Sliding Mode Pulsewidth Modulation

This paper presents sliding mode pulsewidth modulation (SMPWM) control methodologies for a current-controlled inverter. Discussion begins with circuit analysis and the selection of proper references. Based on this formulation, switching methodologies are developed. Two novel approaches adopting the sliding mode concept are proposed to make the system tracking reference inputs. Phase currents and the neutral point voltage are controlled simultaneously. Optimization of different operational criteria is offered by SMPWM via the control of neutral point voltage. Simulations and experiments are carried out to confirm the effectiveness of proposed control algorithms.

I. Introduction

The output current control of an inverter appears frequently in applications such as ac motor driving. Various pulsewidth modulation (PWM) control technologies are being used in inverter control. For example, sine-triangle PWM [1], harmonic elimination PWM [2], [3], hysteresis band control, space vector PWM [4]–[6], hybrid PWM [7], etc. Some of these approaches are open-loop control using a pre-calculated switching pattern, such as harmonic elimination PWM. Some of them are close-loop control whose switching action depends on feedback information, such as hysteresis band PWM approach. Some of them can be used in both open-loop and close-loop schemes, such as space vector PWM [4]. Performance of an inverter is evaluated in different aspects, for example reference tracking ability, harmonic loss factor, robustness against variation of circuit parameters and disturbances, etc. Comparative studies of different PWM techniques can be found in [8], [9], and other literature.