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

Abstract

The invention discloses a closed-loop transformer based on a single-core asymmetric phase-shifting transformer and a control method of the closed-loop transformer. The closed-loop transformer comprises a single-core asymmetric phase-shifting transformer bank and a voltage-regulating transformer bank. One end of a primary side winding of the single-core asymmetric phase-shifting transformer is connected with a three-phase power supply, and a center tap serves as the output end of the single-core asymmetric phase-shifting transformer and is connected with the primary side of the voltage regulating transformer. A secondary side winding of the single-core asymmetric phase-shifting transformer is in triangular connection; the other end of the primary side winding 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. Compared with the prior art, the amplitude-phase decoupling adjustment of the voltage phasor difference on the two sides of the loop closing point can be realized, the control rule and the control mode are simple, the wiring mode is simple, the adjustment mode is flexible, the adjustment range is large, and the adjustment precision is high.

Description

Technical Field

[0001] The present invention relates to the technical field of 10KV power distribution network ring-closing power supply, and in particular to a ring-closing transformer based on a single-core asymmetric phase-shifting transformer and a control method thereof. Background Art

[0002] Since the distribution network is directly facing the power users, its structural design, operation mode and maintenance method will be the key factors that directly affect the reliability of power supply. The distribution network currently mainly adopts a closed-loop design and open-loop operation power supply mode. In the daily power supply mode, the connecting switches between the lines are in a disconnected state, which makes the distribution network usually in a radial operation state. When some lines need to be repaired or a fault occurs and the load needs to be reversed, the grid dispatching and operation personnel usually shut down the power for a short time first, and then restore the power supply after the load is reversed, which will cause short-term power outages for power users.

[0003] As users' requirements for power quality and the safety and stability of the power grid are increasing, in order to maintain the public image of the power grid company, the current power grid dispatching and operation personnel usually try their best to meet the users' wishes to achieve load reversal or line maintenance without power outages. Therefore, achieving load reversal without power outages through closing and opening operations has become an indispensable part of the operation of the distribution network.

[0004] The significant benefit of live closing operation in distribution network is that it reduces the power outage time of users, ensures the reliability of power supply, and improves the user's satisfaction with the service of power enterprises. However, as the structure of distribution network becomes more and more complex, the bus parameters on both sides that actually need to be closed are difficult to meet the closing conditions. There is a voltage difference on both sides of the closing point, and the difference in equivalent impedance of the closing path. During the closing operation, a large closing current may be generated in the closing path, including steady-state current and impulse current. The steady-state current generated during the closing process may trigger the overcurrent protection action of the relay protection device, and the impulse current may also trigger the quick-break protection action of the relay protection.

[0005] Therefore, when the distribution network performs the closing operation, it may cause the distribution line to be overloaded, and in severe cases, it may even burn electrical equipment. It may also trigger the relay protection device to malfunction and cause power failure in a larger area. In the worst case, it may even endanger the life safety of power workers, 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 the amplitude-phase decoupling adjustment of the voltage phasor difference on both sides of the closing point to solve the above problems.

[0006] Chinese invention patent CN114884410B discloses a closed-loop power regulation control method based on the polarity and gear position of a phase-shifting transformer. First, according to the amplitude phase angle difference between the voltage to be regulated and the target voltage, the adjustment vector diagram type of the target phase voltage regulation winding and the target phase phase regulation winding is determined, and then the polarity of the target phase voltage regulation winding and the target phase phase regulation winding is determined according to the adjustment vector diagram, and the gear positions corresponding to the target phase voltage regulation winding and the target phase phase regulation winding are calculated. Finally, based on the determined polarity and gear position of the target phase voltage regulation winding and the target phase phase regulation winding, the polarity and gear position of the target phase voltage regulation winding and the target phase phase regulation winding of the phase-shifting transformer are adjusted to achieve accurate adjustment of the second bus voltage phase angle and amplitude, so that it is as close to the first bus voltage as possible, and the voltage vector difference of the power supplies on both sides is minimized when the loop is closed, so as to achieve the purpose of minimizing the closed-loop current, thereby achieving safe closed-loop. Its disadvantage is that the adjustment requirements are divided into four categories, each corresponding to an adjustment vector diagram, the electrical connection between the windings is relatively complex, and the anti-interference ability is limited. Compared with the Chinese invention patent CN114884410B, the present invention has a simple electrical connection relationship, can realize the phase decoupling compensation adjustment of the voltage phasor difference amplitude on both sides of the loop point, has a simple control law and control method, a flexible adjustment method, a large adjustment range and high adjustment accuracy. Summary of the invention

[0007] In order to solve the deficiencies in the prior art, the present invention provides a ring-closing transformer based on a single-core asymmetric phase-shifting transformer and a control method thereof. Specifically, a ring-closing transformer and a single-core asymmetric phase-shifting transformer are connected in series and a control method thereof are provided to solve the problem of phase difference in voltage on both sides of the closing point proposed in the above background technology.

[0008] The present invention adopts the following technical solution. In a first aspect, the present invention provides a ring-closing transformer based on a single-core asymmetric phase-shifting transformer, the ring-closing transformer comprising:

[0009] A single-core asymmetric phase-shifting transformer group and a voltage-regulating transformer group, wherein the primary coil of the single-core asymmetric phase-shifting transformer group is connected to a power supply, and the secondary coil of each phase of the single-core asymmetric phase-shifting transformer respectively outputs a compensation voltage phasor perpendicular to the power supply of the phase;

[0010] The voltage regulating transformer group is connected in series with the single-core asymmetric phase-shifting transformer group to change the voltage amplitude.

[0011] Preferably, the single-core asymmetric phase-shifting transformer group includes: single-core asymmetric phase-shifting transformer phase a, single-core asymmetric phase-shifting transformer phase b and single-core asymmetric phase-shifting transformer phase c; the voltage-regulating transformer group includes: voltage-regulating transformer phase a, voltage-regulating transformer phase b and voltage-regulating transformer phase c;

[0012] The output ends of the a-phase, b-phase and c-phase of the single-core asymmetric phase-shifting transformer are connected to the primary sides of the a-phase, b-phase and c-phase of the voltage regulating transformer;

[0013] The second terminal of the primary winding of phase a of the voltage regulating transformer is grounded; the first terminal of the secondary winding of phase a of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of phase a of the closed-loop transformer. La , the second terminal is grounded;

[0014] The second terminal of the primary winding of the b phase of the voltage regulating transformer is grounded; the first terminal of the secondary winding of the b phase of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of the b phase of the ring transformer. Lb , the second terminal is grounded;

[0015] The second connection terminal of the primary winding of phase c of the voltage regulating transformer is grounded; the first connection terminal of the secondary winding of phase c of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of phase c of the closed-loop transformer. Lc , the second terminal is grounded.

[0016] Preferably, the first connection terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer is unconnected, and the second connection terminal is connected to the phase a power supply U Sa Directly connected, the middle tap is used as the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer 1a Connected to the first terminal of the primary winding of phase a of the voltage regulating transformer; the first terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer is connected to the second terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer, and the second terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer is connected to the first terminal of the secondary winding of phase c of the single-core asymmetric phase-shifting transformer;

[0017] The first terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer is connected to the power supply U Sb Directly connected, the middle tap is used as the output terminal U of the b phase of the single-core asymmetric phase-shifting transformer 1b Connected to the first connection terminal of the primary winding of phase b of the voltage regulating transformer; the first connection terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer is connected to the second connection terminal of the secondary winding of phase c of the single-core asymmetric phase-shifting transformer;

[0018] The first terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer is connected to the power supply U Sc Directly connected, the middle tap is used as the output terminal U of the c phase of the single-core asymmetric phase-shifting transformer 1c It is connected to the first terminal of the primary winding of phase C of the voltage regulating transformer; the first terminal of the secondary winding of phase C of the single-core asymmetric phase-shifting transformer is connected to the second terminal of the secondary winding of phase A of the single-core asymmetric phase-shifting transformer.

[0019] Preferably, the first connection terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase a of the single-core asymmetric phase-shifting transformer. 1a Connected to the first terminal of the primary winding of phase a of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase a power supply U Sa Directly connected;

[0020] The first connection terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase b of the single-core asymmetric phase-shifting transformer. 1b Connect to the first terminal of the primary winding of phase b of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase b power supply U Sb Directly connected;

[0021] The first connection terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase c of the single-core asymmetric phase-shifting transformer. 1c Connected to the first terminal of the primary winding of phase c of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase c power supply U Sc Directly connected.

[0022] Preferably, the first connection terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase a of the single-core asymmetric phase-shifting transformer. 1a The first terminal is connected to the primary winding of the a phase of the voltage regulating transformer, and the second terminal is connected to the a phase power supply U Sa Directly connected, with the middle tap open;

[0023] The first connection terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase b of the single-core asymmetric phase-shifting transformer. 1b The first terminal is connected to the primary winding of the b phase of the voltage regulating transformer, and the second terminal is connected to the b phase power supply U Sb Directly connected, with the middle tap open;

[0024] The first connection terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase c of the single-core asymmetric phase-shifting transformer. 1c The first terminal is connected to the primary winding of the c-phase voltage regulating transformer, and the second terminal is connected to the c-phase power supply U Sc Directly connected, with the middle tap left empty.

[0025] A second aspect of the present invention provides a control method for a ring-closed transformer based on a single-core asymmetric phase-shifting transformer, comprising the following steps:

[0026] S1. Adjust the connection sequence and connection direction of the primary side terminals in the single-core asymmetric phase-shifting transformer or the secondary side terminals in the single-core asymmetric phase-shifting transformer;

[0027] S2, adjust the actual number of turns of the secondary coil in the single-core asymmetric phase-shifting transformer;

[0028] S3, realizing the commutation of the closed-loop phase-shifting transformer.

[0029] Preferably, in step S1, the connection sequence and connection direction of the primary side terminals in the single-core asymmetric phase-shifting transformer are adjusted as follows: the first terminal of the primary side winding of the a-phase of the single-core asymmetric phase-shifting transformer is connected to the a-phase power supply U Sc Directly connected, the middle tap is used as the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer 1a It is connected to the first terminal of the primary winding of phase a of the voltage regulating transformer, and the second terminal is left unconnected;

[0030] The first connection terminal of the b-phase primary winding of the single-core asymmetric phase-shifting transformer is connected to the b-phase power supply U Sb Directly connected, the middle tap is used as the output terminal U of the b phase of the single-core asymmetric phase-shifting transformer 1b It is connected to the first terminal of the primary winding of phase b of the voltage regulating transformer, and the second terminal is left unconnected;

[0031] The first connection terminal of the c-phase primary winding of the single-core asymmetric phase-shifting transformer is connected to the c-phase power supply U Sc Directly connected, the middle tap is used as the output terminal U of the b phase of the single-core asymmetric phase-shifting transformer 1c It is connected to the first terminal of the primary winding of phase c of the voltage regulating transformer, and the second terminal is left unconnected.

[0032] Preferably, in step S1, the connection sequence and connection direction of the primary-side terminals in the single-core asymmetric phase-shifting transformer are adjusted as follows:

[0033] The first terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase a power supply U Sa The second terminal is directly connected to the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer. 1a connected to the first connection terminal of the primary winding of phase a of the voltage regulating transformer;

[0034] The first terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase b power supply U Sb The second terminal is directly connected to the output terminal U of the single-core asymmetric phase-shifting transformer b phase. 1b connected to the first connection terminal of the primary winding of phase b of the voltage regulating transformer;

[0035] The first terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase c power supply U ScThe second terminal is directly connected to the output terminal U of the single-core asymmetric phase-shifting transformer c phase. 1c Connected to the first connection terminal of the primary winding of phase C of the voltage regulating transformer.

[0036] Preferably, in step S1, the connection sequence and connection direction of the secondary side terminals in the single-core asymmetric phase-shifting transformer are adjusted as follows: the first terminal of the secondary side winding of phase a of the single-core asymmetric phase-shifting transformer is directly connected to the second terminal of the secondary side winding of phase c of the single-core asymmetric phase-shifting transformer; the second terminal of the secondary side winding of phase a of the single-core asymmetric phase-shifting transformer is directly connected to the first terminal of the secondary side winding of phase b of the single-core asymmetric phase-shifting transformer; the second terminal of the secondary side winding of phase b of the single-core asymmetric phase-shifting transformer is directly connected to the first terminal of the secondary side winding of phase c of the single-core asymmetric phase-shifting transformer.

[0037] Preferably, in step S2, the actual number of connected turns of the secondary side coil in the single-core asymmetric phase-shifting transformer is the actual number of connected turns of the secondary side coil in the single-core asymmetric phase-shifting transformer when the ring-closed transformer is adjusted in the forward direction.

[0038] Preferably, the actual number of connected turns of the secondary coil in the single-core asymmetric phase-shifting transformer during forward amplitude and phase regulation is solved by the following steps:

[0039] S2.1. Establish a set of equations to describe the constraint relationship between the compensation voltage phasor output by the ring transformer based on the single-core asymmetric phase-shifting transformer and the actual number of turns connected to the secondary coil in the single-core asymmetric phase-shifting transformer;

[0040] S2.2, iteratively solve the ideal access turns ratio of the secondary coil in the single-core asymmetric phase-shifting transformer, and design the initial value of the primary-to-secondary turns ratio;

[0041] S2.3. In order to minimize the second norm of the difference between the compensation voltage vector output by the closed-loop transformer and the actual expected output voltage vector, the actual number of connected turns of the secondary side coil in the single-core asymmetric phase-shifting transformer is dynamically adjusted.

[0042] Preferably, when the three phases are symmetrical, the a phase equation group is as follows:

[0043]

[0044] in It represents the secondary voltage of phase a of the single-core asymmetric phase-shifting transformer. represents the c-phase power supply voltage, Indicates the b-phase power supply voltage, Single-core asymmetric phase-shifting transformer phase a primary voltage, k ETa It represents the primary-to-secondary transformation ratio of phase a of a single-core asymmetric phase-shifting transformer. represents the output voltage of phase a of the single-core asymmetric phase-shifting transformer, k STa It indicates the primary-to-secondary transformation ratio of phase a of the voltage regulating transformer. Indicates the voltage at the output end of phase a of the closed-loop transformer. Indicates the phase angle difference.

[0045] Preferably, step S3 is controlled by table lookup method, and the specific method is as follows:

[0046] Solve the iterative value of the transformation ratio of each phase of the secondary winding coil in the single-core asymmetric phase-shifting transformer;

[0047] Build a simulation model of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer, set different voltage phasor differences on both sides of the closing point, use the transformation ratio iteration value as the simulation parameter value, observe the simulation waveform or simulation data, and compare whether the second norm of the difference between the simulated output voltage phasor and the theoretically calculated output voltage phasor 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 wrong, and re-derive or solve;

[0048] If the theoretically derived values ​​are correct, the corresponding simulation data are recorded in the table. When the closing-loop transformer based on the single-core asymmetric phase-shifting transformer is actually put into operation, the voltage phase difference on both sides of the closing point is detected in real time, and the best transformation ratio data of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer is selected according to the table lookup, and the actual number of connected turns of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer is dynamically adjusted.

[0049] Preferably, step S3 is controlled by a controller, specifically in the following manner:

[0050] Design closed-loop control algorithms;

[0051] When the closed-loop transformer based on the single-core asymmetric phase-shifting transformer is actually put into operation, the voltage phasor difference on both sides of the closing point is obtained through real-time detection, and the phasor difference is input into the controller as a parameter. The controller calculates and outputs control instructions in real time according to the pre-designed 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 asymmetric phase-shifting transformer in real time.

[0052] Compared with the prior art, the beneficial effects of the present invention include at least:

[0053] 1. The closed-loop transformer based on the single-core asymmetric phase-shifting transformer designed by the present invention, that is, the closed-loop transformer composed of a voltage regulating transformer and a single-core asymmetric phase-shifting transformer connected in series, includes a single-core asymmetric phase-shifting transformer and a voltage regulating transformer, wherein the secondary coil of each phase of the single-core asymmetric phase-shifting transformer respectively outputs a compensation voltage phasor perpendicular to the power supply of the phase, and then the voltage amplitude is changed through the voltage regulating transformer group to realize the amplitude-phase decoupling compensation adjustment of the voltage phasors on both sides of the closing point, the compensation method is more flexible and accurate, and the actual closing effect is more ideal.

[0054] 2. The compensating voltage phasor output by the present invention is a voltage phasor 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 present invention can inject a compensating voltage phasor with a controllable phase angle and amplitude under no-load and load conditions by designing a suitable single-core asymmetric phase-shifting transformer and a primary-to-secondary ratio of the voltage-regulating transformer. By dynamically adjusting the actual number of connected turns of the secondary coil of the single-core asymmetric phase-shifting transformer and the primary-to-secondary ratio of the voltage-regulating transformer, the desired compensating voltage phasor can be output, and the voltage phasor difference amplitude-phase decoupling compensation adjustment on both sides of the loop point can be achieved. The control law and control method are simple, the adjustment method is flexible, the adjustment range is large, and the adjustment accuracy is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a topological structure of a ring transformer based on a single-core asymmetric phase-shifting transformer;

[0057] Figure 2 It is a diagram showing the relationship between input and output voltage vectors during forward amplitude and phase regulation of a ring transformer based on a single-core asymmetric phase-shifting transformer;

[0058] Figure 3 It is a diagram showing the relationship between input and output voltage vectors during negative amplitude and phase regulation of a ring transformer based on a single-core asymmetric phase-shifting transformer;

[0059] Figure 4 This is a PSCAD simulation diagram of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer;

[0060] Figure 5 It is a simulation waveform diagram of the output voltage amplitude of phase A of a ring transformer based on a single-core asymmetric phase-shifting transformer;

[0061] Figure 6 This is a simulation waveform diagram of the phase angle of the output voltage of the phase A of a ring transformer based on a single-core asymmetric phase-shifting transformer;

[0062] Figure 7 This is a simulation waveform of the a-phase line current of a ring transformer based on a single-core asymmetric phase-shifting transformer. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0064] like Figure 1 As shown, embodiment 1 of the present invention provides a closed-loop transformer based on a single-core asymmetric phase-shifting transformer, specifically, it is a closed-loop transformer composed of a voltage-regulating transformer and a single-core asymmetric phase-shifting transformer connected in series, including: a single-core asymmetric phase-shifting transformer group and a voltage-regulating transformer group; the single-core asymmetric phase-shifting transformer group includes: a single-core asymmetric phase-shifting transformer phase a, a single-core asymmetric phase-shifting transformer phase b and a single-core asymmetric phase-shifting transformer phase c; 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.

[0065] One end of the primary winding of the single-core asymmetric phase-shifting transformer is connected to a three-phase power supply, the other end is left unconnected, and the middle tap is connected to the primary side of the voltage regulating transformer as the output end of the single-core asymmetric phase-shifting transformer; or, one end of the primary winding of the single-core asymmetric phase-shifting transformer is connected to a three-phase power supply, the other end is connected to the primary side of the voltage regulating transformer as the output end of the single-core asymmetric phase-shifting transformer, and the middle tap is left unconnected; the secondary winding of the single-core asymmetric phase-shifting transformer is connected in a triangle; the other end of the primary winding of the voltage regulating transformer is grounded; one end of the wire of the secondary winding of the voltage regulating transformer is directly led out as the output end of the ring transformer, and the other end is grounded.

[0066] Specifically, the connection relationship of the ring-closing transformer is:

[0067] The second terminal of the primary winding of phase a of the voltage regulating transformer is grounded; the first terminal of the secondary winding of phase a of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of phase a of the closed-loop transformer. La , the second terminal is grounded;

[0068] The second terminal of the primary winding of the b phase of the voltage regulating transformer is grounded; the first terminal of the secondary winding of the b phase of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of the b phase of the ring transformer. Lb , the second terminal is grounded;

[0069] The second connection terminal of the primary winding of phase c of the voltage regulating transformer is grounded; the first connection terminal of the secondary winding of phase c of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of phase c of the closed-loop transformer. Lc , the second terminal is grounded.

[0070] The first terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer is unconnected, and the second terminal is connected to the phase a power supply U Sa Directly connected, the middle tap is used as the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer 1a Connected to the first terminal of the primary winding of phase a of the voltage regulating transformer; the first terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer is connected to the second terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer, and the second terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer is connected to the first terminal of the secondary winding of phase c of the single-core asymmetric phase-shifting transformer;

[0071] The first terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer is connected to the power supply U Sb Directly connected, the middle tap is used as the output terminal U of the b phase of the single-core asymmetric phase-shifting transformer 1b Connected to the first terminal of the primary winding of phase b of the voltage regulating transformer; the first terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer is connected to the second terminal of the secondary winding of phase c of the single-core asymmetric phase-shifting transformer, and the second terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer is connected to the first terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer;

[0072] The first terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer is connected to the power supply U Sc Directly connected, the middle tap is used as the output terminal U of the c phase of the single-core asymmetric phase-shifting transformer 1c Connected to the first terminal of the primary winding of phase C of the voltage regulating transformer; the first terminal of the secondary winding of phase C of the single-core asymmetric phase-shifting transformer is connected to the second terminal of the secondary winding of phase A of the single-core asymmetric phase-shifting transformer, and the second terminal of the secondary winding of phase C of the single-core asymmetric phase-shifting transformer is connected to the first terminal of the secondary winding of phase A of the single-core asymmetric phase-shifting transformer.

[0073] Each phase of the single-core asymmetric phase-shifting transformer outputs a voltage compensation phasor perpendicular to the power supply of that phase. Through the primary-secondary transformation ratio of the single-core asymmetric phase-shifting transformer, the voltage compensation phasor is connected to the voltage regulating transformer as the output of the single-core asymmetric phase-shifting transformer. Then, the voltage compensation phasor of the single-core asymmetric phase-shifting transformer is transformed in amplitude through the voltage regulating transformer, thereby realizing the adjustment of the voltage amplitude and phase value of each phase output end of the ring transformer.

[0074] When the three phases are symmetrical, the vector relationship between the compensation voltage phasor of each phase and the input and output voltage phasor of each phase is as follows: Figure 2As shown, the ring-closing transformer described in this embodiment is in positive amplitude-phase regulation. Taking phase a as an example, the single-core asymmetric phase-shifting transformer phase a outputs a voltage compensation phasor perpendicular to the phase a power supply. Through the primary-secondary transformation ratio of the single-core asymmetric phase-shifting transformer, the voltage compensation phasor is connected to the voltage regulating transformer as the output of the single-core asymmetric phase-shifting transformer. Then, the voltage compensation phasor of the single-core asymmetric phase-shifting transformer is transformed in amplitude through the voltage regulating transformer, thereby realizing the voltage U of the output terminal of the ring-closing transformer based on the single-core asymmetric phase-shifting transformer. La Adjustment of amplitude and phase value.

[0075] It should be noted that Figure 1 The shown closed-loop transformer based on the single-core asymmetric phase-shifting transformer, i.e., the equivalent topological structure of the closed-loop transformer composed of the voltage regulating transformer and the single-core asymmetric phase-shifting transformer in series, is only one of the wiring modes of the preferred but non-limiting implementation mode of the present invention. By changing the connection mode of the primary winding of the single-core asymmetric phase-shifting transformer, the following two modes can be obtained:

[0076] (1) Wiring method 1:

[0077] The first connection terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase a of the single-core asymmetric phase-shifting transformer. 1a Connected to the first terminal of the primary winding of phase a of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase a power supply U Sa Directly connected;

[0078] The first connection terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase b of the single-core asymmetric phase-shifting transformer. 1b Connect to the first terminal of the primary winding of phase b of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase b power supply U Sb Directly connected;

[0079] The first connection terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase c of the single-core asymmetric phase-shifting transformer. 1c Connected to the first terminal of the primary winding of phase c of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase c power supply U Sc Directly connected;

[0080] (2) Wiring method 2:

[0081] The first connection terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase a of the single-core asymmetric phase-shifting transformer. 1a The first terminal is connected to the primary winding of the a phase of the voltage regulating transformer, and the second terminal is connected to the a phase power supply U Sa Directly connected, with the middle tap open;

[0082] The first connection terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase b of the single-core asymmetric phase-shifting transformer. 1b The first terminal is connected to the primary winding of the b phase of the voltage regulating transformer, and the second terminal is connected to the b phase power supply U Sb Directly connected, with the middle tap open;

[0083] The first connection terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase c of the single-core asymmetric phase-shifting transformer. 1c The first terminal is connected to the primary winding of the c-phase voltage regulating transformer, and the second terminal is connected to the c-phase power supply U Sc Directly connected, with the middle tap left empty.

[0084] The single-core asymmetric phase-shifting transformer in the ring-closing transformer composed of a voltage-regulating transformer and a single-core asymmetric phase-shifting transformer connected in series outputs a compensation voltage phasor in each phase, and then the voltage-regulating transformer performs amplitude adjustment. In this way, adjusting the phase first and then adjusting the amplitude can realize amplitude-phase decoupling compensation, and the compensation of the voltage phasor difference on both sides of various closing points is more flexible and accurate, and the actual closing effect is more ideal.

[0085] Embodiment 2 of the present invention provides a control method for a ring-closing transformer based on a single-core asymmetric phase-shifting transformer, comprising the following steps:

[0086] S1. Adjust the connection sequence and connection direction of the primary side terminals in the single-core asymmetric phase-shifting transformer or the secondary side terminals in the single-core asymmetric phase-shifting transformer;

[0087] Specifically, in step S1, the connection sequence and connection direction of the primary-side terminals in the single-core asymmetric phase-shifting transformer are adjusted as follows:

[0088] The second terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer is unconnected, and the first terminal is connected to the phase a power supply U Sa Directly connected, the middle tap is used as the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer 1a connected to the first connection terminal of the primary winding of phase a of the voltage regulating transformer;

[0089] The second terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer is open, and the first terminal is connected to the phase b power supply U Sb Directly connected, the middle tap is used as the output terminal U of the b phase of the single-core asymmetric phase-shifting transformer 1b connected to the first connection terminal of the primary winding of phase b of the voltage regulating transformer;

[0090] The second terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer is unconnected, and the first terminal is connected to the phase c power supply U ScDirectly connected, the middle tap is used as the output terminal U of the c phase of the single-core asymmetric phase-shifting transformer 1c Connected to the first connection terminal of the primary winding of phase C of the voltage regulating transformer.

[0091] In another embodiment, step S1 is to adjust the connection sequence and connection direction of the primary side terminals in the single-core asymmetric phase-shifting transformer as follows:

[0092] The first terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase a power supply U Sa The second terminal is directly connected to the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer. 1a connected to the first connection terminal of the primary winding of phase a of the voltage regulating transformer;

[0093] The first terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase b power supply U Sb The second terminal is directly connected to the output terminal U of the single-core asymmetric phase-shifting transformer b phase. 1b connected to the first connection terminal of the primary winding of phase b of the voltage regulating transformer;

[0094] The first terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase c power supply U Sc The second terminal is directly connected to the output terminal U of the single-core asymmetric phase-shifting transformer c phase. 1c Connected to the first connection terminal of the primary winding of phase C of the voltage regulating transformer.

[0095] In another embodiment, step S1 is to adjust the connection sequence and connection direction of the secondary side terminals in the single-core asymmetric phase-shifting transformer as follows:

[0096] The first connection terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer is directly connected to the second connection terminal of the secondary winding of phase c of the single-core asymmetric phase-shifting transformer; the second connection terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer is directly connected to the first connection terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer; the second connection terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer is directly connected to the first connection terminal of the secondary winding of phase c of the single-core asymmetric phase-shifting transformer.

[0097] S2, adjust the actual number of turns of the secondary coil in the single-core asymmetric phase-shifting transformer;

[0098] Further, in step S2, the actual number of connected turns of the secondary coil in the single-core asymmetric phase-shifting transformer is respectively the actual number of connected turns of the secondary coil in the single-core asymmetric phase-shifting transformer when the closed-loop transformer is adjusted in the forward phase, that is, the tap position is adjusted to change the primary-secondary turns ratio, and the calculation method is as follows:

[0099] S2.1. Establish a set of equations to describe the constraint relationship between the compensation voltage phasor output by the ring transformer based on the single-core asymmetric phase-shifting transformer and the actual number of turns connected to the secondary coil in the single-core asymmetric phase-shifting transformer. Due to the three-phase symmetrical operation of the ring transformer, only one phase needs to be analyzed. Taking phase a as an example, the relevant set of equations is as follows:

[0100]

[0101] in:

[0102] It represents the secondary voltage of phase a of the single-core asymmetric phase-shifting transformer.

[0103] represents the c-phase power supply voltage,

[0104] Indicates the b-phase power supply voltage,

[0105] The primary voltage of phase a of the single-core asymmetric phase-shifting transformer is:

[0106] k ETa It represents the primary-to-secondary transformation ratio of phase a of a single-core asymmetric phase-shifting transformer.

[0107] Represents the output voltage of phase a of the single-core asymmetric phase-shifting transformer,

[0108] k STa It indicates the primary-to-secondary transformation ratio of phase a of the voltage regulating transformer.

[0109] Indicates the voltage at the output end of phase a of the closed-loop transformer.

[0110] Indicates the phase angle difference.

[0111] S2.2, iteratively solve the ideal access turns ratio of the secondary coil in the single-core asymmetric phase-shifting transformer, and design the initial value of the primary-to-secondary turns ratio;

[0112] S2.3. In order to minimize the second norm of the difference between the compensation voltage vector output by the closing transformer and the actual expected output voltage vector, the actual number of connected turns of the secondary coil in the single-core asymmetric phase-shifting transformer is dynamically adjusted, and then the voltage phasor difference on both sides of the closing point is accurately compensated in real time and dynamically to achieve impact-free closing and power supply.

[0113] It is worth noting that the control methods of single-core phase-shifting transformers can be divided into two categories:

[0114] The first type is table lookup. Theoretically, each voltage phasor difference (on both sides of the closing point) corresponds to a voltage compensation phasor, which corresponds to the actual value of the connected turns of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer. First, solve the iterative value of the transformation ratio of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer; then, build the corresponding simulation model of the closing transformer in PSCAD, set different voltage phasor differences on both sides of the closing point, use the iterative value of the transformation ratio as the simulation parameter value, observe the simulation waveform or simulation data, and compare whether the second norm of the difference between the simulation output voltage phasor and the theoretically calculated output voltage phasor is within the allowable error range, and then verify the correctness of the theoretical calculated value of the transformation ratio of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer. If the error between the simulation data obtained by the iterative solution value as the simulation parameter value and the theoretical derivation value is within the allowable range regardless of how the expected compensation voltage phasor changes, it means that the theoretical derivation is correct. If the error is not within the allowable range, it means that the theoretical derivation may be wrong or the iterative solution value is wrong. If correct, record the corresponding simulation data in the table. When the closing transformer is actually put into operation, the voltage phasor difference on both sides of the closing point detected in real time can be used to select the best transformation ratio data of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer according to the table lookup, and the tap of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer can be dynamically adjusted to accurately compensate for the voltage phasor difference on both sides of the closing point, so as to achieve fast, impact-free and safe closing.

[0115] S3, realizing the commutation of the closed-loop phase-shifting transformer.

[0116] The following is an example of verifying a set of ratios: The closed-loop parameter setting values ​​and the theoretical calculated values ​​of some parameters are shown in the first and second columns of Table 1.

[0117] Table 1 Parameter settings and simulation data of flexible loop closing device

[0118]

[0119] in Indicates the effective value of the voltage at the output end of phase a of the closed-loop transformer. Indicates the effective value of phase a power supply, Indicates the effective value of phase a line current.

[0120] Build in PSCAD Figure 4 The transformer model shown in the figure is based on the single-core asymmetric phase-shifting transformer. The output voltage amplitude simulation waveform of the phase a of the ring transformer is as follows: Figure 5 As shown, the verification formula is: where u La,p is the peak value of phase a voltage; the phase angle simulation waveform of phase a output voltage of the ring transformer based on the single-core asymmetric phase-shifting transformer is as follows Figure 6As shown; the simulation waveform of the phase a line current of the ring transformer based on the single-core asymmetric phase-shifting transformer is as follows Figure 7 As shown; the errors between the simulation data and the theoretically derived values ​​are all within the allowable range, so the theoretical calculated values ​​of a set of transformation ratios of each phase secondary coil of the single-core asymmetric phase-shifting transformer are calculated correctly, and the corresponding data are recorded in Table 1.

[0121] The second category is the controller: a closed-loop control algorithm is designed for the closed-loop transformer body. When the closed-loop transformer is actually put into operation, the voltage phasor difference on both sides of the closing point is obtained through real-time detection, and the phasor difference is input into the controller as a parameter. The controller calculates in real time according to the pre-designed closed-loop control algorithm, and outputs control instructions, thereby dynamically adjusting a group of actual connected turn values ​​of the secondary side coils of each phase of the single-core asymmetric phase-shifting transformer in real time to achieve dynamic and accurate compensation of the voltage phasor difference on both sides of the closing point.

[0122] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A ring transformer based on a single-core asymmetric phase-shifting transformer, characterized in that: The ring-closing transformer comprises: A single-core asymmetric phase-shifting transformer group and a voltage-regulating transformer group, wherein the primary coil of the single-core asymmetric phase-shifting transformer group is connected to a power supply, and the secondary coil of each phase of the single-core asymmetric phase-shifting transformer respectively outputs a compensation voltage phasor perpendicular to the power supply of the phase; The voltage regulating transformer group is connected in series with the single-core asymmetric phase-shifting transformer group to change the voltage amplitude.

2. The ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 1 is characterized in that: The single-core asymmetric phase-shifting transformer group includes: single-core asymmetric phase-shifting transformer phase a, single-core asymmetric phase-shifting transformer phase b and single-core asymmetric phase-shifting transformer phase c; the voltage-regulating transformer group includes: voltage-regulating transformer phase a, voltage-regulating transformer phase b and voltage-regulating transformer phase c; The output ends of the a-phase, b-phase and c-phase of the single-core asymmetric phase-shifting transformer are connected to the primary sides of the a-phase, b-phase and c-phase of the voltage regulating transformer; The second terminal of the primary winding of phase a of the voltage regulating transformer is grounded; the first terminal of the secondary winding of phase a of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of phase a of the closed-loop transformer. La , the second terminal is grounded; The second terminal of the primary winding of the b phase of the voltage regulating transformer is grounded; the first terminal of the secondary winding of the b phase of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of the b phase of the ring transformer. Lb , the second terminal is grounded; The second connection terminal of the primary winding of phase c of the voltage regulating transformer is grounded; the first connection terminal of the secondary winding of phase c of the voltage regulating transformer is left unconnected, and the wire is directly led out as the output terminal U of phase c of the closed-loop transformer. Lc , the second terminal is grounded.

3. The ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 2 is characterized in that: The first terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer is unconnected, and the second terminal is connected to the phase a power supply U Sa Directly connected, the middle tap is used as the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer 1a Connected to the first terminal of the primary winding of phase a of the voltage regulating transformer; the first terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer is connected to the second terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer, and the second terminal of the secondary winding of phase a of the single-core asymmetric phase-shifting transformer is connected to the first terminal of the secondary winding of phase c of the single-core asymmetric phase-shifting transformer; The first terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer is connected to the power supply U Sb Directly connected, the middle tap is used as the output terminal U of the b phase of the single-core asymmetric phase-shifting transformer 1b Connected to the first connection terminal of the primary winding of phase b of the voltage regulating transformer; the first connection terminal of the secondary winding of phase b of the single-core asymmetric phase-shifting transformer is connected to the second connection terminal of the secondary winding of phase c of the single-core asymmetric phase-shifting transformer; The first terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer is connected to the power supply U Sc Directly connected, the middle tap is used as the output terminal U of the c phase of the single-core asymmetric phase-shifting transformer 1c Connected to the first connection terminal of the primary winding of phase C of the voltage regulating transformer.

4. The ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 2 is characterized in that: The first connection terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase a of the single-core asymmetric phase-shifting transformer. 1a Connected to the first terminal of the primary winding of phase a of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase a power supply U Sa Directly connected; The first connection terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase b of the single-core asymmetric phase-shifting transformer. 1b Connect to the first terminal of the primary winding of phase b of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase b power supply U Sb Directly connected; The first connection terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase c of the single-core asymmetric phase-shifting transformer. 1c Connected to the first terminal of the primary winding of phase c of the voltage regulating transformer, the second terminal is open, and the middle tap is connected to the phase c power supply U Sc Directly connected.

5. The ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 2 is characterized in that: The first connection terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase a of the single-core asymmetric phase-shifting transformer. 1a The first terminal is connected to the primary winding of the a phase of the voltage regulating transformer, and the second terminal is connected to the a phase power supply U Sa Directly connected, with the middle tap open; The first connection terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase b of the single-core asymmetric phase-shifting transformer. 1b The first terminal is connected to the primary winding of the b phase of the voltage regulating transformer, and the second terminal is connected to the b phase power supply U Sb Directly connected, with the middle tap open; The first connection terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer serves as the output terminal U of phase c of the single-core asymmetric phase-shifting transformer. 1c The first terminal is connected to the primary winding of the c-phase voltage regulating transformer, and the second terminal is connected to the c-phase power supply U Sc Directly connected, with the middle tap left empty.

6. A control method for a ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Adjust the connection sequence and connection direction of the primary side terminals in the single-core asymmetric phase-shifting transformer or the secondary side terminals in the single-core asymmetric phase-shifting transformer; S2, adjust the actual number of turns of the secondary coil in the single-core asymmetric phase-shifting transformer; S3, realizing the commutation of the closed-loop phase-shifting transformer.

7. The control method of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 6 is characterized in that: In step S1, the connection sequence and connection direction of the primary side terminals in the single-core asymmetric phase-shifting transformer are adjusted as follows: The first connection terminal of the a-phase primary winding of the single-core asymmetric phase-shifting transformer is connected to the a-phase power supply U Sa Directly connected, the middle tap is used as the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer 1a It is connected to the first terminal of the primary winding of phase a of the voltage regulating transformer, and the second terminal is left unconnected; The first connection terminal of the b-phase primary winding of the single-core asymmetric phase-shifting transformer is connected to the b-phase power supply U Sb Directly connected, the middle tap is used as the output terminal U of the b phase of the single-core asymmetric phase-shifting transformer 1b It is connected to the first terminal of the primary winding of phase b of the voltage regulating transformer, and the second terminal is left unconnected; The first connection terminal of the c-phase primary winding of the single-core asymmetric phase-shifting transformer is connected to the c-phase power supply U Sc Directly connected, the middle tap is used as the output terminal U of the b phase of the single-core asymmetric phase-shifting transformer 1c It is connected to the first terminal of the primary winding of phase c of the voltage regulating transformer, and the second terminal is left unconnected.

8. The control method of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 6 is characterized in that: In step S1, the connection sequence and connection direction of the primary side terminals in the single-core asymmetric phase-shifting transformer are adjusted as follows: The first terminal of the primary winding of phase a of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase a power supply U Sa The second terminal is directly connected to the output terminal U of the a phase of the single-core asymmetric phase-shifting transformer. 1a connected to the first connection terminal of the primary winding of phase a of the voltage regulating transformer; The first terminal of the primary winding of phase b of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase b power supply U Sb The second terminal is directly connected to the output terminal U of the single-core asymmetric phase-shifting transformer b phase. 1b connected to the first connection terminal of the primary winding of phase b of the voltage regulating transformer; The first terminal of the primary winding of phase c of the single-core asymmetric phase-shifting transformer is open, and the middle tap is connected to the phase c power supply U Sc The second terminal is directly connected to the output terminal U of the single-core asymmetric phase-shifting transformer c phase. 1c Connected to the first connection terminal of the primary winding of phase C of the voltage regulating transformer.

9. The control method of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 6 is characterized in that: In step S1, the connection sequence and connection direction of the secondary side terminals in the single-core asymmetric phase-shifting transformer are adjusted as follows: the first terminal of the secondary side winding of phase a of the single-core asymmetric phase-shifting transformer is directly connected to the second terminal of the secondary side winding of phase c of the single-core asymmetric phase-shifting transformer; the second terminal of the secondary side winding of phase a of the single-core asymmetric phase-shifting transformer is directly connected to the first terminal of the secondary side winding of phase b of the single-core asymmetric phase-shifting transformer; the second terminal of the secondary side winding of phase b of the single-core asymmetric phase-shifting transformer is directly connected to the first terminal of the secondary side winding of phase c of the single-core asymmetric phase-shifting transformer.

10. The control method of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 6, characterized in that: In step S2, the actual number of turns of the secondary coil in the single-core asymmetric phase-shifting transformer is the actual number of turns of the secondary coil in the single-core asymmetric phase-shifting transformer when the ring transformer is adjusted in the forward direction.

11. The control method of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 10, characterized in that: The actual number of turns of the secondary coil in the single-core asymmetric phase-shifting transformer during forward amplitude and phase regulation is solved by the following steps: S2.

1. Establish a set of equations to describe the constraint relationship between the compensation voltage phasor output by the ring transformer based on the single-core asymmetric phase-shifting transformer and the actual number of turns connected to the secondary coil in the single-core asymmetric phase-shifting transformer; S2.2, iteratively solve the ideal access turns ratio of the secondary coil in the single-core asymmetric phase-shifting transformer, and design the initial value of the primary-to-secondary turns ratio; S2.

3. In order to minimize the second norm of the difference between the compensation voltage vector output by the closed-loop transformer and the actual expected output voltage vector, the actual number of connected turns of the secondary side coil in the single-core asymmetric phase-shifting transformer is dynamically adjusted.

12. The control method of a ring-closed transformer based on a single-core asymmetric phase-shifting transformer according to claim 11, characterized in that: When the three phases are symmetrical, the equations of phase a are as follows: in It represents the secondary voltage of phase a of the single-core asymmetric phase-shifting transformer. represents the c-phase power supply voltage, Indicates the b-phase power supply voltage, Single-core asymmetric phase-shifting transformer phase a primary voltage, k ETa It represents the primary-to-secondary transformation ratio of phase a of a single-core asymmetric phase-shifting transformer. represents the output voltage of phase a of the single-core asymmetric phase-shifting transformer, k STa It indicates the primary-to-secondary transformation ratio of phase a of the voltage regulating transformer. Indicates the voltage at the output end of phase a of the closed-loop transformer. Indicates the phase angle difference.

13. The control method of a ring-closed transformer based on a single-core asymmetric phase-shifting transformer according to claim 6, characterized in that: Step S3 uses a table lookup method for control, and the specific method is as follows: Solve the iterative value of the transformation ratio of each phase of the secondary winding coil in the single-core asymmetric phase-shifting transformer; Build a simulation model of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer, set different voltage phasor differences on both sides of the closing point, use the transformation ratio iteration value as the simulation parameter value, observe the simulation waveform or simulation data, and compare whether the second norm of the difference between the simulated output voltage phasor and the theoretically calculated output voltage phasor 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 wrong, and re-derive or solve; If the theoretically derived values ​​are correct, the corresponding simulation data are recorded in the table. When the closing transformer based on the single-core asymmetric phase-shifting transformer is actually put into operation, the voltage phase difference on both sides of the closing point is detected in real time, and the best transformation ratio data of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer is selected according to the table lookup, and the actual number of connected turns of the secondary coils of each phase of the single-core asymmetric phase-shifting transformer is dynamically adjusted.

14. The control method of a ring-closing transformer based on a single-core asymmetric phase-shifting transformer according to claim 6, characterized in that: Step S3 is controlled by a controller, and the specific method is as follows: Design closed-loop control algorithms; When the closed-loop transformer based on the single-core asymmetric phase-shifting transformer is actually put into operation, the voltage phasor difference on both sides of the closing point is obtained through real-time detection, and the phasor difference is input into the controller as a parameter. The controller calculates and outputs control instructions in real time according to the pre-designed 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 asymmetric phase-shifting transformer in real time.

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