This paper proposes a new concept for the control of voltage-source inverter (VSI)-fed induction machines. The method uses a predictive algorithm and can be split into two parts. The purpose of the first part, i.e., predictive torque control (PTC), is to predict the stator reference flux vector corresponding to the reference torque at the end of the sampling interval. The second part of the method provides accurate tracing of the stator reference flux by selecting either an active or a zero voltage vector. This approach is called immediate flux control (IFC), where two possible variants are suggested. In the first variant, a simple and fast algorithm obtains minimal stator flux error by impressing either an active or a zero voltage vector throughout the entire sampling interval. Consequently, the switching frequency becomes very low, but current and torque ripple are considerable. The second IFC variant generates the stator flux more accurately by applying an active voltage vector only throughout a calculated time slot within a sampling interval, whereas, during the remaining time of the sampling interval, a zero voltage vector is impressed. As a result, higher switching frequency arises, but it is still lower than that with space vector modulation. Both IFC variants, together with PTC, require minimal processing time and were efficiently implemented in a digital signal processor, which controlled a 3-kW induction machine drive. The obtained experimental results confirm the validity of the proposed approach.

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This paper presents a low-cost fault-tolerant system for open-phase fault in a power converter fed permanent magnet synchronous machine. The proposed fault-tolerant system is based on field orientation control with additional fault tolerance functionality. A current predictive method for open-phase fault detection is presented, together with an estimation of the threshold level for detection. The proposed method is based on the prediction of stator current for the next sampling interval. Furthermore, a new method for post-fault operation of the machine is proposed. For optimal performance of the complete drive a pre-firing angle is introduced in order to avoid the temporary generation of negative torque. This improvement increases the average generated post-fault electromagnetic torque, and consequently it reduces the mechanical stress on various machine parts. The proposed fault detection and postfault operation solutions were simulated in Matlab, and they were also tested on an experimental setup. The results show several advantages of the proposed fault-tolerant solution, like its short fault-detection time, substantial robustness against variation of machine parameters or load fluctuations, and negligible implementation costs, since no hardware modifications are needed. The fault detection algorithm does not require high computing power, and it operates well even during transients.

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This paper presents a method for the detection of broken rotor bars in an induction motor. After introducing a simplified dynamic model of an induction motor with broken cage bars in a rotor field reference frame which allows for observation of its internal states, a fault detection algorithm is proposed. Two different motor estimation models are used, and the difference between their rotor flux angles is extracted. A particular frequency component in this signal appears only in the case of broken rotor bars. Consequently, the proposed algorithm is robust enough to load oscillations and/or machine temperature change, and also indicates the fault severity. The method has been verified at different operating points by simulations as well as experimentally. The fault detection is reliable even in cases where traditional methods give ambiguous verdicts.

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In this paper first a current predictive method for single open-phase fault detection in a three phase drive with a permanent magnet synchronous machine is presented. The proposed method is based on a predictive stator current calculation. For each sampling interval the difference between the actual stator current and its predicted value in a previous sampling interval is calculated. To identify the location of a single open-phase fault, an identification method is presented which is based on the analysis of the stator current vector angle. After the single open-phase fault is detected and identified it is desirable for the electrical machine to continue operating with a reduced number of phases. For this purpose, a modified direct torque control algorithm for the fault-tolerant control is implemented. In order to improve the performance of the drive, a pre-firing angle is additionally introduced. All proposed methods have been simulated in Matlab/Simulink and verified on an experimental model. Detekcija odspojene faze i na kvarove otporno upravljanje pretvaračem napajanim sinkronim motorom s permanentnim magnetima. Učlanku je prvo predstavljena metoda za detekciju kvara odspojene faze u trofaznom elektromotornom pogonu sa sinkronim motorom s permanentim magnetima zasnovana na predikciji struja statora. U svakom koraku uzorkovanja računa se razlika izmeu trenutne mjerene struje statora i prediktirane vrijednosti iz prethodnog koraka. U svrhu odreivanja lokacije odspojene faze, predstavljena je metoda identifikacije zasnovana na analizi kuta vektora struje statora. Nakon otkrivene i utvrene odspojene faze, poželjno je nastaviti rad električnog stroja sa smanjenim brojem faza. U ovu svrhu implementiran je izmijenjeni algoritam izravnog upravljanja momentom za postizanje na kvarove otpornog upravljanja. Da bi se unaprijedilo vladanje sustava elektromotornog pogona, dodatno je uveden kut prethoenja aktivacije impulsa. Sve predložene metode simulirane su u Matlab/Simulink okruženju i provjerene na eksperimentalnom postavu.Ključne riječi: Sinkroni motor s permanentnim magnetima, na kvarove otporan sustav, kvar jedne odspojene faze, na kvarove otporno upravljanje, kut prethoenja aktivacije impulsa

This study presents a model-based method for detecting an open-circuit fault in battery supply unit feeding a permanent magnet synchronous motor. Apart from the commonly present DC voltage sensor at converter's input, no additional sensors are required. As a first step, the DC supply system is modelled as a lumped parameter electric circuit. Further, a procedure for estimation of DC supply voltage based on inverter's current and open-circuit battery voltage is proposed. A sliding mode observer is then used to obtain the actual value of open-circuit battery voltage, required by the modelling algorithm. Consequently, an open-circuit fault in a DC supply circuitry is determined based on the analysis of discrepancy between the estimated and measured DC supply voltage. Detection algorithm has been tested on a laboratory setup and its functionality is confirmed by experimental results.