R D'hulst

Multiagent Charging of Electric Vehicles Respecting Distribution Transformer Loading and Voltage Limits

In this paper, a market based multiagent control mechanism that incorporates distribution transformer and voltage constraints for the charging of a fleet of electric vehicles (EVs) is presented. The algorithm solves a utility maximization problem in a distributed way, assigning most charging power to the EVs with the highest need for energy. The algorithm does not rely on an iterative exchange of messages, but finds the optimal solution after the exchange of just one single message. A substation agent is responsible for guaranteeing a safe network operation. It uses the remaining capacity of each of the EV chargers for reactive voltage control. The performance of the algorithm is evaluated on an existing three-phase four-wire distribution grid. Simulation results show that the fleet of EVs can be charged at a minimal increase of costs, without jeopardizing the network.

Micropower generation with microgasturbines: A challenge

Abstract This paper describes the development of a microgasturbine with a rotor diameter of 20 mm. The target electrical power output lies around 1 kW. The total system fits in a cylinder with a diameter of 95 mm and a length of 120 mm. The system contains the same components as a large gasturbine generator: compressor, recuperator, combustion chamber, turbine, and electrical generator. Major challenges are the high rotational speed (500 000 r/min), high turbine inlet temperature (1200 K), and the efficiency of the components. Because of the small dimensions, the flow through compressor and turbine is characterized by relatively low Reynolds numbers. The higher flow losses and inherently lower efficiency require a higher blade tip speed (524 m/s) than for large turbines (300-400 m/s). To minimize wear and frictional losses, the rotor is mounted on aerodynamic bearings. To withstand the high centrifugal stresses, a high-strength steel is used for compressor and shaft. The turbine is made of a Si3N4-TiN ceramic composite to withstand the combination of elevated stress and temperature.

The value of residential flexibility to manage a BRP portfolio: A Belgian case study

This article focuses on the short term management of an energy portfolio with a considerable share of wind generation by a Balance Responsible Party. The portfolio consists of Gas Fired Power Plants and producers of wind energy on the supply side, and industrial and residential consumers on the demand side. Different balancing options are considered to manage the portfolio: upward or downward regulation of Gas Fired Power Plants, electricity market trading and shifting residential flexible demand (i.e. washing machines, dryers, dishwashers and electric hot water heaters). The remaining imbalance is settled via the balancing mechanism. The article presents a qualitative, multi-actor business model, but also includes a quantitative analysis based on a Belgian case study. Simulation results show yearly revenues for a residential consumer offering flexibility of up to €20.

Business case assessment of balancing large scale PV with flexible CHP

In a situation where the share of less predictable electricity production from renewable energy sources (like solar energy) in the overall electricity production-mix increases, the electricity system will be confronted with more imbalance. Balancing markets deal with these imbalances. In this context, a balancing responsible party (BRP) is responsible to maintain the balance in its portfolio on a quarter-hourly basis and is charged for any incurred imbalances. A BRP with less predictable electricity production in its portfolio, like PV production, has a higher imbalance risk and thus on average a higher imbalance cost. The case study under consideration aims at optimizing the portfolio of a BRP, which consists of a large scale PV installation and an industrial CHP unit. A software tool is used that is able to calculate to what extent the imbalance costs of the BRP can be decreased by actively controlling the available flexibility in its portfolio (in this case the CHP installation). The paper presents the results of the simulations and discusses the potential reduction in imbalance costs for the BRP if the flexibility of the CHP is used within different scenarios.