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ABSTRACT: Multilevel DC-DC converters making use of high-frequency transformers are suitable for integration in solid-state solutions for applications in electric power distribution systems. This paper presents a simplified switching scheme for three-level full-bridge DC-DC converters that enables zero-voltage and zero-current switching of all the main power devices. It describes the main operational modes and design equations of the converter as well as provides simulation and experimental results to demonstrate the feasibility of the proposed ideas.
IEEE Transactions on Power Electronics 03/2009; · 4.65 Impact Factor
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ABSTRACT: Distributed energy resources (DERs) are becoming integral components of electric power distribution systems. In most cases, an isolated DC-DC converter forms part of the interface required to connect the DER output to the distribution system. Operation of the converter at high switching frequencies results in size reduction of passive components at the expense of increased switching losses. However, silicon carbide (SiC) power devices have the potential of operating at high switching frequencies without significant loss penalty because of their fast switching times and ability to work at high temperatures when compared to similar Si devices. SiC diodes have already displayed the ability to offer more ideal diode behavior than Si diodes. Engineering samples of SiC MOSFETs are depicting lower switching losses and conduction losses over Si MOSFETs. This display is making SiC devices attractive for DC-DC converters used to connect DERs to the distribution system. This paper particularly deals with the design of a 300 W 100 kHz DC-DC full-bridge converter using zero-voltage zero-current switching for comparison of SiC MOSFETs and diodes against Si MOSFETs and diodes.
IEEE Transactions on Power Electronics 02/2009; · 4.65 Impact Factor
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ABSTRACT: Renewable distributed energy resources (DERs) will play a large role in the future energy infrastructure because of advantages like lower carbon imprints, lower fuel costs, and reduced power flows on transmission lines. The unreliability of many renewable DERs due to the intermittent nature of their supply, especially in the case of solar and wind generators, can be mitigated with energy storage that brings a host of additional benefits including load leveling, frequency control, and power quality compensation. One barrier to adoption of these technologies is the need for interfaces between the different voltage levels and waveforms produced by the various systems. This paper, which is tutorial in nature, examines several possible interfaces presented in the literature and provides a comparison between their advantages and disadvantages.
Energy 2030 Conference, 2008. ENERGY 2008. IEEE; 12/2008
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ABSTRACT: The growth of demand invariably lead to higher and higher fault currents, and as a consequence protection devices must have higher ratings. The integration of distributed energy resources further complicates protection schemes, especially those that assume a radial distribution scheme and power flowing in only one direction. These conditions generate an increasing demand for fault current limiters to keep fault currents within the ratings of existing protection equipment as well as to minimize the impact of distributed generation on the grid during faults. However, placement of protection equipment must be carefully considered in order to keep them cost effective and to prevent the limiters themselves from disrupting existing protective measures. This paper explores several placement and coordination guidelines, as well as provides simulations of fault current limiters placed in substations with ring bus and double bus configurations, respectively.
Energy 2030 Conference, 2008. ENERGY 2008. IEEE; 12/2008
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ABSTRACT: A multiport converter with a high frequency (hf) ac bus is proposed for use as a distributed energy resource (DER) to grid interface with an integrated energy storage system (ESS). The combination of DER and ESS allows the DER to provide load following, load leveling, power quality compensation, voltage and frequency control, and spinning reserve, as well as savings on deferred installation of new transmission lines and centralized power plants, reduced loads on existing transmission lines, increased grid security and reliability, and the potential to adjust power delivery to take advantage of the energy market. The use of the hf-ac bus allows the boost and dc-hf ac conversion functions to be combined into a single converter and reduces the size of the transformer and passives. The proposed design allows independent control of each of the DER and ESS inputs, allowing for modular design and ease of expansion for the system. The digest explores several of the challenges of the design and presents theoretical and simulated waveforms for one of the operating conditions. Seven possible operating conditions are identified, and the applicability of each operating condition is determined when the system is used for power generation, load leveling, and spinning reserve.
Power Electronics Specialists Conference, 2008. PESC 2008. IEEE; 07/2008
