CN109638870B - A camera configuration method for UHV DC transmission end power grid - Google Patents

Abstract

The invention belongs to the technical field of power grid operation and control, and in particular relates to a configuration method for a phase controller of an ultra-high voltage direct current transmission end power grid, in particular to a method for configuring a phase controller of an ultra-high voltage direct current transmission end system power grid. The invention includes: acquiring the operation parameters of the UHV DC transmission end power grid; determining the configuration quantity of the inverters; analyzing the reactive power and voltage sensitivity of the UHV DC transmission end grid to obtain a primary selection set of configuration positions of the inverters; The worker bee colony algorithm is used to calculate the configuration strategy of the camera; The invention can more effectively realize the effective configuration of the condenser in the UHV DC transmission end power grid, improve the voltage operation stability of the power grid, and provide a technical basis and a practical method for the operation and control of the UHV DC power transmission system. With the increase of UHV AC and DC transmission systems, the development of reactive power optimization allocation strategy must have greater demand and good commercial development prospects.

Description

A method for configuring the camera of a UHV DC transmission end power grid

technical field

The invention belongs to the technical field of power grid operation and control, and in particular relates to a configuration method for a phase controller of an ultra-high voltage direct current transmission end power grid, in particular to a method for configuring a phase controller of an ultra-high voltage direct current transmission end system power grid.

Background technique

my country's primary energy and load are distributed inversely. In order to meet the urgent needs of clean energy transmission, load center power supply, energy conservation and emission reduction, State Grid vigorously develops UHV AC and DC technologies suitable for long-distance, large-capacity power transmission. The positioning of UHV AC and DC transmission projects and the long-distance and large-capacity delivery of large-scale energy bases have become the main ways to alleviate the contradiction between China's energy resources and economic layout. At present, my country is in the transition period of UHV power grid development. With the successive commissioning of UHV AC and DC projects, the UHV AC and DC hybrid grid has begun to take shape.

The UHVDC transmission system faces many problems in the stable operation of the voltage. The transmission capacity of the UHVDC transmission system is huge. Once a bipolar blocking accident occurs, the system will suffer huge disturbances, resulting in a large-scale transient voltage rise and wind power off-grid. On the other hand, the DC transmission system itself consumes a lot of reactive power during normal operation, and the system needs a lot of reactive power support. With the continuous increase of wind power installed capacity and grid-connected capacity, the safe and stable operation of UHVDC transmission system is seriously challenged.

The key to solving the problem is how to configure dynamic reactive power compensation for the power grid. Traditional reactive power compensation equipment, such as capacitors and reactors, can only be used as static reactive power compensation equipment, while various dynamic reactive power compensation equipment based on modern power electronic technology. When the system needs reactive power support, the performance of power compensation equipment is often affected by the bus voltage. As a classic dynamic reactive power regulation device, the controller has advantages in terms of small size and performance, and has broad application prospects in UHV DC power grids.

In my country, the application of the camera has a long history. Later, with the maturity of the power electronic device technology and the aging of the camera equipment, the static dynamic reactive power compensation device, SVC, STATCOM, etc. gradually replaced the application of the camera. Since then, the application of the modulator in the power grid has not been developed. However, with the implementation of the UHV DC project, the hazards of power frequency overvoltage control at the sending end, cascading reflection of the receiving end grid and commutation failure have gradually increased. state output requirements, prevent commutation failure and rapid large-capacity reactive power requirements under transient conditions, assist DC rapid recovery, and have insufficient response capability, while the phase advance capability, sub-transient output characteristics and strong excitation capability of the camera just meet the requirements the above requirements.

SUMMARY OF THE INVENTION

In view of the above problems in the prior art, the present invention provides a method for configuring a phase conditioner for a UHVDC transmission-end power grid, the purpose of which is to solve the above problems existing in the operation technology of the UHVDC power transmission system in the prior art by configuring the phase controller. , by establishing the voltage stability evaluation index of the UHVDC grid and the optimal configuration strategy of the inverter, to improve the voltage stability of the UHVDC transmission end grid.

The technical scheme adopted by the present invention to solve its technical problems is:

A method for configuring a camera at the transmission end of an ultra-high voltage DC power grid is to realize the stable operation of the voltage of the ultra-high voltage DC transmission system by optimizing the configuration of the camera based on the dynamic characteristics of the voltage of the system in the power grid at the transmission end of the ultra-high voltage DC. Include the following steps:

Step 1. Obtain the operating parameters of the UHV DC transmission end power grid;

Step 2. Determine the configuration quantity of the camera;

Step 3. Carry out the reactive power and voltage sensitivity analysis of the UHV DC transmission end power grid, and obtain the primary selection set of the configuration position of the modulator;

Step 4. Use the artificial bee colony algorithm to calculate the camera configuration strategy;

Step 5. Obtain the configuration scheme of the UHV DC transmission end grid regulator.

The step 3. Carry out reactive power and voltage sensitivity analysis of the UHV DC transmission end power grid, and obtain a primary selection set of configuration positions of the modulator, including:

a. Calculate the sensitivity of the reactive power injection point and the AC bus voltage of the DC converter station;

b. Calculate the sensitivity of the reactive power injection point and the bus voltage of the key node of the sending end system;

c. Calculate the sensitivity of the bus voltage between the reactive power injection point and the access point of the wind farm group;

d. According to the calculation result of sensitivity, select the position with larger sensitivity value as the primary position for camera configuration.

Described step 4. Adopt artificial bee colony algorithm, carry out the adjustment camera configuration strategy calculation, including:

(1) Initialize the configuration strategy of the camera, that is, the initial bee colony, and randomly give the number of bees, the number of iterations and the maximum number of collections for a single bee;

(2) Establish evaluation indicators and evaluation functions;

(3) Calculate the nectar source, take the bee with the best fitness as the leader bee, and the bee with lower fitness as the follower bee;

(4) Replace the location of the nectar source;

(5) By judging the pros and cons of the leading bee and the nectar source, the general bee colony with good fitness is set as the leading bee, if the search times limit is not reached, return to step (2), and continue to search for the nectar source;

(6) If the search times limit is reached, output the current optimal nectar source position, that is, the optimal configuration strategy of the camera;

In the step 1, the UHV DC transmission end grid refers to the complex transmission end grid power consisting of a plus or minus 800kV UHV DC transmission system, a 500kV AC grid, a thermal power plant, a hydropower plant and a large number of wind power grid-connected power sources. delivery system;

The obtained operation parameters of the UHV DC transmission end power grid are grid structure parameters, transmission line parameters, DC power transmission system parameters, thermal power generating set parameters, hydropower generating set parameters and parameters required for grid calculation and control of wind power generating set parameters.

In the third step, the reactive power and voltage sensitivity analysis of the UHVDC transmission end grid refers to calculating the sensitivity of reactive power injection to the bus voltage according to the following formula:

F(X, T, C) = 0 and

Among them, F is the power balance equation of the power grid; X is the state vector of the power grid, including the voltage amplitude and phase angle of the node bus; T is the control variable of the power grid, including the active and reactive injection power of each node bus; C is the Constant parameters of the power grid, such as the admittance of the line; V is the bus voltage of a certain sensitivity to be determined; Q is the reactive injection power of the bus at a certain node; F is the power balance equation of the power grid; X is the state vector of the power grid, including the node bus The voltage amplitude and phase angle, etc.; T is the control variable of the power grid.

The establishment of the evaluation index and the evaluation function refers to the index evaluation index for evaluating the voltage rise of each main bus after the bipolar blocking fault of the DC system occurs, which is specifically calculated according to the following formula:

为某一电网关键节点母线电压最大限值；VWi为某一风并网节点母线电压；V_Wi ⁰为某一风并网节点母线电压初始量；V_Wimax为某一风并网节点母线电压最大限值；ω为权重系数；N_B为某一电网关键节点的个数，N_W为某一风并网节点的个数，i为节点。Among them, F _V is the evaluation index function; _VL is the AC bus voltage of the converter station; _VL ⁰ is the initial value of the AC bus voltage of the converter station; _VLmax is the maximum limit of the AC bus voltage of the converter station; V _Bi is a certain The busbar voltage of the key node of the power grid; V _Bi ⁰ is the initial value of the busbar voltage of a key node of the power grid;

is the maximum limit value of the busbar voltage of a certain key node of the power grid; VWi is the busbar voltage of a certain wind grid-connected node; V _Wi ⁰ is the initial value of the busbar voltage of a certain wind grid-connected node; V _Wimax is the maximum bus voltage of a certain wind grid-connected node Limit; ω is the weight coefficient; N _B is the number of key nodes in a grid, N _W is the number of wind grid-connected nodes, and i is the node.

The honey source calculation is performed, and the bee with the best fitness is used as the leader bee, and the bee with lower fitness is used as the follower bee finger: the bee searches for the honey source through cross-searching, and generates a new individual.

The replacement of the location of the honey source refers to the following rules:

The selection rules are:

In the formula, P _i is the probability that the nectar source is selected for honey collection; fit( _xi ) is the fitness function of the nectar source; N is the number of nectar source locations, and i is the nectar source location.

The sensitivity calculation is because the DC transmission system is connected to the AC bus of the converter station through the converter transformer, and the change of the control mode and control parameters of the DC transmission system will affect the change of the bus voltage of the AC system, especially the bus voltage of the converter station; The decoupling algorithm is used to analyze the voltage sensitivity factor of the AC-DC system; the DC system is equivalent to a load equivalent to the active and reactive power of the corresponding converter, the sensitivity of the AC system voltage to the converter power is obtained, and the calculation process is simplified. At the same time ensure the accuracy of the results;

According to the above method, the sensitivity of the node voltage to the transmission power of the AC-DC hybrid transmission system is re-transformed into a pure AC system problem; first, the node bus power is set as the control variable T _ac as shown in the following formula, where P _a and Q _a represent AC, respectively The active and reactive power transmitted by the system, P _d and Q _d represent the active and reactive power of the DC system, respectively;

T _ac =[P _a , P _d , Q _a , Q _d ]

Assuming that the voltage amplitude and phase angle of the AC transmission system are state variables denoted as X _ac , and the state variables include the AC bus of the converter station, the power flow equation of the AC and DC transmission system is rewritten as:

In the formula: P(X _ac ), Q(X _ac ) represent the active power and reactive power injected into the node calculated according to the voltage; then, the sensitivity matrix of the control variable T _ac to the state variable X _ac is as follows:

In the formula: J _f represents the Jacobian matrix in the power flow calculation of the AC/DC hybrid transmission system, from which the sensitivity matrix of the node voltage to the node bus power can be obtained;

节点电压对节点母线功率的灵敏度矩阵；

Sensitivity matrix of node voltage to node bus power;

X _ac : The voltage amplitude and phase angle of the AC transmission system are state variables;

T _ac : node bus power;

f _ac : power flow equation for AC and DC transmission systems.

The artificial bee colony algorithm is an optimization method proposed by imitating the behavior of bees. It is a specific application of the swarm intelligence idea. It does not need to know the special information of the problem, but only needs to compare the pros and cons of the problem. The local optimization behavior finally makes the global optimal value emerge in the group, and has a faster convergence speed;

The minimal search model for bee colonies to generate swarm intelligence consists of three basic elements: food source, employed bees and unemployed bees; two most basic behavioral models: recruiting bees for a food source and giving up a food source ;In the formation of swarm intelligence, the exchange of information between bees is the most important part; the dance area is the most important place for information exchange in the hive; the dance of bees is called swing dance; the information of food sources is transmitted through the swing dance in the dance area. The form is shared with other bees, and the leading bee expresses the yield of the food source through the duration of the swing dance, so the following bees can observe a large number of dances and choose which food source to collect honey according to the yield; yield and food source is proportional to the probability of being selected; thus, the probability of bees being recruited to a food source is proportional to the yield of the food source;

The specific steps of using the artificial bee colony algorithm to solve the camera configuration strategy are as follows:

(1) Assign values to the parameters of the artificial bee colony algorithm, such as population size, the number of employed bees, the number of observed bees, the number of reconnaissance bees, the maximum number of local searches, the number of iterations, and the latitude of the solution;

(2) A solution with half the population number is randomly generated by random numbers, and the fitness value of each solution is calculated; that is, the voltage stability index under the configuration of each initial modulator is calculated;

(3) Assign the number of iterations variable in the bee colony algorithm to 1;

(4) Traverse all the previous solutions, and perform the following steps (5)-(8) for each solution;

(5) Discover new solutions within the domain where the solution is located;

(6) Calculate the fitness value of the new solution;

(7) Compare the new solution with the original solution, and retain the solution with high fitness;

(8) If the original solution has not been updated, the number of local searches is increased by 1; if it has been updated, the number of local searches is set to 0;

(9) Calculate the probability value that the observed bee chooses to follow each employed bee in the bee colony algorithm;

(10) According to the calculated probability, randomly select a solution, and perform a local search around the solution, find a new solution, calculate the fitness, and choose whether to retain or update according to the size of the fitness;

(11) Traverse all solutions in the algorithm to see if the maximum number of searches is reached; if so, give up the solution and generate a new solution instead;

(12) Record the currently found optimal solution;

(13) Add 1 every time the loop is executed;

(14) Judging whether the set value of the maximum number of cycles has been reached, and the step (4) has not been reached; when it is reached, the algorithm is ended, and the current record is the global optimal solution.

Compared with the prior art, the beneficial effects of the present invention are:

The invention can more effectively realize the effective configuration of the condenser in the UHV DC transmission end power grid, improve the stability of the grid voltage operation, and provide technical basis and practical method for the operation and control of the UHV DC power transmission system.

The invention considers the dynamic process of the system voltage after the severe fault of the direct current transmission system, can more effectively and reliably carry out the configuration strategy of the phase control, and provides technical basis and practical method for the voltage operation and control of the ultra-high voltage direct current power grid.

Based on the serious fault and sensitivity analysis of the DC system, the invention establishes the voltage dynamic evaluation index, and adopts the artificial bee colony algorithm to solve the problem, thereby greatly improving the reliability and practicability of the camera configuration strategy.

The invention fully considers the voltage transient characteristics of the system, and establishes the evaluation index for evaluating the configuration strategy through the voltage transient characteristics after the DC blocking fault, which can more truly reflect the voltage dynamic characteristics of the UHVDC system, and continuously optimize the transient state through simulation software. operation mode, and obtain a real and reliable reactive power optimization configuration strategy. On the basis of sensitivity analysis, the invention firstly forms an initial optimal configuration set, and then adopts the artificial bee colony algorithm to solve the problem, which makes it easier to find the optimal configuration scheme and easy to implement. With the increase of ultra-high voltage AC and DC power transmission systems, the development of the reactive power optimization configuration strategy of the present invention is bound to have great demands and has a good commercial development prospect.

Description of drawings

In order to facilitate the understanding and implementation of the present invention by those of ordinary skill in the art, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but it should be understood that the scope of the present invention is not limited by the specific embodiments.

Fig. 1 is the overall flow chart of the present invention;

Fig. 2 is the schematic flow chart of sensitivity calculation;

Fig. 3 is a schematic diagram of artificial bee colony algorithm;

Figure 4 is the system simulation comparison curve before and after configuring the camera.

Detailed ways

As shown in Fig. 1 to Fig. 4 , a method for configuring the camera at the transmission end of the UHV DC power grid according to the present invention means that in the power grid at the transmission end of the UHV DC, based on the voltage dynamic characteristics of the system, through the optimized configuration of the camera, To achieve the stable operation of the UHVDC transmission system voltage, including the following steps:

Step 1. Obtain the operating parameters of the UHV DC transmission end power grid;

Step 2. Determine the configuration quantity of the camera;

Step 3. Carry out the reactive power and voltage sensitivity analysis of the UHV DC transmission end power grid, and obtain the primary selection set of the configuration position of the modulator;

a. Calculate the sensitivity of the reactive power injection point and the AC bus voltage of the DC converter station;

b. Calculate the sensitivity of the reactive power injection point and the bus voltage of the key node of the sending end system;

c. Calculate the sensitivity of the bus voltage between the reactive power injection point and the access point of the wind farm group;

d. According to the calculation result of sensitivity, select the position with larger sensitivity value as the primary position for camera configuration.

Step 4. Use the artificial bee colony algorithm to calculate the camera configuration strategy;

(1) Initialize the configuration strategy of the camera, that is, the initial bee colony, and randomly give the number of bees, the number of iterations and the maximum number of collections for a single bee;

(2) Establish evaluation indicators and evaluation functions;

(3) Calculate the nectar source, take the bee with the best fitness as the leader bee, and the bee with lower fitness as the follower bee;

(4) Replace the location of the nectar source;

(5) By judging the pros and cons of the leading bee and the nectar source, the general bee colony with good fitness is set as the leading bee, if the search times limit is not reached, return to step (2), and continue to search for the nectar source;

(6) If the search times limit is reached, output the current optimal nectar source position, that is, the optimal configuration strategy of the camera.

Step 5. Obtain the configuration scheme of the UHV DC transmission end grid regulator.

In the step 1, the UHV DC transmission end grid refers to the complex transmission end grid power consisting of a plus or minus 800kV UHV DC transmission system, a 500kV AC grid, a thermal power plant, a hydropower plant and a large number of wind power grid-connected power sources. Delivery system.

In the step 1, the operation parameters of the UHV DC transmission-end power grid obtained are grid structure parameters, transmission line parameters, DC power transmission system parameters, thermal power generating unit parameters, hydropower generating unit parameters, wind turbine parameters and other power grid calculation and control. required parameters.

In the third step, the reactive power and voltage sensitivity analysis of the UHVDC transmission end grid refers to calculating the sensitivity of reactive power injection to the bus voltage according to the following formula:

F(X, T, C) = 0 and

Among them, F is the power balance equation of the power grid; X is the state vector of the power grid, including the voltage amplitude and phase angle of the node bus; T is the control variable of the power grid, including the active and reactive injection power of each node bus; C is the The constant parameters of the power grid, such as the admittance of the line, etc. V is the bus voltage to be determined for a certain sensitivity; Q is the reactive injected power of the bus at a certain node; F is the power balance equation of the power grid; X is the state vector of the power grid, including the voltage amplitude and phase angle of the node bus; T is the Control variables of the grid.

In the fourth step, establishing the evaluation index and the evaluation function refers to the index evaluation index for evaluating the voltage rise of each main bus after the bipolar blocking fault of the DC system occurs, which is specifically calculated according to the following formula:

为某一电网关键节点母线电压最大限值；V_Wi为某一风并网节点母线电压；V_Wi ⁰为某一风并网节点母线电压初始量；V_WiMAX为某一风并网节点母线电压最大限值；ω为权重系数；N_B为某一电网关键节点的个数，N_W为某一风并网节点的个数，i为节点。Among them, F _V is the evaluation index function; _VL is the AC bus voltage of the converter station; _VL ⁰ is the initial value of the AC bus voltage of the converter station; _VLMAX is the maximum limit of the AC bus voltage of the converter station; V _Bi is a certain The busbar voltage of the key node of the power grid; V _Bi ⁰ is the initial value of the busbar voltage of a key node of the power grid;

V _Wi is the bus voltage of a certain wind grid-connected node; V _Wi ⁰ is the initial value of the bus voltage of a certain wind-connected node; V _WiMAX is the bus voltage of a certain wind-connected node Maximum limit; ω is the weight coefficient; N _B is the number of key nodes in a grid, N _W is the number of wind grid-connected nodes, and i is the node.

In the calculation of the nectar source in the fourth step, the bee with the best fitness is used as the leader bee, and the bee with the lower fitness is used as the follower bee finger: the bee searches for the nectar source through crossover search, and generates a new individual.

The replacement of the location of the honey source in the step 4 refers to the following rules:

The selection rules are:

In the formula, P _i is the probability that the nectar source is selected for honey collection; fit( _xi ) is the fitness function of the nectar source, N is the number of nectar source locations, and i is the nectar source location.

Fig. 1 is the overall flow chart of the present invention, which is consistent with the above calculation steps. It is worth noting that it can be seen from the flow chart in the figure that this method forms an initial set of busbars to be selected by establishing a sensitivity analysis, and establishes a reflection voltage dynamic characteristic. The evaluation index is calculated by the bee colony algorithm, which is the essential difference from other methods.

Figure 2 is a schematic diagram of the sensitivity calculation process. Since the DC transmission system is connected to the AC bus of the converter station through the converter transformer, the change of the control mode and control parameters of the DC transmission system will affect the change of the bus voltage of the AC system, especially the bus of the converter station. Voltage. The invention adopts the decoupling algorithm to analyze the voltage sensitivity factor of the AC-DC system. The DC system is equivalent to a load equivalent to the active and reactive power of the corresponding converter, and the sensitivity of the AC system voltage to the converter power is obtained, which simplifies the calculation process and ensures the accuracy of the results.

In the above-mentioned way, the solution of the sensitivity of the node voltage of the AC-DC hybrid transmission system to the transmission power is re-transformed into a pure AC system problem. First, let the node bus power be the control variable T _ac as shown in the following formula, where P _a and Q _a represent the active and reactive power transmitted by the AC system, respectively, and P _d and Q _d represent the active and reactive power of the DC system, respectively.

T _ac =[P _a , P _d , Q _a , Q _d ]

Assuming that the voltage amplitude and phase angle of the AC transmission system are state variables expressed as X _ac , and the state variable includes the AC bus of the converter station, the power flow equation of the AC and DC transmission system can be rewritten as:

In the formula: P(X _ac ), Q(X _ac ) represent the active power and reactive power injected into the node calculated according to the voltage; then, the sensitivity matrix of the control variable T _ac to the state variable X _ac is as follows:

In the formula: J _f represents the Jacobian matrix in the power flow calculation of the AC/DC hybrid transmission system, from which the sensitivity matrix of the node voltage to the node bus power can be obtained.

节点电压对节点母线功率的灵敏度矩阵；

Sensitivity matrix of node voltage to node bus power;

X _ac : The voltage amplitude and phase angle of the AC transmission system are state variables;

T _ac : node bus power;

f _ac : power flow equation for AC and DC transmission systems.

The calculation of the above equation matrix can refer to the calculation of the power flow of the AC system, which is relatively mature and can be realized by the existing calculation method.

Figure 3 is a schematic diagram of an artificial bee colony algorithm. The artificial bee colony algorithm is an optimization method proposed to imitate the behavior of bees, and it is a specific application of the idea of swarm intelligence. The local optimal behavior of individual worker bees finally makes the global optimal value emerge in the colony, and has a fast convergence speed.

The minimal search model for bee colonies to generate swarm intelligence consists of three basic elements: food source, employed bees and unemployed bees; two most basic behavioral models: recruiting bees for a food source and giving up a food source . In the formation of swarm intelligence, the exchange of information between bees is the most important part. The dance area is the most important exchange of information in the hive. The dance of the bees is called the swing dance. The information of the food source is shared with other bees in the form of swing dance in the dance area, and the leading bee expresses the yield of the food source through the duration of the swing dance, so the follower bee can observe a large number of dances and choose according to the yield. Which food source for honey. The yield is proportional to the likelihood that the food source will be selected. Thus, the probability of bees being recruited to a food source is proportional to the yield of the food source.

The specific steps of using the artificial bee colony algorithm to solve the camera configuration strategy are as follows:

(1) Assign values to the parameters of the artificial bee colony algorithm, such as population size, the number of employed bees, the number of observed bees, the number of reconnaissance bees, the maximum number of local searches, the number of iterations, and the latitude of the solution;

(2) A solution of half the population is randomly generated by random numbers, and the fitness value of each solution is calculated. That is to calculate the voltage stability index under each initial camera configuration;

(3) Assign the number of iterations variable in the bee colony algorithm to 1;

(4) Traverse all the previous solutions, and perform the following steps (5)-(8) for each solution;

(5) Discover new solutions within the domain where the solution is located;

(6) Calculate the fitness value of the new solution;

(7) Compare the new solution with the original solution, and retain the solution with high fitness;

(8) If the original solution has not been updated, the number of local searches is increased by 1; if it has been updated, the number of local searches is set to 0;

(9) Calculate the probability value that the observed bee chooses to follow each employed bee in the bee colony algorithm;

(10) According to the calculated probability, randomly select a solution, and perform a local search around the solution, find a new solution, calculate the fitness, and choose whether to retain or update according to the size of the fitness;

(11) Traverse all solutions in the algorithm to see if the maximum number of searches is reached. If it is reached, discard the solution and generate a new solution instead;

(12) Record the currently found optimal solution;

(13) Add 1 every time the loop is executed;

(14) Judging whether the set value of the maximum number of cycles has been reached, and the step (4) has not been reached; when it is reached, the algorithm is ended, and the current record is the global optimal solution.

For the detailed steps and formulas of the bee colony algorithm, there are quite a few literature references.

Figure 4 is the system simulation comparison curve before and after configuring the camera. Take the Northeast-Shandong UHVDC transmission system as an example for analysis and verification. The Zalut-Qingzhou UHV DC project (hereinafter referred to as Zhaqing DC) starts from Zalute Banner, Tongliao City, East Mongolia in the north, and ends at Heguan Town, Qingzhou City, Shandong Province in the south. It was put into operation at the end of 2017. The rated DC voltage is ±800kV and the designed rated power is 10000MW. It is the first UHV DC project in the Northeast Power Grid. The conductor cross section of the DC transmission line is 8×1250mm2, and the converter station at the sending end is based on the current recommended site of the Bayantala station in Zalut Banner, and the length of the DC line is 1223.6km.

Zarut to Qingzhou UHV DC is planned to be bipolar, with one DC outlet and one grounding outlet. The wiring mode of the valve group is that two 12-pulse valve groups are connected in series for each pole; the recommended scheme of the converter is 28 sets, the single-phase double winding capacity is 509.35MVA, Uk=21%, and the total capacity of the capacitive reactive power compensation of the converter station is about 6665Mvar, temporarily divided into 4 groups and 20 groups.

The Liaoning Power Grid is connected to the Jilin Power Grid through 4 circuits of 500KV lines to the north, Heilongjiang Power Grid is connected to the Yimu DC system through the Yimu DC system, Xiangsi is connected to the East Mongolia Power Grid through 6 circuits of 500KV circuits, and the South is connected to the North China Power Grid through DC back-to-back connections. Before Zalut DC was put into operation, Liaoning Power Grid was the receiving end power grid and load center in Northeast China, receiving electricity from Mengdong, Yimin and Jilin Power Grids. The load center of China carries the abundant power sent by other provinces. After Zarut DC is put into operation, the Northeast Power Grid will mainly transmit electricity from the east to the west, and use Zarut as the power receiving center to transmit power to the outside of the area. Big changes occurred. In particular, the transmission capacity of the UHV DC transmission system is huge. Once a bipolar blocking accident occurs, the system will suffer huge disturbances, resulting in a large-scale transient voltage increase and wind power off-grid; on the other hand, the DC transmission system itself consumes power during normal operation. The system has a lot of reactive power, and the system needs a lot of reactive power support. With the continuous increase of wind power installed capacity and grid-connected capacity, the safe and stable operation of UHV DC transmission system is seriously challenged.

The simulation and modeling of the power grid is carried out under the ADPSS software. The realization of the bee colony algorithm is carried out on the MATLAB software platform; the data interaction and coordination between the two softwares are carried out by manual operation; the initial configuration number of cameras is three. Figure 4 shows the dynamic characteristic curve of the busbar voltage of the converter station after the system has a bipolar blocking fault in the three modes of no camera configuration, manual configuration configuration, and method configuration of the present invention. It can be seen that after the optimal configuration of the camera position, the transient increase of the converter station bus voltage is significantly suppressed, which proves the effectiveness and practicability of the strategy of the present invention.

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, F_VIs an evaluation index function; v_LIs the converter station ac bus voltage; v_L ⁰The initial value of the AC bus voltage of the converter station is obtained; v_LmaxThe maximum value of the AC bus voltage of the converter station is set; v_BiBus voltage of a key node of a certain power grid; v_Bi 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; v_WiA certain wind grid-connected node bus voltage; v_Wi ⁰The initial amount of the bus voltage of a certain wind grid-connected node is obtained; v_WimaxThe 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 hydrogen_BIs the number of key nodes of a certain power grid, N_WThe 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, P_iProbability 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 T_acIs represented by the formula, wherein P_aAnd Q_aRespectively representing active and reactive power, P, transmitted by the AC system_dAnd Q_dRespectively representing active power and reactive power of a direct current system;

T_ac＝[P_a,P_d,Q_a,Q_d]

let AC transmission system voltage amplitude and phase angle be state variables and be expressed as X_acAnd 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(X_ac) The active power and the reactive power are injected into the node obtained by voltage calculation; then, the variable T is controlled_acFor state variable X_acThe sensitivity matrix of (a) is as follows:

in the formula: j. the design is a square_fRepresenting 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;

a sensitivity matrix of node voltage to node bus power;

X_acthe voltage amplitude and the phase angle of the AC power transmission system are state variables;

T_acnode bus power;

f_ac: 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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