Ancillary services from Hydrogen Based Technologies to Support Power System Frequency Stability

Abstract

The share of renewable energy sources in the electricity generation is expected to maintain a steady growth in the future driven by economic and environmental reasons. However, these renewable sources such as wind and solar have fluctuating power output. This fluctuation causes strain on the power system and can cause imbalances between generation and load which may result in frequency instability. In the current liberalized energy market, the system operator uses ancillary services market to procure frequency containment reserve (FCR) which arrests undesirable frequency excursions within the first few seconds after the occurrence of an imbalance and ensures satisfactory primary frequency control. The system operator also procures frequency restoration reserve (FRR) which helps restore the frequency to its nominal value.
Electrolyzers can manage their demand of electrical energy for production of hydrogen (i.e. power-to-gas conversion) and it is possible to store that generated hydrogen for long periods which is an advantage compared to battery storage. This hydrogen can be used for several applications (e.g. transportation), and part of it can be used by fuel cells to provide electrical power back to the power system when needed. One of the technologies used in electrolyzers and fuel cells is the proton exchange membrane (PEM). Fuel cells and electrolyzers based on PEM technology are capable of rapidly changing the power set point to increase or decrease the power demand or supply, respectively.
This thesis studies the PEM electrolyzers and fuel cells and their ability to support the frequency stability through participation in the ancillary services market. Based on DIgSILENT PowerFactory software package, this thesis develops generic dynamic models for PEM fuel cell and electrolyzer for frequency stability studies and uses these models to assess their effectiveness in providing frequency support and participation in the FCR market. Numerical simulations are performed on two dynamic test systems: The North Netherlands 380 kV transmission and its extension to include a reduced size representation of the transmission systems covering the North-West Germany and South Denmark. Both dynamic test systems are developed in PowerFactory based on the detailed model of continental Europe built in PSS®E software package.
The developed model for the fuel cell shows close resemblance to the literature data for both dynamic and static performance especially in the linear operating range. The simulation results show that PEM devices can provide frequency support in the FCR market and results in improved frequency nadir and reduced oscillations during the post-disturbance period which is considerably better than what can be achieved by using the currently in operation primary frequency control of the conventional power plants with synchronous generators.
The numerical simulations also include sensitivity analysis to changing system operating conditions such as network size, location of PEM devices and system inertia. It is found that changing the location of the PEM devices or the size of the network does not affect the performance in supporting the frequency. Also, it is found that PEM devices provide significantly improved frequency response compared with synchronous generators at lower system inertia levels. Sensitivity analysis to changing control parameters for PEM devices such as the bid size and frequency droop showed that increasing the bid size or droop results in improved frequency response in the form of lower nadir.
Some confidential information within this thesis have been removed. To request the full version please contact Dr. Ir. Jose L. Rueda Torres.