Grid-connected and off-grid uninterruptible switching device and method

The invention provides a grid-connected and off-grid uninterruptible switching device and method. The device comprises a battery, a switching module and N power control modules, wherein a first end ofthe switching module is connected with a power grid; a second end of the switching module is connected with load; the N power control modules are connected in parallel; the first ends of the N powercontrol modules are connected to the battery in parallel; the second ends of the N power control modules are connected to a third end of the switching module in parallel; the switching module is usedfor controlling grid-connected and off-grid switching according to a received control instruction and is also used for detecting voltage and current of the power grid and the voltage and current of the load and determining an angular frequency and an amplitude of droop control according to the voltage and current of the power grid and the voltage and current of the load; and the power control modules are used for controllin