A step-down phase-shifting integrated transformer and operation control method

Abstract

The embodiment of the present application provides a step-down phase-shifting integrated transformer and an operation control method. The step-down phase-shifting integrated transformer is connected with at least two power grids, and comprises at least a first winding, a second winding and a third winding. The third winding is provided with a gear adjusting switch, and is magnetically coupled to the first winding and the second winding. The third winding is electrically connected to the first winding or the second winding, so as to realize phase angle control and transmission power control between different power grids through adjusting the gear adjusting switch on the basis of voltage transformation. The step-down and phase-shifting functions are integrated, the step-down phase-shifting integrated transformer is used for connecting two or more power grids with different voltage levels, and flexible control of transformer output power flow is realized. The step-down phase-shifting integrated transformer is suitable for various application scenarios such as power grid interconnection and mutual aid, power regulation between power grids connected by hub substations and the like. Compared with ordinary transformers, transmission power flow control is realized. Compared with the traditional method of arranging transformers and phase shifters respectively, the step-down phase-shifting integrated transformer saves land occupation and investment.

Description

Technical Field

[0001] This invention relates to the field of power systems and their automation, and in particular to a step-down phase-shifting integrated transformer and its operation control method. Background Technology

[0002] The large-scale integration of new energy sources and diverse new loads has led to transmission bottlenecks on some key lines / main transformers, and power flow is exhibiting increased randomness. Flexible power flow control devices are crucial for promoting the integration and consumption of new energy sources and are an effective means of optimizing power flow control in the energy internet. Currently, flexible power flow control devices such as unified power flow controllers, phase shifters, and distributed power flow controllers are mainly used for line power flow control; ordinary transformers do not have power flow control functions.

[0003] With the development trend of new power systems, a large number of fluctuating energy sources and loads are being connected, and some transformers are experiencing reverse feeding or heavy load conditions. In addition, the demand for interconnection of power grids of different voltage levels and power mutual assistance is increasing. Therefore, it is necessary to overcome the technology of integrated step-down and phase-shifting transformers. Summary of the Invention

[0004] This invention provides a step-down and phase-shift integrated transformer and its operation control method, which integrates step-down and phase-shifting functions into one unit. Compared with a transformer, it has port power flow control capability. Compared with the method of using a transformer and arranging phase shifters on its output line, it saves space and investment.

[0005] In a first aspect, this embodiment provides a step-down phase-shifting integrated transformer, which is connected to at least two power grids, and includes at least:

[0006] The first winding, the second winding, and the third winding are three-phase windings.

[0007] The third winding is a phase-adjusting winding and is equipped with a gear adjustment switch. The third winding is magnetically coupled to the first winding and the second winding, and electrically connected to the first winding or the second winding. The phase difference between the voltage of the third winding and the terminal voltage of the first winding or the second winding is 90° or close to 90°, so that the phase angle control and transmission power control between different sides of the power grid can be achieved by adjusting the gear adjustment switch on the basis of the transformer.

[0008] Secondly, this embodiment provides an operation control method for a step-down phase-shifting integrated transformer, applicable to the step-down phase-shifting integrated transformer described in any embodiment of the present invention, the method comprising:

[0009] The step-down phase-shifting integrated transformer is subjected to loop-closed control to connect the step-down phase-shifting integrated transformer to at least two power grids;

[0010] Based on the current power and target power of the integrated step-down phase-shifting transformer port, and the current position of the tap adjustment switch in the integrated step-down phase-shifting transformer, adjust the position of the tap adjustment switch until the current power of the integrated step-down phase-shifting transformer port reaches the target power after adjustment; or,

[0011] Select key nodes in the power grids on both sides connected to the step-down phase-shifting integrated transformer, and control the load rate difference between the key nodes to be less than the set load rate difference threshold.

[0012] This invention provides a step-down phase-shifting integrated transformer and its operation control method. The step-down phase-shifting integrated transformer is connected to at least two power grids. The transformer includes at least a first winding, a second winding, and a third winding, all of which are three-phase windings. The third winding is a phase-adjusting winding and is equipped with a tap position adjustment switch. The third winding is magnetically coupled to the first and second windings and electrically connected to either the first or second winding. The phase difference between the voltage of the third winding and the voltage at the terminals of the first or second winding is 90° or close to 90°. This allows for phase angle control and power transmission control between different power grid sides by adjusting the tap position adjustment switch, based on the transformer's voltage transformation. This technical solution integrates step-down and phase-shifting functions into one unit. The step-down phase-shifting integrated transformer adopts a three-phase, three-winding structure, with one winding being a phase-adjusting winding equipped with a tap position adjustment switch. This enables the step-down phase-shifting integrated transformer to have phase angle offset and power transmission control functions. The step-down phase-shifting integrated transformer is used to connect two or more power grids of different voltage levels, enabling flexible control of the transformer's output power flow. It is suitable for various application scenarios such as interconnection and mutual support between power grids of different voltage levels, and power regulation between power grids connected to hub substations. Compared to ordinary transformers, it achieves transmission power flow control; compared to the traditional method of arranging transformers and phase shifters separately, it saves floor space and investment.

[0013] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of a step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention;

[0016] Figure 2 This is a schematic diagram of the first topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention;

[0017] Figure 3 This is a vector diagram of the voltage of each winding in the first topology of the step-down phase-shift integrated transformer provided in Embodiment 1 of the present invention;

[0018] Figure 4 This is a schematic diagram of the A-phase adjustment principle in the first topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention;

[0019] Figure 5 This is a schematic diagram of the second topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention;

[0020] Figure 6 This is a vector diagram of the winding voltages in the second topology of the step-down phase-shift integrated transformer provided in Embodiment 1 of the present invention.

[0021] Figure 7 This is a schematic diagram of the A-phase adjustment principle in the second topology of the step-down phase-shift integrated transformer provided in Embodiment 1 of the present invention;

[0022] Figure 8 This is a schematic diagram of the third topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention;

[0023] Figure 9 This is a vector diagram of the winding voltages in the third topology of the step-down phase-shift integrated transformer provided in Embodiment 1 of the present invention.

[0024] Figure 10 This is a schematic diagram of the A-phase adjustment principle in the third topology of the step-down phase-shift integrated transformer provided in Embodiment 1 of the present invention;

[0025] Figure 11 This is a flowchart illustrating the operation control method of a step-down phase-shift integrated transformer provided in Embodiment 2 of the present invention;

[0026] Figure 12 This is an example diagram of a step-down phase-shifting integrated transformer with a first topology connected to the power grid, provided in Embodiment 2 of the present invention.

[0027] Figure 13 This is an example diagram of a step-down phase-shifting integrated transformer with a second topology connected to the power grid, provided in Embodiment 2 of the present invention.

[0028] Figure 14This is an example diagram of a step-down phase-shifting integrated transformer with a third topology connected to the power grid, provided in Embodiment 2 of the present invention.

[0029] Figure 15 This is a flowchart illustrating the operation control method of a step-down phase-shift integrated transformer provided in Embodiment 3 of the present invention;

[0030] Figure 16 This is another flowchart illustrating the operation control method of a step-down phase-shifting integrated transformer provided in Embodiment 3 of the present invention;

[0031] Figure 17 Simulation results of step-down phase-shifting integrated transformer with first topology for interconnecting 10kV and 20kV power grids;

[0032] Figure 18 Simulation results of step-down phase-shifting transformer with second topology for interconnecting 220kV and 110kV power grids;

[0033] Figure 19 Simulation results of step-down phase-shifting integrated transformer with third topology for interconnecting 110kV and 35kV power grids. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention 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 the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any other variations, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] Example 1

[0037] Figure 1This is a schematic diagram of a step-down phase-shifting integrated transformer according to Embodiment 1 of the present invention. This step-down phase-shifting integrated transformer is applicable to situations involving step-down transformation and phase angle control of power grids with different voltage levels. Figure 1 As shown in the first embodiment, a step-down phase-shifting integrated transformer is provided. The step-down phase-shifting integrated transformer is connected to at least two power grids. The step-down phase-shifting integrated transformer includes at least a first winding, a second winding, and a third winding. The first winding, the second winding, and the third winding are three-phase windings. The third winding is a phase-shifting winding and is equipped with a tap position adjustment switch. The third winding is magnetically coupled to the first winding and the second winding, and the third winding is electrically connected to the first winding or the second winding. The phase difference between the voltage of the third winding and the terminal voltage of the first winding or the second winding is 90° or close to 90°, so that the phase angle control and transmission power control between different power grids can be realized by adjusting the tap position adjustment switch on the basis of the transformer.

[0038] It should be noted that, Figure 1 The diagram illustrates a configuration where the third winding is electrically connected to the first winding, and the third winding is magnetically coupled to both the first and second windings. The principle behind the configuration where the third winding is electrically connected to the second winding, and the third winding is magnetically coupled to both the first and second windings, is the same. Figure 1 Similarities will not be described here.

[0039] In this embodiment, to realize a step-down phase-shifting transformer integrating voltage transformation and phase angle control functions, a third winding is added as a phase-adjusting winding. The third winding can be electrically connected to either the first or second winding, so that the voltage of the third winding acts on the terminal voltage of the connected first or second winding. When the third winding is electrically connected to the first winding, the phase difference of each phase must be 90° or close to 90°. The third winding is magnetically coupled to the first and second windings, thus achieving phase angle control and power transmission control between different sides of the power grid by adjusting the tap position adjustment switch based on the transformer. When the third winding is connected to the second winding, the phase difference of each phase must be 90° or close to 90°. The third winding is magnetically coupled to the first and second windings, thus achieving phase angle control and power transmission control between different sides of the power grid by adjusting the tap position adjustment switch based on the transformer.

[0040] Optionally, the third winding is equipped with a polarity switching switch to achieve phase angle leading direction adjustment and lagging direction adjustment.

[0041] The above describes the case where the step-down phase-shifting integrated transformer has three windings. In addition, the step-down phase-shifting integrated transformer can also have four windings, divided into high, medium, and low voltage levels, and can also include a phase-adjusting winding. Besides the high-voltage and low-voltage power grids, the medium-voltage power grid can also be used for phase angle control. It can be considered that the step-down phase-shifting integrated transformer provided in this embodiment can be connected to the high-voltage and low-voltage power grids, or the high-voltage and medium-voltage power grids, or the medium-voltage and low-voltage power grids, to achieve phase angle control and power flow control at different voltage levels.

[0042] The aforementioned technical solution utilizes a step-down and phase-shifting integrated transformer, combining voltage transformation and phase shifting functions. It connects one or more high-voltage and low-voltage power grids, simultaneously achieving voltage transformation and phase angle shifting. By connecting two or more power grids of different voltage levels, it enables flexible control of the transformer's output power flow, adapting to various application scenarios such as interconnection and mutual support between power grids of different voltage levels, and power regulation between power grids connected to hub substations. Compared to ordinary transformers, it achieves transmission power flow control; compared to the traditional method of separately arranging transformers and phase shifters, it saves space and investment. It serves as an effective control method for new energy consumption in new power systems and in the energy internet.

[0043] In this embodiment, the step-down phase-shifting integrated transformer mainly has three topologies, referred to as the first topology, the second topology, and the third topology, respectively. As an optional embodiment of the present invention, based on the above embodiments, it can be optimized so that if the step-down phase-shifting integrated transformer adopts the first topology, the first winding is connected to the high-voltage side grid and the second winding is connected to the low-voltage side grid, thereby realizing voltage transformation and phase angle adjustment between the high-voltage side grid and the low-voltage side grid. The specific structure is as follows.

[0044] Based on the clock timings of the first and third windings, the input terminal of the first winding of phase A is connected in series with either the third winding of phase B or the third winding of phase C; based on the clock timings of the first and third windings, the input terminal of the first winding of phase B is connected in series with either the third winding of phase C or the third winding of phase A; based on the clock timings of the first and third windings, the input terminal of the first winding of phase C is connected in series with either the third winding of phase A or the third winding of phase B. If the clock timing between the first and third windings is 11 o'clock, the former is connected in series; if the clock timing is 1 o'clock, the latter is connected in series. Voltage transformation is achieved through the first and second windings; phase angle difference regulation and power control between high-voltage and low-voltage power grids are achieved through the adjustment of the third winding's tap position.

[0045] Figure 2 This is a schematic diagram of the first topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention, as shown below. Figure 2As shown, the first topology of the step-down phase-shifting integrated transformer includes a first winding (shown as #1 in the figure), a second winding (shown as #2 in the figure), and a third winding (shown as #3 in the figure). The first winding and the second winding are connected to the high-voltage power grid and the low-voltage power grid, respectively. The positions of the S-terminal and L-terminal of the incoming and outgoing lines are as follows. Figure 2 As shown, in the first topology, the first winding is delta-connected, the second winding is star-connected, and the clock sequence number between the first and third windings is 11. The third winding is a phase-adjusting winding with a range adjustment switch. The input terminal of the first winding of phase A is connected in series with the third winding of phase B, and the input terminal of the first winding of phase B is connected in series with the third winding of phase C; the input terminal of the first winding of phase C is connected in series with the third winding of phase A.

[0046] Figure 3 This is a vector diagram of the winding voltages in the first topology of the step-down phase-shift integrated transformer provided in Embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the A-phase adjustment principle in the first topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention. Figure 3 As shown, the three-phase voltage vectors at points P and Q (P and Q are two labeled positions) of the first winding (shown as #1 in the figure) are represented as: U1A, U1B, U1C, U4A, U4B, U4C, respectively; the three-phase voltage vectors at the second winding (shown as #2 in the figure) are represented as: U2A, U2B, U2C, respectively; and the three-phase winding voltage vectors of the third winding (shown as #3 in the figure) are represented as: U3A, U3B, U3C, respectively. Figure 4 As shown, φ represents the phase shift angle of the step-down phase-shifting integrated transformer. Taking the A-phase adjustment principle as an example, since the voltage U3B of the third winding of phase B is at 90° with the voltage at point Q at the first winding port (the voltage U3B of the third winding of phase B is at 90° - φ with the voltage at point P at the first winding port), the voltage of the third winding of phase B is connected in series at the first winding port of phase A. By determining the turns ratio of the third winding and adjusting the tap, the voltage phase φ between points P and Q at the first winding port is adjusted, thus realizing the phase shift angle φ between point P at the first winding port and the second winding port, thereby controlling the phase angle difference and transmission power between the high-voltage and low-voltage grids.

[0047] As an optional embodiment of the present invention, based on the above embodiments, the step-down phase-shifting integrated transformer can be optimized by adopting a second topology. The first winding is connected to the high-voltage side grid, and the second winding is connected to two low-voltage side grids. The step-down phase-shifting integrated transformer achieves voltage transformation between the high-voltage side and one of the low-voltage sides, while simultaneously achieving voltage transformation and phase angle control between the high-voltage side and the other low-voltage side. This topology is suitable for substations with multiple transformers. The step-down phase-shifting integrated transformer can operate in parallel with other transformers in the substation for long periods or for short-term uninterrupted load transfer operations via a non-phase-shifting bus. The step-down phase-shifting integrated transformer can be interconnected with and power-regulated by the opposite low-voltage grid via a phase-shifting bus. The specific structure is as follows.

[0048] The first winding is connected to the high-voltage side of the power grid. The second winding has two outgoing lines: the first outgoing line connects to the low-voltage side of the power grid without phase shifting, and the second outgoing line connects to the low-voltage side of the power grid with phase shifting via the third winding. Based on the clock timing of the second and third windings, the second outgoing line of the second winding of phase A is connected in series with either the third winding of phase C or phase B; based on the clock timing of the second and third windings, the second outgoing line of the second winding of phase B is connected in series with either the third winding of phase A or phase C; based on the clock timing of the second and third windings, the second outgoing line of the second winding of phase C is connected in series with either the third winding of phase B or phase A. If the clock timing between the first and third windings is 11 o'clock, the former is connected in series; if the clock timing is 1 o'clock, the latter is connected in series. Voltage transformation is achieved through the first and second windings; phase angle difference regulation and power control between the high-voltage power grid and the low-voltage power grid at the second outgoing line are achieved through the adjustment of the third winding's adjustment range.

[0049] Figure 5 This is a schematic diagram of the second topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention, as shown below. Figure 5 As shown, the second topology of the step-down phase-shifting integrated transformer includes a first winding (shown as #1 in the figure), a second winding (shown as #2 in the figure), and a third winding (shown as #3 in the figure). The positions of the input and output ports S, L1, and L2 are as follows. Figure 5 As shown. The first winding is connected to the high-voltage power grid; the second winding has two outgoing lines, L1 and L2, one connected to the low-voltage side non-phase-shifting bus, and the other connected to the phase-shifting bus via the third winding. The first winding adopts a star connection, and the second winding adopts a delta connection. The clock sequence number between the first and third windings is 11. The third winding is a phase-shifting winding with a tap changer; the output terminal of the second winding of phase A is connected in series with the third winding of phase C, the output terminal of the second winding of phase B is connected in series with the third winding of phase A, and the output terminal of the second winding of phase C is connected in series with the third winding of phase B.

[0050] Figure 6 This is a vector diagram of the winding voltages in the second topology of the step-down phase-shift integrated transformer provided in Embodiment 1 of the present invention. Figure 7 This is a schematic diagram of the A-phase adjustment principle in the second topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention. Figure 6 As shown, the three-phase voltage vectors at the ports of the first winding (shown as #1 in the figure) are represented as U1A, U1B, and U1C, respectively; the three-phase voltage vectors at the ports of the L1 output of the second winding (shown as #2 in the figure) are represented as U2A_L1, U2B_L1, and U2C_L1, respectively; the three-phase voltage vectors at the ports of the L2 output of the second winding are represented as U2A_L2, U2B_L2, and U2C_L2, respectively; and the three-phase voltage vectors of the third winding (shown as #3 in the figure) are represented as U3A, U3B, and U3C, respectively. U1A is the voltage on the high-voltage side of phase A (winding #1), U2A_L1 and U2A_L2 are the voltages on the low-voltage side of phase A (winding #2), respectively, and U3C is the winding voltage of the #3 phase-adjusting winding. Figure 7 As shown, φ represents the phase difference between the L1 output line and the L2 output line of the low-voltage side (#2 winding) of phase A. Taking the A-phase regulation principle as an example, since the voltage U3C of the third winding of phase C is at 90° with the voltage at the L1 port of the second winding, the voltage of the third winding of phase C is connected in series at the L1 port of the second winding of phase A. By determining the transformation ratio of the third winding and adjusting the tap, the voltage phase φ at the L1 and L2 ports of the second winding is adjusted, thereby achieving the phase shift angle φ between the S port of the first winding and the L2 port of the second winding, thus controlling the phase angle difference and transmission power between the high-voltage and low-voltage grids.

[0051] As an optional embodiment of the present invention, based on the above embodiments, the step-down phase-shifting integrated transformer can be optimized by adopting a third topology. The first winding has two outgoing lines, connected to two high-voltage side power grids respectively, and the second winding is connected to the low-voltage side power grid. The step-down phase-shifting integrated transformer realizes power flow control or phase angle control between the two high-voltage sides, and simultaneously achieves voltage transformation between the high-voltage and low-voltage sides. This topology is suitable for application scenarios where the high-voltage side power grid requires power interconnection and mutual support. Its specific structure is as follows.

[0052] Based on the clock timing numbers of the first and third windings, the input terminal of the first winding of phase A is connected in series with either the third winding of phase C or the third winding of phase B; based on the clock timing numbers of the first and third windings, the input terminal of the first winding of phase B is connected in series with either the third winding of phase A or the third winding of phase C; based on the clock timing numbers of the first and third windings, the input terminal of the first winding of phase C is connected in series with either the third winding of phase B or the third winding of phase A. If the clock timing number between the first and third windings is 1, the former is connected; if the clock timing number is 11, the latter is connected. Voltage transformation is achieved through the first and second windings; phase angle difference regulation and power control between two high-voltage power grids are achieved through the adjustment of the third winding's adjustment range.

[0053] Figure 8This is a schematic diagram of the third topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention, as shown below. Figure 8 As shown, the third topology of the step-down phase-shifting integrated transformer includes a first winding (shown as #1 in the figure), a second winding (shown as #2 in the figure), and a third winding (shown as #3 in the figure), as follows: Figure 8 As shown, the overall structure is a three-phase, three-winding configuration. The first winding is delta-connected with two outgoing lines, S1 and S2, which are connected to the high-voltage side power grid 1 and high-voltage side power grid 2, respectively. The second winding is delta-connected and connected to the low-voltage side power grid. The clock sequence number of the first and third windings is 1. The third winding is a phase-adjusting winding with a range adjustment switch. The input terminal of the first winding of phase A is connected in series with the third winding of phase C; the input terminal of the first winding of phase B is connected in series with the third winding of phase A; and the input terminal of the first winding of phase C is connected in series with the third winding of phase B.

[0054] Figure 9 This is a vector diagram of the winding voltages in the third topology of the step-down phase-shift integrated transformer provided in Embodiment 1 of the present invention. Figure 10 This is a schematic diagram of the A-phase adjustment principle in the third topology of the step-down phase-shifting integrated transformer provided in Embodiment 1 of the present invention. Figure 9 As shown, the three-phase voltage vectors of the first winding (shown as #1 in the figure) S1 output are represented as: U1A_S1, U1B_S1, U1A_S1; the three-phase voltage vectors of the first winding S2 output are represented as: U1A_S2, U1B_S2, U1A_S2; the three-phase voltage vectors of the second winding (shown as #2 in the figure) are represented as: U2A, U2B, U2C; and the three-phase voltage vectors of the third winding (shown as #3 in the figure) are represented as: U3A, U3B, U3C. Figure 10 As shown, φ represents the phase angle difference between the two high-voltage side grids in phase A. Taking the phase A regulation principle as an example, since the phase C voltage U3C of the third winding is at 90° with the phase A voltage at port S2 of the first winding (the phase C voltage U3C of the third winding is at 90° - φ with the phase A voltage at port S1 of the first winding), the phase C voltage of the third winding is connected in series at the input terminal of phase A of the first winding. By determining the transformation ratio of the third winding and adjusting the tap, the voltage phase between ports S1 and S2 of the first winding is adjusted to φ, thereby realizing the phase shift angle φ between ports S1 and S2 of the first winding, thus controlling the phase angle difference and transmission power between the two high-voltage side grids.

[0055] The above technical solutions specify the concrete implementation methods of three topologies of the step-down phase-shifting integrated transformer.

[0056] Example 2

[0057] Figure 11This is a flowchart illustrating the operation control method of a step-down phase-shifting integrated transformer provided in Embodiment 2 of the present invention. This method is applicable to situations where step-down transformation and phase angle control are performed on power grids of different voltage levels.

[0058] like Figure 11 As shown in the figure, this embodiment two provides an operation control method for a step-down phase-shifting integrated transformer, which specifically includes the following steps:

[0059] S201. Perform loop control on the step-down phase-shifting integrated transformer to connect the step-down phase-shifting integrated transformer to the power grid on at least two sides.

[0060] In this embodiment, the control modes of the step-down phase-shifting transformer include loop control, port power control, and equalization control. This step is used to perform loop control on the step-down phase-shifting transformer to connect it to at least two power grids. The loop control is related to the topology of the step-down phase-shifting transformer.

[0061] For example, if the step-down phase-shifting integrated transformer adopts the first topology, the step-down phase-shifting integrated transformer is connected to the high-voltage side grid through the first circuit breaker and to the low-voltage side grid through the second circuit breaker. The steps for performing loop control on the step-down phase-shifting integrated transformer to connect it to the grid can be described as follows: control the first circuit breaker to close, so that the step-down phase-shifting integrated transformer is charged; detect the phase angle difference on both sides of the second circuit breaker; if the phase angle difference is less than the set phase angle difference threshold, adjust the gear adjustment switch and return to the step of detecting the phase angle difference on both sides of the second circuit breaker until the phase angle difference is less than the set phase angle difference threshold; control the second circuit breaker to close, so as to complete the connection of the step-down phase-shifting integrated transformer to the grid.

[0062] For example, if the step-down phase-shifting transformer adopts the second topology, the step-down phase-shifting transformer is connected to the high-voltage side grid through the third circuit breaker, connected to a low-voltage side grid through the fourth circuit breaker, and connected to another low-voltage side grid sequentially through the fifth circuit breaker and the second disconnecting switch. The first disconnecting switch is connected to the fourth circuit breaker and the other low-voltage side grid. The steps for performing loop control on the step-down phase-shifting transformer to connect it to the grid can be described as follows: control the third circuit breaker to close, charging the step-down phase-shifting transformer; control the fourth circuit breaker to close, supplying power to the low-voltage side grid; control the second disconnecting switch to close and the first disconnecting switch to open; detect the phase angle difference on both sides of the fifth circuit breaker; if the phase angle difference is less than the set phase angle difference threshold, adjust the gear adjustment switch and return to the step of detecting the phase angle difference on both sides of the fifth circuit breaker until the phase angle difference is less than the set phase angle difference threshold; control the fifth circuit breaker to close, thus completing the connection of the step-down phase-shifting transformer to the grid.

[0063] For example, if the step-down phase-shifting transformer adopts a third topology, it is connected to one high-voltage grid via a sixth circuit breaker, to another high-voltage grid via a seventh circuit breaker, and to the low-voltage grid via an eighth circuit breaker. The steps for loop-closing control of the step-down phase-shifting transformer to connect it to the grid can be described as follows: Control the seventh circuit breaker to close, charging the transformer; control the eighth circuit breaker to close, supplying power to the low-voltage grid; detect the phase angle difference across the sixth circuit breaker; if the phase angle difference is less than a set phase angle difference threshold, adjust the gear shift switch to return to the step of detecting the phase angle difference across the sixth circuit breaker until the phase angle difference is less than the set threshold; control the sixth circuit breaker to close, completing the connection of the step-down phase-shifting transformer to the grid.

[0064] S202. Based on the current power and target power of the step-down phase-shifting transformer port and the current position of the tap position adjustment switch in the step-down phase-shifting transformer, adjust the position of the tap position adjustment switch until the current power of the step-down phase-shifting transformer port reaches the target power after adjustment.

[0065] Port power control and equalization control belong to the power flow control of the step-down phase-shifting transformer. This step describes the steps of port power control. For the first topology, port power refers to the third winding grid terminal (S terminal) or the second winding grid terminal (L terminal); for the second topology, it refers to the first winding grid terminal (S terminal) or the third winding grid terminal (L2 terminal); for the third topology, it refers to the third winding grid terminal (S1 terminal) or the first winding grid terminal (S2 terminal). Current power can be understood as the power at the current moment of the step-down phase-shifting transformer port. Target power can be specifically understood as the power that the step-down phase-shifting transformer port wants to achieve. The current position of the tap position adjustment switch in the step-down phase-shifting transformer is recorded as the current tap position. If the current power is greater than or less than the target power, the tap position adjustment switch is adjusted according to the relationship between the current power and the target power until the current power at the step-down phase-shifting transformer port reaches the target power after adjustment.

[0066] S203, or, select key nodes in the power grids on both sides connected by the step-down phase-shifting integrated transformer, and control the load rate difference between the key nodes to be less than the set load rate difference threshold.

[0067] First, key nodes in the power grids on both sides of the phase shifter are selected. For the first topology, this refers to a node on the high-voltage side and a node on the low-voltage side; for the second topology, it refers to a node on the high-voltage side and a node on the phase-shifted low-voltage side; for the third topology, it refers to nodes on both high-voltage sides. The step of controlling the load rate difference between key nodes to be less than a set load rate difference threshold can be described as follows: obtaining the first current power and first rated capacity of the first key point, and the second current power and second rated capacity of the second key point; determining the first load rate of the first key point based on the first current power and first rated capacity, and determining the second load rate of the second key point based on the second current power and second rated capacity; controlling the absolute value of the difference between the first load rate and the second load rate to be less than a predetermined load rate difference threshold.

[0068] The above technical solution realizes the functions of loop control, port power control, or equalization control for the step-down phase-shifting integrated transformer. Port power control is achieved by adjusting the tap position adjustment switch, and equalization control is achieved by controlling the load rate difference between two key nodes.

[0069] As an optional embodiment of the present invention, based on the above embodiments, it can be optimized that if the step-down phase-shifting integrated transformer adopts the first topology, the step-down phase-shifting integrated transformer is connected to the high-voltage side power grid through the first circuit breaker and connected to the low-voltage side power grid through the second circuit breaker.

[0070] In this embodiment, if the step-down phase-shifting integrated transformer adopts the first topology, the step-down phase-shifting integrated transformer is connected to the high-voltage side power grid, that is, connected to the high-voltage side power grid through the first winding. A circuit breaker, denoted as the first circuit breaker, is installed between the first winding and the high-voltage side power grid. The step-down phase-shifting integrated transformer is connected to the low-voltage side power grid, that is, connected to the low-voltage side power grid through the second winding. A circuit breaker, denoted as the second circuit breaker, is installed between the second winding and the low-voltage side power grid.

[0071] Furthermore, the steps for performing closed-loop control on the step-down phase-shifting integrated transformer to connect it to the power grid can be optimized, including:

[0072] a1) Control the first circuit breaker to close, so that the step-down phase-shifting integrated transformer can be charged.

[0073] In this embodiment, when the step-down phase-shifting integrated transformer changes from the off state to the on state, the first circuit breaker and the second circuit breaker are in the open state in the initial state. Figure 12The following is an example diagram of a step-down phase-shifting integrated transformer connected to the power grid using a first topology, provided for an embodiment of the present invention. As shown in the figure, the first circuit breaker is represented by QF1 and the second circuit breaker is represented by QF2. First, the circuit breaker QF1 (or QF2) is closed to charge the step-down phase-shifting integrated transformer.

[0074] b1) Detect the phase angle difference between the two sides of the second circuit breaker. If the phase angle difference is less than the set phase angle difference threshold, adjust the gear adjustment switch and return to the step of detecting the phase angle difference between the two sides of the second circuit breaker until the phase angle difference is less than the set phase angle difference threshold.

[0075] The phase angle difference threshold can be set according to actual conditions. In this embodiment, the phase angle difference is kept within the allowable range by adjusting the tap position adjustment switch of the step-down phase-shifting integrated transformer. If the phase angle difference is less than the set phase angle difference threshold, the tap position adjustment switch is adjusted, and the process returns to detecting the phase angle difference across the second circuit breaker until the phase angle difference is less than the set phase angle difference threshold. (Continue to refer to...) Figure 12 Following the example above, the phase angle difference between the two sides of QF2 (or QF1) is detected, and the phase angle difference is kept within the allowable range by adjusting the phase shifter position.

[0076] Continue to refer to Figure 12 As described above, by adjusting the tap position adjustment switch of the step-down phase-shifting integrated transformer, the phase angle difference is kept within the allowable range.

[0077] d1) Control the second circuit breaker to close, so as to connect the step-down phase-shifting transformer to the power grid.

[0078] In this embodiment, reference continues to be made to Figure 12 Continuing with the example above, when the phase angle difference across the second circuit breaker is less than the set phase angle difference threshold, QF2 (or QF1) is closed. The step-down phase-shifting integrated transformer connects the high-voltage side grid and the low-voltage side grid, enabling tie-line power control. Mutual power control between the high-voltage and low-voltage side grids is achieved by adjusting the tap position of the step-down phase shifter.

[0079] It should be noted that in this step, the second circuit breaker can also be closed to charge the step-down phase-shifting transformer. In this case, it is necessary to detect the phase angle difference on both sides of the first circuit breaker, adjust the gear adjustment switch to make the phase angle difference less than the set phase angle difference threshold, and control the first circuit breaker to close, so as to connect the step-down phase-shifting transformer to the power grid.

[0080] The above technical solution specifies the steps for performing loop control on the step-down phase-shifting integrated transformer to connect it to the power grid if the step-down phase-shifting integrated transformer adopts the first topology.

[0081] As another optional embodiment of the present invention, based on the above embodiments, it can be optimized that if the step-down phase-shifting integrated transformer adopts the second topology, the step-down phase-shifting integrated transformer is connected to the high-voltage side grid through the third circuit breaker, connected to a low-voltage side grid through the fourth circuit breaker, and connected to another low-voltage side grid in sequence through the fifth circuit breaker and the second disconnecting switch, and the first disconnecting switch is connected to the fourth circuit breaker and the other low-voltage side grid.

[0082] In this embodiment, if the step-down phase-shifting integrated transformer adopts the second topology, the transformer is connected to the high-voltage side power grid via the first winding. A circuit breaker, designated as the third circuit breaker, is installed between the first winding and the high-voltage side power grid. The transformer is also connected to the low-voltage side power grid via the second winding. The second winding has two outgoing lines, connected to the low-voltage side non-phase-shifting bus and the phase-shifting bus, respectively. A circuit breaker, designated as the fourth circuit breaker, is installed between one outgoing line of the second winding and the low-voltage side power grid. A circuit breaker, designated as the fifth circuit breaker, is installed between the other outgoing line of the second winding and the low-voltage side power grid.

[0083] The steps for optimizing the closed-loop control of the step-down phase-shifting transformer to connect it to the power grid can be included:

[0084] a2) Control the closing of the third circuit breaker to charge the step-down phase-shifting transformer.

[0085] Figure 13 This is an example diagram of a step-down phase-shifting integrated transformer with a second topology connected to the power grid, as provided in Embodiment 2 of the present invention. Figure 13 As shown, when the step-down phase shifter changes from the deactivated to the activated state, its circuit breakers on each side, namely the third circuit breaker (QF3), the fourth circuit breaker (QF4), and the fifth circuit breaker (QF5), are initially in the open state, with the first disconnecting switch (K1) and the second disconnecting switch (K2) open. Line 1 is powered by the low-voltage side power grid 2 area power supply; transformer T1 is in operation, and the bus tie switch is closed, supplying power to the low-voltage side power grid 1. The bus tie circuit breaker between the low-voltage bus of transformer T1 and the phase shifter bus of the integrated step-down phase shifter transformer is denoted as QFM. K1 and K2 are connected to the low-voltage side power grid 2 through the main circuit breaker, which is closed. First, circuit breaker QF3 is closed to charge the integrated step-down phase shifter transformer T2.

[0086] b2) Control the fourth circuit breaker to close and supply power to the low-voltage side power grid.

[0087] Continue to refer to Figure 13Following the above description, the circuit breaker QF4 is then closed, and the transformer T1 and the step-down phase shifter T2 operate in parallel for a long or short period of time (i.e., the circuit breaker QFM is closed for a long or short period of time) to supply power to the low-voltage side of the power grid 1.

[0088] c2) Controls the closing of the second isolating switch and the opening of the first isolating switch.

[0089] Continue to refer to Figure 13 As described above, when K2 is closed, K1 remains open.

[0090] d2) Detect the phase angle difference between the two sides of the fifth circuit breaker. If the phase angle difference is less than the set phase angle difference threshold, adjust the gear adjustment switch and return to the step of detecting the phase angle difference between the two sides of the fifth circuit breaker until the phase angle difference is less than the set phase angle difference threshold.

[0091] Continue to refer to Figure 13 The phase angle difference between the two sides of QF5 is detected, and the phase shifter setting is adjusted to keep the phase angle difference within the allowable range.

[0092] e2) Control the fifth circuit breaker to close, so as to complete the connection of the step-down phase-shifting integrated transformer to the power grid.

[0093] Continue to refer to Figure 13 When QF5 is closed, line 1 is powered by the phase-shifting bus II of the step-down phase shifter.

[0094] The above technical solution specifies the steps for performing loop control on the step-down phase-shifting integrated transformer to connect it to the power grid if the step-down phase-shifting integrated transformer adopts the second topology.

[0095] As another optional embodiment of the present invention, based on the above embodiments, it can be optimized that if the step-down phase-shifting integrated transformer adopts a third topology, the step-down phase-shifting integrated transformer is connected to a high-voltage side power grid through a sixth circuit breaker, connected to another high-voltage side power grid through a seventh circuit breaker, and connected to a low-voltage side power grid through an eighth circuit breaker.

[0096] In this embodiment, if the step-down phase-shifting transformer adopts the third topology, the step-down phase-shifting transformer is connected to the high-voltage side power grid, that is, connected to two high-voltage side power grids through two outgoing lines of the first winding. A circuit breaker, denoted as the sixth circuit breaker, is installed between the first winding and one high-voltage side power grid. Another circuit breaker, denoted as the seventh circuit breaker, is installed between the first winding and the other high-voltage side power grid. The step-down phase-shifting transformer is connected to the low-voltage side power grid, that is, connected to the low-voltage side power grid through the second winding. A circuit breaker, denoted as the eighth circuit breaker, is installed between the second winding and the low-voltage side power grid.

[0097] To enable the integrated step-down phase-shifting transformer to connect to the power grid, the following loop control is implemented:

[0098] a3) Control the closing of the seventh circuit breaker to charge the step-down phase-shifting transformer.

[0099] In this embodiment, when the step-down phase-shifting integrated transformer changes from the off state to the on state, the sixth, seventh, and eighth circuit breakers are initially in the open state. Figure 14 An example diagram of a step-down phase-shifting integrated transformer with a third topology connected to the power grid, provided by an embodiment of the present invention, is shown below. Figure 14 As shown, the sixth circuit breaker is designated QF6, the seventh circuit breaker is designated QF7, and the eighth circuit breaker is designated QF8. First, close QF7 to charge the step-down phase-shifting integrated transformer.

[0100] b3) Control the closing of the eighth circuit breaker to supply power to the low-voltage side of the power grid.

[0101] Continue to refer to Figure 14 Following the above description, QF8 is then closed to supply power to the low-voltage side of the power grid.

[0102] c3) Detect the phase angle difference between the two sides of the sixth circuit breaker. If the phase angle difference between the two sides of the sixth circuit breaker is less than the set phase angle difference threshold, adjust the gear adjustment switch and return to the step of detecting the phase angle difference between the two sides of the sixth circuit breaker until the phase angle difference is less than the set phase angle difference threshold.

[0103] Continue to refer to Figure 14 Following the above description, the phase angle difference between the two sides of QF6 is then detected. When the phase angle difference between the two sides of QF6 is less than the set phase angle difference threshold, the phase shifter position is adjusted to make the phase angle difference within the allowable range.

[0104] d3) Control the sixth circuit breaker to close, so as to complete the connection of the step-down phase-shifting integrated transformer to the power grid.

[0105] Continue to refer to Figure 14 As described above, when QF6 is closed, the step-down phase-shifting integrated transformer connects to two high-voltage sides and one low-voltage side of the power grid. The control position of the step-down phase-shifting integrated transformer can be controlled so that the power exchanged between the output of the step-down phase-shifting integrated transformer and a certain high-voltage side power grid is kept within the set value range.

[0106] The above technical solution specifies the steps for performing loop control on the step-down phase-shifting integrated transformer to connect it to the power grid if the step-down phase-shifting integrated transformer adopts a third topology.

[0107] Example 3

[0108] Figure 15This is a flowchart illustrating the operation control method of a step-down phase-shifting integrated transformer according to Embodiment 3 of the present invention. This embodiment is a further optimization of the above embodiment. In this embodiment, the limitation of "adjusting the gear position of the gear adjustment switch according to the current power, target power and current gear position of the gear adjustment switch in the step-down phase-shifting integrated transformer port until the current power of the step-down phase-shifting integrated transformer port reaches the target power" is further optimized, and the limitation of "controlling the load rate difference between the key nodes to be less than the set load rate difference threshold" is further optimized.

[0109] like Figure 15 As shown in the figure, this embodiment 2 provides an operation control method for a step-down phase-shifting integrated transformer, which specifically includes the following steps:

[0110] S301. Perform loop control on the step-down phase-shifting integrated transformer to connect the step-down phase-shifting integrated transformer to the power grid on at least two sides.

[0111] S302. Obtain the current power and target power of the step-down phase-shifting transformer port, as well as the current gear position of the gear adjustment switch in the phase-shifting transformer.

[0112] This step is used to obtain the current power, target power, and current gear position of the gear adjustment switch in the step-down phase-shifting transformer port.

[0113] S303. If the difference between the current power and the target power is greater than the power threshold determined in real time, the adjustment switch will be raised or lowered from the current level until the difference between the adjusted current power and the target power is less than or equal to the power threshold determined in real time.

[0114] The power threshold can be set according to the actual situation. In this embodiment, if the difference between the current power and the target power is greater than the power threshold determined in real time, the power can be increased or decreased by adjusting the gear adjustment switch until the difference between the adjusted current power and the target power is less than or equal to the power threshold determined in real time.

[0115] In this embodiment, the tap position adjustment switch of the step-down phase-shifting integrated transformer has a monotonic function with respect to the port power. It can be configured such that increasing the tap position results in an increase in port power, i.e., increasing the tap position leads to an increase in port power. Alternatively, it can be configured such that decreasing the tap position results in an increase in port power, i.e., decreasing the tap position leads to an increase in port power.

[0116] In this embodiment, the example of increasing the port power by raising the gear adjustment switch is used as an illustration. For instance, if the target power is greater than the current power, the gear adjustment switch is raised by one gear, and the current power of the output port of the step-down phase-shifting transformer after adjustment is obtained. For instance, let the gear limit value of the phase shifter be -kl to kl, the current gear be k, the target port power be y, and the current port power be y0. When y > y0, the phase shifter gear is adjusted to k+1, and the current port power is recorded as y1. If the difference between the adjusted current power and the target power is less than or equal to a set power threshold, the gear adjustment switch is stopped. In this embodiment, if the difference between the adjusted current power and the target power is less than or equal to a set power threshold, that is, the difference between the actual port power and the target port power value is less than the real-time calculated value, it is considered that the adjustment is within the target value range, and the gear adjustment switch is stopped.

[0117] As described above, if the difference between the adjusted current power and the target power is greater than or equal to the set power threshold, the process returns to the step of increasing the adjustment level by one level until the current power at the step-down phase-shifting transformer port reaches the target power. In this embodiment, during the first adjustment, the power threshold used to determine whether the step-down phase-shifting transformer's adjustment level is in place is a set value; for the second and subsequent adjustments, a dynamically updated power threshold is used to determine whether the step-down phase-shifting transformer's adjustment level is in place. The dynamically updated power threshold is calculated as half of the previous adjustment port power change plus an allowable deviation.

[0118] |y1-y|≤α1

[0119] α1=∣y1-y0∣ / 2+ε1

[0120] Where α1 is the power threshold, y is the target power of the port, y0 is the port power before the last gear adjustment, y1 is the port power after the last gear adjustment (i.e. before the current gear adjustment); ε1 is the set allowable error, taking into account the sampling error and the difference in adjustment amount for each gear.

[0121] It should be noted that if the target power is less than the current power, the gear adjustment switch should be adjusted in the opposite direction, with the same adjustment principle as described above, and will not be repeated here. Similarly, if the gear adjustment switch is used to downshift and increase the port power, the adjustment principle is also the same as described above, and will not be repeated here. If the gear reaches its limit -kl or kl, the gear adjustment switch should be stopped. Gear adjustment stops when the current power of the phase shifter changes from a positive deviation from the target value to a negative deviation from the target value, or from a negative deviation from the target value to a positive deviation from the target value.

[0122] The above technical solution specifies the steps of adjusting the gear position of the gear adjustment switch until the current power of the step-down phase-shifting integrated transformer port reaches the target power, thereby realizing the port power control of the step-down phase-shifting integrated transformer.

[0123] Example 4

[0124] Figure 16 This is a flowchart illustrating the operation control method of a step-down phase-shifting integrated transformer provided in Embodiment 3 of the present invention. This embodiment is a further optimization of the above embodiment. In this embodiment, the limitation of "controlling the load rate difference between the key nodes to be less than the set load rate difference threshold" is further optimized.

[0125] like Figure 16 As shown in the figure, this embodiment 2 provides an operation control method for a step-down phase-shifting integrated transformer, which specifically includes the following steps:

[0126] S401. Perform loop control on the step-down phase-shifting integrated transformer to connect the step-down phase-shifting integrated transformer to the power grid on at least two sides.

[0127] S402. Select key nodes in the power grids on both sides connected by the step-down phase-shifting integrated transformer, and obtain the first current power and first rated capacity of the first key point, as well as the second current power and second rated capacity of the second key point.

[0128] In this embodiment, key nodes in the power grid on both sides of the step-down phase-shifting integrated transformer are selected. For example, in a step-down phase-shifting integrated transformer with one high-voltage side and two low-voltage sides, the main transformer connected to the high-voltage side main transformer and the low-voltage phase-shifting busbar can be selected as two key nodes, respectively denoted as the first key point and the second key point. Since the load rate difference between the two key points needs to be automatically controlled within a certain range for the balancing control, this step requires obtaining the current power and rated capacity of the first and second key points. The current power of the first key point is denoted as the first current power, and the rated capacity of the first key point is denoted as the first rated capacity. The current power of the second key point is denoted as the second current power, and the rated capacity of the second key point is denoted as the second rated capacity.

[0129] S403. Determine the first load rate of the first critical point based on the first current power and the first rated capacity, and determine the second load rate of the second critical point based on the second current power and the second rated capacity.

[0130] In this embodiment, the load rate of the critical point is calculated by dividing the current power by its rated capacity. Specifically, the first current power is divided by the first rated capacity to obtain the load rate of the first critical point, which is recorded as the load rate of the first critical point. The second current power is divided by the second rated capacity to obtain the load rate of the second critical point, which is recorded as the load rate of the second critical point.

[0131] The formula for calculating the load rate of key points can be expressed as: Where, η i P represents the load rate of the i-th key point. i S represents the current power at the i-th key point. iN Let i represent the rated capacity of the i-th critical point, where i = 1, 2.

[0132] S404, control the absolute value of the difference between the first load rate and the second load rate to be less than a predetermined load rate difference threshold.

[0133] In this embodiment, the load rate difference between the two key nodes is automatically controlled within a certain range, that is, the absolute value of the difference between the first load rate and the second load rate is less than a predetermined load rate difference threshold.

[0134] Optionally, the step of determining the load rate difference threshold includes:

[0135] During the initial gear adjustment, the load rate difference threshold used to determine whether the gear of the step-down phase-shifting integrated transformer has been adjusted to the correct position is set to the value.

[0136] For the second and subsequent adjustments, a dynamically updated load rate difference threshold is used to determine whether the tap position of the step-down phase-shifting transformer has been adjusted correctly. The calculation method for the dynamically updated load rate difference threshold is half of the load rate difference generated in the previous adjustment plus the allowable deviation.

[0137]

[0138] Where α2 is the load factor difference threshold, Δy i This represents the power change at a key point under the previous adjustment of the step-down phase-shifting integrated transformer, i = 1, 2; ε2 is the set allowable error, taking into account the sampling error and the difference in adjustment amount for each step.

[0139] When the gear adjustment reaches the upper or lower limit of the step-down phase-shifting integrated transformer, the gear adjustment stops; when the current power of the phase shifter changes from a positive deviation from the target value to a negative deviation from the target value, or from a negative deviation from the target value to a positive deviation from the target value, the gear adjustment stops.

[0140] It should be noted that the gear adjustment stops when the gear position reaches the upper or lower limit of the step-down phase-shifting integrated transformer; the gear adjustment stops when the current power of the step-down phase-shifting integrated transformer changes from a positive deviation from the target value to a negative deviation from the target value, or from a negative deviation from the target value to a positive deviation from the target value.

[0141] The above technical solution specifies the steps for controlling the load rate difference between key nodes to be less than the set load rate difference threshold, thereby realizing balanced control of key points of the step-down phase-shifting integrated transformer.

[0142] To more clearly illustrate the phase regulation and voltage transformation effects achieved by the step-down phase-shifting integrated transformer provided in this embodiment of the invention, the simulation results of three topologies of the step-down phase-shifting integrated transformer provided in this embodiment are described below. If the step-down phase-shifting integrated transformer adopts the first topology, the phase regulation and voltage transformation effects of the step-down phase-shifting integrated transformer are simulated. In this simulation, the high-voltage side line voltage of the step-down phase shifter is 20kV, and the low-voltage side line voltage is 10kV.

[0143] To achieve phase adjustment of φ (φ = 5°), the voltage of the third winding is 1kV. Figure 17 The simulation diagram shows the effect of step-down and phase-shifting transformers using the first topology to achieve interconnection of 10kV and 20kV power grids. Figure 17 As shown, the high-voltage line voltage of the step-down phase-shifting integrated transformer is approximately 20kV, and the low-voltage line voltage is approximately 10kV. Simultaneously, the phase angle difference between the third winding voltage (U3B) and the voltage port (U1A) of the first winding on the high-voltage side of the transformer is 85°. The addition of the third winding enables phase angle adjustment. The low-voltage side voltage (U2A) leads the high-voltage side voltage (U1A) by 35°, demonstrating an angle adjustment of φ (φ=5°).

[0144] If the step-down phase-shifting integrated transformer adopts the second topology, the phase regulation and voltage transformation effects of the step-down phase-shifting integrated transformer are simulated. The high-voltage side line voltage of the step-down phase shifter is 220kV, and the low-voltage side line voltage is 110kV; to achieve phase regulation of φ (φ=5°), the third winding voltage is 5.5kV. Figure 18 The simulation diagram shows the effect of step-down and phase-shifting transformers with the second topology used to interconnect 220kV and 110kV power grids. Figure 18 As shown, the high-voltage line voltage of the step-down phase-shifting integrated transformer is approximately 220kV, and the low-voltage line voltage is approximately 110kV. Simultaneously, the voltage of the third winding (U3B) differs from the voltage at the L1 port of the low-voltage side of the step-down phase shifter (U2A_L1) by 90°. The addition of the third winding enables phase angle adjustment. The low-voltage side L2 terminal voltage (U2A_L2) leads the low-voltage side L1 terminal voltage (U2A_L1) by 5° and leads the high-voltage side voltage (U1A) by 35° (the inherent 30° phase angle difference between the high- and low-voltage sides of the power grid). Therefore, an angle adjustment of φ (φ=5°) is achieved.

[0145] If the step-down phase-shifting integrated transformer adopts a third topology, simulate the phase regulation and voltage transformation effect of the step-down phase-shifting integrated transformer. The high-voltage side line voltage of the step-down phase shifter is 110kV, and the low-voltage side line voltage is 35kV; to achieve phase regulation of φ (φ=5°), the third winding voltage is 5.5kV. Figure 19 The simulation diagram shows the effect of step-down and phase-shifting transformers with a third topology used to interconnect 110kV and 35kV power grids. Figure 19 As shown, the high-voltage side line voltage of the step-down phase shifter is approximately 110kV, and the low-voltage side line voltage is approximately 35kV. Simultaneously, the phase angle difference between the third winding voltage (U3C) and the voltage at port S2 of the first winding on the high-voltage side of the step-down phase shifter (U1A_S2) is 90°. The addition of the third winding allows for phase angle adjustment. The low-voltage side voltage (U2A) leads the high-voltage side voltage (U1A) by 5°, thus achieving an angle adjustment of φ (φ=5°).

[0146] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0147] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A step-down phase-shifting integrated transformer, characterized in that, The step-down phase-shifting integrated transformer is connected to at least two power grids, and the step-down phase-shifting integrated transformer includes at least: The first winding, the second winding, and the third winding are three-phase windings. The third winding is a phase-adjusting winding and is equipped with a gear adjustment switch. The third winding is magnetically coupled to the first winding and the second winding, and electrically connected to the first winding or the second winding. The phase difference between the voltage of the third winding and the voltage of the first winding or the second winding is 90° or close to 90°, so that the phase angle control and transmission power control between different sides of the power grid can be achieved by adjusting the gear adjustment switch on the basis of the transformer. When the step-down phase-shifting integrated transformer adopts the first topology, the first winding is connected to the high-voltage side power grid, and the second winding is connected to the low-voltage side power grid; Based on the clock timing numbers of the first winding and the third winding, the input terminal of the first winding of phase A is connected in series with the third winding of phase B or the third winding of phase C. Based on the clock timing numbers of the first winding and the third winding, the input terminal of the first winding of phase B is connected in series with the third winding of phase C or the third winding of phase A; Based on the clock timing numbers of the first winding and the third winding, the input terminal of the first winding of phase C is connected in series with the third winding of phase A or the third winding of phase B; The first winding is connected in a delta configuration, and the second winding is connected in a star configuration.

2. The step-down phase-shifting integrated transformer according to claim 1, characterized in that, When the step-down phase-shifting integrated transformer adopts the second topology, the first winding is connected to the high-voltage side power grid, and the second winding has two outgoing lines. The first outgoing line is connected to the low-voltage side power grid without phase shifting, and the second outgoing line is connected to the low-voltage side power grid with phase shifting via the third winding. Based on the clock sequence numbers of the second winding and the third winding, the second output wire of the second winding of phase A is connected in series with the third winding of phase C or the third winding of phase B. Based on the clock timing numbers of the second winding and the third winding, the second output wire of the second winding of phase B is connected in series with the third winding of phase A or the third winding of phase C. Based on the clock timing numbers of the second winding and the third winding, the second output wire of the second winding of phase C is connected in series with the third winding of phase B or the third winding of phase A; The first winding is connected in a star configuration, and the second winding is connected in a delta configuration.

3. The step-down phase-shifting integrated transformer according to claim 1, characterized in that, When the step-down phase-shifting integrated transformer adopts the third topology, the first winding has two outgoing lines, which are respectively connected to two high-voltage side power grids, and the second winding is connected to the low-voltage side power grid. Based on the clock timing numbers of the first winding and the third winding, the input terminal of the first winding of phase A is connected in series with the third winding of phase C or the third winding of phase B; Based on the clock timing numbers of the first winding and the third winding, the input terminal of the first winding of phase B is connected in series with the third winding of phase A or the third winding of phase C; Based on the clock timing numbers of the first winding and the third winding, the input terminal of the first winding of phase C is connected in series with the third winding of phase B or the third winding of phase A; The first winding adopts a delta connection method, and the second winding adopts a delta connection method.

4. The step-down phase-shifting integrated transformer according to claim 1, characterized in that, The third winding is equipped with a polarity switching switch to achieve phase angle leading direction adjustment and lagging direction adjustment.

5. A method for operating and controlling a step-down phase-shifting integrated transformer, characterized in that, The method, applied to the step-down phase-shifting integrated transformer according to any one of claims 1-4, comprises: The step-down phase-shifting integrated transformer is subjected to loop-closed control to connect the step-down phase-shifting integrated transformer to at least two power grids; Based on the current power and target power of the integrated step-down phase-shifting transformer port, and the current position of the tap adjustment switch in the integrated step-down phase-shifting transformer, adjust the position of the tap adjustment switch until the current power of the integrated step-down phase-shifting transformer port reaches the target power after adjustment; or, Select key nodes in the power grids on both sides connected to the step-down phase-shifting integrated transformer, and control the load rate difference between the key nodes to be less than the set load rate difference threshold.

6. The method according to claim 5, characterized in that, When the step-down phase-shifting integrated transformer adopts the first topology, the step-down phase-shifting integrated transformer is connected to the high-voltage side power grid through the first circuit breaker and to the low-voltage side power grid through the second circuit breaker; The step-down phase-shifting integrated transformer is closed-loop controlled to connect it to the power grid, including: Control the first circuit breaker to close, so that the step-down phase-shifting integrated transformer can be charged; The phase angle difference between the two sides of the second circuit breaker is detected. If the phase angle difference is not less than the set phase angle difference threshold, the gear adjustment switch is adjusted to return to the step of detecting the phase angle difference between the two sides of the second circuit breaker until the phase angle difference is less than the set phase angle difference threshold. The second circuit breaker is controlled to close, thereby connecting the step-down phase-shifting transformer to the power grid.

7. The method according to claim 5, characterized in that, When the step-down phase-shifting integrated transformer adopts the second topology, the step-down phase-shifting integrated transformer is connected to the high-voltage side grid through the third circuit breaker, connected to a low-voltage side grid through the fourth circuit breaker, and connected to another low-voltage side grid in sequence through the fifth circuit breaker and the second disconnecting switch. The first disconnecting switch is connected to the fourth circuit breaker and the other low-voltage side grid. The step-down phase-shifting integrated transformer is closed-loop controlled to connect it to the power grid, including: Control the closing of the third circuit breaker to charge the step-down phase-shifting integrated transformer; The fourth circuit breaker is controlled to close, supplying power to the low-voltage power grid. Controls the closing of the second isolating switch and the opening of the first isolating switch; The phase angle difference between the two sides of the fifth circuit breaker is detected. If the phase angle difference is not less than the set phase angle difference threshold, the gear adjustment switch is adjusted to return to the step of detecting the phase angle difference between the two sides of the fifth circuit breaker until the phase angle difference is less than the set phase angle difference threshold. Control the closing of the fifth circuit breaker to complete the connection of the step-down phase-shifting integrated transformer to the power grid.

8. The method according to claim 5, characterized in that, When the step-down phase-shifting integrated transformer adopts the third topology, the step-down phase-shifting integrated transformer is connected to a high-voltage side power grid through the sixth circuit breaker, connected to another high-voltage side power grid through the seventh circuit breaker, and connected to the low-voltage side power grid through the eighth circuit breaker. The step-down phase-shifting integrated transformer is closed-loop controlled to connect it to the power grid, including: Control the closing of the seventh circuit breaker to charge the step-down phase-shifting integrated transformer; Control the closing of the eighth circuit breaker to supply power to the low-voltage side power grid; The phase angle difference between the two sides of the sixth circuit breaker is detected. If the phase angle difference between the two sides of the sixth circuit breaker is not less than the set phase angle difference threshold, the gear adjustment switch is adjusted to return to the step of detecting the phase angle difference between the two sides of the sixth circuit breaker until the phase angle difference is less than the set phase angle difference threshold. Control the closing of the sixth circuit breaker to complete the connection of the step-down phase-shifting integrated transformer to the power grid.

9. The method according to claim 5, characterized in that, For the first topology, the current power and target power of the step-down phase-shifting integrated transformer port are the current power and target power of the third winding grid terminal or the second winding grid terminal; For the second topology, the current power and target power of the step-down phase-shifting integrated transformer port are the current power and target power of the first winding grid terminal or the third winding grid terminal; For the third topology, the current power and target power of the step-down phase-shifting integrated transformer port are the current power and target power of the third winding grid terminal or the first winding grid terminal.

10. The method according to claim 5, characterized in that, For the first topology, the key nodes in the power grids on both sides connected by the step-down phase-shifting integrated transformer are a node in the high-voltage side power grid and a node in the low-voltage side power grid. For the second topology, the key nodes in the power grids on both sides connected by the step-down phase-shifting integrated transformer are a node in the high-voltage side power grid and a node in the phase-shifting low-voltage side power grid. For the third topology, the key nodes in the power grids on both sides connected by the step-down phase-shifting integrated transformer are nodes of the two high-voltage side power grids, respectively.

11. The method according to claim 5, characterized in that, The step of adjusting the position of the gear adjustment switch according to the current power, target power, and current gear position of the gear adjustment switch in the step-down phase-shifting integrated transformer port until the current power of the step-down phase-shifting integrated transformer port reaches the target power includes: Obtain the current power and target power of the integrated step-down phase-shifting transformer port, as well as the current gear position of the gear adjustment switch in the integrated step-down phase-shifting transformer; If the difference between the current power and the target power is greater than a set power threshold, the gear adjustment switch is adjusted to either increase or decrease the gear until the difference between the adjusted current power and the target power is less than or equal to the power threshold determined in real time.

12. The method according to claim 5, characterized in that, The control of the load rate difference between the key nodes being less than a set load rate difference threshold includes: Obtain the first current power and first rated capacity of the first key point, and the second current power and second rated capacity of the second key point; A first load rate of the first critical point is determined based on the first current power and the first rated capacity, and a second load rate of the second critical point is determined based on the second current power and the second rated capacity; The absolute value of the difference between the first load rate and the second load rate is controlled to be less than a predetermined load rate difference threshold.

13. The method according to claim 11, characterized in that, The steps for determining the power threshold include: During the initial gear adjustment, the power threshold used to determine whether the gear of the step-down phase-shifting integrated transformer has been adjusted to the correct position is the set value. For the second and subsequent adjustments, a dynamically updated power threshold is used to determine whether the tap position of the step-down phase-shifting transformer has been adjusted correctly. The formula for calculating the dynamically updated power threshold is as follows: in, Power threshold The power at the front port during the last gear adjustment. The port power after the last gear adjustment; The allowable error set to account for sampling errors and differences in adjustment ranges at each level.

14. The method according to claim 12, characterized in that, The steps for determining the load rate difference threshold include: During the initial gear adjustment, the load rate difference threshold used to determine whether the gear of the step-down phase-shifting integrated transformer has been adjusted to the correct position is set to the value. For the second and subsequent adjustments, a dynamically updated load rate difference threshold is used to determine whether the tap position of the step-down phase-shifting transformer has been adjusted correctly. The formula for calculating the dynamically updated load rate difference threshold is as follows: in, The load rate difference threshold, Indicates the first i Rated capacity at critical points i =1,2; This indicates the power change at a key point under the previous adjustment of the step-down phase-shifting integrated transformer. i =1,2; The allowable error set to account for sampling errors and differences in adjustment ranges at each level.

15. The method according to claim 11 or 12, characterized in that, When the gear adjustment reaches the upper or lower limit of the step-down phase-shifting transformer, the gear adjustment stops; when the current power of the step-down phase-shifting transformer changes from a positive deviation from the target value to a negative deviation from the target value, or from a negative deviation from the target value to a positive deviation from the target value, the gear adjustment stops.

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