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Power Electronics, IET

Issue 5 • Date May 2013

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Displaying Results 1 - 20 of 20
  • Voltage balancing scheme for flying capacitor multilevel converters

    Publication Year: 2013 , Page(s): 835 - 842
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1060 KB)  

    This study proposes a voltage balancing scheme for flying capacitors multilevel converters. The strategy is based on the redundancy of switching states. By using analytic expressions, the authors study the balancing properties of each switching state. Then, based on such properties, the authors choose the switching state which drives the capacitor voltages towards their reference values, and simultaneously will ensure the desired voltage level. The method can be particulary attractive for those applications where the typical pulse-width modulation control is not used, as direct torque control, hysteresis control and sliding-modes control. Experimental results demonstrate the effectiveness of the proposed control scheme, in steady and dynamic conditions. View full abstract»

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  • Dynamic performance investigation of d-q model with PID controller-based unified power-flow controller

    Publication Year: 2013 , Page(s): 843 - 850
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Reactive power compensation is a main problem in the control of electric power system. Reactive power from the source increases the transmission losses and reduces the power transmission ability of the transmission lines. In addition, reactive power must not be transmitted throughout the transmission line to a longer distance. Consequently, flexible ac transmission systems devices such as static compensator unified power-flow controller (UPFC) and static volt-ampere compensator are used to ease these harms. UPFC is the mainly adaptable and composite power electronic equipment that has emerged as the vital equipment for the control and optimisation of power flow in electrical power transmission system. In this study, a d-q model-based UPFC is developed with proportional-integral (PI) and PID controller. The above controllers are simulated using MATLAB and their performance is analysed. Outcome of the analysis shows the superiority of PID control over the PI control method. Also this study presents comparative evaluation (both controllers) of dynamic response when initial and final load disturbances. View full abstract»

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  • Reactive power allocation for loss minimisation in a stand alone variable speed constant frequency double output induction generator

    Publication Year: 2013 , Page(s): 851 - 861
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1235 KB)  

    Vector control algorithms reported so far for stand alone operation of variable speed constant frequency double output induction generators propose to supply the full magnetisation current of the machine in addition to the torque producing component from the rotor side converter. As the rotor of a normal induction machine is not designed for this additional load this approach leads to underutilisation of the machine torque capacity. Moreover, supplying the entire magnetisation current from the rotor side is not optimal from the point of view of the machine losses. Since the load voltage is regulated by manipulating the magnetising current through a slow acting flux control loop undesirable fluctuations in the load voltage waveforms are observed during fast load transients. An improved stator flux oriented control strategy for this type of generators, proposed in this study, eliminates undesirable load voltage transients by directly regulating the stator flux through the stator side converter. The total reactive power demand of the system is dynamically distributed between the two converters according to an optimum allocation program so as to minimise the losses without disturbing the stator flux. The effectiveness of the proposed algorithms is verified experimentally on a laboratory prototype. View full abstract»

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  • Family of zero-voltage-switching unregulated isolated step-up DC-DC converters

    Publication Year: 2013 , Page(s): 862 - 868
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    This study presents a family of zero-voltage-switching (ZVS) unregulated isolated step-up DC-DC converters. All switches can realise ZVS using the magnetising current of the transformer. The ZVS unregulated isolated step-up DC-DC converters are deduced from the basic ZVS cells using the magnetising current. The ZVS condition for the switches is given. The operating principle is analysed taking the ZVS push-pull forward (PPF) unregulated DC-DC converter as an example. The ZVS-oriented parameter design and example are presented. Finally, the experimental results from a 1 kW ZVS PPF unregulated DC-DC converter support the theory. View full abstract»

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  • Fault diagnosis scheme for open-circuit faults in field-oriented control induction motor drives

    Publication Year: 2013 , Page(s): 869 - 877
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (809 KB)  

    In this study, a new model-based fault detection and isolation (FDI) strategy is proposed for field-oriented control (FOC) induction motor (IM) drives. Actuator faults are addressed, and specifically, single open-circuit faults are considered in this study. The residual signals are synthesised by taking the resulting closed-loop dynamics when a FOC strategy is applied, that is, the residuals are referenced to the synchronous reference frame (dqe-coordinates), which are generated by using a bank of variable structure observers to obtain a robust FDI scheme. Thus, subsystems sensitive to a specific fault, but decoupled from other faults are obtained in a natural way, where only two stator currents and the mechanical position are required for fault isolation purposes. Residual evaluation is carried out in the stator reference frame (dq-coordinates) for the IM model, where the residual direction (angle) is employed to isolate a fault in each one of the six power switches in a voltage source inverter. In addition, the observer FDI scheme can be combined with a fault re-configuration strategy in order to improve the reliability of the motor drive. Experimental results are illustrated for a three-phase 3/4 HP IM drive at different reference frequencies and load torques with single open-circuit faults that verify the ideas presented in this work. View full abstract»

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  • Series H-bridge with stacked multicell inverter to quadruplicate voltage levels

    Publication Year: 2013 , Page(s): 878 - 884
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (881 KB)  

    In this study, a series H-bridge with stacked multicell inverter (SHSI) is suggested which is commonly suitable for a high number of steps and for generating all levels at the output associated with a low number of circuit devices including switches and related gate driver circuits for each switch. The main advantages of the suggested topology compared with traditional flying capacitor multicell and stacked multicell (SM) inverters are increasing the number of output voltage levels and the root-meansquare value as much as four times, and doubles compared with mixed stacked multicell inverter. SHSI is compared with the mentioned structures improving the output voltage harmonic contents and decreasing the number and rating of components thereby reducing the cost and installation area and decreasing the stored energy and rating of flying capacitors. These sufficiencies are obtained by adding only four low-frequency switches and a DC source to the traditional SM inverters structure. Provided simulation and experimental results certify the feasibility and good performance of the suggested inverter. View full abstract»

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  • Implementation of dual-loop controller for positive output elementary luo converter

    Publication Year: 2013 , Page(s): 885 - 893
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (611 KB)  

    two-loop controller has been designed for a positive output elementary Luo (POEL) converter. An H∞ controller is used in the outer loop using the loop-shaping concepts and a sliding mode control (SMC) in the inner loop for the regulation of the output voltage in spite of the perturbations in the line and load voltages. H∞ controller generates the current reference for the converter inductor current, whereas SMC forces the converter inductor current to follow the reference. A practical design that combines the loop-shaping technique with SMC to enhance robustness and sliding performance is proposed. The closed-loop characteristics of a typical low-power POEL converter with the proposed controller implemented in the actual switched model is validated through computer simulations and experimental hardware. The proposed controller is found to be superior because of its low distortion property, good regulating performance and insensitivity to load variations. Nomenclature x iL1 vC1 iL2 v0 T, state variable vector Vo, Vin, Vref instantaneous input voltage, output voltage and reference voltage iref reference View full abstract»

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  • Methods of source current reference generation for predictive control in a direct matrix converter

    Publication Year: 2013 , Page(s): 894 - 901
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (715 KB)  

    Two control strategies that allow the control of source and load currents for direct matrix converters are presented in this study. Both methods use the switching state of the converter in the subsequent sampling time, based on an optimisation algorithm given by a simple cost function and the discrete system model. The control goals include regulation of load currents according to an arbitrary reference and good tracking of the source currents to their references. In the first method, the input current reference is given as a function of the instantaneous active power. In the second case, the source current reference is given as a function of the output current reference and system parameters. Experimental results with an experimental prototype support the theoretical approach. View full abstract»

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  • Improved power quality bridgeless cuk converter fed brushless DC motor drive for air conditioning system

    Publication Year: 2013 , Page(s): 902 - 913
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1554 KB)  

    This study presents a bridgeless Cuk converter-fed brushless DC (BLDC) motor drive for an air conditioning system. A new approach of speed control of BLDC motor is proposed by controlling the voltage at DC bus using a single voltage sensor. The proposed drive utilises a bridgeless Cuk converter operating in discontinuous inductor current mode (DICM) for the power factor correction (PFC) and improved power quality (PQ) at the AC mains for a wide range of speed control. The bridgeless Cuk converter operating in a DICM gives an inherent PFC and requires a simple voltage follower approach for the voltage control. The bridgeless converter topology is designed for obtaining the low conduction losses and requirement of low size of heat sink for the switches. The proposed system is designed and its performance is simulated for an air conditioning system to operate over a wide range of speed control with near unity power factor at AC mains. Finally, the performance of the proposed drive obtained in simulation is validated with test results on a developed drive for its operation over a wide range of speed control with improved PQ at AC mains. View full abstract»

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  • Design and performance evaluation of a bidirectional isolated dc-dc converter with extended dual-phaseshift scheme

    Publication Year: 2013 , Page(s): 914 - 924
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1137 KB)  

    This study describes the design and performance evaluation of a bidirectional isolated dc-dc converter with an extended dual-phase-shift (EDPS) scheme. The operation principle and equivalent circuits with consideration of the deadband are presented. The deadband effect with EDPS is different from the conventional phase-shift (CPS) scheme, and the corresponding compensation coefficient is determined. Different operation modes are identified with respect to phase-shift angles of EDPS and load conditions. The safe operational area is also analysed with the comparison of different operation modes. The output voltage and output power characteristics with open-loop or closed-loop operation are discussed. The average theoretical 48.5% reduction in the output voltage ripple using EDPS has been achieved. The average reduction in inductor peak and rms with EDPS are statistically calculated as 37.8 and 26.8%. The measured efficiency has improved from 68.1% using CPS to 81.9% using EDPS for low-power application. View full abstract»

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  • DC-bus voltage control of grid-connected voltage source converter by using space vector modulated direct power control under unbalanced network conditions

    Publication Year: 2013 , Page(s): 925 - 934
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1126 KB)  

    Unbalanced grid voltage will cause large dc-bus voltage ripple and introduce high harmonic current components on the grid side. This will severely threaten the safety of the grid-connected voltage source converter (VSC) and consequently, affect the healthy operation condition of the load. In this study, a new proportional-integral-resonant (PI-RES) controller-based, space vector modulated direct power control topology is proposed to suppress the dc-bus voltage ripple and in the same time, controlling effectively the instantaneous power of the VSC. A special ac reactive power reference component is introduced in the controller, which is necessary in order to reduce the dc-bus voltage ripple and active power harmonics at the same time. The proposed control topology is implemented in the lab. Simulation and experimental results are provided to validate its performance and the analysis presented in this study. View full abstract»

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  • Analysis and design of reduced-order sliding-mode controller for three-phase power factor correction using cuk rectifiers

    Publication Year: 2013 , Page(s): 935 - 945
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1057 KB)  

    In this study, the analysis and design of reduced-order sliding-mode controller (ROSMC) for power factor correction (PFC) in a three-phase system is presented. A new and systematic technique for the selection of sliding surface co-efficients to implement ROSMC is attempted. The front end is a three-phase diode rectifier followed by DC-DC Cuk converter modules with the common DC output. Instantaneous symmetrical component theory is used for reference current generation. The control strategy uses three inner ROSMC current controllers for source current shaping and an outer voltage loop using proportional integral controller for load voltage regulation. The proposed method offers simple control strategy, fast transient response and power factor close to unity. To validate the proposed method, a prototype controlled by dSPACE 1104 signal processor is set up. Simulation and experimental results indicate that the proposed system offers regulated output voltage for wide load variations and power factor close to unity. View full abstract»

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  • New three-phase discontinuous voltage mode cuk power-factor correction converter for low-p946ower applications

    Publication Year: 2013 , Page(s): 946 - 953
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    In this study, a new three-phase power-factor correction (PFC) rectifier based on Cuk converter is introduced. The proposed converter operates in discontinuous voltage mode and therefore it has inherent PFC characteristics. Thus, it is not necessary to shape the input current using current shaping techniques. The proposed converter applies only one active switch and once the load is constant, the converter operates with constant duty cycle and constant switching frequency and thus, simple and low cost control and gate drive circuits are required. Also, the switch applied in this converter turns off under zero voltage switching condition. The proposed converter is analysed and theoretical analysis is justified using experimental results. View full abstract»

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  • Pulse width modulation technique parameter selection with harmonic injection and frequencymodulated triangular carrier

    Publication Year: 2013 , Page(s): 954 - 962
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (838 KB)  

    This study presents a very important feature of the technique of pulse width modulation (PWM) with injection of harmonic and triangular frequency carrier modulated in frequency. This technique is used to improve the quality of the output voltage signal of the power inverters controlled PWM. The purpose of this study is to show a new feature of controllability by the selection of different parameters. This allows multiple responses, from the point of view of the spectrum and the properties of the signal quality, with the same number of pulses per second, allowing the controllability of the modulated output signal. With this ability to control, it is possible to choose, for example, the total harmonic distortion of the signal output from the inverter, or the value of the fundamental term of voltage. It is also possible to select the low order harmonic, of interest for the selective reduction of harmonics. To show this feature, some examples have been developed with different number of pulses per period and with their corresponding parameter selection. View full abstract»

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  • Analytical winding foil thickness optimisation of inductors conducting harmonic currents

    Publication Year: 2013 , Page(s): 963 - 973
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (727 KB)  

    This study presents analytical winding power loss minimisation of foil inductors conducting ac harmonic currents with and without dc offset. The approximated equation for the ac winding power loss is derived and used to determine the optimum foil thickness of inductors operating with multi-harmonic ac currents. An approximated equation for the total winding power loss is also derived and used to determine the optimum foil thickness of inductors operating with multi-harmonic ac currents superimposed on the dc current. The design procedure for inductors with minimum total winding power loss is presented for a pulsewidth-modulated dc-dc boost converter operating in discontinuous conduction mode. The theoretical predictions have been verified by measurements of inductors with four different foil thicknesses. View full abstract»

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  • Design and implementation of reduced-order sliding mode controller plus proportional double integral controller for negative output elementary super-lift luo-converter

    Publication Year: 2013 , Page(s): 974 - 989
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1949 KB)  

    This study presents a simple sliding surface design of variable frequency-based reduced-order sliding mode controller (ROSMC) plus proportional double-integral controller (PDIC) for the negative output elementary super-lift Luo-converter (NOESLLC) operated in continuous conduction mode (CCM). Owing to the time-varying switched mode operation, the dynamic characteristics of the NOESLLC is non-linear and the developed ROSMC plus PDIC aims at improving the dynamic performance along with the inductor current and the output voltage regulation of the NOESLLC. The developed ROSMC is well suitable to the inherently variable-structured NOESLLC when represented in the reduced-order state-space average-based model. The designed PDIC eliminates the steady-state error and also excellent start-up response of NOESLLC despite of line and load variations. The performance of the developed controller is verified for its robustness to perform over a wide range of operating conditions through both in MATLAB/Simulink models as well as in the laboratory prototype with the comparative study of a typical ROSMC plus proportional-integral-controller. Simulation and experimental results are showed that ROSMC plus PDIC can achieve proficient output voltage and inductor current regulation at various working conditions. View full abstract»

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  • Design and digital implementation of voltage and current mode control for the quasi-Z-source converters

    Publication Year: 2013 , Page(s): 990 - 998
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (973 KB)  

    Two strategies of peak dc-link voltage control of the voltage-fed quasi-Z-source converters (qZSC) are analysed and compared. Different from the currently available literatures, the peak dc-link voltage is estimated by summing the two capacitor voltages of qZSC. The voltage mode and current mode controls are derived based on the fifth-order small-signal model of the quasi-Z-source network with inductive load. Both controllers are digitally implemented using a digital signal processor (DSP)-based direct digital design approach, where the real-time workshop is used for automatic real-time code generation for a TMS320F2808 DSP. Digital compensators are tuned using Bode diagram and discrete frequency response approaches with a graphical MATLAB/single-input single-output tool. The performances of the proposed control strategies are verified by the experimental results during start-up, input voltage and load disturbances. View full abstract»

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  • Dual-output dc-dc buck converters with bidirectional and unidirectional characteristics

    Publication Year: 2013 , Page(s): 999 - 1009
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (976 KB)  

    This study presents single-input double-output unidirectional and bidirectional dc-dc buck converters, for applications that demand two dc-controlled output voltages. The proposed converters present a component count reduction and it is considered as a monolithic device with two output voltages generated by the same power converter. The main advantages of the proposed converters are reduction of costs and better power losses distribution among the semiconductor devices. Besides the proposal of suitable power converters, this study presents their models, control strategies, modulation approaches and design specification. The selected simulated and experimental results are presented as well. View full abstract»

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  • Analysis and implementation of an integrated electronic ballast for high-intensity-discharge lamps featuring high-power factor

    Publication Year: 2013 , Page(s): 1010 - 1018
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    This paper proposes a high-power-factor electronic ballast for metal-halide (MH) lamps. In the proposed circuit, two buck-boost converters and a buck converter are integrated with a full-bridge inverter by sharing the four active switches of the full-bridge inverter. Two active switches are switched at high frequencies, while the other two are switched at lower frequencies. The buck converter is used to step down the DC-link voltage of the full-bridge inverter and filter out the high-frequency components to drive lamps with a low-frequency square-wave (LFSW) current. The buck-boost converters are operated at discontinuous-conduction mode to perform the function of power-factor correction (PFC) to ensure almost unity power factor at the input line. By tactful arrangement of diodes, the DC-link capacitors are discharged in parallel; this helps to operate the high-frequency active switches at a high duty ratio, achieving a small peak value of the PFC-converter current and correspondingly smaller conduction losses. Detailed operation modes and the design equations are provided. A prototype electronic ballast for a 70 W MH lamp is built and tested. Experimental measurements have proven that the proposed electronic ballast has the advantages of high-power factor and being free of acoustic resonance. By integrating the active switches of the converters and the inverter, the proposed electronic ballast is advantageous in terms of cost-effectiveness and high energy-conversion efficiency. View full abstract»

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  • Novel technique for bidirectional series-resonant DC/DC converter in discontinuous mode

    Publication Year: 2013 , Page(s): 1019 - 1028
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (849 KB)  

    This study analyses a novel technique for obtaining a voltage conversion ratio greater than one in a bidirectional seriesresonant DC/DC converter (SRC). The converter works in a discontinuous mode: it transfers energy in packets, but it also accumulates some packets in order to raise the output voltage. This study presents a comprehensive theoretical analysis for the two modes: the step-down mode (common mode) and the novel step-up mode. The converter transfers energy during fixed time intervals (called states), and it is also able to accumulate energy in a novel state called the accumulation state. With this, the circuit can achieve a voltage conversion ratio of up to two. In addition, a design methodology is presented, and it is validated in the design of a high-current bidirectional DC/DC converter for battery applications. The results of the voltage conversion ratio and efficiency measurement are presented along with a comparison with an resonant LLC converter. The converter reaches an efficiency rate of 91% and the voltage conversion ratio varies from 0.8 to 1.22 at maximum power. Using this novel technique, the SRC can now be used in a bidirectional DC/DC converter applied to energy storage devices, such as batteries or supercapacitors. View full abstract»

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Aims & Scope

IET Power Electronics brings together five principal power electronics themes including: applications of power semiconductor technology; circuits; devices; techniques; and performance management.

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