A seamless switching method for off-grid and grid-connected and a household energy storage system

Abstract

This application relates to the field of residential energy storage technology, specifically a seamless switching method and system for off-grid and grid-connected operation. The method includes: in grid-connected mode, when the main unit detects an abnormality in the mains power, the grid-connected operating mode is turned off; the main unit's phase-locked source (PLS) switches from mains power to its natural state; the main unit notifies the slave unit to switch its PLS and sends the PLS result to the slave unit; the slave unit's PLS switches to the main unit's natural state and performs PLS; when the slave unit finishes PLS, the mains power input switch is disconnected; after the input switch is disconnected, the off-grid operating mode is activated. In off-grid mode, when the main unit detects a normal mains power, the main unit's PLS switches from its natural state to mains power; the main unit notifies the slave unit to switch its PLS and sends the PLS result to the slave unit; the slave unit's PLS switches to the mains and performs PLS; after the slave unit finishes PLS, the mains power input switch is closed; the off-grid operating mode is turned off before the input switch is closed, and the grid-connected operating mode is activated after the input switch is closed. This application enables seamless switching between grid-connected and off-grid operation.

Description

Technical Field

[0001] This application relates to the field of residential energy storage technology, and in particular to a seamless switching method between off-grid and grid-connected systems and a residential energy storage system. Background Technology

[0002] While mains power can supply electricity to all production sites, the mains grid is also subject to power outages due to transformer damage or line maintenance, causing inconvenience to people's work and daily life. Data centers, large enterprises, hotels, and banks typically require continuous and uninterrupted power supply. These facilities usually have backup power generation equipment or residential energy storage systems. When a mains power outage is detected, the power generation equipment or residential energy storage system is required to automatically start supplying power. After mains power is restored, the generator set is required to be connected to the mains grid before shutting down, thus avoiding the inconvenience caused by another power outage during the switching process.

[0003] In existing technologies, residential energy storage systems only start automatically after a power outage is detected, which leads to power interruptions. Summary of the Invention

[0004] This application provides a seamless switching method for off-grid and on-grid operation and a residential energy storage system to ensure seamless switching between off-grid and on-grid operation when the mains power fails.

[0005] To address the aforementioned technical problems, embodiments of this application provide a seamless switching method between off-grid and on-grid modes, comprising:

[0006] In grid-connected mode, when the host detects an abnormality in the mains power, the grid-connected working mode is turned off; the host's phase-locked source switches from mains power to self-oscillating state; the host notifies the slave to switch the phase-locked source and sends the phase-locking result to the slave; the slave's phase-locked source switches to the host's self-oscillating state and performs phase-locking; when the slave finishes phase-locking, the mains power input switch is disconnected; after the input switch is disconnected, the off-grid working mode is turned on.

[0007] In the off-grid state, when the host determines that the mains power is normal, the host's phase-locked source switches from the self-oscillating state to the mains power; the host notifies the slave to switch the phase-locked source and sends the phase-locked result to the slave; the slave's phase-locked source switches to the mains power and performs phase-locking; after the slave finishes phase-locking, the mains power input switch is closed; the off-grid working mode is turned off before the input switch is closed, and the grid-connected working mode is turned on after the input switch is closed.

[0008] To address the aforementioned technical problems, this application provides a residential energy storage system, including an energy management module, an energy gateway, a smart power distribution module, and at least one energy storage subsystem.

[0009] The energy management module includes an energy management unit and a communication gateway; the energy management unit is configured to control the energy storage subsystem to charge and discharge, and the communication gateway is configured to detect the operating status of the entire residential energy storage system and communicate with the Internet of Things cloud platform.

[0010] The energy gateway is configured to disconnect the connection between the mains power and the residential energy storage system when the mains power fails, and to restore the connection between the mains power and the residential energy storage system when the mains power is restored.

[0011] The intelligent power distribution module is configured to control the on / off state of the energy storage subsystem and to control the connection of loads and power supply equipment.

[0012] The energy storage subsystem includes a battery management module, an energy storage battery module, and at least one power converter; the battery management module is configured to manage the charging and discharging of the energy storage battery module and acquire signals, and the power converter is configured to convert AC power into DC power that can be charged by the energy storage battery module and to convert DC power into AC power that can be used for grid connection and household loads when the energy storage battery module is discharging.

[0013] In grid-connected mode, when the energy management module detects an abnormality in the mains power, the grid-connected operating mode is turned off; the phase-locked source of the energy management module switches from the mains power to the self-oscillating state; the energy management module notifies the power converter to switch the phase-locked source and sends the phase-locking result to the power converter; the phase-locked source of the power converter switches to the self-oscillating state of the energy management module and performs phase-locking; when the phase-locking of the power converter ends, the mains power input switch is disconnected; after the input switch is disconnected, the off-grid operating mode is turned on.

[0014] In off-grid mode, when the energy management module determines that the mains power is normal, the phase-locked source of the energy management module switches from the self-oscillating state to the mains power; the energy management module notifies the power converter to switch the phase-locked source and sends the phase-locking result to the power converter; the phase-locked source of the power converter switches to the mains power and performs phase-locking; after the phase-locking is completed, the mains power input switch is closed; the off-grid working mode is closed before the input switch is closed, and the grid-connected working mode is opened after the input switch is closed.

[0015] The off-grid and on-grid seamless switching method and residential energy storage system provided in this application embodiment achieve seamless switching between off-grid and on-grid by switching the master and slave phase-locked sources when the mains power is abnormal. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of one embodiment of the seamless switching method between off-grid and on-grid operations according to this application;

[0018] Figure 2 This is a schematic diagram of the grid-connected to off-grid switching timing of one embodiment of the seamless switching method between off-grid and grid-connected networks according to this application;

[0019] Figure 3 This is a schematic diagram of the off-grid switching to grid connection timing of an embodiment of the seamless off-grid and grid-connected switching method of this application;

[0020] Figure 4 A schematic diagram of CAN communication for one embodiment of the seamless switching method between off-grid and on-grid in this application;

[0021] Figure 5 This is yet another flowchart of an embodiment of the seamless switching method between off-grid and on-grid in this application;

[0022] Figure 6 This is yet another flowchart of an embodiment of the seamless switching method between off-grid and on-grid in this application;

[0023] Figure 7 This is yet another flowchart of an embodiment of the seamless switching method between off-grid and on-grid in this application;

[0024] Figure 8 This application can be configured as an exemplary residential energy storage system architecture diagram;

[0025] Figure 9 This is a schematic diagram of the energy management module in one embodiment of the residential energy storage system of this application;

[0026] Figure 10 This is yet another exemplary system architecture diagram of the residential energy storage system of this application;

[0027] Figure 11 This is yet another exemplary system architecture diagram of the residential energy storage system of this application;

[0028] Figure 12 This is a schematic diagram of the energy storage subsystem in one embodiment of the residential energy storage system of this application. Detailed Implementation

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are configured to distinguish different objects, rather than to describe a particular order.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] Please see Figure 1 , Figure 1 This application illustrates a seamless switching method between off-grid and on-grid operation, implemented in a residential energy storage system. This system is equipped with a computer that stores and executes computer instructions. The computer hardware includes, but is not limited to, microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), and embedded devices. The computer's form is not limited to desktop computers, laptops, handheld computers, or cloud servers.

[0033] S101: When the host detects an abnormality in the mains power supply during grid-connected operation, the grid-connected working mode is turned off.

[0034] Among them, mains power, also known as industrial frequency alternating current (AC), is characterized by three common quantities: voltage, current, and frequency. The commonly used AC frequencies worldwide are 50Hz and 60Hz, and the voltage distribution for residential AC ranges from 100V to 380V. Computer rooms typically use three-phase 380V, 50Hz mains power, but the equipment's power rectifier modules use single-phase 220V.

[0035] Among them, the grid-connected working modes refer to the fully self-consumption mode (anti-backflow), the self-consumption surplus power grid connection mode, and the full grid connection mode.

[0036] Specifically, in grid-connected mode, the host performs anomaly detection on the mains power, and shuts down the grid-connected working mode when the detection result indicates an anomaly in the mains power.

[0037] It is easy to understand that when the mains frequency is 50Hz and the phase difference is π / 2, the time difference is 4ms. In order to ensure that the mains abnormality is captured in the shortest time, as a preferred method, this embodiment adopts an abnormality detection time interval of 4ms.

[0038] S102, the main unit's phase-locked source switches from mains power to self-oscillating state.

[0039] In this context, the phase-locked source is the frequency source that locks onto the phase. Phase-locking is a technique that allows the phase of a controlled oscillator to be controlled by a standard signal or an external signal. It is used to achieve phase synchronization with an external signal or to track the frequency or phase of an external signal. Phase-locked is short for phase-locked, indicating phase synchronization between two signals.

[0040] Among them, the self-oscillation state refers to the state of self-sustaining oscillation. Self-sustaining oscillation is a stable periodic motion with a fixed frequency and amplitude generated within a system when there is no external periodic change signal.

[0041] Specifically, in grid-connected mode, when the mains power is normal, the master unit uses the mains power as a phase-locked source for phase-locking processing and sends the phase-locking result to the slave unit so that the slave unit can compensate based on the master unit's phase-locking result and maintain phase synchronization with the mains power.

[0042] S103, the master notifies the slave to switch the phase-locked source and sends the phase-locked result to the slave.

[0043] After the master unit switches the phase-locked source from mains power to self-oscillating state, it notifies the slave unit to switch the phase-locked source and sends the phase-locked result to the slave unit.

[0044] The notification method can be either wired or wireless communication. Preferably, when the notification method is wireless communication, email is used to exchange and transmit the phase-locked loop results.

[0045] S104, the slave phase-locked source switches to the master's self-oscillating state and performs phase-locking.

[0046] After receiving the phase-locked loop (PLL) result, the slave device switches to the master device's natural state and performs phase-locking based on the parameters in the PLL result.

[0047] The parameters in the phase-locked loop result are used for phase adjustment, including but not limited to the host carrier counter value and phase value after the host successfully locks onto the phase.

[0048] S105, when the slave phase lock ends, the mains power input switch is disconnected.

[0049] When the slave phase lock ends, the mains power input switch is disconnected.

[0050] It should be understood that in this embodiment, the mains power input switch refers to a switch used to control the mains power connection, specifically an electrical component such as a relay. In one specific embodiment, when the host detects an abnormality in the mains power, the grid-connected operating mode is turned off, and the relay driver is activated to execute the relay disconnect command.

[0051] It should be noted that the disconnection of the mains input switch in this embodiment is the actual disconnection time. The time from the execution of the disconnection command to the actual disconnection of the mains input switch is the same as the off-grid phase-locked loop time, which is one oscillation cycle of the mains power. For example, when the mains power frequency is 50Hz, the off-grid phase-locked loop time is 20ms.

[0052] Please refer to Figure 2 , Figure 2 This is a specific timing diagram illustrating the grid-connected to off-grid switching in this embodiment. Figure 2In the process, the host detects a grid fault within 4ms, and then the master and slave coordinate to enter the off-grid phase-locked loop (PLL) process. Simultaneously, the relay driver receives the host's disconnect command and disconnects the grid-side relay (the input switch for mains power). Both the off-grid PLL process and the disconnection action last for 20ms (one mains power cycle). After the grid-side relay disconnects, the off-grid driver (the driver program operating in off-grid mode) is started after a 1.5ms delay, entering the off-grid operating mode. Line 1 represents the timing changes of the grid fault, line 2 represents the timing changes of the grid-side relay driver signal, line 3 represents the changes in the grid-side relay signal, and line 4 represents the grid-connected driver... The process of the operation change is shown in line 5, which represents the timing change process of the off-grid drive. The host performs periodic detection on the mains power. From time t0 to time t1, there is one detection cycle. At time t1, a fault is confirmed in the mains power, and the curve of line 1 changes from normal operation to abnormal. At the same time, a drive signal to disconnect the relay is generated to drive the relay to disconnect. From time t1 to time t2, the relay performs the disconnection action. At the same time, the grid-connected drive disconnects, and the off-grid drive begins to perform off-grid phase locking. At time t2, the relay completes the disconnection work and continues to delay (t3-t2). When time t3 is reached, the master and slave phase synchronization is ensured, the off-grid drive is started, and the off-grid mode is entered.

[0053] S106, Off-grid working mode is activated after the input switch is turned off.

[0054] It should be noted that the process from S102 to S104 is off-grid phase-locked loop. When an abnormality in the mains power is detected, the action of disconnecting the mains power switch is executed. After the mains power switch is disconnected, the master and slave units execute off-grid phase-locked loop to ensure uninterrupted power supply when switching from grid-connected to off-grid. After the mains power switch is turned on, the off-grid phase-locked loop process is delayed until the off-grid mode is successfully started.

[0055] In this embodiment, the off-network algorithm is activated by off-network driver to enter the off-network working mode.

[0056] S107, when the host determines that the mains power is normal in the off-grid state, the host's phase-locked source switches from the self-oscillating state to the mains power.

[0057] When in an off-grid state, the host monitors the voltage / frequency of the mains power and determines whether the mains power has returned to normal based on the monitoring results. After confirming that the mains power is normal, the host switches the phase-locked source from the self-oscillating state to the mains power.

[0058] S108, the master notifies the slave to switch the phase-locked source and sends the phase-locked result to the slave.

[0059] After the master unit switches the phase-locked source to the mains power, it notifies the slave unit to switch the phase-locked source and sends its own phase-locked result to the slave unit.

[0060] S109, the slave unit switches the phase-locked source to the mains power and performs phase-locking.

[0061] After receiving a notification from the master unit, the slave unit switches the phase-locked source based on the master unit's phase-locked result to achieve phase synchronization with the mains power.

[0062] S110, the mains input switch closes after the slave phase-locked loop ends.

[0063] After the slave device successfully locks in phase, it sends the phase-locking result to the master device. Upon receiving the successful phase-locking command from the slave device, the master device executes the mains input switch closing command to connect to the mains power grid.

[0064] S111, the grid-connected working mode is activated after the input switch is closed.

[0065] After the input switch is closed, it enters the grid-connected working mode.

[0066] It should be noted that, in order to ensure a seamless connection during the switching process, the power conversion algorithm of the off-grid driver is switched from the off-grid algorithm to the grid-connected algorithm at a preset time before the input switch is actually closed, and the grid-connected driver (the driver that works in grid-connected mode) is started after the preset time after the input switch is actually closed, and the grid-connected working mode is entered.

[0067] Please refer to Figure 3 , Figure 3 This is a specific timing diagram of the off-grid switching to grid connection in this embodiment. Figure 3 In the process, the host detects the restoration of normal mains power within 4ms, and then the master and slave coordinate to enter the grid-connected phase-locked loop (PLL) process. Simultaneously, the relay driver receives the host's activation command and begins to close the grid-side relay (the mains power input switch). The duration of both the PLL process and the activation action is 20ms (one mains power cycle). After the grid-side relay activates, there is a 1.5ms delay before starting the grid-connected drive and entering the grid-connected operating mode. Line 1 represents the timing changes during a grid fault, line 2 represents the timing changes during the grid-side relay drive signal, line 3 represents the changes during the grid-side relay operation, and line 4 represents the grid connection... The driving action changes are shown in line 5, which represents the timing changes of the off-grid drive. The host performs periodic checks on the mains power. One check cycle is from time t4 to time t5. At time t5, the mains power is confirmed to have returned to normal, and the curve of line 1 changes from an abnormal state to normal. At the same time, the host and slave start to lock phase using the mains power as the phase-locked source. By time t6, the phase-locking is completed, and a drive signal for the relay to be energized is generated to drive the relay to perform the energizing operation. At time t7, the relay completes the energizing operation, the off-grid drive is turned off, and after a delay of (t8-t7) until time t8, the grid-connected drive is turned on, and the off-grid mode is entered.

[0068] The off-grid and on-grid seamless switching method and household energy storage system provided in this application embodiment achieve seamless switching between off-grid and on-grid by switching the master-slave phase-locked source when the mains power is abnormal, thereby improving power safety and user experience.

[0069] It should be noted that the execution order of S101 to S111 can be adaptively adjusted according to actual needs. This application provides one such execution order.

[0070] In some optional implementations of this embodiment, the master unit performs phase-locked loop (PLL) on the phase and frequency of the mains power, and the master unit and slave unit communicate via a CAN bus, specifically as follows: Figure 4 As shown, the master unit communicates synchronously with multiple slave units via a CAN bus. CAN stands for Controller Area Network, and is an ISO internationally standardized serial communication protocol.

[0071] like Figure 5 As shown, some optional implementation methods mainly include the following steps:

[0072] S201, the first frame of the synchronization signal sent by the master to the slave when the power frequency cycle crosses zero;

[0073] S202, when the host completes the transmission of the first frame, it triggers a CAN bus interrupt and records the value T1 of the first counter at this time in the CAN bus interrupt;

[0074] S203, The host records the phase value W1, the value M1 of the second counter, and the value T2 of the first counter when the first frame is sent.

[0075] S204, the host calculates the phase value W2 at time T1 and the adjustment step size ΔM of the second counter based on the difference between T1 and T2;

[0076] S205, the master sends the phase value W2 at time T1 and the adjustment step size ΔM of the second counter as the second frame of the synchronization signal to the slave.

[0077] When the mains power is normal, the power supply system is in grid-connected operation mode. At this time, the master unit locks the phase and frequency of the mains power and interacts with the slave unit based on CAN bus communication. During the interaction, the signal transmission generates a certain time difference. In this embodiment, the master and slave units use their respective recorded transmission / reception time points as reference points to calculate the deviation and then make up for it to ensure phase synchronization. Specifically, the master unit sends the first frame of the synchronization signal to the slave unit when the power frequency cycle crosses zero, and triggers a CAN bus interrupt when the first frame is sent. The value T1 of the first counter is recorded in the CAN bus interrupt. Based on the value M1 of the second counter, the phase value W1, and the value T2 of the first counter recorded by the master unit when the first frame is sent, the phase value W2 at time T1 and the adjustment step size ΔM of the second counter are determined. Then, the phase value W2 at time T1 and the adjustment step size ΔM of the second counter are sent to the slave unit as the second frame of the synchronization signal.

[0078] The first counter is configured as a counter for recording host time points, such as a Timer counter, and the second counter is configured as a carrier counter for the host.

[0079] In this embodiment, the required phase step size is determined by using the master and slave devices to calculate the time difference based on their respective recorded transmission / reception times, and then sent to the slave device to quickly achieve phase synchronization between the master and slave devices.

[0080] In some optional implementations of this embodiment, the master unit performs phase-locked loop (PLL) on the phase and frequency of the mains power, and the master unit and slave unit communicate via a CAN bus, such as... Figure 6 As shown, it also includes the following steps:

[0081] S301, when the slave device receives the first frame of the synchronization signal, it records the phase value W3, the value M3 of the third counter, and the value T3 of the fourth counter at this time;

[0082] S302, the slave device adjusts the phase value and the value of the third counter based on the phase value W2 received at time T1 and the adjustment step size ΔM of the second counter, combined with the phase value W3 and the value M3 of the third counter.

[0083] Specifically, when the slave device receives the first frame of the synchronization signal, it records its own phase value W3, the value of the third counter M3, and the value of the fourth counter T3. Based on the phase value W2 received at time T1 and the adjustment step size ΔM of the second counter, it adjusts the phase value and the value of the third counter to perform difference compensation and achieve phase synchronization between the master and slave devices.

[0084] The first counter is configured as the carrier counter for the slave device, and the fourth counter is configured as a counter for recording slave time points.

[0085] In this embodiment, the slave device can quickly achieve difference compensation by using the values ​​it records and the values ​​it receives, which helps to improve the efficiency of phase synchronization.

[0086] In some optional implementations of this embodiment, the host determines mains power anomalies by detecting the mains power voltage, such as... Figure 7 As shown, the specific steps include the following:

[0087] S401 acquires mains voltage sampling data through voltage sampling;

[0088] S402 processes the voltage sampling data through an all-pass filter to obtain the AC quantity;

[0089] S403: Take the absolute value of the voltage sampling data and the corresponding AC quantity of the voltage sampling data and sum them to obtain the reference signal;

[0090] S404 compares the reference signal with a preset threshold. If the reference signal exceeds or equals the preset threshold, the mains power is normal; otherwise, the mains power is abnormal.

[0091] While an all-pass filter (APF) does not change the frequency response of the input signal, it does change its phase. Utilizing this property, all-pass filters can be used as delay devices, delay equalizers, and so on.

[0092] Specifically, in this embodiment, voltage sampling data is obtained by sampling the voltage in the mains power supply. Then, an all-pass filter is used to filter the voltage sampling data to obtain an AC quantity with a certain delay. At the same time, the absolute values ​​of the voltage sampling data and the corresponding AC quantity are taken and summed to obtain a reference signal. The reference signal is then compared with a preset threshold. Based on the comparison result, the mains power status is determined. When the comparison result shows that the reference signal exceeds or equals the preset threshold, the mains power status is normal; otherwise, the mains power is abnormal.

[0093] Optionally, the voltage sampling data is processed by an all-pass filter to have a 90° phase lag, and the reference signal is a signal at 4 times the power frequency.

[0094] It should be noted that using voltage to determine anomalies is a specific embodiment used in this example, but it is not limited to this in practice. In actual applications, frequency or other parameters can also be used for judgment, which is not specifically limited here.

[0095] Optionally, after the input switch is turned off, the slave device enters the offline working mode after a 1.5ms delay in offline drive.

[0096] Optionally, the grid-connected driver is started 1.5ms after the input switch is closed, and the grid-connected working mode is entered.

[0097] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0098] Please see Figure 8 , Figure 8 This application illustrates a residential energy storage system provided in an embodiment of the present application. The residential energy storage system is configured to achieve, as shown in the embodiment of the present application. Figure 1 The seamless switching method between off-grid and on-grid operation shown in the diagram includes a residential energy storage system comprising an energy management module 51, an energy gateway 52, a smart power distribution module 53, and at least one energy storage subsystem 54.

[0099] Please see Figure 9 , Figure 9 This diagram illustrates an energy management module in a residential energy storage system according to an embodiment of this application. The energy management module 51 includes an energy management unit 511 and a communication gateway 512; the energy management unit is configured to control the energy storage subsystem to charge and discharge, and the communication gateway 512 is configured to detect the operating status of the entire residential energy storage system and communicate with the Internet of Things cloud platform.

[0100] Energy gateway 52 is configured to disconnect the connection between the mains power and the residential energy storage system when the mains power fails, and to restore the connection between the mains power and the residential energy storage system when the mains power is restored.

[0101] The intelligent power distribution module 53 is configured to control the on / off state of the energy storage subsystem and to control the access of loads and power supply equipment.

[0102] The energy storage subsystem 54 includes a battery management module 541, an energy storage battery module 542, and at least one power converter 543. The battery management module 541 is configured to manage the charging and discharging of the energy storage battery module 542 and to acquire signals. The power converter 543 is configured to convert AC power into DC power that can be charged by the energy storage battery module 542 and to convert DC power into AC power that can be used by grid-connected and household loads when the energy storage battery module 542 is discharging.

[0103] When the power management module 51 detects an abnormality in the grid-connected state, the grid-connected working mode is turned off; the phase-locked source of the power management module 51 switches from the mains power to the self-oscillating state; the power management module 51 notifies the power converter to switch the phase-locked source and sends the phase-locking result to the power converter 543; the phase-locked source of the power converter 543 switches to the self-oscillating state of the power management module 51 and performs phase-locking; when the phase-locking of the power converter 543 ends, the mains power input switch is disconnected; after the input switch is disconnected, the off-grid working mode is turned on.

[0104] In off-grid mode, when the energy management module 51 determines that the mains power is normal, the phase-locked source of the energy management module 51 switches from the self-oscillating state to the mains power; the energy management module 51 notifies the power converter 543 to switch the phase-locked source and sends the phase-locking result to the power converter 543; the phase-locked source of the power converter 543 switches to the mains power and performs phase-locking; after the phase-locking is completed, the mains power input switch is closed; the off-grid working mode is turned off before the input switch is closed, and the grid-connected working mode is turned on after the input switch is closed.

[0105] The residential energy storage system is configured such that the energy management module 51 performs phase-locked loop (PLL) on the phase and frequency of the mains power. When the energy management module 51 communicates with the power converter 543 via the CAN bus, the specific implementation includes:

[0106] The energy management module 51 sends the first frame of the synchronization signal to the power converter 543 when the power frequency cycle crosses zero.

[0107] When the first frame is sent, the energy management module 51 triggers a CAN bus interrupt and records the value T1 of the first counter at this time in the CAN bus interrupt.

[0108] The energy management module 51 records the phase value W1, the value M1 of the second counter, and the value T2 of the first counter when the first frame is sent.

[0109] The energy management module 51 calculates the phase value W2 at time T1 and the adjustment step size ΔM of the second counter based on the difference between T1 and T2.

[0110] The energy management module 51 sends the phase value W2 at time T1 and the adjustment step size ΔM of the second counter as the second frame of the synchronization signal to the power converter 543.

[0111] The residential energy storage system is configured such that the energy management module 51 performs phase-locked loop (PLL) on the phase and frequency of the mains power. When the energy management module 51 communicates with the power converter 543 via the CAN bus, the specific implementation also includes:

[0112] When the power converter 543 finishes receiving the first frame of the synchronization signal, it records the phase value W3, the value M3 of the third counter, and the value T3 of the fourth counter at this time.

[0113] The power converter 543 adjusts the phase value and the value of the third counter based on the received phase value W2 at time T1, the adjustment step size ΔM of the second counter, and the phase value W3 and the value M3 of the third counter.

[0114] When the residential energy storage system is configured such that the energy management module 51 detects mains voltage to determine mains power anomalies, it is specifically configured as follows:

[0115] Voltage sampling data of mains power is obtained through voltage sampling;

[0116] The voltage sampling data is processed through an all-pass filter to obtain the AC quantity;

[0117] The reference signal is obtained by taking the absolute values ​​of the voltage sampling data and the corresponding AC quantities, and summing them.

[0118] The reference signal is compared with a preset threshold. If the reference signal exceeds or equals the preset threshold, the mains power is normal; otherwise, the mains power is abnormal.

[0119] Optionally, the energy gateway 52 is configured to disconnect the power supply equipment and household loads from the power grid when switching from grid-connected to off-grid, and to restore the connection of the energy storage subsystem and household loads to the mains power when switching from off-grid to grid-connected.

[0120] Optionally, the operating modes of the energy management module 51 include backup power mode, photovoltaic self-consumption mode, and peak shaving and valley filling mode.

[0121] Optionally, such as Figure 10 As shown, the residential energy storage system also includes a smart meter 55, which is communicatively connected to the energy management module 51. The smart meter 55 is configured to measure the power and energy of the power supply equipment on the grid side and send the measurement data to the energy management module through the communication connection.

[0122] Optionally, such as Figure 11 As shown, the residential energy storage system also includes an Internet of Things (IoT) cloud platform 56, which is configured to communicate with the energy management module 51, receive measurement data uploaded by the energy management module 51, and send control commands to the energy management module 51 via wireless communication.

[0123] Furthermore, each storage system includes multiple energy storage subsystems 54, such as Figure 12 As shown, Figure 12 This is a schematic diagram of an energy storage subsystem in an embodiment of this application. The energy storage subsystem 54 includes a battery management module 541, an energy storage battery module 542, and a power converter 543. There can be one or more power converters, specifically AC / DC, DC / AC, etc. The multiple energy storage subsystems 54 are configured to be connected in parallel and are assigned communication addresses through the energy management module 51.

[0124] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A seamless switching method of off-grid and on-grid, applied to a household energy storage system, characterized in that, include: In grid-connected mode, the host detects mains voltage to determine mains power anomalies. This detection includes: acquiring voltage sampling data of the mains power; processing the voltage sampling data through an all-pass filter to obtain an AC quantity; summing the absolute values ​​of the voltage sampling data and the corresponding AC quantity to obtain a reference signal; comparing the reference signal with a preset threshold; if the reference signal exceeds or equals the preset threshold, the mains power is considered normal; otherwise, the mains power is abnormal. When the host detects a mains power anomaly, the grid-connected mode is turned off; the host's phase-locked source switches from mains power to its natural state; the host notifies the slave to switch its phase-locked source and sends the phase-locking result to the slave; the slave's phase-locked source switches to the host's natural state and performs phase-locking; when the slave's phase-locking ends, the mains power input switch is disconnected; after the input switch is disconnected, the off-grid mode is activated. In the off-grid state, when the host determines that the mains power is normal, the host's phase-locked source switches from the self-oscillating state to the mains power; the host notifies the slave to switch the phase-locked source and sends the phase-locked result to the slave; the slave's phase-locked source switches to the mains power and performs phase-locking; after the slave finishes phase-locking, the mains power input switch is closed; the off-grid working mode is turned off before the input switch is closed, and the grid-connected working mode is turned on after the input switch is closed.

2. The seamless switching method between off-grid and on-grid as described in claim 1, characterized in that, The master unit locks the phase and frequency of the mains power, and the master unit communicates with the slave unit via the CAN bus.

3. The seamless switching method between off-grid and on-grid as described in claim 2, characterized in that, The first frame of the synchronization signal sent by the master to the slave when the power frequency cycle crosses zero; When the host completes the transmission of the first frame, it triggers a CAN bus interrupt and records the value T1 of the first counter at this time in the CAN bus interrupt. The host records the phase value W1, the value M1 of the second counter, and the value T2 of the first counter when the first frame is transmitted. The host calculates the phase value W2 at time T1 and the adjustment step size ΔM of the second counter based on the difference between T1 and T2; The master sends the phase value W2 at time T1 and the adjustment step size ΔM of the second counter as the second frame of the synchronization signal to the slave.

4. The seamless switching method between off-grid and on-grid as described in claim 3, characterized in that, When the slave device receives the first frame of the synchronization signal, it records the phase value W3, the value of the third counter M3, and the value of the fourth counter T3 at this time. The slave device adjusts the phase value and the value of the third counter based on the received phase value W2 at time T1 and the adjustment step size ΔM of the second counter, combined with the phase value W3 and the value M3 of the third counter.

5. The seamless switching method between off-grid and on-grid as described in claim 1, characterized in that, The voltage sampling data is processed by an all-pass filter to have a 90° phase lag, and the reference signal is a signal at 4 times the power frequency.

6. The seamless switching method between off-grid and on-grid as described in claim 1, characterized in that, After the input switch is turned off, the slave device enters the offline working mode after a 1.5ms delay in the offline drive.

7. The seamless switching method between off-grid and on-grid as described in claim 1, characterized in that, The grid-connected drive is started 1.5ms after the input switch is closed, and the grid-connected working mode is entered.

8. A residential energy storage system, characterized in that, It includes an energy management module, an energy gateway, a smart power distribution module, and at least one energy storage subsystem; The energy management module includes an energy management unit and a communication gateway; the energy management unit is configured to control the energy storage subsystem to charge and discharge, and the communication gateway is configured to detect the operating status of the entire residential energy storage system and communicate with the Internet of Things cloud platform. The energy gateway is configured to disconnect the connection between the mains power and the residential energy storage system when the mains power fails, and to restore the connection between the mains power and the residential energy storage system when the mains power is restored. The intelligent power distribution module is configured to control the on / off state of the energy storage subsystem and to control the connection of loads and power supply equipment. The energy storage subsystem includes a battery management module, an energy storage battery module, and at least one power converter; the battery management module is configured to manage the charging and discharging of the energy storage battery module and acquire signals, and the power converter is configured to convert AC power into DC power that can be charged by the energy storage battery module and to convert DC power into AC power that can be used for grid connection and household loads when the energy storage battery module is discharging. In grid-connected mode, the energy management module detects mains voltage to determine mains power anomalies, including: acquiring mains voltage sampling data through voltage sampling; processing the voltage sampling data through an all-pass filter to obtain AC quantities; summing the absolute values ​​of the voltage sampling data and the corresponding AC quantities to obtain a reference signal; comparing the reference signal with a preset threshold; if the reference signal exceeds or equals the preset threshold, the mains power is normal; otherwise, the mains power is abnormal; when an abnormality is detected, the grid-connected operating mode is turned off; the phase-locked source of the energy management module switches from mains power to its natural state; the energy management module notifies the power converter to switch its phase-locked source and sends the phase-locking result to the power converter; the power converter's phase-locked source switches to the energy management module's natural state and performs phase-locking; when the power converter finishes phase-locking, the mains power input switch is disconnected; after the input switch is disconnected, the off-grid operating mode is activated. In off-grid mode, when the energy management module determines that the mains power is normal, the phase-locked source of the energy management module switches from the self-oscillating state to the mains power; the energy management module notifies the power converter to switch the phase-locked source and sends the phase-locking result to the power converter; the phase-locked source of the power converter switches to the mains power and performs phase-locking; after the phase-locking is completed, the mains power input switch is closed; the off-grid working mode is closed before the input switch is closed, and the grid-connected working mode is opened after the input switch is closed.

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