Islanding detection method and apparatus, and computer-readable storage medium
View Patent ↗An islanding detection method and apparatus, and a computer-readable storage medium. The detection method includes: determining a harmonic amplitude growth rate and a frequency growth rate of alternating current electricity output by an alternating current port of a grid-tied inverter; determining an islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, where the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship; determining an islanding injection amount based on the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate; controlling, based on the islanding injection amount, the grid-tied inverter to output a reactive power or a reactive current over the alternating current port; and performing islanding detection based on a frequency of the alternating current electricity output by the alternating current port. With this detection method, whether islanding occurs can be accurately detected. When islanding does not occur, disturbance to a power grid is reduced, and grid connection stability is improved. When islanding occurs, it can be quickly detected, and a detection time is relatively short.
1. An islanding detection method comprising:
determining a harmonic amplitude growth rate and a frequency growth rate of alternating current electricity output by an alternating current port of a grid-tied inverter;
determining an islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, wherein the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship;
determining an islanding injection amount based on the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, wherein the islanding injection amount is one of a reactive power size or a reactive current size for performing reactive power disturbance;
controlling, based on the islanding injection amount, the grid-tied inverter to output a reactive power or a reactive current over the alternating current port; and
performing islanding detection based on a frequency of the alternating current electricity output by the alternating current port.
2. The method according to claim 1 , wherein the harmonic amplitude growth rate is a harmonic voltage amplitude growth rate, and the determining a harmonic amplitude growth rate of alternating current electricity output by an alternating current port of a grid-tied inverter comprises:
determining, based on a voltage of the alternating current electricity output by the alternating current port, a harmonic voltage amplitude of the alternating current electricity output by the alternating current port; and
determining, based on the harmonic voltage amplitude, the harmonic voltage amplitude growth rate of the alternating current electricity output by the alternating current port.
3. The method according to claim 1 , wherein the harmonic amplitude growth rate is a harmonic impedance amplitude growth rate, and the determining a harmonic amplitude growth rate of alternating current electricity output by an alternating current port of a grid-tied inverter comprises:
determining, based on a voltage of the alternating current electricity output by the alternating current port, a harmonic voltage amplitude of the alternating current electricity output by the alternating current port;
determining, based on a current of the alternating current electricity output by the alternating current port, a harmonic current amplitude of the alternating current electricity output by the alternating current port;
dividing the harmonic voltage amplitude by the harmonic current amplitude to obtain a harmonic impedance amplitude of the alternating current electricity output by the alternating current port; and
determining, based on the harmonic impedance amplitude, the harmonic impedance amplitude growth rate of the alternating current electricity output by the alternating current port.
4. The method of claim 1 , wherein the determining an islanding disturbance coefficient corresponding to the harmonic amplitude growth rate comprises:
when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a strictly monotonically increasing relationship, obtaining the corresponding islanding disturbance coefficient from a stored correspondence between a harmonic amplitude growth rate and an islanding disturbance coefficient based on the harmonic amplitude growth rate; or
when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a non-strictly monotonically increasing relationship, obtaining the corresponding islanding disturbance coefficient from a stored correspondence between a harmonic amplitude growth rate range and an islanding disturbance coefficient based on the harmonic amplitude growth rate; or
obtaining the corresponding islanding disturbance coefficient based on the harmonic amplitude growth rate by using a reference function.
5. The method of claim 1 , wherein the islanding injection amount is the reactive power size for performing reactive power disturbance, and the determining an islanding injection amount based on the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate comprises:
determining an active power output by the alternating current port; and
multiplying the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, the frequency growth rate, and the active power output by the alternating current port, to obtain the islanding injection amount.
6. The method of claim 1 , wherein the islanding injection amount is the reactive current size for performing reactive power disturbance, and the determining an islanding injection amount based on the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate comprises:
determining an active current output by the alternating current port; and
multiplying the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, the frequency growth rate, and the active current output by the alternating current port, to obtain the islanding injection amount.
7. The method of claim 1 , wherein the performing islanding detection based on a frequency of the alternating current electricity output by the alternating current port comprises:
when the frequency of the alternating current electricity output by the alternating current port is one of continuously greater than a first reference frequency or continuously less than a second reference frequency within reference duration, determining that islanding occurs.
8. The method of claim 1 , wherein after the performing islanding detection based on a frequency of the alternating current port, the method further comprises:
when it is determined that islanding occurs, stopping outputting the alternating current electricity over the alternating current port.
9. An islanding detection apparatus, comprising:
a processor; and
a non-transitory computer readable memory storing instructions that when executed by the processor, cause the processor to perform steps comprising:
determining a harmonic amplitude growth rate and a frequency growth rate of alternating current electricity output by an alternating current port of a grid-tied inverter;
determining an islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, wherein the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship;
determining an islanding injection amount based on the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, wherein the islanding injection amount is one of a reactive power size or a reactive current size for performing reactive power disturbance;
controlling, based on the islanding injection amount, the grid-tied inverter to output a reactive power or a reactive current over the alternating current port; and
performing islanding detection based on a frequency of the alternating current electricity output by the alternating current port.
10. The apparatus according to claim 9 , wherein the harmonic amplitude growth rate is a harmonic voltage amplitude growth rate, and the determining a harmonic amplitude growth rate of alternating current electricity output by an alternating current port of a grid-tied inverter comprises:
determining, based on a voltage of the alternating current electricity output by the alternating current port, a harmonic voltage amplitude of the alternating current electricity output by the alternating current port; and
determining, based on the harmonic voltage amplitude, the harmonic voltage amplitude growth rate of the alternating current electricity output by the alternating current port.
11. The apparatus according to claim 9 , wherein the harmonic amplitude growth rate is a harmonic impedance amplitude growth rate, and the determining a harmonic amplitude growth rate of alternating current electricity output by an alternating current port of a grid-tied inverter comprises:
determining, based on a voltage of the alternating current electricity output by the alternating current port, a harmonic voltage amplitude of the alternating current electricity output by the alternating current port;
determining, based on a current of the alternating current electricity output by the alternating current port, a harmonic current amplitude of the alternating current electricity output by the alternating current port;
dividing the harmonic voltage amplitude by the harmonic current amplitude to obtain a harmonic impedance amplitude of the alternating current electricity output by the alternating current port; and
determining, based on the harmonic impedance amplitude, the harmonic impedance amplitude growth rate of the alternating current electricity output by the alternating current port.
12. The apparatus according to claim 9 , wherein the determining an islanding disturbance coefficient corresponding to the harmonic amplitude growth rate comprises:
when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a strictly monotonically increasing relationship, obtaining the corresponding islanding disturbance coefficient from a stored correspondence between a harmonic amplitude growth rate and an islanding disturbance coefficient based on the harmonic amplitude growth rate; or
when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a non-strictly monotonically increasing relationship, obtaining the corresponding islanding disturbance coefficient from a stored correspondence between a harmonic amplitude growth rate range and an islanding disturbance coefficient based on the harmonic amplitude growth rate; or
obtaining the corresponding islanding disturbance coefficient based on the harmonic amplitude growth rate by using a reference function.
13. The apparatus according to claim 9 , wherein the islanding injection amount is the reactive power size for performing reactive power disturbance, and the determining an islanding injection amount based on the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate comprises:
determining an active power output by the alternating current port; and
multiplying the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, the frequency growth rate, and the active power output by the alternating current port, to obtain the islanding injection amount.
14. The apparatus according to claim 9 , wherein the islanding injection amount is the reactive current size for performing reactive power disturbance, and the determining an islanding injection amount based on the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate comprises:
determining an active current output by the alternating current port; and
multiplying the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, the frequency growth rate, and the active current output by the alternating current port, to obtain the islanding injection amount.
15. The apparatus according to claim 9 , wherein the performing islanding detection based on a frequency of the alternating current electricity output by the alternating current port comprises:
when the frequency of the alternating current electricity output by the alternating current port is one of continuously greater than a first reference frequency or continuously less than a second reference frequency within reference duration, determining that islanding occurs.
16. The apparatus according to claim 9 , wherein after the performing islanding detection based on a frequency of the alternating current port, the steps further comprise:
when it is determined that islanding occurs, stopping outputting the alternating current electricity over the alternating current port.
17. A non-transitory computer-readable storage medium, wherein the computer-readable storage medium stores instructions comprising:
determining a harmonic amplitude growth rate and a frequency growth rate of alternating current electricity output by an alternating current port of a grid-tied inverter;
determining an islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, wherein the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship;
determining an islanding injection amount based on the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, wherein the islanding injection amount is one of a reactive power size or a reactive current size for performing reactive power disturbance;
controlling, based on the islanding injection amount, the grid-tied inverter to output a reactive power or a reactive current over the alternating current port; and
performing islanding detection based on a frequency of the alternating current electricity output by the alternating current port.