High order repetitive control (HORC) has been reported to improve the robustness of the control system that incorporate the non-periodic disturbance. In fact, the higher the order is, the more memory cells are needed, and the more total delay time of the control system is needed. Notably, in practical applications, the reported order of HORC rarely exceeds three, and an application with infinite-order HORC has never been reported. To address this issue, a reduced infinite-order repetitive controller (RIORC), using geometric principles, is introduced in this paper. The RIORC is equivalent to a second order repetitive controller. Compared to the traditional infinite-order repetitive control, the memory cells are largely reduced, and the total delay time of the control system is less needed. The effectiveness of the proposed RIORC scheme is verified through its application in a PWM inverter.