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In renewable energy micro-source applications, a wide range of voltage conversion of the step-up converter is an essential part to equalize the typical low voltage of micro-source with DC-bus voltage of Inverter or motor drives. In order to meet this purpose, an ultra-voltage gain step-up DC-DC converter is proposed in this paper. The proposed converter has made an arrangement of the regenerative-boost fed switched inductor and capacitor configurations. Thereby, due to such an organization of structure, the proposed converter can develop an extremely high voltage-gain even at lower duty ratios. In addition, it has the advantage of lower switching stress across all power semi-conductive diodes. Furthermore, this paper describes the steady-state analysis and comparative features of the converter with existing recent literature. Finally, to validate theoretical analysis and test the feasibility and suitability of the proposed ultra-gain converter, the experimental results were observed by a 500 W fabricated prototype. [ABSTRACT FROM AUTHOR]

Light-emitting diodes (LEDs) are widely used in street lighting, landscape lighting, liquid crystal display (LCD) backlighting, healthcare, etc. As an important part of LED lighting products, LED driver plays a vital role in maintenance costs reduction, energy saving and lifetime prolongation. In this paper, a single-stage LED driver is proposed, which is integrated by a totem-pole bridgeless power factor correction (PFC) unit and several modular LCL-T resonant rectifiers. The totem-pole bridgeless PFC unit and the LCL-T resonant rectifiers are integrated by sharing switches, which can simplify the circuit and reduce the system cost. The output current can be regulated by applying the variable inductor control. Constant duty cycle and fixed switching frequency operation can be achieved as well. The operating principle and the performance of the proposed converter are analyzed in this paper. In addition, a precise parameter design method is proposed by considering the high-order harmonics. At last, an experimental prototype is established to validate the proposed parameter design and variable inductor control method. [ABSTRACT FROM AUTHOR]

The dc-dc converters with high step-up DC-voltage gain play a vital role in integrating low voltage DC sources. Though several converter topologies are reported in the recent past, attempts have been made to reduce the components, especially the switching devices, passive elements, converter losses, etc., of the converter. A novel DC-DC converter topology, viz., single switched impedance network (SSIN)-based converter with n-stage is proposed in this paper. The operation of the SSIN based converter in continuous and discontinuous conduction modes are discussed. The effect of parasitic elements on DC-voltage gain and efficiency of the SSIN is carried out. The small-signal model of the SSIN converter is derived. The performance of the SSIN converter is compared with the similar converter topologies. The 500 W prototypes of the SSIN with n = 1 and n = 2 are fabricated, and the experimental results are presented in this paper. To improve the converter performance, SiC-based semiconductor devices are used. The SSIN converter with two-stage has low switch loss at 500 W load, improved efficiency during high power and high output voltage operation, the switch stress of Vo/2, etc. [ABSTRACT FROM AUTHOR]

Hybrid energy systems with small modular reactors (SMRs)—a fast-emerging nuclear power plant technology—and renewables hold significant promise for the development of clean energy systems. This paper proposes a simulation model of SMR-based hybrid energy system for electricity and district heating (DH) with a detailed dynamic model of the reactor and a quasi-static model of the DH system in Siemens PTI PSS/E and PSS/Sincal. A multi-timescale approach, separating the load following and frequency regulation operation, is proposed to assess the flexible operation in the presence of highly intermittent renewable energy sources (RESs). A portion of a modified IEEE 30-bus system network is used as a test system for an isolated community to simulate the proposed hybrid energy system, and comparative results demonstrate the potential benefits of the DH system, thermal energy storage, and electrical energy storage to the SMR’s flexible operation. [ABSTRACT FROM AUTHOR]

A variable-switching constant-sampling frequency critical soft switching model predictive control (VSCS-MPC) method is proposed in this paper to improve the dynamic behavior, efficiency and power density of the DC/DC power converters. Firstly, this paper analyzes the boundary constraints of critical soft switching that are derived with the key parameters of the interlock time and threshold current for typical SiC and GaN devices. Then, the VSCS-MPC method is proposed for synchronous DC/DC converter. Both the current source load and resistive load converters are validated with the proposed MPC method. VSCS-MPC includes two controlling parts. First is the frequency controller to maintain the critical soft switching operation by adjusting the switching frequency based on the pre-defined boundary conditions with a constant sampling frequency. A discretized frequency controller is developed to improve the stability of the system by maintaining a fixed sampling frequency. Second part is the model predictive controller to track the output voltage/current and maintain critical soft switching during dynamic periods. The explicit optimization and oversampling methods are applied in the MPC controller to meet the high frequency demand. A large current ripple ($\triangle i_L$ $\ge$ 200 %) is introduced to achieve the critical soft switching and reduce the inductance. The switching losses are decreased by the frequency controller and the critical soft switching is maintained especially in dynamic periods due to the fast response of MPC. [ABSTRACT FROM AUTHOR]

This paper presents a high-gain modular input-parallel output-series dc-dc converter for photovoltaic integration with medium-voltage dc grids. A new full-bridge zero-current-switching (FB-ZCS) converter proposed in this paper is used as a fundamental building block. Existing FB-ZCS converters utilize transformer leakage inductance and a shunt-connected resonant capacitor for achieving smooth resonant current commutation and ZCS. The shunt-connected capacitor requires dedicated charging interval in every switching cycle and stores full-load-rated resonant energy at all load/input conditions, resulting in significant duty-cycle loss. Moreover, it suffers from energy leakage through transformer winding and requires overrating. All these factors adversely impact the operation range of the converter, which is important for achieving a wide maximum power point tracking range. Novel improvements in the proposed converter include minimization of duty-cycle loss and resonant capacitor leakage and the realization of the current-adaptive resonant energy storage mechanism, without using additional switches or auxiliary circuits. Operation of the proposed converter is presented and validated with simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, an improved floating interleaved Boost converter is proposed for fuel cell applications. In order to achieve zero-ripple input current and keeping others merits such as high voltage gain and low voltage stress of the conventional floating interleaved Boost converter (FIBC) unchanged, a pair of input current ripple cancellation networks composed of a small inductor and a small capacitor are added into the conventional FIBC. Then, the operating principle and the steady-state and dynamic performances of the proposed converter are performed and compared with the conventional FIBC. Finally, a 240 W experimental prototype has been created for further evaluating the expected performances of the proposed converter. The simulation and experimental results demonstrate that the input current ripple of the proposed converter can be totally removed in all power range without significantly increasing the current stress and power loss. [ABSTRACT FROM AUTHOR]

Cogeneration coupling of small modular reactor (SMR)-based nuclear power plants (NPPs) with district heating (DH) systems enhances an SMR’s ability to provide flexible operation. Coordinated reactor control and DH steam extraction can fulfill the load following requirements, while a battery energy storage system (BESS) and steam bypass system can absorb short-term disturbances, allowing the system to host renewable energy sources (RESs) such as wind and photovoltaics (PV). This paper develops an optimal operation framework for a SMR-RES hybrid energy system for electricity and DH and demonstrates the proposed scheme using a portion of the IEEE-30 bus system. Simulation results from a set of studies are provided to demonstrate load following (LF) and frequency regulation (FR) operation for a month-long period. The operational results for different RES hosting levels are analyzed, evaluating the optimum size of wind and PV plants for the proposed system. The results show the proposed hybrid energy system is feasible as a stand-alone system and can optimally host as high as 50% renewables. [ABSTRACT FROM AUTHOR]

Output filters of the grid inverter usually have a large footprint in the total system. In order to increase the power density of the grid inverter, a passive integrated structure for the output filter with flexible multilayer foils is presented. Compared with a discrete output filter, the volume of the integrated filter is reduced by at least 20%. In this paper, the design of the integrated output filter is discussed. Then, a distributed electromagnetic component model of the integrated filter is used to verify the proposed design. Finally, a prototype of the integrated output filter is built and used in a grid inverter. Experimental results are included and compared with the results derived from the discrete output filter to prove the validity of this integrated filter design. [ABSTRACT FROM AUTHOR]

A high step-up DC–DC converter with active switched LC-network is proposed in this paper, which can be used in the photovoltaic system as the front-end stage to generate the required DC bus voltage. Based on the transformerless DC–DC converter with an active switched inductor (ASL) network, this proposed converter introduces an active switched capacitor (ASC) network, where only one capacitor and one diode are added, while the voltage gain is efficiently increased by a compound of ASL and ASC networks. The structure of the proposed converter is simple and voltage stresses on the additional diode and capacitor are low. In addition, unlike other voltage-boosting structures that utilized switched capacitor, the proposed converter avoids the extreme instantaneous currents of capacitor. The detailed analysis of the proposed converter and performance comparison with recently published ASL network-based converters are presented. Finally, a 100 W, 20/200 V prototype circuit is operated to verify its performance. [ABSTRACT FROM AUTHOR]

An enhanced DC–DC converter is proposed in this paper, based on the combination of the Cuk and SEPIC converters, which is well-suited for solar photovoltaic (PV) applications. The converter uses only one switch (which is ground-referenced, so simple gate drive circuitry may be used), yet provides dual outputs in the form of a bipolar DC bus. The bipolar output from the DC–DC converter is able to send power to the grid via any inverter with a unipolar or bipolar DC input, and leakage currents can be eliminated if the latter type is used without using lossy DC capacitors in the load current loop. The proposed converter uses integrated magnetics cores to couple the input and output inductors, which significantly reduces the input current ripple and hence greatly improves the power extracted from the solar PV system. The design methodology along with simulation, experimental waveforms, and efficiency measurements of a 4-kW DC–DC converter are presented to prove the concept of the proposed converter. Furthermore, a 1-kW inverter is also developed to demonstrate the converter's grid-connection potential. [ABSTRACT FROM AUTHOR]

A new transformer-less three-level grid-tied inverter is proposed in this article. By employing the switched-capacitor (SC) modules, a new topology is derived. The proposed topology has some features which are high efficiency, the capability of voltage boosting without utilization of any additional boost stage, and suppressing the leakage current by using common grounded strategy. In this article, a peak current control is employed to generate the gate pulses of power semiconductor switches and adjustment of both active and reactive powers. By doing so, the grid injected current is controlled and adjusted to have a proper quality. The operation modes, design consideration, and a comparison with some recently proposed grid-connected topologies are done through this paper. Finally, the performance and feasibility of the proposed inverter are confirmed with a 500 W experimental prototype. [ABSTRACT FROM AUTHOR]

The least cell state-of-charge (SOC) in a battery pack directly determines the left runtime of the total battery pack. Hence, an equalizing strategy is often needed to balance the battery cells, especially for lithium-ion batteries. In this paper, it is shown that this can be achieved with a simple equalizing circuit, which only needs a power semiconductor switch and an inductor for each cell. To avoid the intensive requirement on the processing power of existing control algorithms, two simple control schemes are proposed to obtain better modular performance. First, the operating modes under different switching states are illustrated with a four-cell battery module. After that, the required duty cycles to operate the switches are obtained by comparing the SOC of the relevant cells and the average SOC of all cells. By fixing the maximum of the duty cycle of the highest SOC cell, the inductor can be easily designed and the rated currents of switches and cells can also be regulated. Moreover, the multilayer and modular concept is developed to speed up the balancing process and modularize the design of equalizing circuits. Finally, experiments were completed to demonstrate the proposed scheme. [ABSTRACT FROM AUTHOR]

The model of a grid-connected inverter used for the corresponding controller design depends on the equivalent resistance and inductance between the inverter and the grid. These parameters are not fixed and change with operating conditions, temperature, and age. This paper analyses the effectiveness of the application of the model reference adaptive control (MRAC) approach in obtaining an accurate model of a grid-connected inverter system. Active and reactive power based MRAC approaches are used to estimate the equivalent resistance and reactance between the inverter and the grid. Detailed stability analysis of the MRAC approach is presented. The system models for the MRAC controller design are derived and guidelines on the controller parameters selection are proposed. Experimental results validate the feasibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a selective voltage harmonic compensation strategy for stand-alone inverters. The use of LC output filters makes it possible to reduce switching harmonics at the output terminals of the inverter; however, it also produces voltage distortion when feeding nonlinear loads due to the harmonic voltage drop across the filter inductances. To compensate the voltage harmonic distortion and produce sinusoidal voltage, it is proposed to add virtual impedances to the fundamental voltage control. The whole process and considerations for the impedance design are described and a stability analysis of the system is presented. Finally, simulations and experimental results are shown to confirm the good performance of the proposed strategy under both steady state and load steps. [ABSTRACT FROM AUTHOR]

This paper presents a new overall control strategy for small-scale wind energy conversion systems (WECS). The purpose of the proposed strategy is to utilize a maximum power point tracking control (MPPT) to maximize the captured energy when the wind speeds are below the rated speed. For high wind speed region; two stall controllers are developed: The constant speed stall controller which will limit the rotational speed of the generator to its rated value, and the constant power stall controller, which will regulate the captured power to be within the system rating. For the MPPT control, a modified perturb and observe (P&O) algorithm is utilized, where the dc side current is used as a perturbation variable and the dc-link voltage slope information is used to enhance the tracking speed and stability of the algorithm. For the speed and power regulation operation during high wind speeds, the system is controlled in the stall region to limit the rotational speed and the power of the generator. A stabilizing control loop is proposed to compensate for the stall region instability. A new mode transfer control strategy is developed to effectively control the transition between different modes of operation while ensuring the system stability without using any preknowledge of the system parameters. A 1 kW hardware prototype is developed and tested to validate the proposed new control strategy. [ABSTRACT FROM PUBLISHER]

Converter system that does both dc–dc conversion and dc–ac conversion in a single stage is called a single-stage converter system (SSCS). Compared to a two-stage converter, SSCS is more efficient and compact in size. In this paper, a grid-connected SSCS (GCSS) system for photovoltaic (PV) applications is presented. This GCSS transfers power from PV to grid while tracking maximum power point (MPP) continuously. The proposed system has several desirable features such as low switching loss, high gain, and compact size that makes this GCSS suitable for PV systems, where the PV system output voltage is low and varies with time. Design of the presented GCSS components with necessary equations and derivation of both current control loop and voltage control loop required for operation are given. Proposed GCSS is simulated using MATLAB/SIMULINK. Detailed simulation and experimental results are given to verify the efficacy of the proposed GCSS. [ABSTRACT FROM AUTHOR]

The interaction between wind turbines and grid results in increasing short-circuit level and fault ride-through (FRT) capability problem during fault condition. In this paper, the bridge-type fault current limiter (FCL) with discharging resistor is used for solving these problems. For this FCL, a control scheme is proposed, which uses the dc reactor current as control variable, to adjust the terminal voltage of induction generator (IG) without measuring any parameters of system. In this paper, the wind energy conversion system (WECS) is a fixed-speed system equipped with a squirrel-cage IG. The drivetrain is represented by a two-mass model. The analytical and simulation studies of the bridge-type FCL and proposed control scheme for limiting the fault current and improving FRT capability are presented and compared with the impact of the application of the series dynamic braking resistor (SDBR). [ABSTRACT FROM PUBLISHER]

This paper presents power loss comparison of single- and two-stage grid-connected photovoltaic (PV) systems based on the loss factors of double line-frequency voltage ripple (DLFVR), fast irradiance variation + DLFVR, fast dc load variation + DLFVR, limited operating voltage range + DLFVR, and overall loss factor combination. These loss factors will result in power deviation from the maximum power points. In this paper, both single-stage and two-stage grid-connected PV systems are considered. All of the effects on a two-stage system are insignificant due to an additional maximum power point tracker, but the tracker will reduce the system efficiency typically about 2.5%. The power loss caused by these loss factors in a single-stage grid-connected PV system is also around 2.5%; that is, a single-stage system has the merits of saving components and reducing cost, and does not penalize overall system efficiency under certain operating voltage ranges. Simulation results with the MATLAB software package and experimental results have confirmed the analysis. [ABSTRACT FROM PUBLISHER]

AC Input filters in high speed drives are generally large and can even exceed the mass of the motor. This article firstly seeks to reduce the volume and overall mass of the drive through integrating the input inductors with the magnetic circuit of the machine. The magnetic circuits are shared without cross-coupling through careful choice of the filter and motor pole numbers. Finite Element Analysis (FEA) is used to check that normal operation of the base PM machine is not affected by the integration and a demonstrator drive is built. Compared with discrete AC filters, the integration of the LCL filter inductors has given a very large volume reduction of 87.6%, producing a much more compact envelope than with the conventional filter inductors. Through a holistic approach to a combination of electrical, mechanical and thermal aspects of the drive system, the integrated drive exhibits significant mass and volume advantages over conventional discrete motor drives. Two major technical issues related to the power electronics development of the IMD are presented in the paper: investigation of a bus bar solution to manage a large number of winding terminals introduced from integrated LCL filters, and a compact SiC device based power electronics design. [ABSTRACT FROM AUTHOR]

Small modular reactors (SMRs), an emerging nuclear power plant technology, are suitable for large grids as well as remote load centers and offer load following and frequency response capabilities. While the SMRs have expectedly higher response rates, detailed dynamic models including reactor dynamics are necessary for power system dynamic studies. This paper presents a dynamic model of an integral pressurized water reactor (iPWR)-type SMR, modeled in Siemens PTI PSS/E, to assess the contribution of the reactor to the power system dynamics. The proposed SMR model mimics the heat generation process and subsequent heat transfer process with the inclusion of the reactor core based on point kinetics, primary coolant based on natural circulation, and a simplified three lump representation of the steam generator. Controllers are designed to operate the turbine valve and reactor control rod in closed loops. The SMR model is integrated with the modified turbine-governor system and a power system study is conducted. Results show the power system and internal reactor responses when subjected to electrical demand variations of 20 ${\%}$ rated electrical output (REO) with a valve rate limit of $\pm \text{80}{\%}$ REO/min. [ABSTRACT FROM AUTHOR]

With the development of power system electronization, distributed new energy generation-based DC microgrid system has become a hot spot of the current research. Aiming to implement the collection, transformation and transmission of the new energy sources, the dual active bridge (DAB) converter has become a key energy conversion device. Aiming to promote the transmitted efficiency for such DAB converter, a deep reinforcement learning (DRL) optimization scheme with the triple-phase-shift (TPS) is proposed. Specifically, the deep deterministic policy gradient (DDPG) algorithm is used for solving optimal solutions with the minimum power losses. Then, the trained DDPG agent is used as a fast surrogate predictor, which giving the suitable control decisions under whole operation conditions. The main control objective is to minimize the power losses for getting the target maximum efficiency. Besides, the soft switching constrains are added to the DDPG algorithm. Based on this, the proposed optimized method can be used for different operation conditions with excellent performance. The operation principles, the loss analyses, and the training consideration and evaluation of the DDPG algorithm are given. Finally, simulation and experimental results using a 200 W hardware prototype are displayed and compared to prove to effectiveness of theoretical analysis. [ABSTRACT FROM AUTHOR]

A dual-input high step-up DC/DC converter with zero voltage turn-off (ZVT) auxiliary circuit is presented in this paper. The cost of whole photovoltaic (PV) power could be decreased significantly by the proposed converter because it allows two PV panels to be connected at the same time. ZVT auxiliary circuit provides soft switching in a wide range of load variations with six passive components. Turn-off switching losses could be decreased and the efficiency of the whole converter could be improved. In , the operation principle and performance characteristics of the proposed converter have been analyzed and an 800 W experimental prototype has been built to validate the analytical results in. In , a dual-input maximum power point tracking (DMPPT) control algorithm has been designed for the proposed converter. Experimental results show that two PV panels can achieve the maximum power output state separately by the proposed DMPPT control algorithm. [ABSTRACT FROM AUTHOR]

The non-inverting buck-boost converter has emerged as one of the most promising topologies for distributed maximum power point tracking applications. Pressure to reduce cost and volume of photovoltaic module integrated converters often compels bootstrap capacitor type gate drivers. The bootstrap technique is a simple and economical solution to create a floating power supply for high-side gate drivers. However, it comes with a major challenge, as the low-side switch must be periodically turned on, to recharge the high-side bootstrap capacitor. In the buck and the boost mode, one of the switching legs of the converter must be held with the high-side switch on, which eventually discharges the high-side capacitor. When the non-inverting buck-boost input voltage is regulated by means of a single voltage loop, recharging the bootstrap capacitor causes an undesired ripple in the PV module voltage, degrading the regulation quality. In order to mitigate this problem, this paper proposes a cascaded control technique, entailing regulation of the PV module voltage and inductor current. The cascaded controller dramatically improves the rejection of the disturbance induced by the periodic recharge of the bootstrap capacitor, thanks to the fast action of the current loop, regulating the average value of the inductor current. Converter transfer functions and controller design are derived and validated. Experimental results clearly show that the cascaded control scheme outperforms the traditional voltage control scheme, resulting in a better regulation of the PV module voltage. This main advantage comes at the cost of an additional measurement of the average inductor current. [ABSTRACT FROM AUTHOR]

In this paper, fast acting dc-link voltage-based energy management schemes are proposed for a hybrid energy storage system fed by solar photovoltaic (PV) energy. Using the proposed control schemes, quick fluctuations of load are supplied by the supercapacitors and the average load demand is controlled by the batteries. Fast dc-link voltage, effective energy management, and reduced current stress on battery are the main features achieved from the proposed control schemes. The effectiveness of the proposed control schemes are compared with the unified cascaded control. Small-signal control gains are formulated to design the voltage and current loops of the proposed energy management schemes. Detailed stability analysis is also presented to find the boundary values of compensator gains. In addition, a high-gain PV converter is proposed for extraction of maximum power from the solar panels. High voltage gain, reduced reverse recovery of diodes, and less duty cycle operation are the key features obtained from the proposed high-gain converter. The validity of the proposed energy management schemes with high-gain converter is verified by the detailed simulation and experimental studies. [ABSTRACT FROM AUTHOR]

This paper proposes a new diode-clamped multilevel inverter that can effectively balance the voltages of dc capacitors. For the proposed inverter, the inductors are inserted between the diodes and the main switches. Also, the voltage balance of the dc capacitors can be guaranteed by controlling the opening time of the corresponding main switches in particular modes. Thus, the parallel circuits on the dc side in the conventional inverters are canceled. Consequently, the proposed topology requires fewer switches, diodes, and capacitors, although it adds the compensation currents to the corresponding main switches. Both the simulation and experimental results demonstrate the suitability and applicability of the proposed topology. [ABSTRACT FROM AUTHOR]

Present energy need heavily relies on the conventional sources. But the limited availability and steady increase in the price of conventional sources has shifted the focus toward renewable sources of energy. Of the available alternative sources of energy, wind energy is considered to be one of the proven technologies. With a competitive cost for electricity generation, wind energy conversion system (WECS) is nowadays deployed for meeting both grid-connected and stand-alone load demands. However, wind flow by nature is intermittent. In order to ensure continuous supply of power suitable storage technology is used as backup. In this paper, the sustainability of a 4-kW hybrid of wind and battery system is investigated for meeting the requirements of a 3-kW stand-alone dc load representing a base telecom station. A charge controller for battery bank based on turbine maximum power point tracking and battery state of charge is developed to ensure controlled charging and discharging of battery. The mechanical safety of the WECS is assured by means of pitch control technique. Both the control schemes are integrated and the efficacy is validated by testing it with various load and wind profiles in MATLAB/SIMULNIK. [ABSTRACT FROM PUBLISHER]

Module parallel connection for three-phase VSC can increase the system level effectively. However, the circulating currents problem will occur. The circulating currents will distort the three-phase currents, increase the power loss and decrease the system efficiency. A novel deadbeat circuiting currents control method is proposed in this paper. Based on the analysis of the average model of parallel system, a circuiting currents deadbeat controller is designed while presenting the design method. The control strategy is realized by adjusting the voltage zero vector of space-vector pulse-width modulation in each paralleled module. No additional hardware is needed through the method. Fast dynamic response can be achieved and the performance of circulating currents is better compared with conventional PI controller. This method can be applied to common dc-link double parallel three-phase voltage converters with communication line. The validity of proposed theory was verified by simulation and experimental results. It is shown that the parallel converters can operate with different line inductor or different line currents by using this novel control strategy. [ABSTRACT FROM PUBLISHER]

Inductors are a significant contributor to mass in many power applications including the dc link in high-power drives and in dc–dc power conversion equipment. Permanent magnet inductors (PMIs) may be used in place of traditional inductors in dc biased applications with significant (40%) mass savings. This paper sets forth a rigorous, systematic, and multifaceted design paradigm for a PMI, using a buck converter application as an example. The algorithm includes electrical, magnetic, and thermal analysis and minimizes overall converter mass and loss. The algorithm is demonstrated in the design and testing of a 4 kW laboratory scale dc–dc converter. [ABSTRACT FROM PUBLISHER]

Three-phase inductors have a wide variety of applications, such as line and inverter filters. Coupled three-phase inductors are typically smaller than three single-phase inductors; and symmetrical three-phase inductors are advantageous over asymmetrical inductors in terms of reduced negative-sequence components, and in terms of mass and loss. This paper sets forth a magnetic design model of a symmetrical three-phase inductor. The model is meant to be used in the context of multiobjective optimization based design. The model is numerically and experimentally validated. [ABSTRACT FROM AUTHOR]

Microbial fuel cell (MFC) is an emerging technology for sustainable energy production. An MFC employs indigenous microorganisms as biocatalysts and can theoretically convert any biodegradable substrate into electricity, making the technology a viable solution for sustainable waste treatment or autonomous power supply. However, the electric energy currently generated from MFCs is not directly usable due to the low voltage and current output. Moreover, the output power can fluctuate significantly according to the operating conditions, which makes stable harvest of energy difficult. This paper presents an MFC energy harvesting scheme using a hysteresis controller and two layers of DC/DC converters. The proposed energy harvesting system can capture the energy from multiple MFCs at individually controlled operating point and at the same time form the energy into a usable shape. [ABSTRACT FROM AUTHOR]

This paper presents a dual motor drive system based on a multifunctional energy conversion system with energy storage. The proposed structure and control are directly applicable for a tandem compressor drive in heating, ventilation, and air conditioning (HVAC) systems adding an energy storage functionality. Based on the new structure, a multifunctional control scheme has been introduced to manage the charging/discharging of the energy storage and to regulate two capacitor voltages, which are inverter input voltages, simultaneously. Two independent sensorless adjustable speed motor drives, which are connected to the two capacitors, are controlled in real time for HVAC applications. Simulation and experimental results verify that the proposed structure and multifunctional control scheme are able to control both the two inverter input voltages and the charging/discharging current of energy storage for a dual motor drive system. [ABSTRACT FROM AUTHOR]

The high power pulsed charging power supply is usually necessary for the pulsed power devices with high power repetitive discharge. This paper first introduces a new topology structure of a charge and discharge system for high voltage capacitor and its operating principle, then comes up with technical requirements for the pulsed alternator. Afterward, design features of the inductor pulsed alternator, including the structure, main dimensions, and sizes of rotor teeth and slots are studied, and the main parameters of homopolar inductor pulsed alternator (HIPA) prototype are provided. The choice of rotor material and bearing failure phenomenon are also investigated to find a responsible solution. Finally, the experimental waveforms of HIPA prototype without and rated load when charging capacitor are given. The research shows that the pulsed power supply based on the inductor pulsed alternator is competitive for its high energy storage density, moderate power density, and high reliability, which is suited to the charging power supply of pulsed capacitor. [ABSTRACT FROM AUTHOR]

In the design of a fuel cell charger, it is important to find a suitable topology and to design the converter to guarantee the performance of both the fuel cell and the battery. Most of the chargers developed so far have used step-down converters. However, since a small fuel cell stack can only generate a low voltage, it is necessary to use a step-up converter to charge batteries. In this paper, a nonisolated boost charger topology with an additional output inductor for a proton exchange membrane fuel cell is presented to meet the strict ripple requirements for the battery charge, and its control method using a proportional-integral (PI) controller is detailed. The feasibility of the boost charger and its control method is then verified through the experimental results. [ABSTRACT FROM AUTHOR]

This paper investigates the optimal arrangement of the coils in a wound-type interphase reactor to avoid the decreased inductance due to local saturation in the core when operated with high dc current. In theory, the direct currents and the related magnetomotive forces in the two ways of an interphase reactor are equal, and this compensation leads one to conclude that the global flux in the yokes is zero. However, the dc currents in the coils produce a significant leakage flux that flows locally in the core. If the coils are not suitably arranged and if the dc current is high, the leakage flux causes local saturation, a drop in the inductance, and noticeable circulation of a triple harmonic current through the reactor. Such a phenomenon is investigated by means of both a simplified field model and three-dimensional magnetostatic simulations. A number of criteria for the arrangement of the coils to improve operation are derived and applied to a real rectification system used in an electrolysis plant. Some in situ operational measurements of both the original and the improved interphase reactor are reported. [ABSTRACT FROM PUBLISHER]

This paper sets forth a method to obtain scaling laws for low-frequency power magnetic devices using normalized magnetic equivalent circuits. The resulting scaling laws are meant to facilitate the system-level design. While the method is presented in general, it is demonstrated using an inductor as an example. The predictions of the scaling law obtained using the proposed approach are compared to commercially available devices. Experimental validation of the design model is also presented. [ABSTRACT FROM AUTHOR]

In this article, a coupled inductor common-ground single-phase inverter, well-suited for photovoltaic (PV) applications, is presented. The proposed PV inverter is constructed based on a two-stage topology. At the first stage, a high gain DC-DC structure converts low PV voltage to the high bipolar output voltages. The produced bipolar output voltages are the inputs for the conventional half-bridge inverter in the second stage. It is noteworthy that the parasitic capacitors between the PV panel and its ground provide the path for circulating the leakage current in conventional configurations. This problem is tackled in the proposed topology by making a common-ground structure. Furthermore, the first stage contains only one switch with low voltage stress, which leads to a significant suppression in conduction losses. The proposed DC-AC structure has the ability to reduce the input current ripple and also recycle the leakage energy caused by the coupled inductor. The operation principles of the proposed structure are analyzed in detail, and finally, the experimental results are accomplished to confirm the accuracy of the performed analysis. [ABSTRACT FROM AUTHOR]

A single-phase Three-Level Split-Inductor Neutral Point Clamped Inverter-Improved (3L-SI-NPCI2) for transformerless photovoltaic (PV) application is proposed in this article. The proposed inverter utilizes two split inductors, which eliminate the shoot-through issue. Therefore, it is more reliable than conventional converters. Not needing dead time, achieving a high efficiency with lower current THD and low leakage current are other advantages of the proposed inverter. The operation principle, dynamic performance, output filter design and impacts of asymmetric filter inductors on leakage current are illustrated in the 3L-SI-NPCI2. The proposed topology is compared to seven existing transformerless topologies by simulation studies and results. Finally, an experimental prototype has been developed to show the benefits of the proposed inverter. [ABSTRACT FROM AUTHOR]

A new fundamental structure of a single-phase transformer-less grid connected multilevel inverter based on a switched-capacitor structure is presented in this study. By employing the series-parallel switching conversion of the integrated switched-capacitor module in a packed unit, attractive features for the proposed inverter can be obtained such as high efficiency and boosting ability within a single stage operation. Also, using a common grounding technique provides an additional advantage of reducing the leakage current. Moreover, the presented structure generates a multilevel waveform at the output voltage terminals which reduces the harmonics in the system. A peak current controller is utilized for triggering the gate of the power switches and controlling both the active and reactive powers. This results in a tightly controlled current with an appropriate quality that can be injected to the grid using a single source renewable energy resource. Operating procedures, design considerations, comparison studies and test results of a 620 W prototype are also presented to validate the accuracy and feasibility of the proposed multilevel inverter. [ABSTRACT FROM AUTHOR]

A new topology is proposed for direct drive wind turbines that eliminates the use of the failure prone dc-bus electrolytic capacitor, avoids the need for a dc-link inductor by utilizing the synchronous inductance of the wind turbine permanent-magnet generator (PMG), and provides a low-voltage generator design, which decreases the amount of permanent-magnet material used in PMG, and reduces the volume and weight of the generator. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFC) are alternative renewable power sources that can directly produce electricity from biodegradable substances. However, due to their low power and voltage production, power management systems (PMS) are required to process the MFC power to a more readily usable level. For this application, a monolithic PMS with an integrated maximum power extraction algorithm (MPEA) is proposed. The MPEA allows for quick and accurate pin-pointing of the matching conditions for maximum power transfer from the MFC to the PMS. The PMS delivers a regulated fixed voltage from low fluctuating voltages produced by MFC at maximum power point to a supercapacitor from which electronic devices, such as wireless sensors, for extended operation time can be directly powered. Along with the MPEA system, the PMS is composed of a dc–dc boost converter operating in discontinuous conduction mode to maximize efficiency. In addition, a zero current switching tracking loop is proposed to improve overall system efficiency and minimize losses in the PMS through accurate P-type Metal-oxide-semiconductor field-effect transistor on/off timing control. The PMS circuit was fabricated in 0.5-μm CMOS technology. The maximum dynamic efficiency measured was ∼58% for a load of ∼250 μW. [ABSTRACT FROM AUTHOR]

Due to the variable characteristics of renewable generation, batteries used in renewable-power systems can undergo many irregular, partial charge/discharge cycles. In turn, this can also have a detrimental effect on battery lifetime and can increase project costs. This study presents a method of improving battery lifetime in a small-scale remote-area wind-power system by the use of a battery/supercapacitor hybrid energy storage system. The supervisory control algorithm and hardware implementation are described and projected long-term benefits of the proposed system are assessed by simulation. A representative dynamic model of the overall system, incorporating realistic wind-speed and load-power variations has been developed. An analysis is presented of the potential improvement in battery lifetime that is achievable by diverting short-term charge/discharge cycles to a supercapacitor energy-storage system. This study introduces a method by which supercapacitor energy storage systems and control algorithms can be evaluated and implemented in the application area considered. The composition of a prototype test system is described and experimental results are presented to demonstrate system feasibility. [ABSTRACT FROM AUTHOR]

We studied reactor size reduction by applying a slot jet cooling method. In power electronics products such as large power conversion equipments for industry applications (conversion equipments), reactors take up a large proportion of the volume and weight, and miniaturization of reactors is an important issue in reducing the size of conversion equipments. Reactors cooled by forced air convection are generally almost the same size as those cooled by natural air convection. We applied a slot jet cooling method to make cooling air flowing out from two or more slots impinge on the reactor surface at high speed. There have been many reports concerning jets from single slots or two or more slots distributed in parallel. However, many of the details of mutual interference and the exhaust flow along the direction of the slot after jet impingement on a surface remain unknown. Therefore, these basic findings were experimentally verified, and an optimum slot jet giving the greatest improvement in cooling performance, while taking account of exhaust flow, was found. By applying this slot jet cooling, the mass was reduced by about half compared with a conventional reactor. [ABSTRACT FROM AUTHOR]

This letter aims to settle the controversy about whether or not the two-reaction theory is applicable to homopolar inductor alternator (HIA). First, the prerequisite of two-reaction theory is introduced. The direct and quadrature axes of HIA are defined and the corresponding armature reaction fields are calculated respectively based on finite element method. A conclusion that two-reaction theory is applicable to HIA is made using spatial overlay analysis. [ABSTRACT FROM AUTHOR]