Showing papers on "Voltage published in 2015"
TL;DR: In this paper, the rate-dependent hysteresis seen in current-voltage scans of CH3NH3PbI3 perovskite solar cells is related to a slow field-induced process that tends to cancel the electric field in the device at each applied bias voltage.
Abstract: In this work we show that the rate-dependent hysteresis seen in current–voltage scans of CH3NH3PbI3 perovskite solar cells is related to a slow field-induced process that tends to cancel the electric field in the device at each applied bias voltage. It is attributed to the build-up of space charge close to the contacts, independent of illumination and most likely due to ionic displacement, which is enhanced when the device undergoes aging. This process can also lead to a reduction of the open-circuit voltage or the steady-state photocurrent and does not directly correlate with the development of the hysteresis if it is measured at a fixed voltage sweep rate.
1,150 citations
TL;DR: In this paper, a maximum efficiency point tracking control scheme is proposed to maximize the system efficiency while regulating the output voltage, which is unique and prominent in that it fixes the operating frequency at the receiving-side resonant frequency and converts both the input voltage and the load resistance at the same time.
Abstract: With a good balance between power transfer distance and efficiency, wireless power transfer (WPT) using magnetic resonant coupling is preferred in many applications. Generally, WPT systems are desired to provide constant output voltage with the highest possible efficiency as power supplies. However, the highest efficiency is not achieved by the reported closed-loop WPT systems that maintain constant output voltage against coupling and load variations. In this paper, an efficiency evaluation method is put forward to evaluate the closed-loop control schemes. Furthermore, a maximum efficiency point tracking control scheme is proposed to maximize the system efficiency while regulating the output voltage. This control scheme is unique and prominent in that it fixes the operating frequency at the receiving-side resonant frequency and converts both the input voltage and the load resistance at the same time. Thus, the maximum efficiency point on the constant output voltage trajectory can be tracked dynamically. Therefore the system's output voltage can be maintained constant and its efficiency is always the highest. The experimental results show that the maximum efficiency point is tracked and a very high overall efficiency is achieved over wide ranges of coupling coefficient and load resistance.
463 citations
TL;DR: In this paper, a comprehensive framework for understanding and improving the open-circuit voltage of organic solar cells is developed based on equilibrium between charge transfer (CT) states and free carriers.
Abstract: Organic solar cells lag behind their inorganic counterparts in efficiency due largely to low open-circuit voltages (Voc). In this work, a comprehensive framework for understanding and improving the open-circuit voltage of organic solar cells is developed based on equilibrium between charge transfer (CT) states and free carriers. It is first shown that the ubiquitous reduced Langevin recombination observed in organic solar cells implies equilibrium and then statistical mechanics is used to calculate the CT state population density at each voltage. This general result permits the quantitative assignment of Voc losses to a combination of interfacial energetic disorder, non-negligible CT state binding energies, large degrees of mixing, and sub-ns recombination at the donor/acceptor interface. To quantify the impact of energetic disorder, a new temperature-dependent CT state absorption measurement is developed. By analyzing how the apparent CT energy varies with temperature, the interfacial disorder can be directly extracted. 63–104 meV of disorder is found in five systems, contributing 75–210 mV of Voc loss. This work provides an intuitive explanation for why qVoc is almost always 500–700 meV below the energy of the CT state and shows how the voltage can be improved.
369 citations
TL;DR: The paper deals with industry related EV energy storage system issues, EV charging issues, as well as power electronics and traction motor drives issues, and various EV propulsion system architectures and efficient bidirectional DC/DC converter topologies.
Abstract: This paper presents the current research trends and future issues for industrial electronics related to transportation electrification. Specific emphasis is placed on electric and plug-in hybrid electric vehicles (EVs/PHEVs) and their critical drivetrain components. The paper deals with industry related EV energy storage system issues, EV charging issues, as well as power electronics and traction motor drives issues. The importance of battery cell voltage equalization for series-connected lithium-ion (Li-ion) batteries for extended life time is presented. Furthermore, a comprehensive overview of EV/PHEV battery charger classification, standards, and requirements is presented. Several conventional EV/PHEV front-end ac/dc charger converter topologies as well as isolated DC/DC topologies are reviewed. Finally, this paper reviews various EV propulsion system architectures and efficient bidirectional DC/DC converter topologies. Novel DC/AC inverter modulation techniques for EVs are also presented. The architectures are based on the battery voltage, capacity, and driving range.
367 citations
TL;DR: The fabricated IPT system was adapted to the high-speed train, and the train successfully accelerates to a speed of 10 km/h according to startup procedures.
Abstract: Design and fabrication of a 1-MW inductive power transfer (IPT) system that supplies power to the vehicle in real time without any battery charge is proposed for a high-speed train. The IPT system consists of a 1-MW resonant inverter, a 128-m transmitter, four pickups, including rectifiers, and a wireless feedback network to maintain a constant output voltage of the pickups. The operating frequency of the system is 60 kHz to achieve efficient power transfer with a large air gap. The measured efficiency of the IPT system at the 818-kW output power of the pickups for the 5-cm air gap is 82.7%. The electromagnetic field and the induced voltage at the rail are also measured for safety evaluation. The fabricated IPT system was adapted to the high-speed train, and the train successfully accelerates to a speed of 10 km/h according to startup procedures.
352 citations
TL;DR: This method reliably and reproducibly achieve rectification ratios in excess of 200 at voltages as low as 370 mV using a symmetric oligomer of thiophene-1,1-dioxide and provides a general route for tuning nonlinear nanoscale device phenomena.
Abstract: Single-molecule diodes with rectification ratios over 200 at low voltages can be obtained with symmetric molecules by creating an environmental asymmetry using electric double-layers.
346 citations
TL;DR: In this article, the authors analyzed four basic IPT circuits with series-series (SS), series-parallel (SP), parallel series (PS), and parallel parallel (PP) compensations systematically to identify conditions for realizing load-independent output current or voltage, as well as resistive input impedance.
Abstract: The inductive power transfer (IPT) technique in battery charging applications has many advantages compared to conventional plug-in systems. Due to the dependencies on transformer characteristics, loading profile, and operating frequency of an IPT system, it is not a trivial design task to provide the battery the required constant charging current (CC) or constant battery charging voltage (CV) efficiently under the condition of a wide load range possibly defined by the charging profile. This paper analyzes four basic IPT circuits with series–series (SS), series–parallel (SP), parallel–series (PS), and parallel–parallel (PP) compensations systematically to identify conditions for realizing load-independent output current or voltage, as well as resistive input impedance. Specifically, one load-independent current output circuit and one load-independent voltage output circuit having the same transformer, compensating capacitors, and operating frequency can be readily combined into a hybrid topology with fewest additional switches to facilitate the transition from CC to CV. Finally, hybrid topologies using either SS and PS compensation or SP and PP compensation are proposed for battery charging. Fixed-frequency duty cycle control can be easily implemented for the converters.
342 citations
TL;DR: This paper proposes a control strategy of finite-control-set model predictive torque control with a deadbeat (DB) solution for permanent-magnet synchronous motor drives that relieves the big calculation effort of the traditional FCS-MPTC method.
Abstract: This paper proposes a control strategy of finite-control-set model predictive torque control (FCS-MPTC) with a deadbeat (DB) solution for permanent-magnet synchronous motor drives. By using a DB solution, the process of selection of the best switching vector is optimized. The predicted DB voltage sector consisting of the desired voltage vector (VV) avoids the complete enumeration for testing all feasible VVs, which relieves the big calculation effort of the traditional FCS-MPTC method. The proposed system is experimentally carried out both in the steady state and in the transient state.
333 citations
TL;DR: A new method is introduced, which is able to reduce the capacitor voltage ripples compared to the other methods, and a closed-loop control is also proposed which are able to track the circulating current references.
Abstract: This paper studies different circulating current references for the modular multilevel converter. The circulating current references are obtained from the instantaneous values of the output current and modulation signal of the phase leg. Therefore, the determination of the amplitude and phase of the output current is not needed, which is a significant improvement compared to other methods such as those based on injecting specific harmonics in the circulating currents. Among the different methods studied in this paper, a new method is introduced, which is able to reduce the capacitor voltage ripples compared to the other methods. A closed-loop control is also proposed which is able to track the circulating current references. With the discussed methods, the average values of the capacitor voltages are maintained at their reference while the voltage ripples are kept low. Experimental results are presented to demonstrate the effectiveness of the proposed and discussed methods.
333 citations
TL;DR: To integrate the advantages of the high voltage gain of a switched-capacitor (SC) converter and excellent output regulation of a switching-mode dc-dc converter, a method of combining the two types of converters is proposed in this paper.
Abstract: In a photovoltaic (PV)- or fuel-cell-based grid-connected power system, a high step-up dc-dc converter is required to boost the low voltage of a PV or fuel cell to a relatively high bus voltage for the downstream dc-ac grid-connected inverter. To integrate the advantages of the high voltage gain of a switched-capacitor (SC) converter and excellent output regulation of a switching-mode dc-dc converter, a method of combining the two types of converters is proposed in this paper. The basic idea is that when the switch is turned on, the inductor is charged, and the capacitors are connected in series to supply the load, and when the switch is turned off, the inductor releases energy to charge multiple capacitors in parallel, whose voltages are controlled by a pulsewidth modulation technique. Thus, a high voltage gain of the dc-dc converter can be obtained with good regulation. Based on this principle, a series of new topologies are derived, and the operating principles and voltage gains of the proposed converters are analyzed. Finally, the design of the proposed converter is given, and the experiment results are provided to verify the theoretical analysis.
331 citations
TL;DR: In this article, a general implementation of the phase-shifted carrier (PSC) modulation with a capacitor voltage balancing method for MMC is first introduced, and the mathematical analysis of PSC modulation for the modular multilevel converter (MMC) is performed to identify the PWM harmonic characteristics of the output voltage and the circulating current.
Abstract: The modular multilevel converter (MMC) is an emerging topology for high-power applications and is considered as the development trend of the high-voltage power converters. In this paper, general implementation of the phase-shifted carrier (PSC) modulation with a capacitor voltage balancing method for MMC is first introduced. Then, the mathematical analysis of PSC modulation for MMC is performed to identify the PWM harmonic characteristics of the output voltage and the circulating current. Moreover, influence of the carrier displacement angle between the upper and lower arms on these harmonics is also studied. Using this analysis, the optimum displacement angles are specified for the output voltage harmonics minimization and the circulating current harmonics cancellation, respectively. The harmonic features of the line-to-line voltage and the dc-link current are also investigated. Moreover, an extension of the PSC modulation for MMC with full-bridge submodules is also proposed which can increase the equivalent switching frequency of the output voltage and circulating current by two times compared with the conventional MMC. Finally, the findings are verified experimentally on a prototype of MMC.
TL;DR: The topological derivation of H-SLCs is deduced by combining the passive and active switched-inductor unit and the operation modes of the proposed asymmetrical and symmetrical converters are illustrated.
Abstract: In applications where the high voltage gain is required, such as photovoltaic grid-connected system, fuel-cell and high-intensity discharge lamps for automobile, high step-up dc-dc converters have been introduced to boost the low voltage to a high bus voltage. The voltage gain of traditional boost converter is limited, considering the issues such as the system efficiency and current ripple. This paper proposes a class of hybrid switched-inductor converters (H-SLCs) for high step-up voltage gain conversion. First, the topological derivation of H-SLCs is deduced by combining the passive and active switched-inductor unit; second, this paper illustrates the operation modes of the proposed asymmetrical and symmetrical converters; third, the performance of the proposed converters is analyzed in detail and compared with existing converters; finally, a prototype is established in the laboratory, and the experimental results are given to verify the correctness of the analysis.
TL;DR: In this paper, a double-sided LCLC -compensated capacitive power transfer (CPT) system is proposed for the electric vehicle charging application, where two pairs of metal plates are utilized to form two coupling capacitors to transfer power wirelessly.
Abstract: A double-sided LCLC -compensated capacitive power transfer (CPT) system is proposed for the electric vehicle charging application. Two pairs of metal plates are utilized to form two coupling capacitors to transfer power wirelessly. The LCLC -compensated structure can dramatically reduce the voltage stress on the coupling capacitors and maintain unity power factor at both the input and output. A 2.4-kW CPT system is designed with four 610-mm × 610-mm copper plates and an air gap distance of 150 mm. The experimental prototype reaches a dc–dc efficiency of 90.8% at 2.4-kW output power. At 300-mm misalignment case, the output power drops to 2.1 kW with 90.7% efficiency. With a 300-mm air gap distance, the output power drops to 1.6 kW with 89.1% efficiency.
TL;DR: Exploration of the structure-performance relationship between P14AQ and related materials provided deeper understanding for the design of organic electrodes and showed exceptional performance as a lithium-storage cathode, including reversible capacity almost equal to the theoretical value.
Abstract: In spite of recent progress, there is still a lack of reliable organic electrodes for Li storage with high comprehensive performance, especially in terms of long-term cycling stability. Herein, we report an ideal polymer electrode based on anthraquinone, namely, polyanthraquinone (PAQ), or specifically, poly(1,4-anthraquinone) (P14AQ) and poly(1,5-anthraquinone) (P15AQ). As a lithium-storage cathode, P14AQ showed exceptional performance, including reversible capacity almost equal to the theoretical value (260 mA h g(-1); >257 mA h g(-1) for AQ), a very small voltage gap between the charge and discharge curves (2.18-2.14=0.04 V), stable cycling performance (99.4% capacity retention after 1000 cycles), and fast-discharge/charge ability (release of 69% of the low-rate capacity or 64% of the energy in just 2 min). Exploration of the structure-performance relationship between P14AQ and related materials also provided us with deeper understanding for the design of organic electrodes.
TL;DR: This paper provides as a guide and quick reference for researchers and practicing engineers in deciding which control and modulation method to consider for an application in a given topology at a certain power level, switching frequency and demanded dynamic response.
Abstract: Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance-source-network-based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of the most popular control and modulation strategies for impedance-source network-based power converters/inverters. These methods are compared in terms of theoretical complexity and performance, when applied to the respective switching topologies. Further, this paper provides as a guide and quick reference for researchers and practicing engineers in deciding which control and modulation method to consider for an application in a given topology at a certain power level, switching frequency and demanded dynamic response.
TL;DR: In this article, the authors proposed an approach to design high energy and high power battery electrodes by hybridizing a nitroxide-polymer redox supercapacitor (PTMA) with a Li-ion battery material (LiFePO4).
Abstract: High energy and high power electrochemical energy storage devices rely on different fundamental working principles - bulk vs. surface ion diffusion and electron conduction. Meeting both characteristics within a single or a pair of materials has been under intense investigations yet, severely hindered by intrinsic materials limitations. Here, we provide a solution to this issue and present an approach to design high energy and high power battery electrodes by hybridizing a nitroxide-polymer redox supercapacitor (PTMA) with a Li-ion battery material (LiFePO4). The PTMA constituent dominates the hybrid battery charge process and postpones the LiFePO4 voltage rise by virtue of its ultra-fast electrochemical response and higher working potential. We detail on a unique sequential charging mechanism in the hybrid electrode: PTMA undergoes oxidation to form high-potential redox species, which subsequently relax and charge the LiFePO4 by an internal charge transfer process. A rate capability equivalent to full battery recharge in less than 5 minutes is demonstrated. As a result of hybrid's components synergy, enhanced power and energy density as well as superior cycling stability are obtained, otherwise difficult to achieve from separate constituents.
TL;DR: This work experimentally demonstrates the working principle of a new kind of energy harvester, proposed recently, using two capacitively coupled quantum dots, and shows that the directions of charge and heat flow become decoupled, paving the way for a new generation of multi-terminal nanoscale heat engines.
Abstract: Rectification of thermal fluctuations in mesoscopic conductors is the key idea behind recent attempts to build nanoscale thermoelectric energy harvesters to convert heat into useful electric power. So far, most concepts have made use of the Seebeck effect in a two-terminal geometry, where heat and charge are both carried by the same particles. Here, we experimentally demonstrate the working principle of a new kind of energy harvester, proposed recently, using two capacitively coupled quantum dots. We show that, due to the novel three-terminal design of our device, which spatially separates the heat reservoir from the conductor circuit, the directions of charge and heat flow become decoupled. This enables us to manipulate the direction of the generated charge current by means of external gate voltages while leaving the direction of heat flow unaffected. Our results pave the way for a new generation of multi-terminal nanoscale heat engines.
TL;DR: In this article, a direct cell-to-cell battery equalizer based on quasi-resonant LC converter (QRLCC) and boost dc-dc converter (BDDC) is proposed.
Abstract: In conventional equalizers, the facts of bulky size and high cost are widespread. Particularly, the zero-switching loss and zero-voltage gap (ZVG) between cells are difficult to implement due to the high-frequency hard switching and the voltage drop across power devices. To overcome these difficulties, a direct cell-to-cell battery equalizer based on quasi-resonant LC converter (QRLCC) and boost dc-dc converter (BDDC) is proposed. The QRLCC is employed to gain zero-current switching, leading to a reduction of power losses. The BDDC is employed to enhance the equalization voltage gap for large balancing current and ZVG between cells. Moreover, through controlling the duty cycle of the BDDC, the topology can online adaptively regulate the equalization current according to the voltage difference, which not only effectively prevents overequalization but also abridges the overall balancing time. Instead of a dedicated equalizer for each cell, only one balancing converter is employed and shared by all cells, reducing the size and implementation cost. Simulation and experimental results show the proposed scheme exhibits outstanding balancing performance, and the energy conversion efficiency is higher than 98%. The validity of the proposed equalizer is further verified by a quantitative and systematic comparison with the existing active balancing methods.
TL;DR: In this article, a non-isolated multi-input multi-output dc-dc boost converter is proposed for hybridizing alternative energy sources in electric vehicles, where the loads power can be flexibly distributed between input sources and charging or discharging of energy storages by other input sources can be controlled properly.
Abstract: A new nonisolated multiinput multioutput dc-dc boost converter is proposed in this paper. This converter is applicable in hybridizing alternative energy sources in electric vehicles. In fact, by hybridization of energy sources, advantages of different sources are achievable. In this converter, the loads power can be flexibly distributed between input sources. Also, charging or discharging of energy storages by other input sources can be controlled properly. The proposed converter has several outputs with different voltage levels which makes it suitable for interfacing to multilevel inverters. Using of a multilevel inverter leads to reduction of voltage harmonics which, consequently, reduces torque ripple of electric motor in electric vehicles. Also, electric vehicles which using dc motor have at least two different dc voltage levels, one for ventilation system and cabin lightening and other for supplying electric motor. The proposed converter has just one inductor. Depending on charging and discharging states of the energy storage system (ESS), two different power operation modes are defined for the converter. In order to design the converter control system, small-signal model for each operation mode is extracted. The validity of the proposed converter and its control performance are verified by simulation and experimental results for different operation conditions.
TL;DR: An instantaneous energy conversion efficiency of up to 55% was demonstrated and the high durability of the device was confirmed, presenting a substantial advancement of the triboelectric nanogenerators toward large-scope energy harvesting and self-powered systems.
Abstract: In comparison to in-pane sliding friction, rolling friction not only is likely to consume less mechanical energy but also presents high robustness with minimized wearing of materials. In this work, we introduce a highly efficient approach for harvesting mechanical energy based on rolling electrification and electrostatic induction, aiming at improving the energy conversion efficiency and device durability. The rolling triboelectric nanogenerator is composed of multiple steel rods sandwiched by two fluorinated ethylene propylene (FEP) thin films. The rolling motion of the steel rods between the FEP thin films introduces triboelectric charges on both surfaces and leads to the change of potential difference between each pair of electrodes on back of the FEP layer, which drives the electrons to flow in the external load. As power generators, each pair of output terminals works independently and delivers an open-circuit voltage of 425 V, and a short-circuit current density of 5 mA/m2. The two output terminals ...
TL;DR: Simulation and experimental results are presented to validate the proposed charging station architecture and provide complementary balancing capabilities by the use of an additional NPC leg acting as a bidirectional dc-dc stage, simulating the minimal load condition and allowing the modulator to keep the control on the dc voltages under any load scenario.
Abstract: This paper proposes a novel architecture for plug-in electric vehicles (PEVs) dc charging station at the megawatt level, through the use of a grid-tied neutral point clamped (NPC) converter. The proposed bipolar dc structure reduces the step-down effort on the dc–dc fast chargers. In addition, this paper proposes a balancing mechanism that allows handling any difference on the dc loads while keeping the midpoint voltage accurately regulated. By formally defining the unbalance operation limit, the proposed control scheme is able to provide complementary balancing capabilities by the use of an additional NPC leg acting as a bidirectional dc–dc stage, simulating the minimal load condition and allowing the modulator to keep the control on the dc voltages under any load scenario. The proposed solution enables fast charging for PEVs concentrating several charging units into a central grid-tied converter. In this paper, simulation and experimental results are presented to validate the proposed charging station architecture.
TL;DR: In this article, the authors proposed a p-NC NG by combining the barium titanate nanoparticles (BaTiO3 NPs) with the polyvinylidene fluoride (PVDF).
TL;DR: In this paper, a novel ECM was proposed by adding a moving average (MA) noise to the one resistor-capacity (RC) circuit model to accurately capture the battery dynamics and retain a simple topology.
TL;DR: In this article, an advanced vector current control for a voltage source converter (VSC) connected to a weak grid is proposed, which permits high-performance regulation of the active power and the voltage for the feasible VSC range of operation.
Abstract: This paper addresses an advanced vector current control for a voltage source converter (VSC) connected to a weak grid. The proposed control methodology permits high-performance regulation of the active power and the voltage for the feasible VSC range of operation. First, the steady state characteristics for a power converter connected to a very weak system with a short circuit ratio (SCR) of 1 are discussed in order to identify the system limits. Then, the conventional vector control (inner loop) and the conventional power/voltage control (outer loop) stability and frequency responses are analyzed. From the analysis of the classic structure, an enhanced outer loop based on a decoupled and gain-scheduling controller is presented and its stability is analyzed. The proposed control is validated by means of dynamic simulations and it is compared with classic vector current control. Simulation results illustrate that the proposed control system could provide a promising approach to tackle the challenging problem of VSC in connection with weak AC grids.
TL;DR: In this paper, the feasibility of HVDC cables and the development of different types of cables and accessories are reviewed and the non-uniform electric field distribution caused by the applied voltage, temperature dependent conductivity, and space charge accumulation is briefly discussed.
Abstract: Increased renewable energy integration and international power trades have led to the construction and development of new HVDC transmission systems. HVDC cables, in particular, play an important role in undersea power transmission and offshore renewable energy integration having lower losses and higher reliability. In this paper, the current commercial feasibility of HVDC cables and the development of different types of HVDC cables and accessories are reviewed. The non-uniform electric field distribution caused by the applied voltage, temperature dependent conductivity, and space charge accumulation is briefly discussed. Current research in HVDC cable for higher operation voltage level and larger power capacity is also reviewed with specific focus on the methodologies of space charge suppression for XLPE extruded cables.
TL;DR: An enhanced sag compensation strategy is proposed, which mitigates the phase jump in the load voltage while improving the overall sag compensation time and significantly increases the DVR sag support time compared with the existing phase jump compensation methods.
Abstract: This paper deals with improving the voltage quality of sensitive loads from voltage sags using a dynamic voltage restorer (DVR). The higher active power requirement associated with voltage phase jump compensation has caused a substantial rise in size and cost of the dc link energy storage system of DVR. The existing control strategies either mitigate the phase jump or improve the utilization of dc link energy by the following: 1) reducing the amplitude of the injected voltage or 2) optimizing the dc bus energy support. In this paper, an enhanced sag compensation strategy is proposed, which mitigates the phase jump in the load voltage while improving the overall sag compensation time. An analytical study shows that the proposed method significantly increases the DVR sag support time (more than 50%) compared with the existing phase jump compensation methods. This enhancement can also be seen as a considerable reduction in dc link capacitor size for new installation. The performance of the proposed method is evaluated using simulation study and finally verified experimentally on a scaled laboratory prototype.
Patent•
02 Jul 2015
TL;DR: In this article, a resonant transmitting power-supply device is provided with the following: a pulse input circuit (134) that inputs voltage pulses to a transmission antenna (2) at set intervals; a frequency-characteristics detection circuit (12) that detects the frequency characteristics of the transmission antenna when the resonant frequency-varying circuit (11) performs the aforementioned resonant-frequency sweep detection; a foreign-object detection circuit that uses detection results from the frequency characteristics detection circuits to detect the presence or absence of foreign objects in an electromagnetic field generated by
Abstract: This resonant transmitting power-supply device is provided with the following: a pulse input circuit (134) that inputs voltage pulses to a transmission antenna (2) at set intervals; a resonant-frequency-varying circuit (11) that, when a voltage pulse is inputted by the pulse input circuit (134), varies the resonant frequency of the transmission antenna (2) so as to perform resonant-frequency sweep detection; a frequency-characteristics detection circuit (12) that detects the frequency characteristics of the transmission antenna (2) when the resonant-frequency-varying circuit (11) performs the aforementioned resonant-frequency sweep detection; a foreign-object detection circuit (136) that uses detection results from the frequency-characteristics detection circuit (12) to detect the presence or absence of foreign objects in an electromagnetic field generated by the transmission antenna (2); and a power control circuit (137) that reduces or stops the supply of power to the transmission antenna (2) if a foreign object has been detected by the foreign-object detection circuit (136).
TL;DR: A review of the recent progress in the EDLTs and the impacts of EDLT technology on modulating the charge transportation of various electronics is presented in this article, where some interesting electrical transport characteristics such as superconductivity, metal-insulator transition, and tunable thermoelectric behavior have been modulated both theoretically and experimentally in electric double-layer transistors with various semiconductor channel layers and electrolyte materials.
Abstract: With the miniaturization of electronic devices, it is essential to achieve higher carrier density and lower operation voltage in field-effect transistors (FETs). However, this is a great challenge in conventional FETs owing to the low capacitance and electric breakdown of gate dielectrics. Recently, electric double-layer technology with ultra-high charge-carrier accumulation at the semiconductor channel/electrolyte interface has been creatively introduced into transistors to overcome this problem. Some interesting electrical transport characteristics such as superconductivity, metal–insulator transition, and tunable thermoelectric behavior have been modulated both theoretically and experimentally in electric double-layer transistors (EDLTs) with various semiconductor channel layers and electrolyte materials. The present article is a review of the recent progress in the EDLTs and the impacts of EDLT technology on modulating the charge transportation of various electronics.
TL;DR: In this article, the authors proposed a mathematical model which estimates the energy deviation for the stacks of both the MMC and the AAC during steady-state operation under any power factor and for AC voltage magnitude fluctuation of up to ±10%.
Abstract: Multilevel converters, such as the modular multilevel converter (MMC) or the alternate arm converter (AAC), rely on charged capacitors in their cells to generate their AC voltage waveform. Since the cell capacitors are physically large and occupy approximately half the cell volume, their capacitance must be kept minimal while limiting the voltage fluctuation caused by the current passing periodically through these capacitors. This study proposes a mathematical model which estimates the energy deviation for the stacks of both the MMC and the AAC during steady-state operation under any power factor and for AC voltage magnitude fluctuation of up to ±10%. The analysis is then used to calculate the minimum size for the cell capacitors in order to keep their voltage fluctuation within set boundaries for both topologies. The results show that the MMC requires 39 kJ/MVA of capacitive energy storage under sinusoidal modulation but this reduces with triplen injection modulation. The AAC has a lower requirement for storage in its cells of 11 kJ/MVA but the AAC has a six-pulse DC current ripple which requires a filter estimated to have a further 33% capacitive storage.
TL;DR: In this paper, the impact of electric vehicles on power quality in electric distribution system is evaluated using Monte Carlo and voltage deviations such as under/over voltage and voltage imbalance are probabilistically quantified using the Monte Carlo method.
Abstract: The impact of electric vehicles on power quality in electric distribution system is evaluated. Voltage deviations such as under/over voltage and voltage imbalance are probabilistically quantified using Monte Carlo. Moreover, distribution transformers overload and unbalance are assessed for different vehicle types (i.e., plug-in hybrid and battery electric), different vehicle penetration (up to 50%) while considering level 1 and level 2 charging. The results of Monte Carlo reveal that battery electric vehicles can cause more overload to distribution transformers compared to plug-in hybrid electric vehicles. Also level 2 and level 1 can be problematic resulting in secondary bus undervoltage and transformer unbalance, respectively.