Multimode control of a variable-speed wind energy system coupled to standalone DC microgrid

• An effective power transfer operation of variable speed, Doubly Fed Induction Generator (DFIG) based Wind Energy System (WES) coupled to stand-alone DC Microgrid (DCM) is reported. • The system performance during wind dynamics and efficient power transfer operation during possible operational modes when the system is subjected to unbalanced and non-linear loads is discussed. • The system employs only one Rotor Side Converter (RSC) and is controlled by proposed Cascaded Delay Signal Cancellation (CDSC) based sequence control scheme. • The proposed control scheme aims at (i) bidirectional power transfer irrespective of load conditions/ wind velocities, (ii) power transfer at all possible operational modes thereby supplying an uninterrupted power, (iii)oscillation reduction in rotor powers and electromagnetic torque and (iv) reduction of Total Harmonic Distortion (THD) in rotor currents claiming the main merit of the work. • The entire system is implemented in real time using FPGA Spartan 6 XL25T controller to validate the proposed objectives of the CDSC based sequence control and to exhibit the efficacious working of the various modes. A stand-alone system necessitates an effective control for regulation of system parameters with lesser oscillations and uninterrupted power supply. This paper explores Cascaded Delay Signal Cancellation (CDSC) based sequence control scheme for effective power transfer operation in Doubly Fed Induction Generator (DFIG) based Variable Speed Wind Energy System (WES) coupled to stand-alone DC Microgrid (DCM). The stator directly supplies AC loads and the rotor is coupled to Rotor Side Converter (RSC) which in turn is coupled to DCM. The CDSC control aims at (i) bidirectional power transfer irrespective of load conditions/ wind velocities, (ii) power transfer at all possible operational modes thereby supplying an uninterrupted power, (iii)oscillation reduction in rotor powers and electromagnetic torque and (iv) reduction of Total Harmonic Distortion (THD) in rotor currents, claiming to be the main merits of the work. The effectiveness of the proposed control strategy is validated through real-time implementation using an FPGA Spartan-6 controller, demonstrating reliable multimode operation and uninterrupted power transfer.