Nonlinear Adaptive Robust Control Strategy of Doubly Fed Induction Generator Based on Virtual Synchronous Generator

Abstract

Doubly fed induction generator (DFIG) may suffer from huge disturbance owing to the uncertainty of generator parameters and load fluctuation during operation process. Hence, in the context of virtual synchronous generator (VSG) technology and its power-frequency control characteristics, this paper presents a VSG-based nonlinear adaptive robust controller (NARC), aiming to enhance the comprehensive regulation performance of DFIG. Firstly, a nonlinear robust adaptive controller with disturbance rejection and uncertainty adaptive learning ability is designed by establishing an improved dynamic model of the rotor motion equation in VSG, so as to achieve the optimal regulation of DFIG with robustness and adaptability. Secondly, in order to realize the fast dynamic response and autonomous synchronization ability in DFIG, a modified control strategy of the grid side converter (GSC) in DFIG is constructed by voltage and current dual-loop control (DLC) and VSG, which not only retains the significant dynamic response ability of the current inner-loop in DLC, but also improves the inertia and damping of the system. Finally, simulation results indicate that the modified control strategy exhibits satisfied dynamic performance and reliability, and reveals the robustness and adaptability of the control strategy in response to external random interferences and internal uncertain parameters. INDEX TERMS Doubly fed induction generator, virtual synchronous generator, nonlinear adaptive robust control, voltage and current dual-loop control.

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“…In order to reduce system frequency fluctuation caused by wind turbine integration, scholars both at home and abroad have paid close attention to the virtual synchronous generator control strategy [3][4][5]. The concept of virtual inertia was proposed in [6]; when frequency mutation occurred, a large amount of inertia was virtualized to perform frequency modulation by releasing or storing rotational kinetic energy in the unit.…”

Extended Disturbance-Observer-Based Virtual Synchronization Control Strategy for Distributed Generation Clusters

“…The obtained compensation for each DG are obtained according to the compensation allocation (17) and then transmitted to each DG unit;…”

“…To solve this problem, the virtual synchronization control scheme [15][16] is proposed and widely adopted for DGs. What's more, some improved virtual synchronization control such as nonlinear adaptive virtual synchronous control [17], mode-adaptive virtual synchronous control [18], and fuzzy-based virtual synchronous control [19] are also proposed in the existing literatures to furtherly enhance the performance. However, severe active power oscillation problems may occur when several DGs which adopt the virtual synchronization control are parallel [20].…”

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“…iii) Some DFIG characteristics, such as the lack of short circuit capacity, low inertia, and uncertainty of damping, are likely detrimental to overall system voltage stability, frequency stability, and oscillation damping in actual operation [17]. iv) To achieve a smooth active power output of the DFIG system to the grid, the conventional control strategy, similar as, would allow the existence of active power pulsed in the RSC, while the grid side converter (GSC) is controlled to generate the opposite active power pulsation of the same quantity as RSC [18]. v) This paper proposes the machine learning algorithm strategy for both DFIG's RSC and GSC under the unbalanced grid voltage, which can achieve the different control targets for the overall DFIG system [19].…”