In the area of power quality conditioners, the series hybrid active power filter (SHAPF) has been focused more in recent times because of its multi-functionality and lower inverter rating requirement. Existing control strategies for SHAPF are based on extracting either source current harmonics or load voltage harmonics. In this study, a novel control scheme based on decomposing multiphase voltage vector into different vectors that represent different components of power is proposed for SHAPF. The mathematical formulation of the proposed control scheme with its applications to SHAPF is presented. The validity of the proposed control scheme is verified by simulation as well as experimental study.
In this study, a selective harmonic elimination (SHE)-pulse-amplitude modulation method is suggested for the cascaded multilevel inverters. This method is based on the balancing of the voltage-second area under the output voltage waveform and reference sinusoidal signal. The proposed method is free from the conventional transcendental SHE equations as it is based on a composite midpoint rule of numerical integration which works on linear equations. Reduced computational burden enables real-time implementation of the proposed method with great ease even for the inverter with a huge number of levels. The switching angles remain constant for an inverter while the output voltage is controlled by varying voltage of dc sources linearly. The proposed method eliminates more harmonics and offers reduced total harmonic distortion (THD) in comparison to the conventional SHE methods without amplifying the amplitude of higher order harmonics. THD of the output voltage remains constant with variation in modulation index. Performance analysis of the suggested method is validated with simulation and experimental studies on cascaded H-bridge inverter.
The currents drawn by three-phase diode rectifiers with capacitive filters under unbalanced supply conditions are highly non-linear and unbalanced. This configuration draws significantly unbalanced currents even with smaller percentage of unbalance in supply voltages and more unbalance in supply voltages leads to an extreme unbalanced situation like single phasing. This study highlights the unbalance line current problem observed in three-phase diode rectifier and proposes its compensation using series hybrid active power filter (SHAPF) working with appropriate control strategy. Four distinct modes of operation under unbalanced supply are identified. A new control algorithm which simultaneously compensates for supply voltage unbalance and source current harmonics is applied to compensate the configuration. An experimental model of three-phase diode rectifier with capacitive filter working under different supply situation is developed to establish identified modes of operation. This configuration is compensated with SHAPF, manufactured using ARM Cortex M4-based microcontroller and the results of compensation are described in this study.
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