A device and method for controlling the switching of a frequency converter and a power frequency bypass

Abstract

The application discloses a device and method for controlling frequency converter and power frequency bypass switching, and relates to the field of frequency converters.The device comprises a controller; the controller is used for determining to switch the frequency converter from a frequency conversion loop to a power frequency loop and outputting a switching instruction for switching to the power frequency loop from a power frequency switching instruction output end when a frequency converter output failure signal is detected and the frequency converter is not successfully reset; the voltage of a to-be-detected power supply is obtained through a to-be-detected voltage input end after the frequency converter output failure signal is detected and the frequency converter is successfully reset, whether there is a temporary drop change in the voltage of the to-be-detected power supply within a first preset time period before the frequency converter output failure signal is detected is judged; if yes, it is determined to switch the frequency converter from the frequency conversion loop to the power frequency loop and output the switching instruction for switching to the power frequency loop from the power frequency switching instruction output end. The application realizes automatic switching to the power frequency loop when a frequency conversion failure occurs, and reduces the influence on continuous production.

Description

Technical Field

[0001] This invention relates to the field of frequency converter technology, and in particular to a device and method for controlling the switching between a frequency converter and a power frequency bypass. Background Technology

[0002] Variable frequency drives (VFDs) are widely used in industrial control systems. As VFDs are power electronic products with high protection accuracy, they may stop operation due to various protection values ​​exceeding limits. Some faults may be caused by the VFD itself, some by load-side faults, and some by momentary power supply faults. Regardless of the type of fault, the VFD will stop. Some critical operating conditions require continuous operation and cannot be stopped. Generally, a power frequency circuit is provided so that the VFD can be manually switched to power frequency operation when the VFD itself stops due to a fault. However, this still affects production and forces an interruption, causing certain production losses.

[0003] Currently, both the frequency converter and mains frequency circuits are manually switched. This is because when a frequency converter malfunctions, the fault needs to be manually confirmed. Only after confirming that it is not a load-side issue will the system be manually switched back to mains frequency startup. This also applies to malfunctions of the frequency converter itself. However, this delays the restart time and impacts continuous production. Summary of the Invention

[0004] The purpose of this invention is to provide a device and method for controlling the switching between a frequency converter and a power frequency bypass, thereby reducing the impact on continuous production by automatically switching to the power frequency circuit when a frequency converter fails.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A device for controlling the switching between a frequency converter and a power frequency bypass includes a controller. The controller includes a voltage input terminal to be detected and a power frequency switching command output terminal. The voltage input terminal to be detected is connected to the power supply to be detected, and the power frequency switching command output terminal is used to output a switching command to switch to the power frequency circuit.

[0007] The controller is used to determine to switch the frequency converter from the frequency conversion circuit to the power frequency circuit when a fault signal is detected from the frequency converter and the frequency converter fails to reset successfully, and to output a switching command to switch to the power frequency circuit from the power frequency switching command output terminal.

[0008] The controller is also configured to, when a fault signal is detected from the inverter output and the inverter is successfully reset, obtain the voltage of the power supply to be tested through the voltage input terminal to be tested, determine whether there is a voltage dip change in the voltage of the power supply to be tested within a first preset time period before the fault signal is detected from the inverter output and whether the voltage dip reaches a preset value. If so, determine to switch the inverter from the frequency conversion circuit to the power frequency circuit, and output a switching command to switch to the power frequency circuit from the power frequency switching command output terminal.

[0009] Optionally, the controller further includes an inverter status signal input terminal, an inverter fault signal input terminal, and a reset pulse signal output terminal. The inverter status signal input terminal is used to input the status signal of the inverter, the inverter fault signal input terminal is used to receive the fault signal of the inverter, and the reset pulse signal output terminal is used to send a reset pulse signal to the inverter.

[0010] The controller is also used for:

[0011] The inverter is detected in real time whether it outputs a fault signal by the inverter fault signal input terminal.

[0012] When a fault signal is detected from the inverter, a reset pulse is sent to the inverter through the reset pulse signal output terminal within a preset reset time period.

[0013] Whether the frequency converter is reset is determined based on the frequency converter status signal input terminal.

[0014] Optionally, the controller is further configured to, after the power frequency switching command output terminal outputs a switching command to switch to the power frequency circuit, delay for a second preset time and then issue a command to restart the power frequency circuit.

[0015] Optionally, the controller further includes a power supply voltage recording module, which is used to record the voltage of the power supply at various times.

[0016] This invention also discloses a method for controlling the switching between a frequency converter and a power frequency bypass. The method is applied to the aforementioned device for controlling the switching between a frequency converter and a power frequency bypass. The method includes:

[0017] When the controller detects a fault signal output by the frequency converter and the frequency converter fails to reset successfully, it determines to switch the frequency converter from the frequency conversion circuit to the power frequency circuit, and outputs a switching command to switch to the power frequency circuit from the power frequency switching command output terminal.

[0018] When the controller detects a fault signal output by the frequency converter and the frequency converter is successfully reset, it obtains the voltage of the power supply to be tested through the voltage input terminal to be tested, and determines whether there is a voltage dip change in the voltage of the power supply to be tested within a first preset time period before the fault signal output by the frequency converter is detected, and whether the voltage dip reaches a preset value. If so, it determines to switch the frequency converter from the frequency conversion circuit to the power frequency circuit, and outputs a switching command to switch to the power frequency circuit from the power frequency switching command output terminal.

[0019] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0020] This invention uses a controller to determine whether to switch the inverter from the frequency converter circuit to the power frequency circuit by monitoring the inverter reset status and the voltage change of the power supply under test. This achieves automatic switching to the power frequency circuit when the inverter fails, reducing the impact of forced production interruptions on continuous production. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the device structure for controlling the switching between frequency converter and power frequency bypass according to the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The purpose of this invention is to provide a device and method for controlling the switching between a frequency converter and a power frequency bypass, thereby reducing the impact on continuous production by automatically switching to the power frequency circuit when a frequency converter fails.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] like Figure 1As shown, the present invention discloses a device for controlling the switching between a frequency converter and a power frequency bypass, comprising: a controller, the controller including a voltage input terminal to be detected, a frequency converter status signal input terminal, a frequency converter fault signal input terminal, a power frequency switching command output terminal, and a reset pulse signal output terminal; the voltage input terminal to be detected is connected to the power supply to be detected, the frequency converter status signal input terminal is used to input the status signal of the frequency converter, the frequency converter fault signal input terminal is used to receive the fault signal of the frequency converter, the reset pulse signal output terminal is used to send a reset pulse signal to the frequency converter, and the power frequency switching command output terminal is used to output a switching command to switch to the power frequency circuit.

[0028] The frequency converter is connected to both the power supply under test and the load. The voltage of the power supply under test is converted by the frequency converter to supply power to the load.

[0029] The controller is used for:

[0030] When a fault signal is detected from the inverter output and the inverter fails to reset, it is determined to switch the inverter from the frequency conversion circuit to the power frequency circuit, and the power frequency switching command output terminal outputs a switching command to switch to the power frequency circuit.

[0031] The controller is further configured to, when a fault signal is detected from the inverter output and the inverter is successfully reset, obtain the voltage of the power supply to be tested through the voltage input terminal, determine whether the voltage of the power supply to be tested has a voltage dip within a first preset time period before the fault signal from the inverter is detected, and whether the voltage dip reaches a preset value; if so, determine to switch the inverter from the frequency converter circuit to the power frequency circuit, and output a switching command to switch to the power frequency circuit from the power frequency switching command output terminal, and after a second preset time delay, issue a command to restart the power frequency circuit; if not, do not output the power frequency switching command and the command to restart the power frequency circuit.

[0032] The controller is also used for:

[0033] The inverter is detected in real time whether it outputs a fault signal by the inverter fault signal input terminal.

[0034] When a fault signal is detected from the inverter, a reset pulse is sent to the inverter through the reset pulse signal output terminal within a preset reset time period.

[0035] Whether the frequency converter is reset is determined based on the frequency converter status signal input terminal.

[0036] If the inverter is successfully reset, it is determined whether there is a voltage dip in the power supply under test within a first preset time period before the inverter outputs a fault signal, and if the voltage dip reaches a preset threshold, then the inverter is switched from the frequency conversion circuit to the power frequency circuit.

[0037] A successful inverter reset means that after receiving the reset pulse signal, the inverter will not output a fault signal within the preset reset time period.

[0038] If the inverter fails to reset, it means that the inverter will still output a fault signal within the preset reset time period after receiving the reset pulse signal.

[0039] Under normal conditions, the power frequency circuit of the frequency converter is disconnected.

[0040] If the inverter fault signal is detected to have returned, but further investigation reveals that the voltage of the power supply under test does not show a downward trend within the first preset time period of the fault signal change, the controller will not issue switching or restart commands. The switching command is the command to switch the inverter to the mains frequency circuit, and the restart command is the command to start the mains frequency circuit.

[0041] The controller also includes a power supply voltage recording module, which is used to record the voltage of the power supply at various times.

[0042] like Figure 1 As shown, the controller includes three-phase input terminals L1, L2, and L3, and wiring terminals 1 and 2 are single-phase power input terminals to be tested. Depending on actual needs, the controller can detect single-phase voltage or three-phase voltage.

[0043] When the power supply voltage to be tested is a single-phase voltage, the input terminal of the voltage to be tested includes terminal 1 and terminal 2.

[0044] When the power supply voltage to be tested is a three-phase voltage, the input terminals of the voltage to be tested include three-phase input terminals L1, L2, and L3, namely terminal 1, terminal B, and terminal C.

[0045] Terminal 3 and terminal 4 are the inverter status signal input terminals, used to detect the inverter's operating status.

[0046] Terminal 5 and terminal 6 are the start command (restart command) for switching the frequency converter to the mains frequency.

[0047] Terminal 7 and terminal 8 are the power frequency switching command output terminals, which are the switching circuits for switching between variable frequency and power frequency.

[0048] Terminal 9 and terminal 10 are the inverter fault signal input terminals.

[0049] Terminal 11 and terminal 12 are bit pulse signal output terminals, used to output reset pulse signals to the frequency converter.

[0050] Terminals 13 and 14 are used for status output, that is, to maintain the output operating signal during the switching of the frequency converter to the mains frequency.

[0051] Only one of the frequency converter circuit and the mains frequency circuit can be connected at a time. When the frequency converter circuit is connected, the mains frequency circuit is disconnected, and vice versa. The two circuits are interlocked. Therefore, after the controller issues a switching command to switch to the mains frequency circuit (specifically, by switching the frequency converter circuit to the mains frequency circuit via terminals 7 and 8), a second preset time delay is required before issuing a command to restart the mains frequency circuit, specifically by restarting the mains frequency circuit via terminals 5 and 6.

[0052] Example 2

[0053] The present invention also discloses a method for controlling the switching between a frequency converter and a power frequency bypass, wherein the method for controlling the switching between a frequency converter and a power frequency bypass is applied to the device for controlling the switching between a frequency converter and a power frequency bypass described in Embodiment 1.

[0054] The method for switching between the control frequency converter and the power frequency bypass includes:

[0055] When the controller detects a fault signal output by the frequency converter and the frequency converter fails to reset successfully, it determines to switch the frequency converter from the frequency conversion circuit to the power frequency circuit, and outputs a switching command to switch to the power frequency circuit from the power frequency switching command output terminal.

[0056] When the controller detects a fault signal output by the frequency converter and the frequency converter is successfully reset, it obtains the voltage of the power supply to be tested through the voltage input terminal to be tested, and determines whether there is a voltage dip change in the voltage of the power supply to be tested within a first preset time period before the fault signal output by the frequency converter is detected, and whether the voltage dip reaches a preset value. If so, it determines to switch the frequency converter from the frequency conversion circuit to the power frequency circuit, and outputs a switching command to switch to the power frequency circuit from the power frequency switching command output terminal.

[0057] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0058] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the device and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A device for controlling the switching between a frequency converter and a power frequency bypass, characterized in that, The system includes a controller, which includes a voltage input terminal to be detected and a power frequency switching command output terminal. The voltage input terminal to be detected is connected to the power supply to be detected, and the power frequency switching command output terminal is used to output a switching command to switch to the power frequency circuit. The controller is used to determine to switch the frequency converter from the frequency conversion circuit to the power frequency circuit when a fault signal is detected from the frequency converter and the frequency converter fails to reset successfully, and to output a switching command to switch to the power frequency circuit from the power frequency switching command output terminal. The controller is also configured to, when a fault signal is detected from the inverter output and the inverter is successfully reset, obtain the voltage of the power supply to be tested through the voltage input terminal to be tested, determine whether there is a voltage dip change in the voltage of the power supply to be tested within a first preset time period before the fault signal is detected from the inverter output and whether the voltage dip reaches a preset value. If so, determine to switch the inverter from the frequency conversion circuit to the power frequency circuit, and output a switching command to switch to the power frequency circuit from the power frequency switching command output terminal.

2. The device for controlling the switching between the frequency converter and the power frequency bypass according to claim 1, characterized in that, The controller further includes an inverter status signal input terminal, an inverter fault signal input terminal, and a reset pulse signal output terminal. The inverter status signal input terminal is used to input the status signal of the inverter, the inverter fault signal input terminal is used to receive the fault signal of the inverter, and the reset pulse signal output terminal is used to send a reset pulse signal to the inverter. The controller is also used for: The inverter is detected in real time whether it outputs a fault signal by the inverter fault signal input terminal. When a fault signal is detected from the inverter, a reset pulse is sent to the inverter through the reset pulse signal output terminal within a preset reset time period. Whether the frequency converter is reset is determined based on the frequency converter status signal input terminal.

3. The device for controlling the switching between the frequency converter and the power frequency bypass according to claim 1, characterized in that, The controller is further configured to, after the power frequency switching command output terminal outputs a switching command to switch to the power frequency circuit, issue a command to restart the power frequency circuit after a second preset time delay.

4. The device for controlling the switching between the frequency converter and the power frequency bypass according to claim 1, characterized in that, The controller also includes a power supply voltage recording module, which is used to record the voltage of the power supply at various times.

5. A method for controlling the switching between a frequency converter and a power frequency bypass, characterized in that, The method for controlling the switching between the frequency converter and the power frequency bypass is applied to the device for controlling the switching between the frequency converter and the power frequency bypass as described in claims 1-4, and the method for controlling the switching between the frequency converter and the power frequency bypass includes: When the controller detects a fault signal output by the frequency converter and the frequency converter fails to reset successfully, it determines to switch the frequency converter from the frequency conversion circuit to the power frequency circuit, and outputs a switching command to switch to the power frequency circuit from the power frequency switching command output terminal. When the controller detects a fault signal output by the frequency converter and the frequency converter is successfully reset, it obtains the voltage of the power supply to be tested through the voltage input terminal to be tested, and determines whether there is a voltage dip change in the voltage of the power supply to be tested within a first preset time period before the fault signal output by the frequency converter is detected, and whether the voltage dip reaches a preset value. If so, it determines to switch the frequency converter from the frequency conversion circuit to the power frequency circuit, and outputs a switching command to switch to the power frequency circuit from the power frequency switching command output terminal.

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