This paper first introduces the high-frequency link(HFL) concept into the modular multilevel converter(MMC) topology, which can totally reduce the individual DC-link capacitors at the high-voltage(HV) side, and this type converter can be named as Isolated modular multilevel converter(I-M2C) having basic triple ports of high-voltage AC(HVAC), high-voltage DC(HVDC), and low-voltage DC(LVDC), which is especially suitable for hybrid DC and AC application in power generation and transmission, such as Solid-State Transformer(SST), etc. Because of the positive voltage of submodules'(SMs') port based on hybrid AC and DC voltage conversion in I-M2C, there is no need for the bidirectional switches. The fundamental principle and applied Phase shifted Pulse Width Modulation(PWM) control scheme are given in detail. Experimental results are given to illustrate the efficient operating characteristics.