JPH0247560A - System for detecting instantaneous lowering in voltage at high speed - Google Patents

Abstract

PURPOSE:To detect many trouble-states such as an instantaneous voltage lowering power suspension accurately at high speed by combining the detected results of overload current, overcurrent in commercial power source, decrease in commercial power source, zero commercial current and the like, and judging the instantaneous voltage drop. CONSTITUTION:When a current ¦is¦ from a commercial power source 1 is higher than a specified value ISCOMP, when a voltage Vs of the commercial power source is lower than a specified value VSCOMP or when the current ¦is¦ is zero, a high level signal is supplied to a NOR circuit 13. When at least one value is at a high level, the specified judged output is sent into an AND circuit 14 having an inverted terminal. When the judged output is supplied from the NOR circuit 13 and the sum ¦is+ii¦ of the currents from the commercial power source and a compensating power source is lower than an overload current value ILCOMP, it is judged that there is an instantaneous lowering. In this way, various trouble states can be detected accurately at a high speed, and compensation responding time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a high-speed instantaneous voltage drop detection method for compensating for an instantaneous voltage drop in a commercial power source.

B1 Overview of the Invention The present invention provides an instantaneous voltage drop high-speed detection method that compensates for instantaneous voltage drops in commercial power supplies, which detects overload current, commercial power supply overcurrent, and commercial power supply voltage. 'l! By combining the detection results such as R'Wi pressure drop and zero commercial power supply current to determine the instantaneous voltage drop of the commercial power supply, and at the time of this determination, drive the compensation power supply to compensate for the voltage drop of the commercial power supply. This system is designed to accurately and quickly detect various trouble states such as voltage drop, load short circuit, and power outage, and to shorten compensation response time.

C9 Conventional technology Uninterruptible power supply bag W (UPS; Uninterr
up-ible power (5upply) is generally known. The basic system of the uninterruptible i power supply is a constant inverter power supply method that always supplies power with a CVCF inverter regardless of the presence or absence of commercial power supply, and a constant inverter power supply method that always supplies power directly from commercial power supply and only uses a battery when there is a momentary voltage drop or power outage of commercial power supply. There is a constant commercial power supply method in which power is input from a CVCF inverter.

Currently, constant inverter power supply methods are often used (but
The biggest reason for this is that transient fluctuations in the power supply voltage during instantaneous voltage drops or power outages are small (eg -5% or less). On the other hand, the continuous commercial power supply method is advantageous in terms of operational efficiency and noise because it always supplies power with a commercial power source, but the response time is slow because it switches to inverter power supply after detecting a voltage drop in the event of an instantaneous voltage drop or power outage. Become,
This has the disadvantage that transient voltage fluctuations become large.

Here, FIG. 5 shows an example of an uninterruptible power supply device of a constant commercial power supply type. In FIG. 5, 1 is a commercial power source, and the commercial power source 1 is connected to a load 3 via a semiconductor switch 2. In FIG. The semiconductor switch 2 is constructed by, for example, connecting gate turn-off switches 4.5 in parallel. An instantaneous voltage drop compensator 8 is connected to a common connection point G between the semiconductor switch 2 and the load 3 via a filter 7 consisting of a capacitor C and a reactor L. The instantaneous voltage drop compensator 8 includes a battery 9, a bidirectional power converter IO that converts AC into DC or DC into AC, and a transformer 11 connected between the bidirectional power converter IO and the filter 7. It is made up of. 12 is a compensation control device for the instantaneous voltage drop compensator 8. In addition, PT-, PT in the figure
+ is a voltage transformer, CT, CTt is a current transformer.

In the device configured as described above, AC power led from a commercial power source 1 via a semiconductor switch 2 is supplied to a load 3, and is also connected to a filter 7, a transformer 11 of an instantaneous voltage drop compensator 8, and a bidirectional power source. It is supplied to the battery 9 via the converter 10. In addition, the instrument transformer PT
, detects a drop in the AC voltage, the compensation control device 12 supplies an off control signal to the semiconductor switch 2, turning the switch 2 off, and the compensation control device ! A control signal is supplied from 2 to the main semiconductor element constituting the inverter of the bidirectional power converter IO, such as Cyrisk, and the bidirectional power converter IO performs a reverse power conversion operation. As a result, the DC power of the battery 9 is converted into AC by the bidirectional power converter 10, and the AC power is supplied to the load 3 via the transformer 11 and filter 7 without flowing out to the commercial power supply 1, resulting in an instantaneous voltage drop. Compensation will be provided.

D8 Problems to be Solved by the Invention In the device configured as described above, AC voltage drop detection is generally performed by rectifying the AC voltage and converting it into a DC voltage, and then introducing the DC voltage into a comparator to set it. A method is used to determine the magnitude of the voltage. According to this method, since ripples are included not only in single-phase cases but also in three-phase cases, if you want to set the voltage drop detection level to 80 to 90% of the steady state, it is necessary to It is necessary to provide a filter capacitor.

When a filter capacitor is provided in this manner, a problem arises in that the voltage drop detection time takes several milliseconds or more.

Furthermore, since it is not possible to determine whether the cause of the instantaneous voltage drop is a load-side short-circuit accident, the semiconductor switch 2 is turned off as described above and the instantaneous voltage drop operation is performed even in the event of a load-side short-circuit accident. .

Therefore, if the short-circuit fault current exceeds the withstand capacity of the elements of the semiconductor switch 2, the semiconductor switch 2 will not be able to cut off the short-circuit fault current, resulting in destruction of the elements of the semiconductor switch 2.

The present invention has been made in view of the above points, and its purpose is to:
It is an object of the present invention to provide a high-speed instantaneous voltage drop detection method that can accurately and quickly detect various trouble states such as instantaneous voltage drops and load short circuits, and shortens compensation response time.

91 Means for Solving the Problems The present invention provides an instantaneous power supply system in which a semiconductor switch is inserted in an electric line connecting a commercial power source and a load, and a compensation power source is connected to a common connection point between the semiconductor switch and the load. In the instantaneous voltage drop high speed detection method, the HLJ compensating heavy duty power supply compensates for the instantaneous voltage drop when a voltage drop is detected. 'It is the specified state when the current flowing from the source is above a specified value, the commercial power supply voltage is below a specified value, or the current flowing from the commercial power source is zero. a first determining means that generates a determination output; and a sum of the current flowing from the commercial power source and the current flowing from the compensation power source is less than or equal to a predetermined overload current value, and the first determining means outputs a determination output. and a second determining means for determining that there is an instantaneous voltage drop in the commercial power supply when the power is being output, and when the second determining means determines that there is an instantaneous voltage drop, driving the compensation power supply. It is characterized by compensating for voltage drops in commercial power supplies.

When the degree of instantaneous voltage drop due to F0 action is relatively large, the current flowing from the commercial power source exceeds a predetermined value, so that the first determining means issues a determination output. When the degree of the instantaneous voltage drop is relatively small, the first determination means issues a determination output if the commercial power supply voltage is below a predetermined value. Also, when the current flowing from the commercial power supply is zero (power outage), the first determination means also issues a determination output. If the sum of the current flowing from the commercial power supply and the current flowing from the compensation power supply is equal to or less than a predetermined overload current value when the first determination means is issuing the determination output in this way, the second determination means It is determined that there is an instantaneous voltage drop in the commercial power supply. Therefore, the voltage drop can be quickly compensated for by driving the compensation power supply.

In addition, if the sum of the current flowing from the commercial power supply and the current flowing from the compensation power supply is greater than or equal to the predetermined overload current value, the second
The determination means does not determine that there is an instantaneous voltage drop regardless of the presence or absence of the determination output from the first determination means. Therefore, when a fault current exceeding a predetermined overload current value flows due to an accident such as a load short circuit, protective actions such as interrupting the fault current with the AC circuit breaker without performing the voltage drop compensation action are performed. It can be performed.

G. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, numeral 13 is a NOR circuit representing a first determining means. The first input terminal of the NOR circuit 13 receives a current value +sl obtained by detecting and rectifying the current flowing from the commercial power supply l by the current transformer CT shown in FIG. 5, and a predetermined power supply current setting value IS.
For example, a high level signal is input when COMP is in a relationship such that lie>I scoMp. NOR circuit! 3, the voltage value V of the commercial power supply 1 detected by the potential transformer PTs shown in FIG.
For example, a high level signal is input when the relationship is IcOMP. At the third input terminal of the NOR circuit 13,
For example, a high level signal is input when the current value 11.1 is zero. The NOR circuit 13 outputs a low level signal if at least one of the plurality of input signals is at a high level.

Reference numeral 14 denotes an inverted terminal material AND circuit representing a second determining means. The first input terminal of the inverting terminal material AND circuit I4 is connected to a current flowing from the commercial power source l and an instantaneous voltage drop compensator 8.
The current flowing from the current transformer CT s, CT shown in FIG.
The sum is++tl of the current detected and rectified by & and the predetermined overload current setting value I LCONP are l ia+ il
For example, a high level signal is input when there is a relationship such that l>ILCOMP. The output signal of the NOR circuit 13 is input to the second input terminal of the inverted terminal material AND circuit 14 . The inverted terminal material AND circuit 14 connects the first and second
A high level signal is output when the signals supplied to the input terminals of both are low level.

Here, the power supply voltage value V detected by the potential transformer PTs
An example of a detection means for detecting that gh<VB<V8CONF is shown in FIGS. 2(a) and 2(b). In FIG. 2(a), 21 is a phase-locked loop (PhaseLock) that creates a signal synchronized with the commercial power supply voltage.
ed I, oop (hereinafter abbreviated as PLL).

This PLL 21 is configured as shown in FIG. 2(b), for example. That is, for example, the voltage transformer P 'I'
Compare the phase of the signal obtained by waveform-shaping the voltage of the commercial power supply 1 detected in s by the waveform shaping circuit 31 and the frequency of the signal obtained by dividing the output signal of the voltage-controlled oscillator 35 by the frequency divider 32, A phase difference detector 33 that generates a voltage corresponding to the phase difference, a low pass filter 34 that removes high frequency components of the output voltage of the phase difference detector 33 and determines the synchronization characteristics and response characteristics of the PLL, and the low pass filter 3.
The voltage controlled oscillator i35 generates a signal with a frequency corresponding to the output voltage of 4. The output signal of the voltage controlled oscillator 35 of the PLL 21 is counted by a counter 22 and supplied to a memory IC (ROM) 23 as a clock signal synchronized with the commercial power supply voltage. Memory I
Data related to the reference sine wave voltage is digitally written in advance in C23, and these digital data are read out in synchronization with the clock signal supplied from the counter 22. When the digital data read from the memory IC 23 is converted into an analog signal by the digital-to-analog converter 24, a reference sine wave voltage synchronized with the commercial power supply voltage is obtained. The instantaneous value of this reference sine wave voltage is compared in the comparator 25 with the instantaneous value of the commercial power supply voltage. The waveforms of the commercial power supply voltage compared by the comparator 25 and the reference voltage synchronized with the commercial power supply are shown, for example, as shown in FIG.
Detected at a high speed of ms. When an instantaneous voltage drop is detected in this way, a control signal, for example a high level signal, is output from the comparator 25, and the NOR circuit 13 of FIG.
supplied to

Further, the means for detecting the above-mentioned V s<V sco,p,
In FIG. 2(a), the comparison between the commercial power supply voltage and the reference sine wave voltage is performed using an analog signal, but it may also be performed using a digital signal as shown in FIG. That is, in FIG. 4, the commercial power supply voltage is sampled by the sampling circuit 4! When sampling at L, a comparator 43 compares a signal obtained by converting each sampled value into m-digits by an m-converting circuit 42 and a digital signal of a reference sine wave voltage synchronized with the commercial power source read from the memory rc23. and
The PLL 21 and counter 22 are constructed in the same manner as in FIG. 2(a).

Next, the operation when the instantaneous voltage drop high speed detection method configured as described above is applied to the apparatus shown in FIG. 5 will be described. First, if an instantaneous voltage drop occurs while power is being supplied from the commercial power source I to the load 3 via the semiconductor switch 2, then l i
sl>[sco+<p, and the NOR circuit 13
A high level signal is supplied to the first input terminal of the circuit. In general, the source impedance is low, and the bidirectional power converter 10
The impedance of the device is also 10~! Since it is about 5%, if the degree of voltage drop is relatively large, the current i flowing from the commercial power supply 1 becomes an overcurrent, and lie becomes larger than the power supply current setting value 18COMP. In addition, the above-mentioned l+ has a small degree of instantaneous voltage drop.

> l Even if the relationship is not 5cosp, the commercial power supply voltage detection value Vs is the power supply voltage setting value V9CO
Since it is smaller than HP, a high level signal is supplied to the second input terminal of the NOR circuit 13. Further, if the commercial type It has a power outage, the current i flowing from the power supply 1 becomes zero, so the third i of the NOR circuit 13.

A high level signal is supplied to the input terminal. Even if the battery 9 is fully charged and there is no load when the commercial power supply I is normal, the current corresponding to the leading phase of the capacitor C of the filter 7 will flow from the commercial power supply 1, so only a power outage will occur. can be detected. As mentioned above, the Nort circuit 13
Since a high level signal is supplied to the NOR circuit 13, the NOR circuit 13 outputs a low level signal to the second input terminal of the inverting terminal material AND circuit 14. Next, an excessive current flows due to a short circuit accident in load 3 or for other reasons, and l
When the relationship is + i ll > ILCOMF, a high level signal is supplied to the first input terminal of the inverted terminal material AND circuit 14 . In this case, whether the signal input to the second input terminal of the AND circuit 14 with an inverting terminal is at a high level or a low level, its output is always at a low level.

Therefore, the operation of instantaneous voltage drop compensation is locked.

If the relationship l ia+ ill >ILCOMF is detected by the current transformers CT s and CT I as described above,
The operation of the bidirectional power converter IO is stopped, and if it is a short circuit current, it is interrupted by an AC circuit breaker (not shown).

In addition, if the overcurrent has a relationship such that I l-+ izl > Iccoxp, the semiconductor switch 2 is turned off with a time limit characteristic in coordination with the thermal withstand capacity of the semiconductor switch 2, or the voltage trip of an AC circuit breaker (not shown) is performed. Either energize the coil or shut it off.

Next, li-+i+l is the overload current setting value I LCOMP
When it is smaller than that, a low level signal is supplied to the first input terminal of the inverting terminal material AND circuit 14.

At this time, if the output signal of the Nort circuit 13 is at a high level (when no instantaneous voltage drop or power outage occurs), the output signal of the inverted terminal material AND circuit 14 is at a low level.

Also, at this time, the output signal of the NOR circuit 13 is at a low level (
(when a momentary voltage drop or power outage occurs),
The output signal of the inverted terminal material AND circuit 14 becomes high level. In this way, the second determination means (inverted terminal material AND circuit 14) determines that there is an instantaneous voltage drop (inverted terminal material AND circuit 14).
When the output signal of the D circuit 14 becomes high level),
The following instantaneous voltage drop compensation operation is performed.

That is, for example, from the compensation control device 12 to the semiconductor switch 2
The main semiconductor element constituting the inverter of the bidirectional power converter lO from the compensation control device 12 while turning off the power-off control signal;
For example, a control signal is supplied to the Zyrister to cause the bidirectional power converter IO to perform a reverse power conversion operation. As a result, the DC power of the battery 9 is converted into AC by the bidirectional power converter IO, and the AC power is supplied to the load 3 via the transformer 11 and filter 7 without flowing to the commercial power supply 1, thereby reducing the instantaneous voltage drop. Compensation will be made.

Note that the detection means shown in FIG. 2(a) and FIG.
When it is detected that the relationship s< V IICOMP holds, the detection time is 1 to 3 m s and lea>
It takes a little longer than when the relationship I IIcoMP is detected. But l i m l > I 5c
If oNp does not hold and V s < V 5cosp holds, the degree of voltage drop is small, so the amount of voltage drop when switching to power supply from the bidirectional power converter 1O is extremely small, and there is no problem.

In addition, in the case of a three-phase circuit, voltage drop detection is performed when V s < V 5
CONF and I i. For I = 0, it is necessary to compare each digit, but l i * 1 tl > ILc
As for oxp and l i , 1>I 5CONP, the three phases may be matched after rectification and then compared. In addition, in Fig. 5, current transformers C T s, C 'I
'l may be installed so that the load current can be directly measured.

Furthermore, it is economically advantageous to provide current transformers for only two phases and to calculate the other phase current from these phase currents.

Note that the detected current of the current transformer CTt in FIG. 5 is necessary to constantly control the reactive power between the commercial power supply I and the bidirectional power converter IO.

1-I. Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) Instantaneous voltage drops and power outage modes of various commercial power sources in constant commercial power supply systems can be detected reliably and quickly. Therefore, the compensation response time can be shortened, and transient voltage fluctuations can also be suppressed.

(2) When the sum of the current flowing from the commercial power source and the current flowing from the compensation power source is greater than or equal to the predetermined overload current value, the second determining means does not determine that there is an instantaneous voltage drop, so the AC breaker is turned off, etc. Measures can be taken to protect the semiconductor switch from excessive current.

(3) Even when the present invention is incorporated with instantaneous voltage drop compensation as a secondary function of a load leveling or peak cut system using power storage batteries, voltage drops can be quickly and reliably detected and compensated in the same way as described above. Response time can be shortened.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2(a)
is a block diagram showing an embodiment of the instantaneous voltage drop detection means,
FIG. 2(b) is a block diagram showing the specific configuration of the phase-locked loop in FIG. 2(2), FIG. 3 is a signal waveform diagram for explaining the operation of FIG. 2(a), and FIG. 4 5 is a block diagram showing another embodiment of the instantaneous voltage drop detection means, and FIG. 5 is a blower diagram showing a conventional instantaneous voltage drop compensation method in an uninterruptible power supply system of a constant commercial power supply type. l...Commercial power supply, 2...Semiconductor switch, 3...
Load, 7... Filter 8... Instantaneous voltage drop compensator, 9... Battery IO... Bidirectional power converter, 12... Compensation control device, 13... NOR circuit,
14...AND circuit with inversion terminal, 21...Phase locked loop, 22...Counter, 23...Memory IC
, 24... digital-to-analog converter, 25.43
...Comparator, 41...Sampling circuit, 42...
・Quantization circuit, PTs. PTr...Instrument transformer, CTs, CT+...
Current transformer.

Claims (1)

[Claims] (1) When detecting an instantaneous voltage drop in a power supply system consisting of a semiconductor switch inserted in an electrical path connecting a commercial power source and a load, and a compensation power source connected to a common connection point between the semiconductor switch and the load, In a high-speed instantaneous voltage drop detection method that compensates for instantaneous voltage drops using a compensation power supply, the current flowing from the commercial power supply is greater than or equal to a predetermined value, or the commercial power supply voltage is less than or equal to a predetermined value, or the current flowing from the commercial power supply is a first determination means that issues a predetermined determination output when at least one of the states is zero; and a second determining means that determines that there is an instantaneous voltage drop in the commercial power supply when the current value is equal to or less than the current value and a determination output is issued from the first determining means, the second determining means A high-speed instantaneous voltage drop detection method, characterized in that when it is determined that there is an instantaneous voltage drop, the compensation power source is driven to compensate for the voltage drop of the commercial power source.