Direct-current power supply system and method suitable for thermal power plant

Abstract

The invention relates to a direct-current power supply system and method suitable for a thermal power plant. The system comprises a plant alternating-current module, a direct-current power supply module and a direct-current power utilization module. The station AC module is connected with the DC power utilization module, the DC power utilization module is connected with the DC power supply module, and the station AC module is also connected with the generator; the station alternating current module provides electric energy for the direct current power utilization module, and when the power of the direct current power utilization module is excessive, the direct current power utilization module can also serve as a load of the direct current power utilization module; the direct-current power supply module supplies power to the direct-current power utilization module; the direct current power utilization module supplies power to the station-service direct current system, when the power of the direct current power utilization module is excessive, reverse power supply can be provided for the station-service alternating current module, and through direct electric energy transmission and simple converter operation, the energy loss in the electric energy transmission and conversion process is relatively small; and the structure is simple, the possibility of single-point failure is reduced, and the reliability of the system is also improved due to the direct connection between the plant AC module and the DC module.

Description

Technical Field

[0001] The invention relates to a direct current power supply system and method suitable for a thermal power plant, belonging to the technical field of power electronics. Background Art

[0002] With the rapid development of the power industry, thermal power plants, as an important source of electricity, the stability and reliability of their power supply systems are crucial to ensuring the safety of the power grid and improving the quality of power supply. The traditional AC power supply system has problems such as large energy loss and limited transmission distance during power transmission and distribution, which limits the transmission efficiency of power.

[0003] The patent document with the patent number "WO2024146504A1" discloses an uninterruptible power supply system. The problem with this system is that it is necessary to monitor the operating status of multiple modules, including new energy modules, battery units, rectifier modules, etc. Although this provides more comprehensive monitoring capabilities, it also increases the complexity of the system and its dependence on the monitoring system. Because multiple complex modules and units are involved, the initial investment and maintenance costs may be high. For example, power quality compensators, bypass modules, new energy access modules, etc. all require additional costs. There are multiple intermediate conversion processes (such as rectifier modules, DC / DC control units, etc.), which increases the number of power conversions, which may lead to increased energy losses. In addition, the use of power quality compensators and bypass modules will also bring about certain energy losses. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention proposes a DC power supply system and method suitable for a thermal power plant.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, the present invention provides a DC power supply system suitable for a thermal power plant, comprising a plant AC module, a DC power supply module and a DC power module;

[0007] The plant AC module is connected to the DC power module, the DC power module is connected to the DC power supply module, and the plant AC module is also connected to the generator;

[0008] The factory AC module provides electric energy to the DC power module and acts as a load for the DC power module when the DC power module has excess power.

[0009] The DC power supply module provides power to the DC power consumption module;

[0010] The DC power module supplies power to the factory DC system. When the DC power module has excess power, it supplies reverse power to the factory AC module.

[0011] As a preferred embodiment, the plant AC module includes a 20kV to 6.3kV split-winding transformer, a 6.3kV AC plant bus, an AC load switch, a plant AC load, a plant AC-plant DC contact switch, a 6.3kV to 10kV double-winding transformer and a bidirectional PCS converter;

[0012] The factory AC load represents AC power equipment;

[0013] The high-voltage side port of the 20kV to 6.3kV split-winding transformer is connected to the generator, and the low-voltage split-winding side port is connected to the 6.3kV AC plant busbar;

[0014] The factory AC load is connected to the 6.3kV AC factory busbar via an AC load switch;

[0015] The AC port of the bidirectional PCS converter is connected to the low voltage port of the 6.3kV to 10kV double-winding transformer, and the high voltage port of the 6.3kV to 10kV double-winding transformer is connected to the 6.3kV AC plant bus through the plant AC-plant DC connecting switch.

[0016] As a preferred embodiment, the DC power supply module includes a high-speed constant-power multi-pole generator, a multi-pole generator AC grid-connected switch, and a medium-frequency rectifier and filter converter;

[0017] The AC port of the medium frequency rectifier filter converter is connected to the high-speed constant power multi-pole generator through the multi-pole generator AC grid-connected switch.

[0018] As a preferred embodiment, the DC power module includes a medium voltage DC bus, a DC load circuit breaker, a DC load, a plant DC system circuit breaker, a DC-DC converter and a plant DC system;

[0019] The DC load represents a DC power-consuming device;

[0020] The medium voltage DC bus is respectively connected to the DC port of the bidirectional PCS converter and the DC port of the medium frequency rectifier filter converter;

[0021] The DC load is connected to the medium voltage DC busbar via a DC load circuit breaker;

[0022] The plant DC system is connected to the output end of the DC-DC converter, and the input end of the DC-DC converter is connected to the medium voltage DC bus through the plant DC system circuit breaker.

[0023] As a preferred implementation, if the power load of the DC power module is less than the output power of the DC power supply module, the bidirectional PCS converter is set to an inverter state;

[0024] If the power load of the DC power module is greater than the output power of the DC power supply module, the bidirectional PCS converter is set to a rectifying state.

[0025] On the other hand, the present invention also provides a DC power supply method applicable to a thermal power plant, comprising the following steps:

[0026] Constructing a factory AC module, which provides power to the DC power module and acts as a load for the DC power module when the DC power module has excess power;

[0027] Constructing a DC power supply module, wherein the DC power supply module provides power for the DC power consumption module;

[0028] Construct a DC power module, which supplies power to the factory DC system. When the DC power module has excess power, it supplies reverse power to the factory AC module.

[0029] The plant AC module is connected to a DC power module, the DC power module is connected to a DC power supply module, and the plant AC module is also connected to a generator.

[0030] As a preferred embodiment, the plant AC module includes a 20kV to 6.3kV split-winding transformer, a 6.3kV AC plant bus, an AC load switch, a plant AC load, a plant AC-plant DC contact switch, a 6.3kV to 10kV double-winding transformer and a bidirectional PCS converter;

[0031] The factory AC load represents AC power equipment;

[0032] The high-voltage side port of the 20kV to 6.3kV split-winding transformer is connected to the generator, and the low-voltage split-winding side port is connected to the 6.3kV AC plant busbar;

[0033] The factory AC load is connected to the 6.3kV AC factory busbar via an AC load switch;

[0034] The AC port of the bidirectional PCS converter is connected to the low voltage port of the 6.3kV to 10kV double-winding transformer, and the high voltage port of the 6.3kV to 10kV double-winding transformer is connected to the 6.3kV AC plant bus through the plant AC-plant DC connecting switch.

[0035] As a preferred embodiment, the DC power supply module includes a high-speed constant-power multi-pole generator, a multi-pole generator AC grid-connected switch, and a medium-frequency rectifier and filter converter;

[0036] The AC port of the medium frequency rectifier filter converter is connected to the high-speed constant power multi-pole generator through the multi-pole generator AC grid-connected switch.

[0037] As a preferred embodiment, the DC power module includes a medium voltage DC bus, a DC load circuit breaker, a DC load, a plant DC system circuit breaker, a DC-DC converter and a plant DC system;

[0038] The DC load represents a DC power-consuming device;

[0039] The medium voltage DC bus is respectively connected to the DC port of the bidirectional PCS converter and the DC port of the medium frequency rectifier filter converter;

[0040] The DC load is connected to the medium voltage DC busbar via a DC load circuit breaker;

[0041] The plant DC system is connected to the output end of the DC-DC converter, and the input end of the DC-DC converter is connected to the medium voltage DC bus through the plant DC system circuit breaker.

[0042] As a preferred implementation, if the power load of the DC power module is less than the output power of the DC power supply module, the bidirectional PCS converter is set to an inverter state;

[0043] If the power load of the DC power module is greater than the output power of the DC power supply module, the bidirectional PCS converter is set to a rectifying state.

[0044] The present invention has the following beneficial effects:

[0045] The present invention uses a rectifier to rectify and filter the medium-frequency AC power of the high-speed constant-power multi-pole generator to form a medium-voltage DC power. A portion of the electric energy is fed into the factory power system through bidirectional frequency conversion, and the remaining electric energy is sent to the local inverter through the medium-voltage DC power to achieve the frequency conversion of the high-voltage load power that needs to be adjusted. The multi-pole generator AC grid-connected switch is set at the outlet of the high-speed constant-power multi-pole generator, which can avoid the need to set up a DC circuit breaker on the DC side of the rectifier, reduce equipment investment, and increase power supply reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a topological diagram of the system of the present invention.

[0047] Figure 2 This is the topological diagram of the factory AC module of the present invention.

[0048] Figure 3 This is a topological diagram of the DC power supply module of the present invention.

[0049] Figure 4 This is a topological diagram of the DC power module of the present invention.

[0050] The reference numerals indicate:

[0051] 1-1, 20kV to 6.3kV split-winding transformer; 1-2, 6.3kV AC plant bus; 1-4, AC load switch; 1-5, plant AC load; 1-6, plant AC-plant DC interconnecting switch; 1-7, 6.3kV to 10kV double-winding transformer; 1-8, bidirectional PCS converter; 2-1, high-speed constant-power multi-pole generator; 2-2, multi-pole generator AC grid-connected switch; 2-3, medium-frequency rectifier filter converter; 3-1, medium-voltage DC bus; 3-2, DC load circuit breaker; 3-3, DC load; 3-4, plant DC system circuit breaker; 3-5, DC-DC converter; 3-6, DC system. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] It should be understood that the step numbers used in this document are only for convenience of description and are not intended to limit the order in which the steps are executed.

[0054] It should be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0055] The terms “include” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0056] The term "and / or" means and includes any and all possible combinations of one or more of the associated listed items.

[0057] Embodiment 1:

[0058] See also Figure 1 , the present invention provides a DC power supply system suitable for a thermal power plant, comprising a plant AC module, a DC power supply module and a DC power module;

[0059] The plant AC module is connected to the DC power module, the DC power module is connected to the DC power supply module, and the plant AC module is also connected to the generator;

[0060] The factory AC module provides electric energy to the DC power module and acts as a load for the DC power module when the DC power module has excess power.

[0061] The DC power supply module provides power to the DC power consumption module;

[0062] The DC power module supplies power to the factory DC system. When the DC power module has excess power, it supplies reverse power to the factory AC module.

[0063] See also Figure 2 As a preferred embodiment, the plant AC module includes a 20kV to 6.3kV split-winding transformer 1-1, a 6.3kV AC plant bus 1-2, an AC load switch 1-4, a plant AC load 1-5, a plant AC-plant DC contact switch 1-6, a 6.3kV to 10kV double-winding transformer 1-7 and a bidirectional PCS converter 1-8;

[0064] The factory AC loads 1-5 represent AC power equipment;

[0065] The high-voltage side port of the 20kV to 6.3kV split winding transformer 1-1 is connected to the generator, and the low-voltage split winding side port is connected to the 6.3kV AC plant bus 1-2;

[0066] The factory AC load 1-5 is connected to the 6.3kV AC factory bus 1-2 through the AC load switch 1-4;

[0067] The AC port of the bidirectional PCS converter 1-8 is connected to the low voltage port of the 6.3kV to 10kV double-winding transformer 1-7, and the high voltage port of the 6.3kV to 10kV double-winding transformer 1-7 is connected to the 6.3kV AC plant bus 1-2 through the plant AC-plant DC connecting switch 1-6.

[0068] See also Figure 3 As a preferred embodiment, the DC power supply module includes a high-speed constant-power multi-pole generator 2-1, a multi-pole generator AC grid-connected switch 2-2, and a medium-frequency rectifier filter converter 2-3;

[0069] The AC port of the medium frequency rectifying and filtering converter 2-3 is connected to the high-speed constant-power multi-pole generator 2-1 through the multi-pole generator AC grid-connected switch 2-2.

[0070] The medium-frequency rectifier and filter converter 2-3 rectifies and filters the medium-frequency alternating current generated by the DC power supply module including the high-speed constant-power multi-pole generator 2-1 to form a medium-voltage direct current. Part of the electric energy is connected to the factory power system through the bidirectional PCS converter 1-8, and the remaining electric energy is sent to the local inverter through the medium-voltage DC bus 3-1 to realize the frequency conversion of the high-voltage load power that needs to be adjusted.

[0071] The medium frequency rectifier and filter converter 2-3 centrally rectifies and filters the medium frequency alternating current. The technical difficulty is relatively simple, the equipment investment is small, and as an isolated system, there is no harmonic pollution problem to the power grid due to large-scale application.

[0072] The multi-pole generator AC grid-connected switch 2-2 can realize the switching of the high-speed constant-power multi-pole generator 2-1. Compared with adding a circuit breaker on the DC side, adding the multi-pole generator AC grid-connected switch 2-2 on the AC side reduces investment and increases the power supply stability of the high-speed constant-power multi-pole generator 2-1.

[0073] See also Figure 4 As a preferred embodiment, the DC power module includes a medium voltage DC bus 3-1, a DC load circuit breaker 3-2, a DC load 3-3, a plant DC system circuit breaker 3-4, a DC-DC converter 3-5 and a plant DC system 3-6;

[0074] The DC load 3-3 represents a DC power-consuming device;

[0075] The medium voltage DC bus 3-1 is respectively connected to the DC port of the bidirectional PCS converter 1-8 and the DC port of the medium frequency rectifier filter converter 2-3;

[0076] The DC load 3-3 is connected to the medium voltage DC bus 3-1 via a DC load circuit breaker 3-2;

[0077] The plant DC system 3-6 (the plant DC system 3-6 includes the thermal power plant plant DC control load and the plant DC power load) is connected to the output end of the DC-DC converter 3-5, and the input end of the DC-DC converter 3-5 is connected to the medium voltage DC bus 3-1 through the plant DC system circuit breaker 3-4.

[0078] As a preferred embodiment, if the power load of the DC power module is less than the output power of the DC power supply module, the bidirectional PCS converter 1-8 is set to an inverter state;

[0079] If the power load of the DC power module is greater than the output power of the DC power supply module, the bidirectional PCS converter 1-8 is set to the rectification state. When the power generated by the constant power generator does not meet the DC load, the AC module for the plant provides the required power after rectification through the bidirectional PCS converter 1-8.

[0080] Embodiment 2:

[0081] The present invention also provides a DC power supply method applicable to a thermal power plant, comprising the following steps:

[0082] Constructing a factory AC module, which provides power to the DC power module and acts as a load for the DC power module when the DC power module has excess power;

[0083] Constructing a DC power supply module, wherein the DC power supply module provides power for the DC power consumption module;

[0084] Construct a DC power module, which supplies power to the factory DC system. When the DC power module has excess power, it supplies reverse power to the factory AC module.

[0085] The plant AC module is connected to a DC power module, the DC power module is connected to a DC power supply module, and the plant AC module is also connected to a generator.

[0086] As a preferred embodiment, the plant AC module includes a 20kV to 6.3kV split winding transformer 1-1, a 6.3kV AC plant bus 1-2, an AC load switch 1-4, a plant AC load 1-5, a plant AC-plant DC contact switch 1-6, a 6.3kV to 10kV double winding transformer 1-7 and a bidirectional PCS converter 1-8;

[0087] The factory AC loads 1-5 represent AC power equipment;

[0088] The high-voltage side port of the 20kV to 6.3kV split winding transformer 1-1 is connected to the generator, and the low-voltage split winding side port is connected to the 6.3kV AC plant bus 1-2;

[0089] The factory AC load 1-5 is connected to the 6.3kV AC factory bus 1-2 through the AC load switch 1-4;

[0090] The AC port of the bidirectional PCS converter 1-8 is connected to the low voltage port of the 6.3kV to 10kV double-winding transformer 1-7, and the high voltage port of the 6.3kV to 10kV double-winding transformer 1-7 is connected to the 6.3kV AC plant bus 1-2 through the plant AC-plant DC connecting switch 1-6.

[0091] As a preferred embodiment, the DC power supply module includes a high-speed constant-power multi-pole generator 2-1, a multi-pole generator AC grid-connected switch 2-2, and a medium-frequency rectifier filter converter 2-3;

[0092] The AC port of the medium frequency rectifying and filtering converter 2-3 is connected to the high-speed constant-power multi-pole generator 2-1 through the multi-pole generator AC grid-connected switch 2-2.

[0093] As a preferred embodiment, the DC power module includes a medium voltage DC bus 3-1, a DC load circuit breaker 3-2, a DC load 3-3, a plant DC system circuit breaker 3-4, a DC-DC converter 3-5 and a plant DC system 3-6;

[0094] The DC load 3-3 represents a DC power-consuming device;

[0095] The medium voltage DC bus 3-1 is respectively connected to the DC port of the bidirectional PCS converter 1-8 and the DC port of the medium frequency rectifier filter converter 2-3;

[0096] The DC load 3-3 is connected to the medium voltage DC bus 3-1 via a DC load circuit breaker 3-2;

[0097] The plant DC system 3-6 is connected to the output end of the DC-DC converter 3-5, and the input end of the DC-DC converter 3-5 is connected to the medium voltage DC bus 3-1 through the plant DC system circuit breaker 3-4.

[0098] As a preferred embodiment, if the power load of the DC power module is less than the output power of the DC power supply module, the bidirectional PCS converter 1-8 is set to an inverter state;

[0099] If the power load of the DC power module is greater than the output power of the DC power supply module, the bidirectional PCS converter 1-8 is set to a rectifying state.

[0100] In the embodiments of the present application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can be represented by: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, c can be single or multiple.

[0101] Those of ordinary skill in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed herein can be implemented in a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0102] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0103] In several embodiments provided in the present application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory; hereinafter referred to as: ROM), random access memory (Random Access Memory; hereinafter referred to as: RAM), disk or optical disk, and other media that can store program codes.

[0104] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A DC power supply system suitable for a thermal power plant, characterized in that: Including factory AC module, DC power supply module and DC power module; The plant AC module is connected to the DC power module, the DC power module is connected to the DC power supply module, and the plant AC module is also connected to the generator; The factory AC module provides electric energy to the DC power module and acts as a load for the DC power module when the DC power module has excess power. The DC power supply module provides power to the DC power consumption module; The DC power module supplies power to the factory DC system. When the DC power module has excess power, it supplies reverse power to the factory AC module.

2. The DC power supply system suitable for a thermal power plant according to claim 1, characterized in that: The plant AC module comprises a 20 kV to 6.3 kV split-winding transformer (1-1), a 6.3 kV AC plant busbar (1-2), an AC load switch (1-4), a plant AC load (1-5), a plant AC-plant DC contact switch (1-6), a 6.3 kV to 10 kV double-winding transformer (1-7) and a bidirectional PCS converter (1-8); The factory AC load (1-5) represents AC power equipment; The high-voltage side port of the 20kV to 6.3kV split-winding transformer (1-1) is connected to the generator, and the low-voltage split-winding side port is connected to the 6.3kV AC plant bus (1-2); The factory AC load (1-5) is connected to the 6.3 kV AC factory bus (1-2) via an AC load switch (1-4); The AC port of the bidirectional PCS converter (1-8) is connected to the low voltage port of the 6.3 kV to 10 kV double-winding transformer (1-7), and the high voltage port of the 6.3 kV to 10 kV double-winding transformer (1-7) is connected to the 6.3 kV AC plant bus (1-2) through the plant AC-plant DC connecting switch (1-6).

3. The DC power supply system suitable for a thermal power plant according to claim 1, characterized in that: The DC power supply module comprises a high-speed constant-power multi-pole generator (2-1), a multi-pole generator AC grid-connected switch (2-2), and a medium-frequency rectifier and filter converter (2-3); The AC port of the medium frequency rectifying and filtering converter (2-3) is connected to the high-speed constant-power multi-pole generator (2-1) via the multi-pole generator AC grid-connected switch (2-2).

4. The DC power supply system suitable for a thermal power plant according to claim 2 or 3, characterized in that: The DC power module comprises a medium voltage DC busbar (3-1), a DC load circuit breaker (3-2), a DC load (3-3), a plant DC system circuit breaker (3-4), a DC-DC converter (3-5) and a plant DC system (3-6); The DC load (3-3) represents a DC power-consuming device; The medium voltage DC bus (3-1) is respectively connected to the DC port of the bidirectional PCS converter (1-8) and the DC port of the medium frequency rectifier and filter converter (2-3); The DC load (3-3) is connected to the medium voltage DC bus (3-1) via a DC load circuit breaker (3-2); The plant DC system (3-6) is connected to the output end of the DC-DC converter (3-5), and the input end of the DC-DC converter (3-5) is connected to the medium-voltage DC bus (3-1) via the plant DC system circuit breaker (3-4).

5. The DC power supply system suitable for a thermal power plant according to claim 2, characterized in that: If the power load of the DC power module is less than the output power of the DC power supply module, the bidirectional PCS converter (1-8) is set to an inverter state; If the power load of the DC power module is greater than the output power of the DC power supply module, the bidirectional PCS converter (1-8) is set to a rectifying state.

6. A DC power supply method suitable for a thermal power plant, characterized in that: The following steps are involved: Constructing a factory AC module, which provides power to the DC power module and acts as a load for the DC power module when the DC power module has excess power; Constructing a DC power supply module, wherein the DC power supply module provides power for the DC power consumption module; Construct a DC power module, which supplies power to the factory DC system. When the DC power module has excess power, it supplies reverse power to the factory AC module. The plant AC module is connected to a DC power module, the DC power module is connected to a DC power supply module, and the plant AC module is also connected to a generator.

7. The DC power supply method applicable to a thermal power plant according to claim 6, characterized in that: The plant AC module comprises a 20 kV to 6.3 kV split-winding transformer (1-1), a 6.3 kV AC plant busbar (1-2), an AC load switch (1-4), a plant AC load (1-5), a plant AC-plant DC contact switch (1-6), a 6.3 kV to 10 kV double-winding transformer (1-7) and a bidirectional PCS converter (1-8); The factory AC load (1-5) represents AC power equipment; The high-voltage side port of the 20kV to 6.3kV split-winding transformer (1-1) is connected to the generator, and the low-voltage split-winding side port is connected to the 6.3kV AC plant bus (1-2); The factory AC load (1-5) is connected to the 6.3 kV AC factory bus (1-2) via an AC load switch (1-4); The AC port of the bidirectional PCS converter (1-8) is connected to the low voltage port of the 6.3 kV to 10 kV double-winding transformer (1-7), and the high voltage port of the 6.3 kV to 10 kV double-winding transformer (1-7) is connected to the 6.3 kV AC plant bus (1-2) through the plant AC-plant DC connecting switch (1-6).

8. The DC power supply method applicable to a thermal power plant according to claim 6, characterized in that: The DC power supply module comprises a high-speed constant-power multi-pole generator (2-1), a multi-pole generator AC grid-connected switch (2-2), and a medium-frequency rectifier and filter converter (2-3); The AC port of the medium frequency rectifying and filtering converter (2-3) is connected to the high-speed constant-power multi-pole generator (2-1) via the multi-pole generator AC grid-connected switch (2-2).

9. The DC power supply method applicable to a thermal power plant according to claim 7 or 8, characterized in that: The DC power module comprises a medium voltage DC busbar (3-1), a DC load circuit breaker (3-2), a DC load (3-3), a plant DC system circuit breaker (3-4), a DC-DC converter (3-5) and a plant DC system (3-6); The DC load (3-3) represents a DC power-consuming device; The medium voltage DC bus (3-1) is respectively connected to the DC port of the bidirectional PCS converter (1-8) and the DC port of the medium frequency rectifier and filter converter (2-3); The DC load (3-3) is connected to the medium voltage DC bus (3-1) via a DC load circuit breaker (3-2); The plant DC system (3-6) is connected to the output end of the DC-DC converter (3-5), and the input end of the DC-DC converter (3-5) is connected to the medium-voltage DC bus (3-1) via the plant DC system circuit breaker (3-4).

10. The DC power supply method applicable to a thermal power plant according to claim 7, characterized in that: If the power load of the DC power module is less than the output power of the DC power supply module, the bidirectional PCS converter (1-8) is set to an inverter state; If the power load of the DC power module is greater than the output power of the DC power supply module, the bidirectional PCS converter (1-8) is set to a rectifying state.

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