A method and system for preventing large current arcing caused by relay closing

Abstract

The present invention discloses a method and a system for preventing large current arcing caused by the closing of a relay. The method includes the following steps: S1. When the inverter is in the off-grid mode, detect whether there is mains power access. If there is, continue to execute step S2; S2. Capture the mains zero-crossing point and the inverter zero-crossing point, and calculate the time between the two zero-crossing points as the phase difference; S3. Perform offset phase locking, including: before the relay closes, determine the phase difference according to the relay hardware delay time; S4. Determine whether the phase difference is the relay hardware delay time. If it is, continue to execute. Otherwise, return to step S3; S5. Turn off the inverter voltage output at the inverter zero-crossing point, and at the same time close the mains relay; S6. When the zero-crossing point just passes at the phase difference time, the mains relay completes the closing, and the mains power access is completed. The present invention can ensure that the voltage is zero and there is no voltage difference when the relay closes, achieving a smooth switching without impact current arcing, improving the service life of the relay, and at the same time reducing the equipment cost.

Description

Technical Field

[0001] The present invention relates to the technical field of power supplies, and more specifically, to a method and system for preventing large current arcing caused by relay closing. Background Art

[0002] In current inverter technology, when accessing the commercial power in the off-grid mode, it is necessary to lock the phase of the commercial power. When the frequencies are the same and the phases are the same, since the inverter output voltage is turned off at a non-zero crossing point, while the relay closes at the zero crossing point of the commercial power, a voltage difference is generated, resulting in an instantaneous impact current arcing phenomenon in the relay, thereby damaging the service life of the relay. Prolonged operation may increase the risk of abnormal damage to the equipment.

[0003] In addition, there is another existing technology. When accessing the commercial power in the off-grid mode, the voltage source is switched to the current source in advance. The current source control mode can enable the inverter to operate in parallel with the grid voltage / frequency. However, since the grid-connected operation uses active-reactive current control and the off-grid operation uses voltage-frequency or droop control, it is very difficult to switch between voltage control and current control, and there is a risk of switching failure due to voltage and current distortion impacts, thereby reducing the life of the relay and the equipment.

[0004] Therefore, it is necessary to improve the process of relay closing, and design a method for preventing large current arcing caused by relay closing from damaging the inverter to improve its reliability and safety. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for preventing large current arcing caused by relay closing to overcome the defects of the prior art.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for preventing large current arcing caused by relay closing includes the following steps:

[0008] S1. When the inverter is in the off-grid mode, detect whether there is commercial power access. If so, continue to execute step S2;

[0009] S2. Capture the zero crossing point of the commercial power and the zero crossing point of the inversion, and calculate the time of the two zero crossing points as the phase difference;

[0010] S3. Perform misaligned phase locking, including: before the relay closes, determine the phase difference according to the hardware delay time of the relay;

[0011] S4. Judge whether the phase difference is the hardware delay time of the relay. If so, continue to execute; otherwise, return to step S3;

[0012] S5. Turn off the inverter voltage output at the zero-crossing of the inverter, and at the same time, close the mains relay.

[0013] S6. When the phase difference time exactly passes through the zero-crossing, the mains relay is completely closed, and the connection of the mains is completed.

[0014] Further, the relay hardware delay time in step S3 is the time difference from receiving the relay closing instruction to the actual closing of the relay.

[0015] The present invention also provides a system according to the above method for preventing large current arcing caused by relay closing, including:

[0016] A detection module, used to detect whether there is mains access when the inverter is in the off-grid mode. If there is, then according to;

[0017] A capture module, used to capture the zero-crossing of the mains and the zero-crossing of the inverter and calculate the time between the two zero-crossings as the phase difference.

[0018] A misaligned phase-locked module, used for misaligned phase-locking, including: before the relay is closed, determining the phase difference according to the relay hardware delay time;

[0019] A judgment module, used to judge whether the phase difference is the relay hardware delay time;

[0020] An action module, when the judgment module judges that the phase difference is the relay hardware delay time, turns off the inverter voltage output at the zero-crossing of the inverter, and at the same time, closes the mains relay. When the phase difference time exactly passes through the zero-crossing, the mains relay is completely closed, and the connection of the mains is completed.

[0021] Compared with the prior art, the advantages of the present invention are as follows: The present invention can make the voltage zero and there is no voltage difference when the relay is closed, and the smooth switching has no impact current arcing, which improves the service life of the relay. At the same time, it can reduce the equipment cost and avoid equipment damage caused by the impact current arcing of the relay, further improving the reliability and safety of the equipment. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings.

[0023] Figure 1 It is a flowchart of the method for preventing large current arcing caused by relay closing in the present invention.

[0024] Figure 2It is a framework diagram of the system for preventing large current arcing caused by relay closing in the present invention. Embodiment

[0025] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0026] Refer to Figure 1 As shown, this embodiment provides a method for preventing large current arcing caused by relay closing, including the following steps:

[0027] Step S1: When the inverter is in off-grid mode, detect whether there is mains power access. If there is, continue to execute step S2.

[0028] Step S2: Capture the zero-crossing of the mains power and the zero-crossing of the inversion, and calculate the time between the two zero-crossings as the phase difference.

[0029] Step S3: Perform misaligned phase locking, including: before the relay closes, determine the phase difference according to the hardware delay time of the relay.

[0030] Among them, the hardware delay time of the relay refers to the time difference that occurs from receiving the relay closing instruction to the relay actually closing, and this time difference is caused by the characteristics of the relay itself.

[0031] Step S4: Determine whether the phase difference is the hardware delay time of the relay. If it is, continue to execute; otherwise, return to step S3.

[0032] Step S5: Turn off the inversion voltage output at the zero-crossing of the inversion, and at the same time close the mains relay.

[0033] Step S6: When the zero-crossing occurs at the phase difference time, the mains relay completes closing and the mains power access is completed.

[0034] In this embodiment, through the misaligned phase locking method, when the inversion voltage phase is ahead of the mains voltage phase, the phase difference is determined by the hardware delay time of the relay. At the phase of the zero-crossing of the inversion, the inversion voltage output is turned off and the relay is closed at the same time. Due to the relationship between the hardware delay time of the relay, that is, the phase difference, it can meet the condition that the inversion voltage is zero, no voltage difference is generated, and the relay can be closed at the zero-crossing of the mains power.

[0035] In this embodiment, through the misaligned phase locking method, when the inversion voltage phase lags behind the mains voltage phase, the phase difference is determined by the hardware delay time of the relay. At the phase of the zero-crossing of the inversion, the inversion voltage output is turned off and the relay is closed at the same time. Due to the relationship between the hardware delay time of the relay, that is, the phase difference, it can meet the condition that the inversion voltage is zero, no voltage difference is generated, and the relay can be closed at the zero-crossing of the mains power.

[0036] The present invention can achieve zero voltage and zero voltage difference when the relay is closed, without impact current arcing, which can improve the service life of the relay. At the same time, it can reduce the equipment cost and avoid equipment damage caused by the impact current arcing of the relay, further improving the reliability and safety of the equipment.

[0037] Combined with Figure 2 As shown in the figure, this embodiment also provides a system according to the above method for preventing large current arcing caused by relay closing, including:

[0038] The detection module 1 is used to detect whether there is mains power access when the inverter is in the off-grid mode. If there is, then follow;

[0039] The capture module 2 is used to capture the zero-crossing point of the mains power and the zero-crossing point of the inversion and calculate the time of the two zero-crossing points as the phase difference;

[0040] The offset phase-locked module 3 is used to perform offset phase-locking, including: before the relay is closed, determining the phase difference according to the hardware delay time of the relay;

[0041] The judgment module 4 is used to judge whether the phase difference is the hardware delay time of the relay;

[0042] The action module 5, when the judgment module judges that the phase difference is the hardware delay time of the relay, turns off the output of the inversion voltage at the zero-crossing point of the inversion, and at the same time closes the mains relay. When the phase difference time just passes the zero-crossing point, the mains relay is completely closed and the mains power access is completed.

[0043] The present invention can achieve zero voltage and zero voltage difference when the relay is closed, with a smooth switch and no impact current arcing, which can improve the service life of the relay. At the same time, it can reduce the equipment cost and avoid equipment damage caused by the impact current arcing of the relay, further improving the reliability and safety of the equipment.

[0044] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, the patent owner can make various deformations or modifications within the scope of the appended claims. As long as it does not exceed the protection scope described by the claims of the present invention, it should be within the protection scope of the present invention.

Claims

1. A method for preventing large current arcing caused by the closing of a relay, characterized in that, it includes the following steps: S1. When the inverter is in off-grid mode, detect whether there is mains power access. If there is, continue to execute step S2; S2. Capture the zero-crossing of the mains power and the zero-crossing of the inversion, and calculate the time between the two zero-crossings as the phase difference; S3. Perform phase-shifted phase locking, including: before the relay closes, determine the phase difference according to the relay hardware delay time; S4. Judge whether the phase difference is the relay hardware delay time. If it is, continue to execute. Otherwise, return to step S3; S5. Turn off the inversion voltage output at the zero-crossing of the inversion, and at the same time close the mains relay; S6. When the zero-crossing occurs exactly at the phase difference time, the mains relay completes the closing and the mains power access is completed. The relay hardware delay time in step S3 is the time difference from receiving the relay closing instruction to the actual closing of the relay.

2. A system for the method for preventing large current arcing caused by the closing of a relay according to claim 1, characterized in that, it includes: A detection module, used to detect whether there is mains power access when the inverter is in off-grid mode. If there is, then proceed according to; A capture module, used to capture the zero-crossing of the mains power and the zero-crossing of the inversion and calculate the time between the two zero-crossings as the phase difference; A phase-shifted phase-locking module, used to perform phase-shifted phase locking, including: before the relay closes, determine the phase difference according to the relay hardware delay time; A judgment module, used to judge whether the phase difference is the relay hardware delay time; An action module, when the judgment module judges that the phase difference is the relay hardware delay time, turns off the inversion voltage output at the zero-crossing of the inversion, and at the same time closes the mains relay. When the zero-crossing occurs exactly at the phase difference time, the mains relay completes the closing and the mains power access is completed.

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