Voltage regulating structure and voltage regulating method of dual-frequency general transformer

Abstract

The invention discloses a voltage regulating structure and a voltage regulating method of a dual-frequency general transformer, and belongs to the field of wide voltage regulating design of transformers, the voltage regulating structure comprises a low-voltage coil, a variable flux voltage regulating coil connected to the tail end of the low-voltage coil, a variable flux connector, a high-voltage coil, a voltage regulating coil, an on-load voltage regulating switch and a high-voltage series-parallel switch; the high-voltage coil is at least divided into two coil parts which are arranged at intervals along the axial direction of the iron core, the coil parts of the high-voltage coil are connected through the high-voltage series-parallel switch, the high-voltage coil is connected with the on-load voltage regulation switch through the voltage regulation coil, and the variable flux connector is connected with the output end of the low-voltage coil. The problem that in the prior art, wide-range multi-voltage regulation is difficult to carry out can be solved.

Description

Technical Field

[0001] The present invention belongs to the field of wide voltage regulation design of transformers, and in particular relates to a voltage regulation structure and a voltage regulation method of a dual-frequency universal transformer. Background Art

[0002] With the advancement of global integration, the application of power transformers is expanding at an unprecedented rate around the globe. However, traditional power transformer design models have significant limitations: the operating frequency and voltage levels are fixed during the design phase of power plants and power stations. Power system frequency standards vary globally, with 50Hz and 60Hz being the most common. Grid voltages also vary significantly by region and application. This fixed design approach means transformers designed for specific voltage levels or customized for specific projects are often not directly applicable to other projects, limiting their versatility and flexibility. When a transformer fails or a specific region urgently needs power, the long manufacturing cycle and complex process often make it difficult to meet urgent maintenance and replacement needs or emergency power supply requirements.

[0003] Therefore, dual-frequency universal transformers have emerged. These transformers aim to overcome the limitations of traditional design models and achieve adaptability to a wider range of power frequency and input voltages. However, the design of dual-frequency universal transformers faces a significant technical challenge: how to achieve precise regulation across a wide range of voltages. This requires not only stable operation at different power frequencies but also stable and reliable output voltage across a wide range of input voltages. Therefore, overcoming this technical difficulty and achieving the wide, multi-voltage regulation capabilities of dual-frequency universal transformers has become a critical challenge for the power industry. Summary of the Invention

[0004] The object of the present invention is to provide a voltage regulation structure and voltage regulation method for a dual-frequency universal transformer, so as to solve the problem that the prior art is difficult to perform wide-range multi-voltage regulation.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, a voltage regulation structure for a dual-frequency universal transformer includes: a low-voltage coil, a variable flux voltage regulating coil connected to an end of the low-voltage coil, a variable flux connector, a high-voltage coil, a voltage regulating coil, an on-load tap-changer, and a high-voltage series-parallel switch; The high-voltage coil is divided into at least two parts of coils arranged at intervals along the axial direction of the iron core. The coils of each part of the high-voltage coil are connected through the high-voltage series-parallel switch. The high-voltage coil is connected to the on-load tap-changing switch through the voltage-regulating coil, and the variable magnetic flux connector is connected to the output end of the low-voltage coil.

[0006] In some embodiments, the voltage regulating coil includes a coarse voltage regulating coil and a fine voltage regulating coil.

[0007] In some embodiments, the on-load tap changer includes a coarse voltage tap changer and a fine voltage tap changer; The coarse voltage adjustment tap switch is connected to the coarse voltage adjustment coil, and the fine voltage adjustment tap switch is connected to the fine voltage adjustment coil.

[0008] In some embodiments, the high-voltage coil is connected to the coarse voltage adjustment tap changer via the coarse voltage adjustment coil, and is connected to the fine voltage adjustment tap changer via the fine voltage adjustment coil.

[0009] In some embodiments, the low-voltage coil, the variable flux voltage-regulating coil, the high-voltage coil, and the voltage-regulating coil are sequentially arranged outward along the radial direction of the core.

[0010] In some embodiments, the low-voltage coil is divided into at least two parts of coils arranged at intervals along the axial direction of the iron core where the low-voltage coil is located, and the coils of each part of the low-voltage coil are connected in series or in parallel.

[0011] In some embodiments, when the high-voltage coil is connected to a voltage frequency of 60 Hz, the maximum voltage applied to the high-voltage coil is 1.2 times the voltage applied at 50 Hz, and the maximum selected capacity of the dual-frequency universal transformer is 1.2 times the selected capacity at 50 Hz.

[0012] In a second aspect, a voltage regulation method for a voltage regulation structure of a dual-frequency universal transformer comprises the following steps: The variable flux connector is only connected to the low-voltage coil for low-voltage regulation. The coils of the high-voltage coil are connected in parallel through the high-voltage series-parallel switch, and the high-voltage regulation is performed through the voltage regulating coil and the on-load tap-changing switch. The various coils of the high-voltage coil are connected in series through the high-voltage series-parallel switch, and the high voltage is regulated through the voltage regulating coil and the on-load tap-changing switch; Connect a variable flux voltage regulating coil after the low voltage coil to adjust the low voltage and complete wide voltage regulation.

[0013] In a third aspect, a voltage regulation method for a voltage regulation structure of a dual-frequency universal transformer is provided, characterized in that it comprises the following steps: The variable flux connector is connected only to the low voltage coil; The various coils of the high-voltage coil are connected in parallel through the high-voltage series-parallel switch, and are adjusted through the coarse voltage adjustment tap changer and the coarse voltage adjustment coil, and are adjusted through the fine voltage adjustment tap changer and the fine voltage adjustment coil; The various coils of the high-voltage coil are connected in series through the high-voltage series-parallel switch, and are adjusted through the coarse voltage adjustment tap changer and the coarse voltage adjustment coil, and are adjusted through the fine voltage adjustment tap changer and the fine voltage adjustment coil; Finally, a variable flux voltage regulating coil is connected after the low voltage coil to adjust the low voltage and complete the wide voltage regulation.

[0014] In some embodiments, the method further includes the following steps: changing the magnetic flux of the dual-frequency universal transformer to perform voltage regulation.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a voltage regulation structure for a dual-frequency universal transformer. The high-voltage coil is divided into at least two separate coil sections arranged axially along the core. Each section of the high-voltage coil is connected via a high-voltage series-parallel switch. The high-voltage coil is connected to an on-load tap-changing switch via the voltage-regulating coil, and a variable flux connector is connected to the output end of the low-voltage coil. In this structure, the more separate high-voltage coil sections there are, the more voltage regulation methods are possible, allowing for an extremely wide voltage regulation range. This addresses the difficulty of existing dual-frequency universal transformers in achieving wide, multi-voltage regulation.

[0016] Furthermore, the voltage regulating coil of the present invention adopts a coarse voltage regulating coil and a fine voltage regulating coil, and cooperates with the corresponding tap changer to perform coarse and fine adjustments, which can meet the voltage regulation requirements in different application scenarios and improve the practicality and reliability of the transformer.

[0017] Furthermore, the low-voltage coil, variable flux voltage regulating coil, high-voltage coil and voltage regulating coil of the present invention are sequentially arranged outward along the radial direction of the core, which can reduce the volume of the transformer and improve the adaptability of the transformer.

[0018] Furthermore, the present invention changes the magnetic flux of the dual-frequency universal transformer to perform voltage regulation, which can broaden the range and accuracy of voltage regulation and enable the transformer to better adapt to complex power environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A connection principle diagram of a voltage regulation structure of a dual-frequency universal transformer provided by an embodiment of the present invention; Figure 2 A schematic diagram of the arrangement of the voltage regulating structure of a dual-frequency universal transformer provided by an embodiment of the present invention; In the figure, 1. High-voltage winding 1; 2. High-voltage series-parallel switch; 3. High-voltage winding 2; 4. Coarse voltage regulating coil; 5. Coarse voltage regulating tap changer; 6. Fine voltage regulating coil; 7. Fine voltage regulating tap changer; 8. Variable flux connector; 9. Low voltage coil; 10. Variable flux voltage regulating coil. DETAILED DESCRIPTION

[0020] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the specific embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0021] In the following description, numerous details are provided to provide a more thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure can be practiced without one or more of these details. In other instances, certain technical features known in the art are not described to avoid confusion with the present disclosure; that is, all features of actual embodiments are not described herein, nor are well-known functions and structures described in detail.

[0022] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to, or coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on, directly adjacent to, directly connected to, or directly coupled to" another element or layer, there may be no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part. However, when the second element, component, region, layer, or part is discussed, it does not necessarily mean that the first element, component, region, layer, or part exists in the present disclosure.

[0023] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present disclosure. When used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0024] With the continuous development of power grid technology and the growing demand for electricity, higher requirements are placed on the performance and regulation capabilities of transformers. Especially in a dual-frequency power grid environment, how to achieve precise regulation of a wide range of multiple voltages has become an important issue that needs to be urgently addressed in the current power industry. This embodiment proposes an innovative dual-frequency universal transformer voltage regulation structure, which aims to meet the high requirements of the power grid for voltage stability and flexibility. This structure achieves wide and precise voltage regulation through the partitioning and series-parallel connection of high-voltage coils, the flexible configuration of low-voltage coils, and the fine adjustment of the voltage regulating coils. At the same time, the introduction of variable flux voltage regulation technology and on-load tap-changing switches further improves the accuracy and stability of voltage regulation and reduces the energy consumption and losses of the transformer. This voltage regulation structure not only has a compact and orderly layout, but also has excellent adaptability and reliability, providing strong support for technological innovation and efficient operation in the power industry. The specific embodiments are as follows. It should be noted that in the description of this embodiment, the coil is equivalent to the winding.

[0025] Example 1 like Figure 1 and Figure 2 As shown, this embodiment provides a voltage regulation structure of a dual-frequency universal transformer, including a low-voltage coil 9, a variable flux voltage regulating coil 10 connected to the end of the low-voltage coil, a variable flux connector 8, a high-voltage coil, a voltage regulating coil, an on-load tap-changing switch, and a high-voltage series-parallel switch 2; The high-voltage coil includes a high-voltage 1 winding 1 and a high-voltage 2 winding 3. The high-voltage coil is divided into at least two parts of coils arranged at intervals along the axial direction of the iron core. The coils of each part of the high-voltage coil are connected through the high-voltage series-parallel switch. The high-voltage coil is connected to the on-load tap-changing switch through the voltage regulating coil, and the variable magnetic flux connector is connected to the output end of the low-voltage coil.

[0026] The voltage regulating coil includes a coarse voltage regulating coil 4 and a fine voltage regulating coil 6. The on-load tap changer includes a coarse voltage regulating tap changer 5 and a fine voltage regulating tap changer 7. The coarse voltage regulating tap changer 5 is connected to the coarse voltage regulating coil 4, and the fine voltage regulating tap changer 7 is connected to the fine voltage regulating coil 6. The high-voltage coil is connected to the coarse voltage regulating tap changer 5 via the coarse voltage regulating coil 4 and to the fine voltage regulating tap changer 7 via the fine voltage regulating coil 6.

[0027] The low-voltage coil 9, the variable flux voltage regulating coil 10, the high-voltage coil, and the voltage regulating coil are arranged radially outward from the core. The low-voltage coil 9 is divided into at least two separate coil sections along the axial direction of the core, with each section of the low-voltage coil connected in series or in parallel. When the high-voltage coil is connected to a voltage frequency of 60 Hz, the maximum voltage applied to the high-voltage coil is 1.2 times the voltage applied at 50 Hz. The maximum selectable capacity of a dual-frequency universal power transformer is 1.2 times the selectable capacity at 50 Hz.

[0028] The above-mentioned voltage regulation structure mainly has the following points: (1) High-voltage coil partitioning and series-parallel connection: The high-voltage coil is cleverly divided into two parts along the core axis: high-voltage winding 1 and high-voltage winding 3. This design not only helps to reduce the current density of the coil and improve the heat dissipation efficiency, but also provides the possibility of flexible voltage adjustment through the high-voltage series-parallel switch 2. When the high-voltage coil is connected to a grid with different frequencies, the series-parallel state of the high-voltage coil can be easily adjusted by switching the high-voltage series-parallel switch 2 to adapt to the voltage requirements at different frequencies. For example, under a 50Hz grid, the high-voltage coil may be in a parallel state to provide a lower voltage; while under a 60Hz grid, it may be switched to a series state to provide a higher voltage.

[0029] (2) Flexible configuration of low-voltage coils: The low-voltage coil 9 is also divided into at least two parts along the core axis. These parts can be connected in series or in parallel to accommodate different output voltage requirements. By adjusting the series or parallel connection of the low-voltage coils, the output voltage can be further fine-tuned, allowing the transformer to provide stable output over a wider voltage range.

[0030] (3) Fine adjustment of the voltage regulating coil: The voltage regulating coil includes a coarse voltage regulating coil 4 and a fine voltage regulating coil 6. This design makes voltage regulation both fast and accurate. The coarse voltage regulating coil 4 is used to achieve a wide range of voltage adjustment, while the fine voltage regulating coil 6 is used to make fine adjustments based on the coarse adjustment to ensure the accuracy of the output voltage.

[0031] In the voltage regulating structure provided in this embodiment, the voltage regulating coil is divided into a coarse voltage regulating coil and a fine voltage regulating coil. Together with the coarse voltage regulating tap changer and the fine voltage regulating tap changer in the on-load tap-changing switch, a wide and fine voltage regulation can be achieved. This design not only meets the high requirements of the power grid for voltage stability, but also improves the flexibility and reliability of the transformer. By connecting the output end of the low-voltage coil through a variable flux connector and introducing a variable flux voltage regulating coil, this structure realizes the function of regulating voltage by changing the magnetic flux. This technology not only improves the accuracy and stability of voltage regulation, but also reduces the energy consumption and loss of the transformer, and extends the service life of the equipment. The low-voltage coil, variable flux voltage regulating coil, high-voltage coil and voltage regulating coil in this structure are arranged outward in sequence along the radial direction of the iron core, making the structure of the entire transformer compact and orderly.

[0032] Example 2 Based on Example 1, this embodiment provides a voltage regulation method for a voltage regulation structure of a dual-frequency universal transformer, which enables the same dual-frequency transformer to achieve 100 adjustable voltage levels of 25.25 kV to 73 kV at 50 Hz and 30.3 kV to 87.6 kV at 60 Hz. The method specifically includes the following steps: The voltage requirement of this transformer at 50 Hz is 61.75 kV (36.5 kV) ±12×0.938 kV / 11.5 kV, and the voltage requirement at 60 Hz is 74.1 kV (43.8 kV) ±12×1.125 kV / 13.8 kV.

[0033] like Figure 1 As shown, to achieve 36.5±12×0.938 kV at 50Hz, first, the flux connector 8 is connected to the connections a1-a3, b1-b3, and c1-c3, and only the low-voltage coil 9 is connected to achieve a low-voltage voltage of 11.5 kV. Then, the high-voltage winding 1 is connected to the high-voltage winding 2 3 through the high-voltage series-parallel switch 2 (NLTC), so that the high-voltage winding 1 and the high-voltage winding 2 are connected in parallel, achieving a voltage of 25.25 kV after parallel connection. The fine voltage tap changer 7 (OLTC) connects to the fine voltage coil 6, adjusting the voltage by 0.938 kV per step. This creates a total of 12 voltage steps, from 1 to 13, achieving a 12-step voltage range of 36.5 kV to 12 × 0.938 kV. The coarse voltage tap changer 5 (OLTC) connects to the coarse voltage coil 4. At the same time, the fine voltage tap changer 7 (OLTC) connects to the fine voltage coil 6, adjusting the voltage by 0.938 kV per step. This creates a total of 12 voltage steps, from 1 to 13, achieving a 12-step voltage range of 36.5 kV to 12 × 0.938 kV. This achieves 25 voltage steps, from 25.25 kV to 47.75 kV.

[0034] HV1 winding 1 is connected to HV2 winding 3 via high-voltage series-shunt switch 2 (NLTC), placing HV1 and HV2 in series, achieving a voltage of 50.5 kV. Fine-tuning tap changer 7 (OLTC) is then connected to fine-tuning coil 6, with each voltage step increasing by 0.938 kV. This results in a total of 12 voltage steps, from 61.75 kV to 12 × 0.938 kV. Coarse-tuning tap changer 5 (OLTC) is then connected to coarse-tuning coil 4. Fine-tuning tap changer 7 (OLTC) is then connected to fine-tuning coil 6, with each voltage step increasing by 0.938 kV. This results in a total of 12 voltage steps, from 61.75 kV to 12 × 0.938 kV. This achieves 25 voltage steps, from 50.5 kV to 73 kV.

[0035] By switching between series and parallel windings and coarse and fine control, a wide voltage range of 50 levels, from 25.25 kV to 73 kV, is achieved at 50 Hz. Furthermore, by designing the transformer to a lower magnetic density, such as 1.55T, and then adjusting the voltage by varying the magnetic flux, the applicable voltage range can be expanded to 0.7 to 1.15 times the original tap voltage, where 0.7 is not the lower limit and can be lowered. This effectively achieves stepless voltage regulation of the transformer at this level.

[0036] At this voltage, the variable flux voltage regulating coil 10 is connected to the low-voltage coil 9 by connecting the variable flux connector 8 with the connection numbers a1-a2, b1-b2, and c1-c2. The connection of the two coils changes the total number of turns of the low-voltage winding and changes the voltage of the low-voltage turns. This achieves the adjustment of the overall voltage. The above method achieves a wide voltage adjustment with 100 levels of adjustment. Similarly, a wide voltage adjustment with 100 levels can also be achieved when connected to a 60Hz power grid. As shown in Tables 1 and 2 below, this is a voltage table after the dual-frequency transformer is regulated by the voltage regulation method provided in this embodiment.

[0037] Table 1 Voltage table of dual-frequency transformer after voltage regulation at 50Hz

[0038] Table 2 Voltage table of dual-frequency transformer after 60Hz voltage regulation

[0039] The voltage regulation method provided in this embodiment achieves wide-range voltage regulation through the series-parallel connection of high-voltage windings and the coordination of coarse and fine voltage regulating coils, and can achieve 100 levels of fine voltage regulation at each frequency. This wide and fine voltage regulation capability greatly improves the adaptability and flexibility of the transformer, enabling it to meet more diverse power needs. By connecting the windings in series and in parallel and switching between coarse and fine voltage regulating coils, this method achieves rapid and accurate voltage regulation. This design not only improves the efficiency of voltage regulation, but also reduces energy consumption and losses during the regulation process, thereby improving the overall performance of the transformer.

[0040] This method also expands the applicable voltage range by reducing the transformer's magnetic density and regulating the voltage by changing the magnetic flux. This design allows the voltage to be adjusted over a range of 0.7 to 1.15 times the original tap voltage, further improving the transformer's adaptability and flexibility.

[0041] Furthermore, although this method is implemented through step-by-step voltage regulation, the wide and precise voltage regulation range, coupled with the flexibility of regulating voltage by varying magnetic flux, allows this method to achieve a near-stepless voltage regulation effect in practical applications. This stepless voltage regulation capability is particularly important in applications requiring continuous and smooth voltage regulation.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A voltage regulation structure of a dual-frequency universal transformer, characterized in that: include: A low-voltage coil, a variable flux voltage regulating coil connected to the end of the low-voltage coil, a variable flux connector, a high-voltage coil, a voltage regulating coil, an on-load voltage regulating switch and a high-voltage series-parallel switch; The high-voltage coil is divided into at least two parts of coils arranged at intervals along the axial direction of the iron core. The coils of each part of the high-voltage coil are connected through the high-voltage series-parallel switch. The high-voltage coil is connected to the on-load voltage regulating switch through the voltage regulating coil, and the variable magnetic flux connector is connected to the output end of the low-voltage coil.

2. The voltage regulation structure of a dual-frequency universal transformer according to claim 1, characterized in that: The voltage regulating coil comprises a coarse voltage regulating coil and a fine voltage regulating coil.

3. The voltage regulation structure of a dual-frequency universal transformer according to claim 2, characterized in that: The on-load voltage regulating switch comprises a coarse voltage regulating tapping switch and a fine voltage regulating tapping switch; The coarse voltage adjustment tap switch is connected to the coarse voltage adjustment coil, and the fine voltage adjustment tap switch is connected to the fine voltage adjustment coil.

4. The voltage regulation structure of a dual-frequency universal transformer according to claim 3, characterized in that: The high-voltage coil is connected to the coarse-adjusting voltage-adjusting tapping switch via the coarse-adjusting voltage-adjusting coil, and is connected to the fine-adjusting voltage-adjusting tapping switch via the fine-adjusting voltage-adjusting coil.

5. The voltage regulation structure of a dual-frequency universal transformer according to claim 1, characterized in that: The low-voltage coil, the variable flux voltage regulating coil, the high-voltage coil and the voltage regulating coil are sequentially arranged outwardly along the radial direction of the iron core.

6. The voltage regulation structure of a dual-frequency universal transformer according to claim 5, characterized in that: The low-voltage coil is divided into at least two parts of coils arranged at intervals along the axial direction of the iron core where the low-voltage coil is located, and the coils of each part of the low-voltage coil are connected in series or in parallel.

7. The voltage regulation structure of a dual-frequency universal transformer according to claim 1, characterized in that: When the high-voltage coil is connected to a voltage frequency of 60 Hz, the maximum voltage applied to the high-voltage coil is 1.2 times the voltage applied at 50 Hz, and the maximum selected capacity of the dual-frequency universal transformer is 1.2 times the selected capacity at 50 Hz.

8. The voltage regulation method of the voltage regulation structure of a dual-frequency universal transformer according to claim 1, characterized in that: The following steps are involved: The variable flux connector is only connected to the low voltage coil for low voltage regulation, and the various coils of the high voltage coil are selected to be connected in parallel through the high voltage series-parallel switch, and the high voltage regulation is performed through the voltage regulating coil and the on-load voltage regulating switch; The various coils of the high-voltage coil are connected in series through the high-voltage series-parallel switch, and the high voltage is regulated through the voltage regulating coil and the on-load voltage regulating switch; Connect a variable flux voltage regulating coil after the low voltage coil to adjust the low voltage and complete wide voltage regulation.

9. The voltage regulation method of the voltage regulation structure of a dual-frequency universal transformer according to claim 3, characterized in that: The following steps are involved: The variable flux connector is connected only to the low voltage coil; The various coils of the high-voltage coil are selected to be connected in parallel through the high-voltage series-parallel switch, and are adjusted through the voltage coarse adjustment tapping switch and the voltage coarse adjustment coil, and are adjusted through the voltage fine adjustment tapping switch and the voltage fine adjustment coil; The various coils of the high-voltage coil are selected to be connected in series through the high-voltage series-parallel switch, and are adjusted through the voltage coarse adjustment tapping switch and the voltage coarse adjustment coil, and are adjusted through the voltage fine adjustment tapping switch and the voltage fine adjustment coil; Finally, a variable flux voltage regulating coil is connected after the low voltage coil to perform low voltage regulation and complete wide voltage regulation.

10. The voltage regulation method according to claim 8 or 9, characterized in that: The following steps are also included: Voltage regulation is achieved by changing the magnetic flux of a dual-frequency universal transformer.

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