Search

A conventional electric vehicle charger (EVC) charges only one EV concurrently. This leads to underutilization whenever the charging power is less than the EVC-rated capacity. Consequently, the cost-effectiveness of conventional EVCs is limited. Reconfigurable EVCs (REVCs) are a new technology that overcomes underutilization by allowing multiple EVs to be charged concurrently. This brings a cost-effective charging solution, especially in large car parks requiring numerous chargers. Therefore, this paper proposes an optimal planning strategy for car parks deploying REVCs. The proposed planning strategy involves three stages. An optimization model is developed for each stage of the proposed planning strategy. The first stage determines the optimal power rating of power modules inside each REVC, and the second stage determines the optimal number and configuration of REVCs, followed by determining the optimal operation plan for EV car parks in the third stage. To demonstrate the effectiveness of the proposed optimal planning strategy, a comprehensive case study is undertaken using realistic car parking scenarios with 400 parking spaces, electricity tariffs, and grid infrastructure costs. Compared to deploying other conventional EVCs, the results convincingly indicate that the proposed optimal planning strategy significantly reduces the total cost of investment and operation while satisfying charging demands. [ABSTRACT FROM AUTHOR]

Touch voltages are more likely to appear on long‐distance pipelines that lie in shared corridors with transmission lines. The touch voltage level varies with soil resistivity and can become hazardous while maintenance is being undertaken, necessitating risk assessment. Therefore, a novel approach is proposed that achieves better accuracy in the risk assessment of hazardous touch voltages appearing on pipelines than current approaches. The proposed approach incorporates soil resistivity measurements taken over a 1‐year period, allowing for the derivation of soil models, touch voltage hazard profiles versus time and, thus, a probability reduction factor that can be integrated into a probabilistic risk calculation. Using a probability reduction factor is a key aspect to improving the accuracy of risk assessment, allowing pipeline asset operators to clearly identify whether or not, risk mitigation action is required. Further, the proposed approach allows appropriate risk mitigation actions to be identified. The efficacy and significance of the proposed approach are demonstrated through a case study on an area of land near a shared gas pipeline and transmission line corridor. The case study results show how appropriate safety levels can be achieved by adjusting the number of work day per year and temporary protection settings. [ABSTRACT FROM AUTHOR]

A new method for the generation of high-quality sinusoidal signals is presented. Multibit binary signals are represented using uniformly weighted single bit streams that can then be processed by digital logic. Building blocks that are useful for the construction of the sinusoidal generator are also presented. The bit-stream representation has the advantage of having the characteristics of a classical pulsewidth-modulation signal and hence can be used to drive high-power switching devices with minimal conditioning. The technique is simple and can easily be implemented using digital logic on a field-programmable gate array (FPGA). The operation of a single-phase inverter using the proposed technique is demonstrated using an Altera Stratix FPGA and a custom-built power stage. The complete digital design uses less than 200 logic elements. The performance of this technique is quantified using simulations and practical measurements. Practical implementations lead to total harmonic distortion measures ranging between 0.75 % and 4.92 %. Index Terms--Bit streams, inverter, pulsewidth-modulation (PWM) generation, variable-frequency drives.

Field-aligned starting (FAS) is a new technique for starting three-phase cage induction motors on either three-or single-phase supply lines with minimal inrush currents. FAS generates a high impulselike torque to start the motor that is independent of the mains supply, before connecting the already spinning motor to the mains supply. In contrast to conventional starting techniques, FAS imposes higher than normal/rated voltage and current conditions on the machine at starting, and as such, the transient performance of FAS operated motors is complex in nature and largely governed by a number of key circuit variables, the values of which are critical for an efficient and economical design of FAS. A detailed insight into the influence of these key parameters on transient performance during startup is essential to avoid time consuming and inefficient trial and error design methods currently utilized in FAS designs. This paper addresses this need through the investigation of both the functionality and the extent of impact of the key variables on the starting performance of FAS. A transient model is utilized, and both experimental and simulated results suggest that, for a given set of circuit components, the proper selection of variable values is critical to achieve the best possible performance at startup. Index Terms--Energy conversion, induction motors, parameter estimation, transient analysis.

This paper presents a semianalytical technique that predicts the propagation characteristics of high-voltage (HV) transient pulses along a single-wire electric fence line with an earth return. The technique models the fence line in the frequency domain to facilitate an analytical solution for the propagation of HV pulses along the line. The frequency-domain solution is then transformed into time domain through a numerical Laplace inversion algorithm to determine the propagation characteristics of the line at a given location and time. For various line conditions, the propagation characteristics of HV pulses are investigated, and results indicate that the parameters of fence lines are frequency dependent, and an accurate insight into the propagation characteristics of HV pulses along single-wire fence lines can only be achieved through a frequency-dependent fence model. As confirmed by simulations of power systems computer-aided design, the proposed technique based on a frequency-dependent fence model is accurate, and can be considered an invaluable tool for designing complicated electric fence networks. Index Terms--Electric fence, pulse transmission.

Field aligned starting (FAS) is a new technique for starting three-phase cage induction motors on single-phase supply lines with minimal inrush currents. It uses a simple energy storage system to generate a very high impulsive torque by which the motor is started before being connected to the mains supply. The spinning motor can then be connected to the mains to operate in a standard Steinmetz connection without incurring high inrush currents, if the moment of mains connection is properly timed. This paper presents a transient model and an accompanying parameter estimation method through which the transient behavior of three-phase induction motors operated with FAS can be analyzed. The proposed model is based on instantaneous symmetrical components and is used to investigate a 3 kW motor started under various operating conditions. The proposed parameter estimation method and the developed transient model are both validated by experimental results. Index Terms--Energy conversion, induction motors, parameter estimation, transient analysis.

This paper presents a new model that facilitates a comprehensive analysis of split-capacitor push-pull parallel resonant converter (PPRC) topology in three different modes. The three modes, named as Normal, Buck, and Boost, are realized by operating the converter with a variable switching frequency, which is generated by modulating the damped resonant frequency with a variable phase-shift. The proposed modes allow the converter to operate with a variable voltage gain over a wide load range with zero-voltage switching (ZVS). In this paper, the operation and behavior of the converter in Boost mode is analyzed in detail through derivation of explicit analytical expressions for voltage gain, ZVS frequency and other circuit variables. Experimental results of a 150 W prototype PPRC converter, controlled by the proposed technique, are presented and compared with simulations and theoretical results to prove the validity of both the proposed model and control technique. The results indicate that the gain of the prototype converter can be increased up to about 145% of the nominal voltage and the parasitic elements have only minor impact on the performance. Index Terms--Power converters, power electronics, resonant converters.

This paper presents a technique for the suppression of voltage transients through the use of dynamically reconfigurable supercapacitor (SC) banks. The technique requires a minimum of two SC banks to transfer power from a mains supply to load in complete isolation. The banks are operated independently as energy-storing elements in one of the three states of charging, discharging, or idling, and transition of banks from one state to another with isolation is realized dynamically by inductively coupled power-transfer technology with no physical contacts. The proposed technique has no direct connection between the mains supply and load at any given moment, and power transfer takes place in complete isolation with built-in protection for both common- and differential-mode transients. Sizing of the banks with respect to various types of SCs and system parameters is analyzed. Comparisons between simulations and experimental results of two prototype systems, subjected to combination transient surges specified by IEC61000-4-5 standard, are presented with a discussion to show the validity of the proposed concept and its suitability for uninterruptible power systems and emergency power supplies. Index Terms--Electromagnetic induction, power supplies, supercapacitors (SCs), surge protection, uninterruptible power systems (UPSs).

This paper presents an analytical solution for the magnetic field inside an unconventional ironless brushless (ILBL) dc motor design. We discuss the unique characteristics of the design, which adopts an 'inside-out' construction with an internal ironless stator. With the intention of obtaining an analytical solution for the magnetic field, we propose a model based on a magnetic pole concept for representing the magnetic circuit. The magnetic field inside the motor, which has no iron for guiding magnetic flux paths, is obtained by solving Laplace's equation for magnetic scalar potential. We present both analytical and numerical solutions for the magnetic field and compare them with measured results of a 20-pole prototype IL design to show the validity of the model. The IL design is simple, easy to manufacture and, as indicated by the results, has an optimum number of magnets, for which its performance becomes maximum. Index Terms--Brushless machines, Laplace equation, magnetic analysis, permanent magnets.

There is a growing demand in the marketplace for wirelessly powered consumer applications. Some of these low-power applications require wireless power transfer with bidirectional power flow. For such consumer applications, this article proposes a new bidirectional wireless power transfer (BD-WPT) topology that facilitates wireless power transfers in both directions using fewer components. This article describes the operating principles of the topology in detail and presents a mathematical model to predict and investigate its performance. Besides, a control method with synchronization is also proposed for this topology to regulate power transfer in both directions. Simulations and theoretical results are presented in comparison to the measured results of a 60-W prototype BD-WPT to demonstrate the viability of the proposed converter topology. Results are convincing and indicate that the proposed converter is suitable for low-power applications being low cost, reliable, and efficient. [ABSTRACT FROM AUTHOR]

This article presents a simultaneous wireless power and data transfer (SWPDT) system based on double-sided inductor–capacitor–capacitor compensation topology and frequency-shift keying. A simplified method to analyze the power transfer, data transfer, and interference between them is proposed. To obtain higher data transfer gain and lower bit error rate, the data injection and extraction transformers are optimized. A laboratory prototype was built to verify the correctness of the analysis and the methodology. The proposed SWPDT system is less susceptible to interference between the power and data transfer. This is experimentally proven by high signal-to-noise ratio of 47 dB in the worst case. The power transfer efficiency is 90.5% under nominal conditions, and the data rate is 150 kb/s. The proposed system is robust against coupling variations, with effective data transfer even though the coupling coefficient is decreased by 95.3%. [ABSTRACT FROM AUTHOR]

This article presents a method for modifying an electrostatic harvester (EH) to allow autonomous management of its charge. The method involves segmenting a naturally antagonistic (out-of-phase) EH and connecting it with diodes to form an integrated self priming circuit (I-SPC). A model for the I-SPC is presented and shown that an exponential increase in voltage on the EH will occur over 10's of harvesting cycles. Furthermore, the model finds that increasing the segmentation of the EH allows harvesting at lower capacitance change ratios. The model is validated through simulation and experiment. The experiment is performed using a dielectric elastomer EH which consists of eight segments. During experimentation, it is confirmed that an I-SPC charged to 5 V is capable of reaching a voltage of approximately 2600 V after 40 capacitance change cycles. This fast voltage gain highlights the possibilities of self-managed EHs which harvest renewable kinetic energy autonomously to power wireless sensor networks (WSNs). The lack of maintenance associated with these systems will allow cheap WSN powered by renewable energy sources to be implemented in industrial applications. [ABSTRACT FROM AUTHOR]

Track wireless power transfer (WPT) systems are increasingly used for monorail robots, industrial transportation, etc. Conventionally, the track WPT system's primary power supply is designed to be equal or higher than the total running pickups’ rated power. However, in practice, some of the pickups may transiently require more power than their normal operating state. It is not cost effective to increase the power rating of the primary source for the transient case. Hence, this article proposes a method to strengthen the track's power transfer capability by reversely injecting energy from available online pickups to the transiently over-rated one. A bioperation mode is proposed, which includes both the normal operation and the strengthening operation. A bidirectional pickup topology is used, and the equivalent circuit is analyzed accounting the bioperation mode. In addition, a synchronization method of the primary and reverse injection pickups is proposed. A criterion to determine the boundary of the reverse energy injection is also presented. By detecting the peak current, this energy injection method can be practically implemented and the proposed method is verified through the experimental results. [ABSTRACT FROM AUTHOR]

This letter proposes a novel primary-side parameter estimation method for bidirectional inductive power transfer (BD-IPT) systems. This method can estimate mutual inductance at startup and monitor secondary-side phasor information continuously during operation. The proposed method can be used to simplify existing optimal control methods in BD-IPT systems by providing necessary feedback information without a wireless communication link. Besides, it helps to implement new control methods to further improve system performance. A current decoupling concept is utilized to estimate both the mutual inductance and secondary phasor information. A circuit model based on the superposition principle is presented to describe the current decoupling concept. The validity and accuracy of the proposed estimation method are demonstrated using the measured results of a 1-kW prototype BD-IPT system. [ABSTRACT FROM AUTHOR]

This article presents a wireless power transfer topology based on inductive power transfer (IPT) with integrated supercapacitor (SC) energy storage. The proposed topology is suitable for dynamic charging of electric vehicles (EVs), where pulses of energy must be processed without placing excessive strain on the utility grid or the EV battery. This topology extends the functionality of a typical LCL-tuned bidirectional IPT system by adding the ability to store energy in an SC in a controlled manner. Operation of the system is described in terms of the switching patterns and control variables required to transfer energy between the input, output, and the SCs. A mathematical model that predicts the overall transfer of power between the input, output, and SCs is presented along with experimental results at a nominal power level of 3.8 kW to validate the model and the topology under a variety of typical operating conditions. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs), which are becoming increasingly popular, can be charged by either wired or wireless means. The latter, based on wireless power transfer (WPT) technology, is convenient and safe, but pad misalignment is one of the major concerns as it causes a reduction in charging power level, prolonging the charging process. Therefore, wireless charging systems with high tolerance to pad misalignment are necessary. This study proposes a three-phase bi-directional wireless power transfer (BD-WPT) system with a control scheme that offers high tolerance to pad misalignment in EV charging applications. The system uses simple coil designs for pads and utilises the magnetic coupling among pads to compensate for the power variation. A comprehensive mathematical model, incorporating all magnetic cross-coupling effects, is presented to investigate the charging performance of the system under pad misalignment and different pad spacings. To demonstrate the validity of the proposed system, theoretical and simulated results are presented, benchmarking against a single phase WPT system, and in comparison to a prototype 1.3 kW three-phase BD-WPT system. Results are convincing and indicate that the proposed three-phase BD-WPT system with small pad spacing is more tolerant to wide pad misalignment in EV charging applications. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) can be used to charge electric vehicles (EVs) safely and efficiently. Dynamic wireless EV charging systems to charge EVs while moving has been developed but this technology is not yet widespread. One of the key challenges of dynamic charging is the pulsed nature of the transferred power, which may negatively impact battery life and the utility grid. Hybrid energy storage systems have been demonstrated as a potential solution, at the expense of a dedicated converter to interface with the energy storage element. This study presents a possible solution to the problem of adsorption and conditioning of high-power pulses, in the form of a novel converter topology that combines inductive WPT and super capacitor energy storage without the need for an additional converter stage. A suitable switching pattern is presented along with a steadystate mathematical model based on inductive power transfer, providing insight into the operation of the system. Experimental results of a prototype bi-directional WPT system are shown to validate the model and demonstrate the applicability of the proposed converter topology. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) is a promising technology for supplying power to various applications with no physical contacts. Recently, bidirectional WPT (BD-WPT) systems are gaining popularity for grid-to-vehicle and vehicle-to-grid applications which essentially require power transfer in both directions. However, BD-WPT systems are complex in nature, and require sophisticated control strategies to provide synchronization as well as to regulate the power flow between two sides. This paper proposes a new controller that uses measured active power (P) and reactive power (Q) at the resonant network of BD-WPT systems to regulate the power flow in both directions while providing synchronization between two sides without a dedicated communication interface for controlling power transfer. The controller, located on the pickup side, is applicable to BD-WPT systems with either single or multiple loads and ensures that the volt-ampere rating of the pickup converter is at lowest for battery charging, by keeping the reactive power at the resonant tank intake by the load side minimum. Experimental results obtained from a 1-kW prototype system show good agreement with simulated results, validating that the proposed controller can be used to regulate the power flow in BD-WPT systems. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) are becoming increasingly popular as a means of future transport for sustainable living. However, wireless charging of EVs poses a number of challenges related to interoperability, safety, pad misalignment, etc. In particular, pad misalignments invariably cause changes in system parameters which in turn lead to increase in losses as well as reduction in power throughput, making the charging process long and inefficient. Consequently, wireless charging systems that are less sensitive to pad misalignments have become preferable. This paper, therefore, presents a hybrid wireless power transfer (WPT) system that charges EVs at constant rate despite large misalignments between charging pads. The proposed charging system uses a combination of two different resonant networks to realize a constant and efficient charging process. A mathematical model is also developed, showing as to how the two resonant networks can be combined to compensate for pad misalignments. To demonstrate the validity of the proposed concept as well as the accuracy of the mathematical model, theoretical performance is compared with both simulations and experimental results of a prototype 3.3 kW hybrid bidirectional WPT system. Results clearly indicate that the proposed hybrid WPT system is efficient and offers a constant charging profile over a wide range of spatial (three-dimensional) pad misalignments. [ABSTRACT FROM PUBLISHER]

A dielectric elastomer generator (DEG) can be used for converting mechanical energy from natural motion sources, such as walking, waves, trees, etc., into electrical energy. A DEG is comprised of a soft and flexible dielectric elastomer (DE) capacitor, a priming circuit (PC), which transfers high potential charge onto/off the DE electrodes, and a power extraction circuit that harvests the generated power. To generate power, the PC must charge and discharge the DE in synchronization with the DE's capacitance change. A simple circuit to do this exists: the self-priming circuit (SPC). The SPC consists of diodes and capacitors that passively switch between charge delivery and charge receiving states in synchronization with the DE's capacitance change. Until now, there has been no understanding of how to design an SPC in order to maximize harvested energy from the DE. A new mathematical model for an SPC is presented, leading to design and optimization. An accuracy of 0.1% between model, simulation, and experiment over five cycles is obtained, once losses are taken into consideration. The behavior of the SPC is shown to be related to the maximum and minimum capacitances of the DE, but is unaffected by the exact shape of the capacitance waveform. [ABSTRACT FROM PUBLISHER]

Bidirectional contactless grid interfaces based on inductive power transfer technology have shown substantial promise in vehicle-to-grid and grid-to-vehicle applications as an alternative to hardwired interfaces. Such a bidirectional contactless grid interface typically includes a two-stage power conversion in conjunction with a bulky and expensive dc-link capacitor and a large low-frequency inductor to generate voltages at high frequency from low-frequency utility grid. This paper proposes a matrix converter (MC) that directly produces voltages at high frequency from the utility grid to drive resonant networks of the bidirectional contactless interface. A comprehensive mathematical model that predicts the steady-state voltages and currents as well as the power drawn by the system is proposed to gain an insight into the operation of the proposed MC topology. Utilizing the mathematical model, a modulation strategy is also proposed to attenuate the undesirable harmonics in the grid current. Experimental results obtained from a 1-kW prototype system show excellent agreement with those obtained from the mathematical model, validating the practical applicability of the proposed approach. Experimental results of total harmonic distortion of grid currents are also presented to demonstrate the effectiveness of the proposed modulation strategy at attenuation of grid current harmonics. [ABSTRACT FROM AUTHOR]

Model predictive control (MPC) schemes have become popular in the field of power electronics due to their intuitive formulation, flexibility, and ease of implementation. Typically, these schemes have been implemented with the prediction horizon limited to one time-step, and extension of the prediction horizon over multiple time-steps remains an ongoing area of research. In this paper, a variant of the MPC strategy is proposed wherein the slope of the output trajectories is used to emulate long prediction horizons. Each of the outputs, e.g., current, voltage, torque, or flux, is regulated within a set of symmetrical bounds. When switching is necessitated due to collision with a bound, the switching state that yields the set of output trajectories with the minimum slope, relative to the reference trajectory, is applied to the converter. The key benefit of this approach is its ability to achieve low switching frequencies with a minimal level of computational burden. The feasibility of the scheme, which can be adapted easily to different case studies, is demonstrated through simulations of both a medium-voltage induction machine drive and a grid-connected converter. Experimental results, which are presented for a 1.68 kVA prototype grid-connected neutral-point-clamped converter, further demonstrate the practical viability of the proposed strategy. [ABSTRACT FROM PUBLISHER]

This paper proposes an adaptive controller with an improved high‐frequency injection method for sensorless synchronous reluctance drive systems. A mathematical model is presented to show that the use of a high‐frequency injection method that takes into account the effects of unequal mutual‐inductances and the influence of speed reduces the rotor position estimation error. The adaptive speed control algorithm offers improved transient performance in comparison to typical proportional–integral (PI) controllers that are employed in sensorless drive systems. To demonstrate the viability, the proposed adaptive controller and the modified high‐frequency injection method are implemented using a TMS‐320F‐28335A digital signal processor to control a 500 W prototype synchronous reluctance motor drive. Experimental results are presented to show that the transient, load disturbance, and tracking responses of the proposed drive system are superior in comparison to a drive that uses a PI controller. Both experimental and theoretical analyses clearly indicate that the proposed high‐frequency injection method with an adaptive speed‐loop controller offers improved performance in adjustable speed synchronous reluctance drive systems. [ABSTRACT FROM AUTHOR]

This paper proposes a resonant dual-active bridge (DAB) converter, which uses a tuned capacitor–inductor–capacitor network. In comparison to the conventional DABs, the proposed topology significantly reduces the bridge currents, lowering both conduction and switching losses and improving the bridge power factors. A mathematical model, which predicts the behavior of the proposed system, is presented to show that both the magnitude and direction of the power flow can be controlled through either relative phase angle or pulse width modulation of voltages produced by the bridges. The viability of the proposed concept is verified through simulation. Experimental results of a 4- kW prototype converter, which has an efficiency of 95% at rated power, are also presented with discussions to demonstrate the improved performance of this topology. [ABSTRACT FROM AUTHOR]

Unidirectional inductive power transfer systems allow loads to consume power, while bidirectional inductive power transfer (BIPT) systems are more suitable for loads requiring two-way power flow such as vehicle to grid applications with electric vehicles. Many attempts have been made to improve the performance of BIPT systems. In a typical BIPT system, the output power is controlled using the pickup converter phase shift angle, while the primary converter regulates the input current. This paper proposes an optimized phase-shift modulation strategy to minimize the coil losses of a series–series compensated BIPT system. In addition, a comprehensive study on the impact of power converters on the overall efficiency of the system is also presented. A closed-loop controller is proposed to optimize the overall efficiency of the BIPT system. Theoretical results are presented in comparison to both simulations and measurements of a 0.5 kW prototype to show the benefits of the proposed concept. Results convincingly demonstrate the applicability of the proposed system offering high efficiency over a wide range of output power. [ABSTRACT FROM AUTHOR]

This paper presents a torque ripple compensation technique for a brushless dc (BLDC) motor drive that is operated without a DC link capacitor. The motor drive, which uses a single-switch control strategy, resembles that of a buck converter during operation at any switching state. A simple buck-converter-based model is therefore proposed to predict the behavior of the BLDC motor drive at constant speed. Using the model, the impact of operation without the DC link capacitor on the torque produced by the BLDC motor drive is investigated in detail. Theoretical behavior of the BLDC motor drive is compared with MATLAB/Simulink-based simulations to demonstrate the validity of the compensation technique and the analysis. Experimental results of a 250 W prototype motor drive are also presented to further validate the theoretical analysis, as well as the effectiveness of the proposed technique. Results convincingly indicate that the BLDC motor drive with torque ripple compensation offers comparable performance. [ABSTRACT FROM PUBLISHER]

In this paper, a new model predictive direct current control (MPDCC) strategy is proposed for a medium-voltage (MV) neutral-point-clamped converter with an $LCL$ -filter-based connection to the grid. The proposed strategy addresses the issues of resonance damping and harmonic attenuation through the virtual resistor (VR) concept, and is thus, termed MPDCC-VR. Because MPDCC is capable of achieving very long prediction horizons, the VR-based reference terms are predicted in conjunction with the state trajectories at each time-step, thus enabling more accurate decisions to be made by the controller. Simulation results verify the applicability of the MPDCC-VR to an MV case study. It is shown that the proposed approach exhibits a very good level of steady-state performance in the presence of grid voltage distortion, and at the chosen operating point is capable of substantially outperforming multiloop control with space vector modulation. Experimental results, which are provided for a down-scaled prototype, show excellent agreement with those obtained in simulation, further validating the proposed MPDCC-VR strategy. [ABSTRACT FROM AUTHOR]

This paper presents a model predictive direct power control scheme for high-power grid-connected neutral-point-clamped converters. The controller regulates the instantaneous real and reactive powers, as well as the neutral-point potential of the converter, within a set of symmetrical bounds while, at the same time, minimizing the switching frequency of the converter. The proposed approach is distinct from previous predictive power control strategies in that a long prediction horizon is used, allowing lower device switching frequencies to be achieved. A detailed model of the system is provided, and the control algorithm is discussed. Simulation results validate the applicability of the controller to a 3-kV 6.72-MVA system. Experimental results, which are presented for a 240-V 1.68-kVA prototype, show good agreement with those obtained in simulation and further validate the concept. [ABSTRACT FROM PUBLISHER]

Inductively coupled, bidirectional grid interfaces are gaining popularity as an attractive solution for vehicle-to-grid (V2G) and grid-to-vehicle (G2V) systems. However, such systems conventionally employ a large, electrolytic dc-link capacitor as well as a large input inductor, leading to expensive, bulky, and less reliable systems. Although,matrix converter (MC) based bidirectional inductive power transfer (BD-IPT) grid interfaces have been proposed as an alternative, implementation of safe and reliable MCs in BD-IPT applications is still a challenge, owing to the absence of natural freewheeling paths and higher complexity. As a solution, this paper proposes a new, inductively coupled, bidirectional grid interface, without a dc-link capacitor and an input inductor, consisting of two back-to-back connected converters. In contrast to existing bidirectional grid converters, the proposed system employs a simpler switching strategy with a lower switching frequency. A mathematical model, which predicts the behavior of the introduced system, is also presented. The feasibility of the proposed technique and the accuracy of the mathematical model are demonstrated through both simulations and experimental results of a 1.1-kW prototype system. [ABSTRACT FROM AUTHOR]

Historically, cascaded H-bridge, capacitor-clamped, and neutral point-clamped topologies have been used for medium- to high-voltage applications but the modular multilevel converter (M2LC) is becoming a popular alternative. However, in comparison to other topologies, control of the load current, which is inherently coupled with circulating currents, is more difficult in the M2LC topology. This paper proposes a modified M2LC topology that allows for decoupled control of circulating currents from the load current. Each arm of the modified topology comprises a plurality of half-bridge modules and one full-bridge module. The full-bridge module minimizes harmonic currents within the converter without affecting the load current. A state-space model, which is generalized per arm with an N number of half-bridge modules and one full-bridge module, is presented to accurately predict the behavior of the proposed topology. Theoretical as well as experimental results of a single-phase three-level 800-VA prototype converter are presented with a discussion to demonstrate the viability of both the proposed mathematical model and modified topology. A comparative investigation with respect to a conventional topology reveals that the proposed topology offers superior performance. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (M2LCs) are typically controlled by a hierarchical control scheme, which essentially requires at least two control loops: one to control the load current and another to control circulating currents. This paper presents an M2LC with a single controller, which is based on model predictive direct current control (MPDCC) with long prediction horizons. The proposed MPDCC scheme maintains the load current within tight bounds around sinusoidal references and minimizes capacitor voltage variations and circulating currents. An internal prediction model of the M2LC is used to minimize the number of switching transitions for a given current ripple at steady state while providing a fast current response during transient conditions. A state-space model, which is generalized for an N number of modules per each arm of the M2LC, is also presented to investigate the dynamic behavior of arm currents and capacitor voltages. Simulated performance of the converter, under various operating conditions, is presented in comparison to measured performance of a single-phase, three-level 860-VA M2LC prototype to demonstrate the proposed MPDCC philosophy. [ABSTRACT FROM AUTHOR]

This paper presents a new resonant dual active bridge (DAB) topology, which uses a tuned inductor-capacitor-inductor (LCL) network. In comparison to conventional DAB topologies, the proposed topology significantly reduces the bridge currents, lowering both conduction and switching losses and the VA rating associated with the bridges. The performance of the DAB is investigated using a mathematical model under various operating conditions. Experimental results of a 2.5-kW prototype, which has an efficiency of 96% at rated power, are also presented with discussions to demonstrate the improved performance of the tuned LCL DAB topology. Results clearly indicate that the proposed DAB topology offers higher efficiency over a wide range of both input voltage and load in comparison to conventional DAB topologies. [ABSTRACT FROM AUTHOR]

Typical inductive power transfer (IPT) systems employ two power conversion stages to generate a high-frequency primary current from low-frequency utility supply. This paper proposes a matrix-converter-based IPT system, which employs high-speed SiC devices to facilitate the generation of high-frequency current through a single power conversion stage. The proposed matrix converter topology transforms a three-phase low-frequency voltage system to a high-frequency single-phase voltage, which, in turn, powers a series compensated IPT system. A comprehensive mathematical model is developed and power losses are evaluated to investigate the efficiency of the proposed converter topology. Theoretical results are presented with simulations, which are performed in MATLAB/Simulink, in comparison to a conventional two-stage converter. Experimental evident of a prototype IPT system is also presented to demonstrate the applicability of the proposed concept. [ABSTRACT FROM AUTHOR]

Bidirectional inductive power transfer (IPT) systems are suitable for applications that require wireless and two-way power transfer. However, these systems are high-order resonant networks in nature and, hence, design and implementation of an optimum proportional–integral–derivative (PID) controller using various conventional methods is an onerous exercise. Further, the design of a PID controller, meeting various and demanding specifications, is a multiobjective problem and direct optimization of the PID gains often lead to a nonconvex problem. To overcome the difficulties associated with the traditional PID tuning methods, this paper, therefore, proposes a derivative-free optimization technique, based on genetic algorithm (GA), to determine the optimal parameters of PID controllers used in bidirectional IPT systems. The GA determines the optimal gains at a reasonable computational cost and often does not get trapped in a local optimum. The performance of the GA-tuned controller is investigated using several objective functions and under various operating conditions in comparison to other traditional tuning methods. It was observed that the performance of the GA-based PID controller is dependent on the nature of the objective function and therefore an objective function, which is a weighted combination of rise time, settling time, and peak overshoot, is used in determining the parameters of the PID controller using multiobjective GA. Simulated and experimental results of a 1-kW prototype bidirectional IPT system are presented to demonstrate the effectiveness of the GA-tuned controller as well as to show that gain selection through multiobjective GA using the weighted objective function yields the best performance of the PID controller. [ABSTRACT FROM AUTHOR]

Bidirectional inductive power transfer (BD-IPT) systems are high-order resonant circuits, which are complex in nature and sensitive to variations in system parameters and control variables. Consequently, modeling and design of BD-IPT systems are relatively difficult in comparison to unidirectional IPT systems. An accurate model that predicts the behavior of BD-IPT systems under different operating conditions is invaluable but yet to be reported. This paper, therefore, proposes a generalized steady-state model through which the behavior of BD-IPT systems can be accurately characterized. The proposed mathematical model is comprehensive and includes the effects of harmonics and sensitivity to variations in system parameters and control variables. Using the model, this paper investigates the behavior and sensitivity of BD-IPT systems under a range of practical operating conditions. The validity of the proposed generalized model, which is verified using the results of a 1-kW prototype system, provides a clear insight into BD-IPT systems and is expected to be useful at both design and implementation stages. [ABSTRACT FROM AUTHOR]

In medium-voltage (MV) drives, the switching frequency is limited to a few hundred Hz, for which high-performance control and modulation schemes are necessary to maintain acceptable current and torque distortion. Forced machine current control (FMCC) is a predictive control strategy for MV drives which was proposed in the early 1980s, which can be formulated for either torque or current control. Recently, model predictive direct torque control (MPDTC) and model predictive direct current control (MPDCC) have been developed, sharing with FMCC the use of hysteresis bounds, switching and prediction horizons. However, the relative performances of these schemes are yet to be compared. Through simulation, this paper compares the schemes across a range of operating points. It is shown that the steady-state performance of MPDxC and FMCC is similar when the switching horizon of MPDxC is limited. However, when the switching horizon is extended, the performance of MPDxC is shown to be superior to FMCC, the horizon of which is inherently restricted. [ABSTRACT FROM PUBLISHER]

Interfacing converters used in connecting energy storage systems like supercapacitors and battery banks to wind power systems introduce additional cost and power losses. This paper therefore presents a direct integration scheme for supercapacitors used in mitigating short-term power fluctuations in wind power systems. This scheme uses a dual inverter topology for both grid connection and interfacing a supercapacitor bank. The main inverter of the dual inverter system is powered by the rectified output of a wind turbine-coupled permanent-magnet synchronous generator. The auxiliary inverter is directly connected to the supercapacitor bank. With this approach, an interfacing converter is not required, and there are no associated costs and power losses incurred. The operation of the proposed system is discussed in detail. Simulation and experimental results are presented to verify the efficacy of the proposed system in suppressing short-term wind power fluctuations. [ABSTRACT FROM PUBLISHER]

Inductive power transfer (IPT) technology is a well-recognized technique for supplying power to a wide range of applications with no physical contacts. With the emergence of applications such as electric vehicles and vehicle-to-grid systems, IPT systems with bidirectional power flow have become a recent focus. In contrast to simple unidirectional IPT systems, bidirectional systems are complex in nature and essentially require more sophisticated and robust control strategies. This paper proposes a new controller, which is based on power–frequency droop characteristics of IPT systems, to regulate its power flow in both directions without a dedicated communication link. The proposed controller is applicable to unidirectional as well as bidirectional IPT systems with either single or multiple loads and ensures that power intake by the load side is always kept within the capability of the supply side. Analysis, together with both experimental and simulated results, of a 1-kW single-load bidirectional IPT system is presented with discussions to show that the proposed droop controller can successfully be used to regulate the two-way power flow. [ABSTRACT FROM PUBLISHER]

Bidirectional inductive power transfer (IPT) systems are attractive for applications such as electric vehicles and vehicle-to-grid systems which preferably require “contactless” and two-way power transfer. However, in contrast to unidirectional IPT systems, bidirectional IPT systems require more sophisticated control strategies to control the power flow. An indispensible component of such control strategies is the robust and accurate synchronization between the primary- and pickup-side converters, without which the transfer of real power in any direction cannot be guaranteed. This paper proposes a novel technique that synchronizes converters on both the primary and pickup sides of bidirectional IPT systems. The technique uses an auxiliary winding, located on the pickup side, to produce a synchronizing signal which, in turn, can be utilized to regulate the real power flow. This paper also presents a mathematical model for the proposed technique and investigates its sensitivity for component tolerances. The viability of the technique, which is applicable to both single- and multiple-pickup IPT systems, is demonstrated through both simulations and experimental results of a 1-kW prototype bidirectional IPT system. [ABSTRACT FROM PUBLISHER]

This paper introduces a novel cage induction generator and presents a mathematical model, through which its behavior can be accurately predicted. The proposed generator system employs a three-phase cage induction machine and generates single-phase and constant-frequency electricity at varying rotor speeds without an intermediate inverter stage. The technique uses any one of the three stator phases of the machine as the excitation winding and the remaining two phases, which are connected in series, as the power winding. The two-series-connected-and-one-isolated (TSCAOI) phase winding configuration magnetically decouples the two sets of windings, enabling independent control. Electricity is generated through the power winding at both sub- and super-synchronous speeds with appropriate excitation to the isolated single winding at any frequency of generation. A dynamic mathematical model, which accurately predicts the behavior of the proposed generator, is also presented and implemented in MATLAB/Simulink. Experimental results of a 2-kW prototype generator under various operating conditions are presented, together with theoretical results, to demonstrate the viability of the TSCAOI power generation. The proposed generator is simple and capable of both storage and retrieval of energy through its excitation winding and is expected to be suitable for applications, such as small wind turbines and microhydro systems. [ABSTRACT FROM PUBLISHER]

Demand for supplying contactless or wireless power for various applications, ranging from low-power biomedical implants to high-power battery charging systems, is on the rise. Inductive power transfer (IPT) is a well recognized technique through which power can be transferred from one system to another with no physical contacts. This paper presents a novel bidirectional IPT system, which is particularly suitable for applications such as plug-in electric vehicles (EVs) and vehicle-to-grid (V2G) systems, where two-way power transfer is advantageous. The proposed IPT system facilitates simultaneous and controlled charging or discharging of multiple EVs through loose magnetic coupling and without any physical connections. A mathematical model is presented to show that both the amount and direction of power flow between EVs or multiple systems can be controlled through either phase or/and magnitude modulation of voltages generated by converters of each system. The validity of the concept is verified by theoretical analysis, simulations, and experimental results of a 1.5-kW prototype bidirectional IPT system with a 4-cm air gap. Results indicate that the proposed system is an ideal power interface for efficient and contactless integration of multiple hybrid or EVs into typical power networks. [ABSTRACT FROM AUTHOR]

In this paper, a wind energy conversion system interfaced to the grid using a dual inverter is proposed. One of the two inverters in the dual inverter is connected to the rectified output of the wind generator while the other is directly connected to a battery energy storage system (BESS). This approach eliminates the need for an additional dc–dc converter and thus reduces power losses, cost, and complexity. The main issue with this scheme is uncorrelated dynamic changes in dc-link voltages that results in unevenly distributed space vectors. A detailed analysis on the effects of these variations is presented in this paper. Furthermore, a modified modulation technique is proposed to produce undistorted currents even in the presence of unevenly distributed and dynamically changing space vectors. An analysis on the battery charging/discharging process and maximum power point tracking of the wind turbine generator is also presented. Simulation and experimental results are presented to verify the efficacy of the proposed modulation technique and battery charging/discharging process. [ABSTRACT FROM AUTHOR]

An introduction to the special section of the "IEEE Transactions on Industrial Electronics," focusing on contactless energy transfer systems, is presented.

Distribution networks with high electric vehicle (EV) penetration levels can experience transformer overloading and voltage instability issues. A charge scheduling approach is proposed to mitigate against these issues that suits smart home settings in residential areas. It comprises measurement systems located at distribution transformers that communicate directly with fuzzy logic controller (FLC) systems embedded within EV supply equipment (EVSE). This realizes a reduction in data processing requirements compared to more centralized control approaches, which is advantageous for distribution networks with large numbers of transformers and EV scheduling requests. A case study employing the proposed approach is presented. Realistic driver behavior patterns, EV types, and multivariate probabilistic modeling were used to estimate EV charging demands, daily travel mileage, and plug-in times. A Monte Carlo simulation approach was developed to obtain EV charging loads. The effectiveness of mitigation in terms of reducing distribution transformer peak load levels and losses, as well as improving voltage stability is demonstrated for a distribution network in Jakarta, Indonesia. [ABSTRACT FROM AUTHOR]

This paper introduces a novel cage induction generator, and presents a mathematical model, through which its behavior can be accurately predicted. The proposed generator system employs a 3-phase cage induction machine and generates single phase and constant frequency electricity at varying rotor speeds without an intermediate inverter stage. The technique uses any one of the three stator phases of the machine as the excitation winding, and the remaining two phases, connected in series, as the power winding. The two series-connected and one isolated (TSCAOI) phase winding configuration magnetically decouples the two sets of windings, enabling independent control. Electricity is generated through the power winding at both sub-synchronous and super-synchronous speeds with appropriate excitation to the isolated single winding at any frequency of generation. A dynamic mathematical model, which accurately predicts the behavior of the proposed generator, is also presented and implemented in Matlab/Simulink. Experimental results of a 2 kW prototype generator under various operating conditions are presented together with theoretical results to demonstrate the viability of the TSCAOI power generation. The proposed generator is simple and capable of both storage and retrieval of energy through its excitation winding, and is expected to be suitable for applications, such as small wind turbines and micro-hydro systems. [ABSTRACT FROM PUBLISHER]