Dynamic power response shaping using adaptive constraints in feedback control of a contra-rotating pump–turbine

With the rising need for flexible energy storage, recent research shows the potential of contra-rotating reversible pump–turbines (CR RPT) to enable low-head pumped hydropower storage. This study presents a dual variable-speed control architecture for CR RPTs, aimed at providing grid frequency control. The proposed control maximizes the efficiency and shapes the power response to minimize the rise time while averting excessive fluctuations. The control architecture is experimentally validated on a 45 kW reduced-scale CR RPT. The results show that for full reserve activation in frequency containment reserve (FCR), the rise times are <3.92s in turbine mode and <0.23s in pump mode. When scaled to a 10 MW system, with a factor of 1.53 to 2.46, the rise times remain well below the regulatory limit of 30 s. Furthermore, the power response stays within the allowed limits, with root mean square deviations of <58% in turbine mode and <39% in pump mode, relative to the allowed limits. Additionally, the system effectively tracks the varying power setpoints in an actual FCR use case. These findings demonstrate that the proposed control methodology can successfully provide frequency control by dynamically varying the power within imposed power constraints.