Loop closing transformer based on single-core hexagonal phase-shifting transformer and control method thereof

Abstract

The invention discloses a closed-loop transformer based on a single-core hexagonal phase-shifting transformer and a control method of the closed-loop transformer, and belongs to the technical field of closed-loop power supply of a 10KV power distribution network. The closed-loop transformer comprises a single-core hexagonal phase-shifting transformer bank and a voltage-regulating transformer bank. Six windings of the single-core hexagonal phase-shifting transformer are connected in sequence, and the output of the three-phase power supply and the output of the single-core hexagonal phase-shifting transformer are symmetrical according to the center tap of the primary side winding. A first wiring terminal of a primary side winding of the regulating transformer is connected with the output end of the single-core hexagonal phase-shifting transformer, and the other end of the regulating transformer is grounded; a wire at one end of a secondary side winding of the regulating transformer is directly led out as an output end of the closed-loop transformer, and the other end is grounded. Physical isolation of phase angle adjustment and amplitude compensation is achieved, the problem of harmonic superposition caused by amplitude-phase coupling is effectively avoided, the method is suitable for the dynamic stability requirement of a power grid in a high-phase-angle-difference scene, the transformation ratio adjustment process of a voltage regulating transformer is simplified, and the method is suitable for a scene needing quick response.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of 10KV distribution network loop closing power supply, more specifically, relates to a loop closing transformer based on single-core hexagonal phase-shifting transformer and a control method thereof. BACKGROUND

[0002] With the rapid development of national economy, the power users have higher and higher requirements for power supply reliability. In the power system, the distribution network is the part most closely related to the power users, and the power supply reliability problem is a problem that both the power grid company and the power users are concerned about. When some lines of the distribution network need to be repaired or fail to perform load reversal, loop closing operation can be performed to avoid short-term power outage of the power users and ensure the reliability of power supply, but the loop closing operation may also affect the safe and stable operation of the power system, because large steady-state current and impact current may be generated in the process.

[0003] Therefore, the distribution network may be overloaded when performing loop closing operation, and in severe cases, electrical equipment may even be burned out, and the relay protection device may be triggered to malfunction and cause a larger area power failure, and in the most serious case, the life safety of power workers may be endangered, which will pose a great threat to the economic and safe operation of the power grid. Therefore, it is necessary to design a device that can realize amplitude-phase decoupling regulation of the voltage phasor difference on both sides of the loop closing point to solve the above problems.

[0004] Prior art document 1 (CN119109338A) discloses a loop closing transformer based on single-core asymmetric phase-shifting transformer and a control method thereof. The disadvantage is that the amplitude of the output voltage of the single-core asymmetric phase-shifting transformer changes compared to the input voltage due to the existence of the phase shift angle, and when adjusting the turns ratio of the voltage regulating transformer, the voltage amplitude change caused by the phase shift must be considered and compensated. SUMMARY

[0005] To solve the problems in the prior art, the present application provides a loop closing transformer based on single-core hexagonal phase-shifting transformer and a control method thereof, specifically, a loop closing transformer in series with a voltage regulating transformer and a single-core hexagonal phase-shifting transformer and a control method thereof are provided to solve the problem of voltage phasor difference on both sides of the loop closing point proposed in the background art.

[0006] The present application adopts the following technical solutions.

[0007] The first aspect of the present application provides a loop closing transformer based on single-core hexagonal phase-shifting transformer, which comprises a single-core hexagonal phase-shifting transformer group and a voltage regulating transformer group, characterized in that: The six windings of the single-core hexagonal phase-shifting transformer are connected in sequence, the primary side coil of the single-core hexagonal phase-shifting transformer group is connected with a three-phase power supply, and the three-phase power supply and the output of the single-core hexagonal phase-shifting transformer are symmetrical according to the middle tap of the primary side winding of the single-core hexagonal phase-shifting transformer; The single-core hexagonal phase-shifting transformer group comprises a single-core hexagonal phase-shifting transformer a phase, a single-core hexagonal phase-shifting transformer b phase and a single-core hexagonal phase-shifting transformer c phase, and the secondary side coil of each phase of the single-core hexagonal phase-shifting transformer outputs a compensation voltage phase quantity perpendicular to the middle tap voltage of the primary side coil of the phase; The voltage regulating transformer group comprises a voltage regulating transformer a phase, a voltage regulating transformer b phase and a voltage regulating transformer c phase, the first connection terminal of the primary side winding of each phase of the voltage regulating transformer is connected with the output end of the corresponding phase of the single-core hexagonal phase-shifting transformer, and the other end is grounded, so as to change the voltage amplitude; The secondary side winding of each phase of the voltage regulating transformer has one end of a wire directly led out and arranged as an output end of a closed-loop transformer, and the other end is grounded.

[0008] Preferably, the second connection terminal of the primary side winding of each phase of the voltage regulating transformer is grounded. The first connection terminal of the secondary side winding of each phase of the voltage regulating transformer is empty, the wire is directly led out and arranged as the output end of the corresponding phase of the closed-loop transformer, and the second connection terminal is grounded.

[0009] Preferably, the first connection terminal of the primary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected with the first connection terminal of the secondary side winding of the second phase of the single-core hexagonal phase-shifting transformer; the second connection terminal serving as the output end of the first phase of the single-core hexagonal phase-shifting transformer is connected with the first connection terminal of the primary side winding of the first phase of the voltage regulating transformer; the third connection terminal is directly connected with the power supply of the first phase, and the fourth connection terminal is connected with the second connection terminal of the secondary side winding of the third phase of the single-core hexagonal phase-shifting transformer. The first connection terminal of the secondary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected with the first connection terminal of the primary side winding of the third phase of the single-core hexagonal phase-shifting transformer, and the second connection terminal of the secondary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected with the fourth connection terminal of the primary side winding of the second phase of the single-core hexagonal phase-shifting transformer.

[0010] The second aspect of the present application provides a control method of a closed-loop transformer based on a single-core hexagonal phase-shifting transformer, which is applied to the closed-loop transformer based on the single-core hexagonal phase-shifting transformer in the first aspect of the present application, and comprises the following steps: The connection order and connection direction of the primary side connection terminal in the single-core hexagonal phase-shifting transformer and the secondary side connection terminal in the single-core hexagonal phase-shifting transformer are adjusted to obtain the connection mode of the single-core hexagonal phase-shifting transformer; Based on the connection mode of the single-core hexagonal phase-shifting transformer, a constraint relationship between the phase of the compensation voltage and the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer is constructed, and the voltage at the output end of each phase of the loop transformer is obtained; According to the voltage at the output end of each phase of the loop transformer, the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer is dynamically adjusted by a lookup table method or a controller. According to the actual number of turns of the secondary side coil, the voltage phase difference on both sides of the loop point is compensated, and the control of the loop transformer based on the single-core hexagonal phase-shifting transformer is realized.

[0011] Preferably, the connection sequence and connection direction of the primary side wiring terminal in the single-core hexagonal phase-shifting transformer and the secondary side wiring terminal in the single-core hexagonal phase-shifting transformer are adjusted, and the first connection sequence and connection direction specifically includes: The second wiring terminal of the primary side winding of each phase of the single-core hexagonal phase-shifting transformer is directly connected to the power supply of the phase, and the third wiring terminal is connected to the first wiring terminal of the primary side winding of the phase of the voltage regulating transformer as the output end of the phase of the single-core hexagonal phase-shifting transformer.

[0012] Preferably, the connection sequence and connection direction of the primary side wiring terminal in the single-core hexagonal phase-shifting transformer and the secondary side wiring terminal in the single-core hexagonal phase-shifting transformer are adjusted, and the second connection sequence and connection direction specifically includes: The first wiring terminal of the primary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the first wiring terminal of the secondary side winding of the third phase of the single-core hexagonal phase-shifting transformer. The fourth wiring terminal of the primary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the second wiring terminal of the secondary side winding of the second phase of the single-core hexagonal phase-shifting transformer. The first wiring terminal of the secondary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the first wiring terminal of the primary side winding of the second phase of the single-core hexagonal phase-shifting transformer. The second wiring terminal of the secondary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the fourth wiring terminal of the primary side winding of the third phase of the single-core hexagonal phase-shifting transformer. The fourth wiring terminal of the primary side winding of the second phase of the single-core hexagonal phase-shifting transformer is connected to the second wiring terminal of the secondary side winding of the third phase of the single-core hexagonal phase-shifting transformer. The first wiring terminal of the secondary side winding of the second phase of the single-core hexagonal phase-shifting transformer is connected to the first wiring terminal of the primary side winding of the third phase of the single-core hexagonal phase-shifting transformer.

[0013] Preferably, the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer is the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer when the forward amplitude-phase regulation of the looped transformer is performed.

[0014] Preferably, the connection mode based on the single-core hexagonal phase-shifting transformer establishes a constraint relationship between the phase of the compensation voltage and the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer, and obtains the output voltage of each phase of the looped transformer. According to the three-phase symmetrical operation of the looped transformer, the solving process of the output voltage of each phase of the looped transformer includes: solving the output voltage of each phase of the looped transformer according to the product of the primary and secondary side ratio of each phase of the voltage regulating transformer and the output voltage of the corresponding phase of the single-core hexagonal phase-shifting transformer; solving the output voltage of the corresponding phase of the single-core hexagonal phase-shifting transformer according to the sum of the voltage of each phase of the power supply and the compensation voltage of the corresponding phase.

[0015] Preferably, the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer is controlled by the controller according to the output voltage of each phase of the looped transformer, and the dynamic adjustment of the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer includes: solving the iteration value of the ratio of the secondary side coil of each phase of the single-core hexagonal phase-shifting transformer; building a simulation model of the looped transformer based on the single-core hexagonal phase-shifting transformer, setting different voltage phase difference between the two sides of the loop point according to the output voltage of each phase of the looped transformer, taking the iteration value of the ratio as the simulation parameter value, observing the simulation waveform or simulation data, and comparing whether the two-norm of the difference between the simulation output voltage phase and the theoretically calculated output voltage phase is within the allowable error range. If yes, it means that the theoretical derivation value is correct, if not, it means that the equation set is wrong or the iteration solving value is wrong, and the derivation or solving is re-performed; If the theoretical derivation value is correct, the corresponding simulation data is recorded in the table, and when the looped transformer based on the single-core hexagonal phase-shifting transformer is actually put into operation, the best ratio data of the secondary side coil of each phase of the single-core hexagonal phase-shifting transformer is selected according to the real-time detected voltage phase difference between the two sides of the loop point, and the actual number of turns of the secondary side coil of each phase of the single-core hexagonal phase-shifting transformer is dynamically adjusted.

[0016] Preferably, the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer is controlled by the controller according to the output voltage of each phase of the looped transformer, and the dynamic adjustment of the actual number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer includes: When the looped transformer based on the single-core hexagon phase-shifting transformer is actually put into operation, the voltage phase difference between the two sides of the looped point is obtained through the voltage of each phase output end of the looped transformer, the voltage phase difference is taken as a parameter input to the controller, the controller calculates and outputs the control instruction in real time according to the pre-set closed-loop control algorithm, and then the actual turn number of each phase secondary side coil of the single-core hexagon phase-shifting transformer is dynamically adjusted in real time.

[0017] Compared with the prior art, the beneficial effects of the present application at least include: 1、The looped transformer based on the single-core hexagon phase-shifting transformer designed in the present application, that is, the looped transformer in series connection of the voltage regulating transformer and the single-core hexagon phase-shifting transformer, comprises the single-core hexagon phase-shifting transformer and the voltage regulating transformer, wherein the six windings of the single-core hexagon phase-shifting transformer are sequentially connected, and the three-phase power supply and the output of the single-core hexagon phase-shifting transformer are symmetrical according to the middle tap of the primary side winding, so as to realize the change of the voltage phase angle. Then the voltage amplitude is changed through the voltage regulating transformer set, the amplitude-phase decoupling compensation adjustment of the voltage phase of the two sides of the looped point is realized, the compensation mode is more flexible and accurate, and the actual looped effect is more ideal.

[0018] 2、The compensation voltage phase output by the present application is the compensation voltage phase perpendicular to the middle tap voltage of each phase primary side coil of the single-core hexagon phase-shifting transformer and the voltage phase perpendicular to the corresponding phase power supply of the three-phase power supply, and the topological structure and the electrical connection relationship between the windings are relatively simple.

[0019] 3、The present application can inject the compensation voltage phase with controllable phase angle and amplitude under the conditions of no load and load by designing the primary and secondary side turns ratio of the suitable single-core hexagon phase-shifting transformer and the voltage regulating transformer, outputting the expected compensation voltage phase by dynamically adjusting the actual turn number of the secondary side coil of the single-core hexagon phase-shifting transformer and the primary and secondary side turns ratio of the voltage regulating transformer, and realizing the amplitude-phase decoupling compensation adjustment of the voltage phase difference between the two sides of the looped point, the control law and the control mode are simple, the adjustment mode is flexible, the adjustment range is large, and the adjustment precision is high.

[0020] 4、The application realizes the physical isolation of phase angle adjustment and amplitude compensation through the symmetrical winding design of the single-core hexagonal phase-shifting transformer. Compared with the single-core asymmetric phase-shifting transformer, the input and output voltages of the single-core hexagonal phase-shifting transformer have the same amplitude characteristics and only show the difference in phase angle. When adjusting the transformer ratio of the subsequent voltage regulating transformer, there is no need to compensate for the amplitude change caused by the phase shift. The hexagonal winding layout eliminates the need to consider the influence of amplitude fluctuation during phase angle difference adjustment. Through the inherent amplitude stability of the single-core hexagonal phase-shifting transformer, the amplitude compensation required by the single-core asymmetric phase-shifting transformer is eliminated, effectively avoiding the harmonic superposition problem caused by amplitude-phase coupling. This design significantly improves the independence and accuracy of voltage regulation during loop closing operation, especially for power grid dynamic stability requirements in high phase angle difference scenarios, simplifies the transformer ratio adjustment process of the voltage regulating transformer, and is suitable for scenarios that require fast response. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a schematic diagram of the topology of the loop closing transformer based on the single-core hexagonal phase-shifting transformer provided according to an embodiment of the application; Figure 2 is a schematic diagram of the input and output voltage vector relationship of the single-core hexagonal phase-shifting transformer during forward amplitude and phase adjustment according to an embodiment of the application; Figure 3 is a schematic diagram of the input and output voltage vector relationship of the single-core hexagonal phase-shifting transformer during negative amplitude and phase adjustment according to an embodiment of the application; Figure 4 is a schematic diagram of the PSCAD simulation of the loop closing transformer based on the single-core hexagonal phase-shifting transformer according to an embodiment of the application; Figure 5 is a schematic diagram of the a-phase output voltage amplitude simulation waveform of the loop closing transformer based on the single-core hexagonal phase-shifting transformer according to an embodiment of the application; Figure 6 is a schematic diagram of the a-phase output voltage phase angle simulation waveform of the loop closing transformer based on the single-core hexagonal phase-shifting transformer according to an embodiment of the application; Figure 7 is a schematic diagram of the a-phase line current simulation waveform of the loop closing transformer based on the single-core hexagonal phase-shifting transformer according to an embodiment of the application. DETAILED DESCRIPTION

[0022] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present application. The described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the spirit of the present application, all other embodiments obtained by those skilled in the art without creative work shall fall within the protection scope of the present application.

[0023] As shown in Figure 1 Embodiment 1 of the present application provides a closed-loop transformer based on a single-core hexagonal phase-shifting transformer, the closed-loop transformer comprising a single-core hexagonal phase-shifting transformer set and a voltage regulating transformer set, six windings of the single-core hexagonal phase-shifting transformer are connected in sequence, a primary side coil of the single-core hexagonal phase-shifting transformer set is connected with a three-phase power supply, and the three-phase power supply and the output of the single-core hexagonal phase-shifting transformer are symmetrical according to the intermediate tap of the primary side winding of the single-core hexagonal phase-shifting transformer; The single-core hexagonal phase-shifting transformer set comprises a single-core hexagonal phase-shifting transformer a phase, a single-core hexagonal phase-shifting transformer b phase and a single-core hexagonal phase-shifting transformer c phase, and each secondary side coil of the single-core hexagonal phase-shifting transformer outputs a compensation voltage vector perpendicular to the intermediate tap voltage of the primary side coil of the corresponding phase; The voltage regulating transformer set comprises a voltage regulating transformer a phase, a voltage regulating transformer b phase and a voltage regulating transformer c phase, and the output end of the single-core hexagonal phase-shifting transformer a phase, b phase and c phase is connected with the primary side first connection terminal of the voltage regulating transformer a phase, b phase and c phase in correspondence, that is, the first connection terminal of the primary side winding of each phase of the voltage regulating transformer is connected with the output end of the corresponding phase of the single-core hexagonal phase-shifting transformer, and the other end is grounded, the voltage regulating transformer set is connected in series with the single-core hexagonal phase-shifting transformer set, and is used for changing the voltage amplitude; One end of the secondary side winding of the voltage regulating transformer is directly led out as the output end of the closed-loop transformer, and the other end is grounded.

[0024] It is worth noting that, compared with the prior art "forming a fixed magnetic flux path through the secondary side triangular connection, the compensation voltage can only be constrained to a fixed 90° phase difference, and cannot adapt to the power grid working condition with a phase difference not equal to 90°", the present application constructs a hexagonal closed-loop magnetic circuit through "six windings connected in sequence", and each winding is connected at the head and tail to form a rotating magnetic flux path, which breaks through the orthogonal constraint of the triangular connection of the prior art. According to formula 1 of the present application, the hexagonal closed-loop magnetic circuit can generate an adjustable compensation angle, that is, the phase of the compensation voltage in the present application, as shown in Figure 2 and Figure 3 The phase range of the compensation voltage is [-120°, 120°], which breaks the limitation of the prior art that the compensation angle is fixed at 90° due to the triangular connection of the secondary side; Compared with the prior art "secondary side triangle connection" which fixes the compensation angle to 90°, the present application provides a physical basis for dynamic phase adjustment in combination with "symmetry of the middle tap of the primary side winding", according to which Figure 1 It can be seen that the tap can be moved on different connection terminals to realize dynamic adjustment of the phase of the compensation voltage by ±120°. Further preferably, the connection relationship of the voltage regulating transformer comprises: The second connection terminal of the primary side winding of each phase of the voltage regulating transformer is grounded. The first connection terminal of the secondary side winding of each phase of the voltage regulating transformer is empty, and a wire is directly led out as the output end of the corresponding phase of the looped transformer.

[0025] More preferably, the second connection terminal of the primary side winding of phase a of the voltage regulating transformer is grounded; the first connection terminal of the secondary side winding of phase a of the voltage regulating transformer is empty, and a wire is directly led out as the output end of phase a of the looped transformer , and the second connection terminal is grounded. The second connection terminal of the primary side winding of phase b of the voltage regulating transformer is grounded; the first connection terminal of the secondary side winding of phase b of the voltage regulating transformer is empty, and a wire is directly led out as the output end of phase b of the looped transformer , and the second connection terminal is grounded. The second connection terminal of the primary side winding of phase c of the voltage regulating transformer is grounded; the first connection terminal of the secondary side winding of phase c of the voltage regulating transformer is empty, and a wire is directly led out as the output end of phase c of the looped transformer , and the second connection terminal is grounded.

[0026] It is worth noting that in the prior art, the first connection terminal of the secondary side winding of phase a of the single-core asymmetric phase-shifting transformer is connected to the second connection terminal of the secondary side winding of phase b of the single-core asymmetric phase-shifting transformer; the second connection terminal of the secondary side winding of phase a of the single-core asymmetric phase-shifting transformer is connected to the first connection terminal of the secondary side winding of phase c of the single-core asymmetric phase-shifting transformer, and a wire is used to connect the windings into a conductive closed loop. Any disturbance in the power grid is easy to induce current in this loop and circulate and amplify, resulting in limited anti-interference capability. Even if it is also grounded, it is only for safety grounding and cannot eliminate and block the circulating current generated inside the triangle loop, while the present application Figure 1It can be clearly seen that the six windings are not directly connected by wires, but are coupled by the magnetic flux in the core, and each winding is electrically independent of each other, and is magnetically coupled rather than electrically connected, because there is no closed loop for conducting electricity, so there is no physical condition for generating circulating current, and the power grid interference can be limited in a single winding without circulating and amplifying between multiple windings, and because there is no circulating current, the present application further provides a discharge path for unavoidable common-mode interference by limiting the "first connection terminal of the primary side winding of each phase of the voltage regulating transformer is empty, and the wire is directly led out as the output terminal of the corresponding phase of the loop transformer, and the second connection terminal is grounded". Compared with the wire connection of the prior art, the present application avoids the circulating current of the wire connection through magnetic connection, and improves the anti-interference ability.

[0027] In the preferred but non-limiting embodiment of the present application, the first connection terminal of the primary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the first connection terminal of the secondary side winding of the second phase of the single-core hexagonal phase-shifting transformer, the second connection terminal is connected to the first connection terminal of the primary side winding of the first phase of the voltage regulating transformer as the output terminal of the first phase of the single-core hexagonal phase-shifting transformer, the third connection terminal is directly connected to the power supply of the first phase, and the fourth connection terminal is connected to the second connection terminal of the secondary side winding of the third phase of the single-core hexagonal phase-shifting transformer; the first connection terminal of the secondary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the first connection terminal of the primary side winding of the third phase of the single-core hexagonal phase-shifting transformer, and the second connection terminal of the secondary side winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the fourth connection terminal of the primary side winding of the second phase of the single-core hexagonal phase-shifting transformer.

[0028] It is worth noting that the prior art secondary side triangular connection fixes the compensation angle at 90°, although there are two connection sequences, but limited by the triangular structure, the first structure outputs a compensation vector that lags behind the power supply voltage by 90°, and the second structure can only output a compensation vector that leads the power supply voltage by 90°, and cannot realize non-orthogonal compensation, the compensation range is too narrow, the present application selects to switch different connection terminals for tap shifting, in the first connection sequence and connection direction "the second connection terminal of the primary side winding of each phase of the single-core hexagonal phase-shifting transformer is directly connected to the power supply of the phase, and the third connection terminal is connected to the voltage regulating transformer as the output terminal", the magnetic field is symmetrically distributed and outputs the same fixed 90° compensation as the prior art, in the second connection sequence and connection direction "the first connection terminal of the primary side winding of phase a of the single-core hexagonal phase-shifting transformer is connected to the first connection terminal of the secondary side winding of phase c, and the fourth connection terminal is connected to the second connection terminal of the secondary side winding of phase b", it breaks through the orthogonal constraint, dynamically changes the current path and magnetic field distribution of cross-phase coupling, generates a non-orthogonal horizontal compensation voltage component, and realizes dynamic adjustment of the compensation voltage phase within a range of ±120°, thereby improving the phase compensation range of the compensation voltage.

[0029] Further preferably, the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase a is connected to the first connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase b, and the second connection terminal is the output terminal of the single-core hexagonal phase-shifting transformer of phase a The first connection terminal of the primary side winding of the voltage-regulating transformer of phase a is connected to the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase a, the third connection terminal is directly connected to the power supply of phase a, and the fourth connection terminal is connected to the second connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase a The first connection terminal of the primary side winding of the voltage-regulating transformer of phase a is connected to the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase a, the third connection terminal is directly connected to the power supply of phase a, and the fourth connection terminal is connected to the second connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase a The first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase b is connected to the first connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase c, and the second connection terminal is the output terminal of the single-core hexagonal phase-shifting transformer of phase b The first connection terminal of the primary side winding of the voltage-regulating transformer of phase b is connected to the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase b, the third connection terminal is directly connected to the power supply of phase b, and the fourth connection terminal is connected to the second connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase b The first connection terminal of the primary side winding of the voltage-regulating transformer of phase a is connected to the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase a, the third connection terminal is directly connected to the power supply of phase a, and the fourth connection terminal is connected to the second connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase a The first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase c is connected to the first connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase a, and the second connection terminal is the output terminal of the single-core hexagonal phase-shifting transformer of phase c The first connection terminal of the primary side winding of the voltage-regulating transformer of phase c is connected to the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase c, the third connection terminal is directly connected to the power supply of phase c, and the fourth connection terminal is connected to the second connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase c The first connection terminal of the primary side winding of the voltage-regulating transformer of phase a is connected to the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer of phase a, the third connection terminal is directly connected to the power supply of phase a, and the fourth connection terminal is connected to the second connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer of phase a

[0030] The single-core hexagonal phase-shifting transformer outputs a voltage compensation phase quantity perpendicular to the intermediate tap voltage of the primary side winding of the single-core hexagonal phase-shifting transformer for each phase, and the voltage compensation phase quantity is connected to the voltage regulating transformer as the output of the single-core hexagonal phase-shifting transformer through the primary-secondary side transformation ratio of the single-core hexagonal phase-shifting transformer, and then the voltage compensation phase quantity of the single-core hexagonal phase-shifting transformer is transformed in amplitude by the voltage regulating transformer, thereby realizing the adjustment of the amplitude and phase values of the output voltage of the loop transformer.

[0031] When the three phases are symmetrical, the vector relationship between the compensation voltage phase quantity of each phase and the input and output voltage phase quantity of each phase is as shown in Figure 2 and Figure 3 The loop transformer is in forward amplitude and phase adjustment, and the single-core hexagonal phase-shifting transformer outputs a voltage compensation phase quantity perpendicular to the intermediate tap voltage of the primary side winding of the single-core hexagonal phase-shifting transformer for phase a, and the voltage compensation phase quantity is connected to the voltage regulating transformer as the output of the single-core hexagonal phase-shifting transformer through the primary-secondary side transformation ratio of the single-core hexagonal phase-shifting transformer, and then the voltage compensation phase quantity of the single-core hexagonal phase-shifting transformer is transformed in amplitude by the voltage regulating transformer, thereby realizing the adjustment of the amplitude and phase values of the output voltage of the loop transformer based on the single-core hexagonal phase-shifting transformer.

[0032] The single-core hexagonal phase-shifting transformer in the loop transformer connected in series with the voltage regulating transformer outputs a compensation voltage phase quantity for each phase, and then the amplitude is adjusted by the voltage regulating transformer, so that the phase is adjusted first and then the amplitude is adjusted to realize amplitude and phase decoupling compensation, and the compensation of the voltage phase quantity difference on both sides of various loop points is more flexible and accurate, and the actual loop effect is more ideal.

[0033] Embodiment 2 of the present application provides a control method of a loop transformer based on a single-core hexagonal phase-shifting transformer, comprising the following steps: S1, adjusting the connection order and connection direction of the primary side connection terminal in the single-core hexagonal phase-shifting transformer and the secondary side connection terminal in the single-core hexagonal phase-shifting transformer to realize the commutation of the loop phase-shifting transformer and obtain the connection mode of the single-core hexagonal phase-shifting transformer; In the preferred but non-limiting embodiments of the present application, step S1 comprises: Step S1.1, constructing a first connection order and connection direction.

[0034] Further preferably, step S1.1 comprises: The second connection terminal of the primary side winding of each phase of the single-core hexagonal phase-shifting transformer is directly connected to the power supply of the phase, and the third connection terminal is connected to the first connection terminal of the primary side winding of the phase of the voltage regulating transformer as the output terminal of the phase of the single-core hexagonal phase-shifting transformer. ​

[0035] more preferably, the second connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase a is connected to the power supply of phase a directly, the third connection terminal being the output terminal of the single-core hexagonal phase-shifting transformer of phase a to the first connection terminal of the primary winding of the voltage-regulating transformer of phase a; the second connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase b is connected to the power supply of phase b directly, the third connection terminal being the output terminal of the single-core hexagonal phase-shifting transformer of phase b to the first connection terminal of the primary winding of the voltage-regulating transformer of phase b; the second connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase c is connected to the power supply of phase c directly, the third connection terminal being the output terminal of the single-core hexagonal phase-shifting transformer of phase c to the first connection terminal of the primary winding of the voltage-regulating transformer of phase c.

[0036] Step S1.2, constructing a second connection sequence and connection direction.

[0037] Further preferably, step S1.2 comprises: the first connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase one is connected to the first connection terminal of the secondary winding of the single-core hexagonal phase-shifting transformer of phase three; the fourth connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase one is connected to the second connection terminal of the secondary winding of the single-core hexagonal phase-shifting transformer of phase two; the first connection terminal of the secondary winding of the single-core hexagonal phase-shifting transformer of phase one is connected to the first connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase two; the second connection terminal of the secondary winding of the single-core hexagonal phase-shifting transformer of phase one is connected to the fourth connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase three; the fourth connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase two is connected to the second connection terminal of the secondary winding of the single-core hexagonal phase-shifting transformer of phase three; the first connection terminal of the secondary winding of the single-core hexagonal phase-shifting transformer of phase two is connected to the first connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase three.

[0038] more preferably, the first connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase a is connected to the first connection terminal of the secondary winding of the single-core hexagonal phase-shifting transformer of phase c; the fourth connection terminal of the primary winding of the single-core hexagonal phase-shifting transformer of phase a is connected to the second connection terminal of the secondary winding of the single-core hexagonal phase-shifting transformer of phase b; the first connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer a phase is connected with the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer b phase; the second connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer a phase is connected with the fourth connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer c phase; the fourth connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer b phase is connected with the second connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer c phase; the first connection terminal of the secondary side winding of the single-core hexagonal phase-shifting transformer b phase is connected with the first connection terminal of the primary side winding of the single-core hexagonal phase-shifting transformer c phase.

[0039] The physical connection mode of the single-core hexagonal phase-shifting transformer S1 determines the adjustment range of the phase difference in the compensation voltage and the freedom of voltage synthesis. If the first connection sequence and the connection direction are selected, the subsequent adjustment can only be carried out around the fixed phase difference, and only the amplitude of the compensation voltage can be adjusted. The compensation voltage is orthogonal to the power supply voltage, and only the orthogonal compensation is provided. If the second connection sequence and the connection direction are selected, the phase difference can be dynamically adjusted within the range of ±120°.

[0040] S2. Based on the connection mode of the single-core hexagonal phase-shifting transformer S1, the constraint relationship between the compensation voltage phase of the closed-loop transformer output based on the single-core hexagonal phase-shifting transformer and the actual access number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer is constructed, and the voltage at each output end of the closed-loop transformer is obtained.

[0041] In the preferred but non-limiting embodiments of the present application, step S2 comprises: The actual access number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer is the actual access number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer during the forward amplitude and phase adjustment of the closed-loop transformer. Since the closed-loop transformer operates in three-phase symmetry, only one phase needs to be analyzed. Taking phase a as an example, the related equation set is as follows:

[0042] Wherein: V a represents the output end voltage of the single-core hexagonal phase-shifting transformer a phase, V b represents the output end voltage of the single-core hexagonal phase-shifting transformer b phase, V c represents the output end voltage of the single-core hexagonal phase-shifting transformer c phase, V a represents the a phase power supply voltage, V a represents the a phase compensation voltage, V a represents the phase of the a phase compensation voltage, represents the single-core hexagonal phase-shifting transformer a-phase primary side intermediate tap voltage, represents the closed-loop transformer a-phase output terminal voltage, represents the voltage regulating transformer a-phase primary side and secondary side ratio.

[0043] It is worth noting that the a-phase secondary side of the prior art is not determined by the a-phase itself, but is calculated from the power supply voltages of the b-phase and the c-phase, so the output of the a-phase is strongly coupled with the states of the b-phase and the c-phase. To adjust the a-phase, the states of the b-phase and the c-phase must be monitored and calculated at the same time, and any fluctuation (harmonic, voltage sag) of the b-phase or c-phase power grid cannot be independently controlled, which directly interferes with the compensation effect of the a-phase. The output terminal voltage of the a-phase of the present application only needs the power supply voltage of the a-phase itself and the phase angle to be compensated, and adjusting the a-phase does not affect the b-phase and the c-phase at all. The control system can adjust each phase in parallel, independently and quickly. Because the structure of the present application completely decouples the three phases, the power grid disturbance of the b-phase and the c-phase is completely isolated and cannot be transmitted to the a-phase, thereby improving the anti-interference ability of the present application.

[0044] S3, according to the closed-loop transformer each phase output terminal voltage, through the table lookup method or the controller controls the single-core hexagonal phase-shifting transformer dynamically adjusts the actual access number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer; In the preferred but non-limiting embodiments of the present application, S3 comprises: S3.1, according to the closed-loop transformer each phase output terminal voltage, through the table lookup method controls the single-core hexagonal phase-shifting transformer dynamically adjusts the actual access number of turns of the secondary side coil in the single-core hexagonal phase-shifting transformer.

[0045] Further preferably, S3.1 specifically comprises: solving the ratio iteration value of each phase secondary side winding coil in the single-core hexagonal phase-shifting transformer; building a simulation model of the closed-loop transformer based on the single-core hexagonal phase-shifting transformer, setting different voltage phase difference between the two sides of the closed-loop point according to the closed-loop transformer each phase output terminal voltage, taking the ratio iteration value as the simulation parameter value, observing the simulation waveform or simulation data, and comparing whether the two-norm of the difference between the simulation output voltage phase and the theoretically calculated output voltage phase is within the allowable error range, if yes, it means that the theoretical derivation value is correct, if not, it means that the equation set is wrong or the iteration solution value is wrong, and the derivation or solution is re-performed; If the theoretical derivation value is correct, the corresponding simulation data is recorded in the table, and when the looped transformer based on the single-core hexagonal phase-shifting transformer is actually put into operation, according to the voltage phase difference on both sides of the looped point detected in real time, the best variable ratio data of each phase secondary side coil of the single-core hexagonal phase-shifting transformer is selected according to the table, and the actual turn number of each phase secondary side coil of the single-core hexagonal phase-shifting transformer is dynamically adjusted.

[0046] S3.2, according to the voltage at the output end of each phase of the looped transformer, the actual turn number of the secondary side coil in the single-core hexagonal phase-shifting transformer is dynamically adjusted by the controller.

[0047] Further preferably, S3.2 specifically includes: When the looped transformer based on the single-core hexagonal phase-shifting transformer is actually put into operation, the voltage phase difference on both sides of the looped point is obtained through the voltage at the output end of each phase of the looped transformer, the phase difference is taken as a parameter input to the controller, the controller calculates and outputs the control instruction in real time according to the pre-set closed-loop control algorithm, and then the actual turn number of each phase secondary side coil of the single-core hexagonal phase-shifting transformer is dynamically adjusted in real time.

[0048] S4, the voltage phase difference on both sides of the looped point is compensated based on the actual turn number of the secondary side coil, and the control of the looped transformer based on the single-core hexagonal phase-shifting transformer is realized.

[0049] Embodiment 3 of the present application proposes to verify a group of variable ratio examples: the looped parameter setting values and part of the parameter theoretical calculation values are shown in the first column and the second column in Table 1: Table 1 Flexible loop device parameter setting and simulation data table

[0050] Among them, , and respectively represent the primary-secondary side variable ratio of the a phase, the b phase and the c phase of the single-core hexagonal phase-shifting transformer, , and respectively represent the primary-secondary side variable ratio of the a phase, the b phase and the c phase of the voltage regulating transformer, , and respectively represent the output end voltage effective value of the a phase, the b phase and the c phase of the looped transformer, represents the phase angle of the output end voltage of the looped transformer, , and The line current effective value of the a-phase, b-phase and c-phase respectively, , and The line current effective value of the a-phase, b-phase and c-phase respectively.

[0051] The transformer model as shown in Figure 4 is built in PSCAD, the simulation waveform of the closed loop transformer a-phase output voltage amplitude based on the single-core hexagonal phase-shifting transformer is as shown in Figure 5 , and the verification formula is:

[0052] Among them, is the single-core hexagonal phase-shifting transformer a-phase output voltage peak value; The simulation waveform of the closed loop transformer a-phase output voltage phase angle based on the single-core hexagonal phase-shifting transformer is as shown in Figure 6 ; the simulation waveform of the closed loop transformer a-phase line current based on the single-core hexagonal phase-shifting transformer is as shown in Figure 7 ; the error between the simulation data and the theoretical derivation value is within the allowable range, so the theoretical calculation value of the single-core hexagonal phase-shifting transformer each phase secondary side coil of a group of transformation ratio is correct, and the corresponding data is recorded in Table 1.

[0053] Compared with the prior art, the beneficial effects of the present application at least include: 1. The closed loop transformer based on the single-core hexagonal phase-shifting transformer designed in the present application, that is, the closed loop transformer in series connection of the voltage regulating transformer and the single-core hexagonal phase-shifting transformer, comprises the single-core hexagonal phase-shifting transformer and the voltage regulating transformer, wherein the six windings of the single-core hexagonal phase-shifting transformer are sequentially connected, and the three-phase power supply and the output of the single-core hexagonal phase-shifting transformer are symmetrical according to the middle tap of the primary side winding, so as to realize the change of the voltage phase angle. Then the voltage amplitude is changed through the voltage regulating transformer group, the amplitude-phase decoupling compensation adjustment of the voltage phase quantity on both sides of the closed loop point is realized, the compensation mode is more flexible and accurate, and the actual closed loop effect is more ideal.

[0054] 2. The compensation voltage phase quantity output by the present application is a compensation voltage phase quantity perpendicular to the middle tap voltage of the single-core hexagonal phase-shifting transformer each phase primary side coil, and a voltage phase quantity perpendicular to the corresponding phase power supply in the three-phase power supply, and the topological structure and the electrical connection relationship between the windings are relatively simple.

[0055] 3、The application can inject compensation voltage phase quantities with controllable phase angle and amplitude under no-load and load conditions by designing appropriate single-core hexagonal phase-shifting transformer, primary and secondary side turns ratio of the voltage regulating transformer, dynamically adjusting the actual turn number of the single-core hexagonal phase-shifting transformer secondary side coil and the turns ratio of the voltage regulating transformer, and outputting the expected compensation voltage phase quantity, so as to realize amplitude and phase decoupling compensation adjustment of the voltage phase quantity difference on both sides of the closed loop point, and the control law and control mode are simple, the adjustment mode is flexible, the adjustment range is large, and the adjustment precision is high.

[0056] 4、The application realizes physical isolation of phase angle adjustment and amplitude compensation through the symmetric winding design of the single-core hexagonal phase-shifting transformer.

[0057] The present disclosure can be a system, a method, and / or a computer program product. The computer program product can include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present disclosure.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application rather than limit it, and although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered within the protection scope of the claims of the present application.

Claims

1. A ring-closed transformer based on a single-core hexagonal phase-shifting transformer, comprising a single-core hexagonal phase-shifting transformer group and a voltage-regulating transformer group, characterized in that: The six windings of the single-core hexagonal phase-shifting transformer are connected in sequence, the primary coil of the single-core hexagonal phase-shifting transformer group is connected to the three-phase power supply, and the output of the three-phase power supply and the single-core hexagonal phase-shifting transformer are symmetrical according to the center tap of the primary winding of the single-core hexagonal phase-shifting transformer; The single-core hexagonal phase-shifting transformer group includes a single-core hexagonal phase-shifting transformer phase a, a single-core hexagonal phase-shifting transformer phase b, and a single-core hexagonal phase-shifting transformer phase c. The secondary coil of each phase of the single-core hexagonal phase-shifting transformer outputs a compensation voltage phasor perpendicular to the center tap voltage of the primary coil of the phase. The voltage regulating transformer group includes a voltage regulating transformer phase a, a voltage regulating transformer phase b, and a voltage regulating transformer phase c. The first terminal of the primary winding of each phase of the voltage regulating transformer is connected to the output end of the corresponding phase of the single-core hexagonal phase-shifting transformer, and the other end is grounded for changing the voltage amplitude. One end of the secondary winding of each phase of the voltage regulating transformer is directly led out to be set as the output end of the ring transformer, and the other end is grounded.

2. The ring-type transformer based on a single-core hexagonal phase-shifting transformer according to claim 1, characterized in that: The second connection terminal of the primary winding of each phase of the voltage regulating transformer is grounded; The first terminal of the secondary winding of each phase of the voltage regulating transformer is unconnected, the wire is directly led out and is set to the output end of the ring transformer corresponding to the phase, and the second terminal is grounded.

3. The ring-closed transformer based on a single-core hexagonal phase-shifting transformer according to claim 1, characterized in that: The first terminal of the primary winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the first terminal of the secondary winding of the second phase of the single-core hexagonal phase-shifting transformer; the second terminal, as the output end of the first phase of the single-core hexagonal phase-shifting transformer, is connected to the first terminal of the primary winding of the first phase of the voltage regulating transformer; the third terminal is directly connected to the power supply of the first phase, and the fourth terminal is connected to the second terminal of the secondary winding of the third phase of the single-core hexagonal phase-shifting transformer; The first terminal of the secondary winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the first terminal of the primary winding of the third phase of the single-core hexagonal phase-shifting transformer, and the second terminal of the secondary winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the fourth terminal of the primary winding of the second phase of the single-core hexagonal phase-shifting transformer.

4. A control method for a ring-closed transformer based on a single-core hexagonal phase-shifting transformer, operating on a ring-closed transformer based on a single-core hexagonal phase-shifting transformer according to any one of claims 1 to 3, characterized in that: The following steps are involved: Adjusting the connection sequence and connection direction of the primary side terminal in the single-core hexagonal phase-shifting transformer and the secondary side terminal in the single-core hexagonal phase-shifting transformer to obtain a connection mode of the single-core hexagonal phase-shifting transformer; Based on the connection mode of the single-core hexagonal phase-shifting transformer, a constraint relationship between the phase of the compensation voltage and the actual number of turns connected to the secondary coil of the single-core hexagonal phase-shifting transformer is constructed to obtain the output voltage of each phase of the ring-closed transformer; According to the output terminal voltage of each phase of the ring-closing transformer, the actual number of turns connected to the secondary side coil in the single-core hexagonal phase-shifting transformer is dynamically adjusted by controlling the single-core hexagonal phase-shifting transformer through a table lookup method or a controller; According to the actual number of turns of the secondary coil, the voltage phasor difference on both sides of the closing point is compensated to realize the control of the closing transformer based on the single-core hexagonal phase-shifting transformer.

5. The control method of a ring-closed transformer based on a single-core hexagonal phase-shifting transformer according to claim 4, characterized in that: The first connection sequence and connection direction of adjusting the connection sequence and connection direction of the primary side terminal in the single-core hexagonal phase-shifting transformer and the secondary side terminal in the single-core hexagonal phase-shifting transformer specifically include: The second terminal of the primary winding of each phase of the single-core hexagonal phase-shifting transformer is directly connected to the power supply of that phase, and the third terminal serves as the output end of that phase of the single-core hexagonal phase-shifting transformer and is connected to the first terminal of the primary winding of that phase of the voltage regulating transformer.

6. The control method of a ring-closed transformer based on a single-core hexagonal phase-shifting transformer according to claim 4, characterized in that: The second connection sequence and connection direction of adjusting the connection sequence and connection direction of the primary side terminal in the single-core hexagonal phase-shifting transformer and the secondary side terminal in the single-core hexagonal phase-shifting transformer specifically include: The first connection terminal of the primary winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the first connection terminal of the secondary winding of the third phase of the single-core hexagonal phase-shifting transformer; The fourth connection terminal of the primary winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the second connection terminal of the secondary winding of the second phase of the single-core hexagonal phase-shifting transformer; The first connection terminal of the secondary winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the first connection terminal of the primary winding of the second phase of the single-core hexagonal phase-shifting transformer; The second connection terminal of the secondary winding of the first phase of the single-core hexagonal phase-shifting transformer is connected to the fourth connection terminal of the primary winding of the third phase of the single-core hexagonal phase-shifting transformer; The fourth connection terminal of the second phase primary winding of the single-core hexagonal phase-shifting transformer is connected to the second connection terminal of the third phase secondary winding of the single-core hexagonal phase-shifting transformer; The first connection terminal of the secondary winding of the second phase of the single-core hexagonal phase-shifting transformer is connected to the first connection terminal of the primary winding of the third phase of the single-core hexagonal phase-shifting transformer.

7. The control method of a ring-closed transformer based on a single-core hexagonal phase-shifting transformer according to claim 4, characterized in that: The actual number of turns of the secondary coil in the single-core hexagonal phase-shifting transformer is respectively the actual number of turns of the secondary coil in the single-core hexagonal phase-shifting transformer when the ring transformer is adjusted in the forward direction.

8. The control method of a ring-closed transformer based on a single-core hexagonal phase-shifting transformer according to claim 4 or 7, characterized in that: Based on the connection mode of the single-core hexagonal phase-shifting transformer, a constraint relationship between the phase of the compensation voltage and the actual number of turns connected to the secondary coil of the single-core hexagonal phase-shifting transformer is established to obtain the output terminal voltage of each phase of the ring-closing transformer. According to the three-phase symmetrical operation of the ring-closing transformer, the solution process of the output terminal voltage of each phase of the ring-closing transformer includes: The output voltage of each phase of the ring-closing transformer is calculated based on the product of the primary-to-secondary ratio of each phase of the voltage-regulating transformer and the output voltage of the corresponding phase of the single-core hexagonal phase-shifting transformer. The output voltage of the corresponding phase of the single-core hexagonal phase-shifting transformer is calculated based on the sum of the power supply voltage of each phase and the compensation voltage of the corresponding phase.

9. The control method of a ring-closed transformer based on a single-core hexagonal phase-shifting transformer according to claim 4, characterized in that: The method of dynamically adjusting the actual number of turns of the secondary coil in the single-core hexagonal phase-shifting transformer by controlling the single-core hexagonal phase-shifting transformer according to the voltage at each phase output terminal of the ring-closed transformer by a table lookup method specifically includes: Solve the iterative value of the transformation ratio of each phase secondary winding coil in a single-core hexagonal phase-shifting transformer; Build a simulation model of a ring-closing transformer based on a single-core hexagonal phase-shifting transformer. Set different voltage phasor differences on both sides of the closing point according to the output voltage of each phase of the ring-closing transformer. Use the transformation ratio iteration value as the simulation parameter value. Observe the simulation waveform or simulation data. Compare the second norm of the difference between the simulated output voltage phasor and the theoretically calculated output voltage phasor to see if it is within the allowable error range. If so, it means that the theoretically derived value is correct. If not, it means that the equation group is wrong or the iterative solution value is incorrect, and re-derive or solve; If the theoretically derived values ​​are correct, the corresponding simulation data will be recorded in the table. When the ring-closing transformer based on the single-core hexagonal phase-shifting transformer is actually put into operation, the voltage phasor difference on both sides of the closing point is detected in real time, and the optimal transformation ratio data of the secondary side coils of each phase of the single-core hexagonal phase-shifting transformer is selected according to the table lookup, and the actual number of connected turns of the secondary side coils of each phase of the single-core hexagonal phase-shifting transformer is dynamically adjusted.

10. The control method of a ring-closed transformer based on a single-core hexagonal phase-shifting transformer according to claim 4, characterized in that: The method of dynamically adjusting the actual number of turns of the secondary coil in the single-core hexagonal phase-shifting transformer by controlling the single-core hexagonal phase-shifting transformer through the controller according to the output terminal voltage of each phase of the ring-closed transformer specifically includes: When the ring-closing transformer based on the single-core hexagonal phase-shifting transformer is actually put into operation, the voltage phasor difference on both sides of the closing point is obtained through the voltage at the output end of each phase of the ring-closing transformer. This phasor difference is input as a parameter into the controller. The controller calculates and outputs control instructions in real time according to the preset closed-loop control algorithm, and then dynamically adjusts the actual connected turns value of the secondary side coil of each phase of the single-core hexagonal phase-shifting transformer in real time.

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