Janusz Nieznanski

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.

Open-transistor fault diagnostics in voltage-source inverters by analyzing the load current

A novel method is presented for the detection and isolation of open-transistor faults in voltage-source inverters feeding low-power AC motors. The method is based on monitoring two diagnostic signals, one indicating sustained near-zero values of output current and thus permitting fault detection, the other permitting the isolation of the particular transistor which went faulty. The latter signal is the ratio of the average phase current and the average magnitude thereof. The method proves to work reliably, enabling detection and isolation of all possible cases of single and multiple faults. It enjoys high immunity to transients and noise and requires no extra hardware on top of that normally used for basic control purposes.

Performance characterization of vector sigma-delta modulation

The paper derives the idea of vector sigma-delta modulation (SDM) based on distortion minimization premises. It gives basic characterization of this modulation, along with comparisons with alternative SDM structures and space-vector PWM. The results obtained thus far show that the vector SDM definitely outperforms the other SDMs, while also providing an interesting alternative to the PWM, particularly for higher modulation indices. A DSP implementation of a vector SDM is also discussed, and sample test results are provided obtained in a simple inverter-fed induction motor drive.

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

Circuit-oriented model of the switched reluctance motor for drive systems simulation

Switched reluctance motors, unlike other types of motors, for their operation require a control system and the supply from a converter. For simulation purposes of the complete switched reluctance drive system it is desirable to have a circuit-oriented model of the switched reluctance motor. A circuit-oriented model is especially useful when simulations are to be made for different algorithms and control parameters. A method of modeling, the developed circuit-oriented model of the switched reluctance motor, and simulation results of the complete switched reluctance drive system are presented in the paper.

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.