Current distribution device for nps permanent magnet synchronous motor and application thereof

Abstract

The application provides a current distribution device for an NPS permanent magnet synchronous motor and application thereof, and the current distribution device comprises: a constraint updating module, which updates multiple constraint conditions related to operation of the NPS permanent magnet synchronous motor in real time based on electromagnetic parameters and operation data of the NPS permanent magnet synchronous motor, and the constraint conditions comprise a minimum copper loss constraint condition, an instruction torque constraint condition and a voltage constraint condition; a working condition judgment module, which judges a working condition interval in which the NPS permanent magnet synchronous motor is located in real time based on constraint conditions that can be simultaneously satisfied by the NPS permanent magnet synchronous motor; and a current distribution module, which determines a target current for controlling the NPS permanent magnet synchronous motor in real time based on the working condition interval in which the NPS permanent magnet synchronous motor is located. The current distribution device provided by the application can finely divide the working condition interval according to the driving-boosting characteristics of the NPS and determine an adaptive current distribution strategy.

Description

Technical Field

[0001] This application belongs to the field of motor control technology, and relates to NPS permanent magnet synchronous motor control technology. Specifically, it provides a current distribution device for NPS permanent magnet synchronous motors and its application. Background Technology

[0002] NPS permanent magnet synchronous motor refers to a permanent magnet synchronous motor that adopts a neutral point supply (NPS) structure. It brings out the neutral point of the three-phase armature winding of the inverter and connects the DC power supply for the motor between the neutral point and the negative terminal of the inverter, so that the inverter can boost the input voltage without adding any additional power devices.

[0003] However, the neutral point current introduced by this structure breaks the constraint of zero-axis current in traditional control, leading to increased copper losses in the motor and causing current ripple. Some studies have proposed using a series "zero-axis inductor" to suppress this adverse effect, but the required inductance value is large and difficult to implement in engineering. In addition, most existing current distribution strategies use a simple constant torque region determined by the MTPA curve. The target current for the shaft is determined by using the MTPV curve in the field weakening region. This method is relatively effective for current distribution of permanent magnet synchronous motors with conventional power supply structures. However, when a permanent magnet synchronous motor uses neutral point power supply, the coupling between drive control and boost control makes the factors affecting the motor's operating conditions interrelated. If a matching current distribution strategy cannot be established, it is easy to cause a mismatch between the target current distribution and the motor's operating conditions, and the advantages of the NPS power supply structure cannot be fully utilized. Summary of the Invention

[0004] This application provides a current distribution device for NPS permanent magnet synchronous motors through embodiments, the current distribution device comprising: The constraint update module updates multiple constraints involved in the operation of the NPS permanent magnet synchronous motor in real time based on the electromagnetic parameters and operating data of the NPS permanent magnet synchronous motor. The constraints include minimum copper loss constraint, command torque constraint, and voltage constraint. The operating condition judgment module determines the operating condition range of the NPS permanent magnet synchronous motor in real time based on the constraints that the NPS permanent magnet synchronous motor can simultaneously satisfy. The current distribution module, based on the operating range of the NPS permanent magnet synchronous motor, determines the target current for controlling the NPS permanent magnet synchronous motor in real time. The target current includes at least... Shaft target current and Target current of the shaft.

[0005] This application also provides a control system for an NPS permanent magnet synchronous motor through embodiments. The control system uses the aforementioned current distribution device for NPS permanent magnet synchronous motors to determine the target current for controlling the NPS permanent magnet synchronous motor in real time.

[0006] The current distribution device for NPS permanent magnet synchronous motors provided in the embodiments of this application establishes multiple constraints that match the NPS topology based on the coupling characteristics of the drive control circuit and the boost control circuit of the permanent magnet synchronous motor with neutral point power supply structure. Based on the constraints satisfied by the motor under different operating conditions, a current distribution scheme adapted to it is formulated to ensure that the performance of the drive-boost topology in the NPS permanent magnet synchronous motor can be fully utilized. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the architecture of an NPS permanent magnet synchronous motor. Figure 2 This is a schematic diagram of a control architecture for driving and boosting an NPS permanent magnet synchronous motor. Figure 3 This is a schematic diagram of torque variation in a non-NPS architecture permanent magnet synchronous motor. Figure 4 A schematic diagram illustrating the principle of a current distribution strategy for a non-NPS architecture permanent magnet synchronous motor. Figure 5 This is a schematic diagram of the current distribution device architecture for an NPS permanent magnet synchronous motor according to an embodiment of this application; Figure 6 For application Figure 5 The diagram shows the NPS permanent magnet synchronous motor control system of the current distribution device. Figure 7 This is a schematic diagram of an NPS permanent magnet synchronous motor in the first operating condition range according to an embodiment of this application; Figure 8 This is a schematic diagram of an NPS permanent magnet synchronous motor in the second operating condition range according to an embodiment of this application; Figure 9 This is a schematic diagram of an NPS permanent magnet synchronous motor in the second operating condition range according to an embodiment of this application; Figure 10 This is a schematic diagram of an NPS permanent magnet synchronous motor in the third operating condition range according to an embodiment of this application; Figure 11 This is a schematic diagram illustrating the workflow of the working condition judgment module provided in the embodiments of this application; Figure 12 This is a schematic diagram of the target current distribution scheme for an NPS permanent magnet synchronous motor in the first operating condition range according to an embodiment of this application; Figure 13 This is a schematic diagram of the target current distribution scheme when the NPS permanent magnet synchronous motor is in a second operating range according to an embodiment of this application; Figure 14 This is a schematic diagram of the target current distribution scheme when the NPS permanent magnet synchronous motor is in another case of the second operating range according to the embodiments of this application; Figure 15 This is a schematic diagram of the target current distribution scheme for an NPS permanent magnet synchronous motor in the third operating condition range according to an embodiment of this application; Figure 16 This is a schematic diagram of the code flow for determining the operating condition range and the corresponding target current in Embodiment 1 of this application; Figure 17 This is a schematic diagram of the operating state of the NPS permanent magnet synchronous motor under unsteady conditions according to specific embodiment 1 of this application; Figure 18 This is a schematic diagram illustrating the loss reduction effect of the current distribution device provided according to specific embodiment 1 of this application; Figure 19 This is a schematic diagram showing the target current change determined by the current distribution device according to specific embodiment 1 of this application. Detailed Implementation

[0008] The present application will now be further described based on preferred embodiments and with reference to the accompanying drawings.

[0009] In the description of the embodiments of this application, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product of this application is in use, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, in the description of this application, the terms "first," "second," etc., are used to distinguish different units, but these are not limited by the manufacturing order, nor should they be construed as indicating or implying relative importance. Their names may differ in the detailed description and claims of this application. In addition, for ease of understanding, various components in the drawings have been enlarged or reduced, but this is not intended to limit the scope of protection of this application.

[0010] The vocabulary used in this specification is for illustrative purposes and is not intended to limit the scope of this application. It should also be noted that, unless otherwise expressly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection via an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of these terms in this application.

[0011] Figure 1 A schematic diagram of the architecture of a permanent magnet synchronous machine (PMSM) using neutral point supply (NPS) is shown, as follows. Figure 1 As shown, the armature winding of the three-phase inverter is connected in a star configuration, and the neutral point of the three-phase winding is... After being led out, it is connected to the positive terminal of the motor's DC power supply, while the negative terminal of the DC power supply is connected to the inverter's grounding terminal. connect.

[0012] Figure 2 The present invention illustrates a control architecture for driving and boosting an NPS permanent magnet synchronous motor with this structure, as proposed by the applicant earlier. For detailed implementation, please refer to Chinese Invention Patent CN118100719A. In this patent, in order to address the integral saturation phenomenon that occurs in the controller during the control process, an improvement scheme is proposed by adding a desaturation unit in the drive control loop or the boost control loop, respectively.

[0013] Currently, when driving and controlling permanent magnet synchronous motors with non-NPS architectures, the input drive control loop... Axis target current and Axis target current Generally, the MTPA (maximum torque-to-current ratio) curve or MTPV (maximum torque-to-voltage ratio) curve is selected based on the load and speed of the permanent magnet synchronous motor. For example, like... Figure 3 , Figure 4 As shown, when the motor load is small or the speed is slow, it can stably track the command torque. To determine the target, along the MTPA curve , As the load and speed increase, when changing the target current can no longer track the commanded torque, increasing the current is necessary. Demagnetization is followed by weakening of the magnetism, and the transition in the weakening region is selected on the MTPV curve. , .

[0014] Figure 3 , Figure 4 The current distribution strategy shown can respond well to permanent magnet synchronous motors with conventional power supply architectures. However, when applied to NPS permanent magnet synchronous motors with coupling between drive control and boost control, on the one hand, since the zero-axis current is no longer constrained to zero and flows through the power supply circuit, additional copper losses will be generated and ripple may be caused. On the other hand, the actual usable voltage amplitude of the inverter is modulated by the neutral point potential. The radius of the voltage limit ellipse depends not only on the speed but also on the boost ratio. Therefore, directly applying the MTPV curve derived under a fixed bus voltage to NPS permanent magnet synchronous motors will lead to a mismatch between the target current and the actual voltage / current limit, which in turn causes a mismatch between the current distribution and the actual operating conditions, affecting the NPS's ability to simultaneously perform boost-drive.

[0015] To address the aforementioned issues, this application provides a current distribution device for NPS permanent magnet synchronous motors through embodiments. This current distribution device can be applied to the NPS permanent magnet synchronous motor control system. Based on the drive-boost coupling characteristics of the NPS inverter topology, it establishes multiple constraints on the target current during the change of the NPS permanent magnet synchronous motor's operating state. According to the relationship between these constraints, it achieves accurate and rapid division of the NPS permanent magnet synchronous motor's operating range, so as to formulate a current distribution strategy that matches the operating range of the motor in real time and accurately.

[0016] Figure 5 The illustrated embodiment demonstrates the architecture of this current distribution device for NPS permanent magnet synchronous motors. Figure 6 The illustrated embodiment demonstrates an NPS permanent magnet synchronous motor control system employing this current distribution device. For example... Figure 5 As shown, the current distribution device for an NPS permanent magnet synchronous motor consists of a constraint update module, an operating condition judgment module, and a current distribution module. The constraint update module updates multiple constraints related to the operation of the NPS permanent magnet synchronous motor in real time based on the electromagnetic parameters and operating data of the motor. The operating condition judgment module determines the operating condition range of the NPS permanent magnet synchronous motor in real time based on the constraints that the motor can simultaneously satisfy. The current distribution module determines the target current for controlling the NPS permanent magnet synchronous motor in real time based on the operating condition range. In the embodiments of this application, the target current includes at least... Axis target current and Axis target current .

[0017] The preferred implementation of each module in the current distribution device will be described in detail below with reference to the accompanying drawings.

[0018] <Constraint Update Module> refer to Figure 5 and Figure 6 In the embodiments of this application, the constraint update module acquires the operating data of the NPS permanent magnet synchronous motor in real time, such as the command torque determined in real time based on the pressing depth of the accelerator pedal or brake pedal. and the electric angular velocity obtained by real-time measurement and neutral point current By combining pre-measured or determined electromagnetic parameters (such as the internal resistance, inductance, flux linkage, and number of pole pairs of the armature winding) with the specific technical specifications of the motor, the specific expressions of various constraints involved in the operation of the NPS permanent magnet synchronous motor are calculated in real time. These real-time calculated constraints are then transmitted to the operating condition judgment module as the basis for the module to determine the motor's current operating range in real time. In the embodiments of this application, the constraints include minimum copper loss constraints, command torque constraints, and voltage constraints. The expressions of each constraint and their determination process are described in detail below.

[0019] 1.1 Command Torque Constraint Conditions Command torque constraint refers to the constraint condition in order to achieve the command torque during the operation of an NPS permanent magnet synchronous motor. , Axis target current and Axis target current The required relationships must be satisfied. For an NPS permanent magnet synchronous motor, its electromagnetic torque... With the dq0 axis coordinate system shaft current , shaft current The following relationship must be satisfied: (1), in, This represents the number of pole pairs of the motor. , The armature windings in the dq0 axis coordinate system are respectively Shaft inductance, Shaft inductor, For the magnetic flux linkage of the permanent magnet in the motor, without loss of generality, it is possible to make... for and The difference, that is ,but: (2), command torque Substituting into equation (2) and rearranging, we can obtain equation (3) as shown. , Curve with independent variable: (3).

[0020] Each point on the curve shown in equation (3) represents a point on the curve. axis- A set of axial current planes , The combination, and under the premise of meeting the motor performance (achievable maximum voltage), is based on each group , As the target current, both can achieve the commanded torque. Therefore, in this application, this curve is referred to as the commanded torque constant curve of the NPS permanent magnet synchronous motor. Obviously, the commanded torque constant curve is... Axis target current The command torque constraint conditions that need to be met.

[0021] 1.2 Minimum Copper Loss Constraint When the utilization of voltage can achieve command torque At that time, priority should be given to ensuring The command torque constraint condition is met, that is, at this time... The curve should be selected from the constant curve of the command torque shown in equation (3), since this constraint condition is satisfied. Since there is no set number, it is necessary to determine the NPS permanent magnet synchronous motor's operating conditions in conjunction with other constraints. The specific combination. When the motor is at low speed and light load, the command torque... The voltage is relatively low, and the system has sufficient voltage margin to accurately generate the command torque. Therefore, in this state, reducing the copper loss in the drive-boost circuit can be the objective. By constructing a minimum copper loss constraint and combining it with the command torque constraint, the optimal result can be achieved. In this state, in addition to meeting the command torque, the copper loss can also be minimized.

[0022] For NPS permanent magnet synchronous motors, due to coupling constraints with the drive control circuit and the boost control circuit, the two circuits share the bridge arm duty cycle resources of the power devices, causing additional zero-sequence current to be generated in all three phases (A, B, and C). Thus in , In addition, it will also be due to This results in additional copper losses, considering the neutral point power supply architecture. and The relationship between them is At the same time, combined with constant amplitude transformation axis, Shaft copper loss expression, copper loss of NPS permanent magnet synchronous motor It can be represented as: (4), in, This is the internal resistance of the armature winding.

[0023] After obtaining the copper loss expression in equation (4), the optimization problem shown in equation (5) can be solved to obtain the copper loss expression. To achieve the required torque while minimizing copper loss, the following constraints must be met: (5), Equation (5) is a minimum optimization problem with equality constraints, which can be solved by constructing a Lagrangian function containing the objective function and constraints and solving for its extrema: Firstly , To optimize the variables, a system with Lagrange multipliers is constructed. Lagrange's equation: (6), Then respectively , Differentiate: (7), Then the Lagrange multipliers are eliminated. ,get: (8).

[0024] exist axis- The trajectory curve described by equation (8) in the shaft current plane represents the ability to handle various command torques. Achieving minimum copper loss The curve corresponding to the point, in the embodiments of this application, is referred to as the minimum copper loss curve of the NPS permanent magnet synchronous motor. Accordingly, The constraints imposed when the motor lies on this trajectory curve are called the minimum copper loss constraints of the NPS permanent magnet synchronous motor.

[0025] 1.3 Voltage Constraint Conditions The minimum copper loss constraint condition for the NPS permanent magnet synchronous motor shown in equation (8) can be used in conjunction with the command torque constant curve when the motor is in a low-speed, light-load state. However, when the motor load or speed increases to the point where the intersection of the command torque constant curve and the minimum copper loss curve exceeds the maximum allowable phase voltage amplitude of the three-phase inverter, the constraint condition becomes more critical. When these two constraints can no longer be satisfied simultaneously, it is obviously necessary to combine the voltage constraints with the command torque condition to determine the appropriate target current under this condition.

[0026] Unlike conventional structures, the NPS-permanent magnet synchronous motor has coupling constraints between its boost circuit and drive circuit, and the bus voltage... Furthermore, the ability to dynamically adjust further exacerbates the complexity of voltage equation coupling, therefore The dynamic changes and complex mechanisms require specific analysis of the coupling constraints.

[0027] First, for a neutral point power supply structure, it can be defined that... , , These are the coordinates in the dq0 synchronization system. axis, axis, shaft inverter pole voltage, , , They are respectively axis, axis, Given the equivalent duty cycle of the axis, the voltage equation of the NPS permanent magnet synchronous motor in the dq0 axis coordinate system is: (9), in, , , The motors in the dq0 synchronous coordinate system are respectively axis, 0-axis and 0-axis voltages (i.e., armature winding voltages) axis, (0-axis voltage). Let be the electric angular velocity of the motor.

[0028] Equation (9) reflects that, under the dq0 synchronous coordinate system, the derivation of the neutral point will not affect Axial components, therefore Inverter pole voltage of shaft , Equal to motor shaft voltage , The 0-axis inverter electrode voltage Then by and It consists of two parts, namely the total zero-sequence voltage of the motor at this time. It can be represented as ,in This represents the zero-axis voltage of the motor in the dq0 synchronous coordinate system (i.e., the zero-sequence voltage component formed at the neutral point of the three-phase armature winding). This is due to the neutral point being grounded relative to the DC bus caused by connecting a DC power supply. The voltage at that point.

[0029] The voltage constraint conditions of the NPS permanent magnet synchronous motor are established by analyzing the coupling relationship between the drive part and the boost part in equation (9).

[0030] It is easy to see that the drive control related part in equation (9) is... , The expression for is constrained by the actual physical system, namely: (10) in, This represents the voltage vector magnitude of the three-phase armature windings of the motor. Let (9) be the maximum phase voltage amplitude actually available for drive control in the NPS permanent magnet synchronous motor. Substituting equation (9) into equation (10), considering that the differential term in the equation can be ignored when the motor is in steady-state operation, and that the internal resistance of the motor is usually small, the internal resistance voltage drop can be ignored under high-speed conditions, the final result is: (11).

[0031] The last term in equation (9), namely the expression for the zero-axis voltage of the inverter, reflects that when voltage is injected into the neutral point of the motor by an external DC power supply, the zero-sequence component of the motor is no longer zero. This zero-sequence component, in conjunction with the modulation of the three-phase inverter, can effectively improve the voltage utilization rate of the three-phase inverter, thereby achieving the boost characteristic.

[0032] Furthermore, the duty cycle of the upper arm of phases A, B, and C of the three-phase inverter can be used as a basis. , , Define average duty cycle By adjusting This can achieve DC bus voltage Dynamic control is achieved without the aid of additional power devices. arrive The boost, combined And based on the average duty cycle From the definition, we can obtain: (12).

[0033] The essence of the NPS structure's ability to achieve equivalent boost conversion is that its inverter simultaneously performs both voltage conversion and motor drive functions: the duration during which all three phase upper bridge arms of the inverter are either fully on or fully off determines the boost effect, i.e., the resources required for bus voltage boost. Analysis can yield the average duty cycle. This actually corresponds to the percentage of time during which all three phase upper arms are conducting within a cycle, therefore The closer it is to 0, the greater the increase in bus voltage; The closer the bus voltage is to 1, the closer it is to the power supply voltage. To ensure modulation symmetry, the bus voltage must not exceed the power supply voltage. twice as much, therefore It is limited to [0.5,1].

[0034] Generally, for the PWM modulation algorithm used in NPS permanent magnet synchronous motors, the duty cycle of the three-phase bridge arms is... , , It can be represented as: (13) in , , These are the target phase voltages of the A, B, and C phase inverters in the ABC three-phase stationary coordinate system, i.e., the output terminals of each phase relative to the motor neutral point. The target value of the voltage.

[0035] As can be seen from equation (13), Used for boosting the bus voltage of the motor. , , It is used for motor drive control. Therefore, in the NPS structure, the bus voltage boost and motor drive control share the duty cycle resources within one cycle.

[0036] Can be defined For equivalent driving duty cycle Therefore, there are constraints: (14).

[0037] To ensure modulation symmetry, it is required Not exceeding the smaller of the absolute values ​​of the upper and lower boundaries, because ,therefore, maximum value for: (15).

[0038] It can be seen that in NPS permanent magnet synchronous motors, the maximum phase voltage amplitude that is actually available for drive control is... It is not a constant value, but rather related to the bus voltage. and power supply voltage There is a strong coupling relationship: (16) For NPS permanent magnet synchronous motors, the DC bus voltage target value Dynamic adjustment and tracking control can be performed based on current power requirements. For example, a low-pass filter can be set according to the following formula: , in, , For the output of the drive control loop Target voltage and Target current of the shaft, For calibration coefficients, This represents a low-pass filter operation. Because the motor output will have certain disturbances under actual driving conditions, these disturbances will be further amplified in the equation. Therefore, a low-pass filter (LPF) is used to filter the bus voltage required for drive control to obtain the desired result. The cutoff frequency of a low-pass filter can be designed based on the system's fundamental frequency. In practical applications, to meet the voltage requirements of transient conditions such as sudden torque changes during motor drive, as well as other specific operating conditions, a minimum value is required to satisfy the drive control needs. Based on this, a certain margin is left; therefore, preferably, the calibration coefficient... It can take a value slightly greater than 1, for example .

[0039] Under steady-state conditions, the differential term in equation (16) can be ignored, and we can further obtain: (17) Furthermore, by combining equations (11) and (17), the voltage limit elliptic expression for the NPS permanent magnet synchronous motor can be obtained: (18).

[0040] Equation (18) reveals the physical constraints on the NPS permanent magnet synchronous motor: the usable voltage range of the motor is within a voltage limit ellipse. Within the enclosed area, the size of this area is determined by the real-time changing DC bus voltage. With DC power supply input voltage The difference, and the real-time changing neutral point current. The decision, rather than the fixed position in the traditional permanent magnet synchronous motor drive topology. This characteristic enables deep coupling between boost control and drive control, and the voltage limit ellipse dynamically changes with the bus voltage command and the current system power. Therefore, in the embodiments of this application, the constraint condition represented by equation (18) is called the voltage constraint condition of the NPS permanent magnet synchronous motor.

[0041] The aforementioned minimum copper loss constraint, command torque constraint, and voltage constraint are the conditions for determining the target current during operation of the NPS permanent magnet synchronous motor. In some optional embodiments, the constraint update module can be constructed using various implementation methods known to those skilled in the art, for example, the algorithm for obtaining the parametric curves corresponding to each constraint can be compiled into executable code. This executable code is pre-stored in a computer-readable storage medium and is called and executed by microcontrollers such as DSPs and ARMs during motor operation to update the pre-determined electromagnetic parameters (such as...). , , , ) and motor operating parameters obtained through real-time measurement or coordinate transformation (such as , , (etc.) are substituted into each parameter-containing curve to update the above constraints in real time.

[0042] <Operating Condition Judgment Module> like Figure 5 As shown, after the constraint update module updates the above constraints in real time based on the motor's electromagnetic parameters and operating status data, the operating condition judgment module determines the target current based on the relationship between the updated constraints. The constraints that can be satisfied simultaneously can be used to determine the current operating range of the motor.

[0043] 2.1 Division of Operating Conditions Figures 7 to 9 The following are some specific embodiments showing the different relationships between the constraints represented by equations (3), (8) and (18) when the NPS permanent magnet synchronous motor is operating in different states.

[0044] like Figure 7 As shown, when the command torque received by the motor is much less than the voltage limit that the motor can provide (this state generally occurs when the motor is under low-speed and light-load conditions), the command torque constant curve intersects the voltage limit ellipse at two points. The curve portion between these two points lies inside the voltage limit ellipse. Simultaneously, since the command torque constant curve is relatively close to the origin in the third quadrant, the intersection point of the command torque constant curve and the minimum copper loss curve also lies inside the voltage limit ellipse. This indicates that the NPS permanent magnet synchronous motor, under the current state, can simultaneously satisfy the command torque constraint, the minimum copper loss constraint, and the voltage constraint. Shaft target current and The target current combination (obviously satisfying the above three constraints is the intersection of the command torque constant curve and the minimum copper loss curve). In the embodiments of this application, when the target current of the NPS permanent magnet synchronous motor can simultaneously satisfy the command torque constraint, the minimum copper loss constraint, and the voltage constraint, the operating condition judgment module determines that the NPS permanent magnet synchronous motor is in the first operating condition range.

[0045] like Figure 8 As shown, when the motor needs to increase its speed or increase its load, the command torque will gradually increase, thus gradually moving away from the origin in the third quadrant. Although the command torque constant curve and the voltage limit ellipse still have two intersection points at this time, the curve length between these two intersection points (i.e., the part inside the voltage limit ellipse) gradually decreases. This indicates that the current combination that simultaneously satisfies the command torque constraint and the voltage constraint will gradually decrease. Furthermore, during this process, the intersection point of the command torque constant curve and the minimum copper loss curve will gradually move outward to outside the voltage limit ellipse. This indicates that under this state, the target current of the NPS permanent magnet synchronous motor can no longer simultaneously satisfy the three constraints.

[0046] like Figure 9 As shown, as the motor speed continues to increase or the load continues to increase, the intersection point of the command torque constant curve and the voltage limit ellipse will become only one, that is, the point of tangency between the two, indicating that at this time there is only one set of curves. It can satisfy the command torque constraint and voltage constraint. At the same time, under this condition, the intersection of the command torque constant curve and the minimum copper loss curve is also outside the voltage limit ellipse.

[0047] In the embodiments of this application, when the target current of the NPS permanent magnet synchronous motor is as follows: Figure 8 , Figure 9 As shown, when the NPS permanent magnet synchronous motor can simultaneously meet the command torque constraint and voltage constraint, but cannot simultaneously meet the command torque constraint, minimum copper loss constraint, and voltage constraint, the operating condition judgment module determines that the NPS permanent magnet synchronous motor is in the second operating condition range.

[0048] like Figure 10 As shown, if the motor speed continues to increase or the load continues to increase, the command torque constant curve will shift outwards to outside the voltage limit ellipse. This indicates that there is no target current that simultaneously satisfies both the command torque constraint and the voltage constraint. Since the area outside the voltage limit ellipse represents the maximum voltage capability that the drive control can provide, it is clear that in this state, the target current can only be located on the voltage limit ellipse, i.e., it can only satisfy the voltage constraint. In the embodiments of this application, when the target current of the NPS permanent magnet synchronous motor cannot simultaneously satisfy both the command torque constraint and the voltage constraint, the operating condition judgment module determines that the NPS permanent magnet synchronous motor is in the third operating condition range.

[0049] 2.2 Workflow of the Operating Condition Judgment Module After the constraint update module sends the real-time updated constraints to the operating condition judgment module, the operating condition judgment module solves for the intersection points of the curves corresponding to each constraint in real time. Based on the intersection points, it determines the current operating condition range of the NPS permanent magnet synchronous motor, ensuring that the current distribution module can determine the appropriate current distribution strategy according to the motor's current operating condition range. Since this constraint update-operating condition range judgment-current distribution process needs to be repeated continuously during motor operation, the real-time solution speed and accuracy of the operating condition judgment module significantly affect the update speed of the current distribution scheme and the response speed and accuracy of the entire drive-boost control system. Therefore, in some preferred embodiments, the judgment process executed by the operating condition judgment module can be optimized to improve the speed and accuracy of operating condition range judgment.

[0050] Specifically, see Figure 11 The flowchart shown illustrates that during each iteration of the operating condition judgment module, the operating condition judgment module first obtains the updated command torque constraint, minimum copper loss constraint, and voltage constraint from the constraint update module through step 110. Specifically, this includes the expression for the command torque constant curve shown in equation (3), the expression for the minimum copper loss curve shown in equation (8), and the expression for the voltage limit ellipse shown in equation (18). Then, in step 120, the first equation set formed by combining equations (3) and (18) is solved: (19) If the first set of equations has no solution, the NPS permanent magnet synchronous motor is directly determined to be in the third operating condition range. The current operating condition range determination process can be ended without further calculation. The process returns to step 110 to obtain updated constraints and then proceeds to the next operating condition range determination.

[0051] If the first set of equations has a solution, then the number of solutions is further determined. If there is only one solution, then it is directly determined that the NPS permanent magnet synchronous motor is currently in the second operating condition range. At this time, no further calculation is required and the process can return to step 110.

[0052] If the first system of equations has two solutions, proceed to step 130 to solve the second system of equations formed by combining equations (3) and (8): (20) If the solution to the second set of equations is within the voltage limit ellipse, the NPS permanent magnet synchronous motor is determined to be in the first operating condition range; otherwise, the NPS permanent magnet synchronous motor is determined to be in the second operating condition range. After completing the above determination, the process can return to step 110 to enter the next operating condition range determination process.

[0053] pass Figure 11 The process shown can avoid the invalid calculation of the intersection of the minimum copper loss curve and the command torque curve when the motor is in the third operating range and part of the second operating range, thus effectively simplifying the judgment process, because in these two cases, there is no need to consider the unreachable intersection position when formulating the target current strategy.

[0054] Similar to the implementation of the constraint update module, the working condition judgment module can be constructed using various implementation methods known to those skilled in the art. For example, the algorithm for solving the first set of equations (19) and the second set of equations (20) can be compiled into executable code. This executable code is pre-stored in a computer-readable storage medium and is called and executed by microcontrollers such as DSP and ARM during motor operation.

[0055] In some preferred embodiments, the speed of determining the operating range of the NPS permanent magnet synchronous motor can be further accelerated by optimizing the solution process of equations (19) and (20).

[0056] 2.3 Optimization Process for the First Equation System As mentioned above, it can be determined whether the motor is in the first operating condition range by judging whether the first set of equations shown in equation (19) has a solution. In order to speed up the judgment, it is preferable to define intermediate variables. , : (twenty one), Substitute equation (21) into equation (19) and note that... It can be by express: Therefore, equation (19) can be rearranged and transformed into a statement about A quartic equation in one variable: (twenty two), The expressions for each coefficient are as follows: (twenty three).

[0057] Obviously when Once confirmed, at the intersection This was also determined, and because , Therefore It must be greater than zero to be meaningful, therefore the problem of solving the first system of equations shown in equation (19) is transformed into the nonlinear equations shown in equation (22). The problem of finding roots within a certain range.

[0058] According to Cartesian sign law, the coefficients to middle, , , Possible can be positive or negative. , Therefore, the coefficient sign changes twice, so equation (22) has at most two positive real roots. In the embodiments of this application, the specific solution method of equation (22) is not limited. Those skilled in the art can use various nonlinear equation solving algorithms they have mastered, such as Newton's iteration method, bisection method and other methods suitable for numerical implementation.

[0059] 2.4 Optimization Process for the Second Equation System If the first set of equations shown in equation (19) or the quartic equation shown in equation (22) has two solutions, it is necessary to further determine whether the solution of the second set of equations shown in equation (20) is located within the voltage limit ellipse. In some preferred embodiments, in order to further accelerate the solution speed of the second set of equations, the solution process can be carried out by a fast iteration method, specifically: First select The initial value is determined, and then the following iterative solution process is performed: First, based on... The value is updated in relation to the command torque constraint (i.e., the command torque constant curve). And then according to the updated Updated again with minimum copper loss constraint (i.e., minimum copper loss curve) Then proceed with a new iteration. Any number of iterations... The iterative solution process can be represented as: (twenty four), The above iterative solution process is repeated until... Convergence means that the difference between two consecutive solutions is less than a preset threshold. (or The difference between the current error threshold and the current error value is less than a preset current error threshold. The preferred range for the current error threshold is, for example, [missing value]. A.

[0060] The initial value can be set to 0, then the solution can converge within 6 iterations. In some preferred embodiments, to accelerate the iteration convergence speed, the value determined in the last iteration by the current distribution module can be used. Axis target current As the solution for this iteration The initial values, simulation and actual measurements show that using this method to set... The initial value ensures that the solution converges in no more than two iterations.

[0061] <Current Distribution Module> After the operating condition judgment module completes the determination of the operating condition range, the current distribution module determines the appropriate operating condition based on the current operating condition range of the NPS permanent magnet synchronous motor. , Send to Figure 6 The NPS permanent magnet synchronous motor control system shown is used to drive and control the NPS permanent magnet synchronous motor.

[0062] 3.1 Current Distribution Strategy for the First Operating Condition Range In some specific embodiments, when the NPS permanent magnet synchronous motor is in the first operating condition range, due to Being able to simultaneously satisfy three constraints, under this operating condition, while ensuring the tracking of the commanded torque and not exceeding the voltage capability, minimizing system copper losses is an additional objective. Therefore, the current distribution module is designed to... Figure 12 The intersection point (red dot) of the constant torque curve and the minimum copper loss curve corresponds to... , As the current target current for NPS permanent magnet synchronous motor .

[0063] 3.2 Current Distribution Strategy for the Second Operating Condition Range In some specific embodiments, when the NPS permanent magnet synchronous motor is in the second operating condition range, and the command torque constant curve and the voltage limit ellipse have only one intersection point (i.e. Figure 13 When the red dot is visible, it indicates that there is only one set corresponding to that intersection point. , If the commanded torque can be achieved without exceeding the voltage limit, then the current distribution module will use the position corresponding to that intersection point. , As the current target current for NPS permanent magnet synchronous motor .

[0064] In some specific embodiments, when the NPS permanent magnet synchronous motor is in the second operating condition range, and the command torque constant curve intersects the voltage limit ellipse at two points, there are multiple sets of target current combinations that can simultaneously satisfy both the command torque constraint and the voltage constraint. In this case, the copper loss situation can be further considered when selecting these options. , Select the combination with the lowest copper loss from the combinations, i.e., select from among them. , The combination of vector sums, considering that the first system of equations has two solutions, can be obtained from the properties of ellipse. The position with the minimum absolute value is Figure 14 (middle red dot) , The vector sum is minimized, therefore the current distribution module uses the two intersection points as the minimum. The position corresponding to the minimum absolute value , As the current target current for NPS permanent magnet synchronous motor .

[0065] 3.3 Current Distribution Strategy for the Third Operating Condition Range When the operating condition judgment module determines that the NPS permanent magnet synchronous motor is in the third operating condition range with no solution, it indicates that the commanded torque has exceeded the motor's voltage capability limit. Under this condition, the current distribution module can refer to the strategy of existing conventional motors, using the intersection of the MTPV (maximum torque-voltage ratio) curve and the voltage limit ellipse (…). Figure 15 The corresponding red dot) , As the current target current for NPS permanent magnet synchronous motor .

[0066] It should be noted that, due to the coupling between the drive control loop and the boost control loop, the influence of the boost at the neutral point needs to be considered when determining the MTPV curve of the NPS permanent magnet synchronous motor. Specifically, the process of determining the MTPV curve can be expressed as the following optimization problem: (25).

[0067] The same method used to find the minimum copper loss curve can be employed to establish a curve with Lagrange multipliers. Lagrange's equation: (26) To each , Differentiate: (27) Then the Lagrange multipliers are eliminated. ,get: (28).

[0068] Equation (28) is the MPTV curve corresponding to the NPS permanent magnet synchronous motor.

[0069] In some preferred embodiments, the current distribution module can determine the location of the intersection point between the MPTV curve and the voltage limit ellipse in the following manner. , value: make Substituting the voltage limit elliptic constraint condition, we get: (29) Substituting into equation (28) and rearranging, we obtain the following about The quadratic equation of : (30).

[0070] It is easy to see from the discriminant that equation (30) has two distinct real roots with opposite signs, expressed as: (31), because Only then does it have physical meaning; therefore, the negative root should be chosen as... The solution is finally obtained through equation (31) to obtain the target current of the NPS permanent magnet synchronous motor when it is in the third operating condition range. : (32).

[0071] It should be noted that in equation (32) With DC bus voltage DC power supply input voltage And the neutral point boost caused by Related.

[0072] Similarly, the current distribution module can be constructed using various implementation methods known to those skilled in the art. For example, the algorithm for solving the intersection of the MPTV curve and the voltage limit ellipse can be compiled into executable code. This executable code is pre-stored in a computer-readable storage medium and is called and executed by microcontrollers such as DSPs and ARMs during motor operation.

[0073] The above provides a detailed description of each module of the current distribution device for NPS permanent magnet synchronous motors, such as... Figure 6 As shown, this current distribution device can be easily applied to existing NPS permanent magnet synchronous motor control systems to distribute the target current determined in real time. In the drive control unit of the input control system.

[0074] In the embodiments of this application, the NPS permanent magnet synchronous motor control system can be constructed in a manner known to those skilled in the art, for example, Figure 6 The specific implementation of the drive control unit, boost control unit, and PWM signal generation unit included in the control system shown can be referred to the specification and drawings of the prior patent application CN118100719A filed by the same inventor. In addition, referring to the specification and drawings of the same prior patent, a functional module for desaturation can be added to the drive control unit and / or boost control unit.

[0075] <Example 1> This embodiment uses Figure 5The current distribution device shown generates the target current of the NPS permanent magnet synchronous motor in real time. This current distribution device is then applied... Figure 6 The NPS permanent magnet synchronous motor control system, implemented on an embedded platform, is shown, and the motor's operating status is tested under unsteady-state (command torque variation) conditions. During the unsteady-state test, the speed is kept constant, and the command torque is dynamically adjusted within the range of 0 to 20 Nm. Figure 16 The code flow for determining the operating range and target current of the current distribution device is illustrated schematically.

[0076] Real-time changes in torque, speed, current, and bus voltage are as follows: Figure 17 As shown, the current distribution device provided in this application can maintain stable motor operation under non-steady torque conditions and accurately track commands for torque, speed and bus voltage.

[0077] Figure 18 The system copper loss during the test is shown, and compared with the case without using the current distribution algorithm (i.e. By comparing the current distribution device provided in this application with the target current distribution using the algorithm described above, it can be seen that when using the current distribution device provided in this application to perform target current distribution under various operating conditions, the copper loss generated is significantly lower than that under 0 control. The current generation algorithms with a value of 0 have all been reduced, and the reduction ratio of copper loss increases accordingly with the increase of torque. This indicates that the current distribution device provided in this application can not only meet the requirement of accurate tracking of commands during the operation of NPS permanent magnet synchronous motor, but also effectively reduce additional operating losses.

[0078] Figure 19 The distribution of the target current combination generated by the current distribution device in the first, second, and third operating condition intervals is further shown as the operating conditions change. It can be seen that the change of the target current is relatively stable during the unsteady operation of the motor, and there are no sudden changes in the target current.

[0079] The specific embodiments of this application have been described in detail above. For those skilled in the art, several improvements and modifications can be made to this application without departing from the principle of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A current distribution device for an NPS permanent magnet synchronous motor, characterized in that, include: The constraint update module updates multiple constraints involved in the operation of the NPS permanent magnet synchronous motor in real time based on the electromagnetic parameters and operating data of the NPS permanent magnet synchronous motor. The constraints include minimum copper loss constraint, command torque constraint, and voltage constraint. The operating condition judgment module determines the operating condition range of the NPS permanent magnet synchronous motor in real time based on the constraints that the NPS permanent magnet synchronous motor can simultaneously satisfy. The current distribution module, based on the operating range of the NPS permanent magnet synchronous motor, determines the target current for controlling the NPS permanent magnet synchronous motor in real time. The target current includes at least... Shaft target current and Shaft target current; When the target current of the NPS permanent magnet synchronous motor can simultaneously meet the command torque constraint, the minimum copper loss constraint, and the voltage constraint, the operating condition judgment module determines that the NPS permanent magnet synchronous motor is in the first operating condition range. When the target current of the NPS permanent magnet synchronous motor can simultaneously meet the command torque constraint and voltage constraint, but cannot simultaneously meet the command torque constraint, minimum copper loss constraint and voltage constraint, the operating condition judgment module determines that the NPS permanent magnet synchronous motor is in the second operating condition range. When the target current of the NPS permanent magnet synchronous motor cannot simultaneously meet the command torque constraint and voltage constraint, the operating condition judgment module determines that the NPS permanent magnet synchronous motor is in the third operating condition range. The command torque constraint, minimum copper loss constraint, and voltage constraint are determined based on the command torque constant curve, minimum copper loss curve, and voltage limit ellipse of the NPS permanent magnet synchronous motor, respectively. The size of the region enclosed by the voltage limit ellipse of the NPS permanent magnet synchronous motor is determined by the difference between the real-time changing DC bus voltage and the DC power supply input voltage, as well as the real-time changing neutral point current. The expressions for the command torque constant curve, minimum copper loss curve, and voltage limit ellipse of the NPS permanent magnet synchronous motor are respectively (3), (8), and (18): （3）， （8）， （18）， in, , The armature windings in the dq0 axis coordinate system are respectively Shaft inductance, Shaft inductor, , The magnetic flux linkage of the permanent magnet in the motor. This represents the number of pole pairs of the motor. For command torque, , They are respectively in the dq0 axis coordinate system shaft current, shaft current, The electric angular velocity of the motor. This represents the maximum practically available phase voltage amplitude for drive control in an NPS permanent magnet synchronous motor. This is the DC bus voltage. This is the DC power supply input voltage. The internal resistance of the armature winding is... This is the neutral point current; When the NPS permanent magnet synchronous motor is in the first operating condition range, the current distribution module uses the intersection point of the command torque constant curve and the minimum copper loss curve as the reference point. , As the current target current for the NPS permanent magnet synchronous motor; When the NPS permanent magnet synchronous motor is in the second operating condition range, and the command torque constant curve and the voltage limit ellipse have only one intersection point, the current distribution module uses the current corresponding to the position of that intersection point. , As the current target current for the NPS permanent magnet synchronous motor; When the NPS permanent magnet synchronous motor is in the second operating condition range, and the command torque constant curve intersects the voltage limit ellipse at two points, the current distribution module uses the value at one of these two intersection points. The position corresponding to the minimum absolute value , As the current target current for the NPS permanent magnet synchronous motor; When the NPS permanent magnet synchronous motor is in the third operating condition range, the current distribution module uses the intersection point of the MTPV curve and the voltage limit ellipse as the reference point. , This serves as the current target current for the NPS permanent magnet synchronous motor.

2. The current distribution device for NPS permanent magnet synchronous motors according to claim 1, characterized in that, In determining the operating condition range of the NPS permanent magnet synchronous motor, the operating condition judgment module first determines whether the first set of equations formed by combining the expression of the command torque constant curve and the expression of the voltage limit ellipse has a solution. If the first set of equations has no solution, the NPS permanent magnet synchronous motor is directly determined to be in the third operating condition range.

3. The current distribution device for NPS permanent magnet synchronous motors according to claim 2, characterized in that, In the process of determining the operating condition range of the NPS permanent magnet synchronous motor, the operating condition judgment module further determines whether the first set of equations has only one solution when there is a solution. If the judgment result is yes, the NPS permanent magnet synchronous motor is directly determined to be in the second operating condition range.

4. The current distribution device for NPS permanent magnet synchronous motors according to claim 3, characterized in that, In determining the operating condition range of the NPS permanent magnet synchronous motor, when the first set of equations has two solutions, the operating condition judgment module determines whether the solution of the second set of equations (formed by simultaneously solving the expression for the command torque constant curve and the expression for the minimum copper loss curve) lies within the voltage limit ellipse. This determines whether the NPS permanent magnet synchronous motor is in the first or second operating condition range. When the solution to the second set of equations is within the voltage limit ellipse, the NPS permanent magnet synchronous motor is determined to be in the first operating condition range; otherwise, the NPS permanent magnet synchronous motor is determined to be in the second operating condition range.

5. The current distribution device for NPS permanent magnet synchronous motors according to claim 1, characterized in that, The operating condition judgment module solves the first set of equations by transforming it into a root-finding problem of a quartic equation in one variable, as shown in the following equation: ， in, The expressions for each coefficient are: 。 6. The current distribution device for NPS permanent magnet synchronous motors according to claim 1, characterized in that, When solving the second system of equations, the operating condition judgment module first selects... The initial value is determined, and then the following iterative solution process is performed: Firstly, according to The value is updated with the command torque constraint condition. And then according to the updated Updated again with the minimum copper loss constraint. Then proceed with a new iteration until... Convergence, where any i-th The iterative solution process is represented as follows: 。 7. The current distribution device for NPS permanent magnet synchronous motors according to claim 1, characterized in that, When the NPS permanent magnet synchronous motor is in the third operating condition range Target current of shaft and Target current of shaft for: 。 8. A control system for an NPS permanent magnet synchronous motor, characterized in that, The current distribution device for NPS permanent magnet synchronous motors described in claim 1 is used to determine the target current for controlling the NPS permanent magnet synchronous motor in real time.

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