Switching Pattern Improvement for One-Cycle Zero-Integral-Error Current Controller

[EN] The one-cycle current control is a non-linear technique based on the cycle-by-cycle calculation of the ON time of the power converter switches. Its application is not common in tracking fast-changing reference currents, due to the necessity of fast and accurate measurements, and high-speed computing. In a previous study, a one-cycle digital current controller based on the minimization of the integral error of the current was developed and applied to the control of a three-phase shunt active power filter. In the present work, the one-cycle controller has been improved by proposing a new switching pattern. It allows an easy implementation that reduces the critical computational cost and avoids the main drawbacks of the previous implementation. The controller has been applied in a three-leg four-wire shunt active power filter, including a stability analysis considering the proposed switching pattern. Simulated and experimental results are presented to validate the proposed controller.Orts-Grau, S.; Balaguer-Herrero, P.; Alfonso-Gil, JC.; Martínez-Márquez, CI.; Martínez-Navarro, G.; Gimeno Sales, FJ.; Segui-Chilet, S. (2022). Switching Pattern Improvement for One-Cycle Zero-Integral-Error Current Controller. IEEE Access. 10:158-167. https://doi.org/10.1109/ACCESS.2021.31377581581671

Small Wind Turbine Emulator Based on Lambda-Cp Curves Obtained under Real Operating Conditions

[EN] This paper proposes a new on-site technique for the experimental characterization of small wind systems by emulating the behavior of a wind tunnel facility. Due to the high cost and complexity of these facilities, many manufacturers of small wind systems do not have a well knowledge of the characteristic lambda-Cp curve of their turbines. Therefore, power electronics converters connected to the wind generator are usually programmed with speed/power control curves that do not optimize the power generation. The characteristic lambda-Cp curves obtained through the proposed method will help manufacturers to obtain optimized speed/power control curves. In addition, a low cost small wind emulator has been designed. Programmed with the experimental lambda-Cp curve, it can validate, improve, and develop new control algorithms to maximize the energy generation. The emulator is completed with a new graphic user interface that monitors in real time both the value of the lambda-Cp coordinate and the operating point on the 3D working surface generated with the characteristic lambda-Cp curve obtained from the real small wind system. The proposed method has been applied to a small wind turbine commercial model. The experimental results demonstrate that the point of operation obtained with the emulator is always located on the 3D surface, at the same coordinates (rotor speed/wind speed/power) as the ones obtained experimentally, validating the designed emulator.Martínez-Márquez, CI.; Twizere-Bakunda, JD.; Lundbäck-Mompó, D.; Orts-Grau, S.; Gimeno Sales, FJ.; Segui-Chilet, S. (2019). Small Wind Turbine Emulator Based on Lambda-Cp Curves Obtained under Real Operating Conditions. Energies. 12(13):1-17. https://doi.org/10.3390/en12132456S1171213Nichita, C., Luca, D., Dakyo, B., & Ceanga, E. (2002). Large band simulation of the wind speed for real time wind turbine simulators. IEEE Transactions on Energy Conversion, 17(4), 523-529. doi:10.1109/tec.2002.805216Pillay, P., & Krishnan, R. (1988). Modeling of permanent magnet motor drives. IEEE Transactions on Industrial Electronics, 35(4), 537-541. doi:10.1109/41.9176Tanvir, A., Merabet, A., & Beguenane, R. (2015). Real-Time Control of Active and Reactive Power for Doubly Fed Induction Generator (DFIG)-Based Wind Energy Conversion System. Energies, 8(9), 10389-10408. doi:10.3390/en80910389Martinez, F., Herrero, L. C., & de Pablo, S. (2014). Open loop wind turbine emulator. Renewable Energy, 63, 212-221. doi:10.1016/j.renene.2013.09.019Castelló, J., Espí, J. M., & García-Gil, R. (2016). Development details and performance assessment of a Wind Turbine Emulator. Renewable Energy, 86, 848-857. doi:10.1016/j.renene.2015.09.010Kojabadi, H. M., Chang, L., & Boutot, T. (2004). Development of a Novel Wind Turbine Simulator for Wind Energy Conversion Systems Using an Inverter-Controlled Induction Motor. IEEE Transactions on Energy Conversion, 19(3), 547-552. doi:10.1109/tec.2004.832070Choy, Y.-D., Han, B.-M., Lee, J.-Y., & Jang, G.-S. (2011). Real-Time Hardware Simulator for Grid-Tied PMSG Wind Power System. Journal of Electrical Engineering and Technology, 6(3), 375-383. doi:10.5370/jeet.2011.6.3.375Wasynczuk, O., Man, D. T., & Sullivan, J. P. (1981). Dynamic Behavior of a Class of Wind Turbine Generators during Random Wind Fluctuations. IEEE Power Engineering Review, PER-1(6), 47-48. doi:10.1109/mper.1981.5511593Dai, J., Liu, D., Wen, L., & Long, X. (2016). Research on power coefficient of wind turbines based on SCADA data. Renewable Energy, 86, 206-215. doi:10.1016/j.renene.2015.08.02

One-Cycle Zero-Integral-Error Current Control for Shunt Active Power Filters

[EN] Current control has, for decades, been one of the more challenging research fields in the development of power converters. Simple and robust nonlinear methods like hysteresis or sigma-delta controllers have been commonly used, while sophisticated linear controllers based on classical control theory have been developed for PWM-based converters. The one-cycle current control technique is a nonlinear technique based on cycle-by-cycle calculation of the ON time of the converter switches for the next switching period. This kind of controller requires accurate measurement of voltages and currents in order achieve a precise current tracking. These techniques have been frequently used in the control of power converters generating low-frequency currents, where the reference varies slowly compared with the switching frequency. Its application is not so common in active power filter current controllers due to the fast variation of the references that demands not only accurate measurements but also high-speed computing. This paper proposes a novel one-cycle digital current controller based on the minimization of the integral error of the current. Its application in a three-leg four-wire shunt active power filter is presented, including a stability analysis considering the switching pattern selection. Furthermore, simulated and experimental results are presented to validate the proposed controller.Orts-Grau, S.; Balaguer-Herrero, P.; Alfonso-Gil, JC.; Martínez-Márquez, CI.; Gimeno Sales, FJ.; Segui-Chilet, S. (2020). One-Cycle Zero-Integral-Error Current Control for Shunt Active Power Filters. Electronics. 9(12):1-16. https://doi.org/10.3390/electronics9122008S116912Orts-Grau, S., Gimeno-Sales, F. J., Abellan-Garcia, A., Segui-Chilet, S., & Alfonso-Gil, J. C. (2010). Improved Shunt Active Power Compensator for IEEE Standard 1459 Compliance. IEEE Transactions on Power Delivery, 25(4), 2692-2701. doi:10.1109/tpwrd.2010.2049033Orts-Grau, S., Gimeno-Sales, F. J., Segui-Chilet, S., Abellan-Garcia, A., Alcaniz-Fillol, M., & Masot-Peris, R. (2009). Selective Compensation in Four-Wire Electric Systems Based on a New Equivalent Conductance Approach. IEEE Transactions on Industrial Electronics, 56(8), 2862-2874. doi:10.1109/tie.2009.2014368Trinh, Q.-N., & Lee, H.-H. (2013). An Advanced Current Control Strategy for Three-Phase Shunt Active Power Filters. IEEE Transactions on Industrial Electronics, 60(12), 5400-5410. doi:10.1109/tie.2012.2229677Bosch, S., Staiger, J., & Steinhart, H. (2018). Predictive Current Control for an Active Power Filter With LCL-Filter. IEEE Transactions on Industrial Electronics, 65(6), 4943-4952. doi:10.1109/tie.2017.2772176Balasubramanian, R., Parkavikathirvelu, K., Sankaran, R., & Amirtharajan, R. (2019). Design, Simulation and Hardware Implementation of Shunt Hybrid Compensator Using Synchronous Rotating Reference Frame (SRRF)-Based Control Technique. Electronics, 8(1), 42. doi:10.3390/electronics8010042Imam, A. A., Sreerama Kumar, R., & Al-Turki, Y. A. (2020). Modeling and Simulation of a PI Controlled Shunt Active Power Filter for Power Quality Enhancement Based on P-Q Theory. Electronics, 9(4), 637. doi:10.3390/electronics9040637Panigrahi, R., Subudhi, B., & Panda, P. C. (2016). A Robust LQG Servo Control Strategy of Shunt-Active Power Filter for Power Quality Enhancement. IEEE Transactions on Power Electronics, 31(4), 2860-2869. doi:10.1109/tpel.2015.2456155Herman, L., Papic, I., & Blazic, B. (2014). A Proportional-Resonant Current Controller for Selective Harmonic Compensation in a Hybrid Active Power Filter. IEEE Transactions on Power Delivery, 29(5), 2055-2065. doi:10.1109/tpwrd.2014.2344770Panigrahi, R., & Subudhi, B. (2017). Performance Enhancement of Shunt Active Power Filter Using a Kalman Filter-Based ${{{\rm H}}_\infty }$ Control Strategy. IEEE Transactions on Power Electronics, 32(4), 2622-2630. doi:10.1109/tpel.2016.2572142Jiang, W., Ding, X., Ni, Y., Wang, J., Wang, L., & Ma, W. (2018). An Improved Deadbeat Control for a Three-Phase Three-Line Active Power Filter With Current-Tracking Error Compensation. IEEE Transactions on Power Electronics, 33(3), 2061-2072. doi:10.1109/tpel.2017.2693325Buso, S., Caldognetto, T., & Brandao, D. (2015). Dead-Beat Current Controller for Voltage Source Converters with Improved Large Signal Response. IEEE Transactions on Industry Applications, 1-1. doi:10.1109/tia.2015.2488644Tarisciotti, L., Formentini, A., Gaeta, A., Degano, M., Zanchetta, P., Rabbeni, R., & Pucci, M. (2017). Model Predictive Control for Shunt Active Filters With Fixed Switching Frequency. IEEE Transactions on Industry Applications, 53(1), 296-304. doi:10.1109/tia.2016.2606364Kumar, M., & Gupta, R. (2017). Sampled-Time-Domain Analysis of a Digitally Implemented Current Controlled Inverter. IEEE Transactions on Industrial Electronics, 64(1), 217-227. doi:10.1109/tie.2016.2609840Ho, C. N.-M., Cheung, V. S. P., & Chung, H. S.-H. (2009). Constant-Frequency Hysteresis Current Control of Grid-Connected VSI Without Bandwidth Control. IEEE Transactions on Power Electronics, 24(11), 2484-2495. doi:10.1109/tpel.2009.2031804Wu, F., Feng, F., Luo, L., Duan, J., & Sun, L. (2015). Sampling period online adjusting-based hysteresis current control without band with constant switching frequency. IEEE Transactions on Industrial Electronics, 62(1), 270-277. doi:10.1109/tie.2014.2326992Holmes, D. G., Davoodnezhad, R., & McGrath, B. P. (2013). An Improved Three-Phase Variable-Band Hysteresis Current Regulator. IEEE Transactions on Power Electronics, 28(1), 441-450. doi:10.1109/tpel.2012.2199133Komurcugil, H., Bayhan, S., & Abu-Rub, H. (2017). Variable- and Fixed-Switching-Frequency-Based HCC Methods for Grid-Connected VSI With Active Damping and Zero Steady-State Error. IEEE Transactions on Industrial Electronics, 64(9), 7009-7018. doi:10.1109/tie.2017.2686331Chang, C.-H., Wu, F.-Y., & Chen, Y.-M. (2012). Modularized Bidirectional Grid-Connected Inverter With Constant-Frequency Asynchronous Sigma–Delta Modulation. IEEE Transactions on Industrial Electronics, 59(11), 4088-4100. doi:10.1109/tie.2011.2176693Mertens, A. (1994). Performance analysis of three-phase inverters controlled by synchronous delta-modulation systems. IEEE Transactions on Industry Applications, 30(4), 1016-1027. doi:10.1109/28.297919Morales, J., de Vicuna, L. G., Guzman, R., Castilla, M., & Miret, J. (2018). Modeling and Sliding Mode Control for Three-Phase Active Power Filters Using the Vector Operation Technique. IEEE Transactions on Industrial Electronics, 65(9), 6828-6838. doi:10.1109/tie.2018.2795528Guzman, R., de Vicuna, L. G., Morales, J., Castilla, M., & Miret, J. (2016). Model-Based Control for a Three-Phase Shunt Active Power Filter. IEEE Transactions on Industrial Electronics, 63(7), 3998-4007. doi:10.1109/tie.2016.2540580Pichan, M., & Rastegar, H. (2017). Sliding-Mode Control of Four-Leg Inverter With Fixed Switching Frequency for Uninterruptible Power Supply Applications. IEEE Transactions on Industrial Electronics, 64(8), 6805-6814. doi:10.1109/tie.2017.2686346E. S., S., E. K., P., Chatterjee, K., & Bandyopadhyay, S. (2014). An Active Harmonic Filter Based on One-Cycle Control. IEEE Transactions on Industrial Electronics, 61(8), 3799-3809. doi:10.1109/tie.2013.2286558Wang, L., Han, X., Ren, C., Yang, Y., & Wang, P. (2018). A Modified One-Cycle-Control-Based Active Power Filter for Harmonic Compensation. IEEE Transactions on Industrial Electronics, 65(1), 738-748. doi:10.1109/tie.2017.2682021Jin, T., & Smedley, K. M. (2006). Operation of One-Cycle Controlled Three-Phase Active Power Filter With Unbalanced Source and Load. IEEE Transactions on Power Electronics, 21(5), 1403-1412. doi:10.1109/tpel.2006.880264Hirve, S., Chatterjee, K., Fernandes, B. G., Imayavaramban, M., & Dwari, S. (2007). PLL-Less Active Power Filter Based on One-Cycle Control for Compensating Unbalanced Loads in Three-Phase Four-Wire System. IEEE Transactions on Power Delivery, 22(4), 2457-2465. doi:10.1109/tpwrd.2007.893450Qiao, C., Smedley, K. M., & Maddaleno, F. (2004). A Single-Phase Active Power Filter With One-Cycle Control Under Unipolar Operation. IEEE Transactions on Circuits and Systems I: Regular Papers, 51(8), 1623-1630. doi:10.1109/tcsi.2004.832801Qiao, C., Jin, T., & MaSmedley, K. (2004). One-Cycle Control of Three-Phase Active Power Filter With Vector Operation. IEEE Transactions on Industrial Electronics, 51(2), 455-463. doi:10.1109/tie.2004.82522

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research