Optimal modulation method suitable for three-phase four-wire system three-level converter

A technology of three-phase four-wire system and modulation method, which is applied in the field of optimal modulation of three-phase four-wire system three-level converters, and can solve problems such as complex modulation strategy midpoint potential balance, complex algorithm, unfavorable digital realization, etc.

Active Publication Date: 2018-10-12
HEFEI UNIV OF TECH
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  • Abstract
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Problems solved by technology

[0002] With the continuous improvement of users' demand for power, three-phase four-wire three-level neutral-point clamped converters are widely used in power equipment because of their ability to control zero-sequence components, but their modulation strategies are complex and The problem of point potential balance still needs to be perfected
[0003] The traditional three-level 3D-SVPWM modulation strateg

Method used

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  • Optimal modulation method suitable for three-phase four-wire system three-level converter
  • Optimal modulation method suitable for three-phase four-wire system three-level converter
  • Optimal modulation method suitable for three-phase four-wire system three-level converter

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Embodiment Construction

[0099] figure 1 Shown is the topological diagram of the three-phase four-wire three-level converter in the present invention, in which the load is a generalized load, which can be a three-phase AC power grid, a structure with resistance-inductive-capacitance characteristics, etc., and the DC side can be connected to an external DC according to different uses Voltage source, load, or no external parts.

[0100] In this embodiment, the optimized modulation method applicable to the three-phase four-wire three-level converter is performed according to the following steps:

[0101] Step 1. According to the 3D-SVPWM method, the reference voltage U ref Projection u on the a-b-c axis aref , u bref and u cref Normalize by formula (1), and calculate the value of j by formula (2):

[0102]

[0103] j=int(u j ) (2),

[0104] where j=a,b,c,u j is the normalized three-phase voltage, U dc half of the DC side voltage.

[0105] Step 2. Simplify the 3D-SVPWM method as follows

[0...

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Abstract

The invention discloses an optimal modulation method suitable for a three-phase four-wire system three-level converter. A multi-phase control midpoint potential balance algorithm is given based on a simplified 3D-SVPWM method under an a-b-c coordinate system, a compensation capacity factor reflects the compensation capacity of each phase on the midpoint potential offset, the potential offset is distributed to phases with the midpoint potential balance capacity according to the compensation capacity and the midpoint potential offset condition, multiple phases jointly participate in midpoint potential balance control, the time quantum needed for compensating for the offset is calculated through an offset mathematical model, then the time quantum acts on the output state of the three-level converter, and therefore the purpose of balancing the midpoint potential is achieved. The simplified optimal modulation method suitable for the three-phase four-wire system three-level converter can precisely control direct current side capacitor voltages.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to an optimal modulation method for a three-phase four-wire system three-level converter. Background technique [0002] With the continuous improvement of users' demand for power, three-phase four-wire three-level neutral-point clamped converters are widely used in power equipment because of their ability to control zero-sequence components, but their modulation strategies are complex and The problem of point potential balance still needs to be perfected. [0003] The traditional three-level 3D-SVPWM modulation strategy is widely used due to its high voltage utilization rate and flexible vector selection, but it does not have the ability to balance the midpoint potential. The neutral point potential balance algorithm based on the traditional 3D-SVPWM divides and expands the space to control the midpoint potential of the DC side, but the method is complex and computational...

Claims

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Application Information

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IPC IPC(8): H02M7/483
CPCH02M7/483
Inventor 张国荣吴一鸣彭勃解润生
Owner HEFEI UNIV OF TECH
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