Power system two-stage scheduling decision-making method considering new energy

Abstract

The invention discloses an electric power system two-stage scheduling decision-making method considering new energy, relates to the field of electric power systems and automation thereof, and aims to effectively represent the total supply capacity of new energy frequency modulation capacity and introduce new energy to participate in scheduling decision-making. Therefore, the output plan and the frequency modulation capacity reservation condition of the conventional thermal power generating unit and the new energy unit are reasonably formulated in the day-ahead scheduling decision-making stage so as to relieve the problem of insufficient power grid regulation capability caused by high-proportion new energy grid connection.

Description

Technical Field

[0001] The present invention relates to the field of power systems and automation thereof, and in particular to a two-stage dispatching decision method for power systems taking new energy sources into account. Background Art

[0002] Building a new power system with new energy as the main body is a key way to implement the "dual carbon" goal; however, with the continuous increase in the proportion of new energy access with strong random fluctuation characteristics, the real-time balance pressure of power grid source and load has increased dramatically, seriously threatening the quality of power grid frequency; on the one hand, the random fluctuation characteristics of new energy have led to an increase in the demand for power grid frequency regulation; on the other hand, traditional controllable units such as thermal power will gradually withdraw due to the large-scale access of new energy, resulting in a decrease in the power grid frequency regulation capacity. Therefore, in a high-proportion new energy power system, it will be difficult to effectively cope with the random fluctuations of new energy by relying solely on conventional controllable units, and it is necessary to introduce new energy to participate in power grid frequency regulation.

[0003] At present, new energy units have the function of frequency regulation. Under the condition of reserving frequency regulation capacity, they can respond to the frequency regulation instructions issued by the power grid. However, there are few studies on embedding the supply characteristics of new energy frequency regulation capacity in the dispatching decision to reasonably formulate the planned output and frequency regulation capacity reservation of new energy units. They mainly include methods based on power reduction and methods based on reliable output of new energy. Among them, the method based on power reduction believes that the space between the planned output of new energy and its predicted output is the upper frequency regulation capacity that new energy can provide, and the space below the planned output is the lower frequency regulation capacity that new energy can provide. However, new energy has prediction errors, and it is difficult to accurately characterize the actual frequency regulation capacity that new energy can provide based on the predicted value. The method based on reliable output of new energy evaluates the output (i.e., reliable output) that can be achieved with a certain confidence level according to the output distribution of new energy, and limits the planned output of new energy to below the reliable output. It is believed that the space between the planned output of new energy and its reliable output is the upper frequency regulation capacity that new energy can provide, and the space below the planned output is the lower frequency regulation capacity that new energy can provide. This type of method can accurately characterize the frequency regulation capacity that renewable energy can actually provide. However, existing studies generally only consider the situation where a single renewable energy participates in frequency regulation. When multiple renewable energy sources jointly participate in scheduling decisions, due to the mutual offset of the prediction errors of renewable energy sources, the overall reliable output of renewable energy sources will be higher than the sum of the reliable outputs of individual renewable energy sources, thereby providing more frequency regulation capacity. In addition, after participating in frequency regulation, renewable energy sources will abandon part of their output, reducing their own random fluctuations, thereby causing a reduction in the system's frequency regulation capacity demand. This can be seen as the "extra frequency regulation capacity supply capacity" generated by renewable energy participating in frequency regulation. Existing studies have not considered this, which will lead to conservative scheduling decision results, that is, too much frequency regulation capacity is arranged to be provided by renewable energy sources, resulting in more renewable energy power abandonment costs. Summary of the invention

[0004] The purpose of the present invention is: in view of the above-mentioned problems, the present invention provides a two-stage dispatching decision method for an electric power system taking into account new energy sources. First, it is judged whether it is necessary to introduce new energy sources to participate in frequency regulation. When new energy sources are needed to participate in frequency regulation, the new energy sources that will participate in frequency regulation are selected in advance through the new energy frequency regulation unit optimization strategy. Finally, the dispatching decision model is used to reasonably formulate the dispatching plans of existing thermal power units and new energy units, so as to reasonably formulate the output plans and frequency regulation capacity reservation of conventional thermal power units and new energy units in the day-ahead dispatching decision stage, so as to alleviate the problem of insufficient grid regulation capacity caused by the high proportion of new energy sources connected to the grid.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A two-stage dispatch decision method for a power system taking into account new energy, wherein the power system includes existing thermal power units and new energy units, and the method includes:

[0007] A dispatch decision model for relaxing the frequency regulation capacity demand constraint is constructed, and the relaxation amount is obtained through the model. According to the relaxation amount, it is determined whether the new energy units need to be dispatched. The specific determination includes:

[0008] If the relaxation amount is 0, the dispatch plan is output through the dispatch decision model that relaxes the frequency regulation capacity demand constraint;

[0009] If the slack is not 0, then the slack is the system demand shortfall;

[0010] A scheduling decision model is constructed to characterize the overall supply capacity of the frequency regulation capacity of renewable energy. According to the slack amount and the output distribution characteristics of the renewable energy units, a heuristic method is used to screen out the renewable energy units that need to participate in the frequency regulation. At the same time, the overall frequency regulation capacity that can be provided by the renewable energy units is obtained and used as the boundary condition to complete the scheduling decision.

[0011] Furthermore, the dispatch decision model for relaxing the frequency regulation capacity demand constraint is constructed including:

[0012] The model objective function is established as follows:

[0013] C=min(C g +C w ) (1)

[0014]

[0015]

[0016] In the formula, C is the system operation cost, C g , C ware the total costs of thermal power units and new energy units respectively; g, t, and w are the numbers of existing thermal power units, dispatch period numbers, and new energy units respectively; G, T, and W are the collections of thermal power units, dispatch period, and new energy units respectively; Indicates the predicted output of new energy units. Provide energy quotation for new energy units; Indicates the output of thermal power units. Energy quotation for thermal power units, and Quote for up / down frequency regulation capacity of the unit; The up / down frequency regulation capacity of the unit won the bid; 1 / T e is the proportion of a single scheduling period duration in the day-ahead scheduling decision model to 1 hour, M is the penalty coefficient for the shortage of frequency regulation capacity demand, and ε UP , ε DN They are respectively the relaxation of the system's upward / downward frequency regulation capacity demand, representing the shortage of the system's upward / downward frequency regulation capacity demand.

[0017] Furthermore, the constraints of the model specifically include:

[0018] Power balance constraint, used to balance the load demand with the sum of the output of thermal power units and new energy units;

[0019] Frequency regulation capacity constraints: establish frequency regulation capacity constraints for thermal power units, system frequency regulation capacity requirements, and relax frequency regulation capacity constraints;

[0020] Output constraints of thermal power units, constructing upper and lower limits of thermal power unit output and up and down climbing capacity constraints;

[0021] Line power flow constraint controls the line transmission power to be no higher than the line transmission power upper limit.

[0022] Furthermore, the constraint condition is specifically implemented by the following formula:

[0023] Power balance constraints:

[0024]

[0025] In the formula, b is the node number; B is the node set; is the load forecast value;

[0026] Frequency regulation capacity constraints:

[0027]

[0028] ε UP ≥0 (9)

[0029] ε DN ≥0 (10)

[0030] In the formula, is the system up / down frequency regulation capacity requirement, R g,max,UP / DN The maximum / minimum frequency regulation capacity that can be provided by existing thermal power;

[0031] Output constraints of thermal power units:

[0032]

[0033]

[0034] Where P g,min With P g,max is the maximum and minimum output of existing thermal power units, r g,UP / DN The up / down ramping capability of existing thermal power units;

[0035] Line flow constraints:

[0036]

[0037] In the formula, l represents the line number, B represents the node set; H lb A represents the transfer distribution factor matrix element between the injected power and the active power flow; b The matrix element representing the relationship between unit g and node b; P l max Indicates the maximum line transmission capacity limit.

[0038] Furthermore, if the slack is not 0, the slack is the system demand shortfall, and a dispatch decision model representing the overall supply capacity of the frequency regulation capacity of new energy units is constructed;

[0039] This includes using heuristic methods to screen out the new energy units that need to participate in frequency regulation, and at the same time obtaining the overall frequency regulation capacity that can be provided by the new energy units, and using it as a boundary condition to construct a scheduling decision model that characterizes the overall supply capacity of the new energy frequency regulation capacity.

[0040] Furthermore, the dispatch decision model that characterizes the overall supply capacity of new energy frequency regulation capacity specifically includes:

[0041] Evaluate the actual frequency regulation capacity of a single renewable energy unit;

[0042] Screening new energy unit combinations that meet the system frequency regulation requirements;

[0043] After considering the mutual offset of prediction errors of multiple renewable energy sources and the participation of renewable energy units in frequency regulation, determine whether the renewable energy units can meet the system frequency regulation requirements. If not, add renewable energy units for re-screening. If the system frequency regulation requirements can be met, adjust the confidence level of the reliable output assessment of a single renewable energy source based on the equal confidence level idea based on the frequency regulation capacity actually provided by the renewable energy sources after the prediction errors are offset, so that the sum of the frequency regulation capacities that can be actually provided by a single renewable energy source after the adjustment is equal to the frequency regulation capacity that can actually be provided when all renewable energy sources are considered together before the adjustment.

[0044] Based on the dispatch decision model that relaxes the frequency regulation capacity demand constraints, the above-mentioned new energy frequency regulation units are added to participate in dispatch.

[0045] Furthermore, the actual frequency regulation capacity of a single renewable energy unit is evaluated as follows:

[0046]

[0047]

[0048] In the formula, Indicates the up / down frequency regulation capacity that new energy can provide. Indicates the new energy plan output, W r Represents the set of new energy units participating in frequency regulation;

[0049] The overall up / down frequency regulation capacity provided by a single renewable energy source is as follows:

[0050]

[0051]

[0052] In the formula, It indicates the frequency regulation capacity provided by a single renewable energy source overall; It indicates the reduction in the demand for up / down frequency regulation capacity of the system after the participation of new energy in frequency regulation;

[0053] The screening of the combination of new energy units that meet the system frequency regulation demand is performed without considering the phenomenon that the new energy prediction errors offset each other, and the combination that can cope with the shortage of system frequency regulation demand and requires the least number of new energy units is selected, and the new energy combination with the largest overall frequency regulation capacity supply capacity is selected from the combination, and the new energy in the combination will participate in the power grid frequency regulation;

[0054] After considering the mutual offset of multiple new energy prediction errors and the participation of new energy units in frequency regulation, the overall frequency regulation capacity supply capacity of new energy units is as follows:

[0055] The overall output distribution of the new energy units participating in frequency regulation follows a normal distribution, with a mean of the sum of the new energy prediction values ​​and a standard deviation of σ oAs shown below:

[0056]

[0057] After considering the total distribution of new energy frequency regulation units, the total frequency regulation capacity that new energy frequency regulation units can actually provide is shown in the following formula:

[0058]

[0059] In the formula, It can provide total frequency regulation capacity for new energy frequency regulation units;

[0060] Without considering the new energy units participating in frequency regulation, the system net load power follows a normal distribution, with a mean of the sum of the predicted values ​​of the new energy units not participating in frequency regulation and a standard deviation of σ b As shown below:

[0061]

[0062] After considering the mutual offset of multiple new energy forecast errors, the actual reduction in system up / down frequency regulation capacity demand caused by the participation of new energy in frequency regulation is shown in the following formula:

[0063] σ R =1.96σ-1.96σ b (twenty one).

[0064] Furthermore, based on the scheduling decision model with relaxed frequency regulation capacity demand constraints, the above-mentioned new energy frequency regulation units are added to participate in scheduling, and the objective function of the scheduling decision model that represents the overall supply capacity of new energy frequency regulation capacity is as follows:

[0065] C=min(C g +C w )(1)

[0066]

[0067]

[0068] Furthermore, the constraints of the objective function are as follows:

[0069] Power balance constraints:

[0070]

[0071] Frequency regulation capacity constraints:

[0072]

[0073] Restrictions on renewable energy output:

[0074]

[0075]

[0076] Formula (27) is the output constraint condition of the new energy frequency-regulating units; Formula (28) is the output constraint of the new energy non-frequency-regulating units, which means that the new energy units not participating in frequency regulation are fully absorbed.

[0077] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0078] Through the method proposed in the present invention, the planned output and frequency regulation capacity reservation of conventional thermal power units and new energy units can be reasonably formulated in the day-ahead scheduling decision-making stage, thereby effectively coping with the real-time source-load balance burden brought about by the large-scale access of new energy, and supporting the construction and advancement of new power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 It is a two-stage dispatch decision framework diagram in a two-stage dispatch decision method for a power system taking into account new energy sources according to the present invention;

[0080] Figure 2 It is a schematic diagram of system frequency regulation capacity demand in a two-stage dispatch decision method of a power system taking into account new energy sources according to the present invention;

[0081] Figure 3 It is a dispatching decision flow chart of the frequency regulation capacity supply capability of new energy units in a two-stage dispatching decision method of a power system taking new energy into account in the present invention;

[0082] Figure 4 A schematic diagram of the reserved capacity and impact of the overall frequency regulation capacity of the frequency regulation units of new energy sources in a two-stage dispatch decision method of a power system taking into account new energy sources in the present invention;

[0083] Figure 5 A schematic diagram of the expected abandonment of renewable energy in a two-stage dispatch decision method for a power system taking renewable energy into account according to the present invention;

[0084] Figure 6 It is a linearized approximate expression of the expected amount of energy curtailment in a two-stage dispatch decision method for an electric power system taking into account new energy sources in the present invention. DETAILED DESCRIPTION

[0085] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0086] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0087] The present invention proposes a two-stage dispatching decision framework for the power system taking into account the overall supply capacity of the frequency regulation capacity of new energy sources. The first stage is to construct a dispatching decision model that relaxes the frequency regulation capacity demand constraint without considering the participation of new energy sources in frequency regulation. According to the value of the relaxation amount, it can be evaluated whether the system frequency regulation capacity demand can be met by the existing thermal power units alone. If it cannot be met, the specific value of the relaxation amount represents the system frequency regulation capacity demand shortage. The second stage adopts a heuristic method to select the new energy units that need to participate in the frequency regulation based on the system frequency regulation capacity demand shortage obtained in the first stage and the output distribution of each new energy unit. On this basis, a dispatching decision model taking into account the overall supply capacity of the new energy frequency regulation capacity is constructed, and a dispatching decision plan for the existing thermal power units and the new energy units is reasonably formulated to effectively respond to the system frequency regulation capacity demand.

[0088] Secondly, the present invention also proposes a fast optimization strategy for new energy frequency modulation units considering the overall supply capacity of frequency modulation capacity; the rapid and reasonable selection of new energy units participating in frequency modulation is the premise for ensuring the rationality of the final scheduling decision plan. To this end, a heuristic method is used to achieve the fast optimization of new energy frequency modulation units: first, without considering the mutual offset of new energy prediction errors, the overall supply capacity of frequency modulation capacity that can be provided by new energy participating in frequency modulation under different combinations is determined according to the output distribution of new energy; then, from many new energy combinations, a combination that can cope with the shortage of system frequency modulation capacity demand and the minimum number of required new energy units is selected to reduce the number of new energy units participating in frequency modulation and reduce the amount of new energy abandoned, and a new energy combination with the largest overall supply capacity of frequency modulation capacity is selected from them, and the new energy in the combination will participate in the frequency modulation of the power grid; finally, considering the overall output distribution of the selected new energy units, it is judged whether the selected new energy units can cope with the shortage of system frequency modulation capacity demand after considering the mutual offset of new energy prediction errors. If it cannot be met, a new new energy unit is introduced to participate in frequency modulation, and the corresponding judgment is re-conducted until the shortage of system frequency modulation capacity demand can be met.

[0089] Example 1

[0090] This embodiment provides a two-stage dispatch decision method for a power system taking into account new energy sources, such as Figure 1 As shown, it specifically includes two stages of regulation:

[0091] Phase 1: Construction of a dispatch decision model that relaxes the frequency regulation capacity demand constraint. Without considering the participation of new energy in frequency regulation, a dispatch decision model that relaxes the frequency regulation capacity demand constraint is constructed to judge whether the existing thermal power units can meet the system frequency regulation capacity demand. If the relaxation value is 0, it means that the existing thermal power units can meet the system frequency regulation capacity demand, and there is no need for new energy units to provide frequency regulation capacity, and the dispatch plan of each unit can be directly obtained. If the relaxation value is greater than 0, it means that the existing thermal power units alone cannot effectively meet the system frequency regulation capacity demand, and the specific value of the relaxation value represents the shortage of the system frequency regulation capacity demand, which provides a reference for the subsequent dispatch decision model considering the participation of new energy in frequency regulation.

[0092] Phase II: a dispatching decision method that accurately characterizes the overall supply capacity of new energy frequency regulation capacity. When existing thermal power units alone cannot effectively meet the system frequency regulation capacity demand, Phase II will use a heuristic method to screen out new energy units that need to participate in frequency regulation based on the frequency regulation capacity demand shortfall obtained in Phase I and the output distribution characteristics of new energy. At the same time, it will obtain the overall frequency regulation capacity that new energy can provide, and use it as a boundary condition to construct a dispatching decision model that characterizes the overall supply capacity of new energy frequency regulation capacity. At this time, since whether new energy participates in frequency regulation has become a known quantity, the difficulty of modeling and solving the dispatching decision model is greatly reduced, so that the dispatching plan for existing thermal power units and new energy units can be efficiently and reasonably formulated under the condition of considering the participation of new energy in frequency regulation.

[0093] Example 2

[0094] This embodiment provides a detailed calculation process of two stages, which are as follows:

[0095] Phase 1:

[0096] The model objective function is established as follows:

[0097] C=min(C g +C w ) (1)

[0098]

[0099]

[0100] In the formula, C is the system operation cost, C g , C w are the total costs of thermal power units and new energy units respectively; g, t, and w are the numbers of existing thermal power units, dispatch period numbers, and new energy units respectively; G, T, and W are the collections of thermal power units, dispatch period, and new energy units respectively; Indicates the predicted output of new energy units. Provide energy quotation for new energy units; Indicates the output of thermal power units. Energy quotation for thermal power units, and Quote for up / down frequency regulation capacity of the unit; The up / down frequency regulation capacity of the unit won the bid; 1 / T e is the proportion of a single scheduling period duration in the day-ahead scheduling decision model to 1 hour. In this embodiment, the scheduling period is 15 minutes. Then T e is 4, M is the penalty coefficient for the shortage of frequency regulation capacity demand, ε UP , ε DN They are respectively the relaxation of the system's upward / downward frequency regulation capacity demand, representing the shortage of the system's upward / downward frequency regulation capacity demand.

[0101] Operation constraints:

[0102] The operation constraints of the day-ahead scheduling decision model are as follows:

[0103] Power balance constraint: the sum of the output of existing thermal power units and new energy units at each dispatching moment should be equal to the system load demand, as shown in the following formula:

[0104]

[0105] In the formula, b is the node number; B is the node set; is the load forecast value;

[0106] Frequency regulation capacity constraints: In the day-ahead dispatch decision model, the frequency regulation capacity provided by the existing thermal power units is subject to the maximum frequency regulation capacity reported by them, and the frequency regulation capacity provided should not be less than 0; at the same time, the sum of the frequency regulation capacity provided by the existing thermal power units should meet the system frequency regulation capacity demand. The frequency regulation capacity constraints of the existing thermal power units, the system frequency regulation capacity demand constraints, and the relaxed frequency regulation capacity constraints are as follows:

[0107]

[0108]

[0109]

[0110]

[0111] ε UP ≥0 (9)

[0112] ε DN ≥0 (10)

[0113] In the formula, is the system up / down frequency regulation capacity requirement, R g,max,UP / DNis the maximum / minimum frequency regulation capacity that the existing thermal power can provide; since conventional thermal power units alone cannot fully meet the system frequency regulation requirements, the relaxation amount ε UP / DN Whether it is 0 can determine whether the existing thermal power units can meet the system frequency regulation requirements. If the slack is equal to 0, it means that the existing thermal power units can meet the system frequency regulation requirements, and the output plan and frequency regulation capacity reservation of the existing thermal power units can be directly output; if the slack is greater than 0, it means that the existing thermal power units cannot meet the system frequency regulation requirements, and the specific value of the slack represents the shortage of system frequency regulation capacity requirements.

[0114] For the setting of the system frequency regulation capacity demand, this embodiment assumes that both the new energy and the load obey the normal distribution with the mean being the predicted value and the standard deviation being the percentage of the predicted value. Then the system net load also obeys the normal distribution with the mean being the predicted value of the net load and the standard deviation being as shown in the following formula:

[0115]

[0116] In the formula, σ l Indicates that the load follows the standard deviation of normal distribution. After obtaining the system net load distribution, the system up / down frequency regulation capacity requirements can be determined. According to the 95% confidence level, the up / down frequency regulation capacity requirements are 1.96 times the standard deviation respectively. The system frequency regulation capacity requirements are shown as follows: Figure 2 As shown;

[0117] Output constraints of thermal power units:

[0118]

[0119]

[0120] Where P g,min With P g,max is the maximum and minimum output of existing thermal power units, r g,UP / DN The up / down ramping capability of existing thermal power units;

[0121] Line power flow constraints, line transmission power should not exceed its upper limit:

[0122]

[0123] In the formula, l represents the line number, B represents the node set; H lb A represents the transfer distribution factor matrix element between the injected power and the active power flow; b The matrix element representing the relationship between unit g and node b; P l max Indicates the maximum line transmission capacity limit.

[0124] According to the relaxation amount ε UP / DNWhether it is 0 can determine whether the existing thermal power units can meet the system frequency regulation demand; if the slack is equal to 0, it means that the existing thermal power units can meet the system frequency regulation demand, and the output plan and frequency regulation capacity reservation of the existing thermal power units can be directly output; if the slack is greater than 0, it means that the existing thermal power units cannot meet the system frequency regulation demand, and the specific value of the slack represents the shortage of system frequency regulation capacity demand, which provides a reference for the subsequent scheduling decision model considering the participation of new energy in frequency regulation.

[0125] Stage 2: If Figure 3 As shown in the figure, the main idea of ​​the scheduling decision method that accurately characterizes the overall supply capacity of the frequency regulation capacity of new energy is: use the heuristic method to screen out the new energy units that need to participate in the frequency regulation, and at the same time obtain the overall frequency regulation capacity that can be provided by the new energy, and use it as the boundary condition to construct a scheduling decision model that characterizes the overall supply capacity of the frequency regulation capacity of new energy.

[0126] Evaluate the actual frequency regulation capacity of a single renewable energy unit:

[0127] Without considering the mutual offset of new energy forecast errors, the overall frequency regulation capacity supply of new energy frequency regulation units is as follows: Figure 4 As shown in the figure, the overall supply capacity of new energy frequency regulation capacity includes the frequency regulation capacity that can actually be provided after the new energy participates in frequency regulation and the reduction in the system frequency regulation capacity demand caused by it; among them, the total frequency regulation capacity that a single new energy can actually provide is as follows:

[0128]

[0129]

[0130] In the formula, Indicates the up / down frequency regulation capacity that new energy can provide. Indicates the new energy plan output, W r Represents the set of new energy units participating in frequency regulation;

[0131] The reduction in frequency regulation capacity demand caused by the participation of new energy in frequency regulation is: the difference between the predicted value of new energy and the maximum possible output value represents the reduced downward frequency regulation demand of the system after the participation of new energy in frequency regulation, and the difference between the predicted value and the reliable output value represents the reduced upward frequency regulation demand of the system. The overall upward / downward frequency regulation capacity provided by a single new energy is as follows:

[0132]

[0133]

[0134] In the formula, It indicates the frequency regulation capacity provided by a single renewable energy source overall; It indicates the reduction in the demand for up / down frequency regulation capacity of the system after the participation of new energy in frequency regulation;

[0135] It should be noted that the up / down frequency regulation capacity that new energy can actually provide is related to its planned output, but the sum of the up / down frequency regulation capacity that it can actually provide is fixed and has nothing to do with the planned output; for the case where new energy participates in frequency regulation, as long as the sum of the up / down frequency regulation capacity that new energy can actually provide can cope with the sum of the up / down frequency regulation capacity shortfall of the system after considering the reduction in frequency regulation capacity demand, new energy will be able to cope with the system frequency regulation capacity demand shortfall, and the specific planned output of new energy will be determined by the subsequent scheduling decision model.

[0136] Screen the combination of new energy units that meet the system frequency regulation needs, without considering the phenomenon of new energy prediction errors offsetting each other, select the combination that can cope with the shortage of system frequency regulation needs and requires the least number of new energy units, and select the new energy combination with the largest overall frequency regulation capacity supply capacity from the combination. The new energy in the combination will participate in the frequency regulation of the power grid.

[0137] After considering the mutual offset of multiple renewable energy prediction errors and the participation of renewable energy units in frequency regulation, determine whether the renewable energy units can still meet the system frequency regulation requirements. If not, add a renewable energy unit to participate in frequency regulation and return to re-screen;

[0138] Specifically, when multiple renewable energy sources participate in grid frequency regulation at the same time, the prediction errors of each renewable energy source offset each other, resulting in changes in the overall supply capacity of the renewable energy source frequency regulation capacity participating in frequency regulation. After the prediction errors offset each other, the overall supply capacity of the renewable energy source frequency regulation capacity is as follows:

[0139] The overall output distribution of the new energy units participating in frequency regulation follows a normal distribution, with a mean of the sum of the new energy prediction values ​​and a standard deviation of σ o As shown below:

[0140]

[0141] After considering the total distribution of new energy frequency-regulating units, the total frequency-regulating capacity that can actually be provided by new energy frequency-regulating units is as shown in the following formula, which is not the sum of the frequency-regulating capacities that can actually be provided by a single new energy source:

[0142]

[0143] In the formula, It can provide total frequency regulation capacity for new energy frequency regulation units;

[0144] Without considering the new energy units participating in frequency regulation, the system net load power follows a normal distribution, with a mean of the sum of the predicted values ​​of the new energy units not participating in frequency regulation and a standard deviation of σ b As shown below:

[0145]

[0146] After considering the mutual offset of multiple new energy forecast errors, the actual reduction in system up / down frequency regulation capacity demand caused by the participation of new energy in frequency regulation is shown in the following formula:

[0147] σ R =1.96σ-1.96σ b (twenty one)

[0148] Since the prediction errors of new energy sources offset each other, the frequency regulation capacity that can actually be provided by the combination of new energy sources participating in frequency regulation is greater than the sum of the frequency regulation capacities actually provided by individual new energy sources, but the reduction in system frequency regulation capacity demand caused by it will be less than the sum of the reduction in system frequency regulation capacity demand caused by individual new energy sources; therefore, it is necessary to determine whether the new energy units participating in frequency regulation can still cope with the shortage of system frequency regulation capacity demand after considering the mutual offset of prediction errors. If the frequency regulation capacity demand cannot be met, an additional new energy unit needs to be added to participate in frequency regulation.

[0149] Adjust the confidence level of the reliable output assessment of a single renewable energy source based on the idea of ​​equal confidence level;

[0150] If the system frequency regulation capacity demand can be met, the confidence level of the reliable output assessment of a single renewable energy source needs to be adjusted based on the idea of ​​equal confidence level based on the frequency regulation capacity actually provided by the renewable energy source after the prediction errors are offset against each other, so as to reduce the risk that the actual output of a single renewable energy source cannot reach the reliable output after adjustment, and make the sum of the frequency regulation capacities that can actually be provided by a single renewable energy source after adjustment equal to the frequency regulation capacity that can actually be provided when all renewable energy sources are considered together before adjustment.

[0151] After determining the new energy frequency regulation units and the corresponding available frequency regulation capacity, the new energy and existing thermal power units are included in the dispatch decision model to determine the output plan and frequency regulation capacity reservation of conventional thermal power units and new energy units. Based on the dispatch decision model of stage one, the energy frequency regulation units are added to participate in the dispatch, as follows:

[0152] The objective function is as follows:

[0153] C=min(C g +C w ) (1)

[0154]

[0155] The operating constraints are as follows:

[0156] Power balance constraint: the output of existing thermal power units and renewable energy in each dispatch period (new energy units participating in frequency regulation are planned output, and new energy units not participating in frequency regulation are fully consumed) must be equal to the load:

[0157]

[0158] Frequency regulation capacity constraints: In the day-ahead dispatch decision model, the frequency regulation capacity provided by new energy sources is limited by reliable output and energy output, and the winning frequency regulation capacity should not be less than 0. At the same time, the sum of the frequency regulation capacity of new energy frequency regulation units and existing thermal power units should meet the system frequency regulation capacity requirements. The frequency regulation capacity constraints of existing thermal power units and new energy sources are as follows:

[0159]

[0160]

[0161] Restriction on renewable energy output, modeling of the output of renewable energy units participating in frequency regulation and those not participating in frequency regulation:

[0162]

[0163]

[0164] Formula (27) is the output constraint condition of the new energy frequency-regulating units; Formula (28) is the output constraint of the new energy non-frequency-regulating units, which means that the new energy units not participating in frequency regulation are fully absorbed.

[0165] Since the rapid optimization strategy of new energy frequency regulation units considering the overall supply capacity of frequency regulation capacity has been solved to determine whether the new energy units participate in frequency regulation, there is no need to introduce integer variables to distinguish the attributes of new energy units. The objective function of the scheduling decision model considering the supply capacity of new energy frequency regulation capacity should also include the cost of existing thermal power units, and the constraints include the existing thermal power units' ramp constraints, output constraints, frequency regulation capacity constraints, and line flow constraints.

[0166] By taking into account the dispatch decision model of the new energy frequency regulation capacity supply capacity, the output plan and frequency regulation capacity reservation of the existing thermal power units and new energy frequency regulation units can be accurately calculated under the condition that the system frequency regulation requirements are met.

[0167] Example 3

[0168] Data collection, in order to verify the effectiveness of the two-stage dispatching decision-making method of the power system proposed in the above embodiment taking into account the overall supply capacity of the frequency regulation capacity of new energy, this embodiment collects the load and new energy data of a provincial grid from January 2023 to February 2023, among which, by proportionally expanding the new energy data, the net load data with high new energy penetration rate is obtained, assuming that both new energy and load obey a normal distribution with a mean of the predicted value and a standard deviation of 20% and 3% of the predicted value respectively.

[0169] Solve the scheduling decision model of the above embodiment to relax the frequency regulation capacity demand constraint. In the scheduling decision model, only the frequency regulation capacity provided by the existing thermal power units is considered. The objective function is the energy cost and capacity cost of the existing thermal power units. The relaxation variables are embedded in the constraint conditions to determine whether the existing thermal power units can meet the system frequency regulation demand. If the relaxation variable is 0, it means that the existing thermal power units can meet the system frequency regulation demand, and the scheduling result is directly output; if the relaxation variable is not 0, it indicates that the system frequency regulation capacity demand is insufficient, providing conditions for the selection of subsequent new energy frequency regulation units.

[0170] The strategy for rapid optimization of new energy frequency-regulating units considering the overall supply capacity of frequency-regulating capacity adopts a heuristic method to select the minimum new energy combination that can meet the shortage of frequency-regulating capacity demand, and selects the new energy combination with the largest overall supply capacity of frequency-regulating capacity from it. The output distribution of new energy frequency-regulating units is forecasted to offset each other, and it is judged whether the overall supply capacity of frequency-regulating capacity after the forecast errors are offset to meet the shortage of system frequency-regulating capacity. If it cannot be met, the new energy frequency-regulating units are reselected for dispatch; if it can be met, the increased frequency-regulating capacity after the forecast errors are offset needs to adjust the confidence level of the reliable output assessment of a single new energy source according to the idea of ​​equal confidence level, so as to reduce the risk that the actual output of a single new energy source cannot reach the reliable output after adjustment, so that the sum of the frequency-regulating capacity that can be actually provided by a single new energy source after adjustment is equal to the frequency-regulating capacity that can be actually provided when all new energy sources are considered together before adjustment.

[0171] Solve the above-mentioned dispatching decision model that takes into account the supply capacity of new energy frequency regulation capacity, embed the new energy frequency regulation units and the existing thermal power units into the dispatching decision model, and construct a dispatching decision model that takes into account the supply capacity of new energy frequency regulation capacity. By solving the model, the frequency regulation capacity and output plan provided by the final new energy and existing thermal power units are obtained.

[0172] The specific simulation results are as follows:

[0173] This section will use the actual operation data of a provincial power grid to verify the effectiveness of the two-stage dispatch decision method for the power system proposed in this invention, which takes into account the overall supply capacity of the new energy frequency regulation capacity. The specific simulation results are as follows:

[0174] (1) Example

[0175] The comparison method is as follows:

[0176] M1: A two-stage dispatch decision method for power systems taking into account the overall supply capacity of new energy frequency regulation capacity;

[0177] M2: The existing dispatching decision-making method that considers the participation of renewable energy in frequency regulation evaluates the frequency regulation capacity that can be provided by the part of renewable energy output that is lower than its reliable output. It does not consider the impact of renewable energy participation in frequency regulation dispatching on the demand for frequency regulation capacity and the impact of the mutual offset of renewable energy prediction errors on the overall frequency regulation capacity supply capacity of renewable energy. The renewable energy that does not participate in frequency regulation will be fully absorbed.

[0178] This embodiment uses the IEEE 30-node system for simulation analysis, and compares and analyzes the impact of different methods on the selection of new energy frequency modulation units on the final scheduling decision results. In the simulation, the actual data described above were scaled to match the parameters of the IEEE 30-node system. The new energy penetration rate is 63.7%. Table 1 shows the operating parameters of the thermal power unit, and Table 2 shows the parameters of the new energy unit.

[0179] Table 1 Thermal power unit operating parameters

[0180]

[0181]

[0182] Table 2 New energy unit operating parameters

[0183]

[0184] (2) The effectiveness of the scheduling decision method taking into account the overall supply capacity of the new energy frequency regulation capacity is verified. The full-day operating costs of M1 and M2 on February 10, 2023, the up / down frequency regulation capacity demand shortfall, and the up / down frequency regulation capacity actually provided by the new energy frequency regulation units are shown in Table 3; the operating costs include the frequency regulation capacity costs of existing thermal power units and new energy units, energy costs, and the power abandonment costs of new energy frequency regulation units; in order to accurately evaluate the power abandonment costs of new energy frequency regulation units, the present invention introduces the new energy power abandonment expectations. Figure 5 As shown in FIG. 1 , the red curve represents the predicted cumulative distribution function of the new energy output, and the shaded part is the expected power abandonment of the new energy. Since the accurate calculation method of the expected term is relatively complicated, this embodiment will use the area of ​​multiple rectangles to approximate the shaded area corresponding to the power abandonment expectation, such as Figure 6 As shown. According to the cumulative distribution function of renewable energy output, with renewable energy reliable power generation capacity as the starting point and maximum output as the end point, it is divided into n segments, and the area of ​​each segment is replaced by the area of ​​the curved trapezoid, so as to achieve an approximation of the expected power abandonment. The overall dispatch results on February 10, 2023 are shown in Table 3.

[0185] Table 3 Performance indicators of M1 and M2 in the IEEE 30-node system on February 10, 2023

[0186]

[0187] As shown in Table 3, both M1 and M2 can meet the system's up / down frequency regulation capacity requirements. However, by comparing M1 and M2, it can be seen that the up / down frequency regulation capacity actually provided by M2 is 12.17% of that of M1. It can be seen that M2 is too conservative. The reason is that M1 considers the mutual offset of new energy prediction errors and the impact of new energy units participating in frequency regulation on the system's frequency regulation requirements.

[0188] After considering the participation of new energy in frequency regulation, by comparing the up / down frequency regulation capacity requirements of the system, it can be seen that M1-M2 are reduced by 9.53% and 12.18% respectively. The reason why M2 has a greater reduction in the up / down frequency regulation capacity requirements than M1 is that the up / down frequency regulation capacity requirements of the system in the M2-embedded scheduling decision model are relatively large, and the embedding does not consider the mutual offset of the prediction errors of new energy, and the up / down frequency regulation capacity requirements of the system, so more new energy is required to participate in frequency regulation, resulting in a greater reduction in the system frequency regulation demand, and at the same time, the amount of new energy abandoned is also much greater than M1. By comparing the up / down frequency regulation capacity actually provided by M1-M2 under the consideration of the mutual influence of the prediction errors of new energy, it can be seen that the actual up / down frequency regulation capacity provided by M2 is greater than the up / down frequency regulation capacity requirements of the system embedded in the scheduling decision model, because M2 does not consider the mutual offset of the prediction errors of the new energy units participating in frequency regulation.

[0189] Comparing the final operating costs of the M1-M2 scheduling decision model, it can be seen that the overall operating cost of the M1 system is reduced by 4.8% compared with that of the M2 system. It can be seen that compared with M2, the proposed M1 improves the economy of the system while ensuring the system frequency regulation capacity requirements.

[0190] In order to further analyze the effectiveness of the method proposed in the present invention, taking M1-M2 in the third scheduling period on February 10, 2023 as an example, the operating performance of different methods after introducing new energy to participate in grid frequency regulation is analyzed in detail. Table 4 shows the up / down frequency regulation capacity reserved for the new energy frequency regulation units.

[0191] Table 4

[0192]

[0193] Since M1 takes into account the reduction in system frequency regulation demand after the participation of renewable energy in frequency regulation, the number of renewable energy frequency regulation units participating in M1 is smaller. Moreover, after the introduction of renewable energy in frequency regulation, all electricity exceeding its reliable power generation capacity will be abandoned. Ultimately, M1 abandons less electricity than M2, and the abandonment cost is also lower. The abandonment cost of M1-M2 is shown in Table 5.

[0194] Table 5 M1-M2 power abandonment cost

[0195]

[0196]

[0197] As shown in Tables 4 and 5, both M1 and M2 can meet the actual frequency regulation capacity demand of the system, but the frequency regulation capacity demand of the M1 system is smaller than that of M2. The reason is that the existing M2 does not consider the impact of the participation of new energy in frequency regulation on the frequency regulation capacity demand of the system, and does not consider the "extra frequency regulation capacity" that can be provided after the new energy forecast error items are offset. As a result, the number of new energy sources used in the M2 method is 6, while the number of new energy sources used in M1 is 4, which in turn leads to the method M1 The power abandonment cost is reduced by 38.91% compared with the method M2; and the up / down frequency regulation capacity provided by M1 is reduced by 32.23% compared with M2. Therefore, it can be proved that the two-stage scheduling decision method proposed in the present invention can effectively reduce the amount of new energy abandoned and improve the economy of the system. In summary, compared with the existing M2 method, the M1 method has a lower power abandonment cost while ensuring the system frequency regulation capacity demand, effectively ensuring the economy of the system;

[0198] In view of the problem that conventional thermal power units cannot effectively cope with power fluctuations during the dispatching period caused by the access of a high proportion of new energy, the present invention proposes a two-stage dispatching decision method for the power system that takes into account the overall supply capacity of the frequency modulation capacity of new energy, and introduces new energy to participate in the dispatching decision. The present invention first constructs a dispatching decision model that relaxes the frequency modulation capacity demand constraint in stage one, embeds a relaxation variable in the system frequency modulation capacity demand constraint, and judges whether the conventional thermal power unit can meet the system demand. If it can be met, there is no need to introduce new energy to participate in the frequency modulation; if it cannot be met, it is necessary to enter the dispatching decision method of stage two to accurately characterize the frequency modulation capacity supply capacity of new energy. Stage two constructs a fast optimization strategy for new energy frequency modulation units that considers the overall supply capacity of the frequency modulation capacity according to the frequency modulation capacity shortage provided in stage one; then, a dispatching decision model that takes into account the frequency modulation capacity supply capacity of new energy is constructed, so as to reasonably formulate the output plan and frequency modulation capacity reservation of conventional thermal power units and new energy units. Through example simulation and comparative analysis methods M1-M2, it is concluded that the method proposed by the present invention ensures that the frequency modulation demand of the power grid is met while the cost of power abandonment is lower.

[0199] The principles and implementation methods of the present invention are described in this article using specific embodiments. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A two-stage dispatch decision method for a power system taking into account new energy, wherein the power system includes existing thermal power units and new energy units, characterized in that: The method comprises: A dispatch decision model for relaxing the frequency regulation capacity demand constraint is constructed, and the relaxation amount is obtained through the model. According to the relaxation amount, it is determined whether the new energy units need to be dispatched. The specific determination includes: If the relaxation amount is 0, the dispatch plan is output through the dispatch decision model that relaxes the frequency regulation capacity demand constraint; If the slack is not 0, then the slack is the system demand shortfall; A scheduling decision model is constructed to characterize the overall supply capacity of the frequency regulation capacity of renewable energy. According to the slack amount and the output distribution characteristics of the renewable energy units, a heuristic method is used to screen out the renewable energy units that need to participate in the frequency regulation. At the same time, the overall frequency regulation capacity that can be provided by the renewable energy units is obtained and used as the boundary condition to complete the scheduling decision.

2. A two-stage dispatch decision method for a power system taking into account new energy sources according to claim 1, characterized in that: The dispatch decision model for building a relaxed frequency regulation capacity demand constraint includes: The model objective function is established as follows: C=min(C g +C w ) (1) In the formula, C is the system operation cost, C g , C w are the total costs of thermal power units and new energy units respectively; g, t, and w are the numbers of existing thermal power units, dispatch period numbers, and new energy units respectively; G, T, and W are the collections of thermal power units, dispatch period, and new energy units respectively; Indicates the predicted output of new energy units. Provide energy quotation for new energy units; Indicates the output of thermal power units. Energy quotation for thermal power units, and Quote for up / down frequency regulation capacity of the unit; The up / down frequency regulation capacity of the unit won the bid; 1 / T e is the proportion of the duration of a single scheduling period in the day-ahead scheduling decision model to 1 hour, M is the penalty coefficient for the shortage of frequency regulation capacity demand, and ε UP , ε DN They are respectively the relaxation of the system's upward / downward frequency regulation capacity demand, representing the shortage of the system's upward / downward frequency regulation capacity demand.

3. A two-stage dispatch decision method for a power system taking into account new energy sources according to claim 2, characterized in that: The constraints of the model specifically include: Power balance constraint, used to balance the load demand with the sum of the output of thermal power units and new energy units; Frequency regulation capacity constraints: establish frequency regulation capacity constraints for thermal power units, system frequency regulation capacity requirements, and relax frequency regulation capacity constraints; Output constraints of thermal power units, constructing upper and lower limits of thermal power unit output and up and down climbing capacity constraints; Line power flow constraint controls the line transmission power to be no higher than the line transmission power upper limit.

4. A two-stage dispatch decision method for a power system taking into account new energy sources according to claim 3, characterized in that: The constraint condition is specifically implemented by the following formula: Power balance constraints: In the formula, b is the node number; B is the node set; is the load forecast value; Frequency regulation capacity constraints: e UP ≥0 (9) e DN ≥0 (10) In the formula, is the system up / down frequency regulation capacity requirement, R g,max,UP / DN The maximum / minimum frequency regulation capacity that can be provided by existing thermal power; Output constraints of thermal power units: Where P g,min With P g,max is the maximum and minimum output of existing thermal power units, r g,UP / DN The up / down ramping capability of existing thermal power units; Line flow constraints: In the formula, l represents the line number, B represents the node set; H lb A represents the transfer distribution factor matrix element between the injected power and the active power flow; b The matrix element representing the relationship between unit g and node b; P l max Indicates the maximum line transmission capacity limit.

5. A two-stage dispatch decision method for a power system taking into account new energy sources according to claim 1, characterized in that: If the slack is not 0, the slack is the system demand shortfall, and a dispatch decision model representing the overall supply capacity of the frequency regulation capacity of new energy units is constructed; This includes using heuristic methods to screen out the new energy units that need to participate in frequency regulation, and at the same time obtaining the overall frequency regulation capacity that can be provided by the new energy units, and using it as a boundary condition to construct a scheduling decision model that characterizes the overall supply capacity of the new energy frequency regulation capacity.

6. A two-stage dispatch decision method for a power system taking into account new energy sources according to claim 5, characterized in that: The dispatch decision model representing the overall supply capacity of new energy frequency regulation capacity specifically includes: Evaluate the actual frequency regulation capacity of a single renewable energy unit; Screening new energy unit combinations that meet the system frequency regulation requirements; After considering the mutual offset of prediction errors of multiple renewable energy sources and the participation of renewable energy units in frequency regulation, determine whether the renewable energy units can meet the system frequency regulation requirements. If not, add renewable energy units for re-screening. If the system frequency regulation requirements can be met, adjust the confidence level of the reliable output assessment of a single renewable energy source based on the equal confidence level idea based on the frequency regulation capacity actually provided by the renewable energy sources after the prediction errors are offset, so that the sum of the frequency regulation capacities that can be actually provided by a single renewable energy source after the adjustment is equal to the frequency regulation capacity that can actually be provided when all renewable energy sources are considered together before the adjustment. Based on the dispatch decision model that relaxes the frequency regulation capacity demand constraints, more new energy frequency regulation units are involved in dispatching.

7. A two-stage dispatch decision method for a power system taking into account new energy sources according to claim 6, characterized in that: The actual frequency regulation capacity of a single new energy unit is evaluated as follows: In the formula, Indicates the up / down frequency regulation capacity that new energy can provide. Indicates the new energy plan output, W r Indicates the set of new energy units participating in frequency regulation; The overall up / down frequency regulation capacity provided by a single renewable energy source is as follows: In the formula, It indicates the frequency regulation capacity provided by a single renewable energy source overall; It indicates the reduction in the demand for up / down frequency regulation capacity of the system after the participation of new energy in frequency regulation; The screening of the combination of new energy units that meet the system frequency regulation demand is performed without considering the phenomenon that the new energy prediction errors offset each other, and the combination that can cope with the shortage of system frequency regulation demand and requires the least number of new energy units is selected, and the new energy combination with the largest overall frequency regulation capacity supply capacity is selected from the combination, and the new energy in the combination will participate in the power grid frequency regulation; After considering the mutual offset of multiple new energy prediction errors and the participation of new energy units in frequency regulation, the overall frequency regulation capacity supply capacity of new energy units is as follows: The overall output distribution of the new energy units participating in frequency regulation follows a normal distribution, with a mean of the sum of the new energy prediction values ​​and a standard deviation of σ o As shown below: After considering the total distribution of new energy frequency regulation units, the total frequency regulation capacity that new energy frequency regulation units can actually provide is shown in the following formula: In the formula, It can provide total frequency regulation capacity for new energy frequency regulation units; Without considering the new energy units participating in frequency regulation, the system net load power follows a normal distribution, with a mean of the sum of the predicted values ​​of the new energy units not participating in frequency regulation and a standard deviation of σ b As shown below: After considering the mutual offset of multiple new energy forecast errors, the actual reduction in system up / down frequency regulation capacity demand caused by the participation of new energy in frequency regulation is shown in the following formula: s R =1.96σ-1.96σ b (21).

8. A two-stage dispatch decision method for a power system taking into account new energy sources according to claim 7, characterized in that: The dispatch decision model based on the relaxation of frequency regulation capacity demand constraints adds the above-mentioned new energy frequency regulation units to participate in the dispatch. The objective function of the dispatch decision model that represents the overall supply capacity of new energy frequency regulation capacity is as follows: C=min(C g +C w )(1) 9. A two-stage dispatch decision method for a power system taking into account new energy sources according to claim 8, characterized in that: The constraints of the objective function are as follows: Power balance constraints: Frequency regulation capacity constraints: Restrictions on renewable energy output: Formula (27) is the output constraint condition of the new energy frequency-regulating units; Formula (28) is the output constraint of the new energy non-frequency-regulating units, which means that the new energy units not participating in frequency regulation are fully absorbed.

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