Holistic modelling, control configuration, and design systematics for locally concentrated Multi-Motor Drive Systems - Follow-up application

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The subject of the project approved in 2017 were industrial reconfigurable multi-motor drive systems, i.e., drive systems in which several induction motors interconnected via a gearbox share the required power. The project was conducted by two departments of the Paderborn University in order to analyze and model both the electrotechnical and the mechanical engineering aspects. During the research work on the electrotechnical tasks, performed by the department of Power Electronics and Electrical Drives (LEA), new questions arose which are to be treated within a one-year follow-up project. In the previous project, LEA developed at first models of the inverter with which the phase voltages of a controlled induction motor can be estimated with high accuracy. Based on this voltage estimation and the modeling of numerous nonlinear electromagnetic effects of an induction motor, a structure for accurate torque and loss estimation was derived. The model parameters contained therein are identified offline using measurement data recorded on the test bench. This method was combined with a thermal model and it was shown for the first time that simultaneous electrical-thermal modeling and offline identification offers high potential for both accurate torque control and efficient operating strategy. These main results of the previous project were published in several conference and journal papers. So far, the electrical and thermal submodels were only slightly coupled. In the follow-up project, both domains are now integrated with respect to further important aspects such as the thermal influence on the saturation behavior of the motor and on the skin effect in the electrical conductors so that a highly accurate torque and temperature estimation of an induction motor is possible, thus exploiting the full potential of the approach. From this multi-domain model, an adaptive operating strategy is derived in the next step, in order to be able to operate a given motor in the complete operating range in an efficiency-optimal way and still with low demands on the necessary control hardware. In the literature, usually only individual nonlinearities of the motor are considered in the torque control or in the operating strategy, resulting in significant inaccuracies or avoidable losses. Further points of the follow-up project concern the structured procedure for optimized measurement data acquisition for offline identification and a detailed evaluation of the extent to which individual measurement variables (e.g. rotor temperature) can be dispensed with during identification.