Smart AC grid integrating dispersed small hydropower sources

The paper presents a variable speed solution for optimal operation of a group of small water turbines integrated in a medium voltage AC grid. As the efficiency of hydro machines is dependent on the water flow, which usually exhibits a large variation, operation at variable speed is considered. Due to the fact that all hydro generators are AC machines, the connection to the 50 Hz power grid can be done using an AC/DC-DC/AC interface. This power electronics-based interface, additional to transferring the energy from the generator to the grid, will also operate as a reactive power and a harmonic voltage compensator. A small AC micro grid was designed, comprising an 45 kW Frances turbo group, an 7 kW diesel synchronous generator, an 1.2 kW Ballard fuel cell, an 1.5 PV solar panel, an 3 kW energy storage acid lead battery and various loads.