• Comparative Performance Modelling of Heat Pump based Heating Systems using Dynamic Carbon Intensity

      Counsell, John M.; Khalid, Yousaf; Stewart, Matt; University of Chester (IET, 2018-11-31)
      Modern buildings and homes utilise multiple systems for energy generation, supply and storage in order to maintain occupant comfort, reduce operating costs and CO2 emissions. In recent times electricity generation and supply network (UK National Grid) have had to manage variable supply from renewable sources such as wind turbines and photovoltaics. This resulting supply mixture has a dynamic profile at intermittent times. To manage excess supply, the options are either to reduce the generation by power stations/renewables or reinforce the power infrastructure with storage capability. This has given rise to calls for electrification of services in streamlining the supply profile through intelligent demand response such as electric heating and vehicles. Furthermore, due to zero carbon energy sources with dynamic supply profile, the carbon intensity is no longer constant. This impacts the seasonal CO2 emissions calculations and also the design and performance of electrical powered heat pump based heating systems. The RISE (Renewable Integrated Sustainable Electric) heating system was developed (funded by the UK Research and Innovation), where an electrical powered Heat pump is combined with electric thermal storage allowing low cost and low carbon electricity to be utilised. For such a system more realistic performance analysis requires dynamic carbon intensity calculations to assess impact on its ability to maintain comfort, low operating costs and low carbon emissions. The paper builds upon previously published research on the RISE system comparing with domestic Gas Condensing Boiler (GCB) using static carbon calculations. This paper presents a comparison between the RISE system and standard domestic electrical powered Air Source Heat Pump (ASHP) when using static and dynamic carbon intensity profiles. The Inverse Dynamics based Energy Assessment and Simulation (IDEAS) framework is utilised for modelling and dynamic simulation of building and heating system, operating cost and estimation of annual emissions based on half hourly (HH) dynamic CO2 intensity figures rather than annual average. The results show that with dynamic carbon intensity calculations, both electric heat pump based heating systems, RISE and ASHP show a significant increase (>15%) in carbon emissions for space heating. The results also show that whilst the RISE system’s thermal storage helps to reduce running costs using a time of use tariff (TOU), it only provides a small benefit in carbon emissions.
    • Flicker mitigation strategy for a doubly fed induction generator by torque control

      Zhang, Yunqian Q.; Hu, Weihao; Chen, Zhe; Cheng, Ming; Hu, Yanting (IET, 2014-03)
      Owing to the rotational sampling of turbulence, wind shear and tower shadow effects grid connected variable speed wind turbines could lead to the power fluctuations which may produce flicker during continuous operation. A model of an megawatt (MW)-level variable speed wind turbine with a doubly fed induction generator is presented to investigate the flicker mitigation. Taking advantage of the large inertia of the wind turbine rotor, a generator torque control (GTC) strategy is proposed, so that the power oscillation is stored as the kinetic energy of the wind turbine rotor, thus the flicker emission could be reduced. The GTC scheme is proposed and designed according to the generator rotational speed. The simulations are performed on the national renewable energy laboratory 1.5 MW upwind reference wind turbine model. Simulation results show that damping the generator active power by GTC is an effective means for flicker mitigation of variable speed wind turbines during continuous operation. keywords: {asynchronous generators;oscillations;power generation control;torque control;wind power plants;wind turbines;GTC strategy;continuous operation;doubly fed induction generator;flicker emission;flicker mitigation strategy;generator active power;generator torque control;kinetic energy;megawatt-level variable speed wind turbine;power oscillation;tower shadow effects grid connected variable speed wind turbines;turbulence;upwind reference wind turbine model;variable speed wind turbines;wind shear;wind turbine rotor
    • Overcurrent relays coordination optimisation methods in distribution systems for microgrids: a review

      Abeid, S; Hu, Yanting; University of Chester
      Electric power networks connected with multiple distributed generations (microgrids) require adequate protection coordination. In this paper, the overcurrent relay coordination concept in distribution system has been presented with details. In this available literature, the previous works on optimisation methods utilised for the coordination of over current relays; classification has been made based on the optimisation techniques, non-standard characteristics, new constraints that have been proposed for optimal coordination and dual setting protection schemes. Then a comprehensive review has been done on optimisation techniques including the conventional methods, heuristic and hybrid methods and the relevant issues have been addressed.
    • Real-time Geometry-Aware Augmented Reality in Minimally Invasive Surgery

      Chen, Long; Tang, Wen; John, Nigel W.; Bournemouth University; University of Chester (IET, 2017-10-27)
      The potential of Augmented Reality (AR) technology to assist minimally invasive surgeries (MIS) lies in its computational performance and accuracy in dealing with challenging MIS scenes. Even with the latest hardware and software technologies, achieving both real-time and accurate augmented information overlay in MIS is still a formidable task. In this paper, we present a novel real-time AR framework for MIS that achieves interactive geometric aware augmented reality in endoscopic surgery with stereo views. Our framework tracks the movement of the endoscopic camera and simultaneously reconstructs a dense geometric mesh of the MIS scene. The movement of the camera is predicted by minimising the re-projection error to achieve a fast tracking performance, while the 3D mesh is incrementally built by a dense zero mean normalised cross correlation stereo matching method to improve the accuracy of the surface reconstruction. Our proposed system does not require any prior template or pre-operative scan and can infer the geometric information intra-operatively in real-time. With the geometric information available, our proposed AR framework is able to interactively add annotations, localisation of tumours and vessels, and measurement labelling with greater precision and accuracy compared with the state of the art approaches.
    • Smart guaranteed time-slot allocation algorithm for industrial wireless sensor networks emergency message transmission

      Chen, Qinyin; Hu, Yanting; Chen, Zhe; Davies, John N.; Excell, Peter (IET, 2015-04-01)
      This paper presents investigation on application of wireless sensor networks (WSNs) in wind power generation systems and highlights an important issue associated with the deadline for the delivery of messages among nodes based on the IEEE 802.15.4E standard. Owing to the limits of standard and the power system application requirements, this research proposes a smart guaranteed time slot (S-GTS) allocation algorithm which is based on the urgent/important matrix. This proposed algorithm promotes the utilisation of contention free period in a superframe. Besides, over seven GTSs can be allocated in a superframe, there are only seven GTSs that can be used in the standard. In addition, this study proves the value of BO and SO upper bound is 6 for the WSN application in power systems. Moreover, the network delay of S-GTS performs better than the 16-time-slot mechanism and i-GAME mechanism.
    • Surface adjustment strategy for a large radio telescope with adjustable dual reflectors

      Lian, Peiyuan; Wang, Congsi; Xue, Song; Xu, Qian; Shi, Yu; Jia, Yu; Xiang, Binbin; Wang, Yan; Yan, Yuefei; Xidian University; University of Chester; Chinese Academy of Sciences (IET, 2019-08-15)
      With the development of large-aperture and high-frequency radio telescopes, a surface adjustment procedure for the compensation of surface deformations has become of great importance. In this study, an innovative surface adjustment strategy is proposed to achieve an automated adjustment for the large radio telescope with adjustable dual reflectors. In the proposed strategy, a high-precision and long-distance measurement instrument is adopted and installed on the back of the sub-reflector to measure the distances and elevation angles of the target points on the main reflector. Here, two surface adjustment purposes are discussed. The first purpose is to ensure that the main reflector and sub-reflector are always positioned at their ideal locations during operation. The second purpose is to adjust the main reflector to the location of the best fitting reflector, and the sub-reflector to the focus of the best fitting reflector. Next, the calculation procedures for the adjustments of the main reflector and the sub-reflector are discussed in detail, and corresponding simulations are carried out to verify the proposed method. The results show that the proposed strategy is effective. This study can provide helpful guidance for the design of automated surface adjustments for large telescopes.