A method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of power systems with high wind and solar power share

Abstract

The present invention provides a method for optimizing the combination of thermal power units considering the low-carbon and efficient operation of a power system with a high proportion of wind and solar power, including: determining the combination and output of thermal power units in the load balancing stage of the power system; determining the combination and output of thermal power units in the standby balancing stage of the power system; the optimal combination of thermal power units finally optimized, and the output of each thermal power unit in the optimal combination, to ensure that after it participates in the power system regulation in conjunction with wind, solar, hydropower and energy storage units, the power system simultaneously reaches a load balance state and a standby balance state. The present invention comprehensively considers the wind and solar power consumption, energy storage utilization and low-carbon operation mode of the thermal power units in the power system, and proposes a method for optimizing the combination of thermal power units considering the low-carbon and efficient operation of a power system with a high proportion of wind and solar power, which can improve the solution efficiency during the optimization of thermal power units, clearly provide decision-making process information, intuitively judge the performance of the combination of thermal power units, and provide guidance for power grid dispatching.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system dispatching automation, and specifically relates to a thermal power unit combination optimization method for low-carbon and high-efficiency operation of a power system with a high proportion of wind and solar power. Background Art

[0002] With the development and construction of new power systems and smart grids, the optimal allocation of power system resources has become increasingly critical. The key link is to determine the appropriate and economical combination optimization plan for thermal power units, which can comprehensively consider the medium- and long-term operating benefits of the system and achieve more significant optimization effects.

[0003] The existing optimization methods for thermal power unit combination mainly include: 1) Data-driven thermal power unit combination methods, which mostly use machine learning and neural network models, have a large demand for historical data, and are "black box models", making it difficult to judge the rationality of the results; 2) Mathematical programming-based thermal power unit combination methods, which use integer programming, mixed integer programming, and intelligent algorithms to solve the problem. The model construction is complex and cannot give a clear decision-making process, which is not conducive to intuitively judging the performance of the thermal power unit combination. Moreover, for large-scale power systems with a large number of thermal power units, the solution efficiency is low; 3) Thermal power unit combination strategies based on engineering experience, such as the priority method, but the existing methods rarely consider the impact of factors such as the benefits of energy storage units, the benefits of wind and solar power generation, and the low carbon of thermal power units. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a method for optimizing the combination of thermal power units taking into account the low-carbon and high-efficiency operation of power systems with a high proportion of wind and solar power, which can effectively solve the above problems.

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

[0006] The present invention provides a method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with a high proportion of wind and solar power, comprising the following steps:

[0007] Step S1, predetermine the power system data in the planning period T, including: the photovoltaic output P of each time period t in the planning period T g (t), wind power output P w (t), hydropower power output P h (t), system load demand Load(t), system reserve capacity demand R(t), hydropower power supply assuming rotating reserve capacity R h (t), characteristic parameters of energy storage units and thermal power units;

[0008] Step S2, determining the system remaining load capacity net_load(t) and the system remaining spare capacity net_R(t) in the initial state:

[0009] According to formula (1), the system residual load capacity net_load(t) is obtained when the output of wind, solar and hydropower sources is considered and the output of thermal power units and energy storage units is not considered;

[0010] net_Load(t)=P g (t)+P w (t)+P h (t)-Load(t) (1)

[0011] According to formula (2), the system remaining reserve capacity net_R(t) is obtained when considering that hydropower can bear the reserve and not considering thermal power units and energy storage units to bear the reserve:

[0012] net_R(t)=R h (t)-R(t) (2)

[0013] Step S3, according to the maintenance status of the thermal power units, all thermal power units that do not need maintenance are formed into a set S of thermal power units to be selected;

[0014] Step S4, determination of the combination and output of thermal power units in the load balancing stage of the power system:

[0015] After the output of wind, solar and hydropower sources is determined, the optimal thermal power unit combination S1 participating in the power system regulation in the load balancing stage and the output of each thermal power unit in the optimal thermal power unit combination S1 are determined in the set of thermal power units to be selected. At the same time, according to the characteristic parameters of the energy storage unit and the system residual load capacity net_load(t), according to the output strategy of the energy storage unit, the pumped power generation condition and the output process of the energy storage unit are determined, so that the thermal power units and energy storage units in the optimal thermal power unit combination S1 jointly participate in the power system regulation, and the power system reaches a load balance state; wherein, the power system reaches a load balance state, which means that in each time period t of the planning period T, the system residual load capacity net_load(t) is 0;

[0016] Step S5, determination of the combination and output of thermal power units in the power system standby balance stage:

[0017] After the output of wind, solar and hydropower sources, the optimal thermal power unit combination S1 and the output of each thermal power unit in the optimal thermal power unit combination S1 are determined, the set of thermal power units to be selected S = S - S1 is updated; in the updated set of thermal power units to be selected S, the optimal thermal power unit combination S2 participating in the regulation of the power system in the standby balance stage and the output of each thermal power unit in the optimal thermal power unit combination S2 are determined. At the same time, according to the characteristic parameters of the energy storage unit and the system residual load capacity net_load(t), according to the output strategy of the energy storage unit, the pumped power generation condition and the output process of the energy storage unit are determined, so that after the thermal power units and the energy storage units in the optimal thermal power unit combination S2 jointly participate in the regulation of the power system, the power system reaches a standby balance state on the basis of satisfying load balance; wherein, the power system reaches a standby balance state, which means that in each time period t of the planning period T, the system residual standby capacity net_R(t) satisfies the relationship: min{net_R(t)|t∈T}≥0;

[0018] Step S6, merging the optimal thermal power unit combination S1 and the optimal thermal power unit combination S2 to obtain the optimal thermal power unit combination S1 obtained by the final optimization. best =S1∪S2, and the optimal combination of thermal power units S best The output of each thermal power unit in the power system is adjusted together with the energy storage unit, and the power system reaches the load balance state and the standby balance state at the same time.

[0019] Preferably, in step S2, the system remaining spare capacity net_R(t) includes the system positive spinning spare remaining capacity net_R + (t) and the system negative spinning reserve remaining capacity net_R - (t), specifically obtained by formula (3):

[0020]

[0021] in: and The positive spinning reserve capacity and the negative spinning reserve capacity of hydropower are respectively assumed by hydropower; R + (t) and R - (t), are the system positive spinning reserve capacity demand and the system negative spinning reserve capacity demand, respectively.

[0022] Preferably, in step S3, the method for determining the maintenance status of the thermal power unit is: in each sequentially arranged planning period T of the power system, the thermal power unit that needs to be maintained in each planning period T is pre-determined according to the annual maintenance plan.

[0023] Preferably, step S4 is specifically:

[0024] Step S4.1, determining a cost estimation algorithm for the load balancing stage of the thermal power unit during the load balancing stage of the power system;

[0025] Step S4.2, traverse the set S of thermal power units to be selected, estimate the total cost of each thermal power unit in the set S of thermal power units to be selected in the planning period T according to the cost estimation algorithm of the thermal power unit load balancing stage, and select the thermal power unit m with the minimum total cost;

[0026] Step S4.3, according to the thermal power unit output optimization model, determine the output P of the selected thermal power unit m in each time period t of the planning period T m (t), so that the thermal power unit m according to the output P m (t) Participate in power system regulation;

[0027] Step S4.4, when the thermal power unit m is output P m When (t) participates in the regulation of the power system, the system residual load capacity net_load(t) is updated according to formula (4) to obtain the system residual load capacity net_load(t) when the wind, solar, hydropower and thermal power outputs are jointly considered:

[0028] net_load(t)=net_load(t)+P m (t) (4)

[0029] Step S4.5, according to the characteristic parameters of the energy storage unit and the latest system residual load capacity net_load(t), according to the output strategy of the energy storage unit, determine the pumped power generation operating condition and output process of the energy storage unit, so that the energy storage unit can jointly participate in the power system regulation;

[0030] Step S4.6, add the thermal power unit m to the optimal thermal power unit combination S1, and record the output P of the thermal power unit m m (t); Update the set of thermal power units to be selected S: delete the thermal power unit m from the set of thermal power units to be selected S;

[0031] Step S4.7, determine whether the power system has reached a load balance state. If so, output the optimal thermal power unit combination S1 and the output of each thermal power unit in the optimal thermal power unit combination S1, as well as the updated set of candidate thermal power units S; if not, return to step S4.2 to continue screening the next thermal power unit and output.

[0032] Preferably, step S4.1 is specifically:

[0033] Step S4.1.1, determine the output P of each thermal power unit k in the set of thermal power units to be selected for cost estimation in the load balancing stage k (t):

[0034] If -net_Load(t)>P k,max , then P k (t) = P k,max , so that the cost of thermal power unit k is estimated according to the maximum output power generation;

[0035] If -net_Load(t)<P k,min , then P k (t) = P k,min , so that the cost of thermal power unit k is estimated according to the minimum technical output;

[0036] If P k,min <-net_Load(t)<P k,max , then P k (t) = -net_Load(t), so that the thermal power unit k can perform cost estimation according to the power generation demanded by the power system;

[0037] Among them, P k,max and P k,min , are the maximum output and minimum technical output of thermal power unit k respectively;

[0038] Step S4.1.2, estimate the start-up and shutdown cost cost_onoff_1, carbon emission control cost cost_C_1, operation coal consumption cost cost_coal_1, wind and solar abandonment cost cost_PW_1 and power shortage cost cost_e of thermal power unit k in the load balancing stage in the planning period T. According to formula (5), the total cost cost_1 of thermal power unit k in the load balancing stage of the power system is obtained:

[0039] cost_1=cost_onoff_1+cost_C_1+cost_coal_1+cost_PW_1+cost_e (5)

[0040] Thus, the total cost cost_1 of thermal power unit k in the load balancing stage of the power system is obtained.

[0041] Preferably, the specific estimation method of each sub-item cost is:

[0042] (1) On-off cost cost_onoff_1:

[0043] Step 1: Determine the on / off state of thermal power unit k at the initial time of planning period T:

[0044] For multiple planning periods T arranged in chronological order in the planning year, each thermal power unit k in the first planning period T is set to be in the on state at the initial moment; for the planning periods T ranked from the second to the last, the on / off state of the thermal power unit k at the initial moment is determined by the optimal combination S of thermal power units determined by the previous adjacent planning period T. best Specifically, for thermal power unit k, if it belongs to the optimal combination S of thermal power units determined in the previous adjacent planning period T, best If it is in the initial time of the current planning period T, it is in the power-on state; otherwise, it is in the power-off state at the initial time of the current planning period T;

[0045] Step 2: If the thermal power unit k is in the shutdown state at the initial time of the current planning period T, it will change from the shutdown state to the startup state, and incur a start-up and shutdown cost; if it is initially in the startup state, it will continue to be in the startup state during the current planning period T, and no start-up and shutdown cost will be incurred; therefore, according to formula (6), its start-up and shutdown cost cost_onoff_1 is obtained:

[0046] cost_onoff_1=(U k -U k,0 )*cost_onoff k (6)

[0047] Among them: U k =1, indicating that thermal power unit k is started and operated in the current planning period T; U k,0 is the on / off state of thermal power unit k at the initial time of the current planning period T. When it is on, U k,0 =1; when the power is off, U k,0 =0; cost_onoff k is the single start-up and shutdown cost of thermal power unit k;

[0048] (2) Carbon emission control cost cost_C_1

[0049] The operation of thermal power unit k will produce carbon dioxide, which needs to be treated before discharge. The carbon emission control cost is calculated by formula (7):

[0050]

[0051] Where: T represents the current planning period T; cost_C k represents the carbon emission control cost per unit kilowatt-hour of thermal power unit k;

[0052] (3) Operating coal consumption cost cost_coal_1

[0053] The fuel cost consumed by thermal power unit k is the operating coal consumption cost, which is calculated by formula (8):

[0054]

[0055] Where: cost_coal k It represents the unit coal consumption cost of thermal power unit k;

[0056] (4) Cost of abandoned wind and solar power cost_PW_1

[0057] When it is assumed that the thermal power unit k is based on the output P k (t) When participating in the regulation of the power system, after the energy storage unit combines with the energy storage function, if there is still excess power that cannot be absorbed by the energy storage unit in time period t, wind and solar power will be abandoned, and the corresponding wind and solar power abandonment cost will be generated. The specific estimation method is:

[0058] Step 1: Determine the output of the energy storage unit according to the output strategy of the energy storage unit:

[0059] Step 1.1, assuming that the thermal power unit k is based on the output P k (t) When participating in the power system regulation, the current latest system residual load capacity net_load is obtained by formula (9) when jointly considering the output of wind, solar, hydropower and thermal power units k. k (t):

[0060] net_load k (t) = net_load (t) + P k (t) (9)

[0061] Step 1.2, based on the latest system remaining load capacity net_load k (t), determine the output P of each energy storage unit i in sequence i (t), i = 1, 2, ..., N, the method is:

[0062] Step 1.2.1, i=1;

[0063] Step 1.2.2, according to the formula net_load1(t) = net_load k (t), and net_load1(t) is obtained; where net_load1(t) is the system residual load capacity when the output of wind, solar, hydropower and thermal power units k is considered together;

[0064] Step 1.2.3, use formula (10) to determine the pumped power generation state and output P of energy storage unit i i (t):

[0065]

[0066] Where: Pi,max represents the single unit capacity of energy storage unit i, i = 1, 2, ..., N; coff i represents the conversion efficiency of energy storage unit i; t=1,2,...,T, represents the sequence number of each time period in the planning cycle T; when t=1, E i (t-1) = E i (0) is the energy storage capacity of energy storage unit i at the initial state of planning period T, which is a known value; E i (t) represents the energy storage capacity of energy storage unit i in time period t; E i (t-1) represents the energy storage capacity of energy storage unit i in time period t-1; E i,max represents the maximum storage energy of energy storage unit i;

[0067] Step 1.2.4, let i = i + 1, calculate net_load i (t) = net_load i-1 (t)+P i-1 (t), return to step 1.2.3, and continue to determine the output of the next energy storage unit until the output of each of the N energy storage units is obtained; where net_load i-1 (t) is the system residual load capacity when the output of wind, solar, hydropower, thermal power unit k and the output of the first i-1 energy storage units are jointly considered;

[0068] Step 2: Use formula (11) to get the cost of abandoned wind and solar power cost_PW_1:

[0069]

[0070] Among them: cost_pw represents the unit cost of abandoned wind and solar power;

[0071] coff is the average conversion efficiency of N energy storage units;

[0072] (5) Power shortage cost cost_e_1

[0073] Using formula (12), we get the power shortage cost cost_e_1:

[0074]

[0075] Among them: cost_p represents the unit kilowatt-hour electricity purchase cost.

[0076] Preferably, step S4.3 is specifically:

[0077] Step S4.3.1, obtaining the latest current system residual load capacity net_load(t) of the power system, specifically: the system residual load capacity when jointly considering the output of wind, solar, and hydropower sources and the output of each thermal power unit in the current optimal thermal power unit combination S1;

[0078] Step S4.3.2: According to the latest residual load capacity net_load(t) of the power system, establish the operation constraints of thermal power unit m, with the output P of thermal power unit m in the planning period T m (t) is the decision variable, with the minimum coal consumption of the power system and the output of thermal power unit m P m (t) The closest to the power demand of the power system is taken as the optimization target, and the unit output optimization model is constructed:

[0079]

[0080] Among them: F1 is the objective function of minimizing coal consumption in power system operation; F2 is the objective function that makes the output of thermal power unit m closest to the power demand of power system; a, b and c are the parameters of coal consumption curve; abs is the absolute value symbol;

[0081] The constraints include: m,min ≤P m (t)≤P m,max

[0082] 0<P m (t)-P m (t-1)<R u

[0083] 0<P m (t-1)-P m (t)<R d

[0084] Where: P m,min and P m,max , are the minimum technical output and maximum output of thermal power unit m respectively;

[0085] P m (t) and P m (t-1), are the outputs of thermal power unit m in time periods t and t-1 of planning period T respectively;

[0086] R u and R d , respectively, are the up and down climbing limits of thermal power unit m;

[0087] Step S4.3.3, solve the unit output optimization model constructed in step S4.3.2 to obtain the output P of thermal power unit m in the planning period T m (t).

[0088] Preferably, step S5 is specifically:

[0089] Step S5.1, determining a cost estimation algorithm for the standby balance phase of the thermal power unit during the standby balance phase of the power system;

[0090] Step S5.2, after the output of wind, solar, and hydropower sources, the optimal thermal power generation unit combination S1, and the output of each thermal power generation unit in the optimal thermal power generation unit combination S1 are determined, the set of thermal power generation units to be selected S=S-S1 is updated;

[0091] Step S5.3, traverse the updated candidate thermal power unit set S, estimate the total cost of each thermal power unit in the candidate thermal power unit set S in the planning period T according to the thermal power unit standby balance stage cost estimation algorithm, and select the thermal power unit n with the minimum total cost;

[0092] Step S5.4, determine the output P of the selected thermal power unit n in each time period t of the planning period T n (t), so that the thermal power unit n according to the output P n (t) Participate in the regulation of the power system by:

[0093] In the standby balance stage, the function of thermal power unit n is to assume hot standby, so its output P in time period t of planning cycle T is n (t), according to the minimum technical output P n,min Run, that is: P n (t) = P n,min ;

[0094] Step S5.5, when the thermal power unit n is based on the output P n When (t) participates in the power system regulation, according to formula (14), the system remaining reserve capacity net_R(t) is updated to obtain the system remaining reserve capacity net_R(t) = (net_R + (t), net_R - (t)):

[0095]

[0096] Where: P n,max is the maximum output of thermal power unit n;

[0097] Step S5.6, add thermal power unit n to the optimal thermal power unit combination S2, and record the output P of thermal power unit n n (t); Update the set of thermal power generation units to be selected S: delete the thermal power generation unit n from the set of thermal power generation units to be selected S;

[0098] Step S5.7, determine whether the power system has reached a standby balance state. If so, output the optimal thermal power unit combination S2 and the output of each thermal power unit in the optimal thermal power unit combination S2; if not, return to step S5.3 and continue to screen the next thermal power unit n and its output.

[0099] Preferably, step S5.1 is specifically:

[0100] Step S5.1.1, determine the output P of each thermal power unit z in the updated candidate thermal power unit set S for the standby balance phase cost estimation z (t):

[0101] Specifically, the function of thermal power unit z is to assume hot standby, so its output P z (t) With minimum technical output P z,min Run the cost estimate, that is, P z (t) = P z,min ;

[0102] Step S5.1.2, estimate the start-up and shutdown cost cost_onoff_2, carbon emission control cost cost_C_2, operation coal consumption cost cost_coal_2, wind and solar abandonment cost cost_PW_2 and reserve gap cost cost_re of thermal power unit z in the reserve balance stage during the planning period T. According to formula (15), the total cost cost_2 of thermal power unit z in the power system reserve balance stage is obtained:

[0103] cost_2=cost_onoff_2+cost_C_2+cost_coal_2+cost_PW_2+cost_re (15)

[0104] Thus, the total cost cost_2 of thermal power unit z during the backup balance stage of the power system is obtained.

[0105] Preferably, the specific estimation method of each sub-item cost is:

[0106] (1) On-off cost cost_onoff_2

[0107] The estimation method of the start-up and shutdown cost of thermal power units in the load balancing stage is the same as that of the start-up and shutdown cost of thermal power units in the load balancing stage, and the estimation is performed using formula (16):

[0108] cost_onoff_2=(U z -U z,0 )*cost_onoff z (16)

[0109] Among them: U z=1, indicating that thermal power unit z is started and operated in the current planning period T; U z,0 is the on / off state of thermal power unit z at the initial time of the current planning period T. When it is on, U z,0 =1; when the power is off, U z,0 =0; cost_onoff z is the single start-up and shutdown cost of thermal power unit z;

[0110] (2) Carbon emission control cost cost_C_2

[0111] Using formula (17), we can obtain the carbon emission control cost of thermal power unit z in the planning period T:

[0112] cost_C_2=P z,min ×T×cost_C z (17)

[0113] Where: cost_C z represents the carbon emission control cost per unit kilowatt-hour of thermal power unit z;

[0114] (3) Operating coal consumption cost cost_coal_2

[0115] Using formula (18), we can get the operating coal consumption cost of thermal power unit z in the planning period T:

[0116] cost_coal_2=P z,min ×T×cost_coal z (18)

[0117] Where: cost_coal z represents the unit coal consumption cost of thermal power unit z;

[0118] (4) Cost of abandoned wind and solar power cost_PW_2

[0119] Using formula (19), we can get the cost of abandoning wind and solar power for thermal power unit z in planning period T:

[0120]

[0121] in: The output of the started thermal power units can be reduced in time period t;

[0122] (5) Reserve gap cost cost_re

[0123] Assuming that thermal power unit z is started and its adjustable capacity is all used for hot standby, formula (20) is used to obtain the system remaining spare capacity net_R after thermal power unit z is used for hot standby: z+ (t):

[0124] net_R z + (t) = net_R + (t)+(P z,max -P z,min ) (20)

[0125] Where: P z,max is the maximum output of thermal power unit z;

[0126] If there is still a reserve gap in the power system, the reserve gap can be supplemented by purchasing electricity from outside. Therefore, the reserve gap cost is obtained through formula (21):

[0127]

[0128] Among them: cost_p represents the unit kilowatt-hour electricity purchase cost.

[0129] The present invention provides a thermal power unit combination optimization method for low-carbon and high-efficiency operation of a power system with high wind and solar power share, which has the following advantages:

[0130] The present invention comprehensively considers the wind and solar power consumption, energy storage utilization and low-carbon operation mode of thermal power units in the power system, and proposes a thermal power unit combination optimization method considering the low-carbon and efficient operation of the power system with a high proportion of wind and solar power. The method can improve the solution efficiency during the optimization of thermal power units, clearly provide decision-making process information, intuitively judge the combination performance of thermal power units, and provide guidance for power grid dispatching. BRIEF DESCRIPTION OF THE DRAWINGS

[0131] Figure 1 A flow chart of a thermal power unit combination optimization method for low-carbon and high-efficiency operation of a power system with a high proportion of wind and solar power provided by the present invention;

[0132] Figure 2 It is a process curve diagram of the system remaining load capacity and the system remaining reserve capacity after considering the output of wind, solar and hydropower sources in a certain embodiment of the present invention;

[0133] Figure 3 It is a curve diagram of adjustable output process of thermal power generation units after load balancing of a power system in a certain embodiment of the present invention;

[0134] Figure 4 It is a process curve diagram of the system positive spinning reserve remaining capacity and the system negative spinning reserve remaining capacity after the power system load is balanced in a certain embodiment of the present invention. DETAILED DESCRIPTION

[0135] In order to make the technical problems, technical solutions and beneficial effects solved by 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 used to limit the present invention.

[0136] Aiming at the problem of optimizing the combination of thermal power units for low-carbon and efficient operation of power systems with a high proportion of wind and solar power, the present invention comprehensively considers the wind and solar power consumption, energy storage utilization and low-carbon operation mode of thermal power units in the power system, and proposes a method for optimizing the combination of thermal power units for low-carbon and efficient operation of power systems with a high proportion of wind and solar power. The method can improve the solution efficiency during the optimization of thermal power units, clearly provide decision-making process information, intuitively judge the combination performance of thermal power units, and provide guidance for power grid dispatching.

[0137] See also Figure 1 The present invention provides a method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with a high proportion of wind and solar power, comprising the following steps:

[0138] Step S1, predetermine the power system data in the planning period T, including: the photovoltaic output P of each time period t in the planning period T g (t), wind power output P w (t), hydropower power output P h (t), system load demand Load(t), system reserve capacity demand R(t), hydropower power supply assuming rotating reserve capacity R h (t), characteristic parameters of energy storage units and thermal power units;

[0139] Step S2, determining the system remaining load capacity net_load(t) and the system remaining spare capacity net_R(t) in the initial state:

[0140] According to formula (1), the system residual load capacity net_load(t) is obtained when the output of wind, solar and hydropower sources is considered and the output of thermal power units and energy storage units is not considered;

[0141] net_Load(t)=P g (t)+P w (t)+P h (t)-Load(t) (1)

[0142] According to formula (2), the system remaining reserve capacity net_R(t) is obtained when considering that hydropower can bear the reserve and not considering thermal power units and energy storage units to bear the reserve:

[0143] net_R(t)=R h (t)-R(t) (2)

[0144] For the system remaining reserve capacity net_R(t), including the system positive spinning reserve remaining capacity net_R + (t) and the system negative spinning reserve remaining capacity net_R - (t), specifically obtained by formula (3):

[0145]

[0146] in: and The positive spinning reserve capacity and the negative spinning reserve capacity of hydropower are respectively assumed by hydropower; R + (t) and R - (t), are the system positive spinning reserve capacity demand and the system negative spinning reserve capacity demand, respectively.

[0147] Step S3, according to the maintenance status of the thermal power units, all thermal power units that do not need maintenance are formed into a set S of thermal power units to be selected;

[0148] The method for determining the maintenance status of the thermal power unit may be: in each sequentially arranged planning period T of the power system, the thermal power unit that needs to be maintained in each planning period T is pre-determined according to the annual maintenance plan. Therefore, in the present invention, the thermal power unit that needs to be maintained in each planning period T is pre-planned, so the set S of thermal power units to be selected in each planning period T is different.

[0149] In the specific implementation, a set of thermal power units formed by all thermal power units in the power system can be pre-constructed; then, at the initial moment of each planning cycle T, all thermal power units are traversed, and according to the maintenance status of the thermal power units, it is determined whether they can be operated within the current planning cycle T, that is, whether they are thermal power units that do not require maintenance, so that all operable thermal power units constitute a set S of candidate thermal power units.

[0150] Step S4, determination of the combination and output of thermal power units in the load balancing stage of the power system:

[0151] After the output of wind, solar and hydropower sources is determined, the optimal thermal power unit combination S1 participating in the power system regulation in the load balancing stage and the output of each thermal power unit in the optimal thermal power unit combination S1 are determined in the set of thermal power units to be selected. At the same time, according to the characteristic parameters of the energy storage unit and the system residual load capacity net_load(t), according to the output strategy of the energy storage unit, the pumped power generation condition and the output process of the energy storage unit are determined, so that the thermal power units and energy storage units in the optimal thermal power unit combination S1 jointly participate in the power system regulation, and the power system reaches a load balance state; wherein, the power system reaches a load balance state, which means that in each time period t of the planning period T, the system residual load capacity net_load(t) is 0;

[0152] The specific idea of ​​step S4 is:

[0153] Taking into account the wind and solar power consumption, energy storage utilization, electricity demand, unit operation and environmental protection benefits of the power system, the total operating cost of each thermal power unit is used as an evaluation indicator, and the thermal power unit with the smallest total cost is selected as the best unit in the current state to participate in the power system regulation in the load balancing stage. The method is: according to the characteristics of the load balancing stage of the power system, the output of the selected thermal power unit is determined, and it is judged whether the power system reaches the load balance state when the output of wind, solar, hydropower, the output of the selected thermal power unit and the output of the energy storage unit are combined at this time; if not, continue to select the next thermal power unit with the smallest total cost, and repeat this cycle continuously to obtain the thermal power unit combination that makes the power system reach the load balance state, which is the best thermal power unit combination in the load balancing stage.

[0154] Step S4 is specifically as follows:

[0155] Step S4.1, determining a cost estimation algorithm for the load balancing stage of the thermal power unit during the load balancing stage of the power system;

[0156] Step S4.1 is specifically as follows:

[0157] Step S4.1.1, determine the output P of each thermal power unit k in the set of thermal power units to be selected for cost estimation in the load balancing stage k (t):

[0158] If -net_Load(t)>P k,max , then P k (t) = P k,max , so that the cost of thermal power unit k is estimated according to the maximum output power generation;

[0159] If -net_Load(t)<P k,min , then P k (t) = P k,min , so that the cost of thermal power unit k is estimated according to the minimum technical output;

[0160] If P k,min <-net_Load(t)<P k,max , then P k (t) = -net_Load(t), so that the thermal power unit k can perform cost estimation according to the power generation demanded by the power system;

[0161] Among them, P k,max and P k,min , are the maximum output and minimum technical output of thermal power unit k respectively;

[0162] Step S4.1.2, estimate the start-up and shutdown cost cost_onoff_1, carbon emission control cost cost_C_1, operation coal consumption cost cost_coal_1, wind and solar abandonment cost cost_PW_1 and power shortage cost cost_e of thermal power unit k in the load balancing stage in the planning period T. According to formula (5), the total cost cost_1 of thermal power unit k in the load balancing stage of the power system is obtained:

[0163] cost_1=cost_onoff_1+cost_C_1+cost_coal_1+cost_PW_1+cost_e (5)

[0164] Thus, the total cost cost_1 of thermal power unit k in the load balancing stage of the power system is obtained.

[0165] In formula (5), the specific estimation method of each sub-item cost is:

[0166] (1) On-off cost cost_onoff_1:

[0167] Step 1: Determine the on / off state of thermal power unit k at the initial time of planning period T:

[0168] For multiple planning periods T arranged in chronological order in the planning year, each thermal power unit k in the first planning period T is set to be in the on state at the initial moment; for the planning periods T ranked from the second to the last, the on / off state of the thermal power unit k at the initial moment is determined by the optimal combination S of thermal power units determined by the previous adjacent planning period T. best Specifically, for thermal power unit k, if it belongs to the optimal combination S of thermal power units determined in the previous adjacent planning period T, best If it is in the initial time of the current planning period T, it is in the power-on state; otherwise, it is in the power-off state at the initial time of the current planning period T;

[0169] Step 2: If the thermal power unit k is in the shutdown state at the initial time of the current planning period T, it will change from the shutdown state to the startup state, and incur a start-up and shutdown cost; if it is initially in the startup state, it will continue to be in the startup state during the current planning period T, and no start-up and shutdown cost will be incurred; therefore, according to formula (6), its start-up and shutdown cost cost_onoff_1 is obtained:

[0170] cost_onoff_1=(U k -U k,0 )*cost_onoff k (6)

[0171] Among them: U k=1, indicating that thermal power unit k is started and operated in the current planning period T; U k,0 is the on / off state of thermal power unit k at the initial time of the current planning period T. When it is on, U k,0 =1; when the power is off, U k,0 =0; cost_onoff k is the single start-up and shutdown cost of thermal power unit k;

[0172] (2) Carbon emission control cost cost_C_1

[0173] The operation of thermal power unit k will produce carbon dioxide, which needs to be treated before discharge. The carbon emission control cost is calculated by formula (7):

[0174]

[0175] Where: T represents the current planning period T; cost_C k represents the carbon emission control cost per unit kilowatt-hour of thermal power unit k;

[0176] (3) Operating coal consumption cost cost_coal_1

[0177] The fuel cost consumed by thermal power unit k is the operating coal consumption cost, which is calculated by formula (8):

[0178]

[0179] Where: cost_coal k It represents the unit coal consumption cost of thermal power unit k;

[0180] (4) Cost of abandoned wind and solar power cost_PW_1

[0181] Specifically, when the power demand during the period is less than the minimum technical output of thermal power unit k, the system will abandon wind and solar power. However, considering the role of energy storage units (pumped storage or new energy storage) in the system, some excess power can be absorbed, stored and reused. After considering the energy storage role of energy storage units, the excess power that cannot be absorbed is the actual abandonment of wind and solar power.

[0182] When it is assumed that the thermal power unit k is based on the output P k (t) When participating in the regulation of the power system, after the energy storage unit combines with the energy storage function, if there is still excess electricity that cannot be absorbed by the energy storage unit in time period t, wind and solar power will be abandoned, and corresponding wind and solar power abandonment costs will be generated.

[0183] The specific estimation method is:

[0184] Step 1: Determine the output of the energy storage unit according to the output strategy of the energy storage unit:

[0185] Step 1.1, assuming that the thermal power unit k is based on the output P k (t) When participating in the power system regulation, the current latest system residual load capacity net_load is obtained by formula (9) when jointly considering the output of wind, solar, hydropower and thermal power units k. k (t):

[0186] net_load k (t) = net_load (t) + P k (t) (9)

[0187] Step 1.2, based on the latest system remaining load capacity net_load k (t), determine the output P of each energy storage unit i in sequence i (t), i = 1, 2, ..., N, the method is:

[0188] Step 1.2.1, i=1;

[0189] Step 1.2.2, according to the formula net_load1(t) = net_load k (t), and net_load1(t) is obtained; where net_load1(t) is the system residual load capacity when the output of wind, solar, hydropower and thermal power units k is considered together;

[0190] Step 1.2.3, use formula (10) to determine the pumped power generation state and output P of energy storage unit i i (t):

[0191]

[0192] Where: P i,max represents the single unit capacity of energy storage unit i, i = 1, 2, ..., N; coff i represents the conversion efficiency of energy storage unit i; t=1,2,...,T, represents the sequence number of each time period in the planning cycle T; when t=1, E i (t-1) = E i (0) is the energy storage capacity of energy storage unit i at the initial state of planning period T, which is a known value; E i (t) represents the energy storage capacity of energy storage unit i in time period t; E i (t-1) represents the energy storage capacity of energy storage unit i in time period t-1; E i,max represents the maximum storage energy of energy storage unit i;

[0193] Step 1.2.4, let i = i + 1, calculate net_load i (t) = net_loadi-1 (t)+P i-1 (t), return to step 1.2.3, and continue to determine the output of the next energy storage unit until the output of each of the N energy storage units is obtained; where net_load i-1 (t) is the system residual load capacity when the output of wind, solar, hydropower, thermal power unit k and the output of the first i-1 energy storage units are jointly considered;

[0194] Step 2: Use formula (11) to get the cost of abandoned wind and solar power cost_PW_1:

[0195]

[0196] Among them: cost_pw represents the unit cost of abandoned wind and solar power;

[0197] coff is the average conversion efficiency of N energy storage units;

[0198] (5) Power shortage cost cost_e_1

[0199] When the power gap of the system is large, unit k operates at maximum output and cannot meet the power demand of the system after energy storage adjustment, thermal power units with large single-unit capacity should be given priority to reduce the number of thermal power units. Because the number of units cannot be directly expressed as cost, it is assumed that after arranging unit k, the system still has a power gap, which is compensated by purchasing electricity, and the power shortage cost can be expressed as:

[0200] Using formula (12), we get the power shortage cost cost_e_1:

[0201]

[0202] Among them: cost_p represents the unit kilowatt-hour electricity purchase cost.

[0203] It should be noted that for time period t, either the wind and solar power are abandoned or the power is short of electricity. Therefore, in a certain time period t, either the wind and solar power abandonment cost or the power shortage cost will be incurred, and the wind and solar power abandonment cost and the power shortage cost will not be incurred at the same time.

[0204] Step S4.2, traverse the set S of thermal power units to be selected, estimate the total cost of each thermal power unit in the set S of thermal power units to be selected in the planning period T according to the cost estimation algorithm of the thermal power unit load balancing stage, and select the thermal power unit m with the minimum total cost;

[0205] Step S4.3, according to the thermal power unit output optimization model, determine the output P of the selected thermal power unit m in each time period t of the planning period T m (t), so that the thermal power unit m according to the output Pm (t) Participate in power system regulation;

[0206] As a specific implementation method, this step can be implemented in the following ways:

[0207] Step S4.3.1, obtaining the latest current system residual load capacity net_load(t) of the power system, specifically: the system residual load capacity when jointly considering the output of wind, solar, and hydropower sources and the output of each thermal power unit in the current optimal thermal power unit combination S1;

[0208] Step S4.3.2: According to the latest residual load capacity net_load(t) of the power system, establish the operation constraints of thermal power unit m, with the output P of thermal power unit m in the planning period T m (t) is the decision variable, with the minimum coal consumption of the power system and the output of thermal power unit m P m (t) The closest to the power demand of the power system is taken as the optimization target, and the unit output optimization model is constructed:

[0209]

[0210] Among them: F1 is the objective function of minimizing coal consumption in power system operation; F2 is the objective function that makes the output of thermal power unit m closest to the power demand of power system; a, b and c are the parameters of coal consumption curve; abs is the absolute value symbol;

[0211] The constraints include: m,min ≤P m (t)≤P m,max

[0212] 0<P m (t)-P m (t-1)<R u

[0213] 0<P m (t-1)-P m (t)<R d

[0214] Where: P m,min ≤P m (t)≤P m,max is the minimum technical output and maximum output constraint; 0<P m (t)-P m (t-1)<R u and 0<P m (t-1)-P m (t)<R d It is the ramp constraint, i.e. the peak load amplitude limit constraint;

[0215] Pm,min and P m,max , are the minimum technical output and maximum output of thermal power unit m respectively;

[0216] P m (t) and P m (t-1), are the outputs of thermal power unit m in time periods t and t-1 of planning period T respectively;

[0217] R u and R d , respectively, are the up and down climbing limits of thermal power unit m;

[0218] Step S4.3.3, solve the unit output optimization model constructed in step S4.3.2 to obtain the output P of thermal power unit m in the planning period T m (t).

[0219] In the present invention, a nonlinear programming algorithm, a particle swarm algorithm, etc. may be specifically used to solve the unit output optimization model, and the present invention does not limit the specific solution algorithm used.

[0220] Step S4.4, when the thermal power unit m is output P m When (t) participates in the regulation of the power system, the system residual load capacity net_load(t) is updated according to formula (4) to obtain the system residual load capacity net_load(t) when the wind, solar, hydropower and thermal power outputs are jointly considered:

[0221] net_load(t)=net_load(t)+P m (t) (4)

[0222] Step S4.5, according to the characteristic parameters of the energy storage unit and the latest system residual load capacity net_load(t), according to the output strategy of the energy storage unit, determine the pumped power generation operating condition and output process of the energy storage unit, so that the energy storage unit can jointly participate in the power system regulation;

[0223] Step S4.6, add the thermal power unit m to the optimal thermal power unit combination S1, and record the output P of the thermal power unit m m (t); Update the set of thermal power units to be selected S: delete the thermal power unit m from the set of thermal power units to be selected S;

[0224] Step S4.7, determine whether the power system has reached a load balance state. If so, output the optimal thermal power unit combination S1 and the output of each thermal power unit in the optimal thermal power unit combination S1, as well as the updated candidate thermal power unit set S; if not, return to step S4.2, continue to screen the next thermal power unit and output until the power system reaches a load balance state. The power system reaches a load balance state, which means that net_Load(t) = 0 is true in any time period t of the planning cycle T, that is, the system's remaining load capacity net_load(t) can be adjusted to a balanced state through the energy storage unit.

[0225] Step S5, determination of the combination and output of thermal power units in the power system standby balance stage:

[0226] After the output of wind, solar and hydropower sources, the optimal thermal power generation unit combination S1 and the output of each thermal power generation unit in the optimal thermal power generation unit combination S1 are determined, the set of thermal power generation units to be selected S = S - S1 is updated; in the updated set of thermal power generation units to be selected, the optimal thermal power generation unit combination S2 participating in the regulation of the power system in the standby balance stage and the output of each thermal power generation unit in the optimal thermal power generation unit combination S2 are determined. At the same time, according to the characteristic parameters of the energy storage unit and the system residual load capacity net_load(t), according to the output strategy of the energy storage unit, the pumped power generation operating conditions and the output process of the energy storage unit are determined, so that after the thermal power generation units and the energy storage units in the optimal thermal power generation unit combination S2 jointly participate in the regulation of the power system, the power system reaches a standby balance state on the basis of satisfying the load balance; wherein, the power system reaches a standby balance state, which means that in each time period t of the planning period T, the system residual standby capacity net_R(t) satisfies the relationship: min{net_R(t)|t∈T}≥0; the specific expression is: min{net_R + (t)|t∈T}≥0 and min{net_R - (t)|t∈T}≥0, that is, the system is spinning reserve remaining capacity net_R + (t) and the system negative spinning reserve remaining capacity net_R - (t) Both meet the backup requirements.

[0227] The specific idea of ​​step S5 is: comprehensively consider the wind and solar power consumption, energy storage utilization, standby demand, unit operation and environmental protection benefits of the power system, take the total operating cost of each thermal power unit as the evaluation index, and select the thermal power unit with the smallest total cost as the best unit in the current state to participate in the power system regulation in the standby balance stage. The method is: according to the characteristics of the standby balance stage of the power system, determine the output of the selected thermal power unit, and judge whether the power system reaches the standby balance state when combining the output of wind, solar, hydropower and the output of the selected thermal power unit; if not, continue to select the next thermal power unit with the smallest total cost, and repeat this cycle to obtain the thermal power unit combination that enables the power system to reach the standby balance state, which is the best thermal power unit combination in the standby balance stage.

[0228] Step S5 is specifically as follows:

[0229] Step S5.1, determining a cost estimation algorithm for the standby balance phase of the thermal power unit during the standby balance phase of the power system;

[0230] In this step, the cost estimation algorithm for the standby balance stage of thermal power units can be:

[0231] Step S5.1.1, determine the output P of each thermal power unit z in the updated candidate thermal power unit set S for the standby balance phase cost estimation z (t):

[0232] Specifically, the function of thermal power unit z is to assume hot standby, so its output P z (t) With minimum technical output P z,min Run the cost estimate, that is, P z (t) = P z,min ;

[0233] Step S5.1.2, estimate the start-up and shutdown cost cost_onoff_2, carbon emission control cost cost_C_2, operation coal consumption cost cost_coal_2, wind and solar abandonment cost cost_PW_2 and reserve gap cost cost_re of thermal power unit z in the reserve balance stage during the planning period T. According to formula (15), the total cost cost_2 of thermal power unit z in the power system reserve balance stage is obtained:

[0234] cost_2=cost_onoff_2+cost_C_2+cost_coal_2+cost_PW_2+cost_re (15)

[0235] Thus, the total cost cost_2 of thermal power unit z during the backup balance stage of the power system is obtained.

[0236] In formula (15), the specific estimation method of each sub-item cost is:

[0237] (1) On-off cost cost_onoff_2

[0238] The estimation method of the start-up and shutdown cost of thermal power units in the load balancing stage is the same as that of the start-up and shutdown cost of thermal power units in the load balancing stage, and the estimation is performed using formula (16):

[0239] cost_onoff_2=(U z -U z,0 )*cost_onoff z (16)

[0240] Among them: U z =1, indicating that thermal power unit z is started and operated in the current planning period T; U z,0 is the on / off state of thermal power unit z at the initial time of the current planning period T. When it is on, U z,0 =1; when the power is off, U z,0 =0; cost_onoff z is the single start-up and shutdown cost of thermal power unit z;

[0241] (2) Carbon emission control cost cost_C_2

[0242] Using formula (17), we can obtain the carbon emission control cost of thermal power unit z in the planning period T:

[0243] cost_C_2=P z,min ×T×cost_C z (17)

[0244] Where: cost_C z represents the carbon emission control cost per unit kilowatt-hour of thermal power unit z;

[0245] (3) Operating coal consumption cost cost_coal_2

[0246] Using formula (18), we can get the operating coal consumption cost of thermal power unit z in the planning period T:

[0247] cost_coal_2=P z,min ×T×cost_coal z (18)

[0248] Where: cost_coal z represents the unit coal consumption cost of thermal power unit z;

[0249] (4) Cost of abandoned wind and solar power cost_PW_2

[0250] Using formula (19), we can get the cost of abandoning wind and solar power for thermal power unit z in planning period T:

[0251]

[0252] in: The output of the started thermal power units can be reduced in time period t;

[0253] It should be noted that, since the thermal power units are operated at the minimum technical output during the calculation of the standby balance stage, the output cannot be reduced any further. Therefore, the output that can be reduced by the thermal power units that have been started in time period t is actually the sum of the output that can be reduced by each thermal power unit in the optimal thermal power unit combination S1 obtained at the end of the load balance stage, which is a fixed value. Therefore, during the calculation of the standby balance stage, No further updates are required.

[0254] (5) Reserve gap cost cost_re

[0255] When the power system reserve demand is high, the adjustable capacity of thermal power unit z is all used to undertake hot standby. If it still cannot meet the power system reserve demand, the reserve gap is made up by purchasing electricity from outside, thus incurring reserve gap costs.

[0256] Therefore, assuming that thermal power unit z is started and its adjustable capacity is all used for hot standby, the remaining spare capacity of the system after thermal power unit z takes on hot standby, net_R, is obtained by using formula (20): z + (t):

[0257] net_R z + (t) = net_R + (t)+(P z,max -P z,min ) (20)

[0258] Where: P z,max is the maximum output of thermal power unit z;

[0259] If there is still a reserve gap in the power system, the reserve gap can be supplemented by purchasing electricity from outside. Therefore, the reserve gap cost is obtained through formula (21):

[0260]

[0261] Among them: cost_p represents the unit kilowatt-hour electricity purchase cost.

[0262] It should be noted that for time period t, either the wind and solar power are in a abandoned condition or the backup gap condition. Therefore, in a certain time period t, either the wind and solar power abandonment cost or the backup gap cost is incurred, and the wind and solar power abandonment cost and the backup gap cost will not be incurred at the same time.

[0263] Step S5.2, after the output of wind, solar, and hydropower sources, the optimal thermal power generation unit combination S1, and the output of each thermal power generation unit in the optimal thermal power generation unit combination S1 are determined, the set of thermal power generation units to be selected S=S-S1 is updated;

[0264] Step S5.3, traverse the updated candidate thermal power unit set S, estimate the total cost of each thermal power unit in the candidate thermal power unit set S in the planning period T according to the thermal power unit standby balance stage cost estimation algorithm, and select the thermal power unit n with the minimum total cost;

[0265] Step S5.4, determine the output P of the selected thermal power unit n in each time period t of the planning period T n (t), so that the thermal power unit n according to the output P n (t) Participate in the regulation of the power system by:

[0266] In the standby balance stage, the function of thermal power unit n is to assume hot standby, so its output P in time period t of planning cycle T is n (t), according to the minimum technical output P n,min Run, that is: P n (t) = P n,min ;

[0267] Step S5.5, when the thermal power unit n is based on the output P n When (t) participates in the power system regulation, according to formula (14), the system remaining reserve capacity net_R(t) is updated to obtain the system remaining reserve capacity net_R(t) = (net_R + (t), net_R - (t)):

[0268]

[0269] Where: P n,max is the maximum output of thermal power unit n;

[0270] Step S5.6, add thermal power unit n to the optimal thermal power unit combination S2, and record the output P of thermal power unit n n (t); Update the set of thermal power generation units to be selected S: delete the thermal power generation unit n from the set of thermal power generation units to be selected S;

[0271] Step S5.7, determine whether the power system has reached a standby balance state. If so, output the optimal thermal power unit combination S2 and the output of each thermal power unit in the optimal thermal power unit combination S2; if not, return to step S5.3 and continue to screen the next thermal power unit n and its output.

[0272] Step S6, merging the optimal thermal power unit combination S1 and the optimal thermal power unit combination S2 to obtain the optimal thermal power unit combination S1 obtained by the final optimization. best =S1∪S2, and the optimal combination of thermal power units S best The output of each thermal power unit in the power system is adjusted together with the energy storage unit, and the power system reaches the load balance state and the standby balance state at the same time.

[0273] An embodiment is described below:

[0274] Step S1, determining the power system data in the planning period T, including the output process, load demand, standby process, characteristic parameters of thermal power units, characteristic parameters of energy storage units and power system parameters;

[0275] The output process refers to the hourly output process of the power system, including: photovoltaic hourly output P g (t), wind power hourly output P w (t), hourly output of hydropower source P h (t); Among them, hydropower sources include hydropower station power sources and nuclear power sources, etc.;

[0276] Load demand refers to the hourly load demand of the system Load(t);

[0277] The reserve process refers to the hourly reserve process of the power system, including the system reserve capacity demand R(t), the rotating reserve capacity R undertaken by hydropower sources, and the h (t); where the system reserve capacity requirement R(t) includes the system positive spinning reserve capacity requirement R + (t) and the system negative spinning reserve capacity requirement R - (t); Hydropower sources bear the spinning reserve capacity R h (t), including hydropower assuming positive spinning reserve capacity and hydropower to assume negative spinning reserve capacity

[0278] Characteristic parameters of thermal power units, including maintenance status, initial status (on or off), maximum output, minimum technical output, ramp constraint, coal consumption cost per kilowatt-hour, carbon emission control cost per kilowatt-hour, single start-up and shutdown cost, and coal consumption curve parameters a, b, and c;

[0279] Energy storage unit characteristic parameters, including installed capacity, maximum storage capacity, and conversion efficiency;

[0280] Power system parameters, including: unit kilowatt-hour electricity purchase cost, unit wind and solar power abandonment cost;

[0281] In this embodiment, the planning period T=168h, the unit kilowatt-hour outsourcing cost and the unit abandoned wind and solar power cost are 0.5 yuan / kW.h and 0.23 yuan / kW.h respectively.

[0282] In this embodiment, the thermal power units involved in the power and electricity balance calculation and their parameters are shown in Table 1, and the energy storage units and their parameters are shown in Table 2.

[0283] Table 1 Thermal power units and their parameters

[0284]

[0285] Table 2 Energy storage unit and its parameters

[0286] Unit No. Installed capacity / MW Maximum storage energy / MW.h Transformation efficiency 1 250 2112.5 0.75 2 250 2112.5 0.75 3 250 2112.5 0.75 4 250 2112.5 0.75 5 300 1816.7 0.75 6 300 1816.7 0.75 7 300 1816.7 0.75

[0287] Step S2, determining the system remaining load capacity net_load(t) and the system remaining spare capacity net_R(t) in the initial state:

[0288] According to formula (1), the system residual load capacity net_load(t) is obtained when the output of wind, solar and hydropower sources is considered and the output of thermal power units and energy storage units is not considered;

[0289] net_Load(t)=P g (t)+P w (t)+P h (t)-Load(t) (1)

[0290] According to formula (3), the system positive spinning reserve remaining capacity net_R is obtained when considering that hydropower can bear the reserve and not considering thermal power units and energy storage units to bear the reserve. + (t) and the system negative spinning reserve remaining capacity net_R - (t):

[0291]

[0292] in: and The positive spinning reserve capacity and the negative spinning reserve capacity of hydropower are respectively assumed by hydropower; R + (t) and R - (t), are the system positive spinning reserve capacity demand and the system negative spinning reserve capacity demand, respectively.

[0293] In this embodiment, the remaining reserve capacity of the system after the hydropower source and the wind and solar power output are considered, and the remaining positive rotation reserve capacity of the system after the hydropower source can bear the reserve is considered. + (t) and the system negative spinning reserve remaining capacity net_R- (t) Figure 2 shown.

[0294] Step S3, according to the maintenance status of the thermal power units, all thermal power units that do not need maintenance are formed into a set S of thermal power units to be selected;

[0295] In this embodiment, the initial set S of thermal power generating units to be selected is:

[0296] S={1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20}.

[0297] Step S4, determination of the combination and output of thermal power units in the load balancing stage of the power system:

[0298] Step S4.1, determining a cost estimation algorithm for the load balancing stage of the thermal power unit during the load balancing stage of the power system;

[0299] Step S4.2, traverse the set S of thermal power units to be selected, estimate the total cost of each thermal power unit in the set S of thermal power units to be selected in the planning period T according to the cost estimation algorithm of the thermal power unit load balancing stage, and select the thermal power unit m with the minimum total cost;

[0300] In this embodiment, in a certain selection in the load balancing stage, the total cost estimation results of each thermal power unit are shown in Table 3. In this selection, the total cost and single unit capacity of thermal power unit No. 3 and thermal power unit No. 4 are the same, and both are the thermal power units with the smallest total cost this time. Since the number of thermal power unit No. 3 is smaller, thermal power unit No. 3 is selected this time.

[0301] Table 3 Total cost estimation results of each thermal power unit in the load balancing stage

[0302]

[0303]

[0304] Step S4.3, according to the thermal power unit output optimization model, determine the output P of the selected thermal power unit m in each time period t of the planning period T m (t), so that the thermal power unit m according to the output P m (t) Participate in power system regulation;

[0305] Step S4.4, when the thermal power unit m is output P m (t) When participating in power system regulation, update the system remaining load capacity net_load(t);

[0306] Step S4.5, according to the characteristic parameters of the energy storage unit and the latest system residual load capacity net_load(t), according to the output strategy of the energy storage unit, determine the pumped power generation operating condition and output process of the energy storage unit, so that the energy storage unit can jointly participate in the power system regulation;

[0307] Step S4.6, add the thermal power unit m to the optimal thermal power unit combination S1, and record the output P of the thermal power unit m m (t); Update the set of thermal power units to be selected S: delete the thermal power unit m from the set of thermal power units to be selected S;

[0308] Step S4.7, determine whether the power system has reached a load balance state. If so, output the optimal thermal power unit combination S1 and the output of each thermal power unit in the optimal thermal power unit combination S1, as well as the updated set of candidate thermal power units S; if not, continue to screen the next thermal power unit and output until the power system reaches a load balance state.

[0309] Step S5, determination of the combination and output of thermal power units in the power system standby balance stage:

[0310] When the power system reaches a load balance state, the adjustable output process curve of the existing thermal power units is as follows: Figure 3 As shown; the process curves of the system positive spinning reserve remaining capacity and the system negative spinning reserve remaining capacity are as follows Figure 4 As shown. Figure 3 and Figure 4 It can be seen that the existing operating thermal power units have met the system's negative spinning reserve demand, but the positive spinning reserve is still insufficient. Therefore, it is necessary to further determine the combination and output of the newly added thermal power units through step S5, so that the power system can simultaneously meet the load balance state and the standby balance state.

[0311] Step S5.1, determining a cost estimation algorithm for the standby balance phase of the thermal power unit during the standby balance phase of the power system;

[0312] Step S5.2, after the output of wind, solar, and hydropower sources, the optimal thermal power generation unit combination S1, and the output of each thermal power generation unit in the optimal thermal power generation unit combination S1 are determined, the set of thermal power generation units to be selected S=S-S1 is updated;

[0313] Step S5.3, traverse the updated candidate thermal power unit set S, estimate the total cost of each thermal power unit in the candidate thermal power unit set S in the planning period T according to the thermal power unit standby balance stage cost estimation algorithm, and select the thermal power unit n with the minimum total cost;

[0314] In this embodiment, in a certain selection in the standby balance stage, the total cost estimation results of each thermal power unit are shown in Table 4. In this selection, the total costs of thermal power units No. 17, No. 18, No. 19 and No. 20 are the same, and they are all the thermal power units with the smallest total costs this time. Then, according to the principle of giving priority to thermal power units with large single-unit capacity, if the single-unit capacities are the same, giving priority to thermal power units with small unit numbers, the thermal power units with large single-unit capacity are first selected, which are thermal power units No. 19 and No. 20, and their single-unit capacities are equal; then, among thermal power units No. 19 and No. 20, since the number of thermal power unit No. 19 is smaller, thermal power unit No. 19 is selected this time.

[0315] Table 4 Total cost estimation table of each thermal power unit in the standby balance stage

[0316] Unit No. Start-Stop Cost Carbon governance costs Coal consumption cost Cost of abandoning wind and solar power Insufficient reserve cost Total Cost 2 0 648224.6 3507840 2452894 0 6608958 9 0 1129524 7596288 4934085 0 13659898 13 0 1193512 8229312 5351953 0 14774777 17 0 0 0 0 0 0 18 0 0 0 0 0 0 19 0 0 0 0 0 0 20 0 0 0 0 0 0

[0317] Step S5.4, determine the output P of the selected thermal power unit n in each time period t of the planning period T n (t), so that the thermal power unit n according to the output P n (t) Participate in power system regulation;

[0318] Step S5.5, when the thermal power unit n is based on the output P n (t) When participating in power system regulation, update the system remaining reserve capacity net_R(t);

[0319] Step S5.6, add thermal power unit n to the optimal thermal power unit combination S2, and record the output P of thermal power unit n n (t); Update the set of thermal power generation units to be selected S: delete the thermal power generation unit n from the set of thermal power generation units to be selected S;

[0320] Step S5.7, determine whether the power system has reached a standby balance state. If so, output the optimal thermal power unit combination S2 and the output of each thermal power unit in the optimal thermal power unit combination S2; if not, continue to screen the next thermal power unit n and its output.

[0321] Step S6, merging the optimal thermal power unit combination S1 and the optimal thermal power unit combination S2 to obtain the optimal thermal power unit combination S1 obtained by the final optimization. best =S1∪S2, and the optimal combination of thermal power units S best The output of each thermal power unit in the power system is adjusted together with the energy storage unit, and the power system reaches the load balance state and the standby balance state at the same time.

[0322] In this embodiment, the optimal combination S1 of thermal power units obtained in the load balancing stage of the power system is [3, 4, 6, 7, 5, 16, 15, 14, 10, 11, 12, 8, 1]; the optimal combination S2 of thermal power units obtained in the standby balancing stage of the power system is [19, 20, 17, 18, 2]. best is: [3,4,6,7,5,16,15,14,10,11,12,8,1,19,20,17,18,2].

[0323] The present invention provides a thermal power unit combination optimization method for low-carbon and high-efficiency operation of a power system with high wind and solar power share, which has the following advantages:

[0324] 1. The present invention discloses a method for optimizing the combination of thermal power units for low-carbon and efficient operation of a power system with a high proportion of wind and solar power. The method considers the differences between the load demand and the reserve demand of the power system, is divided into two stages: load balance and reserve balance, and adopts a divide-and-conquer approach to calculate the total cost of each candidate thermal power unit under the current state of the power system, select the best thermal power unit, and then update the power system state and the set of candidate thermal power units, and continuously iterate to obtain the optimal combination and output of thermal power units.

[0325] 2. The present invention discloses a method for optimizing the combination of thermal power units taking into account the low-carbon and efficient operation of power systems with a high proportion of wind and solar power. It comprehensively considers the wind and solar power consumption, energy storage utilization and low-carbon operation mode of the thermal power units in the power system, and proposes economic evaluation indicators such as start-up and shutdown costs, wind and solar power abandonment costs, carbon emission control costs, operating coal consumption costs, and power shortage (insufficient backup) costs. It compares the advantages and disadvantages of each thermal power unit, clearly gives the decision-making process information, and intuitively judges the performance of the thermal power unit selection. It can be effectively applied to new power systems with a high proportion of wind and solar power.

[0326] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention.

Claims

1. A method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with high wind and solar power ratios, characterized in that: The following steps are involved: Step S1, predetermine the power system data in the planning period T, including: the photovoltaic output P of each time period t in the planning period T g (t), wind power output P w (t), hydropower power output P h (t), system load demand Load(t), system reserve capacity demand R(t), hydropower power supply assuming rotating reserve capacity R h (t), characteristic parameters of energy storage units and thermal power units; Step S2, determining the system remaining load capacity net_load(t) and the system remaining spare capacity net_R(t) in the initial state: According to formula (1), the system residual load capacity net_load(t) is obtained when the output of wind, solar and hydropower sources is considered and the output of thermal power units and energy storage units is not considered; net_Load(t)=P g (t)+P w (t)+P h (t)-Load(t) (1) According to formula (2), the system remaining reserve capacity net_R(t) is obtained when considering that hydropower can bear the reserve and not considering thermal power units and energy storage units to bear the reserve: net_R(t)=R h (t)-R(t) (2) Step S3, according to the maintenance status of the thermal power units, all thermal power units that do not need maintenance are formed into a set S of thermal power units to be selected; Step S4, determination of the combination and output of thermal power units in the load balancing stage of the power system: After the output of wind, solar and hydropower sources is determined, the optimal thermal power unit combination S1 participating in the power system regulation in the load balancing stage and the output of each thermal power unit in the optimal thermal power unit combination S1 are determined in the set of thermal power units to be selected. At the same time, according to the characteristic parameters of the energy storage unit and the system residual load capacity net_load(t), according to the output strategy of the energy storage unit, the pumped power generation condition and the output process of the energy storage unit are determined, so that the thermal power units and energy storage units in the optimal thermal power unit combination S1 jointly participate in the power system regulation, and the power system reaches a load balance state; wherein, the power system reaches a load balance state, which means that in each time period t of the planning period T, the system residual load capacity net_load(t) is 0; Step S5, determination of the combination and output of thermal power units in the power system standby balance stage: After the output of wind, solar and hydropower sources, the optimal thermal power unit combination S1 and the output of each thermal power unit in the optimal thermal power unit combination S1 are determined, the set of thermal power units to be selected S = S - S1 is updated; in the updated set of thermal power units to be selected S, the optimal thermal power unit combination S2 participating in the regulation of the power system in the standby balance stage and the output of each thermal power unit in the optimal thermal power unit combination S2 are determined. At the same time, according to the characteristic parameters of the energy storage unit and the system residual load capacity net_load(t), according to the output strategy of the energy storage unit, the pumped power generation condition and the output process of the energy storage unit are determined, so that after the thermal power units and the energy storage units in the optimal thermal power unit combination S2 jointly participate in the regulation of the power system, the power system reaches a standby balance state on the basis of satisfying load balance; wherein, the power system reaches a standby balance state, which means that in each time period t of the planning period T, the system residual standby capacity net_R(t) satisfies the relationship: min{net_R(t)|t∈T}≥0; Step S6, merging the optimal thermal power unit combination S1 and the optimal thermal power unit combination S2 to obtain the optimal thermal power unit combination S1 obtained by the final optimization. best =S1∪S2, and the optimal combination of thermal power units S best The output of each thermal power unit in the power system is adjusted together with the energy storage unit, and the power system reaches the load balance state and the standby balance state at the same time.

2. According to claim 1, a thermal power unit combination optimization method considering low-carbon and high-efficiency operation of a power system with high wind and solar power ratios is characterized in that: In step S2, the system remaining spare capacity net_R(t), including the system positive spinning spare remaining capacity net_R + (t) and the system negative spinning reserve remaining capacity net_R - (t), specifically obtained by formula (3): in: and The positive spinning reserve capacity and the negative spinning reserve capacity of hydropower are respectively assumed by hydropower; R + (t) and R - (t), are the system positive spinning reserve capacity demand and the system negative spinning reserve capacity demand, respectively.

3. According to claim 1, a thermal power unit combination optimization method for low-carbon and high-efficiency operation of a power system with high wind and solar power ratios is characterized in that: In step S3, the method for determining the maintenance status of the thermal power unit is as follows: in each sequentially arranged planning period T of the power system, the thermal power unit that needs to be maintained in each planning period T is pre-determined according to the annual maintenance plan.

4. According to claim 1, a thermal power unit combination optimization method considering low-carbon and high-efficiency operation of a power system with high wind and solar power ratios is characterized in that: Step S4 is specifically as follows: Step S4.1, determining a cost estimation algorithm for the load balancing stage of the thermal power unit during the load balancing stage of the power system; Step S4.2, traverse the set S of thermal power units to be selected, estimate the total cost of each thermal power unit in the set S of thermal power units to be selected in the planning period T according to the cost estimation algorithm of the thermal power unit load balancing stage, and select the thermal power unit m with the minimum total cost; Step S4.3, according to the thermal power unit output optimization model, determine the output P of the selected thermal power unit m in each time period t of the planning period T m (t), so that the thermal power unit m according to the output P m (t) Participate in power system regulation; Step S4.4, when the thermal power unit m is output P m When (t) participates in the regulation of the power system, the system residual load capacity net_load(t) is updated according to formula (4) to obtain the system residual load capacity net_load(t) when the wind, solar, hydropower and thermal power outputs are jointly considered: net_load(t)=net_load(t)+P m (t) (4) Step S4.5, according to the characteristic parameters of the energy storage unit and the latest system residual load capacity net_load(t), according to the output strategy of the energy storage unit, determine the pumped power generation operating condition and output process of the energy storage unit, so that the energy storage unit can jointly participate in the power system regulation; Step S4.6, add the thermal power unit m to the optimal thermal power unit combination S1, and record the output P of the thermal power unit m m (t); Update the set of thermal power units to be selected S: delete the thermal power unit m from the set of thermal power units to be selected S; Step S4.7, determine whether the power system has reached a load balance state. If so, output the optimal thermal power unit combination S1 and the output of each thermal power unit in the optimal thermal power unit combination S1, as well as the updated set of candidate thermal power units S; if not, return to step S4.2 to continue screening the next thermal power unit and output.

5. According to claim 4, a method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with high wind and solar power ratios is characterized in that: Step S4.1 is specifically as follows: Step S4.1.1, determine the output P of each thermal power unit k in the set of thermal power units to be selected for cost estimation in the load balancing stage k (t): If -net_Load(t)>P k,max , then P k (t) = P k,max , so that the cost of thermal power unit k is estimated according to the maximum output power generation; If -net_Load(t)<P k,min , then P k (t) = P k,min , so that the cost of thermal power unit k is estimated according to the minimum technical output; If P k,min <-net_Load(t)<P k,max , then P k (t) = -net_Load(t), so that the thermal power unit k can be cost-estimated according to the power generation demanded by the power system; Among them, P k,max and P k,min , are the maximum output and minimum technical output of thermal power unit k respectively; Step S4.1.2, estimate the start-up and shutdown cost cost_onoff_1, carbon emission control cost cost_C_1, operation coal consumption cost cost_coal_1, wind and solar abandonment cost cost_PW_1 and power shortage cost cost_e of thermal power unit k in the load balancing stage in the planning period T. According to formula (5), the total cost cost_1 of thermal power unit k in the load balancing stage of the power system is obtained: cost_1=cost_onoff_1+cost_C_1+cost_coal_1+cost_PW_1+cost_e (5) Thus, the total cost cost_1 of thermal power unit k in the load balancing stage of the power system is obtained.

6. A method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with high wind and solar power share according to claim 5, characterized in that: The specific estimation method for each sub-item cost is as follows: (1) On-off cost cost_onoff_1: Step 1: Determine the on / off state of thermal power unit k at the initial time of planning period T: For multiple planning periods T arranged in chronological order in the planning year, each thermal power unit k in the first planning period T is set to be in the on state at the initial moment; for the planning periods T ranked from the second to the last, the on / off state of the thermal power unit k at the initial moment is determined by the optimal combination S of thermal power units determined by the previous adjacent planning period T. best Specifically, for thermal power unit k, if it belongs to the optimal combination S of thermal power units determined in the previous adjacent planning period T, best If it is in the initial time of the current planning period T, it is in the power-on state; otherwise, it is in the power-off state at the initial time of the current planning period T; Step 2: If the thermal power unit k is in the shutdown state at the initial time of the current planning period T, it will change from the shutdown state to the startup state, and incur a start-up and shutdown cost; if it is initially in the startup state, it will continue to be in the startup state during the current planning period T, and no start-up and shutdown cost will be incurred; therefore, according to formula (6), its start-up and shutdown cost cost_onoff_1 is obtained: cost_onoff_1=(U k -U k,0 )*cost_onoff k (6) Among them: U k =1, indicating that thermal power unit k is started and operated in the current planning period T; U k,0 is the on / off state of thermal power unit k at the initial time of the current planning period T. When it is on, U k,0 =1; when the power is off, U k,0 =0; cost_onoff k is the single start-up and shutdown cost of thermal power unit k; (2) Carbon emission control cost cost_C_1 The operation of thermal power unit k will produce carbon dioxide, which needs to be treated before discharge. The carbon emission control cost is calculated by formula (7): Where: T represents the current planning period T; cost_C k represents the carbon emission control cost per unit kilowatt-hour of thermal power unit k; (3) Operating coal consumption cost cost_coal_1 The fuel cost consumed by thermal power unit k is the operating coal consumption cost, which is calculated by formula (8): Where: cost_coal k It represents the unit coal consumption cost of thermal power unit k; (4) Cost of abandoned wind and solar power cost_PW_1 When it is assumed that the thermal power unit k is based on the output P k (t) When participating in the regulation of the power system, after the energy storage unit combines with the energy storage function, if there is still excess power that cannot be absorbed by the energy storage unit in time period t, wind and solar power will be abandoned, and the corresponding wind and solar power abandonment cost will be generated. The specific estimation method is: Step 1: Determine the output of the energy storage unit according to the output strategy of the energy storage unit: Step 1.1, assuming that the thermal power unit k is based on the output P k (t) When participating in the power system regulation, the current latest system residual load capacity net_load is obtained by formula (9) when jointly considering the output of wind, solar, hydropower and thermal power units k. k (t): net_load k (t)=net_load(t)+P k (t) (9) Step 1.2, based on the latest system remaining load capacity net_load k (t), determine the output P of each energy storage unit i in sequence i (t), i = 1, 2, ..., N, the method is: Step 1.2.1, i=1; Step 1.2.2, according to the formula net_load1(t) = net_load k (t), and net_load1(t) is obtained; where net_load1(t) is the system residual load capacity when the output of wind, solar, hydropower and thermal power units k is considered together; Step 1.2.3, use formula (10) to determine the pumped power generation state and output P of energy storage unit i i (t): Where: P i,max represents the single unit capacity of energy storage unit i, i = 1, 2, ..., N; coff i represents the conversion efficiency of energy storage unit i; t=1,2,...,T, represents the sequence number of each time period in the planning cycle T; when t=1, E i (t-1) = E i (0) is the energy storage capacity of energy storage unit i at the initial state of planning period T, which is a known value; E i (t) represents the energy storage capacity of energy storage unit i in time period t; E i (t-1) represents the energy storage capacity of energy storage unit i in time period t-1; E i,max represents the maximum storage energy of energy storage unit i; Step 1.2.4, let i = i + 1, calculate net_load i (t) = net_load i-1 (t)+P i-1 (t), return to step 1.2.3, and continue to determine the output of the next energy storage unit until the output of each of the N energy storage units is obtained; where net_load i-1 (t) is the system residual load capacity when the output of wind, solar, hydropower, thermal power unit k and the output of the first i-1 energy storage units are jointly considered; Step 2: Use formula (11) to get the cost of abandoned wind and solar power cost_PW_1: Among them: cost_pw represents the unit cost of abandoned wind and solar power; coff is the average conversion efficiency of N energy storage units, (5) Power shortage cost cost_e_1 Using formula (12), we get the power shortage cost cost_e_1: Among them: cost_p represents the unit kilowatt-hour electricity purchase cost.

7. The method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with high wind and solar power ratios according to claim 5 is characterized in that: Step S4.3 is specifically as follows: Step S4.3.1, obtaining the latest current system residual load capacity net_load(t) of the power system, specifically: the system residual load capacity when jointly considering the output of wind, solar, and hydropower sources and the output of each thermal power unit in the current optimal thermal power unit combination S1; Step S4.3.2: According to the latest current residual load capacity net_load(t) of the power system, establish the operation constraints of thermal power unit m, with the output P of thermal power unit m in the planning period T m (t) is the decision variable, with the minimum coal consumption of the power system and the output of thermal power unit m P m (t) The closest to the power demand of the power system is taken as the optimization target, and the unit output optimization model is constructed: Among them: F1 is the objective function of minimizing coal consumption in power system operation; F2 is the objective function that makes the output of thermal power unit m closest to the power demand of power system; a, b and c are the parameters of coal consumption curve; abs is the absolute value symbol; The constraints include: m,min ≤P m (t)≤P m,max 0<P m (t)-P m (t-1)<R u 0<P m (t-1)-P m (t)<R d Where: P m,min and P m,max , are the minimum technical output and maximum output of thermal power unit m respectively; P m (t) and P m (t-1), are the outputs of thermal power unit m in time periods t and t-1 of planning period T respectively; R u and R d , respectively, are the up and down climbing limits of thermal power unit m; Step S4.3.3, solve the unit output optimization model constructed in step S4.3.2 to obtain the output P of thermal power unit m in the planning period T m (t).

8. The method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with high wind and solar power ratios according to claim 1 is characterized in that: Step S5 is specifically as follows: Step S5.1, determining a cost estimation algorithm for the standby balance phase of the thermal power unit during the standby balance phase of the power system; Step S5.2, after the output of wind, solar, and hydropower sources, the optimal thermal power generation unit combination S1, and the output of each thermal power generation unit in the optimal thermal power generation unit combination S1 are determined, the set of thermal power generation units to be selected S=S-S1 is updated; Step S5.3, traverse the updated candidate thermal power unit set S, estimate the total cost of each thermal power unit in the candidate thermal power unit set S in the planning period T according to the thermal power unit standby balance stage cost estimation algorithm, and select the thermal power unit n with the minimum total cost; Step S5.4, determine the output P of the selected thermal power unit n in each time period t of the planning period T n (t), so that the thermal power unit n according to the output P n (t) Participate in the regulation of the power system by: In the standby balance stage, the function of thermal power unit n is to assume hot standby, so its output P in time period t of planning cycle T is n (t), according to the minimum technical output P n,min Run, that is: P n (t) = P n,min ; Step S5.5, when the thermal power unit n is based on the output P n When (t) participates in the power system regulation, according to formula (14), the system remaining reserve capacity net_R(t) is updated to obtain the system remaining reserve capacity net_R(t) = (net_R + (t), net_R - (t)): Where: P n,max is the maximum output of thermal power unit n; Step S5.6, add thermal power unit n to the optimal thermal power unit combination S2, and record the output P of thermal power unit n n (t); Update the set of thermal power generation units to be selected S: delete the thermal power generation unit n from the set of thermal power generation units to be selected S; Step S5.7, determine whether the power system has reached a standby balance state. If so, output the optimal thermal power unit combination S2 and the output of each thermal power unit in the optimal thermal power unit combination S2; if not, return to step S5.3 and continue to screen the next thermal power unit n and its output.

9. A method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with high wind and solar power ratios according to claim 8, characterized in that: Step S5.1 is specifically as follows: Step S5.1.1, determine the output P of each thermal power unit z in the updated candidate thermal power unit set S for the standby balance phase cost estimation z (t): Specifically, the function of thermal power unit z is to assume hot standby, so its output P z (t) With minimum technical output P z,min Run the cost estimate, that is, P z (t) = P z,min ; Step S5.1.2, estimate the start-up and shutdown cost cost_onoff_2, carbon emission control cost cost_C_2, operation coal consumption cost cost_coal_2, wind and solar abandonment cost cost_PW_2 and reserve gap cost cost_re of thermal power unit z in the reserve balance stage during the planning period T. According to formula (15), the total cost cost_2 of thermal power unit z in the power system reserve balance stage is obtained: cost_2=cost_onoff_2+cost_C_2+cost_coal_2+cost_PW_2+cost_re (15) Thus, the total cost cost_2 of thermal power unit z during the backup balance stage of the power system is obtained.

10. A method for optimizing the combination of thermal power units for low-carbon and high-efficiency operation of a power system with high wind and solar power ratios according to claim 9, characterized in that: The specific estimation method for each sub-item cost is as follows: (1) On-off cost cost_onoff_2 The estimation method of the start-up and shutdown cost of thermal power units in the load balancing stage is the same as that of the start-up and shutdown cost of thermal power units in the load balancing stage, and the estimation is performed using formula (16): cost_onoff_2=(U z -U z,0 )*cost_onoff z (16) Among them: U z =1, indicating that thermal power unit z is started and operated in the current planning period T; U z,0 is the on / off state of thermal power unit z at the initial time of the current planning period T. When it is on, U z,0 =1; when the power is off, U z,0 =0; cost_onoff z is the single start-up and shutdown cost of thermal power unit z; (2) Carbon emission control cost cost_C_2 Using formula (17), we can obtain the carbon emission control cost of thermal power unit z in the planning period T: cost_C_2=P z,min ×T×cost_C z (17) Where: cost_C z represents the carbon emission control cost per unit kilowatt-hour of thermal power unit z; (3) Operating coal consumption cost cost_coal_2 Using formula (18), we can get the operating coal consumption cost of thermal power unit z in the planning period T: cost_coal_2=P z,min ×T×cost_coal z (18) Where: cost_coal z represents the unit coal consumption cost of thermal power unit z; (4) Cost of abandoned wind and solar power cost_PW_2 Using formula (19), we can get the cost of abandoning wind and solar power for thermal power unit z in planning period T: in: The output of the started thermal power units can be reduced in time period t; (5) Reserve gap cost cost_re Assuming that thermal power unit z is started and its adjustable capacity is all used for hot standby, formula (20) is used to obtain the system remaining spare capacity net_R after thermal power unit z is used for hot standby: z + (t): net_R z + (t)=net_R + (t)+(P z,max -P z,min ) (20) Where: P z,max is the maximum output of thermal power unit z; If there is still a reserve gap in the power system, the reserve gap can be supplemented by purchasing electricity from outside. Therefore, the reserve gap cost is obtained through formula (21): Among them: cost_p represents the unit kilowatt-hour electricity purchase cost.

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