Influence of Dead-time on Design of LCL-filter for Three-phase Voltage Source Converter

Abstract

Today, three-phase voltage source converters (VSC) are connected to the grid through LCL-filters. This is because the LCL-filters can achieve higher damping than L-filters for the same volume, i.e. price. For the purposes of the LCL-filter design and optimization procedures usually all nonlinearities of the converter are neglected. The dead-time is a safety measure used to prevent the simultaneous conduction of semiconductor switches in the same phase leg of a given converter. Essentially, it represents a nonlinearity introduced into the system. This paper focuses on the deadtime concept and its influence on three-phase VSC performance in steady-state. The influence of dead-time is analysed by comparing harmonic spectrums of the converter AC voltage and the current at the point of common coupling for various values of dead-time. The use of simulation model is a simple and straightforward way to carry out this analysis. The simulation results, obtained for the case of zero dead-time and double-edge naturally sampled pulse width modulation (PWM), are numerically validated by comparing harmonic spectrums with well-known analytical solutions for the selected PWM strategy. The results presented in this paper clearly show that the dead-time should not be omitted from the harmonic spectrum analysis, and from the filter design and optimization procedures. This indicates that similar analysis should be done for other nonlinearities present in the system.

Goran Majić

Assistant Professor | Department of Electrical Drives and Industrial Control

Marin Despalatović

Full Professor | Department of Electrical Drives and Industrial Control

Full professor at the Faculty of Electrical Engineering, Mechanical Engineering, and Naval Architecture in Split, where he teaches courses Electric Machines, Electric Drive Systems, and Electromechanical System Modeling. His research focuses on power systems, energy storage, and smart grid technologies, with active participation in multiple national and international projects aimed at advancing energy infrastructure and improving system stability.