Powerline communication is one of the key technologies contributing to grid intelligentization and needs to be specially designed for individual converter-based generators and loads. In this article, a novel power and signal composite modulation (PSCM) strategy is proposed for powerline data transmission in switched reluctance motor (SRM)-based distributed power grids. In detail, the signal modulation is realized by tuning the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> angle of the SRM to produce voltage ripples on the power transmission line, whereas autoregressive power spectrum density method is innovatively utilized to demodulate useful data from the powerline. Hardware experimentation is conducted in this article, which verifies the effectiveness of the proposed PSCM method.