Andrzej M. Trzynadlowski

A comparative study of control techniques for PWM rectifiers in AC adjustable speed drives

Four control techniques for pulse-width modulation (PWM) rectifiers in AC adjustable speed drives are presented. In particular, the so-called virtual-flux oriented control (VFOC) and virtual-flux based direct power control (VF-DPC) schemes are described and compared with their voltage based counterparts. These are the voltage oriented control (VOC) and voltage-based direct power control (V-DPC) techniques. Theoretical background is provided, and results of computer simulations and laboratory experiments are given, documenting advantages and disadvantages of the individual control strategies.

Minimum-loss vector PWM strategy for three-phase inverters

A novel vector PWM method for three-phase voltage-controlled inverters is described. The so-called minimum-loss vector PWM (MLVPWM) strategy is characterized by the minimum amount of switching losses incurred in the inverter switches. Comparative analysis proving superiority of the MLVPWM technique over the existing regular-sampling PWM methods, and results of experimental investigation of a prototype modulator are presented. >

Random pulse width modulation techniques for converter fed drive systems-a review

A review of the state of the art in RPWM (random pulse width modulation) theory and practice is presented. Topics covered include principles of RPWM, means of randomization, a review of the existing RPWM techniques, power spectra, implementation issues, and documented effects of RPWM on electric drive systems. A number of RWPM strategies have been reported, and a beneficial impact on acoustic noise and vibration has been unamiously agreed upon. Published studies have proven that significant improvement of the acoustic noise characteristics of the motors can be achieved at practically no extra expense in comparison with the systems with traditional, deterministic PWM strategies.<<ETX>>

Space vector PWM technique with minimum switching losses and a variable pulse rate [for VSI]

A novel randomized control strategy for three-phase voltage source inverters, based on voltage space vectors, is described. An implicit asymmetrical modulating function results in switching losses in the inverter being reduced by about half in comparison with those using the classic space vector pulsewidth PWM method. The pulse rate is varied within individual 60/spl deg/ sectors of the vector plane, so that the power spectra of the output voltage are spread over a wide frequency range and acquire a continuous part. Relevant theoretical analyses, computer simulations and experimental results are presented.

Instantaneous stator power as a medium for the signature analysis of induction motors

Preventive maintenance of electric drive systems with induction motors involves continuous monitoring of operation, to detect electrical and mechanical conditions that may lead to a failure. Intensive research efforts have, for some time, been focused on motor current signature analysis (MCSA). MCSA techniques utilize results of spectral analysis of the stator current of an induction motor to diagnose abnormal conditions both in the motor and driven system. Reliable interpretation of the current spectra is difficult, as distortions of the current waveform caused by abnormalities in the drive system are usually minute. In this paper, an alternate medium for motor signature analysis, namely the instantaneous stator power, is proposed. It is shown, both by computer simulations and laboratory experiments, that the instantaneous power carries more information than the current itself, since not only the current magnitude but also the phase shift between the current and voltage waveforms are affected by irregularities in the motor or other parts of the drive system. Utilization of the instantaneous stator power as a medium for signature analysis opens new possibilities in the automated diagnosis of induction motor drives.

Comparative investigation of diagnostic media for induction motors: a case of rotor cage faults

Results of a comparative experimental investigation of various media for noninvasive diagnosis of rotor faults in induction motors are presented. Stator voltages and currents in an induction motor were measured, recorded, and employed for computation of the partial and total input powers and of the estimated torque. Waveforms of the current, partial powers p/sub AB/ and p/sub CB/, total power, and estimated torque were subsequently analyzed using the fast Fourier transform. Several rotor cage faults of increasing severity were studied with various load levels. The partial input power p/sub CB/ was observed to exhibit the highest sensitivity to rotor faults. This medium is also the most reliable, as it includes a multiplicity of fault-induced spectral components.

Power spectra of a PWM inverter with randomized pulse position

Random pulse width modulation in static power converters results in the partial transfer of power from the discrete spectrum of the output voltage to the continuous spectrum, with advantageous effects on the operation of the supplied electromechanical systems. In this paper, a random PWM technique with randomized pulse position for three-phase voltage-controlled inverters is analyzed. Closed-form equations for the discrete and continuous power spectra of the line-to-line and line-to-neutral voltages of the inverter have been derived and confirmed by experiments. Presented theory opens the way to numerical optimization of the voltage spectra of randomly modulated inverters. >

Random pulse-width modulation technique for voltage-controlled power inverters

As an alternative to the existing deterministic pulse-width modulation methods, a random pulse-width modulation technique for voltage-controlled power inverters is proposed. Advantages of the technique include non-repetitiveness of the switching pattern, simplicity of the hardware, and uncommonly high limits of switching frequency. A prototype random pulse-width modulator is described and experimental results are presented.

Robust Nonlinear Predictive Controller for Permanent-Magnet Synchronous Motors With an Optimized Cost Function

A robust nonlinear predictive controller for permanent-magnet synchronous motors is proposed. The nonlinear predictive control law is formulated by optimizing a novel cost function. A key feature of the proposed control is that it does not require the knowledge of the external perturbation and parameter uncertainties to enhance the robustness. A zero steady-state error is guaranteed by an integral action of the controller. The stability of the closed-loop system is ensured by convergence of the output-tracking error to the origin. The proposed control strategy is verified via simulation and experiment. High performance with respect to speed tracking and current control of the motor has been demonstrated.

A novel random PWM technique with low computational overhead and constant sampling frequency for high-volume, low-cost applications

A novel random pulse-width modulation (PWM) technique for three-phase voltage-source inverters, characterized by low computational overhead, a variable switching frequency, and a constant sampling frequency, is presented. The technique is based on two strategies: 1) the so-called arithmetic PWM (APWM), which yields the same switching patterns as the classic space-vector modulation, but with minimal computational effort and 2) randomization of switching periods by varying the delay of switching cycles with respect to corresponding sampling cycles. Simplicity of the technique, named a variable-delay random PWM (VDRPWM) method, allows its implementation in cheap, low-end processors. It makes the VDRPWM the best choice for high-volume, low-cost applications, such as domestic and automotive ac drives and UPSs. The random aspect of the technique has a mitigating effect on the acoustic and electromagnetic noise emitted by the supplied system. This feature has been confirmed by experiments with a 40-hp induction motor drive.