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Modulation method for npc type three-level inverter to suppress mid-point low-frequency oscillation on DC side

A three-level inverter, low-frequency oscillation technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc. Implementation of cumbersome problems, etc.

Active Publication Date: 2020-02-18
XIANGTAN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0015] Although the above-mentioned documents also involve the midpoint voltage control of the NPC three-level inverter, and some control methods have been proposed, they are exploring a simple algorithm that can eliminate the low-frequency oscillation of the midpoint of the DC capacitor and facilitate the realization of the controller. There is no breakthrough yet, so the above-mentioned problems of complex algorithm, cumbersome implementation, and heavy computational workload of the controller have not been effectively solved, so further improvement is still needed

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  • Modulation method for npc type three-level inverter to suppress mid-point low-frequency oscillation on DC side
  • Modulation method for npc type three-level inverter to suppress mid-point low-frequency oscillation on DC side
  • Modulation method for npc type three-level inverter to suppress mid-point low-frequency oscillation on DC side

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Embodiment 1

[0097] The accompanying drawing shows an embodiment of the present invention. It can be seen from the accompanying drawings that the present invention relates to a modulation method for suppressing midpoint low-frequency oscillation of the DC side by an NPC-type three-level inverter, directly inverting the three-level The three reference voltages of the device are mapped to the 60-degree coordinate system, and the six sectors of the space vector are modulated according to the odd and even sectors. In the odd sector, the gh axis coordinate system is established, and in the even sector, the hg axis coordinate is established. system, and combined with the virtual space vector algorithm, the virtual vector eliminates the current situation of the low-frequency oscillation of the inverter at the midpoint potential of the DC side capacitor, and achieves the modulation effect of the NPC type three-level inverter to suppress the midpoint low frequency oscillation of the DC side .

[00...

Embodiment 2

[0186] The basic control principle of the second embodiment is the same as that of the first embodiment, but the method is slightly different. It is a modulation method for the NPC type three-level inverter to suppress the low-frequency oscillation at the midpoint of the DC side, directly using the three-level inverter The three reference voltages are mapped to the 60-degree coordinate system, and the six sectors of the space vector are modulated according to the odd and even sectors. In the odd sector, the gh axis coordinate system is established, and in the even sector, the hg axis coordinate system is established. , and combined with the virtual space vector algorithm, the current situation of the low-frequency oscillation of the inverter at the midpoint potential of the DC side capacitor is eliminated by the virtual vector, and the modulation effect of the NPC type three-level inverter suppressing the midpoint low frequency oscillation of the DC side is achieved.

[0187] W...

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Abstract

The invention discloses a modulation method for suppressing direct current side midpoint low frequency oscillation of an NPC type three-level inverter. The modulation method is characterized by comprising the steps of mapping three items of reference voltages of the three-level inverter into a 60-degree coordinate system; based on six major sectors of space vectors, performing different modulationon odd number and even number sectors; in the odd number sectors, establishing a gh-axis coordinate system; in the even number sectors, establishing an hg-axis coordinate system; and by combination with a virtual space vector algorithm, eliminating the low frequency oscillation condition in the midpoint potential of a direct current side capacitor of the inverter through the virtual vector, thereby achieving a modulation effect for suppressing direct current side midpoint low frequency oscillation of the NPC type three-level inverter. By virtue of the modulation method, the low frequency oscillation in the midpoint of the direct current side capacitor can be eliminated; and compared with the conventional SVPWM, the voltage vector acting time and sequence can be directly obtained without needing a large amount of trigonometric function calculation and lookup judgment, so that the operation load of a controller is reduced, the three-level inverter space vector modulation algorithm is simplified, and popularization and application of the space vector modulation algorithm in the multi-level inverter can be facilitated.

Description

technical field [0001] The invention relates to a modulation method for inverter modulation, in particular to a modulation method based on an NPC-type three-level inverter for suppressing midpoint low-frequency oscillation on a DC side, and belongs to the technical field of inverter space vector modulation control. Background technique [0002] In order to ensure the long-term reliable and stable operation of the multilevel NPC inverter, it is necessary to ensure the neutral point voltage balance. At present, there are mainly the following types of control strategies for the neutral point voltage balance of NPC inverters: [0003] (1) Carrier sinusoidal PWM injected with zero-sequence components; [0004] (2) Based on the specific harmonic elimination PWM, by fine-tuning the specific harmonic elimination PWM switching angle to change the action time of the zero state to reach the control midpoint voltage; [0005] (3) Based on the space vector PWM (Space Vector Modulation,...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/483H02M1/12H02M7/5395
Inventor 刘嘉婷黄辉先丁灿周迎春李治国程泊静
Owner XIANGTAN UNIV
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