Modeling and design of filter networks for high power converters utilizing fast hard switching devices

Modeling and design of filter networks for high power converters has become an important research area in the last decade. High inverter switching speed, which has enabled adjustable speed drives to have greatly improved performance, has raised concerns related to its consequences. One of these concerns is the over-voltage at the motor terminals due to the impedance mismatch between cable and induction motor, depending on the voltage pulse rise time and power cable length.; One of the goals of this research is to develop accurate simulation models for cables and motors that allow a better understanding of the over-voltage problem. Frequency response of the cable and the motor winding are obtained experimentally and suitable models are developed for them to match the experimental results. The cable and induction motor models are implemented using a computational tool like MATLAB©, thereby providing a convenient method to analyze the over-voltage problems that are inherent in long cable PWM drives. A lossy line representation of the cable is proposed, modeled by distributed lumped elements. The model is used to evaluate the traveling wave voltage and an algebraic analysis is developed to choose an adequate number of segments as function of the pulse rise time and cable characteristics. Distributed-parameter representation of the power cable is also studied using the professional software PSCAD/EMTDC©, which is more suitable for very long cable PWM drives. Zero-sequence models for cable and motor are also developed aiming the calculation of the common-mode current. Simulation and experimental results are presented analyzing the over-voltage problem for a range of cable lengths for a standard 3 hp induction motor, showing the suitability of the developed simulation models.; Filter network approaches are suggested to mitigate the over-voltage problem and a filter design is obtained by the advance of the simulation tool built in MATLAB©. Experimental results are also obtained, confirming the suitability of the simulation analysis. Experimental results of the voltage distribution inside the machine winding are also presented demonstrating the impact of the filter topologies on the over-voltage mitigation.