The invention provides an energy-storage voltage-balanced power electronic electric energy converting system and a control method thereof. The energy-storage voltage-balanced power electronic electric energy converting system is composed of an energy storage module, a voltage-balanced converter, a power-grid-side inverter, a power grid load, an energy-storage-side inverter and an independent load. Through control over the high-frequency soft-switching voltage-balanced converter, balanced control over an energy storage unit or module is realized, the service life of energy storage equipment is prolonged, the use cost is reduced, and meanwhile, multiple routes of isolation direct voltage are provided for the power-grid-side inverter. The energy storage unit or module is charged and discharged through the electric energy converting system, electric isolation of energy storage and a power grid is realized, interaction is formed with the power grid, and the purposes of peak load shifting, harmonic suppression and reactive compensation are realized. The energy-storage voltage-balanced power electronic electric energy converting system is realized through modularized design and has the advantages that electric isolation of the power grid and the energy storage side is realized, control is simple, the size is small, the efficiency is high and the cost is low.