Coordination of multiple charging stations for electric vehicles with load balancing functions

The necessity to limit the environmental impact of the transport sector has led the rapid increase of Electric Vehicles (EVs), which guarantee an absence of pollutant emissions during their operation. This trend has boosted the technical development of Electric Vehicle Supply Equipment (EVSEs), as the requirement to provide better charging performances has become more prompted. Among solutions, this actual need introduces the fundamental issue of smart charging. Dynamic load management is one of the E-mobility topics of greatest interest today and will cover an increasingly key role because it is particularly important for managing the EV fleets charging processes while limiting the risk of grid overloads and service interruptions. Thus, enabling the best load balancing solutions, that can ensure optimal EV charging within the grid connection contractual limits, represents a challenging target to which EVSEs producers are devoting their attention. For this reason, an increasing number of EVSEs manufacturers is introducing intelligent load management logic into their EV charging systems. While this provides the user with a valuable opportunity to implement smart charging, it also forces him to refer to a single maker for the multi-EVSE infrastructure realization, since these power orchestration methods are generally closed single-brand systems. These often refer to software or apps not extensible to different products and, sometimes, even applicable only among identical EVSEs. Within an ongoing collaboration between Politecnico di Torino and Edison S.p.A., this thesis aims to analyze the topic of dynamic load balancing and deepen it through the realization of an EV charging energy management system (EMS) capable of interfacing chargers of different brands, power sizes and specifications (e.g. AC or DC charge). The implementation of this hybrid charging control system is performed in the company laboratory which provides the three chargers considered, EVs and other components necessary to execute the experimental tests. The first part of the thesis focuses on characterization tests and comprehension of smart charging modalities of a particular AC charger. Different possible situations, including up to three EVSEs, and also presence of additional domestic load, are investigated. A second AC and a DC chargers are then analyzed, paying particular attention to communication protocols supported. The objective is to identify a possible way to assign desired charging command by using an alternative method to producer’s app or software (e.g. by simulating a smart meter), easily applicable to interface chargers with different specifications. Afterwards, charging control based on Modbus communication protocol (Modbus TCP/IP and Serial RS485) is performed through the implementation of three Python algorithms which enable individual power modulation for each of the three EVSEs considered. Finally, the thesis focuses on the unification of the three aforementioned algorithms into a single aggregated code for the complete charging management of the three EVSEs simultaneously active and supplied by the same power supply. After the description of the organization and the operative behaviour of this EMS, the final part provides results about power orchestration tests. Particularly, the last more articulated test wants to analyze the three different EVSEs dynamic load balancing behaviour with the additional consideration of domestic load absorption and photovoltaic generation on a five-hour time slot.