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Photovoltaic (PV) panels are one of the popular green energy resources and PV panel parameter estimations are one of the popular research topics in PV panel technology. The PV panel parameters could be used for PV panel health monitoring and fault diagnosis. Recently, a PV panel parameters estimation method based in neural network and numerical current predictor methods has been developed. However, in order to further improve the estimation accuracies, a new approach of PV panel parameter estimation is proposed in this paper. The output current and voltage dynamic responses of a PV panel are measured, and the time series of the I–V vectors will be used as input to an artificial neural network (ANN)-based PV model parameter range classifier (MPRC). The MPRC is trained using an I–V dataset with large variations in PV model parameters. The results of MPRC are used to preset the initial particles' population for a particle swarm optimization (PSO) algorithm. The PSO algorithm is used to estimate the PV panel parameters and the results could be used for PV panel health monitoring and the derivation of maximum power point tracking (MMPT). Simulations results based on an experimental I–V dataset and an I–V dataset generated by simulation show that the proposed algorithms can achieve up to 3.5% accuracy and the speed of convergence was significantly improved as compared to a purely PSO approach. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) panels have been widely used as one of the solutions for green energy sources. Performance monitoring, fault diagnosis, and Control of Operation at Maximum Power Point (MPP) of PV panels became one of the popular research topics in the past. Model parameters could reflect the health conditions of a PV panel, and model parameter estimation can be applied to PV panel fault diagnosis. In this paper, we will propose a new algorithm for PV panel model parameters estimation by using a Neural Network (ANN) with a Numerical Current Prediction (NCP) layer. Output voltage and current signals (VI) after load perturbation are observed. An ANN is trained to estimate the PV panel model parameters, which is then fined tuned by the NCP to improve the accuracy to about 6%. During the testing stage, VI signals are input into the proposed ANN-NCP system. PV panel model parameters can then be estimated by the proposed algorithms, and the estimated model parameters can be then used for fault detection, health monitoring, and tracking operating points for MPP conditions. [ABSTRACT FROM AUTHOR]

A wideband series harmonicvoltage compensator (WSHVC) for mitigating the adverse effect of unknown grid impedance and load condition on the stability of microgrids with multiple grid-connected inverters (GCIs) is presented. The concept is based on extending the concept of series active power filter. A wideband series voltage source inverter is used to compensate for the high-frequency harmonic voltage caused by the impedance at the point of common coupling, thereby creating a virtually zero high-frequency impedance at the output of the GCIs. The system stability is then assured under any operating condition. The bandwidth of the WSHVC ranges from the second harmonic of the grid frequency to 8 kHz, which is sufficiently higher than the cut-off frequency of typical GCIs. Such fast dynamic behavior is realized by a novel fixed-frequency predictive control scheme with nonlinear switching surfaces. Since the WSHVC handles harmonic power only, its volt-ampere rating is lower than that of the entire system. A 500 VA prototype for a 6.5 kVA testbed with three commercial GCIs, nonlinear load, and adjustable grid impedance has been evaluated. The power dissipation of the WSHVC is less than 1% of the VA rating of the testbed. The effectiveness of the WSHVC on improving system stability is studied. [ABSTRACT FROM AUTHOR]

A new model of photovoltaic (PV) panel is proposed. The model precisely replicates sub-cell level degradation, such as cracks and interconnect failures, and reproduces their effect at the panel level I–V characteristic. Moreover, a regression method is proposed, which infers the model's parameters from combination of electroluminescent (EL) image and degraded I–V characteristic. The combination of quantitative (EL image) and qualitative (I–V characteristic) enables to characterize the degradation of the cells embedded in the PV panel, without physical access to the cells. The proposed model and the regression problem is experimentally verified on a set of 3 single cell measurements and a set of 4 crystalline PV panels with various levels of degradation. • Model of a PV panel incorporating non-uniform degradation. • Degradation characterization from I–V characteristic and Electroluminescent image. • Efficient model evaluation by Newton–Raphson method. • Model parameter identification using Evolutionary Algorithm. [ABSTRACT FROM AUTHOR]

A single-phase transformerless full-bridge photovoltaic grid-tie inverter is presented. It utilizes 1) a virtual ground technique to mitigate ground leakage current, 2) a hybrid pulsewidth modulation (HPWM) scheme to profile the output current and prevent sudden changes in the common-mode voltage, and 3) a nonlinear output inductor to attenuate current ripple around zero crossings and minimize filter size. The HPWM is effectively the same as unipolar PWM (UPWM), but with soft voltage transition modulation introduced around the zero crossings. Apart from low switching losses, the output filter is implemented with a minimum number of components to achieve high attenuation of ripple current. By deriving the switching trajectory, a mathematical model is formulated, and the ground leakage current and the output current with the traditional UPWM and the proposed HPWM schemes are compared. The output current harmonics caused by the nonlinear output inductor is analyzed by the Volterra theory. A 340 W, 380 Vdc/110 V ac, 50 Hz prototype has been built and evaluated. [ABSTRACT FROM AUTHOR]

Most maximum power point trackers (MPPTs) for electromagnetic energy harvesters (EMEHs) are based on resistive matching technology, where the input resistance of the MPPT is made equal to the magnitude of the output impedance of the harvester. This is valid when the output reactance of the EMEH is much smaller than its output resistance. However, some EMEHs, such as permanent magnet generator, have nonnegligible output reactance. The discrepancy between the power extracted by the resistive matching technology and the maximum extractable power will increase as the output reactance increases. Under high excitation frequency and low operating temperature, the effect of the output reactance will become more dominant. In order to deal with such issue, an MPPT that can counteract the effect of the coil inductance and match with the coil resistance is presented. It does not require knowing coil parameters a priori and the harvester will be operated at its true maximum power point. A 7-W prototype for testing the proposed algorithm has been built and evaluated. Its performance is favorably compared with the amount of power extracted with the resistive matching technology. [ABSTRACT FROM AUTHOR]

Techniques of long-term in vivo electrophysiological recording play important roles in brain research and neural rehabilitation. To avoid interruption of experiment and risk of infection, use of wireless power transfer (WPT) technique has been suggested to eliminate cumbersome wires and batteries attached to the animals in rodent electrophysiological applications. This paper presents a holistic assessment of the relationships among the physical sizes of the transmitting and receiving coils, power transfer characteristics, and specific absorption rate (SAR) in animals of a simple WPT system using two rectangular coaxial transmitting coils. With given space for the animal and size of the receiving coil, a procedure for designing the minimum driving current, and the transmitting coil dimensions and separation to deliver sufficient power to the receiver, and interactions between the transmitting and receiving coils is derived. A π-capacitor network that can match the impedances of the receiving coil and the load to operate the receiver at the maximum power transfer condition is proposed. It is also optimized for the overall volume. A 100-mW prototype with an operating zone of 400 × 240 × 40 mm3 and a receiving coil with a diameter of 11.45 mm is built and studied. The SAR in the animal is evaluated and compared with the recommended restriction level. [ABSTRACT FROM AUTHOR]

A computational model for simulating the time-domain response of lithium batteries under arbitrary charging and discharging profiles is presented. The methodology is based on first formulating a mathematical model that describes the time-domain voltage–current characteristics of constant phase elements (CPEs), and then uses multiple series-connected CPEs, as well as charge transfer resistances, output resistances, and inductances, to form the computational model. The criteria for ensuring the stability of the computational model will be derived. The validity of the computational model is confirmed by comparing the simulation results of a model consisting of three series-connected CPEs with the measurement results of six SANYO 18650, 3300-mAh, 3.7-V rechargeable Li-ion batteries under controlled charging and discharging profiles. Finally, the accuracy of the computational model will be compared to the accuracy of the models using different orders of parallel resistor–capacitor networks. [ABSTRACT FROM AUTHOR]

An active grid impedance cancelator using the concept of series active filter to suppress the effect of the grid disturbance and stabilize the single-phase grid-connected inverters with an inductive–capacitive–inductive filter operating under variable grid condition is presented. Harmonic interaction between the inverter and the grid is thereby avoided owing to the cancelation of equivalent grid impedance. More importantly, the impedance cancelator offers an active damping function to ease the heavy burden of the inverter control, such as power control, phase locked loop, current regulation, impedance shaping, etc. The impedance cancelator is a full-bridge dc–ac converter having no passive inductive–capacitive filter. It is connected in series with the inverter output and is operated as a negative virtual grid impedance. As the volt-ampere rating of the impedance cancelator is low, the efficiency of the entire system is not sacrificed. Starting with the impedance-based analytical modeling method, the basic principle of equivalent grid impedance cancelator is derived and studied. Then, the digital control strategy and the modeling of equivalent grid impedance cancelator are examined. The experimental results of a prototype cancellator for a single-phase inverter are favorably compared with theoretical predictions. [ABSTRACT FROM AUTHOR]

A concept, named as power semiconductor filter, has been demonstrated to be an alternative to perform input harmonic filtering in switched-mode power converters. It utilizes a series pass device (SPD) to profile the wave shape of the supply current, while the voltage across the SPD is regulated at a threshold voltage between the linear and saturation regions of the SPD to minimize its power dissipation. Bulky passive components for input harmonic filtering can then be eliminated or shrunk with such active supply current control. For the sake of circuit elegancy, regulation of the SPD voltage is realized by a bang-bang (peak-voltage) controller to vary the input characteristics of the power conversion stage through adjusting some control parameters, such as duty cycle and switching frequency. Experiments reveal that the entire system might exhibit bifurcation phenomena under some supply and load conditions. This paper will derive a sampled-data model to characterize such system behaviors and to identify the onset of bifurcation and chaos. A compensation ramp will be proposed to introduce into the bang-bang controller to stabilize the system operation. Moreover, the slow-scale dynamics will be studied with small-signal models. The investigations will be exemplified on a 48 W, 40–140 V/24 V buck dc–dc converter prototype. [ABSTRACT FROM PUBLISHER]

This paper extends the application of a solid-state input current harmonic filtering technique, named as power semiconductor filter (PSF), for boost-type power factor corrector (PFC). The filtering technique is based on connecting an active device, namely, series pass device (SPD), in series with the input of the boost converter. By adjusting the control signal to the SPD, the input current of the PFC is profiled to be in phase with the supply voltage and regulate the output voltage. The power dissipation of the SPD is maintained at a low level by operating the SPD at the boundary between the linear and saturation regions. Modeling of the static and dynamical characteristics, design, and analysis of the entire system will be given. A 100 W, 85–265 Vac/400 Vdc PFC with the boost converter operating in discontinuous conduction mode has been built and evaluated. Experimental results reveal that the PSF can reduce the input current harmonics and improve the input power factor. They are in close agreement with the theoretical predictions. Finally, the conducted electromagnetic interference under different supply voltages will also be reported. [ABSTRACT FROM AUTHOR]

Cascaded boundary-deadbeat controller can ensure system stability of single-phase grid-connected inverter operated under different grid conditions. However, it will require using numerous sensors and may experience performance degradation caused by unbalanced filter parameters in controlling a three-phase three-wire inverter. Furthermore, the system is in variable frequency operation. A boundary controller using second-order switching surface with direct current tracking capability, reduced number of current sensors, and fixed frequency operation of three-phase three-wire grid-connected inverter with inductive-capacitive-inductive (LCL) filter is presented. By applying the 60° discontinuous pulsewidth modulation scheme for a fictitious decoupled dual-buck structure in each operation sector, two separate sets of switching criteria for dictating the states of the switches of two half-bridge legs are formulated. Such technique can avoid dealing with the challenges caused by the interactions among three independent current regulators. A switching table with null voltage vectors excluded is designed to dictate the switching actions. Sensitivities of the system transfer characteristics to the parametric variations are investigated. A 3 kW prototype has been built and evaluated under stiff- and weak-grid conditions. The experimental results are favorably compared with theoretical predictions. [ABSTRACT FROM AUTHOR]

Under the partial-shading condition, the voltage-current characteristics of a series-connected solar panel strings are different from that of a single panel. Instead of having a single maximum power point (MPP), they exhibit multiple MPPs. It is thus crucial to operate the string at the global MPP (GMPP). A large body of literature has been devoted to techniques for locating GMPP. However, those techniques typically require knowing the panel characteristics, adding extra sensing components and circuits, and/or causing output power interruption. In order to deal with these issues, a two-step algorithm for tracking the GMPP is proposed. The first step determines the string voltage at which the GMPP appears. It is based on extracting the power-voltage characteristics of the string through varying the input impedance of the power processing unit to determine the approximate location of the GMPP. The second step determines the exact location of the GMPP. It is based on formulating two quadratic functions, namely static and fictitious power functions, and then calculating the intersection point of the two functions to determine the GMPP. The algorithm has been implemented on a 3 kW grid-connected inverter. As the proposed method does not require modifying the hardware and knowing panel characteristics, it can be immediately integrated into existing photovoltaic systems. [ABSTRACT FROM AUTHOR]

An inductive power transfer system for driving multiple organic light-emitting diode (OLED) light panels is presented. Each light panel is driven by an output in a daisy-chained transformer (DCT) structure through a detachable transformer. The DCT structure allows using a single switching network to drive multiple light panels with good current balancing. A primary-side freewheeling (FW) circuit and an open-load protection network are introduced to maintain the current-balancing function of the DCT structure upon abnormal power transfer from the primary side to the secondary side of the detachable transformer. Apart from easy and safe operation, the proposed system also offers a modular, scalable, maintenance-free, and hot-swappable platform for large-area illumination. Modeling, design, and analysis of the system under normal and faulty operating conditions and misalignment of the detachable transformer will be given. A prototype system with four OLED light panels has been built and evaluated. The experimental results show that the circuit has a robust current balancing ability and fault condition tolerance. In addition, a comparison on the cost effectiveness between DCT structure and “one-drive-to-one-load” structure is investigated. [ABSTRACT FROM AUTHOR]

It is well-known that the power transfer efficiency and the power transmitted over a wireless inductive link are significantly affected by the strength of the magnetic coupling and the spatial displacement between the transmitting and receiving coils. Misalignment between the transmitting and receiving coils is practically unavoidable. In order to control and regulate the receiver-side power, on-the-spot measurement of electrical quantities and establishment of communication link between the transmitter and receiver are typically required. This paper will present an investigation into the use of the transmitter-side electrical information to estimate the mutual inductance and regulate the power consumption of the receiver side. The nonlinear input voltage–current characteristics of the diode-bridge rectifier, which causes current distortions in the system, are taken into account in the mathematical formulations. The proposed technique is successfully implemented on a 4-W wireless-powered LED driver prototype. Experimental results reveal that the LED power can be regulated within ±25% spatial misalignment over the operating zone. The estimated mutual inductance is also found to be in close agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]

A modular and scalable voltage-regulation structure for enhancing service continuity and flexibly changing the system power rating is proposed. The methodology is based on paralleling multiple series-voltage compensators, namely multiparallel-connected series-voltage compensator (MSVC), to regulate the load voltage. The output voltage of each compensator is controlled locally by adjusting the phase angle of the output voltage of the inverter in each compensator, while the output current of each compensator is coupled to two adjacent compensators via two coupling transformers. The coupling transformers form a daisy-chained structure. The load current can be shared near-equally among the compensators through the transformer structure. The operating principle, steady-state and transient current-sharing characteristics of the architecture will be discussed and illustrated. A simplified design procedure will be given. A 3-kVA MSVC test bed with three parallel-connected single-phase compensator units has been built and evaluated. The response of the MSVC system with each compensator unit engaged and disengaged momentarily will be investigated. Such structure is applicable for regulating and stabilizing the supply voltage for consumers at the distribution side. [ABSTRACT FROM AUTHOR]

Deadbeat control is commonly used in grid-connected inverter with L filter, but it faces the challenge of having filter resonance in inverter with LCL filter. Although many active damping techniques have been proposed to tackle such phenomenon, their digital implementation would introduce nonminimum phase characteristics. Furthermore, the plant viewed by the deadbeat controller is of high order, making the system performance be susceptible to the drift of the filter parameters. This paper introduces a new perspective of using boundary control with second-order switching surface to reduce the order of the plant viewed by the deadbeat controller. The structure hybridizes the merits of the deadbeat control in its simplicity and the boundary control in achieving wide control bandwidth. Small-signal dynamic modeling of the boundary control is formulated. The performance sensitivities of the overall system to filter parameters and grid inductance variations are studied with the derived models. An online grid inductance estimation algorithm is proposed to assure sufficient phase margin under an extremely weak-grid condition. A 2-kW, 220-V, 50-Hz prototype with the switching frequency of 8 kHz has been built and evaluated. Its steady-state and transient behavior, and harmonic rejection capability under stiff- and weak-grid conditions are discussed. [ABSTRACT FROM PUBLISHER]

A ring diode–capacitor network for current-balancing multiple LED strings is presented. The concept is based on utilizing the charge-balance property of capacitors to balance the currents of two adjacent LED strings in each switching cycle. Such current-balancing mechanism propagates over a ring network. The network has several merits, including 1) high current-balancing accuracy, 2) a simple structure, 3) modular and scalable, 4) current-balancing property being less dependent on the string voltages and the values of the capacitors, 5) inherent galvanic isolation between the driver and the LED strings, and 6) operation of the healthy LED(s) being unaffected by the failure LED(s). In addition, the capacitors in the network can be used as resonant tank components for the front-stage driver. An 80-W prototype for balancing the currents of ten LED strings has been built and evaluated. Each string has eight pieces of 1-W LED connected in series. The prototype is driven by a series-resonant converter. Results reveal that the string current variation is less than ±0.5%, irrespective to the variation of the string voltages and capacitor values. The total LED power can be dimmed to 10% of the rated output by a hybrid switching frequency and duty-cycle control scheme. The overall efficiency from the driver input to all LED strings is around 95% over the operating range. Modeling, design, and analysis of four possible configurations will be given. [ABSTRACT FROM AUTHOR]

Inverter-fed drive systems have been widely used in residential, commercial, and industrial applications. Special emphasis is placed on avoiding overvoltage spikes traveling along the cable and inside the motor, when a long motor cable is used. Such phenomenon would cause premature failure of the motor and cable insulation. Many passive and active overvoltage suppression techniques have been proposed to tackle this issue. Among them, passive overvoltage filters are dominant solutions, as their implementation is simple, cost effective, and robust. However, they have the main drawback of high power dissipation. This paper gives a new perspective on this subject. A generalized model for characterizing the inverter-cable-motor system with the filter included will be formulated to describe the interactions between the filter and the drive system. Then, the characteristics of an ideal overvoltage filter will be derived. Furthermore, a low-loss filter, named as “RL-plus-C” filter that exhibits near ideal characteristics will be proposed. Its performance will be compared with that of the commonly adopted RC and RLC filters, theoretically and experimentally on a 1-hp motor drive system. Results reveal that the proposed filter has the lowest power dissipation. [ABSTRACT FROM AUTHOR]

With the increase in the switching speed and power level in the bridge-leg configuration, the spurious triggering pulse in the synchronous switch is prone to exceed the threshold voltage and cause spurious turn-on. Eliminating the spurious turn-on phenomenon plays an important role in preventing excessive switching loss, self-oscillation, and shoot-through in the bridge-leg configuration. A novel resistor-capacitor-diode ( RCD) level shifter is proposed to generate a negative gate voltage so that the spurious triggering pulse can be shifted below the threshold voltage, and thereby, the spurious turn-on can be avoided. The merits of the devised auxiliary circuit lie not merely in that it consists only of passive components and can easily be co-packaged with the existing gate driver, but also in that the negative voltage level is tunable and independent of the duty cycle of the converter. The effectiveness of this circuit has been verified by the experimental results. It is shown that when the spurious turn-on occurs in a bridge-leg configuration, the adoption of the proposed circuit can eliminate the spurious turn-on and reduce the turn-off switching loss by more than 40%. [ABSTRACT FROM AUTHOR]

This paper derives a circuit-level analytical model for describing the mechanism of the spurious triggering pulse in the gate-source voltage of the synchronous MOSFET (SyncFET) in the synchronous buck converter. The model takes into account not only the parasitic capacitances and inductances of the control MOSFET (CtrlFET) and the SyncFET, but also the reverse recovery characteristics of the body diode of the SyncFET. An exhaustive investigation into the impact of all these factors on the spurious triggering pulse is conducted. The spurious triggering pulse can be attributed to two factors. The first one is the positive gate voltage caused by the displacement current through the gate-drain capacitance of the SyncFET, due to the increase in the drain-source voltage. The second one is the negative source voltage caused by the voltage drop across the source inductance of the SyncFET, due to the decrease in the drain current. It is discovered that the gate impedance of the SyncFET would exert different influence on the magnitude of the spurious triggering pulse, depending on the contributions of these two factors. Experimental results affirm that variation in the magnitude of the spurious triggering pulse with each parasitic element can be correctly inferred by the proposed model. Design guidelines for enhancing spurious turn-on immunity are advanced. [ABSTRACT FROM AUTHOR]

A modified particle swarm optimization algorithm for conducting near-real-time parameter estimation of an electrical model for lithium batteries is presented. The model comprises a dynamic capacitance for characterizing the nonlinear relationship between the battery electromotive force and the state-of-charge, and a resistor-capacitor network for characterizing the static and transient responses. The algorithm is confirmed by successfully determining all parameters in a predefined simulation model. It is also evaluated on a hardware test bed with two samples of 3.3-V, 40-Ah, Lithium Iron Phosphate (LiFePO4) battery driven under six different loading patterns. The intrinsic parameters are estimated by first processing 15-min samples of the battery terminal voltage and current. The whole process takes 2 min. Then, the voltage-current characteristics in the following 15 min are predicted. Results show that the extracted parameters can fit the first 15-min voltage samples with a maximum error of 16 mV and an average error of 3.8 mV. With the extracted parameters, the electrical model can predict voltage-current characteristics in the following 15 min with a maximum error of 31 mV and an average error of 15 mV. The algorithm is further verified by successfully determining the emulated variation of the output resistance. [ABSTRACT FROM AUTHOR]

This paper presents a transformer-isolated resonant driver for parallel strings with robust balancing and stabilization of an individual LED current. The methodology is based on connecting multiple transformers in a daisy chain to balance the string currents and using them to form part of the resonant tank in a series-resonant converter. The input source and output strings are electrically isolated by transformers. Such structure behaves like a constant current source with multiple outputs for multiple LED strings. The string currents are found to be insensitive to the string voltages. In order to ensure service continuity of LEDs, each LED in a string has a bypass thyristor, which is triggered upon an open-circuit failure, so that the rest of the healthy LEDs in the string would still be operated. A 21 W prototype with seven strings has been built. Each string consists of three 1-W LEDs connected in series. Experimental results show that the LED current can still be regulated at the reference value within ±1% error even if the whole lamp has only one piece of LED in operation and the rest of LEDs fail short or open. Modeling, analysis, and design of the proposed driver will be given. [ABSTRACT FROM AUTHOR]

A modular and scalable series compensation technique for enhancing controllability and flexibility in power transmission in distributed power systems is proposed. The concept is based on paralleling multiple static synchronous series compensators (SSSC) through daisy-chained transformers to perform reactive power compensation, and thus control the amount and direction of the power flow over the transmission link. Each compensator unit is under an autonomous control for regulating its output voltage. Its output current is coupled to another compensator unit through one of the daisy-chained transformers, so that the transmission current is shared among the parallel-connected compensators. Modeling, design, and analysis of a compensator unit and the proposed multiparallel-connected SSSC (MSSSC) architecture in an elementary two-machine system will be presented. A 3-kVA MSSSC test bed with three-parallel-connected compensator units for a single-phase system has been built and evaluated. The steady-state and transient current-sharing characteristics in forward and reverse power transmission over the transmission link will be studied. The response of the MSSSC system with each compensator unit engaged sequentially will also be investigated. [ABSTRACT FROM AUTHOR]

A modular and scalable structure that can perform current-balancing multiple LED strings is presented. The current-balancing function is accomplished by connecting multiple transformers in a daisy chain—the primary and secondary windings of each transformer are connected to two different modules, and thus the two module currents are mutually coupled. The modules are shared with the same input, derived from the output of a switching network, and each module is used to drive an LED string. When there is a fault occurred in a string, such as open- or short-circuit of any LED, such string will be disconnected from the corresponding module. As the output voltage of the module will then increase under such situation, an energy-recycling circuit with each module having an OR-ing diode connected to its input will be activated to clamp the module voltage by recycling energy back to the source. Thus, the faulty string(s) will not affect the normal operation of the healthy strings. A prototype with seven 1 W LED strings has been built and evaluated. Experimental results show that the string current has less than ±1% variation under different dimming levels, string voltage variation of ±30%, and faulty operations in some LED string(s). [ABSTRACT FROM AUTHOR]

LED light bulbs are becoming increasingly popular as they consume much less power than traditional incandescent lamps. To enable full compatibility with incandescent lamps, apart from delivering the same light output and quality, they are expected to be operable with standard TRIAC-based light dimmers. However, the input current of the LED light bulbs at dimming could fall below the holding current of the TRIAC, resulting in limited dimming range and lamp flickering. This paper presents a TRIAC-dimmable LED lamp driver allowing wide dimming range. The concept is based on controlling the input reactive power, so that the input current is increased to a level higher than the holding current of the TRIAC, while the LED array power is regulated. The driver consists of two power conversion stages, including a four-quadrant ac–dc converter for shaping the input current and a resonant converter for regulating the output power to the LED array. The two converters share the same switching network. Modeling, analysis, and design of the driver will be presented. An LED prototype has been built and evaluated. Experimental results reveal that the true firing angle of the TRIAC can be adjusted down to 172°, and the lamp power can be dimmed from 7.2 to 0.3 W linearly. [ABSTRACT FROM AUTHOR]

A technique for reduction of the dc-link capacitance in a capacitor-supported system is presented. The concept is based on connecting a voltage source in series with the dc bus line to compensate the ripple voltage on the dc-link capacitor, so as to make the output have a near zero ripple voltage. Since the voltage compensator processes small ripple voltage on the dc link and reactive power only, it can be implemented with low-voltage devices. The overall required energy storage of the dc-link, formed by a reduced value of dc-link capacitor and the voltage compensator, is reduced, allowing the replacement of popularly used electrolytic capacitors with alternatives of longer lifetime, like power film capacitors, or extending the system lifetime even if there is a significant reduction in the capacitance of electrolytic capacitors due to the aging effect. Comprehensive analysis on the static and dynamic characteristics of the system, and hold-up time requirement will be discussed. The proposed technique is exemplified on an ac–dc–dc power conversion system. Theoretical predictions are favorably verified by experimental results. [ABSTRACT FROM AUTHOR]

As inverter-fed motor drives generate fast-switching voltage pulses, the transmission-line effects on long motor cable and motor stator windings lead to overvoltage on the cable and motor terminals, as well as inside motor stator windings, and also an increase in the common-mode current. Such phenomenon would cause premature failure of motor and cable insulation. A general protective measure is the use of a passive filter, such as RC and RLC filter, to reduce the voltage surges by matching the cable impedance and/or altering the rise time of the voltage pulses. However, passive filters are bulky and lossy. This paper presents an active motor terminal filter with energy recovery function that can achieve the same functions as the passive filters, but consumes much less power. The proposed filter recovers energy gained from suppressing motor terminal voltage surges and regenerating the recovered energy back to the whole system. An experimental filter has been built and evaluated on a 1-hp three-phase motor drive system. A comparative study into the performance among commonly used RC filter and RLC filter and the proposed filter will be given. [ABSTRACT FROM AUTHOR]

An LED lamp driver with its input compatible with high- and low-frequency sources is proposed. It can be powered by the ac mains, low-frequency electromagnetic ballast, or high-frequency electronic ballast. Its input impedance is controlled to meet the operational requirements and conditions of different sources and its output is controlled to deliver the required power to the LED array. When the driver is powered by a low-frequency source, like ac mains or low-frequency electromagnetic ballast, it is configured as an active power factor corrector. Its input current follows the wave shape of the source voltage. When the driver is powered by a high-frequency source, like electronic ballast, it is configured as a phase-shifted resonant converter with controllable input resistance and susceptance. Moreover, the driver has a startup mechanism that emulates the ignition process of a fluorescent lamp. Such a wide source compatibility of the driver enables the lamp be applied in new lighting installations or retrofitting fluorescent lamps with LED lamps without modification of existing ballasts and/or lighting infrastructure. A 20-W prototype, which is designed to retrofit a 36-W T8 fluorescent lamp, has been built and evaluated with different sources, including ac mains (110 V/60 Hz, 220 V/50 Hz), electromagnetic ballast, and electronic ballast. [ABSTRACT FROM AUTHOR]

A new concept of high-voltage dc-dc power conversion is presented in this paper. Its distinctive feature lies in distributing the high input voltage asymmetrically between two primary-side series-connected switch pairs. This allows using switches of optimal ratings in their respective class: the low-voltage switch pair implemented with MOSFETs only, and the high-voltage switch pair implemented with insulated gate bipolar transistors (IGBTs) only. As the switches in a switch pair are of the same type and voltage rating, they are maximally utilized. With an active snubber on the secondary side of the isolation transformer, a hybrid zero-voltage-switching-zero-current-switching (ZCS) scheme, which is different from the zero-voltage and zero-current-switching technique, is realized and makes all IGBTs be zero-current-switched and all MOSFETs be zero-voltage-switched from very light load to full load condition with minimal circulating energy. The ZCS snubber energy is completely released to the load, leading also to a duty-cycle gain. The operating principles, dc analysis, and design guidelines will be given. A 2-kW, 1500/48-V experimental prototype has been built and evaluated. The measured efficiency of the converter is found to be 92.4% at the rated condition. [ABSTRACT FROM AUTHOR]

Eco-friendly electronic products can help save the environment by using less electricity. However, saving energy is not only about reducing the electricity consumption of a product; it should also encompass the electricity consumed in the production of the product. After a product is assembled, it has to go through a burn-in process for weeding out infant mortalities and thus improving the product reliability. The use of energy recycling in the burn-in process is popular nowadays in the power supply industry. However, the development of energy-recyclable burn-in system for electronic ballast manufacturing is less impressive. Existing burn-in process for electronic ballasts is conducted by connecting lamps or resistors at their output. All electrical energy is converted into heat and light. Not only does this method waste electricity, it also raises room temperatures in the factory, requiring additional ventilation systems to release the excessive heat. This paper presents an energy-recyclable burn-in technology for electronic ballast. It can emulate the lamp characteristics from start up to the steady state, process high-frequency ballast output power, and recycle the power back into the grid. An experimental 400-W prototype for high-pressure sodium electronic ballast has been built and evaluated. [ABSTRACT FROM AUTHOR]

Power conversion from an input voltage of several kilovolts to a low load voltage is of great significance in various applications, but poses serious challenges. In this paper, a new converter, which is able to realize such a large step-down conversion in a single step, is proposed by introducing a novel concept of dc–dc multiphase conversion and n-phase interleaving rectification. The proposed structure is formed by n switch pairs in the primary side, an n-phase isolation transformer with the primary windings connected to dc blocking capacitors, and an n-phase current multiplier in the output side. The switching patterns applied to the switch pairs have a phase difference of 360^\circ \mathord\left/ \vphantom 360^\circ n \right. \kern-\nulldelimiterspace n, and the output inductor currents are interleaved correspondingly, making necessary a smaller output filter. For a V_i input voltage and I_o load current, the converter features V_i/n voltage stress on the primary-side switches, and I_o/n current stress on the secondary-side inductors and diodes. Thus, the magnetic size of the inductors is considerable reduced. The primary-side switches are commutated with zero-voltage-switching (ZVS). Therefore, rather than using insulated-gate bipolar transistors (IGBTs) or MOSFETs with higher voltage ratings, the most available, notable performing 500/600 V MOSFETs can be used in the proposed converter with several kilovolts supply voltage, allowing for a higher operation frequency and lower conduction losses. Compared with an input-series–output-parallel (ISOP) connection of full-bridge (FB) isolated converters, for the same voltage stress on the switches, the proposed converter requires half of the number of transistors and inherently balances the input voltage among the switch pairs. The switching mechanism of a typical switch pair in the kth interval T_s/n of a switching cycle is analyzed. A dc analysis was carried out to determine the dc conversion ratio and the ZVS conditions in an analytical form. It allows for a tradeoff design of the converter, such that to minimize the duty-cycle loss and maximize the ZVS load range. A 1500/48-V, 2-kW prototype with four switch pairs was designed, implemented, and evaluated. The experimental results prove the soft switching of the switches, the low voltage stress across the primary-side switches, and the low current flowing through the rectifier's diodes and inductors. The efficiency measured at nominal power rating was 90.75%. [ABSTRACT FROM AUTHOR]

A driving technique that can operate with electronic ballasts for fluorescent lamps to drive LEDs without requiring the replacing of any electronic ballast circuitry or modifying the existing infrastructure of a lighting network is presented. This technology provides an eco-friendly and immediate solution to turn a lighting system with fluorescent lamps into the one with LED lamps. The proposed technology is based on controlling the input impedance of an ac/dc converter, which is connected to the output of the ballast, and converting the high-frequency ac power from the ballast into dc power for the LEDs. With such adjustable input impedance, the active and reactive power drawn from the ballast can be controlled. The power supplying to the LED lamp, and thus its brightness, can be adjusted independently by an external means, such as wireless control. An experimental LED lamp prototype for retrofitting a 36-W T8 fluorescent lamp has been built. It is studied together with a fluorescent lamp and with both lamps ballasted by a commercial nondimmable electronic ballast for dual fluorescent lamps. The light output of the LED lamp can be varied from 100% to 51% of full brightness, while the light output of the fluorescent lamp remains unchanged. The input power to the ballast is reduced by 26% over the dimming operation of the LED lamp. A comprehensive study into the electrical performance of the ballast, operational characteristics of the two lamps, system efficiencies, and light outputs under different dimmed conditions is presented. [ABSTRACT FROM PUBLISHER]

A dimming module for controlling the power supplying to a fluorescent lamp ballasted by a nondimmable electronic ballast is proposed. It is physically connected across the lamp tube to perform the dimming operation. The methodology is based on diverting the current supplying to the lamp tube to adjust the lamp power. The current diverted is in phase quadrature with the lamp voltage. The power stage of the module consists of a series-resonant inverter operated as a reactive-power controller. On dimming the lamp, it will increase the filament voltage for maintaining good thermionic emission of electrons from the filament. More importantly, it enables dimming function without detriment to the input-power quality of the ballast and lamp-current crest factor. The operating principle, control of the module, and the design procedure are described in this paper. An experimental prototype for dimming a 28 W T5 lamp has been built. The module is applied to one of the two lamps that are both ballasted by a commercial-electronic ballast for dual lamps. Experimental results show that the proposed module can adjust the power supplying to the lamp with the dimming module from 100% to 30% of the full power. A comprehensive study into the electrical characteristics of the ballast, lamp operational characteristics, and system efficiency at different dimmed conditions will be presented. [ABSTRACT FROM PUBLISHER]

Ant colony optimization (ACO) is typically used to search paths through graphs. The concept is based on simulating the behavior of ants in finding paths from the colony to food. Its searching mechanism is applicable for optimizing electric circuits with components, like resistors and capacitors, available in discrete values. However, power electronic circuits (PECs) generally consist of components, like inductors, manufactured in continuous values. Therefore, the traditional ACO algorithm cannot be applied directly. In this paper, an extended ACO (eACO) that can search the optimal values of components manufactured in discrete and continuous values is presented. The idea is based on using the orthogonal design method (ODM) to dynamically update the database of the components available with continuous values, so that these components will have pseudo-discrete values in the search space. To speed up the optimization process, the ODM performs local search of the best combination around the best ant. The eACO also takes the component tolerances into account in evaluating the fitness value of each ant. The proposed algorithm has been successfully used to optimize the design of a buck regulator. The predicted results have been compared with the Published results available in the literature and verified with experimental measurements. [ABSTRACT FROM AUTHOR]

A major consideration in designing controllers for boost converters is the existence of a right-half-plane zero in the control-to-output transfer function. This property makes the controller impossible to be designed in classical frequency-domain approach to achieve fast dynamic response over wide bandwidth of supply and load variations. In this paper, a time-domain boundary control concept for large-signal control of boost converters is proposed. By transforming the conventionally used state plane into the newly proposed state-energy plane to dictate the switching instants, a well-defined switching surface is derived. The converter can ideally revert to the steady state in two switching actions when it is subject to external disturbances. Of particular importance, experiments show that the same controller is applicable for controlling converters operating in continuous conduction mode, critical conduction mode, or discontinuous conduction mode. Sensitivities of the switching surface to parametric variations will be studied. Theoretical predictions will be verified with the experimental results of a 55 W, 48 V/110 V prototype. [ABSTRACT FROM AUTHOR]

Due to the interaction between the rectified voltage appearing on the dc side of the grid-connected current source inverter (CSI) and the dc inductor, the input current on the dc side inherently consists of the second-order harmonic of the grid frequency. This harmonic component will be modulated by the pulsewidth modulation (PWM) signal that results in generating low-order harmonics at the output and thus injecting into the grid. This paper presents an active nonlinear modulation technique for reducing the low-order harmonics. The method requires simple analog circuitry to modify the modulation function of the sinusoidal PWM (SPWM) scheme. It is based on measuring the dc and ac components of the dc inductor current to compensate the modulation effect from the dc side to the ac side of the CSI. Apart from reducing the harmonic content, this method can also reduce the required value of the dc inductor. Modeling, design, and analysis of the method are given. The proposed method has been tested with a 1 kW, 220 V, 50 Hz prototype, powered by a dc voltage of 80 V. The results are favorably compared with the performance of the CSI with the SPWM scheme. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into the use of saturable inductor to improve the dimming characteristics of frequency-control dimmable electronic ballasts with a half-bridge series resonant parallel-loaded inverter. The concept is based on the fact that the effective resonant frequency increases as the inductor current increases, if the unsaturable inductor in the resonant tank circuit is replaced with a saturable one. Susceptibility of the lamp power to the switching frequency variation at low luminous level can be reduced. This can lessen the problem of lamp flickers at dimmed level and result in a wider dimming range and improved controllability. The method gives a simple solution of improving the dimming characteristics without changing the circuit structure. A fundamental frequency model that includes the characteristics of the nonlinear lamp resistance and filament resistance is applied in the analysis. A PSIM simulation model for the saturable inductor is developed. Theoretical predictions are verified with the experimental results of a 36-W T8 prototype. [ABSTRACT FROM AUTHOR]

Presents a generalized circuit structure of bi-directional switched-capacitor dc/dc converters that feature voltage step-down, voltage step-up, and bi-directional power flow. Derivation of two structures of single-capacitor bi-directional converter cells; Control scheme applied in the capacitor-charging phase; Formulation of a converter string by cascading a number of converter cells.

Presents a current control scheme for switched-capacitor step-down direct current/direct current converters. Principles of operation; Advantages over classical switching schemes in terms of continuous input current and good regulation capability.

Focuses on a study which presented a detailed analysis and the spectral characteristics of a random carrier-frequency technique for suppressing conducted electromagnetic interference in an offline switched-mode power supply. Models and mathematical derivations; Experimental verifications; Conclusions.

Presents a systematic graphing technique for small-signal low-frequency characterization of pulsewidth-modulated direct current-to-direct current converter. Methodology using discrete-time state-space description to formulate a small-signal sensitivity graph; Algorithms integrated for the proposed method.

Estimation of Meteorological visibility from image characteristics is a challenging problem in the research of meteorological parameters estimation. Meteorological visibility can be used to indicate the weather transparency and this indicator is important for transport safety. This paper summarizes the outcomes of the experimental evaluation of a Particle Swarm Optimization (PSO) based transfer learning method for meteorological visibility estimation method. This paper proposes a modified approach of the transfer learning method for visibility estimation by using PSO feature selection. Image data are collected at fixed location with fixed viewing angle. The database images were gone through a pre-processing step of gray-averaging so as to provide information of static landmark objects for automatic extraction of effective regions from images. Effective regions are then extracted from image database and the image features are then extracted from the Neural Network. Subset of Image features are selected based on the Particle Swarming Optimization (PSO) methods to obtain the image feature vectors for each effective sub-region. The image feature vectors are then used to estimate the visibilities of the images by using the Multiple Support Vector Regression (SVR) models. Experimental results show that the proposed method can give an accuracy more than 90% for visibility estimation and the proposed method is effective and robust. [ABSTRACT FROM AUTHOR]

Describes a technique for simulation of power electronics circuits. Derivation of an adaptive stepwise quadratic state-space model by using the Chebyshev polynomials; Analysis of circuit topology in order to achieve a desired accuracy in calculating the state transition matrix; Numerical estimation of switching instants.

Presents information on a study which presented the use of the control scheme in switched-capacitor (SC)-based step-up dc/dc converter. Basic n-stage step-up converter cell and its control philosophy; Principles of operation of an n-stage converter; Experimental results of a 5 V/12 V two-stage step-up converter prototype.

Presents information on a study the described a quadratic state-space modeling technique for analysis of power electronic converters. Major steps of analysis; Illustrative example; Conclusion.

Presents a study which describes the modelling and experimental results of some coreless printed circuit board (PCB)-based transformers. Used for metal oxide semiconductor field-effect transistor (MOSFET) and insulated gate bipolar transistor (IGBT) devices at high-frequency operation; Verification of coreless PCB transformer model; Conclusion.

Presents information on a study that examined a simple and effective approach of turning an isolated hard-switched converter design into a soft-switched one. Description of a zero-current-switching (ZCS) direct current (DC)/DC flyback converter with an auxiliary switch; Theoretical analysis of the study; Experimental results of the study.