An automatically switched energy storage cabinet off-grid system

Abstract

The utility model discloses an automatic switching's energy storage cabinet is from the grid connected system, including battery loop, load loop and net side loop, battery loop includes the battery group of series connection, energy storage converter PCS and first circuit breaker QS1, and the net side loop includes the switching switch loop of series connection, current transformer and first lightning protection circuit, and the load loop includes the second circuit breaker QS2 and second lightning protection circuit of series connection, and the switching switch loop includes the static switching switch STS and third circuit breaker of parallel connection, and battery loop is parallelly connected between the net side loop and load loop through energy storage converter PCS, and energy storage converter PCS is switched between the grid connected mode and off grid mode according to the grid state and current signal, and controls the action of static switching switch STS, realizes the quick seamless switching between off grid and grid connected. Advantages: improved equipment integration, reduced floor area, convenient transportation and installation, realize the quick switching of off grid and grid connected, avoid the instantaneous power failure in switching process, make the power supply reliability improve.

Description

Technical Field

[0001] This utility model relates to the field of energy storage cabinets, specifically an automatic switching energy storage cabinet system for grid connection and disconnection. Background Technology

[0002] The inherent intermittency and instability of distributed renewable energy sources, such as photovoltaics and wind power, pose challenges to the stable operation of the power grid and also have a potential impact on the continuous and reliable power supply for users. On the other hand, traditional power supply models are unable to effectively address the increasingly prominent peak-valley electricity price difference, and the economic efficiency of electricity consumption for users needs to be improved. Against this backdrop, energy storage technology, especially energy storage systems capable of intelligent switching between off-grid (islanded operation) and grid-connected (grid-connected operation) modes, has become key to solving these problems. When the grid is normal, such systems can be connected to the grid, storing surplus electricity generated by distributed energy sources to improve energy self-sufficiency, achieve peak shaving and valley filling, and reduce electricity costs; they can also provide ancillary services to the grid, enhancing grid resilience. When a grid fault or power outage occurs, the system can quickly and reliably switch to off-grid mode automatically, providing uninterrupted power to critical loads and greatly improving power supply reliability.

[0003] Currently, existing off-grid and grid-connected switching technologies have some limitations: the switching process may experience momentary power outages at the millisecond level, which cannot meet the needs of sensitive loads with extremely high power quality requirements; the system integration is not high, and the footprint is large; the level of intelligence is limited, and it has failed to be deeply integrated with advanced applications such as energy management and grid dispatch; or the functions are limited, making it difficult to meet the multi-dimensional requirements of economy, reliability and intelligence at the same time.

[0004] Therefore, it is necessary to provide an automatic switching energy storage cabinet off-grid and on-grid system. Utility Model Content

[0005] This utility model provides an automatic switching energy storage cabinet system that can be connected to or disconnected from the grid, effectively solving the problems of low integration of existing connected and disconnected equipment and easy momentary circuit breakage during the switching between connected and disconnected systems.

[0006] The technical solution adopted in this utility model is: an automatic switching energy storage cabinet off-grid system, including a battery circuit, a load circuit in the outgoing cabinet, and a grid-side circuit. The battery circuit includes a battery pack connected in series, an energy storage converter (PCS), and a first circuit breaker (QS1). The grid-side circuit includes a switching circuit connected in series, a current transformer, and a first lightning protection circuit. The load circuit includes a second circuit breaker (QS2) and a second lightning protection circuit connected in series. The switching circuit includes a static switching switch (STS) connected in parallel and a third circuit breaker. The current transformer (CT) is used to collect grid-side current and transmit the current signal to the energy storage converter (PCS). The battery circuit is connected in parallel between the grid-side circuit and the load circuit through the energy storage converter (PCS). The energy storage converter (PCS) switches between grid-connected mode and off-grid mode according to the grid status and the current signal, and controls the operation of the static switching switch (STS) to achieve fast and seamless switching between grid-connected and off-grid modes.

[0007] Furthermore, the battery pack is composed of multiple battery modules connected in series.

[0008] Furthermore, the first lightning protection circuit includes a second AC fast fuse KK2 and a first three-phase four-wire surge protector THUD1 connected in series.

[0009] Furthermore, the second lightning protection circuit includes a first AC fast fuse KK1 and a second three-phase four-wire surge protector THUD2 connected in series.

[0010] Furthermore, the current transformer includes three independent CT1, CT2 and CT3, which are used to collect the current of each phase of the three-phase power grid.

[0011] Furthermore, the energy storage converter PCS outputs constant voltage and frequency AC power in off-grid mode, establishing a stable islanded power grid for the load.

[0012] Furthermore, the energy storage converter PCS rectifies the AC power from the grid into DC power to charge the battery pack during periods of low grid electricity prices; during periods of high grid electricity prices, it inverts the DC power from the battery pack into AC power and discharges it to the load or the grid.

[0013] The beneficial effects of the utility model are as follows: each component is modularly divided into battery circuit, load circuit and grid-side circuit, which improves the integration of the equipment, reduces the footprint, and facilitates transportation and installation. Through the coordination of the energy storage converter PCS and the static switching switch STS, the off-grid and grid-connected switching is realized, avoiding instantaneous power outages during the switching process, thus improving the reliability of power supply. Attached Figure Description

[0014] Figure 1A circuit diagram of an automatically switching energy storage cabinet grid-connected system provided for an embodiment of this application.

[0015] The diagram is labeled as follows: 1. Battery circuit; 2. Load circuit; 3. Grid-side circuit; 4. Battery pack. Detailed Implementation

[0016] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0017] like Figure 1 As shown, the automatic switching energy storage cabinet grid-connected / off-grid system provided in this application includes a battery circuit 1, a load circuit 2, and a grid-side circuit 3. The battery circuit 1 includes a battery pack 4 connected in series, an energy storage converter (PCS), and a first circuit breaker (QS1). The grid-side circuit 3 includes a switching circuit, a current transformer, and a first lightning protection circuit connected in series. The load circuit 2 includes a second circuit breaker (QS2) and a second lightning protection circuit connected in series. The switching circuit includes a static switching switch (STS) connected in parallel and a third circuit breaker. The current transformer (CT) is used to collect grid-side current and transmit the current signal to the energy storage converter (PCS). The battery circuit 1 is connected in parallel between the grid-side circuit 3 and the load circuit 2 through the energy storage converter (PCS). The energy storage converter (PCS) switches between grid-connected and off-grid modes according to the grid status and the current signal, and controls the operation of the static switching switch (STS) to achieve fast and seamless switching between grid-connected and off-grid modes.

[0018] In actual use, the external power grid is connected to the grid-side circuit 3 of the energy storage cabinet. The grid-side current is collected by the current transformer in grid-side circuit 3 and the current signal is transmitted to the energy storage converter PCS. The energy storage converter PCS switches based on the current signal and the state of the power grid. When the power grid is normal, the system is in grid-connected mode: at this time, the static switching switch STS is closed, the power grid and the energy storage cabinet operate synchronously, the power grid supplies power to the entire system through the static switching switch STS, the current transformer continuously monitors the grid-side current, providing real-time data for control; the first lightning protection circuit, as a barrier at the power grid inlet, is in standby protection mode. Meanwhile, battery circuit 1, located within the battery cabinet, begins operation: the energy storage converter PCS, according to a predetermined energy management strategy, rectifies the AC power from the grid into DC power, charging battery pack 4 through the closed first circuit breaker QS1, or inverting the DC power from battery pack 4 into AC power synchronized with the grid. After passing through the energy storage converter PCS, the electrical energy is delivered to the parallel load circuit 2, where the second circuit breaker QS2 is closed to supply power to the load, and the second lightning protection circuit provides protection for the load side. Switching from grid connection to off-grid: When the current transformer detects a grid fault or power outage, the energy storage converter PCS quickly sends a command to the grid-side circuit 3, causing the static switching switch STS to open rapidly, thereby disconnecting from the faulty grid. Off-grid state: After the grid is isolated, battery circuit 1 becomes the sole power source: battery pack 4 continuously discharges, and the operating mode of the energy storage converter PCS instantly changes from tracking grid synchronization to autonomously establishing a stable grid, i.e., acting as an independent voltage source, outputting constant voltage and frequency AC power. All of this electrical energy is delivered to load circuit 2, which provides uninterrupted high-quality power to critical loads through the closed second circuit breaker QS2 and the line protected by the second lightning protection circuit. Meanwhile, the first lightning protection circuit of grid-side circuit 3 is disconnected from the external power grid due to the disconnection of STS.

[0019] In the above design, each component is modularly divided into battery circuit 1, load circuit 2 and grid-side circuit 3, which improves the integration of the energy storage cabinet, reduces the floor space, and facilitates transportation and installation. Through the coordination of the energy storage converter PCS and the static switching switch STS, the fast switching between off-grid and grid-connected is realized, avoiding instantaneous power outages during the switching process and improving power supply reliability.

[0020] Specifically, the battery pack 4 consists of multiple battery modules connected in series. It can be five, six, or any other number.

[0021] In the above design, by connecting multiple battery modules in series, the DC terminal voltage of battery pack 4 can be effectively increased, the transmission current can be reduced, and the loss can be reduced. The series connection method facilitates the standardized production, testing and replacement of batteries, and reduces maintenance costs and complexity.

[0022] Specifically: the first lightning protection circuit includes a second AC fast fuse KK2 and a first three-phase four-wire surge protector THUD connected in series.

[0023] In the above design, the first lightning protection circuit needs to be connected to the grid-side circuit 3 and grounded to achieve lightning protection. The surge overvoltage is absorbed by the first three-phase four-wire surge protector THUD, the current protection is provided by the first AC fast fuse, and the remaining components are protected by the fuse, thereby achieving protection against lightning strikes to the grid-side circuit 3.

[0024] Specifically: the second lightning protection circuit includes a first AC fast fuse KK1 and a second three-phase four-wire surge protector THUD2 connected in series.

[0025] In the above design, the second lightning protection circuit needs to be connected to the load circuit 2 and grounded to achieve lightning protection. The surge overvoltage is absorbed by the second three-phase four-wire surge protector THUD, the current protection is provided by the second AC fast fuse, and the remaining components are protected by the fuse, thereby achieving protection of the load circuit 2 from lightning strikes.

[0026] Specifically, the current transformer CT includes three independent first current transformers CT1, second current transformers CT2 and third current transformers CT3. The first current transformer CT1, second current transformer CT2 and third current transformer CT3 are used to collect the current of each phase of the three-phase power grid.

[0027] It should be noted that a three-phase power grid consists of three alternating currents with the same frequency and a phase difference of 120 degrees. It is the standard industrial and residential power supply of the power grid and is connected through grid-side circuit 3.

[0028] In the above design, the three-phase current is collected by three independent current transformers CT1, CT2 and CT3, which can collect the current data of each phase in the three-phase power grid in real time and independently, providing accurate system operation status information for the energy storage converter PCS.

[0029] Specifically, the energy storage converter PCS outputs constant voltage and frequency AC power in off-grid mode, establishing a stable islanded power grid for the load.

[0030] In the above design, when the energy storage converter PCS performs off-grid switching, it generates a stable reference waveform through the internal oscillator of the energy storage converter PCS to drive the power devices, thereby outputting constant voltage and constant frequency AC power.

[0031] Specifically: During periods of low grid electricity prices, the energy storage converter PCS rectifies the AC power from the grid into DC power to charge the battery pack 4; during periods of high grid electricity prices, it inverts the DC power from the battery pack 4 into AC power and discharges it to the load or the grid.

[0032] It should be noted that the energy storage converter PCS can communicate with an external management system and switch the power grid through the clock built into the external management system and the preset peak and valley electricity price periods.

[0033] In the above design, by utilizing the peak-valley electricity price difference, users can significantly reduce their electricity costs and generate direct economic returns by charging when prices are low and discharging or selling electricity when prices are high.

[0034] In further detail, it should be understood that the above description is only a specific embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An automatic switching energy storage cabinet grid-connected / off-grid system, characterized in that: The system includes a battery circuit (1), a load circuit (2), and a grid-side circuit (3). The battery circuit (1) includes a battery pack (4) connected in series, an energy storage converter (PCS), and a first circuit breaker (QS1). The grid-side circuit (3) includes a switching circuit, a current transformer (CT), and a first lightning protection circuit connected in series. The load circuit (2) includes a second circuit breaker (QS2) and a second lightning protection circuit connected in series. The switching circuit includes a static switching switch (STS) connected in parallel and a third circuit breaker (QS3). The current transformer (CT) is used to collect grid-side current and transmit the current signal to the energy storage converter (PCS). The battery circuit (1) is connected in parallel between the grid-side circuit (3) and the load circuit (2) through the energy storage converter (PCS). The energy storage converter (PCS) switches between grid-connected mode and off-grid mode according to the grid status and the current signal, and controls the action of the static switching switch (STS) to achieve fast and seamless switching between grid-connected and off-grid modes.

2. The automatic switching energy storage cabinet grid-connected / off-grid system according to claim 1, characterized in that: The battery pack (4) is composed of multiple battery modules connected in series.

3. The automatic switching energy storage cabinet grid-connected / off-grid system according to claim 1, characterized in that: The first lightning protection circuit includes a second AC fast fuse KK2 and a first three-phase four-wire surge protector THUD1 connected in series.

4. The automatic switching energy storage cabinet grid-connected / off-grid system according to claim 1, characterized in that: The second lightning protection circuit includes a first AC fast fuse KK1 and a second three-phase four-wire surge protector THUD2 connected in series.

5. The automatic switching energy storage cabinet grid-connected / off-grid system according to claim 1, characterized in that: The current transformer includes three independent first current transformers CT1, second current transformers CT2 and third current transformers CT3. The first current transformers CT1, second current transformers CT2 and third current transformers CT3 are used to collect the current of each phase of the three-phase power grid.

6. The automatic switching energy storage cabinet grid-connected / off-grid system according to claim 1, characterized in that: In off-grid mode, the energy storage converter PCS outputs constant voltage and frequency AC power to establish a stable islanded power grid for the load.

7. The automatic switching energy storage cabinet grid-connected / off-grid system according to claim 1, characterized in that: During periods of low grid electricity prices, the energy storage converter PCS rectifies the AC power from the grid into DC power to charge the battery pack (4); during periods of high grid electricity prices, it inverts the DC power from the battery pack (4) into AC power and discharges it to the load or the grid.

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