Frequency-coupled clean energy farm output port equivalent impedance modeling method

Abstract

The present invention provides a clean energy field output port equivalent impedance modeling method considering frequency coupling, comprising the following steps: obtaining the admittance value Y of the hydropower plant hg And the line impedance Z2 of the hydropower plant, and determine the admittance value Y of the grid-connected port of the hydropower plant hg_pcc ; Based on the grid-connected port admittance value Y of the hydropower plant hg_pcc and the grid impedance Z g Determine the output port impedance Z of the wind farm or photovoltaic power plant c_out ; Based on the output port impedance value Z of the wind farm or photovoltaic power plant c_out And the frequency coupling factor determines the port equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p ); Based on the admittance value Y of the grid-connected port of the hydropower plant hg_pcc And the equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p ) Determine the output port admittance Y of the clean energy field s ; It can ensure the accuracy of impedance calculation results and provide accurate data support for the stability analysis of the power grid system.

Description

Technical Field

[0001] The present invention relates to an impedance modeling method, and in particular to an equivalent impedance modeling method for a clean energy field output port considering frequency coupling. Background Art

[0002] The energy complementary power generation system is a multi-energy hybrid power generation system based on the complementary characteristics of energy resources, and the stable operation of the complementary system is the key to the system. Figure 2 As shown, Figure 2 The energy complementary power generation system shown in is also called a clean energy field.

[0003] In order to solve the stability problem of energy-complementary power generation systems, existing research has proposed some effective stability research methods. The impedance-based oscillation analysis method has been widely used in the oscillation analysis of traditional power generation systems due to its relatively simple form, good practicality, and strong scalability. However, the impedance characteristics of the multi-energy complementary clean energy base used in impedance oscillation analysis have not yet been clarified. Multiple oscillation accidents at home and abroad have shown that when an interconnected system containing AC and DC power electronic equipment oscillates, there is a frequency coupling phenomenon. This frequency coupling effect changes the original input and output characteristics of the system and will have a significant impact on the system stability. However, there is no effective technical means in the existing technology to solve the impact of frequency coupling on impedance, which in turn affects the subsequent system stability analysis. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an equivalent impedance modeling method for the output port of a clean energy field taking into account frequency coupling. By introducing the impedance factors of hydropower plants, wind farms or photovoltaic power plants and power grids in the modeling process, and taking into account the influence of frequency disturbances, an impedance model of the grid-connected port is finally established, thereby ultimately ensuring the accuracy of the impedance calculation results and providing accurate data support for the subsequent stability analysis of the entire power grid system.

[0005] The present invention provides a clean energy field output port equivalent impedance modeling method considering frequency coupling, comprising the following steps:

[0006] S1. Obtain the admittance value Y of the hydropower plant hg And the line impedance Z2 of the hydropower plant, and determine the admittance value Y of the grid-connected port of the hydropower plant hg_pcc ;

[0007] S2. Based on the grid-connected port admittance value Y of the hydropower plant hg_pcc and the grid impedance Z g Determine the output port impedance Z of the wind farm or photovoltaic power plant c_out ;

[0008] S3. Based on the output port impedance value Z of the wind farm or photovoltaic power plant c_out And the frequency coupling factor determines the port equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p );

[0009] S4. Based on the admittance value Y of the hydropower plant's grid-connected port hg_pcc And the equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p ) Determine the output port admittance Y of the clean energy field s .

[0010] Further, in step S4, the output port admittance Y of the clean energy field s Determined by the following method:

[0011] Y s =Y hg_pcc +Y c .

[0012] Furthermore, the admittance value Y hg_pcc Determined by the following method:

[0013] Y hg_pcc =Y hg +(Z2) -1 .

[0014] Furthermore, the admittance value Y of the hydropower plant is determined by the following method: hg :

[0015]

[0016] in: and are the disturbance current and disturbance voltage at the hydropower plant port respectively.

[0017] Furthermore, the output port impedance value Z of the wind farm or photovoltaic power plant is c_out :

[0018] Z c_out =(Y hg_pcc +(Z g ) -1 ) -1 .

[0019] Furthermore, the port equivalent admittance Y of the wind farm or photovoltaic power plant is c (ω p ) is determined by the following method:

[0020]

[0021] Where: Ysa (ω p ) is the output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The self-admittance under aa (ω p ) is the load disturbance frequency ω at the output port of the wind farm or photovoltaic power plant p The adjoint admittance, ω p is the disturbance frequency, ω0 is the power frequency, Indicates the load disturbance frequency ω at the output port of a wind farm or photovoltaic power plant p The complex conjugate of the adjoint admittance at -2ω0, Indicates the load disturbance frequency ω at the output port of a wind farm or photovoltaic power plant p The complex conjugate of the self-admittance at -2ω0.

[0022] Furthermore, the output port of the wind farm or photovoltaic power plant is at the disturbance frequency ω p Self-admittance Y sa (ω p ) is determined by the following method:

[0023]

[0024] in: The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The disturbance current under The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The disturbance voltage under .

[0025] Furthermore, the output port of the wind farm or photovoltaic power plant is at the disturbance frequency ω p The adjoint admittance Y aa (ω p ) is determined by the following method:

[0026] in, The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p Perturbation current at -2ω0.

[0027] Beneficial effects of the present invention: Through the present invention, by introducing the impedance factors of hydropower plants, wind farms or photovoltaic power plants and power grids in the modeling process, and taking into account the influence of frequency disturbances, the impedance model of the grid-connected port is finally established, thereby ultimately ensuring the accuracy of the impedance calculation results and providing accurate data support for the subsequent stability analysis of the entire power grid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0029] Figure 1 It is a schematic diagram of the process of the present invention.

[0030] Figure 2 This is a schematic diagram of the clean energy field structure of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below:

[0032] The present invention provides a clean energy field output port equivalent impedance modeling method considering frequency coupling, comprising the following steps:

[0033] S1. Obtain the admittance value Y of the hydropower plant hg And the line impedance Z2 of the hydropower plant, and determine the admittance value Y of the grid-connected port of the hydropower plant hg_pcc ;

[0034] S2. Based on the grid-connected port admittance value Y of the hydropower plant hg_pcc and the grid impedance Z g Determine the output port impedance Z of the wind farm or photovoltaic power plant c_out ;

[0035] S3. Based on the output port impedance value Z of the wind farm or photovoltaic power plant c_out And the frequency coupling factor determines the port equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p );

[0036] S4. Based on the admittance value Y of the hydropower plant's grid-connected port hg_pcc And the equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p ) Determine the output port admittance Y of the clean energy field s Through this method, the impedance factors of the hydropower plant, wind farm, or photovoltaic power plant, and the power grid are introduced into the modeling process, and the impact of frequency disturbances is taken into account. Finally, the impedance model of the grid-connected port is established, ultimately ensuring the accuracy of the impedance calculation results and providing precise data support for subsequent stability analysis of the entire power grid system. Among them, the output port of the clean energy field is the two-level inverter during the grid connection process; the admittance of the hydropower plant refers to the admittance of the turbine.

[0037] In this embodiment, in step S4, the output port admittance Y of the clean energy field is s Determined by the following method:

[0038] Y s =Y hg_pcc +Y c .

[0039] In this embodiment, the admittance value Y hg_pcc Determined by the following method:

[0040] Y hg_pcc =Y hg +(Z2) -1 .

[0041] In this embodiment, the admittance value Y of the hydropower plant is determined by the following method: hg :

[0042]

[0043] in: and are the disturbance current and disturbance voltage at the hydropower plant port respectively.

[0044] In this embodiment, the output port impedance value Z of the wind farm or photovoltaic power plant is c_out :

[0045] Z c_out =(Y hg_pcc +(Z g ) -1 ) -1 .

[0046] In this embodiment, the port equivalent admittance Y of the wind farm or photovoltaic power plant is c (ω p ) is determined by the following method:

[0047]

[0048] Where: Y sa (ω p ) is the output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The self-admittance under aa (ω p ) is the load disturbance frequency ω at the output port of the wind farm or photovoltaic power plant p The adjoint admittance, ω p is the disturbance frequency, ω0 is the power frequency, Indicates the load disturbance frequency ω at the output port of a wind farm or photovoltaic power plant p The complex conjugate of the adjoint admittance at -2ω0, Indicates the load disturbance frequency ω at the output port of a wind farm or photovoltaic power plant p The complex conjugate of the self-admittance at -2ω0, Y sa (ω p -2ω0) and Y sa (ω p ) has the same calculation formula structure, only the frequency needs to be replaced.

[0049] Specifically: the output port of the wind farm or photovoltaic power plant is at the disturbance frequency ω p Self-admittance Y sa (ω p ) is determined by the following method:

[0050]

[0051] in: The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The disturbance current under The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The disturbance voltage under .

[0052] The output port of the wind farm or photovoltaic power plant is at the disturbance frequency ω p The adjoint admittance Y aa (ω p ) is determined by the following method:

[0053] in, The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The disturbance current at -2ω0; where:

[0054]

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A clean energy field output port equivalent impedance modeling method considering frequency coupling, characterized by: The following steps are involved: S1. Obtain the admittance value Y of the hydropower plant hg And the line impedance Z2 of the hydropower plant, and determine the admittance value Y of the grid-connected port of the hydropower plant hg_pcc ; S2. Based on the grid-connected port admittance value Y of the hydropower plant hg_pcc and the grid impedance Z g Determine the output port impedance Z of the wind farm or photovoltaic power plant c_out ; S3. Based on the output port impedance value Z of the wind farm or photovoltaic power plant c_out And the frequency coupling factor determines the port equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p ); Where: the port equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p ) is determined by the following method: Where: Y sa (ω p ) is the output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The self-admittance under aa (ω p ) is the load disturbance frequency ω at the output port of the wind farm or photovoltaic power plant p The adjoint admittance, ω p is the disturbance frequency, ω0 is the power frequency, Indicates the load disturbance frequency ω at the output port of a wind farm or photovoltaic power plant p The complex conjugate of the adjoint admittance at -2ω0, Indicates the load disturbance frequency ω at the output port of a wind farm or photovoltaic power plant p The complex conjugate of the self-admittance at -2ω0; The output port of the wind farm or photovoltaic power plant is at the disturbance frequency ω p Self-admittance Y sa (ω p ) is determined by the following method: in: The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The disturbance current under The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p The disturbance voltage under The output port of the wind farm or photovoltaic power plant is at the disturbance frequency ω p The adjoint admittance Y aa (ω p ) is determined by the following method: in, The output port of the wind farm or photovoltaic power plant at the disturbance frequency ω p Disturbance current under -2ω0; S4. Admittance value Y based on the grid-connected port of the hydropower plant hg_pcc And the equivalent admittance Y of the wind farm or photovoltaic power plant c (ω p ) Determine the output port admittance Y of the clean energy field s .

2. The clean energy field output port equivalent impedance modeling method considering frequency coupling according to claim 1 is characterized by: In step S4, the output port admittance Y of the clean energy field s Determined by the following method: AND s =And hg_pcc +Y c 。 3. The clean energy field output port equivalent impedance modeling method considering frequency coupling according to claim 1 is characterized by: Admittance value Y hg_pcc Determined by the following method: Y hg_pcc =Y hg +(Z2) -1 。 4. The clean energy field output port equivalent impedance modeling method considering frequency coupling according to claim 3 is characterized by: Determine the admittance value Y of the hydropower plant by the following method hg : in: and are the disturbance current and disturbance voltage at the hydropower plant port respectively.

5. The clean energy field output port equivalent impedance modeling method considering frequency coupling according to claim 1 is characterized by: The wind farm or photovoltaic power plant output port impedance value Z c_out : Z c_out =(Y hg_pcc +(Z g ) -1 ) -1 。

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