CN108508380B - Rapid detection method for AC voltage power failure - Google Patents
Rapid detection method for AC voltage power failure Download PDFInfo
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- CN108508380B CN108508380B CN201810367092.5A CN201810367092A CN108508380B CN 108508380 B CN108508380 B CN 108508380B CN 201810367092 A CN201810367092 A CN 201810367092A CN 108508380 B CN108508380 B CN 108508380B
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Abstract
The invention discloses a method for rapidly detecting AC voltage power failure, which comprises the following steps: sampling the voltage of the AC power supply to obtain the maximum working voltage peak value Umax and the minimum working voltage of the AC power supplyPeak value Umin and angular frequency ω; thereby obtaining two limit value curves of the AC power supply,
two change rate limit values which are compared in real time are obtained through differentiation,
performing difference processing on the voltage sampling value Ut1 at the current time t1 and the voltage sampling value Ut0 at the previous time t0 to obtain a value delta Ut1-Ut 1-Ut0 and a value delta t-t 1-t 0; 103) and when the Ut1 is smaller than the lowest voltage instantaneous value Uminsin (ω t1), determining that the AC power supply is powered down. The method has good timeliness and high accuracy, can quickly respond to the power supply state change of the power grid, and reduces the influence of the terminal equipment caused by the dynamic change of the power grid.
Description
[ technical field ]
The invention relates to a grid-connected device of a power grid, in particular to a rapid detection method for AC voltage power failure.
[ background art ]
With the wide application of renewable energy sources such as solar photovoltaic energy, wind energy and the like, the energy crisis is effectively relieved. There are two main ways of renewable energy application: the method comprises the steps of firstly, directly supplying power to terminal equipment through conversion, and secondly, generating power through conversion and grid connection. Due to the inherent random fluctuation and instability of renewable energy sources, renewable energy sources such as photovoltaic energy, wind energy and the like are mostly applied in a second mode.
By switching grid-connected power generation, when a connected power grid is tripped due to faults, accidents or power failure maintenance, the power failure state of the power grid needs to be detected in time, and if a grid-connected power generation system is not quickly disconnected from the connected power grid, a self-sufficient power supply island formed by a photovoltaic power generation system and surrounding loads can be formed. After an island is generated, safety hazards are formed on personnel who overhaul in an island power grid, the electric energy quality of the island power grid is deteriorated, the phenomena of voltage fluctuation, frequency fluctuation, power grid distortion and the like exist, and the reliable operation of electric equipment is influenced to form the hazards. Therefore, the rapid detection of the AC voltage power failure plays a very important role in the full utilization of renewable energy sources and the safe, reliable and stable operation of a power grid.
Along with the development of the internet of things and the internet, the reliability requirement of information communication equipment on a power supply device is higher and higher, but a public power grid cannot supply power to the equipment at any time due to factors such as maintenance and faults, and two main solutions are provided at present: firstly, adding UPS (Uninterended Power supply) Power supply device; and secondly, the power supply device increases the Hold Up Time function. The UPS power supply device ensures that an internal battery is started to supply power to the information communication equipment when the power grid is interrupted; and after the Hold Up Time function is interrupted in the power grid, maintaining the energy guarantee information communication equipment for a period of Time for information safety processing. Both of these approaches require the application of a fast detection AC voltage power down technique. The method for rapidly detecting the AC voltage power failure has important effects on guaranteeing uninterrupted power supply of the UPS and reducing the design cost of the Hold UP Time function.
One currently adopted scheme for rapidly detecting AC voltage power failure and recovering is a method of voltage reduction, rectification, filtering and threshold judgment. The basic principle is shown in figure 1:
after the alternating voltage is rectified, filtered and impedance-divided, a direct voltage with small ripples is generated on a capacitor C01, and the direct voltage is compared with a VREF voltage division value through a U5-A comparator. When Vc01 is higher than the divided voltage value of VREF, UVP is high level '1', which represents that the alternating current voltage is normal; when Vc01 is lower than the divided voltage value of VREF, UVP is low level "0" representing ac voltage under-voltage or power-down. The method has a simple structure, but has a slow response speed in judgment due to the RC filtering delay link.
Another scheme currently adopted by the method for rapidly detecting the AC voltage power failure and recovering is to compare and judge a signal to be detected with a sample plate sinusoidal voltage waveform by using software, and for example, in the invention application with the publication number CN101452016A, "voltage sag detection method and device", a voltage sampling change rate mode is adopted to judge whether the voltage sags. The method improves the judgment speed, but has low accuracy and erroneous judgment on the occasion that fluctuation exists in the normal voltage range.
The invention with publication number CN1548965A 'AC voltage under-voltage detection circuit' adopts fast and slow filters to accelerate the response speed and reduce the misjudgment in the situation of fluctuation in the normal range of voltage. However, the working principle of the filter has the phenomena of cross selection and unclear channel selection in the design of the fast and slow filters, and the practical value is not high.
In the design of practical power supply devices, in order to meet the requirements of EMC, EMC filter circuits are added to the alternating current ports, wherein X capacitance is a key component in the EMC circuits. In order to meet global general requirements, power supply devices are generally designed to have a wide voltage input range, taking a single phase as an example, the wide voltage input range: 90-277 Vac. When the alternating current power grid is interrupted, the X capacitor stores energy, and the higher the input voltage is, the larger the energy stored by the X capacitor is. With the enhancement of energy saving and environmental protection awareness of people, the no-load loss requirement of power supply devices is lower and lower, and taking a six-level energy efficiency standard introduced in 2016 as an example, the CoC V5 requires that the power consumption of a power adapter (>0.3W and <49W) in the no-load mode is less than 0.075W. In order to meet the requirement of no-load power consumption, the power supply device generally operates in an intermittent hiccup mode when the power supply device is in no-load, does not work in the interval time, and is approximately zero power consumption, so that the average power consumption is reduced. This brings a new problem to the above past AC voltage power down and recovery detection method: because the power consumption is low under the no-load mode, the X capacitor has obvious delay effect on the alternating current sampling circuit.
In renewable energy grid-connected application, when grid-connected power is small, the situation that the voltage of an AC port is slowly reduced due to the influence of X capacitor energy storage filtering also exists.
With the input voltage: u1 ═ 240V, X capacitance: c ═ 2.2uF, no load power consumption: for example, when P is 0.05W, the discharge time Tdelay is calculated until the X capacitance decays to U2V of 90V.
By calculation, it can be known that: under the no-load state, because of the influence of the energy storage filtering of the X capacitor, the voltage of the port of the alternating current power grid needs more than 1 second to be reduced to the under-voltage range, and the existing method for comparing the threshold value needs more than 1 second to judge whether the AC is powered down, so that the timeliness cannot be met. In the method described in the invention application "voltage sag detection method and apparatus" with publication number CN101452016A, the influence of the X capacitor is to reduce the change rate (Δ U) of the sampled voltage at the AC power grid port, and the determination condition is that Δ U needs to be greater than a certain value, so that the patent application also cannot accurately and timely determine whether the AC is powered down.
[ summary of the invention ]
The invention aims to provide a rapid detection method of AC voltage power failure with good timeliness and high accuracy.
In order to solve the technical problem, the invention adopts the technical scheme that the method for rapidly detecting the AC voltage power failure comprises the following steps:
101) sampling the voltage of the AC power supply to obtain the angular frequency omega of the AC power supply, and obtaining the maximum working voltage peak value according to the maximum allowable working voltage effective value Urmsmax of the AC power supply and the minimum allowable working voltage effective value Urmsmin of the AC power supply
Minimum peak operating voltage
And two limit curves of the AC power source are obtained, respectively,
the two change rate limit values which are compared in real time are obtained by differentiating the above formula, and are respectively:
102) performing difference processing on the voltage sampling value Ut1 at the current time t1 and the voltage sampling value Ut0 at the previous time t0 to obtain a value delta Ut1-Ut 1-Ut0 and a value delta t-t 1-t 0;
103) and when the Ut1 is smaller than the lowest voltage instantaneous value Uminsin (ω t1), determining that the AC power supply is powered down.
According to the method for rapidly detecting the AC voltage power failure, when Ut1 is larger than Uminsin (ω t1), and meanwhile, Δ Ut1 is smaller than DUmax (t0) Δ t and larger than DUmin (t0) Δ t, the AC power supply voltage is judged to be normal.
According to the method for rapidly detecting the AC power failure, when Ut1 is larger than Uminsin (ω t1), but Δ Ut1 is larger than DUmax (t0) Δ t, the AC power failure is judged.
According to the rapid detection method for the AC voltage power failure, when Ut1 is larger than Uminsin (ω t1), and meanwhile Δ Ut1 is smaller than DUmin (t0) Δ t, if the device is in a working state, the AC power supply voltage is judged to be normal; if the device works in a standby state, the rectifying circuit needs to be started, the energy on the X capacitor is transferred to the rectifying circuit, and then sampling is carried out again, and then judgment is carried out.
According to the method for rapidly detecting the AC voltage power failure, the voltage sampling circuit comprises the impedance voltage division attenuation circuit and the rapid filter circuit, and the sampling point of the voltage sampling circuit is selected between the EMC filter circuit and the rectifier circuit of the AC power supply.
The rapid detection method for the AC power supply voltage power failure has good timeliness. The accuracy is high, the power supply state of the power grid can be quickly responded, the dynamic change of the power grid can be timely met, and the influence of the terminal equipment caused by the dynamic change of the power grid is reduced.
[ description of the drawings ]
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a schematic diagram of a prior art fast detection of AC voltage power loss.
Fig. 2 is a schematic diagram of a sampling circuit for AC voltage power down detection according to an embodiment of the present invention.
Fig. 3 is a flowchart of a method for rapidly detecting AC voltage loss according to an embodiment of the present invention.
[ detailed description of the invention ]
Aiming at the current situations that the idle load state in practical application in the prior art is poor in timeliness and misjudgment exists, the invention provides a novel detection method, which makes up the defects in the prior art and improves timeliness and accuracy. The specific method comprises the following steps:
in order to guarantee sampling accuracy, an impedance voltage division attenuation circuit and a rapid filter circuit are adopted in hardware; the rear end of the impedance voltage division attenuation circuit is added with a fast filter circuit, so that timeliness can be guaranteed, interference influence of other circuits on sampling is avoided, and a typical voltage sampling circuit is shown in figure 2.
The microcontroller receives the AC voltage sampling value, detects the zero crossing point time as an initial phase, counts the interval time T/2 before the adjacent zero crossing point, calculates the AC voltage frequency f to be 1/T and the angular frequency omega to be 2 pi f, and calculates the actual AC voltage
The maximum allowable working voltage effective value of the AC power supply is Urmsmax, the minimum allowable working voltage effective value of the AC power supply is Urmsmin, and the maximum working voltage peak value is obtained
Minimum peak operating voltage
Actual ac voltage
According to the calculated omega and the working voltage range of the device, two limit curves which are compared in real time are obtained, wherein the two limit curves are respectively as follows:
Umax(t)＝Umaxsin(ωt)
Umin(t)＝Uminsin(ωt)
the two change rate limit values which are compared in real time are obtained by differentiating the above formula, and are respectively:
DUmax(t)＝ωUmaxcos(ωt)
DUmin(t)＝ωUmincos(ωt)
where Umax is the device maximum operating voltage peak and uman is the device minimum operating voltage peak.
The determination flowchart is shown in fig. 3:
and performing difference processing on the voltage sampling value Ut1 at the current time t1 and the voltage sampling value Ut0 at the previous time t0 to obtain a value of delta Ut1-Ut 1-Ut0 and a value of delta t-t 1-t 0.
When the Ut1 is smaller than the lowest voltage instantaneous value Uminsin (ω t1), the power failure is directly judged.
When Ut1 is larger than Uminsin (ω t1), and Δ Ut1 is smaller than DUmax (t0) Δ t and larger than DUmin (t0) Δ t, the result is judged to be normal because the change rate is within the normal range.
When Ut1 is larger than Uminsin (ω t1) but Δ Ut1 is larger than DUmax (t0) Δ t, the voltage is represented to change rapidly, and the voltage is indicated to be abnormal, and the power failure is determined.
When Ut1 is larger than Uminsin (ω t1) and Δ Ut1 is smaller than DUmin (t0) Δ t, if the device is in a working state, the power grid energy supporting device works, and only the power grid is distorted, the device is judged to be normal; if the device works in a standby state, the rectifying circuit needs to be started to work, energy on the X capacitor is transferred to the rectifying circuit (work disturbance), the influence of energy storage of the X capacitor is eliminated, sampling is carried out again, if the voltage change rate is increased, power failure is considered, and otherwise, the power failure is considered to be normal.
The method for rapidly detecting the AC power supply voltage power failure in the embodiment of the invention has good timeliness and high accuracy, can rapidly respond to the power supply state of the power grid, timely responds to the dynamic change of the power grid, and reduces the influence of terminal equipment caused by the dynamic change of the power grid.
Claims (2)
1. A method for rapidly detecting AC voltage power failure is characterized by comprising the following steps:
101) sampling the voltage of the AC power supply to obtain the angular frequency omega of the AC power supply, and obtaining the maximum working voltage peak value according to the maximum allowable working voltage effective value Urmsmax of the AC power supply and the minimum allowable working voltage effective value Urmsmin of the AC power supply
Minimum peak operating voltage
And two limit curves of the AC power source are obtained, respectively,
the two change rate limit values which are compared in real time are obtained by differentiating the above formula, and are respectively:
102) performing difference processing on the voltage sampling value Ut1 at the current time t1 and the voltage sampling value Ut0 at the previous time t0 to obtain a value delta Ut1-Ut 1-Ut0 and a value delta t-t 1-t 0;
103) when Ut1 is smaller than the lowest voltage instantaneous value Uminsin (ω t1), judging that the AC power supply is powered down; when Ut1 is larger than Uminsin (ω t1), and meanwhile, Δ Ut1 is smaller than DUmax (t0) Δ t and larger than DUmin (t0) Δ t, judging that the AC power supply voltage is normal; when Ut1 is larger than Uminsin (ω t1) but Δ Ut1 is larger than DUmax (t0) Δ t, judging that the AC power supply is powered down; when Ut1 is larger than Uminsin (ω t1) and Δ Ut1 is smaller than DUmin (t0) Δ t, if the device is in a working state, judging that the AC power supply voltage is normal; if the device works in a standby state, the rectifying circuit needs to be started, the energy on the X capacitor is transferred to the rectifying circuit, and then sampling is carried out again, and then judgment is carried out.
2. The method for rapidly detecting AC voltage power failure of claim 1, wherein the voltage sampling circuit comprises an impedance voltage division attenuation circuit and a fast filter circuit, and the sampling point of the voltage sampling circuit is selected between an EMC filter circuit and a rectification circuit of the AC power supply.
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| CN109194106B (en) * | 2018-09-30 | 2024-03-19 | 杰华特微电子（张家港）有限公司 | X capacitor discharging method, discharging circuit and switching circuit |
| CN109444643A (en) * | 2018-12-20 | 2019-03-08 | 武汉海王科技有限公司 | A kind of single-phase sinusoidal signal power down rapid detection method and system |
| CN111103554B (en) * | 2019-11-27 | 2022-10-04 | 九阳股份有限公司 | Power failure detection method, device, circuit system and computer storage medium |
| CN111711263B (en) * | 2020-06-29 | 2024-02-09 | 王军库 | Monitor power supply switching system |
| CN112180284A (en) * | 2020-09-23 | 2021-01-05 | 歌尔科技有限公司 | Power failure detection method and device for alternating current power supply of electric equipment and related equipment |
| CN112068024A (en) * | 2020-09-30 | 2020-12-11 | 中国航空工业集团公司雷华电子技术研究所 | Fault detection method and fault detection circuit for three-phase alternating current source |
| CN114545283A (en) * | 2020-11-24 | 2022-05-27 | 青岛海尔电冰箱有限公司 | Power failure detection method and device and power utilization equipment with same |
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| CN102901936B (en) * | 2012-10-19 | 2015-04-22 | 海信（山东）空调有限公司 | Poweroff detection method of alternating current power supply and poweroff protection method of direct current inverter compressor |
| CN105587476B (en) * | 2016-01-13 | 2018-03-13 | 中国农业大学 | A kind of state monitoring method and device for wind generator system |
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