JPS6147052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an uninterruptible power supply that continuously obtains the required AC power by switching between DC rectified AC and DC from a storage battery as the DC input of an inverter. It is.

As is well known, an uninterruptible power supply device generally includes a DC power source that is a DC power source that has been converted from AC, a storage battery power source, and an inverter, and the inverter normally converts the DC power that has been converted from an AC input into the required AC power. Furthermore, when the AC input is interrupted, the DC power from the storage battery power source is converted to the required AC power via the inverter to continue to provide stable AC power supply. Here, there are various methods for connecting the DC power source converted from AC to the storage battery power source. Fig. 1 shows a circuit diagram of an example of an uninterruptible power supply device generally called a floating charging method, and Fig. 2 2 shows a circuit diagram showing an example of an uninterruptible power supply equipped with a DC thyristor switch.

In FIG. 1, 1 is an AC power source, 2 is a forward converter 3, a smoothing reactor, 4 is a smoothing capacitor, 5 is an inverter, 6 is a DC switch or disconnector, and 7 is a storage battery. In addition, in FIG. 2, numerals 1 to 7 are the same as in FIG. 1, 8 is an AC power supply, 9 is a charger,
11 is the main thyristor, 12 is the auxiliary thyristor, 1
3 is a commutation capacitor, 14 is a commutation reactor, 1
5 is a resistor, and the main thyristor 11, the auxiliary thyristor 12, the commutating capacitor 13, the commutating reactor 14 and the resistor 15 connect the DC thyristor switch A.
is configured.

In FIG. 1, AC power supplied from an AC power supply 1 is converted into DC by a forward converter 2, and smoothed by a DC smoothing circuit consisting of a smoothing reactor 3 and a smoothing capacitor 4. It is supplied to the storage battery 7 via the disconnector 6. Normally, in a floating charging type uninterruptible power supply as shown in FIG. 1, the forward conversion unit 2 is provided with constant current control and constant voltage control functions by a control circuit (not shown), and constant current control is performed during initial charging of the storage battery 7. , during floating charging and equal charging, it is common to perform constant voltage control, and in the above method in which the storage battery 7 is constantly charged in a floating manner, even if the AC power supply 1 has a power outage, the discharge of the storage battery 7 is performed via the inverter 5. The required alternating current power can be continuously and stably supplied with almost no transient fluctuations occurring during discharge from the storage battery 7. Furthermore, since the forward conversion section 2 also has the function of a charger for the storage battery 7, the storage battery 7 does not require a dedicated charger, so the above system is often adopted in small-capacity uninterruptible power supplies. However, in the above method, since the forward converter 2 also has the function of charging the storage battery 7, it is necessary to be able to control the voltage from the uniform charging voltage of the storage battery 7 to the end-of-discharge voltage. 7
In the above case, the forward converter 2 is operated with a slightly larger control delay angle α, so that the input power factor of the forward converter 2 is controlled by the DC thyristor described below. This is worse than a system equipped with a switch. Also, inverter 5
When a commutation failure occurs, the current flowing from the storage battery 7 to the inverter 5 that caused the commutation failure causes the DC current and disconnector 6 to trip. Can lead to destruction due to exposure to overcurrent conditions.

Next, in FIG. 2, the AC power supplied from the AC power supply 1 is converted into DC by the forward converter 2, and the DC power is smoothed by the DC smoothing circuit consisting of the smoothing reactor 3 and the smoothing capacitor 4, and is then transferred to the inverter 5. The inverter 5 converts the AC power into the required AC power, which is then supplied to a load (not shown). Usually, in an uninterruptible power supply system equipped with a DC thyristor switch as shown in FIG. By detecting this and giving an ignition command to the main thyristor 11, the main thyristor 11 becomes conductive and the DC power from the storage battery 7 is transferred to the disconnector 6, the main thyristor 11, and the smoothing reactor 3.
is supplied to the inverter 5 via
The AC power is converted into predetermined AC power and continuously supplied to a load (not shown).

Furthermore, when the output of the forward converter 2 is higher than the output voltage of the storage battery 7 due to power restoration of the AC power supply 1, the main thyristor 11 is automatically extinguished. The detection device detects the return of the AC power supply 1, and after a predetermined period of time, a firing command is given to the auxiliary thyristor 12. Commutation capacitor 1 charged with the polarity shown in Figure 2
3 charge is main thyristor 11 → auxiliary thyristor 1
2→The discharge current is discharged through the path of the commutating reactor 14, and the discharge current becomes free vibration due to the resonance circuit of the commutating capacitor 13 and the commutating reactor 14. When this discharge current becomes larger than the discharge current of the storage battery 7 flowing through the main thyristor 11, the main thyristor 11 is extinguished, and when the discharge current, which has become a free oscillation, flows in the opposite direction to the discharge path, the main thyristor 11 is turned off. The auxiliary thyristor 12 is also extinguished and the storage battery 7 is disconnected. Even when a commutation failure occurs in the inverter 5, the auxiliary thyristor 12 is ignited and the storage battery 7 is disconnected at high speed by the above operation. In addition, according to the above method, since a dedicated charger 9 is provided for the storage battery 7, there is no problem even if the storage battery 7 is switched between floating charging and equal charging while the inverter is operating. By equipping each device with a DC thyristor switch A, the storage battery 7 and charger 9 can be shared. Further, since the forward converter 2 may be a diode pure bridge that does not require a control circuit, the circuit is simplified and the input power factor of the forward converter 2 is improved compared to the floating charging method described above. However, in the above method, the storage battery 7
In addition to requiring a dedicated charger 9, the forward conversion unit 2
Since the output is floating-charged by a dedicated charger 9 regardless of the output of the forward converter 2, it is not always equal to the output of the forward converter 2. Therefore, in the event of a power outage of the AC power supply 1, the storage battery 7 will be charged with DC current, the disconnector 6, and the DC thyristor switch A. When the inverter 5 is connected through the main thyristor 11, the input voltage of the inverter 5 fluctuates, giving a transient fluctuation to the output of the inverter 5. Each of the above two methods has its advantages and disadvantages, and it is difficult to determine which method is better.

The present invention has been made in view of the above points, and provides an uninterruptible power supply device having a storage battery floating charging function and a storage battery connection DC thyristor switch function.

FIG. 3 is a circuit diagram showing one embodiment of the present invention.

In Fig. 3, numerals 1 to 7 are the same as in Fig. 1, 8 is an AC power supply, 9 is a charger, 11 is a main thyristor, 12 is an auxiliary thyristor, 13 is a commutation capacitor, and 14 is a commutation reactor. , 15 is a resistor, 21 is a diode, and the main thyristor 1
1, auxiliary thyristor 12, commutating capacitor 13,
Commutation reactor 14, resistor 15, diode 2
1 constitutes a changeover switch B.

Next, the operation of the present invention will be explained. The AC power supplied from the AC power source 1 is converted into DC by the forward conversion unit 2, and is supplied to the inverter 5 as DC power smoothed by the DC smoothing circuit consisting of the smoothing reactor 3 and the smoothing capacitor 4, and is also supplied to the inverter 5 as DC power. A diode 21 whose direction is from the output positive bus of the DC smoothing circuit to the positive electrode of the storage battery becomes conductive, and the smoothed DC power is supplied to the storage battery 7 via the diode 21, the DC current, and the disconnector 6. Here, if the voltage of the AC power source 1 is selected so that the output voltage of the DC smoothing circuit smoothed after the forward conversion becomes the floating charging voltage of the storage battery 7, the forward conversion section 2
The circuit configuration is simple and requires no control circuit due to the diode pure bridge, and the storage battery 7 is constantly charged in a floating state. When the storage battery 7 requires equal charging, the AC power supply 8 and charger 9 perform equal charging. In this case, the charger 9 may be used only for equal charging and has a small capacity, and can be stopped except when equal charging is required. Furthermore, even if the charger 9 is operated while the inverter 5 is in operation to uniformly charge the storage battery 7, the diode 21 in the changeover switch Since the voltage difference between the equal charging voltage and the output voltage of the DC smoothing circuit is applied as a reverse voltage, the arc naturally extinguishes.
Since the current smoothing circuit output, that is, the input voltage of the inverter 5 is not affected in any way, the output of the inverter 5 can continuously provide the required stable alternating current power.

Next, when the AC power supply 1 has a power outage, a detection device (not shown) detects this and the main thyristor 1
By giving a firing command to main thyristor 1
1 is conductive so that the DC power from the storage battery 7 is connected to the inverter 5 via the DC, disconnector 6, and main thyristor 11.
The AC power is supplied to the inverter 5, converted into the required AC power, and continuously supplied to a load (not shown).
In this case, since the storage battery 7 is constantly floatingly charged by the output of the forward conversion unit 2, the input voltage of the inverter 5 hardly changes when DC power is supplied by discharging from the storage battery 7 due to the above operation. No transient fluctuation is given to the output of the inverter 5. In addition, the diode 21, which was conducting for floating charging, was disconnected from the storage battery 7 due to a power outage of the AC power supply 1.
The arc is naturally extinguished because the voltage is applied as a reverse voltage.

Here, the AC power supply 1 has a power outage, and the above operation causes the DC power due to the discharge of the storage battery 7 to pass through the DC, disconnector 6, and main thyristor 11 to the inverter 5.
If a commutation failure occurs in the inverter 5 while the AC power is supplied to the inverter 5, converted into the required AC power by the inverter 5, and then supplied to a load (not shown),
A detection device (not shown) detects this and stops the firing command of the main thyristor 11, and also gives a firing command to the auxiliary thyristor 12 to fire the auxiliary thyristor 12, thereby causing the commutating capacitor 13 to be connected in advance between the DC bus bars. The electric charge of the commutating capacitor 13 charged to the polarity shown in FIG. 3 by the commutating reactor 14 and resistor 15 is discharged through the path of the main thyristor 11 → auxiliary thyristor 12 → commutating reactor, and the discharge current is commutated. Free vibration occurs due to the resonance circuit of the capacitor 13 and commutation reactor 14. When this discharge current becomes larger than the discharge current of the storage battery 7 flowing through the main thyristor 11, the main thyristor 11 is extinguished, and the discharge current then flows through the path of the diode 21 → auxiliary thyristor 12 → commutation reactor 14. The forward voltage drop value of the diode 21 is applied to the main thyristor 11 as a reverse voltage. At the time when the discharge current, which has become a free oscillation, flows in the opposite direction to the path, the auxiliary thyristor is also extinguished and the storage battery 7 is disconnected. As described above, the changeover switch B has the function of supplying DC power smoothed after forward conversion to the storage battery 7 to perform floating charging, and the function of not transmitting voltage fluctuations during equal charging to the storage battery 7 to the input side of the inverter 5. The AC power supply 1 has a function of supplying DC power from the storage battery 7 to the inverter 5 during a power outage, and a function of disconnecting the storage battery 7 when a commutation failure of the inverter 5 occurs. In the uninterruptible power supply according to the present invention, in which a changeover switch is provided between the DC power source converted from the AC power source and the storage battery, and the storage battery can be connected or disconnected by opening or closing the changeover switch, the forward conversion section controls the Since a pure diode bridge does not require any circuitry, the circuit configuration of the forward conversion section is simplified and the input power factor of the forward conversion section is also improved. In addition, since the storage battery is always floating charged at the same voltage as the inverter's input voltage, transient fluctuations when switching to the storage battery during an AC power outage are reduced, and the storage battery is disconnected at high speed when the inverter fails to commutate. protected. Furthermore, the storage battery charger only needs to be used for equal charging, so it only requires a small capacity, and since it can be turned off unless needed, it is possible to have one in common for multiple uninterruptible power supplies. By connecting accordingly, equipment costs for the entire system can be reduced. This results in the disadvantages of the floating charging method, such as the complexity of the circuit configuration of the forward conversion section, a drop in the input power factor, the occurrence of transient fluctuations when switching between equal charging and floating charging, damage due to insufficient protection of the storage battery when inverter commutation failure occurs, and damage caused by direct current. This improves the shortcomings of the thyristor switch method, such as the occurrence of transient fluctuations when switching to the storage battery during an AC power outage, and the need for a charger corresponding to the storage battery capacity.

Although the foregoing description describes the circuit operation of the changeover switch, it is intended to explain the function of the changeover switch, and the changeover switch B is not limited to the circuit shown in FIG. 3.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a conventional floating charging type uninterruptible power supply, Figure 2 is a circuit diagram showing an example of a conventional uninterruptible power supply equipped with a DC thyristor switch, and Figure 3 is a circuit diagram showing an example of a conventional floating charging type uninterruptible power supply. 1 is a circuit diagram showing an example of an uninterruptible power supply device equipped with a changeover switch according to the invention. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Forward conversion unit, 5... Inverter, 7... Storage battery, 9... Charger, A... DC thyristor switch, B... Changeover switch according to the present invention, 11... Main thyristor , 12... Auxiliary thyristor, 13... Commutation capacitor, 14...
Commutation reactor, 21...diode.

Claims (1)

[Claims] 1. In an uninterruptible power supply device comprising a forward conversion section that converts alternating current to direct current, a storage battery, a charger, and an inverter that converts direct current to alternating current, the direction of flow between the output of the forward conversion section and the storage battery is set to the direction of the storage battery. A thyristor switch equipped with a forced extinguishing circuit and a changeover switch having a diode connected in anti-parallel to the thyristor switch are inserted as the conversion section, and normally the AC input is once converted to DC in the forward conversion section, and the While supplying DC power to the inverter, the storage battery is float-charged through the diode in the changeover switch, and when the storage battery requires equal charging, it is charged equally by the charger, and in the event of an AC input power outage, the changeover switch The thyristor in the changeover switch is turned on and made conductive, and DC power is supplied from the storage battery to the inverter to continuously obtain the required AC power, and when the inverter fails in commutation, the thyristor in the changeover switch is turned on. An uninterruptible power supply device characterized in that the storage battery is disconnected by forcibly extinguishing a switch.