2022 年 35 巻 6 号 p. 153-164
In this paper, nonlinear controllers are designed for buck converters via the Sum of Squares (SOS) method based on their discretized bilinear model. We first consider a class of control laws in a rational funciton. The condition of Lyapunov stability theory is converted to an SOS condition, and by using the SOS method, a nonlinear stabilizing controller for the discrete-time system is derived to ensure that input constraints on buck converters can also be satisfied. However, with such a control law, the rate of convergence may be poor. To solve this problem, we next obtain through the SOS method a control law satisfying the input constraints and maximizing the Lyapunov function decrement in each sampling time. Finally, simulation and experimental results are shown to confirm the effectiveness of the second control law.