The use of pumps working as turbines (PATs) connected to the electric system, in the replacement of pressure reduction valves to reduce the excessive pressure in water distribution networks, have been studied for the last years. The introduction of PATs is very important in the water-energy nexus to promote the increase of the energy savings. As consequence, the majority of the water systems does not have access to the electrical grid and, therefore, the need to study the PATs operation off-grid is necessary. In this line, the novelty of this research is the application and optimization of a PAT in water systems when the recovery solution is off-grid type. To operate correctly, the induction machine requires an external source of reactive power, which is typically provided by the electrical grid. To supply the required reactive power, a bank of capacitors is installed at the machine terminals, so-called self-excited induction generator (SEIG). The analytical model, simulation and experimental works were performed, to analyse the SEIG behaviour. The results were applied in a SEIG-PAT system obtaining the global efficiency of the system for different speeds and loads. The global efficiency decreases 47% when off-grid operation, showing the need to optimize the electrical parameters of the generator to operate as off- grid with acceptable efficiency levels. In this framework, a tuning methodology for the SEIG capacitor bank values was developed to be automatically adjusted according to the operating point of the PAT to maximize its efficiency.

近年来，已经研究了使用用作电气系统的涡轮机（PAT）的泵来代替减压阀，以减少供水网络中的过大压力。在水能关系中，PAT的引入对促进节能量的增加非常重要。结果，大多数水系统无法接入电网，因此有必要研究PATS离网运行。在这一方面，这项研究的新颖之处在于PAT的应用和优化在水系统中，当回收解决方案是离网型时。为了正确运行，感应电机需要外部无功功率源，通常由电网提供。为了提供所需的无功功率，在机器端子处安装了一组电容器，即所谓的自励感应发电机（SEIG）。进行了分析模型，仿真和实验工作，以分析SEIG行为。将结果应用到SEIG-PAT系统中，获得了针对不同速度和负载的系统整体效率。离网运行时，整体效率降低了47％，这表明需要优化发电机的电气参数以使其在离网状态下运行-效率水平可接受的电网。在此框架中，开发了SEIG电容器组值的调整方法，可以根据PAT的工作点自动进行调整，以最大程度地提高效率。