The stable operation of multiport energy complementary equipment under multiple operating conditions and the smooth switching between operating conditions are important supports to ensure the smooth operation of the power grid. To address the volatility of distributed generation within the device, based on the hierarchical control strategy, the paper firstly proposes a method for dividing the multiple operating conditions in the grid-connected and off-grid modes, which maintains the power balance of the device in the proposed multiple operating conditions through the coordination of the port parameters and control commands between the local control layer and the central management layer. Secondly, a smooth switching method is proposed to improve the parallel and off-grid mode, based on which voltage monitoring is added to avoid frequent switching of operating conditions caused by normal voltage fluctuations. Finally, simulation models of three typical operation scenarios are constructed in MATLAB to verify their feasibility. The simulation results show that the DC bus voltage can be quickly restored to a stable state in the switching process of the typical scenarios, and the fluctuation is within 0.5%; meanwhile, the improved phase-locked-loop-less smooth switching method can realize the pre-synchronization within 30ms, which can meet the requirements of stable and fast operation.