CN119448303A

CN119448303A - Master-slave phase-separated flexible interconnection control method and system for low-voltage distribution network

Info

Publication number: CN119448303A
Application number: CN202411665748.3A
Authority: CN
Inventors: 杨金东; 荣飞; 涂春明; 刘红文; 唐立军; 徐肖伟; 聂永杰; 许守东; 尹照宏; 党军朋
Original assignee: Electric Power Research Institute of Yunnan Power Grid Co Ltd
Current assignee: Electric Power Research Institute of Yunnan Power Grid Co Ltd
Priority date: 2024-11-20
Filing date: 2024-11-20
Publication date: 2025-02-14
Anticipated expiration: 2044-11-20
Also published as: CN119448303B

Abstract

The embodiment of the application discloses a master-slave split-phase flexible interconnection control method and system for a low-voltage distribution network, wherein the master-slave split-phase flexible interconnection control method and system comprise the steps of carrying out sequence component decomposition on three-phase currents of two transformer areas to obtain negative sequence currents to be compensated and zero sequence currents to be compensated, solving load currents to be compensated and voltage stabilizing load currents according to target power to be transmitted by the two transformer areas, calculating compensation current reference values according to the negative sequence currents to be compensated, the zero sequence currents to be compensated, the load currents to be compensated and the voltage stabilizing load currents, obtaining a maximum one-phase compensation current reference value if the compensation current reference values are changed, and carrying out compensation current control on the master-slave back-to-back voltage source type transformer according to rated current and the maximum one-phase compensation current reference value of the master-back-to-back voltage source type transformer. The application synchronously solves the flexible capacity expansion and three-phase imbalance treatment of the power distribution network at low cost when the capacity is configured in a lower whole, solves the problems of light and heavy load and three-phase imbalance of the transformer area, and improves the flexibility and the expandability of the system by master-slave combination control.

Description

Master-slave split-phase flexible interconnection control method and system for low-voltage distribution network

Technical Field

The application relates to the technical field of power distribution network management, in particular to a master-slave split-phase flexible interconnection control method and system for a low-voltage power distribution network.

Background

Along with the large input of the distributed power supplies (Distribution generator, DG) and random loads, the interleaving and disordered input of single-phase/three-phase loads are particularly performed in low-voltage power distribution networks with various network structures and users, so that the problems of light heavy load and three-phase unbalance of transformers of the low-voltage power distribution networks are increasingly outstanding, and the safe and reliable operation of the low-voltage power distribution networks is threatened. However, the existing treatment means only aim at the problems of light and heavy load and three-phase unbalance of the transformer, and cannot treat the problems simultaneously. In addition, in the prior art, the low-voltage flexible interconnection technology can adjust the power of two low-voltage power distribution networks, and is applied to the power distribution networks by test points, so that the problems are solved, but the flexibility and the expandability of the conventional flexible interconnection device are insufficient, and the situation that the capacity of the interconnection device is excessive or the capacity of the interconnection device does not meet the power supply requirement and is difficult to expand exists.

Disclosure of Invention

The application mainly aims to provide a master-slave split-phase flexible interconnection control method and a master-slave split-phase flexible interconnection control system for a low-voltage distribution network, which can solve the technical problems that in the prior art, three-phase imbalance treatment and transformer light and heavy load cannot be treated simultaneously, and the flexibility and expandability of the conventional flexible interconnection device are insufficient.

In order to achieve the above object, a first aspect of the present application provides a control method for master-slave split-phase flexible interconnection of a low-voltage distribution network, which is applied to a control module in a master-slave split-phase flexible interconnection control system of the low-voltage distribution network, wherein the master-slave split-phase flexible interconnection control system of the low-voltage distribution network further comprises a master back-to-back voltage source converter, a slave back-to-back voltage source converter and a three-to-one multi-way switch, and the method comprises:

Acquiring three-phase currents of a first station area and three-phase currents of a second station area, respectively performing sequence component decomposition calculation on the three-phase currents of the first station area and the three-phase currents of the second station area, and respectively obtaining to-be-compensated negative sequence currents and to-be-compensated zero sequence currents of the first station area and the second station area;

Acquiring target power which is required to be transmitted to a power receiving station area by a power transmitting station area for realizing equal load rates of a first station area and a second station area;

Solving load current to be compensated of a power receiving station area and stabilized voltage load current required by stabilizing voltage of a power transmission station area according to target power, wherein the power receiving station area and the power transmission station area are different station areas in a first station area and a second station area;

Calculating to obtain a first compensation current reference value of the power receiving station area and a second compensation current reference value of the power transmitting station area according to the negative sequence current to be compensated and the zero sequence current to be compensated of the first station area and the second station area, the load current to be compensated of the power receiving station area and the voltage stabilizing load current of the power transmitting station area;

If the compensation current reference value is changed, the maximum one-phase compensation current reference value in a, b and c three-phase compensation current reference values of the compensation current reference value is obtained through comparison, wherein the compensation current reference value is the first compensation current reference value or the second compensation current reference value, and the compensation current reference value comprises an a-phase compensation current reference value, a b-phase compensation current reference value and a c-phase compensation current reference value;

and according to the rated current and the maximum one-phase compensation current reference value of the main back-to-back voltage source type converter, adopting a corresponding strategy to carry out compensation current control on the main back-to-back voltage source type converter and the auxiliary back-to-back voltage source type converter.

In order to achieve the purpose, the second aspect of the application provides a master-slave split-phase flexible interconnection control system of a low-voltage distribution network, which comprises a master back-to-back voltage source converter, a slave back-to-back voltage source converter, a first one-to-one multi-way switch, a second one-to-one multi-way switch and a control module;

the main back-to-back voltage source type converter comprises a back-to-back three-phase full-bridge converter;

two sides of the back-to-back three-phase full-bridge converter are respectively connected with the three phases of the feeder line of the first station area and the three phases of the feeder line of the second station area;

The back-to-back voltage source type converter comprises a back-to-back single-phase full-bridge converter;

the back-to-back single-phase full-bridge converter is respectively connected with the zero line of the first station area and the zero line of the second station area;

The back-to-back single-phase full-bridge converter is also connected with one phase line in the feeder line of the first station area through a first one-way switch, and connected with one phase line in the feeder line of the second station area through a second one-way switch;

and the control module is used for carrying out three-phase imbalance treatment according to the master-slave split-phase flexible interconnection control method of the low-voltage distribution network.

The embodiment of the application has the following beneficial effects:

The application realizes a low-voltage distribution network master-slave split-phase flexible interconnection control scheme, namely a low-cost solution of flexible capacity expansion and three-phase imbalance management of a distribution network based on master-slave back-to-back voltage source converters (master-slave BTB-VSC), transmits all capacity expansion power and a small amount of three-phase imbalance compensation power through the master-back-to-back voltage source converters (master-BTB-VSC), endows flexible capacity expansion capacity for the master-BTB-VSC through the cooperation of the slave-back voltage source converters (slave-BTB-VSC) and a multi-way switch, and realizes flexible capacity expansion and three-phase imbalance high-quality management of a platform area on the basis of lower overall configuration capacity, thereby effectively and low-cost solving the problems of light and heavy load and three-phase imbalance of the platform area. In addition, the flexibility of the device or the system is improved through various combined control of the master BTB-VSC and the slave BTB-VSC, and the device is more expandable through supplementing when the capacity of the master BTB-VSC converter is insufficient. The application can effectively improve the interconnection and mutual-aid capability of the power distribution network, reduce the running loss of the transformer area, reduce the cost of the treatment device, promote the interconnection and mutual-aid of the novel power distribution network and the distributed power supply absorption process, and has great engineering significance.

Drawings

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Wherein:

FIG. 1 is a flow chart of a master-slave split-phase flexible interconnection control method of a low-voltage distribution network in an embodiment of the application;

FIG. 2 is a block diagram of a master-slave split-phase flexible interconnection control system of a low-voltage distribution network in an embodiment of the application;

FIG. 3 is a circuit diagram of a master-slave split-phase flexible interconnection control system of a low-voltage distribution network in an embodiment of the application;

FIG. 4 is a schematic diagram of compensation current of a master-slave split-phase flexible interconnection control system of a low-voltage distribution network according to an embodiment of the present application;

FIG. 5 is a diagram showing the effect of amplifying compensation currents of a master-slave split-phase flexible interconnection control system of a low-voltage distribution network in an embodiment of the application;

FIG. 6 shows three phase currents under each condition of the first region;

FIG. 7 is a graph showing three phase currents for each condition of the second bay;

FIG. 8 is a schematic diagram of the transfer of current tracking signals from a BTB-VSC (from a back-to-back voltage source converter);

FIG. 9 is a graph showing the current of the first zone load under the condition of disturbance;

FIG. 10 is a tracking signal from a BTB-VSC of a disturbance in the first zone load.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

In the aspect of treating three-phase unbalance of a transformer area, the main treatment means are equipment such as a switching capacitor, a static reactive compensator, a phase changer and the like. The switching capacitor is the most common mode of reactive compensation three-phase unbalanced load of a transformer area, but the action time is long, continuous adjustment of reactive power cannot be realized, and transient impact exists in capacitor switching. A static var compensator can continuously adjust reactive power but still cannot compensate for active power. The phase changer can control active power and reactive power simultaneously, but a large amount of investment is needed to realize the three-phase imbalance treatment effect, the cost is higher, and the equipment utilization rate is low. In general, the existing three-phase unbalanced treatment method has the problems of single function, higher investment cost, low efficiency and the like, and cannot give consideration to the mutual interaction between different stations and the problem of light and heavy load of the treatment station.

In the aspect of managing the light and heavy load of the transformer area, students at home and abroad sequentially put forward a plurality of flexible interconnection series concepts such as a ring network power controller, a ring network power balancer, an intelligent power router, a soft interconnection switch and the like, and the problems of the light and heavy load and the three-phase unbalance of the transformer area are integrated and managed, so that the utilization rate of the device and the comprehensive treatment effect are effectively improved. However, the light and heavy load/three-phase imbalance treatment device of the transformer area in the existing scheme mainly adopts fixed capacity configuration, the fixed capacity is reasonably configured by combining the maximum power required by the three-phase imbalance treatment when rated input/output power, and when the three-phase imbalance is large, the device has larger capacity and is idle, so that the hardware cost is relatively high. Furthermore, the massive access of the random load causes the problem of single-phase heavy overload of the area to be more serious.

Therefore, there is a need to invent a low-cost flexible capacity expansion and three-phase imbalance treatment device for a power distribution network, which can effectively treat the problems of light and heavy load and three-phase imbalance of a platform area and insufficient flexibility and expandability of the conventional flexible interconnection device, and promote the interconnection and intercommunication of a novel power distribution network and the absorption process of a distributed power supply.

As shown in fig. 1, in one embodiment, a master-slave split-phase flexible interconnection control method for a low-voltage distribution network is provided. The master-slave split-phase flexible interconnection control method for the low-voltage distribution network specifically comprises the following steps:

and S100, acquiring three-phase current of the first station area and three-phase current of the second station area, and respectively performing sequence component decomposition calculation on the three-phase current of the first station area and the three-phase current of the second station area to respectively obtain negative sequence current to be compensated and zero sequence current to be compensated of the first station area and the second station area.

Specifically, the control method for the master-slave split-phase flexible interconnection of the low-voltage distribution network, namely the control method for the three-phase unbalance of the distribution network based on the master-slave back-to-back voltage source type converter (master-slave BTB-VSC), can be applied to a control module in a master-slave split-phase flexible interconnection control system of the low-voltage distribution network.

And two sides of a three-phase unbalanced treatment system (or device) of the power distribution network based on the master-slave BTB-VSC are respectively connected with the first station area and the second station area.

Three-phase currents of the first bay and three-phase currents of the second bay (i.e., a-phase current, b-phase current, and c-phase current) may be acquired from the metering automation system by a data acquisition device.

And performing sequence component decomposition calculation on the three-phase current of the first station area to obtain the negative sequence current to be compensated and the zero sequence current to be compensated of the first station area.

And performing sequence component decomposition calculation on the three-phase current of the second station area to obtain the negative sequence current to be compensated and the zero sequence current to be compensated of the second station area.

The negative sequence current to be compensated comprises an a-phase negative sequence current component to be compensated, a b-phase negative sequence current component to be compensated and a c-phase negative sequence current component to be compensated, and the zero sequence current to be compensated comprises an a-phase zero sequence current component to be compensated, a b-phase zero sequence current component to be compensated and a c-phase zero sequence current component to be compensated.

Thus, the negative sequence current to be compensated of the first region comprises three phase negative sequence current components to be compensatedThe zero sequence current to be compensated of the first station area comprises three-phase zero sequence current components to be compensated

The negative sequence current to be compensated of the second station area comprises three-phase negative sequence current components to be compensatedThe zero-sequence current to be compensated of the second station area comprises three-phase zero-sequence current components to be compensated

And S200, obtaining target power which is required to be transmitted to a power receiving station area by the power transmitting station area for realizing equal load rates of the first station area and the second station area.

Specifically, the target power required to be transmitted to the power receiving station area by the power transmitting station area for realizing equal load rates of the first station area and the second station area can be obtained from the metering automation system through the data acquisition device.

The power transmission area is a first area, and the power receiving area is a second area.

The power transmission area is the second area, and the power receiving area is the first area.

Taking the transmission power of the second station area to the first station area as an example, the data acquisition device acquires the target power which needs to be transmitted to the station area 1 by the station area 2 when the load rates of the first station area (the station area 1) and the second station area (the station area 2) are equal from the metering automation system.

Of course, the power may be transmitted from the first station to the second station, which is not described herein.

And S300, solving load current to be compensated of the power receiving station area and stabilized load current required by stabilizing the power transmission station area according to the target power, wherein the power receiving station area and the power transmission station area are different station areas in the first station area and the second station area.

Specifically, the load current to be compensated is a load current to be compensated in the power receiving area, and the load current to be compensated includes an a-phase load current component to be compensated, a b-phase load current component to be compensated, and a c-phase load current component to be compensated, namely:

The regulated load current is the load current required by the power transmission area for stabilizing voltage. The regulated load current comprises an a-phase regulated load current component, a b-phase regulated load current component, and a c-phase regulated load current component, namely:

S400, calculating to obtain a first compensation current reference value of the power receiving station area and a second compensation current reference value of the power transmitting station area according to the negative sequence current to be compensated and the zero sequence current to be compensated of the first station area and the second station area, the load current to be compensated of the power receiving station area and the voltage stabilizing load current of the power transmitting station area.

Specifically, the first compensation current reference value and the second compensation current reference value each include an a-phase compensation current reference value, a b-phase compensation current reference value, and a c-phase compensation current reference value.

S500, if the compensation current reference value is changed, the maximum one-phase compensation current reference value in the a, b and c three-phase compensation current reference values of the compensation current reference value is obtained through comparison, wherein the compensation current reference value is the first compensation current reference value or the second compensation current reference value.

Specifically, if the first compensation current reference value is changed compared with the historical first compensation current reference value, the first maximum phase compensation current reference value I _{c1_max}.I_{c1_max} is obtained by comparing the three-phase compensation current reference values I _{ca1_ref}、I_{cb1_ref}、I_{cc1_ref} of the first compensation current reference value, which is the maximum value in I _{ca1_ref}、I_{cb1_ref}、I_{cc1_ref}.

If the second compensation current reference value is changed compared with the historical second compensation current reference value, the three-phase compensation current reference value I _{ca2_ref}、I_{cb2_ref}、I_{cc2_ref} of the second compensation current reference value is compared, so that the second maximum phase compensation current reference value I _{c2_max}.I_{c2_max} is the maximum value in I _{ca2_ref}、I_{cb2_ref}、I_{cc2_ref}.

Whether the first compensation current reference value and the second compensation current reference value are changed is determined independently of each other. The two may be changed one to the other without being changed, it is also possible that both are changed, or that both are unchanged.

If the first compensation current reference value is not changed, the steps related to the power receiving station in steps S100 to S400 are re-performed.

If the second compensation current reference value is not changed, the steps related to the power transmission region in steps S100 to S400 are re-performed.

And S600, carrying out compensation current control on the main back-to-back voltage source converter and the slave back-to-back voltage source converter by adopting a corresponding strategy according to the rated current and the maximum one-phase compensation current reference value of the main back-to-back voltage source converter.

Specifically, based on the comparison result between the rated current of the main back-to-back voltage source type converter and the maximum one-phase compensation current reference value, the main back-to-back voltage source type converter and the slave back-to-back voltage source type converter are subjected to compensation current control by adopting corresponding strategies.

The embodiment realizes a low-cost solution of flexible capacity expansion and three-phase imbalance management of the power distribution network based on the master-slave back-to-back voltage source converter BTB-VSC, transmits all capacity expansion power and a small amount of three-phase imbalance compensation power through the master BTB-VSC, endows the master BTB-VSC with flexible phase-splitting capacity expansion capacity through the cooperation of the slave BTB-VSC and a multi-way switch, realizes flexible capacity expansion and three-phase imbalance high-quality management of a platform section on the basis of lower overall configuration capacity, and effectively solves the problems of light and heavy load and three-phase imbalance of the platform section at low cost. In addition, the flexibility of the device is improved through various combined control of the master BTB-VSC, and the device or system can be more expandable through supplementing the slave BTB-VSC when the capacity of the master BTB-VSC converter is insufficient. The method and the device can effectively improve interconnection capacity of the power distribution network, reduce running loss of a platform area, reduce cost of treatment devices, realize high equipment utilization rate, effectively treat three-phase imbalance, promote novel interconnection and intercommunication of the power distribution network and the distributed power supply absorption process, and have great engineering significance.

In one embodiment, if the compensation current reference value changes in step S500, obtaining the maximum one phase compensation current reference value of the three phase compensation current reference values a, b, and c by comparing includes:

if the first compensation current reference value is changed, comparing and acquiring the maximum one-phase compensation current reference value in the a, b and c three-phase compensation current reference values of the first compensation current reference value to obtain a first maximum-phase compensation current reference value;

If the second compensation current reference value is changed, obtaining a maximum one-phase compensation current reference value in a, b and c three-phase compensation current reference values of the second compensation current reference value through comparison, and obtaining a second maximum-phase compensation current reference value;

In step S600, according to the rated current and the maximum one-phase compensation current reference value of the main back-to-back voltage source converter, a corresponding strategy is adopted to perform compensation current control on the main back-to-back voltage source converter and the sub-back voltage source converter, including:

If the first compensation current reference value is changed, performing first compensation current control on a first side of the main back-to-back voltage source converter and a first side of the slave back-to-back voltage source converter according to a comparison between a first rated current of the main back-to-back voltage source converter and the first maximum phase compensation current reference value, wherein the first rated current is a rated current of a side, connected with a power receiving station, of the main back-to-back voltage source converter, and the first side is a side, connected with the power receiving station;

And if the second compensation current reference value is changed, performing second compensation current control on the second sides of the main back-to-back voltage source converter and the slave back-to-back voltage source converter by adopting a second strategy according to the comparison of the second rated current of the main back-to-back voltage source converter and the second maximum phase compensation current reference value, wherein the second rated current is the rated current of the side, connected with the power transmission area, of the main back-to-back voltage source converter, and the second side is the side, connected with the power transmission area.

Specifically, the first compensation current reference value and the second compensation current reference value each include an a-phase compensation current reference value, a b-phase compensation current reference value and a c-phase compensation current reference value.

If the first compensation current reference value is changed compared with the historical first compensation current reference value, the a, b and c three-phase compensation current reference values I _{ca1_ref}、I_{cb1_ref}、I_{cc1_ref} of the first compensation current reference value are compared to obtain a first maximum phase compensation current reference value I _{c1_max}.I_{c1_max} which is the maximum value in I _{ca1_ref}、I_{cb1_ref}、I_{cc1_ref}.

If the second compensation current reference value is changed compared with the historical second compensation current reference value, the a, b and c three-phase compensation current reference values I _{ca2_ref}、I_{cb2_ref}、I_{cc2_ref} of the second compensation current reference value are compared to obtain a second maximum phase compensation current reference value I _{c2_max}.I_{c2_max} which is the maximum value in I _{ca2_ref}、I_{cb2_ref}、I_{cc2_ref}.

And if the first compensation current reference value is changed, executing corresponding steps to realize the first compensation current control.

And if the second compensation current reference value is changed, executing corresponding steps to realize second compensation current control.

Both are independently operated.

In one embodiment, if the first compensation current reference value changes, performing a first compensation current control on the first side of the main back-to-back voltage source converter and the slave back-to-back voltage source converter using a first strategy according to a magnitude comparison between a first rated current of the main back-to-back voltage source converter and the first maximum phase compensation current reference value, including:

If the first maximum phase compensation current reference value is larger than the first rated current of the main back-to-back voltage source type converter, switching the first side of the back-to-back single-phase full-bridge converter to be connected with a first target phase line of the power receiving platform through a three-way switch corresponding to the power receiving platform, wherein the first target phase line is a phase line corresponding to the first maximum phase compensation current reference value in a feeder line of the power receiving platform;

And controlling the compensation current of the first side of the main back-to-back voltage source converter to be the first rated current of the main back-to-back voltage source converter, and controlling the compensation current of the first side of the sub-back voltage source converter to be the difference between the first maximum phase compensation current reference value and the first rated current of the main back-to-back voltage source converter.

Specifically, a master back-to-back voltage source converter is the master BTB-VSC, and a slave back-to-back voltage source converter is the slave BTB-VSC. The rated current in this embodiment is a single-phase rated current.

Comparing whether the first maximum phase compensation current reference value I _{c1_max} of the power receiving bay is greater than the first rated current I _N1 of the main back-to-back voltage source converter (i.e., the main BTB-VSC), if the first maximum phase compensation current reference value I _{c1_max} is greater than the first rated current I _N1 of the main BTB-VSC, the corresponding one-to-three multi-way switch of the power receiving bay will switch from the grid-connected point of the back-to-back voltage source converter (from the BTB-VSC) to the corresponding phase line (i.e., the first target phase line) of the first maximum phase compensation current reference value of the power receiving bay, the compensation current on the first side of the connection of the main BTB-VSC to the power receiving bay is the first rated current I _N1 of the main BTB-VSC by PI closed loop control, and the compensation current on the first side of the connection of the BTB-VSC to the power receiving bay is the difference between the first maximum phase compensation current reference value and the first current of the main BTB-VSC by PI closed loop control.

The three-way switch corresponding to the power receiving station area is switched from the grid connection point of the BTB-VSC to the corresponding phase line connection with the first maximum phase compensation current reference value in the power receiving station area, the compensation current I _cx1 (x=a, b, c) of the main BTB-VSC is the first rated current I _N1 of the main BTB-VSC through PI closed loop control, and the compensation current I _c3 of the sub BTB-VSC is the difference (I _{c1_max}-I_N1) between the first maximum phase compensation current reference value and the first rated current of the main BTB-VSC through PI closed loop control.

In one embodiment, if the first compensation current reference value is changed, performing a first compensation current control on the first side of the main back-to-back voltage source converter and the slave back-to-back voltage source converter according to a magnitude comparison between a first rated current of the main back-to-back voltage source converter and the first maximum phase compensation current reference value by using a first strategy, including:

And if the first maximum phase compensation current reference value is smaller than the first rated current of the main back-to-back voltage source type converter, controlling the three-way switch state corresponding to the power receiving platform area to be unchanged, controlling the compensation current of the first side of the main back-to-back voltage source type converter to be the first maximum phase compensation current reference value, and controlling the compensation current of the first side of the slave back-to-back voltage source type converter to be 0.

Specifically, whether the first maximum phase compensation current reference value I _{c1_max} is greater than the first rated current I _N1 of the main back-to-back voltage source converter (i.e., the main BTB-VSC) is compared, and if the first maximum phase compensation current reference value I _{c1_max} is less than or not greater than the first rated current I _N1 of the main BTB-VSC, the three-way switching state corresponding to the power receiving bay is kept unchanged, the compensation current of the first side connected to the power receiving bay by PI closed loop control of the main back-to-back voltage source converter (the main BTB-VSC) is the first maximum phase compensation current reference value, and the compensation current of the first side connected to the power receiving bay by PI closed loop control of the slave back-to-back voltage source converter (the slave BTB-VSC) is 0.

The three-phase compensation current of the compensation current I _cx1 (x=a, b, c) of the first side of the main BTB-VSC is the first maximum phase compensation current reference value I _{c1_max} through PI closed-loop control, and the compensation current I _c3 of the slave BTB-VSC is 0 through PI closed-loop control.

In one embodiment, if the second compensation current reference value is changed, performing second compensation current control on the second sides of the main back-to-back voltage source converter and the slave back-to-back voltage source converter according to a magnitude comparison between the second rated current of the main back-to-back voltage source converter and the second maximum phase compensation current reference value by using a second strategy, including:

If the second maximum phase compensation current reference value is larger than the second rated current of the main back-to-back voltage source type converter, switching the second side of the back-to-back single-phase full-bridge converter to be connected with a second target phase line of the power transmission platform through a three-way switch corresponding to the power transmission platform, wherein the second target phase line is a phase line corresponding to the second maximum phase compensation current reference value in a feeder line of the power transmission platform;

And controlling the compensation current of the second side of the main back-to-back voltage source type converter to be the second rated current of the main back-to-back voltage source type converter, and controlling the compensation current of the second side of the auxiliary back-to-back voltage source type converter to be the difference between the second maximum phase compensation current reference value and the second rated current of the main back-to-back voltage source type converter.

Specifically, a master back-to-back voltage source converter is the master BTB-VSC, and a slave back-to-back voltage source converter is the slave BTB-VSC.

Comparing whether the second maximum phase compensation current reference value I _{c2_max} is greater than the second rated current I _N2 of the main back-to-back voltage source converter (i.e., the main BTB-VSC), if the second maximum phase compensation current reference value I _{c2_max} is greater than the main BTB-VSC rated current I _N2, the one-to-three multi-way switch corresponding to the power transmission block will switch from the grid-connection point of the BTB-VSC to the corresponding phase line (i.e., the second target phase line) of the second maximum phase compensation current reference value in the power transmission block, the compensation current on the second side of the connection of the main BTB-VSC to the power transmission block is the second rated current I _N2 of the main BTB-VSC by PI closed loop control, and the compensation current on the second side of the connection of the sub BTB-VSC to the power transmission block is the difference between the second maximum phase compensation current reference value I _{c2_max} and the second rated current I _N2 of the main BTB-VSC by PI closed loop control.

The grid connection point of the power transmission platform area from the BTB-VSC and the grid connection point of the power receiving platform area from the BTB-VSC are two different grid connection points.

The three-way switch corresponding to the power transmission platform region is used for switching the grid connection point of the BTB-VSC to be connected with a corresponding phase line of the second maximum phase compensation current reference value, the compensation current I _cx2 (x=a, b, c) of the second side of the main BTB-VSC is the second rated current I _N2 of the main BTB-VSC through PI closed loop control, and the compensation current I _c4 of the second side of the BTB-VSC is the difference between the second maximum phase compensation current reference value I _{c2_max} and the second rated current I _N2 of the main BTB-VSC through PI closed loop control, namely (I _{c2_max}-I_N2).

and if the second maximum phase compensation current reference value is smaller than the second rated current of the main back-to-back voltage source type converter, controlling the one-to-three multi-channel switch state corresponding to the power transmission platform area to be unchanged, controlling the compensation current of the second side of the main back-to-back voltage source type converter to be the second maximum phase compensation current reference value, and controlling the compensation current of the second side of the slave back-to-back voltage source type converter to be 0.

Specifically, whether the second maximum phase compensation current reference value I _{c2_max} is greater than the second rated current I _N2 of the main back-to-back voltage source converter (i.e., the main BTB-VSC) is compared, and if the second maximum phase compensation current reference value I _{c2_max} is less than or not greater than the second rated current I _N2 of the main BTB-VSC, the three-way switching state corresponding to the power transmission bay is kept unchanged, the compensation current on the second side of the main back-to-back voltage source converter (main BTB-VSC) is controlled to be the second maximum phase compensation current reference value by PI closed loop, and the compensation current on the second side of the slave back-to-back voltage source converter (slave BTB-VSC) is controlled to be 0 by PI closed loop.

The three-phase compensation current of the compensation current I _cx2 (x=a, b, c) on the second side of the main BTB-VSC is the second maximum phase compensation current reference value I _{c2_max} through PI closed loop control, and the compensation current I _c4 on the second side of the slave BTB-VSC is 0 through PI closed loop control.

In one embodiment, in step S400, according to the to-be-compensated negative sequence currents and to-be-compensated zero sequence currents of the first and second bays, to-be-compensated load currents of the power receiving bays, and to-be-compensated regulated load currents of the power transmitting bays, a first compensation current reference value of the power receiving bays and a second compensation current reference value of the power transmitting bays are calculated, including:

According to the negative sequence current to be compensated, the zero sequence current to be compensated and the load current to be compensated of the power receiving station area, calculating to obtain a first compensation current reference value of the power receiving station area;

and calculating a second compensation current reference value of the power transmission platform area according to the negative sequence current to be compensated, the zero sequence current to be compensated and the regulated load current of the power transmission platform area.

Specifically, taking the transmission power of the second station area to the first station area as an example, according to the negative sequence current to be compensated of the first station areaZero sequence current to be compensatedLoad current to be compensatedAnd calculating a first compensation current reference value of the first station area, namely the power receiving station area, wherein the three-phase compensation current reference values are I _{ca1_ref}、I_{cb1_ref}、I_{cc1_ref} respectively.

Negative sequence current to be compensated according to the second station areaZero sequence current to be compensatedLoad current required for voltage stabilizationAnd calculating to obtain a second compensation current reference value of the second station area, namely the power transmission station area, wherein the three-phase compensation current reference values are respectively I _{ca2_ref}、I_{cb2_ref}、I_{cc2_ref}.

The power of the first station transmitting to the second station is the same, and will not be described here again.

In one embodiment, if the first station is a power receiving station and the second station is a power transmitting station, the first compensation current reference value and the second compensation current reference value are calculated by the following formula:

Wherein, Respectively an a-phase negative sequence current component to be compensated, a b-phase negative sequence current component to be compensated and a c-phase negative sequence current component to be compensated of the first station area,The a-phase zero-sequence current component to be compensated, the b-phase zero-sequence current component to be compensated and the c-phase zero-sequence current component to be compensated of the first station area are respectively, I _{ca1_ref}、I_{cb1_ref}、I_{cc1_ref} is a phase a first compensation current reference value, a phase b first compensation current reference value and a phase c first compensation current reference value of a first compensation current reference value of the first station area respectively;

Respectively an a-phase negative sequence current component to be compensated, a b-phase negative sequence current component to be compensated and a c-phase negative sequence current component to be compensated of the second station area, The a-phase zero-sequence current component to be compensated, the b-phase zero-sequence current component to be compensated and the c-phase zero-sequence current component to be compensated of the second station area are respectively,I _{ca2_ref}、I_{cb2_ref}、I_{cc2_ref} is a phase a second compensation current reference value, a phase b second compensation current reference value and a phase c second compensation current reference value of a second compensation current reference value of the second station region respectively.

Specifically, the transmission power formula of the first station area to the second station area is similar, and will not be described herein.

The first compensation current reference value is a compensation current reference value of a master-slave back-to-back voltage source converter of the power receiving station area.

The second compensation current reference value is the compensation current reference value of the master-slave back-to-back voltage source type converter of the power transmission area.

Referring to fig. 2, the application further provides a master-slave phase-splitting flexible interconnection control system 1 of a low-voltage power distribution network, namely a device or system for treating three-phase imbalance of a power distribution network based on master-slave back-to-back voltage source type converters, wherein the master-slave phase-splitting flexible interconnection control system 1 of the low-voltage power distribution network comprises a master-back voltage source type converter 10, a slave-back voltage source type converter 20, a first three-way switch 30, a second three-way switch 40 and a control module (not shown in the figure);

the main back-to-back voltage source converter 10 comprises a back-to-back three-phase full bridge converter;

the back-to-back voltage source converter 20 comprises a back-to-back single phase full bridge converter;

One side of the back-to-back single-phase full-bridge converter can be connected with a target phase line in a feeder line of the first station area through a first multi-way switch 30, wherein the target phase line of the first station area is a phase line corresponding to the maximum one-phase compensation current reference value in the compensation current reference values of the first station area;

The other side of the back-to-back single-phase full-bridge converter can be connected with a target phase line in a feeder line of the second station area through a second one-way switch 40, wherein the target phase line of the second station area is a phase line corresponding to the maximum one-phase compensation current reference value in the compensation current reference values of the second station area;

Specifically, back-to-Back voltage source converters, i.e., back-to-Back voltage source converter, BTB-VSCs.

The main back-to-back voltage source converter 10 has a larger capacity and the slave back-to-back voltage source converter 20 has a smaller capacity.

The back-to-back three-phase full-bridge converter comprises two three-phase full-bridge converters back-to-back.

Wherein, a three-phase full bridge current transformer is connected with the three phases (namely a phase line, b phase line and c phase line) of the feeder line of the first area through different terminals respectively. The other three-phase full-bridge converter is connected with the three phases (namely an a-phase line, a b-phase line and a c-phase line) of the feeder line of the second station area through different terminals respectively.

The three first connection ends of the first three-way switch 30 are respectively connected with three phases of the feeder lines of the first station area.

The three first connection ends of the second alternative multi-way switch 40 are respectively connected with the three phases of the feeder lines of the second station area.

The back-to-back voltage source converter 20 comprises two single-phase full-bridge converters back-to-back.

Wherein, a single-phase full-bridge converter is connected with the zero line of the first station area, and is also connected with a target phase line in the feeder line of the first station area through the second connecting end of the first three-way switch 30.

The other single-phase full-bridge converter is connected with the zero line of the second station area and is also connected with a target phase line in the feeder line of the second station area through a second connecting end of the second three-way switch 40.

In one embodiment, the back-to-back three-phase full-bridge inverter comprises two back-to-back and parallel first and second three-phase full-bridge inverters and a first direct-current side energy storage capacitor connected in parallel and located between the two three-phase full-bridge inverters;

The first three-phase full-bridge inverter comprises three first sub-circuits which are respectively connected with the three phases of the feeder line of the first area, and each first sub-circuit comprises two IGBTs which are connected in series;

the second three-phase full-bridge inverter comprises three second sub-circuits which are respectively connected with the three phases of the feeder line of the second station area, and each second sub-circuit comprises two IGBTs connected in series;

Specifically, the first three-phase full-bridge inverter and the second three-phase full-bridge inverter are both three-phase full-bridge converters.

The first three-phase full-bridge inverter comprises three phases or three first sub-circuits, each first sub-circuit is connected with one phase line of the first station area through a filter inductor, and different first sub-circuits are connected with different phase lines of the first station area.

The second three-phase full-bridge inverter comprises three phases or three second sub-circuits, each second sub-circuit is connected with one phase line of the second station area through a filter inductor, and different second sub-circuits are connected with different phase lines of the second station area.

Each of the first sub-circuit and the second sub-circuit comprises two IGBTs connected in series.

Each first sub-circuit and each second sub-circuit are connected with a corresponding phase line through a common node of two IGBTs which are connected in series and are contained in the first sub-circuit and the second sub-circuit.

IGBT (Insulated Gate Bipolar Transistor), an insulated gate bipolar transistor is a composite fully-controlled voltage-driven power semiconductor device composed of a BJT (bipolar transistor) and a MOS (insulated gate field effect transistor), and has the advantages of high input impedance of a MOSFET and low conduction voltage drop of a GTR.

Referring specifically to fig. 3, the back-to-back three-phase full-bridge converter includes 12 IGBT devices S11 to S16 and S21 to S26, 6 filter inductors L1, and a dc-side energy storage capacitor C _dc1.

Specifically, the first sub-circuit comprises two IGBTs (S11 and S12) connected in series, respectively, the second first sub-circuit comprises two IGBTs (S13 and S14) connected in series, respectively, and the third first sub-circuit comprises two IGBTs (S15 and S16) connected in series, respectively. The three first sub-circuits are respectively connected with corresponding phase lines of the first station area through different filter inductors (L11, L12 and L13).

The first second sub-circuit comprises two IGBTs (S21 and S22) connected in series, respectively, the second sub-circuit comprises two IGBTs (S23 and S24) connected in series, respectively, and the third second sub-circuit comprises two IGBTs (S25 and S26) connected in series, respectively. The three second sub-circuits are respectively connected with corresponding phase lines of the second station area through different filter inductors (L21, L22 and L23).

The two series-connected IGBTs are formed by connecting an emitter node of a first IGBT with a collector node of a second IGBT in series.

A first direct-current side energy storage capacitor C _dc1 is connected in parallel between the first three-phase full-bridge inverter and the second three-phase full-bridge inverter.

The dc side energy storage capacitor C _dc1 is mounted on the dc side of the main back-to-back voltage source converter 10 (i.e., the main BTB-VSC), the C _dc1 capacitor positive electrode is connected to the collector node of the first IGBT (i.e., S11, S13, S15, S21, S23, S25) in each of the first and second sub-circuits, and the C _dc1 capacitor negative electrode is connected to the emitter node of the second IGBT (i.e., S12, S14, S16, S22, S24, S26) in each of the first and second sub-circuits.

The function of the control module is specifically referred to the description in the above method, and will not be repeated here.

The embodiment realizes a low-cost solution of flexible capacity expansion and three-phase imbalance management of a power distribution network based on a master-slave back-to-back voltage source converter (BTB-VSC), transmits all capacity expansion power and a small amount of three-phase imbalance compensation power through a master BTB-VSC, endows the master BTB-VSC with flexible capacity expansion capacity through cooperation of a slave BTB-VSC and a multi-way switch, realizes flexible capacity expansion and three-phase imbalance high-quality management of a platform section on the basis of lower overall configuration capacity, and effectively solves the problems of light and heavy load and three-phase imbalance of the platform section at low cost. In addition, the flexibility of the device is improved through various combined control of the master BTB-VSC, and the device is more expandable through supplementing the slave BTB-VSC when the capacity of the master BTB-VSC is insufficient. The method and the device can effectively improve interconnection capacity of the power distribution network, reduce running loss of a platform area, reduce cost of treatment devices, realize high equipment utilization rate, effectively treat three-phase imbalance, promote novel interconnection and intercommunication of the power distribution network and the distributed power supply absorption process, and have great engineering significance.

In one embodiment, the back-to-back single-phase full-bridge inverter comprises two first single-phase full-bridge inverters and a second single-phase full-bridge inverter which are back-to-back and connected in parallel, and a second direct-current side energy storage capacitor which is connected in parallel and is positioned between the two single-phase full-bridge inverters;

The first single-phase full-bridge inverter comprises two third sub-circuits which are respectively connected with a zero line of the first station area and a second connecting end of the first one-out-of-three multi-way switch 30;

the second single-phase full-bridge inverter includes two fourth sub-circuits respectively connected to the zero line of the second bay and the second connection terminal of the second one-out-of-three multi-way switch 40.

Specifically, the first single-phase full-bridge inverter includes two third sub-circuits, wherein one of the third sub-circuits is connected to the zero line of the first station area, and the other third sub-circuit is connected to the second connection end of the first one-third multi-way switch 30 through the filter inductor L1.

The second single-phase full-bridge inverter comprises two fourth sub-circuits, wherein one of the fourth sub-circuits is connected with a zero line of the second station area, and the other fourth sub-circuit is connected with a second connecting end of the second one-out-of-three multi-way switch 40 through a filter inductor L2.

Each of the third sub-circuit and the fourth sub-circuit comprises two IGBTs connected in series.

Each third sub-circuit and each fourth sub-circuit are connected with a zero line or a second connecting end through a common node of two IGBTs which are connected in series and are contained in the third sub-circuit and the fourth sub-circuit.

Referring specifically to fig. 3, the back-to-back single-phase full-bridge converter includes 8 IGBT devices Q11 to Q14 and Q21 to Q24, 2 filter inductors (L1, L2), and a dc-side energy storage capacitor C _dc2.

Specifically, the first and third sub-circuits respectively comprise two IGBTs (Q11 and Q12) connected in series, and the second and third sub-circuits respectively comprise two IGBTs (Q13 and Q14) connected in series.

The first fourth sub-circuit comprises two IGBTs (Q21 and Q22) connected in series, respectively, and the second fourth sub-circuit comprises two IGBTs (Q23 and Q24) connected in series, respectively.

A second direct-current side energy storage capacitor C _dc2 is connected in parallel between the first single-phase full-bridge inverter and the second single-phase full-bridge inverter.

In one embodiment, all IGBTs are provided with one anti-parallel diode.

Specifically, each IGBT comprises an anti-parallel diode, so that the IGBT can be protected.

Fig. 4 shows a schematic diagram of the compensation current, and fig. 5 is an enlarged effect diagram of the schematic diagram of the compensation current. Taking the first station area as a power receiving area and the second station area as a power transmitting area as an example, the three-phase compensation currents of the main back-to-back voltage source converter 10 in the first station area are respectively I _ca1、I_cb1、I_cc1. The three-phase compensation currents of the main back-to-back voltage source converter 10 in the second transformer area are I _ca2、I_cb2、I_cc2 respectively. The compensation current from the back-to-back voltage source converter 20 in the first bay is I _c3 and the compensation current from the back-to-back voltage source converter 20 in the second bay is I _c4.

Fig. 6 shows three-phase currents under each condition of the first bay, fig. 7 shows three-phase currents under each condition of the second bay, and fig. 8 shows current tracking signals transmitted from the back-to-back voltage source converter (from the BTB-VSC).

In the simulink of matlab, simulation is performed based on a three-phase imbalance treatment method of a master-slave BTB-VSC (master-slave back-to-back voltage source converter), the total capacity of a platform area 1 and a platform area 2 is set to 400kVA in a simulation mode, before interconnection is performed, the total load of the platform area 1 is 375kw, the load of an a phase is 145kW, the load of a b phase is 130kW, the load of a c phase is 105kW, the total load of the platform area 2 is 195kW, the load of the a phase is 45kW, the load of the b phase is 65kW, the load of the c phase is 85kW, the two platform areas are in a three-phase imbalance state, and the platform area 1 is in a heavy load state, so that large system loss is caused. The main BTB-VSC is set, wherein the capacity of each phase of the main BTB-VSC is 25kVA, and according to the principle of the above-described three-phase imbalance management method and system based on the main BTB-VSC, it can be known that the power required to be transmitted in the a phase is the most, in the main BTB-VSC, the capacity of the a phase is smaller than the power to be transmitted, and the a phase current to be compensated is greater than the rated current of the main BTB-VSC, so that the main BTB-VSC transmits the power of the B phase and the C phase and the power of a phase first, and the remaining power required to be transmitted in the a phase is transmitted through the main BTB-VSC, and a part of the a phase current to be compensated and B, C treat each other compensating current in the station 1 are compensated by the main BTB-VSC.

In the transformer area 2, the a-phase compensation current is larger than the rated current of the slave BTB-VSC, so that the a-phase transmission current in the master BTB-VSC is the rated current of the slave BTB-VSC, and the transmission current of the slave BTB-VSC is the residual a-phase compensation current. After the current value to be compensated changes, the conclusion is the same as above.

It can be seen from fig. 6 that the three phases are unbalanced before 0.1s, the current value is higher, the main BTB-VSC is put into the circuit during 0.1s, the B, C phase current is in the balanced state, the a phase current is not enough due to the capacity of the main BTB-VSC, and a part of the current is not compensated to be about 100A higher than the B, C phase current value, the a phase current is better compensated after the circuit is put into the circuit in fig. 6 from the BTB-VSC during 0.2s, the current tracking signal is better transmitted from the BTB-VSC, and the A, B, C three phases are in the three-phase balanced state after the compensation, as can be seen from fig. 8. From fig. 7, the same conclusion as that of fig. 6 can be obtained, and the current of each phase of the two zones is about the effective value 431A, so that the load rates are equal, and the heavy load of the zone 1 is effectively solved.

FIG. 9 shows the working condition current of the disturbance of the load of the first zone, and FIG. 10 shows the tracking signal of the slave BTB-VSC of the disturbance of the load of the first zone.

Taking the zone 1 (the first zone) as an example, as can be seen from fig. 10, when the disturbance occurs in the a-phase load of the zone 1 at 0.3s, the load power of the a-phase load of the zone 2 is increased by 5kW, and at the same time, the a-phase compensation current is changed, the load rate of the balancing back-end zone is not changed, and according to the principle of the above-described method and system for managing three-phase imbalance based on master-slave BTB-VSC, the a-phase compensation current is still greater than the rated current of the master BTB-VSC, and the a-phase compensation current is continuously transmitted from the BTB-VSC to the zone 1. In fig. 10, the disturbance of the a phase is compensated for by 0.35s from the BTB-VSC, so that the three-phase equilibrium state is restored, and the same applies to the station area 2, which is not repeated here.

Those skilled in the art will appreciate that implementing all or part of the above-described methods in accordance with the embodiments may be accomplished by way of a computer program stored in a non-transitory computer-readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in embodiments provided herein may include non-volatile and/or volatile memory. The nonvolatile memory can include Read Only Memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (SYNCHLINK) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), among others.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims

1. The utility model provides a control method of low voltage distribution network principal and subordinate split phase flexible interconnection, its characterized in that is applied to the control module in the flexible interconnection control system of low voltage distribution network principal and subordinate split phase, the flexible interconnection control system of low voltage distribution network principal and subordinate split phase still includes principal back-to-back voltage source converter, principal back-to-back voltage source converter and three one-out-of-three multiway switch, the method includes:

Solving load current to be compensated of the power receiving station area and voltage stabilizing load current required by voltage stabilization of the power transmission station area according to the target power, wherein the power receiving station area and the power transmission station area are different station areas in the first station area and the second station area;

If the compensation current reference value is changed, the maximum one-phase compensation current reference value in the a, b and c three-phase compensation current reference values of the compensation current reference value is obtained through comparison, wherein the compensation current reference value is the first compensation current reference value or the second compensation current reference value;

2. The method according to claim 1, wherein if the compensation current reference value is changed, obtaining the largest one of the a, b, c three-phase compensation current reference values of the compensation current reference value by comparison comprises:

The compensation current control of the main back-to-back voltage source type converter and the auxiliary back-to-back voltage source type converter according to the rated current and the maximum one-phase compensation current reference value of the main back-to-back voltage source type converter by adopting corresponding strategies comprises the following steps:

3. The method of claim 2, wherein if the first compensation current reference value changes, performing a first compensation current control on the first side of the back-to-back voltage source converter and the back-to-back voltage source converter using a first strategy based on a magnitude comparison between a first rated current of the back-to-back voltage source converter and the first maximum phase compensation current reference value, comprising:

4. The method of claim 2, wherein if the first compensation current reference value changes, performing a first compensation current control on the first side of the back-to-back voltage source converter and the back-to-back voltage source converter using a first strategy based on a magnitude comparison between a first rated current of the back-to-back voltage source converter and the first maximum phase compensation current reference value, comprising:

5. The method of claim 2, wherein if the second compensation current reference value changes, performing a second compensation current control on the main back-to-back voltage source converter and the secondary side of the back-to-back voltage source converter using a second strategy based on a magnitude comparison between a second rated current of the main back-to-back voltage source converter and the second maximum phase compensation current reference value, comprising:

6. The method of claim 2, wherein if the second compensation current reference value changes, performing a second compensation current control on the main back-to-back voltage source converter and the secondary side of the back-to-back voltage source converter using a second strategy based on a magnitude comparison between a second rated current of the main back-to-back voltage source converter and the second maximum phase compensation current reference value, comprising:

7. The method according to claim 1, wherein calculating a first compensation current reference value of the power receiving station and a second compensation current reference value of the power transmitting station according to the negative sequence current to be compensated and the zero sequence current to be compensated of the first station and the second station, the load current to be compensated of the power receiving station, and the regulated load current of the power transmitting station comprises:

Calculating a first compensation current reference value of the power receiving station area according to the negative sequence current to be compensated, the zero sequence current to be compensated and the load current to be compensated of the power receiving station area;

And calculating a second compensation current reference value of the power transmission platform region according to the negative sequence current to be compensated, the zero sequence current to be compensated and the regulated load current of the power transmission platform region.

8. The method of claim 7, wherein if the first zone is a power receiving zone and the second zone is a power transmitting zone, the first compensation current reference value and the second compensation current reference value are calculated by the following formula:

Wherein, Respectively an a-phase negative sequence current component to be compensated, a b-phase negative sequence current component to be compensated and a c-phase negative sequence current component to be compensated of the first station area,The a-phase zero-sequence current component to be compensated, the b-phase zero-sequence current component to be compensated and the c-phase zero-sequence current component to be compensated of the first station area are respectively, The load current components are respectively an a-phase load current component to be compensated, a b-phase load current component to be compensated and a c-phase load current component to be compensated of the power receiving station area; I _{ca1_ref}、I_{cb1_ref}、I_{cc1_ref} is an a-phase first compensation current reference value, a b-phase first compensation current reference value and a c-phase first compensation current reference value of the first platform region respectively;

Respectively an a-phase negative sequence current component to be compensated, a b-phase negative sequence current component to be compensated and a c-phase negative sequence current component to be compensated of the second station area, The a-phase zero-sequence current component to be compensated, the b-phase zero-sequence current component to be compensated and the c-phase zero-sequence current component to be compensated of the second station area are respectively,I _{ca2_ref}、I_{cb2_ref}、I_{cc2_ref} is a phase a second compensation current reference value, a phase b second compensation current reference value and a phase c second compensation current reference value of the second station region respectively.

9. The master-slave split-phase flexible interconnection control system of the low-voltage distribution network is characterized by comprising a master back-to-back voltage source converter, a slave back-to-back voltage source converter, a first one-out-of-three multi-way switch, a second one-out-of-three multi-way switch and a control module;

One side of the back-to-back single-phase full-bridge converter can be connected with a target phase line in a feeder line of the first station area through a first multi-way switch, wherein the target phase line of the first station area is a phase line corresponding to the maximum phase compensation current reference value in the compensation current reference values of the first station area;

The other side of the back-to-back single-phase full-bridge converter can be connected with a target phase line in a feeder line of the second station area through a second multi-way switch, wherein the target phase line of the second station area is a phase line corresponding to the maximum phase compensation current reference value in the compensation current reference values of the second station area;

the control module is used for carrying out three-phase imbalance treatment according to the master-slave phase-splitting flexible interconnection control method of the low-voltage distribution network according to any one of claims 1-8.

10. The system of claim 9, wherein the back-to-back three-phase full-bridge inverter comprises two back-to-back and parallel first and second three-phase full-bridge inverters and a first dc-side energy storage capacitor connected in parallel and located between the two three-phase full-bridge inverters;

The first three-phase full-bridge inverter comprises three first sub-circuits which are respectively connected with the three phases of the feeder lines of the first area, and each first sub-circuit comprises two IGBTs connected in series;

The second three-phase full-bridge inverter comprises three second sub-circuits which are respectively connected with the three phases of the feeder lines of the second transformer area, and each second sub-circuit comprises two IGBTs connected in series;

The back-to-back single-phase full-bridge converter comprises two first single-phase full-bridge inverters and second single-phase full-bridge inverters which are back-to-back and connected in parallel, and a second direct-current side energy storage capacitor which is connected in parallel and positioned between the two single-phase full-bridge inverters;

the first single-phase full-bridge inverter comprises two third sub-circuits which are respectively connected with a zero line of the first station area and a second connecting end of the first one-out-of-three multi-way switch;

The second single-phase full-bridge inverter comprises two fourth sub-circuits which are respectively connected with a zero line of the second station area and a second connecting end of the second three-way switch.