Thermal power generating unit load coordination control method based on shared heat storage

Abstract

The invention discloses a thermal power generating unit load coordination control method based on shared heat storage, which utilizes the heat storage capacity of a heat supply pipe network and takes the heat supply pipe network as an intermediate energy storage link on the premise of not adding energy storage battery, compressed air energy storage and fused salt energy storage system equipment. The large-capacity high-parameter unit with good load response is indirectly adopted to supplement the small-capacity low-parameter unit with poor load response, and the load adjusting rate of the whole plant is increased. The heat supply network jointly connected with the units in the same power plant is used as an energy storage transfer medium, the large-capacity unit with the high load response capacity is used for supplementing the small-capacity unit with the low load response capacity, and the small-capacity unit with the low load response capacity quickly responds to a load instruction through heat storage of the unit and the heat supply network before boiler response. The large-capacity unit with the high load response capacity quickly supplements heat storage of the heat supply network, operation safety of the heat supply network is guaranteed, and the load response rate of the small-capacity unit is increased on the premise that the load response rate of the large-capacity unit is not affected.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power generation units, and in particular relates to a load coordination control method for thermal power generation units based on shared heat storage. Background Art

[0002] With the development of the energy industry, the role of thermal power units has gradually changed from capacity-based power generation to peak and frequency regulation. Thermal power units also have various types according to pressure parameters, including subcritical units and ultra / ultra-supercritical units. There are also obvious differences according to the size of the units. According to the current operating conditions of each type of units, the rate response is slightly different.

[0003] The conventional load coordination control method for thermal power units is as follows: the unit receives the dispatching AGC instruction, which is converted into a load instruction through speed limit operation. The load instruction is sent to the boiler master control and steam turbine master control operation loops respectively, and the boiler instruction and steam turbine instruction are calculated. In the CCS (boiler-machine coordination) mode, the boiler master control closes the loop to adjust the main steam pressure. The boiler instruction is then sent to the fuel master control, air supply master control and water supply master control respectively, and the steam turbine master control closes the loop to adjust the unit power. Each unit has a different load response rate according to the characteristics of the equipment. With the development of the energy industry, the role of thermal power units has gradually changed from capacity-based power generation to peak and frequency regulation, which has put forward higher requirements on the load response rate of the unit. After a long period of operation, the equipment is old, and the shortcoming of insufficient load response rate is exposed due to its own slow boiler response time. In order to improve the load rate response, the existing technologies are roughly divided into:

[0004] 1. Combined with the thermal storage of energy storage batteries, the load response is assisted by the charging and discharging of the energy storage batteries. Limited by the capacity of the energy storage batteries, this method works well when the load command amplitude of the unit is small and the load is not continuously changed in the opposite direction. When the load command amplitude is large or the load is continuously changed in one direction, the effect is not good. In addition, the cost of energy storage batteries is relatively high.

[0005] 2. Utilize the heat storage of the heating network to temporarily adjust the opening of the heating regulating valve to reduce or increase the steam extraction volume to assist in the active power regulation of the unit.

[0006] 3. The use of shared energy storage systems such as compressed air and molten salt energy storage can achieve large-scale access to renewable energy power generation and improve the consumption of renewable energy. As a supporting setting for thermal power units, it can also assist in peak and frequency regulation of thermal power units.

[0007] Among them, the load response rate of the 330MW subcritical unit is slower than that of the 660MW and 1000MW super / ultra-supercritical units. The subcritical units have been in operation for a long time and their auxiliary equipment is old. Due to their own slow boiler response time, the shortcomings of insufficient load response rate are exposed during grid-related operation. It is difficult to increase the load response rate to the expected value by adjusting the control strategy of the unit units.

[0008] Auxiliary load regulation relying on external energy storage also has obvious shortcomings. The existing combined thermal energy storage system has a high cost, and the degree of auxiliary load response rate is limited by the capacity of the energy storage battery, especially when there is a large command or continuous one-way load increase or decrease, the auxiliary effect is poor, and the investment cost may not be recovered considering the battery life. The same problem also exists in the auxiliary load regulation of heat storage relying solely on the heating network. The auxiliary regulation amount is limited by the capacity of the heating network, and the effect of large-scale or continuous one-way load increase or decrease is limited. Shared energy storage systems such as compressed air and molten salt energy storage are in the development stage. It takes a certain amount of time to convert energy storage into electrical energy. They are not suitable for rapid regulation of auxiliary loads, but are more suitable for absorbing renewable energy generation such as wind and solar power. In addition, the capacity of compressed air and molten salt energy storage systems also limits the margin of auxiliary load regulation. Therefore, it is necessary to improve the existing auxiliary load regulation method of thermal power units and propose a new load coordination control method for thermal power units. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a method for load coordination control of thermal power units based on shared heat storage, which makes full use of the heat storage capacity of a heating network, uses the heating network as an intermediate energy storage link, and indirectly adopts large-capacity and high-parameter units with better load response to supplement small-capacity and low-parameter units with poor load response, thereby improving the load regulation rate of the entire plant.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is: providing a load coordination control method for thermal power units based on shared heat storage, the steps comprising:

[0011] S1. According to the historical AGC data, determine the large-capacity unit A with better AGC response performance and the small-capacity unit B with poor AGC response performance in the same heating network, and measure the boiler response time T of unit A and unit B respectively. A0 and T B0 , T A0 <T B0 .

[0012] S2, according to the unit turbine high-pressure valve opening V, the actual value of the main steam pressure p, the sliding pressure setting value p set And the main steam pressure setting value p set1 , where the turbine high-speed opening is the main factor, the actual value of the main steam pressure, the main steam pressure setting value and the sliding pressure setting value are used as reference factors to calculate the load margin S of unit A and unit B respectively A With S B , S = f(p,p set ,p set1 ,V), unit: MW.

[0013] S3. Calculate the heating load and adjustable load capacity of the heating network based on the temperature, pressure and flow parameters of the heating network and their limits. The enthalpy value h=f(T,P). The temperature limits required by the heating network are T h , T l , the pressure limit is P h , P l , the flow rate is Q, and the upper limit of the load that can be allocated is Q×{f(T0,P0)-f(T l ,P l )}, the lower limit of the load that can be deployed is Q×{f(T h ,P h )-f(T0,P0)}, the deployable load shall not be higher than the maximum heating load of the unit; where P0 and T0 are the real-time pressure value and real-time temperature value of the heating network respectively.

[0014] S4, after the boiler responds, the unit can respond to the load command, so it only needs to supplement the insufficient energy storage before the boiler responds, according to the load change amplitude and rate requirements R B , calculate the load adjustment time T0 required to meet the rate requirement (required load adjustment time T0 = variable load amplitude / rate requirement R B ), synchronously adjust the variable load parameters of the boiler of unit B to prevent over-adjustment after the heating network assistance, such as T0<T B0 , then after the load instruction is issued, the load that computer group B needs to supplement before the boiler responds is W S =R B ×T0-S B , the action time is T0, and the variable load feedforward value of boiler 1 is adjusted to 0 within T0. If T0>T B0 , W S =R B ×T B0 -S B , the action time is T B0 , in T B0 Reduce R in time B ×T B0 Boiler feedforward amount as a proportion of the command amplitude. W under load increase condition of unit B S >0: Heating network auxiliary load adjustment, W S ≤0 indicates that the energy storage is sufficient and no heating network assistance is required. Under the load reduction condition of unit B, W S <0: Heating network auxiliary load adjustment, W S ≥0 indicates that the energy storage is sufficient and no heating network assistance is needed. S The opening bias of the heating regulating valve on the B side of the unit is calculated and generated, and the heating regulating valve is directly actuated when the heating network assistance is required. Among them, the rate requirement R B It is generally a known value, based on the dispatch requirements of the power grid in each region, or a clear requirement put forward for a specific unit.

[0015] S5, Unit A boiler has a fast response time, supplements the heat network heat storage, and indirectly assists Unit B in load regulation. The supplementary amount is W S , W S The load is converted into the opening bias of the heating regulating valve of unit A, W S When the heating regulating valve opening is increased to supplement the steam flow entering the heating network, W S When the temperature is less than 0, the opening of the heating regulating valve is reduced to reduce the steam flow entering the heating network. While supplementing the heat storage of the heating network, the boiler variable load feedforward increases W S The equal variable load feedforward bias has an action time of T0, and after T0, the feedforward bias is recovered to 0.

[0016] S6. When the energy storage of unit A is insufficient, the auxiliary load regulation of unit B is stopped, that is, the energy storage S of unit A in the load-raising condition is A Less than -5% rated power, close the heating regulating valve on the A side of the additional unit, or reduce the energy storage S under load conditions A If the rated power is greater than 5%, the heating regulating valve on the A side of the unit will be locked.

[0017] The technical solution of the present invention does not require the installation of additional energy storage batteries, compressed air energy storage and molten salt energy storage system equipment. The present invention utilizes the heating pipeline network commonly connected to the units in the same power plant as the energy storage transfer medium, and adopts large-capacity units with strong load response capabilities to supplement small-capacity units with weak load response capabilities. The small-capacity units with weak load response capabilities use the heat storage of the units themselves and the heat network to quickly respond to load instructions before the boiler responds. The large-capacity units with strong load response capabilities quickly supplement the heat storage of the heat network, which not only ensures the safe operation of the heat network, but also improves the load response rate of the small-capacity units without affecting the load response rate of the large-capacity units. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of calculating the energy storage capacity of the unit of the present invention;

[0019] Figure 2 It is a schematic diagram for calculating the load limit that can be allocated and the load that needs to be allocated for the heating network;

[0020] Figure 3 Schematic diagram of load calculation for shared thermal storage supplementation;

[0021] Figure 4 This is the control logic diagram of the heating regulating valve of unit B;

[0022] Figure 5 This is the control logic diagram of the heating regulating valve of unit A;

[0023] Explanation of symbols in the figure:

[0024] Solid line: analog signal representation; dotted line: switch signal representation;

[0025] H: If the input analog value is higher than a certain set value, the switch signal 1 is sent, otherwise the switch signal 0 is output;

[0026] L: If the input analog value is lower than a certain set value, the switch signal 1 is sent, otherwise the switch signal 0 is output;

[0027] f(x): correspondence function;

[0028] Σ: addition, those with +- are subtraction;

[0029] ×: multiplication;

[0030] AND: phase and;

[0031] OR: phase or;

[0032] T: Switch, if the input switch signal is 1, select the Y-end input as output, if the input switch signal is 0, select the N-end input as output;

[0033] ><: limited amplitude and speed;

[0034] ABS: find the absolute value;

[0035] T-OFF: When the switch input changes from 0 to 1, the switch output is 1 directly. When the input changes from 1 to 0, the switch output is kept at 1 within the set time. After the set time, the output switches to 0. DETAILED DESCRIPTION

[0036] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0037] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a method for load coordination control of thermal power units based on shared heat storage, which makes full use of the heat storage capacity of a heating network, uses the heating network as an intermediate energy storage link, and indirectly adopts large-capacity and high-parameter units with better load response to supplement small-capacity and low-parameter units with poor load response, thereby improving the load regulation rate of the entire plant.

[0038] Taking a power plant model as an example, unit A and unit B are 1000MW ultra-supercritical units and 330MW subcritical units in the power plant respectively. The 1000MW ultra-supercritical unit has a large capacity and a short boiler response time, while the 330MW subcritical unit has a small capacity and a long boiler response time. The 1000MW ultra-supercritical unit is used to supplement the load regulation capacity of the 330MW subcritical unit, including:

[0039] S1. According to the historical AGC data, the large-capacity unit A with better AGC response performance and the small-capacity unit B with poor AGC response performance in the same heat network are determined. The boiler response time of unit A and unit B is 2 minutes and 10 minutes respectively. The boiler response time specifically refers to the interval time from the increase or decrease of the boiler master control instruction to the actual main steam pressure taking effect.

[0040] S2. According to the high-pressure regulating valve position of the steam turbine, the actual value of the main steam pressure of the unit, the sliding pressure setting value and the main steam pressure setting value, the heat storage capacity S of unit A and unit B are calculated in real time. A With S B ,S=f(V,p,p set ,p set1 ),like Figure 1 As shown in MW, different steam turbine equipment types have differences, and generally it is necessary to conduct high-pressure regulating valve switch tests in combination with the unit conditions to obtain different heat storage capacities under different high-pressure regulating valve positions.

[0041] S3. Calculate the heating load and adjustable load capacity of the heating network based on the temperature, pressure and flow parameters of the heating network and their limits. The heating network is a medium-pressure heating network, such as Figure 2 As shown in the figure, the adjustable load limit is calculated based on the operating pressure and temperature range of the heating main pipe and the heating flow rate. The operating pressure range of the medium pressure main pipe is 2.4-2.8 MPa, the operating temperature range of the medium pressure main pipe is 270-330 °C, the enthalpy value h=f(T,P), and the temperature limits required by the heating network are T h =330℃、T l =270℃, the pressure limit is P h =2.8MPa, P l =2.4MPa, the flow rate is Q, and the upper limit of the adjustable load is Q×{f(T0,P0)-f(T l ,P l )}, the upper limit of load reduction that can be adjusted is Q×{f(T h ,P h )-f(T0,P0)}, f(T l ,P l )=2938.35kJ / kg,f(T h ,P h)=3073.45kJ / kg, when the operating pressure and temperature are 2.6MPa and 300℃ respectively, f(T0,P0)=3006.62kJ / kg, assuming that the total medium-pressure heating capacity of the plant is Q=1000t / h, according to the above adjustable load limit calculation formula, it can be concluded that the upper limit of the adjustable load of the heating network is 18.96MW, and the lower limit of the adjustable load is -18.56MW.

[0042] S4, after the boiler responds, the unit can respond to the load command, so it only needs to replenish the insufficient energy storage before the boiler responds, such as Figure 2 As shown in , the insufficient storage capacity is supplemented within the range of the load that can be dispatched by the heat network. Assume that at a certain time, unit B receives a dispatch instruction to increase the load by 15MW, and the rate requirement of unit B is R B =5MW / min, calculate the load adjustment time T0=3min required to meet the rate requirement, which is less than the boiler response time of unit B, indicating that the unit load needs to be supplemented by the unit heat storage and the heat network before the boiler starts to pressurize to reach the target value. After the load instruction is issued, the load that computer unit B needs to supplement before the boiler responds is W S =R B ×T0-S B , if the energy storage capacity of unit B is S B =5MW, the supplementary load is 10MW. Within the range of the heat network load, the heat network assists in adjusting the load by 10MW, such as Figure 3 As shown, the action time is 3 minutes. The opening bias of the heating regulation on the B side of the unit is calculated by the 10MW load. It should be noted that under different heating temperature, pressure and flow parameters, different units have obvious differences in the capacity of the heating regulating valve and the pressure, temperature and flow parameters of the heating network. The corresponding relationship with the load change of the unit is different, and the unit needs to be tested and determined. Simultaneously adjust the variable load feedforward of the unit B boiler to 0 within 3 minutes, quickly adjust the opening of the heating regulating valve on the B side of the unit to reduce the steam extraction, and stop the heating pressure PID calculation on the B side of the unit during the auxiliary load adjustment and keep the output unchanged, such as Figure 4 As shown. Unit A supplements the heat network with 10MW of heat storage simultaneously, quickly adjusts the heating regulating valve on the A side of unit to increase the heat supply, and stops the PID calculation of the heating pressure on the A side of unit during the auxiliary load adjustment period and keeps the output unchanged, as shown. Figure 5 As shown, the boiler variable load feedforward amount is increased by 10MW within 3 minutes. Assume S B =20MW, indicating that the unit has sufficient energy storage and can meet the load requirements by relying on its own energy storage, so it does not need the assistance of the heating network.

[0043] When the energy storage of unit A is insufficient, the auxiliary unit B load adjustment is stopped, such as Figure 5 As shown in the figure, the energy storage S of unit A under load condition is ALess than -50MW, close the heating regulating valve on the A side of the additional unit, or reduce the energy storage S under load conditions A If the power is greater than 50MW, close the heating regulating valve on the A side of the reducing unit.

[0044] In summary, the present invention provides a load coordination control method for thermal power units based on shared heat storage. Under the premise of not adding energy storage devices such as energy storage batteries, compressed air energy storage and molten salt energy storage systems, only relying on the supporting heating pipeline network as an intermediate energy storage medium, the thermal power units connected to the same heat network form complementary load regulation capabilities. Small-capacity units generally have lower pressure parameters, and the load response capabilities of old equipment with a long operating time are relatively weak. Large-capacity units generally have higher pressure parameters and storage capacity than small-capacity units, and their load response capabilities are significantly better than those of small-capacity units. The heat storage of the heat network is used as a load regulation transmission medium, and large-capacity units with better load response capabilities are used to assist small-capacity units with slower load regulation to regulate the load response.

[0045] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A load coordination control method for thermal power units based on shared heat storage, It is characterized in that The steps include: S1: Determine the large-capacity unit A with better AGC response performance and the small-capacity unit B with poor AGC response performance in the same heating network based on historical AGC data, and measure the boiler response time T of unit A and unit B respectively. A0 and T B0 , T A0 <T B0 ; S2: According to the opening of the high-pressure valve of the unit steam turbine V, the actual value of the main steam pressure p, and the sliding pressure setting value p set And the main steam pressure setting value p set1 , where the turbine high-pressure valve opening is the main factor, the actual value of the main steam pressure, the main steam pressure setting value and the sliding pressure setting value are used as reference factors, and the load margin S of unit A and unit B are calculated respectively A With S B ,S=f(V,p,p set ,p set1 ), unit: MW; S3: Calculate the heating load and adjustable load capacity of the heating network according to the temperature, pressure and flow parameters of the heating network and their limits; S4: According to the variable load amplitude and rate requirements R B , calculate the load adjustment time T required to meet the rate requirements 0 , synchronously adjust the variable load parameters of the boiler of unit B to prevent over-adjustment after the heating network assists; S5: Unit A boiler has a fast response time, supplements the heat storage of the heating network, and indirectly assists unit B in load regulation; S6: When the energy storage of unit A is insufficient, the auxiliary load regulation of unit B is stopped, that is, the energy storage S of unit A in the load increase condition is A Less than -5% rated power, close the heating regulating valve on the A side of the additional unit, or reduce the energy storage S under load conditions A If the rated power is greater than 5%, the heating regulating valve on the A side of the unit will be locked.

2. According to claim 1, a method for coordinated control of thermal power unit loads based on shared heat storage, It is characterized in that The specific step S3 is: enthalpy value h = f (T, P), the temperature limits required by the heating network are T h , T l , the pressure limit is P h , P l , the flow rate is Q, and the upper limit of the adjustable load is Q×{f(T 0 ,P 0 )-f(T l ,P l )}, the upper limit of load reduction that can be adjusted is Q×{f(T h ,P h )-f(T 0 ,P 0 )}, the load that can be deployed shall not be higher than the maximum heating load of the unit, where P 0 and T 0 They are the real-time pressure value and real-time temperature value of the heating network respectively.

3. According to claim 1, a method for coordinated control of thermal power unit loads based on shared heat storage, It is characterized in that The boiler variable load parameters of unit B are adjusted synchronously in step S4 as follows: 0 <T B0 , then after the load instruction is issued, the load that computer group B needs to supplement before the boiler responds is W S =R B ×T 0 -S B , the action time is T 0 , synchronized at T 0 Adjust the variable load feedforward value of boiler 1 to 0 within the time, such as T 0 >T B0 , W S =R B ×T B0 -S B , the action time is T B0 , in T B0 Reduce R in time B ×T B0 The amount of boiler feedforward as a percentage of the command amplitude.

4. According to claim 3, a method for coordinated control of thermal power unit loads based on shared heat storage, It is characterized in that In step S4, under the load increase condition of unit B, W S >0: Heating network auxiliary load adjustment, W S ≤0 indicates that the energy storage is sufficient and no heating network assistance is required; Unit B under load reduction condition W S <0: Heating network auxiliary load adjustment, W S ≥0 indicates that the energy storage is sufficient and no heating network assistance is needed; S The opening bias of the heating control valve on the B side of the unit is calculated and generated, and the heating control valve is directly activated when heating network assistance is needed.

5. According to claim 4, a method for coordinated control of thermal power unit loads based on shared heat storage, It is characterized in that In step S5, the boiler of unit A supplements the heat network to store heat, indirectly assisting unit B in load regulation, and the supplement amount is W S , W S The load is converted into the opening bias of the heating regulating valve of unit A, W S When the heating regulating valve opening is increased to supplement the steam flow entering the heating network, W S When <0, reduce the opening of the heating regulating valve to reduce the steam flow entering the heating network.

6. A method for coordinated control of thermal power unit loads based on shared heat storage according to claim 5, It is characterized in that In step S5, while supplementing the heat storage of the heating network, the boiler variable load feedforward increases W S Equal variable load feedforward bias, action time is T 0 , T 0 After the time has passed, the feedforward bias is recovered to 0.

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