On DC to AC power conversion: a differential flatness approach

Abstract

A DC-to-AC power conversion scheme is presented which uses a conventional DC-to-DC switched power converter of the "boost" type. The control scheme is constituted by a sliding mode controller which indirectly tracks a suitable inductor current reference trajectory resulting in a corresponding tight approximation to the desired AC capacitor voltage as the corresponding trajectory for the ideal sliding dynamics. The differential flatness property of the "boost" converter allows one to approximately express the (input) inductor current reference trajectory in terms of a static nonlinear differential function of the (output) desired capacitor voltage AC signal. The AC signal generation features of the approach are demonstrated on a biased sinusoidal signal but, in fact, any sufficiently biased differentiable voltage reference signal is achievable in principle. This approximate differential relation between the reference current and the desired voltage is obtained as the outcome of a rapidly convergent offline iterative procedure devised as part of a trajectory planning task (only one or two iterations are sufficient to obtain a remarkable precision). Simulation results are presented for the first few sliding surface candidates obtained from the proposed algorithm.