Coordination control method for rapid peak regulation of thermal power generating unit based on heat supply steam extraction

Abstract

The invention discloses a coordinated control method for rapid peak regulation of a thermal power generating unit based on heat supply steam extraction, and the thermal power generating unit at least comprises an adjustable medium-pressure steam extraction valve and an adjustable low-pressure steam extraction valve, so that the thermal power generating unit establishes a coordinated control system mathematical model of the medium-pressure steam extraction valve, the low-pressure steam extraction valve, a steam turbine main regulating valve and coal feeding quantity. And when the thermal power generating unit receives a variable load adjusting instruction, the medium-pressure steam extraction valve, the low-pressure steam extraction valve and the steam turbine main adjusting valve give a response. The peak regulation capacity of the unit can be improved on the premise that the steam supply quality is not reduced, and the method has practical engineering significance.

Description

Technical Field

[0001] The present invention relates to the field of optimization control of thermal power generation, and particularly to a coordinated control method for rapid peak shaving of thermal power units based on extraction steam for heating. Background Art

[0002] Currently, coal-fired power plays a fundamental role in China's power system. Its installed capacity and total power generation account for the dominant position. Its dynamic regulation ability conforms to the operation mechanism of the "source-load interaction" power system. The technological evolution has always focused on energy efficiency improvement, emission reduction control, and cost-benefit optimization.

[0003] In recent years, the industry has put forward higher requirements for the deep peak shaving technology and load change rate technology of thermal power units. How to explore the flexibility regulation ability on the boiler side faces new challenges. Industrial steam supply / residential heating units have the characteristics of large heating flow and long pipelines. Their heating has great heat storage potential. The peak shaving auxiliary service ability of the steam turbine for heating can be further explored. By quickly adjusting the extraction steam flow of the steam turbine, the regulation rate of the unit can be improved, and by slowly restoring the extraction steam flow, the quality of industrial steam supply / residential heating can be ensured not to be affected, so as to further improve the peak shaving auxiliary service ability of the unit and ensure the further improvement of the profitability of the unit.

[0004] The control structure of the commonly used coordinated control system of existing thermal power units is as Figure 2 shown. Currently, the commonly used rapid peak shaving methods for thermal power units mainly focus on the following aspects: 1) Boiler side transformation: Adopt low-load stable combustion technologies (such as micro-oil ignition, oxygen-enriched combustion), broaden the boiler load range, and transform the boiler side; utilize the thermal inertia of boiler metal and working medium to overgenerate or quickly reduce the load in a short time. 2) Steam turbine side optimization: Increase the capacity of high / low pressure bypasses to decouple the steam turbine from the boiler and accelerate load regulation; improve the thermal efficiency at partial loads through dynamic adjustment of main steam pressure. 3) Hybrid energy storage cooperation method: Use devices such as electrochemical energy storage (such as lithium batteries), heat storage systems, and hydrogen energy coupling to work jointly with thermal power units, and improve through the "rapid response of energy storage / heat storage + stable follow-up of thermal power" mode to achieve second-level frequency modulation and peak shaving. However, the transformation work on the boiler side and the steam turbine side has basically been completed, lacking the potential for further exploration. However, the implementation cost of the hybrid energy storage cooperation method is too high, which has certain economic resistance to technology promotion. This project utilizes the unique large heat storage potential of industrial steam supply / residential heating units to carry out the transformation of the regulating valves of the medium-pressure extraction steam valve and the low-pressure extraction steam valve of the unit and the coordinated optimization design of control, so as to improve the peak shaving ability of the unit on the premise of ensuring that the steam supply quality does not decrease and further enhance the peak shaving ability of the unit. Summary of the Invention

[0005] The purpose of the present invention is to accelerate the rapid peak shaving method of thermal power units, and a coordinated control method for rapid peak shaving of thermal power units based on extraction steam for heating is proposed. First, the intermediate-pressure extraction steam valve and the low-pressure extraction steam valve of the unit are modified into adjustable valves; the unit load change command is distributed to the intermediate-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command; then the intermediate-pressure extraction steam valve load command and the low-pressure extraction steam valve load command are converted into extraction steam quantities; next, a mathematical model of the coordinated control system including the intermediate-pressure extraction steam valve, the low-pressure extraction steam valve, the main control valve of the steam turbine, and the coal feeding quantity is established; then, control strategies based on proportional-integral-derivative / active disturbance rejection control / model predictive control, etc. are designed to adjust the coordinated control system; finally, the unit transient load command is restored to the load change command, and the intermediate-pressure extraction steam valve and the low-pressure extraction steam valve gradually restore the opening before steady state. The present invention can improve the peak shaving ability of the unit on the premise of ensuring that the steam supply quality does not decrease, and has practical engineering significance.

[0006] In order to achieve the above purpose, the technical solution of the present invention is:

[0007] A coordinated control method for rapid peak shaving of thermal power units based on extraction steam for heating, wherein the thermal power unit at least includes adjustable intermediate-pressure extraction steam valve and low-pressure extraction steam valve, so as to establish a mathematical model of the coordinated control system of the intermediate-pressure extraction steam valve, the low-pressure extraction steam valve, the main control valve of the steam turbine, and the coal feeding quantity. When the thermal power unit receives a load change regulation command, the intermediate-pressure extraction steam valve, the low-pressure extraction steam valve, and the main control valve of the steam turbine give responses.

[0008] As an improvement to the above technical solution, the specific steps of the coordinated control method are:

[0009] S1. When the thermal power unit receives a load change regulation command, the load change regulation command is distributed to the intermediate-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command through thermal calculation, and the distribution constraint condition is:

[0010] ΔP AGC ≤ΔP z +ΔP d +ΔP zt (1)

[0011] Where ΔP AGC 、ΔP z 、ΔP d 、ΔP zt are the load change regulation command, the intermediate-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command respectively;

[0012] S2. Convert the intermediate-pressure extraction steam valve load command and the low-pressure extraction steam valve load command into extraction steam quantities

[0013]

[0014] where Δm z , Δh z , η z are the intermediate pressure extraction steam flow rate, the enthalpy drop from the intermediate pressure extraction steam point to the low pressure cylinder outlet, and the power generation efficiency from the intermediate pressure extraction steam point to the low pressure cylinder outlet, respectively; Δm d , Δh d , η d are the low pressure extraction steam flow rate, the enthalpy drop from the low pressure extraction steam point to the low pressure cylinder outlet, and the power generation efficiency from the low pressure extraction steam point to the low pressure cylinder outlet, respectively;

[0015] S3. Establish a coordinated control system mathematical model including the intermediate pressure extraction steam valve, the low pressure extraction steam valve, the main governing valve of the steam turbine, and the coal feeding amount. By using the open-loop step method, establish a four-input and four-output mathematical model with the intermediate pressure extraction steam valve, the low pressure extraction steam valve, the main governing valve of the steam turbine, and the coal feeding amount as input variables, and the intermediate pressure extraction steam flow rate, the low pressure extraction steam flow rate, the unit transient load command, and the main steam pressure as output variables. The mathematical model expression is:

[0016]

[0017] where s is the Laplace operator, and Y(s) is the transfer function of the coordinated control system mathematical model; m d (s), m z (s), P z (s), P pre (s) are the Laplace transforms of the low pressure extraction steam flow rate, the intermediate pressure extraction steam flow rate, the unit transient load command, and the main steam pressure, respectively; U1(s), U2(s), U3(s), and U4(s) are the Laplace transforms of the low pressure extraction steam control valve, the intermediate pressure extraction steam control valve, the main governing valve of the steam turbine, and the coal feeding, respectively; G ij (s) (i = 1,..., 4; j = 1,..., 4) is the transfer function from the low pressure extraction steam control valve, the intermediate pressure extraction steam control valve, the main governing valve of the steam turbine, and the coal feeding to the low pressure extraction steam flow rate, the intermediate pressure extraction steam flow rate, the unit transient load command, and the main steam pressure;

[0018] S4. Adjust the coordinated control system based on the model established in Equation (4). Design the control structures from the low pressure extraction steam control valve, the intermediate pressure extraction steam control valve, the main governing valve of the steam turbine, and the coal feeding to the low pressure extraction steam flow rate, the intermediate pressure extraction steam flow rate, the unit transient load command, and the main steam pressure respectively for G i (s) (i = 1,..., 4); Design the overall control structure for the model control strategy for G ij (s) (i = 1,..., 4; j = 1,..., 4);

[0019] S5. After a certain period of time when the actual low pressure extraction steam flow rate and the actual intermediate pressure extraction steam flow rate reach the calculated values in Equations (2) and (3), restore the unit transient load command to the variable load command, that is

[0020] ΔP zt = ΔP AGC (5)

[0021] And the medium-pressure extraction steam valve and the low-pressure extraction steam valve gradually resume the opening before regulation.

[0022] As an improvement to the above technical solution, the magnitude relationship among the variable load regulation command, the medium-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command is ΔP zt ≥ 2(ΔP AGC - ΔP z - ΔP d ).

[0023] As an improvement to the above technical solution, the medium-pressure extraction steam valve and the low-pressure extraction steam valve are respectively an electric adjustable medium-pressure extraction steam valve and an electric adjustable low-pressure extraction steam valve.

[0024] Compared with the prior art, the present invention includes but is not limited to the following advantages and positive effects:

[0025] The present invention first transforms the medium-pressure extraction steam valve and the low-pressure extraction steam valve of the unit into adjustable valves; distributes the unit variable load command to the medium-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command; then converts the medium-pressure extraction steam valve load command and the low-pressure extraction steam valve load command into extraction steam quantities; then establishes a coordinated control system mathematical model including the medium-pressure extraction steam valve, the low-pressure extraction steam valve, the main control valve of the steam turbine, and the coal feeding quantity; then designs control strategies based on proportional-integral-derivative / active disturbance rejection control / model predictive control, etc. to adjust the coordinated control system; finally, restores the unit transient load command to the variable load command, and the medium-pressure extraction steam valve and the low-pressure extraction steam valve gradually resume the opening before steady state; the present invention can realize improving the peak load regulation ability of the unit on the premise of ensuring that the steam supply quality does not decrease, and has practical engineering significance. Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a schematic diagram of the implementation steps of the coordinated control method of the present invention;

[0028] Figure 2 It is a schematic diagram of the control structure of the commonly used coordinated control system of a thermal power unit;

[0029] Figure 3Schematic diagram of the control structure of the coordinated control system for thermal power units proposed by the present invention;

[0030] Figure 4 Schematic diagram of the transformation of the thermal power unit of the present invention. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

[0032] As Figure 4 shown, in order to achieve the coordinated control of the rapid peak shaving of the thermal power unit with extraction steam for heating, the present invention improves the existing thermal power unit, wherein the medium-pressure extraction steam valve and the low-pressure extraction steam valve of the unit are transformed into adjustable valves; the adjustable valves adopt electric control valves, and the corresponding motor stroke is controlled through a voltage regulator. The connecting rod drives the rotating baffle to control its opening degree to achieve the adjustment of the extraction steam volume. Figure 4 HP represents the high-pressure state, and LP represents the low-pressure state.

[0033] As Figure 1 and 3 shown, based on the above improvements, a coordinated control method for the rapid peak shaving of a thermal power unit with extraction steam for heating proposed by the present invention has a process as Figure 1 shown, including the following steps:

[0034] Allocate the unit load change command to the medium-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command: when the unit receives the load change adjustment command from the automatic generation system, the load change adjustment command is allocated to the medium-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command through thermal calculation. The allocation constraint condition is:

[0035] ΔP AGC ≤ΔP z +ΔP d +ΔP zt (1)

[0036] where ΔP AGC , ΔP z , ΔP d , ΔP zt are respectively the load change adjustment command of the automatic generation system, the medium-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command; generally, it is recommended that ΔP zt ≥2(ΔP AGC -ΔPz -ΔP d );

[0037] Then convert the medium - pressure extraction steam valve load command and the low - pressure extraction steam valve load command into extraction steam flow rates

[0038]

[0039] where Δm z , Δh z , η z are the medium - pressure extraction steam flow rate, the enthalpy drop from the medium - pressure extraction steam point to the outlet of the low - pressure cylinder, and the power generation efficiency from the medium - pressure extraction steam point to the outlet of the low - pressure cylinder respectively; Δm d , Δh d , η d are the low - pressure extraction steam flow rate, the enthalpy drop from the low - pressure extraction steam point to the outlet of the low - pressure cylinder, and the power generation efficiency from the low - pressure extraction steam point to the outlet of the low - pressure cylinder respectively;

[0040] Establish a coordinated control system mathematical model including the medium - pressure extraction steam valve, the low - pressure extraction steam valve, the main governor valve of the steam turbine, and the coal feed rate. By the open - loop step method, establish a four - input and four - output mathematical model with the medium - pressure extraction steam valve, the low - pressure extraction steam valve, the main governor valve of the steam turbine, and the coal feed rate as input variables, and the medium - pressure extraction steam flow rate, the low - pressure extraction steam flow rate, the unit transient load command, and the main steam pressure as output variables. The mathematical model expression is:

[0041]

[0042] where s is the Laplace operator, and Y(s) is the transfer function of the coordinated control system mathematical model; m d (s), m z (s), P zt (s), P pre (s) are the Laplace transforms of the low - pressure extraction steam flow rate, the medium - pressure extraction steam flow rate, the unit transient load command, and the main steam pressure respectively; U1(s), U2(s), U3(s), and U4(s) are the Laplace transforms of the low - pressure extraction steam control valve, the medium - pressure extraction steam control valve, the main governor valve of the steam turbine, and the coal feed respectively; G ij (s)(i = 1, …, 4; j = 1, …, 4) is the transfer function from the low - pressure extraction steam control valve, the medium - pressure extraction steam control valve, the main governor valve of the steam turbine, and the coal feed to the low - pressure extraction steam flow rate, the medium - pressure extraction steam flow rate, the unit transient load command, and the main steam pressure;

[0043] Design control strategies such as proportional - integral - derivative / active disturbance rejection control / model predictive control to adjust the coordinated control system: Based on the model established in Equation (4), design control strategies such as proportional - integral - derivative / active disturbance rejection control or model predictive control to adjust the coordinated control system; The proportional - integral - derivative / active disturbance rejection control strategy is for G i(s) (i = 1, …, 4) are respectively designed for the low-pressure extraction steam control valve, the intermediate-pressure extraction steam control valve, the main steam control valve of the steam turbine, and the coal feeding to control the structures of the low-pressure extraction steam flow, the intermediate-pressure extraction steam flow, the transient load command of the unit, and the main steam pressure; the model control strategy is for G ij (s) (i = 1, …, 4; j = 1, …, 4) design the overall control structure;

[0044] Restore the transient load command of the unit to the variable load command, and the intermediate-pressure extraction steam valve and the low-pressure extraction steam valve gradually restore the opening before steady state: after a certain time when the actual low-pressure extraction steam flow and the actual intermediate-pressure extraction steam flow reach the calculated values of formulas (2) and (3), restore the transient load command of the unit to the variable load command, that is

[0045] ΔP zt = ΔP AGC (5)

[0046] And the intermediate-pressure extraction steam valve and the low-pressure extraction steam valve gradually restore the opening before regulation, and complete the design of the coordinated control method for the fast peak shaving of the thermal power unit based on the extraction steam for heating.

[0047] The present invention transforms the intermediate-pressure extraction steam valve and the low-pressure extraction steam valve of the unit into adjustable valves; distributes the variable load command of the unit to the intermediate-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the transient load command of the unit; converts the intermediate-pressure extraction steam valve load command and the low-pressure extraction steam valve load command into extraction steam flows; establishes a mathematical model of the coordinated control system including the intermediate-pressure extraction steam valve, the low-pressure extraction steam valve, the main steam control valve of the steam turbine, and the coal feeding amount; designs control strategies based on proportional-integral-differential / active disturbance rejection control / model predictive control, etc. to adjust the coordinated control system; restores the transient load command of the unit to the variable load command, and the intermediate-pressure extraction steam valve and the low-pressure extraction steam valve gradually restore the opening before steady state; the present invention can improve the peak shaving ability of the unit on the premise of ensuring that the steam supply quality does not decrease, and has practical engineering significance.

Claims

1. A coordinated control method for rapid peak shaving of thermal power units based on extraction steam for heating, characterized in that: The thermal power unit at least includes adjustable medium-pressure extraction steam valves and low-pressure extraction steam valves, so as to establish a coordinated control system mathematical model for the medium-pressure extraction steam valves, low-pressure extraction steam valves, main control valves of the steam turbine, and coal feeding amount of the thermal power unit. When the thermal power unit receives a variable load regulation command, the medium-pressure extraction steam valves, low-pressure extraction steam valves, main control valves of the steam turbine, and coal feeding amount respond.

2. The coordinated control method for rapid peak shaving of a thermal power unit based on extraction steam for heating according to claim 1, characterized in that: The specific steps of the coordinated control method are as follows: S1. When the thermal power unit receives a variable load regulation command, the variable load regulation command is distributed to the medium-pressure extraction steam valve load command, low-pressure extraction steam valve load command, and unit transient load command through thermal calculation. The distribution constraint conditions are: ΔP AGC ≤ΔP z +ΔP d +ΔP zt where ΔP AGC , ΔP z , ΔP d , ΔP zt are the variable load regulation command, the medium-pressure extraction steam valve load command, the low-pressure extraction steam valve load command, and the unit transient load command respectively; S2. Convert the medium-pressure extraction steam valve load command and low-pressure extraction steam valve load command into theoretical extraction steam amounts where Δm z , Δh z , η z are respectively the intermediate-pressure theoretical extraction steam flow rate, the enthalpy drop from the intermediate-pressure extraction steam point to the outlet of the low-pressure cylinder, and the power generation efficiency from the intermediate-pressure extraction steam point to the outlet of the low-pressure cylinder; Δm d , Δh d , η d are respectively the low-pressure theoretical extraction steam flow rate, the enthalpy drop from the low-pressure extraction steam point to the outlet of the low-pressure cylinder, and the power generation efficiency from the low-pressure extraction steam point to the outlet of the low-pressure cylinder; S3. Establish a coordinated control system mathematical model that includes the medium-pressure extraction steam valve, low-pressure extraction steam valve, main steam control valve of the steam turbine, and coal feed rate. Through the open-loop step method, establish a four-input and four-output mathematical model with the medium-pressure extraction steam valve, low-pressure extraction steam valve, main steam control valve of the steam turbine, and coal feed rate as input variables, and the medium-pressure extraction steam flow rate, low-pressure extraction steam flow rate, unit transient load command, and main steam pressure as output variables. The mathematical model expression is: where s is the Laplace operator and Y(s) is the transfer function of the coordinated control system mathematical model; m d (s), m z (s), P zt (s), P pre (s) are the Laplace transforms of the low-pressure extraction steam flow rate, intermediate-pressure extraction steam flow rate, unit transient load command, and main steam pressure, respectively; U1(s), U2(s), U3(s), and U4(s) are the Laplace transforms of the low-pressure extraction steam control valve, intermediate-pressure extraction steam control valve, turbine main control valve, and coal feeding, respectively; G ij (s) (i = 1,..., 4; j = 1,..., 4) are the transfer functions from the low-pressure extraction steam control valve, intermediate-pressure extraction steam control valve, turbine main control valve, and coal feeding to the low-pressure extraction steam flow rate, intermediate-pressure extraction steam flow rate, unit transient load command, and main steam pressure; S4. Adjust the coordinated control system based on the model established by the four-input and four-output mathematical model, and separately design the control structures of the low-pressure extraction steam control valve, medium-pressure extraction steam control valve, turbine main control valve, and coal feeder to the low-pressure extraction steam flow, medium-pressure extraction steam flow, unit transient load command, and main steam pressure for G i (s) (i = 1,..., 4); S5. After a certain period of time when the actual low-pressure extraction steam volume and the actual intermediate-pressure extraction steam volume reach the calculated values of the theoretical extraction steam volume, restore the transient load command of the unit to the variable load command, i.e., ΔP zt = ΔP AGC ; and the intermediate-pressure extraction steam valve and the low-pressure extraction steam valve gradually return to the opening before regulation.

3. The coordinated control method for rapid peak shaving of a thermal power unit based on extraction steam for heating according to claim 2, characterized in that: The magnitude relationship among the variable load regulation command, the intermediate pressure extraction steam valve load command, the low pressure extraction steam valve load command, and the unit transient load command is ΔP zt ≥2(ΔP AGC -ΔP z -ΔP d ).

4. The coordinated control method for rapid peak shaving of a thermal power unit based on extraction steam for heating according to claim 1, characterized in that: The medium-pressure extraction steam valve and the low-pressure extraction steam valve are respectively an electrically adjustable medium-pressure extraction steam valve and an electrically adjustable low-pressure extraction steam valve.

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