ANPC type three-level converter modulation method and ANPC type three-level converter

Abstract

The present invention discloses an ANPC-type three-level converter modulation method and an ANPC-type three-level converter. The ANPC-type three-level converter includes a controller and a main circuit, wherein the main circuit includes first, second, third, fourth, fifth, and sixth switching tubes connected in an ANPC topology. The controller is configured to output a modulation signal to the main circuit according to a specific modulation method to control the switching tubes to be turned on or off. Using the modulation method herein to modulate the converter can reduce the current of a long commutation loop occurring during the switching process to half the total current, effectively reducing switch stress, parasitic inductance, and avoiding damage to the switching tubes. Furthermore, the switching tubes that may cause long commutation loops can be concentrated on the fifth and sixth switching tubes, thereby reducing the number and range of switching tubes that may cause long commutation loops.

Description

Technical Field

[0001] The present invention relates to the technical field of ANPC modulation, and in particular to an ANPC type three-level converter modulation method and an ANPC type three-level converter. Background Art

[0002] ANPC (Active Neutral-point-clamped) three-level converter is an important power electronic circuit. Its main circuit topology is as follows: Figure 1 As shown, it can operate in both rectification and inverter modes. Specifically, the ANPC three-level topology includes an upper arm consisting of a first, second, and fifth switching tube connected together, and a lower arm consisting of a third, fourth, and sixth switching tube connected together. The first and fourth switching tubes are connected to the positive and negative terminals of the DC bus, respectively. The connection point between the fifth and sixth switching tubes is connected to the neutral terminal of the DC bus. The connection point between the second and third switching tubes is connected to the AC terminal.

[0003] In practical applications, virtual space vector modulation (VSVPWM) is often used to address the midpoint potential imbalance inherent in ANPC topologies. However, this modulation method results in switching between positive, zero, and negative voltage levels near the zero-crossing point of the modulation wave, which can lead to long commutation loops. This can alter the duty cycle of the converter, increasing harmonics in the converter's output waveform, and increase the voltage spikes that the switching devices must withstand. If these voltage spikes exceed the device's withstand voltage, they can damage the switches. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects or problems existing in the background technology and provide an ANPC type three-level converter modulation method and an ANPC type three-level converter, which can effectively reduce switch stress, reduce parasitic inductance, and avoid damage to the switch tube.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A modulation method for an ANPC-type three-level converter, wherein the ANPC-type three-level converter is suitable for operating in an inverter mode and / or a rectifier mode and includes an upper bridge arm consisting of a first switch tube, a second switch tube, and a fifth switch tube connected together, and a lower bridge arm consisting of a third switch tube, a fourth switch tube, and a sixth switch tube connected together; the first switch tube and the fourth switch tube are respectively connected to the positive terminal and the negative terminal of a DC network, the connection point of the fifth switch tube and the sixth switch tube is connected to the neutral terminal of the DC network, and the connection point of the second switch tube and the third switch tube is connected to the AC network; the first switch tube and the fifth switch tube are packaged in the same switch tube packaging module, and the fourth switch tube and the sixth switch tube are packaged in the same switch tube packaging module; in a switching cycle In the modulation method, when the converter is in the inverter mode and the level state switches between the negative level and the zero level, the sixth switch tube is controlled to be turned on before the second switch tube and turned off after the second switch tube; when the converter is in the inverter mode and the level state switches between the positive level and the zero level, the sixth switch tube is controlled to be turned off before the fifth switch tube and turned on after the fifth switch tube; when the converter is in the rectifier mode and the level state switches between the positive level and the zero level, the fifth switch tube is controlled to be turned on before the third switch tube and turned off after the third switch tube; when the converter is in the rectifier mode and the level state switches between the negative level and the zero level, the fifth switch tube is controlled to be turned off before the sixth switch tube and turned on after the sixth switch tube.

[0007] Furthermore, in one switching cycle, the modulation method:

[0008] When the converter is in the inverter mode and the level state is switched from a negative level to a zero level, controlling the sixth switch tube to be turned on before the second switch tube;

[0009] When the converter is in the inverter mode and the level state switches from zero level to positive level, controlling the sixth switch tube to be turned off before the fifth switch tube;

[0010] When the converter is in an inverter mode and the level state switches from a positive level to a zero level, controlling the sixth switch tube to be turned on after the fifth switch tube;

[0011] When the converter is in an inverter mode and the level state switches from a zero level to a negative level, controlling the sixth switch tube to be turned off after the second switch tube;

[0012] When the converter is in a rectification mode and the level state switches from a positive level to a zero level, controlling the fifth switch tube to be turned on before the third switch tube;

[0013] When the converter is in a rectification mode and the level state switches from a zero level to a negative level, controlling the fifth switch tube to be turned off before the sixth switch tube;

[0014] When the converter is in a rectification mode and the level state is switched from a negative level to a zero level, controlling the fifth switch tube to be turned on before the sixth switch tube is turned on;

[0015] When the converter is in the rectification mode and the level state is switched from zero level to positive level, the fifth switch tube is controlled to be turned off after the third switch tube.

[0016] Furthermore, when the converter is in the inversion mode and the level state switches between the positive level and the zero level, the sixth switch tube and the third switch tube are controlled to be turned off and turned on at the same time; when the converter is in the rectification mode and the level state switches between the negative level and the zero level, the fifth switch tube and the second switch tube are controlled to be turned off and turned on at the same time.

[0017] Furthermore, in one switching cycle, each switch switches to the following states in sequence:

[0018] State 1: the first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube and the fourth switch tube are turned on;

[0019] State 2: the first switch tube, the second switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube is turned on;

[0020] State three: the first switch tube, the second switch tube, the fourth switch tube, and the fifth switch tube are turned off, and the third switch tube and the sixth switch tube are turned on;

[0021] State 4: the first and fourth switches are turned off, and the second, third, fifth, and sixth switches are turned on.

[0022] State 5: the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned off, and the second switch tube and the fifth switch tube are turned on;

[0023] State six: the first switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the second switch tube is turned on;

[0024] State seven: the first and second switches are on, and the third, fourth, fifth, and sixth switches are off.

[0025] State 8: The first switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the second switch tube is turned on;

[0026] State nine: the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned off, and the second switch tube and the fifth switch tube are turned on;

[0027] State 10: the first and fourth switches are turned off, and the second, third, fifth, and sixth switches are turned on.

[0028] State 11: the first switch tube, the second switch tube, the fourth switch tube, and the fifth switch tube are turned off, and the third switch tube and the sixth switch tube are turned on;

[0029] State 12: the first switch tube, the second switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube is turned on;

[0030] State thirteen: the first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube and the fourth switch tube are turned on.

[0031] Furthermore, the time difference between the sixth switch tube being turned on before the second switch tube and being turned off after the second switch tube is 0.01 times the switching period; the time difference between the fifth switch tube being turned on before the third switch tube and being turned off after the third switch tube is 0.01 times the switching period.

[0032] Furthermore, each of the switch tubes is a controllable switch tube with an anti-parallel diode.

[0033] In addition, the present invention also provides an ANPC type three-level converter, including a controller and a main circuit; the ANPC type three-level converter is suitable for operating in an inverter mode and / or a rectifier mode, and includes an upper bridge arm composed of a first switch tube, a second switch tube and a fifth switch tube connected together, and a lower bridge arm composed of a third switch tube, a fourth switch tube and a sixth switch tube connected together; the first switch tube and the fourth switch tube are respectively connected to the positive terminal and the negative terminal of the DC network, the connection point of the fifth switch tube and the sixth switch tube is connected to the neutral terminal of the DC network, and the connection point of the second switch tube and the third switch tube is connected to the AC network; the first switch tube and the fifth switch tube are packaged in the same switch tube packaging module, the fourth switch tube and the sixth switch tube are packaged in the same switch tube packaging module, and the second switch tube and the third switch tube are packaged in the same switch tube packaging module; the controller modulates each switch tube in the main circuit according to the modulation method described in any one of the above items.

[0034] From the above description of the present invention, it can be seen that compared with the prior art, the present invention has the following beneficial effects:

[0035] The converter of the present invention encapsulates the first and fifth switching transistors, and the fourth and sixth switching transistors, respectively, in the same switching transistor encapsulation module. The modulation method of the present invention controls the sixth switching transistor to turn on before the second switching transistor and to turn off after the second switching transistor when the converter is in the inverter mode and the level state switches between a negative level and a zero level. Furthermore, the modulation method controls the fifth switching transistor to turn on before the third switching transistor and to turn off after the third switching transistor when the converter is in the rectifier mode and the level state switches between a positive level and a zero level. This allows a short commutation loop or a long commutation loop with a relatively small current to be maintained during level switching. The relatively small current is only half of the total current, thereby avoiding the generation of a long commutation loop with a relatively large current. This effectively reduces switching stress, reduces parasitic inductance, and prevents damage to the switching transistors.

[0036] Furthermore, the present invention further controls the sixth switch to be turned off before the fifth switch and turned on after the fifth switch when the converter is in inverter mode and the voltage level switches between a positive level and a zero level. Furthermore, when the converter is in rectifier mode and the voltage level switches between a negative level and a zero level, the fifth switch to be turned off before the sixth switch and turned on after the sixth switch. This allows the switch tubes that cause a long commutation loop to be concentrated on the fifth and sixth switches, thereby reducing the number and range of switch tubes that cause a long commutation loop. This allows for unified control of these switch tubes, for example, by correspondingly controlling the reverse peak power and temperature rise caused by the long commutation loop, and is suitable for implementing various layouts of the switch tubes in the physical structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 A circuit topology diagram of an ANPC type three-level converter in an embodiment of a modulation method for an ANPC type three-level converter provided by the present invention;

[0039] Figure 2 A switching timing diagram of each switch tube of an ANPC type three-level converter in one switching cycle in an embodiment of a modulation method of an ANPC type three-level converter provided by the present invention;

[0040] Figure 3 for Figure 2 A schematic diagram of commutation of an ANPC three-level converter in an inverter mode using the modulation method provided by the present invention;

[0041] Figure 4 for Figure 2 FIG. 3 is a commutation diagram of an ANPC three-level converter in a rectification mode using the modulation method provided by the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be regarded as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] In the claims, description and drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" is for the purpose of distinguishing different objects rather than for describing a specific order.

[0044] In the claims, description and drawings of the present invention, if the terms "include", "have" and their variations are used, they are intended to mean "including but not limited to".

[0045] This embodiment provides a modulation method for an ANPC type three-level converter and an ANPC type three-level converter, wherein the ANPC type three-level converter is suitable for operating in an inverter mode and / or a rectifier mode, and includes a controller and a main circuit, wherein the main circuit includes an upper bridge arm composed of a first switch tube T1, a second switch tube T2, and a fifth switch tube T5 connected together, and a lower bridge arm composed of a third switch tube T3, a fourth switch tube T4, and a sixth switch tube T6, wherein the first switch tube T1 and the fourth switch tube T4 are connected to the positive terminal and the negative terminal of the DC network, respectively. The negative terminal, the connection point of the fifth switch tube T5 and the sixth switch tube T6 are connected to the neutral end of the DC network, and the connection point of the second switch tube T2 and the third switch tube T3 are connected to the AC network. The first switch tube T1 and the fifth switch tube T5 are packaged in the same switch tube packaging module, the fourth switch tube T4 and the sixth switch tube T6 are packaged in the same switch tube packaging module, and the second switch tube T2 and the third switch tube T3 are packaged in the same switch tube packaging module; the controller is used to modulate each switch tube in the main circuit according to the modulation method provided in this embodiment.

[0046] Among them, each switching tube is a controllable switching tube with an anti-parallel diode, and the diode corresponding to each switching tube is represented by D1, D2, D3, D4, D5, and D6.

[0047] It should be noted that during the modulation process, when the current is transformed from flowing through one switch tube package module to flowing through another switch tube package module, the two adjacent commutation states are called "long commutation loops" because the commutation path is long; when the current flows through the same switch tube package module when transforming between two adjacent commutation states, the commutation path is short and therefore it is called a "short commutation loop."

[0048] The modulation method provided in this embodiment mainly includes: in a switching cycle, when the converter is in the inverter mode and the power level state switches between a negative level and a zero level, controlling the sixth switch tube T6 to turn on before the second switch tube T2 and to turn off after the second switch tube T2; when the converter is in the inverter mode and the power level state switches between a positive level and a zero level, controlling the sixth switch tube T6 to turn off before the fifth switch tube T5 and to turn on after the fifth switch tube T5; when the converter is in the rectifier mode and the power level state switches between a positive level and a zero level, controlling the fifth switch tube T5 to turn on before the third switch tube T3 and to turn off after the third switch tube T3; when the converter is in the rectifier mode and the power level state switches between a negative level and a zero level, controlling the fifth switch tube T5 to turn off before the sixth switch tube T6 and to turn on after the sixth switch tube T6.

[0049] Specifically, in one switching cycle, when the converter is in the inverter mode and the level state switches from a negative level to a zero level, the sixth switch tube T6 is controlled to be turned on before the second switch tube T2; when the converter is in the inverter mode and the level state switches from a zero level to a positive level, the sixth switch tube T6 is controlled to be turned off before the fifth switch tube T5; when the converter is in the inverter mode and the level state switches from a positive level to a zero level, the sixth switch tube T6 is controlled to be turned on after the fifth switch tube T5; when the converter is in the inverter mode and the level state switches from a zero level to a negative level, the sixth switch tube T6 is controlled to be turned on after the second switch tube T2. The switch tube T2 is turned off; when the converter is in the rectification mode and the level state switches from a positive level to a zero level, the fifth switch tube T5 is controlled to be turned on before the third switch tube T3; when the converter is in the rectification mode and the level state switches from a zero level to a negative level, the fifth switch tube T5 is controlled to be turned off before the sixth switch tube T6; when the converter is in the rectification mode and the level state switches from a negative level to a zero level, the fifth switch tube T5 is controlled to be turned on after the sixth switch tube T6; when the converter is in the rectification mode and the level state switches from a zero level to a positive level, the fifth switch tube T5 is controlled to be turned off after the third switch tube T3.

[0050] In a specific implementation, the aforementioned "controlling the sixth switch T6 to be turned off before the fifth switch T5 and turned on after the fifth switch T5" and "controlling the fifth switch T5 to be turned off before the sixth switch T6 and turned on after the sixth switch T6" can be controlled respectively in the following manners. When the converter is in the inverter mode and the power level switches between a positive level and a zero level, the sixth switch T6 and the third switch T3 are controlled to be turned off and turned on simultaneously. When the converter is in the rectifier mode and the power level switches between a negative level and a zero level, the fifth switch T5 and the second switch T2 are controlled to be turned off and turned on simultaneously.

[0051] The time difference between the sixth switch T6 being turned on before the second switch T2 and turned off after the second switch T2 is 0.01 times the switching period; the time difference between the fifth switch T5 being turned on before the third switch T3 and turned off after the third switch T3 is 0.01 times the switching period.

[0052] See also Figure 2 Specifically, in one switching cycle, each switch switches to the following states in sequence:

[0053] State 1: the first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube and the fourth switch tube are turned on;

[0054] State 2: the first switch tube, the second switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube is turned on;

[0055] State three: the first switch tube, the second switch tube, the fourth switch tube, and the fifth switch tube are turned off, and the third switch tube and the sixth switch tube are turned on;

[0056] State 4: the first and fourth switches are turned off, and the second, third, fifth, and sixth switches are turned on.

[0057] State 5: the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned off, and the second switch tube and the fifth switch tube are turned on;

[0058] State six: the first switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the second switch tube is turned on;

[0059] State seven: the first and second switches are on, and the third, fourth, fifth, and sixth switches are off.

[0060] State 8: The first switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the second switch tube is turned on;

[0061] State nine: the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned off, and the second switch tube and the fifth switch tube are turned on;

[0062] State 10: the first and fourth switches are turned off, and the second, third, fifth, and sixth switches are turned on.

[0063] State 11: the first switch tube, the second switch tube, the fourth switch tube, and the fifth switch tube are turned off, and the third switch tube and the sixth switch tube are turned on;

[0064] State 12: the first switch tube, the second switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube is turned on;

[0065] State thirteen: the first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube and the fourth switch tube are turned on.

[0066] When the current in the ANPC three-level converter is output from the DC network to the AC network, the current direction is forward. The following takes the forward current direction as an example to illustrate the current commutation during each state switching process.

[0067] Reference Figure 3 In state one, the converter level state is negative, T1, T2, T5, and T6 are turned off, and the current reaches the output end through D4 and D3. Then the switch tube switches to state two. At this time, the converter level state is negative, T1, T2, T4, T5, and T6 are turned off, and the current still reaches the output end through D4 and D3, and there is no commutation.

[0068] State 2 switches to state 3. At this time, the converter level state is zero level, T1, T2, T4, and T5 are turned off, and the current reaches the output end through T6 and D3. The commutation occurs between D4 and T6, which is the commutation between the same switch tube package modules. Therefore, it is a short commutation loop of the same switch tube package module.

[0069] State three switches to state four. At this time, the converter level state is zero level, T1 and T4 are turned off, and the current reaches the output end through two paths, T6, D3 and D5, T2. During this switching process, half of the current is commutated from T6 to D5. The commutation occurs between different switch tube packaging modules, so it is a long commutation loop. However, since T6 and D3 still form a path at this time, the current of the long commutation loop is half of the total current, reducing the impact of the long commutation.

[0070] State four switches to state five. At this time, the converter level state is zero level, T1, T3, T4, and T6 are turned off, and the current reaches the output end through D5 and T2. During this switching process, the current is commutated from T6 to D5, which is a long commutation loop of different switch tube packaging modules. However, since only half of the current is output through T6 and D3 in state four, the current of this long commutation loop is also half of the total current, reducing the impact of long commutation.

[0071] State five switches to state six. At this time, the converter level state is zero level, T1, T3, T4, T5, and T6 are turned off, and the turning off of T5 does not affect the current path in state five, so there is no commutation.

[0072] State six switches to state seven. At this time, the converter level state is positive, T1 and T2 are turned on, T3, T4, T5, and T6 are turned off, and the current reaches the output end through T1 and T2. The commutation occurs between T1 and D5, which is a short commutation loop of the same switch tube packaging module.

[0073] The switching from state 7 to state 13 is a symmetrical process of the switching from state 1 to state 7, and will not be described in detail here.

[0074] In addition, when the current in the ANPC three-level converter is output from the AC network to the DC network, its current direction is negative. The following uses the negative current direction as an example to illustrate the current commutation during each state switching process.

[0075] Reference Figure 4 In state one, the converter level state is negative, T1, T2, T5, and T6 are turned off, and the current reaches the neutral end through T3 and T4. Then the switch tube switches to state two. At this time, the converter level state is zero level, T1, T2, T4, T5, and T6 are turned off, and the current reaches the neutral end through T3 and D6. It is a short commutation loop of the same switch tube packaging module.

[0076] State 2 switches to state 3. At this time, the converter level state is zero level, T1, T2, T4, and T5 are turned off, and the current reaches the neutral end through T3 and D6, and there is no commutation.

[0077] State three switches to state four. At this time, the converter level state is zero level, T1 and T4 are turned off, and the current reaches the neutral end through two paths, T3, D6 and T2, D5. During this switching process, half of the current is commutated from D6 to T5, which is a long commutation loop of different switch tube packaging modules. However, since T3 and D6 still form a path at this time, the current of this long commutation loop is half of the total current.

[0078] State four switches to state five. At this time, the converter level state is zero level, T1, T3, T4, and T6 are turned off, and the current reaches the neutral end through D2 and T5. During this switching process, the current is commutated from D6 to T5, which is a long commutation loop of different switch tube packaging modules. However, since only half of the current reaches the neutral end through T3 and D6 in state four, the current of this long commutation loop is also half of the total current.

[0079] State five switches to state six. At this time, the converter level is positive, T1, T3, T4, T5, and T6 are turned off, and commutation occurs at T5 and D1, which is a short commutation loop of the same switch tube package module.

[0080] State six switches to state seven. At this time, the converter level is positive, T1 and T2 are turned on, T3, T4, T5, and T6 are turned off, and the current is still output to the neutral end through D2 and D1 without commutation.

[0081] The switching from state 7 to state 13 is a symmetrical process of the switching from state 1 to state 7, which will not be described in detail here.

[0082] From the transformation of the current loop between the above states, it can be seen that regardless of whether the current direction is positive or negative, four long commutation loops are included in one switching cycle. However, using the modulation method provided by the present invention, the current in each long commutation loop is only half of the total current. Therefore, the impact of the long commutation loop in the ANPC topology is reduced, which can effectively reduce switch stress, reduce parasitic inductance, and avoid damage to the switch tube.

[0083] Furthermore, in an embodiment of the present invention, when the converter is in inverter mode and the power level switches between a positive level and a zero level, the sixth switch is controlled to be turned off before the fifth switch and turned on after the fifth switch. Furthermore, when the converter is in rectifier mode and the power level switches between a negative level and a zero level, the fifth switch is controlled to be turned off before the sixth switch and turned on after the sixth switch. In this way, the switches that cause long commutation loops are concentrated on the fifth and sixth switches, thereby reducing the number and range of switches that cause long commutation loops. This allows for unified control of these switches, for example, by correspondingly controlling the reverse peak power and temperature rise caused by the long commutation loops, and by implementing various layouts of the switches in the physical structure.

[0084] The above description and embodiments are intended to explain the scope of protection of the present invention, but do not constitute a limitation thereto. Modifications, equivalent substitutions, or other improvements to the embodiments of the present invention or portions thereof that can be obtained by a person of ordinary skill in the art through logical analysis, reasoning, or limited experimentation based on the teachings of the present invention or the above embodiments, combined with common knowledge, ordinary technical knowledge in the field, and / or prior art, should all be included within the scope of protection of the present invention.

Claims

1. A modulation method for an ANPC-type three-level converter, wherein the ANPC-type three-level converter is adapted to operate in an inverter mode and / or a rectifier mode and comprises an upper bridge arm consisting of a first switching transistor, a second switching transistor, and a fifth switching transistor connected together, and a lower bridge arm consisting of a third switching transistor, a fourth switching transistor, and a sixth switching transistor connected together; the first switching transistor and the fourth switching transistor are connected to a positive terminal and a negative terminal of a DC network, respectively; the connection point between the fifth switching transistor and the sixth switching transistor is connected to a neutral terminal of the DC network; and the connection point between the second switching transistor and the third switching transistor is connected to an AC network; Its characteristics are: The first switch tube and the fifth switch tube are packaged in the same switch tube packaging module, and the fourth switch tube and the sixth switch tube are packaged in the same switch tube packaging module; In one switching cycle, the modulation method: When the converter is in the inverter mode and the level state switches between a negative level and a zero level, the sixth switch tube is controlled to be turned on before the second switch tube and turned off after the second switch tube; when the converter is in the inverter mode and the level state switches between a positive level and a zero level, the sixth switch tube is controlled to be turned off before the fifth switch tube and turned on after the fifth switch tube; When the converter is in a rectification mode and the level state switches between a positive level and a zero level, the fifth switch tube is controlled to be turned on before the third switch tube and turned off after the third switch tube; when the converter is in a rectification mode and the level state switches between a negative level and a zero level, the fifth switch tube is controlled to be turned off before the sixth switch tube and turned on after the sixth switch tube; When the converter is in an inverter mode and the level state switches between a positive level and a zero level, controlling the sixth switch tube and the third switch tube to be turned off and on simultaneously; When the converter is in a rectification mode and the level state switches between a negative level and a zero level, controlling the fifth switch tube and the second switch tube to be turned off and on simultaneously; In one switching cycle, each switch switches to the following states in sequence: State 1: the first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube and the fourth switch tube are turned on; State 2: the first switch tube, the second switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube is turned on; State three: the first switch tube, the second switch tube, the fourth switch tube, and the fifth switch tube are turned off, and the third switch tube and the sixth switch tube are turned on; State 4: the first and fourth switches are turned off, and the second, third, fifth, and sixth switches are turned on. State 5: the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned off, and the second switch tube and the fifth switch tube are turned on; State six: the first switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the second switch tube is turned on; State seven: the first and second switches are on, and the third, fourth, fifth, and sixth switches are off. State 8: The first switch tube, the third switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the second switch tube is turned on; State nine: the first switch tube, the third switch tube, the fourth switch tube, and the sixth switch tube are turned off, and the second switch tube and the fifth switch tube are turned on; State 10: the first and fourth switches are turned off, and the second, third, fifth, and sixth switches are turned on. State 11: the first switch tube, the second switch tube, the fourth switch tube, and the fifth switch tube are turned off, and the third switch tube and the sixth switch tube are turned on; State 12: the first switch tube, the second switch tube, the fourth switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube is turned on; State thirteen: the first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are turned off, and the third switch tube and the fourth switch tube are turned on.

2. A modulation method for an ANPC type three-level converter as claimed in claim 1, characterized in that In one switching cycle, the modulation method is: When the converter is in the inverter mode and the level state is switched from a negative level to a zero level, controlling the sixth switch tube to be turned on before the second switch tube; When the converter is in the inverter mode and the level state switches from zero level to positive level, controlling the sixth switch tube to be turned off before the fifth switch tube; When the converter is in an inverter mode and the level state switches from a positive level to a zero level, controlling the sixth switch tube to be turned on after the fifth switch tube; When the converter is in an inverter mode and the level state switches from a zero level to a negative level, controlling the sixth switch tube to be turned off after the second switch tube; When the converter is in a rectification mode and the level state switches from a positive level to a zero level, controlling the fifth switch tube to be turned on before the third switch tube; When the converter is in a rectification mode and the level state switches from a zero level to a negative level, controlling the fifth switch tube to be turned off before the sixth switch tube; When the converter is in a rectification mode and the level state is switched from a negative level to a zero level, controlling the fifth switch tube to be turned on before the sixth switch tube is turned on; When the converter is in the rectification mode and the level state is switched from zero level to positive level, the fifth switch tube is controlled to be turned off after the third switch tube.

3. The modulation method of an ANPC type three-level converter according to claim 1, wherein: The time difference between when the sixth switch tube is turned on before the second switch tube and turned off after the second switch tube is 0.01 times the switching period; the time difference between when the fifth switch tube is turned on before the third switch tube and turned off after the third switch tube is 0.01 times the switching period.

4. The modulation method of an ANPC type three-level converter according to claim 1, wherein: Each of the switch tubes is a controllable switch tube with an anti-parallel diode.

5. An ANPC type three-level converter, characterized in that: Including controller and main circuit; The ANPC three-level converter is suitable for operating in an inverter mode and / or a rectifier mode, and includes an upper bridge arm consisting of a first switching tube, a second switching tube, and a fifth switching tube connected together, and a lower bridge arm consisting of a third switching tube, a fourth switching tube, and a sixth switching tube connected together; the first switching tube and the fourth switching tube are respectively connected to the positive terminal and the negative terminal of a DC network, the connection point between the fifth switching tube and the sixth switching tube is connected to the neutral terminal of the DC network, and the connection point between the second switching tube and the third switching tube is connected to the AC network; the first switching tube and the fifth switching tube are packaged in the same switching tube packaging module, the fourth switching tube and the sixth switching tube are packaged in the same switching tube packaging module, and the second switching tube and the third switching tube are packaged in the same switching tube packaging module; The controller modulates each switch tube in the main circuit according to the modulation method according to any one of claims 1 to 4.

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