JP3167534B2 - Uninterruptible power system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply provided with a power supply switch for switching power supply to a load from inverter power supply to commercial power supply when an inverter operated in synchronization with a commercial power supply fails or is inspected. The present invention relates to a power supply device, and more particularly to an uninterruptible power supply device that can continuously supply power to a load without instantaneously switching from an inverter to a commercial power supply during a stop operation or failure of the inverter and causing a power failure.

[0002]

2. Description of the Related Art A power supply system using an inverter, in particular,
In the case of uninterruptible power supply, independent inverters or multiple inverters are operated in synchronization with commercial power supply independently or in parallel to maintain the power supply to the load without generating an instantaneous power failure even during inverter maintenance or failure. In many cases, the power supply to the power supply is provided with a power supply switch that switches between the commercial power supply and the inverter without interruption.

FIG. 8 is a block diagram showing a conventional uninterruptible power supply of this type. In the figure, 1 is a commercial power supply, 2 is a rectifier for converting AC to DC, 3 is a storage battery, 4 is an inverter for converting a DC voltage from the rectifier 2 or the storage battery 3 to AC voltage, and 5 is a power supply to a load. Contactor 51 for selecting inverter 4 or commercial power supply 1
And a power switch 6 composed of a thyristor circuit 52 connected in parallel with the contact 51 and two thyristors connected in anti-parallel. The inverter 4 operates in synchronization with the commercial power supply 1 and outputs a constant AC voltage. When the commercial power source 1 is out of service, the vehicle is operated at a predetermined 50 Hz or 60 Hz. The power supply switch 5 detects the output voltage of the inverter 4 with the voltage detector 7, monitors this detected voltage with the voltage monitoring device 8, and when the detected voltage becomes abnormal, sends a switching signal to the power supply switch 5 to send the switching signal to the inverter 5. Switch from power supply to commercial power supply.

[0004] At the time of power supply switching, the contact of the contactor 51 connected to one power supply is once separated and then connected to the other contact. That is, there is a time when the load 6 is not connected to either of the power supplies, and at that time, the power supply to the load 6 is momentarily cut off. Therefore, when the power supply is switched, the thyristor circuit 52
Is fired, the switching time of the contactor 51 is always connected to the commercial power supply side, and the power supply to the load 6 is continued even when the power supply is switched. A voltage monitoring device 8 of the inverter 6 includes a voltage detector (not shown), a rectifier circuit,
It comprises a filter circuit and a level comparison circuit.

[0005]

In the voltage monitoring circuit 8 having the above-described configuration, the rectification method of the three-phase voltage prevents erroneous detection due to noise, and eliminates ripples in the waveform to improve the detection accuracy by several tens msec. Is used. Therefore, even if the voltage rapidly becomes 0 due to the stop of the inverter 4, the power failure detection is delayed by the filter time constant.

If the power failure detection is delayed, the power supply switching command itself is also delayed, and the load voltage becomes 0 until the inverter 4 stops and the power supply switching signal is output, and a power failure occurs.

[0007] Therefore, an object of the present invention is to make the voltage monitoring device high-accuracy and high-speed detection, so that even if the inverter stops or a failure occurs, the power supply switch eliminates a delay in the power failure detection and instantaneously supplies the inverter side. The present invention is to provide an uninterruptible power supply that can continue power supply to a load without interruption by switching from a power supply to a commercial power supply.

[0008]

[0009]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The invention according to claim 1 provides an uninterruptible power supply provided with a power supply switch for switching the power supply to the load from the inverter power supply to the commercial power supply at the time of failure or inspection of the inverter operated in synchronization with the commercial power supply. In a power supply device, a phase synchronization circuit that outputs a phase signal synchronized with a load voltage applied to the load, and a sine wave generation circuit that generates a sine wave signal having a desired amplitude in synchronization with an output phase of the phase synchronization circuit when the comparator circuit the difference by comparing the load voltage and the output of the sine wave generating circuit for generating an output signal when it exceeds a predetermined value,
Load fluctuation abnormality detecting means for detecting a load current flowing through the load and generating an output signal when a signal corresponding to the amount of change in the load current becomes a predetermined value or more, and an output signal of the load fluctuation abnormality detecting means And a limiting circuit for invalidating the output signal of the comparison circuit.

[0010]

Further , according to a second aspect of the present invention, there is provided a power supply switch for switching the power supply to the load from the inverter power supply to the commercial power supply at the time of failure or inspection of an inverter operated in synchronization with the commercial power supply. An uninterruptible power supply device comprising: a phase-locked loop that outputs a phase signal synchronized with a load voltage applied to the load; and a sine wave signal having a desired amplitude in synchronization with an output phase of the phase-locked loop. A sine wave generation circuit, a dq conversion circuit to which an output of the sine wave generation circuit and an output voltage of the inverter are applied to generate a DC signal proportional to an amplitude value of the output voltage of the inverter, and the dq conversion A comparison circuit that compares an output of the circuit with a preset set value and generates an output signal when the difference exceeds a predetermined value; and detects a load current flowing through the load, and detects a load current flowing through the load. A load fluctuation abnormality detecting means for generating an output signal when the signal becomes a predetermined value or more, and a limiting circuit for invalidating an output signal of the comparison circuit with an output signal of the load fluctuation abnormality detecting means. And

[0012]

[0013]

According to the first aspect of the present invention, when the load fluctuation abnormally changes, the limit circuit operates by the load fluctuation abnormality detecting means, and the output signal of the comparison circuit is invalidated. It is possible to prevent a malfunction of the power supply switch due to a transient change in the output voltage of the inverter due to an abnormal change.

[0014]

[0015] Further, according to the invention described in claim 2, wherein
As in the first aspect of the present invention, when the load fluctuation abnormally changes, the limit circuit operates by the load fluctuation abnormality detecting means, and the output signal of the comparison circuit is invalidated. A malfunction of the power supply switch due to a transient fluctuation of the output voltage can be prevented.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the same parts as in FIG.
FIG. 1 is a block diagram showing one embodiment of the invention described in claim 1. Note that components denoted by the same reference numerals as those in FIG. 8 indicate the same components, and a description thereof will be omitted.

In FIG. 1, a voltage detector 7 of a load 6
And a phase synchronization circuit 9 for outputting a phase synchronized with the detection voltage
And a sine wave generation circuit 10 to which an output signal of the phase synchronization circuit 9 is applied to generate a sine wave having a predetermined amplitude in the same phase as the load voltage, and a difference between the sine wave generation circuit 10 and the load voltage having a predetermined value. A comparison circuit 11 that generates a voltage abnormality signal when the voltage exceeds the threshold voltage is provided, and the output signal of the comparison circuit 11 activates the power supply switch 5 to switch from inverter power supply to commercial power supply.

FIG. 2 is a block diagram showing a specific example of the phase synchronization circuit 9 of FIG. This phase-locked loop 9 has input voltages R, S, and T where the peak value of each phase of the load voltage is E and the angular frequency is ωti.

[0019]

R = Esinωti, S = Esin (ωti + 120 °) T = Esin (ωti + 240 °) Variable frequency oscillator 91 whose oscillation frequency changes according to
And a counter 92 for counting the output pulses of the variable frequency oscillator 91, and a digital count signal θ of the counter 92 and three-phase AC voltages R, S, and T, and an analog phase difference signal Δθ is applied to the variable frequency oscillator 91. Phase comparator 93
And a low-pass filter 94 for removing harmonic components of the phase comparator 93.

In this case, the phase comparator 93 synchronizes the three-phase AC voltages R, S and T with the three-phase AC voltages R, S and T and has a phase difference of 90 °.
A three-phase / two-phase converter 931 for converting into phase AC voltages V1 α and V1 β; a ROM 932 in which sine wave data is stored in advance to output digital sine wave data from the digital count signal θ of the counter 92; A digital converter that converts signals into analog and outputs two-phase AC voltages V2α and V2β corresponding to the two-phase AC voltages V1α and V1β, respectively.
A phase difference signal Δθ is calculated by calculating vector cross products of analog converters 933a and 933b (hereinafter referred to as D / A converters) and two-phase AC voltages V1α and V1β and corresponding V2α and V2β. And an arithmetic circuit 934 that outputs It is assumed that sine wave data having a phase shift of 90 degrees is written in the ROM 932.

Since the phase synchronization circuit 9 operates to make the phase difference signal Δθ zero, the digital count signal θ of the counter 92 is equal to the load voltage phase. FIG. 3 is a block diagram showing a specific example of the sine wave generation circuit 10 and the comparison circuit 11 of FIG.

The sine wave generation circuit 10 has a ROM 101 and a ROM 101 which store sine wave data in advance to output digital sine wave data from the phase signal θ of the output voltage of the phase synchronization circuit 9.
/ A converter 102, a unitary three-phase AC voltage having a constant amplitude and no distortion,

[0023]

## EQU2 ## r = sin.omega.to, s = sin (.omega.to + 120 DEG) t = sin (.omega.to + 240 DEG)

The comparator 11 compares the output of the sine wave generator 10 with the load voltage and detects that the difference exceeds a predetermined value. The comparator 11 subtracts the difference between the output of the sine wave generator 10 and the load voltage. A comparator 111, an absolute value circuit 112 for obtaining an absolute value of a subtraction result, and a comparator 113 for detecting that an absolute value output value exceeds a predetermined value.

With the above-described configuration, when the load voltage falls below a predetermined value with respect to the output of the sine wave generation circuit 10, which is the voltage that should be held, the comparison circuit 11 detects an abnormal voltage. Then, the power supply switch 5 switches the power supply to the load 6 from the inverter 4 to the commercial power supply 1. Since the abnormality of the load voltage waveform, that is, the AC waveform, is determined every moment, it is possible to determine the voltage abnormality due to the stop or failure of the inverter 4 without time delay. As a result, when the output voltage of the inverter 4 is abnormal, the inverter 4 is disconnected without delay in detection and the power supply to the load 6 is switched to the commercial power supply 1, so that the power supply to the load 6 is not interrupted momentarily.

FIG. 4 showing the same parts as in FIG.
FIG. 4 is a block diagram showing an embodiment of the invention described in claim 2. Here, the components denoted by the same reference numerals as those in FIG. 1 indicate the same components, and the description thereof will be omitted.

The embodiment of FIG. 4 is obtained by adding the following circuit to the circuit of FIG. That is, the load current is detected by the current transformer 12, the change amount of the detected load current is obtained by the differentiating circuit 13, the absolute value of the value is obtained by the absolute value circuit 14, and the absolute value becomes equal to or more than a desired value. As a result, the determination circuit 15 for determining that the amount of change in the load current has changed abnormally.
When it is detected that the load fluctuates abnormally,
The limiting circuit 16 is added to the circuit of FIG. 1 so as not to execute the power failure detection.

As a result, in addition to the effect of the first aspect of the present invention, even if a short circuit or the like occurs on the load side and the load current changes rapidly and the load voltage drops, the added circuit at this time allows A change in load can be detected from the amount of change in load current, and when a load fluctuates due to a short-circuit accident on the load side, power failure detection due to a drop in load voltage is limited. The effect of preventing erroneous detection of determination can be obtained.

FIG. 5 showing the same parts as in FIG.
FIG. 7 is a block diagram showing an embodiment of the invention described in claim 3. Here, the components denoted by the same reference numerals as those in FIG. 1 indicate the same components, and the description thereof will be omitted.

FIG. 5 shows that the AC output signal of the sine wave generation circuit 10 of FIG. 1 is converted by the dq conversion circuit 17 into a DC signal corresponding to the peak value of the AC output voltage of the sine wave generation circuit 10. The DC signal is compared with a preset set value by a comparison circuit 18, and when the difference exceeds a predetermined value, a switching signal is generated.

The sine wave generation circuit 10 of FIG. 6 is the same as the sine wave generation circuit 10 of FIG. 3, and outputs digital sine wave data from the phase signal θ of the output voltage of the phase synchronization circuit 9 of FIG. ROM 101 storing sine wave data and D
A / A converter 102, a unit three-phase AC voltage having a constant amplitude and no distortion,

[0032]

## EQU3 ## r = sin.omega.to, s = sin (.omega.to + 120 DEG) t = sin (.omega.to + 240 DEG)

The unit three-phase AC voltages r, s, t are applied to a dq conversion circuit 17 for obtaining voltages Vd, Vq of two axes of a rotating coordinate system. The dq conversion circuit 17 outputs the output voltages R, S, and T of the inverter 4 and the unit three-phase AC voltages r, s, and t.
, For each phase, and an adder 172 for adding the output signal of the multiplier 171. The output Vq of the adder 172 is

[0034]

Vq = R · r + S · s + T · t = Esinωti · sinωto + Esin (ωti +
120 °) · sin (ωto + 120 °) + Esin
(Ωti + 240 °) · sin (ωto + 240 °), and in the steady state, ωto = ωti, so Vq = Esin ² ωti + Esin ² (ωti + 120)
°) + Esin ² (ωto + 240 °) = (3/2) E.

As described above, the output V of the dq conversion circuit 17 is
For q, a signal proportional to the peak value E of the output voltage of the inverter 4 can be obtained. This signal Vq is applied to the next-stage comparison circuit 18 and is compared with a preset value.
When the difference exceeds a predetermined value, the switching signal is output to the power switch 5.
When the output voltage of the inverter 4 is abnormal, the inverter 4 can be disconnected and the power supply to the load 6 can be switched to the commercial power supply 1 without a detection delay when the output voltage of the inverter 4 is abnormal.

FIG. 7 is a block diagram showing one embodiment of the fourth aspect of the present invention. In FIG. 7, components denoted by the same reference numerals as those in FIGS. 4 and 5 indicate the same components, and the description thereof is omitted here.

FIG. 7 shows the circuit of FIG. 5 in which the load current is detected by the current transformer 12, the change amount of the detected load current is obtained by the differentiating circuit 13, and the absolute value of the value is calculated by the absolute value circuit 14. A determination circuit 15 is provided for determining that the amount of change in the load current has changed abnormally when the absolute value has become equal to or greater than the desired value. Is added to the limiting circuit 16 so as not to carry out.

In this way, the power supply can be switched instantaneously in the event of a power failure or failure of the inverter, a short circuit or the like occurs on the load side, the load current changes rapidly, and the amount of change in the load current even if the load voltage drops. This makes it possible to detect a change in load from the power supply, and when a load fluctuates due to a short-circuit accident on the load side, etc., the detection of a power failure due to a drop in load voltage is limited. Can be prevented.

[0039]

[0040]

As described above, the invention according to claim 1 is described above.
According to this configuration, it is possible to prevent the power supply switch from malfunctioning due to a transient change in the output voltage of the inverter due to an abnormal change in the load. According to the second aspect of the present invention, the same as the first aspect is provided.
Various effects can be obtained.

[0041]

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the invention described in claim 1;

FIG. 2 is a block diagram showing a specific example of the phase locked loop circuit of FIG. 1;

FIG. 3 is a block diagram showing a specific example of a sine wave generation circuit and a comparison circuit of FIG. 1;

FIG. 4 is a block diagram showing one embodiment of the invention described in claim 2;

FIG. 5 is a block diagram showing one embodiment of the invention described in claim 3;

FIG. 6 is a block diagram showing a specific example of a sine wave generation circuit and a dq conversion circuit of FIG. 5;

FIG. 7 is a block diagram showing an embodiment of the invention described in claim 4.

FIG. 8 is a block diagram of a conventional uninterruptible power supply.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 2 ... Rectifier 3 ... Storage battery 4 ... Inverter 5 ... Power supply switch 6 ... Load 7 ... Voltage detector 8 ... Voltage monitoring device 9 ... Phase synchronous circuit 10 ... Sine wave generation circuit 11 ... Comparison circuit 12 ... Current transformation Unit 13 Differentiating circuit 14 Absolute value circuit 15 Discriminating circuit 16 Limiting circuit 17 dq conversion circuit 18 Comparison circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02M 7/48 G01R 19/165 H02J 9/00 H02J 9/06 504

Claims (2)

(57) [Claims] An invar operated in synchronization with a commercial power supply
The inverter supplies power to the load when the
Equipped with a power switch to switch from power supply to commercial power supply
In the uninterruptible power supply obtained, the negative voltage applied to the load is
A phase-locked loop that outputs a phase signal synchronized with the load voltage;
A positive signal having a desired amplitude synchronized with the output phase of the phase locked loop
A sine wave generating circuit for generating a sine wave signal;
Circuit output and the load voltage, and the difference exceeds a predetermined value.
A comparison circuit that generates an output signal when the
Load current detected, and a signal corresponding to the amount of change in the load current is detected.
A load that generates an output signal when the signal exceeds a specified value
Fluctuation abnormality detecting means, and an output signal of the load fluctuation abnormality detecting means.
A limiting circuit for invalidating the output signal of the comparison circuit with a signal.
When the load fluctuation abnormality detecting means is not operating,
The output of the circuit switches the power switch from inverter power supply to commercial power.
An uninterruptible power supply that switches to power supply. 2. Invar operated in synchronization with a commercial power supply
The inverter supplies power to the load when the
Equipped with a power switch to switch from power supply to commercial power supply
In the uninterruptible power supply obtained, the negative voltage applied to the load is
A phase-locked loop that outputs a phase signal synchronized with the load voltage;
A positive signal having a desired amplitude synchronized with the output phase of the phase locked loop
A sine wave generating circuit for generating a sine wave signal;
Output of the inverter and the output voltage of the inverter
Generates a DC signal proportional to the output voltage amplitude of the inverter
Conversion circuit, and the output of the dq conversion circuit
Compares with the set value and determines that the difference exceeds the specified value.
A comparison circuit for generating an output signal when
The load current is detected, and a signal corresponding to the change amount of the load current is generated.
A load fluctuation that generates an output signal when the
Normal detection means and the output signal of the load fluctuation abnormality detection means.
A limiting circuit for invalidating the output signal of the comparing circuit;
When the load fluctuation abnormality detection means does not operate, the comparison circuit
With the output, the power switch is switched from inverter power supply to commercial power supply.
Uninterruptible power supply that switches to electricity.