Energy storage circuit for uninterruptible power supply and uninterruptible power supply

Abstract

The utility model provides an energy storage circuit for an uninterruptible power supply and the uninterruptible power supply, and the energy storage circuit comprises a first converter unit which is connected between a positive direct current bus and the ground and is used for receiving alternating current from an external power supply, rectifying and boosting the alternating current and then supplying power to the positive direct current bus; the second converter unit is connected between the negative direct-current bus and the ground and is used for receiving alternating current from an external power supply, rectifying and boosting the alternating current and then supplying power to the negative direct-current bus; the first energy storage device is connected between the positive direct current bus and the ground and is used for storing the electric energy from the first converter unit; the second energy storage device is connected between the negative direct current bus and the ground and is used for storing the electric energy from the second converter unit; the inverter is used for receiving the electric energy from the direct-current bus, inverting the electric energy into alternating current and outputting the alternating current to a load; wherein each of the first energy storage device and the second energy storage device comprises a plurality of capacitors which are connected in parallel.

Description

Technical Field

[0001] The utility model relates to the field of uninterruptible power supplies, in particular to an energy storage circuit for uninterruptible power supplies and the uninterruptible power supply. Background Art

[0002] The statements in this section are only intended to provide background information related to the present invention to help understand the present invention. Such background information does not necessarily constitute prior art.

[0003] An uninterruptible power supply (UPS) is an AC power supply with an energy storage device that can use the energy storage device to provide uninterrupted power supply to the load during a power outage. An uninterruptible power supply usually uses a battery as a backup power source and requires an independent battery boost circuit. Especially in a three-phase UPS, a higher bus voltage is required, so more batteries are required in series or a higher-power battery boost circuit, which increases the energy consumption and cost of the uninterruptible power supply. Utility Model Content

[0004] In view of the above problems in the prior art, the utility model provides an energy storage circuit for an uninterruptible power supply, characterized in that it includes:

[0005] A first converter unit is connected between the positive DC bus and the ground, and is used to receive AC power from an external power source, rectify and boost the AC power, and then supply power to the positive DC bus;

[0006] A second converter unit is connected between the negative DC bus and the ground, and is used to receive AC power from an external power source, rectify and boost the AC power, and then supply power to the negative DC bus;

[0007] a first energy storage device connected between the positive DC bus and ground and configured to store electrical energy from the first converter unit;

[0008] a second energy storage device connected between the negative DC bus and ground and configured to store electrical energy from the second converter unit;

[0009] An inverter, used to receive electric energy from the DC bus and invert it into AC power and then output it to the load; and

[0010] Wherein, the first energy storage device and the second energy storage device both include a plurality of capacitors connected in parallel.

[0011] In one embodiment, the capacitor is an electrolytic capacitor having a withstand voltage higher than a peak value of the external power source.

[0012] In one embodiment, the overall capacitance of the first energy storage device and the second energy storage device is:

[0013]

[0014] Where C is the overall capacitance of the first energy storage device and the second energy storage device, U is the voltage between the positive DC bus and the negative DC bus, P is the output power of the uninterruptible power supply, T is the backup time, E eff For the efficiency of uninterruptible power supply.

[0015] In one embodiment, the energy storage circuit further includes a discharge circuit configured to discharge the first energy storage device and the second energy storage device when the uninterruptible power supply is powered off.

[0016] In one embodiment, the discharge circuit comprises a first resistor, a second resistor and a switch device,

[0017] The switch device comprises a power supply terminal connected to an internal power supply of the uninterruptible power supply, and a first switch and a second switch, the switch device being used to disconnect the first switch and the second switch when the internal power supply is at a high level and to connect the first switch and the second switch when the uninterruptible power supply is powered off and the internal power supply is reduced to below a threshold;

[0018] The positive DC bus is connected to the ground via the first resistor and the first switch, and the negative DC bus is connected to the ground via the second resistor and the second switch.

[0019] In one embodiment, the switching device is a relay, a circuit breaker, a mechanical switch or a semiconductor switch.

[0020] In one embodiment, the energy storage circuit further includes a discharge completion indication circuit for indicating that the discharge of the first energy storage device and the second energy storage device is completed.

[0021] In one embodiment, the discharge completion indication circuit includes a third resistor, a voltage stabilizing diode, and a light emitting diode connected in series between the positive DC bus and the negative DC bus.

[0022] In one embodiment, the first converter unit and the second converter unit each include a rectifying unit and a boosting unit, and the boosting unit is a flyback circuit.

[0023] The utility model also provides an uninterruptible power supply, comprising the energy storage circuit for the uninterruptible power supply, wherein the uninterruptible power supply only uses the energy storage circuit to store electric energy.

[0024] The energy storage circuit and uninterruptible power supply of the utility model save batteries and battery wiring, and save costs. The capacitor allows a larger charging current, a faster charging speed, and better protection of the load. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of an energy storage circuit for an uninterruptible power supply according to an embodiment of the utility model is shown.

[0026] Figure 2 A circuit diagram of an energy storage circuit for an uninterruptible power supply according to an embodiment of the utility model is shown.

[0027] Figure 3 A schematic diagram of an automatic discharge circuit according to an embodiment of the utility model is shown.

[0028] Figure 4 A schematic diagram of a discharge completion indication circuit according to an embodiment of the utility model is shown.

[0029] Figure 5 A schematic diagram of an uninterruptible power supply according to an embodiment of the utility model is shown.

[0030] Figure 6 A schematic diagram of an uninterruptible power supply according to another embodiment of the utility model is shown. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model will be further described in detail through specific embodiments in conjunction with the accompanying drawings. It should be noted that the embodiments given in the utility model are only for illustration and do not limit the protection scope of the utility model.

[0032] Figure 1 FIG. 1 is a schematic diagram of an energy storage circuit for an uninterruptible power supply according to an embodiment of the utility model. Figure 1 As shown, the energy storage circuit 100 is connected between the external power supply 101 of the uninterruptible power supply and the load 106. The energy storage circuit 100 includes a converter 102, which is used to receive the AC power from the external power supply 101, rectify and boost it to charge the DC bus; a first energy storage device 103, which is connected between the positive DC bus DC+ and the ground GND, and is used to store the electric energy from the converter 102; a second energy storage device 104, which is connected between the negative DC bus DC- and the ground, and is used to store the electric energy from the converter 102; and an inverter 105, which is used to receive the electric energy from the DC bus and invert it into AC power and then output it to the load 106.

[0033] In one embodiment, the converter 102 includes a first converter unit 102a, which is connected between the positive DC bus DC+ and the ground, and is used to receive AC power from an external power source, rectify and boost it to supply power to the positive DC bus DC+; and a second converter unit 102b, which is connected between the negative DC bus DC- and the ground, and is used to receive AC power from an external power source, rectify and boost it to supply power to the negative DC bus DC-. The first converter unit 102a and the second converter unit 102b can charge the first energy storage device 103 and the second energy storage device 104 independently. In one embodiment, the first converter unit 102a and the second converter unit 102b can be isolated or non-isolated.

[0034] The first energy storage device 103 includes a plurality of capacitors connected in parallel, and the second energy storage device 104 includes a plurality of capacitors connected in parallel. In one embodiment, the capacitor is a capacitor with a relatively high withstand voltage, for example, a withstand voltage higher than a peak value of an external power supply. In one embodiment, the withstand voltage of the capacitor is greater than 450V, for example, the withstand voltage may be 550V.

[0035] In one embodiment, the capacitor is built into the uninterruptible power supply.

[0036] In one embodiment, the capacitor is an electrolytic capacitor. In the energy storage circuit for the uninterruptible power supply, the electrolytic capacitor is used to replace the backup battery, which saves the battery and the battery connection, and saves the cost. The capacitor allows a larger charging current, a faster charging speed, and better protection of the load.

[0037] The number and capacity of the capacitors can be selected and designed according to the length of the backup time and the size of the output power. The overall capacitance of the first energy storage device and the second energy storage device (i.e., the overall capacitance between the positive DC bus and the negative DC bus) is calculated by the following formula (1):

[0038]

[0039] Where C is the overall capacitance of the first energy storage device and the second energy storage device, U is the voltage between the positive DC bus and the negative DC bus, P is the output power of the uninterruptible power supply, T is the backup time, E eff For the efficiency of uninterruptible power supply.

[0040] In one embodiment, without any other external energy storage device, the overall capacitance of the first energy storage device and the second energy storage device enables the uninterruptible power supply to be able to provide full power backup for more than 100ms.

[0041] In one embodiment, for a 15kVA three-phase backup uninterruptible power supply, a backup time of 1 second requires 30 electrolytic capacitors with a capacitance of 1800uF and a withstand voltage of 450V on each of the positive and negative sides.

[0042] In one embodiment, the external power source 101 is AC power.

[0043] Figure 1 The charging and discharging modes of the energy storage circuit for the uninterruptible power supply are as follows. In the charging mode, the electric energy of the external power supply 101 is charged to the first energy storage device 103 and the second energy storage device 104 via the converter 102. In the discharging mode, the electric energy of the first energy storage device 103 and the second energy storage device 104 is used to output to the inverter 105 to supply power to the load 106.

[0044] Figure 2 A circuit diagram of an energy storage circuit for an uninterruptible power supply according to an embodiment of the utility model is shown. Figure 2 It shows the specific circuit of the converter and the inverter. Among them, the converter 202 includes a first converter unit and a second converter unit. The first converter unit includes a first rectifier unit 207a, which is used to receive the AC power from the first external power source 201a, rectify it into DC power and output it; and a first boost unit 208a, which is used to receive the DC power from the first rectifier unit 207a, and output it to the positive DC bus DC+ after boosting it. The second converter unit includes a second rectifier unit 207b, which is used to receive the AC power from the second external power source 201b, rectify it into DC power and output it; and a second boost unit 208b, which is used to receive the DC power from the second rectifier unit 207b, and output it to the negative DC bus DC- after boosting it.

[0045] like Figure 2 As shown, the first boost unit 208a and the second boost unit 208b are both flyback circuits. The first boost unit 208a includes a switch tube Q1, a transformer T1, and a diode D1, wherein the primary side of the transformer T1 is connected to the first rectifier unit 207a, the secondary side is connected between the positive DC bus DC+ and the ground, the switch tube Q1 is connected to the primary side of the transformer T1, and the diode D1 is connected between the secondary side of the transformer T1 and the positive DC bus DC+. The second boost unit 208b includes a switch tube Q2, a transformer T2, and a diode D2, wherein the primary side of the transformer T2 is connected to the second rectifier unit 207b, the secondary side is connected between the negative DC bus DC- and the ground, the switch tube Q2 is connected to the primary side of the transformer T2, and the diode D2 is connected between the secondary side of the transformer T2 and the negative DC bus DC-.

[0046] The inverter 205 includes a switch tube Q3 and a switch tube Q4 connected in series between the DC bus bars, a diode D3 connected in anti-parallel to the switch tube Q3, a diode D4 connected in anti-parallel to the switch tube Q4, one end of an inductor L1 connected between the switch tube Q3 and the switch tube Q4, and the other end connected to a capacitor C1, and the other end of the capacitor C1 is connected to the ground. The inverter 205 is connected to the load 206 through a switch S1.

[0047] Although the first boost unit 208a and the second boost unit 208b are shown in the above embodiment as flyback circuits, the present invention is not limited thereto, and the first boost unit 208a and the second boost unit 208b can be any boost circuit known in the art. Similarly, the inverter 205 can also be any inverter circuit known in the art. The first rectifier unit 207a and the second rectifier unit 207b can be any rectifier circuit known in the art.

[0048] Although two external power sources are shown in the above embodiment, those skilled in the art should understand that, as required, the first rectifying unit 207a and the second rectifying unit 207b may also be connected to the same external power source.

[0049] When the uninterruptible power supply fails and needs to be repaired, it is also necessary to discharge the circuit ( Figure 1 The first energy storage device and the second energy storage device are discharged to ensure the safety of the maintenance personnel. Any discharge circuit known in the art can be used to discharge the first energy storage device and the second energy storage device.

[0050] Figure 3 FIG. 1 is a schematic diagram of an automatic discharge circuit according to an embodiment of the present utility model. Figure 1 and Figure 3 The automatic discharge circuit 300 includes a first resistor 301, a second resistor 302 and a switch device 303. The switch device 303 includes a power supply terminal connected to an internal power supply VCC (e.g., 24V) of an uninterruptible power supply, and a first switch 3031 and a second switch 3032. The switch device 303 is used to disconnect the first switch 3031 and the second switch 3032 when the internal power supply VCC is at a high level, and to connect the first switch 3031 and the second switch 3032 when the uninterruptible power supply is powered off and the internal power supply VCC is reduced to below a threshold value (e.g., a low level). The positive DC bus DC+ is connected to the ground via the first resistor 301 and the first switch 3031, and the negative DC bus DC- is connected to the ground via the second resistor 302 and the second switch 3032.

[0051] In one embodiment, the internal power supply VCC is connected to a control board inside the uninterruptible power supply.

[0052] When the uninterruptible power supply is working normally, the internal power supply VCC is at a high level (e.g., 24V), at which time the switch device 303 is disconnected, that is, the first switch 3031 and the second switch 3032 are disconnected, and the first energy storage device 103 and the second energy storage device 104 are not discharged. When the uninterruptible power supply is powered off, the internal power supply VCC is reduced to below the threshold value (e.g., 0V), at which time the switch device 303 is turned on, that is, the first switch 3031 and the second switch 3032 are turned on, and the first energy storage device 103 and the second energy storage device 104 are discharged.

[0053] In one embodiment, the switch device 303 is a relay, a circuit breaker, a mechanical switch, a semiconductor switch, etc. In one embodiment, the switch device 303 is a normally closed relay.

[0054] In one embodiment, the values ​​of the first resistor 301 and the second resistor 302 can be calculated by the required discharge time.

[0055] In one embodiment, the internal power supply VCC is located on a control board of the uninterruptible power supply. When the control board of the uninterruptible power supply is powered off, the internal power supply VCC is reduced to 0V.

[0056] In this embodiment, the uninterruptible power supply is disconnected from the outside (including external power supply and load). In one embodiment, the uninterruptible power supply is disconnected when the uninterruptible power supply fails and when the uninterruptible power supply is normally maintained.

[0057] In order to ensure the safety of maintenance personnel, a discharge completion indication circuit is also required to indicate that the first energy storage device and the second energy storage device have completed discharge. Any indication circuit known in the art can be used to indicate that the first energy storage device and the second energy storage device have completed discharge.

[0058] Figure 4 FIG. 1 is a schematic diagram of a discharge completion indication circuit according to an embodiment of the present utility model. Figure 1 and Figure 4 , the discharge completion indication circuit 400 includes a resistor 401, a voltage stabilizing diode 402 and a light emitting diode 403 connected in series between the positive DC bus DC+ and the negative DC bus DC-. The cathode of the voltage stabilizing diode 402 is connected to the resistor 401, the anode is connected to the anode of the light emitting diode 403, and the cathode of the light emitting diode 403 is connected to the negative DC bus DC-. The voltage stabilizing diode 402 is used for voltage stabilization and current limiting to avoid damage to the light emitting diode 403. In one embodiment, the resistor 401 is 50 kΩ. When the positive DC bus DC+ and the negative DC bus DC- are discharged, the light emitting diode 403 goes out, indicating that the discharge is completed.

[0059] Figure 5FIG. 1 is a schematic diagram of an uninterruptible power supply according to an embodiment of the present utility model. Figure 5 As shown, the uninterruptible power supply 500 includes Figure 1 The energy storage circuit shown. The uninterruptible power supply 500 includes a converter 502, whose input end is connected to an external power source 501 via an internal input switch 508, and whose output end is connected to a DC bus DC; an energy storage device 503 (including a first energy storage device and a second energy storage device), connected between the DC bus DC and the ground; an inverter 505, whose input end is connected to the DC bus DC, and whose output end is connected to a first end of an inverter switch 509; a bypass switch 507 connected between the input end of the converter 502 and the second end of the inverter switch 509; and a first maintenance switch 510 for selectively connecting the external power source 501 and one of the second ends of the inverter switch 509 to a load 506. The energy storage device 503 includes a plurality of capacitors connected in parallel.

[0060] The following describes the working mode of the uninterruptible power supply 500 by taking a backup power supply as an example.

[0061] When the external power source 501 is operating normally, the internal input switch 508 is turned on, the bypass switch 507 is turned on, the inverter switch 509 is turned off, and the first maintenance switch 510 is connected to the second end of the inverter switch 509. The electric energy is directly output from the power source 501 to the load 506 via the bypass. At the same time, the energy storage device 503 is in the charging mode, and the electric energy is charged from the external power source 501 via the converter.

[0062] When the external power supply 501 is abnormal, the internal input switch 508 is turned off, the bypass switch 507 is turned off, the inverter switch 509 is turned on, and the first maintenance switch 510 is connected to the second end of the inverter switch 509. The energy storage device 503 is in a discharge mode, and electric energy is output from the energy storage device 503 to the load 506 via the inverter 505.

[0063] When the UPS needs maintenance, the first maintenance switch 510 is connected to the external power supply 501, and the uninterruptible power supply does not work. The internal input switch 508 is disconnected, the bypass switch 507 is disconnected, the inverter switch 509 is disconnected, and the energy storage device 503 starts to discharge.

[0064] In this embodiment, when maintenance is required, the first maintenance switch 510 needs to be switched, and the action of the first maintenance switch 510 may be delayed, resulting in a longer switching time.

[0065] Figure 6 FIG. 1 is a schematic diagram of an uninterruptible power supply according to another embodiment of the present utility model. Figure 5The same parts are not repeated here, and the difference is that the uninterruptible power supply 600 also includes an optional second maintenance circuit. The uninterruptible power supply 500 also includes an external input switch 511, which is connected between the internal input switch 508 and the external power supply 501; an external output switch 513, which is connected between the first maintenance switch 510 and the load 506; and a second maintenance switch 512, which is connected between the external power supply 501 and the load 506.

[0066] In this embodiment, when maintenance is required, the second maintenance switch 512 can be directly turned on, while the external input switch 511 and the external output switch 513 are turned off, so that the maintenance mode can be quickly entered and the uninterruptible power supply can be quickly disconnected to avoid damage to the uninterruptible power supply.

[0067] In one embodiment, the switch involved in the present invention may be a relay, a circuit breaker, a mechanical switch, a semiconductor switch, etc.

[0068] The uninterruptible power supply of the present invention includes the aforementioned energy storage circuit for uninterruptible power supply, and only uses the energy storage circuit to store electric energy, and does not include other energy storage devices such as batteries.

[0069] In the energy storage circuit and uninterruptible power supply of the utility model, the energy storage capacitor is built into the uninterruptible power supply, and the capacitor has an external discharge interface for easy maintenance. The energy storage circuit and uninterruptible power supply of the utility model also save batteries and battery connections, saving costs. The capacitor allows a larger charging current and a faster charging speed, which can better protect the load.

[0070] The energy storage circuit and the uninterruptible power supply of the utility model can be applied to a three-phase uninterruptible power supply with a relatively high bus voltage, for example, a three-phase backup uninterruptible power supply.

[0071] Although the present invention has been described through preferred embodiments, the present invention is not limited to the embodiments described herein, but also includes various changes and modifications without departing from the scope of the present invention.

Claims

1. An energy storage circuit for an uninterruptible power supply, characterized in that: include: A first converter unit is connected between the positive DC bus and the ground, and is used to receive AC power from an external power source, rectify and boost the AC power, and then supply power to the positive DC bus; A second converter unit is connected between the negative DC bus and the ground, and is used to receive AC power from an external power source, rectify and boost the AC power, and then supply power to the negative DC bus; a first energy storage device connected between the positive DC bus and ground and configured to store electrical energy from the first converter unit; a second energy storage device connected between the negative DC bus and ground and configured to store electrical energy from the second converter unit; as well as The inverter is used to receive the electric energy from the DC bus and invert it into AC power and then output it to the load; Wherein, the first energy storage device and the second energy storage device both include a plurality of capacitors connected in parallel.

2. The energy storage circuit for an uninterruptible power supply according to claim 1, characterized in that: The capacitor is an electrolytic capacitor having a withstand voltage higher than a peak value of the external power source.

3. The energy storage circuit for an uninterruptible power supply according to claim 1 or 2, characterized in that: The overall capacity of the first energy storage device and the second energy storage device is: Where C is the overall capacitance of the first energy storage device and the second energy storage device, U is the voltage between the positive DC bus and the negative DC bus, P is the output power of the uninterruptible power supply, T is the backup time, E eff For the efficiency of uninterruptible power supply.

4. The energy storage circuit for an uninterruptible power supply according to claim 1, characterized in that: The energy storage circuit also includes a discharge circuit configured to discharge the first energy storage device and the second energy storage device when the uninterruptible power supply is powered off.

5. The energy storage circuit for an uninterruptible power supply according to claim 4, characterized in that: The discharge circuit includes a first resistor, a second resistor and a switch device, The switch device comprises a power supply terminal connected to an internal power supply of the uninterruptible power supply, and a first switch and a second switch, the switch device is used to disconnect the first switch and the second switch when the internal power supply is at a high level and to connect the first switch and the second switch when the uninterruptible power supply is powered off and the internal power supply is reduced to below a threshold; The positive DC bus is connected to the ground via the first resistor and the first switch, and the negative DC bus is connected to the ground via the second resistor and the second switch.

6. The energy storage circuit for an uninterruptible power supply according to claim 5, characterized in that: The switch device is a relay, a circuit breaker, a mechanical switch or a semiconductor switch.

7. The energy storage circuit for an uninterruptible power supply according to claim 1, characterized in that: The energy storage circuit further includes a discharge completion indication circuit for indicating that the discharge of the first energy storage device and the second energy storage device is completed.

8. The energy storage circuit for an uninterruptible power supply according to claim 7, characterized in that: The discharge completion indication circuit includes a third resistor, a voltage stabilizing diode and a light emitting diode connected in series between the positive DC bus and the negative DC bus.

9. The energy storage circuit for an uninterruptible power supply according to claim 1, characterized in that: The first converter unit and the second converter unit each include a rectifying unit and a boosting unit, and the boosting unit is a flyback circuit.

10. An uninterruptible power supply, characterized in that: An energy storage circuit for an uninterruptible power supply comprising any one of claims 1 to 9, wherein the uninterruptible power supply only uses the energy storage circuit to store electrical energy.

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