A Simplified Quadrangle Current Modulation for Four-Switched Buck-Boost Converter (FSBB) with a Novel Small Signal Model

With the fast development of energy storage systems, the four-switch buck-boost (FSBB) converter has been widely used because of the bi-directional power flow and wide step-up/down voltage conversion capabilities. With the quadrangle current modulation (QCM) method, the converter can achieve zero voltage switching with a small RMS current. However, the existing QCM approaches impede the wide adoption of FSBB due to their implementation complexity. To address this issue and obtain a simple closed-loop control for output voltage, a real-time simplified four-quadrangle modulation was found without look-up tables or extra current detection. With this simplified control method, the whole control system can be fully implemented in digital controllers. Meanwhile, to aid the compensator design, a small signal model was proposed under QCM operation. The proposed small signal model shows a good agreement with the simulation results in the frequency domain. Finally, a Silicon Carbide (SiC)-based 50kW, 900V input, and 500V-1000V output FSBB converter was built to verify the proposed control scheme and the small-signal model.