Vladimir Blasko

Recent advances in power electronics technology for industrial and traction machine drives

This paper presents a review of the state of the art of power electronics technology in both industrial and traction drive application. Key development trends include the dominance of AC adjustable-speed drives in new applications, with the squirrel-cage induction machine as the preferred machine in most cases. Particularly striking has been the rapid ascendance of the insulated-gate bipolar transistor (IGBT) as the predominant power switch in both industrial and traction applications ranging from fractional kilowatts to multimegawatts. Key current issues such as industrial drive input power quality and the effects of fast IGBT switching transients on the machines and electromagnetic interference (EMI) production are reviewed. Developments in electric traction for both rail and road vehicles are discussed, including the increasing modularity of new traction inverters in all sizes and the market introduction of new hybrid vehicles using advanced power electronics. The paper concludes with a discussion of expected future trends in power electronics technology that will likely expand the markets for industrial and traction drives during coming years.

Simple efficiency maximizer for an adjustable frequency induction motor drive

A new method of efficiency maximization that utilizes sensing of the third-harmonic component of air-gap flux is proposed. This signal is used to determine the resulting instantaneous position of the fundamental component of the air gap flux and, consequently, the torque- and flux-producing components of the stator current. In addition, the third harmonic signal is also used to determine the rotor speed. Hence, the output power of the machine can be calculated with only a single sensor wire attached to the neutral point of the machine. The flux-producing component can be readily adjusted to produce the minimum input power for a fixed amount of output power (fixed speed). >

A modified C-dump converter for variable-reluctance machines

A type of converter for variable reluctance machine (VRM) drives is described. In this converter topology the energy extracted from an offgoing phase is stored in a dump capacitor. The energy stored is consequently used to either quickly turn on the next ongoing phase or energize the conducting phase frequently during the conduction interval instead of being returned to the supply as for a conventional C-dump circuit. Since the additional switch used to pass the energy to the C-dump capacitor is switched under a relatively low voltage condition and its switching frequency is relatively low, the rating of the additional switch is modest.<<ETX>>

Observer-Based Control Methods for Combined Source-Voltage Harmonics and Unbalance Disturbances in PWM Voltage-Source Converters

In this paper, computationally efficient sinusoidal-disturbance estimation and elimination methods are introduced into the control of an active front end (AFE) voltage-source converter (VSC) to achieve effective disturbance rejection in high power systems with slower pulsewidth-modulation switching frequencies (e.g., 5 kHz) and limited current-controller bandwidth. Since the active rectifier is in series with the source and the load, there is no need to add additional hardware for harmonic elimination. The input positive- and negative-sequence voltages are extracted using the new observer methods, and negative-sequence currents are injected to eliminate the dc-link 120-Hz ripple. The observer-based disturbance-rejection methods are proven to be very effective when all three types of disturbances (input-voltage harmonics, unbalance, and inductor unbalance) coexist simultaneously, even under input-inductance variations of 30%. Simulation results are verified experimentally using a 15-hp adjustable-speed-drive system that includes an AFE VSC coupled to a dSpace controller.

Observer-Based Active Damping of

Voltage source converters (VSCs) with

LCL

LCL

Resonance in Grid-Connected Voltage Source Converters

filters are attractive in grid-connected applications because they greatly reduce the pollution of the utility voltage due to switching harmonics. However,

New Control Method Including State Observer of Voltage Unbalance for Grid Voltage-Source Converters

LCL

Input Harmonic Estimation and Control Methods in Active Rectifiers

networks have very low impedance at frequencies close to the resonance, and therefore, even small voltage magnitudes at those frequencies can excite currents of large magnitudes or even cause instability. In this paper, a novel current controller structure is proposed that uses a Luenberger observer as a sensor replacement and state predictor to predict the filter capacitor current which is passed through a virtual resistor to achieve a damping effect. The predicted filter capacitor current through a virtual resistor is the inner fast loop, while the outer loop containing the appropriate feedforward terms ensures fast command tracking and zero steady-state error. The use of the predicted states alleviates the impact of computational and sampling delays which greatly improves the active damping (AD) capability. The proposed solution eliminates the need for additional sensors. This paper presents simulation and experimental results which demonstrate AD and the effectiveness of the virtual resistance in actively stiffening the input impedance of the AFE drive at frequencies close to resonance.

Low cost efficiency maximizer for an induction motor drive

New observer-based disturbance-estimation and control algorithms are introduced in this paper that compensate source voltage unbalances. The algorithms are also designed to compensate the detrimental impact of delay effects caused by the digital-signal processing. Consequently, these techniques are appropriate for higher power systems with reduced pulsewidth modulation switching frequency and limited current-controller bandwidth. Analytical, simulation, and experimental results are presented to illustrate the effectiveness of the new observer-based control techniques.