CN109217281B - Direct-current tie line power optimization method considering reactive power equipment adjustment cost - Google Patents

Direct-current tie line power optimization method considering reactive power equipment adjustment cost Download PDF

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CN109217281B
CN109217281B CN201811010053.6A CN201811010053A CN109217281B CN 109217281 B CN109217281 B CN 109217281B CN 201811010053 A CN201811010053 A CN 201811010053A CN 109217281 B CN109217281 B CN 109217281B
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tie line
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CN109217281A (en
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张海波
马伸铜
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North China Electric Power University
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract

The invention discloses a direct current tie line power optimization method considering reactive power equipment adjustment cost, and belongs to the technical field of power system operation and scheduling. The method comprises the steps that firstly, according to the reactive power regulation characteristic of the traditional direct current transmission, the feasible region and the infeasible region of the transmission power of the direct current tie line are determined, so that the action times of reactive power equipment are reduced; and secondly, establishing a reactive power equipment adjusting cost model, converting the action times of the reactive power equipment into reactive power adjusting cost for optimization, so as to avoid frequent actions of the reactive power equipment on two sides of the direct current and reduce the loss of the service life of the reactive power equipment. And finally, a direct current tie line power optimization model is established, and the comprehensive benefit of a power grid at a transmitting end and a receiving end is improved while the wind power consumption proportion is improved. The invention fully excavates the coordination optimization benefit between the flexible regulation capability and the DC reactive power regulation characteristic of the DC tie line, and the wind power is consumed in a larger space range, thereby improving the consumption level of wind power resources and realizing the operation economy of the DC cross-regional interconnected power grid.

Description

Direct-current tie line power optimization method considering reactive power equipment adjustment cost
Technical Field
The invention belongs to the technical field of operation and scheduling of electric power systems, and particularly relates to a direct-current tie line power optimization method considering reactive power equipment adjustment cost.
Background
Currently, the energy distribution in China is extremely uneven, large energy bases are mainly distributed in remote northwest areas, the local power grid load level is low, and more electric power is abundant; although the east region is economically developed and has high load level, the energy supply is relatively insufficient. Therefore, large-scale energy base development and power grid trans-regional direct current interconnection are promoted, large-scale and high-efficiency optimized configuration of clean energy is realized, and the method is an important direction of power grid development.
Most of traditional direct current day-ahead plans are compiled according to the load peak-valley change of a receiving-end power grid, the operation mode adopts two-section type fixed power operation, the capacity of coping with the wind power output fluctuation of a transmitting-end power grid is lacked, the coordination with the power of the receiving-end power grid is difficult, and in addition, the frequent adjustment of high-voltage direct current reactive power equipment cannot be avoided. Therefore, how to establish a reasonable and effective direct current tie line power optimization model and give full play to the flexible adjustment capability of direct current transmission is an urgent problem to be solved by the current scheduling plan. In order to solve the above problems, in document 1, "new mode for optimizing and improving new energy absorption capacity by using dc link operation mode", dc link power is divided into N steps, and the stepped operation characteristic of the dc link is simulated by using the idea of unit combination, but it is difficult to fully exert the regulation capacity of the dc system by discretely controlling dc transmission power. Document 2, "direct current link power optimization model and analysis for promoting cross-regional new energy consumption", regards each stepped power of a direct current link as a feasible state of the direct current link, and establishes a direct current link power stepped operation model, but also is discrete control of a power point. Document 3, "dc cross-regional interconnected power grid power generation and transmission planning model and method" proposes a multi-unit coordination modeling method for dc tie line power, which divides the dc tie line power into the sum of a plurality of transmission unit powers and considers the dc operating characteristic constraints in a refined manner.
Although the method considers the flexible operation characteristic of the direct current tie line and is continuously refined in the aspect of a direct current tie line power optimization model, the reactive power equipment characteristics at two sides of the direct current tie line are not considered. Therefore, it is necessary to specify a feasible region and an infeasible region of the dc power according to the dc reactive power regulation characteristic, and to make a dc link power optimization method considering the regulation cost of the reactive power equipment, so as to fully exploit the coordination optimization benefit between the flexible regulation capability of the dc link and the dc reactive power regulation characteristic.
Disclosure of Invention
In order to solve the problems, the invention provides a direct current tie line power optimization method considering reactive power equipment adjustment cost, which is characterized by comprising the following steps of:
step 1: dividing feasible regions and infeasible regions of the transmission power of the direct current tie line according to the reactive power regulation characteristics of the traditional direct current transmission, and establishing a direct current tie line power model according to the divided feasible regions;
step 2: establishing a reactive power equipment adjusting cost model according to the feasible interval and the infeasible interval determined in the step 1;
and step 3: establishing a direct-current tie line power optimization model considering reactive power equipment adjusting cost by using load and wind power short-term prediction data, considering direct-current operation constraint conditions and alternating-current system safe operation constraint conditions and taking the minimum total power generation cost of a power grid as a target function; the total power generation cost of the power grid comprises the power generation cost, the wind abandoning punishment cost and the reactive equipment adjusting cost of the thermal power generating unit of the power grid at the transmitting end and the receiving end;
and 4, step 4: and (4) obtaining an optimization result of the direct-current connecting line and a power output plan of the thermal power generating unit of the power grid at the sending end by adopting a GAMS solving model.
The step 1 specifically comprises the following steps:
step 1-1: determining the direct current active change size corresponding to the action of the reactive equipment on two sides of the direct current tie line according to the direct current reactive power regulation characteristic and the reactive equipment action characteristic;
step 1-2: determining a feasible interval and an infeasible interval of the transmission power of the direct current tie line according to a corresponding direct current power operating point when the reactive power equipment acts;
feasible interval:
Figure BDA0001784821290000031
Figure BDA0001784821290000032
in the formula, n is the serial number of the feasible interval of the transmission power of the direct current tie line; n is the total feasible interval number of the power of the direct current tie line;
Figure BDA0001784821290000033
respectively an upper limit value and a lower limit value of the nth feasible interval; i isd,n,tThe discrete variable is 0-1 and represents whether the direct current tie line power in the t period is in the feasible interval n;
infeasible intervals:
Figure BDA0001784821290000034
in the formula, YnIs an infeasible interval n;
Figure BDA0001784821290000035
is the upper limit value of the nth feasible interval,
Figure BDA0001784821290000036
the lower limit value of the (n + 1) th feasible interval;
step 1-3: establishing a DC link power model to ensure DC link powerIn the same time period, the system is operated in only one feasible interval, namely, the conditions are met
Figure BDA0001784821290000037
The power model of the direct current tie line is as follows:
Figure BDA0001784821290000038
in the formula, Pd,tThe direct current tie line power is in a time period t; pd,n,tThe power of the direct current tie line is the nth feasible interval of the t period.
The specific method for establishing the reactive power equipment adjusting cost model in the step 2 comprises the following steps:
step 2-1: determining the sequence number of the feasible interval where the power of the direct current tie line in each time period is located, wherein the calculation formula is as follows:
Figure BDA0001784821290000039
step 2-2: determining the action times of the direct current reactive power equipment in the period according to the power feasible interval sequence number difference value of the adjacent period, wherein the calculation formula is as follows:
Figure BDA00017848212900000310
in the formula (I), the compound is shown in the specification,
Figure BDA00017848212900000311
the number of reactive equipment actions from t-1 time period to t time period;
Figure BDA00017848212900000312
is the feasible interval serial number of the direct current tie line power in the t period,
Figure BDA00017848212900000313
the serial number of the feasible interval where the direct current tie line power in the t-1 time period is located;
step 2-3: calculating the adjustment cost of the reactive power equipment, wherein the calculation formula is as follows:
Figure BDA0001784821290000041
in the formula, K is a cost factor for synthesizing the alternating current filter and the converter transformer adjustment,
Figure BDA0001784821290000042
adjusting the cost for the reactive equipment in the t period;
step 2-4: linearizing reactive equipment regulation cost:
Figure BDA0001784821290000043
in the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000044
two non-negative variables introduced for linearization;
after linearization, the obtained reactive power equipment adjusting cost model is as follows:
Figure BDA0001784821290000045
in the formula, λtAnd adjusting the cost of the linearized reactive power equipment in the t period.
The direct current tie line power optimization model considering the reactive power equipment adjusting cost established in the step 3 is as follows:
an objective function:
Figure BDA0001784821290000046
in the formula, F is the total cost of the all-day operation of the direct-current trans-regional interconnected power grid;
Figure BDA0001784821290000047
the linear power generation cost of the thermal power generating unit i in the four sections in the t period is obtained; kwIn order to discard the wind penalty factor,
Figure BDA0001784821290000048
the wind power waste air volume is obtained;
constraint conditions are as follows:
a) direct current operation constraint conditions:
i) DC link line output constraints
Figure BDA0001784821290000049
In the formula, Pd,tThe running power of the direct current connecting line d in the time period t;
Figure BDA00017848212900000410
respectively is the output upper limit and the output lower limit of the direct current connecting line in the t period;
ii) direct current adjacent time interval output force adjustment direction constraint
Figure BDA0001784821290000051
In the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000052
all the discrete variables are 0-1 discrete variables which respectively represent whether the direct current tie line climbs or not and whether the direct current tie line slides or not in the time period t; if yes, the value is 1, otherwise the value is 0;
iii) direct Current Outlet adjustment Rate constraint
Figure BDA0001784821290000053
In the formula (I), the compound is shown in the specification,dcthe amplitude is adjusted for the minimum of the dc link,
Figure BDA0001784821290000054
adjusting the amplitude value for the maximum of the direct current tie line;
iv) direct-current output adjustment continuity constraint
Figure BDA0001784821290000055
V) direct current adjustment interval constraint
Figure BDA0001784821290000056
In the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000057
all the discrete variables are 0-1 discrete variables, and respectively represent that the output of the direct current connecting line starts to be adjusted and finishes to be adjusted at the moment t;
vi) restriction of adjustment times of DC output
Figure BDA0001784821290000058
In the formula, NmaxMaximum number of daily adjustments for dc link power;
vii) direct Current daily transaction volume constraints
Figure BDA0001784821290000059
In the formula, E is daily planned transaction electric quantity of the direct current connecting line, and rho is an allowable transmission deviation proportion;
b) safety operation constraint condition of AC system
I) output constraint of thermal power generating unit
Figure BDA0001784821290000061
In the formula, Pi Gmax、Pi GminRespectively representing the upper limit and the lower limit of the output of the thermal power generating unit i,
Figure BDA0001784821290000062
the output of the thermal power generating unit i in the time period t is obtained;
ii) thermal power generating unit climbing restraint
Figure BDA0001784821290000063
In the formula, RUi、RDiThe climbing speed and the landslide speed of the unit i are respectively set;
iii) Power balance constraints
Figure BDA0001784821290000064
In the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000065
the system comprises a thermal power generating unit and a wind power plant which are respectively a power grid A at a sending end;
Figure BDA0001784821290000066
a set of load nodes of a sending-end power grid A;
Figure BDA0001784821290000067
the output of the wind power plant w in the time period t;
Figure BDA0001784821290000068
a predicted value of a load node k of a sending end power grid A in a t period is obtained;
iv) Positive and negative rotation backup constraints
Positively rotating for standby:
Figure BDA0001784821290000069
Figure BDA00017848212900000610
in the formula (I), the compound is shown in the specification,
Figure BDA00017848212900000611
for the predicted force values of the wind farm w during the time period t,
Figure BDA00017848212900000612
the positive reserve capacity required by the sending-end power grid A at the moment t; w is au、wDRespectively is a wind power positive standby coefficient and a load standby coefficient;
negative rotation for standby:
Figure BDA00017848212900000613
Figure BDA00017848212900000614
in the formula (I), the compound is shown in the specification,
Figure BDA00017848212900000615
the negative reserve capacity required by the sending-end power grid A at the moment t; w is adThe wind power negative standby coefficient;
v) tidal current safety constraints
Figure BDA0001784821290000071
In the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000072
respectively representing power transfer distribution factors of a thermal power generating unit i, a wind power plant w, a load k and a direct current connecting line;
Figure BDA0001784821290000073
F lthe upper limit and the lower limit of the transmission of the AC line l are respectively;
vi) wind power constraints
Figure BDA0001784821290000074
The invention has the beneficial effects that:
(1) the direct current connecting line provided by the invention can be used for transmitting the feasible region and the infeasible region of the power, the direct current reactive power equipment can be prevented from reciprocating due to the fluctuation of the direct current power near the reactive power equipment action point, and the adjustment precision of a direct current system is improved.
(2) The invention establishes a reactive power equipment adjusting cost model. On the basis of specifying a feasible interval and an infeasible interval of the direct current power, the action times of the reactive power equipment are converted into reactive power adjustment cost for optimization, so that frequent actions of the reactive power equipment on two sides of the direct current can be avoided, and the loss of the service life of the reactive power equipment is reduced.
(3) The direct-current connecting line power optimization model for the reactive power equipment adjusting cost enables the output of the thermal power generating unit of the power grid at the transmitting end to be gentle, avoids large fluctuation of the output of the thermal power generating unit, does not bring heavy adjusting burden to the thermal power generating unit at the transmitting end while improving the wind power consumption proportion, and improves the comprehensive benefit of the power grid at the transmitting end and the receiving end.
(4) The invention fully excavates the coordination optimization benefit between the flexible regulation capability and the DC reactive power regulation characteristic of the DC tie line, and the wind power is consumed in a larger space range, thereby improving the consumption level of wind power resources and realizing the operation economy of the DC cross-regional interconnected power grid.
Drawings
Fig. 1 is a schematic diagram of a dc link power optimization method taking into account reactive power equipment adjustment cost;
FIG. 2 is a schematic diagram of an active power interval corresponding to the action of a reactive device on a rectification side;
FIG. 3 is a schematic diagram of an active power interval corresponding to the action of the reactive power equipment on the inversion side;
FIG. 4 is a schematic diagram of an active power interval corresponding to actions of reactive devices on two sides of a direct current;
FIG. 5 is a schematic diagram of division of a DC feasible region and an infeasible region;
FIG. 6 is a schematic diagram of a comparison of DC power transmission plans before and after optimization;
FIG. 7 is a schematic diagram of the comparison of the actual output of the thermal power generating units of the power grid at the front and rear optimized sending ends;
FIG. 8 is a schematic diagram showing the comparison of the air flow before and after optimization;
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
Fig. 1 is a schematic diagram of a dc link power optimization method considering reactive power equipment adjustment cost, as shown in fig. 1, the method includes the following steps:
step 1: dividing feasible regions and infeasible regions of the transmission power of the direct-current connecting line according to the reactive power regulation characteristics of traditional direct-current transmission, and establishing a direct-current connecting line power model according to the divided feasible regions so as to ensure that the direct-current connecting line runs in the feasible regions for a long time;
step 2: establishing a reactive power equipment adjusting cost model according to the feasible interval and the infeasible interval determined in the step 1;
and step 3: establishing a direct-current tie line power optimization model considering reactive power equipment adjusting cost by using load and wind power short-term prediction data, considering direct-current operation constraint conditions and alternating-current system safe operation constraint conditions and taking the minimum total power generation cost of a power grid as a target function; the total power generation cost of the power grid comprises the power generation cost, the wind abandoning punishment cost and the reactive equipment adjusting cost of the thermal power generating unit of the power grid at the transmitting end and the receiving end;
and 4, step 4: and (4) obtaining an optimization result of the direct-current connecting line and a power output plan of the thermal power generating unit of the power grid at the sending end by adopting a GAMS solving model.
Specifically, in the step 1, since the active adjustment of the dc link may cause frequent actions of the dc reactive power adjustment device, which affects the service life of the device, the invention provides a feasible region and an infeasible region of the dc link for transmitting power, so as to reduce the number of actions of the reactive power device and improve the adjustment accuracy of the dc system. The design principle of the feasible region and the infeasible region is that an approximately linear relation exists between reactive power regulation requirements and active transmission power of a traditional direct current system, namely an approximately linear relation exists between the switching of direct current reactive power control equipment and the size of a direct current active power change range. Therefore, the magnitude of the active direct current change corresponding to the action of the reactive equipment on the rectifying side and the inverting side of the direct current connecting line can be determined approximately linearly. In order to avoid the reciprocating action of the DC reactive equipment caused by the fluctuation of the DC power near the action point of the reactive equipment, the invention provides that the action point of the reactive equipment is taken as the center of an interval, the interval with a certain margin as the radius of the interval is a DC infeasible interval, and the interval outside the interval is a feasible interval. The specific division method is as follows:
step 1-1: according to the direct current reactive power regulation characteristic and the reactive equipment action characteristic, determining the direct current active power change size corresponding to the action of the reactive equipment on two sides of the direct current tie line approximately linearly;
step 1-2: determining a feasible interval and an infeasible interval of the transmission power of the direct current tie line according to a corresponding direct current power operating point when the reactive power equipment acts;
feasible interval:
Figure BDA0001784821290000091
Figure BDA0001784821290000092
in the formula, n is a feasible interval serial number of the transmission power of the direct current tie line, and includes the condition of considering the overlapping of the action points of the reactive power equipment; n is the total feasible interval number of the power of the direct current tie line;
Figure BDA0001784821290000093
respectively an upper limit value and a lower limit value of the nth feasible interval; i isd,n,tThe discrete variable is 0-1 and represents whether the direct current tie line power in the t period is in the feasible interval n;
infeasible intervals:
Figure BDA0001784821290000094
in the formula, YnIs an infeasible interval n;
Figure BDA0001784821290000095
is the upper limit value of the nth feasible interval,
Figure BDA0001784821290000096
the lower limit value of the (n + 1) th feasible interval;
in order to avoid that the direct current tie line runs in an infeasible interval, the invention also providesA direct current tie line power model is established to ensure that the direct current tie line power is in the same time period and only operates in a feasible interval, namely, the direct current tie line power model meets the following requirements:
Figure BDA0001784821290000097
the power model of the direct current tie line is as follows:
Figure BDA0001784821290000101
in the formula, Pd,tThe direct current tie line power is in a time period t; pd,n,tThe power of the direct current tie line is the nth feasible interval of the t period.
Fig. 2 is a schematic diagram of an active power interval corresponding to the action of a rectifier-side reactive device, fig. 3 is a schematic diagram of an active power interval corresponding to the action of an inverter-side reactive device, fig. 4 is a schematic diagram of an active power interval corresponding to the action of a direct-current two-side reactive device, fig. 5 is a schematic diagram of division of a direct-current feasible interval and a direct-current infeasible interval, and a in fig. 2i(i is 1,2, …) is the cut-off point of the ac filter on the rectifying side. Lower part of the figure "+" corresponds to ci(i ═ 1,2, …) indicating where the rectifier side converter transformer taps are adjusted. Considering that the capacity of the filter disposed in the inverter-side converter station is slightly larger, the active power interval corresponding to the operation of the inverter-side reactive device is slightly larger, as shown in fig. 3. And synthesizing the active power interval corresponding to the action of the reactive equipment on the two sides of the direct current to obtain the active power interval corresponding to the action of the reactive equipment on the two sides of the direct current shown in the figure 4. On the basis of fig. 4, the operating point of the reactive power equipment in the graph is taken as the center of the section, a certain margin is taken as the radius of the section to define a direct current infeasible section, and the magnitude of the margin can be reasonably set according to the direct current operating characteristics, so that the direct current tie line power is divided into the situations of alternating feasible sections and infeasible sections shown in fig. 5. If a plurality of reactive equipment action points are overlapped, the action points can be converted into feasible intervals with the interval width of 0, and the feasible intervals are sequentially included in a feasible interval sequence, so that the establishment of a subsequent reactive equipment adjusting cost model is facilitated.
Specifically, in the step 2, on the basis of the feasible and infeasible dc power intervals divided in the step 1, an adjustment cost model for calculating the reactive power device action caused by the dc link power adjustment is established. The model takes into account economic factors to optimize the limit on the number of reactive equipment actions into adjustment costs as part of the objective function. The action of the reactive equipment is caused by the fact that the direct current power is adjusted from one feasible interval to another feasible interval. Therefore, the number of times of the reactive equipment action in the period can be determined according to the sequence number difference value of the feasible interval where the tie line power in the adjacent period is located. The cost factors of the alternating current filter and the converter transformer adjustment are comprehensively considered, the reactive equipment action times can be converted into a reactive power adjustment cost model, and the adjustment cost containing an absolute value is linearized. The specific method for establishing the reactive power equipment adjusting cost model is as follows:
step 2-1: determining the sequence number of the feasible interval where the power of the direct current tie line in each time period is located, wherein the calculation formula is as follows:
Figure BDA0001784821290000111
step 2-2: determining the action times of the direct current reactive power equipment in the period according to the power feasible interval sequence number difference value of the adjacent period, wherein the calculation formula is as follows:
Figure BDA0001784821290000112
in the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000113
the number of reactive equipment actions from t-1 time period to t time period;
Figure BDA0001784821290000114
is the feasible interval serial number of the direct current tie line power in the t period,
Figure BDA0001784821290000115
at the power level of the DC link for the period t-1The number of the feasible interval;
step 2-3: calculating the adjustment cost of the reactive power equipment, wherein the calculation formula is as follows:
Figure BDA0001784821290000116
in the formula, K is a cost factor for synthesizing the alternating current filter and the converter transformer adjustment,
Figure BDA0001784821290000117
adjusting the cost for the reactive equipment in the t period;
step 2-4: linearizing reactive equipment regulation cost:
Figure BDA0001784821290000118
in the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000119
two non-negative variables introduced for linearization;
after linearization, the obtained reactive power equipment adjusting cost model is as follows:
Figure BDA00017848212900001110
in the formula, λtAnd adjusting the cost of the linearized reactive power equipment in the t period.
Specifically, the dc link power optimization model considering the reactive power device adjustment cost established in step 3 is as follows:
an objective function:
Figure BDA0001784821290000121
in the formula, F is the total cost of the all-day operation of the direct-current trans-regional interconnected power grid;
Figure BDA0001784821290000122
four-segment line for thermal power generating unit i in t periodCost of sexual power generation; kwIn order to discard the wind penalty factor,
Figure BDA0001784821290000123
the wind power waste air volume is obtained;
constraint conditions are as follows:
a) direct current operation constraint conditions:
i) DC link line output constraints
Figure BDA0001784821290000124
In the formula, Pd,tThe running power of the direct current connecting line d in the time period t;
Figure BDA0001784821290000125
respectively is the output upper limit and the output lower limit of the direct current connecting line in the t period;
ii) direct current adjacent time interval output force adjustment direction constraint
Figure BDA0001784821290000126
In the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000127
all the discrete variables are 0-1 discrete variables which respectively represent whether the direct current tie line climbs or not and whether the direct current tie line slides or not in the time period t; if yes, the value is 1, otherwise the value is 0;
iii) direct Current Outlet adjustment Rate constraint
Figure BDA0001784821290000128
In the formula (I), the compound is shown in the specification,dcthe amplitude is adjusted for the minimum of the dc link,
Figure BDA0001784821290000129
adjusting the amplitude value for the maximum of the direct current tie line;
iv) direct-current output adjustment continuity constraint
Figure BDA00017848212900001210
V) direct current adjustment interval constraint
Figure BDA00017848212900001211
In the formula (I), the compound is shown in the specification,
Figure BDA00017848212900001212
all the discrete variables are 0-1 discrete variables, and respectively represent that the output of the direct current connecting line starts to be adjusted and finishes to be adjusted at the moment t;
vi) restriction of adjustment times of DC output
Figure BDA0001784821290000131
In the formula, NmaxMaximum number of daily adjustments for dc link power;
vii) direct Current daily transaction volume constraints
Figure BDA0001784821290000132
In the formula, E is daily planned transaction electric quantity of the direct current connecting line, and rho is an allowable transmission deviation proportion;
b) safety operation constraint condition of AC system
I) output constraint of thermal power generating unit
Figure BDA0001784821290000133
In the formula, Pi Gmax、Pi GminRespectively representing the upper limit and the lower limit of the output of the thermal power generating unit i,
Figure BDA0001784821290000134
the output of the thermal power generating unit i in the time period t is obtained;
ii) thermal power generating unit climbing restraint
Figure BDA0001784821290000135
In the formula, RUi、RDiThe climbing speed and the landslide speed of the unit i are respectively set;
iii) Power balance constraints
Figure BDA0001784821290000136
In the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000137
the system comprises a thermal power generating unit and a wind power plant which are respectively a power grid A at a sending end;
Figure BDA0001784821290000138
a set of load nodes of a sending-end power grid A;
Figure BDA0001784821290000139
the output of the wind power plant w in the time period t;
Figure BDA00017848212900001310
a predicted value of a load node k of a sending end power grid A in a t period is obtained;
iv) Positive and negative rotation backup constraints
Positively rotating for standby:
Figure BDA0001784821290000141
Figure BDA0001784821290000142
in the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000143
for the predicted force values of the wind farm w during the time period t,
Figure BDA0001784821290000144
the positive reserve capacity required by the sending-end power grid A at the moment t; w is au、wDRespectively is a wind power positive standby coefficient and a load standby coefficient;
negative rotation for standby:
Figure BDA0001784821290000145
Figure BDA0001784821290000146
in the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000147
the negative reserve capacity required by the sending-end power grid A at the moment t; w is adThe wind power negative standby coefficient;
v) tidal current safety constraints
Figure BDA0001784821290000148
In the formula (I), the compound is shown in the specification,
Figure BDA0001784821290000149
respectively representing power transfer distribution factors of a thermal power generating unit i, a wind power plant w, a load k and a direct current connecting line;
Figure BDA00017848212900001410
F lthe upper limit and the lower limit of the transmission of the AC line l are respectively;
vi) wind power constraints
Figure BDA00017848212900001411
Example 1
In this embodiment, a modified IEEE-24 node system is taken as an example to respectively simulate two regional power grids of a sending end and a receiving end, and the grids are interconnected by using a direct current tie line. The system comprises 48 nodes, 21 thermal power generating units and 2 wind power plants, the scheduling period is 24 hours, the four-segment linear function is used for approximating the power generation cost of the thermal power generating units, and the absolute value function linearization method is used for processing the reactive power equipment adjustment cost. The related calculation is completed on a 3.00GHz and 8GB memory computer of an Intel core i5-7400 processor, and the program solution is carried out on the example by adopting GAMS25.0.3.
In order to comparatively analyze the effectiveness and the correctness of the optimized model established by the invention, the following three operation modes are established:
mode 1: the power of the direct current tie line is in a two-section type constant power operation mode;
mode 2: the power of the direct current connecting line does not take limited optimization of reactive power regulation cost into account;
mode 3: the dc link power is a constrained optimization that accounts for reactive regulation cost.
The ratio of the wind curtailment rate of the optimization plan obtained based on the method of the invention to the number of actions of the reactive equipment is shown in table 1:
TABLE 1 comparison of wind curtailment before and after optimization and number of actions of reactive equipment
Type (B) Air loss rate/%) Number of idle device actions
Mode
1 8.7 14
Mode 2 0 12
Mode 3 0 6
As can be seen from table 1, mode 2 after optimization can completely consume wind power compared with mode 3 and mode 1, and mode 3 promotes wind power consumption and has fewer actions of reactive equipment.
Fig. 6-8 show comparison results of power plans of the direct current connecting line before and after optimization, wherein fig. 6 is a comparison schematic diagram of direct current power transmission plans before and after optimization, fig. 7 is a comparison schematic diagram of actual output of a thermal power generating unit of a power grid at a sending end before and after optimization, and fig. 8 is a comparison schematic diagram of air abandoning before and after optimization; in the figure, the dotted line represents mode 1, i.e., a constant power operation mode in which the dc link power is two-stage; the dotted and dashed line represents mode 2, i.e. the dc link power does not account for the limited optimization of the reactive regulation cost; the solid line represents mode 3, i.e. the dc link power is a limited optimization to account for reactive regulation costs.
As can be seen from fig. 6, compared to the mode 1, during the load valley period, the optimized mode 2 and mode 3 dc link power is increased to some extent, which is beneficial to increase the cross-region consumption level of the wind power, and during the load peak period, the optimized dc link power is decreased under the constraint of daily transaction power. Compared with a two-stage direct current plan in a mode 1, the multi-step direct current plans in the modes 2 and 3 improve the adjustment accuracy of the direct current system, but the mode 3 can effectively avoid the situation that a connecting line runs near a switching point of reactive power equipment due to the existence of a direct current infeasible interval, and the action times of the reactive power equipment are few.
It can be seen from fig. 7 that after optimization, the output of the thermal power generating unit at the sending end in the mode 3 becomes smoother, large fluctuation of the thermal power generating unit is avoided, and the adjustment burden of the thermal power generating unit at the sending end is reduced.
It can be seen from fig. 8 that after optimization, the wind curtailment amount of the sending end of the mode 3 is 0, and the wind power consumption level of the sending end power grid is effectively improved.
The present invention is not limited to the above embodiments, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (3)

1. A direct current tie line power optimization method considering reactive power equipment adjusting cost is characterized by comprising the following steps:
step 1: dividing feasible regions and infeasible regions of the transmission power of the direct current tie line according to the reactive power regulation characteristics of the traditional direct current transmission, and establishing a direct current tie line power model according to the divided feasible regions;
the step 1 specifically comprises the following steps:
step 1-1: determining the direct current active change size corresponding to the action of the reactive equipment on two sides of the direct current tie line according to the direct current reactive power regulation characteristic and the reactive equipment action characteristic;
step 1-2: determining a feasible interval and an infeasible interval of the transmission power of the direct current tie line according to a corresponding direct current power operating point when the reactive power equipment acts;
feasible interval:
Figure FDA0002603628150000011
Figure FDA0002603628150000012
in the formula, n is the serial number of the feasible interval of the transmission power of the direct current tie line; n is the total feasible interval number of the power of the direct current tie line;
Figure FDA0002603628150000013
respectively an upper limit value and a lower limit value of the nth feasible interval; i isd,n,tThe discrete variable is 0-1 and represents whether the direct current tie line power in the t period is in the feasible interval n;
infeasible intervals:
Figure FDA0002603628150000014
in the formula, YnIs an infeasible interval n;
Figure FDA0002603628150000015
is the upper limit value of the nth feasible interval,
Figure FDA0002603628150000016
the lower limit value of the (n + 1) th feasible interval;
step 1-3: establishing a direct current tie line power model to ensure that the direct current tie line power has the same period and only operates in a feasible interval, namely, the direct current tie line power model meets the requirement
Figure FDA0002603628150000017
The power model of the direct current tie line is as follows:
Figure FDA0002603628150000021
in the formula, Pd,tThe direct current tie line power is in a time period t; pd,n,tThe power of the direct current tie line in the nth feasible interval in the t period;
step 2: establishing a reactive power equipment adjusting cost model according to the feasible interval and the infeasible interval determined in the step 1;
and step 3: establishing a direct-current tie line power optimization model considering reactive power equipment adjusting cost by using load and wind power short-term prediction data, considering direct-current operation constraint conditions and alternating-current system safe operation constraint conditions and taking the minimum total power generation cost of a power grid as a target function; the total power generation cost of the power grid comprises the power generation cost, the wind abandoning punishment cost and the reactive equipment adjusting cost of the thermal power generating unit of the power grid at the transmitting end and the receiving end; and finally obtaining an optimization result of the direct current connecting line and a power output plan of the thermal power generating unit of the power grid at the sending end.
2. The method for optimizing the power of the direct current tie line considering the reactive power equipment regulation cost according to claim 1, wherein the specific method for establishing the reactive power equipment regulation cost model in the step 2 is as follows:
step 2-1: determining the sequence number of the feasible interval where the power of the direct current tie line in each time period is located, wherein the calculation formula is as follows:
Figure FDA0002603628150000022
step 2-2: determining the action times of the direct current reactive power equipment in the period according to the power feasible interval sequence number difference value of the adjacent period, wherein the calculation formula is as follows:
Figure FDA0002603628150000023
in the formula (I), the compound is shown in the specification,
Figure FDA0002603628150000024
the number of reactive equipment actions from t-1 time period to t time period;
Figure FDA0002603628150000025
for the number of reactive device actions in the period t,
Figure FDA0002603628150000031
the number of reactive equipment actions in the t-1 time period;
step 2-3: calculating the adjustment cost of the reactive power equipment, wherein the calculation formula is as follows:
Figure FDA0002603628150000032
in the formula, K is a cost factor for synthesizing the alternating current filter and the converter transformer adjustment,
Figure FDA0002603628150000033
adjusting costs for reactive equipment for time period t；
Step 2-4: linearizing reactive equipment regulation cost:
Figure FDA0002603628150000034
in the formula (I), the compound is shown in the specification,
Figure FDA0002603628150000035
two non-negative variables introduced for linearization;
after linearization, the obtained reactive power equipment adjusting cost model is as follows:
Figure FDA0002603628150000036
in the formula, λtAnd adjusting the cost of the linearized reactive power equipment in the t period.
3. The method for optimizing the power of the dc link considering the reactive power equipment regulation cost according to claim 1, wherein the dc link power optimization model considering the reactive power equipment regulation cost established in the step 3 is:
an objective function:
Figure FDA0002603628150000037
in the formula, F is the total cost of the all-day operation of the direct-current trans-regional interconnected power grid;
Figure FDA0002603628150000038
the linear power generation cost of the thermal power generating unit i in the four sections in the t period is obtained; kwIn order to discard the wind penalty factor,
Figure FDA0002603628150000039
the wind power waste air volume is obtained; t is the total time period number compiled by the power generation and transmission plan; n is a radical ofGThe total number of the thermal power generating units at the transmitting end and the receiving end; w is the total number of the wind turbine generators;
constraint conditions are as follows:
a) direct current operation constraint conditions:
i) DC link line output constraints
Figure FDA0002603628150000041
In the formula, Pd,tThe running power of the direct current connecting line d in the time period t;
Figure FDA0002603628150000042
respectively is the output upper limit and the output lower limit of the direct current connecting line in the t period;
ii) direct current adjacent time interval output force adjustment direction constraint
Figure FDA0002603628150000043
In the formula, xtAn indication of whether the dc link power is adjusted during the time period t,
Figure FDA0002603628150000044
all the discrete variables are 0-1 discrete variables which respectively represent whether the direct current tie line climbs or not and whether the direct current tie line slides or not in the time period t; if yes, the value is 1, otherwise the value is 0;
iii) direct Current Outlet adjustment Rate constraint
Figure FDA0002603628150000045
In the formula (I), the compound is shown in the specification,dcthe amplitude is adjusted for the minimum of the dc link,
Figure FDA0002603628150000046
adjusting the amplitude value for the maximum of the direct current tie line;
iv) direct-current output adjustment continuity constraint
Figure FDA0002603628150000047
V) direct current adjustment interval constraint
Figure FDA0002603628150000048
In the formula, H is the set number of the interval time of the direct current adjustment,
Figure FDA0002603628150000049
all the discrete variables are 0-1 discrete variables, and respectively represent that the output of the direct current connecting line starts to be adjusted and finishes to be adjusted at the moment t;
vi) restriction of adjustment times of DC output
Figure FDA0002603628150000051
In the formula, NmaxMaximum number of daily adjustments for dc link power;
vii) direct Current daily transaction volume constraints
Figure FDA0002603628150000052
In the formula, E is daily planned transaction electric quantity of the direct current connecting line, and rho is an allowable transmission deviation proportion;
b) safety operation constraint condition of AC system
I) output constraint of thermal power generating unit
Figure FDA0002603628150000053
In the formula, Pi Gmax、Pi GminRespectively representing the upper limit and the lower limit of the output of the thermal power generating unit i,
Figure FDA0002603628150000054
the output of the thermal power generating unit i in the time period t is obtained;
ii) thermal power generating unit climbing restraint
Figure FDA0002603628150000055
In the formula, RUi、RDiThe climbing speed and the landslide speed of the unit i are respectively set;
iii) Power balance constraints
Figure FDA0002603628150000056
In the formula (I), the compound is shown in the specification,
Figure FDA0002603628150000057
the system comprises a thermal power generating unit and a wind power plant which are respectively a power grid A at a sending end;
Figure FDA0002603628150000058
a set of load nodes of a sending-end power grid A;
Figure FDA0002603628150000059
the output of the wind power plant w in the time period t;
Figure FDA00026036281500000510
a predicted value of a load node k of a sending end power grid A in a t period is obtained;
iv) Positive and negative rotation backup constraints
Positively rotating for standby:
Figure FDA0002603628150000061
Figure FDA0002603628150000062
in the formula (I), the compound is shown in the specification,
Figure FDA0002603628150000063
for the predicted force values of the wind farm w during the time period t,
Figure FDA0002603628150000064
the positive reserve capacity required by the sending-end power grid A at the moment t; w is au、wDRespectively is a wind power positive standby coefficient and a load standby coefficient;
negative rotation for standby:
Figure FDA0002603628150000065
Figure FDA0002603628150000066
in the formula, Rt -AThe negative reserve capacity required by the sending-end power grid A at the moment t; w is adThe wind power negative standby coefficient;
v) tidal current safety constraints
Figure FDA0002603628150000067
In the formula (I), the compound is shown in the specification,
Figure FDA0002603628150000068
respectively representing power transfer distribution factors of a thermal power generating unit i, a wind power plant w, a load k and a direct current connecting line;
Figure FDA0002603628150000069
Flthe upper limit and the lower limit of the transmission of the AC line l are respectively;
vi) wind power constraints
Figure FDA00026036281500000610
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