Frequency conversion control method and device for current sampling

Abstract

The invention belongs to the field of motor control, and discloses a frequency conversion control method and device for current sampling. The method comprises the following steps: acquiring the current rotating speed of the direct current motor, the current carrier period duration and a plurality of components of the carrier period; determining a vector angle and a vector modulus length of the current control voltage according to the current rotating speed; determining the component duration of each component in the current carrier period duration according to the vector angle, the vector modulus length, the preset maximum included angle, the current carrier period duration and the standard component modulus length; based on a pre-stored sampling duration threshold and the plurality of component durations, determining a sampling method of the direct current motor in the current carrier period, and judging whether the duration of the current carrier period is adjusted or not; according to a sampling method, single / double-phase current of the direct current motor is obtained, three-phase current reconstruction is carried out through the Kirchhoff's law, and target three-phase current of the direct current motor is obtained. By adopting the method, the obtained three-phase current of the direct current motor can be more accurate.

Description

Technical Field

[0001] The present application relates to the technical field of motor control, and in particular to a variable frequency control method and device for current sampling. Background Art

[0002] During the operation control of the DC motor, the precise sampling of the three-phase current of the DC motor is very demanding. In the prior art, there are two methods for sampling the three-phase current: dual-resistance sampling and single-resistance sampling. However, the dual-resistance sampling method is easy to implement but has some limitations on the extreme performance of the motor. The single-resistance sampling method has a simple circuit but insufficient sampling time, resulting in complex software processing logic. Therefore, there is an urgent need for a method for sampling the current of the motor. Summary of the invention

[0003] Based on this, it is necessary to provide a variable frequency control method and device for current sampling to address the above technical problems.

[0004] In a first aspect, a variable frequency control method for current sampling is provided, the method being applied to a sampling hardware circuit, the method comprising: Obtain the current speed of the DC motor, the current carrier cycle duration, and multiple components of the carrier cycle; Determining the vector angle and vector modulus of the current control voltage according to the current rotation speed; Determine the component duration of each component within the current carrier cycle duration according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus; Based on a pre-stored sampling duration threshold and a plurality of component durations, determining a sampling method of the DC motor within the current carrier cycle, and determining whether to adjust the current carrier cycle duration according to the sampling method; According to the sampling method, the single-phase current and / or two-phase current of the DC motor collected by the sampling hardware circuit is obtained, and the three-phase current is reconstructed according to Kirchhoff's law to obtain the target three-phase current of the DC motor.

[0005] As an optional implementation manner, determining the vector angle and vector modulus of the current control voltage according to the current speed includes: In the pre-stored correspondence between the control voltage and the rotation speed of the DC motor, query the current control voltage corresponding to the current rotation speed; The current control voltage is mapped to a space vector pulse width modulation diagram to obtain a vector angle and a vector modulus of the current control voltage.

[0006] As an optional implementation manner, determining the component duration of each component within the current carrier cycle duration according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration, and the pre-stored standard component modulus, includes: According to the vector modulus, the vector angle and the preset maximum angle, the current control voltage is vector-decomposed into two side components to obtain a first modulus of the first component and a second modulus of the second component, and the preset maximum angle is the maximum angle between the first component and the second component; The first component duration is determined by multiplying the ratio of the first modulus length to the pre-stored standard component modulus length by the product of the current carrier cycle duration; The ratio of the second modulus length to the pre-stored standard component modulus length is multiplied by the product of the current carrier cycle duration to determine the second component duration; The component durations corresponding to the remaining components are determined as the ratio of the difference between the current carrier cycle duration and the first component duration and the second component duration to the number of remaining components.

[0007] As an optional implementation manner, the multiple components of the current carrier cycle include a first component, a second component, and a third component, and the sampling method of the DC motor in the current carrier cycle is determined based on a pre-stored sampling duration threshold and a plurality of component durations, and whether to adjust the current carrier cycle duration according to the sampling method, including: If the pre-stored sampling duration threshold is less than the first component duration of the first component and the second component duration of the second component, and is greater than or equal to the third component duration of the third component, it is determined that the sampling method of the DC motor in the current carrier cycle is single-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient, the first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when the DC motor is controlled in this way, and the third component is a component of the two-phase current output by the sampling hardware circuit when the DC motor is controlled in this way; If the sampling time threshold is less than the first component time and the second component time, and less than the third component time, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling and single-resistance sampling; If the sampling duration threshold is greater than or equal to the first component duration and the second component duration, and less than the third component duration, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient.

[0008] As an optional implementation, the sampling method is used to obtain the single-phase current and / or two-phase current of the DC motor collected by the sampling hardware circuit, and the three-phase current is reconstructed according to Kirchhoff's law to obtain the target three-phase current of the DC motor, including: When the sampling method is single-resistance sampling, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components by Kirchhoff's law, another single-phase current in the three-phase current is determined, and the three single-phase currents are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is dual-resistance sampling, the Kirchhoff's law is used to determine another single-phase current in the three-phase current for a two-phase current collected from the sampling hardware circuit, and the two-phase current and the single-phase current are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is the single-resistance sampling and the dual-resistance sampling, Kirchhoff's law is used to collect two single-phase currents and one two-phase current of the sampling hardware circuit for adjacent components, determine the other single-phase current in each of the two sets of three-phase currents, and average the two sets of reconstructed three-phase currents to obtain the target three-phase current of the DC motor after reconstruction.

[0009] In a second aspect, a variable frequency control device for current sampling is provided, the device is applied to a sampling hardware circuit, and the device comprises: An acquisition module is used to acquire the current speed of the DC motor, the current carrier cycle duration, and multiple components of the carrier cycle; A first determination module, used to determine the vector angle and vector modulus of the current control voltage according to the current rotation speed; A second determination module is used to determine the component duration of each component within the current carrier cycle duration according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus; A third determination module is used to determine a sampling method of the DC motor in the current carrier cycle based on a pre-stored sampling duration threshold and a plurality of component durations, and to determine whether to adjust the current carrier cycle duration according to the sampling method; The reconstruction module is used to obtain the single-phase current and / or two-phase current of the DC motor collected by the sampling hardware circuit according to the sampling method, and reconstruct the three-phase current through Kirchhoff's law to obtain the target three-phase current of the DC motor.

[0010] As an optional implementation manner, the first determining module is specifically configured to: In the pre-stored correspondence between the control voltage and the rotation speed of the DC motor, query the current control voltage corresponding to the current rotation speed; The current control voltage is mapped to a space vector pulse width modulation diagram to obtain a vector angle and a vector modulus of the current control voltage.

[0011] As an optional implementation manner, the second determining module is specifically configured to: According to the vector modulus, the vector angle and the preset maximum angle, the current control voltage is vector-decomposed into two side components to obtain a first modulus of the first component and a second modulus of the second component, and the preset maximum angle is the maximum angle between the first component and the second component; The first component duration is determined by multiplying the ratio of the first modulus length to the pre-stored standard component modulus length by the product of the current carrier cycle duration; The ratio of the second modulus length to the pre-stored standard component modulus length is multiplied by the product of the current carrier cycle duration to determine the second component duration; The component durations corresponding to the remaining components are determined as the ratio of the difference between the current carrier cycle duration and the first component duration and the second component duration to the number of remaining components.

[0012] As an optional implementation manner, the multiple components of the current carrier cycle include a first component, a second component, and a third component, and the third determination module is specifically configured to: If the pre-stored sampling duration threshold is less than the first component duration of the first component and the second component duration of the second component, and is greater than or equal to the third component duration of the third component, it is determined that the sampling method of the DC motor in the current carrier cycle is single-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient, the first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when the DC motor is controlled in this way, and the third component is a component of the two-phase current output by the sampling hardware circuit when the DC motor is controlled in this way; If the sampling time threshold is less than the first component time and the second component time, and less than the third component time, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling and single-resistance sampling; If the sampling duration threshold is greater than or equal to the first component duration and the second component duration, and less than the third component duration, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient.

[0013] As an optional implementation, the reconstruction module is specifically used to: When the sampling method is single-resistance sampling, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components by Kirchhoff's law, another single-phase current in the three-phase current is determined, and the three single-phase currents are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is dual-resistance sampling, the Kirchhoff's law is used to determine another single-phase current in the three-phase current for a two-phase current collected from the sampling hardware circuit, and the two-phase current and the single-phase current are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is the single-resistance sampling and the dual-resistance sampling, Kirchhoff's law is used to collect two single-phase currents and one two-phase current of the sampling hardware circuit for adjacent components, determine the other single-phase current in the two sets of three-phase currents, and average the two sets of reconstructed three-phase currents to obtain the target three-phase current of the DC motor after reconstruction.

[0014] In a third aspect, a variable frequency control system for current sampling is provided, and the variable frequency control system for current sampling comprises: the variable frequency control method for current sampling as described in the first aspect and the variable frequency control device for current sampling as described in the second aspect.

[0015] In a fourth aspect, a computer device is provided, comprising a memory and a processor, wherein the memory stores a computer program executable on the processor, and when the processor executes the computer program, the method steps described in the first aspect are implemented.

[0016] In a fifth aspect, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the method steps described in the first aspect are implemented.

[0017] The present application provides a variable frequency control method for current sampling, and the technical solution provided by the embodiment of the present application brings at least the following beneficial effects: obtaining the current speed of the DC motor, the current carrier cycle duration, and multiple components of the carrier cycle; according to the current speed, determining the vector angle and vector modulus of the current control voltage; according to the vector angle, the vector modulus, the current carrier cycle duration, and the pre-stored standard component modulus, determining the component duration of each component within the current carrier cycle duration; based on the pre-stored sampling duration threshold and multiple component durations, determining the sampling method of the DC motor within the current carrier cycle, and judging whether to adjust the current carrier cycle duration according to the sampling method; according to the sampling method, collecting the single-phase current and / or two-phase current of the DC motor in the sampling hardware circuit, and reconstructing the three-phase current through Kirchhoff's law, to obtain the target three-phase current of the DC motor. In this way, based on the sampling hardware circuit, by judging whether the component duration of each component within the current carrier cycle duration meets the sampling duration of the DC motor, the corresponding sampling method is determined. The sampling method includes dual-resistance sampling and single-resistance sampling. The DC motor's extreme performance under the current control voltage is fully utilized, and the dual-resistance sampling and single-resistance sampling methods are integrated. The DC motor can maintain a good phase current sinusoidal degree under high and low speed extreme operating conditions to avoid the DC motor from losing steps, so as to maintain the smooth operation of the motor and make the sampling current more accurate. Different sampling methods are selected in a timely manner through the frequency conversion strategy. The three-phase current is reconstructed for the sampled current, and the final phase current value is calculated comprehensively, making the algorithm estimation result more credible and improving the reliability of the result without increasing the hardware cost.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A schematic diagram of the structure of a variable frequency control system for current sampling provided in an embodiment of the present application; Figure 2 A flow chart of a variable frequency control method for current sampling provided in an embodiment of the present application; Figure 3 A schematic diagram of a sampling hardware circuit provided in an embodiment of the present application; Figure 4 A schematic diagram of an equivalent circuit of a sampling hardware circuit provided in an embodiment of the present application; Figure 5 A space vector pulse width modulation diagram provided in an embodiment of the present application; Figure 6 A schematic diagram of vector decomposition of a control voltage provided in an embodiment of the present application; Figure 7 A vector decomposition diagram of another control voltage provided in an embodiment of the present application; Figure 8 A schematic diagram of the duration of a component within a carrier cycle provided in an embodiment of the present application; Fig. 9 A vector decomposition schematic diagram of a control voltage provided by an embodiment of the present application as a maximum vector voltage; Fig.10 A schematic diagram of an equivalent circuit of a single resistor sampling when a component acts according to an embodiment of the present application; Fig.11 A schematic diagram of an equivalent circuit of single resistor sampling when another component acts according to an embodiment of the present application; Fig.12 A schematic diagram of an equivalent circuit of dual-resistance sampling when a component acts according to an embodiment of the present application; Fig.13 A schematic diagram of the structure of a frequency conversion control device for current sampling provided in an embodiment of the present application; Fig.14 A schematic diagram of the structure of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0022] The variable frequency control method for current sampling provided in the embodiment of the present application can be applied to a variable frequency control system for current sampling. Figure 1 As shown, the variable frequency control system for current sampling includes a controller 101, a sampling hardware circuit 102 and a DC motor 103. The controller 101 is connected to the sampling hardware circuit 102 and the DC motor 103 respectively, and the sampling hardware circuit 102 is connected to the DC motor 103.

[0023] The controller 101 is used to obtain the current speed, the current carrier cycle duration and multiple components of the carrier cycle of the DC motor 103. According to the current speed, the vector angle and vector modulus of the current control voltage are determined. According to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus, the component duration of each component within the current carrier cycle duration is determined. Based on the pre-stored sampling duration threshold and multiple component durations, the sampling method of the DC motor 103 within the current carrier cycle is determined, and it is determined whether to adjust the current carrier cycle duration according to the sampling method. According to the sampling method, the single-phase current and / or two-phase current of the DC motor 103 collected by the sampling hardware circuit 102 is obtained, and the three-phase current is reconstructed by Kirchhoff's law to obtain the target three-phase current of the DC motor 103.

[0024] The sampling hardware circuit 102 is used to collect the three-phase current of the DC motor 103 and send the collected three-phase current to the controller 101 .

[0025] The DC motor 103 is used to operate according to the current control voltage output by the control 101.

[0026] The following will describe in detail a variable frequency control method for current sampling provided by an embodiment of the present application in conjunction with a specific implementation method. Figure 2 A flow chart of a variable frequency control method for current sampling provided in an embodiment of the present application, Figure 2 Applied to sampling hardware circuits, such as Figure 2 As shown, the specific steps are as follows: Step 201, obtaining the current speed of the DC motor, the current carrier cycle duration, and multiple components of the carrier cycle.

[0027] In implementation, during the operation control of the DC motor, the precise sampling of the three-phase current of the DC motor is very demanding. In the prior art, the sampling of the three-phase current is divided into two methods: dual resistor sampling and single resistor sampling. However, the dual resistor sampling method is easy to implement but has some limitations on the extreme performance of the motor. The single resistor sampling method has a simple circuit but insufficient sampling time, resulting in complex software processing logic. Therefore, a method for obtaining the three-phase current of the DC motor is needed to avoid the problem of limiting the duty cycle of the effective output signal due to the long sampling time during dual resistor sampling, thereby limiting the extreme performance of the motor when the DC motor is running at high speed. At the same time, it also avoids the problem that the DC motor cannot maintain the phase current sinusoidality well when the variable carrier cycle of the single resistor sampling is used when the DC motor is running at extremely low speed, resulting in the DC motor losing step. Therefore, the present application can adopt a method combining single resistor sampling and dual resistor sampling. Under the high and low speed extreme operating conditions of the motor, combined with the variable carrier cycle, the phase current of the DC motor can maintain a good sinusoidality, avoid the motor losing step, and at the same time, improve the extreme performance of the motor when running at high speed. Then, the current speed of the DC motor can be obtained first, and the subsequent steps can determine the current control voltage of the vector of the DC motor according to the current speed. The current control voltage of the vector is determined by the carrier cycle of the DC motor. The components in the carrier cycle are different, and the current direction of the current control voltage input to the DC motor is different, and the phase current of the DC motor collected is also different. Because different carrier cycles can contain different components. When different components act on the sampling hardware circuit, the corresponding phase current of the DC motor collected is different. When determining the sampling method of the DC motor through the sampling hardware circuit in the current carrier cycle, it is necessary to judge the various components and component durations in the current carrier cycle. Only in the subsequent steps can it be determined whether the corresponding collected current is single-phase current or two-phase current according to the various components in the current carrier cycle, and whether the component duration of the component meets the sampling duration of the corresponding sampling method. Among them, the single-phase current is collected by single-resistance sampling, and the two-phase current is collected by dual-resistance sampling. When the phase current of the DC motor is collected by the sampling hardware circuit, the phase current of the DC motor collected under the action of each component in the carrier cycle is fixed. That is to say, different components correspond to different sampling methods. When determining the sampling method of the DC motor in the current carrier cycle, it is necessary to first determine whether the component duration of the component meets the sampling duration. Only when it meets the duration can the phase current of the DC motor be collected according to the sampling method corresponding to the component. If the sampling duration is not met, the component duration can be increased by increasing the current carrier cycle duration so that the component duration can meet the sampling duration. Therefore, it is also necessary to obtain the current speed of the DC motor, the current carrier cycle duration, and multiple components of the carrier cycle in advance, and then the sampling method in the current carrier cycle can be determined and sampled according to the sampling method.

[0028] Figure 3A schematic diagram of a sampling hardware circuit provided in an embodiment of the present application. Figure 3 As shown, the U, V, and W phases of the DC motor are controlled by power switch tubes (IGBT) M1 and M4, M3 and M6, M5 and M2 respectively, where Ru of the U phase and Rv of the V phase are sampling resistors of the two phase currents, and Rbus is the sampling resistor of the bus current. Figure 4 for Figure 3 Simplified equivalent circuit diagram.

[0029] Step 202: Determine the vector angle and vector modulus of the current control voltage according to the current rotation speed.

[0030] In implementation, the magnitude of the vector modulus of the control voltage of the DC motor depends on the magnitude of the zero vector of the control voltage. The larger the modulus of the vector modulus, the shorter the duration of the zero vector, the larger the effective control current output to the DC motor, and the higher the performance ceiling of the DC motor. The smaller the modulus of the vector modulus, the longer the duration of the zero vector, the smaller the effective control current output to the DC motor, and the lower the speed of the DC motor. Since the sampling duration of the phase current of the DC motor is a fixed duration stored in advance, and sampling is required at the zero vector. Then, when determining the sampling method corresponding to different components, it is necessary to determine whether the duration of the zero vector is sufficient. If the duration of the zero vector is short, the duration of the dual-resistance sampling cannot be met, so at this time, the vector modulus is maximized by single-resistance sampling, thereby maximizing the limit performance of the DC motor. If the duration of the zero vector is long, it will occupy the component duration, and single-resistance sampling cannot be performed. Therefore, at this time, dual-resistance sampling is used to minimize the modulus of the vector modulus, so as to keep the motor running at an extremely low speed without losing step. Since the larger the vector modulus is, the shorter the duration of the zero vector is, the vector angle and vector modulus of the current control voltage can be determined first, and the subsequent steps are used to determine the sampling method of the DC motor. Therefore, after obtaining the current speed of the DC motor, the vector angle and vector modulus of the current control voltage of the DC motor can be determined according to the current speed of the DC motor. The subsequent steps can determine the component duration of each component within the current carrier cycle duration of the DC motor according to the vector angle and vector modulus of the current control voltage.

[0031] Specifically, the specific steps of executing step 202 are as follows: Step 1: In the pre-stored correspondence between the control voltage and the rotation speed of the DC motor, query the current control voltage corresponding to the current rotation speed.

[0032] In implementation, when determining the vector angle and vector modulus of the current control voltage of the DC motor, it is necessary to first determine the current control voltage according to the current speed of the DC motor, and then obtain the vector angle and vector modulus of the current control voltage according to the current control voltage. Since the DC motor has different speeds under different control voltages. The technician applies different control voltages to the DC motor in advance, determines the speed of the DC motor under each control voltage, and stores the correspondence between the control voltage and the speed of the DC motor. Therefore, the current control voltage corresponding to the current speed can be queried in the pre-stored correspondence between the control voltage and the speed of the DC motor.

[0033] Step 2: correspond the current control voltage to the space vector pulse width modulation diagram to obtain the vector angle and vector modulus of the current control voltage.

[0034] In implementation, after the current control voltage of the DC motor is determined, the current control voltage is mapped to the space vector pulse width modulation diagram to obtain the vector angle and vector modulus of the current control voltage. Figure 5 A space vector pulse width modulation diagram is provided in the embodiment of the present application. Figure 5 As shown in the figure, the space vector pulse width modulation diagram divides the DC motor into 6 sector intervals in one electrical cycle. Each interval is composed of 2 vectors to synthesize a final vector control voltage. Following the vector parallelogram synthesis law, each interval corresponds to a carrier cycle, and multiple connected intervals can also be regarded as a carrier cycle. In this way, the vector angle and vector modulus of the current control voltage are obtained through the space vector pulse width modulation diagram.

[0035] Step 203, determining the component duration of each component within the current carrier cycle duration according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus.

[0036] In implementation, when determining the sampling method of the DC motor, it is necessary to determine whether the component duration of each component in the current carrier cycle meets the sampling duration of the corresponding sampling method. If it meets the requirements, the corresponding sampling method is adopted for sampling. Therefore, it is necessary to first determine the component duration of each component in the current carrier cycle duration. The first modulus of the first component and the second modulus of the second component corresponding to the current control voltage can be determined by the vector angle, the vector modulus and the preset maximum angle. The modulus determines the duration ratio of the component in the carrier cycle. Then, based on the corresponding ratio of the first modulus, the second modulus and the pre-stored standard component modulus, it is equal to the first component duration of the first component, the second component duration of the second component and the current carrier cycle duration. Therefore, the first modulus component and the second modulus component in the current carrier cycle duration can be determined according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus. Then the ratio of the remaining duration of the current carrier cycle duration to the number of remaining components is determined as the component duration corresponding to the remaining components. Among them, the preset maximum angle can be 60 degrees. In this way, the component duration of each component within the current carrier cycle duration is determined.

[0037] Specifically, the process of executing step 203 is as follows: Step A, according to the vector modulus, vector angle and preset maximum angle, vector decomposes the current control voltage into two side components to obtain the first modulus of the first component and the second modulus of the second component, and the preset maximum angle is the maximum angle between the first component and the second component.

[0038] In implementation, the six sectors in the space vector pulse width modulation diagram all have corresponding vector modulus and vector angle of the control voltage. According to the vector modulus, vector angle and preset maximum angle of the current control voltage, the current control voltage can be vector-decomposed into two side components to obtain the first modulus of the first component and the second modulus of the second component, and the preset maximum angle is the maximum angle between the first component and the second component. The preset maximum angle can be 60 degrees.

[0039] Figure 6 A vector decomposition diagram of a control voltage provided in an embodiment of the present application is shown in FIG. Figure 6 As shown in the figure, the target voltage vector (current control voltage) of the first sector interval is decomposed, VS1 is the target voltage vector (current control voltage), and its magnitude and direction can also be determined by two factors: the speed and rotor position of the DC motor. In the first sector interval, the two components are V1 (1, 0, 0) and V2 (1, 1, 0), where the number of components is Figure 4 In the equivalent circuit diagram, 1 means the upper tube is on and the lower tube is off, and 0 means the upper tube is off and the lower tube is on. Figure 6The control voltages VS1 and VS2 of the final vector in the figure are two different synthetic vectors. It can be seen that the different directions of VS2 and VS1 depend on the different modulus sizes of the components V1 and V2, and the modulus sizes of V1 and V2 are reflected in the software control as the length of time V1 and V2 are controlled; and the different modulus sizes of VS2 and VS1 depend on the different sizes of the zero vectors, and the size of the zero vector is reflected in the software control as the duration of the zero vector within a carrier cycle. Figure 7 As shown, VS1 is decomposed toward V1 and V2 to obtain the target voltage components VS1-V1 and VS1-V2. VS1-V1 determines the proportion of the first component duration of the V1 component action time T1 in a carrier cycle, and VS1-V2 determines the proportion of the second component duration of the V2 component action time T2 in a carrier cycle. The rest is the action time of the V0 and V7 components. According to the preset maximum angle of 60° between the first component and the second component, Ɵ represents the vector angle (preset maximum angle), and the specific time conversion relationship is: Modulus length operation: , .

[0040] Figure 8 This is a schematic diagram of the duration of a component within a carrier cycle provided by an embodiment of the present application. Figure 8 As shown, 1 means the upper tube is on and the lower tube is off, and 0 means the upper tube is off and the lower tube is on. The duration of the zero vector V0 (0, 0, 0) is T0, and the duration of V7 (1, 1, 1) is T7. The duration of the two components V1 (1, 0, 0) is T1, and the duration of V2 (1, 1, 0) is T2. T0+T1+T2+T7=T, T is the length of a carrier cycle.

[0041] Step B: multiplying the ratio of the first modulus length to the pre-stored standard component modulus length by the product of the current carrier cycle length to determine the first component length.

[0042] In implementation, the modulus determines the duration ratio of the component in the carrier cycle, that is, the ratio of the component modulus to the standard component modulus is equal to the ratio of the component duration to the carrier cycle duration. Therefore, the first component duration can be determined by multiplying the ratio of the first modulus to the pre-stored standard component modulus by the product of the current carrier cycle duration.

[0043] For example, according to the obtained modulus of the component, convert it to the duration of the component. Fig. 9As shown, in each sector interval, the control voltage of the maximum vector voltage is defined as an inscribed circle. Assuming the radius of the inscribed circle is R, |V1|=|V2|=R+S, then R / (R+S)=cos30°, and the proportional relationship S / R=(1-cos30°) / cos30° is derived. According to the conversion of the modulus and duration of the maximum inscribed circle: S corresponds to the total time of T0+T7, R corresponds to the total time of T1+T2, and the total time is a carrier cycle duration T. For example, if the carrier frequency is 16KHZ, the carrier cycle duration T=62.5us. According to the proportional relationship, the maximum total time of T1+T2=T·cos30° / ((1-cos30°)+cos30°)us is obtained. Since the modulus length |VS1| is determined, that is, |VS1| / |V1| is determined, and it is set as |VS1| / |V1|=k, then |VS1|=|V1|k, |V1| corresponds to the full carrier cycle length T=62.5us, |VS1-V1| corresponds to the V1 action time T1, |VS1-V2| corresponds to the V2 action time T2, and T1=T·k·(cosƟ-sinƟ / tan60°)us; T2=T·k·(cos(60°-Ɵ)-sin(60°-Ɵ) / tan60°)us. That is, the proportion of the component modulus length in the standard component modulus length is equal to the proportion of the component duration in the carrier cycle duration. The ratio of the first modulus length to the pre-stored standard component modulus length can be multiplied by the product of the current carrier cycle duration to determine the first component duration.

[0044] Step C: multiply the ratio of the second modulus length to the pre-stored standard component modulus length by the product of the current carrier cycle length to determine the second component length.

[0045] In implementation, the modulus determines the duration ratio of the component in the carrier cycle, that is, the ratio of the component modulus to the standard component modulus is equal to the ratio of the component duration to the carrier cycle duration. Therefore, in the same way, the ratio of the second modulus to the pre-stored standard component modulus can be multiplied by the product of the current carrier cycle duration to determine the second component duration.

[0046] Step D: Determine the component duration corresponding to each remaining component as the ratio of the difference between the current carrier cycle duration and the first component duration and the second component duration to the number of remaining components.

[0047] In implementation, after determining the decomposed first component duration and second component duration of the sector interval where the current control voltage is located, the remaining duration of the current carrier cycle duration can be evenly divided into the component durations of the remaining components. That is, the ratio of the difference between the current carrier cycle duration minus the first component duration and the second component duration to the number of remaining components can be determined as the component duration corresponding to the remaining components.

[0048] Step 204, based on the pre-stored sampling duration threshold and multiple component durations, determine the sampling method of the DC motor in the current carrier cycle, and determine whether to adjust the current carrier cycle duration according to the sampling method.

[0049] In implementation, in one carrier cycle, under different components, when the control voltage of the vector acts on the DC motor, the three-phase current of the DC motor collected by the sampling hardware circuit is different. Some components can collect a single-phase current in the three-phase current, and some can collect a two-phase current. In other words, there is a corresponding sampling method for the DC motor under the action of each component. That is, when the component of the single-phase current is collected, the sampling method can be single-resistance sampling; when the component of the bidirectional current is collected, the sampling method can be double-resistance sampling. However, when using the sampling method to sample the phase current, a certain sampling time is required. When the component time of each component meets the sampling time of the corresponding sampling method, the sampling method corresponding to the component can be determined as the sampling method of the DC motor in the current carrier cycle. Therefore, when determining the sampling method of the DC motor, it is necessary to determine whether the component time of each component in the current carrier cycle meets the sampling time required by the corresponding sampling method. If it meets, the corresponding sampling method can be determined according to the number of phase currents collected under the control of the component. For example, if a single-phase current is collected, single-resistance sampling is used; if a two-phase current is collected, double-resistance sampling is used. Then, after determining the sampling method, it can also be determined based on the sampling method whether to adjust the current carrier cycle duration. If the sampling method is single resistor sampling, the component duration of the component corresponding to the single resistor sampling is reduced and adjusted to the sampling duration of the single resistor sampling. If the sampling method is double resistor sampling, the component duration of the component for double resistor sampling is reduced and adjusted to the sampling duration of the double resistor sampling. Among them, the sampling duration of the single resistor sampling and the sampling duration of the double resistor sampling can be equal, or 50%. Because the duration ratio of each component in a carrier cycle is fixed. After the component duration of the component to be sampled is reduced, the component duration of the remaining components is correspondingly reduced according to the reduction ratio generated. In this way, the current carrier cycle duration is adjusted to the duration of the corresponding sampling method.

[0050] Fig.10 This is a schematic diagram of an equivalent circuit of a single resistor sampling when a component is applied in an embodiment of the present application. Fig.10 As shown, the component is V1 (1, 0, 0). At this time, the upper tube of the U phase is turned on and the lower tube is turned off, and the upper tubes of the V and W phases are turned off and the lower tubes are turned on. The current of the current control voltage passes through the U phase of the DC motor, and then passes through the parallel circuit composed of the V phase and the W phase, and finally converges to the bus sampling resistor Rbus, so the Rbus current = the U phase current. Therefore, at this time, when the component V1 (1, 0, 0) of the current carrier cycle acts on the DC motor, the U phase current of the DC motor is collected.

[0051] Fig.11 This is a schematic diagram of an equivalent circuit of a single resistor sampling when another component is applied in an embodiment of the present application. Fig.11 As shown, the component is V2 (1, 1, 0). At this time, the upper tubes of the U phase and the V phase are turned on and the lower tubes are turned off, and the upper tube of the W phase is turned off and the lower tube is turned on. The current of the current control voltage passes through the parallel circuit composed of the U phase and the V phase, and then passes through the W phase of the DC motor, and finally converges to the bus sampling resistor Rbus. Therefore, the Rbus current = - the motor W phase current, that is, the two are equal in magnitude and opposite in direction. Therefore, at this time, when the component V2 (1, 1, 0) of the current carrier cycle acts on the DC motor, the W phase current of the DC motor is collected.

[0052] Furthermore, when the component V7 (1, 1, 1) is applied as a vector Figure 4 The current sampling equivalent circuit is shown in Figure 1. At this time, the sampling hardware circuit is in freewheeling mode, so no current flows through the three sampling resistors, which is not suitable for current sampling. Therefore, when the component is V7 (1, 1, 1), no sampling is performed.

[0053] Fig.12 This is a schematic diagram of an equivalent circuit of dual-resistance sampling when a component is applied in an embodiment of the present application. Fig.12 As shown, the component is V0 (0, 0, 0). At this time, current flows through Ru of the U phase and Rv of the V phase, which is the best time for dual-resistance sampling. Therefore, at this time, when the component V0 (0, 0, 0) of the current carrier cycle acts on the DC motor, the current collected is the U phase current and V phase current of the DC motor.

[0054] Specifically, the multiple components of the current carrier cycle include a first component, a second component, and a third component. The process of executing step 204 is as follows: Step a. If the pre-stored sampling time threshold is less than the first component time of the first component, the second component time of the second component, and is greater than or equal to the third component time of the third component, then the sampling method of the DC motor in the current carrier cycle is determined to be single-resistance sampling, and the current carrier cycle time is reduced to the current carrier cycle time of the preset proportional coefficient. The first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when the DC motor is controlled in this way, and the third component is a component of the two-phase current output by the sampling hardware circuit when the DC motor is controlled in this way.

[0055] In implementation, when determining the sampling method of the DC motor, it is necessary to determine whether the component duration of each component in the current carrier cycle meets the sampling duration required by the corresponding sampling method. If it does, the corresponding sampling method can be determined. Therefore, the pre-stored sampling duration threshold is compared with the first component duration of the first component, the second component duration of the second component, and the third component duration of the third component. If the pre-stored sampling duration threshold is less than the first component duration of the first component and the second component duration of the second component, and is greater than or equal to the third component duration of the third component, it is determined that the sampling method of the DC motor in the current carrier cycle is single-resistance sampling. Among them, the first component and the second component are adjacent components of the sampling hardware circuit outputting a single-phase current when the DC motor is controlled in this way. The first component can be (1, 0, 0) and the second component can be (1, 1, 0). The third component is a component of the sampling hardware circuit outputting a two-phase current when the DC motor is controlled in this way, and the third component can be (0, 0, 0). That is to say, the first component duration and the second component duration are long enough to be sampled, and the first component and the second component are adjacent components, and two single-phase currents are collected under the action of the first component and the second component. Then, the sampling method of the DC motor can be single resistor sampling. The duration of the third component is short and cannot meet the sampling duration threshold, so sampling cannot be performed under the third component. Therefore, it is determined that the sampling method of the DC motor in the current carrier cycle is single resistor sampling. At this time, the sampling method is single resistor sampling, and the duration of the first component and the duration of the second component are reduced and adjusted to the sampling duration of single resistor sampling. Since the duration ratio of each component in a carrier cycle is fixed. After reducing the duration of the first component and the duration of the second component, the component durations of the remaining components are correspondingly reduced according to the reduction ratio generated. In this way, the current carrier cycle duration is adjusted to the current carrier cycle duration of the preset proportional coefficient. The preset proportional coefficient is the ratio of the sampling duration of the single resistor sampling to the duration of the first component / the duration of the second component. In this way, the carrier cycle duration is gradually reduced to just meet the single resistor sampling duration, and the sinusoidality of the phase current waveform at the extreme high speed is strengthened, which is conducive to the smooth operation of the DC motor under this working condition.

[0056] Step b: If the sampling time threshold is less than the first component time and the second component time, and less than the third component time, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling and single-resistance sampling.

[0057] In implementation, the pre-stored sampling duration threshold is compared with the first component duration of the first component, the second component duration of the second component, and the third component duration of the third component. If the sampling duration threshold is less than the first component duration and the second component duration, and less than the third component duration, that is, the first component duration and the second component duration are long enough to be sampled, and the first component and the second component are adjacent components, and two single-phase currents are collected under the action of the first component and the second component. Then, the sampling method of the DC motor can be single-resistance sampling. The third component duration is also long enough to be sampled, and a two-phase current is collected under the third component, so the sampling method of the DC motor can be double-resistance sampling. In this way, it is explained that within the current carrier cycle, there is enough time for single-resistance sampling and double-resistance sampling, so that the final value of the target three-phase current is comprehensively judged according to the sampling values ​​of the two methods, and the reliability of the result is improved without increasing the hardware cost. Regardless of whether the DC motor is in a high-speed or low-speed limit operating condition, the DC motor can be maintained to run smoothly at the target speed.

[0058] Step c, if the sampling duration threshold is greater than or equal to the first component duration and the second component duration, and less than the third component duration, then determine that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling, and reduce the current carrier cycle duration to the current carrier cycle duration of the preset proportional coefficient.

[0059] In implementation, the pre-stored sampling duration threshold is compared with the first component duration of the first component, the second component duration of the second component, and the third component duration of the third component. If the sampling duration threshold is greater than or equal to the first component duration and the second component duration, and is less than the third component duration, the first component duration and the second component duration are both short and cannot meet the sampling duration threshold, then sampling cannot be performed under the first component and the second component. The third component duration is also long enough to be sampled, and a two-phase current is collected under the third component, then the sampling method of the DC motor can be dual-resistance sampling. Therefore, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling. At this time, the sampling method is dual-resistance sampling, and the third component duration is reduced and adjusted to the sampling duration of dual-resistance sampling. Since the duration ratio of each component in a carrier cycle is fixed. After the third component duration is reduced, the component durations of the remaining components are correspondingly reduced according to the reduction ratio generated. The current carrier cycle duration is adjusted to the current carrier cycle duration of the preset proportional coefficient. The preset proportional coefficient is the ratio of the sampling duration of the dual-resistance sampling to the duration of the third component. In this way, the carrier cycle duration is gradually reduced to just meet the dual-resistance sampling duration, thereby maintaining a good phase current sinusoidality of the DC motor at an extreme high speed and ensuring smooth operation of the motor.

[0060] Furthermore, if the sampling duration threshold is greater than or equal to the first component duration and the second component duration, and greater than the third component duration, the current carrier cycle duration is gradually increased so that the duration of the component within the current carrier cycle can meet the sampling duration threshold, so that the DC motor does not lose step.

[0061] Step 205 , according to the sampling method, obtain the single-phase current and / or two-phase current of the DC motor collected by the sampling hardware circuit, and reconstruct the three-phase current by Kirchhoff's law to obtain the target three-phase current of the DC motor.

[0062] In implementation, after determining the sampling method, the single-phase current and / or two-phase current of the DC motor collected by the sampling hardware circuit is obtained according to the sampling method. The sampling method can be single-resistance sampling and / or dual-resistance sampling, and the collected single-phase current and / or two-phase current of the DC motor is reconstructed into three-phase current through Kirchhoff's law to obtain the target three-phase current of the DC motor. Among them, Kirchhoff's law is U-phase current + V-phase current + W-phase current = 0, so the three-phase current can be reconstructed through any two-phase current, that is, the three-phase current can be reconstructed by collecting two single-phase currents through adjacent components, or collecting two-phase currents through one component. Alternatively, both single-resistance sampling and dual-resistance sampling are performed within one carrier cycle to obtain two sets of reconstructed phase current values: Iu1, Iv1, Iw1; Iu2, Iv2, Iw2. The phase current values ​​obtained by comprehensive processing are: Iu=(Iu1+Iu2) / 2, Iv=(Iv1+Iv2) / 2, Iw=(Iw1+Iw2) / 2. In this way, the target three-phase current is more accurate.

[0063] Step d, when the sampling method is single-resistance sampling, Kirchhoff's law is used to collect two single-phase currents of the sampling hardware circuit for adjacent components, determine another single-phase current in the three-phase current, and determine the three single-phase currents as the target three-phase current after reconstruction of the DC motor.

[0064] In implementation, when the sampling method is single-resistance sampling, a single-phase current of the DC motor is collected through the sampling hardware circuit. When you want to get the three-phase current of the DC motor, you can collect two single-phase currents of the adjacent components into the sampling hardware circuit respectively, regard them as two single-phase currents collected at the same time, and reconstruct the three-phase current. Then, when reconstructing the three-phase current, you can use Kirchhoff's law to determine the other single-phase current in the three-phase current, and determine the three single-phase currents as the target three-phase current after reconstruction of the DC motor. Among them, Kirchhoff's law is that the sum of the three-phase current is zero. After determining that the adjacent components collect two single-phase currents of the sampling hardware circuit respectively, the opposite of the sum of the two single-phase currents is determined as another single-phase current. The positive and negative of the three-phase current indicate the direction of the current. The current flowing into the DC motor is a positive current, and the current flowing out of the DC motor is a negative current.

[0065] Step e, when the sampling method is dual-resistance sampling, Kirchhoff's law is used to determine another single-phase current in the three-phase current for a two-phase current collected from the sampling hardware circuit, and the two-phase current and the single-phase current are determined as the target three-phase current after reconstruction of the DC motor.

[0066] In implementation, when the sampling method is dual-resistance sampling, a two-phase current of the DC motor is collected through the sampling hardware circuit. When you want to obtain the three-phase current of the DC motor, you can reconstruct the three-phase current of the two-phase current. Then, when reconstructing the three-phase current, you can use Kirchhoff's law to determine the other single-phase current in the three-phase current, and determine the bidirectional current and the single-phase current as the target three-phase current after reconstruction of the DC motor. Among them, Kirchhoff's law is that the sum of the three-phase current is zero. After determining a two-phase current of the sampling hardware circuit, the opposite of the sum of the two-phase current is determined as the single-phase current. In this way, the target three-phase current of the DC motor after reconstruction is obtained.

[0067] Step f, when the sampling method is single-resistance sampling and dual-resistance sampling, Kirchhoff's law is used to collect two single-phase currents and one two-phase current of the sampling hardware circuit for adjacent components, determine the other single-phase current in each of the two sets of three-phase currents, and average the two sets of reconstructed three-phase currents to obtain the target three-phase current of the DC motor after reconstruction.

[0068] In implementation, when the sampling method is single-resistance sampling and dual-resistance sampling, two sets of reconstructed three-phase currents can be determined respectively through the steps in step d and step e. The specific process has been described in the above steps and will not be repeated here. After determining the two sets of reconstructed three-phase currents, the two sets of reconstructed three-phase currents can be averaged to obtain the target three-phase current of the DC motor after reconstruction. The two current sampling methods are effective at the same time, and the final target three-phase current is calculated comprehensively based on the current values ​​sampled by the two methods, making the algorithm estimation results more credible.

[0069] The embodiment of the present application provides a variable frequency control method for current sampling, which is based on a sampling hardware circuit. By judging whether the component duration of each component within the current carrier cycle duration meets the sampling duration of the DC motor, the corresponding sampling method is determined. The sampling methods include dual-resistance sampling and single-resistance sampling. The DC motor's limit performance under the current control voltage is fully utilized, and the two methods of dual-resistance sampling and single-resistance sampling are integrated. When the DC motor is in high and low speed limit operating conditions, the sinusoidality of the phase current can be maintained well, and the DC motor is prevented from losing step, so as to maintain the smooth operation of the motor. Different sampling methods are selected in a timely manner through the frequency conversion strategy. The three-phase current is reconstructed for the sampled current obtained by sampling, and the final phase current value is comprehensively calculated, so that the algorithm estimation result is more credible, and the reliability of the result is improved without increasing the hardware cost.

[0070] It should be understood that although Figure 2 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 2 At least part of the steps may include multiple steps or multiple stages. These steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed in turn or alternately with other steps or at least part of the steps or stages in other steps.

[0071] It can be understood that the same / similar parts between the various embodiments of the above method in this specification can refer to each other, and each embodiment focuses on the differences from other embodiments. For related points, please refer to the description of other method embodiments.

[0072] The present application also provides a variable frequency control device for current sampling, such as Fig.13 As shown, the device comprises: An acquisition module 1301 is used to acquire the current speed of the DC motor, the current carrier cycle duration, and multiple components of the carrier cycle; A first determination module 1302 is used to determine a vector angle and a vector modulus of a current control voltage according to the current rotation speed; A second determination module 1303 is used to determine the component duration of each component within the current carrier cycle duration according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus; The third determination module 1304 is used to determine the sampling method of the DC motor in the current carrier cycle based on the pre-stored sampling duration threshold and the multiple component durations, and determine whether to adjust the current carrier cycle duration according to the sampling method; The reconstruction module 1305 is used to obtain the single-phase current and / or two-phase current of the DC motor collected by the sampling hardware circuit according to the sampling method, and reconstruct the three-phase current through Kirchhoff's law to obtain the target three-phase current of the DC motor.

[0073] As an optional implementation manner, the first determining module 1302 is specifically configured to: In the pre-stored correspondence between the control voltage and the rotation speed of the DC motor, query the current control voltage corresponding to the current rotation speed; The current control voltage is mapped to a space vector pulse width modulation diagram to obtain a vector angle and a vector modulus of the current control voltage.

[0074] As an optional implementation manner, the second determining module 1303 is specifically configured to: According to the vector modulus, the vector angle and the preset maximum angle, the current control voltage is vector-decomposed into two side components to obtain a first modulus of the first component and a second modulus of the second component, and the preset maximum angle is the maximum angle between the first component and the second component; The first component duration is determined by multiplying the ratio of the first modulus length to the pre-stored standard component modulus length by the product of the current carrier cycle duration; The ratio of the second modulus length to the pre-stored standard component modulus length is multiplied by the product of the current carrier cycle duration to determine the second component duration; The component durations corresponding to the remaining components are determined as the ratio of the difference between the current carrier cycle duration and the first component duration and the second component duration to the number of remaining components.

[0075] As an optional implementation manner, the multiple components of the current carrier cycle include a first component, a second component, and a third component, and the third determination module 1304 is specifically configured to: If the pre-stored sampling duration threshold is less than the first component duration of the first component and the second component duration of the second component, and is greater than or equal to the third component duration of the third component, it is determined that the sampling method of the DC motor in the current carrier cycle is single-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient, the first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when the DC motor is controlled in this way, and the third component is a component of the two-phase current output by the sampling hardware circuit when the DC motor is controlled in this way; If the sampling time threshold is less than the first component time and the second component time, and less than the third component time, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling and single-resistance sampling; If the sampling duration threshold is greater than or equal to the first component duration and the second component duration, and less than the third component duration, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient.

[0076] As an optional implementation, the reconstruction module 1305 is specifically used to: When the sampling method is single-resistance sampling, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components by Kirchhoff's law, another single-phase current in the three-phase current is determined, and the three single-phase currents are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is dual-resistance sampling, the Kirchhoff's law is used to determine another single-phase current in the three-phase current for a two-phase current collected from the sampling hardware circuit, and the two-phase current and the single-phase current are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is the single-resistance sampling and the dual-resistance sampling, Kirchhoff's law is used to collect two single-phase currents and one two-phase current of the sampling hardware circuit for adjacent components, determine the other single-phase current in the two sets of three-phase currents, and average the two sets of reconstructed three-phase currents to obtain the target three-phase current of the DC motor after reconstruction.

[0077] The embodiment of the present application provides a variable frequency control device for current sampling, which is based on a sampling hardware circuit and determines the corresponding sampling method by judging whether the component duration of each component within the current carrier cycle duration meets the sampling duration of the DC motor. The sampling methods include dual-resistance sampling and single-resistance sampling. The DC motor's limit performance under the current control voltage is fully utilized, and the two methods of dual-resistance sampling and single-resistance sampling are integrated. The DC motor can maintain a good phase current sinusoidality under high and low speed limit operating conditions, avoid the DC motor from losing step, and maintain the smooth operation of the motor. Different sampling methods are selected in a timely manner through the frequency conversion strategy. The three-phase current is reconstructed for the sampled current obtained by sampling, and the final phase current value is comprehensively calculated, so that the algorithm estimation result is more credible, and the reliability of the result is improved without increasing the hardware cost.

[0078] The specific definition of the variable frequency control device for current sampling can be found in the definition of the variable frequency control method for current sampling above, which will not be repeated here. Each module in the above-mentioned variable frequency control device for current sampling can be implemented in whole or in part by software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory in the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0079] In one embodiment, a computer device is provided, such as Fig.14 As shown, it includes a memory and a processor, the memory stores a computer program that can be run on the processor, and the processor implements the above-mentioned current sampling frequency conversion control method steps when executing the computer program.

[0080] In one embodiment, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the variable frequency control method for current sampling are implemented.

[0081] 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 in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0082] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0083] It should also be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for display, data for analysis, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0084] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0085] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A variable frequency control method for current sampling, characterized in that: The method is applied to a sampling hardware circuit, and the method comprises: Obtain the current speed of the DC motor, the current carrier cycle duration, and multiple components of the carrier cycle; Determining the vector angle and vector modulus of the current control voltage according to the current rotation speed; Determine the component duration of each component within the current carrier cycle duration according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus; Based on a pre-stored sampling duration threshold and a plurality of component durations, determining a sampling method of the DC motor within the current carrier cycle, and determining whether to adjust the current carrier cycle duration according to the sampling method; According to the sampling method, the single-phase current and / or two-phase current of the DC motor collected by the sampling hardware circuit is obtained, and the three-phase current is reconstructed according to Kirchhoff's law to obtain the target three-phase current of the DC motor.

2. The method according to claim 1, characterized in that The step of determining the vector angle and vector modulus of the current control voltage according to the current rotation speed includes: In the pre-stored correspondence between the control voltage and the rotation speed of the DC motor, query the current control voltage corresponding to the current rotation speed; The current control voltage is mapped to a space vector pulse width modulation diagram to obtain a vector angle and a vector modulus of the current control voltage.

3. The method according to claim 1, characterized in that The determining, according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus, the component duration of each component within the current carrier cycle duration includes: According to the vector modulus, the vector angle and the preset maximum angle, the current control voltage is vector-decomposed into two side components to obtain a first modulus of the first component and a second modulus of the second component, and the preset maximum angle is the maximum angle between the first component and the second component; The first component duration is determined by multiplying the ratio of the first modulus length to the pre-stored standard component modulus length by the product of the current carrier cycle duration; The ratio of the second modulus length to the pre-stored standard component modulus length is multiplied by the product of the current carrier cycle duration to determine the second component duration; The component durations corresponding to the remaining components are determined as the ratio of the difference between the current carrier cycle duration and the first component duration and the second component duration to the number of remaining components.

4. The method according to claim 1, characterized in that: The multiple components of the current carrier cycle include a first component, a second component, and a third component. The method of determining a sampling method of the DC motor in the current carrier cycle based on a pre-stored sampling duration threshold and multiple component durations, and determining whether to adjust the current carrier cycle duration according to the sampling method includes: If the pre-stored sampling duration threshold is less than the first component duration of the first component and the second component duration of the second component, and is greater than or equal to the third component duration of the third component, it is determined that the sampling method of the DC motor in the current carrier cycle is single-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient, the first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when the DC motor is controlled in this way, and the third component is a component of the two-phase current output by the sampling hardware circuit when the DC motor is controlled in this way; If the sampling time threshold is less than the first component time and the second component time, and less than the third component time, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling and single-resistance sampling; If the sampling duration threshold is greater than or equal to the first component duration and the second component duration, and less than the third component duration, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient.

5. The method according to claim 1, characterized in that The method of acquiring the single-phase current and / or the two-phase current of the DC motor collected by the sampling hardware circuit according to the sampling method, and reconstructing the three-phase current according to Kirchhoff's law to obtain the target three-phase current of the DC motor includes: When the sampling method is single-resistance sampling, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components by Kirchhoff's law, another single-phase current in the three-phase current is determined, and the three single-phase currents are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is dual-resistance sampling, the Kirchhoff's law is used to determine another single-phase current in the three-phase current for a two-phase current collected from the sampling hardware circuit, and the two-phase current and the single-phase current are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is the single-resistance sampling and the dual-resistance sampling, Kirchhoff's law is used to collect two single-phase currents and one two-phase current of the sampling hardware circuit for adjacent components, determine the other single-phase current in each of the two sets of three-phase currents, and average the two sets of reconstructed three-phase currents to obtain the target three-phase current of the DC motor after reconstruction.

6. A variable frequency control device for current sampling, characterized in that: The device is applied to a sampling hardware circuit, and the device comprises: An acquisition module is used to acquire the current speed of the DC motor, the current carrier cycle duration, and multiple components of the carrier cycle; A first determination module, used to determine the vector angle and vector modulus of the current control voltage according to the current rotation speed; A second determination module is used to determine the component duration of each component within the current carrier cycle duration according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus; A third determination module is used to determine a sampling method of the DC motor in the current carrier cycle based on a pre-stored sampling duration threshold and a plurality of component durations, and to determine whether to adjust the current carrier cycle duration according to the sampling method; The reconstruction module is used to obtain the single-phase current and / or two-phase current of the DC motor collected by the sampling hardware circuit according to the sampling method, and reconstruct the three-phase current through Kirchhoff's law to obtain the target three-phase current of the DC motor.

7. The device according to claim 6, characterized in that The first determining module is specifically configured to: In the pre-stored correspondence between the control voltage and the rotation speed of the DC motor, query the current control voltage corresponding to the current rotation speed; The current control voltage is mapped to a space vector pulse width modulation diagram to obtain a vector angle and a vector modulus of the current control voltage.

8. The device according to claim 6, characterized in that The second determining module is specifically used to: According to the vector modulus, the vector angle and the preset maximum angle, the current control voltage is vector-decomposed into two side components to obtain a first modulus of the first component and a second modulus of the second component, and the preset maximum angle is the maximum angle between the first component and the second component; The first component duration is determined by multiplying the ratio of the first modulus length to the pre-stored standard component modulus length by the product of the current carrier cycle duration; The ratio of the second modulus length to the pre-stored standard component modulus length is multiplied by the product of the current carrier cycle duration to determine the second component duration; The component durations corresponding to the remaining components are determined as the ratio of the difference between the current carrier cycle duration and the first component duration and the second component duration to the number of remaining components.

9. The device according to claim 6, characterized in that The multiple components of the current carrier cycle include a first component, a second component and a third component, and the third determination module is specifically configured to: If the pre-stored sampling duration threshold is less than the first component duration of the first component and the second component duration of the second component, and is greater than or equal to the third component duration of the third component, it is determined that the sampling method of the DC motor in the current carrier cycle is single-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient, the first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when the DC motor is controlled in this way, and the third component is a component of the two-phase current output by the sampling hardware circuit when the DC motor is controlled in this way; If the sampling time threshold is less than the first component time and the second component time, and less than the third component time, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling and single-resistance sampling; If the sampling duration threshold is greater than or equal to the first component duration and the second component duration, and less than the third component duration, it is determined that the sampling method of the DC motor in the current carrier cycle is dual-resistance sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of the preset proportional coefficient.

10. The device according to claim 6, characterized in that The reconstruction module is specifically used for: When the sampling method is single-resistance sampling, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components by Kirchhoff's law, another single-phase current in the three-phase current is determined, and the three single-phase currents are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is dual-resistance sampling, the Kirchhoff's law is used to determine another single-phase current in the three-phase current for a two-phase current collected from the sampling hardware circuit, and the two-phase current and the single-phase current are determined as the target three-phase current of the DC motor after reconstruction; When the sampling method is the single-resistance sampling and the dual-resistance sampling, Kirchhoff's law is used to collect two single-phase currents and one two-phase current of the sampling hardware circuit for adjacent components, determine the other single-phase current in each of the two sets of three-phase currents, and average the two sets of reconstructed three-phase currents to obtain the target three-phase current of the DC motor after reconstruction.

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