Offshore wind power system reliability evaluation method and device considering feeder load rate

Abstract

The application relates to a kind of offshore wind power system reliability evaluation method and equipment considering feeder load rate, comprising the following steps: S1, obtaining offshore wind power system parameters;S2, according to the failure rate and repair time of equipment, the failure rate and average repair time of each wind farm are calculated;S3, according to the failure rate and average repair time of each wind farm, and the time and success rate of power supply line power supply, the failure rate and total repair time of offshore wind power system are calculated;S4, according to the load rate of power supply line, the transferable capacity of offshore wind power system is calculated, and then the lack of power supply capacity coverage of wind farm main transmission line is calculated;S5, according to the lack of power supply capacity coverage of wind farm main transmission line, the failure rate and total repair time of offshore wind power system calculated in step S3 are corrected, and the reliability of offshore wind power system is evaluated according to the result after correction.Compared with the prior art, the comprehensiveness and accuracy of offshore wind power system reliability evaluation can be further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power distribution network safety, and in particular relates to a reliability assessment method and device for an offshore wind power system taking feeder load rate into consideration. Background Art

[0002] Wind power is a clean, renewable energy source. Offshore wind power systems offer advantages such as flexible installation scale and relatively simple operation and maintenance. Reliability calculation is a crucial process for assessing the stability and reliability of power systems, focusing primarily on power stations, generators, transmission systems, and distribution systems. Offshore wind power systems incorporate numerous devices and components, such as wind turbines, generators, and converters. Factors such as the probability of failure, repair time, and cost of these devices affect the reliability of the wind power system. Furthermore, the complex interrelationships and interactions between these devices complicate reliability calculations.

[0003] Traditional reliability calculations mainly consider the reliability indicators of devices in the power supply path. Chinese invention patent CN108564252B proposes a method for calculating the power supply reliability of a distribution network that takes into account multifunctional distribution automation. The parameters used for calculating the reliability of load points under failures of main feeder elements and branch elements are calculated according to the determined automation function mode. The power supply reliability of the line under four different automation function modes, namely non-automation mode, automatic positioning mode, automatic isolation mode, and automatic transfer mode, is quantitatively analyzed, and a reliability indicator that takes into account power outages due to faults is given. However, during the actual power transfer operation, as the line load rate increases, the available capacity of the power transfer line may not be able to meet the power supply shortage. As a result, even if the power transfer is successful, some loads may still be unable to use electricity, affecting the safety of the power system. Therefore, it is necessary to design a reliability assessment method for offshore wind power systems to further improve the comprehensiveness and accuracy of offshore wind power system reliability assessments. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method and device for offshore wind power system reliability assessment taking feeder load rate into consideration, so as to further improve the comprehensiveness and accuracy of offshore wind power system reliability assessment.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The present invention provides an offshore wind power system reliability assessment method considering feeder load rate, which is applicable to an offshore wind power system including a substation and multiple wind farms connected to the substation in a ring topology, and includes the following steps:

[0007] S1. Obtain offshore wind power system parameters, including equipment failure rate and repair time, as well as power supply line transfer time and transfer success rate;

[0008] S2. Calculate the failure rate and average repair time of each wind farm based on the equipment failure rate and repair time;

[0009] S3. Calculate the failure rate and total repair time of the offshore wind power system based on the failure rate and average repair time of each wind farm, as well as the transfer time and transfer success rate of the power transfer line;

[0010] S4. Calculate the transferable capacity of the offshore wind power system based on the load rate of the transfer power supply line, and calculate the power shortage coverage rate of the main transmission line of the wind farm based on the transferable capacity of the offshore wind power system;

[0011] S5. According to the power shortage coverage rate of the main transmission line of the wind farm, the failure rate and total repair time of the offshore wind power system calculated in step S3 are corrected, and the reliability of the offshore wind power system is evaluated based on the corrected results.

[0012] Furthermore, in step S2, the failure rate and mean repair time of each wind farm are calculated as follows:

[0013] λ loss (n) = λ main +λ T +l(n)λ l +n b (n)λ b

[0014]

[0015] Among them, λ loss (n) is the failure rate of the n-th wind farm installation point relative to the main grid power supply, t loss (n) is the average repair time of the main grid power failure corresponding to the n-th wind farm installation point, λ main is the main grid power failure rate corresponding to the nth wind farm, λ T is the transformer failure rate at the nth wind farm installation point, l is the cable length, n b (n) is the sum of the number of circuit breakers and switches installed at the nth wind farm, λ b (n) is the failure rate of circuit breakers and switches at the nth wind farm installation point, t main is the average repair time of the main grid power failure corresponding to the nth wind farm installation point, t T The transformer repair time at the nth wind farm installation point, t l is the cable repair time at the nth wind farm installation point, t b Repair time for circuit breakers and switches at the nth wind farm installation point.

[0016] Furthermore, in step S3, the failure rate and total repair time of the offshore wind power system are calculated as follows:

[0017] λ loss ′=λ loss,AI

[0018] t loss ′=t loss,AI (1-p A )+p A t zg

[0019] Among them, λ loss ′ is the failure rate of the main transmission line of the offshore wind power system, t loss ′ is the total repair time of the main transmission line of the offshore wind power system, λ loss,AI is the expected failure rate of the main transmission line of the wind farm, t loss,AI is the expected average repair time of the main transmission line of the wind farm, p A is the power transfer success rate of the main transmission line of the wind power system, t zg The transfer line is the transfer time of the main transmission line of the wind power system.

[0020] Furthermore, the expected failure rate of the main transmission line of the wind farm is loss,AI and the expected mean repair time t loss,AI The calculation methods are as follows:

[0021]

[0022]

[0023] Among them, N load is the number of wind farm installation points on the line, λ loss (n) is the failure rate of the n-th wind farm installation point relative to the main grid power supply, t loss (n) is the average repair time of the main grid power failure corresponding to the n-th wind farm installation point.

[0024] Furthermore, in step S4, the transferable capacity of the offshore wind power system is calculated as follows:

[0025]

[0026] Among them, S max is the transferable capacity of the offshore wind power system, m is the number of transfer power lines, S i is the transferable power supply of the i-th transfer power line, p is the average transfer rate of the system, and p A The transfer line is the transfer success rate of the main transmission line of the wind power system.

[0027] Furthermore, the power transfer capacity S of the i-th power transfer line is i The calculation method is:

[0028] S i =S i,s (1-μ i )

[0029] Among them, S i,s is the line capacity of the power supply line i, μ i is the average load rate of the power supply line i.

[0030] Furthermore, in step S4, the power shortage coverage rate of the main transmission line of the wind farm is calculated as follows:

[0031]

[0032] Among them, η is the coverage rate of power shortage of the main transmission line of the wind farm, S max is the transferable capacity of the offshore wind power system, S q It is the power shortage of the main transmission line of the wind farm.

[0033] Furthermore, in step S5, the failure rate of the offshore wind power system is corrected as follows based on the power shortage coverage rate of the main transmission line of the wind farm:

[0034] λ loss ”=ηλ loss '+(1-η)λ loss,AI

[0035] Among them, λ loss ′″ is the corrected failure rate of the main transmission line of the offshore wind power system, η is the power supply coverage rate of the main transmission line of the wind farm, λ loss ′ is the failure rate of the main transmission line of the offshore wind power system before correction, λ loss,AI is the expected failure rate of the main transmission line of the wind farm.

[0036] Furthermore, in step S5, the total repair time of the offshore wind power system is corrected as follows according to the power shortage coverage rate of the main transmission line of the wind farm:

[0037] t loss ”=ηt loss '+(1-η)t loss,AI

[0038] Among them, t loss ″ is the total repair time of the main transmission line of the offshore wind power system after correction, η is the power supply coverage rate of the main transmission line of the wind farm, t loss ′ is the total repair time of the main transmission line of the offshore wind power system before correction, t loss,AIis the expected average repair time of the main transmission line of the wind farm.

[0039] The present invention also provides an electronic device, comprising a memory, a processor, and a program stored in the memory, wherein the processor implements the above method when executing the program.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention proposes a reliability assessment method for an offshore wind power system with a ring topology structure. The offshore wind power system's transferable capacity is calculated based on the load rate of the transfer power supply line, and then the power shortage coverage rate of the wind farm's main transmission line is calculated. The calculated failure rate and total repair time of the offshore wind power system are corrected accordingly, and the reliability of the offshore wind power system is evaluated based on the corrected results. The present invention performs reliability analysis while considering the load rate of the transfer power supply line, which is more in line with actual production and operation conditions, further improves the comprehensiveness and accuracy of the offshore wind power system reliability assessment, helps to better optimize the allocation of power resources, and improves the reliability of the offshore wind power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flow chart of the method of the present invention;

[0043] Figure 2 This is a schematic diagram of the ring topology of offshore wind power grid connection via flexible DC transmission.

[0044] Wherein, WF and VSC represent wind farm and voltage source converter respectively, and the subscript numbers are numbers;

[0045] Figure 3 This is a schematic diagram of the ring-shaped collection topology of an offshore wind farm.

[0046] Among them, a, b, c, l, m, h, i, j, and k are transmission lines and corresponding equipment. DETAILED DESCRIPTION

[0047] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0048] Example 1

[0049] This embodiment provides a reliability assessment method for an offshore wind power system taking feeder load factor into consideration, which is applicable to an offshore wind power system comprising a substation and multiple wind farms connected to the substation in a ring topology. Figure 2As shown in the figure, WF and VSC represent wind farm and voltage source converter, respectively. A ring topology connects all offshore wind farms and onshore substations in a ring, allowing a portion of the line to transmit all system power when the ring is open. A ring topology for flexible HVDC transmission can install a DC circuit breaker and a disconnector at each end of each line. In the event of a line fault, the DC circuit breaker on that line and the nearest DC circuit breaker on the adjacent line are disconnected, and the disconnector is opened. Once the fault is isolated, the DC circuit breakers on the remaining disconnected lines are reclosed. This fault isolation method temporarily shuts down wind farms connected to adjacent lines. Another approach involves installing a circuit breaker at each end of the line. In the event of a line fault, the DC circuit breakers at both ends are opened, placing the system in an open-loop state. The advantages of using a ring topology for grid connection are: when a fault occurs somewhere on the ring, the system can be opened by operating the circuit breaker, so that the current does not pass through the fault point but is diverted and transmitted through other paths. This is more flexible and reliable than the point-to-point topology. Figure 3 As shown in the figure, Longxing Station serves as the starting station for line transmission; the collection station is connected to Longxing Station and is connected to all wind farms through a ring topology; the switch of line equipment a is in the open state under normal system operation and is closed in the event of a fault; a, b, c, l, m, h, i, j, and k are all transmission lines and corresponding equipment.

[0050] like Figure 1 As shown, the offshore wind power system reliability assessment method considering feeder load rate provided in this embodiment includes the following steps:

[0051] S1. Obtain offshore wind power system parameters, including the failure rate and repair time of equipment such as lines, switches, and transformers, as well as the transfer time and transfer success rate of power supply lines.

[0052] S2. Calculate the failure rate and average repair time of each wind farm based on the equipment failure rate and repair time.

[0053] The failure rate and mean repair time of each wind farm are calculated as follows:

[0054] λ loss (n) = λ main +λ T +l(n)λ l +n b (n)λ b

[0055]

[0056] Among them, λloss (n) is the failure rate of the n-th wind farm installation point relative to the main grid power supply, t loss (n) is the average repair time of the main grid power failure corresponding to the n-th wind farm installation point, λ main is the main grid power failure rate corresponding to the nth wind farm, λ T is the transformer failure rate at the nth wind farm installation point, l is the cable length, n b (n) is the sum of the number of circuit breakers and switches installed at the nth wind farm, λ b (n) is the failure rate of circuit breakers and switches at the nth wind farm installation point, t main is the average repair time of the main grid power failure corresponding to the nth wind farm installation point, t T The transformer repair time at the nth wind farm installation point, t l is the cable repair time at the nth wind farm installation point, t b Repair time for circuit breakers and switches at the nth wind farm installation point.

[0057] S3. Calculate the failure rate and total repair time of the offshore wind power system based on the failure rate and average repair time of each wind farm, as well as the transfer time and transfer success rate of the power transfer line.

[0058] Expected value of failure rate of main transmission line of wind farm λ loss,AI and the expected mean repair time t loss,AI The calculation methods are as follows:

[0059]

[0060]

[0061] Among them, N load is the number of wind farm installation points on the line, λ loss (n) is the failure rate of the n-th wind farm installation point relative to the main grid power supply, t loss (n) is the average repair time of the main grid power failure corresponding to the n-th wind farm installation point.

[0062] Considering that all fault loads are successfully transferred, since the transfer cannot increase the failure rate of the line itself, it only reduces the repair time of the feeder. Figure 3 For example, feeder a in the diagram is disconnected during normal system operation, and the planned wind farm transmits power through feeder b. When a fault occurs somewhere between the transformer of planned wind farm 10 and planned wind farm 9, feeder a switches to a closed state and supplies power to planned wind farm 9, thereby shortening the outage time and improving system reliability. At this point, the failure rate and total repair time of the offshore wind power system are:

[0063] λloss ′=λ loss,AI

[0064] t loss ′=t loss,AI (1-p A )+p A t zg

[0065] Among them, λ loss ′ is the failure rate of the main transmission line of the offshore wind power system, t loss ′ is the total repair time of the main transmission line of the offshore wind power system, λ loss,AI is the expected value of the failure rate of the main transmission line of the wind farm, t loss,AI is the expected average repair time of the main transmission line of the wind farm, p A is the power transfer success rate of the main transmission line of the wind power system, t zg The transfer line is the transfer time of the main transmission line of the wind power system.

[0066] S4. Calculate the transferable capacity of the offshore wind power system based on the load rate of the transfer power supply line, and calculate the power shortage coverage rate of the main transmission line of the wind farm based on the transferable capacity of the offshore wind power system.

[0067] In actual production operation, as the line load rate increases, the available capacity of the power supply line may not be able to meet the power shortage, resulting in a situation where some loads cannot use electricity even if the power supply is successfully transferred. A It is related to the average transfer rate p of the system, but it should also consider whether there are faults in the transfer lines. In addition to considering only the case where all lines transfer successfully, it should be further considered that there may be a case where a line fails to transfer. In this case, the transferable power supply of the system is equal to the transferable power supply of the other m-1 tie lines in normal operation. Since the probability of two or more tie lines failing at the same time is low, it can be ignored. The power that a tie line can provide is the sum of the transferable power of all tie lines. Then the total transferable power supply of the system S max The expectation is:

[0068]

[0069] Among them, m is the number of power supply lines, S i is the transferable power supply of the i-th transfer power line, p is the average transfer rate of the system, and p A The transfer line is the transfer success rate of the main transmission line of the wind power system.

[0070] The transferable power supply S of the i-th transfer power line i The calculation method is:

[0071] S i =S i,s(1-μ i )

[0072] wherein S i,s is the line capacity of the transfer supply line i, μ i is the average load rate of the transfer supply line i.

[0073] The calculation method of the lack supply capacity coverage of the wind farm main transmission line is as follows:

[0074]

[0075] wherein η is the lack supply capacity coverage of the wind farm main transmission line, S max is the transferable capacity of the offshore wind power system, S q is the lack supply capacity of the wind farm main transmission line.

[0076] S5, according to the lack supply capacity coverage of the wind farm main transmission line, the failure rate and the total repair time of the offshore wind power system calculated in step S3 are corrected, and the offshore wind power system reliability is evaluated according to the corrected results.

[0077] According to the lack supply capacity coverage η of the wind farm main transmission line, the failure rate and the total repair time of the offshore wind power system are respectively corrected as follows:

[0078] λ loss " = η λ loss + (1-η) λ loss,AI

[0079] t loss " = η t loss + (1-η) t loss,AI

[0080] wherein λ loss " is the corrected failure rate of the offshore wind power system main transmission line, t loss " is the corrected total repair time of the offshore wind power system main transmission line.

[0081] The above method can be extended from a certain site to the calculation of all points of the system, has the advantages of simplicity and practicality, can effectively take into account the load rate of the power supply line, and is more in line with the actual situation; based on the ring topology, when any device in the offshore wind power system fails, other devices can timely transfer power supply, further improving the reliability of the offshore wind power system.

[0082] Embodiment 2

[0083] This embodiment provides an electronic device comprising a memory and a processor, wherein the processor is configured to execute a program stored in the memory, wherein the program comprises a number of instructions and can execute all or part of the steps of the method described in Example 1. The memory comprises a computer-readable storage medium, which can specifically be a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, among other media capable of storing program code.

[0084] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A reliability assessment method for an offshore wind power system considering feeder load rate, applicable to an offshore wind power system comprising a substation and a plurality of wind farms connected to the substation in a ring topology, characterized in that: The following steps are involved: S1. Obtain offshore wind power system parameters, including equipment failure rate and repair time, as well as power supply line transfer time and transfer success rate; S2. Calculate the failure rate and average repair time of each wind farm based on the equipment failure rate and repair time; S3. Calculate the failure rate and total repair time of the offshore wind power system based on the failure rate and average repair time of each wind farm, as well as the transfer time and transfer success rate of the power transfer line; S4. Calculate the transferable capacity of the offshore wind power system based on the load rate of the transfer power supply line, and calculate the power shortage coverage rate of the main transmission line of the wind farm based on the transferable capacity of the offshore wind power system; S5. According to the power shortage coverage rate of the main transmission line of the wind farm, the failure rate and total repair time of the offshore wind power system calculated in step S3 are corrected, and the reliability of the offshore wind power system is evaluated based on the corrected results; In step S4, the power shortage coverage rate of the main transmission line of the wind farm is calculated as follows: Among them, η is the coverage rate of power shortage of the main transmission line of the wind farm, S max is the transferable capacity of the offshore wind power system, S q It is the power shortage of the main transmission line of the wind farm.

2. The offshore wind power system reliability assessment method considering feeder load rate according to claim 1, characterized in that: In step S2, the failure rate and mean repair time of each wind farm are calculated as follows: l loss (n)=λ main +λ T +l(n)λ l +n b (n)λ b Among them, λ loss (n) is the failure rate of the n-th wind farm installation point relative to the main grid power supply, t loss (n) is the average repair time of the main grid power failure corresponding to the n-th wind farm installation point, λ main is the main grid power failure rate corresponding to the nth wind farm, λ T is the transformer failure rate at the nth wind farm installation point, l is the cable length, n b (n) is the sum of the number of circuit breakers and switches installed at the nth wind farm, λ b (n) is the failure rate of circuit breakers and switches at the nth wind farm installation point, t main is the average repair time of the main grid power failure corresponding to the nth wind farm installation point, t T The transformer repair time at the nth wind farm installation point, t l is the cable repair time at the nth wind farm installation point, t b Repair time for circuit breakers and switches at the nth wind farm installation point.

3. The offshore wind power system reliability assessment method considering feeder load rate according to claim 1, characterized in that: In step S3, the failure rate and total repair time of the offshore wind power system are calculated as follows: l loss ′ =λ loss,AI t loss ′ =t loss,AI (1-p A )+p A t zg Among them, λ loss ′ is the failure rate of the main transmission line of the offshore wind power system, t loss ′ is the total repair time of the main transmission line of the offshore wind power system, λ loss,AI is the expected value of the failure rate of the main transmission line of the wind farm, t loss,AI is the expected average repair time of the main transmission line of the wind farm, p A is the power transfer success rate of the main transmission line of the wind power system, t zg The transfer line is the transfer time of the main transmission line of the wind power system.

4. The offshore wind power system reliability assessment method considering feeder load rate according to claim 3 is characterized in that: Expected value of failure rate of main transmission line of wind farm λ loss,AI and the expected mean repair time t loss,AI The calculation methods are as follows: Among them, N load is the number of wind farm installation points on the line, λ loss (n) is the failure rate of the n-th wind farm installation point relative to the main grid power supply, t loss (n) is the average repair time of the main grid power failure corresponding to the n-th wind farm installation point.

5. The offshore wind power system reliability assessment method considering feeder load rate according to claim 1, characterized in that: In step S4, the transferable capacity of the offshore wind power system is calculated as follows: Among them, S max is the transferable capacity of the offshore wind power system, m is the number of transfer power lines, S i is the transferable power supply of the i-th transfer power line, p is the average transfer rate of the system, and p A The transfer line is the transfer success rate of the main transmission line of the wind power system.

6. The offshore wind power system reliability assessment method considering feeder load rate according to claim 5, characterized in that: The transferable power supply S of the i-th transfer power line i The calculation method is: S i =S i,s (1-m i ) Among them, S i,s is the line capacity of the power supply line i, μ i is the average load rate of the power supply line i.

7. The offshore wind power system reliability assessment method considering feeder load rate according to claim 1, characterized in that: In step S5, the failure rate of the offshore wind power system is corrected as follows based on the power shortage coverage rate of the main transmission line of the wind farm: l loss "=el" loss '+(1-n)λ loss,AI Among them, λ loss ″ is the corrected failure rate of the main transmission line of the offshore wind power system, η is the power supply coverage rate of the main transmission line of the wind farm, λ loss ′ is the failure rate of the main transmission line of the offshore wind power system before correction, λ loss,AI is the expected failure rate of the main transmission line of the wind farm.

8. The offshore wind power system reliability assessment method considering feeder load rate according to claim 1, characterized in that: In step S5, the total repair time of the offshore wind power system is corrected as follows according to the power shortage coverage rate of the main transmission line of the wind farm: t loss ”=ηt loss '+(1-η)t loss,AI Among them, t loss ″ is the total repair time of the main transmission line of the offshore wind power system after correction, η is the power supply coverage rate of the main transmission line of the wind farm, t loss ′ is the total repair time of the main transmission line of the offshore wind power system before correction, t loss,AI is the expected average repair time of the main transmission line of the wind farm.

9. An electronic device comprising a memory, a processor, and a program stored in the memory, wherein: When the processor executes the program, the method according to any one of claims 1 to 8 is implemented.

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