Global local cooperative partition cooperative resonance suppression method and device

Abstract

The invention relates to the technical field of cable line power distribution network harmonic resonance treatment, in particular to a global and local cooperative partition cooperative resonance suppression method and device. The method comprises the steps of determining a harmonic conductance sensitivity index of each node in a power distribution network according to a target power distribution network admittance matrix parameter, and performing node region division; performing modal analysis on the admittance matrix parameters to obtain modal impedance and participation factors; determining a global optimal virtual admittance instruction value according to the modal impedance, the participation factor and the voltage distortion rate; according to the global optimal virtual admittance instruction value and the voltage distortion rate, determining a regional optimal virtual admittance instruction value in the region; and determining a harmonic compensation current value according to the regional optimal virtual admittance instruction value and the harmonic voltage. According to the method, harmonic suppression is realized for the whole power distribution network by adopting a partition and cooperation mode, and meanwhile, for background harmonic injection change, external interference such as resonance center offset and the like can be effectively overcome, so that the optimal harmonic suppression effect is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of harmonic resonance control in cable line distribution networks, and in particular to a method and device for global-local cooperative partition collaborative resonance suppression. Background Art

[0002] With the proposal of the "dual carbon" goal, a large number of new energy sources have been integrated into the distribution network. Inverters and other power electronic equipment are connected to the grid as interface devices, injecting a large amount of background harmonics into the grid. At the same time, with the evolution of urbanization, underground cable lines are widely used in the current urban distribution network. Due to the high ground capacitance characteristics of underground cable lines, they are easy to resonate with grid-connected power electronic equipment, resulting in background harmonic amplification and reduced power quality. Traditional harmonic control equipment samples harmonic currents and injects compensation currents to control harmonics. This is a "point-to-point" control mode, and it is difficult to play a role in harmonic control of the entire distribution network. At the same time, changes in distribution network parameters or changes in the number of grid-connected inverters will cause the resonance center of the distribution network to shift, and traditional harmonic control modes cannot achieve effective harmonic control. Summary of the invention

[0003] The present invention proposes a global-local cooperative partition collaborative resonance suppression method and device to solve the problem that the existing harmonic control method of the distribution network is a point-to-point control mode, which cannot be used for the entire distribution network and has a resonance center offset, resulting in the failure to achieve the best control effect.

[0004] According to one aspect of the present invention, a global-local cooperation partition collaborative resonance suppression method is provided, comprising:

[0005] Obtain the target distribution network admittance matrix parameters, node voltage distortion rate and harmonic voltage;

[0006] Determine the harmonic conductivity sensitivity index of each node in the distribution network according to the admittance matrix parameters, and divide the nodes into regions according to the harmonic conductivity sensitivity index;

[0007] Performing modal analysis according to the admittance matrix parameters to obtain modal impedance and participation factor corresponding to each node;

[0008] Determining a global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate;

[0009] Determining a regional optimal virtual admittance command value within the region according to the global optimal virtual admittance command value and the voltage distortion rate;

[0010] A harmonic compensation current value is determined according to the optimal virtual admittance command value and the harmonic voltage in the area, and harmonic resonance suppression is performed by inputting the harmonic compensation current into the target distribution network.

[0011] Preferably, the method for determining the harmonic conductivity sensitivity index of each control node and controlled node in the distribution network according to the admittance matrix parameters comprises:

[0012] The harmonic conductivity sensitivity index of each node is calculated using formula (1);

[0013]

[0014] Where: U h,j is the hth harmonic voltage at node j; G h,ci is the equivalent conductance of the harmonic control equipment at node j with respect to the hth harmonic; δ is the differential operator.

[0015] Preferably, the method for dividing nodes into regions according to the harmonic conductivity sensitivity index comprises:

[0016] Each inverter in the power grid is regarded as a control node, and the remaining nodes are regarded as controlled nodes;

[0017] According to the capacity of the inverter of the control node, setting the sensitivity index threshold corresponding to each control node;

[0018] Taking each of the control nodes as a partition, in the harmonic conductivity sensitivity index, the controlled nodes whose sensitivity index threshold value is greater than that corresponding to a certain control node are divided into the partition corresponding to the control node;

[0019] After the division is completed, the number of controlled nodes in each partition is adjusted so that the inverter capacity within the area matches the number of controlled nodes.

[0020] Preferably, the method of performing modal analysis according to the admittance matrix parameters to obtain modal impedance includes:

[0021] The modal impedance is calculated using formula (2);

[0022] TU h =Λ -1 TI h (2);

[0023] Where: T is the right eigenvalue vector of the node admittance matrix Y decomposition; Λ -1 is the modal impedance parameter vector; U h is the node voltage vector; I h is the node current vector.

[0024] Preferably, the method of performing modal analysis according to the admittance matrix parameters to obtain the participation factor corresponding to each node includes:

[0025] According to the modal impedance, the participation factor is calculated using formula (3);

[0026]

[0027] Where: L is the left eigenvalue vector of the node admittance matrix Y decomposition; is the system modal impedance parameter under m mode; PF n,m is the participation factor of node n in mode m; -1 is the modal impedance parameter vector; T is the right eigenvalue vector of the node admittance matrix Y decomposition; I h is the node current vector.

[0028] Preferably, the method for determining the global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate includes:

[0029] The global optimal virtual admittance command value is calculated using equations (4) to (6);

[0030]

[0031]

[0032]

[0033] Where: N is the number of system nodes; a i is the participation factor weight of node i; β i is the modal impedance weight of node i; THDV i is the harmonic voltage distortion rate of node i; H is the maximum harmonic order considered; PF i,h is the participation factor of node i in mode h; Z mod,i,h is the modal impedance value of node i under the hth harmonic; I h,i is the hth harmonic voltage value of node i; Y h,ii is the hth harmonic admittance of node i; G h,i0 is the global optimal virtual admittance command value; U h,i is the hth harmonic voltage value of node i; V h,i is the hth harmonic amplitude of node i, and V1 is the fundamental voltage amplitude.

[0034] Preferably, the capacity limiting condition when calculating the global optimal virtual admittance command value is as shown in formula (7);

[0035]

[0036] Where: S ci,MFGCI is the working capacity of the multifunctional grid-connected inverter in the target distribution network; It is the remaining capacity of the multifunctional grid-connected inverter;

[0037] When calculating the global optimal virtual admittance command value, the voltage distortion rate of all nodes and their harmonics of each order meets the restrictions as shown in formula (8);

[0038]

[0039] Where: THDV j is the harmonic voltage distortion rate of node j; THDV max is the maximum harmonic voltage distortion rate value of each node; HRU j,h is the hth harmonic voltage distortion rate value of node j; HRU h,max is the maximum voltage distortion rate value of the hth harmonic at each node.

[0040] Preferably, the method for determining the regional optimal virtual admittance command value within the region according to the global optimal virtual admittance command value and the voltage distortion rate includes:

[0041] The optimal virtual admittance command value of the region is calculated using formula (9);

[0042]

[0043] Where: x i is the state variable in the formula; t is the time value; T is the maximum time considered; H is the maximum harmonic order considered; m E is the number of nodes considered; G h,i0 is the global optimal virtual admittance command value; G h,i is the virtual admittance command value in the region; n is the number of nodes in the region; m is the number of management equipment in the region; THDV j,t is the harmonic voltage distortion rate of node j at time t; f1 is the objective function 1; f 2,t is the objective function 2; f m,t is the optimal objective function for the overall region.

[0044] Preferably, the method for determining the harmonic compensation current value according to the regional optimal virtual admittance command value and the harmonic voltage includes:

[0045] Harmonic compensation current value = regional optimal virtual admittance command value × harmonic voltage.

[0046] According to one aspect of the present invention, a global-local cooperation partition collaborative resonance suppression device is provided, comprising:

[0047] A global controller is used to obtain the target distribution network admittance matrix parameters and node voltage distortion rate; determine the harmonic conductivity sensitivity index of each node in the distribution network according to the admittance matrix parameters, and divide the nodes into regions according to the harmonic conductivity sensitivity index; perform modal analysis according to the admittance matrix parameters to obtain the modal impedance and participation factor corresponding to each node; determine the global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate;

[0048] The regional controller is used to determine the regional optimal virtual admittance command value within the region at a second predetermined time interval based on the global optimal virtual admittance command value and voltage distortion rate sent by the global controller at the first predetermined time interval, and determine the harmonic compensation current value based on the regional optimal virtual admittance command value and the harmonic voltage, and send the harmonic compensation current value to the harmonic control equipment in the corresponding area, so that the harmonic control equipment inputs the current of the harmonic compensation current value into the distribution network to suppress harmonic resonance.

[0049] The present invention has at least the following beneficial effects:

[0050] The present invention proposes a global-local cooperation partition collaborative resonance suppression method and device, which divides the distribution network into regions, determines the optimal virtual admittance command value for each region, and then determines the harmonic compensation current value to achieve harmonic resonance suppression. The partition and cooperation mode is adopted to achieve harmonic control of the entire distribution network. At the same time, the background harmonic injection changes can effectively overcome external interference such as resonance center offset and achieve the best harmonic control effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present invention and, together with the specification, are used to explain the technical solutions of the present invention.

[0052] Figure 1 A flow chart of a global-local cooperation partition collaborative resonance suppression method according to an embodiment of the present invention is shown.

[0053] Figure 2 A schematic diagram of area division according to an embodiment of the present invention is shown;

[0054] Figure 3 A schematic diagram of system modal impedance according to an embodiment of the present invention is shown;

[0055] Figure 4 A schematic diagram of node harmonic voltage distortion rate under a global optimal virtual admittance instruction value according to an embodiment of the present invention is shown;

[0056] Figure 5A schematic diagram of node harmonic voltage distortion rate under global optimal and regional optimal virtual admittance instruction values ​​according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0057] Various exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0058] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0059] The term "and / or" herein is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the term "at least one" herein represents any combination of at least two of any one or more of a plurality of. For example, including at least one of A, B, and C can represent including any one or more elements selected from the set consisting of A, B, and C.

[0060] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0061] Figure 1 A flow chart of a global-local cooperation partition collaborative resonance suppression method according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of area division according to an embodiment of the present invention is shown; Figure 3 A schematic diagram of system modal impedance according to an embodiment of the present invention is shown; Figure 4 A schematic diagram of node harmonic voltage distortion rate under a global optimal virtual admittance instruction value according to an embodiment of the present invention is shown; Figure 5 A schematic diagram of node harmonic voltage distortion rate under global optimal and regional optimal virtual admittance instruction values ​​according to an embodiment of the present invention is shown. Figure 1-5As shown, a global-local cooperative partition collaborative resonance suppression method includes: step S01: obtaining the target distribution network admittance matrix parameters, node voltage distortion rate and harmonic voltage; step S02: determining the harmonic conductivity sensitivity index of each node in the distribution network according to the admittance matrix parameters, and dividing the nodes into regions according to the harmonic conductivity sensitivity index; step S03: performing modal analysis according to the admittance matrix parameters to obtain the modal impedance and participation factor corresponding to each node; step S04: determining the global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate; step S05: determining the regional optimal virtual admittance command value within the region according to the global optimal virtual admittance command value and the voltage distortion rate; step S06: determining the harmonic compensation current value according to the regional optimal virtual admittance command value and the harmonic voltage, and suppressing harmonic resonance by inputting the harmonic compensation current into the target distribution network.

[0062] The global-local cooperation partition collaborative resonance suppression method provided by the embodiment of the present invention specifically includes the following steps:

[0063] Step S01: Obtain target distribution network admittance matrix parameters, node voltage distortion rate, and harmonic voltage.

[0064] In the embodiment of the present invention, basic grid operation information such as the target distribution network admittance matrix and node voltage distortion rate that need to be managed is obtained.

[0065] Step S02: determining the harmonic conductivity sensitivity index of each node in the distribution network according to the admittance matrix parameters, and dividing the nodes into regions according to the harmonic conductivity sensitivity index.

[0066] In the present invention, the method for determining the harmonic conductivity sensitivity index of each control node and controlled node in the distribution network according to the admittance matrix parameters comprises: calculating the harmonic conductivity sensitivity index of each node using formula (1);

[0067]

[0068] Where: U h,j is the hth harmonic voltage at node j; G h,ci is the equivalent conductance of the harmonic control equipment at node j with respect to the hth harmonic; δ is the differential operator.

[0069] In the present invention, the method for dividing nodes into regions according to the harmonic conductivity sensitivity index includes: taking each inverter in the power grid as a control node and the remaining nodes as controlled nodes; setting a sensitivity index threshold corresponding to each control node according to the capacity of the control node inverter; taking each control node as a partition, and in the harmonic conductivity sensitivity index, dividing the controlled nodes whose sensitivity index threshold is greater than the sensitivity index threshold corresponding to a certain control node into the partition corresponding to the control node; after the division is completed, adjusting the number of controlled nodes in each partition so that the inverter capacity within the region matches the number of controlled nodes.

[0070] In the embodiment of the present invention, the process of dividing the entire distribution network into regions according to the distribution network admittance matrix parameters is as follows:

[0071] In order to make full use of the remaining capacity of the multifunctional grid-connected inverter, the installation node of the multifunctional grid-connected inverter is used as the control node, and the remaining nodes (other equipment in the distribution network) are used as controlled nodes. The number of multifunctional grid-connected inverters is the number of partitions, and the controlled nodes within the region are controlled by the harmonic control equipment (multifunctional grid-connected inverter) within the region.

[0072] Use formula (1) to obtain the harmonic conductivity sensitivity index S corresponding to each control node and controlled node: h,j,ci .

[0073] The obtained harmonic conductivity sensitivity (sensitivity) indexes are sorted from large to small.

[0074] Different sensitivity index thresholds are set for different areas, that is, according to the capacity of each control node management device (multi-functional grid-connected inverter), the number of controlled node devices that can be managed is set, that is, the sensitivity index threshold. If the number of controlled node devices corresponding to the control node management device is too large, the management effect will be reduced.

[0075] After the sensitivity index threshold is set, the area is divided, that is, each control node corresponds to a region, and each control node harmonic control device is the center of the region. Starting from the control node with the largest harmonic conductivity sensitivity index, it is determined whether the sensitivity index corresponding to a controlled node is greater than the sensitivity threshold corresponding to the control node. If so, the controlled node is divided into the control node area, otherwise, the controlled node does not belong to the area.

[0076] And so on, complete the division of all node areas, and after the division is completed, adjust the threshold values ​​of sensitivity indicators in different areas, that is, adjust the number of controlled nodes in the area, so that the capacity of harmonic control equipment in the area is proportional to the number of controlled nodes in the area.

[0077] Step S03: Performing modal analysis according to the admittance matrix parameters to obtain the modal impedance and participation factor corresponding to each node.

[0078] In the present invention, the method of performing modal analysis according to the admittance matrix parameters to obtain modal impedance includes: calculating the modal impedance using formula (2);

[0079] TU h =Λ -1 TI h (2);

[0080] Where: T is the right eigenvalue vector of the node admittance matrix Y decomposition; Λ -1 is the modal impedance parameter vector; U h is the node voltage vector; I h is the node current vector.

[0081] In the embodiment of the present invention, modal analysis is performed according to the admittance matrix parameter information of the distribution network to obtain modal impedance parameters.

[0082] Firstly, the LT eigenvalue decomposition of the distribution network admittance matrix is ​​performed to obtain the expression relationship between the node voltage and the node injection current, and the relationship is simplified to obtain the expression between the modal voltage and the modal current as shown in formula (2).

[0083] The modal impedance is calculated using formula (2), and multiple modal impedances constitute the modal impedance vector Λ -1 The modal impedance parameter establishes a mathematical relationship between the modal voltage and modal current of the node, and corresponds one to one. The high modal impedance value can determine the resonant frequency and the resonant center.

[0084] In the present invention, the method of performing modal analysis according to the admittance matrix parameters to obtain the participation factor corresponding to each node includes: calculating the participation factor according to the modal impedance using formula (3);

[0085]

[0086] Where: L is the left eigenvalue vector of the node admittance matrix Y decomposition; is the system modal impedance parameter under m mode; PF n,m is the participation factor of node n in mode m; -1 is the modal impedance parameter vector; T is the right eigenvalue vector of the node admittance matrix Y decomposition; I h is the node current vector. nm is the nth row and mth column L matrix element, T mn is the mth row and nth column T matrix element; I mis the element of the mth row of the current vector I, and N is the maximum number of rows in the current matrix.

[0087] In the embodiment of the present invention, when a certain mode resonates, the impedance value of this mode is much greater than the impedance of other modes, and the relationship between the node voltage and the node current can be approximately obtained as shown in formula (3).

[0088] According to the modal impedance parameter vector obtained by formula (2), the participation factor PF corresponding to each node is calculated using formula (3): n,m .

[0089] The value of the participation factor represents the probability of resonance at different nodes when modal resonance occurs. The larger the value of the participation factor, the higher the probability of resonance at the node. The participation factor is used as a calculation parameter for the global optimal virtual admittance command value, which can take into account the possibility of resonance at different nodes and suppress resonance for frequency offset.

[0090] Step S04: determining the global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate.

[0091] In the present invention, the method for determining the global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate includes: using equations (4) to (6) to calculate the global optimal virtual admittance command value;

[0092]

[0093]

[0094]

[0095] Where: N is the number of system nodes; a i is the participation factor weight of node i; β i is the modal impedance weight of node i; THDV i is the harmonic voltage distortion rate of node i; H is the maximum harmonic order considered; PF i,h is the participation factor of node i in mode h; Z mod,i,h is the modal impedance value of node i under the hth harmonic; I h,i is the hth harmonic voltage value of node i; Y h,ii is the hth harmonic admittance of node i; G h,i0 is the global optimal virtual admittance command value; U h,i is the hth harmonic voltage value of node i; V h,i is the hth harmonic voltage amplitude of node i, and V1 is the fundamental voltage amplitude.

[0096] In the embodiment of the present invention, the global optimal virtual admittance instruction value is calculated according to the influencing factor parameters and the modal impedance parameters determined in step S03.

[0097] The time scale for calculating the global optimal virtual admittance command value is 15 minutes, that is, every 15 minutes, the node admittance matrix information uploaded by each node in the distribution network is used to calculate the global optimal virtual admittance command value G using equations (4) to (6). h,i0 calculate.

[0098] The participation factor term indicates the possibility of resonance at different nodes, overcoming the poor harmonic suppression caused by the offset of the resonance center. The modal impedance term represents the magnitude of the node resonant voltage at different resonant frequencies, achieving a good effect on global resonance suppression.

[0099] In the present invention, the capacity limiting condition when calculating the global optimal virtual admittance command value is as shown in formula (7);

[0100]

[0101] Where: S ci,MFGCI is the working capacity of the multifunctional grid-connected inverter in the target distribution network; It is the remaining capacity of the multifunctional grid-connected inverter;

[0102] When calculating the global optimal virtual admittance command value, the voltage distortion rate of all nodes and their harmonics of each order meets the restrictions as shown in formula (8);

[0103]

[0104] Where: THDV j is the harmonic voltage distortion rate of node j; THDV max is the maximum harmonic voltage distortion rate value of each node; HRU j,h is the hth harmonic voltage distortion rate value of node j; HRU h,max is the maximum voltage distortion rate value of the hth harmonic at each node.

[0105] In an embodiment of the present invention, when resonance suppression is performed, a device such as a multifunctional grid-connected inverter is used. The device uses the remaining capacity to suppress harmonics. For this reason, the multifunctional grid-connected inverter should meet the capacity limitation when working. When calculating the global virtual admittance command value, the capacity limitation condition needs to be considered. The limiting expression is shown in formula (7).

[0106] In the process of calculating the global optimal virtual admittance command value, it is also necessary to ensure that the voltage distortion rate of all nodes and their harmonics of each order meets the restrictions. The restricted expression is shown in formula (8).

[0107] Based on equations (8) and (9), in the process of calculating the global optimal virtual admittance command value, it is ensured that the voltage distortion rate of all nodes is within the set requirements and the harmonic control equipment meets the working requirements.

[0108] Step S05: Determine the regional optimal virtual admittance command value within the region according to the global optimal virtual admittance command value and the voltage distortion rate.

[0109] In the present invention, the method for determining the regional optimal virtual admittance command value within the region according to the global optimal virtual admittance command value and the voltage distortion rate includes:

[0110] The optimal virtual admittance command value of the region is calculated using formula (9);

[0111]

[0112] Where: x i is the state variable in the formula; t is the time value; T is the maximum time considered; H is the maximum harmonic order considered; m E is the number of nodes considered; G h,i0 is the global optimal virtual admittance command value; G h,i is the virtual admittance command value in the region; n is the number of nodes in the region; m is the number of management equipment in the region; THDV j,t is the harmonic voltage distortion rate of node j at time t; f1 is the objective function 1; f 2,t is the objective function 2; f m,t is the optimal objective function for the overall region.

[0113] In the embodiment of the present invention, the optimal virtual admittance instruction value within the region is calculated according to the region division result and the global optimal virtual admittance instruction value.

[0114] Due to the continuous change of background harmonic current value, the harmonic voltage distortion rate of nodes within the region may not meet the demand. It is necessary to perform rolling optimization on the global optimization result (global optimal virtual admittance command value). The time scale of rolling optimization is 5 minutes, that is, every 5 minutes, according to the latest global optimal virtual admittance command value calculated in step S04, the regional optimal virtual admittance command value G is calculated using formula (9): h,i .

[0115] In the calculation, f m,t minimum, and the corresponding virtual admittance command value in the area is the virtual admittance command value in the required area.

[0116] In the process of calculating the optimal virtual admittance command value in the region, the harmonic voltage distortion rate of different nodes in the region at different times is distinguished, and at the same time, the updated harmonic conductance command value (virtual admittance command value in the region) does not deviate too much from the global optimal result (global optimal virtual admittance command value), ultimately achieving the best effect of harmonic control within the region.

[0117] Step S06: Determine a harmonic compensation current value according to the optimal virtual admittance command value and the harmonic voltage in the area, and suppress harmonic resonance by inputting the harmonic compensation current into the target distribution network.

[0118] In the present invention, the method for determining the harmonic compensation current value according to the regional optimal virtual admittance command value and the harmonic voltage includes: harmonic compensation current value = regional optimal virtual admittance command value × harmonic voltage.

[0119] In an embodiment of the present invention, the calculated optimal virtual admittance command value within the region is sent to the harmonic control device within the region, and the harmonic control device within the region collects the real-time harmonic voltage within the corresponding region, and multiplies the harmonic voltage by the received optimal virtual admittance command value within the region, thereby calculating the harmonic compensation current value within the region. The harmonic control device within the region inputs the harmonic compensation current value into the distribution network within the region where it is located, so as to suppress the harmonic resonance of the region.

[0120] In the embodiment of the present invention, a target distribution network is taken as an example to illustrate the method of the present invention:

[0121] The target distribution network is an IEEE33-node network topology with a transformer ratio of 10kV / 380V and a multifunctional grid-connected inverter capacity of 0.8MW.

[0122] Obtain basic grid operation information such as the target distribution network admittance matrix and node voltage distortion rate.

[0123] The harmonic conductivity sensitivity index of each node is obtained using formula (1).

[0124] The number of partitions is based on the number of multifunctional grid-connected inverters. The area is divided into four parts, and each area is controlled by a multifunctional grid-connected inverter for harmonic control.

[0125] Set the sensitivity index threshold ρ of the four regional control nodes cthre,i , the controlled nodes whose harmonic conductivity sensitivity index is greater than the threshold are divided into this area.

[0126] By continuously adjusting the sensitivity index thresholds of different areas, the number of different nodes in the area is proportional to the capacity of the harmonic control equipment in the area. The area where the equipment with large control capacity is located has more controlled nodes, and the corresponding sensitivity index threshold is smaller. The sensitivity index thresholds of each partition are finally determined as: 0.52, 0.43, 0.41, and 0.37. The schematic diagram of the distribution network area division is finally obtained as shown in the figure. Figure 2 shown.

[0127] According to the relationship between modal voltage and modal current, that is, formula (2), the modal impedance value can be calculated, which represents the position and frequency of the system resonance, and the system modal impedance diagram can be drawn as follows: Figure 3 As shown. According to the modal impedance, the participation factor is calculated using formula (3).

[0128] According to the influencing factor (participation factor) parameters and modal impedance parameters, the global optimal virtual admittance command value is calculated using equations (4) to (6). The objective function is optimized by the particle swarm optimization algorithm to obtain the optimal global admittance optimal command value.

[0129] This value takes into account the capacity constraints of multifunctional grid-connected inverters and other management equipment, as well as the harmonic voltage distortion rate constraints of each node in the system. The global optimal virtual admittance command value is re-solved every 15 minutes to obtain the node voltage harmonic distortion rate under the setting of the global optimal virtual admittance command value. Figure 4 shown.

[0130] The regional optimal virtual admittance command value is calculated using formula (9) every 5 minutes. The calculation process of the command value takes into account that the value of the node harmonic voltage distortion rate within the region meets the limit conditions, and at the same time, the optimal virtual admittance command value within the region does not deviate too much from the global optimal calculation value.

[0131] The optimal virtual admittance command value within the region is sent to the harmonic control equipment within the region, and a schematic diagram of node voltage harmonic distortion rate under the setting of the global optimal virtual admittance command value and the regional optimal virtual admittance command value is obtained for different nodes. Figure 5 shown.

[0132] In the present invention, a global-local cooperative partitioned collaborative resonance suppression device is also proposed, including: a global controller, used to obtain the target distribution network admittance matrix parameters and node voltage distortion rate; according to the admittance matrix parameters, determine the harmonic conductivity sensitivity index of each node in the distribution network, and divide the nodes into regions according to the harmonic conductivity sensitivity index; perform modal analysis according to the admittance matrix parameters to obtain the modal impedance and participation factor corresponding to each node; determine the global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate; a regional controller, used to determine the regional optimal virtual admittance command value within the region according to the global optimal virtual admittance command value and voltage distortion rate sent by the global controller at the first predetermined time interval at a second predetermined time interval, and determine the harmonic compensation current value according to the regional optimal virtual admittance command value and harmonic voltage, and send the harmonic compensation current value to the harmonic control equipment in the corresponding area, so that the harmonic control equipment inputs the current of the harmonic compensation current value into the distribution network to suppress harmonic resonance.

[0133] In the embodiment of the present invention, each area is provided with a corresponding regional controller, and the multifunctional inverter in the area, i.e., the harmonic control device, is connected to the corresponding regional controller. The global controller is connected to the regional controllers of each area. The controller is the information transmission center of the harmonic control method.

[0134] During governance, the regional controller uploads the node data information within the region to the global controller. The global controller calculates the global optimal virtual admittance command value based on the acquired standard grid admittance matrix parameters and node voltage distortion rate. The global controller re-acquires and calculates the global optimal virtual admittance command value every 15 minutes and sends it to the regional controller.

[0135] After the regional controller receives the global optimal virtual admittance command value sent by the global controller, it calculates the regional optimal virtual admittance command value every 5 minutes based on the last received global optimal virtual admittance command value, and sends it to the corresponding regional harmonic control equipment.

[0136] The regional harmonic control equipment, i.e., the multifunctional inverter, receives the regional optimal virtual admittance command value optimized within the region, multiplies it by the detected harmonic voltage, obtains the harmonic compensation current value, and injects the compensation current into the cable distribution network to suppress harmonic resonance.

[0137] It can be understood that the above-mentioned various method embodiments mentioned in the present invention can be combined with each other to form a combined embodiment without violating the principle logic. Due to space limitations, the present invention will not go into details.

[0138] Those skilled in the art will appreciate that, in the above method of specific implementation, the order in which the steps are written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of the steps should be determined by their functions and possible internal logic.

[0139] Compared with the prior art, the present invention provides at least the following beneficial effects: 1. Compared with the traditional current detection type harmonic compensation control mode, it can control the harmonics of the entire distribution network. At the same time, the zoning mode adopted makes the harmonic control effect within the region more effective than the traditional method. 2. The modal analysis method is adopted, which can achieve a good suppression effect on the problem of resonance center offset caused by changes in distribution network parameters, thereby improving the level of harmonic control. At the same time, the global and local cooperation mode adopted can effectively deal with the harmonic distortion problems of all nodes, and achieve better control effects than traditional methods. 3. The external interference such as changes in background harmonic injection can be effectively overcome through rolling optimization calculation results.

[0140] The present invention achieves a more effective control effect on the harmonic pollution of the distribution network on the basis of ensuring the stability of the distribution network system. Compared with the traditional harmonic control means, this method can achieve harmonic control of the entire distribution network. At the same time, for the resonance shift phenomenon caused by the change of background harmonic injection in the distribution network and the change of grid structure parameters, a more effective resonance suppression effect can be achieved compared with the traditional resonance suppression method.

[0141] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A global-local cooperative partition collaborative resonance suppression method, characterized in that: include: Obtain the target distribution network admittance matrix parameters, node voltage distortion rate and harmonic voltage; Determine the harmonic conductivity sensitivity index of each node in the distribution network according to the admittance matrix parameters, and divide the nodes into regions according to the harmonic conductivity sensitivity index; Performing modal analysis according to the admittance matrix parameters to obtain modal impedance and participation factor corresponding to each node; Determining a global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate; Determining a regional optimal virtual admittance command value within the region according to the global optimal virtual admittance command value and the voltage distortion rate; A harmonic compensation current value is determined according to the optimal virtual admittance command value and the harmonic voltage in the area, and harmonic resonance suppression is performed by inputting the harmonic compensation current into the target distribution network.

2. The global-local cooperation partition collaborative resonance suppression method according to claim 1 is characterized in that: The method for determining the harmonic conductivity sensitivity index of each control node and controlled node in the distribution network according to the admittance matrix parameters includes: The harmonic conductivity sensitivity index of each node is calculated using formula (1); Where: U h,j is the hth harmonic voltage at node j; G h,ci is the equivalent conductance of the harmonic control equipment at node j with respect to the hth harmonic; δ is the differential operator.

3. The global-local cooperation partition collaborative resonance suppression method according to claim 1 is characterized in that: The method for dividing nodes into regions according to the harmonic conductivity sensitivity index comprises: Each inverter in the power grid is regarded as a control node, and the remaining nodes are regarded as controlled nodes; According to the capacity of the inverter of the control node, setting the sensitivity index threshold corresponding to each control node; Taking each of the control nodes as a partition, in the harmonic conductivity sensitivity index, the controlled nodes whose sensitivity index threshold value is greater than that corresponding to a certain control node are divided into the partition corresponding to the control node; After the division is completed, the number of controlled nodes in each partition is adjusted so that the inverter capacity within the area matches the number of controlled nodes.

4. The global-local cooperation partition collaborative resonance suppression method according to claim 1 is characterized in that: The method of performing modal analysis according to the admittance matrix parameters to obtain modal impedance includes: The modal impedance is calculated using formula (2); YOU h =Λ -1 YOU h (2); Where: T is the right eigenvalue vector of the node admittance matrix Y decomposition; Λ -1 is the modal impedance parameter vector; U h is the node voltage vector; I h is the node current vector.

5. The global-local cooperation partition collaborative resonance suppression method according to claim 4 is characterized in that: The method of performing modal analysis according to the admittance matrix parameters to obtain the participation factor corresponding to each node includes: According to the modal impedance, the participation factor is calculated using formula (3); Where: L is the left eigenvalue vector of the node admittance matrix Y decomposition; is the system modal impedance parameter under m mode; PF n,m is the participation factor of node n in mode m; -1 is the modal impedance parameter vector; T is the right eigenvalue vector of the node admittance matrix Y decomposition; I h is the node current vector.

6. The global-local cooperation partition collaborative resonance suppression method according to claim 1 is characterized in that: The method for determining the global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate includes: The global optimal virtual admittance command value is calculated using equations (4) to (6); Where: N is the number of system nodes; a i is the participation factor weight of node i; β i is the modal impedance weight of node i; THDV i is the harmonic voltage distortion rate of node i; H is the maximum harmonic order considered; PF i,h is the participation factor of node i in mode h; Z mod,i,h is the modal impedance value of node i under the hth harmonic; I h,i is the hth harmonic voltage value of node i; Y h,ii is the hth harmonic admittance of node i; G h,i0 is the global optimal virtual admittance command value; U h,i is the hth harmonic voltage value of node i; V h,i is the hth harmonic amplitude of node i, and V1 is the fundamental voltage amplitude.

7. The global-local cooperation partition cooperative resonance suppression method according to claim 6 is characterized in that: The capacity limitation condition when calculating the global optimal virtual admittance command value is shown in formula (7); Where: S ci,MFGCI is the working capacity of the multifunctional grid-connected inverter in the target distribution network; It is the remaining capacity of the multifunctional grid-connected inverter; When calculating the global optimal virtual admittance command value, the voltage distortion rate of all nodes and their harmonics of each order meets the restrictions as shown in formula (8); Where: THDV j is the harmonic voltage distortion rate of node j; THDV max is the maximum harmonic voltage distortion rate value of each node; HRU j,h is the hth harmonic voltage distortion rate value of node j; HRU h,max is the maximum voltage distortion rate value of the hth harmonic at each node.

8. The global-local cooperation partition collaborative resonance suppression method according to claim 1, characterized in that: The method for determining the regional optimal virtual admittance command value within the region according to the global optimal virtual admittance command value and the voltage distortion rate includes: The optimal virtual admittance command value of the region is calculated using formula (9); Where: x i is the state variable in the formula; t is the time value; T is the maximum time considered; H is the maximum harmonic order considered; m E is the number of nodes considered; G h,i0 is the global optimal virtual admittance command value; G h,i is the virtual admittance command value in the region; n is the number of nodes in the region; m is the number of management equipment in the region; THDV j,t is the harmonic voltage distortion rate of node j at time t; f1 is the objective function 1; f 2,t is the objective function 2; f m,t is the optimal objective function for the overall region.

9. The global-local cooperation partition collaborative resonance suppression method according to any one of claims 1 to 8, characterized in that: The method for determining the harmonic compensation current value according to the regional optimal virtual admittance command value and the harmonic voltage includes: Harmonic compensation current value = regional optimal virtual admittance command value × harmonic voltage.

10. A global-local cooperative partition collaborative resonance suppression device, characterized in that: include: A global controller is used to obtain the target distribution network admittance matrix parameters and node voltage distortion rate; determine the harmonic conductivity sensitivity index of each node in the distribution network according to the admittance matrix parameters, and divide the nodes into regions according to the harmonic conductivity sensitivity index; perform modal analysis according to the admittance matrix parameters to obtain the modal impedance and participation factor corresponding to each node; determine the global optimal virtual admittance command value corresponding to each control node according to the modal impedance, participation factor and voltage distortion rate; The regional controller is used to determine the regional optimal virtual admittance command value within the region at a second predetermined time interval based on the global optimal virtual admittance command value and voltage distortion rate sent by the global controller at the first predetermined time interval, and determine the harmonic compensation current value based on the regional optimal virtual admittance command value and the harmonic voltage, and send the harmonic compensation current value to the harmonic control equipment in the corresponding area, so that the harmonic control equipment inputs the current of the harmonic compensation current value into the distribution network to suppress harmonic resonance.

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