Method for realizing seamless switching between isolated-network mode and grid-connected mode in CCHP (combined cooling, heating and power) system

The invention discloses a method for realizing seamless switching between an isolated-network mode and a grid-connected mode in a CCHP (combined cooling, heating and power) system. The method for switching the isolated-network mode into the grid-connected mode comprises the following steps: a synchronizing device is added with a mode switching function; when a CCHP mode controller receives a request instruction for switching the isolated-network mode into the grid-connected mode and a power grid runs in a normal state, the synchronizing device is started to adjust the frequency and voltage of a generator; when the frequency and voltage of the generator meet synchronous connection requirement, and the absolute value of phase difference of the generator and network voltage is smaller than a fixed value 1, an action instruction for switching the isolated-network mode into the grid-connected mode is output; the CCHP mode controller changes from frequency regulation and voltage regulation control to power control; when the frequency and voltage of the generator meet synchronous connection requirement, and the absolute value of phase difference of the generator and network is smaller than a fixed value 2, a generator grid connection instruction is output; and the isolated-network mode is switched into the grid-connected mode. Therefore, the problems of power failure in the switching process and overlarge disturbance and the like of the mode switching process in the CCHP system due to stop of output power of the generator are solved.