Dual Natural Switching Surface Control for Multilevel Noninverting Buck-Boost Converter With Pulsed Power Loads

Pulsed power loads (PPLs) have the requirements of fast dynamic and high-power ratings, which may cause periodic power oscillations in traditional dc microgrid systems. Therefore, an improved dual natural switching surface (DNSS) boundary control law is proposed for multilevel noninverting buck-boost converter to dynamically synchronize the periodic power of PPLs within the minimum switching cycle by deriving and tracking the controlled trajectories. First, the variable structure model is established to derive the natural switching surfaces. Then, a graphical characteristic analysis of the transient switching trajectory is presented for the derivation of DNSSs, which can be divided into the primary and the secondary switching. Also, the control strategy based on DNSS is proposed. Due to the super dynamic performance of boundary control and the load characteristic of PPLs, the inductor current may be over the maximum permissible current, and online over-current protection is designed to achieve fast dynamic performance by limiting the inductor current. Finally, simulations and experiments are given to verify the proposed control law. The results show the proposed method has great dynamic performance for PPLs.