It is well known that in the last decade, due to the need to preserve the environment, both in industry and in academia, considerable efforts have been made to replace conventional energy sources with renewable energy sources (also known as “green” energy sources). This trend has also influenced the automotive industry, as electric vehicles (EVs) are beginning to acquire an increasingly significant share of the market.
In order to ease and accelerate the development of control systems for electrical or mechanical equipment with a degree of complexity similar to on-board systems of EVs or the related charging infrastructure, Hardware In the Loop simulations have been proposed in literature (HIL). Recently developed devices based on silicon carbide (SiC) or gallium nitride (GaN) allow an increased efficiency of converters in the structure of battery chargers enabling increased switching frequency, thus reducing the amplitude of the characteristic waveforms’ ripple and the size of the components (especially the magnetic ones). A higher switching frequency allows an increased cut-off frequency of the control loop, which further constrains the latency of the control system. To obtain accurate models, real-time simulators also require very low latencies. Furthermore, taking into account the complexity of the control algorithms used and the number of functionalities to be implemented in the digital system of an EV, programmable devices known as “Field Programmable Gate Array” (FPGA) are increasingly emerging as solutions in applications that require low computational latencies or need to integrate a large number of functions on a single device. While the use of FPGAs for rapid prototyping development platforms is already the norm, such devices are already being used in mass consumer products as well.
Given the increasing complexity of digital control systems related to the charging and battery management functions described previously, the increasing interest in the use of FPGA devices both in the development phase (for rapid prototyping) and in production, this thesis aims to design a hardware platform and a procedure to help reduce costs, increase reliability, integrate, accelerate and facilitate the development of the battery charging and management system.
Personal contributions:
- The architecture of the proposed system that facilitates and accelerates the process of developing the digital control system of the EV battery charger.
- The manner in which the AD and DA interfaces are used to experimentally determine the frequency response of power converters (or their real-time simulators) when the control loop is open and the loop gain when the loop is closed.
- The discrete PWM generator architecture that maximizes the performance that can be obtained on FPGA devices.
- The comparative analysis of the methods that can be employed to numerically solve ODE systems from the perspective of implementing real-time simulators of electrical circuits.
- The development of a real-time simulator based on a switched function model for the PS topology.
- The low value (20ns on a ZYNQ XC7Z020 device) of the simulation time step obtained for the real-time simulators of the Boost and PS converters.
- The portability, fidelity, simplicity and the small amount of digital resources required for the real-time simulators implementation.
- The study of the impact that the time step has on the ability to model limit cycling.
- The ability of the developed platform to exemplify the use of the real-time simulator developed both in HIL simulations and in error detection systems.
- The use of low-cost development boards and tools for applications that are conventionally implemented on much higher-cost platforms.