With the rapid development of the economy and the continuous innovation of technology, the automobile industry is developing at a high speed. While providing convenient transportation and improving the efficiency of production and living, it has also caused a series of problems such as the energy shortage and environmental pollution. Electric vehicles (EVs) are getting more and more attention and support because of their unique advantages such as the energy saving and zero emission. Once the electric vehicle can charge from the clean and sustainable energy source such as the solar and wind energy, it can be an environment-friendly mode of transportation. Therefore, the photovoltaic (PV)
integrated EV charging system appears in recent years. In the meanwhile, ABB is also interested in finding a way to combine their PV products and the EV chargers to make a more compact and efficient PV integrated EV charging system.
A possible solution of making a more compact PV integrated EV charging system is to use the multiport converter which can integrate the separated DC-DC converters. However, the traditional multiport converter needs a large number of active switches and the control of the whole converter is complex. Moreover, the zero voltage switching (ZVS) operation cannot be achieved easily in the traditional multiport converter. Therefore, a dual boost integrated dual active bridge (DAB) converter used for the PV integrated bidirectional EV charging system is investigated in this master thesis project.
This master thesis is the first step to investigate the dual boost integrated DAB converter working with a large output voltage range, which can be compatible with the new CHAdeMO standard (CHAdeMO 2.0) regarding the charging voltage range and make the whole PV integrated EV charging system more compact and efficient. The investigation is divided into three parts which are: the working principle and control analysis, the power loss modeling and analysis and the experimental verification tests.
First of all, the specifications of the converter are clarified, the circuit structure, the working principle of the two interleaved boost converters in the primary side and the working principle of the whole converter are analyzed. Secondly, the parameters of the converter are calculated according to the specifications and all the equations in terms of the voltage, the current and the output power are
deduced. The power modes and the control structure of the converter are also introduced. Afterwards, the soft switching characteristics of the switches and the circulating power in the dual boost integrated DAB converter are investigated by considering the DC bus voltage, PV voltage, and the EV battery voltage, and then the ZVS region is enlarged by applying the DC blocking capacitor voltage control. Besides, the transistor candidates are chosen and the power loss model and the thermal model of the candidates are built. The loss breakdown, the loss ratio and the thermal performance of the switches are analyzed and evaluated.
An analysis tool which can analyze the voltage and current at different points, the output power, the soft switching region and the circulating power of the dual boost integrated DAB converter is developed in Mathcad. This analysis tool is not only suitable for this project but also can be used to do other customized designs, which helps to decrease the time and cost for the development. The simulation model including the control loop and the thermal model of this converter is built in PLECS to check the feasibility of the design. Finally, a test bench is built and the experimental tests are implemented to verify the analysis and the simulation results.