Towards optimization of harmonic currents emissions in plants for production of green hydrogen

This paper aims to present one approach to minimise harmonic current emissions in electrolyser plants through optimal design and layout of electrolyser units and grid components under varying operating conditions. Harmonics pose significant challenges in power systems affecting the quality of supply, stability and efficiency. The methodology used involves modelling a green hydrogen plant and its harmonic-generating components using DigSILENT PowerFactory and conducting frequency domain simulations with the Harmonic Load Flow tool. Rectifiers in electrolyser units, key sources of harmonic emissions, are modelled as balanced harmonic current sources with its magnitudes and phase angles for each harmonic order. Harmonic voltages and currents at various busbars and lines are calculated using the respective harmonic impedances. Four primary scenarios were developed based on different electrolyser plant configurations, each with an 80 MW nominal capacity, comprising electrolyser units rated at either 1 MW or 5 MW. Located near to a 120 MW wind power plant, both plants are connected to the HV distribution network via a Point of Common Coupling (PCC). Extensive simulations identified an optimal configuration in each scenario with minimal harmonic current emissions. This study demonstrates that the harmonic emissions of electrolyser plants can be significantly reduced through optimal plant layout and operation of electrolysers, facilitating easier grid connection.