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A midpoint potential equalization control method for three-level npc inverters based on midpoint current

A control method and potential equalization technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve the problem of reducing the quality of the inverter output voltage waveform, affecting the normal operation of the system, and voltage stress. Inconsistency and other problems, to achieve the effect of ensuring normal and stable operation, improving waveform quality, and simple methods

Active Publication Date: 2018-01-12
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The mid-point potential DC imbalance will introduce a large number of even harmonic components, especially the second harmonic component, into the output voltage of the AC side of the three-level NPC inverter, which reduces the waveform quality of the inverter output voltage
At the same time, the DC imbalance will lead to inconsistent voltage stress on the power switching devices of the three-level NPC inverter, which may damage the switching devices and affect the normal operation of the system.

Method used

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  • A midpoint potential equalization control method for three-level npc inverters based on midpoint current
  • A midpoint potential equalization control method for three-level npc inverters based on midpoint current
  • A midpoint potential equalization control method for three-level npc inverters based on midpoint current

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Embodiment Construction

[0020] The specific embodiment of the present invention is described below in conjunction with accompanying drawing:

[0021] figure 1 It is a three-phase three-level NPC inverter main circuit topology, and the DC side bus voltage is U dc , bus capacitance C 1 and bus capacitance C 2 The capacitor voltages are u dc1 and u dc2 , set the capacitor voltage difference Δu=u dc1 -u dc2 , when the capacitor voltage is balanced, the capacitor voltage difference Δu = 0, at this time each phase can output three levels + U dc / 2, 0, -U dc / 2, the corresponding output level states are 1, 0, -1 respectively. Therefore, the three phases can output a total of 27 level state combinations. According to the size of the combined voltage amplitude of each output level state combination, the 27 level state combinations are divided into 3 zero vectors, 12 small vectors, and 6 medium vector and 6 large vectors, when the output level state is combined as zero vector and large vector, the mid...

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Abstract

The invention discloses a middle-point potential equalization control method of a three-level NPC inverter based on the middle-point current. Real-time sampling of the upper and lower capacitor voltages and the midpoint current, and compare the upper and lower capacitor voltages to obtain the capacitor voltage difference. According to the capacitor voltage difference, the midpoint current polarity and the polarity of the original modulation wave of the three phases, the voltage equalization adjustment amount is calculated to adjust the three phases. Phase original modulation waves vma, vmb, vmc are adjusted to obtain three-phase modulation waves vma', vmb', vmc', compare the three-phase modulation waves with the triangular carrier wave Cup and Cdown respectively, and output PWM signals to control the inverter Switching state of the switching tube, so as to realize the adjustment of the midpoint potential. In the method of the present invention, since the pulsation frequency of the voltage equalization adjustment value is greater than the carrier frequency, the adjustment of the midpoint potential by this method has high-frequency characteristics, and the adjustment of the midpoint potential of the NPC inverter can be realized in a very short time. Good real-time performance and high control precision.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to a midpoint potential equalization control method of a three-level NPC inverter based on midpoint current. Background technique [0002] Compared with the two-level topology, the three-level neutral point clamp (NPC) inverter has the advantages of effectively reducing the harmonic content of the output voltage, reducing the voltage stress of the switch tube, and reducing electromagnetic interference, etc., and is widely used in For new energy power generation, active power filter (APF), flexible AC transmission (FACTS), motor drive and other high-voltage and high-power occasions, the topology structure is as follows: figure 1 shown. [0003] Three-level NPC converter topology DC side bus must use two capacitors in series, the AC side can output three-level phase voltage and five-level line voltage. Theoretically, the voltage of each capacitor is half of the...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/487
Inventor 陈仲许亚明那显龙
Owner NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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