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The high common-mode voltage (CMV) generated by conventional synchronized space vector pulsewidth modulation (SVPWM) strategies may lead to bearing failure and electromagnetic interference problems. However, existing CMV reduction methods are based on asynchronized SVPWM, which will cause unacceptable harmonic distortion at low switching frequency. In this article, four modified synchronized SVPWM (MS-SVPWM) strategies are presented to reduce the CMV and improve the output performance of three-phase voltage source inverters (VSIs) at low switching frequency. In the proposed methods, only nonzero vectors are employed to reduce CMV, and the constraint conditions of preserving three-phase, half-wave, and quarter-wave symmetries of PWM waveforms in terms of active vectors are established. A precorrection scheme is proposed and applied to the presented MS-SVPWM strategies to achieve an accurate output voltage of inverters. Moreover, the linearity characteristics of the output voltage, the harmonic performance of line-line voltage and CMV, and the stator flux trajectories of the proposed strategies are investigated and compared. Experimental results for a 2.2-kW induction motor fed by a two-level VSI are presented to illustrate the effectiveness of the proposed MS-SVPWM strategies. [ABSTRACT FROM AUTHOR]

Single-phase pulse-width modulation (PWM) rectifier is commonly used in a high-speed railway electric traction system. Occurrence of unexpected failure in the sensors of the detection system may lead to feedback values deviation and system degradation, which can be extremely detrimental to the operation safety of the electric locomotive. This paper presents a fast and reliable fault diagnosis and fault resilient control strategy for catenary current and dc-link voltage sensor faults in the control system for an electric traction single-phase PWM rectifier. Sliding mode observers are designed to produce analytical redundancy. In order to avoid unobservable states and fluctuation introduced by discrete dynamics in observer design, a novel description for switching variables is presented in system modeling. Normalized residuals are generated using measured and observed values. The fault diagnosis unit proposed can detect and isolate three types of sensor faults online by comparing residuals with thresholds. System reconfiguration is realized by substituting the observed values for the information of faulty sensors. Simulation and experimental results are demonstrated to validate the effectiveness of the strategy. [ABSTRACT FROM AUTHOR]