Multiport Electric Vehicle Charger with Multiple Outputs and Energy Storage
In this project, the concept of a multiport, flexible and intelligent Electric Vehicle (EV) DC-type charger which features multiple output charging spots through the implementation of multiplexing techniques will be developed.
As multiple EVs are connected to a single charging unit, the maximization of the utilization of power installed can be achieved. Output power and voltage scalability is a key feature of the system by usage of Power Electronics Building Blocks (PEBB), i.e. the total power can be scalable to several MW. This leads to manufacturing cost advantages (or low investment of €/kW) because a single circuit building block design can satisfy a plurality of business applications and many charging standards (conventional and new - CCS and CHAdeMO). More importantly, the system can be adapted to allow higher battery voltages, e.g. up to 1 kV, following the trend of the EV market. Additionally, to counter act to the expected reduction of governmental subsidies and consequent increment of the charging cost, the system can incorporate energy storage into the charger inner DC-grid. This is advantageous to buffer the power demand from the AC grid and to reduce energy consumption costs. This also allows the participation in the network ancillary service market generating extra profits for the stakeholders. All in all, the technical advantages of the propose charging concept allows reduction of the cost of charging EVs. The study verifying the advantages and requirements for the energy storage integration will be shared between TUD and ALFEN.
Finally, this work will define rules, guidelines, and techniques for the design and selection of economically sound DC-type EV chargers with multiples outputs. This includes the definition of important circuit components and distinctive control features which should be incorporated in its structure, such as battery storage. This will be used for the development, construction and experimentation of a 10 kW EV charger concept in the TUD laboratories.
The main challenges are:
- Selection of suited DC-type EV charging structure: The proposed multiport DC-type EV charger employing multiplexing technique can be implemented in many different ways with several suited power electronic circuits and low or medium frequency galvanic isolation. Therefore, analytical models will be derived in order to evaluate the merits of each suited systems (cost, efficiency, power density, etc); and finally, the benchmarking of EV fast DC chargers through multi-objective design will be done;
- Identification of EV charger adaptable to future demands: In order to cope with the growing demand of power of the EV market for higher power capabilities, e.g. 350kW@1kV following new 2020 CHAdeMO protocol, the PEBB concept is implemented allowing easier power and voltage level upgrades;
- Provide high conversion efficiency: A total target conversion efficiency for power flow from Grid-to-Vehicle higher than 98% is desired, which ensures that each power conversion stage of the EV charger display very high efficiencies. Therefore, the PEBB will be developed using a multi-objective design approach;
- Sizing the integration of energy storage: Power system studies will be carried out providing insights of the requirements for the sizing and design of battery energy storage, which can be integrated into the DC-grid of the charging station. This will take into account: the power of the infrastructure; the economic aspects such as profit, energy cost, electricity tariffs; the cost of storage; the available governmental subsidies and ancillary service market; and the benefits for the grid power quality and stability.
The main goals of this tasks are:
- The identification of suited applications/business where the multiport EV charger can be used, including the definition of economically advantageous circuit structure and the selection of components, including the utilization of newly developed IGBT technology;
- The development of intelligent charging control which exploits the multiplexing technique while ensuring both, the fast charging requirements and the maximization of monetary profits and reduction of charging costs by guaranteeing a high utilization of the installed power of the infrastructure;
- The final definition of rules and guidelines for the design and selection of the fast DC charger systems and the important circuit/control features which should be incorporated in its structure which gives a market competitive advantage;
- Verification of this work through the designing, construction and testing of hardware prototypes.
A laboratory scale demonstrator of 10 kW will be constructed, implementing the selected PEBB concept, which will verify the multiplexing circuit technique functionality and charging power flows. Additionally, an extra 10 kW prototype to test the integration of energy storage into the EV charge will be developed and tested