A control method and system for a thyristor current source inverter output transformer

Abstract

The present invention discloses a control method and system for a thyristor current source inverter output transformer. On the basis of determining the output loop resistance on the high-voltage side of the inverter, the relationship between the output amplitude of the DC current on the high-voltage side and the maximum duration is determined, and the relationship between the starting torque of the inverter and the maximum duration is further determined. Finally, the maximum angle at which the unit can be dragged to rotate when the inverter is directly running with the output transformer is calculated, and the operation mode of the bypass knife switch on the output side of the inverter is determined. The present invention uses the AC rated parameters of the transformer for DC current transmission, and on this basis determines the rotation angle of the unit that the inverter can drag before the transformer is saturated, so as to determine whether it is necessary to use the bypass output transformer mode to start the unit, which greatly reduces the number of times the bypass knife switch is opened and closed, effectively avoids the start-up failure caused by the abnormality of the bypass knife switch when the inverter starts the unit, and improves the success rate of the unit start-up.

Description

Technical Field

[0001] The invention relates to a control method and system for a thyristor current source inverter output transformer, belonging to the technical field of thyristor current source inverters of power systems. Background Art

[0002] Pumped storage is the most mature, economical and large-scale energy storage method. It is a green, low-carbon and clean flexible power source for the power system. It has the functions of peak regulation, frequency regulation, phase regulation, energy storage, system standby and black start, as well as technical and economic advantages such as large capacity, multiple operating conditions, fast speed, high reliability and good economy. It plays a fundamental role in ensuring the safety of large power grids, promoting the consumption of new energy and improving the performance of the whole system. Under the background of dual carbon, accelerating the development of pumped storage is an urgent requirement for building a new power system, an important support for ensuring the safe and stable operation of the power system, and an important guarantee for the large-scale development of renewable energy.

[0003] The thyristor current source converter (SFC) is the preferred starting device for pumped storage units under pumping conditions, and it mostly adopts a high-low-high voltage topology with an input transformer and an output transformer. Under low-frequency (less than 3-6Hz) output state, in order to prevent the output transformer from saturation, the output transformer needs to be bypassed through a bypass switch, and the SFC bridge-side valve group is directly connected to the unit; when the frequency increases (greater than 3-6Hz), the bypass switch switches to the operation mode with output transformer, and the SFC switches from directly dragging the unit to dragging the unit through the output transformer. Each time the pumped storage unit is started, the bypass switch needs to be switched once. The occasional failure of the bypass switch has become an important factor affecting the success rate of pumped storage unit startup. If the SFC can start directly with the transformer, or reduce the number of times the bypass switch is switched, the success rate of pumped storage unit startup will be greatly improved. Summary of the invention

[0004] The object of the present invention is to overcome the deficiencies in the prior art and to provide a control method and system for an output transformer of a thyristor current source inverter.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0006] In a first aspect, the present invention provides a method for controlling an output transformer of a thyristor current source inverter, comprising:

[0007] Obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator, and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC;

[0008] The relationship between the DC current on the high-voltage side of the output transformer and the maximum duration is calculated by using the resistance of the output circuit on the high-voltage side of the SFC and the DC current of a set amplitude pre-applied on the low-voltage side of the SFC;

[0009] The starting torque of the SFC during low-frequency operation is obtained through the DC current on the high-voltage side of the transformer, and the relationship between the SFC starting torque and the maximum duration is calculated;

[0010] Obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle that the SFC can drag the unit to rotate within the set starting torque and its corresponding maximum duration based on the torque drag formula;

[0011] The operation mode of the bypass switch on the output side of the SFC is determined according to the maximum angle of rotation of the unit that can be dragged by the SFC and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

[0012] Furthermore, the resistance parameter R2 of the SFC high-voltage side output circuit is the resistance R T1 , Generator stator resistance R G , output circuit cable or closed bus resistance R L , output circuit breaker contact resistance R DL twice the sum.

[0013] Furthermore, the relationship between the DC current on the high voltage side of the output transformer and the maximum duration is calculated by using the resistance of the output circuit on the high voltage side of the SFC and the DC current of the set amplitude pre-applied on the low voltage side of the SFC, including:

[0014] Input current I on the low voltage side of the output transformer d1 When the high-voltage side transmits a certain ratio of I d2 , at this time the voltage on the high voltage side is:

[0015]

[0016] Among them: U2 is the voltage on the high voltage side of the output transformer; N1 and N2 are the number of turns on the low voltage side and high voltage side of the output transformer;

[0017] The DC current I applied on the low voltage side of the output transformer d1 , before the transformer is saturated, the induced potential on the high voltage side is:

[0018]

[0019] in: is the maximum flux value that the output transformer can operate, t m is the maximum operating time when passing through DC;

[0020] Since the internal resistance of the high-voltage winding of the output transformer has been equivalent to the output loop resistance R2, U2 = e2, then:

[0021]

[0022] According to the output transformer design:

[0023]

[0024] Among them: U 2N is the rated voltage of the high-voltage side of the output transformer, f N is the rated frequency of the output transformer, and from formula (4):

[0025]

[0026] Substituting formula (5) into formula (3), we get:

[0027]

[0028] Formula (6) determines the DC current I on the high-voltage side of the output transformer d2 Relationship with maximum duration t m Inversely proportional and uniquely corresponding.

[0029] Furthermore, obtaining the starting torque of the SFC when it is running at a low frequency by using the DC current on the high-voltage side of the transformer, and calculating the relationship between the SFC starting torque and the maximum duration, include:

[0030] According to the SFC drag torque formula, the average value of the variable frequency drag torque is:

[0031]

[0032] Where: m is the number of pole pairs of the unit, Ψ is the magnetic flux of the unit, γ0 is the commutation redundancy angle, and μ is the commutation overlap angle;

[0033] In the low frequency stage, SFC adopts pulse commutation mode. Then formula (7) can be simplified as:

[0034]

[0035] in: At the initial start-up of the unit, the unit flux is controlled by the excitation current and remains constant, so k T is a fixed value, substituting formula (8) into formula (6) to obtain:

[0036]

[0037] Formula (9) determines the inverter starting torque T d With the maximum duration t m Inversely proportional and uniquely corresponding.

[0038] Furthermore, the torque-based drag formula calculates the maximum angle of rotation of the SFC-driven unit within the set starting torque and its corresponding maximum duration, including:

[0039] According to the principle of torque drag:

[0040]

[0041]

[0042] Where: T d is the starting torque, T r is the resistance torque, Ω is the rotation angular velocity, and θ is the rotation angle;

[0043] The unit starts from a stationary state, and the starting torque T d , resistance torque T r Approximately unchanged, the unit rotation acceleration Ω is a constant value. Based on formulas (10) and (11), we can get:

[0044]

[0045] θ m The maximum angle that the SFC can drag the unit to rotate before the output becomes saturated.

[0046] Further, the operation mode of the bypass switch on the output side of the SFC is determined according to the maximum angle of rotation of the unit that can be dragged by the SFC and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit, including:

[0047] When the SFC system changes phase once, the unit needs to rotate by:

[0048]

[0049] Where p is the number of pole pairs of the unit; n is the number of pulses on the machine bridge side;

[0050] When θ m ≥θ c When θ m <θ c When starting, the non-bypass switch mode can be used only when the output transformer cannot be saturated in the first two phase-changing intervals;

[0051] The first camera group needs to rotate by an angle of (θ c-θ0), the time is t1, based on formula (12), we can get:

[0052]

[0053] During the second phase change, the total rotation angle of the unit is (2θ c -θ0), the time is t2, based on formula (12), we can get:

[0054]

[0055] Only when t1 and (t2-t1) are both less than t m When the SFC is started, it adopts the direct start mode with output transformer. Otherwise, it needs to start after bypassing the output transformer, that is:

[0056]

[0057] Substituting equations (12), (14), and (15) into (16), we obtain:

[0058]

[0059] In a second aspect, the present invention provides a control system for a thyristor current source inverter output transformer, comprising:

[0060] The first calculation unit is used to obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC;

[0061] The second calculation unit is used to calculate the relationship between the DC current on the high-voltage side of the output transformer and the maximum duration through the resistance of the output circuit on the high-voltage side of the SFC and the DC current of the set amplitude pre-applied on the low-voltage side of the SFC;

[0062] The third calculation unit is used to obtain the starting torque of the SFC when it is running at a low frequency through the DC current on the high-voltage side of the transformer, and calculate the relationship between the SFC starting torque and the maximum duration;

[0063] The fourth calculation unit is used to obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle of rotation of the unit that the SFC can drag based on the torque drag formula within the set starting torque and its corresponding maximum duration;

[0064] The operation mode determination unit is used to determine the operation mode of the bypass switch on the output side of the SFC according to the maximum angle of rotation of the unit that can be dragged by the SFC and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

[0065] In a third aspect, the present invention provides a control device for a thyristor current source inverter output transformer, comprising:

[0066] The first calculation module is used to obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC;

[0067] The second calculation module is used to calculate the relationship between the DC current on the high-voltage side of the output transformer and the maximum duration through the resistance of the output circuit on the high-voltage side of the SFC and the DC current of the set amplitude pre-applied on the low-voltage side of the SFC;

[0068] The third calculation module is used to obtain the starting torque of the SFC when it is running at a low frequency through the DC current on the high-voltage side of the transformer, and calculate the relationship between the SFC starting torque and the maximum duration;

[0069] The fourth calculation module is used to obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle of rotation of the unit that the SFC can drag based on the torque drag formula within the set starting torque and its corresponding maximum duration;

[0070] The operation mode determination module is used to determine the operation mode of the bypass switch on the SFC output side according to the maximum angle of rotation of the SFC-driven unit and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

[0071] In a fourth aspect, the present invention provides a control device for a thyristor current source inverter output transformer, comprising a processor and a storage medium;

[0072] The storage medium is used to store instructions;

[0073] The processor is configured to operate according to the instructions to execute the steps of any of the aforementioned methods.

[0074] In a fifth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the aforementioned methods.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] (1) The present invention determines the switch operation control mode based on the inverter output circuit resistance parameters, output transformer design parameters, unit resistance torque, etc., and has higher reliability and higher accuracy;

[0077] (2) Based on this method, newly built stations can optimize the resistance parameters of the inverter output circuit and the transformer design parameters to ensure that the inverter can start directly with the output transformer, so as to avoid the impact of bypass switch abnormalities on the success rate of unit startup and improve the success rate of startup;

[0078] (3) Based on this method, existing stations can calculate the angle range for direct start-up with the output transformer, effectively reducing the number of times the bypass switch is opened and closed, which can not only increase the life of the bypass switch, but also reduce the risk of start-up failure caused by abnormal opening and closing of the bypass switch;

[0079] (4) When the output transformer is abnormally started, the equipment can be started directly through the bypass switch to avoid continuous starting failures caused by residual magnetism of the output transformer, thereby improving the reliability of starting. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 It is the main circuit diagram of the high-low-high 6-6 pulse topology thyristor current source type converter circuit;

[0081] Figure 2 It is the DC current transmission equivalent diagram of the output transformer of the current source inverter. DETAILED DESCRIPTION

[0082] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0083] Example 1

[0084] This embodiment introduces a control method for a thyristor current source inverter output transformer, including:

[0085] Obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator, and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC;

[0086] The relationship between the DC current on the high-voltage side of the output transformer and the maximum duration is calculated by using the resistance of the output circuit on the high-voltage side of the SFC and the DC current of a set amplitude pre-applied on the low-voltage side of the SFC;

[0087] The starting torque of the SFC during low-frequency operation is obtained through the DC current on the high-voltage side of the transformer, and the relationship between the SFC starting torque and the maximum duration is calculated;

[0088] Obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle that the SFC can drag the unit to rotate within the set starting torque and its corresponding maximum duration based on the torque drag formula;

[0089] The operation mode of the bypass switch on the output side of the SFC is determined according to the maximum angle of rotation of the unit that can be dragged by the SFC and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

[0090] The control method of the output transformer of the thyristor current source inverter provided in this embodiment specifically involves the following steps:

[0091] (1) Determine the resistance of the SFC high-voltage side output circuit, including the resistance of the high-voltage side winding of the output transformer, the resistance of the stator winding of the generator, and the resistance of the line between the two.

[0092] The resistance parameter R2 of the SFC high-voltage output circuit is the resistance R of the high-voltage winding of the output transformer. T1 , Generator stator resistance R G , output circuit cable or closed bus resistance R L , output circuit breaker (including switch, etc.) contact resistance R DL It can be determined directly through design parameters or obtained through actual measurement. For parts with relatively large changes during operation, actual measurement and a certain margin are required to ensure the reliability of starting.

[0093] (2) According to the design parameters of the output transformer, when the output circuit resistance of the SFC high-voltage side is determined, when a DC current of a certain amplitude is applied to the low-voltage side, the relationship between the amplitude and the maximum duration of the DC current of the output transformer high-voltage side transformer can be determined.

[0094] Combination Figure 2 , the input current I on the low voltage side of the output transformer d1 When the high-voltage side transmits a certain ratio of I d2 , at this time the voltage on the high voltage side is:

[0095]

[0096] Among them: U2 is the voltage on the high-voltage side of the output transformer; N1 and N2 are the number of turns on the low-voltage side and high-voltage side of the output transformer.

[0097] The DC current I applied on the low voltage side of the output transformer d1 , before the transformer is saturated, the induced potential on the high voltage side is:

[0098]

[0099] in: is the maximum flux value that the output transformer can operate, t m is the maximum operating time when passing direct current.

[0100] Since the internal resistance of the high-voltage winding of the output transformer has been equivalent to the output loop resistance R2, U2 = e2, then:

[0101]

[0102] According to the output transformer design:

[0103]

[0104] Among them: U 2N is the rated voltage of the high-voltage side of the output transformer, f N is the rated frequency of the output transformer. From formula (4), we get:

[0105]

[0106] Substituting formula (5) into formula (3), we get:

[0107]

[0108] Formula (6) determines the DC current I on the high-voltage side of the output transformer d2 Relationship with maximum duration t m Inversely proportional and uniquely corresponding.

[0109] (3) When the SFC is running at a low frequency, the amplitude of the unit excitation current is constant, and the SFC starting torque is proportional to the DC current on the high-voltage side of the output transformer. The relationship between the SFC starting torque and the maximum duration can be further determined.

[0110] According to the SFC drag torque formula, the average value of the variable frequency drag torque is:

[0111]

[0112] Where: m is the number of pole pairs of the unit, Ψ is the magnetic flux of the unit, γ0 is the commutation redundancy angle, and μ is the commutation overlap angle.

[0113] In the low frequency stage, SFC adopts pulse commutation mode. Then formula (7) can be simplified as:

[0114]

[0115] in: At the initial start-up of the unit, the unit flux is controlled by the excitation current and remains constant, so kT is a fixed value. Substituting equation (8) into equation (6) yields:

[0116]

[0117] Formula (9) determines the inverter starting torque Td With the maximum duration t m Inversely proportional and uniquely corresponding.

[0118] (4) Determine the starting torque and resistance torque parameters of the unit when starting from a stationary state. Based on the torque drag formula, calculate the maximum angle that the SFC can drag the unit to rotate within the maximum duration corresponding to a certain starting torque.

[0119] According to the principle of torque drag:

[0120]

[0121]

[0122] Where: T d is the starting torque, T r is the resistance torque, Ω is the angular velocity of rotation, and θ is the rotation angle.

[0123] The unit starts from a stationary state, and the starting torque T d , resistance torque T r Approximately unchanged, the unit rotation acceleration Ω is a constant value. Based on formulas (10) and (11), we can get:

[0124]

[0125] θ m The maximum angle that the SFC can drag the unit to rotate before the output becomes saturated.

[0126] (5) Determine the operating mode of the bypass switch on the SFC output side based on the maximum angle of rotation of the unit that can be driven by the SFC, the number of pulses on the machine bridge side, and the number of pole pairs of the unit.

[0127] When the SFC system changes phase once, the unit needs to rotate by:

[0128]

[0129] Where p is the number of pole pairs of the unit; n is the number of pulses on the machine bridge side, n = 6, 12...

[0130] When θ m ≥θ c When the SFC is started, it can always start in the mode without bypass switch, that is, switch the bypass switch to the mode with output transformer. Figure 1 The upper contact position of the bypass switch; when θ m <θ c Otherwise, it is necessary to adjust the initial position of the rotor before starting the commutation interval θ0 (0≤θ0≤θ c) is used to determine that the non-bypass knife switch mode can be used for starting only when the output transformer cannot be saturated in the first two commutation intervals.

[0131] The first camera group needs to rotate by an angle of (θ c -θ0), the time is t1, based on formula (12), we can get:

[0132]

[0133] During the second phase change, the total rotation angle of the unit is (2θ c -θ0), the time is t2, based on formula (12), we can get:

[0134]

[0135] Only when t1 and (t2-t1) are both less than t m When the SFC is started, it can be started directly with the output transformer. Otherwise, the output transformer must be bypassed before starting, that is:

[0136]

[0137] Substituting equations (12), (14), and (15) into (16), we obtain:

[0138]

[0139] The present invention uses the transformer's AC rated parameters for DC current transmission, and on this basis determines the rotation angle of the unit that the inverter can drag before the transformer is saturated, so as to determine whether it is necessary to adopt the bypass output transformer mode to start the unit, which greatly reduces the number of times the bypass switch is opened and closed, effectively avoids the start-up failure caused by the abnormal bypass switch when the inverter starts the unit, and improves the success rate of the unit start-up.

[0140] The above description is only based on the example of a single 6-pulse conversion topology on the inverter side. When the inverter side uses 12-pulse, 18-pulse, 24-pulse and other conversion topologies, its logic is completely similar to that of a single 6-pulse conversion topology. Therefore, the bypass switch control method when the inverter side uses 12-pulse, 18-pulse, 24-pulse and other conversion topologies is also completely within the protection scope of the present invention.

[0141] Example 2

[0142] This embodiment provides a control system for a thyristor current source inverter output transformer, including:

[0143] The first calculation unit is used to obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC;

[0144] The second calculation unit is used to calculate the relationship between the DC current on the high-voltage side of the output transformer and the maximum duration through the resistance of the output circuit on the high-voltage side of the SFC and the DC current of the set amplitude pre-applied on the low-voltage side of the SFC;

[0145] The third calculation unit is used to obtain the starting torque of the SFC when it is running at a low frequency through the DC current on the high-voltage side of the transformer, and calculate the relationship between the SFC starting torque and the maximum duration;

[0146] The fourth calculation unit is used to obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle of rotation of the unit that the SFC can drag based on the torque drag formula within the set starting torque and its corresponding maximum duration;

[0147] The operation mode determination unit is used to determine the operation mode of the bypass switch on the output side of the SFC according to the maximum angle of rotation of the unit that can be dragged by the SFC and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

[0148] Example 3

[0149] This embodiment provides a control device for a thyristor current source inverter output transformer, comprising:

[0150] The first calculation module is used to obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC;

[0151] The second calculation module is used to calculate the relationship between the DC current on the high-voltage side of the output transformer and the maximum duration through the resistance of the output circuit on the high-voltage side of the SFC and the DC current of the set amplitude pre-applied on the low-voltage side of the SFC;

[0152] The third calculation module is used to obtain the starting torque of the SFC when it is running at a low frequency through the DC current on the high-voltage side of the transformer, and calculate the relationship between the SFC starting torque and the maximum duration;

[0153] The fourth calculation module is used to obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle of rotation of the unit that the SFC can drag based on the torque drag formula within the set starting torque and its corresponding maximum duration;

[0154] The operation mode determination module is used to determine the operation mode of the bypass switch on the SFC output side according to the maximum angle of rotation of the SFC-driven unit and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

[0155] Example 4

[0156] This embodiment provides a control device for a thyristor current source inverter output transformer, including a processor and a storage medium;

[0157] The storage medium is used to store instructions;

[0158] The processor is used to operate according to the instructions to execute the steps of the method according to any one of Embodiment 1.

[0159] Example 5

[0160] This embodiment provides a computer-readable storage medium on which a computer program is stored, characterized in that when the program is executed by a processor, the steps of any one of the methods described in Embodiment 1 are implemented.

[0161] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A control method for a thyristor current source inverter output transformer, characterized in that: include: Obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator, and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC; The relationship between the DC current on the high-voltage side of the output transformer and the maximum duration is calculated by using the resistance of the output circuit on the high-voltage side of the SFC and the DC current of a set amplitude pre-applied on the low-voltage side of the SFC; The starting torque of the SFC during low-frequency operation is obtained through the DC current on the high-voltage side of the transformer, and the relationship between the SFC starting torque and the maximum duration is calculated; Obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle that the SFC can drag the unit to rotate within the set starting torque and its corresponding maximum duration based on the torque drag formula; The operation mode of the bypass switch on the output side of the SFC is determined according to the maximum angle of rotation of the unit that can be dragged by the SFC and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

2. The control method of the thyristor current source inverter output transformer according to claim 1, characterized in that: The resistance parameter R2 of the SFC high-voltage side output circuit is the resistance R of the high-voltage side winding of the output transformer. T1 , Generator stator resistance R G , output circuit cable or closed bus resistance R L , output circuit breaker contact resistance R DL twice the sum.

3. The control method of the thyristor current source inverter output transformer according to claim 2, characterized in that: The relationship between the DC current on the high voltage side of the output transformer and the maximum duration is calculated by using the resistance of the output circuit on the high voltage side of the SFC and the DC current of the set amplitude pre-applied on the low voltage side of the SFC, including: Input current I on the low voltage side of the output transformer d1 When the high-voltage side transmits a certain ratio of I d2 , at this time the voltage on the high voltage side is: Among them: U2 is the voltage on the high voltage side of the output transformer; N1 and N2 are the number of turns on the low voltage side and high voltage side of the output transformer; The DC current I applied on the low voltage side of the output transformer d1 , before the transformer is saturated, the induced potential on the high voltage side is: in: is the maximum flux value that the output transformer can operate, t m is the maximum operating time when passing through DC; Since the internal resistance of the high-voltage winding of the output transformer has been equivalent to the output loop resistance R2, U2 = e2, then: According to the output transformer design: Among them: U 2N is the rated voltage of the high-voltage side of the output transformer, f N is the rated frequency of the output transformer, and from formula (4) we get: Substituting formula (5) into formula (3), we get: Formula (6) determines the DC current I on the high-voltage side of the output transformer d2 Relationship with maximum duration t m Inversely proportional and uniquely corresponding.

4. The control method of the thyristor current source inverter output transformer according to claim 3, characterized in that: The method of obtaining the starting torque of the SFC when the SFC is running at a low frequency by using the DC current on the high-voltage side of the transformer, and calculating the relationship between the SFC starting torque and the maximum duration, includes: According to the SFC drag torque formula, the average value of the variable frequency drag torque is: Where: m is the number of pole pairs of the unit, Ψ is the magnetic flux of the unit, γ0 is the commutation redundancy angle, and μ is the commutation overlap angle; In the low frequency stage, SFC adopts pulse commutation mode. Then formula (7) can be simplified as: in: At the initial start-up of the unit, the unit flux is controlled by the excitation current and remains constant, so k T is a fixed value, substituting formula (8) into formula (6) to obtain: Formula (9) determines the inverter starting torque T d With the maximum duration t m Inversely proportional and uniquely corresponding.

5. The control method of the thyristor current source inverter output transformer according to claim 4, characterized in that: The torque-based drag formula calculates the maximum angle of rotation of the SFC-driven unit within the set starting torque and its corresponding maximum duration, including: According to the principle of torque drag: Where: T d is the starting torque, T r is the resistance torque, Ω is the rotation angular velocity, and θ is the rotation angle; The unit starts from a stationary state, and the starting torque T d , resistance torque T r Approximately unchanged, the unit rotation acceleration Ω is a constant value. Based on formulas (10) and (11), we can get: θ m The maximum angle that the SFC can drag the unit to rotate before the output becomes saturated.

6. The control method of the thyristor current source inverter output transformer according to claim 5, characterized in that: Determining the operation mode of the bypass switch on the output side of the SFC according to the maximum angle of rotation of the unit that can be dragged by the SFC and the number of pulses on the bridge side and the number of pole pairs of the unit obtained in advance, includes: When the SFC system changes phase once, the unit needs to rotate by: Where p is the number of pole pairs of the unit; n is the number of pulses on the machine bridge side; When θ m ≥θ c When θ m <θ c When starting, the non-bypass switch mode can be used only when the output transformer cannot be saturated in the first two phase-changing intervals; The first camera group needs to rotate by an angle of (θ c -θ0), the time is t1, based on formula (12), we can get: During the second phase change, the total rotation angle of the unit is (2θ c -θ0), the time is t2, based on formula (12), we can get: Only when t1 and (t2-t1) are both less than t m When the SFC is started, it adopts the direct start mode with output transformer. Otherwise, it needs to start after bypassing the output transformer, that is: Substituting equations (12), (14), and (15) into (16), we obtain:

7. A control system for a thyristor current source inverter output transformer, characterized in that: include: The first calculation unit is used to obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC; The second calculation unit is used to calculate the relationship between the DC current on the high-voltage side of the output transformer and the maximum duration through the resistance of the output circuit on the high-voltage side of the SFC and the DC current of the set amplitude pre-applied on the low-voltage side of the SFC; The third calculation unit is used to obtain the starting torque of the SFC when it is running at a low frequency through the DC current on the high-voltage side of the transformer, and calculate the relationship between the SFC starting torque and the maximum duration; The fourth calculation unit is used to obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle of rotation of the unit that the SFC can drag based on the torque drag formula within the set starting torque and its corresponding maximum duration; The operation mode determination unit is used to determine the operation mode of the bypass switch on the output side of the SFC according to the maximum angle of rotation of the unit that can be dragged by the SFC and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

8. A control device for a thyristor current source inverter output transformer, characterized in that: include: The first calculation module is used to obtain the resistance of the high-voltage side winding of the output transformer, the stator winding resistance of the generator and the resistance of the line between the two, and calculate the resistance of the high-voltage side output circuit of the thyristor current source inverter SFC; The second calculation module is used to calculate the relationship between the DC current on the high-voltage side of the output transformer and the maximum duration through the resistance of the output circuit on the high-voltage side of the SFC and the DC current of the set amplitude pre-applied on the low-voltage side of the SFC; The third calculation module is used to obtain the starting torque of the SFC when it is running at a low frequency through the DC current on the high-voltage side of the transformer, and calculate the relationship between the SFC starting torque and the maximum duration; The fourth calculation module is used to obtain the starting torque and resistance torque parameters of the unit when starting from a stationary state, and calculate the maximum angle of rotation of the unit that the SFC can drag based on the torque drag formula within the set starting torque and its corresponding maximum duration; The operation mode determination module is used to determine the operation mode of the bypass switch on the SFC output side according to the maximum angle of rotation of the SFC-driven unit and the pre-acquired pulse number on the machine bridge side and the number of pole pairs of the unit.

9. A control device for a thyristor current source inverter output transformer, characterized in that: including processor and storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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