CN112564163B - Micro-grid island detection method and system based on small signal synchronous injection - Google Patents
Micro-grid island detection method and system based on small signal synchronous injection Download PDFInfo
- Publication number
- CN112564163B CN112564163B CN202011340365.0A CN202011340365A CN112564163B CN 112564163 B CN112564163 B CN 112564163B CN 202011340365 A CN202011340365 A CN 202011340365A CN 112564163 B CN112564163 B CN 112564163B
- Authority
- CN
- China
- Prior art keywords
- small signal
- current
- impedance
- small
- grid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- 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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
-
- 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
-
- 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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P80/00—Climate change mitigation technologies for sector-wide applications
- Y02P80/10—Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier
- Y02P80/14—District level solutions, i.e. local energy networks
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Mathematical Physics (AREA)
- Theoretical Computer Science (AREA)
- Supply And Distribution Of Alternating Current (AREA)
- Inverter Devices (AREA)
Abstract
The invention discloses a micro-grid island detection method and system based on small signal synchronous injection. The time required for each inverter to detect the island is about 100ms, and no detection blind area exists. The method can automatically limit the output small signal current amplitude in the grid-connected mode, and further reduce the influence on the electric energy quality while keeping synchronization. The method can be used for a droop control inverter with wide application or other types of voltage source type inverters with reserved voltage control loops, and provides good reference value for engineering application.
Description
Technical Field
The invention belongs to the power grid detection technology, and particularly relates to a micro-grid island detection method and system based on small signal synchronous injection.
Background
With the increasing environmental and energy crisis, distributed power generation systems integrating new energy power generation have gained more attention and application. In a distributed power generation system, if an unplanned island occurs, all inverters are required to detect the island within 2 seconds according to the IEEE 1547 standard and power supply to the power grid is stopped. While micro-grids are becoming a powerful strategy for integrating distributed power sources, they are becoming a growing concern, and the basic requirement is to operate in both grid-tie and island modes. When planned islanding occurs in the micro-grid, a switch for connecting the islanding with the power grid needs to be disconnected so as to avoid impact on the power grid caused by grid connection without presynchronization, and mode switching is also needed by the islanding detection information. Thus, island detection is very important in both cases.
To reduce the cost, there is a trend to adopt an island detection method independent of communication, which can be classified into an active detection method and a passive detection method according to whether disturbance is injected. The active detection method is used for detecting corresponding variable changes to judge whether island occurs or not by injecting certain disturbance, the detection dead zone of the method is small or none, but the method has a certain influence on the electric energy quality of the system, and the disturbance injection coordination problem exists in the multi-inverter system; the passive detection method does not inject disturbance into the system, has no interference to the power grid, but generally has a larger detection blind area. In the active detection method, the method for detecting the impedance seen by the output end of the inverter through the small signal can detect the island when the fundamental wave power is completely matched, can not cause voltage or frequency out of limits after the island occurs, can be used for detecting the mode of converting the island mode into the grid-connected mode, and has wide application prospect.
In the active detection method based on impedance detection, if a system contains a plurality of inverters, the problem of disturbance injection synchronization exists, and if the problem is not reasonably solved, the detection method may fail due to the existence of large harmonic circulation. In the existing solution to the problem, manual offline synchronization exists, but the method cannot realize automatic synchronization, and is time-consuming and labor-consuming; there are documents that propose dynamic master-slave control, the master inverter is injected, the slave inverter is not injected, and a new master inverter is automatically selected when the master inverter fails, the method ensures that the slave inverter does not influence the detection effect of the master inverter, but in the grid-connected mode, if the master inverter fails, the slave inverter is difficult to switch modes without communication, and the slave inverter relies on other mechanisms to learn island occurrence; it is proposed that the phase is given by an integer multiple of the fundamental phase when injecting integer harmonics, however the synchronisation effect is affected by the fundamental phase, i.e. by the fundamental power distribution.
When the harmonic is injected, the problem of influencing the power quality also exists. If voltage injection is always adopted, harmonic voltage is limited in an island mode, but in a grid-connected mode, harmonic current is large due to small impedance of an output end of the inverter; if current injection is always adopted, harmonic current is limited in a grid-connected mode, but in an island mode, harmonic voltage is very large due to high impedance of an output end of an inverter, so that after island occurs, the electric energy quality does not meet the requirement any more, and the method is not suitable for the situation of island in a plan. Therefore, current injection is suitable for grid-connected mode, and voltage injection is suitable for island mode. Although the literature mentions that the injection mode is switched according to different impedance when grid connection is performed, the synchronization method adopts integral harmonic injection as described above, and particularly, good injection signal synchronization cannot be realized in the voltage injection mode.
Disclosure of Invention
The invention aims to solve the problems of the impedance measurement active island detection method in the aspects of injection signal synchronization and electric energy quality, and provides a micro-grid island detection method and system based on small signal synchronization injection, which have the function of automatic current limiting in a grid-connected mode.
In order to achieve the above purpose, a micro-grid island detection method based on small signal synchronous injection comprises the following steps:
s1, converting output current of a multi-inverter system through coordinate transformationChanging to a static coordinate system, and preliminarily extracting small signal current i osαβx Then to small signal current i osαβx Filtering to obtain the final small signal current i osαβ ；
S2, according to the small signal current i osαβ Establishing the droop relation of the active power and the frequency of the small signal to obtain the frequency omega of the small signal s Realizing the synchronization of the small signal frequency and the complete equipartition of the small signal active power by introducing the virtual impedance Z at the small signal frequency point vs Dividing the reactive power of the small signal equally;
s3, comparing the small signal current amplitude I calculated by the variables in the static coordinate system s Maximum current amplitude I of given small signal smax And adjust the small signal voltage amplitude reference value V s * ；
S4, small signal voltage amplitude reference value V s * By and with small signal frequency omega s The phase combination of the small signals obtained by integration forms an equivalent small signal voltage command value v sαβ0 * Consider a virtual impedance drop v sαβz * Then the small signal voltage command v is obtained sαβ * By small-signal voltage command v sαβ * Extracted small signal current i osαβ Calculating the small signal impedance amplitude |Z seen by the output end of the inverter os I and phase angle
According to the small signal impedance amplitude |Z os I and phase angle ++>
It is determined whether islanding has occurred.
S1, primarily extracting small signal current i osαβx The output current is passed through multiple second-order generalized integrator, and the small signal current i osαβx And second order bandpass filtering is used for the filtering.
In S2, when Z vs When the impedance of the line is matched with the impedance of the line, the small signal reactive power can be completely equally divided, the complete injection synchronization is realized, and when Z vs And lineWhen the path impedances are not completely matched, approximate injection synchronization can be realized, and the small signal current flowing to the common junction point is completely or approximately evenly distributed on each inverter circuit, and the small signal impedance amplitude |Z measured by each inverter os I and phase angle phi z The micro-grid changes obviously when the grid-connected mode is changed into the island mode.
S3, in the island mode, the small signal voltage amplitude is limited to the rated value V smax * In the grid-connected mode, the small signal voltage amplitude is lower than the rated value, and the small signal current is limited at I smax At this time, the synchronization condition is still established.
S4, setting an impedance threshold Z according to the line impedance and the load range t Setting a time threshold T t When the impedance amplitude value is Z os I is in succession T t Greater than the impedance threshold Z for a period of time t And when the island is judged to occur.
A micro-grid island detection system based on small signal synchronous injection comprises a signal extraction module, a small signal sagging module, a small signal virtual impedance module, a small signal current limiting module and a mode judging module;
the signal extraction module is used for extracting fundamental wave, small signal and harmonic current of the output current of each inverter;
the small signal sagging module is used for equally dividing the small signal active power injected by each inverter, so that each inverter preliminarily realizes the synchronization of small signal current injection;
the small signal virtual impedance module is used for improving the equipartition of the small signal reactive power and further realizing the synchronization of the small signal injection;
the small signal current limiting module is used for limiting the small signal current amplitude by reducing the signal voltage amplitude when in a grid-connected mode, so that the influence on the electric energy quality is reduced;
the mode judging module is used for calculating small signal impedance according to the signal output by the signal extracting module and the signal output by the small signal current limiting module and judging whether island occurs or not.
The signal extraction module converts the output current of each inverter into a static coordinate system through coordinate transformation, and initially extractsSmall signal current i osαβx Then to small signal current i osαβx Filtering to obtain the final small signal current i osαβ 。
The small signal sagging module is used for controlling the current i according to the small signal osαβ Establishing the sagging relation between the small signal active power and the frequency, realizing the synchronization of the small signal frequency and the complete equipartition of the small signal active power, and introducing the virtual impedance Z at the small signal frequency point vs And equally dividing the reactive power of the small signals.
The small signal current limiting module is used for comparing small signal current amplitude I calculated by variables in a static coordinate system s Maximum current amplitude I of given small signal smax And adjust the small signal voltage amplitude reference value V s * Make I s Not exceeding I smax 。
The mode determination module calculates the equivalent small signal voltage command v before the virtual impedance voltage drop sαβ0 * Extracted small signal current i osαβ Calculating the small signal impedance amplitude |Z seen by the output end of the inverter os I and phase angle
According to the small signal impedance amplitude |Z os I and phase angle ++>
It is determined whether islanding has occurred.
Compared with the prior art, the invention superimposes the small signal voltage command on the fundamental wave voltage command value generated by the original sagging control under the static coordinate system, measures the impedance seen by the output end in a mode of synchronously injecting the small signal, and judges whether the island occurs or not according to the impedance. The time required for each inverter to detect the island is about 100ms, and no detection blind area exists. The method can automatically limit the output small signal current amplitude in the grid-connected mode, and further reduce the influence on the electric energy quality while keeping synchronization. The method can be used for a droop control inverter with wide application or other types of voltage source type inverters with reserved voltage control loops, and provides good reference value for engineering application.
The system of the invention is provided with the signal extraction module, the small signal sagging module, the small signal virtual impedance module, the small signal current limiting module and the mode judging module on the original voltage outer ring to realize that each inverter synchronously injects small signals independent of fundamental wave variables to carry out island detection, and limit the small signal current amplitude when grid connection is carried out. The injection synchronization of the small signals is completed by a small signal control module independent of fundamental wave control, and the system does not depend on manual operation under the line, communication and fundamental wave power distribution. The control structures of the inverters are identical, the positions of the inverters are equal, and the reliability is high.
Drawings
FIG. 1 is a block diagram of a parallel inverter system of interest in the present invention;
FIG. 2 is a control block diagram for a grid-tie inverter of the present invention;
fig. 3 is a simulated waveform diagram, wherein (a) is a grid-connected line current waveform, (b) is an impedance amplitude measurement value of each inverter, (c) is a small signal voltage amplitude reference value, (d) is a small signal current amplitude value, and (e) is an impedance angle measurement value of each inverter.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The invention ensures that the status of each inverter injected with the small signal is equal, the synchronization of the small signal injection does not need manual adjustment, is not influenced by fundamental wave variables, and reduces the influence on the quality of electric energy by limiting the current, voltage and current amplitude of the maximum small signal. The structure of the multi-inverter system is shown in fig. 1, and S is generated after island occurs u Is disconnected under the control of the protected device, and S i Is dependent on the island detection result. As shown in the upper part of fig. 2, the small signal control module generates a fundamental wave voltage command value v under the original droop control in a static coordinate system fαβ * Superimposed small signal voltage command v sαβ * And judging whether island occurs or not according to the small signal impedance. The inner loop control adopts a voltage inner loop and a current inner loop, the current inner loop adopts a proportional controller, the voltage inner loop adopts a proportional-resonance controller, and the resonance controller comprisesIncludes parallel connection of resonant links corresponding to the fundamental wave and the small signal.
The purpose of the signal extraction module is to extract the fundamental, small signals and possibly harmonic currents. After the output current is transformed into a static coordinate system through coordinate transformation, a small signal current i which is primarily extracted is obtained through a multiple second-order generalized integrator osαβx The signal is further passed through an additional second-order band-pass filter to obtain a final purer small signal current i osαβ 。
The mechanism for realizing the synchronous injection of the small signals by the method is that the small signal current with the same amplitude and the same phase is injected into each inverter by equally dividing the active power and the reactive power of the small signals injected into each inverter. The synchronization of the small signal frequency and the equipartition of the small signal active power are realized through the sagging relation of the small signal active power and the frequency, and the small signal reactive power is equipartited or approximately equipartited through the small signal virtual impedance. First, the small signal frequency synchronization and the complete equipartition of the small signal active power are realized by establishing the sagging relation of the small signal active power and the frequency, wherein omega is shown as (1) s For small signal reference frequency omega s0 For small signal nominal frequency, k s Is a small signal frequency droop coefficient. Because the even harmonic content in the three-phase system is very small, the small signal rated frequency omega s0 The even harmonic frequency is chosen, in this case 200Hz. Although omega s0 Coinciding with the fourth harmonic frequency, the actual frequency omega of the small signal s Independent of the fundamental frequency.
ω s ＝ω s0 -k s P s (1)
Wherein P is s For small signal active power, the voltage reference value v of the small signal before adding the virtual impedance sαβ0 Current sampling value i osαβ Calculated, the specific expression is
Then, by introducing a virtual impedance Z at the small signal frequency point vs And realizing or improving the equipartition of the small-signal reactive power. When Z is vs When the impedance is matched with the line impedance, the reactive power of the small signal can be completely equally divided, and even if the line impedance value is not clear, a larger Z is set vs The reactive power equipartition of the small signal can be improved, the synchronous injection of the small signal current can be approximately realized, and the effectiveness of the invention is not affected. When the synchronization of the small signal injection is realized, the impedance measurement theoretical value Z of the inverter i can be deduced because the small signal current flowing to the common junction Point (PCC) is evenly distributed on each inverter circuit osi As shown in (3), n is the number of parallel inverters, Z lsi For the line impedance of inverter i, Z PCCsi For equivalent PCC impedance Z to inverter i gs For net side impedance, Z loads Is the PCC load impedance. Due to Z gs Is much smaller than Z loads Z when the grid-connected mode is changed into the island mode osi The amplitude of (c) increases significantly.
The current limiting module aims to limit the amplitude of the small signal current by reducing the amplitude of the signal voltage in the grid-connected mode, so that the influence on the quality of electric energy is reduced. The module compares the small signal current amplitude I calculated from the variables in the stationary coordinate system s Maximum current amplitude I of given small signal smax And adjusting the small signal voltage reference value V by a proportional-integral controller with amplitude limitation s * . In island mode, the proportional-integral controller is saturated at an upper limit value V smax * The small signal voltage amplitude is limited to the nominal value V smax * In the grid-connected mode, the proportional-integral controller works normally, the amplitude of the small signal voltage is lower than the rated value, and the small signal current is limited in I smax At this time, the synchronization condition is still established, and similar to the island mode, when the small signal virtual impedance is matched with the line impedance, the inverters realize complete synchronous injection, and when the small signal virtual impedance is matched with the line impedance, approximate synchronous injection can be achieved.
The mode judging module is used for judging whether island happens or not and outputting Flag bit Flag during grid connection isl 0 and 1 after island occurrence. The module takes into account the small signal voltage command v before the virtual impedance drop sαβ0 * Extracted small signal current i osαβ Calculating the small signal impedance amplitude |Z seen by the output end of the inverter os I and phase angle
As shown in (4). Since the impedance includes a virtual impedance, the calculated impedance of each inverter is equal in steady state when the virtual impedance matches the line. In this example, the small signal impedance magnitude is used as a criterion, but the impedance angle can also be used as a criterion in some cases. According to the line impedance and the load range, estimating the range of impedance values in grid-connected and island modes by the method (3), and setting an impedance threshold Z t Setting a time threshold T to be greater than (3) the maximum value in the normal grid-connected mode and less than the minimum value in the normal island mode t When the impedance amplitude value is Z os I is in succession T t Internal is greater than Z t When the island is judged to occur, the Flag bit Flag is set isl 1.
The effectiveness of the invention is demonstrated by simulation. The configuration of the parallel inverter system is shown in fig. 1, and includes three inverters, i.e., n=3. The line impedances were 3mH+0.8ohm,3.1mH+0.8ohm, and 3.2mH+0.8ohm, respectively. PCC loading included a star-coupled 10Ohm resistive load and a 0.1H inductive load. According to the control block diagram of fig. 2, the fundamental control of each inverter adopts droop control, and small signals are injected according to the proposed method. The amplitude of the fundamental wave phase voltage is 200V, and the rated value V of the small signal voltage smax * Is set to 1% of the fundamental wave, namely 2V, the maximum value of the small signal current I smax Set to 0.1A. Small signal virtual impedance Z of each inverter vs Is set to 0.1mH,0mH and-0.1 mH, so that the equivalent impedance of each circuit is completely matched and is 3.1mH. Sag coefficient k s Selected to be 5. The specific island detection steps are as follows:
1) Before the time t=2s, the grid is normal, the parallel inverter system works in a grid-connected mode, and the grid-connected current is not 0, as shown in fig. 3 (a). Each inverter calculates the impedance from the sampled small signal current, and its amplitude stabilizes around a small value of 4.3Ohm, as shown in fig. 3 (b), and in steady state, the impedance measurements of the three inverters are completely equal due to the small signal injection synchronization. Under the action of proportional-integrator in current-limiting module, the small signal voltage of each inverter is lower than rated value V smax * As shown in FIG. 3 (c), the small signal current amplitude is limited to I smax As shown in fig. 3 (d).
2) Island occurrence at time t=2s, and fig. 3 (a) shows that the grid-connected current drops to 0. From fig. 3 (b), after a short dynamic process, the impedance magnitude measurement of each inverter increases significantly. Setting an impedance threshold Z t For 20Ohm, a time threshold T is set t For 50ms, each inverter impedance magnitude measurement reaches Z at about 44ms after islanding occurs t Each inverter can detect the occurrence of islanding within a time of around 100 ms. After island entry, each inverter impedance magnitude measurement stabilized around 30Ohm, consistent with the theoretical calculation of (3), where n=3, z loads And approximately 10Ohm. The small signal current amplitude tends to decrease after island, and under the action of the proportional-integral controller of the current limiting module, the small signal voltage amplitude of each inverter rises and is finally limited at V smax * As shown in FIG. 3 (c), the current amplitude is always less than I smax As shown in fig. 3 (d). Fig. 3 (e) shows that the small signal impedance angle measurement value is about 66 ° before island, and after the island is subjected to transient dynamics, the small signal impedance angle measurement value is reduced to about 12 ° and can also be used as island criterion.
Claims (9)
1. A micro-grid island detection method based on small signal synchronous injection is characterized by comprising the following steps:
s1, converting output current of a multi-inverter system into small signal current i which is preliminarily extracted under a static coordinate system through coordinate transformation osαβx Then to small signal electricityStream i osαβx Filtering to obtain the final small signal current i osαβ ；
S2, according to the small signal current i osαβ Establishing the droop relation of the active power and the frequency of the small signal to obtain the frequency omega of the small signal s Realizing the synchronization of the small signal frequency and the complete equipartition of the small signal active power by introducing the virtual impedance Z at the small signal frequency point vs Dividing the reactive power of the small signal equally;
s3, comparing the small signal current amplitude I calculated by the variables in the static coordinate system s Maximum current amplitude I of given small signal smax And adjust the small signal voltage amplitude reference value V s * ；
S4, small signal voltage amplitude reference value V s * By and with small signal frequency omega s The phase combination of the small signals obtained by integration forms an equivalent small signal voltage command value v sαβ0 * Consider a virtual impedance drop v sαβz * Then the small signal voltage command v is obtained sαβ * By calculating the equivalent small signal voltage command v before virtual impedance voltage drop sαβ0 * Extracted small signal current i osαβ Calculating the small signal impedance amplitude |Z seen by the output end of the inverter os I and phase angle phi z According to the small signal impedance magnitude |Z os I and phase angle phi z It is determined whether islanding has occurred.
2. The micro-grid island detection method based on small signal synchronous injection according to claim 1, wherein in S1, the preliminary extraction of the small signal current ios alpha beta x is to pass the output current through a multiple second-order generalized integrator, and the filtering of the small signal current ios alpha beta x adopts second-order bandpass filtering.
3. The micro-grid island detection method based on small signal synchronous injection as claimed in claim 1, wherein in S2, when Z vs When the impedance of the line is matched with the impedance of the line, the small signal reactive power can be completely equally divided, the complete injection synchronization is realized, and when Z vs And lineWhen the path impedances are not completely matched, approximate injection synchronization can be realized, and the small signal current flowing to the common junction point is completely or approximately evenly distributed on each inverter circuit, and the small signal impedance amplitude |Z measured by each inverter os I and phase angle phi z The micro-grid changes from grid-connected mode to island mode.
4. The micro-grid island detection method based on small signal synchronous injection as claimed in claim 1, wherein in S3, in island mode, small signal voltage amplitude is limited to rated value V smax * In the grid-connected mode, the small signal voltage amplitude is lower than the rated value, and the small signal current is limited at I smax At this time, the synchronization condition is still established.
5. The micro-grid island detection method based on small signal synchronous injection according to claim 1, wherein in S4, an impedance threshold Z is set according to line impedance and a load range t Setting a time threshold T t When the impedance amplitude value is Z os I is in succession T t Greater than the impedance threshold Z for a period of time t And when the island is judged to occur.
6. The micro-grid island detection system based on small signal synchronous injection is characterized by comprising a signal extraction module, a small signal sagging module, a small signal virtual impedance module, a small signal current limiting module and a mode judging module;
the signal extraction module is used for extracting fundamental wave, small signal and harmonic current of the output current of each inverter;
the small signal sagging module is used for equally dividing the small signal active power injected by each inverter, so that each inverter preliminarily realizes the synchronization of small signal current injection;
the small signal virtual impedance module is used for improving the equipartition of the small signal reactive power and further realizing the synchronization of the small signal injection;
the small signal current limiting module is used for limiting the small signal current amplitude by reducing the signal voltage amplitude when in a grid-connected mode, so that the influence on the electric energy quality is reduced;
the mode determination module is used for calculating an equivalent small signal voltage command v before virtual impedance voltage drop sαβ0 * Extracted small signal current i osαβ Calculating the small signal impedance amplitude |Z seen by the output end of the inverter os I and phase angle phi z According to the small signal impedance magnitude |Z os And I and a phase angle phi determine whether island occurs.
7. The micro-grid island detection system based on small signal synchronous injection as set forth in claim 6, wherein the signal extraction module converts the output current of each inverter into a stationary coordinate system through coordinate transformation, and initially extracts the small signal current i osαβx Then to small signal current i osαβx Filtering to obtain the final small signal current i osαβ 。
8. The micro-grid island detection system based on synchronous injection of small signals according to claim 6, wherein the small signal sagging module is used for detecting the island according to the small signal current i osαβ Establishing the sagging relation between the small signal active power and the frequency, realizing the synchronization of the small signal frequency and the complete equipartition of the small signal active power, and introducing the virtual impedance Z at the small signal frequency point vs And equally dividing the reactive power of the small signals.
9. The micro-grid island detection system based on synchronous injection of small signals according to claim 6, wherein the small signal current limiting module is used for comparing small signal current amplitude I calculated by variables in a stationary coordinate system s Maximum current amplitude I of given small signal smax And adjust the small signal voltage amplitude reference value V s * Make I s Not exceeding I smax 。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011340365.0A CN112564163B (en) | 2020-11-25 | 2020-11-25 | Micro-grid island detection method and system based on small signal synchronous injection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011340365.0A CN112564163B (en) | 2020-11-25 | 2020-11-25 | Micro-grid island detection method and system based on small signal synchronous injection |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112564163A CN112564163A (en) | 2021-03-26 |
| CN112564163B true CN112564163B (en) | 2023-06-20 |
Family
ID=75043722
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202011340365.0A Active CN112564163B (en) | 2020-11-25 | 2020-11-25 | Micro-grid island detection method and system based on small signal synchronous injection |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN112564163B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113364038B (en) * | 2021-06-25 | 2022-06-03 | 山东理工大学 | Inverter frequency control-based multi-distributed power supply island detection method |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103983873A (en) * | 2014-05-19 | 2014-08-13 | 国网宁夏电力公司 | Island detection method suitable for multi-inverter parallel operation and based on impedance measurement |
| CN104578168A (en) * | 2015-02-04 | 2015-04-29 | 国家电网公司 | Smooth switching control method for operating mode of micro-grid inverter of different capacity micro sources |
| CN107069818A (en) * | 2017-04-26 | 2017-08-18 | 西安交通大学 | A kind of seamless switching control system and method based on hybrid control strategy |
| CN108594046A (en) * | 2018-06-04 | 2018-09-28 | 西安科技大学 | Island detection method based on comprehensive impedance fundametal compoment |
| CN109490638A (en) * | 2018-11-27 | 2019-03-19 | 华北电力大学 | The impedance measurement formula isolated island detection method of the grid-connected direct current power system of more photo-voltaic power supplies |
| CN109936169A (en) * | 2017-12-15 | 2019-06-25 | 台达电子企业管理（上海）有限公司 | Uneven and harmonic power distribution control method and device between shunt chopper |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10935588B2 (en) * | 2017-05-31 | 2021-03-02 | Schneider Electric Solar Inverters Usa, Inc. | Systems and methods for islanding detection |
-
2020
- 2020-11-25 CN CN202011340365.0A patent/CN112564163B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103983873A (en) * | 2014-05-19 | 2014-08-13 | 国网宁夏电力公司 | Island detection method suitable for multi-inverter parallel operation and based on impedance measurement |
| CN104578168A (en) * | 2015-02-04 | 2015-04-29 | 国家电网公司 | Smooth switching control method for operating mode of micro-grid inverter of different capacity micro sources |
| CN107069818A (en) * | 2017-04-26 | 2017-08-18 | 西安交通大学 | A kind of seamless switching control system and method based on hybrid control strategy |
| CN109936169A (en) * | 2017-12-15 | 2019-06-25 | 台达电子企业管理（上海）有限公司 | Uneven and harmonic power distribution control method and device between shunt chopper |
| CN108594046A (en) * | 2018-06-04 | 2018-09-28 | 西安科技大学 | Island detection method based on comprehensive impedance fundametal compoment |
| CN109490638A (en) * | 2018-11-27 | 2019-03-19 | 华北电力大学 | The impedance measurement formula isolated island detection method of the grid-connected direct current power system of more photo-voltaic power supplies |
Non-Patent Citations (4)
| Title |
|---|
| A Small-AC-Signal Injection-Based Decentralized Secondary Frequency Control for Droop-Controlled Islanded Microgrids;Zeng Liu;《 IEEE Transactions on Power Electronics》;20200330;全文 * |
| Active Islanding Detection for Multiple Parallel-Connected Inverter-Based Distributed Generators Using High-Frequency Signal Injection;David Reigosa;《IEEE Transactions on Power》;20130517;全文 * |
| 基于本地检测法的微电网孤岛检测方法研究;刘忠强等;《发电技术》;20190430(第02期);全文 * |
| 基于电网阻抗测量的新型主动式孤岛检测法;唐婷等;《电源学报》;20121115(第06期);全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN112564163A (en) | 2021-03-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Shafiee et al. | Distributed secondary control for islanded microgrids—A novel approach | |
| US9331486B2 (en) | Method and apparatus for detecting islanding conditions of a distributed grid | |
| Gurule et al. | Grid-forming inverter experimental testing of fault current contributions | |
| Kou et al. | Fault ride through strategy of inverter-interfaced microgrids embedded in distributed network considering fault current management | |
| CN108847676B (en) | Low voltage ride through control method based on Boost circuit | |
| CN112564163B (en) | Micro-grid island detection method and system based on small signal synchronous injection | |
| Hariprasad et al. | Island detection in inverter based distributed generation using a hybrid method | |
| CN116250156A (en) | Fault control device and method for power distribution system | |
| Bahrani et al. | Grid-Forming Inverter-Based Resource Research Landscape: Understanding the Key Assets for Renewable-Rich Power Systems | |
| CN112260315A (en) | Seamless switching control system and strategy based on improved droop control | |
| CN116526482A (en) | Grid-connected self-adaptive coordination control method and device for multi-low-voltage flexible interconnection device | |
| Zhou et al. | Energy-based directional pilot protection for distribution networks with IBDGs considering unmeasured load switching | |
| Altaf et al. | Effective ROCOF based islanding detection technique for different types of microgrid | |
| CN108594046B (en) | Island detection method based on comprehensive impedance fundamental component | |
| CN111257670B (en) | Method for determining island detection positive feedback gain range | |
| CN108445424B (en) | Hybrid inverter type distributed power supply island detection method | |
| Guo et al. | Research on marine VSG grid-connected pre-synchronization control strategy | |
| Pazos et al. | Failure analysis of inverter based anti-islanding systems in photovoltaic islanding events | |
| Sreeja et al. | Islanding detection and Transfer of Distributed Generation system from Grid connected to Standalone mode | |
| Maulik et al. | Dynamic phasor based anti-islanding detection with zero non detection zone | |
| Menniti et al. | Islanding detection active methods: implementation of simulation models using ATP-EMTP | |
| Li et al. | Grid code formulation recommendations on inverter-based generation during asymmetrical grid faults | |
| Gulipalli et al. | Frequency-locked loop based new automatic phase-shift method for active islanding detection of three-phase microGrid | |
| Manohar et al. | Performance of grid connected dg inverter system by using intelligent controllers | |
| Soni et al. | Impact of Control Parameters on Short-Circuit Capacity of Inverter Based Sources |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| CB03 | Change of inventor or designer information |
Inventor after: Liu Zeng Inventor after: Zheng Haoyang Inventor after: Su Xianjin Inventor after: Liu Jinjun Inventor after: Lin Zhenhuang Inventor after: An Ronghui Inventor before: Liu Zeng Inventor before: Zheng Haoyang Inventor before: Liu Jinjun Inventor before: An Ronghui |
|
| CB03 | Change of inventor or designer information | ||
| TA01 | Transfer of patent application right |
Effective date of registration: 20220316 Address after: Beilin District Xianning West Road 710049, Shaanxi city of Xi'an province No. 28 Applicant after: XI'AN JIAOTONG University Applicant after: ZHANGZHOU KEHUA TECHNOLOGY Co.,Ltd. Address before: 710049 No. 28 West Xianning Road, Shaanxi, Xi'an Applicant before: XI'AN JIAOTONG University |
|
| TA01 | Transfer of patent application right | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |