Slip frequency phase lock loop (PLL) for decoupled P-Q control of doubly-fed induction generator (DFIG)

The term "sensor-less" in power electronic drives refers to measurement of mechanical shaft position and/or speed from the currents and voltages of the electrical machine. This thesis presents innovative sensor-less means (a Slip Frequency Phase Lock Loop (PLL) and a gamma-delta Axes Aligner) for implementing decoupled P-Q control of a doubly-fed induction generator (DFIG) for wind-turbine application. Proofs of concepts are by digital simulations.; The accuracy of the Slip Frequency Phase Lock Loop in speed estimation is evaluated; the origin of a shortcoming (small phase lag) located and compensated for.; The Slip Frequency Phase Lock Loop (PLL) and a gamma-delta Axes Aligner are then evaluated as parts of the decoupled P-Q control of a wind turbine driven doubly-ed induction generator. The research succeeds in realizing robust decoupled P-Q control, that is one in which the generator parameters do not have to be known precisely and can have minor variations such as drifts with temperature. The system has been successfully tested for optimal wind power acquisition.