A coordinated control method for main pipe pressure of main pipe control unit

Abstract

The present invention discloses a method for coordinated control of the main pipe pressure of a main pipe control unit, including a main pipe pressure controller that obtains energy demand according to the main pipe pressure set value, the main pipe pressure feedback value and the heat user steam flow feedforward, and outputs it to an energy balance distribution module; the energy balance distribution module performs a balancing operation according to the output of the main pipe pressure controller and the energy instructions or feedback signals of all boilers to obtain the energy instruction of the pressure regulating boiler; the energy controller of the pressure regulating boiler obtains the coal quantity instruction according to the energy instruction issued by the energy balance distribution module, using the sum of the superheated steam flow of the boiler and the differential signal of the drum pressure as the feedback signal, and distributes it to each coal feeder; for non-pressure regulating boilers, a fixed heat load control method is adopted. The present invention can effectively overcome the side effects of non-pressure regulating furnaces in the main pipe pressure regulation and realize the stable regulation of the main pipe pressure.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power generation main pipe pressure control, and in particular relates to a main pipe pressure coordinated control method for a main pipe control unit. Background Art

[0002] For the main pipe control unit, the control of the main pipe pressure is not only the difficulty of the unit, but also the focus of the unit control. The change of the main pipe pressure reflects the balance between energy demand and supply: if the energy demand is greater than the energy supply, the main pipe pressure will decrease; if the energy demand is less than the energy supply, the main pipe pressure will increase. The main steam pressure of the main pipe control unit has a greater delay characteristic than that of the unit unit, and the boilers running in parallel also have a strong coupling.

[0003] At present, the existing control strategies for the coordinated control of the mother pipe pressure can be divided into a combination of a pressure regulating furnace and a non-pressure regulating furnace or a coordinated control of the whole furnace. Different control strategies are similar in control methods, that is, a cascade control method with the mother pipe pressure as the main adjustment and energy balance as the secondary adjustment. The output of the secondary adjustment is the energy demand signal, which is then distributed to each pressure regulating furnace as the boiler main control instruction through a distributor. This control method can solve the coupling effect between the pressure regulating furnaces and avoid the situation where the pressure regulating furnaces "grab the output", and the operation mode is flexible and can meet more control requirements. However, this method also has shortcomings, that is, it cannot solve the coupling effect between the pressure regulating furnace and the non-pressure regulating furnace. In this control system, the non-pressure regulating furnace takes the steam flow rate at the boiler outlet as the control object, and the purpose is to maintain a constant boiler load. However, the steam flow rate at the boiler outlet will fluctuate with the change of the mother pipe pressure, which is not conducive to the regulation of the mother pipe pressure. Taking the increase in energy demand as an example, the system energy supply is insufficient, the mother pipe pressure decreases, and the pressure regulating boiler increases the output to make up for the energy gap. However, for non-pressure-regulated boilers, due to the drop in the main pipe pressure, the steam flow rate will increase briefly. At this time, the non-pressure-regulated boiler will reduce its output, causing the energy supply to further decrease, and the main pipe pressure will also decrease, which is not conducive to the normal regulation of the main pipe pressure. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for coordinating the mother pipe pressure of a mother pipe control unit in view of the deficiencies of the above-mentioned prior art, so as to effectively overcome the side effects of non-pressure regulating furnaces in the mother pipe pressure regulation, realize stable regulation of the mother pipe pressure, and solve the problem that the coupling effect between the pressure regulating furnace and the non-pressure regulating furnace cannot be solved in the mother pipe pressure coordination of the existing mother pipe control unit.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] A main pipe pressure coordinated control method for a main pipe control unit, comprising:

[0007] Step S1: The main pipe pressure controller obtains the energy demand according to the main pipe pressure setting value, the main pipe pressure feedback value and the steam flow feedforward of the heat user, and outputs it to the energy balance allocation module;

[0008] Step S2: the energy balance distribution module performs a balance operation according to the output of the main pipe pressure controller and the energy instructions or feedback signals of all boilers to obtain the energy instruction of the pressure regulating boiler;

[0009] Step S3: The energy controller of the pressure regulating boiler obtains the coal feeding instruction according to the energy instruction issued by the energy balance distribution module, using the sum of the superheated steam flow rate of the boiler and the differential signal of the drum pressure as the feedback signal, and distributes it to each coal feeder;

[0010] Step S4: For non-pressure-regulated boilers, a constant heat load control method is adopted, that is, the product of the boiler superheated steam flow rate and the steam enthalpy value is used as the regulated variable. This is only to overcome the internal disturbance of the boiler itself, and does not respond to the mother pipe pressure fluctuation, so as to keep its own heat load constant.

[0011] To optimize the above technical solutions, the specific measures taken also include:

[0012] The above boilers are divided into pressure regulating state and non-pressure regulating state;

[0013] When the boiler is in a non-pressure regulating state, the heat load controller participates in the operation, the energy controller is in a tracking state, and its energy feedback signal is sent back to the energy balance distribution module in step S2;

[0014] When the boiler is in the pressure regulating state, the energy controller participates in the calculation and the heat load controller is in the tracking state, so the pressure regulating and non-pressure regulating states can be switched without disturbance.

[0015] The calculation formula of the energy demand in step S1 above is as follows:

[0016]

[0017] Where: E SP (t) is the energy requirement, P sp (t) is the main pipe pressure setting value, P PV (t) is the mother pipe pressure feedback value, F(t) is the heat user steam flow feedforward, K p is the proportional gain, T i is the integration time constant, T d is the differential time constant, and t represents the time.

[0018] The energy balance distribution module described in the above step S2 adopts a pure integral link to collect energy command signals received by the pressure regulating boilers to balance and distribute the commands of each pressure regulating boiler; at the same time, it collects energy feedback signals of non-pressure regulating boilers, responds to energy changes of non-pressure regulating boilers, and realizes system energy balance.

[0019] The calculation formula of the coal feeding instruction in step S3 is as follows:

[0020]

[0021] Where: M(t) is the coal supply instruction, E' SP (t) is the energy instruction issued by the energy balance allocation module, F'(t) is the boiler superheated steam flow, P0(t) is the drum pressure, K p is the proportional gain, T i is the integration time constant, and t represents the time.

[0022] The specific formula of the coal supply instruction using the constant heat load control method in step S4 is as follows:

[0023]

[0024] Q PV (t) = H (P, T) × F′ (t)

[0025] Where: M(t) is the coal supply instruction, Q SP (t) is the boiler heat load setting value, Q PV (t) is the boiler heat load feedback value, H(P, T) is the superheated steam enthalpy, P is the superheated steam pressure, T is the superheated steam temperature, F′(t) is the superheated steam flow rate, K p is the proportional gain, T i is the integration time constant, and t represents the time.

[0026] The present invention has the following beneficial effects:

[0027] The non-pressure-regulated boiler in the present invention aims to control the stability of the boiler heat load. When the mother pipe pressure changes, although the superheated steam flow rate will change, the superheated steam enthalpy will also change. These two effects offset each other, thereby effectively overcoming the side effects of the non-pressure-regulated boiler in the mother pipe pressure regulation, solving the coupling effect between the pressure-regulated boiler and the non-pressure-regulated boiler, realizing stable regulation of the mother pipe pressure, and realizing disturbance-free switching between the pressure-regulated boiler and the non-pressure-regulated boiler through the energy balance module. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the control method of the present invention. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0030] See also Figure 1 The present invention provides a main pipe pressure coordinated control method for a main pipe unit, comprising:

[0031] Step S1: The main pipe pressure controller obtains the energy demand according to the main pipe pressure setting value, the main pipe pressure feedback value and the steam flow feedforward of the heat user, and outputs it to the energy balance allocation module;

[0032] In the embodiment, the boiler is divided into a pressure regulating state and a non-pressure regulating state;

[0033] When the boiler is in a non-pressure regulating state, the heat load controller participates in the operation, the energy controller is in a tracking state, and its energy feedback signal is fed back to the energy balance distribution module in step S2.

[0034] When the boiler is in the pressure regulating state, the energy controller participates in the calculation and the heat load controller is in the tracking state, so the pressure regulating and non-pressure regulating modes can be switched without disturbance.

[0035] In the embodiment, the mother pipe pressure controller uses proportional, integral and differential actions, outputs pressure correction and superimposes the heat user steam flow feedforward, and outputs energy demand. The corresponding formula is as follows:

[0036]

[0037] Where: E SP (t) is the energy requirement, P sp (t) is the main pipe pressure setting value, P PV (t) is the mother pipe pressure feedback value, F(t) is the heat user steam flow feedforward, K p is the proportional gain, T i is the integration time constant, T d is the differential time constant, and t represents the time.

[0038] Step S2: the energy balance distribution module performs a balance operation according to the output of the main pipe pressure controller and the energy instructions or feedback signals of all boilers to obtain the energy instruction of the pressure regulating boiler;

[0039] In the embodiment, the energy balance distribution module adopts a pure integral link to collect energy command signals received by the pressure regulating boilers to balance and distribute the commands of each pressure regulating boiler; at the same time, it collects energy feedback signals of non-pressure regulating boilers, responds to energy changes of non-pressure regulating boilers, and realizes system energy balance.

[0040] Step S3: The energy controller of the pressure regulating boiler obtains the coal feeding instruction according to the energy instruction issued by the energy balance distribution module, using the sum of the superheated steam flow rate of the boiler and the differential signal of the drum pressure as the feedback signal, and distributes it to each coal feeder;

[0041] In the embodiment, the energy controller of the pressure regulating boiler adopts proportional and integral action, and its feedback signal is the sum of the superheated steam flow rate and the drum pressure differential signal of the boiler. The superheated steam flow rate represents the existing energy of the boiler, and the drum pressure differential signal represents the heat storage of the boiler (i.e., expected energy). The output is the coal supply instruction, and the corresponding formula is as follows:

[0042]

[0043] Where: M(t) is the coal supply instruction, E' SP (t) is the energy instruction issued by the energy balance allocation module, F'(t) is the boiler superheated steam flow, P0(t) is the drum pressure, K p is the proportional gain, T i is the integration time constant, and t represents the time.

[0044] Step S4: For non-pressure-regulated boilers, a constant heat load control method is adopted, that is, the product of the boiler superheated steam flow rate and the steam enthalpy value is used as the regulated variable. This is only to overcome the internal disturbance of the boiler itself, and does not respond to the mother pipe pressure fluctuation, so as to keep its own heat load constant.

[0045] In the embodiment, the heat load controller of the non-pressure regulating boiler also adopts proportional and integral action, and takes the product of the boiler superheated steam flow and the superheated steam enthalpy as the controlled variable. The enthalpy of the superheated steam is obtained according to the pressure and temperature of the superheated steam. The specific formula of the coal supply instruction is as follows:

[0046]

[0047] Q PV (t) = H(P, T) × F'(t)

[0048] Where: M(t) is the coal supply instruction, Q SP (t) is the boiler heat load setting value, Q PV (t) is the boiler heat load feedback value, H(P, T) is the superheated steam enthalpy, P is the superheated steam pressure, T is the superheated steam temperature, F'(t) is the superheated steam flow rate, K p is the proportional gain, T i is the integration time constant, and t represents the time.

[0049] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for coordinated control of main pipe pressure of a main pipe unit, characterized in that: include: Step S1: The main pipe pressure controller obtains the energy demand according to the main pipe pressure setting value, the main pipe pressure feedback value and the steam flow feedforward of the heat user, and outputs it to the energy balance allocation module; Step S2: the energy balance distribution module performs a balance operation according to the output of the main pipe pressure controller and the energy instructions or feedback signals of all boilers to obtain the energy instruction of the pressure regulating boiler; Step S3: The energy controller of the pressure regulating boiler obtains the coal feeding instruction according to the energy instruction issued by the energy balance distribution module, using the sum of the superheated steam flow rate of the boiler and the differential signal of the drum pressure as the feedback signal, and distributes it to each coal feeder; Step S4: For non-pressure-regulated boilers, a constant heat load control method is adopted, that is, the product of the boiler superheated steam flow rate and the steam enthalpy value is used as the regulated variable. This is only to overcome the internal disturbance of the boiler itself, and does not respond to the mother pipe pressure fluctuation, so as to keep its own heat load constant.

2. A method for coordinated control of main pipe pressure of a main pipe unit according to claim 1, characterized in that: The boiler is divided into a pressure regulating state and a non-pressure regulating state; When the boiler is in a non-pressure regulating state, the heat load controller participates in the operation, the energy controller is in a tracking state, and its energy feedback signal is sent back to the energy balance distribution module in step S2; When the boiler is in the pressure regulating state, the energy controller participates in the calculation and the heat load controller is in the tracking state, so the pressure regulating and non-pressure regulating states can be switched without disturbance.

3. The method for coordinated control of main pipe pressure of a main pipe unit according to claim 1, characterized in that: The calculation formula of the energy demand in step S1 is as follows: Where: E SP (t) is the energy requirement, p sp (t) is the main pipe pressure setting value, P PV (t) is the mother pipe pressure feedback value, F(t) is the heat user steam flow feedforward, K p is the proportional gain, T i is the integration time constant, T d is the differential time constant, and t represents the time.

4. The method for coordinated control of main pipe pressure of a main pipe unit according to claim 1, characterized in that: The energy balance distribution module in step S2 adopts a pure integral link to collect energy command signals received by the pressure regulating boilers to balance and distribute the commands of each pressure regulating boiler; at the same time, it collects energy feedback signals of non-pressure regulating boilers, responds to energy changes of non-pressure regulating boilers, and realizes system energy balance.

5. The method for coordinated control of main pipe pressure of a main pipe unit according to claim 1, characterized in that: The calculation formula of the coal feeding instruction in step S3 is as follows: Where: M(t) is the coal supply instruction, E' SP (t) is the energy instruction issued by the energy balance allocation module, F'(t) is the boiler superheated steam flow, P0(t) is the drum pressure, K p is the proportional gain, T i is the integration time constant, and t represents the time.

6. The method for coordinated control of main pipe pressure of a main pipe unit according to claim 1, characterized in that: The specific formula of the coal supply instruction using the constant heat load control method in step S4 is as follows: Q PV (t)=H(P,T)×F’(t) Where: M(t) is the coal supply instruction, Q SP (t) is the boiler heat load setting value, Q PV (t) is the boiler heat load feedback value, H(P, T) is the superheated steam enthalpy, P is the superheated steam pressure, T is the superheated steam temperature, F'(t) is the superheated steam flow rate, K p is the proportional gain, T i is the integration time constant, and t represents the time.

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