Interconnected transformer area regulation and control method and system based on cooperation of F-SOP and phase converters

Abstract

The invention discloses an interconnected transformer area regulation and control method and system based on F-SOP and phase converter cooperation. The method comprises the following steps: S1, acquiring operation parameters of a low-voltage distribution area; s2, calculating the three-phase unbalance degree and the load rate of the output power of the transformer and the voltage of each node of each phase, and judging whether the three-phase unbalance degree and the load rate are in a constraint interval; if the standard is reached, enabling the phase converter and the F-SOP not to act, and returning to S1; if not, starting the phase converter; s3, determining a first optimal action state of the phase converter, and secondarily judging whether the indexes reach the standard or not; if the standard is reached, the phase converter acts according to a first optimal state, otherwise, F-SOP is started; s4, constructing an optimal objective function of the coordinated action economy; and S5, solving the function, determining a second optimal action state of the phase converter and an F-SOP power scheduling instruction, and sending the second optimal action state and the F-SOP power scheduling instruction to the phase converter and the F-SOP. According to the invention, the problem of three-phase imbalance of the transformer in the transformer area and the problem of light and heavy loads are effectively solved, and meanwhile, the problem of three-phase imbalance of the transformer area line is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to an interconnected substation control method and system based on the collaboration of F-SOP and a phase converter. Background Art

[0002] Distributed energy has rapidly increased its penetration rate in distribution networks due to its clean and flexible characteristics. However, with the access of large-scale and high-proportion distributed energy and the widespread existence of random loads, the safe and economic operation of distribution networks faces unprecedented challenges. In particular, the distribution substations have complex network structures, a wide variety of user types, and random mixed access of single-phase and three-phase loads, which greatly increases the complexity of operation. The rapid changes in these random loads have led to the aggravation of problems such as three-phase imbalance in distribution substations, light and heavy loads on transformers, and prominent line losses, which poses a great threat to the safe and stable operation of low-voltage distribution networks.

[0003] In recent years, four-leg soft open point (F-SOP) and phase converters have been used to treat the above problems; currently, scholars have conducted some research on the application of F-SOP and phase converters in distribution stations. For example, Chinese patent document CN116054210A discloses a three-phase imbalance optimization control method for flexible interconnected distribution stations based on F-SOP, which uses F-SOP to achieve internal imbalance management and power mutual assistance between different stations, and greatly reduces the light and heavy load operation and three-phase imbalance problems of transformers in the station area. However, F-SOP is usually connected to the low-voltage bus side of the station area, which can only treat the three-phase imbalance and light and heavy load problems of the transformer in the station area itself, but cannot alleviate the three-phase imbalance problems on the line side of the station area and the problems of line overload and increased loss. In the field of phase converters, Chinese patent document CN114977225A discloses a three-phase imbalance management method for distribution stations, and proposes to connect a phase converter on the load side to realize the phase change operation of the load, thereby reducing the imbalance problem of the line. However, as a discrete action device, the phase converter can only completely switch the connected load to the remaining two phases, and cannot achieve continuous regulation of the three-phase unbalanced power. Therefore, it can only alleviate the three-phase imbalance problem of the line to a certain extent, and cannot completely eliminate the three-phase imbalance problem in the substation.

[0004] In summary, F-SOP has the advantages of real-time continuous power regulation and interconnection between substations, and the phase converter has the advantage of alleviating the three-phase imbalance of the line from the load side. Therefore, the coordinated regulation of F-SOP with continuous regulation capability and the phase converter with discrete action can effectively solve the global three-phase imbalance and light and heavy load problems in the distribution substation, improve the economy and reliability of system operation, and achieve complementary advantages between the two. However, how to establish a dynamic phase converter model that does not change the power flow network architecture and a comprehensive model of the three-phase four-wire network loss in the distribution substation, and design a control strategy for the coordinated operation of the phase converter and F-SOP are current problems that need to be solved urgently. Summary of the invention

[0005] In order to overcome the above technical defects, the present application provides an interconnected substation control method and system based on the collaboration of F-SOP and phase converter.

[0006] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0007] An interconnected substation control method based on the coordination of F-SOP and phase converter, wherein the phase converter includes three parallel bridge arms containing upper and lower power electronic switch devices, the three bridge arms are respectively connected to the three phases of the transmission line, and the output ends after parallel connection are connected to the phase-changing users; multiple low-voltage distribution substations are interconnected through a multi-port F-SOP, and the F-SOP includes multiple three-phase four-bridge-arm converters connected in parallel on the common DC side, the output end of each three-phase four-bridge-arm converter serves as a port of the F-SOP, and the a, b, and c three-phase bridge arms of each converter are respectively connected to three busbars of a low-voltage distribution substation; F-SOP controls the three-phase output power of each low-voltage distribution station area to achieve interconnected station area regulation, including the following steps: Step S1: Collecting operation-related parameters of each low-voltage distribution substation interconnected by a multi-port F-SOP at one time, wherein the operation-related parameters of the low-voltage distribution substation include normal operation data of the low-voltage distribution substation and equipment parameters of the transformer, F-SOP and inverter; Step S2: Calculate the output power three-phase imbalance of the transformer in each low-voltage distribution substation, the load rate of the transformer, and the voltage of each phase at each node in each low-voltage distribution substation according to the low-voltage distribution substation operation related parameters collected once, and determine whether the output power three-phase imbalance of the transformer in each low-voltage distribution substation, the load rate of the transformer, and the voltage of each phase at each node in each low-voltage distribution substation are within the constraint interval at the same time; If yes, the inverter and F-SOP do not operate, and the process returns to step S1 to continue real-time monitoring; If not, start the phase converter and go to step S3; Step S3: According to the pre-constructed large-scale loss model of the phase converter access area, an economic optimal objective function of the low-voltage distribution area connected only to the phase converter is constructed to determine the first optimal operation state of the phase converter; the large-scale loss model of the phase converter access area includes a transformer loss characteristic model, a phase converter loss characteristic model, and a three-phase four-wire independent power flow network loss characteristic model; causing the phase converter to operate in a first optimal operating state; Secondary collection of operation-related parameters of each low-voltage distribution station area; According to the secondary collected operation related parameters of each low-voltage distribution station area, the output power three-phase imbalance of the transformer in each low-voltage distribution station area, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution station area are calculated for the second time, and it is determined whether the output power three-phase imbalance of the transformer in each low-voltage distribution station area, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution station area are simultaneously within the constraint range; If yes, F-SOP does not take action and returns to step S1 to continue real-time monitoring; If not, start F-SOP and go to step S4; Step S4: Based on the inverter access area loss large model and the pre-constructed F-SOP loss characteristic model, construct the economic optimal objective function of the low-voltage interconnected area control strategy of the coordinated action of F-SOP and inverter; Step S5: Solve the economic optimal objective function of the low-voltage interconnected area control strategy for the coordinated action of the F-SOP and the inverter, determine the second optimal action state of the inverter and the optimal power scheduling instruction of the F-SOP, and send them to the inverter and F-SOP respectively.

[0008] Further, Transformer The load factor of the phase is determined by Transformer The apparent power delivered by the first phase is divided by the Transformer The capacity of the phase is obtained as follows:

[0009] in, Indicates Transformer Phase load factor, , respectively Three-phase; For the Transformer The apparent power transferred between the phases; For the Transformer Phase capacity; No. The three-phase imbalance of the output power of the transformer is determined by The maximum value of the three-phase output power of the transformer minus the The average value of the three-phase output power of the transformer is divided by the The average value of the three-phase output power of the transformer is obtained as follows:

[0010] in, Indicates The output power three-phase imbalance of the transformer is For the The maximum value of the three-phase output power of the transformer, For the The average value of the three-phase output power of a transformer.

[0011] Furthermore, the load factor constraint of the transformer is that the load factor of each phase of each transformer does not exceed the transformer economic operation range specified in the national standard (Economic Operation of Power Transformers), as follows:

[0012] in, Indicates Transformer Phase load factor, , and Respectively represent the upper and lower limits of the economic operation range; The constraint condition for the three-phase imbalance of the transformer output power is that the output power imbalance of each transformer does not exceed the imbalance threshold specified in the "Distribution Network Operation and Maintenance Regulations", as follows:

[0013] in, is the load three-phase imbalance threshold; Indicates The three-phase imbalance of the transformer; The voltage constraint conditions of each node and each phase are that the voltage of each node and each phase of each low-voltage distribution substation area does not exceed the upper and lower limits of the node voltage specified for safe operation of the low-voltage distribution substation area, as follows:

[0014] in, It is a collection of all nodes in the low voltage distribution area; It is the first in the low voltage distribution area Nodes The node voltage of the phase, , respectively Three phases and zero phase; and They are respectively Nodes The upper and lower limits of the node voltage amplitude of the phase.

[0015] Furthermore, in the transformer loss characteristic model, the transformer loss is calculated, including the comprehensive power no-load loss of each phase of each transformer, the comprehensive power rated load loss and the zero-sequence loss generated when the three-phase load of each transformer is unbalanced, as follows:

[0016] in, is the transformer loss, For the Transformer The comprehensive power no-load loss of each phase, , For the Transformer The combined power rating load loss of each phase; For the Zero-sequence loss generated when the three-phase load of a transformer is unbalanced; Indicates Transformer Phase load factor; In the inverter loss characteristic model, the inverter loss is calculated by multiplying the inverter resistance coefficient by the sum of the apparent power of the a-phase load of each group of inverter access nodes, as follows:

[0017] in, is the commutator loss, is the set inverter resistance coefficient, Indicates Group commutator access node Phase load apparent power; In the three-phase four-wire independent power flow network loss characteristic model, the total loss of the three-phase four-wire network is calculated by multiplying the current of each phase of each branch by the resistance of the corresponding phase of the corresponding branch, as follows:

[0018] in, is the bus loss of the three-phase four-wire network, for Branch Road Phase current, , The branch is the first in the low voltage distribution area Nodes and The lines between nodes; for Branch Road The resistance of the phase, It is the collection of all branches in the low-voltage distribution area.

[0019] Furthermore, the economic optimal objective function of the low-voltage distribution area connected only to the inverter is the minimum value of the sum of the transformer loss cost, the inverter comprehensive operation cost and the three-phase four-wire network line loss cost, as follows:

[0020] in, The comprehensive operating cost of the low-voltage distribution station area connected only to the phase converter; According to the transformer loss characteristic model, the transformer loss cost It is obtained by multiplying the grid electricity price by the transformer loss, as follows:

[0021] in, is the grid electricity price; is the transformer loss; Comprehensive operating cost of inverter Including the inverter loss cost and the inverter action cost, as follows:

[0022] According to the inverter loss characteristic model, the inverter loss cost It is obtained by multiplying the grid electricity price by the inverter loss, as follows:

[0023] in, is the commutator loss; Phase converter operation cost It is obtained by multiplying the inverter action cost coefficient by the sum of all inverter action times, as follows:

[0024] in, is the commutator action cost coefficient, To indicate the Action state scalar of the group commutator; Based on the three-phase four-wire independent power flow network loss characteristic model, the line loss cost of the three-phase four-wire network It is obtained by multiplying the grid electricity price by the bus loss of the three-phase four-wire network, as follows:

[0025] in, It is the bus loss of three-phase four-wire network.

[0026] Furthermore, the constraints of the transformer loss characteristic model are that the apparent power output of each phase of each transformer cannot exceed the capacity of the corresponding phase of the corresponding transformer, and the total apparent power output of the three-phase of each transformer cannot exceed the total capacity of the three-phase of the corresponding transformer, as follows:

[0027] in, For the Transformer The apparent power transferred between the two phases, , For the Transformer The active power output of the phase, For the Transformer The reactive power output of the phase, For the Transformer Phase capacity, For the The total apparent power transmitted by the transformers is For the Total three-phase capacity of the transformer; The constraints of the inverter loss characteristic model are The sum of the active power and reactive power output by the three-phase bridge arm of the phase converter should be equal to 0. Group commutator The active power and reactive power output by the phase bridge arm are equal to the opposite of the state scalar and the Group commutator access node The product of the active power and reactive power of the phase load, Group commutator , The product of the active power output of the phase bridge arm is 0. Group commutator , The product of the reactive power output by the phase bridge arm is also 0, as follows:

[0028] in, For the Group commutator Phase bridge arm to a node The active power injected into the phase, For the Group commutator Phase bridge arm to a node Reactive power injected into the phase; and For the Group commutator access node Phase load active power and reactive power, Indicates Action state scalar of the group commutator; The safety constraints for the operation of each phase of the three-phase four-wire loss characteristic model are that the voltage amplitude of each phase of each node in the low-voltage distribution station area does not exceed the upper and lower limits of the node voltage specified for the safe operation of the low-voltage distribution station area; the current amplitude of each phase of each branch in the low-voltage distribution station area does not exceed the upper limit of the branch current specified for the safe operation of the low-voltage distribution station area; the amplitude of the active power injected by each phase of each node in the low-voltage distribution station area does not exceed the upper and lower limits of the node injection power, as follows:

[0029] in, It is a collection of all nodes in the low voltage distribution area; It is the first in the low voltage distribution area Nodes The node voltage of the phase, , respectively Three phases and zero phase; and They are respectively Nodes The upper and lower limits of the phase node voltage amplitude, for Branch Road Phase current, The branch is the first in the low voltage distribution area Nodes and The lines between nodes, for The upper limit of the amplitude of It is a collection of all branches in the low-voltage distribution area; It is the first in the low voltage distribution area Nodes Phase power, and They are The upper and lower limits of the amplitude; The power flow constraint condition of the three-phase four-wire loss characteristic model is that each phase of each low-voltage distribution station area must satisfy the optimal power flow constraint after second-order cone relaxation (Gao Hongjun, Liu Junyong, Shen Xiaodong, Xu Rui. Research on Optimal Power Flow of Active Distribution Network and Its Application Examples [J]. Proceedings of the CSEE, 2017, 37(6): 1634-1645. DOI: 10.13334 / j.0258-8013.pcsee.152839), as follows: make , ,have:

[0030] In the formula, Indicates that the power grid is All upstream nodes that inject power into the node The collection composed of Indicates that from The power from each node flows through the power grid to all downstream nodes A collection of components; and Respectively represent Nodes Active and reactive power injected into the phase; and Respectively Branch Road Active power and reactive power of each phase; express Branch Road The resistance of the phase, express Branch Road Phase reactance.

[0031] Furthermore, in the F-SOP loss characteristic model, the comprehensive operating cost of F-SOP is calculated, including the loss cost and operation and maintenance cost of F-SOP, as follows:

[0032] F-SOP loss cost The grid electricity price is multiplied by the transmission power loss of F-SOP, as follows:

[0033] F-SOP Power Transfer Loss It is obtained by subtracting the product of transmission efficiency and transmission power from the transmission power of each phase bridge arm of each port, as follows:

[0034] In the formula, is the power transmission loss of F-SOP, Indicates F-SOP Ports The transmission power of the phase bridge arm; Indicates F-SOP Ports Power transfer efficiency of the phase bridge arm; F-SOP operation and maintenance costs The operation and maintenance cost coefficient is multiplied by the sum of the transmission power of each bridge arm of each port of F-SOP, as follows:

[0035] In the formula, is the operation and maintenance cost coefficient, Indicates F-SOP Ports The apparent power transmitted by the phase bridge arm, ; Based on the comprehensive operating cost of the F-SOP and the large model of the inverter access area loss, the economic optimal objective function of the low-voltage interconnected area control strategy with coordinated action of F-SOP and inverter is constructed, which is the minimum value of the sum of transformer loss cost, inverter comprehensive operating cost, three-phase four-wire network line loss cost and F-SOP comprehensive operating cost, as follows:

[0036] In the formula, It is the comprehensive operating cost of the low-voltage distribution substation under the collaborative strategy.

[0037] Furthermore, the power transmission conservation constraint of the F-SOP loss characteristic model is that the sum of active power transmitted by each bridge arm of each port of the F-SOP is 0, as follows:

[0038] In the formula, Indicates F-SOP Ports Active power flowing out of the phase bridge arm; The capacity constraint condition of the F-SOP loss characteristic model is that the apparent power transmitted by each bridge arm of each port of the F-SOP should be less than or equal to the capacity of the bridge arm corresponding to the corresponding port; the total apparent power transmitted by the F-SOP should also be less than or equal to the overall capacity of the F-SOP:

[0039] In the formula, Indicates F-SOP Ports The apparent power flowing through the phase bridge arm; Indicates F-SOP Ports The capacity of the phase bridge arm, is the total transmission power of F-SOP, is the overall capacity of F-SOP.

[0040] Furthermore, in step S5, the optimal economic objective function of the low-voltage interconnected area control strategy in which the F-SOP and the phase converter work together is solved to obtain the optimal power scheduling instruction of the F-SOP, including the active power and reactive power transmitted by each phase bridge arm of the F-SOP of each port.

[0041] The interconnected substation control system based on the collaboration of F-SOP and phase converter includes the following modules: Data acquisition module: collects the operation-related parameters of each low-voltage distribution substation interconnected by the multi-port F-SOP at one time, wherein the operation-related parameters of the low-voltage distribution substation include the normal operation data of the low-voltage distribution substation and the equipment parameters of the transformer, F-SOP and inverter; The first calculation and judgment module: according to the low-voltage distribution substation operation related parameters collected once, the output power three-phase imbalance of the transformer in each low-voltage distribution substation, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution substation are calculated once, and it is judged once whether the output power three-phase imbalance of the transformer in each low-voltage distribution substation, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution substation are within the constraint range at the same time; If yes, the phase converter and F-SOP do not operate, and return to start the data acquisition module to continue real-time monitoring; If not, start the phase converter and start the second calculation and judgment module; The second calculation and judgment module: according to the pre-built large model of the loss of the phase converter access area, the economic optimal objective function of the low-voltage distribution area only connected to the phase converter is constructed, and the first optimal action state of the phase converter is determined; the large model of the loss of the phase converter access area includes a transformer loss characteristic model, a phase converter loss characteristic model, and a three-phase four-wire independent power flow network loss characteristic model; causing the phase converter to operate in a first optimal operating state; Secondary collection of operation-related parameters of each low-voltage distribution station area; According to the secondary collected operation related parameters of each low-voltage distribution station area, the output power three-phase imbalance of the transformer in each low-voltage distribution station area, the load rate of the transformer and the voltage of each phase of each node are calculated for the second time, and it is determined whether the output power three-phase imbalance of the transformer in each low-voltage distribution station area, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution station area are simultaneously within the constraint range; If yes, F-SOP does not take action and returns to start the data acquisition module to continue real-time monitoring; If not, F-SOP is started to start the instruction acquisition module; Instruction acquisition module: Based on the large model of the inverter access area loss and the pre-built F-SOP loss characteristic model, the economic optimal objective function of the low-voltage interconnected area control strategy with the coordinated action of F-SOP and the inverter is constructed; the economic optimal objective function of the low-voltage interconnected area control strategy with the coordinated action of F-SOP and the inverter is solved, the second optimal action state of the inverter and the optimal power scheduling instruction of F-SOP are determined, and sent to the inverter and F-SOP respectively.

[0042] Compared with the prior art, the present invention has the following beneficial effects: The interconnected substation control method based on the collaboration of F-SOP and phase converter proposed in the present invention can effectively control the three-phase imbalance and light and heavy load problems of the substation transformer, and can also effectively solve the three-phase imbalance problem of the substation line. Compared with the existing technical solutions, the total loss of the method proposed in the present invention is effectively reduced, the safety of the operation of the low-voltage distribution substation is improved, the service life of the equipment is extended, and the economy of the long-term operation of the low-voltage distribution substation is also improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the structural topology of the four-bridge-arm intelligent soft switch in an embodiment of the present invention.

[0044] Figure 2 Schematic diagram of the topological structure of the phase converter in the embodiment of the present invention.

[0045] Figure 3 It is a flow chart of the interconnected substation control method based on the cooperation of F-SOP and phase converter in an embodiment of the present invention.

[0046] Figure 4 It is a diagram of a flexible interconnection area based on a two-port F-SOP and four sets of inverters in an embodiment of the present invention.

[0047] Figure 5 1 is a diagram of a node architecture of two low-voltage distribution station areas in an embodiment of the present invention.

[0048] Figure 6a , Figure 6b , Figure 6c and Figure 6d 3 is a comparison diagram of transformer load rates under four schemes in the embodiment of the present invention.

[0049] Figure 7a , Figure 7b , Figure 7c and Figure 7d3 is a comparison diagram of the three-phase imbalance of the transformer output power in the embodiment of the present invention.

[0050] Figure 8a , Figure 8b , Figure 8c and Figure 8d It is a comparison chart of the total loss and loss composition of the low-voltage distribution station area under four schemes in the embodiment of the present invention.

[0051] Fig. 9 It is a comprehensive operating cost curve of the low-voltage distribution station area in the embodiment of the present invention. DETAILED DESCRIPTION

[0052] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0053] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0054] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0055] In one embodiment, an interconnected substation control method based on the cooperation of F-SOP and phase converter, the phase converter includes three parallel bridge arms containing upper and lower power electronic switch devices, the three bridge arms are respectively connected to the three phases of the transmission line, and the output ends after parallel connection are connected to the phase-changing users, and multiple low-voltage distribution substations are interconnected through a multi-port F-SOP, and the F-SOP includes multiple three-phase four-bridge-arm converters connected in parallel on the common DC side, and the output end of each three-phase four-bridge-arm converter serves as a port of the F-SOP, and the a, b, and c three-phase bridge arms of each converter are respectively connected to three busbars of a low-voltage distribution substation; in one embodiment, the structural topology of the four-leg soft open point (Four-leg soft open point, F-SOP) and the phase converter are respectively as follows Figure 1 and Figure 2 shown.

[0056] F-SOP controls the three-phase output power of each low-voltage distribution station area to achieve interconnected station area regulation, such as Figure 3 As shown, the following steps are included: Step S1: Collecting operation-related parameters of each low-voltage distribution substation interconnected by a multi-port F-SOP at one time, wherein the operation-related parameters of the low-voltage distribution substation include normal operation data of the low-voltage distribution substation and equipment parameters of the transformer, F-SOP and inverter; In one embodiment, taking the two-port F-SOP and the inverter flexible interconnection area as an example, the loss characteristics of the F-SOP, the transformer and the inverter are analyzed respectively. The overall structure of the two-port F-SOP flexible interconnection area is as follows: Figure 4 As shown, the structure is: the phase converter is formed by three bridge arms containing upper and lower power electronic switching devices connected in parallel, the three bridge arms are respectively connected to the three phases of the transmission line, and the output end is connected to the phase-changing user after parallel connection. The substations are interconnected through a two-port F-SOP, and the F-SOP is formed by a plurality of three-phase four-bridge-arm converters connected in parallel on the DC side. The output end of each three-phase four-bridge-arm converter serves as a port of the F-SOP, and the a, b, and c three-phase bridge arms of each converter are respectively connected to three busbars of a low-voltage distribution substation, and the F-SOP controls the three-phase output power of each low-voltage distribution substation. Figure 4 middle, , Both represent 10kV low voltage distribution station area. , They represent distribution transformers with a transformation ratio of 10 / 0.4kV, For the Transformer The active power output of the phase, For the Transformer The reactive power output of the phase, , the direction of inflow into the busbar is the positive direction; the two ports of F-SOP are connected to the busbars of the two low-voltage distribution stations respectively, and Respectively represent F-SOP Ports The active power and reactive power flowing out of the phase bridge arm, , the direction of flowing into the busbar is also taken as the positive direction; , Respectively represent Area Active load and reactive load on the phase bus, , with the direction of outflow from the busbar as the positive direction.

[0057] The 22-node three-phase low-voltage distribution area and the 15-node three-phase low-voltage distribution area are selected as the first low-voltage distribution area and the second low-voltage distribution area to form an interconnected area. The specific three-phase node architecture diagram, F-SOP, and inverter access location of the low-voltage distribution area are as follows: Figure 5 As shown in the figure. The three layers from top to bottom of the same low-voltage distribution substation are phases a, b, and c. The transformer nodes of the two low-voltage distribution substations (i.e. Figure 5 Nodes 22 and 37 in the low-voltage distribution area are connected to the two ports of the two-port F-SOP respectively, and nodes 12 and 20 in the first low-voltage distribution area, as well as nodes 12 and 14 in the second low-voltage distribution area are connected to the phase converter in phase a respectively.

[0058] It is necessary to collect the relevant parameters of the low-voltage distribution area operation at one time. The relevant parameters of the low-voltage distribution area operation include the normal operation data of the low-voltage distribution area and the parameters of the transformer, F-SOP, and inverter equipment. The normal operation data of the low-voltage distribution area includes the impedance parameters of the three-phase and zero-sequence branches of the low-voltage distribution area, the three-phase load power of each node, the three-phase voltage and the zero-sequence voltage. Transformer parameters include the capacity of each phase of the transformer, zero-sequence impedance, comprehensive power no-load loss, comprehensive power rated load loss, real-time output power of the three-phase on the secondary side, three-phase voltage, and three-phase current. F-SOP parameters include the capacity, access position, and efficiency parameters of the F-SOP. Inverter equipment parameters include the access position and resistance coefficient of the inverter.

[0059] Step S2: Calculate the output power three-phase imbalance of the transformer in each low-voltage distribution substation, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution substation according to the low-voltage distribution substation operation related parameters collected once; No. Transformer The load factor of the phase is determined by Transformer The apparent power delivered by the first phase is divided by the Transformer The capacity of the phase is obtained as follows:

[0060] in, Indicates Transformer Phase load factor, , respectively Three-phase; For the Transformer The apparent power transferred between the phases; For the Transformer Phase capacity; No. The three-phase imbalance of the output power of the transformer is determined by The maximum value of the three-phase output power of the transformer minus the The average value of the three-phase output power of the transformer is divided by the The average value of the three-phase output power of the transformer is obtained as follows:

[0061] in, Indicates The output power three-phase imbalance of the transformer is For the The maximum value of the three-phase output power of the transformer, For the The average value of the three-phase output power of a transformer.

[0062] The constraint condition of the transformer load rate is that the load rate of each phase of each transformer does not exceed the transformer economic operation range specified in the national standard (Economic Operation of Power Transformers), as follows:

[0063] in, Indicates Transformer Phase load factor, , and Respectively represent the upper and lower limits of the economic operation range; The constraint condition for the three-phase imbalance of the transformer output power is that the output power imbalance of each transformer does not exceed the imbalance threshold specified in the "Distribution Network Operation and Maintenance Regulations", as follows:

[0064] in, is the load three-phase imbalance threshold; Indicates The three-phase imbalance of the transformer; The voltage constraint conditions of each node and each phase are that the voltage of each node and each phase of each low-voltage distribution substation area does not exceed the upper and lower limits of the node voltage specified for safe operation of the low-voltage distribution substation area, as follows:

[0065] in, It is a collection of all nodes in the low voltage distribution area; It is the first in the low voltage distribution area Nodes The node voltage of the phase, , respectively Three phases and zero phase; and They are respectively Nodes The upper and lower limits of the node voltage amplitude of the phase.

[0066] Determine at one time whether the three-phase imbalance of the output power, the load factor of the transformer and the voltage of each phase of each node in the low-voltage distribution station area are simultaneously within the constraint range; If satisfied, it means that the entire operation of the current transformer is in good condition and there is no need to adjust the operation instruction. At this time, the inverter and F-SOP do not operate, and return to step S1 to continue real-time monitoring; If the above constraints are not met at the same time, that is, at least one of the load rate of the transformer in the substation, the three-phase imbalance of the transformer output power in the substation, and the voltage of each phase of each node obtained does not meet the constraint condition, it means that there is a problem in the operation of the substation and adjustment is required, then the phase converter is started and the process goes to step S3; Step S3: According to the pre-constructed large-scale loss model of the phase converter access area, an economic optimal objective function of the low-voltage distribution area connected only to the phase converter is constructed to determine the first optimal operation state of the phase converter; the large-scale loss model of the phase converter access area includes a transformer loss characteristic model, a phase converter loss characteristic model, and a three-phase four-wire independent power flow network loss characteristic model; In the transformer loss characteristic model, transformer losses are calculated, including the comprehensive power no-load loss of each phase of each transformer, the comprehensive power rated load loss, and the zero-sequence loss generated when the three-phase load of each transformer is unbalanced, as follows:

[0067] in, is the transformer loss, For the Transformer The comprehensive power no-load loss of each phase, , For the Transformer The combined power rating load loss of each phase; For the Zero-sequence loss generated when the three-phase load of a transformer is unbalanced; Indicates Transformer Phase load factor; No-load loss refers to the loss caused by the excitation current and core loss in the core when the transformer is running at no load. It is related to factors such as the material, structure and power supply voltage of the transformer core, and can usually be considered as a relatively fixed loss. Load loss is the heat loss generated by the winding resistance when the load current passes through the transformer winding. It is proportional to the square of the load current and is also related to factors such as the material, structure and temperature of the transformer winding. Transformer zero-sequence loss is the additional loss caused by the zero-sequence current in the winding and core caused by the unbalanced three-phase current. When the three-phase load is asymmetrical, the zero-sequence current flows through the neutral point or closed magnetic circuit, causing heating of the winding resistance and eddy current loss of the core. The magnitude is directly related to the three-phase imbalance. The higher the imbalance, the more significant the zero-sequence loss. The transformer loss characteristic model is based on the generation mechanism of these losses and uses mathematical methods to describe the relationship between transformer losses and various operating parameters.

[0068] In the inverter loss characteristic model, the inverter loss is calculated by multiplying the inverter resistance coefficient by the sum of the apparent power of the a-phase load of each group of inverter access nodes, as follows:

[0069] in, is the commutator loss, is the set inverter resistance coefficient, Indicates Group commutator access node Phase load apparent power; The losses of the inverter (such as grid-connected inverters and rectifiers) are mainly caused by the following mechanisms: Switching loss: Energy loss caused by the overlap of voltage and current during the turn-on and turn-off process of semiconductor devices (such as IGBTs and MOSFETs). The higher the switching frequency, the greater the switching loss. Conduction loss: When the device is turned on, the power loss caused by the on-resistance (such as the saturation voltage drop of IGBTs or the on-resistance of MOSFETs) is proportional to the square of the current. Drive loss: The energy required by the control circuit to drive the semiconductor device is related to the drive circuit design and the switching frequency. Stray loss: Additional loss caused by parasitic parameters (such as stray inductance, capacitance), electromagnetic radiation, or cooling system power consumption. The inverter model associates these losses with the operating parameters of the inverter (such as current, voltage, switching frequency) through mathematical formulas or simulation methods to quantify the loss distribution and efficiency characteristics.

[0070] In the three-phase four-wire independent power flow network loss characteristic model, the total loss of the three-phase four-wire network is calculated by multiplying the current of each phase of each branch by the resistance of the corresponding phase of the corresponding branch, as follows:

[0071] in, is the bus loss of the three-phase four-wire network, for Branch Road Phase current, , The branch is the first in the low voltage distribution area Nodes and The lines between nodes; for Branch Road The resistance of the phase, It is the collection of all branches in the low-voltage distribution area.

[0072] Neutral zero sequence current The formula is as follows:

[0073] In the formula, and They are respectively Nodes and Zero-sequence voltage of each node; The node zero-sequence voltage formula is as follows:

[0074] In the formula, , and They are respectively The voltage of phases a, b, and c at each node; The low-voltage distribution station area with three-phase four-wire structure characteristics contains three phase lines (a, b, c phases and a neutral line (N line), allowing single-phase, two-phase or three-phase loads to be connected, resulting in unbalanced three-phase current. The existence of the neutral line may cause the neutral point to shift (the voltage is not zero), and the neutral line current further increases the line loss. Repeated grounding (the neutral point is connected to the earth through multiple grounding points) will introduce additional impedance and affect the power flow distribution.

[0075] The loss mechanism is: Phase line loss: the product of the square of each phase current and the line resistance, which is directly related to the load distribution. Neutral line loss: the product of the square of the neutral line current and the neutral line resistance, which only occurs when the three phases are unbalanced. Earth conductor loss: If the earth is considered as a conductive medium (such as long-distance lines), the loss caused by the earth impedance must be taken into account.

[0076] Characteristics of power flow calculation: It is necessary to simultaneously deal with the asymmetry of three-phase voltage and current, as well as the coupling effect between the neutral line and the earth. The traditional three-phase three-wire model (ignoring the neutral line) cannot accurately reflect the unbalanced loss and needs to be corrected by a special model.

[0077] The economic optimal objective function of the low-voltage distribution area connected only to the inverter is the minimum value of the sum of the transformer loss cost, the inverter comprehensive operation cost and the three-phase four-wire network line loss cost, as follows:

[0078] in, The comprehensive operating cost of the low-voltage distribution station area connected only to the phase converter; According to the transformer loss characteristic model, the transformer loss cost It is obtained by multiplying the grid electricity price by the transformer loss, as follows:

[0079] in, is the grid electricity price; is the transformer loss; Comprehensive operating cost of inverter Including the inverter loss cost and the inverter action cost, as follows:

[0080] According to the inverter loss characteristic model, the inverter loss cost It is obtained by multiplying the grid electricity price by the inverter loss, as follows:

[0081] in, is the commutator loss; Phase converter operation cost It is obtained by multiplying the inverter action cost coefficient by the sum of all inverter action times, as follows:

[0082] in, is the commutator action cost coefficient, To indicate the Action state scalar of the group commutator; Based on the three-phase four-wire independent power flow network loss characteristic model, the line loss cost of the three-phase four-wire network It is obtained by multiplying the grid electricity price by the bus loss of the three-phase four-wire network, as follows:

[0083] in, It is the bus loss of three-phase four-wire network.

[0084] The constraints of the transformer loss characteristic model are that the apparent power output of each phase of each transformer cannot exceed the capacity of the corresponding phase of the corresponding transformer, and the total apparent power output of the three-phase output of each transformer cannot exceed the total capacity of the three-phase of the corresponding transformer, as follows:

[0085] in, For the Transformer The apparent power transferred between the two phases, , For the Transformer The active power output of the phase, For the Transformer The reactive power output of the phase, For the Transformer Phase capacity, For the The total apparent power transmitted by the transformers is For the Total three-phase capacity of the transformer; The constraints of the inverter loss characteristic model are The sum of the active power and reactive power output by the three-phase bridge arm of the phase converter should be equal to 0. Group commutator The active power and reactive power output by the phase bridge arm are equal to the opposite of the state scalar and the Group commutator access node The product of the active power and reactive power of the phase load, Group commutator , The product of the active power output of the phase bridge arm is 0. Group commutator , The product of the reactive power output by the phase bridge arm is also 0, as follows:

[0086] in, For the Group commutator Phase bridge arm to a node The active power injected into the phase, For the Group commutator Phase bridge arm to a node Reactive power injected into the phase; and For the Group commutator access node Phase load active power and reactive power, Indicates Action state scalar of the group commutator; The safety constraints for the operation of each phase of the three-phase four-wire loss characteristic model are that the voltage amplitude of each phase of each node in the low-voltage distribution station area does not exceed the upper and lower limits of the node voltage specified for the safe operation of the low-voltage distribution station area; the current amplitude of each phase of each branch in the low-voltage distribution station area does not exceed the upper limit of the branch current specified for the safe operation of the low-voltage distribution station area; the amplitude of the active power injected by each phase of each node in the low-voltage distribution station area does not exceed the upper and lower limits of the node injection power, as follows:

[0087] in, It is a collection of all nodes in the low voltage distribution area; It is the first in the low voltage distribution area Nodes The node voltage of the phase, , respectively Three phases and zero phase; and They are respectively Nodes The upper and lower limits of the phase node voltage amplitude, for Branch Road Phase current, The branch is the first in the low voltage distribution area Nodes and The lines between nodes, for The upper limit of the amplitude of It is a collection of all branches in the low-voltage distribution area; It is the first in the low voltage distribution area Nodes Phase power, and They are The upper and lower limits of the amplitude; The power flow constraint condition of the three-phase four-wire loss characteristic model is that each phase of each low-voltage distribution station area must satisfy the optimal power flow constraint after second-order cone relaxation (Gao Hongjun, Liu Junyong, Shen Xiaodong, Xu Rui. Research on Optimal Power Flow of Active Distribution Network and Its Application Examples [J]. Proceedings of the CSEE, 2017, 37(6): 1634-1645. DOI: 10.13334 / j.0258-8013.pcsee.152839), as follows: make , ,have:

[0088] In the formula, Indicates that the power grid is All upstream nodes that inject power into the node The collection composed of Indicates that from The power from each node flows through the power grid to all downstream nodes A collection of components; and Respectively represent Nodes Active and reactive power injected into the phase; and Respectively Branch Road Active power and reactive power of each phase; express Branch Road The resistance of the phase, express Branch Road Phase reactance.

[0089] causing the phase converter to operate in a first optimal operating state; Secondary collection of operation-related parameters of each low-voltage distribution station area; According to the secondary collected operation-related parameters of each low-voltage distribution station area, the output power three-phase imbalance of each transformer, the load rate of the transformer and the voltage of each phase of each node are calculated for the second time, and it is determined whether the output power three-phase imbalance, the load rate of the transformer and the voltage of each phase of each node of each low-voltage distribution station area are simultaneously within the constraint range; If yes, F-SOP does not take action and returns to step S1 to continue real-time monitoring; If not, start F-SOP and go to step S4; The principle of the phase converter is to achieve a more balanced three-phase load by switching the load of one phase to another phase. At the same time, it does not change the original power flow network architecture of the low-voltage distribution station area, and has the advantage of easy installation and withdrawal. The phase converter used in the present invention can switch the load of the corresponding node to the other phase. Phase load overall switching to Phase or Phase to achieve the above purpose. The three ports of the phase converter are connected to the three phases of the same node respectively; The specific working mode of the phase converter is as follows: Set up a 0-1 state scalar ,when = 1, the commutator operates, and:

[0090] or:

[0091] when = 0, the commutator does not work, and there is:

[0092] In the formula, , , For the The active power injected by the three-phase bridge arm of the group inverter into the three-phase of a certain node; , , For the The reactive power injected by the three-phase bridge arm of the group inverter into the three-phase of a certain node; and For the Group commutator access node Phase load active power and reactive power, Indicates Action state scalar of the group commutator; Step S4: Based on the inverter access area loss large model and the pre-constructed F-SOP loss characteristic model, construct the economic optimal objective function of the low-voltage interconnected area control strategy of the coordinated action of F-SOP and inverter; In the F-SOP loss characteristic model, the comprehensive operating cost of F-SOP is calculated, including the loss cost and operation and maintenance cost of F-SOP, as follows:

[0093] F-SOP loss cost The grid electricity price is multiplied by the transmission power loss of F-SOP, as follows:

[0094] F-SOP Power Transfer Loss It is obtained by subtracting the product of transmission efficiency and transmission power from the transmission power of each phase bridge arm of each port, as follows:

[0095] In the formula, is the power transmission loss of F-SOP, Indicates F-SOP Ports The transmission power of the phase bridge arm; Indicates F-SOP Ports Power transfer efficiency of the phase bridge arm; F-SOP operation and maintenance costs The operation and maintenance cost coefficient is multiplied by the sum of the transmission power of each phase of each port of F-SOP, as follows:

[0096] In the formula, is the operation and maintenance cost coefficient, Indicates F-SOPF-SOP Ports The apparent power transmitted by the phase bridge arm, ; Based on the comprehensive operating cost of the F-SOP and the large model of the inverter access area loss, the economic optimal objective function of the low-voltage interconnected area control strategy with coordinated action of F-SOP and inverter is constructed, which is the minimum value of the sum of transformer loss cost, inverter comprehensive operating cost, three-phase four-wire network line loss cost and F-SOP comprehensive operating cost, as follows:

[0097] In the formula, It is the comprehensive operating cost of the low-voltage distribution substation under the collaborative strategy.

[0098] The power transmission conservation constraint of the F-SOP loss characteristic model is that the sum of the active power transmitted by each bridge arm of each port of the F-SOP is 0, as follows:

[0099] In the formula, Indicates F-SOP Ports Active power flowing out of the phase bridge arm; The capacity constraint condition of the F-SOP loss characteristic model is that the apparent power transmitted by each bridge arm of each port of the F-SOP should be less than or equal to the capacity of the bridge arm corresponding to the corresponding port; the total apparent power transmitted by the F-SOP should also be less than or equal to the overall capacity of the F-SOP:

[0100] In the formula, Indicates F-SOP Ports The apparent power flowing through the phase bridge arm; Indicates F-SOP Ports The capacity of the phase bridge arm, is the total transmission power of F-SOP, is the overall capacity of F-SOP.

[0101] Step S5: In this embodiment, the Cplex commercial solver is used to solve the economic optimal objective function of the low-voltage interconnected area control strategy with the coordinated action of the F-SOP and the inverter, and the second optimal action state of the inverter and the optimal power scheduling instruction of the F-SOP are determined, and sent to the inverter and F-SOP respectively.

[0102] The optimal power scheduling instruction of the F-SOP shown includes the active power and reactive power transmitted by each phase bridge arm of the F-SOP of each port.

[0103] The interconnected substation control system based on the collaboration of F-SOP and phase converter includes the following modules: Data acquisition module: collects the operation-related parameters of each low-voltage distribution substation interconnected by the multi-port F-SOP at one time, wherein the operation-related parameters of the low-voltage distribution substation include the normal operation data of the low-voltage distribution substation and the equipment parameters of the transformer, F-SOP and inverter; The first calculation and judgment module: according to the low-voltage distribution station operation related parameters collected once, the output power three-phase imbalance of the transformer in each low-voltage distribution station, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution station are calculated once, and the output power three-phase imbalance, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution station are judged once whether they are within the constraint interval at the same time; If yes, the phase converter and F-SOP do not operate, and return to start the data acquisition module to continue real-time monitoring; If not, start the phase converter and start the second calculation and judgment module; The second calculation and judgment module: according to the pre-built large model of the loss of the phase converter access area, the economic optimal objective function of the low-voltage distribution area only connected to the phase converter is constructed, and the first optimal action state of the phase converter is determined; the large model of the loss of the phase converter access area includes a transformer loss characteristic model, a phase converter loss characteristic model, and a three-phase four-wire independent power flow network loss characteristic model; causing the phase converter to operate in a first optimal operating state; Secondary collection of operation-related parameters of each low-voltage distribution station area; According to the secondary collected operation-related parameters of each low-voltage distribution station area, the output power three-phase imbalance of the transformer in each low-voltage distribution station area, the load rate of the transformer and the voltage of each phase of each node are calculated for the second time, and it is determined whether the output power three-phase imbalance, the load rate of the transformer and the voltage of each phase of each node of each low-voltage distribution station area are simultaneously within the constraint interval; If yes, F-SOP does not take action and returns to start the data acquisition module to continue real-time monitoring; If not, F-SOP is started to start the instruction acquisition module; Instruction acquisition module: Based on the large model of the inverter access area loss and the pre-built F-SOP loss characteristic model, the economic optimal objective function of the low-voltage interconnected area control strategy with the coordinated action of F-SOP and the inverter is constructed; the economic optimal objective function of the low-voltage interconnected area control strategy with the coordinated action of F-SOP and the inverter is solved, the second optimal action state of the inverter and the optimal power scheduling instruction of F-SOP are determined, and sent to the inverter and F-SOP respectively.

[0104] In one embodiment, in order to verify the feasibility and superiority of the method provided in this application, four schemes are set for comparative analysis, and the verification is performed based on the three-phase four-wire 22-node area and 15-node area load. The four comparative schemes are: 1) Each low-voltage distribution substation area is not interconnected through F-SOP and is not connected to the phase converter; 2) Each low-voltage distribution substation is interconnected via F-SOP and is not connected to the phase converter; 3) Each low-voltage distribution substation area is connected to the phase converter without interconnection through F-SOP; 4) Each low-voltage distribution substation is interconnected via F-SOP and connected to the inverter, which is the interconnected substation control method based on the coordination of F-SOP and inverter proposed by the present invention.

[0105] The equipment installation status of the four schemes is shown in Table 1.

[0106] Table 1 Equipment installation of four solutions

[0107] The main features of the four solutions are as follows: The transformers in the first low-voltage distribution substation area and the second low-voltage distribution substation area are transformer No. 1 and transformer No. 2 respectively. Figure 6a , Figure 6b , Figure 6c and Figure 6d The following are comparison diagrams of transformer load rates under four schemes. Figure 6a and Figure 6c As shown in Figure 1, in Scheme 1 and Scheme 3, the transformer end lacks the power compensation of F-SOP. During the peak period of electricity consumption during the day, the load rate of the two transformers exceeds the economic operation range. In Scheme 2 and Scheme 4, as shown in Figure 1, Figure 6b and Figure 6d As shown, the low-voltage busbar in the substation is connected to F-SOP, and the transformer operates within the economic operation range at all times.

[0108] Figure 7a , Figure 7b , Figure 7c and Figure 7d Given are comparison diagrams of the three-phase imbalance of transformer output power under four schemes.

[0109] Under Scheme 1, if Figure 7a As shown in the figure, when there is no F-SOP and no phase converter to treat the three-phase imbalance, the transformer has a serious three-phase imbalance problem, and the imbalance of the transformer output power can reach up to 50%; Under Scheme 2, if Figure 7b As shown in the figure, the low-voltage busbars of the two substations are connected to the F-SOP, and the three-phase imbalance of the transformer output power is significantly reduced. However, due to the capacity limitation of the F-SOP, the three-phase imbalance of the output power still does not meet the standard for more than half of the time; Under Scheme 3, if Figure 7c As shown, the inverter has very limited ability to control the three-phase imbalance at the transformer end, and the transformer three-phase imbalance problem is still obvious; Under Scheme 4, if Figure 7dAs shown, the F-SOP works in coordination with the inverter, acting on the transformer end and the line load side respectively, so that the three-phase imbalance is within the threshold at all times.

[0110] Figure 8a , Figure 8b , Figure 8c and Figure 8d The total loss and loss composition of the low-voltage distribution station area under four schemes are given respectively.

[0111] Under Scheme 1, if Figure 8a As shown in the figure, since the two sections are not interconnected by F-SOP and the phase converter is not switched, the transformer bears all the load, which makes the zero-sequence loss and line loss of the transformer prominent and the total loss large; Under Scheme 2, if Figure 8b As shown in the figure, after incorporating F-SOP, the three-phase imbalance and light and heavy loads of the transformer were controlled, and the transformer loss was greatly reduced, but the line loss was still prominent; Under Scheme 3, if Figure 8c As shown in the figure, the incorporation of the phase converter significantly reduces line losses. At noon and evening when the load is high, line losses can be reduced by about 35%, and at other times, line losses can be reduced by 10% to 20%. However, the transformer losses of this solution have not been controlled, and the total losses are still very high. Under Scheme 4, if Figure 8d As shown in the figure, under the comprehensive treatment of F-SOP and inverter, the transformer loss and line loss are significantly reduced, the total loss is the smallest among the three schemes, and the treatment effect is good.

[0112] Fig. 9 The following are the comprehensive operation cost curves of low voltage distribution substations under four schemes. Fig. 9 It can be seen that although the method proposed in this application increases the comprehensive operating cost of F-SOP and the phase converter, the comprehensive operating cost of the low-voltage distribution station area is also lower than that of other schemes because the total loss is less than that of other schemes, and the economy is the best. At the same time, in the long run, this strategy effectively manages the three-phase imbalance and light and heavy load problems in the entire area, and improves the safety of low-voltage distribution station area operation.

[0113] To sum up, the interconnected substation control method based on the collaboration of F-SOP and phase converter proposed in this application, while effectively controlling the three-phase imbalance problem of the substation transformer, also effectively solves the three-phase imbalance problem of the substation line. Compared with the existing solutions, the total loss of the method proposed in this application is effectively reduced, the safety of the operation of the low-voltage distribution substation is improved, the service life of the equipment is extended, and the economy of the long-term operation of the low-voltage distribution substation is also improved.

[0114] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The interconnected area control method based on the cooperation of F-SOP and phase converter is characterized by: The steps include: Step S1: Collect the operation-related parameters of each low-voltage distribution substation interconnected by F-SOP at one time; Step S2: Based on the collected low-voltage distribution station operation related parameters, calculate and determine whether the output power three-phase imbalance of the transformer in each low-voltage distribution station, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution station are within the constraint range at the same time; if so, the phase converter and F-SOP do not operate, and return to step S1 to continue monitoring; if not, start the phase converter and enter step S3; Step S3: According to the large loss model of the phase converter access area, an economic optimal objective function of the low-voltage distribution area only connected to the phase converter is constructed to determine the first optimal operation state of the phase converter; the large loss model of the phase converter access area includes a transformer loss characteristic model, a phase converter loss characteristic model and a three-phase four-wire independent power flow network loss characteristic model; Make the inverter operate in the first optimal operating state; collect the relevant parameters of each low-voltage distribution station for the second time; calculate and determine whether the output power three-phase imbalance of the transformer in each low-voltage distribution station, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution station are within the constraint range at the same time; if so, the F-SOP does not operate and returns to step S1 to continue monitoring; If not, start F-SOP and go to step S4; Step S4: Based on the large-scale loss model of the inverter access area and the pre-built F-SOP loss characteristic model, the economic optimal objective function of the low-voltage interconnected area control strategy with coordinated action of F-SOP and inverter is constructed; Step S5: Solve the economic optimal objective function of the low-voltage interconnected area control strategy with coordinated action of F-SOP and inverter, determine the second optimal action state of the inverter and the optimal power dispatch instruction of F-SOP, and send them to the inverter and F-SOP respectively.

2. The interconnected area control method based on F-SOP and phase converter collaboration according to claim 1, characterized in that: No. Transformer The load factor of the phase is determined by Transformer The apparent power delivered by the first phase is divided by the Transformer The capacity of the phase is obtained; No. The three-phase imbalance of the output power of the transformer is determined by The maximum value of the three-phase output power of the transformer minus the The average value of the three-phase output power of the transformer is divided by the The average value of the three-phase output power of the transformer is obtained.

3. The interconnected area control method based on F-SOP and phase converter collaboration according to claim 1, characterized in that: The constraint condition of the transformer load factor is that the load factor of each phase of each transformer does not exceed the specified transformer economic operation range; The constraint condition of the three-phase imbalance of the transformer output power is that the output power imbalance of each transformer does not exceed the specified imbalance threshold; The constraint condition for the voltage of each phase at each node is that the voltage of each phase at each node in each low-voltage distribution station area does not exceed the upper and lower limits of the node voltage specified for safe operation of the low-voltage distribution station area.

4. The interconnected area control method based on F-SOP and phase converter collaboration according to claim 1, characterized in that: In the transformer loss characteristic model, transformer losses are calculated, including the comprehensive power no-load loss of each phase of each transformer, the comprehensive power rated load loss and the zero-sequence loss generated when the three-phase load of each transformer is unbalanced; In the inverter loss characteristic model, the inverter loss is calculated by multiplying the inverter resistance coefficient by the sum of the apparent power of the a-phase load of each group of inverter access nodes; In the three-phase four-wire independent power flow network loss characteristic model, the total loss of the three-phase four-wire network is calculated, which is obtained by multiplying the current of each phase of each branch by the resistance of the corresponding phase of the corresponding branch.

5. The interconnected area control method based on F-SOP and phase converter collaboration according to claim 4 is characterized in that, The economic optimal objective function of the low-voltage distribution area connected only to the inverter is the minimum value of the sum of the transformer loss cost, the inverter comprehensive operation cost and the three-phase four-wire network line loss cost; According to the transformer loss characteristic model, the transformer loss cost is obtained by multiplying the grid electricity price by the transformer loss; The comprehensive operating cost of the inverter includes the inverter loss cost and the inverter operation cost; According to the inverter loss characteristic model, the inverter loss cost is obtained by multiplying the grid electricity price by the inverter loss; The commutator action cost is obtained by multiplying the commutator action cost coefficient by the sum of all commutator action times; Based on the three-phase four-wire independent power flow network loss characteristic model, the line loss cost of the three-phase four-wire network is obtained by multiplying the grid electricity price by the total line loss of the three-phase four-wire network.

6. The interconnected area control method based on F-SOP and phase converter collaboration according to claim 1 is characterized in that, The constraints of the inverter loss characteristic model are The sum of the active power and reactive power output by the three-phase bridge arm of the phase converter should be equal to 0. Group commutator The active power and reactive power output by the phase bridge arm are equal to the opposite of the state scalar and the Group commutator access node The product of the active power and reactive power of the phase load, Group commutator , The product of the active power output of the phase bridge arm is 0. Group commutator , The product of the reactive power output by the phase bridge arm is also 0; specifically as follows: in, For the Group commutator Phase bridge arm to a node The active power injected into the phase, For the Group commutator Phase bridge arm to a node Reactive power injected into the phase; and For the Group commutator access node Phase load active power and reactive power, Indicates The action state scalar of the group commutator.

7. The interconnected area control method based on F-SOP and phase converter collaboration according to claim 1 is characterized in that: The constraints of the transformer loss characteristic model are that the apparent power output of each phase of each transformer cannot exceed the capacity of the corresponding phase of the corresponding transformer, and the total apparent power output of the three-phase of each transformer cannot exceed the total capacity of the three-phase of the corresponding transformer; The safety constraint condition for the operation of each phase of the three-phase four-wire loss characteristic model is that the voltage amplitude of each phase of each node in the low-voltage distribution station area does not exceed the upper and lower limits of the node voltage specified for the safe operation of the low-voltage distribution station area; The current amplitude of each phase of each branch in the low-voltage distribution station area shall not exceed the upper limit of branch current specified for safe operation of the low-voltage distribution station area; The amplitude of the active power injected into each phase of each node in the low-voltage distribution station area shall not exceed the upper and lower limits of the node injection power; The power flow constraint condition of the three-phase four-wire loss characteristic model is that each phase of each low-voltage distribution station area must satisfy the optimal power flow constraint after second-order cone relaxation.

8. The interconnected area control method based on F-SOP and phase converter collaboration according to any one of claims 1 to 7, characterized in that: In the F-SOP loss characteristic model, the comprehensive operating cost of the F-SOP is calculated, including the loss cost and operation and maintenance cost of the F-SOP; The loss cost of F-SOP is obtained by multiplying the grid electricity price by the transmission power loss of F-SOP; The F-SOP power transmission loss is obtained by subtracting the product of transmission efficiency and transmission power from the transmission power of each phase bridge arm of each port; The operation and maintenance cost of F-SOP is obtained by multiplying the operation and maintenance cost coefficient by the sum of the transmission power of each bridge arm of each port of F-SOP; Based on the large model of F-SOP comprehensive operating cost and inverter access area loss, the economic optimal objective function of the low-voltage interconnected area control strategy with coordinated action of F-SOP and inverter is constructed, which is the minimum value of the sum of transformer loss cost, inverter comprehensive operating cost, three-phase four-wire network line loss cost and F-SOP comprehensive operating cost.

9. The interconnected area control method based on F-SOP and phase converter collaboration according to claim 1 is characterized in that: In step S5, after solving the economic optimal objective function of the low-voltage interconnected area control strategy in which the F-SOP and the phase converter work together, the optimal power scheduling instruction of the F-SOP is obtained, including the active power and reactive power transmitted by each phase bridge arm of the F-SOP of each port.

10. A system for implementing the interconnected area control method based on F-SOP and phase converter collaboration as described in claim 1, characterized in that: Includes the following modules: Data acquisition module: collects the operation parameters of each low-voltage distribution substation interconnected by multi-port F-SOP at one time; The first calculation and judgment module: based on the low-voltage distribution substation operation related parameters collected once, the output power three-phase imbalance of the transformer in each low-voltage distribution substation, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution substation are calculated and judged at once whether they are within the constraint range at the same time; The second calculation and judgment module: based on the pre-built large-scale loss model of the phase converter access area, construct the economic optimal objective function of the low-voltage distribution area connected only to the phase converter, determine the first optimal action state of the phase converter; make the phase converter operate according to the first optimal action state; Secondary collection of operation-related parameters of each low-voltage distribution substation, secondary calculation and determination of whether the output power three-phase imbalance of the transformer in each low-voltage distribution substation, the load rate of the transformer and the voltage of each phase of each node in each low-voltage distribution substation are simultaneously within the constraint range; Instruction acquisition module: Based on the large model of inverter access area loss and the pre-built F-SOP loss characteristic model, the economic optimal objective function of the low-voltage interconnected area control strategy with coordinated action of F-SOP and inverter is constructed; the economic optimal objective function of the low-voltage interconnected area control strategy with coordinated action of F-SOP and inverter is solved, the second optimal action state of the inverter and the optimal power scheduling instruction of F-SOP are determined, and sent to the inverter and F-SOP respectively.

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