Current distribution method for a zero-sequence field boost type hybrid excitation synchronous machine

Abstract

The application provides a current distribution method of a zero-sequence excitation boost type hybrid excitation synchronous motor, comprising: establishing a boost-driving topology and a control framework of the zero-sequence excitation boost type hybrid excitation synchronous motor; establishing a control model of the zero-sequence excitation boost type hybrid excitation synchronous motor based on the boost-driving topology and the control framework, wherein the control model comprises a voltage, an electromagnetic torque, a boost and a copper loss model of the zero-sequence excitation boost type hybrid excitation synchronous motor; establishing a plurality of constraint conditions involved in a running process of the zero-sequence excitation boost type hybrid excitation synchronous motor based on the control model and classifying working condition intervals; and formulating a current distribution scheme when the zero-sequence excitation boost type hybrid excitation synchronous motor is in different working condition intervals. The current distribution method provided by the application can realize optimal current distribution of the zero-sequence excitation boost type hybrid excitation synchronous motor under various working conditions.

Description

Technical Field

[0001] This application belongs to the field of motor control, specifically providing a current distribution method for a zero-sequence excitation type hybrid excitation motor. Background Technology

[0002] Hybrid excitation synchronous motors combine permanent magnet excitation with electrical excitation. The rotor is equipped with both permanent magnets and excitation windings (or adopts a hybrid magnetic circuit design). By adjusting the excitation current, the motor can always operate in the high-efficiency range across the entire speed range. Therefore, it is regarded as an important development direction for the next generation of high-performance automotive motors.

[0003] In conventional hybrid excitation motors, the armature winding and excitation winding are set separately, and an additional H-bridge circuit is required to provide DC excitation to the excitation winding, resulting in a complex system structure and low torque density. To solve the above problems, a drive topology for zero-sequence current excitation motors has been proposed. This drive topology integrates the functions of excitation and armature windings. By adjusting the DC component in the current, the air gap magnetic field can be flexibly changed, thus having good magnetic field regulation capability. In order for the zero-sequence excitation motor to operate normally, the neutral point of the three-phase windings must be opened (drawn out), and a power supply / circuit capable of injecting zero-sequence current into the neutral point must be constructed. Currently known zero-sequence excitation drive motor drive topologies include common DC bus type open winding drive topology, dual three-phase drive topology, and three-phase four-bridge arm drive topology, etc. However, the above-mentioned existing zero-sequence excitation motor drive topologies all improve the motor structure by simplifying the number of windings. Although the winding structure has been successfully simplified (reduced from two sets to one set), the generation of zero-sequence current still requires additional inverter bridge arms or independent converters, resulting in an increase in the number of power devices and an increase in system cost.

[0004] Furthermore, the existing drive topologies of various zero-sequence excitation hybrid excitation motors cannot achieve dynamic adjustment of the bus voltage through the neutral point. In fact, a neutral point power supply topology already exists in existing permanent magnet synchronous motors. This structure can dynamically adjust the bus voltage without adding additional power devices by leading out the motor neutral point, thus achieving the effect of "neutral point boost". However, the neutral point current introduced by this structure breaks the constraint that the zero-axis current is zero in traditional control, resulting in increased copper losses in the motor and causing current ripple.

[0005] Furthermore, if we wish to modify the drive topology of existing zero-sequence excitation hybrid excitation motors by introducing a "neutral point power supply" control method to broaden the dynamic adjustment capability of the bus voltage of zero-sequence excitation hybrid excitation synchronous motors, the system coupling complexity will increase dramatically. The physical merging of the excitation current and the neutral point current will result in a fully coupled system between the drive circuit, the boost circuit, the armature winding, and the excitation winding, causing various current distribution strategies aimed at reducing copper losses that are applicable to existing hybrid excitation motors and neutral point power supply permanent magnet motor topologies to become completely ineffective. Summary of the Invention

[0006] This application provides a current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor through embodiments, including the following steps: A boost-drive topology and control framework for a zero-sequence excitation boost-type hybrid excitation synchronous motor are established, wherein the excitation winding and the three-phase armature winding in the boost-drive topology are connected at the neutral point and generate coupling constraints on the boost circuit and the drive circuit. Based on the aforementioned boost-drive topology and control framework, a control model for a zero-sequence excitation boost hybrid excitation synchronous motor is established. The control model includes voltage, electromagnetic torque, boost voltage, and copper loss models for the zero-sequence excitation boost hybrid excitation synchronous motor. Based on the control model, multiple constraints involved in the operation of the zero-sequence excitation boost hybrid excitation synchronous motor are established, and the operating range of the zero-sequence excitation boost hybrid excitation synchronous motor is classified based on the constraints. Develop current distribution schemes for zero-sequence excitation boost type hybrid excitation synchronous motors under different operating conditions.

[0007] The current distribution method for the zero-sequence excitation boost-type hybrid excitation synchronous motor provided in this application firstly combines a neutral point boost topology with the existing drive topology of hybrid excitation synchronous motors. While using the zero-sequence current output from the neutral point of the armature three-phase winding to excite the excitation winding, it also has the ability to boost the input voltage of the power supply, thus forming a drive-boost topology for the hybrid excitation synchronous motor. Secondly, addressing the coupling constraints formed by the excitation winding and armature winding on the drive and boost circuits in the newly proposed topology, a targeted division method for the motor's operating range is proposed. Furthermore, a current distribution scheme is formulated to adapt to the constraints that can be met in different operating ranges, so as to fully utilize the performance of the newly proposed zero-sequence excitation boost-type hybrid excitation synchronous motor drive-boost topology. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of a drive topology for a conventional hybrid excitation synchronous motor. Figure 2This is a schematic diagram of a drive topology for an existing improved hybrid excitation synchronous motor. Figure 3 This is a schematic diagram of another existing improved hybrid excitation synchronous motor drive topology. Figure 4 This is a flowchart of a current distribution method for a zero-sequence excitation boost hybrid excitation synchronous motor according to an embodiment of this application; Figure 5 This is a topology diagram of a zero-sequence excitation boost-type hybrid excitation synchronous motor according to an embodiment of this application; Figure 6 This is a schematic diagram of the control framework for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to an embodiment of this application; Figure 7 This is a schematic diagram of several command torque constant curves provided according to embodiments of this application; Figure 8 This is a schematic diagram showing the minimum copper loss curve provided according to an embodiment of this application and its intersection with the command torque constant curve; Figure 9 A schematic diagram of a dynamic time-varying voltage limit ellipse provided according to an embodiment of this application; Figure 10 This is a schematic diagram illustrating the current distribution scheme for the first operating condition interval according to an embodiment of this application; Figure 11 This is a schematic diagram illustrating the current distribution scheme for the second operating condition interval according to an embodiment of this application; Figure 12 This is a schematic diagram illustrating the current distribution scheme for the third operating condition interval according to an embodiment of this application; Figure 13 This is a schematic diagram of the motor's operating state under steady-state conditions according to a specific embodiment 1 of this application; Figure 14 This is a schematic diagram of the motor operating state under unsteady conditions according to specific embodiment 1 of this application; Figure 15 This is a schematic diagram illustrating the loss reduction effect of the current distribution scheme provided in Specific Embodiment 1 of this application. Detailed Implementation

[0009] The present application will now be further described based on preferred embodiments and with reference to the accompanying drawings.

[0010] 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.

[0011] 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.

[0012] To clearly illustrate the technical solutions provided in the embodiments of this application, we will first briefly introduce various existing hybrid excitation synchronous motor drive topologies.

[0013] The hybrid excitation synchronous motor's drive topology combines the topologies of permanent magnet synchronous motors and electrically excited synchronous motors. Its rotor is equipped with both permanent magnets (providing basic magnetic flux) and excitation windings (generating adjustable magnetic flux), while the stator is a standard three-phase armature winding. The air gap magnetic field can be enhanced or weakened by adjusting the current in the excitation winding. Figure 1 This paper illustrates a classic hybrid-excitation synchronous motor drive topology. The main inverter on the left controls the current of the three-phase armature winding through a three-phase bridge arm to achieve torque and speed regulation. The excitation winding on the right is set independently relative to the three-phase armature winding, and the current flowing through the excitation winding is controlled by an H-bridge circuit to achieve regulation of the air gap magnetic field.

[0014] Figure 1The hybrid excitation synchronous motor shown has a complex structure and low torque density. To address these issues, a drive topology for a winding-integrated hybrid excitation synchronous motor is proposed. This type of drive topology integrates the excitation and armature winding functions. By adjusting the DC component (zero-sequence current) in the current, the air gap magnetic field can be flexibly changed, thus exhibiting excellent magnetic field regulation capabilities. To address the problem that the neutral point of traditional three-phase motors is usually left floating or directly grounded, preventing the flow of zero-sequence current, the neutral point of the three-phase windings needs to be opened or brought out to construct a power supply / circuit capable of injecting zero-sequence current, enabling the zero-sequence excitation motor to operate normally.

[0015] Figure 2 A novel zero-sequence excitation hybrid excitation synchronous motor drive topology based on the above-mentioned approach is shown. This drive topology is also known as a common DC bus type dual three-phase drive topology. In this topology, both the armature winding and the excitation winding are three-phase windings, and their neutral points are connected to each other, thus obtaining an integrated winding structure consisting of two sub-windings. Each of the two sub-windings is controlled by a three-phase inverter and powered by the same DC power supply. One sub-winding satisfies the same polarity, while the other satisfies the opposite polarity. Through the control of the two three-phase inverters, the zero-sequence current required for excitation can be generated in the windings.

[0016] Figure 3 Another improved zero-sequence excitation hybrid excitation synchronous motor drive topology is shown, referred to as the three-phase four-arm drive topology. As shown in the figure, this drive topology contains only one set of three-phase windings, and a zero-sequence path is formed to provide excitation by connecting an asymmetric arm to the motor neutral point.

[0017] The aforementioned improvements to the drive topology of classic hybrid-excitation synchronous motors all aim to integrate the armature winding and the excitation winding. While these solutions successfully simplify the winding structure (e.g., changing from two independent windings to one integrated winding), additional inverter arms or independent converters are still required to generate zero-sequence current for excitation, leading to an increase in the number of power devices and higher system costs. Furthermore, although... Figure 2 , Figure 3 The provided drive topologies all adopt a three-phase winding neutral point connection topology, but the DC bus voltage is consistent with the power supply voltage, which does not fully utilize the boost capability of the neutral point connection method.

[0018] It is evident that to achieve the boost capability of zero-sequence excitation hybrid synchronous motors, further improvements are needed to the existing drive topology of zero-sequence excitation boost hybrid synchronous motors. By adjusting the connection relationships between the armature three-phase windings, the excitation winding, the DC bus capacitor, and the DC power supply, a new boost-drive topology can be formed. This topology enables the motor to excite the excitation winding using the zero-sequence current output from the neutral point of the armature three-phase windings, while also boosting the input voltage of the power supply.

[0019] At the same time, it should be noted that the neutral point current introduced to achieve voltage boost will inevitably break the constraint that the zero-axis current is zero in traditional control, causing current ripple and increasing the copper loss of the motor. Moreover, this problem is more complicated due to the coupling between the excitation winding and the armature winding. Therefore, in order to fully improve the performance of the hybrid excitation synchronous motor under the new topology, it is necessary to carefully select the current distribution scheme under various operating conditions.

[0020] To achieve the above objectives, this application provides a current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor through embodiments. Figure 4 The following diagram illustrates the implementation of the method in some embodiments, such as... Figure 4 As shown, the method includes the following steps: Step 1: Establish the boost-drive topology and control framework of the zero-sequence excitation boost-type hybrid excitation synchronous motor, wherein the excitation winding and armature winding in the boost-drive topology are connected at the neutral point and generate coupling constraints on the boost circuit and drive circuit. Step 2: Based on the aforementioned boost-drive topology and control framework, establish a control model for the zero-sequence excitation boost hybrid excitation synchronous motor. The control model includes voltage, electromagnetic torque, boost voltage, and copper loss models for the zero-sequence excitation boost hybrid excitation synchronous motor. Step 3: Based on the control model, establish multiple constraints involved in the operation of the zero-sequence excitation boost type hybrid excitation synchronous motor, and classify the operating range of the zero-sequence excitation boost type hybrid excitation synchronous motor based on the constraints. Step 4: Develop a current distribution scheme for the zero-sequence excitation boost type hybrid excitation synchronous motor under different operating conditions.

[0021] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, illustrates the specific implementation process of the current distribution method for the zero-sequence excitation boost type hybrid excitation synchronous motor proposed in this application.

[0022] <Step 1: Establish the boost-drive topology and control framework for the zero-sequence excitation boost-type hybrid excitation synchronous motor> In the embodiments of this application, step one is used to establish a novel boost-drive topology for a hybrid excitation synchronous motor, and to construct a control framework adapted to the novel boost-drive topology.

[0023] As analyzed above, to achieve the bus voltage boosting capability under the hybrid excitation synchronous motor architecture, it is necessary to further boost the input voltage based on generating zero-sequence current at the neutral point of its three-phase armature windings. Therefore, in step one, a novel topology for hybrid excitation synchronous motors is first established, such as... Figure 5 As shown, the drive topology consists of a DC bus capacitor, a three-phase inverter, a three-phase armature winding, and a field winding.

[0024] The three-phase armature windings are connected in a star (Y) configuration, which is the configuration of the three-phase inverter. Mutually, Harmony The output terminals of the phase bridge arms are respectively connected to one end of each phase armature winding in the three-phase armature winding, and the other ends of each phase armature winding are interconnected to form a neutral point. It is understood that, in the embodiments of this application, the structure of the three-phase inverter section is not limited; that is, the three-phase inverter can adopt various structures. Figure 5 In the three-phase two-level configuration, each phase inverter circuit consists of a bridge arm, and the output terminal of each phase is the midpoint of the upper and lower switching devices in that phase bridge arm. Other variations known to those skilled in the art can also be used, such as two or more sets of three-phase inverters connected in parallel to increase load capacity, with the output terminals of the same phase in each set of inverters connected in parallel to form a unified output terminal connected to the armature winding of the corresponding phase; or a three-phase inverter with a parallel multi-level topology can be used, where each phase contains multiple parallel bridge arms, and wires are drawn from the midpoint of each bridge arm in the same phase to finally form a unified output terminal connected to the armature winding of the corresponding phase.

[0025] Back Figure 5 One end of the DC bus capacitor is connected to the common anode of the three-phase inverter, and the other end is connected to the common cathode of the three-phase inverter and the ground terminal. O The voltage across the DC bus capacitor, i.e., the DC bus voltage between the common anode and common cathode of the three-phase inverter, is, without loss of generality, expressed as: Meanwhile, the end of the DC bus capacitor connected to the ground terminal also serves as the negative terminal of the entire drive topology. This negative terminal is used when the motor is connected to an input voltage of... When using a DC power supply, it is used to connect to the negative terminal of the DC power supply.

[0026] In this boost-drive topology, one end of the excitation winding is directly connected to the neutral point of the three-phase armature winding, while the other end serves as the positive terminal of the entire boost-drive topology. This positive terminal operates when the motor is connected to a voltage of... When using a DC power supply, it is used to connect to the positive terminal of the DC power supply. Through Figure 5 As can be seen, when the positive extreme (i.e. Figure 5 The end of the excitation winding that is not connected to the neutral point is connected to the positive terminal of the DC power supply, and the negative terminal (i.e., the end of the DC bus capacitor connected to the ground terminal and the common cathode of the three-phase inverter) is connected to the negative terminal of the DC power supply. That is, when the motor is powered by the DC power supply, no structure is provided in the circuit between the positive terminal and the positive terminal of the DC power supply, or in the circuit between the negative terminal and the negative terminal of the DC power supply, for adjusting the direction and / or magnitude of the magnetic field generated by the excitation winding.

[0027] In the embodiments of this application, the structure for adjusting the direction and / or magnitude of the magnetic field generated by the excitation winding refers to a structure that changes the magnitude and / or direction of the current between the two terminals of the excitation winding in an inverter manner, thereby causing a change in the direction and / or magnitude of the magnetic field generated by the excitation winding. For example, Figure 1 The H-bridge structure located on the right side of the excitation winding comprises two parallel bridge arms. Each bridge arm consists of two identical switching devices connected in series, with terminals leading out from the midpoint. When these two bridge arms are powered by a DC power supply, the direction and / or magnitude of the magnetic field generated by the excitation winding can be changed by switching the on and off states of the four switching devices; For example, Figure 2 A dedicated inverter with three bridge arms is installed to generate and regulate the direction and / or magnitude of the zero-sequence current, thereby causing a change in the direction and / or magnitude of the excitation magnetic field; for example, Figure 3 Another type of bridge arm is set between the midpoint of the three-phase winding integrating the armature winding and the excitation winding and the DC power supply. A diode and a MOSFET are connected in series on the bridge arm, and the midpoint of the two are connected to the neutral point of the integrated winding. The two ends of the bridge arm are connected to the positive and negative terminals of the power supply, respectively. This bridge arm and the three bridge arms of the three-phase inverter form four parallel bridge arms. The direction and / or magnitude of the zero-sequence current can be adjusted by switching the switching devices, thereby adjusting the direction and / or magnitude of the excitation magnetic field in the integrated three-phase winding.

[0028] Without loss of generality, it can be Figure 1 , Figure 2 A bridge arm is a structure in which two identical switching devices are connected in series and wires are led out from the midpoint between the two switching devices. Figure 3 The structure on the far right, which connects two different functional devices (including at least one switching device) in series and draws wires from the midpoint between the two functional devices, is called an asymmetrical bridge arm structure. Therefore, in the embodiments of this application, the structure used to adjust the direction and / or magnitude of the magnetic field generated by the excitation winding includes at least the aforementioned symmetrical bridge arm and / or asymmetrical bridge arm.

[0029] and Figures 1 to 3 The various hybrid excitation synchronous motor drive topologies shown differ. In the boost-drive topology provided in this application, when connected to a DC power supply, no structures are provided between the positive terminal formed at one end of the excitation winding and the positive terminal of the DC power supply, or between the negative terminals of the DC power supply and the negative terminals of the DC power supply, to change the direction and / or magnitude of the magnetic field of the excitation winding. In other words, in the drive topology provided in this application, the zero-sequence current (i.e., the current used to adjust the direction and / or magnitude of the magnetic field generated by the excitation winding) is not present. Figure 5 The current flowing from the excitation winding to the neutral point, or from the neutral point to the excitation winding. The size and / or direction of the inverter are controlled only by the three-phase inverter connected to the three-phase armature winding.

[0030] Furthermore, it should be emphasized that, although Figure 5 In the illustrated embodiment, the positive terminal is directly electrically connected to the positive terminal of the DC power supply, and the negative terminal is directly connected to the negative terminal of the DC power supply via wires. Therefore, there are no other components. In other optional embodiments, those skilled in the art may, as needed, provide at least one functional component or module between the positive terminal and the positive terminal of the DC power supply, and between the negative terminal and the negative terminal of the DC power supply, as long as the provided functional component or module does not participate in the process of adjusting the direction and / or magnitude of the magnetic field generated by the excitation winding.

[0031] For example, to ensure motor safety, in some optional embodiments, components or modules for overcurrent protection can be installed between the positive terminal of the excitation winding and the positive terminal of the DC power supply, or between the negative terminal of the DC power supply and the ground terminal. These components or modules can be passive protection devices such as current-limiting resistors, fuses, thermal relays, and circuit breakers, or active protection devices composed of overcurrent detection modules and controllable switching devices such as transistors or MOSFETs. It is understood that although the active protection devices installed in the above locations may include switching devices such as MOSFETs for switching on and off states, their function is to disconnect the current path when an overcurrent occurs, rather than acting like... Figure 2 Three-phase inverter in, or Figure 3 Like the switching devices in the asymmetric bridge arm, the magnetic field of the excitation winding is adjusted in an inverter manner.

[0032] To better leverage the boost-drive capability of this novel topology for hybrid-excitation synchronous motors, a compatible control framework needs to be established to guide the design and optimization of the motor controller. Therefore, in step one, further steps are taken to address... Figure 5 Based on the boost-drive topology shown, a control framework for a zero-sequence excitation boost-type hybrid excitation synchronous motor is established. Figure 6A schematic diagram of the control framework for a zero-sequence excitation boost-type hybrid excitation synchronous motor, based on some specific embodiments, is shown. (Refer to...) Figure 6 The control framework includes a current closed-loop control loop (also known as a drive control module), a boost control loop (also known as a boost control module), and a modulation module. The current closed-loop control loop is used to generate the three-phase target voltage for the drive motor. , , The boost control loop generates an average duty cycle based on a preset boost target. , , , and After input to the modulation module, a preset modulation algorithm, such as the ZSVIPWM algorithm, is used to generate switching signals to control the various power devices of the three-phase inverter. , , and its complementary signal , , Under the control of these switching signals, the three-phase inverter can generate three-phase current to drive the motor based on the preset DC bus voltage.

[0033] In the embodiments of this application, the specific implementation methods of the above-mentioned current closed-loop control circuit, boost control circuit and modulation module are not limited. Those skilled in the art can refer to the control framework of various existing neutral-point powered permanent magnet synchronous motors to build the above-mentioned functional modules.

[0034] In addition to the parts that are the same as those in existing neutral-point powered motor control architectures, Figure 6 The control framework shown also includes, according to a preset current distribution strategy, supplying current suitable for the target operating condition to the current closed-loop control circuit. Axis target current and Axis target current .

[0035] Compare Figure 5 and Figures 1 to 3 As can be seen, in the boost-drive topology of the hybrid excitation synchronous motor provided in the embodiments of this application, the connection between the DC bus capacitor, the three-phase inverter, the three-phase windings, and the neutral point constitutes the drive circuit (used to generate the three-phase current of the drive motor); the connection between the DC power supply, the excitation winding, the neutral point, the three-phase windings, and the ground terminal constitutes the boost circuit (used to convert the DC power supply, the excitation winding, the neutral point, the three-phase windings, and the ground terminal into a ...). Boost to Clearly, in this boost-drive integrated topology, the connection between the excitation winding and the three-phase armature winding at the neutral point will impose coupling constraints on the boost circuit and the drive circuit; simultaneously, since the excitation current flowing through the excitation winding is numerically equal to the neutral point current... This means that under this topology, the excitation current is no longer a variable that can be directly and independently controlled. Its magnitude is determined by the overall current balance in the neutral point circuit and the system power. Therefore, the current distribution strategy of the traditional hybrid excitation synchronous motor has completely failed. It is necessary to redefine the operating range of the zero-sequence excitation boost hybrid excitation synchronous motor according to its operating status, and formulate corresponding operating targets and suitable target current distribution schemes based on the redefinition operating range.

[0036] Step 2: Establish the control model for the zero-sequence excitation boost-type hybrid excitation synchronous motor. In order to establish a current distribution strategy for zero-sequence excitation boost-type hybrid excitation synchronous motors, in step two of this application, according to Figure 5 The boost-drive topology shown and Figure 6 The control framework shown establishes a control model for the zero-sequence excitation boost-type hybrid excitation synchronous motor, including a voltage model, an electromagnetic torque model, a boost model, and a copper loss model. These models characterize the voltage-current relationship, electromagnetic torque-current relationship, DC bus boost characteristic-current relationship, and system additional loss-current relationship of the zero-sequence excitation boost-type hybrid excitation synchronous motor, respectively. In step three, based on the electrical parameters and current relationships characterized by these models, the control parameters can be determined... axis, The constraints that the target shaft current should follow under different operating conditions, thus providing multiple selectable options. Determine the optimal option from the combinations.

[0037] 2.1 Voltage model and electromagnetic torque model of zero-sequence excitation boost type hybrid excitation synchronous motor.

[0038] Specifically, considering the voltage equation of a conventional hybrid excitation synchronous motor as shown in equation (1): (1), in, , The motors in the dq0 synchronous coordinate system are respectively axis, Shaft voltage (i.e., the three-phase armature winding) axis, (axis voltage) This is the excitation voltage of the excitation winding. , The motors in the dq0 synchronous coordinate system are respectively axis, shaft current, The excitation current of the excitation winding. , These are the internal resistances of the armature winding and the field winding, respectively. , armature windings axis, Shaft inductor, The magnetizing inductance of the excitation winding. This is the equivalent mutual inductance between the armature winding and the field winding. The magnetic flux linkage of the permanent magnet in the motor. Let be the electric angular velocity of the motor.

[0039] Starting from equation (1), and combining... Figure 5 The neutral-point boost power supply and armature winding-excitation winding coupling relationship in the boost-drive topology shown can be used to further derive the voltage equation of the zero-sequence excitation boost hybrid excitation motor. Obviously, the analysis of the zero-sequence excitation boost hybrid excitation motor must take into account the characteristics of both the neutral-point power supply topology and the hybrid excitation motor structure. For a neutral point power supply structure, the lead-out of the neutral point will not affect... The shaft component only causes an additional zero-sequence component to be generated on the neutral line. Based on the voltage relationship on the neutral line circuit, the voltage equation of the zero-sequence excitation boost-type hybrid excitation synchronous motor in the ABC three-phase stationary coordinate system can be obtained: (2), in, , , These are the inverter pole voltages of phases A, B, and C in the three-phase stationary coordinate system, i.e., the output terminals (midpoints of bridge arms) of each phase relative to the DC bus reference point. voltage, , , These represent the duty cycles of the upper arms of phases A, B, and C of the three-phase inverter. , , These are the phase voltages of the inverter in the A, B, and C phases of the ABC three-phase stationary coordinate system, i.e., the output terminals of each phase relative to the motor neutral point. voltage, Neutral point of the motor Relative to DC bus reference point voltage, This is the input voltage, i.e., the voltage of the DC voltage source.

[0040] The voltage equations in the ABC three-phase stationary coordinate system are transformed using constant amplitude coordinates, and the following definitions are made: , , These are the coordinates in the dq0 synchronization system. axis, axis, From the pole voltage of the shaft inverter, the voltage equation in the synchronous coordinate system dq0 can be obtained: (3), in, , , They are respectively axis, axis, The equivalent duty cycle of the shaft, For motor Shaft voltage.

[0041] The above equation reveals the relationship between the zero-axis voltage components on the neutral line: in the dq0 synchronous coordinate system, The shaft is unaffected by the neutral point boost, 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 the voltage of the neutral point relative to the DC bus reference point generated by the connection of a DC power supply (which can be obtained through the neutral point loop structure).

[0042] Furthermore, for Figure 5 The zero-sequence excitation boost-drive topology of the hybrid excitation synchronous motor shown here, with the neutral line connected to a DC power supply, also couples to an excitation winding. According to the characteristics of the hybrid excitation synchronous motor, when an excitation current flows through the excitation winding, an excitation voltage is generated. If it is specified that from... arrive If the voltage drop direction is positive, then we have Meanwhile, considering the excitation winding current under the hybrid excitation topology of zero-sequence excitation boost, It is the neutral point current. Ultimately, a voltage model for a zero-sequence excitation boost hybrid excitation synchronous motor that simultaneously possesses hybrid excitation and neutral point boost characteristics can be established: (4), in, This represents the motor's zero-axis current in the dq0 synchronous coordinate system. The zero-axis inductance of the armature winding; And the electromagnetic torque model of the zero-sequence excitation boost-type hybrid excitation synchronous motor: (5), in, The electromagnetic torque of the motor. This represents the number of pole pairs of the motor.

[0043] 2.2 Voltage boosting model of zero-sequence excitation boosting hybrid excitation synchronous motor.

[0044] For structures using neutral point power supply boost, the average duty cycle can be defined. To achieve DC bus voltage Dynamic control, thereby achieving [the desired result] without the aid of additional power devices. arrive As analyzed above, under the topology of hybrid excitation stack and neutral point power supply boost coupling, the expression for the zero-sequence component of the motor is: (6), In the formula Replace with ( ), and according to the definition of average duty cycle We can obtain the boost model of the zero-sequence excitation boost type hybrid excitation synchronous motor: (7), From equation (7), it can be seen that in Figure 5 In the boost-drive topology shown, by injecting voltage into the motor neutral point through 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 of the three-phase inverter, thereby achieving boost characteristics. Furthermore, since the excitation winding and the three-phase armature winding are connected to the neutral point... Therefore, the boost performance of a zero-sequence excitation boost-type hybrid excitation synchronous motor is related to the neutral point current of the motor. In addition to the electrical parameters of the three-phase armature winding and the field winding, the mutual inductance between the three-phase armature winding and the field winding is also involved. as well as Changes in shaft current.

[0045] 2.3 Copper loss model of zero-sequence excitation boost type hybrid excitation synchronous motor.

[0046] As analyzed above, under a neutral-point boost topology, all three phases (A, B, and C) of the motor will generate additional zero-sequence current, resulting in additional copper losses. These copper losses can be expressed as... For hybrid excitation topologies, the excitation current on the excitation winding also causes additional copper losses. Combined with constant amplitude transformation shaft and The copper loss caused by shaft current, therefore, the copper loss model of a zero-sequence excitation boost-type hybrid excitation synchronous motor can be expressed as: (8), in, This represents the total copper loss in the boost-drive topology of a zero-sequence excitation boost-type hybrid excitation synchronous motor.

[0047] Step 3: Divide the operating condition ranges and formulate current distribution strategies for different operating conditions. After establishing the drive-boost topology and control framework of the zero-sequence excitation boost hybrid excitation synchronous motor in step one, and obtaining the models describing the voltage, electromagnetic torque, boost voltage, and copper loss of the zero-sequence excitation boost hybrid excitation synchronous motor through equations (4), (5), (7), and (8) in step two, we can further establish the control model for the zero-sequence excitation boost hybrid excitation synchronous motor during operation in step three. The various constraints involved in the shaft current are considered, and based on the changes in the different constraints that the zero-sequence excitation boost type hybrid excitation synchronous motor can satisfy under different operating conditions, the operating condition range of the zero-sequence excitation boost type hybrid excitation synchronous motor under various states is divided. Then, in step four, based on the expected operating goals of the zero-sequence excitation boost type hybrid excitation synchronous motor under different operating conditions, an optimal target current allocation scheme adapted to it is formulated.

[0048] In the embodiments of this application, the reason why it is necessary to determine the operating range of the zero-sequence excitation boost hybrid excitation synchronous motor according to various constraints is that: the drive control and boost control of the zero-sequence excitation boost hybrid excitation synchronous motor, as well as the excitation winding and the three-phase armature winding, are all coupled through the neutral point, resulting in its energy loss characteristics (manifested as line copper loss) and maximum voltage availability characteristics (voltage limit ellipse described later) being more complex than those of conventional non-neutral point boost topologies and conventional hybrid excitation topologies. For example, the voltage limit ellipse will change with the real-time change of torque, making it more difficult to control the motor during torque changes. The voltage and current constraints of the zero-sequence excitation boost hybrid excitation synchronous motor are completely different from those of conventional topologies. This also leads to a significant difference in the timing of the switching of constraints between the zero-sequence excitation boost hybrid excitation synchronous motor and conventional topology motors. Obviously, using the conventional method of finding the intersection of the MTPV curve, MTPA curve and voltage limit ellipse to switch the target current strategy will cause a mismatch between the operating condition switching and the target current strategy switching of the zero-sequence excitation boost hybrid excitation synchronous motor. This mismatch may cause the target current switching to fail to keep up with the changes in operating conditions, thus failing to achieve the performance of neutral point boost, or it may cause increased energy loss.

[0049] Therefore, after obtaining the complete control model of the zero-sequence excitation boost type hybrid excitation synchronous motor, we should first construct the various constraints involved in the target current of the zero-sequence excitation boost type hybrid excitation synchronous motor according to equations (4), (5), (7), and (8). Then, based on the corresponding changes in the constraints that the motor can meet as the target torque changes during operation, we can determine which operating condition range it enters. Then, we can formulate the working target of the motor for each specific operating condition range, and select the optimal current distribution scheme that is suitable for it.

[0050] It should be noted that, due to the neutral point boost-drive control architecture, shaft current (or the corresponding neutral point current) It is located in the boost control loop and is used to achieve... arrive The target value of the boost voltage can be determined based on the desired DC bus voltage value (i.e., the boost factor). Therefore, in some specific embodiments of this application, the excitation current (equal to the neutral point current) can be considered as a non-independent controllable variable. Accordingly, formulating a current distribution scheme refers to... target value (or target value Given a given timeframe, determine the matching parameters for the operating range of the motor. Axis target current and Axis target current The optimal value.

[0051] <Establish multiple constraints related to the target current of the zero-sequence excitation boost-type hybrid excitation synchronous motor and divide the operating range> Step 3 is used to construct multiple pairs involved in the operation of the zero-sequence excitation boost-type hybrid excitation synchronous motor. The conditions for constraining the target current of the shaft are determined, and the operating range of the zero-sequence excitation boost type hybrid excitation synchronous motor is divided based on these constraints.

[0052] Specifically, these constraints include: 3.1 Command Torque Constraints The electromagnetic torque equation shown in equation (5) gives , The relationship between electromagnetic torque and common salient-pole motors is as follows: Therefore, when the target value of the electromagnetic torque is given, i.e., the command torque... Substituting this into equation (5), we can obtain the command torque constant curve shown in equation (9): (9).

[0053] by , Establish coordinate axes axis- In the shaft current plane, the command torque constant curve shown in equation (9) is a hyperbolic curve on this plane. Each point on this curve corresponds to a set of points that can realize the command torque. of shaft current and shaft current combination , In other words, the command torque constant curve is Axis target current The command torque constraint conditions that need to be met.

[0054] The command torque constraint condition shown in equation (9) is for a zero-sequence excitation boost-type hybrid excitation synchronous motor. The core constraint that the shaft target current should meet is that, during motor operation, the voltage utilization can achieve the commanded torque. At that time, the command torque constraint conditions shown in equation (9) should all be satisfied, that is, the torque determined under these conditions should be satisfied. Axis target current The optimal value should be located at the given command torque. On the corresponding identity curve.

[0055] Figure 7 Several different command torques are schematically given. exist axis- The corresponding isotropic curves on the shaft current plane show that, as the commanded torque increases, the hyperbolic isotropic curves gradually move away from the origin in the fourth quadrant.

[0056] 3.2 Minimum Copper Loss Constraint like Figure 7 As shown, when the motor is in a low-speed, light-load state, the command torque is... The voltage is relatively small, and correspondingly, the system has sufficient voltage margin to accurately generate the commanded torque. Therefore, the minimum copper loss constraint can be further increased, making the optimized... In this state, the shaft target current not only meets the command torque but also achieves minimal copper loss.

[0057] The above analysis shows that the minimum copper loss constraint characterizes the relationship between the minimum copper loss and any given command torque. (When the system can achieve the commanded torque) The minimum copper loss corresponding to this constraint condition is actually a numerical problem of minimum value optimization with equality constraints. According to the electromagnetic torque expression shown in equation (5) and the copper loss expression shown in equation (8), this optimization problem can be expressed mathematically as follows: (10) For the optimization problem shown in equation (10), a Lagrangian function containing the objective function and constraints can be constructed, and its extremum conditions can be solved to obtain a formula composed of the various command torques. The minimum copper loss can be achieved. The trajectory curve formed by connecting points.

[0058] Specifically, first, we establish the Lagrange multiplier shown in equation (11). The Lagrange equation, where the optimization variable is , : (11).

[0059] This optimization problem can be solved using techniques known to those skilled in the art, for example, firstly by... , Differentiating, we obtain equation (12): (13) Then the Lagrange multipliers are eliminated. ,get: (14).

[0060] Equation (14) in axis- In the shaft current plane, it is represented by a trajectory curve, which is the aforementioned curve that can be used for various commanded torques. Achieving minimum copper loss The curve corresponding to the point is referred to as the minimum copper loss curve in the embodiments of this application. Accordingly, Shaft target current and The constraint condition that the target current of the shaft is subject to when it is located on this curve is called the minimum copper loss constraint condition.

[0061] Figure 8 The minimum copper loss curve and its relationship with different command torques are schematically shown. The intersection of the identity curves.

[0062] 3.3 Dynamically Time-Varying Voltage Constraints Understandable Figure 8 The intersection points of the torque constant curves and the minimum copper loss curve for each command are... Shaft target current and Axis target current combination While it can achieve minimal copper loss, this is contingent on the intersection point. Capable of reaching the maximum allowable value of a three-phase inverter Within this range, it is clear that as the motor load or speed increases, the command torque also increases. When the intersection of the command torque constant curve and the minimum copper loss curve is taken as... When the target current of the shaft causes the voltage to exceed the limit, the motor is effectively unable to track the group. The target current of the shaft, therefore, needs to be... The constraint conditions satisfied by the target current of the axis are transformed into voltage constraint conditions characterized by the voltage limit ellipse.

[0063] According to equation (4), in the dq0 synchronous coordinate system, the part of the voltage equation corresponding to the drive circuit of the zero-sequence excitation boost type hybrid excitation synchronous motor is: (15) In real physical systems, , The value of cannot be infinitely large, but is limited by the maximum output voltage of the three-phase inverter. (i.e., the actual usable maximum phase voltage amplitude for drive control in a zero-sequence excitation boost-type hybrid excitation synchronous motor) is limited, at which point the voltage vector amplitude of the motor's three-phase armature windings is... Satisfy the following formula: (16).

[0064] During steady-state operation, the differential terms in the equation can be ignored, and the internal resistance of the motor is usually small. Under high-speed conditions, the voltage drop across the internal resistance can be ignored. In this case, substituting equation (15) into equation (16) and rearranging, we get: (17).

[0065] exist Given, satisfying equation (17) Dot at axis- The axial current plane lies within an ellipse, that is, within the region enclosed by the ellipse corresponding to the equality of equation (17). Accordingly, this ellipse (or the ellipse and the internal region it encloses) is called the voltage limit ellipse.

[0066] It should be noted that in traditional non-neutral point boost electric drive systems, the maximum output voltage of the three-phase inverter is... Due to a fixed DC bus voltage Decisions, for example, under SVPWM modulation, Therefore, at a given speed, the voltage limit ellipse has a definite geometric boundary (monotonically shrinking only as the speed increases). However, the zero-sequence excitation boost-type hybrid excitation synchronous motor structure provided in this application combines the characteristics of the NPS structure and the hybrid excitation synchronous motor. There is a coupling constraint between the boost circuit and the drive circuit, and the excitation winding is coupled and induced by the stator winding. The coupling complexity of the voltage equation is further increased, leading to... The dynamic changes and complex mechanisms require specific analysis of the coupling constraints.

[0067] The NPS (Neutral Point Shift) architecture results in a high degree of multiplexing in the three-phase inverter at the topology level, simultaneously undertaking the dual tasks of "neutral point equivalent boost" and "motor armature drive." This multi-functional multiplexing necessitates that the boost circuit and drive circuit physically share the same duty cycle resource during the same switching cycle. Specifically, to achieve neutral point boost, the three-phase inverter must allocate a certain proportion of zero-vector time, which severely squeezes the actual available duty cycle margin left for drive control. This actually corresponds to the percentage of time during which all three phase upper arms are on within a cycle. 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 cannot exceed twice the power supply voltage. It is limited to [0.5,1].

[0068] For a neutral point boost topology, the duty cycle of the bridge arms of the ABC three-phase system... It can be represented as: (18) in ( )Right now , , The target value.

[0069] In formula (18) Used for bus voltage boost control. This is used for motor drive control. Therefore, it can be seen that in the zero-sequence excitation boost type hybrid excitation synchronous motor structure, the boost control of the bus voltage needs to share the duty cycle resource within one cycle with the drive control of the motor. Defined as equivalent drive duty cycle ,but The constraints are: (19).

[0070] To ensure modulation symmetry, it is required Not exceeding the smaller of the absolute values ​​of the upper and lower boundaries, taking into account You can get The maximum value is: (20).

[0071] As can be seen from equation (20), the maximum practically available phase voltage amplitude for drive control in a zero-sequence excitation boost-type hybrid excitation synchronous motor is... It is no longer a constant, but related to the bus voltage. and power supply voltage There is a strong coupling relationship: (twenty one).

[0072] Under steady-state conditions, the differential term can be ignored, and equation (21) can be simplified to: (twenty two), This leads to the expression for the dynamic time-varying voltage limit ellipse of the zero-sequence excitation boost-type hybrid excitation synchronous motor: (twenty three).

[0073] Equation (23) is the voltage constraint condition for the zero-sequence excitation boost-type hybrid excitation synchronous motor, which characterizes the voltage constraint condition during the operation of the zero-sequence excitation boost-type hybrid excitation synchronous motor. The actual physical constraints that the target shaft current needs to satisfy, according to its expression, are as follows: For a zero-sequence excitation boost-type hybrid excitation synchronous motor, its... The voltage constraint (i.e. the available voltage limit) that the target current of the shaft satisfies is dynamic and time-varying.

[0074] Furthermore, according to equation (23), it can also be seen that another major characteristic of the zero-sequence excitation boost type hybrid excitation synchronous motor system compared with the traditional motor structure is the neutral point current. It has a dual role: it is both the neutral line current that determines the total power and boost characteristics of the system, and the hybrid excitation current that directly participates in torque generation. This physical phenomenon directly leads to a deep nonlinear coupling between torque generation and voltage limit boundary in the system: Torque coupling: The total electromagnetic torque output by the system is no longer solely determined by the armature AC and DC axis currents ( The determination is also influenced by the neutral line / magnetic current, which is strongly correlated with system power. Direct modulation of ).

[0075] Dynamic evolution of constraint boundaries: When the torque command or external load changes, the system input power changes accordingly, which causes the neutral point current ( This includes fluctuations in the bus boost state. Changes in the boost state will reshape the drive duty cycle resources, causing the size and center position of the voltage limit ellipse to no longer depend solely on the motor speed, but to become dynamically coupled with the bus boost control command, system real-time power, and torque command.

[0076] The above analysis shows that in the zero-sequence excitation boost-type hybrid excitation synchronous motor structure, the boundary of the voltage limit ellipse is an elastic boundary that changes in real time with the operating conditions (speed, torque, boost ratio), such as... Figure 9 As shown, the voltage limit ellipse changes accordingly with the change of motor torque. This is why the elliptical region or its boundary represented by equation (23) is called the dynamic time-varying voltage limit ellipse in this application.

[0077] The linkage between this voltage limit ellipse and the operating conditions causes traditional fixed-constraint optimization strategies (such as classical field weakening control or classical MTPV control) to fail in zero-sequence excitation boost-type hybrid excitation synchronous motor systems. Therefore, it is necessary to determine the operating condition range of the motor in real time based on the changes in the relationship between this dynamic time-varying voltage constraint and other constraints during the motor state change process in order to formulate the optimal current distribution scheme for the zero-sequence excitation boost-type hybrid excitation synchronous motor in different operating condition ranges.

[0078] After constructing the above constraints, the current operating condition range of the zero-sequence excitation boost-type hybrid excitation synchronous motor can be determined based on the interrelationships between these constraints. Specifically, in the embodiments of this application, the operating condition range of the zero-sequence excitation boost-type hybrid excitation synchronous motor includes the following three types: In the first operating condition range, when the zero-sequence excitation boost-type hybrid excitation synchronous motor is in this range, the intersection of the command torque constant curve and the minimum copper loss curve lies inside the dynamic time-varying voltage limit ellipse. As analyzed above, when the zero-sequence excitation boost-type hybrid excitation synchronous motor is in this operating range, the voltage margin is sufficient to simultaneously satisfy both the command torque constraint and the minimum copper loss constraint. It also does not exceed the maximum voltage that the system can achieve. Therefore, the first operating condition range is the operating condition range in which the target current can simultaneously meet the three constraints.

[0079] In the second operating condition range, when the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the second operating condition range, the intersection of the command torque constant curve and the minimum copper loss curve is outside the dynamic time-varying voltage limit ellipse. However, the command torque constant curve and the dynamic time-varying voltage limit ellipse do intersect. As analyzed above, as the motor load or speed increases, the command torque will gradually increase. In the fourth quadrant, the intersection of the command torque constant curve and the minimum copper loss curve gradually moves outward, while the dynamic time-varying voltage limit ellipse gradually moves inward. When the intersection of the command torque constant curve and the minimum copper loss curve gradually moves outward beyond the dynamic time-varying voltage limit ellipse, the minimum copper loss constraint can no longer be achieved, but the voltage limit has not yet been reached, and the command torque can still be achieved. Therefore, the second operating condition range is the operating condition range in which the target current can simultaneously satisfy the command torque constraint condition and the dynamic time-varying voltage constraint condition, but cannot simultaneously satisfy the command torque constraint condition, the minimum copper loss constraint condition, and the dynamic time-varying voltage constraint condition.

[0080] In the third operating condition range, when the zero-sequence excitation boost type hybrid excitation synchronous motor is in the third operating condition range, the dynamic time-varying voltage limit ellipse of the command torque constant curve has no intersection point, indicating that as the motor load further increases, the command torque can no longer be reached. However, the motor is still limited by physical constraints, that is, no matter how the target current is set at this time, it is impossible to exceed the range limited by the dynamic time-varying voltage limit ellipse. Therefore, the third operating condition range is the operating condition range in which the target current cannot simultaneously meet the command torque constraint condition and the dynamic time-varying voltage constraint condition.

[0081] In some specific embodiments, command torque can be continuously acquired during the operation of the zero-sequence excitation boost-type hybrid excitation synchronous motor. and real-time acquisition of the motor's current status and real-time torque, and The measured values ​​allow for the real-time plotting of the constant command torque curve, dynamic time-varying voltage limit ellipse, and minimum copper loss curve corresponding to the current state of the motor, thus determining the current operating range of the motor.

[0082] Step 4: Establish a current distribution scheme adapted to each operating condition range. In the embodiments of this application, step four is used to generate the current distribution scheme executed by the zero-sequence excitation boost type hybrid excitation synchronous motor when it is in three different operating condition ranges.

[0083] 4.1 Current distribution scheme corresponding to the first operating condition range When the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the first operating condition range, all three constraints can be satisfied. Therefore, minimizing copper loss can be taken as the optimization objective of the current distribution scheme. Based on this objective, the following can be done: Figure 10 As shown, the intersection point of the command torque constant curve and the minimum copper loss curve is directly corresponding to... Combination as Axis target current and Axis target current .

[0084] 4.2 Current distribution scheme for the second operating condition range Specifically, when the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the second operating condition range, the minimum copper loss constraint condition can no longer be achieved, that is... Since it's impossible to select from the minimum copper loss curve, the optimization objective for the current distribution scheme in this operating range can be set as minimizing copper loss while meeting the command torque constraint. (Observation follows.) Figure 11 It can be observed that when both the command torque constraint and the dynamically time-varying voltage constraint are satisfied, the command torque identity curve and the dynamically time-varying voltage limit ellipse have two intersection points or one intersection point (tangent), that is... Figure 11 As shown in parts (a) and (b).

[0085] In the case of tangency, the point of tangency can be directly... Combination as Axis target current and Axis target current In the case of two intersection points, choose from these two intersection points. The smaller intersection point, the corresponding intersection point Combination as Axis target current and Axis target current This is because, under the premise of satisfying the command torque, The smaller, The smaller the amplitude of the current vector synthesized by the shaft, the lower the copper loss, which matches the characteristics of "excitation current coupled with power and copper loss more sensitive to armature current" in zero-sequence excitation boost type hybrid excitation synchronous motor.

[0086] 4.3 Current distribution scheme for the third operating condition zone When the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the third operating condition range, the command torque constant curve and the dynamically time-varying voltage limit ellipse no longer intersect. This indicates that due to the voltage limit constraint, the target current can no longer meet the requirements for generating the command torque. Therefore, in some specific embodiments, the objective of motor operation in this operating condition range is to achieve the maximum torque under physical constraints, that is, to maximize torque generation while satisfying the dynamically time-varying voltage constraint conditions. This objective is also an optimization problem that achieves a constrained objective function, which can be expressed mathematically as follows: (twenty four), The same method as solving the optimization problem shown in equation (10) can be used to construct a Lagrangian function containing the objective function and constraints, and solve its extremum conditions, thereby obtaining a path that can achieve the maximum electromagnetic torque under each voltage limit ellipse. Point, that is Figure 12 The trajectory curve formed by connecting the point of tangency between the actual achievable maximum torque constant curve and the voltage limit ellipse is referred to as the maximum electromagnetic torque curve in this application, and its expression is as follows: (25) Obviously, when the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the third operating condition range, the intersection point of this curve and the dynamically time-varying voltage limit ellipse can be considered as... Combination as Axis target current and Axis target current .

[0087] The constraints that the optimization problem represented by equation (25) needs to satisfy include As analyzed above, when the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the third operating condition range, the commanded torque has exceeded the voltage limit constraint. During this process, the neutral point current (excitation current) participates in torque generation and can also affect the center position and shape of the voltage limit ellipse. When optimizing the current distribution scheme in this operating condition range, the objective function (torque) and the constraint condition (voltage limit ellipse) of the optimization problem are due to... The resulting power coupling will change dynamically. Therefore, in some preferred embodiments, it is possible to further... (or equivalently) As the third optimization objective, specifically when the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the third operating condition range, the optimization objective for the current distribution scheme will simultaneously involve... , and neutral point target current (Right now ).

[0088] Specifically, set The electrical power input to the armature of the DC power supply, This refers to the mechanical power output by the motor. The conversion efficiency between the electrical power input to the motor and the mechanical power output by the motor. ),but: (26) in, The mechanical angular velocity and electrical angular velocity of a zero-sequence excitation boost-type hybrid excitation synchronous motor. The relationship is .

[0089] Equation (26) is the power conservation equation, which means that we hope the zero-sequence excitation boost type hybrid excitation synchronous motor can maintain a stable power output in the third operating condition range. After introducing this condition into the optimization problem, As a variable to be optimized, the target current optimization problem now becomes: (27).

[0090] in, The maximum allowable total current amplitude (peak value) of the system is determined by both the capacity of the three-phase inverter and the thermal limitations of the motor, and can be determined through temperature rise experiments or the device manual. Preferably, Not exceeding 1.5 times the rated phase current.

[0091] Equation (27) indicates that when the neutral point current is... (or zero-sequence current) When this is also considered as an optimization target, the current limit that the system can withstand also needs to be considered. In this case, optimization needs to be performed while satisfying the constraints of voltage limits, current limits, and electromechanical conversion efficiency. , , The target value is to make the electromagnetic torque that the motor can achieve as close as possible to the command torque.

[0092] Specifically, due to the conversion efficiency in solving the optimization problem shown in equation (27), Since the operating conditions change in real time, a recursive estimation method known to those skilled in the art can be used, such as the recursive least squares (RLS) online estimation algorithm, based on the measured values ​​of the torque sensor. Compared with the current torque estimate The error between The estimated value is calculated iteratively according to formula (28): (28) in, The number of iterations in the recursion. For the first In the next iteration, the torque sensor measured the actual torque. Measured speed of rotary transformer The product of For the first The covariance matrix of the next iteration has a dimension of 1 (i.e., a one-dimensional scalar). The forgetting factor is preferably between 0.95 and 0.99.

[0093] In some preferred embodiments, initial value The nominal efficiency of the motor can be used. , initial value Depending on the degree of prior knowledge of the motor parameters, the preferred value range is within to between.

[0094] Equation (28) is iteratively updated until the result of two consecutive iterations is obtained. Convergence (e.g., obtained through two iterations) The difference is less than ), then you can determine The latest value, then Substituting the latest value into equation (27) to solve the optimization problem, we obtain the following result. The latest value is then used to further acquire the measured value from the torque sensor at the next moment. With the estimated value of torque Then, the iterative update of equation (28) is performed again. In the above iterative solution process, after each update... Input to boost control circuit By inputting the drive control loop, the optimal allocation of the target current can be achieved. Specific Implementation Example 1 This embodiment uses Figure 4 The method shown generates the target current of a zero-sequence excitation boost-type hybrid excitation synchronous motor in real time, wherein the motor's drive-boost topology is as follows: Figure 5 As shown, the implementation is based on an embedded platform. Figure 6 The control framework shown is used to test the motor's operating status under steady-state and non-steady-state (speed variation) conditions.

[0096] In the steady-state test, the commanded torque was set to 25 Nm, the commanded speed to 200 rpm, and the simulation duration was 0.5 s. The motor operating state was as follows: Figure 13 As shown, through Figure 13It can be seen that using the current distribution method provided in this application, the motor can remain stable and accurately track the desired torque.

[0097] In the unsteady-state test, the commanded torque remained constant at 25 Nm. The commanded speed increased from 0 rpm to 200 rpm between 0.05 s and 0.15 s, remained constant between 0.15 s and 0.25 s, continued to increase to 250 rpm between 0.25 s and 0.3 s, and then gradually decreased to 150 rpm. The test duration was 0.5 s. The test results are as follows: Figure 14 As shown, the current distribution method provided in this application can maintain stable motor operation and achieve accurate torque tracking during dynamic speed changes.

[0098] Figure 15 The system copper loss during the test is shown, and compared with... By comparing the current generation strategy with a value of 0, it can be seen that using the method provided in this application for target current allocation results in significantly lower copper losses under various operating conditions compared to... The current generation strategies with a current of 0 all show a reduction, and the reduction ratio of copper loss increases accordingly with the increase of torque. Copper loss was calculated by randomly sampling other current operating points, and it was verified that the copper loss was always between the two curved surfaces. Therefore, it can be verified that the method provided in this application can effectively reduce additional operating losses while ensuring accurate command tracking during the operation of the zero-sequence excitation boost hybrid synchronous motor.

[0099] 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 method for a zero-sequence excitation boost-type hybrid excitation synchronous motor, characterized in that, Includes the following steps: A boost-drive topology and control framework for a zero-sequence excitation boost-type hybrid excitation synchronous motor are established, wherein the excitation winding and the three-phase armature winding in the boost-drive topology are connected at the neutral point and generate coupling constraints on the boost circuit and the drive circuit. Based on the aforementioned boost-drive topology and control framework, a control model for a zero-sequence excitation boost hybrid excitation synchronous motor is established. The control model includes voltage, electromagnetic torque, boost voltage, and copper loss models for the zero-sequence excitation boost hybrid excitation synchronous motor. Based on the control model, multiple constraints involved in the operation of the zero-sequence excitation boost hybrid excitation synchronous motor are established, and the operating range of the zero-sequence excitation boost hybrid excitation synchronous motor is classified based on the constraints. Develop current distribution schemes for zero-sequence excitation boost type hybrid excitation synchronous motors under different operating conditions.

2. The current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to claim 1, characterized in that, The boost-drive topology of the zero-sequence excitation boost-type hybrid excitation synchronous motor includes a DC bus capacitor, a three-phase inverter, three-phase armature windings, and an excitation winding, wherein... The three-phase armature winding is star-connected. One end of the DC bus capacitor is connected to the common anode of the three-phase inverter, and the other end is connected to the common cathode of the three-phase inverter and the ground terminal and is used to connect to the negative terminal of the DC power supply. One end of the excitation winding is directly connected to the neutral point of the three-phase armature winding, and the other end is used to connect to the positive terminal of the DC power supply. When the boost-drive topology is connected to a DC power supply, the magnitude and / or direction of the zero-sequence current used to adjust the direction and / or magnitude of the magnetic field generated by the excitation winding are controlled only by the three-phase inverter.

3. The current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to claim 2, characterized in that, The voltage model, electromagnetic torque model, boost model, and copper loss model of the zero-sequence excitation boost hybrid excitation synchronous motor are as follows: ， ， ， ， in, , , These are the coordinates in the dq0 synchronization system. axis, axis, shaft inverter pole voltage, , Motors in the dq0 synchronous coordinate system axis, shaft voltage, , , Motors in the dq0 synchronous coordinate system axis, Zero axis current, zero axis current , These are the internal resistances of the armature winding and the field winding, respectively. , , armature windings axis, Axis and zero-axis inductors The magnetizing inductance of the excitation winding. This is the equivalent mutual inductance between the armature winding and the field winding. The magnetic flux linkage of the permanent magnet in the motor. The electric angular velocity of the motor. The electromagnetic torque of the motor. This represents the number of pole pairs of the motor. For neutral point current, This is the DC bus voltage. This is the DC power supply voltage. For average duty cycle, This represents the total copper loss of the boost-drive topology.

4. The current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to claim 3, characterized in that, The constraints involved in the operation of the zero-sequence excitation boost type hybrid excitation synchronous motor include: Command torque constraint, minimum copper loss constraint, and dynamically time-varying voltage constraint.

5. The current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to claim 4, characterized in that, The command torque constraint condition is determined based on the command torque identity curve shown in the following equation: ， in, This is the command torque; The minimum copper loss constraint is determined based on the minimum copper loss curve shown in the following formula: ； The dynamically time-varying voltage constraint condition is determined based on the dynamically time-varying voltage limit ellipse shown in the following equation: 。 6. The current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to claim 4, characterized in that, The operating range of the zero-sequence excitation boost-type hybrid excitation synchronous motor includes a first operating range, a second operating range, and a third operating range, wherein... The first operating condition range is the operating condition range in which the target current can simultaneously meet the command torque constraint, the minimum copper loss constraint, and the dynamically time-varying voltage constraint. The second operating condition range is the operating condition range in which the target current can simultaneously meet the command torque constraint condition and the dynamic time-varying voltage constraint condition, but cannot simultaneously meet the command torque constraint condition, the minimum copper loss constraint condition, and the dynamic time-varying voltage constraint condition. The third operating condition interval is the operating condition interval in which the target current cannot simultaneously meet the command torque constraint condition and the dynamically time-varying voltage constraint condition.

7. The current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to claim 6, characterized in that, When the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the first operating condition range, the intersection point of the command torque constant curve and the minimum copper loss curve is... Combination as Axis target current and Axis target current ; When the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the second operating condition range, if the command torque constant curve and the dynamic time-varying voltage limit ellipse are tangent, then the point corresponding to the tangency point will be... Combination as Axis target current and Axis target current If the command torque constant curve and the dynamic time-varying voltage limit ellipse have two intersection points, then select from these two intersection points. The smaller intersection point, the corresponding intersection point Combination as Axis target current and Axis target current .

8. The current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to claim 6, characterized in that, When the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the third operating condition range, the intersection point of the maximum electromagnetic torque curve and the dynamically time-varying voltage limit ellipse is... Combination as Axis target current and Axis target current The maximum electromagnetic torque curve is determined based on the following formula: 。 9. The current distribution method for a zero-sequence excitation boost-type hybrid excitation synchronous motor according to claim 6, characterized in that, When the zero-sequence excitation boost-type hybrid excitation synchronous motor is in the third operating condition range, the following optimization problem is solved to determine... Target current of shaft , Target current of shaft and neutral point target current : ， in, The conversion efficiency between the electrical power input to the motor and the mechanical power output by the motor. The mechanical angular velocity of the zero-sequence excitation boost-type hybrid excitation synchronous motor. This represents the maximum allowable total current amplitude of the system.

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