Jeroen 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.

Integration of energy storage in distribution grids

Electrical energy storage services can bring benefit to multiple stakeholders in the distribution grid. Energy storage owners maximize their profit on an external energy market. This can cause a conflict with the distribution system operator because a grid is designed in terms of peak power, not energy. The subject of this paper is a optimization method for the siting and sizing of energy storage in distribution grids. The optimization is implemented multi-objective as to visualize the trade-offs between storage stakeholders and distribution system operators.

Automated residential demand response based on dynamic pricing

Against the background of more renewable energy, limited investment in power generation, ageing distribution and transmission infrastructure, and the electrification of energy, the demand side of the electricity system is gaining attention. Moreover, the increasing ability to automate household appliances allows to involve the demand side more easily. Therefore, this paper examines demand response of residential consumers possessing smart appliances. Starting from day ahead wholesale prices and renewable energy production, different cost reflective Real Time Pricing (RTP) schemes are developed. According to these schemes, white goods are scheduled to the lowest price period taking into account user preferences. These demand modifications bring about new insights in the impact of the introduction of RTP.

Parameter identification of unknown radial grids for theft detection

This paper proposes an algorithm to detect the stealing of electricity by illegal connections in smart grids with unknown or uncertain cable lengths. Many new applications in the rising smart grid context will require information of the grid topology. We show that with measurement data of smart meters, the grid can be identified, as well as the phase of connection. One of the applications requiring grid information is the detection of electricity theft by double feeding. Electricity theft is a problem faced by all power utilities. Financial impacts are a reduced income for the system operator and the necessity to charge more to other customers. Stealing of electricity by double feeding can not be detected by the smart meter or by analysing the load profiles. Therefore it is suggested in this paper to use measurements of smart meters to identify the grid parameters and detect irregularities of specific customers.

Inverter modelling techniques for protection studies

Traditional fault calculation techniques are not capable of accurately modelling the short-circuit behaviour of inverter interfaced distributed generation (IIDG). As the share of IIDG continues to rise, more accurate fault simulations are required. This paper gives an overview of fault calculation techniques described in literature. All techniques are evaluated from the viewpoint of protection studies in medium and low voltage grids with a high share of IIDG. The averaged value modelling technique is selected. The merits of this technique are illustrated in a Simulink/PLECS simulation environment, where averaged value models are compared to full time-domain switched models in terms of simulation time and accuracy.

Power electronics for electric vehicles: A student laboratory platform

This paper presents a laboratory platform used in a problem solving and design course for first year engineering master students at the KU Leuven. The platform implements three power electronic systems that are found in electric vehicles: a field oriented controlled motor drive capable of regenerative braking, a bidirectional DC-DC converter and a battery charger. The battery charger is implemented as a bidirectional single phase grid-tied inverter that enables vehicle-to-grid support. Students learn to understand the hardware and control systems in simulation models. Afterwards they can test their models on real hardware through a rapid prototyping platform. The platform has a motor test bench to emulate driving conditions and regenerative braking. Measurable grid voltage deviations are observed while using the grid-tied inverter, demonstrating the impact of electric vehicles on the residential distribution grid.

Influence of voltage support by converter based distributed generation on the short-circuit power

This paper describes the influence of replacing centralised generation by distributed generation (DG) with a full converter (e.g. type 4 wind turbines, solar power) from a short-circuit power and a voltage support point of view. To allow investigating the influence the settings of the voltage support of the DG units, an iterative approach based on linear network calculations is used. Inherently, the short-circuit capability of these DG units is limited. However, it is shown that DG units can contribute to the short-circuit power of higher voltage levels to compensate (partially) for the short-circuit reduction that arises when DG units replace centralised generation. Additionally, it is verified that any increase of the short-circuit power is concentrated on the local grids where the DG units are connected. Other local grids are influenced far less. This allows to tune the voltage support settings based on the requirements of the high voltage grid, but to take into account constraints in the short-circuit power of the local grid.

Event-driven simulation of power electronics in the complementarity systems framework

A new event-driven method is proposed for the numerical simulation of power electronic circuits with ideal switches and diodes, and their accompanying control systems. The power electronic circuit is modeled as a complementarity system and the control system is modeled separately. It is shown that the diode state determination problem can be formulated as a complementarity problem. Discontinuous jumps in the state variables are allowed after a switching event. The method is applied to two examples and the numerical accuracy with respect to the step size is compared with time-stepping methods. The importance of the event localization accuracy is discussed.

Accurate second-order interpolation for power electronic circuit simulation

This paper presents a second-order accurate method for circuit simulation with idealized power electronic switches. The method combines the integration method TR-BDF2 with an improved quadratic interpolation technique for the localization of switch events. Next to preserving second-order accuracy after interpolation, the technique also preserves the capability to damp fast transients caused by small on-resistances and large off-resistances. Conventional interpolation techniques for integration methods do not have this damping property. This results in a loss of accuracy if a switch event occurs shortly after a transition to discontinuous conduction mode. Consequently, the step size required to achieve the desired level of accuracy is sometimes smaller than expected. With the improved interpolation technique, the second-order accuracy associated with TR-BDF2 is not affected at switch events. Numerical experiments confirm the improved accuracy of the proposed method. The method is compared with the simulation tools PSIM and PSCAD, and with the conventional interpolation polynomial of TR-BDF2 as used in Simulink.

Generic circuit partitioning method for efficient simulation of modular multilevel converter topologies

A generic circuit partitioning method is proposed which reorders the equations and variables of power electronic circuits with idealized switches and diodes in a specific bordered block-triangular form, where each block on the diagonal is dependent only on a small number of switches. The number of floating-point operations for sparse matrix triangularization, needed after a change of switch configuration, is reduced significantly by using the possibility to individually store the triangular LU factors of the diagonal blocks in memory for each possible switch configuration. The method is applicable to any power electronic circuit, but is especially beneficial for electromagnetic transient simulation involving modular multilevel converter (MMC) HVDC topologies where the number of switching components is usually very large.