the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Reinforcement-Learning–Based Collaborative Optimization of Load Regulation and Opportunistic Maintenance of Wind Turbines
Abstract. To address the difficulty in coordinating component-degradation regulation strategies with opportunistic maintenance timings over the full lifecycle of wind turbines, this study proposes a reinforcement-learning–based collaborative optimization method for wind-turbine load regulation and opportunistic maintenance (RL-OppOM).The proposed method establishes a full-lifecycle simulation environment for wind turbines by coupling wind conditions, power-load characteristics, component reliability, and maintenance restoration, and formulates graded power derating, multicomponent maintenance combinations, and operational feasibility constraints within a unified Markov decision process. A lifecycle risk-aware reward function is developed and a factorized dual-clip masked proximal policy optimization algorithm is proposed. By incorporating policy factorization, action masking, and dual clipping, the algorithm reduces the complexity of policy learning and improves training stability. Simulation validation is conducted using SCADA data from a wind farm in northern China. The results show that RL-OppOM achieves a comprehensive cost of 7.320 M CNY, which is 13.80 % and 11.65 % lower than the costs of CBM and OppM, respectively, while increasing the net profit by 2.36 % and 1.93 %. The mean and minimum turbine-health indicators are 0.6413 and 0.4491, respectively, and the number of high-risk operating days is zero.
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Status: open (until 06 Nov 2026)
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RC1: 'Comment on wes-2026-157', Anonymous Referee #1, 05 Oct 2026
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The comment was uploaded in the form of a supplement: https://wes.copernicus.org/preprints/wes-2026-157/wes-2026-157-RC1-supplement.pdfReplyCitation: https://doi.org/
10.5194/wes-2026-157-RC1 -
RC2: 'Comment on wes-2026-157', Anonymous Referee #2, 20 Oct 2026
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General assessment
The manuscript presents a reinforcement learning approach for combining power derating and opportunistic maintenance of wind turbines. For this, a component degradation and reliability model is combined with a modified PPO algorithm to optimize turbine operation and maintenance activities. The topic is relevant for wind turbine operation and maintenance, and the combination of operational control and maintenance scheduling is an interesting approach. However, several assumptions related to the degradation, maintenance and economic models are not sufficiently justified. In addition, some inconsistencies in the reported results and limitations of the considered reference strategies make it difficult to evaluate the reliability of the presented improvements. The following comments should therefore be addressed before the manuscript can be considered for publication.
Major comments
- The degradation model relates equivalent aging to power-dependent loading and abnormal fluctuations (Eq. 10). However, the calibration of the corresponding parameters is not sufficiently described. Please explain how these parameters were determined and validated for the four considered components.
- The system reliability R_sys is calculated as the product of the four component reliabilities, while the minimum component reliability R_min is used to classify the turbine condition and determine the number of high-risk days. Please explain the reason for using these two different reliability indicators.
- 6(a) labels “System reliability”, but it is apparent that the graph shows the minimum reliability R_min
- Minor, major and corrective maintenance are represented using predefined reliability restoration functions, fixed maintenance costs and fixed repair durations (Eqs. 14–16, Table 2). However, the physical basis for these assumptions is not sufficiently explained. Please specify which maintenance interventions are represented by the different categories and how the reliability restoration parameters were determined.
- The manuscript describes how access costs C_fix can be shared when several maintenance activities are performed simultaneously (Eq. 19). However, the calculation of the corresponding downtime is not sufficiently clear. Please explain how simultaneous minor and major maintenance activities are scheduled and how their repair durations are combined. It should also be clarified how weather restrictions are considered for maintenance activities extending over several days.
- The relationship between power derating and component loading is a central assumption of the proposed approach, since it determines how operational control influences component degradation (Eqs. 5-6). However, reducing electrical power output does not necessarily result in a proportional reduction in mechanical loading, as this depends on the derating strategy, turbine control behaviour and operating conditions. Please clarify how the assumed relationship between power derating, component loading and degradation was established for the four considered components, and whether it is based on simulations, measurements or simplified assumptions.
- The economic calculations are not sufficiently transparent and cannot be reproduced based on the provided information. For example, the 29 minor and 8 major maintenance interventions reported for RL-OppOM would result in direct maintenance costs of 18.890 million CNY based on the unit costs in Table 2, while Table 4 reports only 5.934 million CNY. In addition, the reported lifecycle net profit of 75.269 million CNY cannot be reproduced using Eq. 39 and the provided electricity price, energy production and maintenance costs. The results appear to require the additional revenue scaling factor of 1.51 given in Table 2, which is not included in the equation. Please explain these discrepancies and provide a more detailed description of the economic model.
- The considered reference strategies CBM and OppM differ from RL-OppOM in several aspects simultaneously (Table 4). It is therefore difficult to determine which part of the reported improvements can be attributed to reinforcement learning, power derating or opportunistic maintenance. Please provide a more detailed description of the decision rules used for the reference strategies. In addition, comparisons with a maintenance-only reinforcement learning approach, rule-based power derating combined with opportunistic maintenance, and conventional PPO variants without the proposed modifications should be considered.
- The reward function combines electricity revenue, maintenance costs, reliability risk penalties and expected failure costs (Eqs. 30). However, the selection of the corresponding weighting parameters w and the calculation of expected failure costs F(d) are not sufficiently explained. Please provide the complete formulation used to determine failure probabilities and expected costs, and explain how the different reward terms are scaled. Furthermore, the influence of the selected weights and reliability indicator on the resulting policy should be investigated.
- A daily discount factor of gamma=0.995 is used for the reinforcement learning algorithm, although the optimization considers a period of 19 years. With this discount factor, rewards occurring several years in the future have a very small contribution to the optimization objective. Please justify the selection of this parameter and investigate whether alternative discount factors affect the learned maintenance strategy and the resulting lifecycle economic performance.
- The reported results appear to be based on a limited number of stochastic simulation runs, without information about the variability between different training seeds and wind speed sequences (Fig. 4). Please provide results from repeated simulations, including measures of variability or confidence intervals for economic performance, number of maintenance interventions, availability and reliability risk. This is particularly important since the differences in net profit between the considered strategies are relatively small.
Minor comments
- Equation 17 contains a Chinese character
- Please check the wind speed interval used for the rated power region in Eq. 4, as the specified cut-in and cut-out wind speed boundaries appear to be incorrect.
- The lower boundary of the opportunistic maintenance candidate interval is denoted by \(R_{\mathrm{low}}\) in Eq. 18 and \(R_m\) in Eq. 27 (Sections 2.3 and 3.3). Please clarify whether both parameters refer to the same quantity.
- Please check the indexing of Reliabilities in Eq. 32, which appears to be inconsistent with Eq 13.
Overall recommendation: Major revision
The manuscript addresses a relevant optimization problem and proposes an interesting approach for combining power derating and opportunistic maintenance based on reinforcement learning. However, several aspects of the underlying degradation, reliability and maintenance models are not sufficiently justified and require further validation. In addition, the inconsistencies in the reported maintenance costs need to be clarified to allow for a reproducible assessment of the proposed method. A more detailed comparison with suitable reference strategies and an evaluation of the individual algorithm modifications would also be useful to better understand their contribution to the overall performance. I therefore recommend major revision.
Citation: https://doi.org/10.5194/wes-2026-157-RC2
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