Modular multilevel converters have several features which make them very interesting for high voltage direct current transmission applications. In this paper, an alternative topology of a three-phase to three-phase modular multilevel converter is is analysed and its controller is designed. This topology can be used to interconnect asynchronous AC systems with different amplitudes and frequencies. The resulting converter exhibit similar features than standard modular multilevel converter, featuring almost sinusoidal currents and voltages. The proposed controller can manage bidirectional power flow and independent reactive power at each side of the converter. Simulation results show the performance of the proposed system.