A Multilevel Inverter Scheme With Dodecagonal Voltage Space Vectors Based on Flying Capacitor Topology for Induction Motor Drives

Abstract

This paper presents a multilevel inverter topology suitable for the generation of dodecagonal space vectors instead of hexagonal space vectors as in the case of conventional schemes. This feature eliminates all the 6n ± 1 (n = odd) harmonics from the phase voltages and currents in the entire modulation range with an increase in the linear modulation range. The topology is realized by flying capacitor-based three-level inverters feeding from two ends of an open-end winding induction motor with asymmetric dc links. The flying capacitor voltages are tightly controlled throughout the modulation range using redundant switching states for any load power factor. A simple and fast carrier-based space-vector pulsewidth modulation (PWM) scheme is also proposed for the topology which utilizes only the sampled amplitudes of the reference wave for the PWM timing computation. Index Terms-Dodecagonal space vectors, flying capacitor, multilevel inverters, open-end winding, space-vector pulsewidth modulation (PWM).

A Dual Three-Level Inverter Based Open-end Winding Induction Motor Drive with Averaged Zero-Sequence Voltage Elimination and Neutral-Point Voltage Balance

“…The main difference between Fig.6 and Fig.8 is that in Fig.8, the share of the T0 between the two redundant switching states is a variable 'y', while in Fig.6 it is assumed the T0 is shared equally between the two switching states (T0/2). With (13) and (14) as well the relationship given earlier in (1), (2) and (5), the Toffset for eliminating the averaged zero-sequence voltage can be derived step by step as given in (15). (1 ) 1 2 1 ( ) 3 3 3 2 1 ( ) 3 3 2 1 ( ) 3 3 2 2 2 2 ( ) 3 3 3 3 2 3 T y T T T T T T T T T T T T T T T T T T T T T T As can be seen, the necessary condition to eliminate the averaged zero-sequence voltage is to simply set the Toffset=2/3Ts.…”

“…It will also generate unintended losses and affect the normal operation and control. To solve this problem, two isolated dc power supplies are adopted to feed each individual inverter to cut off the route of the zero-sequence current [14,15]. However, using isolated dc power supplies increases the cost of the system and moreover it is not practical for a four-quadrant operation where regenerative energy is required.…”

A Hybrid Modulation Strategy with Reduced Switching Losses and Neutral Point Potential Balance for Three-Level NPC Inverter

“…3 (a). As the output voltage of each phase has three levels, 3 3 space voltage vectors can be obtained in the three-level inverter. Table 1.…”

“…Multilevel inverter topologies have received special attention during the last two decades due to their significant contributions to medium/high-voltage and highpower applications [1], such as ac motor drives [2,3], electric energy quality management and reactive power compensation [4,5]. Even in low-power low-voltage fields, this topology is used in more and more applications [6,7].…”

Improved SHEPWM Strategy By The Robustness Optimization Algorithm In Multilevel Inverters With Equal DC Sources

“…The most common topologies which are used in the prior article for multilevel inverter are included cascaded full bridge structure [7][8][9], the diode clamped structure [10] and flying capacitor structure [11]. The full-bridge structure needs fewer components to produce the same output waveform.…”