Introduction  This article aims to study the issue of the melting capacity and reactive output capacity of the full bridge modular multi-level converter (MMC) type DC (Direct Current) melting ice device under different operating modes.

  Method  Calculation of current AC (Alternating Current) component, DC component, rms value and peak value of bridge arm converter of full-bridge MMC type DC ice melting device, selection of number of bridge arm modules, IGBT (Insulated-Gate Bipolar Transistor) power module support capacitance calculation, bridge arm reactor inductance calculation, start-up loop resistance calculation were elaborated; The maximum reactive power output capacity of the device under the set ice melting capacity and the maximum ice melting capacity of the device under the set reactive power output capacity were analyzed in detail, and the coupling relationship and decoupling calculation between the ice melting capacity and the reactive power output capacity were explored.

  Result  Research has shown that there is a coupling relationship between the melting capacity and reactive output capacity after the parameters of the melting device are determined.

  Conclusion  The reason is that the bridge arm current contains both AC and DC components, and the AC component is determined by both the melting mode and reactive compensation mode, while the DC component only depends on the line melting current.