A local flattening design method for frequency stability control systems

Abstract

The present invention discloses a method for locally flattening a frequency stability control system, comprising: 1. establishing a topological model of a power grid frequency stability control system; 2. calculating the control capability of the frequency stability control system based on the controllable capacity and path failure rate of the control substation; 3. selecting the control substation with the highest path failure rate and the capacity lower limit, and calculating the control capability threshold; 4. if the control capability of the frequency stability control system is lower than the control capability threshold, establishing horizontal connections between the control substation and other sites of the same level to form a flat structure; if the control capability is higher than the control capability threshold, selecting individual control substations to establish horizontal connections with other sites of the same level, comparing the construction costs and control capability impacts of different schemes, and selecting the optimal scheme; 5. establishing horizontal connections between control master stations, comparing the control capability impacts of different schemes, and selecting the optimal scheme. The present invention can improve the control capability and reliability of the frequency stability control system.

Description

Technical Field

[0001] The present invention relates to the technical field of reliability analysis and planning of frequency stability control systems, and in particular to a local flattening design method for a frequency stability control system. Background Art

[0002] Frequency stability control systems for large power grids typically consist of a coordinated control station, a master control station, sub-control stations, and load shedding execution stations. These implement control functions such as DC modulation, load shedding, generator shedding, and load splitting, preventing safety issues such as severe power shortages, low frequency, power angle instability, and low-frequency oscillation. With the rapid growth of regional power grid interconnection, UHV AC / DC construction, and the integration of new energy sources, the power grid's requirements for frequency stability control systems have become more stringent. The existing frequency stability control system framework and operating mechanism are insufficient to meet these stability control needs.

[0003] Existing large-scale power grid frequency stability control systems are designed according to a tree-like structure and employ vertical control. When a fault occurs in a middle layer, the upper-level power plant loses control of the lower-level power plants connected to the faulty site. Horizontal connections and information exchange between master control stations and sub-grids are lacking, preventing the sharing of control resources. With the interconnection of large-scale power grids nationwide, the number of frequency stability control system layers is increasing. Failures in sites and communication channels can lead to control failures at all lower-level execution stations, increasing the risk of failure. The larger the capacity controlled by an execution station, the more severe the fault. Summary of the Invention

[0004] In order to address the deficiencies in the prior art, the present invention provides a local flattening design method for a frequency stability control system, thereby conducting reliability analysis on the frequency stability control system, increasing communication channels between sites of the same level, and determining a functional framework of a frequency stability control system suitable for the national interconnected power grid, thereby reducing the failure risk of the frequency stability control system and improving the control capability, providing theoretical support for the safe and stable control of the interconnected power grid.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical solutions:

[0006] The local flattening design method of a frequency stabilization control system of the present invention is characterized in that it includes the following steps:

[0007] Step 1: Establish a frequency stability control system model based on the station as the basic unit, including: cooperative control station, control master station, control substation and execution station;

[0008] Step 2: Calculate the control capability CA of the frequency stability control system based on the controllable capacity of the control substation and the path failure rate;

[0009] Step 3: Select the control substation with the highest path failure rate and the capacity lower limit, and calculate the control capacity threshold CAmin ;

[0010] Step 4: If the control capability CA of the frequency stability control system is lower than the control capability threshold CA min , then while maintaining the capacity of the control substation, establish horizontal connections between the control substation and other sites at the same level to form a flat structure between substations;

[0011] If the control capability CA is higher than the control capability threshold CA min , then select individual control substations to establish horizontal connections with other sites at the same level, forming a corresponding flat structure between substations, and compare the construction costs and control capabilities of different flat structures between substations to select the optimal substation solution;

[0012] Step 5: Assume that the number of control master stations is M, establish horizontal connections between the control master stations, form a flat structure between the master stations, and compare the control capability impact under the flat structure between different master stations to select the optimal master station solution.

[0013] The local flattening design method for a frequency stability control system according to the present invention is also characterized in that the control capability CA in step 2 is calculated according to the following steps:

[0014] Step 2.1, let the number of control substations of the frequency stability control system be N;

[0015] Select the zth control substation, find all the paths from the cooperative control station to the zth control substation, and get the total number of paths as n;

[0016] Step 2.2: Use formula (1) to get the communication channel failure rate λ of the frequency stability control system: L :

[0017] λ L =λ0L (1)

[0018] In formula (1), λ0 represents the failure rate of the communication channel per unit length, and L represents the length of the communication channel;

[0019] Step 2.3: Consider the geographical location of the communication channel and define the correction coefficient as a. Then, use formula (2) to obtain the corrected failure rate λ of the kth communication channel: L,k :

[0020] λ L,k =aλ0L k (2)

[0021] In formula (2), L k represents the length of the kth communication channel;

[0022] Step 2.4: Use equation (3) to get the failure probability λ of the hth path of the zth control substation: z,h :

[0023]

[0024] In formula (3), K h represents the total number of communication channels passed under the h-th path;

[0025] Step 2.5: Use formula (4) to define the importance coefficient α of the hth path h :

[0026]

[0027] In formula (4), MS indicates that the station type is a cooperative control station, MN indicates that the station type is a control master station, and n h,MS Indicates the number of MS type sites in the hth path, n h,MN represents the number of MN type sites in the hth path, I MS is the importance of the co-control master station, I MN To control the importance of the master station, and I MS ≥I MN ;

[0028] Step 2.6: Calculate the failure probability UR of the zth control substation using equation (5) z , z=1,…,N:

[0029]

[0030] Step 2.7: Calculate the control capability ca of the zth control substation using equation (6): z , and then use formula (7) to get the control capability CA of the frequency stability control system:

[0031] ca z =S z (1-UR z ) (6)

[0032]

[0033] In formula (6), S z Indicates the controllable capacity of the zth control substation.

[0034] The control capability threshold CA in step 3 min It is calculated as follows:

[0035] Step 3.1: Use formula (8) to define the control capability threshold ca of the control substation min :

[0036]

[0037] Step 3.2: Set the redundancy coefficient to b and use formula (9) to calculate the control capability threshold CA of the frequency stability control system: min :

[0038] CA min =b×N×ca min (9).

[0039] The construction cost and control capability impact in step 4 are measured using the flattening transformation index shown in formula (10), and the optimal substation solution is selected using formula (11):

[0040]

[0041] In formula (10), C represents the investment cost of the local flattening design of the frequency stability control system; f represents the cost-control capability balance index of the frequency stability control system;

[0042]

[0043] In formula (11), f j represents the cost-control capability balance index value of the frequency stability control system under the j-th scheme, and Y represents the total number of schemes.

[0044] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0045] 1. This invention proposes a flat design method for weak sites in a frequency stability control system applicable to national power grid interconnection. Compared with the existing technology, this method reduces the system layers, improves the reliability of the frequency stability control system, and reduces the probability of failure and investment costs.

[0046] 2. The control capability index of the frequency stability control system proposed in this invention makes up for the problem that the existing index only considers the structural reliability of the frequency stability control system. It quantifies the functional reliability index and provides theoretical support for the theory of safe and stable control of the interconnected power grid.

[0047] 3. The cost-control capability balance index of the frequency stability control system proposed in the present invention balances the construction cost and control capability, providing theoretical support for designing the optimal frequency stability control system architecture solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a flow chart of a local flattening design method for a frequency stabilization control system according to the present invention;

[0049] Figure 2 A topological model of the frequency stabilization control system of the present invention;

[0050] Figure 3 This is a locally flattened topological diagram of the frequency stabilization control system of the present invention. DETAILED DESCRIPTION

[0051] In this embodiment, a method for designing a local flattening of a frequency stability control system is provided, as shown in the flow chart. Figure 1 The topology model of the frequency stability control system is shown in Figure 2 As shown in the figure, the frequency stability control system usually includes a cooperative control station, a control master station, a control substation, and an execution station. For the flat design of the weak sites of the frequency stability control system, for different control substations, one-way or two-way communication channels are added between the statistical sites to form a local flat design of the frequency stability control system. The local flat topology of the frequency stability control system is shown in the figure. Figure 3 As shown. Among them, v1~v4 are auxiliary control stations, v5~v8 are control master stations, v9~v 12 To control the substation, v k ~v m The local flattening design method of the frequency stabilization control system includes the following steps:

[0052] Step 1: Based on the actual model of the existing project and taking the site as the basic unit, establish the topology model of the power grid frequency stability control system, including the cooperative control station, the control master station, the control substation and the execution station;

[0053] Step 2: Calculate the control capability CA of the frequency stability control system based on the controllable capacity of the control substation and the path failure rate;

[0054] Step 2.1: Let the number of control substations of the frequency stability control system be N, select the zth control substation, find all paths from the cooperative control station to the zth control substation, and obtain the total number of paths as n;

[0055] Step 2.2: The failure rate of the communication channel of the frequency stability control system is related to the type and length of the communication channel. The communication channel types in the frequency stability control system include optical fiber direct communication channels and 2M interface communication channels. Using formula (1), the communication channel failure rate λ of the frequency stability control system is obtained L :

[0056] λ L =λ0L (1)

[0057] In formula (1), λ0 represents the failure rate of the communication channel per unit length, and L represents the length of the communication channel.

[0058] Step 2.3: Consider the geographical location of the communication channel and the fact that adverse geological and environmental factors may increase or decrease the failure rate, and define the correction factor a;

[0059] Taking the overhead lines in plain areas as the benchmark, the outage rate is the outage rate when it is not affected by terrain factors, and the terrain coefficient is 1; for terrain where the surrounding environment and terrain will enhance the impact of wind on the outage rate, such as wind vents and windward slopes, the terrain coefficient is greater than the benchmark value and is taken as 1 to 1.6; for terrain where the surrounding environment and terrain will weaken the impact of wind on the outage rate, such as forests and residential areas, the terrain coefficient is less than and is taken as 0.9 to 1.

[0060] Using formula (2), we can get the corrected failure rate λ of the kth communication channel: L,k :

[0061] λ L,k =aλ0L k (2)

[0062] In formula (2), L k Indicates the length of the kth communication channel.

[0063] Step 2.4: Use equation (3) to get the failure probability λ of the hth path of the zth control substation z,h :

[0064]

[0065] In formula (3), K h Indicates the total number of communication channels passed by the h-th path.

[0066] Step 2.5: Since there are usually multiple paths from the cooperative control station to the control substation, and the flow probability of each path is not equal, in order to quantify the impact of the hth path on the frequency stability control system, the path importance coefficient α is defined using formula (4): h :

[0067]

[0068] Path importance coefficient α h The total number of paths n is determined by the number of all control level stations on path h and the importance of each control level. In formula (4), MS represents the co-control station, MN represents the control master station, and n h,MS Indicates the number of MS type sites in the hth path, n h,MN represents the number of MN type sites in the hth path, and I MS ≥I MN .

[0069] Step 2.6: Calculate the failure probability UR of the zth control substation using equation (5) z , z=1,…,N:

[0070]

[0071] Step 2.7: Calculate the control capability ca of the zth control substation using equation (6): z , and then use formula (7) to get the control capability CA of the frequency stability control system:

[0072] ca z =S z (1-UR z ) (6)

[0073]

[0074] In formula (6), S z It represents the controllable capacity of the control substation in the zth frequency stability control system.

[0075] Step 3: Considering only path failures, select the site with the highest path unavailability rate and select the capacity lower limit S min , define and calculate the control capability threshold CA min ;

[0076] Step 3.1: Calculate the control capability of N control substations as ca, compare the control capability index of each control substation, and define ca min is the control capability threshold of the control substation, as shown in formula (9):

[0077]

[0078] Step 3.2: Set the redundancy coefficient b and use formula (9) to calculate the control capability threshold CA of the frequency stability control system min :

[0079] CA min =b×N×ca min (9)

[0080] Step 4: If the control capability CA of the frequency stability control system is lower than the control capability threshold CA min , then while maintaining the capacity of the control substation, establish horizontal connections between the control substation and other sites at the same level to form a flat structure between substations;

[0081] If the control capability CA is higher than the control capability threshold CA min , then select individual control substations to establish horizontal connections with other sites at the same level, forming a corresponding flat structure between substations, and compare the construction costs and control capabilities of different flat structures between substations to select the optimal substation solution;

[0082] In this embodiment, the construction cost and control capability impact are measured using the flattening transformation index shown in formula (10), and the optimal substation solution is selected using formula (11):

[0083]

[0084] In formula (10), C represents the investment cost of the flat design of the frequency stability control system; f represents the cost-control capability balance index of the frequency stability control system.

[0085]

[0086] In formula (11), f j represents the cost-control capability balance index value of the frequency stability control system under the j-th scheme, and Y represents the total number of schemes.

[0087] Step 5: Assume that the number of control master stations is M, establish horizontal connections between the control master stations, form a flat structure between the master stations, and compare the control capability impact under the flat structure between different master stations to select the optimal master station solution.

Claims

1. A local flattening design method for a frequency stability control system, characterized in that: The steps include: Step 1: Establish a frequency stability control system model based on the station as the basic unit, including: cooperative control station, control master station, control substation and execution station; Step 2: Calculate the control capability CA of the frequency stability control system based on the controllable capacity of the control substation and the path failure rate; Step 2.1, let the number of control substations of the frequency stability control system be N; Select the zth control substation, find all the paths from the cooperative control station to the zth control substation, and get the total number of paths as n; Step 2.2: Use formula (1) to get the communication channel failure rate of the frequency stability control system: : (1) In formula (1), λ0 represents the failure rate of the communication channel per unit length, and L represents the length of the communication channel; Step 2.3: Consider the geographical location of the communication channel and define the correction coefficient as a; then use formula (2) to obtain the corrected failure rate of the kth communication channel: : (2) In formula (2), represents the length of the kth communication channel; Step 2.4: Use equation (3) to get the failure probability λ of the hth path of the zth control substation: z,h : (3) In formula (3), K h represents the total number of communication channels passed under the h-th path; Step 2.5: Use formula (4) to define the importance coefficient α of the hth path h : (4) In formula (4), MS indicates that the station type is a cooperative control station, MN indicates that the station type is a control master station, and n h,MS Indicates the number of MS type sites in the hth path, n h,MN represents the number of MN type sites in the hth path, I MS is the importance of the co-control master station, I MN To control the importance of the master station, and I MS ≥I MN ; Step 2.6: Calculate the failure probability UR of the zth control substation using equation (5) z , z=1,…,N: (5) Step 2.7: Calculate the control capability ca of the zth control substation using equation (6): z , and then use formula (7) to get the control capability CA of the frequency stability control system: (6) (7) In formula (6), S z represents the controllable capacity of the zth control substation; Step 3: Select the control substation with the highest path failure rate and the capacity lower limit, and calculate the control capacity threshold CA min ; Step 3.1: Use formula (8) to define the control capability threshold ca of the control substation min : (8) Step 3.2: Set the redundancy coefficient to b and use formula (9) to calculate the control capability threshold CA of the frequency stability control system: min : (9) Step 4: If the control capability CA of the frequency stability control system is lower than the control capability threshold CA min , then while maintaining the capacity of the control substation, establish horizontal connections between the control substation and other sites at the same level to form a flat structure between substations; If the control capability CA is higher than the control capability threshold CA min , then select individual control substations to establish horizontal connections with other sites at the same level, forming a corresponding flat structure between substations, and compare the construction costs and control capabilities of different flat structures between substations to select the optimal substation solution; Step 5: Assume that the number of control master stations is M, establish horizontal connections between the control master stations, form a flat structure between the master stations, and compare the control capability impact under the flat structure between different master stations to select the optimal master station solution.

2. The local flattening design method for a frequency stability control system according to claim 1, characterized in that: The construction cost and control capability impact in step 4 are measured using the flattening transformation index shown in formula (10), and the optimal substation solution is selected using formula (11): (10) In formula (10), C represents the investment cost of the local flattening design of the frequency stability control system; f represents the cost-control capability balance index of the frequency stability control system; (11) In formula (11), f j represents the cost-control capability balance index value of the frequency stability control system under the j-th scheme, and Y represents the total number of schemes.

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