The Three-Level Zero Harmonic Distortion Grid-Forming Converter: A Practical Filterless Solution for Sinusoidal Voltages

The world is rapidly shifting from centralized power generation to distributed generation (DG) with renewable sources near consumers. This transition enhances voltage and frequency stability in microgrids (MGs) and islanded systems, thanks to inverter-based resources. This work introduces the Three-Level Zero Harmonic Distortion (ZHD) grid-forming converter, which produces a sinusoidal voltage without needing costly and inefficient capacitive filters that can cause resonance issues. By combining harmonic cancellation in a three-winding transformer with Selective Harmonic Elimination Pulse Width Modulation (SHE PWM), the ZHD converter maintains voltage and frequency delivering sinusoidal waveforms even under nonlinear loads. This paper aims to address the main elements of the Three-Level Zero Harmonic Distortion (ZHD) grid-forming concept, including practical implementation considerations, applicable topologies, and simulation results.