CN112147427A

CN112147427A - Fault detection method and fault detection circuit of power module

Info

Publication number: CN112147427A
Application number: CN201910581136.9A
Authority: CN
Inventors: 符松格
Original assignee: Xinjiang Goldwind Science and Technology Co Ltd
Current assignee: Xinjiang Goldwind Science and Technology Co Ltd
Priority date: 2019-06-29
Filing date: 2019-06-29
Publication date: 2020-12-29
Anticipated expiration: 2039-06-29
Also published as: CN112147427B

Abstract

The application provides a fault detection method and a fault detection circuit of a power module. The fault detection method of the power module comprises the following steps: controlling a first switch unit in a first detection circuit to be turned off at a first moment, and controlling a first power unit in a power module to be turned on at a second moment which is not earlier than the first moment, so that a first charging and discharging unit in the first detection circuit is charged by a charging current provided by the first power unit in the turning-on transient process of the first power unit; the method comprises the steps of collecting charging voltage of a first charging and discharging unit, and determining a first voltage difference between an auxiliary terminal and a power terminal of the first power unit in the switching transient process of the first power unit according to the charging voltage of the first charging and discharging unit; and judging whether the first power unit has a fault according to the first voltage difference.

Description

Fault detection method and fault detection circuit of power module

Technical Field

The present disclosure relates to the field of power module technologies, and in particular, to a fault detection method and a fault detection circuit for a power module.

Background

Along with the continuous improvement of the capacity of the wind generating set, the power of the wind power converter system is also increased more and more. In the field of low-voltage wind power converters, the capacity of the wind power converter is generally expanded by parallel application of power devices.

In the parallel application of the power devices, when one of the power devices is not controlled by a PWM (Pulse Width Modulation) Pulse, the power device cannot normally operate (i.e., cannot normally conduct), and the remaining power devices still normally operate, and at this time, the current passing through the power device is redistributed. The uncontrolled power device does not work and does not conduct current, the controlled power device distributes total current evenly, and when the average distributed current of the controlled power device exceeds the design current of a single power device, the power device can generate an over-temperature phenomenon.

In the parallel application process of the power devices, whether the power devices are controlled or not needs to be identified so as to judge the fault condition of the power devices. Because the power terminals of the parallel power devices are directly connected in parallel, the voltage of the parallel terminals is kept consistent, and therefore uncontrolled power devices cannot be identified through voltage differences.

If a Current sampling and processing device is added to each AC (Alternating Current) output terminal of the parallel power device, the uncontrolled power device can be analyzed through processing and judgment of the controller, but the number of the required Current sampling and processing devices is too large, which affects the cost and reliability of the converter.

Disclosure of Invention

The application provides a fault detection method and a fault detection circuit of a power module aiming at the defects of the existing mode, and is used for solving the technical problem that the fault detection cannot be reliably carried out in the prior art.

In a first aspect, an embodiment of the present application provides a method for detecting a fault of a power module, including:

controlling a first switch unit in a first detection circuit to be turned off at a first moment, and controlling a first power unit in a power module to be turned on at a second moment which is not earlier than the first moment, so that a first charging and discharging unit in the first detection circuit is charged by a charging current provided by the first power unit in the turning-on transient process of the first power unit;

the method comprises the steps of collecting charging voltage of a first charging and discharging unit, and determining a first voltage difference between an auxiliary terminal and a power terminal of the first power unit in the switching transient process of the first power unit according to the charging voltage of the first charging and discharging unit;

and judging whether the first power unit has a fault according to the first voltage difference.

In a second aspect, an embodiment of the present application provides a fault detection circuit for a power module, including a control circuit and a first detection circuit;

the first detection circuit includes: the first switch unit, the first charge and discharge unit and the first unidirectional conduction unit;

a first control end and a second control end of the control circuit are respectively and electrically connected with a control end of a first power unit and a control end of a first switch unit in the power module;

the first end and the second end of the first switch unit are respectively and electrically connected with the first end and the second end of the first charge-discharge unit;

the third end of the first charge-discharge unit is electrically connected with the power terminal of the first power unit;

the first end and the second end of the first unidirectional conduction unit are respectively and electrically connected with the auxiliary terminal of the first power unit and the first end of the first charge-discharge unit;

the control circuit is used for: controlling a first switch unit in a first detection circuit to be turned off at a first moment, and controlling a first power unit in a power module to be turned on at a second moment which is not earlier than the first moment, so that a first charging and discharging unit in the first detection circuit is charged by a charging current provided by the first power unit in the turning-on transient process of the first power unit; the method comprises the steps of collecting charging voltage of a first charging and discharging unit, and determining a first voltage difference between an auxiliary terminal and a power terminal of the first power unit in the switching transient process of the first power unit according to the charging voltage of the first charging and discharging unit; and judging whether the first power unit has a fault according to the first voltage difference.

The technical scheme provided by the embodiment of the application at least has the following beneficial effects:

the control circuit and the first detection circuit are arranged between the auxiliary terminal and the power terminal of the first power unit, the on-off of the first switch unit in the power unit and the detection circuit is controlled, the rapid detection of the potential difference between the auxiliary terminal and the power terminal of the first power unit in the on-off transient process can be realized, and whether the first power unit is controlled or not can be rapidly and accurately judged based on the potential difference, so that the fault of the first power unit can be rapidly and accurately identified, and the reliability of fault detection is improved.

Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.

Drawings

The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram illustrating an electrical principle of a parallel connection of power units according to the prior art;

fig. 2 is an electrical schematic diagram of a fault detection circuit of a power module according to an embodiment of the present disclosure;

fig. 3 is an electrical schematic diagram of a fault detection circuit of another power module according to an embodiment of the present disclosure;

fig. 4 is an electrical schematic diagram of a fault detection circuit of another power module according to an embodiment of the present disclosure;

fig. 5 is an electrical schematic diagram of a three-level power module to which a fault detection circuit of the power module provided in the embodiment of the present application is applied;

fig. 6 is a schematic flowchart of a method for detecting a fault of a power module according to an embodiment of the present disclosure;

fig. 7 is a schematic flowchart of another fault detection method for a power module according to an embodiment of the present disclosure;

fig. 8 is a partial schematic flowchart of a fault detection method for a power module according to an embodiment of the present disclosure;

fig. 9 is a partial flowchart of a further method for detecting a fault of a power module according to an embodiment of the present application.

Detailed Description

Reference will now be made in detail to the present application, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar parts or parts having the same or similar functions throughout. In addition, if a detailed description of the known art is not necessary for illustrating the features of the present application, it is omitted. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application.

It will be understood by those within the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items.

Fig. 1 shows an electrical schematic diagram of parallel connection of power cells, and taking an Insulated Gate Bipolar Transistor (IGBT) as an example, the electrical structure shown in fig. 1 includes power cells T1, T2, T3 and T4 (including a first IGBT, a second IGBT, a third IGBT and a fourth IGBT, respectively) connected between DC + (Direct Current +, positive Direct Current bus) and DC- (Direct Current-, negative Direct Current bus), where T1 and T2 are connected in parallel, and T3 and T4 are connected in parallel. Alternating current output ends of the T1 to the T4 are all connected to an AC alternating current terminal in parallel, a power terminal Co1 (collector of the first IGBT) of the T1 and a power terminal Co2 (collector of the second IGBT) of the T2 are connected to a DC + busbar in parallel, and a power terminal E1 (emitter of the first IGBT) of the T1 and a power terminal E2 (emitter of the second IGBT) of the T2 are connected to the AC alternating current terminal in parallel; t1 and T2 in fig. 1 also include a control terminal G1 (gate of first IGBT) and a control terminal G2 (gate of second IGBT), respectively.

The inventors of the present application have conducted studies to find that, due to the internal characteristics of the IGBTs, there is a stray inductance (equivalent inductance shown by the inductance symbol of the T1 portion in fig. 1) between the auxiliary terminal E1 (auxiliary emitter of the first IGBT) and the power terminal E1 (emitter of the first IGBT) in fig. 1, and also between the auxiliary terminal E2 (auxiliary emitter of the second IGBT) and the power terminal E2 (emitter of the second IGBT). When the IGBT is in a switching-on steady state, the influence of stray inductance is basically negligible, the E1 potential is equal to the E1 potential, and the E2 potential is equal to the E2 potential; when the power unit is in the on transient state, under the influence of the stray inductance, the E1 potential is not equal to the E1 potential, and the E2 potential is not equal to the E2 potential.

During the transient process of the turn-on instant of the IGBT, the current change rate di/dt of the IGBT can generally reach 3A/ns (ampere/nanosecond) or more, the stray inductance L inside the IGBT is generally greater than 5nH (nanohenry), and then the potential difference between E1 and E1 can reach at least L × di/dt (3A/us) × (5nH) ═ 15V, and E2 and E2 are the same; during the turn-on steady state of the IGBT, it can be considered that the potential difference between E1 and E1 is about 0V (actually, there is wire resistance between E1 and E1, and the potential difference in the steady state is about 0.3V to 0.7V).

However, the duration of the turn-on transient process of the IGBT is short, generally less than 100ns, and the turn-on transient process enters the turn-on steady-state stage quickly, so that it is difficult to detect the potential difference between E1 and E1 directly during the transient process.

The existing detection method for adding the current sampling and processing device has very high requirement on the current sharing property, and the current sampling and processing device added at each AC output terminal needs to additionally add a section of AC alternating-current copper bar, so that the parallel current sharing design is greatly influenced.

The fault detection method and the fault detection circuit for the power module can detect the potential difference between E1 and E1 in the transient switching-on process, and further achieve the purpose of detecting the fault of the power module.

The following describes the technical solutions of the present application and how to solve the above technical problems with specific embodiments. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments. Embodiments of the present application will be described below with reference to the accompanying drawings.

An embodiment of the present application provides a fault detection circuit of a power module, as shown in fig. 2, the fault detection circuit includes: the circuit comprises a control circuit 201 and a first detection circuit 202, wherein the first detection circuit 202 comprises a first switch unit, a first charging and discharging unit and a first one-way conduction unit.

A first control end and a second control end of the control circuit 201 are electrically connected to a control end of a first power unit T1 and a control end of a first switch unit in the power module, respectively; the first end and the second end of the first switch unit are respectively and electrically connected with the first end and the second end of the first charge-discharge unit; the third end of the first charge and discharge unit is electrically connected with a power terminal E1 of a first power unit T1; the first end and the second end of the first unidirectional conducting unit are electrically connected with the auxiliary terminal e1 of the first power unit T1 and the first end of the first charging and discharging unit, respectively.

The control circuit 201 is configured to: controlling a first switch unit in the first detection circuit 202 to be turned off at a first time, controlling a first power unit T1 in the power module to be turned on at a second time no earlier than the first time, and enabling a charging current provided by the first power unit T1 to charge a first charging and discharging unit in the first detection circuit 202 during a turning-on transient state of the first power unit T1; collecting the charging voltage of the first charging and discharging unit, and determining a first voltage difference between an auxiliary terminal E1 and a power terminal E1 of the first power unit T1 in the switching transient process of the first power unit T1 according to the charging voltage of the first charging and discharging unit; and judging whether the first power unit T1 has a fault according to the first voltage difference.

In an alternative embodiment, the control circuit 201 includes a Gate Driver (Gate Driver), and the first driving terminal and the second driving terminal of the Gate Driver are respectively used as the first control terminal and the second control terminal of the control circuit 201, and are respectively electrically connected to the control terminal of the first power unit T1 and the control terminal of the first switch unit.

In another alternative embodiment, the control circuit 201 includes a controller and a gate driver electrically connected, and a first driving terminal and a second driving terminal of the gate driver are respectively used as a first control terminal and a second control terminal of the control circuit 201, and are respectively electrically connected to a control terminal of the first power unit T1 and a control terminal of the first switch unit; the controller may output a control signal to the gate driver, and the gate driver drives the first power unit T1 or the first switching unit according to the control signal.

In the example shown in fig. 2, the power terminal E1 of the first power unit T1 and the power terminal E2 of the second power unit T2 are connected in parallel, and the potentials of the power terminals E1 and E2 are equal; there is a driving resistor Re1 between the control circuit 201 and the auxiliary terminal e1 of the first power unit T1, and there is a driving resistor Re2 between the control circuit 201 and the auxiliary terminal e2 of the second power unit T2, so that the potentials of the auxiliary terminals e1 and e2 may not be equal.

Optionally, as shown in fig. 3 or fig. 4, the fault detection circuit of the power module provided in the embodiment of the present application further includes at least one second detection circuit 203; at least one second power unit T2 in the power module is connected in parallel with the first power unit T1, and the control end of each second power unit T2 is electrically connected with the first control end of the control circuit 201; the second detection circuit 203 includes a second switch unit, a second charge and discharge unit, and a second unidirectional conduction unit.

The control circuit 201 is further configured to perform the following operations for any one of the at least one second power unit T1 of the at least one second power unit T1:

controlling the second switch unit in the second detection circuit 203 to be turned off at the third time, controlling the second power unit T1 in the power module to be turned on at the fourth time no earlier than the third time, so that the charging current provided by the second power unit T1 charges the second charge and discharge unit in the second detection circuit 203 during the on transient of the second power unit T1; collecting the charging voltage of the second charging and discharging unit, and determining a second voltage difference between an auxiliary terminal of the second power unit T1 and a power terminal E1 in the transient switching-on process according to the charging voltage of the second charging and discharging unit; and judging whether the second power unit T1 has a fault according to the second voltage difference.

Fig. 3 and 4 each show the case of one second power cell T2 and the corresponding one second detection circuit 203, and the cases of two or more second power cells T2 and the corresponding two or more second detection circuits 203 are similar.

In an optional embodiment, a control end of the second switch unit is electrically connected to a second control end of the control circuit 201, and a first end and a second end of the second switch unit are electrically connected to a first end and a second end of the second charge and discharge unit, respectively; the third end of the second charge and discharge unit is electrically connected with a power terminal E2 of a second power unit T2; the first end and the second end of the second unidirectional conducting unit are electrically connected with the auxiliary terminal e2 of the second power unit T2 and the first end of the second charging and discharging unit, respectively.

Optionally, as shown in fig. 3, the first charge and discharge unit includes a first capacitor C1 and a first resistor R1, and the second charge and discharge unit includes a second capacitor C2 and a second resistor R2.

A first end of the first capacitor C1 is used as a first end of the first charge-discharge unit, a first end of the first resistor R1 is used as a second end of the first charge-discharge unit, and a second end of the first capacitor C1 and a second end of the first resistor R1 are both used as third ends of the first charge-discharge unit; the first end of the second capacitor C2 is used as the first end of the second charge and discharge unit, the first end of the second resistor R2 is used as the second end of the second charge and discharge unit, and the second end of the second capacitor C2 and the second end of the second resistor R2 are both used as the third end of the second charge and discharge unit.

In another optional embodiment, a control end of the second switch unit is electrically connected to a first control end of the control circuit 201, and a first end and a second end of the second switch unit are electrically connected to a first end of the second charge and discharge unit and a second end of the first charge and discharge unit, respectively; the second ends of the second charge and discharge units are respectively and electrically connected with a power terminal E2 of a second power unit T2; the first end and the second end of the second unidirectional conducting unit are electrically connected with the auxiliary terminal e2 of the second power unit T2 and the first end of the second charging and discharging unit, respectively.

Optionally, as shown in fig. 4, the first charge and discharge unit includes a first capacitor C1 and a first resistor R1, and the second charge and discharge unit includes a second capacitor C2.

A first end of the first capacitor C1 is used as a first end of the first charge-discharge unit, a first end of the first resistor R1 is used as a second end of the first charge-discharge unit, and a second end of the first capacitor C1 and a second end of the first resistor R1 are both used as third ends of the first charge-discharge unit; two ends of the second capacitor C2 are respectively used as a first end and a second end of the second charge and discharge unit.

Optionally, the first switch unit in the embodiment of the present application includes a first MOSFET tube S1 as shown in fig. 3 or fig. 4, the first MOSFET tube S1 is generally of an N-channel enhancement type, in which a gate thereof is used as a control terminal of the first switch unit and is electrically connected to the second control terminal of the control circuit 201, a drain thereof is used as a first terminal of the first switch unit and is electrically connected to the first terminal of the first capacitor C1, and a source thereof is used as a second terminal of the first switch unit and is electrically connected to the first terminal of the first resistor R1.

Optionally, the first unidirectional conducting unit in the embodiment of the present application includes a first diode D1 as shown in fig. 2 or fig. 3, an anode of the first diode D1 is electrically connected to the auxiliary terminal e1 of the first power unit T1 as the first end of the first unidirectional conducting unit, and a cathode of the first diode D1 is connected to the first end of the first capacitor C1 as the second end of the first unidirectional conducting unit.

In an alternative embodiment, the second switch unit in the embodiment of the present application includes a second MOSFET transistor S2 as shown in fig. 3, and the second MOSFET transistor S2 is generally of an N-channel enhancement type, and the gate, the source and the drain are connected in the same manner as the MOSFET transistor S1.

In another alternative implementation, the second switch unit in the embodiment of the present application includes a second MOSFET transistor S2 as shown in fig. 4, where the second MOSFET transistor S2 is generally of an N-channel enhancement type, and when the gate of the second MOSFET transistor S2 is electrically connected to the second control terminal of the control circuit 201 as the control terminal of the second switch unit, the drain of the second MOSFET transistor S is electrically connected to the first terminal of the second capacitor C2 as the first terminal of the second switch unit, and the source of the second MOSFET transistor S1 is electrically connected to the first terminal of the first resistor R1 as the second terminal of the second switch unit.

Optionally, the second unidirectional conducting unit in the embodiment of the present application includes a second diode D2 as shown in fig. 3 and fig. 4, and the connection manner of the second diode D2 is the same as that of the first diode D1, which is not described herein again.

In an alternative implementation, the fault detection circuit of the power module provided in the embodiment of the present application may be further applied to a two-level power module as shown in fig. 3 or fig. 4, where the first power unit T1 includes a first switching device, and the second power unit T2 includes a second switching device.

The first switching device may be an IGBT as shown in fig. 3 or fig. 4 (hereinafter referred to as "first IGBT"), and the second switching device may be an IGBT as shown in fig. 3 or fig. 4 (hereinafter referred to as "second IGBT").

In another alternative implementation, the fault detection circuit of the power module provided in this embodiment of the present application may be further applied to a three-level power module as shown in fig. 5, where the first power unit T1 includes a first leg of the first three-level leg module, and the second power unit T2 includes a first leg of the second three-level leg module.

The first bridge arm may be a zero-level bridge arm in a three-level bridge arm module, or an upper half bridge arm or a lower half bridge arm of a non-zero-level bridge arm, both the zero-level bridge arm and the non-zero-level bridge arm may be composed of IGBTs as shown in fig. 5, in the three-level bridge arm module shown in fig. 5, a bridge arm located within a dotted frame and electrically connected to NP (Neutral Point bus) is the zero-level bridge arm, a bridge arm connected between DC + and DC-is the non-zero-level bridge arm, a portion above NP is the upper half bridge arm, and a portion below NP is the lower half bridge arm.

The specific principle of the fault detection circuit of the power module provided in the embodiment of the present application will be described in detail in the following method embodiments, which are not described herein again.

In the examples of fig. 2 to 4 in the embodiment of the present application, the structures of the power cells T1 to T4 are the same as those of fig. 1, and each power cell T1 to T4 includes two parts, i.e., an IGBT symbol and an inductance symbol (used to represent a stray inductance instead of an actual inductance device) in the drawing, and a dashed frame for marking the structural ranges of T1 to T4 is omitted in fig. 2 to 4 to avoid complexity of lines.

Based on the same inventive concept, the present application provides a method for detecting a fault of a power module, which can be applied to a control circuit 201 in a fault detection circuit of the power module provided by the present application, as shown in fig. 6, the method for detecting a fault includes:

s601, controlling the first switch unit in the first detection circuit 202 to turn off at a first time, and controlling the first power unit T1 in the power module to turn on at a second time no earlier than the first time, so that the charging current provided by the first power unit T1 charges the first charge/discharge unit in the first detection circuit 202 during the on transient of the first power unit T1.

The second time is not earlier than the first time, so that the first switch unit is turned on synchronously while the first power unit T1 is turned off, or the first switch unit is turned on in advance before the first power unit T1 is turned off, so that the detection circuit can detect the charging current of the first power unit T1 in time and perform charging.

Taking the fault detection circuit shown in fig. 3 as an example (fig. 4 and the same reason), in the off state of the first IGBT, the control circuit outputs a high level signal through the first control terminal to control the first IGBT to be turned on to enter the on-transient stage, and outputs a low level signal through the second control terminal to synchronously control the first MOSFET tube S1 to be turned off, when the first IGBT is in the on-transient stage, a potential difference is generated between the auxiliary emitter E1 and the emitter E1, and a charging current generated by the potential difference charges the first capacitor C1 through the first diode D1.

S602, collecting the charging voltage of the first charging and discharging unit, and determining a first voltage difference between the auxiliary terminal E1 and the power terminal E1 of the first power unit T1 during the turn-on transient of the first power unit T1 according to the charging voltage of the first charging and discharging unit.

Optionally, a real-time voltage difference between two ends of a first capacitor in the first charge-discharge unit in the switching transient process of the first power unit T1 is collected; when it is determined that the real-time voltage difference across the first capacitor reaches the stable value, it is determined that the first power unit T1 is in the on-steady state process, and the real-time voltage difference across the first capacitor is taken as the first voltage difference.

Taking the fault detection circuit shown in fig. 3 as an example (the same applies to fig. 4), the gate driver collects the real-time voltage difference between two ends of the first capacitor C1, and when it is determined that the real-time voltage difference reaches a stable value, it can be determined that the first IGBT is in a switching-on steady-state stage at this time, and the potential difference between the auxiliary emitter E1 and the emitter E1 is negligible, so that the stable value can reflect the potential difference between the auxiliary emitter E1 and the emitter E1 (i.e., the first voltage difference) in the switching-on transient process.

In case the capacitance value of the first capacitor C1 is sufficiently small, the voltage across it may reach

S603, it is determined whether the first power unit T1 has a fault according to the first voltage difference.

Alternatively, when the first voltage difference is detected to be lower than the preset voltage difference threshold value, it is determined that the first power unit T1 has a fault; when it is detected that the first voltage difference is not lower than the preset voltage difference threshold, it is determined that the first power unit T1 has no fault.

The voltage difference threshold value can be set according to empirical values or actual requirements, and different voltage difference threshold values can be set for different semiconductor power devices; the voltage difference threshold may be set to a lower value to improve the reliability of the first detection circuit 202.

Taking the fault detection circuit shown in fig. 3 as an example (fig. 4 and the same reason), when it is detected that the potential difference between the auxiliary emitter E1 and the emitter E1 is lower than the preset voltage difference threshold of the IGBT during the turn-on transient, it can be determined that the first IGBT is in an uncontrolled state (i.e., a fault state), otherwise, it can be determined that the first IGBT is in a controlled state (i.e., a normal operating state).

Optionally, as shown in fig. 7, the method for detecting a fault of a power module according to the embodiment of the present application further includes, on the basis of the steps S601 to S603, the following steps:

s604, the first switch unit is controlled to be turned on, and the first power unit T1 is controlled to be turned off, so that the first charge/discharge unit is discharged.

The on and off frequencies of the first power unit T1 are the same as the off and on frequencies of the first switching unit. When the first power unit T1 includes a first IGBT, the on and off frequency of the first IGBT is generally 3kHz (kilohertz), and one on and off period is about 300 μ s (microseconds).

Taking the fault detection circuit shown in fig. 3 as an example (fig. 4 and the same reason), in the on steady state process of the first IGBT, the control circuit 201 outputs a low level signal through the first control terminal thereof to drive the first IGBT to turn off, and outputs a high level signal through the second control terminal to synchronously control the conduction of the first MOSFET tube S1, the first capacitor C1 discharges through the first MOSFET tube S1 and the first resistor R1, and the voltage difference between the two ends of the first capacitor C1 gradually decreases to zero.

Optionally, as shown in fig. 8, the method for detecting a fault of a power module according to the embodiment of the present application further includes, on the basis of the steps S601 to S603, executing the following steps S801 to S803 for any one second power unit T2 of at least one second power unit T2 in the power module:

s801, controlling the second switch unit in the second detection circuit 203 to turn off at the third time, controlling the second power unit T2 in the power module to turn on at the fourth time no earlier than the third time, so that the charging current provided by the second power unit T2 charges the second charge/discharge unit in the second detection circuit 203 during the on transient of the second power unit T2.

The specific principle of step S801 is similar to that of step S601, and is not described herein again.

S802, collecting the charging voltage of the second charging and discharging unit, and determining a second voltage difference between the auxiliary terminal E2 and the power terminal E2 of the second power unit T2 in the turn-on transient process of the second power unit T2 according to the charging voltage of the second charging and discharging unit.

Optionally, acquiring a real-time voltage difference between two ends of a second capacitor in a second charge-discharge unit in the switching transient process of the second power unit T2; when it is determined that the real-time voltage difference across the second capacitor reaches the stable value, it is determined that the second power unit T2 is in the on-steady state process, and the real-time voltage difference across the second capacitor is taken as the second voltage difference.

The specific principle of step S802 is similar to that of step S602, and is not described herein again.

S803, it is determined whether the second power unit T2 has a fault according to the second voltage difference.

Optionally, when the second voltage difference is detected to be lower than the preset voltage difference threshold, determining that the second power unit T2 has a fault; when it is detected that the second voltage difference is not lower than the preset voltage difference threshold, it is determined that the second power unit T2 has no fault.

The specific principle of step S803 is similar to that of step S603, and is not described here again.

Optionally, as shown in fig. 9, the method for detecting a fault of a power module according to the embodiment of the present application further includes, on the basis of the steps S801 to S803, the following steps:

and S804, controlling the second switch unit to be turned on, and controlling the second power unit T2 to be turned off to discharge the second charge and discharge unit.

The on and off frequencies of the second power unit T2 are the same as the off and on frequencies of the second switching unit.

In the embodiment of the present application, the sequence of steps S601 to S604 and steps S801 to S804 is not limited, and steps S601 to S604 may be executed before or after steps S801 to S804, or may be executed synchronously with steps S801 to S804.

Optionally, before step S603 and step S803, the method for detecting a fault of a power module according to the embodiment of the present application further includes:

determining a difference between the first voltage difference and the second voltage difference; when the difference value of the first voltage difference and the second voltage difference is detected to be larger than a preset difference value threshold value, determining that the first power unit T1 or the second power unit T2 has a fault; and when the difference value between the first voltage difference and the second voltage difference is not larger than the preset difference value threshold value, determining that no fault exists in the first power unit T1 and the second power unit T2, and stopping fault detection in the current detection period.

Whether one of the two power units connected in parallel has a fault can be preliminarily judged by comparing the first voltage difference with the second voltage difference, and when the two power units connected in parallel have the fault, the steps S603 and S803 can be executed to further judge which one of the two power units has the fault, so that the two detection modes are combined to realize accurate fault detection.

The fault detection method for the power module provided by the embodiment of the application can be applied to one detection period, and for fault detection in a plurality of detection periods, the fault detection method for the power module provided by the embodiment of the application can be executed in each detection period; one detection period coincides with the period of turning on and off of the first power unit T1 or the second power unit T2 and also coincides with the period of the control pulse of the control circuit to the first power unit T1 or the second power unit T2. In a detection period, when the two power units are judged to have no fault preliminarily, the fault detection process of the current detection period can be stopped, and the fault detection process of the next detection period is started.

Taking the fault detection circuit shown in fig. 3 as an example, in the on-steady-state process of the second IGBT, the gate driver outputs a low-level signal through the first driving terminal of the gate driver to drive the second IGBT to turn off, and outputs a high-level signal through the second driving terminal to synchronously drive the second MOSFET tube S2 to turn on, the second capacitor C2 discharges through the second MOSFET tube S2 and the second resistor R2, and the voltage difference between the two ends of the second capacitor C2 gradually decreases to zero.

Taking the fault detection circuit shown in fig. 4 as an example, in the on-steady-state process of the second IGBT, the gate driver outputs a low-level signal through the first driving terminal of the gate driver to drive the second IGBT to turn off, and outputs a high-level signal through the second driving terminal to synchronously drive the second MOSFET tube S2 to turn on, the second capacitor C2 discharges through the second MOSFET tube S2 and the first resistor R1, and the voltage difference between the two ends of the second capacitor C2 gradually decreases to zero.

The method for detecting a fault of a power module according to the embodiment of the present application may further detect the power units T3 and T4 in fig. 3 or fig. 4, and the detection principle is the same as that of the power units T1 and T2, that is, T3 and T4 are respectively T1 and T2, the first detection circuit is connected between the auxiliary terminal E1 of T1 and the power terminal E1, and the second detection circuit 203 is connected between the auxiliary terminal E2 of T2 and the power terminal E2, and detection is performed by using the above detection method, which is not described herein again.

By applying the technical scheme provided by the embodiment of the application, at least the following beneficial effects can be realized:

1) by arranging a control circuit and a detection circuit (a first detection circuit or a second detection circuit) between an auxiliary terminal and a power terminal of a power unit (a first power unit or a second power unit), and controlling the on-off of a switch unit (the first switch unit or the second switch unit) in the power unit and the detection circuit, the rapid detection of the potential difference between the auxiliary terminal and the power terminal in the process of switching on a transient state can be realized, and whether the power unit is controlled or not can be rapidly judged based on the potential difference, so that the fault (such as thermal failure) of the power unit can be identified;

2) according to the embodiment of the application, the detection of the potential difference between the auxiliary terminal and the power terminal in the switching transient process can be realized by detecting the capacitor voltage in the steady-state switching-on process of the power unit, and the problem that the potential difference between the auxiliary terminal and the power terminal is inconvenient to detect due to short switching transient time is solved;

3) this application embodiment can adopt same control circuit to control power unit and switch element in the same detection circuitry, makes switching on or turn-off that two units correspond to make the electric capacity among the detection circuitry can respond to the charging current that power unit provided and charge under this charging current's effect, thereby realize opening the short-term test of the potential difference between transient state in-process auxiliary terminal and the power terminal, avoid delaying the detection.

4) The first detection circuit and the second detection circuit provided by the embodiment of the application are both composed of low-voltage components, and the voltage difference threshold value for detecting faults can be set to be a lower numerical value, so that the reliability of the first detection circuit and the second detection circuit is improved, and the cost is well controlled;

5) the first detection circuit and the second detection circuit provided by the embodiment of the application have small current and low voltage, can be integrated on the driving circuit board, and can further reduce the cost; the device that detection circuitry that this application embodiment adopted is less than current sampling and processing apparatus now, and the AC copper bar quantity that needs to set up is less, has reduced like the influence to the current sharing nature among the prior art, and this application embodiment adopts the fault detection based on voltage simultaneously, has avoidd the influence of current sharing nature to the fault detection reliability.

Those of skill in the art will appreciate that the various operations, methods, steps in the processes, acts, or solutions discussed in this application can be interchanged, modified, combined, or eliminated. Further, other steps, measures, or schemes in various operations, methods, or flows that have been discussed in this application can be alternated, altered, rearranged, broken down, combined, or deleted. Further, steps, measures, schemes in the prior art having various operations, methods, procedures disclosed in the present application may also be alternated, modified, rearranged, decomposed, combined, or deleted.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

It should be understood that, although the steps in the flowcharts of the figures are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and may be performed in other orders unless explicitly stated herein. Moreover, at least a portion of the steps in the flow chart of the figure may include multiple sub-steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed alternately or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

The foregoing is only a partial embodiment of the present application, and it should be noted that, for those skilled in the art, several modifications and decorations can be made without departing from the principle of the present application, and these modifications and decorations should also be regarded as the protection scope of the present application.

Claims

1. A method of fault detection for a power module, comprising:

controlling a first switch unit in a first detection circuit to be turned off at a first time, controlling a first power unit in the power module to be turned on at a second time which is not earlier than the first time, and enabling a charging current provided by the first power unit to charge a first charging and discharging unit in the first detection circuit in the process of the turning-on transient state of the first power unit;

collecting the charging voltage of the first charging and discharging unit, and determining a first voltage difference between an auxiliary terminal and a power terminal of the first power unit in the switching transient process of the first power unit according to the charging voltage of the first charging and discharging unit;

2. The method of claim 1, further comprising:

controlling the first switch unit to be switched on, and controlling the first power unit to be switched off, so that the first charge and discharge unit discharges;

the turn-on and turn-off frequency of the first power unit is the same as the turn-off and turn-on frequency of the first switching unit.

3. The method of claim 1, wherein the collecting the charging voltage of the first charging and discharging unit, and determining the first voltage difference between the auxiliary terminal and the power terminal of the first power unit during the turn-on transient of the first power unit according to the charging voltage of the first charging and discharging unit comprises:

acquiring a real-time voltage difference between two ends of a first capacitor in the first charge-discharge unit in the switching transient process of the first power unit;

and when the real-time voltage difference between the two ends of the first capacitor is determined to reach a stable value, determining that the first power unit is in a switching-on steady state process, and taking the real-time voltage difference between the two ends of the first capacitor as the first voltage difference.

4. The method according to any one of claims 1-3, wherein said determining whether the first power cell is faulty based on the first voltage difference comprises:

when the first voltage difference is detected to be lower than a preset voltage difference threshold value, determining that the first power unit has a fault;

and when the first voltage difference is detected to be not lower than the preset voltage difference threshold value, determining that the first power unit has no fault.

5. The method of claim 1, further comprising, for any of the at least one second power cell in the power module:

controlling a second switch unit in a second detection circuit to be turned off at a third moment, and controlling a second power unit in the power module to be turned on at a fourth moment which is not earlier than the third moment, so that a second charging and discharging unit in the second detection circuit is charged by a charging current provided by the second power unit in the on-transient process of the second power unit;

collecting the charging voltage of the second charging and discharging unit, and determining a second voltage difference between an auxiliary terminal and a power terminal of the second power unit in the switching transient process of the second power unit according to the charging voltage of the second charging and discharging unit;

and judging whether the second power unit has a fault according to the second voltage difference.

6. The method of claim 5, wherein before determining whether the first power cell is faulty based on the first voltage difference and determining whether the second power cell is faulty based on the second voltage difference, further comprising:

determining a difference between the first voltage difference and the second voltage difference;

when detecting that the difference value between the first voltage difference and the second voltage difference is greater than a preset difference value threshold value, determining that the first power unit or the second power unit has a fault;

and when detecting that the difference value between the first voltage difference and the second voltage difference is not greater than the preset difference value threshold value, determining that no fault exists in the first power unit and the second power unit, and stopping fault detection in the current detection period.

7. The method of claim 5, further comprising:

controlling the second switch unit to be switched on, and controlling the second power unit to be switched off to discharge the second charge and discharge unit;

the on and off frequency of the second power unit is the same as the off and on frequency of the second switching unit.

8. The method of claim 5, wherein the collecting the charging voltage of the second charging/discharging unit and determining a second voltage difference between the auxiliary terminal and the power terminal of the second power unit during the turn-on transient of the second power unit according to the charging voltage of the second charging/discharging unit comprises:

acquiring a real-time voltage difference between two ends of a second capacitor in the second charge-discharge unit in the switching transient process of the second power unit;

and when the real-time voltage difference between the two ends of the second capacitor is determined to reach a stable value, determining that the second power unit is in a switching-on steady state process, and taking the real-time voltage difference between the two ends of the second capacitor as the second voltage difference.

9. The method according to any one of claims 5-8, wherein the determining whether the second power unit has a fault according to the second voltage difference comprises:

when the second voltage difference is detected to be lower than a preset voltage difference threshold value, determining that the second power unit has a fault;

and when the second voltage difference is detected to be not lower than the preset voltage difference threshold value, determining that no fault exists in the second power unit.

10. A fault detection circuit of a power module is characterized by comprising a control circuit and a first detection circuit;

the third end of the first charge and discharge unit is electrically connected with the power terminal of the first power unit;

a first end and a second end of the first unidirectional conduction unit are respectively and electrically connected with an auxiliary terminal of the first power unit and a first end of the first charge-discharge unit;

the control circuit is configured to: controlling a first switch unit in a first detection circuit to be turned off at a first time, controlling a first power unit in the power module to be turned on at a second time which is not earlier than the first time, and enabling a charging current provided by the first power unit to charge a first charging and discharging unit in the first detection circuit in the process of the turning-on transient state of the first power unit; collecting the charging voltage of the first charging and discharging unit, and determining a first voltage difference between an auxiliary terminal and a power terminal of the first power unit in the switching transient process of the first power unit according to the charging voltage of the first charging and discharging unit; and judging whether the first power unit has a fault according to the first voltage difference.

11. The circuit of claim 10, further comprising at least one second detection circuit; at least one second power unit in the power module is connected with the first power unit in parallel, and the control end of each second power unit is electrically connected with the first control end of the control circuit;

the second detection circuit includes: the second switch unit, the second charge and discharge unit and the second unidirectional conduction unit;

the control end of the second switch unit is electrically connected with the second control end of the control circuit, and the first end and the second end of the second switch unit are respectively and electrically connected with the first end and the second end of the second charge and discharge unit;

the third end of the second charging and discharging unit is electrically connected with the power terminal of the second power unit;

a first end and a second end of the second unidirectional conducting unit are respectively and electrically connected with an auxiliary terminal of the second power unit and a first end of the second charging and discharging unit;

the control circuit is further configured to perform the following operations for any one of the at least one second power unit:

controlling a second switch unit in a second detection circuit to be turned off at a third moment, and controlling a second power unit in the power module to be turned on at a fourth moment which is not earlier than the third moment, so that a second charging and discharging unit in the second detection circuit is charged by a charging current provided by the second power unit in the on-transient process of the second power unit; collecting the charging voltage of the second charging and discharging unit, and determining a second voltage difference between an auxiliary terminal and a power terminal of the second power unit in the switching transient process of the second power unit according to the charging voltage of the second charging and discharging unit; and judging whether the second power unit has a fault according to the second voltage difference.

12. The circuit of claim 11, wherein the first charge and discharge unit comprises a first capacitor and a first resistor, and the second charge and discharge unit comprises a second capacitor and a second resistor;

a first end of the first capacitor is used as a first end of the first charge-discharge unit, a first end of the first resistor is used as a second end of the first charge-discharge unit, and a second end of the first capacitor and a second end of the first resistor are both used as third ends of the first charge-discharge unit;

the first end of the second capacitor is used as the first end of the second charge and discharge unit, the first end of the second resistor is used as the second end of the second charge and discharge unit, and the second end of the second capacitor and the second end of the second resistor are both used as the third end of the second charge and discharge unit.

13. The circuit of claim 10, further comprising at least one second detection circuit; at least one second power unit in the power module is connected with the first power unit in parallel, and the control end of each second power unit is electrically connected with the first control end of the control circuit;

the control end of the second switch unit is electrically connected with the first control end of the control circuit, and the first end and the second end of the second switch unit are respectively and electrically connected with the first end of the second charge and discharge unit and the second end of the first charge and discharge unit;

the second ends of the second charge and discharge units are respectively and electrically connected with the power terminals of the second power unit;

14. The circuit of claim 13, wherein the first charge and discharge unit comprises a first capacitor and a first resistor, and the second charge and discharge unit comprises a second capacitor;

and two ends of the second capacitor are respectively used as a first end and a second end of the second charge-discharge unit.

15. The circuit of claim 11 or 13, wherein the first power cell comprises a first switching device and the second power cell comprises a second switching device;

or the first power unit comprises a first bridge arm in a first three-level bridge arm module, and the second power unit comprises a first bridge arm in a second three-level bridge arm module.