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Patent Issued for Method and system for fast reconfiguration of power supply network in tens of milliseconos after power grid failure (USPTO 11355961)

  • Jun 24, 2022
  • 148 views
Source: 
China Business Day

2022 JUN 24 (NewsRx) -- By a News Reporter-Staff News Editor at China Business Day -- From Alexandria, Virginia, NewsRx journalists report that a patent by the inventors Duan, Gang (Beijing, CN), Liu, Nian (Beijing, CN), Lou, Xiaonan (Beijing, CN), Zhang, Qi (Beijing, CN), Zhang, Yuhan (Beijing, CN), Zheng, Liangliang (Beijing, CN), filed on July 31, 2020, was published online on June 7, 2022.

The patent’s assignee for patent number 11355961 is Beijing Sifang Automation Co. Ltd. (Beijing, People’s Republic of China).

News editors obtained the following quote from the background information supplied by the inventors: “After the external network accident or internal network failure occurs in a regional power grid, due to the interruption of part of the power supply path, the whole regional power grid or part of the regional power grid may be islanded. When the loss of power supply accounts for a large proportion, or there is a large power difference between the power generation and load in the island, it is necessary to take generator tripping or load shedding measures to achieve the frequency stability of the islanded power grid. The measures will not only have a great impact on the production and power supply, but also make it difficult for the temporarily stable islanded power grid to keep continuous and stable running in the follow-up. Therefore, in order to ensure continuous and stable power supply, it is the most direct and effective measure to quickly reconstruct new power supply paths, restore the connectivity and integrity of the power grid, and form a power grid as large as possible.

“If the terminal voltage of a motor is lower than 0.8 times the rated voltage and the duration exceeds 150 ms, the motor will be switched off by undervoltage protection. Therefore, the rapid power recovery after island formation should be completed within 100 ms. The existing power supply fast switching devices usually can start operation within 10 ms after some breakers disconnecting the power grid, and completes the power supply switching within 100 ms. However, the existing power supply fast switching device has the following disadvantages:

“(1) The existing power supply fast switching device can only obtain the information of local bus or incoming line, and can’t consider the recovery of power supply path from the perspective of the whole network, especially can’t carry out multi-point switching based on the remote fault information, so it limits the alternative paths of recovering power supply and reduces the probability of restoring the connectivity and integrity of power grid.

“(2) Conventional power supply fast switching devices rely on switch-off signal of breakers or related relay protection to start the switch-on operations. Therefore, when the fault occurs in the external power grid, and there is no switch-off signal in the monitoring area of conventional power supply fast switching device, the fast switching devices cannot be started; however, the frequency and voltage of the part of the internal power grid is collapsing, if the is part of the internal power grid cannot be isolated from the external power grid with fault, and be switched to the other part of the internal power grid with normal power supply sources, the loads in the part of the internal power grid affected by the external fault will stop running.

“(3) The hot standby power source in a local area may not have enough capacity, so more hot standby power sources should be selected in the distance for support.

“(4) A single power supply path can be overloaded, where multiple power supply paths are required.

“(5) There is the possibility that the fast switching of power supply fails because the synchronous conditions do not meet the requirements. After the failure of a conventional fast switching of power supply with only one switch-on breaker, the reconnection of the isolated power grids fails without backup measures.

“In addition, the existing methods known as power grid reconfiguration or power grid self-healing are all based on conventional slow switching operation, that is the power supply is resumed after a longtime power outage of loads, and loads have stopped continuous running. Therefore, such solutions cannot meet the requirement of restoring power supply within 150 ms after the removal of fault, and cannot achieve the purpose of restoring power supply without stopping the continuous running of loads, such as motors, so these methods of power supply restoring are not in the same scope as the problems solved by the invention.”

As a supplement to the background information on this patent, NewsRx correspondents also obtained the inventors’ summary information for this patent: “In order to overcome the defects of existing power supply fast switching devices, this invention presents a method and system for fast reconfiguration of is power supply network in time of millisecond scale after power grid failure.

“According to one aspect of the invention, a fast millisecond reconfiguration method for power supply network after power grid failure is provided, and the method includes the following characteristic steps:

“Step 1: The master station of fast reconfiguration collects all the state information of the monitored power grid from the client stations of fast reconfiguration located in transformer substations or power plant, and compares it with the characteristics of built-in fault set that may occur, to judge whether the monitored power grid has breaker disconnection or the fault that will cause breaker disconnection, that is to say, real-time sense of grid disconnection fault;

“Step 2: When the master station of fast reconfiguration detects a preset fault that may cause the breaker to switch-off, it sends pre-start switch-on instructions to the client stations of fast reconfiguration where the multiple networking recovery breakers corresponding to the class I breaker are located, in which the class I breaker is the breaker that may switch off;

“Step 3: If the master station of fast reconfiguration detects the external network has been isolated and has been collapsing, the class II breaker will be switched off, and the instructions of synchronous switch-on will be sent to the client stations of fast reconfiguration where the multiple networking recovery breakers corresponding to the class II breaker are located, wherein the class II breaker is the tie breaker between internal network and external network; Step 4: The client stations of fast reconfiguration receiving the pre-start switch-on instructions identify the fault clearing time in real time according to the local measurement information. When it is found that the fault is cleared or is being cleared, it will immediately or after delaying the designated time send the instructions of synchronous switch-on to the networking recovery breakers corresponding to the class I breaker;”

The claims supplied by the inventors are:

“1. A fast reconfiguration method of power supply network in tens of milliseconds after power grid failure, comprising the following characteristic steps: Step 1: a master station of fast reconfiguration collects all state information of a monitored power grid from client stations of fast reconfiguration located in transformer substations or a power plant, and compares it with characteristics of a set of possible faults to determine whether the monitored power grid has a breaker disconnection; Step 2: based on determining that the master station of fast reconfiguration detects a preset fault that causes a breaker to switch-off, the master station sends pre-start switch-on instructions to the client stations of fast reconfiguration where networking recovery breakers corresponding to a class I breaker are located, wherein the class I breaker is a breaker that may be triggered to switch off by the preset fault; Step 3: based on determining that the master station of fast reconfiguration detects that an external network has been isolated and has been collapsing, a class II breaker is switched off, and instructions of synchronous switch-on are sent to the client stations of fast reconfiguration where networking recovery breakers corresponding to the class II breaker are located, wherein the class II breaker is a tie breaker between an internal network and the external network; Step 4: the client stations of fast reconfiguration receiving the pre-start switch-on instructions identify a fault clearing time in real time according to local measurement information, and based on determining that the fault is cleared or is being cleared, immediately or after delaying a designated time, sending the instructions of synchronous switch-on to the networking recovery breakers corresponding to the class I breaker; Step 5: the master station of fast reconfiguration monitors an opening signal of the class I breaker in the monitored power grid, and based on determining that one of the class I breakers has been switched off or being switched off, the master station immediately or after delaying a designated time sends the instructions of synchronous switch-on to the networking recovery breakers corresponding to the class I breaker; Step 6: wherein execution of the instructions of synchronous switch-on comprises: determining that two sides of a networking recovery breaker to be switched on meet a synchronous switch-on condition, determining that there is no fault blocking in a power outage area, determining there is no fault blocking in an area of standby power source, and based on determining all these conditions are satisfied, a switch-on implementation signal is sent to the networking recovery breaker; Step 7: after an interconnection of the power grid is restored, disconnecting an over-current networking recovery breaker or decreasing a current by using a current limiting reactor; Step 8: uncoupling existing high and low voltage electromagnetic ring network; and Step 9: resetting a fast reconfiguration system of power supply network comprising: after finishing step 8 for 200 ms, resetting all devices of the fast reconfiguration system of power supply network, and returning to step 1 to monitor a next power grid disconnection event.

“2. The method of claim 1, wherein in the step 1, for information acquisition and transmission of the fast reconfiguration master station and the fast reconfiguration client stations, the step comprises: S2-1) acquiring electrical measurements of a substation or a plant in a fast reconfiguration client substation using hardwiring; S2-2) transmitting through a network communication the information and instructions between the fast reconfiguration master station and the fast reconfiguration client station; S2-3) setting a sampling rate of power frequency recording data of the fast reconfiguration substation equal to or greater than 1200 Hz; S2-4) setting a data processing period of the fast reconfiguration client station to equal to or less than 0.83 ms; S2-5) setting an information transmission period and instruction scanning period between the fast reconfiguration master station and the fast reconfiguration client station to equal to or less than 1.67 ms; S2-6) switching value inputs or digital inputs acquired by the fast reconfiguration client stations in transformer substations or power plants include: breaker position, trip signal of relay protection devices and trip signal of stability control devices; S2-7) analog inputs acquired by the fast reconfiguration client stations in the transformer substations or power plants includes voltages of critical buses, currents and voltages of branches of external power sources, transformers, generators, tie lines and bus couplers.

“3. The method of claim 1, wherein in the step 1, in the master station, determining that there is or will be a fault of causing the breaker to open according to acquired power grid information, and wherein the fault includes: S3-1) short circuit fault; S3-2) over current fault; S3-3) power or voltage oscillation; S3-4) Remote disconnection of external network to form isolated network; Among them, the short circuit fault, the over current fault, the power or voltage oscillation fault triggers devices other than a fast reconfiguration system of power supply network to disconnect the corresponding class I breaker, which causes the power grid to be separated and form an electrical island, after being separated, an island power grid without an original fault appears, and wherein the devices other than the fast reconfiguration system of the power supply network include relay protection devices and power grid stability control devices; based on determining that a remote separation of the external network forms an isolated network, the fast reconfiguration system of power supply network actively disconnects the monitored power grid and the external network at the tie line breaker corresponding to the class II breaker, and the monitored power grid forms a new isolated electrical island.

“4. The method of claim 1, wherein in the step 2, detecting the preset fault comprising: S4-1) the master station of fast reconfiguration evaluates voltages of all buses of the monitored power grid in real time, based on determining that a lowest bus voltage is lower than a first voltage threshold and lasts for a time period longer than a first time threshold, a bus corresponding to the lowest bus voltage is selected as a fault bus, wherein the first voltage threshold is set to 0.5 times a rated voltage, and the first time threshold is set to 10 ms; S4-2) according to a current of each branch connected to the fault bus, a branch with a largest current is selected as a fault branch, and the breaker close to the fault bus on the fault branch is selected as the class I breaker; S4-3) in response to determining that the fault occurs at the fault bus, determining the class I breaker using step of S4-2).

“5. The method of claim 1, wherein in the step 2 and 3, the networking recovery breaker has following characteristics: S5-1) The networking recovery breaker reconnects an isolated power grid with other power grids through a switch-on operation; S5-2) After the networking recovery breaker is switched on, an overcurrent protection is not triggered to act in a time period of a second time threshold, wherein the second time threshold is set to 20 s; S5-3) based on determining that there are more than one networking recovery breakers for an electrical island formed by the class I or class II breaker and these networking recovery breakers belong to three or more voltage levels, only networking recovery breakers at highest two voltage levels are reserved; S5-4) Each networking recovery breaker belongs to a fast reconfiguration client station, and the instructions sent by the master station to the networking recovery breaker are forwarded by the fast reconfiguration client station.

“6. The method of claim 1, wherein in the step 3, determining that an external grid has been isolated and has been collapsing based on determining that all of the following criteria are met simultaneously: S6-1) a frequency deviation of a bus connected by a tie line of the external grid from a rated frequency exceeds a first frequency deviation threshold, wherein the first frequency deviation threshold is set to 0.1 Hz; S6-2) The frequency deviation between the bus connected by the tie line of the external power grid and a bus of a standby power source exceeds a second frequency deviation threshold, wherein the second frequency deviation threshold is set to 0.2 Hz; S6-3) a frequency of the standby power bus is within a first frequency range, wherein the first frequency range is set to 49 Hz˜51 Hz; S6-4) a frequency change rate of the bus connected by the tie line of the external power grid exceeds a first frequency change rate threshold, wherein the first frequency change rate threshold is set to 0.2 Hz/s; S6-5) a duration is greater than a time period of a third time threshold, wherein the third time threshold is set to 150 ms.

“7. The method of claim 1, wherein in the step 2, based on determining that the master station of fast reconfiguration detects an occurrence of the preset fault, the master station sends the pre-start switch-on instructions to the client stations where the networking recovery breakers are located before the class I breaker is switched off due to the preset fault.”

There are additional claims. Please visit full patent to read further.

For additional information on this patent, see: Duan, Gang. Method and system for fast reconfiguration of power supply network in tens of milliseconos after power grid failure. U.S. Patent Number 11355961, filed July 31, 2020, and published online on June 7, 2022. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=11355961.PN.&OS=PN/11355961RS=PN/11355961

 

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