DC Bus System Research Articles

Two-stage soft-switched converter for the electrolyser application

An 'electrolyser' is part of a renewable energy system (RES), which breaks water down into hydrogen and oxygen gases by passing an electric current through water. A dc-to-dc converter is needed to couple the electrolyser to the system dc bus of the RES. This study proposes a two-stage soft-switched high-frequency transformer isolated dc-to-dc converter for this application. A zero-voltage transition boost converter is used as the front stage followed by an inductor-capacitor-inductor (LCL)-type series resonant converter (SRC) with a capacitive output filter. Since the boost converter maintains almost a constant bus voltage, the LCL SRC can operate with zero-voltage switching (ZVS) for the specified supply and load variations. A systematic design procedure is given followed by a detailed personal simulation program with integrated circuit emphasis (PSPICE) simulation and experimental results for the designed 2.4 kW converter cell to show the performance of the proposed converter configuration.

Transient Analysis of Large Scale PV Systems with Floating DC Section

The increasing penetration of renewable sources with power-electronic interfaces in power systems is raising technical problems and the overall efficiency of photovoltaic systems can decrease dramatically. In this context, the optimal layout for the photovoltaic system is required. The most adequate strategy to connect the renewable system to the electrical power grid or to supply the end users must be adopted. The present paper proposes a design layout of a PV plant using a DC bus system to improve the overall energy conversion efficiency. An analysis of steady-state system stability, voltage drop and DC cable conduction losses is conducted. The leakage currents to the ground are investigated through simulations. Experimental results are shown focused on the analysis of optimal layout of photovoltaic systems under particular operating conditions.

A High-Efficiency PV Module-Integrated DC/DC Converter for PV Energy Harvest in FREEDM Systems

The future renewable electric energy delivery and management (FREEDM) system provides a dc interface for alternative energy sources. As a result, photovoltaic (PV) energy can be easily delivered through a dc/dc converter to the FREEDM system's dc bus. The module-integrated converter (MIC) topology is a good candidate for a PV converter designed to work with the FREEDM system. This paper compares the parallel connected dc MIC structure with its counterpart, the series connected MIC architecture. From the presented analysis, the parallel connected architecture was shown to have more advantages. In this paper, a high-efficiency dual mode resonant converter topology is proposed for parallel connected dc MICs. This new resonant converter topology can change resonant modes adaptively depending on the panel operation conditions. The converter achieves zero-voltage switching for primary-side switches and zero-current switching for secondary-side diodes for both resonant modes. The circulation energy is minimized particularly for 5-50% of the rated power level. Thus, the converter can maintain a high efficiency for a wide input range at different output power levels. This study explains the operation principle of the proposed converter and presents a dc gain analysis based on the fundamental harmonic analysis method. A 240-W prototype with an embedded maximum power point tracking controller was built to evaluate the performance of the proposed converter. The prototype's maximum efficiency reaches 96.5% and an efficiency increase of more than 10% under light load conditions is shown when compared with a conventional LLC resonant converter.

EMBEDDED CONTROLLED ZVS DC-DC CONVERTER FOR ELECTROLYZER APPLICATION

An Electrolyser is part of a renewable energy system (RES) and generates hydrogen from water electrolysis that is used in fuel cells. A static DC-DC converter is required to couple the Electrolyser to the system DC bus. This paper presents the design of three soft-switched high-frequency transformer isolated DC-DC converters for this application based on the given specifications. It is shown that LCL- type series resonant converter with capacitive output filter is suitable for this application. Detailed theoretical and simulation results are presented. Due to the wide variation in input voltage and load current, no converter can maintain zero-voltage switching for the complete operating range. The experimental results are compared with the simulation results and they are almost similar.

Photovoltaic-Battery-Powered DC Bus System for Common Portable Electronic Devices

Renewable energy sources based on photovoltaic (PV) along with battery-based energy storage necessitate power conditioning to meet load requirements and/or be connected to the electrical grid. The power conditioning is achieved via a dc-dc converter and a DC-AC inverter stages to produce the desired AC source. This is also the case even when the load is of dc type, such as the typical portable electronic devices that require AC adaptors to be powered from the AC mains. The letter presents a hybrid PV-battery-powered dc bus system that eliminates the DC-AC conversion stage, resulting in lower cost and improved overall energy conversion efficiency. It is also shown experimentally that the switching ac adaptors associated with the various commonly used portable electronic devices can be reused with the proposed dc bus system. A novel high-gain hybrid boost-flyback converter is also introduced with several times higher voltage conversion ratio than the conventional boost converter topology. This arrangement results in higher DC bus levels and lower cable conduction losses. Moreover, the voltage stress on the hybrid boost-flyback converter power switch is within half the output voltage. Experimental results taken from a laboratory prototype are presented to confirm the effectiveness of the proposed converter/system.

Copper-to-aluminum transitions in high DC bus systems

A number of papers have discussed issues related to electrical applications of various types of copper-to-aluminum transitions. Little field experience, however, has been discussed. This paper describes techniques used at a large electrochemical manufacturing site for making copper-to-aluminum transitions in high DC bus systems. After a brief historical treatment of problems with bolted copper-to-aluminum transitions, various explosion-bonded and roll-bonded bus transition designs and experiences are discussed. Two roll-bonded copper-to-aluminum transition designs are described, with mixed performance records. Some specific explosion-bonded transition designs are described, along with an explosion-bonded copper-to-aluminum transition with a titanium interlayer to permit the use of higher fabrication temperatures, without detriment to the strength of the metal-to-metal bond. Explosion-bonded transitions are shown to have good performance records.

Rectifier and DC bus system design for the copper electrowinning industry

Some of the design features of the rectifier and DC bus system that supply the direct current for the electrowinning process as discussed. As background information, a brief description of the solvent extraction (SX) and electrowinning (EW) process is given. The four basic steps to the SC/EW process include leaching, extraction, stripping, and electrowinning. Some of the design features of large DC rectifier systems, and the design basis for the DC bus systems are discussed. Some of the problems encountered with the operation of the systems and suggested means to correct these problems on existing and future systems are also discussed. A properly designed and installed rectifier and DC bus system is an important feature of the SX/EW process.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design and Specification Considerations for Construction of Large Industrial Rectifiers and Their Associated Facilities

Proper preparation of specifications is essential to obtain competitive bids for purchase and installation of large industrial rectifiers and associated facilities. Specification requirements for a power rectifier installation are presented. The article discusses the development of design specifications for purchase of the rectifier equipment, considerations in selection of a supplier, design of the dc bus system for connecting the rectifier to the load, and preparation of installation specifications. Also included is an example of how the computer may be used to determine optimum bus bar material. A sample problem is included.