A comprehensive resource optimization configuration method after large-scale application of electric kilns

Abstract

With the vigorous promotion of the "coal to electricity" project, electric kiln equipment has begun to be connected to the distribution network on a large scale. In order to solve the problem of voltage deviation and high harmonic distortion rate after the large-scale connection of electric kilns to the distribution network, a comprehensive resource optimization configuration method after the large-scale application of electric kilns is proposed. By establishing a multi-objective optimization mathematical model, the site selection and capacity determination of the series compensation device and the parallel compensation device of the distribution network are realized, the goal of improving the distribution network voltage is achieved, and the harmonics are centrally and uniformly managed, which effectively reduces the distribution network loss and the distribution network harmonic content, and significantly improves the distribution network voltage.

Description

[Technical field]

[0001] The present invention relates to power quality analysis and management measures after large-scale application of electric kiln loads, and in particular to power quality optimization management of low voltage problems and harmonic wave problems after large-scale application of electric kilns. [Background technology]

[0002] Due to the rapid economic development and the consumption of conventional energy, environmental pollution and energy crisis have become issues that cannot be ignored. As the first batch of electric energy replacement products, electric kilns have been widely promoted and used in Jingdezhen. Compared with wood kilns, coal kilns and gas kilns, they have a series of advantages such as small footprint, high thermal efficiency and good product firing quality. However, the large-scale access to the power grid of electric energy replacement products represented by electric kilns will cause a series of power quality problems such as low voltage, high harmonic distortion rate and high reactive power loss in the distribution network, which will greatly affect the safe and reliable operation of the distribution network. In this context, it is necessary to make reasonable application planning for the treatment device to solve the power quality problems such as harmonics, reactive power and low voltage caused by large-scale access, so as to ensure the safe and stable operation of the system and the voltage quality at the user end is within the standard range.

[0003] At present, in actual operation, the scale of alternative loads such as electric kilns and electric heating has a significant impact on the power supply capacity of the distribution network. However, existing literature rarely studies the reactive power optimization and harmonic suppression problems after large-scale access of electric kilns to the distribution network. In this context, it is necessary to make reasonable application planning for the treatment device to solve the power quality problems such as harmonics, reactive power and low voltage caused by large-scale access, so as to ensure the safe and stable operation of the system and the voltage quality at the user end is within the standard range.

[0004] Reactive compensation management devices are divided into two forms: parallel compensation and series compensation. Parallel compensation connects compensation capacitors to the feeder, which can reduce the flow of inductive reactive power on the user side. It has the ability to reduce line losses and reduce voltage drops, but the reactive power it provides is proportional to the square of the voltage. When the load increases significantly, the line voltage is too low to achieve the management effect. Series compensation capacitors can reduce the reactance of the line, increase the voltage at the end of the line and improve the voltage quality, but series compensation cannot reduce the reactive power on the user side, resulting in reactive power still flowing in the line and still having large network losses. This article proposes to use a combination of parallel compensators and series compensators for reactive compensation in the distribution network system.

[0005] There are two main aspects of harmonic control. On the one hand, the harmonic source itself is restricted. On the other hand, passive filters (PPF) or active filters (APF) are installed in the power grid to suppress harmonics and make the harmonic content meet national standards. Although passive filters have the advantages of low cost, simple structure and easy implementation, their filtering characteristics are not good. Therefore, this paper configures active filters with superior performance in the distribution network. [Summary of the invention]

[0006] The purpose of the present invention is to provide a comprehensive resource optimization configuration method after large-scale application of electric kilns, which can solve the power quality problems such as harmonics, reactive power and low voltage caused by large-scale access of electric kilns. It is a comprehensive resource optimization configuration method that is simple to operate and easy to implement, and provides a certain theoretical basis for the supporting power grid transformation project of "coal to electricity".

[0007] The technical solution of the present invention is: a comprehensive resource optimization configuration method after large-scale application of electric kilns, characterized in that it includes two parts: configuration of reactive power optimization link and optimization configuration of harmonic control link; wherein the reactive power optimization link is used to establish an optimization model from three aspects of investment, network loss and voltage deviation, evaluate the impact of the electric kiln on the system after being connected to the distribution network, and use the particle swarm optimization algorithm (PSO, Particle Swarm Optimization) to optimize the site selection and capacity setting of the series compensation device and the parallel compensation device of the distribution network; the harmonic control link refers to configuring a filter in the distribution network to eliminate harmonics, so as to centrally and uniformly control the harmonics.

[0008] The configuration of the reactive power optimization link includes the following steps:

[0009] (1-1) Choice of objective function:

[0010] When electric kilns are used in distribution networks on a large scale, the equivalent model of the distribution network consists of electric kiln loads, reactive power compensation devices, active power filter devices, and the upper power grid system. Therefore, the three objective functions of minimizing the investment in reactive power compensation devices, minimizing voltage deviation, and minimizing network losses are used to perform multi-objective reactive power optimization of the system according to formulas (1)-(4).

[0011] F=min[f cost ,f V ,f lOss ] (1)

[0012]

[0013] In the formula, f cost 、fV 、f loss They represent the minimum investment in reactive power compensation equipment, the minimum voltage deviation, and the minimum network loss; C invest , C cap are the total investment and unit capacity investment of reactive power compensation device respectively; Q c is the reactive capacity connected at node i; U i , ΔU are the voltage of node i, the reference voltage amplitude during normal operation and the total voltage deviation respectively; N b is the number of branches in the system; R i The resistance of branch i; P i , Q i , P loss are the active power, reactive power and network loss of the distribution system of branch i respectively;

[0014] (1-2) Determination of constraints:

[0015] The inequality constraints are divided into control variable constraints and state variable constraints. The generator node voltage and reactive power compensation device capacity are selected as control variable constraints, and the load node voltage and distribution network power factor are selected as state variable constraints, as shown in formula (5) and formula (6) respectively:

[0016]

[0017] Where U Gi , U Gimin , U Gimax are the breakpoint voltage of generator node i and its lower and upper limits respectively; Q Ci , Q Cimin , Q Cimax are the reactive power compensation capacity and its lower and upper limits respectively; U Li , U Limin , U Limax are the voltage of load node i and its lower and upper limits respectively; pu is the power factor during distribution network operation; N G 、N C 、N L They are the number of power grid generator nodes, reactive power compensation nodes, and PQ nodes;

[0018] (1-3) Normalization

[0019] Since the dimensions and units of voltage deviation, active power loss and investment cost are different, they cannot be simply connected by weights. It is necessary to normalize the weights first to obtain the minimum value of the objective function. The normalization process is shown in equations (7), (8) and (9):

[0020]

[0021] Where: ΔU dc , ΔP loss and ΔC invest ΔU is the voltage deviation, active power loss and equipment investment before adding reactive power compensation. max and ΔU min , P max and P min , C max and C min are the maximum and minimum values ​​of voltage deviation, active power loss and equipment investment respectively;

[0022] (1-4) Choice of weight

[0023] The optimal configuration of reactive power compensation device should meet the voltage quality requirements. Voltage deviation is an important assessment criterion for reactive power compensation device planning. Therefore, voltage deviation is used as the first level weight W. 1 ; Since the network loss cost value is relatively small, it is used as the second level weight W 2 After meeting the voltage requirements and network loss requirements, it is necessary to consider certain economic factors, that is, the fixed investment cost in the power company investment cost, as the third level weight W 3 ; Then the objective function of multi-objective optimization after large-scale application of electric kilns is as shown in formula (10):

[0024] F=W 1 f 1 +W 2 f 2 +W 3 f 3 (10)

[0025] Where: W 1 , W 2 , W 3 are the 1st, 2nd and 3rd level weights respectively, and F is the objective function of multi-objective optimization after large-scale application of electric kiln.

[0026] The weights of the steps (1-4) are determined by the expert decision-making method, namely the Delphi method; the traditional hierarchical analysis method is used to judge the importance of each target based on expert experience to obtain the indicator judgment matrix J shown in formula (11), which is a 3*3 matrix:

[0027]

[0028] According to the process Figure 2 The weight W of the first-level index calculated by expert experience is:

[0029] W=[0.071927 0.64912 0.27895](12) Therefore, the objective function of multi-objective optimization after large-scale application of electric kiln is:

[0030] minF=0.071927f 1 +0.64912f 2 +0.27895f 3 (13) The optimization of the harmonic control link includes the following steps:

[0031] (2-1) Establishment of active filter equivalent model

[0032] The essence of the active filter APF is a controlled current source with current feedback control. Its equivalent model should include two parts: a three-level inverter and a power grid. Among them, the three-level inverter part includes the command current I ref and output impedance Z 1 The grid part consists of the grid voltage E and the grid impedance Z E Assuming that the active filter absorbs only part of the harmonic current of this node according to a certain proportion, use A h It represents the coefficient of the hth harmonic current generated by the harmonic source at the active filter absorption node. Then the hth harmonic current I absorbed by each active filter is Ah The harmonic current I injected by the harmonic source h The relationship between is as shown in formula (14):

[0033] I Ah =A h I h h=3,5,…,H (14)

[0034] (2-2) Establishment of mathematical model for filter APF optimization configuration

[0035] The optimal configuration of the filter means that after the filter is installed, the harmonic content rate, harmonic voltage distortion rate and the allowable value of each harmonic current at each node of the network meet the requirements of the national standard, ensuring the safe operation of the filter while minimizing the initial investment of the filter and achieving the maximum economic benefit; therefore, the filter optimization configuration model takes the cost of the active power filter installed on the low-voltage side of the transformer in the distribution network as the objective function, as shown in formulas (15) and (16), and takes the allowable value of the harmonic current injected into the common connection point, the distortion rate and content rate of the harmonic voltage as the constraint conditions, as shown in formulas (17)-(19);

[0036]

[0037] S=3I Ah U (16)

[0038] HRU h =(U h / U 1 )×100%≤3.2% (17)

[0039]

[0040] I Bh ≤I h0 (19)

[0041] Where S is the rated capacity of the active filter, b 0 and b 1 The base price of the active filter is RMB 400,000 and the coefficient between capacity and cost is RMB 450,000 / MVA, HRU h is the voltage content of harmonics of order h, U h is the effective value of the hth harmonic voltage, U 1 is the effective value of the fundamental voltage, U THD is the total distortion rate of harmonic voltage, I Bh and I h0 It is the harmonic current injected into the common connection point and the allowable value of harmonic current.

[0042] The harmonic voltage content limit value in step (2-2) is 3.2%, the total harmonic voltage distortion limit value is 4%, and the allowable value of odd harmonic current injected into the common connection point (the reference short-circuit capacity is 100MVA) is shown in Table 1, all of which are applicable to 10kV distribution network.

[0043] Table 1 Allowable values ​​of odd harmonic current injected into the common connection point

[0044]

[0045] The advantages of the present invention are as follows: a two-stage grid comprehensive resource optimization configuration model and method for reactive power optimization and harmonic control of the distribution network is proposed, which solves the problem of voltage deviation and high harmonic distortion rate after electric kilns are connected to the distribution network on a large scale. By establishing a multi-objective optimization mathematical model, the site selection and capacity determination of the series compensation device and the parallel compensation device of the distribution network are realized, and the goal of improving the distribution network voltage is achieved. Secondly, an optimization configuration model with the cost of the active filter as the objective function is established, and harmonics are centrally and uniformly controlled at the system level. It can also effectively reduce the distribution network loss and the harmonic content of the distribution network, and significantly improve the distribution network voltage.

Brief Description of the Drawings

[0046] Figure 1 This is a schematic diagram of the structure of a MATLAB and OpenDSS joint simulation platform for a comprehensive resource optimization configuration method after large-scale application of an electric kiln involved in the present invention.

[0047] Figure 2The present invention is a schematic diagram of an algorithm flow of a comprehensive resource optimization configuration method after large-scale application of an electric kiln.

[0048] FIG3 is a comparison diagram of node voltages before and after reactive power optimization at different penetration rates in the embodiment of the present invention (wherein, Figure 3-a The penetration rate is 20%, Figure 3-b The penetration rate is 30%, Figure 3-c The penetration rate is 40%, Figure 3-d is a penetration rate of 50%).

[0049] Figure 4 This is an optimal configuration diagram of the active filter under different permeabilities in the embodiment of the present invention.

[0050] Figure 5 The APF equivalent model of the present invention [Specific implementation method]

[0051] Embodiment: A comprehensive resource optimization configuration method after large-scale application of electric kilns, such as Figure 1 As shown, it is characterized in that it includes two parts: the configuration of reactive power optimization link and the optimization configuration of harmonic control link; wherein, the reactive power optimization link is used to establish an optimization model from three aspects of investment, network loss and voltage deviation, evaluate the impact of the electric kiln on the system after connecting to the distribution network, and use the particle swarm optimization algorithm to optimize the site selection and capacity setting of the series compensation device and the parallel compensation device of the distribution network; the harmonic control link refers to configuring filters in the distribution network to eliminate harmonics, so as to centrally and uniformly control the harmonics.

[0052] Configuration of reactive power optimization link, such as Figure 2 As shown, the specific implementation process includes the following steps:

[0053] (1-1) Choice of objective function:

[0054] When electric kilns are used on a large scale in distribution networks, such as Figure 1 As shown in the figure, the equivalent model of the distribution network consists of electric kiln load, reactive power compensation device, active power filter device and upper power grid system; therefore, the minimum investment in reactive power compensation device, the minimum voltage deviation and the minimum network loss are taken as three objective functions, and the multi-objective reactive power optimization of the system is carried out according to formulas (1)-(4);

[0055] F=min[f cost ,f V ,f loss ] (5)

[0056]

[0057]

[0058] In the formula, f cost 、f V 、f loss They represent the minimum investment in reactive power compensation equipment, the minimum voltage deviation, and the minimum network loss; C invest , C cap are the total investment and unit capacity investment of reactive power compensation device respectively; Q c is the reactive capacity connected at node i; U i , ΔU are the voltage of node i, the reference voltage amplitude during normal operation and the total voltage deviation respectively; N b is the number of branches in the system; R i The resistance of branch i; P i , Q i , P loss are the active power, reactive power and network loss of the distribution system of branch i respectively;

[0059] (1-2) Determination of constraints:

[0060] The inequality constraints are divided into control variable constraints and state variable constraints. The generator node voltage and reactive power compensation device capacity are selected as control variable constraints, and the load node voltage and distribution network power factor are selected as state variable constraints, as shown in formula (5) and formula (6) respectively:

[0061]

[0062] Where U Gi , U Gimin , U Gimax are the breakpoint voltage of generator node i and its lower and upper limits respectively; Q Ci , Q Cimin , Q Cimax are the reactive power compensation capacity and its lower and upper limits respectively; U Li , U Limin , U Limax are the voltage of load node i and its lower and upper limits respectively; pu is the power factor during distribution network operation; N G 、N c 、N L They are the number of power grid generator nodes, reactive power compensation nodes, and PQ nodes;

[0063] (1-3) Normalization

[0064] Since the dimensions and units of voltage deviation, active power loss and investment cost are different, they cannot be simply connected by weights. It is necessary to normalize the weights first to obtain the minimum value of the objective function. The normalization process is shown in equations (7), (8) and (9):

[0065]

[0066] Where: ΔU dc , ΔP loss and ΔC invest ΔU is the voltage deviation, active power loss and equipment investment before adding reactive power compensation. max and ΔU min , P max and P min , C max and C min are the maximum and minimum values ​​of voltage deviation, active power loss and equipment investment respectively;

[0067] (1-4) Choice of weight

[0068] The optimal configuration of reactive power compensation device should meet the voltage quality requirements. Voltage deviation is an important assessment criterion for reactive power compensation device planning. Therefore, voltage deviation is used as the first level weight W. 1 ; Since the network loss cost value is relatively small, it is used as the second level weight W 2 After meeting the voltage requirements and network loss requirements, it is necessary to consider certain economic factors, that is, the fixed investment cost in the power company investment cost, as the third level weight W 3 ; Then the objective function of multi-objective optimization after large-scale application of electric kilns is as shown in formula (10):

[0069] F=W 1 f 1 +W 2 f 2 +W 3 f 3 (10)

[0070] Where: W 1 , W 2 , W 3 are the 1st, 2nd and 3rd level weights respectively, and F is the objective function of multi-objective optimization after large-scale application of electric kiln.

[0071] The weights of the steps (1-4) are selected by the expert decision-making method, namely the Delphi method; the traditional hierarchical analysis method is used to judge the importance of each target based on expert experience to obtain the indicator judgment matrix J shown in formula (11), which is a 3*3 matrix:

[0072]

[0073] According to the process Figure 2 The weight W of the first-level index calculated by expert experience is:

[0074] W=[0.071927 0.64912 0.27895](12) Therefore, the objective function of multi-objective optimization after large-scale application of electric kiln is:

[0075] minF=0.071927f 1 +0.64912f 2 +0.27895f 3 (13)

[0076] Optimization of harmonic control links, such as Figure 2 As shown, the specific implementation process includes the following steps:

[0077] (2-1) Establishment of active filter equivalent model

[0078] The essence of the active filter APF is a controlled current source with current feedback control, such as Figure 5 As shown in Figure 2, its equivalent model should include two parts: a three-level inverter and a power grid. The three-level inverter part includes the command current I ref and output impedance Z 1 The grid part consists of the grid voltage E and the grid impedance Z E Assuming that the active filter absorbs only part of the harmonic current of this node according to a certain proportion, use A h It represents the coefficient of the hth harmonic current generated by the harmonic source at the active filter absorption node. Then the hth harmonic current I absorbed by each active filter is Ah The harmonic current I injected by the harmonic source h The relationship between is as shown in formula (14):

[0079] I Ah =A h I h h=3,5,…,H (14)

[0080] (2-2) Establishment of mathematical model for filter APF optimization configuration

[0081] The optimal configuration of the filter means that after the filter is installed, the harmonic content rate, harmonic voltage distortion rate and the allowable value of each harmonic current at each node of the network meet the requirements of the national standard, ensuring the safe operation of the filter while minimizing the initial investment of the filter and achieving the maximum economic benefit; therefore, the filter optimization configuration model takes the cost of the active power filter installed on the low-voltage side of the transformer in the distribution network as the objective function, as shown in formulas (15) and (16), and takes the allowable value of the harmonic current injected into the common connection point, the distortion rate and content rate of the harmonic voltage as the constraint conditions, as shown in formulas (17)-(19);

[0082]

[0083] S=3I Ah U (16)

[0084] HRU h =(U h / U 1 )×100%≤3.2% (17)

[0085]

[0086] I Bh ≤I h0 (19)

[0087] Where S is the rated capacity of the active filter, b 0 and b 1 The base price of the active filter is RMB 400,000 and the coefficient between capacity and cost is RMB 450,000 / MVA, HRU h is the voltage content of harmonics of order h, U h is the effective value of the hth harmonic voltage, U 1 is the effective value of the fundamental voltage, U THD is the total distortion rate of harmonic voltage, I Bh and I h0 It is the harmonic current injected into the common connection point and the allowable value of harmonic current.

[0088] The harmonic voltage content limit value in step (2-2) is 3.2%, the total harmonic voltage distortion limit value is 4%, and the allowable value of odd harmonic current injected into the common connection point (the reference short-circuit capacity is 100MVA) is shown in Table 1, all of which are applicable to 10kV distribution network.

[0089] Table 1 Allowable values ​​of odd harmonic current injected into the common connection point

[0090]

[0091] In order to enable those skilled in the art to better understand the present application, the present application will be further described in detail below in conjunction with the accompanying drawings.

[0092] like Figure 1 As shown in the figure, in order to optimize the comprehensive resource configuration of the power grid after the large-scale electric kiln is connected to the distribution network, it is necessary to effectively solve the multi-objective reactive power optimization model and the filter optimization configuration model. This paper builds the following model based on Matlab and OpenDSS platform. Figure 1The computing platform shown in the figure. The entire computing platform mainly includes two computing modules: 1) distribution network three-phase power flow calculation module, 2) distribution network harmonic calculation module, and 3) comprehensive resource optimization configuration module. OpenDSS is used to perform distribution network three-phase power flow calculation and harmonic calculation, and comprehensive resource optimization configuration is implemented on the MATLAB platform. Based on the component object (OpenDSSEngine.DLL), data communication between the OpenDSS computing program and other computing and analysis modules of the MATLAB platform can be realized.

[0093] An OpenDSS / MATLAB joint simulation platform was built: first, a distribution network model of the substation was built on the OpenDSS software and rapid power flow calculation and harmonic calculation were performed. Secondly, the model of the treatment device and parameter setting were completed in MATLAB, as well as the establishment of the improved particle swarm optimization algorithm mentioned above. The two softwares exchanged information through the COM interface. Direct control of the treatment device was achieved in MATLAB, and the node voltage, power loss and harmonic components obtained by the OpenDSS power flow calculation were returned to the MATLAB optimization algorithm part through the COM interface to determine whether the constraints were met. The above process was repeated until the optimization was completed.

[0094] The specific steps include:

[0095] Step 1: Optimization process of comprehensive resources of distribution network for large-scale application of electric kilns

[0096] like Figure 2 The overall flow chart for establishing and solving the comprehensive resource optimization configuration model for the distribution network after large-scale application of electric kilns. The specific steps are as follows:

[0097] 1) Build a distribution network model of IEEE33 nodes after large-scale access of electric kilns in OpenDSS, set network operation parameters and harmonic source spectrum parameters for fast power flow calculation, and realize data transmission of node voltage, power factor and active power between OpenDSS and MATLAB through COM interface;

[0098] 2) Carry out the optimization of phase I, build a multi-objective reactive power optimization model in MATLAB, solve it using the particle swarm algorithm, and determine the optimal installation location and capacity of parallel and series reactive power compensation devices;

[0099] 3) Perform harmonic analysis on the distribution network and transmit the harmonic components of each node in OpenDSS and MATLAB through the COM interface;

[0100] 4) Carry out optimization in phase II, build the active filter optimization configuration model in MATLAB, use the particle swarm algorithm to solve, and determine the optimal compensation capacity of the APF.

[0101] 5) Output the optimization results of phase I and phase II.

[0102] Step 2, Phase I reactive power optimization configuration plan

[0103] As shown in Figure 3, the installation location and capacity of the optimized management device after the electric kiln is connected on a large scale based on the IEEE33 node network as the prototype. The penetration rate of the electric kiln starts from 20% and gradually increases to 30%, 40%, and 50%. When the distribution network is connected to electric kiln loads with different penetration rates, the optimal configuration of reactive power compensation is used to optimize the reactive power configuration of the distribution network after the electric kiln is connected on a large scale. The comparison of the voltage amplitude of the distribution network node before and after optimization is shown in Figure 3.

[0104] 1) According to the optimization configuration results, reactive power optimization is performed when the penetration rate of electric kilns gradually increases. In low penetration scenarios, the reactive power problem can be solved by simple parallel compensation, but as the penetration rate increases, simple parallel reactive power optimization is not enough to solve the reactive power problem. The combination of series compensation and parallel compensation can quickly and significantly improve the voltage level of the distribution network.

[0105] 2) As shown in Figure 3, after the distribution network with electric kiln load penetration rate of 20%-50% is reasonably configured with reactive compensation devices, the lowest node voltage of each node increases from 0.8739pu, 0.8159pu, 0.7366pu and 0.5497pu to 0.9552pu, 0.9857pu, 0.9853pu and 0.9346pu before and after optimization, and the lowest node voltage is greater than 0.93pu, and the voltage qualification rate is significantly improved. After compensation, the power factor can reach above 0.95, which significantly improves the power supply quality of users.

[0106] Step 3: Phase II Harmonic Control Device Optimization Configuration Plan

[0107] Phase II calculation example continues to use the IEEE33 node distribution system, the system base voltage is 10.5kV, the base capacity is 10MVA, and the harmonic control of the large-scale application of the harmonic source electric kiln is considered. The four application scenarios with a penetration rate of 20%-50% are mainly considered. The active filter is optimized for the IEEE33 distribution network connected to the electric kiln on a large scale. The optimal configuration of the active filter is as follows: Figure 4 shown.

[0108] After optimizing the configuration of active filters in the distribution network, the total harmonic voltage distortion rates of the distribution networks in various scenarios under different penetration rates were 0.42%, 0.64%, 0.89% and 1.23%, respectively, all dropping to within 4%. The harmonic currents at the common connection points were all lower than the allowable values ​​of harmonic currents specified in the national standard, improving the operating conditions of the system.

[0109] In summary, after the large-scale connection of kiln equipment, a two-stage power grid comprehensive resource optimization configuration model considering reactive power optimization and harmonic control is proposed for four scenarios after the large-scale application of electric kilns. A multi-objective optimization algorithm based on the joint simulation platform of Matlab and OpenDSS is proposed. The low voltage problem, harmonic problem and high reactive power loss problem of the distribution network after the large-scale electric kilns are connected to the distribution network are solved, the power supply quality of the distribution network is improved, and good economic results are achieved.

Claims

1. A comprehensive resource optimization configuration method after large-scale application of electric kilns, characterized in that It includes two parts: configuration of reactive power optimization link and optimization configuration of harmonic control link; wherein, the reactive power optimization link is used to establish optimization models from three aspects of investment, network loss and voltage deviation, evaluate the impact of electric kilns on the system after they are connected to the distribution network, and use particle swarm optimization algorithm to optimize the site selection and capacity setting of series compensation devices and parallel compensation devices in the distribution network; the harmonic control link refers to configuring filters in the distribution network to eliminate harmonics, so as to centrally and uniformly control harmonics; The configuration of the reactive power optimization link includes the following steps: (1-1) Choice of objective function: When electric kilns are used in distribution networks on a large scale, the equivalent model of the distribution network consists of electric kiln loads, reactive power compensation devices, active power filter devices, and the upper power grid system. The three objective functions are to minimize the investment in reactive power compensation devices, minimize voltage deviation, and minimize network loss, and perform multi-objective reactive power optimization of the system according to formulas (1)-(4). F=min[f cost ,f V ,f loss ] (1) In the formula, f cost 、f V 、f loss They represent the minimum investment in reactive power compensation equipment, the minimum voltage deviation, and the minimum network loss; C invest , C cap are the total investment and unit capacity investment of reactive power compensation device respectively; Q c is the reactive capacity connected at node i; U i , ΔU are the voltage of node i, the reference voltage amplitude during normal operation and the total voltage deviation respectively; N b is the number of branches in the system; R i The resistance of branch i; P i , Q i , P loss are the active power, reactive power and network loss of the distribution system of branch i respectively; (1-2) Determination of constraints: The inequality constraints are divided into control variable constraints and state variable constraints. The generator node voltage and reactive power compensation device capacity are selected as control variable constraints, and the load node voltage and distribution network power factor are selected as state variable constraints, as shown in formula (5) and formula (6), respectively: Where U Gi , U Gimin , U Gimax are the breakpoint voltage of generator node i and its lower and upper limits respectively; Q Ci , Q Cimin , Q Cimax are the reactive power compensation capacity and its lower and upper limits respectively; U Li , U Limin , U Limax are the voltage of load node i and its lower and upper limits respectively; pu is the power factor during distribution network operation; N G 、N C 、N L They are the number of power grid generator nodes, reactive power compensation nodes, and PQ nodes; (1-3) Normalization Since the dimensions and units of voltage deviation, active power loss and investment cost are different, they cannot be simply connected by weights. It is necessary to normalize the weights first and find the minimum value of the objective function, which is a cost-based quantitative target. (1-4) Choice of weight The voltage deviation is taken as the first-level weight W1; the network loss cost value is taken as the second-level weight W2; the fixed investment cost in the power company is taken as the third-level weight W3; then the objective function of the multi-objective optimization after large-scale application of electric kilns is as shown in formula (10): F=W1f1+W2f2+W3f3 (10) Where: W1, W2, W3 are the 1st, 2nd, and 3rd level weights respectively, and F is the objective function of multi-objective optimization after large-scale application of electric kilns.

2. According to claim 1, a comprehensive resource optimization configuration method after large-scale application of electric kilns, characterized in that The weights of the steps (1-4) are selected by the expert decision-making method, namely the Delphi method; the importance of each target is judged by the traditional analytic hierarchy process according to the expert experience, and the indicator judgment matrix J shown in formula (11) is a 3*3 matrix: Using expert experience, the weight W of the first-level index is obtained as: W＝[0.071927 0.64912 0.27895] (12) Therefore, the objective function of multi-objective optimization after large-scale application of electric kilns is: min F=0.071927f1+0.64912f2+0.27895f3 (13).

3. The comprehensive resource optimization configuration method after large-scale application of electric kilns according to claim 1 is characterized in that The optimization of the harmonic control link includes the following steps: (2-1) Establishment of active filter equivalent model The essence of the active filter APF is a controlled current source with current feedback control. Its equivalent model should include two parts: a three-level inverter and a power grid. Among them, the three-level inverter part includes the command current I ref and output impedance Z1, the grid part consists of grid voltage E and grid impedance Z E Assuming that the active filter absorbs only part of the harmonic current of this node according to a certain proportion, use A h It represents the coefficient of the hth harmonic current generated by the harmonic source at the active filter absorption node. Then the hth harmonic current I absorbed by each active filter is Ah The harmonic current I injected by the harmonic source h The relationship between is as shown in formula (14): I Ah =A h I h h=3,5,...,H (14) (2-2) Establishment of mathematical model for filter APF optimization configuration The filter optimization configuration model takes the cost of the active power filter installed on the low-voltage side of the transformer in the distribution network as the objective function, as shown in formulas (15) and (16), and takes the allowable value of the harmonic current injected into the common connection point, the distortion rate and content rate of the harmonic voltage as the constraints, as shown in formulas (17) to (19); S=3I Ah U (16) HRU h =(U h / U1)×100%≤3.2% (17) I Bh ≤I h0 (19) In the formula, S is the rated capacity of the active filter, b0 and b1 are the base price of the active filter, 400,000 yuan, and the coefficient between capacity and cost, 450,000 yuan / MVA, respectively. k is the voltage content of harmonics of order h, U h is the effective value of the hth harmonic voltage, U1 is the effective value of the fundamental voltage, and U THD is the total distortion rate of harmonic voltage, I Bh and I h0 It is the harmonic current injected into the common connection point and the allowable value of harmonic current.

4. According to claim 3, the comprehensive resource optimization configuration method after large-scale application of electric kilns is characterized in that The harmonic voltage content rate limit value in step (2-2) is 3.2%, the total harmonic voltage distortion rate limit value is 4%, and the allowable value of the odd harmonic current injected into the common connection point is: 。

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