Three-level module test system with inductive current discharge protection device

Abstract

The invention provides a three-level module test system with an inductive current discharge protection device, and the system comprises a quasi-H-bridge test main power circuit which comprises a load inductor and a tested module, and applies electric thermal stress to the tested module under a test condition to test electric thermal parameters; the inductive current discharge protection circuit is connected to the two ends of the load inductor in parallel and provides an energy discharge current loop for the load inductor; and the control and protection processing module is connected with the quasi-H-bridge test main power circuit and the inductive current discharge protection circuit, controls the quasi-H-bridge test main power circuit to perform PWM switching operation, and receives fault alarm information on the inductive current discharge protection circuit to execute shutdown operation protection under a fault working condition. Through collaborative design of the quasi-H-bridge test main power circuit and the inductive current discharge protection circuit, the test safety is improved, the damage risk of test equipment is reduced, and the application is suitable for electric heating parameter test and reliability verification of high-power and high-switching-frequency power semiconductors.

Description

Technical Field

[0001] This application relates to the field of power module testing, and more specifically, to a three-level module testing system with an inductor current discharge protection device. Background Technology

[0002] In inverter applications, the performance of power semiconductor modules (such as IGBTs and SiC MOSFETs) directly affects the inverter's efficiency, reliability, and lifespan. Therefore, conducting accurate and comprehensive electrothermal parameter tests on power semiconductor modules, as well as reliability verification under simulated real-world operating conditions, are crucial steps in ensuring product quality and performance.

[0003] With the rapid development of power electronics technology towards higher power density and higher frequency, the testing requirements for power modules have expanded from conventional pulse testing conditions to PWM switching operation conditions at power levels of several kilowatts and hundreds of kHz. Traditional power semiconductor device testing systems face numerous technical challenges and safety hazards when dealing with high-power, high-switching-frequency testing requirements. On the one hand, special test topologies are needed to apply control conditions and PWM switching conditions similar to those in actual converters. On the other hand, under high-power, high-switching-frequency testing, power semiconductor devices often operate at higher voltages and temperatures, which can easily lead to problems such as overvoltage and overheating breakdown, increasing the instability and failure risk of the testing system.

[0004] Especially when simulating the actual operating conditions of an inverter in a test circuit with an inductive load, the power semiconductor module may encounter abnormal situations such as open circuit faults. When an open circuit fault occurs, the energy stored in the load inductor cannot be released quickly, the inductor current is forced to stop, and high voltage is generated across the inductor due to electromagnetic induction. This may not only damage other components in the test circuit, but also pose a safety threat to the operators.

[0005] In the prior art, patent application number CN201410474715.0 discloses a turn-off test platform and method for a single bridge arm in a three-level H-bridge inverter. The platform includes any one bridge arm under test in a three-level H-bridge power module, a voltage regulator, a rectifier bridge, a reactor, a current Hall effect sensor, a test control board, and a human-machine interface connected to the test control board. The output of the voltage regulator is connected to the rectifier bridge. The DC bus of the three-level H-bridge power module is connected to the DC output of the rectifier bridge. The AC output of the bridge arm under test in the three-level H-bridge power module is connected to one end of the reactor, and the other end of the reactor passes through the current Hall effect sensor and is connected to the midpoint of the DC capacitor in the three-level H-bridge power module. The current Hall effect sensor is also connected to the test control board. The test control board is connected to the three-level H-bridge power module via optical fiber. In the above technical solution, there is a lack of effective energy discharge mechanisms and rapid protection measures, making it difficult to cut off the power supply or provide an energy discharge path in time when a fault occurs, leading to damage to the test system. Summary of the Invention

[0006] In view of one of the defects in the prior art, the purpose of this application is to provide a three-level module test system with an inductor current discharge protection device.

[0007] A first aspect of this application provides a three-level module test system with an inductor current discharge protection device, comprising:

[0008] A quasi-H-bridge test main power circuit includes: a bus DC voltage source, a load inductor, and a module under test (DUT). The DUT is connected to the bus DC voltage source and the load inductor. Under test conditions, electrothermal stress is applied to the DUT to test electrothermal parameters. The DUT includes: device under test (DUT) Q1, DUT Q2, DUT Q3, and DUT Q4, as well as diodes D5 and D6. The negative terminal of DUT Q1 is connected in series with the cathode of diode D5 to form the A-phase bridge arm of the quasi-H-bridge test main power circuit. The positive terminal of DUT Q4 is connected in series with the anode of diode D6 to form the B-phase bridge arm of the quasi-H-bridge test main power circuit. One end of DUT Q2 and one end of DUT Q3 are connected in series with one end and the other end of the load inductor, respectively, to form a load branch. The two ends of the load branch are connected to the midpoints of the A-phase bridge arm and the B-phase bridge arm, respectively.

[0009] The inductor current discharge protection circuit includes: a current sensor, a forward withstand voltage device and a reverse conduction device, which are connected in series and then in parallel across the load inductor. The entire parallel circuit is located between the device under test Q2 and the device under test Q3. When the tested module experiences an open circuit fault, it provides an energy discharge current loop for the load inductor.

[0010] The control and protection processing module includes: a drive control component, which is connected to the quasi-H-bridge test main power circuit and the inductor current discharge protection circuit, receives fault alarm information sent by the inductor current discharge protection circuit, and controls the quasi-H-bridge test main power circuit to operate normally or perform shutdown protection under fault conditions by issuing or cutting off PWM drive signals.

[0011] Optionally, the positive port of the device under test Q1 in the A-phase bridge arm is connected to the cathode of the diode D6 in the B-phase bridge arm to form a positive voltage bus.

[0012] The negative port of the device under test Q4 in the B-phase bridge arm is connected to the anode of the diode D5 in the A-phase bridge arm, forming a negative voltage bus.

[0013] The positive voltage busbar and the negative voltage busbar are connected to a DC voltage source.

[0014] When the quasi-H-bridge test main power circuit is running in PWM switching mode, the DC bus voltage borne by the A-phase bridge arm and the B-phase bridge arm is equivalent to half the bus voltage of the three-level module in the actual inverter. The maximum output voltage of the bus DC voltage source is higher than half of the actual operating voltage of the three-level module in the inverter.

[0015] Optionally, during the testing of the module under test, in the normal testing phase, the quasi-H-bridge test main power circuit applies control behaviors and PWM switching actions to the module under test that are similar to the actual operating state of the inverter, including:

[0016] The control and protection processing module performs PWM control on the quasi-H-bridge main power circuit to control the current in the load branch where the load inductor is located to be the waveform required for testing.

[0017] In the load branch, the devices under test (DUTs) Q2 and Q3 remain on, and the devices under test Q1 and Q4 in the A-phase bridge arm and the B-phase bridge arm are switched on and off. The load current is controlled to be a test waveform with the flow direction from the midpoint of the A-phase bridge arm to the midpoint of the B-phase bridge arm as the reference direction.

[0018] Optionally, when the module under test is tested, if the load branch is damaged due to overcurrent, overvoltage or overheating of the device under test Q2 and the device under test Q3, or if the drive signal is malfunctioning and causes an open circuit, a fault protection phase is performed.

[0019] When a fault occurs in the load branch, the load current cannot flow through the load branch. Instead, a load inductor energy discharge current loop is generated in the inductor current discharge protection circuit. The inductor energy is gradually released in the form of current through the inductor current discharge protection circuit until the load current is completely reduced to 0.

[0020] Optionally, the reverse conduction device is used to generate a certain voltage during the current discharge process to adjust the current discharge rate and control the duration of the fault protection phase.

[0021] The reverse conduction device is selected from circuit elements with resistance-voltage characteristics or circuit elements with voltage regulation function.

[0022] Optionally, the circuit element having resistive volt-ampere characteristics is a power resistor;

[0023] When the power resistor is selected as the reverse conduction device, let the total resistance of the reverse conduction device be R, the inductance of the load be L, and the current of the load branch be I during normal testing. Then, according to the first-order circuit characteristics during the inductor current discharge process, the time t required for the load inductor energy to be completely discharged is t = 5L / R, and the highest voltage V across the inductor during the discharge process is V = RI. Under the premise that the highest voltage V across the load inductor during the discharge process is lower than the rated voltage of the inductor, increasing R can shorten the duration of the fault condition.

[0024] Optionally, the circuit element with voltage regulation function is a transient suppression diode;

[0025] When the transient suppression diode is selected as the reverse conduction device, let the voltage regulation value be V, the load inductance value be L, and the load branch current be I during normal testing. Then, the time required for the load inductance energy to be completely discharged is t = L1 / V. Increasing V can shorten the duration of the fault condition.

[0026] Optionally, the current sensor is used to monitor the discharge current information in the inductor current discharge protection circuit to determine whether the load inductor has an open circuit fault.

[0027] When the quasi-H-bridge test main power circuit is in the normal test phase, the inductor current discharge protection circuit has no current flowing through it due to the forward cutoff characteristic of the forward withstand voltage device. It only generates inductor energy discharge current when an open circuit fault occurs. When the current sensor detects that the current of the inductor current discharge protection circuit exceeds the set threshold for protection triggering, it generates a fault alarm message to the control and protection processing module.

[0028] Optionally, when the control and protection processing module receives the load branch open circuit fault alarm information, it performs fault handling actions, including:

[0029] The drive signals of all devices in the module under test are cut off. When the load branch open circuit fault alarm information is received, the drive signals of all devices in the module under test are immediately cut off to prevent the generation of new current paths that could cause a short circuit in the DC voltage source of the bus.

[0030] Disconnect the DC voltage source of the bus, reduce its voltage output to 0 by turning off the DC voltage source switch of the bus, and power down the test system.

[0031] Optionally, the inductor current discharge protection circuit generates an inductor energy discharge current when a circuit breaker fault occurs. The inductor energy is gradually released in the form of current through the inductor current discharge protection circuit until the load current is completely reduced to 0, which is the fault end stage.

[0032] During the fault termination phase, the quasi-H-bridge main power circuit safely stops operating and is powered down. After the fault is cleared, normal testing resumes.

[0033] The procedure for resuming normal testing after troubleshooting includes:

[0034] Ensure the system is completely powered down: check if the DC bus voltage source is turned off and determine if the current of the load inductor has been completely reduced to 0;

[0035] Check if the module under test is damaged: The control and protection processing module applies an enable drive signal to the device under test in the load branch, and uses a multimeter to check whether the device unit is conductive. If it is not conductive, it indicates that the device is open-circuited and damaged, and the device under test should be replaced.

[0036] Check if the drive signal of the module under test is damaged: The control and protection processing module applies a fixed duty cycle PWM drive signal to the device under test in the load branch, and uses an oscilloscope to observe whether the signal is abnormal. If there is an abnormality, it indicates that the drive signal is interfered with, and the source of external electromagnetic interference should be investigated.

[0037] Check the test circuit for broken connections: Use a multimeter to check whether the connection between the device under test and the load inductor in the load branch is conducting normally. If an open circuit is detected, it means that the connection is damaged and the corresponding connection should be replaced.

[0038] Re-energize and restore test: After completing the above checks, turn the DC bus voltage source back on and enter the normal test phase to carry out the test.

[0039] The three-level module test system with inductor current discharge protection provided in this application adopts a collaborative design of a quasi-H-bridge test main power circuit and an inductor current discharge protection circuit. The quasi-H-bridge test main power circuit accurately applies electrothermal stress to test the electrothermal parameters of the power semiconductor module. The inductor current discharge protection circuit utilizes the reverse current conduction characteristics of the forward withstand voltage device and the reverse conduction device to provide an energy discharge current loop for the load inductor when the module under test experiences an open circuit fault, preventing induced high voltage from damaging the test circuit. At the same time, the control and protection processing module receives fault alarm information and executes shutdown protection, realizing effective protection for the entire test process (normal test, fault, fault termination), significantly improving test safety, reducing the risk of damage to test equipment, and providing reliable assurance for the electrothermal parameter testing and reliability verification of high-power, high-switching-frequency power semiconductors.

[0040] Other technical effects resulting from the additional features will be further illustrated in the corresponding embodiments. Attached Figure Description

[0041] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0042] Figure 1 This is a circuit schematic diagram of a power semiconductor device test system with inductor current discharge protection function according to an exemplary embodiment.

[0043] Figure 2 This is a schematic diagram illustrating a fault condition and the principle of an inductor protection circuit according to an exemplary embodiment;

[0044] Figure 3 This is a timing diagram illustrating the operation under an inductor branch open circuit fault according to an exemplary embodiment. Detailed Implementation

[0045] The present application will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all fall within the protection scope of the present application. Parts not described in detail in the following embodiments can be implemented using existing technology.

[0046] In the description of the embodiments of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0048] In the description of the embodiments in this application, "multiple" means two or more, unless otherwise explicitly specified. In this application, unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0049] The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or devices.

[0050] In existing technologies, power semiconductor modules may encounter abnormal conditions such as open circuit faults during testing under simulated inverter operating conditions. To address these issues, this application provides a power semiconductor device testing system with inductor current discharge protection to resolve these problems.

[0051] Reference Figure 1 As shown in one embodiment of this application, a three-level module test system with an inductor current discharge protection device includes a quasi-H-bridge test main power circuit, an inductor current discharge protection circuit, and a control and protection processing module.

[0052] The quasi-H-bridge test main power circuit includes a bus DC voltage source, a load inductor, and a module under test. The load inductor is connected to the module under test, and the bus DC voltage source is also connected to the module under test. This circuit is used to apply electrothermal stress to the module under test under test conditions to test the electrothermal parameters.

[0053] The tested module includes: device under test Q1, device under test Q2, device under test Q3 and device under test Q4, and diodes D5 and D6; the negative port of device under test Q1 and the cathode of diode D5 are connected in series to form the A-phase bridge arm of the quasi-H-bridge test main power circuit; the positive port of device under test Q4 and the anode of diode D6 are connected in series to form the B-phase bridge arm of the quasi-H-bridge test main power circuit; one end of device under test Q2 and one end of device under test Q3 are connected in series with one end and the other end of the load inductor, respectively, to form a load branch, and the two ends of the load branch are connected to the midpoints of the A-phase bridge arm and the B-phase bridge arm, respectively.

[0054] The inductor current discharge protection circuit includes a current sensor, a forward withstand voltage device, and a reverse conduction device. These three parts are connected in series and then in parallel across the load inductor. The entire parallel circuit is located between the device under test (Q2) and the device under test (Q3). When the module under test experiences an open circuit fault, it provides an energy discharge current loop for the load inductor.

[0055] The control and protection processing module includes: a drive control component, which is connected to the quasi-H-bridge test main power circuit and the inductor current discharge protection circuit. It receives fault alarm information sent by the inductor current discharge protection circuit and controls the quasi-H-bridge test main power circuit to operate normally or perform shutdown protection under fault conditions by sending or cutting PWM drive signals.

[0056] Specifically, during the normal testing phase, the drive control component of the control and protection processing module applies a PWM control signal to the quasi-H-bridge test main power circuit, causing it to apply electrothermal stress to the module under test for electrothermal parameter testing. When the module under test experiences an open circuit fault, the inductor current discharge protection circuit connected in parallel across the load inductor provides an energy discharge current loop for the load inductor, preventing high voltage damage to the circuit caused by the current being forced to interrupt across the inductor. At the same time, the inductor current discharge protection circuit sends a fault alarm message to the control and protection processing module. Upon receiving this message, the control and protection processing module cuts off the drive signal of the module under test through the drive control component, stops the operation of the quasi-H-bridge test main power circuit, and sends a shutdown signal to the bus DC voltage source to power down the quasi-H-bridge test main power circuit. After the fault ends (the inductor energy is discharged completely and the load current is completely reduced to 0), the inductor current discharge protection circuit returns to standby mode. After checking and eliminating any damage to the module under test, drive signal, and test circuit, the system can re-enter the normal testing phase and resume PWM switching operation.

[0057] In the embodiments described above, the quasi-H-bridge test main power circuit precisely applies electrothermal stress to test the electrothermal parameters of the power semiconductor module. The inductor current discharge protection circuit utilizes reverse current characteristics to provide an energy discharge current loop for the load inductor when an open-circuit fault occurs in the module under test, effectively preventing induced high voltage from damaging the test circuit. At the same time, the control and protection processing module receives fault alarm information and executes shutdown protection, achieving effective protection for the entire test process (normal test, fault, fault termination), significantly improving test safety, reducing the risk of damage to test equipment, and providing reliable assurance for the electrothermal parameter testing and reliability verification of high-power, high-switching-frequency power semiconductors.

[0058] In the above embodiments, the current sensor, the forward withstand voltage device, and the reverse conduction device are connected in series and then in parallel across the load inductor. The entire parallel connection is located between the device under test (DUT) Q2 and DUT Q3. Compared to the conventional inverter circuit topology which uses two Type I three-level modules to form an H-bridge structure for PWM control, this application can use a single Type I three-level module for PWM control. Furthermore, the proposed circuit structure simulates the same switching state in an actual inverter, saving testing costs.

[0059] It should be noted that the device units that make up the quasi-H-bridge topology can be composed of power semiconductor devices of various types or packages, including but not limited to four single-transistor power semiconductor devices, two dual-unit power semiconductor modules, a single four-unit power semiconductor module, or a single three-level module.

[0060] The diodes that form the quasi-H-bridge topology can be composed of single-transistor power diodes, diodes built into the module under test, or point clamping diodes of the three-level module under test.

[0061] Specifically, each of the two bridge arms is composed of a device unit and a built-in diode from the module under test. The load branch is composed of two device units from the module under test connected in series across the load inductor. Under the control method of high-frequency switching of the bridge arm devices and keeping the load branch devices on, PWM control similar to the working state of the actual three-level inverter module can be applied to the module under test.

[0062] For example, the quasi-H-bridge test main power circuit is composed of one or more modules under test connected according to a specific topology, and has multiple controllable and uncontrollable devices. Among them, the controllable devices can be composed of IGBTs or MOSFETs, including: device under test Q1, device under test Q2, device under test Q3, and device under test Q4; the uncontrollable devices are composed of power diodes, including: diode D5 and diode D6.

[0063] Furthermore, the control and protection processing module includes: a drive control component and a fault alarm information display component. The drive control component is used to disconnect or connect the drive signals of the system; the fault alarm information display component is used to display the system open circuit fault alarm information.

[0064] Among them, displaying fault alarm information involves displaying load branch open circuit fault alarm information in the corresponding display component of the control and protection processing module, informing the system operator of the current protection trigger status and the time and type of the fault.

[0065] In the above embodiments of this application, after receiving the fault alarm information sent by the inductor current discharge protection circuit through the control and protection processing module, the drive control component cuts off the drive signal of the module under test to stop the operation of the quasi-H-bridge test main power circuit, and sends a shutdown signal to the bus DC voltage source to power down the quasi-H-bridge test main power circuit. At the same time, a fault alarm visual prompt is generated on the fault alarm information display component.

[0066] In some specific embodiments of this application, the positive port of the device under test Q1 in phase A bridge arm is connected to the cathode of diode D6 in phase B bridge arm to form a positive voltage bus; the negative port of the device under test Q4 in phase B bridge arm is connected to the anode of diode D5 in phase A bridge arm to form a negative voltage bus; a bus DC voltage source is connected between the positive voltage bus and the negative voltage bus.

[0067] When the quasi-H-bridge test main power circuit is running in PWM switching mode, the DC bus voltage borne by the A-phase bridge arm and the B-phase bridge arm is equivalent to half the bus voltage of the three-level module in the actual inverter. The maximum output voltage of the bus DC voltage source is higher than half of the actual operating voltage of the three-level module in the inverter.

[0068] Specifically, the main power circuit for the quasi-H-bridge test consists of one device unit from the module under test (DUT) and one built-in diode, forming the A and B phase arms of the quasi-H-bridge respectively. Two device units from the DUT are connected to the two ends of the load inductor to form a load branch, which is connected at the midpoint between the two arms of the quasi-H-bridge. The positive port of the A-phase device unit of the DUT is connected to the cathode lead of the B-phase diode to form a positive voltage bus, and the negative port of the B-phase device unit is connected to the anode lead of the A-phase diode to form a negative voltage bus. A DC voltage source is connected between the positive and negative voltage buses. During normal testing, when the PWM is running, the DC bus voltage across the DUT's bridge arm device unit is equivalent to half the bus voltage of a three-level module in an actual inverter. The maximum output voltage of the DC voltage source should be higher than half the actual operating voltage of the three-level module in the inverter.

[0069] It should be noted that the upper half of the bridge arm for phase A is Q1, and the lower half of the bridge arm is D5; the upper half of the bridge arm for phase B is D6, and the lower half of the bridge arm is Q4.

[0070] In some specific embodiments of this application, the inductor current discharge protection circuit includes a forward withstand voltage device, a reverse conduction device, and a current sensor. The forward withstand voltage device and the reverse conduction device are connected and connected in parallel across the two ends of the load inductor, and are used to provide an energy discharge current loop for the load inductor when an open circuit fault occurs in the module under test; the current sensor is used to monitor the discharge current information in the inductor current discharge protection circuit, determine whether an open circuit has occurred in the load inductor, and send the fault alarm information to the control and protection processing module.

[0071] In the above embodiments of this application, when the tested module experiences an open circuit fault, the forward withstand voltage device and the reverse conduction device in the inductor current discharge protection circuit connected in parallel across the load inductor utilize the reverse current conduction characteristics to provide an energy discharge current loop for the load inductor, preventing high voltage damage to the circuit caused by the current being forced to stop across the inductor.

[0072] Specifically, for the inductor current discharge protection circuit, the current sensor, the forward withstand voltage device, and the reverse conduction device are connected in series in sequence according to the load current reference direction. The withstand voltage polarity of the forward withstand voltage device is the same as the load current reference direction. When an open circuit fault occurs in the load branch, the inductor current discharge protection circuit generates a load inductor energy discharge current loop for discharge.

[0073] The energy discharge current loop is formed by sequentially passing through the load inductor, the reverse conduction device, and the forward withstand voltage device, following the load inductor current discharge path. Furthermore, during normal testing, due to the withstand voltage of the forward withstand voltage device, no current flows through the inductor energy discharge current loop, thus not affecting the operation of the PWM switch in the quasi-H-bridge test main power circuit.

[0074] Specifically, the inductor current discharge protection circuit is connected in parallel across the load inductor of the quasi-H-bridge test main power circuit, inside the device under test. The current sensor, forward withstand voltage device, and reverse conduction device are connected in series sequentially according to the load current reference direction, and the polarity of the forward withstand voltage device should be the same as the load current reference direction. When an open circuit fault occurs in the load branch, the load current cannot flow through the original load branch. Instead, a load inductor energy discharge current path is generated in the inductor current discharge protection circuit: load inductor – reverse conduction device – forward withstand voltage device. The inductor energy is gradually discharged in the form of current at a certain rate, thereby avoiding the forced rapid disconnection of the load current and the generation of induced high voltage across the inductor.

[0075] In some specific embodiments of this application, during the testing of the module under test (DUT) in the normal testing phase, a quasi-H-bridge test main power circuit applies control behaviors and PWM switching actions to the DUT that are similar to the actual operating state of the inverter, including:

[0076] The control and protection processing module performs PWM control on the main power circuit of the H-bridge, and the current in the load branch where the load inductor is located is controlled to the waveform required for testing.

[0077] In the load branch, the devices under test (DUTs) Q2 and Q3 remain on. The devices under test Q1 and Q4 in the A-phase and B-phase bridge arms are switched on and off. The load current is controlled as a test waveform with the reference direction being the flow from the midpoint of the A-phase bridge arm to the midpoint of the B-phase bridge arm.

[0078] Among them, the inductor current discharge protection circuit has no current flowing through it during the normal test phase due to the forward cutoff characteristic of the forward withstand voltage device, which does not affect the circuit's PWM control.

[0079] In the above embodiments of this application, the module under test is tested in the above manner during the normal testing phase. By using a quasi-H-bridge to test the main power circuit, the control behavior and PWM switching action of the inverter are applied to simulate the actual working state of the inverter. This can accurately and realistically reproduce the actual working conditions, making the test results more reliable and valuable for reference. The control and protection processing module performs PWM control on the main power circuit, so that the current in the branch where the load inductor is located presents the required waveform, meeting diverse testing needs. At this time, the inductor current discharge protection circuit does not interfere with the circuit PWM control due to the characteristics of the forward withstand voltage device, thus achieving stability and accuracy in the testing process.

[0080] In some specific embodiments of this application, when the module under test is tested, the load branch is damaged due to overcurrent, overvoltage or overheating of the device under test Q2 and Q3, or the drive signal is malfunctioned and an open circuit is generated, causing a fault protection phase.

[0081] When a fault occurs in the load branch, the load current cannot flow through the load branch. Instead, a load inductance energy discharge current loop is generated in the inductance current discharge protection circuit. The inductance energy is gradually released in the form of current through the inductance current discharge protection circuit until the load current is completely reduced to 0.

[0082] Simultaneously, the current sensor detects the discharge current and sends a load branch open circuit fault alarm to the control and protection processing module when the current exceeds the set threshold. This causes the control and protection processing module to disconnect the drive signal of the tested module and terminate the system operation when the open circuit fault occurs.

[0083] It should be noted that the threshold value should be determined based on the load current of the module under test during the actual test. Theoretically, as long as a fault current is detected in the inductor current discharge protection circuit, a fault alarm message should be sent. In practice, considering sensitivity and preventing false triggering, it is usually set to 10% to 30% of the load current during normal testing.

[0084] For example, the fault conditions that may occur when the above control is applied during testing are as follows: Figure 2 As shown. Because the inner IGBT is continuously conducting, its conduction loss is higher than that of the outer IGBT when switching with a certain duty cycle, thus posing a certain risk of damage during high-power testing. If either inner IGBT Q2 or Q3 in the circuit fails due to thermal breakdown or other reasons such as driver malfunction, without any protection, one end of the inductor's circuit will be disconnected. Its stored energy will lack a discharge current path, and the inductor load current IL will be forced to drop to 0 in a short time. Due to electromagnetic induction, a high voltage will be induced in the inductor, potentially breaking down the inductor insulation. If it can be handled according to... Figure 2 The connection shown provides an inductor protection circuit that provides a path for the inductor current discharge to flow through both sides of the inductor. When a circuit breaker fault occurs, it provides a current path for the inductor energy discharge. The discharge current IP generated in the inductor protection circuit releases the stored energy, which can prevent the inductor from being damaged by induced high voltage.

[0085] In some specific implementations, the reverse conduction device is used to generate a certain voltage during the current discharge process to adjust the current discharge rate and control the duration of the fault protection phase; the reverse conduction device is selected from circuit elements with resistance-voltage characteristics or circuit elements with voltage regulation function.

[0086] Specifically, a circuit element with resistive volt-ampere characteristics is a power resistor. When a power resistor is selected as a reverse conduction device, let the total resistance of the reverse conduction device be R, the load inductance be L, and the load branch current be I during normal testing. Then, based on the first-order circuit characteristics during the inductor current discharge process, the time t required for the load inductor to completely discharge energy can be simplified to t = 5L / R, and the highest voltage V across the inductor during the discharge process can be calculated as V = RI. When the highest voltage V across the load inductor during the discharge process is lower than the inductor's rated voltage, increasing R can shorten the duration of the fault condition.

[0087] It should be noted that the reverse conduction device can be selected from circuit elements with resistive volt-ampere characteristics, including but not limited to resistors, transient suppression diodes, or a combination of both. During the fault protection phase, a certain voltage is generated across the load inductor due to the discharge current flowing through it, which is used to regulate the current discharge rate.

[0088] In the above embodiments of this application, the component composition and model need to be selected according to the test requirements, including: the forward withstand voltage device can be selected from electrical components with forward cutoff and withstand voltage functions, including but not limited to power diodes, depletion-type MOSFETs, etc. During normal testing, it needs to withstand the DC bus voltage applied across its terminals during the charging process of the load inductor; therefore, the withstand voltage value needs to be higher than the output voltage of the DC voltage source of the quasi-H-bridge main power circuit. If it is necessary to connect the selected components in series to improve the withstand voltage level, then for withstand voltage levels U... iThe series connection of each component must ensure that the sum of the withstand voltages of all components is higher than the output voltage U of the DC voltage source. bus ,Right now

[0089]

[0090] In some specific implementations, the circuit element with voltage regulation function is a transient suppression diode.

[0091] When a transient suppression diode is selected as the reverse conduction device, assuming the voltage regulation value is V, the load inductance value is L, and the load branch current is I during normal testing, then the time required for the load inductance energy to be completely discharged is t = L1 / V. Increasing V can shorten the duration of the fault condition.

[0092] In some specific implementations, the current sensor is used to monitor the discharge current information in the inductor current discharge protection circuit to determine whether the load inductor has experienced an open circuit fault.

[0093] When the main power circuit of the quasi-H-bridge test is in the normal test phase, the inductor current discharge protection circuit has no current flowing through it due to the forward cutoff characteristic of the forward withstand voltage device. It only generates inductor energy discharge current when an open circuit fault occurs. When the current sensor detects that the current of the inductor current discharge protection circuit exceeds the set threshold for protection triggering, it generates a fault alarm message to the control and protection processing module.

[0094] In some specific embodiments of this application, when the control and protection processing module receives a load branch open circuit fault alarm information, it performs fault handling actions including: cutting off all device drive signals of the module under test; immediately cutting off all device units of the module under test by cutting off drive signals upon receiving the load branch open circuit fault alarm information to prevent the generation of new current paths that could cause a short circuit in the bus DC voltage source; cutting off the bus DC voltage source by turning off the bus DC voltage source switch to reduce its voltage output to 0 and powering down the test system.

[0095] In some specific embodiments of this application, the inductor current discharge protection circuit generates an inductor energy discharge current when an open circuit fault occurs. The inductor energy is gradually released in the form of current through the inductor current discharge protection circuit until the load current is completely reduced to 0, and then the fault ends.

[0096] During the fault termination phase, the main power circuit of the quasi-H bridge safely stops operating and is powered off. Normal testing can be resumed after the fault is eliminated.

[0097] The procedure for resuming normal testing after troubleshooting includes:

[0098] Ensure the system is completely powered down: check whether the DC bus voltage source is turned off and determine whether the current of the load inductor has been completely reduced to 0;

[0099] Check if the module under test is damaged: The control and protection processing module applies an enable drive signal to the device under test in the load branch. Use a multimeter to check if the device unit is conductive. If it is not conductive, it means that the device is open-circuited and damaged, and the module under test needs to be replaced.

[0100] Check if the drive signal of the module under test is damaged: The control and protection processing module applies a fixed duty cycle PWM drive signal to the device under test in the load branch. Use an oscilloscope to observe whether the signal is abnormal. If there is an abnormality, it means that the drive signal is interfered with and the source of external electromagnetic interference needs to be investigated.

[0101] Check the test circuit for broken wires: Use a multimeter to check whether the connection between the device under test and the load inductor in the load branch is conducting normally. If an open circuit is detected, it means that the connection is damaged and the corresponding connection needs to be replaced.

[0102] Re-energize and resume testing: After completing the above checks, the DC bus voltage source can be restarted to enter the normal testing phase and conduct the test.

[0103] For example, the timing sequence of the test system under an open-circuit fault in the inductor branch is as follows: Figure 3 As shown. Before the fault occurred, the power circuit used PWM control, and the inductor current IL was controlled as DC. When the fault occurred, the inductor current discharge protection circuit created a current discharge path. Current sensor A detected that the discharge current IP of the protection circuit was higher than the protection set threshold Iprotect and sent a fault alarm to the central processing unit. The central processing unit received the alarm information and determined that an open circuit fault had occurred in the inductor branch, and immediately cut off all drive signals V of the module under test. GE Stop its operation to prevent further damage. As the inductor energy is gradually discharged, the inductor current gradually decreases. Once the inductor energy is completely discharged and the inductor current drops to 0, the protection circuit ends and returns to standby mode, allowing testing to continue after the load branch open circuit fault is cleared.

[0104] In some specific embodiments of this application, the control and protection processing module has fault state operation interlocking logic to prevent accidental start-up under fault conditions from damaging the test system.

[0105] Specifically, when no load branch short-circuit fault occurs, the fault state operation interlocking logic is closed, allowing testers to perform operations such as setting test parameters, powering on the bus DC voltage source, and PWM control. Upon receiving a fault alarm message, the fault state operation interlocking logic is activated, terminating the current test and preventing testers from performing any operations on the test system. Simultaneously, the fault alarm information display component is activated by displaying warning colors on indicator lights and displaying fault information on the screen. After troubleshooting, testers can clear the fault state operation interlocking logic by inputting specific commands, at which point they can resume normal testing of the test system.

[0106] The preferred features in the above embodiments can be used individually in any embodiment, or in any combination thereof, provided they do not conflict with each other. Furthermore, parts not described in detail in the embodiments can be implemented using existing technologies.

[0107] The foregoing has described some specific embodiments of this application. It should be understood that this application is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of this application. The above-described preferred features can be used in any combination without conflict.

Claims

1. A three-level module test system with inductance current discharge protection device, characterized in that, The application relates to a quasi-H-bridge test main power circuit, an inductance current discharge protection circuit and a control and protection processing module. The quasi-H-bridge test main power circuit comprises a bus DC voltage source, a load inductor and a measured module, the measured module is connected with the bus DC voltage source and the load inductor, and an electric heating stress test electric heating parameter is applied to the measured module under a test working condition; wherein the measured module comprises measured devices Q1, Q2, Q3 and Q4 and diodes D5 and D6; the negative port of the measured device Q1 is connected with the cathode of the diode D5 in series to form an A-phase bridge arm of the quasi-H-bridge test main power circuit; the positive port of the measured device Q4 is connected with the anode of the diode D6 in series to form a B-phase bridge arm of the quasi-H-bridge test main power circuit; one end of the measured device Q2 and one end of the measured device Q3 are connected with one end and the other end of the load inductor in series to form a load branch, and the two ends of the load branch are connected to the midpoints of the A-phase bridge arm and the B-phase bridge arm respectively; The inductance current discharge protection circuit comprises a current sensor, a forward voltage resistance device and a reverse conduction device which are connected in series and then connected in parallel at the two ends of the load inductor, and the parallel connection is located between the measured device Q2 and the measured device Q3, and the inductance current discharge protection circuit provides an energy discharge current loop for the load inductor when a circuit breaking fault occurs in the measured module; The control and protection processing module comprises a drive control component which is connected with the quasi-H-bridge test main power circuit and the inductance current discharge protection circuit, receives fault alarm information sent by the inductance current discharge protection circuit, and controls the quasi-H-bridge test main power circuit to normally power on and run or execute shutdown operation protection under a fault working condition by issuing or cutting off a PWM drive signal.

2. The three-level module test system with inductance current discharge protection device according to claim 1, characterized in that, The positive port of the measured device Q1 in the A-phase bridge arm is connected with the cathode of the diode D6 in the B-phase bridge arm to form a positive voltage bus; The negative port of the measured device Q4 in the B-phase bridge arm is connected with the anode of the diode D5 in the A-phase bridge arm to form a negative voltage bus; The bus DC voltage source is connected between the positive voltage bus and the negative voltage bus; When the quasi-H-bridge test main power circuit is in PWM switching operation, the DC bus voltage borne by the A-phase bridge arm and the B-phase bridge arm is equivalent to half of the bus voltage of a three-level module in an actual inverter, and the maximum output voltage of the bus DC voltage source is higher than half of the actual operation voltage of the three-level module in the inverter.

3. The three-level module test system with inductance current discharge protection device according to claim 2, characterized in that, When the measured module is tested, in a normal test stage, the quasi-H-bridge test main power circuit applies a control behavior and a PWM switching action similar to an actual working state of an inverter to the measured module, and the control and protection processing module controls the current of the load branch where the load inductor is located to be a waveform required by the test. ​ The measured devices Q2 and Q3 in the load branch remain conducting, the measured devices Q1 and Q4 in the A-phase bridge arm and the B-phase bridge arm are switched, and the load current is controlled to be a test waveform with the A-phase bridge arm midpoint flowing to the B-phase bridge arm midpoint as a reference direction.

4. The three-level module test system with inductance current discharge protection device according to claim 1, characterized in that, When the measured module is tested, the load branch is damaged due to overcurrent, overvoltage or overheating of the measured devices Q2 and Q3 or is caused to be open-circuited due to misoperation of the driving signal, and a fault protection phase is performed. In the fault protection phase, the load current cannot flow through the load branch, and a load current energy discharge current loop is generated in the inductor current discharge protection circuit, the electric energy is gradually released in the form of current through the inductor current discharge protection circuit, and the load current is completely reduced to 0.

5. The three-level module test system with inductance current discharge protection device according to claim 4, characterized in that, The reverse conduction device is used to generate a certain voltage during current discharge to adjust the current discharge rate and control the duration of the fault protection phase. The reverse conduction device is selected from a circuit element with resistance volt-ampere characteristics or a circuit element with voltage stabilizing function.

6. The three-level module test system with inductance current discharge protection device according to claim 5, characterized in that, The circuit element with resistance volt-ampere characteristics is a power resistor. When the power resistor is selected as the reverse conduction device, the total resistance of the reverse conduction device is R, the inductance of the load is L, and the load branch current during normal testing is I. According to the first-order circuit characteristics during inductor current discharge, the time t required for complete discharge of the load energy is t = 5L / R, and the maximum voltage V across the inductor during discharge is V = RI. Under the premise that the maximum voltage V across the inductor during discharge is lower than the rated voltage of the inductor, increasing R can shorten the duration of the fault condition.

7. The three-level module test system with inductance current discharge protection device according to claim 5, characterized in that, The circuit element with voltage stabilizing function is a transient voltage suppression diode. When the transient voltage suppression diode is selected as the reverse conduction device, the voltage stabilizing value is V, the inductance of the load is L, and the load branch current during normal testing is I. The time t required for complete discharge of the load energy is t = LI / V, and increasing V can shorten the duration of the fault condition.

8. The three-level module test system with inductance current discharge protection device according to claim 6, characterized in that, The current sensor is used to monitor the discharge current information in the inductor current discharge protection circuit and determine whether the load inductor has an open-circuit fault. In the normal testing phase of the quasi-H-bridge test main power circuit, no current flows through the inductor current discharge protection circuit due to the forward blocking characteristic of the forward voltage device, and only when an open-circuit fault occurs, the electric energy discharge current is generated. When the current sensor detects that the current in the inductor current discharge protection circuit exceeds the set threshold value of the protection trigger, the fault alarm information is generated to the control and protection processing module.

9. The three-level module test system with inductance current discharge protection device according to claim 8, characterized in that, When the control and protection processing module receives the load branch open-circuit fault alarm information, the fault handling action is performed, including: The driving signals of all devices in the measured module are cut off. When the load branch open-circuit fault alarm information is received, all device units in the measured module are immediately turned off by cutting off the driving signals to prevent the bus DC voltage source from being short-circuited due to the generation of a new current path. The bus DC voltage source is cut off, and the voltage output of the bus DC voltage source is reduced to 0 by closing the bus DC voltage source switch, and the system is powered off.

10. The three-level module test system with inductance current discharge protection device according to claim 8, characterized in that, The inductive current discharge protection circuit generates an electric energy discharge current when a circuit breaking fault occurs, wherein the electric energy is gradually released in the form of current through the inductive current discharge protection circuit until the load current is completely reduced to 0, and the fault ends; In the fault ending stage, the quasi-H bridge main power circuit stops running safely and is powered off, and normal testing is resumed after the fault is eliminated; The operation process of resuming normal testing after eliminating the fault includes: Ensure that the system has been completely powered off: check whether the DC bus voltage source has been closed, and determine whether the current of the load inductor has been completely reduced to 0; Check whether the measured module is damaged: the control and protection processing module applies an opening driving signal to the measured device of the load branch, uses a multimeter to detect whether the device unit is turned on, and if not, it means that the device is damaged, and the measured device is replaced; Check whether the measured module driving signal is damaged: the control and protection processing module applies a fixed duty ratio PWM driving signal to the measured device of the load branch, and uses an oscilloscope to observe whether the signal is abnormal, if there is an abnormality, it means that the driving signal is disturbed, and the source of external electromagnetic interference is checked; Check whether the test circuit has a connection line breakage: use a multimeter to detect whether the connection line between the measured device of the load branch and the load inductor is normally turned on, if a breakage is detected, it means that the connection line is damaged, and the corresponding connection line is replaced; Re-powering to resume testing: after the above checks are completed, the DC bus voltage source is turned on again, and the testing is carried out in the normal testing stage.

Images