CN114623073B - Sequential decision method for pump starting scheme of liquid pipeline for multi-batch sequential transportation - Google Patents
Sequential decision method for pump starting scheme of liquid pipeline for multi-batch sequential transportation Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/06—Control using electricity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/22—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves
- F04B49/225—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves with throttling valves or valves varying the pump inlet opening or the outlet opening
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Abstract
The invention discloses a sequential decision method for a multi-batch sequential transport liquid pipeline pump opening scheme, which relates to the technical field of pipeline transport liquid and solves the technical problems of poor accuracy and poor reliability of the existing pipeline transport pump opening valve opening scheme, and the method comprises the following steps: reading basic parameters and an initial production schedule of the pipeline, and predicting the initial operation condition of the pipeline according to the basic parameters and the initial production schedule; adjusting the initial operation condition according to the implementation condition; introducing model prediction control, and predicting the operation condition of a pipeline at the next stage in real time according to the actual operation condition at the current moment; establishing a pump opening valve opening scheme sequential decision model according to the actual operation condition of the pipeline; solving a sequential decision model of a pump opening valve solving scheme, and outputting the pump opening valve solving scheme in a corresponding period; judging whether a pump opening and valve opening scheme corresponding to the whole plan is solved, and performing the next calculation according to the solving result.
Description
Technical Field
The invention relates to the technical field of pipeline transportation liquid, in particular to a sequential decision method for a pump-on scheme of a multi-batch sequential transportation liquid pipeline.
Background
For the optimization problem of the pump opening and valve opening scheme of the liquid pipeline for multi-batch sequential transportation, the optimization is mainly performed in a manual decision mode at present, the workload is large, the efficiency is low, and the energy-saving factor is difficult to consider. In this regard, corresponding researches have been carried out by the present scholars, and the current optimization method of the pump opening and valve opening scheme of the liquid pipeline for multi-batch sequential transportation predicts the operation condition of the pipeline only according to the initial production plan of the pipeline, and calculates the pump opening and valve opening scheme in the whole planning period according to the operation condition. The pipeline operation condition is complex, and the actual operation condition of the pipeline and the prediction result have deviation; meanwhile, in the running process of the pipeline, the running working condition of the pipeline can be possibly adjusted; in addition, the pressure loss in the pipeline operation process has a continuous time change relation, but the discrete time modeling adopted by the traditional model cannot take the working condition change in the time window into consideration, and at the moment, if the pump opening valve opening scheme still decided according to the original production plan operates, the safety problem is obviously brought, and the effectiveness and the safety of the decided pump opening valve opening scheme are reduced. Moreover, in the traditional model, the pressure reducing valve is not mature, so the model does not consider the action of the pressure reducing valve and has deviation from the actual working condition. In order to adapt to the condition of pipeline operation condition adjustment, the pump opening valve scheme of the current time period needs to be calculated in real time and continuous decision is carried out on the internal working condition of the time window, but if calculation is carried out on all the remaining time periods each time, the solving efficiency is reduced, and real-time calculation is difficult to realize.
Disclosure of Invention
The invention aims to solve the technical problems in the prior art and aims to provide a sequential decision method for a multi-batch sequential transportation liquid pipeline pump starting scheme, which can improve accuracy and reliability.
The technical scheme of the invention is as follows: a method for sequentially deciding on a pump-on scheme of a liquid pipeline for multi-batch sequential transportation, comprising:
s1, reading basic parameters and an initial production schedule of a pipeline, and predicting an initial operation condition of the pipeline according to the basic parameters and the initial production schedule;
s2, adjusting the initial operation condition according to the implementation condition; introducing model prediction control, and predicting the operation condition of the pipeline in the next stage in real time according to the actual operation condition at the current moment;
s3, establishing a pump opening valve opening scheme sequential decision model according to the actual operation condition of the pipeline;
s4, solving the sequential decision model of the pump opening valve opening scheme, and outputting the pump opening valve opening scheme in a corresponding period;
and S5, judging whether a pump opening valve opening scheme corresponding to the whole plan is solved, and performing the next calculation according to the solving result.
As a further improvement, the basic parameters include the in-station pressure, the out-station pressure, the number of pumps, the characteristic parameters of each pump, the pipe diameter of each pipe section, the length of each pipe section and the physical characteristics of liquid of each station along the pipeline;
the initial operating conditions include the following information:
the type of liquid and the corresponding injection flow rate of the liquid injected at each injection station along the pipeline in each period of time in the future;
the liquid types and the corresponding downloading flow downloaded by each downloading station along the pipeline in each time period in the future;
the type of liquid transported by the pipeline along each pipe section in each future period and the corresponding transport flow;
the time when the pipeline performs various operations comprises the time of changing the types of the liquid injected by the pipeline at various injection stations along the pipeline and the corresponding flow, and the time of changing the types of the liquid downloaded by various downloading stations and the corresponding flow;
predicting the time when each liquid mixing interface reaches each station according to the distribution condition of the liquid mixing interface in the pipeline and the flow of the liquid in each pipe section in each period, and dividing the running time of the whole pipeline into T time windows by combining the time when the liquid mixing interface reaches each station and the time when each operation is carried out on the pipeline;
according to the liquid distribution condition of each pipe section of the pipeline at each moment, the linear change relation of the pressure loss between the head and the tail of each pipe section along with the time sequence is predicted, and the decision of a pipeline pump opening and valve opening scheme is carried out based on the linear change relation, and a small time window is automatically divided when the pressure loss exceeds the time limit.
Further, in step S3, the basic structure of the sequential decision model of the pump-opening valve-opening scheme is as shown in formula (1):
in the method, in the process of the invention,
in order to make the objective function of the decision of the tau-th pump opening and valve opening scheme, the running cost of the pipeline in H time periods corresponding to the current time period of the required decision pump opening and valve opening scheme is started, H is the time period number of the optimized pump opening and valve opening scheme for each decision, BP is the basic parameter of the pipeline, IP is the initial production plan of the pipeline, and AP τ For the adjustment of the operating conditions of the pipeline at the beginning of the τ -th period, < >>
The decision variables comprise the start-stop state of each pump in each pump station in the period from t to t+H-1, the lift and pressure provided by each pump station in the period from t to t+H-1 and the station inlet and outlet pressure of each station in the period from t to t+H-1, D is a feasible region, H i And g j Equality constraints and inequality constraints corresponding to the optimization problem, respectively.
Further, if the number T of the time windows to be solved is more than or equal to H, the time period of model solving is H large time windows next to the current moment, and the result of the first large time window in the H large time windows is taken as a pump opening valve opening scheme of the current time period; the objective function when solving the pump opening valve scheme of the current τ period is shown as formula (2):
if the number T < H of time windows to be solved is remained currently, the time period of model solving is T large time windows next to the current moment, and the solving result is taken as a pump opening and valve opening scheme of the last T large time windows; the objective function when solving the pump opening valve scheme for the remaining T time periods is as shown in equation (3):
(2) In the formula (3):
for the pipeline running cost of H time windows corresponding to the τ solving, FE is the unit price of electric quantity,
is a binary variable of the start-stop state of a kth pump in an ith station yard in an nth small time window of a nth large time window, +.>
For the lift of the kth pump in the ith yard in the nth small time window within the nth large time window, +.>
The density of the overdump liquid for the ith yard in the nth small time window within the nth large time window, g is the gravitational acceleration, +.>
For the overdump flow of the ith yard in the nth small time window within the nth large time window, +.>
For the duration in the nth small time window of the nth large time window,/-for the duration in the nth small time window of the nth large time window>
The operating efficiency of the kth pump in the ith yard in the nth small time window within the nth large time window is set.
Further, the relevant constraints in performing the solution of the τ -th pump-on valve-opening scheme include the main pump characteristic constraints,
in the nth small time window in the nth time window, the functional relation constraint between the lift of the kth station pump in the ith station and the pump passing flow of the ith station in the time window is shown as a formula (4):
in the nth small time window in the nth time window, the functional relation constraint between the efficiency of the kth pump in the ith station and the over-pump flow of the ith station in the time window is shown as a formula (5):
the upper and lower limit constraints of the overpump flow rate in the ith yard in the nth small time window within the nth time window are as shown in formulas (6) and (7):
wherein: k (K) i For the number of pumps contained in the ith yard,
is the lower limit of the pump flow of the kth pump in the ith station yard, +.>
The upper limit of the pump flow of the kth pump in the ith yard.
Further, the relevant constraints in performing the solution of the τ -th pump-on valve-opening scheme include pressure constraints,
in the nth small time window within the time window t, the pressure provided by the yard i may be represented by the following formula (8):
the pressure of the inlet of the pipeline at the first station along the line is equal to the pressure provided by the injection pump, namely the pressure constraint of the inlet of the first station is shown as the formula (9):
wherein: PG is the pressure provided by the injection pump;
the ingress/egress pressure constraints for each yard at the beginning and ending times in the nth small time window of the nth time window are shown in equations (10) - (13):
wherein:
for the outbound pressure at the beginning of the ith yard in the nth small time window of the nth large time window, +.>
For the outbound pressure at the end of the ith yard in the nth small time window of the nth large time window,
for the incoming pressure of the ith yard at the beginning of the nth small time window of the nth large time window, +.>
For the incoming pressure of the ith yard at the end time in the nth small time window of the nth large time window, +.>
For the pressure loss of the ith pipe section at the beginning of the nth small time window of the nth large time window,/->
For the pressure loss of the ith pipe section at the end of the nth small time window of the nth large time window,/->
Valve reduced pressure for the ith pipe segment in the nth small time window of the nth large time window;
the inbound pressure upper/lower limit constraints and the outbound pressure upper/lower limit constraints of the yard are as shown in formulas (14) - (17):
further, relevant constraints in performing the solution of the τ -th pump-open valve scheme include, the pump on-off time constraints,
in the nth small time window within the nth time window, the on-off state change constraint for the kth pump in the ith yard is as shown in formulas (18) - (21):
BC t,n,i,k ≥BS t,n,i,k -BS t,n-1,i,k t∈T,n>1,i∈IP,k∈K i (18)
BC t,n,i,k ≥BS t,n-1,i,k -BS t,n,i,k t∈T,n>1,i∈IP,k∈K i (19)
the pump on-off time constraint is as shown in equation (22):
wherein: TA (TA) t' For the start time of the t' th time window, TA t For the start time of the t-th time window, M is a constant, TS i,k Is the minimum continuous running or shut-down time of the kth pump in the ith yard.
Further, the relevant constraints in performing the solution of the τ -th pump-on valve-opening scheme include valve pressure constraints,
the opening degree and the flow coefficient of the outlet regulating valve are shown in the formula (23):
Φ＝Φ 0 e nh (23)
wherein Φ represents the opening of the valve, h represents the flow coefficient, Φ 0 And n is a parameter to be determined;
the flow coefficient and the pressure change before and after valve passing are shown in the formula (24):
wherein C is v Representing flow coefficient, Q representing flow, SG representing fluid gravity, deltaP representing pressure change before and after valve passing;
in the nth small time window in the nth large time window, the state change constraint of the valve in the ith station yard is shown as a formula (25);
further, the relevant constraints in performing the solution of the τ pump-on valve-opening scheme include operating condition adjustment constraints,
the constraints for operating conditions adjustment are shown in equations (26) - (28):
PP τ ＝(1-A τ )PP τ-1 +A τ (PP τ-1 +AP τ ) (26)
wherein: PP (Polypropylene) τ For equivalent production plan when solving the τ -th pump-on valve-opening scheme, A τ In the adjustment state of the operation condition at the tau th moment, if the operation condition is adjusted, A τ =1, otherwise, a τ ＝0，Qpredict(PP τ ) And Dprediction (PP) τ ) Respectively according to PP τ The over-pump flow rate and the over-pump liquid density of each station at each future time are predicted.
Further, if the pump opening and valve opening scheme corresponding to the whole plan is solved, the solution is ended; otherwise, according to the adjustment condition of the actual operation condition;
for the situation that the calculation of the next stage is still needed, according to the constraints (26) - (28), if the operation condition is not adjusted, returning to the step 3 for solving in the dividing mode of the current time window, and subtracting 1 from the number of the time windows which are needed to be solved at the moment on the basis of the original time window, namely changing the number into T-1;
if the operation conditions are adjusted, returning to the step 3 by combining the adjustment conditions of the operation conditions, and predicting the future operation conditions of the pipeline again according to the adjustment, and continuing to execute according to the flow until the solution of the pump opening valve scheme in all time periods is completed.
Advantageous effects
Compared with the prior art, the invention has the advantages that:
1. according to the invention, the continuous time change working condition of pressure loss is considered, the pump opening and valve opening scheme is automatically adjusted if the pressure is over-limited in the discrete large time window, and the small time window is automatically divided for decision making, so that the system safety is ensured.
2. According to the invention, only the pump opening valve opening scheme (except the last T time windows) in the current time window is solved each time, the solving efficiency is high, the actual operation condition adjustment of the pipeline can be taken into consideration by solving the pump opening valve opening scheme each time, and the determined pump opening valve opening scheme has higher precision and better engineering practicability.
3. The invention adopts the model predictive control method, has a certain prospective, can consider the influence of the running condition of the subsequent time period on the current time period, avoids the problem that the single time period decision result is difficult to ensure the global optimality, can effectively improve the global optimality of the decision process while improving the accuracy of the pump opening valve opening scheme, ensures the economy of the decision, and further promotes the energy conservation and consumption reduction.
Drawings
FIG. 1 is a flow chart of a sequential decision making method for a pump-on valve-on scheme for multiple batch sequential transport of liquid pipelines;
FIG. 2 is a schematic diagram of a topology of a plurality of batch sequential transport liquid pipelines in an example;
FIG. 3 is a diagram of a lot migration corresponding to an original production plan in an example;
FIG. 4 is a diagram of a solved pump on scheme;
FIG. 5 is a schematic illustration of the in-out pressure of yard 1;
FIG. 6 is a schematic illustration of the in-out pressure of yard 2;
FIG. 7 is a schematic illustration of the in-out pressure of yard 3;
FIG. 8 is a schematic representation of the in-out pressure of yard 4;
FIG. 9 is a schematic illustration of the in-out pressure of yard 5;
FIG. 10 is a schematic illustration of the in-out pressure of yard 6;
fig. 11 is a schematic diagram of the in-out pressure of the yard 7.
Detailed Description
The invention will be further described with reference to specific embodiments in the drawings.
Referring to fig. 1 to 11, a method for sequentially deciding on a pump-on scheme of a liquid pipeline for multi-batch sequential transportation includes:
s1, reading basic parameters and an initial production schedule of a pipeline, and predicting the initial operation condition of the pipeline according to the basic parameters and the initial production schedule;
s2, adjusting initial operation conditions according to the implementation conditions; introducing model prediction control, and predicting the operation condition of a pipeline at the next stage in real time according to the actual operation condition at the current moment;
s3, establishing a pump opening valve opening scheme sequential decision model according to the actual operation condition of the pipeline;
s4, solving a sequential decision model for unlocking a pump valve opening scheme, and outputting the pump valve opening scheme in a corresponding period;
and S5, judging whether a pump opening valve opening scheme corresponding to the whole plan is solved, and performing the next calculation according to the solving result.
In step S1, the basic parameters include the in-station pressure, the out-station pressure, the number of pumps, the characteristic parameters of each pump, the pipe diameter of each pipe section, the length of each pipe section and the physical characteristics of the liquid in each station along the pipeline.
For the transportation and downloading plans of the pipelines for transporting liquids in sequence in a plurality of batches in the next operation period, related planning staff generally make up according to the demand conditions of the pipelines in the next period of time in each downstream market along the pipeline, and the made pipeline operation plans are generally given in the form of production plans, wherein the production plans are initial production plans of the pipelines. According to the initial production schedule of the pipeline, the initial operating conditions of the pipeline in each period of time in the scheduled execution time, namely, the operating conditions of the initial production schedule, can be predicted. The initial operating conditions include the following information:
(1) the type of liquid and the corresponding injection flow rate of the liquid injected at each injection station along the pipeline in each period of time in the future;
(2) the liquid types and the corresponding downloading flow downloaded by each downloading station along the pipeline in each time period in the future;
(3) the type of liquid transported by the pipeline along each pipe section in each future period and the corresponding transport flow;
(4) the time when the pipeline performs various operations comprises the time of changing the types of the liquid injected by the pipeline at various injection stations along the pipeline and the corresponding flow, and the time of changing the types of the liquid downloaded by various downloading stations and the corresponding flow;
(5) the pipeline adopts a mode of sequential delivery of multiple batches, namely, different types of liquids are delivered in batch sequence through the same pipeline, so that the situation that multiple liquid products exist simultaneously in the pipeline is likely to occur, the mixing section can be formed among the different types of liquids, the length of the mixing section can be ignored compared with the liquid delivery pipeline, the mixing section is regarded as an interface, and the types of the liquids in front of and behind the liquid mixing interface determine the types of the mixing interface. According to the distribution condition of the liquid mixing interfaces in the pipeline and the flow of the liquid in each pipe section in each period, the time when each liquid mixing interface reaches each station is predicted, the time when the liquid mixing interface reaches the station and the time when each operation is carried out on the pipeline are combined, the running time of the whole pipeline is divided into T time windows (time periods), and the adjustment of the pump opening and valve opening scheme of the pipeline is only carried out at each time point of dividing the time windows;
in addition, according to the liquid distribution condition of each time in each pipe section of the pipeline, the linear change relation of the pressure loss between the head and the tail of each pipe section along with the time sequence is predicted, and the decision of a pipeline pump opening and valve opening scheme is carried out based on the linear change relation, and a small time window is automatically divided when the pressure loss exceeds the limit.
In step S2, the operation conditions of the pipeline are predicted due to the basic parameters of the liquid pipeline transported in the step 1 according to the batch sequence and the initial production schedule. The operation condition of the liquid pipeline is complex in a multi-batch sequential transportation mode, the control on each flow and each operation time in the actual operation process is difficult to achieve complete accuracy, namely, certain deviation exists between the actual operation process and the prediction process, in order to ensure that the pipeline can smoothly complete a transportation plan, a dispatcher often adjusts the operation condition of the pipeline, the deviation exists between the actual operation condition of the pipeline and the initial operation condition predicted according to the pipeline initial production plan table, if the decision of a pump opening valve scheme is made according to the initial operation condition in the whole plan execution process of the pipeline, the accuracy and the effectiveness of the decided pump opening valve scheme are gradually reduced along with the continuous increase of the deviation between the operation condition and the prediction condition in the actual operation process, and even the safe operation of the pipeline is difficult to ensure.
In order to improve the effectiveness of a pump opening and valve opening scheme and ensure the safety of pipeline operation, the method introduces a model prediction control method in the decision process of the pump opening and valve opening scheme of the liquid pipeline in multiple batches for sequential transportation, predicts the operation working condition of the pipeline in the next stage in real time according to the actual operation working condition at the current moment, and reduces the deviation between the predicted operation working condition and the actual operation working condition of the pipeline in each period.
The method takes the adjustment of the operation condition of the pipeline at the starting time of the current period as an input parameter, predicts the operation condition of the pipeline in the next period by combining the initial production schedule and the basic parameters of the pipeline, and makes a decision of a pump opening and valve opening scheme based on the prediction.
In addition, for the situation that the constraint overrun exists in the actual operation process of the traditional modeling method possibly caused by the change of the working condition in the time window, the method introduces mixed time modeling, and utilizes the cooperation of the time windows with the size to cope with the dynamic change in the time window.
For the influence of the physical model of the pressure reducing valve on the working condition, the method adopts a data-driven fitting method to approximate the working condition of the pressure reducing valve, so that the pump opening and valve opening model is closer to the real working condition.
In step S3, according to the analysis of the optimization problem characteristics of the pump-opening and valve-opening scheme of the liquid pipeline for multi-batch sequential transportation, a sequential decision model of the pump-opening and valve-opening scheme can be established. The sequential decision model has the characteristics and advantages that real-time optimization can be performed, schemes of a plurality of time intervals in the future can be optimized for each decision, a certain prospective is provided, and the global optimality of the decision process can be improved.
The basic structure of the sequential decision model of the pump opening valve scheme is shown as a formula (1):
in the method, in the process of the invention,
in order to make the objective function of the decision of the tau-th pump opening and valve opening scheme, the running cost of the pipeline in H time periods corresponding to the current time period of the required decision pump opening and valve opening scheme is started, H is the time period number of the optimized pump opening and valve opening scheme for each decision, BP is the basic parameter of the pipeline, IP is the initial production plan of the pipeline, and AP τ For the adjustment of the operating conditions of the pipeline at the beginning of the τ -th period, < >>
The decision variables comprise the start-stop state of each pump in each pump station in the period from t to t+H-1, the lift and pressure provided by each pump station in the period from t to t+H-1 and the station inlet and outlet pressure of each station in the period from t to t+H-1, D is a feasible region, H i And g j Equation reduction corresponding to the optimization problem, respectivelyBeam and inequality constraints. The sequential decision model has the characteristics and advantages that real-time optimization can be performed, schemes of a plurality of time intervals in the future can be optimized for each decision, a certain prospective is provided, and the global optimality of the decision process can be improved.
According to the characteristics of the optimization problem of the pump and valve opening scheme of the liquid pipeline for multi-batch sequential transportation, the specific structure of the sequential decision model is as follows.
(1) Objective function
For each pump opening and valve opening scheme decision solution, if the number T of time windows to be solved is not less than H, the time period of model solution is H large time windows next to the current moment, and the result of the first large time window in the solved H large time windows is taken as the pump opening and valve opening scheme of the current period; if the number T of the divided time windows is less than H, the time period of model solving is T large time windows next to the current moment, namely the last T large time windows, and the solving result is taken as a pump opening valve opening scheme of the last T large time windows.
(1) When the number T of the remaining time windows to be solved is more than or equal to H, solving an objective function when the pump and valve opening scheme of the current tau period is as shown in a formula (2):
(2) when the number T < H of time windows to be solved is remained, the objective function when solving the pump opening valve scheme of the remaining T time periods is as shown in the formula (3):
(2) In the formula (3):
for the pipeline running cost of H time windows corresponding to the τ solving, FE is the unit of electric quantity unit (unit: yuan/kWh), & lt/EN & gt>
For the binary variable of the start and stop state (1 represents the start of the pump, 0 represents the stop of the pump) of the kth pump in the ith station in the nth small time window of the nth large time window, ">
For the lift (unit: m) of the kth pump in the ith yard in the nth small time window within the nth large time window, for the kth pump in the ith yard>
Over-pumped liquid density (unit: kg/m) for the ith yard in the nth small time window within the nth large time window 3 ) G is a gravitational acceleration (unit: m/s 2 )，/>
Over-pump flow (unit: m) for the ith yard in the nth small time window within the nth large time window 3 /h)，/>
Is the duration (unit: h) of the last time window in the nth small time window of the nth large time window, in +>
The operation efficiency (unit:%) of the kth pump in the ith yard in the nth small time window within the nth large time window is set.
(2) Constraint conditions
The relevant constraints when solving for the pump-on valve-opening scheme at the τ -th time (τ=r when the number of time windows remaining to be solved is less than H) are as follows.
(1) Main pump characteristic constraints
In the nth small time window in the nth time window, the functional relation constraint between the lift of the kth station pump in the ith station and the pump passing flow of the ith station in the time window is shown as a formula (4):
in the nth small time window in the nth time window, the functional relation constraint between the efficiency of the kth pump in the ith station and the over-pump flow of the ith station in the time window is shown as a formula (5):
the upper and lower limit constraints of the overpump flow rate in the ith yard in the nth small time window within the nth time window are as shown in formulas (6) and (7):
wherein: k (K) i For the number of pumps contained in the ith yard,
is the lower limit of the pump flow of the kth pump in the ith station yard, +.>
The upper limit of the pump flow of the kth pump in the ith yard.
(2) Pressure constraint
In the nth small time window within the time window t, the pressure provided by the yard i may be represented by the following formula (8):
the pressure of the inlet of the pipeline at the first station along the line is equal to the pressure provided by the injection pump, namely the pressure constraint of the inlet of the first station is shown as the formula (9):
wherein: PG is the pressure provided by the infusion pump.
The ingress/egress pressure constraints for each yard at the beginning and ending times in the nth small time window of the nth time window are shown in equations (10) - (13):
wherein:
for the outbound pressure (unit: MPa) of the ith yard at the beginning of the nth small time window of the nth large time window, +.>
For the outbound pressure (unit: MPa) of the ith yard at the end of the nth small time window of the nth large time window, < +.>
For the incoming pressure (unit: MPa) of the ith yard at the beginning of the nth small time window of the nth large time window, < +.>
For the incoming pressure (unit: MPa) of the ith yard at the end time in the nth small time window of the nth large time window, of +.>
For the pressure loss (unit: MPa) of the ith pipe section at the beginning of the nth small time window of the nth large time window,/h>
For the pressure loss (unit: MPa) of the ith pipe section at the end of the nth small time window of the nth large time window, +.>
The reduced pressure (in MPa) is applied to the ith pipe section in the nth small time window of the nth large time window. In the above constraint, if the (i+1) th station yard appears, i<I, I is the total number of stations arranged along the pipeline.
The inbound pressure upper/lower limit constraints and the outbound pressure upper/lower limit constraints of the yard are as shown in formulas (14) - (17):
(3) pump start-stop time constraints
In the nth small time window within the nth time window, the on-off state change constraint for the kth pump in the ith yard is as shown in formulas (18) - (21):
BC t,n,i,k ≥BS t,n,i,k -BS t,n-1,i,k t∈T,n>1,i∈IP,k∈K i (18)
BC t,n,i,k ≥BS t,n-1,i,k -BS t,n,i,k t∈T,n>1,i∈IP,k∈K i (19)
in order to avoid frequent start-up and shut-down of the pumps, which makes the operation of the pipeline difficult and increases the operation and maintenance costs of the pumps, it is necessary to restrict the continuous operation or shut-down time of each pump, and the start-up and shut-down time restriction of the pumps is as shown in formula (22):
wherein: TA (TA) t' For the start time of the t' th time window, TA t For the starting time of the t-th time window, M is a constant, in particular, M is a very large constant compared with the values of all parameters and variables in the model, and can be regarded as an infinite number, TS i,k Is the minimum continuous running or shut-down time of the kth pump in the ith yard.
(4) Valve pressure restriction
The research shows that the opening degree and the flow coefficient of the outlet regulating valve have an exponential relationship shown in the formula (23). Wherein, the flow coefficient and the pressure change before and after the valve passing are shown in the formula (24). If the opening of the valve is directly introduced into the model, strong nonlinearity is brought to the model, so that for mathematical modeling of the valve, the relation between the opening and the flow coefficient is fitted according to an exponential function relation, then the change range of the flow coefficient is obtained according to the change of the opening from 0 to 90 degrees, then the change range of the flow is found according to historical data, the change range of the pressure loss is obtained according to the flow pressure loss relation, the pressure loss is directly decided in the model as a boundary of a decision variable, and the reverse opening of an equation is solved after a decision result is obtained.
Φ＝Φ 0 e nh (23)
Wherein Φ represents the opening of the valve, h represents the flow coefficient, Φ 0 And n is a parameter to be determined;
wherein C is v Representing flow coefficient, Q representing flow, SG representing fluid gravity, Δp representing pressure change across the valve.
In the nth small time window in the nth large time window, the state change constraint of the valve in the ith station yard is shown as a formula (25);
(5) operating condition adjustment constraints
The adjustment condition of the operation condition is considered in the model, after the operation condition is adjusted, if the pump opening valve opening scheme decision is carried out continuously according to the operation condition predicted according to the production plan before adjustment, the effectiveness of the pump opening valve opening scheme is greatly reduced, at the moment, the production plan is required to be updated according to the adjustment condition of the production plan, the equivalent production plan at the current moment is obtained, the future operation condition is predicted on the basis, the accuracy of the predicted operation condition is ensured, and related constraints are shown in formulas (26) - (28):
PP τ ＝(1-A τ )PP τ-1 +A τ (PP τ-1 +AP τ ) (26)
wherein: PP (Polypropylene) τ For the equivalent production plan when solving the valve opening scheme of the pump at the τ time, i.e. the adjustment condition of the operation condition at each moment is considered on the basis of the initial production plan table, A τ In the adjustment state of the operation condition at the tau th moment, if the operation condition is adjusted, A τ =1, otherwise, a τ ＝0，Qpredict(PP τ ) And Dprediction (PP) τ ) Respectively according to PP τ The over-pump flow rate and the over-pump liquid density of each station at each future time are predicted.
In step S3, if the pump opening and valve opening scheme corresponding to the whole plan is solved, the solution is ended; otherwise, according to the adjustment condition of the actual operation condition;
for the situation that the calculation of the next stage is still needed, according to the constraints (26) - (28), if the operation condition is not adjusted, returning to the step 3 for solving in the dividing mode of the current time window, and subtracting 1 from the number of the time windows which are needed to be solved at the moment on the basis of the original time window, namely changing the number into T-1;
if the operation conditions are adjusted, returning to the step 3 by combining the adjustment conditions of the operation conditions, and predicting the future operation conditions of the pipeline again according to the adjustment, and continuing to execute according to the flow until the solution of the pump opening valve scheme in all time periods is completed.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and improvements can be made by those skilled in the art without departing from the structure of the present invention, and these do not affect the effect of the implementation of the present invention and the utility of the patent.
Claims (8)
1. A method for sequentially deciding a pump-on scheme of a liquid pipeline for multi-batch sequential transportation, which is characterized by comprising the following steps:
s1, reading basic parameters and an initial production schedule of a pipeline, and predicting an initial operation condition of the pipeline according to the basic parameters and the initial production schedule;
s2, adjusting the initial operation condition according to the implementation condition; introducing model prediction control, and predicting the operation condition of the pipeline in the next stage in real time according to the actual operation condition at the current moment;
s3, establishing a pump opening valve opening scheme sequential decision model according to the actual operation condition of the pipeline;
s4, solving the sequential decision model of the pump opening valve opening scheme, and outputting the pump opening valve opening scheme in a corresponding period;
s5, judging whether a pump opening valve opening scheme corresponding to the whole plan is solved, and performing next calculation according to a solving result;
in step S3, the basic structure of the sequential decision model of the pump-opening valve-opening scheme is shown in formula (1):
in the method, in the process of the invention,
in order to make the objective function of the decision of the tau-th pump opening and valve opening scheme, the running cost of the pipeline in H time periods corresponding to the current time period of the required decision pump opening and valve opening scheme is started, H is the time period number of the optimized pump opening and valve opening scheme for each decision, BP is the basic parameter of the pipeline, IP is the initial production plan of the pipeline, and AP τ For the adjustment of the operating conditions of the pipeline at the beginning of the τ -th period, < >>
The decision variables comprise the start-stop state of each pump in each pump station in the period from t to t+H-1, the lift and pressure provided by each pump station in the period from t to t+H-1 and the station inlet and outlet pressure of each station in the period from t to t+H-1, D is a feasible region, H i And g j Equality constraints and inequality constraints corresponding to the optimization problem, respectively;
if the number T of the time windows to be solved is not less than H, the time period of model solving is H large time windows next to the current moment, and the result of the first large time window in the solved H large time windows is taken as a pump opening valve opening scheme of the current period; the objective function when solving the pump opening valve scheme of the current τ period is shown as formula (2):
if the number T < H of time windows to be solved is remained currently, the time period of model solving is T large time windows next to the current moment, and the solving result is taken as a pump opening and valve opening scheme of the last T large time windows; the objective function when solving the pump opening valve scheme for the remaining T time periods is as shown in equation (3):
(2) In the formula (3):
for the pipeline running cost of H time windows corresponding to the τ solving, FE is the unit price of electric quantity,
is a binary variable of the start-stop state of a kth pump in an ith station yard in an nth small time window of a nth large time window, +.>
For the lift of the kth pump in the ith yard in the nth small time window within the nth large time window, +.>
The density of the overdump liquid for the ith yard in the nth small time window within the nth large time window, g is the gravitational acceleration, +.>
For the overdump flow of the ith yard in the nth small time window within the nth large time window, +.>
For the duration in the nth small time window of the nth large time window,/-for the duration in the nth small time window of the nth large time window>
The operating efficiency of the kth pump in the ith yard in the nth small time window within the nth large time window is set.
2. The method for sequentially deciding on a pump-on scheme of a multi-batch sequential transport liquid pipeline according to claim 1, wherein the basic parameters comprise the inlet pressure, outlet pressure, number of pumps, characteristic parameters of each pump, pipe diameter of each pipe section, length of each pipe section and physical characteristics of liquid of each station along the pipeline;
the initial operating conditions include the following information:
the type of liquid and the corresponding injection flow rate of the liquid injected at each injection station along the pipeline in each period of time in the future;
the liquid types and the corresponding downloading flow downloaded by each downloading station along the pipeline in each time period in the future;
the type of liquid transported by the pipeline along each pipe section in each future period and the corresponding transport flow;
the time when the pipeline performs various operations comprises the time of changing the types of the liquid injected by the pipeline at various injection stations along the pipeline and the corresponding flow, and the time of changing the types of the liquid downloaded by various downloading stations and the corresponding flow;
predicting the time when each liquid mixing interface reaches each station according to the distribution condition of the liquid mixing interface in the pipeline and the flow of the liquid in each pipe section in each period, and dividing the running time of the whole pipeline into T time windows by combining the time when the liquid mixing interface reaches each station and the time when each operation is carried out on the pipeline;
according to the liquid distribution condition of each pipe section of the pipeline at each moment, the linear change relation of the pressure loss between the head and the tail of each pipe section along with the time sequence is predicted, and the decision of a pipeline pump opening and valve opening scheme is carried out based on the linear change relation, and a small time window is automatically divided when the pressure loss exceeds the time limit.
3. A sequential decision method for multiple batch sequential transport liquid pipeline pump-on scheme according to claim 1 wherein the relevant constraints in performing the solution for the τ -th pump-on valve-on scheme include a primary pump characteristic constraint,
in the nth small time window in the nth time window, the functional relation constraint between the lift of the kth station pump in the ith station and the pump passing flow of the ith station in the time window is shown as a formula (4):
in the nth small time window in the nth time window, the functional relation constraint between the efficiency of the kth pump in the ith station and the over-pump flow of the ith station in the time window is shown as a formula (5):
the upper and lower limit constraints of the overpump flow rate in the ith yard in the nth small time window within the nth time window are as shown in formulas (6) and (7):
wherein: k (K) i For the number of pumps contained in the ith yard,
is the pump flow lower limit of the kth pump in the ith station,
the upper limit of the pump flow of the kth pump in the ith yard.
4. A sequential decision method for multiple batch sequential transport liquid pipeline pump-on scheme according to claim 1 wherein the relevant constraints in performing the solution for the τ -th pump-on valve-on scheme include pressure constraints,
in the nth small time window within the time window t, the pressure provided by the yard i may be represented by the following formula (8):
the pressure of the inlet of the pipeline at the first station along the line is equal to the pressure provided by the injection pump, namely the pressure constraint of the inlet of the first station is shown as the formula (9):
wherein: PG is the pressure provided by the injection pump;
the ingress/egress pressure constraints for each yard at the beginning and ending times in the nth small time window of the nth time window are shown in equations (10) - (13):
wherein:
for the outbound pressure at the beginning of the ith yard in the nth small time window of the nth large time window, +.>
For the outbound pressure at the end of the ith yard in the nth small time window of the nth large time window, +.>
For the incoming pressure of the ith yard at the beginning of the nth small time window of the nth large time window, +.>
For the incoming pressure of the ith yard at the end time in the nth small time window of the nth large time window, +.>
For the pressure loss of the ith pipe section at the beginning of the nth small time window of the nth large time window,/->
For the pressure loss of the ith pipe section at the end of the nth small time window of the nth large time window,/->
Valve reduced pressure for the ith pipe segment in the nth small time window of the nth large time window;
the inbound pressure upper/lower limit constraints and the outbound pressure upper/lower limit constraints of the yard are as shown in formulas (14) - (17):
5. a sequential decision method for multiple batch sequential transport liquid pipeline pump-on scheme according to claim 1 wherein the relevant constraints in performing the solution for the τ -th pump-on valve-on scheme include the pump start-stop time constraints,
in the nth small time window within the nth time window, the on-off state change constraint for the kth pump in the ith yard is as shown in formulas (18) - (21):
BC t,n,i,k ≥BS t,n,i,k -BS t,n-1,i,k t∈T,n>1,i∈IP,k∈K i (18)
BC t,n,i,k ≥BS t,n-1,i,k -BS t,n,i,k t∈T,n>1,i∈IP,k∈K i (19)
the pump on-off time constraint is as shown in equation (22):
wherein: TA (TA) t' For the start time of the t' th time window, TA t For the start time of the t-th time window, M is a constant, TS i,k Is the minimum continuous running or shut-down time of the kth pump in the ith yard.
6. A sequential decision method for multiple batch sequential transport liquid pipeline pump-on scheme according to claim 1 wherein the relevant constraints in performing the solution for the τ -th pump-on valve-on scheme include valve pressure constraints,
the opening degree and the flow coefficient of the outlet regulating valve are shown in the formula (23):
Φ＝Φ 0 e nh (23)
wherein Φ represents the opening of the valve, h represents the flow coefficient, Φ 0 And n is a parameter to be determined;
the flow coefficient and the pressure change before and after valve passing are shown in the formula (24):
wherein C is v Representing flow coefficient, Q representing flow, SG representing fluid gravity, deltaP representing pressure change before and after valve passing;
in the nth small time window in the nth large time window, the state change constraint of the valve in the ith station yard is shown as a formula (25);
7. a sequential decision method for multiple batch sequential transport liquid pipeline pump-on scheme according to claim 1 wherein the relevant constraints in performing the solution for the τ -th pump-on valve-on scheme include operating condition adjustment constraints,
the constraints for operating conditions adjustment are shown in equations (26) - (28):
PP τ ＝(1-A τ )PP τ-1 +A τ (PP τ-1 +AP τ ) (26)
wherein: PP (Polypropylene) τ For equivalent production plan when solving the τ -th pump-on valve-opening scheme, A τ In the adjustment state of the operation condition at the tau th moment, if the operation condition is adjusted, A τ =1, otherwise, a τ ＝0，Qpredict(PP τ ) And Dprediction (PP) τ ) Respectively according to PP τ The over-pump flow rate and the over-pump liquid density of each station at each future time are predicted.
8. The method for sequentially deciding on pump-on schemes of liquid pipelines for sequential transportation in batches according to claim 7, wherein if the pump-on valve-on scheme corresponding to the whole plan is solved, the solution is finished; otherwise, according to the adjustment condition of the actual operation condition;
for the situation that the calculation of the next stage is still needed, according to the constraints (26) - (28), if the operation condition is not adjusted, returning to the step 3 for solving in the dividing mode of the current time window, and subtracting 1 from the number of the time windows which are needed to be solved at the moment on the basis of the original time window, namely changing the number into T-1;
if the operation conditions are adjusted, returning to the step 3 by combining the adjustment conditions of the operation conditions, and predicting the future operation conditions of the pipeline again according to the adjustment, and continuing to execute according to the flow until the solution of the pump opening valve scheme in all time periods is completed.
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| WO2019125436A1 (en) * | 2017-12-20 | 2019-06-27 | Siemens Aktiengesellschaft | Predictive pump station and pipeline advanced control system |
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| WO2019125436A1 (en) * | 2017-12-20 | 2019-06-27 | Siemens Aktiengesellschaft | Predictive pump station and pipeline advanced control system |
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