Virtual inertia configuration method based on frequency security boundary

Abstract

The invention provides a virtual inertia configuration method based on a frequency security boundary, and relates to the technical field of power system control. The method comprises the following steps: monitoring disturbance change based on a wide area measurement system, and calculating the maximum frequency deviation after a power grid is disturbed; if the maximum frequency deviation is greater than the safety frequency deviation, calculating a critical inertia, and if the actual inertia is smaller than the critical inertia, performing virtual inertia configuration on the fan according to the limit of the critical virtual inertia; and the maximum inertia support is calculated based on the actual rotating speed of the fan, and if the maximum inertia support is smaller than the critical virtual inertia, the stored energy participates in virtual inertia configuration. The method can effectively prevent the generator set and the user equipment from being damaged, and avoids the stability collapse of the power grid; furthermore, the technical problem of insufficient virtual inertia support can be solved, and the stability and effectiveness of virtual inertia configuration can be guaranteed; in addition, the wide-area measurement system can guarantee the safety and stability of the power grid through quick response in combination with virtual inertia configuration.

Description

Technical Field

[0001] The present invention relates to the technical field of power system control, and in particular to a virtual inertia configuration method based on frequency safety margin. Background Art

[0002] The influx of renewable energy into existing power grids has reduced their inertia and damping to a certain extent, exposing them to the risk of low inertia and weak damping. As inertia and damping decrease, frequency fluctuations increase, placing greater pressure on traditional synchronous generators to regulate their frequency.

[0003] Active frequency support technology for wind turbines offers a new approach to addressing these issues: properly configuring the wind turbine's virtual inertia can increase the overall system inertia, improve frequency dynamics, and enhance the system's frequency safety and stability. Current inertia configuration technology is only tailored to renewable energy sources. Due to the fluctuating and intermittent nature of renewable energy sources like wind turbines, they can cause significant frequency deviations in the grid, potentially damaging generators and user equipment and compromising grid stability. Furthermore, wind turbines cannot provide sufficient virtual inertia support when wind speeds are low. Summary of the Invention

[0004] To solve the above technical problems existing in the prior art, the present invention adopts a virtual inertia configuration method based on frequency safety margin, which can ensure that the frequency of the power grid remains within the safety margin after being disturbed by virtual inertia configuration of the power grid.

[0005] Specifically, the technical solution is as follows:

[0006] Monitor the disturbance changes of the power grid and calculate the maximum frequency deviation Δf after the power grid is disturbed max , the formula is as follows:

[0007]

[0008] Where f0 is the grid frequency before the disturbance, P d is the disturbance power, H sys is the grid inertia, t1 is the time it takes to reach the lowest frequency point after the disturbance;

[0009] If the maximum frequency deviation Δf max If it is greater than the safety frequency deviation Δf, then the critical inertia H is calculated. c , the formula is as follows:

[0010]

[0011] If the critical inertia H c Greater than the grid inertia H sys , then the critical virtual inertia H NConfigure virtual inertia for the fan.

[0012]

[0013] Where K is the fan penetration rate, H A is the original virtual inertia of the fan.

[0014] Furthermore, it also includes:

[0015] Get the actual speed of the fan and calculate the maximum inertia support H of the fan wmax , the formula is as follows:

[0016]

[0017] Where, ω w0 is the actual speed of the fan, ω min The minimum speed allowed for normal operation of the fan, ω N is the synchronous angular velocity, Δω N is the synchronous angular velocity change, J w is the inherent mechanical inertia of the fan, S w is the rated capacity of the fan;

[0018] If the maximum inertia support H wmax Less than the critical virtual inertia H N , the energy storage configures the virtual inertia of the wind turbine with the maximum virtual inertia within the specified charging and discharging time.

[0019] Preferably, the disturbance changes of the power grid are monitored by a wide area measurement system (WAMS).

[0020] Compared with existing technologies, the technical solution provided by the present invention can provide timely virtual inertia support when the power grid experiences large frequency deviations, effectively preventing damage to generator sets and user equipment, and avoiding a collapse in power grid stability. Furthermore, by calling on energy storage for virtual inertia configuration, the technical problem of insufficient virtual inertia support caused by the volatility and intermittency of wind turbines can be resolved, helping to ensure the stability and effectiveness of the virtual inertia configuration. In addition, the wide-area measurement system can monitor power grid power on a millisecond time scale, enabling a rapid response to excessive grid frequency deviations, helping to promptly integrate virtual inertia configuration to ensure grid stability and security. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the flow of the virtual inertia configuration method based on frequency safety margin in the present invention.

[0022] Figure 21 is a topological diagram of a power grid to which a virtual inertia configuration method is applied in one embodiment of the present invention; wherein "1" to "39" represent nodes, and G1 to G10 represent generators.

[0023] Figure 3 This is a comparison diagram of frequency responses before and after configuring virtual inertia in one embodiment of the present invention.

[0024] Figure 4 This is a frequency response comparison diagram after configuring energy storage and wind turbine virtual inertia in one embodiment of the present invention. DETAILED DESCRIPTION

[0025] Hereinafter, the technical solution provided by the present invention will be further described in conjunction with embodiments and drawings.

[0026] The virtual inertia configuration method based on frequency safety boundary is as follows Figure 1 shown.

[0027] Step S1: Monitor disturbance changes based on the wide area measurement system. When the power grid is disturbed by a large load change, calculate the maximum frequency deviation Δf after the power grid is disturbed. max , the formula is as follows:

[0028]

[0029] Where f0 is the grid frequency before the disturbance, P d is the disturbance power, H sys is the grid inertia, and t1 is the time it takes to reach the lowest frequency point after the disturbance. The wide-area measurement system can monitor grid power on a millisecond time scale and is suitable for dynamic monitoring of grid power changes.

[0030] Step S2: According to the formula in step S1, based on the disturbance power P d The maximum frequency deviation Δf after the power grid is disturbed can be predicted max If the maximum frequency deviation Δf max If the frequency deviation is greater than the maximum frequency deviation allowed for safety, that is, the safe frequency deviation Δf, it indicates that virtual inertia configuration is required. The critical inertia H is calculated based on the disturbance power and the safe frequency deviation Δf. c , the formula is as follows:

[0031]

[0032] Step S3: Compare the critical inertia H that ensures the frequency safety margin c and grid inertia H sys size.

[0033] Step S4: If the grid inertia H sys Less than critical inertia H c, then configure the virtual inertia of the fan. The critical virtual inertia of the fan is H N :

[0034]

[0035] Where K is the fan penetration rate, H A is the original virtual inertia of the fan.

[0036] Step S5: When the wind speed is low, the actual speed of the fan is low, and it is difficult to provide sufficient inertial support. wmax And the critical virtual inertia H to be configured N Among them, the maximum inertia support H of the fan is calculated wmax The formula is:

[0037]

[0038] Where, ω w0 is the actual speed of the fan, ω min The minimum speed allowed for normal operation of the fan, ω N is the synchronous angular velocity, Δω N is the synchronous angular velocity change, J w is the inherent mechanical inertia of the fan, S w is the rated capacity of the fan.

[0039] Step S6: When the maximum inertia support H is satisfied wmax Less than the critical virtual inertia H N Energy storage participates in virtual inertia configuration. To protect the life of the energy storage battery, the charge and discharge time of the energy storage battery is generally not less than two hours. However, the grid frequency response time is relatively short, so the maximum virtual inertia within the specified charge and discharge time can be directly configured.

[0040] Example 1

[0041] This embodiment is as follows Figure 2 The power grid with 10 machines and 39 nodes shown in the figure is configured with virtual inertia and simulated and verified on PSCAD (Power Systems Computer Aided Design, an electromagnetic transient simulation software).

[0042] With 0.5Hz as the maximum frequency safety boundary, a total of 30% load step disturbance is applied at nodes 7, 13, and 15. At this time, the power transmitters installed at each node monitor the unbalanced power in the area. Calculations show that the maximum frequency deviation will exceed 0.5Hz, and virtual inertia needs to be urgently configured. The critical virtual inertia that needs to be configured for wind turbine G3 is calculated to be 5.61s. Based on the current state of the wind turbine and the rotor angular velocity, the maximum inertia support of the wind turbine is calculated to be 6.20s, which meets the inertia support of the system. The frequency response curves before and after configuring virtual inertia are shown in the figure below. Figure 3 The results show that after configuring the virtual inertia of the wind turbine, the frequency deviation of the power grid remains within the safety limit.

[0043] In the actual operation of the power grid, due to the volatility and intermittency of new energy sources such as wind turbines, when wind turbines cannot provide sufficient virtual inertia support due to low wind speed, the energy storage system can be deployed to configure virtual inertia. A total of 33% load step disturbance is applied at nodes 7, 13, and 15, and the wind speed of wind turbine G3 is reduced to 10m / s. At this time, the speed of the wind turbine decreases and the maximum inertia support of the wind turbine decreases. The wind turbine is not enough to support the system inertia of the power grid, and energy storage participates in the auxiliary configuration of virtual inertia. Before and after configuring energy storage and wind turbine virtual inertia, the frequency response curve of the power grid is as follows: Figure 4 When the wind turbine speed is low and the inertia support is weak, configuring virtual inertia with energy storage can effectively compensate for the lack of system inertia and improve the security of the grid frequency.

[0044] As can be seen from the embodiments and accompanying drawings, compared with the prior art, the technical solution provided by the present invention can provide virtual inertia support in a timely manner when a large frequency deviation occurs in the power grid, thereby effectively preventing damage to generator sets and user equipment and avoiding a collapse of power grid stability. Furthermore, by calling on energy storage for virtual inertia configuration, the technical problem of insufficient virtual inertia support caused by the volatility and intermittency of wind turbines can be solved, which helps to ensure the stability and effectiveness of the virtual inertia configuration. In addition, the wide-area measurement system can monitor the power of the power grid on a time scale of milliseconds, and can achieve a rapid response to excessive frequency deviations of the power grid, which helps to timely combine virtual inertia configuration to ensure the stability and security of the power grid.

Claims

1. A virtual inertia configuration method based on frequency safety margin, characterized in that: include: Monitor the disturbance changes of the power grid and calculate the maximum frequency deviation Δf after the power grid is disturbed max , the formula is as follows: Where f0 is the grid frequency before the disturbance, P d is the disturbance power, H sys is the grid inertia, t1 is the time it takes to reach the lowest frequency point after the disturbance; If the maximum frequency deviation Δf max If it is greater than the safety frequency deviation Δf, then the critical inertia H is calculated. c , the formula is as follows: If the critical inertia H c Greater than the grid inertia H sys , then the critical virtual inertia H N Configure virtual inertia for the fan. Where K is the fan penetration rate, H A is the original virtual inertia of the fan.

2. A virtual inertia configuration method based on frequency safety margin according to claim 1, characterized in that: Also includes: Get the actual speed of the fan and calculate the maximum inertia support H of the fan wmax , the announcement is as follows: Where, ω w0 is the actual speed of the fan, ω min The minimum speed allowed for normal operation of the fan, ω N is the synchronous angular velocity, Δω N is the synchronous angular velocity change, J w is the inherent mechanical inertia of the fan, S w is the rated capacity of the fan; If the maximum inertia support H wmax Less than the critical virtual inertia H N , the energy storage configures the virtual inertia of the wind turbine with the maximum virtual inertia within the specified charging and discharging time.

3. A virtual inertia configuration method based on frequency safety margin according to claim 1 or 2, characterized in that: Monitor disturbance changes in the power grid through a wide-area measurement system.

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