CN110061560B - Off-line uninterrupted power supply and control method thereof - Google Patents

Off-line uninterrupted power supply and control method thereof Download PDF

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Publication number
CN110061560B
CN110061560B CN201910440028.XA CN201910440028A CN110061560B CN 110061560 B CN110061560 B CN 110061560B CN 201910440028 A CN201910440028 A CN 201910440028A CN 110061560 B CN110061560 B CN 110061560B
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switch
controlled
rechargeable battery
alternating current
output
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CN110061560A (en
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胡武华
邓亮
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Lian Zheng Electronics Shenzhen Co Ltd
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Lian Zheng Electronics Shenzhen Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H02J9/062—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems for AC powered loads

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Stand-By Power Supply Arrangements (AREA)

Abstract

The invention provides an off-line uninterrupted power supply and a control method thereof, wherein the off-line uninterrupted power supply comprises: a safety switch connected between the AC input terminal and the AC output terminal; a transformer having one end of a primary side thereof connected to one terminal of the ac output terminal; a first switch, a second switch, and an output switch connected in sequence between the safety switch and the other terminal of the ac output terminal, the first switch being operable to connect the safety switch to one of the other end and the tap of the primary side of the transformer, the second switch being operable to connect the output switch to one of the other end and the tap of the primary side of the transformer; a third switch operable to connect the safety switch to one of the first switch and the other terminal of the alternating current output; and a bidirectional converter. The off-line uninterrupted power supply has higher electric energy transmission efficiency.

Description

Off-line uninterrupted power supply and control method thereof
Technical Field
The invention relates to the field of electronic circuits, in particular to an off-line uninterrupted power supply and a control method thereof.
Background
The off-line uninterrupted power supply is directly supplied to a load by mains supply when the mains supply voltage is normal, and the rechargeable battery is in a charging state; when the voltage of the mains supply is abnormal or power failure occurs, the inverter is switched to a working state, and the direct current in the rechargeable battery is converted into stable alternating current to be output; when the voltage of the commercial power is low or high, the transformer connected to the alternating current input end is used for adjusting the voltage of the commercial power, so that the alternating current output end has stable output voltage.
Fig. 1 is a circuit diagram of an off-line ups in the prior art. As shown in fig. 1, the off-line uninterruptible power supply 1 comprises an electromagnetic compatibility (EMC) filter 11 connected between its ac input 10 and ac output 10'; a safety switch 12 configured as a double pole single throw relay or including a safety switch unit 121 and a safety switch unit 122 that are switched simultaneously; a first switch 131, a second switch 132 and an output switch 14 connected in sequence between the safety switch 12 and the terminal L of the ac output terminal 10'; a transformer Tr1, one terminal T1 of the primary side of the transformer Tr1 being connected between the safety switch 12 and the terminal N of the ac output terminal 10', wherein the first switch 131 is operable to connect the safety switch 12 to one of the other terminal T2 and the tap T3 of the primary side of the transformer Tr1, and the second switch 132 is operable to connect the output switch 14 to one of the other terminal T2 and the tap T3 of the primary side of the transformer Tr 1; and a rechargeable battery 16, a bidirectional converter 15 and an auxiliary power supply system 17, the rechargeable battery 16 is connected to the secondary side of the transformer Tr1 through the bidirectional converter 15, and the input terminal of the auxiliary power supply system 17 is connected to both ends of the rechargeable battery 16, which is used for supplying various required voltages to the off-line uninterruptible power supply 1. In which, in order to simplify the circuit diagram, fig. 1 does not show mains detection means for detecting the mains voltage, battery detection means for detecting the state of charge of the rechargeable battery 16, and control means for controlling the operating state of the bidirectional converter 15 and the switching states of the safety switch 12, the first switch 131, the second switch 132, and the output switch 14.
When the utility voltage is high, the off-line uninterruptible power supply 1 is controlled to be in the automatic voltage step-down regulation mode in which the safety switch 12 and the output switch 14 are controlled to be turned on, the first switch 131 is controlled to be connected to the terminal T2 on the primary side of the transformer Tr1, and the second switch 132 is controlled to be connected to the tap T3 on the primary side of the transformer Tr1, whereby the alternating current output terminal 10' outputs the ac power whose voltage is reduced. While the bidirectional converter 15 is controlled to convert the alternating current on the secondary side of the transformer Tr1 into direct current to charge the rechargeable battery 16 and supply the direct current to the auxiliary power supply system 17.
When the utility voltage is low, the off-line uninterruptible power supply 1 is controlled to be in the automatic voltage boost regulation mode in which the safety switch 12 and the output switch 14 are controlled to be turned on, the first switch 131 is controlled to be connected to the tap T3 on the primary side of the transformer Tr1, and the second switch 132 is controlled to be connected to the terminal T2 on the primary side of the transformer Tr1, whereby the alternating current output terminal 10' outputs the alternating current with the boosted voltage. While the bidirectional converter 15 is controlled to convert the alternating current on the secondary side of the transformer Tr1 into direct current to charge the rechargeable battery 16 and supply the direct current to the auxiliary power supply system 17.
When the mains voltage is abnormal (e.g., the voltage is too high) or there is a power failure, the off-line uninterruptible power supply 1 is controlled to be in the battery mode. The safety switch 12 is controlled to be turned off, the output switch 14 is controlled to be turned on, the second switch 132 is controlled to be connected to the terminal T2 on the primary side of the transformer Tr1, and the bidirectional converter 15 is controlled to operate to convert the dc power of the rechargeable battery 16 into ac power, and the ac power is transformed by the transformer Tr1 to obtain a desired ac power at the ac output terminal 10'. At the same time, the rechargeable battery 16 supplies direct current to the auxiliary power supply system 17.
When the mains voltage is within the normal range, the off-line ups 1 is controlled to be in the normal mode. The safety switch 12 and the output switch 14 are controlled to be on, and the first switch 131 and the second switch 132 are controlled to be both connected to the terminal T2 of the primary side of the transformer Tr 1. While the bidirectional converter 15 is controlled to convert the alternating current on the secondary side of the transformer Tr1 into direct current to charge the rechargeable battery 16 and supply the direct current to the auxiliary power supply system 17.
Fig. 2 is an equivalent circuit diagram of the off-line type ups shown in fig. 1 after the rechargeable battery is fully charged in the normal mode. As shown in fig. 2, the commercial power at the ac input terminal 10 is transmitted to the ac output terminal 10' through the EMC filter 11, the conductive safety switch 12, the first switch 131, the second switch 132, and the output switch 14. On the one hand, the contact of the 3 switches between the safety switch 12 and the terminal L of the ac output 10' reduces the power efficiency. On the other hand, the primary side of the transformer Tr1 is electrically connected to the ac output terminal 10', and therefore the transformer Tr1 has a large no-load loss. Further, the transformer Tr1 is operated at all times, and the bidirectional converter 15 is controlled to be operated at all times, and the rechargeable battery 16 is in a float-charged state after being fully charged. When the rechargeable battery 16 is in a float state, the positive plate of the rechargeable battery 16 is deactivated, and a large amount of PbSO is generated4And absorbed onto the negative plate. This will result in a decrease in activity and an increase in internal resistance, and the capacity of the rechargeable battery 16 will rapidly decrease and the lifetime will be greatly reduced.
Disclosure of Invention
To solve the above technical problems in the prior art, the present invention provides an offline uninterruptible power supply, including:
a safety switch connected between the AC input terminal and the AC output terminal;
a transformer having one end of a primary side thereof connected to one terminal of the ac output terminal;
a first switch, a second switch, and an output switch connected in sequence between the safety switch and the other terminal of the ac output terminal, the first switch being operable to connect the safety switch to one of the other end and the tap of the primary side of the transformer, the second switch being operable to connect the output switch to one of the other end and the tap of the primary side of the transformer;
a third switch operable to connect the safety switch to one of the first switch and the other terminal of the alternating current output; and
a bidirectional converter controllably converting the alternating current of the secondary side of the transformer into direct current to charge the rechargeable battery and converting the direct current of the rechargeable battery into alternating current.
Preferably, the off-line uninterruptible power supply further comprises:
the input end of the charger is connected to the alternating current input end, and the alternating current at the alternating current input end is controllably converted into direct current; and
and the input end of the auxiliary power supply system is connected to the output end of the charger.
Preferably, the third switch includes:
a common terminal connected to the safety switch;
a first switching terminal connected between the output switch and the other terminal of the alternating current output terminal; and
a second switching terminal connected to the first switch.
Preferably, the output terminal of the charger is connected to both ends of the rechargeable battery.
Preferably, the off-line uninterruptible power supply further includes a diode having an anode connected to the positive electrode of the rechargeable battery and a cathode connected to the positive terminal of the output terminal of the charger.
Preferably, the output power of the charger is smaller than the maximum charging power of the rechargeable battery, and the output voltage of the charger is greater than the voltage across the rechargeable battery.
Preferably, the off-line uninterruptible power supply further comprises:
a mains detection device configured to detect a mains voltage of the ac output;
a battery detection device configured to detect a state of charge of the rechargeable battery; and
a control device configured to control operating states of the charger and the bidirectional converter, and to control switching states of the safety switch, the first switch, the second switch, the third switch, and the output switch, according to the mains voltage and a charging state of the rechargeable battery.
Preferably, when the first threshold voltage is less than or equal to the commercial power voltage and less than the second threshold voltage, the control device controls the safety switch to be turned on, controls the third switch to be connected to the first switch, controls the first switch to be connected to a tap on the primary side of the transformer, controls the second switch to be connected to the other end on the primary side of the transformer, and controls the output switch to be turned on; when the chargeable battery is not fully charged, the control device controls the charger to stop working and controls the bidirectional converter to convert the alternating current on the secondary side of the transformer into direct current; and when the rechargeable battery is fully charged, the control device controls the bidirectional converter to stop working and controls the charger to convert the alternating current at the alternating current input end into the direct current.
Preferably, when the second threshold voltage is less than or equal to the mains voltage and less than the third threshold voltage, the control device controls the safety switch to be switched on; when the rechargeable battery is not fully charged, the control device controls the third switch to be connected to the first switch, controls the first switch and the second switch to be connected to the other end of the primary side of the transformer, controls the output switch to be conducted, and controls the bidirectional converter to convert the alternating current on the secondary side of the transformer into direct current; when the rechargeable battery is fully charged, the control device controls the third switch to be connected to the other terminal of the alternating current output end, controls the output switch to be disconnected, controls the bidirectional converter to stop working, and controls the charger to convert alternating current of the alternating current input end into direct current.
Preferably, when the third threshold voltage is less than or equal to the commercial power voltage and less than the fourth threshold voltage, the control device controls the safety switch to be turned on, controls the third switch to be connected to the first switch, controls the first switch to be connected to the other end of the primary side of the transformer, controls the second switch to be connected to a tap of the primary side of the transformer, and controls the output switch to be turned on; when the rechargeable battery is not fully charged, the control device controls the charger to stop working and controls the bidirectional converter to convert the alternating current on the secondary side of the transformer into direct current; when the rechargeable battery is fully charged, the control device controls the bidirectional converter to stop working, and controls the charger to convert the alternating current of the alternating current input end into the direct current.
Preferably, when the mains voltage is less than the first threshold voltage or greater than or equal to a fourth threshold voltage, the control device controls the safety switch to be turned off, controls the second switch to be connected to the other end of the primary side of the transformer, controls the output switch to be turned on, and controls the bidirectional converter to convert the direct current of the rechargeable battery into the alternating current.
The invention also provides a control method for the off-line uninterrupted power supply, which comprises the following steps: and detecting the mains voltage of the alternating current output end and the charging state of the rechargeable battery, controlling the working states of the charger and the bidirectional converter according to the mains voltage and the charging state of the rechargeable battery, and controlling the switching states of the safety switch, the first switch, the second switch, the third switch and the output switch.
Preferably, when the first threshold voltage is less than or equal to the mains voltage and less than the second threshold voltage, the safety switch is controlled to be turned on, the third switch is controlled to be connected to the first switch, the first switch is controlled to be connected to a tap on the primary side of the transformer, the second switch is controlled to be connected to the other end on the primary side of the transformer, and the output switch is controlled to be turned on; when the chargeable battery is not fully charged, the charger is controlled to stop working, and the bidirectional converter is controlled to convert the alternating current on the secondary side of the transformer into direct current; and when the rechargeable battery is fully charged, controlling the bidirectional converter to stop working, and controlling the charger to convert the alternating current at the alternating current input end into the direct current.
Preferably, when the second threshold voltage is less than or equal to the mains voltage and less than the third threshold voltage, the safety switch is controlled to be switched on; when the rechargeable battery is not fully charged, the third switch is controlled to be connected to the first switch, the first switch and the second switch are controlled to be connected to the other end of the primary side of the transformer, the output switch is controlled to be conducted, and the bidirectional converter is controlled to convert the alternating current on the secondary side of the transformer into direct current; when the rechargeable battery is fully charged, the third switch is controlled to be connected to the other terminal of the alternating current output end, the output switch is controlled to be disconnected, the bidirectional converter is controlled to stop working, and the charger is controlled to convert alternating current of the alternating current input end into direct current.
Preferably, when the third threshold voltage is less than or equal to the commercial power voltage and less than the fourth threshold voltage, the safety switch is controlled to be turned on, the third switch is controlled to be connected to the first switch, the first switch is controlled to be connected to the other end of the primary side of the transformer, the second switch is controlled to be connected to a tap of the primary side of the transformer, and the output switch is controlled to be turned on; when the rechargeable battery is not fully charged, the charger is controlled to stop working, and the bidirectional converter is controlled to convert the alternating current on the secondary side of the transformer into direct current; and when the rechargeable battery is fully charged, controlling the bidirectional converter to stop working, and controlling the charger to convert the alternating current at the alternating current input end into the direct current.
Preferably, when the mains voltage is less than the first threshold voltage or greater than or equal to a fourth threshold voltage, the safety switch is controlled to be switched off, the second switch is controlled to be connected to the other end of the primary side of the transformer, the output switch is controlled to be switched on, and the bidirectional converter is controlled to convert the direct current of the rechargeable battery into the alternating current.
The off-line uninterrupted power supply has higher electric energy transmission efficiency, can realize battery-free starting, can select a small charger, reduces the cost of the charger, can prevent the rechargeable battery from being in a floating charging state, prolongs the service life of the rechargeable battery and reduces the cost of the rechargeable battery.
Drawings
Embodiments of the invention are further described below with reference to the accompanying drawings, in which:
fig. 1 is a circuit diagram of an off-line ups in the prior art.
Fig. 2 is an equivalent circuit diagram of the off-line type ups shown in fig. 1 after the rechargeable battery is fully charged in the normal mode.
Fig. 3 is a circuit diagram of an off-line uninterruptible power supply according to a first embodiment of the invention.
Fig. 4 is an equivalent circuit diagram of the off-line type ups shown in fig. 3 after the rechargeable battery is fully charged in the normal mode.
Fig. 5 is a circuit diagram of an off-line ups according to a second embodiment of the invention.
Fig. 6 is an equivalent circuit diagram of the off-line type ups shown in fig. 5 after the rechargeable battery is fully charged in the normal mode.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail by embodiments with reference to the accompanying drawings.
Fig. 3 is a circuit diagram of an off-line uninterruptible power supply according to a first embodiment of the invention. As shown in fig. 3, it is substantially the same as fig. 1 except that the offline type uninterruptible power supply 2 further includes a charger 28 and a third switch 29. The third switch 29 includes a common terminal connected to the second safety switch unit 222 of the safety switch 22, a first switching terminal S1 electrically connected between the output switch 24 and the terminal L of the ac output terminal 20', and a second switching terminal S2 connected to the common terminal of the first switch 231. The third switch 29 is operable such that the safety switch 22 is connected to the first switch 231 and one of the terminals L of the ac output terminal 20', the safety switch 22 being used to implement a feedback protection function. The charger 28 has an input connected to the ac input 20 and an output connected to an input of the auxiliary power supply system 27. In which, for the sake of simplifying the circuit diagram, fig. 3 also does not show mains detection means for detecting the mains voltage, battery detection means for detecting the charging state of the rechargeable battery 26, and control means for controlling the operating states of the charger 28 and the bidirectional converter 25, and control means for controlling the switching states of the safety switch 22, the first switch 231, the second switch 232, the third switch 29 and the output switch 24.
The mode of operation of the off-line ups 2 will be described in part below.
(1) When the mains voltage is within the normal range, the off-line ups 2 is controlled to be in the normal mode. Wherein the safety switch 22 (i.e., the first safety switch unit 221 and the second safety switch unit 222) is controlled to be turned on. If the rechargeable battery 26 is not fully charged, the common terminal of the third switch 29 is controlled to be connected to the second switching terminal S2 (i.e., the third switch 29 is connected to the first switch 231), the first switch 231 and the second switch 232 are controlled to be both connected to the terminal T22 on the primary side of the transformer Tr2, and the output switch 24 is controlled to be turned on, and the alternating current of the alternating current input terminal 20 is transmitted to the alternating current output terminal 20'. While the bidirectional converter 25 is controlled to convert the alternating current on the secondary side of the transformer Tr2 into direct current to rapidly charge the rechargeable battery 26 and supply the direct current to the auxiliary power supply system 27.
If the rechargeable battery 26 is fully charged, at which time the third switch 29 is controlled to have its common terminal connected to the first switching terminal S1 (i.e., the third switch 29 is connected to the terminal L of the ac output terminal 20'), the output switch 24 is controlled to be off, the bidirectional converter 25 is controlled to stop charging the rechargeable battery 26, and the charger 28 is controlled to convert the ac power at the ac input terminal 20 into dc power to charge the rechargeable battery 26 and supply the required dc power to the auxiliary power supply system 27. Fig. 4 is an equivalent circuit diagram of the off-line type ups shown in fig. 3 after the rechargeable battery is fully charged in the normal mode. As compared with the equivalent circuit shown in fig. 2, the equivalent circuit shown in fig. 4 shows: first, the primary side of the transformer Tr2 is not connected in the circuit, so there is no transformer no-load loss, and the bidirectional converter 25 stops operating. Second, the safety switch 22 is directly connected to the terminal L of the ac output 20' through the third switch 29, reducing the contact loss of the 2 switches. Third, the third switch 29 is in a normally closed state and the output switch 24 is in a normally open state, thereby reducing losses in the solenoid (not shown in fig. 3) of the output switch 24. The inventor tests under the same conditions, the power transmission efficiency of the equivalent circuit shown in fig. 2 is 95.62%, and the power transmission efficiency of the equivalent circuit shown in fig. 4 is increased to 98.75%, so that the power transmission efficiency is improved, thereby meeting the energy star certification standard implemented by the u.s.environmental protection agency and the energy department.
(2) When the mains voltage is high, the off-line ups 2 is controlled to be in the automatic voltage step-down regulation mode. Wherein the safety switch 22 is controlled to be on, the third switch 29 is controlled to have its common terminal connected to the second switching terminal S2 (i.e., the third switch 29 is connected to the first switch 231), the first switch 231 is controlled to be connected to the terminal T22 of the primary side of the transformer Tr2, the second switch 232 is controlled to be connected to the tap T23 of the primary side of the transformer Tr2, and the output switch 24 is controlled to be on.
Wherein if the rechargeable battery 26 is not fully charged, the charger 28 stops operating, and the bidirectional converter 25 is controlled to convert the ac power of the secondary side of the transformer Tr2 into dc power to rapidly charge the rechargeable battery 26 and supply the dc power to the auxiliary power supply system 27.
If the rechargeable battery 26 is fully charged, the bi-directional converter 25 is deactivated and the charger 28 is controlled to convert the ac power at the ac input 20 to dc power to charge the rechargeable battery 26 and provide the required dc power to the auxiliary power supply system 27.
(3) When the mains voltage is low, the off-line ups 2 is controlled to be in an automatic voltage boost regulation mode. Wherein the safety switch 22 is controlled to be turned on, the third switch 29 is controlled to have its common terminal connected to the second switching terminal S2 (i.e., the second safety switch unit 222 is connected to the first switch 231), the first switch 231 is controlled to be connected to the tap T23 of the primary side of the transformer Tr2, the second switch 232 is controlled to be connected to the terminal T22 of the primary side of the transformer Tr2, and the output switch 24 is controlled to be turned on.
If the rechargeable battery 26 is not fully charged and the charger 28 stops operating, the bidirectional converter 25 is controlled to convert the alternating current on the secondary side of the transformer Tr2 into direct current to rapidly charge the rechargeable battery 26 and supply the direct current to the auxiliary power supply system 27.
If the rechargeable battery 26 is fully charged, the bi-directional converter 25 is deactivated and the charger 28 is controlled to convert the ac power at the ac input 20 to dc power to charge the rechargeable battery 26 and provide the required dc power to the auxiliary power supply system 27.
(4) When the utility voltage is abnormal or in a power failure, the off-line uninterruptible power supply 2 is controlled to be in a battery mode in which the safety switch 22 is controlled to be off, the second switch 232 is controlled to be connected to the terminal T22 on the primary side of the transformer Tr2, and the output switch 24 is controlled to be on, while the bidirectional converter 25 is controlled to convert the direct current of the rechargeable battery 26 into alternating current, which is transformed by the transformer Tr2, thereby obtaining a desired alternating current at the alternating current output terminal 20'. While the rechargeable battery 26 provides dc power to the auxiliary power supply system 27.
If the off-line ups 2 is started up and it is not connected to the rechargeable battery 26 or the rechargeable battery 26 cannot supply power, the charger 28 starts to operate and supplies power to the auxiliary power supply system 27 because the input terminal of the charger 28 is connected to the ac input terminal 20, so that the off-line ups 2 starts to operate. It can be seen that the off-line ups 2 achieves battery-less startup.
In conjunction with the above-described operation modes, after the rechargeable battery 26 is fully charged, the charger 28 is controlled to operate to supply power to the auxiliary power supply system 27. Since the power of the auxiliary power supply system 27 is much smaller than the maximum charging power of the rechargeable battery 26 in the ups, a small charger adapted to the power of the auxiliary power supply system 27, i.e. the output power of the charger 28 is smaller than the maximum charging power of the rechargeable battery 26, can be selected to reduce the cost of the circuit.
In the normal mode, when the rechargeable battery 26 is not fully charged, the first switch 231 and the second switch 232 are controlled to be both connected to the terminal T22 of the primary side of the transformer Tr2, whereby all windings of the primary side of the transformer Tr2 are electrically connected to the alternating current input terminal 20, and the transformer Tr2 can be effectively prevented from being saturated.
In the battery mode, the second switch 232 is controlled to be connected to the terminal T22 of the primary side of the transformer Tr2, whereby all windings of the primary side of the transformer Tr2 are electrically connected to the alternating current output terminal 20 ', and an alternating current voltage as large as possible can be obtained at the alternating current output terminal 20' with the duty ratio of the bidirectional converter 25 unchanged. The rechargeable battery 26 having a smaller output voltage can be selected as compared with the tap T23 in which the second switch 232 is controlled to be connected to the primary side of the transformer Tr2, thereby reducing the cost of the rechargeable battery 26.
Fig. 5 is a circuit diagram of an off-line ups according to a second embodiment of the invention. Fig. 5 likewise does not show the mains detection device, the battery detection device and the control device. As shown in fig. 5, the off-line ups 3 is substantially the same as the off-line ups 2 shown in fig. 3, except that the off-line ups 3 further includes a diode D3 connected between the positive terminal of the rechargeable battery 36 and the positive terminal of the output of the charger 38, wherein the diode D3 has its anode connected to the positive terminal of the rechargeable battery 36 and its cathode connected to the positive terminal of the output of the charger 38.
The mode of operation of the off-line ups 3 will be described in part below.
(1) When the voltage of the utility power is within the normal range, the control method is the same as that of the off-line ups 2, which is not described herein. Fig. 6 is an equivalent circuit diagram of the off-line type ups shown in fig. 5 after the rechargeable battery is fully charged in the normal mode. As shown in fig. 6, the charger 38 is controlled to supply the required dc power to the auxiliary power supply system 37. The charging voltage of the charger 38 is greater than the voltage across the rechargeable battery 36, the rechargeable battery 36 does not supply power to the auxiliary power supply system 37 through the diode D3, and the charger 38 does not continue to charge the rechargeable battery 36 in a fully charged state due to the reverse blocking function of the diode D3. The rechargeable battery 36 is in a sleep mode at this time, which may extend its useful life.
(2) When the commercial power voltage is higher, the control method is the same as that of the off-line ups 2, and will not be described herein. Also, the rechargeable battery 36 is in a sleep mode after being fully charged, which may extend its useful life.
(3) When the commercial power voltage is low, the control method is the same as that of the off-line ups 2, and will not be described herein. Also, the rechargeable battery 36 is in a sleep mode after being fully charged, which may extend its useful life.
(4) When the utility voltage is abnormal or power is cut off, the control method is the same as that of the off-line ups 2, and will not be described herein.
As can be seen, when the rechargeable battery 36 is fully charged, the bidirectional converter 35 stops charging the rechargeable battery 36, and the charger 38 starts to operate and supply the required dc power to the auxiliary power supply system 37. The charger 38 does not charge the rechargeable battery 36 at this time due to the reverse blocking function of the diode D3. In addition, the output voltage of the charger 38 is made higher than the voltage across the rechargeable battery 36, and the rechargeable battery 36 does not supply power to the auxiliary power supply system 37 through the diode D3. The rechargeable battery 36 is neither charged nor discharged, avoiding being left in a float state at all times.
When it is necessary to charge the rechargeable battery 36, the bidirectional converter 35 operates to rapidly charge the rechargeable battery 36. When the rechargeable battery 36 is fully charged and the bidirectional converter 35 stops operating, the rechargeable battery 36 is automatically in the sleep mode, which greatly prolongs the life of the rechargeable battery 36.
In other control methods of the present invention, in the normal mode or the automatic voltage regulation mode, the charger 38 is controlled to operate at all times when the rechargeable battery 36 is not fully charged to provide the required dc power to the auxiliary power supply system 37.
In the above embodiments of the present invention, the bidirectional converter may be implemented by a single circuit module for implementing the above functions, or may be implemented by a combination of circuit modules, for example, a combination of a circuit module capable of inverting a direct current into an alternating current and a circuit module for inverting an alternating current into a direct current to charge a battery, such as an inverter.
The EMC filter is suitable for restraining power grid noise and high harmonic and noise and high frequency harmonic generated by the switching power supply, so that the off-line uninterrupted power supply can be provided with no EMC filter in an application occasion with low power consumption quality requirement. In other embodiments of the invention the EMC filter is connected to the ac input via a safety switch (i.e. the safety switch is connected between the ac input and the EMC filter).
The control method of the invention selects different working modes based on the mains voltage of the alternating current input end. For example, when the mains voltage < a first threshold voltage, the off-line uninterruptible power supply is in battery mode; when the first threshold voltage is less than or equal to the mains voltage and less than the second threshold voltage, the off-line uninterrupted power supply is in an automatic voltage boosting regulation mode; when the second threshold voltage is less than or equal to the mains voltage and less than the third threshold voltage, the off-line uninterrupted power supply is in a normal mode; when the third threshold voltage is less than or equal to the mains voltage and less than the fourth threshold voltage, the off-line uninterrupted power supply is in an automatic voltage reduction regulation mode; and when the fourth threshold voltage is less than or equal to the mains voltage, the off-line uninterrupted power supply is in a battery mode. The control method of the present invention is not intended to limit the specific values of the first, second, third and fourth threshold voltages, but is selected by the user according to the rated voltage of the utility power, the allowable voltage deviation range of the load and the turn ratio of the transformer. For example, the rated voltage value of the commercial power is 220 volts, the voltage range allowed by the load is 200 volts to 240 volts, and the ratio of the number of turns of the terminal T1 and the tap T3 on the primary side of the transformer Tr1 to the number of turns of the terminal T1 and the terminal T2 is 5: 6, the first threshold voltage may be selected to be 167 volts, the second threshold voltage may be selected to be 200 volts, the third threshold voltage may be selected to be 240 volts, and the fourth threshold voltage may be selected to be 288 volts.
Although the present invention has been described by way of preferred embodiments, the present invention is not limited to the embodiments described herein, and various changes and modifications may be made without departing from the scope of the present invention.

Claims (12)

1. An off-line uninterruptible power supply, comprising:
a safety switch connected between the AC input terminal and the AC output terminal;
a transformer having one end of a primary side thereof connected to one terminal of the ac output terminal;
a first switch, a second switch, and an output switch connected in sequence between the safety switch and the other terminal of the ac output terminal, the first switch being operable to connect the safety switch to one of the other end and the tap of the primary side of the transformer, the second switch being operable to connect the output switch to one of the other end and the tap of the primary side of the transformer;
a third switch operable to connect the safety switch to one of the first switch and the other terminal of the alternating current output;
a bidirectional converter controllably converting alternating current of a secondary side of the transformer into direct current to charge a rechargeable battery and converting direct current of the rechargeable battery into alternating current; and
the input end of the charger is connected between the alternating current input end and the safety switch, and the alternating current of the alternating current input end is controllably converted into direct current;
and the input end of the auxiliary power supply system is connected to the output end of the charger.
2. The off-line uninterruptible power supply of claim 1, wherein the third switch comprises:
a common terminal connected to the safety switch;
a first switching terminal connected between the output switch and the other terminal of the alternating current output terminal; and
a second switching terminal connected to the first switch.
3. The off-line uninterruptible power supply of claim 1, wherein an output of the charger is connected to both ends of the rechargeable battery.
4. The off-line uninterruptible power supply of claim 1, further comprising a diode having an anode connected to the positive pole of the rechargeable battery and a cathode connected to the positive terminal of the output of the charger.
5. The off-line uninterruptible power supply of claim 4, wherein an output power of the charger is less than a maximum charging power of the rechargeable battery, and an output voltage of the charger is greater than a voltage across the rechargeable battery.
6. The off-line uninterruptible power supply of any of claims 1 to 5, further comprising:
a mains detection device configured to detect a mains voltage of the ac output;
a battery detection device configured to detect a state of charge of the rechargeable battery; and
a control device configured to control operating states of the charger and the bidirectional converter, and to control switching states of the safety switch, the first switch, the second switch, the third switch, and the output switch, according to the mains voltage and a charging state of the rechargeable battery.
7. The off-line uninterruptible power supply of claim 6, wherein:
when the first threshold voltage is less than or equal to the mains voltage and less than the second threshold voltage, the control device controls the safety switch to be conducted, controls the third switch to be connected to the first switch, controls the first switch to be connected to a tap on the primary side of the transformer, controls the second switch to be connected to the other end of the primary side of the transformer, and controls the output switch to be conducted; when the rechargeable battery is not fully charged, the control device controls the charger to stop working and controls the bidirectional converter to convert the alternating current on the secondary side of the transformer into direct current; when the rechargeable battery is fully charged, the control device controls the bidirectional converter to stop working and controls the charger to convert the alternating current at the alternating current input end into the direct current;
when the second threshold voltage is less than or equal to the mains voltage and less than the third threshold voltage, the control device controls the safety switch to be conducted; when the rechargeable battery is not fully charged, the control device controls the third switch to be connected to the first switch, controls the first switch and the second switch to be connected to the other end of the primary side of the transformer, controls the output switch to be conducted, and controls the bidirectional converter to convert the alternating current on the secondary side of the transformer into direct current; when the rechargeable battery is fully charged, the control device controls the third switch to be connected to the other terminal of the alternating current output end, controls the output switch to be disconnected, controls the bidirectional converter to stop working, and controls the charger to convert alternating current of the alternating current input end into direct current;
when the third threshold voltage is less than or equal to the commercial power voltage and less than the fourth threshold voltage, the control device controls the safety switch to be conducted, controls the third switch to be connected to the first switch, controls the first switch to be connected to the other end of the primary side of the transformer, controls the second switch to be connected to a tap of the primary side of the transformer, and controls the output switch to be conducted; when the rechargeable battery is not fully charged, the control device controls the charger to stop working and controls the bidirectional converter to convert the alternating current on the secondary side of the transformer into direct current; when the rechargeable battery is fully charged, the control device controls the bidirectional converter to stop working and controls the charger to convert the alternating current at the alternating current input end into the direct current;
or when the mains voltage is less than the first threshold voltage or more than or equal to the fourth threshold voltage, the control device controls the safety switch to be switched off, controls the second switch to be connected to the other end of the primary side of the transformer, controls the output switch to be switched on, and controls the bidirectional converter to convert the direct current of the rechargeable battery into the alternating current.
8. A control method for an off-line uninterruptible power supply as claimed in any of claims 1 to 5, comprising the steps of: and detecting the mains voltage of the alternating current output end and the charging state of the rechargeable battery, controlling the working states of the charger and the bidirectional converter according to the mains voltage and the charging state of the rechargeable battery, and controlling the switching states of the safety switch, the first switch, the second switch, the third switch and the output switch.
9. The control method according to claim 8, wherein when a first threshold voltage is less than or equal to the commercial voltage and less than a second threshold voltage, the safety switch is controlled to be turned on, the third switch is controlled to be connected to the first switch, the first switch is controlled to be connected to a tap on a primary side of the transformer, the second switch is controlled to be connected to the other end of the primary side of the transformer, and the output switch is controlled to be turned on;
when the rechargeable battery is not fully charged, the charger is controlled to stop working, and the bidirectional converter is controlled to convert the alternating current on the secondary side of the transformer into direct current; and
and when the rechargeable battery is fully charged, controlling the bidirectional converter to stop working, and controlling the charger to convert the alternating current at the alternating current input end into the direct current.
10. The control method according to claim 8, wherein when a second threshold voltage is less than or equal to the mains voltage < a third threshold voltage, the safety switch is controlled to be turned on;
when the rechargeable battery is not fully charged, the third switch is controlled to be connected to the first switch, the first switch and the second switch are controlled to be connected to the other end of the primary side of the transformer, the output switch is controlled to be conducted, and the bidirectional converter is controlled to convert the alternating current on the secondary side of the transformer into direct current;
when the rechargeable battery is fully charged, the third switch is controlled to be connected to the other terminal of the alternating current output end, the output switch is controlled to be disconnected, the bidirectional converter is controlled to stop working, and the charger is controlled to convert alternating current of the alternating current input end into direct current.
11. The control method according to claim 8, wherein when a third threshold voltage is less than or equal to the commercial voltage < a fourth threshold voltage, the safety switch is controlled to be turned on, the third switch is controlled to be connected to the first switch, the first switch is controlled to be connected to the other end of the primary side of the transformer, the second switch is controlled to be connected to a tap of the primary side of the transformer, and the output switch is controlled to be turned on;
when the rechargeable battery is not fully charged, the charger is controlled to stop working, and the bidirectional converter is controlled to convert the alternating current on the secondary side of the transformer into direct current;
and when the rechargeable battery is fully charged, controlling the bidirectional converter to stop working, and controlling the charger to convert the alternating current at the alternating current input end into the direct current.
12. The control method according to claim 8, wherein when the utility voltage is less than the first threshold voltage or greater than or equal to a fourth threshold voltage, the safety switch is controlled to be turned off, the second switch is controlled to be connected to the other end of the primary side of the transformer, the output switch is controlled to be turned on, and the bidirectional converter is controlled to convert the direct current of the rechargeable battery into the alternating current.
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