Vehicle-mounted ac-dc hybrid power generation system and control method thereof

Abstract

The application discloses a vehicle-mounted AC-DC composite power generation system and a control method thereof. The power generation system comprises an engine, an axial magnetic field permanent magnet motor connected with the engine, the axial magnetic field permanent magnet motor comprising a first stator component, a second stator component and a rotor component; the first stator component comprises a non-magnetic stator support, n first stator windings are distributed on the non-magnetic stator support in a circumferential direction, and the first stator windings adopt Litz wire distribution windings; the second stator component comprises a magnetic stator core and a second stator winding. The power generation system provided by the application optimizes the performance and function of the motor by using the non-magnetic stator support and the magnetic stator core and by specially designing the layout and installation of the stator winding and the permanent magnet, and in particular, the system realizes high AC output power and voltage adjustment rate and high system power density by using the double stator and double three-phase stator windings and by controlling the length of the two air gaps.

Description

Technical Field

[0001] This invention relates to a vehicle-mounted AC / DC hybrid power generation system and its control method. Background Technology

[0002] The power system requirements for military special operations mobile vehicles are unique and urgent. These vehicles need an independent power system to break free from the constraints of the main power grid and achieve independent power supply, which plays a crucial role in special operations scenarios. However, the loads in special operations scenarios are complex, including both AC and DC loads.

[0003] Therefore, generator sets need to have both DC and AC output capabilities. Due to stringent weight requirements for vehicles, the weight of the power generation system also needs to be kept within a reasonable range. Furthermore, both AC and DC power generation systems have high requirements for power quality. This requirement necessitates the inclusion of components such as capacitors and inductors in the power generation system, and the presence of these components affects the system's power density. Additionally, for the flux permanent magnet motor in the power system, the armature reaction makes it difficult to achieve a stable AC voltage output. Summary of the Invention

[0004] The main objective of this invention is to provide a control method for an on-board AC / DC hybrid power generation system.

[0005] The objective of this invention can be achieved by adopting the following technical solution: A vehicle-mounted AC / DC hybrid power generation system includes an engine and an axial magnetic field permanent magnet motor connected to the engine. The axial magnetic field permanent magnet motor includes a first stator component, a second stator component, and a rotor component. The first stator component includes a non-magnetic stator support, on which n first stator windings are distributed along the circumferential direction. The first stator windings are Litz wire distributed windings. The second stator component includes a magnetically conductive stator core and a second stator winding. The magnetically conductive stator core has m magnetically conductive stator core teeth distributed along the circumferential direction. The second stator winding is wound on the magnetically conductive stator core teeth. The above m and n are both integers, and m≥2 and n≥2. The rotor component is disposed between the first and second stator components. The rotor component includes a rotor support. The rotor support has x permanent magnet slots arranged along the circumferential direction on the side near the non-magnetic stator support and y permanent magnet slots arranged along the circumferential direction on the side near the magnetic stator core. Permanent magnets are disposed in the permanent magnet slots, and their magnetization direction is along the motor axis, with N poles and S poles alternately distributed. A first air gap is provided between the first stator component and the rotor component, and a second air gap is provided between the second stator component and the rotor component, wherein the length of the first air gap is less than the length of the second air gap; The first stator winding and the second stator winding are respectively led out with three-phase lines. The first stator winding is connected to the AC load, and the second stator winding is connected to the controllable rectifier. The controllable rectifier is connected to the power battery and the DC load. The controllable rectifier adopts the control mode of id=0.

[0006] Preferably, the second stator winding is a concentrated winding or a distributed winding.

[0007] Preferably, it also includes an inverter, which is connected to a controllable rectifier and to another AC load.

[0008] Preferably, the controllable rectifier is connected to a power battery.

[0009] A control method for an on-board AC / DC hybrid power generation system includes the following steps: Step 1: Start the engine and initialize the control system of the axial magnetic field permanent magnet motor and the controllable rectifier; Step 2: Monitor the AC load demand and adjust the engine's operating status according to the demand to ensure that the first stator component of the axial magnetic field permanent magnet motor generates AC power that adapts to changes in the AC load. The AC load is connected to the first stator component of the axial magnetic field permanent magnet motor, forming the AC side of the vehicle-mounted AC / DC hybrid power generation system. Step 3: According to the requirements of the DC load, adjust the control parameters of the controllable rectifier between the DC load and the second stator component of the axial magnetic field permanent magnet motor to ensure stable DC output. The controllable rectifier adopts the control mode of id=0. The DC load constitutes the DC side of the vehicle-mounted AC-DC hybrid power generation system. Step 4: If a fault is detected on the AC side, the rotor of the axial magnetic field permanent magnet motor is immediately allowed to idle, and the direct-axis current is applied to the DC side through the controllable rectifier to cancel the magnetic field, thereby reducing the back electromotive force generated by idling, protecting the inverter connected to the AC load and the entire system, and improving the fault tolerance and stability of the system. Step 5: Continuously monitor the operating status and load demand of the power generation system. Based on real-time demand and system status, dynamically adjust the operating status of the engine and axial magnetic field permanent magnet motor to ensure stable system operation and meet load demand.

[0010] Beneficial technical effects of the present invention: 1. The power generation system provided by this invention optimizes the performance and function of the motor by using a non-magnetic stator support and a magnetic stator core, as well as by a specially designed layout and installation of stator windings and permanent magnets. In particular, this invention achieves high AC output power and voltage regulation rate, as well as high system power density by using dual stator and dual three-phase stator windings and by controlling the length of the two air gaps. In addition, the dual stator design of this power generation system can output stable AC and DC power, or output one of them separately, during vehicle operation, to meet the needs of independent power supply. The controllable rectifier and corresponding control strategy ensure the stability of DC output.

[0011] 2. The power generation system provided by the present invention can accurately control the DC output voltage and achieve stable DC output by using a controllable rectifier and an id=0 control strategy. The id=0 control strategy simplifies the control strategy and improves the dynamic performance of the system by controlling the d-axis current to zero in a synchronous rotating coordinate system.

[0012] 3. The first stator component provided by this invention adopts a Litz wire distributed winding. This design effectively increases the output torque performance, has the characteristic of suppressing torque pulsation, and effectively reduces the harmonic content of back EMF. This helps to improve the stability of motor output. In addition, the length of the first air gap is much smaller than the length of the second air gap. The smaller first air gap helps to increase AC output power, thereby increasing the system power density. The controllable rectifier connected to the winding of the second stator component adopts the id=0 control mode, which simplifies the control logic of the power generation system and can obtain stable DC output. At the same time, it reduces the response time of the power generation system and improves dynamic performance. Through the above design optimization and control strategy, the system maintains high power density and output torque, while mitigating the problem of unstable AC side voltage output caused by motor armature reaction by optimizing the control strategy and structural design.

[0013] 4. The power generation system control method provided by the present invention allows the motor rotor to idle when a fault occurs on the AC side, and reduces the back electromotive force by passing a direct-axis current on the DC side to counteract the magnetic field, thereby protecting the inverter and improving the system fault tolerance. At the same time, this strategy also helps to maintain the stable operation of the system and reduce the possibility of AC side voltage instability due to faults. Attached Figure Description

[0014] Figure 1 This is a topology diagram of an axial flux permanent magnet motor according to an embodiment of the present invention; Figure 2 This is a topology diagram of an axial flux permanent magnet motor according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the principle of an axial flux permanent magnet motor according to an embodiment of the present invention; Figure 4 This is a schematic diagram of an on-board AC / DC hybrid power generation system according to an embodiment of the present invention; Figure 5 This is a schematic diagram of AC voltage measurement in a vehicle-mounted AC / DC hybrid power generation system according to an embodiment of the present invention.

[0015] In the diagram: 100-First stator component, 200-Second stator component, 300-Rotor component, 400-AC load, 500-DC load, 600-Controllable rectifier, 700-First air gap, 800-Air gap 2, 101-Non-magnetic stator support, 102-First stator winding, 201-Magnetic stator core, 202-Second stator winding, 301-Rotor support, 302-Permanent magnet. Detailed Implementation

[0016] To enable those skilled in the art to understand the technical solution of the present invention more clearly, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0017] like Figures 1-5 As shown, the vehicle-mounted AC / DC hybrid power generation system provided in this embodiment includes an engine and an axial magnetic field permanent magnet motor connected to the engine. The axial magnetic field permanent magnet motor includes a first stator component 100, a second stator component 200, and a rotor component 300. The crankshaft of the engine and the rotor shaft of the motor are connected by a coupling or by belt drive. The first stator component 100 includes a non-magnetic stator support 101, on which n first stator windings 102 are evenly distributed along the circumferential direction. The first stator windings 102 adopt Litz wire distribution winding. This design effectively increases the output torque performance, has the characteristic of suppressing torque pulsation, and effectively reduces the harmonic content of back EMF, thereby improving the stability of motor output. The second stator component 200 includes a magnetically conductive stator core 201 and a second stator winding 202. The magnetically conductive stator core 201 has m magnetically conductive stator core teeth evenly distributed along the circumferential direction. The second stator winding 202 is wound on the magnetically conductive stator core teeth. The second stator winding 202 can be a concentrated winding or a distributed winding to adapt to different application requirements and performance requirements. The above m and n are both integers, m≥2, n≥2; Three-phase lines are respectively led out from the first stator winding 102 on the first stator component 100 and the second stator winding 202 on the second stator component 200. The first stator winding 102 on the first stator component 100 is directly connected to the AC load, and the second stator winding 202 on the second stator component 200 is connected to a controllable rectifier, which is then connected to the DC load. The controllable rectifier adopts the id=0 control mode, which simplifies the control logic of the power generation system. The aforementioned DC load is a power battery. The controllable rectifier adjusts the DC output voltage according to the power battery's charge level. When the power battery's charge is insufficient, the controllable rectifier controller will output a higher DC output voltage to accelerate the charging speed of the power battery. The controllable rectifier adopts an id=0 control mode, which can reduce the response time of the power generation system and improve dynamic performance, thereby improving the charging efficiency of the power battery. The power generation system also includes an inverter connected to a controlled rectifier and connected to an AC load to convert the DC power generated by the controlled rectifier into AC power for use by other AC loads. The controllable rectifier and its control method (id=0 control method) provide stability for the DC output. By precisely controlling the current, the stability of the DC output can be ensured, meeting the requirements of the vehicle's DC load. Specifically: The id=0 control mode means that the d-axis current (id) is controlled to zero in the synchronous rotating coordinate system. Under this control strategy, the rectifier only generates the q-axis current (iq), which helps to reduce the response time of the power generation system and improve dynamic performance. By precisely controlling iq, precise control of the DC output voltage can be achieved, thereby obtaining a stable DC output. More specifically regarding the control method: a) Use the dq transformation (or Park transformation) to convert the three-phase current into d-axis and q-axis currents. In the synchronous rotating coordinate system, the d-axis and q-axis are related to the position of the magnetic field and the rotor, respectively. b) In the “id=0 control mode”, the generator system is controlled so that the d-axis current is zero, which means that all the current is on the q-axis. This simplifies the control strategy and allows the focus to be on adjusting the q-axis current to control the output voltage. This control strategy is used to achieve fast and accurate voltage control of the vehicle generator system, especially under dynamic conditions. c) By controlling the q-axis current, the controllable rectifier can quickly respond to changes in the vehicle's DC load and system disturbances, thereby achieving a stable DC output; The winding of the first stator component 100 is directly connected to the AC load. Since it adopts Litz wire distributed winding, this winding method can effectively increase the output torque performance, suppress torque pulsation, reduce the harmonic content of back EMF, thereby improving the stability of motor output. This means that the first stator component 100 is mainly for generating stable AC output in the vehicle AC-DC hybrid power generation system. The windings of the second stator component 200 are connected to a controllable rectifier, and then connected to a DC load through the controllable rectifier. The function of the controllable rectifier is to convert the AC power generated by the second stator component 200 into DC power for use by the DC load. By adjusting the control parameters of the controllable rectifier (id=0 control mode), a stable DC output can be obtained. The rotor component 300 is disposed between the first stator component 100 and the second stator component 200, and includes a rotor support 301 and a permanent magnet 302. The rotor support can be a stainless steel support. The rotor support 301 has x permanent magnet slots uniformly arranged circumferentially on the side near the non-magnetic stator support 101. The rotor support 301 has y permanent magnet slots uniformly arranged circumferentially on the side near the magnetic stator core 201. The permanent magnets 302 are installed in the corresponding permanent magnet slots, and their magnetization direction is along the motor axis. The N poles and S poles are alternately distributed, which helps to generate a stable magnetic field. The alternating N poles and S poles can reduce the interference of external magnetic fields on the motor magnetic field, thereby improving the stability and reliability of the motor in complex environments. Moreover, due to the high magnetic field utilization efficiency, the axially magnetized permanent magnets can provide a large output power with a small volume and weight, thereby improving the power density of the motor. The number of permanent magnets in rotor component 300 satisfies the condition: y≥2, and satisfies the relationship 6000 / x, where x is the engine's operating speed, to ensure a 50Hz AC output on the AC side. See details... Figure 5 The AC side output voltage waveform has an electrical frequency of 50Hz.

[0018] A first air gap 700 exists between the first stator component 100 and the rotor component 300, and a second air gap 800 exists between the second stator component 200 and the rotor component 300 to form a dual-stator dual-three-phase stator winding. The length of the first air gap 700 is approximately between 0.8 mm and 1.3 mm, and the length of the second air gap 800 is approximately between 3.0 mm and 4.0 mm. This helps to increase the AC output power and thus improve the system power density. The difference in length between the first and second air gaps can optimize the performance of the axial magnetic field permanent magnet motor. The first air gap is the non-magnetic region between the first stator component 100 and the rotor component 300. The first air gap is smaller, and compared with the second air gap, the magnetic field can be transferred more effectively from the stator component to the rotor component, thereby improving the efficiency and output power of the motor. The smaller air gap can also reduce the pulsation of the magnetic field, thereby enabling the power generation system to output a more stable voltage. The second air gap is larger. A larger air gap can reduce the density of the magnetic field, thereby reducing the loss and heat generated by the magnetic field. This helps to increase the power density (output power per unit volume or weight) of the motor, which is especially important for meeting the weight requirements of the vehicle. Axial magnetic field permanent magnet motors with high power density can be lighter at the same output power, thus helping to reduce the weight of the vehicle.

[0019] In this embodiment, the magnetically conductive stator core 201 is made of silicon steel sheet, and the non-magnetically conductive stator support 101 is made of composite material. This design can meet the requirements of low harmonics and high output characteristics of AC power, while also meeting the requirements of high efficiency and high power density of controllable rectified DC load.

[0020] In this embodiment, when the on-board AC / DC hybrid power generation system malfunctions, the motor rotor spins idling, and the magnetic field of the permanent magnet generates a very high no-load back EMF. The high back EMF will cause a high voltage surge to the switching devices of the inverter and the load on the AC side. In order to improve safety, a direct-axis current is introduced on the DC side at this time. By using the principle of field weakening control, the no-load back EMF surge is reduced, which protects the AC load and the inverter and improves its fault tolerance capability.

[0021] In this embodiment, the vehicle-mounted AC / DC hybrid power generation system achieves stable output of AC and DC power, or one of them alone, during vehicle operation to meet power supply requirements. This not only helps to improve power density but also simplifies the system architecture. The system has low cogging torque and significantly reduced vibration and noise, making it particularly suitable for silent generator sets.

[0022] In this embodiment, the motor used in the vehicle-mounted AC / DC hybrid power generation system includes two stator components and one rotor component. The first stator component 100 and the second stator component 200 each have their own windings. These windings generate electromotive force in response to changes in the magnetic field of the rotor component. Since the windings of the two stator components are separate, the two stator components can generate and adjust the electromotive force separately, and one of them is connected to a controllable rectifier to meet the needs of AC and DC loads.

[0023] A control method for an on-board AC / DC hybrid power generation system includes the following steps: Step 1: Start the engine and initialize the control system of the axial magnetic field permanent magnet motor and the controllable rectifier; Step 2: Monitor the AC load demand and adjust the engine's operating status according to the demand to ensure that the first stator component of the axial magnetic field permanent magnet motor generates AC power that adapts to changes in the AC load. The AC load is connected to the first stator component of the axial magnetic field permanent magnet motor, forming the AC side of the vehicle-mounted AC / DC hybrid power generation system. Step 3: According to the requirements of the DC load, adjust the control parameters of the controllable rectifier between the DC load and the second stator component of the axial magnetic field permanent magnet motor to ensure stable DC output. The controllable rectifier adopts the control mode of id=0. The DC load constitutes the DC side of the vehicle-mounted AC-DC hybrid power generation system. Step 4: If a fault is detected on the AC side, the rotor of the axial magnetic field permanent magnet motor is immediately allowed to idle, and the direct-axis current is applied to the DC side through the controllable rectifier to cancel the magnetic field, thereby reducing the back electromotive force generated by idling, protecting the inverter connected to the AC load and the entire system, and improving the fault tolerance and stability of the system. Step 5: Continuously monitor the operating status and load demand of the power generation system. Based on real-time demand and system status, dynamically adjust the operating status of the engine and axial magnetic field permanent magnet motor to ensure stable system operation and meet load demand.

[0024] In summary, in this embodiment, the control method of the vehicle-mounted AC / DC hybrid power generation system provides the following: when a fault occurs on the AC side, the motor rotor is allowed to idle, and the magnetic field is counteracted by passing a direct-axis current on the DC side, thereby reducing the back electromotive force to protect the inverter and improve the system fault tolerance.

[0025] The above description is merely a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A control method for an on-board AC / DC hybrid power generation system, the system comprising an engine and an axial magnetic field permanent magnet motor connected to the engine, the axial magnetic field permanent magnet motor comprising a first stator component, a second stator component, and a rotor component; The first stator component includes a non-magnetic stator support, on which n first stator windings are distributed along the circumferential direction. The first stator windings are Litz wire distributed windings. The second stator component includes a magnetically conductive stator core and a second stator winding. The magnetically conductive stator core has m magnetically conductive stator core teeth distributed along the circumferential direction. The second stator winding is wound on the magnetically conductive stator core teeth. The above m and n are both integers, and m≥2 and n≥2. The rotor component is disposed between the first and second stator components. The rotor component includes a rotor support. The rotor support has x permanent magnet slots arranged along the circumferential direction on the side near the non-magnetic stator support and y permanent magnet slots arranged along the circumferential direction on the side near the magnetic stator core. Permanent magnets are disposed in the permanent magnet slots, and their magnetization direction is along the motor axis, with N poles and S poles alternately distributed. A first air gap is provided between the first stator component and the rotor component, and a second air gap is provided between the second stator component and the rotor component, wherein the length of the first air gap is less than the length of the second air gap; The first stator winding and the second stator winding are respectively led out with three-phase lines. The first stator winding is connected to the AC load, and the second stator winding is connected to the controllable rectifier. The controllable rectifier is connected to the power battery and the DC load. The controllable rectifier adopts the control mode of id=0. Its features are, The control method includes the following steps: Step 1: Start the engine and initialize the control system of the axial magnetic field permanent magnet motor and the controllable rectifier; Step 2: Monitor the AC load demand and adjust the engine's operating status according to the demand to ensure that the first stator component of the axial magnetic field permanent magnet motor generates AC power that adapts to changes in the AC load. The AC load is connected to the first stator component of the axial magnetic field permanent magnet motor, forming the AC side of the vehicle-mounted AC / DC hybrid power generation system. Step 3: According to the requirements of the DC load, adjust the control parameters of the controllable rectifier between the DC load and the second stator component of the axial magnetic field permanent magnet motor to ensure stable DC output. The controllable rectifier adopts the control mode of id=0. The DC load constitutes the DC side of the vehicle-mounted AC-DC hybrid power generation system. Step 4: If a fault is detected on the AC side, the rotor of the axial magnetic field permanent magnet motor is immediately allowed to idle, and the direct-axis current is applied to the DC side through the controllable rectifier to cancel the magnetic field, thereby reducing the back electromotive force generated by idling, protecting the inverter connected to the AC load and the entire system, and improving the fault tolerance and stability of the system. Step 5: Continuously monitor the operating status and load demand of the power generation system. Based on real-time demand and system status, dynamically adjust the operating status of the engine and axial magnetic field permanent magnet motor to ensure stable system operation and meet load demand.

2. The control method for a vehicle-mounted AC / DC hybrid power generation system according to claim 1, characterized in that, The second stator winding adopts either a concentrated winding or a distributed winding.

3. The control method for a vehicle-mounted AC / DC hybrid power generation system according to claim 2, characterized in that, It also includes an inverter, which is connected to a controllable rectifier and to another AC load.

4. The control method for a vehicle-mounted AC / DC hybrid power generation system according to claim 3, characterized in that, The controllable rectifier is connected to a power battery.

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