TW201929373A - Online uninterruptible power supply and control method thereof - Google Patents

Abstract

The invention provides an online uninterruptible power supply and a control method thereof. The online uninterruptible power supply comprises a bypass input end which is connected to the AC output end through a bypass switch; a commercial power input end which is connected with the AC output end sequentially through a rectifier, positive and negative DC buses and an inverter, wherein no is olationdevice is arranged between the output end of the inverter and the AC output end; a capacitor, of which the two ends are connected between the positive and negative DC buses; a charger which comprises a first pair of input ends, of which the two wiring terminals are connected to the bypass input end; a second pair of input ends, of which the two wiring terminals are connected to the commercial power input end; and an output end connected to the two ends of the capacitor. The size of the online uninterruptible power supply is reduced, and the cost of the online uninterruptible power supply is reduced.

Description

On-line uninterruptible power supply and control method thereof

The invention relates to an uninterruptible power supply, and more particularly to an on-line uninterruptible power supply and a control method thereof.

Online uninterruptible power supplies can continuously supply power to loads and have been widely used in various fields.

FIG. 1 is a circuit diagram of an online uninterruptible power supply in the prior art. As shown in Figure 1, the bypass input terminal Bin is connected to the AC output terminal ACout through the bidirectional thyristor BS11, and the mains input terminal ACin is sequentially connected to the rectifier switch S12, the rectifier 11, the positive DC bus 121, the negative DC bus 122, and the inverter. 13. The fuse 14 and the isolation device S13 are connected to the AC output ACout. The battery 15 is connected to the positive and negative DC buses 121 and 122 through a switch S14 and an inverter 16 in this order. The online uninterruptible power supply 1 also includes a capacitor C, and a charger 17 and a detection control device 18, where the capacitor C is connected between the positive DC bus 121 and the negative DC bus 122, and the input terminal of the charger 17 is connected to the mains input. Terminal ACin, and the output terminal is connected to the positive and negative DC buses 121 and 122. The detection and control device 18 is used to detect the voltage and phase of the AC power provided by the bypass input terminal Bin and the AC power output by the inverter, so that the voltage and phase of the AC power output by the inverter 13 track the AC power provided by the bypass input terminal Bin. Voltage and phase.

In the existing online uninterruptible power supply 1, an output device of the inverter 13 is provided with an isolation device S13. For example, in a high-power online uninterruptible power supply, the contactor is usually selected as the isolation device S13. The contactor S13 has the following functions:

When the capacitor C is not charged and the bypass input terminal Bin supplies power to the AC output terminal ACout, the contactor S13 is controlled to be in an open state, thereby cutting off the connection between the output terminal of the inverter 13 and the bypass input terminal Bin. It is electrically connected to avoid that the AC power provided by the bypass input terminal Bin brings inrush current or inrush current to the capacitor C through the bidirectional thyristor BS11 and the diode in the inverter 13.

The online uninterruptible power supply 1 can be switched from the output terminal of the inverter 13 to the bypass input terminal Bin at any time by disconnecting the contactor S13. When the inverter 13 stops working, disconnect the contactor S13, and immediately control the triac BS11 to be turned on to start the power supply of the bypass input Bin. The AC power provided by the bypass input Bin will not pass through the inverter 13. The diode C causes inrush or inrush current to the capacitor C. When the inverter 13 works, the detection and control device 18 detects the voltage and phase of the AC power provided by the bypass input terminal Bin, and simultaneously detects the voltage and phase of the AC power output by the inverter 13 to control the inversion. The voltage and phase of the AC power output from the transformer track the voltage and phase of the AC power provided by the bypass input terminal Bin, and then control the triac BS11 to turn on to start the power supply of the bypass input terminal Bin and disconnect the contactor S13, isolate the output terminal and inverter The inverter 13 avoids circulating current between the bypass and the inverter 13.

When non-destructive faults such as rectifier 11, inverter 13 overload, over temperature, or overvoltage across capacitor C occur, the output of inverter 13 and AC output ACout can be disconnected by cutting off contactor S13 Electrical connection between.

Therefore, an isolation device is connected between the output end of the inverter of the current online uninterruptible power supply and the AC output end ACout. However, the contactor S13 connected between the output end of the inverter 13 and the AC output end ACout usually has the following disadvantages: large size, high price, limited life, and high failure rate.

In view of the above technical problems existing in the prior art, an embodiment of the present invention provides an online uninterruptible power supply, including: a bypass input terminal connected to an AC output terminal through a bypass switch; a mains input terminal in turn through a rectifier The positive and negative DC buses and the inverter are connected to the AC output terminal, and there is no isolation device between the inverter output terminal and the AC output terminal; the capacitor has two ends connected to the positive and negative DC bus terminals. A charger including: a first pair of input terminals, two connection terminals of the first pair of input terminals being connected to the bypass input terminal; a second pair of input terminals, two of the second pair of input terminals Terminal blocks are connected to the mains input terminal; and output terminals are connected to both ends of the capacitor.

Preferably, the online uninterruptible power supply also includes a detection control device for detecting the voltage and phase of the AC power of the inverter and the bypass input terminal, and controlling the output of the inverter The voltage and phase of the alternating current track the voltage and phase of the alternating current at the bypass input.

Preferably, the online uninterruptible power supply also includes a battery and a converter, and the battery is connected to both ends of the capacitor through the converter.

Preferably, the online uninterruptible power supply also includes a rectifier switch connected between the mains input terminal and the rectifier, and a rectifier switch connected between the output terminal of the inverter and the AC output terminal. Fuse.

Preferably, the bypass switch is a bidirectional thyristor or two thyristors connected in anti-parallel.

An embodiment of the present invention provides a control method for an online uninterruptible power supply as described above. When there is no mains power at the mains input terminal, the control method includes the following steps: S11), controlling the operation of the charger To charge the capacitor; S12), when the voltage across the capacitor reaches a predetermined first threshold voltage, control the charger to stop working; and S13) to control the bypass switch to be turned on.

An embodiment of the present invention provides a control method for an online uninterruptible power supply as described above. The AC power at the bypass input terminal supplies power to the AC output terminal, and when the mains input terminal has mains power, all The control method includes the following steps: S21), controlling the rectifier to work so that the voltage across the capacitor reaches its working voltage; S22), detecting the voltage and phase of the AC power at the bypass input terminal; S23), controlling the rectifier The inverter outputs AC power to the AC output terminal.

Preferably, the step S23) includes the following steps: calculating a pulse width modulation signal to be provided to the inverter; controlling the bypass switch to be turned off, and providing the pulse width modulation to the inverter The signal causes the voltage and phase of the AC power output by the inverter to track the voltage and phase of the AC power at the bypass input terminal.

Preferably, before the step S21), the method further comprises the steps of detecting the voltage across the capacitor, and controlling the rectifier to work if the voltage across the capacitor is not less than a predetermined second threshold voltage; If the voltage across the capacitor is less than a predetermined second threshold voltage, the charger is controlled to operate so that the voltage across the capacitor reaches a predetermined second threshold voltage, the charger is stopped from operating, and the rectifier is controlled to operate.

Another embodiment of the present invention provides a control method for an online uninterruptible power supply as described above. When there is no AC power at the bypass input terminal, the control method includes the following steps: S31), controlling the charging The controller works to charge the capacitor; S32), when the voltage across the capacitor reaches a predetermined third threshold voltage, control the charger to stop working and control the rectifier to work; and S33), when When the voltage across the capacitor reaches its operating voltage, the inverter is controlled to work.

Another embodiment of the present invention provides a control method for an on-line uninterruptible power supply as described above. The mains input terminal supplies power to the AC output terminal. When there is AC power at the bypass input terminal, the The control method includes the following steps: S41), detecting the voltage and phase of the AC power at the bypass input terminal and the AC power output by the inverter; S42), controlling the voltage and phase of the AC power output by the inverter The voltage and phase of the AC power at the bypass input terminal are described; S43), controlling the bypass switch to be turned on and controlling the inverter to stop working.

Preferably, the step S42) comprises: calculating a pulse width modulation signal to be provided to the inverter, and providing the pulse width modulation signal to the voltage and phase of the alternating current output by the inverter Track the voltage and phase of the AC power at the bypass input.

The online uninterruptible power supply of the present invention omits the isolation device connected to the output end of the inverter, reduces the volume of the online uninterruptible power supply, and reduces its cost.

Based on the control method of the present invention, inrush current or inrush current is prevented from being caused to the capacitance of the above-mentioned online uninterruptible power supply, and circulating current is not generated between the bypass input terminal and the inverter.

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

FIG. 2 is a circuit diagram of an online uninterruptible power supply according to a preferred embodiment of the present invention. As shown in FIG. 2, it is basically the same as FIG. 1, so the same components are denoted by similar reference numerals. The difference is that there is no contactor between the output of the inverter 23 and the AC output ACout, and the charger 27 There are two pairs of input terminals, of which two terminals of one pair of input terminals are connected to the mains input terminal ACin, and two terminals of the other pair of input terminals are connected to the bypass input terminal Bin.

Compared with the on-line uninterruptible power supply 1 shown in FIG. 1, the on-line uninterruptible power supply 2 of the present invention omits a contactor connected to the output end of the inverter 23, and thus reduces its volume and cost.

However, based on the existing control method, when the bypass input terminal Bin supplies power, the AC power provided by the bypass input terminal Bin will inevitably bring an inrush current to the capacitor C 'through the diodes in the triac BS21 and the inverter 23 Or inrush current.

Therefore, according to another embodiment of the present invention, a control method for an online uninterruptible power supply 2 is also provided.

(1) When the mains input terminal ACin has no mains power: At this time, the inverter 23 stops working and needs to bypass the input terminal Bin to provide AC power.

FIG. 3 is a control flowchart of a first conversion mode of the online uninterruptible power supply shown in FIG. 2. As shown in FIG. 3, the charger 27 is first controlled to work, and the charger 27 uses the alternating current of the bypass input terminal Bin to charge the capacitor C ′. When the voltage across the capacitor C ′ reaches a predetermined first threshold voltage (for example, 90% of the peak and trough voltage difference of the AC power at the bypass input terminal Bin), the charger 27 is stopped. Finally, the bidirectional thyristor BS21 is controlled to be turned on, thereby switching to the bypass mode.

Because the charger 27 pre-charges the capacitor C ′ so that it has a threshold voltage at both ends, even if there is no isolation device between the output of the inverter 23 and the bypass input Bin, the alternating current of the bypass input Bin cannot The diodes in the inverter 23 are transmitted to the capacitor C ′ to avoid inrush current or inrush current to the capacitor C ′.

(2) When mains input ACin has mains power, it needs to be switched from the bypass power supply mode to the mains power supply mode: where the AC power at the bypass input terminal Bin is passed through the two poles in the inverter 23 before the mains power supply mode is converted The body charges the capacitor C '.

FIG. 4 is a control flowchart of the second conversion mode of the online uninterruptible power supply shown in FIG. 2. As shown in FIG. 4, first, the rectifier 21 is controlled to work to charge the capacitor C ′, so that the voltage across the capacitor C ′ reaches its operating voltage. The detection control device 28 detects the voltage and phase of the AC power at the bypass input Bin, and calculates a pulse width modulation signal (PWM) to be provided to the inverter 23 so that it outputs the same voltage and phase. Control the bidirectional thyristor BS21 to turn off and provide the required PWM signal to the inverter 23 to make it work, and finally switch to the mains power supply mode.

Before the rectifier 21 is controlled to work, there is a certain voltage across the capacitor C ′. Therefore, during the process of controlling the rectifier 21 to charge the capacitor C ′, the inrush current or inrush current brought to the capacitor C ′ is reduced or avoided. In addition, during the transfer time when the bypass power supply is converted into the inverter output power supply, the bypassed AC power and the AC power output by the inverter have the same voltage and phase, avoiding between the bypass input Bin and the inverter 23 Generate circulating current.

In another preferred control method of the present invention, it is basically the same as the control flow shown in FIG. 4. The difference is that before controlling the rectifier 21 to work, it also includes the following steps: detecting the voltage across the capacitor C ′. The voltage across C 'is not less than a predetermined second threshold voltage (for example, 90% of the voltage difference between the peak and trough of the mains at the mains input terminal ACin, there is no need to control the charger 27 to precharge the capacitor C' and directly control the rectifier 21 to start If the voltage across the capacitor C 'is less than 90% of the voltage difference between the peak and trough of the AC power at the AC input terminal, the charger 27 is controlled to use the AC power at the AC input terminal to charge the capacitor C' to After the predetermined second threshold voltage, the control charger 27 is stopped and the rectifier 21 is then started to work. By detecting the voltage across the capacitor C ′, it is ensured that when the rectifier 21 is controlled to work, no inrush current will be brought to the capacitor C ′. Or inrush current.

(3) When the bypass input Bin cannot provide AC power and needs to be converted to the mains input ACin to supply power: Figure 5 is a control flowchart of the third conversion mode of the online uninterruptible power supply shown in Figure 2. As shown in FIG. 5, the charger 27 is first controlled to pre-charge the capacitor C ′ using the mains power of the mains input terminal ACin, so that the voltage across the capacitor C ′ reaches a predetermined third threshold voltage (such as the peak and trough of the mains). 90% of the voltage difference). After that, the charger 27 is controlled to stop working, and the rectifier 21 is controlled to work so that the voltage across the capacitor C ′ reaches its working voltage. The inverter 23 is controlled to operate to output AC power. Therefore, when the rectifier 21 is controlled, inrush current or inrush current can be prevented from being caused to the capacitor C ′.

(4) When the mains input ACin supplies AC power to the AC output ACout through the rectifier 21 and inverter 23, and the bypass input Bin has AC power: At this time, the power from the mains input ACin is converted to the bypass input. Bin power.

FIG. 6 is a control flowchart of a fourth conversion mode of the online uninterruptible power supply shown in FIG. 2. The detection control device 28 detects the voltage and phase of the AC power output by the inverter 23 and the voltage and phase of the AC power provided by the bypass input terminal Bin, calculates a PWM signal to be provided to the inverter 23 and provides the PWM signal The AC power supplied to the inverter 23 is synchronized with the AC power of the bypass input terminal Bin, that is, the two have the same voltage and phase. The bidirectional thyristor BS21 is controlled to be turned on and the inverter 23 is controlled to stop working, so that the bypass power supply is finally realized.

Since the voltage and phase of the AC power output by the inverter 23 track the voltage and phase of the AC power provided by the bypass input terminal Bin, when the bidirectional thyristor BS21 is turned on, there will be no circulating current between the bypass input terminal Bin and the inverter 23 Current.

In other embodiments of the present invention, the bypass switch connected between the bypass input terminal Bin and the AC output terminal ACout is two thyristors connected in antiparallel.

The circuit structure and working principle of the rectifier 21, the charger 27, and the inverter 23 of the present invention are well known to those skilled in the art, and will not be repeated here.

Although the present invention has been described with reference to preferred embodiments, the present invention is not limited to the embodiments described herein, and includes various changes and modifications made without departing from the scope of the present invention.

11‧‧‧ Rectifier

13‧‧‧ Inverter

14‧‧‧ Fuses

15‧‧‧ Battery

16‧‧‧ converter

17‧‧‧ Charger

18‧‧‧ Detection control device

21‧‧‧Control Rectifier

23‧‧‧ Inverter

27‧‧‧Charger

28‧‧‧ Detection control device

121‧‧‧Positive DC Bus

122‧‧‧Negative DC bus

ACin‧‧‧ city power input

ACout‧‧‧AC output

Bin‧‧‧ bypass input

BS11‧‧‧Bidirectional Thyristor

BS21‧‧‧Bidirectional Thyristor

S12‧‧‧Rectifier switch

S13‧‧‧Isolated device

S14‧‧‧Switch

C'‧‧‧ capacitor

The embodiments of the present invention are further described below with reference to the accompanying drawings, wherein: FIG. 1 is a circuit diagram of an online uninterruptible power supply in the prior art. FIG. 2 is a circuit diagram of an online uninterruptible power supply according to a preferred embodiment of the present invention. FIG. 3 is a control flowchart of a first conversion mode of the online uninterruptible power supply shown in FIG. 2. FIG. 4 is a control flowchart of the second conversion mode of the online uninterruptible power supply shown in FIG. 2. 5 is a control flowchart of a third conversion mode of the online uninterruptible power supply shown in FIG. 2. FIG. 6 is a control flowchart of a fourth conversion mode of the online uninterruptible power supply shown in FIG. 2.

Claims (12)

An online uninterruptible power supply is characterized in that it includes: a bypass input connected to an AC output through a bypass switch; a mains input connected to a rectifier, a positive and negative DC bus, and an inverter in order; Said AC output terminal, there is no isolation device between the inverter output terminal and the AC output terminal; a capacitor, whose two ends are connected between the positive and negative DC buses; a charger, comprising: a first pair An input terminal, two terminal terminals of the first pair of input terminals are connected to the bypass input terminal; a second pair of input terminals, two terminal terminals of the second pair of input terminals are connected to the mains input terminal; and To the output terminals across the capacitor. The online uninterruptible power supply according to item 1 of the scope of patent application, wherein the online uninterruptible power supply also includes a detection control device for detecting the inverter and the bypass input. The voltage and phase of the AC power at the terminal, and controlling the voltage and phase of the AC power output by the inverter to track the voltage and phase of the AC power at the bypass input terminal. The online uninterruptible power supply according to item 1 of the scope of patent application, wherein the online uninterruptible power supply also includes a battery and a converter, and the battery is connected to both ends of the capacitor through the converter. . The online uninterruptible power supply according to item 1 of the scope of the patent application, wherein the online uninterruptible power supply also includes a rectifier switch connected between the mains input terminal and the rectifier, and connected to A fuse between the output terminal of the inverter and the AC output terminal. The online uninterruptible power supply according to item 1 of the scope of the patent application, wherein the bypass switch is a bidirectional thyristor or two thyristors connected in anti-parallel. A control method for an online uninterruptible power supply according to any one of items 1 to 5 of the scope of patent application, characterized in that when there is no mains power at the mains input terminal, the control method includes the following Steps: S11), controlling the charger to work to charge the capacitor; S12) controlling the charger to stop working when the voltage across the capacitor reaches a predetermined first threshold voltage; and S13), Controlling the bypass switch to be turned on. A control method for an online uninterruptible power supply according to any one of claims 1 to 5 in the scope of patent application, wherein the AC power at the bypass input terminal supplies power to the AC output terminal, and When the mains input has mains power, the control method includes the following steps: S21), controlling the rectifier to work so that the voltage across the capacitor reaches its working voltage; S22), detecting the The voltage and phase of the AC power; S23), controlling the inverter to output AC power to the AC output terminal. The method for controlling an online uninterruptible power supply according to item 7 of the scope of patent application, wherein the step S23) includes the following steps: calculating a pulse width modulation signal to be provided to the inverter; The bypass switch is turned off, and the PWM signal is provided to the inverter so that the voltage and phase of the AC power output by the inverter track the voltage and phase of the AC power at the bypass input terminal. The control method according to item 7 of the scope of patent application, characterized in that, before step S21), the method further comprises the step of detecting the voltage across the capacitor, and if the voltage across the capacitor is not less than a predetermined Two threshold voltages, control the rectifier to work; if the voltage across the capacitor is less than a predetermined second threshold voltage, control the charger to work so that the voltage across the capacitor reaches a predetermined second threshold voltage, control The charger stops working and controls the rectifier to work. A control method for an online uninterruptible power supply according to any one of claims 1 to 5 in the scope of patent application, characterized in that when there is no AC power at the bypass input terminal, the control method includes The following steps: S31), controlling the charger to charge the capacitor; S32) controlling the charger to stop working when the voltage across the capacitor reaches a predetermined third threshold voltage, and controlling The rectifier works; and S33), when the voltage across the capacitor reaches its working voltage, control the inverter to work. A control method for an on-line uninterruptible power supply according to any one of items 1 to 5 of the scope of patent application, wherein the mains input terminal supplies power to the AC output terminal, and when the When there is AC power at the bypass input terminal, the control method includes the following steps: S41), detecting the voltage and phase of the AC power at the bypass input terminal and the AC power output by the inverter; S42), controlling the inverter The voltage and phase of the AC power output by the inverter track the voltage and phase of the AC power at the bypass input terminal; S43), controlling the bypass switch to be turned on and controlling the inverter to stop working. The method for controlling an online uninterruptible power supply according to item 11 of the scope of patent application, wherein the step S42) comprises: calculating a pulse width modulation signal to be provided to the inverter, and providing the The voltage and phase of the AC power output from the pulse width modulation signal to the inverter tracks the voltage and phase of the AC power at the bypass input terminal.