CN109193678B - Method and system for controlling voltage quality in low-voltage distribution network - Google Patents
Method and system for controlling voltage quality in low-voltage distribution network Download PDFInfo
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- CN109193678B CN109193678B CN201811128795.9A CN201811128795A CN109193678B CN 109193678 B CN109193678 B CN 109193678B CN 201811128795 A CN201811128795 A CN 201811128795A CN 109193678 B CN109193678 B CN 109193678B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
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Abstract
The application provides a method and a system for controlling voltage quality in a low-voltage distribution network, and specifically, the method comprises the steps of firstly obtaining three-phase voltage and current values of a target node in the low-voltage distribution network; then, calculating according to the three-phase voltage and current values to obtain a three-phase reactive power value of the target node, and analyzing the node reactive power unbalance according to the three-phase reactive power value; and finally, judging whether switching of the distributed power supply or the reactive power supply is needed or not according to a set threshold value, if switching operation is needed, sending an instruction to a corresponding change-over switch according to the control logic, and executing the corresponding instruction after the change-over switch receives the instruction so as to solve the problem of system power quality caused by unbalanced voltage or overhigh or overlow voltage of the low-voltage distribution network, realize the optimized operation of the low-voltage distribution network and further provide a new technical support for the promotion of distribution automation.
Description
Technical Field
The disclosure relates to the technical field of low-voltage distribution network operation control, in particular to a method and a system for controlling voltage quality in a low-voltage distribution network.
Background
Distributed power supplies such as low-voltage distributed photovoltaic and the like are used as clean energy, and the large-scale access to a power distribution network is beneficial to solving the problems of environmental pollution, energy shortage and the like. However, the access of the distributed power source to the low-voltage distribution network will have a serious influence on the voltage distribution, and the influence brings about a greater challenge to the operation of the low-voltage distribution network.
Based on the fact that the low-voltage distribution network in China basically adopts a three-phase four-wire system distribution network mode, the proposed operation control method mainly comprises the traditional droop control method, the constant power control method and the like. The PQ control is a short term of an active/reactive control strategy, is usually used for schedulable micro-power output control, and uses a preset power reference value as an active scheduling value and a reactive compensation value. In the PQ control mode, the active and reactive power outputs of the distributed power supply are taken as the set points of the controller. The power output of the inverter is set to a constant accordingly, so that the controller outputs a given power value regardless of the frequency and voltage variations in the grid, in which case the distributed power supply is a voltage controlled current source. And the droop control is the control of power by adjusting the active power/voltage reactive power/frequency. Droop control is similar to the operation characteristics of generators in large power grids, and the output of a voltage inverter is controlled according to the variation characteristics of output power so that the voltage and the frequency of the voltage inverter can automatically track preset droop characteristics.
The power supply adopting PQ control injects certain active power and reactive power into the power grid, and is slightly influenced by load change in a system or output change of other power supplies. However, the electric energy generated by the distributed power supply is not stable, and in order to satisfy the requirement that the power supply injects specified active and reactive power into the power grid, the lowest value of the power supply satisfying conditions is inevitably selected as a reference, so that the electric energy of the power supply is wasted. The function of the droop control technology is realized by a droop controller, and different droop coefficients can be set according to actual needs. The droop controller consists of a voltage droop controller and a frequency droop controller, and the voltage and the frequency are respectively controlled. However, on the premise of keeping the droop coefficient unchanged, the droop controller may cause the output voltage of the power grid to droop excessively, and the amplitude of the power grid voltage is higher due to increased droop adjustment, which affects the voltage quality of the power grid.
Therefore, it is desirable to provide a stable operation control method for the low voltage distribution network to optimize the operation of the low voltage distribution network.
Disclosure of Invention
The embodiment of the invention provides a method and a system for controlling voltage quality in a low-voltage distribution network, which are used for solving the problem of system power quality caused by unbalanced voltage, overhigh voltage or overlow voltage of the low-voltage distribution network in the prior art and realizing stable operation of the low-voltage distribution network.
According to a first aspect of an embodiment of the present invention, there is provided a method for controlling voltage quality in a low-voltage distribution network, the method including:
respectively acquiring a three-phase voltage value and a three-phase current value of a target node in a low-voltage distribution network;
calculating the three-phase reactive power of the target node according to the three-phase voltage value and the three-phase current value;
judging whether a distributed power supply exists near the target node;
if the distributed power supply does not exist, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than the set value of the system according to the three-phase reactive power value;
if the distributed power supply exists, judging whether the reactive power value of a phase line of the distributed power supply is higher than a first preset power value;
if the power value is higher than a first preset power value, cutting off the distributed power supply;
if the power difference value is not higher than the first preset power value, judging whether the power difference value between the phase line where the distributed power supply is located and the phase with the lowest reactive power is higher than a second preset power value;
switching the distributed power supply to the phase with the lowest reactive power if the value is higher than a second preset power value;
And if the reactive power value is not higher than a second preset power value, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance degree is detected to be larger than a system set value according to the three-phase reactive power value.
Optionally, when it is detected that the reactive power imbalance is greater than a system set value according to the three-phase reactive power values, switching a reactive power supply to a phase with a lowest reactive power value in the target node, including:
judging whether the power unbalance degree of the target node is greater than a system set value or not according to the three-phase reactive power;
and if the current value is larger than the set value of the system, searching a reactive power supply near the target node, and switching the reactive power supply to the phase with the lowest reactive power value in the three-phase reactive power values.
Optionally, the determining, according to the three-phase reactive power, whether the power imbalance of the target node is greater than a system set value includes:
according to the three-phase reactive power value, using formula Q sj =(Q i -Q j )/Q i *100%>Q 0 Judging whether the power unbalance degree of the target node is greater than a system set value or not;
wherein Q is sj Representing power imbalance, Q i Representing the highest of said three phase reactive power values, Q j Representing the lowest of said three phase reactive power values, Q 0 Representing the system set point.
Optionally, switching a reactive power source to a phase with the lowest reactive power value in the target node includes:
searching a reactive power supply with the capacity close to delta Q/2 near the target node;
switching the reactive power supply to the phase with the lowest reactive power value in the target node;
wherein, Δ Q ═ Q i -Q j ,Q i Representing the highest of said three phase reactive power values, Q j Representing the lowest phase reactive power value of the three phase reactive power values.
Optionally, if the power value is higher than the first preset power value, cutting off the distributed power supply includes:
if the power value is higher than the first preset power value, judging whether the distributed power supply is locked or not;
and if the locking does not exist, utilizing a fast synchronous change-over switch to cut off the distributed power supply, and recording the action time of the fast synchronous change-over switch.
Optionally, if the value is higher than a second preset power value, switching the distributed power supply to the phase with the lowest reactive power includes:
if the power value is higher than the second preset power value, judging whether the distributed power supply is locked or not;
and if the locking does not exist, switching the distributed power supply to the phase with the lowest reactive power by using a quick synchronous switch, and recording the action time of the quick synchronous switch.
According to a second aspect of the embodiments of the present invention, there is also provided a voltage regulation system in a low-voltage distribution network, the system including a metering automation device and a power supply switching control device, wherein:
the metering automation device is arranged at the main station and is used for acquiring a three-phase voltage value and a three-phase current value of a target node in the low-voltage distribution network;
the power supply switching control device is used for executing the following operation steps according to the three-phase voltage value and the three-phase current value acquired by the metering automation device:
calculating the three-phase reactive power of the target node according to the three-phase voltage value and the three-phase current value;
judging whether a distributed power supply exists near the target node;
if the distributed power supply does not exist, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than the set value of the system according to the three-phase reactive power value;
if the distributed power supply exists, judging whether the reactive power value of a phase line of the distributed power supply is higher than a first preset power value;
if the power value is higher than a first preset power value, cutting off the distributed power supply;
if the power difference value is not higher than the first preset power value, judging whether the power difference value between the phase line where the distributed power supply is located and the phase with the lowest reactive power is higher than a second preset power value;
Switching the distributed power supply to the phase with the lowest reactive power if the value is higher than a second preset power value;
and if the reactive power value is not higher than a second preset power value, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance degree is detected to be larger than a system set value according to the three-phase reactive power value.
Optionally, the power switching control device further includes a fast synchronous change-over switch, where the fast synchronous change-over switch is connected between the three-phase line and the distributed power supply and between the three-phase line and the reactive power supply.
According to the technical scheme, the method and the system for controlling the voltage quality in the low-voltage distribution network provided by the embodiment monitor the three-phase reactive power in each node and according to the preset threshold, when the reactive power of a certain phase is too high or too low or the power among the phases is seriously unbalanced, the distributed power supply and the reactive power supply are switched on the phase lines in time according to the control logic, so that the problem of the system electric energy quality caused by the unbalanced voltage, too high voltage or too low voltage of the low-voltage distribution network is effectively solved, the optimized operation of the low-voltage distribution network is realized, and a new technical support is provided for the promotion of distribution automation.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic flowchart of a method for controlling voltage quality in a low-voltage distribution network according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of a voltage quality control system in a low-voltage distribution network according to an embodiment of the present application.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to solve the problem of system power quality caused by unbalanced voltage, overhigh voltage or overlow voltage of the low-voltage distribution network in the prior art, the embodiment provides a method and a system for controlling the voltage quality in the low-voltage distribution network, and the low-voltage distribution network is operated in an economic optimal mode by switching a distributed power supply and a reactive power supply in the low-voltage distribution network.
Based on the above principle, the method and system provided by the embodiment will be described in detail below. Fig. 1 is a schematic flowchart of a method for controlling voltage quality in a low-voltage distribution network according to an embodiment of the present application. As shown in fig. 1, the method specifically includes the following steps:
s110: and respectively acquiring a three-phase voltage value and a three-phase current value of a target node in the low-voltage distribution network.
Specifically, three-phase voltage values of the load of the target node can be collected at the master station, j represents each important node, the voltage values of each important node are recorded as Uaj, Ubj and Ucj, and the current values are recorded as Iaj, Ibj and Icj.
S120: and calculating the three-phase reactive power of the target node according to the three-phase voltage value and the three-phase current value.
S130: and judging whether a distributed power supply exists near the target node.
If the distributed power supply does not exist, executing step S180 to detect the power unbalance; if the distributed power source exists, step S140 is executed to perform single-item reactive power value detection.
S140: and if the distributed power supply exists, judging whether the reactive power value of the phase line of the distributed power supply is higher than a first preset power value.
Wherein, the judgment formula is shown as the following formula (1):
max(Q i )>Q S1 formula (1)
In the formula, Q i Representing the target node reactive power value, unit: kvar; q S1 The unit of the single-phase reactive power setting threshold is represented as a first preset power value: kvar.
If the first predetermined power value is found, step S150 is executed, otherwise step S160 is executed.
S150: and if the power value is higher than the first preset power value, cutting off the distributed power supply.
Specifically, if the amplitude of the single-phase reactive power is larger than the set power value, the distributed power source can be quickly cut off by using the quick synchronous change-over switch.
Further, in order to effectively and quickly switch the distributed power supply, the step may further include the following steps:
s151: if the power value is higher than the first preset power value, judging whether the distributed power supply is locked or not;
s152: and if the locking does not exist, utilizing a fast synchronous change-over switch to cut off the distributed power supply, and recording the action time of the fast synchronous change-over switch.
S160: and if the power difference value is not higher than the first preset power value, judging whether the power difference value between the phase line where the distributed power supply is located and the phase with the lowest reactive power is higher than a second preset power value.
Wherein, the judgment formula is shown as the following formula (2):
max(Q i -Q j )>ΔQ S2 formula (2)
In the formula, Q i And the unit of the reactive power value of the phase where the distributed power supply is located is as follows: kvar; q j Represents the lowest phase reactive power value, in units: kvar; delta Q S2 The unit of the second preset power value, which represents the reactive power difference setting threshold: kvar.
If so, step S170 is performed, otherwise step S180 is performed.
S170: switching the distributed power supply to the phase with the lowest reactive power if the second preset power value is higher.
In particular, the distributed power source may be switched from a high power phase to a low power phase using a fast synchronous switcher.
Further, in order to effectively and quickly switch the distributed power supply, the step may further include the following steps:
s171: if the power value is higher than the second preset power value, judging whether the distributed power supply is locked or not;
s172: and if the locking does not exist, switching the distributed power supply to the phase with the lowest reactive power by using a quick synchronous switch, and recording the action time of the quick synchronous switch.
S180: and if the reactive power value is not higher than a second preset power value, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than a system set value according to the three-phase reactive power value.
Specifically, the method can comprise the following steps:
s181: and judging whether the power unbalance degree of the target node is greater than a system set value or not according to the three-phase reactive power.
In particular, formula Q may be utilized according to the three-phase reactive power value sj =(Q i -Q j )/Q i *100%>Q 0 Judging whether the power unbalance degree of the target node is greater than a system set value or not;
wherein Q is sj Representing power imbalance, Q i Representing the highest of said three phase reactive power values, Q j Representing the lowest of said three phase reactive power values, Q 0 Representing the system set point.
S182: and if the current value is larger than the set value of the system, searching a reactive power supply near the target node, and switching the reactive power supply to the phase with the lowest reactive power value in the three-phase reactive power values.
After the steps are completed, the next node in the power distribution network can be continuously searched, and the voltage balance is realized by switching the distributed power supply or the reactive power supply (such as a capacitor bank), so that the power distribution network runs economically.
According to the embodiment, through monitoring of three-phase reactive power in each node and according to the preset threshold value, when the situation that the reactive power of a certain phase is too high or too low or the reactive power is seriously unbalanced among the phases appears on the nodes in the power distribution network, the distributed power supply and the reactive power supply are switched in time according to the control logic, so that the problem of system electric energy quality caused by unbalanced voltage, too high voltage or too low voltage of the low-voltage power distribution network is effectively solved, the optimized operation of the low-voltage power distribution network is realized, and a new technical support is provided for the promotion of power distribution automation.
Based on the adjusting method, the embodiment also provides a voltage adjusting system. Fig. 2 is a schematic structural diagram of a voltage regulation system in a low-voltage distribution network according to an embodiment of the present application. As shown in fig. 2, the system mainly includes a power switching control device 210, and a metering automation device 220 connected to the power switching control device 210. Wherein:
the power switching control device 220 may be disposed in the master station, and is configured to collect a three-phase voltage value and a three-phase current value of a target node in the low-voltage distribution network.
The metering automation device 220 is configured to perform the following operation steps according to the three-phase voltage value and the three-phase current value collected by the metering automation device:
calculating the three-phase reactive power of the target node according to the three-phase voltage value and the three-phase current value;
judging whether a distributed power supply exists near the target node;
if the distributed power supply does not exist, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than the set value of the system according to the three-phase reactive power value;
if the distributed power supply exists, judging whether the reactive power value of a phase line of the distributed power supply is higher than a first preset power value;
If the power value is higher than a first preset power value, cutting off the distributed power supply;
if the power difference value is not higher than the first preset power value, judging whether the power difference value between the phase line of the distributed power supply and the phase with the lowest reactive power is higher than a second preset power value;
switching the distributed power supply to the phase with the lowest reactive power if the value is higher than a second preset power value;
and if the reactive power value is not higher than a second preset power value, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than a system set value according to the three-phase reactive power value.
Furthermore, the power supply switching control device further comprises a fast synchronous switch and a switch control module, wherein the fast synchronous switch is connected between the three-phase line and the distributed power supply and between the three-phase line and the reactive power supply, and the switch control module judges the voltage unbalance degree of the node according to the obtained three-phase reactive power value of the target node and controls the fast synchronous switch to switch the distributed power supply or the reactive power supply.
The voltage regulation system provided by the embodiment is based on the power supply switching control device and the metering automation device, controls the metering automation device to collect three-phase voltage and current of each load in the transformer area, and sends the obtained voltage and current to the power supply switching control device. The power supply switching control device judges whether switching of the distributed power supply or the reactive power supply is needed or not according to the set node reactive power unbalance degree, if switching operation is needed, an instruction is sent to the corresponding fast synchronous switch according to the control logic, and after the fast synchronous switch receives the instruction, the corresponding instruction is executed, so that the problem of system power quality caused by unbalanced voltage or overhigh voltage or overlow voltage of the low-voltage distribution network can be effectively solved, the optimized operation of the low-voltage distribution network is realized, and a new technical support is provided for the propulsion of distribution automation.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for apparatus or system embodiments, since they are substantially similar to method embodiments, they are described in relative terms, as long as they are described in partial descriptions of method embodiments. The above-described embodiments of the apparatus and system are merely illustrative, and the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
The foregoing is merely a detailed description of the invention, and it should be noted that modifications and adaptations by those skilled in the art may be made without departing from the principles of the invention, and should be considered as within the scope of the invention.
Claims (8)
1. A method for controlling voltage quality in a low-voltage distribution network is characterized by comprising the following steps:
respectively acquiring a three-phase voltage value and a three-phase current value of a target node in a low-voltage distribution network;
calculating the three-phase reactive power of the target node according to the three-phase voltage value and the three-phase current value;
judging whether a distributed power supply exists near the target node;
if the distributed power supply does not exist, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than the set value of the system according to the three-phase reactive power value;
if the distributed power supply exists, judging whether the reactive power value of a phase line of the distributed power supply is higher than a first preset power value;
if the power value is higher than a first preset power value, cutting off the distributed power supply;
if the power difference value is not higher than the first preset power value, judging whether the power difference value between the phase line where the distributed power supply is located and the phase with the lowest reactive power is higher than a second preset power value;
switching the distributed power supply to the phase with the lowest reactive power if the value is higher than a second preset power value;
and if the reactive power value is not higher than a second preset power value, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than a system set value according to the three-phase reactive power value.
2. The method of claim 1, wherein switching a reactive power source to a phase with a lowest reactive power value in the target node when detecting that the reactive power imbalance is greater than a system set value according to the three-phase reactive power values comprises:
judging whether the power unbalance degree of the target node is greater than a system set value or not according to the three-phase reactive power;
and if the current value is larger than the set value of the system, searching a reactive power supply near the target node, and switching the reactive power supply to the phase with the lowest reactive power value in the three-phase reactive power values.
3. The method of claim 2, wherein determining whether the power imbalance of the target node is greater than a system set point based on the three-phase reactive power comprises:
according to the three-phase reactive power value, using formula Q sj =(Q i -Q j )/Q i *100%>Q 0 Judging whether the power unbalance degree of the target node is greater than a system set value or not;
wherein Q is sj Representing power imbalance, Q i Representing the highest of said three phase reactive power values, Q j Representing the lowest of said three phase reactive power values, Q 0 Representing the system set point.
4. The method of claim 1, wherein switching reactive power to the phase of the target node having the lowest value of reactive power comprises:
Searching a reactive power supply with the capacity close to delta Q/2 near the target node;
switching the reactive power supply to the phase with the lowest reactive power value in the target node;
wherein Δ Q ═ Q i -Q j ,Q i Representing the highest of said three phase reactive power values, Q j Representing the lowest phase reactive power value of the three phase reactive power values.
5. The method of claim 1, wherein switching off the distributed power supply if above a first preset power value comprises:
if the power value is higher than the first preset power value, judging whether the distributed power supply is locked or not;
and if the locking does not exist, utilizing a fast synchronous change-over switch to cut off the distributed power supply, and recording the action time of the fast synchronous change-over switch.
6. The method of claim 1, wherein switching the distributed power supply to the phase with the lowest reactive power if above a second preset power value comprises:
if the power value is higher than the second preset power value, judging whether the distributed power supply is locked or not;
and if the locking does not exist, switching the distributed power supply to the phase with the lowest reactive power by using a quick synchronous switch, and recording the action time of the quick synchronous switch.
7. A control system for the voltage quality in a low voltage distribution network, characterized in that it comprises a metering automation device and a power supply switching control device, wherein:
the metering automation device is arranged at the main station and is used for acquiring a three-phase voltage value and a three-phase current value of a target node in the low-voltage distribution network;
the power supply switching control device is used for executing the following operation steps according to the three-phase voltage value and the three-phase current value acquired by the metering automation device:
calculating the three-phase reactive power of the target node according to the three-phase voltage value and the three-phase current value;
judging whether a distributed power supply exists near the target node;
if the distributed power supply does not exist, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than the set value of the system according to the three-phase reactive power value;
if the distributed power supply exists, judging whether the reactive power value of a phase line of the distributed power supply is higher than a first preset power value;
if the power value is higher than a first preset power value, cutting off the distributed power supply;
if the power difference value is not higher than the first preset power value, judging whether the power difference value between the phase line where the distributed power supply is located and the phase with the lowest reactive power is higher than a second preset power value;
Switching the distributed power supply to the phase with the lowest reactive power if the value is higher than a second preset power value;
and if the reactive power value is not higher than a second preset power value, switching the reactive power supply to the phase with the lowest reactive power value in the target node when the reactive power unbalance is detected to be larger than a system set value according to the three-phase reactive power value.
8. The system of claim 7, wherein the power switching control device further comprises a fast synchronous diverter switch, wherein the fast synchronous diverter switch is connected between a three-phase line and a distributed power source and between a three-phase line and a reactive power source.
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