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Grid-connected inverter parallel system circulating current restraining method under imbalance condition of inductance

A circulation suppression and balance condition technology, applied in the field of circulation suppression, can solve problems such as large circulation

Inactive Publication Date: 2013-10-09
HARBIN INST OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0008] The present invention aims to solve the problem that in the parallel connection system of grid-connected inverters, when the three-phase inductance of the parallel inverters changes or is unbalanced, the circulating current is still relatively large when controlled by the existing method for suppressing the circulating current

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  • Grid-connected inverter parallel system circulating current restraining method under imbalance condition of inductance
  • Grid-connected inverter parallel system circulating current restraining method under imbalance condition of inductance
  • Grid-connected inverter parallel system circulating current restraining method under imbalance condition of inductance

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specific Embodiment approach 1

[0046] Specific implementation mode one: refer to figure 1 and image 3 Describe this embodiment in detail. In the method for suppressing the circulation of grid-connected inverter parallel system under the condition of unbalanced inductance described in this embodiment, the grid-connected inverter in the grid-connected inverter parallel system is a common DC bus, AC The side is directly connected in parallel, and the parallel system is controlled by the PI method. Aiming at the above-mentioned circulation suppression method for the parallel system of grid-connected inverters, this method is for one inverter of the grid-connected inverter in the parallel system of two inverters. The circulation of the device is controlled, which specifically includes the following steps:

[0047] Step 1: To the zero-sequence current i of the second inverter 2 z2 Sampling is performed, and then step 2 is performed;

[0048] Step 2: Using the zero-sequence current PI controller to control the...

specific Embodiment approach 2

[0054] Specific embodiment 2: This embodiment is to further explain the circulating current suppression method of grid-connected inverter parallel system under the condition of inductance imbalance described in specific embodiment 1. In this embodiment, in step 1, the second inverter 2 The zero sequence current i z2 for:

[0055] i z 2 = i a 2 + i b 2 + i c 2 3 - - - ( 1 )

[0056] where i k2 (k=a, b, c) are the a-phase, b-phase and c-phase currents of the second inverter 2 respectively.

specific Embodiment approach 3

[0057] Specific embodiment 3: This embodiment is to further explain the circulating current suppression method of grid-connected inverter parallel system under the condition of inductance imbalance described in specific embodiment 1. In this embodiment, the Δd mentioned in step 3 12 for:

[0058] Δd 12 =(d 21 -d 11 )-(d 22 -d 12 ) (2)

[0059] where d 11 is the duty cycle of the first non-zero vector of the first inverter, d 21 is the duty cycle of the second non-zero vector of the first inverter, d 12 is the duty cycle of the first non-zero vector of the second inverter 2, d 22 is the duty cycle of the second non-zero vector of the second inverter 2.

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Abstract

The invention relates to a grid-connected inverter parallel system circulating current restraining method under an imbalance condition of inductance, relates to the technical field of the circulating current restraining of grid-connected inverter parallel systems, and aims at solving the problems in the grid-connected inverter parallel system that when the three-phase inductance of the parallel inverter is varied or imbalanced, the circulating current is still large through using the existing circulating current restraining method. Since the circulating current flowing between every two inverters is identical in value and opposite in directions, the circulating current between every two inverters can be restrained only by restraining the circulating current of one inverter, so that a purpose for restraining the system circulating current can be achieved. Under the imbalance of the three-phase inductance of the inverter, compared with a PI control method, for the method, the peak value of the circulating current can be reduced by 40 to 65 percent. The grid-connected inverter parallel system circulating current restraining method is suitable for restraining the circulating current in the grid-connected inverter parallel system.

Description

technical field [0001] The invention belongs to the technical field of circulation suppression for grid-connected inverter parallel systems. Background technique [0002] Three-phase PWM inverters have attracted much attention in distributed energy generation systems because of their sinusoidal output current on the AC side, high power factor, and small current distortion. With the increase of the capacity of the distributed energy generation system, higher requirements are placed on the power level of the inverter. In order to meet the power requirements of the system while ensuring the reliability of the system and reduce the cost and volume of the system, the inverters are often directly controlled in parallel, that is, the DC side and the AC side of the inverter are directly connected in parallel. This parallel structure not only increases the system capacity, but also provides a path for the circulation. The circulating current will have adverse effects on the system,...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/48H02J3/38
Inventor 张学广陈佳明张文杰王天一段大坤徐殿国
Owner HARBIN INST OF TECH
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