Spray needle switching and evaluation method of six-spray six-fold large impulse turbine

Abstract

The invention discloses a spray needle switching and evaluation method for a six-spray six-fold large impulse turbine, belongs to the technical field of impulse turbines, and provides a spray needle switching mode and a control strategy, a one-dimensional non-constant flow model is adopted in a water diversion system, and a six-spray six-fold impulse turbine calculation model is constructed. Comprising a spray needle switching mode module, a spray needle callback control module, a power correction module, a power opening conversion function module, a power feedback module and the like, the unit power fluctuation characteristic in the spray needle switching process can be accurately simulated, the power fluctuation in the switching process is effectively reduced, the adjusting quality of a water turbine is improved, and guidance can be provided for design and operation of a power station.

Description

Technical Field

[0001] This invention relates to the field of impulse turbine technology, and in particular to a method for switching and evaluating the nozzles of a large six-jet, six-bend impulse turbine. Background Technology

[0002] An impulse turbine is a hydraulic device that converts the potential energy of water into kinetic energy through jets, and then converts that kinetic energy into mechanical energy through buckets. Large impulse turbine units typically employ a "six-jet, six-bend" water distribution control structure. These large "six-jet, six-bend" impulse turbine generator units often need to participate in regulating fluctuations in renewable energy power to meet users' power supply stability requirements. When the renewable energy output is insufficient, the impulse turbine generator unit needs to increase its power output; in this case, all six jets operate at full capacity. Conversely, when the renewable energy output is sufficient, the impulse turbine generator unit needs to reduce its power output, requiring only some jets to operate. Therefore, when such large "six-jet, six-bend" impulse turbine generator units participate in regulating renewable energy power fluctuations, switching between the six jets is necessary to ensure the turbine operates in its high-efficiency range. However, due to insufficient research on jet switching in large impulse turbines, the unit's power fluctuations are significant during jet switching, affecting the unit's regulation quality and stable operation. Therefore, it is necessary to conduct in-depth research on the causes of power fluctuations during the nozzle switching process of impulse turbines and propose corresponding control methods to achieve smooth power changes during nozzle switching, thereby providing a reference for the design and operation of large-scale impulse turbine generator units with "six nozzles and six folds".

[0003] Currently, there are some improved solutions for the switching control of the nozzles of impact turbines, such as the technical solutions disclosed in patent applications with patent numbers ZL200610021890.X, CN201410512846.3, CN115450827A, CN114412697B, and CN202411985636.6.

[0004] However, during the nozzle switching process of an impulse turbine, changes in the flow rate of each nozzle are inevitable, further causing fluctuations in the water pressure of the distribution loop, and thus fluctuations in turbine output during the switching process. Effectively suppressing the power fluctuations caused by nozzle switching is crucial for giant impulse turbines. Current nozzle switching methods focus primarily on the sequence of nozzle movements, lacking methods to suppress power fluctuations caused by nozzle action. While some methods utilize governor PID program parameters and bucket turbine nozzle switching control, they lack methods for evaluating and suppressing the power fluctuations caused by the nozzle switching process. Therefore, there is an urgent need to improve the nozzle switching mode and control method for large impulse turbines with a "six-jet, six-fold" design, and to evaluate the effectiveness of the switching mode to support the power plant design and operation management needs of giant impulse turbines. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for nozzle switching and evaluation of a large-scale six-jet, six-bend large-scale impulse turbine. The water intake system adopts a one-dimensional unsteady flow model to construct a calculation model of the "six-jet, six-bend" impulse turbine. The characteristics of power fluctuations during nozzle switching are studied, and a control strategy for nozzle switching is proposed, thereby effectively reducing power fluctuations during switching and improving the regulation quality of the turbine. This can provide guidance for power plant design and operation.

[0006] The technical solution of the present invention is as follows: A method for switching and evaluating the nozzles of a large-scale six-jet, six-bend large-scale impact turbine includes the following steps: S1. Number the six nozzles of the six-jet, six-bend impact turbine as nozzle 1, nozzle 2, nozzle 3, nozzle 4, nozzle 5, and nozzle 6 in the order of the extension direction of the water distribution ring pipe. Among them, nozzle 1 and nozzle 4 are the first group of nozzles, nozzle 2 and nozzle 5 are the second group of nozzles, and nozzle 3 and nozzle 6 are the third group of nozzles. Determine the switching order of the nozzles as nozzle 2 → nozzle 4 → nozzle 6 → nozzle 4 → nozzle 2. S2. Based on the characteristic curves of 6 single nozzles, a six-nozzle six-fold turbine model is constructed to obtain the efficiency-power relationship curve. The nozzle switching point is determined by the intersection of the iso-efficiency lines. The switching point between 2 nozzles and 4 nozzles is set as P2_4, and the switching point between 4 nozzles and 6 nozzles is set as P4_6. S3. When the target power P (scheduled power or given opening degree) is less than the power corresponding to the P2_4 switching point, the first group of nozzles starts running; when the target power P is in the power range corresponding to the P2_4 switching point to the P4_6 switching point, the first group of nozzles and the second group of nozzles start running; when the target power P is greater than the power corresponding to the P4_6 switching point, the first group of nozzles, the second group of nozzles and the third group of nozzles all start running. S4. When multiple sets of nozzles need to be started, in order to ensure that the opening of each nozzle is consistent, the nozzle that starts running first is subject to callback control. S5. Compensate for the power fluctuation of the unit according to the deviation between the unit's given power and the target power, and convert the unit's given power into a given opening signal through the power-opening conversion function. At the same time, evaluate the power fluctuation, obtain the deviation ΔP between the actual power and the target power of the unit, multiply it by the power slip coefficient 1 / Pr, and finally obtain the opening feedback signal through PI calculation. Add it to the given opening signal to obtain the actual opening given signal of each nozzle, and control the corresponding nozzle. S6. During the needle switching process, the deviation ΔP between the actual power and the target power of the real-time computer group is used to calculate the power fluctuation rate. If the maximum power fluctuation rate If the value exceeds the set allowable value, the control parameters are further optimized and recalculated until the maximum power fluctuation rate is reached. Until it falls below the set allowable value.

[0007] In a further technical solution, in step S3: When P-P2_4≤0, only the first group of nozzles operates. The power is normalized to obtain the normalized power, which is calculated as follows:

[0008] When P-P2_4>0 and P-P4_6≤0, the second group of nozzles will start running simultaneously with the first group of nozzles. The power will be normalized to obtain the normalized power, which is calculated as follows: When P-P4_6 > 0, the first and second groups of nozzles will operate simultaneously, and the third group of nozzles will also operate. The power will be normalized to obtain the normalized power, which is calculated as follows: .

[0009] In a further technical solution, in step S4: When only the first set of nozzles is running, the nozzles do not need to return to their starting position; When P2_4 < P < P4_6, the second group of nozzles will start running simultaneously with the first group. During the startup of the second group, the first group of nozzles will be redirected. The redirection principle is as follows: when hour:

[0010] when hour:

[0011] When P4_6 < P < Pr, where Pr is the rated power of the unit, the third set of nozzles will start operating simultaneously with the first and second sets of nozzles. At this time, the normalized power of the first and second sets of nozzles is equal. During the opening and closing process of the third set of nozzles, the first and second sets of nozzles are adjusted back. The adjustment principle is as follows: when hour:

[0012] when hour: .

[0013] In a further technical solution, in step S5: When the power P2_4 < P < P4_6, the second set of nozzles will start running simultaneously with the first set of nozzles. The compensated normalized power is as follows: when hour: when hour: When P4_6 < P < Pr, the third group of nozzles will also start running simultaneously with the first and second groups of nozzles. The compensated normalized power is as follows: when hour: when hour: .

[0014] In a further technical solution, in step S5, the power-opening degree conversion function is:

[0015] in, To change the opening degree, The opening degree at rated power. For normalized power, This is the intercept, i.e., the unloaded opening.

[0016] In a further technical solution, in step S5, the calculation formula for the opening feedback signal is as follows:

[0017] in, and These are the proportional coefficient and integral coefficient of the feedback loop, respectively, and S is a complex variable.

[0018] In a further technical solution, in step S6, the formula for calculating the power fluctuation rate is as follows: .

[0019] The beneficial effects of this invention are: In the method of this invention, the water diversion system adopts a one-dimensional unsteady flow model to construct a "six-jet, six-bend" impulse turbine calculation model. A jet needle switching mode and control strategy are proposed, including modules such as jet needle switching method, jet needle callback control, power correction, power opening conversion function and power (or frequency) feedback. This can accurately simulate the power fluctuation characteristics of the unit during the jet needle switching process, effectively reduce the power fluctuation during the switching process, improve the regulation quality of the turbine, and provide guidance for power plant design and operation. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the nozzle numbering according to an embodiment of the present invention; Figure 2 This is the efficiency-power relationship curve described in the embodiments of the present invention; Figure 3 This is a schematic diagram of the nozzle switching mode and control principle described in an embodiment of the present invention; Figure 4 This is a diagram illustrating the nozzle switching process described in an embodiment of the present invention; Figure 5 This is the power diagram of the unit as described in the embodiment of the present invention; Figure 6 yes Figure 5 A magnified view of a portion of the image; Figure 7 This is the power fluctuation rate and evaluation chart described in the embodiments of the present invention. Detailed Implementation

[0021] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0022] This embodiment is based on the characteristic curves of six single nozzles (each nozzle is numbered as follows) Figure 1 As shown), a "six-jet, six-bend" turbine model was constructed, and the efficiency-power relationship curve was obtained (as shown). Figure 2 As shown), this serves as the basis for nozzle switching. Taking the simple and effective switching method of 2 nozzles → 4 nozzles → 6 nozzles → 4 nozzles → 2 nozzles as an example, the nozzle switching point is the intersection of the iso-efficiency lines, such as... Figure 2 P2_4 is the switching point between 2-needle and 4-needle configurations, and P4_6 is the switching point between 4-needle and 6-needle configurations. Needle 1 and 4 form the first group, 2 and 5 form the second group, and 3 and 6 form the third group, as detailed below. Figure 1 As shown, the following switching method is established: When the target power (scheduled power) P (or given opening degree) is less than the power corresponding to the P2_4 switching point, the first group of nozzles starts operating; when the target power P is within the power range corresponding to the P2_4 switching point to the P4_6 switching point, the first and second groups of nozzles start operating; when the target power P is greater than the power corresponding to the P4_6 switching point, all three groups of nozzles start operating, and vice versa. When multiple groups of nozzles need to operate, in order to ensure that the nozzle opening degree is consistent, the nozzles that start operating first need to be subject to callback control. The nozzle callback will cause the unit's given power to deviate from the target power, which will inevitably lead to unit power fluctuations. This will be further compensated by the deviation between the unit's given power and the target power. In this way, both the nozzle callback and the unit's given power equal to the target power are satisfied. The given power is further converted into a given opening degree signal through a power-opening degree conversion function to control the nozzles. To further suppress power fluctuations, the power fluctuation situation can be assessed, and the deviation ΔP between the actual power of the unit and the given power can be obtained as a power feedback signal (or frequency deviation can be used as feedback). This effectively smooths the power fluctuations during the nozzle-needle switching process, and the results can provide guidance for the design and operation of large-scale impulse hydropower stations.

[0023] The nozzle switching mode and control principle of the six-jet, six-bend large impact turbine in this embodiment are as follows: Figure 3 As shown, the specific needle switching and evaluation method includes the following steps: I. Spray Needle Switching Method Let the rated power of the unit be Pr, according to Figure 2 Determine the switching point powers P2_4 and P4_6. If the target power (scheduled power) is P, and (P - P2_4) ≤ 0, then only nozzles 1 and 4 will operate. The power will then be normalized to obtain the normalized power, calculated as follows:

[0024] If (P - P2_4) > 0 and (P - P4_6) ≤ 0, in addition to the operation of nozzles 1 and 4, nozzles 2 and 5 will also start running, and their power will be normalized to obtain the normalized power. The normalized power calculation is as follows: If (P - P4_6) > 0, all 6 nozzles will operate, and the power will be normalized to obtain the normalized power. The normalized power is calculated as follows: .

[0025] II. Needle Retraction Control When multiple groups of injection needles are operating, to make the opening degrees of the injection needles consistent, the injection needles that are initially operating need to be callback. When only the 1st injection needle and the 4th injection needle are operating, the injection needles do not need to be callback.

[0026] When the power P2_4 < P < P4_6, in addition to the 1st injection needle and the 4th injection needle operating, the 2nd injection needle and the 5th injection needle will also start operating. During the opening and closing process of the 2nd injection needle and the 5th injection needle, the 1st injection needle and the 4th injection needle need to be callback. Callback principle: If , then the normalized power of the 1st injection needle and the 4th injection needle is equal to , and the normalized power of the 2nd injection needle and the 5th injection needle is equal to ; otherwise, the normalized power of the 1st injection needle and the 4th injection needle is equal to the normalized power of the 2nd injection needle and the 5th injection needle .

[0027] When : When : When the power P4_6 < P < Pr, in addition to the 1st injection needle, the 4th injection needle, the 2nd injection needle, and the 5th injection needle operating, the 3rd injection needle and the 6th injection needle will also start operating. At this time, the normalized power of the 1st injection needle, the 4th injection needle, the 2nd injection needle, and the 5th injection needle is equal. During the startup process of the 3rd injection needle and the 6th injection needle, the 1st injection needle, the 4th injection needle, the 2nd injection needle, and the 5th injection needle need to be callback. Callback principle: If , then the normalized power of the 1st injection needle, the 4th injection needle, the 2nd injection needle, and the 5th injection needle is equal to , and the normalized power of the 3rd injection needle and the 6th injection needle is equal to ; otherwise, the normalized power of the 1st injection needle, the 4th injection needle, the 2nd injection needle, and the 5th injection needle is equal to the normalized power of the 3rd injection needle and the 6th injection needle .

[0028] When :

[0029] When : .

[0030] III. Compensated power The callback of the injection needles will cause the given power of the unit to deviate from the target power, resulting in power fluctuations of the unit. Further correction is made using the deviation between the given power of the unit and the target power, which not only satisfies the callback of the injection needles but also ensures that the given power of the unit is equal to the target power.

[0031] When the power P2_4 < P < P4_6, in addition to the 1st injection needle and the 4th injection needle operating, the 2nd injection needle and the 5th injection needle will also start operating. The compensated normalized power is as follows: When :

[0032] When :

[0033] When the power P4_6 < P < Pr, in addition to the operation of the 1st injection needle, 4th injection needle and 2nd injection needle, 5th injection needle, the 3rd injection needle and 6th injection needle will also start to operate.

[0034] When : When : .

[0035] IV. Power - Opening Conversion Function After obtaining the normalized power, it cannot be directly used as the opening signal because, at a certain power, if the water head is different, the opening will also be different. That is, the power - opening conversion function needs to consider the influence of the water head. A linear function can be considered for conversion: , where k is the slope and b is the intercept; when the normalized power , y = b is the no - load opening. Therefore, the intercept b can be taken as the no - load opening; when the power , k = yr - b is obtained, which means the unit is operating at the rated power, and the corresponding opening yr can be obtained according to the water head. Thus, the power - opening conversion function is: .

[0036] V. Power Fluctuation Evaluation and Feedback First, the power deviation signal ΔP is obtained from the target power signal and the actual power signal of the unit, then multiplied by the power slip coefficient (1 / Pr), and finally the opening feedback signal is obtained through PI calculation:

[0037] Adding it to the above - mentioned opening signal, the actual opening given signal for each injection needle is obtained.

[0038] If the maximum power deviation signal exceeds the expected value, the control parameters , will be further optimized until the requirements are met.

[0039] VI. Evaluation Method During the switching process of the injection needle, the actual power of the unit and the power deviation signal DP from the target power are calculated in real - time, and the power volatility is obtained using the following model: If the maximum power fluctuation rate If the value exceeds the allowable value, the control parameters are further optimized and recalculated until the requirements are met. The allowable value can be set with reference to the "Technical Conditions for Hydropower Turbine Speed ​​Regulation System" (GB / T 9652.1-2019), the "Regulations on Power Grid Dispatch Management", and the "Regulations on Power Grid Connection Operation Management". In this embodiment, the allowable bandwidth for power fluctuation rate is ±2%.

[0040] Example: Taking a large impulse turbine unit as an example, the method proposed in the above embodiment is adopted. The nozzle switching adopts a 2-needle → 4-needle → 6-needle → 4-needle → 2-needle switching mode, and power compensation and power feedback control are performed. The results are shown in [reference needed]. Figure 4 and Figure 5 The simulation was performed on the unit from rated power → no load → rated power → partial power to verify the rationality of the nozzle switching and evaluation method in this embodiment.

[0041] like Figure 4 As shown, during the process of the unit changing from rated power to no-load: 1. First, the opening of the 6 nozzles is reduced synchronously. Then, nozzles 3 and 6 are reduced to their unloaded opening. No nozzles 1, 4, 2, and 5 are returned to their initial opening. 2. Next, nozzles 1, 4, 2, and 5 are simultaneously reduced in size. Then nozzles 2 and 5 continue to close to their unloaded opening, while nozzles 1 and 4 return to their initial opening. 3. Finally, close the first and fourth nozzles to the no-load opening.

[0042] During the process of the unit moving from no-load to rated power, the action sequence of the nozzles is reversed: 1. First, open the first and fourth nozzles to their corresponding rated openings; 2. Next, the 2nd and 5th nozzles gradually open, while the 1st and 4th nozzles retract. When the openings of the 1st and 4th nozzles are the same as those of the 2nd and 5th nozzles, they open together to their corresponding rated openings. 3. Finally, the 3rd and 6th nozzles are opened, and the 1st, 4th, 2nd, and 5th nozzles are returned to their original positions. Once all 6 nozzles are at the same opening, they are opened together to their corresponding rated openings.

[0043] During the process of the unit changing from rated power to partial power: 1. First, the opening of the 6 nozzles is reduced synchronously. Then, nozzles 3 and 6 are reduced to their unloaded opening. No nozzles 1, 4, 2, and 5 are returned to their initial opening. 2. Next, the nozzles 1, 4, 2, and 5 are simultaneously reduced until the operating opening is stable.

[0044] Meanwhile, during the nozzle closing process, the water pressure in the distribution loop increases; during the nozzle opening process, the water pressure in the distribution loop decreases. The nozzle switching and retraction processes cause fluctuations in the water pressure in the distribution loop, resulting in fluctuations in unit power, such as… Figure 5 As shown.

[0045] like Figure 6 As shown, the unit power fluctuation rate during the nozzle switching process is presented to evaluate the power fluctuation situation during nozzle switching. The results show that when only the nozzle switching and callback processes are considered, and a reasonable control strategy is lacking, the maximum power fluctuation rate is... =4.97%, indicating significant power fluctuation; if the power compensation control proposed in this embodiment is added during the nozzle switching and callback process, the maximum power fluctuation rate will be reduced. =1.84%, meeting the allowable bandwidth of less than ±2% power fluctuation rate; if power (or frequency) feedback control is also considered, the maximum power fluctuation rate is further reduced to =1.30%. The results show that the method in this embodiment is very effective, and the research results can provide guidance for engineering design and unit operation.

[0046] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for switching and evaluating the nozzles of a large-scale six-jet, six-bend large-scale impact turbine, characterized in that, Includes the following steps: S1. Number the six nozzles of the six-jet, six-bend impact turbine as nozzle 1, nozzle 2, nozzle 3, nozzle 4, nozzle 5, and nozzle 6 in the order of the extension direction of the water distribution ring pipe. Among them, nozzle 1 and nozzle 4 are the first group of nozzles, nozzle 2 and nozzle 5 are the second group of nozzles, and nozzle 3 and nozzle 6 are the third group of nozzles. Determine the switching order of the nozzles as nozzle 2 → nozzle 4 → nozzle 6 → nozzle 4 → nozzle 2. S2. Based on the characteristic curves of 6 single nozzles, a six-nozzle six-fold turbine model is constructed to obtain the efficiency-power relationship curve. The nozzle switching point is determined by the intersection of the iso-efficiency lines. The switching point between 2 nozzles and 4 nozzles is set as P2_4, and the switching point between 4 nozzles and 6 nozzles is set as P4_6. S3. When the target power P is less than the power corresponding to the P2_4 switching point, the first group of nozzles starts running; when the target power P is in the power range corresponding to the P2_4 switching point to the P4_6 switching point, the first group of nozzles and the second group of nozzles start running; when the target power P is greater than the power corresponding to the P4_6 switching point, the first group of nozzles, the second group of nozzles and the third group of nozzles all start running. S4. When multiple sets of nozzles need to be started, in order to ensure that the opening of each nozzle is consistent, the nozzle that starts running first is subject to callback control. S5. Compensate for the power fluctuation of the unit according to the deviation between the unit's given power and the target power, and convert the unit's given power into a given opening signal through the power-opening conversion function. At the same time, evaluate the power fluctuation, obtain the deviation ΔP between the actual power and the target power of the unit, multiply it by the power slip coefficient 1 / Pr, and finally obtain the opening feedback signal through PI calculation. Add it to the given opening signal to obtain the actual opening given signal of each nozzle, and control the corresponding nozzle. S6. During the needle switching process, the deviation ΔP between the actual power and the target power of the real-time computer group is used to calculate the power fluctuation rate. If the maximum power fluctuation rate If the value exceeds the set allowable value, the control parameters are further optimized and recalculated until the maximum power fluctuation rate is reached. Until it falls below the set allowable value.

2. The method for switching and evaluating the nozzles of a large-scale impact turbine with six jets and six bends as described in claim 1, characterized in that, In step S3: When P-P2_4≤0, only the first group of nozzles operates. The power is normalized to obtain the normalized power, which is calculated as follows: ； When P-P2_4>0 and P-P4_6≤0, the second group of nozzles will start running simultaneously with the first group of nozzles. The power will be normalized to obtain the normalized power, which is calculated as follows: ； When P-P4_6 > 0, the first and second groups of nozzles will operate simultaneously, and the third group of nozzles will also operate. The power will be normalized to obtain the normalized power, which is calculated as follows: 。 3. The method for switching and evaluating the nozzles of a large-scale impact turbine with six jets and six bends as described in claim 2, characterized in that, In step S4: When only the first set of nozzles is running, the nozzles do not need to return to their starting position; When P2_4 < P < P4_6, the second group of nozzles will start running simultaneously with the first group. During the startup of the second group, the first group of nozzles will be redirected. The redirection principle is as follows: when- hour: ； when- hour: ； When P4_6 < P < Pr, where Pr is the rated power of the unit, the third set of nozzles will start operating simultaneously with the first and second sets of nozzles. At this time, the normalized power of the first and second sets of nozzles is equal. During the opening and closing process of the third set of nozzles, the first and second sets of nozzles are adjusted back. The adjustment principle is as follows: when hour: ； when hour: 。 4. The method for switching and evaluating the nozzles of a large-scale impact turbine with six jets and six bends as described in claim 3, characterized in that, In step S5: When the power P2_4 < P < P4_6, the second set of nozzles will start running simultaneously with the first set of nozzles. The compensated normalized power is as follows: when hour: ； when hour: ； When P4_6 < P < Pr, the third group of nozzles will also start running simultaneously with the first and second groups of nozzles. The compensated normalized power is as follows: when hour: ； when hour: 。 5. The method for switching and evaluating the nozzles of a large-scale impact turbine with six jets and six bends as described in claim 4, characterized in that, In step S5, the power-opening conversion function is: ； in, To change the opening degree, The opening degree at rated power. For normalized power, This is the intercept, i.e., the unloaded opening.

6. The method for switching and evaluating the nozzles of a large-scale impact turbine with six jets and six bends as described in claim 5, characterized in that, In step S5, the calculation formula for the opening feedback signal is as follows: ； in, and denoted as the proportional coefficient and integral coefficient of the feedback loop, respectively, and s is a complex variable.

7. The method for switching and evaluating the nozzles of a large-scale impact turbine with six jets and six bends as described in claim 1, characterized in that, In step S6, the power fluctuation rate The calculation formula is as follows: 。

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