Power distribution network line loss determination method and system

Abstract

The invention discloses a power distribution network line loss determination method comprising the following steps: obtaining line parameters of a to-be-tested line in a power distribution network, and setting a plurality of nodes on the to-be-tested line; wherein each node corresponds to one branch line, and a line section is formed between every two adjacent nodes; calculating the branch current of each branch based on the line parameters; correcting the node voltages of all the nodes and the branch current by adopting an iterative algorithm until a preset convergence condition is met, and obtaining a corrected final branch current; determining the total loss power of the to-be-tested line according to the final branch current and the line parameters of all the branches; the line loss on the power grid line can be accurately calculated, potential safety hazards in operation of the power grid can be found and solved in time, and the safety and reliability of the power distribution network are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution lines, and in particular to a method and system for determining line loss in a power distribution network. Background Art

[0002] During the power transmission process, electric energy will be lost on the transmission line, forming line loss. With the widespread application of distributed power sources, the traditional distribution network structure and operation mode have undergone significant changes. The access of distributed power sources has changed the power flow distribution and voltage level of the distribution network, which has had a great impact on the line loss. Therefore, in the planning and design stage of the distribution network, the line loss assessment on the line must be considered in order to provide a reasonable and efficient power grid configuration.

[0003] As a lower-level medium-voltage distribution network, the 10kV distribution network has complex branches and a large proportion of line loss in the total loss. At present, the calculation method of the theoretical line loss of the medium-voltage distribution network takes the current from the starting end to the load end on the main line of the power grid as a fixed value for calculation, without considering the power loss on the line. The calculation results are usually inaccurate, resulting in inaccurate assessment of the security of the power grid, which in turn affects the safety and reliability of the distribution network. Summary of the invention

[0004] The embodiment of the present invention provides a method for determining line loss in a distribution network, which can accurately calculate line loss on a power grid line, timely discover and resolve potential safety hazards in power grid operation, and improve the safety and reliability of the distribution network.

[0005] In a first aspect, an embodiment of the present invention provides a method for determining line loss in a distribution network, comprising:

[0006] Acquire the line parameters of the line to be tested in the distribution network, and set a plurality of nodes on the line to be tested; wherein each of the nodes corresponds to a branch line, and a line segment is formed between two adjacent nodes;

[0007] Based on the line parameters, calculating the branch current of each branch line;

[0008] Adopting an iterative algorithm to correct the node voltages of all the nodes and the branch currents until a preset convergence condition is met, and obtaining the corrected final branch current; wherein the node voltage is the bus voltage;

[0009] The total power loss of the line to be tested is determined according to the final branch line currents of all the branches and the line parameters.

[0010] Furthermore, the line parameters include line segment length, unit resistance, unit reactance, node parameters and branch parameters.

[0011] Further, the calculating the branch current of each branch based on the line parameters includes:

[0012] Obtaining the load of each of the nodes from the node parameters, and obtaining the active load, reactive load and distributed power supply power of the branch corresponding to each of the nodes from the branch parameters;

[0013] The branch current of each branch is calculated based on the on-load, the active load, the reactive load and the distributed power source power.

[0014] Furthermore, the adopting of an iterative algorithm to correct the node voltages of all the nodes and the branch currents until a preset convergence condition is met and a corrected final branch current is obtained includes:

[0015] Based on the line parameters, the node voltage and the branch current are corrected, and the node voltage change rate before and after the node correction is calculated;

[0016] An iterative algorithm is used to continuously perform correction operations until the node voltage change rate of the node at one end of the busbar in the measured line is less than a preset change rate threshold, and it is determined that the convergence condition is met, and the final branch current after the convergence condition is met is obtained.

[0017] Furthermore, the modifying of the node voltage and the branch current based on the line parameters includes:

[0018] Calculate the voltage drop between every two adjacent nodes based on the line segment length, the unit resistance, the unit reactance and the branch current;

[0019] The node voltage and the branch current are modified according to the voltage drop.

[0020] Further, determining the total power loss of the line to be tested according to the final branch line currents of all the branches and the line parameters includes:

[0021] Calculating the active line loss power of the line segment according to the final branch line current, the line segment length and the unit resistance;

[0022] Calculating reactive line loss power of the line segment according to the final branch line current, the line segment length and the unit reactance;

[0023] The active line loss power and the reactive line loss power of all the line segments are summed up to obtain the total loss power of the line to be tested.

[0024] In a second aspect, an embodiment of the present invention provides a system for determining line loss in a distribution network, comprising:

[0025] A node setting module is used to obtain line parameters of a line to be tested in a distribution network, and to set a number of nodes on the line to be tested; wherein each of the nodes corresponds to a branch line, and a line segment is formed between two adjacent nodes;

[0026] A current calculation module, used for calculating the branch current of each branch line based on the line parameters;

[0027] A current correction module, used to correct the node voltages of all the nodes and the branch currents by adopting an iterative algorithm until a preset convergence condition is met, and obtain the corrected final branch current; wherein the node voltage is the bus voltage;

[0028] The loss calculation module is used to determine the total power loss of the line to be tested according to the final branch line currents of all the branches and the line parameters.

[0029] Furthermore, the line parameters include line segment length, unit resistance, unit reactance, node parameters and branch parameters.

[0030] Furthermore, the current calculation module is also used for:

[0031] Obtaining the load of each of the nodes from the node parameters, and obtaining the active load, reactive load and distributed power supply power of the branch corresponding to each of the nodes from the branch parameters;

[0032] The branch current of each branch is calculated based on the on-load, the active load, the reactive load and the distributed power source power.

[0033] Furthermore, the current correction module is also used for:

[0034] Based on the line parameters, the node voltage and the branch current are corrected, and the node voltage change rate before and after the node correction is calculated;

[0035] An iterative algorithm is used to continuously perform correction operations until the node voltage change rate of the node at one end of the busbar in the measured line is less than a preset change rate threshold, and it is determined that the convergence condition is met, and the final branch current after the convergence condition is met is obtained.

[0036] Compared with the prior art, a method for determining line loss in a distribution network provided by an embodiment of the present invention has the following beneficial effects: by obtaining line parameters of a line to be tested in the distribution network, a plurality of nodes are set on the line to be tested; wherein each of the nodes corresponds to a branch line, and a line segment is formed between two adjacent nodes; based on the line parameters, the branch current of each branch line is calculated; an iterative algorithm is used to correct the node voltages and the branch currents of all the nodes until a preset convergence condition is met, and the corrected final branch current is obtained; based on the final branch currents and the line parameters of all the branches, the total power loss of the line to be tested is determined; the present invention can accurately calculate the line loss on the power grid line, timely discover and solve the potential safety hazards in the operation of the power grid, and improve the safety and reliability of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical features of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 It is a flow chart of a method for determining line loss in a distribution network provided by an embodiment of the present invention;

[0039] Figure 2 It is a schematic diagram of a line to be tested in a method for determining line loss in a distribution network provided by an embodiment of the present invention;

[0040] Figure 3 It is a structural schematic diagram of a distribution network line loss determination system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In a first aspect, an embodiment of the present invention provides a method for determining line loss in a distribution network. Figure 1 , which is a flow chart of an embodiment of a method for determining line loss in a distribution network provided by the present invention.

[0043] like Figure 1 As shown, the method comprises the following steps:

[0044] S1: obtaining line parameters of a line to be tested in a distribution network, and setting a plurality of nodes on the line to be tested; wherein each of the nodes corresponds to a branch line, and a line segment is formed between two adjacent nodes;

[0045] S2: Calculating the branch line current of each branch line based on the line parameters;

[0046] S3: using an iterative algorithm to correct the node voltages of all the nodes and the branch currents until a preset convergence condition is met, and obtaining a corrected final branch current; wherein the node voltage is a bus voltage;

[0047] S4: Determine the total power loss of the line to be tested according to the final branch line currents of all the branches and the line parameters.

[0048] In a specific implementation, the 10kV distribution network is a medium-voltage distribution network of a lower level, and the branches are complex. The line loss accounts for a large proportion of the total loss. A method for accurately calculating the line loss on the power grid line is needed. The present invention first uses a 10kV trunk line in the distribution network as the line to be tested, obtains the line parameters of the line to be tested, and divides the line into several line segments using several nodes. Each node serves as an access point from a source load end to the line. A source load end includes a certain number of loads or distributed power sources. The node and the source load end form a branch line. For example, see Figure 2 As shown, Figure 2 Schematic diagram of the circuit to be tested of the present invention, wherein U0 is the bus voltage at the bus terminal of the circuit to be tested, U1 to U8 are the node voltages of each node, D 0-1 To D 7-8 It represents the line section between each node, I1 to I8 are the branch currents of the branches corresponding to each node, P1 to P8 are the active line loss power of each line section, Q1 to Q8 are the reactive line loss power of each line section, and W1 to W8 are the total loss power of each line section.

[0049] First, based on the obtained line parameters, the branch current on each branch is calculated. The direction of the current from the bus end to the line end and from the line node to the source and load end is stipulated to be positive. The bus voltage is used as the node voltage of each node, and the node voltage and branch current are corrected to determine whether the corrected node meets the preset convergence conditions. If not, continue to correct. If satisfied, obtain the corrected final branch current. According to the final branch current and line parameters, determine the total power loss of the line to be tested.

[0050] It should be noted that the number of node settings is related to the accuracy of line loss calculation, and will also affect the amount of calculation. The present invention is set according to the node load of each node or the output of the distributed power source controlled within 300-600kW. The load of each node and the output of the distributed power source can be obtained by measurement or calculation. The number of node settings can also be set according to the specific requirements in the implementation. No specific limitation is made here. The branches in the present invention can correspond to one or more branches in actual applications.

[0051] In summary, the present invention obtains the line parameters of the line to be tested in the distribution network, and sets several nodes on the line to be tested; wherein each of the nodes corresponds to a branch line, and a line segment is formed between two adjacent nodes; based on the line parameters, the branch current of each branch line is calculated; an iterative algorithm is used to correct the node voltages and the branch currents of all the nodes until the preset convergence conditions are met, and the corrected final branch current is obtained; according to the final branch currents of all the branches and the line parameters, the total power loss of the line to be tested is determined; the present invention corrects the node voltage and uses an iterative algorithm to obtain node data that meets the accuracy requirements, so as to accurately calculate the line loss on the power grid line, timely discover and solve the safety hazards in the operation of the power grid, and improve the safety and reliability of the distribution network.

[0052] In an optional implementation, the line parameters include line segment length, unit resistance, unit reactance, node parameters and branch parameters.

[0053] Specifically, the line parameters of the line to be tested include the line segment length, unit resistance and unit reactance of each line segment, as well as node parameters corresponding to each node and branch parameters corresponding to each branch.

[0054] In an optional implementation manner, the calculating the branch current of each branch based on the line parameter includes:

[0055] Obtaining the load of each of the nodes from the node parameters, and obtaining the active load, reactive load and distributed power supply power of the branch corresponding to each of the nodes from the branch parameters;

[0056] The branch current of each branch is calculated based on the on-load, the active load, the reactive load and the distributed power source power.

[0057] Specifically, the branch current on the branch from each node to its source load end is equal to the ratio of the source load power on the branch to the node voltage. The calculation formula is as follows:

[0058]

[0059] Among them, Ik represents the branch current of the kth branch, P k represents the active load on the kth branch, Q k represents the reactive load on the kth branch, W k represents the distributed generation power on the kth branch, U k Represents the node voltage of the kth node, and the value range of k is 1 to n.

[0060] It should be noted that the node voltage used in the calculation is the voltage in the ideal state, that is, it is assumed that the node voltage of each node is equal to the bus voltage U0, that is, U k =U0.

[0061] Starting from the bus terminal to the end of the line, the line segment between the i-1th node and the i-th node is the i-th line segment D. i-1_i , the i-th line segment D i-1_i The current is equal to the sum of the currents from the ith branch to the nth branch, refer to the following formula:

[0062]

[0063] Among them, I i-1_i represents the current of the ith line segment, I k represents the branch current of the kth branch, and n represents the total number of nodes on the line to be tested.

[0064] In an optional implementation manner, the adopting an iterative algorithm to correct the node voltages of all the nodes and the branch currents until a preset convergence condition is met and a corrected final branch current is obtained includes:

[0065] Based on the line parameters, the node voltage and the branch current are corrected, and the node voltage change rate before and after the node correction is calculated;

[0066] An iterative algorithm is used to continuously perform correction operations until the node voltage change rate of the node at one end of the busbar in the measured line is less than a preset change rate threshold, and it is determined that the convergence condition is met, and the final branch current after the convergence condition is met is obtained.

[0067] Specifically, based on the obtained line parameters, an iterative algorithm is used to correct the node voltage and branch current, and the node voltage change rate before and after the node correction is calculated. The change rate threshold is set in advance, and the node voltage change rate is compared with the change rate threshold. When the absolute value of the node voltage change rate is greater than or equal to the change rate threshold, the convergence condition is not met, and the correction operation needs to be continued. When the absolute value of the node voltage change rate of the node at one end of the busbar in the measured line is less than the change rate threshold, it indicates that all node voltages have converged and are judged to meet the convergence condition, see the following formula:

[0068]

[0069] Among them, U′ i represents the corrected node voltage, U i It represents the node voltage before correction. The ratio of the corrected node voltage to the node voltage before correction minus 1 is the node voltage change rate. f represents the change rate threshold. The value of the change rate threshold can be adjusted according to the calculation accuracy requirements.

[0070] After the convergence conditions are met, the final node voltage of each node, the final branch current of each branch, and the final trunk current of the line to be tested are calculated.

[0071] In an optional implementation manner, the correcting the node voltage and the branch current based on the line parameter includes:

[0072] Calculate the voltage drop between every two adjacent nodes based on the line segment length, the unit resistance, the unit reactance and the branch current;

[0073] The node voltage and the branch current are modified according to the voltage drop.

[0074] Specifically, if there is impedance on the line to be tested, the node voltage and branch current need to be corrected based on the line parameters. First, the voltage drop on each line segment is calculated, that is, the voltage drop ΔU between two adjacent nodes. i-1_i , as shown below:

[0075] ΔU i-1_i =I i-1_i ×(R i-1_i +X i-1_i )×L i-1_i ;

[0076] Among them, I i-1_i represents the current of the ith line segment, R i-1_i represents the unit resistance of the ith line segment, X i-1_i represents the unit reactance of the ith line segment, L i-1_i Represents the length of the i-th line segment.

[0077] The node voltage is corrected based on the calculated voltage drop, as shown in the following equation:

[0078] U′ i =U i -ΔU i-1_i ;

[0079] Among them, U′ i represents the corrected node voltage, U i Indicates the node voltage before correction.

[0080] It can be understood that after the voltage of each node is corrected, the branch line current on each branch is corrected accordingly according to the node voltage.

[0081] In an optional implementation manner, determining the total power loss of the line to be tested according to the final branch line currents of all the branches and the line parameters includes:

[0082] Calculating the active line loss power of the line segment according to the final branch line current, the line segment length and the unit resistance;

[0083] Calculating reactive line loss power of the line segment according to the final branch line current, the line segment length and the unit reactance;

[0084] The active line loss power and the reactive line loss power of all the line segments are summed up to obtain the total loss power of the line to be tested.

[0085] Specifically, according to the final branch line current and line parameters of each line section, the active line loss power, reactive line loss power and total loss power of each line section are calculated. The calculation formula of the active line loss power is as follows:

[0086]

[0087] Among them, P Loss，i-1_i Indicates active line loss power, I i-1_i represents the final branch current of the ith line segment, R i-1_i Represents the unit resistance of the ith line segment, L i-1_i Represents the length of the i-th line segment.

[0088] The calculation formula for reactive line loss power is as follows:

[0089]

[0090] Among them, Q Loss，i-1_i Represents reactive line loss power, I i-1_i represents the final branch current of the ith line segment, X i-1_irepresents the unit reactance of the ith line segment, L i-1_i Represents the length of the i-th line segment.

[0091] The active line loss power and reactive line loss power on all line segments are summed up to obtain the total loss power on the line to be tested, which are the total active line loss power and the total reactive line loss power, respectively, expressed as follows:

[0092]

[0093]

[0094] Among them, P Loss Indicates the total active line loss power, Q Loss Indicates the total reactive line loss power.

[0095] In a second aspect, an embodiment of the present invention provides a system for determining line loss in a distribution network, see Figure 3 , which is a schematic diagram of the structure of a distribution network line loss determination system provided by an embodiment of the present invention.

[0096] like Figure 3 As shown, the system comprises:

[0097] The node setting module 21 is used to obtain the line parameters of the line to be tested in the distribution network, and to set a number of nodes on the line to be tested; wherein each of the nodes corresponds to a branch line, and a line segment is formed between two adjacent nodes;

[0098] A current calculation module 22, configured to calculate a branch line current of each branch line based on the line parameters;

[0099] The current correction module 23 is used to correct the node voltages of all the nodes and the branch currents by using an iterative algorithm until a preset convergence condition is met, and obtain the corrected final branch current; wherein the node voltage is the bus voltage;

[0100] The loss calculation module 24 is used to determine the total power loss of the line to be tested according to the final branch line currents of all the branches and the line parameters.

[0101] In an optional implementation, the line parameters include line segment length, unit resistance, unit reactance, node parameters and branch parameters.

[0102] In an optional implementation, the current calculation module 22 is further used for:

[0103] Obtaining the load of each of the nodes from the node parameters, and obtaining the active load, reactive load and distributed power supply power of the branch corresponding to each of the nodes from the branch parameters;

[0104] The branch current of each branch is calculated based on the on-load, the active load, the reactive load and the distributed power source power.

[0105] In an optional implementation, the current correction module 23 is further used for:

[0106] Based on the line parameters, the node voltage and the branch current are corrected, and the node voltage change rate before and after the node correction is calculated;

[0107] An iterative algorithm is used to continuously perform correction operations until the node voltage change rate of the node at one end of the busbar in the measured line is less than a preset change rate threshold, and it is determined that the convergence condition is met, and the final branch current after the convergence condition is met is obtained.

[0108] In an optional implementation, the current correction module 23 is further used for:

[0109] Calculate the voltage drop between every two adjacent nodes based on the line segment length, the unit resistance, the unit reactance and the branch current;

[0110] The node voltage and the branch current are modified according to the voltage drop.

[0111] In an optional implementation, the loss calculation module 24 is further used for:

[0112] Calculating the active line loss power of the line segment according to the final branch line current, the line segment length and the unit resistance;

[0113] Calculating reactive line loss power of the line segment according to the final branch line current, the line segment length and the unit reactance;

[0114] The active line loss power and the reactive line loss power of all the line segments are summed up to obtain the total loss power of the line to be tested.

[0115] The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. It should be pointed out that for those skilled in the art, several equivalent obvious variations and / or equivalent substitutions can be made without departing from the technical principles of the present invention. These obvious variations and / or equivalent substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A method for determining line loss in a distribution network, characterized in that: include: Acquire the line parameters of the line to be tested in the distribution network, and set a plurality of nodes on the line to be tested; wherein each of the nodes corresponds to a branch line, and a line segment is formed between two adjacent nodes; Based on the line parameters, calculating the branch current of each branch line; Adopting an iterative algorithm to correct the node voltages of all the nodes and the branch currents until a preset convergence condition is met, and obtaining the corrected final branch current; wherein the node voltage is the bus voltage; The total power loss of the line to be tested is determined according to the final branch line currents of all the branches and the line parameters.

2. The method for determining the line loss of a distribution network according to claim 1, characterized in that: The line parameters include line segment length, unit resistance, unit reactance, node parameters and branch parameters.

3. The method for determining the line loss of a distribution network according to claim 2, characterized in that: The calculating the branch current of each branch line based on the line parameters comprises: Obtaining the load of each of the nodes from the node parameters, and obtaining the active load, reactive load and distributed power supply power of the branch corresponding to each of the nodes from the branch parameters; The branch current of each branch is calculated based on the on-load, the active load, the reactive load and the distributed power source power.

4. The method for determining the line loss of a distribution network according to claim 2, characterized in that: The adopting of an iterative algorithm to correct the node voltages of all the nodes and the branch currents until a preset convergence condition is satisfied and a corrected final branch current is obtained includes: Based on the line parameters, the node voltage and the branch current are corrected, and the node voltage change rate before and after the node correction is calculated; An iterative algorithm is used to continuously perform correction operations until the node voltage change rate of the node at one end of the busbar in the measured line is less than a preset change rate threshold, and it is determined that the convergence condition is met, and the final branch current after the convergence condition is met is obtained.

5. The method for determining the line loss of a distribution network according to claim 4, characterized in that: The correcting the node voltage and the branch line current based on the line parameters includes: Calculate the voltage drop between every two adjacent nodes based on the line segment length, the unit resistance, the unit reactance and the branch current; The node voltage and the branch current are modified according to the voltage drop.

6. The method for determining the line loss of a distribution network according to claim 2, characterized in that: The determining the total power loss of the line to be tested according to the final branch line currents of all the branches and the line parameters comprises: Calculating the active line loss power of the line segment according to the final branch line current, the line segment length and the unit resistance; Calculating reactive line loss power of the line segment according to the final branch line current, the line segment length and the unit reactance; The active line loss power and the reactive line loss power of all the line segments are summed up to obtain the total loss power of the line to be tested.

7. A distribution network line loss determination system, characterized in that: include: A node setting module is used to obtain line parameters of a line to be tested in a distribution network, and to set a number of nodes on the line to be tested; wherein each of the nodes corresponds to a branch line, and a line segment is formed between two adjacent nodes; A current calculation module, used for calculating the branch current of each branch line based on the line parameters; A current correction module, used to correct the node voltages of all the nodes and the branch currents by adopting an iterative algorithm until a preset convergence condition is met, and obtain the corrected final branch current; wherein the node voltage is the bus voltage; The loss calculation module is used to determine the total power loss of the line to be tested according to the final branch line currents of all the branches and the line parameters.

8. The distribution network line loss determination system according to claim 7, characterized in that: The line parameters include line segment length, unit resistance, unit reactance, node parameters and branch parameters.

9. The distribution network line loss determination system according to claim 8, characterized in that: The current calculation module is also used for: Obtaining the load of each of the nodes from the node parameters, and obtaining the active load, reactive load and distributed power supply power of the branch corresponding to each of the nodes from the branch parameters; The branch current of each branch is calculated based on the on-load, the active load, the reactive load and the distributed power source power.

10. The distribution network line loss determination system according to claim 8, characterized in that: The current correction module is also used for: Based on the line parameters, the node voltage and the branch current are corrected, and the node voltage change rate before and after the node correction is calculated; An iterative algorithm is used to continuously perform correction operations until the node voltage change rate of the node at one end of the busbar in the measured line is less than a preset change rate threshold, and it is determined that the convergence condition is met, and the final branch current after the convergence condition is met is obtained.

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