Quang Hai Nguyen

• The increase in the number of electric vehicles(EVs) has undoubtedly put stress on the local power grid because these systems were designed without anticipating the charging needs of electric vehicles. To overcome this problem, Smart Charging is introduced to allow the Charging Stations Management System(CSMS) to load-balance the charging needs of the electric vehicles during peak hours. In addition, it allows the EVs to return their energy to the system when needed. Smart Charging uses the de facto standards ISO 15118 and OCPP to enable the CSMS to control the charging profiles of the EVs. Since these protocols are specified by different organizations, their compatibility must be analyzed to ensure their interoperability. In the first part, this thesis aims to apply a theoretical analysis method to analyze the compatibility between ISO 15118 and OCPP. This method uses the Symbolic Transition System to model the interactions between the protocols. Then, the state transitions and message exchanges of the models are analyzed using the flooding algorithm. The result of this analysis is a compatibility matrix, which illustrates the degrees of compatibility between the states of the protocols. Based on the results, this thesis concludes that ISO 15118 and OCPP are compatible. However, their compatibility is not perfect because of data type incompatibility between messages. The reason is that ISO 15118 uses domain data types for its parameters, while OCPP uses generic data types to increase its interoperability with other protocols. The second part of this thesis describes the concept and design of the application to bridge the communication between ISO 15118 and OCPP. The application also demonstrates how to overcome the problems found in the compatibility analysis using facade patterns. In addition, the development of the bridging application highlights several issues that have arisen in practice. The first issue is, due to the large memory footprint of the messages, the OCPP stack is not suitable for running on small embedded systems without extreme optimization. Second, using JSON, a human-readable format, to encode the OCPP messages is unnecessary because most of the messages are processed by machines. In addition, the OCPP application is highly complex due to the nested conditions involved in sending and receiving OCPP messages. Finally, both the JSON and EXI data formats require serializers (parsers) to encode (decode) the messages, adding to the complexity of the system.