A composite relay IGBT fault detection method and detection circuit

Abstract

The present invention relates to a composite relay IGBT fault detection method, which identifies the fault state of the IGBT by monitoring the time required for the current generated by arc energy to be transferred to the IGBT branch. The present invention also relates to a composite relay IGBT fault detection circuit, including a power supply part and a fault detection part, wherein the fault detection part includes a microcontroller MCU, a coil control signal acquisition module connected to the MCU, and an IGBT current acquisition module. The technical solution described in the present invention can accurately determine the fault state of the IGBT, so that the staff can repair the IGBT in time and ensure the normal operation of the overall circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent electrical appliances, and in particular to a composite relay IGBT fault detection method and detection circuit. Background Art

[0002] In the field of switching electrical appliances, mechanical contacts are usually used as devices for disconnecting and connecting loads. Existing mechanical contact relays generally include static upper and lower contacts, moving contacts arranged between the upper and lower contacts, and coils for controlling the movement of the moving contacts. However, when the mechanical contacts are actuated, arcs are generated, which lead to contact erosion, increase the contact resistance of the contacts, increase the thermal effect of the current, and even cause welding of the contacts. Therefore, the life of traditional mechanical switch relays is greatly reduced due to arcs.

[0003] Although the existing all-solid-state relays avoid the problem of arc erosion, they have large switching losses. Since the load current is carried by power electronic devices, they generate severe heat and require the installation of a larger heat sink. In addition, there is the problem of overvoltage and overcurrent damage.

[0004] The general principle of existing composite relays is to carry load current through mechanical contacts, and connect insulated gate bipolar transistors (IGBTs) in parallel on both sides of the moving contact and the upper contact and on both sides of the moving contact and the lower contact. The IGBT with breaking action is turned on only when the mechanical contact is actuated, thereby combining the advantages of the above two relays. However, the IGBT will gradually age with the increase in the number of actions, resulting in problems such as increasing on-resistance, slower current transfer speed, and current transfer failure, which will lead to arc extinguishing failure. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a composite relay IGBT fault detection method and detection circuit.

[0006] The present invention is achieved through the following technical solutions:

[0007] As a first aspect of the present invention, a composite relay IGBT fault detection method is provided, characterized in that it comprises the following steps:

[0008] S10, obtaining the control state of the IGBT by collecting the control signal, and obtaining the current magnitude passing through the IGBT branch by collecting the IGBT branch current signal,

[0009] If the control signal is high level, it indicates that the compound relay starts to act, and S20 is executed.

[0010] If the control signal is at a low level and the current through the IGBT is zero, S10 is executed again.

[0011] If the control signal is at a low level and the current through the IGBT is not zero, it is determined that the IGBT is broken down;

[0012] S20, ADC samples the current passing through the IGBT branch. In each sampling cycle,

[0013] If the sampled current is greater than the first current preset value, it indicates that the current generated by the arc energy begins to transfer to the IGBT branch, and S30 is executed.

[0014] If the sampled current is not greater than the first current preset value and the total execution time of S20 is not greater than the first time preset value, S20 is executed again.

[0015] If the sampled current is not greater than the first current preset value and the total execution time of S20 is greater than the first time preset value, it is determined that the IGBT has failed;

[0016] S30, ADC samples the current passing through the IGBT branch. In each sampling cycle,

[0017] If the sampled current is greater than the second current preset value, it indicates that the current generated by the arc energy has been transferred to the IGBT branch and S40 is executed.

[0018] If the sampled current is not greater than the second current preset value and the total execution time of S30 is not greater than the second time preset value, S30 is executed again.

[0019] If the sampled current is not greater than the second current preset value and the total execution time of S30 is greater than the second time preset value, it is determined that the IGBT has failed;

[0020] S40, calculating the current transfer time, which is the total execution time of S30,

[0021] If the current transfer time is not greater than the third time preset value, it indicates that the IGBT can operate normally.

[0022] If the current transfer time is greater than the third time preset value, it is determined that the IGBT is seriously aged.

[0023] Preferably, the execution time of S20 is determined by the number of current ADC sampling times when S20 is executed, and the execution time of S30 is determined by the number of current ADC sampling times when S30 is executed.

[0024] As a second aspect of the present invention, a composite relay IGBT fault detection circuit is provided, characterized in that it includes a power supply part and a fault detection part, the fault detection part includes a microcontroller MCU, a coil control signal acquisition module and an IGBT current acquisition module connected to the MCU, wherein: the coil control signal acquisition module is used to collect control signals and transmit them to the MCU, the IGBT current acquisition module is used to collect current signals passing through the IGBT branch and transmit them to the MCU, and the MCU performs fault identification on the IGBT based on the signals input by the coil control signal acquisition module and the IGBT current acquisition module.

[0025] Preferably, the IGBT current acquisition module comprises a current sensor and an isolation circuit, the current sensor is connected in series to the branch where the IGBT is located, and the current signal acquired by the current sensor is transmitted to the MCU through the isolation circuit.

[0026] Preferably, the MCU includes two high-speed ADCs, which are respectively used to receive the control signal input by the coil control signal acquisition module and the current signal input by the IGBT current acquisition module.

[0027] Preferably, the MCU is wirelessly connected to a monitoring center.

[0028] The beneficial effects of the present invention are:

[0029] The present invention identifies the fault state of the IGBT by monitoring the time required for the current generated by the arc energy to be transferred to the IGBT branch, and can accurately judge the fault state of the IGBT, so that the staff can repair the IGBT in time and ensure the normal operation of the overall line; the isolation circuit can interfere with and reduce the impact of the IGBT branch current on the microcontroller; the monitoring center can easily remind the staff to repair in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a module structure diagram of the fault detection part of the present invention.

[0031] Figure 2 It is a flow chart of the fault detection method of the present invention.

[0032] Figure 3 It is an equivalent circuit diagram of current transfer when the IGBT of the present invention is turned on.

[0033] Figure 4 It is a graph showing the change in time required for current transfer in the IGBT load test of the present invention. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and the best embodiments.

[0035] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0036] A composite relay IGBT fault detection method, characterized in that it comprises the following steps:

[0037] S10, obtain the control state of the IGBT by collecting the control signal of the coil, obtain the current I passing through the IGBT branch by collecting the current signal of the IGBT branch, and set the variable A.

[0038] If the control signal is high, indicating that the composite relay starts to act and the IGBT is about to turn on, then the variable A is set to zero and S20 is executed.

[0039] If the control signal is low and the sampling current I=0, it indicates that the IGBT is in normal working state, and S10 is executed again.

[0040] If the control signal is low and the sampling current I≠0, it is determined that the IGBT is broken down;

[0041] S20, perform ADC sampling on the current I, set the first current preset value I1, set the variable B, set the first time preset value T1, and calculate A by dividing T1 by the sampling period of I. 1， , in each sampling period,

[0042] If I>I1, it indicates that the current generated by the arc energy begins to transfer to the IGBT branch, then the variable B is set to zero and S30 is executed.

[0043] If I≤I1, A is incremented by one. If A≤A1, it indicates that within the normal preset time limit T1, the current generated by the arc energy has not begun to transfer to the branch where the IGBT is located. At this time, S20 is executed again. If A>A1, it is determined that the IGBT has failed.

[0044] S30, perform ADC sampling on the current I, set a second current preset value I2, set a second time preset value T2, and calculate B by dividing T2 by the sampling period of I. 1， In each sampling period,

[0045] If I>I2, it indicates that the current generated by the arc energy has been transferred to the IGBT branch and S40 is executed.

[0046] If I≤I2, B is incremented by 1. If B≤B1, it indicates that within the normal preset time limit T2, the current generated by the arc energy is being transferred to the IGBT branch. At this time, S30 is executed again. If B>B1, it is determined that the IGBT has failed.

[0047] S40, setting a third time preset value T3, calculating the current transfer time T, the current transfer time is the total execution time of S30, that is, T is equal to the sampling period of I multiplied by B,

[0048] If T≤T3, it indicates that the IGBT can operate normally and is in good condition.

[0049] If T>T3, it indicates that although the IGBT can operate normally, it is seriously aged. This detection method can accurately identify the fault status of the IGBT, making it convenient for the staff to repair the IGBT in time and ensure the normal operation of the overall circuit.

[0050] A composite relay IGBT fault detection circuit for implementing the above-mentioned fault detection method is characterized in that it includes a power supply part and a fault detection part, the power supply part is used to supply power to the fault detection part, the fault detection part includes a microcontroller MCU, a coil control signal acquisition module and an IGBT current acquisition module connected to the MCU, wherein: the coil control signal acquisition module is used to collect control signals and transmit them to the MCU, the IGBT current acquisition module is used to collect current signals passing through the IGBT branch and transmit them to the MCU, the MCU identifies faults of the IGBT based on the signals input by the coil control signal acquisition module and the IGBT current acquisition module, so that the staff can replace severely aged IGBTs in time according to the fault identification situation, reduce the possibility of arc extinguishing failure, and ensure the normal operation of the overall line.

[0051] The IGBT current acquisition module includes a current sensor and an isolation circuit. The current sensor is connected in series to the branch where the IGBT is located. The current signal collected by the current sensor is transmitted to the MCU through the isolation circuit. The isolation circuit can interfere with and reduce the impact of the IGBT branch current on the microcontroller.

[0052] The MCU includes two high-speed ADCs, which are respectively used to receive the control signal input by the coil control signal acquisition module and the current signal input by the IGBT current acquisition module.

[0053] The MCU is wirelessly connected to a monitoring center to remind staff to perform maintenance in a timely manner.

[0054] The working principle of the present invention is to identify the fault state of the IGBT by monitoring the time required for the current generated by the arc energy to transfer to the IGBT branch, thereby facilitating the staff to replace the faulty IGBT in time.

[0055] The current transfer equivalent circuit diagram is as follows Figure 3 As shown, R Q is the on-resistance of IGBT, L Q is the equivalent parasitic inductance of the loop, u Q Equivalent to the sum of the IGBT conduction voltage drops, i Q1 is the IGBT conduction current, u arc is the arc voltage, i arc is the arc current, the following relationship can be obtained:

[0056]

[0057] From the above formula, we can get the current transfer rate:

[0058]

[0059] It can be seen from the above formula that as the on-resistance of the IGBT increases, its on-voltage drop also increases, causing the current transfer rate to slow down. When the on-voltage drop increases to a value greater than u arc- u Q <R Q i Q1 When the current transfer rate is less than zero, it means that the current will not be transferred and the arc extinguishing work of the compound relay fails. Therefore, the aging state of the IGBT can be determined by monitoring the current transfer time of the compound relay.

[0060] The change of the time required for the load test current transfer is shown in the figure Figure 4 As shown, they are all measured under the condition of 1A load current. It can be seen that the time required for current transfer is positively correlated with the number of operations. It also shows that the aging state of the IGBT can be accurately determined by monitoring the current transfer time of the composite relay.

[0061] The present invention identifies the fault state of the IGBT by monitoring the time required for the current generated by the arc energy to be transferred to the IGBT branch, and can accurately judge the fault state of the IGBT, so that the staff can repair the IGBT in time and ensure the normal operation of the overall line; the isolation circuit can interfere with and reduce the impact of the IGBT branch current on the microcontroller; the monitoring center can easily remind the staff to repair in time.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A composite relay IGBT fault detection method, characterized in that: The steps include: S10, obtaining the control state of the IGBT by collecting the control signal, and obtaining the current magnitude passing through the IGBT branch by collecting the IGBT branch current signal, If the control signal is high level, it indicates that the compound relay starts to act, and S20 is executed. If the control signal is at a low level and the current through the IGBT is zero, S10 is executed again. If the control signal is at a low level and the current through the IGBT is not zero, it is determined that the IGBT is broken down; S20, ADC samples the current passing through the IGBT branch. In each sampling cycle, If the sampled current is greater than the first current preset value, it indicates that the current generated by the arc energy begins to transfer to the IGBT branch, and S30 is executed. If the sampled current is not greater than the first current preset value and the total execution time of S20 is not greater than the first time preset value, S20 is executed again. If the sampled current is not greater than the first current preset value and the total execution time of S20 is greater than the first time preset value, it is determined that the IGBT has failed; S30, ADC samples the current passing through the IGBT branch. In each sampling cycle, If the sampled current is greater than the second current preset value, it indicates that the current generated by the arc energy has been transferred to the IGBT branch and S40 is executed. If the sampled current is not greater than the second current preset value and the total execution time of S30 is not greater than the second time preset value, S30 is executed again. If the sampled current is not greater than the second current preset value and the total execution time of S30 is greater than the second time preset value, it is determined that the IGBT has failed; S40, calculating the current transfer time, which is the total execution time of S30, If the current transfer time is not greater than the third time preset value, it indicates that the IGBT can operate normally. If the current transfer time is greater than the third time preset value, it is determined that the IGBT is seriously aged.

2. A composite relay IGBT fault detection method according to claim 1, characterized in that: The execution time of S20 is determined by the number of current ADC sampling times when S20 is executed, and the execution time of S30 is determined by the number of current ADC sampling times when S30 is executed.

3. A composite relay IGBT fault detection method according to claim 1, characterized in that: A composite relay IGBT fault detection circuit is used to implement the method, including a power supply part and a fault detection part, wherein the fault detection part includes a microcontroller MCU, a coil control signal acquisition module connected to the MCU, and an IGBT current acquisition module, wherein: The coil control signal acquisition module is used to collect control signals and transmit them to the MCU, and the IGBT current acquisition module is used to collect current signals passing through the IGBT branch and transmit them to the MCU. The MCU identifies IGBT faults based on the signals input by the coil control signal acquisition module and the IGBT current acquisition module.

4. A composite relay IGBT fault detection method according to claim 3, characterized in that: The IGBT current acquisition module includes a current sensor and an isolation circuit. The current sensor is connected in series to the branch where the IGBT is located, and the current signal collected by the current sensor is transmitted to the MCU through the isolation circuit.

5. A composite relay IGBT fault detection method according to claim 3, characterized in that: The MCU includes two high-speed ADCs, which are respectively used to receive the control signal input by the coil control signal acquisition module and the current signal input by the IGBT current acquisition module.

6. A composite relay IGBT fault detection method according to claim 3, characterized in that: The MCU is wirelessly connected to a monitoring center.

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