CN114113917A - Power grid abnormity detection circuit and method and photovoltaic air conditioner - Google Patents
Power grid abnormity detection circuit and method and photovoltaic air conditioner Download PDFInfo
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- CN114113917A CN114113917A CN202111566854.2A CN202111566854A CN114113917A CN 114113917 A CN114113917 A CN 114113917A CN 202111566854 A CN202111566854 A CN 202111566854A CN 114113917 A CN114113917 A CN 114113917A
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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
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/88—Electrical aspects, e.g. circuits
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
- F24F5/0046—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater using natural energy, e.g. solar energy, energy from the ground
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Abstract
The invention discloses a power grid abnormity detection circuit and method and a photovoltaic air conditioner. Wherein, this circuit includes: the sampling module is connected with the output end of the alternating current power grid and used for respectively detecting the frequency of any two-phase voltage of three-phase voltages output by the alternating current power grid and generating a sampling square wave signal based on the phase difference between the any two-phase voltages; the signal processing module is used for processing the sampling square wave signal and outputting the sampling square wave signal to the microprocessor; and the microprocessor is used for judging whether the power grid is abnormal or not according to the frequency of any two-phase voltage and the sampling square wave signal processed by the signal processing module. According to the invention, whether the frequency of the single-phase voltage is abnormal or not can be judged, whether the phase difference between the two-phase voltages is abnormal or not can be accurately judged, and the accuracy of power grid abnormality detection is improved.
Description
Technical Field
The invention relates to the technical field of electronic power, in particular to a power grid abnormity detection circuit and method and a photovoltaic air conditioner.
Background
The ac power grid is a complex system, the state of which changes in real time and is easily interfered by the outside world, and when a power equipment system (such as a photovoltaic air conditioner) is operated in a grid-connected mode, the operating state of the power grid needs to be monitored in real time. In order to realize the stable operation of the power grid, the power grid specifications released by various countries provide the specification requirements of the grid-connected power generation system on the information such as the power quality, the voltage amplitude, the frequency and the like under the ideal power grid condition. Therefore, the power grid change is accurately and quickly acquired, the power converter of the power equipment system is controlled to work according to the standard requirement, and the basis for completing safe and reliable operation of new energy grid-connected power generation is provided. The operation state of the power grid comprises not only frequency abnormality of single-phase voltage but also phase difference abnormality between any two-phase voltage, and the existing detection mode aiming at the operation state of the power grid usually only detects whether the frequency of the single-phase voltage is accurate, but neglects to detect the phase difference between any two-phase voltage, so that the existing detection scheme of the operation state of the power grid easily has the problem of inaccurate detection result.
Aiming at the problem that a power grid operation state detection scheme in the prior art is prone to have inaccurate detection results, an effective solution is not provided at present.
Disclosure of Invention
The embodiment of the invention provides a power grid abnormity detection circuit and method and a photovoltaic air conditioner, and aims to solve the problem that a power grid operation state detection scheme in the prior art is prone to have inaccurate detection results.
In order to solve the above technical problem, the present invention provides a power grid abnormality detection circuit, including:
the sampling module is connected with the output end of the alternating current power grid and used for respectively detecting the frequency of any two-phase voltage of three-phase voltages output by the alternating current power grid and generating a sampling square wave signal based on the phase difference between the any two-phase voltages;
the signal processing module is used for processing the sampling square wave signal and outputting the sampling square wave signal to the microprocessor;
and the microprocessor is used for judging whether the power grid is abnormal or not according to the frequency of any two-phase voltage and the sampling square wave signal processed by the signal processing module.
Further, the sampling module includes:
the first detection unit and the second detection unit are respectively connected with an output terminal of one phase voltage of the three-phase voltages and are used for generating a voltage signal based on the single-phase voltage output by the alternating current power grid, and the frequency of the voltage signal is equal to that of the single-phase voltage;
and the input end of the exclusive-OR gate phase discriminator is respectively connected with the first detection unit and the second detection unit and used for generating the sampling square wave signal according to the voltage signals output by the first detection unit and the second detection unit and outputting the sampling square wave signal to the signal processing module.
Further, the sampling module further comprises:
and a backup detection unit having an input terminal to which the output terminal connected to the first detection unit or the output terminal connected to the second detection unit is selectively connectable.
Further, the sampling module further comprises:
the first switch is a single-pole double-throw switch, a first contact point of the first switch is connected with an output terminal of one phase voltage of the three-phase voltages, a second contact point of the first switch is connected with the first detection unit, and a third contact point of the first switch is connected with the standby detection unit;
and the second switch is a single-pole double-throw switch, a first contact of the second switch is connected with an output terminal of the other phase voltage of the three-phase voltages, a second contact of the second switch is connected with the second detection unit, and a third contact of the second switch is connected with the standby detection unit.
Further, the detection unit includes:
the non-inverting input end of the voltage follower is connected with the output terminal of one phase voltage of the three-phase voltages through a first resistor, the inverting input end of the voltage follower is grounded through a second resistor, the output end of the voltage follower is connected with the inverting input end of the voltage follower through a third resistor, and the output end of the voltage follower is also connected with the non-inverting input end of the first comparator through a fourth resistor;
the inverting input end of the first comparator is grounded through a fifth resistor, and the output end of the first comparator is connected with a voltage division loop;
the voltage division loop comprises a voltage source, a sixth resistor and a seventh resistor which are sequentially connected in series, the seventh resistor is grounded, and a line led out between the sixth resistor and the seventh resistor is connected with the exclusive-OR gate phase discriminator.
Further, the detection unit further includes:
the first capacitor is arranged at two ends of the third resistor in parallel;
one end of the eighth resistor is connected with the non-inverting input end of the voltage follower, and the other end of the eighth resistor is grounded;
and the second capacitor is arranged at two ends of the eighth resistor in parallel.
Further, the detection unit further includes:
a third capacitor, a first end of which is connected between the non-inverting input end of the first comparator and the fourth resistor, and a second end of which is grounded;
and a fourth capacitor, a first end of which is connected between the inverting input end of the first comparator and the fifth resistor, and a second end of which is grounded.
Further, the detection unit further includes:
and the first one-way element is arranged between the output end of the first comparator and the voltage division loop, the anode of the first one-way element is connected with the output end of the first comparator, and the cathode of the first one-way element is connected with the voltage division loop.
Further, the signal processing module includes:
the input end of the filtering unit is connected with the sampling module, and the output end of the filtering unit is connected with the input end of the analog-to-digital conversion unit and is used for filtering the sampling square wave signal output by the sampling module;
and the output end of the analog-to-digital conversion unit is connected with the microprocessor and is used for converting the sampling square wave signals filtered by the filtering unit into digital signals and outputting the digital signals to the microprocessor.
Further, the circuit further comprises:
and the non-inverting input end of the second comparator is connected between the filtering unit and the analog-to-digital conversion unit, the inverting input end of the second comparator inputs reference voltage, and the output end of the second comparator is connected with the microprocessor.
The invention also provides electric equipment which comprises the power grid abnormality detection circuit.
Further, the electric equipment is a photovoltaic air conditioner.
The invention also provides a power grid abnormity detection method, which comprises the following steps:
respectively detecting the frequency of any two-phase voltage of three-phase voltages output by an alternating current power grid, and generating a sampling square wave signal based on the phase difference between the any two-phase voltages;
processing the sampling square wave signal;
and judging whether the power grid is abnormal or not according to the frequency of any two-phase voltage and the processed sampling square wave signal.
Further, judging whether the power grid is abnormal or not according to the frequency of any two-phase voltage and the processed sampling square wave signal, and the method comprises the following steps:
judging whether the frequency of any two-phase voltage is within a preset range;
if not, judging that the power grid is abnormal;
if yes, whether the power grid is abnormal or not is continuously judged according to the processed sampling square wave signals.
Further, continuously judging whether the power grid is abnormal or not according to the processed sampling square wave signal, comprising:
judging whether the voltage effective value of the sampling square wave signal is equal to a preset value or not;
if so, judging that the power grid is normal;
and if not, judging that the power grid is abnormal.
Further, after determining whether the frequency of any two-phase voltage is within a preset range, the method further includes:
if the judgment result is negative, determining whether the frequency of only one-phase voltage is not in a preset range; if the frequency of only one-phase voltage is not in the preset range, replacing the detection unit connected with the output terminal of the one-phase voltage with a standby detection unit, wherein the frequency of the one-phase voltage is not in the preset range;
judging whether the frequency of any two-phase voltage is within a preset range;
if not, judging that the power grid is abnormal;
if yes, whether the power grid is abnormal or not is continuously judged according to the processed sampling square wave signals.
The present invention also provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the above-described grid anomaly detection method.
By applying the technical scheme of the invention, whether the power grid is abnormal is judged through the frequency of any two-phase voltage of the three-phase voltage output by the alternating-current power grid and the sampling square wave signal generated based on the phase difference between the two-phase voltage, so that whether the frequency of the single-phase voltage is abnormal or not can be judged, whether the phase difference between the two-phase voltage is abnormal or not can be accurately judged, and the accuracy of power grid abnormality detection is improved.
Drawings
Fig. 1 is a structural diagram of a power grid abnormality detection circuit according to an embodiment of the present invention;
fig. 2 is a block diagram of another grid anomaly detection circuit according to an embodiment of the present invention;
FIG. 3 is a block diagram of a detection unit according to an embodiment of the present invention;
fig. 4 is a flowchart of a power grid abnormality detection method according to an embodiment of the present invention;
fig. 5 is a flowchart of another grid abnormality detection method according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
It should be understood that although the terms first, second, etc. may be used to describe the detection units in the embodiments of the present invention, the detection units should not be limited to these terms. These terms are only used to distinguish between detection units disposed at different locations. For example, the first detection unit may also be referred to as the second detection unit, and similarly, the second detection unit may also be referred to as the first detection unit, without departing from the scope of the embodiments of the present invention.
The words "if", as used herein, may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.
It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in the article or device in which the element is included.
Alternative embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Example 1
The present embodiment provides a power grid abnormality detection circuit, and fig. 1 is a structural diagram of a power grid abnormality detection circuit according to an embodiment of the present invention, as shown in fig. 1, the power grid abnormality detection circuit includes:
the sampling module 10 is connected to an output end of the ac power grid, and is configured to detect frequencies of any two-phase voltages of three-phase voltages output by the ac power grid, and generate a sampling square wave signal based on a phase difference between any two-phase voltages.
In specific implementation, the sampling module 10 may be connected to an oscilloscope to display the frequency of any two-phase voltage of the three-phase voltages output by the ac power grid, and further determine whether the frequency of the two-phase voltage is within a preset range, and further determine whether the power grid is abnormal.
And the signal processing module 20 is configured to process the sampled square wave signal and output the processed signal to the microprocessor 30.
And the microprocessor 30 is used for judging whether the power grid is abnormal or not according to the frequency of any two-phase voltage of the three-phase voltage and the sampling square wave signal processed by the signal processing module.
The abnormality of the power grid includes not only the frequency abnormality of the single-phase voltage but also the phase difference abnormality between the two-phase voltages, and therefore, it is necessary to determine whether the respective frequencies of any two-phase voltages are abnormal or not, and also to determine whether the phase difference between the two-phase voltages is abnormal or not according to the sampling square wave signal generated based on the phase difference between the two-phase voltages.
The power grid abnormality detection circuit of the embodiment judges whether the power grid is abnormal or not through the frequency of any two-phase voltage of three-phase voltages output by the alternating-current power grid and a sampling square wave signal generated based on the phase difference between the two-phase voltages, so that the frequency of the single-phase voltage can be judged and the phase difference between the voltages can be accurately judged, and the accuracy of power grid abnormality detection is improved.
In order to separately detect the frequencies of any two-phase voltages of the three-phase voltages, as shown in fig. 1, the sampling module 10 includes: the first detection unit 101 and the second detection unit 102 are respectively connected with an output terminal of one phase voltage of the three-phase voltages, and the first detection unit 101 and the second detection unit 102 respectively generate voltage signals based on the single-phase voltage output by the alternating current power grid, wherein the frequency of the voltage signals is equal to that of the single-phase voltage. The voltage signals generated by the first detection unit 101 and the second detection unit 102 are both square wave signals, and the first detection unit 101 and the second detection unit 102 may be respectively connected to an oscilloscope to respectively display the frequency of the two-phase voltage, and further determine whether the frequency of the two-phase voltage is within a preset range, and further determine whether the power grid is abnormal.
In the present embodiment, the first detection unit 101 is connected to an output terminal of a first phase voltage a phase of three-phase voltages, and the second detection unit 102 is connected to an output terminal of a second phase voltage B phase or a third phase C phase of three-phase voltages.
In order to generate a sampled square wave signal, as shown in fig. 1, the sampling module 10 further includes: an input end of the exclusive or gate phase detector 103 is connected to the first detection unit 101 and the second detection unit 102, respectively, and is configured to generate a sampling square wave signal according to the voltage signals output by the first detection unit 101 and the second detection unit 102, and output the sampling square wave signal to the signal processing module 20.
Because the voltage signals generated by the first detection unit 101 and the second detection unit 102 are both square wave signals, when the voltage signals output by the first detection unit 101 and the second detection unit 102 are the same, the xor gate phase detector 103 outputs 0, and when the voltage signals output by the first detection unit 101 and the second detection unit 102 are different, the xor gate phase detector 103 outputs 1, thereby generating sampling square wave signals.
Example 2
In this embodiment, another power grid abnormality detection circuit is provided, and fig. 2 is a structural diagram of another power grid abnormality detection circuit according to an embodiment of the present invention, in practical application, if a frequency of a voltage signal detected by one path of detection unit is abnormal, which may be due to an abnormal frequency of a single-phase voltage of a power grid, or a fault of the detection unit itself, so as to cause an inaccurate detection result, and in order to eliminate an influence of the fault of the detection unit itself, as shown in fig. 2, the sampling module 10 further includes: the input terminal of the standby detection unit 104 is selectively connectable to the output terminal connected to the first detection unit 101 or the output terminal connected to the second detection unit 102.
Specifically, in order to control the input end of the standby detection unit 104 to alternatively connect the output terminal connected to the first detection unit 101 or the output terminal connected to the second detection unit 102, the sampling module 10 further includes: a first switch S1, as shown in fig. 2, the first switch S1 is a single-pole double-throw switch, a first contact of which is connected to an output terminal of one phase voltage (a-phase voltage) of three-phase voltages, a second contact of which is connected to the first detecting unit 101, and a third contact of which is connected to the standby detecting unit 104; and a second switch S2 which is a single-pole double-throw switch having a first contact connected to the output terminal of the other phase voltage of the three-phase voltages, a second contact connected to the second detecting unit 102, and a third contact connected to the standby detecting unit 104.
In order to obtain a direct voltage signal, the signal processing module 20 comprises: the input end of the filtering unit 201 is connected to the sampling module, and the output end of the filtering unit 201 is connected to the input end of the analog-to-digital conversion unit 202, and is configured to filter the sampling square wave signal output by the sampling module, in this embodiment, the filtering unit 201 adopts an RC filtering circuit; since the sampled square wave signal output by the xor gate phase detector 103 is an analog signal, and the microprocessor can only process a digital signal, the signal processing module 20 further includes an analog-to-digital conversion unit 202, an output end of which is connected to the microprocessor 30, and is configured to convert the sampled square wave signal filtered by the filtering unit 201 into a digital signal, and output the digital signal to the microprocessor 30, so that the microprocessor 30 can determine whether the power grid is abnormal according to the digital signal generated by the sampled square wave signal, and further control whether the electric device is connected to the power grid.
Microprocessor inside is provided with the default of voltage for judge whether sampling square wave signal's voltage virtual value is unusual, in order to realize the dual judgement of software and hardware, guarantee to judge the accuracy, above-mentioned electric wire netting anomaly detection circuitry still includes: the non-inverting input of the second comparator a2 is connected between the filtering unit 201 and the analog-to-digital converting unit 202, the inverting input thereof is input with the reference voltage, and the output thereof is connected to the microprocessor 30. When the effective voltage value of the sampled square wave signal is greater than the preset value, the second comparator a2 outputs a signal 1 to the microprocessor, which indicates that the phase difference between the two-phase voltages is too large and the power grid is abnormal.
Fig. 3 is a structural diagram of a detection unit according to an embodiment of the present invention, and as shown in fig. 3, the detection unit includes: the voltage follower U is connected with the output terminal of one phase voltage of the three-phase voltages through a first resistor R1 at the non-inverting input end, is grounded through a second resistor R2 at the inverting input end, is connected with the inverting input end of the voltage follower U through a third resistor R3 at the output end, and is also connected with the non-inverting input end of a first comparator A1 through a fourth resistor R4 at the output end; the inverting input end of the first comparator A1 is grounded through the fifth resistor R5, and the output end of the first comparator A1 is connected between the sixth resistor R6 and the seventh resistor R7 of the voltage division loop 101-1; the voltage division loop 101-1 comprises a voltage source, a sixth resistor R6 and a seventh resistor R7 which are sequentially connected in series, the seventh resistor R7 is grounded, and a line led out between the sixth resistor R6 and the seventh resistor R7 is used as an output end of the detection unit and is connected with the exclusive-or gate phase detector 103.
In order to realize the function of filtering the voltage output by the voltage follower U, the detection unit further includes: and the first capacitor C1 is connected in parallel at two ends of the third resistor R3.
In order to filter the voltage input by the non-inverting input terminal of the voltage follower U, the detecting unit further includes: an eighth resistor R8, one end of which is connected with the non-inverting input end of the voltage follower U, and the other end of which is grounded; and the second capacitor C2 is arranged at two ends of the eighth resistor R8 in parallel.
Similarly, in order to filter the voltage input from the non-inverting input terminal of the first comparator a1, the detecting unit further includes: a third capacitor C3, a first end of which is connected between the non-inverting input terminal of the first comparator a1 and the fourth resistor R4, and a second end of which is grounded; a fourth capacitor C4 has a first terminal connected between the inverting input terminal of the first comparator a1 and the fifth resistor R5, and a second terminal connected to ground.
In order to control the unidirectional transmission of the voltage, the detection unit further comprises: and a first unidirectional element D1, disposed between the output terminal of the first comparator a1 and the voltage dividing circuit 101-1, having an anode connected to the output terminal of the first comparator and a cathode connected to the voltage dividing circuit 101-1.
The power grid abnormality detection circuit of the embodiment has the following specific working principle:
after the first detection unit 101 and the second detection unit 102 detect the frequency of any two-phase voltage output by the power grid, respectively determining whether the frequency of the two-phase voltage is within a preset range, and determining whether the phase difference of the two-phase voltage is abnormal according to a sampling square wave signal generated according to the phase difference of the two-phase voltage, if the frequency of the two-phase voltage is within the preset range (50 ± 2Hz in this embodiment), and the voltage effective value of the sampling square wave signal is equal to 2/3 of the power supply voltage Vcc provided by the voltage source, that is, the duty ratio of the sampling square wave signal is equal to 2/3, it is indicated that the power grid is not abnormal, and the grid-connected operation of the electric device can be controlled. The preset value is determined according to the phase difference between two phases of voltages in the normal state of the power grid, and the phase difference between any two phases of voltages in the normal state of the power grid is 120 degrees, so that the effective value of the voltages is equal to 2/3 of the power supply voltage Vcc provided by the voltage source. The two paths of square wave voltage signals detected by the first detection unit 101 and the second detection unit 102 are output by the exclusive or gate phase detector 103 to obtain sampling square wave signals, then pass through the filtering unit 201 to obtain direct current voltage signals, and then are input to the microprocessor 30 through the digital-to-analog conversion unit 202 to be compared with a preset value of voltage in a normal state. The second comparator a2 is arranged at the output end of the dc voltage signal filtered by the filtering unit 201, and is used as a protection circuit of hardware, when the effective voltage value of the sampled square wave signal exceeds the preset value, the second comparator a2 outputs a signal to the microprocessor 30, and the microprocessor 30 triggers a protection operation. When the detected frequency of the two-phase voltage exceeds the range of 50 +/-2 Hz, the power grid is abnormal, the electric equipment is controlled to stop grid-connected operation, and an oscilloscope is used for detecting whether the power grid is normal or not. When the frequency of only one-phase voltage is abnormal, the abnormal one-phase voltage change switch (the first switch S1 or the second switch S2) is switched to the standby detection unit 104 to detect the frequency and the phase difference value between two phases, if the frequency of the two-phase voltage is in the range of 50 +/-2 Hz, the detection unit is abnormal, otherwise, the power grid is abnormal. The first switch S1 and the second switch S2 may be implemented by using a relay, an optical coupler, or the like.
Example 3
The embodiment provides an electric device, which includes the power grid abnormality detection circuit in the above embodiment. In this embodiment, the electric device may be a photovoltaic air conditioner.
Example 4
The present embodiment provides a power grid abnormality detection method, and fig. 4 is a flowchart of a power grid abnormality detection method according to an embodiment of the present invention, as shown in fig. 4, the method includes:
s101, respectively detecting the frequency of any two-phase voltage of three-phase voltages output by the alternating current power grid, and generating a sampling square wave signal based on the phase difference between any two-phase voltages.
In specific implementation, the oscilloscope displays the frequency of any two-phase voltage of the three-phase voltages output by the alternating current power grid, and further judges whether the frequency of the two-phase voltage is within a preset range, and further judges whether the power grid is abnormal.
And S102, processing the sampling square wave signal.
And S103, judging whether the power grid is abnormal or not according to the frequency of any two-phase voltage and the processed sampling square wave signal.
The abnormality of the power grid includes not only the frequency abnormality of the single-phase voltage but also the phase difference abnormality between the two-phase voltages, and therefore, it is necessary to determine whether the respective frequencies of any two-phase voltages are abnormal or not, and also to determine whether the phase difference between the two-phase voltages is abnormal or not according to the sampling square wave signal generated based on the phase difference between the two-phase voltages.
According to the power grid abnormality detection method, whether the power grid is abnormal or not is judged through the frequency of any two-phase voltage of three-phase voltages output by the alternating-current power grid and the sampling square wave signal generated based on the phase difference between the two-phase voltages, whether the frequency of the single-phase voltage is abnormal or not can be judged, whether the phase difference between the voltages is abnormal or not can be accurately judged, and the accuracy of power grid abnormality detection is improved.
Example 5
In this embodiment, in order to accurately determine the power grid abnormality, the step S103 includes: judging whether the frequency of any two-phase voltage of the three-phase voltage is within a preset range; if not, judging that the power grid is abnormal; if yes, whether the power grid is abnormal or not is continuously judged according to the processed sampling square wave signals. Continuously judging whether the power grid is abnormal or not according to the processed sampling square wave signals, wherein the judgment comprises the following steps: judging whether the voltage effective value of the sampling square wave signal is equal to a preset value or not; if so, judging that the power grid is normal, and controlling the electric equipment to be connected to the power grid according to the detected frequency; and if not, judging that the power grid is abnormal.
In order to eliminate the influence of the internal fault of the detection unit on the detection result, after determining whether the frequency of any two-phase voltage is within a preset range, the method further includes: if the judgment result is negative, determining whether the frequency of only one-phase voltage is not in a preset range; if the frequency of only one-phase voltage is not in the preset range, replacing the detection unit connected with the output terminal of the one-phase voltage with a standby detection unit, wherein the frequency of the one-phase voltage is not in the preset range; judging whether the frequency of any two-phase voltage of the three-phase voltage is within a preset range; if not, judging that the power grid is abnormal; if yes, whether the power grid is abnormal or not is continuously judged according to the processed sampling square wave signals.
Fig. 5 is a flowchart of another grid abnormality detection method according to an embodiment of the present invention, and as shown in fig. 5, the method includes:
and S01, detecting the frequency of any two-phase voltage of the three-phase voltages, and acquiring the effective voltage value of the sampling square wave signal generated based on the phase difference of the two-phase voltages.
S02, judging whether the frequency of the two-phase voltage is in a preset range; if so, step S06 is performed, and if not, step S03 is performed.
S03, judging whether the frequency of the voltage of only one phase is not in the preset range, if so, executing step S04, and if not, executing step S08.
S04, the detecting means connected to the output terminal of the one-phase voltage whose frequency is not within the preset range is switched to the standby detecting means.
S05, whether the frequency of the two-phase voltage is within the preset range is judged again, if yes, the step S06 is executed, and if not, the step S08 is executed.
S06, continuously judging whether the voltage effective value of the sampling square wave signal generated by the phase difference of the two-phase voltage is equal to a preset value; if so, step S07 is performed, and if not, step S08 is performed.
And S07, judging that the power grid is normal, and controlling the electric equipment to run in a grid-connected mode according to the current frequency.
And S08, judging the power grid is abnormal, and controlling the electric equipment to stop grid-connected operation.
According to the power grid abnormality detection method, the frequency of any two-phase voltage of a three-phase power grid is detected by using the two-way detection unit, the reliability is improved by detecting the phase difference information of the two-phase voltage, the problem that power equipment cannot be connected to the grid to operate due to detection faults is greatly reduced, when the frequency detection result of one-way detection unit is normal and the frequency detection result of the other-way detection unit is abnormal, the detection unit is judged to have a detection error, the standby detection unit can be switched, and if the standby detection unit is switched, the detection result is that the frequency of the two-phase voltage is normal and the phase difference is normal, the power grid is continuously connected to the grid according to the accurate frequency; when the frequency of the two-phase voltage is abnormal, the power grid is abnormal, the unit operation needs to be stopped, and the power grid is abnormal to be overhauled.
Example 6
The present embodiment provides a computer-readable storage medium on which a computer program is stored, which when executed by a processor implements the grid abnormality detection method of the above-described embodiment.
The above-described circuit embodiments are only illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (17)
1. A power grid anomaly detection circuit, the circuit comprising:
the sampling module is connected with the output end of the alternating current power grid and used for respectively detecting the frequency of any two-phase voltage of three-phase voltages output by the alternating current power grid and generating a sampling square wave signal based on the phase difference between the any two-phase voltages;
the signal processing module is used for processing the sampling square wave signal and outputting the sampling square wave signal to the microprocessor;
and the microprocessor is used for judging whether the power grid is abnormal or not according to the frequency of any two-phase voltage and the sampling square wave signal processed by the signal processing module.
2. The circuit of claim 1, wherein the sampling module comprises:
the first detection unit and the second detection unit are respectively connected with an output terminal of one phase voltage of the three-phase voltages and are used for generating a voltage signal based on the single-phase voltage output by the alternating current power grid, and the frequency of the voltage signal is equal to that of the single-phase voltage;
and the input end of the exclusive-OR gate phase discriminator is respectively connected with the first detection unit and the second detection unit and used for generating the sampling square wave signal according to the voltage signals output by the first detection unit and the second detection unit and outputting the sampling square wave signal to the signal processing module.
3. The circuit of claim 2, wherein the sampling module further comprises:
and a backup detection unit having an input terminal to which the output terminal connected to the first detection unit or the output terminal connected to the second detection unit is selectively connectable.
4. The circuit of claim 3, wherein the sampling module further comprises:
the first switch is a single-pole double-throw switch, a first contact point of the first switch is connected with an output terminal of one phase voltage of the three-phase voltages, a second contact point of the first switch is connected with the first detection unit, and a third contact point of the first switch is connected with the standby detection unit;
and the second switch is a single-pole double-throw switch, a first contact of the second switch is connected with an output terminal of the other phase voltage of the three-phase voltages, a second contact of the second switch is connected with the second detection unit, and a third contact of the second switch is connected with the standby detection unit.
5. The circuit of claim 2, wherein the detection unit comprises:
the non-inverting input end of the voltage follower is connected with the output terminal of one phase voltage of the three-phase voltages through a first resistor, the inverting input end of the voltage follower is grounded through a second resistor, the output end of the voltage follower is connected with the inverting input end of the voltage follower through a third resistor, and the output end of the voltage follower is also connected with the non-inverting input end of the first comparator through a fourth resistor;
the inverting input end of the first comparator is grounded through a fifth resistor, and the output end of the first comparator is connected with a voltage division loop;
the voltage division loop comprises a voltage source, a sixth resistor and a seventh resistor which are sequentially connected in series, the seventh resistor is grounded, and a line led out between the sixth resistor and the seventh resistor is connected with the exclusive-OR gate phase discriminator.
6. The circuit of claim 5, wherein the detection unit further comprises:
the first capacitor is arranged at two ends of the third resistor in parallel;
one end of the eighth resistor is connected with the non-inverting input end of the voltage follower, and the other end of the eighth resistor is grounded;
and the second capacitor is arranged at two ends of the eighth resistor in parallel.
7. The circuit of claim 5, wherein the detection unit further comprises:
a third capacitor, a first end of which is connected between the non-inverting input end of the first comparator and the fourth resistor, and a second end of which is grounded;
and a fourth capacitor, a first end of which is connected between the inverting input end of the first comparator and the fifth resistor, and a second end of which is grounded.
8. The circuit of claim 5, wherein the detection unit further comprises:
and the first one-way element is arranged between the output end of the first comparator and the voltage division loop, the anode of the first one-way element is connected with the output end of the first comparator, and the cathode of the first one-way element is connected with the voltage division loop.
9. The circuit of claim 1, wherein the signal processing module comprises:
the input end of the filtering unit is connected with the sampling module, and the output end of the filtering unit is connected with the input end of the analog-to-digital conversion unit and is used for filtering the sampling square wave signal output by the sampling module;
and the output end of the analog-to-digital conversion unit is connected with the microprocessor and is used for converting the sampling square wave signals filtered by the filtering unit into digital signals and outputting the digital signals to the microprocessor.
10. The circuit of claim 9, further comprising:
and the non-inverting input end of the second comparator is connected between the filtering unit and the analog-to-digital conversion unit, the inverting input end of the second comparator inputs reference voltage, and the output end of the second comparator is connected with the microprocessor.
11. An electric consumer characterized by comprising a grid anomaly detection circuit according to any one of claims 1 to 10.
12. The circuit of claim 11, wherein the powered device is a photovoltaic air conditioner.
13. A power grid abnormality detection method is characterized by comprising the following steps:
respectively detecting the frequency of any two-phase voltage of three-phase voltages output by an alternating current power grid, and generating a sampling square wave signal based on the phase difference between the any two-phase voltages;
processing the sampling square wave signal;
and judging whether the power grid is abnormal or not according to the frequency of any two-phase voltage and the processed sampling square wave signal.
14. The method of claim 13, wherein determining whether the grid is abnormal according to the frequency of the any two-phase voltage and the processed sampled square wave signal comprises:
judging whether the frequency of any two-phase voltage is within a preset range;
if not, judging that the power grid is abnormal;
if yes, whether the power grid is abnormal or not is continuously judged according to the processed sampling square wave signals.
15. The method of claim 14, wherein continuing to determine whether the grid is abnormal based on the processed sampled square wave signal comprises:
judging whether the voltage effective value of the sampling square wave signal is equal to a preset value or not;
if so, judging that the power grid is normal;
and if not, judging that the power grid is abnormal.
16. The method of claim 14, wherein after determining whether the frequency of any two-phase voltage is within a predetermined range, the method further comprises:
if the judgment result is negative, determining whether the frequency of only one-phase voltage is not in a preset range; if the frequency of only one-phase voltage is not in the preset range, replacing the detection unit connected with the output terminal of the one-phase voltage with a standby detection unit, wherein the frequency of the one-phase voltage is not in the preset range;
judging whether the frequency of any two-phase voltage is within a preset range;
if not, judging that the power grid is abnormal;
if yes, whether the power grid is abnormal or not is continuously judged according to the processed sampling square wave signals.
17. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, carries out the method according to any one of claims 13 to 16.
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| CN117666334A (en) * | 2024-02-01 | 2024-03-08 | 东方博沃（北京）科技有限公司 | Product parameter self-adaption device, method, system, equipment and medium |
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| CN117666334A (en) * | 2024-02-01 | 2024-03-08 | 东方博沃（北京）科技有限公司 | Product parameter self-adaption device, method, system, equipment and medium |
| CN117666334B (en) * | 2024-02-01 | 2024-04-12 | 东方博沃（北京）科技有限公司 | Product parameter self-adaption device, method, system, equipment and medium |
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