Improved three-resistor current sampling method for permanent magnet synchronous motor based on three-dimensional SVPWM

Abstract

This invention discloses an improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM, comprising: configuring the current sampling time at the midpoint of the PWM period to obtain an optimized timing sequence for the sampling time; and based on the optimized timing sequence, utilizing non-zero vectors and zero vectors... V 000 and zero vector V 111 The modulation space is divided into eight three-dimensional sectors; based on these sectors, the zero vector is allocated using a comparison between the minimum sampling time and the total action time of the zero vector. V 000 and zero vector V 111 The duration of action is used to obtain the allocated zero vector. V 000 Action time; based on the assigned zero vector V 000 The on-time of each phase lower bridge arm at the midpoint of the PWM cycle is obtained by comparing the on-time of each phase lower bridge arm with the minimum sampling time. The three-resistor current sampling strategy is obtained based on the comparison between the on-time of each phase lower bridge arm and the minimum sampling time.

Description

Technical Field

[0001] This invention belongs to the field of power electronics and motor control technology, and particularly relates to an improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM. Background Technology

[0002] Real-time and accurate sampling of stator current is fundamental to achieving torque control and efficient operation of permanent magnet synchronous motors. Currently, shunt-based current sampling strategies are widely used in robotics, drones, and white goods due to their advantages such as low cost and small size. Figure 1 As shown, depending on the shunt's installation location, current sampling strategies are mainly divided into three types: phase-end current sampling, lower-arm current sampling, and bus-end single-resistor current sampling. Among these, the lower-arm three-resistor current sampling strategy connects the shunt in series between the low-side switch and power ground. Its common-mode voltage is zero, and current flows only when the low-side switch is on, resulting in relatively low ohmic losses. This strategy achieves a good trade-off between sampling accuracy and power loss. This strategy typically samples the three-phase current simultaneously at the PWM carrier valley, when all three lower arms are on, effectively avoiding switching ripple interference.

[0003] However, the three-resistor current sampling strategy for the lower bridge arm still has significant technical drawbacks in practical applications. As the modulation index increases, the conduction time of the lower bridge arm switching devices may be less than the minimum time required for current sampling (including dead time, signal settling time, and ADC conversion time), thus creating a sampling dead zone. Depending on the modulation index, this strategy can be divided into three stages: in modulation stage 1, all three phase currents can be sampled; in modulation stage 2, only two phase currents can be sampled, requiring the constraint that the sum of the three phase currents is zero to reconstruct the third phase current; in modulation stage 3, only a single phase current can be sampled, and three-phase current reconstruction is impossible. Especially under traditional SVPWM modulation, the zero vectors V000 and V111 have equal durations, resulting in the sampling window not being fully utilized. This makes the sampling dead zone particularly prominent at high modulation ratios and sector boundaries, leading to current distortion, speed fluctuations, and other problems, severely impacting motor control performance.

[0004] Therefore, this invention proposes an improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes an improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM, thereby resolving the issues present in the prior art.

[0006] To achieve the above objectives, this invention provides an improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM, comprising: By configuring the current sampling time at the midpoint of the PWM cycle, the optimized timing of the sampling time is obtained; Based on the optimized timing, using non-zero vectors and zero vectors V 000 and zero vector V 111 The modulation space is divided into eight three-dimensional sectors, of which six sectors consist of non-zero vectors and are used to synthesize the reference voltage vector, and the zero vector... V 000 and zero vector V 111 Each corresponds to a three-dimensional sector; Based on 3D sectors, the zero vector is allocated by comparing the minimum sampling time with the total action time of the zero vector. V 000 and zero vector V 111 The duration of action is used to obtain the allocated zero vector. V 000 Duration of action; Based on the assigned zero vector V 000 The action time and the action time of the first effective vector of the current sector are used to obtain the conduction time of each lower bridge arm at the midpoint of the PWM cycle; The three-resistor current sampling strategy is derived based on the comparison between the conduction time of each lower bridge arm and the minimum sampling time.

[0007] Optionally, the process of obtaining the optimized timing sequence includes: Based on zero vector V 000 The optimized timing is obtained by comparing the action time with the minimum sampling time; Where, when the zero vector V 000 When the duration of action is greater than or equal to the minimum sampling time, the sampling time is maintained at the carrier peak value. When zero vector V 000 The action time is less than the minimum sampling time and the zero vector V 000 When the sum of the interaction times of the first effective vector and the first effective vector is greater than or equal to the minimum sampling time, the sampling time is shifted to the right by the zero vector. V 000 The difference between the action time and the minimum sampling time is used to obtain the optimized timing.

[0008] Optionally, the total action time of the zero vector is the zero vector. V 000 and zero vector V 111 The sum of the time of action; Among them, the zero vector is allocated based on the comparison between the minimum sampling time and the total action time of the zero vector. V 000 and zero vector V 111 The process of action over time includes: When the total action time of the zero vector is greater than or equal to twice the minimum sampling time, the zero vector is allocated based on the principle of equal division. V 000 With zero vector V 111 Duration of action; When the total action time of the zero vector is less than twice the minimum sampling time but greater than or equal to the minimum sampling time, the entire total action time of the zero vector is allocated to the zero vector based on the priority allocation principle. V 000 The zero vector after allocation is obtained. V 000 Action time and zero vector V 111 The duration of action is zero.

[0009] Optionally, based on the assigned zero vector V 000 The conduction time of each lower bridge arm at the midpoint of the PWM cycle is obtained by combining the action time of the first effective vector of the current sector with the action time of the first effective vector of the current sector. This includes: based on the allocated zero vector. V 000 The sum of the action time and the action time of the first effective vector in the current sector is used to calculate the conduction time of the three-phase lower bridge arm at the midpoint of the PWM cycle.

[0010] Optionally, the process of obtaining the three-resistor current sampling strategy based on the comparison results of the conduction time of each lower bridge arm and the minimum sampling time includes: When the conduction time of all three lower bridge arms is greater than or equal to the minimum sampling time, the three-phase current is sampled directly. When only the conduction time of two lower bridge arms is greater than or equal to the minimum sampling time, the two-phase current is sampled and the third-phase current is reconstructed based on the constraint that the sum of the three-phase currents is zero.

[0011] Optionally, the method further includes: when the sum of the total zero vector action time and the first effective vector action time is less than the minimum sampling time, reducing the first effective vector action time based on the principle of symmetry fine-tuning, so that the sum of the total zero vector action time and the adjusted first effective vector action time is equal to the minimum sampling time, obtaining the conduction time of each phase lower bridge arm at the midpoint of the PWM cycle based on the adjusted first effective vector action time, and sampling the two-phase current and reconstructing the third-phase current based on the obtained conduction time.

[0012] Optionally, the minimum sampling time is the sum of the inverter dead time, the analog circuit sampling signal stabilization time, and the ADC sampling conversion time.

[0013] The present invention also provides a computer, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described thereon.

[0014] The present invention also provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described thereon.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: This invention positions the current sampling time at the midpoint of the PWM cycle, expanding the time window available for three-phase current sampling. By introducing eight three-dimensional sectors composed of non-zero and zero vectors, it provides a spatial basis for dynamically allocating the zero vector's action time. Based on a comparison between the minimum sampling time and the total action time of the zero vectors, the action times of zero vectors V000 and V111 are allocated, prioritizing V000 to meet the minimum sampling time requirement when the total action time of the zero vectors is insufficient. Based on the allocated action time of zero vector V000 and the action time of the first effective vector in the current sector, the conduction time of each lower bridge arm at the midpoint of the PWM cycle is obtained, and the current sampling strategy is determined accordingly. This invention effectively expands the modulation range for simultaneous sampling of three-phase currents while maintaining a constant output voltage, significantly reduces the sampling dead zone area, and enables reliable acquisition of two-phase current and reconstruction of the third-phase current even in the high modulation region. This improves the waveform quality of the reconstructed current, reduces current distortion, and enhances the operational stability of the permanent magnet synchronous motor over a wide modulation range. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a current sampling topology diagram using a shunt in an embodiment of the present invention; Figure 2 This is a timing diagram of current sampling for the conventional lower arm three resistors in an embodiment of the present invention; Figure 3 This is a sampleable area diagram of the conventional lower bridge arm resistance current sampling according to an embodiment of the present invention; Figure 4 This is an optimized timing diagram based on fine-tuning sampling time according to an embodiment of the present invention; Figure 5 This is a diagram of the current sampling region after optimizing the timing according to an embodiment of the present invention; Figure 6 This is a sector model diagram of the three-dimensional SVPWM modulation strategy proposed in this embodiment of the invention; Figure 7 This is a diagram of the stereo SVPWM modulation strategy during modulation stage 1 of this embodiment of the invention. Figure 8 This is a diagram of the three-dimensional SVPWM modulation strategy during modulation stage 2 of this embodiment of the invention; Figure 9 This is a three-dimensional SVPWM waveform diagram during modulation stage 3 of this embodiment of the invention; Figure 10 This is a block diagram of the permanent magnet synchronous motor control system according to an embodiment of the present invention; Figure 11 This is a diagram of the experimental platform according to an embodiment of the present invention; Figure 12 The following is a comparison chart of the experimental results under no-load conditions in the embodiments of the present invention, wherein (a) is the traditional strategy and (b) is the improved strategy; Figure 13 The following is a comparison chart of the test results under load conditions in the embodiments of the present invention, wherein (a) is the traditional strategy and (b) is the improved strategy; Figure 14 The diagram shows the reconstruction error of phase A current under a 0.2 N·m load according to an embodiment of the present invention, where (a) is the traditional strategy and (b) is the improved strategy. Figure 15 This is a comparison chart of the THD results of the remodeling current of phase A under three typical loads according to an embodiment of the present invention; Figure 16 The diagram shows the error of reconstructed phase current under overmodulation conditions in an embodiment of the present invention, where (a) is the traditional strategy and (b) is the improved strategy. Figure 17 The figure shows a comparison of the phase A reconfiguration current THD results under different MIs in the embodiments of the present invention. (a) shows the relationship between MI and phase A reconfiguration current THD under the two schemes, and (b) shows the voltage vector trajectory when MI=1.09. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0019] Example 1 This invention addresses the current distortion and speed fluctuation problems caused by sampling dead time in the high modulation region of three-resistor current sampling in permanent magnet synchronous motors. This embodiment proposes an improved three-resistor current sampling strategy based on 3D SVPWM. By optimizing the timing of fine-tuning the sampling moments, it fully utilizes the duration of the zero vector V000 and the first effective vector throughout the PWM cycle. Furthermore, by introducing a 3D sector model, the duration of the two zero vectors is dynamically allocated, expanding the modulation range that allows simultaneous sampling of the three-phase current and reducing the sampling dead time to 12.5% ​​of the traditional scheme. Experimental results show that the proposed improved current sampling strategy increases the maximum modulation index MImax in the linear modulation region from 0.923 in the traditional strategy to 1.0, resulting in a wider current sampling range. Under the high modulation condition of modulation index MI=1.0, the total harmonic distortion (THD) of the phase current is reduced by 46.2%, and the distortion of the reconstructed current is smaller, verifying the effectiveness of the proposed strategy.

[0020] like Figure 1 As shown, this embodiment provides an improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM. The specific implementation process is as follows: 1. The traditional three-resistor current sampling process for the lower bridge arm includes: using SVPWM, the traditional three-resistor current sampling strategy for the lower bridge arm generally samples the current at the carrier valley. At this time, all three lower bridge arms are in the conducting state, which can realize simultaneous sampling of three-phase current and is not affected by switching ripple. Figure 2 As shown, the generated PWM waveform is about the vector V 111 Symmetric, zero vector V 000 and V 111 The two vectors act for the same duration, and each equally shares the duration of the total zero vector. T zero : (1) in, T 0、 T 7. T 1. T 2 represents the zero vector. V 000 Zero vector V 111 The duration of action of the two effective vectors T pwm This is the PWM period. The conduction time of the three-phase lower bridge arm can be used for current sampling. T a , T b , T c They are respectively: (2) As the modulation index (MI) increases, the on-time of the lower bridge arm device may be less than the minimum time required for current sampling. T min : (3) In the formula, t d The inverter dead time. t stab The settling time of the sampled signal in the analog circuit. t ad This is the ADC sampling and conversion time.

[0021] Furthermore, in modulation stage 1, all three phase currents can be sampled.

[0022] exist T min ≤ T In the low modulation index condition of 0 / 2, the pulse widths of all three lower bridge arms meet the sampling requirements, enabling reliable sampling of the three-phase current at carrier valleys. When T min = T At 0 / 2, the total effective vector time T 1+ T 2= T pwm - 4 T min ,like Figure 3 The regular hexagon of modulation stage 1 is shown. In the linear modulation region, the maximum modulation index that can be generated is its inscribed circle: (4) in, V ref For reference voltage, V dc This is the bus voltage. Therefore, we know that... MI It is impossible to reach 1, and T min The longer the modulation length, the lower the modulation index. For example, when T pwm For 100 μs, T min At 5 μs, MI max1 It is 0.8.

[0023] Furthermore, in modulation stage 2: only two-phase currents can be sampled. When the reference voltage vector further increases, it satisfies... T 0 / 2< Tmin ≤ T 0 / 2 + T At 1 / 2, it is impossible to sample all three phase currents simultaneously, but the constraint that the sum of the three phase currents of the motor is 0 can be utilized. (5) The third-phase current is reconstructed using the acquired two-phase currents, corresponding to... Figure 3 The green area, straight line ac and ah for T 0 / 2 + T 1 / 2 = T min The corresponding voltage vector trajectory. In the linear modulation region, the maximum modulation index that can be generated is the circumcircle of the regular hexagon in modulation stage 1: (6) Substituting the example parameters into formula (4) yields the following results. MI max2 =0.923.

[0024] Further, modulation stage 3: sampling dead zone. When T 0 / 2 + T 1 / 2< T min At this time, while maintaining the symmetry of the PWM waveform, only single-phase current (such as phase C) can be sampled, and the three-phase current cannot be reconstructed. This region is the sampling dead zone. Figure 3 The red area.

[0025] The above analysis shows that the timing of current sampling at the carrier valley does not fully utilize the zero vector at the beginning of the second PWM cycle. V 000 Duration of action T 0ʹ / 2, and also, since the sampling dead zone is located at the sector boundary, the first effective vector of two adjacent PWM cycles may be different (in Figure 2 The middle represents vectors. V 100 and V 010 This results in the first effective vector action time at the start of the second PWM cycle. T 1ʹ / 2 cannot be fully utilized, increasing the area of ​​the sampling dead zone.

[0026] 2. An improved three-resistor current sampling strategy for permanent magnet synchronous motors based on 3D SVPWM.

[0027] Furthermore, based on the optimized timing of fine-tuning the sampling time, i.e., configuring the current sampling time at the midpoint of the PWM cycle, the optimized timing of the sampling time is obtained. The process of obtaining the optimized timing includes: based on the zero vectorV 000 The optimized timing is obtained by comparing the action time with the minimum sampling time; where, when the zero vector V 000 When the effective time is greater than or equal to the minimum sampling time, the sampling time is maintained at the carrier peak value; when the zero vector... V 000 The action time is less than the minimum sampling time and the zero vector V 000 When the sum of the interaction times of the first effective vector and the first effective vector is greater than or equal to the minimum sampling time, the sampling time is shifted to the right by the zero vector. V 000 The difference between the action time and the minimum sampling time is used to obtain the optimized timing.

[0028] As a specific implementation of this embodiment, addressing the problem that the zero vector and first effective vector action time of the second PWM cycle in traditional lower arm three-resistor current sampling cannot be fully utilized, this embodiment proposes an optimized timing based on fine-tuning the sampling time. This involves placing the current sampling time near the midpoint of the PWM to fully utilize the zero vector of the entire PWM cycle. V 000 and the first effective vector V 100 The duration of action, such as Figure 4 As shown. At this point, the conduction time of the three lower transistors used for current sampling becomes twice that of the traditional timing sequence: (7) In modulation phase 1, in order to minimize the sampled current ripple, when in the modulation phase... T min ≤ T In the low modulation index condition of 0 / 2, the sampling time remains at the carrier peak value; when in... T 0 / 2< T min ≤ T At 0, shift the sampling time to the right ( T 0- T min This allows for the simultaneous sampling of three-phase currents. (From when...) T 0= T min The maximum modulation index that the optimized modulation stage 1 can produce in the linear modulation region is: (8) correspond Figure 5 The inscribed circle of region 1 in the modulation stage.

[0029] In modulation stage 2, T 0< T min≤( T 0+ T 1) It can sample two-phase currents and reconstruct the third-phase current. (From...) T min = T 0+ T The maximum modulation index that can be generated in the linear modulation region during modulation stage 2 is: (9) correspond Figure 5 The circumcircle of region 1 in the modulation stage or the incircle of the original hexagonal region.

[0030] In modulation stage 3, T min >( T 0+ T 1) It can only sample the current of one phase, which is a sampling dead zone.

[0031] Substituting into the example of formula (4), we can obtain the maximum modulation index of modulation stage 1. MI max1 The maximum modulation index increased from 0.8 to 0.9 in modulation stage 2. MI max2 The value increased from 0.923 to 1.0, reducing the sampling dead zone area in modulation stage 3 to 25% of its original size. It's worth noting that in modulation stages 1 and 2, the sampling time only needs to be adjusted to the right by a maximum of 2.5 µs. T min / 2), so it will not introduce obvious current ripple.

[0032] Furthermore, based on optimized timing, non-zero vectors and zero vectors are utilized. V 000 and zero vector V 111 The modulation space is divided into eight three-dimensional sectors, of which six sectors consist of non-zero vectors and are used to synthesize the reference voltage vector, and the zero vector... V 000 and zero vector V 111 Each corresponds to a 3D sector; based on the 3D sector, the zero vector is assigned using the comparison between the minimum sampling time and the total action time of the zero vector. V 000 and zero vector V 111 The duration of action is used to obtain the allocated zero vector. V 000 Action time; based on the assigned zero vector V 000The on-time of each phase lower bridge arm at the midpoint of the PWM cycle is obtained by comparing the on-time of each phase lower bridge arm with the minimum sampling time. The three-resistor current sampling strategy is obtained based on the comparison between the on-time of each phase lower bridge arm and the minimum sampling time.

[0033] As a specific implementation of this embodiment, the proposed three-dimensional SVPWM modulation strategy includes: to further reduce the sampling dead time, this embodiment proposes a three-dimensional SVPWM modulation strategy based on timing optimization. In traditional SVPWM, the zero vector is generally considered to be... V 000 and V 111 The generated terminal voltages are both 0, and the two are completely equivalent. However, when sampling the lower bridge arm current, there is a significant difference between the two. V 000 During operation, three-phase current can be sampled simultaneously. V 111 When in operation, it is impossible to sample any phase current. Therefore, in order to distinguish between the two zero vectors when using the lower arm current sampling strategy, V 000 and V 111 This embodiment introduces a three-dimensional SVPWM modulation strategy, and the resulting three-dimensional sector model is as follows: Figure 6 As shown in (a), the model divides the modulation space into eight sectors based on six sets of non-zero vectors and two zero vectors. The first six sectors are responsible for synthesizing the reference voltage vector, as shown in (a). Figure 6 As shown in (b), the latter two sectors are dynamically allocated the action time of the two zero vectors to minimize the sampling dead zone, as follows: Figure 6 As shown in (c).

[0034] Based on the comparison between the minimum sampling time and the total action time of the zero vector, the zero vector is assigned. V 000 and zero vector V 111 The process of determining the effective time of the zero vector includes: when the total effective time of the zero vector is greater than or equal to twice the minimum sampling time, the zero vector is allocated based on the principle of equal division. V 000 With zero vector V 111 The duration of action of the zero vector; when the total duration of action of the zero vector is less than twice the minimum sampling time but greater than or equal to the minimum sampling time, the total duration of action of the zero vector is allocated entirely to the zero vector based on the priority allocation principle. V 000 The zero vector after allocation is obtained. V 000 Action time and zero vector V 111 The duration of action is zero.

[0035] Based on the assigned zero vector V 000 The conduction time of each lower bridge arm at the midpoint of the PWM cycle is obtained by combining the action time of the first effective vector of the current sector with the action time of the first effective vector of the current sector. This includes: based on the allocated zero vector. V 000 The sum of the action time and the action time of the first effective vector in the current sector is used to calculate the conduction time of the three-phase lower bridge arm at the midpoint of the PWM cycle.

[0036] The process of obtaining the three-resistance current sampling strategy based on the comparison results of the conduction time of each phase lower bridge arm and the minimum sampling time includes: when the conduction time of all three phase lower bridge arms is greater than or equal to the minimum sampling time, the three-phase current is directly sampled; when only two phase lower bridge arms have conduction times greater than or equal to the minimum sampling time, the two-phase current is sampled and the third phase current is reconstructed based on the constraint that the sum of the three-phase currents is zero.

[0037] In modulation phase 1, when T zero ≥ 2 T min At that time, the zero vector has sufficient time to act. T 0 and T 7 Bisects the time of action of the zero vector T zero At this time, three-phase current can be sampled simultaneously, and the modulated PWM waveform is exactly the same as that of traditional SVPWM; but when T min ≤ T zero <2 T min When, if adopted T 0 and T The method of equal distribution will lead to T 0< T min Since it is impossible to sample all three phase currents simultaneously, in order to broaden the range of modulation stage 1, based on the principle of "prioritizing sampling feasibility while taking into account the temperature rise balance of switching devices", the three-dimensional SVPWM modulation strategy improves the allocation mechanism of the two zero vectors, prioritizing the allocation of the zero vector's action time to the vector. V 000 ,make sure T 0 satisfies minimum sampling time T min The requirement is that the remaining zero vector time is allocated to V 111 : (10) Depend on T min = Tzero The maximum output that modulation stage 1 can produce in the linear modulation region can be obtained. MI for: (11) correspond Figure 6 (b) The inscribed circle of the modulation stage 1 region, i.e., the three-phase current can be sampled simultaneously. MI The range is further expanded based on equation (8). At this stage, the trajectory of the voltage vector in the three-dimensional SVPWM and the modulated PWM waveform are as follows: Figure 7 As shown.

[0038] In modulation stage 2, T zero < T min ≤ T zero + T 1. It can sample two-phase currents and reconstruct the third-phase current. Because the total zero-vector time is insufficient, all zero-vector time must be allocated to the vector... V 000 : (12) Depend on T min = T zero + T 1. The maximum value that can be generated in the linear modulation region during modulation stage 2 can be obtained. MI for: (13) correspond Figure 6 In (b), the circumcircle of the modulation stage 1 region or the incircle of the original hexagonal region. In this stage, the trajectory of the voltage vector in the three-dimensional SVPWM and the modulated PWM waveform are as follows: Figure 8 As shown.

[0039] In modulation stage 3, T zero + T 1< T min Only one phase current can be sampled, such as Figure 9 Phase C in (a) belongs to the sampling dead zone.

[0040] Substituting into the example of formula (4), we get the maximum modulation index of modulation stage 1. MI max1 The maximum modulation index increased further from 0.9 to 0.95 in modulation stage 2. MI max2The maximum value of 1.0 in the linear modulation region is maintained, and the sampling dead zone area in modulation stage 3 is further reduced from 25% to 12.5% ​​of the traditional method.

[0041] To reduce the impact of modulation stage 3, this embodiment uses symmetrical fine-tuning. T Method 1 makes T zero + T 1= T min Ensure that two-phase current can be sampled, such as Figure 9 Phase B and phase C in (b). The complete block diagram of the permanent magnet synchronous motor control system is as follows: Figure 10 As shown.

[0042] 3. Experimental Verification and Analysis. To verify the proposed improved three-resistance current sampling strategy, a permanent magnet synchronous motor experimental platform was built. A physical diagram is shown below. Figure 11 As shown in Table 1, the specific parameters of the permanent magnet synchronous motor are listed. The main control chip is STM32G431, the control frequency is 10kHz, and the Luneburg observer is used to estimate the rotor position and speed of the motor online to achieve sensorless operation. Experiments are conducted in the following sections to verify the operation under no-load, loaded, and overmodulated conditions.

[0043] Table 1 Furthermore, the no-load condition test included: accelerating the no-load motor to the maximum no-load speed of 2900 rpm, and comparing the experimental results obtained using the traditional lower arm three-resistance current sampling strategy and the proposed improved strategy, for example... Figure 12 As shown, it can be seen that traditional strategies in MI An abnormal value was found in the current sampling when the current value was 1.0. i q After introducing closed-loop control, the motor speed exhibited abnormal fluctuations, with a peak-to-peak value of 675 rpm; using the proposed current sampling strategy, i q Both the motor speed and the speed fluctuation are relatively smooth, with the peak value of the speed fluctuation reduced to 290 rpm.

[0044] Furthermore, the load condition test included: maintaining the motor speed at the rated value of 2200 rpm, and sequentially applying load torques of 0.064 N·m, 0.13 N·m, and the rated 0.2 N·m. The traditional current sampling strategy was applied when the load torque was 0.13 N·m. i q The fluctuations in current and speed increased slightly. MI = 0.93), when the load torque is 0.2 N·m i qThe fluctuations in current and speed have increased significantly. MI = 1.0), the peak-to-peak speed fluctuation was 923 rpm; while the proposed improved strategy showed no significant current fluctuation throughout the loading process, and the speed was relatively stable, with a peak-to-peak speed fluctuation of 238 rpm, such as Figure 13 As shown.

[0045] The reconstructed phase A current is output to an oscilloscope via the MCU's DAC peripheral and compared with the actual current acquired by a high-precision current probe. Under a 0.2 N·m load, the traditional current sampling strategy exhibits outliers, with a total harmonic distortion (THD) of 6.88% for the reconstructed current. In contrast, the proposed improved strategy reduces the THD of the reconstructed phase A current to 3.70%. Figure 14 As shown. The THD data for the three load conditions were summarized to obtain the results. MI When THD = 0.85, the reconfiguration current levels of the two strategies are similar; MI When the reconfiguration current THD is 0.93, it decreases by approximately 28.8%; MI When the THD value is 1.0, the THD decreases by approximately 46.2%, meaning that... MI In the high modulation region ≥0.93, the advantages of the proposed improvement strategy gradually become apparent, consistent with the theoretical analysis in Section 2, such as... Figure 15 As shown, the effectiveness of the proposed improved strategy in the linear modulation region is verified.

[0046] Furthermore, the overmodulation test included: to further verify the proposed current sampling strategy, while maintaining a rated load of 0.2 N·m, the rotational speed was gradually increased to allow the reference voltage vector to enter... MI Over-modulation condition >1. When the motor speed is 2450 rpm, MI = 1.13, the THD of the reconstructed phase current using the traditional sampling strategy is 9.26%, while the THD of the proposed strategy is 6.77%. Figure 16 As shown. Statistical differences MI The reconfiguration current THD at that time can be seen from the fact that when the motor is operating in the overmodulation region, as... MI The THD increases because the circular reference trajectory is confined to the boundary of a regular hexagon; both sampling strategies show an upward trend, but at different... MI The improved strategies all had lower THDs than the traditional strategies, such as Figure 17 As shown, the effectiveness of the proposed strategy in the overmodulation condition is verified.

[0047] To address the current distortion and speed fluctuation issues caused by the sampling dead zone in the three-resistor current sampling strategy of the lower bridge arm, this embodiment proposes an improved current sampling strategy based on three-dimensional SVPWM. This strategy expands the modulation range that can be sampled simultaneously for three-phase currents, reduces the sampling dead zone to 12.5% ​​of the traditional scheme, lowers the THD of the reconstructed current, and has been experimentally verified, showing certain engineering application prospects.

[0048] The present invention also provides a computer, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described thereon.

[0049] The present invention also provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described thereon.

[0050] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM, characterized in that, Includes the following steps: By configuring the current sampling time at the midpoint of the PWM cycle, the optimized timing of the sampling time is obtained; Based on the optimized timing, using non-zero vectors and zero vectors V 000 and zero vector V 111 The modulation space is divided into eight three-dimensional sectors, of which six sectors consist of non-zero vectors and are used to synthesize the reference voltage vector, and the zero vector... V 000 and zero vector V 111 Each corresponds to a three-dimensional sector; Based on 3D sectors, the zero vector is allocated by comparing the minimum sampling time with the total action time of the zero vector. V 000 and zero vector V 111 The duration of action is used to obtain the allocated zero vector. V 000 Duration of action; Based on the assigned zero vector V 000 The action time and the action time of the first effective vector of the current sector are used to obtain the conduction time of each lower bridge arm at the midpoint of the PWM cycle; The three-resistor current sampling strategy is derived based on the comparison between the conduction time of each lower bridge arm and the minimum sampling time.

2. The improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM according to claim 1, characterized in that, The process of obtaining optimized timing sequences includes: Based on zero vector V 000 The optimized timing is obtained by comparing the action time with the minimum sampling time; Where, when the zero vector V 000 When the duration of action is greater than or equal to the minimum sampling time, the sampling time is maintained at the carrier peak value. When zero vector V 000 The action time is less than the minimum sampling time and the zero vector V 000 When the sum of the interaction times of the first effective vector and the first effective vector is greater than or equal to the minimum sampling time, the sampling time is shifted to the right by the zero vector. V 000 The difference between the action time and the minimum sampling time is used to obtain the optimized timing.

3. The improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM according to claim 1, characterized in that, The total action time of the zero vector is the zero vector V 000 and zero vector V 111 The sum of the time of action; Among them, the zero vector is allocated based on the comparison between the minimum sampling time and the total action time of the zero vector. V 000 and zero vector V 111 The process of action over time includes: When the total action time of the zero vector is greater than or equal to twice the minimum sampling time, the zero vector is allocated based on the principle of equal division. V 000 With zero vector V 111 Duration of action; When the total action time of the zero vector is less than twice the minimum sampling time but greater than or equal to the minimum sampling time, the entire total action time of the zero vector is allocated to the zero vector based on the priority allocation principle. V 000 The zero vector after allocation is obtained. V 000 Action time and zero vector V 111 The duration of action is zero.

4. The improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM according to claim 1, characterized in that, Based on the assigned zero vector V 000 The conduction time of each lower bridge arm at the midpoint of the PWM cycle is obtained by combining the action time of the first effective vector of the current sector with the action time of the first effective vector of the current sector. This includes: based on the allocated zero vector. V 000 The sum of the action time and the action time of the first effective vector in the current sector is used to calculate the conduction time of the three-phase lower bridge arm at the midpoint of the PWM cycle.

5. The improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM according to claim 1, characterized in that, The process of obtaining the three-resistor current sampling strategy based on the comparison results of the conduction time of each lower bridge arm and the minimum sampling time includes: When the conduction time of all three lower bridge arms is greater than or equal to the minimum sampling time, the three-phase current is sampled directly. When only the conduction time of two lower bridge arms is greater than or equal to the minimum sampling time, the two-phase current is sampled and the third-phase current is reconstructed based on the constraint that the sum of the three-phase currents is zero.

6. The improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM according to claim 5, characterized in that, The method further includes: when the sum of the total zero vector action time and the first effective vector action time is less than the minimum sampling time, reducing the first effective vector action time based on the principle of symmetry fine-tuning, so that the sum of the total zero vector action time and the adjusted first effective vector action time is equal to the minimum sampling time, obtaining the conduction time of each phase lower bridge arm at the midpoint of the PWM cycle based on the adjusted first effective vector action time, and sampling the two-phase current and reconstructing the third-phase current based on the obtained conduction time.

7. The improved three-resistor current sampling method for permanent magnet synchronous motors based on three-dimensional SVPWM according to claim 1, characterized in that, The minimum sampling time is the sum of the inverter dead time, the analog circuit sampling signal stabilization time, and the ADC sampling conversion time.

8. A computer comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in claim 1.

9. A storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in claim 1.

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