Three-level control circuit, power conversion device and control method thereof

Abstract

The application provides a three-level control circuit, a power conversion device and a control method thereof. The three-level control circuit comprises two first main lines and two second main lines between a three-phase port and a two-phase terminal. The first main line comprises a plurality of first conversion branches, and the second main line comprises two capacitor branches and a plurality of second conversion branches. The first conversion branches and the second conversion branches are connected in an interleaving manner through an inverter interleaving technology. A third capacitor and a fourth capacitor are connected in series on each capacitor branch. A plurality of first conversion branches of each first main line are connected to the corresponding capacitor branch, and the connection points are located between the third capacitor and the fourth capacitor.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile battery, in particular to a three-level control circuit, a power conversion device and a control method. BACKGROUND

[0002] With the popularity of new energy vehicles, the demand for household direct current charging piles is increasing, and the power requirement of charging piles is getting higher and higher. The trend of using automobile storage batteries as residential power supply is accelerating, so the research on bidirectional converters is increasing. By using the device, not only the electric vehicle can be used as an emergency power supply, but also if used properly, it can help save electricity bills; when the grid electricity is relatively cheap, the electric vehicle can be charged, and when the power supply is interrupted due to disasters, it can be used as an emergency power supply for household appliances, and at the same time, it can be connected to the grid to generate electricity when the electricity price is relatively high; therefore, the higher the efficiency of the converter and the cheaper the price, the more benefits the user will get, the better the quality of the grid-connected current and the emergency power supply, and the smaller the pollution to the grid and the damage to the electrical equipment.

[0003] The commonly used power factor correction (PFC) topology in the household charging module is a boost circuit (Boost), a flow controller HPFC, and a totem pole PFC. As shown in Figure 1 As can be seen from the commonly used power module in the market, it is applied to a large current bidirectional converter, and the power is improved by packaging larger devices. Although this scheme is relatively simple and easy to control, the cost of the module is relatively high, and the larger the power, the larger the ripple current, which causes the filter to be high in volume; therefore, this scheme has defects, the volume of the filter is relatively large, and the ripple current is increased; in a high-power application, the inductance is difficult to be small, unless a wide bandgap device is used to increase the switching frequency, which causes the problem of rising cost of the converter to be unable to overcome. Therefore, the industry urgently needs a power conversion circuit that can effectively solve the problems of large power improvement and conversion efficiency and has a low cost. SUMMARY

[0004] In order to overcome at least one defect of the household charging module in the prior art, a power conversion circuit that can overcome the problems of large power improvement and conversion efficiency and has a low cost is provided; the present application provides a three-level control circuit, a power conversion device and a control method, wherein the three-phase port and the two-phase terminal of the three-level control circuit comprise two first main lines and two second main lines;

[0005] The first main circuit comprises a plurality of first conversion branches, and the second main circuit comprises two capacitor branches and a plurality of second conversion branches, the first conversion branches and the second conversion branches are connected in an interleaved manner through an inverter interleaving technology; each of the capacitor branches is connected in series with a third capacitor and a fourth capacitor, and the plurality of first conversion branches of each of the first main circuits are connected to the corresponding capacitor branches and the connection points are located between the third capacitor and the fourth capacitor.

[0006] In an embodiment of the present application, the three-level control circuit further comprises a capacitor circuit, the capacitor circuit comprises a first capacitor and a second capacitor; the three-phase port comprises a first alternating current (AC) port, a second AC port and a third AC port; the two-phase terminal comprises a first direct current (DC) terminal and a second DC terminal; the first capacitor and the second capacitor are coupled between the first AC port and the third AC port, and there is an intermediate node between the first capacitor and the second capacitor, the second AC port is connected to the capacitor branches through the intermediate node, and the connection points are located between the third capacitor and the fourth capacitor of each of the capacitor branches.

[0007] In an embodiment of the present application, one end of the plurality of first conversion branches is connected in parallel to the first main circuit through an inductor coil; the plurality of second conversion branches and the capacitor branches are connected in parallel between the first DC terminal and the second DC terminal; wherein the first conversion branches and the second conversion branches correspond to each other.

[0008] In an embodiment of the present application, the three-level control circuit is a T-type three-level control circuit, a PFC three-level control circuit or an I-type three-level control circuit.

[0009] In an embodiment of the present application, when the three-level control circuit is a T-type three-level control circuit, at least two controllable semiconductor devices are connected in series on each of the first conversion branches, and at least two controllable semiconductor devices are connected in series on each of the second conversion branches; the first conversion branches and the second conversion branches correspond to each other to form an intersection node, and the intersection node is located between the controllable semiconductor devices connected in series on the second conversion branches.

[0010] In an embodiment of the present application, a power conversion device is also provided, the device comprises the three-level control circuit and a control module, one end of the control module is connected to the first conversion branches of the two first main circuits respectively, and the connection points are located between the first main circuit and the first conversion branches; the other end of the control module is connected to the first capacitor, the second capacitor, the third capacitor and the fourth capacitor.

[0011] In an embodiment of the present application, a control method applied to the power conversion device is also provided. The control module provides the same current reference value for each of the first main circuit and the plurality of first conversion branches according to the voltage loop output, and makes each first conversion branch current-sharing through closed-loop regulation.

[0012] In an embodiment of the present application, the voltage loop is the DC side voltage during the charging process and the voltage loop is the AC side voltage during the discharging process; wherein the DC side voltage is equal to the sum of the third capacitor and the fourth capacitor; and the AC side voltage is equal to the sum of the first capacitor and the second capacitor.

[0013] In an embodiment of the present application, the phase difference between the inverter of each of the first conversion branch and the second conversion branch is 360 / N under the high-frequency working state, and N is the number of the first conversion branches on the first main circuit.

[0014] In an embodiment of the present application, the driving level is the same under the low-frequency working state.

[0015] The three-level control circuit, the power conversion device and the control method provided by the present application reduce the switching loss of the switching device, have higher conversion efficiency, and the application of the multi-path inverter interleaving technology also reduces the ripple and volume of the filter device, effectively reducing the actual application cost.

[0016] In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor under the premise of the drawings.

[0018] Figure 1 The topological structure diagram of the three-level control circuit in the prior art;

[0019] Figure 2 The topological structure diagram of the insulated gate bipolar transistor in the prior art;

[0020] Figure 3 The topological structure diagram of the three-level control circuit provided by an embodiment of the present application;

[0021] Figure 4A The topological structure diagram of the PFC three-level control circuit in the prior art;

[0022] Figure 4B A topological structure schematic diagram of a PFC three-level control circuit provided by an embodiment of the present application;

[0023] Figure 4C A topological structure schematic diagram of an I-type three-level control circuit provided by an embodiment of the present application;

[0024] Figure 5 A connection structure schematic diagram of a control module and a three-level control circuit provided by an embodiment of the present application;

[0025] Figure 6 A control principle schematic diagram of a control module provided by an embodiment of the present application;

[0026] Figure 7 A control logic schematic diagram of a control method provided by an embodiment of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without any creative work fall within the protection scope of the present application.

[0028] Specific embodiments of the present application are disclosed in detail below with reference to the following description and drawings. The principles of the present application can be employed in any manner without departing from the spirit of the application. It should be understood that the embodiments of the present application are not limited in scope to the embodiments described. Numerous modifications, alterations, and equivalents can be derived from the embodiments of the present application without departing from the spirit of the present application, which is defined by the following claims and their equivalents.

[0029] Features described and / or illustrated with respect to one embodiment can be used in the same or similar manner in one or more other embodiments, in combination with other features in the other embodiments, or in place of other features in the other embodiments.

[0030] It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0031] Nowadays, domestic power supply in some countries is mostly low-voltage single-phase power. Therefore, for bidirectional application occasions, the network side structure is mostly two-phase three-wire system, i.e., L1, L2, N three-wire system; in the structure, when charging and grid-connected, the N wire has no current, and L1 and L2 bear all the current; when off-grid, in order to provide single-phase power for power consumption equipment, N can independently output voltage, and the specific topological structure can refer to Figure 2The topology shown; the volume of the filter is relatively large in the topology, and it is difficult to reduce the inductance in high-power applications, and the introduction of wide-bandgap devices will increase the cost of the converter.

[0032] Therefore, the three-level control circuit is provided, and the three-phase port and the two-phase terminal of the three-level control circuit comprise two first main lines and two second main lines; the first main line comprises a plurality of first conversion branches, the second main line comprises two capacitor branches and a plurality of second conversion branches, and the first conversion branches and the second conversion branches are connected in an inverter interleaving manner; a third capacitor and a fourth capacitor are connected in series on each capacitor branch, and a plurality of first conversion branches of each first main line are connected to the corresponding capacitor branch and the connection points are located between the third capacitor and the fourth capacitor.

[0033] In this way, the number of inverters is increased in a three-way three-level interleaving parallel manner, the switching loss of the switching device is effectively reduced, the conversion efficiency is higher, and the ripple of the filter device is reduced, so that the volume of the filter can be adaptively reduced.

[0034] Further, the three-level control circuit can further comprise a capacitor circuit comprising a first capacitor and a second capacitor; the three-phase port comprises a first AC port, a second AC port and a third AC port; the two-phase terminal comprises a first DC terminal and a second DC terminal; the first capacitor and the second capacitor are coupled between the first AC port and the third AC port, and the first capacitor and the second capacitor have an intermediate node therebetween, and the second AC port is connected to the capacitor branch through the intermediate node, and the connection points are located between the third capacitor and the fourth capacitor of each capacitor branch. Further, in an embodiment of the present application, the specific way of inverter interleaving technology interleaving connection is that a plurality of first conversion branches are connected in parallel to the first main line through an inductor coil at one end; a plurality of second conversion branches are connected in parallel between the first DC terminal and the second DC terminal; wherein the first conversion branches and the second conversion branches correspond one by one; the specific structure will be described in detail in the subsequent embodiments, and will not be described one by one here. In actual work, the three-level control circuit can be a T-type three-level control circuit or a PFC three-level control circuit or an I-type three-level control circuit or other three-level control circuits; in this way, the application based on the three-level control circuit can reduce the switching loss of the switching device, and the conversion efficiency is relatively high.

[0035] Please refer to Figure 3As shown in the embodiment of the present application, when the three-level control circuit is a T-type three-level control circuit, at least two controllable semiconductor devices are connected in series on each of the first conversion branches, and at least two controllable semiconductor devices are connected in series on each of the second conversion branches; the first conversion branches and the second conversion branches correspond to each other to form an intersection node, and the intersection node is located between the controllable semiconductor devices connected in series on the second conversion branches. Further, an inductor is connected in series between the first conversion branches and the first main circuit.

[0036] Specifically, in order to more clearly explain the connection structure of the three-level control circuit in the application of the inverter interleaving technology, please refer to Figure 2 and Figure 3 for example, the T-type three-level control circuit is used to illustrate the structure of the inverter interleaving technology.

[0037] As shown in Figure 3 , the first AC port, the second AC port and the third AC port are L1, N and L2 in the three-phase port, the first capacitor and the second capacitor are Cap1 and Cap2 respectively, the third capacitor and the fourth capacitor are C BH and C BL ; two first main circuits and two second main circuits are coupled between the three-phase port L1, N, L2 and the two-phase terminal DC+, DC-; wherein one first main circuit is led out from L1, and after the intersection point of the capacitor circuit, three parallel first conversion branches (i.e. S2A1 and S3A1, and S2A2 and S3A2, and S2A3 and S3A3 connected in series with three inductors respectively) are led out, and the three first conversion branches are connected to the capacitor branch connected in series with C BH and C BL ; the other first main circuit led out from L2 is similar to the foregoing structure; one second main circuit is led out from the two-phase terminal DC+ respectively, and then the parallel capacitor branch and the three second conversion branches (i.e. S1A3 and S4A3, and S1A2 and S4A2, and S1A1 and S4A1 connected in series with three inductors respectively) are led out, and the other second main circuit led out from the two-phase terminal DC- is similar to the second main circuit led out from DC+; the second AC port N leads out the line passing through the middle node between the first capacitor Cap1 and the second capacitor Cap2 and then connects to the capacitor branch on the two second main circuits. In this way, compared with Figure 2The three-level circuit shown can know that the multi-path interleaving technology referred to in the present application is that the first main line drawn from the first AC port L1 and the third AC port L2 is drawn into three first conversion branches through three inductors after the first main line intersects with the first capacitor Cap1 and the second capacitor Cap2, and the first conversion branches are respectively connected in series with the inverters S2A1, S2A2, S2A3, S3A1, S3A2, S3A3, S2B1, S2B2, S2B3, S3B1, S3B2, S3B3, and then extended to the capacitor branch constructed by the third capacitor Cap1 and the fourth capacitor Cap2; and the second main line drawn from the first DC terminal DC+ and the second DC terminal DC- is drawn into three second conversion branches after the capacitor branch, and the second conversion branches are respectively connected in series with the inverters S1A1, S1A2, S1A3, S4A1, S4A2, S4A3, S1B1, S1B2, S1B3, S4B1, S4B2, S4B3; wherein the intersection nodes of the first conversion branch and the second conversion branch connected in series with the inverters S2A1 and S3A1 are located between the second conversion branches S1A1 and S4A1, the intersection nodes of the first conversion branch and the second conversion branch connected in series with the inverters S2A2 and S3A2 are located between the second conversion branches S1A2 and S4A2, and the intersection nodes of the first conversion branch and the second conversion branch connected in series with the inverters S2A3 and S3A3 are located between the second conversion branches S1A3 and S4A3, so that each first conversion branch and each second conversion branch correspond to each other to complete the intersection, thereby forming an inverter interleaving structure.

[0038] In the overall principle, the interleaving architecture formed by the first conversion branch and the second conversion branch can be equivalent to a conversion module, for example: the above-mentioned three-level control circuit can include a first capacitor circuit (Cap1 and Cap2), two capacitor bypasses (C BH and C BL ), a first level circuit and a second level circuit (two first main lines drawn from L1 and L2), the first level circuit includes a plurality of first conversion modules (i.e. the interleaving structure of the first conversion branch and the second conversion branch), each first conversion module includes four ports, i.e. a first port, a second port, a third port and a fourth port, a plurality of first conversion modules are interleaved in parallel, the first ports of all first conversion modules are connected to the first AC port L1, the second ports of each first conversion module are connected to the first DC port DC+, the third ports of each first conversion module are connected to the second DC port DC-, and the fourth ports of each first conversion module are connected between the third capacitor C BH and the fourth capacitor C BL in the first capacitor bypass;

[0039] Similarly, the second level circuit includes a plurality of second conversion modules, each of which includes four ports, i.e., a first port, a second port, a third port and a fourth port, the plurality of second conversion modules are staggered in parallel, the first port of each second conversion module is connected to the third AC port L2, the second port of each second conversion module is connected to the first DC port DC+, the third port of each second conversion module is connected to the second DC port DC-, and the fourth port of each second conversion module is connected between the first capacitor bypass third capacitor C BH and the fourth capacitor C BL ; the first capacitor circuit (Cap1 and Cap2) is coupled between the first AC port L1 and the third AC port L2, and the two capacitor bypasses (C BH and C BL ) are coupled between the first DC port DC+ and the second DC port DC- respectively.

[0040] In an embodiment of the present application, the three-level control circuit can also be a PFC three-level control circuit or an I-type three-level control circuit, etc. When the three-level control circuit is a PFC three-level control circuit or an I-type three-level control circuit, etc., the first AC port, the second AC port and the third AC port are L1, N and L2 in the three-phase port, the first capacitor and the second capacitor are Cap1 and Cap2 respectively, the third capacitor and the fourth capacitor are C BH and C BL respectively, and the connection relationship between the first capacitor, the second capacitor, the third capacitor and the fourth capacitor, for the main circuit of the series or parallel inverter, can be divided into a plurality of conversion branches for staggered parallel connection.

[0041] To facilitate the description of its connection method and principle, it can be seen from the aforementioned embodiments that when the three-level control circuit is a T-type three-level control circuit, each first conversion module includes: one inductor and four inverters, namely, a first inductor, a first inverter, a second inverter, a third inverter, and a fourth inverter. The first port of the first inductor is the first port of the first conversion module, and the second port of the first inductor is connected to the first port of the first inverter, the first port of the second inverter, and the first port of the third inverter, respectively. The second port of the first inverter is the second port of the first conversion module, and the second port of the second inverter is the third port of the first conversion module. The second port of the inverter is connected to the first port of the fourth inverter, and the second port of the fourth inverter is the fourth port of the first conversion module. Each second conversion module includes one inductor and four inverters, and the connection structure of the internal components of each second conversion module is the same as that of the first conversion module. When the three-level control circuit is a PFC three-level control circuit, each first conversion module includes one inductor, four inverters, and two diodes, namely, the first inductor, the first inverter, the second inverter, the third inverter, the fourth inverter, the first diode, and the second diode. Each second conversion module includes one inductor, four inverters, and two diodes. For details, please refer to [reference needed]. Figure 4A and Figure 4B As shown, Q1 to Q3 are multiple first conversion modules included in the first level circuit; Q4 to Q6 are multiple second conversion modules included in the second level circuit. The connection relationship between each first conversion module and each second conversion module can be as described above. Figure 3 The connection principle is the same, enabling multiple interleaved parallel connections.

[0042] In one embodiment of this application, when the three-level control circuit is a type I three-level control circuit, each first conversion module includes: one inductor and six inverters, namely, a first inductor, a first inverter, a second inverter, a third inverter, a fourth inverter, a fifth inverter, and a sixth inverter; each second conversion module includes: one inductor and six inverters; for details, please refer to... Figure 4C As shown, its difference from the PFC three-level control circuit lies in the fact that the diodes are all replaced with corresponding inverters, and the overall connection structure is the same. Figure 4B Similarly, I will not go into detail here.

[0043] Therefore, the three-level control circuit provided in this application can reduce the ripple characteristics of the filter devices by using the interleaved parallel connection while maintaining the advantages of the three-level control circuit. This makes the size of the filter more adaptable, thereby reducing the switching losses of the switching devices and improving the conversion efficiency while reducing the hardware cost.

[0044] In view of the difference of domestic power supply in some areas or countries, the second AC port in the network side structure can not be used for bidirectional application occasions. Therefore, in an embodiment of the present application, a controllable switch is connected in series between the second AC port and the intermediate node. When the controllable switch is closed, the three-level control circuit provided by the present application can output two independent load paths in the inverter mode, thereby meeting the demand of low-voltage power grid in those areas or countries. Therefore, based on the above structure, whether to close the controllable switch can be determined according to the actual situation of domestic power supply or the power supply mode of the area, and the control mode of the controllable switch can be realized by using the prior art, which will not be described here.

[0045] In an embodiment of the present application, a control method applied to the above power conversion device is provided. The control module is connected to each of the first conversion branches of the two first main lines respectively, and the connection point is located between the first main line and the first conversion branch. The voltage loop outputs the same current reference value for each first conversion branch of the first main line, so that each first conversion branch flows uniformly. Further, the voltage loop is the DC side voltage during the charging process, and the voltage loop is the AC side voltage during the discharging process. The DC side voltage is equal to the sum of the third capacitor and the fourth capacitor. The AC side voltage is equal to the sum of the first capacitor and the second capacitor.

[0046] Specifically, please refer to Figure 5 As shown in FIG. 6, the control module can switch the controllable switch S1 according to the received control parameters or other control signals. In order to ensure that the currents of the three interleaved lines are equal, the control module is connected to each first conversion branch to provide a current reference value. The inductance control of the three first conversion branches in the L1 branch uses the same current reference value, and through closed-loop adjustment, the purpose of current sharing is achieved. The control method of L2 is similar, and the inductance current reference value is generated by the output of the voltage loop. The control block diagram can be referred to Figure 6 As shown in FIG. 6, the control module outputs a unified current reference value, the sampling current of each first conversion branch is compared with the inductance current reference value to determine the inductance current adjustment parameter, and the duty cycle of each first conversion branch is determined according to the comparison result of the grid voltage feedforward and the inductance current adjustment parameter. The grid voltage feedback is determined by the first capacitor, the second capacitor, the third capacitor and the fourth capacitor. For example, in the charging mode, the voltage loop is the DC side voltage (the sum of the voltages of C BH and C BL CAP1 and CAP2) sampling and target voltage closed loop; in the discharging mode, the voltage loop is the AC side voltage (CAP1, CAP2 voltage) sampling and target voltage closed loop.

[0047] In an embodiment of the present application, the phase difference between the inverters of each of the first and second conversion branches is 360 / N in the high-frequency operation mode, where N is a positive integer. Further, in the low-frequency operation mode, the drive levels are the same. Specifically, please refer to the following figures: Figure 3 and Figure 7 The control logic of the power conversion device is as follows: S1Ai (i=1, 2, 3) and S2Ai are complementary, and S3Ai and S4Ai are complementary. In the positive half cycle of the rectification mode, S1Ai is the freewheeling tube, S2Ai is the main tube, S4Ai is low, and S3Ai is high. In the negative half cycle of the rectification mode, S3Ai is the main tube, S4Ai is the freewheeling tube, S2Ai is high, and S1Ai is low. In the high-frequency operation mode, the drive pulses of S1A1, S1A2, and S1A3 are 120 degrees apart, and in the low-frequency operation mode, the drive pulses of S1A1, S1A2, and S1A3 are either all high or all low.

[0048] The power conversion device and control method provided by the present application reduce the switching loss of the switching device, have higher conversion efficiency, and the application of the multi-inverter interleaving technology also reduces the ripple and volume of the filter device, effectively reducing the actual application cost.

[0049] It should be noted that, in the present document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. The terms "a" and "one" are defined as including one or more than one. The terms "upper" and "lower" are used to indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and thus cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus cannot be understood as limiting the present application. Unless otherwise explicitly specified and limited, the terms "mount", "connect", "connected", and "connection" should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integral connection; can be mechanical connection, can also be electrical connection; can be direct connection, can also be indirect connection through an intermediate medium, and can be internal connection of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0050] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In the description of this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments in this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0051] This application uses specific embodiments to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A three-level control circuit, characterized by The three-phase port and the two-phase terminal of the three-level control circuit comprise two first main lines and two second main lines; The first main line comprises a plurality of first conversion branches, and the second main line comprises two capacitor branches and a plurality of second conversion branches, the first conversion branches and the second conversion branches are connected in an interleaved manner through an inverter interleaving technology; Each of the capacitor branches is connected in series with a third capacitor and a fourth capacitor, and the plurality of first conversion branches of each of the first main lines are connected to the corresponding capacitor branch, and the connection points are located between the third capacitor and the fourth capacitor; The three-phase port comprises a first AC port, a second AC port and a third AC port; and the two-phase terminal comprises a first DC terminal and a second DC terminal; The three-level control circuit further comprises a capacitor circuit, and the capacitor circuit comprises a first capacitor and a second capacitor; The first capacitor and the second capacitor are coupled between the first AC port and the third AC port, and an intermediate node is provided between the first capacitor and the second capacitor, and the second AC port is connected to each of the capacitor branches through the intermediate node, and the connection points are located between the third capacitor and the fourth capacitor of each of the capacitor branches; The three-level control circuit is a T-type three-level control circuit, a PFC three-level control circuit or an I-type three-level control circuit.

2. The three-level control circuit according to claim 1, characterized in that The first conversion branch and the first main line are connected in series with an inductor, and one end of the plurality of first conversion branches is connected in parallel to the first main line through the inductor; the plurality of second conversion branches and the capacitor branches are connected in parallel between the first DC terminal and the second DC terminal; wherein the first conversion branch and the second conversion branch correspond to each other.

3. The three-level control circuit of claim 1, wherein, When the three-level control circuit is a T-type three-level control circuit, at least two controllable semiconductor devices are connected in series on each of the first conversion branches, and at least two controllable semiconductor devices are connected in series on each of the second conversion branches; the first conversion branch and the second conversion branch correspond to each other and intersect to form an intersection node, and the intersection node is located between the controllable semiconductor devices connected in series on the second conversion branch.

4. A power conversion device, characterized by comprising: The device comprises the three-level control circuit of any one of claims 2 to 3 and a control module, one end of the control module is connected to the first conversion branch of each of the first main lines, and the connection point is located between the first main line and the first conversion branch; the other end is connected to the first capacitor, the second capacitor, the third capacitor and the fourth capacitor.

5. A control method for the power conversion device according to claim 4, characterized by, The control module provides the same current reference value for the plurality of first conversion branches of each of the first main lines according to the voltage loop output, and adjusts the current of each first conversion branch through closed-loop regulation.

6. The control method according to claim 5, characterized by In the charging process, the voltage loop is a direct current side voltage, and in the discharging process, the voltage loop is an alternating current side voltage; The direct current side voltage is equal to the sum of the third capacitor and the fourth capacitor; and the alternating current side voltage is equal to the sum of the first capacitor and the second capacitor.

7. The control method according to claim 5, characterized by, The degrees of the inverters in each of the first conversion branch and the second conversion branch are different by 360 / N in the high-frequency working state, and N is the number of the first conversion branches on the first main circuit.

8. The control method according to claim 5, wherein In the low-frequency working state, the driving levels are the same.

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