Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

A Modular Multilevel Converter with Integrated Shared Capacitor Sub-Module for MV Motor Drives Incorporating Symmetrical Six-Phase Machines

This paper proposes a new modular multilevel converter (MMC) configuration as a medium-voltage drive for variable-speed applications incorporating symmetrical six-phase machines. The proposed topology employs six MMC phase-legs feeding two isolated groups of three-phase machine windings, each with 60? spatial phase-displacement. A novel concept of sharing one capacitor between each pair of adjacent-arm submodules (SMs) of MMC phase-legs, while feeding machine windings in a spatial phase-opposition, is realized through a new integrated SM arrangement. The integrated SM allows the shared capacitor to absorb and release the same energy amount in a consecutive switching scheme, where the capacitor is experiencing both charging and discharging arm currents, one after another. This results in a limited voltage variation across the SM shared capacitor, independent of the operating frequency. Also, the proposed approach allows the MMC to utilize half the number of the SM capacitors, compared to a traditional MMC topology, while further diminishes the SM capacitance requirement, reducing the volume of the MMC system and its stored energy. The proposed configuration can efficiently operate at near zero frequency, therefore a machine speed-range from zero speed to the rated speed is possible under rated torque operating condition. The proposed MMC topology is elucidated in detail, and its effective performance is verified using simulation

A Six-Arm Symmetrical Six-Phase Hybrid Modular Multilevel Converter with Unidirectional Current Full-Bridge Submodules

Multiphase converter complexity is one of the concerns that restrict the widespread utilization of multiphase machines. One of the developmental trends to alleviate the converter complexity is reducing passive and active component counts. In this regard, several examples have been reported in the literature for modular multilevel converter (MMC) topologies with a reduced component count for six-phase medium-voltage motor drives. A three-leg nine-arm MMC (9A-MMC) with half-bridge submodules has been proposed with a 25% reduction in the number of employed components, compared to the standard six-leg twelve-arm MMC, however with limited output voltage magnitude. To enhance the dc-link voltage utilization, hybrid designs of the 9A-MMC have been recently suggested with a combination of half-bridge and bidirectional/unidirectional current full-bridge submodules (FB-SMs) in each leg. For further structural reduction, this article proposes a two-leg six-arm hybrid MMC with half-bridge and unidirectional current FB-SMs for symmetrical six-phase machines. The proposed architecture achieves a further reduction in component count, reducing the implementation complexity without compromising the delivered power. Detailed illustrations, analysis, and operational concepts of the proposed topology are presented. To quantify its pros and cons, the proposed topology is assessed versus other existing alternatives in the literature. Simulation and experimental results are presented to validate the concept and effectiveness of the proposed architecture.Scopu

A Dual Modular Multilevel Converter with High-Frequency Magnetic Links between Submodules for MV Open-End Stator Winding Machine Drives

This paper presents a dual modular multilevel converter (MMC) topology that utilizes energy exchange between adjacent-arm submodules (SMs), operating with out-of-phase modulation. The proposed configuration is applicable to medium-voltage high-power variable-speed drives incorporating open-end stator winding machines. A novel concept of power decoupling between adjacent-arm SMs in the dual MMC topology is realized through high-frequency transformer-based dc-dc converter modules. This concept offers a significant reduction in the sizing requirement of the SM capacitance and the stored energy in the MMC system, while avoiding the problem of wide voltage fluctuations of SM capacitors, especially at low operating frequencies. The proposed configuration can produce dc voltage; therefore, a machine speed range from zero speed to the rated speed is possible under the rated torque operating condition. The operating principles of the proposed dual MMC configuration are elaborated and necessary mathematical analysis is derived. Simulation and experimental results verify the concept of the proposed drive configuration. - 1986-2012 IEEE

A Modular Multilevel Converter with Ripple-Power Decoupling Channels for Three-Phase MV Adjustable-Speed Drives

This paper presents a drive system based on a modular multilevel converter (MMC) with high-frequency magnetic channels between adjacent-arm submodules (SMs), suitable for medium-voltage, high-power three-phase variable-speed machines. The configuration employs chains of dual half-bridge (DHB) modules linking adjacent SMs of three-phase symmetrical arms. The DHB modules are operating as power channels enabling energy exchange to restore the power imbalance among the SM capacitors. This allows arms' ripple-powers to be entirely decoupled through bidirectional power transfer between adjacent-arm SMs, resulting in a near ripple-free SM capacitor voltage profile. Therefore, the MMC common problem of wide voltage fluctuation across SM capacitors is comprehensively solved, independent of the operating frequency. Additionally, a significant reduction in the sizing requirement of SM capacitance is achieved. The configuration is able to drive multimegawatt machines from standstill to the rated speed at the rated torque operating condition. The operating principle of the proposed MMC configuration is explained and necessary mathematical analysis is derived. Features and viability of the proposed drive system are verified through simulation and experimentation.Scopu

Oil source rock potential of the lacustrine Jurassic Sim Uuju formation, West Korea Bay Basin. Part 1. Oil source rock correlation and environment of deposition

The offshore West Korea Bay (WKB) Basin is one of several NE-SW rift basins which formed over thick continental crust in Korea and eastern China during the Late Mesozoic and Early Cenozoic, and is characterized by a two-layered structure, with a Cenozoic structure superposed on a pre-Teriary basin. Paraffinic oils recovered from Mesozoic and Tertiary sandstone intervals are thought to have been generated from different source beds. The Sim Ujuu Formation consists mainly of fluvially derived shales and sandstones deposited in a large, open, fresh-water, deep tectonic lake, which occupied wide sub-basins formed by normal faults under a semi-humid climate, as a result of initial rifting during the Upper Jurassic. A probable source bed (400- to 500- m thick) has been geochemically located in the basinal offshore area of the Sim Ujuu sequence penetrated by Well 606. The Jurassic bed could be considered as a potential source for the Mesozoic oil, provided that it contains the right type and amount of organic matter which has reached the stage of oil generation

Quasi two-level PWM operation of a nine-arm modular multilevel converter for six-phase medium-voltage motor drives

This paper proposes a hybrid converter for medium-voltage six-phase machine drive systems that mixes the operation of a traditional two-level voltage-source inverter and the modular multilevel converter (MMC) to enable operation over a wide frequency range. Topologically, the proposed converter consists of nine arms resembling two sets of three-phase MMCs with three common arms, yielding a nine-arm MMC with a 25% reduction in the number of employed arms compared to a traditional dual three-phase MMC. The multilevel property of a standard MMC is emulated in the proposed converter, however on a two-level basis, resulting in a stepped two-level output voltage waveform. The proposed converter has a reduced footprint with advantages of small voltage steps, modular structure, and ease of scalability. Further, it is able to drive high-power six-phase machines within low operating frequencies at the rated torque. The operating principle of the converter is elaborated, and its modulation scheme is discussed. The features of the proposed converter are verified through simulations and experimentally. - 2018 IEEE.Scopu

A Hybrid Nine-Arm Modular Multilevel Converter for Medium-Voltage Six-Phase Machine Drives

The nine-arm modular multilevel converter (9A-MMC) has been recently proposed as a reduced MMC topology variation for six-phase drive applications, with 25% reduction in the number of employed arms and associated components, compared to a standard dual three-phase MMC, however with a limited output voltage amplitude. This paper proposes a hybrid 9A-MMC comprised of half-bridge submodules (SMs) in both the upper and lower arms, and full-bridge SMs in the middle arms. By employing the negative-voltage state of the full-bridge SMs, the hybrid 9A-MMC avoids the limitations imposed on the dc-link voltage utilization, while achieving further reduction in the component count, compared to a standard 9A-MMC with identical half-bridge SMs. The operating principles of the proposed hybrid 9A-MMC are illustrated with mathematical analysis, whereas its characteristics are verified through both simulation and experimentation. An assessment of the proposed topology quantifying its employed components is also provided, in comparison to other MMC-based six-phase machine drives. - 1982-2012 IEEE.Scopu

A new modulation technique for wide-range control of output voltage in Z-source inverters

Z-source inverter (ZSI) is recently proposed as a single-stage power conversion topology. It adds voltage boost capability for complementing the usual voltage buck operation of the traditional voltage source inverter with enhanced reliability. However, its boosting capability could be limited, and therefore, it may not be suitable for some applications requiring very high voltage boost. To enhance the boosting capability, this paper proposes a new modulation technique to control the generation of the shoot-through intervals in the Z-source inverters. The proposed modulation technique achieves reliable high voltage gain operation without adding any extra hardware to the ZSI structure which preserves its single stage nature. The proposed modulation technique is analyzed in details and its performance is validated using both simulation and experimentations.Qatar National Research FundScopu