CN107561346B - Method for rapidly detecting three-phase mains supply voltage abnormity - Google Patents
Method for rapidly detecting three-phase mains supply voltage abnormity Download PDFInfo
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- CN107561346B CN107561346B CN201710624647.5A CN201710624647A CN107561346B CN 107561346 B CN107561346 B CN 107561346B CN 201710624647 A CN201710624647 A CN 201710624647A CN 107561346 B CN107561346 B CN 107561346B
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Abstract
A method for quickly detecting three-phase mains voltage abnormity includes defining a new variable by effective voltage value, listing expression of variable, substituting three effective voltage value expressions into expression of variable to obtain simplified expression of variable only related to amplitude of AC voltage and not related to mains period, comparing value of variable with normal value of mains voltage, judging that mains voltage is abnormal if value of variable is greater than allowable maximum value or smaller than allowable minimum value. The detection method converts the detection of three alternating current variables into the detection of one direct current variable, reduces the detection time from the power failure of commercial power to the work of the rectifier, timely starts the rectifier, reduces the voltage reduction amplitude caused by the fact that the BUS capacitor supplies power to the load all the time due to no energy input, reduces the fluctuation of the voltage of the BUS capacitor, further reduces the fluctuation converted into the alternating current voltage by the inverter, improves the stability of the power supply to the load, and provides a high-quality alternating current power supply for the load.
Description
Technical Field
The invention relates to the technical field of power equipment, in particular to a method for rapidly detecting three-phase mains supply voltage abnormity.
Background
UPS, i.e., an uninterruptible power supply, is a system device in which a storage battery (mostly a lead-acid maintenance-free storage battery) is connected to a host, and dc power is converted into commercial power by a module circuit such as a host inverter. The UPS provides uninterrupted power supply for the customer, and when the commercial power is abnormal, the AC input needs to be cut off, and the power is switched to DC power supply. The key of the abnormal commercial power voltage can be quickly detected, however, the detection technology in the prior art enables the effective value of the commercial power to be used for calculation, then whether the commercial power voltage is abnormal or not is judged according to the result of the effective value calculation of the commercial power, the effective value of the commercial power needs at least half period, the detection time is too long, the voltage fluctuation of a BUS capacitor is too large, the fluctuation of the converted alternating current output voltage is too large, and the normal operation of a load is influenced.
Disclosure of Invention
In view of the above-mentioned drawbacks, the present invention provides a method for rapidly detecting an abnormal voltage of a three-phase mains supply, which greatly reduces the detection time, reduces the fluctuation of the BUS capacitor voltage, reduces the fluctuation of the converted ac output voltage, and ensures the normal operation of the load.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for quickly detecting three-phase mains supply voltage abnormality defines three-phase mains supply voltage, and lists three effective voltage value expressions, namely three effective voltage value expressions, according to an alternating voltage amplitude A, a mains supply period 1/f and a mains supply period omega-2 pi f
And
the method comprises the following steps:
A. defining a new variable udc (t) by the effective value of the voltage, and listing the expression of the variable
Substituting the three effective voltage value expressions into the expression of the variable, and simplifying by using trigonometric function integration and difference formulas to obtain a simplified expression of the variable
The simplified expression of the variable is a direct current quantity, which is only related to the amplitude A of the alternating voltage and is not related to the period f of the mains supply;
B. when the mains voltage is normal, the amplitude A of the alternating voltage is equal to 220V, and the amplitude A of the alternating voltage is substituted into the simplified expression of the variable
At this time, the variable udc (t) is calculated to be 380 volts, namely the normal value of the mains voltage is 380 volts;
C. simplified expression of said variables
Is a direct current quantity, the voltage of the BUS capacitor is equivalent to the amplitude A of the alternating current voltage, namely the voltage of the BUS capacitor for PWM controlled by an inverter is substituted into a simplified expression of the variable
Calculating the variable udc (t), comparing the value of the variable with the normal value of the mains voltage, and if the allowed mains voltage range is +/-20%, if the value of the variable is beyond 380 +/-20% volts, the mains voltage is abnormal;
D. each period of the PWM is 52 microseconds, the PWM is continuously performed for 10 periods, whether the value of the variable is smaller than the normal value of the mains voltage or not is detected, and if the abnormal state occurs, the power supply to the BUS capacitor is started; and if no abnormal state appears after detection, continuing to perform commercial power detection for next continuous 10 PWM periods.
Preferably, the frequency f of the alternating current is 50 Hz; and calculating the voltage effective value through one or half cycle of the alternating current to judge whether the mains supply voltage is normal, wherein the detection time is 20 milliseconds or 10 milliseconds.
Preferably, a rectifier is further provided, and the opening and closing of the rectifier is controlled by the detected state.
Preferably, a voltage drop expression is also provided
The voltage drop expression comprises inverter output power Pinv, detection time Tint from the power failure of mains supply to the work of the rectifier, a BUS capacitor voltage control value V1, a BUS capacitor voltage minimum value V2 and BUS capacitor capacity Cbus.
Preferably, according to the voltage drop expression, the capacity of the BUS capacitor is kept unchanged, and the lowest voltage value of the BUS capacitor is adjusted by changing the detection time.
Preferably, according to the voltage drop expression, the lowest value of the voltage of the BUS capacitor is kept unchanged, and the capacitance of the BUS capacitor is adjusted by changing the detection time.
The invention has the technical effects that: the detection method greatly reduces the detection time from the power failure of the mains supply to the work of the rectifier, starts the rectifier more timely, reduces the voltage reduction amplitude caused by the fact that the BUS capacitor supplies power to the load all the time due to no energy input, reduces the fluctuation of the voltage of the BUS capacitor, further reduces the fluctuation converted into alternating voltage by the inverter, improves the stability of the power supply to the load, and provides a high-quality alternating current power supply for the load.
Drawings
FIG. 1 is a diagram of master-slave synchronization signals of the present invention.
Detailed Description
The technical solution of the present invention is further explained by the specific embodiment mode with reference to the attached drawings.
In an embodiment, when the mains voltage is abnormal in power failure, a method for rapidly detecting the abnormality of the three-phase mains voltage defines the three-phase mains voltage, and three voltage effective value expressions are listed according to an ac voltage amplitude a, a mains period 1/f and a mains period ω ═ 2 π f, where each expression is represented by an ac voltage amplitude a and a ac voltage period 1/f
And
the method comprises the following steps:
A. defining a new variable udc (t) by the effective value of the voltage, and listing the expression of the variable
Substituting the three effective voltage value expressions into the expression of the variable, and simplifying by using trigonometric function integration and difference formulas to obtain a simplified expression of the variable
The simplified expression of the variable is a direct current quantity, which is only related to the amplitude A of the alternating voltage and is not related to the period f of the mains supply;
B. when the mains voltage is normal, the amplitude A of the alternating voltage is equal to 220V, and the amplitude A of the alternating voltage is substituted into the simplified expression of the variable
At this time, the variable udc (t) is calculated to be 380 volts, namely the normal value of the mains voltage is 380 volts;
C. simplified expression of said variables
Is a direct current quantityThe voltage of the BUS capacitor is equivalent to the amplitude A of the alternating voltage, namely the voltage of the BUS capacitor for PWM controlled by the inverter is substituted into the simplified expression of the variable
Calculating the variable udc (t), comparing the value of the variable with the normal value of the mains voltage, and if the allowed mains voltage range is +/-20%, if the value of the variable is beyond 380 +/-20% volts, the mains voltage is abnormal;
D. each period of the PWM is 52 microseconds, the PWM is continuously performed for 10 periods, whether the value of the variable is smaller than the normal value of the mains voltage or not is detected, and if the abnormal state occurs, the power supply to the BUS capacitor is started; and if no abnormal state appears after detection, continuing to perform commercial power detection for next continuous 10 PWM periods.
Firstly, defining the three-phase mains supply voltage, listing related effective voltage value expressions according to an alternating voltage amplitude and a mains supply period, substituting the effective voltage value expressions into the variables by defining the variables, and simplifying to obtain simplified expressions of the variables; the simplified expression is a direct current quantity, and the expression is only related to the amplitude of the alternating current voltage; the variable can be changed by changing the amplitude of the alternating voltage, however, because the variable is a direct current quantity, when the mains voltage is abnormal, if the mains voltage is cut off, the BUS capacitor supplies power to the load, namely the BUS capacitor outputs the direct current voltage, the direct current voltage is converted into the alternating current voltage through the inverter to supply power to the load, the direct current voltage output by the BUS capacitor at the moment is equivalent to the amplitude of the alternating current voltage, the direct current voltage output by the BUS capacitor can be substituted into the simplified expression of the variable to calculate the value of the variable at the moment, the value of the variable is compared with the normal value of the mains voltage, if the value of the variable is lower than the normal value of the mains voltage, the rectifier is started to supply power to the BUS capacitor, each cycle of the PWN is 52 microseconds, 10 continuous cycles are 520 microseconds, and whether the mains voltage is abnormal or not is judged by using the effective value, the detection method greatly reduces the detection time from the power failure of the mains supply to the work of the rectifier, starts the rectifier more timely, reduces the voltage reduction amplitude caused by the fact that the BUS capacitor supplies power to the load all the time due to no energy input, reduces the fluctuation of the voltage of the BUS capacitor, further reduces the fluctuation converted into alternating voltage by the inverter, improves the stability of the power supply to the load, and provides a high-quality alternating current power supply for the load.
More specifically, the frequency f of the alternating current is 50 Hz; and calculating the voltage effective value through one or half cycle of the alternating current to judge whether the mains supply voltage is normal, wherein the detection time is 20 milliseconds or 10 milliseconds.
The frequency of the alternating current is 50 Hz, whether the mains voltage is normal or not is judged by calculating the voltage effective value, however, the voltage effective value can be obtained only by half a period, the detection time is at least 10 milliseconds, and the detection method of the invention reduces the detection time of the mains voltage abnormity from 10 milliseconds to 520 milliseconds, greatly reduces the detection time, reduces the voltage reduction amplitude of the BUS capacitor, and further ensures the normal operation of the load.
Further, a rectifier is provided, and the opening and closing of the rectifier is controlled by the detected state.
When the mains voltage is abnormal, if the power is off, the BUS capacitor still supplies power to the load under the condition of no energy input, at the moment, the voltage of the BUS capacitor starts to be reduced, at the moment, the value of the variable is calculated according to the voltage of the BUS capacitor through PWM controlled by the inverter, the value of the variable is compared with the normal value of the mains voltage, and the value of the variable is correspondingly reduced because the voltage of the BUS capacitor is reduced, so that the value of the variable is lower than the normal value of the mains voltage, the abnormal mains voltage can be judged at the moment, the rectifier is started, the battery supplies power to the BUS capacitor, the voltage of the BUS capacitor is recovered and is stable, the alternating current output voltage converted by the inverter is also stable and unchanged, and the normal operation of the load is ensured.
Further, a voltage drop expression is also provided
The voltage drop expression comprises inverter output power Pinv, detection time Tint from the power failure of mains supply to the work of the rectifier, a BUS capacitor voltage control value V1, a BUS capacitor voltage minimum value V2 and BUS capacitor capacity Cbus.
The BUS capacitor voltage reduction expression is set, the inverter output power and the BUS capacitor voltage control value in the expression are kept unchanged, therefore, the detection time can be changed, the lowest value of the BUS capacitor voltage or the BUS capacitor capacity is changed, the reduced BUS capacitor voltage is equivalent to the lowest value of the BUS capacitor voltage, the variable value can be calculated through the lowest value of the BUS capacitor voltage, and the detection algorithm is simple and fast.
Further, according to the voltage drop expression, the capacity of the BUS capacitor is kept unchanged, and the lowest voltage value of the BUS capacitor is adjusted by changing the detection time.
Keeping the capacity of the BUS capacitor unchanged, reducing the detection time, increasing the lowest voltage value of the BUS capacitor at the moment, and reducing the voltage drop under the condition that the voltage control value of the BUS capacitor is unchanged; the voltage drop amount becomes small, the voltage change range of the BUS capacitor becomes small, the disturbance to the inverter is reduced, the influence on the alternating current output voltage of the inverter becomes small, and the output stability of the UPS is enhanced.
Further, according to the voltage drop expression, the lowest value of the voltage of the BUS capacitor is kept unchanged, and the capacity of the BUS capacitor is adjusted by changing the detection time.
The minimum but suitable BUS capacitor voltage lowest value is set, the BUS capacitor voltage lowest value is kept unchanged, the detection time is shortened, the BUS capacitor capacity is reduced under the condition that the voltage drop is unchanged, therefore, the BUS with the smaller capacitor capacity can be selected by reducing the detection time, and the production cost is reduced.
The technical principle of the present invention is described above in connection with specific embodiments. The description is made for the purpose of illustrating the principles of the invention and should not be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive effort, which would fall within the scope of the present invention.
Claims (4)
1. A method for quickly detecting three-phase mains supply voltage abnormality defines three-phase mains supply voltage, and lists three effective voltage value expressions, namely three effective voltage value expressions, according to an alternating voltage amplitude A, a mains supply period 1/f and a mains supply period omega-2 pi f
the method is characterized in that: the method comprises the following steps:
A. defining a new variable udc (t) by the effective value of the voltage, and listing the expression of the variable
Substituting the three effective voltage value expressions into the expression of the variable, and simplifying by using trigonometric function integration and difference formulas to obtain a simplified expression of the variable
The simplified expression of the variable is a direct current quantity, is only related to the amplitude A of the alternating voltage and is not related to the period 1/f of the mains supply;
B. when the mains voltage is normal, the amplitude A of the alternating voltage is equal to 220V, and the amplitude A of the alternating voltage is substituted into the simplified expression of the variable
At this time, the variable udc (t) is calculated to be 380 volts, namely the normal value of the mains voltage is 380 volts;
C. simplified expression of said variables
Is a direct current quantity, the voltage of the BUS capacitor is equivalent to the amplitude A of the alternating current voltage, namely the inverter is controlled by PWM, and the voltage of the BUS capacitor is substituted into the simplified expression of the variable
Calculating the variable udc (t), comparing the value of the variable with the normal value of the mains voltage, wherein the allowed mains voltage range is +/-20%, and if the value of the variable is out of 380 +/-20% of volts, the mains voltage is abnormal;
D. each period of the PWM is 52 microseconds, the PWM is continuously performed for 10 periods, whether the value of the variable is smaller than the normal value of the mains voltage or not is detected, and if the abnormal state occurs, the power supply to the BUS capacitor is started; if no abnormal state appears after detection, continuing to perform commercial power detection for next continuous 10 PWM periods;
the rectifier is also arranged, and the opening and closing of the rectifier are controlled through the detected state;
and a voltage drop expression is also provided
The voltage drop expression comprises inverter output power Pinv, detection time Tint from commercial power outage to work of the rectifier, and BUS capacitor voltage control value V1BUS capacitor voltage lowest value V2And BUS capacitance Cbus。
2. The method as claimed in claim 1, wherein the method further comprises: the frequency f of the commercial power is 50 Hz; and calculating the voltage effective value through one or half cycle of the alternating current to judge whether the mains supply voltage is normal, wherein the detection time is 20 milliseconds or 10 milliseconds.
3. The method as claimed in claim 1, wherein the method further comprises: and according to the voltage drop expression, keeping the capacity of the BUS capacitor unchanged, and adjusting the lowest voltage value of the BUS capacitor by changing the detection time.
4. The method as claimed in claim 1, wherein the method further comprises: and according to the voltage drop expression, keeping the lowest voltage value of the BUS capacitor unchanged, and adjusting the capacity of the BUS capacitor by changing the detection time.
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| CN112818052A (en) * | 2021-02-25 | 2021-05-18 | 云南电网有限责任公司电力科学研究院 | Abnormal voltage data detection method and device |
| CN114336939B (en) * | 2021-12-30 | 2023-06-16 | 盈帜科技（常州）有限公司 | Method for judging overvoltage and undervoltage of mains supply |
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| CN102338833B (en) * | 2011-06-03 | 2013-04-17 | 厦门科华恒盛股份有限公司 | Method for detecting abnormality of urban power supply quickly |
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