General determination method for optimal switching vector in arbitrary multi-level inverter power supply direct torque control system

Abstract

The invention relates to a general determination method for an optimal switching vector in an arbitrary multi-level inverter power supply direct torque control system, and belongs to the field of multi-level inverter control. The method comprises the steps of sector judgment, level action area determination, amplitude limiting generation, k-moment relative increment determination, k-moment actual increment calculation, optimal origin vector determination and k-moment optimal voltage vector determination. The method can be suitable for a direct torque control system of any multi-level circuit topology power supply, and the speed of determining the optimal switching vector of the constructed complex multi-level circuit is increased; in addition, according to the determined optimal switching vector set, a specific multi-level circuit topology constraint condition can be added, and the optimal switching vector output by a special multi-level circuit is rapidly generated.

Description

Technical Field

[0001] The invention belongs to the field of multi-level inverter control, and in particular relates to a universal method for determining an optimal switching vector in a direct torque control system powered by any multi-level inverter. Background Art

[0002] The direct torque control strategy uses the constructed optimal switching vector table to output the optimal voltage vector to directly control the torque and flux linkage quickly to achieve efficient control of the motor, with the advantages of fast dynamic response and strong parameter robustness. In the traditional two-level converter, since there are only 8 voltage vectors, it is easy to construct the optimal switching vector table, and the optimal switching vector table is relatively simple, resulting in large torque current pulsation.

[0003] In recent years, multilevel converters have been increasingly widely used in motor drive systems due to their advantages such as good output voltage waveform quality and low harmonic content. As the number of output levels of multilevel converters increases, the output voltage vector also increases significantly. There are many comprehensive factors to consider when constructing the optimal switching vector table, which makes the optimal switching vector table very large. How to establish a universal optimal switching vector table for any multilevel inverter-powered direct torque control system is a scientific problem that needs to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a general method for determining an optimal switching vector in an arbitrary multi-level inverter powered direct torque control system in order to quickly construct a multi-level inverter powered direct torque strategy.

[0005] To achieve the above object, the technical scheme of the present invention is: a general method for determining the optimal switching vector in a direct torque control system powered by an arbitrary multi-level inverter, which comprises the following steps: sector judgment, level action area determination, amplitude limit generation, relative increment determination at time k, actual increment calculation at time k, optimal origin vector determination, and optimal voltage vector determination at time k; input torque control variable τ, flux control variable φ, stator flux angle θ s , given speed n * According to the sector judgment link, the basic sector number i and the sub-sector number j are output; according to the relative increment determination link at time k, the relative increments Δx, Δy and Δz of the voltage vector on the abc phase relative to time k-1 are output; according to the actual increment calculation link at time k, the increment Δx relative to the vector origin on the abc phase is output k , Δy k and Δz k ; Δx k , Δy k and Δz k The limit value [X min (k),X max (k)]、[Ymin (k),Y max (k)] and [Z min (k),Z max (k)] is obtained by the limit generation link, where the level action area number m used in the limit generation link is generated by the level action area determination link; according to the optimal origin vector determination link, the optimal origin vector (x0, y0, z0) is output; finally, according to the optimal voltage vector determination link at time k, the optimal switch vector (x k ,y k ,z k ).

[0006] In one embodiment of the present invention, the sector determination step is based on the input stator flux linkage angle θ s and given speed n * , output the basic sector number i and sub-sector number j.

[0007] In one embodiment of the present invention, the sector determination step is specifically implemented as follows:

[0008] 1) Level action vector area division: The rated speed is divided into segments according to the number of levels of the inverter output phase voltage. The number of segments M is expressed as

[0009]

[0010] Where N is the maximum output level of the inverter phase voltage;

[0011] 2) Level action area: according to the given speed n * Determine the inverter output level and obtain the mth level action area where the current voltage vector is located. m is expressed as

[0012]

[0013] Where n nom is the rated speed of the motor, round is the rounding function, for the mth level action area, the voltage vector acts on this area to output 2m+1 level;

[0014] 3) According to the stator flux angle θ s Determine the basic sector number, the formula is as follows:

[0015]

[0016] In the formula, ceil is the upward rounding function;

[0017] 4) Determine the sub-sector number j according to the current level action area m, and the determination formula is as follows:

[0018]

[0019] In one embodiment of the present invention, the relative increment determination link at time k inputs the torque control variable τ, the flux control variable φ and the basic sector number i, and outputs the relative increments Δx, Δy and Δz of the voltage vector in the abc phase relative to time k-1.

[0020] In one embodiment of the present invention, in the actual increment calculation link at time k, the relative increments Δx, Δy, Δz of the voltage vector at time k-1 on the abc phase and the actual increment Δx of the vector origin at time k on the abc phase obtained in the limit generation link are input. k , Δy k , Δz k The limit value [X min (k),X max (k)]、[Y min (k),Y max (k)] and [Z min (k),Z max (k)], calculate the increment Δx of the vector relative to the origin on the abc phase k , Δy k and Δz k ; The calculation formula used is as follows:

[0021]

[0022] In the formula, Δx k-1 , Δy k-1 and Δz k-1 They are the actual increments of the vector origin at time k-1 on the abc phases respectively.

[0023] In one embodiment of the present invention, the Δx obtained in the limit generation link k , Δy k , Δz k The limit value [X min (k),X max (k)]、[Y min (k),Y max (k)] and [Z min (k),Z max (k)] is:

[0024] Based on the sector number ij and the current level action area m, the amplitude limit of each component in the sub-sector in the three-phase stationary coordinate system is obtained, as shown in the following table:

[0025] Sub-sector X-Limit Y Clipping Z Clipping 1.j [-2-j,-j] [m+1,m+2] [j,j+1] 2.j [-2-m,-m] [3-j,5-j] [-j,-j+1] 3.j [-m-2,-m-1] [2-j,3-j] [-j-2,-j] 4.j [-m-2,-m] [-j,-j+1] [m,m+2] 5.j [-3+j,-2+j] [-2-j,-j] [m+1,m+2] 6.j [j,j+1] [-m-2,-m] [3-j,5-j] 7.j [j,j+2] [-m-2,-m-1] [2-j,3-j] 8.j [m,m+2] [-5+j,-3+j] [-j,-j+1] 9.j [m+1,m+2] [-3+j,-2+j] [-2-j,-j] 10.j [3-j,5-j] [-1+j,j] [-m-2,-m] 11.j [2-j,3-j] [j+1,j+2] [-m-2,-m-1] 12.j [-j,-j+1] [m,m+2] [-5+j,-3+j]

[0026] Based on the above table, we can get Δx k , Δy k , Δz kThe limit value [X min (k),X max (k)]、[Y min (k),Y max (k)] and [Z min (k),Z max (k)].

[0027] In one embodiment of the present invention, in the optimal voltage vector determination link at time k, the input is the increment Δx relative to the vector origin on the abc phase. k , Δy k and Δz k and the optimal origin vector (x0, y0, z0), output the optimal switch vector (x k ,y k ,z k ), the calculation formula used is as follows:

[0028]

[0029] In one embodiment of the present invention, the optimal origin vector (x0, y0, z0) is obtained as follows:

[0030] 1) For an N-level inverter, there are N origin vectors in the voltage vector, and the optimal origin vector needs to be selected in each step; first substitute the origin vector set into the boundary constraints to obtain a new origin vector set, where the constraints are

[0031]

[0032] 2) In order to further select the optimal origin vector, constraints are set in combination with the characteristics of the multilevel inverter topology. Here, the principle of minimum common-mode voltage is used as the constraint, and the origin vector plus the increment Δx relative to the vector origin on the abc phase k , Δy k , Δz k It is the actual voltage vector. The sum of the amplitudes of the three phases abc is proportional to the common mode voltage. Let a function f(x,y,z) be substituted into the origin vector to get

[0033] f(x0,y0,z0)=(x0+Δx k ) 2 +(y0+Δy k ) 2 +(z0+Δz k ) 2 .

[0034] In one embodiment of the present invention, the method is applied to a direct torque control system powered by a multi-level inverter, comprising an input voltage module, a multi-level inverter, a central processing unit, a bus voltage sampling circuit, a capacitor voltage sampling circuit, a drive circuit, a phase current sampling circuit, and an encoder circuit; wherein,

[0035] The input voltage module uses AC power or DC power;

[0036] The switch tube of the multi-level inverter adopts an insulated gate bipolar transistor or a metal oxide semiconductor field effect transistor;

[0037] The bus voltage sampling circuit is composed of a signal sampling circuit and a conditioning circuit. The signal sampling circuit selects the Hall voltage sampling or the resistor voltage division sampling mode. The conditioning circuit is composed of an operational amplifier circuit and is designed according to the input signal bandwidth and the requirements of the subsequent input. The output analog signal of the bus voltage sampling circuit is sent to the central processor.

[0038] The capacitor voltage sampling circuit selects the same structure as the bus voltage sampling circuit, or for multi-level topology, adopts a voltage-frequency converter to collect capacitor voltage signals. At this time, the output digital signal of the capacitor voltage sampling circuit requires the central controller to use a counter to count and convert the digital signal to obtain a corresponding analog signal;

[0039] The phase current sampling circuit is composed of a Hall current sensor and an operational amplifier conditioning circuit, and the output analog signal is sent to the central processing unit;

[0040] The encoder circuit uses a photoelectric encoder to generate pulses and send them to the central processor to obtain motor speed information or motor position information;

[0041] The central processing unit adopts a digital processor DSP, a field programmable gate array FPGA or a micro control unit MCU as the control core. The control core adopts a single-core structure or a single-master and multi-slave structure according to the resources occupied by the processed signals; the central processing unit combines the signals sent by each part with the method described above to construct a multi-level direct torque control, and finally outputs a switching signal for driving each switching power device of the multi-level inverter, and generates a driving signal for directly controlling the action of the inverter power device through a driving circuit to achieve control of the speed regulation of the AC motor.

[0042] The present invention also provides a computer-readable storage medium, on which computer program instructions that can be executed by a processor are stored. When the processor executes the computer program instructions, the method steps described above can be implemented.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) Compared with the existing optimal switching vector determination method, the present invention can be applied to a direct torque control system powered by any multi-level circuit topology, thereby improving the speed of determining the optimal switching vector for building a complex multi-level circuit;

[0045] (2) The present invention can add specific multi-level circuit topology constraints according to the determined optimal switching vector set, and quickly generate the optimal switching vector output by the dedicated multi-level circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the flow chart of the general method for determining the optimal switching vector of the present invention.

[0047] Figure 2 This is an example of the hardware structure of the drive system for implementing the present invention.

[0048] Figure 3 Divide the vector area into different levels.

[0049] Figure 4 Divided into sectors. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0051] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0052] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] The present invention provides a general method for determining the optimal switching vector in a direct torque control system powered by an arbitrary multi-level inverter, which comprises the following steps: sector judgment, level action area determination, amplitude limit generation, relative increment determination at time k, actual increment calculation at time k, optimal origin vector determination, and optimal voltage vector determination at time k; input torque control variable τ, flux control variable φ, stator flux angle θ s , given speed n *According to the sector judgment link, the basic sector number i and the sub-sector number j are output; according to the relative increment determination link at time k, the relative increments Δx, Δy and Δz of the voltage vector on the abc phase relative to time k-1 are output; according to the actual increment calculation link at time k, the increment Δx relative to the vector origin on the abc phase is output k , Δy k and Δz k ; Δx k , Δy k and Δz k The limit value [X min (k),X max (k)]、[Y min (k),Y max (k)] and [Z min (k),Z max (k)] is obtained by the limit generation link, where the level action area number m used in the limit generation link is generated by the level action area determination link; according to the optimal origin vector determination link, the optimal origin vector (x0, y0, z0) is output; finally, according to the optimal voltage vector determination link at time k, the optimal switch vector (x k ,y k ,z k ).

[0054] The following is the specific implementation process of the present invention.

[0055] The specific general determination method of the optimal switching vector of the method of the present invention is as follows Figure 1 As shown, it consists of sector judgment, level action area determination, limit generation, relative increment determination at time k, actual increment calculation at time k, optimal origin vector determination and optimal voltage vector determination at time k.

[0056] This method inputs the torque control variable τ, the flux control variable φ, and the stator flux angle θ s , given speed n * , the optimal switching vector (x k ,y k ,z k ). In this method, according to the sector judgment link, the basic sector number i and the sub-sector number j are output; according to the relative increment determination link at time k, the relative increments Δx, Δy and Δz of the voltage vector on the abc phase relative to time k-1 are output; according to the actual increment calculation link at time k, the increment Δx relative to the vector origin on the abc phase is output. k , Δy k and Δz k ; and Δx k , Δy k and Δz kThe value needs to be limited, the limit value [X min (k),X max (k)], [Y min (k),Y max (k)] and [Z min (k),Z max (k)] is obtained by the limit generation link, where the level action area number m used in the limit link is generated by the level action area determination link; according to the optimal origin vector determination link, the optimal origin vector (x0, y0, z0) is output; finally, according to the voltage vector determination link at time k, the optimal switch vector (x k ,y k ,z k ).

[0057] The specific implementation steps of the method of the present invention are as follows:

[0058] (1) The stator flux angle θ s and speed setting n * Send it to the sector judgment link, output the basic sector number i and sub-sector number j;

[0059] (2) The torque control variable τ, flux control variable φ and basic sector number i are sent to the relative increment determination table lookup link at time k, and the relative increments Δx, Δy and Δz of the voltage vector in the abc phase relative to time k-1 are output. The relative displacement table used is shown in Table 1. Among them, τ = 0 means reducing the electromagnetic torque, τ = 1 means increasing the electromagnetic torque; φ = 0 means reducing the flux amplitude, and φ = 1 means increasing the flux amplitude.

[0060] Table 1 Determination of relative increment at time k

[0061]

[0062] (3) The relative increment (Δx, Δy, Δz) of the voltage vector on the abc phase relative to time k-1 and the actual increment (Δx) of the vector origin on the abc phase relative to time k are calculated. k ,Δy k ,Δz k ) limit value [X min (k),X max (k)], [Y min (k),Y max (k)] and [Z min (k),Z max (k)], and sent to the actual increment calculation link at time k to calculate the increment Δx relative to the origin vector on the abc phase k , Δy k and Δz k The calculation formula used is as follows:

[0063]

[0064] In the formula, Δx k-1 , Δy k-1 and Δz k-1 They are the actual increments of the vector origin at time k-1 on the abc phases respectively.

[0065] (4) The increment Δx of the relative vector origin on the abc phase k , Δy k and Δz k and the optimal origin vector (x0, y0, z0) are sent to the optimal switch vector calculation link at time k, and the optimal switch vector (x k ,y k ,z k ), the calculation formula used is as follows:

[0066]

[0067] The sector determination steps required in step (1) are as follows:

[0068] (1.1) Level action vector area division. The rated speed is divided into segments according to the number of levels of the inverter output phase voltage. The number of segments M can be expressed as

[0069]

[0070] Where N is the maximum output level of the inverter phase voltage.

[0071] (1.2) Level action area. According to the speed given n * Determine the inverter output level, and then get the mth level action area where the current voltage vector is located. m can be expressed as

[0072]

[0073] Where n nom is the rated speed of the motor, and round is the rounding function. For the mth level action area, the voltage vector can output 2m+1 levels when acting in this area.

[0074] (1.3) According to the magnetic flux angle θ s Determine the basic sector number, the formula is as follows:

[0075]

[0076] Where ceil is the rounding function.

[0077] (1.4) Determine the sub-sector number j according to the current level action area m, and the determination formula is as follows:

[0078]

[0079] The actual increment Δx of the vector origin at time k on the abc phase in step (3) is k , Δy k and Δz k The limit value [X min (k),X max (k)], [Y min (k),Y max (k)] and [Z min (k),Z max (k)] The details are as follows:

[0080] For any multi-level inverter, the limiting of each component in the sub-sector in the three-phase stationary coordinate system is shown in Table 2, which requires the sector number ij and the current level action area m.

[0081] Table 2 Limits of each component in the sub-sector in the three-phase stationary coordinate system

[0082] Sub-sector X-Limit Y Clipping Z Clipping 1.j [-2-j,-j] [m+1,m+2] [j,j+1] 2.j [-2-m,-m] [3-j,5-j] [-j,-j+1] 3.j [-m-2,-m-1] [2-j,3-j] [-j-2,-j] 4.j [-m-2,-m] [-j,-j+1] [m,m+2] 5.j [-3+j,-2+j] [-2-j,-j] [m+1,m+2] 6.j [j,j+1] [-m-2,-m] [3-j,5-j] 7.j [j,j+2] [-m-2,-m-1] [2-j,3-j] 8.j [m,m+2] [-5+j,-3+j] [-j,-j+1] 9.j [m+1,m+2] [-3+j,-2+j] [-2-j,-j] 10.j [3-j,5-j] [-1+j,j] [-m-2,-m] 11.j [2-j,3-j] [j+1,j+2] [-m-2,-m-1]

[0083]

[0084] The optimal origin vector (x0, y0, z0) in step (4) is obtained as follows:

[0085] (4.1) For an N-level inverter, the voltage vector has N origin vectors, and the optimal origin vector needs to be selected in each step. First, substitute the origin vector set into the boundary constraints to obtain a new origin vector set. Here, the constraints are

[0086]

[0087] (4.2) In order to further select the optimal origin vector, the constraints can be set in combination with the characteristics of the multilevel inverter topology. Here, the principle of minimum common-mode voltage is used as the constraint, and the origin vector plus the increment (Δx k ,Δy k ,Δz k ) is the actual voltage vector. The sum of the three-phase amplitudes abc is proportional to the common-mode voltage, so it is used as a constraint. Here, a function f(x, y, z) is assumed. Substituting the origin vector into the function, we get

[0088] f(x0,y0,z0)=(x0+Δx k ) 2+(y0+Δy k ) 2 +(z0+Δz k ) 2

[0089] The hardware structure of the drive system of the present invention is as follows: Figure 2 The direct torque control system powered by a multi-level inverter includes an input voltage (which can be an AC power supply or a DC power supply), a multi-level inverter, a central processing unit, an AC motor, a bus voltage sampling circuit, a capacitor voltage sampling circuit, a drive circuit, a phase current sampling circuit, an encoder circuit, a host computer, etc.

[0090] The switch tube of the multi-phase inverter can be an insulated gate bipolar transistor or a metal oxide semiconductor field effect transistor. The central processing unit can use a digital processor DSP, a field programmable gate array FPGA or a micro control unit MCU as the control core. The control core can adopt a single-core structure or a single-master-multiple-slave structure according to the resources occupied by the processed signal. The bus voltage sampling circuit is generally composed of a signal sampling circuit and a conditioning circuit, wherein the signal sampling circuit can select the Hall voltage sampling or the resistor voltage division sampling method, and the conditioning circuit is composed of an operational amplifier circuit, which can be designed according to the input signal bandwidth and the input requirements of the subsequent stage; the output analog signal of the bus voltage sampling circuit is sent to the central processing unit. The capacitor voltage sampling circuit can choose the same structure as the bus voltage sampling circuit. Of course, for some multi-level topologies, the capacitor voltages required to be sampled are more, and the voltage-frequency converter can also be used to collect the capacitor voltage signal. Then the output of the capacitor voltage sampling circuit is a digital signal, and the central controller needs to use a counter to count and convert the digital signal to obtain the corresponding analog signal. For the phase current sampling circuit, a Hall current sensor and an operational amplifier conditioning circuit can be used, and the output analog signal is sent to the central processing unit. The encoder circuit can use a photoelectric encoder to generate pulses to the central processor to obtain motor speed information or motor position information. The central processor combines the signals sent by each part with the optimal switching vector universal determination method proposed by the present invention to construct a multi-level direct torque control, and finally outputs a switching signal for driving each switching power device of the multi-level inverter, and generates a driving signal for directly controlling the action of the inverter power device through the driving circuit to achieve the control of the AC motor speed regulation.

[0091] The basic principle is described as follows:

[0092] Level action area division. The rated speed is divided into segments according to the number of levels of the inverter output phase voltage. For an N-level inverter, the number of segments can be M according to the rated speed. M can be expressed as

[0093]

[0094] The number of level action regions is equal to the number of speed segments. For example, for a five-level inverter, the output level N = 5, then the number of segments M = 2, and the level action vector regions are three-level action regions and five-level action regions. For an N-level inverter, the level action vector region distribution is as follows: Figure 3 As shown in the figure, the number of speed segments is N, and the level action vector area is divided into M areas, namely, a three-level action area, a five-level area, ..., an N-level action area.

[0095] Sector division. For any voltage vector diagram of level 3 and above, it is evenly divided into 12 basic sectors. Taking the positive semi-axis of the a-axis as the baseline, rotating counterclockwise, it is basic sector 1, basic sector 2 to basic sector 12, each basic sector occupies a 30° sector area. According to the different levels, the basic sectors are further divided. Figure 4 The sub-sector division within the first basic sector is given. In the figure, the three-level vector action area is not divided, and the entire action area is still 12 areas; for the five-level vector action area, each basic sector is divided once evenly, and one basic sector is divided into two sub-sectors, so the entire five-level action area can be divided into 24 vector action areas, and the sub-sector naming format is the basic sector plus the sub-sector number, for example, the first sector of the first partition is called the 1.1 sector. For the N (N = 3, 5, 7..) level action area, each basic sector is divided into M-1 parts evenly, and one basic sector is divided into M sub-sectors, so the entire N-level action area can be divided into 12M vector action areas.

[0096] The amplitude limit values ​​of each component of the voltage vector at time k in the three-phase stationary coordinate system [X min (k),X max (k)]、[Y min (k),Y max (k)] and [Z min (k),Z max (k)] is obtained. For the basic sector, the limiting conditions of each component in the three-phase stationary coordinate system are shown in Table 3. For the N-level situation above three levels, each basic sector is further divided into M sub-sectors, and the limiting values ​​of each component in each sub-sector are obtained according to the limiting law of the basic sector and combined with the sector division situation, and the limiting conditions of each component in the sub-sector in the three-phase stationary coordinate system are obtained, as shown in Table 3.

[0097] Table 3 Limits of each component in the basic sector in the three-phase stationary coordinate system

[0098]

[0099]

[0100] The following is an analysis of the limiting of sub-sectors in the basic sector in Table 3. For an N-level inverter, each basic sector will be divided into m. In the first basic sector, the limits of X, Y, and Z of the 1.j (j=1,2,…,m) sub-sector are [-2-j,-j], [m+1,m+2], and [j,j+1] respectively. Taking the five-level as an example, the number of segments of the five-level is m=2, and each basic sector is evenly divided into 2. Then in the first basic sector, for the j-th sub-sector, j=1, the limit of X is [-3,-1], the limit of Y is [3,4], and the limit of Z is [1,2]; for the 1.2 sub-sector, j=2, the limit of X is [-4,-2], the limit of Y is [3,4], and the limit of Z is [2,3].

[0101] The present invention also provides a computer-readable storage medium, on which computer program instructions that can be executed by a processor are stored. When the processor executes the computer program instructions, the method steps described above can be implemented.

[0102] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0103] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0104] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1A function specified in one or more boxes.

[0105] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0106] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A general method for determining the optimal switching vector in a direct torque control system powered by any multi-level inverter, characterized in that: It consists of sector judgment, level action area determination, limit generation, relative increment determination at time k, actual increment calculation at time k, optimal origin vector determination, and optimal voltage vector determination at time k; input torque control variable τ, flux control variable φ, stator flux angle θ s , given speed n * According to the sector judgment link, the basic sector number i and the sub-sector number j are output; according to the relative increment determination link at time k, the relative increments Δx, Δy and Δz of the voltage vector on the abc phase relative to time k-1 are output; according to the actual increment calculation link at time k, the increment Δx relative to the vector origin on the abc phase is output k , Δy k and Δz k ; Δx k , Δy k and Δz k The limit value [X min (k),X max (k)], [Y min (k),Y max (k)] and [Z min (k),Z max (k)] is obtained by the limit generation link, where the level action area number m used in the limit generation link is generated by the level action area determination link; according to the optimal origin vector determination link, the optimal origin vector (x0, y0, z0) is output; finally, according to the optimal voltage vector determination link at time k, the optimal switch vector (x k ,y k ,z k ).

2. The method for determining the optimal switching vector in a direct torque control system powered by any multi-level inverter according to claim 1, characterized in that: Sector judgment link, based on the input stator flux linkage angle θ s and given speed n * , output the basic sector number i and sub-sector number j.

3. The general method for determining the optimal switching vector in any multi-level inverter powered direct torque control system according to claim 1 or 2, characterized in that: The sector judgment link is specifically implemented as follows: 1) Level action vector area division: The rated speed is divided into segments according to the number of levels of the inverter output phase voltage. The number of segments M is expressed as Where N is the maximum output level of the inverter phase voltage; 2) Level action area: according to the given speed n * Determine the inverter output level and obtain the mth level action area where the current voltage vector is located. m is expressed as Where n nom is the rated speed of the motor, round is the rounding function, for the mth level action area, the voltage vector acts on this area to output 2m+1 level; 3) According to the stator flux angle θ s Determine the basic sector number, the formula is as follows: In the formula, ceil is the upward rounding function; 4) Determine the sub-sector number j according to the current level action area m, and the determination formula is as follows:

4. The general method for determining the optimal switching vector in a direct torque control system powered by any multi-level inverter according to claim 1, characterized in that: In the relative increment determination link at time k, the torque control variable τ, the flux control variable v and the basic sector number i are input, and the relative increments Δx, Δy and Δz of the voltage vector in the abc phase relative to time k-1 are output.

5. The general method for determining the optimal switching vector in a direct torque control system powered by any multi-level inverter according to claim 1, characterized in that: In the calculation phase of the actual increment at time k, the relative increments Δx, Δy, Δz of the voltage vector at time k-1 on the abc phase and the actual increment Δx of the vector origin at time k on the abc phase obtained in the amplitude limiting generation phase are input. k , Δy k , Δz k The limit value [X min (k),X max (k)], [Y min (k),Y max (k)] and [Z min (k),Z max (k)], calculate the increment Δx of the vector relative to the origin on the abc phase k , Δy k and Δz k ; The calculation formula used is as follows: In the formula, Δx k-1 , Δy k-1 and Δz k-1 They are the actual increments of the vector origin at time k-1 on the abc phases respectively.

6. The general method for determining the optimal switching vector in any multi-level inverter powered direct torque control system according to claim 1 or 5, characterized in that: Δx obtained in the limit generation link k , Δy k , Δz k The limit value [X min (k),X max (k)], [Y min (k),Y max (k)] and [Z min (k),Z max (k)] is: Based on the sector number ij and the current level action area m, the amplitude limit of each component in the sub-sector in the three-phase stationary coordinate system is obtained, as shown in the following table: Based on the above table, we can get Δx k , Δy k , Δz k The limit value [X min (k),X max (k)], [Y min (k),Y max (k)] and [Z min (k),Z max (k)].

7. The general method for determining the optimal switching vector in a direct torque control system powered by any multi-level inverter according to claim 1, characterized in that: The optimal voltage vector determination link at time k is to input the increment Δx relative to the vector origin on the abc phase. k , Δy k and Δz k and the optimal origin vector (x0, y0, z0), output the optimal switch vector (x k ,y k ,z k ), the calculation formula used is as follows:

8. The general method for determining the optimal switching vector in any multi-level inverter powered direct torque control system according to claim 1 or 7, characterized in that: The optimal origin vector (x0, y0, z0) is obtained as follows: 1) For an N-level inverter, there are N origin vectors in the voltage vector, and the optimal origin vector needs to be selected in each step; first substitute the origin vector set into the boundary constraints to obtain a new origin vector set, where the constraints are 2) In order to further select the optimal origin vector, constraints are set in combination with the characteristics of the multilevel inverter topology. Here, the principle of minimum common-mode voltage is used as the constraint, and the origin vector plus the increment Δx relative to the vector origin on the abc phase k , Δy k , Δz k It is the actual voltage vector. The sum of the amplitudes of the three phases abc is proportional to the common mode voltage. Let us assume a function f(x,y,z) and substitute the origin vector into it to get f(x0,y0,z0)=(x0+Δx k ) 2 +(y0+Δy k ) 2 +(z0+Δz k ) 2 。 9. The general method for determining the optimal switching vector in a direct torque control system powered by any multi-level inverter according to claim 1, characterized in that: The method is applied to a direct torque control system powered by a multi-level inverter, comprising an input voltage module, a multi-level inverter, a central processing unit, a bus voltage sampling circuit, a capacitor voltage sampling circuit, a drive circuit, a phase current sampling circuit, and an encoder circuit; wherein, The input voltage module uses AC power or DC power; The switch tube of the multi-level inverter adopts an insulated gate bipolar transistor or a metal oxide semiconductor field effect transistor; The bus voltage sampling circuit is composed of a signal sampling circuit and a conditioning circuit. The signal sampling circuit selects the Hall voltage sampling or the resistor voltage division sampling mode. The conditioning circuit is composed of an operational amplifier circuit and is designed according to the input signal bandwidth and the requirements of the subsequent input. The output analog signal of the bus voltage sampling circuit is sent to the central processor. The capacitor voltage sampling circuit selects the same structure as the bus voltage sampling circuit, or for multi-level topology, adopts a voltage-frequency converter to collect capacitor voltage signals. At this time, the output digital signal of the capacitor voltage sampling circuit requires the central controller to use a counter to count and convert the digital signal to obtain a corresponding analog signal; The phase current sampling circuit is composed of a Hall current sensor and an operational amplifier conditioning circuit, and the output analog signal is sent to the central processing unit; The encoder circuit uses a photoelectric encoder to generate pulses and send them to the central processor to obtain motor speed information or motor position information; The central processing unit adopts a digital processor DSP, a field programmable gate array FPGA or a micro control unit MCU as the control core. The control core adopts a single-core structure or a single-master-multiple-slave structure according to the resources occupied by the processed signals; the central processing unit combines the signals sent by each part with the method described in claim 1, 2, 4, 5 or 7 to construct a multi-level direct torque control, and finally outputs a switching signal for driving each switching power device of the multi-level inverter, and generates a driving signal for directly controlling the action of the inverter power device through a driving circuit to achieve control of the speed regulation of the AC motor.

10. A computer-readable storage medium having stored thereon computer program instructions that can be executed by a processor, and when the processor executes the computer program instructions, the method steps according to any one of claims 1 to 8 can be implemented.

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