WO2021017547A1 - 孤岛现象检测方法、装置和计算机可读存储介质 - Google Patents

孤岛现象检测方法、装置和计算机可读存储介质 Download PDF

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Publication number
WO2021017547A1
WO2021017547A1 PCT/CN2020/086491 CN2020086491W WO2021017547A1 WO 2021017547 A1 WO2021017547 A1 WO 2021017547A1 CN 2020086491 W CN2020086491 W CN 2020086491W WO 2021017547 A1 WO2021017547 A1 WO 2021017547A1
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Prior art keywords
islanding
port
growth rate
harmonic
amplitude
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PCT/CN2020/086491
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English (en)
French (fr)
Inventor
于心宇
辛凯
李俊杰
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华为技术有限公司
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Priority to EP20847358.7A priority Critical patent/EP3923003B1/en
Publication of WO2021017547A1 publication Critical patent/WO2021017547A1/zh
Priority to US17/479,820 priority patent/US11342757B2/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—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
    • 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
    • H02J3/007—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources
    • 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
    • H02J3/01—Arrangements for reducing harmonics or ripples

Definitions

  • This application relates to the field of electric power technology, and in particular to a method, device and computer-readable storage medium for detecting islanding.
  • the grid-connected inverter is an important part of the new energy power generation system. It converts the direct current generated by the photovoltaic cells and wind turbines in the new energy power generation system into alternating current and feeds it to the grid. New energy power generation systems are prone to islanding during operation. Islanding phenomenon refers to an electrical phenomenon in which the new energy power generation system is separated from the grid when the grid is out of power due to problems such as faults and maintenance, and the grid-connected inverter continues to supply power to the local load.
  • the islanding phenomenon is easy to cause harm to the equipment in the new energy power generation system, and even endanger personal safety. For example, when the power grid returns to normal, the voltage phase of the power grid is deviated from the voltage phase of the new energy power generation system where islanding occurs, which may cause equipment damage due to overvoltage or overcurrent. For another example, when the maintenance personnel fail to know the islanding phenomenon of the new energy power generation system in time, the maintenance personnel may mistakenly think that the new energy power generation system is no longer live, thus causing an electric shock accident. For this reason, islanding needs to be detected quickly so that protective measures can be implemented in time.
  • This application provides an islanding phenomenon detection method, device, and computer-readable storage medium, which can solve the problem of low islanding detection accuracy in related technologies.
  • the technical solution is as follows:
  • an islanding phenomenon detection method includes: determining the harmonic amplitude growth rate and frequency growth rate of the alternating current output from the AC port of the grid-connected inverter; and determining the harmonic amplitude growth rate
  • the islanding disturbance coefficient corresponding to the rate, the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship; according to the frequency growth rate and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate, the islanding injection amount is determined, The amount of islanding injection is the amount of reactive power or reactive current used for reactive power disturbance; according to the amount of islanding injection, the grid-connected inverter is controlled to output reactive power or reactive current through the AC port; The islanding phenomenon is detected according to the frequency of the alternating current output from the alternating port.
  • harmonics are components greater than the fundamental frequency obtained by Fourier series decomposition of periodic non-sinusoidal alternating currents.
  • Harmonic amplitude is the maximum absolute value of the instantaneous occurrence of harmonics in a period.
  • the growth rate of the harmonic amplitude is the ratio of the increase in the harmonic amplitude within a period of time to the harmonic amplitude at the beginning of this period of time.
  • the harmonics in the AC power output by the AC port may be the k-th harmonic, and k is the harmonic order of the harmonic, that is, the ratio of the harmonic frequency to the fundamental frequency.
  • the frequency is the number of times the periodic change is completed in a unit time
  • the frequency of the alternating current may be the frequency of the voltage of the alternating current, or may be the frequency of the current of the alternating current.
  • the frequency growth rate is the ratio of the increase in frequency within a period of time to the frequency at the beginning of this period of time.
  • the monotonic increasing relationship between the harmonic amplitude growth rate and the islanding disturbance coefficient means that as the harmonic amplitude growth rate increases, the islanding disturbance coefficient increases or does not decrease, and as the harmonic amplitude increases With the increase of, the overall islanding disturbance coefficient shows an increasing trend (that is, non-constant, non-decreasing).
  • the islanding disturbance coefficient is used to determine the magnitude of the reactive power disturbance that needs to be carried out, and the islanding disturbance coefficient has a positive correlation with the magnitude of the reactive power disturbance.
  • reactive power disturbance refers to the disturbance of the reactive power output by the AC port of the grid-connected inverter, so that the frequency of the AC power output by the AC port of the grid-connected inverter changes.
  • Reactive power is the electrical power required to establish an alternating magnetic field and induced magnetic flux. It is used in the electric and magnetic fields in the circuit, and used to establish and maintain the magnetic field in electrical equipment.
  • the reactive current is the current that is 90 degrees out of phase with the voltage.
  • the harmonic amplitude growth rate of the AC power output by the AC port is small, and the islanding disturbance coefficient is small at this time, and the control is connected to the grid.
  • the reactive power or reactive current output by the inverter through the AC port is also small, which helps to reduce the disturbance to the grid, improve the stability of the grid, and then improve the weak grid adaptability of the grid-connected inverter .
  • the grid-connected inverter is connected to the grid, the frequency of the alternating current output by the AC port will not be disturbed, so that it can be accurately detected that no islanding has occurred.
  • the harmonics in the AC power output by the AC port will have a sudden change, that is, the growth rate of the harmonic amplitude of the AC power output by the AC port will increase, and the islanding disturbance coefficient will also increase at this time.
  • the reactive power or reactive current output by the grid-connected inverter through the AC port is also relatively large. Since the reactive power or reactive current output by the AC port is also determined by the frequency growth rate of the AC power output by the AC port, under the action of the positive frequency feedback characteristic of the islanding phenomenon, the AC port can be quickly The frequency of the output AC is disturbed, so that the islanding phenomenon can be accurately detected.
  • the grid-connected inverter when islanding does not occur, even if the harmonics in the AC output from the AC port are suddenly changed due to fluctuations in the grid itself, the grid-connected inverter will not directly perform islanding protection, but will first control the grid-connected reverse The reactive power or reactive current output by the converter through the AC port increases, and then the islanding phenomenon detection is performed according to the frequency of the AC power output by the AC port to determine whether to perform islanding protection. Since islanding does not occur, that is, when the grid-connected inverter is connected to the grid, even if the reactive power or reactive current output by the AC port is large, the frequency of the AC power output by the AC port will not be disturbed. Therefore, it can be accurately detected that no islanding has occurred, so that the grid-connected inverter can avoid islanding protection by mistake due to the fluctuation of the grid itself.
  • the harmonic amplitude growth rate is the harmonic voltage amplitude growth rate
  • the determining the harmonic amplitude growth rate of the alternating current output from the AC port of the grid-connected inverter includes: The voltage of the alternating current output by the AC port is used to determine the harmonic voltage amplitude of the alternating current output from the AC port; the harmonic voltage amplitude growth rate of the alternating current output from the AC port is determined according to the harmonic voltage amplitude .
  • the harmonic amplitude growth rate is the harmonic impedance amplitude growth rate
  • the determining the harmonic amplitude growth rate of the alternating current output from the AC port of the grid-connected inverter includes: Determine the harmonic voltage amplitude of the AC power output by the AC port according to the voltage of the AC power output by the AC port; determine the harmonic current amplitude of the AC power output by the AC port according to the current of the AC power output by the AC port Value; divide the harmonic voltage amplitude by the harmonic current amplitude to obtain the harmonic impedance amplitude of the alternating current output by the AC port; determine the AC port output according to the harmonic impedance amplitude The growth rate of the harmonic impedance amplitude of the alternating current.
  • the growth rate of the harmonic amplitude of the AC output from the AC port of the grid-connected inverter can be the growth rate of the harmonic voltage amplitude or the growth rate of the harmonic impedance amplitude, etc.
  • the harmonic voltage amplitude is within one
  • the maximum absolute value of the harmonic voltage in a period and the harmonic impedance amplitude is the maximum absolute value of the harmonic impedance in a period.
  • the amplitude of the harmonic current is the maximum absolute value of the harmonic current in a period.
  • the determining the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude includes: when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a strictly monotonically increasing relationship, according to the harmonic amplitude growth rate, from Obtain the corresponding islanding disturbance coefficient in the stored correspondence between the harmonic amplitude growth rate and the islanding disturbance coefficient; or, when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a non-strict monotonic increasing relationship, according to the Harmonic amplitude growth rate, obtain the corresponding islanding disturbance coefficient from the correspondence between the stored harmonic amplitude growth rate range and the islanding disturbance coefficient; or, according to the harmonic amplitude growth rate, use a reference function Obtain the corresponding island disturbance coefficient.
  • the relationship between the growth rate of harmonic amplitude and the islanding disturbance coefficient is strictly monotonically increasing, which means that as the growth rate of the harmonic amplitude increases, the islanding disturbance coefficient increases; the growth rate of harmonic amplitude and the islanding disturbance coefficient A non-strictly monotonic increasing relationship means that in a harmonic amplitude growth rate range, as the harmonic amplitude growth rate increases, the island disturbance coefficient increases, and in another harmonic amplitude growth rate range, As the growth rate of harmonic amplitude increases, the island disturbance coefficient remains unchanged.
  • the islanding disturbance coefficient is used to determine the magnitude of the reactive power disturbance that needs to be performed subsequently. Since the corresponding islanding disturbance coefficient is determined according to the growth rate of the harmonic amplitude of the AC output from the AC port, and the harmonic amplitude growth rate is related to the possibility of islanding, the harmonic amplitude growth rate is in turn related to the islanding disturbance coefficient It is a monotonic increasing relationship. Therefore, when the possibility of islanding is low, the growth rate of the harmonic amplitude is small, so the determined islanding disturbance coefficient is also small. When the possibility of islanding is high, the harmonic The growth rate of the wave amplitude is larger, so the determined island disturbance coefficient is also larger.
  • the islanding injection amount is a magnitude of reactive power used for reactive power disturbance
  • the islanding disturbance coefficient corresponding to the frequency growth rate and the harmonic amplitude growth rate is determined
  • the amount of islanding injection includes: determining the active power output by the AC port; multiplying the islanding disturbance coefficient corresponding to the increase rate of the harmonic amplitude, the frequency increase rate and the active power output by the AC port to obtain the The injection volume of the island.
  • the islanding injection amount is the magnitude of the reactive current used for reactive power disturbance
  • the islanding disturbance coefficient corresponding to the frequency growth rate and the harmonic amplitude growth rate is Determining the amount of islanding injection includes: determining the active current output by the AC port; multiplying the islanding disturbance coefficient corresponding to the increase rate of the harmonic amplitude, the frequency increase rate and the active current output by the AC port to obtain The amount of island injection.
  • the active power is the average value of the instantaneous power emitted by the power supply in a cycle. It is the electrical power required to maintain the normal operation of electrical equipment, that is, to convert electrical energy into other forms of energy (mechanical energy, light energy, thermal energy) Electric power.
  • the active current is the current in the same phase as the voltage.
  • both the frequency growth rate and the islanding disturbance coefficient are positively correlated with the islanding injection amount. That is, the smaller either of the two, the smaller the island injection volume, the smaller the subsequent reactive power disturbance; the larger either of the two, the greater the island injection volume, and the subsequent reactive power The greater the disturbance.
  • the detection of islanding phenomenon according to the frequency of the alternating current output by the AC port includes: when the frequency of the alternating current output by the AC port is continuously greater than the first reference frequency or continuously less than the second reference frequency within a reference period of time, Determine that islanding occurs.
  • the frequency of the AC power output by the AC port when the frequency of the AC power output by the AC port is continuously greater than the first reference frequency or continuously less than the second reference frequency within the reference time period, it indicates that the frequency of the AC power output by the AC port is continuously higher for a period of time. Small or persistently large, so it can be determined that islanding has occurred.
  • the method further includes: when it is determined that the islanding phenomenon occurs, stopping the output of AC power through the AC port. In this way, the grid-connected inverter will not continue to supply power to the load, which can realize islanding protection.
  • an islanding phenomenon detection device in a second aspect, is provided, and the islanding phenomenon detection device has the function of realizing the behavior of the islanding phenomenon detection method in the first aspect.
  • the islanding phenomenon detection device includes at least one module, and the at least one module is used to implement the islanding phenomenon detection method provided in the first aspect.
  • an islanding phenomenon detection device in a third aspect, includes a processor and a memory, and the memory is used for storing and supporting the islanding phenomenon detection device to perform the islanding phenomenon detection provided in the first aspect.
  • the processor is configured to execute a program stored in the memory.
  • the islanding phenomenon detection device may further include a communication bus for establishing a connection between the processor and the memory.
  • a computer-readable storage medium stores instructions that, when run on a computer, cause the computer to execute the islanding phenomenon detection method described in the first aspect.
  • a computer program product containing instructions which when run on a computer, causes the computer to execute the islanding phenomenon detection method described in the first aspect.
  • the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude of the alternating current output from the AC port is determined, and the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship.
  • the islanding injection amount is determined.
  • the grid-connected inverter is controlled to output reactive power or reactive current through the AC port.
  • the islanding phenomenon is detected according to the frequency of the AC output from the AC port.
  • Fig. 1 is a schematic structural diagram of a grid-connected inverter control system provided by an embodiment of the present application
  • Figure 2 is a schematic structural diagram of a computer device provided by an embodiment of the present application.
  • FIG. 3 is a flowchart of an islanding phenomenon detection method provided by an embodiment of the present application.
  • Figure 4 is a schematic diagram of a new energy power generation system provided by an embodiment of the present application.
  • FIG. 5 is a schematic diagram of an islanding phenomenon detection process provided by an embodiment of the present application.
  • FIG. 6 is a schematic diagram of another islanding phenomenon detection process provided by an embodiment of the present application.
  • FIG. 7 is a schematic structural diagram of an islanding phenomenon detection device provided by an embodiment of the present application.
  • Fig. 1 is a schematic structural diagram of a grid-connected inverter control system provided by an embodiment of the present application.
  • the grid-connected inverter control system includes a grid-connected inverter, a data sampling unit, a data calculation unit, a control unit, and a drive unit.
  • the grid-connected inverter control system can be used in scenarios where grid-connected inverters are used to supply power to the grid, such as large-scale centralized power stations, small and medium-sized distributed power stations, and household new energy power generation scenarios.
  • the grid-connected inverter can convert the direct current generated by the power generation device into alternating current and feed it to the grid;
  • the data sampling unit can collect the voltage and current of the alternating current output by the AC port of the grid-connected inverter;
  • the data calculation unit can calculate the alternating current The frequency growth rate of the AC power output by the port, the harmonic amplitude growth rate of the AC power output by the AC port, the islanding disturbance coefficient and the islanding injection amount;
  • the control unit can control the grid-connected inverter to output reactive power or no power through the AC port Power current;
  • the drive unit can perform islanding protection when islanding occurs.
  • Fig. 2 is a schematic structural diagram of a computer device provided by an embodiment of the present application.
  • the grid-connected inverter control system shown in Fig. 1 can be implemented by the computer device shown in Fig. 2.
  • the computer device includes at least one processor 201, a communication bus 202, a memory 203, and at least one communication interface 204.
  • the processor 201 may be a general-purpose central processing unit (Central Processing Unit, CPU), a microprocessor, an application-specific integrated circuit (ASIC), or may be one or more programs for controlling the program of this application Implementation of integrated circuits.
  • CPU Central Processing Unit
  • ASIC application-specific integrated circuit
  • the communication bus 202 may include a path for transferring information between the aforementioned components.
  • the memory 203 can be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, or it can be a random access memory (RAM) or can store information and instructions.
  • Other types of dynamic storage devices can also be Electrically Erasable Programmable Read-Only Memory (EEPROM), CD-ROM (Compact Disc Read-Only Memory, CD-ROM) or other optical disk storage , CD storage (including compressed CDs, laser disks, CDs, digital universal CDs, Blu-ray CDs, etc.), disk storage media or other magnetic storage devices, or can be used to carry or store desired program codes in the form of instructions or data structures And any other media that can be accessed by the computer, but not limited to this.
  • the memory 203 may exist independently and is connected to the processor 201 through the communication bus 202.
  • the memory 203 may also be integrated with the processor 201.
  • the communication interface 204 uses any device such as a transceiver to communicate with other devices or communication networks, such as Ethernet, Radio Access Network (RAN), and Wireless Local Area Networks (WLAN).
  • a transceiver uses any device such as a transceiver to communicate with other devices or communication networks, such as Ethernet, Radio Access Network (RAN), and Wireless Local Area Networks (WLAN).
  • RAN Radio Access Network
  • WLAN Wireless Local Area Networks
  • the processor 201 may include one or more CPUs, such as CPU0 and CPU1 as shown in FIG. 2.
  • the computer device may include multiple processors, such as the processor 201 and the processor 205 as shown in FIG. 2.
  • processors can be a single-core processor (single-CPU) or a multi-core processor (multi-CPU).
  • the processor here may refer to one or more devices, circuits, and/or processing cores for processing data (such as computer program instructions).
  • the above-mentioned computer equipment may be a general-purpose computer equipment or a special-purpose computer equipment.
  • the computer device may be a desktop computer, a portable computer, a network server, a PDA (Personal Digital Assistant, PDA), a mobile phone, a tablet computer, a wireless terminal device, a communication device, or an embedded device.
  • PDA Personal Digital Assistant
  • the embodiments of this application do not Limit the type of computer equipment.
  • the memory 203 is used to store the program code 210 for executing the solution of the present application, and the processor 201 is used to execute the program code 210 stored in the memory 203.
  • the computer device can implement the islanding phenomenon detection method provided in the embodiment of FIG. 3 below through the processor 201 and the program code 210 in the memory 203.
  • Fig. 3 is a flowchart of a method for detecting islanding provided by an embodiment of the present application. Referring to Figure 3, the method includes:
  • Step 301 Determine the harmonic amplitude growth rate and frequency growth rate of the alternating current output from the AC port of the grid-connected inverter.
  • the grid-connected inverter is an important part of the new energy power generation system. It converts the direct current generated by the photovoltaic cells and wind turbines in the new energy power generation system into alternating current and feeds it to the grid.
  • the AC port of the grid-connected inverter is used to transmit AC power to the grid.
  • harmonics are components greater than the fundamental frequency obtained by Fourier series decomposition of periodic non-sinusoidal alternating currents.
  • Harmonic amplitude is the maximum absolute value of the instantaneous occurrence of harmonics in a period.
  • the growth rate of the harmonic amplitude is the ratio of the increase in the harmonic amplitude within a period of time to the harmonic amplitude at the beginning of this period of time.
  • the growth rate of the harmonic amplitude of the AC output from the AC port of the grid-connected inverter can be the growth rate of the harmonic voltage amplitude or the growth rate of the harmonic impedance amplitude, etc.
  • the harmonic voltage amplitude is the harmonic voltage in one cycle
  • the maximum absolute value that appears and the amplitude of the harmonic impedance is the maximum absolute value of the harmonic impedance that appears in a cycle.
  • the harmonics in the AC power output by the AC port may be the k-th harmonic, and k is the harmonic order of the harmonic, that is, the ratio of the harmonic frequency to the fundamental frequency.
  • k can be set in advance, for example, k can be greater than 1 and less than 40.
  • k can also be other values greater than 1, which is not limited in the embodiment of the present application.
  • the frequency is the number of times the periodic changes are completed in a unit time
  • the frequency of the alternating current may be the frequency of the voltage of the alternating current, or may be the frequency of the current of the alternating current.
  • the frequency growth rate is the ratio of the increase in frequency within a period of time to the frequency at the beginning of this period of time.
  • the harmonic amplitude growth rate of the AC power output by the AC port of the grid-connected inverter may be determined first, so as to determine the magnitude of the reactive power disturbance that needs to be performed subsequently.
  • the frequency of the AC power output by the AC port can be detected in real time, and the frequency growth rate of the AC power output by the AC port can be determined according to the detected frequency.
  • the frequency of the AC power output by the AC port may be the frequency of the voltage of the AC power output by the AC port, or may be the frequency of the AC current output by the AC port.
  • a zero-crossing point detection method can be used to determine the frequency of the alternating current output by the alternating current port.
  • the operation of determining the growth rate of the harmonic amplitude of the AC output from the AC port of the grid-connected inverter can be implemented in two possible ways.
  • the growth rate of the harmonic amplitude is the growth rate of the harmonic voltage amplitude
  • the harmonic voltage amplitude of the AC power output by the AC port can be determined according to the voltage of the AC power output by the AC port;
  • the growth rate of the harmonic voltage amplitude of the alternating current output from the AC port is determined.
  • the harmonic voltage amplitude of the AC power output by the AC port can be determined according to the voltage of the AC power output by the AC port ; Determine the harmonic current amplitude of the alternating current output by the AC port according to the current of the alternating current output by the AC port; divide the harmonic voltage amplitude of the alternating current output by the AC port by the harmonic current amplitude to obtain the AC port The harmonic impedance amplitude of the output AC power; according to the harmonic impedance amplitude of the AC power output by the AC port, the growth rate of the harmonic impedance amplitude of the AC power output by the AC port is determined.
  • the voltage of the AC power output by the AC port can be detected in real time, and then the harmonic voltage amplitude of the AC power output by the AC port can be determined according to the detected voltage.
  • the operation of determining the amplitude of the harmonic voltage of the alternating current output from the AC port according to the voltage of the alternating current output from the AC port is similar to the operation of determining the amplitude of the harmonic voltage according to a certain voltage in the related art.
  • a discrete Fourier transform may be performed on the voltage of the alternating current output from the AC port to obtain the harmonic voltage amplitude of the alternating current output from the AC port.
  • the harmonic voltage amplitude of the AC power output by the AC port can be determined in real time, and then the harmonic voltage amplitude growth rate of the AC power output by the AC port can be determined according to the determined harmonic voltage amplitude.
  • the current of the AC power output by the AC port can be detected in real time, and then the harmonic current amplitude of the AC power output by the AC port can be determined according to the detected current, and the harmonic current amplitude is The maximum absolute value of the harmonic current in a period.
  • the operation of determining the amplitude of the harmonic current of the alternating current output by the AC port according to the current of the alternating current output by the AC port is similar to the operation of determining the amplitude of the harmonic current according to a certain current in the related art.
  • discrete Fourier transform can be performed on the current of the alternating current output from the AC port to obtain the harmonic current amplitude of the alternating current output from the AC port.
  • the harmonic voltage amplitude and harmonic current amplitude of the AC power output by the AC port can be determined in real time, and then the harmonic impedance amplitude of the AC power output by the AC port can be determined in real time according to The determined harmonic impedance amplitude determines the growth rate of the harmonic impedance amplitude of the alternating current output from the AC port.
  • Step 302 Determine the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude of the AC power output by the AC port.
  • the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship. That is, as the growth rate of the harmonic amplitude increases, the islanding disturbance coefficient increases or does not decrease, and with the increase of the harmonic amplitude growth rate, the islanding disturbance coefficient increases as a whole (that is, non-constant For unabated).
  • the monotonic increase relationship can include strict monotonic increase and non-strict monotonic increase.
  • the islanding disturbance coefficient increases;
  • the islanding disturbance coefficient increases, and in another harmonic In the wave amplitude growth rate range, as the harmonic amplitude growth rate increases, the island disturbance coefficient remains unchanged.
  • the islanding disturbance coefficient is used to determine the magnitude of the reactive power disturbance that needs to be carried out later, and the islanding disturbance coefficient and the magnitude of the reactive power disturbance are positively correlated.
  • the corresponding islanding disturbance coefficient is determined according to the growth rate of the harmonic amplitude of the alternating current output from the alternating current port. Since the growth rate of the harmonic amplitude is related to the possibility of islanding, and the relationship between the growth rate of the harmonic amplitude and the islanding disturbance coefficient is monotonically increasing, the harmonic amplitude increases when the possibility of islanding is low Therefore, the determined islanding disturbance coefficient is also small. When the possibility of islanding is high, the growth rate of the harmonic amplitude is relatively large, so the determined islanding disturbance coefficient is also relatively large.
  • step 302 is: when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a strictly monotonically increasing relationship, according to the harmonic amplitude growth rate of the alternating current output from the AC port, increase from the stored harmonic amplitude Obtain the corresponding islanding perturbation coefficient in the correspondence relationship between the frequency and the islanding perturbation coefficient; or, when the harmonic amplitude growth rate and the islanding perturbation coefficient are in a non-strictly monotonic increasing relationship, according to the harmonics of the alternating current output from the AC port
  • the amplitude growth rate is to obtain the corresponding islanding disturbance coefficient from the corresponding relationship between the stored harmonic amplitude growth rate range and the islanding disturbance coefficient; or, according to the harmonic amplitude growth rate of the alternating current output from the AC port, Obtain the corresponding island disturbance coefficient through the reference function.
  • the corresponding relationship between the harmonic amplitude growth rate and the islanding disturbance coefficient can be set in advance, and in this correspondence, the harmonic amplitude growth rate and the islanding disturbance coefficient are strictly monotonically increasing.
  • the harmonic amplitude growth rate of the AC power output by the AC port can be 100%, from the harmonic amplitude increase shown in Table 1 below In the corresponding relationship between the rate and the islanding disturbance coefficient, the corresponding islanding disturbance coefficient is 0.5.
  • Harmonic amplitude growth rate Island disturbance coefficient 100% 0.5 200% 1 400% 4 ... ...
  • the growth rate of the harmonic amplitude of the AC output from the AC port is between the two adjacent harmonic amplitude growth rates in Table 1 above, it can be increased according to the amplitude of the two harmonics.
  • the two islanding disturbance coefficients corresponding to the one-to-one rate are determined by linear interpolation to determine the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude of the alternating current output from the AC port.
  • the corresponding relationship between the harmonic amplitude growth rate range and the islanding disturbance coefficient can be set in advance, and in this correspondence, the average value of the harmonic amplitude growth rate range and the islanding disturbance coefficient are strictly monotonic Increasing relationship, and the harmonic amplitude growth rate and island disturbance coefficient are not strictly monotonic increasing relationship. All the harmonic amplitude growth rates included in this correspondence relationship do not overlap each other.
  • the harmonic amplitude growth rate of the AC power output by the AC port can be 100%, from the harmonic amplitude increase shown in Table 2 below In the corresponding relationship between the rate range and the islanding disturbance coefficient, the corresponding islanding disturbance coefficient is 0.5.
  • Harmonic amplitude growth rate Island disturbance coefficient [100%, 150%) 0.5 [200%, 350%) 1 [400%, 650%) 4 ... ...
  • the growth rate of the harmonic amplitude of the AC output from the AC port is between the two adjacent harmonic amplitude growth rates in Table 2 above, it can be based on the amplitude of the two harmonics.
  • the two islanding disturbance coefficients corresponding to the growth rate range one-to-one, the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude of the alternating current output from the AC port is determined by linear interpolation.
  • the reference function can be set in advance.
  • the reference function can be a strictly monotonic increasing function or a non-strict monotonic increasing function.
  • Step 303 Determine the islanding injection amount according to the frequency growth rate of the alternating current output from the AC port and the islanding disturbance coefficient corresponding to the harmonic amplitude growth rate of the alternating current output from the AC port.
  • the amount of island injection is the amount of reactive power or reactive current used for reactive power disturbance.
  • Reactive power disturbance refers to the disturbance of the reactive power output from the AC port of the grid-connected inverter so as to change the frequency of the AC power output from the AC port of the grid-connected inverter.
  • Reactive power is the electrical power required to establish an alternating magnetic field and induced magnetic flux. It is used in the electric and magnetic fields in the circuit, and used to establish and maintain the magnetic field in electrical equipment.
  • the reactive current is the current that is 90 degrees out of phase with the voltage.
  • both the frequency growth rate and the islanding disturbance coefficient are positively correlated with the islanding injection volume. That is, the smaller either of the two, the smaller the island injection volume, the smaller the subsequent reactive power disturbance; the larger either of the two, the greater the island injection volume, and the subsequent reactive power The greater the disturbance.
  • the island injection amount is the amount of reactive power used for reactive power disturbance.
  • the operation of step 303 may be: determine the active power output by the AC port; and the harmonics of the AC power output by the AC port.
  • the islanding disturbance coefficient corresponding to the amplitude growth rate, the frequency growth rate of the alternating current output from the AC port and the active power output from the AC port are multiplied to obtain the islanding injection volume.
  • the active power is the average value of the instantaneous power emitted by the power supply in a cycle. It is the electrical power required to maintain the normal operation of electrical equipment, that is, to convert electrical energy into other forms of energy (mechanical energy, light energy, thermal energy) Electric power.
  • the active power output by the AC port can be determined according to the voltage and current of the AC power output by the AC port.
  • the operation of determining the active power output by the AC port according to the voltage and current of the AC power output by the AC port may refer to related technologies, which are not described in detail in the embodiment of the present application.
  • the instantaneous reactive power theory or other methods may be used to determine the active power output by the AC port.
  • the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude of the AC power output by the AC port, the frequency growth rate of the AC power output by the AC port and the active power output by the AC port are all positive for the islanding injection amount. Correlation, that is, the larger any of the three, the larger the island injection volume, and the smaller any of the three, the smaller the island injection volume.
  • the island injection amount is the magnitude of the reactive current used for reactive power disturbance
  • the operation of step 303 may be: determine the active current output by the AC port; The islanding disturbance coefficient corresponding to the growth rate of the wave amplitude, the frequency growth rate of the alternating current output by the AC port and the active current output by the AC port are multiplied to obtain the islanding injection amount.
  • the active current is the current with the same phase as the voltage.
  • the active current output by the AC port can be determined according to the current of the AC power output by the AC port.
  • the operation of determining the active current output by the AC port according to the current of the AC power output by the AC port can refer to related technologies, which are not described in detail in the embodiment of the present application.
  • the active current output by the AC port can be determined according to the current of the AC power output by the AC port, using methods such as DQ coordinate transformation.
  • the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude of the AC power output by the AC port, the frequency growth rate of the AC power output by the AC port and the active current output by the AC port are all positive for the islanding injection amount. Correlation, that is, the larger any of the three, the larger the island injection volume, and the smaller any of the three, the smaller the island injection volume.
  • Step 304 Control the grid-connected inverter to output reactive power or reactive current through the AC port according to the injection amount of the island.
  • the grid-connected inverter when the island injection amount is the reactive power used for reactive power disturbance, the grid-connected inverter is controlled to output the reactive power through the AC port with the magnitude of the reactive power indicated by the island injection amount. ;
  • the islanding injection quantity is the reactive current used for reactive power disturbance, control the grid-connected inverter to output a reactive current with the magnitude of the reactive current indicated by the islanding injection quantity through the AC port.
  • the growth rate of the harmonic amplitude of the AC output from the AC port when the growth rate of the harmonic amplitude of the AC output from the AC port is small, it means that the possibility of islanding is low. At this time, the determined islanding disturbance coefficient is small, and the control and The reactive power or reactive current output by the grid inverter through the AC port is also relatively small.
  • the growth rate of the harmonic amplitude of the AC power output by the AC port is large, it indicates that the possibility of islanding is higher.
  • the islanding disturbance coefficient determined is large, and the grid-connected inverter is controlled to output through the AC port.
  • the reactive power or reactive current is also larger.
  • the grid-connected inverter when controlling the grid-connected inverter to output reactive power or reactive current through the AC port, it can pass a reactive power/reactive current control loop (such as a reactive power loop decoupled by PQ or a DQ Decoupled reactive current loop) for closed-loop control.
  • a reactive power/reactive current control loop such as a reactive power loop decoupled by PQ or a DQ Decoupled reactive current loop
  • the grid-connected inverter can be controlled through the AC port to output a magnitude indicated by the island injection amount.
  • the reactive power is of the magnitude of the reactive power
  • the closed-loop control can be realized according to the acquired reactive power.
  • the reactive current output by the AC port can be obtained at the same time, and then the grid-connected inverter can be controlled to output the reactive current indicated by the island injection amount through the AC port.
  • the reactive current is large or small, the closed-loop control can be realized according to the obtained reactive current.
  • Step 305 Perform islanding detection according to the frequency of the AC output from the AC port.
  • the harmonic amplitude growth rate of the AC power output by the AC port is small, and the islanding disturbance coefficient is small at this time, and the control is connected to the grid.
  • the reactive power or reactive current output by the inverter through the AC port is also small, which helps to reduce the disturbance to the grid, improve the stability of the grid, and then improve the weak grid adaptability of the grid-connected inverter .
  • the grid-connected inverter is connected to the grid, the frequency of the alternating current output by the AC port will not be disturbed, so that it can be accurately detected that no islanding has occurred.
  • the harmonics in the AC power output by the AC port will have a sudden change, that is, the growth rate of the harmonic amplitude of the AC power output by the AC port will increase, and the islanding disturbance coefficient will also increase at this time.
  • the reactive power or reactive current output by the grid-connected inverter through the AC port is also relatively large. Since the reactive power or reactive current output by the AC port is also determined by the frequency growth rate of the AC power output by the AC port, under the action of the positive frequency feedback characteristic of the islanding phenomenon, the AC port can be quickly The frequency of the output AC is disturbed, so that the islanding phenomenon can be accurately detected.
  • the grid-connected inverter when islanding does not occur, even if the harmonics in the AC output from the AC port are suddenly changed due to fluctuations in the grid itself, the grid-connected inverter will not directly perform islanding protection, but will first control the grid-connected reverse The reactive power or reactive current output by the converter through the AC port increases, and then the islanding phenomenon detection is performed according to the frequency of the AC power output by the AC port to determine whether to perform islanding protection. Since islanding does not occur, that is, when the grid-connected inverter is connected to the grid, even if the reactive power or reactive current output by the AC port is large, the frequency of the AC power output by the AC port will not be disturbed. Therefore, it can be accurately detected that no islanding has occurred, so that the grid-connected inverter can avoid islanding protection by mistake due to the fluctuation of the grid itself.
  • step 305 may be: when the frequency of the AC power output by the AC port is continuously greater than the first reference frequency or continuously less than the second reference frequency within the reference time period, it is determined that islanding occurs.
  • the islanding phenomenon can also be detected in other ways according to the frequency of the AC power output by the AC port, which is not limited in the embodiment of the present application.
  • the reference duration, the first reference frequency, and the second reference frequency can all be set in advance, and the first reference frequency can be set to be smaller, and the second reference frequency can be set to be larger. In this way, when the frequency of the AC power output by the AC port is continuously greater than the first reference frequency or continuously less than the second reference frequency within the reference time period, it indicates that the frequency of the AC power output by the AC port is continuously small or continuously large for a period of time , So it can be determined that islanding has occurred.
  • islanding protection can be performed. Specifically, it can stop outputting AC power through the AC port of the grid-connected inverter.
  • islanding protection can also be performed in other ways. This application implements The example does not limit this.
  • the new energy power generation system includes a grid-connected inverter, a transformer, and a load.
  • the AC port of the grid-connected inverter is connected to the transformer through a first switch, and the output of the transformer is connected to the grid through a second switch. , And the output terminal of the transformer is connected to the load.
  • the second switch is turned on, and the connection between the new energy power generation system and the grid is disconnected.
  • the grid-connected inverter continues to supply power to the load, resulting in islanding.
  • the first switch can be turned on to stop the output of AC power through the AC port of the grid-connected inverter, so the grid-connected inverter will not continue Supply power to the load to realize islanding protection.
  • the frequency f of the voltage U of the AC output from the AC port of the grid-connected inverter can be detected, and the frequency of the AC output from the AC port can be determined according to the detected frequency f The growth rate ⁇ f.
  • the voltage U and current I of the alternating current output by the AC port can be detected in real time, and the harmonic impedance amplitude Z g,k of the alternating current output by the AC port can be determined according to the detected voltage U and current I, and determined accordingly
  • the harmonic impedance amplitude growth rate ⁇ Z g,k of the alternating current output from the AC port, and then the islanding disturbance coefficient K p corresponding to the harmonic impedance amplitude growth rate ⁇ Z g,k of the alternating current output from the AC port is determined.
  • the active power P and reactive power Q output by the AC port can be determined based on the voltage U and current I detected in real time.
  • the frequency growth rate ⁇ f, the island disturbance coefficient K p and the active power P are multiplied to obtain the reactive power Q ai used for reactive power disturbance.
  • the grid-connected inverter is controlled according to the amount of reactive power Q ai for reactive power disturbance, the amount of detected reactive power Q Q fdb , and the amount of reactive power required to be output by the grid-connected inverter Q ref
  • the reactive power of Q ai is output through the AC port.
  • the frequency f of the voltage U of the AC output from the AC port of the grid-connected inverter can be detected, and the frequency f of the AC output from the AC port can be determined according to the detected frequency f.
  • the voltage U and current I of the alternating current output by the AC port can be detected in real time, and the harmonic impedance amplitude Z g,k of the alternating current output by the AC port can be determined according to the detected voltage U and current I, and determined accordingly
  • the harmonic impedance amplitude growth rate ⁇ Z g,k of the alternating current output from the AC port, and then the islanding disturbance coefficient K p corresponding to the harmonic impedance amplitude growth rate ⁇ Z g,k of the alternating current output from the AC port is determined.
  • the active current i d and the reactive current i q output by the AC port can be determined according to the current I detected in real time.
  • the frequency growth rate ⁇ f, the island disturbance coefficient K p and the active current i d are multiplied to obtain the reactive current magnitude i ai used for reactive power disturbance. Then, according to the magnitude of reactive power i ai for reactive power disturbance, the magnitude of the detected reactive current i q i fdb , and the magnitude of reactive current i ref required by the grid-connected inverter to control the grid-connected inverter The inverter outputs a reactive current of i ai through the AC port.
  • the harmonic amplitude growth rate and frequency growth rate of the alternating current output from the AC port of the grid-connected inverter are determined.
  • the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude of the alternating current output from the AC port is determined, and the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship.
  • the islanding injection amount is determined.
  • the grid-connected inverter is controlled to output reactive power or reactive current through the AC port.
  • the islanding phenomenon is detected according to the frequency of the AC output from the AC port. In this way, it can be accurately detected whether islanding occurs. Moreover, when islanding does not occur, not only can the disturbance to the grid be reduced, and the stability of the grid connection can be improved, but also the false detection caused by the fluctuation of the grid itself can be avoided. When islanding occurs, it can be quickly detected, and the detection time is short.
  • Fig. 7 is a schematic structural diagram of an islanding phenomenon detection device provided by an embodiment of the present application.
  • the device can be implemented as part or all of computer equipment by software, hardware, or a combination of the two.
  • the computer equipment can be the one shown in Fig. 2 Computer equipment.
  • the device includes: a first determination module 701, a second determination module 702, a third determination module 703, a control module 704, and a detection module 705.
  • the first determining module 701 is configured to execute step 301 in the embodiment of FIG. 3;
  • the second determining module 702 is configured to execute step 302 in the embodiment of FIG. 3;
  • the third determining module 703 is configured to perform step 303 in the embodiment of FIG. 3;
  • the control module 704 is configured to execute step 304 in the embodiment of FIG. 3;
  • the detection module 705 is configured to execute step 305 in the embodiment of FIG. 3.
  • the harmonic amplitude growth rate is the harmonic voltage amplitude growth rate
  • the first determining module 701 includes:
  • the first determining unit is configured to determine the harmonic voltage amplitude of the AC power output by the AC port according to the voltage of the AC power output by the AC port;
  • the second determining unit is used to determine the growth rate of the harmonic voltage amplitude of the alternating current output from the AC port according to the harmonic voltage amplitude.
  • the harmonic amplitude growth rate is the harmonic impedance amplitude growth rate
  • the first determining module 701 includes:
  • the first determining unit is configured to determine the harmonic voltage amplitude of the AC power output by the AC port according to the voltage of the AC power output by the AC port;
  • the third determining unit is configured to determine the harmonic current amplitude of the AC power output by the AC port according to the current of the AC power output by the AC port;
  • the first calculation unit is used to divide the harmonic voltage amplitude by the harmonic current amplitude to obtain the harmonic impedance amplitude of the alternating current output from the AC port;
  • the fourth determining unit is used to determine the growth rate of the harmonic impedance amplitude of the alternating current output from the AC port according to the harmonic impedance amplitude.
  • the second determining module 702 includes:
  • the first acquisition unit is used to calculate the correspondence between the stored harmonic amplitude growth rate and the islanding disturbance coefficient according to the harmonic amplitude growth rate when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a strictly monotonically increasing relationship In the relationship, obtain the corresponding island disturbance coefficient; or
  • the second acquisition unit is used for when the harmonic amplitude growth rate and the islanding disturbance coefficient are in a non-strictly monotonically increasing relationship, according to the harmonic amplitude growth rate, from the stored harmonic amplitude growth rate range and the islanding disturbance coefficient In the corresponding relationship, obtain the corresponding island disturbance coefficient; or
  • the third obtaining unit is used to obtain the corresponding island disturbance coefficient through the reference function according to the growth rate of the harmonic amplitude.
  • the island injection amount is the amount of reactive power used for reactive power disturbance
  • the third determining module 703 includes:
  • the fifth determining unit is used to determine the active power output by the AC port
  • the second calculation unit is used to multiply the islanding disturbance coefficient and frequency growth rate corresponding to the growth rate of the harmonic amplitude by the active power output by the AC port to obtain the islanding injection amount.
  • the island injection amount is the magnitude of the reactive current used for reactive power disturbance
  • the third determining module 703 includes:
  • the sixth determining unit is used to determine the active current output by the AC port
  • the third calculation unit is used to multiply the islanding disturbance coefficient and the frequency growth rate corresponding to the growth rate of the harmonic amplitude by the active current output by the AC port to obtain the islanding injection amount.
  • the detection module 705 is used to:
  • the device is also used for:
  • the harmonic amplitude growth rate and frequency growth rate of the alternating current output from the AC port of the grid-connected inverter are determined.
  • the islanding disturbance coefficient corresponding to the growth rate of the harmonic amplitude of the alternating current output from the AC port is determined, and the harmonic amplitude growth rate and the islanding disturbance coefficient are in a monotonically increasing relationship.
  • the islanding injection amount is determined.
  • the grid-connected inverter is controlled to output reactive power or reactive current through the AC port.
  • the islanding phenomenon is detected according to the frequency of the AC output from the AC port. In this way, it can be accurately detected whether islanding occurs. Moreover, when islanding does not occur, not only can the disturbance to the grid be reduced, and the stability of the grid connection can be improved, but also the false detection caused by the fluctuation of the grid itself can be avoided. When islanding occurs, it can be quickly detected, and the detection time is short.
  • the islanding phenomenon detection device detects the islanding phenomenon
  • only the division of the above functional modules is used as an example for illustration.
  • the above functions can be allocated by different functional modules according to needs.
  • the internal structure of the device is divided into different functional modules to complete all or part of the functions described above.
  • the islanding phenomenon detection device provided in the foregoing embodiment and the islanding phenomenon detection method embodiment belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.
  • the computer program product includes one or more computer instructions.
  • the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices.
  • the computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center.
  • the computer-readable storage medium may be any available medium that can be accessed by a computer, or a data storage device such as a server or data center integrated with one or more available media.
  • the usable medium can be a magnetic medium (for example: floppy disk, hard disk, tape), optical medium (for example: Digital Versatile Disc (DVD)) or semiconductor medium (for example: Solid State Disk (SSD)) Wait.

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Abstract

一种孤岛现象检测方法、装置和计算机可读存储介质，检测方法包括：确定并网逆变器的交流端口输出的交流电的谐波幅值增长率和频率增长率（301）；确定该谐波幅值增长率对应的孤岛扰动系数（302），谐波幅值增长率与孤岛扰动系数为单调递增关系；根据该频率增长率和该谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量（303）；按照该孤岛注入量，控制并网逆变器通过交流端口输出无功功率或无功电流（304）；根据该交流端口输出的交流电的频率进行孤岛现象检测（305）。该检测方法能准确检测出是否发生孤岛现象，且在未发生孤岛现象时，减小了对电网的扰动，提升了并网稳定性，在发生孤岛现象时，可以快速检测出孤岛现象，检测时间较短。

Description

孤岛现象检测方法、装置和计算机可读存储介质
本申请要求于2019年07月30日提交的申请号为201910692755.5、发明名称为“孤岛现象检测方法、装置和计算机可读存储介质”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电力技术领域，特别涉及一种孤岛现象检测方法、装置和计算机可读存储介质。
背景技术
并网逆变器是新能源发电系统中的重要组成部分，它将新能源发电系统中的光伏电池、风机等发电装置产生的直流电转换为交流电后馈送给电网。新能源发电系统在运行过程中容易发生孤岛现象。孤岛现象是指电网因故障、检修等问题而断电时，新能源发电系统从电网中脱离出来，其中的并网逆变器继续给本地负载供电的一种电气现象。
孤岛现象容易对新能源发电系统中的设备造成危害，甚至危及人身安全。例如，在电网恢复正常时，由于电网的电压相位与发生孤岛现象的新能源发电系统的电压相位存在偏差，所以可能会导致设备因过压或过流而损坏。又例如，当检修人员未能及时获知新能源发电系统发生孤岛现象时，检修人员可能误以为新能源发电系统已不带电，从而造成触电事故。为此，需要迅速检测出孤岛现象，以便可以及时执行保护措施。
现有技术中，在进行孤岛现象检测时，往往是对并网逆变器的交流端口输出的交流电的电压幅值、频率、谐波等状态量进行检测，当检测到这些状态量发生跳变时，确定发生孤岛现象。然而，电网波动时也可能会导致并网逆变器的交流端口输出的交流电的电压幅值、频率、谐波等状态量出现短时的跳变，因而这种方式很容易出现误检测。
发明内容
本申请提供了一种孤岛现象检测方法、装置和计算机可读存储介质，可以解决相关技术中孤岛现象检测准确度较低的问题。所述技术方案如下：
第一方面，提供了一种孤岛现象检测方法，所述方法包括：确定并网逆变器的交流端口输出的交流电的谐波幅值增长率和频率增长率；确定所述谐波幅值增长率对应的孤岛扰动系数，谐波幅值增长率与孤岛扰动系数为单调递增关系；根据所述频率增长率和所述谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量，所述孤岛注入量为用于进行无功扰动的无功功率大小或无功电流大小；按照所述孤岛注入量，控制所述并网逆变器通过所述交流端口输出无功功率或无功电流；根据所述交流端口输出的交流电的频率进行孤岛现象检测。
需要说明的是，谐波是对周期性非正弦交流量进行傅里叶级数分解所得到的大于基波频率的分量。谐波幅值为在一个周期内谐波瞬间出现的最大绝对值。谐波幅值增长率为在一段 时长内谐波幅值的增长量与在这一段时长的起始时间点时的谐波幅值的比值。该交流端口输出的交流电中的谐波可以为k次谐波，k为该谐波的谐波次数，即为谐波频率与基波频率的比值。
另外，频率为在单位时间内完成周期性变化的次数，交流电的频率可以为该交流电的电压的频率，或者可以为该交流电的电流的频率。频率增长率为在一段时长内频率的增长量这与在这一段时长的起始时间点时的频率的比值。
再者，谐波幅值增长率与孤岛扰动系数为单调递增关系是指，随着谐波幅值增长率的增大，孤岛扰动系数递增或不减，并且，随着谐波幅值增长率的增大，孤岛扰动系数整体呈增大趋势(即非恒为不减)。孤岛扰动系数用于确定需要进行的无功扰动大小，且孤岛扰动系数与无功扰动大小为正相关关系。
最后，无功扰动是指对并网逆变器的交流端口输出的无功进行扰动，以使并网逆变器的交流端口输出的交流电的频率发生变化。无功功率是为建立交变磁场和感应磁通而需要的电功率，其用于电路内电场与磁场，并用来在电气设备中建立和维持磁场。无功电流是和电压有90度相位差的电流。
由于在未发生孤岛现象时，该交流端口输出的交流电中的谐波未发生突变，即该交流端口输出的交流电的谐波幅值增长率较小，此时孤岛扰动系数较小，控制并网逆变器通过该交流端口输出的无功功率或无功电流也较小，从而有助于减小对电网的扰动，提升并网稳定性，进而可以提升并网逆变器的弱网适应性。并且，由于此时未发生孤岛现象，即并网逆变器与电网连接，所以该交流端口输出的交流电的频率不会被扰偏，从而可以据此准确检测到未发生孤岛现象。
而在孤岛现象发生后，该交流端口输出的交流电中的谐波会发生突变，即该交流端口输出的交流电的谐波幅值增长率会增大，此时孤岛扰动系数也会增大，控制并网逆变器通过该交流端口输出的无功功率或无功电流也较大。由于该交流端口输出的无功功率或无功电流的大小同时也由该交流端口输出的交流电的频率增长率决定，所以在孤岛现象特有的频率正反馈特征的作用下，可以快速将该交流端口输出的交流电的频率扰偏，从而据此可以准确检测到发生孤岛现象。
并且，在未发生孤岛现象时，即便因电网本身发生波动而引起该交流端口输出的交流电中的谐波突变，并网逆变器也不会直接进行孤岛保护，而是会先控制并网逆变器通过该交流端口输出的无功功率或无功电流增大，后续再根据该交流端口输出的交流电的频率来进行孤岛现象检测，以确定是否要进行孤岛保护。而由于在未发生孤岛现象时，即并网逆变器与电网连接时，即使该交流端口输出的无功功率或无功电流较大，该交流端口输出的交流电的频率也不会被扰偏，所以可以据此准确检测到未发生孤岛现象，这样就可以避免因电网本身发生波动而引起并网逆变器误进行孤岛保护。
由上可知，本申请实施例中，一方面可以在未发生孤岛现象，即并网逆变器正常工作时，减小孤岛现象检测操作对电网的扰动，提升并网稳定性。另一方面可以在发生孤岛现象时，快速检测到孤岛现象的发生，减少检测时间，提升可靠性和安全性，进而可以快速实现孤岛保护。
一种可能的实现方式中，所述谐波幅值增长率为谐波电压幅值增长率，所述确定并网逆变器的交流端口输出的交流电的谐波幅值增长率，包括：根据所述交流端口输出的交流电的 电压，确定所述交流端口输出的交流电的谐波电压幅值；根据所述谐波电压幅值，确定所述交流端口输出的交流电的谐波电压幅值增长率。
另一种可能的实现方式中，所述谐波幅值增长率为谐波阻抗幅值增长率，所述确定并网逆变器的交流端口输出的交流电的谐波幅值增长率，包括：根据所述交流端口输出的交流电的电压，确定所述交流端口输出的交流电的谐波电压幅值；根据所述交流端口输出的交流电的电流，确定所述交流端口输出的交流电的谐波电流幅值；将所述谐波电压幅值除以所述谐波电流幅值，得到所述交流端口输出的交流电的谐波阻抗幅值；根据所述谐波阻抗幅值，确定所述交流端口输出的交流电的谐波阻抗幅值增长率。
需要说明的是，并网逆变器的交流端口输出的交流电的谐波幅值增长率可以为谐波电压幅值增长率或谐波阻抗幅值增长率等，谐波电压幅值为在一个周期内谐波电压出现的最大绝对值，谐波阻抗幅值为在一个周期内谐波阻抗出现的最大绝对值。谐波电流幅值为在一个周期内谐波电流出现的最大绝对值。
其中，所述确定所述谐波幅值增长率对应的孤岛扰动系数，包括：当谐波幅值增长率与孤岛扰动系数为严格单调递增关系时，根据所述谐波幅值增长率，从存储的谐波幅值增长率与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者，当谐波幅值增长率与孤岛扰动系数为非严格单调递增关系时，根据所述谐波幅值增长率，从存储的谐波幅值增长率范围与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者，根据所述谐波幅值增长率，通过参考函数获取对应的孤岛扰动系数。
需要说明的是，谐波幅值增长率与孤岛扰动系数为严格单调递增关系是指，随着谐波幅值增长率的增大，孤岛扰动系数递增；谐波幅值增长率与孤岛扰动系数为非严格单调递增关系是指，在一个谐波幅值增长率区间内，随着谐波幅值增长率的增大，孤岛扰动系数递增，在另一个谐波幅值增长率区间内，随着谐波幅值增长率的增大，孤岛扰动系数不变。
在本申请实施例中，孤岛扰动系数用于确定后续需要进行的无功扰动大小。由于是根据该交流端口输出的交流电的谐波幅值增长率确定对应的孤岛扰动系数，且谐波幅值增长率与孤岛现象发生的可能性相关，谐波幅值增长率又与孤岛扰动系数为单调递增关系，因此，在发生孤岛现象的可能性较低时，谐波幅值增长率较小，因而确定出的孤岛扰动系数也较小，在发生孤岛现象的可能性较高时，谐波幅值增长率较大，因而确定出的孤岛扰动系数也较大。
一种可能的实现方式中，所述孤岛注入量为用于进行无功扰动的无功功率大小，所述根据所述频率增长率和所述谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量，包括：确定所述交流端口输出的有功功率；将所述谐波幅值增长率对应的孤岛扰动系数、所述频率增长率与所述交流端口输出的有功功率相乘，得到所述孤岛注入量。
另一种可能的实现方式中，所述孤岛注入量为用于进行无功扰动的无功电流大小，所述根据所述频率增长率和所述谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量，包括：确定所述交流端口输出的有功电流；将所述谐波幅值增长率对应的孤岛扰动系数、所述频率增长率与所述交流端口输出的有功电流相乘，得到所述孤岛注入量。
需要说明的是，有功功率是电源在一个周期内发出瞬时功率的平均值，是保持用电设备正常运行所需的电功率，也就是将电能转换为其他形式能量(机械能、光能、热能)的电功率。有功电流是与电压相位相同的电流。
在本申请实施例中，频率增长率和孤岛扰动系数这两者均与孤岛注入量为正相关关系。 也即是，这两者中的任意一个越小，孤岛注入量越小，后续进行的无功扰动越小；这两者中的任意一个越大，孤岛注入量越大，后续进行的无功扰动越大。
其中，所述根据所述交流端口输出的交流电的频率进行孤岛现象检测，包括：当所述交流端口输出的交流电的频率在参考时长内持续大于第一参考频率或持续小于第二参考频率时，确定发生孤岛现象。
在本申请实施例中，当该交流端口输出的交流电的频率在参考时长内持续大于第一参考频率或持续小于第二参考频率时，表明该交流端口输出的交流电的频率在一段时间内持续较小或持续较大，因而可以确定发生了孤岛现象。
进一步地，所述根据所述交流端口的频率进行孤岛现象检测之后，还包括：当确定发生孤岛现象时，停止通过所述交流端口输出交流电。如此，并网逆变器将不会继续给负载供电，从而可以实现孤岛保护。
第二方面，提供了一种孤岛现象检测装置，所述孤岛现象检测装置具有实现上述第一方面中孤岛现象检测方法行为的功能。所述孤岛现象检测装置包括至少一个模块，所述至少一个模块用于实现上述第一方面所提供的孤岛现象检测方法。
第三方面，提供了一种孤岛现象检测装置，所述孤岛现象检测装置的结构中包括处理器和存储器，所述存储器用于存储支持孤岛现象检测装置执行上述第一方面所提供的孤岛现象检测方法的程序，以及存储用于实现上述第一方面所述的孤岛现象检测方法所涉及的数据。所述处理器被配置为用于执行所述存储器中存储的程序。所述孤岛现象检测装置还可以包括通信总线，所述通信总线用于在所述处理器与所述存储器之间建立连接。
第四方面，提供了一种计算机可读存储介质，所述计算机可读存储介质中存储有指令，当其在计算机上运行时，使得计算机执行上述第一方面所述的孤岛现象检测方法。
第五方面，提供了一种包含指令的计算机程序产品，当其在计算机上运行时，使得计算机执行上述第一方面所述的孤岛现象检测方法。
上述第二方面、第三方面、第四方面和第五方面所获得的技术效果与上述第一方面中对应的技术手段获得的技术效果近似，在这里不再赘述。
本申请提供的技术方案至少可以带来以下有益效果：
确定并网逆变器的交流端口输出的交流电的谐波幅值增长率和频率增长率。之后，确定该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数，谐波幅值增长率与孤岛扰动系数为单调递增关系。根据该交流端口输出的交流电的频率增长率和该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量。并按照该孤岛注入量，控制并网逆变器通过该交流端口输出无功功率或无功电流。最后，根据该交流端口输出的交流电的频率进行孤岛现象检测。如此，可以准确检测出是否发生孤岛现象。并且，在未发生孤岛现象时，不仅可以减小对电网的扰动，提升并网稳定性，而且可以避免因电网本身发生波动而引起的误检测。在发生孤岛现象时，可以快速检测出孤岛现象，检测时间较短。
附图说明
图1是本申请实施例提供的一种并网逆变器控制系统的结构示意图；
图2是本申请实施例提供的一种计算机设备的结构示意图；
图3是本申请实施例提供的一种孤岛现象检测方法的流程图；
图4是本申请实施例提供的一种新能源发电系统的示意图；
图5是本申请实施例提供的一种孤岛现象检测流程的示意图；
图6是本申请实施例提供的另一种孤岛现象检测流程的示意图；
图7是本申请实施例提供的一种孤岛现象检测装置的结构示意图。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合附图对本申请的实施方式作进一步地详细描述。
在对本申请实施例进行详细地解释说明之前，先对本申请实施例的系统架构予以说明。
图1是本申请实施例提供的一种并网逆变器控制系统的结构示意图。如图1所示，该并网逆变器控制系统包括并网逆变器、数据采样单元、数据计算单元、控制单元以及驱动单元。该并网逆变器控制系统可以用于使用并网逆变器给电网供电的场景下，如可以应用于大型集中式电站场景、中小型分布式电站场景、户用新能源发电场景等。
其中，并网逆变器可以将发电装置产生的直流电转换为交流电后馈送给电网；数据采样单元可以采集并网逆变器的交流端口输出的交流电的电压和电流；数据计算单元可以计算该交流端口输出的交流电的频率增长率、该交流端口输出的交流电的谐波幅值增长率、孤岛扰动系数和孤岛注入量；控制单元可以控制并网逆变器通过该交流端口输出无功功率或无功电流；驱动单元可以在发生孤岛现象时，进行孤岛保护。
图2是本申请实施例提供的一种计算机设备的结构示意图，图1所示的并网逆变器控制系统可以通过图2所示的计算机设备实现。参见图2，该计算机设备包括至少一个处理器201、通信总线202、存储器203以及至少一个通信接口204。
处理器201可以是一个通用中央处理器(Central Processing Unit，CPU)、微处理器、特定应用集成电路(application-specific integrated circuit，ASIC)，或者可以是一个或多个用于控制本申请方案程序执行的集成电路。
通信总线202可包括一通路，用于在上述组件之间传送信息。
存储器203可以是只读存储器(read-only memory，ROM)或可存储静态信息和指令的其它类型的静态存储设备，也可以是随机存取存储器(random access memory，RAM)或者可存储信息和指令的其它类型的动态存储设备，也可以是电可擦可编程只读存储器(Electrically Erasable Programmable Read-Only Memory，EEPROM)、只读光盘(Compact Disc Read-Only Memory，CD-ROM)或其它光盘存储、光碟存储(包括压缩光碟、激光碟、光碟、数字通用光碟、蓝光光碟等)、磁盘存储介质或者其它磁存储设备，或者是能够用于携带或存储具有指令或数据结构形式的期望的程序代码并能够由计算机存取的任何其它介质，但不限 于此。存储器203可以是独立存在，并通过通信总线202与处理器201相连接。存储器203也可以和处理器201集成在一起。
通信接口204使用任何收发器一类的装置，用于与其它设备或通信网络通信，如以太网，无线接入网(Radio Access Network，RAN)、无线局域网(Wireless Local Area Networks，WLAN)等。
在具体实现中，作为一种实施例，处理器201可以包括一个或多个CPU，如图2中所示的CPU0和CPU1。
在具体实现中，作为一种实施例，计算机设备可以包括多个处理器，如图2中所示的处理器201和处理器205。这些处理器中的每一个可以是一个单核处理器(single-CPU)，也可以是一个多核处理器(multi-CPU)。这里的处理器可以指一个或多个设备、电路、和/或用于处理数据(如计算机程序指令)的处理核。
上述的计算机设备可以是一个通用计算机设备或一个专用计算机设备。在具体实现中，计算机设备可以是台式机、便携式电脑、网络服务器、掌上电脑(Personal Digital Assistant，PDA)、移动手机、平板电脑、无线终端设备、通信设备或嵌入式设备，本申请实施例不限定计算机设备的类型。
其中，存储器203用于存储执行本申请方案的程序代码210，处理器201用于执行存储器203中存储的程序代码210。该计算机设备可以通过处理器201以及存储器203中的程序代码210，来实现下文图3实施例提供的孤岛现象检测方法。
图3是本申请实施例提供的一种孤岛现象检测方法的流程图。参见图3，该方法包括：
步骤301：确定并网逆变器的交流端口输出的交流电的谐波幅值增长率和频率增长率。
需要说明的是，并网逆变器是新能源发电系统中的重要组成部分，它将新能源发电系统中的光伏电池、风机等发电装置产生的直流电转换为交流电后馈送给电网。并网逆变器的交流端口用于向电网传输交流电。
另外，谐波是对周期性非正弦交流量进行傅里叶级数分解所得到的大于基波频率的分量。谐波幅值为在一个周期内谐波瞬间出现的最大绝对值。谐波幅值增长率为在一段时长内谐波幅值的增长量与在这一段时长的起始时间点时的谐波幅值的比值。并网逆变器的交流端口输出的交流电的谐波幅值增长率可以为谐波电压幅值增长率或谐波阻抗幅值增长率等，谐波电压幅值为在一个周期内谐波电压出现的最大绝对值，谐波阻抗幅值为在一个周期内谐波阻抗出现的最大绝对值。该交流端口输出的交流电中的谐波可以为k次谐波，k为该谐波的谐波次数，即为谐波频率与基波频率的比值。例如，k可以预先进行设置，如k可以大于1且小于40，当然，k也可以为大于1的其它数值，本申请实施例对此不作限定。
再者，频率为在单位时间内完成周期性变化的次数，交流电的频率可以为该交流电的电压的频率，或者可以为该交流电的电流的频率。频率增长率为在一段时长内频率的增长量这与在这一段时长的起始时间点时的频率的比值。
在并网逆变器接入电网时，并网逆变器的交流端口输出的谐波会流入电网，由于电网阻抗很小，所以并网逆变器的交流端口的总谐波畸变率通常比较低。而在电网断电时，如果发生孤岛现象，则由于本地负载阻抗通常要比电网阻抗大的多，所以并网逆变器的交流端口将产生很大的谐波。如此，孤岛现象的发生会导致并网逆变器的交流端口的谐波突变。因此， 本申请实施例中可以先确定并网逆变器的交流端口输出的交流电的谐波幅值增长率，以据此确定后续需要进行的无功扰动大小。
其中，确定并网逆变器的交流端口输出的交流电的频率增长率时，可以实时检测该交流端口输出的交流电的频率，根据检测到的频率，确定该交流端口输出的交流电的频率增长率。
例如，该交流端口输出的交流电的频率增长率可以通过公式Δf(t n)＝(f(t n)-f(t n-m))/f(t n-m)确定；其中，Δf(t n)为该交流端口输出的交流电在m时长内的频率增长率，f(t n)为t n时刻时该交流端口输出的交流电的频率，f(t n-m)为t n-m时刻时该交流端口输出的交流电的频率。
需要说明的是，该交流端口输出的交流电的频率可以为该交流端口输出的交流电的电压的频率，或者可以为该交流端口输出的交流电的电流的频率。检测该交流端口输出的交流电的频率的方式可以参考相关技术，本申请实施例对此不进行详细阐述。例如，可以采用过零点检测的方式，确定该交流端口输出的交流电的频率。
其中，确定并网逆变器的交流端口输出的交流电的谐波幅值增长率的操作可以通过两种可能的方式实现。一种可能的实现方式中，当谐波幅值增长率为谐波电压幅值增长率时，可以根据该交流端口输出的交流电的电压，确定该交流端口输出的交流电的谐波电压幅值；根据该交流端口输出的交流电的谐波电压幅值，确定该交流端口输出的交流电的谐波电压幅值增长率。另一种可能的实现方式中，当谐波幅值增长率为谐波阻抗幅值增长率时，可以根据该交流端口输出的交流电的电压，确定该交流端口输出的交流电的谐波电压幅值；根据该交流端口输出的交流电的电流，确定该交流端口输出的交流电的谐波电流幅值；将该交流端口输出的交流电的谐波电压幅值除以谐波电流幅值，得到该交流端口输出的交流电的谐波阻抗幅值；根据该交流端口输出的交流电的谐波阻抗幅值，确定该交流端口输出的交流电的谐波阻抗幅值增长率。
需要说明的是，本申请实施例中可以实时检测该交流端口输出的交流电的电压，然后根据检测到的电压，来确定该交流端口输出的交流电的谐波电压幅值。根据该交流端口输出的交流电的电压，确定该交流端口输出的交流电的谐波电压幅值的操作与相关技术中根据某个电压确定谐波电压幅值的操作类似，本申请实施例对此不进行详细阐述。例如，可以对该交流端口输出的交流电的电压进行离散傅里叶变换，得到该交流端口输出的交流电的谐波电压幅值。
另外，本申请实施例中可以实时确定该交流端口输出的交流电的谐波电压幅值，然后根据确定出的谐波电压幅值，确定该交流端口输出的交流电的谐波电压幅值增长率。例如，该交流端口输出的交流电的谐波电压幅值增长率可以通过公式ΔU g,k(t n)＝(U g,k(t n)-U g,k(t n-m))/U g,k(t n-m)确定；其中，ΔU g,k(t n)为该交流端口输出的交流电在m时长内的谐波电压幅值增长率，U g,k(t n)为t n时刻时该交流端口输出的交流电的谐波电压幅值，U g,k(t n-m)为t n-m时刻时该交流端口输出的交流电的谐波电压幅值。
需要说明的是，本申请实施例中可以实时检测该交流端口输出的交流电的电流，然后根据检测到的电流，来确定该交流端口输出的交流电的谐波电流幅值，谐波电流幅值为在一个周期内谐波电流出现的最大绝对值。根据该交流端口输出的交流电的电流，确定该交流端口输出的交流电的谐波电流幅值的操作与相关技术中根据某个电流确定谐波电流幅值的操作类似，本申请实施例对此不进行详细阐述。例如，可以对该交流端口输出的交流电的电流进行离散傅里叶变换，来得到该交流端口输出的交流电的谐波电流幅值。
另外，本申请实施例中可以先实时确定该交流端口输出的交流电的谐波电压幅值和谐波电流幅值，再据此实时确定该交流端口输出的交流电的谐波阻抗幅值，然后根据确定出的谐波阻抗幅值，确定该交流端口输出的交流电的谐波阻抗幅值增长率。例如，该交流端口输出的交流电的谐波阻抗幅值增长率可以通过公式ΔZ g,k(t n)＝(Z g,k(t n)-Z g,k(t n-m))/Z g,k(t n-m)确定；其中，ΔZ g,k(t n)为该交流端口输出的交流电在m时长内的谐波阻抗幅值增长率，Z g,k(t n)为t n时刻时该交流端口输出的交流电的谐波阻抗幅值，Z g,k(t n-m)为t n-m时刻时该交流端口输出的交流电的谐波阻抗幅值。
步骤302：确定该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数。
需要说明的是，谐波幅值增长率与孤岛扰动系数为单调递增关系。也即是，随着谐波幅值增长率的增大，孤岛扰动系数递增或不减，并且，随着谐波幅值增长率的增大，孤岛扰动系数整体呈增大趋势(即非恒为不减)。单调递增关系可以包括严格单调递增和非严格单调递增，当谐波幅值增长率与孤岛扰动系数为严格单调递增关系时，随着谐波幅值增长率的增大，孤岛扰动系数递增；当谐波幅值增长率与孤岛扰动系数为非严格单调递增关系时，在一个谐波幅值增长率区间内，随着谐波幅值增长率的增大，孤岛扰动系数递增，在另一个谐波幅值增长率区间内，随着谐波幅值增长率的增大，孤岛扰动系数不变。孤岛扰动系数用于确定后续需要进行的无功扰动大小，且孤岛扰动系数与无功扰动大小为正相关关系。
另外，本申请实施例中是根据该交流端口输出的交流电的谐波幅值增长率确定对应的孤岛扰动系数。由于谐波幅值增长率与孤岛现象发生的可能性相关，且谐波幅值增长率与孤岛扰动系数为单调递增关系，因此，在发生孤岛现象的可能性较低时，谐波幅值增长率较小，因而确定出的孤岛扰动系数也较小，在发生孤岛现象的可能性较高时，谐波幅值增长率较大，因而确定出的孤岛扰动系数也较大。
具体地，步骤302的操作为：当谐波幅值增长率与孤岛扰动系数为严格单调递增关系时，根据该交流端口输出的交流电的谐波幅值增长率，从存储的谐波幅值增长率与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者，当谐波幅值增长率与孤岛扰动系数为非严格单调递增关系时，根据该交流端口输出的交流电的谐波幅值增长率，从存储的谐波幅值增长率范围与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者，根据该交流端口输出的交流电的谐波幅值增长率，通过参考函数获取对应的孤岛扰动系数。
需要说明的是，谐波幅值增长率与孤岛扰动系数之间的对应关系可以预先进行设置，且在此对应关系中，谐波幅值增长率与孤岛扰动系数为严格单调递增关系。
例如，该交流端口输出的交流电的谐波幅值增长率为100％，则可以根据该交流端口输出的交流电的谐波幅值增长率100％，从如下表1所示的谐波幅值增长率与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数为0.5。
表1
谐波幅值增长率 孤岛扰动系数
100％ 0.5
200％ 1
400％ 4
…… ……
需要说明的是，当该交流端口输出的交流电的谐波幅值增长率位于上表1中相邻的两个谐波幅值增长率之间时，可以根据与这两个谐波幅值增长率一一对应的两个孤岛扰动系数，通过线性插值的方式确定该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数。
另外，本申请实施例中仅以上表1所示的谐波幅值增长率与孤岛扰动系数之间的对应关系为例进行说明，上表1并不对本申请实施例构成限定。
需要说明的是，谐波幅值增长率范围与孤岛扰动系数之间的对应关系可以预先进行设置，且在此对应关系中，谐波幅值增长率范围的平均值与孤岛扰动系数为严格单调递增关系，且谐波幅值增长率与孤岛扰动系数为非严格单调递增关系。此对应关系中包括的所有谐波幅值增长率范围互不重叠。
例如，该交流端口输出的交流电的谐波幅值增长率为100％，则可以根据该交流端口输出的交流电的谐波幅值增长率100％，从如下表2所示的谐波幅值增长率范围与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数为0.5。
表2
谐波幅值增长率 孤岛扰动系数
[100％，150％) 0.5
[200％，350％) 1
[400％，650％) 4
…… ……
需要说明的是，当该交流端口输出的交流电的谐波幅值增长率位于上表2中相邻的两个谐波幅值增长率范围之间时，可以根据与这两个谐波幅值增长率范围一一对应的两个孤岛扰动系数，通过线性插值的方式确定该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数。
另外，本申请实施例中仅以上表2所示的谐波幅值增长率范围与孤岛扰动系数之间的对应关系为例进行说明，上表2并不对本申请实施例构成限定。
需要说明的是，参考函数可以预先进行设置，例如，参考函数可以为严格单调递增函数或非严格单调递增函数。例如，参考函数可以为y＝kx+b，k和b均可以预先进行设置，且k可以为正数，x和y中的一个可以为谐波幅值增长率，另一个可以为孤岛扰动系数。
步骤303：根据该交流端口输出的交流电的频率增长率和该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量。
需要说明的是，孤岛注入量为用于进行无功扰动的无功功率大小或无功电流大小。无功扰动是指对并网逆变器的交流端口输出的无功进行扰动，以使并网逆变器的交流端口输出的交流电的频率发生变化。无功功率是为建立交变磁场和感应磁通而需要的电功率，其用于电路内电场与磁场，并用来在电气设备中建立和维持磁场。无功电流是和电压有90度相位差的电流。
另外，频率增长率和孤岛扰动系数这两者均与孤岛注入量为正相关关系。也即是，这两者中的任意一个越小，孤岛注入量越小，后续进行的无功扰动越小；这两者中的任意一个越大，孤岛注入量越大，后续进行的无功扰动越大。
一种可能的实现方式中，孤岛注入量为用于进行无功扰动的无功功率大小，步骤303的 操作可以为：确定该交流端口输出的有功功率；将该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数、该交流端口输出的交流电的频率增长率与该交流端口输出的有功功率相乘，得到孤岛注入量。
需要说明的是，有功功率是电源在一个周期内发出瞬时功率的平均值，是保持用电设备正常运行所需的电功率，也就是将电能转换为其他形式能量(机械能、光能、热能)的电功率。确定该交流端口输出的有功功率时，可以根据该交流端口输出的交流电的电压和电流，来确定该交流端口输出的有功功率。并且，根据该交流端口输出的交流电的电压和电流，确定该交流端口输出的有功功率的操作可以参考相关技术，本申请实施例对此不进行详细阐述。例如，可以根据该交流端口输出的交流电的电压和电流，采用瞬时无功功率理论等方式，确定该交流端口输出的有功功率。
再者，该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数、该交流端口输出的交流电的频率增长率和该交流端口输出的有功功率这三者均与孤岛注入量为正相关关系，即这三者中的任意一个越大，孤岛注入量就越大，这三者中的任意一个越小，孤岛注入量就越小。
另一种可能的实现方式中，孤岛注入量为用于进行无功扰动的无功电流大小，步骤303的操作可以为：确定该交流端口输出的有功电流；将该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数、该交流端口输出的交流电的频率增长率与该交流端口输出的有功电流相乘，得到孤岛注入量。
需要说明的是，有功电流是与电压相位相同的电流。确定该交流端口输出的有功电流时，可以根据该交流端口输出的交流电的电流，来确定该交流端口输出的有功电流。并且，根据该交流端口输出的交流电的电流，确定该交流端口输出的有功电流的操作可以参考相关技术，本申请实施例对此不进行详细阐述。例如，可以根据该交流端口输出的交流电的电流，采用DQ坐标变换等方式，确定该交流端口输出的有功电流。
再者，该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数、该交流端口输出的交流电的频率增长率与该交流端口输出的有功电流这三者均与孤岛注入量为正相关关系，即这三者中的任意一个越大，孤岛注入量就越大，这三者中的任意一个越小，孤岛注入量就越小。
步骤304：按照该孤岛注入量，控制并网逆变器通过该交流端口输出无功功率或无功电流。
也即是，当该孤岛注入量为用于进行无功扰动的无功功率大小时，控制并网逆变器通过该交流端口输出大小为该孤岛注入量指示的无功功率大小的无功功率；当该孤岛注入量为用于进行无功扰动的无功电流大小时，控制并网逆变器通过该交流端口输出大小为该孤岛注入量指示的无功电流大小的无功电流。
值得说明的是，本申请实施例中，该交流端口输出的交流电的谐波幅值增长率较小时，表示发生孤岛现象的可能性较低，此时确定出的孤岛扰动系数较小，控制并网逆变器通过该交流端口输出的无功功率或无功电流也较小。该交流端口输出的交流电的谐波幅值增长率较大时，表示发生孤岛现象的可能性较高，此时确定出的孤岛扰动系数较大，控制并网逆变器通过该交流端口输出的无功功率或无功电流也较大。
值得注意的是，控制并网逆变器通过该交流端口输出无功功率或无功电流时，可以通过 无功功率/无功电流控制环路(如PQ解耦的无功功率环路或DQ解耦的无功电流环路)来进行闭环控制。这种情况下，在上述获取该交流端口输出的有功功率时，可以同时获取该交流端口输出的无功功率，然后在控制并网逆变器通过该交流端口输出大小为该孤岛注入量指示的无功功率大小的无功功率时，可以根据获取到的无功功率来实现闭环控制。或者，在上述获取该交流端口输出的有功电流时，可以同时获取该交流端口输出的无功电流，然后在控制并网逆变器通过该交流端口输出大小为该孤岛注入量指示的无功电流大小的无功电流时，可以根据获取到的无功电流来实现闭环控制。
步骤305：根据该交流端口输出的交流电的频率进行孤岛现象检测。
由于在未发生孤岛现象时，该交流端口输出的交流电中的谐波未发生突变，即该交流端口输出的交流电的谐波幅值增长率较小，此时孤岛扰动系数较小，控制并网逆变器通过该交流端口输出的无功功率或无功电流也较小，从而有助于减小对电网的扰动，提升并网稳定性，进而可以提升并网逆变器的弱网适应性。并且，由于此时未发生孤岛现象，即并网逆变器与电网连接，所以该交流端口输出的交流电的频率不会被扰偏，从而可以据此准确检测到未发生孤岛现象。
而在孤岛现象发生后，该交流端口输出的交流电中的谐波会发生突变，即该交流端口输出的交流电的谐波幅值增长率会增大，此时孤岛扰动系数也会增大，控制并网逆变器通过该交流端口输出的无功功率或无功电流也较大。由于该交流端口输出的无功功率或无功电流的大小同时也由该交流端口输出的交流电的频率增长率决定，所以在孤岛现象特有的频率正反馈特征的作用下，可以快速将该交流端口输出的交流电的频率扰偏，从而据此可以准确检测到发生孤岛现象。
并且，在未发生孤岛现象时，即便因电网本身发生波动而引起该交流端口输出的交流电中的谐波突变，并网逆变器也不会直接进行孤岛保护，而是会先控制并网逆变器通过该交流端口输出的无功功率或无功电流增大，后续再根据该交流端口输出的交流电的频率来进行孤岛现象检测，以确定是否要进行孤岛保护。而由于在未发生孤岛现象时，即并网逆变器与电网连接时，即使该交流端口输出的无功功率或无功电流较大，该交流端口输出的交流电的频率也不会被扰偏，所以可以据此准确检测到未发生孤岛现象，这样就可以避免因电网本身发生波动而引起并网逆变器误进行孤岛保护。
由上可知，本申请实施例中，一方面可以在未发生孤岛现象，即并网逆变器正常工作时，减小孤岛现象检测操作对电网的扰动，提升并网稳定性。另一方面可以在发生孤岛现象时，快速检测到孤岛现象的发生，减少检测时间，提升可靠性和安全性，进而可以快速实现孤岛保护。
具体地，步骤305的操作可以为：当该交流端口输出的交流电的频率在参考时长内持续大于第一参考频率或持续小于第二参考频率时，确定发生孤岛现象。当然，也可以根据该交流端口输出的交流电的频率，通过其它方式进行孤岛现象检测，本申请实施例对此不作限定。
需要说明的是，参考时长、第一参考频率和第二参考频率均可以预先进行设置，且第一参考频率可以设置的较小，第二参考频率可以设置的较大。如此，当该交流端口输出的交流电的频率在参考时长内持续大于第一参考频率或持续小于第二参考频率时，表明该交流端口输出的交流电的频率在一段时间内持续较小或持续较大，因而可以确定发生了孤岛现象。
进一步地，在步骤305之后，当确定发生孤岛现象时，可以进行孤岛保护，具体可以通 停止通过并网逆变器的交流端口输出交流电，当然，也可以通过其它方式进行孤岛保护，本申请实施例对此不作限定。
例如，如图4所示，新能源发电系统包括并网逆变器、变压器和负载，并网逆变器的交流端口通过第一开关与变压器连接，变压器的输出端通过第二开关与电网连接，且变压器的输出端与负载连接。在电网断电时，第二开关打开，新能源发电系统与电网之间的连接断开，此时并网逆变器继续给负载供电，从而发生孤岛现象。在通过本申请实施例提供的孤岛现象检测方法检测到发生孤岛现象时，可以将第一开关打开，以停止通过并网逆变器的交流端口输出交流电，如此并网逆变器将不会继续给负载供电，从而实现孤岛保护。
为了便于理解，下面结合图5和图6来对上述孤岛现象检测方法进行举例说明。
一种可能的实现方式中，如图5所示，可以检测并网逆变器的交流端口输出的交流电的电压U的频率f，根据检测到的频率f，确定该交流端口输出的交流电的频率增长率Δf。并且，可以实时检测该交流端口输出的交流电的电压U和电流I，根据检测到的电压U和电流I，确定该交流端口输出的交流电的谐波阻抗幅值Z g,k，并据此确定该交流端口输出的交流电的谐波阻抗幅值增长率ΔZ g,k，然后确定该交流端口输出的交流电的谐波阻抗幅值增长率ΔZ g,k对应的孤岛扰动系数K p。同时，可以根据实时检测到的电压U和电流I，确定该交流端口输出的有功功率P和无功功率Q。之后，将该频率增长率Δf、该孤岛扰动系数K p与该有功功率P相乘，得到用于进行无功扰动的无功功率大小Q ai。之后，根据用于进行无功扰动的无功功率大小Q ai、检测到的无功功率Q的大小Q fdb、并网逆变器要求输出的无功功率大小Q ref，控制并网逆变器通过交流端口输出大小为Q ai的无功功率。
另一种可能的实现方式中，如图6所示，可以检测并网逆变器的交流端口输出的交流电的电压U的频率f，根据检测到的频率f，确定该交流端口输出的交流电的频率增长率Δf。并且，可以实时检测该交流端口输出的交流电的电压U和电流I，根据检测到的电压U和电流I，确定该交流端口输出的交流电的谐波阻抗幅值Z g,k，并据此确定该交流端口输出的交流电的谐波阻抗幅值增长率ΔZ g,k，然后确定该交流端口输出的交流电的谐波阻抗幅值增长率ΔZ g,k对应的孤岛扰动系数K p。同时，可以根据实时检测到的电流I，确定该交流端口输出的有功电流i d和无功电流i q。之后，将该频率增长率Δf、该孤岛扰动系数K p与该有功电流i d相乘，得到用于进行无功扰动的无功电流大小i ai。之后，根据用于进行无功扰动的无功功率大小i ai、检测到的无功电流i q的大小i fdb、并网逆变器要求输出的无功电流大小i ref，控制并网逆变器通过交流端口输出大小为i ai的无功电流。
在本申请实施例中，确定并网逆变器的交流端口输出的交流电的谐波幅值增长率和频率增长率。之后，确定该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数，谐波幅值增长率与孤岛扰动系数为单调递增关系。根据该交流端口输出的交流电的频率增长率和该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量。并按照该孤岛注入量，控制并网逆变器通过该交流端口输出无功功率或无功电流。最后，根据该交流端口输出的交流电的频率进行孤岛现象检测。如此，可以准确检测出是否发生孤岛现象。并且，在未发生孤岛现象时，不仅可以减小对电网的扰动，提升并网稳定性，而且可以避免因电网本身发生波动而引起的误检测。在发生孤岛现象时，可以快速检测出孤岛现象，检测时间较短。
图7是本申请实施例提供的一种孤岛现象检测装置的结构示意图，该装置可以由软件、硬件或者两者的结合实现成为计算机设备的部分或者全部，该计算机设备可以为图2所示的计算机设备。参见图7，该装置包括：第一确定模块701、第二确定模块702、第三确定模块703、控制模块704和检测模块705。
第一确定模块701，用于执行图3实施例中的步骤301；
第二确定模块702，用于执行图3实施例中的步骤302；
第三确定模块703，用于执行图3实施例中的步骤303；
控制模块704，用于执行图3实施例中的步骤304；
检测模块705，用于执行图3实施例中的步骤305。
可选地，谐波幅值增长率为谐波电压幅值增长率，第一确定模块701包括：
第一确定单元，用于根据交流端口输出的交流电的电压，确定交流端口输出的交流电的谐波电压幅值；
第二确定单元，用于根据谐波电压幅值，确定交流端口输出的交流电的谐波电压幅值增长率。
可选地，谐波幅值增长率为谐波阻抗幅值增长率，第一确定模块701包括：
第一确定单元，用于根据交流端口输出的交流电的电压，确定交流端口输出的交流电的谐波电压幅值；
第三确定单元，用于根据交流端口输出的交流电的电流，确定交流端口输出的交流电的谐波电流幅值；
第一计算单元，用于将谐波电压幅值除以谐波电流幅值，得到交流端口输出的交流电的谐波阻抗幅值；
第四确定单元，用于根据谐波阻抗幅值，确定交流端口输出的交流电的谐波阻抗幅值增长率。
可选地，第二确定模块702包括：
第一获取单元，用于当谐波幅值增长率与孤岛扰动系数为严格单调递增关系时，根据谐波幅值增长率，从存储的谐波幅值增长率与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者
第二获取单元，用于当谐波幅值增长率与孤岛扰动系数为非严格单调递增关系时，根据谐波幅值增长率，从存储的谐波幅值增长率范围与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者
第三获取单元，用于根据谐波幅值增长率，通过参考函数获取对应的孤岛扰动系数。
可选地，孤岛注入量为用于进行无功扰动的无功功率大小，第三确定模块703包括：
第五确定单元，用于确定交流端口输出的有功功率；
第二计算单元，用于将谐波幅值增长率对应的孤岛扰动系数、频率增长率与交流端口输出的有功功率相乘，得到孤岛注入量。
可选地，孤岛注入量为用于进行无功扰动的无功电流大小，第三确定模块703包括：
第六确定单元，用于确定交流端口输出的有功电流；
第三计算单元，用于将谐波幅值增长率对应的孤岛扰动系数、频率增长率与交流端口输出的有功电流相乘，得到孤岛注入量。
可选地，检测模块705用于：
当交流端口输出的交流电的频率在参考时长内持续大于第一参考频率或持续小于第二参考频率时，确定发生孤岛现象。
可选地，该装置还用于：
当确定发生孤岛现象时，停止通过交流端口输出交流电。
在本申请实施例中，确定并网逆变器的交流端口输出的交流电的谐波幅值增长率和频率增长率。之后，确定该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数，谐波幅值增长率与孤岛扰动系数为单调递增关系。根据该交流端口输出的交流电的频率增长率和该交流端口输出的交流电的谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量。并按照该孤岛注入量，控制并网逆变器通过该交流端口输出无功功率或无功电流。最后，根据该交流端口输出的交流电的频率进行孤岛现象检测。如此，可以准确检测出是否发生孤岛现象。并且，在未发生孤岛现象时，不仅可以减小对电网的扰动，提升并网稳定性，而且可以避免因电网本身发生波动而引起的误检测。在发生孤岛现象时，可以快速检测出孤岛现象，检测时间较短。
需要说明的是：上述实施例提供的孤岛现象检测装置在检测孤岛现象时，仅以上述各功能模块的划分进行举例说明，实际应用中，可以根据需要而将上述功能分配由不同的功能模块完成，即将装置的内部结构划分成不同的功能模块，以完成以上描述的全部或者部分功能。另外，上述实施例提供的孤岛现象检测装置与孤岛现象检测方法实施例属于同一构思，其具体实现过程详见方法实施例，这里不再赘述。
在上述实施例中，可以全部或部分地通过软件、硬件、固件或者其任意结合来实现。当使用软件实现时，可以全部或部分地以计算机程序产品的形式实现。所述计算机程序产品包括一个或多个计算机指令。在计算机上加载和执行所述计算机指令时，全部或部分地产生按照本申请实施例所述的流程或功能。所述计算机可以是通用计算机、专用计算机、计算机网络或其他可编程装置。所述计算机指令可以存储在计算机可读存储介质中，或者从一个计算机可读存储介质向另一个计算机可读存储介质传输，例如，所述计算机指令可以从一个网站站点、计算机、服务器或数据中心通过有线(例如：同轴电缆、光纤、数据用户线(Digital Subscriber Line，DSL))或无线(例如：红外、无线、微波等)方式向另一个网站站点、计算机、服务器或数据中心进行传输。所述计算机可读存储介质可以是计算机能够存取的任何可用介质，或者是包含一个或多个可用介质集成的服务器、数据中心等数据存储设备。所述可用介质可以是磁性介质(例如：软盘、硬盘、磁带)、光介质(例如：数字通用光盘(Digital Versatile Disc，DVD))或半导体介质(例如：固态硬盘(Solid State Disk，SSD))等。
以上所述为本申请提供的实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (18)

  1. 一种孤岛现象检测方法，其特征在于，所述方法包括：
    确定并网逆变器的交流端口输出的交流电的谐波幅值增长率和频率增长率；
    确定所述谐波幅值增长率对应的孤岛扰动系数，谐波幅值增长率与孤岛扰动系数为单调递增关系；
    根据所述频率增长率和所述谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量，所述孤岛注入量为用于进行无功扰动的无功功率大小或无功电流大小；
    按照所述孤岛注入量，控制所述并网逆变器通过所述交流端口输出无功功率或无功电流；
    根据所述交流端口输出的交流电的频率进行孤岛现象检测。
  2. 如权利要求1所述的方法，其特征在于，所述谐波幅值增长率为谐波电压幅值增长率，所述确定并网逆变器的交流端口输出的交流电的谐波幅值增长率，包括：
    根据所述交流端口输出的交流电的电压，确定所述交流端口输出的交流电的谐波电压幅值；
    根据所述谐波电压幅值，确定所述交流端口输出的交流电的谐波电压幅值增长率。
  3. 如权利要求1所述的方法，其特征在于，所述谐波幅值增长率为谐波阻抗幅值增长率，所述确定并网逆变器的交流端口输出的交流电的谐波幅值增长率，包括：
    根据所述交流端口输出的交流电的电压，确定所述交流端口输出的交流电的谐波电压幅值；
    根据所述交流端口输出的交流电的电流，确定所述交流端口输出的交流电的谐波电流幅值；
    将所述谐波电压幅值除以所述谐波电流幅值，得到所述交流端口输出的交流电的谐波阻抗幅值；
    根据所述谐波阻抗幅值，确定所述交流端口输出的交流电的谐波阻抗幅值增长率。
  4. 如权利要求1-3任一所述的方法，其特征在于，所述确定所述谐波幅值增长率对应的孤岛扰动系数，包括：
    当谐波幅值增长率与孤岛扰动系数为严格单调递增关系时，根据所述谐波幅值增长率，从存储的谐波幅值增长率与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者
    当谐波幅值增长率与孤岛扰动系数为非严格单调递增关系时，根据所述谐波幅值增长率，从存储的谐波幅值增长率范围与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者
    根据所述谐波幅值增长率，通过参考函数获取对应的孤岛扰动系数。
  5. 如权利要求1-4任一所述的方法，其特征在于，所述孤岛注入量为用于进行无功扰动 的无功功率大小，所述根据所述频率增长率和所述谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量，包括：
    确定所述交流端口输出的有功功率；
    将所述谐波幅值增长率对应的孤岛扰动系数、所述频率增长率与所述交流端口输出的有功功率相乘，得到所述孤岛注入量。
  6. 如权利要求1-4任一所述的方法，其特征在于，所述孤岛注入量为用于进行无功扰动的无功电流大小，所述根据所述频率增长率和所述谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量，包括：
    确定所述交流端口输出的有功电流；
    将所述谐波幅值增长率对应的孤岛扰动系数、所述频率增长率与所述交流端口输出的有功电流相乘，得到所述孤岛注入量。
  7. 如权利要求1-6任一所述的方法，其特征在于，所述根据所述交流端口输出的交流电的频率进行孤岛现象检测，包括：
    当所述交流端口输出的交流电的频率在参考时长内持续大于第一参考频率或持续小于第二参考频率时，确定发生孤岛现象。
  8. 如权利要求1-7任一所述的方法，其特征在于，所述根据所述交流端口的频率进行孤岛现象检测之后，还包括：
    当确定发生孤岛现象时，停止通过所述交流端口输出交流电。
  9. 一种孤岛现象检测装置，其特征在于，所述装置包括：
    第一确定模块，用于确定并网逆变器的交流端口输出的交流电的谐波幅值增长率和频率增长率；
    第二确定模块，用于确定所述谐波幅值增长率对应的孤岛扰动系数，谐波幅值增长率与孤岛扰动系数为单调递增关系；
    第三确定模块，用于根据所述频率增长率和所述谐波幅值增长率对应的孤岛扰动系数，确定孤岛注入量，所述孤岛注入量为用于进行无功扰动的无功功率大小或无功电流大小；
    控制模块，用于按照所述孤岛注入量，控制所述并网逆变器通过所述交流端口输出无功功率或无功电流；
    检测模块，用于根据所述交流端口输出的交流电的频率进行孤岛现象检测。
  10. 如权利要求9所述的装置，其特征在于，所述谐波幅值增长率为谐波电压幅值增长率，所述第一确定模块包括：
    第一确定单元，用于根据所述交流端口输出的交流电的电压，确定所述交流端口输出的交流电的谐波电压幅值；
    第二确定单元，用于根据所述谐波电压幅值，确定所述交流端口输出的交流电的谐波电压幅值增长率。
  11. 如权利要求9所述的装置，其特征在于，所述谐波幅值增长率为谐波阻抗幅值增长率，所述第一确定模块包括：
    第一确定单元，用于根据所述交流端口输出的交流电的电压，确定所述交流端口输出的交流电的谐波电压幅值；
    第三确定单元，用于根据所述交流端口输出的交流电的电流，确定所述交流端口输出的交流电的谐波电流幅值；
    第一计算单元，用于将所述谐波电压幅值除以所述谐波电流幅值，得到所述交流端口输出的交流电的谐波阻抗幅值；
    第四确定单元，用于根据所述谐波阻抗幅值，确定所述交流端口输出的交流电的谐波阻抗幅值增长率。
  12. 如权利要求9-11任一所述的装置，其特征在于，所述第二确定模块包括：
    第一获取单元，用于当谐波幅值增长率与孤岛扰动系数为严格单调递增关系时，根据所述谐波幅值增长率，从存储的谐波幅值增长率与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者
    第二获取单元，用于当谐波幅值增长率与孤岛扰动系数为非严格单调递增关系时，根据所述谐波幅值增长率，从存储的谐波幅值增长率范围与孤岛扰动系数之间的对应关系中，获取对应的孤岛扰动系数；或者
    第三获取单元，用于根据所述谐波幅值增长率，通过参考函数获取对应的孤岛扰动系数。
  13. 如权利要求9-12任一所述的装置，其特征在于，所述孤岛注入量为用于进行无功扰动的无功功率大小，所述第三确定模块包括：
    第五确定单元，用于确定所述交流端口输出的有功功率；
    第二计算单元，用于将所述谐波幅值增长率对应的孤岛扰动系数、所述频率增长率与所述交流端口输出的有功功率相乘，得到所述孤岛注入量。
  14. 如权利要求9-12任一所述的装置，其特征在于，所述孤岛注入量为用于进行无功扰动的无功电流大小，所述第三确定模块包括：
    第六确定单元，用于确定所述交流端口输出的有功电流；
    第三计算单元，用于将所述谐波幅值增长率对应的孤岛扰动系数、所述频率增长率与所述交流端口输出的有功电流相乘，得到所述孤岛注入量。
  15. 如权利要求9-14任一所述的装置，其特征在于，所述检测模块用于：
    当所述交流端口输出的交流电的频率在参考时长内持续大于第一参考频率或持续小于第二参考频率时，确定发生孤岛现象。
  16. 如权利要求9-15任一所述的装置，其特征在于，所述装置还用于：
    当确定发生孤岛现象时，停止通过所述交流端口输出交流电。
  17. 一种孤岛现象检测装置，所述装置包括：处理器和存储器；
    所述存储器中存储有至少一条指令，所述至少一条指令由所述处理器加载并执行以实现上述权利要求1-8任意一项所述的方法。
  18. 一种计算机可读存储介质，所述计算机可读存储介质中存储有指令，当其在计算机上运行时，使得计算机执行如权利要求1-8任意一项所述的方法。
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