Flywheel and lithium battery hybrid energy storage system

Abstract

The utility model provides a kind of flywheel and lithium battery hybrid energy storage system, including grid-connected unit, at least one energy storage unit, energy storage unit includes DC bus, at least one flywheel energy storage branch, at least one lithium battery energy storage branch, the output end of flywheel energy storage branch is connected to DC bus by DC / DC module, the output end of lithium battery energy storage branch is connected to DC bus, and grid-connected unit at least includes one grid-side converter, grid-side converter and energy storage unit one-to-one correspondence, the input end of grid-side converter is connected to the DC bus of its corresponding energy storage unit, adopts the wiring scheme of DC side coupling, the voltage regulation scheme of parallel loop is optimized, effectively solve the problem that the overall utilization of flywheel and lithium battery hybrid energy storage system equipment is not high, while optimizing and reducing equipment, it can also reduce the land area of equipment arrangement, further improve system overall utilization, reduce system investment.

Description

Technical Field

[0001] This utility model relates to the field of novel energy storage technology, and in particular to a hybrid energy storage system of flywheel and lithium battery. Background Technology

[0002] As intermittent renewable energy sources such as wind and solar power increasingly account for a larger share of the power generation structure, the diurnal fluctuations caused by these renewable energy generation methods are also increasing due to their susceptibility to weather conditions. Simultaneously, the rising proportion of residential electricity consumption is leading to more severe fluctuations in grid load. To address these challenges, the grid's regulation capabilities need to be strengthened to adapt to increasingly complex supply and demand fluctuations in the future. Energy storage technology, with its rapid regulation speed and flexible configuration, can meet this need and effectively address the challenges of grid regulation.

[0003] Among various forms of new energy storage systems, lithium iron phosphate batteries and lead-acid batteries have high energy density, long charge-discharge duration, and fewer cycle times; while supercapacitors and flywheel energy storage have lower energy density, shorter charge-discharge duration, and more cycle times. To increase the overall lifespan and improve the economics of energy storage systems, hybrid energy storage systems of two types are typically constructed in engineering projects. Flywheel energy storage is used in scenarios with frequent short-term fluctuations, while lithium iron phosphate energy storage is used in scenarios with large long-term energy demands. Both types of energy storage devices are independently boosted to 35kV by converters, and then converged at the 35kV busbar of the substation for further boosting before being connected to the grid (e.g., ...). Figure 2 (as described).

[0004] However, due to the short charging and discharging time of flywheel energy storage devices, which typically operate for only 30 seconds to 3 minutes, most of the power exchange components of flywheel energy storage devices, except for the rotating parts, are in a hot standby state most of the time. As a result, the overall utilization rate of flywheel and lithium battery hybrid energy storage systems is not high, and the economic benefits are poor. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flywheel and lithium battery hybrid energy storage system that can solve the problems of low grid-connected power equipment utilization and poor overall economic benefits caused by short-term operation of the flywheel energy storage system in the flywheel and lithium battery hybrid energy storage system.

[0006] Therefore, the present invention adopts the following technical solution: A flywheel and lithium battery hybrid energy storage system includes a grid-connected unit and at least one energy storage unit. The energy storage unit includes a DC bus, at least one flywheel energy storage branch, and at least one lithium battery energy storage branch. The output of the flywheel energy storage branch is connected to the DC bus via a DC / DC module, and the output of the lithium battery energy storage branch is also connected to the DC bus. The grid-connected unit includes at least one grid-side converter, which corresponds one-to-one with each energy storage unit. The input of each grid-side converter is connected to the DC bus of its corresponding energy storage unit.

[0007] Based on the above technical solutions, the present invention may also adopt the following further technical solutions, or combine these further technical solutions: The flywheel energy storage branch includes a flywheel body and a flywheel-side converter connected in sequence, and the output terminal of the flywheel-side converter is connected to the input terminal of the DC / DC module.

[0008] The lithium battery energy storage branch includes a lithium battery, and the output terminal of the lithium battery is directly connected to the DC bus.

[0009] The grid-connected unit also includes a low-voltage AC busbar, a low-voltage circuit breaker, a step-up transformer, a medium-voltage circuit breaker, and a medium-voltage AC collection busbar connected in sequence, wherein the medium-voltage AC collection busbar is connected to the high-voltage power grid.

[0010] The output terminal of the grid-side converter is connected to the low-voltage AC bus.

[0011] The total power of the flywheel-side converters connected to the same DC bus is matched with the total power of the lithium battery.

[0012] Compared with the prior art, this utility model has the following advantages and beneficial effects: it adopts a DC-side coupling wiring scheme, optimizes the voltage regulation scheme of the parallel circuit, effectively solves the problem of low overall equipment utilization rate of the flywheel and lithium battery hybrid energy storage system, optimizes and reduces equipment while reducing the land area for equipment layout, further improves the overall system utilization rate and reduces system investment. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the present invention.

[0014] Figure 2 This is a wiring diagram of an existing project's flywheel and lithium battery hybrid energy storage system. Detailed Implementation

[0015] To enable those skilled in the art to better understand the technical solution of this utility model, the preferred embodiments of this utility model are described below in conjunction with specific examples. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote elements with the same or similar functions throughout. However, it should be understood that the drawings are for illustrative purposes only and should not be construed as limiting this utility model. To better illustrate this embodiment, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product size. It is understandable for those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting this utility model.

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0017] This utility model provides a flywheel and lithium battery hybrid energy storage system, including a grid-connected unit and at least one energy storage unit. The energy storage unit includes a DC bus 4, at least one flywheel energy storage branch, and at least one lithium battery energy storage branch. The output end of the flywheel energy storage branch is connected to the DC bus 4 through a DC / DC module 3, and the output end of the lithium battery energy storage branch is connected to the DC bus 4. The grid-connected unit includes at least one grid-side converter 6, and the grid-side converter 6 corresponds one-to-one with the energy storage unit. The input end of the grid-side converter 6 is connected to the DC bus 4 of its corresponding energy storage unit.

[0018] The grid-side converter 6 is used to convert DC voltage into a stable AC power supply.

[0019] The flywheel energy storage branch includes a flywheel body 1 and a flywheel-side converter 2 connected in sequence. The output terminal of the flywheel-side converter 2 is connected to the input terminal of the DC / DC module 3.

[0020] In this embodiment, the flywheel body 1 is connected to the flywheel machine-side converter 2 to realize the conversion of mechanical energy into AC power, and then the AC power is converted into DC power; the DC / DC module 3 realizes the voltage regulation function. The flywheel body 1 contains a built-in motor, which functions as both a motor and a generator. During charging, it acts as a motor to accelerate the flywheel; during discharging, it acts as a generator to supply power to external devices, at which point the flywheel's speed continuously decreases; and when the flywheel is idle, the entire device operates with minimal losses. Different speed states of the flywheel body result in different input and output power and voltage. DC / DC module 3 is a device that converts voltage or current through switching, used in DC circuits to convert electrical energy of one voltage value to another.

[0021] The lithium battery energy storage branch includes lithium battery 5, and the output of lithium battery 5 is directly connected to DC bus 4.

[0022] In this embodiment, the lithium battery 5 is composed of multiple cells connected in series and parallel. During charging, electrical energy is converted into chemical energy; during discharging, chemical energy is converted into electrical energy. Different states of charge of the cells will result in different input and output DC voltages.

[0023] The grid-connected unit also includes a low-voltage AC busbar 7, a low-voltage circuit breaker 8, a step-up transformer 9, a medium-voltage circuit breaker 10, and a medium-voltage AC collection busbar 11 connected in sequence. The medium-voltage AC collection busbar 11 is connected to the high-voltage power grid to further boost the voltage.

[0024] The output of the grid-side converter 6 is connected to the low-voltage AC bus 7 to realize energy collection between different groups of mixed energy storage rooms.

[0025] The total power of the flywheel-side converter 2, which is connected to the same DC bus 4, is matched with the total power of the lithium battery 5.

[0026] In the aforementioned flywheel and lithium battery hybrid energy storage system, the N energy storage branches connected to the DC bus should be based on the voltage of one of the energy storage branches, and DC / DC modules should be configured on the remaining N-1 energy storage branches to ensure that the voltage of all energy storage branches connected to the DC bus is consistent. In particular, due to the operating losses of the DC / DC module, in the aforementioned flywheel and lithium battery hybrid energy storage system, energy storage branches with shorter operating times and lower energy density are selected, i.e., DC / DC modules are configured on the flywheel branches to improve the overall conversion efficiency of the hybrid energy storage system.

[0027] The aforementioned flywheel and lithium battery hybrid energy storage system shares the same grid-side converter, low-voltage AC bus, low-voltage circuit breaker, step-up transformer, and medium-voltage circuit breaker. Although the flywheel and lithium battery operate at different times, to ensure the reliable operation of the shared equipment, the total power of the flywheel equipment branch should be equivalent to the total power of the lithium battery equipment branch.

[0028] The aforementioned flywheel and lithium battery hybrid energy storage system, compared to existing flywheel and lithium battery hybrid energy storage systems, eliminates the need for two grid-side converters, one low-voltage circuit breaker, one step-up transformer, and one medium-voltage circuit breaker, which require less time to operate.

[0029] This embodiment provides a wiring scheme using DC-side coupling. By adding a DC / DC converter, the voltage of different energy storage devices is made consistent. Then, the flywheel and lithium battery devices are matched in terms of power. Finally, the two types of energy storage share a set of converter and boost equipment, thereby improving the overall utilization rate of the hybrid energy storage system and reducing system investment.

[0030] like Figure 2 As shown, in the existing flywheel and lithium battery hybrid energy storage system, the flywheel energy storage system consists of a flywheel body 1, a flywheel-side converter 2, a grid-side converter 6, a low-voltage AC bus 7, a low-voltage circuit breaker 8, a step-up transformer 9, a medium-voltage circuit breaker 10, and a medium-voltage AC busbar 11; the lithium battery energy storage system consists of a lithium battery 5, a grid-side converter 6, a low-voltage AC busbar 7, a low-voltage circuit breaker 8, a step-up transformer 9, a medium-voltage circuit breaker 10, and a medium-voltage AC busbar 11; there is no direct electrical connection between the two systems below the medium-voltage AC busbar 11.

[0031] like Figure 2 As shown, in the existing flywheel and lithium battery hybrid energy storage system, the flywheel body 1 in the flywheel energy storage system is a 1MW / 45kWh device. The flywheel-side converter 2 is a 1MW device. The grid-side converter 6 is a 2000kW 1000-1500V / 0.69kV converter. The low-voltage AC busbar 7 is a 3*2*TMY-140*12 copper busbar. The low-voltage circuit breaker 8 is a 3P5000AAC690 frame circuit breaker. The step-up transformer 9 is an SCB13-4000 / 3737±2*2.5% / 0.69kV dry-type transformer. The medium-voltage circuit breaker 10 is a 40.5kV / 630A-31.5kA vacuum circuit breaker. The medium-voltage AC collection busbar 11 is a 3*TMY-50*5 copper busbar. The flywheel body 1 and the flywheel-side converter 2 are directly connected in a one-to-one manner. The flywheel-side converter 2 and the grid-side converter 6 are connected in a two-to-one manner. The grid-side converter 6 and the low-voltage AC bus 7 are connected in a two-to-one manner. The low-voltage AC bus 7, the low-voltage circuit breaker 8, the step-up transformer 9, and the medium-voltage circuit breaker 10 are directly connected in a one-to-one manner in sequence. The flywheel energy storage system and the lithium battery energy storage system are connected at the medium-voltage AC bus 11.

[0032] like Figure 2As shown, in the existing flywheel and lithium battery hybrid energy storage system, lithium battery 5 in the lithium battery energy storage system uses a single 3.2V 280Ah cell. 416 cells are connected in series to form a 1331.2V 280Ah battery cluster. Every 5 battery clusters are then connected in parallel, ultimately forming a 1331.2V 1863.68kW 1863.68kWh battery stack. The grid-side converter 6 is a 2000kW 1000-1500V / 0.69kV converter. The low-voltage AC bus 7 is a 3*2*TMY-140*12 copper busbar. The low-voltage circuit breaker 8 is a 3P5000AAC690 frame circuit breaker, and the step-up transformer 9 is an SCB13-4000 / 3737±2*2.5% / 0.69kV dry-type transformer. Medium-voltage circuit breaker 10 is a 40.5kV / 630A-31.5kA vacuum circuit breaker. Medium-voltage AC busbar 11 is a 3*TMY-50*5 copper busbar. Lithium battery 5 and grid-side converter 6 adopt a one-to-one connection method, and grid-side converter 6 and low-voltage AC busbar 7 adopt a two-to-one connection method. Low-voltage AC busbar 7, low-voltage circuit breaker 8, step-up transformer 9, and medium-voltage circuit breaker 10 are directly connected one-to-one in sequence. The lithium battery energy storage system and flywheel energy storage system are connected at medium-voltage AC busbar 11.

[0033] like Figure 1 As shown, in this embodiment, the DC / DC module 3 is a 500-1500V 1000kW DC-DC converter, and the DC bus 4 is a 2*TMY-100*10 copper bus. The flywheel body 1, flywheel-side converter 2, lithium battery 5, grid-side converter 6, low-voltage AC bus 7, low-voltage circuit breaker 8, step-up transformer 9, medium-voltage circuit breaker 10, and medium-voltage AC collection bus 11 are consistent with the selection parameters of the existing flywheel and lithium battery hybrid energy storage system. The flywheel body 1 and the flywheel-side converter 2 are connected in a one-to-one direct wiring manner. The flywheel-side converter 2 and the DC / DC module 3 are connected in a one-to-one direct wiring manner. The two sets of DC / DC modules 3 and one set of lithium batteries 5 are connected in a three-to-one combined wiring manner. The DC bus 4 and the grid-side converter 6 are connected in a one-to-one wiring manner. The grid-side converter 6 and the low-voltage AC bus 7 are connected in a two-to-one combined wiring manner. The low-voltage AC bus 7, the low-voltage circuit breaker 8, the step-up transformer 9, and the medium-voltage circuit breaker 10 are connected in a one-to-one direct wiring manner in sequence.

[0034] like Figure 1As shown, in this embodiment, under short-term, frequent frequency fluctuations, electrical energy flows sequentially through the flywheel body 1, flywheel-side converter 2, DC / DC module 3, DC bus 4, grid-side converter 6, low-voltage AC bus 7, low-voltage circuit breaker 8, step-up transformer 9, medium-voltage circuit breaker 10, and medium-voltage AC collecting bus 11 until it reaches the high-voltage grid. This scenario lasts from 30 seconds to 3 minutes. Under long-term, high-energy peak-shaving scenarios, electrical energy flows sequentially through the lithium battery 5, DC bus 4, grid-side converter 6, low-voltage AC bus 7, low-voltage circuit breaker 8, step-up transformer 9, medium-voltage circuit breaker 10, and medium-voltage AC collecting bus 11 until it reaches the high-voltage grid. The flywheel and lithium battery hybrid energy storage system switches between the two operating modes according to grid dispatch requirements. Under the two different operating modes, DC bus 4, grid-side converter 6, low-voltage AC bus 7, low-voltage circuit breaker 8, step-up transformer 9, medium-voltage circuit breaker 10, and medium-voltage AC collection bus 11 are shared equipment.

[0035] like Figure 1 As shown, in this embodiment, by optimizing the wiring of the lithium battery energy storage system and the flywheel energy storage system through DC coupling and power coordination of the flywheel and lithium battery equipment, the following savings are achieved: two 2000kW 1000-1500V / 0.69kV grid-side converters 6, one 3P5000AAC690 low-voltage circuit breaker 8, one SCB13-4000 / 3737±2*2.5% / 0.69kV step-up transformer 9, and one 40.5kV / 630A-31.5kA medium-voltage circuit breaker 10. This embodiment optimizes the configuration and reuses equipment while reducing the overall equipment footprint, effectively lowering system investment.

[0036] Based on the description and accompanying drawings of this utility model, those skilled in the art can easily manufacture or use the flywheel and lithium battery hybrid energy storage system of this utility model, and can produce the positive effects described in this utility model.

[0037] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this utility model are intended to cover non-exclusive inclusion. The terms "installed," "set," "equipped with," "connected," "connected," and "sleeve-in" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two mechanisms, elements, or components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0038] In the description of this utility model, it should be understood that the terms "one end," "the other end," "outer side," "inner side," "horizontal," "end," "length," "outer end," "left," and "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the mechanism or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. The terms "first" and "second" are also used only for the sake of brevity in description and do not indicate or imply relative importance.

[0039] Furthermore, in practicing the claims of this utility model, those skilled in the art can understand and influence variations to the disclosed embodiments through a study of the drawings, the disclosure, and the appended claims. Additionally, in the claims and description, words such as "comprising" and "containing" do not exclude other elements or steps, and non-plural nouns do not exclude their plural forms.

[0040] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the scope of the present utility model. All equivalent changes and modifications made in accordance with the present utility model are covered by the scope of the claims of the present utility model, and will not be listed here.

Claims

1. A hybrid energy storage system combining a flywheel and a lithium battery, characterized in that, The system includes a grid-connected unit and at least one energy storage unit. The energy storage unit includes a DC bus (4), at least one flywheel energy storage branch, and at least one lithium battery energy storage branch. The output end of the flywheel energy storage branch is connected to the DC bus (4) through a DC / DC module (3). The output end of the lithium battery energy storage branch is connected to the DC bus (4). The grid-connected unit includes at least one grid-side converter (6). The grid-side converter (6) corresponds to the energy storage unit one by one. The input end of the grid-side converter (6) is connected to the DC bus (4) of the corresponding energy storage unit.

2. The flywheel and lithium battery hybrid energy storage system as described in claim 1, characterized in that, The flywheel energy storage branch includes a flywheel body (1) and a flywheel-side converter (2) connected in sequence. The output end of the flywheel-side converter (2) is connected to the input end of the DC / DC module (3).

3. The flywheel and lithium battery hybrid energy storage system as described in claim 2, characterized in that, The lithium battery energy storage branch includes a lithium battery (5), and the output end of the lithium battery (5) is directly connected to the DC bus (4).

4. The flywheel and lithium battery hybrid energy storage system as described in claim 1, characterized in that, The grid-connected unit also includes a low-voltage AC busbar (7), a low-voltage circuit breaker (8), a step-up transformer (9), a medium-voltage circuit breaker (10), and a medium-voltage AC collection busbar (11) connected in sequence. The medium-voltage AC collection busbar (11) is connected to the high-voltage power grid.

5. The flywheel and lithium battery hybrid energy storage system as described in claim 4, characterized in that, The output terminal of the grid-side converter (6) is connected to the low-voltage AC bus (7).

6. The flywheel and lithium battery hybrid energy storage system as described in claim 3, characterized in that, The total power of the flywheel-side converter (2) connected to the same DC bus (4) is matched with the total power of the lithium battery (5).

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