Suppression of common-mode voltage in a PWM rectifier/inverter system

This paper proposes a PWM rectifier/inverter system capable of suppressing not only supply harmonic currents but also electromagnetic interference (EMI). An active common-noise canceler (ACC) developed for this system is characterized by sophisticated connection of a common-mode transformer which can compensate for common-mode voltages produced by both PWM rectifier and inverter. As a result, the size of the common-mode transformer can be reduced to 1/3, compared with the previously proposed ACC. A prototype PWM rectifier/inverter system (2.2 kW) has been implemented and tested. Some experimental results show reduction characteristics of the supply harmonic current and EMI</p

An application of sensorless drive technology to a three-phase hybrid stepping motor drive

This paper presents a three-phase hybrid stepping motor drive system to which sensorless drive technology of brushless DC motors is applied. The drive system is characterized by measurement of back EMF in the motor windings. As a result, the drive system can damp rotor natural vibration of the three-phase hybrid stepping motor. Moreover, an acceleration and deceleration pattern is proposed to suppress undesirable transient vibration in acceleration, deceleration, and positioning operations. Some experimental results show that the experimental system can damp the rotor natural vibration even if the rotor inertia varies</p

Analysis and reduction of EMI conducted by a PWM inverter-fed AC motor drive system having long power cables

This paper analyzes conducted EMI generated by a PWM inverter-fed induction motor drive system. It is shown experimentally and analytically that resonant phenomena in a high-frequency range beyond a dominant resonant frequency are originated from the behavior of power cables as a distributed-constant circuit. Spectra of common-mode and differential-mode currents are simulated by means of introducing a distributed-constant model of the power cables, which consists of a 20-step ladder circuit. As a result, it is also shown that these resonances can be damped out by a single common-mode transformer (CMT) and three differential-mode filters (DMFs), both of which have been proposed by the authors</p

Implementation and position control performance of a position-sensorless IPM motor drive system based on magnetic saliency

This paper describes position-sensorless control of an interior permanent magnet synchronous (IPM) motor, which is characterized by real-time position estimation based on magnetic saliency. The real-time estimation algorithm detects motor current harmonics and determines the inductance matrix, including rotor position information. An experimental system consisting of an IPM motor and a voltage-source pulsewidth modulation inverter has been implemented and tested to confirm the effectiveness and versatility of the approach. Some experimental results show that the experimental system has the function of electrically locking the loaded motor, along with a position response of 20 rad/s and a settling time of 300 ms</p

An approach to real-time position estimation at zero and low speed for a PM motor based on saliency

This paper presents a magnetic saliency-based position estimation approach for a permanent magnet (PM) motor fed by a voltage-source pulse width modulation (PWM) inverter. The proposed real-time estimation algorithm detects motor current harmonics and calculates the inductance matrix, including rotor position information. Position estimation can be performed every period of PWM or carrier cycle. An experimental system using an interior permanent magnet (IPM) synchronous motor has been constructed. Experimental results verify that position estimation within 10° in electrical angle is obtained at standstill and at speeds as low as 1 r/min by the proposed approach</p

Circuit configurations and performance of the active common-noise canceler for reduction of common-mode voltage generated by voltage-source PWM inverters

This paper discusses two different circuit configurations of the active common-noise canceler (ACC) which has been proposed by the authors. One is characterized by its DC power supply isolated from the DC link of a PWM inverter. The configuration makes it possible to integrate the ACC with a medium-voltage PWM inverter. The other compensates a partial frequency component of the common-mode voltage. The purpose is not to achieve complete cancellation, but to restrict only a slope in a change of the common-mode voltage applied to an AC motor. As a result, the core size of the common-mode transformer used in the ACC becomes considerably small. Experimental results show good effects of the proposed active circuits on both ground current and conducted EMI</p

Analysis of variation of neutral point potential in neutral-point-clamped voltage source PWM inverters

The authors present the analysis of the neutral-point potential variation of the neutral-point-clamped voltage source PWM (pulse-width-modulation) inverter (NPC-VSI) for AC motor drives and static VAr compensators (SVC). The potential variation is analyzed with the focus on the current flowing out of or into the neutral point of the DC link. The theoretical minimum capacity of the DC link capacitors is discussed for its application to both a vector-controlled induction motor system of 2.2 kW and a SVC system of 10 MVA, 6.6 kV, 60 Hz. It is shown that the proposed control scheme makes it possible to suppress the neutral-point potential variation within a few percent, so that the total capacity of the DC link capacitors in the NPC-VSI is almost the same as that in the conventional voltage source inverter</p

Rotor position estimation based on magnetic saliency of an IPM motor-realization of a wide-speed range from zero to the rated speed

This paper describes position estimation based on magnetic saliency of an interior permanent magnet synchronous motor (IPM motor) for the purpose of achieving a wide-speed range. The position estimation, which has been proposed by the authors, is characterized by the real-time algorithm estimating the rotor position at every PWM period. Selection of PWM patterns proposed in this paper expands the speed range capable of estimating the rotor position to a higher-speed range. The PWM patterns are switched over, depending on an amplitude and phase of the average output voltage vector. Experimental results obtained from an IPM motor drive system of 100 W demonstrate that the selection of the PWM patterns makes it possible to estimate the rotor position in a wide-speed range from zero to the rated speed</p

An approach to real-time position estimation at zero and low speed for a PM motor based on saliency

This paper presents a magnetic saliency based position estimation approach for a PM motor fed by a voltage-source PWM inverter. The proposed real-time estimation algorithm detects the motor current harmonics and calculates the inductance matrix including the rotor position information. The position estimation can be performed every period of pulse-width-modulation or carrier cycle. An experimental system using an interior permanent magnet (IPM) synchronous motor has been constructed. Experimental results verify that the position estimation within 10 degrees in electrical angle is obtained at standstill and such an extremely low-speed as 1 r/min by the proposed approach</p

Modeling and damping of high-frequency leakage currents in PWM inverter-fed AC motor drive systems

This paper presents an equivalent circuit for high-frequency leakage currents in pulsewidth modulation (PWM) inverter-fed AC motors, which forms a series resonant circuit. The analysis based on the equivalent circuit leads to such a conclusion that the connection of a conventional common-mode choke or reactor in series between the AC terminals of a PWM inverter and those of an AC motor is not effective to reduce the rms and average values of the leakage current, but effective to reduce the peak value. Furthermore, this paper proposes a common-mode transformer which is different in damping principle from the conventional common-mode choke. It is shown theoretically and experimentally that the common-mode transformer is able to reduce the rms value of the leakage current to 25%, where the core used in the common-mode transformer is smaller than that of the conventional common-mode choke</p