An automatic control method for on-load tap changers of parallel-operating main transformers in substations

Abstract

The present invention discloses an automatic control method for parallel main transformer on-load tap changers in substations, which mainly solves the gear adjustment problem when the types of parallel main transformer on-load tap changers are inconsistent. The method is based on the principle of consistent ratio of parallel main transformer tap changers, and presets the gear correspondence relationship S f ; Set the automatic voltage control period T c 0 , collecting busbar voltage data from the grid dispatch center's monitoring system. When the busbar voltage exceeds a limit, a control strategy is calculated to eliminate the overshoot. If tap adjustment is required and the main transformers are operating in parallel, both main transformers must be adjusted synchronously: if the types are consistent, the gears are simultaneously shifted up / down; if the types are inconsistent, adjustments are made according to a pre-set gear correspondence. If no correspondence exists, an alarm is triggered for manual intervention. This method eliminates the problem of excessive circulating reactive current in the main transformers caused by inconsistent tap ratios, ensuring grid voltage stability and the safety of the main transformer equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of voltage control, and in particular relates to an automatic control method for on-load voltage regulating tap changers of parallel-operated main transformers in a transformer substation. Background Art

[0002] Automatic Voltage Control (AVC) systems are a key means of ensuring safe (improving voltage stability margin), economical (reducing network losses), and high-quality (improving voltage compliance) operation of transmission networks. Built on the power grid's energy management system (EMS), the AVC system utilizes real-time transmission network operating data to scientifically determine optimal reactive power and voltage adjustment plans from a global perspective, automatically distributing them to power plants, substations, and lower-level grid dispatching organizations for implementation. Sun Hongbin, Zhang Boming, and Guo Qinglai describe the architecture of large-scale automatic voltage control in their paper "Design of a Global Voltage Optimization Control System Based on Soft Partitioning" (Automation of Electric Power Systems, Vol. 27, No. 8, 2003, pp. 16-20). The master station portion of the AVC system is implemented in software within the power system control center. Its voltage control strategies for the transmission network primarily fall into two categories: reactive power control strategies for power plant generators and reactive power control strategies for substations. The current primary reactive power control strategy for each generator in a power plant is as follows: The dispatch center's AVC master station system calculates reactive power regulation for each unit through reactive power optimization and transmits this information to the plant's AVC substation system via a data communication channel. Upon receiving the reactive power regulation, the AVC substation adjusts the reactive power output of each generator in a step-by-step manner based on the current operating status of each generator in the plant until the reactive power regulation value issued by the AVC master station is reached. Substation control involves switching commands for reactive power compensation equipment and adjusting the transformer's on-load tap changer. Reactive power devices primarily include capacitors and reactors. When capacitors are switched on or reactors are switched off, the bus voltage increases; when capacitors are switched off or reactors are switched on, the bus voltage decreases. Transformer on-load tap changers are typically installed on the high-voltage side of the transformer winding. Raising the tap position increases the medium- and low-voltage bus voltages, while lowering them decreases. The AVC master station issues instructions for switching on or off reactive equipment and instructions for raising or lowering taps. The automated monitoring system in the substation completes the switching on or off of reactive equipment or adjustment of taps in the station based on the instructions received.

[0003] Currently, with economic development, the design capacity of existing substation main transformers is unable to meet the growing electricity demand. This necessitates the addition of parallel main transformers to increase the substation's power transmission capacity and improve power supply reliability. However, if the capacity of the newly added main transformers is inconsistent with the original capacity, and when operating in parallel, the voltage difference between the high-voltage and low-voltage sides must be equal to prevent circulating currents within the two transformers. Excessive circulating currents in the transformers consume the transformer capacity, preventing full load operation and underutilizing the total capacity, reducing output power, increasing losses, and even damaging the transformer. Only by matching tap positions in real time according to the principle of consistent ratios can reactive circulating currents within the transformers be reduced, thereby increasing main transformer output power and capacity. However, the tap position mapping calculated according to the principle of consistent ratios for parallel main transformer on-load tap changes can lead to inconsistent tap types within the parallel main transformers. In such cases, the parallel main transformers may operate in mismatched gears or have one gear corresponding to two gears. Conventional automatic voltage control systems are unable to meet the control requirements for inconsistent on-load tap changer types within the parallel main transformers.

[0004] In summary, with the rapid construction of power grid scale and the widespread application of power grid automatic voltage control system, it is urgent to solve the problem of on-load tap changer adjustment when the on-load tap changer types of parallel main transformers in substations are inconsistent, so as to ensure the safety of power grid voltage. Summary of the Invention

[0005] The purpose of the present invention is to provide an automatic control method for on-load tap changers of parallel main transformers in a substation, mainly to solve the problem of gear adjustment when the on-load tap changers of parallel main transformers in the substation are of inconsistent types.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] An automatic control method for parallel operation main transformer on-load tap changers of a substation comprises the following steps:

[0008] S1, according to the principle of consistent transformation ratio of on-load tap changers of parallel main transformers in substation, set the corresponding relationship of tap position S f , and set the automatic voltage control period to T c 0 ;

[0009] S2, when the control cycle arrives, the automatic voltage control system reads the bus voltage information of all substations from the dispatch monitoring system of the power grid dispatch center. When the substation bus voltage exceeds the set voltage limit, the control strategy is calculated to eliminate the voltage limit;

[0010] S3, according to the operating status of the main transformer in the substation, select the corresponding method to adjust the main transformer tap to eliminate the voltage limit;

[0011] In step S4, if the main transformer of the substation fails to adjust the tap changer to eliminate the voltage over-limit, an alarm is issued to prompt manual processing; if the adjustment is successful, the process returns to step S3 to adjust the tap changer of the next substation, and the process continues until all tap changes are completed and then proceeds to step S5;

[0012] S5: When the next control cycle arrives, return to step S2 and start a new round of substation automatic voltage control.

[0013] Furthermore, in step S1, the tap position correspondence S f It is the set of gear correspondences of all parallel main transformers in substations with inconsistent on-load tap changer types.

[0014] Furthermore, in step S2, determining the voltage limit of the substation bus voltage includes:

[0015] A, if the voltage of busbar i in substation m is V i Satisfaction: V i >V i max , V i max is the set voltage upper limit of bus i, then the voltage of bus i is judged to be above the upper limit, and the substation m is judged. If Then add substation m to the set S a , if m∈S a , it means that substation m is already in the set S a In the above, there is no need to add repeatedly; the set S a Includes: Substation set where bus voltage exceeds set voltage upper limit or lower limit. When initialized, set set S a is an empty set;

[0016] B, if the voltage of busbar i in substation m is V i Satisfaction: V i <V i min , V i min is the set voltage lower limit of bus i, then it is determined that the voltage of bus i exceeds the lower limit, and the substation m is judged. If Then add substation m to the set S a , if m∈S a , it means that substation m is already in the set S a No need to add repeatedly.

[0017] Furthermore, in step S2, the specific steps of calculating the control strategy to eliminate voltage over-limit are:

[0018] S21, when the cycle T of the automatic voltage control system c 0 When the reactive power of the substation is unreasonable or the high-voltage side bus voltage exceeds the limit, the reactive power equipment is adjusted to eliminate the voltage exceeding the limit;

[0019] S22, if the substation reactive power is reasonable and the bus voltage on the medium and low voltage sides exceeds the limit, choose to adjust the main transformer tap to eliminate the voltage limit, and add tap k to the set S k ;

[0020] S23, if there is no adjustable equipment, go back to step S21 to eliminate the over-limit of the next substation; until the set S a All voltage limit violations are checked.

[0021] Furthermore, in step S3, if the main transformer is in split operation, the main transformer taps are adjusted respectively to eliminate voltage exceeding the limit;

[0022] If the parallel main transformers have the same OLTC tap type, adjust the OLTC taps of both main transformers simultaneously. If the OLTC tap adjustment of one main transformer fails, adjust the OLTC tap that failed again. If it fails again, adjust the successfully adjusted OLTC tap back to its original position and issue an alarm to prompt manual processing.

[0023] If the parallel main transformer on-load tap changer types are inconsistent, if the tap changer gear correspondence relationship set S f If the tap position correspondence of substation m cannot be found in the set S, an alarm is issued to remind manual processing; if the tap position correspondence set S f If the corresponding relationship of the tap position of substation m can be found, control is performed according to the corresponding relationship of the tap position.

[0024] Furthermore, if the tap position correspondence relationship set S f The corresponding relationship of the tap position of substation m can be found in , and the specific steps of controlling according to the corresponding relationship of the tap position are as follows:

[0025] S31, if the main transformer tap positions correspond continuously, the main transformer on-load tap changers are adjusted to the next corresponding set of main transformer tap positions according to the corresponding relationship. If one main transformer on-load tap changer fails to be adjusted, the main transformer on-load tap changer that failed to be adjusted is adjusted again. If it fails again, the main transformer on-load tap changer that was successfully adjusted is adjusted back to its original position, and an alarm is issued to prompt manual processing;

[0026] S32, if the main transformer tap position is not continuously corresponding, it is necessary to first adjust the main transformer on-load tap changer to the middle position according to the corresponding relationship; if the adjustment to the middle position fails, the on-load tap changer of the main transformer that failed to control is adjusted again. If it fails again, the on-load tap changer of the main transformer that was successfully adjusted is adjusted back to the original position, and an alarm is issued to remind manual processing; if the adjustment to the middle position is successful, the main transformer on-load tap changer is adjusted again to the target position. If the adjustment to the target position fails, it is adjusted again to the target position. If it fails again, the on-load tap changer of the main transformer is adjusted back to the initial position, and the on-load tap changer of the other main transformer is also adjusted to the initial position, and an alarm is issued to remind manual processing.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The method of the present invention evaluates the current substation bus voltage. When the bus voltage exceeds the limit and the main transformer on-load tap changer needs to be adjusted, if a tap position correspondence is set for the main transformers with inconsistent on-load tap changer types in the substation parallel main transformers in the automatic voltage control system, control is performed according to the on-load tap changer position correspondence of the parallel main transformers. When the on-load tap changer of the main transformer fails to be controlled, callback control is performed according to the control method of the on-load tap changer of the parallel main transformers in the substation to ensure that the real-time gear position of the main transformer meets the set correspondence. If the on-load tap changer position correspondence is not set, the main transformer gear position is locked and an alarm message is issued. The present invention is suitable for automatically controlling the on-load tap changers of parallel main transformers in a substation when the main transformer is expanded and the types of on-load tap changers of parallel main transformers are inconsistent due to inconsistent main transformer capacities, and the bus voltage is unqualified. The present invention eliminates the problem of excessive reactive circulating current of the main transformers when the types of on-load tap changers of parallel main transformers are inconsistent, thereby ensuring the safety and stability of the grid voltage and the safety of the main transformer equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a topological diagram of a transformer substation in an example of the method of the present invention.

[0030] Figure 2 It is a flowchart of the method of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and examples. The embodiments of the present invention include but are not limited to the following examples.

[0032] like Figure 2 As shown, the present invention discloses an automatic control method for parallel operation main transformer on-load tap changers of a substation. The method sets the gear correspondence relationship S of the parallel main transformer on-load tap changers according to the principle of consistent transformation ratio of the parallel main transformer on-load tap changers. f, corresponding relationship S f It is the set of gear correspondences of all parallel main transformers with inconsistent on-load tap changer types. Set the automatic voltage control period to T c 0 ; where T c 0 Set by the operator, Tc 0 The value range is 3 to 7 minutes.

[0033] When the control cycle arrives, the automatic voltage control system reads all substation bus voltage information from the grid dispatch center's dispatch monitoring system. When the substation bus voltage exceeds the set voltage limit, the control strategy is calculated to eliminate the voltage limit. The voltage limit judgment of the substation bus voltage includes:

[0034] A, if the voltage of busbar i in substation m is V i Satisfaction: V i >V i max , V i max is the set voltage upper limit of bus i, then the voltage of bus i is judged to be above the upper limit, and the substation m is judged. If Then add substation m to the set S a , if m∈S a , it means that substation m is already in the set S a In the above, there is no need to add repeatedly; the set S a Includes: Substation set where bus voltage exceeds set voltage upper limit or lower limit. When initialized, set set S a is an empty set;

[0035] B, if the voltage of busbar i in substation m is V i Satisfaction: V i <V i min , V i min is the set voltage lower limit of bus i, then it is determined that the voltage of bus i exceeds the lower limit, and the substation m is judged. If Then add substation m to the set S a , if m∈S a , it means that substation m is already in the set S a No need to add repeatedly.

[0036] The specific steps of calculating the control strategy to eliminate voltage over-limit are:

[0037] (1) When the cycle T of the automatic voltage control system c 0When it arrives, if the reactive power of the substation is unreasonable or the high-voltage side bus voltage exceeds the limit, choose to adjust the reactive power equipment to eliminate the voltage exceeding the limit.

[0038] (2) If the substation reactive power is reasonable and the bus voltage on the medium and low voltage sides exceeds the limit, choose to adjust the main transformer tap to eliminate the voltage limit, and add tap k to the set S k .

[0039] (3) If there is no adjustable equipment, go back to step S21 to eliminate the over-limit of the next substation; until the set S a All voltage limit violations are checked.

[0040] Based on the operating status of the main transformers in the substation, the corresponding method is selected to adjust the main transformer tap to eliminate the voltage limit. If the parallel main transformers have the same OLTC tap type, the OLTC taps of both main transformers are adjusted simultaneously. If the OLTC tap adjustment of one main transformer fails, the OLTC tap adjustment of the failed one is adjusted again. If it fails again, the successfully adjusted OLTC tap is returned to its original position and an alarm is issued to prompt manual processing.

[0041] If the types of parallel main transformer on-load tap changers are inconsistent, if the parallel main transformer on-load tap changer gear correspondence relationship set S f If the tap position correspondence of substation m is not found in the set S, an alarm is issued to remind manual processing; if the tap position correspondence of parallel main transformer on-load tap changer is not found in the set S f If the corresponding relationship between the on-load tap changer gear positions of substation m can be found, control is performed according to the corresponding relationship between the on-load tap changer gear positions.

[0042] If the on-load tap changer position correspondence relationship set S f The corresponding relationship between the on-load tap changer gears of substation m can be found in , and the specific steps for controlling according to the corresponding relationship between the on-load tap changer gears are as follows:

[0043] (1) If the on-load tap changer positions of the main transformers correspond continuously, the on-load tap changers of the parallel main transformers are adjusted to the next corresponding position according to the corresponding relationship. When the on-load tap changer of one main transformer fails to be adjusted, the on-load tap changer that failed to be adjusted is adjusted again. If it fails again, the on-load tap changer that was successfully adjusted is adjusted back to its original position, and an alarm is issued to remind manual processing;

[0044] (2) If the on-load tap changer positions of the main transformers are not continuously corresponding, the on-load tap changer of the parallel main transformers needs to be adjusted to the middle position according to the corresponding relationship; if the adjustment to the middle position fails, the on-load tap changer that failed to be controlled is adjusted again. If it fails again, the on-load tap changer that was successfully adjusted is adjusted back to its original position, and an alarm is issued to remind manual processing; if the adjustment to the middle position is successful, the on-load tap changer is adjusted to the target position again. If the adjustment to the target position fails, the on-load tap changer is adjusted to the target position again. If it fails again, the on-load tap changer is adjusted back to the initial position, and the on-load tap changer of the other main transformer is also adjusted to the initial position, and an alarm is issued to remind manual processing.

[0045] In the corresponding operating state of the substation main transformer, if the adjustment of the main transformer tap to eliminate the voltage over-limit adjustment fails, an alarm will be issued to remind manual processing; if the adjustment is successful, the tap adjustment of the next substation will be carried out until all tap adjustments are completed. When the next control cycle arrives, a new round of substation automatic voltage control will begin.

[0046] by Figure 1 Taking the topology of substation A shown in the figure as an example, substation A has two main transformers operating in parallel (voltage levels of 110 / 35 / 10 kV, respectively). Main transformer No. 1 has a gear adjustment range of 7 gears, from 1 to 7, and main transformer No. 2 has a gear adjustment range of 17 gears, from 1 to 17. Due to the limitations of parallel operation of main transformers, the lowest gear of No. 1 main transformer is 1, and the highest gear is 6. The lowest gear of No. 2 main transformer is 6, and the highest gear is 16. Substation A is under closed-loop control of the automatic voltage control system. The capacitors on the low-voltage side of substation A are in the locked state, and the gear taps are normal and not locked.

[0047] (1) According to the principle of consistent transformation ratio of parallel main transformers on-load tap changers in substations, the corresponding relationship of the on-load tap changers of the two parallel main transformers in substation A is calculated as shown in Table 1. The corresponding relationship of the on-load tap changers of the parallel main transformers in substation A is set in the automatic voltage control system, and the set S is added. f :

[0048] Table 1 - Corresponding relationship between the on-load tap changer positions of parallel main transformers

[0049] Serial number Main shift position 1 Main shift position 2 1 1 6 2 2 8 3 3 10 4 4 12 5 5 14 6 6 16

[0050] (2) Set the control period of the substation automatic voltage control system to T c 0 for 5 minutes, then go to step (3).

[0051] (3) Read the substation bus voltage information from the grid dispatching center dispatching monitoring system and scan the buses of all substations one by one:

[0052] In this embodiment, the bus voltages and over-limit conditions of each level of substation A obtained from the dispatching and monitoring system of the power grid dispatching center are statistically shown in Table 2 below.

[0053] Table 2-Statistics of bus voltages at all levels in substation A

[0054]

[0055] The 10kV bus voltage on the low-voltage side of substation A meets the condition V1>V1 max , V1=10.63kV, V1 max =10.6kV, V1 is the measured voltage of 10kV busbar on the low voltage side of A, V1 max is the voltage upper limit of the 10kV busbar. If the 10kV busbar voltage on the low-voltage side of substation A exceeds the upper limit, substation A will be included in the set Sa, Sa={A}.

[0056] (4) When the period T of the automatic reactive voltage control system c 0 When the voltage exceeds the limit, the equipment in the substation is selected according to the calculation method of the automatic reactive voltage control strategy to eliminate the voltage exceeding the limit in the set Sa. The specific steps are as follows:

[0057] (4-2) The busbar voltage on the low-voltage side of the substation exceeds the limit. Select to reduce the main transformer tap position to eliminate the voltage limit, and add tap k to the set S. k ;

[0058] (5) When the tap of substation p is in the set S k During operation, select the corresponding tap adjustment mode according to whether the main transformers in the substation are in parallel or split operation:

[0059] (5-3) The two main transformers of substation A are running in parallel and the types of on-load tap changers are different. The gear correspondence of tap changer k is in the set S f You can find it in the , follow the steps below to adjust:

[0060] (5-3-2) The gear positions of the main transformer tap changers of substation A are not continuously corresponding. The current gear position of main transformer No. 1 is gear 3, and the current gear position of main transformer No. 2 is gear 10. According to the downshifting requirements of the parallel main transformers, the tap changer No. 1 is first downshifted to gear 2, and the tap changer No. 2 is downshifted by one gear to the middle gear 9; if the downshifting of the tap changer No. 1 fails, the tap changer No. 1 is downshifted again. If the downshifting of the tap changer No. 1 fails again, the downshifting operation of the tap changer No. 2 is canceled, and an alarm is issued to remind manual processing; if the tap changer No. 1 is successfully adjusted to gear 2, the tap changer No. 2 is downshifted to the middle gear 9. If If the No. 2 main transformer tap changer fails to be adjusted to gear 9, the No. 2 main transformer tap changer is downshifted to gear 9 again. If the No. 2 main transformer tap changer fails to be downshifted again, the No. 1 main transformer tap changer is upshifted to the initial gear 3, and an alarm is issued to remind manual processing. If the No. 2 main transformer tap changer is successfully adjusted to gear 9, the No. 2 main transformer tap changer is adjusted to the target gear 8 again. If the No. 2 main transformer tap changer fails to be adjusted to the target gear 8, the No. 2 main transformer tap changer is adjusted to gear 8 again. If the adjustment fails again, the No. 2 main transformer tap changer is upshifted back to the initial gear 10, the No. 1 main transformer tap changer is upshifted to the initial gear 3, and an alarm is issued to remind manual processing.

[0061] (6) Return to step (5) and adjust the tap of the next substation. After all the taps of all substations are adjusted, proceed to step (7);

[0062] (7) When the next control cycle arrives, return to step (4) and start a new round of substation automatic voltage control.

[0063] The above embodiment is only one of the preferred implementation methods of the present invention and should not be used to limit the scope of protection of the present invention. Any changes or modifications that have no substantive meaning made to the main design concept and spirit of the present invention, as long as the technical problems solved are still consistent with the present invention, should be included in the scope of protection of the present invention.

Claims

1. An automatic control method for parallel operation of main transformer on-load tap changers in substations, characterized in that: The following steps are involved: S1, according to the principle of consistent transformation ratio of parallel main transformer on-load tap changer, set the corresponding relationship of tap position S f , and set the automatic voltage control period to T c 0 ; S2, when the control cycle arrives, the automatic voltage control system reads the bus voltage information of all substations from the dispatch monitoring system of the power grid dispatch center. When the substation bus voltage exceeds the set voltage limit, the control strategy is calculated to eliminate the voltage limit; S3, according to the operating status of the main transformer in the substation, select a corresponding method to adjust the main transformer tap to eliminate the voltage limit; if the main transformer is in split operation, adjust the main transformer taps separately to eliminate the voltage limit; If the main transformers are running in parallel and have the same tap type, the OLTC taps of both main transformers are adjusted simultaneously. If the OLTC tap adjustment of one main transformer fails, the OLTC tap adjustment that failed to be adjusted is adjusted again. If it fails again, the OLTC tap adjustment that was successfully adjusted is returned to its original position, and an alarm is issued to prompt manual processing. If the main transformers are operated in parallel and the tap types are inconsistent, if the tap position correspondence relationship set S f If the tap position correspondence of substation m cannot be found in the set S, an alarm is issued to remind manual processing; if the tap position correspondence set S f If the corresponding relationship of the tap position of substation m can be found, control is performed according to the corresponding relationship of the tap position; In step S4, if the main transformer of the substation fails to adjust the tap changer to eliminate the voltage exceeding the limit, an alarm is issued to prompt manual processing; if the adjustment is successful, the process returns to step S3 to adjust the tap changer of the next substation, and the process proceeds to step S5 after all tap changes are completed. S5: When the next control cycle arrives, return to step S2 and start a new round of substation automatic voltage control.

2. The automatic control method for parallel operation main transformer on-load tap changers of a substation according to claim 1 is characterized in that: In step S1, the tap position correspondence S f It is the set of correspondences of all parallel main transformers with inconsistent on-load tap changer types.

3. The automatic control method for parallel operation main transformer on-load tap changers of a substation according to claim 2, characterized in that: In step S2, determining the voltage limit of the substation bus voltage includes: A, if the voltage of busbar i in substation m is V i Satisfaction: V i >V i max , V i max is the set voltage upper limit of bus i, then the voltage of bus i is judged to be above the upper limit, and the substation m is judged. If m∉S a , then add substation m to the set S a , if m∈S a , it means that substation m is already in the set S a In the above, there is no need to add repeatedly; the set S a Includes: Substation set where bus voltage exceeds set voltage upper limit or lower limit. When initialized, set set S a is an empty set; B, if the voltage of busbar i in substation m is V i Satisfaction: V i <V i min , V i min is the set voltage lower limit of bus i, then the voltage of bus i is judged to be over the lower limit, and the substation m is judged. If m∉S a , then add substation m to the set S a , if m∈S a , it means that substation m is already in the set S a No need to add repeatedly.

4. The automatic control method for parallel operation main transformer on-load tap changers of a substation according to claim 3 is characterized in that: In step S2, the specific steps of calculating the control strategy to eliminate voltage over-limit are: S21, when the cycle T of the automatic voltage control system c 0 When the reactive power of the substation is unreasonable or the high-voltage side bus voltage exceeds the limit, the reactive power equipment is adjusted to eliminate the voltage exceeding the limit; S22, if the substation reactive power is reasonable and the bus voltage on the medium and low voltage sides exceeds the limit, choose to adjust the main transformer tap to eliminate the voltage limit, and add tap k to the set S k ; S23, if there is no adjustable equipment, return to step S21 to eliminate the over-limit of the next substation; until the set S a All voltage limit violations are checked.

5. The automatic control method for parallel operation main transformer on-load tap changers of a substation according to claim 4, characterized in that: If the tap position correspondence relationship set S f The corresponding relationship of the tap position of substation m can be found in , and the specific steps of controlling according to the corresponding relationship of the tap position are as follows: S31: If the main transformer tap position is continuously corresponding, the main transformer gear is adjusted to the next corresponding gear according to the tap position correspondence. If the on-load tap changer of a main transformer fails to be adjusted, the on-load tap changer that failed to be adjusted is adjusted again. If it fails again, the on-load tap changer that was successfully adjusted is returned to its original position, and an alarm is issued to prompt manual processing. S32, if the main transformer tap position is not continuously corresponding, it is necessary to first adjust the on-load tap changer to the middle position according to the tap position correspondence; if adjustment to the middle position fails, adjust the on-load tap changer that failed to be controlled again. If it fails again, adjust the successfully adjusted on-load tap changer back to its original position and issue an alarm to remind manual processing; if adjustment to the middle position is successful, adjust the main transformer on-load tap changer to the target position again. If adjustment to the target position fails, adjust it to the target position again. If it fails again, adjust the on-load tap changer back to the initial position, adjust the other main transformer on-load tap changer to its initial position, and issue an alarm to remind manual processing.

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