Series cascade hydropower station flow cooperative operation control method

Abstract

The invention discloses a flow cooperative operation control method for cascade hydropower stations in series connection, which comprises the following steps of: responding to a planned load adjustment instruction from a power grid, obtaining unit guide vane opening degrees in a stable state by a load distribution method of each unit based on a cascade hydropower station flow cooperative principle, and taking the unit guide vane opening degrees as target guide vane opening degrees; then the current unit guide vane opening degree is opened / closed to the target guide vane opening degree in a linear mode; or unplanned load disturbance from a user side is responded, a proportional regulation module is added in the PID speed regulator, and the opening degree of the guide vane of the unit is regulated in real time according to the flow deviation of the upper-level hydropower station and the lower-level hydropower station, so that the output of the unit is regulated. The method is used for maintaining the flow collaboration among the cascade power stations after planned load adjustment / unplanned micro load disturbance occurs in the cascade power stations, and it is guaranteed that the power stations can meet the requirement for flow collaboration during normal operation.

Description

Technical Field

[0001] The present invention relates to the technical field of coordinated flow control of series cascade hydropower stations, and in particular to a coordinated flow operation control method of series cascade hydropower stations. Background Art

[0002] Hydropower plays an important role in the development of renewable energy. Its operational flexibility and high response speed enable it to undertake important tasks such as peak load regulation and frequency regulation in the power grid, which is of great significance for maintaining the safety and stability of the power grid. Due to the limitations of conventional hydropower stations and turbines, it is currently impossible to develop and utilize ultra-high head water energy resources. Therefore, it is possible to consider using series cascade hydropower stations to develop ultra-high head water energy resources in stages.

[0003] Cascade hydropower stations are usually connected by regulating ponds and diversion tunnels. Figure 1 As shown, each power station includes a surge tank and at least one unit. The first power station is connected to the upper reservoir (upstream reservoir) through a water diversion tunnel, and the last power station is connected to the lower reservoir (downstream reservoir). The regulating pool acts as a large surge tank, which can reduce the fluctuation of the operating head of the cascade hydropower station and play a certain regulating role under accident conditions. Under normal circumstances, the regulating pool is not formed naturally and needs to be excavated artificially, and its volume is relatively small. Therefore, when the series cascade hydropower station is operating normally, it is necessary to ensure that the flow of the upper and lower power stations is equal to prevent large fluctuations in the water level of the regulating pool due to flow mismatch, which will affect the normal operation of the entire series cascade hydropower station system.

[0004] Therefore, when the series cascade hydropower station is operating normally, it is necessary to combine the waterway parameters and unit characteristics to give hydraulic control measures that meet the flow coordination. At the micro level, an operation control strategy that meets the flow coordination during the daily operation of the cascade hydropower station is given. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings and defects of the prior art and to provide a flow coordinated operation control method for a series of cascade hydropower stations, which is used to maintain the flow coordination between the cascade power stations after a planned load adjustment / unplanned small load disturbance occurs in the cascade power stations, so as to ensure that the power stations can meet the flow coordination requirements during normal operation.

[0006] A flow coordinated operation control method for a series cascade hydropower station includes responding to a planned load adjustment instruction from a power grid, a load distribution method for each unit based on the flow coordination principle of the cascade power station, obtaining the guide vane opening of the unit in a stable state as a target guide vane opening, and then opening / closing the current guide vane opening of the unit in a linear manner to the target guide vane opening; or responding to an unplanned load disturbance from a user end, adding a proportional regulation module to a PID speed regulator, and regulating the guide vane opening of the unit in real time according to the flow deviation of the upper and lower hydropower stations, thereby realizing the regulation of the unit output.

[0007] Wherein, based on the load distribution method of each unit in the cascade power station, the guide vane opening of the unit in a stable state is obtained, including the steps of:

[0008] S1. Assume that the reference flow of each power station is Q total ;

[0009] S2. According to the proportion of the output of different units in the same power station to the output of the entire power station, the total reference flow Q of the power station total Allocate and obtain the reference flow Q of each unit T ;

[0010] S3. Based on the reference flow Q of each unit T , calculate the head loss of each pipe section, and deduce the working head H of each unit in the cascade power station according to the water levels of upstream and downstream reservoirs and regulating pools. T ;

[0011] S4. Based on the working water head H of each unit T , Citation flow Q T And the rated speed to obtain the unit speed n of the unit 11 And the unit flow Q 11 ;

[0012] S5. According to the unit speed n 11 And the unit flow Q 11 , by analyzing the unit speed-unit flow characteristic curve Q 11 =f(n 11 , τ) to interpolate and obtain the unit opening τ;

[0013] S6. According to the guide vane opening τ and unit speed n 11 , by analyzing the unit speed-unit torque characteristic curve m 11 =f(n 11 , τ) to obtain the unit moment m of the unit 11 ;

[0014] S7. Based on the unit moment m 11 , perform torque conversion calculation to obtain the unit output P;

[0015] S8. Sum the outputs P of all units in the cascade hydropower station to obtain the total output, and compare it with the target output; if the difference between the total output and the target output is greater than the allowable error, correct the assumed reference flow Q according to the output deviation total And return to execute steps S2-S8, otherwise end the loop calculation to obtain the unit guide vane opening.

[0016] Among them, the unit speed n of the unit 11 And the unit flow Q 11 The calculation formula is:

[0017]

[0018] Where D is the impeller diameter and n is the rated speed of the unit.

[0019] The calculation formula of the unit output is as follows:

[0020]

[0021] Among them, in response to the unplanned load disturbance from the user side, the PID speed regulator first performs unit control adjustment to obtain the first relative guide vane opening caused by the PID speed regulator control, and then based on the additional proportional adjustment link, the second relative guide vane opening caused by the proportional adjustment link is calculated according to the flow deviation of the upper and lower hydropower stations, and based on the first relative guide vane opening and the second relative guide vane opening, the relative opening value of the actual unit guide vane is obtained to realize the adjustment of the unit opening.

[0022] The relative opening value of the actual unit guide vane is the sum of the first relative guide vane opening caused by the PID speed regulator control and the second relative guide vane opening caused by the proportional regulation link.

[0023] Wherein, the PID speed regulator control equation includes:

[0024]

[0025] where b t 、b p 、T d and T n They are the transient slip coefficient, permanent slip coefficient, buffer time constant and differential time constant of the speed regulator; and μ are the relative values ​​of unit speed deviation and guide vane opening deviation respectively.

[0026] The additional proportional adjustment link is controlled by the following formula:

[0027]

[0028] Where T k It is the proportional adjustment coefficient corresponding to the additional proportional adjustment link. It refers to the real-time reference flow deviation of the same numbered unit in the upper and lower hydropower stations. μ1 refers to the relative guide vane opening caused by the PID governor control, and μ2 refers to the relative guide vane opening caused by the proportional regulation link; μ1+μ2 is the relative opening value of the actual unit guide vane.

[0029] Among them, the following formula is used to reverse the relative reference flow of the unit to realize the monitoring of the real-time reference flow of the unit;

[0030]

[0031] Among them, S8, S9 and S 10 is the characteristic parameter of the unit, p represents the relative value of the unit output deviation, and q represents the real-time reference flow of the unit.

[0032] The speed regulator is arranged on the unit, and each unit is equipped with a speed regulator.

[0033] The present invention is applied to the operation control strategy of load adjustment occurring in the normal operation of a series cascade hydropower station. For a planned load adjustment instruction from the power grid, the operation adjustment mode and load distribution strategy that meet the requirements of each unit in the cascade power station are given according to the waterway system parameters of the entire cascade power station and the unit characteristic curves. For an unplanned load disturbance from the user end, the unit flow is inferred by monitoring the output, rotation speed and guide vane opening information of each unit in the cascade power station, and adjustment is performed according to the flow deviation of the upper and lower power stations. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the system layout of a cascade hydropower station with regulating tanks in series according to the technical application of the embodiment of the present invention;

[0035] Figure 2 A flow chart of load distribution for each unit of a series cascade hydropower station proposed in an embodiment of the present invention;

[0036] Figure 3 This is the change process of the total reference flow of each level of power station after the load distribution method of each unit proposed by the present invention is used in the embodiment of the present invention.

[0037] Figure 4 It is the stable domain when an unpredictable small load disturbance occurs when the speed governor control strategy of the present invention is used in the embodiment of the present invention;

[0038] Figure 5 The total flow deviation variation process between power station A and power station B when the speed governor control strategy of the present invention is adopted in the embodiment of the present invention;

[0039] Figure 6The figure shows the variation process of the total flow deviation between power station C and power station B when the speed regulator control strategy of the present invention is adopted in the embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] In view of the requirements for the synergy of the operating flow that needs to be met when developing ultra-high head water resources in the form of cascade hydropower stations, the present invention proposes an operation control strategy for the entire cascade hydropower station system when the load changes. For the planned load adjustment from the power grid, based on the system parameters of the entire cascade power station waterway and the unit characteristic curve, a strategy for determining the reference flow that meets the total output of the cascade power station is given.

[0042] In response to unplanned load disturbances from the user side, the unit flow is inferred by monitoring the output, speed, and guide vane opening information of each unit in the cascade power station, and adjustments are made based on the flow deviation between the upper and lower power stations to eliminate the flow deviation between the cascade power stations in a stable state and ensure flow coordination.

[0043] In response to planned load adjustment instructions from the power grid, Figure 2 The paper presents a load distribution method for the steady-state units of the series-connected cascade hydropower stations that meets the flow coordination requirement. The main steps include the following:

[0044] (a) Assume that the reference flow of each power station is Q total ;

[0045] (b) According to the proportion of the output of different units in the same power station to the total power station output, the total reference flow Q of the power station total Distribute to obtain the reference flow Q of each unit T ;

[0046] (c) After knowing the reference flow of each unit, the head loss of each pipe section can be calculated, and then the working head H of each unit in the cascade power station can be calculated based on the water levels of upstream and downstream reservoirs and regulating pools. T ;

[0047] (d) Obtain the unit speed n of each unit based on the operating head, reference flow and rated speed of each unit 11 And the unit flow Q 11 , the specific formula is: Where D is the runner diameter, n is the rated speed of the unit;

[0048] (e) According to the unit speed n 11 And the unit flow Q 11, by analyzing the unit speed-unit flow characteristic curve (Q 11 =f(n 11 , τ)) to interpolate and obtain the unit opening τ;

[0049] (f) According to the guide vane opening τ and unit speed n 11 , by analyzing the unit speed-unit torque characteristic curve (m 11 =f(n 11 , τ)) to interpolate and obtain the unit moment m of the unit 11 ;

[0050] (g) Based on the unit moment m 11 , combined with the torque conversion formula to obtain the unit output

[0051] (h) The output P of all units in the cascade hydropower station is summed up to obtain the total output, which is then compared with the target output.

[0052] (i) If the difference between the total output and the target output is greater than the allowable error, the assumed reference flow Q is corrected according to the output deviation total And re-execute step (b). If the difference between the total output and the target output is less than the allowable error, the loop calculation ends.

[0053] Through the above steps, all the operating parameters of the unit can be obtained, including guide vane opening, reference flow, working head, unit output and other information. The above steps are the load distribution methods of each unit in the cascade power station that meet the flow coordination requirements. According to the above steps, the guide vane opening of the unit in the stable state can be obtained.

[0054] When the power station receives the load adjustment instruction from the power grid, it can determine the guide vane opening of the unit before and after the load adjustment according to the above steps; and open (or close) the guide vane of the unit in a linear manner to the target guide vane opening. When the hydraulic transition process reaches a stable state, the flow coordination requirements of the cascade power station can be met.

[0055] In response to unplanned load disturbances from the user side, the present invention adds a proportional adjustment link based on the flow deviation of the upper and lower hydropower stations on the basis of the previous PID governor. In the original PID governor control model, a proportional adjustment module based on the flow deviation is added to eliminate the flow deviation between the cascade power stations in a stable state and ensure the flow coordination. The governor control mode proposed by the present invention establishes a hydraulic connection between the upstream and downstream power stations of the cascade hydropower station, so as to carry out unified regulation.

[0056] Among them, the original PID speed regulator control equation is:

[0057]

[0058] where b t 、b p , T d and T n They are the transient slip coefficient, permanent slip coefficient, buffer time constant and differential time constant of the speed regulator; and μ are the relative values ​​of unit speed deviation and guide vane opening deviation respectively.

[0059] The proportional adjustment module added by the present invention on the basis of the original speed regulator is:

[0060]

[0061] Where T k It is the proportional adjustment coefficient corresponding to the additional proportional adjustment module.

[0062] In the above formula, Refers to the flow deviation of the same numbered unit in the upper and lower hydropower stations, μ1 refers to the relative guide vane opening caused by the original PID governor control mode, and μ2 is the relative guide vane opening caused by the proportional adjustment link proposed in the present invention. The actual relative opening value of the guide vane of the unit is: μ1+μ2.

[0063] Since the unit flow cannot be directly monitored, in the present invention, the relative output, relative speed and relative guide vane opening of the unit are monitored in real time, and the formula The relative reference flow of the unit can be inferred by the reverse wave, thereby realizing the monitoring of the real-time reference flow of the unit.

[0064] Among them, S8, S9 and S 10 is the characteristic parameter of the unit, p represents the relative value of the unit output deviation, and q represents the real-time reference flow of the unit.

[0065] The operation control strategy of the present invention is applied to the load adjustment of the series cascade hydropower station during normal operation. The system layout of the series cascade hydropower station is shown in FIG. Figure 1 shown.

[0066] Assuming that the load adjustment instruction from the power grid is 10% of the original output, the total output of the cascade hydropower station under the target state can be obtained according to the load adjustment instruction of the power grid, and the total output is brought into the invention in Figure 2 In the load distribution flow shown, let the total output equal to Figure 2 P set , and calculate to obtain the target guide vane opening of each unit in the cascade hydropower station under the target state. By adjusting the guide vane of the unit to the target guide vane opening in a linear adjustment manner, the total reference flow of the upper and lower hydropower stations can be balanced after reaching a stable state, such as Figure 3 shown.

[0067] Depend on Figure 3 It can be seen that after the cascade hydropower station uses the operation control method for planned load adjustment proposed in the present invention, when the system reaches a stable state, the total reference flow of each level of the power station is consistent.

[0068] Figure 4 It is the system operation stability domain obtained after using the operation control method proposed by the present invention for unplanned small load disturbances.

[0069] Depend on Figure 4 It can be seen that the cascade hydropower station can meet the stability requirements in the joint operation mode by using the speed governor control strategy proposed in the present invention.

[0070] Assuming that the system load disturbance from the user end is 5%, the transient slip coefficient and buffer time constant b in the PID speed regulator are t With T d The value is Figure 4 The winning number is P1. Figure 5 and 6 The allocation is the difference between the total reference flow of power stations A and B and power stations B and C.

[0071] Depend on Figure 5 and Figure 6 It can be seen that for unplanned small load disturbances, after adopting the PID speed regulator control strategy proposed in this invention (T k =0 means that the PID speed regulator control strategy proposed in the present invention is not adopted), the flow difference between the upper and lower hydropower stations gradually approaches 0, which verifies the effectiveness of the PID speed regulator control strategy proposed in the present invention.

[0072] The basic principles and main features of the present invention and the advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0073] Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is therefore intended that all changes falling within the meaning and range of equivalent elements of the claims are included in the present invention.

[0074] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A flow coordinated operation control method for series cascade hydropower stations, characterized in that: In response to the planned load adjustment command from the power grid, the planned load adjustment is distributed among the cascade power stations based on the flow coordination principle of the cascade power stations, the guide vane opening of each unit in a stable state is obtained as the target guide vane opening, and then the guide vane opening of the current unit is opened / closed in a linear manner to the target guide vane opening; Or in response to unplanned load disturbances from the user side, a proportional control module is added to the PID speed regulator to adjust the guide vane opening of the unit in real time according to the flow deviation of the upper and lower hydropower stations, thereby realizing the adjustment of the unit output and at the same time meeting the flow coordination principle of cascade power stations and stability under small load disturbance conditions.

2. The operation control method of the series cascade hydropower station under planned load adjustment according to claim 1 is characterized in that: The load distribution method for each unit based on the flow coordination principle of the cascade power station is used to obtain the guide vane opening of the unit in a stable state, including the following steps: S1. Assume that the reference flow of each power station is Q total ; S2. According to the proportion of the output of different units in the same power station to the output of the entire power station, the total reference flow Q of the power station total Allocate and obtain the reference flow Q of each unit T ; S3. Based on the reference flow Q of each unit T , calculate the head loss of each pipe section, and deduce the working head H of each unit in the cascade power station according to the water levels of upstream and downstream reservoirs and regulating pools. T ; S4. Based on the working water head H of each unit T , Citation flow Q T And the rated speed to obtain the unit speed n of the unit 11 And the unit flow Q 11 ; S5. According to the unit speed n 11 And the unit flow Q 11 , by analyzing the unit speed-unit flow characteristic curve Q 11 =f(n 11 , τ) to interpolate and obtain the unit opening τ; S6. According to the guide vane opening τ and unit speed n 11 , by analyzing the unit speed-unit torque characteristic curve m 11 =f(n 11 , τ) to obtain the unit moment m of the unit 11 ; S7. Based on the unit moment m 11 , perform torque conversion calculation to obtain the unit output P; S8. summing the outputs P of all units in the cascade hydropower station to obtain a total output, and comparing it with the target output; If the difference between the total output and the target output is greater than the allowable error, the assumed reference flow Q is corrected according to the output deviation. total And return to execute steps S2-S8, otherwise end the loop calculation to obtain the unit guide vane opening.

3. The method for coordinated flow control of series cascade hydropower stations according to claim 2, characterized in that: The unit speed n of the unit 11 And the unit flow Q 11 The calculation formula is: Where D is the impeller diameter and n is the rated speed of the unit.

4. The method for coordinated flow operation control of series cascade hydropower stations according to claim 2 is characterized in that: The calculation formula of the unit output is as follows:

5. The method for coordinated flow operation control of series cascade hydropower stations according to claim 1, characterized in that: In response to the unplanned load disturbance from the user side, the PID speed regulator first performs unit control adjustment to obtain the first relative guide vane opening caused by the PID speed regulator control, and then based on the additional proportional adjustment link, the second relative guide vane opening caused by the proportional adjustment link is calculated according to the flow deviation of the upper and lower hydropower stations. Based on the first relative guide vane opening and the second relative guide vane opening, the relative opening value of the actual unit guide vane is obtained to realize the adjustment of the unit opening.

6. The method for coordinated flow operation control of series cascade hydropower stations according to claim 5, characterized in that: The actual relative opening value of the guide vane of the unit is the sum of the first relative guide vane opening caused by the PID speed regulator control and the second relative guide vane opening caused by the proportional control link.

7. The method for coordinated flow operation control of series cascade hydropower stations according to claim 5, characterized in that: The PID speed regulator control equation includes: where b t 、b p , T d and T n They are the transient slip coefficient, permanent slip coefficient, buffer time constant and differential time constant of the speed regulator; and μ are the relative values ​​of unit speed deviation and guide vane opening deviation respectively.

8. The method for coordinated flow operation control of series cascade hydropower stations according to claim 6, characterized in that: The additional proportional regulation link is controlled by the following formula: Where T k It is the proportional adjustment coefficient corresponding to the additional proportional adjustment link. It refers to the real-time reference flow deviation of the same numbered unit in the upper and lower hydropower stations. μ1 refers to the relative guide vane opening caused by the PID governor control, and μ2 refers to the relative guide vane opening caused by the proportional regulation link; μ1+μ2 is the relative opening value of the actual unit guide vane.

9. The method for coordinated flow control of series cascade hydropower stations according to claim 7, characterized in that: The relative reference flow of the unit can be inferred by the following formula to monitor the real-time reference flow of the unit; Among them, S8, S9 and S 10 is the characteristic parameter of the unit, p represents the relative value of the unit output deviation, and q represents the real-time reference flow of the unit.

10. The flow coordinated operation control method of series cascade hydropower stations according to claim 5, characterized in that: The speed regulator is arranged on the unit, and each unit is equipped with a speed regulator.

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