Analysis and Mitigation of Dead-Time Harmonics in the Single-Phase Full-Bridge PWM Converter With Repetitive Controllers

Abstract

Abstract-In order to prevent the power switching devices (e.g., the Insulated-Gate-Bipolar-Transistor, IGBT) from shootthrough in voltage source converters during a switching period, the dead time is added either in the hardware driver circuits of the IGBTs or implemented in software in Pulse-Width Modulation (PWM) schemes. Both solutions will contribute to a degradation of the injected current quality. As a consequence, the harmonics induced by the dead time (referred to as "dead time harmonics" hereafter) have to be compensated in order to achieve a satisfactory current quality as required by standards. In this paper, the emission mechanism of dead time harmonics in single-phase PWM inverters is thus presented considering the modulation schemes in details. More importantly, a repetitive controller has been adopted to eliminate the dead time effect in single-phase grid-connected PWM converters. The repetitive controller has been plugged into a proportional resonant-based fundamental current controller so as to mitigate the dead time harmonics and also maintain the control of the fundamentalfrequency grid current in terms of dynamics. Simulations and experiments are provided, which confirm that the repetitive controller can effectively compensate the dead time harmonics and other low-order distortions, and also it is a simple method without hardware modifications.

Control Strategies of Mitigating Dead-time Effect on Power Converters: An Overview

“…Dead time can be seen as a periodic disturbance signal that can be compensated by a repetitive controller [105]. Repetitive control is based on the internal model principle [106].…”

Limitations of Harmonics Control in Power Converters

“…Satisfactory results can be achieved only by advanced types of controllers that are usually implemented into the current control loop, e.g., resonant, multiple resonant, or repetitive controllers. Typical applications requiring a mitigation of harmonics are grid-connected in single-phase [4] and three-phase pulse width modulated (PWM) inverters [5,6], photovoltaic systems [7], uninterruptable power supplies [8,9], active power filters [10][11][12], and microgrids [13]. Moreover, harmonics control is used in permanent magnet synchronous machine drives to reduce torque ripple, to compensate for dead-time effects [14,15], or to improve efficiency [3].…”

“…While studies present various modifications or new approaches [4,13,16,17], all of them evaluate proposed solutions through comparison with other methods, instead of evaluating absolute performance. The current spectra or total harmonic distortion (THD) are compared in steady-state; the approach with the lowest harmonic content is deemed better.…”

“…), fail to do so without further comments by the authors. While in some cases additional harmonics can be caused due to the dead-time effects or output filter resonance, these two cases have been studied in detail and their effects and mitigations are well known [4,19]. In rare occasions when the authors noted the difference between the theoretical limits of their approach and measured results, these discrepancies were disregarded as either having a low enough amplitude [20][21][22] or occuring above the frequency band of interest [23].…”

Improving Performance of Three-Phase Slim DC-Link Drives Utilizing Virtual Positive Impedance-Based Active Damping Control

“…Owing to the harmonic problem, active damping control (ADC) and VPI can be used to decrease THD. Even through these methods achieve harmonics suppression, the cogging torque also needs to be solved by harmonic effect, because motor current harmonics cause the higher cogging torque [11][12][13][14][15][16]. When the 3DSVPWM aims to optimize switching waveforms, it can achieve a lower cogging torque.…”