A three-stage vector modulation method and system

Abstract

The application belongs to the technical field of vector modulation, and discloses a three-section vector modulation method and system.The three-section vector modulation method comprises the following steps: generating a reference voltage vector based on a controller, obtaining the sector number of the reference voltage vector by using a sector partition rule, and obtaining the vector sequence and the vector action time of the reference voltage vector based on the sector number and a phase rotation calculation technology; generating a three-phase switch sequence of the reference voltage vector according to a three-section vector calculation rule based on the vector sequence and the vector action time, and outputting a three-phase pulse width modulation signal by using the three-phase switch sequence and a modulation signal generation technology.The three-section vector modulation proposed in the application can still operate under a fixed carrier and a control frequency under the condition that the fundamental frequency is variable, and the switching capability of a power device is fully utilized.

Description

Technical Field

[0001] This invention relates to the field of vector modulation technology, and in particular to a three-segment vector modulation method and system. Background Technology

[0002] The demand for high-capacity converters is growing rapidly in transportation, industrial traction, and power grid equipment, showing a trend towards higher power levels and higher voltages. High-speed permanent magnet synchronous motors, with their advantages of high efficiency, high power density, and high control precision, are widely used in household appliances, rail transportation, textile industry, and aerospace. To fully utilize the converter's capacity and further increase the motor's operating frequency under the limitation of DC bus voltage, it is usually necessary to extend the modulation range to overmodulation, and ultimately to six-step modulation. This expands the torque output capability and operating range of the permanent magnet synchronous motor without requiring hardware modifications.

[0003] Traditional overmodulation strategies are mainly divided into single-mode and dual-mode overmodulation strategies. Single-mode overmodulation strategies mainly include minimum phase error algorithms, minimum distance error algorithms, and minimum vector error algorithms. Dual-mode overmodulation divides the entire overmodulation region into two stages, employing different modulation algorithms in each stage. However, overmodulation strategies often lead to a nonlinear voltage gain region, requiring correction using inverse function premultiplication or additional signal injection. This is typically achieved through the use of inverse function tables and / or curve fitting, complicating its implementation.

[0004] Due to their high power and voltage levels, large-capacity converters typically need to operate at high efficiency to reduce power consumption and overall operation and maintenance costs. Switching losses of power devices account for a significant proportion of the total converter losses. Therefore, reducing the switching frequency can effectively reduce converter losses. In addition, high-speed motor drivers are limited by the upper limit of the switching frequency of power devices and usually operate under low carrier ratio conditions. Therefore, low carrier ratio operation is a typical operating condition for large-capacity converters and high-speed motor drivers.

[0005] Furthermore, there is a difference between the overmodulation voltage gain under low carrier ratio and the voltage gain under high carrier ratio. The lower the carrier ratio, the greater this difference becomes. Therefore, methods such as inverse function premultiplication or additional signal injection for correction cannot meet the accuracy of voltage gain correction under all operating conditions. At the same time, the current harmonic problem caused by the gain correction strategy under low carrier ratio also needs to be taken seriously. As the carrier ratio decreases, the AC side current THD increases significantly, and the larger current ripple will increase the thermal stress of the device.

[0006] Therefore, how to provide a three-segment vector modulation method and system is an urgent problem to be solved. Summary of the Invention

[0007] This invention provides a three-segment vector modulation method and system to solve the problem of the difference between overmodulation voltage gain at low carrier ratio and voltage gain at high carrier ratio in the prior art.

[0008] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or to describe the scope of protection of these embodiments. Its sole purpose is to present some concepts in a simple form as a prelude to the detailed description that follows.

[0009] According to a first aspect of the present invention, a three-segment vector modulation method is provided.

[0010] In one embodiment, the three-segment vector modulation method includes:

[0011] The reference voltage vector is generated based on the controller. The sector number of the reference voltage vector is obtained by using the sector zoning rule. The vector sequence and vector action time of the reference voltage vector are obtained based on the sector number and phase rotation calculation technology.

[0012] Based on the vector sequence and vector action time, a three-phase switching sequence of reference voltage vector is generated according to the three-segment vector calculation rule, and a three-phase pulse width modulation signal is output using the three-phase switching sequence and modulation signal generation technology.

[0013] In one embodiment, a reference voltage vector is generated based on the controller, the sector number of the reference voltage vector is obtained using sector zoning rules, and the vector sequence and vector application time of the reference voltage vector are obtained based on the sector number and phase rotation calculation technique, including:

[0014] The controller generates a modulator input command, which is used as a reference voltage vector. The reference voltage vector includes the reference vector amplitude and the reference vector phase.

[0015] The phase range of the reference voltage vector is determined by matching the reference vector phase with the sector zoning rules, and the sector number of the reference voltage vector is obtained based on the phase range.

[0016] The reference vector phase is converted to a preset range, and the converted reference vector is calculated based on the sector number. The phase change of the reference vector phase within the carrier period is obtained by using phase rotation calculation technology.

[0017] Based on the phase change results and the converted reference vector phase, the vector sequence and vector action time of the reference voltage vector are obtained.

[0018] In one embodiment, obtaining the vector sequence and vector application time of the reference voltage vector based on the phase change result and the phase of the converted reference vector includes:

[0019] The boundary of the carrier period within the sector is determined based on the phase range of the reference voltage vector, and the vector sequence of the reference voltage vector is output based on the boundary determination result.

[0020] The effective vector and zero vector of the reference voltage vector are obtained from the vector sequence. The effective vector's duration is calculated based on the phase change result and the phase of the converted reference vector. The duration of the zero vector is then calculated using the effective vector's duration and the carrier period.

[0021] In one embodiment, the vector sequence includes a start sequence, an end sequence, and an intermediate sequence;

[0022] The initial sequence consists of two sets of initial valid vectors and one set of zero vectors;

[0023] The final sequence consists of two sets of final valid vectors and one set of zero vectors;

[0024] The intermediate sequence consists of a set of intermediate valid vectors and a set of zero vectors.

[0025] In one embodiment, the formula for calculating the effective vector's duration of action is:

[0026]

[0027]

[0028] In the formula, t a1 t represents the duration of action of the first set of effective vectors. a2 V represents the duration of action of the second set of effective vectors. r θ represents the magnitude of the reference vector in the reference vector. cor θ is the phase occupied by the rotation of the corner vector within each sector. ref T represents the initial phase of the reference vector in the reference vector. s θ represents the carrier period, θ′ represents the phase of the referred reference vector, and θ ref ′ represents the phase at the end of the reference vector in the reference vector.

[0029] In one embodiment, a three-phase switching sequence of a reference voltage vector is generated based on the vector sequence and vector action time, according to a three-segment vector calculation rule, and a three-phase pulse width modulation signal is output using the three-phase switching sequence and modulation signal generation technology.

[0030] Based on the sector number and vector sequence of the reference voltage vector, the three-phase initial level corresponding to the reference voltage vector is found according to the three-segment vector calculation rule;

[0031] The rising edge switching time and the falling edge switching time of the reference voltage vector are calculated based on the vector action time. The three-phase switching sequence of the reference voltage vector is generated based on the three-phase initial level, rising edge switching time and falling edge switching time.

[0032] A comparison value is generated based on the maximum counting period of the three-phase switching sequence and the carrier counter, and a three-phase pulse width modulation signal is output based on the comparison value and the modulation signal generation technique.

[0033] In one embodiment, generating a comparison value based on the maximum counting period of the three-phase switching sequence and the carrier counter, and outputting a three-phase pulse width modulation signal according to the comparison value and the modulation signal generation technique includes:

[0034] Obtain the corresponding sequence values ​​within the three-phase switching sequence, and combine each phase sequence value with the maximum counting period of the carrier counter to generate pulse width modulation signal comparison value one and pulse width modulation signal comparison value two.

[0035] The pulse width modulation signal comparison values ​​1 and 2 are compared with the carrier signal respectively. Based on the comparison results, the three-phase voltage level is analyzed. The three-phase voltage level is combined with the modulation signal to generate a three-phase pulse width modulation signal.

[0036] According to a second aspect of the present invention, a three-segment vector modulation system is provided.

[0037] In one embodiment, the three-segment vector modulation system includes:

[0038] The sector determination and time calculation unit is used to generate a reference voltage vector based on the controller, obtain the sector number of the reference voltage vector using the sector zoning rules, and obtain the vector sequence and vector action time of the reference voltage vector based on the sector number and phase rotation calculation technology.

[0039] The sequence generation and signal output unit is used to generate a three-phase switching sequence of reference voltage vector based on the vector sequence and vector action time, according to the three-segment vector calculation rule, and output a three-phase pulse width modulation signal using the three-phase switching sequence and modulation signal generation technology.

[0040] In one embodiment, the sector determination and time calculation unit includes:

[0041] The reference voltage vector acquisition module is used to generate a modulator input command using the controller and use the input command as a reference voltage vector, wherein the reference voltage vector includes a reference vector amplitude and a reference vector phase.

[0042] The sector number acquisition module is used to determine the phase range of the reference voltage vector by matching the reference vector phase with the sector zoning rules, and to obtain the sector number of the reference voltage vector based on the phase range.

[0043] The phase change analysis module is used to convert the reference vector phase to a preset range, calculate the converted reference vector based on the sector number, and use phase rotation calculation technology to obtain the phase change of the reference vector phase within the carrier period.

[0044] The application time acquisition module is used to obtain the vector sequence and application time of the reference voltage vector based on the phase change result and the converted reference vector phase.

[0045] In one embodiment, obtaining the vector sequence and vector application time of the reference voltage vector based on the phase change result and the phase of the converted reference vector includes:

[0046] The boundary of the carrier period within the sector is determined based on the phase range of the reference voltage vector, and the vector sequence of the reference voltage vector is output based on the boundary determination result.

[0047] The effective vector and zero vector of the reference voltage vector are obtained from the vector sequence. The effective vector's duration is calculated based on the phase change result and the phase of the converted reference vector. The duration of the zero vector is then calculated using the effective vector's duration and the carrier period.

[0048] According to a third aspect of the present invention, a computer device is provided.

[0049] In one embodiment, the computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the method described above.

[0050] According to a fourth aspect of the present invention, a computer-readable storage medium is provided.

[0051] In one embodiment, a computer program is stored on the computer-readable storage medium, which, when executed by a processor, implements the steps of the above method.

[0052] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects:

[0053] 1. The present invention provides a three-segment vector modulation method applicable to low carrier ratio applications. The vector sequence of the proposed three-segment vector modulation is derived from SOPWM (sinusoidal output pulse width modulation) with high modulation ratio, which ensures superior harmonic performance. The lower the carrier ratio, the more obvious the harmonic performance advantage of the three-segment vector modulation over SVPWM (space vector pulse width modulation) becomes. Furthermore, the duty cycle of the output PWM wave can be updated in each carrier cycle, enabling fast dynamic response.

[0054] 2. In the case of a variable fundamental frequency, the proposed three-segment vector modulation can still operate under a fixed carrier and control frequency, making full use of the switching capability of power devices. At the same time, it can be implemented at a switching frequency lower than the control frequency, maintaining linear voltage gain throughout the modulation range, and can smoothly switch to six-step modulation.

[0055] 3. The three-segment vector modulation method proposed in this invention outputs two effective vectors in each switching cycle at the sector boundary and only one effective vector in the remaining switching cycles. It achieves harmonic performance close to that of synchronous optimal modulation under high modulation ratio and low carrier ratio. It can smoothly transition to six-step modulation without additional strategies and can update the duty cycle in real time under a fixed carrier frequency, providing high dynamic performance and helping to make full use of the available switching frequency of the power device.

[0056] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0057] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0058] Figure 1 This is a flowchart illustrating a three-segment vector modulation method according to an exemplary embodiment;

[0059] Figure 2 This is a block diagram illustrating the principle of a three-segment vector modulation system according to an exemplary embodiment;

[0060] Figure 3 This is a flowchart illustrating a single effective vector modulation method of a three-segment vector modulation method according to an exemplary embodiment;

[0061] Figure 4 This is a PWM signal diagram of SOPWM illustrated according to an exemplary embodiment;

[0062] Figure 5 This is a diagram of a two-level three-phase inverter according to an exemplary embodiment;

[0063] Figure 6 This is a spatial vector diagram of a two-level inverter according to an exemplary embodiment;

[0064] Figure 7 This is the SOPWM switching angle solution when N=2, as shown in an exemplary embodiment.

[0065] Figure 8 This is the SOPWM switching angle solution when N=3, as shown in an exemplary embodiment.

[0066] Figure 9 This is the SOPWM switching angle solution when N=4, as shown in an exemplary embodiment.

[0067] Figure 10 This is a schematic diagram of reference vector phase and sector division according to an exemplary embodiment;

[0068] Figure 11 This is a schematic diagram of a single effective vector modulation PWM signal and a vector, according to an exemplary embodiment.

[0069] Figure 12 The V-segment vector modulation shown according to an exemplary embodiment az Spectrum;

[0070] Figure 13 The V of synchronous space vector modulation is shown according to an exemplary embodiment. az Spectrum;

[0071] Figure 14 V is a synchronously optimally modulated V as illustrated in an exemplary embodiment. az Spectrum;

[0072] Figure 15 This is a schematic diagram of the structure of a computer device according to an exemplary embodiment. Detailed Implementation

[0073] The following description and accompanying drawings fully illustrate specific embodiments described herein to enable those skilled in the art to practice them. Some embodiments may include or substitute parts and features of other embodiments. The scope of the embodiments herein encompasses the entire scope of the claims and all available equivalents thereof. Throughout this document, the terms “first,” “second,” etc., are used only to distinguish one element from another without requiring or implying any actual relationship or order between the elements. Indeed, a first element can also be referred to as a second element, and vice versa. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a structure, apparatus, or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a structure, apparatus, or device. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the structure, apparatus, or device that includes said element. The various embodiments described herein are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0074] The terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" used in this document to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings. They are used solely for the convenience of describing the document and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description herein, unless otherwise specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two elements; they can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0075] In this document, unless otherwise stated, the term "multiple" means two or more.

[0076] In this article, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0077] In this article, the term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0078] It should be understood that although the steps in the flowchart 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 constraint on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the diagram may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0079] The modules in the apparatus or system of this application can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0080] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0081] Figure 1An embodiment of the three-segment vector modulation method of the present invention is shown.

[0082] In this optional embodiment, the three-segment vector modulation method includes:

[0083] Step S101: Generate a reference voltage vector based on the controller, obtain the sector number of the reference voltage vector using the sector zoning rule, and obtain the vector sequence and vector action time of the reference voltage vector based on the sector number and phase rotation calculation technology.

[0084] Step S103: Based on the vector sequence and vector action time, generate a three-phase switching sequence of the reference voltage vector according to the three-segment vector calculation rule, and output a three-phase pulse width modulation signal using the three-phase switching sequence and modulation signal generation technology.

[0085] In this optional embodiment, when generating a reference voltage vector based on the controller, obtaining the sector number of the reference voltage vector using sector zoning rules, and obtaining the vector sequence and vector action time of the reference voltage vector based on the sector number and phase rotation calculation technology, the controller can generate a modulator input command, which is used as the reference voltage vector. The reference voltage vector includes a reference vector amplitude and a reference vector phase. The phase range of the reference voltage vector is determined by matching the reference vector phase with the sector zoning rules, and the sector number of the reference voltage vector is obtained based on the phase range. The reference vector phase is converted to a preset range, and the converted reference vector is calculated based on the sector number. The phase change of the reference vector phase within the carrier period is obtained using phase rotation calculation technology. Based on the phase change result and the converted reference vector phase, the vector sequence and vector action time of the reference voltage vector are obtained.

[0086] In this optional embodiment, when obtaining the vector sequence and vector action time of the reference voltage vector based on the phase change result and the phase of the converted reference vector, the boundary of the carrier period within the sector can be determined based on the phase range of the reference voltage vector, and the vector sequence of the reference voltage vector can be output according to the boundary determination result; the effective vector and zero vector of the reference voltage vector can be obtained according to the vector sequence, the action time of the effective vector can be calculated based on the phase change result and the phase of the converted reference vector, and the action time of the zero vector can be calculated using the action time of the effective vector and the carrier period.

[0087] In this optional embodiment, when generating a three-phase switching sequence of a reference voltage vector based on the vector sequence and vector action time according to the three-segment vector calculation rule, and outputting a three-phase pulse width modulation signal using the three-phase switching sequence and modulation signal generation technology, the three-phase initial level corresponding to the reference voltage vector can be found based on the sector number and vector sequence of the reference voltage vector according to the three-segment vector calculation rule; the rising edge switching time and falling edge switching time corresponding to the reference voltage vector are calculated according to the vector action time; a three-phase switching sequence of the reference voltage vector is generated based on the three-phase initial level, rising edge switching time, and falling edge switching time; a comparison value is generated based on the three-phase switching sequence and the maximum counting period of the carrier counter; and a three-phase pulse width modulation signal is output based on the comparison value and modulation signal generation technology.

[0088] In this optional embodiment, when generating a comparison value based on the maximum counting period of the three-phase switch sequence and the carrier counter, and outputting a three-phase pulse width modulation signal based on the comparison value and the modulation signal generation technology, the corresponding sequence values ​​within the three-phase switch sequence can be obtained respectively. The sequence values ​​of each phase are combined with the maximum counting period of the carrier counter to generate a pulse width modulation signal comparison value one and a pulse width modulation signal comparison value two. The pulse width modulation signal comparison value one and the pulse width modulation signal comparison value two are compared with the carrier signal respectively. Based on the comparison results, the three-phase voltage level is analyzed, and the three-phase voltage level is combined with the modulation signal to generate a three-phase pulse width modulation signal.

[0089] Figure 2 An embodiment of a three-segment vector modulation system according to the present invention is shown.

[0090] In this optional embodiment, the three-segment vector modulation system includes:

[0091] The sector determination and time calculation unit 201 is used to generate a reference voltage vector based on the controller, obtain the sector number of the reference voltage vector using the sector zoning rules, and obtain the vector sequence and vector action time of the reference voltage vector based on the sector number and phase rotation calculation technology.

[0092] The sequence generation and signal output unit 203 is used to generate a three-phase switching sequence of reference voltage vector based on vector sequence and vector action time according to the three-segment vector calculation rule, and output a three-phase pulse width modulation signal using three-phase switching sequence and modulation signal generation technology.

[0093] In this optional embodiment, the sector determination and time calculation unit 201 includes: a reference voltage vector acquisition module (not shown in the figure), a sector number acquisition module (not shown in the figure), a phase change analysis module (not shown in the figure), and an action time acquisition module (not shown in the figure); wherein:

[0094] The module includes a reference voltage vector acquisition module, which generates a modulator input command using the controller and uses the input command as a reference voltage vector, the reference voltage vector including a reference vector amplitude and a reference vector phase; a sector number acquisition module, which determines the phase range of the reference voltage vector by matching the reference vector phase with sector segmentation rules, and obtains the sector number of the reference voltage vector based on the phase range; a phase change analysis module, which converts the reference vector phase to a preset range and calculates the converted reference vector based on the sector number, and obtains the phase change of the reference vector phase within the carrier period using phase rotation calculation technology; and an action time acquisition module, which obtains the vector sequence and vector action time of the reference voltage vector based on the phase change result and the converted reference vector phase.

[0095] In this optional embodiment, when obtaining the vector sequence and vector action time of the reference voltage vector based on the phase change result and the phase of the converted reference vector, the boundary of the carrier period within the sector can be determined based on the phase range of the reference voltage vector, and the vector sequence of the reference voltage vector can be output according to the boundary determination result; the effective vector and zero vector of the reference voltage vector can be obtained according to the vector sequence, the action time of the effective vector can be calculated based on the phase change result and the phase of the converted reference vector, and the action time of the zero vector can be calculated using the action time of the effective vector and the carrier period.

[0096] like Figures 4 to 9 As shown, combining the waveform characteristics of synchronous optimal modulation at high modulation ratios and the modulation rules of synchronous space vector modulation, this embodiment proposes a three-segment vector modulation method. By vectorizing the waveform of synchronous optimal modulation, it can be found that the waveform outputs two effective vectors in each switching cycle at the sector boundary, and only one effective vector in the remaining switching cycles (effective vectors refer to vectors other than the zero vector, including V1, V2, V3, V4, V5, and V6). The corresponding vector sequence exhibits a three-segment characteristic, hence the name three-segment vector modulation method. Figure 4 As shown.

[0097] By combining the rules of vector sequence with space vector modulation, the three-segment vector modulation method proposed in this embodiment is obtained. While ensuring high dynamic performance, it achieves harmonic performance close to that of synchronous optimal modulation and can smoothly transition to six-step modulation.

[0098] Space vector modulation represents both the multiphase reference voltage and the inverter's output state in the form of space vectors. Then, it decomposes the reference voltage into several switching states through vector synthesis. Specifically, the topology of a two-level three-inverter is as follows: Figure 5 As shown.

[0099] All states of a two-level three-phase inverter can be represented by 3-bit binary numbers, namely

[000] ,

[001] ,

[010] ,

[011] ,

[100] ,

[101] , and

[111] , for a total of eight states. Each set of switching states corresponds to an output voltage vector. For example, when the inverter is operating in switching state

[100] , the corresponding bridge arm voltages are u... an =V dc u bn =0, u cn =0, using the vector calculation formula, the output voltage vector is calculated as v. inv =u an =V dc The vector calculation formula is:

[0100]

[0101] In the formula, e represents the base of the natural logarithm, and j represents the imaginary unit.

[0102] Similarly, the output voltage vectors corresponding to all switching states of the converter can be obtained as shown in Table 1.

[0103] Table 1 Vector Table of Two-Level Converters

[0104]

[0105] like Figure 6 The vectors shown are plotted in a Cartesian αβ coordinate system, forming the space vector diagram of the converter. Space vector modulation (SVM) utilizes the converter's inherent vectors to equivalently output the reference voltage vector. Synchronous space vector modulation (SVM) refers to a space vector modulation method where the carrier ratio is constant and the sampling point phase remains consistent in each fundamental frequency cycle. It updates the duty cycle of the output PWM signal in each carrier cycle, thus exhibiting good dynamic performance. Furthermore, synchronous space vector modulation is simpler to implement than synchronous optimal modulation, but its harmonic performance is inferior.

[0106] Synchronous optimal modulation refers to a modulation method that aims to minimize the weighted total harmonic distortion (WTHD) while ensuring half-wave symmetry, quarter-cycle symmetry, and three-phase symmetry. The specific definition of weighted total harmonic distortion (WTHD) is as follows:

[0107]

[0108] In the formula, n represents the number of times the switch is turned on within 1 / 4 of a cycle.

[0109] like Figures 7 to 9 As shown, based on the switching angle solution of SOPWM, the corresponding PWM signal can be obtained, with n=3, m aFor example, with a value of 1.1, according to Figure 8 The switching angle solution of SOPWM can be used to obtain the corresponding PWM signal, such as Figure 4 As shown.

[0110] Synchronous optimal pulse width modulation (SVPWM) theoretically offers the best harmonic performance, but its poor dynamic performance limits its widespread application. When the fundamental frequency changes, the switching frequencies of synchronous SVPWM and SOPWM fluctuate drastically. This is because as the fundamental frequency increases, the carrier ratio should decrease to a smaller integer to prevent the switching frequency from exceeding its limit, leading to drastic harmonic variations and underutilization of the power device's switching frequency.

[0111] like Figure 3 As shown, the input command for the modulator comes from the controller, and the input command is a reference voltage vector, including the amplitude V. r (Reference voltage vector amplitude) and phase θ (Reference voltage vector phase), wherein the "three-segment vector synthesis algorithm" module executes once per switching cycle, generating the three-phase switching sequence for the next switching cycle. The switching sequence of each phase includes three parameters, namely the initial level p x0 Rising edge time t ap and falling edge time t an The "PWM modulation" module generates PWM signals in real time using a counter and a comparator.

[0112] (1) Sector determination:

[0113] Determine the sector number n of the reference vector by its phase θ, and the determination rule is as follows:

[0114] Sector I: Phase range is (-30°, 30°], sector number n = 1;

[0115] Sector II: Phase range is (30°, 90°], sector number n = 2;

[0116] Sector III: Phase range is (90°, 150°], sector number n = 3;

[0117] Sector IV: Phase range is (150°, 210°], sector number n = 4;

[0118] Sector V: Phase range is (210°, 270°], sector number n = 5;

[0119] Sector VI: Phase range is (270°, 330°), sector number n = 6.

[0120] (2) Calculation of vector action time:

[0121] To facilitate the calculation of the vector action time, the reference vector phase θ needs to be converted to the range of (-30°, 30°) to obtain the converted phase θ′:

[0122] θ′=θ-(n-1)×60°;

[0123] Where n represents the sector number.

[0124] Within one carrier cycle, the reference vector V r From the initial phase θ ref Rotate to the last phase θ ref ′:

[0125] θ ref =θ-0.5ω0T s ;

[0126] θ ref ′=θ+0.5ω0T s ;

[0127] Where ω0 represents the fundamental angular velocity, T s Indicates the carrier period.

[0128] In this embodiment, the effective vector's duration of action is an approximation, and there are multiple calculation rules. Depending on the position of the carrier period, there are three cases, corresponding to three vector sequences and vector duration calculation methods:

[0129] 1. Starting sequence;

[0130] When the carrier period is located at the upper boundary of the sector, the output start sequence includes two valid vectors (start valid vectors) and one zero vector. The start valid vectors are the valid vector of the previous sector (named the corner vector) and the valid vector of the current sector, and their action times are t and t, respectively. a1 and t a2 The specific calculation formula is as follows:

[0131]

[0132]

[0133] Where, θ cor θ is the phase occupied by the rotation of the corner vector within each sector. cor It affects the PWM waveform, and there are multiple options. This embodiment provides one of them, namely θ. cor =8°, thus zero vector V z The time of action t z for:

[0134] t z =T s -t a1-t a2 ;

[0135] 2. End sequence;

[0136] When the carrier period is located at the lower boundary of the sector, the output end sequence includes two valid vectors (end valid vectors) and a zero vector. The end valid vectors are the valid vector of the current sector and the valid vector of the next sector (named the corner vectors), and their durations are t. a1 and t a2 The specific calculation formula is as follows:

[0137]

[0138]

[0139] Where, θ cor θ is the phase occupied by the rotation of the corner vector within each sector. cor It affects the PWM waveform, and there are multiple options. This embodiment provides one of them, namely θ. cor =8°, thus zero vector V z The time of action t z for:

[0140] t z =T s -t a1 -t a2 ;

[0141] 3. Intermediate sequence;

[0142] When the carrier period is not located at the sector boundary, the output intermediate sequence includes an effective vector (intermediate effective vector) and a zero vector, with the effective vectors having durations t and t, respectively. a1 and t a2 The specific calculation formula is as follows.

[0143] t a1 =0.8V r T s ;

[0144] t a2 =0;

[0145] Then the zero vector V z The time of action t z The calculation formula is:

[0146] t z =T s -t a1 -t a2 ;

[0147] (3) Switch sequence generation:

[0148] Based on the principle of three-segment vector modulation, a switching sequence for each phase is generated. Each phase switching sequence includes three parameters, with an initial level p. x0 Rising edge switching time t xp Falling edge switching time t xn x represents phases a, b, and c. The specific calculation rules are shown in Table 2.

[0149] Table 2. Calculation Rules for Switch Sequence Generation

[0150]

[0151]

[0152] (4) PWM signal output:

[0153] The PWM signal of each phase can be output according to the switching sequence of each phase. The method of generating the PWM signal is relatively flexible. This embodiment gives a commonly used method. Taking the first sector as an example, as shown in Table 2, the intermediate vector sequence of this sector is [V0 V1V0].

[0154] In this sector, the initial level of phase A is 0, and the rising edge time is t. ap Falling edge time t an At this point, the two comparison values ​​of the PWM modulation module are set to CompA-A = t. ap *PRD / T s CompB-A = t an *PRD / T s PRD is the period value of the carrier counter, i.e. the maximum value of the carrier counter. The initial level of the generated PWM signal is set to 0. When CompA-A is equal to the carrier signal, the PWM signal outputs a high level; when CompB-A crosses the carrier signal, the PWM signal outputs a low level.

[0155] In this sector, the initial levels of phases B and C are both 0 and remain at 0. Therefore, the initial PWM levels of phases B and C are set to 0, and the comparison value is set to -1, indicating that these two phases will not cross with the carrier and will not generate PWM transitions.

[0156] Based on the above steps, construct as follows: Figure 5 The diagram shows a two-level three-phase inverter.

[0157] With carrier ratio m r Equals 18, modulation ratio m a Taking 1.11 as an example, when the phase of the reference vector is 20°, the position of the reference vector is as follows: Figure 10As shown by the xy line, the vector is located in sector I according to the phase of the reference vector, the carrier period is located at the lower boundary of the sector, and the vector sequence is the last sequence, i.e. [V0 V1 V2].

[0158] Calculate the duration t of the effective vector V1. a1 The interaction time t with the effective vector V2 a2 and the duration t of the zero vector V0 z .

[0159] Finally, based on the effective vector V1's duration t... a1 The effective vector V2's duration t a2 and the duration t of the zero vector V0 z The vector sequence [V0 V1 V2] can output the PWM signal g of phase A. A PWM signal g of phase B B PWM signal g of phase C C ,like Figure 10 and Figure 11 As shown.

[0160] Similarly, the PWM signal for other carrier cycles is output according to the above method, such as... Figure 11 As shown. The vector sequence throughout the entire fundamental period is also... Figure 11 Listed in.

[0161] Carrier ratio m r When it equals 18, the pulse ratio P r The number of pulses per phase within one fundamental frequency cycle is equal to 7. Figures 12 to 14 The voltage V of phase A relative to the load midpoint was compared when three modulation methods were applied: three-segment vector modulation, synchronous space vector modulation, and synchronous optimal modulation. az The spectrum of three-segment vector modulation (3VDC) is close to that of synchronous optimal modulation (WTHD), and superior to synchronous space vector modulation (SVM). Furthermore, 3VDC can update the duty cycle of the PWM signal within each carrier cycle, resulting in better dynamic performance than synchronous optimal modulation. It also ensures that the voltage gain is always 1, eliminating the need for over-modulation gain correction.

[0162] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 15As shown, the computer device includes a processor, memory, and a network interface connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database stores static and dynamic information data. The network interface communicates with external terminals via a network connection. When the computer program is executed by the processor, it implements the steps in the above method embodiments.

[0163] Those skilled in the art will understand that Figure 15 The structure shown is merely a block diagram of a portion of the structure related to the present invention and does not constitute a limitation on the computer device to which the present invention is applied. A specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0164] In addition, the present invention 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 in the above method embodiments.

[0165] In addition, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the above method embodiments.

[0166] 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 methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0167] This invention is not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this invention is limited only by the appended claims.

Claims

1. A three-stage vector modulation method, characterized in that, The three-stage vector modulation method comprises: generating a reference voltage vector based on a controller, obtaining a sector number of the reference voltage vector by using a sector partition rule, and obtaining a vector sequence and a vector action time of the reference voltage vector based on the sector number and a phase rotation calculation technology; generating a three-phase switch sequence of the reference voltage vector according to a three-stage vector calculation rule based on the vector sequence and the vector action time, and outputting a three-phase pulse width modulation signal by using the three-phase switch sequence and a modulation signal generation technology; wherein the vector sequence comprises a start sequence, an end sequence and an intermediate sequence; the start sequence is composed of two groups of start effective vectors and one group of zero vectors, and the start effective vectors are respectively a previous sector effective vector and a current sector effective vector; the end sequence is composed of two groups of end effective vectors and one group of zero vectors, and the end effective vectors are respectively the current sector effective vector and a next sector effective vector; and the intermediate sequence is composed of one group of intermediate effective vectors and one group of zero vectors.

2. The three-stage vector modulation method of claim 1, wherein, The method of generating the reference voltage vector based on the controller, obtaining the sector number of the reference voltage vector by using the sector partition rule, and obtaining the vector sequence and the vector action time of the reference voltage vector based on the sector number and the phase rotation calculation technology comprises: generating a modulator input instruction by using the controller, taking the input instruction as the reference voltage vector, and the reference voltage vector comprising a reference vector amplitude and a reference vector phase; correspondingly judging the phase range of the reference voltage vector by using the sector partition rule and the reference vector phase, and obtaining the sector number of the reference voltage vector based on the phase range; converting the reference vector phase to a preset range, and calculating the converted reference vector phase based on the sector number, and obtaining the phase change of the reference vector phase in a carrier cycle by using the phase rotation calculation technology; obtaining the vector sequence and the vector action time of the reference voltage vector based on the phase change result and the converted reference vector phase.

3. The three-stage vector modulation method of claim 2, wherein, The method of obtaining the vector sequence and the vector action time of the reference voltage vector based on the phase change result and the converted reference vector phase comprises: judging the boundary of the carrier cycle in the sector based on the phase range of the reference voltage vector, and outputting the vector sequence of the reference voltage vector according to the boundary judgment result; obtaining the effective vector and the zero vector of the reference voltage vector according to the vector sequence, calculating the action time of the effective vector based on the phase change result and the converted reference vector phase, and calculating the action time of the zero vector by using the action time of the effective vector and the carrier cycle.

4. The three-stage vector modulation method of claim 3, wherein, The calculation formula of the action time of the effective vector is: where t a1 denotes the time of action of the first set of active vectors, t a2 denotes the time of action of the second set of active vectors, V r denotes the reference vector amplitude in the reference vector, θ cor is the phase occupied by the corner vector rotation within each sector, θ ref denotes the reference vector start phase in the reference vector, T s denotes the carrier period, θ' denotes the reduced reference vector phase, θ ref ' denotes the reference vector end phase in the reference vector.

5. The three-stage vector modulation method of claim 4, wherein, The method of generating the three-phase switch sequence of the reference voltage vector according to the three-stage vector calculation rule based on the sector number and the vector sequence of the reference voltage vector, and outputting the three-phase pulse width modulation signal by using the three-phase switch sequence and the modulation signal generation technology comprises: looking up the three-phase initial level corresponding to the reference voltage vector according to the three-stage vector calculation rule based on the sector number and the vector sequence of the reference voltage vector; calculating the rising edge switch time and the falling edge switch time corresponding to the three-phase of the reference voltage vector according to the vector action time, and generating the three-phase switch sequence of the reference voltage vector based on the three-phase initial level, the rising edge switch time and the falling edge switch time. The comparison value is generated based on the maximum counting period of the three-phase switch sequence and the carrier counter, and the three-phase pulse width modulation signal is generated according to the comparison value and the modulation signal generation technology.

6. The three-stage vector modulation method of claim 5, wherein, The comparison value is generated based on the maximum counting period of the three-phase switch sequence and the carrier counter, and the three-phase pulse width modulation signal is generated according to the comparison value and the modulation signal generation technology. The sequence values corresponding to each phase in the three-phase switch sequence are obtained respectively, and the pulse width modulation signal comparison value one and the pulse width modulation signal comparison value two are generated by combining the sequence values of each phase and the maximum counting period of the carrier counter; The pulse width modulation signal comparison value one and the pulse width modulation signal comparison value two are compared with the carrier signal respectively, the three-phase voltage level is analyzed based on the comparison result, and the three-phase pulse width modulation signal is generated by combining the three-phase voltage level and the modulation signal.

7. A three-stage vector modulation system, characterized by, The three-stage vector modulation system comprises: A sector judgment and time calculation unit is configured to generate a reference voltage vector based on a controller, obtain a sector number of the reference voltage vector by using a sector partition rule, and obtain a vector sequence and a vector action time of the reference voltage vector based on the sector number and a phase rotation calculation technology. A sequence generation and signal output unit is configured to generate a three-phase switch sequence of the reference voltage vector based on the vector sequence and the vector action time according to a three-stage vector calculation rule, and output a three-phase pulse width modulation signal by using a three-phase switch sequence and a modulation signal generation technology. The vector sequence comprises a start sequence, an end sequence, and an intermediate sequence; the start sequence is composed of two groups of start effective vectors and one group of zero vectors, and the start effective vectors are respectively a previous sector effective vector and a current sector effective vector; the end sequence is composed of two groups of end effective vectors and one group of zero vectors, and the end effective vectors are respectively the current sector effective vector and a next sector effective vector; and the intermediate sequence is composed of one group of intermediate effective vectors and one group of zero vectors.

8. The three-stage vector modulation system of claim 7, wherein, The sector judgment and time calculation unit comprises: A reference voltage vector acquisition module is configured to generate a modulator input instruction by using a controller, and take the input instruction as a reference voltage vector, wherein the reference voltage vector comprises a reference vector amplitude and a reference vector phase. A sector number acquisition module is configured to correspondingly judge a phase range of the reference voltage vector by using the reference vector phase and a sector partition rule, and obtain a sector number of the reference voltage vector based on the phase range. A phase change analysis module is configured to fold the reference vector phase to a preset range, and obtain a folded reference vector phase based on the sector number, and obtain a phase change of the reference vector phase in a carrier period by using a phase rotation calculation technology. An action time acquisition module is configured to obtain a vector sequence and a vector action time of the reference voltage vector based on the phase change result and the folded reference vector phase.

9. The three-stage vector modulation system of claim 8, wherein, The vector sequence and the vector action time of the reference voltage vector are obtained based on the phase change result and the folded reference vector phase, and the vector sequence of the reference voltage vector is output based on the boundary of the carrier period in the sector determined according to the phase range of the reference voltage vector. ​ According to the vector sequence, an effective vector and a zero vector of a reference voltage vector are obtained, the action time of the effective vector is calculated based on the phase change result and the converted reference vector phase, and the action time of the zero vector is calculated by using the action time of the effective vector and a carrier cycle.

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