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Five-level inverter neutral-point balancing control method and system

A technology of balance control and inverter, which is applied in the direction of electrical components, AC power input conversion to DC power output, output power conversion devices, etc.

Active Publication Date: 2015-03-25
SUNGROW POWER SUPPLY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The switch state and current on the grid side and the Boost converter side both affect the midpoint potential. There are more switch combinations in the five-level inverter than in the three-level inverter. Therefore, the midpoint balance control method of the three-level inverter Not suitable for five-level inverters

Method used

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  • Five-level inverter neutral-point balancing control method and system
  • Five-level inverter neutral-point balancing control method and system
  • Five-level inverter neutral-point balancing control method and system

Examples

Experimental program
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Effect test

Embodiment 1

[0072] see figure 1 , which is a flow chart of Embodiment 1 of the midpoint balance control method for a five-level inverter provided by the present invention.

[0073] The mid-point balance control method of the five-level inverter provided in this embodiment is applied to the five-level photovoltaic inverter system. The schematic diagram of the system can be found in figure 2 As shown, the five-level inverter is a three-phase five-level inverter.

[0074] The system includes: a PV array, a first Boost circuit, a second Boost circuit, and a five-level inverter; a first capacitor C1Pos, a second capacitor C1Neg, a third capacitor C2Pos, and a fourth capacitor C2Neg; the positive electrode of the PV array The output terminal is connected to the +1 level input terminal of the five-level inverter, the negative output terminal of the PV array is connected to the -1 level input terminal of the five-level inverter, and the first capacitor C1Pos The two ends of the second capacito...

Embodiment 2

[0088] see image 3 , which is a flow chart of Embodiment 2 of the midpoint balance control method for a five-level inverter provided by the present invention.

[0089] It should be noted that the first embodiment of the method is a method for performing balance control on positive and negative two levels in a five-level inverter, and this embodiment also introduces a method for performing balance control on positive and negative one level.

[0090] In addition, in this embodiment, when the inverter works at three levels, it refers to working at zero level and positive and negative two levels.

[0091] S301: Detect the +1 level voltage V1Pos on the first capacitor and the -1 level voltage V1Neg on the second capacitor;

[0092] S302: Comparing the V1Pos and V1Neg with half of the PV array output voltage command, respectively controlling the positive PV bus voltage and the negative PV bus voltage according to the comparison result.

[0093] S303-S305 are the same as S101-S103...

Embodiment 3

[0146] see Figure 6 , which is a schematic diagram of Embodiment 3 of the device provided by the present invention.

[0147] This embodiment introduces that when the inverter works at five levels, the positive and negative midpoint voltages of one level are balanced.

[0148] When the inverter works at five levels, it also includes: a positive and negative one level detection module 700 and a positive and negative one level modulation module 800;

[0149] The positive and negative one level detection module 700 is used to detect the +1 level voltage V1Pos on the first capacitor and the -1 level voltage V1Neg on the second capacitor;

[0150] The positive and negative one-level modulation module 800 is used to compare both the V1Pos and V1Neg with half of the PV array output voltage command, and respectively control the positive PV bus voltage and the negative PV bus voltage according to the comparison result.

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Abstract

The invention provides a five-level inverter neutral-point balancing control method and system. The method includes the steps of detecting V2Pos and V2Neg; obtaining a two-level neutral-point voltage balancing adjusting result Vout through a difference of the V2Pos and the V2Neg according to a preset adjusting algorithm; obtaining a first total positive and negative bus charging current difference I1 by overlapping a net-side three-phase bridge arm voltage command Vx and the positive zero sequence offset; obtaining a second total positive and negative bus charging current difference I2 by overlapping the Vx and the negative zero sequence offset; obtaining the positive zero sequence offset and the negative zero sequence offset in advance, wherein the Vx is the three-phase bridge arm voltage command before amendment is carried out; determining the overlapped offset V1 according to the Vout, the I1 and the I2, wherein the amended three-phase bridge arm voltage command Vx1 is equal to a sum of V0 and the Vx, and V0=V1*|Vout|; guaranteeing that a positive bus and a negative bus keep symmetrical during working so that risks caused by over-high voltage stress caused by the neutral-point voltage offset in the switching tube motion process can be eliminated.

Description

technical field [0001] The invention relates to the technical field of photovoltaic power generation, in particular to a method and system for controlling midpoint balance of a five-level inverter. Background technique [0002] In the photovoltaic power generation system, the five-level inverter has lower grid-connected current ripple and lower switching loss than the two-level and three-level inverters, so it has the same output filter size Lower grid-connected current total harmonic distortion (THD, Total Harmonic Distortion) and higher efficiency. [0003] However, the five-level inverter is similar to the three-level inverter, and it also has the problem of midpoint potential shift, which causes the voltage stress of the switching tubes to be asymmetrical, so that some switching tubes are subjected to excessively high voltage during the switching process. voltage, and may even cause an explosion. Therefore, in order to ensure the safety of the switching tube, it is nec...

Claims

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Application Information

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IPC IPC(8): H02M7/483
CPCH02M7/487
Inventor 丁杰邹海晏陶磊徐涛涛张成
Owner SUNGROW POWER SUPPLY CO LTD