Investigations on Generalization of Current Error Space Phasor Based Pulse Width Modulation Controller for Multi Level Front End Converters

Abstract

Three-phase ac-dc converters are integral part of many industrial applications. Diode and newlinethyristor based rectifiers are classical examples of unidirectional non-linear loads. To mitigate newlinethe current harmonics generated by these rectifiers, and to improve the quality of power, newlinepassive and/or active power filters are suggested in literature. Filters provide costly solution newlinefor power quality improvement by demanding additional hardware. Hence, it is always newlinepreferred to produce the converter which do not create such issues. Multi-pulse rectifiers are newlineused for power quality improvement in high-power applications, but they require phase newlineshifting transformers which make system bulky and costly. IGBT based multi-level converters newlineare used as front-end topology for high-power applications with bi-directional power flow newlinecapability. Most of the high-performance converters employ current controlled pulse width newlinemodulation techniques for fast dynamic response and inherent protection against overcurrents. newlineSelection of current control strategy is very crucial in the case of front-end converter (FEC), newlineas it directly affects the performance of converter in terms of improvement in harmonic newlineprofile of source current and obtaining unity power factor at supply side in association with newlinegood dynamic response. newlineCurrent error space phasor based hysteresis controller (CESP based HC) is proposed in this newlinethesis. The controller deals with current error space phasor, which signifies the combined newlineeffect of the current errors in the individual phases. It monitors the movement of CESP and newlineenables the use of zero voltage vector along with active voltage vectors of FEC. The newlinecontroller allows switching of only adjacent voltage vectors in a given sector of voltage space newlinephasor structure of FEC, which eliminates the selection of random voltage vectors, as newlineobserved with conventional hysteresis controller. The proposed controller ensures effective newlinetracking of actual current with reference current by continuously restricting the current error newlinespace phasor