Power transformer and photovoltaic power generation system

Abstract

The application provides a power transformer and a photovoltaic power generation system. The power transformer comprises a low-voltage unit, an iron core and a high-voltage unit, the high-voltage unit comprises a three-phase high-voltage part, a first voltage regulation switch and a second voltage regulation switch, one phase high-voltage part in the three-phase high-voltage part comprises a first high-voltage branch and a second high-voltage branch, the first high-voltage branch comprises a first high-voltage coil, the first voltage regulation switch and a first voltage regulation coil, the second high-voltage branch comprises a second high-voltage coil, the second voltage regulation switch and a second voltage regulation coil, and the first high-voltage branch and the second high-voltage branch are connected in parallel between a high-voltage part inlet end and a high-voltage part tail end of the phase high-voltage part. The power transformer can reduce the volume, reduce the cost, reduce the space occupation and make the reliability higher.

Description

Technical Field

[0001] This invention relates to the field of power generation equipment, and in particular to a power transformer and a photovoltaic power generation system. Background Technology

[0002] In photovoltaic power plants, power transformers are used for voltage step-up or step-down regulation, enabling the electricity generated by the photovoltaic power plant to be connected to the grid and output. As a core component, the power transformer's high-voltage coil typically adopts a center-entry structure, and the corresponding voltage regulating coil also uses a center-entry method. Under this connection method, the on-load tap changer needs to carry the current of all three phases of the high-voltage side, thus placing high demands on its current withstand capability.

[0003] When the three-phase tap changer current of a transformer is large, a single three-phase on-load tap changer capable of handling a larger current is generally selected. If the current exceeds the upper limit of the three-phase on-load tap changer, three single-phase on-load tap changers are used. However, using three single-phase switches significantly increases the complexity of the overall transformer layout and introduces numerous structural problems. Specifically, three single-phase switches occupy more internal space in the oil tank than a single three-phase switch, forcing a corresponding increase in tank size and consequently increasing transformer oil consumption. Furthermore, the support structure for three single-phase switches is more complex, and the installation and interconnection on the tank cover are more cumbersome, adversely affecting the transformer's mechanical design, assembly process, and long-term operational reliability. Summary of the Invention

[0004] To at least address some of the aforementioned problems, this invention proposes a power transformer and a photovoltaic power generation system.

[0005] According to a first aspect of the present invention, a power transformer is provided, comprising a low-voltage unit, an iron core, and a high-voltage unit. The high-voltage unit includes a three-phase high-voltage section, a first voltage regulating switch, and a second voltage regulating switch. One phase of the three-phase high-voltage section includes: a first high-voltage branch, comprising a first high-voltage coil and a first voltage regulating coil, the first voltage regulating coil including a plurality of first leads, wherein the first voltage regulating switch includes a first selection terminal, a first tail terminal, and a plurality of first heads, one of the first leads is connected to one of the first heads, and the tail terminal of the first high-voltage coil is connected to the first selection terminal; and a second high-voltage branch, comprising a second high-voltage coil and a second... The voltage regulating coil includes multiple second lead terminals. The second voltage regulating switch includes a second selection terminal, a second tail terminal, and multiple second start terminals. One of the multiple second lead terminals is connected to one of the multiple second start terminals. The tail terminal of the second high-voltage coil is connected to the second selection terminal. The first tail terminal of the first voltage regulating switch and the second tail terminal of the second voltage regulating switch are connected to the high-voltage section tail terminal of a phase high-voltage section. Thus, when the power transformer is running, the sum of the current flowing between the first high-voltage coil, the first voltage regulating coil, and the first voltage regulating switch, and the current flowing between the second high-voltage coil, the second voltage regulating coil, and the second voltage regulating switch, is equal to the current flowing at the high-voltage section tail terminal of a phase high-voltage section.

[0006] Optionally, in the height direction, the first high-voltage coil of the first high-voltage branch is disposed above the second high-voltage coil of the second high-voltage branch, and the input terminals of the first high-voltage coil of the first high-voltage branch and the second high-voltage coil of the second high-voltage branch are adjacent to each other and connected to the input terminal of the high-voltage section of a phase high-voltage section.

[0007] Optionally, the first voltage regulating switch includes a first polarity selector, which has a first selection terminal, a first positive terminal, and a first negative terminal. The tail end of the first high-voltage coil is connected to the first selection terminal. The first positive terminal is connected to one of a plurality of first terminals, and the first negative terminal is connected to another of the plurality of first terminals. The first polarity selector controls the first selection terminal to be connected to either the first positive terminal or the first negative terminal. The second voltage regulating switch includes a second polarity selector, which has a second selection terminal, a second positive terminal, and a second negative terminal. The tail end of the second high-voltage coil is connected to the second selection terminal. The second positive terminal is connected to one of a plurality of second terminals, and the second negative terminal is connected to another of the plurality of second terminals. The second polarity selector controls the second selection terminal to be connected to either the second positive terminal or the second negative terminal.

[0008] Optionally, the first voltage regulating switch includes a first terminal selector, the first terminal selector including a first moving contact, the first end of the first moving contact being connected to the first tail end of the first voltage regulating switch, and the second end of the first moving contact being operated to connect the second end of the first moving contact to one of a plurality of first heads; the second voltage regulating switch includes a second terminal selector, the second terminal selector including a second moving contact, the first end of the second moving contact being connected to the second tail end of the second voltage regulating switch, and the second end of the second moving contact being operated to connect the second end of the second moving contact to one of a plurality of second heads.

[0009] Optionally, the high-voltage section of one phase is connected to the neutral point.

[0010] Optionally, the first voltage regulating switch is a three-phase voltage regulating switch with a rated current value greater than or equal to half of the current flowing at the end of the high-voltage section of a single-phase high-voltage section and less than the current flowing through the end of the high-voltage section of a single-phase high-voltage section; and / or, the second voltage regulating switch is a three-phase voltage regulating switch with a rated current value greater than or equal to half of the current flowing through the end of the high-voltage section of a single-phase high-voltage section and less than the current flowing through the end of the high-voltage section of a single-phase high-voltage section.

[0011] Optionally, the neutral point terminal of the first voltage regulating switch and the neutral point terminal of the second voltage regulating switch are grounded.

[0012] According to a second aspect of the present invention, the present invention provides a photovoltaic power generation system, which includes a photovoltaic power generation device and a power transformer connected to the photovoltaic power generation device, wherein the power transformer is the aforementioned power transformer.

[0013] In this invention, the power transformer includes a low-voltage unit, an iron core, and a high-voltage unit. In this embodiment, the high-voltage unit of the power transformer includes a three-phase high-voltage section, a first voltage regulating switch, and a second voltage regulating switch. One phase of the three-phase high-voltage section includes a first high-voltage branch and a second high-voltage branch. Since the first high-voltage branch and the second high-voltage branch are configured separately, the first voltage regulating switch connected to the first high-voltage branch and the second voltage regulating switch connected to the second high-voltage branch respectively bear the current of their respective high-voltage branches, avoiding a single voltage regulating switch bearing the entire current, thus greatly reducing the current carrying capacity requirements of the voltage regulating switches. Compared to the method of connecting the voltage regulating coils of two high-voltage branches in parallel to a single voltage regulating switch, the solution of this application can use two three-phase voltage regulating switches in the three-phase high-voltage section. Structurally, two three-phase voltage regulating switches can save half the space compared to three single-phase switches, thereby reducing the required tank size and transformer oil consumption, and simplifying internal support and cover connection. For the first high-voltage branch, multiple first leads of the first voltage regulating coil are connected to multiple first terminals of the first voltage regulating switch, and are connected to the first high-voltage coil through the first voltage regulating switch. For the second high-voltage branch, multiple second leads of the second voltage regulating coil are connected to multiple second terminals of the second voltage regulating switch, and are connected to the second high-voltage coil through the second voltage regulating switch. In this way, the direction (e.g., positive or negative connection) and number of turns of the corresponding voltage regulating coil connected to the corresponding high-voltage coil can be controlled by the operation of the corresponding voltage regulating switch, thereby controlling the transformation ratio of the power transformer. Attached Figure Description

[0014] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which will make the above and other features and advantages of the present invention more apparent to those skilled in the art. In the drawings: Figure 1 This is a schematic diagram of a power transformer including a high-voltage coil, a voltage regulating coil, and a voltage regulating switching switch, provided as an embodiment of the present invention.

[0015] Figure 2 This is a schematic diagram of the three-phase first high-voltage branch connection of a power transformer provided in an embodiment of the present invention.

[0016] Figure 3 This is a schematic diagram showing the connection of a first high-voltage coil, a first voltage regulating coil, and a first voltage regulating switching switch in a power transformer, as provided in an embodiment of the present invention.

[0017] Figure 4 This is a schematic diagram of a power transformer provided in an embodiment of the present invention.

[0018] The accompanying figure is labeled as follows: 1. First phase high voltage section; 2. Second phase high voltage section; 3. Third phase high voltage section; 100. First high voltage branch; 111. First high voltage coil; 121. First voltage regulating switch; 1211. First selection terminal; 1212. First tail terminal; 1213. First head terminal; 1214. First polarity selector; 1215. First positive terminal; 1216. First negative terminal; 1217. First moving contact; 131. First voltage regulating coil; 1311. First lead terminal; 200. Second high voltage branch; 211. Second high voltage coil; 221. Second voltage regulating switch; 2212. Second tail terminal; 2213. Second head terminal; 231. Second voltage regulating coil; 2311. Second lead terminal. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the following embodiments are provided to further illustrate the present invention in detail.

[0020] like Figures 1 to 4As shown, an embodiment of the present invention provides a power transformer and a photovoltaic power generation system. The power transformer includes a low-voltage unit, an iron core, and a high-voltage unit. The high-voltage unit includes a three-phase high-voltage section, a first voltage regulating switch 121, and a second voltage regulating switch 221. One phase of the three-phase high-voltage section includes a first high-voltage branch 100 and a second high-voltage branch 200. The first high-voltage branch 100 includes a first high-voltage coil 111 and a first voltage regulating coil 131. The first voltage regulating coil 131 includes a plurality of first lead-out terminals 1311. The first voltage regulating switch 121 includes a first selection terminal 1211, a first tail terminal 1212, and a plurality of first head terminals 1213. One of the first lead-out terminals 1311 is connected to one of the first head terminals 1213. The tail terminal E of the first high-voltage coil 111 is connected to the first selection terminal 1211. The second high-voltage branch 200 includes a second high-voltage coil 211 and a second voltage regulating coil 231. The second voltage regulating coil 231 includes a plurality of second lead-out terminals 2311. The second voltage regulating switch 221 includes a second selection terminal, a second tail terminal 2212, and a plurality of second start terminals 2213. One of the second lead-out terminals 2311 is connected to one of the second start terminals 2213. The tail terminal of the second high-voltage coil 211 is connected to the second selection terminal. The first tail terminal 1212 of the first voltage regulating switch 121 and the second tail terminal 2212 of the second voltage regulating switch 221 are connected to the high-voltage section tail terminal of a phase high-voltage section. Thus, when the power transformer is running, the sum of the current flowing between the first high-voltage coil 111, the first voltage regulating coil 131, and the first voltage regulating switch 121 and the current flowing between the second high-voltage coil 211, the second voltage regulating coil 231, and the second voltage regulating switch 221 is equal to the current flowing at the high-voltage section tail terminal of a phase high-voltage section.

[0021] The power transformer includes a low-voltage unit, a core, and a high-voltage unit. In this embodiment, the high-voltage unit of the power transformer includes a three-phase high-voltage section, a first voltage regulating switch 121, and a second voltage regulating switch 221. One phase of the three-phase high-voltage section includes a first high-voltage branch 100 and a second high-voltage branch 200. Since the first high-voltage branch 100 and the second high-voltage branch 200 are configured separately, the first voltage regulating switch 121 connected to the first high-voltage branch 100 and the second voltage regulating switch 221 connected to the second high-voltage branch 200 respectively bear the current of their respective high-voltage branches, avoiding a single voltage regulating switch bearing the entire current, thus greatly reducing the current carrying capacity requirements of the voltage regulating switches. Compared to the method of connecting the voltage regulating coils of two high-voltage branches in parallel to a single voltage regulating switch, the solution of this application can use two three-phase voltage regulating switches in the three-phase high-voltage section. Structurally, two three-phase voltage regulating switches can save half the space compared to three single-phase switches, thereby reducing the required tank size and transformer oil consumption, and simplifying internal support and cover connection. For the first high-voltage branch 100, multiple first leads 1311 of the first voltage regulating coil 131 are connected to multiple first terminals 1213 of the first voltage regulating switch 121, and are connected to the first high-voltage coil 111 through the first voltage regulating switch 121. For the second high-voltage branch 200, multiple second leads 2311 of the second voltage regulating coil 231 are connected to multiple second terminals 2213 of the second voltage regulating switch 221, and are connected to the second high-voltage coil 211 through the second voltage regulating switch 221. In this way, the direction (e.g., positive or negative connection) and number of turns of the corresponding voltage regulating coil connected to the corresponding high-voltage coil can be controlled by the operation of the corresponding voltage regulating switch, thereby controlling the transformation ratio of the power transformer.

[0022] In this embodiment, the low-voltage unit can be the power input side, and the high-voltage unit can be the power output side, that is, the power transformer can step up the voltage. Alternatively, the low-voltage unit can be the power output side, and the high-voltage unit can be the power input side, that is, the power transformer can step down the voltage. There are no restrictions on this.

[0023] Compared to the scheme of connecting the voltage regulating coils of two high-voltage branches in parallel and then connecting them to a voltage regulating switch, this method makes the first voltage regulating coil 131 and the second voltage regulating coil 231 independent of each other, and connects them to their respective first voltage regulating switch 121 and second voltage regulating switch 221. This allows the current to flow through the corresponding voltage regulating switch before being connected in parallel, thereby achieving forced current shunting and reducing the current that each voltage regulating switch needs to carry.

[0024] Optionally, in the height direction, the first high-voltage coil 111 of the first high-voltage branch 100 is disposed above the second high-voltage coil 211 of the second high-voltage branch 200, and the input end of the first high-voltage coil 111 of the first high-voltage branch 100 and the input end of the second high-voltage coil 211 of the second high-voltage branch 200 are adjacent to each other and connected to the input end of the high-voltage section of a phase high-voltage section.

[0025] For example, such as Figure 1 and Figure 4 As shown, in some specific examples, a single-phase high-voltage section includes two high-voltage branches, namely a first high-voltage branch 100 and a second high-voltage branch 200. The first high-voltage coil 111 of the first high-voltage branch 100 is positioned above the second high-voltage coil 211 of the second high-voltage branch 200, and the input terminals S of the first and second high-voltage coils 111 and 211 are adjacent to each other. These two input terminals are connected to the high-voltage section input terminal A (or B or C) of the high-voltage section, thereby achieving a central input. This central input method can effectively reduce the voltage carried by the coil, optimize the insulation structure, and improve heat distribution.

[0026] Reference Figure 2 In this embodiment, the high-voltage section of one phase is connected to the neutral point N. For example, the high-voltage sections of the first phase 1, the second phase 2, and the third phase 3 are each connected to the neutral point N. This Y-connection method effectively utilizes the neutral point N, enabling the power transformer to adapt to the needs of grounding, harmonic suppression, voltage regulation, and power supply methods.

[0027] Optionally, the first voltage regulating switch 121 is a three-phase voltage regulating switch with a rated current value greater than or equal to half the current flowing at the tail end of the high-voltage section of one phase, and less than the current flowing through the tail end of the high-voltage section of one phase; and / or, the second voltage regulating switch 221 is a three-phase voltage regulating switch with a rated current value greater than or equal to half the current flowing at the tail end of the high-voltage section of one phase, and less than the current flowing through the tail end of the high-voltage section of one phase. Thus, the current value flowing from the first voltage regulating switch 121 and the current value flowing from the second voltage regulating switch 221 are half the current value at the tail end of the high-voltage section.

[0028] For example, if the output current of each phase of the three-phase high-voltage section is X, and a scheme using parallel voltage regulating coils connected to a voltage regulating switch is adopted, a voltage regulating switch with a rated current of X needs to be selected, or three single-phase switches need to be selected. However, the scheme of this application can use two three-phase voltage regulating switches with a rated current of half X. This reduces the space occupied compared to three single-phase switches, and allows for the selection of switches with a lower rated current compared to the scheme using one voltage regulating switch.

[0029] like Figure 1 As shown, the neutral point terminal of the first voltage regulating switch 121 and the neutral point terminal O of the second voltage regulating switch 221 are grounded to ensure safety and to help maintain the stability of the neutral point potential during voltage regulation switching.

[0030] See also Figures 1 to 3 The first voltage regulating switch 121 includes a first polarity selector 1214, which has a first selection terminal 1211, a first positive terminal 1215, and a first negative terminal 1216. The tail end of the first high-voltage coil 111 is connected to the first selection terminal 1211, the first positive terminal 1215 is connected to one of the plurality of first terminals 1213, and the first negative terminal 1216 is connected to another of the plurality of first terminals 1213. The first polarity selector 1214 controls the first selection terminal 1211 to be connected to either the first positive terminal 1215 or the first negative terminal 1216. By using the first polarity selector 1214, the first voltage regulating coil 131 can be connected to the first high voltage coil 111 in either the positive or negative direction without changing the physical structure of the first voltage regulating coil 131 and the first high voltage coil 111. This allows the total effective number of coil turns in the first high voltage branch 100 to be more or less than the number of turns in the first high voltage coil 111, thereby increasing the voltage regulation range and the richness of adjustable levels in the first high voltage branch 100. For example, when the first polarity selector 1214 controls the first selection terminal 1211 to connect with the first positive terminal 1215, so that the first voltage regulating coil 131 is connected in the positive direction, the direction of current flowing through the first voltage regulating coil 131 is the same as the direction of current flowing through the first high voltage coil 111, which can increase the magnetic flux and strengthen the first high voltage coil 111, so that the number of effective turns is the number of turns of the first high voltage coil 111 plus the number of turns of the connected first voltage regulating coil 131; when the first polarity selector 1214 controls the first selection terminal 1211 to connect with the first negative terminal 1216, so that the first voltage regulating coil 131 is connected in the reverse direction, the direction of current flowing through the first voltage regulating coil 131 is different from the direction of current flowing through the first high voltage coil 111, which can reduce the magnetic flux and weaken the first high voltage coil 111, so that the number of effective turns is the number of turns of the first high voltage coil 111 minus the number of turns of the connected first voltage regulating coil 131.

[0031] The second voltage regulating switch 221 includes a second polarity selector, which has a second selection terminal, a second positive terminal, and a second negative terminal. The tail end of the second high-voltage coil 211 is connected to the second selection terminal. The second positive terminal is connected to one of the plurality of second heads 2213, and the second negative terminal is connected to another of the plurality of second heads 2213. The second polarity selector controls the second selection terminal to be connected to either the second positive terminal or the second negative terminal.

[0032] The principle of the second voltage regulating switch 221 is similar to that of the first voltage regulating switch 121. Through the second polarity selector of the second voltage regulating switch 221, the second voltage regulating coil 231 can be connected to the second high-voltage coil 211 in either the positive or negative direction without changing the physical structure of the second voltage regulating coil 231 and the second high-voltage coil 211. This allows the total effective coil turns of the second high-voltage branch 200 to be more or less than the number of turns of the second high-voltage coil 211, thereby increasing the voltage regulation range and the adjustability of the voltage levels in the second high-voltage branch 200. For example, when the second polarity selector controls the second selection terminal to connect to the second positive terminal, causing the second voltage regulating coil 231 to be connected in the positive direction, the direction of current flowing through the second voltage regulating coil 231 is the same as the direction of current flowing through the second high-voltage coil 211. This increases the magnetic flux and strengthens the second high-voltage coil 211, so that the effective number of turns is the number of turns of the second high-voltage coil 211 plus the number of turns of the connected second voltage regulating coil 231. When the second polarity selector controls the second selection terminal to connect to the second negative terminal, causing the second voltage regulating coil 231 to be connected in the reverse direction, the direction of current flowing through the second voltage regulating coil 231 is different from the direction of current flowing through the second high-voltage coil 211. This decreases the magnetic flux and weakens the second high-voltage coil 211, so that the effective number of turns is the number of turns of the second high-voltage coil 211 minus the number of turns of the connected second voltage regulating coil 231. It should be noted that... Figure 2 and Figure 3 The diagram shows a schematic of the connection of the first high-voltage branch section.

[0033] Optionally, such as Figure 3 As shown, the first voltage regulating switch 121 includes a first terminal selector, which includes a first moving contact 1217. The first end of the first moving contact 1217 is connected to the first tail end 1212 of the first voltage regulating switch 121. The second end of the first moving contact 1217 is operated to connect to one of a plurality of first heads 1213. The second voltage regulating switch 221 includes a second terminal selector, which includes a second moving contact. The first end of the second moving contact is connected to the second tail end 2212 of the second voltage regulating switch 221. The second end of the second moving contact is operated to connect to one of a plurality of second heads 2213. Since the effective number of turns of the voltage regulating coils corresponding to different first leads 1311 and different second leads 2311 are different, the first moving contact 1217 and the second moving contact can be connected to different first ends to realize the switching of the number of turns of the first voltage regulating coil 131 and the second voltage regulating coil 231 connected to the corresponding high voltage coil.

[0034] In addition to the terminal selector and polarity selector mentioned above, the first voltage regulating switch 121 and / or the second voltage regulating switch 221 may also include a load switch, which can switch after the corresponding moving contact is switched to the appropriate start end, thereby achieving output switching without interrupting power.

[0035] In summary, the power transformer in this embodiment solves the problem in traditional power transformer designs where the current flowing into the voltage regulating switch is the sum of the currents of all parallel branches. If a single three-phase voltage regulating switch is used, it requires a high current carrying capacity, resulting in higher cost and larger size. If the current exceeds the limit of a single voltage regulating switch, only three single-phase voltage regulating switches can be used. Although the current load of each switch is smaller, this increases the number of switches by two, leading to a larger space requirement for the power transformer.

[0036] In this scheme, a forced current shunting method is adopted, connecting the first high-voltage branch 100 corresponding to the first high-voltage coil 111 and the first voltage regulating coil 131 to the first voltage regulating switch 121, and connecting the second high-voltage branch 200 corresponding to the second high-voltage coil 211 and the second voltage regulating coil 231 to the second voltage regulating switch 221. The two voltage regulating coils are not connected in parallel before being connected to the same voltage regulating switch; instead, after passing through their respective voltage regulating switches, the first high-voltage branch 100 and the second high-voltage branch 200 are connected in parallel between the high-voltage section inlet and outlet of a single-phase high-voltage section. Therefore, the current borne by each voltage regulating switch is the current of the corresponding high-voltage branch, reducing the current that the voltage regulating switch needs to carry, thus reducing the cost and size of the voltage regulating switches. Compared to the scheme with three single-phase voltage regulating switches, the number of voltage regulating switches is reduced, the space occupied is reduced, saving half the space, thereby reducing the size of the oil tank and the amount of transformer oil used, and lowering the manufacturing cost of the oil tank and the cost of transformer oil. Furthermore, the internal support is simple, and the cover connection is simple, reducing the workload of design and installation.

[0037] According to another aspect of this application, a photovoltaic power generation system is provided, comprising a photovoltaic power generation device and a power transformer connected to the photovoltaic power generation device, wherein the power transformer is any of the aforementioned power transformers. The power generation system using this power transformer occupies less space, has higher reliability, and lower cost.

[0038] Optionally, the photovoltaic power generation equipment is connected to the low-voltage unit of a power transformer, and the power transformer boosts the electrical energy output from the photovoltaic power generation equipment at a first voltage to a second voltage. This power transformer can effectively boost the electrical energy output from the photovoltaic power generation equipment, thereby achieving low-loss, long-distance transmission and effectively and fully utilizing clean energy.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A power transformer, characterized in that, The power transformer includes a low-voltage unit, an iron core, and a high-voltage unit. The high-voltage unit includes a three-phase high-voltage section, a first voltage regulating switch (121), and a second voltage regulating switch (221). One phase of the three-phase high-voltage section includes: The first high-voltage branch (100) includes a first high-voltage coil (111) and a first voltage regulating coil (131). The first voltage regulating coil (131) includes a plurality of first lead-out terminals (1311). The first voltage regulating switch (121) includes a first selection terminal (1211), a first tail terminal (1212) and a plurality of first heads (1213). One of the first lead-out terminals (1311) is connected to one of the first heads (1213). The tail terminal of the first high-voltage coil (111) is connected to the first selection terminal (1211). The second high-voltage branch (200) includes a second high-voltage coil (211) and a second voltage regulating coil (231). The second voltage regulating coil (231) includes a plurality of second lead-out terminals (2311). The second voltage regulating switch (221) includes a second selection terminal, a second tail terminal (2212) and a plurality of second head terminals (2213). One of the plurality of second lead-out terminals (2311) is connected to one of the plurality of second head terminals (2213). The tail terminal of the second high-voltage coil (211) is connected to the second selection terminal. Wherein, the first tail end (1212) of the first voltage regulating switch (121) and the second tail end (2212) of the second voltage regulating switch (221) are connected to the high voltage tail end of the one-phase high voltage section, so that when the power transformer is running, the sum of the current flowing between the first high voltage coil (111), the first voltage regulating coil (131) and the first voltage regulating switch (121) and the current flowing between the second high voltage coil (211), the second voltage regulating coil (231) and the second voltage regulating switch (221) is equal to the current flowing at the high voltage tail end of the one-phase high voltage section.

2. The power transformer according to claim 1, characterized in that, In the height direction, the first high-voltage coil (111) of the first high-voltage branch (100) is disposed above the second high-voltage coil (211) of the second high-voltage branch (200), and the input end of the first high-voltage coil (111) of the first high-voltage branch (100) and the input end of the second high-voltage coil (211) of the second high-voltage branch (200) are adjacent to each other and connected to the input end of the high-voltage section of the phase high-voltage section.

3. The power transformer according to claim 1 or 2, characterized in that, The first voltage regulating switch (121) includes a first polarity selector (1214), the first polarity selector (1214) has a first selection terminal (1211), the first polarity selector (1214) also has a first positive terminal (1215) and a first negative terminal (1216), the tail end of the first high voltage coil (111) is connected to the first selection terminal (1211), the first positive terminal (1215) is connected to one of the plurality of first terminals (1213), the first negative terminal (1216) is connected to another of the plurality of first terminals (1213), and the first polarity selector (1214) controls the first selection terminal (1211) to be connected to the first positive terminal (1215) or the first negative terminal (1216); The second voltage regulating switch (221) includes a second polarity selector, which has a second selection terminal, a second positive terminal, and a second negative terminal. The tail end of the second high-voltage coil (211) is connected to the second selection terminal. The second positive terminal is connected to one of the plurality of second terminals (2213), and the second negative terminal is connected to another of the plurality of second terminals (2213). The second polarity selector controls the second selection terminal to be connected to either the second positive terminal or the second negative terminal.

4. The power transformer according to claim 1, characterized in that, The first voltage regulating switch (121) includes a first terminal selector, the first terminal selector includes a first moving contact (1217), a first end of the first moving contact (1217) is connected to a first tail end (1212) of the first voltage regulating switch (121), and a second end of the first moving contact (1217) is operated to connect the second end of the first moving contact (1217) to one of the plurality of first heads (1213); The second voltage regulating switch (221) includes a second terminal selector, the second terminal selector includes a second moving contact, the first end of the second moving contact is connected to the second tail end (2212) of the second voltage regulating switch (221), and the second end of the second moving contact is operated to connect the second end of the second moving contact to one of the plurality of second head ends (2213).

5. The power transformer according to claim 1, characterized in that, The high-voltage section of the first phase is connected to the neutral point at its tail end.

6. The power transformer according to claim 1, characterized in that, The first voltage regulating switch (121) is a three-phase voltage regulating switch with a rated current value greater than or equal to half of the current flowing at the tail end of the high-voltage section of the one-phase high-voltage section and less than the current flowing through the tail end of the high-voltage section of the one-phase high-voltage section; and / or, the second voltage regulating switch (221) is a three-phase voltage regulating switch with a rated current value greater than or equal to half of the current flowing through the tail end of the high-voltage section of the one-phase high-voltage section and less than the current flowing through the tail end of the high-voltage section of the one-phase high-voltage section.

7. The power transformer according to claim 1, characterized in that, The neutral point terminal of the first voltage regulating switch (121) and the neutral point terminal of the second voltage regulating switch (221) are grounded.

8. A photovoltaic power generation system, characterized in that, It includes a photovoltaic power generation device and a power transformer connected to the photovoltaic power generation device, wherein the power transformer is any one of claims 1-7.

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