Single-phase half-bridge three-level circuit and three-level converter

Abstract

The embodiment of the invention discloses a single-phase half-bridge three-level circuit, comprising a first direct current input end, a midpoint level end, a second direct current input end, a first switching device, a second switching device, a third switching device, a fourth switching device, a fifth switching device and a sixth switching device, as well as a fifth diode, a sixth diode, a seventh diode and an eighth diode, wherein the first end of the first switching device and the second end of the seventh diode are connected with the first direct current input end; the second end of the fourth switching device and the first end of the eighth diode are connected with the second direct current input end; the first switching device, the second switching device, the third switching device and the fourth switching device are respectively connected in parallel with the diodes in a reverse way; and a connection point between the second end of the fifth switching device and the first end of the sixth switching device is used as an alternating current output end. The embodiment of the invention also discloses a three-level converter with the single-phase half-bridge three-level circuit; in the occasion of needing to apply a unit power factor and a non-unit power factor simultaneously, the selection ranges of the switching devices are large; moreover, the loss of the switching devices can be decreased; the service lives of the switching devices can be prolonged; and the whole conversion efficiency can be improved.

Description

technical field [0001] The invention belongs to the field of power electronics, and in particular relates to a single-phase half-bridge three-level circuit and a three-level converter including the circuit. Background technique [0002] The traditional I-shaped three-level circuit such as figure 1 As shown, T1, T2, T3, T4 are switching devices, D1, D2, D3, D4 are anti-parallel diodes of T1, T2, T3, T4 respectively, D1, D2, D3, D4 are body diodes of switching devices. The mode of the I-shaped three-level circuit working at unity power factor is shown in Figure 2. Figure 2a , the current flows from terminal M to AC output A through T1 and T2; Figure 2b In the middle, the current flows from the O terminal to the AC output A through T1 and T2; Figure 2c , the current flows from the AC output A to the N terminal through T3 and T4; Figure 2d , the current flows from the AC output A to the O terminal through T3 and D6. The mode of the I-shaped three-level circuit working a...

AI Technical Summary

Problems solved by technology

Therefore, there are the following technical problems in applications where unity power factor and non-unity power factor are required at the same time: (1) When selecting T2 and T3, it is necessary to consider both the switching performance and conduction performance of the device. Under the current semiconductor technology, Only a compromise can be considered when choosing, resulting in low efficiency when working at unit power factor; (2) Since T2 and T3 both participate in work at unit power factor and non-unity power factor, the loss is large, which is not conducive to heat dissipation and reduces The service life of the device is reduced, and the conversion efficiency of the circuit is reduced; (3) The reactive current needs to pass through the body diodes D1, D2, D3, and D4 of T1, T2, T3, and T4, and the loss is large, which is not conducive to heat dissipation of the device, reducing The service life of the device is shortened, the increase of the switching frequency is limited, and the conversion efficiency of the circuit is also reduced.

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