Advances in Power Electronics The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. A Dynamic Model for Direct and Indirect Matrix Converters Tue, 08 Apr 2014 07:18:52 +0000 The complicated modulation algorithm and the high switching frequency are two main hindrances in the analysis and simulation of matrix converters (MCs) based systems. To simplify the analysis and accelerate the simulation of MCs, a unique dynamic model is presented for the MC, which is independent of MC type (direct or indirect) and the modulation algorithm. All the input and output variables are transferred to the respective reference frames and their relations and limits are calculated. Based on the proposed equations, an equivalent circuit model is presented which can predict all the direct and indirect matrix converters dynamic and steady state behaviors without the need for small simulation time steps. Validity of the proposed model is evaluated using simulation of the precise model. Moreover, experimental results from a laboratory matrix converter setup are provided to verify the accuracy of the simulation results. Mohamad Hosseini Abardeh and Reza Ghazi Copyright © 2014 Mohamad Hosseini Abardeh and Reza Ghazi. All rights reserved. A Torque Discontinuity Free New Hybrid PWM Approach for High Speed Induction Motor Drives Wed, 02 Apr 2014 09:40:49 +0000 This paper designs a hybrid speed controller in which a Sine Triangle Pulse Width Modulated (SPWM) inverter is used below the base speed and a square wave inverter is employed above the base speed. The two inversion techniques complement each other for their advantages and disadvantages below and above the base speed. This paper proposes a unique strategy for the transition between SPWM and square wave by simply setting the frequency of the carrier signal equal to zero. The proposed methodology in a way uses only one inversion technique and realizes a seamless transition from the SPWM to square wave compared to conventional method in which modes are simply switched from SPWM to square wave and vice versa when the speed changes above and below the base speed, respectively. Computer simulations show that the proposed technique has smoother torque transition and thus a better speed response compared to conventional approach of inverter mode switching around the base speed. The performance of proposed hybrid approach is also validated on a small prototype induction motor through experimental results. Habibur Rehman, Roufin Mahmood, and Taimoor Shah Copyright © 2014 Habibur Rehman et al. All rights reserved. Simulation to Implementation as Good Practices for Teaching Power Electronics to Undergraduate Students: Fuzzy Sliding Mode Control for DC Motors Mon, 24 Feb 2014 13:34:37 +0000 How can students be given experience in the confused realities of engineering processes? How can undergraduate students be convinced that processes can be analyzed and improved? Computer simulations properly designed and applied could answer these challenges revolutionizing education in Power Electronics. In recent years, computer simulation has been commonly used in education to motivate students in their learning and help teachers to improve their teaching level. The present paper focuses on developing a speed controller for DC motors starting from theoretical aspects, passing through simulations, and finally reaching a control prototype. The control theory is based on a nonlinear technique known as Sliding Mode Control (SMC) involving artificial intelligence for optimization such as Fuzzy Logic (FL), Adaptive Neurofuzzy Inference Systems (ANFIS), and Genetic Algorithms (GAs). Paul Cepeda, Pedro Ponce, and Arturo Molina Copyright © 2014 Paul Cepeda et al. All rights reserved. An FPGA Chaos-Based PWM Technique Combined with Simple Passive Filter for Effective EMI Spectral Peak Reduction in DC-DC Converter Mon, 24 Feb 2014 12:47:37 +0000 A new and simple but effective electromagnetic interference suppression technique based on field programmable logic array (FPGA) technology to provide a significant EMI noise attenuation in DC-DC converters is discussed. The voltage controlled boost converter for EMI reduction is analyzed using FFT under traditional PWM technique and chaotic mode operation. This technique aids the DC-DC converters to comply in specified EMI limits and replace conventional bulky passive filter with a simple passive filter. A prototype model has been tested and hardware results show significant reduction of EMI in chaotic mode operation of the boost converter. Sudhakar Natarajan and Rajasekar Natarajan Copyright © 2014 Sudhakar Natarajan and Rajasekar Natarajan. All rights reserved. An FPGA Based Controller for a SOFC DC-DC Power System Sat, 28 Dec 2013 09:09:53 +0000 Fuel cells are an attractive option for alternative power and of use in a variety of applications. This paper proposes a state space model for the solid oxide fuel cell (SOFC) based power system that comprises fuel cell, DC-DC buck converter, and load. In this investigation we have taken up a case study for SOFC feeding a DC load where a DC-DC buck converter acts as the interface between the load and the source. A proportional-integral (PI) controller is used in conjunction with pulse width modulation (PWM) that computes the pulse width and switches the MOSFET at the right instant so that the desired voltage is obtained. The proposed model is validated through extensive simulation using MATLAB/SIMULINK. Controller for the fuel cell power system (FCPS) is prototyped using XC3S500E development board containing a SPARTAN 3E Xilinx FPGA that simplifies the entire control circuit besides providing additional flexibility for further improvement. The results clearly indicate improved performance and validate our proposed model. Kanhu Charan Bhuyan, Sumit Kumar Sao, and Kamalakanta Mahapatra Copyright © 2013 Kanhu Charan Bhuyan et al. All rights reserved. Control of DFIG Wind Turbines Based on Indirect Matrix Converters in Short Circuit Mode to Improve the LVRT Capability Thu, 12 Dec 2013 14:00:54 +0000 Nowadays, the doubly-fed induction generators (DFIGs) based wind turbines (WTs) are the dominant type of WTs. Traditionally, the back-to-back converters are used to excite the rotor circuit of DFIG. In this paper, an indirect matrix converter (IMC) is proposed to control the generator. Compared with back-to-back converters, IMCs have numerous advantages such as higher level of robustness, reliability, and reduced size and weight due to the absence of bulky electrolytic capacitor. According to the recent grid codes wind turbines must have low voltage ride-through (LVRT) capability. In this paper a new crowbar system is proposed so that along with the control system it protects the IMC from large fault currents and supports the grid voltage dips during grid faults. This crowbar system is provided using the existing converter switches to establish a short circuit mode without any extra circuitry. Even in severe fault conditions, the duration of short circuit mode is quite small so the control system will be activated shortly after the fault to inject reactive power as required by new LVRT standards. Therefore, the new LVRT standards are well satisfied without any extra costs. PSIM simulation results confirm the efficiency of the proposed method. Ahmad Khajeh and Reza Ghazi Copyright © 2013 Ahmad Khajeh and Reza Ghazi. All rights reserved. Selection of Design Parameters to Reduce the Zero-Sequence Circulating Current Flow in Parallel Operation of DC Linked Multiple Shunt APF Units Sun, 08 Dec 2013 09:59:50 +0000 Capacity enhancement and operational flexibility are two of the important limitations of the centralized shunt APF () unit. These limitations can be conquered by the operation of multiple APF units in parallel and connected back to back by a common DC link capacitor. In that case, a circulating current (CC) flows within the units. This CC flow becomes out of control when the units operate in hysteresis based current controlled mode. One of the difficulties of this CC flow control or reduction is the variable switching frequency of the units. In this paper, the model for CC flow is derived by the switching dynamics study of the units. It is found that the selection of design parameters plays an important role in the amount of CC flow. Detailed simulation, analysis, and real-time performance show how the selection of design parameters affects the CC flow and the reduction of CC flow can also be achieved at an acceptable level by the proper selection of design parameters. Shafiuzzaman K. Khadem, Malabika Basu, and Michael F. Conlon Copyright © 2013 Shafiuzzaman K. Khadem et al. All rights reserved. Development of a New Research Platform for Electrical Drive System Modelling for Real-Time Digital Simulation Applications Tue, 06 Aug 2013 11:23:49 +0000 This paper presents the research platform for real-time digital simulation applications which replaces the requirement for full-scale or partial-scale validation of physical systems. To illustrate this, a three-phase AC-DC-AC converter topology has been used consists of diode rectifier, DC link, and an IGBT inverter with inductive load. In this topology, rectifier as well as inverter decoupled and solved separately using decoupled method, which results in the reduced order system so that it is easy to solve the state equation. This method utilizes an analytical approach to formulate the state equations, and interpolation methods have been implemented to rectify the zero-crossing errors, with fixed step size of 100 μsec is used. The proposed algorithm and the model have been validated using MATLAB simulation as m-file program and also in real-time DSP controller domain. The performance of the real-time system model is evaluated based on accuracy, zero crossing, and step size. S. Umashankar, Mandar Bhalekar, Surabhi Chandra, D. Vijayakumar, and D. P. Kothari Copyright © 2013 S. Umashankar et al. All rights reserved. Variable Speed Drive Characterization: Review of Measurement Techniques and Future Trends Wed, 31 Jul 2013 08:33:18 +0000 The significant advances in power electronics have permitted the implementation of sophisticated methods for control of electric motors. Each innovative electrical apparatus for industrial and automotive application must be correctly and exhaustively tested, both during the developing process and finally for the compliance test. The development of a new electrical system should be associated with a parallel design of an ad hoc measurement system, whose performance should be defined according to the features of the system under test. In recent years, the increasing interest for sensorless electric motor drives involved the development and implementation of a wide set of control techniques. This paper reviews the state and the trends of measurement techniques and instruments applied for the experimental characterization of variable speed drives. Edoardo Fiorucci, Giovanni Bucci, Fabrizio Ciancetta, Daniele Gallo, Carmine Landi, and Mario Luiso Copyright © 2013 Edoardo Fiorucci et al. All rights reserved. A 25 kW, 25 kHz Induction Heating Power Supply for MOVPE System Using L-LC Resonant Inverter Wed, 17 Jul 2013 10:20:24 +0000 A topology named L-LC resonant inverter (RI) for induction heating (IH) applications takes most of the merits of the conventional series and parallel resonant schemes, while eliminating their limitations. In this paper, fundamental frequency AC analysis of L-LC RI is revisited, and a new operating point is suggested featuring enhanced current gain and near in-phase operation as compared to the conventional operating point. An approximate analysis of the circuit with square-wave voltage source is also described highlighting the effect of auxiliary inductor on the source current waveform. The analysis also leads to an optimum choice of the auxiliary inductance. The requirements of the metal organic vapour phase epitaxy (MOVPE) system in which a graphite susceptor is required to be heated to 1200°C demanding a 25 kW, 25 kHz IH power supply, the configuration of developed IH system, and experimental results are presented. Mangesh Borage and Sunil Tiwari Copyright © 2013 Mangesh Borage and Sunil Tiwari. All rights reserved. Performance Analysis of Grid Integrated Hydro and Solar Based Hybrid Systems Mon, 17 Jun 2013 11:31:19 +0000 The renewable energy systems (RESs) are an attractive option to electrify the community as they are environment friendly, free of cost, and all-pervading. The efficiency of these energy systems is very low and can be improved by integrating them in parallel. In this paper, hydro (7.5 kW) and solar systems (10 kW) are taken as RESs and connected with the utility grid. Due to the intermittent nature of both the hydro and photovoltaic energy sources, utility grid is connected to the system for ensuring the continuous power flow. The hydro power generation system uses the self excited induction generator (SEIG) and converters. The AC/DC/AC converter is used as interface to connect the hydro turbine to the utility grid to adjust the generated voltage to the utility grid voltage. The solar generation system is the combination of PV array, boost converter, and solar inverter. The control of both the hydro and solar power plants is provided through the constant current controller. The analysis has been done to verify the existence of the proposed system. Results demonstrate that the proposed system is able to be put into service and can feed the community. Sweeka Meshram, Ganga Agnihotri, and Sushma Gupta Copyright © 2013 Sweeka Meshram et al. All rights reserved. Implementation of Novel Technique for Selective Harmonic Elimination in Multilevel Inverters Based on ICA Mon, 17 Jun 2013 09:17:29 +0000 Eliminating the specific harmonics especially low-order harmonics of the output voltage of 9-level inverter using SHE-PWM control scheme is investigated. Harmonic minimization is the intricate optimization problems because the nonlinear transcendental equations have multiple local optima. Increasing the degrees of freedom in the suggested method means that the number of switching angles increases. The suggested method is able to eliminate high number of undesired harmonics. As the number of switching angles increases, using either traditional iterative techniques or resultant theory method gets useless. In this paper to overcome this problem the imperialist competitive algorithm (ICA) is used. Also a DC-DC converter is used to enhance the SHE performance in the range for which the conventional SHE methods do not have any solution. Experimental and simulation results of a 9-level inverter show that the proposed method effectively minimizes a large number of particular harmonics so the total harmonics distortion of output voltage will be lower. Ali Ajami, Mohammad Reza Jannati Oskuee, and Ata Ollah Mokhberdoran Copyright © 2013 Ali Ajami et al. All rights reserved. Fault Tolerant Ancillary Function of Power Converters in Distributed Generation Power System within a Microgrid Structure Wed, 08 May 2013 14:04:56 +0000 Distributed generation (DG) is deeply changing the existing distribution networks which become very sophisticated and complex incorporating both active and passive equipment. The simplification of their management can be obtained assuming a structure with small networks, namely, microgrids, reproducing, in a smaller scale, the structure of large networks including production, transmission, and distribution of the electrical energy. Power converters in distributed generation systems carry on some different ancillary functions as, for example, grid synchronization, islanding detection, fault ride through, and so on. In view of an optimal utilization of the generated electrical power, fault tolerant operation is to be considered as a suitable ancillary function for the next future. This paper presents a complete modeling of fault tolerant inverters able to simulate the main fault type occurrence and a control algorithm for fault tolerant converters suitable for microgrids. After the model description, formulated in terms of healthy device and leg binary variables, and the illustration of the fault tolerant control strategy, the paper shows how the control preserves power quality when the converter works in the linear range. The effectiveness of the proposed approach and control is shown through computer simulations and experimental results. Antonino O. Di Tommaso, Fabio Genduso, Rosario Miceli, and Giuseppe Ricco Galluzzo Copyright © 2013 Antonino O. Di Tommaso et al. All rights reserved. Transformer Magnetization Losses Using a Nonfiltered Voltage-Source Inverter Wed, 08 May 2013 13:27:49 +0000 Results from the magnetization of an 80 kVA power transformer, using a directly coupled nonfiltered three-phase voltage-source inverter (VSI), are presented. The major benefits of this topology are reduction in switching filter size as well as filter losses. Drawbacks include higher stress on the transformer windings and higher transformer magnetization losses. In this paper, the total magnetization losses are presented for different voltage levels. The transformer has been magnetized with the rated frequency of 50 Hz at various voltage levels. The saturation characteristics as well as the magnetizing resistance are derived as functions of the voltage. These are used as inputs for the simulations. The magnetization losses have been experimentally measured and simulated for three different DC levels. Results from the simulations show good agreement with the experimental results. As expected, the pulsed voltage waveforms generate larger magnetization losses than the corresponding 50 Hz case. The losses are strongly dependent on the DC level. Rickard Ekström, Senad Apelfröjd, and Mats Leijon Copyright © 2013 Rickard Ekström et al. All rights reserved. Modeling, Control, and Simulation of a Solar Hydrogen/Fuel Cell Hybrid Energy System for Grid-Connected Applications Thu, 04 Apr 2013 10:39:19 +0000 Different energy sources and converters need to be integrated with each other for extended usage of alternative energy, in order to meet sustained load demands during various weather conditions. The objective of this paper is to associate photovoltaic generators, fuel cells, and electrolysers. Here, to sustain the power demand and solve the energy storage problem, electrical energy can be stored in the form of hydrogen. By using an electrolyser, hydrogen can be generated and stored for future use. The hydrogen produced by the electrolyser using PV power is used in the FC system and acts as an energy buffer. Thus, the effects of reduction and even the absence of the available power from the PV system can be easily tackled. Modeling and simulations are performed using MATLAB/Simulink and SimPowerSystems packages and results are presented to verify the effectiveness of the proposed system. Tourkia Lajnef, Slim Abid, and Anis Ammous Copyright © 2013 Tourkia Lajnef et al. All rights reserved. Simple Hybrid Model for Efficiency Optimization of Induction Motor Drives with Its Experimental Validation Thu, 21 Mar 2013 19:25:10 +0000 New hybrid model for efficiency optimization of induction motor drives (IMD) is presented in this paper. It combines two strategies for efficiency optimization: loss model control and search control. Search control technique is used in a steady state of drive and loss model during transient processes. As a result, power and energy losses are reduced, especially when load torque is significant less related to its rated value. Also, this hybrid method gives fast convergence to operating point of minimal power losses and shows negligible sensitivity to motor parameter changes regarding other published optimization strategies. This model is implemented in vector control induction motor drive. Simulations and experimental tests are performed. Results are presented in this paper. Branko Blanuša and Bojan Knezevic Copyright © 2013 Branko Blanuša and Bojan Knezevic. All rights reserved. Conformal Patch Antenna Arrays Design for Onboard Ship Deployment Using Genetic Algorithms Tue, 12 Mar 2013 16:26:24 +0000 Conformal antennas and antenna arrays (arrays) have become necessary for vehicular communications where a high degree of aerodynamic drag reduction is needed, like in avionics and ships. However, the necessity to conform to a predefined shape (e.g., of an aircraft’s nose) directly affects antenna performance since it imposes strict constraints to the antenna array’s shape, element spacing, relative signal phase, and so forth. Thereupon, it is necessary to investigate counterintuitive and arbitrary antenna shapes in order to compensate for these constraints. Since there does not exist any available theoretical frame for designing and developing arbitrary-shape antennas in a straightforward manner, we have developed a platform combining a genetic algorithm-based design, optimization suite, and an electromagnetic simulator for designing patch antennas with a shape that is not a priori known (the genetic algorithm optimizes the shape of the patch antenna). The proposed platform is further enhanced by the ability to design and optimize antenna arrays and is intended to be used for the design of a series of antennas including conformal antennas for shipping applications. The flexibility and performance of the proposed platform are demonstrated herein via the design of a high-performance GPS patch antenna. Stelios A. Mitilineos, Symeon K. Symeonidis, Ioannis B. Mpatsis, Dimitrios Iliopoulos, Georgios S. Kliros, Stylianos P. Savaidis, and Nikolaos A. Stathopoulos Copyright © 2013 Stelios A. Mitilineos et al. All rights reserved. An Alternative for All-Electric Ships Applications: The Synchronous Reluctance Motor Sun, 10 Mar 2013 10:20:55 +0000 The three-phase synchronous reluctance motor (SynRM) is presented as a possible alternative in all-electric ship applications. The basic features of this motor with regard to the other types of motors are shown. The structure of the motor and specifically the structure of its rotor are analyzed, while the basic operating principles are presented and references on commonly used control strategies are made. In this paper, a demonstration of a reluctance motor fed by a voltage source inverter (VSI) takes place. To demonstrate the operation of the motor fed by a VSI, an example using a scalar control method is implemented, where harmonic injection PWM (HIPWM) is used to drive the VSI. Experimental results on a commercially available motor are shown, focusing on the harmonic content of the current. Ioannis Ch. Proimadis, Dionysios V. Spyropoulos, and Epaminondas D. Mitronikas Copyright © 2013 Ioannis Ch. Proimadis et al. All rights reserved. PV Systems Installed in Marine Vessels: Technologies and Specifications Wed, 06 Mar 2013 17:50:18 +0000 Considerations are held about the specificationin whichthe PV plants have to fulfill so that they can be installed on marine vessels. Initially, a brief description of the typical electrical grid of ships is presented, distinguishing the main parts, reporting the typical electrical magnitudes, and choosing the most preferable installation areas. The technical specifications,in whichthe PV plants have to be compatible with, are fully described. They are determined by the special marine environmental conditions, taking into consideration parameters like wind, humidity, shading, corrosion, and limited installation area. The work is carried out with the presentation of the most popular trends in the field of solar cell types and PV system technologies and their ability to keep up with the aforementioned specifications. Ioannis Kobougias, Emmanuel Tatakis, and John Prousalidis Copyright © 2013 Ioannis Kobougias et al. All rights reserved. A Review on the Faults of Electric Machines Used in Electric Ships Tue, 05 Mar 2013 16:22:08 +0000 Electric propulsion systems are today widely applied in modern ships, including transport ships and warships. The ship of the future will be fully electric, and not only its propulsion system but also all the other services will depend on electric power. The robust and reliable operation of the ship’s power system is essential. In this work, a review on the mechanical and electrical faults of electric machines that are used in electric ships is presented. Dionysios V. Spyropoulos and Epaminondas D. Mitronikas Copyright © 2013 Dionysios V. Spyropoulos and Epaminondas D. Mitronikas. All rights reserved. Harmonic Mitigation Techniques Applied to Power Distribution Networks Sun, 24 Feb 2013 09:55:08 +0000 A growing number of harmonic mitigation techniques are now available including active and passive methods, and the selection of the best-suited technique for a particular case can be a complicated decision-making process. The performance of some of these techniques is largely dependent on system conditions, while others require extensive system analysis to prevent resonance problems and capacitor failure. A classification of the various available harmonic mitigation techniques is presented in this paper aimed at presenting a review of harmonic mitigation methods to researchers, designers, and engineers dealing with power distribution systems. Hussein A. Kazem Copyright © 2013 Hussein A. Kazem. All rights reserved. The Impact of the Rotor Slot Number on the Behaviour of the Induction Motor Tue, 19 Feb 2013 11:32:38 +0000 The impact of the rotor slot number selection on the induction motors is investigated. Firstly, analytical equations will reveal the spatial harmonic index of the air gap magnetic flux density, connected to the geometrical features and the saturation of the induction motor. Then, six motors with different rotor slot numbers are simulated and studied with FEM. The stator is identical in all motors. The motors are examined under time-harmonic analysis at starting and at 1440 rpm. Their electromagnetic characteristics, such as electromagnetic torque, stator current, and magnetic flux density, are extracted and compared to each other. The analysis will reveal that the proper rotor slot number selection has a strong impact on the induction motor performance. Konstantinos N. Gyftakis and Joya Kappatou Copyright © 2013 Konstantinos N. Gyftakis and Joya Kappatou. All rights reserved. Transformer Model in Wide Frequency Bandwidth for Power Electronics Systems Mon, 28 Jan 2013 13:43:02 +0000 The development of the smart grids leads to new challenges on the power electronics equipment and power transformers. The use of power electronic transformer presents several advantages, but new problems related with the application of high frequency voltage and current components come across. Thus, an accurate knowledge of the transformer behavior in a wide frequency range is mandatory. A novel modeling procedure to relate the transformer physical behavior and its frequency response by means of electrical parameters is presented. Its usability is demonstrated by an example where a power transformer is used as filter and voltage reducer in an AC-DC-AC converter. Carlos Gonzalez-Garcia and Jorge Pleite Copyright © 2013 Carlos Gonzalez-Garcia and Jorge Pleite. All rights reserved. Comparative Studies of Different Switching Patterns for Direct and Indirect Space Vector Modulated Matrix Converter Sun, 30 Dec 2012 08:52:16 +0000 This paper presents a MATLAB/Simulink simulation of direct and indirect space vector modulation for matrix converter. Different switching patterns for both direct and indirect methods are simulated and compared. Three criteria are chosen to compare the performance of switching patterns: (1) total harmonic distortion (THD); (2) harmonic spectrum analysis of output voltages; and (3) number of switching in each switching period. Switching strategies are completely implemented using the power library in MATLAB/Simulink environment. Amin Shabanpour, Sasan Gholami, and Ali Reza Seifi Copyright © 2012 Amin Shabanpour et al. All rights reserved. Using Averaged Modeling for Capacitors Voltages Observer in NPC Inverter Thu, 27 Dec 2012 16:36:16 +0000 This paper developed an adaptive observer to estimate capacitors voltages of a three-level neutral-point-clamped (NPC) inverter. A robust estimated method using one parameter is proposed, which eliminates the voltages sensors. An averaged modeling of the inverter was used to develop the observer. This kind of modeling allows a good trade-off between simulation cost and precision. Circuit model of the inverter (implemented in Simpower Matlab simulator) associated to the observer algorithm was used to validate the proposed algorithm. Bassem Omri, Kaiçar Ammous, and Anis Ammous Copyright © 2012 Bassem Omri et al. All rights reserved. Integrating STATCOM and Battery Energy Storage System for Power System Transient Stability: A Review and Application Mon, 17 Dec 2012 11:16:45 +0000 Integration of STATCOM with energy storage devices plays an imperative role in improving the power system operation and control. Significant research has been done in this area for practical realization of benefits of the integration. This paper, however, pays particular importance to the performance improvement for the transients as is achievable by STATCOM with battery-powered storage systems. Application of STATCOM with storage in regard to intermittent renewable energy sources such as wind power generation is also discussed in the paper. At the beginning of this paper, an overall review of the STATCOM and energy storage systems are elaborated. A brief overview of the advantages of using STATCOM in conjunction to energy storage systems in achieving power system stability is presented. In the second part of the paper, a typical transient stability model of a STATCOM is presented. The dynamics of real and reactive power responses of the integrated system to transients is studied. The study is aimed at showing that the combination of STATCOM and battery energy storage significantly improves the performance of the system. The final results show that the STATCOM reactive power/voltage control helps in transient stability enhancement. Arindam Chakraborty, Shravana K. Musunuri, Anurag K. Srivastava, and Anil K. Kondabathini Copyright © 2012 Arindam Chakraborty et al. All rights reserved. Analysis and Minimization of the Oscillatory Currents in Multibranch Thyristor-Switched Capacitors Mon, 17 Dec 2012 08:27:31 +0000 This paper addresses the switching transients in multibranch thyristor-switched capacitors (TSCs). The current transients following the addition of a branch to a group of already connected ones are analyzed. Expressions for both its fundamental and its oscillatory components are given in terms of the power network voltage, frequency, short-circuit level, and the switching angle. The relations include also the compensator parameters such as its total reactive power rating, total number of branches, the number of already connected branches, and the initial voltage on the capacitor involved in the switching transient. An expression for the distortion of the supply current is also given. A minimization procedure is presented for identifying the optimal switching angle leading to the least magnitude of the oscillatory current. Switching when the instantaneous supply voltage is equal to the initial voltage will result in the least oscillatory current only in the two special cases of a single-branch compensator, or in the switching of the first branch of a multi-branch TSC. The effect of both the total number of branches and the branch switching steps on the oscillatory current and on the optimal switching angle is also discussed. The advantage of the suggested procedure is demonstrated by investigating several case studies. Mohamed M. Saied Copyright © 2012 Mohamed M. Saied. All rights reserved. Analysis of a Microgrid under Transient Conditions Using Voltage and Frequency Controller Sun, 09 Dec 2012 10:01:21 +0000 This paper presents an investigation of voltage-and-frequency-(VF-) based battery energy storage system (BESS) controller used in micro grid for analyzing the optimum capability of plant. Microgrid is formed by using three hydropower plants feeding three-phase four-wire load. The proposed controller is used for load balancing, harmonic elimination, load leveling, and neutral current compensation. The proposed BESS controller permits the selection of an optimum voltage level of battery and allows independent current control of each phase. The main emphasis is given on maintaining constant voltage and frequency within the micro grid during transient conditions. Micro grid with power plant and its controller is modeled in MATLAB/Simulink using Power System Blockset (PSB) toolboxes. Monika Jain, Sushma Gupta, Deepika Masand, and Gayatri Agnihotri Copyright © 2012 Monika Jain et al. All rights reserved. Interrupting Short-Circuit Direct Current Using an AC Circuit Breaker in Series with a Reactor Wed, 28 Nov 2012 08:00:30 +0000 This paper describes and demonstrates the principle and efficacy of a novel direct current fault interruption scheme using a reactor in series with a controlled rectifier and a conventional AC circuit breaker. The presence of the series reactor limits the capacitive discharge current from the DC filter capacitor at the output terminals of the phase-controlled rectifier. In addition, the series reactor along with the filter capacitor forms an underdamped series RLC circuit which forces the fault current to oscillate about zero. This synthetic alternating current can then be interrupted using a conventional AC circuit breaker. The selection criteria for the series reactor and overcurrent protection are presented as well. Using the proposed scheme for an example case, a DC fault current magnitude is reduced from 56 kA to 14 kA, while the interruption time is reduced from 44 ms to 25 ms. Saurabh Kulkarni and Surya Santoso Copyright © 2012 Saurabh Kulkarni and Surya Santoso. All rights reserved. A High-Efficiency, Low-Cost Solution for On-Board Power Converters Sun, 25 Nov 2012 16:13:30 +0000 Wide-input, low-voltage, and high-current applications are addressed. A single-ended isolated topology which improves the power efficiency, reduces both switching and conduction losses, and heavily lowers the system cost is presented. During each switching cycle, the transformer core reset is provided. The traditional tradeoff between the maximum allowable duty-cycle and the reset voltage is avoided and the off-voltage of active switches is clamped to the input voltage. Therefore, the system cost is heavily reduced and the converter is well suited for wide-input applications. Zero-voltage switching is achieved for active switches, and the power efficiency is greatly improved. In the output mesh, an inductor is included making the converter suitable for high-current, low-voltage applications. Since the active clamp forward converter is the closest competitor of the proposed converter, a comparison is provided as well. In this paper, the steady-state and small-signal analysis of the proposed converter is presented. Design examples are provided for further applications. Simulation and experimental results are shown to validate the great advantages brought by the proposed topology. V. Boscaino and G. Capponi Copyright © 2012 V. Boscaino and G. Capponi. All rights reserved.