Flywheel energy storage power frequency regulation system

Abstract

The present invention relates to a flywheel energy storage power frequency modulation system, comprising a flywheel system, a frequency converter and a converter, wherein the flywheel system is connected to a power grid through the frequency converter and the converter respectively, wherein the flywheel system is used to transfer the mechanical energy generated by the flywheel rotor to the dual-rotor motor to drive the dual-rotor motor to generate electricity, and / or, to transfer the electricity generated by the dual-rotor motor to the flywheel rotor to drive the flywheel rotor to rotate; the frequency converter is used to adjust the output frequency of the dual-rotor motor to match the output frequency with the frequency of the power grid; the converter is used to control the flywheel system to provide or absorb electricity to the power grid to match the output frequency of the flywheel system with the frequency of the power grid. The present application forms a flywheel energy storage power frequency modulation system with a flywheel system, a frequency converter and a converter, and utilizes the large inertia and fast response characteristics of the flywheel energy storage to absorb or release reactive / active power from the power system, thereby performing stable frequency regulation on the power grid.

Description

Technical Field

[0001] The present invention relates to the field of power grid control equipment, and in particular to a flywheel energy storage power frequency modulation system. Background Art

[0002] The power grid usually provides electric energy with stable frequency. For example, the rated frequency of my country's power grid is 50Hz. The frequency stability of the existing power system mainly relies on the original thermal power units. However, most of the current new energy power generation methods, such as wind power and photovoltaic power generation, do not have the function of power grid frequency regulation.

[0003] At present, most frequency-modulating units in the power grid system are used for frequency modulation of thermal power generation. Although thermal power units have good frequency modulation effects, they have environmental problems such as slow response and serious carbon emissions. Not only does renewable energy power generation lack the ability to modulate the frequency of the grid, but the high-frequency harmonics of power electronic devices in renewable energy power generation systems also have a negative impact on the stability of the grid frequency. Summary of the invention

[0004] Based on this, it is necessary to provide a flywheel energy storage power frequency regulation system to address at least one of the above-mentioned problems.

[0005] A flywheel energy storage power frequency modulation system is connected to a power grid, comprising a flywheel system, and a frequency converter and a converter respectively connected between the flywheel system and the power grid, wherein the flywheel system comprises a flywheel rotor and a dual-rotor motor, and the dual-rotor motor comprises a stator, an outer rotor and an inner rotor; the flywheel rotor is connected to the outer rotor of the dual-rotor motor through a transmission shaft, the stator of the dual-rotor motor is connected to the power grid through a switch, the stator of the dual-rotor motor is also connected to the power grid through the converter, and the inner rotor of the dual-rotor motor is connected to the power grid through the frequency converter;

[0006] The flywheel system is used to transmit the mechanical energy generated by the flywheel rotor to the dual-rotor motor through the transmission shaft to drive the dual-rotor motor to generate electrical energy, and / or to transmit the electrical energy generated by the dual-rotor motor to the flywheel rotor through the transmission shaft to drive the flywheel rotor to rotate;

[0007] The frequency converter is used to adjust the output frequency of the dual-rotor motor in the flywheel system so that the output frequency of the flywheel system matches the frequency of the power grid;

[0008] The converter is used to control the electric energy provided by the flywheel system to the grid or absorbed from the grid, so that the output frequency of the flywheel system matches the frequency of the grid.

[0009] Furthermore, in some embodiments of the present application, the frequency converter includes a machine-side converter, a capacitor and a grid-side converter; wherein the machine-side converter is connected to the inner rotor of the dual-rotor motor, the capacitor is respectively connected in parallel with the machine-side converter and the grid-side converter, and the grid-side converter is also connected to the power grid.

[0010] Furthermore, in some embodiments of the present application, the frequency converter is also used for:

[0011] Obtaining the operating status of the converter;

[0012] When a fault of the converter is detected, the output frequency of the dual-rotor motor of the flywheel system is adjusted by the frequency converter so that the output frequency of the flywheel system matches the frequency of the power grid.

[0013] Furthermore, in some embodiments of the present application, the converter includes a machine-side converter and a grid-side converter; wherein one end of the machine-side converter is connected to the stator of the dual-rotor motor, the other end of the machine-side converter is connected to the grid-side converter, and the other end of the grid-side converter is connected to the power grid.

[0014] Furthermore, in some embodiments of the present application, the converter is also used for:

[0015] Obtaining the operating status of the frequency converter;

[0016] When a fault of the frequency converter is detected, the output frequency of the dual-rotor motor of the flywheel system is adjusted through the converter so that the output frequency of the flywheel system matches the frequency of the power grid.

[0017] Further, in some embodiments of the present application, adjusting the output frequency of the dual-rotor motor in the flywheel system so as to match the output frequency of the flywheel system with the frequency of the power grid includes:

[0018] If it is monitored that the frequency of the power grid is the same as the speed of the flywheel rotor, the speed of the inner rotor and the outer rotor of the dual-rotor motor is controlled by the frequency converter so that the output frequency of the dual-rotor motor is equal to the frequency of the power grid;

[0019] If it is monitored that the frequency of the power grid is in an ascending or descending stage, a reverse slip frequency is applied to the inner rotor of the dual-rotor motor through the frequency converter so that the output frequency of the stator of the dual-rotor motor is equal to the frequency of the power grid.

[0020] Furthermore, in some embodiments of the present application, the step of adjusting the output frequency of the dual-rotor motor in the flywheel system so as to match the output frequency of the flywheel system with the frequency of the power grid further includes:

[0021] If the flywheel system is in the acceleration stage, the inner rotor of the dual-rotor motor is switched from three-phase short-circuiting to inverter control mode, the switch is disconnected, and the inner rotor and outer rotor of the dual-rotor motor are controlled by the inverter to reach a preset speed, so that the flywheel rotor completes acceleration and reaches the designed speed;

[0022] If the flywheel system is in the frequency stabilization stage and the flywheel rotor reaches the designed speed, the switch is closed and a reverse slip frequency is applied to the inner rotor of the dual-rotor motor through the frequency converter so that the output frequency of the stator of the dual-rotor motor is equal to the frequency of the power grid.

[0023] Furthermore, in some embodiments of the present application, when the power frequency regulation system receives a start-up command, the dual-rotor motor is also used to control the closure of the switch according to the start-up command, and to control the rotation of the flywheel rotor, so that the flywheel system absorbs electrical energy from the power grid through the switch and converts it into mechanical energy.

[0024] Furthermore, in some embodiments of the present application, the switch is also used to: when it is monitored that the frequency decrease rate of the power grid is greater than a preset threshold, control the switch to close to provide inertia support to the power grid, and control the switch to open during the frequency regulation stage.

[0025] Further, in some embodiments of the present application, controlling the electric energy provided by the flywheel system to the power grid or absorbed from the power grid so that the output frequency of the flywheel system matches the frequency of the power grid includes:

[0026] If it is monitored that the frequency of the power grid is in an ascending or descending stage, the switch is disconnected, and the converter is controlled so that the output frequency of the stator of the dual-rotor motor is equal to the frequency of the power grid.

[0027] The technical solution provided in the embodiments of the present invention brings the following beneficial technical effects:

[0028] The flywheel energy storage power frequency modulation system provided by the present invention connects a flywheel system, a dual-rotor motor, a frequency converter and a converter into a device system, directly connects the stator of the dual-rotor motor to the grid, senses the power imbalance of the power system in real time online, controls the inner rotor current of the dual-rotor motor by the frequency converter to adjust the output voltage of the stator end of the dual-rotor motor, can realize stepless speed regulation of the flywheel system, and can also make the entire system absorb or release reactive or active power to the power system to adjust the unbalanced power in the power grid, thereby realizing the function of power grid frequency modulation; in addition, the flywheel energy storage power frequency modulation system of the present application also adds a set of converters that can directly adjust the frequency of the flywheel system, in case the frequency converter fails and cannot perform frequency modulation, the frequency of the flywheel system is directly adjusted by the converter, thereby adding another adjustment method on the basis of the original system, increasing the redundancy of the system, and effectively ensuring the stability and reliability of the power frequency modulation system.

[0029] Additional aspects and advantages of the present application will be given in subsequent parts and will be understood in detail from the subsequent description or learned through specific implementations of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structural framework of a flywheel energy storage power frequency modulation system in one embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the structure of a dual-rotor motor in an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of the structural framework of a flywheel energy storage power frequency modulation system in another embodiment of the present invention;

[0033] Figure 4 A schematic diagram of the power frequency regulation stage of the present invention;

[0034] Figure 5 This is a schematic diagram of the structural framework of a flywheel energy storage power frequency modulation system in another embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the structural framework of a flywheel energy storage power frequency modulation system in yet another embodiment of the present invention.

[0036] Among them, the symbols of the main components are as follows: flywheel system-100; flywheel rotor-110, dual-rotor motor-200; inverter-300; stator-210; outer rotor-220; inner rotor-230; inverter-300; converter-400; machine-side converter-410; grid-side converter-420. DETAILED DESCRIPTION

[0037] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Possible embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein by the drawings. The embodiments described with reference to the drawings are exemplary and are used to make the understanding of the disclosure of the present invention more thorough and comprehensive, and cannot be interpreted as limiting the present invention. In addition, if the detailed description of the known technology is non-essential technology for the features of the present invention shown, these technical details may be omitted.

[0038] It will be understood by those skilled in the relevant art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with those in the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as herein.

[0039] It will be understood by those skilled in the art that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that the term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0040] The technical solution of the present invention and how the technical solution solves the above-mentioned technical problems are described in detail below with specific embodiments.

[0041] The flywheel energy storage power frequency modulation system provided by the present invention is connected to the power grid, such as Figure 1 As shown, the flywheel energy storage power frequency modulation system specifically includes a flywheel system 100, a dual-rotor motor 200, a frequency converter 300 and a converter 400, wherein the dual-rotor motor 200 includes a stator 210, an outer rotor 220 and an inner rotor 230; the system naturally includes other parts or electrical components, such as the mounting bracket of the flywheel 100, including bearings, connecting shafts, etc., and also the controller and memory of the flywheel energy storage power frequency modulation system. The dual-rotor motor 200 has two mechanical shafts (i.e., rotors), which can realize the independent transmission of energy of the two mechanical shafts. The dual-rotor motor 200 can significantly reduce the volume and weight of the equipment, improve work efficiency, can well meet the requirements of energy saving and speed regulation, and has excellent operating performance.

[0042] like Figure 1 As shown, the flywheel energy storage power frequency modulation system provided in this embodiment includes a flywheel system 100, and a frequency converter 300 and a converter 400 respectively connected between the flywheel system 100, wherein the flywheel system 100 includes a flywheel rotor 110 and a dual-rotor motor 200, the flywheel rotor 110 is connected to the outer rotor 220 of the dual-rotor motor 200 through a transmission shaft, the stator 210 of the dual-rotor motor 200 is connected to the power grid through a switch, the stator 210 of the dual-rotor motor 200 is also connected to the power grid through the converter 400, and the inner rotor 230 of the dual-rotor motor 200 is connected to the power grid through the frequency converter 300.

[0043] The flywheel system 100 is used to transmit the mechanical energy generated by the flywheel rotor 110 to the dual-rotor motor 200 through the transmission shaft to drive the dual-rotor motor 200 to generate electricity, and / or to transmit the electrical energy generated by the dual-rotor motor 200 to the flywheel rotor 110 through the transmission shaft to drive the flywheel rotor 110 to rotate;

[0044] The frequency converter 300 is used to adjust the output frequency of the dual-rotor motor 200 in the flywheel system 100 so that the output frequency of the flywheel system 100 matches the frequency of the power grid;

[0045] The converter 400 is used to control the electric energy provided to or absorbed from the grid by the flywheel system 100 so that the output frequency of the flywheel system 100 matches the frequency of the grid.

[0046] Specifically, the flywheel energy storage power frequency modulation system provided in this embodiment connects the flywheel system 100 and the frequency converter 300 to form a system that can perform power frequency modulation and phase modulation at the same time. The stator 210 of the dual-rotor motor 200 is directly connected to the grid, and the power imbalance of the power system is sensed online in real time. The current of the inner rotor 230 of the dual-rotor motor 200 is controlled by the frequency converter 300 to adjust the output voltage of the stator 210 end of the dual-rotor motor 200. The flywheel rotor 110 in the flywheel system 100 can be infinitely regulated, and the entire system can absorb or release reactive or active power to the power system to adjust the unbalanced power in the power grid, thereby achieving rapid frequency modulation and phase modulation of the power grid and reducing carbon emissions. At the same time, by connecting the flywheel system 100 to the converter 400 and adding a set of converters that can directly adjust the frequency of the flywheel system 100, in case the frequency converter fails and cannot be used for frequency regulation, the frequency of the flywheel system can be directly adjusted through the converter, thereby adding another frequency regulation method to the original system, increasing the redundancy of the power frequency regulation system, and effectively ensuring the stability and reliability of the power frequency regulation system.

[0047] It can be understood that the flywheel rotor 110 of the flywheel system 100 in this embodiment is transmission-connected to the outer rotor 220 of the dual-rotor motor 200, such as Figure 2 As shown, the flywheel rotor 110 and the outer rotor 220 of the dual rotor motor 200 can be connected through a transmission shaft, and the outer rotor 220 rotates synchronously with the flywheel rotor 110. The energy of the outer rotor 220 of the dual rotor motor 200 is transferred to the flywheel rotor 110 through the transmission shaft, or the mechanical energy on the flywheel rotor 110 is transferred to the dual rotor motor 200, driving the dual rotor motor 200 to generate electricity. The output frequency of the dual rotor motor 200 is adjusted through the frequency converter 300 to match the power grid system. In addition, the output frequency of the flywheel system 100 can also be adjusted through the newly added converter 400 to match the frequency of the power grid system.

[0048] In summary, the flywheel energy storage power frequency regulation system provided in the embodiment of the present application organically combines the flywheel energy storage unit and the dual-rotor motor technology, utilizes the large inertia and fast response characteristics of the flywheel energy storage, and controls the charging and discharging of the large inertia flywheel to absorb and release reactive and active power to the power system, thereby performing stable real-time frequency regulation on the power grid, achieving rapid frequency regulation, and at the same time achieving a good inhibitory effect on carbon emissions.

[0049] Furthermore, in some embodiments, Figure 1 As shown, the inverter 300 may specifically include a machine-side converter, a capacitor and a grid-side converter; wherein the machine-side converter is connected to the inner rotor of the dual-rotor motor, the capacitor is respectively connected in parallel with the machine-side converter and the grid-side converter, and the grid-side converter is also connected to the power grid.

[0050] Specifically, the inverter 300 in this example mainly includes a machine-side converter, a capacitor and a grid-side converter. The machine-side converter is electrically connected to the inner rotor 230 of the dual-rotor motor 200, the grid-side converter is electrically connected to the grid, and the capacitor is connected in parallel with the machine-side converter and the grid-side converter, respectively. The inverter 300 in this embodiment is mainly used to obtain the frequency of the grid, thereby adjusting the current angular frequency of the inner rotor 230 according to the grid frequency, and then adjusting the output frequency of the dual-rotor motor 200.

[0051] Furthermore, in some embodiments, the machine-side converter is an AC / DC rectifier, and the grid-side converter is a bidirectional DC / AC converter.

[0052] Specifically, Figure 3 As shown, Figure 3Another structural schematic diagram of a flywheel energy storage power frequency modulation system is provided, the machine-side converter can be an AC / DC (alternating current / direct current) rectifier, the grid-side converter can be a bidirectional DC / AC (direct current / alternating current) converter, and the types of the machine-side converter and the grid-side converter can be set according to actual conditions. In this embodiment, the stator of the dual-rotor generator is directly connected to the grid, and the inner rotor current of the dual-rotor motor is controlled by the frequency conversion device to adjust the output voltage of the stator end of the dual-rotor motor, so as to realize the stepless speed regulation of the flywheel system, so that the stator can input constant frequency electricity to the grid, and realize the function of grid frequency modulation.

[0053] Furthermore, in some embodiments, the converter 400 may specifically include a machine-side converter and a grid-side converter; wherein one end of the machine-side converter is connected to the stator 210 of the dual-rotor motor 200, the other end of the machine-side converter is connected to the grid-side converter, and the other end of the grid-side converter is connected to the power grid.

[0054] Specifically, the converter 400 in this embodiment includes a machine-side converter and a grid-side converter. The machine-side converter is electrically connected to the stator of the dual-rotor motor 200, and the grid-side converter is electrically connected to the machine-side converter. The grid-side converter is also connected to the power grid. The converter 400 obtains the frequency of the power grid, thereby adjusting the voltage phase and amplitude of the stator 210 according to the frequency of the power grid, thereby adjusting the output frequency of the dual-rotor motor 200.

[0055] In a specific embodiment, the converter 400 may specifically include a machine-side converter, a capacitor and a grid-side converter, and the capacitor is respectively connected in parallel with the machine-side converter and the grid-side converter, wherein the machine-side converter may be an AC / DC (alternating current / direct current) converter, and the grid-side converter may be a bidirectional DC / AC (direct current / alternating current) converter.

[0056] Furthermore, in some embodiments, the frequency converter 300 is also used to: obtain the operating status of the converter; when a converter failure is detected, adjust the output frequency of the dual-rotor motor of the flywheel system through the frequency converter to match the output frequency of the flywheel system with the frequency of the power grid.

[0057] Specifically, the frequency converter 300 in this embodiment is also used to replace the converter 400 to adjust the output frequency of the flywheel system when the converter 400 fails. First, the current operating state of the converter 400 is obtained through the control device or controller. When the control device or controller detects that the current operating state of the converter 400 is abnormal, for example, it fails and cannot operate, and the flywheel system 100 cannot be adjusted normally through the converter 400, a switching instruction can be issued through the control device or controller, so as to switch the adjustment method of the flywheel system 100 according to the switching instruction, from adjusting through the converter 400 to adjusting through the frequency converter 300, and adjust the output frequency of the dual-rotor motor 200 of the flywheel system 100 through the frequency converter 300 that can work normally, so that the output frequency of the flywheel system 100 matches the frequency of the power grid, avoiding the situation that the output frequency of the flywheel system cannot be adjusted normally due to the failure of the converter. This embodiment proposes multiple adjustment methods to solve the problem that the stability of the power frequency regulation system is reduced due to only a single adjustment method (such as the converter adjustment method).

[0058] Furthermore, in some embodiments, the converter 400 is also used to: obtain the operating status of the inverter; when a fault in the inverter is detected, adjust the output frequency of the dual-rotor motor of the flywheel system through the converter to match the output frequency of the flywheel system with the frequency of the power grid.

[0059] Specifically, the converter 400 in this embodiment is also used to replace the frequency converter 300 to adjust the output frequency of the flywheel system when the frequency converter 300 fails. First, the current operating state of the frequency converter 300 is obtained through the control device or controller. When the control device or controller detects that the current operating state of the frequency converter 300 is abnormal, for example, it fails and cannot operate, and the flywheel system 100 cannot be adjusted normally through the frequency converter 300, a switching instruction can be issued through the control device or controller, so as to switch the adjustment method of the flywheel system 100 according to the switching instruction, from adjusting through the frequency converter 300 to adjusting through the converter 400, and adjust the output frequency of the dual-rotor motor 200 of the flywheel system 100 through the converter 400 that can work normally, so that the output frequency of the flywheel system 100 matches the frequency of the power grid, avoiding the situation that the output frequency of the flywheel system cannot be adjusted normally due to the failure of the frequency converter. This embodiment proposes multiple adjustment methods to solve the problem that the stability of the power frequency regulation system is reduced due to only a single adjustment method (such as the frequency converter adjustment method).

[0060] Furthermore, in some embodiments, controlling the electric energy provided to or absorbed from the power grid by the flywheel system through the converter so that the output frequency of the flywheel system matches the frequency of the power grid may specifically include:

[0061] If it is monitored that the frequency of the power grid is in an ascending or descending stage, the switch is disconnected, and the converter is controlled so that the output frequency of the stator of the dual-rotor motor is equal to the frequency of the power grid.

[0062] Specifically, Figure 3 As shown, Figure 3 Another structural schematic diagram of a flywheel energy storage power frequency modulation system is provided. The converter 400 provided in this embodiment includes a machine-side converter and a grid-side converter, wherein the machine-side converter is electrically connected to the stator 210 of the dual-rotor motor 200, the grid-side converter is electrically connected to the machine-side converter, and the grid-side converter is also electrically connected to the grid. In a specific implementation process, the speed of the dual-rotor motor can be reduced by controlling the voltage and frequency of the machine-side converter on the dual-rotor motor side. At the same time, active power is exchanged through the grid-side converter on the grid side, such as absorbing or releasing active power, so as to adjust the output frequency of the flywheel system, so that the output power of the flywheel system is highly controllable. When the grid frequency needs to be adjusted, the flywheel system can be directly controlled by the converter to absorb electric energy from the grid or provide electric energy to the grid. The frequency of the dual-rotor motor is changed to inject it into the grid as electric energy to reduce the energy stored in the flywheel system, or the kinetic energy is stored in the flywheel system to reduce the energy of the grid; and there is no need to apply a reverse slip frequency to the dual-rotor motor through a frequency converter, so that the frequency of the grid remains constant. In this embodiment, by connecting the flywheel system 100 to the converter 400, a set of converters that can directly adjust the frequency of the flywheel system 100 is added to prevent the frequency converter from failing and failing to adjust the frequency, thereby increasing the redundancy of the power frequency adjustment system and effectively ensuring the stability and reliability of the power frequency adjustment system. The converter 400 in this embodiment can be arranged in a back-to-back configuration including a DC link.

[0063] In addition, in other embodiments, the converter 400 may be a matrix converter or a modular multi-level matrix converter, or may be a static frequency converter providing bidirectional power flow.

[0064] Furthermore, in some embodiments, adjusting the output frequency of the dual-rotor motor in the flywheel system by a frequency converter so that the output frequency of the flywheel system matches the frequency of the power grid may specifically include:

[0065] If it is detected that the frequency of the power grid is the same as the speed of the flywheel rotor, the speed of the inner rotor 230 and the outer rotor 220 of the dual-rotor motor 200 is controlled by the frequency converter 300 so that the output frequency of the dual-rotor motor 200 is equal to the frequency of the power grid;

[0066] If it is monitored that the frequency of the power grid is in an ascending or descending stage, a reverse slip frequency is applied to the inner rotor of the dual-rotor motor through the frequency converter so that the output frequency of the stator of the dual-rotor motor is equal to the frequency of the power grid.

[0067] Furthermore, in some embodiments, adjusting the output frequency of the dual-rotor motor in the flywheel system by a frequency converter so that the output frequency of the flywheel system matches the frequency of the power grid may specifically include:

[0068] If the flywheel system is in the acceleration stage, the inner rotor of the dual-rotor motor is switched from three-phase short circuit to inverter control mode, the switch is disconnected, and the inner and outer rotors of the dual-rotor motor are controlled by the inverter to reach the preset speed, so that the flywheel rotor completes the acceleration and reaches the designed speed;

[0069] If the flywheel system is in the frequency stabilization stage and the flywheel rotor reaches the designed speed, the switch is closed and a reverse slip frequency is applied to the inner rotor of the dual-rotor motor through the frequency converter to make the output frequency of the stator of the dual-rotor motor equal to the frequency of the power grid.

[0070] In a specific embodiment, the working state of the flywheel energy storage power frequency modulation system provided in this embodiment mainly includes a flywheel acceleration stage and a flywheel frequency stabilization stage. The specific working principles of the power frequency modulation system in these two stages will be described in detail below.

[0071] In the flywheel acceleration stage, when the speed of the flywheel rotor 110 reaches the same frequency as the grid frequency, the inner rotor 230 is switched from three-phase short circuit to being controlled by the inverter 300, and the switch S1 is turned off. At this time, the inverter 300 can make the inner and outer rotors 220 of the dual-rotor motor 200 reach a relatively stable speed, and the speed relationship between the two is: n out *p out =n in *p in , where n out The outer rotor speed is 220, n in The speed of the inner rotor is 230, p out is the number of rotor pole pairs, p in The number of pole pairs of the inner rotor is 230. Maintain the electrical frequency with the grid electrical frequency f 电 For example, the frequency converter 300 is used to adjust the electrical frequency of the inner rotor 230 winding. For example, when the electrical frequency of the inner rotor 230 winding increases, the frequency of the outer rotor 220 will also increase due to the magnetic field coupling effect. The outer rotor 220 is coaxially connected to the flywheel rotor 110, and the speed of the flywheel rotor 110 increases. The frequency converter 300 absorbs active power from the power grid and converts it into mechanical energy of the flywheel rotor 110, thereby increasing the speed of the flywheel rotor 110 and making the flywheel rotor 110 reach the designed speed.

[0072] In the flywheel frequency stabilization stage, when the flywheel rotor 110 accelerates to the design speed N, that is, n out =N, after stabilization, the speed of the inner and outer rotors remains the same as n out *pout =n in *p in The flywheel rotor 110 completes acceleration, and the inner and outer rotors 220 maintain constant speed operation without energy exchange (except for the self-consumption of the flywheel system 100). The switch is closed because the flywheel rotor 110 is in a high-speed state at this time, and the electrical frequency is much greater than f 电 In order to stabilize the power grid on the motor stator 210 side, a reverse slip frequency is applied by the inverter 300:

[0073]

[0074] The grid side voltage can be made to have the same phase and amplitude as the stator 210 side voltage. 电 When fluctuations occur, such as a drop, the reverse slip frequency S1 is controlled by the inverter 300, and the voltage on the stator 210 side has the same amplitude and phase as the voltage on the grid side. The flywheel rotor 110 feeds power to the grid at this time, ensuring the stability of the grid and providing good frequency support for the regulation of the grid.

[0075] In addition, when the kinetic energy stored in the flywheel system 100 is consumed to a set lower limit, the above-mentioned work content of the acceleration stage of the flywheel rotor 110 is repeated.

[0076] Furthermore, in some embodiments, when the power frequency regulation system receives a start-up command, the dual-rotor motor is also used to control the closure of the switch according to the start-up command, and control the rotation of the flywheel rotor, so that the flywheel system absorbs electrical energy from the power grid through the switch and converts it into mechanical energy.

[0077] Specifically, in the startup phase of the flywheel energy storage power frequency modulation system, when the flywheel system 100 is started, the grid-connected control system controls the switch S1 to close. At this time, the stator 210 of the dual-rotor motor 200 is connected to the power grid. Because the outer rotor 220 contains a self-starting induction cage, the inner rotor 230 excitation winding is short-circuited in series with the three-phase motor. The entire system is equivalent to the electric state of the motor, driving the flywheel rotor 110 of the flywheel system 100 to rotate. The flywheel rotor 110 absorbs electrical energy from the power grid through the switch, and converts the stored electrical energy into mechanical energy, completing the startup phase of the system.

[0078] Furthermore, in some embodiments, the switch is also used to: when it is monitored that the frequency decrease rate of the power grid is greater than a preset threshold, control the switch to close to provide inertia support to the power grid, and control the switch to open during the frequency regulation stage.

[0079] Specifically, Figure 4 As shown, Figure 4 Provides frequency curves corresponding to different adjustment stages of the power frequency regulation system. Figure 4It can be seen that the regulation stage of the power frequency regulation system is divided into three stages, including the inertial response stage, the primary frequency regulation stage and the secondary frequency regulation stage. Specifically, when the frequency drop change rate of the power grid is detected to be greater than the preset threshold, it is considered that the power frequency regulation system is in the inertial response stage. At this time, when it is judged that the power grid needs to provide inertia support, the inertia support is provided to the power grid by closing the switch, and the switch is opened in the primary frequency regulation stage or the secondary frequency regulation stage, and the converter works to provide the frequency regulation function.

[0080] Furthermore, in some embodiments, Figure 5 As shown, this embodiment also provides another structural schematic diagram of a flywheel energy storage power frequency modulation system, including a flywheel system, a frequency converter, a bottom-level controller, a middle-level controller and an upper-level controller, wherein the flywheel system is connected to the power grid through the frequency converter, and the flywheel system can also be connected to the power grid through a switch S1, one end of the bottom-level controller is connected to the frequency converter, the bottom-level controller is also connected to the middle-level controller, the middle-level controller is also respectively connected to the rotor, the inner stator and the power grid of the dual-rotor motor, and the middle-level controller is also connected to the upper-level controller, the rotor speed and position of the connected dual-rotor motor are detected by the middle-level controller, the voltage and current of the inner stator of the connected dual-rotor motor are detected by the middle-level controller, and the current of the connected power grid is detected by the middle-level controller, so that the bottom-level controller is controlled by the middle-level controller according to the monitored voltage and current of the power grid, so that the bottom-level controller issues a control instruction, so that the frequency converter adjusts the output frequency of the flywheel system according to the control instruction issued by the bottom-level controller, and the middle-level controller determines whether the current frequency modulation is completed according to the detected rotor speed and the voltage and current of the inner stator to determine whether to continue the frequency modulation.

[0081] Furthermore, in some embodiments, Figure 6 As shown, this embodiment also provides another structural schematic diagram of a flywheel energy storage power frequency modulation system, including a flywheel system, a frequency converter and a control device, wherein the flywheel system includes a flywheel and a dual-rotor motor, the flywheel system is connected to the power grid through the frequency converter, and is connected to the power grid through a switch S1, the control device is respectively connected to the inner rotor of the dual-rotor motor, the machine-side converter and the grid-side converter in the frequency converter, and the control device is also connected to the power grid, so as to issue a frequency modulation instruction to the frequency converter according to the acquired frequency of the power grid and the speed of the inner rotor, so that the frequency converter adjusts the frequency of the inner rotor of the dual-rotor motor of the flywheel system, so that the output frequency of the flywheel system is consistent with the power grid frequency, thereby completing this power frequency modulation task.

[0082] Furthermore, in some embodiments, the outer rotor of the dual-rotor motor adopts a squirrel-cage rotor, and the inner rotor of the dual-rotor motor adopts a wound electromagnetic excitation rotor.

[0083] Specifically, the outer rotor of the dual-rotor motor 200 in this embodiment adopts a squirrel cage rotor, and the inner rotor of the dual-rotor motor 200 adopts a wound electromagnetic excitation rotor. The dual-rotor motor 200 specifically includes dual-rotor asynchronous motors, squirrel cage dual-rotor motors, counter-rotating dual-rotor permanent magnet motors, and permanent magnet brushless dual-rotor motors. In one embodiment of the present invention application, the outer rotor adopts a squirrel cage rotor with a relatively simple structure, which can form the system structure required by the present application at a relatively low cost.

[0084] Furthermore, in some embodiments, the inner rotor and the outer rotor of the dual-rotor motor each include an electrical interface, and the inner rotor and the outer rotor are magnetically coupled to each other.

[0085] Specifically, the dual-rotor motor in this embodiment contains an electrical interface on each rotor. Compared with an ordinary doubly-fed motor, the inner and outer rotor magnetic fields are separated and there is no strong coupling. When controlling the dual-rotor motor, it can be more convenient to decouple and separate it, so that the control accuracy of the entire system is much greater than that of an ordinary doubly-fed motor, greatly increasing the robustness of the system.

[0086] To summarize, the flywheel energy storage power frequency regulation system provided in the embodiment of the present application, compared with the existing thermal power frequency regulation technology, the embodiment of the present application organically combines the flywheel energy storage unit and the dual-rotor motor technology, and directly connects the stator of the dual-rotor motor to the grid, so as to sense the power imbalance of the power system in real time online. When the power grid fluctuates, the inner rotor current of the dual-rotor motor is controlled by the frequency conversion device, thereby controlling the charging and discharging of the large inertia flywheel, and realizing stepless speed regulation of the flywheel system, as well as regulation of the output voltage of the stator end of the dual-rotor motor, absorbing and releasing active power or reactive power to the power grid, regulating the unbalanced power in the power grid, achieving the effect of power grid frequency regulation, and playing a real-time supporting role in the power balance of the power grid.

[0087] Those skilled in the art will appreciate that the various operations, methods, steps, measures, and schemes in the processes discussed in this application may be alternated, altered, combined, or deleted. Further, other steps, measures, and schemes in the various operations, methods, and processes discussed in this application may also be alternated, altered, rearranged, decomposed, combined, or deleted. Further, the steps, measures, and schemes in the prior art that are similar to those disclosed in this application may also be alternated, altered, rearranged, decomposed, combined, or deleted.

[0088] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0089] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0090] The above description is only a partial implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A flywheel energy storage power frequency modulation system connected to a power grid, characterized in that: The invention comprises a flywheel system, and a frequency converter and a converter respectively connected between the flywheel system and a power grid, wherein the flywheel system comprises a flywheel rotor and a dual-rotor motor, and the dual-rotor motor comprises a stator, an outer rotor and an inner rotor; the flywheel rotor is connected to the outer rotor of the dual-rotor motor through a transmission shaft, the stator of the dual-rotor motor is connected to the power grid through a switch, the stator of the dual-rotor motor is also connected to the power grid through the converter, and the inner rotor of the dual-rotor motor is connected to the power grid through the frequency converter; The flywheel system is used to transmit the mechanical energy generated by the flywheel rotor to the dual-rotor motor through the transmission shaft to drive the dual-rotor motor to generate electrical energy, and / or to transmit the electrical energy generated by the dual-rotor motor to the flywheel rotor through the transmission shaft to drive the flywheel rotor to rotate; The frequency converter is used to adjust the output frequency of the dual-rotor motor in the flywheel system so that the output frequency of the flywheel system matches the frequency of the power grid, including: if it is monitored that the frequency of the power grid is the same as the speed of the flywheel rotor, the speed of the inner rotor and the outer rotor of the dual-rotor motor are controlled by the frequency converter so that the output frequency of the dual-rotor motor is equal to the frequency of the power grid; if it is monitored that the frequency of the power grid is in an ascending or descending stage, the reverse slip frequency is applied to the inner rotor of the dual-rotor motor by the frequency converter so that the output frequency of the stator of the dual-rotor motor is equal to the output frequency of the stator of the dual-rotor motor. equal to the frequency of the power grid; if the flywheel system is in the acceleration stage, the inner rotor of the dual-rotor motor is switched from three-phase short-circuiting to the inverter control mode, the switch is disconnected, and the inner rotor and the outer rotor of the dual-rotor motor are controlled by the inverter to reach a preset speed, so that the flywheel rotor completes the acceleration and reaches the designed speed; if the flywheel system is in the frequency stabilization stage, and the flywheel rotor reaches the designed speed, the switch is closed, and the reverse slip frequency is applied to the inner rotor of the dual-rotor motor through the inverter, so that the output frequency of the stator of the dual-rotor motor is equal to the frequency of the power grid; The converter is used to disconnect the switch and control the converter so that the output frequency of the stator of the dual-rotor motor is equal to the frequency of the power grid if it is monitored that the frequency of the power grid is in an ascending or descending stage; the converter is also used to: obtain the operating status of the frequency converter; when a fault is detected in the frequency converter, adjust the output frequency of the dual-rotor motor of the flywheel system through the converter so that the output frequency of the flywheel system matches the frequency of the power grid.

2. The flywheel energy storage power frequency modulation system according to claim 1, characterized in that: The frequency converter includes a machine-side converter, a capacitor and a grid-side converter; wherein the machine-side converter is connected to the inner rotor of the dual-rotor motor, the capacitor is respectively connected in parallel with the machine-side converter and the grid-side converter, and the grid-side converter is also connected to the power grid.

3. The flywheel energy storage power frequency modulation system according to claim 1, characterized in that: The converter includes a machine-side converter and a grid-side converter; wherein one end of the machine-side converter is connected to the stator of the dual-rotor motor, the other end of the machine-side converter is connected to the grid-side converter, and the other end of the grid-side converter is connected to the power grid.

4. The flywheel energy storage power frequency modulation system according to claim 1, characterized in that: The frequency converter is also used for: Obtaining the operating status of the converter; When a fault of the converter is detected, the output frequency of the dual-rotor motor of the flywheel system is adjusted by the frequency converter so that the output frequency of the flywheel system matches the frequency of the power grid.

5. The flywheel energy storage power frequency modulation system according to claim 1, characterized in that: When the power frequency regulation system receives a start-up instruction, the dual-rotor motor is also used to control the closure of the switch and the rotation of the flywheel rotor according to the start-up instruction, so that the flywheel system absorbs electrical energy from the power grid through the switch and converts it into mechanical energy.

6. The flywheel energy storage power frequency modulation system according to claim 5, characterized in that: The switch is also used to: when it is monitored that the frequency decrease rate of the power grid is greater than a preset threshold, control the switch to close to provide inertia support to the power grid, and control the switch to open during the frequency regulation stage.

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