CN111337777A - Island detection method and device, grid-connected inverter and computer readable storage medium - Google Patents
Island detection method and device, grid-connected inverter and computer readable storage medium Download PDFInfo
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Abstract
The disclosure provides an island detection method and device, a grid-connected inverter and a computer readable storage medium, and relates to the technical field of power systems. The island detection method comprises the following steps: acquiring the angle and frequency of the AC end voltage of the grid-connected inverter; determining angle disturbance applied to the alternating-current end current of the grid-connected inverter according to the angle and the frequency of the alternating-current end voltage of the grid-connected inverter; adding the angle disturbance and the angle of the alternating-current end voltage of the grid-connected inverter to obtain an angle sum; and detecting the occurrence of the islanding effect under the condition that the angle sum is larger than a preset value. The island detection method and device can effectively reduce the detection blind area of the island detection, thereby improving the accuracy and reliability of the island detection.
Description
Technical Field
The disclosure relates to the technical field of power systems, and in particular relates to an island detection method and device, a grid-connected inverter and a computer-readable storage medium.
Background
With global climate change, sustainable development of energy is gradually a research hotspot. Solar energy is one of the major new energy sources today as a renewable energy source and is therefore widely used. The important component of photovoltaic application is photovoltaic grid-connected power generation, but the photovoltaic grid-connected power generation belongs to unstable energy, and the environmental climate and the connected load can generate certain influence on the power of the photovoltaic grid-connected power generation.
In a photovoltaic grid-connected system, generating photovoltaic is connected to a power grid through a grid-connected inverter, the power grid is connected with a local load, the power grid stops running due to faults, artificial reasons or natural reasons, the grid-connected power generation system cannot detect the running stop state of the power grid in time, and the grid-connected power generation system and the local load form an uncontrolled independent power supply system, namely an island effect.
After the island effect occurs, when the power grid is switched on again, the power grid and the grid-connected power generation system may not be synchronous in frequency and angle of the electric signal, so that very high impact current is generated, the grid-connected power generation system is damaged, and even the power grid is tripped again. Meanwhile, very high impact current also causes potential safety hazards to maintenance personnel, so that the occurrence of the islanding effect needs to be accurately detected by an islanding detection method. The island detection method comprises active detection and passive detection, wherein the passive detection is mainly used for indirectly judging whether the island effect occurs by detecting physical quantities such as voltage amplitude, frequency, harmonic waves and the like of a grid-connected power generation system, a large detection blind area exists, and the reliability and the accuracy are low. Traditional active detection is for passive form detection, can only reduce to a certain extent and detect the blind area, therefore reliability and accuracy are still lower.
Disclosure of Invention
One technical problem solved by the present disclosure is how to effectively reduce the detection blind area of island detection.
According to an aspect of the embodiments of the present disclosure, there is provided an island detection method, including: acquiring the angle and frequency of the AC end voltage of the grid-connected inverter; determining angle disturbance applied to the alternating-current end current of the grid-connected inverter according to the angle and the frequency of the alternating-current end voltage of the grid-connected inverter; adding the angle disturbance and the angle of the alternating-current end voltage of the grid-connected inverter to obtain angle sum; and detecting the occurrence of the islanding effect when the angle sum is larger than a preset value.
In some embodiments, the islanding detection method further comprises: and under the condition that the angle sum is not greater than the preset value, determining the current at the alternating current end of the grid-connected inverter according to the cosine value of the angle sum and the voltage loop adjusting signal output by the voltage loop adjuster.
In some embodiments, determining the angular disturbance applied to the grid-tied inverter ac terminal current based on the angle and frequency of the grid-tied inverter ac terminal voltage comprises: determining the absolute value of the frequency difference between the frequency of the AC end voltage of the grid-connected inverter obtained this time and the frequency of the AC end voltage of the grid-connected inverter obtained last time; under the condition that the frequency of the AC voltage of the grid-connected inverter obtained this time is not in a preset frequency interval, determining the angle difference between the angle of the AC voltage of the grid-connected inverter obtained this time and the angle of the AC voltage of the grid-connected inverter obtained last time, and determining the angle disturbance this time according to the absolute value of the frequency difference and the angle difference, wherein the angle disturbance this time is positively correlated with the absolute value of the frequency difference and the angle difference respectively.
In some embodiments, the current angular disturbance is determined by the formula θ '+ f × n, θ represents the current angular disturbance, θ' represents the angular difference, f represents the absolute value of the frequency difference, and n represents a preset coefficient.
In some embodiments, determining the angle disturbance applied to the grid-tied inverter ac terminal current based on the angle and frequency of the grid-tied inverter ac terminal voltage further comprises: and under the condition that the frequency of the alternating-current terminal voltage of the grid-connected inverter obtained at this time is within a preset frequency interval, determining the angle disturbance at this time according to the absolute value of the frequency difference, wherein the angle disturbance at this time is positively correlated with the absolute value of the frequency difference.
In some embodiments, the current angular disturbance is determined by the formula θ ═ f × n, θ represents the current angular disturbance, f represents an absolute value of the frequency difference, and n represents a preset coefficient.
In some embodiments, the preset frequency interval is a continuous interval containing the rated frequency of the grid voltage.
In some embodiments, determining the angle disturbance applied to the grid-tied inverter ac terminal current based on the angle and frequency of the grid-tied inverter ac terminal voltage further comprises: replacing the value of the angle disturbance with the first threshold value under the condition that the angle disturbance is greater than the first threshold value; and under the condition that the angle disturbance is smaller than a second threshold value, replacing the value of the angle disturbance with the second threshold value, wherein the second threshold value is smaller than the first threshold value.
According to another aspect of the embodiments of the present disclosure, there is provided a grid-connected inverter including: a memory; and a processor coupled to the memory, the processor configured to perform the aforementioned islanding detection method based on instructions stored in the memory.
In some embodiments, the grid-tied inverter further comprises: a phase-locked loop configured to detect an angle of an ac terminal voltage of the grid-connected inverter; and a frequency detector configured to detect a frequency of the grid-connected inverter ac terminal voltage.
In some embodiments, the grid-tied inverter further comprises: a voltage loop regulator configured to output a voltage loop regulation signal according to a reference value and an actual value of a bus voltage of the grid-connected inverter; a multiplier configured to multiply the angle-added cosine value by the voltage loop adjustment signal; and the current loop regulator is configured to output the grid-connected inverter alternating current terminal current according to the output signal of the multiplier and the grid-connected side current value.
According to yet another aspect of the embodiments of the present disclosure, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions, and the instructions, when executed by a processor, implement the aforementioned islanding detection method.
According to still another aspect of the embodiments of the present disclosure, there is provided an islanding detection apparatus including: the signal acquisition module is configured to acquire the angle and the frequency of the alternating-current end voltage of the grid-connected inverter; the disturbance determining module is configured to determine angle disturbance applied to the alternating-current end current of the grid-connected inverter according to the angle and the frequency of the alternating-current end voltage of the grid-connected inverter; the angle adding module is configured to add the angle disturbance and the angle of the alternating-current end voltage of the grid-connected inverter to obtain angle addition; and the island detection module is configured to detect the occurrence of the island effect when the angle sum is larger than a preset value.
In some embodiments, the islanding detection apparatus further comprises a current determination module configured to: and under the condition that the angle sum is not greater than the preset value, determining the current at the alternating current end of the grid-connected inverter according to the cosine value of the angle sum and the voltage loop adjusting signal output by the voltage loop adjuster.
In some embodiments, the disturbance determination module is configured to: determining the absolute value of the frequency difference between the frequency of the AC end voltage of the grid-connected inverter obtained this time and the frequency of the AC end voltage of the grid-connected inverter obtained last time; under the condition that the frequency of the AC voltage of the grid-connected inverter obtained this time is not in a preset frequency interval, determining the angle difference between the angle of the AC voltage of the grid-connected inverter obtained this time and the angle of the AC voltage of the grid-connected inverter obtained last time, and determining the angle disturbance this time according to the absolute value of the frequency difference and the angle difference, wherein the angle disturbance this time is positively correlated with the absolute value of the frequency difference and the angle difference respectively.
In some embodiments, the disturbance determining module is configured to determine the angular disturbance of the present time by a formula θ '+ f × n, θ represents the angular disturbance of the present time, θ' represents the angular difference, f represents the absolute value of the frequency difference, and n represents a preset coefficient.
In some embodiments, the disturbance determination module is further configured to: and under the condition that the frequency of the alternating-current terminal voltage of the grid-connected inverter obtained at this time is within a preset frequency interval, determining the angle disturbance at this time according to the absolute value of the frequency difference, wherein the angle disturbance at this time is positively correlated with the absolute value of the frequency difference.
In some embodiments, the disturbance determining module is configured to determine the angular disturbance of the present time by using a formula θ ═ f × n, θ represents the angular disturbance of the present time, f represents an absolute value of the frequency difference, and n represents a preset coefficient.
In some embodiments, the preset frequency interval is a continuous interval containing the rated frequency of the grid voltage.
In some embodiments, the disturbance determination module is further configured to: replacing the value of the angle disturbance with the first threshold value under the condition that the angle disturbance is greater than the first threshold value; and under the condition that the angle disturbance is smaller than a second threshold value, replacing the value of the angle disturbance with the second threshold value, wherein the second threshold value is smaller than the first threshold value.
The island detection method and device can effectively reduce the detection blind area of the island detection, thereby improving the reliability and accuracy of the island detection.
Other features of the present disclosure and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.
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In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and for those skilled in the art, other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 shows a schematic diagram of a grid-connected inverter according to some embodiments of the present disclosure.
Fig. 2 shows a schematic flow diagram of an island detection method according to some embodiments of the present disclosure.
Fig. 3 shows a schematic structural diagram of an islanding detection apparatus according to some embodiments of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.
The island detection method is introduced by taking a grid-connected inverter to execute the island detection method as an example. The direct current end of the grid-connected inverter is connected with the grid-connected side, and the alternating current end of the grid-connected inverter is connected with the grid side, so that direct current generated by photovoltaic is converted into alternating current to be supplied to a power grid or a local load.
Fig. 1 shows a schematic diagram of a grid-connected inverter according to some embodiments of the present disclosure. As shown in fig. 1, the grid-connected inverter 10 may include an island detector 101, a phase-locked loop 102, a frequency detector 103, a voltage loop regulator 104, a multiplier 105, and a current loop regulator 106.
The islanding detector 101 may specifically include a memory and a processor coupled to the memory, the processor being configured to execute an islanding detection method based on instructions stored in the memory, the specific detection steps of the islanding detection method being described in detail in the subsequent embodiments. The memory may include, for example, system memory, fixed non-volatile storage media, and the like. The system memory stores, for example, an operating system, an application program, a Boot Loader (Boot Loader), and other programs. The islanding detector may also include input-output interfaces, network interfaces, storage interfaces, and the like. These interfaces and the memory and processor may be connected by a bus, for example. The input and output interface provides a connection interface for input and output equipment such as a display, a mouse, a keyboard, a touch screen and the like. The network interface provides a connection interface for various networking devices. The storage interface provides a connection interface for external storage equipment such as an SD card and a U disk.
The input signals of the phase-locked loop 102 and the frequency detector 103 are the inverter ac voltage. The phase-locked loop 102 is configured to detect an angle of a grid-connected inverter ac terminal voltage, the frequency detector 103 is configured to detect a frequency of the grid-connected inverter ac terminal voltage,
the voltage loop regulator 104 is configured to output a voltage loop regulation signal according to a reference value and an actual value of a bus voltage of the grid-connected inverter. In some embodiments, the voltage loop regulator 104 may specifically adopt a voltage outer loop control method when operating.
The multiplier 105 is configured to multiply the output signal of the island detector 101 with the voltage loop adjustment signal.
The current loop regulator 106 is configured to output a grid-connected inverter ac terminal current according to the output signal of the multiplier and the grid-connected side current value. In some embodiments, when the current loop regulator 106 operates, a current inner loop control method may be specifically adopted to control the current output by the grid-connected inverter to the power grid.
Some embodiments of the disclosed island detection method are described below in conjunction with fig. 2.
Fig. 2 shows a schematic flow diagram of an island detection method according to some embodiments of the present disclosure. As shown in fig. 2, the present embodiment includes steps S201 to S206.
In step S201, the angle and frequency of the grid-connected inverter ac terminal voltage are acquired.
After the grid-connected inverter is powered on and started, the island detector can initialize some parameters firstly. These parameters include: the angle of the grid-connected inverter alternating-current terminal voltage is obtained from the phase-locked loop (the initialization value is 0) at the current time, the angle of the grid-connected inverter alternating-current terminal voltage is obtained from the phase-locked loop at the last time (the initialization value is 0), the frequency of the grid-connected inverter alternating-current terminal voltage is obtained from the frequency detector at the current time (the initialization value is 0), and the frequency of the grid-connected inverter alternating-current terminal voltage is obtained from the frequency detector at the last time.
After the initialization parameters are completed, the phase-locked loop can monitor the angle of the alternating-current voltage of the inverter in real time, the frequency detector can monitor the frequency of the alternating-current voltage of the inverter in real time, the island detector acquires the angle of the alternating-current voltage of the grid-connected inverter from the phase-locked loop for multiple times, and meanwhile, the frequency detector acquires the angle of the alternating-current voltage of the grid-connected inverter from the frequency detector for.
In step S202, an angle disturbance applied to the grid-connected inverter ac terminal current is determined according to the angle and frequency of the grid-connected inverter ac terminal voltage.
Firstly, determining the absolute value f of the frequency difference between the frequency of the AC end voltage of the grid-connected inverter obtained this time and the frequency of the AC end voltage of the grid-connected inverter obtained last time.
And then, judging whether the frequency of the AC end voltage of the grid-connected inverter obtained at this time is within a preset frequency interval.
In some embodiments, the preset frequency interval is a continuous interval containing the rated frequency of the grid voltage. For example, the predetermined frequency interval may be (f)0-0.5，f0+0.2)，f0Representing the nominal frequency of the grid voltage.
Case (one): the frequency of the voltage of the alternating current end of the grid-connected inverter obtained at this time is not in a preset frequency interval.
And under the condition that the frequency of the AC voltage of the grid-connected inverter obtained at this time is not in a preset frequency interval, determining an angle difference theta' between the angle of the AC voltage of the grid-connected inverter obtained at this time and the angle of the AC voltage of the grid-connected inverter obtained at the last time, and determining the angle disturbance theta at this time according to the absolute value f of the frequency difference and the angle difference. The current angle disturbance is respectively in positive correlation with the absolute value of the frequency difference and the angle difference.
For example, the current angular disturbance may be determined by a formula θ '+ f × n, θ represents the current angular disturbance, θ' represents an angular difference, f represents an absolute value of the frequency difference, n represents a preset coefficient, and a specific value of n may be configured according to system requirements. One specific way to determine the value of n may be, for example, n 2 pi T200, where T represents the sampling period of the analog-to-digital conversion.
Under the condition that the frequency of the alternating-current terminal voltage of the grid-connected inverter obtained at this time is not within the preset frequency interval, if an island effect occurs, the absolute value of angle disturbance is always increased, and the increase of the accumulated value is increased more and more. Therefore, if the islanding causes that the grid side cannot effectively limit the angle of the current at the ac end of the inverter, and causes that the frequency and the angle of the voltage at the ac end of the inverter slightly change, the grid-connected inverter can amplify the slight change to detect the islanding.
Case (ii): the frequency of the alternating-current terminal voltage of the grid-connected inverter obtained at this time is in a preset frequency interval.
And under the condition that the frequency of the AC end voltage of the grid-connected inverter obtained at this time is within a preset frequency interval, determining the angle disturbance theta at this time according to the absolute value f of the frequency difference. The angle disturbance and the absolute value of the frequency difference are in positive correlation.
For example, the current angular disturbance is determined by the formula θ ═ f × n, θ represents the current angular disturbance, f represents the absolute value of the frequency difference, and n represents a preset coefficient.
The inventor considers that the angle disturbance applied by the traditional active detection mode has a great influence on the power generation quality. Therefore, under the condition that the frequency of the alternating-current end voltage of the grid-connected inverter is stabilized near the rated frequency, the angle disturbance is not calculated on the basis of the angle disturbance applied last time (namely, theta' is assigned to be 0), so that the influence on the power generation quality can be reduced in the process of actively detecting the island effect, the detection blind area of the island detection is reduced, and the power generation quality is considered at the same time.
In step S203, the angle disturbance is added to the angle of the grid-connected inverter ac voltage to obtain an angle sum.
In step S204, it is determined whether the angle sum is greater than a preset value.
And if the angle sum is larger than the preset value, executing step S205, detecting the occurrence of the islanding effect and alarming.
When the islanding occurs, the sum of the angle of the alternating-current end voltage of the inverter and the angle of the angle disturbance can be obviously increased, so that the islanding can be detected and an alarm can be given to remind related workers when the sum of the angles is larger than a preset value.
And if the angle sum is not greater than the preset value, executing step S206, and determining the current at the ac terminal of the grid-connected inverter according to the cosine value of the angle sum and the voltage loop adjusting signal output by the voltage loop adjuster.
For example, the cosine value of the angle summation may be multiplied by the voltage loop regulation signal output by the voltage loop regulator to serve as a current loop set value, and then the output grid-connected inverter ac terminal current may be determined further according to the current loop set value and the grid-connected side current value.
In the above embodiment, the real-time frequency and the real-time angle of the ac terminal voltage of the inverter are introduced into the active island detection at the same time, so that the detection blind area of the island detection can be effectively reduced, and the reliability and accuracy of the island detection are improved.
In some embodiments, step S202 further comprises: and limiting the amplitude of the angle disturbance.
Replacing the value of the angle disturbance with a first threshold value (e.g., 0.5) if the angle disturbance is greater than the first threshold value; in the case where the angular disturbance is smaller than a second threshold (e.g., -0.5), the value of the angular disturbance is replaced with the second threshold, which is smaller than the first threshold.
Carry out the amplitude limit through the angle disturbance, can avoid exerting too big angle disturbance suddenly, lead to the power generation quality to seriously worsen and even cause the system to seriously damage to further reduce the influence of active island detection to the power generation quality, promoted the security of active island detection process.
Some embodiments of the island detection arrangement of the present disclosure are described below in conjunction with fig. 3.
Fig. 3 shows a schematic structural diagram of an islanding detection apparatus according to some embodiments of the present disclosure. As shown in fig. 3, the islanding detection device 30 in the present embodiment includes: a signal acquisition module 301 configured to acquire an angle and a frequency of a grid-connected inverter ac terminal voltage; a disturbance determination module 302 configured to determine an angle disturbance applied to the grid-connected inverter ac terminal current according to the angle and frequency of the grid-connected inverter ac terminal voltage; an angle summation module 303 configured to sum the angle disturbance and an angle of an ac terminal voltage of the grid-connected inverter to obtain an angle summation; and an islanding detection module 304 configured to detect that an islanding effect occurs if the angle sum is greater than a preset value.
In some embodiments, the islanding detection apparatus 30 further includes a current determination module 305 configured to: and under the condition that the angle sum is not greater than the preset value, determining the current at the alternating current end of the grid-connected inverter according to the cosine value of the angle sum and the voltage loop adjusting signal output by the voltage loop adjuster.
In some embodiments, the disturbance determination module 302 is configured to: determining the absolute value of the frequency difference between the frequency of the AC end voltage of the grid-connected inverter obtained this time and the frequency of the AC end voltage of the grid-connected inverter obtained last time; under the condition that the frequency of the AC voltage of the grid-connected inverter obtained this time is not in a preset frequency interval, determining the angle difference between the angle of the AC voltage of the grid-connected inverter obtained this time and the angle of the AC voltage of the grid-connected inverter obtained last time, and determining the angle disturbance this time according to the absolute value of the frequency difference and the angle difference, wherein the angle disturbance this time is positively correlated with the absolute value of the frequency difference and the angle difference respectively.
In some embodiments, the disturbance determining module 302 is configured to determine the angular disturbance of the present time by using a formula θ ═ θ '+ f × n, θ represents the angular disturbance of the present time, θ' represents the angular difference, f represents the absolute value of the frequency difference, and n represents a preset coefficient.
Under the condition that the frequency of the alternating-current terminal voltage of the grid-connected inverter obtained at this time is not within the preset frequency interval, if an island effect occurs, the absolute value of angle disturbance is always increased, and the increase of the accumulated value is increased more and more. Therefore, if the islanding causes that the grid side cannot effectively limit the angle of the current at the ac end of the inverter, and causes that the frequency and the angle of the voltage at the ac end of the inverter slightly change, the grid-connected inverter can amplify the slight change to detect the islanding.
In some embodiments, the disturbance determination module 302 is further configured to: and under the condition that the frequency of the alternating-current terminal voltage of the grid-connected inverter obtained at this time is within a preset frequency interval, determining the angle disturbance at this time according to the absolute value of the frequency difference, wherein the angle disturbance at this time is positively correlated with the absolute value of the frequency difference.
In some embodiments, the disturbance determining module 302 is configured to determine the angular disturbance of this time by using a formula θ ═ f × n, θ represents the angular disturbance of this time, f represents an absolute value of the frequency difference, and n represents a preset coefficient.
The inventor considers that the angle disturbance applied by the traditional active detection mode has a great influence on the power generation quality. Therefore, under the condition that the frequency of the alternating-current end voltage of the grid-connected inverter is stabilized near the rated frequency, the angle disturbance is not calculated on the basis of the angle disturbance applied last time (namely, theta' is assigned to be 0), so that the influence on the power generation quality can be reduced in the process of actively detecting the island effect, the detection blind area of the island detection is reduced, and the power generation quality is considered at the same time.
In some embodiments, the preset frequency interval is a continuous interval containing the rated frequency of the grid voltage.
In some embodiments, the disturbance determination module 302 is further configured to: replacing the value of the angle disturbance with the first threshold value under the condition that the angle disturbance is greater than the first threshold value; and under the condition that the angle disturbance is smaller than a second threshold value, replacing the value of the angle disturbance with the second threshold value, wherein the second threshold value is smaller than the first threshold value.
Carry out the amplitude limit through the angle disturbance, can avoid exerting too big angle disturbance suddenly, lead to the power generation quality to seriously worsen and even cause the system to seriously damage to further reduce the influence of active island detection to the power generation quality, promoted the security of active island detection process.
In the above embodiment, the real-time frequency and the real-time angle of the ac terminal voltage of the inverter are introduced into the active island detection at the same time, so that the detection blind area of the island detection can be effectively reduced, and the reliability and accuracy of the island detection are improved.
The present disclosure also includes a computer-readable storage medium having stored thereon computer instructions that, when executed by a processor, implement the islanding detection method in any of the foregoing embodiments.
The present disclosure is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the disclosure. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only exemplary of the present disclosure and is not intended to limit the present disclosure, so that any modification, equivalent replacement, or improvement made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.
Claims (20)
1. An islanding detection method, comprising:
acquiring the angle and frequency of the AC end voltage of the grid-connected inverter;
determining angle disturbance applied to the alternating-current end current of the grid-connected inverter according to the angle and the frequency of the alternating-current end voltage of the grid-connected inverter;
adding the angle disturbance and the angle of the alternating-current end voltage of the grid-connected inverter to obtain an angle sum;
and detecting the occurrence of the islanding effect under the condition that the angle sum is larger than a preset value.
2. The islanding detection method of claim 1, further comprising:
and under the condition that the angle sum is not greater than a preset value, determining the current of the alternating current end of the grid-connected inverter according to the cosine value of the angle sum and a voltage loop adjusting signal output by the voltage loop adjuster.
3. The islanding detection method of claim 1, wherein the determining the angle disturbance applied to the grid-connected inverter ac terminal current according to the angle and frequency of the grid-connected inverter ac terminal voltage comprises:
determining the absolute value of the frequency difference between the frequency of the AC end voltage of the grid-connected inverter obtained this time and the frequency of the AC end voltage of the grid-connected inverter obtained last time;
and under the condition that the frequency of the AC voltage of the grid-connected inverter obtained this time is not in a preset frequency interval, determining the angle difference between the angle of the AC voltage of the grid-connected inverter obtained this time and the angle of the AC voltage of the grid-connected inverter obtained last time, and determining the angle disturbance this time according to the absolute value of the frequency difference and the angle difference, wherein the angle disturbance this time is positively correlated with the absolute value of the frequency difference and the angle difference respectively.
4. The islanding detection method according to claim 3, wherein the angular disturbance of this time is determined by a formula θ '+ f n, θ represents the angular disturbance of this time, θ' represents the angular difference, f represents the absolute value of the frequency difference, and n represents a preset coefficient.
5. The islanding detection method of claim 3, wherein the determining the angle disturbance applied to the grid-connected inverter AC terminal current according to the angle and frequency of the grid-connected inverter AC terminal voltage further comprises:
and under the condition that the frequency of the AC end voltage of the grid-connected inverter obtained at this time is within a preset frequency interval, determining the angle disturbance at this time according to the absolute value of the frequency difference, wherein the angle disturbance at this time is positively correlated with the absolute value of the frequency difference.
6. The islanding detection method according to claim 5, wherein the angular disturbance of this time is determined by a formula θ ═ f × n, θ represents the angular disturbance of this time, f represents the absolute value of the frequency difference, and n represents a preset coefficient.
7. An islanding detection method according to any of claims 3 to 6, wherein the predetermined frequency interval is a continuous interval containing a rated frequency of the grid voltage.
8. The island detection method according to any one of claims 3 to 6, wherein the determining of the angle disturbance applied to the grid-connected inverter AC terminal current according to the angle and frequency of the grid-connected inverter AC terminal voltage further comprises:
replacing the value of the angle disturbance with a first threshold value under the condition that the angle disturbance is greater than the first threshold value;
and under the condition that the angle disturbance is smaller than a second threshold value, replacing the value of the angle disturbance with the second threshold value, wherein the second threshold value is smaller than the first threshold value.
9. A grid-tied inverter comprising:
a memory; and
a processor coupled to the memory, the processor configured to perform the islanding detection method of any of claims 1-8 based on instructions stored in the memory.
10. The grid-connected inverter according to claim 9, further comprising:
a phase-locked loop configured to detect an angle of an ac terminal voltage of the grid-connected inverter;
and a frequency detector configured to detect a frequency of the grid-connected inverter ac terminal voltage.
11. The grid-connected inverter according to claim 9 or 10, further comprising:
a voltage loop regulator configured to output a voltage loop regulation signal according to a reference value and an actual value of a bus voltage of the grid-connected inverter;
a multiplier configured to multiply the angle-summed cosine value by a voltage loop adjustment signal;
and the current loop regulator is configured to output the grid-connected inverter alternating current terminal current according to the output signal of the multiplier and the grid-connected side current value.
12. A computer readable storage medium, wherein the computer readable storage medium stores computer instructions which, when executed by a processor, implement the islanding detection method of any of claims 1 to 8.
13. An islanding detection apparatus, comprising:
the signal acquisition module is configured to acquire the angle and the frequency of the alternating-current end voltage of the grid-connected inverter;
the disturbance determining module is configured to determine angle disturbance applied to the alternating-current end current of the grid-connected inverter according to the angle and the frequency of the alternating-current end voltage of the grid-connected inverter;
the angle adding module is configured to add the angle disturbance and the angle of the alternating-current voltage of the grid-connected inverter to obtain angle addition;
and the island detection module is configured to detect that the island effect occurs under the condition that the angle sum is greater than a preset value.
14. The islanding detection device of claim 13, further comprising a current determination module configured to: and under the condition that the angle sum is not greater than a preset value, determining the current of the alternating current end of the grid-connected inverter according to the cosine value of the angle sum and a voltage loop adjusting signal output by the voltage loop adjuster.
15. The islanding detection device of claim 13, wherein the disturbance determination module is configured to:
determining the absolute value of the frequency difference between the frequency of the AC end voltage of the grid-connected inverter obtained this time and the frequency of the AC end voltage of the grid-connected inverter obtained last time;
and under the condition that the frequency of the AC voltage of the grid-connected inverter obtained this time is not in a preset frequency interval, determining the angle difference between the angle of the AC voltage of the grid-connected inverter obtained this time and the angle of the AC voltage of the grid-connected inverter obtained last time, and determining the angle disturbance this time according to the absolute value of the frequency difference and the angle difference, wherein the angle disturbance this time is positively correlated with the absolute value of the frequency difference and the angle difference respectively.
16. The islanding detection device of claim 15, wherein the disturbance determination module is configured to determine the angular disturbance this time by a formula θ ═ θ '+ f × n, θ represents the angular disturbance this time, θ' represents the angular difference, f represents the absolute value of the frequency difference, and n represents a preset coefficient.
17. The islanding detection device of claim 15, wherein the disturbance determination module is further configured to: and under the condition that the frequency of the AC end voltage of the grid-connected inverter obtained at this time is within a preset frequency interval, determining the angle disturbance at this time according to the absolute value of the frequency difference, wherein the angle disturbance at this time is positively correlated with the absolute value of the frequency difference.
18. The islanding detection device of claim 17, wherein the disturbance determination module is configured to determine the angular disturbance this time by a formula θ ═ f × n, θ represents the angular disturbance this time, f represents the absolute value of the frequency difference, and n represents a preset coefficient.
19. An islanding detection device according to any one of claims 15 to 18, wherein the predetermined frequency interval is a continuous interval containing a rated frequency of the grid voltage.
20. The islanding detection device of any of claims 15 to 18, wherein the disturbance determination module is further configured to: replacing the value of the angle disturbance with a first threshold value under the condition that the angle disturbance is greater than the first threshold value; and under the condition that the angle disturbance is smaller than a second threshold value, replacing the value of the angle disturbance with the second threshold value, wherein the second threshold value is smaller than the first threshold value.
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| WO2021189873A1 (en) * | 2020-03-23 | 2021-09-30 | 珠海格力电器股份有限公司 | Island detection method and apparatus, grid-connected inverter, and computer readable storage medium |
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