PESC Record - IEEE Annual Power Electronics Specialists Conference Journal Impact Factor & Information

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ISSN 0275-9306

Publications in this journal

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    ABSTRACT: When Ultra-Capacitors are used for providing energy to power downstream switch mode converters used for power conversion, the significant change in their capacitance with frequency can result in significantly higher voltage ripple and current ripple in these capacitors. This results in over voltage and temperature rise in these capacitors resulting in their consequent lifetime reduction. Based on extensive measurements of these voltage ripple and current ripple at different converter switching frequencies, design considerations that can significantly reduce these voltage and current ripple is proposed in this paper.
    Power Electronics and Applications, 2009. EPE '09. 13th European Conference on; 10/2009
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    ABSTRACT: Based on commonly used parameters for a generic transcutaneous transformer model, a remote power supply using resonant topology for artificial heart is analyzed and designed for easy controllability and high efficiency. Primary and secondary windings of the transcutaneous transformer are positioned outside and inside human body respectively for energy transfer. The two large leakage inductances and the mutual inductance of the transformer are varying parameters of the coupling-coefficient which varies with transformer alignment and gap due to external positioning. Varying resonant-frequency resonant-tank circuits are formed using the transformer inductors and external capacitors to obtain a load insensitive frequency for the voltage transfer function at given range of coupling coefficients and loads. Previous researches usually use frequency modulation which may require a wide control frequency range well above the load insensitive frequency. In this paper, fundamental frequency study of the input-to-output voltage transfer function is carried out. Using the proposed control method, the switching frequency can be locked at just above the load insensitive frequency at heavy load for best efficiency. Specifically, above resonant operation in driving the resonant circuits when varying the coupling-coefficient is maintained using a digital-phase-lock-loop (PLL) technique to achieve zero-voltage switching of a full-bridge switches configuration which is also programmed to provide pulse-width-modulation (PWM) in controlling the output voltage. A prototype transcutaneous power regulator is built and found to have good efficiency and regulation in responding to changing alignment or gap of the transcutaneous transformer, load and input voltage dynamically. Author name used in this publication: Chi K. Tse
    PESC Record - IEEE Annual Power Electronics Specialists Conference 01/2009; DOI:10.1109/PESC.2008.4592210
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    ABSTRACT: This paper deals with flatness based control of a multi-source/multi-load electrical hybrid system (EHS) composed of a fuel cell and a supercapacitor (SC) as the main and auxiliary source, respectively. The proposed method does not contain any commutation algorithm whereas the different operating modes (normal mode and overload mode) exist in the system. This DC-power source supplies two independent 5 V and 12 V loads which are connected to a DC link through the buck converters. An observer system based on monitoring the supercapacitor voltage is also designed and proposed to estimate the output V - I characteristic of fuel cell which varies with some physical and environmental parameters like temperature, humidity, etc. Experimental results prove validity of the proposed approach.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In this paper, unbalanced three-phase control method is proposed to increase the fault tolerance for H-bridge multilevel inverter under the conditions of faulty power cells. It is possible to generate a balanced three-phase line-to-line voltage by phase-shifting and bypassing faulty power cells with a minimum voltage drop. In this method, the concept of voltage modulation by using offset voltage is applied to an unbalanced three-phase control method. Especially, it is possible to use the maximum output voltage of inverter by adopting the real time unbalanced control method of phase voltage irrespective of the fault location and the number of disabled power cells. Also, the feasibility of the proposed method is proved by the H-bridge multilevel inverter test composed of 7-level.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: A new half bridge converter for the personal computer (PC) power supply is proposed in this paper. Generally, PC power supply has two unique input/output specifications which are wide input voltage range and long hold up time. Therefore, it has to be operated with a small duty ratio. That makes it difficult to apply ZVS PWM topology to the PC power supply. The proposed ZVS half bridge converter controls the primary current which flows through blocking capacitor with an auxiliary switch of the secondary side. As a result, it can ensure zero DC offset of the magnetizing current even if it is operated with a small duty ratio. Moreover, ZVS conditions are maintained by reflected load current without disturbance due to the DC offset of the magnetizing current. Therefore, it shows a high efficiency and a low EMI at the PC power specifications. The operational principle, analysis and design of the proposed converter will be presented. Experimental results demonstrate that the proposed converter can achieve a significant efficiency improvement in a 280 W (12 V, 23.3 A) prototype converter.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: A new sensorless method of estimating the permanent magnet synchronous motor speed is presented. The method is based on sliding mode observer theory using Lyapunov stability criteria. The observation algorithm makes use of the machine model equations allowing the estimation of flux/current, stator resistance, rotor angle and rotor speed from the motor terminal measurement of currents and voltages. Speed/position observer is based on a modified back EMF state observer, which is considered in cascade with stator flux/current and resistance observers. The presented application has been implemented using an estimated gamma-delta reference frame instead of alpha-beta stationary reference frame. It is shown that the overall observation system gives exceptional estimation results at high and low speed ranges, without initial rotor angle knowledge. Simulation results of permanent magnet synchronous motor sensorless speed estimation are also presented.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In this paper, a real time wind turbine simulator (WTS) is proposed to simulate the dynamic behavior of wind turbine and generator. A novel torque sensorless inertia compensation algorithm is developed to simulate in real-time the dynamic mechanical performance of actual wind turbine with either larger or smaller inertia than the testing system. And the torque transducers are eliminated by using estimated generator electromagnetic torque. In addition, the proposed configuration of WTS is capable of fast response, rejecting grid voltage disturbance and grid-friendly connection. The experimental results verify the performance of proposed WTS.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: Switching mode power supply (SMPS) behavior depends entirely upon known component values and often unknown load impedances. Load change produces voltage over- and undershoots and a design-point shift. In most cases, the controller is blind to these shifts. However, load knowledge is an essential design parameter and should precede optimal and adaptive control techniques. System identification algorithms implemented on digital processors open new opportunities in control and system performance. Typical studies in SMPS identification are based on offline steady-state measurements that form nonparametric frequency-domain models. This paper investigates real-time system identification algorithms that generate parametric models - a practical form for pole-placement and root-locus design. Two key metrics are introduced: parameter error and convergence time to describe algorithm accuracy and speed, respectively, after abrupt parameter changes - a common SMPS load scenario. Hardware and simulation results will show that an algorithm called recursive least squares, in its most basic form, could reasonable approximate the input-to-inductor current plant for static loads during startup, but not for abrupt load steps.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: This paper examines quantization effects and limit cycling in the voltage control loop of digitally controlled single-phase power factor correction (PFC) rectifiers. Low-frequency limit cycling in the voltage loop can result in undesirable DC components, even harmonics in the AC line current and flicker. It is shown that two mechanisms can result in low-frequency limit-cycling: nonsynchronous sampling of the output voltage and quantization of the power command signal. Conditions for avoiding limit cycling are presented and verified in simulations and experiments on digital average current mode (DACM) and digital non-linear carrier (DNLC) [1] controlled PFCs.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In this paper, the usefulness of several topologies of DC-DC converters for measuring the characteristic curves of photovoltaic (PV) modules is theoretically analyzed. Eight topologies of DC-DC converters with step-down/step-up conversion relation (buck-boost single inductor, CSC (canonical switching cell), Cuk, SEPIC (single-ended primary inductance converter), zeta, flyback, boost-buck-cascaded, and buck-boost-cascaded converters) are compared and evaluated. This application is based on the property of these converters for emulating a resistor when operating in continuous conduction mode. Therefore, they are suitable to implement a system capable of measuring the I-V curve of PV modules. Other properties have been taken into account: input ripple, devices stress, size of magnetic components and input-output isolation. The study determines that SEPIC and Cuk converters are the most suitable for this application mainly due to the low input current ripple, allow input-output insulation and can be connected in parallel in order to measure PV modules o arrays with greater power. CSC topology is also suitable because it uses fewer components but of a larger size. Experimental results validate the comparative analysis.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In this paper, a novel diagnostic and protection algorithm based on wavelet neural network is developed and implemented in real-time for inverter faults in the vector controlled induction motor drives. The phase currents of an induction motor drive for different faulted and unfaulted conditions are preprocessed by wavelet packet transform in order to minimize the structure and timing of the proposed diagnostic technique. The wavelet packet transformed coefficients of line currents are used as inputs of a three-layer wavelet neural network. The performance of the proposed diagnosis and protection scheme is evaluated by simulation and experimental results. The proposed technique is evaluated and tested on-line for a laboratory 1-hp induction motor drive using the ds1102 digital signal processor board. In all the tests carried out, the type of fault is identified promptly and properly, and the tripping action is initiated almost at the instant or within one cycle of the fault occurrence.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: With the fast growing information technologies, AC-DC front-end power supply design is facing extremely tough challenges due to the continuously increasing power density and efficiency requirement. For the PFC stage, how to reduce the boost inductor and the EMI filter size without compromising the efficiency is the key to meet the challenges. Lots of techniques has been studied and proposed during the last several years. Among these techniques, multi-channel interleaving is a quite promising one. By staggering the channels at uniform intervals, multichannel interleaved PFC can reduce the EMI filter size significantly due to the ripple cancellation effect. In addition, the interleaving multi-channel configuration makes it possible to implement the phase-shedding to improve the PFC light load efficiency. Today, the power supply industry is spending tremendous effort on improving the PFC light efficiency due to the economic reasons and environmental concerns. By decreasing the number of active channels according to the load, the PFC light load efficiency can be optimized. In this paper, the phase-shedding control is proposed to improve the PFC light load efficiency and the issues on the EMI filter design are investigated. To improve the light load efficiency without compromising the EMI filter size, the asymmetrical phase angle control strategy is proposed, and is verified and demonstrated by the experimental results.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: This paper describes the high frequency behavior modeling method of an Adjustable Speed Drive (ASD) that will be used to estimate the conducted emissions. In order to study the influence of various elements of the ASD on the electromagnetic interferences (EMI) level, it is necessary to use a precise model of the PWM inverter, energy cable and AC motor which take into account various phenomena that appear when the frequency increases. A model of the shielded 4-wire energy cable that taking into account of the dissymmetry structure is proposed and validated in the frequency domain for two different lengths. The obtained high frequency ASD model is used to estimate the common mode conducted emissions on all inverter functioning period. In this study, PSPICE software is used to simulate the ASD in the time domain. The comparison of measurement and simulation results of conducted emissions (with LISN) shows the good compromise between the simulation duration and accuracy of the results.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: Cascaded H bridge multilevel inverters are traditionally controlled using phase shifted PWM. This method allows an even power distribution among the different cells of the converter, which enables input current harmonic cancellations due to the isolation multipulse transformer and rectifier system. For high power applications a selective harmonic elimination based method, also known as staircase modulation, has been proposed. This method is devised to reduce switching losses to a minimum, improving the efficiency of the converter. The switching angles are calculated to eliminate low order harmonics at the output voltage. However, this method does not provide even power distribution among the cells, avoiding the input current harmonic cancellation. This work proposes a redistribution of the switching angles between the cells, maintaining the overall switching pattern of the staircase modulation. The methods maintains the harmonic elimination characteristic at the output voltage, while improving the power distribution and consequently the input current harmonic performance. Mathematical analysis and simulation results are presented to support the strategy.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: The proton exchange membranes fuel cell (PEMFC) is known as a slow dynamic response application. The transient load power may bring damage to the stack and shorten lifetime of the fuel cell. In this paper, an energy management design, which consists of a bi-DC/DC converter and super capacitor, is introduced to compensate the slow dynamic response of the PEMFC power source. The energy management principle is analyzed. The controller and the filter design based on these analyses are given. The capacity of the auxiliary energy buffer is calculated. The Bi-DC/DC converter, as the hardware realization is then introduced. Finally, the experiment results on a 5 kW fuel cell power system with energy management are given to verify the theoretical analysis.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: Power converters with semiconductors switching only at predefined, equidistant instants - known as ldquodiscrete-time switchingrdquo, ldquosynchronized switchingrdquo or ldquoclocked commutationrdquo - show considerably different current control behavior compared to pulse-width modulated (PWM) converters with linear current con trollers. This paper presents and explains some of the effects of discrete-time-switching on output current waveforms, especially when using a predictive switching state selection algorithm. Typical characteristics of generated switching state patterns are presented. A single-phase and a three-phase inverter controlled by a predictive discrete-time modulation strategy are considered. Analytical, experimental and simulation results show that average switching frequency and error current RMS are well defined, in spite of the inherent randomness of the control scheme.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: A new method of synchronised pulsewidth modulation (PWM) has been applied for control of six-phase (dual three-phase) converter feeding symmetrical induction motor which has two sets of windings spatially shifted by 60 electrical degrees. Basic schemes of synchronised continuous and discontinuous PWM, disseminated for control of symmetrical systems, have been analyzed and compared. It has been shown, that combined (hybrid) schemes of synchronized PWM provide better weighted THD factor of the useful components of the phase voltages in comparison with the identical (continuous+continuous or discontinuous+discontinuous) schemes of PWM in symmetrical dual three-phase systems. Simulation results illustrate the behavior of symmetrical six-phase converters with low switching frequency, controlled by algorithms of synchronised PWM.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In this paper, a high dimming ratio LED drive controller without color shift issue was proposed, fabricated and tested. It is composed of a boost power stage and some dimming control circuits. To fit high ratio dimming, it is necessary for the power stage to have fast enough transient response during the LED load switching. Therefore, a constant on time (COT) controlled boost converter was proposed. The boost switch on time is fixed by a current capacitor timer and the inductor current is just sampled during the off time modulation with COT control. This control scheme simplifies the current sensing since in this case the equivalent series resistor (ESR) of the output capacitor samples the inductor current directly. The chip is implemented with 1.5 mum BiCMOS process, and the final die area is 1.31 x 1.43 mm<sup>2</sup>. Simulation and experiment results have shown that the proposed LED drive system features the minimum LED dimming on interval as small as 1 mus and the corresponding dimming ratio is 1000:1 at 1K Hz dimming frequency. In addition, the PFM operation comes free at dimming off interval.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008