CN108695905B - Safety constraint optimization scheduling method for 110 kV-level-contained power grid - Google Patents
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Abstract
The invention discloses a safety constraint optimization scheduling method for a 110 kV-level-contained power grid, which comprises the steps of firstly, improving a direct current power flow model, aiming at the simplified condition that the ratio of the reactance and the resistance of a line in the 110 kV-level power grid is relatively small and does not meet X > R, so that the resistance of the line cannot be ignored, the voltage amplitude of each node is approximately considered to be near a rated value, the phase angle difference of the voltage of the nodes at two ends of the line is very small and is approximately 0, and a grounding branch in the power grid is ignored, so that the alternating current power flow model is simplified, and the accuracy of the calculated result of the line power is higher; the improved direct current power flow model is applied to the optimization scheduling problem of power generation before the day of safety constraint of the power grid with the 110kV voltage level for solving, the solving speed is high, and the solving result is more reasonable and accurate.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to a safety constraint optimization scheduling method for a 110 kV-level power grid.
Background
The method is characterized in that a current power generation dispatching plan curve of each generator set in a power grid is a key link in power system operation dispatching, and safety is the most basic requirement of power grid operation, so that the formulated power generation dispatching plan curve needs to be checked for network safety, and active power of all power transmission lines corresponding to each time period is guaranteed not to exceed the maximum transmission power of all power transmission lines. The calculation of tidal current in electric power system is based on the grid structure, branch parameters andunder the operating conditions of the load and the node power of the generator, the states of the voltage amplitude and the phase angle of each node in the power system, the transmission power of each line, the power loss of the network and the like are calculated, and the states can be used for checking whether network elements are overloaded, whether the voltage of each node meets requirements, whether the power distribution and distribution are reasonable and the like, so that the method can be applied to the optimization scheduling problem of the power system to check the network security. The load flow calculation can be divided into alternating current load flow and direct current load flow according to different solved mathematical models, an alternating current load flow equation is nonlinear, the accuracy of a calculation result is high, the real situation of a system can be comprehensively reflected, but the solving efficiency is low, so that the method is generally not suitable for line power safety check in the large power grid optimized operation scheduling problem. The direct current power flow is obtained by simplification on the basis of the alternating current power flow, and the following simplification process is carried out on the basis of the alternating current power flow: 1) ignoring a grounding branch in the power grid; 2) under normal operation conditions, the voltage amplitude of each node in the power system is close to the rated value, so that V is approximately consideredi1 is approximately distributed; 3) the phase angle of the voltage at the nodes at the two ends of the line being very small, i.e. theta ij0, hence approximately sin θij≈θij,cosθ ij1 is approximately distributed; 4) in an ultrahigh voltage network, the condition that the branch reactance is far greater than the branch resistance, namely X>>R, and therefore the branch resistance can be neglected. The direct current power flow model does not consider reactive power distribution and loss in a network, is a group of linear equations, can effectively reduce calculated amount, greatly improves solving efficiency, and is widely applied to safety check of a power system day-ahead power generation plan, electric power market blocking management, safety constraint economic dispatching, static safety analysis, safety constraint unit combination and other problems at present.
At present, a plurality of central urban power grids are independent from provincial power grids in China and directly belong to regional power grid management, for example, Guangzhou and Shenzhen power grids are independent from Guangdong power grids and directly belong to southern power grid management. The central city power grid dispatching center is small in administration range, not only pays attention to the operation state of 220kV and above grade power grids in the administration area, but also pays attention to the operation state of 110kV grade power grids in the administration area in daily operation, and when the formulated power generation dispatching plan curve is checked for network safety, the safe operation of the 110kV grade power grids needs to be considered. At present, in the optimization scheduling problem of the main network considering the network safety constraint, a direct current power flow model is generally adopted, because it is generally considered that the main network is generally a high-voltage network, includes a grid structure of 220kV and above, meets 4 simplified conditions of X > R and the like, and has high calculation accuracy. However, because the ratio of the line reactance to the resistance in the 110kV power grid is relatively small, and does not satisfy the simplified condition of X > > R, when safety constraint optimization scheduling needs to be performed on the 110 kV-class power grid, if a direct current power flow model is still used for analysis, it may cause the calculated line power to be inaccurate, so that a large deviation occurs from the actual situation when performing line power safety verification, which affects the accuracy of the obtained power grid optimization scheduling result, and in a serious case, the obtained optimization scheduling result may not satisfy the actual network safety constraint. Therefore, in the problem of optimization scheduling including 110 kV-class power grid safety constraint, it is necessary to improve the dc power flow model, so that the calculation result of the line power is more accurate, and the obtained power grid optimization scheduling result also better conforms to the actual situation.
For a power grid with a 110kV level, because the ratio of the line reactance to the resistance in the 110kV net rack is relatively small, and does not meet the simplified condition of X > R, if the direct current power flow model is directly adopted to calculate the line power for network security check, the calculated line power is inaccurate, so that great deviation occurs between the calculated line power and the actual situation when the line power security check is carried out, and the optimal scheduling operation result of the power grid is influenced.
At present, in the problem of power grid safety constraint optimization scheduling at home and abroad, a direct current power flow model is directly adopted to calculate line power to carry out network safety check; and moreover, for the safety constraint optimization scheduling problem containing a 110 kV-level power grid (not meeting X > > R conditions), a network analysis model can be adopted to accurately calculate the line power, and related research is not carried out.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a safety constraint optimization scheduling method for a 110 kV-level power grid so as to obtain a power grid optimization scheduling result which is more consistent with the actual situation.
In order to achieve the purpose, the invention adopts the following technical scheme:
a safety constraint optimization scheduling method for a 110 kV-level power grid comprises the following steps:
neglecting a grounding branch in a power grid, and obtaining the active power of a line under an alternating current power flow model as follows:
Pij＝ViVj(Gijcosθij+Bijsinθij)-Vi 2Gij (1)
in the formula: pijIs the active power of line ij; viAnd VjThe voltage amplitudes of the node i and the node j are respectively; thetaijIs the voltage phase angle difference between node i and node j; gij、BijRespectively are mutual conductance and mutual susceptance between a node i and a node j;
the active power of the line under the alternating current power flow model is simplified to obtain an improved direct current tide model, and the improved direct current tide model comprises an active power equation of any line ij:
and, the injection active power balance equation of any node i:
the improved direct current tide model is applied to the safety constraint day-ahead power generation optimization scheduling problem of the power grid with the 110kV voltage level so as to obtain the power grid optimization scheduling result.
The invention has the beneficial effects that:
the method comprises the steps that firstly, a direct current power flow model is improved, the direct current power flow model cannot ignore line resistance because the ratio of line reactance to resistance in a 110kV voltage-class power grid is relatively small and does not meet the simplifying condition of X > R, the voltage amplitude of each node is approximately considered to be close to a rated value, the phase angle difference of the voltage of the nodes at two ends of the line is very small and is approximately 0, and a grounding branch in the power grid is ignored, so that the alternating current power flow model is simplified, and the accuracy of the obtained line active power calculation result is high; the improved direct current power flow model is applied to the optimization scheduling problem of power generation before the day of safety constraint of the power grid with the 110kV voltage level for solving, the solving speed is high, and the solving result is more reasonable and accurate.
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FIG. 1 is a wiring diagram of a grid structure of an IEEE-9 node system;
FIG. 2 is a graph of total load prediction;
FIG. 3 is a graph of the trend of the change in line power count over time;
fig. 4a-4c are graphs comparing the output plan curves of the unit.
Detailed Description
The invention will be further described with reference to the accompanying drawings and the detailed description below:
the embodiment provides a safety constraint optimization scheduling method for a 110 kV-class power grid, which comprises the following steps
(1) Establishing an improved DC power flow model
Neglecting the grounding branch in the power grid, the active power of the line under the alternating current power flow model is as follows:
Pij＝ViVj(Gijcosθij+Bijsinθij)-Vi 2Gij (1)
in the formula: pijIs the active power of line ij; viAnd VjThe voltage amplitudes of the node i and the node j are respectively; thetaijIs the voltage phase angle difference between node i and node j; gij、BijRespectively, the mutual conductance and the mutual susceptance between the node i and the node j.
The process is simplified:
1) because of the normal operation, each section in the power systemThe point voltage amplitude is near the rated value, so approximately V is consideredi≈1,Vj≈1。
2) The phase angle of the voltage at the nodes at the two ends of the line being very small, i.e. theta ij0, hence approximately sin (θ)ij/2)≈θij/2,cos(θij/2)≈1。
Therefore, the line active power equation (1) can be simplified as follows:
and then obtaining an injection power balance equation of any node i:
(2) safety constraint optimization scheduling model for 110 kV-level-contained power grid
A. Objective function
The method aims to minimize the sum of the operating costs of all units in the system, wherein the operating costs of the units comprise the starting and stopping costs and the power generation fuel consumption costs, and the formula (4):
wherein T is the total number of time periods of the scheduling cycle, and the day is divided into 96 time periods, each time period is 15min, and N is1Is the total number of conventional thermal power generating units, CiU,tAnd CiD,tThe starting and stopping costs of the conventional thermal power generating unit i in the time period t are Fi,tGenerating cost of a conventional thermal power generating unit i in a time period t; n is a radical of2Total number of pumping units, CsU,tAnd CsD,tThe starting cost and the stopping cost of the pumping unit s in the time period t are respectively, and the power generation cost is zero because the operation of the pumping unit does not consume fuel.
For a conventional thermal power generating unit, the power generation cost is as follows (5):
Fi,t＝Ai×Pi,t (5)
in the formula, AiCharacteristic coefficient of fuel consumption, P, for the generation cost of a unit ii,tAnd (4) the output of the unit i in the time period t.
B. Constraint conditions
1) Start-stop cost constraint of unit
And (3) constraint of starting-up cost:
and (4) stopping cost restraint:
in the formula, KiAnd JiThe cost of single start-up and shut-down, K, of a conventional unit isAnd JsThe single start-up and shut-down costs of the pump storage unit s, respectively. I isi,t/Zs,tThe starting state value of the conventional unit i/pumping storage unit s is 1, and the stopping state value is 0 in the starting and stopping states of the conventional unit i/pumping storage unit s in the time period t.
2) System power balance constraints
In the formula, PLoad,tTotal system load for time period t, PLoss,tThe system network loss of the time period t is approximated by taking a certain percentage of the total load power; ppg,s,tAnd Ppp,s,tThe generated power and the pumping power of the pumping storage unit s in the time period t are respectively, the generated power is positive, and the pumping power is negative.
3) Upper limit of output of conventional machine set
Ii,tPi,min≤Pi,t≤Ii,tPi,max (9)
In the formula, Pi,minIs the minimum output, P, of the conventional unit ii,maxThe maximum output of the conventional unit i.
4) Unit hill climbing/landslide restraint
Considering that the unit does not exceed the minimum output of the unit during the first period of start-up or the last period of shutdown, the unit ramp/landslide constraint may be expressed as follows:
in the formula, ruiAnd rdiThe climbing rate and the landslide rate of the unit i, T15For an operating period of 15 min.
5) Minimum on-off time constraint of unit
Minimum boot time constraint:
minimum downtime constraint:
in the formula of Ui/DiThe period of time during which the unit i must be powered on/off at the beginning of the scheduling cycle is determined by the state of the unit at the end of the previous scheduling cycle, Ton_i/Toff_iMinimum on-time/minimum off-time, X, for unit ion_i,0/Xoff_i,0For the time that unit i has been continuously powered on/off at the beginning of the scheduling period.
6) Operation constraint of pumped storage unit
And (3) restraining an upper limit and a lower limit of output:
in the formula, Ppg,s,maxAnd Ppp,s,maxMaximum generated power and maximum generated power of the pumping storage unit s respectivelyHigh pumping power, Zpg,s,tAnd Zpp,s,tThe power generation state and the water pumping state of the storage unit s in the time period t are respectively, the state is in a corresponding state when the value is 1, and the state is not in a corresponding state when the value is 0.
The complementary constraint of operating condition, namely the pumping unit can not be in the water pumping and power generation operating condition at the same time period, as follows:
Zs,t＝Zpg,s,t+Zpp,s,t≤1 (14)
in actual operation, the daily power balance constraint also needs to be satisfied, as follows:
where ξ is the conversion efficiency of the storage unit, which is usually 75%.
In order to prolong the service life of the pumping unit, the switching between two operating conditions of the pumping unit in actual operation needs to satisfy a certain time limit, and the switching time is defined to be half an hour in this embodiment, that is, the switching time in 2 periods is needed, so the following constraints need to be satisfied:
7) system rotational back-up constraint
Enough system rotation spare capacity is reserved to cope with the influence of load prediction errors. The positive rotation reserve capacity is used to compensate for the influence of underestimated system load, and the negative rotation reserve capacity is used to compensate for the influence of overestimated system load.
And (3) conventional unit rotation standby constraint:
in the formula, sui,tAnd sdi,tRespectively providing positive and negative rotation reserve capacity T for the unit i in the time period T10For the rotating standby response time of the unit, 10min is taken in this embodiment.
And (3) rotating standby constraint of the pumping unit:
the rotating standby requirements of the system are obtained by accumulating the rotating standby of all the units as follows:
in the formula, Su,tAnd Sd,tRespectively, the positive and negative rotation reserve capacity, L, of the system in the time period tu% and Ld% is the demand coefficient of the load forecast deviation to the system positive and negative rotation reserve capacity respectively.
8) Node injection active power balance constraint
In the formula (I), the compound is shown in the specification,
is the injected active power of node i at time t; pij,tThe active power of line ij is time period t; thetaij,tIs the voltage phase angle difference between node i and node j for time period t.
9) Network security constraints
According to the improved direct current power flow model, the transmission power of the line is constrained as follows:
wherein l is a line to be checked for safety, Pl,km,tTransmission power of line l (k, m) for time period t; (ii) a Thetakm,tIs the voltage phase angle difference between node k and node m for time period t;
is the transmission power limit for line l (k, m).
In a practical large power grid, the number of lines is very large, and if the transmission power safety constraints of all the lines in all the time periods are directly put into a model for solving, the scale of the model is too large, and the solving is very time-consuming. Many lines are not out of limit in view of the actual grid operating conditions, and therefore many line power safety constraints are not functional. In order to improve the solving efficiency of the model, a method of checking-adding-rechecking-adding is adopted for solving: firstly, solving a model without line power safety constraint to obtain an optimization result of unit start-stop and output; then, carrying out network security verification on the group of solutions, adding the line power constraint which does not pass the security verification into the model, and solving once again to obtain an optimization result; and if all the safety checks cannot be met, adding the line power constraint which does not pass the safety checks into the model for re-solving and checking until the obtained optimization result meets all the safety checks.
It can be seen that the 110 kV-class power grid security constraint optimization scheduling model described by the above equations (4) to (21) is a mixed integer nonlinear programming model, and can be solved by using DICOPT or SBB solver in GAMS software.
The effectiveness of the method is verified in conjunction with an example analysis as follows:
an example analysis is performed by taking an IEEE9 node system as an example, and the grid structure of the system is shown in fig. 1. The number of load nodes of the system is 3, the number of transformer branches is 3, the number of lines is 6, the 6 line parameters are shown in table 1, and the ratio of reactance to resistance is almost the same as that of an actual 110kV line; the system comprises 3 generator sets, wherein 1 pumped storage unit is connected with BUS-1, 2 conventional thermal power generating units are respectively connected with BUS-2 and BUS-3, and the characteristic parameters of the 3 generator sets are shown in a table 2. As shown in fig. 2, the total load prediction curve has a maximum power of 385MW and a minimum power of 226.1875MW, and since the specific load power prediction value of each node cannot be obtained, the load prediction value of each node at each time is obtained by distributing the total load prediction value at each time according to the percentage of the load of each node in the BPA operation data, and the system reference power is 100 MW. Respectively adopting an improved direct current power flow model and a direct current power flow model to carry out power flow calculation, and comparing with an alternating current power flow result to compare accuracy; the accurate improved direct current power flow model is applied to the power grid safety constraint day-ahead power generation optimization scheduling problem to be solved, 96 time intervals in the whole day are considered, and the day-ahead start-stop and output plans of the unit are optimized and formulated. The computer used is Intel (R) Xeon (R) CPU E3-1270v5@3.60GHz, 32GB memory.
TABLE 1 line parameters
TABLE 2 characteristic parameters of the unit
The active power of the line is calculated by using the improved direct current power flow model and the direct current power flow model, and compared with the alternating current power flow calculation result, and the result is shown in table 3. In order to avoid the situation that the relative error is too large due to the fact that the transmission power is too small, the branch circuits with the power of the alternating current power flow circuit being 10% smaller than the maximum power value of the circuit in the network are removed for statistics.
TABLE 3 comparison of different load flow model calculations
As can be seen from table 3, the relative error of the line power calculated by the direct current power flow model exceeds 20%, the error is large, the power flow result calculated by the improved direct current power flow model is more accurate than that of the direct current power flow model, and the relative error of the line power is less than 5%, so that the improved direct current power flow model is more suitable for calculating the active power of the line of the power grid with the 110kV voltage class, and the accuracy is high.
In the established optimized scheduling model, the positive and negative rotation standby demand coefficients L of the load prediction erroru% of 3%, Ld% is 1%, and the percentage of network loss in the total load power is 2.2%. And respectively solving a safety constraint optimization scheduling model (which is a mixed integer linear programming model MILP) based on the direct current power flow model and a safety constraint optimization scheduling model (which is a mixed integer nonlinear programming model MINLP) based on the improved direct current power flow model established by the embodiment by using a CPLEX solver and a DICOPT solver in GAMS software. The objective function values and the calculation time ratios obtained by solving the two models are shown in table 4. It can be seen that the solving speed of the two models is very fast, the objective function value obtained by solving the safety constraint optimization scheduling model based on the improved direct current power flow model is slightly lower than that of the safety constraint optimization scheduling model based on the direct current power flow model, and the line power calculated by the improved direct current power flow model is more accurate, so that the optimized scheduling result obtained by the MINLP model is more in line with the actual situation.
TABLE 4 comparison of the results of the two models
In the solving process based on the two models respectively, the change trend of the out-of-limit count of the line power along with the iteration times is shown in fig. 3, and the count is accumulated when the same line is out-of-limit in different time periods. It can be seen that in the solving process of the safety constraint optimization scheduling model based on the direct current power flow model, the line power safety constraint is checked and added for 4 times; and in the solving process of the safety constraint optimization scheduling model based on the improved direct current power flow model, the line power safety constraint is verified-added for 3 times. This is due to the improved accuracy of the line power calculation, which reduces the number of required security checks.
The machine set output plan curve pair obtained by solving based on the two power flow models is shown in figure 4. It can be seen that the fluctuation of the power generation dispatching plan curve obtained by solving the MINLP model is small, and the power generation dispatching plan curve is more consistent with the actual operation condition.
Therefore, compared with the prior art, the optimized scheduling method for the safety constraint of the power grid with the 110kV level provided by the embodiment has the following advantages:
1) the direct current power flow model is improved, so that the calculation result of the line power in the 110 kV-level power grid is more accurate.
2) The improved direct current power flow model with high accuracy is applied to a power grid safety constraint day-ahead power generation optimization scheduling model with a 110kV voltage level for solving, the solving speed is high, and the solving result is more reasonable and accurate.
Various other modifications and changes may be made by those skilled in the art based on the above-described technical solutions and concepts, and all such modifications and changes should fall within the scope of the claims of the present invention.
Claims (10)
1. A safety constraint optimization scheduling method for a 110 kV-level power grid is characterized by comprising the following steps:
neglecting a grounding branch in a power grid, and obtaining the active power of a line under an alternating current power flow model as follows:
Pij＝ViVj(Gijcosθij+Bijsinθij)-Vi 2Gij (1)
in the formula: pijIs the active power of line ij; viAnd VjThe voltage amplitudes of the node i and the node j are respectively; thetaijIs the voltage phase angle difference between node i and node j; gij、BijRespectively are mutual conductance and mutual susceptance between a node i and a node j;
the active power of the line under the alternating current power flow model is simplified to obtain an improved direct current power flow model, and the improved direct current power flow model comprises an active power equation of any line ij:
and, the injection active power balance equation of any node i:
the improved direct current power flow model is applied to the safety constraint day-ahead power generation optimization scheduling problem of the power grid with the 110kV voltage level so as to obtain the power grid optimization scheduling result.
2. The optimal scheduling method for safety constraint of power grid with 110kV level as claimed in claim 1, wherein in the optimal scheduling problem of power generation before the improved direct current power flow model is applied to the safety constraint of power grid with 110kV voltage level, the optimal scheduling takes the minimum total power generation operation cost of the power grid as an objective function, and the constraint conditions include start-stop cost constraint of a unit, system power balance constraint, upper limit constraint of output of a conventional unit, unit climbing/landslide constraint, minimum start-stop time constraint of the unit, operation constraint of a pumped storage unit, system rotation standby constraint, node injection active power balance constraint and network safety constraint.
3. The optimization scheduling method of the safety constraint of the power grid with the 110kV level as claimed in claim 2, wherein the active power of the line under the alternating current power flow model is simplified, and the process of obtaining the improved direct current power flow model is as follows:
1) under normal operation conditions, the voltage amplitude of each node in the power grid power system is close to a rated value, so that V is approximately consideredi≈1,Vj≈1；
2) The phase angle of the voltage at the nodes at the two ends of the line being very small, i.e. thetaij0, hence approximately sin (θ)ij/2)≈θij/2,cos(θij/2)≈1；
Therefore, equation (1) can be simplified as:
and further obtaining an injection power balance equation of any node i of the improved direct current power flow model:
4. the optimal scheduling method of the safety constraint of the 110 kV-class power grid as claimed in claim 3, wherein the objective function is:
the method aims to minimize the total power generation operation cost of a power grid, namely the sum of the operation expenses of all units, wherein the operation expenses of the units comprise the startup and shutdown expenses and the power generation fuel consumption expenses, and the formula (4):
wherein T is the total number of time periods of the scheduling cycle, and the day is divided into 96 time periods, each time period is 15min, and N is1Is the total number of conventional thermal power generating units, CiU,tAnd CiD,tThe starting and stopping costs of the conventional thermal power generating unit i in the time period t are Fi,tGenerating cost of a conventional thermal power generating unit i in a time period t; n is a radical of2Total number of pumping units, CsU,tAnd CsD,tThe starting cost and the stopping cost of the pumping unit s in the time period t are respectively, and the power generation cost is zero because the operation of the pumping unit does not consume fuel;
for a conventional thermal power generating unit, the power generation cost is as follows (5):
Fi,t＝Ai×Pi,t (5)
in the formula, AiCharacteristic coefficient of fuel consumption, P, for the generation cost of a unit ii,tAnd (4) the output of the unit i in the time period t.
5. The optimal scheduling method of the safety constraint of the 110 kV-class power grid as claimed in claim 4, wherein the constraint of the start-up and shutdown costs of the unit is as follows:
and (3) constraint of starting-up cost:
and (4) stopping cost restraint:
in the formula, KiAnd JiThe cost of single start-up and shut-down, K, of a conventional unit isAnd JsThe single startup and shutdown costs of the pumping unit s are respectively; i isi,t/Zs,tThe starting state value of the conventional unit i/pumping storage unit s is 1, and the stopping state value is 0 in the starting and stopping states of the conventional unit i/pumping storage unit s in the time period t.
6. The optimal scheduling method of the safety constraint of the 110 kV-class power grid as claimed in claim 5, wherein the power balance constraint of the system is as follows:
in the formula, PLoad,tTotal system load for time period t, PLoss,tThe system network loss of the time period t is approximated by taking a certain percentage of the total load power; ppg,s,tAnd Ppp,s,tRespectively generating power and pumping power of the pumping storage unit s in a time period t, wherein the generating power is positive, and the pumping power is negative;
the upper and lower output limits of the conventional unit at the i time period t are constrained as follows:
Ii,tPi,min≤Pi,t≤Ii,tPi,max (9)
in the formula, Pi,minIs the minimum output, P, of the conventional unit ii,maxThe maximum output of the conventional unit i.
7. The optimal scheduling method of the safety constraint of the 110 kV-level-contained power grid as claimed in claim 6, wherein the unit climbing/landslide constraint is as follows:
considering that the unit does not exceed the minimum output of the unit in the first time period of starting up or the last time period of stopping up, the unit climbing/landslide constraint is expressed as follows:
in the formula, ruiAnd rdiThe climbing rate and the landslide rate of the unit i, T15One operation period is 15 min;
the minimum start-up and shut-down time constraint of the unit is as follows:
minimum boot time constraint:
minimum downtime constraint:
in the formula of Ui/DiThe period of time during which the unit i must be powered on/off at the beginning of the scheduling cycle is determined by the state of the unit at the end of the previous scheduling cycle, Ton_i/Toff_iMinimum on-time/minimum off-time, X, for unit ion_i,0/Xoff_i,0For the time that unit i has been continuously powered on/off at the beginning of the scheduling period.
8. The optimal scheduling method of the safety constraint of the 110 kV-class power grid as claimed in claim 7, wherein the operation constraint of the pumped storage unit is as follows:
and (3) restraining an upper limit and a lower limit of output:
in the formula, Ppg,s,maxAnd Ppp,s,maxRespectively the maximum generating power and the maximum pumping power of the pumping storage unit s, Zpg,s,tAnd Zpp,s,tRespectively representing the power generation state and the water pumping state of the storage unit s at a time t, wherein the value of 1 represents that the storage unit is in a corresponding state, and the value of 0 represents that the storage unit is not in a corresponding state;
the complementary constraint of operating condition, namely the pumping unit can not be in the water pumping and power generation operating condition at the same time period, as follows:
Zs,t＝Zpg,s,t+Zpp,s,t≤1 (14)
in actual operation, the daily power balance constraint also needs to be satisfied, as follows:
in the formula, xi is the conversion efficiency of the pump storage unit, and is 75%;
in order to prolong the service life of the pumping unit, the switching of two operating conditions of the pumping unit in actual operation needs to meet the time limit, and the switching time is defined to be half an hour, namely the switching time of 2 time periods is needed, so that the following constraints need to be met:
9. the optimal scheduling method of the safety constraint of the 110 kV-class power grid as claimed in claim 8, wherein the system rotation standby constraint is:
enough system rotation reserve capacity is reserved to cope with the influence caused by load prediction errors, positive rotation reserve capacity is used for compensating the influence caused by underestimating system load, and negative rotation reserve capacity is used for compensating the influence caused by overestimating system load;
and (3) conventional unit rotation standby constraint:
in the formula, sui,tAnd sdi,tRespectively providing positive and negative rotation reserve capacity T for the unit i in the time period T10The response time is reserved for the rotation of the unit;
and (3) rotating standby constraint of the pumping unit:
the rotating standby requirements of the system are obtained by accumulating the rotating standby of all the units as follows:
in the formula, Su,tAnd Sd,tRespectively, the positive and negative rotation reserve capacity, L, of the system in the time period tu% and Ld% is the demand coefficient of the load forecast deviation to the system positive and negative rotation reserve capacity respectively.
10. The optimal scheduling method of the safety constraint of the 110 kV-class power grid as claimed in claim 9, wherein the node injection active power balance constraint is:
in the formula (I), the compound is shown in the specification,
is the injected active power of node i at time t; pij,tThe active power of line ij is time period t; thetaij,tIs the voltage phase angle difference between node i and node j for time period t;
the network security constraint
According to the improved direct current power flow model, the transmission power of the line is constrained as follows:
wherein l is a line to be checked for safety, Pl,km,tTransmission power of line l (k, m) for time period t; thetakm,tIs the voltage phase angle difference between node k and node m for time period t;
is the transmission power limit for line l between node k and node m.
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