Wavelet based fast fault detection in LVDC micro-grid
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This Low Voltage DC (LVDC) distribution system is gaining momentum which includes Distributed energy resources and DC sensitive electronic loads. However, due to lack of standards and mature experience in DC protection, LVDC application is still an elusive issue. In order to ameliorate these deficiencies, a wavelet based fast fault protection scheme using local measurements has been proposed for eliminating threat to Voltage Source Converters during fault. The wavelet energy and change in energy are the key indicators to identify the fault with wide variations in operating conditions including the impact of grid-connected and islanded mode of operation. Further, the robustness of the proposed fast fault detection scheme has been validated for high impedance ground fault. The proposed scheme validation using Real Time Digital Simulation indicates that the proposed fault detector for LVDC micro-grid has potential ability in performing the desired task.Keywords:
Robustness
Differential Power Processing (DPP) converters have been recently utilized for reducing the losses in partially shaded PV systems. Through enabling new paths for currents, shaded panels have less impact on blocking higher currents from series connected PV modules. This ultimately results in harvesting more power from partially shaded PV units. Unfortunately, the number of required DPP converters increases linearly with the number of series PV units. To address this challenge, this paper investigates the possibility of reconfiguring DPP converters reducing the number of needed converters. Instead of using a complete set of DPP converters, reconfiguring DPP converters could substantially reduce the number of needed converters. The used DPP converters will be connected to shaded units and reconfigured online with changes in shadings to reduce the mismatch power losses. Validation and verification through simulation is conducted to demonstration the effectiveness of the proposed idea.
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The paper presents the survey of architectures and conversion algorithms used in so called adaptive analog-to-digital converters considered during the studies on these converters carried out by the author and his colleagues. The key idea that distinguishes the adaptive analog-to-digital converters from other sub-ranging converters consists in application of the iterative digital signal processing algorithm for calculation of the output codes of the converters and for calculation of the values of residue signal gains in subsequent steps of conversion. Application of this approach in the proposed converters allows to achieve better parameters of the converters in comparison with parameters of conventional sub-ranging analog-to-digital converters.
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Paralleling active front end (AFE) two-level converters is a good solution when high power and redundancy are needed. The connection of multiple converters in parallel raises challenges regarding electrical energy quality and operating conditions of converters. Converters connected in parallel create paths for circulating current (CC) when converters' control systems are not synchronized. Hardware variances can also influence the converters' performance as examined in simulations. The paper contains simulation and experimental results of two 15kVA paralleled AFE converters working with different power factors.
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Ac-dc power conversion can either be done with two separate converter stages or with a single converter stage. Two-stage ac-dc converters, however, can be costly and complex and the performance of single-stage converters is compromised due to a reduced number of components. Several researchers have therefore proposed adding some sort of auxiliary circuit consisting of a second switch and some passive elements to single-stage converters to improve their performance. Although these quasi-single-stage (QSS) converters may have two converters, they are not two-stage converters as they do not have two separate and independently controlled converters that are always operating to convert power from one form to another. In the paper, the operation of ac-dc single-stage converters is first reviewed and their characteristics are noted. The operation of several QSS converters, including one proposed by the authors, is then discussed, and the paper concludes by presenting experimental results that confirm the feasibility of the proposed converter.
Single stage
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This study presents a procedure for modelling of switching converters with reduced redundant power processing (R2P2). This class of converters consists of two basic DC–DC switching converters connected in non-cascading structure. The proposed procedure uses signal flow graphs on converters with R2P2, according to currents and voltages relationship of each non-cascading structure. In the beginning, the procedure does not require specific knowledge of the basic converters being used, but only the structure of the converter with R2P2. The corresponding basic converters are incorporated later. Although the procedure is applied to converters with R2P2, it can also be applied to other configurations that are based on the interconnection of two converters. The resulting models are validated using simulations and experimental results.
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This paper describes smart converters and presents results from real industrial application. The auxiliary converters in public transport vehicles are very important part of vehicles. The auxiliary converters consist from three-phase, inverters, single-phase inverters, chargers, power supplies of several different voltages. Nowadays converters contain powerful digital signal processors (DSP) with a lot of peripheries. High performance of the DSP predisposes new converters for complex systems. Working principle of converters is often very similar. Based on the similarity of converters were designed and created universal, adjustable control programs for each group of converters. The creation of universal adjustable control programs allowed to design and create smart converters. The smart converters are adjusted automatically. When the smart converters are connected to the auxiliary converters, they are adjusted automatically. The converters accept correct settings without external support (service staff). After that the converters are ready for work. The implementation of the smart converter improves reliability and reparability. Repair time is shorter. Requirements on staff are low.
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1. Terminology, specifications and evaluation techniques 2. Scaled D to A converters 3. High resolution scaled D to A converters 4. Feedback A to D converters 5. Algorithmic converters 6. Rampfunction converters 7. Delta-sigma converters 8. Fast A to D converters Appendix: simulations
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The new enlarged third edition of this textbook presents the latest concepts and basics of dc-dc converters, including analysis, simulation, control, and selected applications. Several new chapters and paragraphs,recent references, and a complete new chapter presenting design case studies of switching converters have been added. The book now has 14 chapters all together, covering the following topics: 1) Introduction to Switching Converters; Basic Switching Converter Topologies; Resonant Converters; Isolated Switching Converters; Control Schemes of Switching Converters; Continuous-Time Modeling of Switching Converters; Analog Control of Switching Converters; Discrete-Time Modeling of Switching Converters; Digital Control of Switching Converters; Interleaved Converters; Switched Capacitor Converters; Simulation of Switching Converters; Applications of Switching Converters; and Switching Converter Design Case Study.
Switching power
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A methodology for designing analog to digital (A/D) converters based on a hierarchic network is explored. The principle of this methodology and design procedure are presented. The characteristics and performances of the converter are compared with the converter based on the Hopfield network. Two circuit models for the A/D converters are described in this paper. As a hierarchic network is used, the A/D converters designed have no local minima in their operation, With the method proposed in the paper, high bit number A/D converters can be easily designed, and the converters designed are fast in signal conversion and stable in operation.
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Maxima and minima
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The industrial application of power electronic converters and systems of converters are varied (Motorola, 1991, 1993). Power electronic converters of electrical energy for electrical engineering technologies have a wide spread in industry.
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