Modularized low-cost grid-connected and off-grid switching system and method

Abstract

The invention relates to the technical field of energy storage control, in particular to a modular low-cost grid-connected and off-grid switching system and method, and the system comprises a grid-connected and off-grid switching module, two ends of which are respectively used for connecting a power grid side and a user side; the off-grid action module is used for collecting the voltage on the power grid side to control the grid-connected and off-grid switch module to act to the off-grid state; the grid-connected action module is used for controlling the grid-connected and off-grid switch module to act to a closed state according to the input signal; the grid-connected feedback module is used for collecting real-time voltage information to generate a grid-connected feedback signal; the energy storage control unit is electrically connected to the grid-connected feedback module to obtain a grid-connected feedback signal, generates a switching-on control signal based on the grid-connected feedback signal and sends the switching-on control signal to the grid-connected action module to serve as an input signal; and the energy storage control unit collects the switching-on feedback signal and performs matching analysis based on the grid-connected feedback signal and the switching-on feedback signal so as to switch the working mode. The method and the device have the effect of realizing low-cost and high-applicability grid-connected and off-grid switching.

Description

Technical Field

[0001] This application relates to the technical field of energy storage control, and particularly to a modular low-cost grid-connected and off-grid switching system and method. Background Art

[0002] Grid-connected and off-grid switching refers to the process of switching a device from a grid-connected state to an off-grid state or from an off-grid state to a grid-connected state in a power system. This switching usually occurs when there is a power grid fault or power outage. The system automatically or manually switches to the off-grid mode to ensure uninterrupted power supply to the load. When the power grid returns to normal, the system automatically switches back to the grid-connected mode.

[0003] In the current existing technology, a seamless grid-connected and off-grid switching method is adopted. The STS module (static double-path switch) is used to monitor the power failure state of the power grid. At the moment of power failure, the STS module will send a signal to the PCS (energy storage converter management unit) in the energy storage. The energy storage will switch its grid-connected state to the off-grid state within dozens of milliseconds after receiving the signal, so as to realize the load power supply in the off-grid state.

[0004] However, due to the extremely high price of the PCS unit on the current market, for some low-cost power consumption environments or some scenarios with little requirement for the accuracy of grid-connected and off-grid power consumption, the development, design, and use costs of this grid-connected and off-grid switching scheme are relatively high. At the same time, the load adaptability is limited, and there are problems of high loss and high heat generation. Summary of the Invention

[0005] In order to achieve low-cost and highly applicable grid-connected and off-grid switching, this application provides a modular low-cost grid-connected and off-grid switching system and method.

[0006] In the first aspect, this application provides a modular low-cost grid-connected and off-grid switching system, adopting the following technical solutions: A modular low-cost grid-connected and off-grid switching system includes: A grid-connected and off-grid switch module, with both ends respectively used to connect to the grid side and the user side. Among them, the user side includes an energy storage end and a load end; An off-grid action module, coupled to the grid-connected and off-grid switch module and electrically connected to the grid side, for collecting the voltage on the grid side to control the grid-connected and off-grid switch module to act to the open state; A grid-connected action module, coupled to the grid-connected and off-grid switch module, for controlling the grid-connected and off-grid switch module to act to the closed state according to an input signal; A grid-connected feedback module, electrically connected between the grid side and the grid-connected and off-grid switch module, for collecting real-time voltage information to generate a grid-connected feedback signal; The energy storage control unit is electrically connected to the grid-connected feedback module to obtain the grid-connected feedback signal, and generates a closing control signal based on the grid-connected feedback signal and sends it to the grid-connected action module as the input signal; The energy storage control unit is also electrically connected to the grid-connected and off-grid switch module to collect the closing feedback signal, and performs matching analysis based on the grid-connected feedback signal and the closing feedback signal to switch the working mode, and the working mode includes a grid-connected mode and an off-grid mode.

[0007] In some embodiments, the grid-connected and off-grid switch module includes a low-voltage circuit breaker QF, and the off-grid action module includes an under-voltage release X1. The under-voltage release X1 collects the voltage on the grid side and judges whether it is less than a first preset value; If it is not less than the first preset value, the under-voltage release X1 is energized to control the low-voltage circuit breaker QF to remain in the closed state; If it is less than the first preset value, the under-voltage release X1 loses power to perform a tripping action to control the low-voltage circuit breaker QF to open.

[0008] In some embodiments, the grid-connected action module includes an electric operation switch X2, and the grid-connected feedback module includes a voltage relay D1; The voltage relay D1 is used to detect the magnitude of the real-time voltage information between the low-voltage circuit breaker QF and the grid side, and generates a grid-connected feedback signal to the energy storage control unit when the real-time voltage information is greater than a second preset value. Wherein, the grid-connected feedback signal is a level signal; The energy storage control unit obtains the grid-connected feedback signal and correspondingly generates a closing control instruction to send to the electric operation switch X2. After the electric operation switch X2 obtains the input signal containing the closing control instruction, it drives the low-voltage circuit breaker QF to close through the motor M.

[0009] In some embodiments, the energy storage control unit collects the action state of the grid-connected and off-grid switch module in real time to obtain the closing feedback signal, and performs consistency comparison with the collected grid-connected feedback signal. Specifically, If the grid-connected feedback signal corresponds to the grid-connected level signal and the closing feedback signal corresponds to closing, enter the grid-connected mode. At this time, control the energy storage terminal to shut down and send a grid-connected instruction to the PCS to perform the grid-connected charge and discharge control logic; If the grid-connected feedback signal does not correspond to the grid-connected level signal and the closing feedback signal corresponds to opening, enter the off-grid mode. At this time, control the energy storage terminal to start up and send an off-grid instruction to the energy storage terminal to perform the off-grid charge and discharge control logic.

[0010] In some of these embodiments, when the voltage on the grid side is less than a first preset value, the energy storage control unit obtains the power supply priority of the load end; If the power supply priority is high, a thermal response instruction is generated based on the current voltage and sent to the energy storage end. After obtaining the thermal response instruction, the energy storage end enters the thermal start power supply mode to turn on; If the power supply priority is low, a cold response instruction is generated based on the current voltage and sent to the energy storage end. After obtaining the cold response instruction, the energy storage end enters the cold start power supply mode to turn on.

[0011] In some of these embodiments, the second preset value includes a pre-stage sub-value and a post-stage sub-value, where the pre-stage sub-value is less than the post-stage sub-value; When the real-time voltage information is greater than the pre-stage sub-value and stably maintains for a first duration, the grid connection feedback signal is sent to the energy storage control unit; When the real-time voltage information is greater than the post-stage sub-value and stably maintains for a second duration, a grid connection instruction is sent to the PCS and the signal quality is calculated to generate a fluctuation coefficient; Among them, after the energy storage control unit obtains the grid connection feedback signal, a reaction reserved time is generated and sent to the energy storage end. The energy storage end shuts down after the reaction reserved time arrives, and the reaction reserved time is the second duration multiplied by the fluctuation coefficient.

[0012] In some of these embodiments, during the second duration, the energy storage control unit real-time collects the real-time voltage information, real-time frequency information, and real-time phase information and generates a synchronous change amount. The synchronous change rate is calculated through the ratio of the synchronous change amount to the reaction reserved time; The energy storage control unit dynamically adjusts the output power of the energy storage end based on the synchronous change rate until it changes to 0 and shuts down.

[0013] In some of these embodiments, if the grid connection feedback signal does not correspond to the grid connection level signal and the closing feedback signal corresponds to closing, a first verification task with a preset duration is generated to send a first error correction trigger instruction to the under-voltage release X1, and it is judged whether the closing feedback signal changes during the first verification task. If it does not change, a fault alarm information is generated; If the grid connection feedback signal corresponds to the grid connection level signal and the closing feedback signal corresponds to opening, a second verification task with a preset duration is generated to send a second error correction instruction to the electric operation switch X2, and it is judged whether the closing feedback signal changes during the second verification task. If it does not change, a fault alarm information is generated.

[0014] In some of these embodiments, a controllable load module is further included, and a photovoltaic terminal is further included on the user side; In the off-grid energy storage mode: The photovoltaic terminal is used to supply power to the load terminal through a photovoltaic panel; The controllable load module is used to respectively collect the energy storage power of the energy storage terminal, the photovoltaic power generation of the photovoltaic terminal, and the energy consumption power of the load terminal; The controllable load module compares the size of the energy storage power with a preset safe power. If the energy storage power is less than the preset safe power, it enters the load control mode; In the load control mode, the controllable load module judges the size between the photovoltaic power generation and the energy consumption power; If the energy consumption power is greater than the photovoltaic power generation, the connection between the energy storage terminal and the load terminal is cut off and the photovoltaic terminal is controlled to charge the energy storage terminal; If the energy consumption power is not greater than the photovoltaic power generation, the photovoltaic terminal is controlled to supply power to the load terminal and a signal to shut down the energy storage is generated and sent to the energy storage control unit, and the energy storage control unit controls the energy storage terminal to shut down based on the signal to shut down the energy storage.

[0015] In a second aspect, the present application provides a modular low-cost grid-connected and off-grid switching method, adopting the following technical solution: A modular low-cost grid-connected and off-grid switching method, implemented based on the above system, includes the following steps: When the grid side loses power, the off-grid action module collects the voltage of the grid side to control the on-grid and off-grid switch module connected between the grid side and the user side to act to the off state, and the load terminal in the user side loses power; The energy storage control unit collects the closing feedback signal to obtain the disconnection of the on-grid and off-grid switch module, and obtains the grid connection feedback signal generated by the grid connection feedback module by collecting real-time voltage information to control the energy storage terminal in the user side to switch to the off-grid mode to start up and supply power to the load terminal; When the grid side has power, the grid connection feedback module detects the real-time voltage information between the grid side and the on-grid and off-grid switch module to generate a grid connection feedback signal and sends it to the energy storage control unit, and the energy storage control unit controls the energy storage terminal to shut down to switch to the grid-connected mode based on the grid connection feedback signal; The energy storage control unit generates a closing control signal based on the grid connection feedback signal and sends it to the grid connection action module as the input signal, and the grid connection action module controls the on-grid and off-grid switch action module to act to the closed state based on the input signal.

[0016] Through the technical solution provided by the embodiments of the present application, the following technical effects are achieved: Modularize the components in the grid-connected and off-grid process. Through the module combination composed of conventional relay protection devices, cooperate with software logic to realize the grid-connected and off-grid switching function, achieve low-cost grid-connected and off-grid switching, and be applicable to occasions with low requirements for power continuity, some high-power energy storage systems. The scheme has a simple structure, low cost, high reliability, can withstand large currents and powers, and at the same time, the operating principles of each component are relatively simple, making it easy to understand and maintain. Description of the Drawings

[0017] Figure 1 It is a connection schematic diagram of the modular low-cost grid-connected and off-grid switching system provided by this embodiment.

[0018] Figure 2 It is a step schematic diagram of the modular low-cost grid-connected and off-grid switching method provided by the embodiment of this application.

[0019] Description of the reference numerals: 1. Grid-connected and off-grid switch module; 2. Off-grid action module; 3. Grid-connected action module; 4. Grid-connected feedback module; 5. Energy storage control unit; 6. Controllable load module. Detailed Embodiments

[0020] To more clearly understand the purpose, technical solution and advantages of this application, the following describes and explains this application in combination with the drawings and embodiments. However, those of ordinary skill in the art should understand that this application can be implemented without these details. In some cases, in order to avoid unnecessary descriptions from making various aspects of this application obscure, well-known methods, processes, systems, components and / or circuits that have been described at a higher level will not be elaborated too much. For those of ordinary skill in the art, it is obvious that various changes can be made to the disclosed embodiments of this application, and without departing from the principles and scope of this application, the general principles defined in this application can be applied to other embodiments and application scenarios. Therefore, this application is not limited to the shown embodiments, but conforms to the broadest scope consistent with the scope required to be protected by this application.

[0021] It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] In the description of this application, "several" means one or more, "multiple" means two or more, and understandings such as "greater than", "less than", "exceeding", etc. do not include the base number, while understandings such as "above", "below", "within", etc. include the base number. If there is a description of "first" and "second", it is only used to distinguish technical features and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features or implicitly specifying the sequence relationship of the indicated technical features.

[0023] In the description of this application, descriptions with reference terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a combined manner.

[0024] As Figure 1 shown, the embodiment of this application discloses a modular low-cost grid-connected and off-grid switching system, including: A grid-connected and off-grid switch module, with both ends respectively used to connect to the grid side and the user side. Among them, the user side includes an energy storage end and a load end.

[0025] The grid-connected and off-grid switch module is mainly used to switch or connect the power circuit between the user side and the grid side. When performing grid-connected and off-grid switching, when the grid-connected and off-grid switch module is disconnected, it means that the power consumption circuit between the user side and the grid side is disconnected, and at this time it is in the off-grid state. When the grid-connected and off-grid switch module is connected, it means that the power consumption circuit between the user side and the grid side is connected, and at this time it is in the grid-connected state.

[0026] The grid side corresponds to the grid bus, and the grid side may also include a diesel generator end for supplementary power generation.

[0027] The user side corresponds to the energy storage end and the load end. The energy storage end corresponds to the energy storage device, and the load end corresponds to the user's electrical equipment.

[0028] An off-grid action module, coupled to the grid-connected and off-grid switch module and electrically connected to the grid side, is used to collect the voltage on the grid side to control the grid-connected and off-grid switch module to act to the off state.

[0029] The off-grid action module first collects the voltage on the grid side. When the grid side voltage drops to a preset value, it triggers an off-grid action, and it controls the coupled grid-connected and off-grid switch module to perform an off-grid action to disconnect the power supply circuit between the grid and the load.

[0030] A grid-connected action module, coupled to the grid-connected and off-grid switch module, is used to control the grid-connected and off-grid switch module to act to the closed state according to the input signal.

[0031] The action target of the grid-connected action module is opposite to that of the off-grid action module. It uses the signal sent by the subsequent energy storage control unit as the input signal. When there is an input signal, it is considered that the power has been restored on the current grid side and is in a stable state. At this time, the grid-connected action needs to be triggered. Therefore, the grid-connected action module controls the coupled grid-connected / off-grid switch module to perform a closing action to connect the power supply loop between the grid and the load.

[0032] The grid-connected feedback module is electrically connected between the grid side and the grid-connected / off-grid switch module, and is used to collect real-time voltage information to generate a grid-connected feedback signal.

[0033] The grid-connected feedback module collects the real-time voltage magnitude between the grid and the grid-connected / off-grid switch module in real time to determine whether the off-grid state of power failure from the grid changes to the grid-connected state of grid power restoration, and generates a corresponding grid-connected feedback signal when the grid-connected condition is met.

[0034] The energy storage control unit is electrically connected to the grid-connected feedback module to obtain the grid-connected feedback signal, and generates a closing control signal based on the grid-connected feedback signal and sends it to the grid-connected action module as the input signal.

[0035] The energy storage control unit includes several functional sub-modules. It first judges the state of the current grid by whether it can obtain the grid-connected feedback signal uploaded by the grid-connected feedback module. At the same time, when it obtains the grid-connected feedback signal, it confirms that the grid-connected action needs to be performed to generate a closing control signal and send it to the grid-connected action module to control its grid-connected closing action.

[0036] The energy storage control unit is also electrically connected to the grid-connected / off-grid switch module to collect the closing feedback signal, and performs a matching analysis based on the grid-connected feedback signal and the closing feedback signal to switch the working mode. The working modes include the grid-connected mode and the off-grid mode.

[0037] The energy storage control unit is also used to collect the action feedback of the grid-connected / off-grid switch module as the closing feedback signal. At the same time, it judges the current grid-connected / off-grid state and determines the final grid-connected / off-grid control mode based on the consistency of the grid-connected feedback signal and the closing feedback signal.

[0038] In some other embodiments, the grid-connected / off-grid switch module includes a low-voltage circuit breaker QF, and the off-grid action module includes an under-voltage release X1. The under-voltage release X1 collects the voltage on the grid side and judges whether it is less than the first preset value.

[0039] If it is not less than the first preset value, the under-voltage release X1 is not powered on to control the low-voltage circuit breaker QF to remain closed; If it is less than the first preset value, the under-voltage release X1 is powered on to perform a tripping action to control the low-voltage circuit breaker QF to open.

[0040] The low-voltage circuit breaker switch QF and the coupled under-voltage release X1 together constitute a simple circuit breaker structure, which can also achieve switch actions based on voltage detection, and at the same time, the cost is much lower than that of the STS module.

[0041] The under-voltage release X1 is composed of components such as an iron core, a coil, and an armature. It judges whether the voltage meets the preset magnitude in the electrical circuit. When the voltage is normal, the coil of the under-voltage release X1 is normally energized to generate sufficient electromagnetic force. At this time, the armature is attracted and the coupled low-voltage circuit breaker switch QF is in the closed on state; when the voltage drops to, for example, 30% of the stable grid voltage, the voltage is low enough to cause insufficient electromagnetic force. At this time, the armature cannot maintain the attracted state and trips. At this time, the low-voltage circuit breaker switch QF will be disconnected through transmission.

[0042] The combination of the under-voltage release X1 and the low-voltage circuit breaker switch QF is used to achieve the same effect as the network disconnection action of the STS with the lowest cost, greatly reducing the cost, and at the same time, problems such as high loss and high heat generation will not occur.

[0043] In some other embodiments, the grid connection action module includes an electric operation switch X2, and the grid connection feedback module includes a voltage relay D1.

[0044] In the actual scenario, the exciting coil of the under-voltage release X1 has an interlock mechanism. As long as the switch of the circuit breaker is disconnected, it cannot actively close in the subsequent scenario of the grid power on. Generally, manual closing is required.

[0045] Therefore, when the grid changes from power-off to power-on, it is necessary to switch from the off-grid state to the grid-connected state, that is, it is necessary to change the low-voltage circuit breaker switch QF from the disconnected state to the re-closed state. At the same time, to solve the problem that the circuit breaker cannot actively close due to interlock, this application also sets an electric operation switch X2 for controlling the switch action and a voltage relay D1 for feedback the real-time grid connection situation.

[0046] The voltage relay D1 is used to detect the magnitude of the real-time voltage information between the low-voltage circuit breaker switch QF and the grid side, and generate a grid connection feedback signal to the energy storage control unit when the real-time voltage information is greater than the second preset value. Among them, the grid connection feedback signal is a level signal.

[0047] First, the coil of the voltage relay D1 corresponds to the grid side to collect the real-time voltage magnitude, and the switch action occurs after the voltage is greater than the preset magnitude. In this way, the state of whether the grid is grid-connected can be converted into an on or off state. Then, according to the on or off action, a corresponding level signal of 1 or 0 can be output.

[0048] Specifically, for example, when the voltage relay D1 monitors that the voltage on the grid side reaches 200V and remains stable for a time length of, for example, 5 minutes, then it can be switched to the grid-connected state at this time. Therefore, the switch of the voltage relay D1 closes to generate a corresponding loop-connected "1" level signal, and the grid feedback signal at this time can inform the energy storage control unit of the current grid state.

[0049] The energy storage control unit obtains the grid-connected feedback signal and correspondingly generates a closing control instruction to send to the electric operation switch X2. After the electric operation switch X2 obtains the input signal containing the closing control instruction, it drives the low-voltage circuit breaker QF to close through the motor M.

[0050] The electric operation switch has a functional module for receiving external control signals. This signal can be sent manually through a control button or a control panel, or may come from an automation control system, a protection device, etc. The control signal is usually transmitted to the electric operation switch in the form of an electrical signal.

[0051] When a closing operation is required, a specific closing control signal is input; when a tripping is required, a tripping control signal is input.

[0052] The electric operation switch is internally equipped with a motor. When receiving a control signal, the drive circuit of the motor controls the forward or reverse rotation of the motor according to the signal type (closing or tripping).

[0053] In this application, after the energy storage control unit obtains the grid-connected feedback signal, it needs to control the system to switch to the grid-connected state. Therefore, an electronic instruction (closing control instruction) is sent to the electric operation switch X2 at this time. After the electric operation switch X2 obtains this instruction, it controls the internal motor M to rotate forward, and at the same time, through the transmission mechanism connected to the motor M, it pushes the low-voltage circuit breaker QF to close.

[0054] In this way, the grid-connected control effect corresponding to the expensive STS can also be achieved through the combination of the simple-structured and low-cost electric operation switch X2 and the voltage relay D1. The voltage relay D1 judges whether grid connection is required, and when it is necessary to switch to the grid-connected state, it issues a software control instruction of the system to control the electric operation switch X2 to perform a closing operation on the interlocked low-voltage circuit breaker QF.

[0055] Thus, this system uses a simple relay protection device to replace the STS to realize the detection of the trigger conditions for off-grid and grid connection, as well as the corresponding off-grid switching action and grid-connected switching action.

[0056] In some other embodiments, the energy storage control unit collects the action state of the off-grid switch module in real time to obtain a closing feedback signal, and compares it with the collected grid-connected feedback signal for consistency.

[0057] There is a closing state detection function unit in the energy storage control unit, which can obtain the action feedback corresponding to the disconnection and closing actions of the low-voltage circuit breaker QF. Through this closing feedback signal, the energy storage control unit can clearly know the state of the current low-voltage circuit breaker QF.

[0058] At the same time, the energy storage control unit compares the collected closing feedback signal with the grid connection feedback signal to determine whether both signals match the grid-connected state or the off-grid state at the same time, and selects the corresponding grid connection control logic or off-grid control logic according to the comparison result.

[0059] If the grid connection feedback signal corresponds to the grid connection level signal and the closing feedback signal corresponds to closing, enter the grid connection mode. At this time, control the energy storage terminal to shut down and send a grid connection command to the PCS to perform the grid connection charge and discharge control logic.

[0060] If the grid connection feedback signal corresponds to the grid connection level signal and the closing feedback signal indicates that the low-voltage circuit breaker QF has been closed. Then it is determined that the grid connection mode has been entered. In the grid connection mode, the energy storage terminal does not need to charge and discharge the energy storage power to the load terminal, and the grid terminal then supplies power to the load terminal. Therefore, at this time, control the energy storage to shut down, and at the same time send a grid connection command to the PCS. The PCS starts up and executes the corresponding grid connection charge and discharge logic to control the power consumption between the grid terminal and the load terminal.

[0061] If the grid connection feedback signal does not correspond to the grid connection level signal and the closing feedback signal corresponds to opening, enter the off-grid mode. At this time, control the energy storage terminal to start up and send an off-grid command to the energy storage terminal to perform the off-grid charge and discharge control logic.

[0062] If the grid connection feedback signal does not indicate that the grid terminal is powered on, and at the same time the closing feedback signal indicates that the current low-voltage circuit breaker QF is in the open state, then it is determined that the off-grid mode has been entered. In the off-grid mode, since the grid terminal cannot charge the load, the energy storage terminal needs to start up and switch to the off-grid power supply state according to the off-grid command. In this scenario, the energy storage control unit sends an off-grid command to the energy storage terminal to perform the off-grid charge and discharge control logic.

[0063] In some other embodiments, when the voltage on the grid side is less than the first preset value, the energy storage control unit obtains the power supply priority of the load terminal.

[0064] When the power grid experiences a power outage instantaneously, although the energy storage side will switch from the shutdown state to the startup state to charge the load side, in actual scenarios, the power outage speed of the power grid is often greater than the startup speed of the energy storage. Therefore, the time difference in the middle will cause the load side to be in a power-off state for a period of time. Different load sides have different degrees of influence on power loss. For example, in areas such as residential areas, the power loss for a period of time has little impact, while in some important places or important electrical equipment, such as communication equipment, factories, data centers, etc., a power outage will have a greater impact.

[0065] Then, based on the different priorities of the load side, different energy storage device startup methods can be selected when detecting an upcoming power outage scenario.

[0066] If the power supply priority is high, a thermal response command is generated based on the current voltage and sent to the energy storage side. After the energy storage side obtains the thermal response command, it enters the thermal startup power supply mode to start up.

[0067] If the power supply priority of the load side is relatively high, it means that the importance of these load sides is relatively high. At this time, the energy storage side can be maintained in the thermal startup mode during daily grid connection standby. In the thermal startup mode, the energy storage device is in the thermal standby state, and its control module, communication module, etc. are all in the low-power standby state. When receiving the sent thermal response command, the energy storage side can directly respond and enter the working state without parameter configuration, system self-check, and module power-on.

[0068] The overall startup response speed is fast in the thermal startup mode, but the power consumption in the standby state is relatively high.

[0069] If the power supply priority is low, a cold response command is generated based on the current voltage and sent to the energy storage side. After the energy storage side obtains the cold response command, it enters the cold startup power supply mode to start up.

[0070] When the power supply priority of the load side is low, it means that the importance of these load sides is relatively low. At this time, the energy storage side can be maintained in the cold startup mode during daily grid connection. In the cold startup mode, the energy storage device is in a full shutdown and sleep state, and each module in the system is powered off. When obtaining the sent cold response command, the energy storage side first performs steps such as power-on of each module unit, system self-check, and parameter configuration. After the steps are completed, it enters the working state of supplying power to the load side.

[0071] The overall startup response speed is slow in the cold startup mode, but the power consumption in the standby state is relatively low.

[0072] In some other embodiments, the second preset value includes a pre-stage sub-value and a post-stage sub-value, where the pre-stage sub-value is less than the post-stage sub-value.

[0073] The second preset value is characterized as a voltage reference quantity used to determine whether the grid side is in a grid-connected mode. When the reference quantity is met, it is considered that grid connection operation is required, that is, the energy storage side is shut down. However, generally, the closing operation during grid connection and the shutdown operation of the energy storage device cannot be completely simultaneous. The energy storage device requires a certain amount of time to shut down, while the breaker switch requires a relatively short time to close.

[0074] At this time, there is often a state where the switch has closed, but the energy storage side has not been completely shut down. At this time, the electrical energy of the energy storage device and the electrical energy of the grid are discharged to the load device together. On the one hand, this will cause a certain fluctuation at the load end during the closing instant, and on the other hand, it will also cause part of the electrical energy of the energy storage to flow back to the grid and pose a risk.

[0075] Therefore, in order to optimize the synchronization between the closing operation and the energy storage shutdown operation, in the embodiments of the present application, the second preset value is divided into a pre-stage value and a post-stage value. Among them, the voltage value in the pre-stage period is less than the voltage value in the post-stage period.

[0076] Among them, the pre-stage value is used to first send the corresponding information that the grid side is about to enter the grid-connected state to the energy storage control unit, and the post-stage value is used to wait for the energy storage control unit to send a corresponding instruction to enable the energy storage side to start pre-shutdown preparation.

[0077] When the real-time voltage information is greater than the pre-stage sub-value and stably maintains for the first duration, a grid connection feedback signal is sent to the energy storage control unit.

[0078] When the real-time voltage information is greater than the pre-stage sub-value and stably maintains for the first duration, at this time, it is considered that the grid has a tendency to resume power-on. At this time, it is necessary to send the grid connection feedback signal to the energy storage control unit in advance so that the energy storage control unit can perform grid connection operation in advance.

[0079] When the real-time voltage information is greater than the post-stage sub-value and stably maintains for the second duration, a grid connection instruction is sent to the PCS and the signal quality is calculated to generate a fluctuation coefficient.

[0080] When the real-time voltage information continuously rises until it is greater than the post-stage sub-value and stably maintains for the second duration, at this time, it is confirmed that the grid is about to resume power-on and grid connection. At this time, a grid connection instruction is first sent to the PCS to enable the PCS to switch to the grid-connected state to prepare for the grid-side grid connection control logic. At the same time, in order to determine the linear rate of voltage drop of the energy storage system from power supply to shutdown, the energy storage control unit also needs to calculate the signal instruction of the grid-side voltage based on the current voltage value, frequency, phase and other data and obtain the fluctuation coefficient.

[0081] The larger the fluctuation coefficient is, the more unstable the process of the current power grid resuming power supply is. If the power grid is unstable, in order to prevent subsequent re - entry into the power - off state, at this time, the energy storage system needs to slowly reduce the output voltage to shut down. On the contrary, the smaller the fluctuation coefficient is, the more stable the process of the current power grid resuming power supply is, and the lower the possibility of subsequent power - off is. Therefore, at this time, the energy storage system can reduce the output voltage relatively quickly and linearly to enter the shutdown state.

[0082] Among them, after the energy storage control unit obtains the grid - connection feedback signal, it generates a reaction reserve time and sends it to the energy storage terminal. The energy storage terminal shuts down after the reaction reserve time arrives. The reaction reserve time is the second duration multiplied by the fluctuation coefficient.

[0083] Then, when the energy storage control unit sends the grid - connection feedback signal in the determination of the previous sub - value, it first generates a reaction reserve time to the energy storage terminal, and the energy storage terminal linearly reduces its output voltage within the duration of the reaction reserve time until it shuts down.

[0084] At the beginning, the reaction reserve time is equal to the second duration. Then, with the fluctuation coefficient corresponding to the sampling of the power fluctuation on the power grid in real - time and dynamically adjusting the length of the reaction reserve time, so the length of the dynamic reaction reserve time is equal to the second duration multiplied by the fluctuation coefficient.

[0085] Therefore, the process of the grid - connection operation is specifically as follows: First, the voltage on the power grid continuously rises. When the previous sub - value is first triggered, the grid - connection feedback signal is sent. The energy storage control unit generates a reaction reserve time equal to the second duration and sends it to the energy storage terminal. The energy storage terminal slowly reduces its output voltage based on the reaction reserve time. At the same time, when the real - time voltage on the power grid is greater than the later sub - value, the fluctuation coefficient of the real - time voltage is calculated, and the current reaction reserve time is adjusted based on the fluctuation coefficient. The energy storage terminal ensures to shut down when the reaction reserve time arrives.

[0086] In some other embodiments, within the second duration, the energy storage control unit real - time collects real - time voltage information, real - time frequency information, and real - time phase information and generates a synchronous change amount. The synchronous change rate is calculated by the ratio of the synchronous change amount to the reaction reserve time; The energy storage control unit dynamically adjusts the output power of the energy storage terminal based on the synchronous change rate until it changes to 0 and shuts down.

[0087] The specific method for real-time dynamic adjustment of the voltage at the energy storage end during the reaction reserved time is to generate a synchronous change quantity based on the real-time voltage information, as well as data such as frequency and phase, collected by the energy storage control unit. The synchronous change quantity is specifically characterized in that the change quantity when the power grid changes from power failure to a stable power-on state is synchronously corresponding to the change quantity of the energy storage end from working power supply to non-working shutdown. Therefore, in order to ensure synchronization between the power-on at the power grid end and the shutdown at the energy storage end, the synchronous change rate can be calculated by the ratio of the synchronous change quantity to the reaction reserved time.

[0088] If the power grid needs to change by an amount X1 from power failure to power-on, then the corresponding synchronous change quantity at the energy storage end is X2, and the synchronous change quantity is X2 / t.

[0089] In some other embodiments, if the grid connection feedback signal does not correspond to the grid connection level signal and the closing feedback signal corresponds to closing, a first verification task with a preset duration is generated to send a first error correction trigger instruction to the under-voltage release X1, and it is determined whether the closing feedback signal is monitored to change during the first verification task. If there is no change, a fault alarm message is generated.

[0090] In some other scenarios, the states represented by the grid connection feedback signal and the closing feedback signal may be different. For example, the grid connection feedback signal indicates that the current is in a power failure state, but at this time the low-voltage circuit breaker QF is in the closed state. Then, when the low-voltage circuit breaker QF closes, the load circuit and the power grid circuit cannot be cut off and isolated. Then, when the energy storage device is powered on, part of the electric energy will flow into the power grid end.

[0091] Therefore, in this case, the energy storage control unit generates a verification task, and in the verification task, a first error correction trigger instruction is sent to the under-voltage release X1 to actively control the under-voltage release X1 to perform a tripping action so that the low-voltage circuit breaker QF performs an opening action. Then, if the closing feedback signal still does not change during the time corresponding to the verification task, it indicates that the low-voltage circuit breaker QF cannot be disconnected, and then a fault alarm signal will be generated, indicating that the system has a fault.

[0092] In the embodiments of the present application, the duration corresponding to the first verification task is 10s.

[0093] If the grid connection feedback signal corresponds to the grid connection level signal and the closing feedback signal corresponds to opening, a second verification task with a preset duration is generated to send a second error correction instruction to the electric operation switch X2, and it is determined whether the closing feedback signal is monitored to change during the second verification task. If there is no change, a fault alarm message is generated.

[0094] If the grid connection feedback signal indicates that the grid connection state has been restored at the current grid side, and the closing feedback signal corresponds to the open state of the low-voltage circuit breaker QF, then the grid circuit and the load circuit are still in a disconnected state, and the grid still cannot supply power to the load.

[0095] Therefore, in this case, the energy storage control unit will generate another verification task. In the verification task, a second error correction instruction is sent to the electric operation switch X2 to actively control the electric operation switch X2 to switch the low-voltage circuit breaker QF to the closing operation through the system software instruction. Then, if the closing feedback signal still does not change in the event corresponding to the verification task, it indicates that the low-voltage circuit breaker QF cannot be closed, and a fault alarm signal will be generated, indicating that the system has a fault.

[0096] In the embodiment of the present application, the duration corresponding to the second verification task is 10s.

[0097] In some other embodiments, a controllable load module is further included, and the user side further includes a photovoltaic side.

[0098] In the off-grid energy storage mode: The photovoltaic side is used to supply power to the load side through photovoltaic panels.

[0099] In some actual power consumption scenarios (such as residential communities), during off-grid energy storage, in addition to the energy storage system being able to supply power to the load, power can also be supplied through photovoltaic.

[0100] When the energy storage power in the energy storage system is small, it is necessary to stop the energy storage system from supplying power to the load, because when the energy storage system has no power at all, it will cause irreversible harm to the energy storage battery, shorten the service life of the battery, and even may permanently damage the battery and make it unable to be charged again; the performance of some capacitor components may decline in a long-term power-off state, resulting in the system being unable to work properly after being powered on again.

[0101] Therefore, when the energy storage system has less power, the best response is to disconnect the load side and the energy storage side. Then, when the system also includes a photovoltaic charging method, how to control the load to allocate the power consumption decision between the power-deficient energy storage side and the photovoltaic side is relatively important.

[0102] The controllable load module is used to collect the energy storage power of the energy storage side, the photovoltaic power generation of the photovoltaic side, and the energy consumption power of the load side respectively.

[0103] The controllable load module compares the size of the energy storage power with the preset safe power. If the energy storage power is less than the preset safe power, it enters the load control mode.

[0104] The controllable load module is used to collect the magnitudes of the energy storage power, photovoltaic power generation, and power consumption, and is also used to analyze whether the current energy storage power is at a safe level. If not, it corresponds to the load control mode, which means that certain adjustments need to be made to the power consumption between the load and the energy storage.

[0105] In the load control mode, the controllable load module determines the magnitude relationship between the photovoltaic power generation and the power consumption.

[0106] If the power consumption is greater than the photovoltaic power generation, the connection between the energy storage end and the load end is disconnected, and the photovoltaic end is controlled to charge the energy storage end.

[0107] If the power consumption is not greater than the photovoltaic power generation, the photovoltaic end is controlled to supply power to the load end, and a signal to shut down the energy storage is generated and sent to the energy storage control unit. The energy storage control unit controls the energy storage end to shut down based on the energy storage shutdown signal.

[0108] Under load control, first, the magnitude relationship between the photovoltaic power generation and the power consumption is compared, that is, it is determined whether the performance of the photovoltaic power generation matches the power consumption demand of the load. If it is satisfied, it indicates that the photovoltaic power generation situation is good. At this time, the energy storage end is shut down, and at the same time, the power supply to the load is switched to be through the photovoltaic power generation. If it is not satisfied, it means that the photovoltaic power generation situation is not good and cannot meet the power consumption demand of the load. On the one hand, even if the photovoltaic power generation supplies power to the load, the load cannot have a stable power consumption experience. On the other hand, to avoid the problem that the energy storage end cannot be powered on again due to complete power shortage, the circuit between the energy storage end and the load end is directly disconnected and the energy storage end is shut down. At the same time, to avoid wasting the photovoltaic power generation, the photovoltaic power generation is used to charge the energy storage end. When the energy storage end resumes the safe power level after a period of photovoltaic charging, the circuit with the load is reconnected to supply power to the load again.

[0109] In some other embodiments, The present application also discloses a modular low-cost grid-connected and off-grid switching method, which is implemented based on the above system and includes the following steps: S100, when the grid side loses power, the off-grid action module collects the voltage on the grid side to control the on-grid and off-grid switch module connected between the grid side and the user side to operate to the disconnected state, and the load end in the user side loses power.

[0110] S200, the energy storage control unit collects the closing feedback signal to obtain the disconnection of the on-grid and off-grid switch module, and obtains the grid connection feedback signal generated by the grid connection feedback module by collecting the real-time voltage information to control the energy storage end in the user side to switch to the off-grid mode to start and supply power to the load end.

[0111] In S300, when there is power on the grid side, the grid connection feedback module detects the real-time voltage information between the grid side and the grid-connected / off-grid switch module to generate a grid connection feedback signal and send it to the energy storage control unit. The energy storage control unit controls the shutdown of the energy storage terminal based on the grid connection feedback signal to switch to the grid connection mode.

[0112] In S400, the energy storage control unit generates a closing control signal based on the grid connection feedback signal to send to the grid connection action module as an input signal. The grid connection action module controls the grid-connected / off-grid switch action module to act to the closed state based on the input signal.

[0113] The implementation principle is as follows: The components in the grid-connected / off-grid process are designed modularly. Through the module combination composed of conventional relay protection devices, combined with software logic, the function of grid-connected / off-grid switching is realized, and low-cost grid-connected / off-grid switching is achieved. It is suitable for occasions with low requirements for power continuity, some high-power energy storage systems. The scheme has a simple structure, low cost, high reliability, can withstand large currents and powers, and at the same time, the action principles of each component are relatively simple, easy to understand and maintain.

[0114] It should be understood that although the steps in the flowchart of the accompanying drawings are shown in sequence according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit and can be executed in other orders.

[0115] The above are all the preferred embodiments of this application, and do not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A modular low-cost on-grid and off-grid switching system, characterized in that: include: The on-grid and off-grid switch module has two ends respectively used to connect to the grid side and the user side, wherein the user side includes an energy storage end and a load end; An off-grid action module, coupled to the on-grid and off-grid switch module and electrically connected to the grid side, for collecting the voltage on the grid side to control the on-grid and off-grid switch module to move to an off state; A grid-connected action module, coupled to the grid-connected and off-grid switch module, and used to control the grid-connected and off-grid switch module to move to a closed state according to an input signal; A grid-connected feedback module, electrically connected between the grid side and the grid-connected and off-grid switch module, for collecting real-time voltage information to generate a grid-connected feedback signal; An energy storage control unit, electrically connected to the grid-connected feedback module to obtain the grid-connected feedback signal, and generates a closing control signal based on the grid-connected feedback signal and sends the closing control signal to the grid-connected action module as the input signal; The energy storage control unit is also electrically connected to the grid-connected and off-grid switch module to collect a closing feedback signal, and performs a matching analysis based on the grid-connected feedback signal and the closing feedback signal to switch a working mode, wherein the working mode includes a grid-connected mode and an off-grid mode.

2. The modular low-cost on-grid and off-grid switching system according to claim 1, characterized in that: The on-grid and off-grid switch module includes a low-voltage circuit breaker QF, and the off-grid action module includes an undervoltage release X1. The undervoltage release X1 collects the voltage on the grid side and determines whether it is less than a first preset value; If it is not less than the first preset value, the undervoltage release X1 is energized to control the low-voltage circuit breaker QF to remain in a closed state; If it is less than the first preset value, the undervoltage release X1 loses power to generate a tripping action to control the low-voltage circuit breaker QF to disconnect.

3. The modular low-cost on-grid and off-grid switching system according to claim 2, characterized in that: The grid-connected action module includes an electric switch X2, and the grid-connected feedback module includes a voltage relay D1; The voltage relay D1 is used to detect the real-time voltage information between the low-voltage circuit breaker QF and the grid side, and generate a grid-connected feedback signal to the energy storage control unit when the real-time voltage information is greater than a second preset value, wherein the grid-connected feedback signal is a level signal; The energy storage control unit obtains the grid-connected feedback signal and generates a corresponding closing control instruction to send to the electric switch X2. After the electric switch X2 obtains the input signal including the closing control instruction, it drives the low-voltage circuit breaker QF to close through the motor M.

4. The modular low-cost on-grid and off-grid switching system according to claim 1, characterized in that: The energy storage control unit collects the action state of the grid-connected and off-grid switch module in real time to obtain the closing feedback signal, and compares the consistency with the collected grid-connected feedback signal. Specifically, If the grid-connected feedback signal corresponds to the grid-connected level signal and the closing feedback signal corresponds to the closing, the grid-connected mode is entered, at which time the energy storage terminal is controlled to shut down and a grid-connected instruction is sent to the PCS to perform grid-connected charging and discharging control logic; If the grid-connected feedback signal does not correspond to the grid-connected level signal and the closing feedback signal corresponds to opening the switch, the off-grid mode is entered. At this time, the energy storage end is controlled to start up and an off-grid instruction is sent to the energy storage end to perform off-grid charging and discharging control logic.

5. The modular low-cost on-grid and off-grid switching system according to claim 2, characterized in that: When the voltage on the grid side is less than a first preset value, the energy storage control unit obtains the power supply priority of the load end; If the power supply priority is high, a thermal response instruction is generated based on the current voltage and sent to the energy storage end. After the energy storage end obtains the thermal response instruction, it enters a hot start power supply mode to start up; If the power supply priority is low, a cold response instruction is generated based on the current voltage and sent to the energy storage end. After the energy storage end obtains the cold response instruction, it enters the cold start power supply mode to start up.

6. The modular low-cost on-grid and off-grid switching system according to claim 3, characterized in that: The second preset value includes an early sub-value and a late sub-value, wherein the early sub-value is smaller than the late sub-value; When the real-time voltage information is greater than the previous sub-value and is stably maintained for a first period of time, sending the grid-connected feedback signal to the energy storage control unit; When the real-time voltage information is greater than the later sub-value and is stable for a second time period, a grid connection instruction is issued to the PCS and a signal quality is calculated to generate a fluctuation coefficient; Among them, after the energy storage control unit obtains the grid-connected feedback signal, it generates a reaction reserved time and sends it to the energy storage end. The energy storage end is shut down after the reaction reserved time is reached. The reaction reserved time is the second time length multiplied by the fluctuation coefficient.

7. The modular low-cost on-grid and off-grid switching system according to claim 6, characterized in that: During the second time period, the energy storage control unit collects the real-time voltage information, the real-time frequency information, and the real-time phase information in real time and generates a synchronous change amount, and calculates the synchronous change rate by the ratio of the synchronous change amount to the reaction reserved time; The energy storage control unit dynamically adjusts the output power of the energy storage end based on the synchronization change rate until it changes to 0 and shuts down.

8. The modular low-cost on-grid and off-grid switching system according to claim 4, characterized in that: If the grid-connected feedback signal does not correspond to the grid-connected level signal and the closing feedback signal corresponds to closing, a first verification task of a preset duration is generated to issue a first error correction trigger instruction to the undervoltage release X1, and it is determined whether a change in the closing feedback signal is monitored in the first verification task. If no change is detected, a fault alarm message is generated; If the grid-connected feedback signal corresponds to the grid-connected level signal and the closing feedback signal corresponds to the opening of the switch, a second verification task of a preset duration is generated to issue a second error correction instruction to the electric switch X2, and it is determined whether a change in the closing feedback signal is detected in the second verification task. If no change is detected, a fault alarm message is generated.

9. The modular low-cost on-grid and off-grid switching system according to claim 1, characterized in that: It also includes a controllable load module, and the user side also includes a photovoltaic terminal; In the off-grid energy storage mode: The photovoltaic end is used to supply power to the load end through a photovoltaic panel; The controllable load module is used to collect the energy storage power of the energy storage end, the photovoltaic power generation of the photovoltaic end, and the energy consumption of the load end respectively; The controllable load module compares the energy storage power with the preset safety power, and enters the load control mode if the energy storage power is less than the preset safety power; In the load control mode, the controllable load module determines the size between the photovoltaic power generation and the energy consumption; If the energy consumption is greater than the photovoltaic power generation, the connection between the energy storage end and the load end is cut off and the photovoltaic end is controlled to charge the energy storage end; If the energy consumption is not greater than the photovoltaic power generation, the photovoltaic end is controlled to supply power to the load end and an energy storage shutdown signal is generated to the energy storage control unit, and the energy storage control unit controls the energy storage end to shut down based on the energy storage shutdown signal.

10. A modular low-cost on-grid and off-grid switching method, characterized in that: The system according to any one of claims 1 to 9 is implemented, comprising the following steps: When the grid side loses power, the off-grid action module collects the voltage on the grid side to control the on-grid and off-grid switch module connected between the grid side and the user side to move to a disconnected state, and the load end on the user side is powered off; The energy storage control unit collects the closing feedback signal to obtain the disconnection of the grid-connected and off-grid switch module, and obtains the grid-connected feedback signal generated by the grid-connected feedback module by collecting real-time voltage information to control the energy storage end on the user side to switch to the off-grid mode to start up and supply power to the load end; When there is electricity on the grid side, the grid-connected feedback module detects the real-time voltage information between the grid side and the grid-connected and off-grid switch module to generate a grid-connected feedback signal and sends it to the energy storage control unit. The energy storage control unit controls the energy storage end to shut down based on the grid-connected feedback signal to switch to the grid-connected mode; The energy storage control unit generates a closing control signal based on the grid-connected feedback signal to send to the grid-connected action module as the input signal, and the grid-connected action module controls the grid-connected and off-grid switch action module to a closed state based on the input signal.

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