Computation of rotor position of DFIM using Rotor side Phase Locked Loop

A new sensor-less technique to compute the rotor position of a Doubly Fed Induction Generator (DFIG) using a Rotor side Phase Locked Loop (RPLL) is proposed in this paper. The rotor speed and position are computed using the basic induction machine model in a simple and unique procedure. The idea of using RPLL method for rotor position computation is evolved in a similar way as a grid side PLL is used for determining the frequency or position of the grid flux. The necessity for computing the rotor speed and position is mainly to target high performance closed loop control of drives in motoring operation and for a precise decoupled control of active and reactive power in generating operation. The proposed scheme is simulated in MATLAB/Simulink environment and also validated using experiments. The experimental setup comprises of a 3-hp grid connected Doubly Fed Induction Machine (DFIM) along with a ALTERA cyclone II FPGA based digital controller for control implementation.