A current-sourced DC-DC converter derived via the duality principle from the half-bridge converter

A new current-sourced switch-mode power supply topology is developed by the application of a duality principle to a voltage-sourced half-bridge converter. The new converter has boost converter characteristics and is suited to low-voltage high-current input applications. The new converter is shown to compare favorably with the center-tapped transformer converterthat has found wide application at low voltages. Two optional enhancements - nondissipative snubber networks and inductor clamping windings - are also examined. Some results obtained with a low-power prototype are also presented

An economic assessment of “second use” lithium-ion batteries for grid support

The lithium-ion vehicle battery market is forecast to grow to tens of thousands of megawatt hours and exceed $USD 30 billion annually in 2020. Retired batteries will typically retain 80% of their initial amp-hour capacity at the end of life and can either be recycled or disposed of in secondary markets. Given the volumes involved many markets may saturate and price will be determined by the economic return in a given application. This paper proposes an infrastructure for the large scale processing of battery packs for utility support and assesses their residual cycle life and the economic return expected

A Scott transformer based single to three phase power converter for SWER applications

Three phase power, especially for pumping applications, is highly desired in many rural applications. For economic reasons, many of these installations are supplied from single phase medium voltage networks. This paper shows that a well-balanced three phase supply, suitable for induction machine supply, can be produced with a Scott transformer connection of a single phase inverter and the existing single phase supply. The single phase converter only processes half of the load power. A regulation scheme based in the DQ frame is proposed and it is shown the single phase inverter directly controls the quadrature axis voltage. A well balanced supply can be produced by regulating this inverter to eliminate any negative sequence voltages

Capacity improvements for rural single wire earth return systems

The single wire earth return, (SWER), system is a low cost power distribution method that finds international use in rural areas, it is a key technology for the extension of grid systems. In Australia, SWER systems can cover vast areas. A single SWER system may typically supply 100 kW to several dozen customers and may extend more than 300 km. Recent changes in the Australian retail energy market structure and significant load growth are driving a requirement for new low cost methods of capacity improvement. Shunt reactors are often used in SWER systems to compensate for line charging current effects. As voltage regulation is the determining capacity factor, the replacement of fixed shunt reactors with controllable reactors provides an opportunity to significantly increase the system capacity. A case study of the North Jericho SWER system is presented which shows a capacity increase of approximately 85% can be achieved

The impact of sympathetic magnetization transients on harmonic filters in auto-transformer fed railway traction applications

The operation of mixed fleets of modern PWMrectifier and older thyristor locomotives and the tightening ofharmonic emission standards globally will lead to more complexharmonic filter installations in railway applications. This papershows that track switching operations in an auto-transformer fedsystem can generate sympathetic transformer magnetizationcurrents that have very significant magnitudes, high harmoniccontent and last for some seconds. A sympathetic transient canoccur when un-energized auto-transformers are switched intoservice and paralleled with energized transformers at the feederstation or in adjacent track sections. The harmonic loads imposedby these currents need to be considered in the design of theharmonic filter elements and protection

The use of Thevenin/Norton models for the rapid assessment of harmonic filter performance for power system contingencies

Large harmonic filter installations must perform over a broad set of impedance conditions that change according to operational contingencies at the point of common coupling, (PCC). A complex harmonic load, such as a railway feeder station, may be compactly characterized by a Thevenin or Norton network for each harmonic. Spread-sheet based tools can be developed to rapidly assess the harmonic impacts for contingency driven variations in the PCC conditions. Maximum power transfer calculations show that voltage-based harmonic distortion standards force limits for high order harmonics that can correspond to extremely low harmonic power levels in practical systems. The potential to review the use of voltage based standards is raised

Energy storage options for hybrid diesel electric shunting locomotives

Shunting locomotives are required to produce high powers during shunting operations but may be idle for many hours each day. A key issue with a hybrid conversion is battery life. Shunting locomotives are required to develop typically 1000hp to 2000hp for periods of perhaps a few minutes and the battery is sized for its capacity to deliver instantaneous power. This paper will examine typical shunting duty cycles for a 1000 hp case study where a 520Ah 880V battery is applied. Methods of estimating battery life based on amp-hours exchanged with correction factors for time duration and peak currents are explored. Alternate storage devices such as ultra capacitors can provide methods of significantly reducing the peak battery discharge current and could potentially halve the battery mass

A UPFC with reduced DC bus capacitance for LV distribution networks with high PV penetrations

A low voltage (LV) distribution level unified power flow controller (UPFC) is shown capable of regulating the positive sequence voltage with a network while simultaneously correcting phase unbalance voltages that can be produced by high levels of distributed photovoltaic (PV) generation. Instantaneous reactive power theory shows that DC-bus capacitor power will fluctuate at twice mains frequency during any unbalanced operation. Instantaneous power balance can be maintained by allowing the input converter to draw a small negative sequence current. This allows a hundred-fold reductionin the value of the DC bus capacitance allowing long life ceramic or polypropylene capacitors to replace electrolytic capacitors in this application

Boost rectifier power factor correction circuits with improved harmonic and load voltage regulation responses

The time domain step response for rapid load changes can be improved in boost type power factor correction circuits by using a capacitor voltage model. In single phase PFC circuits, the dc bus voltage must have a significant voltage ripple at twice the mains frequency due to energy balance requirements. In traditional implementations, the presence of this ripple voltage causes a trade-off between line current wave shape and speed of the dc output regulatory response. The capacitor voltage model provides a ripple free estimate of the storage capacitor voltage. This allows the bandwidth of the dc bus voltage regulation loop to increase without causing a degradation of line current wave shape. Simulations show that the dc regulatory response is complete within one mains cycle and significant reductions in voltage over and under-shoots are achieve

A unity power factor boost rectifier with a predictive capacitor model for high bandwidth DC bus voltage control

Single-phase rectifiers with power factor correction circuits based on the boost converter have broad application in consumer equipment. A fundamental design difficultly is caused by the need to trade-off the input line current wave shape and the dynamic response of the output energy storage capacitor voltage regulation loop. The energy balance requirement inherent in single-phase systems forces a significant 100 Hz voltage ripple on the output capacitor. A highband width voltage regulation loop will feed back enough of the 100 Hz component to distort the current reference signals for the inner current control loop distorting the line wave shape. A reference model can be used to construct a ripple-free estimate of the capacitor voltage. This paper shows that improved output capacitor voltage regulation can be achieve simultaneously with a high quality input current spectrum