| DC-DC converters are an important class of power converters that find applications in diverse applications such as portable electronic devices (cellular phones and laptop computers), hybrid electric vehicles (HEVs), and interfacing distributed generation (DG) sources such as photovoltaics (PVs) to the electric grid or microgrids. Almost all converters today are switching converters, i.e., contain power semiconductor switches that can be turned ON or OFF at high frequencies to achieve the desired power conversion, and invariably require a controller to meet performance objectives. The switching action makes these hybrid systems, and the relationship between the duty ratio of the switch (control input) and the converter voltage (controlled output) is nonlinear. Classical controller methods can be applied to these hybrid nonlinear switching converters using averaging and linearization. In this thesis, we compare linear voltage mode (that use the converter voltage) and current mode (that use the converter inductor current) designs for fixed frequency pulse width modulation (PWM) DC-DC converters. In addition to classical PID design, we also tune the PID controller gains using an LQR optimal control design that employs a high-gain observer (HGO) to estimate derivatives. The efficacy of these designs is verified through simulations and hardware implementation. |
