Uninterruptible power supply and control method therefor

An uninterruptible power supply, comprising:

• an alternating current input node and an alternating current output node;
• a voltage regulating rectifier circuit, comprising a positive output node, a negative output node, and a first input node and a second input node that are electrically connected to the alternating current input node, and further comprising a first diode and a first switch that are connected in series between the first input node and the positive output node, a second diode and a second switch that are connected in series between the second input node and the positive output node, a third diode electrically connected between the negative output node and the first input node, and a fourth diode electrically connected between the negative output node and the second input node;
• a voltage regulating inverter circuit, comprising a positive input node, a negative input node, a first output node, and a second output node, and further comprising a third switch and a fifth diode that are connected in series between the positive input node and the first output node, a fourth switch and a sixth diode that are connected in series between the positive input node and the second output node, a fifth switch electrically connected between the negative input node and the first output node, and a sixth switch electrically connected between the input node and the second output node;
• an inductor electrically connected between the positive output node and the positive input node;
• a capacitor electrically connected between the first output node and the second output node;
• a chargeable/dischargeable device for providing a direct current;
• a seventh switch, connected in series to an output node of the chargeable/dischargeable device between the negative output node and the positive output node;
• a safety diode connected in series to the seventh switch, for preventing a current from flowing to the negative output node from the positive output node through the chargeable/dischargeable device;
• a charger, for charging the chargeable/dischargeable device using an alternating current of the alternating current output node;
• and
• an eighth switch that selectively electrically connects the alternating current input node or one of the first output node and the second output node of the inverter circuit to the alternating current output node.