Variable-speed generator system design to improve grid resilience

Increasing the integration of wind and pumped hydro variable-speed power plants in future power systems is highly required to meet the requirements on reducing greenhouse gas emissions and increasing the target of renewable resources in the energy mix. Developing new generator system design approaches is of the utmost importance to ensure reliable and resilient grid operation. To this aim, we will define controllability metrics to enhance the inertial-frequency response of variable-speed power plants, and include these as additional criteria for the electro-magnetic design of converter-interfaced generators. This project will, thus, enable a significantly more straightforward integration of wind and pumped hydro variable-speed power plants in future power systems, leading to more profitable, and, thus, even greener electric power generation without compromising grid reliability and resilience. As a matter of fact, the many governmental targets mandate the reduction of greenhouse gases, such as the European Green Deal, that sets the blueprint for all EU member states, turning the EU into the first climate-neutral continent by 2050, with reduced emissions by at least 55 % by 2030 compared to 1990 levels, where one of the proposals is to increase the binding target of renewable sources in the EU's energy mix to 40 % by 2030. Furthermore, the joint ENTSOG and ENTSO-E Ten-year network development plan 2020 for Europe predicts that wind will cover 29 % of the electricity production in 2030 and 41 % in 2040. Electric generators play a central role in electricity production. Generators in the wind and pumped hydropower plants operate at variable speeds, and, thus, are connected to the grid mainly through power electronic converters. The EU Regulation 2016/631 for converter-interfaced units requires reactive power provision, inertial-frequency response, power oscillation damping, fault-ride-through capability and fast-fault current injection, to ensure stable electric power generation, which has already been implemented in national grid codes. Inevitably, the converter-interfaced units will change the dynamic responses of a power system significantly. Such converter-interfacing also offers new optimisation possibilities for the electric machine so that the generators can be designed to have smaller volumes, lower material costs, reduced excitation demand, and higher efficiencies than conventionally designed ones. Consequently, as proposed here, the unification of the generator design techniques and the grids' control demands will enable a wide range of possible operating conditions of these modern variable-speed power plants. The main objective, thus, is to unify the generator design techniques and the grids' control demands through controllability metrics based electro-magnetic design for converter-interfaced generators in large variable-speed power plants, i.e., wind and pumped hydro, to enable enhanced inertial-frequency response and, thus, improve grid resilience. To this aim, we will: (i) Define and prove such controllability metrics for enhanced inertial-frequency responses of converter-interfaced synchronous generator and doubly-fed induction generator-based wind and pumped hydropower plants, (ii) Include these metrics as additional criteria in the electro-magnetic design of such generators and derive the scaling laws, (iii) Develop and investigate their control solutions experimentally to demonstrate and improve grid resilience.