Short-circuit protection method and device for uninterruptible power supply

Abstract

The invention discloses a short-circuit protection method and device for an uninterruptible power supply. The method comprises the following steps: when the uninterruptible power supply is turned on, an output switch connects an inversion branch to a load end, and after a preset delay time, an input switch is closed; controlling the inversion branch to work, and obtaining the output voltage and the output current of the uninterruptible power supply; according to the output voltage, the output current, a preset voltage threshold value and a preset current threshold value, whether the load end has a short-circuit fault or not is judged; and under the condition that the load end has the short-circuit fault, the inverter branch is controlled to be closed. When the uninterruptible power supply is started up, the output switch is preferentially switched to the output end of the inversion module, the inversion branch is communicated to the load end, and the input switch is closed after the preset delay time, so that the short circuit risk at the starting-up moment can be avoided, and the problem that the short circuit at the starting-up moment cannot be protected in the prior art is solved. And therefore, the safety of the operation of the uninterruptible power supply is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit protection equipment, and in particular to a short-circuit protection method and device for an uninterruptible power supply. Background Art

[0002] Since the short-circuit current can usually reach several times or even dozens of times the normal working current, it will inevitably generate excessive heat, causing insulation damage, equipment burning, and even electrical fires; the strong short-circuit current will also generate huge electric force, which may cause mechanical damage to the equipment; the voltage at the short-circuit point drops to zero, which significantly reduces the surrounding voltage and causes the surrounding equipment to not operate normally. Therefore, the short-circuit fault must be quickly removed for protection to prevent the accident from further expanding.

[0003] Currently, most short-circuit protection is limited to output short-circuit under normal working conditions, ignoring the short-circuit risk at the moment of power-on, resulting in the failure of the protection mechanism. Summary of the invention

[0004] The present invention provides a short-circuit protection method and device for an uninterruptible power supply, so as to solve the problem that the prior art cannot protect against a short circuit at the moment of startup, resulting in failure of the protection mechanism.

[0005] According to one aspect of the present invention, a short-circuit protection method for an uninterruptible power supply is provided, wherein the uninterruptible power supply comprises an inverter branch and a bypass branch, an input switch and an output switch, wherein an input end of the inverter branch is connected in parallel with an input end of the bypass branch and is connected to the input switch, and the output switch selectively connects the inverter branch or the bypass branch to a load end, and the short-circuit protection method comprises:

[0006] When the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, closes the input switch;

[0007] Controlling the inverter branch to work, and obtaining the output voltage and output current of the uninterruptible power supply;

[0008] Determining whether there is a short circuit fault at the load end according to the output voltage, the output current, a preset voltage threshold and a preset current threshold;

[0009] When a short circuit fault occurs at the load end, the inverter branch is controlled to be closed.

[0010] Optionally, judging whether there is a short circuit fault at the load end according to the output voltage, the output current, a preset voltage threshold and a preset current threshold includes:

[0011] Determining whether the output voltage is less than the preset voltage threshold, and whether the output current exceeds the preset current threshold;

[0012] If the output voltage is less than the preset voltage threshold and the output current exceeds the preset current threshold, it is determined that a short circuit fault exists at the load end.

[0013] Optionally, after controlling the inverter branch to be closed, the method further includes:

[0014] Restarting the inverter module at a preset time interval and recording the number of restarts, and determining whether the load end still has a short circuit fault after restarting;

[0015] When the short circuit fault still exists at the load end, the inverter branch is controlled to be closed and the next restart is started.

[0016] Optionally, the preset time interval is positively correlated with the number of restart times, and the greater the number of restart times, the longer the preset time interval is.

[0017] Optionally, when the restart times reach a preset restart times, if a short circuit fault still exists at the load end, the inverter branch is controlled to be closed, and the next restart is not entered.

[0018] Optionally, when the number of restarts reaches a preset number of restarts, when the short circuit fault is eliminated at the load end, the duration of the normal state is recorded, and when the duration of the normal state is greater than a preset waiting time, the number of restarts is cleared.

[0019] Optionally, when the restart times do not reach the preset restart times and the short circuit fault at the load end is eliminated, the restart times are reset to zero.

[0020] Optionally, the determining whether there is a short circuit fault at the load end further includes:

[0021] When there is no short-circuit fault at the load end, the inverter branch is maintained in operation.

[0022] Optionally, after maintaining the inverter branch in operation for a certain period of time, the output switch disconnects the inverter branch from the load end and connects the bypass branch to the load end.

[0023] According to another aspect of the present invention, a short-circuit protection device for an uninterruptible power supply is provided, which is used to perform the short-circuit protection method described in any embodiment of the present invention, and the short-circuit protection device comprises:

[0024] A closing module, wherein when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, closes the input switch;

[0025] An acquisition module, the acquisition module is used to control the operation of the inverter branch and acquire the output voltage and output current of the uninterruptible power supply;

[0026] A judgment module, the judgment module is used to judge whether there is a short circuit fault at the load end according to the output voltage, the output current, a preset voltage threshold and a preset current threshold;

[0027] A control module is used to control the inverter branch to close when a short circuit fault occurs at the load end.

[0028] The technical solution provided by the embodiment of the present invention is that when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, the input switch is closed; the inverter branch is controlled to work to obtain the output voltage and output current of the uninterruptible power supply; according to the output voltage, output current, preset voltage threshold and preset current threshold, it is judged whether there is a short circuit fault at the load end; in the case of a short circuit fault at the load end, the inverter branch is controlled to be closed. The technical solution provided by the embodiment of the present invention is that when the uninterruptible power supply is turned on, the output switch is preferentially switched to the output end of the inverter module, the inverter branch is connected to the load end, and after a preset delay time, the input switch is closed, which can avoid the risk of short circuit at the moment of power on, solves the problem that the prior art cannot protect against short circuit at the moment of power on, resulting in failure of the protection mechanism, and effectively improves the safety of the operation of the uninterruptible power supply.

[0029] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A flow chart of a short-circuit protection method for an uninterruptible power supply provided by an embodiment of the present invention;

[0032] Figure 2 An internal schematic diagram of an uninterruptible power supply provided by an embodiment of the present invention;

[0033] Figure 3 A flow chart of another short-circuit protection method for an uninterruptible power supply provided by an embodiment of the present invention;

[0034] Figure 4 A flow chart of another short-circuit protection method for an uninterruptible power supply provided by an embodiment of the present invention;

[0035] Figure 5 A flow chart of another short-circuit protection method for an uninterruptible power supply provided by an embodiment of the present invention;

[0036] Figure 6 A schematic diagram of the structure of a short-circuit protection device for an uninterruptible power supply provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0039] Figure 1 A flow chart of a short-circuit protection method for an uninterruptible power supply provided in an embodiment of the present invention. This embodiment can be applied to a short circuit that occurs at the moment when the device is turned on, to avoid bypassing during the startup process. The short-circuit protection method can be executed by a short-circuit protection device of the uninterruptible power supply. Figure 2 For the internal schematic diagram of the uninterruptible power supply provided by the embodiment of the present invention, see Figure 2The uninterruptible power supply includes an inverter branch and a bypass branch, an input switch and an output switch, the input end of the inverter branch is connected in parallel with the input end of the bypass branch and connected to the input switch, and the output switch selectively connects the inverter branch or the bypass branch to the load end, wherein the inverter branch includes a rectifier module, a bus module and an inverter module, the rectifier module, the bus module and the inverter module are connected in sequence, the bypass branch includes a bypass circuit module, and the output switch selectively connects the inverter module output end N0 or the bypass circuit module output end NC to the load end. The uninterruptible power supply also includes a battery pack connected to the bus module.

[0040] The working modes of the uninterruptible power supply are divided into mains mode and battery mode. In mains mode, the mains is used as input, and the AC input source AC passes through the rectifier module, bus module, and inverter module to achieve a stable and pure 220Vac AC output to power the load equipment; in battery mode, the battery pack provides input, and through the inverter module, a stable and pure 220Vac AC output is achieved to power the load equipment.

[0041] See also Figure 1 , the short circuit protection method comprises:

[0042] S110, when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, closes the input switch.

[0043] The preset delay time can be preset according to the short circuit protection requirement, and the preset delay time is generally set to 20ms. The input switch can be a single-pole single-position switch, and the output switch can be a single-pole double-position switch.

[0044] Specifically, since the output switch is at the output end NC of the bypass circuit module by default, assuming that the load end is short-circuited and the AC input source AC is connected, the customer sets the default machine to have an initial bypass output. When the input switch is closed, the city power will be directly output to the load end through the bypass circuit module. At this time, there is a short circuit at the load end. If the input switch cannot be disconnected in time, the bypass circuit module line of the uninterruptible power supply will be partially short-circuited, causing a mechanical failure of the uninterruptible power supply. When the AC input source AC is connected and the uninterruptible power supply is turned on, the output switch Output Relay is preferentially switched to the output end NO of the inverter module, and the inverter branch is connected to the load end. After a preset delay time, the input switch is closed. That is to say, the input switch Input Relay is delayed by 20ms compared to the output switch Output Relay before closing, so as to avoid the short circuit of the user equipment when the bypass circuit module is directly output during the startup process.

[0045] S120, controlling the inverter branch to operate, and obtaining the output voltage and output current of the uninterruptible power supply.

[0046] Specifically, after closing the input switch, the uninterruptible power supply will send a pulse width modulation wave PWM (Pulse Width Modulation, PWM) to the inverter to control the operation of the insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT) of the inverter, so that the inverter starts to output voltage and current. At this time, the output voltage and output current of the uninterruptible power supply are respectively collected through the voltage sensor and current sensor inside the uninterruptible power supply.

[0047] S130. Determine whether there is a short circuit fault at the load end according to the output voltage, the output current, the preset voltage threshold, and the preset current threshold.

[0048] The preset voltage threshold is 10% of the rated voltage of the uninterruptible power supply; and the preset current threshold is 70% of the rated current of the uninterruptible power supply.

[0049] Specifically, the output voltage is compared with a preset voltage threshold, and the output current is compared with a preset current threshold. When the output voltage is less than 10% of the rated voltage of the uninterruptible power supply and the output current exceeds 70% of the rated current of the uninterruptible power supply, it is determined that a short circuit fault exists at the load end.

[0050] S140. When a short circuit fault occurs at the load end, the inverter branch is controlled to be closed.

[0051] Specifically, in the event of a short-circuit fault at the load end, the uninterruptible power supply will shut down the inverter waveform output to control the IGBT inside the inverter module to stop working, thereby playing an effective protective role. Only after the inverter detects that the output device is normal will the machine be allowed to use bypass power supply. If there is no short-circuit fault in the output, the bypass power supply can be switched to when overheating or overload occurs. Even if the customer sets the bypass enable initialization, the machine will resume bypass without output after shutting down and restarting.

[0052] The technical solution provided by the embodiment of the present invention is that when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, the input switch is closed; the inverter branch is controlled to work to obtain the output voltage and output current of the uninterruptible power supply; according to the output voltage, output current, preset voltage threshold and preset current threshold, it is judged whether there is a short circuit fault at the load end; in the case of a short circuit fault at the load end, the inverter branch is controlled to be closed. The technical solution provided by the embodiment of the present invention is that when the uninterruptible power supply is turned on, the output switch is preferentially switched to the output end of the inverter module, the inverter branch is connected to the load end, and after a preset delay time, the input switch is closed, which can avoid the risk of short circuit at the moment of power on, solves the problem that the prior art cannot protect against short circuit at the moment of power on, resulting in failure of the protection mechanism, and effectively improves the safety of the operation of the uninterruptible power supply.

[0053] Figure 3 This is a flow chart of another short-circuit protection method for an uninterruptible power supply provided by an embodiment of the present invention. The embodiment of the present invention further refines the above embodiment on the basis of the above embodiment. Figure 3 , the short circuit protection method comprises:

[0054] S310, when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, closes the input switch.

[0055] S320, control the inverter branch to work, and obtain the output voltage and output current of the uninterruptible power supply.

[0056] S330, determine whether the output voltage is less than a preset voltage threshold, and whether the output current exceeds a preset current threshold; if so, execute S340.

[0057] Specifically, the output voltage is compared with a preset voltage threshold, and the output current is compared with a preset current threshold. When the output voltage is less than 10% of the rated voltage of the uninterruptible power supply and the output current exceeds 70% of the rated current of the uninterruptible power supply, it is determined that a short circuit fault exists at the load end.

[0058] S340: Determine whether a short circuit fault exists at the load end.

[0059] S350: When a short circuit fault occurs at the load end, the inverter branch is controlled to be closed.

[0060] Figure 4 This is a flow chart of another uninterruptible power supply short circuit protection method provided by an embodiment of the present invention. The embodiment of the present invention further refines the above embodiments based on the above embodiments. Figure 4 , the short circuit protection method comprises:

[0061] S410, when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, closes the input switch.

[0062] S420, controlling the inverter branch to operate, and obtaining the output voltage and output current of the uninterruptible power supply.

[0063] S430, judging whether there is a short circuit fault at the load end according to the output voltage, the output current, the preset voltage threshold and the preset current threshold.

[0064] S440: When a short circuit fault occurs at the load end, the inverter branch is controlled to be closed.

[0065] S450: Restart the inverter module at every preset time interval and record the number of restarts.

[0066] The preset time interval is positively correlated with the number of restarts. The more restarts there are, the longer the preset time interval is.

[0067] S460: After restarting, determine whether the short circuit fault still exists at the load end; if so, return to execute S440.

[0068] S470: Determine whether the restart times reaches the preset restart times.

[0069] S480: When the restart times reach the preset restart times, if the short circuit fault still exists at the load end, the inverter branch is controlled to be closed, and the next restart is not entered.

[0070] Among them, the preset number of restarts can be pre-set according to engineering requirements. Exemplarily, the embodiment of the present invention takes 3 times as an example. If there is still a short circuit fault at the load end, the inverter module is automatically restarted every preset time interval N minutes and the number of restarts is recorded. When the number of restarts reaches 3 times, the 4th restart will not be performed.

[0071] S490: When the restart times reach the preset restart times, and the short circuit fault is eliminated at the load end, the duration of the normal state is recorded; when the duration of the normal state is greater than the preset waiting time, the restart times are cleared.

[0072] Among them, the preset waiting time can be pre-set according to engineering requirements. For example, the embodiment of the present invention takes 10min as an example. When the number of restarts reaches 3 times, there is no short circuit fault at this time, and the duration of the normal state is recorded. When the duration of the normal state is greater than 10min, the number of restarts is cleared.

[0073] S491. When the restart times do not reach the preset restart times and the short circuit fault at the load end is eliminated, the restart times are reset to zero.

[0074] The technical solution provided by the embodiment of the present invention is to automatically restart the inverter module output at every preset time interval N minutes after the output triggers a short-circuit fault to detect whether there is a short-circuit fault at the load end. If there is no short-circuit fault at the load end, the inverter module is controlled to start the inverter waveform output; if there is a short-circuit fault at the load end, the next short-circuit fault detection is automatically entered. Assuming that the output is set to short-circuit 3 times, after the output is short-circuited 3 times, the fourth time will not be restarted; if the machine output detects that there is no short-circuit fault for a cumulative 10 minutes, the restart times will be cleared to 0 and the short-circuit detection logic will be exited. The technical solution provided by the embodiment of the present invention can be applied to the situation where the uninterruptible power supply and the load equipment are installed at a remote distance. If the output short-circuit fault occurs, only the short-circuit equipment needs to be removed, and the uninterruptible power supply can be maintained without manual operation, which effectively improves the efficiency of operation and maintenance work, enables the system to quickly restore power supply, and improves power supply efficiency.

[0075] Figure 5 This is a flow chart of another uninterruptible power supply short circuit protection method provided by an embodiment of the present invention. The embodiment of the present invention further refines the above embodiments based on the above embodiments. Figure 5 , the short circuit protection method comprises:

[0076] S510, when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, closes the input switch.

[0077] S520, control the inverter branch to work, and obtain the output voltage and output current of the uninterruptible power supply.

[0078] S530: Determine whether there is a short circuit fault at the load end according to the output voltage, the output current, the preset voltage threshold and the preset current threshold.

[0079] S540: When there is no short-circuit fault at the load end, the inverter branch is maintained in operation.

[0080] S550: When a short circuit fault occurs at the load end, the inverter branch is controlled to be closed.

[0081] Optionally, after the inverter branch maintains operation for a certain period of time, the output switch disconnects the inverter branch from the load end and connects the bypass branch to the load end.

[0082] Specifically, when there is no short-circuit fault at the load end, the inverter branch is maintained in operation. After working for a certain period of time, the output switch disconnects the inverter branch from the load end, and at the same time connects the bypass branch to the load end, thereby realizing the transition from inverter branch power supply to bypass branch power supply, which has the beneficial effect of being able to arbitrarily select one of the two branches to supply power to the load end, thereby improving the flexibility and safety of power supply.

[0083] Figure 6 A schematic structural diagram of a short-circuit protection device for an uninterruptible power supply provided by an embodiment of the present invention, the short-circuit protection device comprises: a closing module 610, an acquisition module 620, a judgment module 630 and a control module 640.

[0084] The closing module 610 is used when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, the input switch is closed;

[0085] The acquisition module 620 is used to control the operation of the inverter branch and obtain the output voltage and output current of the uninterruptible power supply.

[0086] The determination module 630 is used to determine whether there is a short circuit fault at the load end according to the output voltage, the output current, the preset voltage threshold and the preset current threshold.

[0087] The control module 640 is used to control the inverter branch to close when a short circuit fault occurs at the load end.

[0088] The short-circuit protection device for an uninterruptible power supply provided in the embodiment of the present invention can execute the short-circuit protection method for an uninterruptible power supply provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0089] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0090] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A short-circuit protection method for an uninterruptible power supply, the uninterruptible power supply comprising an inverter branch and a bypass branch, an input switch and an output switch, the input end of the inverter branch is connected in parallel with the input end of the bypass branch and connected to the input switch, the output switch selectively connects the inverter branch or the bypass branch to the load end, characterized in that: The short circuit protection method comprises: When the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, closes the input switch; Controlling the inverter branch to work, and obtaining the output voltage and output current of the uninterruptible power supply; Determining whether there is a short circuit fault at the load end according to the output voltage, the output current, a preset voltage threshold and a preset current threshold; When a short circuit fault occurs at the load end, the inverter branch is controlled to be closed.

2. The short circuit protection method according to claim 1, characterized in that: The determining whether there is a short circuit fault at the load end according to the output voltage, the output current, the preset voltage threshold and the preset current threshold comprises: Determining whether the output voltage is less than the preset voltage threshold, and whether the output current exceeds the preset current threshold; If the output voltage is less than the preset voltage threshold and the output current exceeds the preset current threshold, it is determined that a short circuit fault exists at the load end.

3. The short circuit protection method according to claim 1, characterized in that: After controlling the inverter branch to be closed, the method further includes: Restarting the inverter module at a preset time interval and recording the number of restarts, and determining whether the load end still has a short circuit fault after restarting; When the short circuit fault still exists at the load end, the inverter branch is controlled to be closed and the next restart is started.

4. The short circuit protection method according to claim 3, characterized in that: The preset time interval is positively correlated with the number of restart times. The greater the number of restart times, the longer the preset time interval is.

5. The short circuit protection method according to claim 3, characterized in that: When the restart times reach the preset restart times, if the short circuit fault still exists at the load end, the inverter branch is controlled to be closed, and the next restart is not entered.

6. The short circuit protection method according to claim 3, characterized in that: When the restart times reach the preset restart times, in the case that the short circuit fault is eliminated at the load end, the duration of the normal state is recorded, and when the duration of the normal state is greater than the preset waiting time, the restart times are reset to zero.

7. The short circuit protection method according to claim 3, characterized in that: When the restart times do not reach the preset restart times and the short circuit fault at the load end is eliminated, the restart times are reset to zero.

8. The short circuit protection method according to claim 1, characterized in that: The determining whether there is a short circuit fault at the load end also includes: When there is no short-circuit fault at the load end, the inverter branch is maintained in operation.

9. The short circuit protection method according to claim 8, characterized in that: After maintaining the inverter branch in operation for a certain period of time, the output switch disconnects the inverter branch from the load end and connects the bypass branch to the load end.

10. A short-circuit protection device for an uninterruptible power supply, characterized in that: Used to perform the short-circuit protection method according to any one of claims 1 to 9, the short-circuit protection device comprising: A closing module, wherein when the uninterruptible power supply is turned on, the output switch connects the inverter branch to the load end, and after a preset delay time, closes the input switch; An acquisition module, the acquisition module is used to control the operation of the inverter branch and acquire the output voltage and output current of the uninterruptible power supply; A judgment module, the judgment module is used to judge whether there is a short circuit fault at the load end according to the output voltage, the output current, a preset voltage threshold and a preset current threshold; A control module is used to control the inverter branch to close when a short circuit fault occurs at the load end.

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