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This paper proposes, a novel soft‐switching bidirectional direct current to direct current (DC–DC) converter based on switched‐capacitor and coupled‐inductor. The proposed converter has a simple structure and utilizes four switches and a three‐winding coupled inductor and can achieve a high voltage conversion ratio in both step‐up/step‐down operations. By employing the switched‐capacitor technique, voltage stress across the power switches is low and therefore low voltage rating switches can be adopted to reduce the losses of their conduction. Soft‐switching characteristic of the proposed converter reduces the switching loss of active power switches and raises the conversion efficiency. This paper presents theoretical analysis for all operating modes of the converter, voltage conversion ratio, voltage and current stresses of all power switches. Finally, to test the validity of theoretical results and demonstrate the performance of the converter, experimental results are provided. [ABSTRACT FROM AUTHOR]

This paper proposes a switched Z‐source inverter with high voltage gain and low current stress on elements. Also, a new switching method corresponding to the proposed topology is introduced. This method is based on the usual Maximum Constant Boost (MCB) method. Hence, it has the advantages of the MCB method, such as low voltage stress on the inverter switches and high voltage gain. Also, eliminating part of the inverter's switching in this modulation method improves the inverter's efficiency. In addition to the Shoot‐Through (ST) duty cycle, another variable (N) affects the inverter's boost factor in this switching method. The proposed inverter's dynamic analysis shows that introducing N in the modulation method improved the dynamic characteristic of the inverter. Also, this variable as a control input can stabilize the dc side of the inverter in the closed‐loop control of the inverter. For the proposed topology, steady‐state analysis, dynamic analysis, elements design and efficiency calculation are performed. Also, the proposed topology is compared with the conventional topologies regarding boost factor, the number of elements, current stress on elements and efficiency to show its superiority. Finally, the experimental results are presented to verify theoretical discussions. [ABSTRACT FROM AUTHOR]

The paper presents a sliding-mode observer that utilizes sigmoid function for speed and position sensorless control of permanent-magnet linear synchronous motor (PMLSM). In conventional sliding mode observer method there are the chattering phenomenon and the phase lag. Thus, in order to avoid the usage of the low pass filter and the phase compensator based on back EMF, in this paper a sliding mode observer with sigmoid function for detecting the back EMF in a PMLSM is designed to estimate the speed and the position of the rotor. Most of conventional sliding mode observers use sign or saturation functions which need low pass filter in order to detect back electromotive force (back EMF). In this paper a sigmoid function is used instead of discontinuous sign function to decrease undesirable chattering phenomenon. By reducing the chattering, detecting of the back EMF can be made directly from switching signal without any low pass filter. Thus the delay time in the proposed observer is eliminated because of the low pass filter. Furthermore, there is no need to compensate phase fault in position and speed estimating of linear-PMSM. Advantages of the proposed observer have been shown by simulation with MATLAB software.

In this article, two compact three-phase multilevel inverters are proposed. The first proposed topology consists of three dc sources and ten power switches. The merit of the first proposed topology is reducing two switches from its structure to the conventional topologies. The second proposed topology is similar to the first one, except that one of the dc sources is replaced by a capacitor. This capacitor is balanced by an additional switch and one of the dc sources. How to apply two modulation methods for these inverters has been studied in detail. These modulation methods are level-shifted pulsewidth modulation and phase-shifted pulsewidth modulation (PS-PWM). Also, the value of the capacitor for each of the modulation methods has been calculated. Finally, the experimental results are provided to confirm the performance of the proposed topologies. [ABSTRACT FROM AUTHOR]

This paper introduces a multi‐objective optimal design for an axial magnetic gear (AMG). In this study, the condition for high torque density and low cogging torque was deduced while the cost of the active materials was also reduced. The number and direction of permanent magnets and their arrangement were unchanged in the optimisation process, and the considered AMG's main dimensions were optimised using the particle swarm optimisation method. The optimised AMG was compared with the latest and similar structures with a relatively high torque density. To extract the produced torque density and cogging torque, three‐dimensional (3D) finite element analyses were conducted. The results showed that while torque density increased and cogging torque decreased, the total volume and magnetic materials used decreased significantly. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage bidirectional power electronic transformer (PET) for lighting systems as a three-phase electronic ballast. The lighting system supplies multilamp units that are controlled simultaneously by a bidirectional PET using a pulsewidth modulation scheme. The PET contains a single-input multioutput high-frequency isolating transformer to control the illumination of the lamps as well as providing galvanic isolation in each unit simultaneously. The high-frequency operation, direct ac to ac conversion, and bidirectional power flow capabilities help the PET to operate without any bulky storage elements. So good efficiency, and low weight, volume, and cost of the power conversion system can be achieved. The control strategy promotes the ballast performance to let fluorescent lamps operate free from both voltage flicker and disturbances. As a result, improved dimmable illumination, lamps protection, and increasing lifetime of lamps can be achieved. A design procedure based on equivalent circuit is presented to determine the resonant output circuit parameters. The experimental results of the prototype, which converts 110 V/3[phi]/50 Hz input voltage to 130 V/1[phi]/25 kHz and 70 V/1[phi]/25 kHz output voltages, show the practical aspects of the proposed PET. Index Terms--Electronic dimmable ballasts, fluorescent lamps, illumination control, power electronic transformer (PET).

A three-phase squirrel-cage induction motor is used as a propulsion system of an electric vehicle (EV). The motor is controlled at different operating conditions using a direct torque control (DTC) technique combined with a new switching pattern producing low harmonics. The operating flux of the motor is chosen optimally for losses minimization and good dynamic response. Since speed estimation is sensitive to rotor resistance variations, the rotor resistance value is calculated and modified in real time continuously. Simulation and experimental results show that the proposed DTC is able to follow the reference speed (which may be only input reference of the system) with a reasonable dynamic and relatively low error. Index Terms--DTC control technique, electrical vehicle.

In this article, a new soft switching isolated push–pull dc–dc converter using a three-winding transformer is proposed. The proposed hybrid resonant and pulse width modulated converter employs a conventional push–pull structure in the primary side, a voltage doubler in the secondary side, and a bidirectional switch besides the transformer, altogether help offering a high efficiency over a wide range of input and output voltage signals with an unsophisticated fixed-frequency control mechanism. The primary-side switches are commutated under zero voltage switching with low switching current and the secondary-side diodes are commutated under zero current switching. In this article, we first present an in-depth analysis of various operation modes and design constraints. Our analysis is further complemented with a comprehensive reliability evaluation of the proposed converter under various short circuit and open circuit fault scenarios. Different from the previous research, the derated operating states of the proposed converter are detailed and characterized in the reliability evaluations. A comparison study is then provided to evaluate the performance of the proposed converter against other similar converters from the operation, components count, efficiency, and reliability perspectives. Finally, the theoretical analyses are verified via tests and experiments performed on a 280 W/34.7 kHz prototype. [ABSTRACT FROM AUTHOR]

A high step‐up/high‐efficiency converter is one of the essential requirements of a low power grid‐connected photovoltaic system that provides the maximum power point tracking ability and injects the low voltage extracted power to AC or DC distribution network. This study presents a common‐ground non‐isolated high‐gain DC/DC converter whit a naturally wide range of soft‐switching conditions. The proposed converter has two resonant loops, and a new simple structure consists of an active switch, three diodes, two inductors and two capacitors, work in two useful operation modes. In the optimum operation mode (OOM), the switch turns on/off in zero current switching (ZCS)/zero voltage switching condition, and at the sub‐OOM, the switch turns on in ZCS condition and turns off in hard switching condition. The mathematical analysis and MATLAB/SIMULINK simulation results are described in detail. Also, a prototype 100 W converter is built and tested to validate the simulation analysis on a 100 W photovoltaic panel. [ABSTRACT FROM AUTHOR]

In this study, a new multi-input high step-up inverter, based on isolated soft-switching DC-DC converter blocks is proposed. Each of these blocks can provide zero-voltage and zero-current switching for its semiconductors, which improve power efficiency. The interesting feature of this DC-DC converter is using bidirectional switches to generate both positive and negative output voltage levels in each DC-DC block with an appropriate control scheme. Each DC-DC converter operates by simple pulse width modulation control through fixed frequency and has two degrees of freedom, which provide the capability of output voltage regulation or maximum power point tracking. The proposed inverter consists of the cascaded connection of these DC-DC converters at their output terminal. This inverter can operate with high voltage gain, where the output voltage of each DC-DC converter is regulated. Furthermore, it can generate more output voltage levels with less number of DC-DC blocks. All these advantages make the proposed inverter suitable for photovoltaic power conditioning systems. In this study, the theoretical analysis with steady-state waveforms, design constraints, resonant tank analysis and comparison study are given. Then, experimental results of both the proposed inverter and its DC-DC blocks are presented. [ABSTRACT FROM AUTHOR]

Uncertainty management is a challenging task in decision making of the operators of the power systems. Prediction of the system state is vital for the operation of a system with stochastic behavior especially in a power system with a significant amount of renewable energies such as wind power. Predictable power systems are in more interest of operators, of course. This paper proposes a multiobjective framework for optimal placement and parameters setting of a unified power flow controller (UPFC) considering system predictability. The well-known multiobjective nondominated sorting genetic algorithm is implemented to handle various objective functions such as active power losses and predictability of system in the presence of operational constraints and uncertainties. The point estimate method is used for modeling probabilistic nature of the wind power. Using the proposed method, statistical information of voltage magnitude and apparent power of converters of UPFCs can be obtained, which are very useful in making decision on the sizing of UPFCs. Comprehensive discussions are provided using the simulations on the IEEE 57-bus test system. Also, in order to validate the obtained results, a multiobjective particle swarm optimization algorithm is implemented and the results of two algorithms are compared with each other. [ABSTRACT FROM AUTHOR]

Abstract Parallel connected electrical machines drive systems have received significant attention due to their use in special purpose applications. Recently, control of such systems using a single inverter has been considered for improving stability during uneven load conditions on machines. In this paper, a synchronized control strategy for stable operation of dual parallel brushless direct current motors using a single three-phase inverter is proposed. Control of parallel connected brushless direct current motors suffers from instability under different load torques. To obtain the stability, an effective control method based on master-slave strategy is presented. To analysis the stability, the detail model of the proposed system is developed for an electric vehicle propulsion system. Therein, the motor with the highest load or with lagging rotor position is selected as the master and is directly controlled. The effectiveness of the proposed system is demonstrated by a series of case studies in different operation conditions. [ABSTRACT FROM AUTHOR]

During the extremely-hot weather or transient heat waves, air conditioners are the main contributors to highest peak electricity demand which may lead to the widespread blackouts or brownouts. Meanwhile, electric drive vehicles are rapidly gaining popularity due to the global warming and energy crisis. Hence, this paper schedules on optimal charge and discharge decisions of plug-in electric vehicles (PEV) in a residential cooling and power microgrid that is driven by a solar Stirling engine. In the presented microgrid, the solar dish Stirling heat engine is employed as an external combustion engine to supply the electricity requirement of compressor, evaporator and condenser fans and charge the PEVs in the off-peak cooling-load hours. During the on-peak periods, optimal discharge of PEVs increases total energy and emission savings, significantly. A thermodynamic based mixed integer nonlinear programming (MINLP) problem is solved to minimize total electricity cost for a benchmark residential building located in a tropical region taking into account the operational constraints of the Stirling engine and the refrigeration cycle. Simulation results demonstrate that this micro-cogeneration system can be introduced as a near-zero energy building with zero-carbon footprint in the presence of PEVs. [ABSTRACT FROM AUTHOR]

A new nonisolated multiinput multioutput dc-dc boost converter is proposed in this paper. This converter is applicable in hybridizing alternative energy sources in electric vehicles. In fact, by hybridization of energy sources, advantages of different sources are achievable. In this converter, the loads power can be flexibly distributed between input sources. Also, charging or discharging of energy storages by other input sources can be controlled properly. The proposed converter has several outputs with different voltage levels which makes it suitable for interfacing to multilevel inverters. Using of a multilevel inverter leads to reduction of voltage harmonics which, consequently, reduces torque ripple of electric motor in electric vehicles. Also, electric vehicles which using dc motor have at least two different dc voltage levels, one for ventilation system and cabin lightening and other for supplying electric motor. The proposed converter has just one inductor. Depending on charging and discharging states of the energy storage system (ESS), two different power operation modes are defined for the converter. In order to design the converter control system, small-signal model for each operation mode is extracted. The validity of the proposed converter and its control performance are verified by simulation and experimental results for different operation conditions. [ABSTRACT FROM AUTHOR]

A simple structure and a quick and robust response of the direct torque control (DTC) makes it attractive in ac drives. However, in sensorless applications, a precise estimation of the rotor speed is a crucial issue as along with the torque and flux estimation. In this paper an adaptive flux observer is introduced with a stator current and flux vector components as state variables and rotor speed as an unknown parameter which is estimated by using an adaptive scheme. A non-linear inverter model is proposed to obtain a more accurate response. Also, torque, flux and current pulsations, during the steady-state conditions, are considered as the disadvantages of the classical DTC method. A combined DTC and space vector modulation strategy is presented by using fuzzy logic control (FLC). FLCs are designed to obtain a fast response in the transients, and a high accuracy during the steady-state conditions. [ABSTRACT FROM AUTHOR]

The voltage sags at the connecting point of the wind turbine equipped with double fed induction generator (DFIG) to the grid can result in over current in the stator winding. Due to the magnetic coupling between stator and rotor, similar high current appears in the rotor winding, consequently, the rotor side converter may be damaged. Therefore, it may be necessary for the wind turbines with DFIG to be interrupted during some voltage sags in the power systems. This paper proposes a new method which uses energy capacitor system (ECS) to achieve uninterrupted operation of the wind turbine with DFIG during grid faults. This system controls the active and reactive powers at the connecting point of wind turbine to the grid. Simulation results clearly show that ECS enhances the transient stability and therefore helps the wind turbine generator system to remain in the service during grid faults. [ABSTRACT FROM AUTHOR]

Development of Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) will offer many new opportunities and challenges to the power electronics industry, especially in the development of the main traction motor drive. Both HEVs and EVs need a traction motor and a power inverter to drive the vehicle motor. The requirements for the power inverter include high peak power, low output harmonics, inexpensive circuit and low continuous power rating. Cascade H-bridge (CHB) multilevel inverter with minimum output harmonics for electric/hybrid electric vehicle applications is proposed in this paper. Switching angles of switch devices are determined by selective harmonic elimination technique. So, the effect of low order harmonics are reduced, as a result the efficiency of system has improved. Moreover, the number of DC voltage sources that used in the proposed inverter is less than conventional multilevel inverters that leads to reduce the inverter costs. A fundamental frequency switching methods has been used for modulation of inverter and to produce a seven-level phase voltages. The effectiveness of the proposed system has been validated by simulation results on various conditions using PSCAD/EMTDC software. [ABSTRACT FROM AUTHOR]

This paper proposes a new topology for bidirectional multiinput direct dc–ac converter for clean-power-generation system, therefore, at the input port, a boost converter is used to meet the requirement of many distributed generation systems, such as photovoltaic, and fuel cell systems. The boost converter can increase the dc input voltage. This point results in a turn ratio reduction of high-frequency isolating link transformer. Furthermore, the boost inductor reduces the input current ripple, therefore, the saturation of the transformer can be avoided for higher output currents. The count of used devices has been reduced in the proposed converter. As a result, the cost, size, and the volume of the converter can be reduced. The reduced conversion steps increase the efficiency of the converter. The converter is analyzed step by step to show the principles of the operation in providing energy management based on duty-cycle variations. The system capability in different operation conditions has been simulated, and the simulation results have been compared with measurement results. Dynamic analysis and control design of the bidirectional dc–ac converter is presented based on nonlinear control by input–output feedback linearization. [ABSTRACT FROM AUTHOR]

A new detailed model of 3-ph squirrel cage induction motor based on modified winding function theory is presented in this paper. Slotting, skewing and linear MMF rise across the rotor and stator slots are considered in the model. The state space equations in terms of flux linkages as well as motor currents, and a more general form of nonlinear state space equation are obtained Three methods for calculating mutual inductance matrix between stator and rotor, and two schemes for incorporating rotor faults into the model are discussed Also general formulas for rotor inductance calculation in healthy and broken bar motor are proposed Simulation results of healthy and broken bar motors show the ability of the model. [ABSTRACT FROM AUTHOR]