CLAMP MODULATION METHOD FOR MULTI-LEVEL INVERTER, DEVICE, AND INVERTER

摘要

A clamp modulation method for a multi-level inverter, a device, and an inverter. When an output voltage of the inverter crosses a zero point, a switch element in the inverter is controlled. The switch element of each inverter bridge arm of the multi-level inverter comprises: an inner tube (T5, T6), an outer tube (T1, T4) and a clamp tube (T2, T3), the inner tube and the outer tube being connected in series between a positive bus (Bus+) and a negative bus (Bus-), and the clamp tube being connected between a common end of the inner tube and the outer tube and a bus (Bus_N), thereby constituting an active clamp multi-level inverter. The inner tube is a low-frequency switch element, and the outer tube and the clamp tube are high-frequency switch elements. The method comprises: detecting whether the output voltage of an active clamp multi-level inverter bridge arm crosses a zero point; if so, controlling a corresponding clamp tube to be always turned on within a predetermined period of time after the output voltage crosses the zero point, or controlling two clamp tubes to be always turned on within a predetermined period of time after the output voltage crosses the zero point; and clamping the voltage on each switch element to be within a safe range. The present invention solves the problem that a low-frequency switch element is damaged due to excessive voltage stress during switching when the output voltage crosses zero.