Simplified model and corrective measures for induction motor instability caused by PWM inverter blanking time

Colby, R.S.; Simlot, A.K.; Hallouda, M.A.

doi:10.1109/pesc.1990.131254

Cited by 44 publications

(21 citation statements)

References 6 publications

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“…The electromagnetic torque is then given by (27) We now show that is also a valid expression for torque in the nonlinear magnetics case: (28) For a three-phase machine with pole-pairs, the torque equation becomes (29) Hence, the above expression for torque is valid, even in the case of saturable rotor leakage. He has published technical papers on power distribution systems, induction machine control, and the design of synchronous reluctance machines.…”

Section: Appendix Torque Calculation With Saturating Rotor Leakagementioning

confidence: 78%

Stator-flux-based vector control of induction machines in magnetic saturation

Hofmann¹,

Sanders²,

Sullivan³

IAS '95. Conference Record of the 1995 IEEE Industry Applications Conference Thirtieth IAS Annual Meeting

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Abstract-In many variable-torque applications of induction machines, it is desirable to operate the machine at high flux levels, thus allowing the machine to produce higher torques. This can lead to saturation of the main flux path, introducing crosscoupling effects which can severely disrupt the performance of controllers dependent on knowledge of the machine's magnetic parameters. Stator-flux-oriented torque-control schemes need not depend on the magnetic parameters of the machine and, hence, are potentially more robust and easier to implement in magnetic saturation than rotor-flux-oriented control. In this paper, we present and analyze a stator-flux-oriented torque-control scheme. This controller only requires knowledge of the stator voltage, stator current, and stator resistance. An analytical expression for the maximum achievable torque output of the machine using a linear magnetics model is compared with values calculated using a nonlinear magnetics model incorporating saturation of the main flux path and is shown to be a good approximation at high flux levels, when the main flux path is heavily saturated. Experiments carried out on a 3-hp 1800-r/min wound-rotor induction machine show smooth operation of the control scheme at torque levels up to at least four times rated torque.

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Section: Appendix Torque Calculation With Saturating Rotor Leakagementioning

confidence: 78%

Stator-flux-based vector control of induction machines in magnetic saturation

Hofmann¹,

Sanders²,

Sullivan³

IAS '95. Conference Record of the 1995 IEEE Industry Applications Conference Thirtieth IAS Annual Meeting

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show abstract

Section: Appendix Torque Calculation With Saturating Rotor Leakagementioning

confidence: 85%

“…We attempt to cancel the fundamental component of this voltage by subtracting it from . This technique is motivated by the describing function method and has been reported to be effective in [29].…”

Section: Methodsmentioning

confidence: 99%

Stator-flux-based vector control of induction machines in magnetic saturation

Hofmann

Sanders

Sullivan

1997

IEEE Trans. on Ind. Applicat.

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In many variable-torque applications of induction machines, it is desirable to operate the machine at high flux levels, thus allowing the machine to produce higher torques. This can lead to saturation of the main flux path, introducing crosscoupling effects which can severely disrupt the performance of controllers dependent on knowledge of the machine's magnetic parameters. Stator-flux-oriented torque-control schemes need not depend on the magnetic parameters of the machine and, hence, are potentially more robust and easier to implement in magnetic saturation than rotor-flux-oriented control. In this paper, we present and analyze a stator-flux-oriented torque-control scheme. This controller only requires knowledge of the stator voltage, stator current, and stator resistance. An analytical expression for the maximum achievable torque output of the machine using a linear magnetics model is compared with values calculated using a nonlinear magnetics model incorporating saturation of the main flux path and is shown to be a good approximation at high flux levels, when the main flux path is heavily saturated. Experiments carried out on a 3-hp 1800-r/min wound-rotor induction machine show smooth operation of the control scheme at torque levels up to at least four times rated torque.

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“…To avoid shorting the DC voltage bus, the gate pulses of the upper and lower transistors on the same switch pole need to be separated by the dead-time. The dead-time causes output voltage error and results in decreased fundamental voltage, current distortion, and motor torque ripples (1) (2) . The dead-time also affects the current tracking performance even if the inverter operates under the current control mode (3) .…”

Section: Introductionmentioning

confidence: 99%

An Integrated Pulse Width Modulator/Dead-time Generator with Improved Output Voltage Precision

2006

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This paper presents an integrated pulse width modulator with dead-time generation capability. The proposed modulator can place proper dead-time around gating pulses while maintaining the correct volt-second of the output voltage on a pulse-by-pulse basis. The proposed method is suitable for digital implementation of the pulsewidth modulator (PWM). Compared to the conventional dead-time compensation by average voltage correction, the proposed method provides improved accuracy of output voltages and hence better dynamic response. Experimental results on a variable speed drive platform and a shunt active filter platform are provided to verify the proposed method. Comparisons with the conventional dead-time generation and compensation method on the same platforms are also presented. Fig. 1 shows a typical inverter switch pole with transistors T A1 , T A2 , and free wheeling diodes D 1 , D 2 . Dead-time is introduced between the gate signals of T A1 , and T A2 to avoid shorting the DC bus.During the dead-time the output voltage is determined by the polarity of the current, rather than the PWM gate signal. In order to maintain the correct timing and volt.-sec. of the output voltage pulse, the proposed scheme uses main PWM carrier T ri, and the auxiliary carriers T ri + and T ri − as illustrated in Fig. 2. For positive output current, ie. i > 0, the free-wheeling diode D 2 conducts during the dead-time, thus forcing the actual output voltage V AN to follow the ideal upper switch gate pulse V g10 . V g10 . So the actual gate pulse V g1 is generated by comparing V re f and T ri , and is maintained identical to V g10 . To place proper dead-time, V g2 is generated by comparing V re f and T ri− , so the dead-time T d is created between the actual gate pulses V g1 and V g2 as illustrated in Fig. 2. For negative output current, ie. i < 0, V re f is compared to T ri and T ri + to produce the gate pulses.The proposed integrated pulse-width modulator provides a solution to integrate the dead-time generator and the pulse-width modulator altogether. The proposed method is very convenient for digital implementation, as it is implemented on a CPLD in this paper. The proposed method produces output voltage pulses which are identical to the ideal gate pulses without any time delay. The dead-time placement also ensures the correctness of volt.-sec. on a per pulse basis. The proposed method is verified by a conventional V/ f inverter drive, and the motor current distortion is clearly improved.The shunt active filter test shows even more improvement in the precision of the current-controlled inverter. Non-memberHung-Chih Lin * Non-memberChung-Chuan Hou * Non-memberThis paper presents an integrated pulse width modulator with dead-time generation capability. The proposed modulator can place proper dead-time around gating pulses while maintaining the correct volt-second of the output voltage on a pulse-by-pulse basis. The proposed method is suitable for digital implementation of PWM, and the required computational resource is very low. Com...

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Simplified model and corrective measures for induction motor instability caused by PWM inverter blanking time

Cited by 44 publications

References 6 publications

Stator-flux-based vector control of induction machines in magnetic saturation

Stator-flux-based vector control of induction machines in magnetic saturation

Stator-flux-based vector control of induction machines in magnetic saturation

An Integrated Pulse Width Modulator/Dead-time Generator with Improved Output Voltage Precision

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