A midpoint active clamped three-level inverter, control method and control device

Abstract

The present invention is applicable to the technical field of inverters, and provides a midpoint active clamped three-level inverter, a control method and a control device. The midpoint active clamped three-level inverter includes: a bridge arm unit, a clamping unit connected to the bridge arm unit, and a bridge arm output end connected to the bridge arm unit; the bridge arm unit includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a first diode, a second diode, a third diode and a fourth diode connected in anti-parallel to the first switch tube, the second switch tube, the third switch tube and the fourth switch tube; the clamping unit includes a fifth switch tube, a sixth switch tube, a fifth switch tube and a sixth diode connected in anti-parallel to the sixth switch tube; the fifth diode and the sixth diode are silicon carbide diodes. The present invention can reduce uneven heating of each switch tube and improve the efficiency and stability of electric energy conversion.

Description

Technical Field

[0001] The present invention belongs to the technical field of inverters, and in particular relates to a midpoint active clamped three-level inverter, a control method and a control device. Background Art

[0002] An inverter is an energy conversion device that converts direct current into alternating current. In practical applications, two-level and three-level topologies are the most common. The three-level topology is further divided into T-type three-level, I-type three-level, and midpoint active clamped three-level. Existing inverter expansion and control solutions: 1. T-type three-level is suitable for 1000V systems due to the limitation of switch tube specifications. I-type three-level can choose switch tubes of different specifications to deal with 1000V systems and 1500V systems respectively. However, the performance of the inner tube and clamping diode in the I-type three-level is greatly limited. The midpoint active clamping three-level adds a clamping switch tube, which is flexible to control. However, the direct loss of the clamping diode is large, which easily causes uneven heating of each switch tube. In addition, the utilization rate of each switch tube is low, so that each switch tube is affected by the stress between each switch tube, which leads to low power conversion efficiency and poor stability of the circuit. Summary of the invention

[0003] The embodiment of the present invention provides a midpoint active clamped three-level inverter, which aims to solve the problems of uneven heating of various switch tubes in the circuit, low power conversion efficiency and poor stability.

[0004] In a first aspect, an embodiment of the present invention provides a midpoint active clamped three-level inverter, comprising: a bridge arm unit, a clamping unit connected to the bridge arm unit, and a bridge arm output terminal connected to the bridge arm unit;

[0005] The bridge arm unit includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube connected in series in sequence, and a first diode, a second diode, a third diode, and a fourth diode connected in anti-parallel with the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube in a one-to-one correspondence;

[0006] The clamping unit comprises a fifth switch tube and a sixth switch tube connected in series in sequence, and a fifth diode and a sixth diode connected in anti-parallel with the fifth switch tube and the sixth switch tube in one-to-one correspondence, an end of the fifth switch tube away from the sixth switch tube is arranged on a connection line between the first switch tube and the second switch tube, and an end of the sixth switch tube away from the fifth switch tube is arranged on a connection line between the third switch tube and the fourth switch tube;

[0007] A bridge arm output end provided on a connection line between the second switch tube and the third switch tube;

[0008] The fifth switch tube or the fifth diode and the second switch tube or the second diode form a first freewheeling loop, the sixth switch tube or the sixth diode and the third switch tube or the third diode form a second freewheeling loop, and the first freewheeling loop and the second freewheeling loop form a double freewheeling loop for changing the freewheeling path;

[0009] The fifth diode and the sixth diode are silicon carbide diodes.

[0010] In a second aspect, an embodiment of the present invention further provides a control method for a midpoint active clamped three-level inverter, which is used for the midpoint active clamped three-level inverter provided in the above embodiment, and the method includes:

[0011] Obtaining a first drive signal, a second drive signal, a third drive signal, a fourth drive signal, a fifth drive signal, and a sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube;

[0012] According to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, the on-off states of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube are controlled based on the preset power switching mode to form a dual freewheeling loop to realize the commutation path and power conversion.

[0013] In a third aspect, an embodiment of the present invention further provides a control device for a midpoint active clamped three-level inverter, which is used for the midpoint active clamped three-level inverter provided in the above embodiment, and the device includes:

[0014] an acquisition unit, configured to acquire a first drive signal, a second drive signal, a third drive signal, a fourth drive signal, a fifth drive signal, and a sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube;

[0015] A control unit is used to control the on-off states of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on a preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal to form a dual freewheeling loop to realize a commutation path and power conversion.

[0016] The beneficial effects achieved by the present invention are that the fifth and sixth diodes are silicon carbide diodes, which reduces the turn-on loss of the first and fourth switch tubes. Controlling the conduction of the fifth and sixth switch tubes can reduce the direct loss of the fifth and sixth diodes, so that each switch tube is heated evenly. Only the fifth and sixth diodes are silicon carbide diodes, which reduces the demand for silicon carbide diodes and can reduce material costs. A double freewheeling circuit is also used to change the freewheeling path, which disperses the thermal stress between each switch tube. Before the first switch tube and / or the fourth switch tube is turned on, the sixth switch tube or the fifth switch tube of the corresponding half cycle is turned off to avoid the disadvantage that the second diode and the third diode of the second and third switch tubes are anti-parallel silicon diodes, which cause the first and fourth switch tubes to generate additional turn-on losses. The voltage stress of the corresponding switch tube is reduced, the forward direct loss of the fifth and sixth diodes is reduced, the power conversion efficiency of the circuit is improved, and the stability of the reliable operation of the inverter is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a circuit diagram of a midpoint active clamped three-level inverter provided by an embodiment of the present invention;

[0018] Figure 2 is a flow chart of a control method of a midpoint active clamped three-level inverter provided by an embodiment of the present invention;

[0019] Figure 3 It is a schematic diagram of a wave generation situation during a positive and negative half cycle provided by an embodiment of the present invention;

[0020] Figure 4 is a modal schematic diagram provided by mode 1 in an embodiment of the present invention;

[0021] Figure 5 is a modal schematic diagram provided by mode 2 in an embodiment of the present invention;

[0022] Figure 6 It is a modal schematic diagram provided by mode three in an embodiment of the present invention;

[0023] Figure 7 is a modal schematic diagram provided by mode 4 in an embodiment of the present invention;

[0024] Figure 8 is a flow chart of a method provided in step 102 of an embodiment of the present invention;

[0025] Fig. 9 is a modal schematic diagram provided by mode five in an embodiment of the present invention;

[0026] Fig.10 is a modal schematic diagram provided by mode six in an embodiment of the present invention;

[0027] Fig.11 is a modal schematic diagram provided by mode seven in an embodiment of the present invention;

[0028] Fig.12 is another method flow chart provided in step 102 in an embodiment of the present invention;

[0029] Fig.13 1 is a schematic structural diagram of a control device for a midpoint active clamped three-level inverter provided by an embodiment of the present invention;

[0030] Fig.14 is a structural schematic diagram provided by a control unit in an embodiment of the present invention;

[0031] Fig.15 It is another structural schematic diagram provided by the control unit in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] The present invention takes advantage of the fifth diode and the sixth diode being silicon carbide diodes, reduces the turn-on loss of the first switch tube and the fourth switch tube, and controls the conduction of the fifth switch tube and the sixth switch tube to reduce the direct loss of the fifth diode and the sixth diode, so that each switch tube is heated evenly. And only the fifth diode and the sixth diode are silicon carbide diodes, which reduces the demand for silicon carbide diodes and can reduce material costs. A double freewheeling circuit is also used to change the freewheeling path, which disperses the thermal stress between each switch tube. Before the first switch tube and / or the fourth switch tube is turned on, the sixth switch tube or the fifth switch tube of the corresponding half cycle is turned off to avoid the disadvantage that the second diode and the third diode of the second switch tube and the third switch tube are anti-parallel silicon diodes, which cause the first switch tube and the fourth switch tube to generate additional turn-on loss. The voltage stress of the corresponding switch tube is reduced, the forward direct loss of the fifth diode and the sixth diode is reduced, the power conversion efficiency of the circuit is improved, and the stability of the reliable operation of the inverter is improved.

[0034] Embodiment 1

[0035] like Figure 1 As shown, Figure 1 1 is a circuit diagram of a midpoint active clamped three-level inverter provided by an embodiment of the present invention. The midpoint active clamped three-level inverter comprises: a bridge arm unit 2, a clamping unit 3 connected to the bridge arm unit 2, and a bridge arm output terminal 1 connected to the bridge arm unit 2.

[0036] The bridge arm unit 2 includes a first switch tube T1, a second switch tube T2, a third switch tube T3, and a fourth switch tube T4 connected in series in sequence, and a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4 connected in anti-parallel with the first switch tube T1, the second switch tube T2, the third switch tube T3, and the fourth switch tube T4, one by one.

[0037] The clamping unit 3 includes a fifth switch tube T5 and a sixth switch tube T6 which are connected in series in sequence, and a fifth diode D5 and a sixth diode D6 which are anti-parallel connected to the fifth switch tube T5 and the sixth switch tube T6 in a one-to-one correspondence. An end of the fifth switch tube T5 away from the sixth switch tube T6 is arranged on a connecting line between the first switch tube T1 and the second switch tube T2, and an end of the sixth switch tube T6 away from the fifth switch tube T5 is arranged on a connecting line between the third switch tube T3 and the fourth switch tube T4.

[0038] A bridge arm output terminal 1 is arranged on a connection line between the second switch tube T2 and the third switch tube T3.

[0039] The fifth switch tube T5 or the fifth diode D5 and the second switch tube T2 or the second diode D2 form a first freewheeling circuit, the sixth switch tube T6 or the sixth diode D6 and the third switch tube T3 or the third diode D3 form a second freewheeling circuit, and the first freewheeling circuit and the second freewheeling circuit form a double freewheeling circuit for changing the freewheeling path.

[0040] Among them, the first switch tube T1, the second switch tube T2, the third switch tube T3, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 correspond to each other and include the first MOS tube, the second MOS tube, the third MOS tube, the fourth MOS tube, the fifth MOS tube and the sixth MOS tube, or the first triode, the second triode, the third triode, the fourth triode, the fifth triode and the sixth triode. The first switch tube T1, the second switch tube T2, the third switch tube T3, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 can all be Si-IGBT (silicon insulated gate bipolar transistor). The above-mentioned bridge arm output end 1 is also connected to an inductor L.

[0041] The first switch tube T1 and the fourth switch tube can be called outer tubes, the second switch tube T2 and the third switch tube T3 can be called outer tubes, and the fifth switch tube T5 and the sixth switch tube T6 can be called clamping tubes.

[0042] The first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 respectively include a first silicon diode, a second silicon diode, a third silicon diode and a fourth silicon diode. The silicon diode can be represented by Si-DIODE or Si diode.

[0043] The fifth diode D5 and the sixth diode D6 are silicon carbide diodes. The silicon carbide diode can be a Schottky diode. The two most important performance indicators of the Schottky diode are its low reverse recovery charge (Qrr) and recovery softening coefficient. When the diode voltage becomes reverse biased, the low reverse recovery charge Qrr greatly shortens the time required for the shutdown process, that is, the reverse recovery time trr. The trr of the silicon carbide diode is less than 0.01 microseconds. It is convenient for use in a high frequency range. The high softening coefficient will reduce the electromagnetic interference noise generated by the diode shutdown and reduce the commutation operation interference. The silicon carbide diode can be represented by SiC-DIODE or SiC diode.

[0044] The first freewheeling circuit can be called a 0+ circuit, and the second freewheeling circuit can be called a 0- circuit. When only the first freewheeling circuit or the second freewheeling circuit works alone, the first freewheeling circuit or the second freewheeling circuit can be called a single freewheeling circuit. When the first freewheeling circuit and the second freewheeling circuit work at the same time, the first freewheeling circuit and the second freewheeling circuit form a double freewheeling circuit, and the double freewheeling circuit can be called a double freewheeling circuit 0+, 0-. When the double freewheeling circuit is freewheeling, it can be called double freewheeling 0+, 0- freewheeling.

[0045] In one embodiment of the present invention, the midpoint active clamping three-level inverter further includes a voltage dividing unit 4 connected to the bridge arm unit 2 and the clamping unit 3 respectively; the voltage dividing unit 4 includes a first voltage dividing capacitor C1 and a second voltage dividing capacitor C2 connected in series, an end of the first voltage dividing capacitor C1 away from the second voltage dividing capacitor C2 is connected to an end of the first switch tube T1 away from the second switch tube T2, and an end of the second voltage dividing capacitor C2 away from the first voltage dividing capacitor C1 is connected to an end of the fourth switch tube T4 away from the third switch tube T3. The first voltage dividing capacitor C1 and the fifth switch tube T5 or the fifth diode D5 and the second switch tube T2 or the second diode D2 form a first freewheeling loop, and the second voltage dividing capacitor C2 and the sixth switch tube T6 or the sixth diode D6 and the third switch tube T3 or the third diode D3 form a second freewheeling loop.

[0046] The first voltage-dividing capacitor C1 and the second voltage-dividing capacitor C2 play a voltage-dividing role and are used to divide the voltage of the circuit. The first voltage-dividing capacitor C1 and the second voltage-dividing capacitor C2 can also play a filtering role.

[0047] Specifically, the input end of the first switch tube T1 is connected to an end of the first voltage-dividing capacitor C1 away from the second voltage-dividing capacitor C2, the output end of the first switch tube T1 is respectively connected to the input end of the second switch tube T2 and the input of the fifth switch tube T5, the output end of the second switch tube T2 is respectively connected to the input end of the third switch tube T3 and the bridge arm output end 1, the output end of the third switch tube T3 is respectively connected to the input end of the fourth switch tube T4 and the output end of the sixth switch tube T6, and the output end of the fourth switch tube T4 is connected to an end of the second voltage-dividing capacitor C2 away from the first voltage-dividing capacitor C1.

[0048] The cathode of the first diode D1 is connected to the input end of the first switch tube T1, the anode of the first diode D1 is connected to the output end of the first switch tube T1, the cathode of the second diode D2 is connected to the input end of the second switch tube T2, the anode of the second diode D2 is connected to the output end of the second switch tube T2, the cathode of the third diode D3 is connected to the input end of the third switch tube T3, the anode of the third diode D3 is connected to the output end of the third switch tube T3, the cathode of the fourth diode D4 is connected to the input end of the fourth switch tube T4, the anode of the fourth diode D4 is connected to the output end of the fourth switch tube T4, the cathode of the fifth diode D5 is connected to the input end of the fifth switch tube T5, the anode of the fifth diode D5 is connected to the output end of the fifth switch tube T5, the cathode of the sixth diode D6 is connected to the input end of the sixth switch tube T6, and the anode of the sixth diode D6 is connected to the output end of the sixth switch tube.

[0049] It can be understood that when the first switch tube T1, the second switch tube T2, the third switch tube T3, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 correspond one by one to the first MOS tube, the second MOS tube, the third MOS tube, the fourth MOS tube, the fifth MOS tube and the sixth MOS tube, the input ends corresponding to the first switch tube T1, the second switch tube T2, the third switch tube T3, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 are all D poles (drains) corresponding to the first MOS tube, the second MOS tube, the third MOS tube, the fourth MOS tube, the fifth MOS tube and the sixth MOS tube.

[0050] The output ends corresponding to the first switch tube T1, the second switch tube T2, the third switch tube T3, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 are all the S poles (sources) corresponding to the first MOS tube, the second MOS tube, the third MOS tube, the fourth MOS tube, the fifth MOS tube and the sixth MOS tube.

[0051] When the first switch tube T1, the second switch tube T2, the third switch tube T3, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 correspond one by one to the first triode, the second triode, the third triode, the fourth triode, the fifth triode and the sixth triode, the input ends corresponding to the first switch tube T1, the second switch tube T2, the third switch tube T3, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 are all the C poles (collectors) corresponding to the first triode, the second triode, the third triode, the fourth triode, the fifth triode and the sixth triode.

[0052] The output ends corresponding to the first switch tube T1, the second switch tube T2, the third switch tube T3, the fourth switch tube T4, the fifth switch tube T5 and the sixth switch tube T6 are all the E poles (emitters) corresponding to the first transistor, the second transistor, the third transistor, the fourth transistor, the fifth transistor and the sixth transistor.

[0053] The embodiment of the present invention also provides a preset power switching mode and a driving signal of each switch tube, and flexibly controls the on and off of each switch tube and each diode according to the driving signal of each switch tube and the preset power switching mode, so as to form a switch between a single freewheeling loop and a double freewheeling loop, thereby flexibly switching the current path to realize power conversion. The specific control method is as follows: the specific steps and effects in the control method of the midpoint active clamped three-level inverter in the second embodiment.

[0054] In the embodiment of the present invention, the present invention takes advantage of the fifth diode D5 and the sixth diode D6 being silicon carbide diodes, reduces the turn-on loss of the first switch tube T1 and the fourth switch tube T4, and controls the conduction of the fifth switch tube T5 and the sixth switch tube T6 to reduce the direct-through loss of the fifth diode D5 and the sixth diode D6, so that each switch tube is heated evenly. And only the fifth diode D5 and the sixth diode D6 are silicon carbide diodes, which reduces the demand for silicon carbide diodes and can reduce material costs. A double freewheeling circuit is also used to change the freewheeling path, dispersing the thermal stress between each switch tube. Before the first switch tube T1 and / or the fourth switch tube T4 are turned on, the sixth switch tube T6 or the fifth switch tube T5 of the corresponding half cycle is turned off, avoiding the disadvantage that the second diode D2 and the third diode D3 connected in anti-parallel with the second switch tube T2 and the third switch tube T3 are silicon diodes, which causes the first switch tube T1 and the fourth switch tube T4 to generate additional turn-on loss. The voltage stress of the corresponding switch tube is reduced, the forward direct loss of the fifth diode D5 and the sixth diode D6 is reduced, the power conversion efficiency of the circuit is improved, and the stability of the reliable operation of the inverter is improved.

[0055] Embodiment 2

[0056] like Figure 2 As shown, Figure 2 1 is a flow chart of a control method of a midpoint active clamped three-level inverter provided in an embodiment of the present invention, which is used for the midpoint active clamped three-level inverter provided in the above embodiment. The control method of the midpoint active clamped three-level inverter includes the following steps:

[0057] Step 101: Obtain a first drive signal, a second drive signal, a third drive signal, a fourth drive signal, a fifth drive signal and a sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube.

[0058] Among them, the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal are used to drive the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube. The first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal can be pulse signals, including high level and low level, when the pulse signal is high level, it is in the on state, and when the pulse signal is low level, it is in the off state. The first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal can also include timing information. The first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal can be pre-set or temporarily generated.

[0059] For details, see Figure 3 , Figure 3 Schematic diagram of the wave generation during positive and negative half cycles provided by an embodiment of the present invention. Figure 3 In, Vge_T1~Vge_T6 are the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube respectively. It should be noted that the overall logic of the fifth switch tube and the sixth switch tube for the third switch tube and the second switch tube is to open first and then close, the first switch tube and the third switch tube complement each other, and the second switch tube and the fourth switch tube complement each other. Figure 3 It includes the wave conditions of the positive half cycle 5 and the wave conditions of the negative half cycle 6.

[0060] exist Figure 3 In the embodiment, the dead zone between the first switch tube (fourth switch tube) being turned on and the third switch tube (second switch tube) being turned off is t1.

[0061] The dead zone between the turning on of the third switch tube (the second switch tube) and the turning off of the first switch tube (the fourth switch tube) is t2.

[0062] The fifth switch tube (sixth switch tube) as a whole follows the opening and closing of the third switch tube (second switch tube). The fifth switch tube (sixth switch tube) is turned off before the fourth switch tube (first switch tube) is turned on, and the fifth switch tube (sixth switch tube) is turned on after the fourth switch tube (first switch tube) is turned on t7.

[0063] The delay from the turning on of the first switch tube (the sixth switch tube) to the turning on of the third switch tube (the second switch tube) is t6.

[0064] The delay time of turning off the fifth switch tube (sixth switch tube) to turning off the third switch tube (second switch tube) is t3.

[0065] Step 102: Control the on / off states of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on a preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal to form a dual freewheeling circuit to realize a commutation path and power conversion.

[0066] Specifically, the preset power switching mode includes a forward power switching mode and a reverse power switching mode.

[0067] In one embodiment of the present invention, the forward power switching mode includes:

[0068] Mode 1: Control the first switch tube and the second switch tube to be turned on.

[0069] Specifically, Figure 4 As shown, at this time, the circuit outputs power in the forward direction. Since the fifth diode is a silicon carbide diode, there is basically no reverse recovery, which can greatly reduce the turn-on loss of the first switch tube, and increase its turn-on speed under the same working conditions. The current flows to the output end of the bridge arm through the first switch tube and the second switch tube, and the output end of the bridge arm outputs a first preset level. The first preset level can be a P level, or can be called a high level.

[0070] Mode 2: Based on Mode 1, the first switch tube, the second switch tube and the sixth switch tube are controlled to be turned on.

[0071] Specifically, Figure 5 As shown, at this time, the bridge arm outputs the first preset level, the current path does not change, only the sixth switch tube is turned on, and the circuit still outputs power in the forward direction to prepare for the dual freewheeling loop freewheeling. The current flows to the output end of the bridge arm through the first switch tube and the second switch tube, and the output end of the bridge arm outputs the first preset level.

[0072] Mode three: on the basis of mode two, the first switch tube is controlled to be turned off, and the fifth diode, the second switch tube, the sixth switch tube and the third diode are controlled to be turned on.

[0073] Specifically, Figure 6 As shown, due to the presence of the second freewheeling loop, the freewheeling current of the SiC diode in the first freewheeling loop is reduced, the capacity of the fifth diode 5 can be reduced, and the cost can be saved. Moreover, due to the presence of the dual freewheeling loop, the thermal stress between the switch tubes can be dispersed. The current is made to flow from the first freewheeling loop formed by the first voltage-dividing capacitor, the first voltage-dividing capacitor, the fifth diode, and the second switch tube to the output end of the bridge arm, and the current is made to flow from the second freewheeling loop formed by the second voltage-dividing capacitor, the second voltage-dividing capacitor, the sixth switch tube, and the third diode to the output end of the bridge arm, so as to realize the freewheeling of the dual freewheeling loops, and the output end of the bridge arm outputs the second preset level.

[0074] And, mode four: based on mode three, the sixth switch tube is controlled to be turned off, and the fifth diode and the second switch tube are controlled to be turned on.

[0075] Specifically, Figure 7 As shown, at this time, the single freewheeling loop 0+ performs freewheeling, and when the freewheeling at the second preset level is about to end, the sixth switch tube is turned off to prepare for the opening of the first switch tube, ensuring that the sixth switch tube is turned off before the first switch tube is turned on, which can avoid the problem of additional opening loss when the first switch tube is turned on due to the presence of the third diode (the third diode is a silicon diode). The current flows to the output end of the bridge arm through the first freewheeling loop formed by the first voltage-dividing capacitor, the fifth diode and the second switch tube, and the output end of the bridge arm outputs the second preset level.

[0076] More specifically, Figure 8 As shown, step 102 includes the steps of:

[0077] Step 201: according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, respectively, based on mode one, mode two and mode three, the output level of the output end of the bridge arm is switched from a first preset level to a second preset level.

[0078] And / or, step 202, according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, the output level of the bridge arm output end is switched from the second preset level to the first preset level through the mode three, the mode four and the mode one in sequence.

[0079] According to step 201 and step 202, this power switching path fully utilizes the advantage of the midpoint active clamping three-level dual freewheeling loop to disperse the thermal stress between the switch tubes, and avoids the influence of the third diode being a Si diode on the first switch tube causing additional turn-on loss. Thus, the level of the output of the bridge arm output terminal is switched, and the current conversion is further realized.

[0080] In one embodiment of the present invention, the reverse power switching mode includes:

[0081] Mode five: controlling the third switch tube and the fifth switch tube to be turned off, and controlling the first diode and the second diode to be turned on.

[0082] Specifically, Fig. 9 As shown, at this time, the current flows from the output end of the bridge arm to the second diode and the first diode, and the output end of the bridge arm outputs a P level.

[0083] Mode six: on the basis of mode five, the fifth switch tube and the second diode are controlled to be turned on.

[0084] Specifically, Fig.10 As shown, at this time, the single freewheeling loop 0+ is output. The fifth switch tube is turned on better than the third switch tube. The fifth switch tube switches the small loop, which can reduce the influence of the larger parasitic parameters of the large loop on the loop switching and reduce the voltage stress of the switch tube. The current flows from the output end of the bridge arm to the second diode, the fifth switch tube and the first voltage-dividing capacitor to form the first freewheeling loop, and the output end of the bridge arm outputs the P level.

[0085] And, mode seven: based on mode six, the fifth switch tube, the second diode, the sixth diode and the third switch tube are controlled to be turned on.

[0086] Specifically, Fig.11 As shown, at this time, a dual freewheeling loop 0+, 0- output is formed. Due to the dual-loop chopping, the thermal stress between the switch tubes can be dispersed. The current is made to flow from the output end of the bridge arm to the second diode, the fifth switch tube and the first voltage-dividing capacitor to form a first freewheeling loop, and the output end of the bridge arm outputs a first preset level; and the current is made to flow from the output end of the bridge arm to the second freewheeling loop formed by the third switch tube, the sixth diode, and the second voltage-dividing capacitor, and the output end of the bridge arm inputs a second preset level.

[0087] More specifically, Fig.12 As shown, step 102 includes:

[0088] Step 301: Switch the output level of the bridge arm output end from a first preset level to a second preset level based on mode five, mode six and mode seven in turn according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal.

[0089] And / or, step 302, according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, the output level of the bridge arm output end is switched from the second preset level to the first preset level through the mode seven, the mode six and the mode five in sequence.

[0090] According to step 301 and step 302 , the power switching path adopts dual-loop chopping to reduce the voltage stress of the switch tube and disperse the thermal stress between the switch tubes.

[0091] It should be noted that the negative half-cycle commutation path is similar to the forward power switching and reverse power switching methods and will not be described here.

[0092] In an embodiment of the present invention, by obtaining the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube; and controlling the on-off state of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on the preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, a double freewheeling loop is formed to realize the commutation path and the power conversion. In this way, the on-off state of each switch tube and each diode can be controlled by the drive signal of each switch tube and the preset power switching state, and the freewheeling is switched by the single freewheeling loop and the double freewheeling loop, so as to reduce the thermal stress between each switch tube, reduce the reverse recovery loss of the diode, improve the power conversion efficiency of the circuit, and improve the stability of the reliable operation of the inverter.

[0093] Embodiment 3

[0094] like Fig.13 As shown, Fig.13 1 is a schematic structural diagram of a control device for a midpoint active clamped three-level inverter provided in an embodiment of the present invention. The control device 400 for a midpoint active clamped three-level inverter includes:

[0095] The acquisition unit 401 is used to acquire the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube.

[0096] Among them, the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal are used to drive the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube. The first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal can be pulse signals, including high level and low level, when the pulse signal is high level, it is in the on state, and when the pulse signal is low level, it is in the off state. The first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal can also include timing information. The first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal can be pre-set or temporarily generated.

[0097] For details, see Figure 3 , FIG. 1 is a schematic diagram of a wave generation condition during a positive and negative half cycle provided by an embodiment of the present invention. Figure 3 In, Vge_T1~Vge_T6 are the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube respectively. It should be noted that the overall logic of the fifth switch tube and the sixth switch tube for the third switch tube and the second switch tube is to open first and then close, the first switch tube and the third switch tube complement each other, and the second switch tube and the fourth switch tube complement each other. Figure 3 It includes the wave conditions of the positive half cycle 5 and the wave conditions of the negative half cycle 6.

[0098] exist Figure 3 In the embodiment, the dead zone between the first switch tube (fourth switch tube) being turned on and the third switch tube (second switch tube) being turned off is t1.

[0099] The dead zone between the turning on of the third switch tube (the second switch tube) and the turning off of the first switch tube (the fourth switch tube) is t2.

[0100] The fifth switch tube (sixth switch tube) as a whole follows the opening and closing of the third switch tube (second switch tube). The fifth switch tube (sixth switch tube) is turned off before the fourth switch tube (first switch tube) is turned on, and the fifth switch tube (sixth switch tube) is turned on after the fourth switch tube (first switch tube) is turned on t7.

[0101] The delay from the turning on of the first switch tube (the sixth switch tube) to the turning on of the third switch tube (the second switch tube) is t6.

[0102] The delay time of turning off the fifth switch tube (sixth switch tube) to turning off the third switch tube (second switch tube) is t3.

[0103] The control unit 402 is used to control the on-off state of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on a preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal to form a dual freewheeling loop to realize a commutation path and power conversion.

[0104] Specifically, the preset power switching mode includes a forward power switching mode and a reverse power switching mode.

[0105] In one embodiment of the present invention, the forward power switching mode includes:

[0106] Mode 1: Control the first switch tube and the second switch tube to be turned on.

[0107] Specifically, Figure 4 As shown, at this time, the circuit outputs power in the forward direction. Since the fifth diode is a silicon carbide diode, there is basically no reverse recovery, which can greatly reduce the turn-on loss of the first switch tube, and increase its turn-on speed under the same working conditions. The current flows to the output end of the bridge arm through the first switch tube and the second switch tube, and the output end of the bridge arm outputs a first preset level. The first preset level can be a P level, or can be called a high level.

[0108] Mode 2: Based on Mode 1, the first switch tube, the second switch tube and the sixth switch tube are controlled to be turned on.

[0109] Specifically, Figure 5 As shown, at this time, the bridge arm outputs the first preset level, the current path does not change, only the sixth switch tube is turned on, and the circuit still outputs power in the forward direction to prepare for the dual freewheeling loop freewheeling. The current flows to the output end of the bridge arm through the first switch tube and the second switch tube, and the output end of the bridge arm outputs the first preset level.

[0110] Mode three: on the basis of mode two, the first switch tube is controlled to be turned off, and the fifth diode, the second switch tube, the sixth switch tube and the third diode are controlled to be turned on.

[0111] Specifically, Figure 6As shown, due to the presence of the second freewheeling loop, the freewheeling current of the SiC diode in the first freewheeling loop is reduced, the capacity of the fifth diode 5 can be reduced, and the cost can be saved. Moreover, due to the presence of the dual freewheeling loop, the thermal stress between the switch tubes can be dispersed. The current is made to flow from the first freewheeling loop formed by the first voltage-dividing capacitor, the first voltage-dividing capacitor, the fifth diode, and the second switch tube to the output end of the bridge arm, and the current is made to flow from the second freewheeling loop formed by the second voltage-dividing capacitor, the second voltage-dividing capacitor, the sixth switch tube, and the third diode to the output end of the bridge arm, so as to realize the freewheeling of the dual freewheeling loops, and the output end of the bridge arm outputs the second preset level.

[0112] And, mode four: based on mode three, the sixth switch tube is controlled to be turned off, and the fifth diode and the second switch tube are controlled to be turned on.

[0113] Specifically, Figure 7 As shown, at this time, the single freewheeling loop 0+ performs freewheeling, and when the freewheeling at the second preset level is about to end, the sixth switch tube is turned off to prepare for the opening of the first switch tube, ensuring that the sixth switch tube is turned off before the first switch tube is turned on, which can avoid the problem of additional opening loss when the first switch tube is turned on due to the presence of the third diode (the third diode is a silicon diode). The current flows to the output end of the bridge arm through the first freewheeling loop formed by the first voltage-dividing capacitor, the fifth diode and the second switch tube, and the output end of the bridge arm outputs the second preset level.

[0114] More specifically, Fig.14 As shown, the control unit 402 includes:

[0115] The first switching module 4021 is used to switch the output level of the bridge arm output end from a first preset level to a second preset level based on mode one, mode two and mode three in turn according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal.

[0116] And / or, a second switching module 4022 is used to switch the output level of the bridge arm output end from the second preset level to the first preset level through the mode three, mode four and mode one in turn according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal.

[0117] According to the first switching module 4021 and the second switching module 4022, this power switching path fully utilizes the advantage of the midpoint active clamping three-level dual freewheeling loop to disperse the thermal stress between the switch tubes, and avoids the influence of the third diode being a Si diode on the first switch tube causing additional turn-on loss, thereby achieving the switching of the output level of the bridge arm output end, and further achieving the current conversion.

[0118] In one embodiment of the present invention, the reverse power switching mode includes:

[0119] Mode five: controlling the third switch tube and the fifth switch tube to be turned off, and controlling the first diode and the second diode to be turned on.

[0120] Specifically, Fig. 9 As shown, at this time, the current flows from the output end of the bridge arm to the second diode and the first diode, and the output end of the bridge arm outputs a P level.

[0121] Mode six: on the basis of mode five, the fifth switch tube and the second diode are controlled to be turned on.

[0122] Specifically, Fig.10 As shown, at this time, the single freewheeling loop 0+ is output. The fifth switch tube is turned on better than the third switch tube. The fifth switch tube switches the small loop, which can reduce the influence of the larger parasitic parameters of the large loop on the loop switching and reduce the voltage stress of the switch tube. The current flows from the output end of the bridge arm to the second diode, the fifth switch tube and the first voltage-dividing capacitor to form the first freewheeling loop, and the output end of the bridge arm outputs the P level.

[0123] And, mode seven: based on mode six, the fifth switch tube, the second diode, the sixth diode and the third switch tube are controlled to be turned on.

[0124] Specifically, Fig.11 As shown, at this time, a dual freewheeling loop 0+, 0- output is formed. Due to the dual-loop chopping, the thermal stress between the switch tubes can be dispersed. The current is made to flow from the output end of the bridge arm to the second diode, the fifth switch tube and the first voltage-dividing capacitor to form a first freewheeling loop, and the output end of the bridge arm outputs a first preset level; and the current is made to flow from the output end of the bridge arm to the second freewheeling loop formed by the third switch tube, the sixth diode, and the second voltage-dividing capacitor, and the output end of the bridge arm inputs a second preset level.

[0125] More specifically, Fig.15 As shown, the control unit 402 includes:

[0126] A third switching module 4023 is used to switch the output level of the bridge arm output end from the first preset level to the second preset level based on mode five, mode six and mode seven in sequence according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal;

[0127] And / or, a fourth switching module 4024 is used to switch the output level of the bridge arm output end from the second preset level to the first preset level through the mode seven, mode six and mode five in turn according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal.

[0128] According to the third switching module 4023 and the fourth switching module 4024 , the power switching path adopts double-loop chopping to reduce the voltage stress of the switch tube and disperse the thermal stress between the switch tubes.

[0129] It should be noted that the negative half-cycle commutation path is similar to the forward power switching and reverse power switching methods and will not be described here.

[0130] In an embodiment of the present invention, the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube are obtained by the acquisition unit 401. And the on-off state of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube is controlled by the control unit 402 based on the preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, so as to form a double freewheeling loop to realize the commutation path and the power conversion. In this way, the on-off state of each switch tube and each diode can be controlled by the drive signal of each switch tube and the preset power switching state, and the freewheeling is switched by the single freewheeling loop and the double freewheeling loop, so as to reduce the thermal stress between each switch tube, reduce the reverse recovery loss of the diode, improve the power conversion efficiency of the circuit, and improve the stability of the reliable operation of the inverter.

[0131] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A midpoint active clamped three-level inverter, characterized in that: include: A bridge arm unit, a clamping unit connected to the bridge arm unit, and a bridge arm output end connected to the bridge arm unit; The bridge arm unit includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube connected in series in sequence, and a first diode, a second diode, a third diode, and a fourth diode connected in anti-parallel with the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube in a one-to-one correspondence; The clamping unit comprises a fifth switch tube and a sixth switch tube connected in series in sequence, and a fifth diode and a sixth diode connected in anti-parallel with the fifth switch tube and the sixth switch tube in one-to-one correspondence, an end of the fifth switch tube away from the sixth switch tube is arranged on a connection line between the first switch tube and the second switch tube, and an end of the sixth switch tube away from the fifth switch tube is arranged on a connection line between the third switch tube and the fourth switch tube; A bridge arm output end provided on a connection line between the second switch tube and the third switch tube; The fifth switch tube or the fifth diode and the second switch tube or the second diode form a first freewheeling loop, the sixth switch tube or the sixth diode and the third switch tube or the third diode form a second freewheeling loop, and the first freewheeling loop and the second freewheeling loop form a double freewheeling loop for changing the freewheeling path; The fifth diode and the sixth diode are silicon carbide diodes; At the same time, it also includes a control method for a midpoint active clamped three-level inverter, the method comprising: Obtaining a first drive signal, a second drive signal, a third drive signal, a fourth drive signal, a fifth drive signal, and a sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube; Controlling the on / off states of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on a preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal to form a dual freewheeling loop to realize a commutation path and power conversion; Wherein, the preset power switching mode includes a forward power switching mode and a reverse power switching mode; The forward power switching mode includes: Mode 1: Control the first switch tube and the second switch tube to be turned on; Mode 2: Based on Mode 1, the first switch tube, the second switch tube and the sixth switch tube are controlled to be turned on; Mode 3: on the basis of Mode 2, the first switch tube is controlled to be turned off, and the fifth diode, the second switch tube, the sixth switch tube and the third diode are controlled to be turned on; And, mode four: based on mode three, the sixth switch tube is controlled to be turned off, and the fifth diode and the second switch tube are controlled to be turned on.

2. The neutral point active clamped three-level inverter according to claim 1, characterized in that: Also includes: A voltage-dividing unit connected to the bridge arm unit and the clamping unit respectively, the voltage-dividing unit includes a first voltage-dividing capacitor and a second voltage-dividing capacitor connected in series in sequence, an end of the first voltage-dividing capacitor away from the second voltage-dividing capacitor is connected to an end of the first switch tube away from the second switch tube, and an end of the second voltage-dividing capacitor away from the first voltage-dividing capacitor is connected to an end of the fourth switch tube away from the third switch tube.

3. The neutral point active clamped three-level inverter according to claim 2, characterized in that: The input end of the first switching tube is connected to an end of the first voltage-dividing capacitor away from the second voltage-dividing capacitor, the output end of the first switching tube is respectively connected to the input end of the second switching tube and the input of the fifth switching tube, the output end of the second switching tube is respectively connected to the input end of the third switching tube and the output end of the bridge arm, the output end of the third switching tube is respectively connected to the input end of the fourth switching tube and the output end of the sixth switching tube, and the output end of the fourth switching tube is connected to an end of the second voltage-dividing capacitor away from the first voltage-dividing capacitor.

4. The neutral point active clamped three-level inverter according to any one of claims 1 to 3, characterized in that: The first diode, the second diode, the third diode and the fourth diode include a first silicon diode, a second silicon diode, a third silicon diode and a fourth silicon diode in a one-to-one correspondence.

5. The neutral point active clamped three-level inverter according to any one of claims 1 to 3, characterized in that: The first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube correspond to each other and include a first MOS tube, a second MOS tube, a third MOS tube, a fourth MOS tube, a fifth MOS tube and a sixth MOS tube, or a first triode, a second triode, a third triode, a fourth triode, a fifth triode and a sixth triode.

6. A control method for a midpoint active clamped three-level inverter, used for the midpoint active clamped three-level inverter according to any one of claims 1 to 5, characterized in that: The method comprises: Obtaining a first drive signal, a second drive signal, a third drive signal, a fourth drive signal, a fifth drive signal, and a sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube; Controlling the on / off states of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on a preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal to form a dual freewheeling loop to realize a commutation path and power conversion; Wherein, the preset power switching mode includes a forward power switching mode and a reverse power switching mode; The forward power switching mode includes: Mode 1: Control the first switch tube and the second switch tube to be turned on; Mode 2: Based on Mode 1, the first switch tube, the second switch tube and the sixth switch tube are controlled to be turned on; Mode 3: on the basis of Mode 2, the first switch tube is controlled to be turned off, and the fifth diode, the second switch tube, the sixth switch tube and the third diode are controlled to be turned on; And, mode four: based on mode three, the sixth switch tube is controlled to be turned off, and the fifth diode and the second switch tube are controlled to be turned on.

7. The control method of the neutral point active clamped three-level inverter according to claim 6, characterized in that: The steps of controlling the on / off states of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on the preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal to form a dual freewheeling loop to realize the commutation path and the power conversion include: Switching the output level of the bridge arm output end from a first preset level to a second preset level based on mode 1, mode 2 and mode 3 in sequence according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal; And / or, according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, the output level of the bridge arm output end is switched from the second preset level to the first preset level through the mode three, the mode four and the mode one in sequence.

8. The control method of the neutral point active clamped three-level inverter according to claim 6, characterized in that: The reverse power switching mode includes: Mode 5: controlling the third switch tube and the fifth switch tube to be turned off, and controlling the first diode and the second diode to be turned on; Mode 6: Based on Mode 5, the fifth switch tube and the second diode are controlled to be turned on; And, mode seven: based on mode six, the fifth switch tube, the second diode, the sixth diode and the third switch tube are controlled to be turned on.

9. The control method of the neutral point active clamped three-level inverter according to claim 8, characterized in that: The steps of controlling the on / off states of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on the preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal to form a dual freewheeling loop to realize the commutation path and the power conversion include: Switching the output level of the bridge arm output end from a first preset level to a second preset level based on mode five, mode six and mode seven in sequence according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal; And / or, according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, the output level of the bridge arm output end is switched from the second preset level to the first preset level through the mode seven, the mode six and the mode five in sequence.

10. A control device for a midpoint active clamped three-level inverter, used for the midpoint active clamped three-level inverter according to any one of claims 1 to 5, characterized in that: The device comprises: an acquisition unit, configured to acquire a first drive signal, a second drive signal, a third drive signal, a fourth drive signal, a fifth drive signal, and a sixth drive signal corresponding to the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube; a control unit, configured to control the on / off states of the first switch tube, the second switch tube, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube based on a preset power switching mode according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal, so as to form a dual freewheeling loop to realize a commutation path and electric energy conversion; Wherein, the preset power switching mode includes a forward power switching mode and a reverse power switching mode; The forward power switching mode includes: Mode 1: Control the first switch tube and the second switch tube to be turned on; Mode 2: Based on Mode 1, the first switch tube, the second switch tube and the sixth switch tube are controlled to be turned on; Mode 3: on the basis of Mode 2, the first switch tube is controlled to be turned off, and the fifth diode, the second switch tube, the sixth switch tube and the third diode are controlled to be turned on; And, mode four: based on mode three, the sixth switch tube is controlled to be turned off, and the fifth diode and the second switch tube are controlled to be turned on.

11. The control device for a neutral point active clamped three-level inverter according to claim 10, characterized in that: The control unit comprises: A first switching module, configured to switch the output level of the bridge arm output end from a first preset level to a second preset level based on mode 1, mode 2, and mode 3 in sequence according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal, and the sixth drive signal; And / or, a second switching module, used to switch the output level of the bridge arm output end from the second preset level to the first preset level through the mode three, mode four and mode one in turn according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal.

12. The control device for a neutral point active clamped three-level inverter according to claim 10, characterized in that: The reverse power switching mode includes: Mode 5: controlling the third switch tube and the fifth switch tube to be turned off, and controlling the first diode and the second diode to be turned on; Mode 6: Based on Mode 5, the fifth switch tube and the second diode are controlled to be turned on; And, mode seven: based on mode six, the fifth switch tube, the second diode, the sixth diode and the third switch tube are controlled to be turned on.

13. The control device for a neutral point active clamped three-level inverter according to claim 12, characterized in that: The control unit comprises: A third switching module is used to switch the output level of the bridge arm output end from the first preset level to the second preset level based on mode five, mode six and mode seven in sequence according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal; And / or, a fourth switching module, used to switch the output level of the bridge arm output end from the second preset level to the first preset level through the mode seven, mode six and mode five in turn according to the first drive signal, the second drive signal, the third drive signal, the fourth drive signal, the fifth drive signal and the sixth drive signal.

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