ANPC type three-level inverter modulation method

Abstract

The invention discloses an ANPC type three-level inverter modulation method, and belongs to the technical field of electric power and electronics. The modulation method comprises the following steps:1, in the positive half cycle of a modulation voltage U<o>, when the output voltage is changed from +U<dc> / 2 to 0, two switching state changing moments of t<1> and t<2> pass by; at the t<1> moment, aT<2> tube is switched off, and at the t<2> moment, a T<3> tube is switched on; when the output voltage is changed from 0 to +U<dc> / 2, two switching state changing moments of t<3> and t<4> pass by; atthe t<3> moment, the T<3> tube is switched off, and at the t<4> moment, the T<2> tube is switched on; in the negative half cycle of the modulation voltage U<o>, the modulation method is correspondingto the abovementioned method; and 2, when the modulation voltage U<o> is in transition from the positive half cycle to the negative half cycle, four switching state changing moments of t<5>, t<6>, t<7> and t<8> pass by; at the zero-crossing point t<5> moment when the modulation voltage U<o> is changed from the positive half cycle to the negative half cycle, a T<1> tube is switched off; at the t<6>moment, T<2> and T<5> tubes are switched on; at the t<7> moment, T<3> and T<6> tubes are switched off; at the t<8> moment, the T<4> tube is switched on; and when the modulation voltage U<o> is in transition from the negative half cycle to the positive half cycle, the modulation method is corresponding to the abovementioned method. By virtue of the method provided by the invention, the problem ofbus capacitor short circuit in current conversion can be overcome; and in addition, a long current conversion circuit can be avoided in a position close to the zero crossing point of the modulation wave U<o>, so that the method has certain engineering practical value.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a modulation method for an ANPC type three-level inverter. Background technique [0002] ANPC (Active Neutral-point-clamped) type three-level inverter is an important power electronic circuit, and its main circuit topology is as follows: figure 1 shown. This topology consists of 2 DC bus capacitors C 1 、C 2 , 6 switching tubes T 1 ~T 6 , 6 diodes D 1 ~D 6 . Among them, C 1 、C 2 Respectively connected between DC+~0, 0~DC-; D 1 ~D 6 respectively antiparallel to T 1 ~T 6 ; T 5 , T 6 、D 5 、D 6 for the clamp tube. Define the output voltage of the ANPC type three-level inverter as +U dc / 2, it works in the P state, and the current path is T 1 , T 2 or D 2 、D 1 ;The output voltage is 0, and the current path is T 6 、D 3 or T 3 、D 6 When it works at O - state; the output voltage is 0, and the current path is T 5 、D 2 or T 2 、D 5 When i...

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Problems solved by technology

[0006] At present, scholars at home and abroad have proposed many ANPC-type three-level inverter commutation methods, such as the improved strategy for the first modulation strategy used in existing projects, but no scholars have yet addressed the second modulation strategy The strategy proposes a more complete commutation method

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