A bi-directional resonant DC/DC converter with frequency tracking control

A two-stage bi-directional resonant DC/DC converter with frequency tracking control is analyzed. The first stage is Buck/Boost converter which is used to regulate the voltage gain. The second stage is series resonant converter (SRC) that acts as a solid state transformer (SST) to achieve isolation with high efficiency and high power density. To realize accurate and fast frequency tracking for series resonant converter, the dynamic model and design method of phase lock loop (PLL) control are investigated. In addition, the design of power factor angle of the resonant network is discussed to achieve higher efficiency. The controller of the bi-directional resonant DC/DC converter which consists of bi-directional inner current loop and outer voltage loop and frequency tracking loop is given. Finally, the control scheme is verified on a 5kW prototype.