CN113740760B - Method and device for rapid fault detection of alternating current power supply - Google Patents
Method and device for rapid fault detection of alternating current power supply Download PDFInfo
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- G01R19/16538—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the application in AC or DC supplies
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Abstract
Embodiments of the present disclosure disclose a method and apparatus for rapid fault detection of an ac power source. The method for carrying out rapid fault detection on the alternating current power supply comprises the following steps: detecting zero crossing points of input voltage provided by the alternating current power supply to obtain a period T of the input voltage; when the zero crossing point is detected, calculating the root mean square of the input voltage in the period before the period where the current moment is located; determining a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage; and comparing the fault detection function with the input voltage to determine whether the ac power source is faulty.
Description
Technical Field
The present disclosure relates to the field of electronic devices, and more particularly, to methods and apparatus for rapid fault detection of ac power sources.
Background
Early line fault detection for Alternating Current (AC) power supplies can issue warnings to take rapid action to ensure power stability and reduce damage to equipment, and is therefore critical for high performance power converters. Accordingly, many single-phase or three-phase power systems require rapid AC power failure detection to take early action. For example, a fast AC power failure signal may trigger an Automatic Transfer Switch (ATS), or signal a computer to save data to persistent memory.
In order to perform fast AC power failure detection, some solutions have been proposed in recent years. In patent document 1, the interval length between the rising edge and the falling edge may be measured with a microprocessor to indirectly measure the amplitude (for example, the mean square error (RMS) or the peak value) of the main power supply voltage. However, non-sinusoidal alternating current distortion may lead to measurement errors. In patent document 2, whether or not the three-phase power supply is broken is determined from the ripple voltage delta V. However, delta V is filtered by a bulk capacitor, which results in a reduced detection speed. In patent document 3, a power failure condition is declared when the voltage across the tank circuit decays below a selected threshold or no current to the tank circuit is detected for a selected time. However, the earliest detection time is at least a half-cycle time. In patent document 4, an impending failure in the power grid is detected by checking line data in the frequency domain. In practice, this is a later analysis, not immediate AC power failure detection. In patent document 5, the output waveform of the synchronous bandpass filter is post-processed to determine whether or not there is a fault in the power supply system by comparing a waveform representing the amplitude of a predefined harmonic frequency component with an unbalance reference value, thereby generating a fault detector output signal. However, this method cannot be applied to distorted non-sinusoidal AC power sources.
Prior art literature
Patent literature
Patent document 1: EP2861997A1
Patent document 2: CN103033769A
Patent document 3: US4642616
Patent document 4: US7490013
Patent document 5: US8513951
Disclosure of Invention
In view of the above, the present disclosure proposes a method and apparatus for rapid fault detection of an AC power source, thereby being capable of rapidly detecting an AC power source fault, being capable of solving the problem of multi-phase voltage unbalance, and being effectively applied to any shape of input voltage waveform provided by an AC power source.
According to a first aspect of the present disclosure, there is provided a method for rapid fault detection of an ac power source, comprising:
detecting zero crossing points of input voltage provided by the alternating current power supply to obtain a period T of the input voltage;
when the zero crossing point is detected, calculating the root mean square of the input voltage in the period before the period where the current moment is located;
determining a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage; and
the fault detection function is compared to the input voltage to determine whether the ac power source is faulty.
In one embodiment, determining the fault detection function based on the warning level of the ac power source and the root mean square of the input voltage comprises:
for a positive half-cycle of the input voltage, the fault detection function F (t) is determined according to:
f (T) =R (T) ·V (T-T) -B, when R (T) ·V (T-T) -B is not less than 0,
f (T) =0, when R (T) ·v (T-T) -B <0;
for a negative half-cycle of the input voltage, the fault detection function F (t) is determined according to:
f (T) =R (T) ·V (T-T) +B, when R (T) ·V (T-T) +B is less than or equal to 0,
f (T) =0, when R (T) ·V (T-T) +B >0,
wherein ,
t is time, V (t) is the input voltage, V warning Is the warning level, V rms_fil (0) Is a predetermined value, V rms (t) is the root mean square, V, of the input voltage in the period preceding the period in which the current time t is located rms_fil (T-T) is a filtered value of the root mean square of the input voltage in the period immediately preceding the period in which the current time T is located, n is a natural number, A is an adjustable gain value, and B is a predetermined value.
In one embodiment, the warning level of the ac power source is an under-voltage warning level,
determining a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage includes: determining an under-voltage fault detection function according to the under-voltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
Comparing the fault detection function with the input voltage to determine whether the ac power source is faulty includes: and determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is larger than the absolute value of the input voltage.
In one embodiment, the method further comprises:
when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining an overvoltage fault detection function according to an overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and
and determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is smaller than the absolute value of the input voltage.
In one embodiment, the method further comprises:
and when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining that the alternating current power supply has no fault.
In one embodiment, the warning level of the ac power source is an over-voltage warning level,
determining a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage includes: determining an overvoltage fault detection function according to the overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
Comparing the fault detection function with the input voltage to determine whether the ac power source is faulty includes: and determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is smaller than the absolute value of the input voltage.
In one embodiment, the method further comprises:
when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining an undervoltage fault detection function according to the undervoltage warning level of the alternating current power supply and the root mean square of the input voltage; and
and determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is larger than the absolute value of the input voltage.
In one embodiment, the method further comprises:
and when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining that the alternating current power supply has no fault.
According to a second aspect of the present disclosure, there is provided an apparatus for rapid fault detection of an ac power source, comprising:
a detection module configured to detect zero crossings of an input voltage provided by the ac power source to obtain a period T of the input voltage;
a calculation module configured to calculate, when the zero crossing point is detected, a root mean square of the input voltage in a period preceding a period in which the current time is located;
a determining module configured to determine a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage; and
a comparison module is configured to compare the fault detection function with the input voltage to determine whether the ac power source is faulty.
In one embodiment, the determination module is further configured to:
for a positive half-cycle of the input voltage, the fault detection function F (t) is determined according to:
f (T) =R (T) ·V (T-T) -B, when R (T) ·V (T-T) -B is not less than 0,
f (T) =0, when R (T) ·v (T-T) -B <0;
for a negative half-cycle of the input voltage, the fault detection function F (t) is determined according to:
f (T) =R (T) ·V (T-T) +B, when R (T) ·V (T-T) +B is less than or equal to 0,
f (T) =0, when R (T) ·V (T-T) +B >0,
wherein ,
t is time, V (t) is the input voltage, V warning Is the warning level, V rms_fil (0) Is a predetermined value, V rms (t) is the root mean square, V, of the input voltage in the period preceding the period in which the current time t is located rms_fil (T-T) is a filtered value of the root mean square of the input voltage in the period immediately preceding the period in which the current time T is located, n is a natural number, A is an adjustable gain value, and B is a predetermined value.
In one embodiment, the warning level of the ac power source is an under-voltage warning level,
the determination module is further configured to: determining an under-voltage fault detection function according to the under-voltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
The comparison module is further configured to: and determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is larger than the absolute value of the input voltage.
In one embodiment, the determination module is further configured to:
when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining an overvoltage fault detection function according to an overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
The comparison module is further configured to: and determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is smaller than the absolute value of the input voltage.
In one embodiment, the comparison module is further configured to: and when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining that the alternating current power supply has no fault.
In one embodiment, the warning level of the ac power source is an over-voltage warning level,
the determination module is further configured to: determining an overvoltage fault detection function according to the overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
The comparison module is further configured to: and determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is smaller than the absolute value of the input voltage.
In one embodiment, the determination module is further configured to:
when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining an undervoltage fault detection function according to the undervoltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
The comparison module is further configured to: and determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is larger than the absolute value of the input voltage.
In one embodiment, the comparison module is further configured to: and when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining that the alternating current power supply has no fault.
Drawings
FIG. 1 shows a schematic diagram of an AC power sampling circuit according to an embodiment of the present disclosure;
FIG. 2 illustrates a flow chart of a method for rapid fault detection of an AC power source in accordance with an embodiment of the present disclosure;
FIG. 3 illustrates a block diagram of an apparatus for rapid fault detection of an AC power source in accordance with an embodiment of the present disclosure;
FIG. 4 illustrates a normal waveform diagram of an AC voltage and fault detection function for brown-out detection in accordance with an embodiment of the present disclosure;
FIG. 5 illustrates an example of AC voltage drop detection for brown-out detection in accordance with an embodiment of the present disclosure;
FIG. 6 illustrates an example of AC slump detection for brown-out detection according to an embodiment of the present disclosure;
FIG. 7 illustrates a waveform diagram of an AC voltage with flat top and fault detection function for brown-out detection in accordance with an embodiment of the present disclosure;
FIG. 8 illustrates a normal waveform diagram of an AC voltage and fault detection function for overvoltage detection according to an embodiment of the present disclosure; and
fig. 9 illustrates an example of AC voltage frequency offset detection according to an embodiment of the present disclosure.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is only exemplary and is not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the concepts of the present disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The words "a", "an", and "the" as used herein are also intended to include the meaning of "a plurality", etc., unless the context clearly indicates otherwise. Furthermore, the terms "comprises," "comprising," and the like, when used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It should be noted that the terms used herein should be construed to have meanings consistent with the context of the present specification and should not be construed in an idealized or overly formal manner.
First, an AC power sampling circuit according to an embodiment of the present disclosure is described with reference to fig. 1. Fig. 1 shows a schematic diagram of an AC power sampling circuit according to an embodiment of the present disclosure. As shown in fig. 1, an AC power source 101 is connected to a device 103 through a fuse 102 and is used to power the device 103. A sampling device, such as a microcontroller unit (MCU), may accurately sample the AC input voltage provided by AC power source 101 via sensing points 104 and 105. The sampling device may store the entire waveform of a complete AC cycle of the AC power source 101 for later use in rapid AC power failure detection.
Fig. 2 illustrates a flow chart of a method 200 for rapid fault detection of an ac power source according to an embodiment of the present disclosure.
The method 200 may begin at step S210. In step S210, a zero crossing of an input voltage (i.e., an AC voltage) supplied from an AC power source (e.g., AC power source 101 shown in fig. 1) may be detected to obtain a period T of the input voltage. Here, the zero crossing point refers to a point at which the waveform of the AC voltage intersects the horizontal axis (i.e., a point at which the AC voltage is zero), at which the voltage difference between the sensing points 104 and 105 shown in fig. 1 is 0.
In step S220, when the zero crossing point is detected, the root mean square of the input voltage in the period preceding the period in which the current time is located may be calculated.
In step S230, a fault detection function may be determined based on the warning level of the ac power source and the root mean square of the input voltage. The warning level of the alternating voltage may be an under-voltage warning level or an over-voltage warning level. Step S230 may include: for a positive half-cycle of the input voltage (i.e., a half-cycle in which the input voltage is positive), the fault detection function F (t) is determined according to equation 1:
f (T) =R (T) ·V (T-T) -B, when R (T) ·V (T-T) -B is not less than 0,
equation 1
F (T) =0, when R (T) ·v (T-T) -B <0;
for negative half cycles of the input voltage (i.e., half cycles where the input voltage is negative), the fault detection function F (t) is determined according to equation 2:
f (T) =R (T) ·V (T-T) +B, when R (T) ·V (T-T) +B is less than or equal to 0,
equation 2
F (T) =0, when R (T) ·V (T-T) +B >0,
wherein ,
and R (t) is typically for under-voltage detection<1, R (t) for overpressure detection>1，/>
t is time, V (t) is the input voltage, V warning Is a warning level, V rms_fil (0) Is a predetermined value, V rms (t) is the root mean square, V, of the input voltage in the period preceding the period in which the current time t is located rms_fil (T-T) is a filtered value of the root mean square of the input voltage in the period immediately preceding the period in which the current time T is located, n is a natural number, a is an adjustable gain value, and is typically taken to be 1, and B is a predetermined value. In one example, n=4 and a=1 to ensure that for V rms_fil Is sufficient for filtering.
In the first embodiment, the warning level of the ac power source may be an under-voltage warning level, and step S230 may include: the brown-out fault detection function is determined based on the brown-out warning level of the ac power supply and the root mean square of the input voltage.
In step S240, the fault detection function may be compared to the input voltage to determine whether the ac power source is faulty.
In the first embodiment, step S240 may include: when the absolute value of the brown-out fault detection function is greater than the absolute value of the input voltage (i.e., equation 3 is satisfied), it is determined that a brown-out fault is detected.
V (t) | < F (t) |Eq.3
In a first embodiment, the method 200 may further include: the overvoltage fault detection function is determined according to an overvoltage warning level of the ac power supply and a root mean square of the input voltage when an absolute value of the overvoltage fault detection function is less than or equal to an absolute value of the input voltage, and it is determined that the overvoltage fault is detected when the absolute value of the overvoltage fault detection function is less than the absolute value of the input voltage (i.e., equation 4 is satisfied), and it is determined that the ac power supply has not failed when the absolute value of the overvoltage fault detection function is greater than or equal to the absolute value of the input voltage.
V (t) | > F (t) |Eq.4
It should be noted that the overvoltage fault detection function may also be determined based on the overvoltage warning level of the ac power supply and the root mean square of the input voltage, and whether an overvoltage fault occurs based on the overvoltage fault detection function, and if not, then the undervoltage fault detection function may be determined based on the undervoltage warning level of the ac power supply and the root mean square of the input voltage, and whether an undervoltage fault occurs based on the undervoltage fault detection function.
Specifically, in the second embodiment, the warning level of the ac power source may be an overvoltage warning level, and step S230 may include: an overvoltage fault detection function is determined based on the rms of the input voltage and the overvoltage warning level of the ac power supply.
In the second embodiment, step S240 may include: when the absolute value of the overvoltage fault detection function is less than the absolute value of the input voltage, it is determined that an overvoltage fault is detected.
In a second embodiment, the method 200 may further include: the under-voltage fault detection function is determined according to the under-voltage warning level of the ac power supply and the root mean square of the input voltage when the absolute value of the under-voltage fault detection function is greater than or equal to the absolute value of the input voltage, and the under-voltage fault is determined to be detected when the absolute value of the under-voltage fault detection function is greater than the absolute value of the input voltage, and the ac power supply is determined to have not failed when the absolute value of the under-voltage fault detection function is less than or equal to the absolute value of the input voltage.
Since there is no input voltage (e.g., the input voltage value has not been stored in the sampling device) when the AC power source is initially powered up, a second trigger condition may also be set in order to prevent false triggering from occurring, as shown in equation 5:
V rms_uvw <V rms_fil (t)<V rms_ovw equation 5
wherein Vrms_uvw Is a voltage threshold for under-voltage warning, and V rms_ovw Is the voltage threshold for an over-voltage warning.
Thus, in the above-described first and second embodiments, instead of determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is greater than the absolute value of the input voltage (i.e., equation 3 is satisfied), it is determined that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is greater than the absolute value of the input voltage (i.e., equation 3 is satisfied) and equation 5 is also satisfied; and instead of determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is less than the absolute value of the input voltage (i.e., equation 4 is satisfied), the overvoltage fault is determined to be detected when the absolute value of the overvoltage fault detection function is less than the absolute value of the input voltage (i.e., equation 4 is satisfied) and equation 5 is also satisfied.
Further, in the case where the AC power source is a multi-phase voltage source, an input signal provided by the multi-phase voltage source may be divided into a plurality of single-phase signals, and then a method for rapid fault detection of the AC power source according to an embodiment of the present disclosure is separately applied to each of the multi-phase signals for fault detection.
Fig. 3 illustrates a block diagram of an apparatus 300 for rapid fault detection of an ac power source in accordance with an embodiment of the present disclosure. The apparatus 300 may include: the detection module 310, the calculation module 320, the determination module 330, and the comparison module 340.
The detection module 310 may be configured to detect zero crossings of an input voltage provided by the ac power source to obtain a period T of the input voltage.
The calculation module 320 may be configured to calculate a root mean square of the input voltage in a period preceding a period in which the current time is located when the zero crossing point is detected.
The determination module 330 may be configured to determine the fault detection function based on the warning level of the ac power source and the root mean square of the input voltage. The determination module 330 may be further configured to: the fault detection function F (t) is determined according to equation 1 for the positive half-cycle of the input voltage and according to equation 2 for the negative half-cycle of the input voltage.
The comparison module 340 may be configured to compare the fault detection function to the input voltage to determine whether the ac power source is malfunctioning.
The warning level of the ac power supply may be an under-voltage warning level or an over-voltage warning level, and two embodiments will be described below in a different order of detecting an under-voltage fault and detecting an over-voltage fault.
In one embodiment, when the warning level of the ac power source is an under-voltage warning level, the determination module 330 may be further configured to: determining an undervoltage fault detection function according to the undervoltage warning level of the alternating current power supply and the root mean square of the input voltage; and the comparison module 340 may be further configured to: when the absolute value of the under-voltage fault detection function is greater than the absolute value of the input voltage, it is determined that an under-voltage fault is detected. The determination module 330 may be further configured to: when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining the overvoltage fault detection function according to the overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and the comparison module 340 may be further configured to: the overvoltage fault is determined to be detected when the absolute value of the overvoltage fault detection function is less than the absolute value of the input voltage, and the ac power supply is determined to be not faulty when the absolute value of the overvoltage fault detection function is greater than or equal to the absolute value of the input voltage.
In another embodiment, when the warning level of the ac power source is an over-voltage warning level, the determination module 330 may be further configured to: determining an overvoltage fault detection function according to the overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and the comparison module 340 may be further configured to: when the absolute value of the overvoltage fault detection function is less than the absolute value of the input voltage, it is determined that an overvoltage fault is detected. The determination module 330 may be further configured to: when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining the undervoltage fault detection function according to the undervoltage warning level of the alternating current power supply and the root mean square of the input voltage; and the comparison module 340 may be further configured to: the under-voltage fault is determined to be detected when the absolute value of the under-voltage fault detection function is greater than the absolute value of the input voltage, and the ac power supply is determined to be not faulty when the absolute value of the under-voltage fault detection function is less than or equal to the absolute value of the input voltage.
Fig. 4 shows a normal waveform diagram of the AC voltage and fault detection function for brown-out detection.
As can be seen from fig. 4, 401 represents an AC input voltage Vac, which is sinusoidal in waveform. 402 represents a fault detection function F (t) calculated for undervoltage detection by equations 1 and 2, where B in equations 1 and 2 takes a positive value. Suppose V for under-voltage detection warning Less than V rms_fil . If the instantaneous voltage Vac suddenly drops below the fault detection function F (t), the trigger condition for rapid under-voltage detection is satisfied, i.e., equation 3 is satisfied. Some prompt measures may be taken to protect the system or reduce damage, such as notifying a computer (load) to save data to persistent memory before the energy buffer of the converter is exhausted.
Fig. 5 and 6 show waveforms of AC voltage and fault detection function for undervoltage detection, respectively.
The AC voltage drop is shown in fig. 5. 501 represents an AC input voltage Vac.502 represents a fault detection function F (t) calculated for brown-out detection by equations 1 and 2. 503 denotes a detection point at which Vac falls below F (t). Since F (t) is generally closer to Vac than to zero-crossing except near the zero-crossing, and because of the slope of the falling path of Vac, the detection point 503 occurs slightly earlier than when Vac contacts the zero-crossing. For example, at detection point 503, an under-voltage fault can be detected.
In addition to the case of the AC voltage dip shown in fig. 5, fig. 6 also shows that the AC voltage dip is V warning The following is the case. 601 denotes an AC input voltage Vac, which is a sinusoidal voltage waveform. 602 represents a fault detection function F (t) calculated for brown-out detection by equations 1 and 2, the waveform of which has a root-mean-square value V warning And + -B. 603 represents a voltage dip trigger point where the AC voltage drops from normal to F (t). For example, at the slump trigger point 603, an brown-out fault can be detected.
Fig. 7 shows a waveform diagram of an AC voltage with flat top and fault detection function for brown-out detection according to an embodiment of the present disclosure. In fig. 7, 701 represents a distorted AC voltage waveform with a flat top, which is very common in AC lines or more severe at the output of an Uninterruptible Power Supply (UPS) inverter. Suppose for under-voltage detection, V warning Less than V rms_fil Then 702 represents the fault detection function F (t) calculated for brown-out detection by equations 1 and 2, where B in equations 1 and 2 takes a positive value. For the waveform diagram of fig. 7, when the brown-out fault occurs, the detection point of the brown-out fault is determined in a manner similar to that of the detection points 503 and 603 of fig. 5 and 6.
Similar to the normal AC voltage waveforms for under-voltage detection in fig. 4, fig. 8 shows a normal waveform diagram of AC voltage and fault detection functions for over-voltage detection according to an embodiment of the present disclosure. 801 represents an AC input voltage Vac, which is sinusoidal. 802 denotes a fault detection function F (t) calculated for overvoltage detection by equations 1 and 2, wherein B in equations 1 and 2 takes a negative value. Suppose for overvoltage detection, V warning Greater than V rms_fil . If the instantaneous voltage Vac suddenly rises above F (t), the trigger condition for rapid overvoltage detection is satisfied, i.e., equation 4 is satisfied. The power consuming device at the output may consider taking appropriate action after receiving the fast AC fault detection signal.
Fig. 9 illustrates an example of AC voltage frequency offset detection according to an embodiment of the present disclosure. The method according to the present disclosure is able to detect sudden changes in line frequency even if the RMS voltage remains unchanged. In fig. 9, 901 and 902 respectively represent the frequency f 0 An AC line voltage waveform Vac and a fault detection function F (t). 903 indicates that the frequency starts from f 0 Change to f 1 (in this example, f 1 >f 0 ). 906 is the same waveform as 901 for reference, and 905 is an ac voltage waveform after the frequency change after 903. Reference numeral 904 denotes a detection point at which the waveform 905 falls below the waveform 902, and 902 denotes a fault detection function F (t) calculated by equations 1 and 2 for the waveform 901 before 903. The time required for detection is less than one cycle. Furthermore, the method according to the present disclosure may also be applied to detect the slave f 0 To f 1 (f 1 <f 0 ) Is a frequency change of (c).
It should be noted that the method for rapid fault detection of an ac power source according to embodiments of the present disclosure may also be applied to other distorted ac waveforms. For example, in some ATS applications having multiple source inputs, ac line switching operations may cause phase changes. Alternating currents recovered at different angles may also be detected according to the methods of the present disclosure. As another example, the loading of certain power devices may cause the local AC line voltage level to be non-uniform between positive and negative periods. Since the method according to the present disclosure uses the previous complete cycle to form F (t), the detection is still valid in this case.
According to the embodiments of the present disclosure, since the method and apparatus according to the embodiments of the present disclosure use the previous full-period AC voltage waveform for current waveform detection, fault detection can be rapidly implemented, and furthermore, since a fault detection function can be flexibly formed by the original periodic waveform, the method and apparatus according to the embodiments of the present disclosure can be effectively applied to any shape of input voltage waveform.
Some of the block diagrams and/or flowchart illustrations are shown in the figures. It will be understood that some blocks of the block diagrams and/or flowchart illustrations, or combinations of blocks in the block diagrams and/or flowchart illustrations, 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, or other programmable data processing apparatus, such that the instructions, when executed by the processor, create means for implementing the functions/acts specified in the block diagrams and/or flowchart.
Thus, the techniques of this disclosure may be implemented in hardware and/or software (including firmware, microcode, etc.). Additionally, the techniques of this disclosure may take the form of a computer program product on a computer-readable medium having instructions stored thereon, the computer program product being usable by or in connection with an instruction execution system (e.g., one or more processors). In the context of this disclosure, a computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the instructions. For example, a computer-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. Specific examples of the computer readable medium include: magnetic storage devices such as magnetic tape or hard disk (HDD); optical storage devices such as compact discs (CD-ROMs); a memory, such as a Random Access Memory (RAM) or a flash memory; and/or a wired/wireless communication link.
The foregoing detailed description has set forth numerous embodiments of methods and apparatus for rapid fault detection of ac power sources using schematics, flowcharts, and/or examples. Where such diagrams, flowcharts, and/or examples contain one or more functions and/or operations, it will be understood by those skilled in the art that each function and/or operation of such diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of structures, hardware, software, firmware, or virtually any combination thereof. In one embodiment, portions of the subject matter described in embodiments of the present disclosure may be implemented by Application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs), digital Signal Processors (DSPs), or other integrated formats. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein, in whole or in part, can be equivalently implemented in integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the software and/or firmware code therefor would be well within the skill of one of skill in the art in light of this disclosure. Moreover, those skilled in the art will appreciate that the mechanisms of the subject matter described in this disclosure are capable of being distributed as a program product in a variety of forms, and that an exemplary embodiment of the subject matter described herein applies regardless of the particular type of signal bearing media used to actually carry out the distribution. Examples of signal bearing media include, but are not limited to: recordable media such as floppy disks, hard disk drives, compact Discs (CDs), digital Versatile Discs (DVDs), digital magnetic tapes, computer memory, and the like; and transmission media such as digital and/or analog communications media (e.g., fiber optic cables, waveguides, wired communications links, wireless communications links, etc.).
Claims (14)
1. A method for rapid fault detection of an ac power source, comprising:
detecting zero crossing points of input voltage provided by the alternating current power supply to obtain a period T of the input voltage;
when the zero crossing point is detected, calculating the root mean square of the input voltage in the period before the period where the current moment is located;
determining a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage; and
comparing the fault detection function with the input voltage to determine whether the ac power source is faulty,
wherein determining a fault detection function based on the warning level of the ac power source and the root mean square of the input voltage comprises:
for a positive half-cycle of the input voltage, the fault detection function F (t) is determined according to:
f (T) =R (T) ·V (T-T) -B, when R (T) ·V (T-T) -B is not less than 0,
f (T) =0, when R (T) ·V (T-T) -B <0,
for a negative half-cycle of the input voltage, the fault detection function F (t) is determined according to:
f (T) =R (T) ·V (T-T) +B, when R (T) ·V (T-T) +B is less than or equal to 0,
f (T) =0, when R (T) ·V (T-T) +B >0,
wherein ,
t is time, V (t) is the input voltage, V warning Is the warning level, V rms_fil (0) Is a predetermined value, V rms (t) is the root mean square, V, of the input voltage in the period preceding the period in which the current time t is located rms_fil (T-T) is a filtered value of the root mean square of the input voltage in the period immediately preceding the period in which the current time T is located, n is a natural number, A is an adjustable gain value, and B is a predetermined value.
2. The method of claim 1, wherein,
the warning level of the ac power source is an under-voltage warning level,
determining a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage includes: determining an under-voltage fault detection function according to the under-voltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
Comparing the fault detection function with the input voltage to determine whether the ac power source is faulty includes: and determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is larger than the absolute value of the input voltage.
3. The method of claim 2, further comprising:
when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining an overvoltage fault detection function according to an overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and
and determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is smaller than the absolute value of the input voltage.
4. A method according to claim 3, further comprising:
and when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining that the alternating current power supply has no fault.
5. The method of claim 1, wherein,
the warning level of the ac power source is an overvoltage warning level,
determining a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage includes: determining an overvoltage fault detection function according to the overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
Comparing the fault detection function with the input voltage to determine whether the ac power source is faulty includes: and determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is smaller than the absolute value of the input voltage.
6. The method of claim 5, further comprising:
when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining an undervoltage fault detection function according to the undervoltage warning level of the alternating current power supply and the root mean square of the input voltage; and
and determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is larger than the absolute value of the input voltage.
7. The method of claim 6, further comprising:
and when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining that the alternating current power supply has no fault.
8. An apparatus for rapid fault detection of an ac power source, comprising:
a detection module configured to detect zero crossings of an input voltage provided by the ac power source to obtain a period T of the input voltage;
a calculation module configured to calculate, when the zero crossing point is detected, a root mean square of the input voltage in a period preceding a period in which the current time is located;
a determining module configured to determine a fault detection function based on a warning level of the ac power source and a root mean square of the input voltage; and
a comparison module configured to compare the fault detection function with the input voltage to determine whether the ac power source is faulty,
wherein the determination module is further configured to:
for a positive half-cycle of the input voltage, the fault detection function F (t) is determined according to:
f (T) =R (T) ·V (T-T) -B, when R (T) ·V (T-T) -B is not less than 0,
f (T) =0, when R (T) ·v (T-T) -B <0;
for a negative half-cycle of the input voltage, the fault detection function F (t) is determined according to:
f (T) =R (T) ·V (T-T) +B, when R (T) ·V (T-T) +B is less than or equal to 0,
f (T) =0, when R (T) ·V (T-T) +B >0,
wherein ,
t is time, V (t) is the input voltage, V warning Is the warning level, V rms_fil (0) Is a predetermined value, V rms (t) is the root mean square, V, of the input voltage in the period preceding the period in which the current time t is located rms_fil (T-T) is a filtered value of the root mean square of the input voltage in the period immediately preceding the period in which the current time T is located, n is a natural number, A is an adjustable gain value, and B is a predetermined value.
9. The apparatus of claim 8, wherein the warning level of the AC power source is an under-voltage warning level,
the determination module is further configured to: determining an under-voltage fault detection function according to the under-voltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
The comparison module is further configured to: and determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is larger than the absolute value of the input voltage.
10. The apparatus of claim 9, wherein the determination module is further configured to:
when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining an overvoltage fault detection function according to an overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
The comparison module is further configured to: and determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is smaller than the absolute value of the input voltage.
11. The apparatus of claim 10, wherein the comparison module is further configured to: and when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining that the alternating current power supply has no fault.
12. The apparatus of claim 8, wherein the warning level of the AC power source is an over-voltage warning level,
the determination module is further configured to: determining an overvoltage fault detection function according to the overvoltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
The comparison module is further configured to: and determining that an overvoltage fault is detected when the absolute value of the overvoltage fault detection function is smaller than the absolute value of the input voltage.
13. The apparatus of claim 12, wherein the determination module is further configured to:
when the absolute value of the overvoltage fault detection function is larger than or equal to the absolute value of the input voltage, determining an undervoltage fault detection function according to the undervoltage warning level of the alternating current power supply and the root mean square of the input voltage; and is also provided with
The comparison module is further configured to: and determining that the under-voltage fault is detected when the absolute value of the under-voltage fault detection function is larger than the absolute value of the input voltage.
14. The apparatus of claim 13, wherein the comparison module is further configured to: and when the absolute value of the undervoltage fault detection function is smaller than or equal to the absolute value of the input voltage, determining that the alternating current power supply has no fault.
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