Distributed ac power systems using inverters connected in parallel are becoming increasingly widespread with the development of autonomous microgrids. Inverters can be controlled to emulate the dynamics of nonlinear oscillators, such that multiple inverters coupled through an electrical network will synchronize and share load in proportion to their ratings. In this paper, a communication-less control method is developed for islanded parallel inverters based on the Van der Pol oscillator and a virtual impedance technique. The controller can be tuned to guarantee fast synchronization of inverters, as well as optimal load power sharing, regardless of differences in the physical parameters of the inverters and their respective filters. A methodology for parameter selection is presented to tune the controller so that the system voltage amplitude remains within prescribed bounds whilst ensuring optimal load sharing and minimizing synchronization time. Simulation results demonstrate the performances which can be obtained with several parallel-connected inverters using this control method with correctly tuned parameters.