A method for a steam-electric dual-drive unit to participate in primary frequency regulation and load change of the power grid

Abstract

This invention relates to a method for a steam-electric dual-drive unit to participate in primary frequency regulation and load change in the power grid. The steam-electric dual-drive unit includes a small steam turbine and an asynchronous motor. The method involves closing the regulating valve of the small steam turbine to reduce the steam intake, releasing the stored energy of the extracted steam that serves as the steam source for the small turbine, allowing more steam to enter the main steam turbine to perform work, thus achieving the primary frequency regulation and load increase function. Conversely, when the grid frequency rises to a set second threshold, opening the regulating valve of the small steam turbine to increase the steam intake, reducing the amount of steam entering the main steam turbine to perform work, thereby achieving the primary frequency regulation and load reduction function. Compared with existing technologies, this invention has the advantages of ensuring the safety and stability of the unit while achieving economical operation, meeting primary frequency regulation requirements, and contributing to further promoting energy conservation and emission reduction in thermal power units.

Description

Technical Field

[0001] This invention relates to the field of automatic control of thermal power generating units, and in particular to a method for a steam-electric dual-drive unit to participate in primary frequency regulation and load change of the power grid. Background Technology

[0002] Under the constraints of clean energy consumption and environmental protection, higher requirements are being placed on power generation companies. In recent years, the steam-electric dual-drive induced draft fan technology, with its advantages such as low plant power consumption, high heating flexibility, and low coal consumption for power generation, has gradually begun to be promoted and applied in the power generation field.

[0003] The dual-drive steam-electric induced draft fan technology selects a back-pressure dual-drive steam-electric induced draft fan unit. This unit includes a back-pressure steam turbine, a constant-ratio gearbox, an asynchronous motor, and a fan. To improve the operating efficiency of the back-pressure steam turbine and ensure it always operates in its high-efficiency range, the control valve of the back-pressure steam turbine is fully open under load, and primary frequency regulation is not designed. Meanwhile, grid-connected steam turbine generator sets generally require primary frequency regulation.

[0004] Therefore, how to fill the technical gap in the technology of steam-electric dual-drive induced draft fan that does not involve primary frequency regulation function based on the operating characteristics of steam-electric dual-drive units has become a technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for a steam-electric dual-drive unit to participate in the primary frequency regulation and load change of the power grid. This method can achieve economical operation while ensuring the safety and stability of the unit, and can also meet the requirements of primary frequency regulation, which helps to further promote energy conservation and emission reduction of thermal power units.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] According to one aspect of the present invention, a method is provided for a steam-electric dual-drive unit to participate in primary frequency regulation and load change of the power grid. The steam-electric dual-drive unit includes a small steam turbine and an asynchronous motor. The method reduces the steam intake of the small steam turbine by closing the regulating valve of the small steam turbine when the grid frequency drops to a set first threshold, thereby releasing the stored energy of the extracted steam that serves as the steam source for the small steam turbine, allowing more steam to enter the main steam turbine to perform work, thus realizing the primary frequency regulation and load increase function. When the grid frequency rises to a set second threshold, the steam intake of the small steam turbine is increased by opening the regulating valve of the small steam turbine, thereby reducing the amount of steam entering the main steam turbine to perform work, thus realizing the primary frequency regulation and load reduction function.

[0008] As a preferred technical solution, when the power grid frequency changes beyond the set frequency difference during the operation of the steam-electric dual-drive unit, the method calculates and determines the primary frequency regulation load demand based on the power grid frequency difference and the actual output of the unit.

[0009] As a preferred technical solution, this method determines the primary frequency regulation load demand and then calculates the direction and amplitude of the small turbine inlet steam regulating valve's operation by combining the CCS and DEH side control strategies.

[0010] As a preferred technical solution, when adjusting the regulating valve of the small steam turbine, the method coordinates the control system to change the controlled variables of the main regulating system of the unit accordingly, including fuel quantity, feedwater flow rate and air volume, to quickly compensate for the unit's energy demand, provide the required amplitude and continuous frequency regulation power output, and reduce the fluctuation of the main parameters of the unit's steam pressure and steam temperature.

[0011] As a preferred technical solution, this method involves the small turbine MEH automatically issuing a command during load increase to directly and quickly close the small turbine inlet steam regulating valve to a preset opening, allowing more steam to enter the main turbine to do work, thereby instantly increasing the unit output and responding to the primary frequency regulation load increase demand.

[0012] As a preferred technical solution, the specific process of applying the load is as follows:

[0013] Step 1: When the small steam turbine is put into normal operation, when the grid frequency drops below the set first threshold, the primary frequency regulation load demand is determined based on the grid frequency difference and the actual output of the unit.

[0014] Step 2: Determine if it is within the safety boundary. If yes, close the small turbine regulating valve and proceed to step 3; otherwise, do not operate.

[0015] Step 3: Add corresponding boiler main control commands to increase boiler output;

[0016] Step 4: After the shutdown command is issued and the set time is reached, the extracted steam originally supplied to the small steam turbine will enter the main steam turbine to do work, and the unit load will increase rapidly, realizing the primary frequency regulation and load increase function.

[0017] Step 5: After the grid frequency deviation is restored, adjust the small turbine control valve, and the unit will gradually return to normal operation.

[0018] As a preferred technical solution, closing the turbine control valve in step 2 specifically involves:

[0019] Calculate whether adjusting one small steam turbine can meet the frequency regulation requirements. If it can, adjust one small steam turbine directly; otherwise, adjust two small steam turbines for frequency regulation.

[0020] As a preferred technical solution, increasing boiler output in step 3 includes increasing boiler fuel quantity, feedwater flow rate, and air volume.

[0021] As a preferred technical solution, this method reduces the amount of steam entering the main turbine for power generation by immediately opening the regulating valves of the large and small steam turbines during load reduction, thereby achieving load reduction.

[0022] As a preferred technical solution, this method is applicable to turbine units with full-circuit steam inlet throttling and steam distribution and sequential valve steam distribution units. At the same time, this method can respond to primary frequency regulation alone or be integrated with several existing primary frequency regulation technologies.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. Based on the operating characteristics of the steam-electric dual-drive unit, this invention fills the technical gap in the steam-electric dual-drive induced draft fan technology that does not involve primary frequency regulation function, and also adds a new technical means to realize primary frequency regulation for the unit, giving operators more options.

[0025] 2. When the steam-electric dual-drive unit of the present invention is running, when the grid frequency change exceeds the set frequency difference, the primary frequency regulation load demand is calculated and determined based on the grid frequency difference and the actual output of the unit. Combined with the control strategies of CCS and DEH, the required action range of the small turbine inlet steam regulating valve is calculated to prevent the disturbance caused by excessive change in the opening of the induced draft fan inlet steam regulating valve. At the same time, it prevents the unit's response frequency regulation output from exceeding the unit's current maximum actual output capacity, thus ensuring the stable and safe operation of the unit.

[0026] 3. The coordinated control system of this invention adjusts the unit's fuel quantity, feedwater flow rate, and air volume accordingly to quickly compensate for the unit's energy demand, provide the required amplitude and continuous frequency regulation power output, and reduce fluctuations in the unit's main parameters such as steam pressure and steam temperature.

[0027] 4. This invention improves the economic efficiency of unit operation. Firstly, for main turbine units with full-circuit throttling steam distribution, this invention helps maintain the main turbine control valve in fully open sliding pressure operation, thereby significantly improving the unit's operating economy. Secondly, for main turbine units with sequential valve steam distribution, this method can also be used as a supplement to the original primary frequency regulation function. When the grid frequency drops to a certain level, the control valve of the small turbine with the induced draft fan is triggered to participate in primary frequency regulation.

[0028] 5. This invention improves the flexibility of unit frequency regulation. It can respond to primary frequency regulation independently or be integrated with several existing primary frequency regulation technologies. Examples include dual-drive steam and electric power combined with main turbine regulating valve throttling frequency regulation, dual-drive steam and electric power combined with condensate throttling frequency regulation, dual-drive steam and electric power combined with high-pressure heater extraction frequency regulation, and dual-drive steam and electric power combined with high-pressure heater, low-pressure heater, and heating supply cutoff frequency regulation. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the dual-drive (steam and electric) arrangement of the suction fan;

[0030] Figure 2 This is a flowchart illustrating the specific process of frequency regulation and load variation in this invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] This invention provides a technical means for the dual-drive steam-electric suction fan unit to respond to primary frequency regulation of the power grid.

[0033] First, it improves frequency regulation flexibility, effectively combining primary frequency regulation technology on the boiler and main turbine sides, enriching the technical means of responding to primary frequency regulation, and requiring no additional equipment, thus achieving low cost.

[0034] Secondly, it can minimize the throttling losses of the main steam turbine and improve the economic efficiency of unit operation.

[0035] In response to low-frequency load increases in the power grid, the system can rapidly close the regulating valve of the small steam turbine when the grid frequency drops to a certain level. This reduces the steam intake of the small steam turbine and releases the stored energy of the extracted steam, which serves as the steam source for the small steam turbine, thus achieving the function of rapid load increases in primary frequency regulation. Response to high-frequency load reduction in the power grid is similar.

[0036] This approach ensures the safety and stability of the generating units while achieving economical operation, meeting primary frequency regulation requirements, enhancing the competitiveness of the power auxiliary service market, and contributing to further promoting energy conservation and emission reduction in thermal power units.

[0037] like Figure 1 As shown, a 1000MW ultra-supercritical steam turbine generator unit is equipped with two 50% BMCR dual-drive induced draft fans. The exhaust steam regeneration system of the induced draft fans adopts a configuration of "back-pressure steam turbine + constant speed ratio gearbox + asynchronous motor + dynamic adjustment fan". Simultaneously, each induced draft fan is equipped with a small steam turbine (hereinafter referred to as the small turbine) and features a clutch-equipped reduction gearbox, lubrication system, shaft sealing system, and small turbine steam supply and exhaust system. The steam source for the small turbine is the unit's medium-pressure inlet steam, i.e., the outlet steam from the boiler's first-stage reheater, and the exhaust steam returns to the No. 6 low-pressure heater of the main unit. During operation, the moving blades of the induced draft fans control the furnace negative pressure, and the motors on the entire shaft system are responsible for balancing the unbalanced power. The main steam turbine normally operates in an economical mode with the high-pressure regulating valve fully open and sliding pressure running.

[0038] For steam-electric dual-drive units, the suction fan system is designed with the following states: "pure electric drive, steam-electric dual drive, steam-driven power generation, and pure steam drive". When any of the above states are met, it indicates that the suction fan system is in operation.

[0039] For example, in the case of steam-driven power generation, all of the following conditions must be met:

[0040] 1) The clutch is engaged, and the speed of the small machine (after selection 3) is higher than the engagement speed;

[0041] 2) The motor is in generator mode;

[0042] 3) The suction fan switch is closed.

[0043] like Figure 2 As shown, the specific steps for controlling a dual-drive steam-electric turbine to participate in primary frequency regulation and load transformation of the power grid are as follows:

[0044] Step 1: When the unit is running in steam-driven power generation mode, when the grid frequency drops to a certain level, the logic automatically judges the frequency difference signal, calculates whether it is within the safety boundary, including calculating whether to trigger the adjustment of one small generator or two small generators, as well as the direction and magnitude of the action.

[0045] Step 2: The instruction is sent to the MEH control system of the small suction fan to close the steam inlet regulating valve of the small steam turbine.

[0046] Step 3: At the same time, instructions are sent to the boiler main control, which automatically increases the boiler feedwater, fuel and air volume to increase the boiler output and make up for the unit's energy storage utilization.

[0047] Step 4: The aforementioned small turbine inlet steam regulating valve is partially closed. Consequently, the steam that was previously drawn out of the boiler's first-stage reheater outlet to perform work on the small turbine now enters the intermediate-pressure cylinder of the main turbine to perform work, increasing the unit load and realizing the primary frequency regulation load increase function. At this time, the steam-electric dual-drive unit may undergo a state change, such as switching from steam-driven power generation mode to steam-electric dual-drive mode;

[0048] Step 5: When the grid frequency returns to normal, the MEH control system will receive a command to automatically open the steam regulating valve of the main generator, and the unit will then return to its original steam-driven power generation state and return to normal operation.

[0049] like Figure 2 As shown, the frequency regulation and load reduction process is similar, except that the steam inlet regulating valve is changed from being closed to being opened.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for a steam-electric dual-drive unit to participate in primary frequency regulation and load change of a power grid, wherein the steam-electric dual-drive unit includes a small steam turbine and an asynchronous motor, characterized in that, The method reduces the steam intake of the small steam turbine by closing its regulating valve when the grid frequency drops to a set first threshold, releasing the stored energy of the extracted steam that serves as the steam source for the small steam turbine, allowing more steam to enter the main steam turbine to perform work, thus achieving the primary frequency regulation and load increase function; when the grid frequency rises to a set second threshold, it increases the steam intake of the small steam turbine by opening its regulating valve, reducing the amount of steam entering the main steam turbine to perform work, thereby achieving the primary frequency regulation and load reduction function. When the load is increased, the method automatically issues a command from the small turbine MEH to directly and quickly close the steam inlet regulating valve of the small turbine to the preset opening, so that more steam enters the main turbine to do work, thereby instantly increasing the unit output and responding to the load increase demand of primary frequency regulation; The specific process of applying the load is as follows: Step 1: When the small steam turbine is put into normal operation, when the grid frequency drops below the set first threshold, the primary frequency regulation load demand is determined based on the grid frequency difference and the actual output of the unit. Step 2: Determine if it is within the safety boundary. If yes, close the small turbine regulating valve and proceed to step 3; otherwise, do not operate. Step 3: Add corresponding boiler main control commands to increase boiler output; Step 4: After the shutdown command is issued and the set time is reached, the extracted steam originally supplied to the small steam turbine will enter the main steam turbine to do work, and the unit load will increase rapidly, realizing the primary frequency regulation and load increase function. Step 5: After the grid frequency deviation is restored, adjust the small turbine control valve, and the unit will gradually return to normal operation.

2. The method for a dual-drive steam-electric generator unit to participate in primary frequency regulation and load change of the power grid according to claim 1, characterized in that, When the steam-electric dual-drive unit is running, this method calculates and determines the primary frequency regulation load demand based on the grid frequency difference and the actual output of the unit when the grid frequency change exceeds the set frequency difference.

3. The method for a dual-drive steam-electric generator unit to participate in primary frequency regulation and load change of the power grid according to claim 2, characterized in that, After determining the primary frequency regulation load demand, this method calculates the direction and magnitude of the required action of the small turbine inlet steam regulating valve by combining the CCS and DEH side control strategies.

4. The method for a dual-drive steam-electric generator unit to participate in primary frequency regulation and load change of the power grid according to claim 2, characterized in that, When adjusting the regulating valve of the small steam turbine, this method coordinates the control system to change the controlled variables of the main regulating system of the unit, including fuel quantity, feedwater flow rate and air volume, to quickly compensate for the unit's energy demand, provide the required amplitude and continuous frequency regulation power output, and reduce the fluctuation of the main parameters of the unit's steam pressure and steam temperature.

5. A method for a dual-drive steam-electric generator unit to participate in primary frequency regulation and load change of the power grid according to claim 1, characterized in that, The specific steps in step 2, such as closing the turbine control valve, are as follows: Calculate whether adjusting one small steam turbine can meet the frequency regulation requirements. If it can, adjust one small steam turbine directly; otherwise, adjust two small steam turbines for frequency regulation.

6. A method for a dual-drive steam-electric generator unit to participate in primary frequency regulation and load change of the power grid according to claim 1, characterized in that, Increasing boiler output in step 3 includes increasing boiler fuel quantity, feedwater flow rate, and air volume.

7. A method for a dual-drive steam-electric generator unit to participate in primary frequency regulation and load change in the power grid according to claim 1, characterized in that, This method reduces the amount of steam entering the main turbine for power generation by immediately opening the regulating valves of the large and small steam turbines during load reduction, thereby achieving the primary frequency regulation and load reduction function.

8. A method for a dual-drive steam-electric generator unit to participate in primary frequency regulation and load change of the power grid according to claim 1, characterized in that, This method is applicable to turbine units with full-circuit steam inlet throttling and steam distribution, as well as turbine units with sequential valve steam distribution. This method can respond to primary frequency regulation independently or be integrated with several existing primary frequency regulation technologies.

Images