A condensate throttling system and method for thermal power units

Abstract

The present invention discloses a condensate throttling system for a thermal power unit, comprising: a converter and a plurality of control modules connected to the converter, wherein the plurality of control modules are composed of a condensate throttling control module, a deaerator frequency conversion logic switching module, a condenser water level regulating module, a deaerator water level regulating module and a coordinated control water level recovery module. The condensate throttling control module comprises a condensate throttling PID controller, and the deaerator frequency conversion logic switching module comprises a condensate pump frequency conversion switching logic unit, a converter, a deaerator water level PID controller and a condensate pump frequency conversion output instruction unit. A corresponding method is also disclosed, which improves the load response at the initial stage of load change and can improve the delay of load response caused by the lag on the boiler side.

Description

Technical Field

[0001] The invention relates to the technical field of control optimization of boilers and unit systems in thermal power plants, and in particular to a condensate throttling system and method for thermal power units. Background Art

[0002] Existing power generation companies generally have problems such as inconsistent coal supply sources, poor unit equipment performance, two detailed rules, and multiple environmental protection index assessments, which have led to severe challenges to the economic efficiency and safety of the units. Mainly manifested in:

[0003] (1) There are more detailed assessments on AGC and primary frequency modulation.

[0004] (2) The regulation performance deviation of superheating and reheating desuperheating water is large, especially during rapid load changes, which makes it difficult to effectively control.

[0005] (3) Large changes in coal quality lead to large changes in boiler combustion conditions, which prevent the boiler from operating at the optimal operating point, resulting in boiler efficiency and environmental protection problems.

[0006] It is an urgent task to carry out large-scale, scientific and reasonable research on key technologies for integrated solutions for optimization control of modern thermal power units. In view of the current problems of units such as low load rise and fall rate, poor adjustment accuracy, poor anti-disturbance ability and large fluctuation range of main adjusted parameters, key technologies such as weak steady-state automatic detection based on massive historical data of thermal processes of coordinated control systems, thermal control system identification driven by disturbance data and neural network predictive control with self-optimization characteristics are developed to improve the operating efficiency of units and the control quality under stable and variable conditions, so as to reduce the heat consumption of units, coal consumption for power generation, energy conservation and emission reduction. The existing technology is particularly lacking in condensate throttling systems and methods for thermal power units based on this. Summary of the invention

[0007] The object of the present invention is to provide a condensate throttling system and method for a thermal power unit, so as to improve the load response at the initial stage of load change and improve the delay of load response caused by the lag on the boiler side.

[0008] The object of the present invention is to provide a condensate throttling system for a thermal power unit, comprising: a converter and a plurality of control modules connected to the converter, wherein the plurality of control modules are composed of a condensate throttling control module, a deaerator frequency conversion logic switching module, a condenser water level regulating module, a deaerator water level regulating module and a coordinated control water level recovery module.

[0009] Preferably, the condensate throttling control module includes a condensate throttling PID controller, which is used to control the following parameters:

[0010] 1. Design of start and stop conditions for condensate throttling function

[0011] (1) Conditions for the condensate throttling function to be put into use:

[0012] When performing condensate throttling optimization control, it is necessary to monitor some parameters of the control system to prevent unit operation accidents. The permissible conditions for condensate throttling control are:

[0013] m. Coordinated control is in the operational state;

[0014] n. The water level of the deaerator and the condenser are both in normal condition;

[0015] o. No RB occurs in the unit, ensuring that no trip alarm is issued;

[0016] p. The condensate pump frequency conversion has been put into use;

[0017] q. The operator allows the condensate throttling control system to be adjusted;

[0018] r. The optimized controller is allowed to be put into operation.

[0019] When the above conditions are met, the condensate throttling automatically enters the operating state;

[0020] (2) Design of the conditions for starting and stopping the condensate throttling function:

[0021] After the unit is put into AGC, the condensate throttling system is put into operation and stopped under the conditions of load increase and decrease, and the conditions for putting in and stopping are set separately in the process of load increase and decrease.

[0022] 1) The conditions for increasing load condensate throttling include the conditions af and:

[0023] a. When the output command derivative of the unit load command calculator is positive, the load increase command issues a 60S pulse or a frequency modulation action and the frequency modulation load is greater than 2MW, the 60S pulse or the output command derivative of the unit load command calculator is positive and the deviation between the load command and the actual load reaches ±20MW, which is within the allowable range of condensate throttling;

[0024] b. The deaerator water level is above the lower alarm limit, the deaerator water level is >700mm, and the delay is 60S. During the load increase process, the condensate flow rate decreases, which will cause the deaerator water level to decrease. Too low a deaerator water level is not conducive to the safe operation of the unit;

[0025] c. When the condenser water level is above the lower alarm limit and the condenser water level is less than 750mm, the timer will be delayed for 60S to prevent the condenser water level from being too high;

[0026] d. The condensate pump frequency is above the alarm lower limit by >15Hz, to prevent the condensate pump frequency from being too low;

[0027] e. There is a certain interval since the last condensate pump frequency adjustment. Frequent frequency adjustment of the condensate pump is not conducive to the safe operation of the unit.

[0028] 2) Load increase condensate throttling exit conditions include conditions ag phase or:

[0029] a. The unit LDC command derivative becomes negative, and the throttling process is completed;

[0030] b. The deviation between the AGC instruction and the actual load is reduced to a range that meets the requirements;

[0031] c. The deaerator water level drops to the lower alarm limit to prevent the deaerator water level from further dropping and posing a threat to the safe operation of the unit;

[0032] d. The condensate flow rate reaches the lower alarm limit to prevent the condensate flow rate from being too low and affecting the safe operation of the unit;

[0033] e. The condenser water level reaches the upper alarm limit > 1050mm;

[0034] f. The condensate throttling time reaches the specified time;

[0035] g. If the unit power is greater than 300MW, the delay is 30S;

[0036] 3) The load reduction condensate throttling conditions include conditions ae and:

[0037] a. The unit LDC command derivative is negative, that is, the load reduction command is issued or a frequency modulation action is taken and the frequency modulation load is less than -2MW with a delay of 5S or 60S pulse, or the output command derivative of the unit load command calculator LDC is positive and the deviation between the load command and the actual load reaches ±20MW, which is within the allowable range of condensate throttling;

[0038] b. The water level of the deaerator is below the upper alarm limit, the water level is less than 1030mm, and the delay is 60S;

[0039] c. When the steam-water level in the condenser is below the upper alarm limit and the water level is less than 1050mm, the timer will be delayed for 60 seconds to prevent the condenser water level from being too low;

[0040] d. There is a certain interval from the last condensate pump frequency modulation;

[0041] e. If the unit power is greater than 300MW, the delay is 30S;

[0042] 4) Load reduction condensate throttling exit conditions include conditions af phase or:

[0043] a. The unit LDC command derivative becomes positive, and the throttling process is completed;

[0044] b. The deviation between the AGC instruction and the actual load is reduced to a range that meets the requirements;

[0045] c. The water level of the deaerator rises to the upper alarm limit of 1030mm;

[0046] d. The condensate flow rate reaches the alarm upper limit;

[0047] e. The condenser water level reaches the lower alarm limit of 750mm;

[0048] f. The condensate throttling time reaches the specified time;

[0049] When all the above conditions are met, condensate throttling automatically enters the operating state.

[0050] Preferably, the control logic of the condensate throttling control module includes: in the condensate throttling control state, the condensate pump frequency is determined by the deviation of the unit load, and the load reaches the target value by controlling the flow of condensate.

[0051] Preferably, the deaerator variable frequency logic switching module includes a condenser pump variable frequency switching logic unit, a converter, a deaerator water level PID controller and a condenser pump variable frequency output instruction unit.

[0052] Preferably, the working process of the deaerator frequency conversion logic switching module includes: the switching of the condensate pump frequency conversion instruction must be done without disturbance. When the system is in the condensate throttling control mode, the condensate pump frequency conversion instruction is adjusted by the condensate throttling PID controller, and the water level setting value of the deaerator tracks the feedback value of the actual water level. At this time, the deaerator water level PID controller is in the tracking mode, and the condensate pump frequency conversion output instruction unit sends the output instruction to the hand operator, and the output of the hand operator tracks the condensate throttling PID controller instruction; when the throttling process is over, the system switches back to the coordinated control water level recovery mode, and the deaerator water level PID controller switches back to the automatic adjustment state again, and the condensate throttling PID setting value tracks the actual load of the thermal power unit.

[0053] Preferably, the condenser water level regulating module is used to regulate the condenser water level, and the working process of the condenser water level regulating module includes:

[0054] In the condensate throttling control state, when the load command decreases, the condensate flow increases, causing the exhaust device water level to drop. The make-up water volume should be increased to maintain the normal state of the exhaust device water level. In this process, the deaerator water level will increase. After the condensate throttling state ends, the condensate flow should be appropriately reduced to restore the deaerator water level. At the same time, the make-up water volume of the exhaust device should be reduced. Similarly, when the load command increases, due to the condensate throttling effect, the condensate flow decreases, causing the exhaust device water level to rise. The make-up water volume should be reduced to maintain the normal state of the condenser water level. After the condensate throttling state ends, the condensate flow is increased, the deaerator water level returns to normal, and the exhaust device water level is kept stable. The data obtained through the test is used to control the exhaust device water level by feedforward or overrun.

[0055] Preferably, the deaerator water level regulation module is used to modify the deaerator water level regulation, and its working process includes: similar to the modification of the condensate pump frequency conversion regulation logic, when the original system logic is modified, when the system is in the condensate throttling state, the deaerator water level setting tracks the feedback value of the actual water level, the condensate throttling PID controller is in the tracking mode, and the output of the handheld operator tracks the instructions of the optimization controller; when the throttling process is over, the condensate throttling PID switches back to the automatic adjustment state again.

[0056] Preferably, it also includes an interface for connecting the condensate throttling system for the thermal power unit with the original DCS of the thermal power unit, and the interface has two functions: on the one hand, it realizes the activation and deactivation functions of the condensate throttling control system on the DCS end, and on the other hand, it switches the DCS condensate pump frequency conversion command; the condensate throttling system for the thermal power unit sends the following signals to the DCS control system: throttling function activation signal, throttling function activation condition signal and condensate pump frequency converter command signal; the signals sent by the DCS to the condensate throttling system for the thermal power unit include: throttling function activation signal and frequency converter command signal.

[0057] Preferably, the conditions for cutting off condensate throttling through the interface DCS side include:

[0058] (1) Automatic cut-off of deaerator water level;

[0059] (2) LC card communication failure;

[0060] (3) Abnormal heartbeat signal;

[0061] (4) The condensate throttling optimization function group is abnormal;

[0062] (5) The quality of the condensate inverter or deaerator water level adjustment gate command is bad;

[0063] (6) The deviation between the condensate throttling optimization communication command and the hard wiring command is greater than 1.

[0064] The present invention also aims to provide a condensate throttling method for a thermal power unit, comprising:

[0065] Step 1: Control the following parameters through the condensate throttling PID controller:

[0066] 1. Design of start and stop conditions for condensate throttling function

[0067] (1) Conditions for the condensate throttling function to be put into use:

[0068] When performing condensate throttling optimization control, it is necessary to monitor some parameters of the control system to prevent unit operation accidents. The permissible conditions for condensate throttling control are:

[0069] s. Coordinated control is in the operational state;

[0070] t. The water levels of the deaerator and condenser are both in normal condition;

[0071] u. No RB occurs in the unit, ensuring that no trip alarm is issued;

[0072] v. The condensate pump frequency conversion has been put into use;

[0073] w. The operator allows the condensate throttling control system to be adjusted;

[0074] x. The optimized controller is allowed to be put into operation.

[0075] When the above conditions are met, the condensate throttling automatically enters the operating state;

[0076] (2) Design of the conditions for starting and stopping the condensate throttling function:

[0077] After the unit is put into AGC, the condensate throttling system is put into operation and stopped under the conditions of load increase and decrease, and the conditions for putting in and stopping are set separately in the process of load increase and decrease.

[0078] 1) The conditions for increasing load condensate throttling include the conditions af and:

[0079] a. When the output command derivative of the unit load command calculator is positive, the load increase command issues a 60S pulse or a frequency modulation action and the frequency modulation load is greater than 2MW, the 60S pulse or the output command derivative of the unit load command calculator is positive and the deviation between the load command and the actual load reaches ±20MW, which is within the allowable range of condensate throttling;

[0080] b. The deaerator water level is above the lower alarm limit, the deaerator water level is >700mm, and the delay is 60S. During the load increase process, the condensate flow rate decreases, which will cause the deaerator water level to decrease. Too low a deaerator water level is not conducive to the safe operation of the unit;

[0081] c. When the condenser water level is above the lower alarm limit and the condenser water level is less than 750mm, the timer will be delayed for 60S to prevent the condenser water level from being too high;

[0082] d. The condensate pump frequency is above the alarm lower limit by >15Hz, to prevent the condensate pump frequency from being too low;

[0083] e. There is a certain interval since the last condensate pump frequency adjustment. Frequent frequency adjustment of the condensate pump is not conducive to the safe operation of the unit.

[0084] 2) Load increase condensate throttling exit conditions include conditions ag phase or:

[0085] a. The unit LDC command derivative becomes negative, and the throttling process is completed;

[0086] b. The deviation between the AGC instruction and the actual load is reduced to a range that meets the requirements;

[0087] c. The deaerator water level drops to the lower alarm limit to prevent the deaerator water level from further dropping and posing a threat to the safe operation of the unit;

[0088] d. The condensate flow rate reaches the lower alarm limit to prevent the condensate flow rate from being too low and affecting the safe operation of the unit;

[0089] e. The condenser water level reaches the upper alarm limit > 1050mm;

[0090] f. The condensate throttling time reaches the specified time;

[0091] g. If the unit power is greater than 300MW, the delay is 30S;

[0092] 3) The load reduction condensate throttling conditions include conditions ae and:

[0093] a. The unit LDC command derivative is negative, that is, the load reduction command is issued or a frequency modulation action is taken and the frequency modulation load is less than -2MW with a delay of 5S or 60S pulse, or the output command derivative of the unit load command calculator LDC is positive and the deviation between the load command and the actual load reaches ±20MW, which is within the allowable range of condensate throttling;

[0094] b. The water level of the deaerator is below the upper alarm limit, the water level is less than 1030mm, and the delay is 60S;

[0095] c. When the steam-water level in the condenser is below the upper alarm limit and the water level is less than 1050mm, the timer will be delayed for 60 seconds to prevent the condenser water level from being too low;

[0096] d. There is a certain interval from the last condensate pump frequency modulation;

[0097] e. If the unit power is greater than 300MW, the delay is 30S;

[0098] 4) Load reduction condensate throttling exit conditions include conditions af phase or:

[0099] a. The unit LDC command derivative becomes positive, and the throttling process is completed;

[0100] b. The deviation between the AGC instruction and the actual load is reduced to a range that meets the requirements;

[0101] c. The water level of the deaerator rises to the upper alarm limit of 1030mm;

[0102] d. The condensate flow rate reaches the alarm upper limit;

[0103] e. The condenser water level reaches the lower alarm limit of 750mm;

[0104] f. The condensate throttling time reaches the specified time;

[0105] When the above conditions are met, the condensate throttling automatically enters the operating state;

[0106] The control logic of the condensate throttling control module includes: in the condensate throttling control state, the condensate pump frequency is determined by the deviation of the unit load, and the load reaches the target value by controlling the flow of condensate;

[0107] Step 2, controlling the deaerator frequency conversion logic switching through the deaerator frequency conversion logic switching module, including: the switching of the condensate pump frequency conversion instruction must be done without disturbance switching, when the system is in the condensate throttling control mode, the condensate pump frequency conversion instruction is adjusted by the condensate throttling PID controller, and the water level setting value of the deaerator tracks the feedback value of the actual water level, at this time, the deaerator water level PID controller is in the tracking mode, the condensate pump frequency conversion output instruction unit sends the output instruction to the hand operator, and the output of the hand operator tracks the condensate throttling PID controller instruction; when the throttling process is completed, the system switches back to the coordinated control water level recovery mode, at this time, the deaerator water level PID controller switches back to the automatic adjustment state again, and the condensate throttling PID setting value tracks the actual load of the thermal power unit;

[0108] Step 3: regulating the condenser water level through the condenser water level regulating module. The working process of the condenser water level regulating module includes:

[0109] In the condensate throttling control state, when the load command decreases, the condensate flow rate increases, causing the exhaust device water level to drop. The make-up water volume should be increased to maintain the exhaust device water level in a normal state. During this process, the deaerator water level will increase. After the condensate throttling state ends, the condensate flow rate should be appropriately reduced to restore the deaerator water level. At the same time, the make-up water volume of the exhaust device should be reduced. Similarly, when the load command increases, due to the condensate throttling effect, the condensate flow rate decreases, causing the exhaust device water level to rise. The make-up water volume should be reduced to maintain the condenser water level in a normal state. After the condensate throttling state ends, the condensate flow rate is increased, the deaerator water level returns to a normal state, and the exhaust device water level is kept stable. The data obtained through the test is used to control the exhaust device water level using feedforward or overrun effects;

[0110] Step 4, adjust the deaerator water level through the deaerator water level adjustment module, and its working process includes: when the original system logic is modified, when the system is in the condensate throttling state, the deaerator water level setting tracks the feedback value of the actual water level, the condensate throttling PID controller is in the tracking mode, and the output of the handheld operator tracks the instructions of the optimization controller; when the throttling process is over, the condensate throttling PID switches back to the automatic adjustment state again.

[0111] The present invention has the following beneficial effects:

[0112] The influence of condensate throttling on the unit load when the turbine three valves are fully open when operating at different loads is determined, and the optimal control of condensate throttling of thermal power units is achieved, the load response in the initial stage of load change is improved, and the delay in load response caused by the lag on the boiler side can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0113] Figure 1 The figure is a logical schematic diagram of condensate throttling control provided according to the present invention.

[0114] Figure 2 The figure is a schematic diagram of the principle of the deaerator frequency conversion logic switching module provided by the present invention.

[0115] Figure 3 The figure is a schematic structural diagram of the working principle of the condenser water level regulating module provided according to the present invention. DETAILED DESCRIPTION

[0116] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0117] The method provided by the present invention can be implemented in the following terminal environment, and the terminal may include one or more of the following components: a processor, a memory, and a display screen. The memory stores at least one instruction, and the instruction is loaded and executed by the processor to implement the method described in the following embodiment.

[0118] The processor may include one or more processing cores. The processor uses various interfaces and lines to connect various parts of the entire terminal, and executes various functions of the terminal and processes data by running or executing instructions, programs, code sets or instruction sets stored in the memory, and calling data stored in the memory.

[0119] The memory may include a random access memory (RAM) or a read-only memory (ROM). The memory may be used to store instructions, programs, codes, code sets or instructions.

[0120] The display screen is used to display the user interface of each application.

[0121] In addition, those skilled in the art can understand that the structure of the above terminal does not constitute a limitation on the terminal, and the terminal may include more or fewer components, or combine certain components, or arrange the components differently. For example, the terminal also includes components such as a radio frequency circuit, an input unit, a sensor, an audio circuit, and a power supply, which will not be described in detail here.

[0122] The control principle of the condensate throttling system is as follows: condensate throttling means that when the unit changes load, within the allowable water level change range of the condenser and deaerator, the condensate pump outlet regulating valve (or the frequency of the condensate pump) is changed to change the condensate flow rate, thereby changing the extraction steam flow rate in the low-pressure heater, temporarily obtaining or releasing part of the unit's load. The condensate load regulation technology is essentially a technology that utilizes energy storage, which utilizes the changes in energy storage in the steam turbine heat recovery / heating system. The main function of condensate load regulation is to improve the load response at the initial stage of load change, and can improve the delay in load response caused by the lag on the boiler side, but the final load response of the unit still depends on the change in the boiler combustion rate.

[0123] The condensate throttling system for a thermal power unit of this embodiment includes: a converter and multiple control modules connected to the converter, wherein the multiple control modules are composed of a condensate throttling control module, a deaerator frequency conversion logic switching module, a condenser water level regulating module, a deaerator water level regulating module and a coordinated control water level recovery module.

[0124] As a preferred embodiment, the condensate throttling control module includes a condensate throttling PID controller, and its working principle includes:

[0125] 1. Design of start and stop conditions for condensate throttling function

[0126] (1) Conditions for the condensate throttling function to be put into use:

[0127] When performing condensate throttling optimization control, it is necessary to monitor some parameters of the control system to prevent unit operation accidents. The permissible conditions for condensate throttling control are:

[0128] y. The coordinated control is in the operational state;

[0129] z. The deaerator water level (650mm-1080mm) and condenser water level (700mm-1100mm) are both in normal condition;

[0130] aa. No RB occurs in the unit, ensuring that no trip alarm is issued;

[0131] ab. The condensate pump frequency conversion has been put into use;

[0132] ac. The operator allows the condensate throttling control system to be adjusted;

[0133] ad. The optimized controller allows commissioning.

[0134] When all the above conditions are met, condensate throttling automatically enters the operating state.

[0135] (2) Design of the conditions for starting and stopping the condensate throttling function:

[0136] After the unit is put into AGC, the condensate throttling system is put into operation and stopped under the conditions of load increase and decrease, and the conditions for putting in and stopping are set separately in the process of load increase and decrease.

[0137] 1) The conditions for increasing load condensate throttling include (and relationship):

[0138] a. The output command derivative of the unit load command calculator (LDC) is positive, when a 60S pulse (load increase command is issued) or a frequency modulation action occurs and the frequency modulation load is greater than 2MW, the 60S pulse or the output command derivative of the unit load command calculator (LDC) is positive and the deviation between the load command and the actual load reaches ±20MW, which is within the allowable range of condensate throttling;

[0139] b. The deaerator water level is above the lower alarm limit, the deaerator water level is > 700mm, and the delay is 60S (during the load increase process, the condensate flow rate decreases, which will cause the deaerator water supply to decrease. Too low a deaerator water level is not conducive to the safe operation of the unit);

[0140] c. When the condenser water level is above the lower alarm limit and the condenser water level is less than 750mm, the timer will be delayed for 60S (to prevent the condenser water level from being too high);

[0141] d. The condensate pump frequency is above the alarm lower limit by >15Hz (to prevent the condensate pump frequency from being too low);

[0142] e. There is a certain interval since the last condensate pump frequency adjustment (frequent frequency adjustment of the condensate pump is not conducive to the safe operation of the unit).

[0143] 2) The load-increasing condensate throttling exit conditions include (or relationships):

[0144] a. The unit LDC command derivative becomes negative (the throttling process is completed);

[0145] b. The deviation between the AGC instruction and the actual load is reduced to a range that meets the requirements;

[0146] c. The deaerator water level drops to the lower alarm limit (to prevent the deaerator water level from further dropping and posing a threat to the safe operation of the unit);

[0147] d. The condensate flow rate reaches the lower alarm limit (to prevent the condensate flow rate from being too low and affecting the safe operation of the unit);

[0148] e. The condenser water level reaches the upper alarm limit > 1050mm;

[0149] f. The condensate throttling time reaches the specified time (the condensate throttling technology is designed to change the load in a short period of time and should not be put into use for too long).

[0150] g. If the unit power is greater than 300MW, the delay is 30S

[0151] 3) The conditions for throttling condensate water under load reduction include (the following conditions apply):

[0152] a. The unit LDC command derivative is negative (load reduction command is issued) or a frequency modulation action is performed and the frequency modulation load is less than -2MW with a delay of 5S or 60S pulse, or the output command derivative of the unit load command calculator (LDC) is positive and the deviation between the load command and the actual load reaches ±20MW, which is within the allowable range of condensate throttling;

[0153] b. The deaerator water level is below the alarm upper limit, the water level is less than 1030mm, and the delay is 60S (during the load reduction process, the condensate flow rate increases, which will cause more water to flow into the deaerator. Too high a deaerator water level is not conducive to the safe operation of the unit);

[0154] c. When the steam-water level in the condenser is below the upper alarm limit and the water level is less than 1050mm, the time delay is 60S (to prevent the condenser water level from being too low);

[0155] d. There is a certain interval since the last condensate pump frequency adjustment (frequent frequency adjustment of the condensate pump is not conducive to the safe operation of the unit).

[0156] e. If the unit power is greater than 300MW, the delay is 30S

[0157] 4) The load reduction condensate throttling exit conditions include (or relationships):

[0158] a. The unit LDC command derivative becomes positive (the throttling process is completed);

[0159] b. The deviation between the AGC instruction and the actual load is reduced to a range that meets the requirements;

[0160] c. The deaerator water level rises to the alarm upper limit of 1030mm (to prevent the deaerator water level from further rising and posing a threat to the safe operation of the unit);

[0161] d. The condensate flow rate reaches the alarm upper limit (to prevent the condensate flow rate from being too large and affecting the safe operation of the unit);

[0162] e. The condenser water level reaches the lower alarm limit of 750mm;

[0163] f. The condensate throttling time reaches the specified time (the condensate throttling technology is designed to change the load in a short period of time and should not be put into use for too long).

[0164] When all the above conditions are met, condensate throttling automatically enters the operating state.

[0165] (3) Condensate throttling control logic design

[0166] like Figure 1 As shown in the figure, under the condensate throttling control state, the condensate pump frequency is determined by the deviation of the unit load, and the load reaches the target value by controlling the condensate flow rate.

[0167] like Figure 2 As shown, as a preferred embodiment, the deaerator frequency conversion logic switching module includes a condensate pump frequency conversion switching logic unit, a converter, a deaerator water level PID controller and a condensate pump frequency conversion output instruction unit. Its working principle is: the condensate throttling control must not only effectively improve the load regulation rate, but also avoid causing greater interference to the original control system. Therefore, when the control logic of the original system is modified, the switching of the condensate pump frequency conversion instruction must be achieved without disturbance. When the system is in the condensate throttling control mode, the condensate pump frequency conversion instruction is adjusted by the condensate throttling PID controller, and the water level setting value of the deaerator tracks the feedback value of the actual water level. At this time, the deaerator water level PID controller is in the tracking mode, and the condensate pump frequency conversion output instruction unit sends the output instruction to the hand operator, and the output of the hand operator tracks the condensate throttling PID controller instruction; when the throttling process is completed, the system switches back to the coordinated control water level recovery mode, and the deaerator water level PID controller switches back to the automatic adjustment state again, and the condensate throttling PID setting value tracks the actual load of the thermal power unit.

[0168] As a preferred embodiment, the condenser water level regulating module is used to regulate the condenser water level. Figure 3 As shown, including:

[0169] In the condensate throttling control state, when the load command decreases, the condensate flow rate increases, causing the exhaust device water level to drop. The make-up water volume should be increased to maintain the normal state of the exhaust device water level. During this process, the deaerator water level will increase. After the condensate throttling state ends, the condensate flow rate should be appropriately reduced to restore the deaerator water level. At the same time, the make-up water volume of the exhaust device should be reduced. Similarly, when the load command increases, due to the condensate throttling effect, the condensate flow rate decreases, causing the exhaust device water level to rise. The make-up water volume should be reduced to maintain the normal state of the condenser water level. After the condensate throttling state ends, the condensate flow rate is increased, the deaerator water level returns to normal, and the exhaust device water level is kept stable. The data obtained through the test uses feedforward or overrunning to control the exhaust device water level.

[0170] As a preferred embodiment, the deaerator water level adjustment module is used to modify the deaerator water level adjustment, and its working principle is: similar to the modification of the condensate pump frequency conversion adjustment logic, when the original system logic is modified, when the system is in the condensate throttling state, the deaerator water level setting tracks the feedback value of the actual water level, the condensate throttling PID controller is in the tracking mode, and the output of the hand operator tracks the instructions of the optimization controller. When the throttling process is completed, the condensate throttling PID is switched back to the automatic adjustment state again.

[0171] As a preferred embodiment, it also includes an interface for connecting the condensate throttling system for the thermal power unit to the original DCS of the thermal power unit. The interface has two functions: on the one hand, it realizes the activation and deactivation functions of the condensate throttling control system on the DCS side, and on the other hand, it switches the DCS condensate pump frequency conversion command. In terms of interface signals, the condensate throttling system for the thermal power unit sends the following signals to the DCS control system: throttling function activation signal, throttling function activation condition signal and condensate pump frequency converter command signal. The signals sent by the DCS to the condensate throttling system for the thermal power unit include: throttling function activation signal and frequency converter command signal.

[0172] As a preferred implementation, the conditions for cutting off condensate throttling on the DCS side through the interface include:

[0173] (1) Automatic cut-off of deaerator water level;

[0174] (2) LC card communication failure;

[0175] (3) Abnormal heartbeat signal;

[0176] (4) The condensate throttling optimization function group is abnormal;

[0177] (5) The quality of the condensate inverter or deaerator water level adjustment gate command is bad;

[0178] (6) The deviation between the condensate throttling optimization communication command and the hard wiring command is greater than 1.

[0179] The condensate throttling method of this embodiment includes theoretical calculation and field test. The basis of the theoretical calculation includes the steam turbine heat balance diagram under TRL working conditions provided by the steam turbine factory. According to the steam turbine heat balance diagram, the maximum range of the unit power generation that can be increased in a short period of time after all low-pressure heaters are withdrawn in theory can be calculated.

[0180] (1) Obtaining object characteristics

[0181] Considering that the condensate system is subject to many restrictions in the actual operation of the unit, the condensate load adjustment capacity obtained by theoretical calculation is lower than the actual value. In order to obtain the condensate load adjustment capacity in the actual operation of the unit, it is necessary to conduct a condensate load adjustment characteristic test, and the value obtained by theoretical calculation can be used as a reference for the characteristic test.

[0182] Taking into account the different flow characteristics and power responses of the unit in different load sections, the characteristic test of condensate water load regulation should be carried out under different load conditions. Taking 100MW as a breakpoint, the characteristic test of condensate water load change should be carried out in the load range of 300-600MW.

[0183] This test is to determine the influence of condensate throttling on the unit load when the turbine three valves are fully open when running at different loads. The following two tests are performed under each load:

[0184] Release the automatic water level of the deaerator, adjust the water supply valve of the deaerator to change the condensate flow rate, and observe the load response time and change range of the unit;

[0185] Release the automatic water level of the deaerator, change the condensate flow rate by changing the command output of the condensate pump inverter, and observe the load response time and change range of the unit;

[0186] The above tests were carried out in the 300MW, 400MW, 500MW, and 600MW load sections, and the values ​​of unit load, deaerator water level, condenser water level, etc. before and after each test were recorded. The transfer function of each variable was obtained according to the changes of each number, and the parameter values ​​set in the logic were preliminarily calculated.

[0187] After the condensate water load changing characteristic test is completed, a condensate water load adjustment function module can be built in the unit DCS. This module accepts power instructions and condensate pump frequency conversion instructions from the coordinated control system.

[0188] In order to ensure the safe and stable operation of the unit, it is necessary to perform logic optimization on the water level control loops of the deaerator, condenser, and low-pressure heater of the unit. After completing the logic optimization, a specific water level disturbance test is performed to ensure that the water level of the deaerator, condenser, and low-pressure heater is controlled within a safe range after the condensate flow rate changes. The logic optimization of the deaerator, condenser, and low-pressure heater liquid level control is mainly to complete a fast feedforward loop. In the condensate variable load characteristic test, the valve position changes of the deaerator, condenser, and low-pressure heater liquid level control valve can be used as the basis for the feedforward loop.

[0189] (2) Load change test

[0190] Carry out load change test in the load range of 300MW-600MW. The load step change amount can be gradually changed from 50MW to 100MW, and the load change rate can also be gradually changed from 1.5%THA to 2.5%THA. During the load change process, observe whether the load response, superheated steam temperature, reheated steam temperature, deaerator and low-pressure heater water level changes meet the requirements. And adjust the parameters.

[0191] This embodiment uses the following 27 measuring points to test the control effect of the throttling system to determine the influence of condensate throttling on the unit load when the turbine three valves are fully open when operating at different loads.

[0192]

[0193]

[0194] This embodiment determines the influence of condensate throttling on the unit load when the turbine three valves are fully open when operating at different loads, realizes the optimal control of condensate throttling of the thermal power unit, improves the load response at the initial stage of load change, and can improve the delay in load response caused by the lag on the boiler side.

[0195] Although preferred embodiments of the present invention have been described, additional changes and modifications may be made to these embodiments by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A condensate throttling system for a thermal power unit, characterized in that include: A converter and a plurality of control modules connected to the converter, wherein the plurality of control modules are composed of a condensate throttling control module, a deaerator frequency conversion logic switching module, a condenser water level regulating module, a deaerator water level regulating module and a coordinated control water level recovery module; The condensate throttling control module includes a condensate throttling PID controller, which is used to control the following parameters: (I) Design of the conditions for starting and stopping the condensate throttling function (1) Conditions for putting the condensate throttling function into operation: When performing condensate throttling optimization control, it is necessary to monitor some parameters of the control system to prevent unit operation accidents. The condensate throttling control allowable conditions are: Coordinated control is in the operational state; The water levels of the deaerator and condenser are both in normal condition; There is no RB occurrence in the unit, ensuring that there is no trip alarm in the unit; The frequency conversion of the condensate pump has been put into use; The operator allows the condensate throttling control system to be adjusted; The optimized controller allows commissioning; When the above conditions are met, the condensate throttling automatically enters the operating state; (2) Design of the start and stop conditions of the condensate throttling function: After the unit is put into AGC, the condensate throttling system is activated and deactivated under load conditions. The activation and deactivation conditions are set separately during the load activation and deactivation process. 1) The conditions for increasing load condensate throttling include conditions ae and: a. The output command derivative of the unit load command calculator is positive, the load increase command issues a 60S pulse or a frequency modulation action and the frequency modulation load is greater than 2MW, the 60S pulse or the output command derivative of the unit load command calculator is positive and the load command and actual load deviation reaches ±20MW within the allowable range of condensate throttling; b. The deaerator water level is above the lower alarm limit, the deaerator water level is >700mm, and the delay is 60S. During the load increase process, the condensate flow rate decreases, which will cause the deaerator water level to decrease. Too low a deaerator water level is not conducive to the safe operation of the unit; c. When the condenser water level is above the lower alarm limit and the condenser water level is less than 750mm, the timer will be delayed for 60S to prevent the condenser water level from being too high; d. The condensate pump frequency is above the alarm lower limit, and the condensate pump frequency is greater than 15Hz, to prevent the condensate pump frequency from being too low; e. There is a certain interval since the last condensate pump frequency adjustment. Frequent frequency adjustment of the condensate pump is not conducive to the safe operation of the unit. 2) The load-increasing condensate throttling exit conditions include the conditions ag phase or: a. The unit LDC command derivative becomes negative, and the throttling process is completed; b. The deviation between the AGC command and the actual load is reduced to a range that meets the requirements; c. The deaerator water level drops to the lower alarm limit to prevent the deaerator water level from further dropping and posing a threat to the safe operation of the unit; d. The condensate flow rate reaches the lower alarm limit to prevent the condensate flow rate from being too low and affecting the safe operation of the unit; e. The condenser water level reaches the upper alarm limit > 1050mm; f. The condensate throttling time reaches the specified time; g. If the unit power is greater than 300MW, the delay is 30S; 3) The load reduction condensate throttling conditions include conditions ae and: a. The unit LDC command derivative is negative, that is, the load reduction command is issued or a frequency modulation action is taken and the frequency modulation load is less than -2MW with a delay of 5S or 60S pulse, or the output command derivative of the unit load command calculator LDC is positive and the deviation between the load command and the actual load reaches ±20MW, which is within the allowable range of condensate throttling; b. The water level of the deaerator is below the upper alarm limit, the water level is less than 1030mm, and the delay is 60S; c. When the steam-water level in the condenser is below the upper alarm limit and the water level is less than 1050mm, the timer will be delayed for 60 seconds to prevent the condenser water level from being too low; d. There is a certain interval from the last condensate pump frequency modulation; e. If the unit power is greater than 300MW, the delay is 30S; 4) Load reduction condensate throttling exit conditions include conditions af phase or: a. The unit LDC command derivative becomes positive, and the throttling process is completed; b. The deviation between the AGC command and the actual load is reduced to a range that meets the requirements; c. The deaerator water level rises to the alarm upper limit of 1030mm; d. The condensate flow rate reaches the upper alarm limit; e. The condenser water level reaches the alarm lower limit of 750mm; f. The condensate throttling time reaches the specified time; When all the above conditions are met, condensate throttling automatically enters the operating state.

2. A condensate throttling system for a thermal power unit according to claim 1, characterized in that The control logic of the condensate throttling control module includes: in the condensate throttling control state, the condensate pump frequency is determined by the deviation of the unit load, and the load reaches the target value by controlling the flow of condensate.

3. A condensate throttling system for a thermal power unit according to claim 2, characterized in that The deaerator variable frequency logic switching module includes a condenser pump variable frequency switching logic unit, a converter, a deaerator water level PID controller and a condenser pump variable frequency output instruction unit.

4. A condensate throttling system for a thermal power unit according to claim 3, characterized in that The working process of the deaerator frequency conversion logic switching module includes: the switching of the condensate pump frequency conversion instruction must be done without disturbance. When the system is in the condensate throttling control mode, the condensate pump frequency conversion instruction is adjusted by the condensate throttling PID controller, and the water level setting value of the deaerator tracks the feedback value of the actual water level. At this time, the deaerator water level PID controller is in the tracking mode, and the condensate pump frequency conversion output instruction unit sends the output instruction to the hand operator, and the output of the hand operator tracks the condensate throttling PID controller instruction; when the throttling process is over, the system switches back to the coordinated control water level recovery mode, and the deaerator water level PID controller switches back to the automatic adjustment state again, and the condensate throttling PID setting value tracks the actual load of the thermal power unit.

5. The condensate throttling system for a thermal power unit according to claim 1, characterized in that The condenser water level regulating module is used to regulate the condenser water level. The working process of the condenser water level regulating module includes: Under the condensate throttling control state, when the load command decreases, the condensate flow rate increases, causing the exhaust device water level to drop. The make-up water amount should be increased to maintain the normal state of the exhaust device water level. During this process, the deaerator water level will increase. After the condensate throttling state ends, the condensate flow rate should be appropriately reduced to restore the deaerator water level. At the same time, the make-up water amount of the exhaust device should be reduced; similarly, when the load command increases, due to the condensate throttling effect, the condensate flow rate decreases, causing the exhaust device water level to rise. The make-up water amount should be reduced to maintain the normal state of the condenser water level. After the condensate throttling state ends, the condensate flow rate is increased, the deaerator water level returns to normal, and the exhaust device water level is kept stable. The data obtained through the test is used to control the exhaust device water level using feedforward or overrun.

6. The condensate throttling system for a thermal power unit according to claim 1, characterized in that The deaerator water level regulation module is used to modify the deaerator water level regulation, and its working process includes: similar to the modification of the condensate pump frequency conversion regulation logic, when the original system logic is modified, when the system is in the condensate throttling state, the deaerator water level setting tracks the feedback value of the actual water level, the condensate throttling PID controller is in the tracking mode, and the output of the handheld operator tracks the instructions of the optimization controller; when the throttling process is over, the condensate throttling PID switches back to the automatic adjustment state again.

7. The condensate throttling system for a thermal power unit according to claim 1, characterized in that It also includes an interface for connecting the condensate throttling system for the thermal power unit with the original DCS of the thermal power unit. The interface has two functions: on the one hand, it realizes the activation and deactivation functions of the condensate throttling control system at the DCS end, and on the other hand, it switches the DCS condensate pump frequency conversion command; the condensate throttling system for the thermal power unit sends the following signals to the DCS control system: throttling function activation signal, throttling function activation condition signal and condensate pump frequency converter command signal; the DCS sends the following signals to the condensate throttling system for the thermal power unit: throttling function activation signal and frequency converter command signal.

8. The condensate throttling system for a thermal power unit according to claim 7, characterized in that The throttling conditions for cutting off condensate on the DCS side through the interface include: (1) Automatic cut-off of deaerator water level; (2) LC card communication failure; (3) Abnormal heartbeat signal; (4) The condensate throttling optimization function group is abnormal; (5) The quality of the condensate inverter or deaerator water level adjustment gate command is poor; (6) The deviation between the condensate throttling optimization communication command and the hard wiring command is greater than 1.

9. A condensate throttling method for a thermal power unit, characterized in that include: Step 1: Control the following parameters through the condensate throttling PID controller: (I) Design of the conditions for starting and stopping the condensate throttling function (1) Conditions for putting the condensate throttling function into operation: When performing condensate throttling optimization control, it is necessary to monitor some parameters of the control system to prevent unit operation accidents. The condensate throttling control allowable conditions are: Coordinated control is in the operational state; The water levels of the deaerator and condenser are both in normal condition; There is no RB occurrence in the unit, ensuring that there is no trip alarm in the unit; The frequency conversion of the condensate pump has been put into use; The operator allows the condensate throttling control system to be adjusted; The optimized controller allows commissioning; When the above conditions are met, the condensate throttling automatically enters the operating state; (2) Design of start and stop conditions for condensate throttling function After the unit is put into AGC, the condensate throttling system is activated and deactivated under load conditions. The activation and deactivation conditions are set separately during the load activation and deactivation process. 1) The conditions for increasing load condensate throttling include conditions ae and: a. The output command derivative of the unit load command calculator is positive, the load increase command issues a 60S pulse or a frequency modulation action and the frequency modulation load is greater than 2MW, the 60S pulse or the output command derivative of the unit load command calculator is positive and the load command and actual load deviation reaches ±20MW within the allowable range of condensate throttling; b. The deaerator water level is above the lower alarm limit, the deaerator water level is >700mm, and the delay is 60S. During the load increase process, the condensate flow rate decreases, which will cause the deaerator water level to decrease. Too low a deaerator water level is not conducive to the safe operation of the unit; c. When the condenser water level is above the lower alarm limit and the condenser water level is less than 750mm, the timer will be delayed for 60S to prevent the condenser water level from being too high; d. The condensate pump frequency is above the alarm lower limit, and the condensate pump frequency is greater than 15Hz, to prevent the condensate pump frequency from being too low; e. There is a certain interval since the last condensate pump frequency adjustment. Frequent frequency adjustment of the condensate pump is not conducive to the safe operation of the unit. 2) The load-increasing condensate throttling exit conditions include the conditions ag phase or: a. The unit LDC command derivative becomes negative, and the throttling process is completed; b. The deviation between the AGC command and the actual load is reduced to a range that meets the requirements; c. The deaerator water level drops to the lower alarm limit to prevent the deaerator water level from further dropping and posing a threat to the safe operation of the unit; d. The condensate flow rate reaches the lower alarm limit to prevent the condensate flow rate from being too low and affecting the safe operation of the unit; e. The condenser water level reaches the upper alarm limit > 1050mm; f. The condensate throttling time reaches the specified time; g. If the unit power is greater than 300MW, the delay is 30S; 3) The load reduction condensate throttling conditions include conditions ae and: a. The unit LDC command derivative is negative, that is, the load reduction command is issued or a frequency modulation action is taken and the frequency modulation load is less than -2MW with a delay of 5S or 60S pulse, or the output command derivative of the unit load command calculator LDC is positive and the deviation between the load command and the actual load reaches ±20MW, which is within the allowable range of condensate throttling; b. The water level of the deaerator is below the upper alarm limit, the water level is less than 1030mm, and the delay is 60S; c. When the steam-water level in the condenser is below the upper alarm limit and the water level is less than 1050mm, the timer will be delayed for 60 seconds to prevent the condenser water level from being too low; d. There is a certain interval from the last condensate pump frequency modulation; e. If the unit power is greater than 300MW, the delay is 30S; 4) Load reduction condensate throttling exit conditions include conditions af phase or: a. The unit LDC command derivative becomes positive, and the throttling process is completed; b. The deviation between the AGC command and the actual load is reduced to a range that meets the requirements; c. The deaerator water level rises to the alarm upper limit of 1030mm; d. The condensate flow rate reaches the upper alarm limit; e. The condenser water level reaches the alarm lower limit of 750mm; f. The condensate throttling time reaches the specified time; When the above conditions are met, the condensate throttling automatically enters the operating state; Among them, the control logic of the condensate throttling control module includes: in the condensate throttling control state, the condensate pump frequency is determined by the deviation of the unit load, and the load reaches the target value by controlling the flow of condensate; Step 2, controlling the deaerator frequency conversion logic switching through the deaerator frequency conversion logic switching module, including: the switching of the condensate pump frequency conversion instruction must be done without disturbance switching, when the system is in the condensate throttling control mode, the condensate pump frequency conversion instruction is adjusted by the condensate throttling PID controller, and the water level setting value of the deaerator tracks the feedback value of the actual water level, at this time, the deaerator water level PID controller is in the tracking mode, the condensate pump frequency conversion output instruction unit sends the output instruction to the hand operator, and the output of the hand operator tracks the condensate throttling PID controller instruction; when the throttling process is completed, the system switches back to the coordinated control water level recovery mode, at this time, the deaerator water level PID controller switches back to the automatic adjustment state again, and the condensate throttling PID setting value tracks the actual load of the thermal power unit; Step 3: regulating the condenser water level through the condenser water level regulating module. The working process of the condenser water level regulating module includes: In the condensate throttling control state, when the load command decreases, the condensate flow rate increases, causing the exhaust device water level to drop. The make-up water volume should be increased to maintain the normal state of the exhaust device water level. During this process, the deaerator water level will increase. After the condensate throttling state ends, the condensate flow rate should be appropriately reduced to restore the deaerator water level. At the same time, the make-up water volume of the exhaust device should be reduced; similarly, when the load command increases, due to the condensate throttling effect, the condensate flow rate decreases, causing the exhaust device water level to rise. The make-up water volume should be reduced to maintain the normal state of the condenser water level. After the condensate throttling state ends, the condensate flow rate is increased, the deaerator water level returns to a normal state, and the exhaust device water level is kept stable. The exhaust device water level is controlled by feedforward or overrunning through the data obtained through the test; Step 4, adjust the deaerator water level through the deaerator water level adjustment module, and its working process includes: when the original system logic is modified, when the system is in the condensate throttling state, the deaerator water level setting tracks the feedback value of the actual water level, the condensate throttling PID controller is in the tracking mode, and the output of the handheld operator tracks the instructions of the optimization controller; when the throttling process is over, the condensate throttling PID switches back to the automatic adjustment state again.

Images