Online ISSN
1755-4543
Print ISSN
1755-4535
IET Power Electronics
Volume 5, Issue 8, September 2012
Volumes & issues:
Volume 5, Issue 8
September 2012
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- Author(s): H. Ghoreishy ; A.Y. Varjani ; S. Farhangi ; M. Mohamadian
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1245 –1253
- DOI: 10.1049/iet-pel.2012.0111
- Type: Article
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For high-power applications, cascaded H-bridge (CHB) inverters are conventionally controlled by selective harmonic mitigation (SHM) strategy. This technique is applied to reduce the switching loss and the optimised switching angles are calculated to mitigate low-order harmonics at the output voltage. However, this strategy causes an uneven power distribution among the CHB cells. Also mitigating more harmonics needs more number of pulses and consequently higher switching frequency and dissipated power. This study proposes a new hybrid CHB inverter with optimised dc sources. Considering the optimisation of the CHB dc sources' values along with the optimised switching angles, significant improvements such as mitigating more low-order harmonics, even power distribution among the CHB cells and reducing the switching loss are achieved. Analysis and simulations are carried out on a five-level CHB inverter. Experimental verifications also validate the simulation results. The results demonstrate that the new hybrid CHB inverter considerably improves the performance of the conventional SHM strategy. - Author(s): P. Acuña ; L. Moran ; J. Dixon
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1254 –1261
- DOI: 10.1049/iet-pel.2012.0057
- Type: Article
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A series active filter to compensate current harmonics injected by high-power rectifiers [such as in copper electro-winning (EW) and electro-refining (ER) processes] is presented and analysed. The proposed current harmonic compensation method is accomplished by injecting a corresponding series voltage distortion at the rectifier ac terminals. The distorted ac voltage generated at the high-power rectifier ac terminal forces the line current to be sinusoidal and increases dc voltage distortion, but it does not affect the EW or ER processes. A complete design procedure for the series active system is presented. In conjunction with simulated results obtained from a 10 MVA copper EW facility, a 2 kVA laboratory prototype is used to validate the current harmonic compensator scheme. The results obtained through simulation and from the experimental prototype confirm the viability of the proposed compensator and associated control strategy. - Author(s): Y.J. Bao ; K.W.E. Cheng ; N.C. Cheung ; S.L. Ho
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1262 –1269
- DOI: 10.1049/iet-pel.2012.0115
- Type: Article
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Renewable energy sources require power electronics for the power processing in order to enhance the operation and performance. In this study, a method of harnessing wind power on-board of an electric vehicle using switched reluctance generator (SRG) coupled to a wind turbine, which is mounted on the vehicle is discussed. The wind turbine integrated with SRG poses a number of challenges for vehicle application as the location and the design are special. The present investigation aims at acquiring the first hand experience in the practical implementation of such a system for on-board power generation. Various configurations of wind turbines are studied. The experimental test from a prototype is presented to validate the theoretical predictions. - Author(s): G.L. Calzo ; A. Lidozzi ; L. Solero ; F. Crescimbini
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1270 –1281
- DOI: 10.1049/iet-pel.2012.0130
- Type: Article
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Z-source converter configurations make it possible to overcome intrinsic limits present in conventional ac–dc and dc–ac converters. A typical three-phase inverter cannot supply output voltages greater than the voltages at its input; in the same manner, a typical three-phase boost rectifier cannot supply output voltages lower than input voltages. Using Z-source topology permits overcoming both these limits. In fact, a Z-source boost rectifier can theoretically either step-up or step-down the output voltage to any desired value starting from the conventional three-phase diode bridge rectifier output voltage level. In addition, it presents intrinsic immunity to shoot-through states, resulting in improved reliability of the entire system. In this study, attention is focused on the mathematical modelling of a three-phase Z-source boost rectifier for power factor correction power supply applications; using such a topology as first-stage converter allows designing the second-stage converters with the same voltage constraints of single-phase units. - Author(s): R. Shillington ; P. Gaynor ; M. Harrison ; W. Heffernan
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1282 –1290
- DOI: 10.1049/iet-pel.2011.0404
- Type: Article
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Recent advances have resulted in the availability of a new generation of silicon carbide (SiC) junction field effect transistors (JFETs), which unlike previous generations, exhibit highly desirable normally off characteristics. Normally off SiC JFETs are characterised with particular focus on previously unknown reverse conduction characteristics. Refinements are proposed to JFET gate driving circuits that allow their implementation as a single-chip solution. Reverse recovery characteristics of SiC JFETs were measured using diode testing techniques and found to be significantly faster than typical silicon metal oxide semi-conductor field effect transistor (MOSFET) body diodes. SiC JFETs are compared with silicon MOSFETs in power factor correction boost converters, including a real-world application where superior power conversion efficiency utilising SiC JFETs is demonstrated. - Author(s): C. Carretero ; O. Lucia ; J. Acero ; R. Alonso ; J.M. Burdio
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1291 –1297
- DOI: 10.1049/iet-pel.2012.0113
- Type: Article
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Domestic induction heating systems are usually modelled as an electrical equivalent composed of the series or parallel connection of an equivalent resistor and inductor. This model allows obtaining useful time-domain results in order to extract design conclusions for the power electronic converter. However, this model neglects the dependence of the equivalent electrical parameters with frequency. This dependence becomes a key parameter when the induction system varies the excitation frequency with the purpose of adapting the output power. In order to overcome this limitation, this study proposes a modelling strategy to take into account the influence of frequency divided into two steps. First, the frequency-dependent impedance is obtained by means of a finite-element analysis tool. Afterwards, a passive network composed of several inductors and resistors in series and parallel connection are used to fit the frequency response of the induction load. The proposed strategy allows obtaining a more accurate model of the induction heating load. Moreover, as there is no need to build previous prototypes, the design process is optimised. The feasibility of this proposal has been tested by comparing time-domain simulations with oscilloscope measurements in a real domestic induction heating system. - Author(s): M. Sadeghi ; S.H. Hosseini ; R. Alizadeh ; M.R. Banaei
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1298 –1304
- DOI: 10.1049/iet-pel.2012.0128
- Type: Article
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Multilevel converters are very interesting alternatives for medium and high-power applications. This study presents a new configuration of multicell converters. The main advantages of the proposed converter, in comparison with conventional flying capacitor multicell (FCM) and stacked multicell (SM) converters, are doubling the number of output voltage levels and the root mean square (RMS), improving the output voltage frequency spectrum and lowering the number and rating of components and decreasing the converter losses. Furthermore, the stored energy and rating of flying capacitors will be decreased to half in this topology in comparison with FCM and SM converters. These improvements are achieved by adding only four low-frequency switches to the conventional SM converters configuration. In this topology, the number of high-frequency switches is decreased while the voltage ratings of them during a full cycle are kept constant. Also, a modified phase shifted pulse-width-modulation-based control method has been applied to the proposed topology, which can decrease the harmonic distortions and THD. The circuit is simulated using PSCAD/EMTDC software and simulation results are presented to validate the effectiveness and advantages of the proposed configuration. In addition, the experimental results of proposed configuration prototype have been presented to examine its practicability. - Author(s): A.M. Shiddiq Yunus ; A. Abu-Siada ; M.A.S. Masoum
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1305 –1314
- DOI: 10.1049/iet-pel.2012.0135
- Type: Article
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Application of distributed wind energy conversion systems (WECS) in modern power systems and smart grids has significantly increased during the last decade. In particular, wind turbines equipped with doubly fed induction generator (DFIG) have dominated the market since 2004 as they represented about 55% of the worldwide total wind capacity during this year. This study investigates the application of superconducting magnetic energy storage (SMES) units to improve the dynamic performance of DFIG-based WECS during small and large disturbances in the grid side. A new control approach for the SMES unit using hysteresis current regulator and fuzzy logic is introduced. Detailed simulation results show that the proposed SMES controller is very effective in improving the dynamic performance of the WECS and is able to maintain its parameters within the safety margins of various grid codes during disturbance events considered in this study. - Author(s): M.S. Hamad ; M.I. Masoud ; B.W. Williams ; S. Finney
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1315 –1323
- DOI: 10.1049/iet-pel.2011.0373
- Type: Article
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In this study, a shunt active power filter (APF), with predictive current control is coupled to the 12-pulse converter in two different configurations where the same performance is achieved. The proposed configuration (the second configuration) utilises a three-winding transformer (star/tapped-star/delta) with an APF connected to the secondary taps. This transformer configuration reduces the filter side voltage avoiding the need of a high bandwidth step-down transformer. This reduces the voltage rating of the APF switches, consequently, increases the switching frequency limit. Moreover, the APF-injected compensation current is minimised, as it utilises the natural mitigation of the current harmonic components generated by each 6-pulse converter, because of the phase shift property of the front-end transformer. The APF is controlled to compensate system reactive power, distortion and the oscillating power at the converter ac side. The compensated sinusoidal input current has acceptable total harmonic distortion (THD) and near unity power factor. The converter operates under a specific power locus that compromises between a symmetrical firing power locus and asymmetrical firing loci. This locus provides minimum input current THD when the reactive power is less than 0.5 pu. The simulation results for compensating a 3.3-kV, medium voltage, MV, 12-pulse converter system are experimentally verified using a scaled prototype 12-pulse converter with a shunt APF. - Author(s): K. Mathew ; J. Mathew ; N.A. Azeez ; A. Dey ; L. Umanand ; K. Gopakumar
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1324 –1332
- DOI: 10.1049/iet-pel.2012.0095
- Type: Article
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This study proposes an inverter circuit topology capable of generating multilevel dodecagonal (12-sided polygon) voltage space vectors by the cascaded connection of two-level and three-level inverters. By the proper selection of DC-link voltages and resultant switching states for the inverters, voltage space vectors whose tips lie on three concentric dodecagons, are obtained. A rectifier circuit for the inverter is also proposed, which significantly improves the power factor. The topology offers advantages such as the complete elimination of the fifth and seventh harmonics in phase voltages and an extension of the linear modulation range. In this study, a simple method for the calculation of pulse width modulation timing was presented along with extensive simulation and experimental results in order to validate the proposed concept. - Author(s): A. Kavitha ; G. Uma ; M. Beni Reesha
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1333 –1340
- DOI: 10.1049/iet-pel.2011.0175
- Type: Article
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This study investigates fast-scale instability in a power factor correction (PFC) Cuk converter under peak current-mode control. The converter is operated in continuous conduction mode. Computer simulations are performed to study the effects of various circuit parameters on fast-scale instabilities. A prototype of a PFC Cuk converter of 35 W is developed to verify the simulated results and the experimental results are presented. This work provides a clear picture of how the variation of certain parameters can render such a circuit fast scale unstable. Hence, a PFC Cuk converter can be designed to avoid distortion because of fast-scale bifurcation. - Author(s): S.P. Litrán and P. Salmerón
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1341 –1350
- DOI: 10.1049/iet-pel.2012.0055
- Type: Article
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A configuration consisting of a combination of a series active power filter (APF) and a parallel passive filter is shown to be an efficient system for non-linear load compensation. For this topology, different compensation strategies are proposed to control the series APF. The most effective strategies determine the APF compensation voltage in proportion to the source current harmonics. The proportionality constant ‘k’ in the control algorithm implementation is related to the APF gain and complete system dynamic. In this study, the system state model is obtained for three control strategies of series APF: compensation voltage proportional to source current harmonics, compensation voltage opposite to the load voltage harmonics and a hybrid strategy which combines both previous strategies. The analyses of the resulting models provide the information needed to establish design criteria with respect to harmonic filtering and system stability. The methodology proposed in this study eliminates the arbitrary choice of the proportionality constant. The three strategies were analysed in two different situations: sinusoidal supply voltages and distorted supply voltages. Finally, results of an experimental prototype developed for this purpose allowed the proposed analysis to be verified. - Author(s): J. Duarte ; L. Ricardo Lima ; L. Oliveira ; L. Michels ; C. Rech ; M. Mezaroba
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1351 –1358
- DOI: 10.1049/iet-pel.2012.0072
- Type: Article
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This study presents a single-stage (S2) isolated current rectifier with power factor correction, based on a full-bridge flyback converter. This converter is designed to operate with adjustable output voltage so that it can operate in two distinct operation modes, step-up or step-down, depending on the input and output voltages. The proposed converter presents some features that make it attractive for many applications, such as constant switching frequency, step-down and step-up operation, high power level capability and the absence of an auxiliary pre-loading circuit to control the inrush current. This study presents the theoretical analysis of the converter for continuous conduction mode as well as experimental results based on a 3 kW prototype. - Author(s): M. Shahparasti ; A. Yazdian ; M. Mohamadian ; A.S. Larijani ; A. Fatemi
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1359 –1366
- DOI: 10.1049/iet-pel.2011.0403
- Type: Article
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One limitation of the conventional parallel uninterruptible power supplies (UPSs) is that the battery and rectifier output DC voltages must be almost equal to each other and higher than the AC output peak voltage. To remove this constraint, a new configuration of parallel UPSs based on Z-source inverters (ZSIs) is proposed. This system supplies a common AC load with DC sources of different voltages and power ratings. Control of the proposed system consists of the ZSI and the current sharing control. To control the ZSI output voltage, dual-loop control technique is implemented. For ZSI DC link voltage control, direct and indirect methods are discussed and their effects on circulating current and system characteristic equation are studied. Moreover, two strategies are proposed for current sharing: equal current sharing (ECS) and proportional DC source nominal power rating current sharing (PCS). For implementing these strategies, a new current sharing algorithm based on 3C method is developed. The system operation with these methods is compared from the viewpoint of Z-source network response and maximum power supply duration. The performance of the proposed system is verified by simulation and is validated via experimental results. - Author(s): B. Li ; W. Yao ; L. Hang ; L.M. Tolbert
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1367 –1373
- DOI: 10.1049/iet-pel.2012.0102
- Type: Article
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Based on the introduction of a dual-loop current control strategy for a grid-connected inverter, an averaged switching model of a grid-connected inverter with an LCL-filter in discrete domain is built under a stationary frame and a proportional resonant (PR) regulator is adopted in the current loop to track the given fundamental sinusoidal current. The impacts of PR parameters, LCL parameters and digital delay on the root locus are studied, respectively. The parameters of the LCL-filter and the PR current regulator loop are designed to assure system stability and dynamic response during a wide power range by using the pole placements method. Finally, a 10 kW prototype of a grid-connected inverter with an LCL-filter is set up to verify the effectiveness, the practicality and robustness of the proposed PR current design method. - Author(s): S.M. Dabour and E.M. Rashad
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1374 –1378
- DOI: 10.1049/iet-pel.2012.0014
- Type: Article
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This study introduces a detailed analysis, design and implementation of a three-phase matrix converter based on space-vector modulation technique. The modulation strategy is described and modelled. All steps of hardware design using discrete semiconductor devices are given. The modulator is implemented using a digital signal processor. The experimental results for passive loading and three-phase induction motor conditions are given. Then the converter performance is discussed. - Author(s): H.-K. Liao ; T.-J. Liang ; L.-S. Yang ; J.-F. Chen
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1379 –1388
- DOI: 10.1049/iet-pel.2011.0102
- Type: Article
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This study presents a non-inverting buck–boost converter with an interleaved technique for fuel-cell systems. The converter transforms the fuel-cell energy into an electric current for efficiently running electric mobility systems. Two non-inverting buck–boost converters are integrated with an interleaved operation. Thus, a switch and a diode can be omitted, reducing cost. The interleaved operation reduces both the current ripple at the output and the current stress of the diodes. The operating principles and steady-state analysis are discussed in detail. An 800 W prototype circuit of the proposed converter that converts an input source (fuel-cell battery 24–45 V) into an output voltage (28 V) is built to verify performance. The synchronous rectifier technique is adopted to increase efficiency. Power loss and efficiency are also discussed. - Author(s): T.B. Salah ; S. Khachroumi ; H. Morel
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1389 –1396
- DOI: 10.1049/iet-pel.2010.0337
- Type: Article
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Wide band-gap semiconductor devices like silicon–carbide junction field effect transistor (SiC JFET) are being applied in several industrial applications. Converters using these advanced devices have been introduced. SiC JFETs from SiCED/Infineon enable design of diodeless inverters. This is a positive argument regarding reliability issues for a harsh environment. From a design point of view, primary circuit models of SiC JFET have already been published but the internal diode has not been addressed so far. There is thus an interest for an accurate model of the SiC JFET built-in diode. In this study, this internal diode is demonstrated to be a power PiN diode. A novel analytical state-space model of this diode is proposed and the design parameters are identified. It is important to note, that these parameters are crucial for the device behaviour, modelling and fabrication procedure. The proposed model and associated parameters are validated with built-in diodes of several SiC JFETs. The validity domains are discussed. - Author(s): A.H. Bhat ; N. Langer ; T. Hussain ; P. Agarwal
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1397 –1407
- DOI: 10.1049/iet-pel.2011.0125
- Type: Article
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In this study, parameter plane synthesis of a three-phase neutral-point clamped bidirectional rectifier has been performed. The converter involves one outer-loop PI voltage controller and two inner-loop proportional–integral (PI) current controllers for closed-loop control. A D-partition technique has been employed for precise design of the current controllers. The performance of the converter has been evaluated using MATLAB/Simulink software. An experimental prototype of the converter has been developed and the experimental investigation of the converter performance in closed loop has been carried out. DSP ‘DS1104’ of digital signal processing and control engineering (dSPACE) has been used for real-time implementation of the designed controllers. The converter gives a very good performance in steady-state and dynamic state (for rectification as well as inversion modes of operation) using the designed controller parameters. - Author(s): T.-J. Tseng ; C.-H. Wu ; L.-R. Chang-Chien
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1408 –1417
- DOI: 10.1049/iet-pel.2011.0206
- Type: Article
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A ramp signal with variable DC-offset (RSVDC) scheme implemented in a voltage-mode controlled buck voltage regulator is proposed. To enhance the response of the voltage-mode controlled buck regulator during the load transient, the variable DC-offset ramp signal is applied to drive the duty cycle full or zero, so that the output voltage can instantly respond with load change. The model, compensator and loop gain of the proposed buck regulator are derived and demonstrated. The transistor-level of the RSVDC circuit including the hysteretic comparator, oscillator and the output feedback voltage amplifier is also presented. The controller using the RSVDC scheme was implemented by the TSMC 0.35 µm 2P4M process. The simulated and experimental results show that the transient response using the RSVDC scheme is about 10 µs, when the load changes from 0.1 to 1 A under a 5–1.8 V voltage conversion. The test results validate the feasibility of the RSVDC control scheme in a buck voltage regulator to fulfil a simple structure, assured stability and fast transient response requirements. - Author(s): N. Ghasemi ; F. Zare ; A.A. Boora ; A. Ghosh ; C. Langton ; F. Blaabjerg
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1418 –1429
- DOI: 10.1049/iet-pel.2011.0457
- Type: Article
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Multilevel converters, because of the benefits they attract in generating high quality output voltage, are used in several applications. Various modulation and control techniques are introduced by several researchers to control the output voltage of the multilevel converters like space vector modulation and harmonic elimination (HE) methods. Multilevel converters may have a DC link with equal or unequal DC voltages. In this study a new HE technique based on the HE method is proposed for multilevel converters with unequal DC link voltage. The DC link voltage levels are considered as additional variables for the HE method and the voltage levels are defined based on the HE results. Increasing the number of voltage levels can reduce lower order harmonic content because of the fact that more variables are created. In comparison to previous methods, this new technique has a positive effect on the output voltage quality by reducing its total harmonic distortion, which must take into consideration for some applications such as uninterruptable power supply, motor drive systems and piezoelectric transducer excitation. In order to verify the proposed modulation technique, MATLAB simulations and experimental tests are carried out for a single-phase four-level diode-clamped converter. - Author(s): J. Korhonen ; T. Itkonen ; J.-P. Ström ; J. Tyster ; P.T. Silventoinen
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1430 –1437
- DOI: 10.1049/iet-pel.2011.0232
- Type: Article
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Electrical motor fed by voltage source inverters has been known to face transient overvoltage problems caused by the inverter switching operations. With the parallel inverter topology and with the modulation strategy presented in thisstudy, the motor terminal overvoltage can be reduced without any passive filtering. The parallel inverter topology has individual motor leads from each inverter connected at the motor terminals. Modulation strategy for any number of parallel inverters with current balancing is presented. Experimental results are presented for two and three parallel standard industry frequency converters to verify the method. - Author(s): M.E. Meral
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1438 –1445
- DOI: 10.1049/iet-pel.2012.0036
- Type: Article
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Static series compensator (SSC) topologies including shunt connected power electronic rectifier with no energy storage have some potential advantages such as an extra saving and the ability exists to compensate longer dips. However, this topology has the disadvantage that the uncontrolled DC link is connected to the supply with a shunt rectifier during the fault, and more importantly, the conventional diode bridge rectifier (C-DBR) does not draw sinusoidal current from the supply and inject current harmonics to the network. In this study, an improved topology for the SSCs using a single-switch active power factor correction (A-PFC) boost rectifier is proposed. Single-phase SSC topologies with load side shunt connected C-DBR and A-PFC are compared by obtaining the results for the DC-link voltages, the supply currents and the load voltages. The results show that the proposed new topology offers solutions to problems of the topology including C-DBR such as supply current harmonics and uncontrolled DC-link voltage and so a considerable performance improvement is achieved by using the proposed SSC topology. - Author(s): A.R. Beig
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1446 –1455
- DOI: 10.1049/iet-pel.2011.0490
- Type: Article
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Three-level voltage source inverters are preferred for high-power variable speed drives. Owing to low switching frequency the inverter output voltage will be rich in harmonics. The synchronised space vector pulse width modulation (SVPWM) guarantees half-wave, quarter-wave and three-phase symmetry in the output voltages, resulting in improved harmonic distortion even at low switching frequency. This study presents the experimental implementation details of the synchronised SVPWM algorithm for the complete operating region of the drive including the overmodulation region and six-step operation. The synchronised SVPWM is applied and tested on a constant v/f induction motor drive powered from a three-level cascaded H-bridge inverter. The performance of the algorithm at transient and steady-state conditions are studied. The experimental results are presented. - Author(s): H. Rodríguez-Cortés ; R. Alvarez-Salas ; M. Flota-Bañuelos ; M.F. Escalante
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1456 –1462
- DOI: 10.1049/iet-pel.2012.0040
- Type: Article
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Active rectifiers are commonly used to address two issues in electric power delivery: DC voltage regulation and AC power factor improvement, through current tracking. In this study, the authors propose a non-linear controller that solves the DC voltage regulation and the AC current tracking for the single-phase active rectifier. The proposed controller is based on a partial input–output feedback linearisation and an adaptive indirect control of the zero dynamics. Numerical simulations are included to evaluate the performance of the proposed controller. - Author(s): V.S.S.P.K. Hari and G. Narayanan
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1463 –1471
- DOI: 10.1049/iet-pel.2012.0078
- Type: Article
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Pulse width modulation (PWM) techniques involving different switching sequences are used in space vector-based PWM generation for reducing line current ripple in induction motor drives. This study proposes a hybrid PWM technique employing five switching sequences. The proposed technique is a combination of continuous PWM, discontinuous PWM (DPWM) and advanced bus clamping PWM methods. Performance of the proposed PWM technique is evaluated and compared with those of the existing techniques on a constant volts per hertz induction motor drive. In terms of total harmonic distortion in the line current, the proposed method is shown to be superior to both conventional space vector PWM (CSVPWM) and DPWM over a fundamental frequency range of 32–50 Hz at a given average switching frequency. The reduction in harmonic distortion is about 42% over CSVPWM at the rated speed of the drive. - Author(s): M. Chau ; A. Luo ; F. Ma ; Z. Shuai ; T. Nguyen ; W. Wang
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1472 –1482
- DOI: 10.1049/iet-pel.2011.0405
- Type: Article
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This paper proposes a novel online control method with time-delay compensation for HAPF with Injection Circuit. It includes two closed-control loops: the lower closed-control loop contains a conventional proportional-integral (PI) controller and HAPF with Injection Circuit model, whereas the upper closed-control loop is composed of predictive neural network, generalised predictive control and HAPF with Injection Circuit model. The purpose of the upper closed-control loop is to find a set of optimal PI parameters for the lower closed-control loop. A π-Smith predictive compensator is established to generalised current time-delay compensate and makes a 180° delay between the output current of HAPF with Injection Circuit and load harmonic current. The proposed control method is analysed for stability by ‘Lyapunov’ theorem. Compared with the conventional PI control method, the proposed control method shows the advantages of shorter response time, effectiveness in reducing harmonics and able to online control very well. It is implemented in HAPF with Injection Circuit with a 100 kVA active power filter installed in a copper mill in Northern China. The simulations and experiments as well as industrial applications have verified the effectiveness of this control method. - Author(s): B. Jacob and M.R. Baiju
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1483 –1490
- DOI: 10.1049/iet-pel.2012.0047
- Type: Article
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In this study, sigma–delta (ΣΔ) modulation-based random pulse width modulations (PWM) scheme with vector quantisation for three-level inverter is proposed. In the proposed scheme, the instantaneous reference space vector is mapped to an equivalent two-level inverter and the proposed space-vector-based ΣΔ modulation is applied on this mapped reference space vector. The scheme uses the principle of vector quantisation for quantising the mapped reference space vector in the ΣΔ modulator. The switching signals are generated directly from the amplitude of the three-phase reference signal without using lookup table and complex arithmetic calculations. The resultant vectors of the two-level inverter can be easily translated to the actual switching vectors, and this proposed method of working on the mapped reference space vector makes the proposed scheme suitable for any general n-level inverter. The switching vectors of the inverter are naturally selected ensuring optimum switching sequence under all conditions including the over-modulation region. The proposed scheme is implemented for three-level inverter driving a two-horse power (HP) three-phase induction motor. The performance of the proposed scheme is compared with space-vector PWM scheme and random PWM schemes with different modulation indices and experimental results are presented. - Author(s): E. Koutroulis and F. Blaabjerg
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1491 –1499
- DOI: 10.1049/iet-pel.2012.0105
- Type: Article
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The transformerless photovoltaic (PV) inverters are the major functional units of modern grid-connected PV energy production systems. In this study, a new optimisation technique is presented for the calculation of the optimal types and values of the components comprising a transformerless PV inverter, such that the PV inverter levelised cost of the generated electricity is minimised. The proposed method constitutes a systematic design process, which is capable to explore the impact of the PV inverter configuration on the trade-off between the PV inverter manufacturing cost and the power losses affecting the corresponding energy production. The design optimisation results demonstrate that the optimal values of the PV inverter design variables depend on the inverter specifications, the technical and economical characteristics of the components used to build the PV inverter and the meteorological conditions prevailing at the installation area. Compared with non-optimised transformerless inverters, the PV inverter structures derived using the proposed design optimisation methodology exhibit lower manufacturing cost and simultaneously are capable of producing more energy into the electric grid system. - Author(s): N.N.V. Surendra Babu and B.G. Fernandes
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1500 –1509
- DOI: 10.1049/iet-pel.2012.0120
- Type: Article
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A static VAr compensation scheme using 12-sided polygonal voltage space vectors for high power application is proposed in this study. Using the polygonal voltage space vectors, the dc bus utilisation is increased in linear modulation region and total harmonic distortion (THD) is improved significantly in over modulation region. The power circuit topology consists of two standard two-level inverters, which are connected in cascade through an open-ended winding transformer. In order to obtain the polygonal voltage space vectors, the dc-link voltage of inverter 2 is maintained at 0.366 times the dc-link voltage of inverter 1. A simple control strategy to maintain the required dc-link voltage ratio as well as for reactive power compensation is proposed. To verify the proposed strategy, simulation is carried in MATLAB/SIMULINK. Simulation study is performed in linear, over modulation regions of the inverter and also with unbalanced network voltages. A laboratory prototype is designed and developed to validate the simulation results. Further, this scheme is compared with a sinusoidal pulse width modulation-based VAr compensation scheme using the same topology. - Author(s): P.S. Almeida and H.A.C. Braga
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1510 –1518
- DOI: 10.1049/iet-pel.2011.0402
- Type: Article
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The aim of this study is to analyse the application to fluorescent lighting of a non-resonant electronic ballast, focusing on a specific low-cost single-switch topology. Its complete mathematical analysis, which has not been fully explored in the past, and its practical implementation as a DC-fed electronic ballast unit are provided. The ballast here presented was successfully prototyped and is capable of pre-heating, igniting and driving two or more fluorescent light bulbs associated in series, having also an intrinsic protection against broken filaments and lamp absence. Furthermore, it relies solely on a single power switch and a relatively small-sized inductor per lamp, plus simple op-amp-based control circuitry. An additional protection circuitry is also presented in this study, for protecting the power switch against lamp faulty conditions. Good efficiency was achieved with ballast prototype and cost effectiveness for the proposed lighting system is demonstrated in this work. - Author(s): S. Sharma and B. Singh
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1519 –1526
- DOI: 10.1049/iet-pel.2011.0367
- Type: Article
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This study deals with an implementation of a constant speed permanent magnet synchronous generator (PMSG)-based three-phase stand-alone wind energy conversion system (SWECS). The voltage and frequency controller is realised using only a single voltage source converter (VSC) and a battery energy storage system (BESS). The BESS is used to provide load levelling under varying wind speeds and to control frequency of SWECS. The voltage of PMSG is regulated under varying wind speeds and loads by supplying the reactive power from VSC. The performance of SWECS is demonstrated as a load leveller, a load balancer, a harmonic compensator and a voltage and frequency controller. - Author(s): J. Merry Geisa and M. Rajaram
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1527 –1534
- DOI: 10.1049/iet-pel.2011.0472
- Type: Article
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In today's commercial world, uninterruptible power supply (UPS) is playing a significant role in preventing the computer from power failure. Inverter is one of the essential components of UPS that performs DC–AC conversion. In this process, there is a possibility of generation of harmonic peaks because majority of the power utilities are nonlinear loads. In UPS powered by a multilevel inverter, the harmonics can be eliminated by an optimal selection of switching angles. In this study, the authors propose a hybrid technique to entirely eliminate the harmonics. The proposed hybrid technique utilises an iterative technique and fuzzy logic for the optimal selection of switching angles. A hybrid evaluation technique is used to evaluate the optimum switching angles that are obtained from the iteration as well as the fuzzy logic. The proposed technique is tested with a three-level H-bridge inverter and the resultant fundamental and harmonics voltage are analysed. The experimental result shows the efficiency of the proposed technique in eliminating the harmonics that are generated by the inverter. The proposed technique is implemented in MATLAB and its performance is evaluated using diverse test results. - Author(s): Z. Chen ; L. Shi ; F. Ji ; S. Liu
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1535 –1543
- DOI: 10.1049/iet-pel.2011.0502
- Type: Article
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A phase-shift full-bridge zero-voltage-switching (ZVS) pulse-width-modulated (PWM) converter with commutation capacitor and inductor-capacitor (LC) auxiliary circuit is proposed. This converter contains the advantages of small rectifier voltage oscillation as well as no duty cycle loss, and realises ZVS for all primary switches over a wide load range. In this study, the mechanism of the rectifier voltage oscillation is discussed in detail. The operation principle of the circuit is described and design considerations of the converter are discussed. Finally, the experimental results from a 650 W/28 V, 100 kHz prototype are given to confirm the operation, validity and features of the proposed converter. - Author(s): M. Monfared ; M. Sanatkar ; S. Golestan
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1544 –1550
- DOI: 10.1049/iet-pel.2012.0131
- Type: Article
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In this study, a simple digital power control technique for single-phase grid-tie converters is proposed. The suggested technique is based on the application of dead-beat control theory to the instantaneous powers in the virtual two-axis reference frame. A voltage estimation scheme is added to the proposed direct power control algorithm that allows grid voltage sensorless operation. The simulation and experimental results confirm that the proposed control strategy provides fast, accurate and decoupled power control with a lower alternating current distortion. - Author(s): C.-H. Wu and L.-R. Chang-Chien
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1551 –1559
- DOI: 10.1049/iet-pel.2011.0286
- Type: Article
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Low-dropout voltage regulators (LDOs) have been widely used in the mobile electronic devices. Owing to the energy saving purpose, LDOs are required to perform fast-transient response with low quiescent current as they operate at low supply voltage condition. Generally, designing the high gain operational amplifier is more challenging under the low supply voltage. The situation would be more complex when the ultra fast-transient response of the LDO is preferred in the design specification. This study proposes a LDO that adopts cascading technique using ‘multipath nested Miller compensation’ for solving the low supply voltage problem. To further improve the transient response, a full quiescent current enhancement circuit is supplemented to the LDO control loop. Compared with the other dynamic bias approaches, the proposed technique raises the quiescent current to the maximum quantity during the load transient so that the load response of the LDO is further improved. Systematic analyses show that the stability is guaranteed. The designed LDO was implemented by a 0.35-µm complementary metal-oxide-semiconductor (CMOS) process. Test results show that the voltage spike under the 50-mA load change within 300 ns is improved ∼62% compared to that of the LDO without the proposed circuit. The recovery time is less than 1 µs. - Author(s): Y.-W. Cho and B.-H. Kwon
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1560 –1568
- DOI: 10.1049/iet-pel.2011.0355
- Type: Article
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This study proposes a novel topology of the ac–dc converter using direct power conversion that has a simple structure and achieves high efficiency. The proposed converter is derived by integrating the step-down ac chopper and the output-voltage doubler. The proposed converter provides direct ac–dc conversion and isolated dc output voltage without using any full-bridge diode rectifier. The step-down ac chopper using an active-clamp mechanism serves to clamp the voltage spike across the main switches and provides zero-voltage turn-on switching. The resonant-current path formed by the leakage inductance of the transformer and the resonant capacitor of the output-voltage doubler achieves the zero-current turn-off switching of the output diodes. The operation principle of the converter is analysed and verified. A 500 W prototype is implemented to show the performance of the proposed converter. The prototype provides maximum efficiency of 95.1% at the full load. - Author(s): J.B. Wang
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1569 –1580
- DOI: 10.1049/iet-pel.2012.0216
- Type: Article
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In this study, a primary droop current sharing controller with output current commitment capability for a stand-alone renewable energy source was proposed. The specially designed DC/DC converter for renewable energy source consists of feedforward, voltage and droop current sharing control loops; furthermore, the droop voltage compensated scheme is also designed to improve current sharing performance under variation of the input voltage. When the renewable energy is abundant, the DC/DC converter with respect to this energy source can provide more load current and also can save energy bill from utility. The output voltage magnitude of the maximum power point tracking (MPPT)-controlled converter is used to signal the status of the renewable energy for the output current commitment judgment, and then shifts the output voltage droop characteristics to adjust output current through an 8 bits microprocessor PIC16F876. Finally, the design and analysis of the proposed scheme are introduced in this paper and some simulation and experimental results are also provided. - Author(s): Y. Jiang and J.A. Abu Qahouq
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1581 –1592
- DOI: 10.1049/iet-pel.2012.0157
- Type: Article
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This study presents a maximum power point tracking (MPPT) method and controller for a multi-channel (N-channel) photovoltaic solar system. The N-channel single-sensor MPPT (SS-MPPT) controller is able to track the maximum power point (MPP) of each solar panel using only one output current sensor in the N-channels. Compared with a conventional N-channel MPPT system which requires N voltage sensors, N current sensors, 2N analogue-to-digital converters (ADCs) (or an ADC with 2N channels) and N-MPPT controllers along with the associated conditioning circuitries, the proposed method only requires one sensor, one ADC and one MPPT controller. In the proposed N-channel SS-MPPT controller, the MPPT for each channel is achieved by tracking the maxima of the output (load) current (resulting in the maxima of the system output power) using the Perturb and Observe algorithm and the maxima of each channel power via channel output current difference optimisation. Two algorithms which can be used to realise the SS-MPPT controller are discussed and compared. The concept and operation of the SS-MPPT controller is presented, analysed and verified by results obtained from a proof-of-concept experimental prototype. - Author(s): K. Ramash Kumar and S. Jeevananthan
- Source: IET Power Electronics, Volume 5, Issue 8, p. 1593 –1604
- DOI: 10.1049/iet-pel.2011.0442
- Type: Article
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This study presents a reduced-order state-space average model and a fixed switching frequency (FSF) sliding mode controller (SMC) for the negative output elementary super lift Luo-converter (NOESLLC) operated in continuous conduction mode for application fields requiring the constant power source such as medical, telecommunication, industrial, military etc. The NOESLLC is an attractive dc-dc converter that can provide high-voltage transfer gain. Owing to the time-varying switched mode operation, the dynamic performance of the NOESLLC becomes highly non-linear. In order to enhance the dynamics performance and output voltage regulation of the NOESLLC, the FSFSMC is developed. The proposed FSFSMC is more appropriate to the inherently variable-structured NOESLLC when represented in the reduced-order state-space average-based mathematical model. The three conditions of FSMSMC applicable to the NOESLLC, namely, existence, reaching and stability conditions are analysed. The performance of the developed controller is validated for its robustness to perform over a wide range of working conditions through both in MATLAB/Simulink models and as well as in the laboratory prototype with the comparative study of a typical proportional-integral-controller. Theoretical analysis, simulation and experimental results are presented to demonstrate the feasibility of the designed FSFSMC along with the complete systematic design procedure.
Hybrid cascaded H-bridge inverter with even power distribution and improved total harmonic distortion: analysis and experimental validation
Current harmonics compensation for electrolytic processes using a series active scheme
Experimental examination on a new switched reluctance wind power generator system for electric vehicles
Three-phase Z-source power supply design
Silicon carbide JFET reverse conduction characteristics and use in power converters
Frequency-dependent modelling of domestic induction heating systems using numerical methods for accurate time-domain simulation
New mixed stacked multicell converter with interesting advantages
Improving dynamic performance of wind energy conversion systems using fuzzy-based hysteresis current-controlled superconducting magnetic energy storage
Medium voltage 12-pulse converter: ac side compensation using a shunt active power filter in a novel front end transformer configuration
Multilevel dodecagonal space-vector generation for induction motor drives by cascading three-level and two-level inverters
Analysis of fast-scale instability in a power factor correction Cuk converter
Analysis and design of different control strategies of hybrid active power filter based on the state model
Single-stage high power factor step-up/step-down isolated AC/DC converter
Parallel uninterruptible power supplies based on Z-source inverters
Robust proportional resonant regulator for grid-connected voltage source inverter (VSI) using direct pole placement design method
Analysis and implementation of space-vector-modulated three-phase matrix converter
Non-inverting buck–boost converter with interleaved technique for fuel-cell system
Silicon–carbide junction field effect transistor built-in diode: an experimentally verified electrical model
Synthesis and performance investigation of a digitally controlled three-phase neutral-point clamped bidirectional rectifier
Fast transient voltage-mode buck regulator applying ramp signal with a variable DC-offset scheme
Harmonic elimination technique for a single-phase multilevel converter with unequal DC link voltage levels
Active motor terminal overvoltage mitigation method for parallel voltage source inverters
Using active power factor correction (PFC) boost rectifiers for an improved topology of static series compensators with no energy storage
Constant v/f induction motor drive with synchronised space vector pulse width modulation
Power factor compensation and DC-link voltage regulation for a single-phase PWM multilevel rectifier
Space-vector-based hybrid pulse width modulation technique to reduce line current distortion in induction motor drives
Online control method with time-delay compensation for hybrid active power filter with Injection Circuit
Simple multilevel inverter-based induction motor drive scheme using sigma–delta converter with space-vector quantiser
Methodology for the optimal design of transformerless grid-connected PV inverters
Cascaded two-level inverter-based multilevel static VAr compensator using 12-sided polygonal voltage space vector modulation
Single-switch non-resonant electronic ballast to integrate a low-cost fluorescent lighting system
Control of permanent magnet synchronous generator-based stand-alone wind energy conversion system
Selective elimination of harmonic contents in an uninterruptible power supply: an enhanced adaptive hybrid technique
Mechanism and suppression countermeasure of voltage oscillation for full bridge converter
Direct active and reactive power control of single-phase grid-tie converters
Design of the output-capacitorless low-dropout regulator for nano-second transient response
Novel topology of ac–dc converter using direct power conversion
Parallel DC/DC converters system with a novel primary droop current sharing control
Single-sensor multi-channel maximum power point tracking controller for photovoltaic solar systems
Modelling and implementation of fixed switching frequency sliding mode controller for negative output elementary super lift Luo-converter
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