Peter Tant

Multiobjective Battery Storage to Improve PV Integration in Residential Distribution Grids

This paper investigates the potential of using battery energy storage systems in the public low-voltage distribution grid, to defer upgrades needed to increase the penetration of photovoltaics (PV). A multiobjective optimization method is proposed to visualize the trade-offs between three objective functions: voltage regulation, peak power reduction, and annual cost. The method is applied to a near-future scenario, based on a real residential feeder. The results provide insight into the dimensioning and the required specifications of the battery and the inverter. It is found that an inverter without batteries already achieves part of the objectives. Therefore, the added value of batteries to an inverter is discussed. Furthermore, a comparison between lithium-ion and lead-acid battery technologies is presented.

LINEAR breakthrough project: Large-scale implementation of smart grid technologies in distribution grids

The LINEAR project (Local Intelligent Networks and Energy Active Regions) focuses on the introduction and implementation of innovative smart-grid technologies in the Flanders region, and aims at a breakthrough in the further development and deployment of these solutions. It consists of a research component and a large-scale residential pilot, both focusing on active demand-side management of domestic loads. This paper describes the unique approach, the main objectives and the current status of this project. Selected business cases and target applications are discussed in detail.

Comparative analysis of coordination strategies for electric vehicles

This paper gives a structured literature overview of coordinated charging of electric vehicles (EVs). The optimization objective, scale and method of each coordination strategy are the three parameters used to characterize and compare different approaches. The correlation between the three parameters and the research category are investigated, resulting in a correlation mapping of the different approaches.

Design and Application of a Field Mill as a High-Voltage DC Meter

Field mill instruments are often employed for the measurement of electric fields, electric charges, voltage potentials and atmospheric effects. This paper discusses in more detail the application of a field mill for measuring DC voltages in high-voltage laboratories. Some specific problems, arising when voltages in the kV or MV range have to be measured, are emphasized. Safety, signal transmission and electrode design are dealt with. Field meter theory is summarized and generalized in function of this application. The design of a practical, field mill based electrostatic voltmeter is described along with some useful enhancements. Finally, test results of the voltmeter are presented

Fast robust gate-drivers with easily adjustable voltage ranges for driving normally-on wide-bandgap power transistors

Wide-bandgap (WBG) semiconductors, such as gallium nitride (GaN), are more and more being used in switching power devices. An AlGaN/GaN/AlGaN Double Heterojunction Field Effect transistor (DHFET) was developed in previous work and needed to be tested. The used test circuit was a buck converter. This type of converter, in addition with the normally-on switching behaviour of the GaN-based transistors, requires dedicated gate drive circuitry, resulting in the development of three types of gate-drivers. This paper presents the topology and performance of these drivers. Because of the type of converter, the drivers need to be galvanically isolated. Furthermore, because the experimental GaN transistors are normally-on, the drivers need to be robust so that they apply a negative gate-to-source voltage to switch off the transistor in case an error occurs in the driver. A third requirement for the drivers is that it has to be easy to adjust the voltage levels, in order to test the devices at different gate-to-source voltage conditions. A final requirement is that it has to be possible to construct the drivers with readily available electronic components. Because the drivers are galvanically isolated, there is a parasitic isolation capacitance in the DC-DC-converter of the drivers. This gives rise to a common-mode current which possibly can disturb the operation of the driver. The article also discusses this common-mode problem.

Virtual circuit control for multi-converter smart grid applications

This paper presents a scalable synchronous buck converter design. Innovation lies with the design method and control algorithms. Firmware makes the converters half-bridges switch as to emulate a resistively terminated ladder network. This actively damps filter resonances and prevents circulating currents when multiple converters operate in parallel.

A hybrid electric kart with energy flow management as a student project

A hybrid electric Kart is built as a didactical project for the students of the Master of Engineering: Energy of the K.U.Leuven. In order to cope with the growing number of students, a modular hybrid electric kart is conceived. The hybrid configuration allows to diversify between several tasks that have to be addressed by the students. The tasks include a control scheme for an induction motor, a control scheme and design of a power-factor-correction converter which enables power flow between the DC-link and a gasoline generator and finally the control scheme and design of a DC/DC converter allowing bidirectional power flow between a low voltage battery and the DC-link. All control schemes are supervised by a top level control scheme which maximises efficiency. The control schemes are programmed in Matlab/Simulink. A rapid-prototyping control board runs the model made in Matlab/Simulink. The control board interfaces between the different sensors and power electronics present on the kart.

Virtual circuit design of grid-connected half-bridge converters with higher-order filters

This paper presents a structured design method for half-bridge converters with higher-order lossless output filters, focusing on the popular LCL filters. The method builds on the theory of terminated ladder networks and on a control algorithm actively emulating the ladder networks termination. Given a desired transfer function, a normalized ladder network is accordingly synthesized and scaled to meet the physical requirements. The component sizing and the active damping of filter resonances are simultaneously tackled. The associated digital-control architecture for LCL filters is explained. A Kalman observer is employed to deal with the inherent sample delay. An LCL filter is designed based on the proposed method and is experimentally validated with the half-bridge converters operating as active front end. The grid reactive currents are stepped and the results show properly damped responses. The system has good disturbance rejection and is passive according to the simulated input admittance. The robustness of the system is also demonstrated by numerical sensitivity analysis. These excellent characteristics can facilitate the design of the upper-layer or incorporated outer-loop controller, and can enhance the performance of the complete system.

Virtual circuit control for active damping of LCL resonance in grid-connected voltage source converters

This paper presents a virtual circuit controller (VCC), which provides a systematic structured method to stabilize the resonance of an LCL filter in a grid-connected voltage source converter. The semiconductor switches are controlled to mimic the behaviour of a virtual reference circuit. The properly-damped circuit by a resistor in parallel with a filter capacitor is focused on and selected as the reference circuit. A linear transformation matrix is introduced indicating the resemblance between the physical and virtual circuits, and is employed to map the states between both circuits. Accordingly both analog and digital control laws are systematically computed. The insight into the feedback of the capacitor current and voltage through proportional gains is clarified. While the consequence of the former is conventionally known to emulate a resistor for damping purpose, the latter is newly used to emulate an inductor for adjusting the inner-loop control bandwidth and improving the robustness. A Kalman filter is used to deal with the inherent time delay. The detailed discrete-time state-space model of the complete system is derived. The design example of the proportional current controller is demonstrated. The simulation results illustrate the effectiveness of the damping and the robustness of the system against component-value variations.

Electric vehicle impact assessment study based on data-logged vehicle and driver behavior

Traditionally, the impact of charging electric vehicles in the electricity grid is determined through scenario-analysis and based on statistical data. In this paper, instead of making assumptions on driving behavior, the energy consumption was calculated with measured driving profiles of conventional vehicles in order to quantify the future impact on the grid in more detail. As a function of the penetration of the Plug-in Hybrid Electric Vehicles and Battery Electric Vehicles, the increase in the peak power requirement in the grid is assessed.