A short-circuit current control method for a new energy power station and an energy storage station

Abstract

The application discloses a short-circuit current control method for new energy power stations and energy storage stations, and aims at solving the problem of short-circuit current rising or even exceeding the standard caused by densely connecting new energy power stations and energy storage stations to regional power grids. The application firstly determines the original short-circuit current control strategy of the new energy power stations and the energy storage stations; then calculates the short-circuit current of the regional power grid through the simulation of the large power grid, adjusts the short-circuit current control parameters of the new energy power stations and the energy storage stations according to the calculation result of the short-circuit current of the regional power grid, and realizes the low-voltage ride-through requirement while ensuring that the short-circuit current of the key bus does not exceed the standard; finally, the short-circuit current characteristic curve of the new energy power stations and the energy storage stations is remodeled to form the optimized short-circuit current control strategy. The application replaces the network structure adjustment by optimizing the control parameters of the new energy power stations and the energy storage stations, improves the carrying capacity of the power grid, and optimizes the power grid planning scheme.

Description

Technical Field

[0001] This invention belongs to the field of power system current control, specifically a short-circuit current control method for new energy power plants and energy storage stations. Background Technology

[0002] Currently, power systems are increasingly connecting a large number of new energy power plants and energy storage stations. At some points of dense connection of new energy power plants and energy storage stations in some power systems, there are instances of high or even excessive short-circuit currents, making it impossible to further expand the scale of new energy power plants and energy storage stations connected.

[0003] Therefore, it is necessary to adjust the low voltage ride-through strategy and optimize the short-circuit current control method for new energy power plants and energy storage stations to alleviate the problem of excessive short-circuit current in the power supply area. Summary of the Invention

[0004] This invention provides a short-circuit current control method for new energy power plants and energy storage stations, which is used to solve the problem of increased or even excessive short-circuit current after new energy power plants and energy storage stations are connected to the power grid, thereby improving the grid's absorption capacity of new energy power plants and energy storage stations.

[0005] Therefore, the present invention adopts the following technical solution: a short-circuit current control method for new energy power plants and energy storage stations, comprising the following steps:

[0006] 1) Determine the original dynamic reactive current control strategy for new energy power plants and energy storage stations, and obtain the original short-circuit current characteristic curve;

[0007] 2) By simulating the large power grid, the short-circuit current and the points where the short-circuit current exceeds the standard are obtained, which is the calculation result of the short-circuit current of the regional power grid;

[0008] 3) Based on the calculation results of the short-circuit current of the regional power grid, adjust the short-circuit current control parameters of the new energy power station and energy storage station to meet the low voltage ride-through requirements while ensuring that the short-circuit current of the key busbar does not exceed the standard.

[0009] 4) After adjusting the short-circuit current control parameters of the new energy power station and the energy storage station, reshape the short-circuit current characteristic curves of the new energy power station and the energy storage station to form an optimized short-circuit current control strategy.

[0010] Furthermore, the application scenarios of the short-circuit current control method for the new energy power station and energy storage station include photovoltaic power stations with low voltage ride-through function, offshore wind farms, onshore wind farms and electrochemical energy storage power stations.

[0011] Furthermore, in step 3), the slope coefficient K in the short-circuit current control parameters is adjusted. T and maximum short-circuit current I Tmax .

[0012] Furthermore, in step 3), three control strategies are adopted based on whether the calculated short-circuit current of the regional power grid exceeds the standard.

[0013] Furthermore, in step 3), if the short-circuit current of the regional power grid does not exceed the standard, the output current of the new energy power station and energy storage station is limited to within the maximum overload capacity, and the maximum short-circuit current I is increased. Tmax and slope coefficient K T The absolute value of.

[0014] Furthermore, in step 3), if the short-circuit current of the regional power grid exceeds the limit, the maximum short-circuit current I is reduced. Tmax and slope coefficient K T The absolute value of.

[0015] Furthermore, in step 3), if the short-circuit current of the regional power grid exceeds the standard, a refined short-circuit current control method is provided: determine the short-circuit boundary point (U2, I2), where U2 represents the boundary point voltage and I2 represents the boundary point current; if the residual voltage at the grid connection point is lower than U2 during the fault, the new energy power station and energy storage station provide a larger short-circuit current, and if the residual voltage at the grid connection point is higher than U2 during the fault, the new energy power station and energy storage station provide a smaller short-circuit current.

[0016] Furthermore, in step 3), if the short-circuit current of the regional power grid exceeds the standard, in the refined short-circuit current control method, the maximum value of the short-circuit current provided by the new energy power station and energy storage station during the remote fault is set as the boundary point current I2. The residual voltage at the grid connection point of the new energy power station and energy storage station is calculated when the fault exceeds the standard at different short-circuit current points, and its minimum value is taken as U1. The voltage safety margin ΔU is set, and U1-ΔU=U2 is set to obtain the boundary point voltage U2.

[0017] Furthermore, in step 3), if the short-circuit current of the regional power grid exceeds the standard, in the refined short-circuit current control method, the residual voltage U at the grid connection point during the fault period... T When the value is higher than U2, to avoid excessive short-circuit current on the distant busbar, the new energy power station and energy storage station provide a smaller short-circuit current, and the adjusted slope coefficient K is used. T The absolute value of is reduced to K1.

[0018] Furthermore, in step 3), if the short-circuit current of the regional power grid exceeds the standard, in the refined short-circuit current control method, the residual voltage U at the grid connection point during the fault period... T Below U2, to achieve low voltage ride-through requirements, new energy power plants and energy storage stations provide a larger short-circuit current, and the adjusted slope coefficient K T The absolute value of K is increased to K2, and the adjusted maximum short-circuit current is I. Tmax2 .

[0019] The present invention has the following beneficial effects: The short-circuit current control method for new energy power plants and energy storage stations proposed in this invention can flexibly adjust the short-circuit current control strategy of new energy power plants and energy storage stations according to the actual short-circuit current level of the system. By adjusting the short-circuit current control parameters of new energy power plants and energy storage stations, the grid structure adjustment can be replaced, thereby improving the carrying capacity of the power grid and optimizing the operation and planning of the power grid. Attached Figure Description

[0020] Figure 1 This is a flowchart of the short-circuit current control method for new energy power plants and energy storage stations according to the present invention;

[0021] Figure 2 The original and optimized short-circuit current characteristic curves of new energy power plants and energy storage stations when the short-circuit current of the regional power grid does not exceed the standard.

[0022] Figure 3 The short-circuit current characteristic curves of new energy power plants and energy storage stations under the original and unadopted refined short-circuit current control strategies when the short-circuit current of the regional power grid exceeds the standard.

[0023] Figure 4 The short-circuit current characteristic curves of new energy power plants and energy storage stations under the original and refined short-circuit current control strategies when the short-circuit current of the regional power grid exceeds the standard. Detailed Implementation

[0024] The following detailed description of the embodiments of the present invention, in conjunction with the accompanying drawings, will provide a thorough understanding of how the present invention uses technical means to solve technical problems and achieve technical effects, enabling its implementation accordingly. It should be noted that, provided there is no conflict, other embodiments obtained by those skilled in the art based on the embodiments of the present invention without innovative technical effort are all embodiments protected by the present invention.

[0025] Example

[0026] When a short-circuit fault in the power system causes a voltage drop, the original short-circuit current control strategy of the new energy power station and energy storage station satisfies:

[0027]

[0028] Where I T This is the short-circuit current, i.e., the dynamic reactive current, K. T U is the slope coefficient. T I represents the per-unit value of the residual voltage at the grid connection point during the fault period. N For the rated current, U L U is the per-unit value of the lower limit voltage of the low voltage ride-through threshold. H I is the per-unit value of the upper limit voltage of the low voltage ride-through threshold. Tmax This is the maximum short-circuit current.

[0029] Based on the original short-circuit current control strategy of new energy power plants and energy storage stations, it can be seen that the short-circuit current during a fault is mainly determined by three parameters: firstly, the slope coefficient K. T Second, the maximum short-circuit current I Tmax Third, the upper and lower limits of the low voltage ride-through threshold voltage U. H U L By adjusting these three parameters in the converter, the short-circuit current control strategy of the new energy power station and energy storage station can be adjusted.

[0030] This embodiment provides a short-circuit current control method for new energy power plants and energy storage stations, the flowchart of which is shown below. Figure 1 As shown, this is used to address the issue of increased or even excessive short-circuit current after new energy power plants and energy storage stations are connected to the power grid, thereby improving the grid's capacity to absorb new energy power plants and energy storage stations.

[0031] A short-circuit current control method for a new energy power station and an energy storage station, comprising:

[0032] 1) Determine the original short-circuit current control strategy for new energy power plants and energy storage stations, and obtain the original short-circuit current characteristic curves;

[0033] 2) For regional power grids with dense access to new energy power plants and energy storage stations, the short-circuit current and the points where the short-circuit current exceeds the standard are obtained through large power grid simulation calculations, which are the calculation results of the short-circuit current of the regional power grid.

[0034] 3) Based on the calculation results of the short-circuit current of the regional power grid, adjust the short-circuit current control parameters of the new energy power station and energy storage station to meet the low voltage ride-through requirements while ensuring that the short-circuit current of the key busbar does not exceed the standard.

[0035] 4) After adjusting the short-circuit current control parameters of the new energy power station and the energy storage station, reshape the short-circuit current characteristic curves of the new energy power station and the energy storage station to form an optimized short-circuit current control strategy.

[0036] Furthermore, in step 3), based on the simulation results of the large power grid, to determine whether the short-circuit current of the regional power grid exceeds the standard, three different short-circuit current control strategies are adopted:

[0037] (1) If the short-circuit current of the regional power grid does not exceed the standard, increase I according to the overload multiple of the new energy power station and energy storage station. Tmax The absolute value of the slope coefficient of the corresponding short-circuit current characteristic curve increases to K2. For example... Figure 2 As shown, the short-circuit current characteristic curves of new energy power stations and energy storage stations before and after optimization are presented when the short-circuit current of the regional power grid does not exceed the standard.

[0038] (2) If the short-circuit current of the regional power grid exceeds the standard, I can be directly reduced. TmaxAnd the absolute value of the slope coefficient of the corresponding short-circuit current characteristic curve decreases to K2. For example... Figure 3 As shown, the short-circuit current characteristic curves of new energy power stations and energy storage stations before and after optimization are displayed when the short-circuit current of the regional power grid exceeds the standard.

[0039] (3) If the short-circuit current of the regional power grid exceeds the standard, the following refined short-circuit current control method can also be adopted. Set the maximum short-circuit current I2 provided by the new energy power station and energy storage station when the fault occurs in the remote area. Calculate the grid connection voltage of the new energy power station and energy storage station when the short-circuit fault occurs at different short-circuit current exceeding points, take the minimum value as U1, set the voltage safety margin ΔU, let U1-ΔU=U2, and obtain the short-circuit current control strategy boundary voltage U2. Take (U2, I2) as the boundary point of the short-circuit current control strategy. Compared with the original short-circuit current control strategy, the grid connection residual voltage U2 is higher. T When the voltage is higher than U2, to avoid excessive short-circuit current on the distant busbar, the new energy power station and energy storage station provide a smaller short-circuit current, and the adjusted slope coefficient is K1; the residual voltage at the grid connection point U T Below U2, to meet low voltage ride-through requirements, new energy power plants and energy storage stations provide a larger short-circuit current. The adjusted slope coefficient is K2, and the adjusted maximum short-circuit current is I. Tmax2 .like Figure 4 As shown, the original current characteristic curve and the refined short-circuit current control characteristic curve are displayed when the short-circuit current of the regional power grid exceeds the standard.

[0040] Application examples

[0041] 500kV substation A is connected to 220kV substation B via a double-circuit line, while photovoltaic power station C is connected to 220kV substation B via a single-circuit line. Under specific operating conditions, the calculated three-phase short-circuit current of the 220kV busbar of 500kV substation A is affected by the short-circuit current control parameters of photovoltaic power station C, as shown in Table 1.

[0042] Table 1. Calculation results of three-phase short-circuit current of 220kV busbar at 500kV substation A

[0043]

[0044] As shown in Table 1, after the photovoltaic power station C was connected to the power supply area, the three-phase short-circuit current of the 220kV busbar of the 500kV substation A increased from 49.1kA to 50.7kA, indicating that the short-circuit current exceeded the standard. The original short-circuit current control parameter K of photovoltaic power station C is also shown. T =2.6, I Tmax =1.6, adopting a non-fine-grained short-circuit current optimization strategy, adjusting the short-circuit current control parameter to K. T =1.0, I TmaxAfter reaching 1.1, without adjusting the grid structure, the three-phase short-circuit current of the 220kV busbar of the 500kV substation A meets the standard.

[0045] While the embodiments disclosed in this invention are as described above, these descriptions are for the purpose of facilitating understanding of the invention and are not intended to limit the invention. Any person skilled in the art can make modifications and variations in form and detail of the implementation without departing from the spirit and scope of this invention; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A short-circuit current control method for a new energy power station and energy storage station, characterized in that, Including the following steps: 1) Determine the original dynamic reactive current control strategy for new energy power plants and energy storage stations, and obtain the original short-circuit current characteristic curve; 2) By simulating the large power grid, the short-circuit current and the points where the short-circuit current exceeds the standard are obtained, which is the calculation result of the short-circuit current of the regional power grid; 3) Based on the calculation results of the short-circuit current of the regional power grid, adjust the short-circuit current control parameters of the new energy power station and energy storage station to meet the low voltage ride-through requirements while ensuring that the short-circuit current of the key busbar does not exceed the standard. 4) After adjusting the short-circuit current control parameters of the new energy power station and the energy storage station, reshape the short-circuit current characteristic curves of the new energy power station and the energy storage station to form an optimized short-circuit current control strategy. In step 3), adjust the slope coefficient in the short-circuit current control parameters. K T and maximum short-circuit current I Tmax Based on whether the calculated short-circuit current of the regional power grid exceeds the limit, two control strategies are adopted: If the short-circuit current of the regional power grid does not exceed the limit, the output current of new energy power plants and energy storage stations should be limited to within the maximum overload capacity, and the maximum short-circuit current should be increased. I Tmax and slope coefficient K T The absolute value; If the short-circuit current in the regional power grid exceeds the limit, determine whether refined short-circuit current control is needed. If not, reduce the maximum short-circuit current. I Tmax and slope coefficient K T The absolute value; if so, a refined short-circuit current control method is adopted; The refined short-circuit current control method is as follows: Determine the short-circuit boundary point ( U 2, I 2), U 2 represents the dividing point voltage. I 2 indicates the breaking point current; if the residual voltage at the grid connection point is lower than the fault period... U At time 2, the new energy power station and energy storage station provide a large short-circuit current, and the adjusted slope coefficient K T The absolute value increases to K 2. The adjusted maximum short-circuit current is I Tmax2 If the residual voltage at the grid connection point is higher than 0.5% during the fault period U At time 2, the new energy power station and energy storage station provide a smaller short-circuit current, and the adjusted slope coefficient K T The absolute value decreased to K 1.

2. The short-circuit current control method for a new energy power station and energy storage station according to claim 1, characterized in that, Its application scenarios include photovoltaic power stations with low voltage ride-through capabilities, offshore wind farms, onshore wind farms, and electrochemical energy storage power stations.

3. The short-circuit current control method for a new energy power station and energy storage station according to claim 1, characterized in that, In step 3), if the short-circuit current of the regional power grid exceeds the standard, the refined short-circuit current control method sets the maximum short-circuit current provided by the new energy power station and energy storage station during remote faults as the dividing point current. I 2. When calculating the residual voltage at the grid connection point of the new energy power station and energy storage station under different short-circuit current exceeding fault conditions, take the minimum value. U 1. Set the voltage safety margin Δ U ,make U 1-Δ U= U 2. Obtain the boundary point voltage. U 2.

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