Boundary control (BC) has the advantages of fast dynamical response and accurate steady-state regulation when applied to the control of power converter systems. However, it has the drawback of wide variation in switching frequency, and usually requires an oversized filter to remove unwanted signals. This situation becomes more severe when BC is applied to dc-ac inverters that have a time-varying reference. In this paper, we provide a thorough study into this problem, and propose an enhanced BC method to restrict the variation of the switching frequency of dc-ac inverters. Based on the ripple information of the state variables, a BC method with ripple-derived switching surface is developed and implemented in the inverter. Experimental results show that the proposed control method is capable of limiting the switching frequency variation while maintaining the characteristics of fast dynamical response and accurate steady-state regulation.