Converter and Driving Method of Its ANPC Circuit

Abstract

This application provides a converter and a driving method for its ANPC circuit. According to the driving method of the ANPC circuit, first, with the aim of enabling the ANPC circuit in the converter to bear the switching loss using the internal transistor and the external transistor respectively in two half-switching periods of the switching cycle, the output state switching sequence of the ANPC circuit is determined. Then, based on the output state switching sequence, control signals for each switching transistor of the ANPC circuit are generated and output. Thereby, the ANPC circuit can achieve the equalization of the switching losses of the internal transistor and the external transistor. Moreover, the equalization granularity of the switching loss is a half-switching period, the equalization effect is fine, and the loss fluctuation is low.

Description

Technical Field

[0001] This application relates to the technical field of power electronics, and in particular, to a converter and a driving method for its ANPC circuit.

[0002] This application claims the priority of a Chinese patent application filed with the China National Patent Office on February 17, 2023, with an application number of 202310153254.6 and an invention title of "Converter and Driving Method for Its ANPC Circuit", and all of its contents are incorporated herein by reference.

Background Art

[0003] The ANPC (Active Neutral Point Clamped) converter uses a fully controlled switching device (and its freewheeling diode) instead of a diode to realize neutral point clamping compared with the conventional NPC (Neutral Point Clamped) converter. Thereby, it has a redundant driving distribution method, improves the degree of freedom of system control. In its single-phase topology structure, the switching tubes connected to the positive and negative poles on the DC side are called external tubes, the switching tubes connected to the AC side are called internal tubes, and the switching tubes connected to the neutral point on the DC side are called clamp tubes.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the ANPC single-phase circuit, there are many driving distribution methods for its six fully controlled switching devices. As common ones, there are the driving distribution method ANPC-1 in which the external tube and the clamp tube operate at high frequency and the internal tube operates at the power frequency, and the driving distribution method ANPC-2 in which the internal tube operates at high frequency and the other transistors operate at the power frequency. However, in the former case, the switching loss of the external tube is larger than that of the internal tube, and in the latter case, the switching loss of the internal tube is larger than that of the external tube. Neither of them can achieve the equalization (i.e., balance) of the switching loss of the device.

[0005] This application provides a converter for realizing the equalization of the switching loss of a device and a driving method for its ANPC circuit.

Means for Solving the Problem

[0006] In order to achieve the above object, this application provides the following technical solutions. The first aspect of this application provides a driving method for the ANPC circuit of a converter, aiming to enable the internal tube and the external tube to bear the switching loss respectively in two half-switching periods of the switching period of the ANPC circuit of the converter, and determining the output state switching sequence of the ANPC circuit; generating and outputting control signals for each switching tube of the ANPC circuit based on the output state switching sequence.

[0007] Preferably, aiming to enable the internal tube and the external tube to bear the switching loss respectively in two half-switching periods of the switching period of the ANPC circuit of the converter, the step of determining the output state switching sequence of the ANPC circuit includes determining the zero-level output state of the output state switching sequence in two half-switching periods within the switching period of the ANPC circuit. The zero-level output state includes a first zero-level output state in which the internal transistor bears the switching loss and a second zero-level output state in which the external transistor bears the switching loss, respectively.

[0008] Preferably, before determining the output state switching sequence of the ANPC circuit, It further includes a step of combining the purpose of equalizing the on-state losses borne by the internal transistors.

[0009] Preferably, aiming to enable the ANPC circuit of the converter to bear the switching loss by using the internal and external transistors respectively in two half-switching periods of the switching period, the step of determining the output state switching sequence of the ANPC circuit is including the step of determining the zero-level output state of the output state switching sequence in two half-switching periods within the switching period of the ANPC circuit, The zero-level output state includes a first zero-level output state in which the internal transistor bears the switching loss, a second zero-level output state in which the external transistor bears the switching loss, and a third zero-level output state in which there are two parallel branches when the phase current flows into or out of the bridge arm, respectively.

[0010] Preferably, in the ANPC circuit, the two external transistors are respectively a first switching transistor connected to the positive pole of the DC side and a fourth switching transistor connected to the negative pole of the DC side, the two internal transistors are respectively a second switching transistor connected between the first switching transistor and the AC side and a third switching transistor connected between the AC side and the fourth switching transistor, and the two clamping transistors are respectively a fifth switching transistor connected between the first switching transistor and the DC side neutral point and a sixth switching transistor connected between the DC side neutral point and the fourth switching transistor. During the positive half-cycle of the output voltage on the AC side of the ANPC circuit, in the first zero-level output state, the first switching tube, the third switching tube, and the sixth switching tube are in the on state, and the other switching tubes are in the off state. During the negative half-cycle of the output voltage on the AC side of the ANPC circuit, in the first zero-level output state, the second switching tube, the fourth switching tube, and the fifth switching tube are in the on state, and the other switching tubes are in the off state.

[0011] Preferably, in the ANPC circuit, the two external tubes are respectively the first switching tube connected to the positive pole of the DC side and the fourth switching tube connected to the negative pole of the DC side, and the two internal tubes are respectively the second switching tube connected between the first switching tube and the AC side and the third switching tube connected between the AC side and the fourth switching tube, and the two clamp tubes are respectively the fifth switching tube connected between the first switching tube and the DC side neutral point and the sixth switching tube connected between the DC side neutral point and the fourth switching tube. During the positive half-cycle of the output voltage on the AC side of the ANPC circuit, in the second zero-level output state, the second switching tube, the third switching tube, and the sixth switching tube are in the on state, and the other switching tubes are in the off state. During the negative half-cycle of the output voltage on the AC side of the ANPC circuit, in the second zero-level output state, the second switching tube, the third switching tube, and the fifth switching tube are in the on state, and the other switching tubes are in the off state.

[0012] Preferably, in the ANPC circuit, the two external tubes are respectively a first switching tube connected to the positive electrode on the DC side and a fourth switching tube connected to the negative electrode on the DC side, and the two internal tubes are respectively a second switching tube connected between the first switching tube and the AC side and a third switching tube connected between the AC side and the fourth switching tube, and the two clamping tubes are respectively a fifth switching tube connected between the first switching tube and the DC side neutral point and a sixth switching tube connected between the DC side neutral point and the fourth switching tube. During the positive half-cycle of the output voltage on the AC side of the ANPC circuit, in the third zero-level output state, the third switching tube, the fifth switching tube, and the sixth switching tube are in the on state, and the other switching tubes are in the off state. During the negative half-cycle of the output voltage on the AC side of the ANPC circuit, in the third zero-level output state, the second switching tube, the fifth switching tube, and the sixth switching tube are in the on state, and the other switching tubes are in the off state.

[0013] Preferably, the output state switching sequence is the third zero-level output state, the first zero-level output state, the positive-level or negative-level output state, the second zero-level output state, the third zero-level output state, or the third zero-level output state, the second zero-level output state, the positive-level or negative-level output state, the first zero-level output state, the third zero-level output state appear in sequence.

[0014] Preferably, during the positive half-cycle of the output voltage on the AC side of the ANPC circuit, in the third zero-level output state, when the phase current flows into the bridge arm, there are two parallel branches. During the negative half-cycle of the output voltage on the AC side of the ANPC circuit, in the third zero-level output state, when the phase current flows out of the bridge arm, there are two parallel branches.

[0015] Preferably, based on the output state switching sequence, the step of generating and outputting control signals for the switching tubes of the ANPC circuit includes: In each output state in the output state switching sequence, generating and outputting control signals for the switching tubes based on the on / off states of the switching tubes in the ANPC circuit, or, Targeting to implement the output state switching sequence, adopting a carrier comparison method, and including the step of generating and outputting control signals for the switching tubes of the ANPC circuit.

[0016] The second aspect of this application provides a converter, including a main circuit and a control device, The main circuit includes at least one ANPC circuit, The main circuit is controlled by the control device, and the control device executes the driving method of the ANPC circuit of the converter described in any one of the above first aspects.

[0017] Preferably, the ANPC circuit includes six switching tubes, The first to fourth switching tubes are sequentially connected in series, The other end of the first switching tube is connected to the positive pole of the DC side of the ANPC circuit, the other end of the fourth switching tube is connected to the negative pole of the DC side of the ANPC circuit, and the first switching tube and the fourth switching tube each function as two external tubes of the ANPC circuit, The connection point between the second switching tube and the third switching tube is connected to the AC side of the ANPC circuit, and the second switching tube and the third switching tube each function as two internal tubes of the ANPC circuit, The connection point between the first switching tube and the second switching tube is connected to the neutral point of the DC side of the ANPC circuit through the fifth switching tube, the connection point between the third switching tube and the fourth switching tube is connected to the neutral point of the DC side of the ANPC circuit through the sixth switching tube, and the fifth switching tube and the sixth switching tube each function as two clamping tubes of the ANPC circuit.

[0018] Preferably, the main circuit includes three of the ANPC circuits, The DC sides of the ANPC circuits are connected in parallel, and the AC sides of the ANPC circuits are each one phase of the AC side of the main circuit.

Advantages of the Invention

[0019] According to the driving method of the ANPC circuit of the converter provided by the present application, first, aiming at enabling the ANPC circuit of the converter to bear the switching loss by using the internal tube and the external tube respectively in two half-switching cycles of the switching period, the output state switching sequence of the ANPC circuit is determined, and based on the output state switching sequence, control signals of each switching tube of the ANPC circuit are generated and output. Thereby, the ANPC circuit can realize the equalization of the switching losses of the internal tube and the external tube, and the equalization granularity of the switching loss is a half-switching cycle, the equalization effect is fine, and the loss fluctuation is low.

[0020] To more clearly explain the embodiments of the present invention or the technical solutions of the prior art, the following briefly introduces the necessary drawings for the description of the embodiments or the prior art. The drawings described below are only the embodiments of the present invention. On the premise that those skilled in the art do not perform labor worthy of inventive step, other drawings can be obtained based on the provided drawings.

Brief Description of the Drawings

[0021]

Figure 1

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Figure 13

Embodiments for Carrying Out the Invention

[0022] Hereinafter, in combination with the drawings of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described. The described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained on the premise that those skilled in the art do not perform inventive labor belong to the protection scope of the present invention.

[0023] In this application, the terms "comprise", "include" or any other variation thereof are intended to include non-exclusive inclusion, such that a process, method, article or apparatus that comprises a series of elements includes not only those elements but also other elements not expressly listed, or further includes elements specific to such a process, method, article or apparatus. Unless otherwise limited, an element defined by the phrase "comprising ○○" does not exclude the presence of further identical elements in the process, method, article or apparatus that comprises the element.

[0024] As shown in FIG. 1, the ANPC circuit includes six switching tubes (S1 to S6 in the drawing), and each switching tube is provided with a corresponding flywheel diode (D1 to D6 in the drawing). The first switching tube S1 to the fourth switching tube S4 are connected in series in sequence. The other end of the first switching tube S1 is connected to the positive pole P of the DC side of the ANPC circuit, and the other end of the fourth switching tube S4 is connected to the negative pole N of the DC side of the ANPC circuit. The connection point between the second switching tube S2 and the third switching tube S3 is connected to the AC side of the ANPC circuit (its output voltage is Vout). The connection point between the first switching tube S1 and the second switching tube S2 is connected to the neutral point O of the DC side of the ANPC circuit via the fifth switching tube S5. The connection point between the third switching tube S3 and the fourth switching tube S4 is connected to the neutral point O of the DC side of the ANPC circuit via the sixth switching tube S6. The first switching tube S1 and the fourth switching tube S4 connected to the positive and negative poles of the DC side (P and N in FIG. 1) are called external tubes, the second switching tube S2 and the third switching tube S3 connected to the AC side are called internal tubes, and the fifth switching tube S5 and the sixth switching tube S6 connected to the neutral point O of the DC side are called clamp tubes.

[0025] In the driving distribution method of ANPC-1 (refer to FIG. 2 for its driving distribution method), the external tubes (S1, S4) and the clamp tubes (S5, S6) operate at high frequency, and the internal tubes (S2, S3) operate at the power frequency. At this time, the switching loss of the external tubes is larger than that of the internal tubes. In the driving distribution method of ANPC-2 (refer to FIG. 3 for its driving distribution method), the internal tubes (S2, S3) operate at high frequency, and the other transistors (S1, S4, S5, S6) operate at the power frequency. At this time, the switching loss of the internal tubes is larger than that of the external tubes. Therefore, neither of the two driving distribution methods can achieve the equalization of the switching loss of the device.

[0026] As discovered by research, in the rectification process of the output voltage Vout of the phase bridge arm midpoint (i.e., the AC side) of the ANPC circuit, 0→P→0→N→0, for the internal tubes and the external tubes, the switching tube that turns on first does not change the rectification path, and the current changes the flow path only when the switching tube that turns on later turns on. Therefore, in the conduction process of the switching tube that turns on first, there is no current, so there is no conduction loss. In the conduction process of the switching tube that turns on later, current flows, so it bears the conduction loss. Similarly, current flows through the switching tube that turns off first, so it bears the turn-off loss. Therefore, the switching tube that turns off first and the switching tube that turns on later bear the switching loss. Based on this principle, in order to actively equalize the switching loss of each device in the ANPC circuit, the driving distribution methods of both modes are adopted. The two defined modes are the stress-in mode in which the internal tubes bear the switching loss and the stress-out mode in which the external tubes bear the switching loss respectively. The driving distribution method of both modes is a pulse width modulation method of carrier comparison, forming the driving of six switching tubes corresponding to the stress-in mode and the stress-out mode respectively. For details, refer to FIGS. 4 to 7, V AB is the AC side output voltage Vout, V PVrepresents the voltage between the positive and negative terminals on the DC side. Taking the positive half-cycle of the AC-side output voltage Vout as an example for analysis, the modulating wave Sr and the auxiliary modulating wave Sr' are set such that Sr' > Sr. As shown in Fig. 4, when comparing the modulating wave Sr with the triangular carrier to generate the drive of the switching tube S2 and comparing the auxiliary modulating wave Sr' with the triangular carrier to generate the drive of the switching tube S1, in the current switching period, the switching tube S1 turns on first and then off, and the switching tube S2 turns on later and turns off first (corresponding to the 0+In output state stage that appears twice in the drawing). Therefore, it belongs to the stress-in mode, and the switching tube S2 bears the switching loss. Conversely, as shown in Fig. 5, when comparing the modulating wave Sr with the triangular carrier to generate the drive of the switching tube S1 and comparing the auxiliary modulating wave Sr' with the triangular carrier to generate the drive of the switching tube S2, in the current switching period, the switching tube S2 turns on first and then off, and the switching tube S1 turns on later and turns off first (corresponding to the 0+Out output state stage that appears twice in the drawing). Therefore, it belongs to the stress-out mode, and the switching tube S1 bears the switching loss. In fact, by adjusting the ratio occupied by the stress-in mode and the stress-out mode to, for example, 50% each, the equalization of the switching losses between the internal tube and the external tube can be achieved. Regarding the situation of the negative half-cycle of the AC-side output voltage Vout (shown in Figs. 6 and 7), a similar analysis may be carried out based on symmetry and will not be repeated here.

[0027] However, in each switching period of this two-mode drive distribution method, the stress-in mode (for example, the 0+In output state stage that appears twice in Fig. 4 and the 0-In output state stage that appears twice in Fig. 6) or the stress-out mode (for example, the 0+Out output state stage that appears twice in Fig. 5 and the 0-Out output state stage that appears twice in Fig. 7) appears twice to be symmetric. Therefore, the equalization granularity of the switching loss is large, which is one switching period. As the carrier ratio decreases, this defect becomes more prominent, and the equalization performance of the loss also further decreases.

[0028] This application provides a driving method for an ANPC circuit of a converter that reduces the leveling granularity of switching losses while achieving leveling of the switching losses of a device.

[0029] Referring to FIG. 8, the driving method for the ANPC circuit of the converter includes the following steps. S101: With the goal of enabling the ANPC circuit of the converter to bear the switching losses using the internal and external tubes respectively in two half-switching periods of the switching period, determine the output state switching sequence of the ANPC circuit.

[0030] The switching period of the ANPC circuit includes two half-switching periods. In these two half-switching periods, the internal and external tubes of the ANPC circuit bear the switching losses respectively, and the leveling of the switching losses between the internal and external tubes can be achieved.

[0031] In order for the internal and external tubes to bear the switching losses respectively, it can be achieved in the zero-level output state of different switching combinations. That is, specifically, S101 includes the step of determining the zero-level output state of the output state switching sequence in two half-switching periods within the switching period of the ANPC circuit. The zero-level output state includes a first zero-level output state where the internal tube bears the switching loss and a second zero-level output state where the external tube bears the switching loss.

[0032] In actual application, the zero-level output state in the first half of the switching period may be set to include the first zero-level output state, and the zero-level output state in the second half of the switching period may be set to include the second zero-level output state, or the zero-level output state in the first half of the switching period may be set to include the second zero-level output state, and the zero-level output state in the second half of the switching period may be set to include the first zero-level output state. Here, there is no limitation, and it may be determined according to the specific application environment.

[0033] Within the positive half-cycle of the AC-side output voltage Vout, the first zero-level output state is denoted as 0+in. At this time, the switching combination of the ANPC circuit is as follows: the first switching tube S1, the third switching tube S3, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state. The second zero-level output state is denoted as 0+out. At this time, the switching combination of the ANPC circuit is as follows: the second switching tube S2, the third switching tube S3, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state.

[0034] In the negative half-cycle of the AC-side output voltage Vout, the first zero-level output state is denoted as 0-in. At this time, the switching combination of the ANPC circuit is as follows: the second switching tube S2, the fourth switching tube S4, and the fifth switching tube S5 are in the on state, and the other switching tubes are in the off state. The second zero-level output state is denoted as 0-out. At this time, the switching combination of the ANPC circuit is as follows: the second switching tube S2, the third switching tube S3, and the fifth switching tube S5 are in the on state, and the other switching tubes are in the off state.

[0035] S102: Generate and output the control signals of each switching tube of the ANPC circuit based on the output state switching sequence.

[0036] The control signal of the corresponding switching tube can be transmitted through the corresponding drive circuit to realize the drive of the corresponding switching tube.

[0037] According to the driving method of the ANPC circuit of the converter provided by this embodiment, through the above process, the ANPC circuit can achieve the equalization of the switching losses of the internal and external tubes. For each half-switching period, the stress-in mode and the stress-out mode can be flexibly selected to reduce the equalization granularity of the switching losses to the half-switching period, so that the equalization effect is fine and the loss fluctuation is low.

[0038] Here, there is another defect in the dual-mode driving distribution method, that is, only the equalization of the switching losses is considered, and the equalization situation of the on-state losses is not actively improved. Since the on-state losses and the switching losses are of the same order, this embodiment provides a driving method for other ANPC circuits. Based on the above embodiment, before executing the determination of the output state switching sequence of the ANPC circuit in S101, it further includes the step of combining the purpose of equalizing the on-state losses borne by the internal tube, that is, S101 aims to equalize the on-state losses borne by the internal tube with the goal that the ANPC circuit uses the internal and external tubes respectively to bear the switching losses in two half-switching periods of the switching period, and includes the step of determining the output state switching sequence of the ANPC circuit.

[0039] At this time, the specific process of S101 is as follows, that is, determine the zero-level output state of the output state switching sequence in two half-switching periods within the switching period of the ANPC circuit. The zero-level output state includes the first zero-level output state where the internal tube bears the switching losses, the second zero-level output state where the external tube bears the switching losses, and the third zero-level output state where there are two parallel branches when the phase current flows into or out of the bridge arm respectively.

[0040] Within the positive half-cycle of the AC-side output voltage Vout, the third zero-level output state is denoted as 0+, and at this time, the switching combination of the ANPC circuit is as follows: The third switching tube S3, the fifth switching tube S5, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state.

[0041] In the negative half-cycle of the AC-side output voltage Vout, the third zero-level output state is denoted as 0-, and at this time, the switching combination of the ANPC circuit is as follows: The second switching tube S2, the fifth switching tube S5, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state.

[0042] Referring to FIGS. 9 and 10, within the positive half-cycle of the AC-side output voltage of the ANPC circuit, in the third zero-level output state, when the phase current flows into the bridge arm, there are two parallel branches (see FIG. 9). Therefore, the current flowing through the devices on each branch is half of the phase current, which plays a leveling role for the on-state loss, reduces the current stress. Referring to FIGS. 11 and 12, in the negative half-cycle of the AC-side output voltage of the ANPC circuit, in the third zero-level output state, when the phase current flows out of the bridge arm, there are two parallel branches (see FIG. 12). Therefore, the current flowing through the devices on each branch is half of the phase current, which plays a leveling role for the on-state loss and reduces the current stress.

[0043] In this embodiment, by optimizing the switching combination when outputting the zero level, a zero-level parallel branch is constructed to actively level the on-loss. At this time, the driving method of the ANPC circuit has the ability to level the switching loss and also has the ability to actively level the on-state loss.

[0044] As shown in FIG. 1, in the ANPC circuit, the two external tubes are respectively the first switching tube S1 connected to the DC side positive electrode P and the fourth switching tube S4 connected to the DC side negative electrode N. The two internal tubes are respectively the second switching tube S2 connected between the first switching tube S1 and the AC side, and the third switching tube S3 connected between the AC side and the fourth switching tube S4. The two clamping tubes are respectively the fifth switching tube S5 connected between the first switching tube S1 and the DC side neutral point O, and the sixth switching tube S6 connected between the DC side neutral point O and the fourth switching tube S4. In this case, for each output state mentioned in the above embodiment, the following may be referred to.

[0045] That is, within the positive half-cycle of the AC side output voltage Vout of the ANPC circuit, in the first zero-level output state 0+in, the first switching tube S1, the third switching tube S3, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state. In the second zero-level output state 0+out, the second switching tube S2, the third switching tube S3, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state. In the third zero-level output state 0+, the third switching tube S3, the fifth switching tube S5, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state. In the positive-level output state P, the first switching tube S1, the second switching tube S2, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state.

[0046] In the negative half-cycle of the AC-side output voltage Vout of the ANPC circuit, in the first zero-level output state 0-in, the second switching tube S2, the fourth switching tube S4, and the fifth switching tube S5 are in the on state, and the other switching tubes are in the off state. In the second zero-level output state 0-out, the second switching tube S2, the third switching tube S3, and the fifth switching tube S5 are in the on state, and the other switching tubes are in the off state. In the third zero-level output state 0-, the second switching tube S2, the fifth switching tube S5, and the sixth switching tube S6 are in the on state, and the other switching tubes are in the off state. In the negative-level output state N, the third switching tube S3, the fourth switching tube S4, and the fifth switching tube S5 are in the on state, and the other switching tubes are in the off state.

[0047] That is, this embodiment designs the switching state combinations in Table 1. Specifically, it shows the switching states of the switching tubes S1 to S6 in eight different bridge arm output states, where 1 represents on and 0 represents off.

[0048]

Table 1

[0049] Table 1 includes the following six zero-level output states. O+in: The first zero-level output state where the internal tube bears the switching loss in the positive half-cycle of the AC-side output voltage; O+out: The second zero-level output state where the external tube bears the switching loss in the positive half-cycle of the AC-side output voltage; O+: The third zero-level output state in the positive half-cycle of the AC-side output voltage; O-in: The first zero-level output state where the internal tube bears the switching loss in the negative half-cycle of the AC-side output voltage; O-out: The second zero-level output state where the external tube bears the switching loss in the negative half-cycle of the AC-side output voltage; O-: The third zero-level output state in the negative half-cycle of the AC-side output voltage.

[0050] The output levels of the bridge arms in the six zero-level output states are all 0. However, due to different rectifier circuits, the corresponding switching losses and on-state losses are different. By combining the six zero-level output states, the switching loss and the on-state loss can be equalized.

[0051] Regarding the switching loss, when the 0 level is output in the positive half-cycle, if O+in is selected, the internal transistor bears the switching loss; when the 0 level is output in the positive half-cycle, if O+out is selected, the external transistor bears the switching loss; when the 0 level is output in the negative half-cycle, if O-in is selected, the internal transistor bears the switching loss; when the 0 level is output in the negative half-cycle, if O-out is selected, the external transistor bears the switching loss.

[0052] Regarding the on-state loss, when the 0 level is output in the positive half-cycle, if O+ is selected, for the phase current path, as shown in FIGS. 9 and 10, when the phase current flows into the bridge arm, there are two parallel current branches. Therefore, the current flowing through the devices on each branch is half of the phase current, which plays an equalizing role for the on-state loss, reduces the current stress. Similarly, when the 0 level is output in the negative half-cycle, if O- is selected, for the phase current path, as shown in FIGS. 11 and 12, when the phase current flows out of the bridge arm, there are two parallel current branches. Therefore, the current flowing through the devices on each branch is half of the phase current, which plays an equalizing role for the on-state loss and reduces the current stress.

[0053] Based on the concept of equalizing switching losses and on-state losses according to different zero-level output states, the following driving distribution method is determined. That is, in the positive half-cycle of the AC-side output voltage, an output state switching sequence of O+→O+in, or O+out→P→O+out, or O+in→O+ is adopted; in the negative half-cycle of the AC-side output voltage, an output state switching sequence of O-→O-in, or O-out→P→O-out, or O-in→O- is adopted, and then the driving of switching tubes S1~S6 is determined corresponding to each output state in Table 1. That is, based on the above embodiments, this embodiment lists the following as some specific examples of the output state switching sequence. (1) Within the positive half-cycle of the AC-side output voltage Vout of the ANPC circuit, in this output state switching sequence, the third zero-level output state, the first zero-level output state, the positive-level output state, the second zero-level output state, and the third zero-level output state appear in sequence, that is, 0+→0+in→P→0+out→0+. (2) Within the positive half-cycle of the AC-side output voltage Vout of the ANPC circuit, in this output state switching sequence, the third zero-level output state, the second zero-level output state, the positive-level output state, the first zero-level output state, and the third zero-level output state appear in sequence, that is, 0+→0+out→P→0+in→0+. (3) In the negative half-cycle of the AC-side output voltage Vout of the ANPC circuit, in this output state switching sequence, the third zero-level output state, the first zero-level output state, the negative-level output state, the second zero-level output state, and the third zero-level output state appear in sequence, that is, 0-→0-in→N→0-out→0-. (4) In the negative half-cycle of the AC-side output voltage Vout of the ANPC circuit, in this output state switching sequence, the third zero-level output state, the second zero-level output state, the negative-level output state, the first zero-level output state, and the third zero-level output state appear in sequence, that is, 0-→0-out→N→0-in→0-.

[0054] In the driving method of the ANPC circuit provided by this embodiment, both its zero-level switching combination and zero-level flywheel loop are different from the prior art. Specifically, by setting two zero-level output states, 0+ and 0-, in the output state switching sequence, the flatness of the on-state loss is actively improved, and by flexibly selecting 0+in or 0+out, and 0-in or 0-out, the flatness of the switching loss is actively improved to reduce the granularity of the switching loss leveling.

[0055] For one switching period of the bridge arm output, FIG. 13 exemplarily shows a selectable and specific output state switching sequence of 0+ → 0+in → P → 0+out → 0+. In this case, the switching loss is borne by the internal tube in the first half of the switching period and by the external tube in the second half of the switching period. Therefore, the granularity of the switching loss distribution becomes smaller.

[0056] Based on the above embodiment, preferably, S102 in the driving method of the ANPC circuit specifically includes the step of generating and outputting control signals for each switching tube based on the on / off state of each switching tube in the ANPC circuit at each output state in the output state switching sequence, that is, the pulses of each switching tube can be directly obtained according to Table 1 of the bridge arm output voltage comparison. For the two-mode driving distribution method, its implementation method is more flexible.

[0057] Alternatively, S102 may further include the step of generating and outputting control signals for each switching tube of the ANPC circuit by adopting a carrier comparison method with the goal of realizing the output state switching sequence. FIG. 13 exemplarily shows the process of realizing the output state switching sequence of 0+ → 0+in → P → 0+out → 0+ by the carrier comparison method.

[0058] Regarding the specific implementation form of S102, it can be determined according to its application environment. Here, it is not limited, and any of them falls within the protection scope of this application.

[0059] Other embodiments of the present application further provide a converter, which includes a main circuit and a control device. The main circuit includes at least one ANPC circuit. The structure of the ANPC circuit is shown in FIG. 1, and specifically includes six switching tubes (S1 to S6 in the drawing). Each switching tube is provided with a corresponding flywheel diode (D1 to D6 in the drawing). The first switching tube S1 to the fourth switching tube S4 are sequentially connected in series. The other end of the first switching tube S1 is connected to the positive pole P of the DC side of the ANPC circuit. The other end of the fourth switching tube S4 is connected to the negative pole N of the DC side of the ANPC circuit. The first switching tube S1 and the fourth switching tube S4 each function as two external tubes of the ANPC circuit. The connection point between the second switching tube S2 and the third switching tube S3 is connected to the AC side of the ANPC circuit (the output voltage thereof is Vout). The second switching tube S2 and the third switching tube S3 each function as two internal tubes of the ANPC circuit. The connection point between the first switching tube S1 and the second switching tube S2 is connected to the neutral point O of the DC side of the ANPC circuit through the fifth switching tube S5. The connection point between the third switching tube S3 and the fourth switching tube S4 is connected to the neutral point O of the DC side of the ANPC circuit through the sixth switching tube S6. The fifth switching tube S5 and the sixth switching tube S6 each function as two clamp tubes of the ANPC circuit.

[0060] The main circuit includes only one ANPC circuit to form a single-phase converter. Or, the main circuit includes three ANPC circuits. The DC sides of each ANPC circuit are connected in parallel. The AC sides of each ANPC circuit are respectively used as one phase of the AC side of the main circuit to form a three-phase converter. Further, the converter may be an inverter, a rectifier, or a device including at least two-stage conversion circuits, where one stage is an ANPC circuit. Here, it is not limited, and all fall within the protection scope of the present application.

[0061] The main circuit is controlled by a control device, and the control device executes the driving method of the ANPC circuit of the converter described in any of the above embodiments. For the specific process and principle of the driving method of the ANPC circuit, reference may be made to the above embodiments, and no redundant description is provided here.

[0062] By executing the driving method of the ANPC circuit, the control device can adjust the on / off sequence of the switching tubes to achieve the leveling of the switching losses between the internal tubes and the external tubes, and can realize the leveling of the on-state losses by selecting and turning on appropriate switching tubes. The converter has the ability to level the switching losses, and also has the ability to actively level the on-state losses. Moreover, the leveling granularity of its switching losses becomes smaller, and the loss fluctuation becomes smaller.

[0063] For the same or similar parts among the embodiments of this specification, reference may be made to each other, and each embodiment mainly describes the differences from other embodiments. In particular, for a system or a system embodiment, since it is basically similar to the method embodiment, its description is brief, and for related parts, reference may be made to some descriptions of the method embodiment. The systems and system embodiments described above are merely exemplary. The units described as individual members may or may not be physically separated. The members shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed among multiple network units. According to actual needs, some or all of the modules can be selected to achieve the purpose of the solution of this embodiment. A person skilled in the art can understand and implement it without performing inventive labor.

[0064] Those skilled in the art should be further aware that, for each exemplary unit and algorithm step described by combining the embodiments disclosed in this specification, they can be implemented by electronic hardware, computer software, or a combination of both. In order to clearly explain the interchangeability between hardware and software, in the above description, each exemplary combination and step are generally described according to their functions. Whether these functions are executed in the form of hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods for each specific application to implement the described functions, but such implementation should not be considered as exceeding the scope of the present invention.

[0065] Regarding the above description of the disclosed embodiments, the features described in each embodiment of this specification may be interchanged or combined with each other, so that those skilled in the art can implement or use the present invention. Multiple corrections to these embodiments are obvious to those skilled in the art, and the general principles defined in this specification may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to these embodiments described in this specification, but conforms to the broadest scope that is consistent with the principles and novel features disclosed in this specification.

Claims

1. A driving method for an ANPC circuit of a converter, comprising: determining an output state switching sequence of the ANPC circuit with the aim of enabling the ANPC circuit of the converter to bear switching losses by using an internal tube and an external tube respectively in two half-switching cycles of a switching period; generating and outputting control signals for each switching tube of the ANPC circuit based on the output state switching sequence; A driving method for an ANPC circuit of a converter, characterized by comprising the above steps.

2. The step of determining the output state switching sequence of the ANPC circuit with the aim of enabling the ANPC circuit of the converter to bear switching losses by using an internal tube and an external tube respectively in two half-switching cycles of a switching period includes: determining zero-level output states of the output state switching sequence in two half-switching cycles within the switching period of the ANPC circuit; The zero-level output states respectively include a first zero-level output state in which the internal tube bears switching losses and a second zero-level output state in which the external tube bears switching losses. A driving method for an ANPC circuit of a converter according to Claim 1, characterized by the above.

3. Before determining the output state switching sequence of the ANPC circuit, further including the step of combining the purpose of equalizing the on-state losses borne by the internal tube. A driving method for an ANPC circuit of a converter according to Claim 1, characterized by the above.

4. The step of determining the output state switching sequence of the ANPC circuit with the aim of enabling the ANPC circuit of the converter to bear switching losses by using an internal tube and an external tube respectively within two half-switching cycles of a switching period includes: determining zero-level output states of the output state switching sequence in two half-switching cycles within the switching period of the ANPC circuit; The zero-level output states respectively include a first zero-level output state in which the internal tube bears switching losses, a second zero-level output state in which the external tube bears switching losses, and a third zero-level output state in which there are two parallel branches when the phase current flows into or out of the bridge arm. The driving method of the ANPC circuit of the converter according to claim 3, characterized in that...

5. In the ANPC circuit, the two external tubes are respectively a first switching tube connected to the positive electrode on the DC side and a fourth switching tube connected to the negative electrode on the DC side. The two internal tubes are respectively a second switching tube connected between the first switching tube and the AC side and a third switching tube connected between the AC side and the fourth switching tube. The two clamping tubes are respectively a fifth switching tube connected between the first switching tube and the DC side neutral point and a sixth switching tube connected between the DC side neutral point and the fourth switching tube. Within the positive half-cycle of the output voltage on the AC side of the ANPC circuit, in the first zero-level output state, the first switching tube, the third switching tube, and the sixth switching tube are in the on state, and the other switching tubes are in the off state. In the negative half-cycle of the output voltage on the AC side of the ANPC circuit, in the first zero-level output state, the second switching tube, the fourth switching tube, and the fifth switching tube are in the on state, and the other switching tubes are in the off state. The driving method of the ANPC circuit of the converter according to claim 4, characterized in that...

6. In the ANPC circuit, the two external tubes are respectively a first switching tube connected to the positive electrode on the DC side and a fourth switching tube connected to the negative electrode on the DC side. The two internal tubes are respectively a second switching tube connected between the first switching tube and the AC side and a third switching tube connected between the AC side and the fourth switching tube. The two clamping tubes are respectively a fifth switching tube connected between the first switching tube and the DC side neutral point and a sixth switching tube connected between the DC side neutral point and the fourth switching tube. Within the positive half-cycle of the output voltage on the AC side of the ANPC circuit, in the second zero-level output state, the second switching tube, the third switching tube, and the sixth switching tube are in the on state, and the other switching tubes are in the off state. In the negative half-cycle of the output voltage on the AC side of the ANPC circuit, in the second zero-level output state, the second switching tube, the third switching tube, and the fifth switching tube are in the on state, and the other switching tubes are in the off state. The driving method of the ANPC circuit of the converter according to claim 4, characterized in that...

7. In the ANPC circuit, the two external tubes are respectively the first switching tube connected to the positive pole of the DC side and the fourth switching tube connected to the negative pole of the DC side, and the two internal tubes are respectively the second switching tube connected between the first switching tube and the AC side and the third switching tube connected between the AC side and the fourth switching tube. The two clamping tubes are respectively the fifth switching tube connected between the first switching tube and the DC side neutral point and the sixth switching tube connected between the DC side neutral point and the fourth switching tube. Within the positive half-cycle of the output voltage on the AC side of the ANPC circuit, in the third zero-level output state, the third switching tube, the fifth switching tube, and the sixth switching tube are in the on state, and the other switching tubes are in the off state. In the negative half-cycle of the output voltage on the AC side of the ANPC circuit, in the third zero-level output state, the second switching tube, the fifth switching tube, and the sixth switching tube are in the on state, and the other switching tubes are in the off state. The driving method of the ANPC circuit of the converter according to claim 4, characterized in that...

8. The output state switching sequence is... The third zero-level output state, the first zero-level output state, the positive level or negative level output state, the second zero-level output state, the third zero-level output state, or The third zero-level output state, the second zero-level output state, the positive level or negative level output state, the first zero-level output state, the third zero-level output state, which appear in sequence. The driving method of the ANPC circuit of the converter according to claim 4, characterized in that...

9. Within the positive half-cycle of the output voltage on the AC side of the ANPC circuit, in the third zero-level output state, when the phase current flows into the bridge arm, there are two parallel branches. In the negative half-cycle of the output voltage on the AC side of the ANPC circuit, in the third zero-level output state, when the phase current flows out of the bridge arm, there are two parallel branches. The driving method of the ANPC circuit of the converter according to claim 4, characterized in that...

10. The step of generating and outputting control signals for each switching tube of the ANPC circuit based on the output state switching sequence is as follows: Based on the on / off states of the switching tubes in the ANPC circuit in each output state in the output state switching sequence, generating and outputting control signals for each switching tube, or A step of generating and outputting control signals for each switching tube of the ANPC circuit by adopting a carrier comparison method with the goal of realizing the output state switching sequence is included. The driving method of the ANPC circuit of the converter according to any one of claims 1 to 9, characterized by the above.

11. A converter, comprising a main circuit and a control device, wherein the main circuit includes at least one ANPC circuit, the main circuit is controlled by the control device, and the control device executes the driving method of the ANPC circuit of the converter according to any one of claims 1 to 10. The converter is characterized by the above.

12. The ANPC circuit includes six switching tubes, the first to fourth switching tubes are connected in series in sequence, the other end of the first switching tube is connected to the positive pole of the DC side of the ANPC circuit, the other end of the fourth switching tube is connected to the negative pole of the DC side of the ANPC circuit, and the first switching tube and the fourth switching tube each function as two external tubes of the ANPC circuit. The connection point between the second switching tube and the third switching tube is connected to the AC side of the ANPC circuit, and the second switching tube and the third switching tube each function as two internal tubes of the ANPC circuit. The connection point between the first switching tube and the second switching tube is connected to the neutral point of the DC side of the ANPC circuit via the fifth switching tube, the connection point between the third switching tube and the fourth switching tube is connected to the neutral point of the DC side of the ANPC circuit via the sixth switching tube, and the fifth switching tube and the sixth switching tube each function as two clamp tubes of the ANPC circuit. The converter according to claim 11, characterized by the above.

13. The main circuit includes three of the ANPC circuits, the DC sides of the ANPC circuits are connected in parallel, and the AC sides of the ANPC circuits are each one phase of the AC side of the main circuit. The converter according to claim 11 or 12, characterized by the above.

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