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Point potential balance control method in three-level NPC inverter

A potential balance and control method technology, which is applied to electrical components, AC power input conversion to DC power output, output power conversion devices, etc., can solve the uncontrollable area of ​​midpoint potential, uneven charging and discharging of capacitors, and increase the power switch. Tube switching frequency and other issues, to achieve the effect of expanding the range of possible values

Active Publication Date: 2016-02-03
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] When the three-level NPC inverter is modulated by the sinusoidal pulse-width modulation (SPWM) strategy and the traditional space vector pulse-width modulation (SVPWM) strategy, there is a midpoint potential due to the uneven charging and discharging of the capacitor. imbalance problem
This type of method does not have an uncontrollable midpoint potential when the midpoint potential is balanced, but it will increase the switching frequency of the power switch tube to 4 / 3 times that without decomposition
[0006] Although the above prior art can realize the midpoint potential balance of the three-level NPC inverter, there is an uncontrollable midpoint potential area or at the expense of the switching frequency of the power switch tube

Method used

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  • Point potential balance control method in three-level NPC inverter
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  • Point potential balance control method in three-level NPC inverter

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Embodiment 1

[0037] In the embodiment of the present invention, positive and negative modulation waves are obtained by decomposing the modulation wave of the three-phase reference voltage obtained by injecting the three-phase positive sequence voltage into the zero sequence voltage, and the decomposed positive and negative modulation wave constraints and midpoint potential balance are obtained condition. described as follows:

[0038] Three-level NPC inverter topology such as figure 1 As shown in the figure, U dc is the DC side voltage, U C1 , U C2 is the voltage of capacitors C1 and C2, i a i b i c is the three-phase load current. Each phase of the three-level NPC inverter has three switch states, taking phase a as an example, S a1 and S a2 Open, S a3 and S a4 When turned off, the output phase voltage is U dc / 2, set to state "p"; S a2 and S a3 Open, S a1 and S a4 When shutting down, the output phase voltage is 0, set to state "o"; S a3 and S a4 Open, S a1 and S a2 Whe...

Embodiment 2

[0125] In order to verify the effectiveness of this method, use Matlab / Simulink tools for simulation verification. Take U in the model dc =100V, capacitance C 1 =C 2 =1mF, fundamental frequency f 0 =50Hz, carrier frequency f s =5kHz, the load adopts resistive inductive load In the simulation, the method in this paper is compared with the existing single and double modulated wave methods respectively.

[0126] Figure 8 for m=0.7, When the traditional single modulation wave method, the existing double modulation wave method and the modulation wave, capacitor voltage and switch tube S of this method a1 The switching sequence vs. waveform. In the simulation, at t=0.252s, the modulation method adopted by the three-level NPC inverter is changed from the traditional single modulation wave method to the existing dual modulation method; after t=0.312s, this method is adopted. Depend on Figure 8 It can be seen that this method can effectively achieve midpoint potential bal...

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Abstract

The invention discloses a point potential balance control method in a three-level NPC inverter. The point potential balance control method comprises the following steps of performing modulated wave decomposition on a three-phase reference voltage which is acquired after injecting a three-phase positive-sequence voltage into a zero-sequence voltage, obtaining a three-phase positive and negative modulated wave expression which satisfies middle-point potential balance; performing optimized selection on the zero-sequence voltage in a value range in a manner that the switching frequency of a power switch tube is used as an index; improving an interference resistance by means of a positive modulated wave compensation strategy; and comparing the compensated modulated wave with a carrier wave, and finally obtaining a switching sequence of all power switch tubes of the three-level NPC inverter. Compared with an existing single-modulated-wave zero-sequence voltage injection carrier wave modulation method, The point potential balance control method has a function of widening the value range of the zero-sequence voltage which satisfies middle-point potential balance and furthermore has no region with uncontrollable middle-point potential.

Description

technical field [0001] The invention relates to the field of power converter control for driving motors, in particular to a control method for a three-level NPC inverter based on zero-sequence voltage injection carrier modulation and dual modulation wave modulation principles, which is used to solve the problem of midpoint potential imbalance question. Background technique [0002] For medium-high voltage and high-power applications, compared with traditional two-level converters, multi-level converters have better output voltage and current quality at the same switching frequency, and the withstand voltage and output voltage du / dt of each switching tube Significantly reduced, so it has been widely used. Three-level neutral-point-clamped (NPC) inverter is a commonly used multilevel converter topology, and has been applied in wind power generation, photovoltaic power generation, locomotive traction and other fields. [0003] When the three-level NPC inverter is modulated by...

Claims

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Application Information

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IPC IPC(8): H02M7/487
Inventor 夏长亮崔福耀史婷娜谷鑫
Owner TIANJIN UNIV
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