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A Fundamental study on the effects of Electrically Heated Catalyst on State of Charge of the battery pack for a series hybrid electric vehicle at cold start.
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
Battery models are recently being developed as one of a component of the powertrain system of Hybrid Electric Vehicle (HEV) to predict the State of Charge (SOC) accurately. The electric components like the Electrically Heated Catalyst (EHC) which is used to reach the catalyst light off temperature in advance are being employed in the powertrain of HEVs. The EHC draws power from the battery pack of the HEV. Therefore, sufficient energy should be stored in the battery pack of an HEV to power the auxiliary components in the powertrain. In a series hybrid electric vehicle system, the engine is primarily used to charge the battery pack. Therefore, it is important to develop a control strategy that triggers the engine start/stop conditions and reduces the frequency of engine operation to minimize the equivalent fuel consumption. A battery pack model was constructed in MATLAB-Simulink to investigate the SOC variation of a high-power lithium ion battery during extreme engine cold start conditions (-7°C) with and without the application of EHC. An electrically heated catalyst (EHC) was also simulated in MATLAB to determine the energy required to heat the catalyst during the cold start condition and the effect of EHC in emission purification at -7°C was studied with the three-way catalyst (TWC) model. The EHC was operated only during the initial few seconds before the engine start to increase the bed temperature of the catalyst. Increasing the bed temperature of the catalyst had a significant impact on exhaust gas emission even in such a cold start condition. However, powering the EHC causes lowering of the SOC of the battery pack which eventually induces the engine to run and consume more fuel. Hence, an engine ON/OFF control strategy was proposed to control the engine operation condition and effectively charge the battery pack. The SOC variation of the battery pack and the effects on emission reduction were simulated and compared with and without EHC. The battery model was validated with control strategy proposed in the simulation at 23ºC and a parameter study was conducted at -7ºC. The SOC and fuel consumption variation was simulated when EHC was employed.