Three level T-type isolated bidirectional DC-DC converter design and real-time application

Bi-directional converters play a key role in the storage of energy in various industries such as energy, automotive and railway, aviation and space, uninterruptible power supply. For bi-directional converters, there are also three-level modern topologies in the industry, as well as traditional topologies and two-level hybrid topologies which are derived from those topologies. However, when available topologies are considered in terms of cost, efficiency and reliability, each has its own specific deficiencies. Generally, tendency in the industry is towards from two-level traditional topologies to three-level modern topologies. For many years, three-level neutral point clamped (NPC) known as I-type has been used in inverter, rectifier, and converter applications. However, cost and reliability pressures have led to the emergence of a three-level T neutral point clamped (TNPC) topology, known as the T-type, which is equivalent to the I-type topology in the industry. In this study, analysis, simulation, experimental study and closed-loop control of an isolated bidirectional DC-DC converter which is symmetrical, easy to control, low cost, highly efficient and reliable have been presented by using three level T-type topology that successfully applied in inverter and rectifier design in recent years. In this study, application areas of bi-directional DC-DC converters have been addressed initially. Then, the topologies encountered in the literature, and current modulation methods have been presented. Afterwards, steady state voltage gain, power transfer characteristic and formulation of leakage inductance, which is critical in power transfer, have been derived as well as the theoretical analysis of proposed topology. In the simulation study, theoretical results have been verified and voltage waveforms of the circuit elements used in converter have been analyzed. In the experimental study, analyses in the theoretical and simulation phases have been verified using the 2kW prototype. In this context, input voltage and power transfer characteristics of the converter have been examined and the obtained efficiency results in the load conditions between 20% and 100% have been shared. Finally, closed loop control of converter has been performed in discrete time with a DSP, using the controller coefficients obtained by the help of the simulation. Closed loop performance of the converter has been verified by considering the worst cases.