Direct active and reactive power control of variable-speed doubly-fed induction generator on micro-hydro energy conversion system

This paper proposes a direct power control technique applied to a variable-speed doubly-fed induction generator (DFIG) of a micro-hydro energy conversion system. This assembly consists of a permanent-magnet synchronous machine (PMSM) linked mechanically and electrically (through back-to-back power electronic converters) to the DFIG (on the rotor side). The PMSM has the role to recover or supply the slip power of the DFIG. The main advantages related to this system are that the energy conversion system is completely autonomous (can supply isolated load or can be connected to power grid) and also, the PMSM and the power converters are designed for only about 25 % of the hydro-plant rated power.