Battery system comprising battery management device having hierarchical structure

Abstract

A battery system, according to one embodiment of the present invention, may comprise: an upper BMS; and a plurality of lower BMSs. Here, the upper BMS and the lower BMSs may be communicatively connected via a communication bus. In addition, 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 for compensating for attenuation of a communication signal caused by the filters.

Description

Battery system including a battery management device with a hierarchical structure

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

[0002] The present invention relates to a battery system, and more particularly, to a battery system including a battery management device having a hierarchical structure.

[0003] Secondary batteries are batteries that can be reused by charging even after discharge, and can be used as an energy source for small devices such as mobile phones, tablet PCs, and vacuum cleaners, and are also used as an energy source for medium and large devices such as automobiles and ESS (Energy Storage Systems) for smart grids.

[0004] Secondary batteries are applied to systems in the form of assemblies, such as battery packs, where multiple battery cells are electrically connected, or battery racks, where multiple battery packs are electrically connected, depending on the system requirements. For ESS for smart grids, high-capacity battery systems, where multiple battery racks are connected in parallel, can be applied to meet the system's capacity requirements.

[0005] Typically, a battery rack may include a Battery Protection Unit (BPU) to protect the battery from abnormal currents 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, and a Rack Battery Management System (RBMS) for monitoring and managing the battery packs.

[0006] RBMS communicates with the PBMS (Pack Battery Management System) included in each battery pack for rack-level control, and collects status information from the PBMS to diagnose abnormalities and perform charge / discharge control.

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

[0008] Related prior literature includes KR 10-2024-0064259 A

[0009] An object of the present invention to solve the above problems is to provide a battery system including a compensation circuit for compensating for attenuation of a communication signal due to filters applied to each of the lower BMSs.

[0010] Another object of the present invention to solve the above problems is to provide an upper battery management device included in a battery system.

[0011] According to one embodiment of the present invention, a battery system for achieving the above-described purpose may include an upper BMS and a plurality of lower BMSs. Here, the upper BMS and the lower BMSs may be connected to each other through a communication bus. In addition, a filter for reducing communication noise may be connected to each of the lower BMSs, and a compensation circuit for compensating for attenuation of a communication signal caused by the filters may be connected to the upper BMS.

[0012] The above upper BMS and lower BMS can be connected to each other through a CAN (Controller Area Network) bus.

[0013] The above filter may be an RC filter connected to the communication line of the lower BMS.

[0014] The above compensation circuit may be a circuit having a negative capacitance to offset the composite capacitance of the filters.

[0015] The above compensation circuit can be connected to the communication line of the upper BMS.

[0016] The above compensation circuit can be connected to each of the CAN HIGH line of the upper BMS and the CAN LOW line of the upper BMS.

[0017] The above compensation circuit may include an operational amplifier, a first resistor, a second resistor, and a capacitor.

[0018] Here, the positive input terminal of the operational amplifier is connected to the communication line of the lower BMS, the capacitor is arranged between the positive input terminal and the output terminal of the operational amplifier, one side of the first resistor is grounded and the other side is connected to the negative input terminal of the operational amplifier, and the second resistor can be arranged between the negative input terminal and the output terminal of the operational amplifier.

[0019] The resistance value of the first resistor, the resistance value of the second resistor, and the capacitance of the capacitor can be determined according to the number of filters and the capacitance of each of the filters.

[0020] The above compensation circuit can be connected to the communication line of the upper BMS when new lower BMSs are additionally installed in the battery system.

[0021] When new lower BMSs are additionally installed in the battery system, a compensation circuit having a negative capacitance that attenuates the composite capacitance of the additionally installed lower BMSs to a preset range may be connected to the communication line of the upper BMS.

[0022]

[0023] According to one embodiment of the present invention for achieving the above-described other purpose, a battery management device is a battery management device connected to a plurality of lower battery management devices through a communication bus, and a compensation circuit may be connected to compensate for attenuation of a communication signal by filters for reducing communication noise, which are connected to each of the lower battery management devices.

[0024] The above compensation circuit may be a circuit having a negative capacitance for offsetting the composite capacitance of RC filters connected to the communication line of each of the lower battery management devices.

[0025] The above compensation circuit may include an operational amplifier, a first resistor, a second resistor, and a capacitor.

[0026] According to the above-described embodiment of the present invention, the attenuation effect of the communication signal due to the filters applied to each of the lower BMSs can be minimized, thereby improving the communication quality.

[0027] In addition, according to the embodiment of the present invention as described above, when battery assemblies (e.g., battery packs) are additionally installed in a battery system, communication optimization is possible by adding a compensation circuit to an upper BMS or replacing or adjusting an existing compensation circuit without replacing the filters of lower BMSs included in each of the battery assemblies.

[0028] Figure 1 is a block diagram of a typical energy storage system.

[0029] Figure 2 shows the structure of a typical battery rack.

[0030] Figure 3 is a block diagram of a battery system according to an embodiment of the present invention.

[0031] Figure 4 is a block diagram of a battery system to which a compensation circuit according to an embodiment of the present invention is applied.

[0032] Figure 5 is a circuit diagram of a compensation circuit according to an embodiment of the present invention.

[0033] FIG. 6 is a reference diagram for explaining a battery system to which a compensation circuit is added in an operating process according to an embodiment of the present invention.

[0034] Figure 7 is a graph to explain the effect of applying a compensation circuit.

[0035] 100: Top BMS

[0036] 200: Lower BMS

[0037] 300: Compensation circuit

[0038] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. Throughout the description of each drawing, similar reference numerals have been used to designate similar components.

[0039] Terms such as "first," "second," "A," and "B" may be used to describe various components, but these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, the first component could be referred to as the "second component," and similarly, the second component could also be referred to as the "first component." The term "and / or" includes any combination of multiple related items listed or any one of multiple related items listed.

[0040] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0041] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0042] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0043]

[0044] Some terms used in this specification are defined as follows:

[0045] A battery cell is the smallest unit that stores electricity, and a battery module is a collection of multiple battery cells that are electrically connected.

[0046] A battery rack is a single-structure system that connects module units specified by the battery manufacturer in series or parallel, enabling monitoring and control via a Battery Management System (BMS). It can be configured to include multiple battery packs and a single BPU or protection device. Depending on the device or system in which the battery is used, the battery pack may also be referred to as a battery module.

[0047] A battery bank can refer to a large-scale battery rack system composed of multiple racks connected in parallel. A battery bank-level BMS (BBMS) can monitor and control the rack BMS (RBMS) at the battery rack level.

[0048] A battery assembly is a collection of multiple electrically connected battery cells that function as a power source when applied to a specific system or device. Here, the battery assembly may refer to a battery module, battery pack, battery rack, or battery bank, but the scope of the present invention is not limited to these entities.

[0049] BSC (Battery System Controller) is a device that performs top-level control of a battery system, including a battery bank unit battery system, and is also used as a control device in a battery system with multiple bank level structures.

[0050] SOC (State of Charge) is the current charged state of the battery expressed as a percentage [%], and SOH (State of Health) is the current remaining state of the battery expressed as a percentage [%].

[0051]

[0052] Figure 1 is a block diagram of a typical energy storage system.

[0053] In an energy storage system (ESS), the smallest unit of a battery that stores power is typically a battery cell. A series / parallel combination of battery cells forms a battery pack, and multiple battery packs can form a battery rack. In other words, a battery rack, consisting of a series / parallel combination of battery packs, can be the smallest unit of a battery system. Depending on the device or system in which the battery is used, a battery pack may also be referred to as a battery module.

[0054] Referring to Fig. 1, a single battery rack may include multiple battery packs and a single BPU (50) or protection device. The battery rack can be monitored and controlled through a Rack Battery Management System (RBMS). The RBMS monitors the current, voltage, and temperature of each battery rack under its control, and based on the monitoring results, calculates the battery's SOC (State of Charge) and controls charging and discharging.

[0055] Meanwhile, the battery protection unit (BPU) (50) is a device for protecting the battery from abnormal current and fault current in the battery rack unit. The BPU may include a main contactor (MC), a fuse, a circuit breaker (CB), or a disconnect switch (DS). The BPU can control the battery system in the rack unit by turning the main contactor on and off according to the control of the RBMS. The BPU can also protect the battery from short-circuit current using a fuse in the event of a short-circuit. In this way, the existing battery system can be controlled through protection devices such as the BPU and switch gear.

[0056] Meanwhile, a battery system controller (BSC) (20) is installed in each battery section including a plurality of batteries and peripheral circuits, devices, etc. to monitor and control control targets such as voltage, current, temperature, circuit breakers, etc. The BSC is the top-level control device of a battery system including a bank-level battery system including a plurality of battery packs, and is also used as a control device in a battery system having a multiple bank-level structure. Here, the battery system having a bank-level structure may each include a BBMS (Bank BMS), and the BBMS may monitor and control each rack by interworking with the RBMSs of the battery racks it manages.

[0057] In addition, a power conversion system (PCS) (40) installed in each battery section controls the charging and discharging of the battery by controlling the power supplied from an external rotor and the power supplied externally from the battery section, and may include a DC / AC inverter. Meanwhile, if the ESS system is linked to a PV (Photovoltaic; solar power generation system) module farm (70), a PV inverter may be included.

[0058] Meanwhile, the output of each BPU can be connected to the PCS (40) via a DC bus, and the PCS (40) can be connected to the grid (60). In addition, the EMS (Energy Management System) / PMS (Power Management System) (30) manages the ESS system as a whole.

[0059]

[0060] Figure 2 shows the structure of a typical battery rack.

[0061] The battery rack may include a BPU and a plurality of battery packs. Here, the BPU and the plurality of battery packs may be combined in a vertically stacked structure.

[0062] The BPU located at the top of the battery rack may include a circuit breaker (CB) and a RBMS.

[0063] The interior of the RBMS may include a main contactor (MC), a fuse, an MCU (Micro Controller Unit), memory, a power supply unit, and a current sensor.

[0064] Each of the battery packs arranged at the bottom of the BPU may include a plurality of batteries and a PBMS that monitors and manages the batteries.

[0065] The batteries provided inside each of the battery packs are electrically connected in a series and / or parallel configuration, and can be connected to a power terminal provided in the BPU and connected to a DC link.

[0066] The PBMSs included in each battery pack can communicate with the RBMS located within the BPU. The PBMS collects battery status data, such as voltage, current, and temperature, from the PBMSs of the battery packs it manages, and can monitor and control each pack.

[0067]

[0068] Figure 3 is a block diagram of a battery system according to an embodiment of the present invention.

[0069] Referring to FIG. 3, the battery system may include an upper battery management system (BMS) (100) and a plurality of lower battery management systems (BMS) (200-1 to 200-N).

[0070] The upper BMS (100) can monitor and manage a battery assembly including the lower BMS (200) by interworking with a plurality of lower BMSs (200-1 to 200-N). For example, the upper BMS may be an RBMS, and the lower BMS may be a PBMS. In another example, the upper BMS may be a BBMS, and the lower BMS may be an RBMS.

[0071] The upper BMS (100) can be connected to multiple lower BMSs (200-1 to 200-N) through a communication bus. For example, the upper BMS (100) and multiple lower BMSs (200-1 to 200-N) can be connected to each other through a CAN (Controller Area Network) bus.

[0072] Each of the lower BMSs (200-1 to 200-N) may be connected to a filter for reducing communication noise, or may include such a filter. Here, the filter may be an RC filter connected to the communication line of the lower BMS.

[0073] Typically, when multiple BMSs are connected in parallel to a CAN bus and communicate, they communicate at a frequency in the 1 to 2 MHz range. However, since various electronic devices other than the BMS are included within the battery system, 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. The RC filter can be connected to each of the lower-level BMS's CAN HIGH and CAN LOW lines.

[0074] When the number of lower BMS included in the battery system is small (i.e., the number of battery assemblies included in the battery system is small), the phenomenon of communication performance degradation due to the noise reduction filter is minimal. However, as the number of lower BMS connected in parallel to the CAN bus increases, the composite capacitance (NX Cf) of the capacitor (Cf) included in each of the noise reduction filters increases, which may lower the communication signal strength (Gain).

[0075] To address these issues, one option is to replace the capacitors (Cf) in each filter with new capacitors of appropriate capacitance. However, this approach is highly inefficient in terms of system design costs. Specifically, when designing a new battery system or adding a battery assembly to an existing one, capacitance optimization is required for the communication frequency range, and all filters within the battery system must be replaced.

[0076] To solve these technical problems, the battery system according to an embodiment of the present invention may include a compensation circuit (300) to compensate for attenuation of a communication signal by a filter of a lower BMS.

[0077] The compensation circuit (300) can be connected to the communication line of the upper BMS (100). Here, the compensation circuit (300) can be connected to each of the CAN HIGH line and the CAN LOW line of the upper BMS (100).

[0078]

[0079] FIG. 4 is a block diagram of a battery system to which a compensation circuit according to an embodiment of the present invention is applied, and FIG. 5 is a circuit diagram of a compensation circuit according to an embodiment of the present invention.

[0080] Referring to FIG. 4, the battery system may include an upper battery management system (BMS) (100) and a plurality of lower battery management systems (BMS) (200-1 to 200-N).

[0081] The upper BMS (100) can monitor and manage a battery assembly including the lower BMS (200) by interworking with a plurality of lower BMSs (200-1 to 200-N).

[0082] The upper BMS (100) can be connected to multiple lower BMSs (200-1 to 200-N) through a communication bus. Here, the upper BMS (100) and multiple lower BMSs (200-1 to 200-N) can be connected to each other through a CAN (Controller Area Network) bus.

[0083] Each of the lower BMSs (200-1 to 200-N) may be connected to a filter for reducing communication noise. Here, the filter may be an RC filter connected to each of the CAN HIGH line and the CAN LOW line of the lower BMS.

[0084] The upper BMS (100) may be connected to a compensation circuit (300) to compensate for attenuation of communication signals by filters. Here, the compensation circuit (300) may be connected to each of the CAN HIGH line and the CAN LOW line of the upper BMS (100).

[0085] The compensation circuit (300) may be a circuit having negative capacitance to offset the composite capacitance (NX Cf) of the filters.

[0086] A 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.

[0087] 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), as illustrated in FIG. 5. Here, the positive input terminal (+) of the operational amplifier may be connected to a communication line (a of FIG. 4) of the lower BMS. In addition, the capacitor (Cnc0) may be arranged between the positive input terminal (+) of the operational amplifier and an output terminal. In addition, the first resistor (R1) may have one side grounded (b of FIG. 4) and the other side connected to the negative input terminal (-) of the operational amplifier. In addition, the second resistor (R2) may be arranged between the negative input terminal (-) of the operational amplifier and an output terminal.

[0088] The capacitance of the compensation circuit (300) illustrated in Fig. 5 can be expressed as the product of the Miller gain of the operational amplifier and the feedback capacitance. That is, the capacitance (- Cnc) of the compensation circuit (300) can have a value of the product of the Miller gain (R2 / R1) and the feedback capacitance (- Cnc0) (- Cnc0 X (R2 / R1)).

[0089] The resistance value (R1) of the first resistor, the resistance value (R2) of the second resistor, and the capacitance (Cnc0) of the capacitor included in the compensation circuit (300) can be determined according to the number of filters included in the battery system (or the number of lower BMSs) and the capacitance (Cf) of each of the filters.

[0090] Specifically, since the compensation circuit (300) according to the present invention is a configuration applied to the communication line of the upper BMS in order to offset the composite capacitance (NX Cf) of the filters, the capacitance (- Cnc) of the compensation circuit (300) can be designed to have a value capable of attenuating the composite capacitance (NX Cf) of the filters to an appropriate value.

[0091] The capacitance (- Cnc) of the compensation circuit (300) may be determined to be a value that causes the gain of the communication signal at the communication frequency used in the battery system to be greater than or equal to a set value. Here, the capacitance (- Cnc) of the compensation circuit (300) may be determined to be a value that causes the gain of the communication signal according to the overall composite capacitance (NX Cf - Cnc) to be greater than or equal to -3 dB. Thereafter, the resistance value (R1) of the first resistor, the resistance value (R2) of the second resistor, and the capacitance (Cnc0) of the capacitor, which cause the capacitance (- Cnc) of the compensation circuit (300) to have the intended value, are determined, and the compensation circuit (300) is designed accordingly and can be applied to the communication line of the upper BMS (100).

[0092] For example, in Fig. 4, when Cf is 100 pF and N is 21, the composite capacitance of the filters is 2100 pF (21 X 100 pF). In this case, a signal strength attenuation of about -5 dB at 2 MHz may occur due to the composite capacitance of the filters. In order to adjust the signal strength attenuation to about -2 dB, if it is desired to compensate (adjust) the entire composite capacitance to 1300 pF, a compensation circuit (300) having a capacitance of -800 pF may be applied to the upper BMS (100). Here, a resistance of 100 kΩ is applied to R1, a resistance of 400 kΩ is applied to R2, and a capacitor of 200 pF is applied to Cnc0, so that a compensation circuit (300) exhibiting an intended negative capacitance (-800 p ) can be manufactured.

[0093]

[0094] FIG. 6 is a reference diagram for explaining a battery system to which a compensation circuit is added in an operating process according to an embodiment of the present invention, and FIG. 7 is a graph for explaining the effect according to application of the compensation circuit.

[0095] The compensation circuit can be added to the upper BMS during the operation of the battery system, rather than during the design phase of the battery system.

[0096] For example, as illustrated in Fig. 6(A), the battery system includes 12 battery assemblies, and a noise reduction filter may be applied to the lower BMSs (#1 to #12) included in each of the battery assemblies. In the case of such a battery system (Case 1), as illustrated in Fig. 7, the communication signal gain at 2 MHz is approximately -2 dB, and the battery system can be operated without a compensation circuit being applied to the upper BMS.

[0097] During the operation of the battery system, new battery assemblies may be added as needed. In this case, the noise reduction filter included in the added battery assembly may increase the synthetic capacitance, thereby reducing the communication signal gain.

[0098] For example, as illustrated in Fig. 6(B), during the operation of a battery system including 12 battery assemblies, 9 battery assemblies may be additionally installed in the battery system. In this case (Case 2), the noise reduction filter included in the added battery assembly increases the synthetic capacitance, and as illustrated in Fig. 7, the communication signal gain at 2 MHz may be attenuated to approximately -5 dB, resulting in deterioration of communication performance.

[0099] To prevent such degradation in communication performance, a compensation circuit may be connected to the communication line of the upper BMS. For example, as illustrated in Fig. 6(B), the battery system may have a compensation circuit (-Cnc) with negative capacitance connected to the communication line of the upper BMS.

[0100] Here, the compensation circuit connected to the upper BMS may have a negative capacitance that can attenuate the composite capacitance of the additionally installed lower BMSs within a preset range. For example, when nine lower BMSs are added as shown in Fig. 6(B) and the composite capacitance increases by 900 pF (9 X 100 pF), a compensation circuit (300) having a capacitance of -800 pF may be applied to the upper BMS (100) so as to attenuate the increased composite capacitance within 15%. In this case (Case 3), the total composite capacitance is reduced from 2100 pF to 1300 pF by the added compensation circuit, and as shown in Fig. 7, the communication signal gain at 2 MHz is adjusted to about -2 dB, so that communication performance can be improved.

[0101]

[0102] Although the present invention has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

Claims

1. Upper BMS (Battery Management System); and Contains multiple sub-BMSs, The above upper BMS and lower BMS are connected to each other through a communication bus, Each of the above sub-BMSs, A filter is connected to reduce communication noise, The above upper BMS is, A battery system, to which a compensation circuit is connected for compensating for attenuation of a communication signal by the above filters.

2. In claim 1, The above upper BMS and lower BMS, A battery system that communicates via the CAN (Controller Area Network) bus.

3. In claim 1, The above filter is, A battery system, which is an RC filter, connected to the communication line of the above lower BMS.

4. In claim 3, The above compensation circuit is, A battery system having a circuit having negative capacitance to offset the composite capacitance of the above filters.

5. In claim 4, The above compensation circuit is, A battery system connected to the communication line of the above upper BMS.

6. In claim 5, The above compensation circuit is, A battery system connected to each of the CAN HIGH line of the upper BMS and the CAN LOW line of the upper BMS.

7. In claim 3, The above compensation circuit is, A battery system comprising an operational amplifier, a first resistor, a second resistor, and a capacitor.

8. In claim 7, The positive input terminal of the above operational amplifier is connected to the communication line of the lower BMS, The above capacitor is placed between the positive input terminal and the output terminal of the operational amplifier, The above first resistor has one side grounded and the other side connected to the negative input terminal of the operational amplifier, The second resistor is a battery system arranged between the negative input terminal and the output terminal of the operational amplifier.

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

10. In claim 1, The above compensation circuit is, A battery system, in which new lower BMSs are additionally installed in the battery system, and are connected to the communication line of the upper BMS.

11. In claim 4, A battery system, wherein when new lower BMSs are additionally installed in the battery system, a compensation circuit having a negative capacitance that reduces the composite capacitance of the additionally installed lower BMSs to a preset range is connected to the communication line of the upper BMS.

12. A battery management device connected to multiple lower battery management devices through a communication bus, A battery management device, wherein a compensation circuit is connected to compensate for attenuation of a communication signal by filters for reducing communication noise, each of which is connected to each of the above-mentioned lower battery management devices.

13. In claim 12, The above compensation circuit is, A battery management device, which is a circuit having a negative capacitance for canceling out the composite capacitance of RC filters connected to the communication line of each of the above-mentioned lower battery management devices.

14. In claim 13, The above compensation circuit is, A battery management device comprising an operational amplifier, a first resistor, a second resistor, and a capacitor.

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