Energy Storage System

Abstract

An energy storage system includes at least one energy storage unit cluster and a centralized monitoring system for the energy storage unit cluster. The energy storage unit cluster is composed of at least two energy storage modules connected in series. One energy storage module includes an energy storage element group and a switch bridge arm. The switch bridge arm is composed of a main control switch and a bypass switch. One end of the main control switch is connected to the energy storage element group, and the other end of the main control switch serves as the first input / output end of the energy storage module. One end of the bypass switch is connected to the first input / output end, and the other end of the bypass switch is connected to the second input / output end of the energy storage module. The energy storage unit cluster is coupled to a DC bus through a DC / DC converter. The centralized monitoring system is connected to the energy storage unit cluster through a control bus, and is used to control the conduction or disconnection of the main control switch and the bypass switch in any energy storage module in the energy storage unit cluster. The management flexibility of the energy storage system can be improved, the stability of the energy storage system can be improved, and the applicability is higher.

Description

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on July 15, 2020, with application number 202010683032.1 and application name “Energy Storage System”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery energy storage technology, and in particular to an energy storage system. Background Art

[0003] In order to overcome the serious intermittent problem of large-scale photovoltaic and wind power generation, and with the rapid decline in battery costs, battery energy storage has developed rapidly both on the power generation side and on the power consumption side due to its application flexibility, controllability and high energy density. Since the voltage of a single battery module is usually small, even if multiple battery modules are connected in series, it cannot meet the needs of large-scale energy storage. Therefore, in order to balance cost and performance, such as Figure 1 The industry’s usual practice is to connect multiple battery modules (BM) (such as battery module 11 to battery module 1n, battery module 21 to battery module 2n) in series to obtain multiple battery clusters (such as battery cluster 1 and battery cluster 2), and connect the multiple battery clusters in parallel, and then share a direct current (DC) / alternating current (AC) inverter to achieve energy exchange between energy storage batteries and the grid in large-scale energy storage. However, with the increase in years of use, the battery’s state of health (SOH) continues to decline, and the capacity that can be stored in the battery also decreases year by year. Due to the differences between individual batteries, the discreteness of the health of different batteries is also becoming increasingly significant, such as Figure 2 As shown in the figure, the battery health of battery 1 and battery 2 gradually decreases with the age of the battery. In the 10th year, the SOH of battery 1 is 70%, and the SOH of battery 2 is 60%. The battery health of battery 1 and battery 2 differs by 10%. The series connection of battery modules makes the charge and discharge time of each battery module in the same battery cluster the same, while the differences between battery modules are getting bigger and bigger. In order to ensure the safety and availability of any battery module in a single battery cluster, the limitation of the bottleneck battery module must be considered and the entire battery cluster must be derated, resulting in battery waste. Due to the difference in battery internal resistance and battery port voltage, the simple parallel connection of battery clusters will lead to inconsistent charge and discharge between different battery clusters, thereby limiting the utilization of the battery.

[0004] The inventors of the present application have found in the process of research and practice that in order to solve the battery differences between batteries, such as Figure 3The existing technology is to introduce a DC / DC converter in each battery module. The DC / DC converters of each battery module in the same battery cluster share a set of buses, and use the DC / DC converters followed by each battery module to achieve energy management and compensate for the differences caused by battery attenuation. Figure 3 , the DC / DC converters of each battery module in battery cluster 1 share a set of buses, and the DC / DC converters of each battery module in battery cluster 2 share a set of buses. However, the existing technology cannot solve the differences between batteries in battery clusters. At the same time, due to the introduction of each DC / DC converter, additional wiring is required to achieve energy transfer between different battery modules. The wiring is highly complex and has a high probability of error, making the delivery of the energy storage system difficult, the delivery quality cannot be guaranteed, and the applicability is poor. Summary of the invention

[0005] The present application provides an energy storage system that can improve the management flexibility of the energy storage system, enhance the stability of the energy storage system, and has higher applicability.

[0006] In a first aspect, the present application provides an energy storage system, which includes at least one energy storage unit cluster and a centralized monitoring system for the energy storage unit cluster. It can be understood that if the energy storage system includes more than one energy storage unit cluster, one energy storage unit cluster corresponds to one centralized monitoring system. Any energy storage unit cluster includes at least two energy storage modules and the at least two energy storage modules are connected in series. An energy storage module includes an energy storage element group and a switch bridge arm, and the switch bridge arm is composed of a main control switch and a bypass switch. One end of the main control switch is connected to the energy storage element group, and the other end of the main control switch is used as the first input / output end of the energy storage module. One end of the bypass switch is connected to the first input / output end, and the other end of the bypass switch is connected to the second input / output end of the energy storage module. An energy storage unit cluster is coupled to a DC bus through a DC / DC converter, and the centralized monitoring system of the energy storage unit cluster is connected to the energy storage unit cluster through a control bus, which is used to control the conduction or disconnection of the main control switch and the bypass switch in any energy storage module in the energy storage unit cluster to access or bypass any energy storage module. In the present application, each energy storage unit cluster is coupled to the DC bus through a DC / DC converter to achieve simple parallel expansion of multiple energy storage unit clusters, which can increase the energy storage capacity of the energy storage system. The DC / DC converter can also realize flexible control of the energy of a single energy storage unit cluster and rapid switching of a single energy storage unit cluster under abnormal conditions, which has strong applicability. Through the switch bridge arm in the energy storage module, combined with the energy management capability of the DC / DC converter connected to the energy storage unit cluster where the energy storage module is located, flexible control of a single energy storage module can be achieved, which can improve the management flexibility of the energy storage system and the stability of the energy storage system, and has high applicability.

[0007] In combination with the first aspect, in a first possible implementation, the centralized monitoring system of the energy storage unit cluster is integrated into the DC / DC converter, which can simplify the system structure of the energy storage system. At the same time, since the energy storage unit cluster is usually installed in close proximity to the DC / DC converter, integrating the centralized monitoring system of the energy storage unit cluster into the DC / DC converter is conducive to the connection of the control bus and has higher applicability. Here, the DC / DC converter can be a bidirectional DC / DC converter, the circuit topology of the bidirectional DC / DC converter can be a non-isolated circuit topology, and the boost ratio of the bidirectional DC / DC converter is determined by the voltage of the DC bus and the port voltage of the energy storage unit cluster.

[0008] In combination with the first possible implementation method of the first aspect, in a second possible implementation method, one of the at least two energy storage modules mentioned above also includes a battery management unit BMU; the centralized monitoring system of the energy storage unit cluster is connected to the BMUs of each energy storage module in the energy storage unit cluster through a control bus, and controls the conduction or shutdown of the main control switch and bypass switch of any energy storage module through the BMU of any energy storage module, which is simple to operate and highly applicable.

[0009] In combination with the second possible implementation method of the first aspect, in a third possible implementation method, the main control switch and bypass switch of any of the above-mentioned energy storage modules are integrated in the BMU of any of the energy storage modules, which can simplify the system structure of the energy storage system and at the same time improve the control flexibility of the switch bridge arm of the energy storage module, making it more applicable.

[0010] In combination with the third possible implementation of the first aspect, in the third possible implementation, the main control switch and the bypass switch of any energy storage module in the energy storage unit cluster are in the off state, which can improve the maintenance safety of the energy storage system.

[0011] In combination with the fourth possible implementation method of the first aspect, in a fifth possible implementation method, the power supply module of the BMU of any energy storage module is powered by the energy storage element group of any energy storage module or the control bus, and the operation is flexible, and the control capability of the energy storage module can be guaranteed, so that the normal operation of the entire battery cluster is not affected when the energy storage module is in a bypass state, and the applicability is high.

[0012] In combination with the fifth possible implementation of the first aspect, in a sixth possible implementation, the centralized monitoring system of the energy storage unit cluster is used to control the main switch of each energy storage module to be turned on one by one through the BMU of each energy storage module in the energy storage unit cluster when the energy storage system is started. In the present application, when the main switch and bypass switch of each battery module in the energy storage unit cluster are in the off state, the centralized monitoring system of the energy storage unit cluster controls the main switch S1 of the energy storage module one by one through the BMU of each energy storage module, which can increase the port voltage of the energy storage unit cluster in a step-by-step manner, reduce the current impact of the energy storage unit cluster, and further significantly simplify the soft start circuit of the DC / DC converter, and even do not require a soft start circuit, which is simple to operate and highly applicable.

[0013] In combination with the sixth possible implementation of the first aspect, in a seventh possible implementation, the BMU of any energy storage module is used to turn off the main control switch of any energy storage module and turn on the bypass switch of any energy storage module when detecting that the charging and discharging port voltage of the energy storage element group in any energy storage module is equal to the protection voltage threshold. The present application can control the switch bridge arm of the energy storage module through the BMU of each energy storage module to achieve the cutting in or cutting out of a single energy storage module, which is flexible in operation and highly applicable.

[0014] In combination with the sixth possible implementation of the first aspect, in an eighth possible implementation, the BMU of any energy storage module is used to turn off the main control switch of any energy storage module and turn on the bypass switch when an abnormality of the energy storage element group in any energy storage module is detected. Here, the abnormality of the energy storage element group includes that the health state SOH of the energy storage element group is less than the SOH threshold, the energy storage element group is short-circuited, or the energy storage element group is overheated. The present application controls the switch bridge arm of the energy storage module through the BMU of each energy storage module, and can automatically cut off the faulty energy storage module, while ensuring the normal operation of the energy storage unit cluster and even the energy storage system, with flexible operation and high applicability.

[0015] In combination with the seventh possible implementation of the first aspect or the eighth possible implementation of the first aspect, in a ninth possible implementation, the BMU of any energy storage module is used to send a current adjustment request to the centralized monitoring system. The centralized monitoring system is used to control the DC / DC converter to reduce the battery charge and discharge current of the energy storage unit cluster when receiving the current adjustment request. The BMU of any of the above energy storage modules is also used to turn off or turn on the main control switch or bypass switch of any energy storage module when it detects that the battery charge and discharge current is equal to a preset current threshold, which can achieve smooth cutting in and out of the energy storage module, while protecting the high reliability operation of the switching device, and has high applicability.

[0016] In combination with the ninth possible implementation manner of the first aspect, in a tenth possible implementation manner, the preset current threshold is 50%, 20% or 10% of the rated operating current of the energy storage unit cluster.

[0017] In combination with the sixth possible implementation method of the first aspect, in the eleventh possible implementation method, the BMU of any energy storage module is also used to turn off the main control switch and bypass switch of any energy storage module when the control signal of the centralized monitoring system is not detected, so as to make the output of the energy storage module a high impedance state, thereby preventing the energy storage module from affecting the normal operation of the battery cluster, thereby improving the stability of the energy storage system and having high applicability.

[0018] In combination with the first aspect to the eleventh possible implementation of the first aspect, in the twelfth possible implementation, the switch bridge arm is a low-voltage metal oxide semiconductor field effect transistor MOSFET, and the voltage of the low-voltage MOSFET includes 60V, 80V, 100V, 120V, 150V or 200V. In the present application, the on-resistance of the low-voltage MOSFET is low, and the use of the low-voltage MOSFET in the switch bridge arm can reduce the conduction loss in the on state. At the same time, the low-voltage MOSFET can work in a synchronous rectification state, and low on-resistance can be achieved during the charging and discharging process, and the applicability is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the energy storage system;

[0020] Figure 2 It is a curve diagram showing the relationship between battery health status and service life;

[0021] Figure 3 It is another structural schematic diagram of the energy storage system;

[0022] Figure 4 It is a structural schematic diagram of the energy storage system provided by the present application;

[0023] Figure 5a It is a structural schematic diagram of a battery module provided by the present application;

[0024] Figure 5b is another structural schematic diagram of the battery module provided by the present application;

[0025] Figure 6 is another structural schematic diagram of the energy storage system provided by the present application;

[0026] Figure 7 It is a schematic diagram of a battery cluster connected to a DC / DC converter in an energy storage system provided by the present application;

[0027] Figure 8 It is a schematic diagram of the change of the battery cluster port voltage of the energy storage system provided by the present application;

[0028] Fig. 9 is another structural schematic diagram of the energy storage system provided by the present application;

[0029] Fig.10 It is a schematic diagram of the changes in battery parameters when the battery modules in the battery cluster are switched. DETAILED DESCRIPTION

[0030] The energy storage system provided in this application is applicable to various types of power generation equipment such as photovoltaic power generation equipment or wind power generation equipment, and can be applied to the automotive field, etc. The energy storage system provided in this application is applicable to the energy storage of different types of energy storage elements. Here, different types of energy storage elements may include lithium-ion batteries, lead-acid batteries (or lead-acid batteries), and supercapacitors (also known as electrochemical capacitors), etc. This application does not specifically limit the specific types of energy storage elements. For the convenience of description, this application will take batteries as an example to illustrate the energy storage system provided in this application.

[0031] Whether it is large-scale photovoltaic power generation or wind power generation, the grid voltage is usually high, such as an AC voltage of 400V to 800V, which results in a DC side voltage of 550V to 1500V. However, the voltage of a single battery module is usually small, such as a single battery module The voltage is usually less than 60V. In order to meet the grid voltage requirements, multiple battery modules are usually directly connected in series to obtain high voltage. In the energy storage system provided in the present application, a battery module may be a battery pack, and a battery pack may be composed of one or more battery cells (battery cells may be single cells, etc., and the voltage of battery cells is usually between 2.5V and 4.2V) connected in series and in parallel to form a minimum energy storage and management unit. For the convenience of description, the battery module will be used as an example for explanation below. In other words, in the energy storage system provided in the present application, the battery module is the smallest energy storage and management unit composed of one or more battery cells connected in series and in parallel, which will not be repeated below. The energy storage system provided in the present application has a simple structure and high safety, can improve the control flexibility of each energy storage module in the energy storage system, and at the same time can improve the effective utilization rate of the energy storage module, enhance the management effectiveness of the energy storage module, and has strong applicability.

[0032] The structure of the energy storage system:

[0033] See also Figure 4 , Figure 4 It is a structural diagram of the energy storage system provided by the present application. The energy storage system provided by the present application includes one or more energy storage unit clusters (i.e., at least one energy storage unit cluster), and an energy storage unit cluster may include at least two energy storage modules, and each energy storage module is connected in series with each other. In other words, an energy storage unit cluster may be composed of at least two energy storage modules connected in series. In the present application, various types of energy storage elements are explained by taking batteries as an example, energy storage unit clusters will be explained by taking battery clusters as an example, and energy storage modules will be explained by taking battery modules as an example, which will not be repeated below. Figure 4As shown, in the energy storage system provided in the present application, one or more energy storage unit clusters can be illustrated by taking battery clusters 1 to 1n as examples, wherein battery cluster 1 can be composed of battery modules 11 to 1n connected in series, and battery cluster 2 can be composed of battery modules 21 to 2n connected in series, and n is an integer.

[0034] In some feasible implementations, each battery cluster in the energy storage system may be coupled to a DC bus via a DC / DC converter, and one battery cluster may be coupled to a DC bus via one DC / DC converter, such as Figure 4 As shown, battery cluster 1 can be coupled to the DC bus through converter DC / DC1, and battery cluster 2 can be coupled to the DC bus through converter DC / DC2. Each battery cluster is coupled to the DC bus through a DC / DC converter to achieve simple parallel expansion of multiple battery clusters, which can increase the energy storage capacity of the energy storage system. The DC / DC converter can also realize flexible control of the energy of a single battery cluster and rapid switching of a single battery cluster under abnormal conditions, which has strong applicability.

[0035] Here, the DC / DC converter can be a bidirectional DC / DC converter, and the circuit topology of the bidirectional DC / DC converter can be an isolated circuit topology or a non-isolated circuit topology. The boost ratio of the bidirectional DC / DC converter is determined by the voltage of the DC bus and the port voltage of the battery cluster. Taking battery cluster 1 as an example, since the port voltage of the battery changes with the energy storage capacity and the state of charge (SOC) of the battery, the port voltage of battery cluster 1 changes with the number of battery modules connected in series in battery cluster 1. When the number of battery modules connected in series in battery cluster 1 changes greatly, the port voltage of battery cluster 1 will also change greatly. For example, assuming that the port voltage of the battery module is 50V, when 2 battery modules are connected in series in battery cluster 1, the port voltage of battery cluster 1 is 100V, and when 30 battery modules are connected in series in battery cluster 1, the port voltage of battery cluster 1 is 1500V, that is, the upper limit voltage of the low voltage system, so the port voltage of battery cluster 1 can be a wide range of output voltages, such as 100V to 1500V. In order to match the port voltage variation range of the battery cluster 1, the converter DC / DC1 can usually be implemented using a non-isolated circuit topology, and can be designed as a converter with a wide range of input / output capabilities, so that it can flexibly adapt to different input / output voltages. Here, the circuit topology of the bidirectional DC / DC converter (including converters DC / DC1 and DC / DC2, etc.) can be selected from boost circuits, flying capacitor boost circuits, flying capacitor multilevel circuits, positive and negative symmetrical three-level boost circuits, four-switch buck-boost circuits, etc., which can be determined according to the actual application scenario requirements and are not limited here. The boost ratio of the converter DC / DC1 can be determined by the voltage of the DC bus and the port voltage of the battery cluster 1, which can be determined according to the actual application scenario and are not limited here.

[0036] In some feasible embodiments, each battery module (such as battery module 11 to battery module 1n) in any battery cluster (such as battery cluster 1) of the energy storage system may include an energy storage element group (i.e., battery group) and a switch bridge arm composed of a main control switch and a bypass switch, that is, a battery module includes a switch bridge arm. In any battery module, one end of the main control switch is connected to the battery group in the battery module, and the other end of the main control switch serves as the first input / output end of the battery module. One end of the bypass switch is connected to the first input / output end of the battery module, and the other end of the bypass switch is connected to the second input / output end of the battery module. For example, in the battery cluster 1, the battery module 11 may include a battery group (such as battery group 1) and a switch bridge arm (for convenience of description, it can be assumed to be switch bridge arm 1), and the switch bridge arm 1 is composed of a main control switch S1 and a bypass switch S2. One end of the main control switch S1 is connected to the battery group 1, and the other end of the main switch S1 serves as the first input / output end of the battery module 11. One end of the bypass switch S2 is connected to the first input / output end of the battery module 11, and the other end of the bypass switch S2 is connected to the second input / output end of the battery module 11. When the energy storage system charges the battery module 11, the first input / output end of the battery module 11 is the input end of the battery module 11, and the second input / output end of the battery module 11 is the output end of the battery module 11. When the battery module 11 is discharged, the first input / output end of the battery module 11 is the output end of the battery module 11, and the second input / output end of the battery module 11 is the input end of the battery module 11. Whether the input / output end of each battery module is used as an input end or an output end can be determined according to the actual application scenario, and is not limited here. In the battery module 11, when the main control switch S1 is turned on and the bypass switch S2 is turned off, the battery module 11 is connected to the battery cluster 1 to achieve high-power charging and discharging control. When the main control switch S1 is disconnected and the bypass switch S2 is turned on, the battery module 11 is removed from the battery cluster 1, and the battery module 11 does not participate in the high-power charge and discharge control. Through the switch bridge arm in the battery module, combined with the energy management capability of the DC / DC converter connected to the battery cluster where the battery module is located, flexible control of a single battery module can be achieved, such as charge and discharge management of each battery module, charge state balancing, and battery module damage bypass, etc., with more flexible operation and higher applicability.

[0037] In some feasible implementations, in order to achieve the management of a single battery cluster, a centralized monitoring system can be added for each battery cluster, wherein one battery cluster corresponds to one centralized monitoring system, or several battery clusters correspond to one centralized monitoring system, which can be determined according to the actual application scenario and is not limited here. For example, battery cluster 1 can correspond to the centralized monitoring system in converter DC / DC1, and centralized monitoring system 1 can be used as an example for convenience of description. Battery cluster 2 can correspond to the centralized monitoring system in converter DC / DC2, and centralized monitoring system 2 can be used as an example for convenience of description. The centralized monitoring system of each battery cluster can connect each battery module in the battery cluster through a control bus, and the centralized monitoring system can interact with each battery module in the battery cluster in real time, so as to achieve real-time and unified monitoring of the battery modules in each battery cluster, thereby achieving flexible control of the energy storage system, and having strong applicability. Optionally, when the centralized monitoring system is used as an independently placed circuit module, the centralized monitoring system corresponding to a single battery cluster interacts with the controller in the DC / DC converter to achieve information exchange, and the centralized monitoring system connects each battery module in the battery cluster through a control bus. In the specific implementation, the information interaction mode between the centralized monitoring system and the battery module can also be wireless communication, DC power carrier communication, etc., which can be determined according to the actual application scenario, with flexible operation and high applicability. Optionally, when the centralized monitoring system of a single battery cluster is integrated as a separate circuit board or circuit module in the DC / DC converter connected to the battery cluster, the system structure of the energy storage system can be simplified. At the same time, since a single battery cluster is usually installed in close proximity to the DC / DC converter, the centralized monitoring system of a single battery cluster is integrated in the DC / DC converter, which is conducive to the connection of the control bus. The centralized monitoring system of each battery cluster is connected to the battery modules of each battery cluster through a control bus, which is used to control the conduction or disconnection of the main control switch and the bypass switch in any battery module in the battery cluster to access or bypass the battery module. Optionally, the centralized monitoring system can be placed in a battery module to achieve the management of the entire battery cluster. In this application, the physical placement location of the centralized monitoring system is not specifically limited. The centralized monitoring system can directly control the switch bridge arm in each battery module through the control bus. For example, the centralized monitoring system can send a switch control signal through the control bus to control the on or off of the main control switch and the bypass switch of the switch bridge arm in each battery module. Here, the switch control signal can be a pulse width modulation (PWM) signal, or a binary signal of 0 or 1, or any other signal that can be used to control the on or off of the switch. The specific signal can be determined according to the actual application scenario and is not limited here. Optionally, the centralized monitoring system can also control the switch bridge arm in each battery module through indirect communication. For example, the centralized monitoring system can send a control signal to each battery module, and then the battery management unit in each battery module controls the switch bridge arm.

[0038] Optionally, in some feasible implementations, in order to realize the status monitoring and control of the battery module, a battery management unit (BMU) may be added to the battery module of each battery cluster. The BMU may include a module battery management system (mBMS) and corresponding sampling control modules, communication modules, power supply modules, switch bridge arm drive control circuits, etc., for realizing the status detection and control of each energy storage element group (i.e., each battery group) in the battery module. Optionally, the switch bridge arm in any battery module may be integrated on the BMU in the battery module, and the BMU controls the on or off of the main switch and bypass switch in the switch bridge arm. The centralized monitoring system of the battery cluster 1 can connect the BMUs of each battery module in the battery cluster through a control bus, and can send control signals to the BMUs in each battery module, and control the on or off of the main switch and bypass switch in the battery module through the BMUs of each battery module. Figure 4 As shown, the centralized monitoring system 1 of the battery cluster 1 can connect the battery module 11 to the BMU of each battery module in the battery module 1n through the control bus, and control the on or off of the main switch and bypass switch of each battery module through the BMU of each battery module. For example, the centralized monitoring system 1 can control the on or off of the main switch and bypass switch of the switch bridge arm 1 through the BMU in the battery module 11, that is, the BMU in the battery module 11 controls the on or off of the main switch S1 and the bypass switch S2.

[0039] The structure of the battery module:

[0040] For the convenience of description, the following will be combined Figure 5a and Figure 5b The main components of the battery module in the energy storage system provided in the present application are illustrated. Here, the battery module can be any battery module in any battery cluster in the energy storage system, such as any one of the battery modules 11 to 1n, and the battery modules 21 to 2n. For the convenience of description, the battery module will be directly used as an example below. Figure 5a , Figure 5aIt is a structural schematic diagram of the battery module provided by the present application. In the energy storage system provided by the present application, the battery module includes a battery pack, a switch bridge arm and a BMU, wherein the switch bridge arm can be integrated in the BMU. The battery pack is composed of one or more battery cells (the voltage of the battery cell is usually between 2.5V and 4.2V) connected in series and parallel, and can usually be composed of 10 to 20 battery cells directly connected in series. The BMU is usually integrated on a circuit board to realize the state detection and control of each battery cell (or single cell) in the battery pack, and at the same time realize the control of the entire battery module. The BMU may include an mBMS and a corresponding sampling control module, a power supply module, a communication module, a switch bridge arm and a drive control circuit of the switch bridge arm (not shown in the figure), wherein the switch bridge arm includes two main control switches S1 and a bypass switch S2. Optionally, the switch bridge arm in any battery module can be placed separately on a power board and controlled by a separate controller. The controller exchanges information with the mBMS through a communication bus. On the other hand, the switch bridge arm on the power board can be controlled by the centralized monitoring system by directly sending a switch control signal through the control bus, which can improve the response speed of the centralized monitoring system. Due to the physical separation of the power board and the mBMS board, the board can be flexibly processed, and the power board and the control board can be decoupled at the same time, thereby enhancing the reliability of the circuit and reducing the spread of faults caused by the power circuit. In this application, the specific situation between the switch bridge arm and the controller can be determined according to the actual application scenario, and is not limited here.

[0041] In some feasible implementations, the power supply module of the BMU of the battery module can directly draw power from the battery pack of the battery module to supply power to the sampling control module and the communication module of the mBMS, that is, the power supply module of the BMU of the battery module can be powered by the battery pack of the battery module. Optionally, the power supply module of the BMU of the battery module can also be powered by the control bus, that is, the power supply module of the BMU of the battery module can draw power from the control bus to supply power to the sampling control module and the communication module of the mBMS. When the battery pack of the battery module is damaged or the SOH of the battery pack is very low, the battery pack cannot provide enough energy to each functional module in the BMU. At this time, the power supply module of the battery module can be powered by an external power supply through the control bus to maintain the conduction of the bypass switch S2 in the switch bridge arm of the battery module to bypass the battery module. At this time, even if the battery module is in the bypass state, the BMU of the battery module can still be kept in an activated state, thereby ensuring the control capability of the battery module, so that the normal operation of the entire battery cluster is not affected when the battery module is in the bypass state. Since the energy required to drive the bypass switch S2 is very limited, the implementation of providing energy by an external voltage through a control bus is also very simple, without additional cost and with high applicability.

[0042] In some possible implementations, see Figure 5b , Figure 5bIt is another structural schematic diagram of the battery module provided by the present application. The switch bridge arm in the BMU of the battery module can adopt a low-voltage metal oxide semiconductor field-effect transistor (MOSFET), and the voltage of the low-voltage MOSFET can be 60V, 80V, 100V, 120V, 150V, 200V, etc., which can be determined according to the actual application scenario and is not limited here. The low-voltage MOSFET has a low on-resistance, which can reduce the conduction loss in the on state. At the same time, the low-voltage MOSFET can work in a synchronous rectification state, and can achieve low on-resistance during the charging and discharging process, and has high applicability.

[0043] Working principle of energy storage system:

[0044] For the convenience of description, the following will be combined Figures 6 to 10 The working principle of the energy storage system provided in this application is explained by example:

[0045] See also Figure 6 , Figure 6 It is another structural schematic diagram of the energy storage system provided by the present application. In the energy storage system provided by the present application, in any battery module (such as battery module 11) of any battery cluster (such as battery cluster 1), when the main switch S1 is turned on and the bypass switch S2 is turned off, the battery module 11 is connected to the battery cluster 1 to achieve high-power charge and discharge control. When the main switch S1 is turned off and the bypass switch S2 is turned on, the battery module 11 is cut off from the battery cluster 1, and the battery module 11 does not participate in the high-power charge and discharge control. When both the main switch S1 and the bypass switch S2 are turned off, the port of the battery module is in a high-impedance state, that is, the battery module 11 is open circuited. As Figure 6 As shown, Figure 6For example, when the main control switch S1 in the battery module is turned on and the bypass switch S2 is turned off, the port voltage of the battery module is the output voltage of the battery group. Since the port of the battery module is charged, when the number of battery modules in the battery cluster (such as battery cluster 1) increases, the voltage of the port of the battery cluster to the safe ground also increases. Taking the port voltage of a single battery module as 50V as an example, when two battery modules are connected in series in battery cluster 1, the port voltage of the battery cluster is 100V. When 20 battery modules are connected in series in battery cluster 1 (i.e., n is 20), the port voltage of battery cluster 1 can reach up to 1000V. If there is a problem of poor electrical contact in the energy storage system, when the operator performs electrical connection operations, the battery cluster port voltage of up to 1000V will threaten the personal safety of the operator. In the energy storage system provided in the present application, the main switch S1 and bypass switch S2 of each battery module in the battery cluster can be in the off state by default, that is, when the energy storage system is in the assembly or maintenance state, the switch bridge arm of each battery module in the energy storage system is in the off state (that is, the main switch S1 and the bypass switch S2 are both in the off state), which can make the port of each battery module in a high impedance state, which can significantly reduce the danger of the port voltage of the battery cluster to the personal safety of the operator, thereby ensuring the personal safety of the operator. Figure 6 As shown in the battery cluster 2, the main control switch S1 and the bypass switch S2 of each battery module in the battery cluster 2 are both in the off state. At this time, the port voltage of each battery module is 0V, so that the port voltage of the battery cluster 2 is 0V. When the operator assembles or maintains the battery cluster 2, the port voltage of the battery cluster 2 is 0V, which poses no threat to the personal safety of the operator and has high applicability.

[0046] In some feasible implementations, no matter the battery cluster is coupled to the busbar via a DC / DC converter or a DC / AC converter (the present application takes the battery cluster coupled to the DC busbar via a DC / DC converter as an example), capacitors are required on the battery cluster side for filtering to smooth the high-frequency current ripple on the battery, such as Figure 7 shown. Figure 7It is an equivalent schematic diagram of the battery cluster connected to the DC / DC converter in the energy storage system provided by the present application. Taking battery cluster 1 as an example, Vbat may be the port voltage of battery cluster 1, Cin is the filter capacitor, R1 is the circuit impedance, K1 is the switch between the battery cluster end and the DC / DC converter, and lin is the current on the line. At this time, if the switch K1 is directly closed, it will bring a very serious current shock to the DC / DC converter. Taking the port voltage of battery cluster 1 as 1000V and the line impedance as 50mΩ as an example, when K1 is closed, lin is 20kA, and this current can directly cause damage to the components of the circuit. Therefore, a soft start circuit is usually added to the battery end side of the DC / DC converter to reduce the current shock. The energy storage system provided by the present application can improve the current shock problem by actively controlling the conduction or disconnection of the switch bridge arm of each battery module in the battery cluster. As Figure 8 As shown, Figure 8 It is a schematic diagram of the change of the port voltage of the battery cluster of the energy storage system provided by the present application. In the energy storage system provided by the present application, assuming that the port voltage of the battery cluster 1 is 1000V, the line impedance is 50mΩ, and the main control switch and bypass switch of each battery module in the battery cluster are in the off state, if the main control switches of each battery module in the battery cluster are closed at the same time, the port voltage of the battery cluster can quickly reach 1000V, which will bring serious current shock. In the energy storage system provided by the present application, when the main control switch and bypass switch of each battery module in the battery cluster (such as battery cluster 1) are in the off state, the centralized monitoring system of the battery cluster can control the main control switch S1 of the energy storage module one by one through the BMU of each energy storage module to turn on, so that the port voltage of the battery cluster increases in steps until the main control switches of all battery modules in the battery cluster are turned on, and the port voltage of the battery cluster 1 reaches 1000V. At this time, the voltage step value of the battery cluster (i.e., the value of the port voltage step increase of the battery cluster, which can be the port voltage value of a single battery module, such as 50V) is much smaller than the port voltage value of the battery cluster (such as 1000V), and the current impact will be significantly reduced. The startup method of the energy storage system provided by the present application can significantly simplify the soft start circuit of the DC / DC converter, and even eliminate the need for a soft start circuit, which is simple to operate and highly applicable.

[0047] In some feasible implementations, the energy storage system provided by the present application can achieve balanced management between battery modules, simplify the on-site wiring of the energy storage system, reduce the difficulty of on-site delivery of the energy storage system, enhance the stability of the energy storage system, and has high applicability. Fig. 9 , Fig. 9This is another structural schematic diagram of the energy storage system provided by the present application. In any battery module of any battery cluster, when the main control switch S1 is turned on and the bypass switch S2 is turned off, the battery module is connected to the battery cluster to achieve high-power charge and discharge control. When the main control switch S1 is turned off and the bypass switch S2 is turned on, the battery module is removed from the battery cluster, that is, the battery module does not participate in high-power charge and discharge control.

[0048] In some feasible implementations, during the charging process of the battery cluster, when the BMU (specifically, the mBMS in the BMU, which will not be described in detail below) in any battery module of any battery cluster detects that the charging port voltage of the battery module is equal to the protection voltage threshold of battery charging (i.e., the upper limit protection voltage threshold of charging), the BMU of the battery module can turn off the main control switch S1 of the battery module and turn on the bypass switch S2 to make the battery module work in bypass mode. At this time, the DC / DC converter connected to the battery cluster no longer charges the battery module. Fig. 9As shown in the battery cluster 2 in FIG, when the charging port voltage of BM21 reaches the upper limit protection threshold and reaches the charging upper limit protection voltage threshold, the BMU of BM21 can turn off the main control switch S1 in BM21 and turn on the bypass switch D2 to control the BM21 to enter the bypass mode. Similarly, during the discharge process of the battery cluster, when the BMU of any battery module of any battery cluster detects that the discharge port voltage of the battery module is equal to the protection voltage threshold of battery discharge (i.e., the lower limit protection voltage threshold of discharge), the BMU of the battery module can turn off the main control switch S1 of the battery module and turn on the bypass switch S2, so that the battery module works in the bypass mode, and the DC / DC converter connected to the battery cluster no longer discharges the battery module. Optionally, when the BMU of any battery module of any battery cluster detects that the parameters of the battery group in the battery module exceed the threshold, the main control switch of the battery module is turned off and the bypass switch of the battery module is turned on. Here, the parameters of the battery pack include charge and discharge time, state of charge, depth of discharge (DOD), health status, and port voltage, etc., which can be determined according to the actual application scenario and are not limited here. Here, the battery pack parameter exceeding the threshold value may include that the charge and discharge time of the battery pack is greater than the time threshold, the SOH of the battery pack is less than the SOH threshold, or the port voltage of the battery pack is equal to the protection voltage threshold, etc. The way in which the battery pack parameter exceeds the threshold value can be determined according to the type of parameter, which is not limited here. In the present application, since the DC / DC converter connected to the battery cluster can operate within a wide range of input / output voltages, the cutting in and cutting out of a single battery module in the battery cluster from the battery cluster does not affect the normal operation of the battery cluster, which can realize the control of a single battery module without affecting the normal operation of the battery cluster, and has high applicability. The action of the switch bridge arm can realize the flexible cutting in and cutting out of the battery module in the battery cluster, and the conditions for cutting in and cutting out can be determined according to the parameters such as the charge and discharge time, state of charge, depth of discharge, health status, and port voltage of the battery module, which can be determined according to the actual application scenario and are not limited here.

[0049] In some feasible implementations, the BMU of any battery module in the energy storage system can also shut down the main control switch of the battery module and turn on the bypass switch when detecting an abnormality in the battery pack of the battery module, so as to automatically cut off the faulty energy storage module and ensure the normal operation of the battery cluster and even the energy storage system. Here, the abnormality of the battery pack may include the SOH of the battery pack being less than the SOH threshold, or the battery pack being short-circuited or the battery pack being overheated, etc., which can be determined according to the actual application scenario and is not limited here. Under normal circumstances, such as Fig. 9In the battery cluster 1 in the energy storage system shown, the main control switch S1 in all battery modules is in the on state, and the charge and discharge management of all battery modules can be realized through the converter DC / DC1. When the BMU in any battery module (i.e., a certain battery module) detects that the SOH of the battery pack of the battery module is lower than a certain threshold (which can be a preset SOH threshold), or the battery pack of the battery module has an abnormal operating condition such as short circuit or overtemperature, the BMU of the battery module will automatically turn off the main control switch S1 and turn on the bypass switch S2, that is, automatically control the battery module to work in bypass mode. In other words, the battery module is removed from the battery cluster (the battery module is in a short circuit state). Optionally, the BMU of the battery module can also send an alarm signal at the same time. When the number of battery modules removed from the battery cluster reaches a certain number or when the spare battery module arrives, the energy storage system can be maintained manually on site, which can greatly reduce the maintenance cycle of the energy storage system, and at the same time ensure the uninterrupted operation of the energy storage system, with high applicability, and enhance the value and market competitiveness of the energy storage system.

[0050] In some feasible implementations, the BMU of each battery module in the energy storage system is in uninterrupted communication with the centralized monitoring system of the battery cluster. When the BMU of any battery module detects that it cannot receive a control signal from the centralized control system (i.e., the BMU cannot detect the control signal from the centralized monitoring system), the BMU of the battery module can control the switch bridge arm in the battery module to be in a disconnected state, i.e., the BMU of the battery module can turn off the main control switch and bypass switch of the battery module, so that the battery module output is in a high impedance state, thereby preventing the battery module from affecting the normal operation of the battery cluster, thereby improving the stability of the energy storage system and having high applicability.

[0051] See also Fig.10 , Fig.10 Schematic diagram of battery parameter changes when battery modules in a battery cluster are switched. Here, the battery parameter changes when battery modules in a battery cluster are switched may include changes in the battery cluster port voltage and changes in the battery cluster charge and discharge current.

[0052] In some feasible implementations, when each battery module in the battery cluster operates at the rated operating current of the battery cluster, if the switch bridge arm of a battery module is directly switched to cut in or cut out the battery module, the parasitic inductance and high current change rate (i.e., di / dt) of the battery module will cause severe voltage stress, thereby damaging the power device. When the battery cluster port voltage is Vr, if the BMU of a battery module (such as battery module 11) directly switches the switch bridge arm of the battery module to cut in the battery module (the main control switch S1 is turned on and the bypass switch S2 is turned off), at this time, if Fig.10As shown, the battery cluster port voltage can be increased to V2, where the voltage difference between V2 and Vr can be the port voltage of the battery module (for example, 50V). When the battery cluster port voltage is Vr, if the BMU of the battery module 11 directly switches the switch bridge arm of the battery module to cut off the battery module (the main control switch S1 is turned off, and the bypass switch S2 is turned on), at this time, as Fig.10 As shown, the port voltage of the battery cluster can drop to V1, where the voltage difference between Vr and V1 can be the port voltage of the battery module (e.g., 50V). The BMU of any battery module in the energy storage system provided by the present application can send a current adjustment request to the centralized monitoring system of the battery cluster when the port voltage of the battery module is detected by the mBMS to be close to a critical value (e.g., a preset voltage threshold). After receiving the current adjustment request, the centralized monitoring system can control the DC / DC converter of the battery cluster to reduce the battery charge and discharge current of the battery cluster. At time t1, when the BMU of the battery module detects that the charge and discharge current of the battery cluster (also the charge and discharge current of the battery module) drops from the rated working current Ir to a certain current threshold (such as a preset current threshold) Is, the switch bridge arm of the battery module can be controlled to switch (turn off the main control switch and turn on the bypass switch (cut off the battery module), or turn on the main control switch and turn off the bypass switch (cut in the battery module)), so as to achieve smooth cutting in or cutting out of the battery module (assuming that the battery module is cut in or cut out at time t2), while protecting the high-reliability operation of the switch device. Here, the above-mentioned preset current threshold Is can be 50%, 20% or 10% of the rated working current Ir of the battery cluster, etc., which can be determined according to the actual application scenario and is not limited here. At time t3, after the battery module is smoothly cut in or cut out, the centralized monitoring system can control the DC / DC of the battery cluster to increase the battery charge and discharge current of the battery cluster, and the battery charge and discharge current of the battery cluster starts to rise at time t3 until the rated working current Ir of the battery cluster.

[0053] The energy storage system provided by the present application can realize the rapid switching in or out of the battery module through the switch bridge arm of each battery module, realize the flexible control of each battery cluster in the energy storage system, and enhance the maintenance convenience and safety of the energy storage system. Based on the communication between the BMU in the battery module of each battery cluster and the centralized monitoring system of each battery cluster, as well as the flexible control capability of the DC / DC converter connected to each battery cluster, the energy management flexibility of each battery cluster can be improved, the stability of the energy storage system can be improved, and the applicability can be higher.

Claims

1. An energy storage system, characterized in that: The energy storage system includes at least one energy storage unit cluster and a centralized monitoring system for the energy storage unit cluster, wherein the energy storage unit cluster includes at least two energy storage modules, and the at least two energy storage modules are connected in series; an energy storage module includes an energy storage element group and a switch bridge arm, and the switch bridge arm is composed of a main control switch and a bypass switch, one end of the main control switch is connected to the energy storage element group, and the other end of the main control switch serves as a first input / output end of the energy storage module, one end of the bypass switch is connected to the first input / output end, and the other end of the bypass switch is connected to a second input / output end of the energy storage module; The energy storage unit cluster is coupled to a DC bus via a DC / DC converter; The centralized monitoring system is connected to the energy storage unit cluster via a control bus, and is used to control the on or off of the main control switch and the bypass switch in any energy storage module in the energy storage unit cluster to access or bypass any energy storage module; Wherein, one of the at least two energy storage modules further includes a battery management unit BMU; The centralized monitoring system is connected to the BMU of each energy storage module in the energy storage unit cluster via a control bus; Wherein, the BMU of any energy storage module is used to send a current adjustment request to the centralized monitoring system; The centralized monitoring system is used to control the DC / DC converter to reduce the battery charging and discharging current of the energy storage unit cluster when receiving the current adjustment request; The BMU of any energy storage module is also used to turn off or turn on the main control switch or bypass switch of any energy storage module when it detects that the battery charging and discharging current is equal to a preset current threshold, so as to cut in or cut out any energy storage module.

2. The energy storage system according to claim 1, characterized in that: The centralized monitoring system is integrated in the DC / DC converter.

3. The energy storage system according to claim 2, characterized in that: The centralized monitoring system is used to control the on or off of the main control switch and the bypass switch of any energy storage module through the BMU of any energy storage module.

4. The energy storage system according to claim 2, characterized in that: The centralized monitoring system is used to send a switch control signal through the control bus to control the on or off of the main switch and the bypass switch of any energy storage module.

5. The energy storage system according to any one of claims 2 to 4, characterized in that: The main control switch and bypass switch of any energy storage module are integrated in the BMU of any energy storage module.

6. The energy storage system according to claim 5, characterized in that: The BMU of any energy storage module is composed of a single board.

7. The energy storage system according to claim 5, characterized in that: The BMU of any energy storage module is composed of multiple boards, including a module battery management system mBMS board and a switch bridge arm board, and the main control switch and bypass switch of any energy storage module are integrated on the switch bridge arm board.

8. The energy storage system according to claim 5, characterized in that: The main control switch and bypass switch of any energy storage module in the energy storage unit cluster are in the off state.

9. The energy storage system according to claim 8, characterized in that: The power supply module of the BMU of any energy storage module is powered by the energy storage element group of any energy storage module or the control bus.

10. The energy storage system according to claim 9, characterized in that: The centralized monitoring system is used to control the main control switches of each energy storage module in the energy storage unit cluster to turn on one by one through the BMU of each energy storage module when the energy storage system is started.

11. The energy storage system according to claim 10, characterized in that: The BMU of any energy storage module is used to turn off the main control switch of any energy storage module and turn on the bypass switch of any energy storage module when it is detected that the charging and discharging port voltage of the energy storage element group in any energy storage module is equal to the protection voltage threshold.

12. The energy storage system according to claim 10, characterized in that: The BMU of any energy storage module is used to turn off the main control switch of any energy storage module and turn on the bypass switch of any energy storage module when it is detected that the parameter of the energy storage element group in any energy storage module exceeds a threshold.

13. The energy storage system according to claim 12, wherein the parameters of the energy storage element group include one or more of charge and discharge time, state of charge SOC, depth of discharge DOD, state of health SOH and port voltage.

14. The energy storage system according to claim 10, characterized in that: The BMU of any energy storage module is used to turn off the main control switch of any energy storage module and turn on the bypass switch when an abnormality of the energy storage element group in any energy storage module is detected; The abnormality of the energy storage element group includes that the health state SOH of the energy storage element group is less than the SOH threshold, the energy storage element group is short-circuited, or the energy storage element group is over-heated.

15. The energy storage system according to claim 1, characterized in that: The preset current threshold is 50%, 20% or 10% of the rated operating current of the energy storage unit cluster.

16. The energy storage system according to claim 10, characterized in that: The BMU of any energy storage module is also used to turn off the main control switch and bypass switch of any energy storage module when the control signal of the centralized monitoring system cannot be detected.

17. The energy storage system according to claim 1, characterized in that: The switch bridge arm is a low-voltage metal oxide semiconductor field effect transistor MOSFET, and the voltage of the low-voltage metal oxide semiconductor field effect transistor MOSFET includes 60V, 80V, 100V, 120V, 150V or 200V.

18. A control method for an energy storage system, characterized in that: The method is applicable to a centralized monitoring system in an energy storage system according to any one of claims 1 to 17, and the method comprises: The centralized monitoring system is connected to the energy storage unit cluster via a control bus; The centralized monitoring system controls the on or off of the main switch and the bypass switch in any energy storage module in the energy storage unit cluster to access or bypass any energy storage module; Wherein, the method further comprises: When the centralized monitoring system receives a current adjustment request from the BMU of any energy storage module, controlling the DC / DC converter to reduce the battery charge and discharge current of the energy storage unit cluster; When the centralized monitoring system detects through the BMU of any energy storage module that the battery charge and discharge current is equal to a preset current threshold, the BMU of any energy storage module turns off or turns on the main control switch or bypass switch of any energy storage module; The preset current threshold is 50%, 20% or 10% of the rated working current of the energy storage unit cluster.

19. The control method according to claim 18, characterized in that: The centralized monitoring system is connected to the energy storage unit cluster via a control bus and includes: The centralized monitoring system is connected to the battery management unit BMU of each energy storage module in the energy storage unit cluster via a control bus; The centralized monitoring system controls the on or off of the main switch and the bypass switch in any energy storage module in the energy storage unit cluster, including: The centralized monitoring system controls the on or off of the main control switch and the bypass switch of any energy storage module through the BMU of any energy storage module.

20. The control method according to claim 18, characterized in that: The centralized monitoring system controls the on or off of the main switch and the bypass switch in any energy storage module in the energy storage unit cluster, including: The centralized monitoring system sends a switch control signal through the control bus to control the on or off of the main switch and the bypass switch of any energy storage module.

21. The control method according to claim 19, characterized in that: The centralized monitoring system controls the on or off of the main switch and the bypass switch in any energy storage module in the energy storage unit cluster, including: When the energy storage system is started, the centralized monitoring system controls the main control switches of each energy storage module in the energy storage unit cluster to turn on one by one through the BMU of each energy storage module.

22. The control method according to claim 19 or 21, characterized in that: The method further comprises: When the centralized monitoring system detects through the BMU of any energy storage module that the charging and discharging port voltage of the energy storage element group in any energy storage module is equal to the protection voltage threshold, the BMU of any energy storage module turns off the main control switch of any energy storage module and turns on the bypass switch of any energy storage module.

23. The control method according to claim 19 or 21, characterized in that: The method further comprises: When the centralized monitoring system detects through the BMU of any energy storage module that the parameter of the energy storage element group in any energy storage module exceeds a threshold value, the BMU of any energy storage module turns off the main control switch of any energy storage module and turns on the bypass switch of any energy storage module; The parameters of the energy storage element group include one or more of the charge and discharge time, the state of charge SOC, the depth of discharge DOD, the state of health SOH and the port voltage.

24. The control method according to claim 19 or 21, characterized in that: The method further comprises: When the centralized monitoring system detects an abnormality in the energy storage element group in any energy storage module through the BMU of any energy storage module, the BMU of any energy storage module turns off the main control switch of any energy storage module and turns on the bypass switch; The abnormality of the energy storage element group includes that the SOH of the energy storage element group is less than the SOH threshold, the energy storage element group is short-circuited, or the energy storage element group is over-heated.

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