Input-admittance modeling of grid-connected single-phase voltage-source converters (VSCs) is here enhanced by the derivation of a generic linear time-periodic (LTP) model of the pulsewidth modulation (PWM) process. Models for bipolar and unipolar PWM with single as well as double update are obtained as special cases. Linear time-invariant approximations are shown to give accurate results, both as stand-alone PWM models as well as when applied in a multifrequency input-admittance model. The results are applicable to three-phase converters as well, which is illustrated by an example for space-vector modulation (SVM).