System Identification and <i>H_∞ </i> Mixed Sensitivity Control for LLC Resonant Converter With Parameter Perturbations

Performance of LLC resonant converters (RC), such as zero-voltage switching (ZVS) characteristic, heavily depends on control of the oscillation circuit. It is thus crucial to understand how the system behavior varies with different working conditions and tune the controller accordingly. In this article, a system identification method and an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> mixed sensitivity control strategy are proposed for LLC RC against parameter perturbations. Frequency response is derived through correlation analysis from the input- and the output signals by injecting a pseudo random binary sequence (PRBS) to the control input of the resonant converter. The eigen-system realization algorithm is used to acquire a parametric model. The proposed identification approach enjoys low complexity, and an accurate model of LLC RC can be obtained. The frequency response to different parameter perturbations is investigated to obtain bound of system uncertainties. This way a model-based, precise control synthesis is facilitated. An optimal controller is obtained through <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> mixed sensitivity design, which can effectively improve the robustness and dynamic performance of system. Finally, an in-house built prototype is used to verify feasibility of the proposed identification and control schemes. The converter features satisfactory voltage regulation capability and fast dynamic performance. ZVS over a wide range is approached, too.