General determination method of optimal switching vector in any multi-level inverter-fed direct torque control system

Abstract

The present application relates to a kind of optimal switching vector universal determination method in arbitrary multi-level inverter power supply direct torque control system, belong to multi-level inverter control field.The method is determined by sector judgment, level effect area, limiting amplitude generation, k time relative increment determination, k time actual increment calculation, optimal origin vector determination and k time optimal voltage vector determination link section constitute.The present application can be applicable to the direct torque control system of arbitrary multi-level circuit topology power supply, improves the optimal switching vector determination speed of constructing complex multi-level circuit;The present application can also add specific multi-level circuit topology constraint condition according to the optimal switching vector set determined, and the optimal switching vector of the output of specific multi-level circuit is quickly generated.

Description

Technical Field

[0001] This invention belongs to the field of multilevel inverter control, specifically relating to a general method for determining the optimal switching vector in a direct torque control system for power supply of any multilevel inverter. Background Technology

[0002] Direct torque control (DTC) utilizes a constructed optimal switching vector table to output the optimal voltage vector, directly and rapidly controlling torque and flux linkage to achieve efficient motor control. It offers advantages such as fast dynamic response and strong parameter robustness. In traditional two-level converters, with only eight voltage vectors, it is easy to construct an optimal switching vector table, but this table is relatively simple, leading to large torque current ripple.

[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 number of output voltage vectors also increases significantly. The optimal switching vector table that needs to be constructed must consider many comprehensive factors, resulting in a very large optimal switching vector table. Therefore, 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 this invention is to provide a general method for determining the optimal switching vector in an arbitrary multilevel inverter power supply direct torque control system in order to quickly construct a direct torque strategy for multilevel inverter power supply.

[0005] To achieve the above objectives, the technical solution of this invention is: a general method for determining the optimal switching vector in a direct torque control system for arbitrary multilevel inverter power supply, comprising the following steps: sector judgment, level action area determination, amplitude limiting 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 linkage control variable φ, and stator flux linkage argument θ. s Given rotational speed n * Based on the sector determination step, the basic sector number i and sub-sector number j are output; based on the relative increment determination step at time k, the relative increments Δx, Δy, and Δz of the voltage vector at time k-1 on phases abc are output; based on the actual increment calculation step at time k, the increment Δx of the relative vector origin on phases abc 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 from the limiting generation stage, where the level action region number m used in the limiting generation stage is generated by the level action region determination stage; based on the optimal origin vector determination stage, the optimal origin vector (x0, y0, z0) is output; finally, based on the optimal voltage vector determination stage at time k, the optimal switching vector (x0, y0, z0) is output. 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 argument θ. s and a given rotational speed n * Output the basic sector number i and the sub-sector number j.

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

[0008] 1) Level-based vector region division: The rated speed is segmented according to the number of levels of the inverter output phase voltage. The number of segments, M, is represented as...

[0009]

[0010] In the formula, N is the maximum number of output voltage levels of the inverter phase;

[0011] 2) Level operating range: based on the given rotational speed n * Determine the inverter output level to obtain the m-th level's active region where the current voltage vector is located, where m is denoted as...

[0012]

[0013] In the formula, n nom The rated speed of the motor is , and round is the floor function. For the m-th level operating region, the voltage vector acts on the region and outputs a 2m+1 level.

[0014] 3) Based on the stator flux linkage argument θ s The basic sector number is determined using the following formula:

[0015]

[0016] In the formula, ceil is the floor function;

[0017] 4) Determine the sub-sector number j based on the current level operating region m, using the following formula:

[0018]

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

[0020] In one embodiment of the present invention, the actual increment calculation step at time k is input to the relative increments Δx, Δy, and Δz of the voltage vector at time k-1 on the abc phase, and the actual increment Δx of the relative vector origin at time k on the abc phase obtained from the limiting generation step. 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 in phase abc. 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 These represent the actual increments of the relative vector origin on the abc phase at time k-1.

[0023] In one embodiment of the present invention, the Δx obtained in the amplitude limiting generation stage... 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 The method of (k)] is:

[0024] Based on the sector number ij and the current level operating region m, the amplitude limiting of each component within the sub-sector in the three-phase stationary coordinate system is obtained, as shown in the table below:

[0025] Subsectors X clip Y clip Z clip 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 table above, Δx can be obtained. 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, the optimal voltage vector determination step at time k is input with the increment Δx relative to the vector origin on phases abc. k Δy k and Δz k Given the optimal origin vector (x0, y0, z0), output the optimal switching vector (x0, y0, z0) at time k. 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, the voltage vector has N origin vectors, and the optimal origin vector needs to be selected in each step. First, substitute the set of origin vectors into the boundary constraints to obtain a new set of origin vectors. Here, the constraints are:

[0031]

[0032] 2) To further select the optimal origin vector, constraints are set based on the characteristics of the multilevel inverter topology. Here, the principle of minimizing the common-mode voltage is used as the constraint, and the origin vector is added to the increment Δx of the relative vector origin on phases abc. k Δy k Δz k This refers to the actual voltage vector. The sum of the amplitudes of the three phases a, b, and c is proportional to the common-mode voltage. Let there be a function f(x,y,z), and substituting the origin vector into it yields...

[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 multilevel inverter, including an input voltage module, a multilevel 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 either AC or DC power.

[0036] The switching transistors of the multilevel inverter are insulated gate bipolar transistors or metal-oxide-semiconductor field-effect transistors;

[0037] The bus voltage sampling circuit consists of a signal sampling circuit and a conditioning circuit. The signal sampling circuit uses either Hall voltage sampling or resistor divider sampling, and the conditioning circuit is composed of an operational amplifier circuit, 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.

[0038] The capacitor voltage sampling circuit can be selected with the same structure as the bus voltage sampling circuit, or for multi-level topologies, a voltage-to-frequency converter can be used to collect the capacitor voltage signal. In this case, the output digital signal of the capacitor voltage sampling circuit needs to be counted and converted by the central controller using a counter to obtain the 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 processing unit to obtain motor speed information or motor position information;

[0041] The central processing unit (CPU) uses a digital signal processor (DSP), field-programmable gate array (FPGA), or microcontroller unit (MCU) as the control core. The control core adopts a single-core structure or a single-master-multiple-slave structure depending on the resources occupied by the processed signals. The CPU combines the signals sent from various parts as described above to construct multi-level direct torque control. Finally, it outputs the switching signals that drive the switching power devices of the multi-level inverter. The drive circuit generates drive signals that directly control the operation of the inverter power devices to achieve speed control of the AC motor.

[0042] The present invention also provides a computer-readable storage medium having stored thereon computer program instructions that can be executed by a processor, wherein when the processor executes the computer program instructions, it can implement the steps of the method described above.

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

[0044] (1) Compared with existing optimal switching vector determination methods, this invention can be applied to direct torque control systems powered by arbitrary multilevel circuit topologies, and improves the speed of constructing optimal switching vector determination for complex multilevel circuits.

[0045] (2) Based on the determined optimal switch vector set, the present invention can add specific multilevel circuit topology constraints to quickly generate the optimal switch vector for the output of the proprietary multilevel circuit. Attached Figure Description

[0046] Figure 1 This is a schematic flowchart 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 driving system for implementing the present invention.

[0048] Figure 3 Divide the vector regions for different voltage levels.

[0049] Figure 4 To divide into sectors. Detailed Implementation

[0050] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings.

[0051] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0052] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0053] This invention provides a general method for determining the optimal switching vector in a direct torque control system for arbitrary multilevel inverters. The method comprises sector determination, level action region determination, amplitude limiting 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. Inputs include torque control variable τ, flux linkage control variable φ, and stator flux linkage argument θ. s Given rotational speed n *Based on the sector determination step, the basic sector number i and sub-sector number j are output; based on the relative increment determination step at time k, the relative increments Δx, Δy, and Δz of the voltage vector at time k-1 on phases abc are output; based on the actual increment calculation step at time k, the increment Δx of the relative vector origin on phases abc 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 from the limiting generation stage, where the level action region number m used in the limiting generation stage is generated by the level action region determination stage; based on the optimal origin vector determination stage, the optimal origin vector (x0, y0, z0) is output; finally, based on the optimal voltage vector determination stage at time k, the optimal switching vector (x0, y0, z0) is output. k ,y k ,z k ).

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

[0055] The specific method for determining the optimal switching vector in this invention is as follows: Figure 1 As shown, it consists of the following steps: sector judgment, level action area determination, amplitude limiting 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 takes into account the torque control variable τ, the flux linkage control variable φ, and the stator flux linkage argument θ. s Given rotational speed n * The optimal switching vector (x) is output using the general determination method proposed in this invention. k ,y k ,z k In this method, based on the sector determination step, the basic sector number i and the sub-sector number j are output; based on the determination step of the relative increment at time k, the relative increments Δx, Δy, and Δz of the voltage vector at time k-1 on the abc phase are output; based on the actual increment calculation step at time k, the increment Δx of the relative 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 limiting value [X] min (k),X max (k)]、[Y min (k),Y max (k)] and [Z min (k),Z max [k] is obtained from the limiting generation stage, where the level action region number m used by the limiting stage is generated by the level action region determination stage; the optimal origin vector is output by the optimal origin vector determination stage (x0, y0, z0); finally, the optimal switching vector (x0, y0, z0) is output by the voltage vector determination stage at time k. k ,y k ,z k ).

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

[0058] (1) Set the stator flux linkage argument θ s and given rotational speed n * The data is sent to the sector determination stage, which outputs the basic sector number i and the sub-sector number j.

[0059] (2) The torque control variable τ, flux linkage control variable φ, and basic sector number i are sent to the relative increment lookup table at time k. The relative increments Δx, Δy, and Δz of the voltage vector in phases abc at time k-1 are output. The table of relative displacements used is shown in Table 1. Among them, τ = 0 indicates a decrease in electromagnetic torque, and τ = 1 indicates an increase in electromagnetic torque; φ = 0 indicates a decrease in flux linkage amplitude, and φ = 1 indicates an increase in flux linkage amplitude.

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

[0061]

[0062] (3) The relative increments (Δx, Δy, Δz) of the voltage vector at time k-1 in phase abc and the actual increments (Δx, Δy, Δz) of the relative vector origin at time k in phase abc. 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 sent to the actual increment calculation stage at time k to calculate the increment Δx of the vector relative to the origin in phase abc. 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 These represent the actual increments of the relative vector origin on the abc phase at time k-1.

[0065] (4) The increment Δx of the relative vector origin on phase abc k Δy k and Δz k The optimal origin vector (x0, y0, z0) is fed into the optimal switch vector calculation stage at time k, and the optimal switch vector at time k is output (x0, y0, z0). k ,y k ,z k The calculation formula used is as follows:

[0066]

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

[0068] (1.1) Level-of-Speed ​​Vector Region Division. The rated speed is segmented based on the number of levels of the inverter output phase voltage. The number of segments M can be expressed as:

[0069]

[0070] In the formula, N represents the maximum number of output voltage levels of the inverter phase.

[0071] (1.2) Level operating region. Based on the given rotational speed n... * Determine the inverter output level, and then obtain the m-th level's effective region where the current voltage vector is located. m can be represented as...

[0072]

[0073] In the formula, n nom is the rated speed of the motor, and round is the floor function. For the m-th level operating region, the voltage vector applied in this region can output a 2m+1 level.

[0074] (1.3) Based on the magnetic flux linkage argument θ s The basic sector number is determined using the following formula:

[0075]

[0076] In the formula, ceil is the floor function.

[0077] (1.4) Determine the sub-sector number j based on the current level operating area m, using the following formula:

[0078]

[0079] In step (3), the actual increment Δx of the relative vector origin at time k on the abc phase 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 The specific details of (k) 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. The sector number ij and the current level operating area m are required.

[0081] Table 2. Amplitude limits of each component within a sub-sector in the three-phase stationary coordinate system.

[0082]

[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 from them in each step. First, substitute the set of origin vectors into the boundary constraints to obtain a new set of origin vectors. Here, the constraints are:

[0086]

[0087] (4.2) To further select the optimal origin vector, constraints can be set based on the characteristics of the multilevel inverter topology itself. Here, the principle of minimizing the common-mode voltage is used as the constraint, and the origin vector is added to the increment (Δx) on phases abc obtained in step (3). k ,Δy k ,Δz k The sum of the amplitudes of the three phases a, b, and c is proportional to the common-mode voltage, so it is used as a constraint. Here, we define a function f(x,y,z), and substitute the origin vector into it to obtain...

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

[0089] Examples of hardware structures for implementing the present invention's driving system Figure 2 As shown, a direct torque control system powered by a multilevel inverter includes an input voltage (which can be either AC or DC power), a multilevel 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, and a host computer.

[0090] The switching transistors of a multiphase inverter can be insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs). The central processing unit (CPU) can use a digital signal processor (DSP), a field-programmable gate array (FPGA), or a microcontroller unit (MCU) as its control core. The control core can adopt a single-core or single-master-multiple-slave structure depending on the resources required for the processed signals. The bus voltage sampling circuit generally consists of a signal sampling circuit and a conditioning circuit. The signal sampling circuit can use Hall effect voltage sampling or resistor divider sampling, while the conditioning circuit is composed of operational amplifiers (op-amps) and can be designed according to the input signal bandwidth and subsequent input requirements. The output analog signal of the bus voltage sampling circuit is sent to the CPU. The capacitor voltage sampling circuit can have the same structure as the bus voltage sampling circuit. However, for some multi-level topologies requiring sampling of multiple capacitor voltages, a voltage-to-frequency converter can be used to acquire the capacitor voltage signal. In this case, the output of the capacitor voltage sampling circuit is a digital signal, which the CPU needs to convert using a counter to obtain the corresponding analog signal. The phase current sampling circuit can be composed of a Hall effect current sensor and an operational amplifier conditioning circuit, with the output analog signal sent to the CPU. The encoder circuit can use a photoelectric encoder to generate pulses and send them to the central processing unit to obtain motor speed information or motor position information. The central processing unit combines the signals from various parts with the optimal switching vector general determination method proposed in this invention to construct multi-level direct torque control, and finally outputs the switching signals driving each switching power device of the multi-level inverter. The drive circuit generates drive signals that directly control the operation of the inverter power devices to achieve speed control of the AC motor.

[0091] The basic principle is described as follows:

[0092] Level operating region division. The rated speed is segmented based on the number of levels of the inverter's output phase voltage. For an N-level inverter, the number of segments M can be determined based on the rated speed, where M can be expressed as...

[0093]

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

[0095] Sector division. For any voltage vector diagram with a voltage level of 3 or higher, it is uniformly divided into 12 basic sectors. Using the positive half-axis of the a-axis as the baseline, rotating counter-clockwise, these are designated as basic sector 1, basic sector 2, through basic sector 12, each occupying a 30° sector area. Based on different voltage levels, the basic sectors are further subdivided. Figure 4 The diagram shows the sub-sector divisions within the first basic sector. For the three-level vector action region, no division is made, and the entire action region remains 12 regions. For the five-level vector action region, each basic sector is divided into two sub-sectors, resulting in 24 vector action regions for the entire five-level action region. Sub-sectors are named by adding the sub-sector number to the basic sector name; for example, the first partition of the first sector is called sector 1.1. For the N (N = 3, 5, 7...) level action region, each basic sector is divided into M-1 equal parts, resulting in M ​​sub-sectors for each basic sector. Therefore, the entire N-level action region can be divided into 12M vector action regions.

[0096] The limiting 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 The acquisition of (k)]. For the basic sector, the limiting of each component in the three-phase stationary coordinate system is shown in Table 3. For the N-level case with three or more levels, each basic sector is further divided into M sub-sectors, and the limiting value of each component in each sub-sector is obtained according to the limiting law of the basic sector and combined with the sector division, so as to obtain the limiting of each component in the sub-sector in the three-phase stationary coordinate system, as shown in Table 3.

[0097] Table 3. Amplitude limits of each component within the basic sector in the three-phase stationary coordinate system.

[0098]

[0099]

[0100] The following analysis examines the limiting conditions of sub-sectors within the basic sector in Table 3. For an N-level inverter, each basic sector is divided into m segments. Within the first basic sector, the limiting conditions for X, Y, and Z of the 1.j (j = 1, 2, ..., m) sub-sectors are [-2 -j, -j], [m + 1, m + 2], and [j, j + 1], respectively. Taking a five-level inverter as an example, the number of segments in the five-level inverter is m = 2, dividing each basic sector into two segments. Therefore, within the first basic sector, for the j-th sub-sector (j = 1), the limiting conditions for X are [-3, -1], Y is [3, 4], and Z is [1, 2]. For the 1.2 sub-sector (j = 2), the limiting conditions for X are [-4, -2], Y is [3, 4], and Z is [2, 3].

[0101] The present invention also provides a computer-readable storage medium having stored thereon computer program instructions that can be executed by a processor, wherein when the processor executes the computer program instructions, it can implement the steps of the method described above.

[0102] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0103] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0104] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0105] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A general method for determining the optimal switching vector in a direct torque control system for an arbitrary multilevel inverter, characterized in that, It consists of several steps: sector determination, level operation area determination, amplitude limiting 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 linkage control variable φ, and stator flux linkage argument θ. s Given rotational speed n * Based on the sector determination step, the basic sector number i and sub-sector number j are output; based on the relative increment determination step at time k, the relative increments Δx, Δy, and Δz of the voltage vector at time k-1 on phases a, b, and c are output; based on the actual increment calculation step at time k, the increment Δx of the relative vector origin on phases a, b, and c 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 from the limiting generation stage, where the level action region number m used in the limiting generation stage is generated by the level action region determination stage; based on the optimal origin vector determination stage, the optimal origin vector (x0, y0, z0) is output; finally, based on the optimal voltage vector determination stage at time k, the optimal switching vector (x0, y0, z0) is output. k ,y k ,z k ); The sector determination process is implemented as follows: 1) Level-based vector region division: The rated speed is segmented according to the number of levels of the inverter output phase voltage. The number of segments, M, is represented as... In the formula, N is the maximum number of output voltage levels of the inverter phase; 2) Level operating range: based on the given rotational speed n * Determine the inverter output level to obtain the m-th level's active region where the current voltage vector is located, where m is denoted as... In the formula, n nom The rated speed of the motor is , and round is the floor function. For the m-th level operating region, the voltage vector acts on the region and outputs a 2m+1 level. 3) Based on the stator flux linkage argument θ s The basic sector number is determined using the following formula: In the formula, ceil is the floor function; 4) Determine the sub-sector number j based on the current level operating region m, using the following formula:

2. The general method for determining the optimal switching vector in a direct torque control system for arbitrary multilevel inverter power supply according to claim 1, characterized in that, The sector determination process is based on the input stator flux linkage argument θ. s and a given rotational speed n * Output the basic sector number i and the sub-sector number j.

3. The general method for determining the optimal switching vector in a direct torque control system for arbitrary multilevel inverter power supply according to claim 1, characterized in that, The relative increment determination step at time k takes into account the torque control variable τ, the flux linkage control variable φ, and the basic sector number i, and outputs the relative increments Δx, Δy, and Δz of the voltage vector at time k-1 in phases a, b, and c.

4. The general method for determining the optimal switching vector in a direct torque control system for arbitrary multilevel inverter power supply according to claim 1, characterized in that, In the actual increment calculation stage at time k, the relative increments Δx, Δy, and Δz of the voltage vector at time k-1 in phases a, b, and c are input, along with the actual increment Δx of the relative vector origin at time k in phases a, b, and c obtained from the limiting generation stage. 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 in phases a, b, and c. 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 These represent the actual increments of the relative vector origin at time k-1 in phases a, b, and c, respectively.

5. The general method for determining the optimal switching vector in a direct torque control system for any multilevel inverter power supply according to claim 1 or 4, characterized in that, Δx obtained in the amplitude limiting generation process 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 The method of (k)] is: Based on the sector number ij and the current level operating region m, the amplitude limiting of each component within the sub-sector in the three-phase stationary coordinate system is obtained, as shown in the table below: Based on the table above, Δx can be obtained. 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)].

6. The general method for determining the optimal switching vector in a direct torque control system for arbitrary multilevel inverter power supply according to claim 1, characterized in that, The optimal voltage vector determination process at time k inputs the increment Δx relative to the vector origin on phases a, b, and c. k Δy k and Δz k Given the optimal origin vector (x0, y0, z0), output the optimal switching vector (x0, y0, z0) at time k. k ,y k ,z k The calculation formula used is as follows:

7. The general method for determining the optimal switching vector in a direct torque control system for any multilevel inverter power supply according to claim 1 or 6, characterized in that, The optimal origin vector (x0, y0, z0) is obtained as follows: 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 set of origin vectors into the boundary constraints to obtain a new set of origin vectors. Here, the constraints are: 2) To further select the optimal origin vector, constraints are set based on the characteristics of the multilevel inverter topology. Here, the principle of minimizing the common-mode voltage is used as the constraint, and the origin vector is added to the increment Δx relative to the origin on phases a, b, and c. k Δy k Δz k This refers to the actual voltage vector; the sum of the amplitudes of phases a, b, and c is proportional to the common-mode voltage. Let there be a function f(x,y,z), and substituting the origin vector into it yields... f(x0,y0,z0)=(x0+Δx k ) 2 +(y0+Δy k ) 2 +(z0+Δz k ) 2 .

8. The general method for determining the optimal switching vector in a direct torque control system for arbitrary multilevel inverter power supply according to claim 1, characterized in that, The method is applied to a direct torque control system powered by a multi-level inverter, including 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 either AC or DC power. The switching transistors of the multilevel inverter are insulated gate bipolar transistors or metal-oxide-semiconductor field-effect transistors; The bus voltage sampling circuit consists of a signal sampling circuit and a conditioning circuit. The signal sampling circuit uses either Hall voltage sampling or resistor divider sampling, and the conditioning circuit is composed of an operational amplifier circuit, 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 be selected with the same structure as the bus voltage sampling circuit, or for multi-level topologies, a voltage-to-frequency converter can be used to collect the capacitor voltage signal. In this case, the output digital signal of the capacitor voltage sampling circuit needs to be counted and converted by the central controller using a counter to obtain the 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 processing unit to obtain motor speed information or motor position information; The central processing unit (CPU) uses a digital signal processor (DSP), field-programmable gate array (FPGA), or microcontroller unit (MCU) as the control core. The control core adopts a single-core structure or a single-master-multiple-slave structure depending on the resources occupied by the processed signals. The CPU combines the signals sent from each part with the methods described in claims 1, 2, 3, 4, or 6 to construct multi-level direct torque control. Finally, it outputs switching signals to drive the switching power devices of the multi-level inverter. The drive circuit generates drive signals that directly control the operation of the inverter power devices to achieve speed control of the AC motor.

9. A computer-readable storage medium having stored thereon computer program instructions executable by a processor, wherein when the processor executes the computer program instructions, it is able to implement the steps of the method as described in any one of claims 1-7.

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