A robust switching predictive control (RSPC) method based on switched affine models is proposed for three-phase voltage source converters (VSCs). The method establishes a switching affine model, designs a switching rule for direct subsystem control, and incorporates a state observer to predict system states and signals within constant switching periods. This approach addresses issues of unfixed switching frequency and performance degradation under parameter uncertainty. Compared with traditional linearized-model-based methods, it provides an accurate model, a simple structure, eliminates complex transformations and modulation, and demonstrates strong robustness. Simulation results confirm its effectiveness and superiority.