Conclusion

In Summary, due to the ongoing trend of the increase in the demand of EV globally, the need for developing the battery charging techniques became more critical. therefore, the main goal of this project is to design a reliable, intelligent, and efficient OBC embedded in an electric vehicle. Besides, the OBC needs to deliver constant power to the battery with no interruption, it should also be cost-effective, and environmentally friendly. The OBC is supplied by an AC power supply of a single phase 240 V (50Hz).

The OBC designed in this project was aimed at small EVs. After that, a literature review was made to grasp general information about the topology of chargers and charging methods. Then, different methods of executing this project were studied and made. Designing an OBC requires “power electronics” and “control” background where the control part is used to adjust the OBC control circuit parameters. After searching and observing other OBC researches, some OBC models were chosen.

The first model was an FWR followed by a boost converter followed by a buck converter. Where the input voltage is 240 V (50Hz), and the output voltage going to the battery of 48 V voltage. Then this model was compared to other models such as Ćuk and SEPIC where the buck converter is no longer needed. Later, an attempt to develop the SEPIC model for charging was made through deriving a mathematical representation of the system, to obtain the most optimum control parameters. And a simulation of the modal was made where the results did not match. The development of this model needs further work to be done for designing a reliable OBC.

The constraints specified in chapter 2 were accomplished through the rectifier-boost-buck model were

• Power Factor >90%
• THD<5%
• Switching frequency ≥20KHz
• DC Output voltage <50V

While the SEPIC model that was aimed to be developed did not meet these constraints.

Then, the system was simulated under open-loop and closed-loop conditions. Furthermore, the system has been tested practically under the open-loop case with scaling down ratio of (1/10). Besides, the intelligent part was started by building the mobile application and testing the temperature sensor. The general topology and block diagram of the monitoring system was made but was not fully implemented due to the ongoing COVID 19 crisis.

Future Work

The system can be improved and achieve the design constraints and goals that were originally aimed. Future works may aim to improve through these aspects. The following points describe some improvements.

• The intelligent system: this part of the project will be done by designing a fully mobile application that monitors the battery temperature, charging time, distance, and status. It also provides controlling commands where the client can choose the level of charging as well as switched off or on via Wi-Fi.
• The constrains, and efficiency are evaluated and improved to meet the IEEE standards for the simulation of the SEPIC model.
• Implementation of the SEPIC model practically as developed.
• The system size: the size of the circuit is minimized as possible to meet the IEEE.
• Marketing: There are marketing tools to promote OBC products such as website and other advertisements.

Corona virus Effects (COVID-19)

Due to the emergency that is taken by Qatar University related to COVID-19, it was obligatory to modify the procedure of a senior design project. The new plan should be compatible with the current situation, and at the same time, it should ensure an acceptable level of performance.

The project consists of two parts, which are designing/simulation and practical implementation. Consequently, the practical part has not been completed, while the other part is the focus of this project. The new designing part contains more design studies, simulations, and calculations. For the isolated SEPIC converters will be designed for low voltage electrical vehicles OBC. Besides, the average state-space model for the SEPIC was developed. Charging by the constant current will be considered in the modelling of the system in addition to a constant voltage. Moreover, some analysis was established for measuring the efficiency of the SEPIC model, correction of power factor, and THD to show the performance of the system.

On the other hand, it was agreed to stop any attempts regarding the demonstration of the practical implementation, IoT part, and enhancing the prototype. Table Appendix A is showing the previous strategies and the new strategies taken.