CN109638870B - Phase modulator configuration method of extra-high voltage direct current transmission end power grid - Google Patents
Phase modulator configuration method of extra-high voltage direct current transmission end power grid Download PDFInfo
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- H—ELECTRICITY
- 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 utility model belongs to the technical field of power grid operation and control, and particularly relates to a phase modulator configuration method of an extra-high voltage direct current transmission end power grid, in particular to a phase modulator configuration method of an extra-high voltage direct current transmission end system power grid. The utility model comprises the following steps: acquiring operating parameters of an extra-high voltage direct current transmission end power grid; determining the configuration number of phase modulators; performing reactive power and voltage sensitivity analysis on an extra-high voltage direct current transmission end power grid to obtain a primary selection set of configuration positions of a phase modulator; calculating a phase modulator configuration strategy by adopting an artificial bee colony algorithm; and obtaining the configuration scheme of the phase modulator of the extra-high voltage direct current transmission end power grid. The utility model can more effectively realize the effective configuration of the phase modulator on the power grid of the extra-high voltage direct current transmission end, improve the voltage operation stability of the power grid and provide a technical basis and a practical method for the operation and control of an extra-high voltage direct current transmission system. With the increase of extra-high voltage alternating current and direct current transmission systems, the development of a reactive power optimization configuration strategy has great demand inevitably, and the method has good commercial development prospect.
Description
Technical Field
The utility model belongs to the technical field of power grid operation and control, and particularly relates to a phase modulator configuration method of an extra-high voltage direct current transmission end power grid, in particular to a phase modulator configuration method of an extra-high voltage direct current transmission end system power grid.
Background
The primary energy and load in China are distributed in a reverse direction, and in order to meet the urgent requirements of clean energy delivery, load center power supply, energy conservation, emission reduction and the like, the national power grid is vigorously developed to be suitable for the ultra-high voltage alternating current and direct current technology of long-distance and large-capacity power transmission. The extra-high voltage alternating current and direct current transmission project positioning and the long-distance and large-capacity delivery of large-scale energy bases become main ways for relieving the contradiction between the Chinese energy resources and the economic layout. At present, China is in the development transition period of an extra-high voltage power grid, and the extra-high voltage alternating current and direct current hybrid power grid is initially scaled along with the successive production of extra-high voltage alternating current and direct current projects.
The ultra-high voltage direct current transmission system has more problems in the aspect of voltage stable operation, the transmission capacity of the ultra-high voltage direct current transmission system is huge, once a bipolar locking accident occurs, the system suffers huge disturbance, large-range transient voltage is increased, and wind power is disconnected; on the other hand, the direct current transmission system consumes a large amount of reactive power of the system during normal operation, and a large amount of reactive power supplies are needed to support the system. With the continuous increase of installed wind power and grid-connected capacity, the safe and stable operation of the voltage of the extra-high voltage direct current transmission system is seriously challenged.
The key point of the problem is how to perform dynamic reactive compensation configuration on a power grid, traditional reactive compensation equipment such as a capacitor and a reactor can only be used as static reactive compensation equipment, and various dynamic reactive compensation equipment based on modern power electronic technology is often affected by bus voltage in performance when a system needs reactive support. The phase modulator is used as a classical dynamic reactive power regulation device, has advantages in small size and performance, and has wide application prospect in an extra-high voltage direct current network.
In China, the application history of the phase modifier is long, and later, with the maturity of the power electronic device technology and the aging of phase modifier equipment, the static dynamic reactive compensation device, SVC, STATCOM and the like gradually replace the application of the phase modifier, and after a plant network is separated, the application of the phase modifier in a power grid is not developed. However, with the implementation of the extra-high voltage direct current project, the hazards of sending end power frequency overvoltage control, receiving end power grid interlocking reflection and commutation failure are gradually increased, dynamic reactive compensation equipment such as SVC and STATCOM which are affected by voltage and output the power has a demand for sub-transient state output, fast large-capacity reactive demand under commutation failure and transient state is prevented, direct current fast recovery is assisted, the response capability is insufficient, and the phase feeding capability, the sub-transient state output characteristic and the excitation capability of the phase modulator can just meet the demand.
Disclosure of Invention
The utility model provides a phase modulator configuration method of an extra-high voltage direct current transmission end power grid, aiming at solving the problems of the operation technology of an extra-high voltage direct current transmission system in the prior art by configuring a phase modulator and improving the voltage stability of the extra-high voltage direct current transmission end power grid by establishing a voltage stability evaluation index of an extra-high voltage direct current power grid and an optimized configuration strategy of the phase modulator.
The technical scheme adopted by the utility model for solving the technical problems is as follows:
a phase modulator configuration method of an extra-high voltage direct current transmission end power grid is used for realizing the stable operation of the voltage of an extra-high voltage direct current transmission system through the optimal configuration of a phase modulator based on the voltage dynamic characteristics of the system in the extra-high voltage direct current transmission end power grid, and comprises the following steps:
acquiring operation parameters of an extra-high voltage direct current transmission end power grid;
determining the configuration number of phase modulators;
analyzing reactive power and voltage sensitivity of the extra-high voltage direct current transmission end power grid to obtain a primary selection set of configuration positions of the phase modulator;
step four, adopting an artificial bee colony algorithm to calculate a phase modulator configuration strategy;
and step five, obtaining a configuration scheme of the phase modulator of the extra-high voltage direct current transmission end power grid.
And step three, carrying out reactive power and voltage sensitivity analysis on the extra-high voltage direct current transmission end power grid to obtain a primary selection set of the configuration positions of the phase modulator, wherein the primary selection set comprises the following steps:
a. calculating the sensitivity of a reactive power injection point and the alternating current bus voltage of the direct current converter station;
b. calculating the sensitivity of reactive power injection points and the bus voltage of key nodes of a sending end system;
c. calculating the sensitivity of the reactive power injection point and the bus voltage of the access point of the wind power plant group;
d. and selecting the position with larger sensitivity value as the initial selection position of the phase modulator configuration according to the sensitivity calculation result.
Adopting an artificial bee colony algorithm to calculate a phase modulator configuration strategy, comprising the following steps of:
(1) initializing a configuration strategy of a phase modulator, namely an initial bee colony, and randomly giving the number of bees, the iteration times and the maximum acquisition times of a single bee;
(2) establishing an evaluation index and an evaluation function;
(3) performing honey source calculation, taking the bee with the best fitness as a leading bee, and taking the bee with the lower fitness as a following bee;
(4) carrying out honey source position replacement;
(5) setting a general bee colony with good fitness as a leading bee by judging the advantages and disadvantages of the leading bee and the honey source, returning to the step (2) if the search frequency limit is not reached, and continuously searching the honey source;
(6) if the search times limit is reached, outputting the current optimal honey source position, namely the optimal configuration strategy of the phase modulator;
in the first step, the extra-high voltage direct current transmission end power grid is a complex transmission end power grid power transmission system consisting of a positive and negative 800 kilovolt high-voltage direct current transmission system, a 500 kilovolt alternating current power grid, a thermal power plant, a hydraulic power plant and a large number of wind power grid-connected power supplies;
the obtained operation parameters of the ultra-high voltage direct current transmission end power grid are grid structure parameters, transmission line parameters, direct current transmission system parameters, thermal generator set parameters, hydroelectric generator set parameters and wind turbine set parameters required by power grid calculation and control.
In the third step, the reactive power and voltage sensitivity analysis of the extra-high voltage direct current transmission end power grid refers to the sensitivity of reactive power injection to the bus voltage is calculated according to the following formula:
f (X, T, C) ═ 0 and
wherein F is a power balance equation of the power grid; x is a state vector of the power grid, and comprises a voltage amplitude value, a phase angle and the like of a node bus; t is a control variable of the power grid, and comprises active and reactive injection power of each node bus; c is a constant parameter of the power grid, such as admittance of a line; v is a bus voltage to be solved with a certain sensitivity; q is reactive injection power of a certain node bus; f is a power balance equation of the power grid; x is a state vector of the power grid, and comprises a voltage amplitude value, a phase angle and the like of a node bus; and T is a control variable of the power grid.
The establishment of the evaluation index and the evaluation function refers to the evaluation of the index of the voltage rise of each main bus after the bipolar latching fault of the direct current system occurs, and is specifically calculated according to the following formula:
wherein, FVIs an evaluation index function; vLIs the converter station ac bus voltage; vL 0The initial value of the AC bus voltage of the converter station is obtained; vLmaxThe maximum value of the AC bus voltage of the converter station is set; vBiBus voltage of a key node of a certain power grid; vBi 0The initial value of the bus voltage of a key node of a certain power grid is obtained;
the maximum limit value of the bus voltage of a key node of a certain power grid is obtained; VWi is the bus voltage of a certain wind grid-connected node; vWi 0The initial amount of the bus voltage of a certain wind grid-connected node is obtained; vWimaxFor a certain windThe maximum limit value of the bus voltage of the grid-connected node; omega is a weight coefficient; n is a radical ofBIs the number of key nodes of a certain power grid, NWAnd i is a node, wherein the number of the wind grid-connected nodes is a certain number.
The honey source calculation is carried out, the bee with the best fitness serves as a leading bee, and the bee with the lower fitness serves as a following bee: the honeybees search for honey sources through cross search to generate new individuals.
The honey source position replacement is carried out according to the following rules:
the selection rule is as follows:
in the formula, PiProbability of selecting honey for honey source; fit (x)i) A fitness function for the honey source; n is the number of the positions of the honey sources, and i is the position of the honey sources.
The sensitivity calculation is that the direct current transmission system is connected with the alternating current bus of the converter station through the converter transformer, and the change of the control mode and the control parameter of the direct current transmission system can influence the change of the bus voltage of the alternating current system, particularly the bus voltage of the converter station; analyzing voltage sensitivity factors of the alternating current and direct current system by adopting a decoupling algorithm; the direct current system is equivalent to the load equivalent to the active power and the reactive power of the corresponding converter, the sensitivity of the voltage of the alternating current system to the power of the converter is obtained, the calculation process is simplified, and meanwhile, the accuracy of the result is guaranteed;
processing according to the mode, solving the sensitivity of the node voltage of the alternating-current and direct-current hybrid power transmission system to the transmission power, and converting the node voltage into a pure alternating-current system; firstly, setting node bus power as a control variable TacIs represented by the formula, wherein PaAnd QaRespectively representing active and reactive power, P, of AC system transmissiondAnd QdRespectively representing active power and reactive power of a direct current system;
Tac＝[Pa，Pd，Qa，Qd]
let AC transmission system voltage amplitude andphase angle is a state variable expressed as XacAnd if the state variable comprises an alternating current bus of the converter station, rewriting a power flow equation of the alternating current and direct current transmission system into:
in the formula: p (X)ac)、Q(Xac) The active power and the reactive power are injected into the node obtained by voltage calculation; then, the variable T is controlledacFor state variable XacThe sensitivity matrix of (a) is as follows:
in the formula: j. the design is a squarefRepresenting a Jacobian matrix during load flow calculation of the AC/DC hybrid power transmission system, and thus obtaining a sensitivity matrix of node voltage to node bus power;
Xac: the voltage amplitude and the phase angle of the AC power transmission system are state variables;
Tac: node bus power;
fac: and (3) a power flow equation of the alternating current and direct current power transmission system.
The artificial bee colony algorithm is an optimization method provided by simulating bee behaviors, is a specific application of a cluster intelligence idea, does not need to know special information of problems, only needs to compare the advantages and the disadvantages of the problems, finally enables a global optimum value to be highlighted in a colony through the local optimization behavior of each artificial bee individual, and has higher convergence speed;
the minimal search model for swarm intelligence comprises three basic components: food sources, employed bees and non-employed bees; two of the most basic behavioral models: recruiting bees and abandoning a food source for it; in the formation process of swarm intelligence, the exchange of information among bees is the most important ring; the dance area is the most important information exchange place in the honeycomb; the dance of bees is called swinging dance; the information of the food source is shared with other bees in a dance area in a swinging dance mode, and the bee is led to express the earning rate of the food source through the duration of the swinging dance and the like, so that the following bees can observe a large amount of dances and select which food source to collect honey according to the earning rate; the rate of return is proportional to the likelihood of the food source being selected; thus, the probability of bees being recruited to a food source is directly proportional to the profitability of the food source;
the specific steps for solving the phase modulator configuration strategy by adopting the artificial bee colony algorithm are as follows:
(1) assigning values to various parameters of the artificial bee colony algorithm, such as the size of a colony, the number of hired bees, the number of observed bees, the number of detected bees, the local maximum search times, the iteration times and the solution latitude;
(2) generating a half of solution of the population number through random numbers, and calculating the fitness value of each solution; namely, calculating a voltage stability index under the configuration condition of each initial phase modulator;
(3) the iteration number variable in the bee colony algorithm is assigned to be 1;
(4) traversing all previous solutions, and executing the following steps (5) - (8) for each solution;
(5) finding a new solution within the domain in which the solution is located;
(6) calculating the fitness value of the new solution;
(7) comparing the new solution with the original solution, and keeping the solution with high fitness;
(8) if the original solution is not updated, adding 1 to the local search times; if the local search times are updated, setting the local search times to be 0;
(9) calculating probability values of observation bee selection following each hiring bee in the bee colony algorithm;
(10) randomly selecting a solution according to the calculation probability, carrying out local search around the solution, finding a new solution, calculating the fitness, and selecting to keep or update according to the fitness;
(11) traversing all solutions in the algorithm to see whether the maximum searching times is reached; if so, abandoning the solution and generating a new solution to replace;
(12) recording the currently found optimal solution;
(13) adding 1 for each execution of the loop;
(14) judging whether a maximum cycle number set value is reached or not, and turning to the step (4) if not; and ending the algorithm, and recording the current solution, namely the global optimal solution.
Compared with the prior art, the utility model has the beneficial effects that:
the utility model can more effectively realize the effective configuration of the phase modulator on the power grid of the extra-high voltage direct current transmission end, improve the voltage operation stability of the power grid and provide a technical basis and a practical method for the operation and control of an extra-high voltage direct current transmission system.
The utility model considers the dynamic process of the system voltage after the serious fault of the direct current transmission system, can more effectively and reliably carry out the configuration strategy of the phase modulator, and provides a technical basis and a practical method for the voltage operation and control of the extra-high voltage direct current power grid.
The method is based on the analysis of serious faults and sensitivity of a direct current system, establishes a voltage dynamic evaluation index, and adopts an artificial bee colony algorithm to solve, so that the reliability and the practicability of a phase modulator configuration strategy are greatly improved.
The method fully considers the voltage transient characteristics of the system, establishes the evaluation index of the evaluation configuration strategy through the voltage transient characteristics after the direct current blocking fault, can reflect the voltage dynamic characteristics of the extra-high voltage direct current system more truly, and obtains a real and reliable reactive power optimization configuration strategy by continuously optimizing the transient operation mode through simulation software. On the basis of sensitivity analysis, an initial optimal configuration set is formed firstly, and then an artificial bee colony algorithm is adopted for solving, so that an optimal configuration scheme is easier to find, and the method is easy to implement. With the increase of extra-high voltage alternating current and direct current transmission systems, the development of the reactive power optimization configuration strategy of the utility model has great demand and good commercial development prospect.
Drawings
The utility model will be described in further detail with reference to the drawings and specific embodiments for facilitating understanding and practicing the utility model by those skilled in the art, but it should be understood that the scope of the utility model is not limited to the specific embodiments.
FIG. 1 is a general flow diagram of the present invention;
FIG. 2 is a schematic diagram of a sensitivity calculation flow;
FIG. 3 is a schematic diagram of an artificial bee colony algorithm;
FIG. 4 is a comparison graph of system simulation before and after configuring a phase modulator.
Detailed Description
As shown in fig. 1 to 4, the phase modulator configuration method for an extra-high voltage dc transmission end power grid of the present invention is a method for implementing stable operation of an extra-high voltage dc transmission system voltage by optimal configuration of a phase modulator based on the voltage dynamic characteristics of the system in the extra-high voltage dc transmission end power grid, and includes the following steps:
acquiring operation parameters of an extra-high voltage direct current transmission end power grid;
determining the configuration number of phase modulators;
analyzing reactive power and voltage sensitivity of the extra-high voltage direct current transmission end power grid to obtain a primary selection set of configuration positions of the phase modulator;
a. calculating the sensitivity of the reactive power injection point and the alternating current bus voltage of the direct current converter station;
b. calculating the sensitivity of reactive power injection points and the bus voltage of key nodes of a sending end system;
c. calculating the sensitivity of the reactive power injection point and the busbar voltage of the access point of the wind power plant group;
d. and selecting the position with larger sensitivity value as the initial selection position of the phase modulator configuration according to the sensitivity calculation result.
Step four, adopting an artificial bee colony algorithm to calculate a phase modulator configuration strategy;
(1) initializing a configuration strategy of a phase modulator, namely an initial bee colony, and randomly giving the number of bees, the iteration times and the maximum acquisition times of a single bee;
(2) establishing an evaluation index and an evaluation function;
(3) performing honey source calculation, taking the bee with the best fitness as a leading bee, and taking the bee with the lower fitness as a following bee;
(4) replacing the position of the honey source;
(5) setting a general bee colony with good fitness as a leading bee by judging the advantages and disadvantages of the leading bee and the honey source, returning to the step (2) if the search frequency limit is not reached, and continuously searching the honey source;
(6) and if the search times limit is reached, outputting the current optimal honey source position, namely the optimal configuration strategy of the phase modulator.
And step five, obtaining a configuration scheme of the phase modulator of the extra-high voltage direct current transmission end power grid.
In the first step, the extra-high voltage direct current transmission end power grid is a complex transmission end power grid power transmission system consisting of a positive and negative 800 kilovolt high-voltage direct current transmission system, a 500 kilovolt alternating current power grid, a thermal power plant, a hydraulic power plant and a large number of wind power grid-connected power supplies.
In the first step, the operation parameters of the ultra-high voltage direct current transmission end power grid are parameters required by power grid calculation and control, such as grid structure parameters, transmission line parameters, direct current transmission system parameters, thermal generator set parameters, hydroelectric generator set parameters, wind turbine set parameters and the like.
In the third step, the reactive power and voltage sensitivity analysis of the extra-high voltage direct current transmission end power grid refers to the sensitivity of reactive power injection to the bus voltage is calculated according to the following formula:
f (X, T, C) ═ 0 and
wherein F is a power balance equation of the power grid; x is a state vector of the power grid, and comprises a voltage amplitude value, a phase angle and the like of a node bus; t is a control variable of the power grid, and comprises active and reactive injection power of each node bus; and C is a constant parameter of the power grid, such as admittance of a line and the like. V is a bus voltage to be solved with a certain sensitivity; q is reactive injection power of a certain node bus; f is a power balance equation of the power grid; x is a state vector of the power grid, and comprises a voltage amplitude value, a phase angle and the like of a node bus; and T is a control variable of the power grid.
In the fourth step, establishing the evaluation index and the evaluation function means evaluating the index evaluation index of the voltage rise of each main bus after the bipolar latching fault of the direct current system occurs, and specifically calculating according to the following formula:
wherein, FVIs an evaluation index function; vLIs the converter station ac bus voltage; vL 0The initial value of the AC bus voltage of the converter station is obtained; vLMAXThe maximum value of the AC bus voltage of the converter station is set; vBiBus voltage of a key node of a certain power grid; vBi 0The initial value of the bus voltage of a key node of a certain power grid is obtained;
the maximum limit value of the bus voltage of a key node of a certain power grid is obtained; vWiA certain wind grid-connected node bus voltage; vWi 0The initial amount of the bus voltage of a certain wind grid-connected node is obtained; vWiMAXThe maximum limit value of the bus voltage of a certain wind grid-connected node is obtained; omega is a weight coefficient; n is a radical of hydrogenBIs the number of key nodes of a certain power grid, NWAnd i is a node, wherein the number of the wind grid-connected nodes is a certain number.
And in the fourth step, honey source calculation is carried out, the bee with the best fitness serves as a leading bee, and the bee with the lower fitness serves as a following bee: the honeybees search for honey sources through cross-sense search to generate new individuals.
The honey source position replacement in the fourth step is performed according to the following rules:
the selection rule is as follows:
in the formula, PiProbability of selecting honey for honey source; fit (x)i) The fitness function N of the honey source is the number of the positions of the honey source, and i is the position of the honey source.
Fig. 1 is a general flow chart of the present invention, which is consistent with the above calculation steps, and it is worth explaining that it can be seen from the flow in the chart, the method forms an initial candidate bus set by establishing sensitivity analysis, establishes an evaluation index reflecting voltage dynamic characteristics, and solves the evaluation index by a bee colony algorithm, which is the essential difference from other methods.
Fig. 2 is a schematic diagram of a sensitivity calculation process, and since the dc transmission system is connected to the ac bus of the converter station through the converter transformer, the variation of the dc transmission system control mode and control parameters may affect the variation of the ac system bus voltage, especially the converter station bus voltage. The utility model adopts a decoupling algorithm to analyze the voltage sensitivity factor of the AC/DC system. The direct current system is equivalent to the load equivalent to the active power and the reactive power of the corresponding converter, the sensitivity of the voltage of the alternating current system to the power of the converter is obtained, the calculation process is simplified, and meanwhile, the accuracy of the result is guaranteed.
And processing according to the mode, solving the sensitivity of the node voltage of the alternating-current and direct-current hybrid power transmission system to the transmission power, and converting the node voltage into a pure alternating-current system. Firstly, setting node bus power as control variable TacIs represented by the formula, wherein PaAnd QaRespectively representing active and reactive power, P, transmitted by the AC systemdAnd QdRespectively representing the active and reactive power of the dc system.
Tac＝[Pa，Pd，Qa，Qd]
Let AC transmission system voltage amplitude and phase angle be state variables and be expressed as XacAnd if the state variable comprises an alternating current bus of the converter station, the alternating current and direct current transmission system power flow equation can be rewritten as follows:
in the formula: p (X)ac)、Q(Xac) The active power and the reactive power are injected into the node obtained by voltage calculation; then, the variable T is controlledacFor state variable XacThe sensitivity matrix of (a) is as follows:
in the formula: j. the design is a squarefAnd representing a jacobian matrix in the load flow calculation of the AC/DC hybrid power transmission system, thereby obtaining a sensitivity matrix of the node voltage to the node bus power.
Xac: the voltage amplitude and the phase angle of the AC power transmission system are state variables;
Tac: node bus power;
fac: and (3) a power flow equation of the alternating current and direct current power transmission system.
The calculation of the equation matrix can refer to the load flow calculation of an alternating current system, is relatively mature and can be realized by the existing calculation method.
Fig. 3 is a schematic diagram of an artificial bee colony algorithm. The artificial bee colony algorithm is an optimization method provided by simulating bee behaviors, is a specific application of a colony intelligent idea, and is mainly characterized in that special information of problems does not need to be known, only the advantages and the disadvantages of the problems need to be compared, and finally, a global optimum value is highlighted in a colony through local optimization behaviors of each artificial bee individual, so that the convergence rate is high.
The minimal search model for swarm intelligence comprises three basic components: food sources, employed bees and non-employed bees; two of the most basic behavioral models: recruiting bees and abandoning a food source. In the formation of swarm intelligence, the exchange of information between bees is one of the most important. The dance area is the most important information exchange place in the honeycomb. The dance of bees is called swinging dance. The information of the food source is shared with other bees in the dance area in a swinging dance mode, and the bee is led to express the earning rate of the food source through the duration of the swinging dance and the like, so that the following bees can observe a large amount of dances and select which food source to collect honey according to the earning rate. The rate of return is proportional to the likelihood that the food source is selected. Thus, the probability of bees being recruited to a food source is directly proportional to the profitability of the food source.
The specific steps for solving the phase modulator configuration strategy by adopting the artificial bee colony algorithm are as follows:
(1) assigning values to various parameters of the artificial bee colony algorithm, such as the size of a colony, the number of hired bees, the number of observed bees, the number of detected bees, the local maximum search times, the iteration times and the solution latitude;
(2) and generating half of solutions of the population number through random numbers, and calculating the fitness value of each solution. Namely, calculating a voltage stability index under the configuration condition of each initial phase modulator;
(3) assigning an iteration variable in the bee colony algorithm to be 1;
(4) traversing all previous solutions, and executing the following steps (5) - (8) for each solution;
(5) finding a new solution within the domain in which the solution is located;
(6) calculating the fitness value of the new solution;
(7) comparing the new solution with the original solution, and keeping the solution with high fitness;
(8) if the original solution is not updated, adding 1 to the local search times; if the local search times are updated, setting the local search times to be 0;
(9) calculating probability values of observation bee selection following each hiring bee in the bee colony algorithm;
(10) randomly selecting a solution according to the calculation probability, carrying out local search around the solution, finding a new solution, calculating the fitness, and selecting to keep or update according to the fitness;
(11) and traversing all solutions in the algorithm to see whether the maximum searching times is reached. If so, abandoning the solution and generating a new solution to replace;
(12) recording the currently found optimal solution;
(13) adding 1 for each execution of the loop;
(14) judging whether a maximum cycle number set value is reached or not, and turning to the step (4) if not; and ending the algorithm, and recording the current solution, namely the global optimal solution.
The detailed steps and formulas of the bee colony algorithm are referred to by corresponding literature references.
Fig. 4 is a simulation comparison curve of the system before and after the phase modulator is configured. And (4) analyzing and verifying by taking the northeast to Shandong extra-high voltage direct current transmission system as an example. Zalutte-Qingzhou extra-high voltage direct current engineering (hereinafter referred to as Zaqing direct current) is put into production at the end of 2017 in the Hezhou town of Qingzhou city in south to Shandong. The direct current rated voltage is +/-800 kilovolts, the designed rated power is 10000MW, and the direct current engineering is the first extra-high voltage direct current engineering of the northeast power grid. The cross section of the wire of the direct current transmission line is 8 multiplied by 1250mm2, the transmitting end converter station is the Zalutte Bayanta station address according to the current recommended station address, and the length of the direct current line is 1223.6 km.
And (3) the extra-high voltage direct current programming bipolar from Zalutte to Qingzhou, wherein a direct current outlet wire is 1 loop, and a grounding electrode outlet wire is 1 loop. The valve group wiring mode is that two 12-pulse valve groups are connected in series for each pole; the recommended scheme of the converter station is 28, the capacity of a single-phase double winding is 509.35MVA, Uk is 21%, the total capacity of the capacity reactive compensation of the converter station is about 6665Mvar, and the converter station is divided into 4 groups and 20 groups temporarily.
The Liaoning power grid is connected with the Jilin power grid in the north direction through a 4-circuit 500KV line, is connected with the Heilongjiang power grid through an Yimu direct current system, is connected with the Mongolian power grid in the fourth direction through a 6-circuit 500KV line, and is connected with the North China power grid in the south direction through direct currents back to back. Before the Zulute direct current is put into operation, the Liaoning power grid is a receiving end power grid and a load center in the northeast region, power is received from Mongolian, Yimin and Jilin power grids, the northeast power grid is in the trend of west power supply to east and north power supply to south, and Liaoning is used as the load center of the northeast power grid and bears abundant power supplied by other provinces. After the zalutter direct current is put into operation, the northeast power grid mainly transmits electricity from east to west and transmits electricity to the outside of the area by taking the zalutter as a power receiving center, the overall pattern of the power distribution of the northeast power grid is greatly changed, and the dynamic characteristics of the system are also greatly changed. Particularly, the transmission capacity of an extra-high voltage direct current transmission system is large, once a bipolar locking accident occurs, the system suffers from large disturbance, large-range transient voltage is increased, and wind power is disconnected; on the other hand, the direct current transmission system consumes a large amount of reactive power of the system during normal operation, and a large amount of reactive power supplies are needed to support the system. With the continuous increase of installed wind power and grid-connected capacity, the safe and stable operation of the voltage of an extra-high voltage direct current transmission system is seriously challenged, and the voltage stability of the system needs to be improved by configuring dynamic reactive compensation equipment such as a phase modulator and the like.
The simulation and modeling of the power grid are performed under the ADPSS software. The implementation of the swarm algorithm is carried out on an MATLAB software platform; data interaction and coordination between the two pieces of software are carried out by manual operation; the number of the configured initial phase modulators is 3. Under three modes of not configuring a phase modulator and manually configuring the phase modulator and the phase modulator configured by the method, the dynamic characteristic curve of the bus voltage of the converter station is shown in figure 4 after the bipolar locking fault occurs in the system. It can be seen that after the phase modulator position is optimally configured, the transient improvement of the bus voltage of the converter station is obviously inhibited, and the effectiveness and the practicability of the strategy are proved.
Claims (7)
1. A phase modulator configuration method of an extra-high voltage direct current transmission end power grid is characterized by comprising the following steps: in an extra-high voltage direct current transmission end power grid, based on the voltage dynamic characteristics of the system, the stable operation of the voltage of an extra-high voltage direct current transmission system is realized through the optimized configuration of a phase modulator, and the method comprises the following steps:
acquiring operation parameters of an extra-high voltage direct current transmission end power grid;
determining the configuration number of phase modulators;
analyzing reactive power and voltage sensitivity of the extra-high voltage direct current transmission end power grid to obtain a primary selection set of configuration positions of the phase modulator; the method comprises the following steps:
a. calculating the sensitivity of a reactive power injection point and the alternating current bus voltage of the direct current converter station;
b. calculating the sensitivity of reactive power injection points and the bus voltage of key nodes of a sending end system;
c. calculating the sensitivity of the reactive power injection point and the bus voltage of the access point of the wind power plant group;
d. selecting a position with a larger sensitivity value as a primary selection position configured by the phase modulator according to the sensitivity calculation result;
step four, adopting an artificial bee colony algorithm to calculate a phase modulator configuration strategy; the method comprises the following steps:
(1) initializing a configuration strategy of a phase modulator, namely an initial bee colony, and randomly giving the number of bees, the iteration times and the maximum acquisition times of a single bee;
(2) establishing an evaluation index and an evaluation function; the establishment of the evaluation index and the evaluation function refers to the evaluation of the index of the voltage rise of each main bus after the bipolar latching fault of the direct current system occurs, and is specifically calculated according to the following formula:
wherein, FVIs an evaluation index function; vLIs the converter station ac bus voltage; vL 0The initial value of the AC bus voltage of the converter station is obtained; vLmaxThe maximum value of the AC bus voltage of the converter station is set; vBiBus voltage of a key node of a certain power grid; vBi 0The initial value of the bus voltage of a key node of a certain power grid is obtained;
the maximum limit value of the bus voltage of a key node of a certain power grid is obtained; vWiA certain wind grid-connected node bus voltage; vWi 0The initial amount of the bus voltage of a certain wind grid-connected node is obtained; vWimaxThe maximum limit value of the bus voltage of a certain wind grid-connected node is obtained; omega is a weight coefficient; n is a radical of hydrogenBIs the number of key nodes of a certain power grid, NWThe number of a certain wind grid-connected node is I;
(3) performing honey source calculation, taking the bee with the best fitness as a leading bee, and taking the bee with the lower fitness as a following bee;
(4) carrying out honey source position replacement;
(5) setting a general bee colony with good fitness as a leading bee by judging the advantages and disadvantages of the leading bee and the honey source, returning to the step (2) if the search frequency limit is not reached, and continuously searching the honey source;
(6) if the search times limit is reached, outputting the current optimal honey source position, namely the optimal configuration strategy of the phase modulator;
and step five, obtaining a configuration scheme of the phase modulator of the extra-high voltage direct current transmission end power grid.
2. The phase modulator configuration method of the extra-high voltage direct current transmission end power grid according to claim 1, characterized by comprising the following steps: in the first step, the extra-high voltage direct current transmission end power grid is a complex transmission end power grid power transmission system consisting of a positive and negative 800 kilovolt high-voltage direct current transmission system, a 500 kilovolt alternating current power grid, a thermal power plant, a hydraulic power plant and a large number of wind power grid-connected power supplies;
the operation parameters of the ultra-high voltage direct current transmission end power grid are grid structure parameters, transmission line parameters, direct current transmission system parameters, thermal generator set parameters, hydroelectric generator set parameters and parameters required by wind turbine generator set parameter power grid calculation and control.
3. The phase modulator configuration method of the extra-high voltage direct current transmission end power grid according to claim 1, characterized by comprising the following steps: in the third step, the reactive power and voltage sensitivity of the extra-high voltage direct current transmission end power grid are analyzed as follows:
f (X, T, C) ═ 0 and
wherein F is a power balance equation of the power grid; x is a state vector of the power grid and comprises a voltage amplitude value and a phase angle of a node bus; t is a control variable of the power grid, and comprises active and reactive injection power of each node bus; c is a constant parameter of the power grid, including the admittance of the line; v is a bus voltage to be solved with a certain sensitivity; q is reactive injection power of a certain node bus; f is a power balance equation of the power grid; x is a state vector of the power grid and comprises a voltage amplitude value and a phase angle of a node bus; and T is a control variable of the power grid.
4. The phase modulator configuration method of the extra-high voltage direct current transmission end power grid according to claim 1, characterized by comprising the following steps: the honey source calculation is carried out, the bee with the best fitness serves as a leading bee, and the bee with the lower fitness serves as a following bee: the honeybees search for honey sources through cross search to generate new individuals.
5. The phase modulator configuration method of the extra-high voltage direct current transmission end power grid according to claim 1, characterized by comprising the following steps: the honey source position replacement is carried out according to the following rules:
the selection rule is as follows:
in the formula, PiProbability of selecting honey for honey source; fit (x)i) A fitness function for the honey source; n is the number of positions of the honey sources, and i is the position of the honey sources.
6. The phase modulator configuration method of the extra-high voltage direct current transmission end power grid according to claim 1, characterized by comprising the following steps: the sensitivity calculation is that the direct current transmission system is connected with the alternating current bus of the converter station through the converter transformer, and the change of the control mode and the control parameter of the direct current transmission system can influence the change of the bus voltage of the alternating current system, including the bus voltage of the converter station; analyzing voltage sensitivity factors of the alternating current and direct current system by adopting a decoupling algorithm; the direct current system is equivalent to the load equivalent to the active power and the reactive power of the corresponding converter, the sensitivity of the voltage of the alternating current system to the power of the converter is obtained, the calculation process is simplified, and meanwhile, the accuracy of the result is guaranteed;
processing according to the mode, solving the sensitivity of the node voltage of the alternating-current and direct-current hybrid power transmission system to the transmission power, and converting the node voltage into a pure alternating-current system; firstly, setting node bus power as control variable TacIs represented by the formula, wherein PaAnd QaRespectively representing active and reactive power, P, transmitted by the AC systemdAnd QdRespectively representing active power and reactive power of a direct current system;
Tac＝[Pa,Pd,Qa,Qd]
let AC transmission system voltage amplitude and phase angle be state variables and be expressed as XacAnd if the state variable comprises an alternating current bus of the converter station, rewriting a power flow equation of the alternating current and direct current transmission system into:
in the formula: p (X)ac)、Q(Xac) The active power and the reactive power are injected into the node obtained by voltage calculation; then, the variable T is controlledacFor state variable XacThe sensitivity matrix of (a) is as follows:
in the formula: j. the design is a squarefRepresenting a Jacobian matrix during load flow calculation of the AC/DC hybrid power transmission system, and thus obtaining a sensitivity matrix of node voltage to node bus power;
Xacthe voltage amplitude and the phase angle of the AC power transmission system are state variables;
Tacnode bus power;
fac: and (3) a power flow equation of the alternating current and direct current power transmission system.
7. The phase modulator configuration method of the extra-high voltage direct current transmission end power grid according to claim 1, characterized by comprising the following steps: the artificial bee colony algorithm is an optimization method provided by simulating bee behaviors, is a specific application of a cluster intelligence idea, does not need to know special information of problems, only needs to compare the advantages and the disadvantages of the problems, finally enables a global optimum value to be highlighted in a colony through the local optimization behavior of each artificial bee individual, and has higher convergence speed;
the minimal search model for swarm intelligence comprises three basic components: food sources, employed bees and non-employed bees; two of the most basic behavioral models: recruiting bees and abandoning a food source for it; in the formation process of swarm intelligence, the exchange of information among bees is the most important ring; the dance area is the most important information exchange place in the honeycomb; the dance of bees is called swinging dance; the information of the food source is shared with other bees in a dance area in a swinging dance mode, and the bee is led to express the earning rate of the food source through the duration of the swinging dance, so that the following bees observe a large amount of dance and select which food source to collect honey according to the earning rate; the rate of return is proportional to the likelihood of the food source being selected; thus, the probability of bees being recruited to a food source is directly proportional to the profitability of the food source;
the specific steps for solving the phase modulator configuration strategy by adopting the artificial bee colony algorithm are as follows:
(1) assigning values to various parameters of the artificial bee colony algorithm, comprising the following steps: population size, number of hired bees, number of observed bees, number of reconnaissance bees, local maximum search times, iteration times and solution latitude;
(2) generating a half of solution of the population number through random numbers, and calculating the fitness value of each solution; namely, calculating a voltage stability index under the configuration condition of each initial phase modulator;
(3) assigning an iteration variable in the bee colony algorithm to be 1;
(4) traversing all previous solutions, and executing the following steps (5) - (8) for each solution;
(5) finding a new solution within the domain in which the solution is located;
(6) calculating the fitness value of the new solution;
(7) comparing the new solution with the original solution, and keeping the solution with high fitness;
(8) if the original solution is not updated, adding 1 to the local search times; if the local search times are updated, setting the local search times to be 0;
(9) calculating probability values of observation bee selection following each hiring bee in the bee colony algorithm;
(10) randomly selecting a solution according to the calculation probability, carrying out local search around the solution, finding a new solution, calculating the fitness, and selecting to keep or update according to the fitness;
(11) traversing all solutions in the algorithm to see whether the maximum searching times is reached; if so, abandoning the solution and generating a new solution to replace;
(12) recording the currently found optimal solution;
(13) adding 1 for each execution of the loop;
(14) judging whether a maximum cycle number set value is reached or not, and turning to the step (4) if not; and ending the algorithm, and recording the current solution, namely the global optimal solution.
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| CN111725815B (en) * | 2020-06-11 | 2022-01-14 | 国网湖南省电力有限公司 | Configuration method of synchronous phase modulator of extra-high voltage direct current weak receiving end power grid |
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