Gravity-flywheel-converter device ternary hybrid energy storage system and smart grid

Abstract

The application provides a gravity-flywheel-converter equipment ternary hybrid energy storage system and a smart grid, the gravity-flywheel-converter equipment ternary hybrid energy storage system comprising a gravity energy storage equipment, a flywheel energy storage equipment and a power electronic converter equipment for electrical connection with a power grid, and further comprising a master controller in communication connection with the gravity energy storage equipment, the flywheel energy storage equipment, the power electronic converter equipment and the power grid respectively, the master controller being configured to control the discharge of the capacitor in the power electronic converter equipment, the discharge of the flywheel energy storage equipment and the discharge of the gravity energy storage equipment upon receiving an emergency instruction sent by the power grid, the start time of the discharge of the flywheel energy storage equipment being prior to the cutoff time of the discharge of the power electronic converter equipment, and the start time of the discharge of the gravity energy storage equipment being prior to the cutoff time of the discharge of the flywheel energy storage equipment. The application solves the problem that the single energy storage technology in the prior art cannot meet the demand of the new power system for multi-time scale continuous power support.

Description

TECHNICAL FIELD

[0001] The present application relates to the electrical technical field, in particular to a gravity-flywheel-conversion equipment ternary hybrid energy storage system and smart grid. BACKGROUND

[0002] With the development of new energy technology, a large number of renewable energy power generation is connected to the power system through power electronic converters, which further changes the structure of the power system. When the new power system is coping with complex scenarios such as weak grid, high proportion of new energy penetration and extreme weather, higher requirements are put forward for the safety, active support characteristics, response speed and continuous charging and discharging time of the power supply and energy storage system. The single energy storage technology in the prior art cannot meet the demand of continuous power support in multiple time scales. SUMMARY

[0003] The main purpose of the present application is to provide a gravity-flywheel-conversion equipment ternary hybrid energy storage system and smart grid, so as to at least solve the problem that the single energy storage technology in the prior art cannot meet the demand of continuous power support in multiple time scales of the new power system.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a gravity-flywheel-conversion equipment ternary hybrid energy storage system is provided, which comprises: a gravity energy storage device, which is electrically connected with a power grid; a flywheel energy storage device, which is electrically connected with the power grid; a power electronic conversion device, which is electrically connected with the power grid, and comprises a capacitor; a master controller, which is respectively communicatively connected with the gravity energy storage device, the flywheel energy storage device, the power electronic conversion device and the power grid, and is configured to control the capacitor in the power electronic conversion device to discharge, the flywheel energy storage device to discharge and the gravity energy storage device to discharge to transmit electric energy to the power grid in the case that an emergency instruction sent by the power grid is received, the emergency instruction representing an instruction that the power grid is faulty and needs to be charged; wherein the start time of the flywheel energy storage device discharging is before the cutoff time of the power electronic conversion device discharging, and the start time of the gravity energy storage device discharging is before the cutoff time of the flywheel energy storage device discharging.

[0005] Optionally, the power electronic conversion device further comprises a DC bus, which is used to connect the power grid with the gravity energy storage device and the power grid with the flywheel energy storage device.

[0006] Optionally, the master controller is further configured to: acquire current energy levels of the flywheel energy storage device, the gravity energy storage device and the power electronic converter device respectively in a case where a power surplus instruction sent by the power grid is received, the power surplus instruction representing an instruction that the power grid has a power surplus; control the flywheel energy storage device to acquire electric energy from the power grid to complete energy storage in a case where the current energy level of the flywheel energy storage device is less than a preset first energy threshold; control the gravity energy storage device to acquire electric energy from the power grid to complete energy storage in a case where the current energy level of the gravity energy storage device is less than a preset second energy threshold; and control the power electronic converter device to acquire electric energy from the power grid to complete energy storage in a case where the current energy level of the power electronic converter device is less than a preset third energy threshold.

[0007] Optionally, the gravity energy storage device comprises: an energy storage object; a gravity energy storage driving structure mechanically connected with the energy storage object; and a gravity energy storage controller electrically connected with the gravity energy storage driving structure and communicatively connected with the master controller, the gravity energy storage controller being configured to control the gravity energy storage driving structure to drive the energy storage object to move downward in a case where a first control instruction or a second control instruction is received, the first control instruction being an instruction sent by the master controller in a case where the emergency instruction is received, and the second control instruction being an instruction sent by the master controller in a case where a power shortage instruction sent by the power grid is received, the power shortage instruction representing an instruction that the power grid has a power shortage.

[0008] Optionally, the flywheel energy storage device comprises: a rotor structure; a flywheel energy storage driving structure mechanically connected with the rotor structure; and a flywheel energy storage controller electrically connected with the flywheel energy storage driving structure and communicatively connected with the master controller, the flywheel energy storage controller being configured to control the flywheel energy storage driving structure to slow down rotation of the rotor structure in a case where a third control instruction or a fourth control instruction is received, the third control instruction being an instruction sent by the master controller in a case where the emergency instruction is received, and the fourth control instruction being an instruction sent by the master controller in a case where the power shortage instruction sent by the power grid is received and it is monitored that output power of the gravity energy storage device is less than a target power, the power shortage instruction representing an instruction that the power grid has a power shortage, and the target power representing power that needs to be supplemented by the power grid.

[0009] Optionally, the power electronic converter further comprises: a power electronic controller, electrically connected with the capacitor and communicatively connected with the master controller, the power electronic controller being configured to control the capacitor to discharge in response to receiving a fifth control instruction, wherein the fifth control instruction is an instruction sent by the master controller in response to receiving the emergency instruction.

[0010] Optionally, the master controller is further configured to: in response to receiving a power shortage instruction sent by the power grid and monitoring that the sum of the output powers of the flywheel energy storage device and the gravity energy storage device is less than a target power, send a sixth control instruction to the power electronic controller to control the capacitor to discharge, wherein the power shortage instruction represents an instruction that the power grid is short of power, and the target power represents the power that needs to be supplemented by the power grid.

[0011] Optionally, the control of the capacitor in the power electronic converter to discharge, the flywheel energy storage device to discharge and the gravity energy storage device to discharge comprises: controlling the capacitor in the power electronic converter to start discharging; determining whether the output power of the power electronic converter starts to decrease; in response to the output power of the power electronic converter starting to decrease, controlling the flywheel energy storage device to start discharging; determining whether the sum of the output powers of the flywheel energy storage device and the power electronic converter starts to decrease; in response to the sum of the output powers of the flywheel energy storage device and the power electronic converter starting to decrease, controlling the gravity energy storage device to start discharging, so that the curve of the total output power of the gravity-flywheel-converter ternary hybrid energy storage system is a monotonically increasing function, wherein the total output power is the sum of the output power of the power electronic converter, the output power of the flywheel energy storage device and the output power of the gravity energy storage device.

[0012] According to another aspect of the present application, there is provided an intelligent power grid, comprising: any of the gravity-flywheel-converter ternary hybrid energy storage systems.

[0013] The technical scheme of the application is applied to a gravity-flywheel-conversion equipment ternary hybrid energy storage system, which comprises a gravity energy storage equipment, a flywheel energy storage equipment and a power electronic conversion equipment for electrical connection with a power grid, and further comprises a master controller in communication connection with the gravity energy storage equipment, the flywheel energy storage equipment, the power electronic conversion equipment and the power grid, and the master controller is configured to control discharge of a capacitor in the power electronic conversion equipment, discharge of the flywheel energy storage equipment and discharge of the gravity energy storage equipment to transmit electric energy to the power grid in the case of receiving an emergency instruction sent by the power grid, wherein a start time of the discharge of the flywheel energy storage equipment is before a cutoff time of the discharge of the power electronic conversion equipment, and a start time of the discharge of the gravity energy storage equipment is before a cutoff time of the discharge of the flywheel energy storage equipment. Compared with the problem that a single energy storage technology in the prior art cannot meet the demand of a new power system for multi-time scale continuous power support, in the application, the capacitor in the power electronic conversion equipment can quickly respond and start discharging when the master controller receives the emergency instruction sent by the power grid, thereby providing instantaneous power support, which is the fastest first layer response to the power grid and ensures immediate response of the system to power grid emergencies; the flywheel energy storage equipment starts discharging before the discharge of the power electronic conversion equipment ends, thereby seamlessly connecting after the short-term power support provided by the power electronic conversion equipment, extending the time of power output and achieving support in the order of seconds to minutes; the gravity energy storage equipment, as a third layer energy storage resource, has a longer response time, but starts discharging before the discharge of the flywheel energy storage equipment ends, thereby providing power support in the order of hours to the power grid, which is effective support for large-scale energy demand and is the key to solving long-term power shortage; the gravity-flywheel-conversion equipment ternary hybrid energy storage system of the application can form multi-level and multi-time scale power support through the quickly started capacitor, the flywheel energy storage equipment following the capacitor and the gravity energy storage equipment following the flywheel energy storage equipment when the power grid encounters an emergency, thereby effectively alleviating power shortage during power grid failure, enhancing the flexibility and stability of the power grid, improving the rapid response capability to power grid failure and maintaining stable power output for a long time. BRIEF DESCRIPTION OF DRAWINGS

[0014] The drawings accompanying the specification of the application form a part thereof, serve to provide further understanding of the application, and together with the specification explain the application. The use of these drawings in explaining the application does not imply that the application should be limited to the embodiments illustrated therein. In the drawings:

[0015] Figure 1 A structural block diagram of a gravity-flywheel-conversion equipment ternary hybrid energy storage system provided in an embodiment of the application is shown;

[0016] Figure 2 A control flow diagram of a gravity-flywheel-conversion equipment ternary hybrid energy storage system provided in an embodiment of the application is shown;

[0017] Figure 3Fig. 3 shows a diagram of energy release and response time of each device in a gravity-flywheel-converter ternary hybrid energy storage system according to an embodiment of the present application;

[0018] Figure 4 Fig. 4 shows a diagram of output power of a gravity-flywheel-converter ternary hybrid energy storage system in an emergency mode according to an embodiment of the present application;

[0019] Figure 5 Fig. 5 shows another structural block diagram of a gravity-flywheel-converter ternary hybrid energy storage system according to an embodiment of the present application.

[0020] In the above drawings, the following reference signs are used:

[0021] 100, gravity-flywheel-converter ternary hybrid energy storage system; 101, gravity energy storage device; 102, power grid; 103, flywheel energy storage device; 104, power electronic converter device; 105, DC bus; 106, AC bus; 107, wind-solar power station. DETAILED DESCRIPTION

[0022] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0024] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0025] As introduced in the background, the single energy storage technology in the prior art cannot meet the demand of the new power system for the multi-time scale continuous power support, in order to solve the above problem, the embodiment of the present application provides a gravity-flywheel-converter equipment ternary hybrid energy storage system and a smart grid.

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0027] The embodiment of the present application provides a gravity-flywheel-converter equipment ternary hybrid energy storage system, as shown in the figure, Figure 1 The gravity-flywheel-converter equipment ternary hybrid energy storage system 100 includes:

[0028] The gravity energy storage equipment 101 is used for electrical connection with the power grid 102;

[0029] The flywheel energy storage equipment 103 is used for electrical connection with the power grid 102;

[0030] The power electronic converter equipment 104 is used for electrical connection with the power grid 102, and the power electronic converter equipment 104 includes a capacitor (not shown);

[0031] In actual application, the person skilled in the art can flexibly select the appropriate power electronic converter equipment according to actual needs, and the present application does not make specific limitation. In the embodiment of the present application, the power electronic converter equipment includes a modular multilevel converter (MMC).

[0032] The master (not shown) is respectively communicatively connected with the gravity energy storage equipment 101, the flywheel energy storage equipment 103, the power electronic converter equipment 104 and the power grid 102, and is used for discharging the capacitor in the power electronic converter equipment 104, discharging the flywheel energy storage equipment 103 and discharging the gravity energy storage equipment 101 to transmit electric energy to the power grid 102 when receiving an emergency instruction sent by the power grid 102, and the emergency instruction represents an instruction that the power grid 102 fails and needs to be charged;

[0033] The start time of discharging the flywheel energy storage equipment 103 is before the cutoff time of discharging the power electronic converter equipment 104, and the start time of discharging the gravity energy storage equipment 101 is before the cutoff time of discharging the flywheel energy storage equipment 103.

[0034] Through the above embodiment, the gravity-flywheel-conversion device ternary hybrid energy storage system includes a gravity energy storage device, a flywheel energy storage device and a power electronic conversion device for electrical connection with a power grid, and further includes a master controller in communication connection with the gravity energy storage device, the flywheel energy storage device, the power electronic conversion device and the power grid respectively, and the master controller is configured to, in the case of receiving an emergency instruction sent by the power grid, control discharge of a capacitor in the power electronic conversion device, discharge of the flywheel energy storage device and discharge of the gravity energy storage device to transmit electric energy to the power grid, wherein a start time of the discharge of the flywheel energy storage device is before a cutoff time of the discharge of the power electronic conversion device, and a start time of the discharge of the gravity energy storage device is before a cutoff time of the discharge of the flywheel energy storage device. Compared with the problem that a single energy storage technology in the prior art cannot meet the demand of a new power system for multi-time scale continuous power support, in the present application, when the master controller receives the emergency instruction sent by the power grid, the capacitor in the power electronic conversion device can quickly respond and start discharging to provide instantaneous power support, which is the fastest first layer response to the power grid, ensuring the immediate response of the system to the power grid emergency; the flywheel energy storage device starts discharging before the discharge of the power electronic conversion device ends, which can seamlessly connect after the short-term power support provided by the power electronic conversion device, extend the time of power output, and achieve support at the level of seconds to minutes; the gravity energy storage device as a third level energy storage resource has a longer response time, but starts discharging before the discharge of the flywheel energy storage device is completed, which can provide power support at the level of hours to the power grid, which is an effective support for large-scale energy demand and is the key to solving the long-term power shortage; the gravity-flywheel-conversion device ternary hybrid energy storage system of the present application can form multi-level and multi-time scale power support through the quickly started capacitor, the flywheel energy storage device followed by it and the gravity energy storage device followed by it when the power grid encounters an emergency, effectively alleviate the power shortage during the power grid failure, enhance the flexibility and stability of the power grid, not only improve the rapid response capability to the power grid failure, but also maintain stable power output for a long time.

[0035] It should be noted that the modular multilevel converter (MMC) is a technology widely used in long-distance, large-capacity high-voltage direct current power transmission systems. Because the device has a large-capacity capacitor inside, it has intrinsic energy storage characteristics and extremely fast action characteristics. However, because the energy storage capacity of the capacitor is limited, the energy storage time is extremely short, usually within one second. The principle of flywheel energy storage is relatively simple and the technology is relatively mature. In recent years, the application of flywheel energy storage array has made it more flexible in power system applications. Flywheel energy storage devices have high-power charging and discharging characteristics, fast response time, large mechanical inertia, and long charging and discharging time, and are widely used in power system frequency modulation, inertia support, and other scenarios. Gravity energy storage has the advantages of simple principle, flexible site selection, large capacity, high efficiency, and the like. Existing gravity energy storage technologies have various types and modular expansion capabilities, and can be flexibly arranged in various application scenarios to meet various energy storage needs. Gravity energy storage is expected to be widely used in new power systems. The response time of gravity energy storage is s~min level, and the energy storage charging and discharging time can be flexibly adjusted between hours and days. Although the above-mentioned single energy storage technology has good performance and intrinsic safety, it cannot solve all problems of the power system in application due to configuration, control and other factors, resulting in a lot of waste. Therefore, in view of the demand of new power systems for energy storage systems, a gravity-flywheel-conversion device ternary hybrid energy storage system with full time scale and active support characteristics and safety is urgently needed.

[0036] To meet the demand of new power systems for energy storage technology, the present application proposes and constructs a ternary gravity-flywheel-conversion device ternary hybrid energy storage system composed of power electronic conversion devices, flywheel energy storage devices and gravity energy storage devices and proposes a corresponding control strategy. Through collaborative design, the system realizes accurate response to multi-time scale energy storage demand: the power electronic conversion device provides transient fault support and voltage / frequency stability with millisecond-level response, the flywheel energy storage device meets the frequency regulation and auxiliary service demand from seconds to minutes with high power characteristics, and the gravity energy storage device undertakes energy time shift and large-scale renewable energy accommodation tasks above the hour level with its large capacity advantage.

[0037] In an alternative, as shown in Figure 1 The above-mentioned power electronic conversion device 104 further includes a DC bus 105, which is used to connect the above-mentioned power grid 102 and the above-mentioned gravity energy storage device 101, the above-mentioned power grid 102 and the above-mentioned flywheel energy storage device 103. In this embodiment, the DC bus serves as a common energy collection point, ensuring efficient energy transfer between the power electronic conversion device, the flywheel energy storage and the gravity energy storage, simplifying the system structure and reducing the cost. Through the integration of the DC bus, the collaborative work of the hybrid energy storage system is realized.

[0038] Specifically, the electric energy of the gravity energy storage device and the flywheel energy storage device is exchanged with the power grid through the power electronic converter.

[0039] In an example embodiment, the master controller is further configured to: in response to receiving a power surplus instruction sent by the power grid, obtain current energy levels of the flywheel energy storage device, the gravity energy storage device and the power electronic converter, wherein the power surplus instruction represents an instruction that the power grid has a power surplus; in response to the current energy level of the flywheel energy storage device being less than a first preset energy threshold, control the flywheel energy storage device to store energy from the power grid; in response to the current energy level of the gravity energy storage device being less than a second preset energy threshold, control the gravity energy storage device to store energy from the power grid; and in response to the current energy level of the power electronic converter being less than a third preset energy threshold, control the power electronic converter to store energy from the power grid. In this embodiment, the master controller can accurately control the storage of energy when the power grid has a power surplus by monitoring the energy state of each device in real time, fully utilize the power surplus of the power grid, provide sufficient energy storage for the energy storage of each device, avoid energy waste, improve the utilization rate of the energy storage system, and enhance the response capability and continuous power supply capability of the subsequent system in an emergency.

[0040] Specifically, the current energy level of the flywheel energy storage device can be represented by the speed of the rotor structure rotation, the current energy level of the gravity energy storage device can be represented by the height of the energy storage object, and the current energy level of the power electronic converter can be represented by the voltage or current of the capacitor.

[0041] In actual application, the first energy threshold, the second energy threshold and the third energy threshold can be set according to experience values by those skilled in the art, or can be obtained through multiple experiments, and the present application does not make a specific limitation.

[0042] In other embodiments, the gravity energy storage device comprises: an energy storage object; a gravity energy storage driving structure mechanically connected to the energy storage object; a gravity energy storage controller electrically connected to the gravity energy storage driving structure and communicatively connected to the main controller, the gravity energy storage controller being configured to control the gravity energy storage driving structure to drive the energy storage object to move downward when receiving a first control instruction or a second control instruction; wherein the first control instruction is an instruction sent by the main controller when receiving the emergency instruction, and the second control instruction is an instruction sent by the main controller when receiving a power shortage instruction sent by the power grid, the power shortage instruction representing an instruction that the power grid has a power shortage. In this embodiment, when the gravity energy storage controller receives the first control instruction or the second control instruction, i.e., when the power grid needs to supplement power, the energy release of the gravity energy storage device provides continuous high-power support for the power system, further improving the stability of the power grid.

[0043] Specifically, the power shortage instruction refers to an instruction that the power grid only has a power shortage but has not failed.

[0044] Specifically, the gravity energy storage device realizes the mutual conversion of electric energy and gravitational potential energy by transferring the energy storage object between the upper and lower stockyards, providing large-capacity, long-time energy storage and release capability for the system.

[0045] Specifically, the gravity energy storage device comprises: a gravity energy storage upper stockyard, a gravity energy storage lower stockyard, a gravity energy storage channel, a gravity energy storage driving structure, a gravity energy storage transmission structure, a gravity energy storage controller, a gravity energy storage protection structure, necessary automatic operation structure, gravity energy storage measurement and auxiliary structure, and an energy storage object. The gravity energy storage channel connects the gravity energy storage upper stockyard and the gravity energy storage lower stockyard, and is a channel for the energy storage object to run; the gravity energy storage controller is electrically connected to the gravity energy storage driving structure, and controls the rotation of the gravity energy storage driving structure to complete the mutual conversion of electric energy and kinetic energy; the gravity energy storage driving structure is mechanically connected to the gravity energy storage transmission structure, and is used to transfer the kinetic energy of the energy storage driving structure and the kinetic energy of the energy storage object; the gravity energy storage protection structure is located in the gravity energy storage transmission structure, and is used to protect the energy storage object and other structures of the gravity energy storage device in a fault scenario; the automatic operation structure is located in the gravity energy storage upper stockyard and the gravity energy storage lower stockyard, and is used to perform functions such as stacking, pre-acceleration and deceleration of the energy storage object; the measurement and auxiliary structure is located in each structure of the gravity energy storage device, and is used to measure various physical quantities and auxiliary functions such as communication.

[0046] Specifically, the gravity energy storage device realizes mutual conversion between electric energy and gravity potential energy by transferring the energy storage objects between the upper and lower stockyards. When the gravity energy storage device operates in the energy storage mode, the gravity energy storage driving structure obtains electric energy from the power grid to drive the gravity energy storage transmission structure, and at the same time, the energy storage objects are pushed out from the lower stockyard of the gravity energy storage device through the automatic operation structure, enter the gravity energy storage channel, are lifted upward by the gravity energy storage transmission structure until the energy storage objects reach the upper stockyard of the gravity energy storage device and are stacked by the automatic operation structure. In this process, the electric energy in the power grid is converted into the gravity potential energy of the energy storage objects by the gravity energy storage device for storage. When the gravity energy storage device operates in the energy release mode, the energy storage objects are pushed out from the upper stockyard of the gravity energy storage device through the automatic operation structure, enter the gravity energy storage channel, drive the gravity energy storage transmission structure to run downward until the energy storage objects reach the lower stockyard of the gravity energy storage device and are stacked by the automatic operation structure, and at the same time, the gravity energy storage driving structure drives the gravity energy storage transmission structure to rotate so as to convert the kinetic energy into electric energy and feed back to the power grid. In this process, the gravity potential energy of the energy storage objects is converted into electric energy by the gravity energy storage device. In the energy storage and energy release processes, the mechanical action and electrical characteristics of the gravity energy storage device are controlled by the gravity energy storage controller, and the abnormal state of the gravity energy storage device is detected and protected by the gravity energy storage protection structure.

[0047] According to some example embodiments of the present application, the flywheel energy storage device comprises: a rotor structure; a flywheel energy storage driving structure mechanically connected with the rotor structure; a flywheel energy storage controller electrically connected with the flywheel energy storage driving structure and communicatively connected with the main controller, the flywheel energy storage controller being configured to control the flywheel energy storage driving structure to drive the rotation of the rotor structure to decelerate in the case that the third control instruction or the fourth control instruction is received. The third control instruction is an instruction sent by the main controller in the case that the emergency instruction is received, and the fourth control instruction is an instruction sent by the main controller in the case that the power shortage instruction sent by the power grid is received and it is monitored that the output power of the gravity energy storage device is less than the target power. The power shortage instruction represents an instruction that the power shortage occurs in the power grid, and the target power represents the power required to be supplemented by the power grid. In this embodiment, the flywheel energy storage device can quickly respond to the third control instruction or the fourth control instruction, that is, when the power grid has an emergency or a power shortage, the flywheel energy storage device can quickly start discharging to provide the required power.

[0048] Specifically, the flywheel energy storage device realizes rapid storage and release of energy through the high-speed rotating rotor structure. When the flywheel energy storage device releases energy, the rotation speed of the rotor structure decreases, and the kinetic energy is converted into electric energy to supply power to the power grid. When the flywheel energy storage device stores energy, electric energy is obtained from the power grid, the rotation speed of the rotor structure increases, and the electric energy is converted into kinetic energy for storage.

[0049] Specifically, when the master controller receives the power shortage instruction, the gravity energy storage device is preferentially discharged, and when the discharge cannot meet the power demand of the power grid, the flywheel energy storage device is discharged.

[0050] Specifically, the flywheel energy storage device includes a rotor structure, a bearing structure, a drive motor (i.e., a flywheel energy storage drive structure), a converter, a vacuum chamber, and a flywheel energy storage controller. The rotor structure is the core component of the flywheel energy storage device, which stores kinetic energy through high-speed rotation of the rotor structure. The bearing structure connects and fixes the rotor structure with the flywheel housing, and the bearing structure of the flywheel energy storage should have small friction characteristics to ensure the overall efficiency of the flywheel energy storage device. The converter is electrically connected with the drive motor to drive the rotor structure to rotate, thereby realizing the mutual conversion of electric energy and kinetic energy. The vacuum chamber surrounds the rotor structure to provide a vacuum environment for the rotor structure, thereby reducing the friction loss of the rotor structure.

[0051] Specifically, the flywheel energy storage device realizes the mutual conversion of electric energy and flywheel rotor kinetic energy by controlling the acceleration and deceleration of the rotor structure. As a typical power storage, the flywheel energy storage generally operates in a power release standby state, i.e., the rotor structure maintains a rated speed operating state under the action of the bearing structure, the drive motor, the converter, the vacuum chamber, and the flywheel energy storage controller. Therefore, only the power release process of the flywheel energy storage is analyzed: when the power grid has a power shortage (i.e., the power grid sends a power shortage instruction) or an emergency occurs (i.e., the power grid sends an emergency instruction), the rotor structure starts to decelerate under the control of the converter and the drive motor, and the kinetic energy stored in the rotor structure is converted into electric energy through the drive motor and the converter to feedback to the power grid.

[0052] According to some example embodiments of the present application, the above-mentioned power electronic converter device further includes a power electronic controller electrically connected with the capacitor and in communication connection with the master controller. The power electronic controller is configured to control the capacitor to discharge when receiving a fifth control instruction, wherein the fifth control instruction is an instruction sent by the master controller when receiving the emergency instruction. In this embodiment, the power electronic controller can effectively cope with the instantaneous power shortage of the power grid when receiving the fifth control instruction, and through the rapid discharge of the power electronic converter device, the power system is provided with immediate power compensation, further enhancing the overall stability and reliability of the system.

[0053] In some optional solutions of the present application, the master controller is further configured to: in a case where the power shortage instruction sent by the power grid is received and the sum of the output powers of the gravity energy storage device and the flywheel energy storage device is less than the target power, send a sixth control instruction to the power electronic controller, so that the power electronic controller controls the capacitor to discharge; the power shortage instruction represents an instruction that the power grid has a power shortage; and the target power represents the power that needs to be supplemented by the power grid. In this embodiment, the master controller can intelligently determine whether to start the discharge of the power electronic converter by monitoring the power demand of the power grid and the output powers of the gravity energy storage device and the flywheel energy storage device, thereby ensuring accurate matching between the overall power output of the system and the power demand of the power grid.

[0054] Specifically, the modular multilevel converter (MMC) includes sub-modules, bridge arm structures, phase units and topological structures, a control unit (i.e., a power electronic controller) and related auxiliary units. The topological structure of a three-phase MMC is generally a three-phase six-bridge-arm structure, i.e., each phase unit is composed of an upper bridge arm and a lower bridge arm, and each bridge arm is composed of a plurality of sub-modules. The sub-module includes a capacitor, and the sub-module is the core of the MMC, which is usually in a half-bridge or full-bridge topology. The control unit controls the MMC by calculation. The related auxiliary units undertake the implementation of functions such as cooling, protection and measurement.

[0055] Specifically, the MMC, as a high-performance large-power power electronic converter, is widely used in large-scale power transmission projects such as high-voltage direct-current transmission. When the MMC is in normal operation, the bridge arm capacitor is in a charged state. Therefore, the bridge arm capacitor in each sub-module can be regarded as an energy storage structure, which is similar to the flywheel energy storage device and is also in a standby energy release state. Similarly, only the energy release process is analyzed: when there is a power shortage, the control unit of the MMC controls the capacitor in each bridge arm sub-module to release electric energy. This process is completed instantaneously upon receiving the fifth control instruction or the sixth control instruction, thereby supporting the power grid at an extremely fast speed. At this time, the electric energy stored in the capacitor is transferred to the power grid to realize the function of the energy storage device.

[0056] Specifically, the gravity-flywheel-converter ternary hybrid energy storage system of the present application adopts a hybrid energy storage control strategy with a layered control strategy as the core. Specifically, the layered control strategy includes a lower layer control strategy for each energy storage unit of the flywheel energy storage device, the gravity energy storage device and the power electronic converter, and an upper layer control strategy dominated by the master controller. The upper layer control strategy controls the energy exchange between the flywheel energy storage device, the gravity energy storage device, the power electronic converter and the power grid through the master controller as the hub. The master controller receives the upper control instruction and sends it to each lower layer control strategy. Each lower layer control strategy controls the controller of each energy storage unit. In addition to responding to the upper layer control instruction, each energy storage unit controller also has the function of motor control.

[0057] Specifically, as shown in FIG. 1, the gravity-flywheel-converter ternary hybrid energy storage system of the present application includes a flywheel energy storage device 1, a gravity energy storage device 2 and a power electronic converter 3. Figure 2As shown, the gravity-flywheel-conversion equipment ternary hybrid energy storage system is in standby state daily, when power shortage occurs in the power grid (i.e. the power grid sends an emergency instruction or a power shortage instruction), the main controller generates control instructions to act on the flywheel energy storage equipment, the gravity energy storage system equipment and the MMC controller (i.e. the power electronic controller), the MMC (i.e. the power electronic conversion equipment) sends the electric energy in the bridge arm capacitor into the power grid, the flywheel energy storage equipment releases active power after completing the starting process and the active power is merged into the power grid through the MMC, the gravity energy storage equipment also transmits active power to the power grid after completing the starting process, at this time, the gravity-flywheel-conversion equipment ternary hybrid energy storage system is fully started and can continuously transmit active power to the power grid until the power grid has power surplus, the flywheel energy storage equipment and the gravity energy storage equipment are charged and then re-enter the standby state of the gravity-flywheel-conversion equipment ternary hybrid energy storage system.

[0058] Specifically, the operation state of the gravity-flywheel-conversion equipment ternary hybrid energy storage system of the present application can be divided into daily operation mode and emergency operation mode.

[0059] The daily operation mode is based on large-scale gravity energy storage equipment and mainly provides the function of power shifting for the gravity-flywheel-conversion equipment ternary hybrid energy storage system. In the energy storage working condition of the daily operation mode, the gravity-flywheel-conversion equipment ternary hybrid energy storage system absorbs electric energy from the power grid through the power electronic conversion equipment to maintain the stability of the DC bus voltage, the gravity energy storage drive structure and the gravity energy storage transmission structure transfer the energy storage objects from the energy storage lower yard to the energy storage upper yard to complete energy storage, in this process, through centralized control, the flywheel energy storage equipment handles the power fluctuation in the operation process of the gravity energy storage equipment, the power in the gravity-flywheel-conversion equipment ternary hybrid energy storage system is smoothed, and the stability of the power of the gravity-flywheel-conversion equipment ternary hybrid energy storage system is ensured. In the energy release working condition of the daily operation mode, the gravity-flywheel-conversion equipment ternary hybrid energy storage system sends electric energy to the power grid through the power electronic conversion equipment to maintain the stability of the DC bus voltage, the energy storage objects located in the upper yard fall through the energy storage transmission structure and drive the energy storage drive structure to rotate to complete energy release and power generation, in this process, through centralized control, the flywheel energy storage equipment handles the power fluctuation in the operation process of the gravity energy storage equipment, the power in the gravity-flywheel-conversion equipment ternary hybrid energy storage system is smoothed, and the stability of the power of the gravity-flywheel-conversion equipment ternary hybrid energy storage system is ensured.

[0060] The emergency operation mode is a working mode for quickly responding to power support to ensure the safe and stable operation of the power grid in the face of sudden emergencies in the power grid, including sudden generator off-grid, new energy output sudden drop, transmission line short circuit, key tie-line disconnection, load sudden surge and system split operation, etc. When the power grid suddenly lacks power, the power grid sends an emergency command to the main controller. The role of the emergency operation mode is to quickly act to provide power to the power grid when an emergency occurs in the power grid. Since the emergency operation mode is only started when an emergency occurs in the power grid, the gravity-flywheel-conversion device ternary hybrid energy storage system should be in standby state before the emergency occurs in the power grid. When an emergency occurs in the power grid, the upper layer control (i.e. the main controller) of the gravity-flywheel-conversion device ternary hybrid energy storage system receives the instruction and responds, controls the discharge of the capacitor in the power electronic conversion device to output electric energy, and the process time is in the order of milliseconds. At the same time, the flywheel energy storage device is started to act, and the flywheel energy storage device transmits electric energy to the power grid before the capacitor discharge in the power electronic conversion device is cut off, and the process time is in the order of seconds. At the same time, the gravity energy storage device is started to release energy mode, and the gravity energy storage device releases energy to the power grid before the flywheel energy storage device discharge is cut off, providing long-time and high-power power support for the power grid, and the process time is in the order of minutes.

[0061] In the emergency operation mode, the gravity energy storage device may operate in the energy storage mode, the static mode and the release energy mode before the release energy mode is started. The response time of the three modes increases in turn, i.e. the longest response time is the time from switching from the energy storage mode to the release energy mode. Therefore, the support time of the flywheel energy storage device should match the mode switching time of the gravity energy storage device.

[0062] Specifically, Figure 3 The release energy and response time of the MMC, the flywheel energy storage device and the gravity energy storage device are shown in the figure. Figure 3 In the figure, the red curve represents the release energy curve of the MMC, the blue curve represents the release energy curve of the flywheel energy storage device, the black curve represents the release energy curve of the gravity energy storage device, and the green dotted line represents the response time of the MMC, the flywheel energy storage device and the gravity energy storage device, respectively. The horizontal axis is time, and the vertical axis is power.

[0063] As Figure 3As shown, when the emergency operation mode is running (i.e. when the power grid sends an emergency instruction), power instructions are simultaneously sent to the gravity energy storage device, the flywheel energy storage device and the MMC at time t0, the MMC responds fastest and sends active power to the power grid at time t1; at time t2, the flywheel energy storage device responds to the power instruction and sends active power to the power grid; at time t3, the capacitor energy in the MMC sub-module is exhausted, but at this time the flywheel energy storage device has started to maintain the DC bus voltage, and the gravity-flywheel-converter three-element hybrid energy storage system continues to send active power to the power grid; at time t4, the gravity energy storage device starts and responds to the power instruction, and together with the flywheel energy storage device maintains the DC bus voltage and sends active power to the power grid through the MMC; at time t5, the flywheel energy storage device discharges, at this time the gravity energy storage system device completes the climbing and undertakes the task of continuously sending power to the power grid until the power grid power appears surplus, and after charging the flywheel energy storage device and the gravity energy storage device, the system enters standby mode, therefore, t0-t1 is the response time of the MMC, t0-t2 is the response time of the flywheel energy storage device, t0-t4 is the response time of the gravity energy storage device, t1-t3 is the discharge time of the MMC, t2-t5 is the discharge time of the flywheel energy storage device, and t4 is the discharge time of the gravity energy storage device.

[0064] Specifically, in order to ensure that the gravity-flywheel-converter three-element hybrid energy storage system continuously and stably supports the power grid in emergency situations, it is necessary to ensure that: Figure 3 As shown, it is necessary to ensure that: t2

[0065] According to some example embodiments of the present application, the control of the capacitor discharge in the power electronic converter, the flywheel energy storage device discharge and the gravitational energy storage device discharge includes: controlling the capacitor in the power electronic converter to start discharging; determining whether the output power of the power electronic converter starts to decrease; in the case that the output power of the power electronic converter starts to decrease, controlling the flywheel energy storage device to start discharging; determining whether the sum of the output power of the flywheel energy storage device and the output power of the power electronic converter starts to decrease; in the case that the sum of the output power of the flywheel energy storage device and the output power of the power electronic converter starts to decrease, controlling the gravitational energy storage device to start discharging, so that the curve of the total output power of the gravitational-flywheel-converter ternary hybrid energy storage system is a monotonically increasing function, wherein the total output power is the sum of the output power of the power electronic converter, the output power of the flywheel energy storage device and the output power of the gravitational energy storage device. In this embodiment, through the control strategy, it is ensured that the total output power curve of the gravitational-flywheel-converter ternary hybrid energy storage system presents a monotonically increasing trend from the beginning to the end in an emergency, which guarantees that stable power can be provided to the power grid, effectively reduces the sudden change of the power grid voltage, and further enhances the stability and reliability of the gravitational-flywheel-converter ternary hybrid energy storage system.

[0066] Specifically, as shown in Figure 4 To ensure that the gravitational-flywheel-converter ternary hybrid energy storage system provides stable power to the power grid in an emergency, it is also necessary to ensure that the curve of the total output power of the gravitational-flywheel-converter ternary hybrid energy storage system (i.e., the sum of the output power of the MMC, the output power of the flywheel energy storage device and the output power of the gravitational energy storage device) is a monotonically increasing function. Figure 4 In the figure, the red curve represents the output power curve of the MMC, the blue curve represents the output power curve of the flywheel energy storage device, the black curve represents the output power curve of the gravitational energy storage device, the horizontal coordinate is time, and the vertical coordinate is power. The meanings of t0-t5 at each time are the same as those in Figure 4

[0067] It should be noted that the power in the present application refers to active power.

[0068] In other embodiments, the master controller is configured to send a first control instruction to the gravitational energy storage controller in the case that a fault prediction instruction sent by the power grid is received, and the fault prediction instruction represents an instruction that the power grid is about to fail. In this embodiment, when it is predicted that the power grid is about to fail, the first control instruction is sent to the gravitational energy storage controller first, and since the gravitational energy storage device has the longest response time, the gravitational energy storage device can be made to enter the energy release mode in advance, so that the electrical energy can be transmitted to the power grid in time subsequently.

[0069] ​Specifically, the controller of the power grid can acquire current load data, current operating state data and current meteorological data of the power grid; input the current load data, the current operating state data and the current meteorological data into the neural network model, so that the neural network model analyzes the current load data, the current operating state data and the current meteorological data, and outputs a prediction result; the machine learning model is trained by using a plurality of sets of data, and each set of data in the plurality of sets of data includes historical load data, historical operating state data, historical meteorological data and historical fault result; in the case that the prediction result represents that the probability of the power grid to be in fault is greater than a preset probability threshold, the controller of the power grid sends a fault prediction instruction to the master controller.

[0070] In other embodiments, the flywheel energy storage controller is configured to, in response to receiving the third control instruction, control the flywheel energy storage driving structure to drive the rotation of the rotor structure to decelerate according to a preset deceleration rule, wherein in the preset deceleration rule, the deceleration rate increases over time; and the gravity energy storage controller is configured to, in response to receiving the first control instruction, control the gravity energy storage driving structure to drive the energy storage object to move downward according to a preset downward rule, wherein in the preset downward rule, the downward speed increases over time. In this embodiment, it can be ensured that the flywheel energy storage driving structure and the gravity energy storage driving structure can provide a large power support in a short time, and the problem that the output power of the flywheel energy storage device and the gravity energy storage device decreases over time is reduced.

[0071] In other embodiments, the gravity-flywheel-conversion equipment ternary hybrid energy storage system further comprises an AC bus for connecting the power grid with the gravity energy storage device, the power grid with the flywheel energy storage device, and the power grid with the power electronic conversion equipment. In this embodiment, the presence of the AC bus allows each device to operate independently or cooperatively, improving the overall flexibility of the system.

[0072] Specifically, in order to better generality, as Figure 5 As shown in FIG. 1, in special cases such as the voltage of the gravity energy storage device 101 and the flywheel energy storage device 103 not matching the voltage of the power electronic conversion equipment 104, the gravity energy storage device 101 and the flywheel energy storage device 103 can collect energy through the AC bus 106 and the power electronic conversion equipment 104. One end of the power electronic conversion equipment 104 is used to connect with the power grid 102 through the AC bus 106, and the other end of the power electronic conversion equipment 104 is used to connect with the wind-solar field station 107. The power electronic conversion equipment 104 obtains electric energy from the wind-solar field station 107, thereby discharging the power grid 102, i.e., the power electronic conversion equipment 104 effectively accesses and transmits the electric energy generated by the wind-solar field station 107 to the power grid 102, and the power electronic conversion equipment 104 supports large-scale wind-solar field station 107 power generation.

[0073] Further, the gravity energy storage device can adopt a power electronic converter interface and a synchronous motor interface; the flywheel energy storage device can also adopt a synchronous motor interface and a power electronic converter interface, and the flywheel shaft system can be a traditional mechanical shaft system and a shaft system with a magnetic gear.

[0074] In summary, the gravity-flywheel-converter device ternary hybrid energy storage system of the present application uses the capacitor in the power electronic converter device for energy storage, and can obtain the energy storage effect with extremely short response time without additional energy storage devices; covers energy storage technologies with response time from ms level to minute level, and realizes the response of the energy storage system in multiple time scales; covers energy storage technologies with energy storage time from second level to several hours, and can provide fast response, large capacity and long time energy support function.

[0075] The embodiments of the present application also provide an intelligent power grid, which comprises any of the above gravity-flywheel-converter device ternary hybrid energy storage systems.

[0076] Obviously, those skilled in the art should understand that each module or each step of the above-mentioned application can be realized by a general computing device, which can be concentrated on a single computing device or distributed on a network composed of multiple computing devices, and can be realized by program codes executable by the computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in different order, or they can be manufactured into each integrated circuit module respectively, or multiple modules or steps can be manufactured into a single integrated circuit module. Therefore, the application is not limited to any specific combination of hardware and software.

[0077] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can adopt a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer usable storage media containing computer usable program codes (including but not limited to disk storage, CD-ROM, optical storage, etc.).

[0078] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or combination thereof. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or combination thereof.

[0079] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or combination thereof. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or combination thereof.

[0080] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or combination thereof. Figure 1 one or more flowcharts and / or blocks in the flowcharts and / or combination thereof.

[0081] In one typical configuration, the computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0082] The memory can include non-persistent memory and / or volatile memory, such as a random access memory (RAM) including a cache area for the temporary storage of data. A

[0083] Computer-readable media includes permanent and non-permanent, movable and non-movable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device. According to the definition herein, computer-readable media does not include transitory media such as modulated data signals and carriers.

[0084] The technical features of the above-mentioned embodiments can be combined in any manner. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described, but as long as the combinations of the technical features do not exist contradictory, it should be considered as the scope of the present disclosure.

[0085] It should also be noted that the terms "comprising", "including", or any other variant thereof are intended to cover non-exclusive inclusion, so that processes, methods, articles or devices including a series of elements not only include those elements, but also include other elements not explicitly listed, or inherent to such processes, methods, articles or devices. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0086] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0087] In the gravity-flywheel-converter three-element hybrid energy storage system of the application, the gravity-flywheel-converter three-element hybrid energy storage system comprises a gravity energy storage device, a flywheel energy storage device and a power electronic converter device for electrical connection with a power grid, and further comprises a master controller in communication connection with the gravity energy storage device, the flywheel energy storage device, the power electronic converter device and the power grid, respectively, and the master controller is configured to control discharge of a capacitor in the power electronic converter device, discharge of the flywheel energy storage device and discharge of the gravity energy storage device to transmit electric energy to the power grid in the case of receiving an emergency instruction sent by the power grid, wherein a start time of the discharge of the flywheel energy storage device is before a cutoff time of the discharge of the power electronic converter device, and a start time of the discharge of the gravity energy storage device is before a cutoff time of the discharge of the flywheel energy storage device. Compared with the problem that a single energy storage technology in the prior art cannot meet the demand of a new power system for multi-time scale continuous power support, in the application, when the master controller receives the emergency instruction sent by the power grid, the capacitor in the power electronic converter device can quickly respond and start discharging to provide instantaneous power support, which is the fastest first layer response to the power grid and ensures immediate response of the system to power grid emergencies; the flywheel energy storage device starts discharging before the discharge of the power electronic converter device ends, can seamlessly connect after the short-term power support provided by the power electronic converter device, prolongs the time of power output and achieves support in the order of seconds to minutes; the gravity energy storage device as a third level energy storage resource has a longer response time, but starts discharging before the discharge of the flywheel energy storage device ends, can provide power support in the order of hours to the power grid, which is effective support for large-scale energy demand and is the key to solving long-term power shortage; the gravity-flywheel-converter three-element hybrid energy storage system of the application can form multi-level and multi-time scale power support through the quickly started capacitor, the flywheel energy storage device following it and the gravity energy storage device following the flywheel energy storage device when the power grid encounters an emergency, effectively alleviates power shortage during power grid failure, enhances the flexibility and stability of the power grid, not only improves the rapid response capability to power grid failure, but also maintains stable power output for a long time.

[0088] The above only describes the preferred embodiments of the application and is not intended to limit the application. The application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A gravity-flywheel-converter device ternary hybrid energy storage system, characterized in that, The gravity-flywheel-conversion device ternary hybrid energy storage system comprises: a gravity energy storage device, which is electrically connected with a power grid; a flywheel energy storage device, which is electrically connected with the power grid; a power electronic conversion device, which is electrically connected with the power grid, and comprises a capacitor and an MMC (modular multilevel converter) comprising the capacitor; a master controller, which is communicatively connected with the gravity energy storage device, the flywheel energy storage device, the power electronic conversion device and the power grid, and is configured to control the capacitor in the power electronic conversion device, the flywheel energy storage device and the gravity energy storage device to discharge to transmit electric energy to the power grid when receiving an emergency instruction sent by the power grid, the emergency instruction representing an instruction that the power grid is faulty and needs to be charged; wherein a start time of the flywheel energy storage device discharging is before a stop time of the power electronic conversion device discharging, and a start time of the gravity energy storage device discharging is before the stop time of the flywheel energy storage device discharging, when receiving the emergency instruction, the master controller simultaneously issues a power instruction to the gravity energy storage device, the flywheel energy storage device and the MMC at time t0, the MMC responds to the power instruction at time t1, the flywheel energy storage device responds to the power instruction at time t2, and the capacitor in the MMC is exhausted at time t3, t0-t1 is a response time of the MMC to the power instruction, t0-t2 is a response time of the flywheel energy storage device to the power instruction, t1-t3 is a discharging time of the MMC, and t2<t3.

2. The gravity-flywheel-converter device ternary hybrid energy storage system according to claim 1, characterized in that, The power electronic conversion device further comprises a DC bus, which is used to connect the power grid with the gravity energy storage device and the flywheel energy storage device.

3. The gravity-flywheel-converter device ternary hybrid energy storage system of claim 1, wherein, The master controller is further configured to: when receiving a power surplus instruction sent by the power grid, acquire current energy levels of the flywheel energy storage device, the gravity energy storage device and the power electronic conversion device, respectively, the power surplus instruction representing an instruction that power of the power grid is surplus; when the current energy level of the flywheel energy storage device is less than a preset first energy threshold, control the flywheel energy storage device to acquire electric energy from the power grid to complete energy storage; when the current energy level of the gravity energy storage device is less than a preset second energy threshold, control the gravity energy storage device to acquire electric energy from the power grid to complete energy storage; when the current energy level of the power electronic conversion device is less than a preset third energy threshold, control the power electronic conversion device to acquire electric energy from the power grid to complete energy storage.

4. The gravity-flywheel-converter device ternary hybrid energy storage system of claim 1, wherein, The gravity energy storage device comprises: an energy storage object; a gravity energy storage driving structure, which is mechanically connected with the energy storage object; A gravity energy storage controller, which is electrically connected with the gravity energy storage driving structure and communicatively connected with the main controller, is configured to control the gravity energy storage driving structure to drive the energy storage object to move downward in the case of receiving a first control instruction or a second control instruction. The first control instruction is an instruction sent by the main controller in the case of receiving the emergency instruction, and the second control instruction is an instruction sent by the main controller in the case of receiving a power shortage instruction sent by the power grid, the power shortage instruction representing an instruction that the power grid has a power shortage.

5. The gravity-flywheel-converter device ternary hybrid energy storage system of claim 1, wherein, The flywheel energy storage device comprises: a rotor structure; a flywheel energy storage driving structure, which is mechanically connected with the rotor structure; a flywheel energy storage controller, which is electrically connected with the flywheel energy storage driving structure and communicatively connected with the main controller, is configured to control the flywheel energy storage driving structure to drive the rotation of the rotor structure to decelerate in the case of receiving a third control instruction or a fourth control instruction. The third control instruction is an instruction sent by the main controller in the case of receiving the emergency instruction, and the fourth control instruction is an instruction sent by the main controller in the case of receiving a power shortage instruction sent by the power grid and monitoring that the output power of the gravity energy storage device is less than a target power, the power shortage instruction representing an instruction that the power grid has a power shortage, and the target power representing a power that needs to be supplemented by the power grid.

6. The gravity-flywheel-converter device ternary hybrid energy storage system of claim 1, wherein, The power electronic converter device further comprises: a power electronic controller, which is electrically connected with the capacitor and communicatively connected with the main controller, is configured to control the capacitor to discharge in the case of receiving a fifth control instruction, wherein the fifth control instruction is an instruction sent by the main controller in the case of receiving the emergency instruction.

7. The gravity-flywheel-converter device ternary hybrid energy storage system of claim 6, wherein, The main controller is further configured to: send a sixth control instruction to the power electronic controller to make the power electronic controller control the capacitor to discharge in the case of receiving a power shortage instruction sent by the power grid and monitoring that the sum of the output powers of the gravity energy storage device and the flywheel energy storage device is less than a target power, the power shortage instruction representing an instruction that the power grid has a power shortage, and the target power representing a power that needs to be supplemented by the power grid.

8. The gravity-flywheel-converter device ternary hybrid energy storage system of claim 1, wherein, Controlling the capacitor in the power electronic converter device to discharge, the flywheel energy storage device to discharge, and the gravity energy storage device to discharge comprises: controlling the capacitor in the power electronic converter device to start discharging; determining whether the output power of the power electronic converter device starts to decrease; controlling the flywheel energy storage device to start discharging in the case of the output power of the power electronic converter device starting to decrease; determining whether the sum of the output powers of the flywheel energy storage device and the power electronic converter device starts to decrease; In a case where the sum of the output power of the flywheel energy storage device and the power electronic converter device starts to decrease, the gravity energy storage device is controlled to start discharging, so that the curve of the total output power of the gravity-flywheel-converter ternary hybrid energy storage system is a monotonically increasing function, wherein the total output power is the sum of the output power of the power electronic converter device, the output power of the flywheel energy storage device and the output power of the gravity energy storage device.

9. The gravity-flywheel-converter device ternary hybrid energy storage system of claim 1, wherein, The gravity-flywheel-converter ternary hybrid energy storage system further comprises: An alternating current bus for connecting the power grid with the gravity energy storage device, the power grid with the flywheel energy storage device, and the power grid with the power electronic converter device.

10. A smart grid, characterized by Comprise: The gravity-flywheel-converter ternary hybrid energy storage system of any one of claims 1 to 9.

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