A distributed electrical energy storage system and hybrid energy storage system

Abstract

This application provides a distributed energy storage system and a hybrid energy storage system, belonging to the field of energy storage technology. The distributed energy storage system includes an energy storage converter, a first controller, a second controller, and an energy storage module. The energy storage module is connected to the DC side of the energy storage converter, and the AC side of the energy storage converter is used to connect to an AC load. The first controller and the second controller are communicatively connected. The first controller is configured to control the energy storage converter, and the second controller is configured to control the energy storage module. This application separates the energy storage converter and the energy storage module, facilitating modular design and flexible expansion of the distributed energy storage system. Furthermore, the energy storage converter is located close to the AC load, reducing AC line losses and voltage drop, and enabling precise control of the AC load. The energy storage module can be placed outdoors or in other safe environments, avoiding the influence of the AC load's environment on the energy storage module and ensuring the safety of the distributed energy storage system.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a distributed energy storage system and a hybrid energy storage system. Background Technology

[0002] A power conversion system (PCS) converts direct current (DC) supplied by a battery into alternating current (AC) to power AC loads. Some AC loads have high requirements for the AC power converted by the PCS; for example, the AC voltage needs to be very close to a certain value. However, since the PCS is usually integrated with the battery in a prefabricated compartment, and the location and environment of the compartment meet certain safety requirements, when the AC load is in an environment that does not meet the safety standards of electrochemical energy storage systems, the spatial and electrical distance between the PCS and the AC load increases. This makes it difficult for the PCS to accurately control the voltage at the AC load terminals, thus hindering its ability to precisely control the AC load voltage. Summary of the Invention

[0003] This application provides a distributed energy storage system and a hybrid energy storage system for providing accurate voltage to AC loads.

[0004] To achieve the above objectives, the embodiments of this application adopt the following technical solutions: In a first aspect, a distributed energy storage system is provided. This distributed energy storage system includes an energy storage converter, a first controller, a second controller, and an energy storage module. The energy storage module is connected to the DC side of the energy storage converter, and the AC side of the energy storage converter is used to connect to an AC load. The energy storage converter is located close to the AC load, and the distance between the energy storage converter and the AC load is less than the distance between the energy storage converter and the energy storage module. The first controller is communicatively connected to the second controller, and the first controller is also connected to the energy storage converter and configured to control the energy storage converter; the second controller is also connected to the energy storage module and configured to control the energy storage module.

[0005] This embodiment separates the energy storage converter from the energy storage module, and establishes distributed control by having a first controller controlling the energy storage converter communicate with a second controller controlling the energy storage module. This facilitates modular design, flexible expansion, and improved reliability of the distributed energy storage system. Furthermore, the energy storage converter's proximity to the AC load shortens the AC line length, reduces AC line losses and voltage drop, and facilitates precise control of the AC load voltage. Simultaneously, the greater distance between the energy storage converter and the energy storage module allows the energy storage module to be placed in safer environments such as outdoors, avoiding the influence of the AC load's environment on the energy storage module and ensuring the safety of the distributed energy storage system.

[0006] In some possible implementations, the AC load includes a synchronous motor to be connected to the grid, and the first controller is specifically configured to control the energy storage converter to convert the DC power provided by the energy storage module into AC power, which is used to start the synchronous motor or connect to the grid.

[0007] The embodiment of this application utilizes an energy storage converter to drive the synchronous motor for starting, which can smoothly facilitate the starting and stopping process of the synchronous motor. Furthermore, the energy storage converter is located close to the synchronous motor, with a short electrical distance between them, enabling precise control of the synchronous motor. This allows the terminal voltage of the synchronous motor to closely approximate the grid voltage at the moment of grid connection, thereby ensuring that the starting of the synchronous motor has almost zero impact on the grid and guaranteeing the stability of grid operation.

[0008] In some possible implementations, the distributed energy storage system also includes a DC bus that is connected to the DC side of the energy storage converter and the energy storage modules.

[0009] In the embodiments of this application, the DC bus centrally connects the energy storage module and the energy storage converter, which facilitates the parallel connection or expansion of the distributed energy storage system and improves the system integration and maintainability.

[0010] In some possible implementations, the first controller is further configured to: control the energy storage converter to maintain voltage stability on the DC bus and send a first command to the second controller. The second controller is configured to: control the energy storage module to output a fixed current to the DC bus in response to the first command.

[0011] The embodiments of this application employ a voltage source. The current source coordinated control system employs a first controller as the main controller, which controls the energy storage converter to stabilize the voltage on the DC bus, exhibiting voltage source characteristics. A second controller, acting as a co-controller, responds to the first command sent by the first controller and controls the energy storage module to output a certain current, exhibiting current source characteristics. This avoids parallel connection of voltage sources or series connection of current sources, achieving stable power distribution and ensuring the operational reliability of the distributed energy storage system.

[0012] In some possible implementations, the first controller is further configured to: control the energy storage converter to draw a certain current from the DC bus and send a second command to the second controller. The second controller is configured to: control the energy storage module to maintain voltage stability on the DC bus in response to the second command.

[0013] In this embodiment, the first controller acts as the main controller, controlling the energy storage converter to absorb a certain current from the DC bus as a current source, exhibiting current source characteristics. The second controller acts as a co-controller, responding to a second command sent by the first controller to control the energy storage module to act as a voltage source to stabilize the voltage on the DC bus, exhibiting voltage source characteristics. This avoids parallel connection of voltage sources or series connection of current sources, achieving stable power distribution and ensuring the operational reliability of the distributed energy storage system.

[0014] In some possible implementations, the second controller is configured to control the energy storage module to maintain voltage stability on the DC bus and send a third command to the first controller. The first controller is also configured to control the energy storage converter to draw a fixed current from the DC bus in response to the third command.

[0015] In this embodiment, the second controller acts as the main controller, controlling the energy storage module as a voltage source to stabilize the voltage on the DC bus. The first controller acts as a co-controller, responding to a third command sent by the second controller to control the energy storage converter as a current source to absorb a fixed current from the DC bus. This avoids parallel connection of voltage sources or series connection of current sources, achieving stable power distribution and ensuring the operational reliability of the distributed energy storage system.

[0016] In some possible implementations, the second controller is configured to control the energy storage module to output a fixed current to the DC bus and send a fourth command to the first controller. The first controller is also configured to, in response to the fourth command, control the energy storage converter to maintain voltage stability on the DC bus.

[0017] In this embodiment, the second controller acts as the main controller, controlling the energy storage module to output a fixed current as a current source. The first controller acts as a co-controller, responding to a fourth command sent by the second controller to control the energy storage converter to act as a voltage source to stabilize the voltage on the DC bus. This avoids parallel connection of voltage sources or series connection of current sources, achieving stable power distribution and ensuring the operational reliability of the distributed energy storage system.

[0018] In some possible implementations, the energy storage module includes a battery cluster and a bidirectional DC-DC converter, the battery cluster being connected to a DC bus via the bidirectional DC-DC converter, and a second controller being connected to the bidirectional DC-DC converter and configured to control the bidirectional DC-DC converter.

[0019] In this embodiment, the energy storage module uses a battery cluster connected in series with a bidirectional DC-DC converter connected to the DC bus, and the converter is controlled by a second controller. This achieves voltage matching, precise current control, and electrical isolation between the battery side and the bus side, optimizes battery charging and discharging management, and improves safety, efficiency, and battery life.

[0020] Secondly, a hybrid energy storage system is provided. This hybrid energy storage system includes a physical energy storage system and the distributed electric energy storage system described in the first aspect above. The physical energy storage system includes a synchronous motor, and the distributed electric energy storage system is connected to the synchronous motor.

[0021] In some possible implementations, physical energy storage systems include pumped hydro storage systems, compressed air storage systems, flywheel energy storage systems, gravity energy storage systems, and liquid air energy storage systems.

[0022] It should be understood that the technical effects of the second aspect can be referred to the technical effects of the first aspect and any of its embodiments, and will not be repeated here. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a hybrid energy storage system provided in an embodiment of this application; Figure 2 A schematic diagram of the structure of the hybrid energy storage system and its included distributed energy storage system provided in the embodiments of this application; Figure 3 This is a schematic diagram of a first control flow for the first controller and the second controller in a distributed energy storage system provided in an embodiment of this application; Figure 4 This is a schematic diagram of a second control flow for the first controller and the second controller in a distributed energy storage system provided in an embodiment of this application; Figure 5 A schematic diagram of a third control flow for the first controller and the second controller in a distributed energy storage system provided in an embodiment of this application; Figure 6 This is a schematic diagram of a fourth control flow for the first controller and the second controller in a distributed energy storage system provided in an embodiment of this application.

[0024] Reference numerals: 100, Hybrid energy storage system; 110, Physical energy storage system; 111, Synchronous motor; 120, Distributed energy storage system; 130, AC bus; 140, Outgoing circuit breaker; 210, Energy storage converter; 220, First controller; 230, Second controller; 240, Energy storage module; 241, Battery cluster; 242, Bidirectional DC-DC converter; 250, DC bus. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0026] The terms "first" and "second" used in the embodiments of this application are only used to distinguish features of the same type and should not be construed as indicating relative importance, quantity, order, etc.

[0027] The terms "exemplary" or "for example" used in the embodiments of this application are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0028] The terms "coupling" and "connection" used in the embodiments of this application should be interpreted broadly. For example, they can refer to a physical direct connection or an indirect connection achieved through electronic devices, such as a connection achieved through resistors, inductors, capacitors or other electronic devices.

[0029] An electric power system is an electrical energy production and consumption system consisting of power generation, transmission, transformation, distribution, and consumption. It is used to convert primary energy from nature into electrical energy through power generation devices (such as hydropower, thermal power, nuclear power, wind power, and solar power generation devices), and then supply the electrical energy to various users through transmission, transformation, and distribution.

[0030] The most fundamental characteristic of a power system is its time-balanced nature, which means that at any given moment, the total power output of generators in the power grid is always equal to the total power consumed by all loads, plus losses during transmission. However, with the development of the new energy industry, the inherent randomness, intermittency, and volatility of new energy sources such as wind power and photovoltaics make it impossible for them to output power as stably as traditional thermal power. Large-scale grid connection poses a severe challenge to power grid security.

[0031] An energy storage power station is a device system that uses electrochemical cells or physical energy storage media to store, convert, and release cyclical electrical energy. It absorbs and stores electricity from the grid during off-peak hours and releases the stored electricity stably during peak hours (i.e., peak shaving and valley filling) to ensure a real-time balance between power supply and demand.

[0032] like Figure 1 As shown, this application provides a hybrid energy storage system 100, which includes a physical energy storage system 110 and a distributed energy storage system 120. The physical energy storage system 110 and the distributed energy storage system 120 are connected through an AC bus 130, which is also connected to the power grid through an output circuit breaker 140.

[0033] The physical energy storage system 110 includes a synchronous motor (SM). In some examples, the physical energy storage system 110 includes a pumped hydro storage system, a compressed air storage system, a flywheel energy storage system, a gravity energy storage system, and a liquid air energy storage system. The physical energy storage system 110 can drive the synchronous motor rotor to rotate through means such as water flow impact, air pressure, flywheel inertia, the gravity of a heavy object, or the expansion of liquid air. As long as the synchronous motor rotor runs at a constant speed, it can output AC power of a constant frequency without the need for an additional converter.

[0034] For example, taking a pumped-storage system as an example, the synchronous motor in the system can be used for both pumping water and generating electricity. For instance, during off-peak electricity demand, the synchronous motor acts as a motor, absorbing excess electrical energy from the grid and converting it into mechanical energy to drive a turbine. This pumps water from a low level to a higher level and injects it into a reservoir, thus storing excess electrical energy in the reservoir as potential energy of the water. During peak electricity demand, the synchronous motor acts as a generator. When water is released from the reservoir, the water's potential energy impacts the turbine, causing it to rotate. The turbine then drives the synchronous motor's rotor, which in turn cuts the stator's magnetic field, converting mechanical energy into electrical energy to be transmitted to the grid.

[0035] Due to its inherent structure, a synchronous motor has a constant relationship between the rotor speed and the frequency of the mains voltage during steady-state operation: n = 60f / p; where f is the frequency of the mains voltage (e.g., 50Hz), p is the number of pole pairs of the synchronous motor, and n is the rotor speed (also known as the synchronous speed).

[0036] When a synchronous motor is used as an electric motor, and three-phase alternating current is applied to its stator windings, the stator immediately generates a rotating magnetic field at synchronous speed. However, at this time, the rotor has stationary fixed magnetic poles. From the rotor's perspective, the rotating magnetic field generated by the stator is passing over it at an extremely high speed (synchronous speed). Due to the rotor's large mechanical inertia, it cannot respond to this alternating force in a very short time. During a complete alternating cycle, the average electromagnetic torque on the rotor is zero, and the rotor will only vibrate violently and cannot continuously accelerate in any direction. Therefore, a synchronous motor cannot be started directly when used as an electric motor.

[0037] Therefore, this application provides a distributed energy storage system 120, which is connected to the synchronous motor 111 in the physical energy storage system 110. For example... Figure 2 As shown, the distributed energy storage system 120 includes an energy storage converter 210, a first controller 220, a second controller 230, and an energy storage module 240.

[0038] Energy storage module 240 is connected to the DC side of energy storage converter 210 via DC bus 250. The AC side of energy storage converter 210 is used to connect AC loads (i.e., synchronous motors 111) via AC bus 130. In other words, DC bus 250 is connected to both the DC side of energy storage converter 210 and energy storage module 240, while AC bus 130 is connected to both the AC side of energy storage converter 210 and synchronous motors 111. The centralized connection of energy storage module 240 and energy storage converter 210 via DC bus 250 facilitates the parallel connection or expansion of distributed energy storage system 120, improving system integration and maintainability. AC bus 130 enables distributed energy storage system 120 to supply power to more synchronous motors 111, facilitating the parallel connection or expansion of hybrid energy storage system 100.

[0039] The first controller 220 is also connected to the energy storage converter 210 and is used to control the energy storage converter 210. The first controller 220 may include a field-programmable gate array (FPGA) or a microcontroller unit (MCU) or other device with logic processing and control functions. In some embodiments, the first controller 220 can control the energy storage converter 210 to convert the DC power provided by the energy storage module 240 into AC power to supply AC loads, which may be AC ​​synchronous generators / motors. For example, when the output circuit breaker 140 is open, the energy storage converter 210 can invert (i.e., DC to AC) the DC power provided by the energy storage module 240 into AC power with a continuously adjustable frequency starting from zero, supplying it to the stator windings of the synchronous motor 111. Since the frequency of the AC power starts from zero, the rotational speed of the rotating magnetic field increases slowly from zero, thereby driving the rotor of the synchronous motor 111 to start and smoothly accelerate. When the terminal voltage of the synchronous motor 111 meets the requirements, the output circuit breaker 140 closes, thereby connecting the synchronous motor 111 into the power grid to absorb excess electrical energy in the power grid.

[0040] In this embodiment, the energy storage converter 210 is positioned close to the AC load (i.e., the synchronous motor 111). The short electrical distance between the energy storage converter 210 and the synchronous motor 111 allows for precise control of the synchronous motor 111, ensuring that the terminal voltage of the synchronous motor 111 is very close to the grid voltage at the moment of grid connection. This results in almost zero impact of the synchronous motor 111 on the grid, thus ensuring the stability of the grid operation.

[0041] In other embodiments, after the output circuit breaker 140 is closed, the first controller 220 can also control the energy storage converter 210 to convert the AC power from the grid into DC power to supply power to the energy storage module 240.

[0042] The second controller 230 is also connected to the energy storage module 240 and is used to control the energy storage module 240. The first controller 220 may also include devices with logic processing and control functions, such as a field-programmable gate array (FPGA) or a microcontroller. In some embodiments, the energy storage module 240 includes a battery cluster 241 and a bidirectional DC-DC converter 242, with the battery cluster 241 connected to the DC bus 250 via the bidirectional DC-DC converter 242. The second controller 230 is connected to the bidirectional DC-DC converter 242 and is used to control the bidirectional DC-DC converter 242. The bidirectional DC-DC converter 242 can respond to the second controller 230 to achieve DC voltage rise / fall and DC output or input current control, thereby achieving voltage matching, precise current control, and electrical isolation between the battery side and the bus side, optimizing battery charging and discharging management, and improving safety, efficiency, and battery life.

[0043] In some examples, the DC bus 250 can be implemented using cables, which offer high insulation strength and are easy to lay. The battery cluster 241 is placed in a safe environment, such as outdoors, isolated from the installation environment of the synchronous motor 111 (e.g., a damp dam or mountain interior), thus ensuring the safety of the distributed energy storage system 120. That is, the distance between the energy storage converter 210 and the AC load is less than the distance between the energy storage converter 210 and the energy storage module 240. The line impedance mainly occurs between the energy storage converter 210 and the energy storage module. Since the energy storage converter 210 is located close to the synchronous motor 111, the line impedance between the energy storage converter 210 and the synchronous motor 111 can be ignored.

[0044] The first controller 220 and the second controller 230 are communicatively connected. This communication connection can be wireless or cable-based (including fiber optic or signal cable) communication. Figure 3 As shown, in some embodiments, the first controller 220 can act as a main controller, monitoring the voltage on the DC bus 250, controlling the energy storage converter 210 to stabilize the voltage on the DC bus 250, and sending a first command to the second controller 230. The second controller 230 acts as a co-controller, responding to the first command sent by the first controller 220, and controlling the energy storage module 240 to output a fixed current to the DC bus 250.

[0045] For example, the second controller 230 can disregard the voltage on the DC bus 250, focusing solely on precisely controlling the current output from the energy storage module 240 to the DC bus 250 according to the first instruction. The first controller 220, however, monitors the voltage on the DC bus 250. When the voltage rises, the first controller 220 controls the energy storage converter 210 to draw more current from the DC bus 250; conversely, when the voltage drops, the first controller 220 controls the energy storage converter 210 to reduce the current drawn from the DC bus 250. This achieves a balance, stabilizing the voltage on the DC bus 250 at a set value. Furthermore, since the energy storage converter 210 acts as a voltage source and the energy storage module 240 as a current source, parallel connection of voltage sources or series connection of current sources is avoided, ensuring the operational reliability of the distributed energy storage system 120.

[0046] like Figure 4 As shown, in some other embodiments, the first controller 220 acts as the main controller, controlling the energy storage converter 210 to absorb a fixed current from the DC bus 250 and sending a second command to the second controller 230. The second controller 230 acts as a co-controller, responding to the second command sent by the first controller 220, controlling the energy storage module 240 to stabilize the voltage on the DC bus 250.

[0047] For example, the first controller 220 can control the energy storage converter 210 to draw current from the DC bus 250 as needed (e.g., the torque required to drive the synchronous motor 111). The second controller 230 monitors the voltage on the DC bus 250 and automatically controls the energy storage module 240 to provide corresponding current to maintain voltage stability on the DC bus 250, regardless of changes in the current drawn from the DC bus 250 by the energy storage converter 210.

[0048] like Figure 5 As shown, in some other embodiments, the second controller 230 can also act as the main controller, controlling the energy storage module 240 as a voltage source to stabilize the voltage on the DC bus 250, and sending a third command to the first controller 220. The first controller 220 acts as a co-controller, responding to the third command sent by the second controller 230, controlling the energy storage converter 210 as a current source to absorb a fixed current from the DC bus 250.

[0049] like Figure 6 As shown, in other embodiments, the second controller 230 can also act as the main controller, controlling the energy storage module 240 as a current source to output a fixed current to the DC bus 250, and sending a fourth command to the first controller 220. The first controller 220 acts as a co-controller, responding to the fourth command sent by the second controller 230, controlling the energy storage converter 210 as a voltage source to stabilize the voltage on the DC bus 250.

[0050] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the descriptions of each implementation method in the above embodiments have different focuses. For any part not described in detail in a certain implementation method, please refer to the corresponding process in the aforementioned implementation methods, which will not be repeated here.

[0051] This application provides a distributed energy storage system and a hybrid energy storage system. The distributed energy storage system 120 separates the energy storage converter 210 from the energy storage module 240. A first controller 220 controlling the energy storage converter 210 communicates with a second controller 230 controlling the energy storage module 240, achieving distributed control. This facilitates modular design, flexible expansion, and improved reliability of the distributed energy storage system 120. Furthermore, the energy storage converter 210 is positioned close to the AC load, shortening the AC line length, reducing AC line losses and voltage drop, and facilitating precise control of the AC load. Simultaneously, the greater distance between the energy storage converter 210 and the energy storage module 240 allows the energy storage module 240 to be placed in safer environments such as outdoors, avoiding the influence of the AC load's environment on the energy storage module 240 and ensuring the safety of the distributed energy storage system 120.

[0052] In the embodiments provided in this application, it should be understood that the disclosed distributed energy storage system and hybrid energy storage system can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or modules may be electrical, mechanical, or other forms.

[0053] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located on one device or distributed across multiple devices. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0054] In addition, the functional modules in the various embodiments of this application can be integrated into one device, or each module can exist physically separately, or two or more modules can be integrated into one device.

[0055] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A distributed electrical energy storage system, characterized by, It includes an energy storage converter, a first controller, a second controller, and an energy storage module; among which, The energy storage module is connected to the DC side of the energy storage converter, and the AC side of the energy storage converter is used to connect to the AC load. The energy storage converter is located close to the AC load, and the distance between the energy storage converter and the AC load is less than the distance between the energy storage converter and the energy storage module. The first controller is communicatively connected to the second controller, and the first controller is also connected to the energy storage converter and configured to control the energy storage converter; the second controller is also connected to the energy storage module and configured to control the energy storage module.

2. The distributed energy storage system according to claim 1, characterized in that, The AC load includes a synchronous motor to be connected to the power grid, and the first controller is specifically configured as follows: The energy storage converter is controlled to convert the DC power provided by the energy storage module into AC power, which is used to start the synchronous motor.

3. The distributed electrical energy storage system of claim 1 or 2, wherein, It also includes a DC bus, which is connected to the DC side of the energy storage converter and the energy storage module respectively.

4. The distributed electrical energy storage system of claim 3, wherein, The first controller is further configured to: control the energy storage converter to maintain voltage stability on the DC bus, and send a first instruction to the second controller; The second controller is configured to, in response to the first instruction, control the energy storage module to output a fixed current to the DC bus.

5. The distributed electrical energy storage system of claim 3, wherein, The first controller is also configured to: control the energy storage converter to absorb a fixed current from the DC bus, and send a second command to the second controller; The second controller is configured to, in response to the second instruction, control the energy storage module to maintain voltage stability on the DC bus.

6. The distributed electrical energy storage system of claim 3, wherein, The second controller is configured to: control the energy storage module to maintain voltage stability on the DC bus, and send a third command to the first controller; The first controller is also configured to, in response to the third instruction, control the energy storage converter to draw a fixed current from the DC bus.

7. The distributed electrical energy storage system of claim 3, wherein, The second controller is configured to: control the energy storage module to output a fixed current to the DC bus, and send a fourth command to the first controller; The first controller is also configured to, in response to the fourth instruction, control the energy storage converter to maintain voltage stability on the DC bus.

8. The distributed electrical energy storage system of claim 3, wherein, The energy storage module includes a battery cluster and a bidirectional DC-DC converter. The battery cluster is connected to the DC bus through the bidirectional DC-DC converter. The second controller is connected to the bidirectional DC-DC converter and is configured to control the bidirectional DC-DC converter.

9. A hybrid energy storage system characterized by, The system includes a physical energy storage system and a distributed energy storage system as described in any one of claims 1-8, wherein the physical energy storage system includes a synchronous motor, and the distributed energy storage system is connected to the synchronous motor.

10. The hybrid energy storage system of claim 9, wherein, The physical energy storage system includes pumped hydro storage system, compressed air storage system, flywheel energy storage system, gravity energy storage system, and liquid air energy storage system.

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