CN1324781C - Backup power supply system with zero power-off transition time - Google Patents

Abstract

A spare power supply system with zero power-off conversion time is provided, which is powered by a first alternating current power supply when the first alternating current power supply is normal, and is automatically converted to be powered by a second alternating current power supply in a mode of zero power-off conversion time when the first alternating current power supply fails. When the first AC power supply is normal, the output current of the DC/AC power converter generating the second AC power supply is controlled to approach zero, so that the output mechanical switch of the DC/AC power converter can be maintained in a closed state when the first AC power supply is normal, and no circulating current is generated between the first AC power supply and the DC/AC power converter; the mechanical output switch is always kept closed without switching, so that the function of zero power-off conversion time can be achieved.

Description

Backup power supply system with zero power-off transition time

technical field

The present invention relates to a backup power supply system with zero power-off conversion time, especially to solve the short-term power interruption caused by the output mechanical switching operation of a DC/AC power converter (DC/AC Power converter) at the moment of power source conversion The problem.

Background technique

As shown in Fig. 1, it is a circuit block diagram of a standby power supply system (1) with known zero power-off conversion time, its input end is connected to a first AC power source 2 and a DC power source 3, its output end is connected to a load 4, The backup power supply system 10 includes a first switch ( S11 ) 101 , a second switch ( S12 ) 102 and a DC/AC power converter 104 . The function of the DC/AC power converter 104 is to convert the DC power from the DC power source 3 into a second AC power source 105 . When the first AC power source 2 is normal, the first switch (S11) 101 is closed (Close), and at the same time, the first switch (S11) 101 is opened (Open). At this time, the power of the load 4 is directly supplied by the first AC power source 2 , and the DC/AC power converter 104 operates in a thermal standby state of no-load operation. When the first AC power supply 2 fails, the first switch (S11) 101 is turned off, and the second switch (S12) 102 is operated to be turned on at the same time. The first switch (S11) 101 and the second switch (S12) 102 are both solid-state switches (Static Switch), such as TRIAC or two SCR reversely connected in parallel, the switching action only takes a few microseconds (μs) to It can be completed in tens of microseconds, and even sensitive equipment is not affected by microsecond-level power interruptions. Therefore, the backup power supply system 10 can switch the power source of the load 4 from the first The AC power source 2 is switched to the second AC power source 105 . However, since a solid-state switch has a large voltage drop (typically greater than 1 volt, compared to a very low voltage drop for a mechanical switch) when it is turned on, it is less effective in the DC/AC power converter 104 than a mechanical switch. When the load is 4, it will produce poor voltage regulation (Poor Voltage Regulation) at the load end, and also reduce the overall efficiency due to the large loss, and require additional heat dissipation devices. Therefore, although the second switch ( S12 ) 102 uses a solid-state switch to achieve the function of zero power-off switching time, it also has the aforementioned disadvantages.

As shown in Figure 2, it is another conventional backup power supply system (2) circuit block diagram with zero power-off conversion time, its input terminal is connected to a first AC power supply 2 and a DC power supply 3, and its output terminal is connected to a load 4. The standby power supply system 20 includes a first switch ( S21 ) 201 , a second switch ( S22 ) 202 , a third switch ( S23 ) 203 , and a DC/AC power converter 204 . The function of the DC/AC power converter 204 is to convert the DC power from the DC power source 3 into a second AC power source 205 . Wherein the first switch (S21) 201 and the second switch (S22) 202 are solid state switches, and the third switch (S23) 203 is a mechanical switch, such as a relay or a contactor. When the first AC power source 2 is normal, the first switch ( S21 ) 201 is turned on, and at the same time, the second switch ( S22 ) 202 and the third switch ( S23 ) 203 are both turned off. At this time, the power of the load 4 is directly supplied by the first AC power source 2 , and the DC/AC power converter 204 operates in a thermal standby state of no-load operation. When the first AC power source 2 fails, the first switch ( S21 ) 201 is turned off, and the second switch ( S22 ) 202 and the third switch ( S23 ) 203 are both turned on simultaneously. The first switch (S21) 201 and the second switch (S22) 202 are both solid-state switches, and the switching action only takes a few microseconds (μs) to tens of microseconds to complete, even sensitive equipment is not affected by microseconds Therefore, the backup power supply system 20 can switch the power supply source of the load 4 from the first AC power source 2 to the second AC power source 205 under the condition of completely uninterrupted switching. And after a few milliseconds (ms) to tens of milliseconds, the third (mechanical) switch (S23) 203 with a slower switching speed has also formed a closed state, because the conduction of the mechanical contact of the third switch (S23)) 203 The on-resistance is much lower than the second switch (S22) 202, so the third switch (S23) 203 will completely bypass the second switch (S22) 202, so that the aforementioned backup power supply system can be improved Issues such as large conduction voltage drop and large efficiency loss caused by using solid-state switches in 10. However, the backup power supply system 20 still has the problem of increasing the use of components. Compared with the aforementioned backup power supply system 10, the backup power supply system 20 has a higher cost and a larger required volume, and may even be caused by components. Increases lead to disadvantages such as reduced reliability.

In view of this, the present invention improves the above-mentioned shortcomings, and controls a DC/AC power converter in a standby power supply system with zero power-off conversion time, so that the first AC power source controls the DC/AC power converter when it is normal. The output current is close to zero, and the output switch of the DC/AC power converter is kept closed no matter whether the first AC power source is normal or faulty, so the DC/AC power converter can directly supply power to the load at the moment of the first AC power source failure , without causing a momentary loss of power to the output. In addition, because the switch adopts a mechanical switch, it does not have problems such as poor voltage regulation rate, additional voltage drop loss and heat dissipation device generated by solid-state switches.

Contents of the invention

The main purpose of the present invention is to provide a backup power supply system with zero power-off switching time, which adopts a mechanical switch between the DC/AC power converter and the load, so as to overcome the aforementioned disadvantages caused by the solid-state switch, while avoiding the mechanical It takes several milliseconds to tens of milliseconds for the switching operation to cause the problem of power failure.

The standby power supply system with zero power-off conversion time includes:

a first switch, which is a solid-state switch, connected between the first AC power source and the load;

A second switch, which is a mechanical switch, is connected between the DC/AC power converter and the load; and

A DC/AC power converter, the DC terminal of which is connected to the DC power supply at the input terminal for converting DC power into a second AC power supply, and the AC terminal is connected to the second switch. When the first AC power supply is normal, not only Closing the solid-state switch between the first AC power source and the load also keeps the mechanical switch between the DC/AC power converter and the load in a closed state, while controlling the output current of the DC/AC power converter so that It tends to zero so that no circulating current will be generated between the first AC power source and the DC/AC power converter;

When the first AC power source fails, the DC/AC power converter can immediately establish a sine wave voltage and supply the required power to the load. Therefore, the mechanical switch between the DC/AC power converter and the load is always closed without switching, so the function of zero power-off switching time can be achieved. The mechanical switch is disconnected only when the DC/AC power converter fails or stops running, and is disconnected from the DC/AC power converter.

The DC/AC power converter can be operated in a current control mode, by feeding back the output current of the DC/AC power converter, the feedback output current and a reference current signal are closed-loop controlled, so that the DC/AC The output current of the power converter can approach the reference current signal.

The reference current signal is generated by a reference current signal generating circuit, and a switch is connected between the output terminal of the reference current signal generating circuit and the ground level; when the first AC power supply is normal, the switch is closed, forcing the reference The output signal of the current signal generating circuit becomes ground level, so that the reference current signal is zero, and the output current of the DC/AC power converter can be driven to approach zero through the closed-loop current control mode; when the first AC power supply fails, the The switch is turned off, the reference current signal generating circuit can output a non-zero level reference current signal, and the closed-loop current control method can drive the DC/AC power converter to output the current required by the load, and the DC/AC A sine wave voltage is established at the output terminal of the AC power converter.

Description of drawings

Fig. 1 is the circuit block schematic diagram of the conventional backup power supply system (1) with zero power-off switching time;

Fig. 2 is the circuit block schematic diagram of the backup power supply system (2) of conventional zero power-off switching time;

Fig. 3 is the circuit block schematic diagram of the standby power supply system of zero power-off conversion time in a preferred embodiment of the present invention;

4 is a circuit block diagram of a backup power supply system with zero power-off switching time and a control block diagram of a DC/AC power converter according to a preferred embodiment of the present invention.

Description of figure number:

2. The first AC power supply 3. DC power supply

4. Load 10. Backup power supply system

101. The first switch (S11) 102. The second switch (S12)

104. DC/AC power converter 105. Second AC power supply

20. Backup power supply system 201. First switch (S21)

202. Second switch (S22) 203. Third switch (S23)

204. DC/AC power converter 205. Second AC power supply

30. Backup power supply system 301. First switch (S31)

302. Second switch (S32) 304. DC/AC power converter

305. The first AC power supply 31. DC/AC power converter control block diagram

311. Reference current generation circuit 312. First AC power supply fault detection circuit

313. Switch 314. Subtractor

315. Controller 316. Pulse width modulation circuit

317. DC/AC power converter output current feedback signal

318、Ground level

Detailed ways

In order to make the above and other objects, features and advantages of the present invention more clearly understood, preferred embodiments of the present invention will be cited below in detail with accompanying drawings.

As shown in Figure 3, it is the circuit block diagram of the standby power supply system of zero power-off conversion time of the present invention, its input terminal is connected with a first AC power supply 2 and a DC power supply 3, its output terminal is connected with a load 4, the standby power supply The power supply system 30 includes a first switch ( S31 ) 301 , a second switch ( S32 ) 302 and a DC/AC power converter 304 . The function of the DC/AC power converter 304 is to convert the DC power from the DC power source 3 into a second AC power source 305 . Wherein the first switch (S31) 301 is a solid state switch, and the second switch (S32) 302 is a mechanical switch. When the first AC power source 2 is normal, both the first switch (S31) 301 and the second switch (S32) 302 are closed, and the output current of the DC/AC power converter 304 is controlled to make it close to Zero, and no circulating current will be generated between the first AC power source 2 and the DC/AC power converter 304. At this time, the power of the load 4 is directly supplied by the first AC power source 2. When the first AC power source 2 fails, the first switch (S31) 301 is turned off, the second switch (S32) 302 remains closed without switching, and the DC/AC power converter 304 immediately creates a sine wave The voltage supplies power to the load 4 to continue to use, so the backup power supply system 30 can switch the power source of the load 4 from the first AC power source 2 to the second AC power source 305 under the condition of completely uninterrupted power conversion.

The standby power supply system with zero power-off conversion time of the present invention improves the poor voltage regulation rate, extra voltage drop loss and the need for heat dissipation devices caused by the use of solid-state switches in the aforementioned standby power supply system 10, and does not have the aforementioned backup power supply system 10. The power supply system 20 has the disadvantages of increased components, higher cost, and larger required volume.

FIG. 4 shows a block diagram 31 of a standby power supply system 30 and its DC/AC power converter control circuit with zero power-off transition time according to a preferred embodiment of the present invention. The DC/AC power converter 304 adopts a current control mode. Please refer to FIG. 4, the DC/AC power converter control block 31 of the backup power supply system 30 of the preferred embodiment of the present invention includes a reference current generation circuit 311, a first AC power failure detection Measuring circuit 312 , a switch 313 , a subtractor 314 , a controller 315 , and a pulse width modulation circuit 316 .

Please refer to FIG. 4 again, the DC/AC power converter control block 31 of the backup power supply system 30 of the preferred embodiment of the present invention with zero power-off conversion time, wherein the reference current generation circuit 311 generates a reference current signal, the After the reference current signal and the actual DC/AC power converter output current feedback signal 317 are closed-loop controlled, the DC/AC power converter 304 can output a sine wave voltage; the first AC power failure detection circuit 312 is used for Detect the state of the first AC power supply; the switch 313 is used to determine whether to connect the output of the reference current generation circuit 311 to the ground level 318 according to the detection state result of the first AC power failure detection circuit 312: the subtractor The output signal of 314 is used to drive the DC/AC power converter 304 to complete the current control mode through the controller 315 and the pulse width modulation circuit 316, then the output current of the DC/AC power converter 304 can approach the reference The reference current signal output by the current generation circuit 311 .

Please refer to FIG. 4 again, the backup power supply system 30 and its DC/AC power converter control circuit block diagram 31 of a preferred embodiment of the present invention with zero power-off conversion time. When the first AC power supply 2 is normal, the first The AC power failure detection circuit 312 sends a control signal to control the switch 313 to close, so that the output of the reference current generating circuit 311 is connected to the ground level 318, so that the reference current signal becomes zero level, and the zero level reference The current signal and the output current feedback signal 317 of the DC/AC power converter are closed-loop controlled by the subtractor 314 and the controller 315, and then the control signal of the controller 315 is output to the pulse width modulation circuit 316 to generate the DC/AC power converter. A drive signal for the AC power converter 304 . At this time, since the reference current signal is at zero level, the output current of the DC/AC power converter 304 can approach zero after current closed-loop control, and at this time, not only the first switch (S31) 301 is closed , the second switch (S32) 302 is also closed, and no circulating current will be generated between the first AC power source 2 and the DC/AC power converter 304, and since the output current of the DC/AC power converter 304 approaches Therefore, no additional loss will be generated on the DC/AC power converter 304 . At this time, the power required by the load 4 is supplied by the first AC power source 2 .

Please refer to Fig. 4 again, the backup power supply system 30 and its DC/AC power converter control block 31 of the preferred embodiment of the present invention with zero power-off conversion time, when the first AC power supply 2 fails at the moment, the first switch (S31) 301 will be turned off immediately, and the detection circuit 312 will immediately detect the first AC power failure, and send a control signal to control the switch 313 to turn off. At this time, the signal sent by the reference current generating circuit 311 to the subtractor 314 has formed an open circuit with the ground level 318, and becomes the reference current signal (not equal to zero) of the normal current control loop. The normal reference current signal and the DC The output current feedback signal 317 of the /AC power converter is closed-loop controlled by the subtractor 314 and the controller 315, and the control signal of the controller 315 is output to the pulse width modulation circuit 316 to generate the DC/AC power converter 304. drive signal. At this time, the reference current signal of the normal level can generate a sine wave voltage at the output terminal of the DC/AC power converter 304 after the current closed-loop control, so the second AC power output by the DC/AC power converter 304 305 supplies power to the load 4 through the second switch (S32) 302. Since the second switch (S32) 302 remains closed when the first AC power supply 2 is normal, it is not used for switching when the first AC power supply 2 fails. Short power outages caused by switching of the second switch (S22) 202 can be avoided.

Please refer to FIG. 4 again, the DC/AC power converter control block 31 of the backup power supply system 30 of the preferred embodiment of the present invention with zero power-off conversion time, wherein the reference current generating circuit 311 and the first AC power supply fail The detection circuit 312, the subtractor 314, the controller 315, and the pulse width modulation circuit 316 are all basic control blocks when the traditional current-controlled DC/AC power converter is used as a backup power supply system, so the present invention has zero power failure In the DC/AC power converter control block 31 of the standby power supply system 30, only the switch 313 is added and connected to the first AC power failure detection circuit 312 to complete the conversion time of zero power failure. control function.

Common applications of the backup power supply system with zero power-off switching time of the present invention include hot-standby off-line uninterruptible power systems, and online uninterruptible power systems in economical operation modes and other backup power supply systems that require uninterruptible power conversion. In the normal operation mode of the on-line uninterruptible power system, its DC/AC power converter is in the state of load operation. However, in order to pursue higher power conversion efficiency, in recent years, the on-line uninterruptible power system has also been designed with an economical operation mode for use choose. The so-called economical operation mode is to set its DC/AC power converter to run in the hot state, and the load is directly supplied with power by the mains. Once the mains fails, the load is switched to DC/AC through the transfer switch (Transfer Switch) The power converter supplies power. Therefore, the conduction characteristic of the output switch of the DC/AC power converter also has a significant impact on the regulation rate of the load terminal voltage and the overall power conversion efficiency in the normal operation mode of the on-line uninterruptible power system. Therefore, the excellent performance of the standby power supply system with zero power-off switching time of the present invention is more obvious when the on-line uninterruptible power system is equipped with an economical operation mode.

Although the present invention has been disclosed by the aforementioned preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the invention is subject to the scope defined by the claims.

Claims (3)

1, a kind of zero stand-by power supply electric power system of cutting off the power supply change-over time is characterized in that, comprising:

One first switch is solid-state switch, and it is connected between first AC power and the load;

A second switch is mechanical switch, and it is connected between AC/DC electric power converter and the load; And

An AC/DC electric power converter, its dc terminal are that dc supply input is connected to DC power supply, in order to direct current energy is converted to second AC power, are connected to second switch and exchange end;

When first AC power just often, first switch and second switch all maintain closure state, the output current of controlling the AC/DC electric power converter simultaneously levels off to zero; When first AC power failure, disconnect first switch, second switch maintains closure state, and the AC/DC electric power converter is set up a sine voltage at its output and is continued offered load; Can not supply electric power to this load owing to do not need to switch second switch during first AC power failure, therefore can reach zero function of cutting off the power supply change-over time.

2, the zero stand-by power supply electric power system of cutting off the power supply change-over time as claimed in claim 1, it is characterized in that, this AC/DC electric power converter is operable in current control mode, output current by this AC/DC electric power converter of feedback, the output current of this AC/DC electric power converter should feed back output current and a reference current signal is done closed-loop control, so that can level off to this reference current signal.

3, the zero stand-by power supply electric power system of cutting off the power supply change-over time as claimed in claim 2, it is characterized in that, this reference current signal produces circuit by reference current signal and produces, and is connected with a switch between this reference current signal produces circuit output end and earth level; When first AC power just often this switch form closure, force reference current signal to produce circuit output signal and become earth level, so that this reference current signal is zero, can orders about this AC/DC electric power converter output current via the current control mode of closed loop and level off to zero; This switch forms and turn-offs when first AC power failure, this reference current signal produces the reference current signal that circuit can be exported a non-zero level, current control mode via closed loop can order about the required electric current of this AC/DC electric power converter output loading, and sets up a sine voltage at this AC/DC electric power converter output.

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