Due to the presence of power electronics interfaced generation, voltage stability is a key design goal for converter control systems, such as in Medium-Voltage DC in naval vessels. In the presence of power electronic converter interfaced loads that can display high-bandwidth constant power load (CPL) behavior, the nonlinearity of the negative incremental resistance can induce instability. This paper employs a local and switched affine model for buck converters interfacing the generation units. Load behavior and system interaction are modelled via a virtual disturbance approach and included as an additional state in an augmented local Kalman filter (ALKF). Stored energy in inductor and capacitor are used to derive a Lyapunov function defining stability regions for the switching states and subsequently a switching rule ensuring quadratic stability is chosen. The simulation of an exemplary system shows how voltage stability is achieved. The controller is then further extended to avoid steady-state errors and limit the converters switching frequency.