CN-121984150-A - Micro-grid integrated protection method based on multi-criterion self-adaptive identification

CN121984150ACN 121984150 ACN121984150 ACN 121984150ACN-121984150-A

Abstract

The invention belongs to the technical field of micro-grid protection, and in particular relates to a micro-grid integrated protection method based on multi-criterion self-adaptive identification, which comprises the steps of constructing a sensing layer-decision layer-execution layer three-layer control architecture in a micro-grid; the method comprises the steps of acquiring electric quantity data of a micro-grid in real time by utilizing a sensing layer, identifying a current running mode of the micro-grid in real time by utilizing a decision layer based on power flow direction and frequency deviation of a grid connection point, adopting a multi-dimensional feature fusion algorithm to fuse fault feature parameters in the grid connection mode or island mode to judge a fault state, identifying the current running mode of the micro-grid by the decision layer, generating a command and issuing the command to an execution layer, executing mode switching by the execution layer, locating and isolating a fault position when the fault is judged to occur, attempting reclosing recovery by transient faults, and ensuring power supply of a non-fault area by a permanent fault adjustment running strategy. The invention can realize accurate fault identification and stable control in the grid-connected/island mode switching process.

Inventors

LIU XIANGGANG
ZHAO JINQIANG
LIU TAO
Bian Fenglin
ZHAO BENLEI
WANG ZHIHUA
ZHAO LIN
WANG YANAN
ZHAO ZHIHUAN
JIANG MINGMING
Jiao Pihua
ZHU JIAN
LIU XIANGSHAN
LIU XIANGJIN
JIANG YAN
Bi Yujun
Zong Peifu
WANG WENHAO
LIU TAIBAO

Assignees

山东惠杰电气工程技术有限公司

Dates

Publication Date: 20260505
Application Date: 20251224

Claims (10)

1. The micro-grid integrated protection method based on multi-criterion self-adaptive identification is characterized by comprising the following steps of: s1, constructing a three-layer control architecture of a sensing layer, a decision layer and an execution layer in a micro-grid, wherein the sensing layer acquires electric quantity data of the micro-grid in real time, wherein the electric quantity data comprises voltage, current, frequency and harmonic content, the decision layer carries out mode identification and fault judgment based on the electric quantity data, and the execution layer carries out mode switching and fault processing operation; S2, acquiring electric quantity data of the micro-grid in real time by utilizing a sensing layer, and identifying a current running mode of the micro-grid in real time based on power flow direction and frequency deviation of a grid connection point in a decision layer, wherein the running mode comprises a grid connection mode and an island mode; S3, extracting fault characteristic parameters at a decision layer, matching weight coefficients for each fault characteristic parameter, and adopting a multidimensional characteristic fusion algorithm to fuse the fault characteristic parameters in a grid-connected mode or an island mode to judge a fault state; S4, the decision layer recognizes the current running mode of the micro-grid and generates a command to be issued to an execution layer, when the execution layer executes grid connection-island switching, the execution layer pre-judges the island running power requirement, and executes the switching-off of a breaker and the mode switching of a distributed power supply controller after cutting off non-important loads; s5, when the fault is judged to occur, the fault position is positioned and isolated, the reclosing recovery is tried by the transient fault, and the power supply of the non-fault area is ensured by the permanent fault adjustment operation strategy.
2. The micro-grid integrated protection method based on multi-criterion self-adaptive recognition according to claim 1, wherein in the step S1, a sensing layer is specifically arranged at the outlet of each distributed power supply and at grid connection points where the micro-grid is connected with a power grid, and each of the micro-grid integrated protection method is provided with 1 distributed detection unit to collect electric quantity data in real time; the decision layer is specifically provided with a central controller with a built-in fault characteristic database and a control strategy library, and the current running mode of the micro-grid is identified in real time based on the sensing layer data, fault judgment is carried out, and a generated instruction is issued to the execution layer; the execution layer comprises a grid-connected point breaker, a distributed power supply controller and a load change-over switch, and receives instructions of the decision layer to execute operation.
3. The microgrid integrated protection method based on multi-criterion self-adaptive identification according to claim 1 is characterized in that in S2, a microgrid grid connection/island mode is identified in real time based on power flow direction and frequency deviation of a grid connection point, wherein if the total active power P of the grid connection point is more than or equal to 0 and the frequency deviation delta f is less than or equal to +/-0.1 Hz, the power grid supplies power to the microgrid, the grid connection mode is judged, if the total active power P of the grid connection point is less than 0 and the frequency deviation delta f is +/-0.1 Hz, the microgrid supplies power to a load, the island mode is judged, and the rest is in an abnormal operation state.
4. The microgrid integrated protection method based on multi-criterion self-adaptive recognition according to claim 2, wherein in the step S3, fault characteristic parameters are extracted respectively for a grid-connected mode and an island mode, wherein for the grid-connected mode, a fault current amplitude I f is detected and extracted through a wavelet transformation mode maximum value, an extraction voltage drop depth delta U is calculated through an effective value, an n-order harmonic effective value is extracted through fast fourier transformation, and a total harmonic distortion THD is obtained; For the island mode, extracting the frequency change rate df/dt by a first-order differential method, wherein f is frequency, t is time, acquiring the voltage sag duration t drop based on the duration that the voltage is lower than the rated value by 85%, and calculating the energy storage SOC change rate dSOC/dt by integrating the energy storage charging and discharging power; Taking I f and delta U, THD as grid-connected fault characteristic parameters, taking df/dt, t drop and dSOC/dt as island fault characteristic parameters, carrying out standardized processing on each fault characteristic parameter, matching corresponding weight coefficients for each fault characteristic parameter, and fusing the fault characteristic parameters through a multi-dimensional characteristic fusion algorithm to obtain a fault judgment index F 1 = sigma (grid-connected characteristic parameter multiplied by weight coefficient) and F 2 = sigma (island characteristic parameter multiplied by weight coefficient); A grid-connected mode threshold T grid and an island mode threshold T island are set, and in the grid-connected mode, a fault state is determined when F 1 ≥T grid is performed, and in the island mode, a fault state is determined when F 2 ≥T island is performed.
5. The microgrid integrated protection method based on multi-criterion self-adaptive recognition according to claim 4, wherein the obtaining mode of T grid is as follows: ; In the formula, The real-time running capacity of the micro-grid; Is a reference value for the capacity of the microgrid; to adjust the step length; The acquisition mode of T island is as follows: 。
6. The micro-grid integrated protection method based on multi-criterion self-adaptive recognition according to claim 4, wherein in the step S4, when a grid-connected mode is determined that a fault state occurs on a grid side, if I f collected in real time by a sensing layer is not less than 1.5 times of rated current, a decision layer immediately triggers a pre-judging mechanism, and the minimum power P min required by island operation is calculated; If P min is less than or equal to 0, the distributed power supply can meet the load demand and directly execute switching, if P min is more than 0, firstly issuing a load cutting instruction, and preferentially cutting non-important loads including street lamps and commercial loads until P min is less than or equal to 0; the executive layer executes switching, namely, a grid-connected point breaker is disconnected, the switching-off time is less than or equal to 20ms, meanwhile, a distributed power supply controller is switched from a PQ mode to a V/f mode, and the grid-connected mode is switched to an island mode; the decision layer monitors the energy storage overload fault in the island mode in real time, and if the energy storage overload fault with dSOC/dt < -5%/min is detected, the standby energy storage unit is started immediately; and within 300ms after the switching is finished, the executive layer adjusts the distributed power supply output to restore the frequency to 50+/-0.02 Hz and the voltage to be +/-1% of the rated value.
7. The micro-grid integrated protection method based on multi-criterion self-adaptive recognition according to claim 4, wherein in the S4, in the island mode, a sensing layer collects voltage and frequency data of a grid side, a decision layer judges whether the grid meets a synchronous condition or not, if not, the micro-grid frequency is adjusted through energy storage charge and discharge, voltage deviation is compensated through a static reactive generator, and if so, a switching instruction is triggered; the execution layer adopts a soft grid-connected strategy to control the closing angle of a grid-connected point breaker, the closing time is 50ms, the impact current is less than or equal to 1.2 times of rated current, the distributed power supply controller is switched from a V/f mode to a PQ mode, and the distributed power supply controller operates according to a preset power instruction to switch the island mode to the grid-connected mode; the protection mechanism is that in 1s after switching, if detecting that the grid-connected side delta U is more than or equal to 30%, the grid-connected point circuit breaker is immediately disconnected, and the island mode is returned.
8. The micro-grid integrated protection method based on multi-criterion self-adaptive recognition according to claim 1 is characterized in that in the step S5, fault isolation is that a decision layer positions a fault position based on fault characteristic parameters, an execution layer separates a fault area through a breaker, isolation time is less than or equal to 150ms, reclosing is attempted within 3S after fault isolation if transient faults are detected, normal operation is restored after reclosing is successful, and if permanent faults are detected, the decision layer adjusts an operation strategy, including reducing output of a distributed power supply, cutting off load of the fault area and ensuring normal power supply of a non-fault area.
9. Micro-grid integrated protection device based on multi-criterion self-adaptive recognition is characterized by comprising: One or more processors; a memory for storing one or more computer programs; wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to perform the method of any of claims 1-8.
10. A computer readable storage medium having stored thereon executable instructions, which when executed by a processor cause the processor to perform the method of any of claims 1-8.

Description

Micro-grid integrated protection method based on multi-criterion self-adaptive identification Technical Field The invention belongs to the technical field of micro-grid protection, and particularly relates to a micro-grid integrated protection method based on multi-criterion self-adaptive identification. Background The micro-grid is used as a key carrier for distributed energy consumption and flexible operation of the power distribution network, and needs to be frequently switched between a grid-connected mode and an island mode (such as switching to island operation when the power grid fails and switching back to grid-connected operation after the power grid recovers). However, there are substantial differences in the fault signature in the two modes of operation: the grid-connected mode is that the fault current is supported by a large power grid, the amplitude is large, the attenuation is slow, the fault type is mainly three-phase short circuit and two-phase short circuit, and the harmonic interference at the power grid side exists; Island mode, wherein fault current is only provided by a distributed power supply (such as photovoltaic, energy storage and micro-combustion engine), the amplitude is small, the attenuation is rapid, the fault type is mostly single-phase grounding, transient faults caused by load abrupt change are caused, and the voltage drop amplitude is larger. At present, the prior art is difficult to adapt to the fault characteristic difference, and has obvious defects that firstly, a single fault detection algorithm (such as overcurrent protection and voltage mutation detection) is adopted, the fault characteristics of two modes cannot be considered, misoperation or refusal of a protection device is easily caused, the power supply stability is affected, secondly, a fault pre-judging mechanism is lacking in a mode switching process, if sudden faults are encountered after a switching instruction is issued, voltage sag and frequency fluctuation are extremely easily caused, distributed power supply equipment can be damaged in serious cases, thirdly, a fault isolation and recovery strategy is not designed in a cooperative manner with the mode switching, so that the fault treatment time is long, the power supply reliability of a micro-grid is reduced, and the actual operation requirements cannot be met. Disclosure of Invention According to the defects in the prior art, the invention aims to provide the micro-grid integrated protection method based on multi-criterion self-adaptive identification, and the accurate identification and stable control of faults in the grid connection/island mode switching process can be realized through multi-dimensional fault feature fusion detection and layered cooperative control strategies. In order to achieve the above purpose, the invention provides a micro-grid integrated protection method based on multi-criterion self-adaptive identification, which comprises the following steps: s1, constructing a three-layer control architecture of a sensing layer, a decision layer and an execution layer in a micro-grid, wherein the sensing layer acquires electric quantity data of the micro-grid in real time, wherein the electric quantity data comprises voltage, current, frequency and harmonic content, the decision layer carries out mode identification and fault judgment based on the electric quantity data, and the execution layer carries out mode switching and fault processing operation; S2, acquiring electric quantity data of the micro-grid in real time by utilizing a sensing layer, and identifying a current running mode of the micro-grid in real time based on power flow direction and frequency deviation of a grid connection point in a decision layer, wherein the running mode comprises a grid connection mode and an island mode; S3, extracting fault characteristic parameters at a decision layer, matching weight coefficients for each fault characteristic parameter, and adopting a multidimensional characteristic fusion algorithm to fuse the fault characteristic parameters in a grid-connected mode or an island mode to judge a fault state; S4, the decision layer recognizes the current running mode of the micro-grid and generates a command to be issued to an execution layer, when the execution layer executes grid connection-island switching, the execution layer pre-judges the island running power requirement, and executes the switching-off of a breaker and the mode switching of a distributed power supply controller after cutting off non-important loads; s5, when the fault is judged to occur, the fault position is positioned and isolated, the reclosing recovery is tried by the transient fault, and the power supply of the non-fault area is ensured by the permanent fault adjustment operation strategy. In the S1, the sensing layer specifically includes that 1 distributed detection unit is deployed at the outlet of each distributed power supply and at grid connection points where th