Sven De Breucker

Impact-analysis of the charging of plug-in hybrid vehicles on the production park in Belgium

Internal combustion engines (ICE) are combined with electric motors and batteries in both hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (PHEV) to improve efficiency and achieve a limited all electric range. This paper determines the electrical power required for charging a fleet of PHEVs in Belgium. A stochastic model based on the driving behavior of Western European drivers, determines the availability of the PHEVs for grid charging.

Layout and performance of the power electronic converter platform for the VSYNC project

This paper presents the power electronic platform used for the VSYNC project. In this project, inverters are controlled in such a way as to exhibit a virtual rotational inertia towards the grid, in order to limit grid frequency variations in grids containing a high share of inverter-connected DER. First the layout and operation of the platform are described in detail, showing its versatility for research purposes. Next the performance of the platform is illustrated using experimental results obtaining using a grid-connected inverter in a laboratory setup.

Possible applications of plug-in hybrid electric ships

This paper presents the evolution of hybrid electric ships and the upcoming changes in hybrid electric propulsions by the addition of a battery based ESS. The inverter topology most suited for the expansion of the hybrid electric drive is the VSI inverter because this topology allows a DC/DC converter to control the power flow between the battery and the DC-bus of the propulsion motor. Different battery technologies are discussed by comparing the specifications of a 1 MWh reference battery. The impact of the addition of the batteries on the propulsion system is discussed. The battery allows the diesel generators to operate closer to their optimal efficiency by charging the battery when load is below optimal and by discharging the battery when load is above optimal. During anchoring, harbour docking, maneuvering and low speed cruising, the required power drops significantly and battery can take over from the diesel generators. The limited all-electric range allows the ship to shut off its engines some tens of km away from the harbour, improving local air quality. A large capacity battery can also improve safety by offering a few hours of all-electric low-speed cruising. In naval applications the all-electric range improves the stealth capabilities of the ship by reducing its acoustic and thermal signature. In the CODLAG configuration top speeds can be achieved with less prime movers by installing larger electric motors that are fed from both normal generators as well as the battery.

Impact of Current Ripple on Li-ion Battery Ageing

The aim of this paper is to investigate the impact of the current ripple, originating from the dc-dc converter of e.g. a PHEV powertrain, on the ageing of Li-ion batteries. Most research concerning batteries focuses on very low (μHz) to low (Hz) frequencies and low current ripples to create very accurate battery models which can determine e.g. the State of Charge of the battery. On the other hand the design of dc-dc converters tries to reduce the current ripple by using multiple phases with interleaving technique and capacitors in parallel with the battery. The interaction between the current ripple of the dc-dc converter and the battery has received little attention so far. A test set-up is build with two identical 304 V, 12 kWh Li-ion batteries and two 100 A dc-dc converters. The dc-dc converter can be connected to an LCL-filter or solely to the primary inductor of this filter, such that the battery current contains a small or large current ripple respectively. The batteries are discharged and charged to simulate the circumstances in which a plug-in hybrid electric vehicle is used. After each month, during which the battery either experiences a small or large current ripple, characterization tests are performed to establisch the ageing of the batteries. Based on the test results, the current ripple does not appear to have a measurable impact on the battery resistance and the Discharge and Regen Power. There is an increase of the resistance and a decrease of the Discharge and Regen Power, but this is to be expected as the battery packs are submitted to 3 months of Combined Cycle Life Testing. The temperature of the battery turns out to be far more important for the resistance and attained power levels of the batteries. The absent effect of the current ripple on the ageing of the batteries may be due to the intrinsic double-layer capacitor. This capacitor at the surface of the electrodes carries part of the current ripple and reduces the current ripple as experienced by the actual charge transfer reaction which carries the dc-part of the current.

Analysis of three-level converters with voltage balancing capability in bipolar DC distribution networks

The growing number of distributed energy resources, DC loads and energy storage systems drive the adoption of DC distribution networks. This paper in particular addresses three-wire bipolar DC distribution networks (b-DCDN), that provide two voltage levels to connect low- and high-power loads, while transferring twice the amount of power with less conduction losses as compared to the two-wire unipolar network configuration. To stabilize and control these two voltage levels, converters with voltage balancing capability are essential. Although dedicated voltage balancing converters that transfer power between both poles exist, this paper shows the extent to which certain three-level DC-DC converters can both interface DC devices such as battery energy storage systems and balance the pole-to-neutral voltages in the presence of unbalanced currents. More in particular, this paper identifies and analyzes the members of the non-isolated three-level converter family that feature a bipolar DC front-end in different unbalanced conditions, thereby explicitly deriving the operating area of these converters, based upon a decomposition in balanced and unbalanced components. Furthermore, the paper demonstrates the influence of the modulation scheme in unbalanced conditions on the current ripple and required inductance.

Comparing an unbalance compensating converter with and without a neutral connection

Voltage unbalances in low voltage grids have a renewed interest due to the massive deployment of single-phase grid-coupled PV inverters. Three-phase converters have the potential to compensate voltage unbalance, but commonly only have three legs. The goal of this paper is to theoretically compare unbalance compensation with or without a neutral connection, independent of the technology used for that neutral connection. It will determine how loads can be compensated and what the influence on the grid losses is. The results show that a converter with a neutral connection offers some distinct advantages and is able to compensate unbalance completely. But also the common three-phase converter has potential. The results are crucial in the decision whether or not to include a neutral connection to an unbalance compensating converter.