Experimental validation on a 700 W hardware platform has demonstrated that a Unified Dual-Loop Linear Active Disturbance Rejection Control (UDL-LADRC) framework significantly improves grid-side converter performance in direct-drive wind energy conversion systems. Developed specifically for direct-drive wind turbines employing a novel Axial Field Flux-Switching Sandwiched Permanent Magnet Machine with Twisted Structure (AFFSSPM-TS), the unified control approach was implemented and evaluated using a dSPACE DS1103 real-time system. During experimental wind speed variations, the proposed UDL-LADRC reduced the DC-link voltage deviation to within ± 1.1%, representing a substantial improvement over conventional proportional-integral (PI) control, which exhibited a ± 11.3% deviation. Furthermore, the controller achieved a DC-link voltage recovery time of 0.09 seconds under these wind speed fluctuations, compared to the 0.25 seconds required by conventional PI control.
The investigation addressed major operational difficulties associated with the large-scale integration of direct-drive wind turbine systems into weak electrical grids. Connecting these generation systems to weak grids imposes stringent operational requirements on grid-side power converters, necessitating robust DC-link voltage regulation, high power quality, and dependable fault ride-through capability under dynamic operating conditions. The authors highlighted that conventional PI control methods and existing partial LADRC implementations suffer from limited disturbance rejection capabilities. Moreover, partial implementations lack a unified control architecture, leaving grid-connected converters susceptible to performance degradation when confronted with grid irregularities and dynamic operational disturbances.
To overcome these operational constraints, the researchers formulated the UDL-LADRC framework as an integrated, multi-tier control structure designed for the grid-side converter. The architecture deploys a second-order linear active disturbance rejection controller to govern the outer DC-link voltage loop, while first-order linear active disturbance rejection controllers regulate the inner direct-quadrature (dq) current loops. By coordinating these stages, the framework ensures consistent disturbance estimation and active rejection across all control layers of the converter. In addition, the design incorporates an integrated Least Error Squares (LES) filter, which provides rapid and accurate detection of grid voltage during fault occurrences. This rapid sensing capability enables precise reactive current injection, which is essential for satisfying low-voltage ride-through demands during network disruptions.
The performance of the UDL-LADRC system was experimentally evaluated across an extensive range of demanding grid conditions, including wind speed variations, voltage sags, voltage swells, weak grid conditions, and harmonic-distorted grids. Under voltage swells, the controller successfully limited the DC-link voltage deviation to 4.2% and achieved a recovery time of 24 milliseconds. The experimental setup also demonstrated stable reactive power support during a severe 66% voltage sag, verifying the converter’s capability to assist the grid during profound voltage drops. When tested under weak grid conditions, the controller maintained a current tracking error below 3.5% root-mean-square (RMS), demonstrating resilience against network impedance fluctuations.
Dynamic power response and grid power quality were also quantitatively measured during the hardware platform trials. The active power settling time was recorded at 0.05 seconds under the proposed control scheme. In terms of power quality, the total harmonic distortion (THD) of the grid current remained below 3.1% throughout testing, confirming that the converter effectively suppressed harmonic contamination even within harmonic-distorted grid environments. These results indicate that the dual-loop control architecture is capable of delivering fast settling times and low harmonic distortion simultaneously, without compromising converter stability or dynamic power delivery.
The experimental findings confirm that the unified architecture delivers several synergistic benefits over partial active disturbance rejection implementations. These advantages include hierarchical disturbance rejection throughout the control structure, the prevention of disturbance propagation across coupled control loops, and consistent, model-independent controller tuning across all layers. Based on the 700 W dSPACE DS1103 validation, the authors concluded that the proposed UDL-LADRC framework provides a robust, grid-code-compliant, and computationally feasible control solution for direct-drive wind energy conversion systems that utilize the novel AFFSSPM-TS machine.
Subject of Research: Unified dual-loop linear active disturbance rejection control for wind turbine grid-side converters
Article Title: Unified dual loop linear active disturbance rejection control for grid connected axial field flux switching permanent magnet wind turbines
Article References: Mohammed, M. J., Rahmani-Fard, J., & Ridha, A. M. (2026). Unified dual loop linear active disturbance rejection control for grid connected axial field flux switching permanent magnet wind turbines. Discover Applied Sciences. https://doi.org/10.1007/s42452-026-09819-z
Image Credits: AI Generated
DOI: 10.1007/s42452-026-09819-z
Keywords: UDL-LADRC, Linear active disturbance rejection control, Grid-side converter, Direct-drive wind turbine, AFFSSPM-TS, DC-link voltage regulation, Fault ride-through, Least Error Squares filter, Low-voltage ride-through, dSPACE DS1103, Weak grids, Voltage sags, Voltage swells, Total harmonic distortion, Proportional-integral control, Reactive current injection, Disturbance rejection, Wind energy conversion systems
Tags: AFFSSPM-TSDC-link voltage regulationDirect-drive wind turbinedisturbance rejectiondSPACE DS1103Fault ride-throughGrid-side converterLeast Error Squares filterLinear active disturbance rejection controlLow-voltage ride-throughProportional-integral controlReactive current injectiontotal harmonic distortionUDL-LADRCvoltage sagsVoltage swellsWeak gridsWind energy conversion systems
