CN110994587A - Safety check method for power grid day-ahead power generation plan - Google Patents

Abstract

The invention provides a safety check method for a day-ahead power generation plan of a power grid, and belongs to the technical field of power grid dispatching. Firstly, obtaining an alternating current power flow solution at each moment in the day, and obtaining a total active power output set and a total active power output upper limit set of a section at each moment in the day; judging whether the active output of the cross section at each moment in the day is over the upper limit, and eliminating the over-limit of the cross section with the over-limit by reducing the active output of the effective unit at the moment; and then, in order to ensure the total balance of the power generation and the load of the power grid, selecting a proper unit to increase the active output to keep consistent with the reduction of the total active output. According to the invention, the problem that the conveying section is out of limit is solved by checking and adjusting the day-ahead power generation plan, and the safe operation of a power grid is ensured.

Description

Safety check method for power grid day-ahead power generation plan

Technical Field

The invention belongs to the technical field of power grid dispatching, and particularly relates to a safety check method for a power grid day-ahead power generation plan.

Background

The day-ahead operation plan of the power system is the main basis of power grid dispatching, and the reasonable day-ahead operation plan is related to the future safe operation of the system. With the expansion of the scale of power grids and the complication of operation modes, power grid companies require security checks on day-ahead plans. Especially, the power generation of new energy generated in large quantity in recent years generates intermittent fluctuation, and when the capacity of receiving the new energy by a power grid is limited, a part of conveying sections possibly exceed the limit.

The transmission section is a group of transmission lines connected between power grid areas, is an important factor and a weak link influencing the normal operation state of a power system, and the transmission power of the transmission section is a key index for measuring the safe operation level of the power grid. However, with the continuous expansion of the power utilization scale in China, the power grid structure is increasingly complex, new energy is connected to the power grid, and the situation that the transmission section line is out of limit sometimes happens, so that great threat is caused to the safe and stable operation of the power grid. Therefore, a reasonable unit output plan is formulated in the day ahead, the out-of-limit of the section is eliminated in advance, and the method has important significance for ensuring the safety of the important transmission section and the normal operation of the power grid.

In the conventional scheduling operation mode, in order to eliminate the cross-limit of the cross-section, when the cross-limit occurs, a scheduler generally selects a unit by virtue of own experience to reduce the active output, so that the cross-limit of the cross-section is eliminated. Although this approach may eliminate the out-of-limit for a certain section, it may allow for a large number of adjustments to be made to a single unit; in order to make up for the influence of power reduction on the power of the power grid, the unit with smaller active power output is selected to increase the active power output to make up for the loss of power. This relatively simple selection method may cause a change in the operation mode of the power grid, which may affect the safe operation of the power grid and increase the system loss of the power grid.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a safety check method for a power grid day-ahead power generation plan. According to the invention, the problem that the conveying section is out of limit is solved by checking and adjusting the day-ahead power generation plan, and the safe operation of a power grid is ensured.

The invention provides a safety check method for a power grid day-ahead power generation plan, which is characterized by comprising the following steps of:

1) dividing the whole day into 96 times by every 15 minutes before the day; on the basis of a similar day power grid topological structure, a day-ahead equipment maintenance plan is considered to obtain a future power grid topological structure, and an alternating current power flow solution at each day-ahead moment is obtained by a day-ahead planned power flow automatic generation algorithm by utilizing bus load prediction data, generator set output plan data and power transmission section exchange plan data;

if the power grid shares a generator set y, the power grid is marked as G₁,G₂...G_yTaking the unit active output in the alternating current power flow solution at each moment in the day as the unit active output planned value at the corresponding moment in the day; for any moment i, reading each unit G from the alternating current power flow solution at the moment_aActive power of is noted as P_{i,g_a}Y, a 1,2.. y; set up the unit G_aThe active power reduction step size of (1) is delta P_a(ii) a Setting the total unit active reduction quantity at each moment to be delta P_decAt each time Δ P_decIs set to 0 and is taken as the current Δ P at each time instant_dec；

2) Let the electric wire netting contain k sections:

U_T＝{T₁,T₂,T₃...T_k}

in the formula of U_TRepresenting a set of k sections;

the method comprises the following steps of obtaining a total active output set and a total active output upper limit set of the section at each moment in the day, wherein the method comprises the following steps:

respectively reading the active power output of each line in each section from the power grid at the moment i, wherein the total active power output of each section is the sum of the active power outputs of all the lines forming the section;

then i time U_TThe corresponding total active power output of the section is integrated as follows:

U_{i,tie_p}＝{P_{i,tie_1},P_{i,tie_2},P_{i,tie_3}...P_{i,tie_k}}

wherein, P_{i,tie_m}Is a section T at the moment i_mTotal active power output of (1), 2 … k;

timing any section T_mHas a total active power output upper limit value of P_{i,max_m}Then i time U_TThe upper limit set of the total active output of the corresponding section is as follows:

U_i,pmax＝{P_{i,max_1},P_{i,max_2},P_{i,max_3}...P_{i,max_k}}

3) calculating the active sensitivity of the active output of the generator set to each line at each moment in the day by using a quasi-steady active sensitivity algorithm based on the alternating current power flow solution obtained in the step 1) at each moment in the day;

summing the active power output of any generator set at any moment to the active sensitivity of each line belonging to the same section to obtain the active sensitivity of the active power output of the generator set at the moment to each section; the unit G at the moment i_aActive power output pair section T_mActive sensitivity of (D) is recorded as S_{i,tie_a_m}；

4) Calculating the network loss ratio of each generator set to the system at each moment in the day by using a network loss allocation algorithm based on the alternating current power flow solution obtained in the step 1) at each moment in the day; the unit G will be at time i_aThe share ratio of the system loss is recorded as: p_{i,loss_a}；

5) Setting a round counter x for each time, and enabling an initial value x of each time counter to be 1;

6) correcting the cross section of each moment in the day ahead to eliminate the out-of-limit of the cross section at the moment; the method comprises the following specific steps:

6.1) for any time i, checking the section set U_TWhether the total active output of any section exceeds the upper limit or not is determined, and the method comprises the following steps: compare set U_{i,tie_p}And U_i,pmaxIf there is P in the data of all corresponding sections_{i,tie_m}＞P_i,maxmThen the section T at that moment_mCounting all the sections with the active output exceeding the upper limit at the moment, and then entering the step 6.2); if P is not present_{i,tie_m}＞P_i,maxmIf the active power of the section does not exist at the moment, the step 7) is carried out;

6.2) acquiring a reduced active effective unit set of each section for all sections with active power exceeding the upper limit obtained in the step 6.1);

for any unit G_aAnd section T_mIf the set and the section meet the following conditions, the set G is judged_aIs a section T_mThe reduction active and effective units:

P_{i,tie_m}> 0 and S_{i,tie_a_m}> α or P_{i,tie_m}< 0 and S_{i,tie_a_m}＜-α

Wherein α is a sensitivity threshold coefficient;

after the judgment is finished, the section T of each moment i, with the upper limit of the active power output higher, is obtained_mCorresponding aggregate U for reducing active and effective units_{i,valid_m}；

6.3) for each unit in the reduced active effective unit set corresponding to each section with the upper limit exceeded by the active power at the moment i, respectively calculating an active power output decrement step length corresponding to the active power output reduction of the unit at the moment i, wherein the active power output obtained by updating after the active power output reduction of each unit at the moment i is:

P′_{i,g_a}＝P_{i,g_a}-ΔP_a

and taking the updated value as the new active power output P of the unit i at the moment_{i,g_a}；

According to the active sensitivity of each active power reduction effective unit to the corresponding section at the moment i, summing the results obtained by multiplying the active power output reduction of each active power reduction effective unit of the same section at the moment by the active sensitivity of the unit to the section at the moment to obtain the total active power output reduction of the section at the moment; subtracting the total active power output reduction of each section at the moment from the total active power output of each section at the moment to obtain the updated total active power output of each section at the moment;

summing all active power output reduction of the reduced active power effective unit at the moment, and comparing the sum with the current delta P_decAdding to obtain the updated current delta P at the moment_dec；

6.4) carrying out-of-limit judgment on the total active power output of each section at the moment i after updating obtained in the step 6.3):

6.4.1) if P is present for all sections_{i,tie_m}<＝P_i,maxmIf yes, all the cross sections at the moment are eliminated and the step 7) is carried out;

6.4.2) if any cross section does not satisfy P_{i,tie_m}<＝P_i,maxmIf yes, returning to the step 6.3) again, and continuously reducing the total active power output of the section;

if any section m exists at the moment, the active power output reduced by the active power effective unit reaches 5 active power output decrementStep size and the cross section still not satisfying P_{i,tie_m}<＝P_i,maxmIf so, ending the cross section off-limit adjustment of the elimination in the current round, and entering the step 7);

7) selecting an effective output increasing unit at each moment in the day so as to increase the total active output at the moment; the method comprises the following specific steps:

7.1) let the total active output increase DeltaP at each moment_addIs 0, i.e. Δ P_add0, and the current total active output increment is taken as the current total active output increment at the moment;

7.2) at the moment i, all the units are judged:

if the active output planned value of the unit at the moment exceeds the active output upper limit value of the unit, the unit is removed;

if the unit reduces the active power output in the step 6) at the moment i, the unit is removed;

after the judgment is finished, all the remaining units form an i moment output increasing effective unit set;

7.3) according to the result of the step 7.2), sequencing all the units in the i-moment output increase effective unit set from small to large according to the network loss sharing ratio corresponding to the unit at the i moment obtained in the step 4);

7.4) at the moment i, sequentially judging the active output increment of each unit according to the sequence obtained in the step 7.3), wherein the method comprises the following specific steps:

7.4.1) letting a be 1;

7.4.2) selecting the a-th unit G in the output increase effective unit set at the moment i_a；

Calculating the active power output increment step length of the unit:

7.4.3) calculating that the updated active output obtained after the unit increases the active output at the moment i is as follows:

P′_{i,g_a}＝P_{i,g_a}+ΔP_{a_add}

if P'_{i,g_a}＝P_{i,g_a}+ΔP_{a_add}If the active output exceeds the upper limit value of the active output of the unit at the moment i, the unit does not increase the active output, and the active output of the unit at the moment i keeps P_{i,g_a}Keeping a equal to a +1, and then returning to the step 7.3.2); otherwise, entering step 7.3.4);

7.4.4) time section T at i_mTotal active power update of is P'_{i,tie_m}＝P_{i,tie_m}+ΔP_a*S_{i,tie_a_m}Then i moment section set U_TIs updated to U'_{i,tie_p}＝{P′_{i,tie_1},P′_{i,tie_2},P′_{i,tie_3}...P′_{i,tie_k}}, mixing U 'with'_{i,tie_p}＝{P′_{i,tie_1},P′_{i,tie_2},P′_{i,tie_3}...P′_{i,tie_k}The sum of the mean and the section set U_TTotal active power output upper limit value set U at moment i_i,pmax＝{P_i,max1,P_i,max2,P_i,max3...P_i,maxkComparing and judging corresponding sections: if any cross section satisfies the condition P'_{i,tie_m}＞＝P_i,maxmIf the unit does not increase the active power output, the unit keeps the active power output P at the moment i_{i,g_a}Keeping a equal to a +1, and then returning to the step 7.3.2); otherwise, taking the active output updated in the step 7.3.3) as the new active output P of the unit at the moment i_{i,g_a}Update Δ P_add＝ΔP_add+ΔP_{a_add}As a new current total active output increment at the moment, then making a equal to a +1, and then returning to step 7.3.2);

7.5) repeating the step 7.4) until all the units in the i moment output increase effective unit set finish the determination of the active output increase, determining the current total active output increase at the moment:

if Δ P_add＜ΔP_decEntering step 8);

if Δ P_add＝ΔP_decAnd if the active power of the section does not exceed the upper limit at the moment or all the sections are eliminated and exceed the limit at the moment in the step 6), the safety check is finished at the moment, and the method is finished;

if Δ P_add＝ΔP_decAnd if all the cross sections at the moment in the step 6) are not out of limit, entering a step 8);

8) and (3) judging x:

if x is less than 3, making x equal to x +1, and then returning to step 6); if x is greater than or equal to 3, the out-of-limit cannot be eliminated at time i in the day ahead, and the method is ended.

The invention has the advantages and beneficial effects that:

the invention provides a safety check method for a power grid day-ahead power generation plan, which is used for forecasting the power flow at 96 moments before the day based on a day-ahead plan and prediction data, and checking the day-ahead power generation plan by adopting a method of combining steady-state sensitivity and a network loss sharing algorithm, so that the data of the day-ahead power generation plan is safer and more reliable and is closer to the actual condition, the network loss of a system is not increased as much as possible while adjustment is carried out, the safe operation of a power grid is ensured, and meanwhile, a dispatcher can be better guided to predict the operation risk of the power grid.

Drawings

FIG. 1 is an overall flow chart of the method of the present invention.

Detailed Description

The invention provides a safety check method for a power grid day-ahead power generation plan, which is further described in detail below by combining the accompanying drawings and specific embodiments.

The invention provides a safety check method for a day-ahead power generation plan of a power grid, which is characterized in that a future power grid topological structure is obtained by considering a day-ahead equipment maintenance plan on the basis of a similar day-ahead power grid topological structure, and a day-ahead alternating current power flow solution is obtained by a day-ahead planning power flow generation algorithm in cooperation with several types of planning data and constraints such as bus load prediction, a generator set output plan, a power transmission section exchange plan and the like. And then combining with algorithms such as steady-state sensitivity, network loss allocation and the like on the basis to obtain a checking result and correspondingly adjusting the generating plan of the unit before the day.

The invention provides a safety check method for a power grid day-ahead power generation plan, the overall flow is shown in figure 1, and the method comprises the following steps:

1) and (3) on the basis of the similar day power grid topological structure, a day-ahead equipment maintenance plan is considered to obtain a future power grid topological structure, and a day-ahead alternating current power flow solution is obtained by a day-ahead planned power flow automatic generation algorithm in cooperation with three types of data, namely bus load prediction data, generator set output plan data and power transmission section exchange plan data. (forest and people, grand son and bin, Wu Wen, military, Zuberming proposed an automatic generation method of a future planned power flow in the future planned safety check technology (power system automation, 10.10.2012, V36N20, pp.68-73))

Dividing the whole day into 96 moments by one moment every 15 minutes before the day, wherein each moment corresponds to an alternating current power flow solution. Let a common generator set y, denoted as G₁,G₂...G_yAnd taking the active output of the unit in the tidal current solution at each moment as the active output planned value of the unit at the corresponding moment in the day ahead, and adjusting the active output of the unit in the tidal current solution at each moment, namely adjusting the power generation plan of the unit in the day ahead. For any moment i, reading each unit G from the alternating current power flow solution at the moment_aActive power of is noted as P_{i,g_a}Y, a is 1,2. Set up the unit G_aThe active power reduction step size of (1) is delta P_a(ii) a Setting the total unit active reduction quantity at each moment to be delta P_decAt each time Δ P_decIs set to 0 and is taken as the current Δ P at each time instant_dec。

2) Reading the definition of the i moment of day transmission sections in the region from the power grid, indicating which transmission lines are formed by each transmission section, and determining the total active power upper limit constraint value of each section in one day.

Let the electric wire netting contain k sections:

U_T＝{T₁,T₂,T₃...T_k}

in the formula of U_TRepresenting a set of k sections;

the method comprises the following steps of obtaining a total active output set and a total active output upper limit set of the section at each moment in the day, wherein the method comprises the following steps:

respectively reading the active power output of each line in each section from the power grid at the moment i, wherein the total active power output of each section is the sum of the active power outputs of all the lines forming the section;

then i time U_TThe corresponding total active power output of the section is integrated as follows:

U_{i,tie_p}＝{P_{i,tie_1},P_{i,tie_2},P_{i,tie_3}...P_{i,tie_k}}

wherein, P_{i,tie_m}Is a section T at the moment i_mTotal active power output of (1), 2 … k;

the upper limit value of the total active power output of each section is included in the definition of the conveying section, and the section T is positioned at the moment i_mThe upper limit value of the total active power output is recorded as P_{i,max_m}，U_TThe upper limit set of the total active output of the corresponding section is as follows:

U_i,pmax＝{P_{i,max_1},P_{i,max_2},P_{i,max_3}...P_{i,max_k}}

3) based on the alternating current power flow solution calculated in the step 1) at 96 moments in the day, calculating the active sensitivity of the active output of the generator set to each line at each moment in the day by using a quasi-steady-state active sensitivity algorithm, wherein the unit of the sensitivity is as follows: megawatts per megawatt (MW/MW). And (3) summing the active output of any generator set at any moment to the active sensitivity of each line belonging to the same section by combining the definition of the sections in the step 2) to obtain the active sensitivity of the active output of the generator set to each section at the moment.

The algorithm of the quasi-steady-state active sensitivity has the physical meaning that after unit active power is injected on a certain bus, the active power of each branch in a power grid changes. Grand bin, zhanberming, and yearly, proposed a quasi-steady-state sensitivity method in the quasi-steady-state sensitivity analysis method (the report of motor engineering in china, V19N 4, 1999, 4 months, pp.9-13), which is different from the conventional static sensitivity analysis method, takes into account the quasi-steady-state physical response of the power system, and takes into account the total change between the new and old steady states before and after the system control, thereby effectively improving the accuracy of the sensitivity analysis.

I time unit G_aActive power output pair section T_mMiddle line

Active sensitivity of (D) is recorded as S_{i,L_a_b}，G_aTo section T_mActive sensitivity of (D) is recorded as S_{i,tie_a_m}Can be understood as G_aAre respectively paired to form a section T_mLine (a) of

The sum of the active sensitivities of (a).

S_{i,tie_a_m}＝S_{i,L_a_1}+S_{i,L_a_2}+...+S_{i,L_a_n}

4) Calculating the network loss ratio of each generator set at each moment in the day by using a network loss allocation algorithm based on the alternating current power flow solution calculated in the step 1) at 96 moments in the day, wherein at the moment i, the generator set G_aThe share ratio of the system loss is recorded as: p_{i,loss_a}。

The active network loss allocation algorithm refers to a network loss allocation method based on flow tracking. The physical meaning of the network loss sharing is as follows: the power grid generates what is a loss of power transmission in order to transfer power from a power source to a load at a certain power plant, or in order to provide power to a certain user. The method for distributing the network loss based on the flow tracking is described in patent 201811640099.6 "a method for distributing the branch tide out-of-limit indexes under the electric power market environment".

5) Setting a round counter x for each time, and enabling an initial value x of each time counter to be 1; in the invention, the adjustment of the out-of-limit section adopts multiple rounds of adjustment, and the adjustment mainly comprises the processes of adjusting the output of the unit in the steps 6) and 7). The active power output can be adjusted by selecting more units through multiple rounds of adjustment, and the variation of each unit is relatively small, so that the variation of a power grid operation mode compared with the variation of a power generation plan and a forecast tidal current result is reduced as much as possible and is relatively close to the power grid mode of an original plan after section correction is performed.

6) Correcting the conveying section at each moment in the day ahead, and eliminating the out-of-limit of the section at the moment; the method comprises the following specific steps:

6.1) for any time i, checking the section set U_TWhether the total active output force of any conveying section exceeds the upper limit or not is determined, and the method comprises the following steps: compare set U_{i,tie_p}And U_i,pmaxIf there is P in the data of all corresponding sections_{i,tie_m}＞P_i,maxmThen the section T at that moment is considered_mCounting all the sections with the active output exceeding the upper limit at the moment, and then entering the step 6.2); if P is not present_{i,tie_m}＞P_i,maxmAnd if the active output of the section is higher than the upper limit, directly entering the step 7). 6.2) acquiring a reduced active effective unit set of each section for all sections with active power exceeding the upper limit obtained in the step 6.1);

whether the active effective unit needs to be reduced or not is judged according to the active sensitivity of the unit to the section, and if the following conditions are met, the unit G is judged_aIs a section T_mThe reduction active and effective units:

P_{i,tie_m}> 0 and S_{i,tie_a_m}> α or P_{i,tie_m}< 0 and S_{i,tie_a_m}＜-α

Wherein α is a sensitivity threshold coefficient, and the value range is 0-1, which can be set according to specific situations, and is generally set to 0.5.

After the judgment is finished, the section T of each moment i, with the upper limit of the active power output higher, is obtained_mCorresponding aggregate U for reducing active and effective units_{i,valid_m}；

6.3) for each unit in the reduced active effective unit set corresponding to each section with the upper limit exceeded by the active power at the moment i, respectively calculating an active power output decrement step length corresponding to the active power output reduction of the unit at the moment i, wherein the active power output obtained by updating after the active power output reduction of each unit at the moment i is:

P′_{i,g_a}＝P_{i,g_a}-ΔP_a

and taking the updated value as the new active power output P of the unit i at the moment_{i,g_a}；

According to the active sensitivity of each active power reduction effective unit to the corresponding section at the moment i, summing the results obtained by multiplying the active power output reduction of each active power reduction effective unit of the same section at the moment by the active sensitivity of the unit to the section at the moment to obtain the total active power output reduction of the section at the moment; subtracting the total active power output reduction of each section at the moment from the total active power output of each section at the moment to obtain the updated total active power output of each section at the moment;

summing the active power output decrement of all the reduced active power units (namely the sum of the active power output decrement step of all the reduced active power units) and comparing the sum with the current delta P_decAdding to obtain the updated current delta P at the moment_dec；

6.4) carrying out-of-limit judgment on the total active power output of each section at the moment i after updating obtained in the step 6.3):

6.4.1) if P is present for all sections_{i,tie_m}<＝P_i,maxmIf yes, all the cross sections at the moment are eliminated and the step 7) is carried out;

6.4.2) if any cross section does not satisfy P_{i,tie_m}<＝P_i,maxmAnd returning to the step 6.3) again to continuously reduce the total active power output for the section.

a) If the active power output reduced by the active power effective unit of any section m reaches 5 active power output decrement step lengths at the moment, the section still can not meet the condition P_{i,tie_m}<＝P_i,maxmIf the cross-limit is not eliminated in the current round, the cross-limit elimination adjustment is continued in the next round, and the step 7) is entered.

7) The updated total active power delta P of the unit needing to be reduced for eliminating cross section out-of-limit at the moment i is obtained in the step 6)_decIn order to ensure the total balance of the power generation and the load of the power grid, a proper unit needs to be selected to increase the active output, and the increase of the total active output is consistent with the decrease of the total active output, namely delta P_add＝ΔP_dec；

7.1) let the total active output increase DeltaP at each moment_addIs 0, i.e. Δ P_add0, and the current total active output increment is taken as the current total active output increment at the moment;

7.2) at the moment i, all the units are judged:

if the active output planned value of the unit at the moment exceeds the active output upper limit value of the unit, the unit is removed;

if the unit reduces the active power output in the step 6) at the moment i, the unit is removed;

and after the judgment is finished, all the remaining units form an effective unit set for increasing the output at the moment.

7.3) according to the result of the step 7.2), sequencing all the units in the i-moment output increase effective unit set from small to large according to the network loss sharing ratio corresponding to the unit at the i moment obtained in the step 4); preferentially selecting the unit with smaller network loss sharing ratio to increase the active power output, and avoiding the increase of the network loss of the power grid after section correction.

7.4) at the moment i, sequentially judging the active output increment of each unit according to the sequence obtained in the step 7.3), wherein the method comprises the following specific steps:

7.4.1) letting a be 1;

7.4.2) selecting the a-th unit G in the output increase effective unit set at the moment i_aAnd calculating the active output increment step length of the unit:

that is, to satisfy Δ P_add＜＝ΔP_decThe increase in total work does not exceed the decrease.

7.4.3) calculating that the updated active output obtained after the unit increases the active output at the moment i is as follows:

P′_{i,g_a}＝P_{i,g_a}+ΔP_{a_add}

if P'_{i,g_a}＝P_{i,g_a}+ΔP_{a_add}If the active output of the unit exceeds the upper limit value of the active output of the unit at the moment i, the unit does not increase the active output, the increment step length of the active output of the unit is 0, and the active output of the unit at the moment i keeps P_{i,g_a}Keeping a equal to a +1, and then returning to the step 7.4.2); otherwise step 7.4.4) is entered.

7.4.4) time section T at i_mTotal active power update of is P'_{i,tie_m}＝P_{i,tie_m}+ΔP_a*S_{i,tie_a_m}Then i moment section set U_TIs updated to U'_{i,tie_p}＝{P′_{i,tie_1},P′_{i,tie_2},P′_{i,tie_3}...P′_{i,tie_k}}, mixing U 'with'_{i,tie_p}＝{P′_{i,tie_1},P′_{i,tie_2},P′_{i,tie_3}...P′_{i,tie_k}The sum of the mean and the section set U_TTotal active power output upper limit value set U at moment i_i,pmax＝{P_i,max1,P_i,max2,P_i,max3...P_i,maxkComparing and judging corresponding sections: if any cross section satisfies the condition P'_{i,tie_m}＞＝P_i,maxmIf the unit does not increase the active output, the active output increment of the unit is 0, and the active output of the unit keeps P at the moment i_{i,g_a}Keeping a equal to a +1, and then returning to the step 7.4.2); otherwise, the output of the unit is increased by delta P_{a_add}If any cross section is not out of limit, the active power value updated in the step 7.4.3) is taken as the new active power P of the unit_{i,g_a}Update Δ P_add＝ΔP_add+ΔP_{a_add}As a new current total active power output increase at this time, then let a be a +1, and then return to step 7.4.2).

7.5) repeating the step 7.4) until all the units in the i moment output increase effective unit set finish the determination of the active output increase, determining the current total active output increase at the moment:

if Δ P_add＜ΔP_decEntering step 8);

if Δ P_add＝ΔP_decAnd if the active power of the section does not exceed the upper limit at the moment or all the sections are eliminated and exceed the limit at the moment in the step 6), the safety check is finished at the moment, and the method is finished;

if Δ P_add＝ΔP_decAnd if all the cross sections at the moment in the step 6) are not out of limit, entering a step 8);

8) and (3) judging x:

if x is less than 3, making x equal to x +1, and then returning to step 6); if x is greater than or equal to 3, the out-of-limit cannot be eliminated at time i in the day ahead, and the method is ended.

In step 6) and step 7), if the section is out of limit and cannot be eliminated, or the increased active power cannot reach the reduced active power, the operations of step 6) and step 7) of the next round need to be repeated. If the total round reaches 3 times, judging that the next round of calculation is needed, stopping the calculation, and showing that the cross section cannot eliminate the out-of-limit at the moment.

The adjustment of multiple rounds limits the step length of increasing the active power of the unit each time, so that more units can be selected to increase the output, and the variation of each unit is relatively small, so that the change of the operation mode of the power grid compared with the results of the power generation plan and the forecast power flow is reduced as much as possible after the section correction, and the operation mode of the power grid is closer to the power grid mode of the original plan as much as possible.

The invention is further illustrated below with reference to a specific embodiment:

the embodiment provides a safety check method for a power grid day-ahead power generation plan, which comprises the following steps:

1) and (3) on the basis of the similar day power grid topological structure, a day-ahead equipment maintenance plan is considered to obtain a future power grid topological structure, and a day-ahead alternating current power flow solution is obtained by a day-ahead planned power flow generation algorithm in cooperation with bus load prediction data, generator set output plan data and power transmission section exchange plan data.

And taking 96 moments which are one moment every 15 minutes before the day, wherein each moment corresponds to an alternating current power flow solution. Let a common generator set y, denoted as G₁,G₂...G_y，

And taking the active output of the unit in the tidal current solution at each moment as the active output planned value of the unit at the corresponding moment in the day ahead, and adjusting the active output of the unit in the tidal current solution at each moment, namely adjusting the power generation plan of the unit in the day ahead. For any moment i, reading each unit G from the alternating current power flow solution at the moment_aActive power of is noted as P_{i,g_a}Y, a is 1,2. Set up the unit G_aThe step length of the active power output decrement is recorded as delta P_a(ii) a Setting the total unit active reduction quantity at each moment to be delta P_decAt each time Δ P_decIs set to 0 and is taken as the current Δ P at each time instant_dec。

In this embodiment, 16 units are set in the system, and at the 1 st time, the active planned tidal current value of each unit is as shown in table 1, and the unit (MW):

table 1 table of planned active power flow values of each unit at the 1 st time in this embodiment

2) And reading the definition of the delivery section at the moment i in the day before in the region from the power grid. In this embodiment, section definition information is read from table 2:

table 2 table of section definition in this embodiment

There are 3 sections:

U_T＝{T₁,T₂,T₃}

wherein the content of the first and second substances,

T₁＝{L₁₁,L₁₂,L₁₃,L₁₄}，

T₂＝{L₂₁,L₂₂,L₂₃,L₂₄}，

T₃＝{L₃₁,L₃₂}

respectively reading the active power output of each line in each section from the power grid at the moment i, wherein the total active power output of each section is the sum of the active power outputs of all the lines forming the section;

in this embodiment, the section T at the 1 st time₁,T₂,T₃The corresponding total active output (unit: MW) is:

P_{1,tie_1}＝P_{1,L_11}+P_{1,L_12}+P_{1,L_13}+P_{1,L_14}＝89.14+88.28+88.20+0＝265.62

P_{1,tie_2}＝P_{1,L_21}+P_{1,L_22}+P_{1,L_23}+P_{1,L_24}＝91.39+92.80+0+88.97＝273.16

P_{1,tie_3}＝P_{1,L_31}+P_{1,L_32}＝100.69+99.38＝200.06

then the 1 st time U_TThe corresponding section total active output set is as follows:

U_{1,tie_p}＝{P_{1,tie_1},P_{1,tie_2},P_{1,tie_3}}＝{265.62,273,16，200.06}

time i, section T_mThe upper limit value of the total active power output is recorded as P_{i,max_m}，U_TThe corresponding section total active output upper limit set:

U_i,pmax＝{P_{i,max_1},P_{i,max_2},P_{i,max_3}...P_{i,max_k}}

at the 1 st moment, the section T is obtained₁,T₂,T₃The corresponding total active power output upper limit set is as follows:

U_1,pmax＝{100,500,500}

3) based on the alternating current power flow result calculated in the step 1) at 96 moments in the day, calculating the active sensitivity of the active injection of the generator to each moment of the line by using a quasi-steady-state active sensitivity algorithm, wherein the unit of the sensitivity is as follows: megawatts per megawatt (MW/MW). And (3) combining the definition of the section in the step 2), and accumulating to obtain the active sensitivity of the active injection of the generator to the section.

In this embodiment, the calculated unit G_aTo line L_bActive sensitivity of (D) is recorded as S_{i,L_a_b}，G_aTo section T_mActive sensitivity of (D) is recorded as S_{i,tie_a_m}Can be understood as G_aTo make up section T_mLine L of₁,L₂,L₃...L_nThe sum of the respective sensitivities of (a).

S_{i,tie_a_m}＝S_{i,L_a_1}+S_{i,L_a_2}+...+S_{i,L_a_n}

The sensitivity data of the unit with large influence on the section at the 1 st moment obtained by calculation are shown in table 3:

table 3 in this embodiment, the active sensitivity data of the unit having a large influence on the section at the 1 st time

From table 3 it can be derived:

S_{1,tie_11_1}＝S_{1,L_11_11}＝0.999，

S_{1,tie_12_1}＝S_{1,L_12_12}＝0.999，

S_{1,tie_13_1}＝S_{1,L_13_13}＝0.999，

S_{1,tie_21_2}＝S_{1,L_21_21}＝0.999，

S_{1,tie_22_2}＝S_{1,L_22_22}＝0.999，

S_{1,tie_24_2}＝S_{1,L_24_24}＝0.999，

S_{1,tie_31_3}＝S_{1,L_31_31}+S_{1,L_31_32}＝0.502+0.497＝0.999，

S_{1,tie_32_3}＝S_{1,L_32_31}+S_{1,L_32_32}＝0.502+0.497＝0.999

4) based on the alternating current power flow solution calculated in the step 1) at 96 moments in the day, calculating the network loss ratio of each generator set in each moment in the day by using a network loss allocation algorithm, wherein the unit G at the ith moment_aThe share ratio of the system loss is recorded as: p_{i,loss_a}。

In this embodiment, the 1 st time is obtained by calculation and arranged from small to large according to the network loss sharing ratio of the unit, and some values which are earlier are taken and recorded in table 4:

table 4 table of unit loss sharing ratio at the 1 st time in this embodiment

Serial number	Name of unit Ga	Loss share ratio P1,loss_a
			1	G1	0
2	G2	0
			3	G3	0
4	G4	0
			5	G5	0.00009
6	G6	0.00013
			7	G7	0.00033
8	G8	0.00053
			9	G11	0.01053
10	G12	0.0108
			11	G13	0.01426
12	G21	0.03419
			13	G22	0.03434
14	G24	0.04569
			15	G31	0.04692
16	G32	0.07308

5) Setting a round counter x for each time, and enabling an initial value x of each time counter to be 1;

6) correcting the conveying section at each moment in the day ahead, and eliminating the out-of-limit of the section at the moment; the method comprises the following specific steps:

6.1) for any time i, checking the section set U_TWhether the total active output force of any conveying section exceeds the upper limit or not is determined, and the method comprises the following steps: compare set U_{i,tie_p}And U_i,pmaxIf there is P in the data of all corresponding sections_{i,tie_m}＞P_i,maxmThen the section T at that moment is considered_mCounting all the sections with the active output exceeding the upper limit at the moment, and then entering the step 6.2); if P is not present_{i,tie_m}＞P_i,maxmAnd if the active output of the section is higher than the upper limit, directly entering the step 7).

In this embodiment, at time 1, U is compared_{1,tie_p}{265.62,273.16, 200.06} and U_1,pmaxThe value of the corresponding position in {100,500,500} can give 265.62>100 is section T₁The upper limit of the total active power is needed to be adjusted.

6.2) acquiring a reduced active effective unit set of each section for all sections with active power exceeding the upper limit obtained in the step 6.1);

whether the active effective unit needs to be reduced or not is judged according to the active sensitivity of the unit to the section, and if the following conditions are met, the unit G is judged_aIs a section T_mThe reduction active and effective units:

P_{i,tie_m}> 0 and S_{i,tie_a_m}> α or P_{i,tie_m}< 0 and S_{i,tie_a_m}＜-α

α is a sensitivity threshold coefficient, and the range is (0-1), and can be set according to specific situations, and is generally set to 0.5.

According to the determination condition, the present embodiment sets α to 0.5, and the section current value obtained in step 1) and the unit sensitivity to the section result obtained in step 3), so that:

unit G₁₁,G₁₂,G₁₃Is a section T₁The effective unit of (2);

unit G₂₁,G₂₂,G₂₄Is a section T₂The effective unit of (2);

unit G₃₁,G₃₂Is a section T₃Active power reduction effective unit

6.3) according to the result of the step 6.2), for each unit in the reduced active effective unit set corresponding to each section with higher active limit at the moment i, respectively reducing the active output of the unit at the moment by a corresponding active output reduction step length, and calculating the updated active output of each unit at the moment i after the active output is reduced by the unit at the moment i as follows:

P′_{i,g_a}＝P_{i,g_a}-ΔP_a

and taking the updated value as the new active power output P of the unit i at the moment_{i,g_a}；

According to the active sensitivity of each active power reduction effective unit to the corresponding section at the moment i, summing the results obtained by multiplying the active power output reduction of each active power reduction effective unit of the same section at the moment by the active sensitivity of the unit to the section at the moment to obtain the total active power output reduction of the section at the moment; subtracting the total active power output reduction of each section at the moment from the total active power output of each section at the moment to obtain the updated total active power output of each section at the moment;

summing the active power output decrement of all the reduced active power units (namely the sum of the active power output decrement step of all the reduced active power units) and comparing the sum with the current delta P_decAdding to obtain the updated current delta P at the moment_dec；

In this example, at time 1, the cross section T is determined₁The total active power exceeds the upper limit, wherein G₁₁,G₁₂,G₁₃Is a section T₁Reduction of active units, G needs to be reduced₁₁,G₁₂,G₁₃Active output of three units eliminates section T₁Out-of-limit, active units (MW), sensitivity units (MW/MW), forming the regulatory process shown in table 5:

TABLE 5 1 st step of the 1 st time of this example to the section T₁Meter for reducing total active power output

6.4) carrying out-of-limit judgment on the total active power output of each section at the moment i after updating obtained in the step 6.3):

6.4.1) if P is present for all sections_{i,tie_m}<＝P_i,maxmIf yes, all the cross sections at the moment are eliminated and the step 7) is carried out;

6.4.2) if any cross section does not satisfy P_{i,tie_m}<＝P_i,maxmAnd returning to the step 6.3) again to continuously reduce the total active power output for the section.

If the active power output reduced by the active power effective unit of any section m reaches 5 active power output decrement step lengths at the moment, the section still can not meet the condition P_{i,tie_m}<＝P_i,maxmIf the threshold is not eliminated, the next round is continued to adjust, and the step 7) is entered.

In this embodiment, the section T₁The one-step adjustment in step 6.3) is not eliminated, so that the multi-step adjustment in step 6.3) also needs to be repeated:

TABLE 6 step 2 of the 1 st time of the present example for section T₁Meter for reducing total active power output

TABLE 7 step 3 of section alignment T at time 1 in this example₁Meter for reducing total active power output

P 'after the adjustment of the 3 rd step is completed'_{1,tie_1}(195.13)<P_1,max1(200) Cross section T₁The out-of-limit elimination of (c).

Obtaining the current total active output reduction delta P of the co-reduced units_dec＝72MW。

7) The updated total active power delta P of the unit needing to be reduced for eliminating cross section out-of-limit at the moment i is obtained in the step 6)_decIn order to ensure the total balance of the power generation and the load of the power grid, a proper unit needs to be selected to increase the active output, and the increase of the total active output is consistent with the decrease of the total active output, namely delta P_add＝ΔP_dec；

7.1) let the total active output increase DeltaP at each moment_addIs 0, i.e. Δ P_add0, and the current total active output increment is taken as the current total active output increment at the moment;

7.2) at the moment i, all the units are judged: if the active output planned value of the unit at the moment exceeds the active output upper limit value of the unit, the unit is removed;

if the unit reduces the active power output in the step 6) at the moment i, the unit is removed;

and after the judgment is finished, all the remaining units form an effective unit set for increasing the output at the moment.

7.3) according to the result of the step 7.2), sequencing all the units in the i-moment output increase effective unit set from small to large according to the network loss sharing ratio corresponding to the unit at the i moment obtained in the step 4); preferentially selecting the unit with smaller network loss sharing ratio to increase the active power output, and avoiding the increase of the network loss of the power grid after section correction.

7.4) at the moment i, sequentially judging the active output increment of each unit according to the sequence obtained in the step 7.3), wherein the method comprises the following specific steps:

7.4.1) letting a be 1;

7.4.2) selecting the a-th unit G in the output increase effective unit set at the moment i_aAnd calculating the active output increment step length of the unit:

that is, to satisfy Δ P_add＜＝ΔP_decThe increase in total work does not exceed the decrease.

7.4.3) calculating that the updated active output obtained after the unit increases the active output at the moment i is as follows:

P′_{i,g_a}＝P_{i,g_a}+ΔP_{a_add}

if P'_{i,g_a}＝P_{i,g_a}+ΔP_{a_add}If the active output of the unit exceeds the upper limit value of the active output of the unit at the moment i, the unit does not increase the active output, the increment step length of the active output of the unit is 0, and the active output of the unit at the moment i keeps P_{i,g_a}Keeping a equal to a +1, and then returning to the step 7.4.2); otherwise step 7.4.4) is entered.

7.4.4) time section T at i_mTotal active power update of is P'_{i,tie_m}＝P_{i,tie_m}+ΔP_a*S_{i,tie_a_m}Then i moment section set U_TIs updated to U'_{i,tie_p}＝{P′_{i,tie_1},P′_{i,tie_2},P′_{i,tie_3}...P′_{i,tie_k}}, mixing U 'with'_{i,tie_p}＝{P′_{i,tie_1},P′_{i,tie_2},P′_{i,tie_3}...P′_{i,tie_k}The sum of the mean and the section set U_TTotal active power output upper limit value set U at moment i_i,pmax＝{P_i,max1,P_i,max2,P_i,max3...P_i,maxkComparing and judging corresponding sections: if any cross section satisfies the condition P'_{i,tie_m}＞＝P_i,maxmIf the unit does not increase the active output, the active output increment of the unit is 0, and the active output of the unit keeps P at the moment i_{i,g_a}Keeping a equal to a +1, and then returning to the step 7.4.2); otherwise, the output of the unit is increased by delta P_{a_add}Will not cause any breakIf the surface is out of limit, the updated active output value in the step 7.4.3) is taken as the new active output P of the unit_{i,g_a}Update Δ P_add＝ΔP_add+ΔP_{a_add}As a new current total active power output increase at this time, then let a be a +1, and then return to step 7.4.2).

7.5) repeating the step 7.4) until all the units in the i moment output increase effective unit set finish the determination of the active output increase, determining the current total active output increase at the moment:

if Δ P_add＜ΔP_decEntering step 8);

if Δ P_add＝ΔP_decAnd if the active power of the section does not exceed the upper limit at the moment or all the sections do not exceed the upper limit at the moment in the step 6), completing safety check at the moment and ending the method;

if Δ P_add＝ΔP_decAnd if all the cross sections at the moment in the step 6) are not out of limit, entering a step 8);

in this embodiment, the network loss sharing ratios of the units obtained in step 4) are arranged from small to large, and these units do not reach the upper limit, so that the adjustment for increasing the power can be performed, where the unit is: MW. The unit with reduced active power output cannot increase the active power output any more, so that G needs to be excluded₁₁,G₁₂,G₁₃These three units.

Table 8 in this embodiment, an active and effective unit list is added at the 1 st time

In this example, Δ P is satisfied after just circulating all units_add＝ΔP_decAnd if all the cross sections are out of limit at the moment in the step 6), completing safety check at the moment, and ending the method;

8) and (3) judging X:

if X is less than 3, making X equal to X +1, and then returning to the step 6); if X is greater than or equal to 3, the out-of-limit can not be eliminated at the moment i in the day, and the method is ended.

In step 6) and step 7), if the section is out of limit and cannot be eliminated, or the increased active power cannot reach the reduced active power, the operations of step 6) and step 7) of the next round need to be repeated. If the total round reaches 3 times, the calculation of the next round is judged to be needed, the calculation is stopped, and a warning that the out-of-limit cannot be eliminated is given. The adjustment of multiple rounds limits the step length of increasing the active power of the unit each time, so that more units can be selected to increase the output, and the variation of each unit is relatively small, so that the change of the operation mode of the power grid compared with the results of the power generation plan and the forecast power flow is reduced as much as possible after the section correction, and the operation mode of the power grid is closer to the power grid mode of the original plan as much as possible.

In this example, the out-of-limit is eliminated in the first adjustment round, and sufficient units are found to increase the active power output, and the calculation can be ended. The unit output redistribution may be completed to form the data, in units (MW), shown in table 9 below:

table 9 in this embodiment, the active power output meter after the safety check at the 1 st time is completed

Claims (1)

1. A safety check method for a power grid day-ahead power generation plan is characterized by comprising the following steps:

1) dividing the whole day into 96 times by every 15 minutes before the day; on the basis of a similar day power grid topological structure, a day-ahead equipment maintenance plan is considered to obtain a future power grid topological structure, and an alternating current power flow solution at each day-ahead moment is obtained by a day-ahead planned power flow automatic generation algorithm by utilizing bus load prediction data, generator set output plan data and power transmission section exchange plan data;

if the power grid shares a generator set y, the power grid is marked as G₁,G₂...G_yTaking the unit active output in the alternating current power flow solution at each moment in the day as the unit active output planned value at the corresponding moment in the day; for any moment i, reading each unit G from the alternating current power flow solution at the moment_aActive power of is noted as P_{i,g_a}Y, a 1,2.. y; set up the unit G_aThe active power reduction step size of (1) is delta P_a(ii) a Setting the total unit active reduction quantity at each moment to be delta P_decAt each time Δ P_decIs set to 0 and is taken as the current Δ P at each time instant_dec；

2) Let the electric wire netting contain k sections:

U_T＝{T₁,T₂,T₃...T_k}

in the formula of U_TRepresenting a set of k sections;

the method comprises the following steps of obtaining a total active output set and a total active output upper limit set of the section at each moment in the day, wherein the method comprises the following steps:

respectively reading the active power output of each line in each section from the power grid at the moment i, wherein the total active power output of each section is the sum of the active power outputs of all the lines forming the section;

then i time U_TThe corresponding total active power output of the section is integrated as follows:

U_{i,tie_p}＝{P_{i,tie_1},P_{i,tie_2},P_{i,tie_3}...P_{i,tie_k}}

wherein, P_{i,tie_m}Is a section T at the moment i_mTotal active power output of (1), 2 … k;

timing any section T_mHas a total active power output upper limit value of P_{i,max_m}Then i time U_TThe upper limit set of the total active output of the corresponding section is as follows:

U_i,pmax＝{P_{i,max_1},P_{i,max_2},P_{i,max_3}...P_{i,max_k}}

3) calculating the active sensitivity of the active output of the generator set to each line at each moment in the day by using a quasi-steady active sensitivity algorithm based on the alternating current power flow solution obtained in the step 1) at each moment in the day;

summing the active power output of any generator set at any moment to the active sensitivity of each line belonging to the same section to obtain the active sensitivity of the active power output of the generator set at the moment to each section; the unit G at the moment i_aActive power output pair section T_mActive sensitivity of (D) is recorded as S_{i,tie_a_m}；

4) Calculating the network loss ratio of each generator set to the system at each moment in the day by using a network loss allocation algorithm based on the alternating current power flow solution obtained in the step 1) at each moment in the day; the unit G will be at time i_aThe share ratio of the system loss is recorded as: p_{i,loss_a}；

5) Setting a round counter x for each time, and enabling an initial value x of each time counter to be 1;

6) correcting the cross section of each moment in the day ahead to eliminate the out-of-limit of the cross section at the moment; the method comprises the following specific steps:

6.1) for any time i, checking the section set U_TWhether the total active output of any section exceeds the upper limit or not is determined, and the method comprises the following steps: compare set U_{i,tie_p}And U_i,pmaxIf there is P in the data of all corresponding sections_{i,tie_m}＞P_i,maxmThen the section T at that moment_mCounting all the sections with the active output exceeding the upper limit at the moment, and then entering the step 6.2); if P is not present_{i,tie_m}＞P_i,maxmIf the active power of the section does not exist at the moment, the step 7) is carried out;

6.2) acquiring a reduced active effective unit set of each section for all sections with active power exceeding the upper limit obtained in the step 6.1);

for any unit G_aAnd section T_mIf the set and the section meet the following conditions, the set G is judged_aIs a section T_mThe reduction active and effective units:

P_{i,tie_m}> 0 and S_{i,tie_a_m}> α or P_{i,tie_m}< 0 and S_{i,tie_a_m}＜-α

Wherein α is a sensitivity threshold coefficient;

after the judgment is finished, the section T of each moment i, with the upper limit of the active power output higher, is obtained_mCorresponding aggregate U for reducing active and effective units_{i,valid_m}；

6.3) for each unit in the reduced active effective unit set corresponding to each section with the upper limit exceeded by the active power at the moment i, respectively calculating an active power output decrement step length corresponding to the active power output reduction of the unit at the moment i, wherein the active power output obtained by updating after the active power output reduction of each unit at the moment i is:

P′_{i,g_a}＝P_{i,g_a}-ΔP_a

and taking the updated value as the new active power output P of the unit i at the moment_{i,g_a}；

According to the active sensitivity of each active power reduction effective unit to the corresponding section at the moment i, summing the results obtained by multiplying the active power output reduction of each active power reduction effective unit of the same section at the moment by the active sensitivity of the unit to the section at the moment to obtain the total active power output reduction of the section at the moment; subtracting the total active power output reduction of each section at the moment from the total active power output of each section at the moment to obtain the updated total active power output of each section at the moment;

summing all active power output reduction of the reduced active power effective unit at the moment, and comparing the sum with the current delta P_decAdding to obtain the updated current delta P at the moment_dec；

6.4) carrying out-of-limit judgment on the total active power output of each section at the moment i after updating obtained in the step 6.3):

6.4.1) if P is present for all sections_{i,tie_m}<＝P_i,maxmIf yes, all the cross sections at the moment are eliminated and the step 7) is carried out;

6.4.2) if any cross section does not satisfy P_{i,tie_m}<＝P_i,maxmIf yes, returning to the step 6.3) again, and continuously reducing the total active power output of the section;

if the active power output reduced by the active power effective unit with any section m reaches 5 active power output decrement step lengths at the moment, and the section still does not meet the requirement of P_{i,tie_m}<＝P_i,maxmIf so, ending the cross section off-limit adjustment of the elimination in the current round, and entering the step 7);

7) selecting an effective output increasing unit at each moment in the day so as to increase the total active output at the moment; the method comprises the following specific steps:

7.1) let the total active output increase DeltaP at each moment_addIs 0, i.e. Δ P_add0, and the current total active output increment is taken as the current total active output increment at the moment;

7.2) at the moment i, all the units are judged:

if the active output planned value of the unit at the moment exceeds the active output upper limit value of the unit, the unit is removed;

if the unit reduces the active power output in the step 6) at the moment i, the unit is removed;

after the judgment is finished, all the remaining units form an i moment output increasing effective unit set;

7.3) according to the result of the step 7.2), sequencing all the units in the i-moment output increase effective unit set from small to large according to the network loss sharing ratio corresponding to the unit at the i moment obtained in the step 4);

7.4) at the moment i, sequentially judging the active output increment of each unit according to the sequence obtained in the step 7.3), wherein the method comprises the following specific steps:

7.4.1) letting a be 1;

7.4.2) selecting the a-th unit G in the output increase effective unit set at the moment i_a；

Calculating the active power output increment step length of the unit:

7.4.3) calculating that the updated active output obtained after the unit increases the active output at the moment i is as follows:

P′_{i,g_a}＝P_{i,g_a}+ΔP_{a_add}

if P'_{i,g_a}＝P_{i,g_a}+ΔP_{a_add}If the active output upper limit value of the unit at the moment i is exceeded, the unit does not increase the active outputThe unit i keeps the active output at the moment P_{i,g_a}Keeping a equal to a +1, and then returning to the step 7.3.2); otherwise, entering step 7.3.4);

7.4.4) time section T at i_mTotal active power update of is P'_{i,tie_m}＝P_{i,tie_m}+ΔP_a*S_{i,tie_a_m}Then i moment section set U_TIs updated to U'_{i,tie_p}＝{P′_{i,tie_1},P′_{i,tie_2},P′_{i,tie_3}...P′_{i,tie_k}}, mixing U 'with'_{i,tie_p}＝{P′_{i,tie_1},P′_{i,tie_2},P′_{i,tie_3}...P′_{i,tie_k}The sum of the mean and the section set U_TTotal active power output upper limit value set U at moment i_i,pmax＝{P_i,max1,P_i,max2,P_i,max3...P_i,maxkComparing and judging corresponding sections: if any cross section satisfies the condition P'_{i,tie_m}＞＝P_i,maxmIf the unit does not increase the active power output, the unit keeps the active power output P at the moment i_{i,g_a}Keeping a equal to a +1, and then returning to the step 7.3.2); otherwise, taking the active output updated in the step 7.3.3) as the new active output P of the unit at the moment i_{i,g_a}Update Δ P_add＝ΔP_add+ΔP_{a_add}As a new current total active output increment at the moment, then making a equal to a +1, and then returning to step 7.3.2);

7.5) repeating the step 7.4) until all the units in the i moment output increase effective unit set finish the determination of the active output increase, determining the current total active output increase at the moment:

if Δ P_add＜ΔP_decEntering step 8);

if Δ P_add＝ΔP_decAnd if the active power of the section does not exceed the upper limit at the moment or all the sections are eliminated and exceed the limit at the moment in the step 6), the safety check is finished at the moment, and the method is finished;

if Δ P_add＝ΔP_decAnd if all the cross sections at the moment in the step 6) are not out of limit, entering a step 8);

8) and (3) judging x:

if x is less than 3, making x equal to x +1, and then returning to step 6); if x is greater than or equal to 3, the out-of-limit cannot be eliminated at time i in the day ahead, and the method is ended.

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