Safety assessment method for excitation system of black start of double-circuit transmission line on the same tower under induction

Abstract

The invention discloses a safety assessment method for an excitation system of a black start under induction of a double-circuit line on the same tower. The induced voltage and current of the double-circuit line on the same tower are calculated by simulating the double-circuit line on the same tower, and the induced voltage of the rotor excitation winding of the unit is obtained by transformation. The induced voltage of the rotor excitation winding of the unit is input as an interference signal and connected to the excitation system model. The influence of the induced voltage invading the excitation system on the start of the excitation system is judged by thyristor voltage interference simulation, thereby completing the safety assessment of the excitation system. The invention solves the technical problem that when there is induction of the double-circuit line on the same tower during the black start of the hydro-turbine unit, the existing safety assessment method of the excitation system is difficult to judge whether the excitation system can work normally under the interference of induced voltage and current.

Description

Technical Field

[0001] The invention relates to the technical field of power system simulation, and in particular to a method for safety assessment of an excitation system for a black start of a double-circuit line on the same tower under induction. Background Art

[0002] A large power outage in the power grid will bring huge losses to the national economy and the power system itself. Although it is possible to prevent and reduce large power outages by strengthening preventive measures, the power grid may still have serious faults that exceed the stability verification level, especially in large-scale natural disasters (such as typhoons, lightning disasters, ice disasters, earthquakes, etc.), multiple complex faults will occur continuously, exceeding the stability verification level, leading to large-scale power outages, and even causing a large power outage in the entire network. Therefore, in response to possible large power outages or blackouts, it is of utmost importance to formulate a black start plan and power grid recovery plan after a large power outage, shorten the processing time after the accident, quickly restore the power grid, and reduce losses.

[0003] In order to deal with possible blackouts, the grid dispatching department needs to formulate black start and grid restoration plans in a targeted manner, and requires the generator sets with self-excitation capability in the area grid to conduct simulated black start tests. Hydro turbine units are generally synchronous motors, and they need to cooperate with the grid dispatching department to carry out start-up tests. In the grid black start plan, when there are two or more parallel lines in the start path, only one of them will be restored first. However, under actual working conditions, due to power outage difficulties and other reasons, induced voltage and induced current will be generated on the double-circuit line on the same tower during the unit black start test, which may invade the excitation system of the hydro turbine unit and cause an accident. At present, the analysis method for the intrusion of induced voltage and current into the excitation system is not perfect. During the black start test, the voltage and current of the line and the unit are generally monitored in real time by means of the station recording system or external measuring instruments. However, the wiring measurement on the rotor side of the unit is troublesome, and the voltage and current measurement of the thyristor in the excitation system is difficult. It is impossible to obtain the influence of the intrusion of induced voltage and current on the waveform of the electrical parameters of the thyristor, and it is difficult to judge whether the excitation system can work normally under the interference of induced voltage and current. Summary of the invention

[0004] The present invention provides a safety assessment method for an excitation system during a black start under induction of a double-circuit line on the same tower, which is used to solve the technical problem that when there is induction of a double-circuit line on the same tower during the black start of a hydro turbine unit, the existing safety assessment method for the excitation system is difficult to judge whether the excitation system can work normally under the interference of induced voltage and current.

[0005] In view of this, a first aspect of the present invention provides a method for safety assessment of an excitation system for a black start of a double-circuit line on the same tower under induction, comprising:

[0006] Establish a coupled simulation model of double-circuit lines on the same tower in electromagnetic transient simulation software;

[0007] According to the actual operating conditions of the double-circuit lines on the same tower, the operating parameters of the coupled simulation model of the double-circuit lines on the same tower are adjusted to calculate the induced voltage and induced current of the outage lines;

[0008] Perform symmetrical phasor decomposition on the induced voltage and induced current to obtain the negative sequence voltage and negative sequence current invading the turbine unit;

[0009] Input the negative sequence voltage and negative sequence current into the stator-rotor coupling model of the unit to obtain the 100Hz induced voltage on the rotor excitation winding;

[0010] The 100Hz induced voltage on the rotor excitation winding is input as an interference signal into the excitation system model to simulate the thyristor voltage interference;

[0011] Based on the simulation results of thyristor voltage interference, it is judged whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower.

[0012] Optionally, judging whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower according to the thyristor voltage interference simulation result includes:

[0013] According to the voltage and current waveforms and working status of the thyristor obtained by the thyristor voltage interference simulation, it is judged whether the commutation voltage crosses the zero point, resulting in an error in the valve group conduction sequence or whether the thyristor has overcurrent. If so, the excitation system cannot be safely started under the induced voltage and current interference of the double-circuit line on the same tower. Otherwise, the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower.

[0014] Optionally, the electromagnetic transient simulation software is EMTP.

[0015] Optionally, judging whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower according to the thyristor voltage interference simulation result, and then further comprising:

[0016] If the excitation system can start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the unit black start test shall be carried out under the induction condition of the double-circuit line on the same tower;

[0017] If the excitation system cannot start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the black start plan should be modified and the unit black start test should be carried out under the condition of complete power outage of the double-circuit line on the same tower.

[0018] A second aspect of the present invention provides an excitation system safety assessment system for black start of a double-circuit line on the same tower under induction, comprising:

[0019] Modeling unit, used to establish a coupled simulation model of double-circuit lines on the same tower in electromagnetic transient simulation software;

[0020] The line induced voltage and current calculation unit is used to adjust the operating parameters of the same-tower double-circuit line coupling simulation model according to the actual operating conditions of the same-tower double-circuit line, and calculate the induced voltage and induced current of the outage line;

[0021] A decomposition unit is used to perform symmetrical phase decomposition on the induced voltage and the induced current to obtain the negative sequence voltage and the negative sequence current invading the turbine unit;

[0022] The excitation winding induced voltage calculation unit is used to input the negative sequence voltage and negative sequence current into the stator-rotor coupling model of the unit to obtain the 100Hz induced voltage on the rotor excitation winding;

[0023] The thyristor voltage interference simulation unit is used to input the 100Hz induced voltage on the rotor excitation winding as an interference signal into the excitation system model to perform thyristor voltage interference simulation;

[0024] The safety assessment unit is used to determine whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower based on the thyristor voltage interference simulation results.

[0025] Optionally, the safety assessment unit is specifically used for:

[0026] According to the voltage and current waveforms and working status of the thyristor obtained by the thyristor voltage interference simulation, it is judged whether the commutation voltage crosses the zero point, resulting in an error in the valve group conduction sequence or whether the thyristor has overcurrent. If so, the excitation system cannot be safely started under the induced voltage and current interference of the double-circuit line on the same tower. Otherwise, the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower.

[0027] Optionally, the electromagnetic transient simulation software is EMTP.

[0028] Optionally, a decision making unit is also included;

[0029] The decision-making unit is used to:

[0030] If the excitation system can start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the unit black start test shall be carried out under the induction condition of the double-circuit line on the same tower;

[0031] If the excitation system cannot start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the black start plan should be modified and the unit black start test should be carried out under the condition of complete power outage of the double-circuit line on the same tower.

[0032] A third aspect of the present invention provides an excitation system safety assessment device for a black start of a double-circuit line on the same tower under induction, the device comprising a processor and a memory:

[0033] The memory is used to store program code and transmit the program code to the processor;

[0034] The processor is used to execute the excitation system safety assessment method for black start of double-circuit lines on the same tower under induction according to any one of the first aspects according to the instructions in the program code.

[0035] A fourth aspect of the present invention provides a computer-readable storage medium for storing program code, wherein the program code is used to execute the excitation system safety assessment method for black start of a double-circuit line on the same tower under induction as described in any one of the first aspects.

[0036] It can be seen from the above technical solutions that the excitation system safety assessment method for black start of double-circuit lines on the same tower provided by the present invention has the following advantages:

[0037] The invention provides a safety assessment method for an excitation system during a black start under induction of a double-circuit line on the same tower. The induced voltage and current of the double-circuit line on the same tower are calculated by simulating the double-circuit line on the same tower, and the induced voltage of the excitation winding of the unit rotor is obtained by transformation. The induced voltage of the excitation winding of the unit rotor is input as an interference signal and connected to the excitation system model. The influence of the induced voltage intruding into the excitation system on the start of the excitation system is judged by simulating the interference of thyristor voltage, thereby completing the safety assessment of the excitation system. There is no need to use a recording system in the station or an external measuring instrument to monitor the voltage and current of the line and the unit in real time. There is no problem of troublesome measurement of the wiring on the rotor side of the unit and difficulty in measuring the voltage and current of the thyristor in the excitation system, and the influence of the intrusion of the induced voltage and current on the waveform of the electrical parameters of the thyristor cannot be obtained. The invention solves the technical problem that when there is induction of the double-circuit line on the same tower during the black start of the hydro-turbine unit, the existing safety assessment method of the excitation system is difficult to judge whether the excitation system can work normally under the interference of the induced voltage and current.

[0038] At the same time, the safety assessment method of the excitation system for black start under induction of double-circuit lines on the same tower provided by the present invention can predict the size of the induced voltage invading the excitation system in advance, and judge the safety impact through modeling and simulation of the excitation system, providing more detailed theoretical and data support for the formulation of black start plans and safety assurance of turbine units. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 A schematic flow chart of a method for safety assessment of an excitation system for a black start of a double-circuit line on the same tower provided in the present invention;

[0041] Figure 2 It is another flow chart of the method for safety assessment of the excitation system of the double-circuit line on the same tower under induction black start provided by the present invention;

[0042] Figure 3 The present invention is a schematic structural diagram of an excitation system safety assessment system for black start of a double-circuit line on the same tower provided by the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] For easier understanding, see Figure 1 and Figure 2 The present invention provides an embodiment of a method for safety assessment of an excitation system for a black start of a double-circuit line on the same tower under induction, comprising:

[0045] Step 101: Establish a coupled simulation model of double-circuit lines on the same tower in electromagnetic transient simulation software.

[0046] It should be noted that, according to the line ground wire parameters, tower model, line transposition, etc., a coupled simulation model of double-circuit lines on the same tower corresponding to the actual double-circuit line scenario on the same tower is established in the electromagnetic transient simulation software. The electromagnetic transient simulation software selected is EMTP (Electro-Magnetic Transjent Program) software.

[0047] Step 102: adjust the operating parameters of the coupled simulation model of the double-circuit lines on the same tower according to the actual operating conditions of the double-circuit lines on the same tower, and calculate the induced voltage and induced current of the out-of-service lines.

[0048] It should be noted that according to the actual operating conditions of the double-circuit line on the same tower, the operating parameters of the coupled simulation model of the double-circuit line on the same tower are adjusted to make the transmission power on the line consistent with the actual situation, simulate the power outage event, and calculate the induced voltage and induced current of the outage line at this time.

[0049] Step 103: perform symmetrical phasor decomposition on the induced voltage and the induced current to obtain the negative sequence voltage and the negative sequence current invading the turbine unit.

[0050] It should be noted that, according to the electromagnetic induction principle of the generator, the positive-sequence magnetic field generated by the positive-sequence current on the stator rotates synchronously with the rotor, and no induced electromotive force is generated on the rotor. The zero-sequence component cannot enter the stator winding of the generator due to the blocking of the triangle winding on the low-voltage side of the transformer, while the negative-sequence current on the stator generates a negative-sequence magnetic field. The rotor cuts this magnetic field to generate an induced electromotive force of 2 times the power frequency. Therefore, in the embodiment of the present invention, the induced voltage and induced current on the out-of-service line are symmetrically decomposed to obtain the negative-sequence voltage and negative-sequence current invading the turbine unit.

[0051] Step 104: input the negative sequence voltage and the negative sequence current into the stator-rotor coupling model of the unit to obtain the 100 Hz induced voltage on the rotor excitation winding.

[0052] It should be noted that, through the parameters such as the self-inductance, mutual inductance and distributed capacitance of the internal winding of the turbine unit, the electromagnetic transient simulation software is used to establish the stator and rotor coupling calculation model inside the generator, that is, the unit stator-rotor coupling model, and the negative sequence voltage and negative sequence current are input into the unit stator-rotor coupling model as the input conditions to obtain the 100Hz induced voltage on the rotor excitation winding.

[0053] Step 105: input the 100 Hz induced voltage on the rotor excitation winding as an interference signal into the excitation system model to perform thyristor voltage interference simulation.

[0054] It should be noted that the excitation system model is established using electromagnetic transient simulation software, and the 100 Hz induced voltage on the rotor excitation winding obtained by solving step 104 is input as an interference signal into the excitation system model to perform thyristor voltage interference simulation.

[0055] Step 106: Determine whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower according to the thyristor voltage interference simulation result.

[0056] It should be noted that the 100Hz induced voltage on the rotor excitation winding obtained by solving step 104 is the induced voltage that invades the excitation system. Therefore, after the simulation of step 105, according to the simulation results, the working state of the excitation system when facing the intrusive induced voltage can be understood, so that the safety of the excitation system can be evaluated. If the excitation system can be safely started under the interference of the induced voltage and current of the double-circuit line on the same tower, it can be considered to carry out a black start test of the turbine unit under the inductive working condition of the double-circuit line on the same tower. If the excitation system cannot be safely started under the interference of the induced voltage and current of the double-circuit line on the same tower, it is necessary to modify the black start plan and require the double-circuit line to be completely shut down for the black start test of the unit. Specifically, according to the voltage and current waveforms and working states of the thyristor obtained by the thyristor voltage interference simulation, it is judged whether the commutation voltage crosses the zero point to cause the valve group conduction sequence error or whether the thyristor has an overcurrent. If so, the excitation system cannot be safely started under the interference of the induced voltage and current of the double-circuit line on the same tower. Otherwise, the excitation system can be safely started under the interference of the induced voltage and current of the double-circuit line on the same tower. If the commutation voltage crosses zero and causes the valve group conduction sequence to be incorrect, it means that the interference voltage has caused the commutation failure, and the DC current has increased significantly, exceeding the average current of the thyristor in the on-state, indicating that the thyristor has an overcurrent and may be damaged.

[0057] The invention provides a safety assessment method for an excitation system during a black start under induction of a double-circuit line on the same tower. The induced voltage and current of the double-circuit line on the same tower are calculated by simulating the double-circuit line on the same tower, and the induced voltage of the excitation winding of the unit rotor is obtained by transformation. The induced voltage of the excitation winding of the unit rotor is input as an interference signal and connected to the excitation system model. The influence of the induced voltage intruding into the excitation system on the start of the excitation system is judged by simulating the interference of thyristor voltage, thereby completing the safety assessment of the excitation system. There is no need to use a recording system in the station or an external measuring instrument to monitor the voltage and current of the line and the unit in real time. There is no problem of troublesome measurement of the wiring on the rotor side of the unit and difficulty in measuring the voltage and current of the thyristor in the excitation system, and the influence of the intrusion of the induced voltage and current on the waveform of the electrical parameters of the thyristor cannot be obtained. The invention solves the technical problem that when there is induction of the double-circuit line on the same tower during the black start of the hydro-turbine unit, the existing safety assessment method of the excitation system is difficult to judge whether the excitation system can work normally under the interference of the induced voltage and current.

[0058] At the same time, the existing real-time monitoring method of the voltage and current of the line and the unit by means of the station recording system or external measuring instruments cannot predict the size of the induced voltage on the unit rotor excitation winding in advance. The excitation system safety assessment method for black start under induction of double-circuit lines on the same tower provided by the present invention can predict the size of the induced voltage invading the excitation system in advance, and judge the safety impact through modeling and simulation of the excitation system, providing more detailed theoretical and data support for the formulation of black start plans and safety assurance of turbine units.

[0059] For easier understanding, see Figure 3 The present invention provides an embodiment of an excitation system safety assessment system for black start of a double-circuit line on the same tower under induction, comprising:

[0060] Modeling unit, used to establish a coupled simulation model of double-circuit lines on the same tower in electromagnetic transient simulation software;

[0061] The line induced voltage and current calculation unit is used to adjust the operating parameters of the same-tower double-circuit line coupling simulation model according to the actual operating conditions of the same-tower double-circuit line, and calculate the induced voltage and induced current of the outage line;

[0062] A decomposition unit is used to perform symmetrical phase decomposition on the induced voltage and the induced current to obtain the negative sequence voltage and the negative sequence current invading the turbine unit;

[0063] The excitation winding induced voltage calculation unit is used to input the negative sequence voltage and negative sequence current into the stator-rotor coupling model of the unit to obtain the 100Hz induced voltage on the rotor excitation winding;

[0064] The thyristor voltage interference simulation unit is used to input the 100Hz induced voltage on the rotor excitation winding as an interference signal into the excitation system model to perform thyristor voltage interference simulation;

[0065] The safety assessment unit is used to determine whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower based on the thyristor voltage interference simulation results.

[0066] The safety assessment unit is specifically used for:

[0067] According to the voltage and current waveforms and working status of the thyristor obtained by the thyristor voltage interference simulation, it is judged whether the commutation voltage crosses the zero point, resulting in an error in the valve group conduction sequence or whether the thyristor has overcurrent. If so, the excitation system cannot be safely started under the induced voltage and current interference of the double-circuit line on the same tower. Otherwise, the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower.

[0068] The electromagnetic transient simulation software is EMTP.

[0069] It also includes decision-making units;

[0070] The decision-making unit is used to:

[0071] If the excitation system can start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the unit black start test shall be carried out under the induction condition of the double-circuit line on the same tower;

[0072] If the excitation system cannot start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the black start plan should be modified and the unit black start test should be carried out under the condition of complete power outage of the double-circuit line on the same tower.

[0073] The invention provides an excitation system safety assessment system for black start under induction of a double-circuit line on the same tower. The induced voltage and current of the double-circuit line on the same tower are calculated by simulating the double-circuit line on the same tower, and the induced voltage of the excitation winding of the unit rotor is obtained by transformation. The induced voltage of the excitation winding of the unit rotor is input as an interference signal and connected to the excitation system model. The influence of the induced voltage intruding into the excitation system on the start of the excitation system is judged by thyristor voltage interference simulation, thereby completing the safety assessment of the excitation system. There is no need to use a recording system in the station or an external measuring instrument to monitor the voltage and current of the line and the unit in real time. There is no problem of troublesome measurement of the wiring on the rotor side of the unit and difficulty in measuring the voltage and current of the thyristor in the excitation system, and the influence of the intrusion of the induced voltage and current on the waveform of the electrical parameters of the thyristor cannot be obtained. The technical problem that when there is induction of the double-circuit line on the same tower during the black start of the turbine unit is solved, the existing safety assessment method of the excitation system is difficult to judge whether the excitation system can work normally under the interference of the induced voltage and current.

[0074] At the same time, the existing real-time monitoring method of the voltage and current of the line and the unit by means of the station recording system or external measuring instruments cannot predict the size of the induced voltage on the unit rotor excitation winding in advance. The excitation system safety assessment system for black start under induction of the double-circuit line on the same tower provided by the present invention can predict the size of the induced voltage invading the excitation system in advance, and judge the safety impact through modeling and simulation of the excitation system, providing more detailed theoretical and data support for the formulation of black start plans and safety assurance of turbine units.

[0075] The present invention also provides an embodiment of an excitation system safety assessment device for a water turbine unit with a double-circuit line on the same tower under induction black start, the device comprising a processor and a memory:

[0076] The memory is used to store program code and transmit the program code to the processor;

[0077] The processor is used to execute any one of the above-mentioned methods for safety assessment of the excitation system for black start of double-circuit lines on the same tower under induction according to the instructions in the program code.

[0078] The present invention also provides a computer-readable storage medium for storing program code, and the program code is used to execute any one of the aforementioned methods for safety assessment of the excitation system for black start under induction of a double-circuit line on the same tower in the embodiments of the method.

[0079] The excitation system safety assessment system and device for a black start of a hydro-turbine unit under induction of a double-circuit line on the same tower, as well as a computer-readable storage medium, provided in an embodiment of the present invention, are used to execute the excitation system safety assessment method for a black start of a double-circuit line on the same tower in the aforementioned embodiment of the excitation system safety assessment method for a black start of a double-circuit line on the same tower. The principle of the excitation system safety assessment method for a black start of a double-circuit line on the same tower under induction is the same as that of the excitation system safety assessment method for a black start of a double-circuit line on the same tower in the aforementioned embodiment of the excitation system safety assessment method for a black start of a double-circuit line on the same tower, and will not be repeated here.

[0080] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for safety assessment of the excitation system of a double-circuit line on the same tower under induction black start, characterized in that: include: Establish a coupled simulation model of double-circuit lines on the same tower in electromagnetic transient simulation software; According to the actual operating conditions of the double-circuit lines on the same tower, the operating parameters of the coupled simulation model of the double-circuit lines on the same tower are adjusted to calculate the induced voltage and induced current of the outage lines; Perform symmetrical phasor decomposition on the induced voltage and induced current to obtain the negative sequence voltage and negative sequence current invading the turbine unit; Input the negative sequence voltage and negative sequence current into the stator-rotor coupling model of the unit to obtain the 100Hz induced voltage on the rotor excitation winding; The 100Hz induced voltage on the rotor excitation winding is input as an interference signal into the excitation system model to simulate the thyristor voltage interference; Based on the simulation results of thyristor voltage interference, it is judged whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower.

2. The method for safety assessment of the excitation system of a double-circuit line on the same tower under induction black start according to claim 1 is characterized in that: Based on the thyristor voltage interference simulation results, it is judged whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower, including: According to the voltage and current waveforms and working status of the thyristor obtained by the thyristor voltage interference simulation, it is judged whether the commutation voltage crosses the zero point, resulting in an error in the valve group conduction sequence or whether the thyristor has overcurrent. If so, the excitation system cannot be safely started under the induced voltage and current interference of the double-circuit line on the same tower. Otherwise, the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower.

3. The method for safety assessment of the excitation system of a double-circuit line on the same tower under induction black start according to claim 1 is characterized in that: The electromagnetic transient simulation software is EMTP.

4. The method for safety assessment of the excitation system of a double-circuit line on the same tower under induction black start according to claim 1 is characterized in that: According to the simulation results of thyristor voltage interference, it is judged whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower, and then it also includes: If the excitation system can start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the unit black start test shall be carried out under the induction condition of the double-circuit line on the same tower; If the excitation system cannot start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the black start plan should be modified and the unit black start test should be carried out under the condition of complete power outage of the double-circuit line on the same tower.

5. A safety assessment system for the excitation system of a double-circuit line on the same tower under induction black start, characterized in that: include: Modeling unit, used to establish a coupled simulation model of double-circuit lines on the same tower in electromagnetic transient simulation software; The line induced voltage and current calculation unit is used to adjust the operating parameters of the same-tower double-circuit line coupling simulation model according to the actual operating conditions of the same-tower double-circuit line, and calculate the induced voltage and induced current of the outage line; A decomposition unit is used to perform symmetrical phasor decomposition on the induced voltage and the induced current to obtain the negative sequence voltage and negative sequence current invading the turbine unit; The excitation winding induced voltage calculation unit is used to input the negative sequence voltage and negative sequence current into the stator-rotor coupling model of the unit to obtain the 100Hz induced voltage on the rotor excitation winding; The thyristor voltage interference simulation unit is used to input the 100Hz induced voltage on the rotor excitation winding as an interference signal into the excitation system model to perform thyristor voltage interference simulation; The safety assessment unit is used to determine whether the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower according to the thyristor voltage interference simulation results.

6. The excitation system safety assessment system for black start of double-circuit lines on the same tower according to claim 5 is characterized in that: The safety assessment unit is specifically used for: According to the voltage and current waveforms and working status of the thyristor obtained by the thyristor voltage interference simulation, it is judged whether the commutation voltage crosses the zero point, resulting in an error in the valve group conduction sequence or whether the thyristor has overcurrent. If so, the excitation system cannot be safely started under the induced voltage and current interference of the double-circuit line on the same tower. Otherwise, the excitation system can be safely started under the induced voltage and current interference of the double-circuit line on the same tower.

7. The excitation system safety assessment system for black start of double-circuit lines on the same tower according to claim 5 is characterized in that: The electromagnetic transient simulation software is EMTP.

8. The excitation system safety assessment system for black start of double-circuit lines on the same tower according to claim 5 is characterized in that: It also includes decision-making units; The decision-making unit is used to: If the excitation system can start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the unit black start test shall be carried out under the induction condition of the double-circuit line on the same tower; If the excitation system cannot start safely under the interference of induced voltage and current of the double-circuit line on the same tower, the black start plan should be modified and the unit black start test should be carried out under the condition of complete power outage of the double-circuit line on the same tower.

9. A safety assessment device for the excitation system of a double-circuit line on the same tower under induction black start, characterized in that: The device comprises a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the excitation system safety assessment method for black start of double-circuit lines on the same tower under induction according to the instructions in the program code described in any one of claims 1-4.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store program codes, and the program codes are used to execute the excitation system safety assessment method for black start of double-circuit lines on the same tower under induction as described in any one of claims 1-4.

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