Discontinuous Space Vector PWM Strategy for Three-Phase Three-Level Electric Vehicle Traction Inverter Fed Two-Phase Load

Abstract

Discontinuous pulse width modulation (DPWM) strategies are usually adopted to reduce the switching loss and output current ripple of three-phase three-level traction inverters under three-phase load conditions. However, if there is a short circuit in any arbitrary phase or the inverter is used to feed a two-phase load, the output performance of conventional DPWM strategies will be deteriorated. Here, four improved DPWM (IDPWM) strategies for three-phase three-level neutral-point-clamped (NPC) traction inverter fed two-phase load are proposed. Unlike three-phase load conditions, the phase angle and the amplitude of each basic voltage vector in the space vector diagram are modified under two-phase load conditions. Consequently, sectors are re-divided and duty cycles of basic vectors during synthesis are recalculated. Clamping intervals of each phase for the four type discontinuous PWM (DPWM) strategies are rearranged according to the modified space vector diagram; then, the proposed DPWM strategies can be obtained. Compared with the conventional DPWM strategies, the output current waveform quality of the proposed strategy is significantly improved. Meanwhile, the amplitude of the neutral-point voltage ripple is also reduced.

A New Control Approach of a Three-Phase Inverter Two Levels

“…A combinatorial analysis of all the possible states of the switches makes it possible to calculate the voltage vector ( v α , v β ), according to the System (1). [6] [20]…”

“…It consists in considering the three-phase system globally, and in applying a Concordia transformation to it to be brought back to the plane ( v α , v β ) [5] [20] [22]. The sampling time can then be represented as a single vector in this plane [6]. The major drawback of SVPWM is the enormous computational time required for its implementation due to the trigonometric functions used to determine the times T k and T k+1 [20].…”

“…and non-linear techniques (sliding mode control (SMC), space vector modulation (SVM), prediction, etc.) [3] [6] [7] [8] are available in the literature. Modulation theory has a major research area in signal transmission, signal processing, Analog-to-Digital Conversion (ADC), Digital-to-Analog Conversion (DAC) and control of power electronic converters and continues to attract considerable attention and interest [9] [10] [11].…”