Abstract:
An energy storage system having a number of trays with each tray having a number of battery cells in which power is controllably stored and discharged. A first Battery Management System (BMS) is electrically coupled to a tray contained in a rack of trays. A second BMS is electrically coupled to and controls the first BMS. The first BMS includes a control unit electrically coupled to and controlling the battery cells. It further includes a switch unit electrically coupled to the control unit and selectively applying driving power according to a control signal from the second BMS.

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims priority to and the benefit of Provisional Application No. 61/536,791, filed on 20 Sep. 2011, in the United States Patent and Trademark Office, the entire content of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to a battery managing apparatus, a battery pack using the battery managing apparatus, and an energy storage system using the battery pack. 
         [0004]    2. Description of the Related Art 
         [0005]    Due to problems of environment destruction, resource exhaustion, and the like, there is increasing demand for a system capable of efficiently using stored power. Also, there is increasing demand for renewable energy that does not cause pollution during power generation. An energy storage system is a system that connects renewable energy, a power storing battery, and existing power from a grid, and much research has been conducted to conform to environmental changes. 
         [0006]    The above information disclosed in this Related Art section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has been made in an effort to provide a battery managing apparatus, a battery pack using the battery managing apparatus, and an energy storage system using the battery pack. 
         [0008]    An exemplary embodiment of the present invention provides for an energy storage system, having a plurality of trays with each tray having a plurality of battery cells; a first BMS (Battery Management System) electrically coupled to a tray of the plurality of trays; a rack comprising the plurality of the trays; and a second BMS (Battery Management System) electrically coupled to and controlling the first BMS. The first BMS, further comprises: a control unit electrically coupled to and controlling the plurality of battery cells; and a switch unit electrically coupled to the control unit and selectively applying a driving power according to a control signal from the second BMS. 
         [0009]    The energy storage system also includes: a first converter converting the driving power and outputting a first converting signal; a second converter converting a battery power and outputting a second converting signal; and an AND gate electrically coupled to the first converter and the second converter. The AND gate sends the driving signal to the control unit when both the first converting signal and the second converting signal are more than a predetermined signal level. 
         [0010]    The first BMS of the energy storage system further includes: a plurality of first BMSs; a synchronization signal delivering unit connected to a neighboring first BMS of the plurality of first BMSs to deliver a synchronization signal, wherein the synchronization signal is transmitted from the second BMS to one of the plurality of first BMSs, and transmitted from said one of the first BMSs of the plurality of first BMSs to another first BMS of the plurality of first BMSs in a cascade manner; a tray ON/OFF unit connected to the synchronization signal delivering unit; a first DC/DC converter connected to the tray ON/OFF unit; a second DC/DC converter connected to an analog front end (AFE); a microcontroller (MCU) ON/OFF unit connected to the first and second DC/DC converter; a third DC/DC converter connected to the microcontroller (MCU) ON/OFF unit; a MCU connected to the synchronization signal delivering unit and the third DC/DC converter; and a communication driving unit connected to the MCU and the rack BMS. 
         [0011]    The energy storage system further includes: an AND gate electrically coupled to the first DC/DC converter and the second DC/DC converter, wherein the AND gate sends the driving signal to the control unit when both a first converting signal from the first DC/DC converter and a second converting signal from the second DC/DC converter are more than a predetermined signal level. 
         [0012]    In the energy storage system, the plurality of battery cells receive power from a power generating system or supply power to a grid or supply power to a load. 
         [0013]    The energy storage system also includes: a power conversion system connected to the plurality of battery cells and the power generating system to convert power from the power generating system, the grid or the plurality of battery cells and supply the power to the load; a first switch connected to the power conversion system and connected to the load; and a second switch serially connected to the first switch and connected to the power conversion system, the grid and the load. The first switch is turned on when power from the power generating system and/or the plurality of battery cells is supplied to the load, or when power from the grid is supplied to the battery pack. The second switch is turn on when power from the power generating system and/or the plurality of battery cells is supplied to the grid, or when power from the grid is supplied to the load and/or the plurality of battery cells. The second switch is turned off and the first switch is turned on when a power failure occurs in the grid. 
         [0014]    In the energy storage system when the synchronization signal is set to a first level, the tray ON/OFF unit delivers driving power the first DC/DC converter, and when the synchronization signal is set to a second level that is different from the first level, the tray ON/OFF unit does not deliver the driving power to the first DC/DC converter. 
         [0015]    The rack BMS determines whether the first tray BMS through the n th  tray BMS operate based whether the tray ON/OFF unit delivers the driving power. 
         [0016]    The first DC/DC converter receives the driving power delivered via the tray ON/OFF unit and adjusts a voltage level of the driving power and inputs the driving power to the MCU ON/OFF unit. 
         [0017]    The analog front end (AFE) monitors voltage, current, temperature, remaining amount of power, and charge status of the first battery tray through an n th  battery trays transmitting monitoring data to the MCU. 
         [0018]    The AFE delivers a current output from the first battery tray through an n th  battery tray to the second DC/DC converter, upon receipt of the current output the second DC/DC converter outputs the current to the MCU. 
         [0019]    In the Energy Storage System when the MCU ON/OFF unit receives power from both the first DC/DC converter and the second DC/DC converter does the MCU ON/OFF unit input power received from first DC/DC converter or the second DC/DC converter to the third DC/DC converter. 
         [0020]    Another exemplary embodiment of the present invention details a battery system, comprising: a battery rack to store power from at least one of a plurality of power generating units and a grid, the battery rack comprising: a first battery tray through an n th  battery tray connected in series or in parallel; and a first BMS (Battery Management System) comprising a first tray BMS (Battery Management System) through an n th  tray BMS (Battery Management System) connected to and corresponding to the first battery tray through the n th  battery tray, respectively; and a second battery management system (BMS) to control an operation of the battery rack by monitoring data of the battery rack and transmitting a power control signal, wherein the first BMS is triggered in response to a power control signal (PCS) from the second BMS. 
         [0021]    The battery system also includes: a first converter converting the driving power and outputting a first converting signal; a second converter converting a battery power and outputting a second converting signal; and an AND gate electrically coupled to the first converter and the second converter. The AND gate sends the driving signal to the control unit when both the first converting signal and the second converting signal are more than a predetermined signal level. 
         [0022]    The first BMS also includes a plurality of first BMSs; a synchronization signal delivering unit connected to a neighboring first BMS of the plurality of first BMSs to deliver a synchronization signal, wherein the synchronization signal is transmitted from the second BMS to one of the plurality of first BMSs, and transmitted from said one of the first BMSs of the plurality of first BMSs to another first BMS of the plurality of first BMSs in a cascade manner; a tray ON/OFF unit connected to the synchronization signal delivering unit; a first DC/DC converter connected to the tray ON/OFF unit; a second DC/DC converter connected to an analog front end (AFE); a microcontroller (MCU) ON/OFF unit connected to the first and second DC/DC converter; a third DC/DC converter connected to the microcontroller (MCU) ON/OFF unit; a MCU connected to the synchronization signal delivering unit and the third DC/DC converter; and a communication driving unit connected to the MCU and the rack BMS. 
         [0023]    In a power saving mode, the first tray BMS through the n th  tray BMS are deactivated in response to the PCS that is applied to the rack BMS reducing power consumption. 
         [0024]    Another aspect of the present invention is that only the first tray BMS through the n th  tray BMS are deactivated while the rack BMS remains activated reducing power consumption while a basic function of the battery pack is maintained. 
         [0025]    Another embodiment of the present invention entails a battery system electrically connectable to a power conversion system. The battery system includes: a battery rack to store power from at least one of the power generating unit and the grid, the battery rack comprising: a first battery tray through an n th  battery tray connected in series or in parallel; and first BMSs comprising a first tray BMS through an n th  tray BMS that connected to and correspond to the first battery tray through the n th  battery tray, respectively; and a second battery management system (BMS) connectable to the power conversion system to control an operation of the battery rack by monitoring data of the battery rack and transmitting a power control signal, wherein the first BMSs are triggered in response to a power control signal (PCS) from the second BMS. 
         [0026]    A power conversion system is connected to the battery rack and the power generating system to convert power from the power generating system, the grid or the battery rack and supply the power to the load; a first switch connected to the power conversion system and connected to the load; and a second switch serially connected to the first switch and connected to the power conversion system, the grid and the load. The first switch is turned on when power from the power generating system and/or the plurality of battery cells is supplied to the load, or when power from the grid is supplied to the battery pack. The second switch is turn on when power from the power generating system and/or the plurality of battery cells is supplied to the grid, or when power from the grid is supplied to the load and/or the plurality of battery cells. The second switch is turned off and the first switch is turned on when a power failure occurs in the grid. 
         [0027]    The battery system also includes a first converter converting the driving power and outputting a first converting signal; a second converter converting a battery power and outputting a second converting signal; and an AND gate electrically coupled to the first converter and the second converter. The AND gate sends the driving signal to the control unit when both the first converting signal and the second converting signal are more than a predetermined signal level. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
           [0029]      FIG. 1  is a diagram illustrating a configuration of an energy storage system according to an embodiment of the present invention; 
           [0030]      FIG. 2  is a diagram illustrating a configuration of a battery pack, according to an embodiment of the present invention; 
           [0031]      FIG. 3  is a diagram illustrating a configuration of a battery rack, according to an embodiment of the present invention; 
           [0032]      FIG. 4  is a diagram illustrating a structure of a k th  battery tray and a k th  tray battery management system (BMS), according to an embodiment of the present invention; 
           [0033]      FIG. 5  is a diagram for describing a delivery of a synchronization signal, according to an embodiment of the present invention; and 
           [0034]      FIG. 6  is a diagram for describing an ON/OFF control of the kth tray BMS, according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0035]    The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those of ordinary skill in the art. Meanwhile, all examples and conditional language recited herein are to be construed as being without limitation to such specifically recited examples and conditions. Throughout the specification, a singular form may include plural forms, unless there is a particular description contrary thereto. Also, terms such as “comprise” or “comprising” are used to specify existence of a recited form, a number, a process, an operations, a component, and/or groups thereof, not excluding the existence of one or more other recited forms, one or more other numbers, one or more other processes, one or more other operations, one or more other components and/or groups thereof. While terms “first” and “second” are used to describe various components, it is obvious that the components are not limited to the terms “first” and “second”. The terms “first” and “second” are used only to distinguish between each component. 
         [0036]    Recognizing that sizes and thicknesses of constituent members shown in the accompanying drawings are arbitrarily given for better understanding and ease of description, the present invention is not limited to the illustrated sizes and thicknesses. 
         [0037]    In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like elements throughout the specification. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. Alternatively, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
         [0038]    In order to clarify the present invention, elements extrinsic to the description are omitted from the details of this description, and like reference numerals refer to like elements throughout the specification. 
         [0039]    In several exemplary embodiments, constituent elements having the same configuration are representatively described in a first exemplary embodiment by using the same reference numeral and only constituent elements other than the constituent elements described in the first exemplary embodiment will be described in other embodiments. 
         [0040]      FIG. 1  is a diagram illustrating a configuration of an energy storage system  1  according to an embodiment of the present invention. 
         [0041]    Referring to  FIG. 1 , the energy storage system  1  according to the present embodiment supplies power to a load  4 , in conjunction with a power generating system  2  and a grid  3 . 
         [0042]    The power generating system  2  is a system for generating power by using an energy source, and supplies the generated power to the energy storage system  1 . The power generating system  2  may be a solar power generating system, a wind power generating system, a tidal power generating system, or the like. However, examples of the power generating system  2  are not limited thereto and thus, the power generating system  2  may include power generating systems for generating power by using a renewable energy including solar heat, terrestrial heat, or the like. 
         [0043]    For example, a solar cell that generates electric energy by using a solar ray is easily installed in a house or a factory and thus the solar cell may be applied to the energy storage system  1 , which may be distributed in each of houses. The power generating system  2  includes a plurality of power generating modules arranged in parallel with each other, and generates power via each of the power generating modules, so that the power generating system  2  may be a large capacity energy system. 
         [0044]    The grid  3  includes a power generating station, a substation, a power transmission line, and the like. When the grid  3  is in a normal status, the grid  3  supplies power to the energy storage system  1  so as to allow the power to be supplied to the load  4  and/or a battery pack  20 , and receives power from the energy storage system  1 . When the grid is in an abnormal status, a power supply from the grid  3  to the energy storage system  1  is stopped, and a power supply from the energy storage system  1  to the grid  3  is also stopped. 
         [0045]    The load  4  consumes power generated by the power generating system  2 , power stored in the battery pack  20 , or power supplied from the grid  3 . Examples of the load  4  include a house, a factory, or the like. 
         [0046]    The energy storage system  1  may store power generated by the power generating system  2  in the battery pack  20 , or may supply the power to the grid  3 . Also, the energy storage system  1  may supply power stored in the battery pack  20  to the grid  3 , or may store power supplied from the grid  3  in the battery pack  20 . In addition, when the grid  3  is in an abnormal status, e.g., when a power failure occurs in the grid  3 , the energy storage system  1  may perform an Uninterruptible Power Supply (UPS) operation and then supply power to the load  4 . When the grid  3  is in a normal status, the energy storage system  1  may supply power generated by the power generating system  2  or the power stored in the battery pack  20  to the load  4 . 
         [0047]    The energy storage system  1  may include a power conversion system  10  for controlling power conversion, the battery pack  20 , a first switch  30 , and a second switch  40 . 
         [0048]    The power conversion system  10  converts power from the power generating system  2 , the grid  3 , and the battery pack  20  according to required specification, and then supplies the power to desired components. The power conversion system  10  may include a power converting unit  11 , a direct current (DC) link unit  12 , an inverter  13 , a converter  14 , and an integrated controller  15 . 
         [0049]    The power converting unit  11  is a power converting device that is connected between the power generating system  2  and the DC link unit  12 . The power converting unit  11  may convert a voltage output from the power generating system  2  into a DC link voltage, and delivers power generated by the power generating system  2  to the DC link unit  12 . 
         [0050]    According to the power generating system  2 , the power converting unit  11  may be formed as a power converting circuit that may include a converter, a rectifier circuit, or the like. In a case where the power generating system  2  generates DC power, the power converting unit  11  may function as a DC/DC converter. In a case where the power generating system  2  generates alternating current (AC) power, the power converting unit  11  may function as a rectifier circuit for converting AC power into DC power. In particular, when the power generating system  2  is a solar power generating system, the power converting unit  11  may include a maximum power point tracking (MPPT) converter for performing MPPT control so as to maximally obtain power generated by the power generating system  2  according to a change in solar radiation intensity, temperature, and the like. When the power generating system  2  does not generate power, the power converting unit  11  may stop its operation so as to reduce power consumed by a converter, or the like. 
         [0051]    A level of the DC link voltage may be unstable due to an instant voltage drop in the power generating system  2  or the grid  3  or a peak load occurrence in the load  4 . However, it may be necessary to stabilize the level of the DC link voltage for a normal operation of the converter  14  and the inverter  13 . The DC link unit  12  may be connected between the power converting unit  11  and the inverter  13 , thereby constantly maintaining the level of the DC link voltage. For example, a large-capacity capacitor may be used as the DC link unit  12 . 
         [0052]    The inverter  13  is a power converting device connected between the DC link unit  12  and the first switch  30 . The inverter  13  may include an inverter that converts the DC link voltage output from the power generating system  2  and/or the battery pack  20  into an AC voltage appropriate for the grid  3 , and then output the AC voltage. Also, in order to store power from the grid  3  in the battery pack  20 , the inverter  13  may include a rectifier circuit that rectifies an AC voltage of the grid  3 , converts the AC voltage into the DC link voltage, and then outputs the DC link voltage. That is, the inverter  13  may be a bidirectional inverter whose input and output directions may be changed. 
         [0053]    The inverter  13  may include a filter for removing a harmonic from the AC voltage output from the grid  3 . Also, the inverter  13  may include a phase locked loop (PLL) circuit for synchronizing a phase of an AC voltage output from the inverter  13  with a phase of the AC voltage output from the grid  3  so as to prevent occurrence of reactive power. In addition, the inverter  13  may perform functions including restriction of a voltage variation range, improvement of a power factor, removal of a DC component, transient phenomenon protection, and the like. When the inverter  13  is not used, an operation of the inverter  13  may be stopped to reduce power consumption. 
         [0054]    The converter  14  is a power converting device connected between the DC link unit  12  and the battery pack  20 . In a discharge mode, the converter  14  may include a converter that DC-DC converts a voltage of power stored in the battery pack  20  into the DC link voltage, i.e., a voltage level required by the inverter  13 . Also, in a charge mode, the converter  14  may include a converter that DC-DC converts a voltage of power output from the power converting unit  11  or the inverter  13  into a charge voltage, i.e., a voltage level required by the battery pack  20 . That is, the converter  14  may be a bidirectional converter whose input and output directions may be changed. When it is not necessary to charge or discharge the battery pack  20 , an operation of the converter  14  may be stopped to reduce power consumption. 
         [0055]    The integrated controller  15  monitors the statuses of the power generating system  2 , the grid  3 , the battery pack  20 , and the load  4 , and controls operations of the power converting unit  11 , the inverter  13 , the converter  14 , the battery pack  20 , the first switch  30 , and the second switch  40  according to a result of the monitoring. The integrated controller  15  may monitor whether a power failure occurs in the grid  3 , whether power may be generated by the power generating system  2 , the amount of power generation if the power generating system  2  generates power, a charge status of the battery pack  20 , power consumption of the load  4 , a time, or the like. Also, in a case where power to be supplied to the load  4  is not sufficient due to the power failure in the grid  3  or the like, the integrated controller  15  may decide a priority order with respect to power consuming devices included in the load  4  and then may control the load  4  to supply power to a power consuming device having higher priority. 
         [0056]    The first switch  30  and the second switch  40  are serially connected between the inverter  13  and the grid  3 , and perform on/off operations according to a control by the integrated controller  15 , so that the first switch  30  and the second switch  40  control a flow of a current between the power generating system  2  and the grid  3 . The first switch  30  and the second switch  40  may be turned on or off according to the status of the power generating system  2 , the grid  3 , and the battery pack  20 . 
         [0057]    In more detail, when power from the power generating system  2  and/or the battery pack  20  is supplied to the load  4 , or when power from the grid  3  is supplied to the battery pack  20 , the first switch  30  is turned on. When power from the power generating system  2  and/or the battery pack  20  is supplied to the grid  3 , or when power from the grid  3  is supplied to the load  4  and/or the battery pack  20 , the second switch  40  is turned on. 
         [0058]    When the power failure occurs in the grid  3 , the second switch  40  may be turned off and the first switch  30  may be turned on. That is, the power from the power generating system  2  and/or the grid  3  may be supplied to the load  4 , and simultaneously, it is possible to prevent the power, which is to be supplied to the load  4 , from flowing to the grid  3 . In this manner, by preventing the operation of the energy storage system  1 , it is possible to prevent a worker who is working with a power line of the grid  3  from being injured by the power from the energy storage system  1 . 
         [0059]    A switching device may include a relay or the like capable of enduring a large current may be used as the first switch  30  and the second switch  40 . 
         [0060]    The battery pack  20  may receive and store power from the power generating system  2  and/or the grid  3 , and supply stored power to the load  4  or the grid  3 . The battery pack  20  may include a part for storing power, and a controlling unit. Hereinafter, the battery pack  20  will now be described in detail with reference to  FIG. 2 . 
         [0061]      FIG. 2  is a diagram illustrating a configuration of the battery pack  20 , according to an embodiment of the present invention. 
         [0062]    Referring to  FIG. 2 , the battery pack  20  may include a battery rack  100  and a rack battery management system (BMS)  200 . 
         [0063]    The battery rack  100  stores power supplied from an external source, that is, the power generating system  2  and/or the grid  3 , and supplies stored power to the power generating system  2  and/or the grid  3 . The battery rack  100  may include a plurality of sub-units which will be described in detail with reference to  FIG. 3 . 
         [0064]      FIG. 3  is a diagram illustrating a configuration of the battery rack  100 , according to an embodiment of the present invention. 
         [0065]    Referring to  FIG. 3 , the battery rack  100  may include a first battery tray  110 - 1  through an n th  battery tray  110 - n  that are sub-units connected in series and/or in parallel. Each of the first battery tray  110 - 1  through the n th  battery tray  110 - n  may include a plurality of battery cells as sub-units. One of various chargeable secondary batteries may be used as the battery cell. For example, the various secondary batteries to be used as the battery cell include nickel-cadmium battery, a lead battery, a nickel metal hydrate (NiMH) battery, a lithium ion battery, a lithium polymer battery, or the like. 
         [0066]    The battery rack  100  may be adjusted to output desired power according to connection between the first battery tray  110 - 1  through the n th  battery tray  110 - n,  and may output power by using a positive output terminal R+ and a negative output terminal R−. 
         [0067]    Also, the battery rack  100  may include a plurality of first BMSs. The plurality of first BMSs may comprise a first tray BMS  120 - 1  through an n th  tray BMS  120 - n  that correspond to the first battery tray  110 - 1  through the n th  battery tray  110 - n,  respectively. The first tray BMS  120 - 1  through the n th  tray BMS  120 - n  may be triggered in response to a power control signal PCS that is input from a second BMS, e.g. the rack BMS  200 . According to the present embodiment, a synchronization signal Ss that is generated in response to the power control signal PCS may be delivered to the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  in a cascade manner, so that the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  are activated and thus operate. 
         [0068]    According to one or more embodiments of the present invention, in a power saving mode, while the rack BMS  200  operates, the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  may be deactivated in response to the power control signal PCS that is applied to the rack BMS  200 , so that power consumption by the battery pack  20  is significantly decreased. In the battery pack  20 , the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  require high power consumption due to a large number of the first tray BMS  120 - 1  through the n th  tray BMS  120 - n,  so that power consumption may be significantly decreased by deactivating the first tray BMS  120 - 1  through the n th  tray BMS  120 - n.    
         [0069]    Also, only the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  are deactivated while the rack BMS  200  is activated, so that it is possible to significantly decrease power consumption of the battery pack  20  while a basic function of the battery pack  20  is maintained. For example, in the power saving mode, the battery pack  20  deactivates the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  while the battery pack  20  performs a signal exchange between the rack BMS  200  and the integrated controller  15 , and the battery pack  20  activates the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  only when their operation is necessary. By doing so, power consumption by the battery pack  20  may be significantly decreased. 
         [0070]    The first tray BMS  120 - 1  through the n th  tray BMS  120 - n  monitor a voltage, a current, a temperature, or the like of the first battery tray  110 - 1  through the n th  battery tray  110 - n,  respectively. A result of the monitoring by the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  may be transmitted to the rack BMS  200 . 
         [0071]    Referring back to  FIG. 2 , the rack BMS  200  may be connected to the battery rack  100 , and controls charging and discharging operations of the battery rack  100 . Also, the rack BMS  200  may perform an over-charge protection function, an over-discharge protection function, an. over-current protection function, an over-voltage protection function, an over-heat protection function, a cell balancing function, and the like. To do so, the rack BMS  200  transmits the power control signal PCS to the battery rack  100 , and receives monitoring data Dm regarding a voltage, a current, the temperature, a remaining amount of power, the lifetime, a charge status, and the like from each of the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  of the battery rack  100 . Also, the rack BMS  200  may apply the monitoring data Dm to the integrated controller  15 , and may receive a command regarding a control of the battery rack  100  from the integrated controller  15 . 
         [0072]      FIG. 4  is a diagram illustrating a structure of a k th  battery tray  110 - k  and a k th  tray BMS  120 - k,  according to an embodiment of the present invention. Here, k is an integer that is greater than 0 and equal to or less than n. According to the present embodiment, the k th  battery tray  110 - k  indicates a structure of each of the first battery tray  110 - 1  through the n th  battery tray  110 - n,  and the k th  tray BMS  120 - k  indicates a structure of each of the first tray BMS  120 - 1  through the n th  tray BMS  120 - n.    
         [0073]    The k th  battery tray  110 - k  may include one or more battery cells that are serially connected to each other. As described above, the one or more battery cells may be embodied by using one of various chargeable secondary batteries. 
         [0074]    The k th  tray BMS  120 - k  may include one or more analog front end (AFE)  410   a  and  410   b,  a synchronization signal delivering unit  415 , a tray ON/OFF unit  420 , a first DC/DC converter  425 , a second DC/DC converter  430 , an MCU ON/OFF unit  435 , a third DC/DC converter  440 , an MCU  445 , a fan driving unit  450 , and a communication driving unit  455 . 
         [0075]    The synchronization signal delivering unit  415  may receive a synchronization signal Ss and then delivers it to the MCU  445  and the tray ON/OFF unit  420 . According to the embodiment of  FIG. 3  in which the synchronization signal Ss is delivered in a direction from the n th  tray BMS  120 - n  to the first tray BMS  120 - 1 , the synchronization signal Ss may be input from a (k+1) th  tray BMS  120 -( k+ 1) and may be delivered to a (k−1) th  tray BMS  120 -( k− 1). In a case where the k th  tray BMS  120 - k  is an n th  tray BMS  120 - k,  the synchronization signal Ss that is delivered to the synchronization signal delivering unit  415  may be the power control signal PCS input from the rack BMS  200 . 
         [0076]    However, one or more embodiments of the present invention are not limited to a configuration in which the synchronization signal Ss is delivered in the direction from the n th  tray BMS  120 - n  to the first tray BMS  120 - 1 . Conversely, it is possible that the synchronization signal Ss is delivered in an opposite direction from the first tray BMS  120 - 1  to the n th  tray BMS  120 - n.  In this case, the power control signal PCS may be input to the synchronization signal delivering unit  415  of the first tray BMS  120 - 1 . 
         [0077]    The tray ON/OFF unit  420  may receive driving power PIN. If the synchronization signal Ss has a first level, the tray ON/OFF unit  420  delivers the driving power PIN to the first DC/DC converter  425 , and if the synchronization signal Ss has a second level, the tray ON/OFF unit  420  does not deliver the driving power PIN to the first DC/DC converter  425 . According to whether the tray ON/OFF unit  420  delivers the driving power PIN, whether the k th  tray BMS  120 - k  operates is decided. According to this configuration, the rack BMS  200  may control whether to operate the first tray BMS  120 - 1  through the n th  tray BMS  120 - n.  The tray ON/OFF unit  420  may be embodied by using a switching device such as a field effect transistor (FET) or the like. 
         [0078]    The first DC/DC converter  425  receives the driving power PIN delivered via the tray ON/OFF unit  420 , and then firstly adjusts a voltage level of the driving power PIN. Power output from the first DC/DC converter  425  may be input to the MCU ON/OFF unit  435 . 
         [0079]    The AFE  410   a  and  410   b  monitors a voltage, a current, the temperature, a remaining amount of power, the lifetime, a charge status, and the like of the k th  battery tray  110 - k.  Also, the AFE  410   a  and  410   b  performs AC-DC conversion on measured monitoring data and then delivers the measured monitoring data to the MCU  445 . According to the present embodiment, as illustrated in  FIG. 4 , the AFE  410   a  and  410   b  may be serially connected to each other. In another embodiment, the AFE  410   a  and  410   b  may be formed as one integrated chip (IC). 
         [0080]    The monitoring data measured by the AFE  410   a  and  410   b  may be delivered to the MCU  445 . A data transmission from the AFE  410   a  and  410   b  may be performed according to an I2C method. 
         [0081]    Also, the AFE  410   a  and  410   b  may operate according to a control by the MCU  445 . For example, the MCU  445  may control the AFE  410   a  and  410   b  to generate monitoring data by monitoring the k th  battery tray  110 - k  or may control the AFE  410   a  and  410   b  to perform a cell balancing operation, an over-current protection operation, an over-heat protection operation, or the like. 
         [0082]    For an operation of the MCU  445 , the AFE  410   a  and  410   b  delivers a current output from the k th  battery tray  110 - k  to the second DC/DC converter  430 . The second DC/DC converter  430  may perform DC/DC conversion on the current output from the AFE  410   a  and  410   b  and then may output the current to the MCU  445 . 
         [0083]    Only when the MCU ON/OFF unit  435  receives power, which is equal to or greater than a predetermined voltage level, from both the first DC/DC converter  425  and the second DC/DC converter  430 , does the MCU ON/OFF unit  435  input power received from first DC/DC converter  425  and/or the second DC/DC converter  430  to the third DC/DC converter  440 . The MCU ON/OFF unit  435  may be formed as an AND gate logic circuit. 
         [0084]    If the power is received from the MCU ON/OFF unit  435 , the third DC/DC converter  440  performs DC/DC conversion on the power according to a level satisfying an operation specification, and then outputs the power to the MCU  445 . 
         [0085]    The MCU ON/OFF unit  435  inputs the power to the MCU  445  only when the power having a predetermined level is received from the first DC/DC converter  425 , and the first DC/DC converter  425  receives the driving power PIN only when the synchronization signal Ss has a first level, so that whether the MCU  445  operates is decided according to a control by the power control signal PCS input from the rack BMS  200 . 
         [0086]    The MCU  445  controls operations of the k th  battery tray  110 - k  and the k th  tray BMS  120 - k.  The MCU  445  controls operations of the AFE  410   a  and  410   b,  and collects the monitoring data from the AFE  410   a  and  410   b.  Also, the MCU  445  controls operations of the fan driving unit  450  and the communication driving unit  455 . 
         [0087]    The MCU  445  may exchange a control signal and monitoring data Dmk with the rack BMS  200  via the communication driving unit  455 . For example, the communication driving unit  455  may perform communication between the rack BMS  200  and the MCU  445  by using a controller area network (CAN) communication method. 
         [0088]    The fan driving unit  450  drives a fan so as to cool the rack BMS  200 . The fan driving unit  450  may control a speed of the fan by using the control signal and/or data received from the MCU  445 . For example, the fan driving unit  450  may adjust the speed of the fan according to a temperature of the kth battery tray  110 - k.    
         [0089]      FIG. 5  is a diagram for describing a delivery of the synchronization signal Ss, according to an embodiment of the present invention.  FIG. 5  illustrates a synchronization signal delivering unit of the n th  tray BMS  120 - n  (hereinafter, referred to as ‘n th  synchronization signal delivering unit  415   n ′), and a synchronization signal delivering unit of an (n−1) th  tray BMS  120 -( n− 1) (hereinafter, referred to as ‘(n−1) th  synchronization signal delivering unit  415 (n−1)’). 
         [0090]    According to the present embodiment, a first synchronization signal Ss 1  may be delivered via a first chain CH 1 , and a second synchronization signal Ss 2  may be delivered via a second chain CH 2 . The second synchronization signal Ss 2  may be input to a microcomputer (MICOM) arranged in each of the n th  synchronization signal delivering unit  415   n  and the (n−1) th  synchronization signal delivering unit  415 ( n− 1). The MICOM may store statuses of the n th  synchronization signal delivering unit  415   n  and the (n−1) th  synchronization signal delivering unit  415 ( n− 1), and may control the n th  synchronization signal delivering unit  415   n  and the (n−1) th  synchronization signal delivering unit  415 ( n− 1). 
         [0091]    Photo-couplers (PC) may be arranged in the first chain CH 1  and the second chain CH 2  so as to function as an insulating switch when the first synchronization signal Ss 1  and the second synchronization signal Ss 2  are delivered. 
         [0092]    The delivery of the first and second synchronization signals Ss 1  and Ss 2  via the first chain CH 1  and the second chain CH 2  may be triggered in response to the power control signal PCS and a sampling control signal (SCS). 
         [0093]      FIG. 6  is a diagram for describing an ON/OFF control of the k th  tray BMS  120 - k,  according to an embodiment of the present invention. 
         [0094]    The k th  tray BMS  120 - k  receives driving power PIN, allows the driving power PIN to pass a first noise removal filter CMF 1 , converts the driving power PIN into a predetermined voltage level by using the first DC/DC converter  425 , and inputs the driving power PIN to the tray ON/OFF unit  420 . 
         [0095]    Also, a synchronization signal Ss that is received from the (k+1) th  tray BMS  120 -( k+ 1) or the (k−1) th  tray BMS  120 -( k− 1) is input to a control terminal of a first switch BJT via a photo-coupler PC, and the first switch BJT generates and inputs a first control signal to the tray ON/OFF unit  420 . The first switch BJT may be a bipolar junction transistor. In this case, the synchronization signal Ss that is input to the k th  tray BMS  120 - k  is input to a base terminal of the bipolar junction transistor. Also, in a case where the synchronization signal Ss that is input to the k th  tray BMS  120 - k  has a turn-on level with respect to the bipolar junction transistor, a first control signal CON 1  having a first level to turn on the tray ON/OFF unit  420  is output via a collector of the bipolar junction transistor. 
         [0096]    If the first control signal CON 1  has the first level, the tray ON/OFF unit  420  delivers power, which may be received from the first DC/DC converter  425 , to the communication driving unit  455  and the MCU ON/OFF unit  435 . If the first control signal CONI has a second level to turn off the tray ON/OFF unit  420 , power is not input to the communication driving unit  455  and the MCU ON/OFF unit  435 , so that the communication driving unit  455  and the MCU  445  may be deactivated. 
         [0097]    The power that is output from the first DC/DC converter  425  is also output to the fan driving unit  450 . 
         [0098]    Also, the synchronization signal Ss that is input to the k th  tray BMS  120 - k  is delivered to the (k+1) th  tray BMS  120 -( k+ 1) or the (k−1) th  tray BMS  120 -( k− 1) via the photo-coupler PC. 
         [0099]    A battery voltage Vbat is input from the k th  battery tray  110 - k  to the k th  tray BMS  120 - k.  The battery voltage Vbat is filtered by a second noise removal filter CMF 2  and then is input to the MCU ON/OFF unit  435 . In a case where the tray ON/OFF unit  420  is turned on so that power is output from the first DC/DC converter  425 , the MCU ON/OFF unit  435  inputs the power to the third DC/DC converter  440 . The third DC/DC converter  440  may include a 3−1 th  DC/DC converter DC/DC  3 - 1  for generating an MCU driving voltage, and a 3−2 th  DC/DC converter DC/DC  3 - 2  for generating a reference voltage. The MCU driving voltage and the reference voltage generated by the third DC/DC converter  440  are supplied to the MCU  445 . 
         [0100]    According to the aforementioned configuration, the operations of the communication driving unit  455  and the MCU  445  may be controlled by a control in response to the power control signal PCS that is received from the rack BMS  200 , so that power consumption by the first tray BMS  120 - 1  through the n th  tray BMS  120 - n  may be significantly decreased. 
         [0101]    While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For example, the one or more embodiments of the present invention are described with reference to a case in which the battery pack  20  is used in the energy storage system  1  but the present invention is not limited to the embodiments and thus include various embodiments in which the battery pack  20  is used other various devices. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.