The invention belongs to the technical field of microgrids and relates to a method for reliable grid connection of a microgrid, in particular to a microgrid with a bidirectional relay protection device and a grid-connected operation control method of the microgrid. Under the condition that the microgrid is in need of grid connection, a main controller issues commands to the bidirectional relay protection device and an energy storage inverter simultaneously through communication, the energy storage inverter adjusts the amplitude, phase angle and frequency of a microgrid system, the bidirectional relay protection device detects whether the voltage, amplitude, phase and the like of two sides of grid-connected contact are consistent or not, and after the voltage, amplitude, phase and the like are completely consistent according to detection, a grid connection instruction is issued to a grid-connected contactor through the bidirectional relay protection device, so that reliable grid connection of the microgrid is realized; the grid-connected control method of the microgrid is simple and reliable, and impact on the grid and the grid-connected contactor is reduced effectively. Reaction and execution time of control signals is shortened, reliability in grid connection of the microgrid is improved greatly, and impact on the grid-connected contactor and the grid by high current at the moment of grid connection is reduced.