A method for power system impedance estimation is presented. The method employs a power converter to inject a voltage transient onto the supply system. As the technique employs controlled power electronic devices it may be used as a stand alone piece of a portable measurement equipment, or it may be embedded into the functions of an active shunt filter for improved harmonic control. The impedance is estimated through correlation of the measured voltage and current transients. Simulations and experimental results demonstrate the measurement technique is highly accurate and effective.

This paper presents a new device for the compensation of common-mode (CM) disturbance in induction motor drives, based on the active cancellation approach. The detailed design and the experimental implementation issues of the new active compensation device for a 380-V/50-Hz pulsewidth-modulation (PWM) induction motor drive are discussed. Starting from the idea of the active common-noise canceller, the proposed active compensation device is suitably improved in order to overcome the limitations of similar previously proposed circuits. In fact, it can be successfully used within a drive system with a rated voltage of 380 V or higher by employing an improved active circuit with a dedicated dc power supply derived from the ac power supply line. In addition, the design follows the criteria of compactness and minimum cost. The performance of the realized active compensation device is verified through experimental measurements of the CM voltage, the CM current, and the motor shaft voltage. The effectiveness of the proposed solution is demonstrated by experimental results.

This paper deals with the active common-mode (CM) voltage compensation in an induction motor drive where the inverter is supplied by a dc source, which is typical of vehicle applications. The CM voltage at motor terminals, creating a shaft voltage through the motor air gap with possible rise in bearing current, can endanger motor reliability and reduce its lifetime. Therefore, CM voltage filtering is desirable. On the other hand, the operation of an active filter has an impact on drive efficiency due to its specific losses and can affect the electromagnetic interference (EMI) emissions that are generated by the drive. Such effects are investigated in this paper. A detailed description of a CM active filter (CMAF) is presented. An analysis of the CM voltage and current on the motor ground connection before and after the introduction of the CMAF is performed. The power losses due to the CMAF operation are analyzed and experimentally evaluated. Furthermore, the EMI toward the vehicle dc power supply line is investigated. All phenomena are studied by simulation and experimentally. The simulated results “are obtained developing” a high-frequency circuit model of the drive system, including the CMAF, which is implemented using the PSpice software. To accurately perform the experimental tests, a new dedicated high voltage dual dc line impedance stabilization network (LISN) is designed and set up on purpose. The CMAF is found to be an effective solution for the increase in motor reliability and drive electromagnetic compatibility, and its operation does not significantly reduce drive efficiency. Moreover, the CMAF does not worsen the EMI toward the dc supply line. Therefore, its presence does not imply the need for additional filters with respect to the case where no CMAF is used. Simulated results are in good agreement with the experimental ones, confirming the validity of the proposed modeling of the drive system.

This paper proposes a common mode (CM) electromagnetic interference active filter devised for application in automotive induction motor drives. The active filter is based on a feedback scheme and it is realized using linear amplifiers. It performs the compensation of the CM voltage at the motor input, allowing an increase of the drive reliability and a reduction of the harmonic content of leakage high-frequency CM currents that affect the vehicle electromagnetic compatibility. A size-optimized layout is proposed and the influence of the power linear amplifier performance on the CM voltage compensation is discussed. General guidelines for the active filter design are given and its experimental implementation is presented. Finally, the filter performance is assessed by simulations and experimental tests.