| 22 Jun 2026
Research on Direct Speed Control Strategy for Maximum Power Point Tracking (MPPT) of Wind Turbines
Abstract. Maximum Power Point Tracking (MPPT) below the rated wind speed is a key technology to improve the wind energy utilization efficiency of wind turbines. The existing commercial optimal torque control strategy is essentially an indirect speed control method, which has such problems as lacking optimal speed tracking error term, having non-adjustable convergence speed, and invalid control logic in the constant speed zone. To address the above shortcomings, this paper proposes a dynamic optimal speed estimation method based on the generator electromagnetic torque by analyzing the aerodynamic torque characteristics of the wind rotor under different wind speeds and the torque-speed operation trajectory of the generator at each maximum power tracking point, in accordance with the principle of the balance between aerodynamic torque and generator torque at the maximum power point. Taking this optimal speed as the control target, a direct speed controller based on speed deviation feedback is designed to achieve unified control of both constant speed zone and variable speed zone. A MATLAB/Simulink simulation model was built based on a 1.5 MW variable-speed variable-pitch wind turbine, and simulation verification was carried out under the conditions of gradient wind and turbulent wind in the minimum speed zone, variable speed zone and maximum speed zone, followed by field tests in wind farms. The results show that the proposed direct speed control strategy can stably realize MPPT under full operating conditions, effectively avoid torque and power oscillation, and keep the wind energy utilization coefficient stable at around 0.49. Moreover, it features simple control logic, can adapt to smooth switching of different wind speed conditions, and has good engineering application prospects.
The authors propose an alternative to conventional optimal torque control (OTC) that uses generator speed as the explicit control target. However, major weaknesses in the turbine description, simulation model, controller analysis, and presentation prevent a reliable assessment of the method. I therefore stopped the detailed review at the simulation section and would reject the paper in the given version.
Scientific significance
The practical advantage of the proposed direct speed control (DSC) over conventional OTC is not sufficiently demonstrated. Beyond the explicit speed-error feedback and the treatment of constant-speed regions, the method appears closely related to standard OTC. The authors should quantify whether DSC actually improves energy capture, convergence time, torque fluctuations, drivetrain loads, robustness, or operating-region transitions — especially since minimum- and maximum-speed regions can already be handled by conventional supervisory control and saturation logic.
The choice of a 1.5 MW turbine is not justified. The authors should explain why this turbine is representative and whether the conclusions transfer to larger, more modern turbines.
Scientific quality
The turbine is described in only one short paragraph plus a parameter table, and the origin of the model and parameters remains unclear. Several values also appear inconsistent: using the listed rotor diameter, gearbox ratio, rated generator speed, and rated wind speed gives a tip-speed ratio of about 7.5, not the stated optimum of 10. The Cp-lambda curve, power curve, torque curve, speed curve, and relevant efficiency assumptions should be provided.
The MATLAB/Simulink model itself is not described. The authors should specify the aerodynamic model, drivetrain dynamics and inertias, generator and converter models, losses and efficiencies, and the wind input/turbulence model — without this, the results can neither be assessed nor reproduced.
It also remains unclear whether torque and speed values refer to the low-speed shaft or the high-speed shaft, which creates ambiguity throughout the figures, parameters and results. All quantities should be assigned to a single reference shaft, with conversions specifying gearbox ratio and efficiency. In particular, aerodynamic and generator torque cannot be directly equated unless they are given with a transmission ratio and efficiency term.
The proposed controller is explained mainly in qualitative terms. The authors should clarify whether DSC is fundamentally different from OTC or largely reproduces the same steady-state relation via an explicit speed-control loop. The condition Ta = Tg only holds at steady state (neglecting losses, or once these are treated consistently); during transients, the inertia term must be included. DSC should be compared quantitatively against a properly tuned OTC baseline under identical conditions.
The literature basis is rather narrow and unbalanced; in particular, the substantial overlap with the apparently already published non-english predecessor study should be transparently disclosed and cited, otherwise the novelty, originality, and clear distinction of the present manuscript cannot be reliably assessed:
Li Jiajun, Lou Yaolin, Ying Jingliang, Lin Zhiming. RESEARCH ON MAXIMUM POWER POINT TRACKING STRATEGY OF WIND TURBINE BASED ON DIRECT SPEED CONTROL[J]. Acta Energiae Solaris Sinica. 2024, 45(10): 607-615 https://doi.org/10.19912/j.0254-0096.tynxb.2023-0994
Presentation quality
Many figures suffer from poor resolution, missing units, overlapping labels, typographical errors, and captions that are too short. I found Section 2.3 particularly hard to follow — a block diagram with a concise, step-by-step explanation of the controller would help considerably.
Several terms are used incorrectly, e.g. "maximum wind energy utilization coefficient" should be "power coefficient", and "optimal modal gain" should likely be "optimal mode gain" or "optimal torque gain". Standard end-matter statements (funding, conflicts of interest, author contributions, data availability, acknowledgements) also appear to be missing.
Further comments can be found in the attached manuscript pdf.