Dynamic Frequency Tracking for Voltage and Frequency Regulation of Wind Driven Doubly Fed Induction Generator in Standalone mode

Abstract

This paper presents a simple and effective method for dynamic regulation of stator frequency and voltage in wind-driven doubly fed induction generator (DFIG) for standalone operation. The proposed Dynamic Frequency Tracker (DFT) is a combination of feed forward–feedback control loops to maintain stator frequency and voltage at the rated values when the load, or the wind power, or both vary independently. The measured rotor speed is used in the feedforward loop to obtain the reference rotor frequency, whereas the rotor reference voltage is obtained from the feedback loop. The magnetic stability of the DFIG is ensured by keeping the voltage-to-frequency ratio constant in the inverter reference voltage calculations. Validation of the proposed DFT has been carried out through laboratory tests involving hardware units of wind turbine emulator and DFIG. Tests are conducted under steady state and transient state conditions, separately for super synchronous and sub synchronous modes of the generator, wherein wind speed and load on the stator are varied too. Stator loads of unity and lagging power factors have been considered. Results of all the tests confirmed stable and satisfactory regulation of the stator voltage and frequency.