A frequency conversion control method and device for current sampling

Abstract

This application belongs to the field of motor control and discloses a variable-frequency control method and device for current sampling. The method includes: obtaining the current speed, the current carrier period duration, and multiple components of the carrier period of a DC motor; determining the vector angle and vector modulus of the current control voltage according to the current speed; determining the component durations of the respective components within the current carrier period duration according to the vector angle, the vector modulus, a preset maximum included angle, the current carrier period duration, and the standard component modulus; determining the sampling method of the DC motor within the current carrier period based on a pre-stored sampling duration threshold and multiple component durations, and judging whether to adjust the current carrier period duration; obtaining the single-phase / double-phase current of the DC motor according to the sampling method, and reconstructing the three-phase current through Kirchhoff's law to obtain the target three-phase current of the DC motor. Using this application can make the three-phase current of the obtained DC motor 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 a DC motor, there are high requirements for the accurate sampling of the three-phase current of the DC motor. In the prior art, the sampling of the three-phase current is divided into two methods: double-resistance sampling and single-resistance sampling. However, the double-resistance sampling method is easy to implement but has limitations on the ultimate performance of the motor, and the single-resistance sampling method has a simple circuit but there will be a situation where the sampling time is insufficient, resulting in a 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, in view of the above technical problems, it is necessary to provide a variable frequency control method and device for current sampling.

[0004] In a first aspect, a variable frequency control method for current sampling is provided. The method is applied to a sampling hardware circuit, and the method includes:

[0005] Obtain the current speed, the current carrier period duration, and multiple components of the carrier period of the DC motor;

[0006] Determine the vector angle and vector modulus of the current control voltage according to the current speed;

[0007] Determine the component durations of each component within the current carrier period duration according to the vector angle, the vector modulus, a preset maximum angle, the current carrier period duration, and a pre-stored standard component modulus;

[0008] Based on a pre-stored sampling duration threshold and multiple component durations, determine the sampling method of the DC motor within the current carrier period, and determine whether to adjust the current carrier period duration according to the sampling method;

[0009] 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 through Kirchhoff's law to obtain the target three-phase current of the DC motor.

[0010] As an optional implementation manner, the determining the vector angle and vector modulus of the current control voltage according to the current speed includes:

[0011] Query the current control voltage corresponding to the current speed in the pre-stored correspondence between the control voltage and the speed of the DC motor;

[0012] Map the current control voltage to the space vector pulse width modulation diagram to obtain the vector angle and vector magnitude of the current control voltage.

[0013] As an alternative implementation, the determining the component durations of each component within the current carrier period according to the vector angle, the vector magnitude, a preset maximum angle, the current carrier period duration, and a pre-stored standard component magnitude includes:

[0014] According to the vector magnitude, the vector angle, and the preset maximum angle, decompose the current control voltage into two side components to obtain the first magnitude of the first component and the second magnitude of the second component, where the preset maximum angle is the maximum angle between the first component and the second component;

[0015] Determine the duration of the first component by multiplying the ratio of the first magnitude to the pre-stored standard component magnitude by the current carrier period duration;

[0016] Determine the duration of the second component by multiplying the ratio of the second magnitude to the pre-stored standard component magnitude by the current carrier period duration;

[0017] Determine the corresponding component durations of the remaining components by dividing the difference between the current carrier period duration and the sum of the durations of the first component and the second component by the number of remaining components.

[0018] As an alternative implementation, the multiple components of the current carrier period include a first component, a second component, and a third component. The method for determining the sampling method of the DC motor within the current carrier period based on a pre-stored sampling duration threshold and the durations of the multiple components, and determining whether to adjust the current carrier period duration according to the sampling method includes:

[0019] If the pre-stored sampling duration threshold is less than the duration of the first component of the first component and the duration of the second component of the second component, and greater than or equal to the duration of the third component of the third component, then determine that the sampling method of the DC motor within the current carrier period is single-resistance sampling, and reduce the current carrier period duration to the current carrier period duration of a preset proportionality coefficient. The first component and the second component are adjacent components for which the sampling hardware circuit outputs single-phase current when controlling the DC motor in this way, and the third component is the component for which the sampling hardware circuit outputs two-phase current when controlling the DC motor in this way;

[0020] If the sampling duration threshold is less than the durations of the first component and the second component, and less than the duration of the third component, then determine that the sampling methods of the DC motor within the current carrier period are double-resistance sampling and single-resistance sampling;

[0021] 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, determine that the sampling method of the DC motor in the current carrier period is dual-resistance sampling, and reduce the current carrier period duration to the current carrier period duration of a preset proportionality coefficient.

[0022] As an optional implementation manner, according to the sampling method, obtaining the single-phase current and / or the two-phase current of the DC motor collected by 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 includes:

[0023] When the sampling method is single-resistance sampling, through Kirchhoff's law, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components, the other single-phase current in the three-phase current is determined, and these three single-phase currents are determined as the target three-phase current after reconstruction of the DC motor;

[0024] When the sampling method is dual-resistance sampling, through Kirchhoff's law, for a two-phase current collected by the sampling hardware circuit, the other single-phase current in the three-phase current is determined, and this two-phase current and the single-phase current are determined as the target three-phase current after reconstruction of the DC motor;

[0025] When the sampling method is the single-resistance sampling and the dual-resistance sampling, through Kirchhoff's law, two single-phase currents and a two-phase current of the sampling hardware circuit are respectively collected for adjacent components, the other single-phase current in each of the two sets of three-phase currents is determined, and the average value of the two sets of three-phase currents after reconstruction is obtained to obtain the target three-phase current after reconstruction of the DC motor.

[0026] 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 includes:

[0027] An acquisition module, configured to acquire the current speed, the current carrier period duration, and multiple components of the carrier period of the DC motor;

[0028] A first determination module, configured to determine the vector angle and the vector modulus of the current control voltage according to the current speed;

[0029] A second determination module, configured to determine the component durations of the respective components within the current carrier period duration according to the vector angle, the vector modulus, a preset maximum included angle, the current carrier period duration, and a standard component modulus stored in advance.

[0030] A third determination module, configured to determine a sampling method of the DC motor within the current carrier period based on a pre-stored sampling duration threshold and the durations of multiple components, and determine whether to adjust the duration of the current carrier period according to the sampling method;

[0031] A reconstruction module, configured to obtain 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 perform three-phase current reconstruction through Kirchhoff's law to obtain the target three-phase current of the DC motor.

[0032] As an optional implementation manner, the first determination module is specifically configured to:

[0033] Query the current control voltage corresponding to the current speed in the pre-stored correspondence between the control voltage and the speed of the DC motor;

[0034] Map the current control voltage to a space vector pulse width modulation diagram to obtain the vector angle and vector modulus of the current control voltage.

[0035] As an optional implementation manner, the second determination module is specifically configured to:

[0036] Decompose the current control voltage into two side components according to the vector modulus, the vector angle, and a preset maximum included angle to obtain the first modulus of the first component and the second modulus of the second component, where the preset maximum included angle is the maximum included angle between the first component and the second component;

[0037] Determine the duration of the first component by multiplying the ratio of the first modulus to the pre-stored standard component modulus by the duration of the current carrier period;

[0038] Determine the duration of the second component by multiplying the ratio of the second modulus to the pre-stored standard component modulus by the duration of the current carrier period;

[0039] Determine the duration corresponding to each remaining component by dividing the difference between the duration of the current carrier period and the sum of the durations of the first component and the second component by the number of remaining components.

[0040] As an optional implementation manner, the multiple components of the current carrier period include a first component, a second component, and a third component. The third determination module is specifically configured to:

[0041] 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 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 period is single-resistance sampling, and the current carrier period duration is reduced to the current carrier period duration of a preset proportionality coefficient. The first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when controlling the DC motor in this way, and the third component is the component of the two-phase current output by the sampling hardware circuit when controlling the DC motor in this way;

[0042] If the sampling duration threshold is less than 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 period is dual-resistance sampling and single-resistance sampling;

[0043] 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 period is dual-resistance sampling, and the current carrier period duration is reduced to the current carrier period duration of a preset proportionality coefficient.

[0044] As an optional implementation manner, the reconstruction module is specifically configured to:

[0045] When the sampling method is single-resistance sampling, according to Kirchhoff's law, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components, the other single-phase current in the three-phase current is determined, and these three single-phase currents are determined as the target three-phase current after reconstruction of the DC motor;

[0046] When the sampling method is dual-resistance sampling, according to Kirchhoff's law, for a two-phase current collected from the sampling hardware circuit, the other single-phase current in the three-phase current is determined, and this two-phase current and the single-phase current are determined as the target three-phase current after reconstruction of the DC motor;

[0047] When the sampling method is the single-resistance sampling and the dual-resistance sampling, according to Kirchhoff's law, two single-phase currents and a two-phase current of the sampling hardware circuit are respectively collected for adjacent components, the other single-phase current in the two sets of three-phase currents is determined, and the average value of the two sets of three-phase currents after reconstruction is obtained to get the target three-phase current after reconstruction of the DC motor.

[0048] In a third aspect, a variable-frequency control system for current sampling is provided. The variable-frequency control system for current sampling includes: 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.

[0049] In a fourth aspect, a computer device is provided, including a memory and a processor. A computer program that can run on the processor is stored on the memory. When the processor executes the computer program, the method steps described in the first aspect are implemented.

[0050] In a fifth aspect, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the method steps described in the first aspect are implemented.

[0051] The present application provides a variable-frequency control method for current sampling. The technical solutions provided by the embodiments of the present application at least bring the following beneficial effects: obtaining the current speed, the current carrier period duration, and multiple components of the carrier period of a DC motor; determining the vector angle and vector modulus of the current control voltage according to the current speed; determining the component durations of the respective components within the current carrier period duration according to the vector angle, the vector modulus, the current carrier period duration, and a pre-stored standard component modulus; determining the sampling method of the DC motor within the current carrier period based on a pre-stored sampling duration threshold and multiple component durations, and judging whether to adjust the current carrier period duration according to the sampling method; collecting the single-phase current and / or two-phase current of the DC motor in the sampling hardware circuit according to the sampling method, and performing three-phase current reconstruction 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 durations of the respective components within the current carrier period duration meet the sampling duration of the DC motor, the corresponding sampling method is determined. The sampling methods include double-resistance sampling and single-resistance sampling. The limit performance of the DC motor under the current control voltage is fully exerted, and the two methods of double-resistance sampling and single-resistance sampling are integrated. Good phase current sinusoidality can be maintained under high- and low-speed limit operating conditions of the DC motor, avoiding the out-of-step of the DC motor to maintain the stable operation of the motor, and making the sampled current more accurate. Different sampling methods are selected timely through a variable-frequency strategy. And three-phase current reconstruction is performed on the sampled current, and the final phase current value is comprehensively calculated, making the algorithm estimation result more credible and improving the result reliability without increasing the hardware cost.

[0052] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. Description of the Drawings

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0054] Figure 1 Schematic diagram of the structure of a variable-frequency control system for current sampling provided by an embodiment of the present application;

[0055] Figure 2 Flowchart of a variable-frequency control method for current sampling provided by an embodiment of the present application;

[0056] Figure 3 Schematic diagram of a sampling hardware circuit provided by an embodiment of the present application;

[0057] Figure 4 Equivalent circuit schematic diagram of a sampling hardware circuit provided by an embodiment of the present application;

[0058] Figure 5 Spatial vector pulse width modulation diagram provided by an embodiment of the present application;

[0059] Figure 6 Vector decomposition schematic diagram of a control voltage provided by an embodiment of the present application;

[0060] Figure 7 Another vector decomposition schematic diagram of a control voltage provided by an embodiment of the present application;

[0061] Figure 8 Schematic diagram of the duration of components within a carrier period provided by an embodiment of the present application;

[0062] Figure 9 Vector decomposition schematic diagram of a control voltage with the maximum vector voltage provided by an embodiment of the present application;

[0063] Figure 10 Equivalent circuit schematic diagram of single-resistance sampling when components act provided by an embodiment of the present application;

[0064] Figure 11 Another equivalent circuit schematic diagram of single-resistance sampling when components act provided by an embodiment of the present application;

[0065] Figure 12 Equivalent circuit schematic diagram of double-resistance sampling when components act provided by an embodiment of the present application;

[0066] Figure 13Schematic structural diagram of a variable-frequency control device for current sampling provided by an embodiment of the present application;

[0067] Figure 14 Schematic structural diagram of a computer device provided by an embodiment of the present application. Detailed implementation manners

[0068] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to 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.

[0069] The variable-frequency control method for current sampling provided by an embodiment of the present application can be applied to a variable-frequency control system for current sampling. As Figure 1 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 respectively connected to the sampling hardware circuit 102 and the DC motor 103, and the sampling hardware circuit 102 is connected to the DC motor 103.

[0070] The controller 101 is configured to obtain the current speed, the current carrier period duration, and multiple components of the carrier period of the DC motor 103. Determine the vector angle and vector modulus of the current control voltage according to the current speed. Determine the component durations of each component within the current carrier period duration according to the vector angle, vector modulus, preset maximum included angle, current carrier period duration, and pre-stored standard component modulus. Based on the pre-stored sampling duration threshold and multiple component durations, determine the sampling method of the DC motor 103 within the current carrier period, and determine whether to adjust the current carrier period duration according to the sampling method. According to the sampling method, obtain the single-phase current and / or two-phase current of the DC motor 103 collected by the sampling hardware circuit 102, and reconstruct the three-phase current through Kirchhoff's law to obtain the target three-phase current of the DC motor 103.

[0071] The sampling hardware circuit 102 is configured to collect the three-phase current of the DC motor 103 and send the collected three-phase current to the controller 101.

[0072] The DC motor 103 is configured to operate according to the current control voltage output by the control 101.

[0073] Next, a variable-frequency control method for current sampling provided by an embodiment of the present application will be described in detail in combination with the specific implementation manners. Figure 2 Flowchart of a variable-frequency control method for current sampling provided by an embodiment of the present application. Figure 2 Applied to the sampling hardware circuit, as Figure 2 shown, the specific steps are as follows:

[0074] Step 201, obtain the current rotational speed, the current carrier period duration, and multiple components of the carrier period of the DC motor.

[0075] In implementation, during the operation control of a DC motor, high-precision sampling of the three-phase current of the DC motor is required. In the prior art, the sampling of the three-phase current is divided into two methods: double-resistance sampling and single-resistance sampling. However, the double-resistance sampling method is easy to implement but limits the ultimate performance of the motor, and the single-resistance sampling method has a simple circuit but may have insufficient sampling time, resulting in complex software processing logic. Therefore, a method for obtaining the three-phase current of a DC motor is needed to avoid the problem that the sampling duration is long during double-resistance sampling, which limits the duty cycle of the effective output signal and thus restricts the ultimate performance of the DC motor when running at high speed. At the same time, it also avoids the problem that when the DC motor runs at extremely low speed, the variable carrier period of single-resistance sampling cannot well maintain the sinusoidality of the phase current, resulting in the out-of-step of the DC motor. Therefore, this application can adopt a method combining single-resistance sampling and double-resistance sampling. Under the extreme operating conditions of high and low speeds of the motor, combined with the variable carrier period, the phase current of the DC motor can maintain good sinusoidality, avoid the out-of-step of the motor, and at the same time, improve the ultimate 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 period for controlling the DC motor. Different components within the carrier period result in different current directions of the current control voltage input to the DC motor, and the phase current of the DC motor collected is also different. Since different carrier periods 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 for the DC motor through the sampling hardware circuit within the current carrier period, it is necessary to judge the various components and component durations within the current carrier period. Only then can the subsequent steps determine whether the collected current is single-phase current or double-phase current according to the various components within the current carrier period, and judge whether the component duration of the component meets the sampling duration of the corresponding sampling method. Among them, the single-phase current is collected through single-resistance sampling, and the double-phase current is collected through double-resistance sampling. When collecting the phase current of the DC motor through the sampling hardware circuit, the phase current of the DC motor collected under the action of various components within the carrier period is fixed. That is to say, different components correspond to different sampling methods. When determining the sampling method of the DC motor within the current carrier period, it is necessary to first judge whether the component duration of the component meets the sampling duration. Only when it meets 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 duration of the current carrier period can be increased so that the component duration can meet the sampling duration. Therefore, it is also necessary to obtain the current speed, the current carrier period duration, and multiple components of the carrier period of the DC motor in advance, and only then can the sampling method within the current carrier period be determined and sampling be carried out according to this sampling method.

[0076] Figure 3Schematic diagram of a sampling hardware circuit provided by an embodiment of this application. As Figure 3 shown, the U, V, and W phases of the DC motor are controlled by power switching tubes (IGBTs) M1 and M4, M3 and M6, M5 and M2 respectively. Among them, Ru in the U phase and Rv in the V phase are sampling resistors for two-phase currents, and Rbus is the sampling resistor for the bus current. Figure 4 For Figure 3 simplified equivalent circuit schematic diagram.

[0077] Step 202: Determine the vector angle and vector magnitude of the current control voltage according to the current speed.

[0078] In implementation, the magnitude of the vector magnitude of the control voltage of the DC motor depends on the different magnitudes of the zero vectors of the control voltage. The larger the magnitude of the vector magnitude, the shorter the duration of the zero vector, the larger the effective control current output to the DC motor, and the higher the upper limit of the performance exhibited by the DC motor. The smaller the magnitude of the vector magnitude, the longer the duration of the zero vector, the smaller the effective control current output to the DC motor, and the lower the speed exhibited by the DC motor. Since the sampling duration of the phase current of the DC motor is a fixed duration stored in advance and needs to be sampled during the zero vector. Then, when determining the sampling methods corresponding to different components, it is necessary to judge whether the duration of the zero vector is sufficient. If the duration of the zero vector is short, it cannot meet the duration of the double-resistance sampling. Therefore, at this time, single-resistance sampling is used to maximize the magnitude of the vector magnitude, so as to maximize 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, double-resistance sampling is used to minimize the magnitude of the vector magnitude, so as to keep the motor running at an extremely low speed without losing steps. Since the larger the magnitude of the vector magnitude, the shorter the duration of the zero vector, it is possible to first determine the vector angle and vector magnitude of the current control voltage, 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 magnitude of the current control voltage of the DC motor can be determined according to the current speed of the DC motor. So that the subsequent steps can determine the component durations of each component within the current carrier period duration of the DC motor according to the vector angle and vector magnitude of the current control voltage.

[0079] Specifically, the specific steps for executing step 202 are as follows:

[0080] Step 1: Query the current control voltage corresponding to the current speed in the pre-stored correspondence between the control voltage and the speed of the DC motor.

[0081] In implementation, when determining the vector angle and vector magnitude of the current control voltage of a 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 magnitude of the current control voltage based on the current control voltage. Since the DC motor has different speeds corresponding to different control voltages, technicians apply different control voltages to the DC motor in advance, respectively determine the speeds of the DC motor under each control voltage, and store the corresponding relationship between the control voltage and speed of the DC motor. Therefore, the current control voltage corresponding to the current speed can be queried in the pre-stored corresponding relationship between the control voltage and speed of the DC motor.

[0082] Step 2: Map the current control voltage to the space vector pulse width modulation diagram to obtain the vector angle and vector magnitude of the current control voltage.

[0083] In implementation, after determining the current control voltage of the DC motor, map the current control voltage to the space vector pulse width modulation diagram to obtain the vector angle and vector magnitude of the current control voltage. Figure 5 This is a space vector pulse width modulation diagram provided by an embodiment of the present application. As Figure 5 shown, the space vector pulse width modulation diagram divides one electrical cycle of the DC motor into 6 fan-shaped intervals. In each interval, 2 vectors are combined to form 1 final vector control voltage, following the vector parallelogram synthesis rule. Each interval corresponds to a carrier period, and multiple connected intervals can also be regarded as a carrier period. In this way, the vector angle and vector magnitude of the current control voltage are obtained through the space vector pulse width modulation diagram.

[0084] Step 203: Determine the component durations of each component within the current carrier period according to the vector angle, vector magnitude, preset maximum angle, current carrier period duration, and pre-stored standard component magnitude.

[0085] In implementation, when determining the sampling method of a DC motor, it is necessary to judge whether the component duration of each component within the current carrier period meets the sampling duration of the corresponding sampling method. If it is satisfied, the corresponding sampling method is adopted for sampling. Therefore, it is necessary to first determine the component duration of each component within the current carrier period duration. The first modulus length of the first component and the second modulus length of the second component corresponding to the current control voltage can be determined through the vector angle, the vector modulus length, and the preset maximum included angle. The modulus length determines the proportion of the component duration within the carrier period. Then, based on the corresponding ratios of the first modulus length, the second modulus length, and the pre-stored standard component modulus length, it is equal to the corresponding ratios of the first component duration of the first component, the second component duration of the second component, and the current carrier period duration. Therefore, the first modulus length component and the second modulus length component within the current carrier period duration can be determined according to the vector angle, the vector modulus length, the preset maximum included angle, the current carrier period duration, and the pre-stored standard component modulus length. Then, the ratio of the remaining duration of the current carrier period duration to the number of remaining components is determined as the component duration corresponding to each of the remaining components. Among them, the preset maximum included angle can be 60 degrees. In this way, the component duration of each component within the current carrier period duration is determined.

[0086] Specifically, the process of executing step 203 is as follows:

[0087] Step A, according to the vector modulus length, the vector angle, and the preset maximum included angle, the current control voltage is vectorially decomposed into two side components to obtain the first modulus length of the first component and the second modulus length of the second component. The preset maximum included angle is the maximum included angle between the first component and the second component.

[0088] In implementation, in the 6 sectors of the space vector pulse width modulation diagram, there are corresponding vector modulus lengths and vector angles of the control voltage. The current control voltage can be vectorially decomposed into two side components according to the vector modulus length, the vector angle, and the preset maximum included angle of the current control voltage to obtain the first modulus length of the first component and the second modulus length of the second component. The preset maximum included angle is the maximum included angle between the first component and the second component. Among them, the preset maximum included angle can be 60 degrees.

[0089] Figure 6 For a vector decomposition schematic diagram of a control voltage provided by an embodiment of the present application, as Figure 6 shown, the target voltage vector (current control voltage) in the first sector interval is decomposed. VS1 is the target voltage vector (current control voltage), and its magnitude and direction can also be jointly determined by two factors: the rotational speed of the DC motor and the rotor position. In the first sector interval, the two components are V1(1, 0, 0) and V2(1, 1, 0) respectively. Among them, the numbers of the components are in Figure 4 the equivalent circuit diagram, 1 represents the upper tube is on and the lower tube is off, and 0 represents the upper tube is off and the lower tube is on. Figure 6The control voltages VS1 and VS2 of the final vectors in [[]] are two different synthesized vectors. It can be seen that the different directions of VS2 and VS1 depend on the different magnitudes of the components V1 and V2. And the magnitudes of V1 and V2 are reflected in software control as the lengths of time for controlling V1 and V2. The different magnitudes of VS2 and VS1 depend on the different magnitudes of the zero vectors among them. And the magnitude of the zero vector is reflected in software control as the length of time the zero vector persists within a carrier period. As Figure 7 shown, decomposing VS1 in the directions of V1 and V2 gives the target voltage components VS1-V1 and VS1-V2. VS1-V1 determines the proportion of the duration T1 of the first component of the V1 component in a carrier period, and VS1-V2 determines the proportion of the duration T2 of the second component of the V2 component in a carrier period. The remaining is the action time of the V0 and V7 components. Calculated according to the preset maximum angle between the first component and the second component being 60°, Ɵ represents the vector angle (preset maximum angle), and the specific time conversion relationship:

[0090] Magnitude operation:

[0091] ,

[0092] .

[0093] Figure 8 is a schematic diagram of the duration of components within a carrier period provided by an embodiment of the present application. As Figure 8 shown, 1 represents the upper transistor on and the lower transistor off, and 0 represents the upper transistor off and the lower transistor on. Among them, the duration of the zero vector V0(0, 0, 0) is T0, and the duration of V7(1, 1, 1) is T7. The durations of the two components V1(1, 0, 0) and V2(1, 1, 0) are T1 and T2 respectively. T0 + T1 + T2 + T7 = T, where T is the duration of a carrier period.

[0094] Step B: Determine the duration of the first component by multiplying the ratio of the first magnitude to the pre-stored standard component magnitude by the duration of the current carrier period.

[0095] In implementation, the magnitude determines the proportion of the duration of the component within a carrier period. That is to say, the proportion of the component magnitude to the standard component magnitude is equal to the proportion of the component duration to the carrier period duration. Therefore, the duration of the first component can be determined by multiplying the ratio of the first magnitude to the pre-stored standard component magnitude by the duration of the current carrier period.

[0096] For example, convert to the duration of the component according to the calculated magnitude of the component. As Figure 9As shown in the figure, within each sector interval, the control voltage of the maximum vector voltage is defined as the inscribed circle. Let the radius of the inscribed circle be R, and |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 length and duration of the maximum inscribed circle: S corresponds to the total time of T0 + T7, and R corresponds to the total time of T1 + T2. The total time is the duration T of one carrier cycle. For example, if the carrier frequency is 16KHZ, then 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. Since the modulus length |VS1| is determined, that is, |VS1| / |V1| is determined, let it be |VS1| / |V1| = k. So |VS1| = |V1|k. |V1| corresponds to the full carrier cycle duration T = 62.5us. |VS1 - V1| corresponds to the action time T1 of V1, and |VS1 - V2| corresponds to the action time T2 of V2. We get T1 = T·k·(cosƟ - sinƟ / tan60°)us; T2 = T·k·(cos(60° - Ɵ) - sin(60° - Ɵ) / tan60°)us. That is, the ratio of the component modulus length to the standard component modulus length is equal to the ratio of the component duration to the carrier cycle duration. The product of the ratio of the first modulus length to the pre-stored standard component modulus length and the current carrier cycle duration can be determined as the first component duration.

[0097] Step C: Determine the second component duration by multiplying the ratio of the second modulus length to the pre-stored standard component modulus length by the current carrier cycle duration.

[0098] In implementation, the modulus length determines the duration ratio of the component within the carrier cycle. That is, the ratio of the component modulus length to the standard component modulus length is equal to the ratio of the component duration to the carrier cycle duration. Therefore, similarly, the product of the ratio of the second modulus length to the pre-stored standard component modulus length and the current carrier cycle duration can be determined as the second component duration.

[0099] Step D: Determine the component duration corresponding to each remaining component by dividing the difference between the current carrier cycle duration and the sum of the first component duration and the second component duration by the number of remaining components.

[0100] In implementation, after determining the first component duration and the second component duration after decomposition in the sector interval where the current control voltage is located, the remaining duration of the current carrier cycle can be evenly divided into the component durations of the remaining components. That is, the component duration corresponding to each remaining component can be determined by dividing the difference between the current carrier cycle duration and the sum of the first component duration and the second component duration by the number of remaining components.

[0101] Step 204: Based on the pre-stored sampling duration threshold and the durations of multiple components, determine the sampling method of the DC motor within the current carrier cycle, and determine whether to adjust the duration of the current carrier cycle according to the sampling method.

[0102] In implementation, within 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. For some components, only one single-phase current in the three-phase current can be collected, and for some, two-phase current can be collected. That is to say, there is a corresponding sampling method for the DC motor under each component. Specifically, for the component where a single-phase current is collected, the sampling method can be single-resistor sampling; for the component where a two-phase current is collected, the sampling method can be double-resistor sampling. However, when using the sampling method for phase current sampling, a certain sampling duration is required. Only when the component durations of each component meet the sampling duration of the corresponding sampling method can the sampling method corresponding to this component be determined as the sampling method of the DC motor within the current carrier cycle. Therefore, when determining the sampling method of the DC motor, it is necessary to judge whether the component durations of each component within the current carrier cycle meet the sampling duration required by the corresponding sampling method. If so, the corresponding sampling method can be determined according to the number of phase currents collected under the control of this component. For example, if a single-phase current is collected, single-resistor sampling is used; if a two-phase current is collected, double-resistor sampling is used. Then, after determining the sampling method, it can also be judged whether to adjust the duration of the current carrier cycle based on the sampling method. If the sampling method is single-resistor sampling, the component duration of the component corresponding to single-resistor sampling is reduced and adjusted to the sampling duration of single-resistor sampling. If the sampling method is double-resistor sampling, the component duration of the component corresponding to double-resistor sampling is reduced and adjusted to the sampling duration of double-resistor sampling. Among them, the sampling duration of single-resistor sampling and the sampling duration of double-resistor sampling can be equal or 50%. Since the duration ratio of each component within one carrier cycle is fixed. After reducing the component duration of the component to be sampled, the component durations of the remaining components are correspondingly reduced according to the generated reduction ratio. In this way, the duration of the current carrier cycle is adjusted to the duration corresponding to the sampling method.

[0103] Figure 10 This is an equivalent circuit diagram of single-resistor sampling when a component acts provided by the embodiment of the present application. As Figure 10 shown, the component is V1(1, 0, 0). At this time, the upper switch of the U phase is on and the lower switch is off, and the upper switches of the V phase and the W phase are off and the lower switches are on. The current of the current control voltage passes through the U phase of the DC motor, then through the parallel circuit composed of the V phase and the W phase, and finally converges to the bus sampling resistor Rbus. Therefore, the Rbus current = U phase current. So, 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.

[0104] Figure 11 This is another schematic diagram of the equivalent circuit for single-resistance sampling when a component acts, provided by an embodiment of the present application. As Figure 11 shown, the component is V2(1, 1, 0). At this time, the upper switches of the U and V phases are on and the lower switches are off, and the upper switch of the W phase is off and the lower switch is on. The current of the current control voltage passes through the parallel circuit composed of the U and V phases, then passes through the W phase of the DC motor, and finally converges to the bus sampling resistor Rbus. Therefore, the current of Rbus = - the current of the W phase of the motor, that is, the two are equal in magnitude and opposite in direction. So, at this time, when the component V2(1, 1, 0) of the current carrier period acts on the DC motor, the current of the W phase of the DC motor is collected.

[0105] Furthermore, when the component V7(1, 1, 1) acts as a vector Figure 4 of the current sampling equivalent circuit. At this time, the sampling hardware circuit is in freewheeling, so no current flows through the three sampling resistors, and it is not suitable for sampling current. Therefore, when the component is V7(1, 1, 1), no sampling is performed.

[0106] Figure 12 This is a schematic diagram of the equivalent circuit for double-resistance sampling when a component acts, provided by an embodiment of the present application. As Figure 12 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 timing for double-resistance sampling. Therefore, at this time, when the component V0(0, 0, 0) of the current carrier period acts on the DC motor, the currents of the U phase and V phase of the DC motor are collected.

[0107] Specifically, the multiple components of the current carrier period include a first component, a second component, and a third component. The process of performing step 204 is as follows:

[0108] Step a, 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 greater than or equal to the third component duration of the third component, then determine that the sampling method of the DC motor in the current carrier period is single-resistance sampling, and reduce the current carrier period duration to the current carrier period duration of the preset proportionality coefficient. The first component and the second component are adjacent components for which the sampling hardware circuit outputs single-phase current when controlling the DC motor according to this, and the third component is the component for which the sampling hardware circuit outputs double-phase current when controlling the DC motor according to this.

[0109] In implementation, when determining the sampling method of a DC motor, it is necessary to judge whether the component durations of each component within the current carrier period meet the sampling durations required by the corresponding sampling method. If they meet, the corresponding sampling method can be determined. Therefore, the pre-stored sampling duration thresholds are respectively 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 greater than or equal to the third component duration of the third component, it is determined that the sampling method of the DC motor within the current carrier period is single-resistance sampling. Among them, the first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when controlling the DC motor in this way. The first component can be (1, 0, 0) and the second component can be (1, 1, 0). The third component is the component of the two-phase current output by the sampling hardware circuit when controlling the DC motor in this way. 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 perform sampling, and the first component and the second component are adjacent components. 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 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 within the current carrier period is single-resistance sampling. At this time, the sampling method is single-resistance sampling, and the first component duration and the second component duration are reduced and adjusted to the sampling duration of single-resistance sampling. Since the duration ratio of each component within a carrier period is fixed. After reducing the first component duration and the second component duration, the component durations of the remaining components are correspondingly reduced according to the generated reduction ratio. In this way, the current carrier period duration is adjusted to the current carrier period duration of the preset proportional coefficient. The preset proportional coefficient is the ratio of the sampling duration of single-resistance sampling to the first component duration / second component duration. In this way, the carrier period duration is gradually reduced to just meet the single-resistance sampling duration, strengthening the sinusoidality of the phase current waveform at extremely high rotational speeds, which is beneficial to the stable operation of the DC motor under this working condition.

[0110] Step b, if the sampling duration threshold is less than 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 within the current carrier period is dual-resistance sampling and single-resistance sampling.

[0111] In implementation, the pre-stored sampling duration threshold is respectively 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 to say, the first component duration and the second component duration are long enough for sampling, and the first component and the second component are adjacent components, 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 for sampling, and a two-phase current is collected under the third component. Then, the sampling method of the DC motor can be double-resistance sampling. In this way, it shows that there is enough time for single-resistance sampling and double-resistance sampling in the current carrier period, 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 result reliability is improved without increasing the hardware cost. No matter whether the DC motor is in the high-speed or low-speed limit operating condition, the DC motor can be maintained to run smoothly at the target speed.

[0112] 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, it is determined that the sampling method of the DC motor in the current carrier period is double-resistance sampling, and the current carrier period duration is reduced to the current carrier period duration of the preset proportionality coefficient.

[0113] In implementation, the pre-stored sampling duration threshold is respectively 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 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 for sampling, and a two-phase current is collected under the third component. Then, the sampling method of the DC motor can be double-resistance sampling. Therefore, it is determined that the sampling method of the DC motor in the current carrier period is double-resistance sampling. At this time, the sampling method is double-resistance sampling, and the third component duration is reduced and adjusted to the sampling duration of double-resistance sampling. Since the duration ratio of each component in a carrier period is fixed. After reducing the third component duration, according to the generated reduction ratio, the component durations of the remaining components are correspondingly reduced. The current carrier period duration is adjusted to the current carrier period duration of the preset proportionality coefficient. The preset proportionality coefficient is the ratio of the sampling duration of double-resistance sampling to the third component duration. In this way, the carrier period duration is gradually reduced to just meet the double-resistance sampling duration, so as to maintain a good sinusoidality of the phase current of the DC motor at the limit high speed and ensure the smooth operation of the motor.

[0114] Further, if the sampling duration threshold is greater than or equal to the durations of the first component and the second component, and greater than the duration of the third component, the current carrier period duration is gradually increased so that the durations of the components within the current carrier period can meet the sampling duration threshold, thereby preventing the DC motor from losing steps.

[0115] Step 205: According to the sampling method, obtain the single-phase current and / or the two-phase current of the DC motor collected by the sampling hardware circuit, and reconstruct the three-phase current through Kirchhoff's law to obtain the target three-phase current of the DC motor.

[0116] In implementation, after determining the sampling method, according to the sampling method, obtain the single-phase current and / or the two-phase current of the DC motor collected by the sampling hardware circuit. The sampling method can be single-resistor sampling and / or double-resistor sampling, and perform three-phase current reconstruction on the single-phase current and / or the two-phase current of the DC motor collected through Kirchhoff's law to obtain the target three-phase current of the DC motor. Among them, Kirchhoff's law is that the U-phase current + the V-phase current + the W-phase current = 0. Therefore, the three-phase current can be reconstructed through any two-phase current, that is, two single-phase currents are collected from adjacent components, or a two-phase current is collected from one component, and the three-phase current can be reconstructed. Or in a carrier period, both single-resistor sampling and double-resistor sampling are performed to obtain two sets of reconstructed phase current values respectively: Iu1, Iv1, Iw1; Iu2, Iv2, Iw2. And the finally comprehensively processed phase current values are: Iu = (Iu1 + Iu2) / 2, Iv = (Iv1 + Iv2) / 2, Iw = (Iw1 + Iw2) / 2. In this way, the obtained target three-phase current is more accurate.

[0117] Step d: When the sampling method is single-resistor sampling, through Kirchhoff's law, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components, 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.

[0118] In implementation, when the sampling method is single-resistor sampling, a single-phase current of the DC motor is collected through the sampling hardware circuit. When the three-phase currents of the DC motor are to be obtained, the adjacent components can be collected as two single-phase currents in the sampling hardware circuit, regarded as two single-phase currents collected at the same time, and three-phase current reconstruction is performed. Then, during the three-phase current reconstruction, Kirchhoff's law can be used to determine another single-phase current in the three-phase currents, and these three single-phase currents are determined as the target three-phase currents after the reconstruction of the DC motor. Among them, Kirchhoff's law is that the sum of the three-phase currents is zero. After determining the two single-phase currents collected by the sampling hardware circuit for the adjacent components, the opposite number of the sum value of the two single-phase currents is determined as another single-phase current. The positive and negative signs of the three-phase currents represent 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.

[0119] Step e, when the sampling method is dual-resistor sampling, through Kirchhoff's law, for a two-phase current collected by the sampling hardware circuit, determine another single-phase current in the three-phase currents, and determine the two-phase current and the single-phase current as the target three-phase currents after the reconstruction of the DC motor.

[0120] In implementation, when the sampling method is dual-resistor sampling, a two-phase current of the DC motor is collected through the sampling hardware circuit. When the three-phase currents of the DC motor are to be obtained, three-phase current reconstruction can be performed on this two-phase current. Then, during the three-phase current reconstruction, Kirchhoff's law can be used to determine another single-phase current in the three-phase currents, and the two-phase current and the single-phase current are determined as the target three-phase currents after the reconstruction of the DC motor. Among them, Kirchhoff's law is that the sum of the three-phase currents is zero. After determining a two-phase current of the sampling hardware circuit, the opposite number of the sum value of this two-phase current is determined as the single-phase current. In this way, the target three-phase currents after the reconstruction of the DC motor are obtained.

[0121] Step f, when the sampling methods are single-resistor sampling and dual-resistor sampling, through Kirchhoff's law, respectively for the two single-phase currents and a two-phase current collected by the sampling hardware circuit for the adjacent components, determine the other single-phase current in each of the two sets of three-phase currents, and calculate the average value of the two sets of three-phase currents after reconstruction to obtain the target three-phase currents after the reconstruction of the DC motor.

[0122] In implementation, when the sampling methods are single-resistor sampling and dual-resistor sampling, the two sets of reconstructed three-phase currents can be determined respectively through the steps in steps d and e. The specific process has been described in the above steps and will not be elaborated here. After determining the two sets of reconstructed three-phase currents, the average value of the two sets of reconstructed three-phase currents can be calculated to obtain the target three-phase currents after the reconstruction of the DC motor. The two current sampling methods take effect simultaneously, and the final target three-phase currents are comprehensively calculated based on the current values sampled by the two methods, making the algorithm estimation result more credible.

[0123] An embodiment of the present application provides a variable-frequency control method for current sampling. Based on a sampling hardware circuit, by determining whether the component durations of each component within the current carrier period duration meet the sampling duration of a DC motor, the corresponding sampling method is determined. The sampling methods include dual-resistance sampling and single-resistance sampling. Give full play to the ultimate performance of the DC motor under the current control voltage, integrate the two methods of dual-resistance sampling and single-resistance sampling, and maintain good sinusoidality of the phase current under the high- and low-speed limit operating conditions of the DC motor, avoid the out-of-step of the DC motor, and maintain the stable operation of the motor. Select different sampling methods in a timely manner through a variable-frequency strategy. And perform three-phase current reconstruction on the sampled current, and comprehensively calculate the final phase current value, making the algorithm estimation result more credible and improving the result reliability without increasing the hardware cost.

[0124] It should be understood that although Figure 2 the steps in the flowchart of Figure 2 are shown in sequence according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear indication in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover,

[0125] At least a part of the steps in

[0126] An embodiment of the present application also provides a variable-frequency control device for current sampling, as Figure 13 shown. The device includes:

[0127] An acquisition module 1301, configured to acquire the current speed, the current carrier period duration, and multiple components of the carrier period of the DC motor;

[0128] A first determination module 1302, configured to determine the vector angle and vector modulus of the current control voltage according to the current speed;

[0129] The second determination module 1303 is configured to determine the component duration of each component within the current carrier period according to the vector angle, the vector magnitude, a preset maximum included angle, the duration of the current carrier period, and a pre-stored standard component magnitude.

[0130] The third determination module 1304 is configured to determine the sampling method of the DC motor within the current carrier period based on a pre-stored sampling duration threshold and multiple component durations, and determine whether to adjust the duration of the current carrier period according to the sampling method.

[0131] The reconstruction module 1305 is configured to obtain 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 perform three-phase current reconstruction through Kirchhoff's law to obtain the target three-phase current of the DC motor.

[0132] As an optional implementation manner, the first determination module 1302 is specifically configured to:

[0133] Query the current control voltage corresponding to the current speed in the corresponding relationship between the control voltage and the speed of the pre-stored DC motor;

[0134] Map the current control voltage to the space vector pulse width modulation diagram to obtain the vector angle and vector magnitude of the current control voltage.

[0135] As an optional implementation manner, the second determination module 1303 is specifically configured to:

[0136] According to the vector magnitude, the vector angle, and a preset maximum included angle, decompose the current control voltage into two side components to obtain the first magnitude of the first component and the second magnitude of the second component, where the preset maximum included angle is the maximum included angle between the first component and the second component;

[0137] Determine the duration of the first component by multiplying the ratio of the first magnitude to the pre-stored standard component magnitude by the duration of the current carrier period;

[0138] Determine the duration of the second component by multiplying the ratio of the second magnitude to the pre-stored standard component magnitude by the duration of the current carrier period;

[0139] Determine the corresponding component duration of each remaining component by dividing the difference between the duration of the current carrier period and the difference between the duration of the first component and the duration of the second component by the number of remaining components.

[0140] As an alternative implementation, the multiple components of the current carrier cycle include a first component, a second component, and a third component. The third determination module 1304 is specifically configured to:

[0141] 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 greater than or equal to the third component duration of the third component, then determine that the sampling method of the DC motor in the current carrier cycle is single-resistance sampling, and reduce the current carrier cycle duration to the current carrier cycle duration of a preset proportionality coefficient. The first component and the second component are adjacent components of the single-phase current output by the sampling hardware circuit when controlling the DC motor in this way, and the third component is the component of the two-phase current output by the sampling hardware circuit when controlling the DC motor in this way;

[0142] If the sampling duration threshold is less than 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 double-resistance sampling and single-resistance sampling;

[0143] 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 double-resistance sampling, and reduce the current carrier cycle duration to the current carrier cycle duration of a preset proportionality coefficient.

[0144] As an alternative implementation, the reconstruction module 1305 is specifically configured to:

[0145] When the sampling method is single-resistance sampling, according to Kirchhoff's law, two single-phase currents of the sampling hardware circuit are respectively collected for adjacent components, the other single-phase current in the three-phase current is determined, and these three single-phase currents are determined as the target three-phase current after reconstruction of the DC motor;

[0146] When the sampling method is double-resistance sampling, according to Kirchhoff's law, for a two-phase current collected from the sampling hardware circuit, the other single-phase current in the three-phase current is determined, and this two-phase current and the single-phase current are determined as the target three-phase current after reconstruction of the DC motor;

[0147] When the sampling method is single-resistance sampling and double-resistance sampling, according to Kirchhoff's law, two single-phase currents and a two-phase current of the sampling hardware circuit are respectively collected for adjacent components, the other single-phase current in the two sets of three-phase currents is determined, and the average value of the two sets of three-phase currents after reconstruction is calculated to obtain the target three-phase current after reconstruction of the DC motor.

[0148] The embodiment of the present application provides a variable-frequency control device for current sampling. Based on a sampling hardware circuit, by determining whether the component duration of each component within the current carrier period duration meets the sampling duration of the DC motor, the corresponding sampling method is determined. The sampling methods include double-resistance sampling and single-resistance sampling. Give full play to the ultimate performance of the DC motor under the current control voltage, integrate the two methods of double-resistance sampling and single-resistance sampling, and maintain good sinusoidality of the phase current under the high- and low-speed extreme operating conditions of the DC motor, avoid the out-of-step of the DC motor, and maintain the stable operation of the motor. Select different sampling methods in a timely manner through a variable-frequency strategy. And perform three-phase current reconstruction on the sampled current, and comprehensively calculate the final phase current value, making the algorithm estimation result more credible and improving the result reliability without increasing the hardware cost.

[0149] For the specific limitations of the variable-frequency control device for current sampling, reference can be made to the limitations of the variable-frequency control method for current sampling in the above text, which will not be elaborated here. Each module in the above variable-frequency control device for current sampling can be implemented in whole or in part by software, hardware, and their combination. The above-mentioned modules can be embedded in the processor of the computer device in hardware form or independent of it, or stored in the memory of the computer device in software form, so as to facilitate the processor to call and execute the operations corresponding to the above modules.

[0150] In one embodiment, a computer device is provided, as Figure 14 shown, including a memory and a processor. A computer program that can run on the processor is stored on the memory. When the processor executes the computer program, the steps of the above variable-frequency control method for current sampling are implemented.

[0151] 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 above variable-frequency control method for current sampling are implemented.

[0152] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. 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 methods. Among them, any reference to a memory, storage, database, or other medium used in the various embodiments provided in the present application can include non-volatile and / or volatile memories. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM), etc.

[0153] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of another identical element in the process, method, article or device comprising the element.

[0154] 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 for display, data for analysis, etc.) involved in the present application are all information and data authorized by the user or fully authorized by all parties.

[0155] Each embodiment in this specification is described in a related manner. For the same or similar parts among the embodiments, reference can be made to each other. 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. For the related parts, reference can be made to the partial description of the method embodiment.

[0156] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope recorded in this specification.

[0157] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, 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 appended 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: Get the current speed and current carrier cycle length of the DC motor; Determining the vector angle and vector modulus of the current control voltage according to the current rotation speed; Determine, according to the vector angle, the vector modulus, the preset maximum angle, the current carrier cycle duration and the pre-stored standard component modulus, each component corresponding to the current control voltage vector within the current carrier cycle duration and the component duration of each component; Based on a pre-stored sampling duration threshold and a plurality of component durations, a sampling method of the DC motor in the current carrier cycle is determined, and whether the current carrier cycle duration is adjusted is determined according to the sampling method; the plurality of components of the current carrier cycle include a first component, a second component and a third component, and the process of executing this step is: if the pre-stored sampling duration threshold is less than a first component duration of the first component, a second component duration of the second component, and is greater than or equal to a third component duration of the third component, then it is determined that the sampling method of the DC motor in the current carrier cycle is single resistor sampling, and the current carrier cycle duration is reduced to the current carrier cycle duration of a first preset proportional coefficient, and the first component and the second component are adjusted according to the current control The third component is the component of the double-phase current output by the sampling hardware circuit when the DC motor is controlled by the current control voltage vector; 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 double-resistance sampling and single-resistance sampling; if the sampling time threshold is greater than or equal to 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 double-resistance sampling, and the current carrier cycle time is reduced to the current carrier cycle time of the second preset proportional coefficient; 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 a first component corresponding to the current control voltage and a second modulus of a second component corresponding to the current control voltage, wherein 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 third 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 third components.

4. 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.

5. A variable frequency control device for current sampling, characterized in that: The device is applied to a sampling hardware circuit, and the device comprises: The acquisition module is used to obtain the current speed of the DC motor and the current carrier cycle length; 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 each component and component duration of each component corresponding to the current control voltage vector 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 the 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 multiple components of the current carrier cycle include a first component, a second component and a third component, and the process of executing the third determination module is: if the pre-stored sampling duration threshold is less than the first component duration of the first component, the second component duration of the second component, and is greater than or equal to the third component duration of the third component, then determine that the sampling method of the DC motor in the current carrier cycle is single resistor sampling, and reduce the current carrier cycle duration to the current carrier cycle duration of a first preset proportional coefficient, the first component and the second component are proportional to each other. The first component is an adjacent component of the single-phase current output by the sampling hardware circuit when the DC motor is controlled according to the current control voltage vector, and the third component is a component of the two-phase current output by the sampling hardware circuit when the DC motor is controlled according to the current control voltage vector; 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 time threshold is greater than or equal to 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 the current carrier cycle time is reduced to the current carrier cycle time of the second preset proportional coefficient; 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.

6. The device according to claim 5, 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.

7. The device according to claim 5, 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 a first component corresponding to the current control voltage and a second modulus of a second component corresponding to the current control voltage, wherein 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 third 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 third components.

8. The device according to claim 5, 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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