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Multisource inverters (MSIs) as a new approach for the integration of the energy and the power sources in electric vehicle applications have gained considerable attraction. Such structures offer the active control of the dc sources without using any dc/dc converters or magnetic elements, which reduces the weight, and the volume of the power electronics interface between the sources and the load. Moreover, high power density and improved efficiency due to the elimination of the magnetics are the other significant features of an MSI. This article proposes a novel three-phase MSI for integration and active control of a high-voltage dc source and a low-voltage dc source. The proposed MSI structure employs a smaller number of semiconductor devices at the current path in various operating modes in comparison to the previously published counterparts, which results in an improved efficiency operation. Performance of the proposed MSI using a modified space vector modulation technique for all possible operating modes is verified through simulations and experiments on a laboratory prototype

This paper highlights some of the work that the author has done in the field of resonant power conversion for nearly the past 40 years. The work presented here is based on practical resonant converters designed for induction heating, space, telecommunications, and renewable energy applications. This work contains information that can help design similar converters and/or devise new ones.

Light load efficiency and output voltage regulation of a low- $Q$ LLC resonant converter is a critical problem for wide input voltage and load range applications. Parasitic capacitances such as rectifier diode junction capacitance ( $C_j$ ) degrade the soft switching performance. Compact size, high density, and high transformer turns-ratio requirements for microinverter applications add significant distributed capacitance ( $C_d$ ) of the low-profile transformer, worsening the output regulation and zero-voltage-switching (ZVS) capability at light loads. Wide switching frequency requirement for regulation at light loads, which increases core losses and turn- off switching losses in power MOSFETs, further degrades the power conversion efficiency. The conventional phase-shift modulation causes a high circulating current and loss of ZVS at light loads. Therefore, a hybrid adjustable switching-frequency-duty-cycle modulation technique for improving the light load efficiency is proposed and analyzed for a full-bridge $LLC$ resonant converter. Accurate loss analysis for the proposed modulation scheme, including the effect of parasitic capacitances, is performed using time-domain equations. The proposed methodology precalculates the optimal duty cycle at light load conditions for the required input voltage range such that minimum power losses are incurred. Variation in switching frequency at the preselected duty-cycle value regulates the output voltage. ZVS over a wide range of operating conditions is observed. An experimental prototype for a 20–40 V input, 380-V/300-W output $LLC$ converter is tested for the validation of theoretical analysis.

Hybrid energy storage systems using battery packs and super capacitor (SC) banks are gaining considerable attraction in electric vehicle (EV) applications. In this article, a new modular reconfigurable multisource inverter (MSI) is proposed for active control of energy storage systems in EV applications. Unlike the conventional approaches, which use massive high-power dc–dc converters with bulk magnetic elements for combining SC banks and battery packs, the new approach utilizing the MSI offers magnetic-less structures. This reduces the weight and volume of the power electronics interface and offers simple control. Along with the proposed MSI, a space vector modulation technique and a deterministic state of charge (SOC) controller are also introduced for the control of the switching actions and operation of the SC bank. Simulations using MATLAB/Simulink and experimental results on a scaled down lab prototype are studied to assess the concepts.

Power electronic converters for electric vehicles (EVs) have been the subject of great interest over the last several decades. This article presents a thorough review of different EV power electronic converters on which the authors have worked for more than one decade. The readers will find this review interesting to design current products and to devise/invent new converters for emerging applications in EV.

Objective To describe remote triage of ‘potentially’ critically ill or injured children in a western Canadian province and to examine the associated factors with ‘missings’ in vital sign items recorded in centralized telephone triage consultations. Methods This is a provincial-wide prospective cohort study. We included all children under 17 years of age consulted through the central transport coordination centres in Alberta from June 2016 to July 2017. We labeled a value as ‘missing’ when the actual value was not identified in the audio records. Results In total, 429 cases were included in this study. The median duration of triage calls was 6.8 minutes. Although the patients’ demographics and primary diagnoses were similar, backgrounds of the referring physicians and hospitals were significantly different between the two cohorts (i.e., patients referred to Calgary versus Edmonton). The proportion of ‘missings’ among the vital sign items varied significantly, in which capillary refilling time (60%), pupils (86%), Glasgow Coma Scale (GCS) (79%), and level of respiratory effort (50%) were not well recorded, whereas heart rate (proportion of ‘missings’: 12%), SpO2 (20%), and respiratory rate (26%) were recorded reasonably well. The lower proportion of ‘missings’ was observed in older aged patients for several vital sign items including systolic blood pressure and GCS. Conclusions The proportion of missing vital signs recorded varied significantly. The ‘missings’ could be associated with referring physician’s background and patients’ demographics such as ‘age’ that should be considered for the improvement of triage quality in the future.

This paper introduces a technique to optimize the efficiency of wireless power transfer (WPT) systems having one transmitter and two receivers having cross-coupling (crosstalk) among the receivers. It is shown that the presence of crosstalk may or may not be beneficial to system efficiency. The emphasis is on the improvement of efficiency in the presence of crosstalk rather than its elimination, which has not been done in previous works. To enable that, a switched capacitor circuit (SCC) is proposed that varies the resonant frequency of the receivers (by varying the net receiver capacitance) in the presence of crosstalk. This improves the total system efficiency in the presence of variable coupling and load conditions, using a perturb-and-observe algorithm.

Objective: Hypertension is the most important risk factor for cardiovascular morbidity and mortality. There is limited data on hypertension prevalence in India. This study was conducted to estimate the prevalence of hypertension among Indian adults. Methods: A national level survey was conducted with fixed one-day blood pressure measurement camps across 24 states and union territories of India. Hypertension was defined as systolic blood pressure (BP) ≥140 mmHg or a diastolic BP ≥90 mmHg or on treatment for hypertension. The prevalence was age- and gender-standardized according to the 2011 census population of India. Results: Blood pressure was recorded for 180,335 participants (33.2% women; mean age 40.6 ± 14.9 years). Among them, 8,898 (4.9%), 99,791 (55.3%), 35,694 (11.9%), 23,084 (12.8%), 9,989 (5.5%), and 2,878 (1.6%) participants were of the age group 18–19, 20–44, 45–54, 55–64, 65–74, and ≥ 75 years, respectively. Overall prevalence of hypertension was 30.7% (95% confidence interval [CI]: 30.5, 30.9) and the prevalence among women was 23.7% (95% CI: 23.3, 24). Prevalence adjusted for 2011 census population and the WHO reference population was 29.7% and 32.8%, respectively. Conclusion: There is a high prevalence of hypertension, with almost one in every three Indian adult affected. Keywords: Hypertension, India, Prevalence

This paper presents an analysis of a Wireless Power Transfer (WPT) System using a buck-boost converter for voltage regulation with the objective of maximizing efficiency by reducing conduction losses and achieving zero voltage switching (ZVS). Unlike conventional buck-boost converter gain characteristics, the buck-boost converter cascaded with the receiver of a WPT system does not have a monotonically increasing gain curve and instead shows a concave characteristic. Thus, a required output voltage can be obtained with two different values of duty ratio of the buck-boost converter if the voltage gain required is below the maximum attainable gain of the system. This novel work will investigate which duty ratio will yield a higher efficiency at various switching frequencies of the transmitter by considering conduction losses and the ability to obtain ZVS. Discussion on coupling strength between coils and its impact on ZVS capability is also shown. Experimental results on a 5W, 5V output system with the two possible duty ratios are used to verify the analysis.

This paper presents a time domain analysis of a Wireless Power Transfer (WPT) system having one transmitter and one receiver in which constant output voltage is maintained by a buck-boost converter placed after the rectifier on the receiver side. The practical modes of operation of the resonant tank are identified, and exact solutions have been derived for the circuit parameters like gain, currents, and voltages in the tank. This helps in preventing overdesign of components from approximate solutions provided by frequency domain modelling. The system is operated in the strongly coupled region below resonant frequency to achieve zero voltage switching (ZVS), by choosing the appropriate duty ratio of the buck-boost converter, which has not been done in existing literature. Experimental results on a $5\mathrm{W}, 5\mathrm{V}$ prototype are used to verify the analysis.

Background The impact of the 2017 American College of Cardiology (ACC)/American Heart Association (AHA) guidelines for diagnosis and management of hypertension on the prevalence of hypertension in India is unknown. Methods We analyzed data from the Cardiac Prevent 2015 survey to estimate the change in the prevalence of hypertension. The JNC8 guidelines defined hypertension as a systolic blood pressure of ≥140 ​mmHg or diastolic blood pressure of ≥90 ​mmHg. The 2017 ACC/AHA guidelines define hypertension as a systolic blood pressure of ≥130 ​mmHg or diastolic blood pressure of ≥80 ​mmHg. We standardized the prevalence as per the 2011 census population of India. We also calculated the prevalence as per the World Health Organization (WHO) World Standard Population (2000–2025). Results Among 180,335 participants (33.2% women), the mean age was 40.6 ​± ​14.9 years (41.1 ​± ​15.0 and 39.7 ​± ​14.7 years in men and women, respectively). Among them, 8,898 (4.9%), 99,791 (55.3%), 35,694 (11.9%), 23,084 (12.8%), 9,989 (5.5%) and 2,878 (1.6%) participants belonged to age group 18–19, 20–44, 45–54, 55–64, 65–74 and ​≥ ​75 years respectively. The prevalence of hypertension according to the JNC8 and 2017 ACC/AHA guidelines was 29.7% and 63.8%, respectively- an increase of 115%. With the 2011 census population of India, this suggests that currently, 486 million Indian adults have hypertension according to the 2017 ACC/AHA guidelines, an addition of 260 million as compared to the JNC8 guidelines. Conclusion According to the 2017 ACC/AHA guidelines, 3 in every 5 Indian adults have hypertension.

A novel and high fidelity simulation-design tool has been proposed for optimizing the design of DC-DC resonant converters. The design tool uses a generalized time-domain analysis applicable to multiple resonant tank configurations. This tool has been made using a MATLAB app designer. The main features of this tool are as follow: 1) fast and accurate steady-state analysis, 2) user-friendly GUI features, 3) design curves for performance optimization and 4) state-of-the-art design examples. The tool is demonstrated for following wide-range DC-DC applications: 1) Solar PV DC-DC micro-inverter 2) Data Center 48V to 12V DC-DC 3) Front-end DC-DC application using LLC and CLL resonant tanks. A comparative analysis is shown between LLC and CLL resonant tanks using design curves. Experimentation has been done to verify the theoretical findings from this tool on the 320W prototype.

Light load efficiency and output regulation of LLC resonant converter is a critical problem for wide input voltage and load range applications due to converter’s parasitic capacitances such as rectifier diode junction capacitance (C j ). Compact size, high density and high transformer turns-ratio requirements for micro-inverter applications adds significant distributed capacitance (C d ) of low-profile transformer, worsening output regulation and zero- voltage switching (ZVS) capability at light loads. Magnetic core losses and turn-off switching losses in power MOSFETs further degrade power conversion efficiency at light loads. Therefore, an improved loss analysis for a hybrid modulation technique is proposed for full-bridge LLC resonant converter. The proposed methodology calculates duty cycle offline such that minimum power losses are incurred at different light loading condition. Variation in switching frequency at selected duty cycle value regulates output voltage. Time domain analysis of proposed technique including effects of C d and C j is performed to ensure accurate loss calculation. An experimental prototype for 20-40V input, 380V/300W output LLC converter is tested for validation of theoretical analysis.

Gallium nitride (GaN) devices are suitable for high-frequency power converters due to their excellent switching performance. To maximize the performance of GaN devices, it is necessary to study the switching characteristics, which requires measuring the switching current. However, GaN devices have a fast switching speed and are sensitive to parasitic parameters, so the current measurement should have a high bandwidth and should not introduce excessive parasitic inductance into the power converters. Traditional current measurements are difficult to meet these requirements, especially for fast GaN devices. This paper presents a high-bandwidth integrated current measurement for detecting the switching current of fast GaN devices. By effectively utilizing the parasitic inductance in the circuit, a single-Turn coil is embedded in the printed circuit board. This coil could pick up a sufficiently strong voltage signal, which is then processed to reconstruct the switching current. Moreover, corrections are carried out to further improve the accuracy. The current measurement has a small insertion impedance and a high bandwidth with a small influence on the parasitic inductance of the converter. The accuracy of the current measurement is experimentally verified by a 40 V GaN-based double pulse test circuit with a load current up to 25 A.

Background: Internet addiction (IA) among university engineering students and its association with psychological distress can impact their educational progress, academic competence, and long-term career goals. Thus, there is a need to investigate the IA among engineering students. Objectives: This study was a first such attempt to explore internet use behaviors, IA, among a large group of engineering students from India, and its association with psychological distress primarily depressive symptoms. Methods: One thousand eighty six engineering students aged 18–21 years pursuing bachelors in engineering from the south Indian city of Mangalore participated in the study. The socio-educational and internet use behaviors data sheet was used to gather demographic information and patterns of internet use, Internet Addiction Test (IAT) was utilized to assess IA, and Self-Report Questionnaire (SRQ-20) assessed psychological distress primarily depressive symptoms. Results: Among the total N = 1086, 27.1% of engineering students met criterion for mild addictive internet use, 9.7% for moderate addictive internet use, and 0.4% for severe addiction to internet. IA was higher among engineering students who were male, staying in rented accommodations, accessed internet several times a day, spent more than 3 h per day on internet, and had psychological distress. Gender, duration of use, time spent per day, frequency of internet use, and psychological distress (depressive symptoms) predicted IA. Conclusions: A substantial proportion of engineering students have IA which can be detrimental for their educational progress in university studies and long-term career goals. Early identification and management of IA and psychological distress among engineering students is crucial.

In diffuse large B-cell lymphoma (DLBCL), the clinical and biological significance of concordant and discordant bone marrow (BM) involvement have not been well investigated. We evaluated 712 de novo DLBCL patients with front-line rituximab-containing treatment, including 263 patients with positive and 449 with negative BM status. Compared with negative BM disease, concordant BM adversely impacted overall and progression-free survival, independent of the International Prognostic Index (IPI) and cell-of-origin classification. Once BM is concordantly involved, poor prognosis was not associated with the extent of BM involvement. Conversely, patients with discordant BM showed favorable overall survival similar to stage I-II DLBCL. A BM-adjusted IPI, using three parameters: concordant BM involvement, age >60 years, and performance status >1, improves the risk stratification for DLBCL with positive BM. Intensive immunochemotherapy seemingly rendered survival benefit for patients with concordant BM, as did rituximab maintenance for the discordant BM group. Frequently revealing adverse clinical and molecular characteristics, patients with concordant BM demonstrated gene expression signatures relevant to tumor cell proliferation, migration and immune escape. In conclusion, clinical and biological heterogeneity is seen in DLBCL with positive BM but concordant BM involvement represents a distinct subset with unfavorable gene signatures, high-risk clinicopathologic features and poor prognosis.

This paper presents an advanced current controller for grid-connected bidirectional ac/dc converters used for energy storage systems (ESSs). The proposed control scheme is designed to incorporate both the time-domain and frequency-domain dynamics to achieve superior transient and steady-state performance. The advanced current controller can overcome the various challenges faced by the conventional current controllers used in this application, which lead to sluggish transients and steady-state errors when tracking the sinusoidal reference for the grid current. Combining the time-domain dynamics with the frequency-domain dynamics creates a more intelligent controller compared to existing methods, which only consider the dynamics of one domain. The proposed controller is able to eliminate steady-state error by adaptively changing the controller coefficients in the frequency domain according to the current error. In the time domain, the control scheme minimizes the derivative of a defined energy function in order to optimize the transient performance. Simulation and experimental results obtained from a 3.3-kW grid-connected ac/dc converter demonstrate its superior performance.

Although majority of lung cancers have distant metastasis at the time of initial diagnosis, colonic metastases are extremely rare. This report presents a rare clinical case which presented with lower limb deep vein thrombosis and found to have colon polyp incidentally detected while evaluating for occult blood positive in stool. Histopathology of the polyp was suggestive of lung primary and on further evaluation PET scan was suggestive of left lung mass with widespread distant metastasis.

This paper presents a new active/reactive power closed-loop control system for a hybrid renewable energy generation system used for single-phase residential/commercial applications.The proposed active/reactive control method includes a hybrid estimator, which is able to quickly and accurately estimate the active/reactive power values. The proposed control system enables the hybrid renewable energy generation system to be able to perform real-time grid interconnection services such as active voltage regulation, active power control, and fault ride-through.Simulation and experimental results demonstrate the superior performance of the proposed closed-loop control system.

This paper presents a novel series–parallel current-driven (SPCD) full-bridge dc/dc converter, which is able to process and deliver power efficiently over a wide range of load variations. In order to guarantee reliable operation of high-frequency dc/dc converters, the converter should be able to sustain soft switching for a wide range of operating conditions. The SPCD full-bridge converter, proposed in this paper, is able to offer soft switching for the input power semiconductors and smooth commutations for the output diodes. Also, the particular structure of the proposed converter eliminates the need for extra auxiliary circuits to provide reactive current for soft switching at light loads. The proposed topology can fully eliminate voltage spikes across the output diodes by providing smooth and lossless commutations for the output diodes. Thus, the proposed converter can be an efficient and reliable solution for variety of applications with a high switching frequency and a high output voltage. The SPCD full-bridge converter has the ability to integrate all magnetic components into an integrated transformer in order to achieve a high power density. The integrated transformer is thoroughly analyzed using ANSYS high-frequency structure simulator. Simulation and experimental results confirm the superior performance of the proposed SPCD full-bridge dc/dc converter.

Cardiac arrhythmia is not so uncommon in a young infant but recognition in neonate and infant is not easy. The management of cardiac arrhythmia with cardiogenic shock, nonresponsive to pharmacological cardioversion in a young infant, can prove to be a challenge at peripheral hospital, owing to its life-threatening consequences. Delay in management may precipitate more fatal arrhythmias. We report a case of supraventricular tachycardia with haemodynamic compromise in a 32-day-old baby, presumably secondary to viral infection. Pharmacological and physiological methods could not revert arrhythmia to the sinus rhythm and the baby required repeated synchronised cardioversion. The aim of this case report is to highlight the importance of cardioversion to save the life of young infant from potentially fatal arrhythmia.

Background: Excessive internet use, psychological distress, and its inter-relationship among university students can impact their academic progress, scholastic competence, career goals, and extracurricular interests. Thus, a need exists to evaluate the addictive internet use among university students. Objectives: This study was set up to examine the internet use behaviors, internet addiction (IA), and its association with psychological distress primarily depression among a large group of university students from South India. Methods: Totally 2776 university students aged 18–21 years; pursuing undergraduate studies from a recognized university in South India participated in the study. The patterns of internet use and socioeducational data were collected through the internet use behaviors and demographic data sheet, IA test (IAT) was utilized to assess IA and psychological distress primarily depressive symptoms were evaluated with Self-Report Questionnaire-20. Results: Among the total n = 2776, 29.9% (n = 831) of university students met criterion on IAT for mild IA, 16.4% (n = 455) for moderate addictive use, and 0.5% (n = 13) for severe IA. IA was higher among university students who were male, staying in rented accommodations, accessed internet several times a day, spent more than 3 h per day on the Internet and had psychological distress. Male gender, duration of use, time spent per day, frequency of internet use, and psychological distress (depressive symptoms) predicted IA. Conclusions: IA was present among a substantial proportion of university students which can inhibit their academic progress and impact their psychological health. Early identification of risk factors of IA can facilitate the effective prevention and timely initiation of treatment strategies for IA and psychological distress among university students.

Multi Source Inverters (MSI) as a magnetic-less approach for active control of Hybrid Energy Storage Systems (HESS) in Electric Vehicles (EVs) have been proposed lately. Using such technologies leads to more compact and more efficient HESS in EVs. In this paper, a novel Space Vector Modulation (SVM) technique is surveyed for a recently proposed modular MSI. This method is not limited to the proposed MSI and can be applied to any type of MSIs. Since SVM, in general, requires a heavy calculation burden, this method not only simplifies the mathematical computational steps, but also enhances the implementation speed, and lowers the hardware requirements. Different steps of the method are explained through theory and math. Simulation results are implemented on a recently proposed modular MSI for US06 driving cycle using vector speed control of the induction machines in Matlab/Simulink environment. Finally, the method is implemented on a 1 kW lab prototype of the MSI, which validates the theory and the simulations.

This paper presents an energy management method for single-phase telecommunication backup systems operating in islanded mode. The management of energy has been performed through controlling the power electronic interfaces that connect the backup systems to the telecommunication facilities and the utility grid. The proposed control scheme regulates the backup network parameters, such as the voltage and frequency of the supplied power, and the DC-bus voltage simultaneously. Using the proposed control scheme the reliable and efficient operation of the backup system during power outages and islanded mode, can be guaranteed. The simulation and experimental results approve the superior performance of the proposed controller in comparison with the conventional droop-based controller proposed for backup systems in islanded mode.

Design and analysis of a new bridgeless three-level integrated AC-DC converter is presented in this paper. The presented converter combines a bridgeless ac-dc converter and a three-level resonant converter. Variable frequency control along with duty cycle control is implemented for output voltage and bus voltage regulation. The duty cycle control regulates the dc bus voltage while shaping the input current and the variable frequency control regulates the output voltage. A bridgeless rectifier structure eliminates the auxiliary circuit that was usually used to balance the dc bus capacitor voltage in some of previously reported topologies, which achieves simplicity and reduces losses associated with the extra auxiliary circuit. The presented converter also can achieve zero voltage switching (ZVS) for all of MOSFETs, high power factor, and low voltage stresses at the same time. Complete analysis and design is given to verify the performance. A 1kW experiment prototype is built as design example to verify the effectiveness of the presented converter.

Traditionally, energy storage systems in electric drive vehicles can be connected to the high voltage DC link through passive or active configurations. Passive configuration puts sources in parallel without any decoupling converter among sources which increases the number of series cells in battery and Ultra-Capacitor (UC) bank. Also, due to the lack of control over UC, its stored energy cannot be utilized efficiently. Active configurations exploit DC/DC converters to control the sources separately. However, existence of DC/DC converters with bulk magnetics increases the system volume and weight, and decreases the efficiency due to inductors' series resistances. Recently, multisource inverters as a new concept in electric drive vehicle applications have been introduced. Higher efficiency due to single stage conversion and compact structures due to removal of the magnetics are of the advantages of such systems. In this paper, a modular multi-source inverter is proposed for combining battery packs and UC banks as the energy storage systems in electric drive vehicles. Matlab Simulink was used for simulation purposes and a scaled down lab prototype was built to verify the simulations.

This paper presents a double-input solar inverter system with a magnetically coupled AC/DC soft-switched bidirectional converter unit for energy storage application. The presented double-input front-end converter consists of an integrated DC/DC SEPIC and Cuk type circuit with a shared output filter, while the magnetically coupled bi-directional AC/DC converter is a current-fed full-bridge circuit. The presented bi-directional converter unit is able to achieve zero current switching (ZCS) condition when it operates in rectifier mode (i.e. the energy storage unit in charging condition) and is able to achieve zero voltage switching (ZVS) turn-on with ZCS turn-off in its inverter mode (i.e. when supplying energy to the load). Due to the soft-switching function provided by the bidirectional converter interface and the use of a double-input PV converter with an integrated output filter, the proposed circuit is compact and is well suited for residential solar energy conversion applications. The operating principles of the proposed system will be discussed in this paper. Results are given on a 300W double-input PV inverter system to highlight the merits of this work.

This paper investigates the design of digital low pass filters with tight passband for energy management of hybrid energy storage systems used in electric drive vehicles. Filter requirements based on the sources and converter specification are extracted and the results are evaluated for different Infinite Impulse Response (IIR) filters. The filter with the best performance is chosen and used in an EV energy management controller with hybrid battery/UC storage system. Simulation results of the filter performance, energy management controller and battery state of health estimation are provided.

An isolated, single-stage bi-directional AC-DC converter for electric vehicle battery charger with no electrolytic capacitor and 8 active switches is proposed. The proposed converter prevents low frequency power ripple from going to the battery. This prevents extra heat production in the battery and consequently causes the battery to last longer. No use of an electrolytic capacitor in the circuit increases the reliability of the system. To control the circuit, a four-part controller is proposed. The controller obtains ZVS for all the active switches while it optimizes the performance of the system in terms of conduction losses. Simulation results with PSIM, and experimental results to verify the theory, have been carried out.

It is becoming a useful and favorable trend to remove unreliable E-caps from the single-phase AC-DC converters which are being widely used in renewable energy applications and energy storage systems, without letting the low frequency power penetrating into the DC-side. Active filter is an attractive solution for this. Since active filter processes a major part of power, its performance affects the performance of the converter. Therefore, it is important that it operates efficiently for a wide range of operation. A minimum conduction loss ZVS control is proposed for buck-type active filter, which can be used across the DC-link of two-stage converters or across the DC side of the single-stage AC-DC converters. The control minimize the conduction losses for the buck active filter as well as obtaining ZVS for all the switching instants. Loss comparison with hard-switched control and other ZVS control methods are presented and show the effectiveness of the proposed method. Simulation and experimental results are presented.

In recent years, wireless power transfer technology has come to limelight because of its possibility of providing viable solutions to the challenges encountered by electronic device consumers when using traditional methods of charging batteries. This paper presents a multiple receiver wireless power transfer system for charging mobile phone batteries. The circuit consists of a transmitter and two receiver systems. A mathematical analysis of the circuit is carried out and simulated to understand its behavior with variation in coupling coefficient and load. In order to charge mobile phones without an extra communication module over a wide range of coupling coefficients, a variable frequency control algorithm is used. The transmitter circuit uses the algorithm to track the maximum input power of the system. The output voltage of the receiver circuit is controlled to meet the power requirement of the load as coupling coefficient varies by using a switch capacitor modeled as two back to back connected MOSFETs with their drain-to-source capacitance. The proposed converter circuit topology is simulated and the results are presented. The circuit operates over a wide range of coupling coefficient and the power requirement of the mobile phones are met without using an extra communication module. The resonance frequency of the circuit is 5.7MHZ and it is design to deliver 10W (5V, 2A) each to two mobile phones.

Energy-efficient residential lighting such as household light-emitting diode (LED) lamps with ac input require an ac/dc converter (or driver) with large output capacitance to minimize the low frequency LED current ripple. The energy storage capacitor used in the conventional ac/dc LED driver is usually an electrolytic capacitor due to its low cost and high energy density. However, the average lifetime of an electrolytic capacitor is at least 2–3 times less than that of an LED device. Hence, the potential lifetime of the LED lamp is significantly affected by the presence of the electrolytic capacitor in the driver circuit. In this paper, two novel isolated single-switch ac/dc high power factor LED drivers without using any electrolytic capacitors are proposed. In the proposed circuits, the energy storage capacitor is moved to the rectifier side, with a three-winding transformer used to provide isolation; input power factor correction as well as to store and provide the required energy to the output. As a result, the energy storage capacitance is significantly reduced, which allows film capacitor to be used to replace the conventionally used electrolytic capacitors. The circuit’s operating principles and its characteristics are described in this paper. Simulation and experimental results are given on a 120 $\text{V}_{\rm rms}$ , 12 W prototype to confirm that a power factor of at least 0.96 is achieved.

Due to the ever growing global energy demand and pollution levels, clean and renewable alternative energy resources, such as wind, have become indispensable for preserving the planet for future generations. With wind being an unpredictable resource, it is imperative that wind systems extract as much power from the wind as possible while it is available. The conventional maximum power point tracking (MPPT) algorithms that use predetermined mathematical relationships to represent a specific wind system’s power/torque characteristics suffer the drawback of deteriorated efficiency over time whereas the perturb and observe algorithms are susceptible to logical errors when subjected to frequent atmospheric variations. In order to solve the aforementioned drawbacks as well as to reduce the cost of the sensing network required to achieve MPPT, this paper proposes a novel sensorless slope-assisted MPPT algorithm that is able to avoid logical errors attributed to wind fluctuations by detecting and identifying atmospheric changes. Atmospheric changes are detected by a state observer by monitoring the generator output power, the ac/dc rectifier output voltage, and the rate of change of the power-voltage ratio without the need for anemometers and any generator speed sensors. The detailed description of the proposed MPPT control logic will be provided in this paper. The functionality of the proposed control method is verified through the simulation results on a 3-kW system, as well as the experimental results on a proof-of-concept 200-W prototype.

This paper presents a new dc-bus voltage control technique for single-phase bidirectional ac/dc converters. The proposed controller is able to significantly improve the transient response of the dc-bus voltage control loop and provide a robust and reliable closed-loop control system. In the proposed approach, the dc value of the dc-bus voltage is precisely estimated through a specific adaptive filter. The structure of the proposed filter provides a very fast and robust estimation for the dc value of the dc-bus voltage. In particular, the proposed dc-extraction technique is able to precisely estimate the dc value in presence of double-frequency ripple mounted on top of the dc-bus voltage in single-phase ac/dc converters. Simulation and experimental results demonstrate the superior performance of the proposed closed-loop control system compared to the conventional ones.

This paper presents a description and analysis of a full-bridge converter with a novel passive and robust auxiliary circuit for zero-voltage-switching (ZVS) operation. A generalized time-domain state-space analysis is provided to describe the steady-state behavior of the auxiliary circuit. Complete comparison between the well-known single-inductor auxiliary circuit, and the proposed one is presented. For a similar peak current in the auxiliary branch, needed for ZVS, a minimum of 20% reduction in rms current is achieved to decrease the conduction losses in the power switches and in the auxiliary circuit. Also, 65% reduction in switching frequency variation is obtained. This narrower frequency range reduces the need for very high-frequency operation and the associated gate driver losses as well as the difficulty of electromagnetic interference (EMI) filter design. All the theoretical results are experimentally verified.

In this paper, a current sensorless adaptive secondary-side control is proposed for the series resonant converter (SRC), making it a good candidate for MHz 48 voltage regulators. By means of varying ac equivalent resistance, the output voltage regulation is achieved by controlling the duty cycle of the synchronous MOSFET. By taking advantage of the secondary-side control, SRCs can operate under zero-voltage switching at any input voltage and load conditions. A current sensorless adaptive digital control is proposed to control the current-type synchronous MOSFETs, which automatically compensates the delay caused by the current-sensor circuit and the gate driver, and also eliminates the current sensor in the power path. A hybrid control strategy is introduced to overcome the efficiency degradation caused by the secondary-side control.

This paper presents a very fast dc-bus voltage controller for a single-phase grid-connected voltage-source inverter (VSI) with an LCL output filter used in renewable energy applications. In single-phase grid-connected inverters, the design of the dc-bus voltage control scheme is very challenging due to the presence of a second harmonic ripple across the dc-bus voltage. The proposed dc-bus voltage control scheme is able to address the difficulties introduced by the second-harmonic ripple. The dc-bus voltage controller is based on an adaptive droop control technique, which is able to provide a very fast transient response for the closed-loop system and ensures the optimal operation of the VSI during steady-state conditions. Also, the simple structure of the controller makes it very practical for grid-connected VSIs used in renewable energy power conditioning systems. Theoretical analysis and experimental results demonstrate the superior performance of the proposed control approach compared to conventional dc-bus voltage control schemes.

The use of multiple heterogeneous, low-cost, small Unmanned Aerial Vehicles (UAVs) as a tool in several application domains is becoming increasingly important. One critical aspect to enable the use of such vehicles is the coordination/planning system, whose task complexity increases with the number of vehicles and the communications constraints that arise due to their small size and large distances. In this work, we propose a control architecture for a platoon of relay UAVs that are independent of the coordination system. The platoon task consists in interconnecting the communication link between the possibly mobile command station and a UAV in a mission. The relays are actively driven to deploy, create a network and maintain a desired Quality-of-Service (QoS) level, defined in this paper. We present an architecture that is composed by a waypoint generator based on the network QoS and a Time Coordinated Path Following (TCPF) controller with a method to reduce the frequency of information exchange between the relay UAVs, through the use of a self-triggered control strategy. Exploiting this architecture, it is possible to plan a mission operation for a UAV without the need of considering vehicle-to-command-station communication constraints that will be satisfied by the introduction of the relay-UAVs platoon. Simulation results are provided to illustrate the efficacy of the developed strategy. The self-triggered approach results in significant reduction of information exchange between the relay UAVs, while maintaining the user desired network QoS.

In this paper, a fully ZVT auxiliary cell for boost type resonant converters is proposed to achieve soft switching in ON-OFF control mode. In conventional ON-OFF methods, transient and switching losses at the beginning and end of each power pulse decrease the overall efficiency of the system at high modulation frequencies. This ZVT cell offers zero voltage switching without imposing extra resonant current. This structure can be implemented in most boost type resonant converters such as class E, ϕ 2 and quasi-resonant DC-DC converters. The fully ZVS operation, the absence of inductive components, and low voltage and current stress are main advantages of this cell. Thus, the ON-OFF control can be implemented at higher modulation frequencies without any significant drop in the efficiency. Simple structure and timing are other advantages of the proposed cell, which makes it useful for solar applications. The operation of the proposed auxiliary cell is analyzed in individual intervals. To verify the mathematical analysis, the proposed cell is implemented in a 3 MHz quasi-resonant boost converter. A maximum efficiency of 95.8% is obtained at 385 watts output and the efficiency drops about two percent at 80 watts at 500 kHz modulation frequency.

This paper presents a novel hybrid adaptive droop controller to simultaneously regulate both the AC-side and DC-side parameters for power electronic converters in single-phase Microgrids. The main contribution of this paper is to integrate the AC-side and DC-side controllers. Unlike previously presented control schemes, where the DC-bus is considered as an infinite bus or constant voltage bus, the proposed control method incorporates the dynamics of the DC-side while regulating voltage and frequency at the AC-side. Designing the control scheme in single-phase is challenging due to the existence of double-frequency ripples in DC-bus voltage and converter output active/reactive power signals. In order to improve the transient performance of the proposed controller, two adaptive estimators have been used to estimate the real-time values of DC-bus voltage and output active/reactive power signals without the need to add low-pass filters. This controller can provide a tightly regulated voltage required for critical loads in MGs while improving the transient response in both DC and AC side. Simulation and experimental results in a single-phase islanded Microgrid show the superior performance of the proposed control scheme in regulating the desired parameters in AC and DC side in comparison with the conventional droop-based controllers.

Multilevel inverters as the best existing solution for high power/ medium voltage applications have been utilized to incorporate renewable energy sources into electric grid. Solar energy, and fuel-cells as two major sources of power can only provide unidirectional power flow. However, utilizing cascaded H-bridge inverters or other inverters with trinary voltage ratios at the input DC links might cause regeneration phenomenon which results in bidirectional power flow. This paper provides a solution to prevent regenerative current from DC link of multilevel inverters using predictive current control. The controller can simultaneously control the DC-link capacitor voltages and the AC side current by regulating the DC link current. Simulations and experiments have been carried out to prove the validity and performance operation of the proposed method.

This paper presents a boost switched-capacitor nine-level single-phase inverter, which utilizes flying capacitors and an H-bridge. Besides the boosting ability, the inverter is capable of producing redundant switching states that are used as a degree of freedom in controlling the voltage of DC link capacitor. A comprehensive study of the theoretical aspects of the proposed structure and its practical considerations have been conducted. The performance of the inverter has been evaluated using simulation and experimental results.

The concept of microgrid (MG) has been introduced as a solution to future electrical grid challenges such as the rapid increase of electrical demand, harvesting energy from renewable energy sources, and ensuring the quality and reliability of electricity supply. Distributed energy sources, as well as energy storage systems are interfaced with MGs through power electronic inverters. Control systems of the power electronic inverters in MGs play a key role in ensuring the perfect performance of MGs. This paper presents a comprehensive review of various control systems used in MGs. In particular, different levels of MG control systems have been investigated and corresponding control strategies at each level have been compared in detail. This paper categorizes MG control systems into four levels: 1- The converter output control that shapes the output current in order to control the flow of output power, 2- The power sharing algorithm that guarantees the even distribution of the load between parallel inverters, 3- The MG supervisory controller (secondary level) that deals with the supervisory control of the converters within the MG, and 4- The grid supervisory controller (tertiary level) that controls the flow of power between the main grid and the MG.

A novel bi-directional AC/DC converter topology is presented in this paper. This circuit topology offers a single-stage non-isolated solution for power conversion, suitable for ESS applications. In the proposed power circuitry, the DC-bus voltage can be higher or lower than the peak of the AC voltage. The detailed analysis reveals that the converter characteristics are different in the rectification and inversion modes, hence it requires different control strategies for each mode of operation. In the rectification mode, only the DC-bus voltage control is employed whereas in the inversion mode, both the DC-bus voltage control as well as the grid current control have to be used for generating the converter switching pulses. The operation of the proposed topology is validated through simulation and experimental results.