This paper proposes a simple control method of the MMC-HVDC system under the unbalanced voltage conditions by applying proportional-resonant (PR) current controllers. The currents of the MMC-HVDC system are controlled directly in a stationary reference frame. Therefore, the complex analysis of the positive and negative sequence components in a synchronous reference frame is not necessary. With this control method, the currents are kept balanced and the ripple of dc-link voltage is eliminated under the unbalanced fault conditions. The simulation results based on a detailed PSCAD/EMTDC model confirm the effectiveness of the proposed control method.