Performance Evaluation and MPPT Control of a Variable-Speed Pump-as-Turbine System

The pump-as-turbine (PaT) system is a cost-effective alternative to harness hydropower from microscale water resources although its best efficiency point (BEP) is difficult to be estimated without experimental results and its efficiency dramatically drops at partial load. The variable-speed operation of PaT-generator system is proposed in this article to run it at BEP despite changing hydrological conditions. The studies are carried out based on an experimental setup comprising a centrifugal pump, running in turbine mode, coupled with a 3-kW induction generator. The speed control method is based on the rotor field-oriented control and is implemented on an experimental ac/dc converter. Various performance characteristics of the system, including constant-head and constant-speed curves, are extracted and investigated. Then, a modified perturb and observe algorithm is proposed to accurately track the maximum power point of the system. The obtained results clearly demonstrated that the raised issues are resolved well by using the proposed solution.