Artur Cichowski

Open-Transistor Fault Diagnostics in Voltage-Source Inverters by Analyzing the Load Currents

A novel method is presented for the detection and isolation of open-transistor faults in voltage-source inverters feeding AC motors. The method is an extension of the normalized DC-components method. The normalized average currents are combined with additional diagnostic variables which convey information about the percentage of time spent by the phase currents in the near-zero zone. The combined diagnostic signals permit much more robust diagnostics of single-transistor faults and make feasible the diagnostics of multiple-transistor faults. Suggested in this paper is also an alternative solution for the normalization of DC components, which is easier interpreted and simpler to implement.

Self-tuning dead-time compensation method for voltage-source inverters

A new method of dead-time compensation is proposed, capable of self-tuning to the inverter and load properties. The tuning, performed real-time, relies on parameter selection of a generic compensation characteristic. During the parameter search, the quality of compensation is being continuously assessed against the harmonic distortion of output currents. The method enjoys very effective compensation of both harmonic and linear distortion caused by dead time and other parasitic agents.

Real-time fault detection and localization vector-controlled induction motor drives

This paper addresses real-time diagnostics of vector-controlled induction motor drives. The fault type considered is the open transistor in the voltage source inverter (VSI). The proposed methods are capable of diagnosing both permanent failures and short-time faults of inverter transistors. They require no extra hardware on top of that normally used for basic control purposes. The methods have been verified by simulation and laboratory experiments

Modeling the effect of parasitic capacitances on the dead-time distortion in multilevel NPC inverters

A simple model is derived and verified for evaluating the effect of parasitic capacitances on the dead-time related voltage distortion in multilevel NPC voltage source inverters. The model permits well-defined and precise compensation of dead-time distortion, exhibiting meaningful improvement on compensation methods neglecting the effects of parasitic capacitances. A simple formula is given for evaluating the capacitances as serial / parallel connections of transistor capacitances and external capacitances (introduced by the cables and load).

Sensorless startup of super high speed permanent magnet motor

The aim of this paper is to present the method of sensorless startup of super high speed permanent magnet motor. Two types of control methods are taken into consideration. In the first part of the startup the current mode as a control strategy was used. In this article the mode of switching the control strategies from the current mode to the vector control is proposed. The extended Kalman filter (EKF) and the unscented Kalman filter (UKF) were used in the vector control for angular velocity estimation. There is also presented the influence of accuracy of the voltage distortion compensation on the control quality.

Evaluation of selected diagnostic variables for the purpose of assessing the ageing effects in high-power IGBTs

A method is presented and discussed whereby to evaluate two basic diagnostic variables that can be used in the assessment of the health of high-power IGBT packs. The proposed approach attempts to adapt a laboratory-grade method known from the literature for the use on board electric traction vehicles. The diagnostic variables in question are the junction-to-case thermal resistance and the collector-emitter saturation voltage. These variables can be used in the assessment of the depth of IGBT structure delamination and wire-bond lift-off. The proposed approach has been partially validated by experiment.

Shaping the SPL spectra of the acoustic noise emitted by inverter-fed induction motors

Acoustic noise emissions from PWM-VSI driven induction motors is a serious environmental problem. This paper reports on a novel approach to alleviating this problem by influencing the spectra of the sound pressure level (SPL) of the emitted noise. The main objective of the method is a reduction of the effect of mechanical resonances on the resultant SPL spectra. In the first step, the resonances are being identified by using a random pulse width modulation (RPWM) with a uniform probability density function (PDF) of the carrier frequency or, alternatively, by using the sigma-delta modulation (SDM); in the latter case, the current spectrum is inherently flat. Then, the target PDF is being constructed so as to account for the machine properties (notably by avoiding mechanical resonances). The initial results obtained using this approach are promising, particularly in terms of lower acoustic power concentrated in the vicinity of resonance frequencies (as compared to the case of uniform PDF). The resultant noise profile is less annoying to the human ear. Moreover, the total SPL can also be reduced.

Comprehensive distortion compensation of grid-connected inverter currents

The paper presents a comprehensive approach to the compensation of phase current distortion of grid-connected power inverters. Four different sources of current distortion are addressed: imperfect grid synchronization caused by the distortion in the grid voltages, voltage fluctuations in the dc link, time delays in the estimation of grid voltages, and the distortion of inverter output voltages due to dead-time effects and related factors.

Comprehensive compensation of grid current distortion by shunt active power filters

The paper presents a comprehensive approach to the compensation of grid current distortion in shunt active power filter systems. Four sources of current distortion are addressed: imperfect grid synchronization caused by the distortion in the grid voltages, time delays in the evaluation of grid voltages and computation of compensating currents, fluctuations of the dc bus voltage, and the distortion of inverter output voltages due to dead-time effects and related factors. The focus of the paper is on the assessment of the significance of the proposed improvements in the control algorithm for the reduction of harmonic distortion of grid currents.

Simulation of the remanence influence on the transient states of the single-phase transformer including feedback Preisach model

This paper presents the results of the experimental and simulation investigation concerning the influence of remanence in the core of a single-phase transformer at the no-load transient state. Experimental studies consisted of the discharge of the capacitor through the primary winding at several different values of the residual magnetic flux. The paper presents a model of the transformer test system, taking into account the magnetic hysteresis phenomenon based on the Preisach model with feedback. The model was used to simulate the transient and steady state of the test system, taking into account the value and the sign of the remanence in the toroidal tape wound core. It was concluded that the induction of remanence has a significant impact on the value of the inrush current. This model can be used for simulation of the transformer systems transient state, taking into account the magnetic hysteresis and the remanence.