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A multilevel dodecagonal voltage space vector generation scheme for variable-speed drive applications with single-dc-link operation requires a large value of capacitance for cascaded H-bridge (CHB) filters, when operated at lower speeds. In existing schemes, the multilevel dodecagonal structure is obtained by cascading a flying capacitor inverter with a CHB. In this paper, a new scheme has been proposed to minimize the capacitance requirement for full speed operation by creating vector redundancies using modular and equal voltage CHBs. Also, an algorithm has been developed to optimize the selection of vector redundancies among the CHBs in order to minimize the voltage ripple of the floating capacitors. The proposed algorithm considers instantaneous capacitor voltages and phase currents for optimal selection of vector redundancies. A mathematical model for capacitor voltage deviation is presented, and the effectiveness of the proposed algorithm is verified in both the simulation and the experiment. [ABSTRACT FROM AUTHOR]

Generating dense multilevel voltage space structure using polygons of higher sides is one of the novel and elegant method to suppress low-order harmonics and to obtain refined sinusoidal voltages using voltage source inverters for variable frequency drive application without passive filters. Apart from the advantages of conventional multilevel inverter topologies, schemes generating polygonal voltage space vector structure can equip full dc-bus utilization, low switching frequency strategies to eliminate low-order harmonics, and increased linear modulation range. In this paper, an induction motor drive scheme generating a highly dense multilevel 24-sided polygonal voltage space vector structure using a single dc source, which can eliminate harmonics till 23rd order from phase voltages, is presented. Cascaded power circuit topology with a flying capacitor inverter fed with a dc source and two low voltage floating capacitor fed H-bridge inverters is used. Detailed experimentally validated results, under scalar as well as indirect rotor field oriented control of induction motor are provided. Studies on voltage ripple and reactive energy in various floating capacitors, harmonic performance of output voltage for wide range of speed operation, are also included. [ABSTRACT FROM AUTHOR]

In this paper, a new inverter topology is proposed for generating a multilevel dodecagonal voltage space vector structure for open-end winding induction motor (IM) using a single dc source. Dodecagonal voltage space vector structure eliminates fifth- and seventh-order harmonic voltages from phase voltage output and hence eliminates the fifth- and seventh-order harmonic currents through the motor leading to removal of the dominant sixth-order torque ripple generation in the motor over the entire modulation range. Multilevel space vector structure generates output voltage with better THD and low dv/dt. In the proposed topology, two three-level inverters drive an open-end winding IM, one inverter from each side. DC-link of primary inverter is from a dc source which delivers the entire active power, whereas the secondary inverter dc-link is maintained by a capacitor, which is self balanced during the inverter operation. The PWM scheme implemented ensures low switching frequency for primary inverter. Secondary inverter operates at a small dc-link voltage. Hence, switching losses are small for both primary and secondary inverters. Experimental results show the elimination of fifth- and seventh-order harmonic voltages over the entire modulation range, validating effectiveness of the proposed multilevel inverter scheme. [ABSTRACT FROM PUBLISHER]