Working mode switching method and device for five-level inverter

Abstract

The present application discloses a working mode switching method and device for a five-level inverter, wherein the method includes: determining the first three-level working mode as the five-level inverter when the PV input voltage is higher than the grid-connected required When the bridge arm line voltage peaks, it is necessary to switch from the current five-level working mode to the three-level working mode; after the five-level inverter switches to the first three-level working mode, when working in the When the temperature rise of the switching tube in the first three-level working mode exceeds the first preset value, the five-level inverter is switched from the first three-level working mode currently adopted to the second three-level working mode. level working mode; when the temperature rise of the switch tube working in the second three-level working mode exceeds the second preset value, the five-level inverter is switched from the second three-level current mode currently used The flat working mode is switched back to the first three-level working mode, so as to reduce the temperature rise of the switching tubes still in working state after switching the working mode.

Description

technical field [0001] The invention relates to the technical field of photovoltaic power generation, and more specifically, to a working mode switching method and device for a five-level inverter. Background technique [0002] figure 1 The DC side of the shown five-level inverter 10 is connected to the photovoltaic array 20 to receive the DC PV input voltage, and its grid-side output is filtered by the filter 30 and boosted by the transformer 40 before being sent to the grid. The PV input voltage is connected across the positive pole of the capacitor C1 and the negative pole of the capacitor C2, and the voltages on them are respectively V1Pos and V1Neg. At the same time, the PV input voltage is respectively boosted by two boost circuits and then connected across the busbar capacitor C3. The voltages on the positive pole and the negative pole of the bus capacitor C4 are V2Pos and V2Neg respectively. Under different combinations of switch-on states, the five-level inverter ...

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Problems solved by technology

However, because the bus voltage is too high at this time and the output level of the grid side is reduced, the loss of the switching tube that is still in the working state after switching the working mode will increase significantly, causing its temperature rise to be too high, which may trigger the module over-temperature protection, and the module The service life will also be greatly reduced

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