Three-level circuit and test method thereof

Abstract

The invention discloses a three-level circuit and a test method thereof. The method comprises the steps that a controller sends control signals to a three-level circuit, wherein the control signals comprise a first control instruction, a second control instruction and a third control instruction; the detector detects the current rise rate of the first test bridge arm under the state that the first test bridge arm is conducted; in a state that the lower bridge arm of the first test bridge arm is switched on and the upper bridge arm of the first test bridge arm is switched off, the detector detects the current rise rate of the follow current unit and the voltage of the upper bridge arm of the first test bridge arm; when the first test bridge arm is turned off, the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the follow current unit; wherein the current rise rate and the voltage of the first test bridge arm are used for judging the state of the first test bridge arm, and the current rise rate and the voltage of the follow current unit are used for judging the state of the follow current unit. According to the invention, the test efficiency of the three-level circuit is improved, and the test cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a three-level circuit and its testing method. Background Technology

[0002] A three-level circuit can output voltage in three states: positive, negative, and zero. To ensure reliable operation, the reliability of the three-level circuit needs to be tested before power-on. However, traditional testing methods require frequent changes to the test inductor location and testing equipment, resulting in low testing efficiency and high testing costs. Summary of the Invention

[0003] This invention provides a three-level circuit and its testing method to solve the problems of low testing efficiency and high testing cost of three-level circuits.

[0004] According to one aspect of the present invention, a test method for a three-level circuit is provided, which is applied to a three-level circuit, the three-level circuit comprising: a first test bridge arm, a test unit, a freewheeling unit, and an energy storage unit;

[0005] The first end of the first test bridge arm is connected to the first end of the energy storage unit, the second end of the first test bridge arm is connected to the first end of the test unit, and the second end of the test unit is connected to the second end of the freewheeling unit; the first end of the freewheeling unit is connected to the third end of the first test bridge arm, and the second end of the energy storage unit is connected to the second end of the freewheeling unit.

[0006] The test method for the three-level circuit includes:

[0007] The controller sends a control signal to the three-level circuit. The control signal includes a first control instruction, a second control instruction, and a third control instruction. The first control instruction is used to instruct the first test bridge arm to be turned on. The second control instruction is used to instruct the lower bridge arm of the first test bridge arm to be turned on and the upper bridge arm of the first test bridge arm to be turned off. The third control instruction is used to instruct the first test bridge arm to be turned off.

[0008] With the first test bridge arm on, the detector detects the rate of increase of the current in the first test bridge arm;

[0009] With the lower bridge arm of the first test bridge arm on and the upper bridge arm of the first test bridge arm off, the detector detects the current rise rate of the freewheeling unit and the voltage of the upper bridge arm of the first test bridge arm.

[0010] With the first test bridge arm off, the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit.

[0011] The current rise rate and voltage of the first test bridge arm are used to determine the state of the first test bridge arm, and the current rise rate and voltage of the freewheeling unit are used to determine the state of the freewheeling unit.

[0012] Optionally, the test unit includes: a first inductor, a first diode, a second diode, a third diode, and a fourth diode; the anode of the first diode is connected to the second end of the first test bridge arm, the cathodes of the first diode and the second diode are both connected to the first end of the first inductor, and the anode of the second diode is connected to the second end of the freewheeling unit; the cathode of the third diode is connected to the second end of the first test bridge arm, the anodes of the third diode and the fourth diode are both connected to the second end of the first inductor, and the cathode of the fourth diode is connected to the second end of the freewheeling unit;

[0013] The first test bridge arm includes: a first switching transistor, a second switching transistor, a fifth diode, and a sixth diode; the first end of the first switching transistor is connected to the cathode of the fifth diode and serves as the first end of the first test bridge arm; the second end of the first switching transistor is connected to the first end of the second switching transistor; the anode of the fifth diode is connected to the cathode of the sixth diode; the second end of the second switching transistor is connected to the anode of the sixth diode and serves as the second end of the first test bridge arm; and the anode of the fifth diode is connected to the second end of the first switching transistor and serves as the third end of the first test bridge arm.

[0014] When the first test bridge arm is conducting, the detector detects the rate of increase of the current in the first test bridge arm, including:

[0015] The controller sends the first control command to the three-level circuit, the first control command being used to instruct the first switch and the second switch to be turned on;

[0016] The detector detects the rate of rise of the current in the first switch and the second switch.

[0017] Optionally, the freewheeling unit includes: a ninth diode, the cathode of which is connected to the third end of the first test bridge arm, and the anode of which is connected to the second end of the test unit;

[0018] When the lower bridge arm of the first test bridge arm is on and the upper bridge arm of the first test bridge arm is off, the detector detects the current rise rate of the freewheeling unit and the voltage of the upper bridge arm of the first test bridge arm, including:

[0019] The controller sends the second control command to the three-level circuit, the second control command being used to instruct the second switching transistor to be turned on;

[0020] The detector detects the rate of increase of the current in the ninth diode and the voltage of the first switching transistor.

[0021] Optionally, when the first test bridge arm is off, the detector detecting the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit includes:

[0022] The controller sends the third control command to the three-level circuit, the third control command being used to instruct the first switch and the second switch to be turned off;

[0023] The detector detects the voltage of the ninth diode and the voltage of the second switch.

[0024] Optionally, the three-level circuit further includes: a second test bridge arm; the first end of the second test bridge arm is connected to the second end of the first test bridge arm, the second end of the second test bridge arm is connected to the third end of the energy storage unit, and the third end of the second test bridge arm is connected to the third end of the freewheeling unit;

[0025] The control signal further includes a fourth control command, a fifth control command, and a sixth control command. The fourth control command is used to instruct the second test bridge arm to be turned on, the fifth control command is used to instruct the upper bridge arm of the second test bridge arm to be turned on and the lower bridge arm of the second test bridge arm to be turned off, and the sixth control command is used to instruct the second test bridge arm to be turned off.

[0026] With the first test bridge arm off, after the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit, it further includes:

[0027] With the second test bridge arm conducting, the detector detects the rate of increase of the current in the second test bridge arm;

[0028] With the lower bridge arm of the second test bridge arm off and the upper bridge arm of the second test bridge arm on, the detector detects the current rise rate of the freewheeling unit and the voltage of the lower bridge arm of the first test bridge arm.

[0029] With the second test bridge arm off, the detector detects the voltage of the upper bridge arm of the second test bridge arm and the voltage of the freewheeling unit;

[0030] The current rise rate and voltage of the second test bridge arm are used to determine the state of the second test bridge arm, and the current rise rate and voltage of the freewheeling unit are used to determine the state of the freewheeling unit.

[0031] Optionally, the second test bridge arm includes: a third switch, a fourth switch, a seventh diode, and an eighth diode; the first end of the third switch is connected to the cathode of the seventh diode and serves as the first end of the second test bridge arm; the second end of the third switch is connected to the first end of the fourth switch; the anode of the seventh diode is connected to the cathode of the eighth diode; the second end of the fourth switch is connected to the anode of the eighth diode and serves as the second end of the second test bridge arm; and the anode of the seventh diode is connected to the second end of the third switch and serves as the third end of the second test bridge arm.

[0032] When the second test bridge arm is conducting, the detector detects the rate of rise of the current in the second test bridge arm, including:

[0033] The controller sends the fourth control command to the three-level circuit, the fourth control command being used to instruct the third switch and the fourth switch to be turned on;

[0034] The detector detects the rate of increase of the current in the third and fourth switches.

[0035] Optionally, the freewheeling unit further includes: a tenth diode, the cathode of which is connected to the second end of the test unit, and the anode of which is connected to the third end of the second test bridge arm;

[0036] When the lower bridge arm of the second test bridge arm is off and the upper bridge arm of the second test bridge arm is on, the detector detects the current rise rate of the freewheeling unit and the voltage of the lower bridge arm of the first test bridge arm, including:

[0037] The controller sends the fifth control command to the three-level circuit, the fifth control command being used to instruct the third switching transistor to be turned on;

[0038] The detector detects the rate of increase of the current in the tenth diode and the voltage of the fourth switch.

[0039] Optionally, when the second test bridge arm is off, the detector detecting the voltage of the upper bridge arm of the second test bridge arm and the voltage of the freewheeling unit includes:

[0040] The controller sends the sixth control command to the three-level circuit, the sixth control command being used to instruct the third switch and the fourth switch to be turned off;

[0041] The detector detects the voltage of the tenth diode and the voltage of the third switch.

[0042] Optionally, the control signal further includes: the first control command, the second control command, the first control command, and the third control command;

[0043] Alternatively, the control signal may further include: a first control command, a second control command, a seventh control command, a second control command, a first control command, a second control command, and a third control command issued sequentially; the seventh control command is used to instruct the lower bridge arm of the first test bridge arm and the upper bridge arm of the second test bridge arm to be turned on.

[0044] Alternatively, the control signals issued sequentially may further include: the fourth control command, the fifth control command, the fourth control command, and the sixth control command;

[0045] Alternatively, the control signals issued sequentially may further include: the fourth control command, the fifth control command, the seventh control command, the fifth control command, the fourth control command, the fifth control command, and the sixth control command.

[0046] Optionally, the test unit that is issued sequentially further includes: a first resistor connected in parallel with a first inductor;

[0047] When the first test bridge arm is off and the second test bridge arm is off, the first inductor releases electrical energy through the first resistor.

[0048] This invention also provides a three-level circuit, including: a first test bridge arm, a test unit, a freewheeling unit, an energy storage unit, and a controller;

[0049] The first end of the first test bridge arm is connected to the first end of the energy storage unit, the second end of the first test bridge arm is connected to the first end of the test unit, and the second end of the test unit is connected to the second end of the freewheeling unit; the first end of the freewheeling unit is connected to the third end of the first test bridge arm, and the second end of the energy storage unit is connected to the second end of the freewheeling unit; the controller is connected to the first test bridge arm, and the controller is used to execute the test method of the three-level circuit described in any embodiment of the present invention.

[0050] The technical solution provided by this invention allows for the testing of each bridge arm and freewheeling unit in a three-level circuit without changing the position of the test unit. Furthermore, no replacement of the test equipment is required during the testing process, resulting in high testing efficiency and low cost. Since the normal operating state of the three-level circuit is the same as the circuit structure during testing, testing the three-level circuit does not affect its normal operation, thus ensuring high reliability.

[0051] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of a three-level circuit according to an embodiment of the present invention;

[0054] Figure 2 This is a flowchart of a test method for a three-level circuit according to an embodiment of the present invention;

[0055] Figure 3 This is a schematic diagram of another three-level circuit provided according to an embodiment of the present invention;

[0056] Figure 4 This is a flowchart of another test method for a three-level circuit according to an embodiment of the present invention;

[0057] Figure 5 This is a schematic diagram of the current flow direction of a three-level circuit according to an embodiment of the present invention;

[0058] Figure 6 This is a schematic diagram of the current flow direction of another three-level circuit provided according to an embodiment of the present invention;

[0059] Figure 7 This is a flowchart of another test method for a three-level circuit according to an embodiment of the present invention;

[0060] Figure 8 This is a flowchart of another test method for a three-level circuit according to an embodiment of the present invention;

[0061] Figure 9 This is a schematic diagram of the current flow direction of another three-level circuit according to an embodiment of the present invention;

[0062] Figure 10 This is a schematic diagram of the current flow direction of another three-level circuit provided according to an embodiment of the present invention;

[0063] Figure 11 This is a schematic diagram of another three-level circuit provided according to an embodiment of the present invention. Detailed Implementation

[0064] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0065] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0066] This invention provides a testing method for a three-level circuit. Figure 1 This is a schematic diagram of a three-level circuit provided in an embodiment of the present invention. (Reference) Figure 1 The three-level circuit includes: a first test bridge arm 1, a test unit 3, a freewheeling unit 4, and an energy storage unit 5. The first end of the first test bridge arm 1 is connected to the first end of the energy storage unit 5, the second end of the first test bridge arm 1 is connected to the first end of the test unit 3, the second end of the test unit 3 is connected to the second end of the freewheeling unit 4, the first end of the freewheeling unit 4 is connected to the third end of the first test bridge arm 1, and the second end of the energy storage unit 5 is connected to the second end of the freewheeling unit 4.

[0067] Figure 2 A flowchart illustrating a testing method for a three-level circuit according to an embodiment of the present invention. (See reference) Figure 2 The testing methods for three-level circuits include:

[0068] S110, the controller sends a control signal to the three-level circuit.

[0069] The control signals include a first control command, a second control command, and a third control command. The first control command is used to instruct the first test bridge arm to be turned on, the second control command is used to instruct the lower bridge arm of the first test bridge arm to be turned on and the upper bridge arm of the first test bridge arm to be turned off, and the third control command is used to instruct the first test bridge arm to be turned off.

[0070] S120. With the first test bridge arm on, the detector detects the rate of increase of the current in the first test bridge arm.

[0071] When the controller issues the first control command, the first test bridge arm 1 is turned on, the energy storage unit 5 outputs electrical energy, and a circuit is formed through the first test bridge arm 1 and the test unit 3, where the energy is stored. The current of the first test bridge arm 1 rises from 0 to a stable value. Because the characteristics of the first test bridge arm 1 are fixed, the rate of increase of the current of the first test bridge arm 1 should also conform to the current rise characteristics of the first test bridge arm 1. Therefore, by detecting the rate of increase of the current of the first test bridge arm 1, it can be determined whether the current transmission state of the first test bridge arm 1 is normal.

[0072] S130, with the lower bridge arm of the first test bridge arm on and the upper bridge arm of the first test bridge arm off, the detector detects the current rise rate of the freewheeling unit and the voltage of the upper bridge arm of the first test bridge arm.

[0073] When the controller issues the second control command, the lower arm of the first test bridge arm 1 is turned on, and the upper arm of the first test bridge arm is turned off. The energy storage unit 5 cannot output electrical energy to the first test bridge arm 1. At this time, the test unit 3 outputs the stored electrical energy, and forms a circuit through the freewheeling unit 4 and the lower arm of the first test bridge arm 1. The current of the freewheeling unit 4 rises from 0 to a stable value.

[0074] Since the characteristics of the freewheeling unit 4 are fixed, the current rise rate of the freewheeling unit 4 should also conform to the current rise characteristics of the freewheeling unit 4. Therefore, by detecting the current rise rate of the freewheeling unit 4, it can be determined whether the current transmission status of the freewheeling unit 4 is normal.

[0075] In this step, the part of the continuous current unit 4 to be tested is the part connected between the lower bridge arm of the first test bridge arm 1 and the test unit 3.

[0076] Meanwhile, after the upper arm of the first test bridge arm 1 is turned off, the upper arm of the first test bridge arm 1 may generate a voltage spike due to the sudden current change caused by the turn-off. To ensure the reliability of the operation of the first test bridge arm 1, a certain safety margin needs to be reserved. For example, this safety margin can be 20%, that is, the voltage spike of the upper arm of the first test bridge arm 1 should not exceed 80% of the rated voltage of the upper arm of the first test bridge arm 1. Therefore, by detecting the voltage of the upper arm of the first test bridge arm 1, it can be determined whether the voltage status of the upper arm of the first test bridge arm 1 is normal.

[0077] S140. With the first test bridge arm off, the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit.

[0078] When the controller issues the third control command, the lower arm of the first test bridge arm 1 is turned off. The lower arm of the first test bridge arm 1 and the freewheeling unit 4 may generate voltage spikes due to the turn-off. To ensure the reliability of the lower arm of the first test bridge arm 1 and the freewheeling unit 4, a certain safety margin needs to be reserved. Similarly, this safety margin can be 20%, meaning that the peak voltages of the lower arm of the first test bridge arm 1 and the freewheeling unit 4 respectively cannot exceed 80% of their rated voltages.

[0079] In summary, the current rise rate and voltage of the first test bridge arm are used to determine the state of the first test bridge arm, and the current rise rate and voltage of the freewheeling unit are used to determine the state of the freewheeling unit. In this embodiment of the invention, after detecting the various voltage and current parameters, the specific state determination can be performed manually, or the controller can automatically calculate and determine the state after receiving the various parameters detected by the detector.

[0080] The technical solution provided by this invention allows for the testing of each bridge arm and freewheeling unit in a three-level circuit without changing the position of the test unit. Furthermore, no replacement of the test equipment is required during the testing process, resulting in high testing efficiency and low cost. Since the normal operating state of the three-level circuit is the same as the circuit structure during testing, testing the three-level circuit does not affect its normal operation, thus ensuring high reliability.

[0081] Figure 3 This is a schematic diagram of another three-level circuit provided in an embodiment of the present invention. (Refer to...) Figure 3 Based on the above embodiments, optionally, the test unit 3 includes: a first inductor L1, a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; the anode of the first diode D1 is connected to the second end of the first test bridge arm 1, the cathodes of the first diode D1 and the second diode D2 are both connected to the first end of the first inductor L1, the anode of the second diode D2 is connected to the third end of the freewheeling unit 4; the cathode of the third diode D3 is connected to the second end of the first test bridge arm 1, the anodes of the third diode D3 and the fourth diode D4 are both connected to the second end of the first inductor L1, and the cathode of the fourth diode D4 is connected to the third end of the freewheeling unit 4.

[0082] The first test bridge arm 1 includes: a first switch T1, a second switch T2, a fifth diode D5, and a sixth diode D6; the first end of the first switch T1 is connected to the cathode of the fifth diode D5 and serves as the first end of the first test bridge arm 1; the second end of the first switch T1 is connected to the first end of the second switch T2; the anode of the fifth diode D5 is connected to the cathode of the sixth diode D6; the second end of the second switch T2 is connected to the anode of the sixth diode D6 and serves as the second end of the first test bridge arm 1; and the anode of the fifth diode D5 is connected to the second end of the first switch T1 and serves as the third end of the first test bridge arm 1.

[0083] The freewheeling unit 4 includes a ninth diode D9, the cathode of which is connected to the third end of the first test bridge arm 1, and the anode of which is connected to the second end of the test unit 3.

[0084] Energy storage unit 5 includes: a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a second inductor L2, a third inductor L3, an eleventh diode D11, and a twelfth diode D12. The eleventh diode D11, the third capacitor C3, the fourth capacitor C4, and the twelfth diode D12 are connected in series between the first end of the first test bridge arm 1 and the second end of the second test bridge arm 2. The second end of the third capacitor C3 is also connected to the third end of the test unit 3. The second inductor L2 is connected between the first end of the first test bridge arm 1 and the positive power supply, and the third inductor L3 is connected between the second end of the second test bridge arm 2 and the negative power supply. The fourth resistor R4 is connected in parallel between the second end of the second inductor L2 and the cathode of the eleventh diode D11, and the fifth resistor R5 is connected in parallel between the second end of the third inductor L3 and the anode of the twelfth diode D12. The first capacitor C1 and the second capacitor C2 are connected in series between the positive and negative power supplies. The second terminal of the first capacitor C1 is also connected to the third terminal of the test unit 3. The second resistor R2 is connected in parallel with the first capacitor C1, and the third resistor R3 is connected in parallel with the second capacitor C2.

[0085] Figure 4 A flowchart of another test method for a three-level circuit provided in an embodiment of the present invention. Figure 5 This is a schematic diagram of the current flow in a three-level circuit provided in an embodiment of the present invention. (Combined with...) Figure 4 and Figure 5 In S120, with the first test bridge arm conducting, the detector detects the rate of increase of the current in the first test bridge arm, including:

[0086] S121. The controller sends a first control command to the three-level circuit. The first control command is used to indicate that the first switch and the second switch are turned on.

[0087] S122, The detector detects the rate of rise of the current of the first and second switching transistors.

[0088] In this circuit, the first switch T1 and the second switch T2 are turned on according to the first control signal, forming a loop between the energy storage unit 5, the first switch T1, the second switch T2, the first diode D1, the first inductor L1, and the fourth diode D4. The first capacitor C1 in the energy storage unit 5 releases electrical energy, and the current of the first inductor L1 in the test unit 3 is input from the first terminal and output from the second terminal.

[0089] As the first switch T1 and the second switch T2 switch from the off state to the on state, the current in the first switch T1 and the second switch T2 will gradually increase. Since the first switch T1 and the second switch T2 have fixed current rise characteristics, by detecting the current rise rate of the first switch T1 and the second switch T2, it can be determined whether the current transmission state of the first switch T1 and the second switch T2 is normal.

[0090] Figure 6 This is a schematic diagram of the current flow in another three-level circuit provided in an embodiment of the present invention. (Combined with...) Figure 4 and Figure 6 Based on the above embodiments, optionally, in S130, when the lower bridge arm of the first test bridge arm is turned on and the upper bridge arm of the first test bridge arm is turned off, the detector detects the current rise rate of the freewheeling unit and the voltage of the upper bridge arm of the first test bridge arm, including:

[0091] S131. The controller sends a second control command to the three-level circuit. The second control command is used to indicate that the second switching transistor is turned on.

[0092] S132, The detector detects the rate of increase of the current in the ninth diode and the voltage of the first switching transistor.

[0093] The second control command is used to turn off the first switch T1 and turn on the second switch T2. At this time, the first capacitor C1 in the energy storage unit 5 can no longer release electrical energy to the first test bridge arm 1, and the first inductor L1 in the test unit 3 releases energy. The output current of the first inductor L1 passes through the fourth diode D4, the ninth diode D9 in the freewheeling unit 4, and the second switch T2 and the first diode D1 to form a circuit, and the current direction of the first inductor L1 remains unchanged.

[0094] Since no current flowed through the ninth diode D9 at the previous moment, the current in the ninth diode D9 will gradually increase. Similar to the first switch T1 and the second switch T2, the ninth diode D9 has a fixed current rise characteristic. By detecting the rate of current rise of the ninth diode D9, it can be determined whether the current transmission state of the ninth diode D9 is normal.

[0095] When the first switch T1 is turned off, it may experience voltage spikes. To ensure the normal operation of the first switch T1, these spikes must be lower than its rated voltage. Therefore, detecting whether the spike voltage of the first switch T1 is too high can be achieved by monitoring its voltage.

[0096] Continue to refer to Figure 4 S140, In the state where the first test bridge arm is off, the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit, including:

[0097] S141. The controller sends a third control command to the three-level circuit. The third control command is used to instruct the first and second switching transistors to be turned off.

[0098] S142, The detector detects the voltage of the ninth diode and the voltage of the second switch.

[0099] The third control command is used to turn off the first switch T1 and the second switch T2, causing the second switch T2 to switch from the on state to the off state. This also disconnects the current loop of the ninth diode D9. The second switch T2 and the ninth diode D9 may experience voltage spikes due to sudden current changes. By detecting the voltages of the ninth diode D9 and the second switch T2 respectively, it is possible to detect whether the voltage spikes of the ninth diode D9 and the second switch T2 are too high.

[0100] In this invention, during circuit switching, the current direction of the first inductor L1 in test unit 3 remains unchanged; the current flows from the first end to the second end of the first inductor L1. Therefore, this invention effectively solves the test error caused by the inconsistency of the commutation path and has high reliability.

[0101] Combination Figure 1 and Figure 3 The three-level circuit also includes: a second test bridge arm 2; the first end of the second test bridge arm 2 is connected to the second end of the first test bridge arm 1, the second end of the second test bridge arm 2 is connected to the third end of the energy storage unit 5, and the third end of the second test bridge arm 2 is connected to the third end of the freewheeling unit 4.

[0102] Optionally, the control signal further includes a fourth control command, a fifth control command, and a sixth control command. The fourth control command is used to instruct the second test bridge arm to be turned on, the fifth control command is used to instruct the upper bridge arm of the second test bridge arm to be turned on and the lower bridge arm of the second test bridge arm to be turned off, and the sixth control command is used to instruct the second test bridge arm to be turned off.

[0103] Figure 7 This is a flowchart illustrating another testing method for a three-level circuit provided in an embodiment of the present invention. (In conjunction with...) Figure 3 and Figure 7 Based on the above embodiments, optionally, after S140, in the state where the first test bridge arm is off, the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit, the method further includes:

[0104] S150, with the second test bridge arm on, the detector detects the rate of increase of the current in the second test bridge arm.

[0105] When the controller issues the fourth control command, the second test bridge arm 2 is turned on, the energy storage unit 5 outputs electrical energy, and a circuit is formed through the second test bridge arm 2 and the test unit 3, where the energy is stored. The current of the second test bridge arm 2 rises from 0 to a stable value. Because the characteristics of the second test bridge arm 2 are fixed, the rate of increase of the current of the second test bridge arm 2 should also conform to the current rise characteristics of the second test bridge arm 2. Therefore, by detecting the rate of increase of the current of the second test bridge arm 2, it can be determined whether the current transmission status of the second test bridge arm 2 is normal.

[0106] S160, with the lower arm of the second test bridge arm off and the upper arm of the second test bridge arm on, the detector detects the current rise rate of the freewheeling unit and the voltage of the lower arm of the first test bridge arm.

[0107] When the controller issues the fifth control command, the upper arm of the second test bridge arm is turned on and the lower arm of the second test bridge arm is turned off. The energy storage unit 5 cannot output electrical energy to the second test bridge arm 2. At this time, the test unit 3 outputs the stored electrical energy, forming a circuit through the upper arm of the second test bridge arm 2 and the freewheeling unit 4. The current in the freewheeling unit 4 rises from 0 to a stable value.

[0108] Since the characteristics of the freewheeling unit 4 are fixed, the current rise rate of the freewheeling unit 4 should also conform to the current rise characteristics of the freewheeling unit 4. Therefore, by detecting the current rise rate of the freewheeling unit 4, it can be determined whether the current transmission status of the freewheeling unit 4 is normal.

[0109] In this step, the detection part of the continuous current unit 4 is the part connected between the upper bridge arm of the second test bridge arm 2 and the test unit 3.

[0110] Meanwhile, after the lower arm of the second test bridge arm 2 is turned off, a voltage spike may occur in the lower arm due to a sudden change in current. To ensure the reliability of the operation of the second test bridge arm 2, a certain safety margin needs to be reserved. For example, this safety margin can be 20%, that is, the voltage spike of the lower arm of the second test bridge arm 2 should not exceed 80% of the rated voltage of the lower arm of the second test bridge arm 2. Therefore, by detecting the voltage of the lower arm of the second test bridge arm 2, it can be determined whether the voltage status of the lower arm of the second test bridge arm 2 is normal.

[0111] S170. With the second test bridge arm off, the detector detects the voltage of the upper bridge arm of the second test bridge arm and the voltage of the freewheeling unit.

[0112] When the controller issues the sixth control command, the upper arm of the second test bridge arm 2 is turned off. Since the upper arm of the second test bridge arm 2 and the freewheeling unit 4 may generate voltage spikes due to the turn-off, a certain safety margin needs to be reserved to ensure the reliability of the upper arm of the second test bridge arm 2 and the freewheeling unit 4. Similarly, this safety margin can be 20%, meaning that the voltage spikes of the upper arm of the second test bridge arm 2 and the freewheeling unit 4 respectively cannot exceed 80% of their rated voltages.

[0113] In summary, the current rise rate and voltage of the second test arm are used to determine the status of the second test arm, while the current rise rate and voltage of the freewheeling unit are used to determine the status of the freewheeling unit. The statuses of the first test arm, the second test arm, and the freewheeling unit together reflect whether the three-level circuit is functioning correctly.

[0114] Continue to refer to Figure 3 Based on the above embodiments, optionally, the second test bridge arm 2 includes: a third switch T3, a fourth switch T4, a seventh diode D7, and an eighth diode D8; the first end of the third switch T3 is connected to the cathode of the seventh diode D7 and serves as the first end of the second test bridge arm 2, the second end of the third switch T3 is connected to the first end of the fourth switch T4, the anode of the seventh diode D7 is connected to the cathode of the eighth diode D8, the second end of the fourth switch T4 is connected to the anode of the eighth diode D8 and serves as the second end of the second test bridge arm 2, and the anode of the seventh diode D7 is connected to the second end of the third switch T3 and serves as the third end of the second test bridge arm 2. The freewheeling unit 4 further includes: a tenth diode D10, the cathode of the tenth diode D10 is connected to the second end of the test unit 3, and the anode of the tenth diode D10 is connected to the third end of the second test bridge arm 2.

[0115] Figure 8 A flowchart of another testing method for a three-level circuit provided in an embodiment of the present invention. Figure 9 This is a schematic diagram of the current flow in another three-level circuit provided in an embodiment of the present invention. (Combined with...) Figure 8 and Figure 9 Based on the above embodiments, optionally, in S150, when the second test bridge arm is turned on, the detector detects the rate of rise of the current of the second test bridge arm including:

[0116] S151. The controller sends a fourth control command to the three-level circuit. The fourth control command is used to instruct the third and fourth switching transistors to be turned on.

[0117] S152, The detector detects the rate of increase of the current in the third and fourth switching transistors.

[0118] When the controller issues the fourth control command, the third switch T3 and the fourth switch T4 are turned on, forming a circuit between the energy storage unit 5, the second diode D2, the first inductor L1, the third diode D3, the third switch T3, and the fourth switch T4. The second capacitor C2 in the energy storage unit 5 releases electrical energy, and the current of the first inductor L1 in the test unit 3 is input from the first terminal and output from the second terminal.

[0119] As the third switch T3 and the fourth switch T4 switch from the off state to the on state, the current in the third switch T3 and the fourth switch T4 will gradually increase. Since the third switch T3 and the fourth switch T4 have a fixed current rise characteristic, by detecting the current rise rate of the third switch T3 and the fourth switch T4, it can be determined whether the current transmission state of the third switch T3 and the fourth switch T4 is normal.

[0120] Figure 10 This is a schematic diagram of the current flow in another three-level circuit provided in an embodiment of the present invention. (Combined with...) Figure 8 and Figure 10 Based on the above embodiments, optionally, in S160, when the lower bridge arm of the second test bridge arm is off and the upper bridge arm of the second test bridge arm is on, the detector detects the current rise rate of the freewheeling unit and the voltage of the lower bridge arm of the first test bridge arm, including:

[0121] S161. The controller sends a fifth control command to the three-level circuit. The fifth control command is used to indicate that the third switch is turned on.

[0122] S162, The detector detects the current rise rate of the tenth diode and the voltage of the fourth switch.

[0123] When the controller issues the fifth control command, the fourth switch T4 is turned off and the third switch T3 is turned on. The second capacitor C2 in the energy storage unit 5 can no longer release energy to the second test bridge arm 2, and the first inductor L1 in the test unit 3 releases energy. At this time, the output current of the first inductor L1 forms a circuit through the third diode D3, the third switch T3, the tenth diode D10 and the second diode D2 in the freewheeling unit 4, and the current direction of the first inductor L1 remains unchanged.

[0124] Since there was no current flowing through the tenth diode D10 at the previous moment, the current in the tenth diode D10 will gradually increase. The tenth diode D10 has a fixed current rise characteristic. By detecting the rate of current rise of the tenth diode D10, it can be determined whether the current transmission state of the tenth diode D10 is normal.

[0125] When the fourth switch T4 is turned off, it may generate a voltage spike. To ensure the normal operation of the fourth switch T4, the voltage spike must be lower than its rated voltage. The presence or absence of an excessively high voltage spike in the fourth switch T4 can be detected by monitoring its voltage.

[0126] refer to Figure 8 Based on the above embodiments, optionally, in S170, when the second test bridge arm is off, the detector detects the voltage of the upper bridge arm of the second test bridge arm and the voltage of the freewheeling unit, including:

[0127] S171. The controller sends a sixth control command to the three-level circuit. The sixth control command is used to instruct the third and fourth switching transistors to be turned off.

[0128] S172, The detector detects the voltage of the tenth diode and the voltage of the third switching transistor.

[0129] The sixth control command is used to turn off the third switch T3 and the fourth switch T4, switching the third switch T3 from the on state to the off state. This also breaks the current loop of the tenth diode D10, causing voltage spikes in both switches due to the sudden current change. By detecting the voltages of the third switch T3 and the tenth diode D10 respectively, it is possible to detect whether the voltage spikes in these two switches are too high.

[0130] When testing the second test bridge arm 2, the current direction of the first inductor L1 in the test unit 3 remains unchanged. Therefore, throughout the entire three-level circuit testing process, the commutation path of the first inductor L1 remains consistent, effectively solving the test error caused by the inconsistency of the commutation path and demonstrating high reliability.

[0131] Based on the above embodiments, optionally, the control signal further includes: a first control command, a second control command, a third control command, issued sequentially. Alternatively, the control signal further includes: a first control command, a second control command, a seventh control command, a second control command, a first control command, a second control command, and a third control command, issued sequentially. Alternatively, the control signal further includes: a fourth control command, a fifth control command, a fourth control command, and a sixth control command, issued sequentially. Alternatively, the control signal further includes: a fourth control command, a fifth control command, a seventh control command, a fifth control command, a fourth control command, a fifth control command, and a sixth control command, issued sequentially.

[0132] Specifically, by outputting the first control command again after outputting the second control command, the first test bridge arm 1 can be turned on again, which is equivalent to providing a double pulse to the first test bridge arm 1. The current in the circuit containing the first test bridge arm 1 will be superimposed on the current at the previous moment. By detecting the current rise rate of the first switch T1 and the second switch T2 again, it can be determined whether the current transmission state of the first switch T1 and the second switch T2 under this current is normal. This is equivalent to performing a second test on the first test bridge arm 1.

[0133] When the controller outputs the second control command, if the first switch T1 in the upper arm of the first test bridge arm 1 fails to turn off completely at the instant it turns off, the energy storage unit 5 may continue to output electrical energy. By outputting the seventh control command after the second control command, the upper arm of the second test bridge arm 2, i.e., the third switch T3, can be turned on. This can be used to protect the stable operation of the test unit 3 and also to prevent the second test bridge arm 2 from being damaged when the voltage is too high, thus causing the first test bridge arm 1 and the second test bridge arm 2 to be directly connected.

[0134] Specifically, when the voltage is too high, the third switch T3 can discharge energy to the second capacitor C2 through the tenth diode D10. For example, after the first switch T1 is completely turned off, a second control command can be output again, turning off the third switch T3.

[0135] Similarly, by outputting the fourth control command after the fifth control command, the second test bridge arm 2 can be turned on again, which is equivalent to providing a double pulse to the second test bridge arm 2. The current in the circuit containing the second test bridge arm 2 will be superimposed on the current at the previous moment. By detecting the current rise rate of the third switch T3 and the fourth switch T4 again, it can be determined whether the current transmission state of the third switch T3 and the fourth switch T4 under this current is normal. This is equivalent to performing a second test on the second test bridge arm 2.

[0136] When the controller outputs the fifth control command, if the fourth switch T4 in the lower arm of the second test bridge arm 2 fails to turn off completely at the moment it turns off, the energy storage unit 5 may continue to output electrical energy. By outputting the seventh control command after the fifth control command, the lower arm of the first test bridge arm 2, i.e., the second switch T2, can be turned on. This can be used to protect the stable operation of the test unit 3 and also to prevent the first test bridge arm 1 from being damaged when the voltage is too high, thus causing the first test bridge arm 1 and the second test bridge arm 2 to be directly connected.

[0137] Specifically, when the voltage is too high, the second switch T3 can discharge energy to the first capacitor C1 through the fifth diode D5. For example, after the fourth switch T4 is completely turned off, a fifth control command can be output again, turning off the second switch T2.

[0138] By adding control commands, the conduction time of each switch is also increased, and each switch or diode can be tested more times, resulting in better detection performance.

[0139] The control signals provided in this embodiment of the invention are not limited to the aforementioned instructions. In other embodiments, they may also include: a first control instruction, a second control instruction, a seventh control instruction, a second control instruction, a first control instruction, and a third control instruction issued sequentially; or a first control instruction, a second control instruction, a seventh control instruction, a second control instruction, a first control instruction, a second control instruction, a seventh control instruction, a second control instruction, and a third control instruction issued sequentially; or a first control instruction, a second control instruction, a seventh control instruction, a fifth control instruction, a seventh control instruction, a second control instruction, a first control instruction, a second control instruction, a seventh control instruction, a second control instruction, and a third control instruction issued sequentially; or a fourth control instruction, a fifth control instruction, a seventh control instruction, a second control instruction, a seventh control instruction, a fourth control instruction, a fifth control instruction, a seventh control instruction, a fifth control instruction, and a sixth control instruction issued sequentially; or a fourth control instruction, a fifth control instruction, a seventh control instruction, a fifth control instruction, a fourth control instruction, a fifth control instruction, a seventh control instruction, a fifth control instruction, and a sixth control instruction issued sequentially.

[0140] By adding control signals, the conduction time of each switch is effectively increased, and each switch or diode can be tested more times, resulting in better detection performance.

[0141] Figure 11 This is a schematic diagram of another three-level circuit provided in an embodiment of the present invention. (See reference) Figure 11 Optionally, based on the above embodiments, the test unit further includes: a first resistor R1, connected in parallel with a first inductor L1. When the first test bridge arm is off and the second test bridge arm is off, the first inductor releases electrical energy through the first resistor.

[0142] When the first test bridge arm 1 or the second test bridge arm 2 is turned off, there may still be residual electrical energy in the first inductor L1. By setting a first resistor R1 connected in parallel with the first inductor L1, the residual electrical energy in the first inductor L1 can be released when the first test bridge arm 1 or the second test bridge arm 2 is turned off, thus ensuring the safe operation of the three-level circuit.

[0143] This invention also provides a three-level circuit. It includes: a first test bridge arm, a test unit, a freewheeling unit, an energy storage unit, and a controller; a first end of the first test bridge arm is connected to a first end of the energy storage unit, a second end of the first test bridge arm is connected to a first end of the test unit, and a second end of the test unit is connected to a second end of the freewheeling unit; a first end of the freewheeling unit is connected to a third end of the first test bridge arm, and a second end of the energy storage unit is connected to a second end of the freewheeling unit; the controller is connected to the first test bridge arm, and the controller is used to execute the test method for the three-level circuit provided in any embodiment of this invention, possessing similar beneficial effects to the test method for the three-level circuit, which will not be described further.

[0144] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0145] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A test method for a three-level circuit, characterized in that, Applied to a three-level circuit, the three-level circuit includes: a first test bridge arm, a test unit, a freewheeling unit, and an energy storage unit; The first end of the first test bridge arm is connected to the first end of the energy storage unit, the second end of the first test bridge arm is connected to the first end of the test unit, and the second end of the test unit is connected to the second end of the freewheeling unit; the first end of the freewheeling unit is connected to the third end of the first test bridge arm, and the second end of the energy storage unit is connected to the second end of the freewheeling unit. The test method for the three-level circuit includes: The controller sends a control signal to the three-level circuit. The control signal includes a first control instruction, a second control instruction, and a third control instruction. The first control instruction is used to instruct the first test bridge arm to be turned on. The second control instruction is used to instruct the lower bridge arm of the first test bridge arm to be turned on and the upper bridge arm of the first test bridge arm to be turned off. The third control instruction is used to instruct the first test bridge arm to be turned off. With the first test bridge arm on, the detector detects the rate of increase of the current in the first test bridge arm; With the lower bridge arm of the first test bridge arm on and the upper bridge arm of the first test bridge arm off, the detector detects the current rise rate of the freewheeling unit and the voltage of the upper bridge arm of the first test bridge arm. With the first test bridge arm off, the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit. The current rise rate and voltage of the first test bridge arm are used to determine the state of the first test bridge arm, and the current rise rate and voltage of the freewheeling unit are used to determine the state of the freewheeling unit.

2. The test method for a three-level circuit according to claim 1, characterized in that, The test unit includes: a first inductor, a first diode, a second diode, a third diode, and a fourth diode; the anode of the first diode is connected to the second end of the first test bridge arm, the cathodes of the first diode and the second diode are both connected to the first end of the first inductor, and the anode of the second diode is connected to the second end of the freewheeling unit; the cathode of the third diode is connected to the second end of the first test bridge arm, the anodes of the third diode and the fourth diode are both connected to the second end of the first inductor, and the cathode of the fourth diode is connected to the second end of the freewheeling unit. The first test bridge arm includes: a first switching transistor, a second switching transistor, a fifth diode, and a sixth diode; the first end of the first switching transistor is connected to the cathode of the fifth diode and serves as the first end of the first test bridge arm; the second end of the first switching transistor is connected to the first end of the second switching transistor; the anode of the fifth diode is connected to the cathode of the sixth diode; the second end of the second switching transistor is connected to the anode of the sixth diode and serves as the second end of the first test bridge arm; and the anode of the fifth diode is connected to the second end of the first switching transistor and serves as the third end of the first test bridge arm. When the first test bridge arm is conducting, the detector detects the rate of increase of the current in the first test bridge arm, including: The controller sends the first control command to the three-level circuit, the first control command being used to instruct the first switch and the second switch to be turned on; The detector detects the rate of rise of the current in the first switch and the second switch.

3. The test method for a three-level circuit according to claim 2, characterized in that, The freewheeling unit includes a ninth diode, the cathode of which is connected to the third end of the first test bridge arm, and the anode of which is connected to the second end of the test unit. When the lower bridge arm of the first test bridge arm is on and the upper bridge arm of the first test bridge arm is off, the detector detects the current rise rate of the freewheeling unit and the voltage of the upper bridge arm of the first test bridge arm, including: The controller sends the second control command to the three-level circuit, the second control command being used to instruct the second switching transistor to be turned on; The detector detects the rate of increase of the current in the ninth diode and the voltage of the first switching transistor.

4. The test method for a three-level circuit according to claim 3, characterized in that, When the first test bridge arm is off, the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit, including: The controller sends the third control command to the three-level circuit, the third control command being used to instruct the first switch and the second switch to be turned off; The detector detects the voltage of the ninth diode and the voltage of the second switch.

5. The test method for a three-level circuit according to claim 1, characterized in that, The three-level circuit further includes: a second test bridge arm; the first end of the second test bridge arm is connected to the second end of the first test bridge arm, the second end of the second test bridge arm is connected to the third end of the energy storage unit, and the third end of the second test bridge arm is connected to the third end of the freewheeling unit; The control signal further includes a fourth control command, a fifth control command, and a sixth control command. The fourth control command is used to instruct the second test bridge arm to be turned on, the fifth control command is used to instruct the upper bridge arm of the second test bridge arm to be turned on and the lower bridge arm of the second test bridge arm to be turned off, and the sixth control command is used to instruct the second test bridge arm to be turned off. With the first test bridge arm off, after the detector detects the voltage of the lower bridge arm of the first test bridge arm and the voltage of the freewheeling unit, it further includes: With the second test bridge arm on, the detector detects the rate of increase of the current in the second test bridge arm; With the lower bridge arm of the second test bridge arm off and the upper bridge arm of the second test bridge arm on, the detector detects the current rise rate of the freewheeling unit and the voltage of the lower bridge arm of the first test bridge arm. With the second test bridge arm off, the detector detects the voltage of the upper bridge arm of the second test bridge arm and the voltage of the freewheeling unit; The current rise rate and voltage of the second test bridge arm are used to determine the state of the second test bridge arm, and the current rise rate and voltage of the freewheeling unit are used to determine the state of the freewheeling unit.

6. The test method for a three-level circuit according to claim 5, characterized in that, The second test bridge arm includes: a third switch, a fourth switch, a seventh diode, and an eighth diode; the first end of the third switch is connected to the cathode of the seventh diode and serves as the first end of the second test bridge arm; the second end of the third switch is connected to the first end of the fourth switch; the anode of the seventh diode is connected to the cathode of the eighth diode; the second end of the fourth switch is connected to the anode of the eighth diode and serves as the second end of the second test bridge arm; and the anode of the seventh diode is connected to the second end of the third switch and serves as the third end of the second test bridge arm. When the second test bridge arm is conducting, the detector detects the rate of rise of the current in the second test bridge arm, including: The controller sends the fourth control command to the three-level circuit, the fourth control command being used to instruct the third switch and the fourth switch to be turned on; The detector detects the rate of increase of the current in the third and fourth switches.

7. The test method for a three-level circuit according to claim 6, characterized in that, The freewheeling unit further includes a tenth diode, the cathode of which is connected to the second end of the test unit, and the anode of which is connected to the third end of the second test bridge arm. When the lower bridge arm of the second test bridge arm is off and the upper bridge arm of the second test bridge arm is on, the detector detects the current rise rate of the freewheeling unit and the voltage of the lower bridge arm of the first test bridge arm, including: The controller sends the fifth control command to the three-level circuit, the fifth control command being used to instruct the third switching transistor to be turned on; The detector detects the rate of increase of the current in the tenth diode and the voltage of the fourth switch.

8. The test method for a three-level circuit according to claim 7, characterized in that, When the second test bridge arm is off, the detector detects the voltage of the upper bridge arm of the second test bridge arm and the voltage of the freewheeling unit, including: The controller sends the sixth control command to the three-level circuit, the sixth control command being used to instruct the third switch and the fourth switch to be turned off; The detector detects the voltage of the tenth diode and the voltage of the third switch.

9. The test method for a three-level circuit according to claim 5, characterized in that, The control signal further includes: the first control command, the second control command, the first control command and the third control command issued sequentially; Alternatively, the control signal may further include: a first control command, a second control command, a seventh control command, a second control command, a first control command, a second control command, and a third control command issued sequentially; the seventh control command is used to instruct the lower bridge arm of the first test bridge arm and the upper bridge arm of the second test bridge arm to be turned on. Alternatively, the control signal may further include: the fourth control command, the fifth control command, the fourth control command and the sixth control command issued sequentially; Alternatively, the control signal may further include: the fourth control command, the fifth control command, the seventh control command, the fifth control command, the fourth control command, the fifth control command, and the sixth control command issued sequentially.

10. The test method for a three-level circuit according to claim 5, characterized in that, The test unit further includes: a first resistor, connected in parallel with a first inductor; When the first test bridge arm is off and the second test bridge arm is off, the first inductor releases electrical energy through the first resistor.

11. A three-level circuit, characterized in that, include: The first test bridge arm consists of a test unit, a freewheeling unit, an energy storage unit, and a controller. The first end of the first test bridge arm is connected to the first end of the energy storage unit, the second end of the first test bridge arm is connected to the first end of the test unit, and the second end of the test unit is connected to the second end of the freewheeling unit; the first end of the freewheeling unit is connected to the third end of the first test bridge arm, and the second end of the energy storage unit is connected to the second end of the freewheeling unit; the controller is connected to the first test bridge arm, and the controller is used to execute the test method of the three-level circuit according to any one of claims 1-10.

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