Improvement of dynamic performance of doubly fed induction generator-based wind turbine power system under an unbalanced grid voltage condition

Study on PI Parameters Dynamic Tuning Based on Ant Colony Algorithm for Doubly-fed Wind Turbines

“…7) According to the path experienced by the ant k, namely the array path k , the PI controller parameters K k p 、K k I corresponding to the path are calculated by using the equation (10). The objective function value F k corresponding to the ant k is calculated by using the equation (8), and the convergence value ε k is calculated by using the equation (9). To record the optimal path in this cycle, and its corresponding PI controller parameters are stored in K * p 、K * i .…”

“…The control strategy is presented which uses the Nyquist constraint algorithm to design optimization PI controller [8]; this method without additional reactive power compensation device improves the performance of the voltage control system, but it can't realizes the dynamic tuning of PI parameters in the case of wind speed changing or grid failure. The electromagnetic torque and stator instantaneous power of doubly-fed wind turbines would oscillate when the grid voltage is in imbalance, so the method was presented which uses the vector PI controller to eliminate the electromagnetic torque and stator instantaneous power's oscillation [9]. In order to improve the performance constant voltage control system, a new method which introduces the equivalent wind speed as the feed forward control parameter was presented in [10]; this method can effectively restrain the voltage fluctuation because of the wind speed changes.…”

Analysis of the Influence of Asymmetric Grid on Synchronous Hydro Generator

“…So, the main factor that leads to the asymmetrical operation of the synchronous hydro generator is the asymmetry of three-phase current [1]. In real life, the existence of asymmetrical load, such as the electric locomotive in transportation, the electric furnace in metallurgical factory and the asymmetrical impedance of three-phase lines, leads to the generation of asymmetrical current in power grid [2][3][4][5][6][7]. Since the synchronous hydro generator is directly connected to the grid through the transformer, the influence of asymmetrical three-phase current on the generator is inevitable.…”

Lower Gain Adaptive Sliding Mode Control of DFIG Stator Powers

“…In the wind energy conversion systems (WECSs) connected to the grid, the doubly fed induction generators received an important consideration compared to other generators types [1][2], due especially to the static converter size, and the wide speed range. Due to several functionalities, the DFIG active and reactive stator powers control is required [3].…”