Observerless Output Feedback Control of DC-DC Converters Feeding a Class of Unknown Nonlinear Loads via Power Shaping

In microgrids, DC-DC converters play an important role in energy conversion. Existing results mainly deal with the control problem of the converters under several classical loads. Other nonlinear loads do indeed exist in power systems. In this paper, an observerless output feedback control scheme is proposed for DC-DC converters feeding a class of unknown nonlinear loads including boost, buck-boost and buck converters. Borrowing a new power shaping method, control input is introduced to matching equation for easily solving it and then relatively simple controllers for three converters are designed to facilitate their use. Comparing with the existing works, main advantages of the proposed control scheme contain (1) the information of inductor current, nonlinear loads, inductance and capacitance is not required, (2) the implementation of output feedback controllers does not need the construction of adaptive state observer, (3) saturated control property is ensured, (4) the estimation of domain of attraction is given. Then, it is proved that the closed-loop systems are asymptotically stable. Finally, the performance of the controllers are verified by detailed simulations and experimental results.