM operated AC drives and power converters , 2010, The 2010 International Power Electronics Conference - ECCE ASIA -.

[3]  Sandro Calligaro,et al.  Systematic Current Measurement Error Due to Back-EMF in PMSM Drives Adopting Synchronous Sampling , 2018, 2018 IEEE Energy Conversion Congress and Exposition (ECCE).

[4]  Ann C. Mertens,et al.  Voltage and current sensing in power electronic converters using sigma-delta A/D conversion , 1996, IAS '96. Conference Record of the 1996 IEEE Industry Applications Conference Thirty-First IAS Annual Meeting.

[5]  F. S. Merwe,et al.  Voltage harmonics generated by voltage-fed inverters using PWM natural sampling , 1988 .

[6]  Seung-Ki Sul,et al.  Current measurements in digitally controlled AC drives , 2000 .

[7]  V. Blasko,et al.  Sampling of discontinuous voltage and current signals in electrical drives: a system approach , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.

[8]  Fernando Briz,et al.  Analysis of current sampling errors in PWM, VSI drives , 2013 .

[9]  Takashi Sukegawa,et al.  A high accuracy current component detection method for fully digital, vector-controlled PWM VSI-fed AC drives , 1988, PESC '88 Record., 19th Annual IEEE Power Electronics Specialists Conference.

[10]  H. Der Van Broeck.  Analysis of the voltage harmonics of PWM voltage fed inverters using high switching frequencies and different modulation functions , 2007 .