Control Performance Assessment of a Zero Harmonic Distortion Grid-Forming Converter for Medium Voltage Islanded Microgrids

Abstract

The world is currently witnessing a rapid transformation in the production and utilization of electrical energy. The traditional centralized generation model for electric power is swiftly evolving into a more decentralized system, known as Distributed Generation (DG), which incorporates renewable energy sources situated closer to end-users. This shift towards DG has paved the way for the emergence of grid-forming converters, which play a pivotal role in enhancing voltage and frequency stability within microgrids (MGs) and isolated applications. This study focuses on assessing the performance of the Zero Harmonic Distortion (ZHD) in both stand-alone and parallel operation modes. The distinctive feature of this converter lies in its inherent ability to generate a sinusoidal voltage source without the need for capacitive filtering components, which can adversely affect cost, efficiency, and size while potentially contributing to resonance problems. This is achieved through a judicious combination of harmonic cancellation within a three-winding transformer and the utilization of Selective Harmonic Elimination Pulse Width Modulation (SHE PWM) dismissing a closed-loop control structure. Simulation and hardware-in-the-loop results presented in this work demonstrate the satisfactory performance of the ZHD grid-forming converter.

Keywords

• distributed generation
• grid-forming converters
• ac microgrids
• power systems
• selective harmonic elimination
• power converters