Abstract: Three-level Neutral-Point Clamped (NPC) inverter
has become established to be a preferred topology for medium-power motor drive applications
operating at several kilovolts. Still several research
continues to find solutions to the problem of maintaining a stable
neutral-point voltage in the converter.
This paper presents the analysis and simulation of a three-level
diode-clamped multilevel inverter, employing a sine-triangle modulator with
addition of continuous variable offset voltage which regulates the midpoint
potential of the dc bus. By maintaining dc-bus voltage balance, a significant
reduction in the voltage distortion at the neutral point and also allowing a
definitive reduction in the required dc bus capacitance. The effectiveness of
the Pulse Width
Modulation (PWM) strategies developed with continuous offset addition is
demonstrated by MATLAB/SIMULINK based simulation presented in this paper.
Keywords: NPC inverter; 3 phase induction motor; offset addition; carrier based PWM; dq theory; pi control