A heuristic solution method for unit commitment based on priority order method

Abstract

The present invention belongs to the technical field of unit combination solution, and specifically relates to a unit combination heuristic solution method based on a priority method, the steps of which include constructing an objective function of a power system unit combination model and setting constraints; using average full load cost as a ranking factor to sort the units; obtaining an initial solution to the unit combination problem; adjusting the unit output and start-stop status using a unit adjustment strategy based on minimum start-stop time constraints; setting a simple redundant unit adjustment strategy to adjust the unit output and start-stop status, and obtaining an approximate solution to the unit combination problem; adjusting the unit output and start-stop status using a unit adjustment strategy based on climbing constraints; setting a precise redundant unit adjustment strategy to adjust the unit output and start-stop status; performing output adjustment between units to obtain a final solution, and calculating the minimum operating cost. The present invention can improve the solution efficiency of power system unit combination and can improve the quality of the unit combination solution.

Description

Technical Field

[0001] The present invention belongs to the technical field of unit combination solution, and in particular relates to a heuristic solution method for unit combination based on a priority method. Background Art

[0002] Power system unit commitment involves scheduling the start / stop and generation of units (i.e., generators) within a specific dispatch cycle (usually a day or a week) to minimize cost (consumption), achieve system power balance, and meet certain constraints and reserve requirements. Mathematically, unit commitment is a large-scale mixed-integer programming problem, making it difficult to find an exact optimal solution within a reasonable timeframe.

[0003] Currently, the methods commonly used to solve unit commitment problems include heuristic algorithms, mathematical optimization algorithms, and intelligent optimization algorithms. Mathematical optimization methods produce relatively accurate results, but the solution process is computationally intensive and takes a long time. Intelligent optimization algorithms can learn and predict based on previous data, improving the solution speed, but are prone to getting stuck in local optimality during the decision-making process. Heuristic algorithms such as the priority method and the reverse sorting method primarily rely on intuitive judgment and practical experience, employing heuristic strategies within a limited search space to solve unit commitment problems. Among them, the priority method determines a ranking metric based on the economic characteristics of each generator unit and arranges unit switching and load distribution in sequence based on the ranking metric, resulting in a faster convergence rate. However, the solution obtained by the priority method, while considering power balance constraints and spinning reserve constraints, often fails to simultaneously meet the requirements of unit output boundary constraints, minimum start-stop time constraints, and ramp-up constraints, resulting in a low-quality solution. In order to improve the solution quality, the priority method often adopts heuristic adjustment strategies to deal with unit output boundary constraints and minimum start-stop time constraints. When dealing with climbing constraints, it is often combined with mathematical optimization algorithms or intelligent optimization algorithms, which makes it difficult to avoid the shortcomings of other algorithms.

[0004] Therefore, it is necessary to design a heuristic solution method for unit commitment based on the priority method that can handle ramping constraints and improve the solution efficiency of power system unit commitment. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the object of the present invention is to provide a heuristic solution method for unit combination based on the priority method, which can improve the solution efficiency of power system unit combination and improve the quality of unit combination solution.

[0006] To achieve the above objectives, the present invention provides a heuristic solution method for unit commitment based on a priority method, comprising the following steps:

[0007] S1. With the goal of minimizing fuel costs and startup costs, the objective function of the power system unit combination model is constructed, and unit output boundary constraints, system power balance constraints, spinning reserve constraints, unit ramping constraints, start-stop logic constraints, and minimum start-stop time constraints are set;

[0008] S2. Use the average full-load cost as the ranking factor and sort the units in ascending order;

[0009] S3. Determine the start and stop status of the units to satisfy the spinning reserve constraint, and then determine the unit output to satisfy the system power balance constraint and the unit output boundary constraint, thereby obtaining an initial solution to the unit commitment problem;

[0010] S4. Adjust the unit output and start / stop status using a unit adjustment strategy based on minimum start / stop time constraints;

[0011] S5. Set a simple redundant unit adjustment strategy to adjust the unit output and start / stop status, and obtain an approximate solution to the unit combination problem;

[0012] S6. Adjust the unit output and start / stop status using a unit adjustment strategy based on ramp constraints;

[0013] S7. Set precise redundant unit adjustment strategy to adjust unit output and start / stop status;

[0014] S8. Adjust the output between the units to obtain the final solution and calculate the minimum operating cost.

[0015] As a preferred solution of the present invention, in said S1, the objective function OF of the power system unit combination model is:

[0016] ;

[0017] Where N T is the total optimization period, t represents one of the moments; N G is the number of units, g represents one of the units; is the output of unit g at time t; 、 is a 0-1 integer variable, representing the start and stop status of unit g at time t and time t-1 respectively. The value is 1 for start and 0 for stop; is the startup cost of unit g; is the fuel cost of unit g;

[0018] The expression is:

[0019] ;

[0020] Where, 、 、 is the power generation cost coefficient of unit g;

[0021] The expression is:

[0022] ;

[0023] Where, 、 are the hot start cost and cold start cost of unit g respectively; is the continuous downtime of unit g at time t; is the minimum downtime of unit g; is the cold start time of unit g.

[0024] As a preferred solution of the present invention, in S1, the constraint conditions are specifically:

[0025] Unit output boundary constraints:

[0026] ;

[0027] Where, 、 Respectively represent the minimum and maximum values ​​of the unit's g output;

[0028] System power balance constraints:

[0029] ;

[0030] Where, represents the load at time t;

[0031] Spinning reserve constraints:

[0032] ;

[0033] Where, represents the spare capacity at time t;

[0034] Unit climbing constraints:

[0035] ;

[0036] ;

[0037] Where, is the output of unit g at time t-1; 、 They represent the speed limits for the increase and decrease of the unit's g power respectively; and They represent the startup power speed limit and shutdown power speed limit of unit g respectively; and All are 0-1 integer variables. Indicates the startup operation of unit g at time t. A value of 1 indicates that the startup operation was performed at time t, and a value of 0 indicates that the startup operation was not performed; Indicates the shutdown operation of unit g at time t. A value of 1 indicates that the shutdown operation was performed at time t, and a value of 0 indicates that the shutdown operation was not performed;

[0038] Start-stop logic constraints:

[0039] ;

[0040] ;

[0041] Minimum start and stop time constraints, including minimum start time constraints and minimum stop time constraints:

[0042] ;

[0043] ;

[0044] Where, 、 represents a 0-1 integer variable, which represents the start-up and shutdown operations of unit g at time s; is the minimum startup time of unit g; Indicates a universal quantifier.

[0045] As a preferred solution of the present invention, in S2, the average full-load cost refers to the average power generation cost of the unit in the full-power state, which is the power generation cost of the unit in the full-power state divided by the maximum output of the unit. For unit g, its average full-load cost is Expressed as:

[0046] .

[0047] As a preferred solution of the present invention, in S3, the process of obtaining the initial solution of the unit combination is:

[0048] S3.1. Determine the start and stop status of the units to satisfy the spinning reserve constraint. Assuming that the start and stop status of all units is 0 at each moment, the process is as follows:

[0049] S3.1.1, let t = 1;

[0050] S3.1.2. Let g = 1, indicating the first unit after sorting;

[0051] S3.1.3, Order , The sum of the maximum outputs of the units started at time t;

[0052] S3.1.4, Order ;

[0053] S3.1.5 If ,but , let g=g+1, if at this time , go to step S3.1.4, otherwise go to step S3.1.6, where Indicates the last unit after sorting;

[0054] like ,but , go to step S3.1.6;

[0055] S3.1.6, let t = t + 1, if , go to step S3.1.2, otherwise end the adjustment;

[0056] S3.2. Determine the unit output to satisfy the system power balance constraint and the unit output boundary constraint, thereby obtaining the initial solution to the unit combination problem. Assuming that the output of all units at each moment is 0, the process is as follows:

[0057] S3.2.1, let t = 1;

[0058] S3.2.2, let g = 1;

[0059] S3.2.3, Order , is the sum of the power of the units started at time t;

[0060] S3.2.4 If , go to step S3.2.6, otherwise , at this time, if ,but ,like ,but ;

[0061] S3.2.5, let g = g + 1, if , go to step S3.2.4, otherwise go to step S3.2.6;

[0062] S3.2.6, let t = t + 1, if , go to step S3.2.2, otherwise end the adjustment.

[0063] As a preferred solution of the present invention, in said S4, the unit output and start-stop status are adjusted by using the unit adjustment strategy based on the minimum start-stop time constraint. Specifically, if the minimum start-up time constraint cannot be met at a certain moment, the unit is started at the next moment; if the minimum stop time constraint cannot be met at a certain moment, the unit is started at that moment; when the state of unit g at time t changes from 0 to 1, the output of unit g is .

[0064] As a preferred embodiment of the present invention, in S5, a simple redundant unit adjustment strategy is set to adjust the unit output and start-stop status to obtain an approximate solution to the unit combination problem. Specifically, when the sum of the unit outputs exceeds the total load demand, the system output is redundant, and the redundant unit output needs to be adjusted. During the adjustment process, the simple redundant unit adjustment strategy takes into account the influence of the unit output boundary constraint, the system power balance constraint, and the spinning reserve constraint, and does not involve the unit climbing constraint. The adjustment starts from the unit with the lowest priority, and the process is as follows:

[0065] S5.1.1, let t = 1;

[0066] S5.1.2. Calculate the redundant output at time t :

[0067] ;

[0068] S5.1.3, Order ;

[0069] S5.1.4, Order , , Indicates the adjustable amount of the unit g, is the total adjustment amount at time t;

[0070] S5.1.5 Calculation :

[0071] ;

[0072] S5.1.6 If ,but , ; Let g = g - 1. If g ≥ 1, go to step S5.1.5. Otherwise, go to step S5.1.7.

[0073] like ,but , go to step S5.1.7;

[0074] S5.1.7. Let t = t + 1. If , go to step S5.1.2, otherwise end the adjustment.

[0075] As a preferred solution of the present invention, in S6, the unit output and start-stop status are adjusted using a unit adjustment strategy based on a ramp constraint. Specifically, the time periods and units are classified according to the start-stop changes of the units; the unit continuous start period is recorded as a "1" type period, and the unit continuous shutdown period is recorded as a "0" type period; the unit that remains on for the entire period is called a normally-on unit, the unit that remains off for the entire period is called a normally-off unit, and the unit that undergoes start-stop changes is called a start-stop unit; among them, the normally-off unit and the normally-on unit that maintains the maximum output for the entire period always meet the unit climbing constraints, and therefore do not need to be adjusted;

[0076] For the normally-on units, the output of the normally-on units with output changes during the entire period is adjusted to meet the unit climbing constraints. Since the entire period of this type of unit is a "1" type period, the "increase in time and test in reverse time" method is adopted to adjust the unit output to meet the unit climbing constraints. The specific process is as follows:

[0077] S6.1.1. Increase in time, the steps comprising:

[0078] S6.1.1.1, Order ,in is the initial moment of the “1” type period;

[0079] S6.1.1.2 If ,but ;

[0080] like ,but ;

[0081] S6.1.1.3. Let t = t + 1. If , go to step S6.1.1.2, otherwise end the adjustment, where The end time of the "1" type period;

[0082] S6.1.2. Reverse time test, the steps include:

[0083] S6.1.2.1, Order ;

[0084] S6.1.2.2 If ,but ;

[0085] S6.1.2.3. Let t = t - 1. If , go to step S6.1.2.2, otherwise end the adjustment;

[0086] For the start-stop units, the output and start-stop status of the start-stop units are adjusted to meet the unit climbing constraints; the full period of the start-stop units includes both "1" type periods and "0" type periods; first, the "1" type period is adjusted to meet the unit climbing constraints by adopting the "increase in time and check in reverse time" method; then, the start-stop units are adjusted for the "0" type periods at different times. The specific process is as follows:

[0087] S6.2.1. For the first end time, when the "0" type period contains the first end time, the unit output and start / stop status at the right end time of the "0" type period need to be adjusted; assuming that the "0" type period is "1 to t1", t1 is the right end time of the "0" type period, then:

[0088] S6.2.1.1, let t = t1;

[0089] S6.2.1.2 If ,but and , and go to step S6.2.1.3, otherwise end the adjustment, where, is the output of unit g at time t+1;

[0090] S6.2.1.3. Let t = t - 1. If t ≥ 1, go to step S6.2.1.2; otherwise, end the adjustment.

[0091] S6.2.2 For the terminal time, when the “0” type period contains the terminal time, it is necessary to adjust the unit output and start / stop status at the left end of the “0” type period; assuming that the “0” type period is “t2 to N T ", t2 is the left end of the "0" type period, then:

[0092] S6.2.2.1, let t = t2;

[0093] S6.2.2.2, if ,but and , and go to step S6.2.2.3, otherwise end the adjustment, where, is the output of unit g at time t-1;

[0094] S6.2.2.3. Let t = t + 1, if t ≤ N T , go to step S6.2.2.2, otherwise end the adjustment;

[0095] S6.2.3. For intermediate moments, when the "0" period only includes the intermediate moments, the unit output and start / stop status at the left and right ends of the "0" period need to be adjusted simultaneously; assuming that the "0" period is "t3 to t4", t3 and t4 are the left and right ends of the "0" period, respectively, then:

[0096] S6.2.3.1. For the left end adjustment of the "0" type period, let t = t3;

[0097] S6.2.3.2, if ,but and , go to step S6.2.3.3, otherwise end the left end adjustment;

[0098] S6.2.3.3. Let t = t + 1. If t ≤ t4, go to step S6.2.3.2. Otherwise, end the left end adjustment.

[0099] S6.2.3.4. For the right-end adjustment of the "0" type period, let t = t4;

[0100] S6.2.3.5, if ,but and , go to step S6.2.3.6, otherwise end the right end adjustment;

[0101] S6.2.3.6. Let t = t - 1. If t ≥ t3, go to step S6.2.3.5. Otherwise, end the right-end adjustment.

[0102] S6.2.3.7. After the adjustment at both ends is completed, the downtime of the unit in the "0" period is calculated. ;like , indicating that the “0” type period still meets the minimum downtime constraint, and the adjustment is completed; if , indicating that the "0" type period cannot meet the minimum downtime constraint; in order to maintain the system power balance, the "0" type period and the previous and next "1" type periods are combined into a "1" type period; finally, the "increase in time and check in reverse time" method is adopted to adjust the unit output of the newly formed "1" type period to meet the unit climbing constraint.

[0103] As a preferred embodiment of the present invention, in S7, a precise redundant unit adjustment strategy is used to sequentially adjust the unit output and start / stop status at each moment based on satisfying various constraints to obtain a final solution to the unit combination problem. The specific process is as follows: since the unit output at the beginning and end moments is affected by the unit ramping constraint at the adjacent moments at one end, and the intermediate moments are affected by the unit ramping constraint at the adjacent moments at both ends, the adjustment process divides the entire period into a beginning period containing the beginning moment, an intermediate period containing only the intermediate moments, and a terminal period containing the end moment for redundant unit adjustment.

[0104] For the headend period:

[0105] S7.1.1, let t = 1;

[0106] S7.1.2. Calculate the redundant output R1 at the head end:

[0107] ;

[0108] Where, Indicates the output of unit g at the first end moment; Indicates the load at the head end;

[0109] S7.1.3, Order ;

[0110] S7.1.4, Order and ;

[0111] S7.1.5, Computer Group g Adjustable Amount:

[0112] ;

[0113] Where, Indicates the output of unit g at the right end of the first period;

[0114] S7.1.6 If ,but and , let g = g - 1. If g ≥ 1, go to step S7.1.5, otherwise end the adjustment;

[0115] like ,but , end the adjustment;

[0116] For the middle period:

[0117] S7.2.1, let t = 2;

[0118] S7.2.2. Calculate the redundant output at time t:

[0119] ;

[0120] S7.2.3, Order ;

[0121] S7.2.4, Order and ;

[0122] S7.2.5, Computer Group g Adjustable Amount:

[0123] ;

[0124] S7.2.6 If ,but and , let g = g - 1, if g ≥ 1, go to step S7.2.5, otherwise go to step S7.2.7;

[0125] like ,but , go to step S7.2.7;

[0126] S7.2.7. Let t = t + 1. If , then go to step S7.2.2, otherwise end the adjustment;

[0127] For the terminal period, the adjustment process of the terminal period is the same as that of the first period. Only the influence of the output of the unit at one end needs to be considered, that is, the output of the unit at the left end of the terminal period.

[0128] As a preferred embodiment of the present invention, in S8, after the redundant units are adjusted for the head-end period, the middle period, and the end period, the sum of the unit outputs at each moment is fixed. At this time, it is necessary to adjust the outputs between the units. The adjustment method is to divide the entire period into the head-end period, the middle period, and the end period, and adjust by increasing the output of the priority units and reducing the output of the non-priority units. The adjustment process for the middle period is as follows:

[0129] S8.1, let t = 2;

[0130] S8.2, set g = 1;

[0131] S8.3, if , go to step S8.9, otherwise:

[0132] ;

[0133] Where, Indicates the power that the priority unit can increase;

[0134] S8.4, Order , , Indicates the power that can be reduced for non-priority units; Indicates the total reduction in power of non-priority units;

[0135] S8.5, Order , i is the index of the unit;

[0136] S8.6, if ,but:

[0137] ;

[0138] Otherwise, go to step S8.8;

[0139] in, is a 0-1 integer variable, indicating the start / stop status of unit i at time t; 、 、 They represent the output of unit i at time t, time t-1, and time t+1 respectively; 、 They represent the speed limits for increasing and decreasing the power of unit i respectively; is the minimum output of unit i;

[0140] S8.7, if ,but:

[0141] ;

[0142] ;

[0143] ;

[0144] Go to step S8.8;

[0145] like ,but:

[0146] ;

[0147] ;

[0148] Go to step S8.10;

[0149] S8.8. Let i = i - 1. If i > g, go to step S8.6; otherwise, go to step S8.9.

[0150] S8.9, let g = g + 1, if , go to step S8.3, otherwise go to step S8.10;

[0151] S8.10, let t = t + 1, if , go to step S8.2, otherwise end the adjustment;

[0152] For the first and last period, they are only affected by the ramp constraints of the units at adjacent times at one end. Single-end adjustment can be performed in the same way as the adjustment process for the middle period.

[0153] After the adjustment is completed, the minimum operating cost of the group combination problem is calculated based on the obtained unit output and start-stop status.

[0154] The algorithm involved in the present invention can be executed by an electronic device, which includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor. The above-mentioned algorithm calculation is realized by executing the software through the processor.

[0155] The beneficial effects of the present invention are:

[0156] This invention effectively addresses the constraint violations that can occur in the initial solution of traditional priority methods by introducing heuristic adjustment strategies, such as the minimum start / stop time constraint adjustment strategy (a unit adjustment strategy based on minimum start / stop time constraints), the simple redundant unit adjustment strategy, and the ramping constraint adjustment strategy (a unit adjustment strategy based on ramping constraints). These strategies progressively optimize the unit output and start / stop status, ensuring that the final solution meets stringent requirements for system power balance, spinning reserve, unit output boundaries, minimum start / stop time, and unit ramping constraints, significantly improving the quality of the unit combination solution.

[0157] This invention significantly improves solution efficiency while ensuring high computational accuracy. Through phased optimization and adjustment, complex iterative calculation processes are avoided, enabling near-optimal solutions to be obtained in a relatively short period of time. For example, in a simulation verification of a 10-unit test system, compared to the commercial solver Gurobi, although the operating cost was slightly higher by 0.59%, the solution time was reduced by nearly 40.7%. This demonstrates that this method is particularly suitable for solving time-sensitive unit combination problems and is highly practical and economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0158] Figure 1 It is a schematic diagram of the process of the present invention;

[0159] Figure 2 Schematic diagram of output curves of 10 generator sets in the initial solution during the verification process of the present invention;

[0160] Figure 3 Schematic diagram of the start and stop states of 10 generator sets in the approximate solution during the verification process of the present invention;

[0161] Figure 4 Schematic diagram of output curves of 10 generator sets in the approximate solution during the verification process of the present invention;

[0162] Figure 5 Schematic diagram of output curves of 10 generator sets in the final solution during the verification process of the present invention. DETAILED DESCRIPTION

[0163] The embodiments of the present invention are further described below with reference to the accompanying drawings:

[0164] like Figure 1 As shown in FIG, a heuristic solution method for unit commitment based on the priority method includes the following steps:

[0165] S1. With the goal of minimizing fuel costs and startup costs, the objective function of the power system unit combination model is constructed, and unit output boundary constraints, system power balance constraints, spinning reserve constraints, unit ramping constraints, start-stop logic constraints, and minimum start-stop time constraints are set;

[0166] S2. Use the average full-load cost as the ranking factor and sort the units in ascending order;

[0167] S3. Determine the start and stop status of the units to satisfy the spinning reserve constraint, and then determine the unit output to satisfy the system power balance constraint and the unit output boundary constraint, thereby obtaining an initial solution to the unit commitment problem;

[0168] S4. Adjust the unit output and start / stop status using a unit adjustment strategy based on minimum start / stop time constraints;

[0169] S5. Set a simple redundant unit adjustment strategy to adjust the unit output and start / stop status, and obtain an approximate solution to the unit combination problem;

[0170] S6. Adjust the unit output and start / stop status using a unit adjustment strategy based on ramp constraints;

[0171] S7. Set precise redundant unit adjustment strategy to adjust unit output and start / stop status;

[0172] S8. Adjust the output between the units to obtain the final solution and calculate the minimum operating cost.

[0173] In S1, the objective function OF of the power system unit combination model is:

[0174] ;

[0175] Where N T is the total optimization period, t represents one of the moments; N G is the number of units, g represents one of the units; is the output of unit g at time t; 、 is a 0-1 integer variable, representing the start and stop status of unit g at time t and time t-1 respectively. The value is 1 for start and 0 for stop; is the startup cost of unit g; is the fuel cost of unit g;

[0176] The expression is:

[0177] ;

[0178] Where, 、 、 is the power generation cost coefficient of unit g, which is a well-known content, specifically:

[0179] It is the quadratic term coefficient, which represents the nonlinear growth of fuel cost when the unit output increases. It reflects the change in efficiency of the unit when it is running at high load and is usually used to describe the additional fuel consumption of the unit under high load.

[0180] is the linear term coefficient, which indicates the linear growth of fuel cost when the unit output increases. It reflects the unit output cost of the unit and is directly related to the fuel consumption rate.

[0181] is a constant term, which represents the fixed cost of the unit during operation. This cost will be incurred even if the unit output is zero. This cost is usually related to the maintenance and startup costs of the unit;

[0182] The expression is:

[0183] ;

[0184] Where, 、 are the hot start cost and cold start cost of unit g respectively; is the continuous downtime of unit g at time t; is the minimum downtime of unit g; is the cold start time of unit g.

[0185] In this embodiment, for time and time period, time only contains one time, such as time 1, time 5. Time period is usually composed of continuous time, such as time 1 to time 2 is a time period, time 5 to time 9 is a time period. The time period is set to facilitate the analysis of the changes in the unit output and start-stop at different times in each time period. For example, adjust the unit output and start-stop status at a certain time in a certain time period. For the total optimization time period, N T The value is 24, and the total optimization period includes the 1st to the 24th time, representing one day.

[0186] In S1, the constraints are as follows:

[0187] Unit output boundary constraints:

[0188] ;

[0189] Where, 、 Respectively represent the minimum and maximum values ​​of the unit's g output;

[0190] System power balance constraints:

[0191] ;

[0192] Where, represents the load at time t;

[0193] Spinning reserve constraints:

[0194] ;

[0195] Where, represents the spare capacity at time t;

[0196] Unit climbing constraints:

[0197] ;

[0198] ;

[0199] Where, is the output of unit g at time t-1; 、 They represent the speed limits for the increase and decrease of the unit's g power respectively; and They represent the startup power speed limit and shutdown power speed limit of unit g respectively; and All are 0-1 integer variables. Indicates the startup operation of unit g at time t. A value of 1 indicates that the startup operation was performed at time t, and a value of 0 indicates that the startup operation was not performed; Indicates the shutdown operation of unit g at time t. A value of 1 indicates that the shutdown operation was performed at time t, and a value of 0 indicates that the shutdown operation was not performed;

[0200] Start-stop logic constraints:

[0201] ;

[0202] ;

[0203] Minimum start and stop time constraints, including minimum start time constraints and minimum stop time constraints:

[0204] ;

[0205] ;

[0206] Where, 、 Indicates a 0-1 integer variable, which represents the start-up and shutdown operations of unit g at time s (with 、 Similarly); is the minimum startup time of unit g; Indicates a universal quantifier.

[0207] In S2, the average full-load cost refers to the average power generation cost of the unit in the full-power state. In terms of value, it is the power generation cost of the unit in the full-power state divided by the maximum output of the unit. For unit g, its average full-load cost is Expressed as:

[0208] .

[0209] In S3, the process of obtaining the initial solution of the unit commitment is:

[0210] S3.1. Determine the start and stop status of the units to satisfy the spinning reserve constraint. Assuming that the start and stop status of all units is 0 at each moment, the process is as follows:

[0211] S3.1.1, let t = 1;

[0212] S3.1.2. Let g = 1, indicating the first unit after sorting;

[0213] S3.1.3, Order , The sum of the maximum outputs of the units started at time t;

[0214] S3.1.4, Order ;

[0215] S3.1.5 If ,but , let g=g+1, if at this time , go to step S3.1.4, otherwise go to step S3.1.6, where Indicates the last unit after sorting;

[0216] like ,but , go to step S3.1.6;

[0217] S3.1.6, let t = t + 1, if , go to step S3.1.2, otherwise end the adjustment;

[0218] S3.2. Determine the unit output to satisfy the system power balance constraint and the unit output boundary constraint, thereby obtaining the initial solution to the unit combination problem. Assuming that the output of all units at each moment is 0, the process is as follows:

[0219] S3.2.1, let t = 1;

[0220] S3.2.2, let g = 1;

[0221] S3.2.3, Order , is the sum of the power of the units started at time t;

[0222] S3.2.4 If , go to step S3.2.6, otherwise , at this time, if ,but ,like ,but ;

[0223] S3.2.5, let g = g + 1, if , go to step S3.2.4, otherwise go to step S3.2.6;

[0224] S3.2.6, let t = t + 1, if , go to step S3.2.2, otherwise end the adjustment.

[0225] In S4, the unit output and start-stop status are adjusted using the unit adjustment strategy based on the minimum start-stop time constraint. Specifically, if the minimum start-up time constraint cannot be met at a certain moment, the unit will be started at the next moment; if the minimum stop time constraint cannot be met at a certain moment, the unit will be started at that moment; when the state of unit g at time t changes from 0 to 1, the output of unit g is .

[0226] In S5, a simple redundant unit adjustment strategy is set to adjust the unit output and start-up and shutdown status, obtaining an approximate solution to the unit combination problem. Specifically, when the sum of the unit outputs exceeds the total load demand, the system output is redundant, and the redundant unit output needs to be adjusted. During the adjustment process, the simple redundant unit adjustment strategy considers the influence of unit output boundary constraints, system power balance constraints, and spinning reserve constraints, and does not involve unit ramping constraints. To save operating costs, the adjustment starts with the unit with the lowest priority. The process is as follows:

[0227] S5.1.1, let t = 1;

[0228] S5.1.2. Calculate the redundant output at time t :

[0229] ;

[0230] S5.1.3, Order ;

[0231] S5.1.4, Order , , Indicates the adjustable amount of the unit g, is the total adjustment amount at time t;

[0232] S5.1.5 Calculation :

[0233] ;

[0234] S5.1.6 If ,but , ; Let g = g - 1. If g ≥ 1, go to step S5.1.5. Otherwise, go to step S5.1.7.

[0235] like ,but , go to step S5.1.7;

[0236] S5.1.7. Let t = t + 1. If , go to step S5.1.2, otherwise end the adjustment.

[0237] In S6, the unit output and start-stop status are adjusted using a unit adjustment strategy based on ramping constraints. Specifically, the time periods and units are classified according to the start-stop changes of the units. The period when the unit is continuously on is recorded as a "1" period, and the period when the unit is continuously off is recorded as a "0" period. The units that remain on for the entire period are called normally on units, the units that remain off for the entire period are called normally off units, and the units that experience start-stop changes are called start-stop units. Among them, the normally off units and the normally on units that maintain maximum output throughout the entire period always meet the unit ramping constraints and therefore do not need to be adjusted.

[0238] For the normally-on units, the output of the normally-on units with output changes during the entire period is adjusted to meet the unit climbing constraints. Since the entire period of this type of unit is a "1" type period, the "increase in time and test in reverse time" method is adopted to adjust the unit output to meet the unit climbing constraints. The specific process is as follows:

[0239] S6.1.1. Increase in time, the steps comprising:

[0240] S6.1.1.1, Order ,in is the initial moment of the “1” type period;

[0241] S6.1.1.2 If ,but ;

[0242] like ,but ;

[0243] S6.1.1.3. Let t = t + 1. If , go to step S6.1.1.2, otherwise end the adjustment, where The end time of the "1" type period;

[0244] S6.1.2. Reverse time test, the steps include:

[0245] S6.1.2.1, Order ;

[0246] S6.1.2.2 If ,but ;

[0247] S6.1.2.3. Let t = t - 1. If , go to step S6.1.2.2, otherwise end the adjustment;

[0248] For the start-stop units, the output and start-stop status of the start-stop units are adjusted to meet the unit climbing constraints; the full period of the start-stop units includes both "1" type period and "0" type period; the "0" type period may include the first end moment (the first moment), the end moment (the 24th moment), or only the middle moments (the 2nd to 23rd moments); first, the "1" type period adopts the "clockwise increase and counterclockwise test" method to adjust the unit output to meet the unit climbing constraints; then, the "0" type period containing different moments of the start-stop units is adjusted. The specific process is as follows:

[0249] S6.2.1. For the first end moment (the first end moment refers to the first moment, the middle moment refers to any moment from the second to the 23rd moment, and the last end moment refers to the 24th moment), when the "0" type period contains the first end moment, it is necessary to adjust the unit output and start / stop status at the right end moment of the "0" type period; assuming that the "0" type period is "1 to t1" (i.e., from the first moment to the t1th moment), and t1 is the right end moment of the "0" type period, then:

[0250] S6.2.1.1, let t = t1;

[0251] S6.2.1.2 If ,but and , and go to step S6.2.1.3, otherwise end the adjustment, where, is the output of unit g at time t+1;

[0252] S6.2.1.3. Let t = t - 1. If t ≥ 1, go to step S6.2.1.2; otherwise, end the adjustment.

[0253] S6.2.2. For the terminal moment (the 24th moment), when the “0” type period contains the terminal moment, it is necessary to adjust the unit output and start / stop status at the left end moment of the “0” type period; assuming that the “0” type period is “t2 to N T ", t2 is the left end of the "0" type period, then:

[0254] S6.2.2.1, let t = t2;

[0255] S6.2.2.2, if ,but and , and go to step S6.2.2.3, otherwise end the adjustment, where, is the output of unit g at time t-1;

[0256] S6.2.2.3. Let t = t + 1, if t ≤ N T , go to step S6.2.2.2, otherwise end the adjustment;

[0257] S6.2.3. For the intermediate moments (the 2nd to 23rd moments), when the "0" period only includes the intermediate moments, the unit output and start / stop status at the left and right ends of the "0" period need to be adjusted simultaneously; assuming that the "0" period is "t3 to t4", t3 and t4 are the left and right ends of the "0" period, respectively, then:

[0258] S6.2.3.1. For the left end adjustment of the "0" type period, let t = t3;

[0259] S6.2.3.2, if ,but and , go to step S6.2.3.3, otherwise end the left end adjustment;

[0260] S6.2.3.3. Let t = t + 1. If t ≤ t4, go to step S6.2.3.2. Otherwise, end the left end adjustment.

[0261] S6.2.3.4. For the right-end adjustment of the "0" type period, let t = t4;

[0262] S6.2.3.5, if ,but and , go to step S6.2.3.6, otherwise end the right end adjustment;

[0263] S6.2.3.6. Let t = t - 1. If t ≥ t3, go to step S6.2.3.5. Otherwise, end the right-end adjustment.

[0264] S6.2.3.7. After the adjustment at both ends is completed, the downtime of the unit in the "0" period is calculated. ;like , indicating that the “0” type period still meets the minimum downtime constraint, and the adjustment is completed; if , indicating that the "0" type period cannot meet the minimum downtime constraint; in order to maintain the system power balance, the "0" type period and the previous and next "1" type periods are combined into a "1" type period; finally, the "increase in time and check in reverse time" method is adopted to adjust the unit output of the newly formed "1" type period to meet the unit climbing constraint.

[0265] In S7, the precise redundant unit adjustment strategy is used to adjust the unit output and start / stop status at each time based on the satisfaction of various constraints to obtain the final solution to the unit combination problem. The specific process is as follows: Since the unit output at the first and last time is affected by the unit ramping constraint at the adjacent time at one end, and the middle time is affected by the unit ramping constraint at the adjacent time at both ends, the adjustment process divides the entire period into the first-end period containing the first-end time, the middle period containing only the middle time, and the last period containing the last time for redundant unit adjustment.

[0266] For the headend period:

[0267] S7.1.1, let t = 1;

[0268] S7.1.2. Calculate the redundant output R1 at the head end:

[0269] ;

[0270] Where, Indicates the output of unit g at the first end moment; Indicates the load at the head end;

[0271] S7.1.3, Order To ensure economy, reducing the output of redundant units should start from the least prioritized units.

[0272] S7.1.4, Order and ;

[0273] S7.1.5, Computer Group g Adjustable Amount:

[0274] ;

[0275] Where, Indicates the right end time of the first end period (the first end period only includes the first and second moments, in which case the right end time is the second moment, so it is expressed as ) The output of unit g;

[0276] S7.1.6 If ,but and , let g = g - 1. If g ≥ 1, go to step S7.1.5, otherwise end the adjustment;

[0277] like ,but , end the adjustment;

[0278] For the middle period:

[0279] S7.2.1, let t = 2;

[0280] S7.2.2. Calculate the redundant output at time t:

[0281] ;

[0282] S7.2.3, Order ;

[0283] S7.2.4, Order and ;

[0284] S7.2.5, Computer Group g Adjustable Amount:

[0285] ;

[0286] S7.2.6 If ,but and , let g = g - 1, if g ≥ 1, go to step S7.2.5, otherwise go to step S7.2.7;

[0287] like ,but , go to step S7.2.7;

[0288] S7.2.7. Let t = t + 1. If , then go to step S7.2.2, otherwise end the adjustment;

[0289] For the terminal period, the adjustment process of the terminal period is the same as that of the first period. Only the influence of the output of the unit at one end needs to be considered, that is, the output of the unit at the left end of the terminal period (the terminal period only includes the 23rd and 24th moments, and the left end moment is the 23rd moment) is considered.

[0290] In S8, after the redundant units are adjusted for the head, middle, and tail periods, the sum of the unit outputs at each time is fixed. To further reduce unit operating costs, output adjustments between units are required. This adjustment is performed by dividing the entire period into the head, middle, and tail periods, and increasing the output of priority units and decreasing the output of non-priority units. The adjustment process for the middle period is as follows:

[0291] S8.1, let t = 2;

[0292] S8.2, set g = 1;

[0293] S8.3, if , go to step S8.9, otherwise:

[0294] ;

[0295] Where, Indicates the power that the priority unit can increase;

[0296] S8.4, Order , , Indicates the power that can be reduced for non-priority units; Indicates the total reduction in power of non-priority units; the priority order method requires that priority units output more and non-priority units output less;

[0297] S8.5, Order , i is the index of the unit (non-priority unit); here it refers to the unit with the lowest priority (the last unit after sorting) At the beginning, the output of non-priority units is reduced; S8.2 means starting from the highest priority unit 1, the output of priority units is increased, and the two eventually reach a power balance;

[0298] S8.6, if ,but:

[0299] ;

[0300] Otherwise, go to step S8.8;

[0301] in, is a 0-1 integer variable, indicating the start / stop status of unit i at time t ( and similarly); 、 、 They represent the output of unit i at time t, time t-1, and time t+1 respectively; 、 They represent the speed limits for increasing and decreasing the power of unit i respectively; is the minimum output of unit i;

[0302] S8.7, if ,but:

[0303] ;

[0304] ;

[0305] ;

[0306] Go to step S8.8;

[0307] like ,but:

[0308] ;

[0309] ;

[0310] Go to step S8.10;

[0311] S8.8. Let i = i - 1. If i > g, go to step S8.6; otherwise, go to step S8.9.

[0312] S8.9, let g = g + 1, if , go to step S8.3, otherwise go to step S8.10;

[0313] S8.10, let t = t + 1, if , go to step S8.2, otherwise end the adjustment;

[0314] For the first and last period, they are only affected by the ramp constraints of the units at adjacent times at one end. Single-end adjustment can be performed in the same way as the adjustment process for the middle period.

[0315] After the adjustment is complete, the minimum operating cost of the unit combination problem is calculated based on the obtained unit output and start-stop status (minimizing the objective function OF). At this point, the final unit output and start-stop status can be obtained and substituted into the objective function formula to directly solve for the minimum operating cost OF.

[0316] The verification process is:

[0317] This embodiment is analyzed and verified using a 10-unit (generator) test system, demonstrating the heuristic strategy adjustment process based on the priority method. The unit output, start-stop status, operating costs, and solution time are analyzed separately.

[0318] Calculation is performed according to the formula and method provided in this embodiment. First, the 10 units are sorted from small to large using the sorting factor. Second, an initial solution is obtained based on considerations of system power balance constraints, spinning reserve constraints, and unit output boundary constraints. Then, the unit output and start / stop status are adjusted using a unit adjustment strategy based on minimum start / stop time constraints, a simple redundant unit adjustment strategy, and a unit adjustment strategy based on ramping constraints to obtain an approximate solution. Finally, the unit output and start / stop status are adjusted using a precise redundant unit adjustment strategy, and output adjustment between units is performed to obtain a final solution, and the minimum operating cost is calculated.

[0319] Depend on Figure 2It can be seen that the order of the units after sorting is unit 1, 2, 4, 3, 5, 6, 7, 8, 9, and 10. The output curve of the initial solution satisfies the unit output boundary constraints, system power balance constraints, and spinning reserve constraints, but some units violate the minimum start-stop time constraints and unit climbing constraints at some moments. From the perspective of the unit start-stop status, the minimum downtime of unit 5 is 6 hours, but the downtime at the 17th moment is less than 5 hours. The minimum downtime of unit 6 and unit 7 is 3 hours, but the downtime of unit 6 at the 22nd moment and unit 7 at the 22nd moment is less than 3 hours, which violates the minimum start-stop time constraint. From the perspective of unit output changes, units 1, 2, 8, 9, and 10 did not violate the unit climbing constraints. Unit 4 violated the unit ramping constraint at times 5, 6, 17-18, and 23; unit 3 violated the unit ramping constraint at times 6-7, 16, 18-19, and 23; unit 5 violated the unit ramping constraint at times 9, 15, 20, and 22; unit 6 violated the unit ramping constraint at times 10, 14, and 21; and unit 7 violated the unit ramping constraint at times 12-13. Analysis of the initial solution shows that the initial solution of the priority method violates the constraints. The proposed heuristic adjustment strategy will be used to adjust the unit output and start / stop status to meet the unit combination constraints and improve the quality of the solution.

[0320] Depend on Figure 3 As can be seen, the approximate solution for the 10 units has changed its startup and shutdown status. Each colored square, except red, represents the corresponding unit being started. The red square indicates that the unit was restarted at that time after adjustment. This means that the startup and shutdown status of units 5, 6, and 7 have changed. Unit 5's minimum downtime is 6 hours, but at time 17, it was less than 5 hours, so it was started at times 16 and 17. Similarly, unit 6 was started at time 22, and unit 7 was started at time 22.

[0321] Depend on Figure 4It can be seen that after using the unit adjustment strategy based on minimum start-stop time constraints, the simple redundant unit adjustment strategy, and the unit adjustment strategy based on ramping constraints, the unit output curves of units 1, 2, 8, 9, and 10 in the approximate solution remained unchanged. Unit 4 increased its output at times 3-5, 16-17, and 22-23, satisfying the unit ramping constraints for the entire period. Similarly, unit 3 increased its output at times 4-7, 16-18, and 22; unit 5 increased its output at times 6-9, 14-19, and 21-22; unit 6 increased its output at times 9-10 and 13-14; and unit 7 increased its output at times 11 and 13. Overall, the heuristic adjustment method of "forward-time increase and reverse-time verification" solved the problem of large unit output fluctuations and failure to meet unit ramping constraints, resulting in smoother unit output changes and significantly improved unit ramping performance.

[0322] Depend on Figure 5 As can be seen, after using the precise redundant unit adjustment strategy, the output of all units decreased, except for non-priority units 8, 9, and 10, which remained unchanged. Unit 1 reduced its output at time 22; unit 2 reduced its output at times 3-5, 16-19, and 22-23; unit 4 reduced its output at times 5-9, 17-19, and 21-23; unit 3 reduced its output at times 7-9, 13-16, 18-19, and 21-22; unit 5 reduced its output at times 9-11 and 13-16; unit 6 reduced its output at time 11; and unit 7 reduced its output at times 9-11 and 13-16. Overall, the final solution meets the unit ramping constraints and reduces the output of the redundant units.

[0323] Table 1 Comparison of operating results of 10 units

[0324]

[0325] Comparing the test results obtained by the proposed solution method in this example with those obtained using the commercial solver Gurobi 11.0.1, Table 1 shows that the proposed solution method has an operating cost approximately 0.59% higher than that of Gurobi. However, the proposed solution method takes 0.46 seconds less to solve than Gurobi, a reduction of nearly 40.7%. This demonstrates that while the proposed solution method in this example compromises accuracy, it eliminates the need for complex iterative calculations and offers a faster solution speed, making it suitable for solving time-sensitive unit commitment problems.

Claims

1. A heuristic solution method for unit commitment based on priority order method, characterized by The following steps are involved: S1. With the goal of minimizing fuel costs and startup costs, the objective function of the power system unit combination model is constructed, and unit output boundary constraints, system power balance constraints, spinning reserve constraints, unit ramping constraints, start-stop logic constraints, and minimum start-stop time constraints are set; S2. Use the average full-load cost as the ranking factor and sort the units in ascending order; S3. Determine the start and stop status of the units to satisfy the spinning reserve constraint, and then determine the unit output to satisfy the system power balance constraint and the unit output boundary constraint, thereby obtaining an initial solution to the unit commitment problem; S4. Adjust the unit output and start / stop status using a unit adjustment strategy based on minimum start / stop time constraints; S5. Set a simple redundant unit adjustment strategy to adjust the unit output and start / stop status, and obtain an approximate solution to the unit combination problem; S6. Adjust the unit output and start / stop status using a unit adjustment strategy based on ramp constraints; S7. Set precise redundant unit adjustment strategy to adjust unit output and start / stop status; S8. Adjust the output between the units to obtain the final solution and calculate the minimum operating cost; In S1, the objective function OF of the power system unit combination model is: ； Where N T is the total optimization period, t represents one of the moments; N G is the number of units, g represents one of the units; is the output of unit g at time t; 、 is a 0-1 integer variable, representing the start and stop status of unit g at time t and time t-1 respectively. The value is 1 for start and 0 for stop; is the startup cost of unit g; is the fuel cost of unit g; The expression is: ； Where, 、 、 is the power generation cost coefficient of unit g; The expression is: ； Where, 、 are the hot start cost and cold start cost of unit g respectively; is the continuous downtime of unit g at time t; is the minimum downtime of unit g; is the cold start time of unit g.

2. The heuristic solution method for unit commitment based on priority method according to claim 1 is characterized in that: In the above S1, the constraints are specifically: Unit output boundary constraints: ； Where, 、 Respectively represent the minimum and maximum values ​​of the unit's g output; System power balance constraints: ； Where, represents the load at time t; Spinning reserve constraints: ； Where, represents the spare capacity at time t; Unit climbing constraints: ； ； Where, is the output of unit g at time t-1; 、 They represent the speed limits for the increase and decrease of the unit's g power respectively; and They represent the startup power speed limit and shutdown power speed limit of unit g respectively; and All are 0-1 integer variables. Indicates the startup operation of unit g at time t. A value of 1 indicates that the startup operation was performed at time t, and a value of 0 indicates that the startup operation was not performed; Indicates the shutdown operation of unit g at time t. A value of 1 indicates that the shutdown operation was performed at time t, and a value of 0 indicates that the shutdown operation was not performed; Start-stop logic constraints: ； ； Minimum start and stop time constraints, including minimum start time constraints and minimum stop time constraints: ； ； Where, 、 represents a 0-1 integer variable, which represents the start-up and shutdown operations of unit g at time s; is the minimum startup time of unit g; Indicates a universal quantifier.

3. The heuristic solution method for unit commitment based on priority method according to claim 2 is characterized in that: In S2, the average full-load cost refers to the average power generation cost of the unit in full power state, which is the power generation cost of the unit in full power state divided by the maximum output of the unit. For unit g, its average full-load cost is Expressed as: 。 4. The heuristic solution method for unit commitment based on priority method according to claim 2 is characterized in that: In S3, the process of obtaining the initial solution of the unit commitment is: S3.

1. Determine the start and stop status of the units to satisfy the spinning reserve constraint. Assuming that the start and stop status of all units is 0 at each moment, the process is as follows: S3.1.1, let t = 1; S3.1.

2. Let g = 1, indicating the first unit after sorting; S3.1.3, Order , The sum of the maximum outputs of the units started at time t; S3.1.4, Order ; S3.1.5 If ,but , let g=g+1, if at this time , go to step S3.1.4, otherwise go to step S3.1.6, where Indicates the last unit after sorting; like ,but , go to step S3.1.6; S3.1.6, let t = t + 1, if , go to step S3.1.2, otherwise end the adjustment; S3.

2. Determine the unit output to satisfy the system power balance constraint and the unit output boundary constraint, thereby obtaining the initial solution to the unit combination problem. Assuming that the output of all units at each moment is 0, the process is as follows: S3.2.1, let t = 1; S3.2.2, let g = 1; S3.2.3, Order , is the sum of the power of the units started at time t; S3.2.4 If , go to step S3.2.6, otherwise , at this time, if ,but ,like ,but ; S3.2.5, let g = g + 1, if , go to step S3.2.4, otherwise go to step S3.2.6; S3.2.6, let t = t + 1, if , go to step S3.2.2, otherwise end the adjustment.

5. The heuristic solution method for unit commitment based on priority method according to claim 4 is characterized in that: In the above S4, the unit output and start-stop status are adjusted using the unit adjustment strategy based on the minimum start-stop time constraint. Specifically, if the minimum start-up time constraint cannot be met at a certain moment, the unit is started at the next moment; if the minimum stop time constraint cannot be met at a certain moment, the unit is started at that moment; when the state of unit g at time t changes from 0 to 1, the output of unit g is .

6. The heuristic solution method for unit commitment based on priority method according to claim 5, characterized in that: In S5, a simple redundant unit adjustment strategy is set to adjust the unit output and start-up and shutdown status to obtain an approximate solution to the unit combination problem. Specifically, when the sum of the unit outputs exceeds the total load demand, the system output is redundant, and the redundant unit output needs to be adjusted. During the adjustment process, the simple redundant unit adjustment strategy takes into account the influence of the unit output boundary constraint, the system power balance constraint, and the spinning reserve constraint, and does not involve the unit ramping constraint. The adjustment starts from the unit with the lowest priority, and the process is as follows: S5.1.1, let t = 1; S5.1.

2. Calculate the redundant output at time t : ； S5.1.3, Order ; S5.1.4, Order , , Indicates the adjustable amount of the unit g, is the total adjustment amount at time t; S5.1.5 Calculation : ； S5.1.6 If ,but , ; Let g = g - 1. If g ≥ 1, go to step S5.1.5; otherwise, go to step S5.1.

7. like ,but , go to step S5.1.7; S5.1.

7. Let t = t + 1. If , go to step S5.1.2, otherwise end the adjustment.

7. The heuristic solution method for unit commitment based on priority method according to claim 6 is characterized in that: In the aforementioned S6, the unit output and start / stop status are adjusted using a unit adjustment strategy based on ramp constraints. Specifically, the time periods and units are classified according to the start / stop changes of the units; the period of continuous unit startup is recorded as a "1" period, and the period of continuous unit shutdown is recorded as a "0" period; Units that remain on at all times are called normally-on units, units that remain off at all times are called normally-off units, and units that alternate between starting and stopping are called start-stop units. Normally-off units and normally-on units that maintain maximum output at all times always meet the unit ramping constraints, so no adjustments are required. For the normally-on units, the output of the normally-on units with output changes during the entire period is adjusted to meet the unit climbing constraints. Since the entire period of this type of unit is a "1" period, the "increase in time and check in reverse time" method is adopted to adjust the unit output to meet the unit climbing constraints. The specific process is as follows: S6.1.

1. Increase in time, the steps comprising: S6.1.1.1, Order ,in is the initial moment of the "1" type period; S6.1.1.2 If ,but ; like ,but ; S6.1.1.

3. Let t = t + 1. If , go to step S6.1.1.2, otherwise end the adjustment, where The end time of the "1" type period; S6.1.

2. Reverse time test, the steps include: S6.1.2.1, Order ; S6.1.2.2 If ,but ; S6.1.2.

3. Let t = t - 1. If , go to step S6.1.2.2, otherwise end the adjustment; For the start-stop units, the output and start-stop status of the start-stop units are adjusted to meet the unit climbing constraints. The full period of the start-stop units includes both "1" type periods and "0" type periods. First, the "1" type period" is adjusted to meet the unit climbing constraints by using the "increase in time and check in reverse time" method. Then, the start-stop units are adjusted for the "0" type periods at different times. The specific process is as follows: S6.2.

1. For the first end time, when the "0" type period contains the first end time, the unit output and start / stop status at the right end time of the "0" type period need to be adjusted; assuming that the "0" type period is "1 to t1", t1 is the right end time of the "0" type period, then: S6.2.1.1, let t = t1; S6.2.1.2 If ,but and , and go to step S6.2.1.3, otherwise end the adjustment, where, is the output of unit g at time t+1; S6.2.1.

3. Let t = t - 1. If t ≥ 1, go to step S6.2.1.2; otherwise, end the adjustment. S6.2.2 For the terminal time, when the "0" type period contains the terminal time, it is necessary to adjust the unit output and start-stop status at the left end of the "0" type period; assuming that the "0" type period is "t2 to N T ", t2 is the left end of the "0" type period, then: S6.2.2.1, let t = t2; S6.2.2.2, if ,but and , and go to step S6.2.2.3, otherwise end the adjustment, where, is the output of unit g at time t-1; S6.2.2.

3. Let t = t + 1, if t ≤ N T , go to step S6.2.2.2, otherwise end the adjustment; S6.2.3 For intermediate moments, when the "0" period only includes the intermediate moments, the unit output and start / stop status at the left and right ends of the "0" period need to be adjusted simultaneously; assuming that the "0" period is "t3 to t4", t3 and t4 are the left and right ends of the "0" period, respectively, then: S6.2.3.

1. For the left-end adjustment of the "0" type period, let t = t3; S6.2.3.2, if ,but and , go to step S6.2.3.3, otherwise end the left end adjustment; S6.2.3.

3. Let t = t + 1. If t ≤ t4, go to step S6.2.3.

2. Otherwise, end the left end adjustment. S6.2.3.4 For the right-end adjustment of the "0" type period, let t = t4; S6.2.3.5, if ,but and , go to step S6.2.3.6, otherwise end the right end adjustment; S6.2.3.

6. Let t = t - 1. If t ≥ t3, go to step S6.2.3.

5. Otherwise, end the right-end adjustment. S6.2.3.

7. After the adjustment at both ends is completed, the downtime of the unit in the "0" period is calculated. ;like , indicating that the "0" type period still meets the minimum downtime constraint, and the adjustment is completed; if , indicating that the "0"-type period cannot meet the minimum downtime constraint; to maintain system power balance, the "0"-type period and the preceding and succeeding "1"-type periods are combined into a "1"-type period; finally, the "forward-time increase, reverse-time test" method is adopted to adjust the unit output of the newly formed "1"-type period to meet the unit ramp constraint.

8. The heuristic solution method for unit commitment based on priority method according to claim 7 is characterized in that: In S7, the precise redundant unit adjustment strategy is used to sequentially adjust the unit output and start / stop status at each time based on satisfying various constraints to obtain the final solution to the unit combination problem. The specific process is as follows: since the unit output at the first and last time is affected by the unit ramping constraint at the adjacent time at one end, and the middle time is affected by the unit ramping constraint at the adjacent time at both ends, the adjustment process divides the entire period into a first-end period containing the first-end time, a middle period containing only the middle time, and a last period containing the last time for redundant unit adjustment; For the headend period: S7.1.1, let t = 1; S7.1.

2. Calculate the redundant output R1 at the head end: ； Where, Indicates the output of unit g at the first end moment; Indicates the load at the head end; S7.1.3, Order ; S7.1.4, Order and ; S7.1.5, Computer Group g Adjustable Amount: ； Where, Indicates the output of unit g at the right end of the first period; S7.1.6 If ,but and , let g = g - 1. If g ≥ 1, go to step S7.1.5, otherwise end the adjustment; like ,but , end the adjustment; For the middle period: S7.2.1, let t = 2; S7.2.

2. Calculate the redundant output at time t: ； S7.2.3, Order ; S7.2.4, Order and ; S7.2.5, Computer Group g Adjustable Amount: ； S7.2.6 If ,but and , let g = g - 1, if g ≥ 1, go to step S7.2.5, otherwise go to step S7.2.7; like ,but , go to step S7.2.7; S7.2.

7. Let t = t + 1. If , then go to step S7.2.2, otherwise end the adjustment; For the terminal period, the adjustment process of the terminal period is the same as that of the first period. Only the influence of the output of the unit at one end needs to be considered, that is, the output of the unit at the left end of the terminal period.

9. The heuristic solution method for unit commitment based on priority method according to claim 8, characterized in that: In S8, after the redundant units are adjusted for the head-end period, the middle period, and the end period, the sum of the unit outputs at each time is fixed. At this point, the outputs of the units need to be adjusted. The adjustment method is to divide the entire period into the head-end period, the middle period, and the end period, and adjust the output by increasing the output of the priority units and reducing the output of the non-priority units. The adjustment process for the middle period is as follows: S8.1, let t = 2; S8.2, set g = 1; S8.3, if , go to step S8.9, otherwise: ； Where, Indicates the power that the priority unit can increase; S8.4, Order , , Indicates the power that can be reduced for non-priority units; Indicates the total reduction in power of non-priority units; S8.5, Order , i is the index of the unit; S8.6, if ,but: ； Otherwise, go to step S8.8; in, is a 0-1 integer variable, indicating the start / stop status of unit i at time t; 、 、 They represent the output of unit i at time t, time t-1, and time t+1 respectively; 、 They represent the speed limits for increasing and decreasing the power of unit i respectively; is the minimum output of unit i; S8.7, if ,but: ； ； ； Go to step S8.8; like ,but: ； ； Go to step S8.10; S8.

8. Let i = i - 1. If i > g, go to step S8.6; otherwise, go to step S8.

9. S8.9, let g = g + 1, if , go to step S8.3, otherwise go to step S8.10; S8.10, let t = t + 1, if , go to step S8.2, otherwise end the adjustment; For the first and last period, they are only affected by the ramp constraints of the units at adjacent times at one end. Single-end adjustment can be performed in the same way as the adjustment process for the middle period. After the adjustment is completed, the minimum operating cost of the group combination problem is calculated based on the obtained unit output and start-stop status.

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