Let $V$ be a simple vertex operator algebra and $G<$ Aut $V$ a finite abelian subgroup such that $V^{G}$ is rational. We study the representations of $V$ based on certain assumptions on $V^{G}$ -modules. We prove a decomposition theorem for irreducible $V$ -modules. We also define an induced module from $V^{G}$ to $V$ and show that every irreducible $V$ -module is a quotient module of some induced module. In addition, we prove that $V$ is rational in this case.