November 11, 2021
The Open Charge Point Protocol (OCPP) is a protocol for communication between an EV Charging Station and a central Back Office system. OCPP is an international open standard which is available for free, no license fees are required. The version of the protocol was developed in 2009 for the EV infrastructure market and is supported today by many large players in the EV industry such as utilities, Charging Station manufacturers, Charge Point Operators (CPO), and back-office software suppliers.
As such, OCPP is designed to be vendor-independent, thereby providing the opportunity for infrastructure operators in choosing EV Charging Stations, and for vendors to supply EV Charging Stations to any infrastructure operator. Companies like ampcontrol have built their software solutions often around OCPP.
Similar to many IoT protocols, OCPP describes the messages that Charging Station and IT Backend send to each other to authenticate new EV users, track energy meter values, or give charging commands. Following illustration is a small example from the OCPP protocol that refers to the authorization, start, and stop for a charging cycle.
Trends in the electric vehicle world and the energy market are reshaping standards and requirements for charging backends. Software systems become more secure, increasingly flexible, receive new functionalities, and are more and more interoperable. One essential "innovation" is the ISO Standard ISO 15118 that describes the communication between vehicle and charge point. It offers a similar authentication known from PKI (e.g., used for a secure connection for websites) and better communication for data messages between vehicles to charging stations.
A second essential change is the more mature smart charging functionalities for OCPP 2.0 as well as OCPP 1.6. Especially OCPP 2.0 offers a wide range of control functionalities for utilities, Charge Point Operators (CPO), or EVSE owners.
As the number already says, OCPP 2.0 was released after OCPP 1.6 and is the latest version of the open protocol for EV charging. As OCPP 2.0 was published in 2018, major EV charging systems still use OCPP 1.6. Nonetheless, most manufacturers and service providers see OCPP 2.0 as a critical milestone and plan the shift to the newly released version in the next years. Few charge point providers such as Ebee already market charge points based in OCPP 2.0.
Previous OCPP versions have shown a significant lack of data communication. Connected IoT systems such as complex charging networks rely on being up to date with the latest device information. A central system always requires updated information about connected vehicles, use identifications, metering values, and more. Only mature communication protocols have enough data fields and the necessary flexibility integrated into the source code to give the software engineers enough tools and flexibility while integrating a charging network.
A significant improvement is the possibility to communicate the requested energy amount (=the amount of energy in kWh that the vehicle wants to charge). After the vehicle user connects his electric vehicle and the charge point, the vehicle sends the requested energy information in a message to the charge point (only with ISO 15118). The charge point forwards this value as an absolute value (e.g., kWh) to the central charging network, which can plan the charging cycle based on the requested energy amount.
OCPP describes this as "Charging with load leveling based on High-Level Communication," which refers to advanced usage of the charge point (EVSE) and the Charging Station Management System (CSMS). The following illustration shows a part of the primary communication process between EVSE and CSMS. The first three steps show the usage of the requested energy amount:
1. The EV sends a ChargeParameterDiscoveryReq message to the Charging Station.
2. The Charging Station sends a NotifyEVChargingNeedsRequest message to the CSMS.
3. The CSMS sends a NotifyEVChargingNeedsResponse message to the Charging Station.
The Charging Station uses the message "NotifyEVChargingNeedsRequest" to communicate the charging needs as calculated by the EV to the CSMS. The NotifyEVChargingNeedsRequest contains the following fields. The field "chargingNeeds" includes the "energyAmount" of the EV.
OCPP 1.6 doesn't allow the usage of such a field or to send the requested energy amount as an absolute value from the charge point to the OCPP backend. Instead, OCPP 1.6 allows "only" to send a State of Charge (also called SoC) that represents the current state of the vehicle's battery in percentage (State of Charge = 80% means that 20% of the battery needs to be charged with electric energy). The State of Charge is a vital data field but limits the information on the OCPP backend or a possible energy management system. Nevertheless, there are many possibilities to implement Smart Charging in charging networks in OCPP 1.6. For example, at ampcontrol, we have developed cutting-edge interfaces for OCPP 1.6 and OCPP 2.0 backends. Developers can request free access to our documentation and a free trial to implement Smart Charging through ampcontrol for their OCPP backend system. (www.ampcontrol.io)
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