Power control method for combined heat and power production coal generator set

Abstract

The invention relates to the technical field of combined heat and power generation, in particular to a combined heat and power generation coal power unit power control method. According to the method, the strong hysteresis of heat supply temperature parameters of the cogeneration unit and the good heat storage capacity of a heat supply system can be fully excavated and utilized, so that the reserved allowance of primary frequency modulation throttling of the main steam regulating valve is released, and the economic performance and stability of the unit are improved. According to the method, received frequency deviation is coordinated between a primary frequency modulation loop of a heating steam regulating valve and a primary frequency modulation loop of a main steam regulating valve according to deviation characteristics, and a primary frequency modulation service reward and punishment mechanism and a heat supply protocol limiting condition are introduced as constraint conditions of the two regulating loops at the same time; therefore, coordination control of the electric power and the heat supply power is completed, and benefit optimization of overall energy output of the unit is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of cogeneration, and particularly relates to a power control method for a cogeneration coal-fired power generation unit. Background Art

[0002] In the northern region, the heating demand is relatively large, and the installed capacity of heating units accounts for a certain proportion. In addition, with the increase in industrial heat load in industrial parks, the units for industrial heating also account for a certain proportion. With the access of more and more new energy power stations such as wind and light, the power grid is subject to more and more fluctuations. In order to respond to the active power fluctuations of the power grid, heating units set a large throttle degree of the main steam regulating valve, which affects the economy of the units. Since most of the fluctuations in the power grid frequency are small fluctuations with strong randomness, it is of great significance to improve the flexibility and economy of the units in coping with most small fluctuations. At the same time, with the promulgation of the power grid auxiliary service management measures, avoiding the penalty caused by insufficient frequency regulation and striving for the benefits brought by high-quality frequency regulation are important considerations for improving the unit performance. On the other hand, the heat production control of traditional cogeneration units is relatively rough, mostly single-loop flow control or temperature control, lacking interaction and coordination with power production.

[0003] At present, the primary frequency regulation of coal-fired power generation units adopts the method of throttling the main steam regulating valve of the steam turbine. By increasing the set value of the main steam, the opening of the main steam regulating valve is reduced, so that the unit stores enough energy to quickly respond to the demand for power increase by opening the regulating valve when the primary frequency regulation deviation of the power grid exceeds the dead zone set value of the primary frequency regulation loop. The heat production control is mostly single-loop flow control or temperature control.

[0004] At present, the method of using the main steam regulating valve of the steam turbine to throttle for frequency regulation causes the heat obtained by the boiler through fuel combustion to continuously have throttling losses during the entire operation cycle of the unit, affecting the economy of the unit. For cogeneration units, the power generation side unilaterally responds to the power grid frequency fluctuations through the main steam regulating valve. Although it has rapidity and reliability, the obvious lack of economy and the neglect of the relevance of the heat source pipeline make the overall performance of the unit lack flexibility. Therefore, how to take the thermal and electric production of cogeneration units as an organic whole and overall respond to the power grid frequency regulation and the heat demand of the heat network is a problem to be solved. Summary of the Invention

[0005] The problem to be solved by the present invention is to propose a method for organically coordinating the heating steam regulating valve and the main steam regulating valve to respond to the power grid frequency regulation and the heat demand of the heat network, so as to increase the flexibility, economy and self-adaptability of the unit frequency regulation.

[0006] In view of the deficiencies of the prior art, the technical solution adopted by the present invention to solve its technical problems is: a power control method for a cogeneration coal-fired power generation unit, including the following steps:

[0007] S1: The heating steam regulating valve CV1 receives the instruction S of the heat network power regulation loop TP or the instruction S of the frequency regulation control loop FP ;

[0008] S2: The instruction S of the heat network power regulation loop TP switches to the instruction S of the frequency regulation control loop FP when the primary frequency modulation activation signal of the heating steam regulating valve CV1 is present;

[0009] S3: The instruction S of the heat network control loop TP is generated through the cascaded PID controller one and PID controller two; S4: The instruction S of the frequency regulation control loop FP is generated through the output of PID controller three.

[0010] Preferably, the input end of PID controller one receives the output of accumulator S1, an accumulator S2 is arranged between PID controller one and PID controller two, and the output of PID controller two generates the instruction S of the heat network power regulation loop after passing through accumulator S3 TP .

[0011] Preferably, accumulator S1 inputs the set value of the heat network supply water temperature and subtracts the detected value T of the heat network supply water temperature S1 and then outputs;

[0012] The input of accumulator S2 also includes the steam flow set value function and the detected value F of the heating steam flow S3 ;

[0013] The input of accumulator S3 also includes the prediction and influence factor model A.

[0014] Preferably, the calculation method of the prediction and influence factor model A is as follows:

[0015] A = e -αt ΔT 30 + e -βt ΔT 60 + e -γt ΔT 90 ,

[0016] where:

[0017] ΔT 30 is the deviation between the predicted value of the heat network supply water temperature after 30s and the set value of the heat network supply water temperature; ΔT 60 is the deviation between the predicted value of the heat network supply water temperature after 60s and the set value of the heat network supply water temperature; ΔT 90 is the deviation between the predicted value of the heat network supply water temperature after 90s and the set value of the heat network supply water temperature;

[0018] α, β, and γ are set model influence factors, where 0 < α < β < γ.

[0019] Preferably, the trigger condition for sending the prediction and influence factor model A to the accumulator S3 is that, on the premise that the operator does not reject the action of the prediction and influence factor model A, the real-time deviation between the set value of the hot water supply temperature of the heat network and the detected value T of the hot water supply temperature of the heat network S1 is greater than the set value, or the deviation between the set value of the hot water supply temperature of the heat network and the predicted value of the hot water supply temperature of the heat network is greater than the set value.

[0020] Preferably, the difference between the detected value P of the unit power of the three-input of the PID controller W and the set value D of the unit power SP is the output of the accumulator SA1. The accumulator SA1 includes the output of the unit power command through the high / low limiter and the maximum rate limiter, and the output of the frequency deviation through the power function ΔP(Δf, t). SP

[0021] Preferably, the generation of the primary frequency modulation activation signal of the heating steam regulating valve CV1 includes the following steps:

[0022] Step 1: Read the detected value P of the unit power W ;

[0023] Step 2: Determine whether the frequency deviation exceeds the dead zone set threshold. If so, the primary frequency modulation loop of the main steam regulating valve CV5 is started, and at the same time, a timer is started; the timer calculates the cumulative time t S and estimates the theoretical integral power ΔQJY'; calculates the actual integral power ΔQSY according to the theoretical integral power ΔQJY'; the theoretical integral power ΔQJY' and the actual integral power ΔQSY are sent to the assessment evaluator; the assessment evaluator outputs two signals: safe and non-safe;

[0024] Step 3: Condition 1: Determine whether the frequency deviation does not belong to the small deviation; Condition 2: The frequency deviation belongs to the small deviation and the assessment evaluator evaluates it as non-safe. If either Condition 1 or Condition 2 is satisfied, go to Step 4;

[0025] Step 4: Determine whether the detected value T of the hot water supply temperature of the heat network S1 belongs to [t cmin +Δt sb , t cmax -Δt st . If so, generate a true value signal 1 and send it to the true value signal holder;

[0026] Step 5: The true value signal holder sets the trigger condition TR. The trigger condition TR is 1 and while satisfying Step 4 and the output of the true value signal holder is 0, generate the primary frequency modulation activation signal of the heating steam regulating valve CV1.

[0027] Preferably, the condition for the trigger condition TR to be 1 is: the cumulative time t S exceeds its set value or the event drive caused by the prediction of the heat supply network water supply temperature exceeding the limit is established.

[0028] Preferably, the event drive for the prediction of the heat supply network water supply temperature exceeding the limit logic is respectively output by a 2-out-of-3 logic discriminator after the predicted values of the heat supply network water supply temperature exceed the set high and low thresholds after 30s, 60s, and 90s.

[0029] Preferably, the judgment logic of the assessment evaluator in step 2 is:

[0030] Output safety when ΔQSY > Ks * K1 * ΔQJY';

[0031] Output non-safety when ΔQSY ≯ Ks * K1 * ΔQJY';

[0032] where K1 is a coefficient set according to the penalty mechanism of the power grid where the unit is located; Ks is a comprehensive adjustment coefficient.

[0033] The beneficial effects of the present invention are as follows: The method of the present invention can fully exploit and utilize the strong hysteresis of the heating temperature parameters of the cogeneration unit and the good heat storage capacity of the heating system to release the reserved margin of the primary frequency modulation throttling of the main steam control valve, improving the economic performance and stability of the unit. The method of the present invention coordinates the received frequency deviation between the primary frequency modulation loop of the heating steam control valve and the primary frequency modulation loop of the main steam control valve according to the deviation characteristics, and at the same time introduces the primary frequency modulation service reward and punishment mechanism and the heating agreement limit conditions as the constraint conditions for the above two adjustment loops, so as to complete the coordinated control of the electric power and the heating power and realize the benefit optimization of the overall energy output of the unit. Description of the Drawings

[0034] Figure 1 is the schematic diagram of the principle system of the cogeneration coal-fired power unit of the present invention;

[0035] Figure 2 is the unit power regulation control system involved in the present invention;

[0036] Figure 3 is the prediction model of the heat supply network water supply temperature involved in the present invention;

[0037] Figure 4 is the method diagram for generating the primary frequency modulation activation signal of the heating steam control valve CV1 involved in the present invention. Detailed Embodiments

[0038] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are given for purposes of illustration and description, and are not exhaustive or limiting of the invention to the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles of the present invention and its practical applications, and to enable those of ordinary skill in the art to understand the present invention and thus design various embodiments with various modifications suitable for specific purposes.

[0039] A power control method for a cogeneration coal-fired power generation unit proposed by the present invention is based on a cogeneration unit of coal-fired power generation. Its schematic system diagram is as shown in FIG. 1. The coal-fired boiler generates main steam, which is delivered to the steam turbine through the main steam valve DV1 and the main steam regulating valve CV5 for expansion, driving the rotation of the shaft system of the steam turbine generator set to drive the generator to generate electric energy. At the same time, the extracted steam from the steam turbine is used as the heating heat source for the heat network water circuit. After heat exchange with the water circuit through the installed heating heater, it is delivered to the condensate recovery device for recycling. A regulating valve CV2 and a temperature detection element T are provided on the pipeline to the condensate recovery device. C1 An isolation valve MV1 and a heating steam regulating valve CV1 are provided on the pipeline of the extracted steam from the steam turbine to the heater. A heating steam pressure detection element P is provided in front of the isolation valve MV1. S2 a heating steam flow detection element F S2 and a heating steam temperature detection element T S2 are provided. A heating steam pressure detection element P is provided behind the heating steam regulating valve CV1. S3 and a flow detection element F S3 are provided. Another path of the extracted steam from the steam turbine is delivered to the deaerator for the heat network, which is used as the heating heat source for the deaerator. A regulating valve CV3 is provided on the pipeline to the deaerator for the heat network to adjust the pressure P D1 of the deaerator to the set value. The make-up water for the deaerator comes from chemical demineralized water. A regulating valve CV4 is provided on the pipeline from the demineralized water to the deaerator to adjust the liquid level L D1 of the deaerator to the set value. The water in the deaerator is supplemented to the heat network return water circuit through the installed variable-frequency make-up water pump MUP. A flow detection element F is provided at the outlet of the make-up water pump. M1 A pressure detection element P is provided on the heat network return water pipeline. R1 and a pressure detection element P R2 are provided, a temperature detection element T R1 and a temperature detection element T R2 are provided, and a flow detection element F R1 is provided. A filter and a variable-frequency circulating pump CP are provided after the access point of the pipeline from the make-up water pump to the heat network return water pipeline. The circulating pump CP delivers the heat network water to the heater for heat exchange with the heating extracted steam from the steam turbine, and the qualified hot water is sent to the heat network supply water circuit. A pressure detection element P is provided at the outlet of the heater. S1 a flow detection element FS1 and the temperature detection element T S1 .

[0040] The core regulating element of the cogeneration coal-fired power unit adopts the heating steam regulating valve CV1, and its power regulation control strategy is as Figure 2 shown. The heating steam regulating valve CV1 receives the instruction S of the heat network power regulation loop TP or the instruction S of the frequency regulation control loop FP . The heat network power regulation loop of the heating steam regulating valve CV1 is set in a series connection mode of PID controller 1 and PID controller 2. Among them, PID controller 1 receives the output of the accumulator S1, and the output of the accumulator S1 is sent to the deviation between the set value of the heat network supply water temperature and the detected value T S1 of the heat network supply water temperature. The deviation output by the accumulator S1 is used to calculate the control instruction for the deviation through the proportional, integral, and differential actions of PID controller 1. The output of PID controller 1 is accumulated to the accumulator S2. Another input of the accumulator S2 is the steam flow fixed value function. The set value of the steam flow of the heat network heater is the sum of the steam flow fixed value function and the output value of PID controller 1. The set value of the steam flow of the heat network heater and the detected value F S3 of the heating steam flow obtain the deviation through the accumulator S2. The deviation value output by the accumulator S2 is used to calculate the control instruction for the deviation through the proportional, integral, and differential actions of PID controller 2.

[0041] The steam flow fixed value function calculates the steam enthalpy value according to the heating steam temperature T S2 , the heating steam pressure P S3 , and the heat network temperature T S2 . It calculates the circulating water enthalpy value according to the circulating water temperature, and obtains the required heating steam amount under the real-time working conditions on the circulating water side according to the law of conservation of energy to improve the speed of heating temperature control. Specifically:

[0042] F 循环水 = f1 (circulating water pump speed) (Equation 1),

[0043] [F S3 set value × (H 汽 (P S3 , T S2 ) - H 水 (T C1 ))] × (1 - K) = F S1 × H 水 (T S1 ) - F 循环水 × H 水 (T R2 ) (Equation 2),

[0044] Among them:

[0045] F 循环水is the circulating water flow rate;

[0046] f1 is the function for obtaining the circulating water flow rate from the rotational speed of the circulating water pump;

[0047] K is the set loss rate, usually taken as 0.95 - 0.98, and can be corrected according to the system performance test results;

[0048] F S3 The set value is the heating steam flow rate F S3 The corresponding set value;

[0049] H 汽 and H 水 are respectively the enthalpy value calculation functions.

[0050] The outputs of the PID controller II are accumulated to the accumulator S3, and the output S of S3 TP is the command for the heat network power regulation loop. The heating steam regulating valve CV1 receives S TP and performs the control output for the heating loop. Another input to the accumulator S3 is the output influence factor A of the prediction and influence factor model based on the historical operation data of the system, and its calculation is shown in Equation 3:

[0051] A = e -αt ΔT 30 + e -βt ΔT 60 + e -γt ΔT 90 (Equation 3),

[0052] where:

[0053] ΔT 30 is the deviation between the predicted value of the heat network supply water temperature after 30s and the set value of the heat network supply water temperature;

[0054] ΔT 60 is the deviation between the predicted value of the heat network supply water temperature after 60s and the set value of the heat network supply water temperature;

[0055] ΔT 90 is the deviation between the predicted value of the heat network supply water temperature after 90s and the set value of the heat network supply water temperature;

[0056] α, β, γ are the set model influence factors, where 0 < α < β < γ.

[0057] The model selects the RBF neural network model, and the activation function selects the Gaussian function. The weight correction adopts the gradient descent method.

[0058] The evaluation function selects that the mean square error between the predicted value and the actual value is less than the set value.

[0059] Such as Figure 3Shown is the prediction model for the temperature of the hot water supply to the heat network. The relevant input data selects the inlet flow rate of the heating heater (F R1 +F M1 ), the inlet temperature T R2 of the heating heater, the valve position of the steam regulating valve for the hot water supply of the heat network, d(valve position of the steam regulating valve for the hot water supply of the heat network) / dt, the temperature T S2 of the steam supply to the heat network, and the pressure P S3 of the steam supply to the heat network. The screening of historical data needs to cover as many state data as possible, such as steady-state conditions and variable operating conditions, so that the model can better adapt to the operating units. The model is trained externally and continuously iteratively updated according to the accumulation of operation data. The 30s, 60s, and 90s models proposed by this method are trained based on the same input vector database respectively, and the corresponding true values are calibrated according to the true values after time delay, so that the grouped models match the usage scenarios. The predicted values of the temperature of the hot water supply to the heat network after 30s, the predicted values of the temperature of the hot water supply to the heat network after 60s, and the predicted values of the temperature of the hot water supply to the heat network after 90s are compared with their respective set values respectively. If 2 out of the 3 comparison results exceed the limit, an event-driven is established. The establishment of the event-driven means that the prediction of the temperature of the hot water supply to the heat network exceeds the limit. The predicted values of the temperature of the hot water supply to the heat network after 30s, the predicted values of the temperature of the hot water supply to the heat network after 60s, and the predicted values of the temperature of the hot water supply to the heat network after 90s are compared with the set value of the temperature of the hot water supply to the heat network respectively. If 2 out of the 3 comparison results exceed the limit, a large prediction deviation is output.

[0060] To increase the robustness of power control, improve the correction speed of the control loop under large deviation conditions, and avoid frequent disturbances of the control loop under small deviation conditions, a switch T1 is set at the outlet of the prediction and influence factor model. The switching condition of the switch T1 is: when the operator does not reject the action of the prediction and influence factor model A, the real-time deviation between the set value of the temperature of the hot water supply to the heat network and the detected value T S1 of the temperature of the hot water supply to the heat network is greater than the set value, or the deviation between the set value of the temperature of the hot water supply to the heat network and the predicted value of the temperature of the hot water supply to the heat network is greater than the set value. Among them, the logic that the deviation between the set value of the temperature of the hot water supply to the heat network and the predicted value of the temperature of the hot water supply to the heat network is greater than the set value is output respectively by the deviation between the predicted values of the temperature of the hot water supply to the heat network after 30s, 60s, and 90s and the set value of the temperature of the hot water supply to the heat network after passing through a 2-out-of-3 logic discriminator. See Figure 3 the prediction model of the temperature of the hot water supply to the heat network.

[0061] The heating steam regulating valve CV1 will also receive the command S FP of the frequency regulation control loop for primary frequency modulation control. The command S FP of the frequency regulation control loop is output through the PID controller. The command S TP of the hot water network power regulation loop is switched to the command S FPThe switching condition is the primary frequency regulation activation signal of the heating steam control valve CV1. The primary frequency regulation activation signal of the heating steam control valve CV1 triggers the selector T2 to make the frequency regulation control loop command S of the heating steam control valve CV1 FP . The three inputs of the PID controller are the unit power set value D SP and the unit power detection value P W . The deviation of the unit power set value D SP is the output of the accumulator SA1. The two inputs of the accumulator SA1 are: 1) the output value after the received unit power command passes through the high / low limiter and the maximum rate limiter; 2) the frequency modulation power component of the frequency deviation through the power function ΔP(Δf, t).

[0062] The high / low limit and the maximum rate limit control the speed increase and load increase rates of the steam turbine through stress calculation to ensure that the thermal stress in the high-pressure cylinder steam chamber and the high-pressure rotor does not exceed the allowable value.

[0063] The influence of the frequency modulation power component caused by the frequency deviation is that when the grid frequency changes exceed the primary frequency regulation dead zone of the unit, the frequency modulation power component function ΔP(Δf, t) of the generator set responding to the frequency deviation change is as follows:

[0064]

[0065] In the formula, △P(△f,t) is the theoretical response output change; △f(t) is the value of the grid frequency exceeding 50±△fsq at time t, positive for high frequency and negative for low frequency, △fsq is the set frequency modulation dead zone; δ% is the unit regulation coefficient; MCR is the rated active power output of the unit.

[0066] The heating steam control valve CV1 and the main steam control valve CV5 of the generator set coordinate to complete the regulation of electric power and thermal power. Since using the main steam control valve for frequency regulation will inevitably bring throttling losses and affect economy. The method proposed in the present invention is based on making full use of the strong hysteresis of the heating temperature parameter of the cogeneration unit and the good heat storage capacity of the heating system, and releasing the reserved margin of the primary frequency regulation throttling of the main steam control valve to improve the economic performance and stability of the unit.

[0067] The generation process of the primary frequency regulation activation signal of the heating steam control valve CV1 in the present invention is shown in Figure 4 , and mainly includes the following steps:

[0068] Step 1, read the unit power detection value;

[0069] Step 2, determine whether the frequency deviation exceeds the dead zone setting threshold? If so, the primary frequency regulation loop of the main steam control valve CV5 is started, and at the same time, a timer is started;

[0070] The timer calculates the cumulative time tS And estimate the theoretical integral power ΔQJY'. Considering that the frequency difference frequency modulation command acting on the unit is mostly a step signal, the calculation of the theoretical integral power for the control method proposed in the present invention starts from the moment when the frequency difference exceeds the set dead zone, that is, the moment when the frequency modulation loop starts. At this time, there is a time difference of 20 s earlier than the calculation of the theoretical integral power for assessment, and the calculation continues for 30 s. Convert the above calculated value into the cumulative power for 1 minute to obtain the estimated theoretical integral power as follows:

[0071]

[0072] As described above, when the timer starts and calculates the cumulative time t S ≥ 20 s, then calculate the actual integral power ΔQSY.

[0073]

[0074] Where: PST is the average actual output within 10 s before the start of the actual integral power calculation module when the grid frequency exceeds 50 ± △fsq and the duration exceeds 20 s; PSt is the actual output of the unit during the adjustment time of 10 s (which can be adjusted according to actual applications) after the start of the actual integral power calculation module when the grid frequency exceeds 50 ± △fsq and the duration exceeds 20 s.

[0075] The estimated theoretical integral power and the actual integral power are sent to the assessment evaluator (10 s value), and the assessment evaluator (10 s value) makes a judgment according to the following formula:

[0076] ΔQSY > Ks * K1 * ΔQJY'? (Formula 7),

[0077] Where K1 is a coefficient set according to the penalty mechanism of the grid where the unit is located, usually between 0.6 and 0.8.

[0078] Ks is a comprehensive adjustment coefficient that adjusts the calculation time of the actual integral power, the theoretical integral power calculated by the 60 s time caliber, and considers calculation deviations and set safety factors, etc.

[0079] When the judgment state of the assessment evaluator (10 s value) is safe, that is, ΔQSY > Ks * K1 * ΔQJY', which means that the primary frequency modulation performance of the unit during one primary frequency modulation assessment and reward cycle estimated according to the 10 s operation state is in a safe state, then output the information "assessment is safe", and the relevant system maintains the current state unchanged. When the judgment state of the assessment evaluator (10 s value) is not safe, that is, ΔQSY ≯ Ks * K1 * ΔQJY', delay for 2 s and send it to step 4.

[0080] It should be noted that the above setting schemes of the timer and the assessment evaluator are established based on a certain grid-side reward and punishment mechanism. During actual use, it is necessary to make adaptive corrections according to the specific regulations of the power grid where the unit is located. The purpose of setting the assessment evaluator is to use the real-time control strategy and its effect of the control loop as a discriminant selection signal for the unit power regulation means under the constraint of the grid-side ancillary service reward and punishment mechanism to effectively coordinate the overall effect of the unit power regulation.

[0081] Step 3: Determine whether the frequency deviation does not belong to the small deviation? If so, go to Step 4.

[0082] Among them, the setting of the small deviation is determined by considering a suitable safety margin after the frequency modulation ability of the main steam control valve CV5 that meets the primary frequency modulation regulation rate requirement under different unit loads. Specifically, the frequency deviation that the main steam control valve CV5 can probably handle according to its own ability belongs to the small deviation, and the setting of this value is a value strongly related to the unit load, which is determined and corrected based on the unit test data and operation data.

[0083] Step 4: Any of the following conditions is satisfied: 1) It is determined in Step 3 that the frequency deviation does not belong to the small deviation; 2) The frequency deviation belongs to the small deviation and the assessment evaluator evaluates it as unsafe, then determine whether the detected value of the heat network supply water temperature belongs to [t cmin +Δt sb ,t cmax -Δt st ? If so, send the truth signal 1 to the truth signal holder.

[0084] Among them, the truth signal holder always keeps the output as 1 when receiving the signal 1, and the output becomes 0 until its trigger condition TR is 1.

[0085] Among them, t cmin and t cmax are respectively the lower limit value and the upper limit value of the assessment temperature stipulated in the heating contract, and Δt sb and Δt st are respectively the set lower boundary safety value and the upper boundary safety value, which are selected as 1 - 3°C according to the system conditions and safety reliability. The function here is to ensure the safe operation of the heating system at the current moment and the safety of the future moment with a small margin.

[0086] In Step 4, the trigger condition TR of the truth signal holder is set to 1 when any of the following conditions occurs: 1) The grid frequency exceeds 50 ± △fsq and the cumulative time t S of the start timer exceeds the set value (which can be set according to the grid assessment and reward calculation rules, such as 80 s, that is, it meets the primary frequency modulation assessment and reward cycle for one set operation); 2) The event drive caused by the prediction overrun of the heat network supply water temperature is established.

[0087] Among them, the over-limit logic for the predicted hot water supply temperature of the heat network is output by a 2-out-of-3 logic discriminator after the predicted values of the hot water supply temperature of the heat network exceed the set high and low thresholds after 30s, 60s, and 90s respectively. Specifically, as Figure 3 shown, the event-driven is established.

[0088] Step 5: The output of the truth signal holder is used as the primary frequency modulation activation signal for the heating steam control valve CV1, acting on Figure 2 the condition of the selector T2 in FP .

[0089] The power control method for the coal-fired cogeneration unit proposed by the present invention realizes the coordinated optimization of the electric power and the heat power by dynamically coordinating the frequency modulation functions of the heating steam control valve CV1 and the main steam control valve CV5, and combining the predicted model of the hot water supply temperature of the heat network and the reward and punishment mechanism. The technical solution makes full use of the heat storage capacity and the heating temperature lag characteristics of the cogeneration unit, reduces the throttling loss of the main steam valve, and significantly improves the economy and the frequency modulation flexibility. The method of the present invention is applicable to the frequency modulation requirements of the new energy high-penetration power grid and has significant industrial application value.

Claims

1. A power control method for a combined heat and power coal-fired power generation unit, characterized in that, It includes the following steps: S1: The heating steam regulating valve CV1 receives the instruction S from the heat network power regulation loop TP or the instruction S from the frequency regulation control loop FP ; S2: Instruction S of the heat network power regulation loop TP Switch to the instruction S of the frequency regulation control loop FP The switching condition is the primary frequency modulation activation signal of the heating steam regulating valve CV1; S3: Heat network control loop command S TP is generated through cascaded PID controller one and PID controller two; S4: Frequency adjustment control loop command S FP is generated through the three outputs of the PID controller.

2. The power control method for a combined heat and power coal-fired power generation unit according to claim 1, wherein One input terminal of the PID controller receives the output of the accumulator S1. An accumulator S2 is provided between the first PID controller and the second PID controller. The output of the second PID controller generates the heat network power regulation loop command S after passing through the accumulator S3. TP .

3. The power control method for a combined heat and power coal-fired power generation unit according to claim 2, wherein The accumulator S1 inputs the set value of the hot water supply temperature of the heat supply network and the detected value T of the hot water supply temperature of the heat supply network, S1 and outputs the result after taking the difference; the inputs of the accumulator S2 also include the fixed value function of the steam flow rate and the detected value F of the heating steam flow rate S3 ; The input of accumulator S3 also includes the prediction and impact factor model A.

4. The power control method for a cogeneration coal-fired power generation unit according to claim 3, wherein The calculation method of the prediction and impact factor model A is as follows: A = e -αt ΔT 30 + e -βt ΔT 60 + e -γt ΔT 90 , Where: ΔT 30 is the deviation between the predicted value of the hot water supply temperature of the heat network after 30 s and the set value of the hot water supply temperature of the heat network; ΔT 60 is the deviation between the predicted value of the hot water supply temperature of the heating network after 60 s and the set value of the hot water supply temperature of the heating network; ΔT 90 is the deviation between the predicted value of the hot water supply temperature of the heat network after 90s and the set value of the hot water supply temperature of the heat network; α, β, and γ are the set model impact factors, where 0 < α < β < γ.

5. The power control method for a combined heat and power coal-fired power generation unit according to claim 4, characterized in that The trigger condition for the prediction and impact factor model A to be sent to the accumulator S3 is that, on the premise that the operator does not reject the effect of the prediction and impact factor model A, the real-time deviation between the set value of the supply water temperature of the heat network and the detected value T of the supply water temperature of the heat network S1 is greater than the set value, or the deviation between the set value of the supply water temperature of the heat network and the predicted value of the supply water temperature of the heat network is greater than the set value.

6. The power control method for a cogeneration coal-fired power generation unit according to claim 1, wherein The detected value P of the unit power of the PID controller's three inputs W and the set value D of the unit power SP The difference, the set value D of the unit power SP is the output of the accumulator SA1. The accumulator SA1 includes the outputs of the unit power command through the high / low limiter and the maximum rate limiter, as well as the output of the frequency deviation through the power function ΔP(Δf, t).

7. The power control method of the cogeneration coal-fired power generation unit according to claim 1, characterized in that The generation of the primary frequency modulation activation signal of the heating steam regulating valve CV1 includes the following steps: Step 1, read the power detection value P of the reading unit W ; Step 2: Determine whether the frequency deviation exceeds the dead zone setting threshold. If so, the primary frequency modulation loop of the main steam regulating valve CV5 is started, and at the same time, a timer is started; The timer calculates the cumulative time t S and estimates the theoretical integrated charge ΔQJY'; The actual integrated power ΔQSY is calculated according to the theoretical integrated power ΔQJY'; the theoretical integrated power ΔQJY' and the actual integrated power ΔQSY are sent to the assessment evaluator; the assessment evaluator outputs two signals: safe and unsafe; Step 3: Condition 1: Determine whether the frequency deviation does not belong to a small deviation; Condition 2: The frequency deviation belongs to a small deviation and the assessment evaluator evaluates it as unsafe. If either Condition 1 or Condition 2 is satisfied, go to Step 4; Step 4: Determine whether the detected value T of the hot water supply temperature S1 falls within the range of cmin t + Δt sb , t cmax - Δt st . If so, generate a true signal 1 and send it to the true signal holder; Step 5: The truth signal holder sets the trigger condition TR. The trigger condition TR is 1 and while satisfying Step 4, the output of the truth signal holder is 0, generating the primary frequency modulation activation signal of the heating steam regulating valve CV1.

8. The power control method of the cogeneration coal-fired power generation unit according to claim 7, wherein The condition for the trigger condition TR to be 1 is: the cumulative time t S exceeds its set value or the event drive caused by the prediction of the over-limit of the hot water supply temperature is established.

9. The power control method for a combined heat and power coal-fired power generation unit according to claim 8, wherein, The event drive for the prediction overlimit logic of the hot water supply temperature to the heat network is output by a 2-out-of-3 logic discriminator after the predicted values of the hot water supply temperature to the heat network exceed the set high and low thresholds after 30s, 60s, and 90s respectively.

10. The power control method for a combined heat and power coal-fired power generation unit according to claim 7, wherein The judgment logic of the assessment evaluator in Step 2 is: Output safe when ΔQSY > Ks * K1 * ΔQJY'; Output unsafe when ΔQSY ≯ Ks * K1 * ΔQJY'; Where K1 is a coefficient set according to the penalty mechanism of the power grid where the unit is located; Ks is a comprehensive regulation coefficient.

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