An adjusted weight metric to quantify flexibility available in conventional generators for low carbon power systems

With the increasing shares of intermittent renewable sources in the grid, it becomes increasingly essential to quantify the requirements of the power systems flexibility. In this article, an adjusted weight flexibility metric (AWFM) is developed to quantify the available flexibility within individual generators as well as within the overall system. The developed metric is useful for power system operators who require a fast, simple, and offline metric. This provides a more realistic and accurate quantification of the available technical flexibility without performing time-consuming multi-temporal simulations. Another interesting feature is that it can be used to facilitate scenario comparisons. This is achieved by developing a new framework to assure the consistency of the metric and by proposing a new adjusted weighting mechanism based on correlation analysis and analytic hierarchy process (AHP). A new ranking approach based on flexibility was also proposed to increase the share of the renewable energy sources (RESs). The proposed framework was tested on the IEEE RTS-96 test-system. The results demonstrate the consistency of the AWFM. Moreover, the results show that the proposed metric is adaptive as it automatically adjusts the flexibility index with the addition or removal of generators. The new ranking approach proved its ability to increase the wind share from 28% to 37.2% within the test system. The AWFM can be a valuable contribution to the field of flexibility for its ability to provide systematic formulation for the precise analysis and accurate assessment of inherent technical flexibility for a low carbon power system

Digital Twins for Wind Energy Conversion Systems: A Literature Review of Potential Modelling Techniques Focused on Model Fidelity and Computational Load

The Industry 4.0 concept of a Digital Twin will bring many advantages for wind energy conversion systems, e.g., in condition monitoring, predictive maintenance and the optimisation of control or design parameters. A virtual replica is at the heart of a digital twin. To construct a virtual replica, appropriate modelling techniques must be selected for the turbine components. These models must be chosen with the intended use case of the digital twin in mind, finding a proper balance between the model fidelity and computational load. This review article presents an overview of the recent literature on modelling techniques for turbine aerodynamics, structure and drivetrain mechanics, the permanent magnet synchronous generator, the power electronic converter and the pitch and yaw systems. For each component, a balanced overview is given of models with varying model fidelity and computational load, ranging from simplified lumped parameter models to advanced numerical Finite Element Method (FEM)-based models. The results of the literature review are presented graphically to aid the reader in the model selection process. Based on this review, a high-level structure of a digital twin is proposed together with a virtual replica with a minimum computational load. The concept of a multi-level hierarchical virtual replica is presented

Sensorimotor incongruence in people with musculoskeletal pain: a systematic review

Objectives Musculoskeletal pain has major public health implications, but the theoretical framework remains unclear. It is hypothesized that sensorimotor incongruence (SMI) might be a cause of long‐lasting pain sensations in people with chronic musculoskeletal pain. Research data about experimental SMI triggering pain has been equivocal, making the relation between SMI and pain elusive. The aim of this study was to systematically review the studies on experimental SMI in people with musculoskeletal pain and healthy individuals. Methods Preferred reporting items for systematic reviews and meta‐analyses guidelines were followed. A systematic literature search was conducted using several databases until January 2015. To identify relevant articles, keywords regarding musculoskeletal pain or healthy subjects and the sensory or the motor system were combined. Study characteristics were extracted. Risk of bias was assessed using the Dutch Institute for Healthcare Improvement (CBO) checklist for randomized controlled trials, and level of evidence was judged. Results Eight cross‐over studies met the inclusion criteria. The methodological quality of the studies varied, and populations were heterogeneous. In populations with musculoskeletal pain, outcomes of sensory disturbances and pain were higher during all experimental conditions compared to baseline conditions. In healthy subjects, pain reports during experimental SMI were very low or did not occur at all. Discussion Based on the current evidence and despite some methodological issues, there is no evidence that experimental SMI triggers pain in healthy individuals and in people with chronic musculoskeletal pain. However, people with chronic musculoskeletal pain report more sensory disturbances and pain during the experimental conditions, indicating that visual manipulation influences pain outcomes in this population. **Postprint archived after 12 months embargo period*

Does sensorimotor incongruence trigger pain and sensory disturbances in people with chronic low back pain?: a randomized cross-over experiment

Chronic low back pain (CLBP) has major public health implications, and underlying mechanisms are still unclear. Sensorimotor incongruence (SMI)—an ongoing mismatch between top-down motor output and predicted sensory feedback—may play a role in the course of chronic nonspecific low back pain. The hypothesis of this study was that the induction of SMI causes sensory disturbances and/or pain in people with CLBP and healthy volunteers. A sample of 66 people (33 people with CLBP and 33 healthy volunteers) participated in a visual feedback experiment involving real-time images of their own lower backs—either during movement or in a static position—provided via a live video feed. Experimental SMI was induced via distorting visual feedback of the lower back during movement. There were no significant differences in sensory disturbances or pain intensity between experimental SMI and the other movement conditions in people with CLBP and healthy volunteers (P > .05). Static visual feedback had a significant effect on the intensity of sensory disturbances in people with CLBP (P = .038) and healthy volunteers (P < .001). In conclusion, experimental SMI did not affect sensory disturbances or pain in either group. Therefore, the research hypothesis was not supported. Perspective The results of this study show that sensorimotor incongruence does not cause additional symptoms and pain in people with chronic low back pain. The conceptual premise that sensorimotor incongruence is an underlying contributor in the course of pain in this population is not supported. **postprint archived*

The effect of visual feedback of the neck during movement in people with chronic whiplash-associated disorders: an experimental study

Study Design Controlled laboratory study. Background Chronic whiplash-associated disorder (WAD) is an important health issue associated with poor recovery outcomes. Sensorimotor incongruence (SMI), defined as a mismatch between the efference copy in the brain and afferent sensory feedback from the body, is proposed as a possible underlying cause of chronic pain. Objectives To determine whether SMI causes sensory disturbances or pain in people with chronic WAD and healthy controls. Methods Sixty-four participants (30 with chronic WAD and 34 healthy controls) participated in a visual feedback experiment involving the neck and a bimanual coordination experiment involving the arms. In both experimental setups, SMI was induced by modifying the visual feedback during movement. Sensory disturbances and pain were the primary outcomes. Results A statistically significant difference in perceived sensory disturbance between conditions was found in the WAD group (P<.001). Intensity scores were highest for induced SMI, but only for visual feedback of the neck and not for visual feedback of the arms. This effect was not present in the control group (P = .139). Sensorimotor incongruence did not affect pain in either group. Conclusion Persons with chronic WAD are more susceptible to sensory disturbances owing to SMI, and this effect is specific to the region affected by pain. The hypothesis that SMI causes pain was not substantiated by the results of the present study. J Orthop Sports Phys Ther 2017;47(3):190–199. Epub 3 Feb 2017. doi:10.2519/jospt.2017.689