A stand-alone phase-shifting transformer and a control method thereof

Abstract

This invention discloses an independent phase-shifting transformer and its control method, belonging to the field of power system power flow control technology. The independent phase-shifting transformer includes: a primary winding, a secondary winding, a tertiary winding, and a polarity switch; the primary winding is configured as a delta structure, with the nodes of the delta structure being the excitation points; the secondary and tertiary windings are in a three-phase independent state, connected in series on the lines on both sides of the excitation points; the primary winding is connected in parallel with the secondary and tertiary windings respectively through the polarity switch; the primary winding is used to obtain the excitation voltage from the lines based on the excitation points and synthesize the excitation voltage into a compensation voltage; the polarity switch is used to reverse the phase of the compensation voltage; the secondary winding is used to adjust the source-side tap position, and the tertiary winding is used to adjust the load-side tap position; wherein, based on the coordinated adjustment of the source-side and load-side tap positions, the compensation voltage is subjected to equal-amplitude phase shift, increased-amplitude phase shift, or decreased-amplitude phase shift.

Description

Technical Field

[0001] This invention relates to the field of power flow control technology, and in particular to an independent phase-shifting transformer and its control method. Background Technology

[0002] With the continuous advancement of the construction of new power systems, the grid structure is becoming increasingly complex, and the power flow distribution of the power grid is prone to irrational situations. The access of a large number of new energy sources has further exacerbated the uncontrollability of power flow. Irrational and uncontrollable power flow can easily lead to problems such as a decline in transmission capacity, an increase in network losses, a deterioration in power quality, and difficulties in the absorption of new energy sources. Therefore, power flow control equipment is needed.

[0003] The mainstream power flow regulation technology is the phase-shifting transformer (PST). PST uses electromagnetic windings to obtain the line voltage, regulates and reassembles it to inject a suitable compensation voltage into the system, thereby regulating the power flow. PSTs are widely used globally due to their advantages in economy and regulation capacity. The main types of PSTs are: symmetrical PSTs, "Sen" type PSTs (STs), and stand-alone PSTs. Symmetrical PSTs can only achieve phase regulation without amplitude regulation, thus limiting their capabilities. STs, due to their large number of windings, suffer from lower reliability and economy. Stand-alone PSTs, on the other hand, possess both decoupled amplitude and phase regulation capabilities and low cost, making them the most promising for application.

[0004] However, traditional independent PSTs still have some problems. First, limited by the inductive relationship of the electromagnetic winding, the adjustment range of a traditional independent PST presents a pair of diagonal arcs. When adjusting the zero point or the maximum phase shift angle, the adjustment range shrinks to a single point, creating a diagonal breakage problem, causing the device to lose its amplitude modulation capability. The distorted adjustment range weakens the amplitude and phase decoupling adjustment capability of the independent PST, hindering its further application. Second, due to its unreasonable structure, the adjustment range area of ​​a traditional independent PST is small. At the same time, the adjustment points within the narrow range are sparsely distributed in the large phase shift angle region and clustered in the small phase shift angle region. The narrow adjustment range and uneven distribution of adjustment points reduce the adjustment accuracy of the device, hindering its further application. Summary of the Invention

[0005] This invention provides an independent phase-shifting transformer and its control method, which can solve the technical problem in the prior art where the adjustment range shrinks to a single point when adjusting the zero point or maximum phase shift angle, resulting in diagonal scission, causing the equipment to lose amplitude modulation capability, and the distorted adjustment range weakens the amplitude and phase decoupling adjustment capability of the independent PST.

[0006] The present invention provides an independent phase-shifting transformer for use in power systems, comprising: a primary winding, a secondary winding, a tertiary winding, and a polarity switch; The primary winding is configured as a delta structure, with the nodes of the delta structure serving as excitation points. The secondary and tertiary windings are three-phase independent and are connected in series on the lines on both sides of the excitation point. The primary winding is connected in parallel with the secondary and tertiary windings via the polarity switch. The secondary winding is provided with a source-side tap, and the tertiary winding is provided with a load-side tap. The primary winding is used to obtain the excitation voltage from the line based on the excitation point, and to synthesize the excitation voltage into a compensation voltage. The polarity switch is used to reverse the compensation voltage; The secondary winding is used to adjust the source-side gear, and the tertiary winding is used to adjust the load-side gear; wherein, based on the coordinated adjustment of the source-side gear and the load-side gear, the compensation voltage is subjected to equal-amplitude phase shift, increased-amplitude phase shift, or decreased-amplitude phase shift.

[0007] As a preferred embodiment, the primary winding includes: an A-phase excitation winding, a B-phase excitation winding, and a C-phase excitation winding; The A-phase excitation winding, B-phase excitation winding, and C-phase excitation winding are connected in series in pairs to form a triangular structure.

[0008] As a preferred embodiment, the polarity switch includes: a first polarity switch for phase A, a second polarity switch for phase A, a first polarity switch for phase B, a second polarity switch for phase B, a first polarity switch for phase C, and a second polarity switch for phase C. The excitation point formed by the series connection of the A-phase excitation winding and the B-phase excitation winding is connected to the midpoint of the connection between the C-phase first polarity switch and the C-phase second polarity switch; The excitation point formed by the B-phase excitation winding and the C-phase excitation winding connected in series is connected to the midpoint of the connection between the A-phase first polarity switch and the A-phase second polarity switch; The excitation point formed by the series connection of the A-phase excitation winding and the C-phase excitation winding is connected to the midpoint of the connection between the B-phase first polarity switch and the B-phase second polarity switch.

[0009] As a preferred embodiment, the secondary winding includes: an A-phase source winding, a B-phase source winding, and a C-phase source winding; The A-phase source-side winding and the A-phase first polarity switch are connected in series; the B-phase source-side winding and the B-phase first polarity switch are connected in series; the C-phase source-side winding and the C-phase first polarity switch are connected in series. One end of the A-phase source-side winding is connected to one end of the A-phase first polarity switch; the other end of the A-phase source-side winding is connected to the power supply; the other end of the A-phase first polarity switch is connected to the B-phase excitation winding and the C-phase excitation winding. One end of the B-phase source-side winding is connected to one end of the B-phase first polarity switch; the other end of the B-phase source-side winding is connected to the power supply; the other end of the B-phase first polarity switch is connected to the A-phase excitation winding and the C-phase excitation winding. One end of the C-phase source-side winding is connected to one end of the C-phase first polarity switch; the other end of the C-phase source-side winding is connected to the power supply; the other end of the C-phase first polarity switch is connected to the A-phase excitation winding and the B-phase excitation winding. The source-side windings of phase A, phase B, and phase C are all equipped with the source-side positions.

[0010] As a preferred embodiment, the three-phase winding includes an A-phase load-side winding, a B-phase load-side winding, and a C-phase load-side winding. The load-side winding of phase A and the second polarity switch of phase A are connected in series; the load-side winding of phase B and the second polarity switch of phase B are connected in series; the load-side winding of phase C and the second polarity switch of phase C are connected in series. One end of the load-side winding of phase A is connected to one end of the second polarity switch of phase A; the other end of the load-side winding of phase A is connected to the load; the other end of the second polarity switch of phase A is connected to the excitation winding of phase B and the excitation winding of phase C. One end of the load-side winding of phase B is connected to one end of the second polarity switch of phase B; the other end of the load-side winding of phase B is connected to the load; the other end of the second polarity switch of phase B is connected to the excitation winding of phase A and the excitation winding of phase C. One end of the C-phase load-side winding is connected to one end of the C-phase second polarity switch; the other end of the C-phase load-side winding is connected to the load; the other end of the C-phase second polarity switch is connected to the A-phase excitation winding and the B-phase excitation winding. The load-side positions are all provided on the load-side windings of phase A, phase B, and phase C.

[0011] As a preferred embodiment, the A-phase source-side winding, the A-phase load-side winding, the A-phase first polarity switch, and the A-phase second polarity switch constitute the A-phase circuit; The B-phase source-side winding, the B-phase load-side winding, the B-phase first polarity switch, and the B-phase second polarity switch constitute the B-phase circuit. The C-phase source-side winding, C-phase load-side winding, C-phase first polarity switch, and C-phase second polarity switch constitute the C-phase circuit. In this process, the voltage at the excitation point of any two phases is generated by combining the voltage at the excitation point of the other phase by a preset phase value that either leads or lags behind the voltage at the excitation point of the other phase.

[0012] As a preferred embodiment, the A-phase line further includes: an A-phase thyristor, an A-phase first load voltage regulating switch, and an A-phase second load voltage regulating switch; both the A-phase source-side winding and the A-phase load-side winding are connected to the A-phase thyristor; one end of each of the A-phase first load voltage regulating switch and the A-phase second load voltage regulating switch is connected to the A-phase thyristor; the other end of the A-phase first load voltage regulating switch is connected to the A-phase first polarity switch; and the other end of the A-phase second load voltage regulating switch is connected to the A-phase second polarity switch. The B-phase line further includes: a B-phase thyristor, a B-phase first load voltage regulating switch, and a B-phase second load voltage regulating switch; both the B-phase source-side winding and the B-phase load-side winding are connected to the B-phase thyristor; one end of each of the B-phase first load voltage regulating switch and the B-phase second load voltage regulating switch is connected to the B-phase thyristor; the other end of the B-phase first load voltage regulating switch is connected to the B-phase first polarity switch; and the other end of the B-phase second load voltage regulating switch is connected to the B-phase second polarity switch. The C-phase circuit further includes: a C-phase thyristor, a C-phase first load voltage regulating switch, and a C-phase second load voltage regulating switch; both the C-phase source-side winding and the C-phase load-side winding are connected to the C-phase thyristor; one end of each of the C-phase first load voltage regulating switch and the C-phase second load voltage regulating switch is connected to the C-phase thyristor; the other end of the C-phase first load voltage regulating switch is connected to the C-phase first polarity switch; and the other end of the C-phase second load voltage regulating switch is connected to the C-phase second polarity switch.

[0013] As a preferred embodiment, the A-phase thyristor is used to reverse the positions of the A-phase source-side winding and the A-phase load-side winding; The B-phase thyristor is used to reverse the position of the B-phase source-side winding and the B-phase load-side winding; The C-phase thyristor is used to reverse the position of the C-phase source-side winding and the C-phase load-side winding.

[0014] As a preferred embodiment, the maximum turns ratio between the secondary winding and the tertiary winding is equal, and both the secondary winding and the tertiary winding adopt a uniform gear ratio.

[0015] Accordingly, the present invention also provides a control method for an independent phase-shifting transformer, applied to the independent phase-shifting transformer described in any of the above claims, comprising: Adjust the source-side tap of the secondary winding and the load-side tap of the tertiary winding; Based on the source-side tap and the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform equal-amplitude phase shift, increased-amplitude phase shift, or decreased-amplitude phase shift. Specifically, when the source-side tap and the load-side tap are the same, the compensation voltage of the independent phase-shifting transformer is controlled to perform equal-amplitude phase shift; when the source-side tap is greater than the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform increased-amplitude phase shift; when the source-side tap is less than the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform decreased-amplitude phase shift.

[0016] The following benefits can be obtained by implementing the present invention: 1. This invention provides a novel independent phase-shifting transformer topology that utilizes the coordinated oblique amplitude modulation of the secondary and tertiary windings to achieve decoupled phase amplitude regulation. Compared to traditional independent PSTs, this structure rearranges the induction relationship between the electromagnetic windings, optimizes the equipment's adjustment range, and enhances the amplitude modulation capability when adjusting the zero point or maximum phase shift angle. This results in a more powerful ability to regulate and optimize power flow in power systems and can be widely applied in power flow control operations.

[0017] 2. By changing the connection method of the electromagnetic winding, the compensation path of the series winding compensation voltage is improved, realizing the expansion and bias of the adjustment range. Then, by using a bridge circuit composed of anti-parallel thyristors, the bias adjustment range is flipped, further expanding the adjustment range area and doubling the number of adjustment points, effectively increasing the adjustment accuracy of the equipment. It can be widely used in power systems for applications requiring high power flow regulation accuracy or in the suppression of loop-closing impacts in distribution networks. Attached Figure Description

[0018] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the adjustment range and uneven adjustment points of a traditional independent PST.

[0020] Figure 2 This is a topology diagram of the novel independent phase-shifting transformer proposed in this invention.

[0021] Figure 3 This is a topology diagram of a traditional independent phase-shifting transformer.

[0022] Figure 4 This is a schematic diagram of the regulation principle of a dual independent phase-shifting transformer.

[0023] Figure 5 This is a schematic diagram of the adjustment principle of the novel independent phase-shifting transformer proposed in this invention.

[0024] Figure 6 This is the equivalent circuit diagram of the novel independent phase-shifting transformer proposed in this invention.

[0025] Figure 7 This is the phasor diagram of the novel independent phase-shifting transformer proposed in this invention.

[0026] Figure 8 This is a schematic diagram of the original compensation voltage range of the novel phase-shifting transformer proposed in this invention.

[0027] Figure 9 This is a schematic diagram of the final compensation voltage range of the novel phase-shifting transformer proposed in this invention.

[0028] Figure 10 This is a schematic diagram of the simulation model of the novel phase-shifting transformer proposed in this invention.

[0029] Figure 11 This is a simulation waveform diagram of the novel independent phase-shifting transformer proposed in this invention.

[0030] Figure 12 This is a simulation adjustment point distribution diagram of the novel independent phase-shifting transformer proposed in this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0033] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0035] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0036] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0037] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0038] See Figure 1 This diagram illustrates the distorted adjustment range and uneven adjustment points of a traditional independent PST. Due to the inductive characteristics of its electromagnetic windings, the adjustment range of a traditional independent PST exhibits a diagonal arc-shaped distribution. When adjusting to zero or the maximum phase shift angle, the adjustment range degenerates into a single point, creating a diagonal break and causing the device to lose its amplitude modulation capability. This distorted adjustment range not only weakens the independent PST's ability to decouple amplitude and phase adjustment but also limits its wider application. Secondly, the unreasonable structural design of the traditional independent PST results in a small adjustment range area and an uneven distribution of adjustment points. In the large phase shift angle region, the adjustment points are sparse, while in the small phase shift angle region, they are too dense. This narrow and unevenly distributed adjustment range reduces the device's adjustment accuracy, further hindering its widespread adoption in practical applications.

[0039] The present invention primarily addresses the technical problems existing in the prior art by providing a novel independent phase-shifting transformer topology. By independently adjusting the tap positions of the two series windings, it effectively achieves the combined action of two oblique phase-shifting transformers. It utilizes the coordination of the oblique amplitude modulation effects of the source-side winding and the load-side winding to gain an additional degree of adjustment freedom, thereby realizing the ability to decouple the phase amplitude adjustment of the device. Furthermore, compared to traditional independent PSTs, this device rearranges the inductive relationship between the electromagnetic windings, improves the combination of compensation voltages in the series windings, optimizes the adjustment range of the device, and supplements the amplitude modulation capability when adjusting zero or maximum phase shift angles. This results in a more powerful ability to regulate and optimize system power flow, making it widely applicable in power system power flow control operations.

[0040] Another objective of this invention is to provide a novel independent phase-shifting transformer topology. By changing the connection method of the electromagnetic winding, the compensation path of the series winding compensation voltage is improved, the working principle of the source-side winding and the load-side winding is optimized, and the adjustment range and bias are expanded. Then, by using a bridge circuit composed of anti-parallel thyristors to reverse the positions of the source-side and load-side, the bias adjustment range is flipped, further expanding the adjustment range area and doubling the number of adjustment points. The large adjustment range and the doubled number of adjustment points effectively increase the adjustment accuracy of the equipment, which can be widely used in power systems for applications requiring high power flow regulation accuracy or in the suppression of loop-closing impacts in distribution networks.

[0041] Please see Figure 2 This is an embodiment of the present invention, which provides an independent phase-shifting transformer for use in a power system, including: a primary winding, a secondary winding, a tertiary winding, and a polarity switch.

[0042] The primary winding is configured as a delta structure, with the nodes of the delta structure serving as excitation points. The secondary and tertiary windings are three-phase independent and are connected in series on the lines on both sides of the excitation point. The primary winding is connected in parallel with the secondary and tertiary windings via the polarity switch.

[0043] As a preferred embodiment, the primary winding includes: an A-phase excitation winding, a B-phase excitation winding, and a C-phase excitation winding; the A-phase excitation winding, the B-phase excitation winding, and the C-phase excitation winding are connected in series in pairs to form a triangular structure.

[0044] In a preferred embodiment, the polarity switch includes: a first polarity switch for phase A, a second polarity switch for phase A, a first polarity switch for phase B, a second polarity switch for phase B, a first polarity switch for phase C, and a second polarity switch for phase C; the excitation point formed by the series connection of the excitation windings for phase A and phase B is connected to the midpoint of the connection between the first polarity switch for phase C and the second polarity switch for phase C; the excitation point formed by the series connection of the excitation windings for phase B and phase C is connected to the midpoint of the connection between the first polarity switch for phase A and the second polarity switch for phase A; and the excitation point formed by the series connection of the excitation windings for phase A and phase C is connected to the midpoint of the connection between the first polarity switch for phase B and the second polarity switch for phase B.

[0045] In a preferred embodiment, the secondary winding includes: an A-phase source-side winding, a B-phase source-side winding, and a C-phase source-side winding; the A-phase source-side winding is connected in series with the A-phase first polarity switch; the B-phase source-side winding is connected in series with the B-phase first polarity switch; the C-phase source-side winding is connected in series with the C-phase first polarity switch; one end of the A-phase source-side winding is connected to one end of the A-phase first polarity switch; the other end of the A-phase source-side winding is connected to a power supply; the other end of the A-phase first polarity switch is connected to the B-phase excitation winding and the C-phase excitation winding; the B-phase source-side winding... One end of the phase source-side winding is connected to one end of the B-phase first polarity switch; the other end of the B-phase source-side winding is connected to the power supply; the other end of the B-phase first polarity switch is connected to the A-phase excitation winding and the C-phase excitation winding; one end of the C-phase source-side winding is connected to one end of the C-phase first polarity switch; the other end of the C-phase source-side winding is connected to the power supply; the other end of the C-phase first polarity switch is connected to the A-phase excitation winding and the B-phase excitation winding; the A-phase source-side winding, the B-phase source-side winding, and the C-phase source-side winding are all equipped with the source-side position.

[0046] In a preferred embodiment, the tertiary winding includes an A-phase load-side winding, a B-phase load-side winding, and a C-phase load-side winding; the A-phase load-side winding and the A-phase second polarity switch are connected in series; the B-phase load-side winding and the B-phase second polarity switch are connected in series; the C-phase load-side winding and the C-phase second polarity switch are connected in series; one end of the A-phase load-side winding is connected to one end of the A-phase second polarity switch; the other end of the A-phase load-side winding is connected to the load; the other end of the A-phase second polarity switch is connected to the B-phase excitation winding and the C-phase excitation winding; the B-phase load-side winding... One end of the phase load-side winding is connected to one end of the B-phase second polarity switch; the other end of the B-phase load-side winding is connected to the load; the other end of the B-phase second polarity switch is connected to the A-phase excitation winding and the C-phase excitation winding; one end of the C-phase load-side winding is connected to one end of the C-phase second polarity switch; the other end of the C-phase load-side winding is connected to the load; the other end of the C-phase second polarity switch is connected to the A-phase excitation winding and the B-phase excitation winding; the A-phase load-side winding, the B-phase load-side winding, and the C-phase load-side winding are all equipped with load-side positions.

[0047] The core breakthrough of this invention in terms of topology lies first in the comprehensive reconstruction of the spatial layout and electrical connections of the primary, secondary, and tertiary windings. The primary winding is innovatively configured as a closed triangular structure. This design not only meets the basic requirements of suppressing third harmonics and zero-sequence current to improve power quality in conventional transformers, but more importantly, it utilizes the three natural vertices formed by the physical closed loop of this triangular structure as excitation nodes directly connected to the transmission line. By directly obtaining the line voltage as the excitation source based on these nodes, the device can obtain the most robust and phase-fixed base excitation voltage without increasing the size and cost of the excitation transformer, thus laying a solid energy and reference phase foundation for subsequent complex phasor synthesis.

[0048] In the configuration design of the secondary winding (source-side voltage regulating unit) and the tertiary winding (load-side voltage regulating unit), this invention abandons the traditional electrical coupling and adopts a completely independent, isolated three-phase design. The secondary and tertiary windings are electrically embedded in series in the main transmission line on both sides of the primary excitation point. This independent and symmetrical series embedding mode gives the equipment an excellent ability to intervene in the power flow of the line in a "two-way, bidirectional, and independent" manner. The secondary winding, which is closer to the power grid input end, focuses on capturing and modulating the voltage state of the source side; while the tertiary winding, which is closer to the receiving area, sensitively responds to and regulates the voltage demand of the load side.

[0049] Most importantly, this invention cleverly introduces multiple highly reliable polarity switch matrices between the primary winding and the secondary and tertiary windings. The polarity switches are not simply on / off control elements, but rather function as "commutators" for the phasor direction of the compensation voltage. Through precise commands issued by the control system, the polarity switches can instantly change the start-end polarity connection between the secondary or tertiary winding and the primary excitation winding. When the system determines that an overall reverse operation of the injected compensation voltage is required to reverse the power flow, the polarity switches operate synchronously, achieving a smooth reversal of the external compensation voltage vector without altering the continuity of the transformer's internal magnetic flux. The source-side tap adjustment mechanism embedded in the secondary winding and the load-side tap adjustment mechanism embedded in the tertiary winding perform fine-grained amplitude scaling based on the vector direction reference set by the polarity switches. By coordinating the source-side tap depth of the secondary side, the load-side tap depth of the tertiary side, and the conduction state of the polarity switch, this topology can robustly synthesize various complex compensation voltages for equal-amplitude phase shift, increasing-amplitude phase shift, or decreasing-amplitude phase shift within an extremely high safety boundary that does not cause short-circuit impact on the main power grid, thus completely revitalizing the control dimensions of the phase-shifting transformer.

[0050] In a preferred embodiment, the A-phase source-side winding, A-phase load-side winding, A-phase first polarity switch, and A-phase second polarity switch constitute the A-phase circuit; the B-phase source-side winding, B-phase load-side winding, B-phase first polarity switch, and B-phase second polarity switch constitute the B-phase circuit; and the C-phase source-side winding, C-phase load-side winding, C-phase first polarity switch, and C-phase second polarity switch constitute the C-phase circuit. Any two phase circuits can be combined to generate a preset phase value in which the excitation point voltage of the other phase leads or lags behind that voltage.

[0051] As a preferred embodiment, the A-phase line further includes: an A-phase thyristor, an A-phase first load voltage regulating switch, and an A-phase second load voltage regulating switch; both the A-phase source-side winding and the A-phase load-side winding are connected to the A-phase thyristor; one end of each of the A-phase first load voltage regulating switch and the A-phase second load voltage regulating switch is connected to the A-phase thyristor; the other end of the A-phase first load voltage regulating switch is connected to the A-phase first polarity switch; and the other end of the A-phase second load voltage regulating switch is connected to the A-phase second polarity switch. The B-phase line further includes: a B-phase thyristor, a B-phase first load voltage regulating switch, and a B-phase second load voltage regulating switch; both the B-phase source-side winding and the B-phase load-side winding are connected to the B-phase thyristor; one end of each of the B-phase first load voltage regulating switch and the B-phase second load voltage regulating switch is connected to the B-phase thyristor; the other end of the B-phase first load voltage regulating switch is connected to the B-phase first polarity switch; and the other end of the B-phase second load voltage regulating switch is connected to the B-phase second polarity switch. The C-phase circuit further includes: a C-phase thyristor, a C-phase first load voltage regulating switch, and a C-phase second load voltage regulating switch; both the C-phase source-side winding and the C-phase load-side winding are connected to the C-phase thyristor; one end of each of the C-phase first load voltage regulating switch and the C-phase second load voltage regulating switch is connected to the C-phase thyristor; the other end of the C-phase first load voltage regulating switch is connected to the C-phase first polarity switch; and the other end of the C-phase second load voltage regulating switch is connected to the C-phase second polarity switch.

[0052] The coordinated operation logic of the six-phase polarity switches is as follows: the first and second polarity switches in each phase circuit switch in coordination to change the polarity connection relationship between the source-side winding and the load-side winding and the excitation point of that phase. Specifically, when the first and second polarity switches are in the forward conduction position, the synthesized compensation voltage and the excitation voltage maintain positive coordination; when the control system needs to reverse the compensation voltage, the first and second polarity switches are switched to the reverse conduction position, so that the connection terminals of the source-side winding and the load-side winding are reversed, thereby flipping the generated compensation voltage vector by 180 degrees. Combined with the adjustment of the source-side and load-side taps, full-quadrant constant amplitude, increasing amplitude, or decreasing amplitude phase shift control is achieved.

[0053] It should be noted that the independent PST in this embodiment of the invention also uses a single-core three-winding transformer. The primary winding is set in a delta connection, and the delta node is connected to the line as the excitation point. The excitation voltage is obtained from the line as the source of the compensation voltage. The A-phase excitation winding is connected to the B-phase line and the C-phase line. Because the voltage of the B-phase excitation point and the C-phase excitation point lags behind and leads the A-phase excitation point voltage by 120° respectively, the A-phase excitation winding voltage generated by the two will lead or lag the A-phase excitation point voltage by 90°. The same applies to the excitation voltages of the B-phase and C-phase.

[0054] The secondary and tertiary windings are three-phase independent and equipped with load tap changers. The secondary and tertiary windings are connected in series on the lines on both sides of the excitation point. The compensation voltage is introduced into the lines by electromagnetic induction. The winding closer to the power source of the power system is the source-side winding, and the winding closer to the load of the power system is the load-side winding.

[0055] It should be noted that the stand-alone PST in this embodiment is different from that in other embodiments. Figure 3 Traditional stand-alone PST and Figure 4Unlike the dual independent PST, in traditional independent PSTs and dual independent PSTs, the source-side winding and load-side winding of a single phase line are induced by the excitation winding of the current phase. However, in the independent PST of this embodiment, the source-side winding is induced by the excitation winding that leads the current phase, while the load-side winding is induced by the excitation winding that lags the current phase. For the A phase line, its source-side winding induces the C phase excitation winding, and the load-side winding induces the B phase excitation winding. Therefore, the voltage of the source-side winding lags the excitation point voltage by 30°, while the voltage of the load-side winding leads the excitation point voltage by 30°. The same applies to the B and C phase lines. Traditional independent PSTs and dual independent PSTs have the same compensation path for the source-side winding and the load-side winding. Therefore, when the phase shifting effects of the two are offset, the amplitude modulation ratio will inevitably cancel each other out. This manifests as a sharp weakening or loss of amplitude modulation function within a small phase shift angle range, distortion of the adjustment range into a vertical angle, and severe deterioration of adjustment performance. However, the independent phase shifter in this embodiment changes the voltage source of the source-side winding and the load-side winding through structural innovation, realizing the offsetting of their compensation paths. Even when the phase shifts cancel each other out, the amplitude can still be adjusted. Within a small phase shift angle region, the adjustment range can still completely cover the entire range without degenerating into a vertical angle, resulting in superior performance.

[0056] The reason why this invention can completely eradicate the persistent problem of traditional independent phase-shifting transformers losing amplitude modulation capability at zero-degree phase shift or extreme phase shift angles lies in its innovative construction of a new type of induction link of "cross-phase cross electromagnetic coupling". Taking any phase in the system (e.g., phase A line) as an example for in-depth analysis, in the traditional scheme, the source-side and load-side windings of phase A can only be helplessly constrained by the single magnetic flux linkage of the phase A excitation winding. However, under the ingenious design of this invention, the physical routing of phase A and electromagnetic induction are forcibly separated: the source-side winding in phase A line is spatially arranged at a position that can strongly electromagnetically couple with the excitation winding that leads the current phase (i.e., phase C excitation winding); at the same time, the load-side winding in phase A line is precisely arranged at a position that can electromagnetically couple with the excitation winding that lags the current phase (i.e., phase B excitation winding).

[0057] This unconventional cross-induction topology has given rise to a remarkably powerful technological effect in physical phasor space: For phase A, the compensation voltage vector induced on its secondary side (source side) naturally lags behind the excitation point reference voltage of phase A by a fixed and significant angle (i.e., 30 degrees) in spatial phase; while the compensation voltage vector induced on its tertiary side (load side) naturally leads the excitation point reference voltage of phase A by the same angle (i.e., 30 degrees). This means that the compensation voltages injected into the line by the source-side winding and the load-side winding no longer involve simple scalar addition and subtraction along the same straight line, but rather a complex vector synthesis along two oblique spatial paths with a fixed angle between them.

[0058] This staggered compensation path is key to achieving true physical decoupling between amplitude modulation and phase modulation. When the control system issues an extreme command to maintain the phase angle and only adjust the bus voltage amplitude, the phase shift effects generated by the source-side winding and the load-side winding precisely cancel each other out in phasor synthesis. However, due to the physical angle between their action paths, their amplitude projection components along the excitation voltage direction not only do not cancel each other out, but instead form an effective vector superposition. It is this uncancellable residual amplitude component that allows the equipment to maintain ample amplitude modulation voltage output capability even in extreme blind zones with any small phase shift angle or even zero phase shift angle, fundamentally filling the "diagonal breaking" loophole caused by overlapping compensation paths in traditional equipment. As long as the source-side winding and the load-side winding cooperate, this synergy based on the oblique amplitude modulation mechanism ensures that the equipment always maintains a full and continuous voltage regulation boundary across the entire operating range, exhibiting extremely superior and dead-zone-free power flow optimization performance.

[0059] In the novel topology proposed in this invention, the primary winding adopts a delta connection. This structure not only provides a stable excitation reference for the entire transformer, but more importantly, it cleverly utilizes the delta nodes as excitation points to achieve an inherent voltage phase shift between phases. Taking phase A as an example, its core innovation lies in completely breaking the traditional thinking of "phase-to-phase induction". The source-side winding of phase A is configured to induce electromagnetic induction with the phase C excitation winding, which leads phase A by 120°, while the load-side winding of phase A is configured to induce electromagnetic induction with the phase B excitation winding, which lags phase A by 120°. This cross-induction connection method ensures that the compensation voltage vector obtained by the phase A source-side winding naturally lags behind the phase A excitation point voltage by 30°, while the compensation voltage vector obtained by the phase A load-side winding naturally leads the phase A excitation point voltage by 30°.

[0060] This 60° phase offset in the compensation path is the physical basis for optimizing the adjustment range. When the independent phase-shifting transformer in this embodiment operates under small phase-shift angle conditions, or even when the phase-shifting demand is completely offset (i.e., the overall phase-shift angle is zero), because the source-side compensation voltage and the load-side compensation voltage are no longer collinear in the complex plane, they can still generate an effective amplitude component along the excitation voltage direction through vector synthesis. This means that the amplitude regulation ratio of the source-side winding and the load-side winding no longer directly physical opposes each other as in traditional structures, and the equipment maintains a strong amplitude regulation capability throughout the entire phase range, fundamentally eliminating the "vertical angle" type adjustment dead zone.

[0061] Furthermore, this non-perpendicular compensation voltage injection method leads to an asymmetry in the leading and lagging directions of the regulation range (i.e., regulation range bias), specifically, the lagging regulation range is significantly larger than the leading regulation range. To turn this disadvantage into an absolute advantage, this invention cleverly introduces an anti-parallel bridge commutation circuit composed of A-phase thyristors, B-phase thyristors, and C-phase thyristors and their matching on-load tap changers. When the system needs to perform large-scale leading regulation, the connection positions of the source-side winding and the load-side winding are directly reversed on the physical link by controlling the thyristor conduction logic. This reversal operation is equivalent to a perfect mirror flip of the biased regulation range along the real axis (X-axis) on the phasor diagram. By superimposing the regulation ranges before and after the flip, the novel independent PST ultimately forms a huge and highly symmetrical "butterfly-shaped" regulation domain. This not only significantly expands the overall effective regulation area but also directly doubles the number of available regulation range combination points, laying a solid hardware foundation for achieving ultra-high precision control of power system power flow.

[0062] Furthermore, in this embodiment, the maximum turns ratio of the source-side winding and the load-side winding are equal and both use uniform turns. Because the compensation voltages of the two are symmetrical relative to the excitation point voltage, equal amplitude phase shift can be achieved when the turns of the source-side winding and the load-side winding are the same. Thus, when the turns of the source-side winding are greater than those of the load-side winding, increased amplitude phase shift can be achieved, and when the turns of the source-side winding are less than those of the load-side winding, decreased amplitude phase shift can be achieved. Polarity switches are provided on the source-side winding and the load-side winding.

[0063] Furthermore, the independent PST in this embodiment is also equipped with a polarity switch. By toggling the polarity switch, the compensation voltage can be reversed, thereby enabling lead and lag adjustment of the system voltage phase. Meanwhile, because the source-side and load-side compensation voltages of traditional independent PSTs and dual independent PSTs are perpendicular to the excitation point voltage, meaning their compensation paths overlap, when the phase shift angle is 0, the voltages before and after adjustment are equal, resulting in no amplitude modulation capability—the cause of diagonal breaking. However, for the new independent PST, the compensation paths are not the same, and even when their phases clash, amplitude modulation can still occur. Figure 5 As shown, the amplitude modulation capability of the equipment when adjusting the zero point or the maximum phase shift angle has been successfully improved.

[0064] Furthermore, since the compensation voltage of the independent PST in this embodiment is no longer perpendicular to the line excitation point voltage, such as Figure 6As shown, the lead and lag regulation effects of the series windings are no longer asymmetrical. Both the source-side and load-side windings exhibit a large lag regulation range and a small lead regulation range. Therefore, the regulation range of the independent PST in this embodiment is no longer positive and negative symmetrical, and the lead regulation area is smaller than the lag regulation area, resulting in a regulation range bias. The independent PST in this embodiment uses a bridge circuit composed of anti-parallel thyristors to connect the equipment and the line. By controlling the conducting arms of the bridge circuit, the connection direction of the source side and the load side can be changed, thereby reversing the operation of the source-side winding and the load-side winding. The original leading adjustment becomes lagging adjustment, and the lagging adjustment becomes leading adjustment. The adjustment range will also be flipped relative to the X-axis, ultimately achieving positive and negative symmetry of the adjustment range and adjustment points. Because the original adjustment range was biased, the flipping effect will greatly expand the adjustment area and double the adjustment points. The traditional independent PST has a positive and negative symmetry in its adjustment range, so it cannot achieve this effect and advantage. The large adjustment range and doubled adjustment points of the new independent PST effectively increase the adjustment accuracy of the equipment, achieving a high degree of self-consistency in the topology design.

[0065] It is understood that the independent PST in this embodiment realizes independent adjustment of voltage amplitude and phase, makes up for the amplitude adjustment defects of traditional independent PST when adjusting zero point and large phase shift angle, optimizes the equipment adjustment range, greatly expands the adjustment area and doubles the number of adjustment points, and improves the equipment adjustment accuracy.

[0066] The secondary winding is provided with a source-side position, and the tertiary winding is provided with a load-side position.

[0067] The primary winding is used to obtain the excitation voltage from the line based on the excitation point, and to synthesize the excitation voltage into a compensation voltage.

[0068] The polarity switch is used to reverse the compensation voltage; The secondary winding is used to adjust the source-side gear, and the tertiary winding is used to adjust the load-side gear; wherein, based on the coordinated adjustment of the source-side gear and the load-side gear, the compensation voltage is subjected to equal-amplitude phase shift, increased-amplitude phase shift, or decreased-amplitude phase shift.

[0069] As a preferred embodiment, the A-phase thyristor is used to reverse the positions of the A-phase source-side winding and the A-phase load-side winding; The B-phase thyristor is used to reverse the position of the B-phase source-side winding and the B-phase load-side winding; The C-phase thyristor is used to reverse the position of the C-phase source-side winding and the C-phase load-side winding.

[0070] As a preferred embodiment, the maximum turns ratio between the secondary winding and the tertiary winding is equal, and both the secondary winding and the tertiary winding adopt a uniform gear ratio.

[0071] In this embodiment, by combining the topology of the stand-alone PST and the T-type equivalent circuit diagram of the transformer, its equivalent circuit diagram can be obtained, such as... Figure 6 As shown in the diagram, the effects of each winding adjustment are represented by the color blocks. The secondary side taps of the transformer respectively realize the functions of the source-side winding and the load-side winding. U SA , U SB and U SC These are the three-phase source-side voltages. U LA , U LB and U LC These are the three-phase load-side voltages. U AC 、U BC and U CC It is the three-phase voltage of the primary winding. U Ac1 , U Bc1 and U Cc1 It is the voltage of the three-phase source-side winding. U Ac2 , U Bc2 and U Cc2 It is the voltage of the three-phase load-side winding. U A , U B and U C It is the three-phase excitation point voltage. I SA , I SB and I SC It is the three-phase source-side current. I LA , I LB and I LC These are the three-phase load-side currents. I AC 、I BC and I CC It is the three-phase current of the primary winding. Z C It is the leakage impedance of the primary winding. Z c1and Z c2 These are the leakage impedances of the source-side winding and the load-side winding, respectively. K 1 and K 2 represents the source-side winding ratio and the load-side winding ratio, respectively, and their corresponding relationship is as follows: Figure 6 Marking.

[0072] The phasors of the voltage and current at the beginning before compensation and the voltage and current at the end after compensation are respectively: (1.1) (1.2) (1.3) (1.4) (1.5) The voltage and current relationships of each winding can be derived from the turns ratio of a series transformer: (1.6) (1.7) (1.8) Considering that the phase shifter only has a positive sequence component during normal operation, under positive sequence conditions, the electrical connection of the primary winding of the series transformer can be obtained as follows: (1.9) (1.10) (1.11) (1.12) (1.13) The electrical quantities on the power supply side and the load side can be obtained by simplifying equations 1.1 to 1.13. U SA , I SA , U LA The relation is as follows: (1.14) Simplifying equation 1.14, we get: (1.15) (1.16) in K It is the overall amplitude ratio of the new independent PST, and its value is: (1.17) φ It is the overall phase shift angle of the new independent PST, and we have the following about it: (1.18) Z equ The overall internal impedance of the new independent PST is generated by the combined internal impedance of all windings: (1.19) A, B, and C are the contribution coefficients of each winding impedance in the total internal impedance, which are related to the three turns ratios and the overall amplitude ratio of the phase-shifting transformer. (1.20) (1.21) (1.22) From Equation 1.15, i.e., the input-output characteristic equation of the new independent PST, it can be seen that the new independent PST, because... K The existence of this gives it the ability to regulate the amplitude of the system node voltages, because φ The presence of this allows it to regulate the phase of the system node voltages.

[0073] Based on the single-phase equivalent circuit diagram of the independent PST in this embodiment, phasor diagrams of the system and the internal voltage and current of the equipment before and after adjustment can be drawn, such as... Figure 7 As shown, where U This is the equivalent excitation voltage obtained by the independent PST from the system in this embodiment. U S , U L , I S , I L These represent the system voltage and system current before and after adjustment, respectively. As can be seen from the phasor diagram, the adjustment of the system voltage phasor by the independent PST in this embodiment can be divided into three main parts: the effect of the source-side winding, the effect of the load-side winding, and the effect of internal impedance. Regarding the effect of the source-side winding, because the source-side winding compensation voltage and the excitation voltage are 30° out of phase, the source-side winding compensation voltage, the excitation voltage, and the voltage before adjustment form a triangle. According to the cosine theorem, the amplitude modulation effect is related to the phase shift angle. α Related, the ratio is 2sin(150°- αRegarding the load-side winding, the compensation voltage and excitation voltage of the load-side winding are also 30° out of phase. Therefore, the compensation voltage, excitation voltage, and regulated voltage of the load-side winding also form a triangle. Similarly, the amplitude modulation effect of the load-side voltage is related to the phase shift angle. β Related to this, the ratio is 1 / 2sin(150°-). β In the part where internal impedance is involved, because current flows through the internal impedance of the equipment, a certain voltage loss and phase change will be generated, which are related to the load power factor.

[0074] The overall transformation ratio of the novel independent PST can be derived from the geometric relationships in the phasor diagram. K Overall phase shift angle φ Source-side winding ratio K 1 and load-side winding ratio K The relationship between 2: (1.23) (1.24) (1.25) (1.26) For amplitude adjustment requirements K Phase modulation requirements φ After solving the above four equations, the source-side winding ratio can be obtained. K 1 and load-side winding ratio K 2. Thus, the source-side winding tap and the load-side winding tap can be independently controlled based on two parameters, achieving decoupling of phase modulation and amplitude modulation in control.

[0075] Assuming the power system voltage before adjustment is a per-unit value, and ignoring the internal impedance of the independent PST in this embodiment, the voltage phasor after adjustment is: K e jφ Based on actual application cases in power systems, assuming K The range is -0.33 to 0.33. K 2. The range is -0.33 to 0.33. Therefore, according to equations 1.17 and 1.19, the per-unit value range of the original compensation voltage for the new independent PST can be obtained, such as... Figure 8As shown, compared to the traditional independent PST, the shape of the adjustment range of the new independent PST is significantly improved. It no longer presents a distorted diagonal arc shape, and the adjustment range completely covers the area around the adjustment zero point (1, 0). Furthermore, there are no sharp, broken angles within the large phase shift angle range. Therefore, the device effectively compensates for the amplitude modulation capability limitations of the traditional independent PST when adjusting the zero point or the maximum phase shift angle. Simultaneously, it can be seen that the original adjustment range area has expanded and is no longer symmetrical about the X-axis. At this point, by controlling the conducting arms of the bridge circuit, the positions of the source and load sides can be changed, thereby reversing the lead and lag adjustments. The original adjustment range will also be flipped relative to the X-axis, forming the final adjustment range, as shown below. Figure 9 As shown, the final adjustment range is further expanded to present a "butterfly shape", and the number of adjustment points is also doubled. Therefore, the adjustment accuracy of the independent PST in this embodiment is significantly improved and the adjustment effect is optimized.

[0076] This invention also provides another preferred embodiment, which utilizes the multi-winding transformer module in MATLAB / Simulink to build an equivalent simulation model of the independent PST of this embodiment, adopting a structure with 3 windings on the source side and 3 windings on the load side. Its regulation capability and regulation range are verified by placing it in a two-terminal power supply system. The simulation model is as follows: Figure 10 As shown in the table below, the system parameters are set as follows: To visually observe the performance of the novel independent PST in this embodiment, we selected to verify its four basic functions: lead / lag, amplitude increase / decrease. The simulation waveforms under the four adjustment modes are as follows: Figure 11 As shown, where Figure 11 (a) shows the voltage waveforms before and after the lead adjustment of the descent rate. Figure 11 (b) shows the voltage waveforms before and after the amplitude lead adjustment. Figure 11 (c) shows the voltage waveforms before and after the hysteresis adjustment. Figure 11 (d) shows the voltage waveforms before and after the amplitude lag adjustment. It can be seen that the phase and amplitude of the system voltage waveform change significantly according to the adjustment mode, indicating that the new independent PST has complete amplitude lag and lead-lag adjustment functions. Moreover, the waveform phase and amplitude changes conform to Equations 1.17 and 1.18, which fully verifies the performance advantages of the new independent PST.

[0077] To further understand the regulation effect of the new independent PST in the line, the 98 regulation points obtained from the simulation were transformed to a polar coordinate system to observe the actual distribution of the compensation voltage. Figure 12As shown, the new independent PST has a large adjustment range and a large number of adjustment points. The adjustment accuracy far exceeds that of the traditional independent phase-shifting transformer. Moreover, the distribution of the simulated adjustment points completely matches the theoretical range, and the boundaries almost coincide. The error between the simulation and the theoretical range is very small, which fully proves the rationality and correctness of the new independent PST theory and effectively confirms the effect of the new independent PST in optimizing the adjustment range.

[0078] In summary, this embodiment provides a novel independent phase-shifting transformer topology. It utilizes the coordinated oblique amplitude modulation of the source-side winding and the load-side winding to achieve decoupled phase amplitude regulation. Compared to traditional independent PSTs, this embodiment rearranges the inductive relationship between the electromagnetic windings, optimizing the transformer's regulation range and compensating for the amplitude modulation capability when adjusting zero or maximum phase shift angles. This results in a more powerful ability to regulate and optimize power flow in power systems, making it widely applicable in power flow control operations. Furthermore, by changing the connection method of the electromagnetic windings, the compensation path of the series winding compensation voltage is improved, expanding the regulation range and biasing it. The bridge circuit composed of anti-parallel thyristors then flips the biased regulation range, further expanding the regulation range area and doubling the number of regulation points, effectively increasing the equipment's regulation accuracy. This makes it widely applicable in power systems where high power flow regulation accuracy is required, or in the suppression of loop-closing impacts in distribution networks.

[0079] This invention also provides a control method for an independent phase-shifting transformer, applied to any of the independent phase-shifting transformers described above, comprising the following steps S101-S102: Adjust the source-side tap of the secondary winding and the load-side tap of the tertiary winding; Based on the source-side tap and the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform equal-amplitude phase shift, increased-amplitude phase shift, or decreased-amplitude phase shift. Specifically, when the source-side tap and the load-side tap are the same, the compensation voltage of the independent phase-shifting transformer is controlled to perform equal-amplitude phase shift; when the source-side tap is greater than the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform increased-amplitude phase shift; when the source-side tap is less than the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform decreased-amplitude phase shift.

[0080] Having clarified the physical advantages brought by cross-phase induction, the control method of this invention further utilizes the intelligent bridge commutation circuit constructed by anti-parallel thyristors in the topology, pushing the adjustment accuracy and adjustment area of ​​the device to a new level. Due to the non-vertical injection characteristics of the aforementioned source-side lag compensation and load-side lead compensation, the effective adjustment range initially obtained by the device exhibits an "biased" form in phasor space where the lead and lag capabilities are uneven, meaning that the adjustment depth of the device in one phase shift direction is much greater than that in another direction.

[0081] To overcome this inherent bias asymmetry, the control system monitors the control target vector issued by the power grid in real time when performing power flow regulation tasks. When the system assessment finds that the target vector cannot be reached by simply adjusting the gear position, and the target is located in the disadvantageous region on the opposite side of the current bias regulation range, the control center will instantly activate the thyristor-based reverse regulation logic. By precisely triggering the thyristor turn-on and turn-off of specific arms in the A-phase, B-phase, and C-phase bridge circuits, the system can spatially reverse the positions of the secondary (source-side) winding and the tertiary (load-side) winding in the physical electrical circuit within a very short time of milliseconds.

[0082] This thyristor reversal, on a macroscopic level, is equivalent to a perfect mirror flip of the originally biased unilateral adjustment area along the real axis of the phasor diagram. The two areas before and after the flip are seamlessly joined at the edges, ultimately synthesizing a vast, completely symmetrical "butterfly-shaped" panoramic adjustment domain about the real axis. This innovative control logic not only enables a leapfrog expansion of the total available adjustment area of ​​the equipment, but also physically doubles the number of effective gear positions available for scheduling.

[0083] After the panoramic regulation domain is constructed, the system will execute the final refined tap-level coordinated control. Thanks to the meticulous design of the secondary and tertiary windings, which have absolutely equal maximum turns ratios and employ a uniform tap-level distribution structure with consistent step sizes, the mapping logic of the control strategy becomes extremely clear and efficient. When the system determines that the grid only needs a pure phase shift to change the active power flow distribution, the control system will drive the source-side tap on the secondary side and the load-side tap on the tertiary side to move synchronously to the exact same tap sequence. At this time, the equipment outputs a pure phase angle shift, achieving perfect equal-amplitude phase shift. When the system determines that there is a risk of bus voltage drop requiring support during phase shift, the control system will increase the source-side tap, making it numerically significantly greater than the load-side tap. At this time, the amplitude component of the composite vector increases, and the equipment smoothly completes the amplitude compensation during phase shift. Conversely, if a tendency for the system voltage to rise beyond the limit is detected, the control system will make the source-side tap smaller than the load-side tap, and the equipment will immediately switch to a reduced-amplitude phase shift operation mode. This composite control method, based on the large-scale spatial flipping of thyristors and the small-scale fine coordination of uniform tap positions, has completely unleashed the regulation potential of this independent phase-shifting transformer, greatly improving the power flow control accuracy and operating boundary of the power system.

[0084] To effectively translate the aforementioned topological advantages and theoretical calculations into practical power grid operations, the independent phase-shifting transformer control method of this invention provides a logically rigorous and rapidly responsive dynamic collaborative control process. In practical applications, this control method relies on a high-speed data acquisition and monitoring (SCADA) platform for the power system, and the specific execution steps are further detailed as follows: First, the system collects key electrical quantity data in real time, including the bus voltage at the excitation point, the voltage at the beginning of the system, the voltage at the end of the system, and the current of each phase. Then, it extracts the accurate positive sequence fundamental amplitude and phase information through fast Fourier transform.

[0085] Secondly, the control center compares the collected data with the preset optimal power flow target parameters in real time, calculates the required comprehensive compensation voltage, and calculates the target source-side transformer ratio and target load transformer ratio required to maintain the power flow state in real time.

[0086] Subsequently, the polarity and gear position determination stage begins. If the calculated compensation direction exceeds the "bias adjustment range" in the current non-reversed state (e.g., only in a unilateral lag or small-range lead state), the system will prioritize issuing a commutation command. By precisely controlling the thyristors corresponding to phases A, B, and C (e.g., closing the forward bridge arm and opening the reverse bridge arm), the physical connection point of the source-side winding and the load-side winding is instantly reversed, causing a 180-degree relative reversal of the compensation voltage adjustment range, bringing the required adjustment point into the expanded "butterfly" reachable area.

[0087] Finally, stepless or multi-stage coordinated switching is performed. Since both the secondary and tertiary windings employ a uniform tap design with equal maximum turns ratios, the system can directly map the target turns ratio to a specific on-load tap changer tap number. When the system determines that the source-side tap command is the same as the load-side tap command, it synchronously drives both mechanical or power electronic switches, smoothly outputting a constant-amplitude phase-shifted voltage to achieve pure phase power flow transfer. When the command requires the source-side tap to be greater than the load-side tap, the device injects a corresponding compensation amplitude while performing phase shifting, achieving increased amplitude phase shifting to support the system bus voltage. Conversely, if the command requires the source-side tap to be less than the load-side tap, the device performs decreased amplitude phase shifting while performing phase shifting. Throughout the entire control process, the rapid switching capability of the thyristors and the precise tap adjustment capability of the on-load tap changer winding are perfectly integrated, fully unleashing the enormous potential of this new independent phase-shifting transformer in the field of high-capacity, high-precision power flow control from both software algorithm and hardware execution perspectives.

[0088] In this embodiment, the maximum turns ratio of the source-side winding and the load-side winding are equal and both use uniform turns. Since the compensation voltages of the two are symmetrical relative to the excitation point voltage, equal amplitude phase shift can be achieved when the turns of the source-side winding and the load-side winding are the same. Increased amplitude phase shift can be achieved when the turns of the source-side winding are greater than those of the load-side winding. Decreased amplitude phase shift can be achieved when the turns of the source-side winding are less than those of the load-side winding.

[0089] Furthermore, by controlling the bridge circuit composed of anti-parallel thyristors to flip the bias adjustment range, the adjustment range area is further expanded and the number of adjustment points is doubled, effectively increasing the adjustment accuracy of the equipment. It can be widely used in power systems for applications requiring high power flow regulation accuracy or in the suppression of loop-closing impacts in distribution networks.

[0090] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. An independent phase-shifting transformer, characterized in that, Applied to power systems, including: primary winding, secondary winding, tertiary winding and polarity switch; The primary winding is configured as a delta structure, with the nodes of the delta structure serving as excitation points. The secondary and tertiary windings are three-phase independent and are connected in series on the lines on both sides of the excitation point. The primary winding is connected in parallel with the secondary and tertiary windings via the polarity switch. The secondary winding is provided with an active side position, and the tertiary winding is provided with a load side position. The primary winding is used to obtain the excitation voltage from the line based on the excitation point, and to synthesize the excitation voltage into a compensation voltage. The polarity switch is used to reverse the compensation voltage; The secondary winding is used to adjust the source-side gear, and the tertiary winding is used to adjust the load-side gear; wherein, based on the coordinated adjustment of the source-side gear and the load-side gear, the compensation voltage is subjected to equal-amplitude phase shift, increased-amplitude phase shift, or decreased-amplitude phase shift.

2. The independent phase-shifting transformer as described in claim 1, characterized in that, The primary winding includes: phase A excitation winding, phase B excitation winding and phase C excitation winding; The A-phase excitation winding, B-phase excitation winding, and C-phase excitation winding are connected in series in pairs to form a triangular structure.

3. The independent phase-shifting transformer as described in claim 2, characterized in that, The polarity switch includes: a first polarity switch for phase A, a second polarity switch for phase A, a first polarity switch for phase B, a second polarity switch for phase B, a first polarity switch for phase C, and a second polarity switch for phase C. The excitation point formed by the series connection of the A-phase excitation winding and the B-phase excitation winding is connected to the midpoint of the connection between the C-phase first polarity switch and the C-phase second polarity switch; The excitation point formed by the B-phase excitation winding and the C-phase excitation winding connected in series is connected to the midpoint of the connection between the A-phase first polarity switch and the A-phase second polarity switch; The excitation point formed by the series connection of the A-phase excitation winding and the C-phase excitation winding is connected to the midpoint of the connection between the B-phase first polarity switch and the B-phase second polarity switch.

4. The independent phase-shifting transformer as described in claim 3, characterized in that, The secondary winding includes: phase A source winding, phase B source winding, and phase C source winding; The A-phase source-side winding and the A-phase first polarity switch are connected in series; the B-phase source-side winding and the B-phase first polarity switch are connected in series; the C-phase source-side winding and the C-phase first polarity switch are connected in series. One end of the A-phase source-side winding is connected to one end of the A-phase first polarity switch; the other end of the A-phase source-side winding is connected to the power supply; the other end of the A-phase first polarity switch is connected to the B-phase excitation winding and the C-phase excitation winding. One end of the B-phase source-side winding is connected to one end of the B-phase first polarity switch; the other end of the B-phase source-side winding is connected to the power supply; the other end of the B-phase first polarity switch is connected to the A-phase excitation winding and the C-phase excitation winding. One end of the C-phase source-side winding is connected to one end of the C-phase first polarity switch; the other end of the C-phase source-side winding is connected to the power supply; the other end of the C-phase first polarity switch is connected to the A-phase excitation winding and the B-phase excitation winding. The source-side windings of phase A, phase B, and phase C are all equipped with the source-side positions.

5. The independent phase-shifting transformer as described in claim 4, characterized in that, The three-phase winding includes an A-phase load-side winding, a B-phase load-side winding, and a C-phase load-side winding. The load-side winding of phase A and the second polarity switch of phase A are connected in series; the load-side winding of phase B and the second polarity switch of phase B are connected in series; the load-side winding of phase C and the second polarity switch of phase C are connected in series. One end of the load-side winding of phase A is connected to one end of the second polarity switch of phase A; the other end of the load-side winding of phase A is connected to the load; the other end of the second polarity switch of phase A is connected to the excitation winding of phase B and the excitation winding of phase C. One end of the load-side winding of phase B is connected to one end of the second polarity switch of phase B; the other end of the load-side winding of phase B is connected to the load; the other end of the second polarity switch of phase B is connected to the excitation winding of phase A and the excitation winding of phase C. One end of the C-phase load-side winding is connected to one end of the C-phase second polarity switch; the other end of the C-phase load-side winding is connected to the load; the other end of the C-phase second polarity switch is connected to the A-phase excitation winding and the B-phase excitation winding. The load-side positions are all provided on the load-side windings of phase A, phase B, and phase C.

6. The independent phase-shifting transformer as described in claim 5, characterized in that, The A-phase source-side winding, the A-phase load-side winding, the A-phase first polarity switch, and the A-phase second polarity switch constitute the A-phase circuit; The B-phase source-side winding, the B-phase load-side winding, the B-phase first polarity switch, and the B-phase second polarity switch constitute the B-phase circuit. The C-phase source-side winding, C-phase load-side winding, C-phase first polarity switch, and C-phase second polarity switch constitute the C-phase circuit. In this process, the voltage at the excitation point of any two phases is generated by combining the voltage at the excitation point of the other phase by a preset phase value that either leads or lags behind the voltage at the excitation point of the other phase.

7. The independent phase-shifting transformer as described in claim 6, characterized in that, The A-phase line further includes: an A-phase thyristor, an A-phase first load voltage regulating switch, and an A-phase second load voltage regulating switch; both the A-phase source-side winding and the A-phase load-side winding are connected to the A-phase thyristor; one end of each of the A-phase first load voltage regulating switch and the A-phase second load voltage regulating switch is connected to the A-phase thyristor; the other end of the A-phase first load voltage regulating switch is connected to the A-phase first polarity switch; and the other end of the A-phase second load voltage regulating switch is connected to the A-phase second polarity switch. The B-phase line further includes: a B-phase thyristor, a B-phase first load voltage regulating switch, and a B-phase second load voltage regulating switch; both the B-phase source-side winding and the B-phase load-side winding are connected to the B-phase thyristor; one end of each of the B-phase first load voltage regulating switch and the B-phase second load voltage regulating switch is connected to the B-phase thyristor; the other end of the B-phase first load voltage regulating switch is connected to the B-phase first polarity switch; and the other end of the B-phase second load voltage regulating switch is connected to the B-phase second polarity switch. The C-phase circuit further includes: a C-phase thyristor, a C-phase first load voltage regulating switch, and a C-phase second load voltage regulating switch; both the C-phase source-side winding and the C-phase load-side winding are connected to the C-phase thyristor; one end of each of the C-phase first load voltage regulating switch and the C-phase second load voltage regulating switch is connected to the C-phase thyristor; the other end of the C-phase first load voltage regulating switch is connected to the C-phase first polarity switch; and the other end of the C-phase second load voltage regulating switch is connected to the C-phase second polarity switch.

8. The independent phase-shifting transformer as described in claim 7, characterized in that, The A-phase thyristor is used to reverse the position of the A-phase source-side winding and the A-phase load-side winding; The B-phase thyristor is used to reverse the position of the B-phase source-side winding and the B-phase load-side winding; The C-phase thyristor is used to reverse the position of the C-phase source-side winding and the C-phase load-side winding.

9. The independent phase-shifting transformer as described in any one of claims 1-8, characterized in that, The maximum turns ratio between the secondary and tertiary windings is equal, and both the secondary and tertiary windings use uniform gear ratios.

10. A control method for an independent phase-shifting transformer, characterized in that, The independent phase-shifting transformer described in any one of claims 1-9 comprises: Adjust the source-side tap of the secondary winding and the load-side tap of the tertiary winding; Based on the source-side tap and the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform equal-amplitude phase shift, increased-amplitude phase shift, or decreased-amplitude phase shift. Specifically, when the source-side tap and the load-side tap are the same, the compensation voltage of the independent phase-shifting transformer is controlled to perform equal-amplitude phase shift; when the source-side tap is greater than the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform increased-amplitude phase shift; when the source-side tap is less than the load-side tap, the compensation voltage of the independent phase-shifting transformer is controlled to perform decreased-amplitude phase shift.

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