A 6kV auxiliary bus switching and protection system and method for a thermal power plant with photovoltaic access

Abstract

The application provides a thermal power plant 6kV plant bus switching and protection system and method containing photovoltaic access, belongs to the technical field of power systems, and the system comprises: a photovoltaic power generation module containing an inverter and a transformer box, the inverter is connected with the transformer box in two groups, and two photovoltaic transformer box groups are formed after confluence; a 6kV plant bus module is provided with two 6kV buses, four photovoltaic incoming line switches are configured, a double incoming line architecture that two photovoltaic transformer box groups are respectively connected with two buses is realized, and photovoltaic power supply across the bus flexible switching is supported; a power supply module is composed of a high plant transformer, a start standby transformer and corresponding working and standby power switches, and provides double power supply for the two buses; a protection and switching module comprises two bus quick switching devices corresponding to the two buses respectively, and a generator transformer group protection controller responsible for fault monitoring and switch tripping isolation; a locking device is arranged between the two photovoltaic incoming line switches of the same bus. The application guarantees the safe operation of the thermal power unit and meets the grid connection requirement of photovoltaic self-generation and self-use.

Description

Technical Field

[0001] This application belongs to the field of power system technology, specifically relating to a 6kV plant service bus switching and protection system and method for thermal power plants with photovoltaic access. Background Technology

[0002] With the rapid development of new energy power generation technologies, connecting high-power photovoltaic power generation systems to the power plant's auxiliary busbar for self-consumption has become an important way for power plants to save energy, reduce consumption, and achieve green transformation. Directly connecting high-power photovoltaic systems to the high-voltage busbar of a power plant eliminates the need for new main transformers, transmission lines, and energy storage equipment, saving investment. At the same time, it can leverage the AGC and AVC dispatching systems of the power plant units to compensate for the high volatility of photovoltaic power generation, achieving stable and efficient photovoltaic power generation.

[0003] Current technology simply connects the photovoltaic power generation system directly to the plant's auxiliary bus via inverters and transformer substations, completely adopting the original power switching devices and relay protection logic of thermal power plants, without making targeted modifications to address the inherent characteristics of photovoltaics. This presents the following problems: the original fast-switching device lacks photovoltaic interlocking logic; the photovoltaic's built-in islanding protection has a time delay and may fail to operate, easily forming power islands and causing bus parameter drift, leading to switching failures and threatening the safety of large-capacity thermal power units; the photovoltaic short-circuit current is only 1.2 to 1.5 times the rated value, far lower than that of thermal power sources; existing bus protection does not interlock with photovoltaic switches, meaning that during a bus short circuit, photovoltaics may continue to supply power to the fault point, exacerbating the accident; the wiring architecture has safety hazards and is inflexible in operation; the lack of an incoming line switch interlocking device easily leads to accidental closing, and it cannot achieve photovoltaic cross-bus switching, easily violating the grid connection agreement of self-consumption and non-grid connection.

[0004] Therefore, there is an urgent need to develop a technical solution that can effectively solve the above problems and ensure the safe and stable operation of photovoltaic and thermal power units. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a switching and protection system and method for a 6kV plant service bus in a thermal power plant with photovoltaic access. This solves the problems of islanding effect affecting power switching and insufficient protection sensitivity after high-power photovoltaic access to the 6kV plant service bus in a thermal power plant, and realizes the safe and economical integration of photovoltaic and thermal power generation.

[0006] In a first aspect, embodiments of this application provide a 6kV plant service bus switching and protection system for thermal power plants with photovoltaic access, the system comprising: A photovoltaic power generation module includes an inverter with islanding protection and a transformer substation. The inverter includes a first inverter and a second inverter, and the transformer substation includes a first photovoltaic transformer substation and a second photovoltaic transformer substation. The first inverter is connected to the first photovoltaic transformer substation, and the second inverter is connected to the second photovoltaic transformer substation. The 6kV plant busbar module includes a first 6kV busbar, a second 6kV busbar, a first 6kV photovoltaic incoming switch, a second 6kV photovoltaic incoming switch, a third 6kV photovoltaic incoming switch, and a fourth 6kV photovoltaic incoming switch. The first photovoltaic transformer substation is connected to the first 6kV busbar through the first 6kV photovoltaic incoming switch, the second photovoltaic transformer substation is connected to the first 6kV busbar through the second 6kV photovoltaic incoming switch, the first photovoltaic transformer substation is also connected to the second 6kV busbar through the third 6kV photovoltaic incoming switch, and the second photovoltaic transformer substation is also connected to the second 6kV busbar through the fourth 6kV photovoltaic incoming switch. The power module is used to provide dual-path switching for working and backup power supply for the first 6kV bus and the second 6kV bus; The protection and switching module includes a first busbar fast-switching device, a second busbar fast-switching device, and a generator-transformer group protection controller. The first busbar fast-switching device is used for power switching of the first 6kV busbar, the second busbar fast-switching device is used for power switching of the second 6kV busbar, and the generator-transformer group protection controller is used to quickly trip the corresponding switch when a fault or abnormality is detected. The interlocking devices are respectively installed between the first photovoltaic incoming switch and the second photovoltaic incoming switch of the first 6kV bus, and between the third photovoltaic incoming switch and the fourth photovoltaic incoming switch of the second 6kV bus. The interlocking devices are used to prevent two photovoltaic incoming switches on the same bus from closing at the same time.

[0007] Furthermore, the power module includes a generator-transformer group, a standby transformer, a first working power switch, a second working power switch, a first standby power switch, and a second standby power switch. The generator-transformer unit includes a high-voltage transformer and a generator. The primary side of the generator-transformer unit is connected to a 6kV plant service bus module, and the secondary side of the generator-transformer unit is connected to a generator-transformer unit protection controller. The high-voltage transformer is connected to the first 6kV bus via a first working power switch, and to the second 6kV bus via a second working power switch. The standby transformer is connected to the first 6kV bus via a first standby power switch, and to the second 6kV bus via a second standby power switch.

[0008] Furthermore, the generator-transformer unit protection controller includes generator-transformer unit protection controller A, generator-transformer unit protection controller B, and generator-transformer unit protection controller C. The generator-transformer unit protection controller is used to monitor the operating status of the generator-transformer unit and the plant service bus, and to quickly trip the corresponding switch and isolate the fault when a fault is detected. The generator-transformer protection controller A, generator-transformer protection controller B, generator-transformer protection controller C, as well as the first busbar fast-switching device and the second busbar fast-switching device, are all equipped with a secondary circuit for tripping the photovoltaic incoming line switch. The photovoltaic incoming switch tripping secondary circuits of the generator-transformer group protection controller A and generator-transformer group protection controller B are used for both fault switching and bus protection tripping operations, while the photovoltaic incoming switch tripping secondary circuit of the generator-transformer group protection controller C is only used for tripping operations during fault switching. The photovoltaic incoming switch tripping secondary circuits of the first and second busbar fast switching devices are used simultaneously for 6kV photovoltaic incoming switch tripping operations during both fault switching and abnormal switching.

[0009] Furthermore, the secondary circuit configuration for the photovoltaic incoming line switch tripping of the generator-transformer unit protection controller is as follows: When the generator-transformer unit trips, it sends a trip signal to the working power switch of the corresponding bus and at the same time sends a trip signal to all 6kV photovoltaic incoming line switches of that bus. The secondary circuit configuration for the photovoltaic incoming switch tripping of the first busbar fast-switching device and the second busbar fast-switching device is as follows: Upon receiving the trip protection action signal of the generator-transformer unit, a trip signal is simultaneously sent to the working power switch of the corresponding bus and all 6kV photovoltaic incoming line switches. After the working power switch and all 6kV photovoltaic incoming line switches confirm that the trip is initiated and the switching conditions are met, the standby power switch of the corresponding bus is closed.

[0010] Furthermore, the first busbar fast switching device and the second busbar fast switching device include an emergency switching module, an abnormal switching module, a normal manual switching module, and a busbar protection module; The fault switching module is used to simultaneously output the working power switch trip signal and the 6kV photovoltaic incoming line switch trip signal when it receives the trip protection action signal of the generator-transformer group. After both power switches are tripped, it judges the switching conditions and outputs the backup power switch closing signal when the conditions are met. The abnormal switching module is used to confirm the tripping status of the working power switch when it receives a signal of the working power switch tripping or a signal of the bus undervoltage, and at the same time output a 6kV photovoltaic incoming switch tripping signal. After the photovoltaic incoming switch trips, it judges the switching conditions and outputs a backup power switch closing signal when the conditions are met. The normal manual switching module is used to determine the current power supply type of the bus when a manual switching command is received. If it is powered by the standby transformer, the photovoltaic power supply of the bus is prohibited from being put into operation. If it is necessary to switch to the standby transformer power supply, the photovoltaic switching or shutdown command is output first. The bus protection module is used to output a working power switch trip signal and a 6kV photovoltaic incoming switch trip signal when a bus short-circuit fault signal is received, and at the same time block all closing outputs of the bus fast-switching device.

[0011] Secondly, embodiments of this application also provide a method for switching and protecting a 6kV power plant auxiliary busbar with photovoltaic access, the method comprising: S1. The high-power photovoltaic system is connected to two photovoltaic transformer substations via an inverter with islanding protection and a transformer substation. Each photovoltaic transformer substation is connected to two 6kV photovoltaic incoming line switches, which are respectively connected to the first 6kV plant bus and the second 6kV plant bus of the main plant. The two 6kV photovoltaic incoming line switches are equipped with interlocking devices to prevent them from being closed and operated at the same time. S2. Real-time monitoring of the operating status, power supply type, and protection device operation signals of the 6kV plant busbar; S3. When the trip protection action signal of the generator-transformer unit is detected, the bus fast switching device is started, and the working power switch of the trip bus and all 6kV photovoltaic incoming line switches connected to the bus are tripped at the same time. After both power switches are confirmed to be in the open position and the switching conditions are met, the standby power switch is closed to complete the emergency switching. S4. When a bus working power switch trips or a bus undervoltage signal is detected, the bus fast switching device confirms that the working power switch is in the open position or trips the working power switch and confirms that it is in the open position. At the same time, it trips all 6kV photovoltaic incoming line switches connected to the bus. After the photovoltaic incoming line switch is confirmed to be in the open position and the switching conditions are met, the standby power switch is closed to complete the abnormal switching. S5. If the busbar is powered by the Gaochang transformer, then the photovoltaic power on that busbar will be put into operation. If the busbar needs to be switched to the standby transformer, first switch the photovoltaic power on that busbar to another busbar powered by the Gaochang transformer. If the other busbar is also powered by the standby transformer, then all photovoltaic power will be shut down to complete the normal manual switching of the busbar power supply. S6. When a short-circuit fault signal is detected on the busbar when the high-voltage transformer is supplying power, the busbar protection trips the working power switch, simultaneously trips all 6kV photovoltaic incoming line switches connected to the busbar, and locks the busbar fast-switching device to complete the busbar protection.

[0012] Furthermore, in step S3, a photovoltaic incoming line switch tripping secondary circuit is added to the generator-transformer protection controller A, generator-transformer protection controller B, generator-transformer protection controller C, and the first busbar fast-switching device and the second busbar fast-switching device of the corresponding 6kV busbar of the generator unit.

[0013] Furthermore, in step S3, the switching conditions of the busbar fast switching device include fast switching conditions, synchronous capture switching conditions, and residual voltage switching conditions. The three conditions are judged in sequence. If the switching conditions are not met within the preset time of residual voltage switching, the busbar fast switching device automatically exits the switching process.

[0014] Furthermore, in step S4, the secondary circuit of the step of tripping all photovoltaic incoming switches connected to the busbar is shared with the secondary circuit of the photovoltaic incoming switch tripping added to the busbar fast-switching device in step S3.

[0015] Furthermore, in step S6, the function of tripping the photovoltaic incoming line switch is implemented in generator-transformer group protection controller A and generator-transformer group protection controller B, and is shared with the tripping secondary circuit added in generator-transformer group protection controller A and generator-transformer group protection controller B in step S3.

[0016] As can be seen from the above technical solutions, the present invention has the following advantages: The system adopts a wiring structure with dual photovoltaic transformer substations, dual busbars, and dual incoming line switches, enabling flexible switching and operation mode adjustment of photovoltaic power between two 6kV plant auxiliary busbars. This provides a hardware foundation for rapid disconnection of photovoltaic power and elimination of islanding effects, and allows the photovoltaic system to be transferred to another busbar powered by the high-voltage plant substation when the busbar switches to the standby transformer. A dedicated interlocking device is installed between the two photovoltaic incoming line switches on the same busbar to prevent accidental closing of both photovoltaic incoming line switches, thus avoiding electrical accidents such as circulating current and short circuits. The system integrates a protection and switching infrastructure including a busbar fast-switching device and a generator-transformer unit protection controller, and adds photovoltaic interlocking logic to solve the problem of insufficient photovoltaic protection sensitivity, effectively ensuring the safe and stable operation of large-capacity thermal power units and plant auxiliary power systems. Attached Figure Description

[0017] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the 6kV plant service bus switching and protection system for thermal power plants with photovoltaic access included in this application; Figure 2 This is a schematic diagram showing the connection between the 6kV plant busbar module and the power supply module of the 6kV plant busbar switching and protection system for thermal power plants with photovoltaic access in this application. Figure 3 This is a flowchart illustrating the method for switching and protecting the 6kV auxiliary busbar of a thermal power plant with photovoltaic access, as described in this application. Detailed Implementation

[0019] The various embodiments of the present invention will be described more fully in the detailed steps of the method for switching and protecting the 6kV station service busbar of a thermal power plant with photovoltaic access, which will be described in detail below. The present invention may have various embodiments, and adjustments and changes may be made therein. However, it should be understood that there is no intention to limit the various embodiments of the present invention to the specific embodiments disclosed herein, but rather the present invention should be understood to cover all adjustments, equivalents, and / or alternatives falling within the spirit and scope of the various embodiments of the present invention.

[0020] It should be understood that, when used in this specification, the term "comprising" indicates the presence of the described feature, integral, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. The terms "comprising," "including," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0021] The terms "one embodiment" or "some embodiments" used in this application mean that one or more embodiments of this application include the specific features, structures, or characteristics described in that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this application do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0022] To facilitate a clear description of the technical solutions of this application, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" do not necessarily imply that they are different.

[0023] To make the objectives, features, and advantages of this invention more apparent and understandable, specific embodiments and accompanying drawings will be used to clearly and completely describe the technical solutions protected by this invention. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] Please see Figure 1 The diagram shows a 6kV station service bus switching and protection system for a thermal power plant with photovoltaic access. The system includes: A photovoltaic power generation module includes an inverter with islanding protection and a transformer substation. The inverter includes a first inverter and a second inverter, and the transformer substation includes a first photovoltaic transformer substation and a second photovoltaic transformer substation. The first inverter is connected to the first photovoltaic transformer substation, and the second inverter is connected to the second photovoltaic transformer substation. The 6kV plant busbar module includes a first 6kV busbar, a second 6kV busbar, a first 6kV photovoltaic incoming switch, a second 6kV photovoltaic incoming switch, a third 6kV photovoltaic incoming switch, and a fourth 6kV photovoltaic incoming switch. The first photovoltaic transformer substation is connected to the first 6kV busbar through the first 6kV photovoltaic incoming switch, the second photovoltaic transformer substation is connected to the first 6kV busbar through the second 6kV photovoltaic incoming switch, the first photovoltaic transformer substation is also connected to the second 6kV busbar through the third 6kV photovoltaic incoming switch, and the second photovoltaic transformer substation is also connected to the second 6kV busbar through the fourth 6kV photovoltaic incoming switch. like Figure 2 As shown, the power supply module is used to provide dual-path switching for the working and backup power supply of the first 6kV bus and the second 6kV bus; The protection and switching module includes a first busbar fast-switching device, a second busbar fast-switching device, and a generator-transformer group protection controller. The first busbar fast-switching device is used for power switching of the first 6kV busbar, the second busbar fast-switching device is used for power switching of the second 6kV busbar, and the generator-transformer group protection controller is used to quickly trip the corresponding switch when a fault or abnormality is detected. The interlocking devices are respectively installed between the first photovoltaic incoming switch and the second photovoltaic incoming switch of the first 6kV bus, and between the third photovoltaic incoming switch and the fourth photovoltaic incoming switch of the second 6kV bus. The interlocking devices are used to prevent two photovoltaic incoming switches on the same bus from closing at the same time.

[0025] As a refinement and extension of the specific implementation methods described above, and to fully illustrate the specific implementation process in this embodiment, another 6kV power plant auxiliary busbar switching and protection system with photovoltaic access is provided. This system includes: A photovoltaic power generation module includes an inverter with islanding protection and a transformer substation. The inverter includes a first inverter and a second inverter, and the transformer substation includes a first photovoltaic transformer substation and a second photovoltaic transformer substation. The first inverter is connected to the first photovoltaic transformer substation, and the second inverter is connected to the second photovoltaic transformer substation. The 6kV plant busbar module includes a first 6kV busbar, a second 6kV busbar, a first 6kV photovoltaic incoming switch, a second 6kV photovoltaic incoming switch, a third 6kV photovoltaic incoming switch, and a fourth 6kV photovoltaic incoming switch. The first photovoltaic transformer substation is connected to the first 6kV busbar through the first 6kV photovoltaic incoming switch, the second photovoltaic transformer substation is connected to the first 6kV busbar through the second 6kV photovoltaic incoming switch, the first photovoltaic transformer substation is also connected to the second 6kV busbar through the third 6kV photovoltaic incoming switch, and the second photovoltaic transformer substation is also connected to the second 6kV busbar through the fourth 6kV photovoltaic incoming switch. The power module is used to provide dual-path switching for working and backup power supply for the first 6kV bus and the second 6kV bus; The protection and switching module includes a first busbar fast-switching device, a second busbar fast-switching device, and a generator-transformer group protection controller. The first busbar fast-switching device is used for power switching of the first 6kV busbar, the second busbar fast-switching device is used for power switching of the second 6kV busbar, and the generator-transformer group protection controller is used to quickly trip the corresponding switch when a fault or abnormality is detected. The interlocking devices are respectively installed between the first photovoltaic incoming switch and the second photovoltaic incoming switch of the first 6kV bus, and between the third photovoltaic incoming switch and the fourth photovoltaic incoming switch of the second 6kV bus. The interlocking devices are used to prevent two photovoltaic incoming switches on the same bus from closing at the same time.

[0026] In this embodiment of the invention, the power module includes a generator-transformer group, a standby transformer, a first working power switch, a second working power switch, a first standby power switch, and a second standby power switch. The generator-transformer unit includes a high-voltage transformer and a generator. The primary side of the generator-transformer unit is connected to a 6kV plant service bus module, and the secondary side of the generator-transformer unit is connected to a generator-transformer unit protection controller. The high-voltage transformer is connected to the first 6kV bus via a first working power switch, and to the second 6kV bus via a second working power switch. The standby transformer is connected to the first 6kV bus via a first standby power switch, and to the second 6kV bus via a second standby power switch.

[0027] The generator-transformer unit protection controller includes generator-transformer unit protection controller A, generator-transformer unit protection controller B and generator-transformer unit protection controller C. The generator-transformer unit protection controller is used to monitor the operating status of the generator-transformer unit and the plant service bus. When a fault is detected, the corresponding switch is quickly tripped and the fault is isolated. It should be noted that all of the generator-transformer group protection controllers are equipped with display screens; The generator-transformer protection controller A, generator-transformer protection controller B, generator-transformer protection controller C, as well as the first busbar fast-switching device and the second busbar fast-switching device, are all equipped with a secondary circuit for tripping the photovoltaic incoming line switch. The photovoltaic incoming switch tripping secondary circuits of the generator-transformer group protection controller A and generator-transformer group protection controller B are used for both fault switching and bus protection tripping operations, while the photovoltaic incoming switch tripping secondary circuit of the generator-transformer group protection controller C is only used for tripping operations during fault switching. The photovoltaic incoming switch tripping secondary circuits of the first and second busbar fast switching devices are used simultaneously for 6kV photovoltaic incoming switch tripping operations during both fault switching and abnormal switching.

[0028] In this embodiment of the invention, the secondary circuit configuration for tripping the photovoltaic incoming line switch of the generator-transformer unit protection controller is as follows: When the generator-transformer unit trips, it sends a trip signal to the working power switch of the corresponding bus and at the same time sends a trip signal to all 6kV photovoltaic incoming line switches of that bus. The secondary circuit configuration for the photovoltaic incoming switch tripping of the first busbar fast-switching device and the second busbar fast-switching device is as follows: Upon receiving the trip protection action signal of the generator-transformer unit, a trip signal is simultaneously sent to the working power switch of the corresponding bus and all 6kV photovoltaic incoming line switches. After the working power switch and all 6kV photovoltaic incoming line switches confirm that the trip is initiated and the switching conditions are met, the standby power switch of the corresponding bus is closed.

[0029] It should be noted that by adding a secondary circuit for photovoltaic power supply switching to the generator-transformer unit protection controller and busbar fast-switching device, the photovoltaic power supply is quickly disconnected during power switching, fundamentally avoiding the photovoltaic islanding effect and ensuring a high success rate for plant power switching. When the busbar protection operates, all photovoltaic incoming line switches are tripped in tandem, preventing protection failure or delayed tripping due to small photovoltaic short-circuit currents, effectively preventing the escalation of accidents. All functions can be achieved simply by adding the secondary circuit for tripping, without the need for additional large equipment, saving over ten million yuan in investment.

[0030] In this embodiment of the invention, both the first busbar fast switching device and the second busbar fast switching device include an accident switching module, an abnormal switching module, a normal manual switching module, and a busbar protection module. The fault switching module is used to simultaneously output the working power switch trip signal and the 6kV photovoltaic incoming line switch trip signal when it receives the trip protection action signal of the generator-transformer group. After both power switches are tripped, it judges the switching conditions and outputs the backup power switch closing signal when the conditions are met. The abnormal switching module is used to confirm the tripping status of the working power switch when it receives a signal of the working power switch tripping or a signal of the bus undervoltage, and at the same time output a 6kV photovoltaic incoming switch tripping signal. After the photovoltaic incoming switch trips, it judges the switching conditions and outputs a backup power switch closing signal when the conditions are met. The normal manual switching module is used to determine the current power supply type of the bus when a manual switching command is received. If it is powered by the standby transformer, the photovoltaic power supply of the bus is prohibited from being put into operation. If it is necessary to switch to the standby transformer power supply, the photovoltaic switching or shutdown command is output first. The bus protection module is used to output a working power switch trip signal and a 6kV photovoltaic incoming switch trip signal when a bus short-circuit fault signal is received, and at the same time block all closing outputs of the bus fast-switching device.

[0031] For example, the fault switching module: after receiving the trip protection action signal of the generator-transformer group, it simultaneously sends trip signals to the working power switch and all photovoltaic incoming line switches. After both switches confirm the trip, it sequentially judges the conditions for fast switching, synchronous capture switching and residual voltage switching. If the conditions are met, the backup power switch is closed. If the conditions are not met after 30 seconds of switching to residual voltage, the switching process is automatically exited.

[0032] Abnormal switching module: After receiving a signal of the working power switch tripping or the bus undervoltage signal, confirm the working power switch tripping status, and at the same time send a tripping signal to all photovoltaic incoming switches. After the photovoltaic switches trip, determine the switching conditions, and close the backup power switch if the conditions are met.

[0033] Normal manual switching module: Upon receiving a manual switching command, it determines the current power supply type of the bus. If the bus is powered by the Gaochang transformer, the photovoltaic system on that bus is allowed to operate; if it is necessary to switch the bus to the standby transformer, it first outputs a command to switch the photovoltaic system on that bus to another bus powered by the Gaochang transformer. If the other bus is also powered by the standby transformer, it outputs a command to shut down all photovoltaic systems.

[0034] Busbar protection interlocking module: After receiving a busbar short-circuit fault signal, it sends a trip signal to the working power switch and all photovoltaic incoming line switches, and at the same time blocks all closing outputs of the busbar fast switching device to prevent the standby transformer from closing in the fault circuit.

[0035] Please see Figure 3 The diagram shows a flow chart of a method for switching and protecting a 6kV power plant auxiliary busbar with photovoltaic access. The method includes the following steps: S1. The high-power photovoltaic system is connected to two photovoltaic transformer substations via an inverter with islanding protection and a transformer substation. Each photovoltaic transformer substation is connected to two 6kV photovoltaic incoming line switches, which are respectively connected to the first 6kV plant bus and the second 6kV plant bus of the main plant. The two 6kV photovoltaic incoming line switches are equipped with interlocking devices to prevent them from being closed and operated at the same time. S2. Real-time monitoring of the operating status, power supply type, and protection device operation signals of the 6kV plant busbar; S3. When the trip protection action signal of the generator-transformer unit is detected, the bus fast switching device is started, and the working power switch of the trip bus and all 6kV photovoltaic incoming line switches connected to the bus are tripped at the same time. After both power switches are confirmed to be in the open position and the switching conditions are met, the standby power switch is closed to complete the emergency switching. S4. When a bus working power switch trips or a bus undervoltage signal is detected, the bus fast switching device confirms that the working power switch is in the open position or trips the working power switch and confirms that it is in the open position. At the same time, it trips all 6kV photovoltaic incoming line switches connected to the bus. After the photovoltaic incoming line switch is confirmed to be in the open position and the switching conditions are met, the standby power switch is closed to complete the abnormal switching. S5. If the busbar is powered by the Gaochang transformer, then the photovoltaic power on that busbar will be put into operation. If the busbar needs to be switched to the standby transformer, first switch the photovoltaic power on that busbar to another busbar powered by the Gaochang transformer. If the other busbar is also powered by the standby transformer, then all photovoltaic power will be shut down to complete the normal manual switching of the busbar power supply. S6. When a short-circuit fault signal is detected on the busbar when the high-voltage transformer is supplying power, the busbar protection trips the working power switch, simultaneously trips all 6kV photovoltaic incoming line switches connected to the busbar, and locks the busbar fast-switching device to complete the busbar protection.

[0036] As a refinement and extension of the specific implementation methods described above, and to fully illustrate the specific implementation process in this embodiment, another method for switching and protecting the 6kV station service busbar of a thermal power plant with photovoltaic access is provided. This method includes: S1. The high-power photovoltaic system is connected to two photovoltaic transformer substations via an inverter with islanding protection and a transformer substation. Each photovoltaic transformer substation is connected to two 6kV photovoltaic incoming line switches, which are respectively connected to the first 6kV plant bus and the second 6kV plant bus of the main plant. The two 6kV photovoltaic incoming line switches are equipped with interlocking devices to prevent them from being closed and operated at the same time. For example, a 25.55MWp photovoltaic power generation system is configured into two photovoltaic transformer substation groups via 101 inverters with islanding protection and 13 transformer substations. Each substation group is connected to the 6kV IC bus of Unit #1 and the 6kV IIC bus of Unit #2 via two 6kV photovoltaic incoming line switches, respectively. An electrical interlocking device is installed between the two photovoltaic incoming line switches on the same bus to prevent simultaneous closing. Sixteen photovoltaic tripping secondary circuits are added to the generator-transformer group protection controller and the bus fast-switching device, the bus fast-switching device software is upgraded, and the transmission tests of all circuits are completed.

[0037] S2. Real-time monitoring of the operating status, power supply type, and protection device operation signals of the 6kV plant busbar; For example, the system monitors the operating parameters such as voltage, current, and frequency of the two 6kV plant service busbars in real time, monitors the power supply type of the busbars (powered by the high-voltage plant transformer or by the standby transformer), and the operation signals of the generator-transformer group protection and the busbar protection.

[0038] S3. When the trip protection action signal of the generator-transformer unit is detected, the bus fast switching device is started, and the working power switch of the trip bus and all 6kV photovoltaic incoming line switches connected to the bus are tripped at the same time. After both power switches are confirmed to be in the open position and the switching conditions are met, the standby power switch is closed to complete the emergency switching. In step S3, a 6kV photovoltaic incoming line switch tripping secondary circuit is added to the generator-transformer protection controller A, generator-transformer protection controller B, generator-transformer protection controller C, and the first busbar fast-switching device and the second busbar fast-switching device of the corresponding 6kV busbar of the generator unit.

[0039] In step S3, the switching conditions of the busbar fast switching device include fast switching conditions, synchronous capture switching conditions, and residual voltage switching conditions. The three conditions are judged in sequence. If the switching conditions are not met within the preset time of residual voltage switching, the busbar fast switching device will automatically exit the switching process.

[0040] For example, when the #1 generator-transformer unit trip protection operates, the #1 generator-transformer unit protection A / B / C panels simultaneously send trip signals to the #1 unit 6kV ICO bus working power switch, the first photovoltaic incoming line switch, and the second photovoltaic incoming line switch. Simultaneously, the #1 unit 6kV ICO bus fast-switching device activates, also sending trip signals to the aforementioned three switches to ensure reliable tripping. After the working power switch and both photovoltaic incoming line switches are confirmed to be in the open position, the fast-switching device sequentially judges the conditions for fast switching, synchronous capture switching, and residual voltage switching. When the conditions are met, the #1 unit 6kV ICO bus standby power switch is closed, completing the fault switching.

[0041] S4. When a bus working power switch trips or a bus undervoltage signal is detected, the bus fast switching device confirms that the working power switch is in the open position or trips the working power switch and confirms that it is in the open position. At the same time, it trips all 6kV photovoltaic incoming line switches connected to the bus. After the photovoltaic incoming line switch is confirmed to be in the open position and the switching conditions are met, the standby power switch is closed to complete the abnormal switching. In step S4, the secondary circuit of the 6kV photovoltaic incoming line switch is shared with the secondary circuit of the busbar fast-switching device added in step S3. Simultaneously, the logic judgment software of the busbar fast-switching device is upgraded free of charge by the manufacturer to adapt to abnormal switching procedures. The upgraded software is verified to be correct through transmission tests.

[0042] For example, when the 6kV ICO busbar working power switch of Unit #1 trips unexpectedly, the fast-switching device of Unit #1 detects the switch tripping status and the busbar undervoltage signal, and immediately sends tripping signals to the first photovoltaic incoming switch and the second photovoltaic incoming switch. After both photovoltaic incoming switches confirm that they are tripped, the fast-switching device judges the switching conditions, and closes the standby power switch when the conditions are met, completing the abnormal switching.

[0043] S5. If the busbar is powered by the Gaochang transformer, then the photovoltaic power on that busbar will be put into operation. If the busbar needs to be switched to the standby transformer, first switch the photovoltaic power on that busbar to another busbar powered by the Gaochang transformer. If the other busbar is also powered by the standby transformer, then all photovoltaic power will be shut down to complete the normal manual switching of the busbar power supply. When it is necessary to switch the power supply of the #1 unit's 6kV IIC busbar from the Gaochang substation to the Qibei substation, the operators issue a manual switching command through the fast-switching device. The fast-switching device first determines the power supply type of the #2 unit's 6kV IIC busbar. If the #2 unit's 6kV IIC busbar is powered by the Gaochang substation, the first and second photovoltaic incoming switches are disconnected, and the third and fourth photovoltaic incoming switches of the #2 unit's 6kV IIC busbar are closed, transferring the photovoltaic power to the #2 unit's 6kV IIC busbar before proceeding with the normal busbar power switchover. If the #2 unit's 6kV IIC busbar is also powered by the Qibei substation, all photovoltaic incoming switches are disconnected first, shutting down the entire photovoltaic system before proceeding with the busbar switchover.

[0044] S6. When a short-circuit fault signal is detected on the busbar when the high-voltage transformer is supplying power, the busbar protection trips the working power switch, simultaneously trips all 6kV photovoltaic incoming line switches connected to the busbar, and locks the busbar fast-switching device to complete the busbar protection.

[0045] In step S6, the function of tripping the 6kV photovoltaic incoming line switch is implemented in the generator-transformer group protection controller A and generator-transformer group protection controller B, and is shared with the tripping secondary circuit and corresponding tripping pressure plate added in step S3 to the generator-transformer group protection controller A and generator-transformer group protection controller B. All tripping circuits have been verified to be correct through transmission tests.

[0046] When a short-circuit fault occurs on the 6kV ICO busbar of Unit #1, the A / B protection panel of the generator-transformer unit of Unit #1 will activate and send trip signals to the working power switch, the first photovoltaic incoming line switch, and the second photovoltaic incoming line switch of the 6kV ICO busbar of Unit #1. At the same time, the fast-switching device of the 6kV ICO busbar of Unit #1 will be locked, preventing it from closing the standby power switch, thus preventing the standby transformer from closing on the fault circuit and expanding the scope of the accident.

[0047] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0048] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A 6kV plant service busbar switching and protection system for thermal power plants with photovoltaic access, characterized in that, include: A photovoltaic power generation module includes an inverter with islanding protection and a transformer substation. The inverter includes a first inverter and a second inverter, and the transformer substation includes a first photovoltaic transformer substation and a second photovoltaic transformer substation. The first inverter is connected to the first photovoltaic transformer substation, and the second inverter is connected to the second photovoltaic transformer substation. The 6kV plant busbar module includes a first 6kV busbar, a second 6kV busbar, a first photovoltaic incoming switch, a second photovoltaic incoming switch, a third photovoltaic incoming switch, and a fourth photovoltaic incoming switch. The first photovoltaic transformer substation is connected to the first 6kV busbar through the first photovoltaic incoming switch, the second photovoltaic transformer substation is connected to the first 6kV busbar through the second photovoltaic incoming switch, the first photovoltaic transformer substation is also connected to the second 6kV busbar through the third photovoltaic incoming switch, and the second photovoltaic transformer substation is also connected to the second 6kV busbar through the fourth photovoltaic incoming switch. The power module is used to provide dual-path switching for working and backup power supply to the first 6kV bus and the second 6kV bus. The protection and switching module includes a first busbar fast-switching device, a second busbar fast-switching device, and a generator-transformer group protection controller. The first busbar fast-switching device is used for power switching of the first 6kV busbar, the second busbar fast-switching device is used for power switching of the second 6kV busbar, and the generator-transformer group protection controller is used to quickly trip the corresponding switch when a fault or abnormality is detected. The interlocking devices are respectively installed between the first photovoltaic incoming switch and the second photovoltaic incoming switch of the first 6kV bus, and between the third photovoltaic incoming switch and the fourth photovoltaic incoming switch of the second 6kV bus. The interlocking devices are used to prevent two photovoltaic incoming switches on the same bus from closing at the same time.

2. The 6kV plant service bus switching and protection system for thermal power plants with photovoltaic access as described in claim 1, characterized in that, The power module includes a generator-transformer unit, a starter-standby transformer, a first working power switch, a second working power switch, a first standby power switch, and a second standby power switch. The generator-transformer unit includes a high-voltage transformer and a generator. The primary side of the generator-transformer unit is connected to a 6kV plant service bus module, and the secondary side of the generator-transformer unit is connected to a generator-transformer unit protection controller. The high-voltage transformer is connected to the first 6kV bus via a first working power switch, and to the second 6kV bus via a second working power switch. The standby transformer is connected to the first 6kV bus via a first standby power switch, and to the second 6kV bus via a second standby power switch.

3. The 6kV power plant auxiliary busbar switching and protection system with photovoltaic access in thermal power plants according to claim 2, characterized in that, The generator-transformer unit protection controller includes generator-transformer unit protection controller A, generator-transformer unit protection controller B and generator-transformer unit protection controller C. The generator-transformer unit protection controller is used to monitor the operating status of the generator-transformer unit and the plant service bus. When a fault is detected, the corresponding switch is quickly tripped and the fault is isolated. The generator-transformer protection controller A, generator-transformer protection controller B, generator-transformer protection controller C, as well as the first busbar fast-switching device and the second busbar fast-switching device, are all equipped with a secondary circuit for tripping the photovoltaic incoming line switch. The photovoltaic incoming switch tripping secondary circuits of the generator-transformer group protection controller A and generator-transformer group protection controller B are used for both fault switching and bus protection tripping operations, while the photovoltaic incoming switch tripping secondary circuit of the generator-transformer group protection controller C is only used for tripping operations during fault switching. The photovoltaic incoming switch tripping secondary circuits of the first and second busbar fast switching devices are used simultaneously for 6kV photovoltaic incoming switch tripping operations during both fault switching and abnormal switching.

4. The 6kV plant service bus switching and protection system for thermal power plants with photovoltaic access as described in claim 3, characterized in that, The secondary circuit configuration for the photovoltaic incoming line switch tripping of the generator-transformer unit protection controller is as follows: When the generator-transformer unit trips, it sends a trip signal to the working power switch of the corresponding bus and at the same time sends a trip signal to all photovoltaic incoming switches of the bus. The secondary circuit configuration for the photovoltaic incoming switch tripping of the first busbar fast-switching device and the second busbar fast-switching device is as follows: Upon receiving the trip protection action signal of the generator-transformer unit, a trip signal is simultaneously sent to the working power switch of the corresponding bus and all photovoltaic incoming switches. After the working power switch and all photovoltaic incoming switches confirm that the trip is initiated and the switching conditions are met, the standby power switch of the corresponding bus is closed.

5. The 6kV plant service bus switching and protection system for thermal power plants with photovoltaic access as described in claim 1, characterized in that, The first busbar fast switching device and the second busbar fast switching device include an emergency switching module, an abnormal switching module, a normal manual switching module and a busbar protection module; The fault switching module is used to simultaneously output the working power switch trip signal and the photovoltaic incoming line switch trip signal when it receives the trip protection action signal of the generator-transformer group. After both power switches are tripped, it judges the switching conditions and outputs the backup power switch closing signal when the conditions are met. The abnormal switching module is used to confirm the tripping status of the working power switch when it receives a signal of the working power switch tripping or a signal of the bus undervoltage, and at the same time output a signal of the photovoltaic incoming switch tripping. After the photovoltaic incoming switch trips, it determines the switching conditions and outputs a signal of the backup power switch closing when the conditions are met. The normal manual switching module is used to determine the current power supply type of the bus when a manual switching command is received. If it is powered by the standby transformer, the photovoltaic power supply of the bus is prohibited from being put into operation. If it is necessary to switch to the standby transformer power supply, the photovoltaic switching or shutdown command is output first. The bus protection module is used to output a working power switch trip signal and a photovoltaic incoming line switch trip signal when a bus short-circuit fault signal is received, and at the same time block all closing outputs of the bus fast-switching device.

6. A method for switching and protecting a 6kV power plant auxiliary busbar with photovoltaic access, characterized in that, The method is based on the system according to any one of claims 1-5, and the method includes the following steps: S1. The high-power photovoltaic system is connected to two photovoltaic transformer substations through an inverter with islanding protection and a transformer substation. Each photovoltaic transformer substation is connected to two photovoltaic incoming line switches, which are respectively connected to the first 6kV plant bus and the second 6kV plant bus of the main plant. The two photovoltaic incoming line switches are equipped with interlocking devices to prevent them from being closed and operated at the same time. S2. Real-time monitoring of the operating status, power supply type, and protection device operation signals of the 6kV plant busbar; S3. When the trip protection action signal of the generator-transformer unit is detected, the bus fast switching device is started, and the working power switch of the trip bus and all photovoltaic incoming line switches connected to the bus are tripped at the same time. After both power switches are confirmed to be in the open position and the switching conditions are met, the standby power switch is closed to complete the emergency switching. S4. When a bus working power switch trips or a bus undervoltage signal is detected, the bus fast switching device confirms that the working power switch is in the open position or trips the working power switch and confirms that it is in the open position. At the same time, it trips all photovoltaic incoming line switches connected to the bus. After the photovoltaic incoming line switch is confirmed to be in the open position and the switching conditions are met, the standby power switch is closed to complete the abnormal switching. S5. If the busbar is powered by the Gaochang transformer, then the photovoltaic power on that busbar will be put into operation. If the busbar needs to be switched to the standby transformer, first switch the photovoltaic power on that busbar to another busbar powered by the Gaochang transformer. If the other busbar is also powered by the standby transformer, then all photovoltaic power will be shut down to complete the normal manual switching of the busbar power supply. S6. When a short-circuit fault signal is detected on the busbar when the power supply is supplied by the high-voltage transformer, the busbar protection trips the working power switch, and simultaneously trips all photovoltaic incoming line switches connected to the busbar, and locks the busbar fast-switching device to complete the busbar protection.

7. The method for switching and protecting the 6kV station service busbar of a thermal power plant with photovoltaic access according to claim 6, characterized in that, In step S3, a photovoltaic incoming line switch tripping secondary circuit is added to the generator-transformer protection controller A, generator-transformer protection controller B, generator-transformer protection controller C, and the first busbar fast-switching device and the second busbar fast-switching device of the corresponding 6kV busbar of the generator unit.

8. The method for switching and protecting the 6kV station service busbar of a thermal power plant with photovoltaic access according to claim 6, characterized in that, In step S3, the switching conditions of the busbar fast switching device include fast switching conditions, synchronous capture switching conditions, and residual voltage switching conditions. The three conditions are judged in sequence. If the switching conditions are not met within the preset time of residual voltage switching, the busbar fast switching device will automatically exit the switching process.

9. The method for switching and protecting the 6kV station service busbar of a thermal power plant with photovoltaic access according to claim 7, characterized in that, In step S4, the secondary circuit of tripping all photovoltaic incoming line switches connected to the busbar is shared with the secondary circuit of the photovoltaic incoming line switch tripping device added to the busbar fast-switching device in step S3.

10. The method for switching and protecting the 6kV station service busbar of a thermal power plant with photovoltaic access according to claim 7, characterized in that, In step S6, the function of tripping the photovoltaic incoming line switch is implemented in generator-transformer group protection controller A and generator-transformer group protection controller B, and is shared with the tripping secondary circuit added in generator-transformer group protection controller A and generator-transformer group protection controller B in step S3.

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