Andreas F. Raab

A coordinated voltage control algorithm is developed to facilitate the integration of electric vehicles into microgrids. This proposed algorithm reduces the voltage fluctuations via the optimal adjustment of the tap positions of on-load tap changers and of the reactive power injections of inverter-based distributed energy resources. Based on the proposed voltage control algorithm, an industrial implementation framework is established to enable the interactive communications among the on-load tap changers, the inverter-based distributed energy resources, etc. Compared to previous studies on voltage regulation in microgrids, this work is distinguished by the fact that the proposed voltage control algorithm is implemented and tested on a real-world experimental test site, known as the micro smart grid on the EUREF-Campus in Berlin. Constraints such as actual process latencies are readily observed. The micro smart grid comprises a power transformer with on-load tap changer, rooftop photovoltaic systems, battery energy storage systems, and electric vehicle charging stations. The real-world test results confirm that the voltage deviations are significantly reduced by the coordinated voltage control algorithm, as opposed to the uncontrolled state. Thanks to the analysis of the trigger cycle of the proposed algorithm, the lifetime of the on-load tap changer can be extended while ensuring the effectiveness of voltage control

With the share of electric vehicles in the transportation sector rising, solutions for their power system and energy market integration are of increasing importance. In this context, aggregation entities are helpful for addressing the integration process of electric vehicle (EV) fleets. In this paper, a novel methodology for day-ahead charging control of EV fleets is proposed. This includes the prediction of required energy used for charging purposes based on synthetic data and functionalities for optimized energy procurement in the day-ahead energy market to determine the aggregated charging schedule of the fleet. The aggregated charging schedule provides the basis for the proposed charging control algorithm for individual EVs. This algorithm allows for charging flexibility according to the user’s driving preferences while considering data privacy. To avoid data privacy conflicts, the scheduling of the individual charging is decoupled from the upcoming individual driving schedules of the users themselves. This means that the user is not asked to plan and submit expected driving profiles. Instead, realization is by a user-oriented disaggregation that utilizes the aggregated charging schedule as an input to coordinate the individual charging processes itself. The resulting integrative market solution allows to fulfill the contract positions in energy market participation. The simulation results verify the optimality of the proposed methodology for day-ahead operation and its applicability for aggregation entities that serve as an intermediate between the vehicle owners and electrical utilities or the energy market.

For the purpose of utilizing electric bus fleets in metropolitan areas and with regard to providing active energy management at depots, a profound understanding of the transactions between the market entities involved in the charging process is given. The paper examines sophisticated charging strategies with energy procurements in joint market operation. Here, operation procedures and characteristics of a depot including the physical layout and utilization of appropriate charging infrastructure are investigated. A comprehensive model framework for a virtual power plant (VPP) is formulated and developed to integrate electric bus fleets in the power plant portfolio, enabling the provision of power system services. The proposed methodology is verified in numerical analysis by providing optimized dispatch schedules in day-ahead and intraday market operations.