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A high-attenuation wideband active common-mode filter (ACF) section is presented. Each section is composed of an active capacitor and a small common-mode (CM) inductor. The active capacitor is realized by using several coupling capacitors and a class-A bipolar-junction-transistor based amplifier for its low-cost, fast response, and good immunity to high voltage transients. The structure of the amplifier consists of a common-collector amplifier and a high-gain common-emitter amplifier with an active load. The working bandwidth of the ACF ranges from 150 kHz to 30 MHz. By cascading several ACF sections, a multistage structure that exhibits high filtering attenuation can be designed. The number of cascaded sections is optimized by considering the required filtering attenuation. The performance of single-stage and multistage ACFs is evaluated on two commercial power supplies with rated power of 90 and 1000 W, respectively. The CM noise of the power supplies with the proposed ACF and with the original passive filters is compared. The results show that the physical volume of the ACF is significantly smaller than that of the passive filter, and the power dissipation of the ACF is similar to that of the passive filter. [ABSTRACT FROM AUTHOR]

Highlights a technique for steady-state analysis of pulsewidth modulated (PWM) direct current to direct current (dc/dc) switching regulators. Information on a stepwise cycle time-domain simulation using the technique; Methodology which the technique is based on; Illustrative examples using the technique.

Focuses on the development of a new general-oriented time-domain simulation technique for power electronic systems. What the algorithm is based on; Core power of this technique; Presentation of several examples illustrating the generality and computational efficiency of the approach.

Provides information on the presentation of a hybrid time-domain simulation technique for pulse-width-modulated (PWM) switching regulators. Information on the modeling of the error amplifier and its output voltage formulation; Detailed information on the basic principles of the method; Indepth look at illustrative examples.

• Online monitoring module based on differential power processing principles. • Data acquisition of dynamic I-V characteristic of a solar panel in milliseconds. • Intrinsic parameter estimation using evolutionary algorithms. • Fault detection based on deviations in estimated intrinsic parameters. An online diagnostic module for condition monitoring of two series-connected photovoltaic panels is presented. The technique is based on firstly perturbing the terminal voltages and currents of the panels with a switched-inductor circuit, which can also be used for differential power processing, to obtain the large-signal dynamic current-voltage characteristics of the panels. An evolutionary algorithm is used to estimate the intrinsic parameters of the panels from the time series of the sampled panel current and voltage. The conditions of the panels are monitored by observing the long-term changes in the extracted intrinsic parameters. Prototype data acquisition module for studying the conditions of solar panels of different technologies (amorphous and crystalline silicon) with different degrees of damage has been built and evaluated. Results reveal that the estimated intrinsic parameters from large-signal dynamic characteristic correlate with the observed health status of the tested panels. Theoretical predictions are favorably compared with experimental measurements. [ABSTRACT FROM AUTHOR]

A totem-pole bridgeless power factor corrector has been widely used in high-power ac–dc power conversion for its low component count and high energy efficiency. Its active bridge is configured to operate the power circuit as a synchronous boost converter over the line cycles. However, due to some intrinsic and extrinsic factors, input current distortion near the zero crossings is unavoidable. A hybrid pulsewidth modulation (PWM) scheme for mitigating such zero-crossing distortion is proposed. The concept is based on changing the PWM modulation schemes dynamically around the zero crossings, so that the line current can still be profiled with a switching scheme that does not require tracking the polarity of the grid voltage accurately. A generalized model for describing the variation of the inductor current, which is also the input current, from its average value in a switching cycle is formulated and is used to derive the optimal alignment of the PWM pulses for giving the smallest transient variation upon changing the modulation scheme. Results indicate that the voltage pulses generated by the active bridge are preferably symmetrical and center aligned in a switching period. A 1-kW 85–265-Vac/400-Vdc 47–63-Hz SiC-based prototype has been built and evaluated. [ABSTRACT FROM AUTHOR]

In dc microgrid systems, power converters with input filters sometimes encounter unwanted input voltage and current oscillations, due to interactions among the bus impedance, filters, and converters. This paper presents a solid-state single-port series damper (“S3damper”) that can deal with such oscillations. The damper, which is connected in series between the input filter and the converter, is realized by operating a transistor as an ac resistor. It lowers the quality factor of the filter and thus increases the damping effect on the interaction between the filter and the converter. It also increases the input impedance of the filter to avoid voltage and current oscillation between the filter and the bus. In addition, the transistor is regulated at a low dropout voltage to reduce power dissipation. The control mechanism is autonomous. Furthermore, the proposed damper does not require any power capacitor or inductor, favoring high compactness and reliability. Modeling, design, and comprehensive analysis of theS3damper will be provided. A prototype damper for a commercially available 100 W dc–dc converter operated on a 48 V bus has been built and evaluated. [ABSTRACT FROM AUTHOR]

A novel color control method for multicolor light-emitting-diode (LED) systems is proposed. The proposed control method can achieve high color rendering indexes by approximating the spectral power distributions (SPDs) of black bodies. The SPD control of the LED system is accomplished by combining a sensory module and a control module. The sensory module implements a linear function that merges readouts from multiple color sensors and maps the data into the optical powers of the LED channels, while the control module utilizes such data in a feedback loop to control the optical power of each channel. Compared with conventional control methods, the proposed method has the merits of 1) not requiring an accurate electrical-optical system model, 2) requiring only a few spectra data for offline calibration, 3) requiring only red-green-blue (RGB) color sensors for online operations of tetracolor and pentacolor LED systems, 4) providing consistent color with high color rendering index, and 5) being applicable to all multicolor LED systems. The proposed control method is evaluated by applying it to an example of an RGB-amber LED system driven by a buck-type single-inductor-multiple-output LED driver with the LED channels connected in series. Experimental results have verified the effectiveness and robustness with ambient temperature of the proposed control method. [ABSTRACT FROM AUTHOR]

Due to the global environmental issues and energy crisis, the injection of renewable energy sources (RESs) into the power system is continuously increasing. As the interface between RESs and power grid, grid-tied inverters using MOSFET switches, without traditional line frequency transformers, show some potential advantages, in terms of low cost, high efficiency, and lightweight and small size. Among several proposed configurations, the Aalborg inverter was proposed as a new family of high efficiency MOSFET-switch-based hybrid source inverters. For a conventional “half bridge” type Aalborg inverter, due to the imbalance of two independent dc sources, the input dc energies may not be fully utilized, which may reduce the efficiency of whole system. In order to extract the maximum energy from two independent dc sources, a coupled-inductor-based “half bridge” type Aalborg inverter is proposed in this paper. The principle of operation is presented and demonstrated through equivalent circuits. The effectiveness of a new energy balancing technique has been validated through simulations and experiments on a 110 V/ 500 W prototype. [ABSTRACT FROM PUBLISHER]

A single-phase transformer-less unified power quality conditioner (TL-UPQC) is presented. Apart from having no isolation transformer, the proposed structure utilizes four switching devices only, forming two half-bridge voltage-source inverters—one connected in parallel with the load and another one connected in series with the ac mains. The two inverters share the same dc link. The parallel inverter, which is controlled by a hysteresis current controller, is used to shape the current drawn from the ac mains and regulate the dc-link voltage. The series inverter, which is controlled by a boundary controller with second-order switching surface, is used to regulate the steady-state load voltage and provide voltage sag/swell ride-through. A dc-link capacitor voltage balancing control that coordinates the operations of the hysteresis and boundary controllers is designed. Modeling, design, and analysis of the whole system will be given. A 1 kVA, 110 V, 60 Hz prototype has been built and evaluated on a setup with a nonlinear load. The steady-state and transient responses under a voltage sag will be given. Experimental results are favorably compared with the theoretical predictions and the performance of other UPQCs. [ABSTRACT FROM PUBLISHER]

Power filters have been widely used to suppress switching harmonics caused by the modulation of grid-connected inverters. In order to save the total inductance and cost and reduce the volume, different power filters were proposed for the three-phase three-wire grid-connected voltage source inverter. However, in industrial applications, due to the consideration of production cost, the difficulties caused by the deviation of actual parameters have to be addressed. In this article, we propose a new three-phase three-wire power filter with a simple structure, almost the smallest total inductance, and strong resistance to the adverse effects of parameter shifts. The parameters of the proposed filter and the design of the grid-connected system controller are introduced in detail. When studying the influence of parameter offset, a comparison between different types of notch power filters is also given. Simulation and experimental results on a 380 V/50 Hz/6 kW three-phase inverter prototype verify the performance of the proposed power filter. [ABSTRACT FROM AUTHOR]

It is sometimes unavoidable to place light sources and drivers far apart in large-scale LED lighting installation, where a long cable is used to connect the light source to the LED driver. LED drivers typically deliver pulse width-modulated pulses. The long cable inductance will delay the rate of rise of the current pulses and will also cause negative off-state voltage across the light source. Apart from reducing luminous output, such phenomenon also causes an impact on the life expectancy of the light source. A simple passive current compensator, which is connected between the driver and the light source to mitigate the distortion of the current pulses caused by the cable inductance, is presented. The concept is based on recycling the energy stored in the cable after the end of a current pulse to drive the light source synchronously with the driver at the beginning of the next current pulse, so as to modify the rise time of the current pulses. The topological states and operations of the compensator will be discussed. Simplified design procedure for the compensator will be given. A prototype for a 12 V LED driver to drive LED strips of rated current 4.5 A has been built and evaluated. Experimental results are compared with theoretical predictions. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvester (PEH) arrays are promising in many application scenarios. However, few interface circuits have been developed to manage the multiple ac inputs from PEHs. This article proposes an extensible parallel synchronized switch harvesting on inductor array interface scheme to realize a multiinput conversion from PEH arrays. We develop a split-inductor-capacitor topology that can extract electrical energy from multiple PEHs. The proposed circuit topology effectively handles the inductor access conflict in the cases of PEHs with close, identical, and opposite vibration phases, insensitive to ac input phase changes. For demonstrating the capability of dealing with multiple ac inputs from PEHs and the enhancement effect on power output, we construct and test a self-powered three-channel array circuit with the passive peak detection function. Excited by sinusoidal vibrations, our circuit effectively avoids the energy return and efficiently achieves the power combination of the three PEHs. Compared with the classic full-bridge circuit, the proposed circuit helps increase the power output by 4.8 times. Also, to show the universality of the circuit, the circuit's operation under various excitations istested and analyzed. [ABSTRACT FROM AUTHOR]

An investigation into the use of series-pass device (SPD) to filter out input current harmonics of switching converters is presented. The idea is based on connecting a SPD in series with the input of the switching converter so that the input current of the entire system can be profiled by adjusting the biasing condition of the SPD. To minimize the power dissipation of the SPD, the input impedance of the switching converter is controlled to make the SPD operate at the boundary between the linear and saturation modes. Modeling, design, and analysis of the system architecture will be given. Selection guide for the SPD will also be given. The concept has been applied to a 75-W 90–140-V/24-V classical dc–dc buck converter. Investigations reveal that the proposed architecture allows a substantial reduction in the size of the filter section and gives comparable efficiency as the conventional passive-type LC filter. More importantly, the idea makes the input filter amenable to monolithic integration. These investigations lay the foundation for applying the proposed concept for other power electronic converter systems. [ABSTRACT FROM PUBLISHER]

A fault diagnosis technique for photovoltaic (PV) panels is presented. While a PV system is sampling the terminal voltage and current of its connected panel for tracking the maximum power point of the panels, the proposed technique utilizes the sampled data to estimate the intrinsic parameters of the panel simultaneously. Compared with the prior-art approach of using the static current–voltage characteristics, the proposed technique utilizes the dynamic current–voltage characteristics to determine the parameters. Apart from the fast parameter estimation, it also provides an in-depth understanding of the panel condition with the drift of the parameters. Several prototype devices with the proposed algorithm have been built. They are evaluated on a test bed with four 80-W panels, with two of them being healthy and the other two having different degrees of damage on the surfaces. Results reveal that the parameters of the cracked panels deviate significantly from their nominal values, giving a sign of panel failure. Furthermore, the device can communicate with and send the estimated parameters to the central control center over the panel cable via power line communication. The merits of this concept lie in its modularity, scalability, and remote fault diagnosis capability. [ABSTRACT FROM PUBLISHER]

It is sometimes unavoidable to use loosely coupled coils in applications, like biomedical devices, for transferring electric energy wirelessly. However, coil misalignment causes degradation of the power transfer efficiency. It is well known that the power transfer efficiency of classical parallel coils is primarily determined by the quality factors of the coils and the coupling coefficient between the coils, and is maximized by choosing an optimal turns-ratio between the coils. Changing the number of turns of the coils cannot effectively overcome such misalignment effect. This paper presents a structure that comprises two orthogonally placed windings for lessening the variation of the coupling coefficient due to the coil misalignment. An output current summing technique that keeps the windings concurrently energized and combines the output currents of the windings will be studied. A canonical model will also be derived to describe the interactions between the coils. An experimental prototype has been built and evaluated on a test bed, which allows different degrees of lateral and angular misalignments. Results reveal that the proposed structure can effectively increase the minimum efficiency zone, allowing more lateral and angular misalignments. These investigations lay the foundation for future understanding more complex loosely coupled winding structures. [ABSTRACT FROM AUTHOR]

The article discusses the new technique trends to be implemented by the power converters in the system of distributed power generation. It talks about the passivity-based control for handling the current error of the conventional power filters. It discusses the effectiveness of the e thermoelectric generation system and focuses on the use of ac-ac converters based on bridge modular switched capacitors.

This "Special Section on New Technique Trends for Power Converters in Distributed Power Generation Systems" of the IEEE Transactions on Industrial Electronics (TIE) 35 papers selected among 89 submitted papers. Therefore, this Special Section will be published in two parts. In Part I, all the papers are related to dc/ac grid-tied inverters. [ABSTRACT FROM PUBLISHER]

The instability of power systems comprising multiple LCL-filtered grid-connected dc–ac inverters connected in parallel can be caused by any individual inverter due to mutual coupling through the grid impedance. For the stability analysis of a multiparalleled dc–ac inverters system, an effective technique capable to diagnose which particular inverter (i.e., “trouble maker”) causes instability to the overall system has not been developed yet. In this article, a novel autoidentification method is proposed to detect the “trouble maker(s)” of instability in a multiparalleled inverters system, based on the comparison between the root-mean-square value of harmonic voltage at the point of common coupling and the harmonic voltages across the filters capacitors. The theoretical analysis of the proposed identification method is presented in details in this article. Also, simulation and experimental results are provided for the verification of the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

Maximizing the lifetime of wireless sensor networks (WSNs) is a challenging problem. Although some methods exist to address the problem in homogeneous WSNs, research on this problem in heterogeneous WSNs have progressed at a slow pace. Inspired by the promising performance of ant colony optimization (ACO) to solve combinatorial problems, this paper proposes an ACO-based approach that can maximize the lifetime of heterogeneous WSNs. The methodology is based on finding the maximum number of disjoint connected covers that satisfy both sensing coverage and network connectivity. A construction graph is designed with each vertex denoting the assignment of a device in a subset. Based on pheromone and heuristic information, the ants seek an optimal path on the construction graph to maximize the number of connected covers. The pheromone serves as a metaphor for the search experiences in building connected covers. The heuristic information is used to reflect the desirability of device assignments. A local search procedure is designed to further improve the search efficiency. The proposed approach has been applied to a variety of heterogeneous WSNs. The results show that the approach is effective and efficient in finding high-quality solutions for maximizing the lifetime of heterogeneous WSNs. [ABSTRACT FROM PUBLISHER]

An ant colony optimization (ACO) algorithm offers algorithmic techniques for optimization by simulating the foraging behavior of a group of ants to perform incremental solution constructions and to realize a pheromone laying-and-following mechanism. Although ACO is first designed for solving discrete (combinatorial) optimization problems, the ACO procedure is also applicable to continuous optimization. This paper presents a new way of extending ACO to solving continuous optimization problems by focusing on continuous variable sampling as a key to transforming ACO from discrete optimization to continuous optimization. The proposed SamACO algorithm consists of three major steps, i.e., the generation of candidate variable values for selection, the ants' solution construction, and the pheromone update process. The distinct characteristics of SamACO are the cooperation of a novel sampling method for discretizing the continuous search space and an efficient incremental solution construction method based on the sampled values. The performance of SamACO is tested using continuous numerical functions with unimodal and multimodal features. Compared with some state-of-the-art algorithms, including traditional ant-based algorithms and representative computational intelligence algorithms for continuous optimization, the performance of SamACO is seen competitive and promising. [ABSTRACT FROM AUTHOR]

To merge the gap between the low-power output of piezoelectric energy harvesters (PEHs) and the high-power demand of sensors of Internet of Things, researchers recently start to explore PEHs arrays. However, few circuits have been developed to manage the multiple ac inputs from PEHs arrays. This article presents a self-powered PEH array interface circuit based on the synchronized switching and discharging to a storage capacitor through an inductor (SSDCI) technique. The array interface can output a maximum total power greater than the sum of each individual peak power, and achieve a high efficiency when multiple PEHs connect to the SSDCI array circuit. Simulation and experiment are performed to demonstrate the advantages of the SSDCI array interface. The tested results show that the designed SSDCI array circuit achieves an efficiency of 82.3% with three input sources, and allows a gain up to 300% in terms of maximal output power compared to the full-bridge rectifier. In addition, only the peak detection is utilized for the switching control; therefore, the SSDCI array circuit is realized more easily and with fewer components compared to the existing synchronous electric charge extraction array interfaces. [ABSTRACT FROM AUTHOR]

The article discusses the study on a new intelligent testing system for both teachers and students centered on the ant-colony-optimization-based test composition (ACO-TC) method which is intended to generate high quality tests for examinations and multiple requirements. The methods of the study include a question bank, pheromone and heuristic information and system analysis. It concludes that the use computer-assisted testing system for maximum benefits is significant in modern education.

This paper summarizes the test results on several large-scale lighting systems based on a range of high-intensity-discharge (HID) lamps. The study focuses on the energy-saving, energy-efficiency, and dimming characteristics of magnetic- ballast-driven HID lamp systems that are suitable for public lighting networks. A central energy-saving unit that can change the input mains voltage of 220 V to a variable voltage within the range from 220 to 170 V is used to control a large lighting network. This central dimming unit offers a new freedom for users to use lighting energy when and where it is needed and to an appropriate power level. Lamp characteristics under full and reduced voltage operation for six types of HID lamps have been measured. Six large-scaled networks of ballast-lamp sets have been set up and dimmed with a central energy-saving unit with a rated power of 13.2 kVA per phase. The full load current under test was set at about 40 A per phase. The loss of the energy-saving unit on a per-lamp-set basis was measured at different voltage levels. It is found that the energy-saving unit can reduce overall system power at least 40% without causing lamp flickering. Through the controllable voltage range, there is no obvious change in color temperature. The lamp power and light output decrease almost linearly with input voltage within the range from 170 to 220 V, and the power loss of the energy-saving unit is less than 2.4% of the full power in all tests. For these large-scaled lighting networks, it is envisaged that 25%-35% of energy saving can be achieved in large public lighting applications. [ABSTRACT FROM AUTHOR]

Presents a study that described the use of current sensors for the control of power converters. Control philosophy; Characteristics of a family of converters; Illustrative example; Conclusion.

This paper presents an evaluation of the spectral characteristics of switching converters with a chaotic carrier-frequency modulation scheme (CCFMS). By incorporating a Chua's circuit (CC) into the pulsewidth modulator for driving the switches, three modulation schemes, including the standard pulsewidth modulation scheme, periodic carrier-frequency modulation scheme, and CCFMS, can be realized with the CC in equilibrium, limit cycle, and chaos, respectively. The property of frequency spreading in CCFMS is studied by using statistical analysis method. The developed model is applied to formulate the power spectral densities of the input current and the output voltage of the three basic dc/dc converters under CCFMS. Theoretical predictions are verified with experimental measurements. [ABSTRACT FROM AUTHOR]

Features a study which demonstrated a low-profile, low power converter with soft switching and coreless printed circuit board (PCB) isolation transformer. Optimal operation of coreless PCB transformers; Operation of the soft-switched converter; Experimental verification.

A new linear control scheme for operating power MOSFETs in the third quadrant (i.e., synchronous rectifier (SR) operation) is proposed and applied to electromagnetic interference (EMI) mitigation of switching converters. MOSFETs operating in the third quadrant exhibit electrical characteristics equivalent to a voltage-controlled voltage source between the gate-source and the drain-source voltages. Such operation is an alternative to typical SR mode, allowing fast control of the ac drain-source voltage. It is applied to active bridge rectifiers (ABRs) that can produce the necessary high-frequency voltage compensation signal to reduce differential-mode EMI. The ABR can then play the role of ac line rectification and EMI reduction at the same time. Its characteristics are modeled, and experimental verifications are carried out on a boost-type power factor corrector (PFC). The EMI performance of the PFC is improved with the proposed technique. The proposed technique facilitates the reduction of passive filter size and gives the potential of integrating active filtering function into the ABR as a solid-state front-end module. The idea can, thus, help increase the power density of power converters. [ABSTRACT FROM AUTHOR]

Recently, finite control set model predictive control (FCS-MPC) has been successfully applied in the grid-tied inverter with the LCL filter. However, to achieve active damping and grid synchronization, many sensors are required, increasing cost, and complexity. In addition, a considerable computational delay should be addressed when it is experimentally implemented, which may degrade the performance of the overall system. In order to reduce the number of sensors, eliminate the computational delay, and enhance the control reliability of the system, a novel FCS-MPC strategy with merely grid-injected current sensors is proposed, which contains four compositions: virtual flux observer, state observer, delay compensation, and FCS-MPC algorithm based on estimations. A 3-kW/3-phase/110-V experimental platform is established to validate that utilizing the proposed observations-based control method with only grid-injected current sensors is capable to obtain satisfactory performance of grid synchronization and high-quality grid-injected current both under balanced and unbalanced grid voltage condition. [ABSTRACT FROM AUTHOR]

Owing to the strong robustness against system parameter changes and external perturbations, the passivity-based control (PBC) has been widely adopted in grid-tied inverter (GTI). However, for a PBC-based GTI with LCL-filter, there are three damping gains and two interactively coupled-feedforward terms in the control loop, resulting in the controller design challenge for engineers. In order to help electrical engineers to well design the PBC controller for LCL-filtered GTI, a new design of the damping gains is proposed, by limiting the inherent steady-state error of grid-injected current. Furthermore, the state observer is also adopted to reduce the number of sensors. The robustness against the parameters shift and wide grid impedance variation is also addressed. The effectiveness of the proposed control design strategy will be verified through experimental results on a 3 kW/3-phase/110 V experimental lab setup. [ABSTRACT FROM AUTHOR]

A power factor corrector extended from a previously proposed boost-type structure with power semiconductor filter (PSF) is presented. The concept of the PSF is based on using a series pass device (SPD) to profile the input current and regulate the output voltage, and an input capacitor to circulate the ripple current generated by the boost converter. However, the input capacitor is charged up slowly with small input current around the zero crossings, causing high voltage stress on the SPD. Then, a high-voltage device for the SPD is needed. However, high-voltage devices have large channel length modulation effect, high leakage current, large voltage drop, and slow response. To accelerate the capacitor charging and thus reduce the voltage stress, this article proposes to replace the output diode with a controllable switch. The converter is temporarily operated as a buck converter during the zero crossings with the input capacitor charged up swiftly by the output capacitor. The voltage across the SPD can be kept low over the line cycle, resulting in improved input current waveform and reduced power dissipation. A series pass module constructed by multiple parallel-connected low-voltage devices is used to increase current rating. The devices are regulated to operate around the knee point of the output characteristics to reduce power loss. A 1 kW, 85–265 Vac/400 Vdc prototype has been built and evaluated. [ABSTRACT FROM AUTHOR]

An input filtering technology named “power semiconductor filter (PSF)” has been proposed recently. Its operating principle is based on using a series pass device (SPD) to profile the wave shape and magnitude of the input current of converters. The voltage across the SPD is regulated around the “knee point” of the current–voltage characteristic of the SPD to minimize the power dissipation of the SPD. This paper reports the conducted electromagnetic interference (EMI) performance of the converters with the PSF. To suppress differential-mode (DM) EMI, a fast current regulation circuit is proposed to tightly regulate the current through the SPD. To suppress common-mode (CM) EMI, a single CM noise bypass capacitor is proposed. Detailed mathematical models for describing the frequency response of the SPD and main components in the driving network are formulated. A set of selection guidelines for the components will be given. The derived models will be validated by comparing the theoretical prediction with the measurement results of a 100 W, 90–264 Vac LED driver using a buck–boost converter. Results reveal that the PSF reduces the DM noise level by 47.47 dBμV. The CM noise level is reduced by 21.4 dBμV with the bypass capacitor. An integrated circuit for the controller is illustrated to demonstrate the feasibility of reducing the form factor of the filtering section. [ABSTRACT FROM AUTHOR]

Standard TRIAC-based dimmers introduce power quality issues especially for a large-scale lighting network. Other existing dimming protocols involve additional wiring systems and/or additional controllers to light emitting diode (LED) drivers. This paper proposes a central dimming system for a large penetration of LED lamps. The dimming system is remotely controlled through a webpage or a desktop application. Dimming is achieved while maintaining high voltage and current quality waveforms, which results in a high power factor and a low input current harmonic distortion. The system does not require additional wiring or specific adjustments to commercial dimmable LED drivers. The system allows scheduling a dimming profile to endorse energy saving. In the proposed dimming system, dimming function is achieved by connecting a voltage source converter (VSC) between the grid and the LED lamps. An advanced feature is added to the VSC dimmer to remotely send/receive messages between the system and the user through a graphical user interface. Thus, the user can communicate with the VSC dimmer by sending commands and receiving feedback information. The influence of communication delay on system stability is analyzed by using small signal models. A VSC dimmer prototype (500 VA/120 V) has been built with a communication module to provide remote control. Experimental results and comparisons between utilizing the TRIAC-based dimmer and the VSC dimmer for dimming function are discussed in the paper. [ABSTRACT FROM AUTHOR]

A flyback power factor corrector (PFC) using a series-pass module (SPM) to shape its input current is presented. The input current is profiled by the SPM with its waveform controlled to be in the same wave shape and phase with the supply voltage and its magnitude controlled to regulate the output voltage. The SPM is constructed by two series-connected power semiconductor devices in a cascode structure. One of them is a high-voltage device of low on-state resistance for sharing major voltage stress, while the other one is a low-voltage device with high-output impedance for profiling the current through the SPM. The SPM has a local control for clamping the voltage across the low-voltage device. Such arrangement allows the PFC to exhibit lower total input current harmonic distortion than that using a single high-voltage series-pass device. To minimize power loss, the operating point of the low-voltage device is regulated around the boundary between its high-gain and fully turn-on operating region by adjusting the duty cycle of the main switch in the flyback converter. A 100-W 85–265-Vac/36-Vdc prototype has been built and evaluated. The conducted electromagnetic interference under different supply voltages will also be given. [ABSTRACT FROM AUTHOR]

This paper presents the use of an energy recycling technique to extract the intrinsic parameters of lead–acid batteries. The charging and discharging currents of the battery under test are programmed by controlling a bidirectional dc–dc converter to profile the power flow between the battery and a supercapacitor. The sampled battery voltage and current information over the charging and discharging periods are used to estimate the parameters of a high-order electrical battery model with a modified particle swarm optimization algorithm and compare with the battery voltage and current predicted with the extracted parameters.  With the energy recycling mechanism, the proposed parameter extraction process is environment friendly and has low power dissipation, thus increasing the power handling density and allowing long testing duration. A prototype that can extract the intrinsic parameters of eight different types of 12 V, 130 A lead–acid batteries has been built. Its performance has been evaluated with different charging and discharging profiles. The estimated parameters are favorably verified with the theoretical predictions, results obtained by the extended Kalman filter method, and results obtained on a calibrated commercial battery testing system. Results reveal that testing batteries with both charging and discharging processes gives a more accurate prediction of battery performance. [ABSTRACT FROM AUTHOR]

Currently, how the inductive grid impedance variation affects the stability of digitally controlled grid-tied inverters with a high-order (LCL or LLCL) filter has been numerously studied. Note that a distributed power system may contain the capacitive load, the power factor correction (PFC) capacitor, and the long cable. During the design of grid-tied inverters, we should address the effects of the equivalent grid reactance, including both the inductive and the capacitive impedances, on the stability of system. Nevertheless, up to now, to the best knowledge of authors, the detailed parameter design method of the LCL- or LLCL-filter-based grid-tied inverter has not yet been introduced, when the capacitive grid impedance is addressed. In this paper, by using the passivity-based analysis, the detailed stability study on the LLCL-filter-based grid-tied inverter is carried out, when the grid reactance varies in a wide range. Based on the analysis, an exact and robust parameter design of system is proposed. Simulations and experimental results on a 220 V/2 kW prototype confirm that by using the proposed parameter design method, a high-performance grid-tied inverter system can be achieved under the rigid grid condition. [ABSTRACT FROM AUTHOR]

This paper presents a new digital control scheme for active virtual ground-bridgeless PFC (AVG-BPFC), which is able to obtain an optimized solution between the system efficiency and electromagnetic interference performance in the PFC stage. However, a resonant characteristic is generated from the input LCL filter structure of the converter. In addition, there is a phase difference between two inductor currents which also leads the controller design in the AVG-BPFC to become challenging, especially on the system stability and current quality. Thus, a triple loop control's architecture together with an integrated state machine is proposed as the control methodology of the AVG-BPFC. Under the simple control structure in the digital platform, a stable system is achieved together with a precise grid current tracking function. Such control scheme was implemented digitally on a 1.5 kW prototype. In this paper, theoretical models of the whole system were analyzed and the system performance was successfully verified in both steady state and transient state conditions. The experimental results show a good agreement with the theoretical knowledge. [ABSTRACT FROM AUTHOR]

It is sometimes unavoidable to have light-emitting-diode (LED) light sources and their pulsewidth modulation (PWM) drivers connected by long cables in large-scale illuminations. However, long-cable inductance delays the rate of rise of the driving current pulses and thus leads to the reduction of luminous flux output. It also causes the off-state voltage across the light sources negative, which would deteriorate the life expectancy of the LEDs. A switched-capacitor-based current compensator for correcting the wave shape of the driving current pulses is presented. The methodology is based on transferring the energy stored in the cable to a capacitor at the end of the current pulse and then momentarily boosting the voltage with the capacitor applying to the cable at the beginning of the next current pulse. Thus, the rise time of the current pulses can be shortened. The topological states and operations of the compensator will be described. A simplified design procedure will be given. A prototype for a 12-V, 3-A PWM driver has been built and evaluated. Performance comparisons between the proposed current compensator and prior art and between the systems with and without the compensators will be conducted. [ABSTRACT FROM PUBLISHER]

The widespread penetration of electric vehicles (EVs) will cause an increase in energy demand. To achieve an effective demand response approach, the participation of EV users is a crucial factor. Nevertheless, the discharging price found in the literature is generally set in accordance with the spot electricity price. A fair pricing strategy is thus desirable to motivate EV users to regulate their charging behavior for less bill payment, and at the same time to achieve load regulation as well as benefit for power companies. The charging and discharging prices should be cohesively equilibrated to achieve the task. This paper presents a new V2G (Vehicle-to-Grid) pricing policy by incorporating the system load condition, maximum power limit, and price rate for user load in a fair manner. The price setting follows a hierarchical optimization procedure between the operator and end users with the aim to maximize operator's profit and balance end users’ bill and comfort level. The optimization for the operator is achieved via genetic algorithm whereas the energy management of each user is decomposed as a single power optimization problem. Simulation results have confirmed the benefit of liberating the discharging price from the user load tariff and have verified the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

The light-emitting diode (LED) has become a very promising alternative lighting source with the advantages of longer lifetime and higher efficiency than traditional ones. The lifetime prediction of LEDs is important to guide the LED system designers to fulfill the design specifications and to benchmark the cost-competitiveness of different lighting technologies. However, the existing lifetime data released by LED manufacturers or standard organizations are usually applicable only for some specific temperature and current levels. Significant lifetime discrepancies may be seen in the field operations due to the varying operational and environmental conditions during the entire service time (i.e., mission profiles). To overcome the challenge, this paper proposes an advanced lifetime prediction method, which takes into account the field operation mission profiles and also the statistical properties of the life data available from accelerated degradation testing. The electrical and thermal characteristics of LEDs are measured by a T3Ster system, used for the electrothermal modeling. It also identifies key variables (e.g., heat sink parameters) that can be designed to achieve a specified lifetime and reliability level. Two case studies of an indoor residential lighting and an outdoor street lighting application are presented to demonstrate the prediction procedures and the impact of different mission profiles on the lifetime of LEDs. [ABSTRACT FROM AUTHOR]

Grid-tied voltage source inverters using LCL filter have been widely adopted in distributed power generation systems (DPGSs). As high-order LCL filters contain multiple resonant frequencies, switching harmonics generated by the inverter and current harmonics generated by the active/passive loads would cause the system resonance, and thus the output current distortion and oscillation. Such phenomenon is particularly critical when the power grid is weak with the unknown grid impedance. In order to stabilize the operation of the DPGS and improve the waveform of the injected currents, many innovative damping methods have been proposed. A comprehensive overview on those contributions and their classification on the inverter- and grid-side damping measures are presented. Based on the concept of the impedance-based stability analysis, all damping methods can ensure the system stability by modifying the effective output impedance of the inverter or the effective grid impedance. Classical damping methods for industrial applications will be analyzed and compared. Finally, the future trends of the impedance-based stability analysis, as well as some promising damping methods, will be discussed. [ABSTRACT FROM PUBLISHER]

A high-order ( $LCL$ or $LLCL$) power filter with a small grid-side inductor is becoming more preferred for a grid-tied inverter due to less total inductance and reduced costs. In a microgrid, the background harmonic voltage (BHV) may distort the injected currents of the grid-tied inverters. In order to resist the effect of the BHV, a feedforward voltage compensator and a proportional resonant regulator with harmonic compensation are often adopted. However, they still have their own limitations, particularly when there are higher order BHVs at the point of common coupling and when the equivalent grid impedance widely varies due to the different numbers of grid-tied inverters in parallel. Thus, an extra damper should be inserted to keep the system stable. In this paper, the control bandwidth limitation of a multiloop control active damping (AD) method is analyzed and illustrated by the capacitor-current-feedback AD. Based on this, a single-loop current control with a hybrid damper is proposed for a single-phase $LCL$- or $LLCL$-filter-based grid-tied inverter. A step-by-step design of the controller method is also introduced in detail. Experiments on a 2-kW prototype fully demonstrate the strong robustness of the stability and the high harmonic rejection ability of the inverter using the proposed control method. [ABSTRACT FROM PUBLISHER]

Cardiovascular diseases can wreak havoc on human beings and lead to 30% of global death annually. The World Health Organization has always highlighted that there is a severe shortage of medical personnel, especially cardiologists, in most of the countries. In this paper, an electrocardiogram health identifier (ECGHI) has been proposed and developed for swift identification of heart diseases. The ECGHI has been applied to four most common types of cardiovascular diseases, namely Myocardial Infarction, Dysrhythmia, Bundle Branch Block and Heart Failure since these four types of cardiovascular diseases contribute to 25% of the overall population suffering from heart diseases. In the investigation of ECGHI, the binary classifier (BC) and multi-class classifier (MCC) are designed and analyzed. The MCC features a multi-class support vector machine (SVM) to diagnose the exact type of cardiovascular disease. The BC features a two-class SVM to identify healthiness of heart accurately. In this paper, the following indicators have been investigated, namely the overall accuracy, specificity, sensitivity, the dimensionality of feature vector, the total training and testing time of ECGHI and a newly defined confidence index. These six criteria form the basis to derive an analytic hierarchy process (AHP) to facilitate the multiple criteria decision making (MCDM) for the optimal evaluation of hyperplanes. Four kernels have been analyzed from which both the BC and MCC are evaluated and analyzed. The optimized ECGHI using BC yields an AHP Performance Score of 0.079 with score components (overall accuracy, specificity, sensitivity, average confidence index, dimensionality, total time for training and testing time) of 0.982, 0.978, 0.986, 0.608, 6, and 5.77 s respectively. Likewise, the optimized ECGHI using MCC yields an AHP Performance Score of 0.093 with score components of 0.882, 0.89, 0.874, 0.504, 9, and 7.32 s respectively. The BC is employed as a supplement of the MCC to achieve a further improvement in all six criteria. Such a novel process of identification and detection with high accuracy is referred as the MCC–BC scheme. The developed ECGHI (MCC) may identify the FOUR most common and important cardiovascular diseases simultaneously (with BC supplementing the MCC to achieve a high accuracy). Such simultaneous identification of cardiovascular diseases is the first of its kind in this research area, so no comparison can be made. The MCC–BC scheme will pave the way for speedy and accurate identification and detection of heart disease. The instant response of the ECGHI minimizes the probability of death from Myocardial Infarction, Bundle Branch Block, Dysrhythmia, and Heart Failure. [ABSTRACT FROM AUTHOR]

The single-phase power converter topologies evolving of photovoltaic applications are still including passive filters, like the $LCL$- or $LLCL$-filter. Compared with the $LCL$-filter, the total inductance of the $LLCL$-filter can be reduced a lot. However, due to the resonant inductor in series with the bypass capacitor, the differential mode (DM) electromagnetic interference (EMI) noise attenuation of an $LLCL$-filter-based grid-tied inverter declines. Conventionally, a capacitor was inserted in parallel with the $LC$ resonant circuit branch of the $LLCL$-filter to suppress the DM EMI noise. In order to achieve a small value of capacitor as well as to minimize the additional reactive power, a novel simple DM EMI suppressor for the $LLCL$-filter-based system is proposed. The characters of two kinds of DM EMI suppressor are analyzed and compared in detail. Simulations and experiments on a 0.5-kW 110-V/50-Hz single-phase grid-tied inverter prototype are accomplished to confirm the analysis. [ABSTRACT FROM PUBLISHER]

When designing a higher order output power filter for a transformerless grid-tied converter using pulsewidth modulation (PWM), the requirements on the leakage current, the electromagnetic interference (EMI) noise, and the harmonics of the grid-injected current should be addressed. For an LCL-filter-based single-phase grid-tied full-bridge inverter system, it is possible to decrease the total inductance as well as the size and the cost, if the harmonic currents around the switching frequency can be fully suppressed. In this paper, the grid-injected current harmonics and the conducted EMI noise are investigated for the conventional LCL-filter-based system. Based on this, a modified LCL-filter topology using an extra parallel LrCr resonant circuit is proposed to reduce the total inductance value, without increasing the capacitive reactive power. The validity is verified through the experiments on a 500-W 110-V/50-Hz prototype. [ABSTRACT FROM PUBLISHER]

For a transformerless grid-tied converter using pulse width modulation, the harmonics of grid-injected current, the leakage current, and the electromagnetic interference (EMI) noise are three important issues during designing of the output filter. In this paper, the common mode and the differential mode EMI noises are investigated for the LCL- and LLCL-filter-based single-phase full-bridge grid-tied inverters. Based on this, a modified LLCL-filter topology is proposed to provide enough attenuation on the conducted EMI noise as well as to reduce the dc-side leakage current. The parameter design method of the filter is also developed. The comparative analysis and discussion on four filter cases (the conventional LCL filter, the conventional LLCL filter, the modified LCL filter, and the modified LLCL filter) are carried out and verified through simulations and experiments on a 0.5-kW, 110 V/50 Hz single-phase full-bridge grid-tied inverter prototype. [ABSTRACT FROM AUTHOR]

In order to minimize the effect of the grid harmonic voltages, harmonic compensation is usually adopted for a grid-tied inverter. However, a large variation of the grid inductance challenges the system stability in case a high-order passive filter is used to connect an inverter to the grid. Although in theory, an adaptive controller can solve this problem, but in such a case the grid inductance may need to be detected online, which will complicate the control system. This paper investigates the relationship between the maximum gain of the controller that still keeps the system stable and the Q-factor for a grid-tied inverter with an RL series or an RC parallel damped high-order power filter. Then, a robust passive damping method for LLCL-filter-based grid-tied inverters is proposed, which effectively can suppress the possible resonances even if the grid inductance varies in a wide range. Simulation and experimental results are in good agreement with the theoretical analysis. [ABSTRACT FROM AUTHOR]

Vehicle routing problem with time windows (VRPTW) is a well-known NP-hard combinatorial optimization problem that is crucial for transportation and logistics systems. Even though the particle swarm optimization (PSO) algorithm is originally designed to solve continuous optimization problems, in this paper, we propose a set-based PSO to solve the discrete combinatorial optimization problem VRPTW (S-PSO-VRPTW). The general method of the S-PSO-VRPTW is to select an optimal subset out of the universal set by the use of the PSO framework. As the VRPTW can be defined as selecting an optimal subgraph out of the complete graph, the problem can be naturally solved by the proposed algorithm. The proposed S-PSO-VRPTW treats the discrete search space as an arc set of the complete graph that is defined by the nodes in the VRPTW and regards the candidate solution as a subset of arcs. Accordingly, the operators in the algorithm are defined on the set instead of the arithmetic operators in the original PSO algorithm. Besides, the process of position updating in the algorithm is constructive, during which the constraints of the VRPTW are considered and a time-oriented, nearest neighbor heuristic is used. A normalization method is introduced to handle the primary and secondary objectives of the VRPTW. The proposed S-PSO-VRPTW is tested on Solomon's benchmarks. Simulation results and comparisons illustrate the effectiveness and efficiency of the algorithm. [ABSTRACT FROM PUBLISHER]

Due to the development and deployment of renewable DC power sources and their inherent advantages for DC loads in applications, the DC nano-grid has attracted more and more research attentions; especially the topologies of AC/DC converters are increasingly studied. When designing an AC to DC converter for a DC nano-grid system, the grounding configuration, which determines the costs, the efficiency as well as the safety, plays an important role. A three-terminal output AC to DC converter based on united grounding configuration has been presented for DC nano-grid. However, it has to be pointed out that the three-terminal output DC nano-grid is not as popular as the two-terminal DC output one, due to the infrastructure consideration. This paper proposes a new Buck-Boost AC to DC converter with two-terminal output voltage for DC nano-grid. The operating principle, the steady-state analysis, and the small signal modelling for the proposed converter working in continuous conduction mode are presented in detail. A 220 V/50 Hz/800 W prototype was fabricated to verify the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]