Three-level converter, control method, device, storage medium and processor thereof

Abstract

The present invention discloses a control method, device, three-level converter, storage medium, and processor for a three-level converter. The method includes: transforming the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system; re-dividing the sectors of the space vector of the three-level converter under a virtual space vector modulation strategy in the 60° coordinate system; re-synthesizing the space vector of the three-level converter based on the re-divided sectors; calculating the action times of adjacent re-synthesized vectors; and allocating the vector action times of the three-level converter based on the calculated action times of adjacent vectors to control switches in the three-level converter and achieve midpoint potential balance control of the three-level converter. This solution, by re-dividing the sectors and re-synthesizing the vectors using the 60° coordinate system, achieves midpoint potential balance under high modulation index, which is beneficial for improving the output performance of the three-level converter.

Description

Technical Field

[0001] The present invention belongs to the technical field of converters, and specifically relates to a control method, device, three-level converter, storage medium and processor of a three-level converter, and more particularly to a control method, device, three-level converter, storage medium and processor of a three-level converter based on two small sectors. Background Art

[0002] Compared to two-level converters, multilevel converters are widely used in applications with higher voltage levels and higher power ratings due to advantages such as reduced voltage stress on each switch and lower output voltage harmonics. Among multilevel converters, neutral-point-clamped (NPC) three-level converters are widely used, but their development is limited by the disadvantage of midpoint potential imbalance.

[0003] Among the related solutions, there are two main approaches to addressing midpoint potential imbalance: software and hardware. However, the hardware approach requires additional hardware investment, significantly limiting its economic benefits. The software approach has been the most studied. By rationally allocating the action time of redundant small vectors, it can achieve a certain degree of midpoint potential balance. However, it still cannot achieve midpoint balance under high modulation regimes. Therefore, some scholars have proposed a virtual space vector modulation strategy, which theoretically can achieve midpoint potential balance under high modulation regimes. However, due to the large number of sectors, the judgment is very complex, and the calculation of the basic action time is very complex, which is not conducive to programming and real-time system control, and thus affects the output performance of the three-level converter.

[0004] The above content is only used to assist in understanding the technical solution of the present invention and does not constitute an admission that the above content is prior art. Summary of the Invention

[0005] An object of the present invention is to provide a control method, device, three-level converter, storage medium, and processor for a three-level converter, so as to address the problem that, while a virtual space vector modulation strategy can achieve balanced midpoint potential of a midpoint-clamped three-level converter under high modulation index, the large number of sectors affects the output performance of the three-level converter. By redividing the sectors using a 60° coordinate system and re-synthesizing the vectors, balanced midpoint potential under high modulation index is achieved, thereby improving the output performance of the three-level converter.

[0006] The present invention provides a control method for a three-level converter, comprising: transforming a space vector of the three-level converter from a rectangular coordinate system to a 60-degree coordinate system; re-dividing sectors of the space vector of the three-level converter under a virtual space vector modulation strategy of the 60-degree coordinate system; re-synthesizing the space vector of the three-level converter based on the re-divided sectors; calculating action times of adjacent vectors after the re-synthesis; and allocating the vector action time of the three-level converter based on the calculated action times of the adjacent vectors to control switching tubes in the three-level converter and achieve midpoint potential balance control of the three-level converter.

[0007] In some embodiments, the space vector of the three-level converter is transformed from a rectangular coordinate system to a 60° coordinate system, including: using a coordinate transformation and a per-unit model to convert all vectors of the space vector of the three-level converter in the rectangular coordinate system to a 60° coordinate system through coordinate transformation, and then normalizing all voltage vectors in the spatial region to obtain the space vector of the three-level converter in the 60° coordinate system.

[0008] In some embodiments, under the virtual space vector modulation strategy of the 60° coordinate system, the sectors of the space vector of the three-level converter are re-divided, including: under the virtual space vector modulation strategy of the 60° coordinate system, the entire virtual space vector in the space vector of the three-level converter is divided into 6 first sectors, and each of the first sectors is divided into two second sectors.

[0009] In some embodiments, based on the re-divided sectors, the space vector of the three-level converter is resynthesized, including: based on the re-divided sectors, according to the principle that the midpoint potential is zero, constructing a virtual middle vector in the space vector of the three-level converter, and synthesizing a larger vector among adjacent vectors; wherein, synthesizing the larger vector among adjacent vectors includes: using two first vectors and one second vector to synthesize the larger vector among adjacent vectors; the two first vectors include: a positive first vector and a negative first vector.

[0010] In some embodiments, the resynthesized adjacent vectors include: a virtual center vector in the space vector of the three-level converter, and a larger vector among the adjacent vectors; and calculating the action time of the resynthesized adjacent vectors includes: in the odd sectors among the re-divided sectors, based on the volt-second balance principle, calculating the action time of the virtual center vector in the space vector of the three-level converter, the larger vector among the adjacent vectors, and the zero vector as the action time of the resynthesized adjacent vectors.

[0011] Matching the above method, the present invention provides, on the other hand, a control device for a three-level converter, comprising: a conversion unit configured to convert the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system; a division unit, under a virtual space vector modulation strategy of the 60° coordinate system, to re-divide the sectors of the space vector of the three-level converter; a synthesis unit, based on the re-divided sectors, to re-synthesize the space vector of the three-level converter; a calculation unit, calculating the action time of adjacent vectors after the re-synthesis; and an allocation unit, allocating the vector action time of the three-level converter according to the calculated action time of the adjacent vectors, so as to control the switching tubes in the three-level converter and realize the midpoint potential balance control of the three-level converter.

[0012] In some embodiments, the transformation unit transforms the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system, including: using coordinate transformation and a per-unit model to convert all vectors of the space vector of the three-level converter in the rectangular coordinate system to a 60° coordinate system through coordinate transformation, and then normalizing all voltage vectors in the spatial region to obtain the space vector of the three-level converter in the 60° coordinate system.

[0013] In some embodiments, the division unit re-divides the sectors of the space vector of the three-level converter under the virtual space vector modulation strategy of the 60° coordinate system, including: under the virtual space vector modulation strategy of the 60° coordinate system, dividing the entire virtual space vector in the space vector of the three-level converter into 6 first sectors, and then dividing each of the first sectors into two second sectors.

[0014] In some embodiments, the synthesis unit re-synthesizes the space vector of the three-level converter based on the re-divided sectors, including: based on the re-divided sectors, according to the principle that the midpoint potential is zero, constructing a virtual middle vector in the space vector of the three-level converter, and synthesizing a larger vector among adjacent vectors; wherein, synthesizing the larger vector among adjacent vectors includes: using two first vectors and one second vector to synthesize the larger vector among adjacent vectors; the two first vectors include: a positive first vector and a negative first vector.

[0015] In some embodiments, the resynthesized adjacent vectors include: a virtual center vector in the space vector of the three-level converter, and a larger vector among the adjacent vectors; the calculation unit calculates the action time of the resynthesized adjacent vectors, including: in the odd sectors among the re-divided sectors, based on the volt-second balance principle, calculating the action time of the virtual center vector in the space vector of the three-level converter, the larger vector among the adjacent vectors, and the zero vector as the action time of the resynthesized adjacent vectors.

[0016] Matching the above device, the present invention provides a three-level converter in another aspect, including: the control device of the three-level converter described above.

[0017] In accordance with the above method, the present invention further provides a storage medium comprising a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the above-mentioned control method for the three-level converter.

[0018] Matching the above method, the present invention provides a processor on another aspect, wherein the processor is used to run a program, wherein the program executes the above-mentioned control method for the three-level converter when running.

[0019] Therefore, the solution of the present invention further divides the 60° sector into two smaller sectors under a virtual space vector modulation strategy in a 60° coordinate system, synthesizes a reference vector using three adjacent vectors, and achieves midpoint potential balance using a virtual vector. Thus, by redividing the sectors using a 60° coordinate system and re-synthesizing the vectors, midpoint potential balance is achieved under a high modulation index, which is beneficial to improving the output performance of the three-level converter.

[0020] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is a flow chart of an embodiment of a control method for a three-level converter according to the present invention;

[0023] Figure 2 1 is a schematic diagram of the structure of an NPC three-level converter topology, specifically a schematic diagram of the structure of a diode-clamped three-level converter;

[0024] Figure 3 1 is a flow chart of a control method for a three-level converter based on two small sectors;

[0025] Figure 4 A coordinate diagram for space vector sector division and vector synthesis;

[0026] Figure 5 The schematic diagram of the simplified circuit structure showing the effect of vector action on the midpoint current is shown in Figure 100, 211, 221, and 210 from left to right.

[0027] Figure 6 Schematic diagram of the single-phase commutation state of the three-level converter, from left to right are P state, O state, and N state;

[0028] Figure 7 FIG. 1 is a schematic structural diagram of an embodiment of a control device for a three-level converter according to the present invention.

[0029] In conjunction with the accompanying drawings, the reference numerals in the embodiments of the present invention are as follows:

[0030] 102 - transformation unit; 104 - division unit; 106 - synthesis unit; 108 - calculation unit; 110 - allocation unit. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] According to an embodiment of the present invention, a control method for a three-level converter is provided. Figure 1 A flow chart showing an embodiment of the method of the present invention is shown. Figure 2 This is the topological structure diagram of the three-level NPC converter proposed in the present invention. Figure 2 As shown, the three-level NPC converter has a total of 12 switching tubes, each forming a three-phase bridge arm. Each phase bridge arm has two diodes for clamping. The DC side is supported by two capacitors (i.e., capacitor C1 and capacitor C2) and provides a neutral point N. The control method of the three-level converter may include: steps S110 to S150.

[0033] In step S110 , the space vector of the three-level converter is transformed from a rectangular coordinate system to a 60° coordinate system.

[0034] In some embodiments, in step S110, the space vector of the three-level converter is transformed from a rectangular coordinate system to a 60° coordinate system, including: using a coordinate transformation and a per-unit model to convert all vectors of the space vector of the three-level converter in the rectangular coordinate system to a 60° coordinate system through coordinate transformation, and then normalizing all voltage vectors in the spatial region to obtain the space vector of the three-level converter in the 60° coordinate system.

[0035] Figure 3 FIG. 1 is a flow chart of a control method for a three-level converter based on two small sectors. Figure 3 As shown, the solution of the present invention proposes a control method for a three-level converter based on two small sectors, comprising the following steps:

[0036] Step 1: Change the coordinates of the space vector from the rectangular coordinate system to the 60° coordinate system and normalize it.

[0037] Figure 4 The coordinate diagram of space vector sector division and vector synthesis is shown in Figure 1. First, all vectors in the rectangular coordinate system are transformed into the 60° coordinate system (gh coordinate system) through coordinate transformation. Then, all voltage vectors in the spatial region are normalized to obtain the space vector diagram of the three-level converter in the 60° coordinate system, as shown in Figure 1. Figure 4 As shown. The coordinate transformation and per-unit model are as follows:

[0038]

[0039] Wherein, Vα and Vβ are the values ​​of the reference voltage in the α and β coordinate systems, Vg and Vh are the values ​​of the reference voltage in the g and h coordinate systems, and Udc is the bus voltage.

[0040] At step S120 , under the virtual space vector modulation strategy of the 60° coordinate system, sectors of the space vector of the three-level converter are re-divided.

[0041] In some embodiments, in step S120, under the virtual space vector modulation strategy of the 60° coordinate system, the sectors of the space vector of the three-level converter are re-divided, including: under the virtual space vector modulation strategy of the 60° coordinate system, the entire virtual space vector in the space vector of the three-level converter is divided into 6 first sectors, and each of the first sectors is divided into two second sectors.

[0042] like Figure 3 As shown, the control method of a three-level converter based on two small sectors proposed in the solution of the present invention further includes the following steps:

[0043] Step 2: Use the vector after coordinate transformation to perform sector division and judgment.

[0044] Then the virtual space vector is divided into regions. First, the entire virtual space vector is divided into 6 large sectors, and each large sector is divided into two small sectors, for a total of 12 small sectors.

[0045] Taking the first largest sector as an example, in the three-level converter, the current flow diagram of the vector that affects the midpoint current is as follows: Figure 5 As shown, Figure 5 The simplified circuit structure diagram of the effect of vector action on the midpoint current is shown in Figure 100, 211, 221, and 210 from left to right. The P state of the vector action is represented by 2, the O state by 1, and the N state by 0. The single-phase commutation state is as follows: Figure 6 As shown, Figure 6 Figure 1 is a schematic diagram of the single-phase commutation states of a three-level converter, with the P state, O state, and N state from left to right. Since each phase of the NPC converter has the same structure, the commutation method for the other two phases is the same.

[0046] At step S130 , the space vectors of the three-level converter are resynthesized based on the re-divided sectors.

[0047] In some embodiments, in step S130, the space vector of the three-level converter is resynthesized based on the re-divided sectors, including: based on the re-divided sectors, according to the principle that the midpoint potential is zero, constructing a virtual middle vector in the space vector of the three-level converter, and synthesizing a larger vector among adjacent vectors.

[0048] The synthesizing a larger vector among adjacent vectors includes: synthesizing the larger vector among adjacent vectors using two first vectors and one second vector. The two first vectors include: a positive first vector and a negative first vector.

[0049] like Figure 3 As shown, the control method of a three-level converter based on two small sectors proposed in the solution of the present invention further includes the following steps:

[0050] Step 3: Synthesize adjacent vectors and reference vectors based on the principle that the midpoint potential is zero.

[0051] Since the current values ​​of small vectors V221, V100, and V211 flowing through the neutral point are ic, ia, and -ia respectively, and the current of the neutral point flowing through the neutral point is ib, in order to ensure the neutral point potential balance, the current flowing through the neutral point N is ia+ib+ic=0, and the principle that the entire virtual neutral vector has no effect on the neutral point potential can be synthesized by using the basic small vectors and the basic neutral vector. Constructing the virtual neutral vector (V p+1 ) and the larger vector (V p )like Figure 4 As shown, the purpose of having no effect on the midpoint potential is achieved. The synthetic vector is as follows:

[0052]

[0053] Constructing a virtual center vector (V p+1 ) is to make the current flowing through the midpoint zero when the neutral vector acts. p+1 ) and the larger vector (V p ) have no relationship, such as Figure 4 As shown, the vectors in the diagonal direction, such as the vectors in the directions 200 and 220, are the larger vectors among the adjacent vectors (V p ), the angle bisector in the middle of the diagonal, such as the vector in the direction of 210 is the virtual mean vector (V p+1 ). V221 and V100 are small vectors, and V210 is a medium vector.

[0054] The larger vector among the adjacent vectors can be synthesized by two small vectors (positive small vector and negative small vector) and a large vector. Since the large vector has no effect on the neutral point potential, the synthetic vector V p No effect on the neutral point, synthetic vector V p for:

[0055]

[0056] Divide according to the length of the vector, such as Figure 4 The vector on the diagonal of the small hexagon is the small vector, the vector on the diagonal of the large hexagon is the large vector, and the vector in the direction of the dotted line of the large hexagon is the medium vector. V211 and V100 are small vectors, and V200 is the large vector.

[0057] Next, we will make a judgment on the small sectors. Figure 4 This is a small sector division diagram under the 60° coordinate system. Figure 4 ,Table 1 shows the small sector judgment rules.

[0058] Table 1: Judgment of small sectors

[0059] n <![CDATA[V g ]]> <![CDATA[V h ]]> <![CDATA[V g +V h ]]> <![CDATA[V g -V h ]]> <![CDATA[2V g +V h ]]> <![CDATA[V g +2V h ]]> 1 >0 >0 - >0 - - 2 >0 >0 - <0 - - 3 <0 >0 >0 - >0 - 4 <0 >0 >0 - <0 - 5 <0 >0 <0 - - >0 6 <0 >0 <0 - - <0 7 <0 <0 - <0 - - 8 <0 <0 - >0 - - 9 >0 <0 <0 - <0 - 10 >0 <0 <0 - >0 - 11 >0 <0 >0 - - <0 12 >0 <0 >0 - - >0

[0060] n represents the sector, 1 represents the first sector, 2 represents the second sector, and so on.

[0061] In step S140, the action time of the resynthesized adjacent vectors is calculated.

[0062] In some embodiments, the resynthesized adjacent vectors include: a virtual middle vector in the space vector of the three-level converter, and a larger vector in the adjacent vectors.

[0063] In step S140, the action time of the resynthesized adjacent vectors is calculated, including: in the odd sector of the re-divided sector, based on the volt-second balance principle, calculating the action time of the virtual middle vector in the space vector of the three-level converter, the larger vector in the adjacent vectors, and the zero vector as the action time of the resynthesized adjacent vectors.

[0064] like Figure 3 As shown, the control method of a three-level converter based on two small sectors proposed in the solution of the present invention further includes the following steps:

[0065] Step 4: Calculate the action time of the synthesized adjacent vectors.

[0066] Then calculate the vector action time. Participate in the synthesis of V ref The vectors are V p and V p+1 And the zero vector V0, in the odd sector, V p The direction vector is composed of a large vector (V200) and two small vectors (V100 and V211). Suppose the action time of a small vector is T p , a large vector action time is 2T p Based on the volt-second balance principle, the action time of adjacent vectors is as follows:

[0067]

[0068] The calculated T p 、T p+1 , T0 basic vector action time is brought into PWM pulse generation, and the vector action time is reasonably allocated to achieve the function of controlling the converter switch tube. Take the vector action time of small sector 1 as an example:

[0069]

[0070] The order of output voltage vector action within one cycle is: 221-211-210-200-100-000-100-200-210-211-221.

[0071] Ts is a sampling cycle time, T0 is the zero vector action time. The distribution time is based on formula (5). Since it is a symmetrical distribution, the action time needs to be divided by 2. For example, the action time of 221 is V 221 / 2, 211 action time is V 211 / 2. Tp is the action time of the small vector, and Tp+1 is the action time of the virtual medium vector.

[0072] Depend on Figure 4As can be seen, sector 2 is symmetrical with sector 1, and the remaining large sectors are identical to the first. A simple vector rotation can be used to convert the remaining sectors to the first sector. Calculations are performed based on the vector action time of the first sector. This simplifies the generation of the three-level virtual vector drive waveform, significantly reducing the computational effort and facilitating engineering applications. Its unique sector division and vector synthesis approach not only simplifies implementation but also facilitates application in multilevel converters.

[0073] In step S150, the vector action time of the three-level converter is allocated according to the calculated action time of the adjacent vectors to control the switches in the three-level converter and achieve neutral point potential balance control of the three-level converter.

[0074] The present invention provides a control method and system for a three-level converter based on two small sectors. By adopting a 60-degree coordinate system and combining a special sector division method, adjacent vectors and virtual vectors are resynthesized. This solves the problems of virtual space vector modulation methods in related solutions, such as the large number of sector divisions, complex judgments, cumbersome calculations, and poor real-time performance. This method achieves midpoint potential balance under high modulation conditions and improves the output performance of the converter.

[0075] Accordingly, a system for implementing a control method for a three-level converter based on two small sectors includes a coordinate transformation module, a sector division and judgment module, a vector synthesis module, an action time calculation and allocation module, and a three-level converter.

[0076] In the solution of the present invention, using a virtual space vector modulation strategy in a 60° coordinate system, the 60° sector is further divided into two smaller sectors, each with a 30° sector. A reference vector is synthesized using three adjacent vectors—two small vectors and one large vector—to form an adjacent vector. Midpoint potential balance is achieved using virtual vectors, achieving midpoint potential balance at high modulation levels and improving converter output performance. This approach also simplifies the control method, facilitating calculations and enabling real-time system control, making it easier to apply to control systems with a wider range of power levels.

[0077] The solution of the present invention utilizes the GH coordinate system, resolving the numerous trigonometric calculations and complex algorithmic processes inherent in related control methods. This simplifies sector determination and vector action time calculation, shortening computation time and significantly increasing processor speed. Furthermore, the solution of the present invention implements midpoint voltage balancing control, achieving midpoint voltage balancing across the entire modulation range.

[0078] The above embodiment is applicable to the control of a three-level converter. To achieve three-level control and neutral potential balance, a neutral potential balance control method for a neutral-point clamped three-level inverter based on a 60° coordinate system can also achieve the effect of the solution of the present invention.

[0079] This solution adopts the traditional three-level control method, but converts the traditional rectangular coordinate system into a 60-degree coordinate system, which can reduce the calculation of trigonometric functions. Figure 4 As shown in the enlarged portion, the previous solution divides the area into four smaller sectors. Based on which of the smaller sectors the reference vector falls within, vector synthesis is performed to calculate the vector action time. This application divides the area into only two sectors, simplifying the determination method and vector time calculation. Furthermore, this application performs virtual synthesis of the midpoint vector, achieving balanced control of the midpoint voltage.

[0080] The technical solution of this embodiment uses a virtual space vector modulation strategy in a 60° coordinate system to further divide the 60° sector into two smaller sectors. Three adjacent vectors are used to synthesize a reference vector, and midpoint potential balance is achieved using virtual vectors. Consequently, by redividing the sectors and re-synthesizing the vectors using a 60° coordinate system, midpoint potential balance is achieved at high modulation levels, which helps improve the output performance of the three-level converter.

[0081] According to an embodiment of the present invention, a control device for a three-level converter corresponding to the control method for the three-level converter is also provided. Figure 2 This is the topological structure diagram of the three-level NPC converter proposed in the present invention. Figure 2 As shown in Figure 1, the three-level NPC converter has a total of 12 switches, forming three-phase bridge arms. Each phase bridge arm has two diodes for clamping. The DC side uses two capacitors (i.e., capacitor C1 and capacitor C2) as support and provides a neutral point N. Figure 7 FIG2 is a schematic structural diagram of an embodiment of the device of the present invention. The control device of the three-level converter may include: a conversion unit 102 , a division unit 104 , a synthesis unit 106 , a calculation unit 108 and an allocation unit 110 .

[0082] The transformation unit 102, such as a coordinate transformation module, is configured to transform the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system. Specific functions and processing of the transformation unit 102 are described in step S110.

[0083] In some embodiments, the transformation unit 102 transforms the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system, including: the transformation unit 102 is specifically configured to use coordinate transformation and a per-unit model to convert all vectors of the space vector of the three-level converter in the rectangular coordinate system to a 60° coordinate system through coordinate transformation, and then normalize all voltage vectors in the spatial region to obtain the space vector of the three-level converter in the 60° coordinate system.

[0084] Figure 3 Figure 1 is a flow chart of a control device for a three-level converter based on two small sectors. Figure 3 As shown, the solution of the present invention proposes a control device for a three-level converter based on two small sectors, comprising the following steps:

[0085] Step 1: Change the coordinates of the space vector from the rectangular coordinate system to the 60° coordinate system and normalize it.

[0086] Figure 4 The coordinate diagram of space vector sector division and vector synthesis is shown in Figure 1. First, all vectors in the rectangular coordinate system are transformed into the 60° coordinate system (gh coordinate system) through coordinate transformation. Then, all voltage vectors in the spatial region are normalized to obtain the space vector diagram of the three-level converter in the 60° coordinate system, as shown in Figure 1. Figure 4 As shown. The coordinate transformation and per-unit model are as follows:

[0087]

[0088] The division unit 104, such as the sector division and judgment module, re-divides the sectors of the space vector of the three-level converter under the virtual space vector modulation strategy of the 60° coordinate system. The specific functions and processing of the division unit 104 are shown in step S120.

[0089] In some embodiments, the division unit 104 re-divides the sectors of the space vector of the three-level converter under the virtual space vector modulation strategy of the 60° coordinate system, including: the division unit 104 is specifically configured to divide the entire virtual space vector in the space vector of the three-level converter into 6 first sectors under the virtual space vector modulation strategy of the 60° coordinate system, and then divide each of the first sectors into two second sectors.

[0090] like Figure 3 As shown, the control device of a three-level converter based on two small sectors proposed in the solution of the present invention further includes the following steps:

[0091] Step 2: Use the vector after coordinate transformation to perform sector division and judgment.

[0092] Then the virtual space vector is divided into regions. First, the entire virtual space vector is divided into 6 large sectors, and each large sector is divided into two small sectors, for a total of 12 small sectors.

[0093] Taking the first largest sector as an example, in the three-level converter, the current flow diagram of the vector that affects the midpoint current is as follows: Figure 5 As shown, Figure 5 The simplified circuit structure diagram of the effect of vector action on the midpoint current is shown in Figure 100, 211, 221, and 210 from left to right. The P state of the vector action is represented by 2, the O state by 1, and the N state by 0. The single-phase commutation state is as follows: Figure 6 As shown, Figure 6 Figure 1 is a schematic diagram of the single-phase commutation states of a three-level converter, with the P state, O state, and N state from left to right. Since each phase of the NPC converter has the same structure, the commutation method for the other two phases is the same.

[0094] The synthesis unit 106, such as a vector synthesis module, resynthesizes the space vectors of the three-level converter based on the re-divided sectors. The specific functions and processing of the synthesis unit 106 are shown in step S130.

[0095] In some embodiments, the synthesis unit 106 resynthesizes the space vector of the three-level converter based on the re-divided sectors, including: the synthesis unit 106 is specifically configured to construct a virtual center vector in the space vector of the three-level converter based on the re-divided sectors and according to the principle that the midpoint potential is zero, and synthesize the larger vector among the adjacent vectors.

[0096] The synthesizing unit 106 synthesizes the larger vector among the adjacent vectors, including: the synthesizing unit 106 is further configured to synthesize the larger vector among the adjacent vectors using two first vectors and one second vector. The two first vectors include a positive first vector and a negative first vector.

[0097] like Figure 3 As shown, the control device of a three-level converter based on two small sectors proposed in the solution of the present invention further includes the following steps:

[0098] Step 3: Synthesize adjacent vectors and reference vectors based on the principle that the midpoint potential is zero.

[0099] Since the current values ​​of small vectors V221, V100, and V211 flowing through the neutral point are ic, ia, and -ia respectively, and the current of the neutral point flowing through the neutral point is ib, in order to ensure the neutral point potential balance, the current flowing through the neutral point N is ia+ib+ic=0, and the principle that the entire virtual neutral vector has no effect on the neutral point potential can be synthesized by using the basic small vectors and the basic neutral vector. Constructing the virtual neutral vector (V p+1 ) and the larger vector (V p )like Figure 4 As shown, the purpose of having no effect on the midpoint potential is achieved. The synthetic vector is as follows:

[0100]

[0101] The larger vector among the adjacent vectors can be synthesized by two small vectors (positive small vector and negative small vector) and a large vector. Since the large vector has no effect on the neutral point potential, the synthetic vector V p No effect on the neutral point, synthetic vector V p for:

[0102]

[0103] Next, we will make a judgment on the small sectors. Figure 4 This is a small sector division diagram under the 60° coordinate system. Figure 4 ,Table 1 shows the small sector judgment rules.

[0104] Table 1: Judgment of small sectors

[0105] n <![CDATA[V g ]]> <![CDATA[V h ]]> <![CDATA[V g +V h ]]> <![CDATA[V g -V h ]]> <![CDATA[2V g +V h ]]> <![CDATA[V g +2V h ]]> 1 >0 >0 - >0 - - 2 >0 >0 - <0 - - 3 <0 >0 >0 - >0 - 4 <0 >0 >0 - <0 - 5 <0 >0 <0 - - >0 6 <0 >0 <0 - - <0 7 <0 <0 - <0 - - 8 <0 <0 - >0 - - 9 >0 <0 <0 - <0 - 10 >0 <0 <0 - >0 - 11 >0 <0 >0 - - <0 12 >0 <0 >0 - - >0

[0106] The calculation unit 108, such as an action time calculation module, calculates the action time of the resynthesized adjacent vectors. The specific functions and processing of the calculation unit 108 are shown in step S140.

[0107] In some embodiments, the resynthesized adjacent vectors include: a virtual middle vector in the space vector of the three-level converter, and a larger vector in the adjacent vectors.

[0108] The calculation unit 108 calculates the action time of the resynthesized adjacent vectors, including: the calculation unit 108 is specifically further configured to calculate, based on the volt-second balance principle, the action time of the virtual middle vector in the space vector of the three-level converter, the larger vector in the adjacent vectors, and the zero vector in the odd sector in the re-divided sector, as the action time of the resynthesized adjacent vectors.

[0109] like Figure 3As shown, the control device of a three-level converter based on two small sectors proposed in the solution of the present invention further includes the following steps:

[0110] Step 4: Calculate the action time of the synthesized adjacent vectors.

[0111] Then calculate the vector action time. Participate in the synthesis of V ref The vectors are V p and V p+1 And the zero vector V0, in the odd sector, V p The direction vector is composed of a large vector (V200) and two small vectors (V100 and V211). Suppose the action time of a small vector is T p , a large vector action time is 2T p Based on the volt-second balance principle, the action time of adjacent vectors is as follows:

[0112]

[0113] The calculated T p 、T p+1 , T0 basic vector action time is brought into PWM pulse generation, and the vector action time is reasonably allocated to achieve the function of controlling the converter switch tube. Take the vector action time of small sector 1 as an example:

[0114]

[0115] The order of output voltage vector action within one cycle is: 221-211-210-200-100-000-100-200-210-211-221.

[0116] Depend on Figure 4 As can be seen, sector 2 is symmetrical with sector 1, and the remaining large sectors are identical to the first. A simple vector rotation can be used to convert the remaining sectors to the first sector. Calculations are performed based on the vector action time of the first sector. This simplifies the generation of the three-level virtual vector drive waveform, significantly reducing the computational effort and facilitating engineering applications. Its unique sector division and vector synthesis approach not only simplifies implementation but also facilitates application in multilevel converters.

[0117] The allocating unit 110, such as an action time allocation module, allocates the action times of the vectors of the three-level converter based on the calculated action times of the adjacent vectors to control the switches in the three-level converter and achieve midpoint potential balance control of the three-level converter. The specific functions and processing of the allocating unit 110 are described in step S150.

[0118] The present invention provides a control device and system for a three-level converter based on two small sectors. By adopting a 60-degree coordinate system and combining a special sector division method to re-synthesize adjacent vectors and virtual vectors, the present invention solves the problems of virtual space vector modulation devices in related solutions, such as the large number of sector divisions, complex judgment, cumbersome calculations, and poor real-time performance. The system achieves midpoint potential balance under high modulation conditions and improves the output performance of the converter.

[0119] Accordingly, a system for implementing a control device for a three-level converter based on two small sectors includes: a coordinate transformation module, a sector division and judgment module, a vector synthesis module, an action time calculation and allocation module, and a three-level converter.

[0120] In the solution of the present invention, using a virtual space vector modulation strategy in a 60° coordinate system, the 60° sector is further divided into two smaller sectors, each with a 30° sector. A reference vector is synthesized using three adjacent vectors—two small vectors and one large vector—to form an adjacent vector. Midpoint potential balance is achieved using virtual vectors, achieving midpoint potential balance at high modulation levels and improving converter output performance. This approach also simplifies the control device, facilitating calculations and enabling real-time system control, making it easier to apply to control systems with a wider range of power levels.

[0121] Since the processing and functions implemented by the device of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0122] By adopting the technical solution of the present invention, the 60° sector is further divided into two small sectors under the virtual space vector modulation strategy of the 60° coordinate system, the reference vector is synthesized by three adjacent vectors, and the midpoint potential balance is achieved by means of a virtual vector. This simplifies the control method, facilitates calculation, and facilitates real-time control of the system.

[0123] According to an embodiment of the present invention, a three-level converter corresponding to the control device of the three-level converter is also provided. The three-level converter may include: the control device of the three-level converter described above.

[0124] Since the processing and functions implemented by the three-level converter of this embodiment are basically corresponding to the embodiments, principles and examples of the aforementioned devices, any details not fully described in this embodiment can be referred to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0125] By adopting the technical solution of the present invention, the 60° sector is further divided into two small sectors under the virtual space vector modulation strategy of the 60° coordinate system, the reference vector is synthesized by three adjacent vectors, and the midpoint potential balance is achieved by means of a virtual vector, which can be easily extended to control systems of more levels.

[0126] According to an embodiment of the present invention, a storage medium corresponding to the control method of a three-level converter is also provided, wherein the storage medium includes a stored program, wherein when the program is run, the device where the storage medium is located is controlled to execute the control method of the three-level converter described above.

[0127] Since the processing and functions implemented by the storage medium of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0128] By adopting the technical solution of the present invention, the 60° sector is further divided into two small sectors under the virtual space vector modulation strategy of the 60° coordinate system, a reference vector is synthesized by three adjacent vectors, and midpoint potential balance is achieved by means of a virtual vector. This solves the problems of the virtual space vector modulation method in related solutions, such as the large number of sector divisions, very complex judgments, cumbersome calculations, and poor real-time performance.

[0129] According to an embodiment of the present invention, a processor corresponding to the control method of a three-level converter is further provided, wherein the processor is configured to run a program, wherein the control method of the three-level converter described above is executed when the program is run.

[0130] Since the processing and functions implemented by the processor of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0131] By adopting the technical solution of the present invention, the 60° sector is further divided into two small sectors under the virtual space vector modulation strategy of the 60° coordinate system, the reference vector is synthesized by three adjacent vectors, and the midpoint potential balance is achieved by means of a virtual vector. The midpoint potential balance under high modulation index is achieved, and the output performance of the converter is improved.

[0132] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0133] The foregoing description is merely an embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of the claims.

Claims

1. A control method for a three-level converter, characterized in that: include: Converting the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system; Under the virtual space vector modulation strategy of the 60° coordinate system, re-dividing the sectors of the space vector of the three-level converter; Based on the re-divided sectors, the space vectors of the three-level converter are resynthesized, including: based on the re-divided sectors, according to the principle that the midpoint potential is zero, constructing a virtual middle vector in the space vector of the three-level converter, and synthesizing a larger vector among adjacent vectors; wherein synthesizing the larger vector among adjacent vectors includes: synthesizing the larger vector among adjacent vectors using two first vectors and one second vector; the two first vectors include: a positive first vector and a negative first vector; Calculating the action time of the resynthesized adjacent vectors; The vector action times of the three-level converter are allocated based on the calculated action times of the adjacent vectors to control the switching tubes in the three-level converter and achieve midpoint potential balance control of the three-level converter. A 60° sector is further divided into two smaller sectors under a virtual space vector modulation strategy in a 60° coordinate system, a reference vector is synthesized using three adjacent vectors, and midpoint potential balance is achieved under a high modulation index using a virtual vector.

2. The control method of the three-level converter according to claim 1, characterized in that: in, Transforming the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system includes: Using coordinate transformation and a per-unit model, all vectors of the space vectors of the three-level converter in the rectangular coordinate system are converted to a 60° coordinate system through coordinate transformation, and then all voltage vectors in the spatial region are normalized to obtain the space vectors of the three-level converter in the 60° coordinate system; Under the virtual space vector modulation strategy of the 60° coordinate system, sectors of the space vector of the three-level converter are re-divided, including: Under the virtual space vector modulation strategy of the 60° coordinate system, the entire virtual space vector in the space vector of the three-level converter is divided into six first sectors, and each of the first sectors is then divided into two second sectors.

3. The control method of the three-level converter according to claim 1 or 2, characterized in that: The resynthesized adjacent vectors include: a virtual middle vector in the space vector of the three-level converter, and a larger vector in the adjacent vectors; Calculating the action time of the resynthesized adjacent vectors, including: In the odd sectors of the re-divided sectors, based on the volt-second balance principle, the action times of the virtual middle vector in the space vector of the three-level converter, the larger vector among the adjacent vectors, and the zero vector are calculated as the action times of the re-synthesized adjacent vectors.

4. A control device for a three-level converter, characterized in that: include: a conversion unit configured to convert the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system; a dividing unit, which re-divides the sectors of the space vector of the three-level converter under the virtual space vector modulation strategy of the 60° coordinate system; A synthesis unit, based on the re-divided sectors, re-synthesizes the space vectors of the three-level converter, including: constructing a virtual middle vector in the space vector of the three-level converter based on the re-divided sectors and according to the principle that the midpoint potential is zero, and synthesizing a larger vector among adjacent vectors; wherein synthesizing the larger vector among adjacent vectors includes: synthesizing the larger vector among adjacent vectors using two first vectors and one second vector; the two first vectors include: a positive first vector and a negative first vector; a calculation unit, for calculating the action time of the resynthesized adjacent vectors; An allocating unit allocates the vector action time of the three-level converter according to the calculated action time of the adjacent vectors, so as to control the switching tubes in the three-level converter and achieve midpoint potential balance control of the three-level converter; and further divides the 60° sector into two small sectors under a virtual space vector modulation strategy of a 60° coordinate system, synthesizes a reference vector with three adjacent vectors, and achieves midpoint potential balance under a high modulation index by means of a virtual vector.

5. The control device for a three-level converter according to claim 4, wherein: in, The conversion unit converts the space vector of the three-level converter from a rectangular coordinate system to a 60° coordinate system, including: Using coordinate transformation and a per-unit model, all vectors of the space vectors of the three-level converter in the rectangular coordinate system are converted to a 60° coordinate system through coordinate transformation, and then all voltage vectors in the spatial region are normalized to obtain the space vectors of the three-level converter in the 60° coordinate system; The division unit, under the virtual space vector modulation strategy of the 60° coordinate system, re-divides the sectors of the space vector of the three-level converter, including: Under the virtual space vector modulation strategy of the 60° coordinate system, the entire virtual space vector in the space vector of the three-level converter is divided into six first sectors, and each of the first sectors is then divided into two second sectors.

6. The control device for a three-level converter according to claim 4 or 5, characterized in that: The resynthesized adjacent vectors include: a virtual middle vector in the space vector of the three-level converter, and a larger vector in the adjacent vectors; The calculation unit calculates the action time of the resynthesized adjacent vectors, including: In the odd sectors of the re-divided sectors, based on the volt-second balance principle, the action times of the virtual middle vector in the space vector of the three-level converter, the larger vector among the adjacent vectors, and the zero vector are calculated as the action times of the re-synthesized adjacent vectors.

7. A three-level converter, characterized in that: include: The control device for a three-level converter according to any one of claims 4 to 6.

8. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the control method for the three-level converter according to any one of claims 1 to 3.

9. A processor, characterized in that: The processor is configured to run a program, wherein the program executes the control method for a three-level converter according to any one of claims 1 to 3 when running.

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