| Digital control methods for switching power converters offer greater robustness, more flexibility to changing operating characteristics, and better system performance than conventional techniques, which are often model-limited and only work well in a small range of conditions. Digital controllers are broadly classified into five generations, from 0 through 4. Generation 4 methods, such as the three techniques proposed in the present work, use new system formulations to achieve advanced control objectives. The first proposed technique is a singular perturbation analysis that provides a theoretical foundation for time-scale separation. If a buck, boost, buck-boost, or flyback converter meets a simple requirement, then inductor current operates on a fast time scale while the capacitor voltage changes on a slow time scale. This separation enables other control techniques. The second new technique employs a Kalman filter to create a sensorless power factor correction (PFC) controller. The proposed method uses voltage measurements in a switching power converter to eliminate the need for current sensing. An experimental converter that meets regulatory requirements validates the system. Finally, an online optimization method, discrete-time ripple correlation control (DRCC), is shown to automatically operate a switching power converter at an optimal point, such as maximum power from a source. DRCC is derived, stability is proven, and an application to a photovoltaic system is demonstrated experimentally. These three techniques together form a toolbox for future control applications. |
