Permanent magnet synchronous motor phase current reconstruction method based on novel switch state phase shift method

Abstract

The invention discloses a permanent magnet synchronous motor phase current reconstruction method and device for reducing harmonic waves, and belongs to the technical field of motor control. According to the method, a sampling topological structure is optimized, a sampling resistor is shifted from a direct-current bus side to a position between upper bridge arms of two phases A and B of an inverter, and low-harmonic and high-precision phase current reconstruction is realized by combining a novel switch state phase shift method (N switch state phase shift strategy) and a dynamic zero vector distribution strategy. The method specifically comprises the steps that sectors are divided according to a space vector diagram, and sampling vectors are selected; phase shift operation is carried out in a low modulation degree area through minimization of PWM waveform modification, and the average voltage conservation principle is followed; zero vector time is dynamically allocated in a high modulation degree region to extend a linear modulation range. The phase current total harmonic distortion (THD) is remarkably reduced, the modulation range is expanded, meanwhile, the cost effectiveness and the real-time performance are considered, and the method is suitable for low-cost permanent magnet synchronous motor driving systems such as electric automobile fans and water pumps.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet synchronous motor control. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in aerospace, transportation, and new energy fields due to their high efficiency, high power density, and high reliability. In PMSM control systems, accurate three-phase current detection is crucial for achieving high-performance control. Traditional methods typically employ multiple current sensors, but these are costly, bulky, and prone to gain errors. Phase current reconstruction technology based on a single current sensor can effectively reduce cost and size, becoming an important research direction for low-cost applications (such as electric vehicle fans and water pumps).

[0003] Traditional switching-state phase-shifting methods achieve current reconstruction by modifying the PWM waveform, but this leads to PWM waveform asymmetry within the switching cycle, introducing significant phase current harmonics and affecting current waveform quality. Existing hybrid modulation strategies eliminate the reconstruction dead zone by introducing active zero-state PWM, but active zero-state PWM introduces additional harmonics and has a limited modulation range. For example, other methods can only use active zero-state PWM in certain regions, resulting in a high total harmonic distortion rate of the phase current, and the linear modulation range is limited by insufficient sampling vector duration.

[0004] In recent years, some studies have moved the sampling resistor from the DC bus side to between the upper arms of the A and B phases of the inverter, such as... Figure 1 As shown, this topology can acquire current during zero-vector action, improving reconstruction flexibility. However, existing hybrid modulation strategies based on this topology still suffer from high harmonics and narrow modulation range. Therefore, a novel phase current reconstruction method is needed that can simultaneously reduce harmonics and expand the modulation range. Summary of the Invention

[0005] This invention relates to a phase current reconstruction technology for permanent magnet synchronous motors based on a novel switching state phase shift method. The aim is to reduce phase current harmonics and expand the linear modulation range by optimizing the sampling topology and modulation strategy. The technical means of this invention are described in detail below, including the method principle, specific steps, and implementation methods.

[0006] First aspect: Optimization of sampling topology; This invention first improves the sampling topology by moving the traditional DC bus-side sampling resistor to between the upper arms of phases A and B of the inverter, forming a new sampling structure. This topology allows for the acquisition of valid phase current information (such as phase A current) during zero-vector action, improving the flexibility of current reconstruction. Specifically, the sampling resistor connection point is located between the upper arms of the inverter, causing the correspondence between the sampling current and the phase current to change under different switching states (as shown in Table 1), thus laying the foundation for subsequent modulation strategy optimization.

[0007]

[0008] The second aspect: detailed steps of the novel switch state phase shift method; A novel switching state phase shift strategy achieves current reconstruction and reduces harmonics through minimal modification of the PWM waveform. Specific steps include: Region division and sampling vector selection: Based on the spatial vector map, the operating area is subdivided into multiple sectors (such as sector I, II-1, II-2, etc.), and a suitable sampling vector is assigned to each sector. For example: Sector I selects vectors V7 and V2 as sampling vectors, corresponding to a sampled current of -i. a and +i b Sector II selects vectors V7 and V2 or V7 and V3 as sampling vectors, with corresponding sampling currents of -i. a with +i b Other sectors are processed similarly to ensure that the sampling vector covers the entire operating area (as shown in Table 2).

[0009]

[0010] This partitioning takes advantage of the fact that current can be sampled during the action of the zero vector V7 under this topology.

[0011] Reconstruction of the current dead zone in the low-profile institutional region and its sector boundary region: Taking sectors I and II as an example. Figure 2 As shown in (a), when V ref When located in sector I, the entire region is divided into three parts. Part A does not require phase shifting because the durations of V2 and V7 meet the sampling requirements. Part B, however, requires phase shifting to extend the duration of V2 because the duration of V2 does not meet the sampling requirements, while the duration of V7 does. According to the principle of average voltage conservation, the average voltage needs to be compensated while extending the duration of V2. This invention places the sampling position in the latter half of the carrier period, that is, the entire carrier period (T... S It is divided into a compensation period in the first half and a sampling period in the second half. For example... Figure 5 As shown, where T a , T b , T c This is a three-phase modulated wave, with sampling trigger A and B being the starting positions of the sampling transition. To extend the duration of V2 within the sampling period, the C-phase modulated wave T within the sampling period is... c Increasing the value of V2 ensures that its duration perfectly meets the sampling requirements. Simultaneously, to compensate for the average voltage of phase C, the value of T is adjusted during the compensation period. c Subtract its growth value.

[0012] Dynamic zero vector allocation: To address the issue of insufficient zero vector V7 activation time under high-key regimes, this invention proposes dynamic zero vector allocation. When the V7 time is less than T... min At that time, the time of the zero vector V0 is dynamically allocated to V7, with an allocation amount Δt = T. min - t7. This allocation is achieved by adjusting the three-phase modulation wave, and it has been verified that it does not affect voltage synthesis. The dynamic zero-vector allocation improves the linear modulation range by 6.8% compared to conventional methods (under the experimental conditions of this invention).

[0013] The overall process of the new switch state phase shift strategy is as follows: Figure 3 As shown, it includes: (1) Input the voltage in the stationary coordinate system and calculate the sector and three-phase modulation wave.

[0014] (2) Determine whether the sampling vector time satisfies T min If necessary, it can trigger dynamic zero vector allocation or phase shift.

[0015] (3) Set the sampling conversion trigger point and generate the driving pulse.

[0016] This process ensures reliable current reconstruction within a wide modulation range while maintaining low harmonics.

[0017] Beneficial effects of this invention: 1. Harmonic performance is significantly reduced: such as Figure 4 As shown, compared to the traditional switching state phase shift method, this invention reduces the total harmonic distortion (THD) of the phase current by more than 5% under medium and low modulation schemes (e.g., modulation scheme m≤0.5), with an average optimization of 3.69% across the entire modulation scheme range. Compared to existing hybrid modulation strategies, THD is reduced by 35.42% under a typical operating condition with a modulation scheme of 0.4. Maintaining lower THD values ​​under different modulation schemes verifies its harmonic suppression advantages.

[0018] 2. Modulation range extension: The dynamic zero vector allocation strategy increases the linear modulation range from m1=1.016 to m2=1.085, a relative improvement of 6.8%.

[0019] 3. High reconstruction accuracy: The reconstructed current can track the real current in real time, maintaining sinusoidal characteristics and good dynamic performance when the load and speed change suddenly.

[0020] 4. Low cost: Using a single sampling resistor instead of multiple sensors reduces system cost and size.

[0021] 5. Simple algorithm: This invention is implemented through local phase shifting operation and dynamic zero vector allocation. The algorithm logic is clear, the computational complexity is low, and no complex hardware changes or additional computing resources are required, making it easy to deploy and maintain at the software level. Attached Figure Description

[0022] The accompanying drawings, as part of this invention, are provided to further illustrate the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation thereof. Clearly, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0023] Figure 1 This shows the inverter topology and the location of the sampling resistor. Figure 2 The regions are divided into sectors I and II; Figure 3 The overall process of the new switch state phase shift strategy; Figure 4 A comparison of THD of the three methods under three different modulation schemes; Figure 5 This is the phase shifting process for section B in sector I; where (a) is before phase shifting and (b) is after phase shifting. Figure 6 This is the phase shifting process for section D in sector II; where (a) is before phase shifting and (b) is after phase shifting. Figure 7 Dynamic zero vector allocation for section C in sector I; where (a) is before dynamic zero vector allocation and (b) is after dynamic zero vector allocation; Figure 8 This describes the dynamic zero vector allocation and phase shifting process for section B in sector I. (a) shows the initial waveform, and (b) shows the waveform after dynamic zero vector allocation and phase shifting. Figure 9 This is a flowchart of the present invention.

[0024] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0026] To enhance understanding of the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] This invention relates to a novel switch-state phase-shifting method for phase current reconstruction in permanent magnet synchronous motors. The implementation steps of this invention are described in detail below with reference to the accompanying drawings, including sampling topology settings, region division, phase-shifting operation, dynamic zero-vector allocation method, and implementation flow. The implementation method is illustrated with reference to the accompanying drawings: This invention provides a phase current reconfiguration device for a permanent magnet synchronous motor, comprising an inverter topology, a sampling resistor, a control module, and a PWM generation module. The inverter topology is a three-phase bridge structure, and the sampling resistor is positioned between the upper arms of phases A and B of the inverter, as shown below. Figure 1 As shown. The control module is used to calculate the modulation wave, and the PWM generation module outputs the drive signal based on a novel switching state phase shift strategy.

[0028] A method for reconfiguring phase current of a permanent magnet synchronous motor, such as Figure 9 As shown, the method includes the following steps: Step S100: Select sampling topology optimization and vector.

[0029] The sampling resistor is moved from the traditional DC bus side to between the upper arms of phases A and B of the inverter, allowing the A-phase current to be sampled during the operation of zero vector V7. Based on the topology characteristics, the sampling vector is redefined: sector I selects V7 and V2 as the sampling vectors, corresponding to the current signal -i. a and +i b The vector selection for sector II needs to be further divided according to the sub-regions: in region II-1, the sampling vectors are V7 and V2, corresponding to the current signal −i. a and +i b In region II-2, the sampling vectors are V7 and V3, corresponding to the current signal −i. a and −i c Other sectors are processed similarly, as shown in Table 3.

[0030]

[0031] Step S200: Implement the novel switch state phase shift method.

[0032] Based on the selection of the sampling vector, a novel switching state phase shift strategy is adopted to make minimal modifications to the PWM waveform, so as to achieve low voltage regulation and current reconstruction in the sector boundary region. Sector I and sector II are two typical cases throughout the entire power frequency cycle; other sectors can be handled in a similar manner. The following description combines the region division and phase shift operation of sectors I and II.

[0033] First, the division of sectors I and II is as follows: Figure 2 As shown, sector I is divided into three sub-regions (A, B, C), and sector II is divided into multiple sub-regions (such as D, E, F). The region division is based on whether the duration of the sampling vectors (such as V7 and V2) satisfies the minimum sampling time T. min Among them, regions A and E / F have sufficient sampling vector action time and do not require phase shifting; while regions B (sector I) and D (sector II) have insufficient sampling vector action time and require phase shifting.

[0034] For region B of sector I (e.g.) Figure 5 When the sampling vector V2 has an action time of less than T min At this time, phase shifting is required. Specific operations include: changing the carrier period T... s It is divided into a first half (compensation period) and a second half (sampling period). During the sampling period, the C-phase modulation wave T is increased. c The value of V2 extends the duration of V2 to T. min Simultaneously, reduce the C-phase modulation wave T during the compensation period. c The same value is used to compensate for the average voltage, ensuring the reference voltage vector V. ref The synthesis is unaffected. During implementation, the modulation wave needs to be adjusted in real time within the PWM interrupt, and the sampling trigger point needs to be set at the midpoint of the sampling period.

[0035] For region D of sector II (e.g.) Figure 6 As shown), when the duration of both sampling vectors V2 and V3 is insufficient, only one vector (such as V2) needs to be extended to avoid introducing additional harmonics through large-scale phase shift. The operation is similar: increase T in the sampling period. c By extending the V2 time, voltage compensation is performed by decreasing Tc during the compensation period. The phase shift principle follows the conservation of average voltage, ensuring that the total duty cycle of the three-phase modulated wave remains unchanged. Other regions (such as the C portion of sector I or the E / F portion of sector II) do not require processing due to sufficient sampling vector time.

[0036] The switching state phase shift strategy used in this invention achieves harmonic optimization by minimizing the phase shift range. In the low-power region, phase shifting is performed only on a specific phase (such as phase C); in the sector boundary region, phase shifting is performed only on 2 / 6 of the sector boundary region. Other sectors (such as III to VI) can be handled in a similar manner. For example, sectors III and IV correspond to the symmetrical regions of sector I, and sectors V and VI correspond to the symmetrical regions of sector II. Their phase shifting operations can be achieved through mapping relationships.

[0037] Step S300: Extend the modulation range using the dynamic zero vector allocation method.

[0038] When the sampling vector V7 acts for a time t7 < T minAt that time, dynamic zero vector allocation is used to dynamically allocate the time of zero vector V0 to V7 to ensure that it can achieve reliable current sampling.

[0039] Step S310: Dynamic zero vector allocation trigger condition.

[0040] If t7 < T min Then calculate the allocation time: Δt = T min - t7.

[0041] Step S320: Assign operation details.

[0042] Taking sector C of sector I as an example ( Figure 7 ): The time of the zero vector V0 is assigned to V7, and the size of the assignment satisfies the above formula. At this time, V ref The synthesis conforms to the following formula, where T s The carrier period.

[0043] ; Although the dynamic zero-vector allocation results in an increase in the average voltage of the three phases, the increase is proportional to the change, equivalent to the effect of the zero vector, and does not affect V. ref The synthesis of [the substance] has an impact.

[0044] Three-phase modulation wave adjustment formula: ; Theoretical basis: The vector synthesis of the reference voltage remains unchanged after adjustment, because ; The assignment operation is equivalent to the zero vector effect.

[0045] Step S330: Increase the modulation range.

[0046] In the high-intensity regime region (such as part B of sector I), the reference voltage vector V ref The modulation index m is relatively high (usually m>0.8), causing the duration of action of both sampling vectors V2 and V7 to be less than the minimum sampling time T. min Its expression is as follows: ; Among them, t dead To avoid the dead time added by inverter shoot-through, t set For the effective current settling time, t A / D For sample hold and conversion time.

[0047] Using novel switch-state phase-shift strategies or dynamic zero-vector allocation alone cannot fully solve this problem; therefore, a combination of both is needed to achieve reliable current reconstruction and extend the linear modulation range.

[0048] When the system detects that the duration of both V2 and V7 is insufficient, dynamic zero vector allocation should be prioritized. The purpose of dynamic zero vector allocation is to extend the duration of sampling vector V7 by dynamically allocating the time of zero vector V0 to V7, ensuring that it can achieve reliable current sampling.

[0049] Taking part C in sector I as an example, such as Figure 7 As shown in (a). At this time, the action time of V7 does not satisfy T. min Therefore, the time of the zero vector V0 needs to be dynamically allocated to V7, and the allocated time is: ; Where t7 is the duration of V7.

[0050] After completing the dynamic zero vector allocation, a novel switch state phase shift strategy is implemented to extend the duration of the sampling vector V2. For example... Figure 8 As shown, the carrier period T s It is divided into a first half (compensation period) and a second half (sampling period). During the sampling period, the C-phase modulation wave T is increased. c The value of V2 extends the duration of V2 to T. min The expansion quantity Δt=T min −t2.

[0051] Where t2 is the original duration of V2. During the compensation period, T is decreased. c The same value is used to compensate for the average voltage, ensuring that the output voltage vector remains unchanged. The phase shift operation needs to be completed in real time in the PWM interrupt service routine, and the sampling trigger point is set at the midpoint of the sampling period to avoid dead-time interference.

[0052] In T s =50 ms, T min Traditional linear modulation range under the condition of 3 ms: ; Range after dynamic zero vector allocation: ; The linear modulation range was improved by 6.8%.

[0053] Step S400: Real-time current reconstruction.

[0054] This invention is achieved through Figure 2 The software flow shown implements real-time current reconfiguration.

[0055] Step S410: Based on the input stationary coordinate system voltage u a , u b Calculate the sector S in which the current voltage vector is located.

[0056] Step S420: Calculate the three-phase modulation wave T based on the sector. a , T b , T c Size.

[0057] Step S430: Calculate whether the action time of the sampling vector V7 satisfies T based on the magnitude of the three-phase modulated wave. min If the requirements are not met, then dynamic zero vector allocation will be performed.

[0058] Step S440: After the conditions in the previous step are met or the dynamic zero vector allocation is completed, determine whether the action time of the other sampling vector V2 meets the requirement T. min If the requirements are not met, a phase shift operation of the switching state will be performed.

[0059] Step S450: If the conditions are met or the phase shifting operation is completed, the sampling conversion trigger point is set.

[0060] The present invention also provides a phase current reconstruction device, comprising: Sampling module: Used to collect current signals between the upper arms of phases AB.

[0061] Modulation module: Determines the sampling vector and calculates the modulation wave based on the loop calculation results.

[0062] Phase shift control module: Implements a new switching state phase shift strategy and a dynamic zero vector allocation strategy.

[0063] PWM output module: generates drive pulses to achieve current reconstruction.

[0064] The novel switch-state phase-shifting method and its phase current reconstruction system provided in the above embodiments are illustrated using only the division of the aforementioned functional modules (such as the sampling topology configuration module, reconstruction dead-zone analysis module, region division and vector selection module, phase-shifting operation control module, dynamic zero-vector allocation module, current sampling and processing module, PWM generation module, and performance verification module) when executing the permanent magnet synchronous motor phase current reconstruction method. In practical applications, the above functions can be assigned to different functional modules according to specific hardware resources and control requirements. For example, the sampling and processing module can be integrated into the analog front-end, while the phase-shifting algorithm module can be implemented in the digital signal processor, or the entire system function can be integrated into a single system-on-a-chip. Furthermore, the novel switch-state phase-shifting method and its phase current reconstruction system provided in the above embodiments belong to the same concept as the phase current reconstruction method embodiments, and their specific implementation process has been described in detail in the preceding method section, and will not be repeated here.

[0065] It should be noted that the permanent magnet synchronous motor phase current reconstruction device based on the novel switch state phase shift method provided in the above embodiments is only illustrated by the division of the above functional modules when executing the permanent magnet synchronous motor phase current reconstruction method based on the novel switch state phase shift method. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0066] The functional modules in this embodiment of the invention can be integrated into one processing module, or each unit can exist as a separate physical entity, or two or more units can be integrated into one module. The integrated module can be implemented in hardware or as a software functional module.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for reconstructing phase current of a permanent magnet synchronous motor to reduce harmonics, characterized in that, Includes the following steps: Sampling topology optimization steps: Set the sampling resistor between the upper bridge arms of the two phases AB of the inverter so that phase current information can be collected during zero vector action; The steps of the novel switch state phase shift method are as follows: When the sampling vector's action time does not meet the minimum sampling time T min At that time, the sampling vector's action time is extended through phase-shifting operations, and voltage compensation is performed by dividing the carrier period into a compensation period and a sampling period. Specifically, this includes: Sector division and sampling vector selection: The operating area is subdivided into multiple sectors based on the spatial vector diagram, and a sampling vector is assigned to each sector. The sampling vectors include V7 and V2, V7 and V3, V7 and V5, or V7 and V6, corresponding to a sampling current of -i. a and +i b -i a and -i c or -i a and +i c ; Reconstruction of the current dead zone in the low-profile institutional region and its sector boundary region: when V ref When located within a sector, the entire region is divided into three parts. The part where the voltage vector's duration meets the sampling requirements does not require phase shifting. Conversely, the voltage vector's duration needs to be extended through phase shifting. According to the principle of average voltage conservation, the average voltage needs to be compensated while extending the corresponding voltage vector's duration. Dynamic zero vector allocation steps: When the sampling vector V7's duration is less than T... min At that time, the time of the zero vector V0 is dynamically allocated to V7, with an allocation amount Δt = T. min -t7, and is achieved by adjusting the three-phase modulation wave. The overall process of the novel switch state phase shift strategy is shown in Figure 3, including: Input the voltage in the stationary coordinate system and calculate the sector and three-phase modulation wave. Determine if the sampling vector time satisfies T min If necessary, it can trigger dynamic zero vector allocation or phase shift. Set the sampling conversion trigger point and generate the drive pulse. Real-time reconfiguration steps: Based on the above steps, generate PWM drive signals to realize phase current reconfiguration.

2. The method according to claim 1, characterized in that, In the novel switch-state phase-shifting method, the phase-shifting operation includes: increasing the C-phase modulation wave T during the sampling period. c To extend the application time of the sampling vector, while reducing T during the compensation period. c Average voltage compensation is performed to ensure that the reference voltage vector synthesis remains unchanged. This invention places the sampling position in the latter half of the carrier period, that is, the entire carrier period (T) S The sampling period is divided into a first half of the compensation period and a second half of the sampling period. To extend the duration of V2 in the sampling period, the C-phase modulation wave T in the sampling period is... c Increasing the value of V2 ensures that its duration perfectly meets the sampling requirements. Simultaneously, to compensate for the average voltage of phase C, the value of T is adjusted during the compensation period. c Subtract its growth value.

3. The method according to claim 1, characterized in that, In the dynamic zero vector allocation step, the modulation wave adjustment formula is: Furthermore, the allocation operation does not affect voltage vector synthesis.

4. The method according to claim 1, characterized in that, The method improves the linear modulation range from m1 = 1.016 to m2 = 1.085, a relative improvement of 6.8%.

5. A permanent magnet synchronous motor phase current reconfiguration device for implementing the method of claim 1, characterized in that, include: Sampling module: Used to collect current signals between the upper arms of the two phases AB of the inverter; Modulation module: Calculates the three-phase modulation wave based on the voltage vector and determines the sampling vector; Phase-shift control module: Executes a novel switch-state phase-shift method and a dynamic zero-vector allocation algorithm; PWM output module: generates drive pulses to control the inverter's switching state.

Images