Study of multiple terminal active bridge for energy storage system

• Main Author: Liu, Qingxiang
• Other Authors: Zhang Xinan
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: http://hdl.handle.net/10356/75472
• Institution: Nanyang Technological University

Dual active bridge (DAB) is widely used in energy storage systems as a bidirectional DC/DC converter due to its merits, such as symmetrical structure, galvanic isolation, step-up capability, high power density and wide range soft-switching characters. The realization of soft switching is a research focus of DAB and the principle of zero voltage switching (ZVS) is explained in detail in this dissertation. A new modulation strategy which can enable DAB to achieve soft switching in the whole operating range and minimize the reactive power is analyzed in detail. A MATLAB based simulation to verify the effectiveness of this new modulation strategy was carried out. Conventional DAB is a two terminal system. In recent years, with the penetration of DC micro-grid, the demand of providing multiple terminals with different rated voltage is on the rise. However, the modulation strategy of DAB cannot be used in three-port active bridge (TAB) directly. To deal with this problem, in this paper, the realization principle of soft switching is discussed, and a general modulation strategy suitable for TAB is proposed based on the analysis. An ideal waveform based on the proposed strategy is delivered to illustrate its feasibility, taking the energy storage system integrated both battery and super capacitor as an example. Finally, in order to cope with the rapid variations of power and voltage in the energy storage system, model predictive control (MPC) is recommended and its feasibility for the control of TAB is briefly discussed.