In this paper, a new systematic approach for stability analysis and controller design of nonlinear solar photovoltaic (PV) power system is proposed. Based on a nonquadratic Lyapunov function (NQLF), a model-based dynamic nonparallel-distributed compensation (non-PDC) controller and descriptor representation, the problem of the output tracking is formulated in terms of linear matrix inequalities (LMIs). Furthermore, some slack LMI variables are introduced in the problem formulation which lead to more relaxed conditions. Finally, to illustrate the merits of the proposed approach, it is applied to a PV power system in which the reference voltage is calculated from the maximum power point tracking (MPPT) method.