CN113740760A - Method and apparatus for fast fault detection of AC power supply - Google Patents

Method and apparatus for fast fault detection of AC power supply Download PDF

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CN113740760A
CN113740760A CN202010482292.2A CN202010482292A CN113740760A CN 113740760 A CN113740760 A CN 113740760A CN 202010482292 A CN202010482292 A CN 202010482292A CN 113740760 A CN113740760 A CN 113740760A
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input voltage
fault detection
detection function
absolute value
determining
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CN113740760B (en
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潘鸿标
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Murata Manufacturing Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/40—Testing power supplies
    • G01R31/42—AC power supplies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/02—Measuring effective values, i.e. root-mean-square values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16533—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
    • 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
    • G01R19/16547—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 voltage or current in AC supplies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero

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  • Engineering & Computer Science (AREA)
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Abstract

The embodiment of the disclosure discloses a method and a device for carrying out rapid fault detection on an alternating current power supply. The method for rapid fault detection of an alternating current power supply comprises the following steps: detecting a zero crossing point of an 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 previous period of the period in which the current time is located; determining a fault detection function from the warning level of the ac power source and the root mean square of the input voltage; and comparing the fault detection function to the input voltage to determine whether the ac power source is faulty.

Description

Method and apparatus for fast fault detection of AC power supply
Technical Field
The present disclosure relates to the field of electronic devices, and more particularly, to a method and apparatus for fast fault detection for an ac power source.
Background
Early line fault detection for Alternating Current (AC) power supplies is critical to high performance power converters as it is capable of issuing warnings to take rapid action to ensure power supply stability and reduce damage to equipment. Therefore, 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 storage.
In order to perform fast AC power failure detection, several solutions have been proposed in recent years. In patent document 1, the length of the interval between the rising edge and the falling edge may be measured by a microprocessor to indirectly measure the magnitude (e.g., mean square error (RMS) or peak value) of the main power supply voltage. However, non-sinusoidal alternating current distortion may cause measurement errors. In patent document 2, whether the three-phase power supply is broken is determined according to the ripple voltage delta V. However, delta V is filtered by a large-capacity capacitor, which results in a decrease in 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 flow to the tank circuit is detected at a selected time. However, the earliest detection time is at least half a cycle time. In patent document 4, an impending fault in the power grid is detected by checking line data in the frequency domain. In practice, this is a later analysis, not an immediate AC power failure detection. In patent document 5, the output waveform of the synchronous band-pass filter is post-processed to determine whether there is a fault in the power supply system by comparing a waveform representing the amplitude of a predefined harmonic frequency component with an imbalance reference value, thereby generating a fault detector output signal. However, this method cannot be applied to distorted non-sinusoidal AC power supplies.
Prior art documents
Patent document
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 a problem of multi-phase voltage unbalance, and being effectively applied to any shape of input voltage waveform provided by the AC power source.
According to a first aspect of the present disclosure, there is provided a method for fast fault detection of an ac power source, comprising:
detecting a zero crossing point of an 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 previous period of the period in which the current time is located;
determining a fault detection function from the warning level of the ac power source and the root mean square of the input voltage; and
comparing the fault detection function to the input voltage to determine if 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:
determining the fault detection function f (t) according to:
f (T) (T) · R (T) · V (T-T) — B, when R (T) · V (T-T) ≧ 0,
f (T) 0, when r (T) V (T-T) -B < 0;
determining the fault detection function f (t) 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 ,
Figure BDA0002515463420000021
t is time, V (t) is the input voltage, VwarningIs the warning level, Vrms_fil(0) Is a predetermined value, Vrms(t) is the root mean square of the input voltage in the period previous to the period in which the present 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 the warning level of the ac power source and the root mean square of the input voltage comprises: determining an undervoltage fault detection function according to an undervoltage warning level of the alternating current power supply and a root-mean-square of the input voltage; and is
Comparing the fault detection function to the input voltage to determine whether the AC power source is faulty comprises: determining that an undervoltage fault is detected when the absolute value of the undervoltage fault detection function is greater 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 a root-mean-square of the input voltage; and
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.
In one embodiment, the method further comprises:
determining that the AC power source is not malfunctioning when an absolute value of the over-voltage fault detection function is greater than or equal to an absolute value of the input voltage.
In one embodiment, the warning level of the ac power source is an over-voltage warning level,
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: determining an overvoltage fault detection function based on an overvoltage warning level of the AC power source and a root mean square of the input voltage; and is
Comparing the fault detection function to the input voltage to determine whether the AC power source is faulty comprises: 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.
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 an undervoltage warning level of the alternating-current power supply and the root-mean-square of the input voltage; and
determining that an undervoltage fault is detected when the absolute value of the undervoltage fault detection function is greater 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 does not have a fault.
According to a second aspect of the present disclosure, there is provided an apparatus for fast fault detection of an ac power source, comprising:
a detection module configured to detect a zero-crossing point 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 a root mean square of the input voltage in a period previous to a period in which a current time is when the zero-crossing point is detected;
a determination module configured to determine a fault detection function from 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 to the input voltage to determine whether the AC power source is faulty.
In one embodiment, the determination module is further configured to:
determining the fault detection function f (t) according to:
f (T) (T) · R (T) · V (T-T) — B, when R (T) · V (T-T) ≧ 0,
f (T) 0, when r (T) V (T-T) -B < 0;
determining the fault detection function f (t) 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 ,
Figure BDA0002515463420000041
t is time, V (t) is the input voltage, VwarningIs the warning level, Vrms_fil(0) Is a predetermined value, Vrms(t) is the root mean square of the input voltage in the period previous to the period in which the present 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 undervoltage fault detection function according to an undervoltage warning level of the alternating current power supply and a root-mean-square of the input voltage; and is
The comparison module is further configured to: determining that an undervoltage fault is detected when the absolute value of the undervoltage fault detection function is greater 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 a root-mean-square of the input voltage; and is
The comparison module is further configured to: 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.
In one embodiment, the comparison module is further configured to: determining that the AC power source is not malfunctioning when an absolute value of the over-voltage fault detection function is greater than or equal to an absolute value of the input voltage.
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 based on an overvoltage warning level of the AC power source and a root mean square of the input voltage; and is
The comparison module is further configured to: 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.
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 an undervoltage warning level of the alternating-current power supply and the root-mean-square of the input voltage; and is
The comparison module is further configured to: determining that an undervoltage fault is detected when the absolute value of the undervoltage fault detection function is greater 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 does not have a fault.
Drawings
FIG. 1 shows a schematic diagram of an AC power source sampling circuit according to an embodiment of the present disclosure;
FIG. 2 shows a flow diagram of a method for fast fault detection of an AC power source in accordance with an embodiment of the present disclosure;
FIG. 3 shows a block diagram of an apparatus for fast fault detection of an AC power source in accordance with an embodiment of the present disclosure;
FIG. 4 illustrates a normal waveform diagram of the AC voltage and fault detection function for undervoltage detection according to an embodiment of the present disclosure;
FIG. 5 illustrates an example of AC voltage droop 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 a flat top and fault detection function for under-voltage detection according to an embodiment of the present disclosure;
FIG. 8 illustrates a normal waveform diagram of the 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 illustrative only and is not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not 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" and the like as used herein are also intended to include the meanings of "a plurality" and "the" unless the context clearly dictates otherwise. Furthermore, the terms "comprises," "comprising," or the like, as 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 is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.
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 source 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 supply power to the device 103. A sampling device, such as a microcontroller unit (MCU), can accurately sample the AC input voltage provided by the AC power source 101 via sensing points 104 and 105. The sampling device may store the entire waveform of a full AC cycle of the AC power source 101 for later use in fast AC power failure detection.
Fig. 2 shows a flow diagram of a method 200 for fast 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, zero-crossing points of an input voltage (i.e., an AC voltage) provided by an alternating current power source (e.g., the 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), and 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 previous cycle of the cycle in which the present time is present may be calculated.
In step S230, a fault detection function may be determined according to 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) (T) · R (T) · V (T-T) — B, when R (T) · V (T-T) ≧ 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 ,
Figure BDA0002515463420000071
and typically for undervoltage detection, R (t) < 1, for overvoltage detection, R (t) > 1,
Figure BDA0002515463420000072
t is time, V (t) is the input voltage, VwarningIs a warning lightFlat, Vrms_fil(0) Is a predetermined value, Vrms(t) is the root mean square of the input voltage in the period preceding the period in which the present time t is present, n is a natural number, a is an adjustable gain value and usually takes 1, and B is a predetermined value. In one example, n-4 and a-1 to ensure for Vrms_filIs sufficient for filtering.
In the first embodiment, the warning level of the ac power supply may be an under-voltage warning level, and step S230 may include: an undervoltage fault detection function is determined based on an undervoltage warning level of the AC power source and a root-mean-square of the input voltage.
In step S240, the fault detection function may be compared with 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 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 an under-voltage fault is detected.
| V (t) | < | F (t) | equation 3
In the 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 undervoltage fault detection function is less than or equal to an absolute value of the input voltage, and 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 the ac power supply is determined not to have a fault when the absolute value of the overvoltage fault detection function is greater than or equal to the absolute value of the input voltage.
I V (t) | > | F (t) | equation 4
It should be noted that, the overvoltage fault detection function may also be determined according to the overvoltage warning level of the ac power supply and the root-mean-square of the input voltage, and whether an overvoltage fault occurs or not is determined according to the overvoltage fault detection function, and if not, then the undervoltage fault detection function is determined according to the undervoltage warning level of the ac power supply and the root-mean-square of the input voltage, and whether an undervoltage fault occurs or not is determined according to the undervoltage fault detection function.
Specifically, in the second embodiment, the warning level of the alternating-current power supply may be an overvoltage warning level, and step S230 may include: an overvoltage fault detection function is determined based on an overvoltage warning level of the ac power source and a root mean square of the input voltage.
In the second embodiment, step S240 may include: 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.
In the second embodiment, the method 200 may further include: when the absolute value of the overvoltage fault detection function is greater than or equal to the absolute value of the input voltage, determining the undervoltage fault detection function according to an undervoltage warning level of the alternating-current power supply and a root-mean-square of the input voltage, and when the absolute value of the undervoltage fault detection function is greater than the absolute value of the input voltage, determining that an undervoltage fault is detected, and when the absolute value of the undervoltage fault detection function is less than or equal to the absolute value of the input voltage, determining that the alternating-current power supply is not faulty.
Since there is no input voltage when the AC power source is initially powered up (e.g., no input voltage value has been stored in the sampling device), to prevent false triggering from occurring, a second trigger condition may also be set, as shown in equation 5:
Vrms_uvw＜Vrms_fil(t)＜Vrms_ovwequation 5
wherein Vrms_uvwIs a voltage threshold for an under-voltage warning, and Vrms_ovwIs a voltage threshold for an overvoltage warning.
Thus, in the first and second embodiments described above, instead of determining that an 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), an 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 (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), it is determined 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) and equation 5 is also satisfied.
Further, in the case where the AC power source is a multi-phase voltage source, the input signal provided by the multi-phase voltage source may be divided into a plurality of single-phase signals, and then the method for fast fault detection of the AC power source according to the embodiment of the present disclosure is applied to each of the multi-phase signals, respectively, for fault detection.
Fig. 3 shows a block diagram of an apparatus 300 for fast fault detection of an ac power source according to an embodiment of the present disclosure. The apparatus 300 may comprise: a detection module 310, a calculation module 320, a determination module 330, and a comparison module 340.
The detection module 310 may be configured to detect zero-crossing points of an input voltage provided by an ac power source to obtain a period T of the input voltage.
The calculation module 320 may be configured to calculate the root mean square of the input voltage in a period previous to the period in which the present time is 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-cycles of the input voltage and according to equation 2 for the negative half-cycles 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 faulty.
The warning level of the ac power supply may be an undervoltage warning level or an overvoltage warning level, and the two embodiments will be described below in different order of detecting undervoltage faults and detecting overvoltage faults.
In one embodiment, when the warning level of the ac power source is an under-voltage warning level, the determining module 330 may be further configured to: determining an undervoltage fault detection function according to an undervoltage warning level of the alternating-current power supply and a root-mean-square of the input voltage; and the comparison module 340 may be further configured to: when the absolute value of the undervoltage fault detection function is greater than the absolute value of the input voltage, it is determined that an undervoltage 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: 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, and when the absolute value of the overvoltage fault detection function is greater than or equal to the absolute value of the input voltage, it is determined that the ac power supply is not faulty.
In another embodiment, when the warning level of the ac power source is an overvoltage warning level, the determining module 330 may be further configured to: determining an overvoltage fault detection function according to an overvoltage warning level of the alternating current power supply and a root mean square of the input voltage; and the comparison module 340 may be further configured to: 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. 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: when the absolute value of the undervoltage fault detection function is greater than the absolute value of the input voltage, it is determined that an undervoltage fault is detected, and when the absolute value of the undervoltage fault detection function is less than or equal to the absolute value of the input voltage, it is determined that the alternating current power supply is not in fault.
Fig. 4 shows a normal waveform diagram of the AC voltage and fault detection function for undervoltage detection.
As can be seen from fig. 4, 401 represents the AC input voltage Vac, which is a sinusoidal waveform. 402 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. Suppose V for undervoltage detectionwarningLess than Vrms_fil. If the instantaneous voltage Vac suddenly drops to the fault detection functionF (t), the trigger condition for fast brown-out detection is satisfied, i.e., equation 3 is satisfied. Some expeditious action may be taken to protect the system or reduce damage, such as informing the computer (load) to save data to persistent storage before the energy buffer of the converter runs out.
Fig. 5 and 6 show waveform diagrams of AC voltage and fault detection functions, respectively, for under-voltage detection.
The case of the AC voltage drop is shown in fig. 5. 501 denotes an AC input voltage Vac. 502 represents the fault detection function f (t) calculated for undervoltage detection by equations 1 and 2. 503 denotes the detection point at which Vac falls below F (t). Since F (t) is generally closer to Vac than to the zero-crossing point, except near the zero-crossing point, and because of the slope of the decreasing path of Vac, the detection point 503 occurs slightly earlier than when Vac touches the zero-crossing point. For example, at detection point 503, an undervoltage fault can be detected.
FIG. 6 shows that the AC voltage is suddenly dropped to V in addition to the AC voltage drop shown in FIG. 5warningThe following is the case. 601 denotes the AC input voltage Vac, which is a sinusoidal voltage waveform. 602 represents a fault detection function f (t) calculated for undervoltage detection by equations 1 and 2, the waveform of which has a root mean square value VwarningB. 603 denotes the slump trigger point for the AC voltage to drop from the normal level to f (t). For example, at coup de fouet trigger point 603, an under-voltage fault can be detected.
Fig. 7 shows a waveform diagram of an AC voltage with a flat top and fault detection function for undervoltage 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 undervoltage detection, VwarningLess than Vrms_filThen 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. With respect to the waveform diagram of FIG. 7, when an undervoltage fault occurs, the detection points for determining the undervoltage fault are similar to those of FIG. 5 andthe manner in which undervoltage fault detection points 503 and 603 are determined in FIG. 6.
Similar to the normal AC voltage waveform for undervoltage detection in fig. 4, fig. 8 shows a normal waveform diagram of the AC voltage and fault detection function for overvoltage detection according to an embodiment of the disclosure. Reference 801 denotes an AC input voltage Vac, which is a sinusoidal waveform. 802 denotes a fault detection function f (t) calculated for overvoltage detection by equations 1 and 2, where B in equations 1 and 2 takes a negative value. Suppose for overvoltage detection, VwarningGreater than Vrms_fil. If the instantaneous voltage Vac suddenly rises above f (t), the trigger condition for fast overvoltage detection is satisfied, i.e., equation 4 is satisfied. The energy consuming device at the output may take 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 constant. In fig. 9, 901 and 902 represent the frequencies f, respectively0AC line voltage waveform Vac and fault detection function f (t). 903 indicates that the frequency starts from f0Change to f1(in this example, f1＞f0). 906 is the same waveform as 901 for reference, and 905 is the ac voltage waveform after 903 with the frequency changed. 904 denotes a detection point at which the waveform 905 falls below the waveform 902, and 902 denotes a failure 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 secondary f0To f1(f1＜f0) The frequency of (2) is changed.
It should be noted that the method for fast 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 with multiple source inputs, the ac line switching operation may cause a phase change. The method according to the present disclosure may also detect ac power recovered at different angles. 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 cycles. 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 perform the current waveform detection using the previous full-period AC voltage waveform, the fault detection can be rapidly achieved, and furthermore, since the fault detection function can be flexibly formed by the original period waveform, the method and apparatus according to the embodiments of the present disclosure can be effectively applied to any shape of the input voltage waveform.
Some block diagrams and/or flow diagrams are shown in the figures. It will be understood that some blocks of the block diagrams and/or flowchart illustrations, or combinations thereof, 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, which execute via the processor, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks.
Accordingly, the techniques of this disclosure may be implemented in hardware and/or software (including firmware, microcode, etc.). In addition, the techniques of this disclosure may take the form of a computer program product on a computer-readable medium having instructions stored thereon for use 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, the computer readable medium can 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 Drives (HDDs); optical storage devices, such as compact disks (CD-ROMs); a memory, such as a Random Access Memory (RAM) or a flash memory; and/or wired/wireless communication links.
The foregoing detailed description has set forth numerous embodiments of methods and apparatus for rapid fault detection of an ac power source 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 within the art that each function and/or operation within 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 code for the software and or firmware would be well within the skill of one of skill in the art in light of this disclosure. In addition, those skilled in the art will appreciate that the mechanisms of the subject matter described herein are capable of being distributed as a program product in a variety of forms, and that an illustrative 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 type media such as floppy disks, hard disk drives, Compact Disks (CDs), Digital Versatile Disks (DVDs), digital tape, computer memory, etc.; and a transmission type medium such as a digital and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link, etc.).

Claims (16)

1. A method for rapid fault detection of an ac power source, comprising:
detecting a zero crossing point of an 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 previous period of the period in which the current time is located;
determining a fault detection function from the warning level of the ac power source and the root mean square of the input voltage; and
comparing the fault detection function to the input voltage to determine if the AC power source is faulty.
2. The method of claim 1, wherein determining a fault detection function as a function of the warning level of the ac power source and the root mean square of the input voltage comprises:
determining the fault detection function f (t) according to:
f (T) (T) · R (T) · V (T-T) — B, when R (T) · V (T-T) ≧ 0,
f (T) 0, when r (T) V (T-T) -B < 0;
determining the fault detection function f (t) 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 ,
Figure FDA0002515463410000011
t is time, V (t) is the input voltage, VwarningIs the warning level, Vrms_fil(0) Is a predetermined value, Vrms(t) is the root mean square of the input voltage in the period previous to the period in which the present time t is located, n is a natural number, a is an adjustable gain value, and B is a predetermined value.
3. 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 the warning level of the ac power source and the root mean square of the input voltage comprises: determining an undervoltage fault detection function according to an undervoltage warning level of the alternating current power supply and a root-mean-square of the input voltage; and is
Comparing the fault detection function to the input voltage to determine whether the AC power source is faulty comprises: determining that an undervoltage fault is detected when the absolute value of the undervoltage fault detection function is greater than the absolute value of the input voltage.
4. The method of claim 3, 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 a root-mean-square of the input voltage; and
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.
5. The method of claim 4, further comprising:
determining that the AC power source is not malfunctioning when an absolute value of the over-voltage fault detection function is greater than or equal to an absolute value of the input voltage.
6. 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 the warning level of the ac power source and the root mean square of the input voltage comprises: determining an overvoltage fault detection function based on an overvoltage warning level of the AC power source and a root mean square of the input voltage; and is
Comparing the fault detection function to the input voltage to determine whether the AC power source is faulty comprises: 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.
7. The method of claim 6, 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 an undervoltage warning level of the alternating-current power supply and the root-mean-square of the input voltage; and
determining that an undervoltage fault is detected when the absolute value of the undervoltage fault detection function is greater than the absolute value of the input voltage.
8. The method of claim 7, 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 does not have a fault.
9. An apparatus for rapid fault detection of an ac power source, comprising:
a detection module configured to detect a zero-crossing point 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 a root mean square of the input voltage in a period previous to a period in which a current time is when the zero-crossing point is detected;
a determination module configured to determine a fault detection function from 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 to the input voltage to determine whether the AC power source is faulty.
10. The apparatus of claim 9, wherein the determination module is further configured to:
determining the fault detection function f (t) according to:
f (T) (T) · R (T) · V (T-T) — B, when R (T) · V (T-T) ≧ 0,
f (T) 0, when r (T) V (T-T) -B < 0;
determining the fault detection function f (t) 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 ,
Figure FDA0002515463410000031
t is time, V (t) is the input voltage, VwarningIs the warning level, Vrms_fil(0) Is a predetermined value, Vrms(t) is the root mean square of the input voltage in the period previous to the period in which the present time t is located, n is a natural number, a is an adjustable gain value, and B is a predetermined value.
11. The apparatus of claim 9, wherein the warning level of the AC power source is an under-voltage warning level,
the determination module is further configured to: determining an undervoltage fault detection function according to an undervoltage warning level of the alternating current power supply and a root-mean-square of the input voltage; and is
The comparison module is further configured to: determining that an undervoltage fault is detected when the absolute value of the undervoltage fault detection function is greater than the absolute value of the input voltage.
12. The apparatus of claim 11, 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 a root-mean-square of the input voltage; and is
The comparison module is further configured to: 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.
13. The apparatus of claim 12, wherein the comparison module is further configured to: determining that the AC power source is not malfunctioning when an absolute value of the over-voltage fault detection function is greater than or equal to an absolute value of the input voltage.
14. The apparatus of claim 9, 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 based on an overvoltage warning level of the AC power source and a root mean square of the input voltage; and is
The comparison module is further configured to: 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.
15. The apparatus of claim 14, 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 an undervoltage warning level of the alternating-current power supply and the root-mean-square of the input voltage; and is
The comparison module is further configured to: determining that an undervoltage fault is detected when the absolute value of the undervoltage fault detection function is greater than the absolute value of the input voltage.
16. The apparatus of claim 15, 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 does not have a fault.
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