Phase current reconstruction method for dual three-phase permanent magnet synchronous motor based on dual measurement vector insertion

Abstract

The application discloses a double three-phase permanent magnet synchronous motor phase current reconstruction method based on double measurement vector insertion, and the method comprises the following steps: step 1, determining a measurement vector injection scheme according to a sector where a reference voltage vector is located; step 2, injecting a measurement voltage vector after the end of a normal PWM cycle and sampling the direct current bus currents of two sets of inverters; step 3, completing six-phase current reconstruction according to the sampling results of the bus currents; and step 4, compensating for modulation deviation caused by the measurement vector injection. The six-phase currents can be reconstructed through direct current bus sampling, and the reconstruction blind area problems in the low modulation ratio area and the sector boundary area are solved. Compared with the traditional vector insertion method, the application effectively reduces the influence on the effective working area of the system, reduces the switching frequency and switching loss, corrects the measurement error caused by measurement delay, and improves the system control accuracy.

Description

Technical Field

[0001] This invention relates to a method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor, specifically a method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor based on dual measurement vector insertion. Background Technology

[0002] Dual three-phase permanent magnet synchronous motors (DTP-PMSMs) offer advantages such as high power density, high reliability, low torque ripple, and high control flexibility, making them widely used in electric vehicles, marine propulsion systems, and aerospace electric propulsion. Current closed-loop control of DTP-PMSMs typically requires at least four current sensors to acquire phase current information, resulting in high cost, system complexity, and low reliability. Using a single current sensor to reconstruct the three-phase current can reduce costs, improve reliability, and provide redundancy for the control system.

[0003] Current research on phase current reconstruction control focuses on addressing the reconstruction blind zone in the low modulation ratio region and sector boundary region during voltage vector operation. Based on sensor installation location, it can be divided into two categories: DC bus sampling and non-DC bus sampling. A three-phase permanent magnet synchronous motor phase current reconstruction strategy based on DC bus sampling can use the vector pulse insertion method to solve the reconstruction blind zone. This method obtains the three-phase current by inserting three measurement vectors V1 (100), V3 (010), and V5 (001) at the end of each PWM cycle. Although the vector pulse insertion method can effectively solve the reconstruction blind zone problem, inserting three pulse vectors will prolong the PWM cycle, reduce the maximum amplitude of the output voltage vector, and thus shrink the effective operating area of ​​the system; it will also significantly increase the number of switching operations and switching losses per cycle; and the three-phase currents sampled from the three pulse insertion segments have a measurement delay, failing to reflect the true phase current at the same instant, which will reduce the accuracy of the current closed-loop control. Summary of the Invention

[0004] To address the problems of traditional vector pulse insertion methods, this invention improves upon the structural characteristics of dual three-phase permanent magnet synchronous motors by providing a phase current reconstruction method for dual three-phase permanent magnet synchronous motors based on dual measurement vector insertion. This method aims to solve the reconstruction blind zone problem, reduce the impact on the effective working area of ​​the system, reduce the number of switching operations and switching losses, correct measurement errors caused by sampling delay, and improve the system control accuracy.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor based on dual measurement vector injection (DMVIM) is proposed. This method, based on a seven-segment SVPWM control strategy, utilizes the dual measurement vector injection method (DMVIM) to reconstruct the phase current of the dual three-phase permanent magnet synchronous motor. The method includes the following steps:

[0007] Step 1: Determine the measurement vector injection scheme based on the sector where the reference voltage vector is located. The specific steps are as follows:

[0008] Step 1-1: During the seven-segment SVPWM modulation process, determine the space voltage vector sector where the reference voltage vector is located in real time;

[0009] Step 1-2: Based on the sector, select two adjacent basic voltage vectors in the current sector for synthesizing the reference voltage vector as the measurement voltage vectors corresponding to the first and second sets of inverters;

[0010] Step 2: After the normal PWM cycle ends, inject the measurement voltage vector and sample the DC bus current of both inverters. The specific steps are as follows:

[0011] Step 2-1: After the normal PWM cycle of the first and second inverters ends, insert the corresponding measured voltage vector for a period of time respectively.

[0012] Step 2-2: During the voltage vector action time, the DC bus current of the two inverters is synchronously sampled to obtain the corresponding bus current sampling value;

[0013] Steps 2-3: Determine the sampling delay by considering the PWM dead time, driver delay, power device switching delay, ADC sampling delay, and current steady-state settling time. Correct the sampling time accordingly. The formula for calculating the sampling delay is:

[0014]

[0015] In the formula, For the total delay time, For PWM dead time, To drive the switch delay, For MOSFET switching delay, For ADC sampling delay, The steady-state time of the current;

[0016] Step 3: Complete the six-phase current reconstruction based on the bus current sampling results. The specific steps are as follows:

[0017] Step 3-1: Based on the switching state corresponding to the measured voltage vector, establish the mapping relationship between the DC bus current and the current of each phase winding;

[0018] Step 3-2: Obtain the corresponding phase current using the bus current sampling value;

[0019] Step 3-3: Combining the constraint that the corresponding phase currents of the two sets of windings are equal and Kirchhoff's current law, the remaining unmeasured phase currents are obtained.

[0020] Steps 3-4: Complete the six-phase current reconfiguration of the dual three-phase permanent magnet synchronous motor;

[0021] Step 4: Compensate for the modulation deviation caused by the measurement vector injection. The specific steps are as follows:

[0022] Step 4-1: Calculate the additional effect of the measured voltage vector on the original SVPWM modulation based on its duration of action.

[0023] Step 4-2: Subtract the additional action time in the reference voltage vector synthesis process and normalize and correct the PWM carrier period;

[0024] Step 4-3: Restore the original reference voltage vector trajectory to achieve modulation compensation after measurement vector injection.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] This invention reconstructs six-phase currents through DC bus sampling, solving the reconstruction blind zone problem in the low modulation ratio region and sector boundary region. Compared with the traditional vector interpolation method, this invention effectively reduces the impact on the effective operating area of ​​the system, reduces the number of switching operations and switching losses, corrects measurement errors caused by measurement delay, and improves the system control accuracy. Attached Figure Description

[0027] Figure 1 The circuit topology for phase current reconstruction of a dual three-phase permanent magnet synchronous motor based on DC bus sampling method;

[0028] Figure 2 The measurement vectors inserted for each sector under the DMVIM method;

[0029] Figure 3 A schematic diagram of the PWM waveform under the DMVIM method (sector I);

[0030] Figure 4 This is a schematic diagram of voltage vector synthesis under the DMVIM method (sector I).

[0031] Figure 5 To measure the current flow within the parallel voltage source inverter at the vector insertion moment (sector I);

[0032] Figure 6 For the voltage vector trajectory before and after vector insertion;

[0033] Figure 7 The sampling delay is due to the DC bus current during the measurement period;

[0034] Figure 8 To reconstruct blind spots;

[0035] Figure 9 This is a block diagram of the control principle of a dual three-phase permanent magnet synchronous motor based on DMVIM;

[0036] Figure 10 The actual three-phase current is 400 r / min, 0.45 N·m.

[0037] Figure 11 To reconstruct the three-phase current (400 r / min, 0.45 N·m);

[0038] Figure 12 Comparison of actual and reconfigured currents for phases A1 and A2 (400 r / min, 0.45 N·m);

[0039] Figure 13 The actual three-phase current under dynamic experiment (400~800 r / min, 0.45 N·m);

[0040] Figure 14 To reconstruct the three-phase current (400~800 r / min, 0.45 N·m) under dynamic experiment.

[0041] Figure 15 The comparison between the actual and reconstructed currents of phases A1 and A2 under dynamic experiment (400~800 r / min, 0.45 N·m). Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0043] 1. Basic Principle of Phase Current Reconstruction Based on Dual-Vector Pulse Insertion

[0044] The topology of the phase current reconstruction circuit for a dual three-phase permanent magnet synchronous motor based on DC bus sampling is as follows: Figure 1As shown, the system uses a dual three-phase permanent magnet synchronous motor. The stator winding consists of two sets of three-phase windings connected in a double Y-shape, with a mechanical phase difference of 0° between the two sets of windings. The drive section consists of two sets of three-phase full-bridge inverters sharing the same DC voltage source. Each of the six bridge arms is connected to one of the six-phase windings, and each inverter independently drives its corresponding three-phase winding. Furthermore, Hall effect current sensors are installed on the DC side of both sets of windings to acquire the DC bus current information of both sets of windings.

[0045] For a three-phase full-bridge inverter topology, under the seven-segment Space Vector Pulse Width Modulation (SVPWM) strategy, the upper and lower switches of the three-phase bridge arms conduct complementaryly. The switching state of each bridge arm can be represented by a three-bit binary variable, resulting in eight switching states: 000, 001, 010, 011, 100, 101, 110, and 111. Among these, 000 and 111 represent zero-voltage vectors, while the other six are non-zero voltage vectors. These six non-zero voltage vectors are spatially spaced at 60° intervals, dividing the voltage space into six sectors. During modulation, in each switching cycle, based on the sector containing the reference voltage vector, two adjacent non-zero voltage vectors are selected and combined with the zero-voltage vector to synthesize the reference voltage vector. During the steady-state period of the voltage vector's action, the inverter's switching state and current loop remain unchanged, and a definite correspondence exists between the phase current and the DC bus current. By analyzing eight voltage vectors and their corresponding current loops, the relationship between phase current and DC bus current can be summarized in Table 1. Among these, the switching signal function of the power transistor... , The three phases are represented by 1, indicating that the upper phase of the power switch is turned on, and 0, indicating that the upper phase of the power switch is turned off; "+" indicates current inflow and "-" indicates current outflow. As can be seen from Table 1, the three-phase current can be reconstructed by sampling the DC bus current under specific switching conditions.

[0046] Table 1. Relationship between phase current and DC bus current under different voltage vector effects.

[0047]

[0048] The Measurement Vector Injection Method (MVIM) is a method that inserts a specific measurement voltage vector at the end of each PWM cycle to obtain DC bus current information and reconstruct phase currents. This invention proposes a Dual Measurement Vector Injection Method (DMVIM) based on a seven-segment SVPWM control strategy to reconstruct phase currents in a dual three-phase permanent magnet synchronous motor. This method inserts two different non-zero voltage vectors at the end of each of the two inverter's PWM cycles and samples the DC bus current at the corresponding times, allowing the two windings to obtain current information for different phases. Based on the theoretically identical phase currents of the two windings with a 0° phase difference, and Kirchhoff's laws, the six-phase currents are reconstructed. With the injection of measurement vectors, the inverter's switching time and switching losses increase accordingly. To minimize the impact of injection, the DMVIM method adjusts the injected measurement vectors according to different sectors of the space voltage vector hexagon. Figure 2 The figure shows the corresponding measurement vectors inserted in different sectors by two inverters under the DMVIM method. Two adjacent basic voltage vectors in each sector are selected as measurement vectors for synthesizing the reference voltage vector. This configuration can not only minimize switching time and switching losses, but also avoid introducing negative DC bus bias.

[0049] Taking sector I as an example, the schematic diagram of the PWM waveform under the DMVIM method is as follows: Figure 3 As shown, after the normal PWM cycle ends, a V1 (100) vector is inserted for a period of time in the first inverter, and a V2 (110) vector is inserted for the same period of time in the second inverter. The DC bus current is sampled at the same time during the insertion period. The schematic diagram of its voltage vector synthesis is shown below. Figure 4 As shown, the DMVIM method does not introduce voltage vectors that do not belong to the current sector; it only adds to the duration of the two basic voltage vectors originally used to synthesize the reference voltage vector in the current sector. The current flow within the parallel voltage source inverter at the moment of measurement vector insertion is as follows: Figure 5 As shown, the current value at the DC bus of the first inverter can be obtained by sampling with a current sensor. The current value at the DC bus of the second inverter is Based on the theoretically identical characteristic that the corresponding phase currents of two windings with a phase difference of 0° are completely equal, we have:

[0050] (1)

[0051] (2)

[0052] According to Kirchhoff's current law:

[0053] (3)

[0054] (4)

[0055] in , , This refers to the three-phase current corresponding to the first inverter. , , The three-phase currents corresponding to the second inverter are given. The values ​​of the remaining phase currents in the two windings can be calculated using equations (3) and (4), thus achieving the reconstruction of the six-phase currents. By analogy, the measurement vectors inserted in different sectors and their DC bus current sampling results are obtained, as shown in Table 2.

[0056] Table 2. Measurement vectors inserted in different sectors and their DC bus current sampling results.

[0057]

[0058] 2. Compensation for post-injection modulation

[0059] The DMVIM method introduces a measurement vector, which increases the duration of the voltage vector during modulation, altering the original PWM switching frequency and duty cycle distribution, and thus affecting the SVPWM modulation strategy based on the volt-second balance law. Figure 6 The changes in the reference voltage vector trajectories of the two inverters before and after the introduction of the measurement voltage vector are shown. It can be seen that the reference voltage vector shifts after the introduction of the measurement vector. This demonstrates that the DMVIM method introduces voltage synthesis errors while achieving current reconstruction, thus requiring a compensation algorithm to correct these errors and restore the original modulation strategy.

[0060] Because the measurement vectors injected into the two inverters are different, the compensation algorithms for the two inverters also differ. Taking the first inverter as an example, when the reference voltage vector... When located in sector I, the expression for the synthesized voltage vector using traditional SVPWM modulation is:

[0061] (5)

[0062] in , These represent the two fundamental voltage vectors respectively. , Duration of action This represents the PWM carrier period. And the inserted measurement voltage vector... (Right now After that, the new reference voltage vector The synthesis formula is:

[0063] (6)

[0064] in Indicates the duration of the inserted measurement vector. This represents the PWM carrier period after inserting the measurement vector. The calculation formula is:

[0065] (7)

[0066] As can be seen from the above formula, due to the injection, the new PWM carrier period is in the original... Based on the addition And what is added is the basic voltage vector. The duration of action. To restore the original modulation, it is necessary to first start from the reference voltage vector. Subtract the extra time of action from the middle. Multiply by Restore the PWM carrier period to Similarly, the second inverter inserts a measurement voltage vector. (Right now After that, the new reference voltage vector The synthesis formula is:

[0067] (6)

[0068] Similarly, to restore the original modulation of the second inverter, it is necessary to first start from the reference voltage vector. Subtract the extra time of action from the middle. Multiply by Restore the PWM carrier period to The above compensation algorithm can restore the voltage vector trajectory that has shifted after the insertion of the measurement vector to its original trajectory.

[0069] 3. Sampling delay and reconstruction blind zone

[0070] In practical motor control systems, the response of motor current to control signals exhibits a certain lag. Delays in various devices and the dead-time effect of PWM cause a time deviation between the control command and the actual current. These delays primarily originate from the drive circuit, the switching process of power devices, and the current sampling stage. Furthermore, as an inductive load, the motor itself requires time for its current to reach a steady state. If sampling occurs immediately upon switching, the obtained current value often fails to accurately reflect the steady-state current under the current voltage vector. Additionally, the DC bus current sampling window formed by the measurement vector insertion is generally narrow, exhibiting characteristics similar to a short pulse, which places higher demands on the selection of the sampling timing.

[0071] Therefore, when performing current sampling, the ideal sampling time needs to be appropriately shifted to improve sampling accuracy. Figure 7 This demonstrates the main delay factors affecting DC bus current sampling during measurement vector interpolation using the DMVIM method, including PWM dead time. Drive switch delay MOSFET switching delay ADC sampling delay and current steady-state time The typical times for these delay factors are shown in Table 3. The total delay time can then be obtained. :

[0072] (7)

[0073] Table 3. Various Delay Factors and Their Typical Times

[0074]

[0075] While the DMVIM method addresses the reconstruction blind zone in low modulation ratio regions and sector boundary regions, the original PWM carrier period is prolonged after measurement vector insertion, resulting in a reduction in the amplitude of the output voltage vector. This is repeated several times. Subsequently, the duration of the fundamental voltage vector is increased to twice the original duration. This achieves compensation for the modulation process. However, this operation consumes some effective operating time, reducing the limiting amplitude of the output voltage vector to half of its original value. This leads to a reduction in the effective working area, creating an unmeasurable region, i.e., the current reconfiguration dead zone. Figure 8 As shown.

[0076] like Figure 9 As shown, the specific steps of controlling a dual three-phase permanent magnet synchronous motor based on DMVIM are as follows:

[0077] 1. The rotor electrical angle of the dual three-phase permanent magnet synchronous motor is obtained by acquiring the rotor mechanical position through an encoder and calculating it. and actual speed The speed setpoint is compared with the actual speed, and the torque current setpoint is output through the speed PI regulator. Simultaneously set the excitation current setpoint for both sets of windings. and .

[0078] 2. Using DMVIM, measurement vectors are inserted at the end of each PWM cycle of the two inverters. At the insertion time of the measurement vectors, current sensors installed on the DC bus side of the two inverters are used to collect bus current information. Based on the switching state corresponding to the measurement vectors and the mapping relationship between bus current and phase current, the phase currents of the two windings of the dual three-phase permanent magnet synchronous motor are reconstructed. and .

[0079] 3. Based on the rotor electrical angle The reconstructed phase currents are respectively and Perform Clark and Park transformations to obtain the two sets of windings. shaft and Shaft current feedback value; the current feedback value is compared with the current setpoint, and the voltage command is obtained through the current PI regulator. , , and The voltage command in the stationary coordinate system is then obtained through the inverse Park transformation. , , and .

[0080] 4. Transfer the voltage command in the stationary coordinate system , , and Two sets of SVPWM modules are input respectively to calculate the switching time and duty cycle of the corresponding inverters, generate PWM drive signals, and control the two sets of inverters to output the target voltage to the two sets of windings of the dual three-phase permanent magnet synchronous motor, so as to realize the dual closed-loop control of the speed loop and current loop of the dual three-phase permanent magnet synchronous motor.

[0081] 5. Repeat steps 1 to 4 to update rotor position, current feedback and control commands in real time to achieve stable operation control of dual three-phase permanent magnet synchronous motor based on DMVIM phase current reconstruction.

[0082] Figures 10 to 15 Experimental results of the proposed DMVIM phase current reconstruction method under steady-state and dynamic conditions are presented. Figure 10 and Figure 11The actual three-phase current and reconstructed three-phase current waveforms of the motor are shown respectively under the conditions of a speed of 400 r / min and a load torque of 0.45 N·m. Figure 12 The figure shows a comparison between the actual current and the reconstructed current for phases A1 and A2. As can be seen from the figure, the reconstructed current and the actual current are consistent in amplitude, phase, and trend, accurately reflecting the actual operating state of the motor. This indicates that the proposed method has high current reconstruction accuracy under steady-state conditions. Figure 13 and Figure 14 The actual three-phase current and reconstructed three-phase current waveforms are shown respectively during the process of the motor speed dynamically increasing from 400 r / min to 800 r / min while keeping the load torque constant at 0.45 N·m. Figure 15 The figure shows a comparison between the actual current and the reconstructed current of phases A1 and A2 under dynamic testing. As can be seen from the figure, during dynamic changes in rotational speed, the reconstructed current accurately tracks the change in the actual current and remains consistent with it, with the reconstruction error remaining within an acceptable range. The steady-state and dynamic experimental results verify the effectiveness of the proposed method.

Claims

1. A method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor based on dual measurement vector insertion, characterized in that... The method includes the following steps: Step 1: Determine the measurement vector injection scheme based on the sector where the reference voltage vector is located; Step 2: After the normal PWM cycle ends, inject the measurement voltage vector and sample the DC bus current of the two inverters; Step 3: Complete the six-phase current reconstruction based on the bus current sampling results; Step 4: Compensate for the modulation deviation caused by the measurement vector injection.

2. The method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor based on dual measurement vector insertion according to claim 1, characterized in that... The specific steps of step 1 are as follows: Step 1-1: During the seven-segment SVPWM modulation process, determine the space voltage vector sector where the reference voltage vector is located in real time; Step 1-2: Based on the sector, select two adjacent basic voltage vectors within the current sector for synthesizing the reference voltage vector as the measurement voltage vectors corresponding to the first and second sets of inverters.

3. The method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor based on dual measurement vector insertion according to claim 1, characterized in that... The specific steps of step 2 are as follows: Step 2-1: After the normal PWM cycle of the first and second inverters ends, insert the corresponding measured voltage vector for a period of time respectively. Step 2-2: During the voltage vector action time, the DC bus current of the two inverters is synchronously sampled to obtain the corresponding bus current sampling value; Steps 2-3: Determine the sampling delay by combining the PWM dead time, driver delay, power device switching delay, ADC sampling delay, and current steady-state settling time, and correct the sampling time accordingly.

4. The method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor based on dual measurement vector insertion according to claim 3, characterized in that... The formula for calculating the sampling delay is: In the formula, For the total delay time, For PWM dead time, To drive the switch delay, For MOSFET switching delay, For ADC sampling delay, The steady-state time of the current.

5. The method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor based on dual measurement vector insertion according to claim 1, characterized in that... The specific steps of step 3 are as follows: Step 3-1: Based on the switching state corresponding to the measured voltage vector, establish the mapping relationship between the DC bus current and the current of each phase winding; Step 3-2: Obtain the corresponding phase current using the bus current sampling value; Step 3-3: Combining the constraint that the corresponding phase currents of the two sets of windings are equal and Kirchhoff's current law, the remaining unmeasured phase currents are obtained. Steps 3-4: Complete the six-phase current reconfiguration of the dual three-phase permanent magnet synchronous motor.

6. The method for reconstructing phase current of a dual three-phase permanent magnet synchronous motor based on dual measurement vector insertion according to claim 1, characterized in that... The specific steps of step 4 are as follows: Step 4-1: Calculate the additional effect of the measured voltage vector on the original SVPWM modulation based on its duration of action. Step 4-2: Subtract the additional action time in the reference voltage vector synthesis process and normalize and correct the PWM carrier period; Step 4-3: Restore the original reference voltage vector trajectory to achieve modulation compensation after measurement vector injection.

Images