Step-down and phase-shift integrated transformer and operation control method

Abstract

Provided in the embodiments of the present application are a step-down and phase-shift integrated transformer and an operation control method. The step-down and phase-shift integrated transformer is at least connected to power grids on two sides, and at least comprises a first winding, a second winding and a third winding, wherein the third winding is provided with a gear 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, so as to realize phase angle control and transmission power control between the power grids on different sides by means of adjusting the gear adjustment switch on the basis of voltage transformation.

Description

Step-down phase-shifting integrated transformer and operation control method

[0001] The present application claims priority to the Chinese patent application No. 202411383145.4 filed on September 30, 2024 with the China Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of power systems and their automation, for example to a step-down phase-shifting integrated transformer and operation control method. BACKGROUND

[0003] With the large-scale access of new energy and diversified new loads, power transmission bottlenecks occur in some key lines and main transformers, and the power flow presents the characteristics of increased randomness. The power flow flexible control device is an important support for promoting the access and consumption of new energy and an effective means of power flow optimization control in the energy internet. At present, the power flow flexible control devices such as unified power flow controller, phase shifter and distributed power flow controller are mainly applied to line power flow control, and ordinary transformers do not have power flow control function.

[0004] Under the development trend of new power systems, a large number of fluctuating energy sources and loads are accessed, and some transformers are in the working conditions of reverse sending or heavy load. In addition, the demand for interconnection and power exchange of power grids of different voltage levels increases, so it is necessary to overcome the step-down phase-shifting integrated transformer technology.

[0005] SUMMARY

[0006] The embodiments of the present application provide a step-down phase-shifting integrated transformer and operation control method, which integrates step-down and phase-shifting functions, has port power flow control capability compared with transformers, and saves land occupation and investment compared with the method of using transformers and arranging phase shifters on the output lines of the transformers.

[0007] In a first aspect, the embodiments provide a step-down phase-shifting integrated transformer, which is connected to at least two sides of a power grid, and includes at least:

[0008] A first winding, a second winding and a third winding, which are three-phase windings;

[0009] The third winding is a phase-shifting winding and is provided with a gear adjustment switch. The third winding is magnetically coupled to the first winding and the second winding, and is electrically connected to the first winding or the second winding. The phase difference between the voltage of the third winding and the voltage at the end of the first winding or the second winding is 90° or close to 90°, so as to realize phase angle control and transmission power control between different sides of the power grid on the basis of voltage transformation by adjusting the gear adjustment switch.

[0010] In a second aspect, the embodiment provides a method for operating a voltage reduction and phase shifting integrated transformer. The method is applied to the voltage reduction and phase shifting integrated transformer described in any of the embodiments of the present application, and comprises the following steps:

[0011] Performing closed-loop control on the voltage reduction and phase shifting integrated transformer to connect the voltage reduction and phase shifting integrated transformer to at least two power grids;

[0012] Adjusting the gear of the gear adjustment switch according to the current power of the port of the voltage reduction and phase shifting integrated transformer, the target power, and the current gear of the gear adjustment switch in the voltage reduction and phase shifting integrated transformer, until the current power of the port of the voltage reduction and phase shifting integrated transformer reaches the target power after adjustment; or

[0013] Selecting a key node in the two power grids connected by the voltage reduction and phase shifting integrated transformer, and controlling the load rate difference between the key nodes to be less than a set load rate difference threshold.

[0014] The embodiment of the present application provides a voltage reduction and phase shifting integrated transformer and a method for operating the same. The voltage reduction and phase shifting integrated transformer is connected to at least two power grids, and comprises 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 provided with a gear adjustment switch. The third winding is magnetically coupled to the first winding and the second winding, and is 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°. The voltage reduction and phase shifting integrated transformer can realize phase angle control and transmission power control between different power grids by adjusting the gear adjustment switch on the basis of voltage transformation. The above technical solution integrates voltage reduction and phase shifting functions, and the voltage reduction and phase shifting integrated transformer adopts a three-phase three-winding structure. One of the windings is a phase-shifting winding, and the phase-shifting winding is provided with a gear adjustment switch. Therefore, the voltage reduction and phase shifting integrated transformer has the functions of phase angle offset and transmission power control. The voltage reduction and phase shifting integrated transformer is used to connect two or more power grids with different voltage levels, and realizes flexible control of transformer output power flow. The voltage reduction and phase shifting integrated transformer is suitable for various application scenarios such as interconnection and mutual assistance of power grids with different voltage levels, power regulation between power grids connected by hub substations, and the like. Compared with ordinary transformers, the voltage reduction and phase shifting integrated transformer realizes transmission power control. Compared with the traditional method of arranging transformers and phase shifters separately, the voltage reduction and phase shifting integrated transformer saves land area and investment. BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1 is a structural schematic diagram of a voltage reduction and phase shifting integrated transformer according to an embodiment of the present application;

[0016] FIG. 2 is a schematic diagram of a first topological structure of the voltage reduction and phase shifting integrated transformer according to the embodiment of the present application;

[0017] Fig. 3 is a voltage vector diagram of each winding in the first topology of the step-down phase-shifting integrated transformer provided by the embodiment one of the present application;

[0018] Fig. 4 is an A-phase regulation principle diagram in the first topology of the step-down phase-shifting integrated transformer provided by the embodiment one of the present application;

[0019] Fig. 5 is a schematic diagram of the second topology of the step-down phase-shifting integrated transformer provided by the embodiment one of the present application;

[0020] Fig. 6 is a voltage vector diagram of each winding in the second topology of the step-down phase-shifting integrated transformer provided by the embodiment one of the present application;

[0021] Fig. 7 is an A-phase regulation principle diagram in the second topology of the step-down phase-shifting integrated transformer provided by the embodiment one of the present application;

[0022] Fig. 8 is a schematic diagram of the third topology of the step-down phase-shifting integrated transformer provided by the embodiment one of the present application;

[0023] Fig. 9 is a voltage vector diagram of each winding in the third topology of the step-down phase-shifting integrated transformer provided by the embodiment one of the present application;

[0024] Fig. 10 is an A-phase regulation principle diagram in the third topology of the step-down phase-shifting integrated transformer provided by the embodiment one of the present application;

[0025] Fig. 11 is a flowchart of a running control method of a step-down phase-shifting integrated transformer provided by the embodiment two of the present application;

[0026] Fig. 12 is an example diagram of the step-down phase-shifting integrated transformer with the first topology accessing a power grid provided by the embodiment two of the present application;

[0027] Fig. 13 is an example diagram of the step-down phase-shifting integrated transformer with the second topology accessing a power grid provided by the embodiment two of the present application;

[0028] Fig. 14 is an example diagram of the step-down phase-shifting integrated transformer with the third topology accessing a power grid provided by the embodiment two of the present application;

[0029] Fig. 15 is a flowchart of a running control method of a step-down phase-shifting integrated transformer provided by the embodiment three of the present application;

[0030] Fig. 16 is another flowchart of a running control method of a step-down phase-shifting integrated transformer provided by the embodiment three of the present application;

[0031] Fig. 17 is a simulation effect diagram of the step-down phase-shifting integrated transformer with the first topology realizing 10kV power grid and 20kV power grid interconnection step-down phase-shifting;

[0032] Fig. 18 is a simulation effect diagram of the step-down phase-modulation integrated transformer with the second topology for realizing step-down phase modulation of the 220 kV power grid and the 110 kV power grid;

[0033] Fig. 19 is a simulation effect diagram of the step-down phase-modulation integrated transformer with the third topology for realizing step-down phase modulation of the 110 kV power grid and the 35 kV power grid. DETAILED DESCRIPTION

[0034] It should be noted that the terms "first", "second", and the like in the description and in the claims of the present application and the above-described accompanying drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any other variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device including a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to the process, method, product, or device.

[0035] Embodiment One

[0036] Fig. 1 is a structural schematic diagram of a step-down phase-modulation integrated transformer provided by Embodiment One of the present application, which can be applied to the case of step-down transformation and phase angle control of power grids of different voltage levels. As shown in Fig. 1, the step-down phase-modulation integrated transformer provided by Embodiment One of the present application is connected to at least two sides of a power grid, and at least includes a first winding, a second winding, and a third winding, which are three-phase windings. The third winding is a phase-modulation winding and is provided with a gear adjustment switch. The third winding is magnetically coupled to the first winding and the second winding, and 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 as to realize phase angle control and transmission power control between different sides of the power grid on the basis of transformation by adjusting the gear adjustment switch.

[0037] It should be noted that Fig. 1 shows the case that the third winding is electrically connected to the first winding and magnetically coupled to the first winding and the second winding. The principle of the structure for the case that the third winding is electrically connected to the second winding and magnetically coupled to the first winding and the second winding is similar to that of Fig. 1, which is not described here.

[0038] In the embodiment, in order to realize the step-down phase-shifting integrated transformer with voltage conversion and phase angle control functions, a third winding is added as a phase modulation winding, and the third winding can be electrically connected to the first winding or the second winding, so that the voltage of the third winding acts on the terminal voltage of the first winding or the second winding connected. For the case that the third winding is electrically connected to the first winding, the phase difference of each phase when the third winding is connected to the first winding is 90° or close to 90°, the third winding is magnetically coupled to the first winding and the second winding, so that the phase angle control and transmission power control between different side power grids are realized through adjusting the gear adjusting switch on the basis of voltage conversion. For the case that the third winding is connected to the second winding, the phase difference of each phase when the third winding is connected to the second winding is 90° or close to 90°, the third winding is magnetically coupled to the first winding and the second winding, so that the phase angle control and transmission power control between different side power grids are realized through adjusting the gear adjusting switch on the basis of voltage conversion.

[0039] Optionally, the third winding is provided with a polarity conversion switch to realize phase angle lead direction adjustment and lag direction adjustment.

[0040] The above describes the case that the step-down phase-shifting integrated transformer has three windings, in addition, the step-down phase-shifting integrated transformer can also have four windings, which are divided into high, medium and low voltage levels, and a phase modulation winding is added, and in addition to the high voltage side power grid and the low voltage side power grid, the medium voltage side power grid can also be controlled by the phase angle. It can be considered that the step-down phase-shifting integrated transformer provided in the embodiment can be connected to the high voltage side power grid and the low voltage side power grid, or the high voltage side power grid and the medium voltage side power grid, or the medium voltage side power grid and the low voltage side power grid, to realize phase angle control and transmission power flow control of different voltage levels.

[0041] The above technical solution, the step-down phase-shifting integrated transformer has the functions of voltage conversion and phase shifting, and is used for connecting one or more high voltage side and low voltage side power grids, and simultaneously realizing voltage conversion and phase angle offset. By connecting two or more power grids of different voltage levels, flexible control of transformer output power flow is realized, which is suitable for various application scenarios such as power grid interconnection, 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 occupied area and investment are saved. It is an effective control means for new energy consumption in new power systems and energy internet.

[0042] In the embodiment, the voltage step-down and phase-shifting integrated transformer mainly has three topological structures, which are respectively denoted as a first topological structure, a second topological structure and a third topological structure. As an optional embodiment of the present application, on the basis of the above-mentioned embodiment, if the voltage step-down and phase-shifting integrated transformer adopts the first topological structure, 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, so as to realize voltage transformation and phase angle regulation between the high-voltage side power grid and the low-voltage side power grid. The specific structure is as follows.

[0043] Based on the clock time sequence number of the first winding and the third winding, the input end of the A-phase first winding is connected to the B-phase third winding or the C-phase third winding; based on the clock time sequence number of the first winding and the third winding, the input end of the B-phase first winding is connected to the C-phase third winding or the A-phase third winding; and based on the clock time sequence number of the first winding and the third winding, the input end of the C-phase first winding is connected to the A-phase third winding or the B-phase third winding. If the clock time sequence number between the first winding and the third winding is 11 o'clock, the former is connected; if the clock time sequence number is 1 o'clock, the latter is connected. The voltage transformation is realized through the first winding and the second winding; and the phase angle difference regulation and power control between the high-voltage level power grid and the low-voltage level power grid are realized through the gear adjustment of the third winding.

[0044] FIG. 2 is a schematic diagram of the first topological structure of the voltage step-down and phase-shifting integrated transformer according to the first embodiment of the present application. As shown in FIG. 2, the first topological structure of the voltage step-down and 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 level power grid and the low-voltage level power grid, respectively. The in-out line port S end and L end positions are shown in FIG. 2. In the first topological structure, the first winding is angularly connected, the second winding is star-connected, and the clock time sequence number between the first winding and the third winding is 11 o'clock. The third winding is a phase-modulating winding, which has a gear adjustment switch. The input end of the A-phase first winding is connected to the B-phase third winding, the input end of the B-phase first winding is connected to the C-phase third winding, and the input end of the C-phase first winding is connected to the A-phase third winding.

[0045] Figure 3 is a voltage vector diagram of each winding in the first topology of the voltage step-down and phase-shifting integrated transformer according to the first embodiment of the present application, and Figure 4 is a principle diagram of A-phase regulation in the first topology of the voltage step-down and phase-shifting integrated transformer according to the first embodiment of the present application. As shown in Figure 3, the three-phase voltage vectors at P and Q points (P and Q points are two marked positions) of the first winding (shown as #1 in the figure) are represented as U1A, U1B, U1C and U4A, U4B, U4C respectively, the three-phase voltage vectors at the port of 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. As shown in Figure 4, φ represents the phase-shifting angle of the voltage step-down and phase-shifting integrated transformer. Taking the A-phase regulation principle as an example, since the third winding voltage U3B of B-phase and the voltage at Q point of the first winding port are 90° (the third winding voltage U3B of B-phase and the voltage at P point of the first winding port are 90°-φ), the third winding voltage of B-phase is inserted into the first winding port of A-phase, and by determining the third winding ratio and adjusting the gear, the voltage phase φ between P and Q points of the first winding port is adjusted, the phase φ between P point of the first winding port and the second winding port is realized, and thus the phase angle difference and transmission power between the high-voltage side power grid and the low-voltage side power grid are controlled.

[0046] As an optional embodiment of the present application, on the basis of the above-mentioned embodiment, if the voltage step-down and phase-shifting integrated transformer adopts the second topology, the first winding is connected to the high-voltage side power grid, the second winding is connected to two low-voltage side power grids, the voltage step-down and phase-shifting integrated transformer realizes voltage transformation between the high-voltage side and one of the low-voltage sides, and simultaneously realizes voltage transformation and phase angle control between the high-voltage side and the other low-voltage side. This topology is suitable for a substation with multiple transformers, and the voltage step-down and phase-shifting integrated transformer can be operated with other transformers in the substation for a long time or short-term non-power failure load transfer through the non-phase-shifting bus; the voltage step-down and phase-shifting integrated transformer can be interconnected and power regulated with the low-voltage power grid on the opposite side through the phase-shifting bus, and the specific structure is as follows.

[0047] The first winding is connected to a high-voltage side power grid, the second winding has two outgoing lines, one of which is connected to a low-voltage side power grid without phase shift, and the other is connected to a low-voltage side power grid with phase shift through the third winding; based on the clock sequence number of the second winding and the third winding, the second outgoing line of the A-phase second winding is connected to the C-phase third winding or the B-phase third winding; based on the clock sequence number of the second winding and the third winding, the second outgoing line of the B-phase second winding is connected to the A-phase third winding or the C-phase third winding; based on the clock sequence number of the second winding and the third winding, the second outgoing line of the C-phase second winding is connected to the B-phase third winding or the A-phase third winding. If the clock sequence number between the first winding and the third winding is 11 o'clock, the former is connected; if the clock sequence number is 1 o'clock, the latter is connected. The voltage conversion is realized through the first winding and the second winding; the phase angle difference adjustment and power control between the high-voltage level power grid and the low-voltage level power grid of the second outgoing line end are realized through the third winding adjustment.

[0048] Figure 5 is a schematic diagram of a second topology of a step-down and phase-shifting integrated transformer according to an embodiment of the present application. As shown in Figure 5, the second topology of the step-down and 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), and the positions of the incoming and outgoing line ports S, L1, and L2 are shown in Figure 5. The first winding is connected to a high-voltage level power grid; the second winding has two outgoing lines L1 and L2, one of which is connected to a low-voltage side power grid without phase shift, and the other is connected to a phase-shifting power grid through the third winding. The first winding adopts a star connection mode, the second winding adopts an angle connection mode, the clock sequence number between the first winding and the third winding is 11 o'clock, the third winding is a phase-shifting winding, and has a tapping switch; the output end of the A-phase second winding is connected to the C-phase third winding, the output end of the B-phase second winding is connected to the A-phase third winding, and the output end of the C-phase second winding is connected to the B-phase third winding.

[0049] Figure 6 is a voltage vector diagram of each winding in the second topology of the voltage step-down and phase shift integrated transformer according to the first embodiment of the present application, and Figure 7 is a schematic diagram of A-phase regulation in the second topology of the voltage step-down and phase shift integrated transformer according to the first embodiment of the present application. As shown in Figure 6, the three-phase voltage vectors at the port of the first winding (shown as #1 in the figure) are represented as U1A, U1B and U1C, the three-phase voltage vectors at the port of the L1 outgoing line of the second winding (shown as #2 in the figure) are represented as U2A_L1, U2B_L1 and U2C_L1, the three-phase voltage vectors at the port of the L2 outgoing line of the second winding are represented as U2A_L2, U2B_L2 and U2C_L2, and the three-phase voltage vectors of the third winding (shown as #3 in the figure) are represented as U3A, U3B and U3C. U1A is the voltage of the A-phase high-voltage side (#1 winding), U2A_L1 and U2A_L2 are the voltages of the A-phase low-voltage side (#2 winding), and U3C is the winding voltage of the #3 phase-shifting winding. As shown in Figure 7, φ represents the phase difference between the L1 outgoing line of the A-phase low-voltage side (#2 winding) and the L2 outgoing line of the A-phase low-voltage side (#2 winding). Taking the A-phase regulation principle as an example, since the C-phase third winding voltage U3C and the voltage at the port of the second winding L1 are 90°, the C-phase third winding voltage is inserted into the A-phase second winding L1 port, the third winding ratio is determined and the gear is adjusted, the voltage phase φ of the second winding L1 port and L2 port is adjusted, the phase shift angle φ between the first winding S port and the second winding L2 port is realized, and thus the phase angle difference and the transmission power between the high-voltage side and the low-voltage side power grids are controlled.

[0050] As an optional embodiment of the present application, on the basis of the above-mentioned embodiment, if the voltage step-down and phase shift integrated transformer adopts the third topology, the first winding has two outgoing lines, which are connected to two high-voltage side power grids, and the second winding is connected to a low-voltage side power grid. The voltage step-down and phase shift integrated transformer realizes the power flow control or phase angle control between the two high-voltage sides, and simultaneously realizes the voltage conversion between the high-voltage side and the low-voltage side. This topology is suitable for application scenarios in which the high-voltage side power grids need to be interconnected for power exchange. The specific structure is as follows.

[0051] Based on the clock sequence number of the first winding and the third winding, the A-phase first winding input end is inserted into the C-phase third winding or the B-phase third winding; based on the clock sequence number of the first winding and the third winding, the B-phase first winding input end is inserted into the A-phase third winding or the C-phase third winding; based on the clock sequence number of the first winding and the third winding, the C-phase first winding input end is inserted into the B-phase third winding or the A-phase third winding. If the clock sequence number between the first winding and the third winding is 1 point, the former is inserted; if the clock sequence number is 11 points, the latter is inserted. It realizes voltage conversion through the first winding and the second winding; and realizes phase angle difference adjustment and power control between the two high-voltage level power grids through the third winding adjustment.

[0052] Fig. 8 is a schematic diagram of a third topology of the voltage step-down and phase shift integrated transformer according to the first embodiment of the present application. As shown in Fig. 8, the third topology of the voltage step-down and phase shift integrated transformer includes a first winding (shown as #1), a second winding (shown as #2) and a third winding (shown as #3). The three windings form a three-phase three-winding structure. The first winding is an angular connection and has two output terminals S1 and S2, which are connected to a high-voltage side power grid 1 and a high-voltage side power grid 2, respectively. The second winding is an angular connection and is connected to a low-voltage side power grid. The clock time sequence number of the first winding and the third winding is 1 point. The third winding is a phase modulation winding and has a gear adjustment switch. The input terminal of the A-phase first winding is connected to the C-phase third winding in series. The input terminal of the B-phase first winding is connected to the A-phase third winding in series. The input terminal of the C-phase first winding is connected to the B-phase third winding in series.

[0053] Fig. 9 is a voltage vector diagram of each winding in the third topology of the voltage step-down and phase shift integrated transformer according to the first embodiment of the present application. Fig. 10 is an A-phase adjustment principle diagram in the third topology of the voltage step-down and phase shift integrated transformer according to the first embodiment of the present application. As shown in Fig. 9, the three-phase voltage vectors of the S1 output terminal of the first winding (shown as #1) are represented as U1A_S1, U1B_S1 and U1A_S1, respectively. The three-phase voltage vectors of the S2 output terminal of the first winding are represented as U1A_S2, U1B_S2 and U1A_S2, respectively. The three-phase voltage vectors of the second winding (shown as #2) are represented as U2A, U2B and U2C, respectively. The three-phase voltage vectors of the third winding (shown as #3) are represented as U3A, U3B and U3C, respectively. As shown in Fig. 10, φ represents the phase angle difference between the A-phase of the two high-voltage side power grids. Taking the A-phase adjustment principle as an example, since the C-phase voltage U3C of the third winding and the A-phase voltage at the S2 port of the first winding are 90° (the C-phase voltage U3C of the third winding and the A-phase voltage at the S1 port of the first winding are 90°-φ), the A-phase input terminal of the first winding is connected to the C-phase winding voltage of the third winding in series. By determining the third winding ratio and adjusting the gear, the voltage phase of the S1 port and the S2 port of the first winding is adjusted to φ, the phase shift angle φ between the S1 port and the S2 port of the first winding is realized, and the phase angle difference and the transmission power between the two high-voltage side power grids are controlled.

[0054] The above technical solutions respectively embody the specific implementation modes of the three topologies of the voltage step-down and phase shift integrated transformer.

[0055] Embodiment II

[0056] Fig. 11 is a flowchart of a running control method of a voltage step-down and phase shift integrated transformer according to the second embodiment of the present application. The method can be applied to the case of voltage step-down conversion and phase angle control of different voltage grade power grids.

[0057] As shown in FIG. 11, the embodiment two provides a running control method of the voltage reduction and phase shift integrated transformer, which specifically includes the following steps.

[0058] S201, the voltage reduction and phase shift integrated transformer is controlled in loop closing mode to connect the voltage reduction and phase shift integrated transformer to at least two sides of the power grid.

[0059] In the embodiment, the control mode of the voltage reduction and phase shift integrated transformer includes loop closing control, port power control and balance control. The step is used for controlling the voltage reduction and phase shift integrated transformer in loop closing mode to connect the voltage reduction and phase shift integrated transformer to at least two sides of the power grid, and the loop closing control is related to the topological structure of the voltage reduction and phase shift integrated transformer.

[0060] For example, if the voltage reduction and phase shift integrated transformer adopts the first topological structure, the voltage reduction and phase shift integrated transformer is connected to the high-voltage side of the power grid through a first circuit breaker and connected to the low-voltage side of the power grid through a second circuit breaker. The step of controlling the voltage reduction and phase shift integrated transformer in loop closing mode to connect the voltage reduction and phase shift integrated transformer to the power grid can be described as follows: controlling the first circuit breaker to be closed to charge the voltage reduction and phase shift integrated transformer; detecting the phase angle difference between the two sides of the second circuit breaker; if the phase angle difference is less than a set phase angle difference threshold, adjusting the gear adjusting switch, returning 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; and controlling the second circuit breaker to be closed to complete the connection of the voltage reduction and phase shift integrated transformer to the power grid.

[0061] For example, if the voltage reduction and phase shift integrated transformer adopts the second topological structure, the voltage reduction and phase shift integrated transformer is connected to the high-voltage side of the power grid through a third circuit breaker, connected to one low-voltage side of the power grid through a fourth circuit breaker, connected to another low-voltage side of the power grid through a fifth circuit breaker and a second disconnector in turn, and the first disconnector is connected to the fourth circuit breaker and the other low-voltage side of the power grid. The step of controlling the voltage reduction and phase shift integrated transformer in loop closing mode to connect the voltage reduction and phase shift integrated transformer to the power grid can be described as follows: controlling the third circuit breaker to be closed to charge the voltage reduction and phase shift integrated transformer; controlling the fourth circuit breaker to be closed to supply power to the low-voltage side of the power grid; controlling the second disconnector to be closed and the first disconnector to be opened; detecting the phase angle difference between the two sides of the fifth circuit breaker; if the phase angle difference is less than a set phase angle difference threshold, adjusting the gear adjusting switch, returning 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; and controlling the fifth circuit breaker to be closed to complete the connection of the voltage reduction and phase shift integrated transformer to the power grid.

[0062] For example, if the step-up and step-down integrated transformer adopts the third topology structure, the step-up and step-down integrated transformer is connected with one high-voltage side power grid through the sixth circuit breaker, connected with another high-voltage side power grid through the seventh circuit breaker, and connected with a low-voltage side power grid through the eighth circuit breaker. The step of closing the loop control of the step-up and step-down integrated transformer to make the step-up and step-down integrated transformer access the power grid can be described as follows: the seventh circuit breaker is controlled to be closed to charge the step-up and step-down integrated transformer; the eighth circuit breaker is controlled to be closed to supply power to the low-voltage side power grid; the phase angle difference on both sides of the sixth circuit breaker is detected, and if the phase angle difference on both sides of the sixth circuit breaker is less than a set phase angle difference threshold, the gear adjusting switch is adjusted, and the step of detecting the phase angle difference on both sides of the sixth circuit breaker is executed until the phase angle difference is less than the set phase angle difference threshold; and the sixth circuit breaker is controlled to be closed to complete the access of the step-up and step-down integrated transformer to the power grid.

[0063] S202, according to the current power of the port of the step-up and step-down integrated transformer, the target power and the current gear of the gear adjusting switch in the step-up and step-down integrated transformer, the gear of the gear adjusting switch is adjusted until the current power of the port of the step-up and step-down integrated transformer reaches the target power.

[0064] The port power control and the balance control belong to the power flow control of the step-up and step-down integrated transformer, and the step is used to describe the step of the port power control. For the first topology structure, the port power refers to the third winding grid end (S end) or the second winding grid end (L end); for the second topology structure, the port power refers to the first winding grid end (S end) or the third winding grid end (L2 end); and for the third topology structure, the port power refers to the third winding grid end (S1 end) or the first winding grid end (S2 end). The current power can be understood as the power of the port of the step-up and step-down integrated transformer at the current time, and the target power can be understood as the power that the port of the step-up and step-down integrated transformer is expected to reach. The gear of the gear adjusting switch in the step-up and step-down integrated transformer at the current time is recorded as the current gear. If the current power is greater than or less than the target power, the gear of the gear adjusting switch is adjusted according to the size relationship between the current power and the target power until the current power of the port of the step-up and step-down integrated transformer reaches the target power.

[0065] S203, or, a key node in the two sides of the step-up and step-down integrated transformer is selected, and the load rate difference between the key nodes is controlled to be less than a set load rate difference threshold.

[0066] Firstly, key nodes in the power grid on both sides of the phase shifter are selected, and the key nodes in the power grid on both sides connected by the step-down phase-shifting integrated transformer are controlled, which are referred to as a node in the high-voltage side power grid and a node in the low-voltage side power grid for the first topology structure, a node in the high-voltage side power grid and a node in the low-voltage side power grid connected by the phase shifter for the second topology structure, and two nodes in the high-voltage side power grid for the third topology structure, respectively. The step of controlling the load rate difference between the key nodes to be less than a set load rate difference threshold can be described as follows: obtaining a first current power and a first rated capacity of a first key point, and a second current power and a second rated capacity of a second key point; determining a first load rate of the first key point according to the first current power and the first rated capacity, and determining a second load rate of the second key point according to the second current power and the second rated capacity; and 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.

[0067] The above technical solution realizes the functions of loop control, port power control or balance control of the step-down phase-shifting integrated transformer. The port power control is realized by adjusting the gear adjusting switch, and the balance control is realized by controlling the load rate difference between the two key nodes.

[0068] As an optional embodiment of the present application, on the basis of the above embodiment, if the step-down phase-shifting integrated transformer adopts the first topology structure, 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.

[0069] In this embodiment, if the step-down phase-shifting integrated transformer adopts the first topology structure, the step-down phase-shifting integrated transformer is connected to the high-voltage side power grid, i.e., connected to the high-voltage side power grid through the first winding, and a circuit breaker, referred to as the first circuit breaker, is arranged 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, i.e., connected to the low-voltage side power grid through the second winding, and a circuit breaker, referred to as the second circuit breaker, is arranged between the second winding and the low-voltage side power grid.

[0070] Further, the step of performing loop control on the step-down phase-shifting integrated transformer to connect the step-down phase-shifting integrated transformer to the power grid can be optimized, comprising:

[0071] a1) controlling the first circuit breaker to be closed to charge the step-down phase-shifting integrated transformer.

[0072] In the embodiment, when the voltage reduction phase shift integrated transformer is switched from the off state to the on state, the first circuit breaker and the second circuit breaker are in the off state. FIG. 12 is a diagram of the voltage reduction phase shift integrated transformer connected to the power grid in the first topology according to the embodiment. As shown in the figure, the first circuit breaker is denoted as QF1 and the second circuit breaker is denoted as QF2. First, the circuit breaker QF1 (or QF2) is closed to charge the voltage reduction phase shift integrated transformer.

[0073] b1) detecting the phase angle difference on both sides of the second circuit breaker, and if the phase angle difference is less than the set phase angle difference threshold, adjusting the gear adjustment switch, returning 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.

[0074] In the embodiment, the phase angle difference is adjusted to be within the allowable range by adjusting the gear adjustment switch of the voltage reduction phase shift integrated transformer. If the phase angle difference is less than the set phase angle difference threshold, the gear adjustment switch is adjusted, and the step of detecting the phase angle difference on both sides of the second circuit breaker is returned until the phase angle difference is less than the set phase angle difference threshold. Referring to the above example, the phase angle difference on both sides of QF2 (or QF1) is detected, and the gear of the phase shifter is adjusted to make the phase angle difference within the allowable range.

[0075] Referring to the above example, the phase angle difference on both sides of QF2 (or QF1) is detected, and the gear of the phase shifter is adjusted to make the phase angle difference within the allowable range.

[0076] d1) controlling the second circuit breaker to close to connect the voltage reduction phase shift integrated transformer to the power grid.

[0077] In the embodiment, referring to the above example, when the phase angle difference on both sides of the second circuit breaker is less than the set phase angle difference threshold, QF2 (or QF1) is closed, and the voltage reduction phase shift integrated transformer is connected to the high-voltage side power grid and the low-voltage side power grid to perform tie-line power control. The tie-line power control between the high-voltage side power grid and the low-voltage side power grid is achieved by adjusting the gear of the voltage reduction phase shifter.

[0078] It should be noted that in this step, the second circuit breaker can also be controlled to close to charge the voltage reduction phase shift integrated transformer. In this case, the phase angle difference on both sides of the first circuit breaker needs to be detected, and the gear adjustment switch is adjusted to make the phase angle difference less than the set phase angle difference threshold. The first circuit breaker is controlled to close to connect the voltage reduction phase shift integrated transformer to the power grid.

[0079] The above technical solution specifically implements the step of performing loop closing control on the voltage reduction phase shift integrated transformer to connect the voltage reduction phase shift integrated transformer to the power grid when the voltage reduction phase shift integrated transformer adopts the first topology.

[0080] As another optional embodiment of the embodiment of the present application, on the basis of the above embodiment, the step of optimizing the step of connecting the voltage reduction phase shift integrated transformer to the power grid can be performed as follows.

[0081] In the embodiment, if the voltage reduction phase shift integrated transformer adopts the second topology structure, the voltage reduction phase shift 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, and a circuit breaker is arranged between the first winding and the high-voltage side power grid, denoted as a third circuit breaker. The voltage reduction phase shift 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, and the second winding has two outgoing lines, which are connected to the low-voltage side non-phase shift bus and the phase shift bus, respectively. A circuit breaker is arranged between one outgoing line of the second winding and the low-voltage side power grid, denoted as a fourth circuit breaker. A circuit breaker is arranged between the other outgoing line of the second winding and the low-voltage side power grid, denoted as a fifth circuit breaker.

[0082] The step of optimizing the step of connecting the voltage reduction phase shift integrated transformer to the power grid can include the following steps.

[0083] a2) Control the third circuit breaker to be closed to charge the voltage reduction phase shift integrated transformer.

[0084] FIG. 13 is an example diagram of connecting the voltage reduction phase shift integrated transformer adopting the second topology structure to the power grid according to the second embodiment of the present application. As shown in FIG. 13, when the voltage reduction phase shifter is changed from the off state to the on state, the initial state of each side circuit breaker of the voltage reduction phase shifter, that is, the third circuit breaker (QF3), the fourth circuit breaker (QF4), and the fifth circuit breaker (QF5), is in the open state, and the first disconnector (K1) and the second disconnector (K2) are open. The line 1 is powered by the low-voltage side power grid 2 area power supply; the transformer T1 is running, the bus tie switch is closed, and the low-voltage side power grid 1 is powered. The bus tie circuit breaker between the transformer T1 low-voltage bus and the phase shifter bus of the voltage reduction phase shift integrated transformer is denoted as QFM, K1 and K2 are connected to the low-voltage side power grid 2 through the total circuit breaker, and the total circuit breaker (QFL) is closed. First, close the circuit breaker QF3 to charge the voltage reduction phase shift integrated transformer T2.

[0085] b2) Control the fourth circuit breaker to be closed to supply power to the low-voltage side power grid.

[0086] With reference to FIG. 13 and the above description, then, the circuit breaker QF4 is closed, the transformer T1 and the voltage reduction phase shift integrated transformer T2 are long-term or short-term parallel running (that is, the circuit breaker QFM is long-term or short-term closed running), and the low-voltage side power grid 1 is powered.

[0087] c2) controlling the second disconnector to close and the first disconnector to open.

[0088] With continued reference to Fig. 13, as described above, K2 is closed and K1 remains open.

[0089] d2) detecting the phase angle difference across the fifth disconnector, and if the phase angle difference is less than a set phase angle difference threshold, adjusting the tap adjusting switch, and returning to the step of detecting the phase angle difference across the fifth disconnector until the phase angle difference is less than the set phase angle difference threshold.

[0090] With continued reference to Fig. 13, the phase angle difference across QF5 is detected, and the phase shifter tap is adjusted so that the phase angle difference is within an allowable range.

[0091] e2) controlling the fifth disconnector to close to complete the connection of the voltage reduction phase shifter integrated transformer to the power grid.

[0092] With continued reference to Fig. 13, QF5 is closed and line 1 is powered by the phase shifting bus II of the voltage reduction phase shifter.

[0093] The above technical solution specifically implements the step of controlling the voltage reduction phase shifter integrated transformer to close the loop to connect the voltage reduction phase shifter integrated transformer to the power grid if the voltage reduction phase shifter integrated transformer adopts the second topology.

[0094] As another optional embodiment of the present application, on the basis of the above embodiment, if the voltage reduction phase shifter integrated transformer adopts the third topology, the voltage reduction phase shifter integrated transformer is connected to one high-voltage side power grid through a sixth disconnector, to another high-voltage side power grid through a seventh disconnector, and to a low-voltage side power grid through an eighth disconnector.

[0095] In the present embodiment, if the voltage reduction phase shifter integrated transformer adopts the third topology, the voltage reduction phase shifter integrated transformer is connected to the high-voltage side power grid, i.e. connected to two high-voltage side power grids through two outgoing lines of the first winding, a disconnector is arranged between the first winding and one high-voltage side power grid, denoted as a sixth disconnector. Another disconnector is arranged between the first winding and another high-voltage side power grid, denoted as a seventh disconnector. The voltage reduction phase shifter integrated transformer is connected to the low-voltage side power grid, i.e. connected to the low-voltage side power grid through the second winding, a disconnector is arranged between the second winding and the low-voltage side power grid, denoted as an eighth disconnector.

[0096] controlling the voltage reduction phase shifter integrated transformer to close the loop to connect the voltage reduction phase shifter integrated transformer to the power grid, comprising:

[0097] a3) controlling the seventh disconnector to close to charge the voltage reduction phase shifter integrated transformer.

[0098] In the embodiment, when the voltage reduction phase shift integrated transformer is switched from the off state to the on state, the sixth circuit breaker, the seventh circuit breaker and the eighth circuit breaker are in the off state in the initial state. FIG. 14 is an example diagram of the voltage reduction phase shift integrated transformer connected to the power grid in the third topology according to the embodiment of the application. As shown in FIG. 14, the sixth circuit breaker is denoted as QF6, the seventh circuit breaker is denoted as QF7, and the eighth circuit breaker is denoted as QF8. First, QF7 is closed to charge the voltage reduction phase shift integrated transformer.

[0099] b3) controlling the eighth circuit breaker to be closed to supply power to the low-voltage side power grid.

[0100] With reference to FIG. 14, as described above, then QF8 is closed to supply power to the low-voltage side power grid.

[0101] c3) detecting the phase angle difference on both sides of the sixth circuit breaker. If the phase angle difference on both sides of the sixth circuit breaker is less than the set phase angle difference threshold, the gear adjustment switch is adjusted, and the step of detecting the phase angle difference on both sides of the sixth circuit breaker is returned to be executed until the phase angle difference is less than the set phase angle difference threshold.

[0102] With reference to FIG. 14, as described above, then the phase angle difference on both sides of QF6 is detected. When the phase angle difference on both sides of QF6 is less than the set phase angle difference threshold, the phase shifter gear is adjusted to make the phase angle difference within the allowable range.

[0103] d3) controlling the sixth circuit breaker to be closed to complete the connection of the voltage reduction phase shift integrated transformer to the power grid.

[0104] With reference to FIG. 14, as described above, QF6 is closed, and the voltage reduction phase shift integrated transformer is connected to two high-voltage side power grids and one low-voltage side power grid. The voltage reduction phase shift integrated transformer can be controlled to control the gear to make the power exchange between the voltage reduction phase shift integrated transformer outlet and the high-voltage side power grid within the set value range.

[0105] The above technical solution specifically implements the steps of closing the ring to connect the voltage reduction phase shift integrated transformer to the power grid when the voltage reduction phase shift integrated transformer adopts the third topology.

[0106] Embodiment Three

[0107] Fig. 15 is a flow diagram of a method for operating a voltage step-down and phase-shifting integrated transformer according to a third embodiment of the present application. The third embodiment is a further optimization of the first embodiment. In the third embodiment, the step of adjusting the gear of the gear adjustment switch until the current power of the voltage step-down and phase-shifting integrated transformer reaches the target power is further optimized, and the step of controlling the load rate difference between the key nodes to be within a set load rate difference threshold is further optimized.

[0108] As shown in Fig. 15, the second embodiment provides a method for operating a voltage step-down and phase-shifting integrated transformer, which specifically includes the following steps:

[0109] S301, performing loop closing control on the voltage step-down and phase-shifting integrated transformer to connect the voltage step-down and phase-shifting integrated transformer to at least two power grids.

[0110] S302, obtaining the current power of the voltage step-down and phase-shifting integrated transformer, the target power, and the current gear of the gear adjustment switch in the voltage step-down and phase-shifting integrated transformer.

[0111] This step is used to obtain the current power of the voltage step-down and phase-shifting integrated transformer, the target power, and the current gear of the gear adjustment switch in the voltage step-down and phase-shifting integrated transformer.

[0112] S303, if the difference between the current power and the target power is greater than a real-time determined power threshold, adjusting the gear adjustment switch to increase or decrease the gear from the current gear until the difference between the adjusted current power and the target power is less than or equal to the real-time determined power threshold.

[0113] The set power threshold can be set according to actual conditions. In the third embodiment, if the difference between the current power and the target power is greater than a real-time determined power threshold, the gear adjustment switch can be adjusted to increase or decrease the gear from the current gear until the difference between the adjusted current power and the target power is less than or equal to the real-time determined power threshold.

[0114] In the third embodiment, the gear of the gear adjustment switch of the voltage step-down and phase-shifting integrated transformer and the port power are a monotonic function. The gear adjustment switch can be set to increase the gear, and the port power is increased as the associated direction, i.e., the gear adjustment switch is increased, and the port power is increased. Alternatively, the gear adjustment switch can be set to decrease the gear, and the port power is increased as the associated direction, i.e., the gear adjustment switch is decreased, and the port power is increased.

[0115] In this embodiment, the upshift of the gear adjustment switch and the increase of the port power are taken as the associated direction for example. For example, if the target power is greater than the current power, the gear adjustment switch is upshifted by one gear, and the current power of the output port of the step-down phase-shifting integrated transformer after adjustment is obtained. For example, the gear limit value of the phase shifter is -kl to kl, the current gear is k, the target value of the port power is y, and the current port power is y0. When y>y0, the gear of the phase shifter is adjusted to k+1, and the current power of the port at this time is recorded as y1. If the difference between the current power after adjustment and the target power is less than or equal to the set power threshold, the adjustment of the gear adjustment switch is stopped. In this embodiment, if the difference between the current power after adjustment and the target power is less than or equal to the set power threshold, that is, the difference between the actual port power and the target value of the port power at this time is less than the real-time calculation value, it is considered that the target value range is reached, and the adjustment of the gear adjustment switch is stopped.

[0116] According to the above description, if the difference between the current power after adjustment and the target power is greater than or equal to the set power threshold, the step of upshifting the gear adjustment switch by one gear is returned to be executed until the current power of the output port of the step-down phase-shifting integrated transformer reaches the target power. In this embodiment, the power threshold used to determine whether the gear of the step-down phase-shifting integrated transformer is adjusted to the right position is a set value when the gear is adjusted for the first time; the dynamic updated power threshold is used to determine whether the gear of the step-down phase-shifting integrated transformer is adjusted to the right position when the gear is adjusted for the second time and thereafter. The dynamic updated power threshold calculation method is half of the last adjustment port power variation plus the allowable deviation: |y1-y|≤α1 α1=|y1-y0| / 2+ε1

[0117] Wherein, α1 is the power threshold, y is the target value of the port power, y0 is the port power before the last gear adjustment, y1 is the port power after the last gear adjustment (i.e. before this gear adjustment); ε1 is the set allowable error, which considers the sampling error and the difference of each gear adjustment amount.

[0118] It should be noted that if the target power is less than the current power, the gear adjustment switch is adjusted in the opposite direction, and the adjustment principle is the same as above, which will not be described here. In addition, if the gear adjustment switch is downshifted and the port power is increased as the associated direction, the adjustment principle is also the same as above, which will not be described here. If the gear reaches the limit -kl or kl, the adjustment of the gear adjustment switch is stopped; when the current power of the phase shifter deviates from the target value from positive to negative, or deviates from the target value from negative to positive, the gear adjustment is stopped.

[0119] The above technical solution specifically adjusts the gear of the gear adjustment switch until the current power of the output port of the step-down phase-shifting integrated transformer reaches the target power, and realizes the control of the port power of the step-down phase-shifting integrated transformer.

[0120] Embodiment Four

[0121] FIG. 16 is a flowchart of a method for operating a voltage reduction and phase shift integrated transformer according to an embodiment of the present application. The embodiment is a further optimization of the above-mentioned embodiment. In the embodiment, the condition that the load rate difference between the key nodes is less than a set load rate difference threshold is further optimized.

[0122] As shown in FIG. 16, the embodiment provides a method for operating a voltage reduction and phase shift integrated transformer, which specifically includes the following steps:

[0123] S401, performing loop closing control on the voltage reduction and phase shift integrated transformer to connect the voltage reduction and phase shift integrated transformer to at least two power grids.

[0124] S402, selecting key nodes in the two power grids connected by the voltage reduction and phase shift integrated transformer, obtaining a first current power and a first rated capacity of a first key node, and a second current power and a second rated capacity of a second key node.

[0125] In the embodiment, the key nodes in the two power grids connected by the voltage reduction and phase shift integrated transformer are selected. For example, in a voltage reduction and phase shift integrated transformer with one high-voltage side and two low-voltage sides, the main transformer of the high-voltage side and the main transformer of the low-voltage side connected by the phase bus can be selected as the two key nodes, which are respectively referred to as the first key node and the second key node. Since the balanced control is to automatically control the load rate difference between the two key nodes within a certain range, the current power and the rated capacity of the first key node and the second key node need to be obtained in this step. The current power of the first key node is referred to as the first current power, and the rated capacity of the first key node is referred to as the first rated capacity. The current power of the second key node is referred to as the second current power, and the rated capacity of the second key node is referred to as the second rated capacity.

[0126] S403, determining a first load rate of the first key node according to the first current power and the first rated capacity, and determining a second load rate of the second key node according to the second current power and the second rated capacity.

[0127] In the embodiment, the load rate of the key node is calculated by dividing the current power by the rated capacity. Specifically, the first current power is divided by the first rated capacity to obtain the load rate of the first key node, which is referred to as the load rate of the first key node. The second current power is divided by the second rated capacity to obtain the load rate of the second key node, which is referred to as the load rate of the second key node.

[0128] The calculation formula of the load rate of the key node can be expressed as: ηi=Pi / Si i where ηi represents the load rate of the ith key node, Pi represents the current power of the ith key node, and Si represents the rated capacity of the ith key node. i where ηi represents the load rate of the ith key node, Pi represents the current power of the ith key node, and Si represents the rated capacity of the ith key node.iN represents the rated capacity of the i-th key point, i = 1, 2.

[0129] S404, 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.

[0130] In the embodiment, the equalization control automatically controls the load rate difference between the two key points 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.

[0131] Optionally, the determination step of the load rate difference threshold comprises:

[0132] When the first gear is adjusted, the load rate difference threshold used to determine whether the gear of the step-down phase-shifting integrated transformer is adjusted to the right position is a set value;

[0133] When the second and subsequent adjustments are made, a dynamically updated load rate difference threshold is used to determine whether the gear of the step-down phase-shifting integrated transformer is adjusted to the right position, and the calculation method of the dynamically updated load rate difference threshold is half of the load rate difference generated by the last adjustment plus an allowable deviation:

[0134] wherein, a2 is the load rate difference threshold, Dy i represents the power change of the key point under the previous gear adjustment of the step-down phase-shifting integrated transformer, i = 1, 2; ε2 is a set allowable error, considering the sampling error and the difference of each gear adjustment amount.

[0135] When the gear adjustment reaches the upper and lower limits of the gear of the step-down phase-shifting integrated transformer, the gear adjustment stops; when the current power of the phase shifter deviates from the target value from positive to negative, or from negative to positive, the gear adjustment stops.

[0136] It should be noted that when the gear adjustment reaches the upper and lower limits of the gear of the step-down phase-shifting integrated transformer, the gear adjustment stops; when the current power of the step-down phase-shifting integrated transformer deviates from the target value from positive to negative, or from negative to positive, the gear adjustment stops.

[0137] The above technical solution specifically realizes the step of controlling the load rate difference between the key points to be less than the set load rate difference threshold, and realizes the equalization control of the key points of the step-down phase-shifting integrated transformer.

[0138] In order to more clearly describe the phase adjustment and voltage transformation effect realized by the step-down phase-shifting integrated transformer provided in the embodiments of the present application, the simulation results of the three topological structures of the step-down phase-shifting integrated transformer provided in the embodiments are described respectively below. If the step-down phase-shifting integrated transformer adopts the first topological structure, the phase adjustment and voltage transformation effect of the step-down phase-shifting integrated transformer is simulated. In the simulation, the high-voltage side line voltage of the step-down phase-shifter is 20 kV, and the low-voltage side line voltage is 10 kV.

[0139] In order to realize the adjustment of the phase of φ (φ = 5°), the third winding voltage is 1 kV. FIG. 17 is a simulation effect diagram of the step-down phase-shifting integrated transformer adopting the first topological structure to realize the step-down phase-shifting interconnection of the 10 kV power grid and the 20 kV power grid. As shown in FIG. 17, the high-voltage side line voltage of the step-down phase-shifting integrated transformer is about 20 kV, the low-voltage side line voltage is about 10 kV, the phase angle difference between the third winding voltage (U3B) and the high-voltage side first winding voltage port (U1A) of the step-down phase-shifting integrated transformer is 85°, and the addition of the third winding can realize the phase angle adjustment. The low-voltage side voltage (U2A) leads the high-voltage side voltage (U1A) by 35°, and it can be seen that the angle adjustment of φ (φ = 5°) is realized.

[0140] If the step-down phase-shifting integrated transformer adopts the second topological structure, the phase adjustment and voltage transformation effect of the step-down phase-shifting integrated transformer is simulated. In the simulation, the high-voltage side line voltage of the step-down phase-shifter is 220 kV, and the low-voltage side line voltage is 110 kV; in order to realize the adjustment of the phase of φ (φ = 5°), the third winding voltage is 5.5 kV. FIG. 18 is a simulation effect diagram of the step-down phase-shifting integrated transformer adopting the second topological structure to realize the step-down phase-shifting interconnection of the 220 kV power grid and the 110 kV power grid. As shown in FIG. 18, the high-voltage side line voltage of the step-down phase-shifting integrated transformer is about 220 kV, the low-voltage side line voltage is about 110 kV, the phase angle difference between the third winding voltage (U3C) and the low-voltage side second winding L1 port voltage (U2A_L1) of the step-down phase-shifter is 90°, and the addition of the third winding can realize the phase angle adjustment. The low-voltage side L2 end voltage (U2A_L2) leads the low-voltage side L1 end voltage (U2A_L1) by 5° and leads the high-voltage side voltage (U1A) by 35° (the inherent phase angle difference between the high-voltage side and the low-voltage side power grid is 30°), and it can be seen that the angle adjustment of φ (φ = 5°) is realized.

[0141] If the voltage step-down and phase-shifting integrated transformer adopts the third topology structure, the phase adjustment and voltage transformation effect of the simulation voltage step-down and phase-shifting integrated transformer is simulated. Among them, the high-voltage side line voltage of the voltage step-down and phase-shifting integrated transformer is 110 kV, and the low-voltage side line voltage is 35 kV; in order to realize the adjustment of the phase of φ (φ=5°), the third winding voltage is 5.5 kV. FIG. 19 is a simulation effect diagram of the voltage step-down and phase-shifting integrated transformer adopting the third topology structure to realize the voltage step-down and phase-shifting of the interconnection of the 110 kV power grid and the 35 kV power grid. As shown in FIG. 19, the high-voltage side line voltage of the voltage step-down and phase-shifting integrated transformer is about 110 kV, and the low-voltage side line voltage is about 35 kV. At the same time, the third winding voltage (U3C) and the high-voltage side first winding voltage S1 port voltage (U1A_S1) of the voltage step-down and phase-shifting integrated transformer are 90° out of phase, and the addition of the third winding can realize the phase angle adjustment. The low-voltage side voltage (U2A) leads the high-voltage side voltage (U1A) by 5°, and it can be seen that the angle adjustment of φ (φ=5°) is realized.

[0142] It should be understood that the various forms of flow shown above can be reordered, added, or deleted steps. For example, each step described in the present application can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions of the present application can be achieved, and the present application does not limit it here.

Claims

1. A step-down phase-shifting integrated transformer, which is connected to at least two side power grids, and comprises at least: a first winding, a second winding and a third winding, which are three-phase windings; the third winding is a phase-shifting winding and is provided with a gear adjustment switch, the third winding is magnetically coupled to the first winding and the second winding, and is 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 as to realize phase angle control and transmission power control between different side power grids through adjusting the gear adjustment switch on the basis of voltage transformation. If the step-down phase-shifting integrated transformer adopts a first topological structure, the first winding is connected to a high-voltage side power grid, and the second winding is connected to a low-voltage side power grid; based on the clock sequence number of the first winding and the third winding, the input end of the A-phase first winding is connected to the B-phase third winding or the C-phase third winding; 2. The step-down phase-shift integrated transformer of claim 1, wherein, based on the clock sequence number of the first winding and the third winding, the input end of the B-phase first winding is connected to the C-phase third winding or the A-phase third winding; based on the clock sequence number of the first winding and the third winding, the input end of the C-phase first winding is connected to the A-phase third winding or the B-phase third winding; the first winding adopts an angular connection mode, and the second winding adopts a star connection mode. If the step-down phase-shifting integrated transformer adopts a second topological structure, the first winding is connected to a high-voltage side power grid, and the second winding has two outlets, the first outlet is connected to a low-voltage side power grid without phase shifting, and the second outlet is connected to a low-voltage side power grid with phase shifting through the third winding; based on the clock sequence number of the second winding and the third winding, the second outlet of the A-phase second winding is connected to the C-phase third winding or the B-phase third winding; 3. The step-down phase-shift integrated transformer of claim 1, wherein, based on the clock sequence number of the second winding and the third winding, the second outlet of the B-phase second winding is connected to the A-phase third winding or the C-phase third winding; based on the clock sequence number of the second winding and the third winding, the second outlet of the C-phase second winding is connected to the B-phase third winding or the A-phase third winding; the first winding adopts a star connection mode, and the second winding adopts an angular connection mode. If the step-down phase-shifting integrated transformer adopts a third topological structure, the first winding has two outlets, which are connected to two high-voltage side power grids respectively, and the second winding is connected to a low-voltage side power grid; based on the clock sequence number of the first winding and the third winding, the input end of the A-phase first winding is connected to the C-phase third winding or the B-phase third winding; 4. The step-down phase-shift integrated transformer of claim 1, wherein, based on the clock sequence number of the first winding and the third winding, the input end of the B-phase first winding is connected to the A-phase third winding or the C-phase third winding; based on the clock sequence number of the first winding and the third winding, the input end of the C-phase first winding is connected to the B-phase third winding or the A-phase third winding; the first winding adopts an angular connection mode, and the second winding adopts an angular connection mode. The third winding is provided with a polarity conversion switch to realize phase angle lead direction adjustment and lag direction adjustment. ​ 5. The step-down phase-shift integrated transformer of claim 1, wherein, ​ 6. A method for operating a voltage reduction phase-shifting integrated transformer, applied to the voltage reduction phase-shifting integrated transformer of any one of claims 1-5, the method comprising: performing loop closing control on the voltage reduction phase-shifting integrated transformer to connect the voltage reduction phase-shifting integrated transformer to at least two power grids; adjusting the gear of the gear adjustment switch according to the current power of the port of the voltage reduction phase-shifting integrated transformer, the target power, and the current gear of the gear adjustment switch in the voltage reduction phase-shifting integrated transformer, until the current power of the port of the voltage reduction phase-shifting integrated transformer reaches the target power after adjustment; or selecting a key node in the two power grids connected by the voltage reduction phase-shifting integrated transformer, and controlling the load rate difference between the key nodes to be less than a set load rate difference threshold.

7. The method of claim 6, wherein, If the voltage reduction phase-shifting integrated transformer adopts a first topology, the voltage reduction phase-shifting integrated transformer is connected to a high-voltage side power grid through a first circuit breaker, and to a low-voltage side power grid through a second circuit breaker; the loop closing control on the voltage reduction phase-shifting integrated transformer to connect the voltage reduction phase-shifting integrated transformer to a power grid comprises: controlling the first circuit breaker to be closed to charge the voltage reduction phase-shifting integrated transformer; detecting the phase angle difference on both sides of the second circuit breaker, and if the phase angle difference is less than a set phase angle difference threshold, adjusting the gear of the gear adjustment switch, and returning 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; controlling the second circuit breaker to be closed to connect the voltage reduction phase-shifting integrated transformer to the power grid.

8. The method of claim 6, wherein, If the voltage reduction phase-shifting integrated transformer adopts a second topology, the voltage reduction phase-shifting integrated transformer is connected to a high-voltage side power grid through a third circuit breaker, to a low-voltage side power grid through a fourth circuit breaker, to another low-voltage side power grid through a fifth circuit breaker, a second disconnector, and in sequence, and a first disconnector is connected to the fourth circuit breaker and the other low-voltage side power grid; the loop closing control on the voltage reduction phase-shifting integrated transformer to connect the voltage reduction phase-shifting integrated transformer to a power grid comprises: controlling the third circuit breaker to be closed to charge the voltage reduction phase-shifting integrated transformer; controlling the fourth circuit breaker to be closed to supply power to the low-voltage side power grid; controlling the second disconnector to be closed and the first disconnector to be opened; detecting the phase angle difference on both sides of the fifth circuit breaker, and if the phase angle difference is less than a set phase angle difference threshold, adjusting the gear of the gear adjustment switch, and returning 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; controlling the fifth circuit breaker to be closed to complete the connection of the voltage reduction phase-shifting integrated transformer to the power grid.

9. The method of claim 6, wherein, If the voltage reduction phase-shifting integrated transformer adopts a third topology, the voltage reduction phase-shifting integrated transformer is connected to a high-voltage side power grid through a sixth circuit breaker, to another high-voltage side power grid through a seventh circuit breaker, and to a low-voltage side power grid through an eighth circuit breaker; the loop closing control on the voltage reduction phase-shifting integrated transformer to connect the voltage reduction phase-shifting integrated transformer to a power grid comprises: controlling the seventh circuit breaker to be closed to charge the voltage reduction phase-shifting integrated transformer; controlling the eighth circuit breaker to be closed to supply power to the low-voltage side power grid; detecting the phase angle difference between the two sides of the sixth circuit breaker, and if the phase angle difference between the two sides of the sixth circuit breaker is less than a set phase angle difference threshold, adjusting the gear adjustment switch, and returning 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; controlling the sixth circuit breaker to be closed to complete the connection of the step-down phase-shifting integrated transformer to the power grid.

10. The method of claim 6, wherein, for the first topology, the current power and the target power of the port of the step-down phase-shifting integrated transformer are the current power and the target power of the third winding power grid end or the second winding power grid end; for the second topology, the current power and the target power of the port of the step-down phase-shifting integrated transformer are the current power and the target power of the first winding power grid end or the third winding power grid end; for the third topology, the current power and the target power of the port of the step-down phase-shifting integrated transformer are the current power and the target power of the third winding power grid end or the first winding power grid end.

11. The method of claim 6, wherein, for the first topology, the key nodes in the power grid 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 grid 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 grid connected by the step-down phase-shifting integrated transformer are respectively a node in each of the two high-voltage side power grids. the step of adjusting the gear of the gear adjustment switch according to the current power and the target power of the port of the step-down phase-shifting integrated transformer and the current gear of the gear adjustment switch in the step-down phase-shifting integrated transformer until the current power of the port of the step-down phase-shifting integrated transformer reaches the target power, comprises:

12. The method of claim 6, wherein, obtaining the current power and the target power of the port of the step-down phase-shifting integrated transformer and the current gear of the gear adjustment switch in the step-down phase-shifting integrated transformer; if the difference between the current power and the target power is greater than a set power threshold, adjusting the gear of the gear adjustment switch to be increased or decreased from the current gear until the difference between the adjusted current power and the target power is less than or equal to the real-time determined power threshold. the step of controlling the load rate difference between the key nodes to be within a set load rate difference threshold, comprises:

13. The method of claim 6, wherein, obtaining the first current power and the first rated capacity of the first key node, and the second current power and the second rated capacity of the second key node; determining the first load rate of the first key node according to the first current power and the first rated capacity, and determining the second load rate of the second key node according to the second current power and the 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. the step of determining the power threshold, comprises:

14. The method of claim 12, wherein, ​ The power threshold value used to determine whether the step of the integrated voltage reduction and phase shift transformer is adjusted to the right position is a set value during the first step adjustment; The power threshold value used to determine whether the step of the integrated voltage reduction and phase shift transformer is adjusted to the right position is a set value during the first step adjustment; α1=|y1-y0| / 2+ε1 Wherein, α1 is the power threshold value, y0 is the port power before the last step adjustment, y1 is the port power after the last step adjustment; ε1 is the allowable error considering the sampling error and the difference of each step adjustment.

15. The method of claim 13, wherein, The determination step of the load rate difference threshold value comprises: The load rate difference threshold value used to determine whether the step of the integrated voltage reduction and phase shift transformer is adjusted to the right position is a set value during the first step adjustment; In the second and subsequent adjustments, the dynamic updated load rate difference threshold value is used to determine whether the step of the step-down phase-shifting integrated transformer is adjusted to the right position, and the formula of the dynamic updated load rate difference threshold value is represented as: wherein a2 is a load rate difference threshold value, S iN represents the rated capacity of the i-th key point, i = 1, 2; Ay i represents the power change amount of the key point under the previous step regulation of the step-down phase-shifting integrated transformer, i = 1, 2; and ε2 is an allowable error set considering the sampling error and the difference of each step regulation amount.

16. The method of claim 12 or 13, wherein, When the step adjustment reaches the upper and lower limits of the step of the integrated voltage reduction and phase shift transformer, the step adjustment stops; when the current power of the integrated voltage reduction and phase shift transformer deviates from the target value from positive to negative or from negative to positive, the step adjustment stops.

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