A single current sensor phase current reconstruction method based on multi-branch coupling

Abstract

This invention relates to a single-current sensor phase current reconstruction method based on multi-branch coupling, belonging to the field of motor control technology. The invention identifies all 12 potential current sampling locations in the inverter, establishes a general analytical expression for multi-branch coupled current including coupling coefficients, and theoretically derives and exhaustively enumerates all feasible combinations of sensor installation locations and coupling paths based on the constraint that the zero-voltage vector sampling equations are linearly independent. A feasible scheme is selected to construct the hardware topology according to actual needs, and the three-phase current can be reconstructed by sampling during the zero-voltage vector period. This invention addresses the problems of blind spots in the low-modulation region and sector boundary current reconstruction in traditional DC bus single-current sensor reconstruction methods, and the lack of theoretical guidance and application limitations in existing hardware topology improvement methods. It provides design theoretical guidance, greatly improves its application flexibility, and eliminates the current reconstruction blind spot.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a single current sensor phase current reconstruction method based on multi-branch coupling. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) have been widely used in new energy vehicles, industrial drives, and aerospace due to their high power density, high efficiency, and excellent control performance. In the high-performance vector control system of PMSMs, real-time and accurate acquisition of three-phase current information is the core component for achieving closed-loop current control. Traditional phase current detection schemes typically require the installation of at least two Hall current sensors at the inverter output, which not only increases the system size and hardware cost but may also introduce measurement errors due to inconsistencies in gain and bias among multiple sensors.

[0003] To reduce system cost and size, three-phase current reconstruction technology based on a single current sensor on the DC bus has been widely researched and applied. This technology uses only one current sensor on the DC bus of the inverter, sampling the bus current twice at a specific moment within a pulse width modulation (PWM) cycle, and reconstructing the three-phase current by combining this with the inverter's switching state. For example, Chinese patent CN105577062A discloses a three-phase current reconstruction method based on a single current sensor, which avoids the current sampling dead zone by narrowing the pulse width and phase shifting the PWM waveform. However, such traditional DC bus-based methods have inherent limitations: to ensure the accuracy and stability of the sampled current, the duration of the corresponding non-zero voltage vector must be greater than the minimum sampling time required by the system. When the reference voltage vector is located in the low modulation region of space vector pulse width modulation (SVPWM) or near the sector boundary, the duration of a certain non-zero voltage vector will be too short, resulting in the inability to collect effective phase current, thus forming the so-called current reconstruction dead zone.

[0004] To address this reconfiguration blind spot problem, existing solutions mainly fall into two categories: software compensation and hardware topology improvement. While software compensation methods (such as the aforementioned PWM phase shifting method and measurement vector insertion method) do not increase hardware costs, they typically disrupt the symmetry of the PWM waveform, increase the complexity of the control algorithm, and inevitably introduce additional current harmonics, torque ripple, and electromagnetic noise.

[0005] Hardware topology improvement methods, by changing the installation location of the current sensor from the DC bus to a specific branch inside the inverter, and utilizing the sufficient duration of the zero-voltage vector for sampling, avoid the limitation of the short duration of the non-zero voltage vector, providing an effective way to fundamentally eliminate the reconfiguration blind zone. For example, Chinese patent CN109450323A discloses a method that installs a single current sensor between two specific switches in the inverter and achieves phase current reconfiguration by dividing the inverter into twelve sectors and modifying the PWM strategy of specific sectors. Similarly, Chinese patent CN120855977A also proposes a dual-branch single-current sensor sampling scheme, utilizing the zero-voltage vector in the sampling process.

[0006] However, existing studies on hardware topologies for multi-branch coupled single current sensors often only analyze and verify isolated analyses of one or a few pre-selected sensor mounting locations and coupling topologies. These approaches lack systematic theoretical modeling and comprehensive derivation of all potential current sampling locations and coupling paths in voltage source inverters, limiting the engineering application scope of this technology and resulting in a lack of necessary flexibility in hardware circuit design. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a single-current sensor phase current reconstruction method based on multi-branch coupling, applied to a permanent magnet synchronous motor control system driven by a voltage source inverter. The inverter has multiple switching transistors and multiple branch positions available for current sampling. The method samples a single current sensor within one pulse width modulation (PWM) cycle to reconstruct the three-phase current of the motor. The method is characterized by the following steps: All potential current sampling locations in the inverter are identified, and the relationship between the current at each sampling location and the motor phase current and the inverter switching state is established. Define coupling coefficient Let represent the coupling mode of a single current sensor to the current at the nth sampling position, and establish the coupling current measured by the single current sensor. Regarding the coupling coefficient A general analytical expression for inverter switching states and phase currents of two-phase motors; Based on the aforementioned general analytical expression, the zero voltage vector is determined respectively. and The expression for the coupling current during operation and ; The setting makes the above and The system of equations relating the phase currents of the two-phase motor, which consists of expressions, is linearly independent under constraint conditions. Based on the aforementioned constraints, all feasible coupling coefficients are solved. Combination schemes; Choose one feasible coupling coefficient combination scheme to construct the inverter hardware topology, and in the zero voltage vector and During their respective operation periods, the single current sensor is sampled to obtain information on the phase current of the two-phase motor; Based on the acquired two-phase motor phase current information, the third-phase motor phase current is reconstructed by utilizing the relationship that the sum of the three-phase currents is zero.

[0008] As a further preferred technical solution, the identification of all potential current sampling locations in the inverter specifically involves identifying a total of 12 branch locations in the inverter that connect to the positive terminal of the DC bus, between the upper and lower bridge arms of each phase, and the negative terminal circuit of the DC bus as the potential current sampling locations.

[0009] As a further preferred technical solution, the coupling coefficient The value of is 1, -1, or 0, representing the current at the nth sampling position when the single current sensor is forward-coupled, reverse-coupled, or uncoupled, respectively; the general analytical expression is:

[0010] in, For the current at the nth sampling position, and For a two-phase motor, and To and Coefficients related to the switching states (Sa+, Sb+, Sc+) of the three-phase upper bridge arm of the inverter.

[0011] As a further preferred technical solution, the zero-voltage vector and The expression for the coupling current during operation and They are respectively: ; Among them, coefficient , , , By the coupling coefficient The decision is made such that the following relationship is satisfied: .

[0012] The linear independence constraint is as follows: and The determinant of the coefficient matrix is ​​not zero, that is: .

[0013] As a specific implementation scheme, when the coupling coefficient is limited... When the value of (n=1,2,…,12) is 0 or 1, there are 26 feasible coupling coefficient combination schemes that satisfy the constraints.

[0014] For example, one feasible combination scheme for coupling coefficients is: =1、 =1, and the rest =0; where, =1 represents the third sampling position of forward coupling, and the third sampling position is the branch connecting the upper arm of phase C and the power transistor; =1 represents the fourth sampling position of forward coupling, which is the A-phase motor winding branch. Under this scheme, the single current sensor operates at zero voltage vector... and The current values ​​collected during operation are as follows: ; The reconstructed three-phase current expression is: .

[0015] As another exemplary scheme, one of the feasible combinations of coupling coefficients selected is: =1, =1, and the rest =0; where, =1 represents the sixth sampling position of positive coupling, and the sixth sampling position is the C-phase winding branch; =1 represents the twelfth sampling position of the forward coupling, where the twelfth sampling position is the branch connecting the lower arm of phase B and the power transistor. Under this scheme, and with the coupling coefficient combination scheme, the single current sensor operates at zero voltage vector... and The current values ​​collected during operation are as follows: The reconstructed three-phase current expression is: .

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention is the first to systematically model all 12 potential sampling locations of the inverter and establish a general analytical expression for multi-branch coupling current. Through this expression and linear independence constraints, all feasible combinations of sensor installation locations and coupling paths can be theoretically derived and exhaustively enumerated, providing a systematic theoretical basis and design method for multi-location coupled single-current sensor phase current reconstruction technology. When designing hardware circuits, engineers can flexibly select the most suitable sensor installation location and coupling method from a complete library of feasible solutions based on specific requirements such as circuit board layout, wiring convenience, and electromagnetic compatibility characteristics. This greatly expands the application scope of this technology and gives hardware circuit design greater flexibility.

[0017] (2) The method of the present invention eliminates the current reconstruction blind zone in the low modulation region and sector boundary region that exists in the traditional method by shifting the current sampling time from the non-zero voltage vector period with a short action time to the zero voltage vector period with a usually sufficient action time. Simulation results show that even under harsh operating conditions such as low speed, the three-phase current waveform reconstructed by the method of the present invention is extremely smooth, has good sinusoidal characteristics, and is highly consistent with the actual current, which significantly improves the performance and stability of the control system.

[0018] (3) Compared with complex software compensation methods such as PWM phase shifting and measurement vector insertion, the phase current reconstruction algorithm of the present invention is extremely simple after selecting the hardware coupling scheme. It only needs to perform two samplings at a fixed zero voltage vector action time, and the three-phase current can be reconstructed through simple linear operation, which reduces the computational burden of the controller and is easy to implement on various microcontrollers.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a circuit schematic diagram of a traditional three-phase current reconfiguration strategy based on a single DC bus current sensor. Figure 2 This is a schematic diagram of the voltage space vector and the distribution of the basic voltage vector; Figure 3 A schematic diagram of a seven-segment space vector pulse width modulation waveform when the reference voltage vector Uref is applied to the first sector; Figure 4This is a schematic diagram of the current reconstruction blind zone in the traditional phase current reconstruction method based on a single DC bus current sensor. Figure 5 A diagram illustrating all potential selectable sampling positions of a single current sensor in a permanent magnet synchronous motor system driven by a voltage source inverter, provided as an embodiment of the present invention. Figure 6 A schematic diagram of an inverter topology with a single current sensor coupling path selected for an embodiment of the present invention; Figure 7 In order to be in Figure 6 Under the coupled topology shown, the zero voltage vector and A schematic diagram showing the current flow path during operation and the sensor sampling current analysis. Figure 8 The diagram shows a comparison between the reconstructed three-phase current waveform and the actual three-phase current waveform under the condition of a motor speed of 500 rpm, using the method provided in this embodiment of the invention and the traditional method. Figure 9 The diagram shows a comparison between the reconstructed three-phase current waveform and the actual three-phase current waveform under the condition of a motor speed of 1000 rpm, using the method provided in this embodiment of the invention and the traditional method. Detailed Implementation

[0021] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0022] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0023] Example 1 This embodiment provides a single-current sensor phase current reconstruction method based on multi-branch coupling. This method systematically models all potential sampling locations in the inverter, establishes a general analytical expression for the multi-branch coupled current, and exhaustively derives all feasible sensor installation and coupling paths through mathematical derivation. This eliminates the reconstruction blind spots of traditional methods while providing significant flexibility and theoretical guidance for engineering design.

[0024] Step S1: Analyze the traditional DC bus single current sensor reconfiguration strategy and its blind zone.

[0025] Figure 1 The circuit diagram of a traditional three-phase current reconfiguration strategy based on a single current sensor on the DC bus is shown. In this strategy, a single current sensor is connected in series in the DC bus loop.

[0026] Within one pulse width modulation (PWM) switching cycle Ts, two-phase current information can be obtained by sampling the DC bus current twice and combining it with the inverter switching state. Specifically, six switching quantities Sa+, Sa-, Sb+, Sb-, Sc+, and Sc- are defined to represent the on and off states of the upper and lower bridge arms of the three phases A, B, and C of the inverter, respectively, where "1" indicates the switch is on and "0" indicates the switch is off. Under the premise that the upper and lower bridge arms cannot be directly connected, the inverter has a total of 8 effective switching state combinations, which correspond to 8 basic voltage vectors, including 6 non-zero voltage vectors U1(001), U2(010), U3(011), U4(100), U5(101), and U6(110) and 2 zero voltage vectors U0(000) and U7(111), whose spatial distribution is as follows. Figure 2 As shown.

[0027] Taking the reference voltage vector Uref located in the first sector as an example, its synthesis principle is as follows: Figure 3 As shown. Uref consists of two adjacent non-zero voltage vectors U4 and U6, and a zero voltage vector. and The synthesis, with action times of T4, T6, T0, and T7, satisfies the following relationship: (1) Since permanent magnet synchronous motor windings are typically connected in a star configuration, there is a definite correspondence between the DC bus current (idc) and the motor phase current under different voltage vectors. For example, when a non-zero voltage vector U4(100) is applied, the upper bridge arm of phase A is conducting, and the lower bridge arms of phases B and C are conducting. At this time, the bus current is equal to the phase A current (ia). The correspondence between the bus current and the phase current under different voltage vectors is shown in Table 1.

[0028] Table 1

[0029] Combination Figure 3 Within one switching cycle Ts, the DC bus current is sampled during the action time of the non-zero voltage vectors U4 and U6, respectively, and ia and -ic are obtained respectively. Then, according to Kirchhoff's current law that the sum of the three-phase currents is zero, i.e., equation (2), ib is calculated, thereby reconstructing the three-phase current.

[0030] (2) However, in practical engineering applications, in order to obtain an accurate and stable sampling current, it is necessary to ensure that half of the action time of the non-zero voltage vector is greater than the minimum sampling time Tmin of the system. (3) Where Tset is the current-following voltage settling time, Tad is the Ad-conversion time, Tdelay is the device turn-on / turn-off delay time, and Tdead is the anti-shoot-through dead time for the upper and lower transistors.

[0031] Due to the limitation of Tmin, there are regions in the voltage space vector diagram where accurate current sampling is impossible, known as the current reconstruction blind zone. For example... Figure 4 As shown, when the reference voltage vector Uref is located in the low modulation region (near the origin) or sector boundary region of SVPWM, there is a situation where the duration of a certain non-zero voltage vector is too short and does not meet the minimum sampling time requirement, resulting in the inability to collect the correct phase current information, thus causing the current reconstruction failure.

[0032] Step S2: Systematic modeling and selection of the current sensor installation location and coupling path.

[0033] To address the aforementioned reconfiguration blind zone problem, this invention employs a hardware topology improvement approach. By changing the installation position of the current sensor, it couples multiple branches within the inverter and utilizes the sufficient zero-voltage vector action time for current sampling, thereby fundamentally eliminating the reconfiguration blind zone at the low-modulation region and sector boundaries.

[0034] Figure 5 Twelve potential selectable sampling locations for a single current sensor in a voltage-source two-level inverter driving a permanent magnet synchronous motor system are identified. Based on the inverter topology and Kirchhoff's current law, the current at each sampling location under different switching states can be represented by the three-phase upper bridge arm switching states (Sa+, Sb+, Sc+) and phase currents (ia, ib, ic), or combinations thereof. Table 2 lists... Figure 5 The current expression for all 12 sampling locations.

[0035] Table 2

[0036] To theoretically derive all feasible sensor coupling schemes, this invention establishes a general analytical expression for multi-branch coupling current. It assumes the use of a current sensor coupled in any manner. Figure 5 If all or part of the sampling locations are considered, the coupled current *icoupled* measured by the sensor can be expressed as a linear combination of the currents in each branch. Considering the relationship that the sum of the three-phase currents is zero, this coupled current can ultimately be simplified to an expression containing only two-phase currents: (4) Where Kn (n=1,2,...,12) is the coupling coefficient at the nth sampling position, and its value is defined as: Kn=1: This indicates that the current sensor is positively coupled to the current at this location; Kn= 1: Indicates that the current sensor is reverse-coupled to the current at this location; Kn=0: This indicates that the current sensor is not coupled at this location.

[0037] The coefficients KA and KB are functions of Kn and the switching states (Sa+, Sb+, Sc+), and their specific relationship is as follows: (5) The key to this invention lies in utilizing the sufficient duration of the zero-voltage vectors U0(000) and U7(111) for current sampling. By substituting the switch states (Sa+, Sb+, Sc+) = (1,1,1) and (0,0,0) into equations (4) and (5) respectively, the current values ​​collected by the sensor when these two zero-voltage vectors are in effect can be obtained, as shown in equations (6) and (7).

[0038] (6) (7) (8) In order to successfully calculate the two-phase currents ia and ib by sampling twice during the action of the zero voltage vectors U7 and U0 in a single PWM cycle, it is necessary to ensure that the linear equation system of ia and ib composed of equations (6) and (7) has a unique solution, that is, its coefficient determinant is not zero, as shown in equation (9).

[0039] (9) The above formula is the necessary and sufficient condition for theoretically determining whether a set of coupling coefficients K1~K12 is feasible. Through mathematical calculation, all combinations of K1~K12 that satisfy this condition can be exhaustively enumerated.

[0040] When the coupling coefficients K1~K12 are limited to a certain value When 1, 0 or 1, that is, only considering simple forward, reverse or uncoupled, after calculation, there are 104 ways to satisfy the value of equation (9). If the hardware circuit design is further simplified and the value of K1~K12 is limited to 0 or 1, that is, only considering forward coupling or uncoupled, then there are 26 ways to satisfy the value of equation (9).

[0041] Table 3 lists five exemplary coupling paths among these 26 feasible solutions and their corresponding K1~K12 values.

[0042] Table 3

[0043] In Table 3, scheme number 4 represents =1、 =1, the rest =0, which indicates that the current sensor is forward coupled sampling positions 3 and 4. Similarly, scheme number 1 represents forward coupled positions 10 and 11; scheme number 2 represents forward coupled positions 6 and 12; scheme number 3 represents forward coupled positions 5 and 11; and scheme number 5 represents forward coupled positions 2 and 8.

[0044] Step S3: Three-phase current reconstruction principle based on zero-voltage vector sampling.

[0045] To illustrate the specific implementation process of this invention in detail, this embodiment selects the fourth coupling path in Table 3 for detailed explanation, namely... =1、 =1, the rest are 0. The inverter topology built based on this coupling path is as follows: Figure 6 As shown, the single current sensor simultaneously couples the currents at sampling positions 3 and 4. Sampling position 3 is the branch between the upper arm of phase C and the connection point of the power transistor, and sampling position 4 is the branch of the motor winding of phase A.

[0046] Will =1、 =1, the rest Substituting 0 into equations (6) and (7), we can calculate the current values ​​collected by the sensor when the zero voltage vectors U7 (111) and U0 (000) are applied: (10) This theoretical calculation result can be intuitively verified through the analysis of actual circuit topology. Figure 7 Shown in Figure 6 The current flow path under the topology shown is when the zero voltage vector is applied. Figure 7The left side shows the state when U7 (111) is in operation. At this time, all upper bridge arms are on and the lower bridge arms are off. Current flows from the positive terminal of the DC bus through the upper bridge arms of phases A, B, and C into the motor windings. At this time, the sensor coupling path is: the current ia flowing through the upper bridge arm of phase A and the current ic flowing through the upper bridge arm of phase C. However, since the three-phase windings under U7 do not form a loop, the actual current is zero, and the sensor output is -ib. Figure 7 The right side represents the state when U0 (000) is active. At this time, all lower bridge arms are on and the upper bridge arms are off. Current flows from the motor windings through the lower bridge arms and the sensor back to the negative terminal of the DC bus. At this time, the sensor couples the A-phase lower bridge arm current ia and the C-phase lower bridge arm current, and its net output is ia.

[0047] Both theoretical calculations and circuit analysis yielded the same results. Within one PWM switching cycle, the controller samples the current sensor twice, during the periods of U7 and U0, directly obtaining the A-phase current ia and the negative values ​​of the B-phase current ib. Then, using the relationship that the sum of the three-phase currents is zero, the C-phase current ic can be calculated. Thus, the complete three-phase currents of the PMSM are reconstructed, and their expression is: (11) It should be noted that the above reconstruction process does not depend on the duration of the non-zero voltage vector, as long as the duration of the zero voltage vectors U7 and U0 is greater than Tmin. Under most operating conditions, especially in the low modulation region and sector boundary region, the duration of the zero voltage vector is sufficient. Therefore, this method can fundamentally eliminate the current reconstruction blind zone present in traditional methods.

[0048] In addition to the specific description in this embodiment =1、 Besides scheme 1, the other schemes listed in Table 3, as well as the various feasible schemes obtained through the above modeling and solution methods, can all be used to construct and implement inverter topologies in a similar manner. For example, for scheme number 2 ( =1, =1), the sensor will be positively coupled to positions 6 and 12. Substituting into equation (8) and equations (6) and (7), we can obtain By sampling these two current values, the three-phase current can also be reconstructed using equation (2). Different coupling schemes will result in different current phase sequences and polarities obtained by sampling under zero voltage vector, but their core principles are all based on the general expression (4) established by this invention and its derived linear independence condition (9). Therefore, under the theoretical guidance disclosed in this invention, those skilled in the art can choose any feasible coupling path to achieve the purpose of this invention according to actual needs.

[0049] Step S4: Simulation verification.

[0050] To verify the effectiveness of the single-current sensor phase current reconstruction method based on multi-branch coupling proposed in this invention, a simulation model was built for verification. In the simulation, the parameters of the permanent magnet synchronous motor were set as follows: stator resistance of 0.958Ω, d-axis inductance Ld = 5.25mH, q-axis inductance Lq = 12mH, permanent magnet flux linkage of 0.1827Wb, and number of pole pairs of 4. The DC bus voltage was set to 311V, and the PWM switching frequency was 10kHz. Based on the selected devices and circuit characteristics, the minimum sampling time Tmin was set to 4.5μs. The above parameters are only a specific example, and the application of this invention is not limited to the specific parameter values ​​mentioned above.

[0051] To highlight the advantages of the method of this invention in eliminating the reconfiguration blind zone, a comparative analysis was conducted on the actual three-phase current, the reconfiguration current of the traditional DC bus single current sensor, and the reconfiguration current of the method proposed in this invention under two operating conditions: motor speed of 500 rpm (low speed, easier to enter the blind zone) and 1000 rpm (medium speed).

[0052] Figure 8 The comparison of reconfiguration current performance at 500 rpm is shown. Figure 8 (a) The actual three-phase current waveforms directly acquired by three high-precision current sensors are used as a reference. Figure 8 (b) is the three-phase current waveform reconstructed using the traditional DC bus single current sensor method; Figure 8 (c) is the three-phase current waveform reconstructed using the method of the present invention.

[0053] observe Figure 8 (b) It is evident that the traditional DC bus-based reconfiguration strategy exhibits severe current distortion and glitches during operation. This is because, under low-speed conditions of 500 rpm, the reference voltage vector remains in the low-modulation region for an extended period and frequently crosses sector boundaries, resulting in an extremely short duration of action for a non-zero voltage vector, which is less than the minimum sampling time Tmin required by the system. Consequently, it frequently falls into the current reconfiguration dead zone, making it impossible to correctly acquire and resolve the complete phase current.

[0054] In stark contrast to traditional methods, such as Figure 8 As shown in (c), after employing the reconstructing strategy based on zero-voltage vector sampling using a multi-branch coupled single current sensor designed in this invention, the reconstructed three-phase current waveform is very smooth and exhibits good sinusoidal characteristics. Even under extremely harsh reconstructing conditions at a low speed of 500 rpm, the current waveform reconstructed by the method of this invention is still consistent with... Figure 8 (a) The three-phase current waveforms acquired by the actual sensors in the model remain highly consistent, and the problems of current distortion and glitches have been fundamentally solved.

[0055] Figure 9 The comparison of reconfiguration current effects at 1000 rpm is shown. Observation Figure 9 (b) Although the current waveform of the traditional method is improved compared to 500 rpm, obvious current spikes and distortions still exist at the sector boundaries, indicating that the reconstruction dead zone problem still exists. However, the method of this invention... Figure 9 (c) then maintains a smooth, sinusoidal reconstructed current waveform, consistent with... Figure 9 The actual current shown in (a) matches well.

[0056] Furthermore, although the above simulation verification was based on the specific coupling path numbered 4 in Table 3, it is reasonable to expect that all other feasible coupling schemes that satisfy equation (9) can achieve similar technical effects, namely, obtaining a smooth and accurate reconstructed current waveform while eliminating the reconstructed blind zone. This is because all these schemes share the commonality of shifting the sampling time to the zero-voltage vector period with sufficient action time and satisfying the condition of linear independence of the equation set.

[0057] In summary, the single-current sensor phase current reconstruction method based on multi-branch coupling proposed in this invention, through the establishment of a general analytical expression and systematic mathematical derivation, not only theoretically exhaustively lists all feasible sensor installation and coupling schemes, providing great flexibility and a solid theoretical basis for engineering applications, but also successfully and completely eliminates the inherent low-modulation region and sector boundary current reconstruction blind zone in traditional methods by shifting the sampling time to the period of zero voltage vector action. Simulation results fully demonstrate the effectiveness and superiority of this method.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A single-current sensor phase current reconstruction method based on multi-branch coupling, applied to a permanent magnet synchronous motor control system driven by a voltage source inverter, wherein the inverter has multiple switching transistors and multiple branch positions available for current sampling, the method sampling a single current sensor within one pulse width modulation cycle to reconstruct the three-phase current of the motor, characterized in that, Includes the following steps: All potential current sampling locations in the inverter are identified, and the relationship between the current at each sampling location and the motor phase current and the inverter switching state is established. Define coupling coefficient Let represent the coupling mode of a single current sensor to the current at the nth sampling position, and establish the coupling current measured by the single current sensor. Regarding the coupling coefficient A general analytical expression for inverter switching states and phase currents of two-phase motors; Based on the aforementioned general analytical expression, the zero voltage vector is determined respectively. and The expression for the coupling current during operation and ; The setting makes the above and The system of equations relating the phase currents of the two-phase motor, which consists of expressions, is linearly independent under constraint conditions. Based on the aforementioned constraints, all feasible coupling coefficients are solved. Combination schemes; Choose one feasible coupling coefficient combination scheme to construct the inverter hardware topology, and in the zero voltage vector and During their respective operation periods, the single current sensor is sampled to obtain information on the phase current of the two-phase motor; Based on the acquired two-phase motor phase current information, the third-phase motor phase current is reconstructed by utilizing the relationship that the sum of the three-phase currents is zero.

2. The method according to claim 1, characterized in that, The process of identifying all potential current sampling locations in the inverter specifically involves identifying 12 branch locations in the inverter that connect to the positive terminal of the DC bus, between the upper and lower bridge arms of each phase, and the negative terminal circuit of the DC bus as the potential current sampling locations.

3. The method according to claim 2, characterized in that, The coupling coefficient The value of is 1, -1, or 0, representing the current at the nth sampling position when the single current sensor is forward-coupled, reverse-coupled, or uncoupled, respectively; the general analytical expression is: in, For the current at the nth sampling position, and For a two-phase motor, and To and Coefficients related to the switching states (Sa+, Sb+, Sc+) of the three-phase upper bridge arm of the inverter.

4. The method according to claim 3, characterized in that, The zero voltage vector and The expression for the coupling current during operation and They are respectively: ; Among them, coefficient , , , By the coupling coefficient The decision is made such that the following relationship is satisfied: 。 5. The method according to claim 4, characterized in that, The linear independence constraint is as follows: and The determinant of the coefficient matrix is ​​not zero, that is: .

6. The method according to claim 5, characterized in that, When the coupling coefficient is limited When the value of (n=1,2,…,12) is 0 or 1, there are 26 feasible coupling coefficient combination schemes that satisfy the constraints.

7. The method according to claim 6, characterized in that, One of the feasible combinations of coupling coefficients selected is: =1、 =1, and the rest =0; where, =1 represents the third sampling position of forward coupling, and the third sampling position is the branch connecting the upper arm of phase C and the power transistor; =1 represents the fourth sampling position of positive coupling, and the fourth sampling position is the A-phase motor winding branch.

8. The method according to claim 7, characterized in that, Under the aforementioned coupling coefficient combination scheme, the single current sensor operates at zero voltage vector. and The current values ​​collected during operation are as follows: ; The reconstructed three-phase current expression is: .

9. The method according to claim 6, characterized in that, One of the feasible combinations of coupling coefficients selected is: =1, =1, and the rest =0; where, =1 represents the sixth sampling position of positive coupling, and the sixth sampling position is the C-phase winding branch; =1 represents the twelfth sampling position of forward coupling, which is the branch connecting the lower arm of phase B and the power transistor.

10. The method according to claim 9, characterized in that, Under the aforementioned coupling coefficient combination scheme, the single current sensor operates at zero voltage vector. and The current values ​​collected during operation are as follows: The reconstructed three-phase current expression is: .

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