The problem is one of the most important problems in the economic operation of the power system. It is defined as the thermal power unit with the minimum operating cost (fuel cost + start-up fee) under various constraints within one inspection period, such as day, month, etc. Operational plan Obviously, UC is essentially an optimal combination problem. In theory, all the possible combinations of the thermal power units in question can be compared to get the best combination. However, all possible combinations of this kind are in practical problems. The middle is an astronomical number. Take the UC of a 10-machine system as an example. All possible combinations of generators are 1.73<1072. It is almost impossible to investigate them all.
In addition, due to the existence of various constraints, UC becomes an extremely complicated engineering problem. It is very difficult to obtain the best solution. In practice, it is generally adopted to quickly and effectively find the quasi-optimal solution. So far, many effective ways to solve the optimization problem when the generator has a matrix that can be obtained from the following power flow equation, each element is: the starting node of the power takes + 1, the end node takes -1, the other takes 0; And F is the line susceptance matrix, which is a diagonal matrix of /K/; / is the total number of lines of the system.
2.3 As stated in Section 1 of the Proposal Solution, the influence of network factors is not considered in the UC solution. If the solution is applied to the actual system, the SR loss may be caused in some time bands due to the existence of network loss. There is also the possibility of line overload, which has been specifically investigated in the report and in order to further improve the practicability of this UC solution, this paper introduces OPF in the process of repeatedly obtaining the quasi-optimal solution, so as to When solving UC, it is possible to prioritize the starting of each generator of the network.
The processing of the Step3SR constraint first calculates the network loss by the OPF for the initial UC, and detects that the SR does not satisfy the specified time zone when the network loss is included, and then merges the power generation in the time zone in the time zone according to the startup priority order. The machine meets the SR and releases the redundant generator without violating the SR.
Overloading the time zone and overload line, and eliminating the overload by adjusting the output of the parallel generator or changing the configuration of the parallel generator in the UC, and redundantly generating power while ensuring that the SR is satisfied and no overload occurs. The machine is released.
If the planned running time is much shorter than the MUT's short generator, or the motor is replaced by another generator, if the corresponding MDTMUT is not met, the UC solution is corrected to meet the requirements, and then the redundant power generation is checked and released. Check the overload of the Step7 line again. Check if there is any line overload. If there is an outage time to eliminate it, if you need to correct the UC solution Step9 again, calculate the operation fee including the start-up fee, if it gets Further improvement will enter Step10, otherwise the calculation will end. Step 10 update priority will recalculate the utilization of each generator with the UC solution that satisfies all constraints and considers the network loss and line overload, and according to this new utilization rate. Start the update order, and then return to Step3 to explain the various links as follows: The network is taken into consideration and the regulator is added and the driver is changed! If there are more than eight or more generators in the middle solution, an initial UC solution is formed at the same time during the entire planning period and at the bookmark3, and the starting priority of each generator is determined according to this solution. However, it needs to be added here, that is, in the initial outage state, they cannot be prioritized by utilization. In this case, the "unit price of electricity generation" (ie, unit cost of electricity generation) method used herein determines the priority order of these generators. Step3 considers the constraint SR condition when considering the network loss, but if such a generator is inefficient and starts The order of priority is very low, so if it can be achieved, it can achieve the purpose of eliminating overload, but it may also cause large economic losses. On the other hand, from the economic point of view, if the power generation is combined in the starting priority order. Machine, then it may have no effect or less effect on eliminating overload.
Based on the above considerations, this paper proposes the following elimination overload algorithm, enter (2), otherwise go to (6) (5) until all time zones are processed.
According to the above solution, when the output of the generator is insufficient to cancel the line overload and the existing UC solution needs to be changed, the incorporated generator can be both effective for eliminating overload and having a higher starting priority, thereby enabling The economic cost of eliminating overload is small.
Step5 From the economic point of view, when a generator's planned running time is much smaller than its MUT (called short-term operation), it is more appropriate to remove it or replace it with other generators. To this end, this paper proposes the following processing method: detecting the short-time running generator along the reverse priority order, if it is removed and does not violate the SR constraint, then it will be lifted, otherwise it is not listed in the starting priority order. After the paralleling, no short-running generator is formed instead; when there is no generator that can replace the operation, the original UC solution is maintained, and when it is possible to replace the operation, it is further checked in the reverse priority order. Redundant generators, if any, cancel Step 6 one by one, check the outage time of each generator according to the starting priority order, satisfy it if the MDT constraint is not met, and release the priority without violating the SR constraint. The redundant generators with low order then check the running time of each generator and satisfy the MUT constraints. Step7 In Step 5 and Step 6, in order to pursue economical efficiency, the generators are operated for a short time without violating the SR constraints. To cancel or replace the operation and the release of the redundant generator, it is possible to create a new line overload, so it is necessary to throw the Step4 å† again - use the last name to find the line trend. Excessive load is issued by Zhaohuan. This time, when processing constraints, it is not necessary to sculpt/redundantly generate power. After step7, it is possible that the MDT.MUT constraint of some generators will not be satisfied again. They are checked. However, in order to avoid the infinite loop of the solution process.
Step9 In Step 7, the detailed OPF has been performed for all time zones, so it is only necessary to recalculate the time zone after the UC solution changes after Step 8.
In the following, the proposed method is tested by a specific example. 3 Example 3.1 Test System This paper uses an 8-machine 44-bus system (actually a simplified model of the Hokkaido power system in Japan, and the system data presented below is provided by Hokkaido Electric Power Co., Ltd.). The proposed method is trial-calculated. The planned time is taken as 1 day (ie, UC) and divided into 24 time zones as the system connection diagram. Table 1 shows the consumption characteristics (fuel cost characteristics) constant and the upper and lower limits of the generator. Table 2 shows The system load of 24 time zones, Table 3 is the system load of 24 time zones, and Table 4 is the load ratio of each load node (for simplicity, it is assumed that it does not change with time zone), the line parameters are shown in the table. 4 Table 1 Generator characteristic constant Generator (node) No. Generator fuel cost (starting fee) Characteristic constant Generator output / MW / Note: Second approximation, in the table () is the starting fee characteristic constant Table 2 System load table of time zone (t) Table 3 Load ratio of each load node Node ratio % node ratio % node ratio % node ratio % Note: A node not shown is a no-load node.
Table 4 Line parameters (standard value) Note: i is the line start node; j is the line end node u for each constraint condition, here assumes that all generators have MUT= 4h; SR accounts for system load (including network loss) about the line For power flow constraints, only the heavy-duty lines 15~26 located in the middle of the system are considered for simplicity. The maximum capacity is 100MW. 3.2 The trial results In order to investigate the impact of network loss and line overload on UC, the proposed method will be proposed. Apply to the test system shown in the previous section and perform the following four conditions (cases): do not consider network loss and line overload; consider the network loss and line overload according to the trial calculation under various conditions of the day UC The solution is shown in Figure (d), the daily running fee and the calculation time (using the equivalent of å©ä»–-1111,700 çš¿, shown in Table 5, the calculation condition, the operation fee, the 10,000 yen (starting fee), the calculation time/s first comparison. (a) and (b), visible condition (1) and condition (2) UC solution is different from the start and stop plan of the No. 7 and No. 8 machines, the latter running longer than the former because of the condition (1) In the next UC solution, the time zone 1 2021 has fewer SRs (just full) 4 Conclusion Based on the heuristic generator start-stop plan method, the optimal power flow calculation is introduced in the process of repeatedly obtaining the quasi-optimal solution one by one to satisfy the constraint conditions, so as to solve the generator including the influence of network factors. It is possible to stop the plan and propose a method to eliminate the line overload by adjusting the output of the generator and changing the start and stop plan of the generator, so that the practicality of the start-stop planning method for the practical application is further improved. Taking an 8-machine 44-bus system as the test system, the proposed method is simulated under various conditions. From the simulation results, the proposed method can specifically grasp the impact of network loss and line overload on the start-stop plan of the generator. In the study of the start-stop plan problem, the network loss is generally considered to have little effect or because it will make the problem extremely complicated and neglected, but the trial results in this paper indicate that the network loss not only affects the generator output, Moreover, in some time periods, the generator start-stop plan is sometimes affected, so that the acceleration rate of the running fee is often greater than the network loss rate. Considering the influence of network factors on the start-stop plan of the generator, not only the line overload constraint, but also the network loss is necessary, especially for systems with large network losses. However, considering the network loss will greatly increase the calculation time, but it needs to be fast. The large-scale system for online calculation does not allow the calculation time to be too long. In this case, the method of indirectly considering the network loss mentioned in Section 23 can be considered, that is, the operation standby capacity constraint stage is satisfied in the algorithm to properly operate the generator. The capacity margin is larger, so that the network loss can be eliminated for the purpose of fast calculation when performing optimal power flow calculation. In recent years, in the power industry at home and abroad, the power market for the purpose of introducing competition to promote the activation of the power industry and to strengthen various service standards is being formed or will be formed. The power sector such as power generation, power transmission and power supply that has been previously managed and managed will be dismantled. Become independent economic entities. In the power market environment, the traditional power system operation concept and operation technology or method will also change accordingly. In the future, the author will try to study the generator start-stop planning method in this new environment.
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