The invention provides an inequality constraint-based half-bridge/single clamped hybrid MMC self-equalizing topology free of an auxiliary capacitor. In the half-bridge/single clamped hybrid MMC self-equalizing topology, a half-bridge/single clamped hybrid MMC model is electrically connected with a self-equalizing auxiliary loop through 6N auxiliary switches in the auxiliary loop; the auxiliary switches are closed; the half-bridge MMC model and the self-equalizing auxiliary loop form the inequality constraint-based half-bridge/single clamped hybrid MMC self-equalizing topology free of the auxiliary capacitor; the auxiliary switches are opened; and the topology is equivalent to the half-bridge/single clamped hybrid MMC topology. Under the condition of not emphasizing the difference between two topologies, 6N mechanical switches in the auxiliary switches can be omitted; the half-bridge/single clamped hybrid MMC self-equalizing topology can clamp a DC side fault, simultaneously is not dependent on special equalizing control, can spontaneously achieve capacitor voltage equalizing of sub-modules on the basis of finishing AC/DC energy conversion, also can correspondingly reduce the trigger frequencies and the capacitance values of the sub-modules and achieves fundamental frequency modulation of an MMC.