Abstract: When modular multilevel converter (MMC) is used as a medium voltage motor drive system, it has the problem of oversized submodule capacitor, which is more obvious when the motor is running at low speed. This paper proposes a low capacitance MMC (LC-MMC) motor drive system based on horizontal submodule interconnection. It makes use of topological characteristics to realize the capacitor lightweighting in the full speed range of the motor. Based on the three-phase symmetry of the input fluctuating current of the transverse submodule, LC-MMC realizes the cancellation of the fluctuating current in the interconnection channel. Thus, the size of the submodule capacitor is greatly reduced, and its implementation is not affected by the motor operating frequency. This paper first analyzes the specific requirements of the submodule capacitance of the traditional MMC motor drive system. Secondly, the proposed LC-MMC capacitor lightweighting scheme in the full speed range is introduced in detail. Then, two kinds of MMC motor drive systems are compared and evaluated, and the common mode voltage natural suppression characteristics of LC-MMC are analyzed. Finally, the proposed LC-MMC scheme is verified through simulation and experimentation.