A case study on the impact of electrolyser behaviour during faults on transient stability

Europe as part of the hydrogen strategy defined in the REPowerEU plan: the yearly demand could achieve a 20 million tons level, corresponding to 660 TWh, by 2030. These electrolyser units, potentially located close to synchronous machines in the French system, may substantially influence their transient stability during short-circuit events. In particular, the way electrolysers recover their active and reactive power consumption after fault clearance can either support or hinder the ability of synchronous machines to evacuate their excess of mechanical energy and maintain synchronism to the grid. This paper investigates the impact of thyristor-based electrolyser power recovery behaviour on rotor angle stability using a simplified, parametric electrolyser model. A prospective 2040 scenario including an electrolyser located near several synchronous units is studied. Stability indicators are computed for a set of power recovery profiles to evaluate their influence on rotor angle stability. The results show, for this thyristor-based installations, that even if a fast active power consumption recovery tends to support transient stability, a rapid recovery of reactive power consumption will significantly worsen it by lowering post-fault voltage at the connection point.

Consequently, converter technologies for which reactive power is intrinsically tied to active power, such as thyristor-based rectifiers, require slower or conditioned active power recovery to benefit from the reactive power boost provided by the shunt compensator at fault clearing.

Conversely, technologies allowing independent behaviour of active and reactive power, such as IGBT-based converters, can accommodate faster active power recovery without degrading stability. These findings highlight the need to account for the diversity of electrolyser converter technologies when defining future grid connection requirements, particularly within the framework of the upcoming Demand Connection Code v2.