A detection device and a detection method of a power conversion unit

Abstract

The application discloses a detection device and method of a power conversion unit. The detection device comprises a heating current source, a measuring current source, a switch tube control unit, a conduction voltage drop measuring unit and a signal processing unit. The signal processing unit controls the switch tube control unit to turn on each switch tube in the measured bridge arm, so that the heating current is input to each switch tube for a preset time period. The switch tube control unit is controlled to turn on each switch tube in turn. The measuring current is input and the conduction voltage drop is collected during the conduction of each switch tube. Whether the current sharing characteristic of the measured power conversion unit meets the standard is determined based on the conduction voltage drops corresponding to all the switch tubes. The application can realize offline detection of the power conversion unit, and can detect at one time that the current sharing characteristic of the power conversion unit does not meet the standard due to abnormal parameters such as welding resistance and stray inductance of each parallel branch.

Description

Technical Field

[0001] This invention relates to the field of power conversion unit technology, and more specifically, to a detection device and detection method for power conversion units. Background Technology

[0002] Current power conversion units are composed of discrete components connected in parallel. Due to their significant advantages such as flexible specifications and stable supply chain, power conversion units are widely used in fields such as electric motor drives for new energy vehicles. For example, power conversion units are included in common motor controller systems.

[0003] In a power conversion unit, each bridge arm consists of n switching transistors (i.e., switching transistors 1 to n) connected in parallel. Due to differences in the performance parameters of the parallel switching transistors, as well as the welding resistance, stray inductance, and other parameters of each parallel branch, uneven current flows through each switching transistor. If this uneven current flow is severe, it will lead to uneven heating of the parallel switching transistors, thereby affecting the reliability of the entire power conversion unit and even the product.

[0004] Therefore, how to test whether the current sharing characteristics of the power conversion unit meet the standards has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention discloses a detection device and detection method for a power conversion unit, so as to detect whether the current sharing characteristics of the power conversion unit meet the standard.

[0006] A detection device for a power conversion unit, comprising:

[0007] A heating current source, the output terminal of which is connected to the bridge arm input terminal of the bridge arm under test in the power conversion unit under test, and the input terminal of which is connected to the bridge arm output terminal of the bridge arm under test, are used to provide heating current to the power conversion unit under test.

[0008] A measuring current source is provided, the output terminal of which is connected to the input terminal of the bridge arm, and the output terminal of which is connected to the output terminal of the bridge arm. This is used so that after the detection device provides the heating current to the power conversion unit under test, it provides a measuring current to the power conversion unit under test, wherein the measuring current is less than the heating current.

[0009] A switching transistor control unit is connected to the control terminal of each switching transistor in the bridge arm under test, and is used to control the switching transistors to conduct when the detection device provides the heating current and the measuring current.

[0010] The on-state voltage drop measurement unit is connected to the input and output terminals of each of the switching transistors in the bridge arm under test, and is used to measure the on-state voltage drop of the power conversion unit under test when the measuring current flows through the power conversion unit under test;

[0011] The signal processing unit is connected to the control terminal of the heating current source, the control terminal of the measuring current source, the switching transistor control unit, and the on-state voltage drop measurement unit, respectively. It controls the switching transistor control unit to turn on each of the switching transistors in the bridge arm under test, so that the heating current is input to each of the switching transistors for a preset time period. It controls the switching transistor control unit to sequentially turn on each of the switching transistors. During the conduction period of each switching transistor, it controls the measuring current source to input a measuring current to the target switching transistor, and simultaneously controls the on-state voltage drop measurement unit to collect the on-state voltage drop of the target switching transistor. Based on the magnitude of the on-state voltage drops corresponding to all the switching transistors, it determines whether the current sharing characteristics of the power conversion unit transistor under test meet the standard.

[0012] Optionally, when the bridge arm under test is the upper bridge arm, the bus connected to the input end of the bridge arm is used as the positive bus of the power conversion unit under test, and the output end of the bridge arm is used as the AC output end of the power conversion unit under test.

[0013] When the bridge arm under test is the lower bridge arm, the bus connected to the input end of the bridge arm serves as the AC output end of the power conversion unit under test, and the output end of the bridge arm serves as the negative bus of the power conversion unit under test.

[0014] Optionally, the switching control unit includes: the same number of controllable voltage sources as each of the switching transistors in the bridge arm under test;

[0015] The positive terminal of each controllable voltage source serves as a control pin of the switching control unit, used to connect to the control terminal of the target switching transistor, and the negative terminal is used to connect to the output terminal of the target switching transistor. The target switching transistor is any one of the switching transistors in the bridge arm under test, and different controllable voltage sources are connected to different target switching transistors.

[0016] Optionally, the on-state voltage drop measurement unit includes: a voltmeter;

[0017] The first measurement pin of the voltmeter is used to connect to the input terminal of each of the switching transistors in the bridge arm under test, and the second measurement pin of the voltmeter is used to connect to the output terminal of each of the switching transistors in the bridge arm under test.

[0018] Optionally, both the heating current source and the measuring current source are direct current sources.

[0019] A detection method for a power conversion unit, applied to the signal processing unit in the detection device described above, the detection method comprising:

[0020] The control unit turns on each switch in the bridge arm under test, so that the heating current is input to each switch for a preset time period.

[0021] The control unit controls the switching transistors to sequentially turn on each of the switching transistors.

[0022] During each of the switching transistors being turned on, the measurement current source is controlled to input a measurement current into the target switching transistor that is turned on, and the on-state voltage drop measurement unit is controlled to collect the on-state voltage drop of the target switching transistor.

[0023] The current sharing characteristics of the power conversion unit transistor under test are determined based on the on-state voltage drop of all the switching transistors.

[0024] Optionally, determining whether the current sharing characteristics of the power conversion unit transistor under test meet the standard based on the on-state voltage drop of all the switching transistors includes:

[0025] Calculate the average on-state voltage drop for all the aforementioned switching transistors to obtain the average on-state voltage drop.

[0026] Calculate the first voltage drop difference between each of the stated on-state voltage drops and the average of the stated on-state voltage drops;

[0027] Determine whether any of the first voltage drop differences exceeds a first preset threshold value;

[0028] If so, then the current sharing characteristics of the power conversion unit under test are determined to be substandard.

[0029] If not, then the current sharing characteristics of the power conversion unit under test are deemed to meet the standard.

[0030] Optionally, determining whether the current sharing characteristics of the power conversion unit transistor under test meet the standard based on the on-state voltage drop of all the switching transistors includes:

[0031] Calculate the second voltage drop difference between any two of the on-state voltage drops corresponding to all the switching transistors;

[0032] Determine whether any of the second pressure drop differences exceeds a second target pressure drop difference value among all the second pressure drop difference values;

[0033] If so, then the current sharing characteristics of the power conversion unit under test are determined to be substandard.

[0034] If not, then the current sharing characteristics of the power conversion unit under test are deemed to meet the standard.

[0035] Optionally, the magnitude of the heating current is related to the conduction current capability of the switching transistor.

[0036] As can be seen from the above technical solution, this invention discloses a detection device and method for a power conversion unit. The detection device includes: a heating current source, a measuring current source, a switching transistor control unit, a conduction voltage drop measurement unit, and a signal processing unit. The signal processing unit controls the switching transistor control unit to turn on each switching transistor in the bridge arm under test, so that the heating current is input to each switching transistor for a preset time period. Then, the switching transistor control unit is controlled to turn on each switching transistor sequentially. During the conduction period of each switching transistor, the measuring current source is controlled to input the measuring current to the target switching transistor, and the conduction voltage drop measurement unit is controlled to collect the conduction voltage drop of the target switching transistor. Based on the magnitude of the conduction voltage drop corresponding to all switching transistors, it is determined whether the current sharing characteristics of the power conversion unit under test meet the standard. This invention can realize the offline detection of power conversion units and can detect in one go the situation where the current sharing characteristics of the power conversion unit are not up to standard due to abnormal or unbalanced parameters such as welding resistance and stray inductance of parallel branches. The whole process is highly automated and short in time. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the published drawings without creative effort.

[0038] Figure 1 A system architecture diagram of a typical motor controller disclosed in the prior art;

[0039] Figure 2 This is a schematic diagram of a parallel power conversion unit disclosed in the prior art;

[0040] Figure 3 This is a schematic diagram of a detection device for a power conversion unit disclosed in an embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram showing the connection relationship between a power conversion unit detection device and a power conversion unit under test, as disclosed in an embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram illustrating the detection principle of a power conversion unit detection device disclosed in an embodiment of the present invention;

[0043] Figure 6 This is a flowchart of a power conversion unit detection method disclosed in an embodiment of the present invention. Detailed Implementation

[0044] To facilitate understanding of the internal structure of the power conversion unit, the following explanation uses the power conversion unit in a motor controller as an example:

[0045] See Figure 1 The existing technology discloses a typical system architecture diagram of a motor controller. The motor controller consists of three phases and six bridge arms. The upper and lower bridge arms of each phase form a parallel power conversion unit (see details). Figure 2 Therefore, the motor controller has three power conversion units that respectively provide U-phase AC output, V-phase AC output and W-phase AC output to the motor.

[0046] See Figure 2 A schematic diagram of a parallel power conversion unit disclosed in the prior art is shown. The power conversion unit includes an upper bridge arm and a lower bridge arm, each bridge arm consisting of n parallel-connected switching transistors, designated as switch 1 to switch n. Due to differences in the performance parameters of the parallel-connected switching transistors, as well as the welding resistance and stray inductance of each branch, uneven current flow occurs through each switching transistor. If the uneven current flow is severe, it will lead to uneven heating of the parallel-connected switching transistors, thereby affecting the reliability of the entire power conversion unit and even the product. Based on this, the present invention provides a detection method for a power conversion unit to detect uneven current flow among the switching transistors in the power conversion unit.

[0047] 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.

[0048] This invention discloses a testing device and method for a power conversion unit. The testing device includes a heating current source, a measuring current source, a switching transistor control unit, a forward voltage drop measurement unit, and a signal processing unit. The signal processing unit controls the switching transistor control unit to turn on each switching transistor in the bridge arm under test, so that the heating current is input to each switching transistor for a preset time period. Then, the switching transistor control unit sequentially turns on each switching transistor. During the conduction period of each switching transistor, the measuring current source is controlled to input the measuring current to the target switching transistor, and the forward voltage drop measurement unit is controlled to collect the forward voltage drop of the target switching transistor. Based on the magnitude of the forward voltage drop of all switching transistors, it is determined whether the current sharing characteristics of the power conversion unit under test meet the standard. This invention can realize offline testing of power conversion units and can detect in one go the situation where the current sharing characteristics of the power conversion unit are not up to standard due to abnormal or unbalanced parameters such as welding resistance and stray inductance of parallel branches. The whole process is highly automated and short in time.

[0049] See Figure 3 The present invention discloses a schematic diagram of a detection device for a power conversion unit. The detection device includes: a heating current source 11, a measuring current source 12, a switching transistor control unit 13, a conduction voltage drop measurement unit 14, and a signal processing unit 15.

[0050] The output terminal of the heating current source 11 is connected to the input terminal of the bridge arm of the bridge arm under test in the power conversion unit under test 10, and the input terminal of the heating current source 11 is connected to the output terminal of the bridge arm under test, for providing heating current to the power conversion unit under test 10.

[0051] The heating current can be the current when the power conversion unit is operating normally.

[0052] It should be noted that the bridge arm under test in the power conversion unit 10 includes an upper bridge arm and a lower bridge arm. When the bridge arm under test is the upper bridge arm, the bus connected to the input terminal of the bridge arm serves as the positive bus of the power conversion unit under test, and the output terminal of the bridge arm serves as the AC output terminal of the power conversion unit under test. When the bridge arm under test is the lower bridge arm, the bus connected to the input terminal of the bridge arm serves as the AC output terminal of the power conversion unit under test, and the output terminal of the bridge arm serves as the negative bus of the power conversion unit under test.

[0053] Taking the upper bridge arm as an example, the connection relationship between the detection device of the power conversion unit and the power conversion unit 10 under test is as follows: Figure 4 As shown, the output terminal of the heating current source 11 is connected to the positive bus of the power conversion unit 10 under test, and the input terminal of the heating current source 11 is connected to the AC output terminal of the power conversion unit 10 under test. The heating current source 11 is used to input heating current to each switching transistor in the bridge arm under test.

[0054] The magnitude of the heating current is related to the conduction current capability of the switching transistor.

[0055] The output terminal of the measuring current source 12 is connected to the input terminal of the bridge arm, and the output terminal of the measuring current source 12 is connected to the output terminal of the bridge arm. This is used to detect that after the detection device provides the heating current to the power conversion unit 10 under test, it provides a measuring current to the power conversion unit 10 under test, wherein the measuring current is less than the heating current.

[0056] Taking the upper bridge arm as an example, the output terminal of the measuring current source 12 is connected to the positive bus of the power conversion unit 10 under test, and the input terminal of the measuring current source 12 is connected to the AC output terminal of the power conversion unit 10 under test. The measuring current source 12 is used to input the measuring current to each switch in the bridge arm under test.

[0057] Among these requirements, the measuring current is less than the heating current. The value of the measuring current needs to be such that a single switching transistor can be turned on in order to measure the on-state voltage drop of the switching transistor, and the temperature of the switching transistor should not rise too much.

[0058] The switching control unit 13 is connected to the control terminal of each switching transistor in the bridge arm under test, and is used to control the switching transistor to conduct when the detection device provides the heating current and the measuring current.

[0059] In practical applications, the switching transistor can be a bipolar transistor or a MOSFET.

[0060] When the switching transistor is a bipolar junction transistor (BJT), the control terminal of the switching transistor is the base, the input terminal of the switching transistor is the collector, and the output terminal of the switching transistor is the emitter.

[0061] When the switching transistor is a MOSFET, the control terminal of the MOSFET is the gate, the input terminal of the switching transistor is the drain, and the output terminal of the switching transistor is the source.

[0062] The on-state voltage drop measurement unit 14 is connected to the input and output terminals of each of the switching transistors in the bridge arm under test, and is used to measure the on-state voltage drop of the power conversion unit 10 under test when the measuring current flows through it.

[0063] The signal processing unit 15 is connected to the heating current source 11, the measuring current source 12, the switching control unit 13, and the on-state voltage drop measurement unit 14, respectively. The signal processing unit 15 is used to control the switching control unit 13 to turn on each of the switching transistors in the bridge arm under test, so that the heating current is input to each switching transistor for a preset time period. The signal processing unit 15 controls the switching control unit 13 to turn on each of the switching transistors in sequence. During the conduction period of each switching transistor, the signal processing unit 15 controls the measuring current source 12 to input the measuring current to the target switching transistor. At the same time, the signal processing unit 15 controls the on-state voltage drop measurement unit 14 to collect the on-state voltage drop of the target switching transistor. Based on the magnitude of the on-state voltage drop of all the switching transistors, the signal processing unit 15 determines whether the current sharing characteristics of the power conversion unit 10 under test meet the standard.

[0064] The value of the preset time period is determined based on the junction temperature of the switching transistor reaching a preset temperature threshold. The value of the preset temperature threshold depends on actual needs, and this invention does not limit it.

[0065] Specifically, with Figure 4 Taking the connection relationship between the detection device of the power conversion unit shown and the power conversion unit under test 10 as an example, assuming that the bridge arm under test is the upper bridge arm, the bridge arm under test includes: n switching transistors, namely switching transistor 1 to switching transistor n, and the detection principle is as follows. Figure 5 As shown, the entire detection process is as follows:

[0066] At time t0, detection begins. Signal processing unit 15 sends a switching control signal to switching control unit 13, causing switching control unit 13 to ensure that the gate voltages of all n switching transistors (switching transistor 1 to switching transistor n) in the upper bridge arm are significantly higher than their gate turn-on thresholds, thus turning all switching transistors 1 to n on. Signal processing unit 15 controls heating current source 11 to output heating current, which flows through switching transistors 1 to n to heat them, causing their junction temperatures to rise rapidly. Due to device characteristics, loop impedance, and other imbalances, the currents from switching transistors 1 to n will be unbalanced, resulting in junction temperature deviations.

[0067] At time t1, when the junction temperature of each switching transistor reaches the preset temperature threshold, allowing for relatively accurate measurement of the junction temperature, the signal processing unit 15 controls the heating current source 11 to stop outputting the heating current and enters the measurement stage.

[0068] During the measurement phase, the signal processing unit 15 controls the gate voltage of switches 1 to n to be higher than the gate turn-on threshold of the switches through the switch control unit 13, so that switches 1 to n are in the on state. When switches 1 to n are on, the measurement current source 12 is controlled to input the measurement current into the on switches among the n switches, and the on-state voltage drop of switches 1 to n is measured and recorded respectively.

[0069] Specifically, at time t2, the switch control unit 13 controls the gate level of switch 1 to be high, so that switch 1 is in the conducting state and other switches are in the off state. At time t2, the measuring current is output through the measuring current source 12. At this time, the measuring current flows through switch 1. The on-state voltage drop Vce1 of the test switch 1 is recorded by the on-state voltage drop measuring unit 14.

[0070] At time t3, the measurement of switch 1 ends, the current source 12 stops outputting the measurement current, and the switch control unit 13 controls switch 1 to disconnect.

[0071] At time t4, the switch control unit 13 controls the gate level of switch 2 to be high, so that switch 2 is in the conducting state and other switches are in the off state. At time t4, the measuring current source 12 outputs the measuring current. At this time, the measuring current flows through switch 2. The on-state voltage drop measurement unit 14 records the on-state voltage drop Vce2 of switch 2.

[0072] At time t5, the measurement of switch 2 ends, the current source 12 stops outputting the measurement current, and the switch control unit 13 controls switch 2 to disconnect.

[0073] Repeat the above process until the measurement of the on-state voltage Vcen of switch n at time tn+1 is completed.

[0074] It should be noted that since the junction temperature of each switching transistor will slowly decrease after the heating current stops, the measurement phase must be completed quickly to effectively reduce the impact of the natural decrease in the junction temperature of the switching transistor on the measurement results.

[0075] Finally, based on the on-state voltage drop Vce1, on-state voltage drop Vce2, ..., on-state voltage drop Vcen, it is determined whether the current distribution of each switch in the power conversion unit 10 under test is uneven.

[0076] In practical applications, the on-state voltage drops of the n switching transistors can be compared. If the difference in on-state voltage drops is large, it indicates that the current sharing characteristics of the power conversion unit 10 under test are not up to standard; conversely, if the difference in on-state voltage drops is small, it indicates that the current sharing characteristics of the power conversion unit 10 under test are up to standard.

[0077] In summary, this invention discloses a testing device for a power conversion unit. The testing device includes: a heating current source 11, a measuring current source 12, a switching transistor control unit 13, a conduction voltage drop measurement unit 14, and a signal processing unit 15. The signal processing unit 15 controls the switching transistor control unit 13 to conduct each switching transistor in the bridge arm under test, so that the heating current is input to each switching transistor for a preset time period. Then, the switching transistor control unit 13 is controlled to conduct each switching transistor sequentially. During the conduction period of each switching transistor, the measuring current source 12 is controlled to input a measuring current to the target switching transistor, and the conduction voltage drop measurement unit 14 is controlled to collect the conduction voltage drop of the target switching transistor. Based on the magnitude of the conduction voltage drop corresponding to all switching transistors, it is determined whether the current sharing characteristics of the power conversion unit under test 10 meet the standard. This invention can realize the offline testing of power conversion units, and can detect in one go the situation where the current sharing characteristics of the power conversion unit are not up to standard due to abnormal or unbalanced parameters such as welding resistance and stray inductance of parallel branches. The whole process is highly automated and short in time.

[0078] Preferably, both the heating current source 11 and the measuring current source 12 can be DC current sources.

[0079] To further optimize the above embodiments, see [link to relevant documentation]. Figure 3 and Figure 4 The switching control unit 13 may include a controllable voltage source.

[0080] The number of controllable voltage sources is the same as the number of individual switching transistors in the bridge arm under test. For example, if the bridge arm under test contains n switching transistors, then the number of controllable voltage sources is also n. Compared to having only one controllable voltage source connected to all switching transistors, this invention allows each switching transistor to have a unique corresponding controllable voltage source, so that the number of switching transistors turned on can be determined as one or more as needed.

[0081] The positive terminal of each controllable voltage source serves as a control pin of the switch control unit 13, used to connect to the control terminal of the target switch, and the negative terminal is used to connect to the output terminal of the target switch. The target switch is any one of the switches in the bridge arm under test, and different controllable voltage sources are connected to different target switches.

[0082] Each controllable voltage source controls the on and off of a switching transistor. The controllable voltage source controls the switching transistor's conduction by outputting a gate voltage higher than the switching transistor's gate operator turn-on threshold.

[0083] To further optimize the above embodiments, see [link to relevant documentation]. Figure 3 and Figure 4 The on-state voltage drop measurement unit 14 may include: a voltmeter;

[0084] The first measurement pin of the voltmeter is used to connect to the input terminal of each of the switching transistors in the bridge arm under test, and the second measurement pin of the voltmeter is used to connect to the output terminal of each of the switching transistors in the bridge arm under test.

[0085] The voltmeter is used to collect the on-state voltage drop of the switching transistor when it is turned on and when a measurement current is input into the switching transistor, and upload the on-state voltage drop to the signal processing unit 15.

[0086] Corresponding to the above-described device embodiments, the present invention also discloses a method for detecting a power conversion unit.

[0087] See Figure 6 The present invention discloses a flowchart of a detection method for a power conversion unit. This method is applied to a signal processing unit in a detection device, and the detection method includes:

[0088] Step S101: The control switch tube control unit turns on each switch tube in the bridge arm under test, so that the heating current is input to each switch tube for a preset time period.

[0089] Specifically, the signal processing unit sends a switching control signal to the switching control unit, so that the switching control unit controls the gate voltage of n switching transistors (switching transistor 1 to switching transistor n) in the upper bridge arm to be much higher than the gate turn-on threshold of the switching transistors, so that all switching transistors 1 to n are in the turn-on state.

[0090] Heating current passes through switching transistors 1 to 2 to heat the n switching transistors, causing the junction temperature of switching transistors 1 to 2 to 2 to rise rapidly.

[0091] The magnitude of the heating current is related to the conduction current capability of the switching transistor.

[0092] In practical applications, when the detection device also includes a heating current source, the signal processing unit can control the heating current source to input heating current to each of the switching transistors after each of the switching transistors is turned on.

[0093] Step S102: Control the switching transistor control unit to turn on each of the switching transistors in sequence.

[0094] Step S103: During each of the turn-on periods of the switch, control the measurement current source to input the measurement current into the turn-on target switch, and simultaneously control the on-state voltage drop measurement unit to collect the on-state voltage drop of the target switch.

[0095] During the measurement phase, the signal processing unit 15 controls the gate voltage of switches 1 to n to be higher than the gate turn-on threshold of the switches through the switch control unit 13, so that switches 1 to n are in the on state. When switches 1 to n are on, the measurement current source 12 is controlled to input the measurement current into the on switches among the n switches, and the on-state voltage drop of switches 1 to n is measured and recorded respectively.

[0096] Step S104: Determine whether the current sharing characteristics of the power conversion unit transistor under test meet the standard based on the on-state voltage drop of all the switching transistors.

[0097] In practical applications, the on-state voltage drops of the n switching transistors can be compared. If the difference in on-state voltage drops is large, it indicates that the current sharing characteristics of the power conversion unit 10 under test are not up to standard; conversely, if the difference in on-state voltage drops is small, it indicates that the current sharing characteristics of the power conversion unit 10 under test are up to standard.

[0098] In summary, this invention discloses a method for detecting a power conversion unit. A signal processing unit controls a switching control unit to turn on each switching transistor in the bridge arm under test, allowing heating current to be input to each transistor for a preset time period. Then, the switching control unit sequentially turns on each transistor. During the conduction period of each transistor, a measurement current source is controlled to input a measurement current to the target transistor. Simultaneously, a conduction voltage drop measurement unit is controlled to collect the conduction voltage drop of the target transistor. Based on the magnitude of the conduction voltage drops corresponding to all transistors, the current sharing characteristics of the power conversion unit under test are determined to be up to standard. This invention can achieve offline testing of power conversion units, and can detect in one go situations where the current sharing characteristics of the power conversion unit are not up to standard due to abnormal or unbalanced parameters such as welding resistance and stray inductance in parallel branches. The entire process is highly automated and time-saving.

[0099] To further optimize the above embodiments, step S104 may specifically include:

[0100] Calculate the average on-state voltage drop for all the aforementioned switching transistors to obtain the average on-state voltage drop.

[0101] Calculate the first voltage drop difference between each of the stated on-state voltage drops and the average of the stated on-state voltage drops;

[0102] Determine whether any of the first voltage drop differences exceeds a first preset threshold for a first target voltage drop difference;

[0103] If so, then the current sharing characteristics of the power conversion unit under test are determined to be substandard.

[0104] If not, then the current sharing characteristics of the power conversion unit under test are deemed to meet the standard.

[0105] It should be noted that the substandard current sharing characteristics of the power conversion unit under test are mainly due to differences in the performance parameters of each switching transistor, as well as the welding resistance and stray inductance of each parallel branch.

[0106] The value of the first difference threshold is determined according to actual needs, and this invention does not limit it.

[0107] To further optimize the above embodiments, step S104 may specifically include:

[0108] Calculate the second voltage drop difference between any two of the on-state voltage drops corresponding to all the switching transistors;

[0109] Determine whether any of the second pressure drop differences exceeds a second target pressure drop difference value among all the second pressure drop difference values;

[0110] If so, then the current sharing characteristics of the power conversion unit under test are determined to be substandard.

[0111] If not, then the current sharing characteristics of the power conversion unit are deemed to meet the standard.

[0112] The value of the second difference threshold is determined according to actual needs, and is not limited in this invention.

[0113] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0114] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0115] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A detection device for a power conversion unit, characterized in that, include: A heating current source, the output terminal of which is connected to the bridge arm input terminal of the bridge arm under test in the power conversion unit under test, and the input terminal of which is connected to the bridge arm output terminal of the bridge arm under test, are used to provide heating current to the power conversion unit under test. A measuring current source is provided, the output terminal of which is connected to the input terminal of the bridge arm, and the output terminal of which is connected to the output terminal of the bridge arm. This is used so that after the detection device provides the heating current to the power conversion unit under test, it provides a measuring current to the power conversion unit under test, wherein the measuring current is less than the heating current. A switching transistor control unit is connected to the control terminal of each switching transistor in the bridge arm under test, and is used to control the switching transistors to conduct when the detection device provides the heating current and the measuring current. The on-state voltage drop measurement unit is connected to the input and output terminals of each of the switching transistors in the bridge arm under test, and is used to measure the on-state voltage drop of the power conversion unit under test when the measuring current flows through the power conversion unit under test; The signal processing unit is connected to the control terminal of the heating current source, the control terminal of the measuring current source, the switching transistor control unit, and the on-state voltage drop measurement unit, respectively. It controls the switching transistor control unit to turn on each of the switching transistors in the bridge arm under test, so that the heating current is input to each of the switching transistors for a preset time period. It controls the switching transistor control unit to sequentially turn on each of the switching transistors. During the conduction period of each switching transistor, it controls the measuring current source to input a measuring current to the target switching transistor, and simultaneously controls the on-state voltage drop measurement unit to collect the on-state voltage drop of the target switching transistor. Based on the magnitude of the on-state voltage drops corresponding to all the switching transistors, it determines whether the current sharing characteristics of the power conversion unit transistor under test meet the standard.

2. The detection device according to claim 1, characterized in that, When the bridge arm under test is the upper bridge arm, the bus connected to the input end of the bridge arm serves as the positive bus of the power conversion unit under test, and the output end of the bridge arm serves as the AC output end of the power conversion unit under test. When the bridge arm under test is the lower bridge arm, the bus connected to the input end of the bridge arm serves as the AC output end of the power conversion unit under test, and the output end of the bridge arm serves as the negative bus of the power conversion unit under test.

3. The detection device according to claim 1, characterized in that, The switching control unit includes: the same number of controllable voltage sources as each of the switching transistors in the bridge arm under test; The positive terminal of each controllable voltage source serves as a control pin of the switching control unit, used to connect to the control terminal of the target switching transistor, and the negative terminal is used to connect to the output terminal of the target switching transistor. The target switching transistor is any one of the switching transistors in the bridge arm under test, and different controllable voltage sources are connected to different target switching transistors.

4. The detection device according to claim 1, characterized in that, The on-state voltage drop measurement unit includes: a voltmeter; The first measurement pin of the voltmeter is used to connect to the input terminal of each of the switching transistors in the bridge arm under test, and the second measurement pin of the voltmeter is used to connect to the output terminal of each of the switching transistors in the bridge arm under test.

5. The detection device according to claim 1, characterized in that, Both the heating current source and the measuring current source are direct current sources.

6. A method for detecting a power conversion unit, characterized in that, The signal processing unit applied in the detection device according to any one of claims 1 to 5, the detection method comprising: The control unit turns on each switch in the bridge arm under test, so that the heating current is input to each switch for a preset time period. The control unit controls the switching transistors to sequentially turn on each of the switching transistors. During each of the switching transistors being turned on, the measurement current source is controlled to input a measurement current into the target switching transistor that is turned on, and the on-state voltage drop measurement unit is controlled to collect the on-state voltage drop of the target switching transistor. The current sharing characteristics of the power conversion unit transistor under test are determined based on the on-state voltage drop of all the switching transistors.

7. The detection method according to claim 6, characterized in that, The determination of whether the current sharing characteristics of the power conversion unit transistor under test meet the standard based on the on-state voltage drop of all the switching transistors includes: Calculate the average on-state voltage drop for all the aforementioned switching transistors to obtain the average on-state voltage drop. Calculate the first voltage drop difference between each of the stated on-state voltage drops and the average of the stated on-state voltage drops; Determine whether any of the first voltage drop differences exceeds a first preset threshold value; If so, then the current sharing characteristics of the power conversion unit under test are determined to be substandard. If not, then the current sharing characteristics of the power conversion unit under test are deemed to meet the standard.

8. The detection method according to claim 6, characterized in that, The determination of whether the current sharing characteristics of the power conversion unit transistor under test meet the standard based on the on-state voltage drop of all the switching transistors includes: Calculate the second voltage drop difference between any two of the on-state voltage drops corresponding to all the switching transistors; Determine whether any of the second pressure drop differences exceeds a second target pressure drop difference value among all the second pressure drop difference values; If so, then the current sharing characteristics of the power conversion unit under test are determined to be substandard. If not, then the current sharing characteristics of the power conversion unit under test are deemed to meet the standard.

9. The detection method according to claim 6, characterized in that, The magnitude of the heating current is related to the conduction current capability of the switching transistor.

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