Observer-Based Passivity Control for DC/DC Power Converters With Constant Power Loads

DC microgrid is a new trend of future microgrid, which is expected to be more efficient than ac microgrid and more convenient to connect dc loads. Among various types of loads, the constant power load (CPL), which has negative impedance characteristic, can easily cause oscillations in dc microgrid, and may lead to grid collapse. This article proposes an observer-based passivity control scheme to solve the instability problem brought by CPL. A passivity-based controller (PBC) is designed to attenuate the oscillations caused by CPL by adopting the concept of energy dissipation. To improve the control performance, a nonlinear disturbance observer (NDO) is designed to estimate the value of CPL and compensate PBC in real-time. The effectiveness and efficiency of the proposed control scheme are verified through both simulations and experiments. The results show that, compared with existing methods, the proposed control scheme obtains better control performance and reduces computation burden.