Flywheel energy storage system

Abstract

The invention discloses a flywheel energy storage system, and relates to the technical field of energy storage systems. The alternating current side of the rectifying circuit is connected with a power grid; the input end of the step-down circuit is connected with the direct current side of the rectifying circuit; the first end of the first inverter circuit is connected with the output end of the step-down circuit, and the second end of the first inverter circuit is connected with the flywheel motor; the input end of the booster circuit is connected with the output end of the step-down circuit and the first end of the first inverter circuit; and the input end of the second inverter circuit is connected with the output end of the booster circuit, and the output end of the second inverter circuit is connected with the load. According to the flywheel energy storage system, the energy conversion frequency when the flywheel motor supplies power to the load can be reduced, the energy conversion loss of the flywheel energy storage system is reduced, the circuit structure of the flywheel energy storage system is simple, and the reliability of the flywheel energy storage system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to a flywheel energy storage system. Background Art

[0002] In the related art, the existing flywheel energy storage system connects the flywheel motor to the PCS (Power Conversion System, energy storage inverter) and then hangs it on the AC input side of the power grid. When the flywheel needs to release energy, the AC power supply signal output by the flywheel motor is first converted into a DC signal, and then the DC signal is converted into an AC power supply signal through the PCS, and then connected to the AC input side of the power grid. Then, it is converted into a DC signal through the back end of the AC input side to power the DC load. In other words, the existing flywheel energy storage system will undergo multiple energy conversions when supplying power to the DC load, thereby increasing the energy conversion loss. In addition, the circuit structure of the flywheel energy storage system is complex, which reduces the reliability of the flywheel energy storage system. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present invention is to provide a flywheel energy storage system, which can reduce the number of energy conversions when the flywheel motor supplies power to the load, reduce the energy conversion loss of the flywheel energy storage system, and the circuit structure of the flywheel energy storage system is simple, thereby increasing the reliability of the flywheel energy storage system.

[0004] In order to solve the above problems, the first embodiment of the present invention proposes a flywheel energy storage system, including: a flywheel motor; a rectifier circuit, the AC side of the rectifier circuit is connected to the power grid, and the rectifier circuit is used to convert the AC power signal of the power grid into a DC power supply signal; a step-down circuit, the input end of the step-down circuit is connected to the DC side of the rectifier circuit, and the step-down circuit is used to convert the DC power supply signal into a first DC power signal; a first inverter circuit, the first end of the first inverter circuit is connected to the output end of the step-down circuit, the second end of the first inverter circuit is connected to the flywheel motor, and the first inverter circuit is used to convert the first DC power supply signal into a first DC power signal during charging. The invention relates to a flywheel motor comprising a first inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a first inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a second inverter circuit, a third inverter circuit, a DC voltage required by the load.

[0005] According to the flywheel energy storage system of the embodiment of the present invention, based on the circuit structure in which the flywheel motor is arranged on the DC side of the AC input of the power grid, the first inverter circuit directly converts the AC power supply signal output by the flywheel motor into a DC signal, and then changes the voltage of the DC signal through the second inverter circuit to power the DC load, thereby realizing uninterrupted power supply of the load by the flywheel energy storage system. Therefore, compared with the existing flywheel energy storage system in which the flywheel motor is connected to the PCS and then hung on the AC input side of the power grid, the flywheel motor is arranged on the DC side of the AC input of the power grid in the present application, so that when the flywheel energy storage system supplies power to the load, the AC power supply signal output by the flywheel motor is directly converted into a DC signal to power the load, and there is no need to change the AC power supply signal output by the flywheel motor three times, thereby reducing the number of energy conversions and reducing the energy conversion loss of the flywheel energy storage system. In addition, the circuit structure of the flywheel energy storage system is simple, which increases the reliability of the flywheel energy storage system.

[0006] In some embodiments, the rectifier circuit includes: a first diode, an anode of the first diode is connected to the first power supply terminal of the power grid, and a cathode of the first diode is connected to the first input terminal of the step-down circuit; a second diode, an anode of the second diode is connected to the second power supply terminal of the power grid, and a cathode of the second diode and a cathode of the first diode are connected to the first input terminal of the step-down circuit; a third diode, an anode of the third diode is connected to the second input terminal of the step-down circuit, and a cathode of the third diode is connected to the anode of the first diode and the first power supply terminal of the power grid; a fourth diode, an anode of the fourth diode is connected to the anode of the third diode and the second input terminal of the step-down circuit, and a cathode of the fourth diode is connected to the anode of the second diode and the second power supply terminal of the power grid.

[0007] In some embodiments, the step-down circuit includes: a first power tube, the drain of the first power tube is connected to the cathode of the second diode; a first inductor, the first end of the first inductor is connected to the source of the first power tube, and the second end of the first inductor is connected to the input end of the boost circuit and the first end of the first inverter circuit; a fifth diode, the anode of the fifth diode is connected to the anode of the fourth diode and the first end of the first inverter circuit, and the cathode of the fifth diode is connected to the first end of the first inductor and the source of the first power tube; a first capacitor, the first end of the first capacitor is connected to the drain of the first power tube and the cathode of the second diode, and the second end of the first capacitor is connected to the anode of the fifth diode and the anode of the fourth diode; a second capacitor, the first end of the second capacitor is connected to the second end of the first inductor, the input end of the step-down circuit and the first end of the first inverter circuit, and the second end of the second capacitor is connected to the anode of the fifth diode and the first end of the first inverter circuit.

[0008] In some embodiments, the first inverter circuit includes: a second power tube, the drain of the second power tube is connected to the second end of the first inductor and the input end of the boost circuit, and the source of the second power tube is connected to the first output end of the flywheel motor; a third power tube, the drain of the third power tube is connected to the source of the second power tube and the first output end of the flywheel motor, and the source of the third power tube is connected to the second end of the second capacitor; a fourth power tube, the drain of the fourth power tube is connected to the drain of the second power tube, and the source of the fourth power tube is connected to the flywheel motor. a fifth power tube, the drain of the fifth power tube is connected to the source of the fourth power tube and the second output end of the flywheel motor, and the source of the fifth power tube is connected to the source of the third power tube; a sixth power tube, the drain of the sixth power tube is connected to the drain of the fourth power tube, and the source of the sixth power tube is connected to the third output end of the flywheel motor; a seventh power tube, the drain of the seventh power tube is connected to the source of the sixth power tube and the third output end of the flywheel motor, and the source of the seventh power tube is connected to the source of the fifth power tube.

[0009] In some embodiments, the first inverter circuit also includes: an eighth power tube, the drain of the eighth power tube is connected to the second end of the first inductor, the input end of the boost circuit, and the drain of the second power tube; a first resistor, the first end of the first resistor is connected to the source of the eighth power tube, and the second end of the first resistor is connected to the second end of the second capacitor and the source of the third power tube.

[0010] In some embodiments, each power tube includes: a switch tube, the base of which is used to receive a switch control signal; a diode, the anode of which is connected to the source of the switch tube, and the cathode of which is connected to the drain of the switch tube.

[0011] In some embodiments, the boost circuit includes: a second inductor, a first end of the second inductor is connected to the second end of the first inductor and the drain of the eighth power tube, and a second end of the second inductor is connected to an input end of the second inverter circuit; and a ninth power tube, a drain of the ninth power tube is connected to the second end of the second inductor, and a source of the ninth power tube is grounded.

[0012] In some embodiments, the second inverter circuit includes: a tenth power tube, the drain of the tenth power tube is connected to the drain of the ninth power tube, and the source of the tenth power tube is connected to the load; an eleventh power tube, the drain of the eleventh power tube is connected to the source of the tenth power tube and the load, and the source of the eleventh power tube is connected to the source of the ninth power tube; a twelfth power tube, the drain of the twelfth power tube is connected to the drain of the tenth power tube, and the source of the twelfth power tube is connected to the load; a thirteenth power tube, the drain of the thirteenth power tube is connected to the source of the twelfth power tube and the load, and the source of the thirteenth power tube is connected to the source of the eleventh power tube.

[0013] In some embodiments, each power tube includes: a MOS tube, a gate of which is used to receive a conduction control signal; a diode, an anode of which is connected to a source of the MOS tube, and a cathode of which is connected to a drain of the MOS tube.

[0014] In some embodiments, it also includes: a first voltage protection circuit, a first end of the first voltage protection circuit is connected to the drain of the tenth power tube and the drain of the twelfth power tube, and a second end of the first voltage protection circuit is connected to the source of the eleventh power tube and the source of the thirteenth power tube; a second voltage protection circuit, a first end of the second voltage protection circuit is connected to the drain of the twelfth power tube, and a second end of the second voltage protection circuit is connected to the source of the thirteenth power tube.

[0015] In some embodiments, each voltage protection circuit includes: a second resistor, a first end of the second resistor is connected to the drain of the power tube; a third capacitor, a first end of the third capacitor is connected to the second end of the second resistor, and a second end of the third capacitor is connected to the source of the power tube.

[0016] In some embodiments, it also includes: a filter circuit, wherein the first input end of the filter circuit is connected to the source of the tenth power tube and the drain of the eleventh power tube, the second input end of the filter circuit is connected to the source of the twelfth power tube and the drain of the thirteenth power tube, and the output end of the filter circuit is connected to the load.

[0017] In some embodiments, the filtering circuit includes: a third inductor, a first end of the third inductor is connected to the source of the twelfth power tube and the drain of the thirteenth power tube, and a second end of the third inductor is connected to the first end of the load; a fourth inductor, a first end of the fourth inductor is connected to the source of the tenth power tube and the drain of the eleventh power tube, and a second end of the fourth inductor is connected to the second end of the load; a fourth capacitor, a first end of the fourth capacitor is connected to the second end of the third inductor, and a second end of the fourth capacitor is grounded; a fifth capacitor, a first end of the fifth capacitor is connected to the second end of the fourth capacitor, a first end of the fifth capacitor is grounded, and a second end of the fifth capacitor is connected to the second end of the load.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 is a circuit topology diagram of a flywheel energy storage system according to an embodiment of the present invention; Figure 2 is a schematic diagram of a flywheel energy storage system according to an embodiment of the present invention.

[0020] Reference numerals: Flywheel energy storage system 100; power grid 200; load 300; Flywheel motor 10; rectifier circuit 20; buck circuit 30; first inverter circuit 40; boost circuit 50; second inverter circuit 60; first voltage protection circuit 70; second voltage protection circuit 80; filter circuit 90; charging main circuit 91; discharging main circuit 92; photoelectric isolation circuit 93; control circuit 95; sensor 96; a first diode D9; a second diode D10; a third diode D11; a fourth diode D12; a fifth diode D13; a sixth diode D1; a seventh diode D2; an eighth diode D3; a ninth diode D4; a tenth diode D5; an eleventh diode D6; a twelfth diode D7; a thirteenth diode D8; a fourteenth diode D18; a fifteenth diode D14; a sixteenth diode D15; a seventeenth diode D16; an eighteenth diode D17; a first power tube 8; a second power tube 1; a third power tube 3; a fourth power tube 4; a fifth power tube 6; a sixth power tube 5; a seventh power tube 2; an eighth power tube 7; a ninth power tube 9; a tenth power tube 11; an eleventh power tube 12; a twelfth power tube 13; a thirteenth power tube 14; The first switch tube VT1; the second switch tube VT2; the third switch tube VT3; the fourth switch tube VT4; the fifth switch tube VT5; the sixth switch tube VT6; the seventh switch tube VT7; the eighth switch tube VT8; the ninth switch tube VT9; the first MOS tube S1; the second MOS tube S2; the third MOS tube S3; the fourth MOS tube S4; A first inductor L1; a second inductor L2; a third inductor L3; a fourth inductor L4; a first resistor R1; and a second resistor R2; A first capacitor C1; a second capacitor C2; a third capacitor C3; a fourth capacitor C4; and a fifth capacitor C5. DETAILED DESCRIPTION

[0021] Embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. Embodiments of the present invention are described in detail below.

[0022] For power systems with tight power supply, distributed energy storage technology is expected to provide the best solution: first, distributed energy storage systems are modular, can be assembled quickly, and have low on-site installation costs. Secondly, due to the flexibility of modularization, when the load demand in a certain area increases, it is better to use distributed energy storage systems instead of building regional power plants. Thirdly, distributed energy storage systems will not increase the pressure on the power system in terms of environmental protection, but will help reduce fossil fuel consumption and exhaust emissions of main power plants and distributed power generation equipment. Then distributed energy storage systems generally have higher energy conversion efficiency and faster response speed. In addition, the use of distributed energy storage systems can improve the utilization rate and operating economy of existing power generation and transmission and distribution equipment.

[0023] In order to improve the power quality of the energy storage system and enhance the power supply reliability of the energy storage system, the present application proposes a flywheel energy storage system as a power supply that provides uninterrupted high-quality power supply to the load, and can independently choose power supply from the grid or the flywheel energy storage system.

[0024] Reference below Figure 1 A flywheel energy storage system 100 according to an embodiment of the present invention is described. The flywheel energy storage system 100 includes a flywheel motor 10 , a rectifier circuit 20 , a buck circuit 30 , a first inverter circuit 40 , a boost circuit 50 and a second inverter circuit 60 .

[0025] The AC side of the rectifier circuit 20 is connected to the power grid 200, and the rectifier circuit 20 is used to convert the AC power signal of the power grid 200 into a DC power supply signal; the input end of the step-down circuit 30 is connected to the DC side of the rectifier circuit 20, and the step-down circuit 30 is used to convert the DC power supply signal into a first DC power signal; the first end of the first inverter circuit 40 is connected to the output end of the step-down circuit 30, and the second end of the first inverter circuit 40 is connected to the flywheel motor 10. The first inverter circuit 40 is used to convert the first DC power signal into the AC voltage required for charging the flywheel motor 10 during charging, and is also used to rectify the AC power supply signal output by the flywheel motor 10 into a second DC power signal during discharge. The first inverter circuit 40 can be an intelligent power module (IPM, Intelligent Power Module); the input end of the boost circuit 50 is connected to the output end of the buck circuit 30 and the first end of the first inverter circuit 40, and the boost circuit 50 is used to convert the first DC power signal or the second DC power signal into a third DC power signal; the input end of the second inverter circuit 60 is connected to the output end of the boost circuit 50, and the output end of the second inverter circuit 60 is connected to the load 300, and the second inverter circuit 60 is used to convert the third DC power signal into a DC voltage required by the load 300.

[0026] Specifically, when the power grid 200 supplies power to the load 300, wherein the load 300 is a DC load, the rectifier circuit 20 converts the AC power signal output by the power grid 200 into a DC power supply signal, and then the DC power supply signal is converted into a first DC power signal by the step-down circuit 30, and then the first DC power signal is stepped up and converted into a third DC signal by the step-up circuit 50, and finally the third DC signal is converted into a DC voltage required by the load 300 by the second inverter circuit 60, and when the power grid 200 supplies power to the load 300, the power grid 200 also The flywheel motor 10 can be charged. The energy storage process of the flywheel energy storage system 100 is as follows: the power grid 200 supplies power to the flywheel energy storage system 100, and the rectifier circuit 20 converts the AC power signal output by the power grid 200 into a DC power supply signal to realize the rectification of the AC power signal of the power grid 200. Since the equivalent inductance and resistance of the flywheel motor 10 are very small, when the flywheel motor 10 starts to power on, it is easy to burn out the flywheel motor 10 and the first inverter circuit 40 due to excessive voltage. Therefore, the control of the bus voltage by the step-down circuit 30 helps to improve The safety and reliability of the flywheel motor 10 and the first inverter circuit 40 are ensured. Therefore, the step-down circuit 30 steps down the DC power supply signal and converts the DC power supply signal into a first DC signal. Thus, the step-down circuit 30 realizes the control of the bus voltage, and then the first inverter circuit 40 inverts the stepped-down first DC signal into the AC voltage required for charging the flywheel motor 10. In this process, the control circuit of the flywheel energy storage system 100 determines the duty cycle of the control signal according to the state information of the flywheel motor 10 to calculate and obtain the corresponding control signal, wherein the state information includes current and position, and outputs the control signal to the step-down circuit 30. The step-down circuit 30 steps down the DC power supply signal under the action of the control signal to realize the accelerated operation of the flywheel motor 10, thereby converting the electrical energy provided by the power grid 200 into mechanical energy and storing the energy in the high-speed rotating flywheel. Based on this, when the AC signal provided by the power grid 200 is unstable or the power grid cannot provide an AC signal, the load 300 can be powered by the flywheel energy storage system 100 to enhance the power supply reliability of the flywheel energy storage system 100.

[0027] And, the discharge process of the flywheel energy storage system 100 is as follows: the flywheel provides torque to the flywheel motor 10, that is, the flywheel motor 10 is used as a generator to convert the mechanical energy stored in the flywheel into electrical energy and release it, and the electrical energy output by the flywheel motor 10 is an AC power supply signal, and the AC power supply signal is rectified into a second DC power signal through the first inverter circuit 40. Since the voltage of the AC power supply signal output by the flywheel motor 10 is getting smaller and smaller, a boost circuit 50 is set to boost the second DC power signal, and convert the second DC power signal into a third DC power signal, and then the third DC power signal is converted into the DC voltage required by the load 300 through the second inverter circuit 60, so as to realize the uninterrupted power supply of the flywheel energy storage system 100 to the load 300, thereby Compared with the existing flywheel energy storage system that connects the flywheel motor to the PCS and then hangs it on the AC input side of the power grid, the flywheel motor 10 is set on the DC side of the AC input of the power grid 200 in the present application, so that when the flywheel energy storage system 100 supplies power to the load 300, the AC power supply signal output by the flywheel motor 10 is directly converted into a DC power signal to supply power to the load 300, and there is no need to perform AC-DC conversion on the AC power supply signal output by the flywheel motor 10 and then perform DC-AC conversion through the PCS before being connected to the power grid 200 to supply power to the load 300, thereby reducing the number of energy conversions and reducing the energy conversion loss of the flywheel energy storage system 100. In addition, the circuit structure of the flywheel energy storage system 100 is simple, which increases the reliability of the flywheel energy storage system 100.

[0028] According to the flywheel energy storage system 100 of the embodiment of the present invention, based on the circuit structure in which the flywheel motor 10 is arranged on the DC side of the AC input of the power grid, the first inverter circuit 40 directly converts the AC power supply signal output by the flywheel motor 10 into a DC signal, and then changes the voltage of the DC signal through the second inverter circuit 60 to power the DC load, thereby realizing uninterrupted power supply of the flywheel energy storage system 100 to the load 300. Therefore, compared with the existing flywheel energy storage system in which the flywheel motor is connected to the PCS and then connected to the AC input side of the power grid, the flywheel motor 10 is arranged on the DC side of the AC input of the power grid in the present application, so that when the flywheel energy storage system 100 supplies power to the load 300, the AC power supply signal output by the flywheel motor 10 is directly converted into a DC signal to power the load 300, and there is no need to change the AC power supply signal output by the flywheel motor 10 three times, thereby reducing the number of energy conversions and reducing the energy conversion loss of the flywheel energy storage system 100. In addition, the circuit structure of the flywheel energy storage system 100 is simple, which increases the reliability of the flywheel energy storage system 100.

[0029] In some embodiments, Figure 1 As shown, the rectifier circuit 20 includes a first diode D9, a second diode D10, a third diode D11 and a fourth diode D12.

[0030] Among them, the anode of the first diode D9 is connected to the first power supply terminal of the power grid 200, and the cathode of the first diode D9 is connected to the first input terminal of the step-down circuit 30; the anode of the second diode D10 is connected to the second power supply terminal of the power grid 200, and the cathode of the second diode D10 and the cathode of the first diode D9 are connected to the first input terminal of the step-down circuit 30; the anode of the third diode D11 is connected to the second input terminal of the step-down circuit 30, and the cathode of the third diode D11 is connected to the anode of the first diode D9 and the first power supply terminal of the power grid 200; the anode of the fourth diode D12 is connected to the anode of the third diode D11 and the second input terminal of the step-down circuit 30, and the cathode of the fourth diode D12 is connected to the anode of the second diode D10 and the second power supply terminal of the power grid 200. The rectifier circuit 20 can be a rectifier bridge. For example, the rectifier circuit 20 uses a 36MT140 rectifier tube, which has an output current of 35A, a withstand voltage of 1400V, a peak current of about 475A, a very small leakage current, and indicators that can fully meet the requirements. Its packaging form is GBPC-W.

[0031] The first diode D9, the second diode D10, the third diode D11 and the fourth diode D12 can be designed according to parameters such as the maximum output current, the maximum reverse voltage and the operating temperature, and no specific limitation is made here.

[0032] It should be noted that the rectifier circuit 20 is applied to low-frequency alternating current, and therefore, the design of the first diode D9 , the second diode D10 , the third diode D11 , and the fourth diode D12 does not need to consider the junction capacitance factor.

[0033] Specifically, the rectifier circuit 20 converts the AC power signal input from the power grid 200 into a DC power supply signal through the unidirectional conduction principle of the first diode D9 , the second diode D10 , the third diode D11 and the fourth diode D12 .

[0034] In some embodiments, Figure 1 As shown, the step-down circuit 30 includes a first power tube 8, a first inductor L1, a fifth diode D13, a first capacitor C1 and a second capacitor C2.

[0035] Among them, the drain of the first power tube 8 is connected to the cathode of the second diode D10; the first end of the first inductor L1 is connected to the source of the first power tube 8, and the second end of the first inductor L1 is connected to the input end of the boost circuit 50 and the first end of the first inverter circuit 40; the anode of the fifth diode D13 is connected to the anode of the fourth diode D12 and the first end of the first inverter circuit 40, and the cathode of the fifth diode D13 is connected to the first end of the first inductor L1 and the source of the first power tube 8; the first end of the first capacitor C1 is connected to the drain of the first power tube 8 and the cathode of the second diode D10, and the second end of the first capacitor C1 is connected to the anode of the fifth diode D13 and the anode of the fourth diode D12; the first end of the second capacitor C2 is connected to the second end of the first inductor L1, the input end of the boost circuit 50, and the first end of the first inverter circuit 40, and the second end of the second capacitor C2 is connected to the anode of the fifth diode D13 and the first end of the first inverter circuit 40.

[0036] Specifically, the step-down circuit 30 controls the on and off of the first power tube 8 so that the first inductor L1 stores and releases energy during the charging and discharging process, thereby achieving the purpose of stepping down the DC power supply signal, thereby avoiding the problem of burning out the flywheel motor 10 and the first inverter circuit 40 due to excessive voltage when the flywheel motor 10 starts to power on, and realizing the control of the bus voltage.

[0037] The fifth diode D13 is a freewheeling diode, the first inductor L1 is an energy storage inductor, and the second capacitor C2 and the first capacitor C1 are used to support the bus voltage and filter.

[0038] In an embodiment, Figure 1 As shown, the first power tube 8 includes an eighth switch tube VT8 and a thirteenth diode D8. The thirteenth diode D8 is an ultra-fast recovery diode, and its reverse recovery time is very short, and it requires a large output current and a high reverse voltage. Although the junction capacitance of the thirteenth diode D8 as an ultra-fast diode is very small and the switching time is very short, the current will still change greatly, so it is necessary to add an RC absorption circuit next to the thirteenth diode D8. The thirteenth diode D8 can also be a fast diode, and the fast diode can be 30eth06. The reverse withstand voltage of the diode reaches 600V, the average current reaches 30A, the conduction voltage drop is 2.1V, the maximum recovery time is only 40ns, the packaging form is TO-247, and the maximum current at 60Hz is 325A. In addition, the selection of the eighth switch tube VT8 should meet the output current and withstand voltage requirements of the power grid, and a switch tube with low gate charge should be selected to speed up the on and off time of the switch tube, that is, to increase the switching speed, so that the energy consumed when the switch tube is turned on and off is extremely low. Therefore, the eighth switch tube VT8 can be irg4pc50u.

[0039] In the embodiment, the inductor core material of the first inductor L1 is a high-permeability magnetic core made of Sendust material.

[0040] Specifically, using a high-permeability magnetic core of sendust material as the inductor magnetic core material of the first inductor L1 can effectively reduce the number of coil turns of the first inductor L1, reduce copper loss and cost. In addition, the magnetic induction intensity B and magnetic field intensity H curve of the magnetic core material of the first inductor L1 is as straight as possible, and the magnetic induction intensity should be in an unsaturated state, so as to avoid damage to the first inductor L1 during use.

[0041] Exemplarily, the first inductor L1 is made of an iron silicon aluminum magnetic powder core material composed of 85% iron, 9% silicon and 6% aluminum. The air gap is evenly distributed inside the magnetic core. The electromagnetic performance of the magnet is stable in the range of 10kHz-100kHz, and the BH curve is basically a straight line. It is suitable for switching power supply filters, etc. The air gap of the magnetic material is evenly distributed inside the magnetic core, so it is not easy to saturate.

[0042] In the embodiment, the buck circuit 30 has two working modes, namely, the inductor current continuous mode and the inductor current discontinuous mode. There is a working boundary between the two working modes, namely, the critical continuous state of the inductor current. The critical inductance of the buck circuit 30 when it is in the critical continuous state of the inductor current is L c It can be calculated by formula 1-1 that under a certain input power, if the buck circuit 30 operates in a discontinuous working mode, the current when the first inductor L1 is turned on will be very large, which means that the first power tube 8 and the fifth diode D13 of the buck circuit 30 should have higher peak voltage and current. That is to say, in high-power application scenarios, the buck circuit 30 should avoid operating in the inductor current discontinuous mode, and the buck circuit 30 will only operate in the inductor current continuous mode when the inductance value of the first inductor L1 is greater than the critical inductance Lc.

[0043]

[0044] in, is the input voltage, is the output current, is the output voltage, is the switching frequency.

[0045] In the flywheel energy storage system 100, the input voltage The set value is 314V, the output current The output voltage is the rated current multiplied by 0.2. is a variable, the switching frequency 20kHz, from formula 1-1, when the output voltage Input voltage When the critical inductance L cMaximum, then the maximum critical inductance for the flywheel energy storage system 100 is 781μH. Under a certain input power, if the buck circuit 30 operates in a discontinuous working state, the current of the switch tube of the first power tube 8 when it is turned on will be very large, which means that the first power tube 8 and the freewheeling diode of the buck circuit 30 must have higher peak voltage and current. Therefore, in high-power applications, the buck circuit 30 should avoid operating in a discontinuous state. Because it only works in a continuous state when the designed inductance is greater than the critical inductance, the inductance value of the first inductor L1 is determined to be 1000μH. The selection of the first capacitor C1 and the second capacitor C2 mainly considers the self-heating problem and its output voltage ripple. If the first capacitor C1 and the second capacitor C2 are too small, the output voltage will fluctuate greatly, and the output ripple voltage It can be calculated by formula 1-2:

[0046] From formula 1-2, the capacitance solution formula can be obtained as follows:

[0047] In an embodiment, the present application sets the ripple voltage to 0.5% of the output voltage. When the output voltage is half of the bus voltage, the capacitance values ​​of the first capacitor C1 and the second capacitor C2 are the maximum capacitance values, and the maximum capacitance value may be 78 μF. In order to ensure that the step-down circuit can output a more stable voltage, the maximum capacitance value selects a ruby ​​electrolytic capacitor with a capacitance value of 560 μF / rated voltage of 450 V.

[0048] In some embodiments, Figure 1 As shown, the first inverter circuit 40 includes a second power tube 1 , a third power tube 3 , a fourth power tube 4 , a fifth power tube 6 , a sixth power tube 5 and a seventh power tube 2 .

[0049] Among them, the drain of the second power tube 1 is connected to the second end of the first inductor L1 and the input end of the boost circuit 50, and the source of the second power tube 1 is connected to the first output end of the flywheel motor 10; the drain of the third power tube 3 is connected to the source of the second power tube 1 and the first output end of the flywheel motor 10, and the source of the third power tube 3 is connected to the second end of the second capacitor C2; the drain of the fourth power tube 4 is connected to the drain of the second power tube 1, and the source of the fourth power tube 4 is connected to the second output end of the flywheel motor 10; the drain of the fifth power tube 6 is connected to the source of the fourth power tube 4 and the second output end of the flywheel motor 10, and the source of the fifth power tube 6 is connected to the source of the third power tube 3; the drain of the sixth power tube 5 is connected to the drain of the fourth power tube 4, and the source of the sixth power tube 5 is connected to the third output end of the flywheel motor 10; the drain of the seventh power tube 2 is connected to the source of the sixth power tube 5 and the third output end of the flywheel motor 10, and the source of the seventh power tube 2 is connected to the source of the fifth power tube 6.

[0050] Specifically, the power grid 200 supplies power to the flywheel energy storage system 100, and the rectifier circuit 20 converts the AC power signal output by the power grid 200 into a DC power supply signal to achieve rectification of the AC power signal of the power grid 200, and then the step-down circuit 30 steps down the DC power supply signal to convert the DC power supply signal into a first DC power signal, and then the first inverter circuit 40 inverts the stepped-down first DC power signal into the AC voltage required for charging the flywheel motor 10, that is, the control circuit controls the conduction or cutoff of the second power tube 1, the third power tube 3, the fourth power tube 4, the fifth power tube 6, the sixth power tube 5 and the seventh power tube 2 of the first inverter circuit 40, so as to invert the DC power signal into a three-phase AC voltage through the on-off combination of different power tubes, so as to obtain the AC voltage required for charging the flywheel motor 10, thereby achieving energy storage of the flywheel energy storage system 100.

[0051] Alternatively, the electric energy output by the flywheel motor 10 is an AC power supply signal, and the control circuit controls the reverse diodes in the second power tube 1, the third power tube 3, the fourth power tube 4, the fifth power tube 6, the sixth power tube 5 and the seventh power tube 2 of the first inverter circuit 40 to rectify the AC power supply signal into a second DC signal, and then the boost circuit 50 boosts the second DC signal to convert the second DC signal into a third DC signal, and then the second inverter circuit 60 converts the third DC signal into the DC voltage required by the load 300, thereby realizing uninterrupted power supply of the flywheel energy storage system 100 to the load 300.

[0052] In an embodiment, the first inverter circuit 40 may be an IPM module, and the AC power supply signal is rectified into a second DC power signal through a reverse diode of the IPM module.

[0053] It should be noted that the present invention adopts an IPM module as the first inverter circuit 40. The first inverter circuit 40 has the advantages of high current density, low saturation voltage and high voltage resistance of GTR (Giant Transistor) high-power transistors, and also has the characteristics of high input impedance, high switching frequency and low driving power of MOSFET (field effect transistor). It also integrates multiple functions such as logic, control, detection and protection circuits, which reduces the volume and development time of the flywheel energy storage system 100 and enhances the reliability of the flywheel energy storage system 100.

[0054] In some embodiments, Figure 1 As shown, the first inverter circuit 40 further includes an eighth power tube 7 and a first resistor R1.

[0055] Among them, the drain of the eighth power tube 7 is connected to the second end of the first inductor L1, the input end of the boost circuit 50, and the drain of the second power tube 1. The eighth power tube 7 plays a role of resistance-capacitance absorption and suppresses the influence of the reverse peak voltage (surge voltage) on the switch tube in the first inverter circuit 40 to protect the switch tube in the first inverter circuit 40; the first end of the first resistor R1 is connected to the source of the eighth power tube 7, the second end of the first resistor R1 is connected to the second end of the second capacitor C2 and the source of the third power tube 3, and the first resistor R1 has a current limiting effect.

[0056] In some embodiments, each power tube includes a switch tube and a diode.

[0057] The base of the switch tube is used to receive the switch control signal; the anode of the diode is connected to the source of the switch tube, and the cathode of the diode is connected to the drain of the switch tube. That is to say, the second power tube 1, the third power tube 3, the fourth power tube 4, the fifth power tube 6, the sixth power tube 5, the seventh power tube 2 and the eighth power tube 7 of the first inverter circuit 40 include switch tubes and diodes, such as Figure 1 As shown, the second power tube 1 includes a sixth diode D1 and a first switch tube VT1, the third power tube 3 includes an eighth diode D3 and a third switch tube VT3, the fourth power tube 4 includes a ninth diode D4 and a fourth switch tube VT4, the fifth power tube 6 includes an eleventh diode D6 and a sixth switch tube VT6, the sixth power tube 5 includes a tenth diode D5 and a fifth switch tube VT5, the seventh power tube 2 includes a seventh diode D2 and a second switch tube VT2, and the eighth power tube 7 includes a twelfth diode D7 and a seventh switch tube VT7.

[0058] In the embodiment, the maximum speed of the flywheel is 60000 RPM, which is equivalent to 1000 Hz per second. The flywheel motor 10 adopts four pairs of machines, that is, each switch tube will be turned on 8 times. Therefore, the maximum switching frequency of the switch tube of the first inverter circuit 40 is 8kHZ, and the switching frequency of the eighth power tube 7 is set to 20kHZ.

[0059] In some embodiments, Figure 1 As shown, the boost circuit 50 includes a second inductor L2 and a ninth power tube 9 .

[0060] The first end of the second inductor L2 is connected to the second end of the first inductor L1 and the drain of the eighth power tube 7, and the second end of the second inductor L2 is connected to the input end of the second inverter circuit 60; the drain of the ninth power tube 9 is connected to the second end of the second inductor L2, and the source of the ninth power tube 9 is grounded. Figure 1 As shown, the ninth power tube 9 includes a ninth switch tube VT9 and an eighteenth diode D17.

[0061] Specifically, when the flywheel motor 10 supplies power to the load 300, the AC power supply signal output by the flywheel motor 10 is rectified into a second DC power signal, and then the boost circuit 50 converts the second DC power signal into a third DC power signal. Alternatively, when the power grid 200 supplies power to the load 300, the rectifier circuit 20 converts the AC power signal of the power grid 200 into a DC power supply signal, the step-down circuit 30 converts the DC power supply signal into a first DC power signal, and then the boost circuit 50 converts the first DC power signal into a third DC power signal. In this process, the ninth power tube 9 of the boost circuit 50 is turned on or off according to the control circuit to control the charging and discharging of the second inductor L2, so as to boost the second DC power signal or the first DC power signal into a third DC power signal, thereby achieving the purpose of boosting the output voltage.

[0062] In addition, it should be noted that when designing the boost circuit 50, the voltage amplification factor is controlled to be 3 times or less, so that the boost circuit 50 operates in a current continuous state.

[0063] In the embodiment, the maximum voltage of the boost circuit 50 is increased by about 3 times, that is, assuming that the voltage is to be increased to 300V, the minimum input voltage of the boost circuit 50 needs to be 100V. When the input voltage is less than 100V, the flywheel is recharged to ensure that the output bus voltage is 300V. Calculated based on the minimum voltage of the boost circuit 50, assuming that the power design of the discharge main circuit is 300W, the maximum input current of the boost circuit 50 is 3A, and considering a certain margin, that is, the output current of the internal reverse diode of the IPM module is 5A, that is, the first inverter circuit 40 of the present application can adopt an IPM module.

[0064] In the embodiment, considering that the voltage at the generator end, i.e., the flywheel motor end, is getting smaller and smaller, a simple and easy boost circuit 50 is needed to boost the voltage, and the bus voltage of the inverter part is boosted to 310 V. During the design, the voltage amplification factor of the boost circuit 50 is controlled at 3 times or less, so that the circuit works in a continuous current state.

[0065] In some embodiments, Figure 1 As shown, the second inverter circuit 60 includes a tenth power tube 11 , an eleventh power tube 12 , a twelfth power tube 13 and a thirteenth power tube 14 .

[0066] Among them, the drain of the tenth power tube 11 is connected to the drain of the ninth power tube 9, and the source of the tenth power tube 11 is connected to the load 300; the drain of the eleventh power tube 12 is connected to the source of the tenth power tube 11 and the load 300, and the source of the eleventh power tube 12 is connected to the source of the ninth power tube 9; the drain of the twelfth power tube 13 is connected to the drain of the tenth power tube 11, and the source of the twelfth power tube 13 is connected to the load 300; the drain of the thirteenth power tube 14 is connected to the source of the twelfth power tube 13 and the load 300, and the source of the thirteenth power tube 14 is connected to the source of the eleventh power tube 12.

[0067] Specifically, in order to convert the third DC power signal into the voltage required by the load 300, the switching and conduction of the tenth power tube 11, the eleventh power tube 12, the twelfth power tube 13 and the thirteenth power tube 14 of the second inverter circuit 60 are controlled to convert the third DC power signal into the DC voltage required by the load, and the DC voltage can be 220V.

[0068] In an embodiment, the second inverter circuit 40 can be a differential bridge circuit, and the tenth power tube 11, the twelfth power tube 13, the eleventh power tube 12 and the thirteenth power tube 14 form two half-bridges. The difference between the two half-bridge circuits is used to convert the third DC signal into the voltage required by the load, and the load 300 requires 220V DC.

[0069] In some embodiments, each power tube includes a MOS tube and a diode.

[0070] The gate of the MOS tube is used to receive a conduction control signal; the anode of the diode is connected to the source of the MOS tube, and the cathode of the diode is connected to the drain of the MOS tube.

[0071] For example, Figure 1 As shown, the tenth power tube 11 includes a first MOS tube S1 and a fourteenth diode D18, the eleventh power tube 12 includes a third MOS tube S3 and a sixteenth diode D15, the twelfth power tube 13 includes a second MOS tube S2 and a fifteenth diode D14, and the thirteenth power tube 14 includes a fourth MOS tube S4 and a seventeenth diode D16.

[0072] In the embodiment, in the selection of the MOS tube of each power tube in the second inverter circuit 40, if the switching frequency of the MOS tube is high, harmonics can be improved, and the smaller the Qg (gate charge) value of the selected MOS tube, the shorter the MOS tube shut-off and turn-on time, that is, the turn-on and turn-off speed is very fast, the smaller the heat generated by the MOS tube of each power tube, the higher the efficiency, and it helps to reduce harmonics. Among them, the model of the MOS tube can be IRFB9N60A, and the frequency of its output AC voltage is 50Hz.

[0073] In some embodiments, Figure 1 As shown, the flywheel energy storage system 100 further includes a first voltage protection circuit 70 and a second voltage protection circuit 80 .

[0074] Among them, the first end of the first voltage protection circuit 70 is connected to the drain of the tenth power tube 11 and the drain of the twelfth power tube 13, and the second end of the first voltage protection circuit 70 is connected to the source of the eleventh power tube 12 and the source of the thirteenth power tube 14; the first end of the second voltage protection circuit 80 is connected to the drain of the twelfth power tube 13, and the second end of the second voltage protection circuit 80 is connected to the source of the thirteenth power tube 14.

[0075] Specifically, the MOS tube has a relatively fragile ability to withstand short-term overload. Therefore, the first protection circuit 70 is designed to protect the tenth power tube 11 and the eleventh power tube 12, and the second protection circuit 80 is designed to protect the twelfth power tube 13 and the thirteenth power tube 14, so as to suppress the influence of the reverse peak voltage on the MOS tube and ensure that the MOS tube in the second inverter circuit 40 is not damaged.

[0076] In some embodiments, each voltage protection circuit includes a second resistor and a third capacitor, such as Figure 1 As shown, the first voltage protection circuit 70 and the second voltage protection circuit 80 include a second resistor R2 and a third capacitor C3.

[0077] The first end of the second resistor is connected to the drain of the power tube; the first end of the third capacitor is connected to the second end of the second resistor, and the second end of the third capacitor is connected to the source of the power tube. The second resistor and the third capacitor have a resistance-capacitance absorption effect, that is, suppressing the influence of the reverse peak voltage (surge voltage) on the MOS tube, thereby protecting the MOS tube.

[0078] In some embodiments, Figure 1 As shown, the flywheel energy storage system 100 further includes a filter circuit 90 .

[0079] Among them, the first input end of the filter circuit 90 is connected to the source of the tenth power tube 11 and the drain of the eleventh power tube 12, the second input end of the filter circuit 90 is connected to the source of the twelfth power tube 13 and the drain of the thirteenth power tube 14, and the output end of the filter circuit 90 is connected to the load 300.

[0080] In some embodiments, Figure 1 As shown, the filter circuit 90 includes a third inductor L3, a fourth inductor L4, a fourth capacitor C4, and a fifth capacitor C5.

[0081] Among them, the first end of the third inductor L3 is connected to the source of the twelfth power tube 13 and the drain of the thirteenth power tube 14, and the second end of the third inductor L3 is connected to the first end of the load 300; the first end of the fourth inductor L4 is connected to the source of the tenth power tube 11 and the drain of the eleventh power tube 12, and the second end of the fourth inductor L4 is connected to the second end of the load 300; the first end of the fourth capacitor C4 is connected to the second end of the third inductor L3, and the second end of the fourth capacitor C4 is grounded; the first end of the fifth capacitor C5 is connected to the second end of the fourth capacitor C4, the first end of the fifth capacitor C5 is grounded, and the second end of the fifth capacitor C5 is connected to the second end of the load 300. Among them, the fourth capacitor C4 and the fifth capacitor C5 are filter capacitors, and the third inductor L3 and the fourth inductor L4 are filter inductors. Based on this, the filter circuit 90 filters out noise and interference in the DC voltage through the third inductor L3, the fourth inductor L4, the fourth capacitor C4, and the fifth capacitor C5.

[0082] In the embodiment, in order to reduce the reactive component of the output power, the current of the fourth capacitor C4 and the fifth capacitor C5 should not be greater than 1 / 5 of the rated output current of the system. The capacitance C of the fourth capacitor C4 and the fifth capacitor C5 is obtained by formula 1-4. f for:

[0083] in, is the capacitor current, is the frequency, is the voltage of the capacitor.

[0084] When the capacitance of the fourth capacitor C4 and the fifth capacitor C5 is known, the inductance of the third inductor L3 and the fourth inductor L4 The size is:

[0085] in, is the cut-off frequency.

[0086] According to simulation results and experience, the cut-off frequency is set to 2 kHz, and the inductance values ​​of the third inductor L3 and the fourth inductor L4 are 800 μH.

[0087] In an embodiment, Figure 2As shown, the flywheel energy storage system 100 includes a charging main circuit 91 and a discharging main circuit 92. The flywheel energy storage system 100 also includes a sensor 96. The AC signal input from the power grid 200 charges the flywheel motor 10 through the charging main circuit 91. The charging main circuit 91 includes a rectifier circuit, a step-down circuit and a first inverter circuit. The flywheel motor 10 discharges to the load 300 through the discharging main circuit 92. The discharging main circuit 92 includes a first inverter circuit, a boost circuit and a second inverter circuit. The sensor 96 is used to detect information of the flywheel motor 10. The sensor includes a current sensor and a Hall position sensor. The current sensor is used to collect the current signal of the flywheel motor 10. The Hall position sensor collects the position signal of the flywheel motor 10, and then sends the current signal and the position signal to the control circuit 95 after optical coupling through the photoelectric isolation circuit 93. The control circuit 95 can be a DSP (high-speed digital signal The control circuit 95 calculates a control signal according to the position signal and the current signal to provide the control signal to the step-down circuit 30, and the step-down circuit 30 steps down the DC signal according to the control signal.

[0088] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0089] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A flywheel energy storage system, characterized in that: include: Flywheel motor; A rectifier circuit, the AC side of which is connected to a power grid, and the rectifier circuit is used to convert the AC power signal of the power grid into a DC power supply signal; a step-down circuit, wherein an input end of the step-down circuit is connected to a DC side of the rectifier circuit, and the step-down circuit is used to convert the DC power supply signal into a first DC signal; a first inverter circuit, wherein a first end of the first inverter circuit is connected to an output end of the step-down circuit, a second end of the first inverter circuit is connected to the flywheel motor, the first inverter circuit is used to convert the first DC power signal into an AC voltage required for charging the flywheel motor during charging, and is also used to rectify the AC power supply signal output by the flywheel motor into a second DC power signal during discharging; a boost circuit, wherein an input end of the boost circuit is connected to an output end of the buck circuit and a first end of the first inverter circuit, and the boost circuit is used to convert the first DC signal or the second DC signal into a third DC signal; A second inverter circuit, wherein the input end of the second inverter circuit is connected to the output end of the boost circuit, the output end of the second inverter circuit is connected to the load, and the second inverter circuit is used to convert the third DC signal into a DC voltage required by the load.

2. The flywheel energy storage system according to claim 1, characterized in that: The rectifier circuit comprises: a first diode, wherein an anode of the first diode is connected to a first power supply terminal of the power grid, and a cathode of the first diode is connected to a first input terminal of the step-down circuit; a second diode, wherein an anode of the second diode is connected to a second power supply terminal of the power grid, and a cathode of the second diode and a cathode of the first diode are connected to a first input terminal of the step-down circuit; a third diode, wherein an anode of the third diode is connected to the second input terminal of the step-down circuit, and a cathode of the third diode is connected to the anode of the first diode and the first power supply terminal of the power grid; A fourth diode, wherein an anode of the fourth diode is connected to an anode of the third diode and a second input end of the step-down circuit, and a cathode of the fourth diode is connected to an anode of the second diode and a second power supply end of the power grid.

3. The flywheel energy storage system according to claim 2, characterized in that: The step-down circuit comprises: a first power tube, wherein a drain of the first power tube is connected to a cathode of the second diode; A first inductor, wherein a first end of the first inductor is connected to the source of the first power tube, and a second end of the first inductor is connected to the input end of the boost circuit and the first end of the first inverter circuit; a fifth diode, wherein an anode of the fifth diode is connected to an anode of the fourth diode and a first end of the first inverter circuit, and a cathode of the fifth diode is connected to a first end of the first inductor and a source of the first power tube; a first capacitor, wherein a first end of the first capacitor is connected to the drain of the first power tube and the cathode of the second diode, and a second end of the first capacitor is connected to the anode of the fifth diode and the anode of the fourth diode; A second capacitor, wherein a first end of the second capacitor is connected to a second end of the first inductor, an input end of the boost circuit, and a first end of the first inverter circuit; and a second end of the second capacitor is connected to an anode of a fifth diode and a first end of the first inverter circuit.

4. The flywheel energy storage system according to claim 3, characterized in that: The first inverter circuit comprises: a second power tube, wherein a drain of the second power tube is connected to the second end of the first inductor and the input end of the boost circuit, and a source of the second power tube is connected to the first output end of the flywheel motor; a third power tube, wherein the drain of the third power tube is connected to the source of the second power tube and the first output end of the flywheel motor, and the source of the third power tube is connected to the second end of the second capacitor; a fourth power tube, wherein a drain of the fourth power tube is connected to a drain of the second power tube, and a source of the fourth power tube is connected to a second output end of the flywheel motor; a fifth power tube, wherein the drain of the fifth power tube is connected to the source of the fourth power tube and the second output end of the flywheel motor, and the source of the fifth power tube is connected to the source of the third power tube; a sixth power tube, wherein a drain of the sixth power tube is connected to the drain of the fourth power tube, and a source of the sixth power tube is connected to the third output terminal of the flywheel motor; A seventh power tube, wherein the drain of the seventh power tube is connected to the source of the sixth power tube and the third output end of the flywheel motor, and the source of the seventh power tube is connected to the source of the fifth power tube.

5. The flywheel energy storage system according to claim 4, characterized in that: Also includes: an eighth power tube, wherein a drain of the eighth power tube is connected to the second end of the first inductor, the input end of the boost circuit, and the drain of the second power tube; A first resistor, wherein a first end of the first resistor is connected to the source of the eighth power tube, and a second end of the first resistor is connected to the second end of the second capacitor and the source of the third power tube.

6. The flywheel energy storage system according to claim 5, characterized in that: Each power tube includes: A switch tube, wherein the base of the switch tube is used to receive a switch control signal; A diode, wherein the anode of the diode is connected to the source of the switch tube, and the cathode of the diode is connected to the drain of the switch tube.

7. The flywheel energy storage system according to claim 5 or 6, characterized in that: The boost circuit comprises: a second inductor, wherein a first end of the second inductor is connected to a second end of the first inductor and a drain of the eighth power tube, and a second end of the second inductor is connected to an input end of the second inverter circuit; A ninth power tube, wherein a drain of the ninth power tube is connected to the second end of the second inductor, and a source of the ninth power tube is grounded.

8. The flywheel energy storage system according to claim 7, characterized in that: The second inverter circuit comprises: a tenth power tube, wherein a drain of the tenth power tube is connected to the drain of the ninth power tube, and a source of the tenth power tube is connected to the load; an eleventh power tube, wherein the drain of the eleventh power tube is connected to the source of the tenth power tube and the load, and the source of the eleventh power tube is connected to the source of the ninth power tube; a twelfth power tube, wherein a drain of the twelfth power tube is connected to the drain of the tenth power tube, and a source of the twelfth power tube is connected to the load; A thirteenth power tube, the drain of the thirteenth power tube is connected to the source of the twelfth power tube and the load, and the source of the thirteenth power tube is connected to the source of the eleventh power tube.

9. The flywheel energy storage system according to claim 8, characterized in that: Each power tube includes: A MOS tube, wherein the gate of the MOS tube is used to receive a conduction control signal; A diode, wherein an anode of the diode is connected to a source of the MOS tube, and a cathode of the diode is connected to a drain of the MOS tube.

10. The flywheel energy storage system according to claim 8, characterized in that: Also includes: a first voltage protection circuit, wherein a first end of the first voltage protection circuit is connected to the drain of the tenth power tube and the drain of the twelfth power tube, and a second end of the first voltage protection circuit is connected to the source of the eleventh power tube and the source of the thirteenth power tube; A second voltage protection circuit, wherein a first end of the second voltage protection circuit is connected to the drain of the twelfth power tube, and a second end of the second voltage protection circuit is connected to the source of the thirteenth power tube.

11. The flywheel energy storage system according to claim 10, characterized in that: Each voltage protection circuit includes: a second resistor, wherein a first end of the second resistor is connected to the drain of the power tube; A third capacitor, wherein a first end of the third capacitor is connected to the second end of the second resistor, and a second end of the third capacitor is connected to the source of the power tube.

12. The flywheel energy storage system according to any one of claims 8 to 11, characterized in that: Also includes: A filter circuit, wherein a first input end of the filter circuit is connected to the source of the tenth power tube and the drain of the eleventh power tube, a second input end of the filter circuit is connected to the source of the twelfth power tube and the drain of the thirteenth power tube, and an output end of the filter circuit is connected to the load.

13. The flywheel energy storage system according to claim 12, characterized in that: The filtering circuit comprises: a third inductor, wherein a first end of the third inductor is connected to the source of the twelfth power tube and the drain of the thirteenth power tube, and a second end of the third inductor is connected to the first end of the load; a fourth inductor, wherein a first end of the fourth inductor is connected to the source of the tenth power tube and the drain of the eleventh power tube, and a second end of the fourth inductor is connected to the second end of the load; a fourth capacitor, wherein a first end of the fourth capacitor is connected to the second end of the third inductor, and a second end of the fourth capacitor is grounded; a fifth capacitor, wherein a first end of the fifth capacitor is connected to the second end of the fourth capacitor, a first end of the fifth capacitor is grounded, and a second end of the fifth capacitor is connected to the second end of the load.

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