Fail-safe battery storage system

Abstract

The fail-safe battery storage system includes multiple strings of battery modules. Within each string, the battery modules are connected in series and the strings are connected in parallel. Over multiple time periods, different combinations of battery modules are connected with the batteries connected while the remaining battery modules are in an open state, such that battery modules with higher power states spend a longer time in the connected state than battery modules with lower power states. Additionally, over multiple time periods, different combinations of strings are connected while the remaining strings are in an open state, such that strings with higher power states of battery modules spend a longer time in the connected state than strings with lower power states. The battery storage system places a failed battery module in a bypass state and / or places a failed string in an open state.

Description

Technical Field

[0001] Technical Field of the Invention The present invention relates to a fail-safe battery energy storage system for important applications such as aerospace technology. In a fail-safe battery energy storage system, power supply is maintained even when one or more battery modules fail.

[0002] Description of Related Art The functional safety of a device is defined, for example, by the international standard IEC61508 applicable to all industries. This standard defines four safety integrity levels (SIL) that provide the goals to be achieved for each safety function.

Table 1

[0003] Similar standards exist, for example, for automotive devices (ISO 26262 (ASIL)) and aerospace devices (DO178B).

[0004] Particularly for aerospace applications, battery energy storage devices may have to meet the highest level of requirements (SIL 4, ASIL A, DAL A). In most cases, a battery energy storage system may include a plurality of battery cells that can be connected in series. When a failure occurs in one battery cell in a series-connected system, the entire system fails. Therefore, such a system has a significantly higher failure rate than a single battery cell.

[0005] 1]]U.S. Patent Application Publication No. 2013 / 0234667 discloses a battery management system in which each battery management unit includes a battery cell, an insulating element, and a bypass element. Thereby, individual battery cells can be activated or disconnected.

[0006] U.S. Patent Application Publication No. 2014 / 0049230 discloses a multilevel converter topology for generating an AC signal by switching multiple batteries.

[0007] Summary of the Invention The problem that this invention aims to solve is to provide a highly reliable battery and battery storage system with a low failure rate. Such a battery and battery storage system may be used in aerospace applications.

[0008] The means for solving the above-mentioned problems are described in the independent claims. The dependent claims relate to further improvements of the present invention.

[0009] In one embodiment, the battery storage system includes a plurality of battery modules, each module including a switch configured to connect the module's battery in series with another battery and / or module when closed (referred to as the connected state). The switch, which may be a series switch, may also be configured to disconnect the battery from another battery and / or module when open. A parallel switch may be provided in the battery module to bypass the battery module when closed. This state is referred to as the bypass state. When both switches are open, the battery module is in the open state. There may be more switches that can provide further switching states. The battery may include one or more battery cells. For high-power applications, groups of battery cells may be connected in series (e.g., hardwired) to obtain a higher voltage.

[0010] An integer N (where N≧2) of modules are connected to a string, and an integer M (where M≧2) of strings are connected together. Each string may have an individual number of modules N1, N2, N3, ... These strings can be connected together by a parallel circuit. The strings may include inductors and / or diodes to improve current distribution and / or to avoid unwanted current flowing between strings. Since the current can be controlled by pulse-width modulation (PWM) switching between the connected and open states of the strings, the inductors can improve current control of the strings. The inductors may also include connecting cables of sufficient length. The battery storage system may be configured to supply a DC voltage to the load. The battery storage system may also be configured to supply an AC voltage by approximating a sine wave or any other arbitrary waveform by switching the number of connected battery modules to change the number of connected battery modules.

[0011] A string can be configured to balance its battery modules. Typically, the number N of battery modules in a string is selected so that the string can supply an output voltage higher than its nominal output voltage. Therefore, not all battery modules typically need to supply their nominal output voltage, and not all battery modules are always connected. The remaining battery modules are in a bypass state and do not supply power, so only the batteries of the connected battery modules are discharged, while the batteries of the bypassed modules are maintained. To balance the battery modules over time, the battery modules in a string can be configured to be in different states, for example, connected to a bypass state, or bypassed to a connected state, so that all batteries are discharged to a common power state, for example, a charged state. The battery storage system can be configured to select different combinations of battery modules within a string over multiple periods and / or time intervals, with the remaining battery modules in a bypass state relative to the connected state. During discharge of the battery storage system, at least one battery module with a higher power state may be connected for a longer period than at least one battery module with a lower power state.

[0012] The same principle applies when the battery modules of a string are being charged. In this case, the states of the battery modules can be swapped at any time so that all battery modules have similar or the same power state. During charging of the battery storage system, at least one battery module with a lower power state may remain connected for a longer period of time than at least one battery module with a higher power state.

[0013] Power status may be an indicator of the power that a battery or battery module can supply, and may include at least one of the charge status, maximum current capacity, voltage, temperature, health status, or a combination thereof.

[0014] If a battery module is considered to be faulty, defective, or unusable, it can be bypassed to exclude it from being used for charging or power supply. Switching may be performed at a fixed frequency or an adaptive frequency.

[0015] Furthermore, balancing between strings can be performed. This is similar to balancing between battery modules within a string, but performed at a higher level of string. Strings can be configured to be either connected or open. An open state may be one in which at least one battery module is open, thereby ensuring that current does not fail to flow through the string. The distribution of open and connected states among strings can be controlled so that all strings have similar or the same power state for their battery modules. Strings with higher power states may have longer connected state intervals than strings with lower power states. The battery storage system can be configured to select different combinations of strings for connected states over multiple periods and / or time intervals, while the remaining strings are open. During the discharge of the battery storage system, at least one of the strings with higher power states for the battery modules may spend more time connected than strings with lower power states for the battery modules. Furthermore, strings with higher power states can be configured to supply more current compared to strings with lower charge states. If the string includes an inductor, the current can be controlled by pulse width modulation (PWM) depending on the connected and open states of the string. During charging, strings with lower power states may remain connected for longer periods than strings with higher power states. The charging current may also be controlled by PWM.

[0016] During the discharge of a battery storage system, at least one string with a lower power state of battery modules may remain connected for a longer period than at least one string with a higher power state of battery modules. The power state of a string can be determined by summing the power states of the battery modules. There may be a power state weighting that can take into account battery characteristics such as SOH, voltage, or capacity.

[0017] String balancing and / or balancing of battery modules within a string may depend on the power state of the battery modules, as described above. This may also depend on other parameters, such as operating state, which may be temperature. For example, a battery module with a higher temperature may have a longer bypass state, or a string with a higher temperature may have a longer open state compared to a battery module or string with a lower temperature, thereby allowing these battery modules to cool over time.

[0018] The battery module and string balancing disclosed herein can be considered proactive balancing, because it can either transition an unbalanced string or battery module to a balanced state over time, or prevent it from becoming unbalanced, as it can react to even very small imbalances. This balancing is performable under full load for the battery modules and strings and requires no idle time for balancing. Furthermore, this type of balancing does not result in any balancing losses like those known from the prior art, such as resistive or energy-dissipative balancing. Such balancing improves reliability and availability. In a fully balanced battery storage system, all battery modules, if identical, can have the same power state. When different battery modules are used, all battery modules can have the maximum achievable power state, which can be determined by the capacity of each battery module and the overall charge state of the battery storage system. Using a balanced battery module can make it easier to replace a faulty battery module with any other module.

[0019] The balancing disclosed herein operates with combinations of different battery modules, for example, battery modules of different battery sizes and / or types, as well as with combinations of battery modules in different strings, for example, battery modules of different capacities and / or rated currents. This is extremely important for fail-safe systems. For example, in a battery storage system using identical battery modules, one or more battery modules may fail over time. In a string with a failed battery module, the failed battery module can be set to a bypass state permanently or for the duration of its failure. The string will continue to supply its nominal output voltage based on the series connection of the remaining modules. If a string fails, this string can be set to a bypass state permanently or for the duration of its failure. The balancing process will continue using the remaining battery modules and / or string as described above. A battery module can be considered failed if its power supply capacity and / or charging capacity falls by a predetermined amount below the average capacity of other modules in the same string, or if the battery module has a higher temperature or lower health condition than other modules in the same string. For example, a module with 50% of its nominal capacity may be considered faulty. Other fault criteria, such as temperature or health status, may be in place. An emergency mode may be provided in which such low-capacity battery modules that are not completely faulty can continue to be used.

[0020] The advantages of the battery energy storage system outlined above are illustrated in one embodiment. The battery system may include four strings, each configurable for 400V and 100A. Each string may have a minimum of eight battery modules, each supplying a voltage of 50V. If each string has additional modules, the string can supply full power while maintaining its forward-looking internal balancing among the battery modules if one module fails. If two battery modules fail, or, in one embodiment, if only one additional battery module is provided in the string and one battery module in the string fails, the string can continue to supply maximum power, but it cannot maintain internal balancing, which can lead to degradation of the battery modules in the string over time. It is important that the string can maintain full operation, whereas, in the event of the first failure, a string known from the prior art must be disconnected because it can no longer supply the nominal output voltage. For example, in an aircraft, if a battery module fails and the string can continue to supply full power but balancing does not occur, the flight can be safely terminated, and the defective battery module can be replaced before the string's performance deteriorates due to the lack of balancing capability.

[0021] In the event of a second failure, where another battery module fails and a string is unable to supply its nominal output voltage, conventionally, such a string must be disconnected from the other strings. In the battery storage system disclosed herein, the faulty string will be used to supply a reduced output voltage, which may be 7 × 50V = 350V instead of 400V. Three other strings can also be configured to supply 350V each, thereby slightly reducing the overall system voltage while maintaining the overall current supply capability.

[0022] In summary, in the embodiment having one additional battery module per string, in the first failure case, the available power does not decrease and maintains 4×400V×100A = 160kW. In the second failure case, when a failure occurs in a different string, there is no subsequent decrease, and when a failure occurs in the same string, the available power is 4×350V×100A = 140kW. An equivalent system according to the prior art operating with only the remaining three strings at 400V and 100A can supply only 3×400V×100A = 120kW. In the second failure case in another string, the maximum power is 2×400V×100A = 80kW.

[0023] Therefore, the battery power storage system disclosed herein can supply a larger output power between at least the first and second failures of the battery modules.

[0024] Assuming that each battery module has a capacity of 100Ah, the entire system has a capacity of 160kW. When one failure occurs in the system of the present invention, the capacity of one battery module is lost (50V×100Ah = 5kWh). Therefore, the available capacity will be reduced to 155kWh. In an equivalent system, the entire string or 40kWh will be lost, and as a result, only 120kWh will remain. The defective second module will lead to another 5kWh capacity reduction in the system of the present invention (regardless of which string the second failure occurs in), while in an equivalent system, (assuming that in the already bypassed string, the module is not used and another battery module does not fail), another string or here also 40kWh will be lost. These values are summarized in the following table.

Table 2

[0025] The relative power and relative capacity are for the full operating state.

[0026] For example, if a string has a reduced current supply capacity that can be caused by a relatively high temperature of the string or one or more battery modules within the string, in order to reduce the load in this string, the duration of the connection state of this string can be shortened. When the temperature is relatively high, this string can be cooled and return to the same connection state time as another string.

[0027] In one embodiment, an inductor is connected in series with the string, whereby the output current of the string flows through the inductor. The inductor may be included in the string. Each string of the battery energy storage system may include an inductor. The current flowing through the inductor is given by the following equation, that is

Equation

[0028] As long as the output voltage of the string is higher than the output voltage of the battery storage system, current can flow through the inductor to the output of the battery storage system and not back into the string. This avoids unwanted current flowing between the strings. For example, if current is required to charge the string, the string output voltage must be set lower so that current can flow to the battery modules, for example, by reducing the number of battery modules in its series connection. Similarly, current can be controlled by switching the battery modules, or the entire string, between connected and bypassed states.

[0029] In embodiments having an inductor connected in series with a string, the switching method can be slightly modified. The first modification may be timing, because it is possible to supply different currents to the load. Furthermore, the string may initially be in a connected state to supply a voltage across the inductor to increase the current flowing through the inductor. When the current reaches its maximum value, the string is switched to either a bypass state or an open state. In the bypass state, the inductor is reversed across the full load voltage so that the current flowing through the inductor decreases rapidly. In the open state, the inductor still attempts to maintain the current flow, supplying a voltage in the reverse direction to the string voltage, and this current can flow through diodes provided across the string or through parasitic diodes within the string. This also rapidly decreases the current flowing through the inductor. After a predetermined time, the current flowing through the inductor does not necessarily have to decrease to zero, the string can be configured to supply a positive voltage to the inductor, increasing the current flow again, relative to the connected state. This cycle can be continuously repeated.

[0030] To control the modules, each module may include a module controller. The module controller can control the module's switches. The module controller can control a series switch connected in series with the battery, and can also control a parallel switch connected between the module's first and second module connectors, thereby providing a bypass state for the module. The module controller may further have measuring means for measuring operating conditions and detecting the state of components or battery modules. Such states may be the switching state of the series and / or parallel switches, and temperatures such as the battery temperature and / or switch temperature. The battery module controller may further have means for determining the power state of the battery or battery module. Such power states may be indicators of the power that the battery or battery module can supply, and may include at least one of the charge state, maximum current capacity, voltage, current, temperature, health status, or a combination thereof.

[0031] In this specification, the term “battery” is used for the battery of a battery module. Such a battery may contain multiple battery cells. Such battery cells can be monitored individually or in groups by the module controller. The module controller may have a redundant configuration, for example, including two module controllers operating independently. Furthermore, the module controllers can be connected to a control bus to communicate with a master controller and / or further module controllers of another battery module. The control bus may be redundant, including two physical control bus structures or communication means. The master controller may also be a redundant controller, including two or more controllers. For example, two controllers may also be configured to communicate with the master controller by an independent control bus system. The module controllers may be configured to communicate with each other and coordinate the control of the battery energy storage system. The module controllers and / or the master controller form a controller structure.

[0032] The master controller and module controller can be configured to continuously monitor the modules. If a battery module fails, it can be set to a bypass state. If a module previously failed due to overheating, it can be configured to rejoin the redundancy scheme after recovering, for example, through cooling.

[0033] In one embodiment, the string of the battery energy storage system is configured as follows: the string contains all batteries at their minimum operating voltage (V min ) if at least N is sufficient to supply the nominal output voltage. min It may contain several batteries. According to a fully charged battery, the output voltage of the string is (V) max It may be N times the voltage of ). Depending on the number of battery modules in the string, N × (V max -Vmin If the output voltage is greater than approximately half the voltage of the battery module, at least one of the battery modules may be bypassed to reduce the output voltage. Otherwise, the output voltage of the string will be somewhat higher. If an inductor is provided in series with the string, the relatively high output voltage can be reduced by continuously switching the string between connected and bypassed states. Alternatively, the load of the battery storage system can be configured to tolerate different output voltages.

[0034] In one embodiment, the battery module may be provided with different switch configurations. These may include the half-bridge circuit described above, a full-bridge (H-bridge) configurable to supply AC output, or any other known topology of a multilevel converter. Multiple topologies exist, and these topologies allow for the inversion of the battery module output voltage (e.g., an H-bridge topology) or for the individual battery modules to be connected in parallel (e.g., a double H-bridge topology with additional connectors on the battery modules). This can further improve availability and reliability. The drawback is the large number of switches, which are relatively expensive and require space. The embodiments disclosed herein require a minimum of two switches and are therefore inexpensive and can be configured compactly.

[0035] In one embodiment, the battery system is configured as a three-phase AC system. A first fail-safe battery storage system can be connected between the first phase connector and the second connector, and a second fail-safe battery storage system can be connected between the second phase connector and the third phase connector.

[0036] In one embodiment, the battery system is connected to a three-phase grid or load and includes 3 × M strings (where M > 1). The same advantages set out above for DC loads apply. In this embodiment, a failure of a battery module results in only a slight reduction in the capacity of the battery storage system and the power of the strings connected to a particular phase of the three-phase grid. If asymmetric current injection is permitted, another string can compensate for the power loss in that one string. In the prior art, a failure of a battery module results in the shutdown of the entire three-phase battery system.

[0037] In one embodiment, the minimum number of strings required to form a three-phase grid with improved fail-safety is 4 (2*M instead of 3*M, where M>1). The topology in this case is as follows: phase grid A connection point - 1*M parallel strings, phase grid B connection point - 1*M parallel strings - phase grid phase connection point. The three phases of the grid can be connected to grid connection points A, B, or C via inductors. Each string can be connected in series to one or more inductors.

[0038] The battery module can be configured to transition the switch to a safe state if communication with any component, module controller, and / or master controller fails. Such a safe state may be a bypass state that allows current to still flow through the battery module even though the battery is not connected and the module is not supplying any power. A single module in the bypass state allows other modules in the string to still supply power.

[0039] In one embodiment, means may be provided for logging and / or examining the operating parameters of a battery energy storage system. Component parameters, particularly those of the battery and / or battery cells, can be monitored and / or logged. This can make reliability and / or required maintenance predictable.

[0040] In one embodiment, a battery energy storage system can be configured to supply lower and / or higher output voltages, and / or lower and / or higher currents, and / or lower and / or higher power than nominal values. For example, an aircraft may require more power during takeoff, while being able to supply less power during level flight. In particular, the output voltage can be set to the maximum positive output voltage of the string for takeoff, while this output voltage can be reduced to a lower level for level flight, for example, 75% of the nominal value, thereby allowing the aircraft engine to operate at a higher efficiency.

[0041] In one embodiment, multiple different batteries are available. Due to the dynamic switching of batteries within a string and the switching between strings, the voltage of individual batteries in a battery module is not critical as long as that battery can supply the required current. This makes it possible to combine different types of batteries. Also, older batteries can be combined with new or replaced batteries in the system. Therefore, if a single battery in a single battery module fails, only that battery module needs to be replaced. Since multiple batteries are usually matched together, it is not necessary to replace the entire string that may be required in the prior art. Even if a battery in a string has a nominal current and the string cannot supply the nominal current for which it is designed, this string can operate with a smaller current, while another string can compensate for this with a larger current. If the capacity of a string with a lower rated current is similar to the capacity of a string with a higher rated current, the on-time of the string can be adjusted accordingly, so that the string with the lower rated current has a longer on-time compared to the string with the higher rated current.

[0042] The battery module may include at least one battery and a switch, as further described herein. The battery module may further have a housing that can completely enclose it. This may allow the components of the battery module to be protected from ambient influences. The battery module may further include a battery management system that can be connected to sensors for detecting temperature, such as battery temperature and / or switch temperature, housing pressure, pressure, such as battery pressure and ambient pressure, voltage and / or current. The battery module may include a cooling device and / or means for introducing a cooling medium, such as a cooling fluid or cooling gas. In one embodiment, the battery module may have a voltage in the range of 24V to 60V, which may be based on 8 to 16 battery cells connected in series. Furthermore, multiple battery cells may be connected in parallel to increase the rated current. For clarity, here we refer to the battery module when referring to the state in the battery module, for example, the charge state of the battery. The battery module may also have a higher or lower voltage.

[0043] Each string may contain any number of substrings connected in series. The substrings may have the same structure as the string and may include controllers, inductors, and / or diodes.

[0044] As used herein, the term “connector” may refer to a physical connector configurable to connect and / or disconnect battery modules and / or strings. The term may also refer to conductive connections, such as traces on a printed circuit board, which do not necessarily have to be configured to disconnect. Rather, such connectors are like connectors in a schematic diagram that define the boundaries of a circuit.

[0045] One method relates to operating a fail-safe battery storage system comprising at least one string of battery modules, wherein at least two battery modules are connected in series within at least one string. The battery storage system may also include any embodiment of the battery storage system disclosed herein.

[0046] This method involves selecting different combinations of battery modules for multiple periods within at least one string, based on their state of being connected to the battery. When the battery modules are connected, they are connected in series. Furthermore, the remaining battery modules are in a bypass state with the battery disconnected.

[0047] Another method relates to operating a fail-safe battery storage system comprising multiple strings of battery modules, wherein the strings are connected in parallel, and at least two battery modules are connected in series within each string. The battery storage system may also include any embodiment of the battery storage systems disclosed herein.

[0048] This method involves selecting different combinations of battery modules for different states of connection to the battery within each string, over multiple time periods. When the battery modules are connected, they are connected in series. Additionally, the remaining battery modules are in a bypass state with the battery disconnected.

[0049] In another step, different combinations of strings are selected for connection states where the strings are connected in parallel over multiple periods. Furthermore, the remaining battery modules are disconnected in the open state.

[0050] The method steps can be repeated individually or in any order. These steps can also be performed simultaneously.

[0051] Description of the drawing In the following, without limiting the general concept of the invention, the present invention will be described as an example with reference to the drawings, illustrating several embodiments of the invention. [Brief explanation of the drawing]

[0052] [Figure 1] This is a circuit diagram of one embodiment. [Figure 2] This is a block diagram of a battery energy storage system. [Figure 3] This diagram shows the details of the battery module. [Figure 4] This diagram shows the details of the open switching state of the battery module. [Figure 5] This diagram shows the connected switching status of the battery module. [Figure 6] This diagram shows the bypass switching status of the battery module. [Figure 7] This diagram shows multiple connected strings. [Figure 8] This is a diagram of a three-phase system. [Figure 9] This is a switching state transition diagram for a battery energy storage system under low load conditions. [Figure 10] This figure shows the switching state under higher load conditions. [Figure 11] This is a switching diagram with balancing between strings. [Figure 12] This figure shows the output current of a string in one embodiment. [Figure 13] This is a flowchart of the method.

[0053] Figure 1 shows a circuit diagram of one embodiment of the battery energy storage system 100. The battery energy storage system 100 includes multiple strings of battery modules. This figure shows three strings 110, 120, and 130 connected in parallel. There may also be two strings or any number of strings.

[0054] Each string 110, 120, 130, consisting of battery modules, contains multiple battery modules that can be connected in series. In this embodiment, three battery modules are shown exemplarily. Alternatively, there may be at least two battery modules and any more. Each battery module may contain at least one battery, one switch for disconnecting the battery, and another switch for bridging battery modules. In this figure, the first string 110 contains three battery modules 111, 112, and 113 connected in series. The first string may have a first connector 114 connected to the first battery module 111 and a second connector 115 connected to the last battery module of this string, which in this embodiment is the third battery module 113. The same applies to the second string 120, which contains battery modules 121, 122, and 123, which are connected to the first connector 124 of the second string and the second connector 125 of the second string. The third string 130 includes battery modules 131, 132, and 133, which are connected to the first connector 134 of the third string and the second connector 135 of the third string.

[0055] The first connectors 114, 124, and 134 can be connected together to a common first battery storage system connector. Furthermore, the second connectors 115, 125, and 135 can also be connected together to the second battery system connector 142. In this embodiment, the battery storage system 100 can be powered at the first battery system connector 141 and the second system battery connector 142. The battery storage system 100 is also rechargeable via these connectors.

[0056] Each string can be configured to supply different output voltages by connecting any number of batteries in series. If no batteries are connected, the output voltage may be zero. If at least one battery module is open, the impedance may be high.

[0057] Figure 2 shows a block diagram of the battery energy storage system 100. Individual battery modules are shown as blocks. Furthermore, control means are shown. The first string controller 161 can control the battery modules 111, 112 and 113 of the first string via the control bus 164. Since the individual battery modules of the string may have a variable potential depending on the switching state of the battery module, they must be isolated from the bus. This can be done by isolation bus couplers in the battery modules. Alternatively, individual isolation bus lines can be provided between the string controller and the battery modules of the string.

[0058] The second string is controlled by the second string controller 162 via the second control bus 165, and the third string is controlled by the third string controller 163 via the third control bus 166.

[0059] The string controllers are controllable by the master controller 160 via the master control bus 167. Alternatively, a single controller can be provided that includes the functions of both the master controller and the string controllers. System reliability can be improved by having multiple individual string controllers that can operate independently and even autonomously. If the master controller fails, the individual string controllers may revert to their previous configuration or a standard fail-safe configuration. The module controllers and / or master controller form the controller structure.

[0060] A backup master controller 170 may also be provided, which can communicate with the string controller via a backup master control bus 177. Furthermore, a backup string controller and / or backup control bus may be provided within the string.

[0061] Figure 3 shows details of the battery module 200. Each of the individual battery modules 111-113, 121-123, and 131-133 shown previously may have the same or similar structure. The battery module 200 may include a battery 210. Such a battery may be any source of electrical DC power. Typically, such a battery may be based on rechargeable technologies such as LiPo, LiFe, Li-ion, NiCd, or NiMH. This may also include a fuel cell. The battery module 200 may further include a series switch 220, which can be connected in series with the battery and can be configured to connect the battery or disconnect the battery to provide a disconnected state that disconnects the battery from another battery. When the series switch 220 is closed, the battery is connected. The battery 210, together with the series switch 220, can be connected between the first module connector 240 and the second module connector 250. In the illustrated embodiment, the positive terminal (+) of the battery is connected to the second module connector 250, while the negative terminal (-) of the battery is connected to the first module connector 240. Furthermore, a parallel switch 230 may be provided between the first module connector 240 and the second module connector 250, which can be similarly connected. The parallel switch 230 can be configured to form a short circuit between the first module connector 240 and the second module connector 250 in a closed state, which is referred to herein as the bypass state. When the parallel switch 230 is closed, the series switch 220 can be opened to avoid a short circuit in the battery. The battery module 200 can further be configured to form an open state, where both the series switch 220 and the parallel switch 230 are open. In this state, current cannot flow through the battery module and therefore cannot flow through the string into which the battery module is incorporated. This means that in a battery energy storage system, this string is disconnected from another string.

[0062] In summary, there can be three different states for the battery storage system 100: connected state, bypass state, and open state.

[0063] A module controller 260 can be provided to control the switches. This module controller 260 can control the series switches 220 via a series switch control line 261. It can further control the parallel switches 230 via a parallel switch control line 262. A battery signal line or bus 263 can also be provided to receive battery parameters such as battery temperature, battery voltage, battery current, or charge state or health status. Based on these parameters, the module controller can control the switches.

[0064] The module controller 260 can be connected to the control bus of the string controller via the bus connector 270. The module controller can receive commands from the string controller to control the switches and can also transfer switch and / or battery status information to the string controller.

[0065] Figure 4 shows the open switching state of the battery module in detail. The series switch 220 and the parallel switch 230 are open.

[0066] Figure 5 shows in detail the connected switching state of the battery module. The series switch 220 is closed and the parallel switch 230 is open. This allows current to flow in direction 281 when the battery is discharged. To charge the battery, the current flows in the opposite direction.

[0067] Figure 6 shows the bypass switching state of the battery module in detail. The series switch 220 is open and the parallel switch 230 is closed. This allows current to flow in direction 282 or the opposite direction.

[0068] Figure 7 shows a multiplexed string. In this figure, multiple strings 110, 120, and 130 are connected to the first battery system connector 141 by first connectors 114, 124, and 134, respectively. They are further connected to the second battery system connector 142 by second connectors 115, 125, and 135 via inductors 119, 129, and 139. The inductors may be included in the strings. A load and / or power supply 190 can be provided connected to the first battery system connector 141 and the second battery system connector 142. In Figure 7, the inductors are connected in series to the second connector of each string, compared to the simple parallel connection in Figures 1 and 2. In this embodiment, there may be at least two strings of battery modules, and any number of such strings may be provided.

[0069] Inductors simplify the parallel connection of multiple strings. If multiple strings are connected without such inductors, and some of the module voltages on these strings differ only slightly, a large current may flow between the strings and not through the load connectable between the first battery system connector 141 and the second battery system connector 142. With inductors, the current flowing through the inductor is a function of the time integral of the voltage across the inductor. Therefore, the current flowing through the inductor can be limited by limiting the time interval of the current flowing through the inductor. Accordingly, the current can be controlled by pulsing the voltage across the conductor, and furthermore, large currents can be avoided between individual strings. However, if necessary, strings can be switched so that a predetermined current flows between them. This can be useful for charging strings that may have low charge levels during low-load conditions of the battery storage system, so that these strings can supply full output current under high-load conditions.

[0070] Furthermore, diodes 118, 128, and 138 may be provided in antiparallel to each string, so that the diodes do not conduct under the normal output voltage of the string. Diodes can also be incorporated into the string. Diodes can be connected so that they normally conduct when the normal output voltage is supplied by the string. If the voltage across the inductor reverses after the string is opened, such diodes can protect the string. Essentially, when a MOSFET or similar semiconductor is used, the battery module of the string protects itself with parasitic diodes. These parasitic diodes can have the same effect as parallel diodes to the string. Strings parallel to a string have the advantage of being faster and having a lower forward voltage than a larger number of parasitic diodes in a MOSFET.

[0071] Figure 8 shows a three-phase fail-safe battery storage system, connected by three-phase connectors 311, 312, and 313. A first fail-safe battery storage system, including strings 321 and 322, can be connected between the first-phase connector 311 and the second-phase connector 312. Furthermore, a second fail-safe battery storage system can be connected between the second-phase connector 312 and the third-phase connector 313. The functions are essentially the same, with balancing and / or switching performed within each fail-safe battery storage system. Each fail-safe battery storage system may include at least two strings.

[0072] Figure 9 shows a switching state transition diagram of a simple multiplexing configuration of the battery energy storage system 100 under low load. The switching diagram is based on a battery energy storage system having four strings of battery modules connected together in a parallel circuit. Inductors are available but not required in this particular embodiment. The figure shows the switching states of each string, with curve 511 showing the switching state of the first string, curve 512 showing the state of the second string, curve 513 showing the state of the third string, and curve 514 showing the state of the fourth string. Low levels indicate an open string state, and high levels indicate a connected state.

[0073] In section 521, only the fourth string 514 is connected, while the other strings are open. Therefore, only the fourth string supplies voltage and current to the output between the second battery system connector 142 and the first battery system connector 141. In the next section 522, only the third string is connected, while the other strings are bypassed. This sequence is followed by section 523, where only the second string is connected, and the 2 The sequence continues with section 524, where only the string remains connected. After section 524, this sequence restarts again with interval 521.

[0074] As shown in this diagram, at any given time, only one string is connected and therefore supplies voltage and / or current to its output. For example, all strings can be set to the same voltage by configuring the switches on the battery modules so that the same number of battery modules are connected. To balance within the string, the connected battery modules can be changed. Such changes can be made when changing the state of the string, but can also be made while the string is connected.

[0075] Any arbitrary or random sequence of string switching may be provided. This also applies to all other diagrams.

[0076] Figure 10 shows the switching state under higher load conditions. In this figure, all three strings are always connected simultaneously to supply a larger current to the load. In this embodiment, the series inductors for the strings are more important to avoid large currents between individual strings. While the figure shows the switching state of each string, curve 611 shows the switching state of the first string, curve 612 shows the state of the second string, curve 613 shows the state of the third string, and curve 614 shows the state of the fourth string. Low levels indicate an open string state, and high levels indicate a connected state.

[0077] In this figure, in time interval 621, the first string is in the bypass state, as shown by curve 611. In interval 622, the second string is switched to the bypass state, in interval 623, the third string is switched to the bypass state, and in interval 624, the fourth string is switched to the bypass state. At any given time, only one string is in the bypass state, while another string is connected and supplying power. Any other combination may be provided, for example, two strings may be connected simultaneously while another string is in the bypass state. Such combinations can also be changed at any time.

[0078] Figure 11 shows a switching diagram with string balancing. This switching diagram corresponds to the switching diagram before high load conditions. This diagram shows the switching state of each string, while curve 711 shows the switching state of the first string, curve 712 shows the state of the second string, curve 713 shows the state of the third string, and curve 714 shows the state of the fourth string. Low levels indicate an open string state, and high levels indicate a connected state.

[0079] In this diagram, the fourth string is in a bypass state during time interval 721, the third string is in a bypass state during interval 722, the second string is in a bypass state during interval 723, and the first string is in a bypass state during interval 724. In this diagram, the time in interval 724 is significantly shorter than the time in the other intervals. This means that the first string has a longer on-time. Therefore, the battery of the first string will be discharged more than the other batteries. Such a configuration may be effective when the charge level in the battery of the first string is greater than the charge level in the batteries of the other strings. Such on-time adjustments can be made for each string according to the current charge state of the string. These time adjustments can be made by the master controller.

[0080] Figure 12 shows the output current of strings in one embodiment, which includes three strings and inductors between the strings. The figure shows the switching state of each string, with curve 811 showing the switching state of the first string, curve 812 showing the state of the second string, and curve 813 showing the state of the third string. Low levels indicate the open state of the string, and high levels indicate the connected state.

[0081] In this diagram, the first string is in a bypass state at interval 824, following curve 811. The second string is in a bypass state at interval 822, following curve 812, and the third string is in a bypass state at interval 826, following curve 813. At all other times, the strings are connected.

[0082] In output diagram 814, curve 815 shows the output current of the first string. Following the bypass state 824, in state 825, the first string is switched to the connected state. This connected state is maintained over sections 825, 826, 821, 822, and 823. During these sections, the string voltage is maintained in the inductor connected to the string, and this inductor increases the current as shown by curve 815. During interval 824, when the first string is in the bypass state, the current flowing through the inductor decreases more rapidly than when it increases. After the first string is switched to the connected state in section 825, the current increases again. The same applies to the current of the second string 816 and the current of the third string 817. At the second battery system connector 142 and the first battery system connector 141, the string currents are added together, and therefore this multiplexing scheme supplies a total current with less ripple than the individual currents of a single string.

[0083] Figure 13 shows a flowchart of the method. This method begins at 411. The first step 412 is to select different combinations of battery modules 200 within each string (110, 120, 130) for multiple periods, while the remaining battery modules 200 are in a bypass state by the disconnected batteries 210, with the batteries 210 of the battery modules connected in series.

[0084] The second step 413 is to select different combinations of strings 110, 120, and 130 while the remaining strings 110, 120, and 130 are disconnected in an open state, given a connection state in which the strings are connected in parallel over multiple periods. This method is completed in step 414.

[0085] The first and second method steps can be repeated individually or in any order. These steps can also be performed simultaneously. [Explanation of Symbols]

[0086] 100 Battery Energy Storage System 110 First String 111-113 Battery modules for the first string 114 First connector of the first string 115 Second connector of the first string 118 First Diode 119 First Inductor 120 Second string 121-123 Battery Modules for the Second String 124 First connector of the second string 125 Second connector of the second string 128 Second Diode 129 Second Inductor 130 Third String 131-133 Battery Modules for the Third String 134 Third String First Connector 135 Second connector of the third string 138 Third Diode 139 Third Inductor 141 First Battery System Connector 142 Second Battery System Connect Ta 1 60 Master Controllers 161 First String Controller 162 Second String Controller 163 Third String Controller 164 First Control Bus 165 Second control bus 166 Third control bus 167 Master control bus 170 Backup Master Controller 177 Backup Master Control Bus 190 Load or power source 200 Battery Modules 210 batteries 220 series switch 230 Parallel Switches 240 First Module Connector 250 Second module connector 260 Module Controller 261 Series switch control line 262 Parallel Switch Control Line 263 Battery signal line 270 bus connector 281 Current Direction - Battery Connection Status 282 Current Direction - Short Circuit 300 3-phase system 311~313 3-phase connector 321-324 Strings in a 3-phase system 411-414 Method Steps 511~514 Switching state of the four parallel strings 521-524 hour interval 611-614 Switching status of the four heavily loaded connection strings 621-624 hour interval 711-714 Switching state of four balanced connecting strings 721-724 hour interval 811-814 Switching status of the three connection strings 814 Output Current Diagram 815 Output current of the first string 816 Output current of the second string 817 Output current of the third string 821-826 time slot between

Claims

1. A fail-safe battery storage system (100) having multiple strings (110, 120, 130) of a battery module (200), Each string (110, 120, 130) has multiple battery modules (200) connected in series. Each string (110, 120, 130) is connected to another string (110, 120, 130) between the first battery system connector (141) and the second battery system connector (142). Each battery module (200) contains at least: Battery (210), A series switch (220) is configured to connect or disconnect the battery (200) between the first battery system connector (141) and the second battery system connector (142), When closed, the system includes a parallel switch (230) configured to bypass the battery module (200) between the first battery system connector (141) and the second battery system connector (142), Each battery module (200) is, in relation to the following, that is, The connection state in which the series switch (220) is closed and the parallel switch (230) is open, A bypass state in which the series switch (220) is open and the parallel switch (230) is closed, The configuration can be configured for an open state in which the series switch (220) and the parallel switch (230) are open, Each string (110, 120, 130) corresponds to the following, i.e., A connected state in which at least one battery module (200) of the string is in a connected state and the remaining battery modules (200) are in a bypass state, In a fail-safe battery storage system (100) configurable for an open state in which at least one battery module is in an open state, The battery storage system (100) selects different combinations of battery modules (200) over multiple periods within at least one string (110, 120, 130) to be connected, while the remaining battery modules (200) are in a bypass state, so that during the discharge of the battery storage system (100), at least one of the battery modules (200) with a higher power state is connected for a longer period than at least one of the battery modules (200) with a lower power state, and / or during the charging of the battery storage system (100), at least one of the battery modules (200) with a lower power state is connected for a longer period than at least one of the battery modules (200) with a higher power state. The battery storage system (100) selects different combinations of the strings (110, 120, 130) over a plurality of periods with respect to the connected state, while the remaining strings (110, 120, 130) are in an open state, and during the discharge of the battery storage system (100), the time that the strings (110, 120, 130) with a higher power state of the battery module (200) are connected is longer than the time that at least one of the strings (110, 120, 130) with a lower power state of the battery module (200) is connected, and / or during the charging of the battery storage system (100), the time that at least one of the strings (110, 120, 130) with a lower power state of the battery module (200) is connected is longer than the time that at least one of the strings (110, 120, 130) with a higher power state of the battery module (200) is connected. The battery energy storage system (100) is configured to bypass a faulty battery module (200) and / or open a faulty string (110, 120, 130), characterized in that the battery energy storage system (100) is configured to bypass a faulty battery module (200) and / or open a faulty string (110, 120, 130).

2. The fail-safe battery storage system (100) according to claim 1, characterized in that the battery storage system (100) is configured for outputting and / or inputting a DC voltage.

3. The fail-safe battery energy storage system (100) according to claim 1, characterized in that at least one of the plurality of strings (110, 120, 130) includes an inductor (119, 129, 139) connected in series with the battery module (200) of the string.

4. The fail-safe battery energy storage system (100) according to claim 1, characterized in that at least one of the plurality of strings (110, 120, 130) includes diodes (118, 128, 138) connected in parallel to the string, so that the diodes (118, 128, 138) do not conduct at the normal output voltage of the string.

5. The fail-safe battery storage system (100) according to claim 1, characterized in that a load and / or power supply is connected between the first battery system connector (141) and the second battery system connector (142).

6. The fail-safe battery storage system (100) according to claim 1, characterized in that the battery storage system (100) is configured to bypass a faulty battery module (200) and / or open a faulty string (110, 120, 130).

7. The fail-safe battery storage system (100) according to claim 1, characterized in that the battery storage system (100) is configured to restore a faulty battery module (200) and / or a faulty string (110, 120, 130) to normal operation after the fault condition no longer exists.

8. The fail-safe battery energy storage system (100) according to claim 1, characterized in that the power state of the battery module (200) includes at least one of the charge state, maximum current capacity, voltage, temperature, health state, or a combination thereof.

9. The fail-safe battery storage system (100) according to claim 1, characterized in that a failure state is assigned to the battery module if the power supply capacity and / or charging capacity of the battery module falls by a predetermined amount below the average capacity of other modules in the same string or below a predetermined threshold, and / or the battery module has a higher temperature or lower health condition than other modules in the same string.

10. The fail-safe battery storage system (100) according to claim 1, characterized in that at least one battery module (200) includes at least one other switch, and the switch of at least one of the battery modules is further configurable for at least one of parallel switching of battery cells or battery modules or polarity reversal of battery cells.

11. The fail-safe battery storage system (100) according to claim 1, characterized in that the fail-safe battery storage system (100) is configured to adjust the voltage of the remaining strings to the value of the output voltage of the first string that is unavailable in order to maintain the nominal output voltage due to at least one failed battery module (200).

12. A three-phase fail-safe battery storage system comprising two fail-safe battery storage systems (100) according to any one of claims 1 to 11, A first fail-safe battery energy storage system (321, 322) is connected between the first phase connector (311) and the second phase connector (312). A three-phase fail-safe battery storage system characterized in that a second fail-safe battery storage system (323, 324) is connected between the second-phase connector (312) and the third-phase connector (313).

13. A method for operating a fail-safe battery storage system (100) having multiple strings (110, 120, 130) of battery modules (200), wherein the strings are connected in parallel, and at least two of the battery modules (200) are connected in series within each string. The above method includes the following step, namely, Within each string (110, 120, 130), for multiple periods, the batteries (210) of the battery modules are connected in series, and the remaining battery modules (200) are in a bypass state due to the disconnected batteries (210), the step of selecting different combinations of battery modules (200). For multiple periods, while the strings (110, 120, 130) are connected in parallel, and the remaining strings (110, 120, 130) are disconnected in an open state, different combinations of the strings (110, 120, 130) are selected, and during the discharge of the battery storage system (100), the time spent in the connected state of the strings (110, 120, 130) where the power state of the battery module (200) is higher is compared with the time spent in the connected state where the power state of the battery module (200) is lower. A method comprising the step of making the time spent in at least one connected state of the strings (110, 120, 130) longer than the time spent in at least one connected state of the strings (110, 120, 130) where the battery module (200) has a lower power state, and / or making the time spent in at least one connected state of the strings (110, 120, 130) where the battery module (200) has a higher power state longer than the time spent in at least one connected state of the strings (110, 120, 130) where the battery module (200) has a higher power state.

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