Household energy storage system and control method thereof

Abstract

The invention provides a household energy storage system and a control method thereof, the energy storage system comprises a plurality of battery packs and an energy storage inverter PSC, the plurality of battery packs are connected in parallel and are in communication connection through a CAN to form a parallel operation network, the control method comprises the following steps: one of the plurality of battery packs is determined as a host, the other battery packs are determined as slaves, and the host is connected and interacted with a PCS; the host obtains parameter information of the host and the slave and controls the parallel operation state of the host and the slave according to the parameter information; based on the parameter information and the parallel operation state, the host judges whether a target battery pack meeting a triggering condition of a low-power rescue strategy exists in the multiple battery packs or not; when the target battery pack exists in the multiple battery packs, the connection state of the target battery pack is controlled based on the low-electric-quantity rescue strategy, and the connection state comprises cut-in discharging or cut-in charging. According to the invention, the problems of unbalanced electric quantity and unreasonable charging and discharging of the energy storage system in different scenes are solved, and the stability of the energy storage system is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of parallel operation of energy storage batteries, and particularly relates to a household energy storage system and a control method thereof. Background Art

[0002] With the popularization and development of household energy storage systems, in order to meet the customer's demand for battery capacity expansion, a multi-branch battery parallel connection scheme is widely adopted in the industry.

[0003] At present, there are two mainstream parallel operation schemes for household energy storage systems: the first is to adopt the form of adding a hardware current limiting module, which will increase the hardware cost; the second is to adopt a software control scheme. When the voltage difference between battery packs is less than a certain threshold, parallel operation is switched in, and switched out when there is a power discharge or a fault. However, due to the unpredictability of the charge and discharge states, this scheme often causes the battery packs that are switched out to not meet the switching-back conditions, resulting in power discharge and unusability. Moreover, the switching-in and switching-out operations will be re-executed according to the current charge and discharge states. At this time, the switching-in and switching-out operations will be frequent, directly affecting the service life of the switching devices, and because it is necessary to wait for the parallel operation to be completed before continuing to use, the system response timeliness is directly reduced.

[0004] On the other hand, in a low-temperature environment (<0°C), the use of battery packs will be restricted. Most battery packs cannot be charged, and the discharge capacity will also decline. In related technologies, use in a low-temperature environment is prohibited; or the battery packs can only be used after being heated by a power storage inverter (PCS). During the heating process, other batteries of the parallel-connected battery packs cannot be discharged and used. In this way, not only will the cost increase, but the operating conditions will also be greatly restricted. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems in the related technologies to some extent. For this reason,

[0006] According to an embodiment of the present disclosure, a control method for a household energy storage system is provided. The energy storage system includes a plurality of battery packs and a PSC. The plurality of battery packs are connected in parallel and form a parallel operation network through CAN communication. The battery packs include BMS modules. The control method includes the following steps:

[0007] Determine one of the plurality of battery packs as the host, and the remaining battery packs as slaves. The host is connected to and interacts with the PSC, and the PSC is used to control the charging and discharging processes of the host and the slaves;

[0008] The host obtains the parameter information of itself and the slaves, and controls the parallel operation state of itself and the slaves according to the parameter information. The parallel operation state includes a switching-in state of switching into the parallel operation network and a switching-out state of switching out of the parallel operation network;

[0009] Based on parameter information and the parallel operation state, the host determines whether there is a target battery pack among multiple battery packs that meets the trigger conditions of the low battery rescue strategy; among them, the target battery pack is the battery pack with the highest power or the lowest power in the cut-out state.

[0010] When there is a target battery pack among multiple battery packs, based on the low battery rescue strategy, control the connection state of the target battery pack, and the connection state includes cutting in for discharging or cutting in for charging.

[0011] The following are the advantages or beneficial effects in the above technical solution: By introducing the "low battery rescue strategy", the host can automatically determine whether the battery pack meets the trigger conditions of the low battery rescue strategy, and timely control the target battery pack that meets the trigger conditions to cut in for charging or discharging, optimize the operation state of the battery pack, reasonably perform the charge and discharge scheduling of the battery pack, solve the problems of uneven power and unreasonable charge and discharge that may occur in the energy storage system in different scenarios, ensure the stability of the energy storage system, and extend the service life of the battery pack.

[0012] According to an embodiment of the present disclosure, determining whether there is a target battery pack among multiple battery packs that meets the trigger conditions of the low battery rescue strategy includes:

[0013] When the parameter information and the parallel operation state indicate that there are both a battery pack in the cut-in state and a lowest-power battery pack in the cut-out state among multiple battery packs, and the SOC of the lowest-power battery pack in the cut-out state is lower than the preset low battery threshold and it is determined that it has the charging condition, it is determined that the trigger condition is met, and the lowest-power battery pack in the cut-out state is used as the target battery pack;

[0014] Based on the low battery rescue strategy, controlling the connection state of the target battery pack includes:

[0015] Cut out all the battery packs in the parallel network, and cut in the lowest-power battery pack into the parallel network for charging.

[0016] The following are the advantages or beneficial effects in the above technical solution: Automatically identify the uncut-in battery packs with low power for timely charging rescue, avoid the lowest-power battery pack continuously not meeting the cut-in conditions and resulting in power depletion, and extend the service life of the battery pack.

[0017] According to an embodiment of the present disclosure, determining whether there is a target battery pack among multiple battery packs that meets the trigger conditions of the low battery rescue strategy includes:

[0018] When the parameter information and the parallel operation state indicate that there are both a battery pack in the cut-in state and a highest-power battery pack in the cut-out state among multiple battery packs, and the SOC of the parallel network is lower than the preset low battery threshold and it is detected that the parallel network needs to discharge, it is determined that the trigger condition is met, and the highest-power battery pack in the cut-out state is used as the target battery pack;

[0019] Based on the low - power saving strategy, control the connection status of the target battery pack, including:

[0020] Cut out all the battery packs in the parallel network, and cut the battery pack with the highest power into the parallel network for discharging.

[0021] In the above - mentioned technical solution, there are the following advantages or beneficial effects: When the power of the parallel network is low, the host can automatically identify the battery packs with high power and not yet cut in and cut them in for discharging, which can effectively utilize the electric energy stored in the battery packs, avoid the waste phenomenon of "having electricity but unable to discharge", and improve the overall efficiency of the energy storage system.

[0022] According to an embodiment of the present disclosure, the control of the parallel state includes:

[0023] If the battery pack in the cut - out state has no fault and the difference between its voltage and the voltage of the parallel network is less than the first preset threshold, then the battery pack can be controlled to cut into the parallel network; if there is no battery pack cut into the parallel network, the battery pack with the smallest address is cut in first.

[0024] If the battery pack in the cut - in state fails or the difference between its voltage and the voltage of the parallel network is greater than the second preset threshold, then control the battery pack to cut out of the parallel network.

[0025] In the above - mentioned technical solution, there are the following advantages or beneficial effects: By controlling the cut - in and cut - out of the battery packs, it can ensure that the battery packs cut into the parallel network when the voltage match is good, and when the battery pack fails or the voltage difference is too large, immediately cut out the battery pack to avoid the adverse impact of the battery pack on the entire system and maintain the stability and reliability of the system operation.

[0026] According to an embodiment of the present disclosure, the empty and full states of the battery pack are triggered by its own voltage. The charge - discharge circuits of multiple battery packs are of equal length. When the full or empty calibration of one battery pack cut into the parallel network is triggered, the full or empty states of other cut - in battery packs are synchronously calibrated.

[0027] In the above - mentioned technical solution, there are the following advantages or beneficial effects: The equal - length charge - discharge circuits ensure the equalization of the electric quantity among the battery packs. The calibration mechanism of full - empty reduces the cut - in and cut - out times of the battery packs during parallel operation, reduces the loss of the switching devices inside the battery packs, and is beneficial to improving the response speed of the energy storage system for charge - discharge state switching.

[0028] According to an embodiment of the present disclosure, the battery pack includes a heating film. When the battery pack operates in a low - temperature environment below 0°C, the host performs parallel heating control on itself and the slave. The battery pack to be heated applies for a heating current to the PCS based on its own voltage, and the PCS controls the charging process of the battery pack to provide the heating current.

[0029] In the above technical solution, the following advantages or beneficial effects are achieved: The parallel heating control of the energy storage system does not require the PCS or the battery pack to provide an additional heating port, but utilizes the charging function to achieve it, simplifying the system design and hardware structure, and reducing the hardware cost and system complexity. Among them, the heating current value is applied to the PCS through the current battery voltage, and the heating current can be dynamically adjusted according to the real-time voltage state of the battery.

[0030] According to an embodiment of the present disclosure, the parallel heating control includes:

[0031] The host determines whether the battery packs need to be heated based on the temperature and SOC of each battery pack;

[0032] When initially heating and cutting in, after the battery packs meet the voltage stabilization condition that there is at least one battery pack in the cutting-in state that stabilizes the voltage within a preset time, the corresponding cutting-out operation is performed;

[0033] The host dynamically adjusts the number of heating cut-ins according to the currently available heating current, and controls the priority of the battery pack heating cut-in according to the voltage and SOC of the battery pack.

[0034] In the above technical solution, the following advantages or beneficial effects are achieved: By means of intelligent judgment and dynamic adjustment of the number of heating cut-ins, priority, etc., adaptive parallel heating control is realized, optimizing the battery heating process, ensuring that the heating operation is only performed when needed, and avoiding unnecessary energy waste.

[0035] According to an embodiment of the present disclosure, the parallel heating control further includes:

[0036] When multiple battery packs all need to be heated, after the battery packs that need to be heated complete the heating cut-in according to the preset priority, the host determines whether there is a heating high-power battery pack in the cut-out state;

[0037] If so, the battery pack with the highest power is cut into the parallel network to provide discharge support and maintain its heating state until the discharge becomes a heating low-power battery pack and cuts out of the parallel network;

[0038] If not, it is determined whether the battery packs are all heating low-power battery packs;

[0039] If the battery packs are all heating low-power battery packs, the energy storage system prohibits discharging; otherwise, if the energy storage system discharges, it controls the battery packs to exit the heating state, cuts the battery pack with the highest power among the non-heating low-power battery packs into the parallel network for discharging, and re-performs the heating cut-in when the energy storage system charges.

[0040] The above technical solution has the following advantages or beneficial effects: By determining whether there are high - power battery packs in the cut - out state and preferentially using these battery packs to provide discharge while automatically heating, it ensures the efficient utilization of energy, reduces energy waste, and as much as possible meets the uncertain requirements of charging and discharging.

[0041] According to an embodiment of the present disclosure, the parallel heating control further includes:

[0042] When multiple battery packs need to be heated partially, after the battery packs that need to be heated complete the heating cut - in according to the preset priority, if the host identifies that there are non - heating low - power battery packs among the cut - out battery packs that do not need to be heated, then the battery pack with the highest power among them is cut into the parallel network to provide discharge support until the discharge becomes a heating low - power battery pack and cuts out of the parallel network;

[0043] If the host identifies that all the cut - out battery packs that do not need to be heated are heating low - power battery packs, then it is determined whether there are heating high - power battery packs among the cut - out battery packs that need to be heated;

[0044] If so, the battery pack with the highest power among them is cut into the parallel network to provide discharge support and maintain the heating state until the discharge becomes a heating low - power battery pack and cuts out of the parallel network;

[0045] If not, it is determined whether all the cut - out battery packs that need to be heated are heating low - power battery packs. If so, the energy storage system prohibits discharging, and the battery pack with the lowest power among the battery packs that do not need to be heated is cut into the parallel network, and the charging current of the PCS is adjusted to charge it and maintain heating. Otherwise, if the energy storage system discharges, all the battery packs exit the heating state, and the battery pack with the highest power among the non - heating low - power battery packs is cut in for discharging, and re - enters the heating cut - in when the energy storage system charges.

[0046] The above technical solution has the following advantages or beneficial effects: When some battery packs need to be heated, by dynamically switching the high - power battery packs that do not need to be heated for discharging and maintaining heating, it ensures the efficient utilization of energy. In addition, the energy storage system can dynamically adjust the heating, charging and discharging processes of the battery packs to ensure that the charging and discharging requirements can still be met in an uncertain working environment.

[0047] According to an embodiment of the present disclosure, the parallel heating control further includes:

[0048] During the heating process, all the battery packs in the same group as those already in the parallel network cut in and out according to the parallel cut - in conditions.

[0049] In the above technical solution, the following advantages or beneficial effects are achieved: The battery packs in the same group can be flexibly connected in or out according to the parallel connection switching conditions, thereby improving the efficiency of the energy storage system, extending the lifespan of the battery packs, and enhancing the stability of the energy storage system.

[0050] According to an embodiment of the present disclosure, there is also provided a household energy storage system for implementing the household energy storage system control method of any one of the above, including a plurality of battery packs and a PCS. The plurality of battery packs are connected in parallel and connected to the power grid and the load through the PCS. The PCS is used to control the charging and discharging processes of the battery packs. The battery pack includes a BMS module, a CAN communication module, a charge and discharge switch, a heating film, and a heating switch. The BMS module is communicatively connected to the PCS through the CAN communication module. The heating film is connected to the DC side of the PCS. The BMS module is connected to the charge and discharge switch and the heating switch to control the parallel connection state and the heating state of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings described herein are used to provide a further understanding of the present invention, and constitute a part of this application. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0052] Figure 1 is a flowchart of the household energy storage system control method according to an embodiment of the present application;

[0053] Figure 2 is a flowchart of the low battery rescue strategy in the first scenario according to an embodiment of the present application;

[0054] Figure 3 is a flowchart of the low battery rescue strategy in the second scenario according to an embodiment of the present application;

[0055] Figure 4 is a heating control flowchart when all battery packs need to be heated according to an embodiment of the present application;

[0056] Figure 5 is a heating control flowchart when some battery packs need to be heated according to an embodiment of the present application;

[0057] Figure 6 is a structural block diagram of the energy storage system according to an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0058] Next, the technical solutions in the embodiments will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0059] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0060] The terms "first", "second", "third" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third" may explicitly or implicitly include one or more of such features.

[0061] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0062] The present invention provides a control method for a household energy storage system, which can realize functions such as adaptive parallel operation switching and parallel operation heating management, can effectively solve the problems of the use limitation of the battery pack in the existing household energy storage system, the depletion problem of the un-paralleled battery pack, and has less switching loss of switching devices and stronger compatibility, can cover more usage scenarios, and realize convenient and orderly power consumption.

[0063] The energy storage system may include a plurality of battery packs and a power storage inverter PSC. The plurality of battery packs are connected in parallel and form a parallel operation network through CAN communication. The battery pack includes a BMS module for managing and controlling the battery pack.

[0064] Reference Figure 1 , the control method of the energy storage system may include the following steps:

[0065] Step S1, determine one of the plurality of battery packs as the host, and the remaining battery packs as the slaves; wherein, the host is connected and interacts with the PCS, and the PCS is used to control the charging and discharging processes of the host and the slaves.

[0066] Step S2: The host obtains the parameter information of itself and the slave machines, and controls the paralleling state of itself and the slave machines according to the parameter information. The paralleling state includes the cut-in state of cutting into the paralleling network and the cut-out state of cutting out of the paralleling network.

[0067] Step S3: Based on the parameter information and the paralleling state, the host determines whether there is a target battery pack among multiple battery packs that meets the triggering conditions of the low-power rescue strategy; wherein, the target battery packs are the battery packs with the highest power and the lowest power in the cut-out state.

[0068] Step S4: When there are target battery packs among multiple battery packs, based on the low-power rescue strategy, control the connection state of the target battery packs. The connection state includes cutting into discharge or cutting into charge.

[0069] In this embodiment, by introducing the "low-power rescue strategy", the host can automatically determine whether the battery packs meet the triggering conditions of the low-power rescue strategy, and timely control the target battery packs that meet the triggering conditions to cut into charge or discharge, optimize the operating state of the battery packs, reasonably perform the charge and discharge scheduling of the battery packs, solve the problems of uneven power and unreasonable charge and discharge that may occur in the energy storage system in different scenarios, avoid the situation that the power of the lowest-power battery pack in the cut-out state is exhausted and the highest-power battery pack cannot discharge electricity, enable the battery packs to maximize the use of their capacity, improve the use efficiency, ensure the stability of the energy storage system, and extend the service life of the battery packs.

[0070] Specifically, in step S1, the address can be automatically assigned through CAN communication, and a host and multiple slave machines can be distinguished according to the address.

[0071] By automatically assigning the address through CAN communication, the battery packs do not require manual intervention during connection, can automatically identify and assign a unique address through the t communication network, reduce human errors and configuration workload, and are especially suitable for large-scale equipment deployment.

[0072] Of course, in some other embodiments, the address can also be set through a DIP switch in step S1. The unique address is assigned through a simple physical DIP switch, without relying on complex network configurations or software settings, which is convenient for on-site quick debugging and deployment.

[0073] In step S2, the slave machines can transmit their own parameter information to the host through CAN communication. The host is connected to the power conversion system (PCS) of the energy storage, so that the host can transmit the parameter information of the battery packs to the power conversion system (PCS) of the energy storage.

[0074] As the control center, the host can control itself and the slave machines according to its own parameter information, the parameter information of each slave machine, and the control logic. The content of the host controlling itself and the slave machines includes: cutting into the paralleling network and cutting out of the paralleling network.

[0075] It should be noted that each battery pack is divided into a cut-in state and a cut-out state according to whether it is incorporated into the parallel network. That is to say, the parallel state of each battery pack includes the cut-in state of incorporating into the parallel network and the cut-out state of cutting out from the parallel network.

[0076] It can be understood that cutting into the parallel network means turning on the charge and discharge circuit of the battery pack, and cutting out from the parallel network means cutting off the charge and discharge circuit of the battery pack.

[0077] Furthermore, in step S2, the control of the parallel state includes:

[0078] If the battery pack in the cut-out state has no fault and the difference between the voltage of the battery pack and the voltage of the parallel network is less than the first preset threshold, then the battery pack can be controlled to cut into the parallel network;

[0079] If there is no battery pack cut into the parallel network, the battery pack with the smallest address is cut in first.

[0080] In this embodiment, by setting the first preset threshold of the difference between the voltage of the battery pack and the voltage of the parallel network, it can be ensured that the battery pack in the cut-out state without fault cuts in when the voltage matching is good, avoiding voltage fluctuations or instability in the energy storage system.

[0081] The control of the parallel state also includes: If there is no battery pack cut into the parallel network, the battery pack with the smallest address is cut in first.

[0082] In this embodiment, if there is no battery pack cut into the parallel network, when controlling the battery pack to cut in, the battery pack with the smallest address is selected to cut in first, avoiding excessive current impact when multiple battery packs cut in simultaneously.

[0083] The control of the parallel state also includes: If the battery pack in the cut-in state fails, or the difference between the voltage of the battery pack in the cut-in state and the voltage of the parallel network is greater than the second preset threshold, then control the battery pack to cut out from the parallel network.

[0084] When the battery pack incorporated into the parallel network fails or the voltage difference between it and the parallel network is too large, it is immediately cut out, which can prevent the fault from spreading to other devices, avoid adverse effects of the battery pack on the entire system, and maintain the stability and reliability of the operation of the energy storage system.

[0085] Based on its own SOC and the parallel connection status of each slave battery pack, the host can distinguish the following four scenarios: the state where a battery pack is being connected and the lowest - power battery pack is being disconnected, the state where a battery pack is being connected and the highest - power battery pack is being disconnected, the state where all battery packs are disconnected, and the state where all battery packs are connected. In the order described above, they are the first scenario, the second scenario, the third scenario, and the fourth scenario. Among them, the third scenario is the initial state of the energy storage system, the fourth scenario is the final parallel - connection state of the energy storage system, and the first and second scenarios belong to the intermediate process states of the parallel connection of the energy storage system.

[0086] In the related art, if the energy storage system is in the first scenario, the lowest - power battery pack will continuously fail to meet the connection condition until its power is exhausted; if it is in the second scenario, the almost - depleted battery packs that have been connected cannot discharge, but at this time, there are high - power battery packs in the disconnection state, and it is impossible to ensure that the power of the battery packs is fully utilized.

[0087] To solve the drawbacks brought by the above two scenarios, in step S3, the above two scenarios and the target battery packs in the scenarios are identified based on the parameter information and the parallel - connection status, and in step S4, based on the low - power rescue strategy, the connection state of the target battery packs is controlled to effectively solve the problems of possible power imbalance and unreasonable charge - discharge in different scenarios of the energy storage system.

[0088] Among them, the parameter information may include the voltage, current, temperature, SOC, charge - discharge current - limiting value, current working state, fault state, switch device state, etc. of the battery pack.

[0089] It can be understood that the battery pack may include energy - storage battery cells and a BMS (Battery Management System) module connected to the energy - storage battery cells. The BMS module is used to monitor and protect the battery cells and communicate with the PCS to manage the charge - discharge process.

[0090] In some embodiments, in step S3, determining whether there is a target battery pack that meets the trigger condition of the low - power rescue strategy for multiple battery packs includes:

[0091] When the parameter information and the parallel - connection status indicate that there are both battery packs in the connection state and the lowest - power battery pack in the disconnection state among multiple battery packs, and the SOC of the lowest - power battery pack in the disconnection state is lower than the preset low - power threshold and it is determined that it has the charging condition, it is determined that the trigger condition is met, and the lowest - power battery pack in the disconnection state is used as the target battery pack;

[0092] Furthermore, in step S4, based on the low - power rescue strategy, controlling the connection state of the target battery packs includes:

[0093] Disconnect all the battery packs in the parallel - connection network and connect the lowest - power battery pack to the parallel network for charging.

[0094] Specifically, referring to Figure 2 , if the energy storage system enters the first scenario, when it is determined that the SOC of the battery pack with the lowest power cut-off state is lower than the preset low-power threshold and it is detected that charging is currently possible, then all the battery packs in the parallel network are controlled to cut out, enter the third scenario, and the battery pack with the lowest power is cut in for charging.

[0095] In this embodiment, the host can automatically identify the uncut-in battery packs with low power and replenish their power in a timely manner to avoid the battery pack with the lowest power continuously not meeting the cut-in conditions, resulting in complete depletion of power and inability to recover, thereby extending the service life of the battery pack.

[0096] In some embodiments, in step S3, determining whether there is a target battery pack among multiple battery packs that meets the trigger conditions of the low-power rescue strategy includes:

[0097] When the parameter information and the parallel state indicate that among multiple battery packs, there is both a cut-in state of a battery pack and a cut-out state of the battery pack with the highest power, and the SOC of the parallel network is lower than the preset low-power threshold and it is detected that the parallel network needs to discharge, it is determined that the trigger conditions are met, and the battery pack with the highest power in the cut-out state is used as the target battery pack;

[0098] Further, in step S4, based on the low-power rescue strategy, controlling the connection state of the target battery pack includes:

[0099] All the battery packs in the parallel network are cut out, and the battery pack with the highest power is cut into the parallel network for discharging.

[0100] Specifically, referring to Figure 3 , if the energy storage system enters the second scenario, when it is determined that the SOC of the parallel network is lower than the preset low-power threshold and it is detected that the energy storage system needs to discharge, then all the battery packs in the parallel network are controlled to cut out, enter the third scenario, and the battery pack with the highest power is cut in for discharging.

[0101] In this embodiment, when the power of the parallel network is low, the host can automatically identify the battery pack with the highest power and not cut in, and according to the low-power rescue strategy, reasonably schedule the discharge when the battery pack has sufficient power, which can effectively utilize the electric energy stored in the battery pack, avoid the waste phenomenon of "being unable to discharge when there is electricity", and improve the overall efficiency of the energy storage system.

[0102] It should be noted that in this article, the SOC of the battery pack with the lowest power in the parallel network is defined as the SOC of the parallel network.

[0103] In some embodiments, the energy storage system control method further includes a control strategy for fully charging and discharging the parallel battery packs:

[0104] The empty and full states of the battery pack are triggered by its own voltage; wherein the charge and discharge circuits of multiple battery packs are of equal length;

[0105] When a battery pack connected to the parallel network triggers full or empty calibration, the full or empty status of other connected battery packs are calibrated synchronously.

[0106] In this embodiment, the equal-length charge and discharge circuits ensure the balance of charge between the battery packs. The full and empty calibration mechanism reduces the number of times the battery packs are switched in and out during parallel operation, reduces the loss of the switching devices inside the battery pack, and is beneficial to improving the response speed of the charge and discharge state switching of the energy storage system.

[0107] Furthermore, in low-temperature environments below 0°C, most battery packs cannot be charged, and the discharge capacity will also decline. In related technologies, energy storage systems are usually prohibited from being used in low-temperature environments; or the battery packs can only be used after being heated by the energy storage inverter PCS, and other batteries in the parallel network cannot be discharged during the heating process. This will not only increase costs, but also greatly limit the operating conditions.

[0108] In order to solve the above technical problems, in some embodiments of the present application, the battery pack may include a heating film, and the host machine controls the parallel heating of itself and the slave machine. The battery pack in the heating state applies for heating current from the PCS based on its own voltage, and the PCS controls the charging process of the battery pack to provide heating current.

[0109] In this embodiment, the parallel heating control of the energy storage system does not require the PCS or battery pack to provide additional heating ports, but is implemented by using the charging function, which simplifies the system design and hardware structure, and reduces the hardware cost and system complexity. Among them, the heating current value is applied to the PCS through the current battery voltage, and the heating current can be dynamically adjusted according to the real-time voltage state of the battery to ensure effective heating of the battery pack. Applying for an appropriate heating current from the PCS through the current during the charging process not only avoids the need for additional energy supply, but also maximizes the energy utilization efficiency during the battery charging process.

[0110] It should be noted that the two ends of the heating film are connected to the DC side of the PCS to form a heating circuit, wherein a heating switch is provided in the heating circuit to control the conduction or disconnection of the heating circuit. In this application, the battery pack is divided into a heated state and an unheated state according to whether the heating switch (circuit) of the battery pack is turned on, which is independent of the parallel state.

[0111] Furthermore, the parallel heating control may include:

[0112] The host determines whether the battery pack needs to be heated based on the temperature and SOC of each battery pack;

[0113] When initially heating and cutting in, after the battery pack meets the voltage stabilization condition that at least one battery pack in the cutting-in state stabilizes its voltage within a preset time, the corresponding cutting-out operation is executed;

[0114] The host dynamically adjusts the number of heating cut-ins according to the currently available heating current, and controls the priority of heating cut-in of the battery pack according to the voltage and SOC of the battery pack.

[0115] In this embodiment, by means of intelligent judgment and dynamic adjustment of the number of heating cut-ins, priority, etc., adaptive parallel heating control is realized, the battery heating process is optimized, ensuring that the heating operation is only carried out when needed, and avoiding unnecessary energy waste.

[0116] Specifically, during the heating process, the voltage of the battery pack may have instantaneous fluctuations or jumps. If the voltage of the battery pack changes too fast, it may trigger the voltage protection mechanism of the PCS port, resulting in misjudgment of the system and interruption of work.

[0117] To avoid the voltage protection of the PCS port caused by possible voltage jumps, when initially heating and cutting in, at least one battery pack needs to be briefly voltage-stabilized before cutting out, which can effectively reduce the amplitude of voltage fluctuations and ensure that the PCS port will not start protection due to excessive instantaneous voltage changes, thus ensuring the stable operation of the energy storage system.

[0118] Furthermore, in this embodiment, in the parallel state of the battery packs, the number of battery packs for heating cut-in can be flexibly switched according to the currently available heating current, which can avoid unnecessary heating processes and achieve adaptive parallel heating of the battery packs.

[0119] Among them, the battery pack with a smaller voltage difference from the current parallel network voltage has a higher priority for heating cut-in, which helps to maintain the voltage balance between the battery pack and the parallel network. In particular, if the SOC of a battery pack in the battery packs is lower than the preset low battery threshold, its cut-in heating is preferentially ensured, which can prevent its performance decline due to too low SOC. By heating, the temperature of the battery is maintained in the optimal working range, thereby improving the charging and discharging efficiency and extending the service life of the battery.

[0120] In some embodiments of the present application, the parallel heating control further includes:

[0121] When all of the multiple battery packs need heating, after the battery packs to be heated complete heating cut-in according to the preset priority, the host judges whether there is a heating high-power battery pack in the cut-out state;

[0122] If so, the battery pack with the highest power is cut into the parallel network, provides discharge support and maintains its heating state until it becomes a heating low-power battery pack and cuts out of the parallel network;

[0123] If not, determine whether all battery packs are low - power battery packs that need heating;

[0124] If all battery packs are low - power battery packs that need heating, the energy storage system prohibits discharging; otherwise, if the energy storage system discharges, control the battery packs to exit the heating state, and cut the battery pack with the highest power in the non - heating low - power battery packs into the parallel network for discharging. When the energy storage system charges, re - perform heating cut - in.

[0125] In this embodiment, by determining whether there are high - power battery packs in the cut - out state, and preferentially using these battery packs to provide discharge while automatically heating to maintain the heating state of the battery packs, it ensures the efficient utilization of energy, reduces energy waste, and as much as possible meets the uncertain requirements of charge and discharge.

[0126] Specifically, referring to Figure 4 , when all battery packs need heating, control the energy storage system to charge, and control heating cut - in and battery pack cut - out (all battery packs are in the cut - out state). Determine whether there are heating high - power battery packs in the cut - out state. If so, cut the battery pack with the highest power among them. This battery pack can provide discharge support and maintain the heating state, and determine whether there are heating low - power battery packs discharging among the cut - in battery packs. If there are, cut out the heating low - power battery packs.

[0127] After determining whether there are heating high - power battery packs in the cut - out state, if not, determine whether all the battery packs in the cut - out state are heating low - power battery packs. If so, that is, all are heating low - power battery packs, prohibit the energy storage system from discharging and maintain the heating state of the battery packs. If not, further determine whether the energy storage system discharges.

[0128] After determining whether the energy storage system discharges, if so, control all battery packs to exit the heating state, and cut the battery pack with the highest power in the non - heating low - power battery packs into the parallel network for discharging. When the energy storage system charges, all are re - heated.

[0129] After determining whether the energy storage system discharges, if not, maintain the heating state of the battery packs.

[0130] In some embodiments of the present application, the parallel heating control further includes:

[0131] When some of the multiple battery packs need heating, after the battery packs that need heating complete heating cut - in according to the preset priority, if the host identifies that there are non - heating low - power battery packs among the cut - out battery packs that do not need heating, then cut the battery pack with the highest power among them into the parallel network to provide discharge support until the discharging battery pack becomes a heating low - power battery pack and cuts out of the parallel network;

[0132] If all the battery packs that do not need to be heated and are in the initial state recognized by the host are heated low-power battery packs, then it is determined whether there are heated high-power battery packs among the battery packs that need to be heated in the cut-out state;

[0133] If so, the battery pack with the highest power among them is cut into the parallel network to provide discharge support and maintain the heating state until the discharge becomes a heated low-power battery pack and cuts out of the parallel network;

[0134] If not, it is determined whether all the battery packs that need to be heated in the cut-out state are heated low-power battery packs. If so, the energy storage system prohibits discharging, and the battery pack with the lowest power among the battery packs that do not need to be heated is cut into the parallel network, and the PCS charging current is adjusted to charge it and maintain heating. Otherwise, if the energy storage system discharges, all the battery packs exit the heating state, and the battery pack with the highest power among the non-heated low-power battery packs is cut in for discharging, and re-enters heating and cutting in when the energy storage system charges.

[0135] In this embodiment, when some battery packs need to be heated, the high-power battery packs that do not need to be heated are dynamically switched for discharging and maintaining heating to ensure the efficient utilization of energy. In addition, the energy storage system can dynamically adjust the heating, charging, and discharging processes of the battery packs to ensure that the charging and discharging requirements can still be met in an uncertain working environment.

[0136] When some battery packs need to be heated, the heating circuit is controlled to cut in, and the corresponding battery packs are cut out.

[0137] In some other embodiments, referring to Figure 5 , in order to unify the process and simplify the judgment steps, when some battery packs need to be heated, the heating circuit is controlled to cut in, all the battery packs are cut out, and it is determined whether all the battery packs that do not need to be heated in the cut-out state are heated low-power battery packs. If not, the battery pack with the highest power among them is cut in, and this battery pack can provide discharge and support heating. During this process, it is determined whether there is a heated low-power battery pack discharging among the battery packs that have been cut in. If so, the heated low-power battery pack is cut out.

[0138] After determining whether all the battery packs that do not need to be heated in the cut-out state are heated low-power battery packs, if so, it is further determined whether there are heated high-power battery packs among the battery packs that need to be heated in the cut-out state.

[0139] If there are, the battery pack with the highest power is cut in to provide discharge support and maintain the heating state until the discharge becomes a heated low-power battery pack and cuts out.

[0140] If there are not, it is determined whether all the battery packs that need to be heated in the cut-out state are heated low-power battery packs. If so, the system prohibits discharging, and the battery pack with the lowest power among the battery packs that do not need to be heated is cut in to maintain charging and heating.

[0141] If not all the low - power battery packs are heated, further determine whether the energy storage system is discharging. If so, all the battery packs exit the heating state, and the battery pack with the highest power in the non - heated low - power battery packs is switched in for discharging, and re - enter heating when the system charges.

[0142] It should be noted that in some other embodiments, in order to implement the steps, when some battery packs need to be heated, the heating circuit is switched in, and all the battery packs can be switched out, that is, all the battery packs are in the switched - out state.

[0143] In some embodiments, the parallel heating control further includes: during the heating process, the battery packs in the same group already in the parallel network can be switched in and out according to the parallel state control.

[0144] It should be noted that when operating in a low - temperature environment, in the heating control method, a heating entry threshold is defined, that is, the low - temperature threshold for charging. When the lowest temperature of the battery pack is less than the heating entry threshold, it means that charging requires heating. A heating exit threshold is defined. When the highest temperature of the battery pack after heating is greater than the heating exit threshold, the heating state is exited. A heating high - power threshold is defined. The battery packs with a power higher than the heating high - power threshold will be marked as heating high - power battery packs, and provide support when the PCS switches to the discharging state during the heating process and maintain the heating of other battery packs. A heating low - power threshold is defined. The battery packs with a power lower than the heating low - power threshold will be marked as heating low - power battery packs and have a higher heating priority.

[0145] During the entire heating process, according to whether each battery pack needs heating, two possible states can be distinguished: all need heating, and some need heating.

[0146] It can be understood that the battery packs in the same group refer to the battery packs divided into the same group according to battery characteristics (such as power, voltage, etc.) in the energy storage system, such as all being heating high - power battery packs or all being heating low - power battery packs.

[0147] The energy storage system control method provided by the present invention provides a low - cost solution to solve the problem of battery pack usage limitations, can realize functions such as adaptive parallel switching and adaptive parallel heating management, effectively solve the problem of depletion of battery packs not incorporated into the parallel network, has less switching loss of switching devices, stronger compatibility, can cover more usage scenarios, and realizes convenient and orderly power consumption.

[0148] On the other hand, the present invention also provides an energy storage system for implementing the above - mentioned control method.

[0149] Reference Figure 6, the energy storage system may include multiple battery packs and a PCS. The multiple battery packs are connected in parallel and can be connected to the power grid and the load through the PCS.

[0150] The battery pack may include energy storage battery cells for storing electrical energy.

[0151] The battery pack may include a BMS module, a CAN communication module, a charge and discharge switch K1, a heating film, and a heating switch K4. Among them, the BMS module is communicatively connected to the PCS through the CAN communication module.

[0152] Continue to refer to Figure 6 , the heating film and the heating switch K4 are connected in series to form a first branch. The positive electrode of the energy storage battery cell, the charge and discharge switch K1, the first end of the first branch, and the first end of the energy storage converter PCS are sequentially connected. The negative electrode of the energy storage battery cell, the second end of the first branch, and the second end of the PCS are sequentially connected.

[0153] Among them, the first branch is connected to the PCS to form a heating circuit, and closing the heating switch K4 can achieve heating cut-in. In the current embodiment, closing the charge and discharge switch K1 corresponding to the current battery pack can complete the parallel operation of the battery packs.

[0154] In some embodiments, the battery pack may include a precharge switch K2 and a precharge resistor R1. The precharge switch K2 and the precharge resistor R1 are connected in series to form a second branch. Among them, the second branch is connected in parallel with the charge and discharge switch K1.

[0155] In this embodiment, when the battery pack is cut into the parallel operation network, the precharge switch K2 and the precharge resistor R1 cooperate to limit the current impact. The function of the precharge resistor R1 is to slow down the voltage rise speed and avoid large current impact when directly closing the charge and discharge switch K1. After the precharge stage is completed, the precharge switch K2 is disconnected and the charge and discharge switch K1 is closed, and the battery pack is officially incorporated into the parallel operation network.

[0156] In some embodiments of the present application, the battery pack may include a negative relay K3, and the negative relay K3 is connected between the negative electrode of the energy storage battery cell and the second end of the first branch.

[0157] Among them, the BMS module is connected to the charge and discharge switch K1, the heating switch K4, the precharge switch K2, and the negative relay K3 to control the parallel operation state and heating state of the battery pack.

[0158] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A household energy storage system control method, characterized in that: The energy storage system includes a plurality of battery packs and an energy storage inverter PSC, wherein the plurality of battery packs are connected in parallel and connected via CAN communication to form a parallel network, and the control method includes the following steps: Determine that one of the plurality of battery packs is a host, and the other battery packs are slaves, the host is connected and interacts with the PCS, and the PCS is used to control the charging and discharging process of the host and the slaves; The host obtains parameter information of itself and the slave, and controls the parallel state of itself and the slave according to the parameter information, wherein the parallel state includes a switching-in state of switching into the parallel network and a switching-out state of switching out of the parallel network; Based on the parameter information and the parallel status, the host determines whether there is a target battery group among the plurality of battery groups that meets the triggering condition of the low-battery rescue strategy; wherein the target battery group is the battery group with the highest power and the battery group with the lowest power in the cut-out state; When the target battery group exists in a plurality of the battery groups, the connection state of the target battery group is controlled based on the low-battery rescue strategy, and the connection state includes switching into discharge or switching into charge.

2. The household energy storage system control method according to claim 1, characterized in that: Determining whether there is a target battery pack among the plurality of battery packs that meets the triggering condition of the low-battery rescue strategy includes: When the parameter information and the parallel state indicate that a battery pack in the plurality of battery packs is in a cut-in state and a battery pack with the lowest power is in a cut-out state at the same time, and the SOC of the battery pack with the lowest power in the cut-out state is lower than a preset low power threshold and it is determined that it has a charging condition, it is determined that the trigger condition is met, and the battery pack with the lowest power in the cut-out state is used as the target battery pack; Based on the low-battery rescue strategy, controlling the connection state of the target battery pack includes: All battery packs in the parallel network are disconnected, and the battery pack with the lowest power is connected to the parallel network for charging.

3. The household energy storage system control method according to claim 1, characterized in that: Determining whether there is a target battery pack among the plurality of battery packs that meets the triggering condition of the low-battery rescue strategy includes: When the parameter information and the parallel state indicate that a battery pack in the plurality of battery packs is in a cut-in state and a battery pack with the highest power is in a cut-out state at the same time, and the SOC of the parallel network is lower than a preset low power threshold and it is detected that the parallel network needs to be discharged, it is determined that the trigger condition is met, and the battery pack with the highest power in the cut-out state is used as the target battery pack; Based on the low-battery rescue strategy, controlling the connection state of the target battery pack includes: All battery packs in the parallel network are disconnected, and the battery pack with the highest power is connected to the parallel network for discharge.

4. The household energy storage system control method according to claim 1, characterized in that: The control of the parallel state includes: If the battery pack in the cut-out state has no fault and the difference between its voltage and the voltage of the parallel network is less than a first preset threshold, the battery pack can be controlled to cut into the parallel network; if there is no battery pack cut into the parallel network, the battery pack with the smallest address is cut into first; If the battery pack in the cut-in state fails or the difference between its voltage and the voltage of the parallel network is greater than a second preset threshold, the battery pack is controlled to be cut out of the parallel network.

5. The household energy storage system control method according to claim 1, characterized in that: The empty and full states of the battery pack are triggered by their own voltage, and the charge and discharge circuits of the multiple battery packs are of equal length; when a battery pack connected to the parallel network triggers full or empty calibration, the full or empty states of the other battery packs that have been connected are synchronously calibrated.

6. The household energy storage system control method according to claim 1, characterized in that: The battery pack includes a heating film. In a low temperature environment below 0°C, the host performs parallel heating control on itself and the slave. The battery pack in the heating state applies for heating current from the PCS based on its own voltage, and the PCS controls the charging process of the battery pack to provide heating current.

7. The household energy storage system control method according to claim 6, characterized in that: The parallel heating control includes: The host determines whether the battery pack needs to be heated according to the temperature and SOC of each battery pack; when the heating is switched on for the first time, after the battery pack meets the voltage stabilization condition that at least one battery pack in the switched-on state is stable within a preset time, the host performs the corresponding switch-off operation; The host dynamically adjusts the number of heating cut-ins according to the currently available heating current, and controls the priority of the heating cut-ins of the battery pack according to the voltage and SOC of the battery pack.

8. The household energy storage system control method according to claim 7, characterized in that: The parallel heating control further includes: When all of the plurality of battery packs need to be heated, after the battery packs that need to be heated complete heating cut-in according to a preset priority, the host determines whether there is a heated high-capacity battery pack in a cut-out state; If yes, the battery pack with the highest power is switched into the parallel network to provide discharge support and maintain its heating state until the discharge becomes heating and the battery pack with low power is switched out of the parallel network; If not, determining whether the battery packs are all heating low-power battery packs; If all the battery groups are the heated low-power battery groups, the energy storage system is prohibited from discharging; otherwise, if the energy storage system discharges, the battery groups are controlled to exit the heating state, and the battery group with the highest power among the non-heated low-power battery groups is switched into the parallel network for discharge, and the heating is restarted when the energy storage system is charged.

9. The household energy storage system control method according to claim 7 or 8, characterized in that: The parallel heating control further includes: When a plurality of battery packs partially need to be heated, after the battery packs that need to be heated complete heating cut-in according to the preset priority, if the host recognizes that the battery packs that do not need to be heated in the cut-out state are not all heating low-power battery packs, the battery pack with the highest power among them is cut into the parallel network to provide discharge support until the discharge becomes heating low-power battery packs cut out of the parallel network; If the host recognizes that the battery packs in the cut-out state that do not need to be heated are all the battery packs with low heating capacity, it is determined whether there are battery packs in the cut-out state that need to be heated that have high heating capacity; If so, the battery pack with the highest power is switched into the parallel network to provide discharge support and maintain the heating state until the discharge becomes heated and the low-power battery pack is switched out of the parallel network; If not, determine whether the battery packs that need to be heated in the cut-out state are all heating low-power battery packs. If they are, the energy storage system is prohibited from discharging, and the battery pack with the lowest power among the battery packs that do not need to be heated is cut into the parallel network, and the charging current of the PCS is adjusted to charge it and maintain heating. Otherwise, if the energy storage system is discharging, all the battery packs are controlled to exit the heating state, and the battery pack with the highest power among the non-heating low-power battery packs is cut in for discharge, and the heating is re-entered when the energy storage system is charged.

10. A household energy storage system, used to implement the household energy storage system control method described in any one of 1 to 9, characterized in that: It includes multiple battery packs and PCS, and the multiple battery packs are connected in parallel and connected to the power grid and the load through the PCS. The battery pack includes energy storage cells, a BMS module, a CAN communication module, a charge and discharge switch, a heating film and a heating switch. The BMS module is connected to the PCS through the CAN communication module, the heating film is connected to the DC side of the PCS, and the BMS module is connected to the charge and discharge switch and the heating switch to control the parallel state and heating state of the battery pack.

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