Battery system including battery management system having hierarchical structure

Abstract

A battery system may include: a superior battery management device (BMS); and a plurality of lower BMSs. Here, the upper BMS and the lower BMS may be communicatively connected via a communication bus. Further, each of the lower BMSs may be connected to a filter for reducing communication noise, and the upper BMS may be connected to a compensation circuit configured to compensate for attenuation of the communication signal caused by the filter connected to the lower BMSs.

Description

Technical Field

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2024-0121265, filed on September 6, 2024, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

[0002] This invention relates to a battery system, and more particularly to a battery system including a battery management system having a hierarchical structure. Background Technology

[0003] Rechargeable and reusable secondary batteries can be used as a power source for small devices such as mobile phones, tablet PCs and vacuum cleaners, as well as for medium and large devices such as automobiles and energy storage systems (ESS) for smart grids.

[0004] Secondary batteries can be applied to a system as components, depending on system requirements. These components can take the form of battery packs in which multiple battery cells are electrically connected, or battery racks in which battery packs are electrically connected. For ESS (Emerging Power Supply) systems in smart grids, high-capacity battery systems with multiple battery racks connected in parallel can be used to meet the system's capacity requirements.

[0005] Typically, a battery rack may include a battery protection unit (BPU) to protect the batteries from abnormal and fault currents. The BPU may include a circuit breaker (CB) for forcibly disconnecting the electrical connection between the battery rack and the DC link, as well as a rack battery management system (RBMS) for monitoring and managing the battery pack.

[0006] For rack-level control, the RBMS can communicate with the battery pack management system (PBMS) contained in each battery pack and collect status information from the PBMS to diagnose anomalies and perform charge / discharge control.

[0007] Typically, RBMS and PBMS are connected via a Controller Area Network (CAN) bus. However, as the number of battery packs contained in a battery rack increases, this typical communication connection structure may lead to communication signal attenuation.

[0008] Among the prior art documents related to this invention, KR 10-2024-0064259 A is somewhat relevant. Summary of the Invention

[0009] [Technical Issues]

[0010] To eliminate one or more problems in the related art, embodiments of this disclosure provide a battery system including a compensation circuit for compensating for attenuation of communication signals caused by filters applied to each downstream battery management system (BMS).

[0011] To eliminate one or more problems of the related technologies, embodiments of this disclosure also provide a higher-level battery management device included in a battery system.

[0012] [Technical Solution]

[0013] To achieve the objectives of this disclosure, the battery system may include a higher-level battery management system (BMS) and multiple lower-level BMSs. Here, the higher-level BMS and lower-level BMSs may be communicatively connected via a communication bus. Furthermore, each of the lower-level BMSs may be connected to a filter for reducing communication noise, and the higher-level BMS may be connected to a compensation circuit configured to compensate for attenuation of the communication signal caused by the filter.

[0014] The upper-level BMS and the lower-level BMS can be connected and communicate via the Controller Area Network (CAN) bus.

[0015] The filter can be a resistor-capacitor (RC) filter connected to the communication line of the lower-level BMS.

[0016] The compensation circuit can be a circuit with a negative capacitor that serves as a combined capacitor for the cancellation filter.

[0017] The compensation circuit can be connected to the communication line of the upper-level BMS.

[0018] The compensation circuit can be connected to the CAN high-level line and the CAN low-level line of the upper-level BMS respectively.

[0019] The compensation circuit may include an operational amplifier, a first resistor, a second resistor, and a capacitor.

[0020] Here, the positive input terminal of the operational amplifier can be connected to the communication line of the lower-level BMS, the capacitor can be located between the positive input terminal and the output terminal of the operational amplifier, the first resistor can have one end grounded and the other end connected to the negative input terminal of the operational amplifier, and the second resistor can be located between the negative input terminal and the output terminal of the operational amplifier.

[0021] The resistance values ​​of the first resistor, the second resistor, and the capacitor can be determined based on the number of filters and the capacitance of each filter.

[0022] When a new lower-level BMS is additionally installed into the battery system, the compensation circuit can be connected to the communication line of the upper-level BMS.

[0023] When a new lower-level BMS is additionally installed in the battery system, a compensation circuit with a negative capacitance for reducing the combined capacitance of the additionally installed lower-level BMS to a predetermined range can be connected to the communication line of the upper-level BMS.

[0024] According to another embodiment of this disclosure, the battery management device can be connected to a plurality of lower-level battery management devices via a communication bus and connected to a compensation circuit configured to compensate for attenuation of the communication signal caused by a filter connected to each of the lower-level battery management devices to reduce communication noise.

[0025] The compensation circuit can be a circuit with negative capacitance used to offset the combined capacitance of resistor-capacitor (RC) filters connected to each communication line of the lower-level BMS.

[0026] The compensation circuit may include an operational amplifier, a first resistor, a second resistor, and a capacitor.

[0027] [Beneficial Effects]

[0028] According to embodiments of this disclosure, communication signal attenuation due to filters applied to each lower-level BMS can be minimized, thereby improving communication quality.

[0029] Furthermore, according to the above embodiments of the present invention, when additional battery components (e.g., battery packs) are installed in the battery system, communication optimization can be achieved by adding compensation circuits to the upper-level BMS or replacing or adjusting existing compensation circuits without replacing the filters of the lower-level BMS included in each battery component. Attached Figure Description

[0030] Figure 1 This is a block diagram of a general-purpose energy storage system.

[0031] Figure 2 The structure of a universal battery holder is shown.

[0032] Figure 3 This is a block diagram of a battery system according to an embodiment of the present invention.

[0033] Figure 4 This is a block diagram of a battery system that utilizes a compensation circuit according to an embodiment of the present invention.

[0034] Figure 5 This is a circuit diagram of a compensation circuit according to an embodiment of the present invention.

[0035] Figure 6 This is a reference diagram illustrating a battery system with a compensation circuit added during operation, according to an embodiment of the present invention.

[0036] Figure 7 It is a graph used to illustrate the effect of the compensation circuit.

[0037] 100: Superior BMS

[0038] 200: Subordinate BMS

[0039] 300: Compensation circuit Detailed Implementation

[0040] This invention can be modified in various forms and has various embodiments, and specific embodiments thereof are shown by way of example in the accompanying drawings and will be described in detail below. However, it should be understood that the invention is not intended to be limited to the specific embodiments, and rather, the invention is intended to cover all modifications, equivalents, and substitutions falling within the spirit and scope of the invention. Throughout the description of the accompanying drawings, the same reference numerals refer to the same elements.

[0041] It will be understood that although terms such as first, second, A, B, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element without departing from the scope of the invention, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes a combination of a plurality of associated listed items or any one of a plurality of associated listed items.

[0042] It will be understood that when a component is described as "coupled" or "connected" to another component, it can be directly coupled or connected to the other component, or there may be intermediate components. Conversely, when a component is described as "directly coupled" or "directly connected" to another component, there are no intermediate components.

[0043] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that the terms “comprising,” “including,” “containing,” “covering,” and / or “having” as used herein specify the presence of stated features, integers, steps, operations, constituent elements, components, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, constituent elements, components, and / or combinations thereof.

[0044] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will be further understood that terms such as those defined in common dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant field, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0045] Some of the terms used in this article are defined as follows.

[0046] A battery cell is a basic unit used to store electricity, and a battery module is an assembly in which multiple battery cells are electrically connected.

[0047] A battery rack can refer to a single-structure system assembled by connecting modules in series or parallel, as configured by the battery manufacturer, and monitored and controlled by a battery management system (BMS). A battery rack may include several battery modules and battery protection units or any other protection devices. Here, depending on the device or system using the battery, a battery module may also be referred to as a battery pack.

[0048] A battery bank is a large system of battery racks configured by connecting multiple battery racks in parallel. A battery bank BMS can monitor and control several BMSs, with each BMS managing a battery rack.

[0049] A battery assembly may include multiple electrically connected battery cells and refers to an assembly used as a power source by application to a particular system or device. Here, a battery assembly may mean a battery module, battery pack, battery rack, or battery bank, but the scope of the invention is not limited to these entities.

[0050] A battery system controller (BSC) is the top-level device that controls a battery system, including a battery bank-level structure, and can also be used in battery systems with multiple bank-level structures.

[0051] State of charge (SOC) refers to the current state of a battery as a percentage point [%], and state of health (SOH) refers to the current condition of a battery as a percentage point [%] compared to its ideal or original condition.

[0052] Figure 1 This is a block diagram of a general-purpose energy storage system.

[0053] Typically, a battery cell is the basic unit of a battery used to store electricity in an energy storage system (ESS). Series / parallel combinations of battery cells form battery packs, and multiple battery packs form battery racks. In other words, a battery rack, as a series / parallel combination of battery packs, can be the basic unit of a battery system. Here, depending on the device or system using the batteries, a battery pack may be referred to as a battery module.

[0054] refer to Figure 1 A battery rack can include multiple battery packs and battery protection units (BPUs) 50 or protection devices. The battery rack can be monitored and controlled through a rack battery management system (RBMS). The RBMS can monitor the current, voltage, and temperature of each managed battery rack, calculate the state of charge (SOC) of the batteries based on the monitoring results, and control charging and discharging.

[0055] Meanwhile, the BPU 50 is a device used to protect batteries from abnormal and fault currents in the battery rack. The BPU may include a main contactor MC, a fuse, a circuit breaker CB, or a circuit breaker DS. The BPU can control the battery system rack-by-rack by controlling the on / off state of the main contactor according to the control of the RBMS. The BPU can also protect the batteries from short-circuit currents by using fuses in the event of a short circuit. Thus, a general battery system can be controlled by protective devices such as the BPU or switching devices.

[0056] Simultaneously, a Battery System Controller (BSC) 20 can be installed to monitor and control objects in each battery section, including multiple batteries, peripheral circuits, and devices, such as voltage, current, temperature, and circuit breakers. The Battery System Controller is the top-level controller of a library-level battery system comprising multiple battery racks and also serves as a controller in battery systems with multiple library-level structures. Here, each library-level battery system may include a Library Battery Management System (BBMS), and the BBMS can monitor and control each rack via an interface with the RBMS of the battery rack to be managed.

[0057] Furthermore, the power conversion system (PCS) 40 installed in each battery section controls the charging and discharging of the batteries by controlling the power supplied from an external power source and the power supplied from the battery section to the outside, and may include a DC / AC inverter. Additionally, if the ESS system interfaces with a photovoltaic (PV; solar power system) module field 70, a PV inverter may be included.

[0058] Meanwhile, the output of each BPU can be connected to PCS 40 via a DC bus, and PCS 40 is connected to the power grid 60. In addition, the Energy Management System (EMS) / Power Management System (PMS) 30 can control the energy storage system overall.

[0059] Figure 2The structure of a universal battery holder is shown.

[0060] The battery rack may include a battery protection unit (BPU) and multiple battery packs. Here, the BPU and multiple battery packs may be connected in a vertically stacked structure.

[0061] The BPU located on top of the battery rack may include a circuit breaker (CB) and a rack BMS (RBMS).

[0062] RBMS can include a main contactor MC, fuse, microcontroller unit (MCU), memory, power supply unit and current sensor.

[0063] Each battery pack located below the BPU may include multiple batteries and a battery pack management system (PBMS) for monitoring and managing the batteries.

[0064] The batteries within each battery pack can be connected in series and / or in parallel, and connected to power terminals located in the BPU, thereby connecting to a DC link.

[0065] The PBMS included in each battery pack can communicate with the RBMS located within the BPU. The PBMS can collect battery status data such as voltage, current, and temperature from the PBMS of the battery pack being managed, and monitor and control each battery pack.

[0066] Figure 3 This is a block diagram of a battery system according to an embodiment of the present invention.

[0067] refer to Figure 3 The battery system may include a higher-level battery management system (BMS) 100 and multiple lower-level battery management systems (BMS) 200-1 to 200-n.

[0068] The upper-level BMS 100 can connect to multiple lower-level BMSs 200-1 to 200-N to monitor and manage battery assemblies, including those of the lower-level BMSs 200. For example, the upper-level BMS can be a rack BMS (RBMS), and the lower-level BMS can be a group BMS (PBMS). In another example, the upper-level BMS can be a library BMS (BBMS), and the lower-level BMS can be a rack BMS (RBMS).

[0069] The upper-level BMS 100 can be connected to the lower-level BMS 200-1 to 200-N via a communication bus. For example, the upper-level BMS 100 and multiple lower-level BMS 200-1 to 200-N can communicate via a Controller Area Network (CAN) bus.

[0070] Each of the lower-level BMSs 200-1 to 200-N can be connected to or include a filter for reducing communication noise. Here, the filter can be a resistor-capacitor (RC) filter connected to the communication line of the lower-level BMS.

[0071] Typically, when multiple BMSs are connected in parallel to the CAN bus and communicate, the communication occurs at frequencies in the 1 to 2 MHz range. Since the battery system includes various electronic devices besides the BMSs, significant noise can be generated in this frequency range. Therefore, each lower-level BMS can be equipped with an RC filter to reduce this noise. Here, the RC filter can be connected to each of the CAN high-level and CAN low-level lines of the lower-level BMS.

[0072] The communication performance degradation caused by noise reduction filters is minimal when the number of lower-level BMSs included in the battery system is small (i.e., the number of battery components included in the battery system is small). However, as the number of lower-level BMSs connected in parallel to the CAN bus increases, the combined capacitance (N×Cf) of the capacitors (Cf) included in each noise reduction filter increases, potentially reducing the communication signal strength (gain).

[0073] To address this issue, one could consider replacing the capacitors (Cf) included in each filter with new capacitors of appropriate capacitance; however, this is highly inefficient in terms of system design costs. Specifically, when designing a new battery system or adding battery components to an existing one, capacitor optimization is required based on the communication frequency range, necessitating the replacement of all filters included in the battery system.

[0074] To address this technical problem, a battery system according to an embodiment of the present invention may include a compensation circuit 300 to compensate for the attenuation of communication signals caused by the filters of the lower-level BMS.

[0075] The compensation circuit 300 can be connected to the communication lines of the upper-level BMS 100. Specifically, the compensation circuit 300 can be connected to each of the CAN high-level and CAN low-level lines of the upper-level BMS 100.

[0076] Figure 4 This is a block diagram of a battery system that applies a compensation circuit according to an embodiment of the present invention, and Figure 5 This is a circuit diagram of a compensation circuit according to an embodiment of the present invention.

[0077] refer to Figure 4 The battery system may include a higher-level battery management system (BMS) 100 and multiple lower-level battery management systems (BMS) 200-1 to 200-N.

[0078] The upper-level BMS 100 can monitor and manage battery components, including the lower-level BMS 200, by interfaceing with multiple lower-level BMS 200-1 to 200-N.

[0079] The upper-level BMS 100 can be connected to multiple lower-level BMSs 200-1 to 200-N via a communication bus. Here, the upper-level BMS 100 and the multiple lower-level BMSs 200-1 to 200-N can be connected to each other via a Controller Area Network (CAN) bus.

[0080] Each of the lower-level BMSs 200-1 to 200-N can be connected to a filter to reduce communication noise. Here, the filter can be an RC filter connected to each of the CAN high-level and CAN low-level lines of the lower-level BMS.

[0081] The upper-level BMS 100 can be connected to the compensation circuit 300 to compensate for the attenuation of the communication signal caused by the filter. Here, the compensation circuit 300 can be connected to each of the CAN high-level and CAN low-level lines of the upper-level BMS 100.

[0082] The compensation circuit 300 can be a circuit with a negative capacitance to offset the combined capacitance (N×Cf) of the filter.

[0083] The compensation circuit 300 according to an embodiment of the present invention can be implemented as a negative capacitance circuit including an operational amplifier, a first resistor, a second resistor, and a capacitor.

[0084] For example, the compensation circuit 300 may include an operational amplifier (OP-Amp), a first resistor (R1), a second resistor (R1), and a capacitor (Cnc0), such as Figure 5 As shown. Here, the positive input terminal (+) of the operational amplifier can be connected to the communication line of the downstream BMS (BMS). Figure 4 (a) Additionally, the capacitor (Cnc0) can be located between the positive input terminal (+) and the output terminal of the operational amplifier. Furthermore, the first resistor (R1) can have one end grounded ( Figure 4 (b) and the other end connected to the negative input terminal (-) of the operational amplifier. Additionally, a second resistor (R2) can be placed between the negative input terminal (-) and the output terminal of the operational amplifier.

[0085] Figure 5 The capacitance of the compensation circuit 300 shown in the diagram can be expressed as the product of the Miller gain of the operational amplifier and the feedback capacitance. In other words, the capacitance (-Cnc) of the compensation circuit 300 can have a value equal to the product of the Miller gain (R2 / R1) and the feedback capacitance (-Cnc0) (-Cnc0 × (R2 / R1)).

[0086] The resistance values ​​of the first resistor (R1), the second resistor (R2), and the capacitance (Cnc0) of the capacitor included in the compensation circuit 300 can be determined based on the number of filters included in the battery system (or the number of downstream BMS) and the capacitance (Cf) of each filter.

[0087] More specifically, since the compensation circuit 300 according to an embodiment of the present invention is a configuration of the combined capacitor (NX Cf) for the offset filter applied to the communication line of the upper-level BMS, the capacitor (-Cnc) of the compensation circuit 300 can be designed to have a value capable of attenuating the combined capacitor (NX Cf) of the filter to an appropriate value.

[0088] The capacitance (-Cnc) of the compensation circuit 300 can be determined such that the gain of the communication signal at the communication frequency used in the battery system is greater than or equal to a predetermined value. Here, the capacitance (-Cnc) of the compensation circuit 300 can be determined such that the gain of the communication signal based on the total combined capacitance (NX Cf-Cnc) is greater than or equal to -3dB. Subsequently, the resistance values ​​of the first resistor (R1), the second resistor (R2), and the capacitor (Cnc0) can be determined such that the capacitance (-Cnc) of the compensation circuit 300 has the expected value, and therefore, the compensation circuit 300 can be designed accordingly and applied to the communication lines of the upper-level BMS 100.

[0089] For example, in Figure 4 In the example, when Cf is 100pF and N is 21, the combined capacitance of the filter is 2100pF (21 x 100pF). Here, the combined capacitance of the filter can cause a signal strength attenuation of approximately -5dB at 2MHz. To adjust the signal strength attenuation to approximately -2dB, if the total combined capacitance is to be compensated (adjusted) to 1300pF, a compensation circuit 300 with a -800pF capacitor can be applied to the upper-level BMS 100. Here, a 100kΩ resistor is applied to R1, a 400kΩ resistor to R2, and a 200pF capacitor to Cnc0, making it possible to manufacture a compensation circuit 300 exhibiting the expected negative capacitance (-800pF).

[0090] Figure 6 This is a reference diagram illustrating a battery system with a compensation circuit added during operation according to an embodiment of the present invention, and Figure 7 It is a graph used to illustrate the effect of the compensation circuit.

[0091] Compensation circuitry can be added to the upper-level BMS during the operation of the battery system, rather than during the design phase of the battery system.

[0092] For example, such as Figure 6 As shown in (A), the battery system comprises 12 battery modules, and noise reduction filters are applied to the lower-level BMS (#1 to #12) included in each battery module. In this battery system (Case 1), as... Figure 7 As shown, the communication signal gain at 2MHz is approximately -2dB, which allows the battery system to operate without compensation circuitry applied to the upper-level BMS.

[0093] During the operation of the battery system, additional battery modules can be installed as needed. In this case, the noise reduction filter included in the added battery module can increase the combined capacitance, thereby reducing the communication signal gain.

[0094] For example, such as Figure 6 As shown in (B), during the operation of a battery system comprising 12 battery modules, 9 additional battery modules can be installed in the battery system. In this case (Case 2), the noise reduction filter included in the added battery modules increases the combined capacitor, and as... Figure 7 As shown, the communication signal gain at 2MHz attenuates to approximately -5dB, potentially degrading communication performance.

[0095] To prevent this degradation in communication performance, a compensation circuit can be connected to the communication line of the upstream BMS. For example, such as... Figure 6 As shown in (B), the compensation circuit with negative capacitance (-Cnc) can be connected to the communication line of the upper-level BMS in the battery system.

[0096] Here, the compensation circuit connected to the upper-level BMS can have a negative capacitor capable of attenuating the combined capacitor of the additionally installed lower-level BMS within a predetermined range. For example, when... Figure 6 When adding 9 lower-level BMSs as shown in (B) and increasing the combined capacitance by 900pF (9 x 100pF), a compensation circuit 300 with a capacitance of -800pF can be applied to the upper-level BMS 100 to attenuate the increased combined capacitance to within 15%. In this case (Case 3), the total combined capacitance is reduced from 2100pF to 1300pF by the added compensation circuit, and as... Figure 7 As shown, adjusting the communication signal gain at 2MHz to approximately -2dB can improve communication performance.

[0097] In the foregoing, the present invention has been described with reference to exemplary embodiments thereof. However, those skilled in the art will understand that various corrections and modifications may be made to the invention within the scope of the appended claims without departing from the spirit and scope of the invention as described therein.

Claims

1. A battery system, comprising: Superior BMS; as well as Multiple subordinate BMS, The upper-level BMS and the lower-level BMS are connected communicatively via a communication bus. Each of the lower-level BMSs is connected to a filter for reducing communication noise, and The upper-level BMS is connected to a compensation circuit, which is configured to compensate for the attenuation of the communication signal caused by the filter.

2. The battery system according to claim 1, wherein, The upper-level BMS and the lower-level BMS are connected via a CAN bus.

3. The battery system according to claim 1, wherein, The filter is an electrical RC filter connected to the communication line of the lower-level BMS.

4. The battery system according to claim 3, wherein, The compensation circuit is a circuit with a negative capacitor to cancel out the combined capacitance of the filter.

5. The battery system according to claim 4, wherein, The compensation circuit is connected to the communication line of the upper-level BMS.

6. The battery system according to claim 5, wherein, The compensation circuit is connected to the CAN high-level line and the CAN low-level line of the upper-level BMS, respectively.

7. The battery system according to claim 3, wherein, The compensation circuit includes: An operational amplifier, a first resistor, a second resistor, and a capacitor.

8. The battery system according to claim 7, wherein: The positive input terminal of the operational amplifier is connected to the communication line of the lower-level BMS. The capacitor is located between the positive input terminal and the output terminal of the operational amplifier. The first resistor has one end grounded and the other end connected to the negative input terminal of the operational amplifier, and The second resistor is located between the negative input terminal and the output terminal of the operational amplifier.

9. The battery system according to claim 7, wherein, The resistance value of the first resistor, the resistance value of the second resistor, and the capacitance of the capacitor are determined based on the number of filters and the capacitance of each filter.

10. The battery system according to claim 1, wherein, When a new lower-level BMS is additionally installed into the battery system, the compensation circuit is connected to the communication line of the upper-level BMS.

11. The battery system according to claim 4, wherein, When a new lower-level BMS is additionally installed in the battery system, a communication line with a compensation circuit for reducing the combined capacitance of the additionally installed lower-level BMS to a negative capacitance within a predetermined range is connected to the upper-level BMS.

12. A battery management device, wherein the battery management device is connected to a plurality of lower-level battery management devices via a communication bus. in, The battery management device is connected to a compensation circuit configured to compensate for attenuation of the communication signal caused by a filter connected to each of the lower-level battery management devices to reduce communication noise.

13. The battery management device according to claim 12, wherein, The compensation circuit is a circuit with negative capacitance used to offset the combined capacitance of the RC filters connected to each communication line of the lower-level BMS.

14. The battery management device according to claim 13, wherein, The compensation circuit includes: An operational amplifier, a first resistor, a second resistor, and a capacitor.

Images