Off-line uninterrupted power supply device

Abstract

The invention relates to an off-line uninterrupted power supply device, particularly to an off-line uninterrupted power supply device which can output harmonic-shaped AC voltage and has power factor improvement function. The device mainly comprises an AC input coupled to an AC power supply, an AC output coupled to a load end, a DC power supply used for supplying DC voltage, a DC / DC conversion device with the input end coupled to the DC power supply and the output end coupled to a DC bus, a DC / AC conversion device with the input end coupled to the DC bus and the output end coupled to the AC output, and a control circuit; wherein the control circuit controls the uninterrupted power supply device to realize three working modes of supplying harmonic-shaped DC voltage when commercial power is cut off, charging the DC power when the commercial power is normal and charging the DC power supply when the DC bus has excess energy so as to recycle energy.

Description

technical field [0001] The invention relates to an uninterruptible power supply device, especially an improved off-line uninterruptible power supply device. Background technique [0002] An uninterruptible power supply (UPS) is an AC power supply that can provide AC power instantaneously when the mains power is abnormal. Two known off-line uninterruptible power supplies, such as Figure 4 , 5 shown. Figure 4 It is a simple UPS structure. When the mains power is normal, only the mains power is directly connected to the output terminal through the filter device 44 through the relay 45 for use by the load connected to the UPS output end; when the mains power is abnormal (the voltage is too high or too high). low), the UPS converts its internal battery 41 into a high DC voltage through a DC / DC converter 42 (DC / DC converter), and then uses a DC / AC converter 43 to convert the high DC voltage into AC The voltage is switched and outputted through the relay 45 again. Figure 5 It...

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Problems solved by technology

However Figure 4 and Figure 5 There are certain shortcoming in two kinds of known UPS structures: (1) two kinds of UPS structures AC voltage output is a kind of square wave form, for inductive load (as transformer, motor), this kind of square wave output will cause load easily damaged; (2) Figure 4 The UPS structure shown can only be used in places where the mains voltage fluctuation range is small; (3) Figure 5 The UPS structure shown can be used in places where the mains voltage fluctuates widely. However, if the relay is used to directly switch the winding taps of the power frequency transformer, a sharp wave voltage will be generated during the switching, which will affect the quality of the power supply, and the regulator of the mains voltage is always Online power loss

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