An AGC control method based on turbine acceleration regulation

Abstract

The present invention relates to an AGC control method based on turbine acceleration regulation, comprising: determining acceleration permission judgment conditions; after satisfying the acceleration permission judgment conditions, when the deviation between the actual power of the unit and the target power is within a preset range, and the variable load amplitude of the current AGC instruction is less than or equal to the preset variable load amplitude threshold, triggering the acceleration loop action; during the acceleration action process, judging whether there is a situation where the acceleration loop action needs to be canceled; allowing the turbine override control instruction to act on the load instruction of the unit and the feedforward link of the turbine main control at the same time. The beneficial effect of the present invention is that when the actual power of the thermal power unit approaches the target power, the present invention causes the actual power to touch the dead zone range of the AGC instruction assessment through the rapid action of the turbine, and at the same time sets corresponding acceleration permission conditions and acceleration exit conditions, which can improve the AGC rate index of the unit, obtain better AGC assessment benefits, and enhance the competitiveness of the unit in the power auxiliary market.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal power generation units, and more specifically, to an AGC control method based on turbine acceleration regulation. Background Art

[0002] In order to improve the performance of the unit's AGC (automatic generation control) and its competitiveness in the power auxiliary service market, thermal power units urgently need to improve the AGC adjustment rate and accuracy to adapt to the grid's requirements for variable load rates. Conventional AGC control is controlled in real time by a distributed control system (DCS). The DCS limits the received AGC load command and generates the unit load command and main steam pressure set value, and then performs closed-loop adjustment with the unit's real-time power and actual pressure to adjust the boiler's fuel quantity, air supply volume, and feedwater flow to meet the turbine's work requirements. For the turbine side, the DCS system controls the turbine speed regulating valve opening to change the turbine output and adjust the unit's power generation. The DCS coordinates the energy supply and demand balance between the boiler and the turbine, adjusts the unit output in real time, and responds to the AGC command.

[0003] Steam turbine control is generally divided into two modes, corresponding to two main control objects, one is the generator power, and the other is the main steam pressure. PID (proportional integral differential) adjustment is performed according to the deviation between the set value and the feedback. When the steam turbine is operated in the conventional AGC mode, it mainly controls the generator power, responds to the AGC command issued by the power grid dispatch, and adjusts the deviation between the AGC command and the generator power in a closed loop according to the set PID parameters.

[0004] AGC signals generally have two modes, which are defined as AGC dynamic mode and AGC steady-state mode according to the power consumption of the power grid. In the AGC dynamic mode, the AGC command changes greatly, and there are often continuous load increases or decreases. The AGC steady-state mode is the opposite. There is no continuous load increase or decrease and large-scale commands. The AGC command is adjusted slightly around a relatively stable load value for a period of time. In the power grid dispatching system, the AGC rate of thermal power units will be counted. The faster the AGC rate, the more AGC command values ​​can be allocated to the units to obtain more AGC mileage. The AGC rate and AGC mileage of each generator set in the power grid are combined to obtain the final assessment data. The units with higher scores will be rewarded, and the units with lower scores will be assessed.

[0005] The conditions for the actual load of the unit to be in place in the current AGC assessment rules are: the deviation between the actual generator power signal received by the dispatcher and the AGC target is within a clear range. The current requirement of the East China Power Grid is 2MW, that is, when the deviation between the actual generator power and the AGC command is less than 2MW during the load increase and decrease process, the load response is considered to be in place, and the actual AGC rate after the command is automatically calculated. At present, the AGC response rate of many thermal power units is not ideal. On the one hand, due to signal transmission, the power signal received by the grid dispatcher has a certain deviation compared with the unit DCS side, which makes the dispatcher's judgment on the load response in place deviate. On the other hand, in daily operation, AGC commands are mostly in steady-state conditions. AGC commands have the characteristics of high command frequency, short interval time between commands, and small command change amplitude in steady state. Under this condition, the actual load response rate of many thermal power units is obviously insufficient, and new control methods are still needed to improve the AGC rate of thermal power units. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and propose an AGC control method based on turbine acceleration regulation.

[0007] In a first aspect, an AGC control method based on turbine acceleration regulation is provided, comprising:

[0008] S1. Determine the acceleration permission judgment condition;

[0009] S2. After the acceleration permission judgment conditions are met, when the deviation Δ between the actual power of the unit and the target power is within the preset range, and the variable load amplitude of this AGC instruction is less than or equal to the preset variable load amplitude threshold, the acceleration loop action is triggered to assist the unit load to be in place quickly;

[0010] S3. During the acceleration process, determine whether there is a situation where the acceleration loop action needs to be canceled; if so, cancel the acceleration action;

[0011] S4. Let the turbine override control command act on the unit's load command and the feedforward link of the turbine master control at the same time: the override amount is added to the set value of the PID load control component, and the override amount is converted into a turbine flow command. The adjustment command directly acts on the high-pressure regulating valve of the turbine to quickly adjust the load.

[0012] Preferably, in S1, the acceleration permission judgment condition includes: the unit is put into AGC and the AGC instruction is within the steady-state range.

[0013] Preferably, in S1, the unit AGC dynamic mode judgment condition is: within a certain period of time, the difference between the target value of the AGC instruction and the initial stored value is less than a preset threshold; if the difference is always less than the preset threshold after a certain period of time, the stored value is updated to the current AGC target instruction.

[0014] Preferably, in S1, each time after the AGC instruction is issued, the acceleration loop only acts once; and the acceleration loop only works when the AGC instruction changes, and is allowed to act within N seconds after the AGC instruction change ends.

[0015] Preferably, in S1, when the actual load is not in place, if an AGC instruction in the opposite direction appears, the acceleration circuit immediately stops the acceleration action and resets the acceleration permission judgment condition.

[0016] Preferably, in S3, the situation where the acceleration loop action needs to be canceled includes:

[0017] S301, the AGC command issues the same direction command again, and at this time the deviation |Δ| between the actual power and the target power is greater than the upper limit of the preset range;

[0018] S302: The deviation between the actual power and the target power is within the AGC assessment dead zone;

[0019] S303: A reverse frequency modulation action occurs.

[0020] Preferably, in S3, after the current acceleration action is canceled, the overrun output is switched to 0.

[0021] In a second aspect, an AGC control device based on turbine acceleration regulation is provided, comprising:

[0022] A determination module, used to determine acceleration permission judgment conditions;

[0023] The trigger module is used to trigger the acceleration loop to assist the unit load to reach the desired position quickly after the acceleration permission judgment condition is met and the deviation Δ between the actual power of the unit and the target power is within the preset range, and the variable load amplitude of the current AGC instruction is less than or equal to the preset variable load amplitude threshold;

[0024] The judgment module is used to judge whether there is a situation that requires the acceleration loop action to be canceled during the acceleration action; if so, the acceleration action is canceled;

[0025] The regulation module is used to allow the steam turbine override control command to act on the unit's load command and the feedforward link of the steam turbine main control at the same time: the override amount is added to the set value of the PID load control component, and the override amount is converted into a steam turbine flow command. The regulation command directly acts on the high-pressure regulating valve of the steam turbine to quickly adjust the load.

[0026] The beneficial effects of the present invention are:

[0027] Under the current grid AGC assessment rules, the present invention enables the actual power of the thermal power unit to reach the dead zone of the AGC instruction assessment through rapid action of the steam turbine when the actual power is close to the target power. At the same time, corresponding acceleration permission conditions and acceleration exit conditions are set, which can effectively improve the AGC rate index of the unit, obtain better AGC assessment benefits, and enhance the competitiveness of the unit in the power auxiliary market. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the acceleration permission judgment circuit;

[0029] Figure 2 It is a schematic diagram of the structure of the acceleration action trigger circuit;

[0030] Figure 3 It is the load trend curve diagram of conventional units;

[0031] Figure 4 This is a schematic diagram of the unit load trend after the turbine accelerates. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for ordinary persons in the art, without departing from the principle of the present invention, the present invention can also be modified in some ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0033] Embodiment 1:

[0034] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an AGC control method based on rapid steam turbine regulation. When the actual load is close to the target load, the rapid steam turbine regulating valve is used to accelerate the regulation effect and improve the AGC regulation rate of the unit. The specific implementation of the present invention in a 660MW unit is as follows:

[0035] S1. Determine the acceleration permission judgment conditions, including:

[0036] S101, the unit is put into AGC operation and the AGC command is within the steady-state range. The acceleration loop is mainly used to respond to AGC assessment and is not used in non-AGC conditions. The judgment condition for the unit's AGC dynamic mode is: within 20 minutes, the difference between the target value of the AGC command and the initial stored value is less than 30MW. If the difference is still less than 30MW after 20 minutes, the stored value is updated to the current AGC target command.

[0037] S102, single AGC instruction acceleration loop only acts once. Under the premise of meeting the AGC assessment, the number of actions is minimized as much as possible, and it is stipulated that the acceleration loop can only act once after each AGC instruction is issued. The judgment logic is that the difference between the target load instruction and the target load instruction after the 1s inertia link is greater than 2 or less than -2, and the corresponding target load instruction and the unit load instruction after speed limit are greater than 0.5 or less than -0.5. A 2s pulse signal is sent to set the RS trigger, and the RS trigger outputs a switch signal 1. The reset of the RS trigger takes priority, and the output of the single load increase / decrease instruction action is allowed to increase / decrease load.

[0038] S103 only works during command changes and is allowed to act within 30 seconds after the command change is completed to avoid the acceleration circuit action affecting normal load regulation after the actual load deviates due to interference such as primary frequency modulation after the load is in place. If the RS trigger is reset after 30 seconds, the add / subtract load permission signal disappears.

[0039] S104: If the actual load is not in place and an AGC command in the opposite direction suddenly appears, the acceleration action will be stopped immediately, the RS trigger will be reset, and the acceleration action will be allowed to be terminated to prevent the acceleration circuit from malfunctioning and affecting the AGC assessment results.

[0040] The acceleration allows the judgment loop structure to be Figure 1 As shown, A represents the target power; B represents the unit load command or turbine load command after speed limit; C represents the load change amplitude; D represents load addition permission; E represents load addition action; F represents that AGC is not put into operation or is in dynamic state; G represents load reduction action; I represents load reduction permission. In addition, Figure 1 In the figure, the dotted line is the switch quantity, and the solid line is the analog quantity. ABS means to obtain the absolute value. T means the switching function, the input switch quantity is 1, the output is the YES terminal input, the input switch quantity is 0, the output is the NO terminal input. SR means RS trigger, S(set)=1, R(rset)=0, OUT=1; S(set)=0, R(rset)=0, OUT=maintain the output of the previous cycle; S(set)=0, R(rset)=1, OUT=0; the present invention is set to rset optimization, S(set)=1, R(rset)=1, OUT=0. TD-on means the rising edge signal delay, for example, a delay time of n seconds is set, when the input is switched from 0 to 1, the output is switched from 0 to 1 after a delay of n seconds, and when the input is switched from 1 to 0, the output is directly 0. TD-off indicates the delay of the falling edge signal. For example, if a delay time of n seconds is set, when the input switches from 0 to 1, the output switches from 0 to 1 directly. When the input switches from 1 back to 0 again, the output switches to 0 after a delay of n seconds. H indicates that when the input analog value is higher than a certain value set, the output switch value is 1, otherwise it is 0. L indicates that when the input analog value is lower than a certain value set, the output switch value is 1, otherwise it is 0.

[0041] S2. After the acceleration permission conditions are met, when the deviation Δ between the actual power of the unit and the target power is within the preset range (1.5≤|Δ|≤3, unit MW), and the variable load amplitude of this AGC instruction is less than or equal to 15MW, the acceleration loop is triggered, the steam turbine load instruction override increases or decreases the load by 3MW, and the auxiliary unit load is quickly in place.

[0042] The structure of the acceleration action trigger circuit is as follows Figure 2 As shown, M represents the target power; B represents the actual power; C represents the load-increasing action; D represents the primary frequency-modulating load; E represents the variable load amplitude; F represents the load-increasing permission; G represents the load-reducing permission; O represents the load-reducing action; I represents the command switching signal; J represents the turbine command optimization; and K represents the turbine overrun control.

[0043] S3. During the acceleration process, the following situations will directly cancel the action of the turbine acceleration circuit:

[0044] S301, AGC command issues the same direction command again. At this time, the actual power and target power deviation |Δ|>3MW. In order to ensure the normal regulation of subsequent loads, this acceleration action is canceled and the overrun output is switched to 0;

[0045] S302. At present, the dead zone of AGC assessment of Zhejiang Power Grid Dispatching is 2MW. The deviation between actual power and target power is within 2MW. The acceleration action is terminated and the overrun output is switched to 0.

[0046] S303: A reverse frequency modulation action occurs, the acceleration action is canceled, and the overrun output is switched to 0.

[0047] S4. The steam turbine override control command needs to act on the unit's load command and the feedforward link of the steam turbine master control at the same time: the override amount is added to the set value of the PID load control component to prevent the steam turbine master control PID from callback. In addition, the override amount is converted into a steam turbine flow command. The adjustment command directly acts on the high-pressure regulating valve of the steam turbine, 3MW corresponds to 1.4%, -3MW corresponds to -1.25%, and the unit load is quickly adjusted.

[0048] Embodiment 2:

[0049] The unit operation example is shown in the figure Figure 3 , Figure 4 As shown in the figure, the example trend is that when the unit is running at a load of 300MW, it receives an AGC instruction of 315MW, and the variable load rate setting value is 12MW / min. Under the control strategy without turbine acceleration, the actual power follows the speed limit post-load instruction to perform closed-loop regulation of active power. During the load climbing process, the unit power basically increases at a relatively average rate, as shown in Figure 1. Figure 3As shown in the figure, the actual variable rate average is 9.7MW / min, which is slower than the variable load setting rate of 2.5MW / min. After adopting this method, when the deviation between the actual power and the load command is within 3MW, the steam turbine starts to accelerate the adjustment to assist the actual power to be adjusted quickly. Figure 4 As shown, compared with the situation before this method was adopted, the actual average load change rate was 11.2MW / min.

Claims

1. An AGC control method based on turbine acceleration regulation, characterized in that: include: S1. Determine the acceleration permission judgment condition; S2. After the acceleration permission judgment conditions are met, when the deviation Δ between the actual power of the unit and the target power is within the preset range, and the variable load amplitude of this AGC instruction is less than or equal to the preset variable load amplitude threshold, the acceleration loop action is triggered to assist the unit load to be in place quickly; S3. During the acceleration process, determine whether there is a situation where the acceleration loop action needs to be canceled; if so, cancel the acceleration action; S4. Let the steam turbine override control command act on the load command of the unit and the feedforward link of the steam turbine main control at the same time: the override amount is added to the set value of the PID load control component, and the override amount is converted into the steam turbine flow command. The adjustment command directly acts on the high-pressure regulating valve of the steam turbine to quickly adjust the load.

2. The AGC control method based on turbine acceleration regulation according to claim 1 is characterized in that: In S1, the acceleration permission judgment conditions include: the unit is put into AGC and the AGC instruction is within the steady-state range.

3. The AGC control method based on turbine acceleration regulation according to claim 1 is characterized in that: In S3, the situations where the acceleration loop action needs to be canceled include: S301, the AGC command issues the same direction command again, and at this time the deviation |Δ| between the actual power and the target power is greater than the upper limit of the preset range; S302: The deviation between the actual power and the target power is within the AGC assessment dead zone; S303: A reverse frequency modulation action occurs.

4. The AGC control method based on turbine acceleration regulation according to claim 2 is characterized in that: In S3, after the current acceleration action is canceled, the override output is switched to 0.

5. An AGC control device for turbine acceleration regulation, characterized in that: The AGC control method based on turbine acceleration regulation according to any one of claims 1 to 2 comprises: A determination module, used to determine acceleration permission judgment conditions; The trigger module is used to trigger the acceleration loop to assist the unit load to reach the desired position quickly after the acceleration permission judgment condition is met and the deviation Δ between the actual power of the unit and the target power is within the preset range, and the variable load amplitude of the current AGC instruction is less than or equal to the preset variable load amplitude threshold; The judgment module is used to judge whether there is a situation that requires the acceleration loop action to be canceled during the acceleration action; if so, the acceleration action is canceled; The regulation module is used to allow the steam turbine override control command to act on the unit's load command and the feedforward link of the steam turbine main control at the same time: the override amount is added to the set value of the PID load control component, and the override amount is converted into a steam turbine flow command. The regulation command directly acts on the high-pressure regulating valve of the steam turbine to quickly adjust the load.

Images