To ensure security, interchangeability, and compatibility, standards and protocols are essential instruments. They define rules for products, processes, technologies, or services. In principle, their application is not mandatory if not regulated by laws or contracts.
A standard is an accredited document, in which requirements are defined based on a fixed consensus procedure. Such a consensus procedure is designed in a way that allows all interested market actors to introduce their respective positions in opposition proceedings. There are international (e.g., ISO, IEC), European (e.g., CEN, CENELEC) and national (e.g., ISO, DKE) standardization organizations which practice their activities in mutual coordination.
The consensus procedure for the accreditation of a standard usually takes several years. Thus, there are other possibilities to publish recommended courses of action and assessment reports in faster procedures with fixed requirements that do not necessarily require a wide consensus or public opposition proceedings. On a national level, such procedures are, e.g., DIN-specifications (DIN SPEC) and VDE or VDE/DKE application rules (VDE AR, VDE AR-E). On an international level, there are, i.e., IEC technical reports (IEC TR). Besides, industry members can establish and apply non-accredited standards, e.g., communication protocols such as OCPP.
On both a national and an international level, the standardization process for electromobility charging infrastructure is currently in progress. The variety of different market actors, use cases and interfaces in the context of electromobility and their grid integration makes this undertaking very extensive. Some standards already exist on an international level. Furthermore, there are various specifications, application rules and protocols, which often provide solutions to individual interfaces and for a limited number of use cases. The harmonization of these solutions within international standardization frameworks is aimed for and has already begun.
The first part of this article describes a selection of the standards, application rules and protocols around the topic of electromobility and gives an outlook on the current standardization efforts for future standards. The relevant interfaces between electric vehicle, charging station and charge point operator (CPO), as well as the relevant interfaces of this system with a home energy management system (HEMS) and the electricity grid. Figure 1 illustrates the considered interfaces and the associated standards and protocols. Since the work within the scope of the project unIT-e² focuses on other areas, the roaming protocols in figure 1 are not discussed in more detail.
The second part of this article provides an insight into a report of the “Sub-group on Governance & Standards” of the “Sustainable Transport Forum”. This expert group was appointed by the European Commission and their report summarizes their recommendations and preferences concerning the current standardization processes for electromobility.
Communication between electric vehicle and charging station
The Norm IEC 61851 is currently supported by all electric vehicles in Europe. In this low-level communication standard, signals are transmitted by pulse width modulation. It only offers basic charging functionality and does not enable advanced authentication and authorization functionalities. IEC 61851 does not permit digital data transmission beyond basic controlling signals. In the industry, IEC 61851 is only expected to be of future relevance as a fallback solution.
The standard ISO 15118 is a high-level communication standard. It enables substantially more extensive data transmission possibilities than IEC 61851. ISO 15118-2, which was published in 2014, already enables functionalities such as Plug & Charge, encrypted communication, energy management, AC and DC charging. ISO 15118-20, which was published in 2022, also enables bidirectional and inductive charging, as well as storage of multiple charging certificates. ISO 15118-20 is widely presumed to be a prerequisite for grid-friendly charging of electric vehicles   .
Communication between charging station and charge point operator (CPO)
For communication between charging station and CPO, the Open Charge Point Protocol (OCPP) is currently the de-facto standard. It provides compatibility with other protocols of the charging infrastructure, such as OpenADR. OCPP is predominantly used for authentication and authorization and offers a broad range of applications for Smart Charging and Demand Response. The current OCPP version 2.0.1, which was published in 2020, supports ISO 15118-2 and thus enables functionalities such as Plug & Charge. Furthermore, version 2.0.1 offers increased security features beyond version 1.6, which is currently the predominant version on the European market. Bidirectional charging is not yet supported in version 2.0.1. In a successor version which is currently under development, establishment of compatibility with ISO 15118-20 and bidirectional charging are expected.
OCPP is internationally adopted and accepted. There are, however, manufacturers of home energy management systems (HEMS), which rely on the EEBUS communication interface and do not necessarily want to implement an additional protocol stack for the communication between electric vehicles and charging stations within a property.
The standard IEC 63110 is currently under development and is expected to be published by the end of 2023. It will collect and extend the functionalities of OCPP but is, however, not expected to be backward compatible with OCPP. To address potential problems to this end, a document which describes the transition from OCPP to IEC 63110 is currently under development by IEC. The implementation of IEC 63110 is carried out in coordination with ISO 15118, as well as with IEC 63119, which is being designed to standardize the communication with E-roaming platforms in the future  .
Communication with a home energy management system (HEMS)
The VDE application rule AR-E 2122-1000 was published in 2021. AR-E 2122-1000 is an application rule for the communication between electric vehicles and local energy management behind a network connection point under consideration of grid-sided requirements. It serves as a basis for the standard IEC 63380, which is currently under development and is expected to be published by 2024.
The application rule AR-E 2829-6 is a communication protocol for the interface with the low-voltage electricity distribution grid at the property line of the connectee. Regarding the communication between local energy management system and charging infrastructure, AR-E 2829-6 is compatible to AR-E 2122-1000. AR-E 2829-6-1 to 2829-6-4 were published in 2021/2022. AR-E 2122-1000 and AR-E 2829 are based on the specifications of the communication interface EEBUS. The compatibility of AR-E 2829-6 with OpenADR is aimed for .
Communication with the electricity grid
For communication between CPO and electricity grid, the protocol OSCP has been around for several years. The Open Charge Alliance published version 1.0 in 2015 and version 2.0 in 2020. OSCP has not been widely adopted yet. It has been designed for transmission of physical net capacity to the CPO by a distribution service operator.
Another protocol for communication with the electricity grid is OpenADR, which has been designed for communication regarding demand response (DR) and distributed energy resources (DER) applications. At the present time, OpenADR is mainly applied in peak load management, while other DR and DER applications are being tested. Since 2019, OpenADR is officially accredited as IEC 62746-10-1 ED1.
Legislation concerning the communication between charging stations and the electricity grid is currently still under development, and the standardization efforts are still in an initial stage. In the industry, the IEC 61850 series is expected to play a role. IEC 61850 is well-established for station automation in power and telecontrol engineering. IEC 61850-7-420 describes communication for DR and DER applications. The technical report IEC TR 61850-90-8 provides an object model for electromobility based on IEC 61850-7-420. It was published in 2016.
Over the next few years, the standard IEC 63382 is expected to be developed on an international level for grid integration of electric vehicles. To this end, the working group JWG15 has been founded in 2021. The publication of IEC 63382 is aimed for in 2025 .
Outlook and discussion in the industry
In compliance with the EU directive 2014/94/EU regarding the infrastructure for alternative fuels, the European Commission has founded the Sustainable Transport Forum (STF). The STF Sub-group on Governance & Standards consists of 20 companies from the areas of electromobility, charging infrastructure and energy supply. In their report “Mapping of the discussion concerning standards and protocols for communication exchange in the electromobility ecosystem” , the recommendations and preferences of the members regarding EU-wide standards and protocols are summarized. Figure 2 gives an overview of the members’ positions. In the following, some specific opinions from the report are reproduced.
For the communication between electric vehicle and charging station, an EU-wide mandate to implement the ISO 15118 series is supported by a large part of the members, partly with specific proposals for an effective date in the next years. An agreement of all involved market actors on an implementation roadmap is aimed for. Some members propose a mandated provision of ISO-15118-20 under the EU Alternative Fuels Infrastructure Regulation (AFIR), with the additional comment that regulation should cover not only charging infrastructure but also vehicle manufacturers.
It is emphasized that the security level of the entire charging ecosystem must be increased, among other things by implementing the ISO 15118 standards. Several members still see a need for discussion regarding the design of user control, certificate and contract handling, data access and availability, and hardware regulation. Individual members criticize the fact that ISO 15118 only allows power line communication for conductive charging and call for retaining the ability to charge with IEC 61851 with wireless communication.
OCPP is widely accepted in the STF for communication between charging station and CPO. A mandated provision of OCPP is often seen as unnecessary since the protocol is already established as a de facto standard anyway. There is also widespread support for the future ISO 63110 standard, provided that backward compatibility with OCPP is adequately addressed. Individual members still see a need for discussion regarding the cybersecurity of OCPP. Some members do not wish to take a position on ISO 63110 until the exact content of the standard is known. Other criticisms of ISO 63110 by individual members are possible maintenance and rollout problems, and greater flexibility through the alternative use of proprietary protocols.
In the case of communication with the power grid, most members do not yet consider the current state of legislation to be sufficient to agree on international standards. The criticality of harmonizing new communication standards with smart meter standards is emphasized. Several members stress that CPOs must retain control over charging points and that there should not be a direct interface between the distribution system operator and the charging point. They base their comment on the EU directive 2019/944, Article 33.
Finally, STF notes that the existing standards do not sufficiently cover the end-user side. It is unclear so far what information and options the user can or should provide and control. Some members emphasize that the charging infrastructure should be designed in such a way that the user can make settings according to his/her own preferences, and that this should not be done exclusively by the vehicle manufacturers. In the near future, the non-ISO 15118 infrastructure will remain in use and users should be able to choose, for example, whether they use Plug & Charge or not. In addition, the STF members see a need for action in establishing price transparency for radio frequency identification (RFID) and Plug & Charge, and there is criticism that it is not yet possible to authenticate drivers in electric vehicles.
Standardization is of outstanding importance for the interoperability of components in the overall electromobility system. Standards are only helpful if they reflect a broad consensus among the players involved and are therefore widely accepted. Strict adherence to agreed rules by the market actors involved is essential for the timely and user-friendly design of the charging infrastructure for electric vehicles. Conversely, a multitude of different, competing standards and protocols is counterproductive. In addition, proprietary protocols that impose a certain usage behavior can have a negative impact on the acceptance of electromobility.
For the interface between the electric vehicle and the charging station, the ISO 15118 series of standards has met with predominantly positive response from the market actors involved. It is to be expected that the ISO 15118 series will become increasingly widespread in the coming years due to the much more extensive functionalities than with the established IEC 61851 standard, where the ISO 15118 rollout could possibly be forced by legal regulations.
For the interface between the charging station and the CPO, the OCPP protocol is receiving broad support from the industry. It is already widely used and may be replaced in a few years by the ISO 63110 standard which is currently under development.
Regarding the communication of CPO and charging station with the power grid, there is currently no clear picture of the future standardization landscape. Eliminating existing unclarities in legislation can create a basis for consensus among the market actors involved in future standardization activities.
 Neaimeh, M., Andersen, P.B.: Mind the gap- open communication protocols for vehicle grid integration. Energy Inform 3, 1 (2020). DOI: 10.1186/s42162-020-0103-1
 Mapping of the discussion concerning standards and protocols for communication exchange in the electromobility ecosystem. Brüssel: Europäische Kommission, 2022. DOI: 10.2832/6763.
 Roadmap zur Implementierung der ISO 15118 – Standardisierte Kommunikation zwischen Fahrzeug und Ladepunkt. Berlin: Nationale Plattform Zukunft der Mobilität, 2020.
 Ostendorf, L.; Johnsen, D.; Bechberger, M.; Gensch, S.: Steuerung von Ladevorgängen in der Elektromobilität. Köln: TÜV Rheinland Consulting GmbH, 2022.