PESC Record - IEEE Annual Power Electronics Specialists Conference

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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: In this paper, the closed-loop control of a 4-leg voltage source converter-based dynamic voltage restorer has been described. A low-voltage, laboratory model of the dynamic voltage restorer has been constructed. The controller functions have been implemented in a DSP-based digital controller. A program for resolving the 3-phase variables into the sequence components has also been included among the controller functions. The DVR is able to protect the load from voltage sags due to various types of faults.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: Power converters are known to generate spectral components in the range of interest of electromagnetic compatibility measurements. Common approaches to manipulate some selected components in these frequency ranges are shown here. These approaches add components to the input signal of the modulator to derive a slightly varied spectrum. To achieve a rectangular output signal, those modulators use a triangular or saw tooth carrier signal. A novel family of modulators is shown here, using more than one carrier signal to obtain a completely changed spectrum while maintaining the rectangular shaped waveform at the output. The multiple carriers are fed into multiple comparators and their outputs are intelligently combined by logic gates to get a single signal to drive one power stage of any type of converter. This commutation distinguishes between the four members of the novel family: the first one uses an or- gate to combine the signals; the second one utilizes therefore an and-gate. The third modulator combines the outputs of those two and switches between the or-output and the and- output after each pulse. The last described modulator is commutating one of the described outputs dependent on the state of a master clock. The nonlinear operation of all modulators is described with nonlinear algebra in conjunction with Boolean algebra. The benefits for electromagnetic compatibility of the new schemes are presented, all modulators are examined in terms of steady state operation, dynamic behavior, maximum modulation range and added distortion. Finally the implementation of one of the modulators in a switch-mode power supply is presented. Experimental results are verifying the simulation.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: High power current source converters (CSC) are usually implemented with GTOs which present a maximum switching frequency of a few kHz. Space vector modulation (SVM) offers a very elegant way of generating CSC gating signals on-line with increased gain and reduced switching frequency. However, for very low frequency, as required by GTOs, SVM results in non-characteristics low order (5<sup>th</sup> and 7<sup>th</sup> ) harmonics. The reduction of the magnitude of these harmonics has been sought mostly through new sequences of space vectors (states), which present better performance for different ranges of modulation index and power factor. Moderate improvement can be obtained by calculating the states on times at once in the middle of a cycle. This paper shows that larger reductions can be achieved by calculating the states on times at different moments, as the states are used. The effectiveness of the proposed technique for different states sequences is demonstrated by means of simulations.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: A novel current assisted H<sub>infin</sub> controller for boost converter is presented in this paper. The proposed controller combines the H<sub>infin</sub> robust stabilization technique and classical loop-shaping. The current loop of the boost converter is closed with constant gain and then, the H<sub>infin</sub> controller is estimated and applied to the converter, closing the voltage loop. The derived controller has been compared to the popular peak current mode controller in terms of robust stabilization and performance using the concept of uncertainty and the powerful tool of mu-analysis. To verify the theoretical analysis and conclusions, the two control schemes have been simulated under nominal and disturbed conditions considering step load and reference changes.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In this paper, a method for reducing the voltage stresses on switching components and power losses in a shunt current source active power filter (CSAPF) is presented. The method is based on the series capacitor structure which is used to block the fundamental supply voltage component. The results show that the component voltage stresses and power losses are lower in the CSAPF with a series-connected capacitor than in the conventional topology.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: The output current of contemporary AC-DC front-end converters is steadily increasing due to higher power density requirements. The use of shunt resistors to sense the output current is becoming unacceptable due to high power losses and new techniques for current sensing need to be investigated. In this paper, we investigate the possible use of the voltage drop across the trace resistance to sense the output current. This approach promises very low cost since no dedicated shunt resistor is required, no additional power losses occur and no extra space on the printed-circuit-board (PCB) is necessary. To overcome the problems associated with the temperature drift of the copper, and variability in the trace resistance of the copper track, a digital controller can be used to calibrate the trace resistance and implement a temperature drift compensation. This form of microcontroller is readily available on todaypsilas AC-DC front-end converters. However, theoretical and practical investigations revealed that the parasitic inductance and skin effect may limit the bandwidth of this measurement principle down to several hundred Hz. To overcome this limitation, we proposed a compensation technique that has the potential to increase the bandwidth beyond ten kilohertz. Experiments with output currents of up to 240 A demonstrated that the measurement uncertainty for DC currents is less than plusmn1 A for temperatures between 25 to 60 degrees, and that the effective bandwidth can be enhanced using a compensation technique.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: The PMSM is inherently electronically controlled and requires rotor position information for proper drives. However, the problems of the space, cost, and reliability of rotor position sensors have motivated research in the area of position sensorless PMSM drives. Numbers of rotor position sensorless control techniques have been proposed for PMSM drives, but most rely on the estimation of the rotor flux linkage vector. The performance of this method, however, is poor at low speed region due to the voltage distortions caused by the nonlinear behavior of a pulse width-modulation (PWM) voltage source inverter (VSI). In this paper, a new online voltage distortion compensation method is employed to overcome this problem. To prove effectiveness of the voltage distortion compensation method to the improvement of the rotor position estimation, the proposed method is applied to PMSM drive system and implemented in a digital manner using a digital signal processor.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In this paper, the principle and basic structure of the thermoelectric module is introduced. The steady- state and dynamic behaviors of a single TE module are characterized. An electric model of TE modules is developed and can be embedded in the simulation software for circuit analysis and design. The issues associated with the application of the TEG models is analyzed and pointed out. Power electronic technologies provide solutions for thermoelectric generation with features such as load interfacing, maximum power point tracking, power conditioning and failed module bypassing. A maximum power point tracking algorithm is developed and implemented with a DC-DC converter and low cost microcontroller. Experimental results demonstrated that the power electronic circuit can extract the maximum electrical power from the thermoelectric modules and feed electric loads regardless of the thermoelectric module's heat flux and load impedance or conditions.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In this paper, a motion controller based on a Field Programmable Gate Array (FPGA) with a high performance current regulator is presented. This system contains a processor and a high bandwidth current regulator as a peripheral, and all of these are implemented on a single-chip FPGA. The execution time of the current regulator is less than 200 ns at 100 MHz clock frequency. Thanks to this fast execution, the inevitable digital delay, which is 1.5 times the sampling period in a PWM inverter has been reduced to a half of the sampling period. As the result, the control bandwidth of the current regulator has been extended up to about 3 kHz at 10 kHz PWM switching frequency. By exploiting the performance of the current regulator, the speed regulation bandwidth also enhanced up to 700 Hz. The experimental results are presented to demonstrate the validity of the proposed system and the performance of the regulator.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: This paper presents a novel isolated single stage buck-boost inverter for implementing dc-to-ac, ac-to-dc or dc-to-dc. The BBI has better performances, in terms of low cost, high efficiency and high voltage gain. Through the HEV/EV application, the circuit operation principles and characteristics have been analyzed. And then, a novel Synchro-Switching SVPWM have been presented to obtain the maximum buck-boost factor and ZVS or ZCS conditons on the main switches and to reduce the magnetizing inductance value of transformer. The experimental results have confirmed the operating principle and the analysis method.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: In designing a LLC resonant converter, the ratio of magnetizing inductance (L<sub>M</sub>) to resonant inductance (L<sub>M</sub>), the inductor ratio (K) is usually considered. In high power density adapter, both adapter size and efficiency are important factors. considering the size of adapter, high K design can be more attractive. But, wide frequency variation of high K design results in design difficulty of magnetic elements and decrease in efficiency. To solve these drawbacks, an adaptive link voltage variation (ALVV) control is proposed. With the proposed control method, the LLC resonant converter can be operated at the resonant frequency despite the output voltage variation. The control strategy and schematics are presented, and verified experimentally.
    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: This paper investigates the loss characteristics of several commercial rf magnetic materials forpower conversion applications in the 10 MHz to 100 MHz range. A measurement method is proposed that provides a direct measurement of inductor quality factor Q<sub>L</sub> as a function of inductor current at rf frequencies, and enables indirect calculation of core loss as a function of flux density. Possible sources of error in measurement and calculation are evaluated and addressed. The proposed method is used to identify loss characteristics of different commercial rf magnetic core materials. The loss characteristics of these materials, which have not previously been available, are illustrated and compared in tables and figures. The results of this paper are thus useful for design of magnetic components for very high frequency applications.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
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    ABSTRACT: Recent progress in the identification of switching power converters using an all-digital controller has granted network analyzer functionality to the control platform. In particular, the cross-correlation technique provides a nonparametric identification of a converterpsilas small-signal control-to-output frequency response. The literature shows the viability of this technique as well as a few improvements to the basic technique. This online network analyzer functionality allows new flexibility in the areas of online monitoring and adaptive control. In this paper, several improvements to the cross-correlation method of system identification are proposed which aim to further improve the accuracy of the frequency response identification, particularly at high frequencies near the desired closed-loop bandwidth. Additionally, an extension to the cross-correlation method is proposed which allows measurement of the control loop gain without ever opening the feedback loop. Thus, performance and stability margins may be evaluated while maintaining tight regulation of the output. Simulation and experimental results are shown to verify the proposed improvements.
    Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008