An auxiliary frequency modulation system based on variable load of power plant

Abstract

This invention discloses an auxiliary frequency regulation system based on variable load in a power plant, comprising a 220kV high-voltage busbar, a main transformer, a distributed control system (DCS), a remote terminal unit (RTU), a power measurement device, a generator, a high-voltage station service transformer, a 6kV station service busbar, a load transformer, and a variable load system. The coal-fired generator is connected to the main transformer and the high-voltage station service transformer via the power measurement device. The main transformer is connected to the 220kV high-voltage busbar via a first switch. The high-voltage station service transformer is connected to the 6kV station service busbar via a second switch. The 6kV station service busbar is connected to the high-voltage side of the load transformer via a third switch. The low-voltage side of the load transformer is connected to a large-capacity load via a power control device. The DCS establishes a communication connection with the power control device to participate in the unit's AGC (Automatic Generation Control) process, effectively improving the power plant's response speed to AGC commands, assisting in unit frequency regulation, meeting the requirements of power grid performance indicators, and increasing the economic benefits of power generation enterprises.

Description

Technical Field

[0001] This invention belongs to the field of frequency regulation of power plant units, and specifically relates to an auxiliary frequency regulation system based on the variable load of a power plant. Background Technology

[0002] When thermal power plants participate in primary frequency regulation of the power grid, factors such as unstable coal quality and low accuracy of online air-coal measurement systems make it difficult to accurately control various unit parameters when the load of the power plant rapidly increases or decreases, significantly reducing the response speed and accuracy of the unit to load changes. Currently, high-voltage regulating valve throttling technology and multi-variable collaborative optimization systems are commonly used to improve the unit's regulation capability. However, there is still a gap between the actual load change curve of the unit and the load change curve required by the primary frequency regulation assessment of the power grid. Therefore, other methods are needed to further improve the response speed to load changes.

[0003] Large-capacity variable load systems utilize power control devices to control the power of large-capacity loads in real time, offering advantages such as fast response and precise control. Some thermal power plants have large-capacity variable loads connected to their auxiliary power systems, such as electric boiler systems, but their power control systems lack communication with the power plant's DCS, preventing them from participating in unit AGC (Automatic Generation Control). Summary of the Invention

[0004] The purpose of this invention is to address the issue that existing large-capacity variable loads cannot participate in generator AGC and cannot help improve the frequency regulation performance of generators. This invention provides an auxiliary frequency regulation system based on the variable loads of power plants. The system has a simple structure, low modification and maintenance costs, and can enable large-capacity variable loads to participate in AGC together with generators, which greatly improves the speed of power plant response to AGC commands, meets the requirements of power grid assessment indicators, and increases the economic benefits of power generation enterprises.

[0005] The present invention is achieved using the following technical solution:

[0006] An auxiliary frequency regulation system based on variable load in a power plant includes a 220kV high-voltage busbar, a main transformer, a distributed control system (DCS), a remote terminal unit (RTU), a power measurement device, a generator, a high-voltage station service transformer, a 6kV station service busbar, a load transformer, and a variable load system; wherein,

[0007] The coal-fired generator is connected to the main transformer and the high-voltage plant service transformer via a power measurement device. The main transformer is connected to the 220kV high-voltage busbar via the first switch. The high-voltage plant service transformer is connected to the 6kV plant service busbar via the second switch. The 6kV plant service busbar is connected to the high-voltage side of the load transformer via the third switch. The low-voltage side of the load transformer is connected to the variable load system.

[0008] A further improvement of the present invention is that the variable load system includes a power control device and a large-capacity load, wherein the large-capacity load is connected to the load transformer via the power control device.

[0009] A further improvement of the present invention is that the power control device can adjust the output power according to the instructions.

[0010] A further improvement of this invention is that the Distributed Control System (DCS) and the power measurement device establish a communication connection, and the power measurement device transmits the generator power signal to the DCS; the DCS establishes a communication connection with the generator, and the DCS sends a power command to the generator; the DCS establishes a bidirectional communication connection with the power control device, and the power control device transmits the high-capacity load power signal to the DCS, while the DCS transmits the generator power to the power control device; the DCS establishes a bidirectional communication connection with the Remote Terminal Unit (RTU), and the DCS transmits the total unit power signal to the RTU, which is the difference between the generator power and the high-capacity load power, and the RTU sends the total unit power signal to the dispatch center; the dispatch center transmits AGC commands to the DCS and the power control device through the RTU.

[0011] A further improvement of this invention is that, during normal operation of the generating unit and the variable load, the variable load system is connected to the unit's auxiliary power system and participates in the unit's AGC frequency regulation, with the first, second, and third switches in the closed position. The generating unit and the large-capacity load participate in the unit's AGC. The dispatch center sends AGC commands to the distributed control system (DCS) and power control device via the remote terminal unit (RTU). If the AGC command is a load increase command, the DCS sends a load increase command to the generator, and the power control device rapidly reduces the power of the large-capacity load, ensuring that the difference between the generator's increased power and the large-capacity load's decreased power always matches the AGC load increase command. If the AGC command is a load decrease command, the DCS sends a load decrease command to the generator, and the power control device rapidly increases the power of the large-capacity load, ensuring that the difference between the generator's decreased power and the large-capacity load's increased power always matches the AGC load decrease command. Here, the increased power is a positive value, and the decreased power is a negative value.

[0012] A further improvement of this invention is that when the unit is operating normally and the large-capacity load is shut down, the large-capacity load is disconnected from the plant power system and does not participate in the unit's AGC. The first and second switches are in the closed position, and the third switch is in the open position. When the unit participates in AGC frequency regulation, the dispatch center sends AGC commands to the distributed control system (DCS) via the remote terminal unit (RTU). The DCS then sends load increase / decrease commands to the generator, ensuring that the generator's load increase / decrease always matches the AGC load increase / decrease commands.

[0013] The present invention has at least the following beneficial technical effects:

[0014] Existing power plant auxiliary power systems with high loads lack communication links with remote terminal units (RTUs) and distributed control systems (DCS), preventing them from participating in generator AGC (Automatic Generation Control) and assisting generators in frequency regulation. This invention provides an auxiliary frequency regulation system based on variable loads in power plants. High-capacity loads are equipped with power control devices that communicate with both the RTU and DCS. By controlling the power of these high-capacity loads to participate in AGC alongside the generators, the system effectively improves the power plant's response speed to AGC commands, assists generator frequency regulation, meets grid performance requirements, and increases the economic benefits for power generation companies. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a variable load auxiliary frequency regulation system for a power plant.

[0016] Figure 2 This is a schematic diagram of variable load auxiliary frequency regulation operation in a power plant.

[0017] Figure 3 This is a schematic diagram of a power plant operating under variable load shutdown.

[0018] Explanation of reference numerals in the attached figures:

[0019] 1-220kV high-voltage busbar, 2-main transformer, 3-distributed control system (DCS), 4-remote terminal unit (RTU), 5-power measurement device, 6-generator, 7-high-voltage plant transformer, 8-6kV plant busbar, 9-load transformer, 10-power control device, 11-large capacity load.

[0020] 101 - First switch, 201 - Second switch, 202 - Third switch. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] like Figure 1As shown, the present invention provides an auxiliary frequency regulation system based on variable load of a power plant, including a 220kV high-voltage busbar 1, a main transformer 2, a distributed control system (DCS) 3, a remote terminal unit (RTU) 4, a power measurement device 5, a generator 6, a high-voltage plant service transformer 7, a 6kV plant service busbar 8, a load transformer 9, a power control device 10, and a large-capacity load 11; wherein the coal-fired generator 6 is connected to the main transformer 2 and the high-voltage plant service transformer 7 via the power measurement device 5, the main transformer 2 is connected to the 220kV high-voltage busbar 1 via a first switch 101, the high-voltage plant service transformer 7 is connected to the 6kV plant service busbar 8 via a second switch 201, the 6kV plant service busbar 8 is connected to the high-voltage side of the load transformer 9 via a third switch 202, and the low-voltage side of the load transformer 9 is connected to the large-capacity load 11 via the power control device 10.

[0023] The working principle of this invention is as follows:

[0024] The Distributed Control System (DCS3) establishes a communication connection with the power measurement device 5, and the power measurement device 5 transmits the generator power signal to the DCS3. The DCS3 establishes a communication connection with the generator 6, and the DCS3 sends a power command to the generator. The DCS3 establishes a bidirectional communication connection with the power control device 10, and the power control device 10 transmits the high-capacity load power signal to the DCS3. The DCS3 also transmits the generator power to the power control device 10. The DCS3 establishes a bidirectional communication connection with the Remote Terminal Unit (RTU4), and the DCS3 transmits the total unit power signal to the RTU4. The total unit power signal is the difference between the generator power and the high-capacity load power. The RTU4 sends the total unit power signal to the dispatch center. The dispatch center transmits AGC commands to the DCS3 and the power control device 10 through the RTU4.

[0025] like Figure 2As shown, when the unit is operating normally and the variable load is operating normally, the variable load system is connected to the unit's plant power system and participates in the unit's AGC frequency regulation. The first switch 101, the second switch 201, and the third switch 202 are in the closed position. The unit and the large-capacity load participate in the unit's AGC. The dispatch center sends AGC commands to the distributed control system DCS3 and the power control device 10 through the remote terminal unit RTU4. If the AGC command is an increase load command, the distributed control system DCS3 sends an increase load command to the generator 6. The power control device quickly reduces the power of the large-capacity load, so that the difference between the generator's increased power and the large-capacity load's decreased power (increase power is a positive value, decrease power is a negative value) always remains consistent with the AGC increase load command. If the AGC command is a decrease load command, the distributed control system DCS3 sends a decrease load command to the generator 6. The power control device quickly increases the power of the large-capacity load, so that the difference between the generator's decreased power and the large-capacity load's increased power (increase power is a positive value, decrease power is a negative value) always remains consistent with the AGC decrease load command.

[0026] like Figure 3 As shown, when the unit is operating normally and the large-capacity load is shut down, the large-capacity load is disconnected from the plant power system and does not participate in the unit's AGC. The first switch 101 and the second switch 201 are in the closed position, and the third switch 202 is in the open position. When the unit participates in AGC frequency regulation, the dispatch center sends AGC commands to the distributed control system DCS3 through the remote terminal unit RTU4. The distributed control system DCS3 sends load increase / decrease commands to the generator 6, so that the generator load increase / decrease always keeps in line with the AGC increase / decrease.

Claims

1. An auxiliary frequency modulation system based on variable load of a power plant, characterized by, The power generation system comprises a 220kV high-voltage bus (1), a main transformer (2), a distributed control system (DCS) (3), a remote terminal unit (RTU) (4), a power measuring device (5), a generator (6), a high-voltage auxiliary transformer (7), a 6kV auxiliary power bus (8), a load transformer (9) and a variable load system. The coal-fired generator (6) is connected with the main transformer (2) and the high-voltage auxiliary transformer (7) through the power measuring device (5), the main transformer (2) is connected with the 220kV high-voltage bus (1) through a first switch (101), the high-voltage auxiliary transformer (7) is connected with the 6kV auxiliary power bus (8) through a second switch (201), the 6kV auxiliary power bus (8) is connected with the high-voltage side of the load transformer (9) through a third switch (202), and the low-voltage side of the load transformer (9) is connected with the variable load system. The variable load system comprises a power control device (10) and a large-capacity load (11), and the large-capacity load (11) is connected with the load transformer (9) through the power control device (10). The distributed control system (DCS) (3) and the power measuring device (5) are communicatively connected, the power measuring device (5) transmits a generator power signal to the distributed control system (DCS) (3), the distributed control system (DCS) (3) is communicatively connected with the generator (6), the distributed control system (DCS) (3) transmits a power instruction to the generator, the distributed control system (DCS) (3) and the power control device (10) are bidirectionally communicatively connected, the power control device (10) transmits a large-capacity load power signal to the distributed control system (DCS) (3), and the distributed control system (DCS) (3) transmits a generator power to the power control device (10), the distributed control system (DCS) (3) and the remote terminal unit (RTU) (4) are bidirectionally communicatively connected, the distributed control system (DCS) (3) transmits a total power signal of the unit to the remote terminal unit (RTU) (4), the total power signal of the unit is a difference between the generator power and the large-capacity load power, the remote terminal unit (RTU) (4) transmits the total power signal of the unit to a dispatching center, and the dispatching center transmits an AGC instruction to the distributed control system (DCS) (3) and the power control device (10) through the remote terminal unit (RTU) (4). When the unit is in normal operation, the variable load is in normal operation, the variable load system is connected to the unit auxiliary power system and participates in the unit AGC frequency modulation, the first switch (101), the second switch (201) and the third switch (202) are in the closed position; the unit and the large-capacity load participate in the unit AGC, the dispatching center sends an AGC instruction to the distributed control system DCS (3) and the power control device (10) through the remote terminal unit RTU (4), if the AGC instruction is an increase load instruction, the distributed control system DCS (3) sends an increase load instruction to the generator (6), the power control device quickly reduces the large-capacity load power, so that the difference between the power increase of the generator and the power reduction of the large-capacity load always remains consistent with the AGC increase load instruction; if the AGC instruction is a decrease load instruction, the distributed control system DCS (3) sends a decrease load instruction to the generator (6), the power control device quickly increases the large-capacity load power, so that the difference between the power reduction of the generator and the power increase of the large-capacity load always remains consistent with the AGC decrease load instruction; wherein the power increase is positive, and the power reduction is negative; When the large-capacity load is shut down, the large-capacity load is disconnected from the auxiliary power system and does not participate in the unit AGC, the first switch (101) and the second switch (201) are in the closed position, and the third switch (203) is in the open position; the unit participates in the AGC frequency modulation, the dispatching center sends an AGC instruction to the distributed control system DCS (3) through the remote terminal unit RTU (4), and the distributed control system DCS (3) sends an increase / decrease load instruction to the generator (6), so that the increase / decrease load of the generator always remains consistent with the AGC increase / decrease load instruction.

2. A supplementary frequency regulation system based on variable load of power plant as claimed in claim 1 wherein, The power control device (10) can adjust the output power according to the instruction.

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