Clean energy field output port equivalent impedance modeling method considering frequency coupling

Abstract

The invention provides a clean energy field output port equivalent impedance modeling method considering frequency coupling, and the method comprises the following steps: obtaining an admittance value Yhg of a hydraulic power plant and line impedance Z2 of the hydraulic power plant, and determining an admittance value Yhgpcc of a grid-connected port of the hydraulic power plant; determining an output port impedance value Zcout of the wind power plant or the photovoltaic power plant based on the grid-connected port admittance value Yhgpcc of the hydraulic power plant and the power grid impedance value Zg; determining the port equivalent admittance Yc (omega p) of the wind power plant or the photovoltaic power plant based on the impedance value Zcout of the output port of the wind power plant or the photovoltaic power plant and the frequency coupling factor; determining the output port admittance Ys of the clean energy field based on the admittance value Yhgpcc of the grid-connected port of the hydraulic power plant and the port equivalent admittance Yc (omega p) of the wind power plant or the photovoltaic power plant; the accuracy of an impedance calculation result can be ensured, and accurate data support is provided for stability analysis of a power grid system.

Description

Technical Field

[0001] The 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 in the impedance oscillation analysis have not yet been clarified. Many 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 great impact on the stability of the system. 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 a hydropower plant, a wind farm or a photovoltaic power plant and a power grid in the modeling process, and taking into account the influence of frequency disturbances, and finally establishing an impedance model of the grid-connected port, 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. Get 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 value 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. 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 .

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

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

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

[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 a disturbance frequency ω p The 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 a 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 Disturbance current at -2ω0.

[0027] Beneficial effects of the present invention: Through the present invention, by introducing the impedance factors of the hydropower plant, wind farm or photovoltaic power plant and the power grid in the modeling process, and taking into account the influence of frequency disturbance, finally the impedance model of the grid-connected port is 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. Get 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 value 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. 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 . Through the above method, the impedance factors of hydropower plants, wind farms or photovoltaic power plants and power grids are introduced in the modeling process, and the influence of frequency disturbances is taken into account. Finally, the impedance model of the grid-connected port is 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. Among them, the output port of the clean energy field is the two-level inverter in the grid-connected 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:

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

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

[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 conjugate complex number 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 a disturbance frequency ω p The 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 Disturbance current at -2ω0; where:

[0054]

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should 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. Get 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 value 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 ); 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 in that: In step S4, the output port admittance Y of the clean energy field s Determined by: 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 in that: Admittance value Y hg_pcc Determined by: 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: The admittance value Y of the hydropower plant is determined 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 in that: The wind farm or photovoltaic power plant output port impedance value Z c_out : Z c_out =(Y hg_pcc +(Z g ) -1 ) -1 。 6. The clean energy field output port equivalent impedance modeling method considering frequency coupling according to claim 1 is characterized in that: 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.

7. The clean energy field output port equivalent impedance modeling method considering frequency coupling according to claim 6 is characterized by: The output port of the wind farm or photovoltaic power plant is at the disturbance frequency ω p The 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.

8. The clean energy field output port equivalent impedance modeling method considering frequency coupling according to claim 6 is characterized by: 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 at -2ω0.

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