Three-section type vector modulation method and system

Abstract

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

Description

Technical Field

[0001] The present invention relates to the technical field of vector modulation, and in particular to a three-segment vector modulation method and system. Background Art

[0002] The demand for large-capacity converters in the fields of transportation, industrial traction, power grid equipment, etc. is growing rapidly, showing a trend of high power level and high voltage. High-speed permanent magnet synchronous motors have been widely used in household appliances, rail transportation, textile industry and aerospace due to their advantages such as high efficiency, high power density and high control accuracy. In order to make full use of the capacity of the converter and further increase the operating frequency of the motor under the limitation of DC bus voltage, it is usually necessary to expand the modulation range to overmodulation and eventually to six-step modulation, which can expand the torque output capacity and working range of permanent magnet synchronous motors without modifying the hardware.

[0003] Traditional overmodulation strategies are mainly divided into single-mode overmodulation strategies 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 area into two stages, and adopts different modulation algorithms in the two stages. However, overmodulation strategies usually lead to nonlinear voltage gain areas, which require inverse function pre-multiplication or additional signal injection for correction. This is usually achieved by using inverse function tables and / or curve fitting, which complicates its implementation.

[0004] Due to the high power and voltage levels, large-capacity converters usually need to be in a high-efficiency operating state to reduce power loss and reduce the overall operation and maintenance costs. In the total converter loss, the switching loss of the power device accounts for a considerable proportion, so reducing the switching frequency can effectively reduce the converter loss. In addition, high-speed motor drives are limited by the upper limit of the switching frequency of the power device and usually work under low carrier ratio conditions. Therefore, low carrier ratio operation is a typical operating condition for large-capacity converters and high-speed motor drives.

[0005] Moreover, 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 the difference. Therefore, methods such as inverse function premultiplication or additional signal injection for correction cannot meet the accuracy of voltage gain correction under all working 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 a problem that needs to be solved urgently. Summary of the invention

[0007] The embodiment of the present invention provides a three-stage vector modulation method and system to solve the problem in the prior art that there is a difference between the overmodulation voltage gain under a low carrier ratio and the voltage gain under a high carrier ratio.

[0008] In order to have a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended to be a general review, nor is it intended to identify key / important components or to delineate the scope of protection of these embodiments. Its only purpose is to present some concepts in a simple form as a preface to the detailed description that follows.

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

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

[0011] Generate a reference voltage vector based on the controller, obtain the sector number of the reference voltage vector using the sector division 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;

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

[0013] In one embodiment, the controller generates a reference voltage vector, the sector number of the reference voltage vector is obtained by using a sector partition rule, and the vector sequence and vector action time of the reference voltage vector are obtained based on the sector number and phase rotation calculation technology, including:

[0014] Generate a modulator input instruction by using a controller, and use the input instruction as a reference voltage vector, wherein the reference voltage vector includes a reference vector amplitude and a reference vector phase;

[0015] The phase of the reference vector is matched with the sector division rule to determine the phase range of the reference voltage vector, 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 vector is calculated based on the sector number, and the phase change of the reference vector phase within the carrier cycle is obtained by using the phase rotation calculation technology;

[0017] 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.

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

[0019] Determine the boundary of the carrier cycle in the sector based on the phase range of the reference voltage vector, and output a vector sequence of the reference voltage vector according to the boundary determination result;

[0020] The effective vector and the zero vector of the reference voltage vector are obtained according to the vector sequence, the action time of the effective vector is calculated based on the phase change result and the converted reference vector vector phase, and the action time of the zero vector is calculated using the action time of the effective vector and the carrier period.

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

[0022] The starting sequence consists of two groups of starting valid vectors and one group of zero vectors;

[0023] The end sequence consists of two groups of end valid vectors and one group of zero vectors;

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

[0025] In one embodiment, the calculation formula of the effective vector action time is:

[0026]

[0027]

[0028] In the formula, t a1 Represents the action time of the first set of effective vectors, t a2 Represents the action time of the second group of effective vectors, V r represents the reference vector magnitude in the reference vector, θ cor is the phase occupied by the corner vector rotation in each sector, θ ref represents the starting phase of the reference vector in the reference vector, T s represents the carrier period, θ′ represents the reference vector phase after conversion, θ ref ′ represents the reference vector end phase in the reference vector.

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

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

[0031] Calculate the rising edge switching time and the falling edge switching time corresponding to the three reference voltage vectors according to the vector action time, and generate a three-phase switching sequence of the reference voltage vector based on the three-phase initial levels, the rising edge switching time and the falling edge switching time;

[0032] A comparison value is generated based on the three-phase switch sequence and the maximum count cycle of the carrier counter, and a three-phase pulse width modulation signal is output according to the comparison value and the modulation signal generation technology.

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

[0034] Respectively obtain the corresponding sequence values ​​in the three-phase switch sequence, and combine the sequence value of each phase with the maximum counting cycle of the carrier counter to generate a pulse width modulation signal comparison value 1 and a pulse width modulation signal comparison value 2;

[0035] The pulse width modulation signal comparison value 1 and the pulse width modulation signal comparison value 2 are compared with the carrier signal respectively, the three-phase voltage level is analyzed based on the comparison result, and 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 an embodiment of the present invention, a three-segment vector modulation system is provided.

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

[0038] A sector judgment and time calculation unit, used to generate a reference voltage vector based on the controller, obtain the sector number of the reference voltage vector using the sector division 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;

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

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

[0041] A reference voltage vector acquisition module, used to generate a modulator input instruction using a controller, and use the input instruction as a reference voltage vector, wherein the reference voltage vector includes a reference vector amplitude and a reference vector phase;

[0042] A sector number acquisition module, used to determine the phase range of the reference voltage vector by matching the reference vector phase with the sector division rule, and to acquire the sector number of the reference voltage vector based on the phase range;

[0043] A phase change analysis module is used to convert the reference vector phase into a preset range, calculate the converted reference vector vector based on the sector number, and obtain the phase change of the reference vector phase within the carrier cycle using a phase rotation calculation technique;

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

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

[0046] Determine the boundary of the carrier cycle in the sector based on the phase range of the reference voltage vector, and output a vector sequence of the reference voltage vector according to the boundary determination result;

[0047] The effective vector and the zero vector of the reference voltage vector are obtained according to the vector sequence, the action time of the effective vector is calculated based on the phase change result and the converted reference vector vector phase, and the action time of the zero vector is calculated using the action time of the effective vector and the carrier period.

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

[0049] In one embodiment, the computer device includes a memory and a processor, the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

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

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

[0052] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0053] 1. A three-segment vector modulation method provided by the present invention is applicable to low carrier ratio applications. The vector sequence of the proposed three-segment vector modulation comes from SOPWM (sinusoidal output pulse width modulation) quantized under a high modulation ratio, which ensures excellent 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), and the duty cycle of the output PWM wave can be updated in each carrier cycle, so that a fast dynamic response can be provided.

[0054] 2. When the fundamental frequency is variable, the three-stage vector modulation proposed in the present invention can still operate under fixed carrier and control frequency, making full use of the switching capability of the power device. At the same time, it can be implemented at a switching frequency lower than the control frequency, maintaining linear voltage gain in the entire modulation range, and can smoothly switch to six-step modulation.

[0055] 3. The present invention proposes a three-stage vector modulation method, which outputs two effective vectors in each switching cycle at the sector boundary and only outputs one effective vector in the remaining switching cycles, and obtains harmonic performance close to 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 is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings, which are incorporated in and constitute a 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 is a flow chart of a three-segment vector modulation method according to an exemplary embodiment;

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

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

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

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

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

[0064] Figure 7 is a SOPWM switch angle solution when N=2 according to an exemplary embodiment;

[0065] Figure 8 is a SOPWM switch angle solution when N=3 according to an exemplary embodiment;

[0066] Fig. 9 is a SOPWM switch angle solution when N=4 according to an exemplary embodiment;

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

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

[0069] Fig.12 is a three-segment vector modulation V according to an exemplary embodiment. az Spectrum;

[0070] Fig.13 is a synchronous space vector modulation V according to an exemplary embodiment. az Spectrum;

[0071] Fig.14 is a synchronous optimal modulation V according to an exemplary embodiment. az Spectrum;

[0072] Fig.15 The figure is a schematic diagram showing the structure of a computer device according to an exemplary embodiment. DETAILED DESCRIPTION

[0073] The following description and accompanying drawings fully illustrate the specific embodiments of this article so that those skilled in the art can practice them. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. The scope of the embodiments of this article includes the entire scope of the claims, as well as all available equivalents of the claims. Herein, the terms "first", "second", etc. are only used to distinguish one element from another, without requiring or implying any actual relationship or order between these elements. In fact, the first element can also be called the second element, and vice versa. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the structure, device or equipment including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such structure, device or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the structure, device or equipment including the elements. Each embodiment is described in a progressive manner herein, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0074] The terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. in this document indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this document and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of this document, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, it can also be the internal communication of two elements, it can be a direct connection, or it can be an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0075] As used herein, the term "plurality" means two or more than two, unless otherwise specified.

[0076] In this document, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B.

[0077] In this article, the term "and / or" is a description of the association relationship between objects, indicating that three relationships may exist. For example, A and / or B means: A or B, or, A and B.

[0078] It should be understood that, although the various steps in the flow chart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the figure may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0079] Each module in the device or system of the present application can be implemented in whole or in part by software, hardware, or a combination thereof. The above modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to the above modules.

[0080] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may 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, generating a reference voltage vector based on a controller, obtaining a sector number of the reference voltage vector 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 technique;

[0084] Step S103, based on the vector sequence and the vector action time, a three-phase switching sequence of the reference voltage vector is generated 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.

[0085] In this optional embodiment, when a reference voltage vector is generated based on a controller, a sector number of the reference voltage vector is obtained using a sector partition rule, and a vector sequence and a vector action time of the reference voltage vector are obtained based on the sector number and a phase rotation calculation technique, a modulator input instruction can be generated using the controller, and the input instruction is used as a reference voltage vector, wherein the reference voltage vector includes a reference vector amplitude and a reference vector phase; the reference vector phase is matched with the sector partition rule to determine the phase range of the reference voltage vector, 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, and a phase change of the reference vector phase within a carrier period is obtained using a phase rotation calculation technique; based on the phase change result and the converted reference vector phase, a vector sequence and a 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 converted reference vector vector phase, the boundary of the carrier period within the sector can be judged based on the phase range of the reference voltage vector, and the vector sequence of the reference voltage vector is output according to the boundary judgment result; the effective vector and the zero vector of the reference voltage vector are obtained according to the vector sequence, the action time of the effective vector is calculated based on the phase change result and the converted reference vector vector phase, and the action time of the zero vector is calculated using the action time of the effective vector and the carrier period.

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

[0088] In this optional embodiment, when a comparison value is generated based on the three-phase switch sequence and the maximum count period of the carrier counter, and a three-phase pulse width modulation signal is output according to the comparison value and the modulation signal generation technology, the corresponding sequence values ​​in the three-phase switch sequence can be obtained respectively, and the sequence value of each phase is combined with the maximum count period of the carrier counter to generate a pulse width modulation signal comparison value 1 and a pulse width modulation signal comparison value 2; the pulse width modulation signal comparison value 1 and the pulse width modulation signal comparison value 2 are compared with the carrier signal respectively, and the three-phase voltage level is analyzed based on the comparison result, and the three-phase voltage level is combined with the modulation signal to generate a technology to output the three-phase pulse width modulation signal.

[0089] Figure 2 An embodiment of a three-segment vector modulation system of 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 division 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;

[0092] The sequence generation and signal output unit 203 is used to generate a three-phase switching sequence of a reference voltage vector according to a three-segment vector calculation rule based on the vector sequence and the vector action time, and output a three-phase pulse width modulation signal using a three-phase switching sequence and a 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] A reference voltage vector acquisition module is used to generate a modulator input instruction using a controller and use the input instruction as a reference voltage vector, wherein the reference voltage vector includes a reference vector amplitude and a reference vector phase; a 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 partition rule, and obtain the sector number of the reference voltage vector based on the phase range; a phase change analysis module is used to convert the reference vector phase to a preset range, and calculate the converted reference vector based on the sector number, and obtain the phase change of the reference vector phase within the carrier cycle using a phase rotation calculation technique; an action time acquisition module is used to obtain 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 converted reference vector vector phase, the boundary of the carrier period within the sector can be judged based on the phase range of the reference voltage vector, and the vector sequence of the reference voltage vector is output according to the boundary judgment result; the effective vector and the zero vector of the reference voltage vector are obtained according to the vector sequence, the action time of the effective vector is calculated based on the phase change result and the converted reference vector vector phase, and the action time of the zero vector is 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 a high modulation ratio and the modulation rules of synchronous space vector modulation, a three-segment vector modulation method proposed in this embodiment can be obtained by vectorizing the waveform of synchronous optimal modulation. The waveform outputs two valid vectors in each switching cycle at the sector boundary, and only outputs one valid vector in the remaining switching cycles (valid vectors refer to other vectors except the zero vector, including V1, V2, V3, V4, V5, and V6). The corresponding vector sequence presents a three-segment feature, so it is called a three-segment vector modulation method. Figure 4 shown.

[0097] The three-stage vector modulation method proposed in this embodiment is derived by combining the vector sequence with the rules of space vector modulation. It obtains harmonic performance close to synchronous optimal modulation on the basis of ensuring high dynamic performance, and can smoothly transition to six-step modulation.

[0098] Space vector modulation expresses the multi-phase reference voltage and the output state of the inverter in the form of space vectors, and then decomposes the reference voltage into several switching states by vector synthesis. Specifically, the topology of the two-level three-inverter is as follows Figure 5 shown.

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

[000] ,

[001] ,

[010] ,

[011] ,

[100] ,

[101] ,

[111] . There are eight states in total. Each set of switching states corresponds to an output voltage vector. For example, when the inverter works in the 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] Where e represents the base of natural logarithm, and j represents the imaginary unit.

[0102] By analogy, 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 converter

[0104]

[0105] like Figure 6 As shown in the figure, these vectors are drawn in a plane rectangular αβ coordinate system to form the space vector diagram of the converter. Space vector modulation uses the inherent vector of the converter to output the reference voltage vector equivalently. Synchronous space vector modulation refers to a space vector modulation method in which the carrier ratio is equal to a constant and the sampling point phase remains consistent in each fundamental wave cycle. The duty cycle of the output PWM signal can be updated in each carrier cycle, so synchronous space vector modulation has good dynamic performance. The implementation of synchronous space vector modulation is simpler than synchronous optimal modulation, but the harmonic performance is worse than synchronous optimal modulation.

[0106] Synchronous optimal modulation refers to a modulation method that minimizes the weighted total harmonic distortion (WTHD) as the optimization goal while ensuring half-wave symmetry, 1 / 4 cycle symmetry, and three-phase symmetry. The definition of weighted total harmonic distortion (WTHD) is as follows:

[0107]

[0108] Where n is the number of times the switch is turned on and off within a quarter cycle.

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

[0110] Synchronous optimal pulse width modulation has the best harmonic performance in theory, but the dynamic performance is poor, which limits the wide application of synchronous optimal modulation. When the fundamental frequency changes, the switching frequency of synchronous SVPWM and SOPWM will change dramatically. This is because when the fundamental frequency increases, the carrier ratio should be reduced to another smaller integer to prevent the switching frequency from exceeding its limit, which will lead to drastic changes in harmonics and the switching frequency of the power device cannot be fully utilized.

[0111] like Figure 3 As shown, the input command of the modulator comes from the controller, and the input command is the reference voltage vector, including the amplitude V r (reference voltage vector amplitude) and phase θ (reference voltage vector phase), where the "three-stage vector synthesis algorithm" module is executed once per switching cycle to generate a 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 through counters and comparators.

[0112] (1) Sector judgment:

[0113] According to the reference vector phase θ, the sector in which the reference vector is located is determined, and the sector number n is obtained. The judgment 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: The phase range is (270°, 330°], and the sector number n=6.

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

[0121] In order to calculate the vector action time conveniently, 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] In one carrier cycle, the reference vector V r From the starting phase θ ref Rotate to the final 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] The calculation of the effective vector action time in this embodiment is an approximate value, and there are multiple calculation rules. According to the different positions of the carrier cycle, it can be divided into three cases, corresponding to three vector sequences and vector action time calculation methods:

[0129] 1. Starting sequence;

[0130] When the carrier cycle is located at the upper boundary of the sector, the start sequence is output, including two valid vectors (starting valid vectors) and a zero vector. The starting valid vectors are the valid vector of the previous sector (named as the corner vector) and the valid vector of the current sector. The vector action time is t a1 and t a2 , the specific calculation formula is:

[0131]

[0132]

[0133] Among them, θ cor is the phase occupied by the corner vector rotation in each sector, θ cor There are many options for affecting the PWM waveform. This embodiment provides one of them, namely θ cor =8°, and thus the zero vector V z The action time t z for:

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

[0135] 2. End sequence;

[0136] When the carrier cycle is at the lower boundary of the sector, the end sequence is output, including two effective vectors (the end effective vector) and a zero vector. The end effective vectors are the effective vector of the current sector and the effective vector of the next sector (named as the corner vector), and the vector action time is t a1 and t a2 , the specific calculation formula is:

[0137]

[0138]

[0139] Among them, θ cor is the phase occupied by the corner vector rotation in each sector, θ cor There are many options for affecting the PWM waveform. This embodiment provides one of them, namely θ cor =8°, and thus the zero vector V z The action time t z for:

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

[0141] 3. Intermediate sequence;

[0142] When the carrier cycle is not located at the sector boundary, an intermediate sequence is output, including an effective vector (intermediate effective vector) and a zero vector. The effective vector action time is t a1 and t a2 , the specific calculation formula is:

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

[0144] t a2 =0;

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

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

[0147] (3) Switch sequence generation:

[0148] According to the principle of three-stage vector modulation, the switching sequence of each phase is generated. Each phase switching sequence includes three parameters: the 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 Switch sequence generation calculation rules

[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 for generating the PWM signal is relatively flexible. This embodiment provides 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 t ap , falling edge time t an At this time, set the two comparison values ​​of the PWM modulation module CompA-A=t ap *PRD / T s , CompB-A=t an *PRD / T s , where PRD is the period value of the carrier counter, that is, 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 phase B and phase C are both 0 and always remain 0, so the PWM initial levels of phase B and phase C are set to 0, and the comparison value is set to -1, indicating that these two phases will not cross the carrier and no PWM jump will occur.

[0156] Based on the above steps, we can build Figure 5 A two-level three-phase inverter is shown.

[0157] Carrier ratio m r Equal to 18, modulation ratio m a Take 1.11 as an example, when the reference vector phase is 20°, the position of the reference vector is as follows Fig.10As shown by the xy line in the middle, according to the reference vector phase, the vector is located in sector I, the carrier period is located at the lower boundary of the sector, and the vector sequence is the end sequence, that is, [V0 V1 V2].

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

[0159] Finally, according to the action time t of the effective vector V1 a1 , the action time t of effective vector V2 a2 And the action time t of 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 Fig.10 and Fig.11 shown.

[0160] Similarly, the PWM signals in other carrier cycles are output according to the above method, such as Fig.11 The vector sequence within the entire fundamental wave period is also Fig.11 Listed in.

[0161] Carrier ratio m r When it is equal to 18, the pulse ratio P r (the number of pulses per phase in one fundamental wave cycle) is equal to 7, Figure 12 to Figure 14 The A-phase voltage V relative to the load midpoint when three modulation methods, namely three-segment vector modulation, synchronous space vector modulation, and synchronous optimal modulation, are compared. az The spectrum and WTHD of three-segment vector modulation are close to synchronous optimal modulation, which is better than synchronous space vector modulation. In addition, three-segment vector modulation can update the duty cycle of the PWM signal in each carrier cycle, and its dynamic performance is better than synchronous optimal modulation. Moreover, the voltage gain can always be guaranteed to be 1, and there is no need for overmodulation gain correction.

[0162] In one embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as follows: Fig.15As shown. The computer device includes a processor, a memory and a network interface connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store static information and dynamic information data. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, the steps in the above method embodiment are implemented.

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

[0164] In addition, the present invention also provides a computer device, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above method embodiment when executing the computer program.

[0165] In addition, the present invention further provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps in the above method embodiment are implemented.

[0166] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided by the present 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 memory, etc. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0167] The present invention is not limited to the structures which have been described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A three-segment vector modulation method, characterized in that: The three-stage vector modulation method includes: Generate a reference voltage vector based on the controller, obtain the sector number of the reference voltage vector using the sector division 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; Based on the vector sequence and the vector action time, a three-phase switching sequence of a reference voltage vector is generated according to a three-segment vector calculation rule, and a three-phase pulse width modulation signal is output using a three-phase switching sequence and a modulation signal generation technology.

2. The three-segment vector modulation method according to claim 1, characterized in that: The controller-based generation of the reference voltage vector, the use of sector division rules to obtain the sector number of the reference voltage vector, and the vector sequence and vector action time of the reference voltage vector based on the sector number and phase rotation calculation technology include: Generate a modulator input instruction by using a controller, and use the input instruction as a reference voltage vector, wherein the reference voltage vector includes a reference vector amplitude and a reference vector phase; The phase of the reference vector is matched with the sector division rule to determine the phase range of the reference voltage vector, 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 vector is calculated based on the sector number, and the phase change of the reference vector phase within the carrier cycle is obtained by using the 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.

3. The three-segment vector modulation method according to claim 2, characterized in that: The step 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 vector phase includes: Determine the boundary of the carrier cycle in the sector based on the phase range of the reference voltage vector, and output a vector sequence of the reference voltage vector according to the boundary determination result; The effective vector and the zero vector of the reference voltage vector are obtained according to the vector sequence, the action time of the effective vector is calculated based on the phase change result and the converted reference vector vector phase, and the action time of the zero vector is calculated using the action time of the effective vector and the carrier period.

4. The three-segment vector modulation method according to claim 3, characterized in that: The vector sequence includes a starting sequence, an ending sequence and an intermediate sequence; The starting sequence is composed of two groups of starting valid vectors and one group of zero vectors; The end sequence is composed of two groups of end valid vectors and one group of zero vectors; The intermediate sequence consists of a group of intermediate valid vectors and a group of zero vectors.

5. The three-segment vector modulation method according to claim 3, characterized in that: The calculation formula of the action time of the effective vector is: Where, t a1 Indicates the action time of the first set of effective vectors, t a2 Represents the action time of the second group of effective vectors, V r represents the reference vector magnitude in the reference vector, θ cor is the phase occupied by the corner vector rotation in each sector, θ ref represents the starting phase of the reference vector in the reference vector, T s represents the carrier period, θ′ represents the reference vector phase after conversion, θ ref ′ represents the reference vector end phase in the reference vector.

6. The three-segment vector modulation method according to claim 5, characterized in that: The method of generating a three-phase switching sequence of a reference voltage vector according to a three-segment vector calculation rule based on a vector sequence and a vector action time, and outputting a three-phase pulse width modulation signal using a three-phase switching sequence and a modulation signal generation technology includes: Based on the sector number and vector sequence of the reference voltage vector, the three-phase initial levels corresponding to the reference voltage vector are found according to the three-segment vector calculation rule; Calculate the rising edge switching time and the falling edge switching time corresponding to the three reference voltage vectors according to the vector action time, and generate a three-phase switching sequence of the reference voltage vector based on the three-phase initial levels, the rising edge switching time and the falling edge switching time; A comparison value is generated based on the three-phase switch sequence and the maximum count cycle of the carrier counter, and a three-phase pulse width modulation signal is output according to the comparison value and the modulation signal generation technology.

7. The three-segment vector modulation method according to claim 6, characterized in that: The method of generating a comparison value based on the three-phase switch sequence and the maximum count period of the carrier counter, and outputting a three-phase pulse width modulation signal according to the comparison value and the modulation signal generation technology includes: Respectively obtain the corresponding sequence values ​​in the three-phase switch sequence, and combine the sequence value of each phase with the maximum counting cycle of the carrier counter to generate a pulse width modulation signal comparison value 1 and a pulse width modulation signal comparison value 2; The pulse width modulation signal comparison value 1 and the pulse width modulation signal comparison value 2 are compared with the carrier signal respectively, the three-phase voltage level is analyzed based on the comparison result, and the three-phase voltage level is combined with the modulation signal to generate a three-phase pulse width modulation signal.

8. A three-stage vector modulation system, characterized in that: The three-stage vector modulation system includes: A sector judgment and time calculation unit, used to generate a reference voltage vector based on the controller, obtain the sector number of the reference voltage vector using the sector division 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; The sequence generation and signal output unit is used to generate a three-phase switching sequence of a reference voltage vector based on a vector sequence and a vector action time according to a three-segment vector calculation rule, and output a three-phase pulse width modulation signal using a three-phase switching sequence and a modulation signal generation technology.

9. The three-stage vector modulation system according to claim 8, characterized in that: The sector determination and time calculation unit comprises: A reference voltage vector acquisition module, used to generate a modulator input instruction using a controller, and use the input instruction as a reference voltage vector, wherein the reference voltage vector includes a reference vector amplitude and a reference vector phase; A sector number acquisition module, used to determine the phase range of the reference voltage vector by matching the reference vector phase with the sector division rule, and to acquire the sector number of the reference voltage vector based on the phase range; A phase change analysis module is used to convert the reference vector phase into a preset range, calculate the converted reference vector vector based on the sector number, and obtain the phase change of the reference vector phase within the carrier cycle using a phase rotation calculation technique; The action time acquisition module is used to acquire the vector sequence and vector action time of the reference voltage vector based on the phase change result and the converted vector phase of the reference vector.

10. The three-stage vector modulation system according to claim 9, characterized in that: The step 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 vector phase includes: Determine the boundary of the carrier cycle in the sector based on the phase range of the reference voltage vector, and output a vector sequence of the reference voltage vector according to the boundary determination result; The effective vector and the zero vector of the reference voltage vector are obtained according to the vector sequence, the action time of the effective vector is calculated based on the phase change result and the converted reference vector vector phase, and the action time of the zero vector is calculated using the action time of the effective vector and the carrier period.

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