Local public transport has taken on a pioneering role in the transition to alternative drive systems. The EU's "Clean Vehicles Directive" and its mandatory minimum quotas for the procurement of clean and emission-free vehicles are providing strong impetus. Considering this, companies are under increasing pressure to develop a practicable and sustainable electrification strategy.
The major challenge: Only a few companies and suppliers have a comprehensive understanding of the requirements of public transport operations and the management of an electrical infrastructure. However, this is precisely what will be needed to create the necessary infrastructures quickly, use them efficiently for a long time and remain independent of the proprietary technologies of individual manufacturers. It is therefore important to optimize the complex interaction of vehicle operation and charging management as well as to create standards for communication between the various systems. This is englisch
Considering Operational and Electrical Parameters Holistically
Charging electric buses en route or in the depot presents transport companies with new challenges. The central question is: How can it be ensured that the buses are available on time, with the required battery state of charge and this as economically as possible?
It must be considered here that far more influencing factors and dependencies play a role than, for example, the limited battery range. The range of each individual vehicle, for example, is influenced by the age of the battery, the outside temperature or the specific driving style of a bus driver. The decisive factors for charging the vehicles are in turn the
- Charging infrastructure at the route or in the depot,
- Specific connected load and
- Possible restrictions to the electrical supply due to grid conditions and prices.
Finally yet importantly, aspects such as grid-friendly charging, battery conservation or charging at favorable energy prices can become relevant economic factors.
The task is to duly consider and balance a large number of operational and electrical parameters with their complex dependencies in an optimized manner. If a fleet comprises many vehicles, this planning is only possible with the help of software.
Optimizing Complex Dependencies Automatically
Transport companies benefit from integrated depot and charging management systems, which have been specifically designed for emission-free public transport. PSIebus combines the products PSIeDMS for depot management and PSIsmartcharging for charging management. It integrates the data from operational pre-planning with the data from the electrical systems.
Vehicle and operating data, together with weather forecasts, information on infeeds, transformers and charging stations are the basis for resource-saving, demand-oriented charging processes. In the event of an imminent overload or a limited (de-rated) energy supply, PSIebus automatically redistributes the available power adapting to the technical (e.g., power line overload) and commercial (e.g., maximum power limit or prices) constraints while ensuring reliable operations.
The System Determines the Best Charging Process for Each Vehicle
PSI's Qualicision optimization core supports balancing all relevant criteria and their manifold - and in some cases opposing - dependencies at high speed. Depending on their specific structures, companies can prioritize and weight all parameters individually and adjust them flexibly.
An example may clarify the capabilities: The overall planning defines the minimum charging state of the battery for the next tour as a hard restriction, which has to be met. Other criteria may include a reduced maximum charging rate that is gentle on the battery or a reduced target state of charge of the battery. They are prioritized and weighted in relation to each other and are included as criteria in the charging planning. The reduced battery aging is definitely a relevant economic factor for large companies.
Another example is an imminent overload or restrictions in power supply. In this case, the system distributes the power automatically to stay within the imposed limits.
Standardized Communication Processes Between Depot and Charging Management
Because connected systems such as DMS (PSItraffic/DMS) or ITCS (PSItraffic/ITCS) will have to interact closely with charging and load management systems in the future, and these in turn with charging stations, interfaces are required facilitating communication. Economy and technology demand using standardized interfaces. They are the basis for standardized process with a clear definition of responsibilities and investment security. Transport companies are able to select their vendors freely, avoiding vendor lock-in.
The VDV 463 interface standard has its origins in the successful project currently in operation at Hamburger Hochbahn. The standard primarily describes the bilateral exchange of information between the depot and charging management systems and defines the data format as well as the transport protocol. This includes, for example, which operational parameters are transferred from the operations or depot management system to the charging management system (CMS). Also defined are how, where and with what priority the charging requests are transferred to the CMS as well as how it responds with the detailed charging planning as charging information.
Specification of Interfaces Between Charging Management System and Charging Stations
The open and certified OCPP 1.6 (Open Charge Point Control) interface already defines the connection between the charging management systems and charging points. It describes how the messages between the two components are used for monitoring and charging control and, on the other hand, the behavior expected by the charging infrastructure and, in some cases, by the buses, including the relevant data.
The problem is that the specific way in which messages are used in this context remains open. For example, the protocol does not define precisely enough which charging profiles must be used for central charging control and which data has to be provided by the charging station so that central monitoring and charging control is possible. The same applies to the description of the use of the charging profiles in the event of communication failures or disruptions to the energy supply.
Consequently, the different or incomplete implementation of the smart charging profiles may cause high costs when connecting the charging stations to a load and charging management system. Therefore, PSI has published the OCPP 1.6 messages in the "PSIready" document. This includes particularly the consideration of energy supply restrictions and the precise definition of emergency operation, which is missing in most interface descriptions.
Longterm Success With an All-In-One System and Standards
Transitioning to electro-mobility has a significant impact on operational processes in transport companies. It is important to combine the processes of the depot with those of charging management and to balance the various dependencies in an optimized way. Standardization efforts, such as in the context of VDV standard 463, but also in the context of the interaction between charging management systems and charging stations, are also necessary to enable safe and efficient operation as well as manufacturer independence for companies.
