JP2000201485A - Uninterruptible power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sustain power supply to a load even if a battery fails or a circuit is interrupted by setting the output voltage of a rectifier slightly lower than the battery voltage so that power is not recovered from the battery to the AC power supply side when discharge test is started thereby controlling the output voltage of the rectifier to follow up the discharge characteristics. SOLUTION: When the rectifier output voltage Vrdc is controlled below a battery discharge voltage Vbdc, a discharge test voltage command value and battery discharge voltage Vbdc are inputted to a differential amplifier 7. When the battery discharge voltage Vbdc drops, the differential amplifier 7 functions to elevate the rectifier output voltage Vrdc but since an output current signal from a current transformer CT2 is added to a second voltage command value Vref2, the rectifier output voltage Vrdc is controlled below the battery discharge voltage Vbdc so that power is not recovered from the battery to the AC power supply side. More specifically, the rectifier output voltage Vrdc is controlled based on the battery discharge voltage to follow up the battery discharge voltage Vbdc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier for converting AC power into DC power, an inverter for converting DC power output from the rectifier into AC power, and a storage battery for supplying DC power to the inverter when the AC power fails. Etc.,
The present invention relates to an uninterruptible power supply that controls a rectifier output voltage by comparing a first voltage command value with a rectifier output voltage.

[0002]

2. Description of the Related Art FIG. 5 shows a configuration of a general uninterruptible power supply using a PWM control system for a switching converter.
In the figure, reference numeral 1 denotes a rectifier for converting an AC power supply to a DC, and supplies power to an inverter 2 for converting a DC into an AC, and charges a storage battery 3. T1 is a transformer for supplying a reference signal for converting the input current waveform of the uninterruptible power supply into a sine wave,
CT1 is a current transformer that detects an input current. The rectifier 1 constantly controls the DC output voltage to be constant with respect to the fluctuation of the AC input power supply and the fluctuation of the load. The rectifier output voltage is controlled by inputting the rectifier output voltage Vrdc and a first voltage command value Vref1 set to an arbitrary voltage value to the differential amplifier 7,
An error signal detected by the differential amplifier 7 is input to a PWM waveform generation circuit 8. The PWM waveform generation circuit 8 uses the signal of the differential amplifier 7, the input voltage waveform signal supplied from the transformer T1, and the input current signal obtained from the current transformer CT1.
While making the input current waveform of the uninterruptible power supply a sine wave,
A drive signal for controlling the input power factor to be close to 1 is sent to a switching element (not shown) of the rectifier 1.

In the uninterruptible power supply, the storage battery 3 has a deteriorated state depending on the environment in which it is used, and requires periodic inspection. As a method for checking the deterioration state of the storage battery 3, the AC power supply of the uninterruptible power supply is shut off or the switch A of the rectifier input is turned off in the normal operation state, the inverter 2 is operated as the storage battery, and the storage battery 3 is discharged for a certain time. Thus, the deterioration state of the storage battery 3 is determined.

[0004]

However, according to the above-described method in the conventional uninterruptible power supply, the inverter is operated when the storage battery 3 and the discharge circuit of the storage battery 3 are abnormal because the rectifier 1 is stopped. No. 2 is stopped because power is not supplied from either the rectifier 1 or the storage battery 3. That is, there is a problem that when the inverter 2 stops, the power supply to the load also stops.

The present invention has been made in view of such a point, and when checking the deterioration state of the storage battery 3, the inverter 2 does not stop even if the storage battery 3 has reached the end of its life or the storage battery circuit is shut off. An object of the present invention is to provide an uninterruptible power supply that can continuously supply power to a load.

[0006]

According to the uninterruptible power supply of the present invention, when the storage battery is discharged and the deterioration state is determined in the actual operation state, the inverter operation can be continued even if the storage battery and the discharge circuit are abnormal. And a control function of the rectifier output voltage for preventing power regeneration generated by the circuit system of the rectifier. That is, at the start of the discharge test, the rectifier output voltage is set slightly lower than the storage battery voltage so that the rectifier is in a standby state, and follows the discharge voltage characteristics of the storage battery so that power is not regenerated from the storage battery to the AC power supply side. Control. In addition, a decrease in the rectifier output voltage due to a failure in the storage battery or a disconnection in the discharge circuit is prevented from falling below the lower limit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS To achieve the above object, an uninterruptible power supply according to the present invention comprises a rectifier for converting AC power into DC power, an inverter for converting DC power output from the rectifier into AC power, In an uninterruptible power supply device configured to control a rectifier output voltage by comparing a first voltage command value with a rectifier output voltage, the output current of the rectifier 1 is configured by a storage battery or the like that supplies DC power to the inverter when the power supply fails. Current transformer CT2 that detects the current and sends an output current signal
A limiter circuit 4 for limiting the voltage drop below the lower limit value of the rectifier output voltage Vrdc;
A voltage command value Vref2, the first voltage command value Vref1, which serves as a reference during a constant operation, and a second voltage command value Vref.
2 is provided with a switching circuit 6 for switching between the output current signal and a discharge test voltage command value obtained by adding the lower limit value. The switching circuit 6 is switched from the first voltage command value Vref1 by the switching circuit 6 to determine the deterioration state of the storage battery. The discharge test voltage command value, the rectifier output voltage Vrdc / the storage battery discharge voltage V
rectifier output voltage Vrdc
Is controlled to be always lower than the storage battery discharge voltage Vbdc, and is made to follow the storage battery discharge voltage Vbdc.

In order to achieve the above object, an uninterruptible power supply according to the present invention comprises a rectifier for converting AC power to DC power, an inverter for converting DC power output from the rectifier to AC power, and an AC power supply. In an uninterruptible power supply configured to control a rectifier output voltage by comparing a first voltage command value and a rectifier output voltage, the lower limit value of the rectifier output voltage Vrdc is configured by a storage battery or the like that supplies DC power to an inverter when a power failure occurs Limiter circuit 4 for limiting the following step-down
And a divided voltage value obtained by dividing a storage battery voltage serving as a reference when discharging the storage battery, and the first voltage command value V serving as a reference when constantly operating.
ref1 and a switching circuit 6 for switching between the divided voltage value and the discharge test voltage command value obtained by adding the lower limit value. The switching circuit 6 switches from the first voltage command value Vref1 to determine the deterioration state of the storage battery. The rectifier output voltage Vrdc is calculated by comparing the discharge test voltage command value thus obtained with the battery discharge voltage Vbdc.
c and control the battery discharge voltage Vb
dc.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an uninterruptible power supply having a rectifier control circuit according to a first embodiment of the present invention. In the figure, a capacitor C1 and a reactor L1 are input waveform shaping filters, CT1 is a current transformer for controlling an input current, T1
Is a transformer for supplying a reference signal for controlling the input current waveform of the uninterruptible power supply into a sine waveform, 1 is a rectifier for converting AC to DC, CT2 is a current transformer for detecting rectifier output current, and capacitor C2 is rectifier DC. Filter for smoothing the output, 2
Is an inverter for converting DC to AC, and 3 is a storage battery. Normally, the rectifier output voltage Vrdc is input to the differential amplifier 7, the difference between the rectifier output voltage Vrdc and the first voltage command value Vref1 is detected, and a signal for controlling the AC input power supply fluctuation and the output current fluctuation to a constant value is generated as a PWM waveform. The circuit 8 supplies the rectifier 1.

When the storage battery 3 is discharged to determine the deterioration state of the storage battery 3, when a command signal is input to the switching circuit 6 by the test operation switch 5, the rectifier output voltage Vrd
The voltage command value for controlling c is switched to the second voltage command value Vref2. An output current signal based on the detection current detected by the current transformer CT2 is added to the second voltage command value Vref2 via the limiter circuit 4 that limits the voltage drop below the lower limit of the rectifier output voltage Vrdc. Therefore, if the rectifier output voltage Vrdc is higher than the storage battery discharge voltage Vbdc, a current flows through the rectifier 1 in an attempt to supply power from the AC power supply, and the output current signal based on the detection current detected by the current transformer CT2 is the voltage command value Vref2. Is input to the differential amplifier 7 as a discharge test voltage command value added to the lower limit value and the rectifier output voltage Vrdc is controlled to be equal to or lower than the storage battery discharge voltage Vbdc so that the difference between the rectifier output voltage Vrdc and the rectifier output voltage Vrdc becomes zero.

When the rectifier output voltage Vrdc is controlled to be equal to or lower than the battery discharge voltage Vbdc, the discharge test voltage command value and the battery discharge voltage Vbdc are input to the differential amplifier 7. When the storage battery discharge voltage Vbdc decreases, the rectifier output voltage Vrdc is increased by the operation of the differential amplifier 7, but as described above, the output current signal from the current transformer CT2 is changed to the second voltage command value Vref2. Therefore, the rectifier output voltage Vrdc is controlled to be equal to or lower than the storage battery discharge voltage Vbdc. That is, the rectifier output voltage Vrdc is controlled based on the storage battery discharge voltage Vbdc, and follows the storage battery discharge voltage Vbdc.

The limiter circuit 4 supplies power to the inverter 2 from the output of the rectifier when the storage battery 3 has reached the end of its life and a normal voltage is not supplied or when the circuit with the storage battery 3 is interrupted. The current is supplied to the current transformer CT2 provided at the rectifier output so that the entire current flows, and at this time, the rectifier output voltage Vrdc is provided so as not to drop below the lower limit value. The discharge of the storage battery 3 is
When the predetermined holding time has elapsed, the discharge test command signal is released, and the voltage command value is changed to the first voltage command value Vre.
Switching to f1, the current detected by the current transformer CT2 is also released, and the rectifier output voltage Vrdc returns to the state before the start of storage battery discharge.

When the storage battery discharge test is performed when the storage battery 3 is defective or when the discharge circuit from the storage battery 3 is disconnected, the voltage supplied from the storage battery 3 drops sharply, and the rectifier that is on standby The output automatically supplies power to the inverter 2 to continue the operation of the inverter 2 and release the discharge test command signal to return to the state before the start of discharging of the storage battery. In this embodiment, the output current of the rectifier 1 is detected, but the input current of the rectifier 1 may be used.

FIG. 2 is a block diagram of an uninterruptible power supply having a rectifier control circuit according to a second embodiment of the present invention. When discharging the storage battery 3, the voltage of the storage battery 3 is divided by resistors R1 and R2. This is a method of using the obtained signal as a voltage command value of the differential amplifier 7. Capacitor C as in FIG.
1, reactor L1 is an input waveform shaping filter, CT
1 is a current transformer for controlling an input current, T1 is a transformer for supplying a reference signal for controlling an input current waveform of the uninterruptible power supply into a sine waveform, 1 is a rectifier for converting AC to DC, and a capacitor C2 is a rectifier DC. A filter for smoothing the output, 2 is an inverter for converting DC to AC, and 3 is a storage battery. Normally, the rectifier output voltage Vrdc is input to the differential amplifier 7, the difference between the rectifier output voltage Vrdc and the first voltage command value Vref1 is detected, and a signal for controlling the AC input power supply fluctuation and the output current fluctuation to a constant value is generated as a PWM waveform. The circuit 8 supplies the rectifier 1.

When the storage battery 3 is discharged in order to determine the deterioration state of the storage battery 3, when a command signal is input to the switching circuit 6 by the test operation switch 5, the rectifier output voltage Vrd
The voltage command value for controlling c is divided by the voltage dividing resistors R1 and R1 of the storage battery 3.
R2, switches to a discharge test voltage command value determined by the control power supplies Vc, Vs and the lower limit value of the limiter circuit 4, and is compared with the storage battery discharge voltage Vbdc to output a rectifier output voltage Vrdc.
Is controlled in accordance with the storage battery discharge voltage Vbdc.

The limiter circuit 4 lowers the discharge test voltage command value if the storage battery 3 has reached the end of its service life and a normal voltage is not supplied, or if the circuit with the storage battery 3 is interrupted. A lower limit is provided for the purpose of not lowering the rectifier output voltage Vrdc too much or too little. As in the first embodiment, when the predetermined holding time elapses, the discharge test command signal is released, the voltage command value is switched to the first voltage command value Vref1, and the rectifier output voltage Vrdc is discharged. Returns to the state before the start of storage battery discharge. When the storage battery discharge test is performed when the storage battery 3 is defective or the discharge circuit from the storage battery 3 is disconnected, the voltage supplied from the storage battery 3 rapidly decreases, and the output of the standby rectifier automatically decreases. Power is supplied to the inverter 2 to continue the operation of the inverter 2 and release the discharge test command signal to return to the state before the start of storage battery discharge. The second embodiment does not require the shunt CT2 and is therefore superior to the first embodiment.

FIG. 3 is a diagram showing the current sharing relationship between the rectifier output voltage and the storage battery discharge voltage when the storage battery is normal in the uninterruptible power supply of the present invention. During the time (t) from the start of the discharge test to the end of the discharge test, the storage battery discharge voltage is gently reduced by the storage battery discharge current Ib, and the rectifier output voltage is always controlled to be lower than the storage battery discharge voltage. The current Ir does not flow.

FIG. 4 is a diagram showing current sharing between the rectifier output voltage and the battery discharge voltage when the battery is defective or the battery discharge circuit is abnormal in the uninterruptible power supply of the present invention. Even when the discharge test is started, the battery discharge current is 0 because the battery discharge voltage is 0 or extremely low. The rectifier output current Ir temporarily increases because the rectifier output voltage decreases to the lower limit (when the battery discharge circuit, that is, the load of the inverter is constant). It returns to the state before the start of discharge.

[0019]

As described above, in the uninterruptible power supply according to the present invention, whether the storage battery used for the important load equipment whose power supply cannot be stopped functions normally in the event of AC input power failure. When performing a storage battery discharge test under the actual load condition for the purpose of checking the condition, even if the storage battery is defective or the circuit that charges and discharges the storage battery is disconnected and power cannot be supplied from the storage battery, the rectifier that is on standby By supplying power from the inverter, there is an effect that stable power can be supplied to the load device without stopping the inverter.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an uninterruptible power supply according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram of an uninterruptible power supply according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a current sharing relationship between a rectifier output voltage and a storage battery discharge voltage when the storage battery is normal in the uninterruptible power supply of the present invention.

FIG. 4 is a diagram showing current sharing between a rectifier output voltage and a storage battery discharge voltage when the storage battery is defective or the storage battery discharge circuit is abnormal in the uninterruptible power supply of the present invention.

FIG. 5 is a circuit block diagram of a conventional uninterruptible power supply.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectifier 2 Inverter 3 Storage battery 4 Limiter circuit 5 Test operation switch 6 Switching circuit 7 Differential amplifier 8 PWM waveform generation circuit C1 Capacitor C2 Capacitor CT1 Current transformer CT2 Current transformer L1 Reactor R1 Resistance R2 Resistance RF1 Diode T1 Transformer Vbdc Battery Discharge voltage Vrdc Rectifier output voltage Vc Control power supply Vs Control power supply Vref1 First voltage command value Vref2 Second voltage command value

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Kawagoe 3-4-1 Shibaura, Minato-ku, Tokyo Inside NTT Facilities Inc. (72) Inventor Chuichi Aoki 3-4-2 Shibaura, Minato-ku, Tokyo No. 1 Inside NTT Facilities Co., Ltd. (72) Inventor Masahiro Hashiwaki 3-4-1 Shibaura, Minato-ku, Tokyo Inside 72 NTT Co., Ltd. (72) Inventor Ken Doshita Port, Tokyo 3-4-1, Shibaura-ku, F-term in NTT Facilities Inc. (reference) 5G003 AA01 BA01 CA01 CA11 DA05 DA15 DA18 EA09 GB06 5G015 FA18 GA04 JA15 JA21 JA34 JA35 JA54 5H007 AA06 AA17 BB05 CC12 DA06 DB01 DC02 DC05 EA13 FA02 FA12

Claims (2)

[Claims] 1. A rectifier for converting AC power into DC power, an inverter for converting DC power output from the rectifier into AC power, and a storage battery for supplying DC power to the inverter when the AC power fails. (1) In an uninterruptible power supply that controls a rectifier output voltage by comparing a voltage command value with a rectifier output voltage, a current transformer (CT2) that detects an output current of the rectifier (1) and sends out an output current signal. A limiter circuit (4) for limiting the voltage drop below the lower limit of the rectifier output voltage (Vrdc), and a second voltage command value (Vref) serving as a reference when discharging the storage battery.
2) and the first voltage command value (Vref
1) and a switching circuit (6) for switching between a second voltage command value (Vref2) and the discharge test voltage command value obtained by adding the output current signal and the lower limit value to determine a deterioration state of the storage battery. The discharge test voltage command value switched from the first voltage command value (Vref1) by the switching circuit (6), and the rectifier output voltage (Vrdc)
Rectifier output voltage (Vrdc) by comparing the battery discharge voltage (Vbdc) with the battery discharge voltage (Vbdc).
An uninterruptible power supply device characterized in that it is always controlled to be lower than c) and is made to follow a storage battery discharge voltage (Vbdc). 2. A rectifier for converting AC power into DC power, an inverter for converting DC power output from the rectifier into AC power, and a storage battery for supplying DC power to the inverter when the AC power fails. (1) In an uninterruptible power supply that controls a rectifier output voltage by comparing a voltage command value with a rectifier output voltage, a limiter circuit (4) that limits a voltage drop below a lower limit of a rectifier output voltage (Vrdc); A divided voltage value obtained by dividing the storage battery voltage serving as a time reference, and the first voltage command value (Vref
1) and a switching circuit (6) for switching between the divided voltage value and the discharge test voltage command value obtained by adding the lower limit value. The switching circuit (6) determines the deterioration state of the storage battery by using the first voltage. The discharge test voltage command value switched from the command value (Vref1) and the storage battery discharge voltage (Vbdc)
An uninterruptible power supply characterized in that the rectifier output voltage (Vrdc) is always controlled to be lower than the storage battery discharge voltage (Vbdc) and the storage battery discharge voltage (Vbdc) is made to follow the storage battery discharge voltage (Vbdc).