TE - White Papers

TE Connectivity White Paper /// Thermal Modeling for High Power Charging (HPC) of Electric Vehicles Page 8 Thermal Modeling for High Power Charging (HPC) of Electric Vehicles rameters. Within the model, these parameters are applied to algebraic equations which follow Kirchhoff's circuit laws. In essence, the model describes the heat generation and the heat exchange with the environ- ment. The simulation is able to deter- mine, for example: • The location of the heat sources and heat sinks, • When does a temperature level become critical and when it be- gins to shorten a component's service life? • How does this integrate into a larger cluster? • Where can adiabatic states be found and what effect will they have? During the original model develop- ment, iterations between simulation and testing (raw data from lab test- ing) served to refine the algebraic part of the model until the accuracy of the prediction matched the test results. With the resulting simulation meth- odology, dynamic load profiles can be tested for each component on the high voltage path with a minimum of computing power. 7. Safety Gain The computing power needed for thermal simulation, based on equiv- alent circuit diagrams is so low that it is feasible to run this procedure as a continuous routine task on a typ- ical automotive electronic control unit (ECU). Actual load profiles of real-world driving can thus be cal- culated in real time. The simulation delivers data which helps to improve functional safety. Simulation and sensor data mutually complement one another as heterogenous diag- nostic routines. For automated vehi- cles, requiring multiple redundancy for safety reasons, this can be a con- tribution to the safety concept. 8. Designing HV Components for the Vehicle Systemic thermal simulation strongly advances the load-oriented design of high voltage components for the vehicle towards real operating condi- tions. Standard industry high current products are not an option because they are designed for non-applica- ble conditions. For instance, industri- al connectors for 200 to 400 amps are too heavy and bulky for vehicle use. At the same time cost is more prohibitive in vehicle applications. Nevertheless, the terminal surfaces have to carry high currents despite minimal use of material. Under such stringent boundary con- ditions, it is highly valuable to have the capability to predict the perfor- mance of a component during its development phase. The systemic and dynamic thermal simulation pre- cisely reveals the expected effects resulting from wear and aging during operation. Thus, a complex system like the high voltage path can be sim- ulated and its behavior can be pre- dicted. In addition, simulation can cover a breadth of testing which would never be achievable in the testing lab. 9. Conclusion HPC DC represents an exceptional load profile for an EV. This profile cannot be found during any other vehicle operating state. Charging can result in very different tempera- ture profiles of individual compo- nents along the complex and slow high voltage path thermal system. In order to use 350 kW of charging power safely, it is necessary to simu- late the complete high voltage path – applying dynamic load profiles to reveal potential thermal bottle- necks under real-world operating conditions and to assess the conse- quences of those bottlenecks. The simulation required for this also cov- ers the complete value chain from tier 2 to tier 1 suppliers to the OEM. Systemic thermal simulation of high voltage components, based on equivalent circuit diagrams, delivers the data for an optimized design that reflects how often components can be taken to their temperature limit without impacting the required dura- bility and reliability of the complete system. This knowledge flows into an Fig. 6: A connector broken down into loops: Equivalence between the electrical points of contact in a connector and the thermal simulation.

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