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Method and system for extracting positive sequence component and negative sequence component of network voltage

A technology of grid voltage and negative sequence components, which is applied to the phase angle between voltage and current, measuring electrical variables, measuring devices, etc.

Inactive Publication Date: 2013-12-25
SUZHOU UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] At present, it is necessary to realize the control of the grid-connected inverter based on the extraction of the positive and negative sequence components of the grid voltage. In the process of extracting the positive and negative sequence components of the grid voltage when the grid voltage is unbalanced, the actual measurement error and Factors such as errors in the data conversion process will cause the grid voltage to contain a DC component. The grid voltage component extracted by the current traditional method also contains a DC component, which has an adverse effect on the reasonable control of the grid-connected inverter.

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  • Method and system for extracting positive sequence component and negative sequence component of network voltage
  • Method and system for extracting positive sequence component and negative sequence component of network voltage

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Embodiment 1

[0064] Embodiment 1 of the present invention discloses a method for extracting positive-sequence and negative-sequence components of grid voltage, please refer to figure 1 , the method includes:

[0065] S1: The first phase voltage e of the three-phase grid a , the second phase voltage e b , the third phase voltage e c Converted to the voltage in the two-phase stationary coordinate system: α-phase voltage e α , β-phase voltage e β .

[0066] Among them, when the three-phase grid voltage is unbalanced, the three-phase grid voltage e a 、e b 、e c Converted to the voltage e in the two-phase stationary coordinate system α 、e β .

[0067] S2: respectively for e α 、e β Perform two double-order generalized integral processing to obtain the grid voltage α-axis positive sequence component that does not include the DC component of the grid voltage β-axis positive sequence component α axis negative sequence component and the negative sequence component of the β axis th...

Embodiment 2

[0104] Embodiment 2 of the present invention discloses a system for extracting positive-sequence and negative-sequence components of grid voltage. Please refer to Figure 4 , the system for extracting positive sequence and negative sequence components of grid voltage includes a conversion module 100 , a first calculation module 200 , a second calculation module 300 and a control module 400 .

[0105] The conversion module 100 is used to transform the first phase voltage e of the three-phase grid a , the second phase voltage e b , the third phase voltage e c Converted to the voltage in the two-phase stationary coordinate system: α-phase voltage e α , β-phase voltage e β .

[0106] The first calculation module 200 is used to calculate e α 、e β Perform two double-order generalized integral processing to obtain the grid voltage α-axis positive sequence component that does not include the DC component of the grid voltage β-axis positive sequence component α axis negative ...

Embodiment 3

[0112] The third embodiment verifies the feasibility and correctness of the method and system for extracting positive-sequence and negative-sequence components of grid voltage according to the present invention. Specifically, it is verified through experiments on the grid voltage under different unbalanced conditions.

[0113] Condition 1:

[0114] e a =325cosωt, e b =325cos(ωt-2π / 3), e c =325cos(ωt+2π / 3);

[0115] Condition 2:

[0116] e a =325cosωt, e b =262cos(ωt-2π / 3), e c =262cos(ωt+2π / 3);.

[0117] Condition 3:

[0118] e a =325cosωt, e b =115cos(ωt-2π / 3), e c =115cos(ωt+2π / 3);

[0119] Condition 4:

[0120] e a =325cosωt+e ah , e b =115cos(ωt-2π / 3)+e bh , e c =115cos(ωt+2π / 3)+e ch , where e ah , e bh , e ch They are high-order harmonics including 5th and 7th;

[0121] Condition 5:

[0122] e a =325cosωt+30, e b =115cos(ωt-2π / 3)+30, e c =115cos(ωt+2π / 3)+30.

[0123] Using the method of the present invention to extract the positive sequence co...

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Abstract

The invention discloses a method and system for extracting a positive sequence component and a negative sequence component of a network voltage. According to the method, on the basis that a first phase position voltage ea, a second phase position voltage eb and a third phase position voltage ec in a three-phrase power grid are converted to be a voltage ealpha and a voltage ebeta of a two-phase static coordinate system, as two-stage improper integral processing is carried out on the ealpha and ebeta twice respectively, an alpha-axis positive sequence component V+alpha, a beta-axis positive sequence component V+beta, an alpha-axis negative sequence component V-alpha and a beta-axis negative sequence component V-beta of the network voltage are obtained, wherein all the components do not contain direct current components; based on all the components, the positive sequence component V+alpha beta and the negative sequence component V-alpha beta of the network voltage are calculated, and the final calculated positive sequence component V+alpha beta and the final calculated negative sequence component V-alpha beta of the network voltage do not contain the direct current components of the network voltage. Thus, as the two-stage improper integral processing is carried out on the voltage ealpha and voltage ebeta of the two-phase static coordinate system twice respectively, the direct current components of the network voltage are restrained, the extracted positive sequence component and the extracted negative sequence component of the network voltage do not contain the direct current components, and then grid-connected inverter can be controlled effectively when the network voltage is unbalanced.

Description

technical field [0001] The invention belongs to the technical field of application of advanced phase-locked loop methods in distributed power generation systems (photovoltaic power generation, wind power generation, fuel cell power generation, etc.), and in particular relates to a method and system for extracting positive sequence and negative sequence components of grid voltage. Background technique [0002] Renewable energy has increasingly become an important part of the sustainable development strategy of human energy. The power grid is a dynamic system. Factors such as the access of high-power single-phase loads will cause the three-phase voltage imbalance of the power grid. When the grid voltage is unbalanced, the current injected into the grid by the grid-connected inverter is non-sinusoidal or asymmetrical. The active and reactive power formed by this current and the asymmetrical grid voltage will generate uncontrollable oscillations in the grid. In this case, the r...

Claims

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Application Information

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IPC IPC(8): G01R25/02
Inventor 杨勇朱彬彬谢门喜陶雪慧
Owner SUZHOU UNIV
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