Horizontal inertia flywheel system with permanent magnet brushless auxiliary motor and starting method

Abstract

The invention relates to the technical field of permanent magnet brushless direct current motor control, in particular to a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor and a starting method, the flywheel system comprises an energy storage flywheel, an auxiliary motor, an electromagnetic coupler, a synchronous phase modifier, a direct current bus, a rectifier, a first converter and a second converter; the starting method comprises the following steps: disconnecting the second converter from an outer rotor of the electromagnetic coupler, and short-circuiting an outer rotor winding of the electromagnetic coupler; starting a rectifier to supply power to the direct-current bus voltage; the first converter implements subsection control according to rotation speed feedback of the auxiliary motor; when the rotor rotating speed of the synchronous phase modifier reaches the synchronous rotating speed and meets the grid connection condition, the stator side winding is connected into the power grid, and the self-starting process of the whole system is completed. According to the invention, the electrical characteristics of the electromagnetic coupler are fully utilized, the system self-starting is realized by optimizing the control strategy of the auxiliary motor, and the feasibility and reliability are good.

Description

Technical Field

[0001] This application relates to the field of permanent magnet brushless DC motor control technology, and in particular to a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor and its starting method. Background Technology

[0002] With the continuous advancement of global renewable energy development and utilization, new energy systems, represented by wind power and solar power, have become an important part of energy structure transformation. However, compared with traditional fossil fuel-based power generation systems, new energy systems face significant challenges in terms of grid frequency stability. In traditional power generation systems, the rotational inertia provided by numerous rotating mechanical components (such as steam turbines and generator rotors) can effectively buffer sudden changes in grid load and maintain frequency stability. However, new energy power generation equipment (such as wind turbines and photovoltaic inverters) typically lack mechanical rotational inertia. The volatility and intermittency of their output power result in the grid lacking the necessary inertial support when facing sudden load changes, which can easily lead to frequency fluctuations and even stability problems.

[0003] To address the frequency stability issues arising from the integration of new energy sources, existing technologies primarily employ two approaches: one utilizes traditional synchronous condenser technology to improve grid stability by adjusting reactive power output and providing a small amount of mechanical inertia; the other leverages chemical energy storage devices or traditional flywheel energy storage systems to simulate virtual inertia and output active power through grid-connected converters. However, these approaches suffer from drawbacks such as high complexity in coordination and control, and high system construction costs, necessitating a novel device that integrates multiple functions. Summary of the Invention

[0004] This application provides a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor and a starting method. It makes full use of the electrical characteristics of the electromagnetic coupler and achieves system self-starting by optimizing the auxiliary motor control strategy, which has good feasibility and reliability.

[0005] To address the aforementioned technical problems, in a first aspect, embodiments of this application provide a starting method for a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor. This method is applied to a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor. The system includes: an energy storage flywheel, an auxiliary motor, an electromagnetic coupler, a synchronous condenser, a DC bus, a rectifier, a first converter, and a second converter. The electromagnetic coupler includes an inner rotor and an outer rotor. The flywheel rotor of the energy storage flywheel is coaxially connected to the auxiliary motor and the inner rotor of the electromagnetic coupler. The auxiliary motor is connected to the DC bus via the first converter. The outer rotor of the electromagnetic coupler is coaxially connected to the rotor of the synchronous condenser, and the stator winding of the synchronous condenser is directly connected to the power grid. The starting method includes the following steps: First, disconnect the connection between the second converter and the outer rotor of the electromagnetic coupler, and short-circuit the outer rotor winding of the electromagnetic coupler; then, start the rectifier to supply power to the DC bus voltage; next, the first converter implements segmented control based on the auxiliary motor speed feedback; when the rotor speed of the synchronous condenser reaches the synchronous speed and meets the grid connection conditions, its stator winding is connected to the power grid, completing the self-starting process of the entire system.

[0006] In some exemplary embodiments, the first converter implements segmented control based on the auxiliary motor speed feedback, including: when the auxiliary motor speed is lower than the synchronous speed, the first converter adopts a constant torque control strategy, using current closed-loop control to keep the armature current of the auxiliary motor constant, thereby generating a stable starting torque that drives the flywheel rotor of the energy storage flywheel to rotate synchronously with the rotor inside the electromagnetic coupler; during this process, the rotation of the rotor inside the electromagnetic coupler drives the outer rotor and the synchronous condenser rotor to start rotating through electromagnetic induction; when the auxiliary motor speed reaches the synchronous speed, the first converter switches to a constant speed control mode, using speed closed-loop control to maintain the auxiliary motor speed stable at the synchronous speed; at this time, the electromagnetic coupling between the inner and outer rotors of the electromagnetic coupler tends to stabilize, and the outer rotor and the synchronous condenser rotor gradually accelerate to the synchronous speed under the drive of electromagnetic force.

[0007] In some exemplary embodiments, the first converter implements segmented control based on the auxiliary motor speed feedback, including: the first converter receives the auxiliary motor speed signal fed back by the speed sensor; when the speed is detected to be lower than the synchronous speed, it switches to constant torque control mode; through a preset torque command value, the armature current command value is calculated by the current loop, compared with the actual current feedback, and input to the PWM controller to generate a drive signal to control the auxiliary motor to output constant torque; at this time, the auxiliary motor rotor drives the flywheel and the inner rotor of the electromagnetic coupler to rotate, and the rotating magnetic field generated by the rotation of the inner rotor induces a current in the short-circuited outer rotor winding, forming an electromagnetic torque drive. The external rotor and synchronous condenser rotor rotate; when the auxiliary motor speed reaches the synchronous speed, the first AC converter switches to constant speed control mode; the difference between the speed command value and the actual speed is input to the PI regulator, and the current command value is output, which is maintained at a constant auxiliary motor speed through the current loop and PWM controller; at this time, the speed difference between the inner and outer rotors of the electromagnetic coupler gradually decreases, and the synchronous condenser rotor accelerates to the synchronous speed under the action of electromagnetic torque; when the synchronous condenser rotor speed reaches the synchronous speed and the stator voltage and the voltage amplitude, frequency and phase error of the grid are within the allowable range, the grid connection switch is closed to connect its stator side to the grid, completing the system self-start.

[0008] In some exemplary embodiments, during the initial startup state, all components of the system are in a static state before startup. The connection between the second converter and the outer rotor of the electromagnetic coupler is disconnected, and the outer rotor winding of the electromagnetic coupler is short-circuited. During the entire startup phase, the second converter does not participate in the operation, and only the auxiliary motor is responsible for providing the starting torque.

[0009] In some exemplary embodiments, the rectifier controls the input current on the grid side. After the rectifier starts, it converts the power frequency AC power of the grid into stable DC power to supply the DC bus. Through voltage closed-loop control, it maintains the DC bus voltage stability and ensures that the bus voltage is maintained at the rated value.

[0010] Secondly, this application also provides a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor. The system employs the starting method described in the above embodiment to achieve self-starting. The electromagnetic coupler transmits torque through electromagnetic induction between the inner and outer rotors. The flywheel rotor of the energy storage flywheel is coaxially connected to the auxiliary motor and the inner rotor of the electromagnetic coupler via a transmission shaft. The outer rotor of the electromagnetic coupler is coaxially connected to the rotor of the synchronous condenser via a mechanical shaft. The auxiliary motor is a permanent magnet brushless DC motor. The auxiliary motor is responsible for providing driving torque during the startup phase and serves as a backup power source during normal system operation. The synchronous condenser controls reactive power output by adjusting the excitation current. The rectifier converts AC power from the power grid into DC power. The first converter enables bidirectional energy flow between the auxiliary motor and the bus, and the second converter controls the input current frequency of the outer rotor of the electromagnetic coupler.

[0011] In some exemplary embodiments, the input of the rectifier is connected to the power grid, and the output is connected to the DC bus, for converting the power grid frequency AC power into DC power and maintaining the DC bus voltage constant.

[0012] In some exemplary embodiments, the first converter is connected to an auxiliary motor and a DC bus at its two ends, respectively. The first converter can convert the AC power generated by the auxiliary motor into DC power and inject it into the bus, and can also draw power from the bus and invert it into AC power to drive the auxiliary motor.

[0013] In some exemplary embodiments, the two ends of the second converter are respectively connected to the outer rotor winding of the electromagnetic coupler and the DC bus, for inverting the DC bus current into AC current of a specific frequency and passing it into the outer rotor winding, thereby adjusting the rotational speed of the electromagnetic coupler by controlling the current frequency.

[0014] In some exemplary embodiments, when the second converter outputs a positive current, the speed of the synthesized magnetomotive force is higher than the mechanical speed of the outer rotor, and the permanent magnet of the inner rotor is subjected to a positive electromagnetic torque, which drives the flywheel rotor of the energy storage flywheel to accelerate energy storage; when the second converter outputs a negative current, the speed of the synthesized magnetomotive force is lower than the mechanical speed of the outer rotor, and the permanent magnet of the inner rotor is subjected to a negative electromagnetic torque, which drives the flywheel rotor of the energy storage flywheel to decelerate and release energy.

[0015] The technical solution provided in this application has at least the following advantages:

[0016] This application provides a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor and a starting method. The method is applied to a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor. The flywheel system includes: an energy storage flywheel, an auxiliary motor, an electromagnetic coupler, a synchronous condenser, a DC bus, a rectifier, a first converter, and a second converter. The electromagnetic coupler includes an inner rotor and an outer rotor. The flywheel rotor of the energy storage flywheel is coaxially connected to the auxiliary motor and the inner rotor of the electromagnetic coupler. The auxiliary motor is connected to the DC bus through the first converter, and the outer rotor of the electromagnetic coupler is coaxially connected to the rotor of the synchronous condenser. The stator winding of the synchronous condenser is directly connected to the power grid. The starting method includes the following steps: First, disconnect the second converter from the outer rotor of the electromagnetic coupler and short-circuit the outer rotor winding of the electromagnetic coupler; then, start the rectifier to supply power to the DC bus voltage; next, the first converter implements segmented control based on the auxiliary motor speed feedback; when the rotor speed of the synchronous condenser reaches the synchronous speed and meets the grid connection conditions, its stator winding is connected to the power grid, completing the self-starting process of the entire system.

[0017] The core advantage of this starting method lies in fully utilizing the passive coupling characteristics of the electromagnetic coupler. By short-circuiting the outer rotor winding, the auxiliary motor torque can be transferred to the synchronous condenser rotor without the need for additional control of converter two. This avoids the technical difficulties of complex vector control of the electromagnetic coupler in traditional solutions, significantly improving the simplicity and reliability of the starting process. The inner rotor of the electromagnetic coupler is designed with permanent magnet materials, while the outer rotor is directly mechanically connected to the rotor of the synchronous condenser and maintains a constant speed, ensuring that the frequency of the electrical energy generated by the synchronous motor is consistent with the grid frequency and directly connected to the grid. By controlling the current frequency output from converter two to the outer rotor of the electromagnetic coupler, a certain slip can be created between the flywheel and the synchronous condenser, achieving effective transmission of flywheel-side torque to the synchronous condenser. Addressing the complex structure of the inertia flywheel system, this application provides a simple and reliable starting control method using a permanent magnet brushless auxiliary motor in conjunction with an electromagnetic coupler. Through reasonable design of the control logic during the starting process, the system can safely and efficiently complete the self-starting operation. Attached Figure Description

[0018] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0019] Figure 1 This is a schematic diagram of a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor provided in an embodiment of this application.

[0020] Figure 2 This is a flowchart of the flywheel system startup process provided in this application.

[0021] Figure 3 This is a control block diagram of the inertia flywheel system startup method provided in this application.

[0022] Figure 4 This is a partially enlarged view of the control block diagram of the inertia flywheel system startup method provided in this application. Detailed Implementation

[0023] As can be seen from the background technology, existing flywheel systems have drawbacks such as high complexity of coordination and control and high system construction costs, and there is an urgent need for a new type of device that can integrate multiple functions.

[0024] The inertia flywheel system, through innovative structural design, integrates the reactive power regulation capability of a synchronous condenser with the inertia support characteristics of flywheel energy storage, enabling simultaneous output of active power, reactive power, and direct mechanical inertia. The system mainly consists of an energy storage flywheel, an auxiliary motor, an electromagnetic coupler, a synchronous condenser, a rectifier, a DC bus, converter one, and converter two. The synchronous condenser outputs reactive power to the grid and provides basic inertia support. The energy storage flywheel can quickly respond to load changes and provide rotational inertia and active power. The auxiliary motor and its associated converter are responsible for the system's self-starting process and act as a UPS power supply under abnormal conditions. The electromagnetic coupler and its control converter achieve efficient transmission of rotational inertia and active power between the flywheel side and the grid side. Currently, this type of inertia flywheel system is still in the theoretical research stage, and research on its control methods, especially the exploration of starting methods, is still insufficient. Since the flywheel rotor, the inner and outer rotors of the electromagnetic coupler, and the synchronous condenser rotor are all in a high-speed rotation state during normal operation of the system, the components form a complex dynamic system through electromagnetic coupling and mechanical connection. The problems of speed coordination, torque transmission and grid connection condition matching involved in the startup process have become technical difficulties.

[0025] To address the aforementioned technical problems, this application provides a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor and a starting method. The flywheel system includes: an energy storage flywheel, an auxiliary motor, an electromagnetic coupler, a synchronous condenser, a DC bus, a rectifier, a first converter, and a second converter. The electromagnetic coupler includes an inner rotor and an outer rotor. The flywheel rotor of the energy storage flywheel is coaxially connected to the auxiliary motor and the inner rotor of the electromagnetic coupler. The auxiliary motor is connected to the DC bus via the first converter. The outer rotor of the electromagnetic coupler is coaxially connected to the rotor of the synchronous condenser, and the stator winding of the synchronous condenser is directly connected to the power grid. The starting method includes the following steps: First, disconnect the connection between the second converter and the outer rotor of the electromagnetic coupler, and short-circuit the outer rotor winding of the electromagnetic coupler; then, start the rectifier to supply power to the DC bus voltage; next, the first converter implements segmented control based on the auxiliary motor speed feedback; when the rotor speed of the synchronous condenser reaches the synchronous speed and meets the grid connection conditions, its stator winding is connected to the power grid, completing the self-starting process of the entire system. This application proposes a novel horizontal inertia flywheel system and its starting method to address the above problems. This method fully utilizes the electrical characteristics of the electromagnetic coupler and achieves system self-starting by optimizing the auxiliary motor control strategy, possessing good feasibility and reliability.

[0026] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0027] See Figure 1 This application provides a starting method for a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor, applicable to such a system. Figure 1 As shown, the system includes: an energy storage flywheel 10, an auxiliary motor 30, an electromagnetic coupler 40, a synchronous condenser 50, a rectifier 60, a DC bus 70, a first converter 80, and a second converter 90; the electromagnetic coupler 40 includes an inner rotor and an outer rotor; the flywheel rotor of the energy storage flywheel 10 is coaxially connected to the auxiliary motor 30 and the inner rotor of the electromagnetic coupler 40; the auxiliary motor 30 is connected to the DC bus 70 through the first converter 80; the outer rotor of the electromagnetic coupler 40 is coaxially connected to the rotor of the synchronous condenser 50; and the stator winding of the synchronous condenser 50 is directly connected to the power grid 100.

[0028] Please continue reading. Figure 1 The horizontal inertia flywheel system provided in this application mainly consists of the following parts:

[0029] Energy storage flywheel 10: It stores kinetic energy through high-speed rotation. The flywheel rotor of the energy storage flywheel 10 is coaxially connected to the inner rotor of the auxiliary motor 30 and the electromagnetic coupler 40 through the first drive shaft 21 and the second drive shaft 22 to realize the storage and release of energy.

[0030] Auxiliary motor 30: It adopts a permanent magnet brushless DC motor, which is connected to the DC bus 70 through the first converter 80. It is responsible for providing driving torque during the startup phase and serving as a backup power source when the system is running normally.

[0031] Electromagnetic coupler 40: includes an inner rotor (permanent magnet material) and an outer rotor. The inner rotor is coaxially connected to the flywheel rotor, and the outer rotor is connected to the rotor of the synchronous condenser 50 via a third drive shaft 23. Torque transmission is achieved through electromagnetic induction between the inner and outer rotors. The outer rotor winding is connected to the second converter 90 to regulate the input current frequency.

[0032] Synchronous condenser 50: The stator winding is directly connected to the power grid 100. The reactive power output is controlled by adjusting the excitation current. The rotor is coaxially connected to the outer rotor of the electromagnetic coupler to obtain the rotational inertia.

[0033] The rectifier 60, the first converter 80, and the second converter 90 together constitute a power conversion unit. The rectifier 60 converts the AC power from the power grid into DC power. The first converter 80 enables bidirectional energy flow between the auxiliary motor and the bus. The second converter 90 controls the frequency of the input current to the outer rotor of the electromagnetic coupler.

[0034] like Figure 2 As shown in the embodiment of this application, the starting method of the horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor includes the following steps: First, disconnect the connection between the second converter and the outer rotor of the electromagnetic coupler, and short-circuit the outer rotor winding of the electromagnetic coupler; then, start the rectifier to supply power to the DC bus voltage; next, the first converter implements segmented control according to the speed feedback of the auxiliary motor; when the rotor speed of the synchronous condenser reaches the synchronous speed and meets the grid connection conditions, its stator winding is connected to the grid to complete the self-starting process of the entire system.

[0035] In some embodiments, the first converter implements segmented control based on the speed feedback of the auxiliary motor, including: when the speed of the auxiliary motor is lower than the synchronous speed, the first converter adopts a constant torque control strategy, and keeps the armature current of the auxiliary motor constant through current closed-loop control, thereby generating a stable starting torque, which drives the flywheel rotor of the energy storage flywheel to rotate synchronously with the rotor inside the electromagnetic coupler; during this process, the rotation of the rotor inside the electromagnetic coupler drives the outer rotor and the synchronous condenser rotor to start rotating through electromagnetic induction; when the speed of the auxiliary motor reaches the synchronous speed, the first converter switches to a constant speed control mode, and maintains the speed of the auxiliary motor at the synchronous speed through speed closed-loop control; at this time, the electromagnetic coupling between the inner and outer rotors of the electromagnetic coupler tends to stabilize, and the outer rotor and the synchronous condenser rotor gradually accelerate to the synchronous speed under the drive of electromagnetic force.

[0036] Figure 3 The control block diagram for the start-up mode of the inertia flywheel system is shown. (For example...) Figure 3 As shown, in some embodiments, the first converter implements segmented control based on the auxiliary motor speed feedback, including: the first converter receives the auxiliary motor speed signal fed back by the speed sensor; when the speed is detected to be lower than the synchronous speed, it switches to constant torque control mode; through a preset torque command value, the armature current command value is calculated by the current loop, compared with the actual current feedback, and then input to the PWM controller to generate a drive signal to control the auxiliary motor to output constant torque; at this time, the auxiliary motor rotor drives the flywheel and the inner rotor of the electromagnetic coupler to rotate, and the rotating magnetic field generated by the rotation of the inner rotor induces a current in the short-circuited outer rotor winding, forming an electromagnetic torque drive. The external rotor and synchronous condenser rotor rotate; when the auxiliary motor speed reaches the synchronous speed, the first AC converter switches to constant speed control mode; the difference between the speed command value and the actual speed is input to the PI regulator, and the current command value is output, which is maintained at a constant auxiliary motor speed through the current loop and PWM controller; at this time, the speed difference between the inner and outer rotors of the electromagnetic coupler gradually decreases, and the synchronous condenser rotor accelerates to the synchronous speed under the action of electromagnetic torque; when the synchronous condenser rotor speed reaches the synchronous speed and the stator voltage and the voltage amplitude, frequency and phase error of the grid are within the allowable range, the grid connection switch is closed to connect its stator side to the grid, completing the system self-start.

[0037] Figure 4 A partially enlarged view of the control block diagram for the start-up mode of the inertia flywheel system is shown. (See attached image.) Figure 4As shown, the auxiliary brushless DC motor has two operating modes: constant torque control mode and constant speed control mode. The Hall sensor on the auxiliary motor can collect the rotor position and provide the actual motor speed. The actual speed is fed back to the speed loop, compared with the target speed, and then input to the PI controller to output the speed loop reference current. This reference current is then compared with the stator sampling current of the auxiliary motor, and the difference is input to the PI controller. The controller converts the deviation current into a control signal for the three-phase bridge converter, thus achieving constant speed control. Constant torque control obtains the torque loop reference current based on the torque reference value input to the proportional controller, and then proceeds as above. Vector control is used for the rectifier, controlling the energy flow direction through ID to achieve energy exchange balance between the grid and the DC bus, thereby maintaining the DC bus voltage at a constant value. During the flywheel startup phase, the rectifier absorbs energy from the grid and supplies it to the auxiliary motor, which then increases the flywheel speed to the specified value. This application achieves sensorless torque transmission and self-synchronous start-up of a multi-rotor system through a collaborative design of electromagnetic coupler external rotor short-circuiting and auxiliary motor segmented control. This greatly simplifies the control architecture and improves reliability. Furthermore, the auxiliary motor adopts a permanent magnet brushless motor, which has a simpler control structure and lower cost compared to a permanent magnet synchronous motor.

[0038] In some embodiments, during the initial startup state, all components of the system are in a stationary state before startup. The connection between the second converter and the outer rotor of the electromagnetic coupler is disconnected, and the outer rotor winding of the electromagnetic coupler is short-circuited. During the entire startup phase, the second converter does not participate in the operation, and only the auxiliary motor is responsible for providing the starting torque.

[0039] In some embodiments, the rectifier controls the input current on the grid side. After the rectifier starts, it converts the power frequency AC power of the grid into stable DC power to supply the DC bus. Through voltage closed-loop control, it maintains the DC bus voltage stability and ensures that the bus voltage is maintained at the rated value.

[0040] Furthermore, this application also provides a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor, the structural diagram of which is shown below. Figure 1As shown, the starting method of the horizontal inertia flywheel system with permanent magnet brushless auxiliary motor described in the above embodiment achieves self-starting. The electromagnetic coupler 40 transmits torque through the electromagnetic induction between the inner and outer rotors. The flywheel rotor of the energy storage flywheel 10 is coaxially connected to the auxiliary motor 30 and the inner rotor of the electromagnetic coupler 40 through the first drive shaft 21 and the second drive shaft 22. The outer rotor of the electromagnetic coupler 40 is coaxially connected to the rotor of the synchronous condenser 50 through the third drive shaft 23. The auxiliary motor 30 is a permanent magnet brushless DC motor. The auxiliary motor 30 is responsible for providing driving torque during the start-up phase and serves as a backup power source during normal system operation. The synchronous condenser 50 controls the reactive power output by adjusting the excitation current. The rectifier 60 is used to convert the AC power of the power grid into DC power. The first converter 80 is used to realize the bidirectional energy flow between the auxiliary motor and the bus. The second converter 90 is used to control the input current frequency of the outer rotor of the electromagnetic coupler.

[0041] In some embodiments, the input terminal of the rectifier 60 is connected to the power grid 100, and the output terminal is connected to the DC bus 70, for converting the power grid frequency AC power into DC power and maintaining the DC bus voltage constant.

[0042] In some embodiments, the first converter 70 is connected to the auxiliary motor 30 and the DC bus 70 at its two ends respectively. The first converter 70 can convert the AC power generated by the auxiliary motor 30 into DC power and inject it into the bus, and can also draw power from the bus and invert it into AC power to drive the auxiliary motor 30.

[0043] In some embodiments, the two ends of the second converter 90 are respectively connected to the outer rotor winding of the electromagnetic coupler 40 and the DC bus 70, for converting the current of the DC bus 70 into AC current of a specific frequency and passing it into the outer rotor winding, thereby adjusting the rotational speed of the synthetic magnetomotive force of the electromagnetic coupler 40 by controlling the current frequency.

[0044] In some embodiments, when the second converter 90 outputs a positive current, the speed of the synthesized magnetomotive force is higher than the mechanical speed of the outer rotor, and the permanent magnet of the inner rotor is subjected to a positive electromagnetic torque, which drives the flywheel rotor of the energy storage flywheel 10 to accelerate energy storage; when the second converter 90 outputs a negative current, the speed of the synthesized magnetomotive force is lower than the mechanical speed of the outer rotor, and the permanent magnet of the inner rotor is subjected to a negative electromagnetic torque, which drives the flywheel rotor of the energy storage flywheel 10 to decelerate and release energy.

[0045] Based on the above technical solutions, this application provides a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor and a starting method. This method is applied to a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor. The flywheel system includes: an energy storage flywheel, an auxiliary motor, an electromagnetic coupler, a synchronous condenser, a DC bus, a rectifier, a first converter, and a second converter. The electromagnetic coupler includes an inner rotor and an outer rotor. The flywheel rotor of the energy storage flywheel is coaxially connected to the auxiliary motor and the inner rotor of the electromagnetic coupler. The auxiliary motor is connected to the DC bus through the first converter. The outer rotor of the converter is coaxially connected to the rotor of the synchronous condenser, and the stator winding of the synchronous condenser is directly connected to the power grid. The starting method includes the following steps: First, disconnect the connection between the second converter and the outer rotor of the electromagnetic coupler, and short-circuit the outer rotor winding of the electromagnetic coupler; then, start the rectifier to supply power to the DC bus voltage; next, the first converter implements segmented control based on the auxiliary motor speed feedback; when the rotor speed of the synchronous condenser reaches the synchronous speed and meets the grid connection conditions, its stator winding is connected to the power grid, completing the self-starting process of the entire system.

[0046] The core advantage of this starting method lies in fully utilizing the passive coupling characteristics of the electromagnetic coupler. By short-circuiting the outer rotor winding, the auxiliary motor torque can be transferred to the synchronous condenser rotor without the need for additional control of converter two. This avoids the technical difficulties of complex vector control of the electromagnetic coupler in traditional solutions, significantly improving the simplicity and reliability of the starting process. The inner rotor of the electromagnetic coupler is designed with permanent magnet materials, while the outer rotor is directly mechanically connected to the rotor of the synchronous condenser and maintains a constant speed, ensuring that the frequency of the electrical energy generated by the synchronous motor is consistent with the grid frequency and directly connected to the grid. By controlling the current frequency output from converter two to the outer rotor of the electromagnetic coupler, a certain slip can be created between the flywheel and the synchronous condenser, achieving effective transmission of flywheel-side torque to the synchronous condenser. Addressing the complex structure of the inertia flywheel system, this application provides a simple and reliable starting control method using a permanent magnet brushless auxiliary motor in conjunction with an electromagnetic coupler. Through reasonable design of the control logic during the starting process, the system can safely and efficiently complete the self-starting operation.

[0047] Those skilled in the art will understand that the above-described embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of this application. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A starting method for a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor, applicable to a horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor, characterized in that, The system includes: an energy storage flywheel, an auxiliary motor, an electromagnetic coupler, a synchronous condenser, a DC bus, a rectifier, a first converter, and a second converter; the electromagnetic coupler includes an inner rotor and an outer rotor; the flywheel rotor of the energy storage flywheel is coaxially connected to the auxiliary motor and the inner rotor of the electromagnetic coupler; the auxiliary motor is connected to the DC bus through the first converter; the outer rotor of the electromagnetic coupler is coaxially connected to the rotor of the synchronous condenser; and the stator winding of the synchronous condenser is directly connected to the power grid. The startup method includes the following steps: Disconnect the second converter from the outer rotor of the electromagnetic coupler, and short-circuit the outer rotor winding of the electromagnetic coupler; Start the rectifier to supply power to the DC bus voltage; The first converter implements segmented control based on the speed feedback of the auxiliary motor; When the rotor speed of the synchronous condenser reaches the synchronous speed and meets the grid connection conditions, its stator winding is connected to the power grid, completing the self-starting process of the entire system.

2. The starting method of the horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor according to claim 1, characterized in that, The first converter implements segmented control based on the auxiliary motor speed feedback, including: When the auxiliary motor speed is lower than the synchronous speed, the first converter adopts a constant torque control strategy, which keeps the armature current of the auxiliary motor constant through current closed-loop control, thereby generating a stable starting torque, which drives the flywheel rotor of the energy storage flywheel to rotate synchronously with the rotor inside the electromagnetic coupler; during this process, the rotation of the rotor inside the electromagnetic coupler drives the outer rotor and the synchronous condenser rotor to start rotating through electromagnetic induction. When the auxiliary motor reaches the synchronous speed, the first converter switches to constant speed control mode, and maintains the auxiliary motor speed at the synchronous speed through speed closed-loop control. At this time, the electromagnetic coupling between the inner and outer rotors of the electromagnetic coupler tends to stabilize, and the outer rotor and the synchronous condenser rotor gradually accelerate to the synchronous speed under the drive of electromagnetic force.

3. The starting method of the horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor according to claim 1, characterized in that, The first converter implements segmented control based on the auxiliary motor speed feedback, including: The first AC unit receives the auxiliary motor speed signal from the speed sensor. When the speed is detected to be lower than the synchronous speed, it switches to constant torque control mode. The armature current command value is calculated by the current loop through the preset torque command value. After being compared with the actual current feedback, it is input to the PWM controller to generate a drive signal to control the auxiliary motor to output constant torque. At this time, the rotor of the auxiliary motor drives the flywheel and the inner rotor of the electromagnetic coupler to rotate. The rotating magnetic field generated by the rotation of the inner rotor induces current in the short-circuited outer rotor winding, forming an electromagnetic torque to drive the outer rotor and the synchronous condenser rotor to rotate. When the auxiliary motor reaches the synchronous speed, the first AC converter switches to constant speed control mode; the difference between the speed command value and the actual speed is input to the PI regulator, and the current command value is output. The current loop and PWM controller maintain the auxiliary motor speed at a constant speed; at this time, the speed difference between the inner and outer rotors of the electromagnetic coupler gradually decreases, and the synchronous condenser rotor accelerates to the synchronous speed under the action of electromagnetic torque; when the synchronous condenser rotor speed reaches the synchronous speed and the stator voltage and the voltage amplitude, frequency and phase error of the grid are within the allowable range, the grid connection switch is closed to connect its stator side to the grid, completing the system self-start.

4. The starting method of the horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor according to claim 1, characterized in that, In the initial startup state, all components of the system are in a static state before startup. The connection between the second converter and the outer rotor of the electromagnetic coupler is disconnected, and the outer rotor winding of the electromagnetic coupler is short-circuited. During the entire startup phase, the second converter does not participate in the operation, and only the auxiliary motor is responsible for providing the starting torque.

5. The starting method of the horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor according to claim 1, characterized in that, The rectifier controls the input current on the grid side. After the rectifier starts, it converts the power frequency AC power of the grid into stable DC power to supply the DC bus. Through voltage closed-loop control, it maintains the DC bus voltage stability and ensures that the bus voltage is maintained at the rated value.

6. A horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor, the system being used to implement the starting method of the horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor as described in any one of claims 1 to 5, characterized in that, The electromagnetic coupler achieves torque transmission through electromagnetic induction between the inner and outer rotors. The flywheel rotor of the energy storage flywheel is coaxially connected to the auxiliary motor and the inner rotor of the electromagnetic coupler via a transmission shaft; The outer rotor of the electromagnetic coupler is coaxially connected to the rotor of the synchronous condenser via a mechanical shaft. The auxiliary motor is a permanent magnet brushless DC motor; the auxiliary motor is responsible for providing driving torque during the startup phase and serves as a backup power source during normal system operation. The synchronous condenser controls the reactive power output by adjusting the excitation current; The rectifier is used to convert AC power from the power grid into DC power. The first converter is used to realize bidirectional energy flow between the auxiliary motor and the bus. The second converter is used to control the frequency of the input current to the outer rotor of the electromagnetic coupler.

7. The horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor according to claim 6, characterized in that, The input end of the rectifier is connected to the power grid, and the output end is connected to the DC bus. It is used to convert the power grid frequency AC power into DC power and maintain the DC bus voltage constant.

8. The horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor according to claim 6, characterized in that, The first converter is connected to the auxiliary motor and the DC bus at its two ends respectively. The first converter can convert the AC power generated by the auxiliary motor into DC power and inject it into the bus, and it can also draw power from the bus and invert it into AC power to drive the auxiliary motor.

9. The horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor according to claim 6, characterized in that, The two ends of the second converter are respectively connected to the outer rotor winding of the electromagnetic coupler and the DC bus, which is used to invert the DC bus current into AC current of a specific frequency and pass it into the outer rotor winding. The speed of the combined magnetomotive force of the electromagnetic coupler is adjusted by controlling the current frequency.

10. The horizontal inertia flywheel system with a permanent magnet brushless auxiliary motor according to claim 6, characterized in that, When the second converter outputs a positive current, the speed of the synthesized magnetomotive force is higher than the mechanical speed of the outer rotor. The permanent magnet of the inner rotor is subjected to a positive electromagnetic torque, which drives the flywheel rotor of the energy storage flywheel to accelerate energy storage. When the second converter outputs a negative current, the speed of the synthesized magnetomotive force is lower than the mechanical speed of the outer rotor. The permanent magnet of the inner rotor is subjected to a negative electromagnetic torque, which drives the flywheel rotor of the energy storage flywheel to decelerate and release energy.

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