A method for determining the operating tap position of a main transformer in a power plant

Abstract

This invention discloses a method for determining the operating tap position of a substation main transformer. Compared with existing methods for determining the operating tap position of a main transformer, this method is simpler in principle, easier to understand, and has a simpler operation process. It can provide a basis for tap position selection, significantly improve work efficiency, ensure the rational distribution of reactive power in the power grid, and improve voltage quality. This invention can not only optimize the reactive power distribution of different voltage levels in the power grid and improve the voltage regulation capability of the power grid, but is also an important means to achieve high-quality operation of the power grid.

Description

Technical Field

[0001] This invention relates to the field of power system equipment technology, specifically to a method for determining the operating tap position of a main transformer in a power plant. Background Technology

[0002] A power system is a system for the production and consumption of electrical energy, consisting of power plants, transmission and transformation lines, power distribution stations, and electricity consumption. Its function is to convert primary energy from nature into electrical energy through power generation devices, and then supply the electrical energy to various users through transmission, transformation, and distribution.

[0003] In power systems, any new equipment commissioning or capacity expansion project involving main transformers requires determining and selecting the operating tap position of the main transformer taps. Currently, the operating tap positions of main transformer taps in power plants are determined by the plant's dispatching and operation technicians, without a unified calculation method. Due to varying personnel qualifications and different calculation tools and software, it is difficult to guarantee the optimal tap position and minimize calculation errors. Furthermore, the operation process is often cumbersome and inefficient, requiring improvement. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the operating position of the tap changer of a power plant main transformer, so as to solve the problems of cumbersome operation and large error in setting the transformer operating position as mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for determining the operating tap position of a main transformer in a power plant, comprising the following steps:

[0006] S1: Select the initial tap position;

[0007] S2: Determine the high-voltage and low-voltage verification methods;

[0008] S3: Verify the initial gear, +1 gear, and -1 gear;

[0009] S4: Calculate the voltage deviation index under different levels;

[0010] S5: Compare voltage offset indicators to determine the optimal gear;

[0011] S6: If the better gear is the initial gear, then the initial gear is the optimal gear, and the optimal gear is output as the running gear, and the process ends; if the better gear is not the initial gear, then the better gear is reset as the initial gear, and the process returns to S3.

[0012] Preferably, in step S1, the initial tap position is selected, that is, the substation transformer for which the tap position needs to be selected is determined, and the substation A of the same type that is closest to the electrical distance of the substation is selected. The tap position of the main transformer of substation A is recorded as the initial position.

[0013] Preferably, the high-voltage and low-voltage verification methods determined in S2 are used to determine the possible high-voltage and low-voltage operating modes of the power grid under study.

[0014] Preferably, the initial gear in S3 is the gear determined in step 1, and the +1 gear and -1 gear are the gear after and the gear before the initial gear.

[0015] Preferably, in step S3, the verification of the initial gear position, +1 gear position, and -1 gear position involves applying the initial gear position, +1 gear position, and -1 gear position to the high-voltage operation mode and low-voltage operation mode determined in step S2, respectively, performing power flow calculations, and outputting the voltage U of each power station in the power grid. ig and U id U ig For the voltage of plant i under high-voltage operation mode, U id This refers to the voltage at plant i under low-voltage operation.

[0016] Preferably, the different gears in S4 are the initial gear, +1 gear, and -1 gear, and the voltage offset index δ in S4 refers to... U ig The voltage of the power plant under high-voltage operation mode; U id This refers to the voltage of the power plant under low-voltage operation mode; U iset For the target values ​​of the bus voltage at substation i, the target value for the 220kV bus voltage can be set to 230kV, and the target value for the 500kV bus voltage can be set to 530kV. iset The optimal bus voltage value can be set according to the actual operation of the regional power grid; the voltage deviation index δ calculated in S4 for different taps refers to calculating the voltage deviation indices δ0 and δ1 for the initial tap, +1 tap, and -1 tap respectively. +1 δ -1 Where δ0 is the voltage offset index at the initial gear position; δ +1 This refers to the voltage offset indicator at the +1 level; δ -1 This is the voltage offset indicator at the -1 level.

[0017] Preferably, in step S5, comparing the voltage offset index δ to determine the optimal gear level refers to comparing the voltage offset indices δ0 and δ1 under the initial gear level, +1 gear level, and -1 gear level. +1 δ -1 The option with the smallest voltage deviation index is the optimal option among the three methods.

[0018] Preferably, in step S6, if the optimal gear is the initial gear, then the initial gear is the optimal gear, and the optimal gear is output as the operating gear.

[0019] Preferably, in step S6, if the better gear is not the initial gear, then the better gear is reset as the initial gear.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The method for determining the operating position of the tap changer of the main transformer in the power plant is simpler in principle, easier to understand, and easier to operate than the existing method for determining the operating position of the tap changer of the main transformer in the power plant. It can provide a basis for tap changer selection, greatly improve work efficiency, ensure the reasonable distribution of reactive power in the power grid, and improve voltage quality. The present invention can not only optimize the reactive power distribution of different voltage levels in the power grid and improve the voltage regulation capability of the power grid, but also is an important means to achieve high-quality operation of the power grid. Attached Figure Description

[0021] Figure 1 This is a flowchart of a method for determining the operating position of a main transformer tap changer in a power plant according to the present invention.

[0022] Figure 2 This invention provides a method for determining the operating tap position of a main transformer in a power plant, as illustrated in the power grid wiring diagram.

[0023] Figure 3 This is a data diagram of Embodiment 1 of the method for determining the operating position of the tap changer of a power plant main transformer according to the present invention;

[0024] Figure 4 This is a data diagram of Embodiment 1 of the method for determining the operating position of the tap changer of a power plant main transformer according to the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figure 1-4 This invention provides a technical solution: a method for determining the operating tap position of a main transformer in a power plant, comprising the following steps:

[0027] S1: Select the initial tap position; In S1, selecting the initial tap position means determining the substation transformer for which the tap position needs to be selected. Select substation A, which is the closest similar substation in terms of electrical distance to this substation, and record the tap position of the main transformer of substation A as the initial position. S2: Determine the high-voltage and low-voltage verification methods; In S2, determining the high-voltage and low-voltage verification methods is to determine the possible high-voltage and low-voltage operating modes of the power grid under study. High-voltage operating mode refers to: minimum load, wind power zero output, and thermal power output at low load. Low-voltage operating mode refers to: maximum load, wind power full output, and thermal power output at high load. Reactive power compensation is based on actual operation; this method is used to verify the low voltage condition of the power grid. Reactive power compensation is based on actual operation; this method is used to verify the high voltage condition of the power grid. S3: Verify the initial tap, +1 tap, and -1 tap. The initial tap in S3 is the tap determined in step 1, and the +1 and -1 taps are the taps after and before the initial tap. For example, if the initial tap is 3, then the +1 tap is 4, and the -1 tap is 2. Verifying the initial tap, +1 tap, and -1 tap in S3 involves applying the initial tap, +1 tap, and -1 tap to the high voltage operation mode and low voltage operation mode determined in S2, respectively, to perform power flow calculations and output the voltage U of each power station in the power grid. ig and U id U ig For the voltage of plant i under high-voltage operation mode, U id S4: Calculate the voltage deviation index under low voltage operation mode at plant i; The different levels in S4 are the initial level, +1 level, and -1 level; The voltage deviation index δ in S4 refers to... U ig The voltage of the power plant under high-voltage operation mode; U id This refers to the voltage of the power plant under low-voltage operation mode; U iset For the target values ​​of the bus voltage at substation i, the target value for the 220kV bus voltage can be set to 230kV, and the target value for the 500kV bus voltage can be set to 530kV. iset The optimal bus voltage value can be set according to the actual operation of the regional power grid; the voltage deviation index δ calculated in S4 for different taps refers to calculating the voltage deviation indices δ0 and δ1 for the initial tap, +1 tap, and -1 tap respectively. +1 δ -1 Where δ0 is the voltage offset index at the initial gear position; δ +1 This refers to the voltage offset indicator at the +1 level; δ -1S5: Compare voltage offset indices to determine the optimal gear; S5 comparing voltage offset indices δ to determine the optimal gear refers to comparing the voltage offset indices δ0 and δ1 at the initial gear, +1 gear, and -1 gear. +1 δ -1 S5: Select the gear with the smallest voltage deviation index as the optimal gear among the three methods; S6: If the optimal gear is the initial gear, then the initial gear is the optimal gear, and the optimal gear is output as the operating gear, and the process ends; if the optimal gear is not the initial gear, then the optimal gear is reset as the initial gear, and the process returns to S3; if the optimal gear is the initial gear in S6, then the initial gear is the optimal gear, and the optimal gear is output as the operating gear; the process ends when: if the optimal gear obtained in S5 is exactly the initial gear determined in S1, it means that the optimal gear is the middle gear among the initial gear, +1 gear, and -1 gear, then the initial gear is the optimal gear, and the optimal gear is output as the operating gear, and the process ends; if the optimal gear is not the initial gear in S6, then the optimal gear is reset as the initial gear. Returning to S3 means that if the optimal tap position obtained in S5 is not the initial tap position determined in S1, it means that the optimal tap position is not the middle tap position among the initial tap position, +1 tap position, and -1 tap position. It is necessary to reselect the initial tap position, set the optimal tap position as the new initial tap position, and then return to S3. Compared with the existing main transformer tap position selection method, this method for determining the tap position of the main transformer in the power plant is simple in principle, easy to understand, and has a simple operation process. It can provide a basis for tap position selection, greatly improve work efficiency, ensure the reasonable distribution of reactive power in the power grid, and improve voltage quality. This invention can not only optimize the reactive power distribution of different voltage levels in the power grid and improve the voltage regulation capability of the power grid, but also is an important means to achieve high-quality operation of the power grid.

[0028] Working Principle: Example 1 of the method for determining the tap position of the main transformer in this power plant: First, the power grid under study is determined to be the northern power grid of a certain region in Inner Mongolia. The wiring diagram of the northern power grid of a certain region in Inner Mongolia is as follows. Figure 2As shown (only the northern power grid is shown for ease of explanation), the 500kV aluminum substation and its 220kV supporting projects are new power grid projects, requiring the determination of the tap position of the aluminum substation's main transformer. Since the closest equivalent voltage substation to the aluminum substation is the 500kV A substation, and the current tap position of the 500kV A substation's main transformer is set to 3, the initial tap position of the aluminum substation is determined to be 3. The high-voltage and low-voltage verification methods need to be determined. The high-voltage operation mode refers to: minimum load, zero wind power output, thermal power output at low load, and reactive power compensation based on actual operation. This mode is used to verify the high-voltage condition of the power grid. The low-voltage operation mode refers to: maximum load, full wind power output, thermal power output at high load, and reactive power compensation based on actual operation. This mode is used to verify the low-voltage condition of the power grid. The recent maximum and minimum load conditions of each 220kV substation in this northern power grid are shown in the appendix to the instruction manual. Figure 3 As shown; currently, the reactive power compensation devices of all 220kV substations are not in operation; the Jin I and Jin II thermal power plants are not operating during either high or low load periods; the Jing and Huo thermal power plants are operating at 330MW under high load and 210MW under low load respectively; the Kengkou thermal power plant is operating at 600MW under high load and 400MW under low load; see attached manual for reference. Figure 3 The table below shows the recent grid load of 220kV substations in northern Tongliao (unit: MW + jMvar). The initial tap position is 3, so -1 is tap position 2 and +1 is tap position 3. The tap positions of the aluminum transformers, the load sizes, the output of thermal power plants, the output of wind farms, and the reactive power compensation are entered into PSASP (Power System Analysis Program) or other power system simulation software to perform power flow calculations for both high-voltage and low-voltage operating modes. The voltage values ​​U of each substation under different tap positions are obtained for both modes. gi and U id , i≤n, where n is the total number of plants; the following is a reference to the instruction manual appendix. Figure 4 Voltage values ​​for each substation under two different tap positions; unit: kV; the target voltage for the 220kV bus is 230kV, i.e., U iset =230. According to the voltage offset index formula Calculations show that the initial voltage offset index δ0 = 24.5, and the +1 voltage offset index δ +1 =31, -1 level voltage offset index δ -1 =35; Comparison shows that δ0 is the smallest, so the better gear is the initial gear (gear 3); Since the better gear is the initial gear (gear 3), the initial gear (gear 3) is the optimal gear, and gear 3 is output as the operating gear, and the process ends; In summary, the operating gear of the tap changer of the aluminum transformer is determined to be gear 3, which is Example 1 of the method for determining the operating gear of the tap changer of the main transformer of this plant.

[0029] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the operating tap position of a main transformer in a power plant, comprising the following steps: S1: Select the initial tap position; S2: Determine the high-voltage and low-voltage verification methods; S3: Verify the initial gear, +1 gear, and -1 gear; S4: Calculate the voltage deviation index under different levels; S5: Compare voltage offset indicators to determine the optimal gear; S6: If the better gear is the initial gear, then the initial gear is the optimal gear, and the optimal gear is output as the running gear, and the process ends; if the better gear is not the initial gear, then the better gear is reset as the initial gear, and the process returns to S3. In S1, the initial tap position is selected, that is, the substation transformer for which the tap position needs to be selected is determined, and the substation A of the same type that is closest to the electrical distance of the substation is selected. The tap position of the main transformer of substation A is recorded as the initial position. The high-voltage and low-voltage verification methods are determined in S2 to determine the high-voltage and low-voltage operating modes of the power grid under study. The initial gear in S3 is the gear determined in step 1, and the +1 gear and -1 gear are the gear after and the gear before the initial gear. In step S3, the initial voltage level, +1 voltage level, and -1 voltage level are checked by applying these levels to the high-voltage and low-voltage operating modes determined in step S2, respectively, to perform power flow calculations and output the voltage U of each power station in the grid. ig and U id U ig For the voltage of plant i under high-voltage operation mode, U id The voltage of the i-factory station under low-voltage operation mode; The different gears in S4 are the initial gear, +1 gear, and -1 gear; the voltage offset index δ in S4 refers to... U ig The voltage of plant i under high-voltage operation mode; U id The voltage of plant i under low-voltage operation mode; U iset For the target voltage value of the busbar of substation i, the voltage deviation index δ calculated in S4 under different taps refers to calculating the voltage deviation index δ0, δ1, and δ2 under the initial tap, +1 tap, and -1 tap respectively. +1 δ -1 Where δ0 is the voltage offset index at the initial gear position; δ +1 This refers to the voltage offset indicator at the +1 level; δ -1 This refers to the voltage offset indicator at the -1 level. In step S5, comparing the voltage offset index δ to determine the optimal gear level refers to comparing the voltage offset indices δ0 and δ1 at the initial gear level, +1 gear level, and -1 gear level. +1 δ -1 Choose the setting with the smallest voltage deviation as the best setting among the three methods; If the optimal gear is the initial gear in step S6, then the initial gear is the optimal gear, and the optimal gear is output as the operating gear; if the optimal gear is not the initial gear in step S6, then the optimal gear is reset as the initial gear.

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