Northwest China is an ideal region for large-scale grid-connected PV system installation due to its abundant solar radiation and vast areas. For grid-connected PV systems in this region, one of the key issues is how to reduce the shading effect as much as possible to maximize their power generation. In this paper, a shading simulation model for PV modules is established and its reliability is verified under the standard testing condition (STC) in laboratory. Based on the investigation result of a 20 MWp grid-connected PV plant in northwest China, the typical shading phenomena are classified and analyzed individually, such as power distribution buildings shading and wire poles shading, plants and birds droppings shading, and front-row PV arrays shading. A series of experiments is also conducted on-site to evaluate and compare the impacts of different typical shading forms. Finally, some feasible solutions are proposed to avoid or reduce the shading effect of PV system during operation in such region.
Lead‐free metal halides are considered a new generation of optoelectronic materials due to their low toxicity, superior optoelectronic properties, ease of synthesis, structural diversity, and low cost. In particular, Mn2+‐based metal halides have earned intensive attention owing to their high emission quantum efficiency, rich physical properties (e.g., triboluminescence and stimuli‐responsivity), low cost, and toxicity. Due to the different coordination environments of Mn ions, Mn2+‐based metal halides can exhibit green, red, and near‐infrared emissions. This review summarizes the recent progress of Mn2+‐based metal halides in synthesis methods, emission mechanisms, photophysical properties, and representative applications in X‐ray scintillations, white light‐emitting diodes, optical anti‐counterfeiting technologies, and fluorescent sensors. Finally, the challenges and potential research directions toward developing Mn2+‐based metal halides are also predicted.
Battery energy storage systems (BESSs) can provide instantaneous support for frequency regulation (FR) because of their fast response characteristics. However, purely pursuing a better FR effect calls for continually rapid cycles of BESSs, which shortens their lifetime and deteriorates the operational economy. To coordinate the lifespan savings and the FR effect, this paper presents a control strategy for the FR of BESSs based on fuzzy logic and hierarchical controllers. The fuzzy logic controller improves the effect of FR by adjusting the charging/discharging power of the BESS with a higher response speed and precision based on the area control error (ACE) signal and the change rate of ACE in a non-linear way. Hierarchical controllers effectively reduce the life loss by optimizing the depth of discharge, which ensures that the state of charge (SOC) of BESS is always in the optimal operating range, and the total FR cost is the lowest at this time. The proposed method can achieve the optimal balance between ACE reduction and operational economy of BESS. The effectiveness of the proposed strategy is verified in a two-area power system. Index Terms--Battery energy storage system (BESS), frequency regulation (FR), coordinated control strategy, optimal depth of discharge, charging/discharging threshold. NOMENCLATURE A. Variables Custom parameters Capacity conversion coefficient Penalty coefficientCharging and discharging efficiencies of battery energy storage system (BESS)
A tip-sensitive fibre-optic Bragg grating ultrasonic hydrophone (TSFBGUH) with high spatial resolution for measuring high-intensity focused ultrasound (HIFU) fields is reported. When measuring a HIFU field, the sensitive axis of the TSFBGUH with a flexible fibre-optic sensor holder should be in parallel with the acoustic axis of the HIFU transducer to ensure the measured ultrasound impinges on the tip of the TSFBGUH. The TSFBGUH system has been established and tested. The experimental results show that the acoustic pressure sensitivity of the TSFBGUH system is about 31.3 mV/MPa within the measurement range of 10 MHz and the noise equivalent pressure is about 10.4 kPa.Introduction: High-intensity focused ultrasounds (HIFUs) have been used to cure cancers non-invasively by destroying tumours through heating and acoustic cavitations. To ensure the treatment safety, the acoustic pressure distributions and the size of the focal regions of HIFU fields need to be measured and characterised accurately. At present, HIFU fields are commonly measured and characterised by piezoelectric needle hydrophones, fibre-optic hydrophones etc. [1][2][3][4]. The fibre-optic hydrophones possess the merits of simple configuration, miniaturisation and immunity to electromagnetic interference. The fibre-optic Bragg gratings (FBGs) have been developed into various sensors for measuring static pressures [5], ultrasonic pressures [6-13] and other physical parameters. The FBG hydrophones, possessing the capability of multiplexing and withstanding high acoustic pressure, have attracted much interest [9-13]. All the above-mentioned FBG hydrophones sensed ultrasounds through the lateral side of FBGs, which could break the hydrophones by the ultrasonic wave and limit the spatial resolution [2,8]. Up to now, we have not found the literature about the tip-sensitive FBG hydrophones for measuring HIFU fields.In this Letter, a tip-sensitive FBG ultrasonic hydrophone (TSFBGUH) for measuring HIFU fields is described. The TSFBGUH system and the experimental setup have been built to measure the HIFU fields generated by a 0.965 MHz HIFU transducer in continuous mode.
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