Improved NPC three-level inverter
A three-level inverter, power switching device technology, applied in electrical components, AC motor control, output power conversion devices, etc. Unbalanced heat generation and other problems, to achieve the effect of enhancing safety margin, solving unbalanced heat generation, and improving output power
Active Publication Date: 2020-07-10
TIANJIN POLYTECHNIC UNIV
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Problems solved by technology
[0004] There is a problem with the topology of the NPC three-level inverter. During operation, the duration of current flowing through each switching device and diode is different, and the switching times of each switching device are different, resulting in uneven heating of each switching device and a large difference in temperature rise. In particular, the switching loss of the medium-voltage switching device used in the medium-voltage high-power three-level inverter accounts for a large proportion of the total loss of the switching device. When the inverter outputs a high fundamental frequency, the switching frequency of the switching device is relatively high. Further, Exacerbating the problem of uneven heating of switching devices, because the output power of the entire device depends on the switching device with the highest temperature rise among all devices, many switching devices are not fully utilized
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[0031] The present invention aims at the problems in the topological structure of the NPC three-level inverter, that is, the length of time for each controllable power device and diode to flow current during operation is different, and the switching times of each controllable power device are different, resulting in unbalanced heating of each power device, The difference in temperature rise is large, and many power devices are not fully utilized, which affects the output power of the entire device. The invention proposes a novel three-level inverter topology. Each bridge arm is composed of six switching devices, four freewheeling diodes and two clamping diodes, referred to as 6SNPC (6 Switch Device and Neutral Point Clamped, referred to as 6SNPC) three-level inverter topology.
[0032] The specific implementation is as follows, taking the switching device IGCT as an example, the anode of the first IGCT is defined as the first connection point, and its cathode is defined as the...
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The invention relates to an improved NPC three-level inverter. Each bridge arm comprises six switching power devices, four fly-wheel diodes and two clamping diodes. The anode of the first switching power device is defined as a first connection point, the cathode of the first switching power device is defined as a second connection point, and the first switching power device is connected with the first fly-wheel diode in parallel; the branches of the second to fourth switching power devices are similar; the anode of the fifth switching power device is connected to the first connection point andthe cathode of the fifth switching power device is connected to the second connection point; the anode of the sixth switching power device is connected to the fourth connection point, and the cathodeof the sixth switching power device is connected to the fifth connection point; the cathode of the first clamping diode is connected to the second connection point, and the anode of the first clamping diode is defined as a sixth connection point; and the cathode of the second clamping diode is connected to the sixth connection point, and the anode of the second clamping diode is connected to thefourth connection point.
Description
Technical field: [0001] The invention relates to an inverter topology, in particular to an improved NPC three-level inverter. Background technique: [0002] Most high-power motors use medium voltage, especially one of the development directions of high-performance medium-voltage frequency converters is to use three-level inverter topology. The three-level structure has many advantages, such as: reducing the busbar Therefore, low voltage devices can be used to achieve high voltage and high power output; the increase in the number of levels improves the output voltage waveform and reduces harmonic distortion; a relatively good voltage waveform can be obtained with a lower switching frequency, so the switching loss is small , High efficiency; the output voltage change rate is low, which improves the electromagnetic compatibility performance of the device. [0003] At present, a three-level inverter usually adopts a diode to implement clamping, that is, a neutral point clamped ...
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IPC IPC(8): H02M7/487H02P27/14
CPCH02M7/487H02P27/14
Inventor金雪峰陈炜谷鑫王志强张国政李新旻
OwnerTIANJIN POLYTECHNIC UNIV