JPH025630Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a device for pre-charging the smoothing capacitor of an uninterruptible power supply, and in particular, by using the thyristor rectifier and DC switch circuit of the battery charger also during pre-charging. , it is an object of the present invention to provide a preliminary charging device whose circuit configuration is simplified as much as possible.

As an uninterruptible power supply, the forward conversion section is composed of a diode rectifier, and a dedicated battery charger is installed to charge the battery in a floating manner and equally. A so-called DC switch type uninterruptible power supply device that supplies power to an inverter is well known. Such a DC switch type is compared to a floating charging type in which the forward conversion section is composed of a thyristor rectifier.
There are no serious failures caused by the gate circuit, such as false ignition or gate signal failure, and it also has excellent features such as the ability to simplify the circuit configuration.
It is widely used as an uninterruptible power supply for the most important loads. Even in a DC switch-type uninterruptible power supply that has these excellent features, a rush current flows through the large capacity capacitor of the DC filter circuit at startup, and this rush current poses a serious threat to the diode elements in the forward conversion section. In the worst case, a serious failure may occur, such as permanent destruction of the element group and inability to operate. As a method for preventing serious failures caused by such rush current, for example, a pre-charging device consisting of a current-limiting resistor that limits the current, a diode rectifier that rectifies commercial frequency alternating current power, and a contactor contact is available. When starting up the uninterruptible power supply, the capacitor of the DC filter circuit is pre-charged using the pre-charging device, and the charging voltage of the capacitor is approximately the same as the voltage value of the commercial frequency power supply. When it is confirmed that the battery has risen to a certain level, the predetermined preliminary charging is stopped and the uninterruptible power supply is started. With this method, a smooth transition to steady operation is possible without the flow of rush current at startup, but the problem is that the pre-charging device uses contacts, so maintenance problems such as wear of the contacts due to aging are a problem. This makes it extremely complicated. More importantly, a diode rectifier exclusively used for precharging is used, and this diode rectifier has exactly the same configuration as the forward conversion section unless short-time and continuous ratings are taken into account, so it is not necessary to use the thyristor of the battery charger. If you include the rectifier, one uninterruptible power supply has 3
A platform rectifier will be installed. Therefore, the uninterruptible power supply itself becomes large, which not only causes problems in terms of space during installation, but also becomes extremely uneconomical.

The present invention has been devised in view of this point, and will be described in detail below based on Examples.

In the same embodiment, 1 is a forward converter with bridge-connected diodes, and this forward converter converts commercial frequency AC input power into DC power, and 2 is a DC power converter consisting of a DC reactor L and a smoothing capacitor C. In the filter circuit, 3 is an inverse conversion section configured by inversely converting DC power into AC power and thyristors connected in a pure bridge, and 4 is configured by connecting thyristors for floating charging and equal charging of the battery 5 in a pure bridge connection. In the battery charger, 6 is a DC switch circuit for supplying the DC power of the battery to the inverter 3 in the event of an abnormality in the commercial frequency power supply. Although this DC switch circuit 6 is not shown, it leads to the desired DC power. It consists of a main thyristor for forcibly extinguishing the main thyristor, and a forced extinguishing circuit consisting of an auxiliary thyristor, a commutating reactor, a commutating capacitor, and a commutating diode. Reference numeral 7 denotes a pre-charging device which is a main part of the present application, and this pre-charging device 7 is composed of a current limiting resistor R that limits the charging current and a thyristor switch S that merely performs a switching function. CB ₁ - CB ₂ are AC circuit breakers, and CB ₃ is a DC circuit breaker.

To describe the operation of this embodiment configured as described above, at the time of predetermined preliminary charging, first, CB ₁ and
The circuit breaker of CB ₃ is opened and only the AC circuit breaker of CB ₂ is closed, and in parallel, a predetermined firing command is given to the main thyristor of the DC switch circuit 6 and the thyristor switch S of the pre-charging device 7. At the same time, a gate signal is given to the thyristor group of the battery charger 4 based on a command from a control section (not shown) to cause full firing. When each thyristor fires in this way, the following steps occur: commercial frequency power supply → circuit breaker CB ₂ → battery charger 4 → current limiting resistor R → thyristor switch S → main thyristor of DC switch circuit 6 → DC reactor L → smoothing capacitor C → Negative side thyristor of battery charger 4 → Circuit breaker CB ₂ → Charging current flows through the path of the commercial frequency power supply, and this charging current is limited by current limiting resistor R, and at the same time, the smoothing capacitor C of DC filter circuit 2 is charged with the polarity shown. After confirming that this charging voltage has risen to approximately the same level as the voltage value of the commercial frequency power supply, a controller (not shown)
With the OFF command, the auxiliary thyristor (not shown) of the DC switch circuit 6 is ignited, and the charge charged in the commutating capacitor (not shown) is applied to the main thyristor to reverse bias it, thereby forcing the main thyristor. Extinguish the arc. When the main thyristor of the DC switch circuit 6 is extinguished in this way, the smoothing capacitor C of the DC filter circuit 2 is no longer connected.
Since charging current no longer flows through the battery charger 4, when this charging current becomes lower than the holding current of the thyristor switch S of the pre-charging device 7, the thyristor switch S naturally extinguishes, and at the same time, the thyristor switch S of the battery charger 4 Since the gate signal supplied to the battery charger group is blocked, the thyristor group of the battery charger 4 is also automatically extinguished. A predetermined pre-charging is completed through this series of operating steps, and as is clear from the circuit diagram of the embodiment, during this pre-charging, the battery 5 is floatingly charged through the charger 4, but nothing is done. As in the example, there is no need to float-charge the battery during pre-charging, and the battery may be disconnected from the main circuit during pre-charging.

As described above, in the present invention, the battery charger and the DC switch circuit are operated and actively involved during the predetermined pre-charging, so various functions are possible as shown below. It is effective.

Since the preliminary charging device consists only of a thyristor switch and a current limiting resistor, the circuit configuration is simplified and a very economical device can be realized.

Since the thyristor switch of the preliminary charging device does not require a forced arc extinguishing circuit, the circuit configuration can be simplified as much as possible, and an extremely reliable uninterruptible power supply device can be provided.

Since it is a non-contact device, the complexity of maintenance can be eliminated.

[Brief explanation of the drawing]

The figure is a specific circuit configuration diagram when the preliminary charging device, which is the main part of the present invention, is applied to a typical DC switch type uninterruptible power supply. 1 is a forward conversion section, 2 is a DC filter circuit, 3 is an inverse conversion section, 4 is a battery charger, 5 is a battery, 6 is a DC switch circuit, 7 is a preliminary charging device, R is a current limiting resistor, and S is a thyristor. Switch.

Claims (1)

[Scope of utility model registration request] A forward conversion section that forward converts the AC input power of a commercial frequency power supply to DC power and is composed of a diode rectifier, a DC filter circuit consisting of a DC reactor and a smoothing capacitor, and an inverse conversion section that reverse converts DC power to AC power. and a battery charger composed of a thyristor rectifier that rectifies commercial frequency AC power and charges the battery in a floating manner and equally.
An uninterruptible power supply device comprising at least a DC breaker that supplies DC power from a battery to a reverse conversion unit when a commercial frequency power supply is abnormal, and a switch circuit configured with a DC switch circuit connected in series with the breaker. , in which the smoothing capacitor is precharged at the time of starting the device, a precharging device formed by connecting a thyristor switch and a current limiting resistor in series is connected to a DC breaker of the switch circuit and a DC circuit breaker. Connect in parallel between the bridge point of the switch circuit and the bridge point of the DC breaker and battery,
A pre-charging device characterized in that the smoothing capacitor described above is pre-charged through a loop of a battery charger, a pre-charging device and a DC switch circuit.