A midpoint clamping three-level control circuit and control method

Abstract

The application discloses a midpoint clamping three-level control circuit and a control method, wherein the midpoint clamping three-level control circuit comprises a main controller, a sub-controller, a midpoint clamping three-level unit and a driving module; the main controller is provided with a first optical communication module; the sub-controller is provided with a second optical communication module; the first optical communication module and the second optical communication module are connected through an optical fiber; the midpoint clamping three-level unit comprises at least four power switch tubes; the driving module is connected with the controlled ends of the power switch tubes one by one; and the sub-controller is connected with the driving module. The instruction electric signal generated by the main controller is converted into an optical signal through the first optical communication module, and the optical signal can avoid electromagnetic interference of the environment when being transmitted in the optical fiber; the optical signal is converted into the instruction electric signal through the second optical communication module and is acquired by the sub-controller, so that the signal is avoided from being interfered by the electromagnetic interference in the transmission process through the optical communication, and the power switch tubes in the midpoint clamping three-level unit can work strictly according to the action sequence, and the reliability is improved.

Description

Technical Field

[0001] This invention relates to the field of midpoint clamping three-level circuits, and particularly to a midpoint clamping three-level control circuit and control method. Background Technology

[0002] The midpoint clamp three-level circuit (NPC), compared to the general two-level circuit structure, has more output level steps, which can obtain a better output waveform and reduce harmonics. It also has the advantages of reduced loss, high efficiency and high operating frequency. Therefore, it is widely used in various inverters, frequency converters, power units and other equipment or devices.

[0003] In the operation of a midpoint clamping three-level circuit, the sequence of operation of the internal power switches during state switching is strictly required; otherwise, circuit components may be damaged. However, midpoint clamping three-level circuits are often used in high-power operating environments, where the control drive signal is easily affected by electromagnetic interference generated by the high voltage and high current of the power unit during transmission, leading to incorrect operation sequence of the power switches and damage to them. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a midpoint clamping three-level control circuit, which can improve the anti-interference capability of communication between the main controller and the sub-controller.

[0005] The present invention also proposes a control method that can improve the anti-interference capability of communication between the main controller and the sub-controller and reduce the turn-off spike of the switching transistor.

[0006] According to a first aspect of the present invention, a midpoint clamping three-level control circuit includes: a main controller, which is provided with a first optical communication module; a sub-controller, which is provided with a second optical communication module, wherein the first optical communication module and the second optical communication module are connected via optical fiber; a midpoint clamping three-level unit, which includes at least four power switching transistors; and a driving module, which is connected to the controlled terminals of the power switching transistors one by one, wherein the sub-controller is connected to the driving module.

[0007] According to an embodiment of the present invention, a midpoint clamping three-level control circuit has at least the following advantages: the main controller generates instructions and transmits these instructions to the sub-controller via a first optical communication module and a second optical communication module. The sub-controller responds to the instructions and controls the drive module to drive the midpoint clamping three-level unit to operate, that is, controls the drive power switching transistors to switch in the correct sequence. The instruction electrical signal generated by the main controller is converted into an optical signal via the first optical communication module. When the optical signal is transmitted in the optical fiber, electromagnetic interference from the environment can be avoided. The optical signal is converted into an instruction electrical signal via the second optical communication module and acquired by the sub-controller. In this way, electromagnetic interference is avoided during signal transmission through optical communication, which helps to ensure that the power switching transistors in the midpoint clamping three-level unit operate strictly in the correct sequence, thereby improving reliability.

[0008] According to some embodiments of the present invention, the driving module is provided with a first input terminal, a second input terminal and a driving output terminal, the sub-controller is connected to the first input terminal and the second input terminal respectively, the driving output terminal is connected to the controlled terminal corresponding to the power switch, and the driving module controls the corresponding power switch to turn on, hard turn off, soft turn off or staged turn off according to the level of the first input terminal and the level of the second input terminal.

[0009] According to some embodiments of the present invention, the driving module includes a first optocoupler, a second optocoupler, a first processing unit, and an amplification circuit. The sub-controller is connected to the input terminal of the first optocoupler and the input terminal of the second optocoupler, respectively. The output terminal of the first optocoupler and the output terminal of the second optocoupler are both connected to the first processing unit. The first processing unit is connected to the controlled terminal of the corresponding power switch tube through the amplification circuit.

[0010] According to some embodiments of the present invention, an isolation power supply is also included, the isolation power supply having a primary-side input terminal and a secondary-side output terminal corresponding to each of the driving modules, the primary-side input terminal being connected to a power supply terminal, and the secondary-side output terminal being connected to the corresponding driving module and the midpoint clamping three-level unit.

[0011] According to some embodiments of the present invention, the isolated power supply includes a first push-pull switch, a second push-pull switch, a transformer, and rectifier and voltage regulator circuits corresponding to the driving modules. The transformer includes a primary coil and a secondary coil corresponding to the rectifier and voltage regulator circuits. The primary coil is connected to the first push-pull switch, the second push-pull switch, and the power supply terminal, respectively. The primary coil is connected to the corresponding rectifier and voltage regulator circuit, and the rectifier and voltage regulator circuit is connected to the corresponding driving module and the midpoint clamping three-level unit, respectively.

[0012] According to some embodiments of the present invention, the drive module further includes a fault detection unit and a third optocoupler. The fault detection unit is connected to the secondary output terminal and the power switch. The input terminal of the third optocoupler is connected to the fault detection unit, and the output terminal of the third optocoupler is connected to the sub-controller.

[0013] According to some embodiments of the present invention, the midpoint clamping three-level unit includes four IGBTs: IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4. The midpoint clamping three-level unit also includes diodes DA and DB, capacitor C1, and capacitor C2. One end of IGBT_T1 is connected to one end of capacitor C1 and its DC positive terminal. The other end of IGBT_T1 is connected to one end of IGBT_T2 and the cathode of diode DA. The other end of IGBT_T2 is connected to one end of IGBT_T3 and its DC positive terminal. One end of the IGBT_T1 is connected to the AC terminal; the other end of the IGBT_T3 is connected to one end of the IGBT_T4 and the anode of the diode DB; the other end of the IGBT_T4 is connected to one end of the capacitor C2 and the DC negative terminal; the other ends of the capacitor C1, the other ends of the capacitor C2, the anode of the diode DA, and the cathode of the diode DB are all grounded; the controlled terminals of the IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4 are respectively connected to the corresponding drive modules.

[0014] According to some embodiments of the present invention, the level control circuit is characterized in that it further includes a temperature detection module, which is connected to the power switch and the sub-controller respectively.

[0015] According to some embodiments of the present invention, the temperature detection module includes a second processing unit, a fourth optocoupler, and a temperature sensor corresponding to each of the power switching transistors. The temperature sensor is connected to the power switching transistors, the second processing unit is connected to the output terminals of the power switching transistors and the fourth optocoupler, and the output terminal of the fourth optocoupler is connected to the sub-controller.

[0016] According to a second aspect of the present invention, a control method for a midpoint clamping three-level control circuit as described above includes: when the sub-controller does not acquire a fault signal generated by the fault detection unit, the sub-controller responds to the instruction of the main controller to control the drive module, the drive module causing IGBT_T1 and IGBT_T4 to operate in a hard shutdown state and IGBT_T2 and IGBT_T3 to operate in a graded shutdown state; when the sub-controller acquires a fault signal generated by the fault detection unit, the sub-controller controls the drive module to soft shutdown IGBT_T1, IGBT_T2, IGBT_T3 and IGBT_T4.

[0017] The control method according to embodiments of the present invention has at least the following beneficial effects: During normal operation, the electrical signals of the turn-on and turn-off commands generated by the main controller are converted into optical signals through the first optical communication module. When the optical signals are transmitted in the optical fiber, electromagnetic interference from the environment can be avoided. The optical signals are then converted into electrical signals by the second optical communication module and acquired by the sub-controllers. This optical communication avoids electromagnetic interference during signal transmission. The sub-controllers respond to the commands and control each IGBT to turn on and off in the correct sequence through the drive module. This helps prevent interference from affecting the IGBT's operating sequence and improves reliability. When an undervoltage fault or short-circuit fault occurs, it is necessary to safely stop the operation of the midpoint clamping three-level unit. Therefore, soft-turning off IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4 can minimize the voltage spikes generated during turn-off, facilitating the safe stopping of the midpoint clamping three-level unit during faults, improving safety, and maximizing the flexible use of hard turn-off, soft turn-off, and graded turn-off characteristics to improve circuit safety and operating efficiency.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0020] Figure 1 This is a structural block diagram of one embodiment of the present invention;

[0021] Figure 2 This is a circuit diagram of an isolated power supply in one embodiment of the present invention;

[0022] Figure 3 This is a circuit diagram of one embodiment of the point clamping three-level unit of the present invention;

[0023] Figure 4 This is a circuit diagram of a second embodiment of the point clamping three-level unit of the present invention;

[0024] Figure 5 This is a circuit diagram of a third embodiment of the point clamping three-level unit of the present invention. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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 limiting this invention.

[0027] In the description of this invention, the use of "first" and "second" is for the purpose of distinguishing technical features only, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0028] In the description of this invention, unless otherwise explicitly defined, terms such as "setting," "installing," and "connecting" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0029] like Figure 1 As shown, a midpoint clamping three-level control circuit according to an embodiment of the present invention includes: a main controller 100, which is provided with a first optical communication module 110; a sub-controller 200, which is provided with a second optical communication module 210, wherein the first optical communication module 110 and the second optical communication module 210 are connected via optical fiber; a midpoint clamping three-level unit 300, which includes at least four power switching transistors 310; and a drive module 400, which is connected to the controlled terminals of the power switching transistors 310 one by one, wherein the sub-controller 200 is connected to the drive module 400.

[0030] The main controller 100 generates instructions and transmits them to the sub-controller 200 via the first optical communication module 110 and the second optical communication module 210. The sub-controller 200 responds to the instructions by controlling the drive module 400 to operate the midpoint clamping three-level unit 300, i.e., controlling the power switching transistor 310 to switch in sequence. The instruction electrical signal generated by the main controller 100 is converted into an optical signal by the first optical communication module 110. The optical signal, transmitted through the optical fiber, avoids electromagnetic interference from the environment. The optical signal is then converted back into an instruction electrical signal by the second optical communication module 210 and acquired by the sub-controller 200. This optical communication method avoids electromagnetic interference during signal transmission, ensuring that the power switching transistor 310 in the midpoint clamping three-level unit 300 operates strictly according to the sequence, thus improving reliability.

[0031] The main controller 100 and the sub-controller 200 can be implemented using devices or equipment such as FPGAs and PLCs. The first optical communication module 110 and the second optical communication module 210 can be implemented using bidirectional optical modules, or both the first optical communication module 110 and the second optical communication module 210 can include optical transmitters and optical receivers. The main controller 100 and the sub-controller 200 can communicate serially through the first optical communication module 110 and the second optical communication module 210.

[0032] The switching transistor can be an implementation of devices such as IGBTs and MOSFETs.

[0033] In some embodiments of the present invention, in addition to optical communication between the main controller 100 and the sub-controller 200 through the first optical communication module 110 and the second optical communication module 210, both the main controller 100 and the sub-controller 200 may be provided with electrical connection ports, and the main controller 100 and the sub-controller 200 may achieve electrical communication through the electrical connection ports. This allows the selection of optical communication or electrical communication methods according to the environment, meeting different usage scenarios.

[0034] Reference Figure 1 In some embodiments of the present invention, the driving module 400 is provided with a first input terminal, a second input terminal and a driving output terminal, the sub-controller 200 is connected to the first input terminal and the second input terminal respectively, the driving output terminal is connected to the controlled terminal corresponding to the power switch 310, and the driving module 400 controls the corresponding power switch 310 to turn on, hard turn off, soft turn off or staged turn off according to the level of the first input terminal and the level of the second input terminal.

[0035] The controller 200 controls the levels of the first and second input terminals, allowing for four level combinations: high and high, high and low, low and high, and low and low. This enables the drive module 400 to switch between up to four operating states. Consequently, the drive module 400 can be controlled to command the power switch 310 to operate in hard-off, soft-off, and graded-off states, meeting the needs of different situations and making the control of the power switch 310's operating state more flexible and convenient.

[0036] Hard turn-off occurs when the power switch 310 is turned off, with the voltage at the controlled terminal directly pulled down. This allows for rapid turn-off of the power switch 310 but generates a large voltage spike. Soft turn-off occurs when the power switch 310 is turned off, with the voltage at the controlled terminal gradually decreasing, causing the power switch 310 to turn off gradually. This reduces the current change slope and the voltage spike generated during turn-off, but the turn-off time is longer. Stepped turn-off occurs when the power switch 310 is turned off, with the voltage at the controlled terminal decreasing in stages. This allows for faster turn-off of the power switch 310 while minimizing the voltage spike generated during turn-off.

[0037] Reference Figure 1 In some embodiments of the present invention, the driving module 400 includes a first optocoupler 410, a second optocoupler 420, a first processing unit 430, and an amplifier circuit 440. The sub-controller 200 is connected to the input terminals of the first optocoupler 410 and the second optocoupler 420, respectively. The output terminals of the first optocoupler 410 and the second optocoupler 420 are both connected to the first processing unit 430. The first processing unit 430 is connected to the controlled terminal of the corresponding power switch 310 through the amplifier circuit 440.

[0038] The controller 200 controls the input voltages of the first optocoupler 410 and the second optocoupler 420 respectively. The outputs of the first optocoupler 410 and the second optocoupler 420 generate corresponding levels and transmit them to the first processing unit 430. The first processing unit 430 generates drive signals corresponding to hard turn-off, soft turn-off, and graded turn-off based on the combination of the two levels and transmits them to the amplifier circuit 440. The amplifier circuit 440 amplifies the drive signals and transmits them to the controlled terminal of the power switch 310 so that the power switch 310 can perform turn-on, hard turn-off, soft turn-off, and graded turn-off operations.

[0039] Based on the opto-isolation characteristics of the first optocoupler 410 and the second optocoupler 420, the sub-controller 200 is isolated from the processing unit and the amplifier circuit 440, which can reduce mutual interference and make the sub-controller 200 work more stably.

[0040] The first processing unit 430 can be implemented using devices such as a microcontroller or an embedded chip. The amplifier circuit 440 can be implemented as a push-pull amplifier circuit 440 or a common transistor amplifier circuit 440, etc.

[0041] Reference Figure 1 and Figure 2 In some embodiments of the present invention, an isolation power supply 500 is also included. The isolation power supply 500 is provided with a primary side input terminal and a secondary side output terminal corresponding to the driving module 400. The primary side input terminal is connected to the power supply terminal, and the secondary side output terminal is connected to the driving module 400 and the midpoint clamping three-level unit 300.

[0042] The primary input terminal of the isolation power supply 500 obtains power and then supplies power to the corresponding drive module 400 and the midpoint clamping three-level unit 300 through the secondary output terminal. Since the primary input terminal and each secondary output terminal are isolated from each other, the power supply is more stable and reliable.

[0043] Reference Figure 2 In some embodiments of the present invention, the isolation power supply 500 includes a first push-pull switch 510, a second push-pull switch 520, a transformer 530, and a rectifier and voltage regulator circuit 540 corresponding to the drive module 400. The transformer 530 includes a primary coil 531 and a secondary coil 532 corresponding to the rectifier and voltage regulator circuit 540. The primary coil 531 is connected to the first push-pull switch 510, the second push-pull switch 520, and the power supply terminal, respectively. The primary coil 531 is connected to the corresponding rectifier and voltage regulator circuit 540, and the rectifier and voltage regulator circuit 540 is connected to the corresponding drive module 400 and the midpoint clamping three-level unit 300, respectively.

[0044] The first push-pull switch 510 and the second push-pull switch 520 are connected to the primary coil 531 of the transformer 530 to form a push-pull switching power supply, which is beneficial to improving working efficiency. The multiple secondary coils 532 of the transformer 530 supply power to the drive module 400 and the midpoint clamping three-level unit 300. The multiple secondary coils 532 are isolated from each other, which helps to simplify the design of the isolation power supply 500.

[0045] Reference Figure 1 In some embodiments of the present invention, the drive module 400 further includes a fault detection unit 450 and a third optocoupler 460. The fault detection unit 450 is connected to the secondary output terminal and the power switch 310. The input terminal of the third optocoupler 460 is connected to the fault detection unit 450, and the output terminal of the third optocoupler 460 is connected to the sub-controller 200.

[0046] The fault detection unit 450 is connected to the secondary output terminal and the power switch 310 to detect the voltage at the secondary output terminal and the current of the power switch 310. When an undervoltage fault occurs at the secondary output terminal or an overcurrent fault occurs in the power switch 310, the fault detection unit 450 generates a fault signal and transmits it to the sub-controller 200 through the third optocoupler 460, so that the sub-controller 200 can stop the drive module 400 or the key clamping three-level unit in time to improve safety.

[0047] The third optocoupler 460 can opto-isolate the fault detection unit 450 from the sub-controller 200, which is beneficial for the sub-controller 200 to work more stably and improve reliability.

[0048] The fault detection unit 450 can be implemented by including a voltage comparator, a current comparator, a voltage detection circuit, and a current detection circuit. The voltage detection circuit is connected to the voltage comparator. When the voltage detected by the voltage detection circuit at the secondary output terminal is less than the threshold of the voltage comparator, the voltage comparator generates an undervoltage fault signal. The current detection circuit is connected to the current comparator. When the current detected by the current detection circuit at the power switch 310 is greater than the threshold of the current comparator, the current comparator generates an overcurrent fault signal, thereby realizing undervoltage detection at the secondary output terminal and overcurrent detection at the power switch 310.

[0049] Reference Figure 3 In some embodiments of the present invention, the midpoint clamping three-level unit 300 includes four IGBTs namely IGBT_T1, IGBT_T2, IGBT_T3 and IGBT_T4, and the midpoint clamping three-level unit 300 also includes diode DA, diode DB, capacitor C1 and capacitor C2.

[0050] One end of the IGBT_T1 is connected to one end of the capacitor C1 and the DC positive terminal, and the other end of the IGBT_T1 is connected to one end of the IGBT_T2 and the cathode of the diode DA.

[0051] The other end of IGBT_T2 is connected to one end of IGBT_T3 and the AC terminal, respectively.

[0052] The other end of the IGBT_T3 is connected to one end of the IGBT_T4 and the anode of the diode DB, respectively;

[0053] The other end of the IGBT_T4 is connected to one end of the capacitor C2 and the DC negative terminal, respectively.

[0054] The other end of capacitor C1, the other end of capacitor C2, the anode of diode DA, and the cathode of diode DB are all grounded;

[0055] The controlled terminals of IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4 are respectively connected to the corresponding drive modules 400.

[0056] IGBT_T1, IGBT_T2, IGBT_T3, IGBT_T4, diodes DA and DB, capacitors C1 and C2 constitute a type I NPC circuit topology. During normal operation, the sequence of operation and state switching of IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4 follows the order of IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4, with 0 representing off and 1 representing on: 1100→0100→0110→0010→0011→0010→0110→0100→1100. For example, 1100 represents IGBT_T1 and IGBT_T2 being on while IGBT_T3 and IGBT_T4 are off, and this cycle continues.

[0057] IGBTs typically come with a diode connected in reverse parallel between the collector and emitter of the IGBT.

[0058] In some embodiments of the present invention, reference is made to Figure 4 The midpoint clamping three-level unit 300 can also be implemented by including four power switching transistors 310 and two capacitors, with the power switching transistors 310 and the capacitors forming a T-type NPC circuit topology; Reference Figure 5 The midpoint clamping three-level unit 300 can also be implemented by including six power switching transistors 310 and two capacitors, with the power switching transistors 310 and capacitors forming an ANPC circuit topology.

[0059] Reference Figure 1 In some embodiments of the present invention, a temperature detection module 600 is also included, which is connected to the power switch 310 and the sub-controller 200 respectively.

[0060] Since the power switch 310 generates heat during operation, it requires a suitable operating temperature to ensure stable operation. The temperature detection module 600 detects the operating temperature of the power switch 310 and feeds it back to the sub-controller 200. The sub-controller 200 then uploads the operating temperature signals of each power switch 310 to the main controller 100, thus achieving temperature monitoring of each power switch 310.

[0061] Reference Figure 1 In some embodiments of the present invention, the temperature detection module 600 includes a second processing unit 610, a fourth optocoupler 620, and a temperature sensor 630 corresponding to the power switch 310. The temperature sensor 630 is connected to the power switch 310. The second processing unit 610 is connected to the output terminals of the power switch 310 and the fourth optocoupler 620. The output terminal of the fourth optocoupler 620 is connected to the sub-controller 200.

[0062] Temperature sensor 630 detects the operating temperature of the corresponding power switch transistor 310 and transmits the detected temperature signal to the second processing unit 610. The second processing unit 610 transmits multiple temperature signals to the sub-controller 200 via the fourth optocoupler 620. The sub-controller 200 then uploads all the temperature signals to the main controller 100 via the second opto-communication module and the first opto-communication module. Compared to the traditional method of uploading only the temperature signal corresponding to the highest temperature, uploading multiple temperature signals individually allows for more accurate control of the operating temperature of the power switch transistor 310. The use of the fourth optocoupler 620 provides opto-isolation between the second processing unit 610 and the sub-controller 200, which helps to avoid mutual interference and improves the stability of the sub-controller 200.

[0063] The second processor can be implemented using devices such as microcontrollers and embedded chips.

[0064] According to a second aspect embodiment of the present invention, a control method for a midpoint clamping three-level control circuit as described above is applied:

[0065] When the sub-controller 200 does not receive the fault signal generated by the fault detection unit 450, the sub-controller 200 responds to the instruction of the main controller 100 to control the drive module 400 to make the IGBT_T1 and the IGBT_T4 work in hard shutdown state and the IGBT_T2 and the IGBT_T3 work in graded shutdown state.

[0066] When the sub-controller 200 receives a fault signal generated by the fault detection unit 450, the sub-controller 200 controls the drive module 400 to soft-shut down the IGBT_T1, the IGBT_T2, the IGBT_T3, and the IGBT_T4.

[0067] During normal operation, the electrical signals of the turn-on and turn-off commands generated by the main controller 100 are converted into optical signals by the first optical communication module 110. When the optical signals are transmitted in the optical fiber, they can avoid electromagnetic interference from the environment. The optical signals are converted into electrical signals by the second optical communication module 210 and acquired by the sub-controller 200. In this way, the signal is protected from electromagnetic interference during transmission through optical communication. The sub-controller 200 responds to the commands and controls each IGBT to turn on and off in the order of operation through the drive module 400. This helps to prevent interference from affecting the operation sequence of the IGBTs and improves reliability.

[0068] During normal operation, in the 0110 state, the current flows sequentially through the AC line, IGBT_T3, and diode DB. When switching to the 0100 state, IGBT_T3 turns off and commutation occurs. The current then flows sequentially through the AC line, diode D2 (connected in reverse parallel to IGBT_T2), diode D1 (connected in reverse parallel to IGBT_T1), and capacitor C1. During the commutation process when IGBT_T3 turns off, the stray inductance of capacitor C1, diodes D1 and D2, IGBT_T3, and diode DB causes a large voltage spike when IGBT_T3 turns off, potentially damaging circuit components and shortening IGBT lifespan. Therefore, controlling IGBT_T3 to operate in a stepped turn-off state during normal operation can reduce the voltage spike generated during IGBT_T3 turn-off. Similarly, due to the dual circuit topology, IGBT_T2 also faces the same issue. Therefore, operating IGBT_T2 in a stepped turn-off state during normal operation helps improve circuit reliability and extend its lifespan.

[0069] The turn-off commutation of IGBT_T2 and IGBT_T3, which are internal transistors, involves more components and causes larger voltage spikes. In contrast, the turn-off commutation of IGBT_T1 and IGBT_T4, which are external transistors, involves fewer components and can therefore operate in a hard turn-off state, improving turn-off efficiency.

[0070] When an undervoltage fault or short-circuit fault occurs, it is necessary to safely stop the operation of the midpoint clamping three-level unit 300. Therefore, soft-shutting down IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4 can minimize the voltage spikes generated during shutdown, which is beneficial for safely stopping the operation of the midpoint clamping three-level unit 300 in the event of a fault.

[0071] Therefore, during normal operation, IGBT_T1 and IGBT_T4 are operated in hard-shutdown mode, while IGBT_T2 and IGBT_T3 are operated in staged shutdown mode. This balances circuit safety, lifespan, and operating efficiency. In case of a fault, IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4 are soft-shutdown, improving safety. This maximizes the flexibility of hard-shutdown, soft-shutdown, and staged shutdown features, thereby enhancing both circuit safety and operating efficiency.

[0072] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] Of course, the present invention is not limited to the above-described embodiments. Those skilled in the art can make equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A midpoint clamping three-level control circuit, characterized in that, include: The main controller (100) is equipped with a first optical communication module (110). The sub-controller (200) is equipped with a second optical communication module (210), and the first optical communication module (110) and the second optical communication module (210) are connected by optical fiber; The midpoint clamping three-level unit (300) includes at least four power switching transistors (310). The drive module (400) is connected to the controlled terminals of the power switch (310) one by one. The sub-controller (200) is connected to the drive module (400). The drive module (400) is provided with a first input terminal, a second input terminal and a drive output terminal. The sub-controller (200) is connected to the first input terminal and the second input terminal respectively. The drive output terminal is connected to the controlled terminal of the corresponding power switch (310). The drive module (400) controls the corresponding power switch (310) to turn on, hard turn off, soft turn off or staged turn off according to the level of the first input terminal and the level of the second input terminal. An isolation power supply (500) is provided with a primary side input terminal and a secondary side output terminal corresponding to the driving module (400). The primary side input terminal is connected to the power supply terminal, and the secondary side output terminal is connected to the driving module (400) and the midpoint clamping three-level unit (300). The drive module (400) further includes a fault detection unit (450) and a third optocoupler (460). The fault detection unit (450) is connected to the secondary output terminal and the power switch (310). The input terminal of the third optocoupler (460) is connected to the fault detection unit (450), and the output terminal of the third optocoupler (460) is connected to the sub-controller (200). The midpoint clamping three-level unit (300) includes four IGBTs: IGBT_T1, IGBT_T2, IGBT_T3 and IGBT_T4. The midpoint clamping three-level unit (300) also includes diode DA, diode DB, capacitor C1 and capacitor C2. One end of the IGBT_T1 is connected to one end of the capacitor C1 and the DC positive terminal, and the other end of the IGBT_T1 is connected to one end of the IGBT_T2 and the cathode of the diode DA. The other end of IGBT_T2 is connected to one end of IGBT_T3 and the AC terminal, respectively. The other end of the IGBT_T3 is connected to one end of the IGBT_T4 and the anode of the diode DB, respectively; The other end of the IGBT_T4 is connected to one end of the capacitor C2 and the DC negative terminal, respectively. The other end of capacitor C1, the other end of capacitor C2, the anode of diode DA, and the cathode of diode DB are all grounded; The controlled terminals of IGBT_T1, IGBT_T2, IGBT_T3, and IGBT_T4 are respectively connected to the corresponding drive modules (400); Control methods applied to midpoint clamping three-level control circuits include: When the sub-controller (200) does not receive the fault signal generated by the fault detection unit (450), the sub-controller (200) responds to the instruction of the main controller (100) to control the drive module (400), and the drive module (400) causes the IGBT_T1 and the IGBT_T4 to work in hard shutdown state and the IGBT_T2 and the IGBT_T3 to work in graded shutdown state; When the sub-controller (200) receives a fault signal generated by the fault detection unit (450), the sub-controller (200) controls the drive module (400) to soft-shut down the IGBT_T1, the IGBT_T2, the IGBT_T3 and the IGBT_T4.

2. The midpoint clamping three-level control circuit according to claim 1, characterized in that: The driving module (400) includes a first optocoupler (410), a second optocoupler (420), a first processing unit (430), and an amplifier circuit (440). The sub-controller (200) is connected to the input terminal of the first optocoupler (410) and the input terminal of the second optocoupler (420), respectively. The output terminals of the first optocoupler (410) and the second optocoupler (420) are both connected to the first processing unit (430). The first processing unit (430) is connected to the controlled terminal of the corresponding power switch (310) through the amplifier circuit (440).

3. The midpoint clamping three-level control circuit according to claim 1, characterized in that: The isolation power supply (500) includes a first push-pull switch (510), a second push-pull switch (520), a transformer (530), and a rectifier and voltage regulator circuit (540) corresponding to the drive module (400). The transformer (530) includes a primary coil (531) and a secondary coil (532) corresponding to the rectifier and voltage regulator circuit (540). The primary coil (531) is connected to the first push-pull switch (510), the second push-pull switch (520), and the power supply terminal, respectively. The primary coil (531) is connected to the corresponding rectifier and voltage regulator circuit (540), and the rectifier and voltage regulator circuit (540) is connected to the corresponding drive module (400) and the midpoint clamping three-level unit (300), respectively.

4. A midpoint clamping three-level control circuit according to any one of claims 1 to 3, characterized in that: It also includes a temperature detection module (600), which is connected to the power switch (310) and the sub-controller (200) respectively.

5. A midpoint clamping three-level control circuit according to claim 4, characterized in that: The temperature detection module (600) includes a second processing unit (610), a fourth optocoupler (620), and a temperature sensor (630) corresponding to the power switch (310). The temperature sensor (630) is connected to the power switch (310). The second processing unit (610) is connected to the output terminals of the power switch (310) and the fourth optocoupler (620). The output terminal of the fourth optocoupler (620) is connected to the sub-controller (200).

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