Simulation and Analysis of Harmonic Current Emissions of Green Hydrogen Plant Using Harmonics Load Flow

The primary goal of this investigation is to minimize the harmonic current emissions ofelectrolyzer plants. This will be achieved by focusing on the optimal design and layoutof the electrolyzer units and their grid components under different operating conditionsrelated to their loading capacity. Harmonics pose a significant challenge in power systems,especially in renewable energy setups, as they can impact system efficiency and stability.
The methodology for this investigation involves modeling the green hydrogen plant and itscomponents responsible for generating harmonics in DigSILENT PowerFactory and performingsimulations in the frequency domain using the Harmonic Load Flow tool. The rectifiersof the electrolyzer units, which are significant sources of harmonic current emissions,are modeled as balanced harmonic current sources. The current emissions are providedwith their magnitudes and phase angles for the fundamental frequency and each harmonicorder. The harmonic voltages and harmonic currents at the different busbars and cablesare calculated with the harmonic impedances at the respective busbars.
Four main scenarios were developed regarding the electrolyzer units and internal configurationof the plant. Additionally, a more significant number of operational cases consideringthe electrical operational limits of available electrolyzers were elaborated.
For all four scenarios, the electrolyzer plant has a nominal capacity of 80 MW, consisting ofdifferent numbers of electrolyzer units rated either 1 MW or 5 MW. The electrolyzer plantis located within a short distance from a 120 MW wind farm. Both plants (electrolyzer andwind farm) are connected to the HV distribution network via Point of Common Coupling(PCC).
A large number of simulations run for the different scenarios, and operational cases using12-pulse bridge rectifiers have clearly identified one configuration in each scenario withminimal harmonic current emissions on the transmission line to the PCC. This configurationalso appears optimal when using another rectifier technology with a different harmoniccurrent spectrum.
This investigation demonstrated that the harmonic current emissions of the electrolyzerplant could be significantly reduced using an optimal design and layout of the electrolyzerunits and their grid components. This may lead to better performance, reduced losses, andeasier connection to the public grid.