Three-level inverter neutral-point potential equalization control method, device and equipment and storage medium

Abstract

The invention relates to a neutral-point potential equalization control method, device and equipment for a three-level inverter and a storage medium. The method comprises the steps of obtaining a vector modulation factor based on a target voltage difference of upper and lower capacitors of the three-level inverter and a preset voltage difference interval; determining a virtual voltage vector corresponding to the voltage vector space based on the vector modulation factor and an original virtual vector corresponding to the voltage vector space; determining a target sector matched with the reference vector; target virtual voltage vectors and action time corresponding to the target virtual voltage vectors are determined based on the target sector; and determining an execution voltage vector sequence corresponding to the target sector based on the target virtual voltage vector, and determining action time corresponding to each execution voltage vector in the execution voltage vector sequence based on the action time corresponding to each target virtual voltage vector. By remodeling the virtual vector, the neutral-point potential balance speed and the neutral-point potential fluctuation suppression capability of the three-level inverter under the low power factor and high modulation degree can be improved.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a method, apparatus, computer equipment, computer-readable storage medium, and computer program product for controlling the midpoint potential balance of a three-level inverter. Background Technology

[0002] With the continuous development of inverter technology research, the modulation technology of three-level inverters has also developed rapidly. PWM modulation technology, as an important control component of three-level inverters, directly affects the performance of the inverter. Active Neutral Point Clamped (ANPC) three-level topologies have advantages over traditional two-level inverters, such as lower voltage stress on power devices, higher efficiency, lower harmonic distortion rate, and higher power density, and are therefore widely used in medium-voltage energy storage converters. However, this topology inevitably suffers from neutral point potential imbalance during operation, especially under low power factor and high regulation grid reactive power support conditions, where the neutral point potential fluctuations are severe and difficult to suppress effectively. Neutral point potential imbalance not only leads to uneven voltage distribution on the DC side capacitors and switching transistors, but also causes output voltage distortion, increased current harmonics, and shortened lifespan of switching devices and DC capacitors.

[0003] Traditional SVPWM modulation strategies suffer from incomplete balancing in high modulation and low power factor conditions because the vectors lack midpoint potential adjustment capabilities. This is particularly problematic when the reference voltage vector is almost entirely synthesized from the midpoint vector; adjusting the smaller vectors fails to balance the midpoint potential, limiting midpoint potential fluctuation suppression and resulting in slow midpoint potential balancing. Summary of the Invention

[0004] Based on this, it is necessary to provide a method, device, computer equipment, computer-readable storage medium, and computer program product for neutral point potential equalization control of a three-level inverter that can improve the neutral point potential balance speed and the ability to suppress neutral point potential fluctuations under low power factor and high regulation conditions.

[0005] In a first aspect, this application provides a method for neutral point potential equalization control of a three-level inverter, including:

[0006] The vector modulation factor is obtained based on the target voltage difference and the preset voltage difference range of the upper and lower capacitors of the three-level inverter.

[0007] The virtual voltage vector corresponding to the voltage vector space is determined based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space; the partitioning boundary in the voltage vector space of the three-level inverter is determined based on the virtual voltage vector, and the voltage vector space is divided into the target number of sectors according to the partitioning boundary;

[0008] Obtain the reference vector; determine the target sector that matches the reference vector from the target number of sectors;

[0009] The target virtual voltage vector used to synthesize the reference vector and the corresponding action time of each target virtual voltage vector are determined based on the target sector.

[0010] The execution voltage vector sequence corresponding to the target sector is determined based on the target virtual voltage vector, and the execution time of each execution voltage vector in the execution voltage vector sequence is determined based on the execution time of each target virtual voltage vector.

[0011] According to the sequence of executed voltage vectors, each executed voltage vector is sequentially controlled to act on the three-level inverter during its corresponding action time, so as to control the midpoint potential of the three-level inverter.

[0012] Secondly, this application also provides a three-level inverter neutral point potential equalization control device, comprising:

[0013] The factor determination module is used to obtain the vector modulation factor based on the target voltage difference and preset voltage difference range of the upper and lower capacitors of the three-level inverter.

[0014] The sector partitioning module is used to determine the virtual voltage vector corresponding to the voltage vector space based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space; to determine the partitioning boundary in the voltage vector space of the three-level inverter based on the virtual voltage vector; and to divide the voltage vector space into the target number of sectors according to the partitioning boundary.

[0015] The acquisition module is used to acquire a reference vector and determine the target sector that matches the reference vector from the target number of sectors.

[0016] The time determination module is used to determine the target virtual voltage vector used to synthesize the reference vector based on the target sector, as well as the corresponding action time of each target virtual voltage vector;

[0017] The sequence determination module is used to determine the sequence of execution voltage vectors corresponding to the target sector based on the target virtual voltage vector, and to determine the action time of each execution voltage vector in the sequence of execution voltage vectors based on the action time of each target virtual voltage vector.

[0018] The execution module is used to control each execution voltage vector to act on the three-level inverter in sequence according to the execution voltage vector sequence, so as to control the midpoint potential of the three-level inverter.

[0019] Thirdly, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps described in the above method.

[0020] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps described in the above method.

[0021] Fifthly, this application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps described in the above method.

[0022] The aforementioned three-level inverter midpoint potential equalization control method, device, computer equipment, computer-readable storage medium, and computer program product obtain a vector modulation factor based on the target voltage difference between the upper and lower capacitors of the three-level inverter and the interval in which the target voltage difference is located. Then, based on the vector modulation factor, the voltage vector space is divided into multiple large sectors and multiple small sectors, and the original virtual vector is reshaped based on the vector modulation factor to obtain an updated virtual voltage vector. Thus, the action time of the original voltage vector can be adjusted by the vector modulation factor, enabling it to have the ability to actively equalize the midpoint potential of the entire sector. Therefore, under the condition of high proportion of reactive power output in steady-state system operation, it can accelerate the dynamic equalization speed while achieving steady-state accuracy of midpoint potential. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the circuit structure of a three-level inverter in one embodiment;

[0025] Figure 2 This is a flowchart illustrating a method for controlling the midpoint potential balance in a three-level inverter in one embodiment.

[0026] Figure 3 This is a schematic diagram of the second sector in one embodiment;

[0027] Figure 4 This is a schematic diagram of the voltage vector space in one embodiment;

[0028] Figure 5 This is a flowchart illustrating the point potential balancing control method for a three-level inverter in another embodiment.

[0029] Figure 6 The waveform diagram of the midpoint potential control of the existing SVPWM modulation strategy under high-proportion reactive power conditions in one embodiment is shown.

[0030] Figure 7 The waveform diagram of the midpoint potential control of the existing VSVPWM modulation strategy under high-proportion reactive power conditions in one embodiment is shown.

[0031] Figure 8 The diagram shows the midpoint potential control waveform of the sector reshaping VSVPWM modulation strategy proposed in this invention under a high proportion of reactive power in one embodiment.

[0032] Figure 9 This is a structural block diagram of a three-level inverter midpoint potential equalization control device in one embodiment;

[0033] Figure 10 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] In one exemplary embodiment, such as Figure 2 As shown, a method for midpoint potential balancing control in a three-level inverter is provided. This embodiment illustrates the application of this method to a terminal device. (Reference) Figure 1 The terminal is, for example, a three-level inverter. A three-level inverter is a multi-level power electronic converter that, by adding power switching devices and clamping elements (such as diodes or capacitors) to each bridge arm, allows the output phase voltage to present three levels (positive, zero, and negative). Compared to traditional two-level inverters, it has advantages such as a more sinusoidal output voltage waveform, lower harmonic content, lower switching losses, and less electromagnetic interference. To solve the problem of midpoint potential imbalance (i.e., the DC side midpoint potential deviates from zero potential) in three-level inverters, this embodiment includes the following steps:

[0036] Step 202: Based on the target voltage difference between the upper and lower capacitors of the three-level inverter and the preset voltage difference range, the vector modulation factor is obtained.

[0037] The allowable voltage difference between the upper and lower capacitors on the DC side of the three-level inverter is a preset voltage difference range. It can be understood that when the currently measured target voltage difference is within the preset voltage difference range, no charge compensation for the midpoint potential is required. When the currently measured target voltage difference is less than the preset voltage difference range, it indicates that the lower capacitor voltage is too high, and the charge to be compensated should be greater than zero. When the currently measured target voltage difference is greater than the preset voltage difference range, it indicates that the upper capacitor voltage is too high, and the charge to be compensated should be less than zero.

[0038] The vector modulation factor includes a first vector modulation factor that adjusts the original virtual vector.

[0039] In this embodiment, a reshaped virtual voltage vector is obtained by adjusting the existing original virtual vector. The midpoint potential is then controlled based on the reshaped virtual voltage vector. Therefore, this embodiment needs to determine the amount of midpoint charge that the reshaped virtual voltage vector needs to generate. Then, a quantitative relationship with the first vector modulation factor is determined based on the qualitative relationship between this midpoint charge and the modulation factor.

[0040] For example, the reshaped virtual voltage vector is obtained by adjusting the original virtual vector based on the vector modulation factor.

[0041] Specifically, the original virtual vector includes at least one of a first original virtual vector, a second original virtual vector, and a third original virtual vector. The first original virtual vector is greater than the second original virtual vector, which is greater than the third original virtual vector. The reshaped virtual voltage vector also includes at least one of a first virtual voltage vector, a second virtual voltage vector, and a third virtual voltage vector. The second virtual voltage vector is composed of the second original virtual vector and the third original virtual vector. The vector modulation factor includes a first vector modulation factor and a second vector modulation factor. The second virtual voltage vector is obtained by adjusting the third original virtual vector using the first vector modulation factor and adjusting the second original virtual vector using the second vector modulation factor. The sum of the first and second vector modulation factors is 1. Based on the above, the composition of the second virtual voltage vector can be determined. Furthermore, in this embodiment, the voltage vector space can be divided into multiple first sectors. The first original virtual vector, the second original virtual vector, and the third original virtual vector correspond to different first sectors. Correspondingly, the first virtual voltage vector, the second virtual voltage vector, and the third virtual voltage vector are respectively composed of the first original virtual vector, the second original virtual vector, and the third original virtual vector corresponding to the first sector where the first virtual voltage vector, the second virtual voltage vector, and the third virtual voltage vector are located.

[0042] For example, the expression for the second virtual voltage vector is as follows:

[0043]

[0044] in, Represents the second virtual voltage vector. Represents the first vector modulation factor. Indicates the second vector modulation factor. , , This represents the third original virtual vector within the first sector. This represents the second original virtual vector within the first sector.

[0045] It can be understood that, based on the second virtual voltage vector and the duration of its action, the amount of midpoint charge that the second virtual voltage vector can generate can be obtained.

[0046] Accordingly, in one switching cycle T s Within this context, assume the duration of the second virtual voltage vector is T. M The midpoint charge generated by this second virtual voltage vector for:

[0047]

[0048] in, , , These are the three-phase currents output by the three-level inverter, and the sum of the three-phase currents is equal to 0. .

[0049] From the above formula, we can see the qualitative relationship between the midpoint charge and the first vector modulation factor for the second virtual voltage vector. For example, to ensure that the midpoint charge generated by the second virtual voltage vector is zero, the first vector modulation factor should be two-thirds. To ensure that the midpoint charge generated by the second virtual voltage vector is greater than zero, the current... When the value is greater than zero, the first vector modulation factor should be less than two-thirds, in the current... When the value is less than zero, the first vector modulation factor should be greater than two-thirds. Similarly, in order for the midpoint charge generated by the second virtual voltage vector to be less than zero, the current... When the value is greater than zero, the first vector modulation factor should be greater than two-thirds, in the current... When it is less than zero, the first vector modulation factor should be less than two-thirds.

[0050] Therefore, after obtaining the target voltage difference between the upper and lower capacitors of the current three-level inverter, the amount of midpoint charge to be compensated can be determined based on the target voltage difference, and the value of the first vector modulation factor can be obtained based on the qualitative relationship between the amount of midpoint charge and the first vector modulation factor.

[0051] Step 204: Determine the virtual voltage vector corresponding to the voltage vector space based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space; determine the partition boundary in the voltage vector space of the three-level inverter based on the virtual voltage vector, and divide the voltage vector space into the target number of sectors according to the partition boundary.

[0052] As can be seen from the above formula, the way to construct the reshaped virtual voltage vector in each first sector can be determined based on the vector modulation factor obtained in step S202.

[0053] For example, the second virtual voltage vector corresponding to the voltage vector space is determined based on the first vector modulation factor, the second original virtual vector, and the third original virtual vector.

[0054] The sector comprises a first sector and a second sector. The first sector defines the voltage vector space, and the second sector defines the first sector. (Reference) Figure 3 and Figure 4 The first sector I is divided into 7 smaller sectors, namely A1, A2, A3, A4, A5, A6, and A7.

[0055] For example, the boundary is determined based on the coordinate points corresponding to each virtual voltage vector within the first sector. (See reference...) Figure 3 Two first virtual voltage vectors ( , The corresponding coordinates are (2) ,0)(0,2 ), second virtual voltage vector ( The coordinates of the point are () , ), two third virtual voltage vectors ( , The coordinates of the point are () ,0)(0, ).in, This represents one-third of the DC-side voltage of the inverter. Boundary line equations can be established based on these coordinate points, and the boundary can then be determined based on these equations.

[0056] For example, the expression for the boundary line equation can be referred to as follows:

[0057]

[0058] in, = / 3 represents the magnitude of the virtual small vector; Indicates the DC side voltage; Reference voltage vector The horizontal projection length in the 60°gh coordinate system; Reference voltage vector The vertical projection length in the 60°gh coordinate system;

[0059] Based on the above boundary line equations, the reference vector can be obtained ( , After that, the target sector corresponding to the reference vector is determined.

[0060] Step 206: Obtain the reference vector; determine the target sector that matches the reference vector from the target number of sectors.

[0061] The reference vector is the voltage vector expected to be the final output of the three-level inverter (hereinafter referred to as the inverter). Since the inverter can only output discrete execution voltage vectors (not the original virtual vector or virtual voltage vector mentioned above), it is necessary to synthesize the reference vector using these discrete execution voltage vectors. To achieve midpoint potential equalization, the duration of each discrete execution voltage vector needs to be controlled. Different target sectors contain different reference vectors, resulting in different discrete execution voltage vectors that need to be controlled. The duration of each execution voltage vector can be determined using the duration of the virtual voltage vector. In other words, the problem is transformed into determining the virtual voltage vector that can be used to synthesize the reference vector, and the duration of that virtual voltage vector.

[0062] Therefore, to determine the virtual voltage vector that can be used to synthesize the reference vector, it is necessary to first identify target sectors that match the reference vector from the target number of sectors. For example, such as... Figure 2 As shown, in the first sector I, there are two first virtual voltage vectors ( , ), second virtual voltage vector ( ), two third virtual voltage vectors ( , ), zero vector ( Assuming the reference vector is located in sector A1, the corresponding virtual voltage vectors include a second virtual voltage vector and a third virtual voltage vector. Zero vector. Assuming the reference vector is located in sector A7, the corresponding virtual voltage vector includes a second virtual voltage vector and two first virtual voltage vectors.

[0063] Step 208: Determine the target virtual voltage vector used to synthesize the reference vector and the corresponding action time of each target virtual voltage vector based on the target sector.

[0064] For example, after determining the target virtual voltage vector based on the target sector, the duration of action of each target virtual voltage vector within the action period is determined based on the reference vector and the action period.

[0065] Specifically, the action time corresponding to each target virtual voltage vector can be determined using the following formula:

[0066]

[0067] in, , These are the projection lengths of the reference vector onto the g-axis and h-axis in the target coordinate system, respectively. This indicates the operating cycle (i.e., the switching cycle of the inverter). , , These represent the duration of action of each target virtual voltage vector. , , These represent the projection lengths of each target virtual voltage vector onto the g-axis. , , These represent the projected lengths of each target virtual voltage vector along the h-axis. It can be understood that in this embodiment, the number of target virtual voltage vectors is 3.

[0068] By substituting the reference vector and each target virtual voltage vector into the above formula and solving the formula, the respective action times can be obtained.

[0069] Step 210: Determine the execution voltage vector sequence corresponding to the target sector based on the target virtual voltage vector, and determine the execution time corresponding to each execution voltage vector in the execution voltage vector sequence based on the execution time corresponding to each target virtual voltage vector.

[0070] For example, after determining the target sector where the reference vector is located, an execution voltage vector (reference) matching that target sector can be obtained. Figure 4 Since the duration of each target virtual voltage vector has been obtained, as well as the relationship between the preset duration of each target virtual voltage vector and the duration of each execution voltage vector, the duration of each execution voltage vector can be determined.

[0071] Step 212: According to the execution voltage vector sequence, each execution voltage vector is sequentially controlled to act on the three-level inverter during its corresponding action time, so as to control the midpoint potential of the three-level inverter.

[0072] For example, refer to Figure 4If the reference vector falls within the second sector A1 of the first sector I, then the corresponding execution voltage vector sequence is {PPO, POO, OOO, OON, ONN, OON, OOO, POO, PPO}. For example, the inverter's A phase is connected to the P bit, B phase is connected to the P bit, and C phase is connected to the O bit to execute 1 / 4Ta.

[0073] In the above-mentioned three-level inverter midpoint potential equalization control method, a vector modulation factor is obtained based on the target voltage difference between the upper and lower capacitors of the three-level inverter and the interval in which the target voltage difference is located. Then, based on the vector modulation factor, the voltage vector space is divided into multiple large sectors and multiple small sectors, and the original virtual vector is reshaped based on the vector modulation factor to obtain an updated virtual voltage vector. Thus, the action time of the original voltage vector can be adjusted by the vector modulation factor, so that it has the ability to actively equalize the midpoint potential of the entire sector. Therefore, under the condition of high proportion of reactive power output in steady-state system operation, the dynamic equalization speed can be accelerated while achieving steady-state accuracy of midpoint potential.

[0074] In an exemplary embodiment, the vector modulation factor is obtained based on the target voltage difference between the upper and lower capacitors of the three-level inverter and a preset voltage difference range, including: if the target voltage difference is less than a first threshold value of the preset voltage difference range, and the target current of the three-level inverter is less than zero, then the vector modulation factor is determined to be a first vector modulation factor; if the target voltage difference is greater than a second threshold value of the preset voltage difference range, and the target current of the three-level inverter is less than zero, then the vector modulation factor is determined to be a second vector modulation factor; if the target voltage difference is greater than a second threshold value of the preset voltage difference range, and the target current of the three-level inverter is less than zero, then the vector modulation factor is determined to be a second vector modulation factor; if the target current of the three-level inverter is greater than zero, then the vector modulation factor is determined to be a first vector modulation factor.

[0075] The first critical value is less than the second critical value, the preset voltage difference range is located between the first critical value and the second critical value, and the first vector modulation factor and the second vector modulation factor are both calculated based on the target voltage difference.

[0076] Specifically, assuming the allowable voltage difference between the upper and lower capacitors on the DC side is... Based on the amount of midpoint charge generated by the reshaped virtual midpoint vector (i.e., the second virtual voltage vector mentioned above) within a unit switching cycle calculated in equation (2) above, the following control principle can be obtained: when - < < At this time, no charge compensation control of the midpoint potential is required, therefore =2 / 3.

[0077] when <- This indicates that the voltage across the lower capacitor is too high at this point, and the charge generated by the virtual vector should satisfy the following condition. >0. According to equation (2), when When >0, it should be taken as =2 / 3-c*| |, that is The value should be less than 2 / 3. When When <0, it should be taken =2 / 3+c*| |, that is The value should be greater than 2 / 3.

[0078] when > This indicates that the voltage across the capacitor is too high at this time, and the charge generated by the virtual vector should satisfy the following condition. <0. According to equation (2), when When >0, it should be taken as =2 / 3+c*| |。When When <0, it should be taken =2 / 3-c*| |

[0079] The first vector modulation factor mentioned above is determined based on the absolute value of the voltage difference between the upper and lower capacitors of the current inverter. c is a preset empirical value, for example, 0.05.

[0080] In this embodiment, the first vector modulation factor is determined by the charge amount of the midpoint potential that can be compensated by the second virtual voltage vector and the current voltage difference, so that the virtual voltage vector can generate charge on the midpoint potential, thereby achieving balanced control of the midpoint potential.

[0081] In some embodiments, determining the boundary of the voltage vector space of a three-level inverter based on virtual voltage vectors includes: dividing the voltage vector space into a predetermined number of first sectors; the first sector is used to divide into multiple sectors; for each first sector, determining the coordinate points corresponding to each virtual voltage vector; and for each coordinate point, connecting the coordinate point with its corresponding coordinate point to determine each boundary. In this embodiment, the sector is the aforementioned second sector.

[0082] Specifically, after obtaining the boundary line equations according to the above formula (3), the voltage vector space is divided into multiple first sectors and multiple second sectors. For example, as Figure 3 and Figure 4 As shown, the voltage vector space is divided into 6 first sectors, and each first sector is divided into 7 second sectors.

[0083] refer to Figure 5After obtaining the reference vector, the target first sector where the reference vector is located is determined based on the angle of the reference vector in the first coordinate system. The first coordinate system is different from the target coordinate system. For example, the first coordinate system is an α-β coordinate system, and the target coordinate system is a gh coordinate system. Each first sector corresponds to a different angle interval. Therefore, after obtaining the angle of the reference vector in the first coordinate system, this angle can be compared with the angle intervals corresponding to each first sector, and the first sector corresponding to the angle interval in which the angle is located is determined as the target first sector. For example, the correspondence between the angle θ of the reference vector in the first coordinate system and its corresponding first sector (i.e., the large sector) is shown in Table 1.

[0084]

[0085] After determining the large sector where the reference vector resides, the target second sector where the reference vector resides can be determined based on the boundary line equations. Specifically, to simplify calculations, the reference vector is transformed from the first coordinate system to the target coordinate system. For example, the coordinate system transformation of the reference vector can be performed based on the following formula:

[0086]

[0087] Then, in the target coordinate system, the second sector of the target where the reference vector is located can be determined based on the boundary line equation and the reference vector. For example, the value corresponding to the reference vector can be substituted into the boundary line equation, and the obtained parameter value can be judged according to the following judgment conditions to determine the second sector (i.e., the small sector) where the reference vector is located, as shown in Table 2 below.

[0088]

[0089] In this embodiment, by dividing a large sector into multiple smaller sectors, it is convenient to determine the target virtual voltage vector corresponding to the reference vector based on the smaller sector where the reference vector's length is located. Furthermore, the corresponding application time is determined based on the smaller sector where the reference vector is located. This allows for the rapid and accurate determination of the target virtual voltage vector of the synthesized reference vector, and also enables the rapid and accurate determination of the corresponding application time.

[0090] In some embodiments, the original virtual vector includes at least one of a first original virtual vector, a second original virtual vector, and a third original virtual vector. The first original virtual vector is greater than the second original virtual vector, and the second original virtual vector is greater than the third original virtual vector. The vector modulation factor includes at least one of a first vector modulation factor and a third vector modulation factor. The first vector modulation factor is used to adjust the second and third original virtual vectors to obtain a second virtual voltage vector, and the third vector modulation factor is used to adjust the third original virtual vector to obtain a third virtual voltage vector. The virtual voltage vector includes at least one of the second and third virtual voltage vectors. Accordingly, determining the virtual voltage vector corresponding to the voltage vector space based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space includes: dividing the voltage vector space into a preset number of first sectors; for each first sector, determining each first original virtual vector, second original virtual vector, and third original virtual vector matching the first sector; determining a second vector modulation factor based on the first vector modulation factor, wherein the sum of the first vector modulation factor and the second vector modulation factor is a fixed value; adjusting the third original virtual vector based on the first vector modulation factor to obtain an adjusted third original virtual vector; adjusting the second original virtual vector based on the second vector modulation factor to obtain an adjusted second original virtual vector; and obtaining a second virtual voltage vector based on the adjusted third original virtual vector and the adjusted second original virtual vector.

[0091] Specifically, according to the above formula (1), the first vector modulation factor is obtained. Afterwards, based on Sure The value is then substituted into the formula. The corresponding second virtual voltage vector is determined. That is, the second virtual voltage vector is obtained based on the product of the first vector modulation factor and the corresponding third original virtual vector, and the product of the second vector modulation factor and the corresponding second original virtual vector. Here, the third original virtual vector corresponds to the original virtual small vector, and the second original virtual vector corresponds to the original virtual medium vector.

[0092] It should be noted that the expressions for each virtual voltage vector in the above formula (1) correspond to each vector in the first sector I. Each sector has a corresponding first virtual voltage vector, second virtual voltage vector, and third virtual voltage vector. The first virtual voltage vector, second virtual voltage vector, and third virtual voltage vector in the target first sector are determined based on the execution voltage vector in the target first sector.

[0093] In this embodiment, the original mid-vector is reshaped by the determined first vector modulation factor, so that the reshaped mid-vector can generate charge on the mid-point potential, thereby realizing active adjustment of the mid-point potential based on the virtual mid-vector.

[0094] Having completed the above steps, we have obtained the target virtual voltage vectors used to synthesize the reference vector. Next, we need to determine the application time of each target virtual voltage vector to determine the application time of the final executed voltage vector. Therefore, in some embodiments, determining the application time of the target virtual voltage vector based on the target sector includes: determining multiple target virtual voltage vectors based on the coordinate points corresponding to the target sector, whereby these target virtual voltage vectors are used to synthesize the reference vector; and determining the application time of each target virtual voltage vector based on the components of the reference vector in the target coordinate system and the components of the multiple target virtual voltage vectors in the target coordinate system.

[0095] Specifically, based on the corner points corresponding to the second sector where the reference vector is located, multiple target virtual voltage vectors are determined for synthesizing the reference vector. That is, the virtual voltage vector to which the corner point belongs is determined as the target virtual voltage vector. Since the sector determined in this embodiment is triangular, there are three corner points, and therefore three corresponding target virtual voltage vectors. The target virtual voltage vector can also be determined based on the nearest three vector principle.

[0096] Based on the above formula (4), the coordinate points corresponding to each target virtual voltage vector are substituted into formula (4) to obtain the action time corresponding to each target virtual voltage vector. Specifically, taking the second sector A3 in the first sector I as an example, the vector... , , Substituting the coordinates of the points into equation (4), we can obtain the following set of equations, which can be obtained in the gh coordinate system through the volt-second balance principle:

[0097]

[0098] Solving equation (6) yields the following equation:

[0099]

[0100] For the other second sectors within the first sector I, the calculation process for the application time of each virtual voltage vector follows the same principle. The corresponding calculation results are shown in Table 3 below.

[0101]

[0102] In other words, after determining the target virtual voltage vectors used to synthesize the reference vector, the action time corresponding to each target virtual voltage vector can be determined based on the first vector modulation factor and the second sector where the reference vector is located.

[0103] In this embodiment, by determining the duration of action of a pair of redundant small vectors and the original central vector in the reshaped virtual central vector, it is made to have the ability to actively balance the central point potential of the entire sector.

[0104] In the process of synthesizing a reference vector using a target virtual voltage vector, if the target virtual voltage vector includes a third virtual voltage vector, i.e., a virtual small voltage vector, then the selection of redundant small vectors may be involved. This is because each small vector has two switching states in the spatial vector diagram that can generate the same voltage vector. In some embodiments, based on the principle of flexible and optimal virtual small vector control, a target third virtual voltage vector for midpoint potential balancing control is determined. By reshaping the original virtual small vectors, the optimal virtual small vector is flexibly selected for midpoint potential balancing control, which can effectively improve the recovery speed when the midpoint potential deviates. For example, the step of determining the action time of each execution voltage vector in the execution voltage vector sequence based on the action time of each of the target virtual voltage vectors includes: if the target virtual voltage vectors include a third virtual voltage vector, then determining a target third virtual voltage vector from the plurality of third virtual voltage vectors based on the first component and the second component of the reference vector in the target coordinate system; determining a third vector modulation factor corresponding to the target third virtual voltage vector based on the first vector modulation factor, the target voltage difference, and the action time of each of the target virtual voltage vectors; and determining the action time of each of the execution voltage vectors based on the third vector modulation factor, the first vector modulation factor, and the action time of each of the target virtual voltage vectors.

[0105] Specifically, if the synthesized target virtual voltage vector includes a third virtual voltage vector, that is, if it includes a virtual voltage small vector, it indicates that the execution vector sequence includes redundant small vectors. In this application, the third virtual voltage vector is obtained based on the original virtual vector and the corresponding third vector modulation factor, referring to equation (1). Therefore, in order to determine the action time corresponding to the small vector in the execution voltage vector sequence, it is also necessary to determine the third vector modulation factor. Specifically, this application constructs two third virtual voltage vectors, and the corresponding third vector modulation factors also include two (denoted as ). , After determining the action time, based on the original virtual vector and the corresponding action time of each virtual voltage vector, the action time of each executed voltage vector can be obtained.

[0106] In other words, the value of the remodeling virtual small vector's modulating factor is determined based on the calculated midpoint charge and vector action time generated by the remodeled virtual small vector, combined with the strength of different virtual small vectors' effects on the midpoint potential. First, it is determined whether the target virtual voltage vector includes a third virtual voltage vector (i.e., a virtual small vector). Then, based on the g-axis component and h-axis component of the reference vector in the target coordinate system, the strength of the effects of multiple third virtual voltage vectors on the midpoint potential is judged. For example, if the g-axis component of the reference vector in the target coordinate system is greater than the h-axis component, then the horizontal axis third virtual voltage vector (i.e., the virtual small vector)... (Strong effect). If the component of the reference vector along the g-axis in the target coordinate system is less than the component along the h-axis in the target coordinate system, then the third virtual voltage vector along the vertical axis (i.e., (Strong effect). It can also be expressed as the following formula:

[0107]

[0108] in, The length of the reference vector projected onto the g-axis; The length of the reference voltage vector projected onto the h-axis.

[0109] Taking the A3 sector as an example for analysis, both the virtual small vector and the virtual medium vector participate in... The synthesis of virtual small vectors and virtual medium vectors allows for coordinated control of the midpoint potential. Based on the principle of flexible and optimal control using virtual small vectors, the appropriate control method should be selected in sector A3. Midpoint charge compensation control is implemented. The amount of midpoint charge Qs generated by the virtual vector within one switching cycle can be referenced as follows:

[0110]

[0111] Let the voltage difference between the upper and lower capacitors be... The midpoint charge that needs to be compensated is Where C is the capacitor of the inverter. To ensure that the midpoint charge generated by the virtual vector during the switching cycle exactly compensates for the required charge, according to the principle of charge conservation, we can obtain:

[0112]

[0113] Solving equation (10) yields:

[0114]

[0115] As can be seen from the above formula, based on the action time corresponding to each target virtual voltage vector , , Voltage difference First vector modulation factor The three-phase current of the inverter , The third vector modulation factor corresponding to the target third virtual voltage vector can be determined.

[0116] Because the best option is selected from sector A3. Perform midpoint charge compensation control, at this time It does not participate in midpoint potential equalization control, therefore The value is 1 / 2. Similarly, the values ​​for the other smaller sectors within large sector I can be obtained. and The parameter values ​​are shown in Table 4.

[0117]

[0118] After the above steps, each vector modulation factor can be determined, specifically the first vector modulation factor. Second vector modulation factor Third vector modulation factor Fourth vector modulation factor Then, based on the previously calculated duration of each target virtual voltage vector, and combined with the construction information of each virtual voltage vector (i.e., the above formula (1)), each execution voltage vector (e.g., , , , , , , The corresponding action time is the action time of each execution voltage vector in the execution voltage vector sequence corresponding to the current target voltage difference.

[0119] For example, combining equation (1), assume , , The corresponding duration of action is , , The corresponding total The duration of action is As shown in Table 5 below, the executed voltage vector sequence includes two... Therefore, a single The duration of action is Half of it. For example... The total duration of action is This is because When the calculated value is... The value is 1 / 2.

[0120] Through the above steps, the midpoint potential is balanced and controlled based on the reshaped virtual small vector and the reshaped virtual medium vector. In this embodiment, by reshaping the original virtual small vector, the optimal virtual small vector is flexibly selected for midpoint potential balance control according to the strength of the two virtual small vectors on the midpoint potential, which effectively improves the recovery speed when the midpoint potential deviates.

[0121] Finally, the corresponding execution voltage vector sequence is determined based on the finally determined target virtual voltage vectors. The execution voltage vector sequence includes multiple execution voltage vectors. The execution voltage vectors are determined based on each target virtual voltage vector. Then, the execution order of the execution voltage vectors is determined based on the three-phase information corresponding to each execution voltage vector. Specifically, taking the first sector I as an example, after determination, the vector action sequence corresponding to each second sector in the first sector is obtained as shown in Table 5:

[0122]

[0123] In a specific embodiment, virtual voltage vectors (i.e., the first virtual voltage vector, the third virtual voltage vector, and the second virtual voltage vector) in the voltage vector space are reshaped based on preset rules. The first, second, and third virtual voltage vectors are constructed based on the original voltage vectors. The first virtual voltage vector is consistent with the original voltage vector. For midpoint potential equalization control, the original voltage vector and the original voltage vector (the smaller one) are mainly reshaped. Specifically, the virtual voltage vector (the middle one) is constructed using the first and second vector modulation factors. The first virtual voltage vector (the smaller one) is constructed using the third vector modulation factor, and the second virtual voltage vector (the smaller one) is constructed using the fourth vector modulation factor. Refer to equation (1) above for details.

[0124] First, obtain the target voltage difference between the upper and lower capacitors of the current three-level inverter. Based on the qualitative relationship between the target voltage difference and the compensation midpoint charge corresponding to the vector in the virtual voltage, and the relationship between the compensation midpoint charge and the first vector modulation factor, determine the correlation between the target voltage difference and the first vector modulation factor. Based on this correlation, determine the value of the first vector modulation factor (refer to the above for details). After determining the first vector modulation factor, the voltage vector space can be divided into 6 large sectors based on the first vector modulation factor, and each large sector is further divided into 7 small sectors. For details, refer to the above formula (3) for sector division.

[0125] Next, the target sector corresponding to the reference vector is determined. Each sector has a corresponding sequence of execution voltage vectors. Executing each voltage vector (i.e., the aforementioned execution voltage vectors) according to this sequence can achieve midpoint potential equalization control. However, the duration of each voltage vector's action needs to be determined.

[0126] To obtain the duration of each voltage vector, the duration of each virtual voltage vector used to synthesize the reference vector can be calculated first. Since each virtual voltage vector is constructed based on the individual voltage vectors, after calculating the duration of each virtual voltage vector used to synthesize the reference vector, the duration of each individual voltage vector can be obtained based on these durations.

[0127] If the synthesized reference vector includes a virtual voltage vector, then the third and fourth vector modulation factors need to be calculated. Only then can the duration of action of the voltage vector related to the virtual voltage vector be calculated using the above formula (1). , The calculation process for the third vector modulation factor can be found in the above description and will not be repeated here.

[0128] This allows the application time of each voltage vector to be determined based on the various vector modulation factors. The inverter is then controlled according to the execution voltage vector sequence corresponding to the target sector where the reference vector is located and the application time of each voltage vector, thereby achieving midpoint potential balance control.

[0129] It should be noted that the execution voltage vector sequence exemplified in this application is for a specific sector, and other sectors have their corresponding execution voltage vector sequences.

[0130] Then, simulation analysis was performed using Matlab / Simulink, and the results are as follows: Figures 6 to 8 As shown. Set the system active power command Pref to 20kW and the reactive power command Qref to 70kVar, so that the system outputs a high proportion of reactive power in steady state. Figure 6 The simulation waveforms using the SVPWM algorithm show that before balancing control is engaged, a significant voltage deviation of 57V exists because SVPWM struggles to suppress the midpoint potential shift caused by the midpoint vector under low power factor conditions. After 120ms of balancing control being engaged, the midpoint potential reaches a steady-state value, but a steady-state voltage deviation of 20V still exists on the DC side. Figure 7The simulation waveforms using the VSVPWM algorithm show that, since virtual space vector modulation can essentially eliminate the midpoint potential shift caused by the midpoint vector, the DC-side capacitor potential deviation is small, only 11V, before balancing control is engaged. After 167ms of balancing control being engaged, the midpoint potential in the system reaches a steady-state value, with a potential difference of only 0.6V between the upper and lower capacitors. This demonstrates that the VSVPWM algorithm can effectively suppress midpoint potential fluctuations under high-proportion reactive power conditions, but the dynamic balancing speed of the midpoint potential is relatively slow. Figure 8 The simulation waveforms of the sector-reshaped VSVPWM algorithm proposed in this invention show that the voltage difference between the upper and lower capacitors on the DC side is 11V before balancing control is applied. After 58ms of balancing control, the midpoint potential reaches its steady-state value, and the steady-state capacitor voltage difference is only 0.6V. The dynamic balancing speed of the midpoint potential exceeds that of the traditional VSVPWM algorithm, and the steady-state accuracy is higher. The simulation results demonstrate that the proposed midpoint potential balancing control method redefines the virtual midpoint vector, enabling it to actively provide midpoint current for midpoint potential control. Furthermore, it flexibly selects the virtual small vector with the strongest effect on the midpoint potential for control. Under conditions of high reactive power output in the system's steady-state output, the proposed control method can accelerate the dynamic balancing speed while maintaining the steady-state accuracy of the midpoint potential.

[0131] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0132] Based on the same inventive concept, this application also provides a three-level inverter midpoint potential balancing control device for implementing the aforementioned three-level inverter midpoint potential balancing control method. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more three-level inverter midpoint potential balancing control device embodiments provided below can be found in the limitations of the three-level inverter midpoint potential balancing control method described above, and will not be repeated here.

[0133] In one exemplary embodiment, such as Figure 9As shown, a three-level inverter midpoint potential balancing control device 900 is provided, comprising:

[0134] The factor determination module 901 is used to obtain the vector modulation factor based on the target voltage difference and preset voltage difference range of the upper and lower capacitors of the three-level inverter.

[0135] The sector partitioning module 902 is used to determine the virtual voltage vector corresponding to the voltage vector space based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space; to determine the partitioning boundary in the voltage vector space of the three-level inverter based on the virtual voltage vector; and to divide the voltage vector space into the target number of sectors according to the partitioning boundary.

[0136] Module 903 is used to acquire a reference vector and determine the target sector that matches the reference vector from the target number of sectors.

[0137] The timing determination module 904 is used to determine the target virtual voltage vector used to synthesize the reference vector, and the corresponding action time of each target virtual voltage vector, based on the target sector.

[0138] The sequence determination module 905 is used to determine the sequence of execution voltage vectors corresponding to the target sector based on the target virtual voltage vector, and to determine the action time of each execution voltage vector in the sequence of execution voltage vectors based on the action time of each target virtual voltage vector.

[0139] The execution module 906 is used to control each execution voltage vector to act on the three-level inverter in the corresponding action time according to the execution sequence, so as to control the midpoint potential of the three-level inverter.

[0140] In some embodiments, regarding obtaining the vector modulation factor based on the target voltage difference and a preset voltage difference range of the upper and lower capacitors of the three-level inverter, the factor determination module 901 is further configured to: if the target voltage difference is less than a first critical value of the preset voltage difference range, and the target current of the three-level inverter is less than zero, then determine the vector modulation factor as a first vector modulation factor; if the target voltage difference is greater than a second critical value of the preset voltage difference range, and the target current of the three-level inverter is less than zero, then determine the vector modulation factor as a second vector modulation factor; if the target voltage difference is greater than a second critical value of the preset voltage difference range, and the target current of the three-level inverter is less than zero, then determine the vector modulation factor as a second vector modulation factor; if the target current of the three-level inverter is greater than zero, then determine the vector modulation factor as a first vector modulation factor; wherein, the first critical value is less than the second critical value, the preset voltage difference range is located between the first critical value and the second critical value, and both the first vector modulation factor and the second vector modulation factor are calculated based on the target voltage difference.

[0141] In some embodiments, in determining the partitioning boundaries in the voltage vector space of a three-level inverter based on virtual voltage vectors, the sector partitioning module 902 is further configured to: partition the voltage vector space into a preset number of first sectors; partition the first sectors into multiple sectors; for each first sector, determine the coordinate points corresponding to each virtual voltage vector; and for each coordinate point, connect the coordinate point with other corresponding coordinate points to determine each partitioning boundary.

[0142] In some embodiments, the original virtual vector includes at least one of a first original virtual vector, a second original virtual vector, and a third original virtual vector; the first original virtual vector is greater than the second original virtual vector, the second original virtual vector is greater than the third original virtual vector, and the vector modulation factor includes at least one of a first vector modulation factor and a third vector modulation factor. The first vector modulation factor is used to adjust the second and third original virtual vectors to obtain a second virtual voltage vector, and the third vector modulation factor is used to adjust the third original virtual vector to obtain a third virtual voltage vector. The virtual voltage vector includes at least one of the second and third virtual voltage vectors. Voltage is determined based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space. Regarding the virtual voltage vector corresponding to the vector space, the sector division module 902 is further configured to: divide the voltage vector space into a preset number of first sectors; for each first sector, determine each first original virtual vector, second original virtual vector, and third original virtual vector matching the first sector; determine a second vector modulation factor based on the first vector modulation factor, wherein the sum of the first vector modulation factor and the second vector modulation factor is a fixed value; adjust the third original virtual vector based on the first vector modulation factor to obtain the adjusted third original virtual vector; adjust the second original virtual vector based on the second vector modulation factor to obtain the adjusted second original virtual vector; and obtain the second virtual voltage vector based on the adjusted third original virtual vector and the adjusted second original virtual vector.

[0143] In some embodiments, in determining the target virtual voltage vector used to synthesize the reference vector based on the target sector, and the action time corresponding to each of the target virtual voltage vectors, the time determination module 904 is further configured to: determine a plurality of target virtual voltage vectors based on the coordinate points corresponding to the target sector, the target virtual voltage vectors being used to synthesize the reference vector; and determine the action time corresponding to each target virtual voltage vector based on the components of the reference vector in the target coordinate system and the components of the plurality of target virtual voltage vectors in the target coordinate system.

[0144] In some embodiments, in determining the action time of each execution voltage vector in the execution voltage vector sequence based on the action time of each target virtual voltage vector, the time determination module 904 is further configured to: if the target virtual voltage vector includes multiple third virtual voltage vectors, determine a target third virtual voltage vector from the multiple third virtual voltage vectors based on the first and second components of the reference vector in the target coordinate system; determine a third vector modulation factor corresponding to the target third virtual voltage vector based on the first vector modulation factor, the target voltage difference, and the action time of each target virtual voltage vector; the third vector modulation factor is used to determine the third virtual voltage vector; determine a target third virtual voltage vector for midpoint potential control from the multiple third virtual voltage vectors based on the first and second components of the reference vector in the target coordinate system; and determine the action time of each execution voltage vector based on the third vector modulation factor, the first vector modulation factor, and the action time of each target virtual voltage vector. Each module in the above-described three-level inverter midpoint potential equalization control device can be implemented entirely or partially through software, hardware, or a combination thereof. The above modules can be embedded in the processor of the computer device in hardware form or independent of it, or they can be stored in the memory of the computer device in software form, so that the processor can call and execute the corresponding operations of the above modules.

[0145] In one exemplary embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 10As shown. The computer device includes the aforementioned three-level inverter and can control the three-level inverter to achieve midpoint potential equalization control. The computer device includes a processor, memory, input / output interface, communication interface, display unit, and input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are also connected to the system bus via the input / output interface. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The input / output interface is used for exchanging information between the processor and external devices. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, Near Field Communication (NFC), or other technologies. When the computer program is executed by the processor, it implements a method for midpoint potential equalization control of a three-level inverter. The display unit of this computer device is used to form a visually visible image and can be a display screen, a projection device, or a virtual reality imaging device. The display screen can be an LCD screen or an e-ink screen. The input device of this computer device can be a touch layer covering the display screen, or buttons, a trackball, or a touchpad set on the casing of the computer device, or an external keyboard, touchpad, or mouse, etc.

[0146] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0147] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0148] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps in the above method embodiments.

[0149] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0150] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0151] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0152] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for controlling the neutral point potential balance in a three-level inverter, characterized in that, The method includes: The vector modulation factor is obtained based on the target voltage difference and the preset voltage difference range of the upper and lower capacitors of the three-level inverter. Based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space, the virtual voltage vector corresponding to the voltage vector space is determined; based on the virtual voltage vector, the partition boundary in the voltage vector space of the three-level inverter is determined, and the voltage vector space is divided into a target number of sectors according to the partition boundary; Obtain a reference vector; determine the target sector that matches the reference vector from the target number of sectors; Based on the target sector, determine the target virtual voltage vector used to synthesize the reference vector, and the corresponding action time of each target virtual voltage vector; Based on the target virtual voltage vector, determine the execution voltage vector sequence corresponding to the target sector, and based on the execution time corresponding to each of the target virtual voltage vectors, determine the execution time corresponding to each execution voltage vector in the execution voltage vector sequence; According to the execution voltage vector sequence, each execution voltage vector is sequentially controlled to act on the three-level inverter during its corresponding action time, so as to control the midpoint potential of the three-level inverter.

2. The method according to claim 1, characterized in that, The vector modulation factor is obtained by considering the target voltage difference and the preset voltage difference range between the upper and lower capacitors of the three-level inverter, including: If the target voltage difference is less than the first critical value of the preset voltage difference range, and the target current of the three-level inverter is less than zero, then the vector modulation factor is determined to be the first vector modulation factor; if the target current of the three-level inverter is greater than zero, then the vector modulation factor is determined to be the second vector modulation factor. If the target voltage difference is greater than the second critical value of the preset voltage difference range, and the target current of the three-level inverter is less than zero, then the vector modulation factor is determined to be the second vector modulation factor; if the target current of the three-level inverter is greater than zero, then the vector modulation factor is determined to be the first vector modulation factor. Wherein, the first threshold value is less than the second threshold value, the preset voltage difference range is located between the first threshold value and the second threshold value, and the first vector modulation factor and the second vector modulation factor are both obtained based on the target voltage difference.

3. The method according to claim 1, characterized in that, The step of determining the boundary of the voltage vector space of the three-level inverter based on the virtual voltage vector includes: The voltage vector space is divided into a predetermined number of first sectors; the first sectors are further divided into multiple sectors. For each first sector, the coordinate points corresponding to each virtual voltage vector are determined. For each coordinate point, the coordinate point is connected with other corresponding coordinate points to determine each division boundary.

4. The method according to claim 1, characterized in that, The original virtual vector includes at least one of a first original virtual vector, a second original virtual vector, and a third original virtual vector; the first original virtual vector is greater than the second original virtual vector, and the second original virtual vector is greater than the third original virtual vector; the vector modulation factor includes at least one of a first vector modulation factor and a third vector modulation factor; the first vector modulation factor is used to adjust the second original virtual vector and the third original virtual vector to obtain a second virtual voltage vector; the third vector modulation factor is used to adjust the third original virtual vector to obtain a third virtual voltage vector; the virtual voltage vector includes at least one of the second virtual voltage vector and the third virtual voltage vector; determining the virtual voltage vector corresponding to the voltage vector space based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space includes: The voltage vector space is divided into a predetermined number of first sectors; For each first sector, a first original virtual vector, a second original virtual vector, and a third original virtual vector matching the first sector are determined; a second vector modulation factor is determined based on the first vector modulation factor, and the sum of the first vector modulation factor and the second vector modulation factor is a fixed value; the third original virtual vector is adjusted based on the first vector modulation factor to obtain an adjusted third original virtual vector; the second original virtual vector is adjusted based on the second vector modulation factor to obtain an adjusted second original virtual vector; and the second virtual voltage vector is obtained based on the adjusted third original virtual vector and the adjusted second original virtual vector.

5. The method according to claim 1, characterized in that, The step of determining the target virtual voltage vector used to synthesize the reference vector based on the target sector, and the corresponding application time of each target virtual voltage vector, includes: Based on the coordinate points corresponding to the target sector, multiple target virtual voltage vectors are determined, and the target virtual voltage vectors are used to synthesize the reference vector; Based on the components of the reference vector in the target coordinate system and the components of the multiple target virtual voltage vectors in the target coordinate system, the application time corresponding to each of the target virtual voltage vectors is determined.

6. The method according to claim 2, characterized in that, The step of determining the action time of each execution voltage vector in the execution voltage vector sequence based on the action time of each of the target virtual voltage vectors includes: If the target virtual voltage vector includes a third virtual voltage vector, then based on the first and second components of the reference vector in the target coordinate system, a target third virtual voltage vector is determined from the third virtual voltage vector; based on the first vector modulation factor, the target voltage difference, and the action time corresponding to each of the target virtual voltage vectors, a third vector modulation factor corresponding to the target third virtual voltage vector is determined; based on the third vector modulation factor, the first vector modulation factor, and the action time corresponding to each of the target virtual voltage vectors, the action time corresponding to each of the execution voltage vectors is determined.

7. A three-level inverter neutral point potential equalization control device, characterized in that, The device includes: The factor determination module is used to obtain the vector modulation factor based on the target voltage difference and preset voltage difference range of the upper and lower capacitors of the three-level inverter. The sector partitioning module is used to determine the virtual voltage vector corresponding to the voltage vector space based on the vector modulation factor and the original virtual vector corresponding to the voltage vector space; determine the partitioning boundary in the voltage vector space of the three-level inverter based on the virtual voltage vector; and divide the voltage vector space into a target number of sectors according to the partitioning boundary. The acquisition module is used to acquire a reference vector and determine a target sector that matches the reference vector from the target number of sectors. The time determination module is used to determine, based on the target sector, the target virtual voltage vector used to synthesize the reference vector, and the action time corresponding to each target virtual voltage vector; The sequence determination module is used to determine the execution voltage vector sequence corresponding to the target sector based on the target virtual voltage vector, and to determine the action time of each execution voltage vector in the execution voltage vector sequence based on the action time of each target virtual voltage vector; The execution module is used to sequentially control each execution voltage vector to act on the three-level inverter during its corresponding action time according to the execution voltage vector sequence, so as to control the midpoint potential of the three-level inverter.

8. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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