The proliferation of power converters has posed significant challenges to the simulation of power grids. The unit switching circuit (USC) method provides an approach for power electronics grid simulation, but neglects the situation where the switching action time deviates from the time-step boundary. This article presents novel simulation and solving approaches for converters based on computational equivalence to precisely simulate the power electronics grid. This article also introduces a straightforward calculation method for determining equivalent circuit parameters through port quantity observation to achieve computational equivalence. The qualitative error analysis is given and accompanied by comprehensive discussions on its validity, numerical characteristics, and applicable scenarios. A case study is performed to verify the proposed method’s effectiveness and efficiency, yielding results that demonstrate improved accuracy.