Field-oriented power regulation and loss reduction in micro-hydro induction generation PAT off-grid systems

Pumps as Turbines (PATs) provide efficient, decentralized energy generation for remote off-grid areas, typically coupled with induction generators (IGs) for cost-effective robustness. However, using typical capacitors for their excitation limits performance under variable hydraulic and electrical conditions. This study explores field-oriented control (FOC)-based control algorithms to replace capacitor banks and improve the performance of the off-grid PAT-IG system under varying hydraulic conditions. Our main contributions are focused on analyzing system efficiency, along with the electromagnetic behavior of the induction generator and the hydraulic-mechanical dynamics of the PAT, under torque- and mechanical-power-controlled FOC strategies. In addition, flux control has been shown to be critical for maximizing the system’s efficiency. The analysis of the off-grid PAT-IG system is evaluated using dynamic non-linear simulations. The simulation results revealed that FOC techniques with optimal flux control allow for maximizing the efficiency of the system for a wide range of hydraulic and electric variables. With capacitors, the PAT-IG shows a highly variable efficiency with a maximum value of around 40% and several zones where the machine is not capable of operating. However, using torque and mechanical power FOC with flux optimization, the system is capable of operating in a wider range with very stable efficiency for different operational points. However, only mechanical power-controlled FOC can achieve almost constant electric power generation in the presence of hydraulic pressure variation. Therefore, from an electric energy generation point of view, the latter technique should be chosen instead of torque-controlled FOC. These findings highlight the need for advanced control strategies in off-grid PAT-IG systems and support their viability as a sustainable component in off-grid applications.