Harmonic Suppression Strategies and Seamless Transfer Control between Grid-Connected and Islanding Modes in Renewable Energy System for Hydrogen Production

In recent years, using renewable energy to produce hydrogen has become one of the important ways to achieve carbon peak and carbon neutralization. However, thyristor rectifiers are commonly used in industry hydrogen production systems (HPS), which may bring power quality problems such as current harmonics. Besides, renewable energy system for hydrogen production (RSHP) is expected to operate in both grid-connected and islanding mode. Thus, it is necessary to propose uninterruptible harmonic suppression strategies, and have seamless transition between these two modes. Firstly, this paper proposes the impedance regulation strategy for islanding mode and direct harmonic compensation strategy for grid-connected mode, since the harmonic characteristics and control objectives of RSHP in two modes is different. On this basis, the improved voltage loop and the improved phase-locked loop are developed to enable a smooth transition between the grid-connected and islanding mode of the RSHP. Finally, Simulation results verifies the effectiveness of the proposed control strategies.