μ-Approach based robust voltage controller design for a boost converter used in photovoltaic applications

This paper presents a control technique based on structured singular value (μ) approach for a boost converter with voltage-mode control. Boost converter is used in most grid-connected photovoltaic (PV) applications in order to stabilize the fluctuating input voltage. Due to their time-varying uncertainty in the converter structure, control of DC-DC converter is a difficult task. By using this new approach, control of boost converter for all possible parameter variations becomes easier. At first, the derivation of an appropriate linear model for boost converter is explained. After that, the ranges of varying parameters are defined. Input multiplicative perturbation is applied to nominal plant in order to model the effects of unknown time varying parameters. After modeling overall linear fractional transformation (LFT) structure, the robustness of conventional proportional-integral (PI), full and reduced-order μ controllers are evaluated using μ-analysis. Then closed loop responses of nominal model and possible worst case perturbations are given by simulating step responses. Simulation results show that the proposed μ-synthesis based robust control technique is superior to the conventional PI controller. It has a faster dynamics and better robust performance properties than PI controller.