System and method for current control and circuit protection for distributed energy resources

Abstract

This application relates to systems and methods for current control and circuit protection for distributed energy resources. According to one aspect of the invention, an energy storage system includes one or more power sources, one or more energy storage components, and one or more solid state circuit breakers disposed between the one or more power sources and the one or more energy storage components such that electrical power is exchanged between the one or more power sources and the one or more energy storage components through the one or more solid state circuit breakers. The energy storage system also includes a controller configured to operate the one or more solid state circuit breakers to control current exchanged with the one or more energy storage components and to protect the one or more energy storage components from the one or more power sources during a fault condition.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to circuit protection, and more particularly, to solid state circuit breakers. BACKGROUND

[0002] Generally, energy storage systems experience fluctuations in current delivered to certain components, such as batteries configured into battery racks within a battery energy storage system (BESS). Occurrence of overcurrent can damage the batteries and / or other common components of the BESS. A conventional approach to address current imbalance among battery racks is to place a DC-DC converter on each battery rack so that the current supplied to each rack can be controlled. However, DC-DC converters are relatively expensive, can reduce system efficiency, and increase the complexity of the energy storage system. Alternatively, the current imbalance problem can be addressed by reducing the nominal current of individual racks while making the number of battery racks needed to meet dedicated system parameters excessively large. According to this conventional approach, the battery racks tolerate a certain amount of current imbalance by operating well below the overcurrent threshold while the overall system maintains the same total charge and discharge current. Making the BESS excessively large can represent a significant additional cost, as additional batteries are expensive.

[0003] Furthermore, in conventional BESSs, fuses are widely implemented for low cost and reliable overcurrent protection. Complex combinations of high-speed fuses and time-delay fuses at different locations can be used to protect batteries, cables, and other BESS equipment from short circuit and overcurrent faults. Fuses exhibit fixed time-current curves (TCCs) or melting curves such that it is generally difficult to individually utilize fuses to implement fully coordinated circuit protection and selectivity at all fault currents.

[0004] The present disclosure contemplates deploying one or more solid state circuit breakers (SSCBs), where each SSCB has on / off functionality. The present disclosure further contemplates controlling the SSCBs to increase or decrease current delivered to one or more target battery racks in order to mitigate overcurrent and / or overtemperature events and to control the state of charge of battery racks within the BESS. Thus, conventional overcurrent protection methods and their associated drawbacks can be omitted. The SSCBs can also be deployed in conjunction with conventional fuses and / or mechanical breakers in order to extend the life of conventional circuit protection components.

[0005] The description provided in the background section should not be taken as an admission that any of the information provided in the background section is prior art to the present disclosure. The background section can include information obtained from sources believed to be reliable and are provided herewith for putting the disclosure into context. SUMMARY

[0006] According to one aspect of the disclosure, an energy storage system includes one or more power sources, one or more energy storage components, and one or more solid state circuit breakers disposed between the one or more power sources and the one or more energy storage components such that electrical power is exchanged between the one or more power sources and the one or more energy storage components through the one or more solid state circuit breakers. The energy storage system also includes a controller configured to operate the one or more solid state circuit breakers to control current exchanged with the one or more energy storage components and to protect the one or more energy storage components from the one or more power sources during a fault condition.

[0007] According to another aspect of the disclosure, a method of protecting an energy storage system can include directing power through at least one solid state circuit breaker to exchange the power between at least one power converter and a plurality of energy storage components, detecting a state of charge and a temperature of each of the plurality of energy storage components, and operating the at least one solid state circuit breaker to control at least one of the state of charge and the temperature of each of the plurality of energy storage components.

[0008] Yet another aspect of the disclosure contemplates a circuit protection system including a power source electrically coupled with a load, one of a first circuit breaker or a fuse, where the first circuit breaker or fuse has a fixed time current curve, and a second circuit breaker having an adjustable time current curve. This aspect of the disclosure further includes a controller coupled to the second circuit breaker and configured to adjust the time current curve in response to a protection parameter.

[0009] Other aspects and advantages of the present disclosure will become apparent upon consideration of the following detailed description and accompanying drawings, in which like reference characters designate like structures throughout the description. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 FIG. 1 is a diagram illustrating an example embodiment of a circuit protection system and method for implementing one or more battery racks with a power conditioning module, one or more circuit protection devices, and one or more SSCBs;

[0011] Figure 2 FIG. 2 is a diagram illustrating an example embodiment of a system and method in which a battery rack is directly connected to a power conditioning module;

[0012] Figure 3 FIG. 3 is a diagram illustrating an example configuration of SSCB(s) within an example battery pack;

[0013] Figure 4 FIG. 4 is a diagram illustrating an example SSCB;

[0014] Figures 5 to 7It is a current waveform diagram illustrating the current passing through several battery racks over time according to the exemplary control scheme described in the reference.

[0015] Figure 8 This is a diagram illustrating an example embodiment of a system and method for identifying the relative positions of a first fault F1 and a second fault F2, as well as a circuit protection device;

[0016] Figure 9A Indicates that it is aimed at one of them Figure 8 P1 is the overload protection response of the fuse in an example embodiment at the first and second faults; and

[0017] Figure 9B Indicates for one of them Figure 8 P1 is the overload protection response of the mechanical circuit breaker in the first and second faults of an example embodiment;

[0018] In one or more embodiments, not all of the components depicted in each figure may be required, and one or more embodiments may include additional components not shown in the figures. Variations in the arrangement and type of components may be made without departing from the scope of the invention. Within the scope of the invention, additional components, different components, or fewer components may be utilized. Detailed Implementation

[0019] The detailed description set forth below is intended to describe various embodiments and is not intended to represent the only embodiment in which the invention can be practiced. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the scope of the invention. Furthermore, depending on the particular embodiment, the depicted modules and processes may be combined and / or divided into one or more distinct parts, wholly or partially, without departing from the scope of the invention. Therefore, the drawings and descriptions should be considered illustrative and non-limiting in nature.

[0020] Now for reference Figure 1circuit protection system and method 100 is implemented to include a power conditioning module 102, one or more circuit protection devices 104a,... 104n, and one or more solid state circuit breakers (SSCBs) 106a, 106b,... 106n. In this example embodiment, the circuit protection system and method 100 is applied to a battery energy storage system (BESS) 108 that includes a plurality of battery banks 110a,... 110m. Each of the battery banks 110 includes a number of battery racks 112a, 112b,... 112n. Still further, each battery rack 112 can include one or more individual batteries 114. In alternative embodiments, one or more individual batteries 114 can be replaced, supplemented, and / or combined with any other suitable energy storage device (e.g., double layer capacitors, ultracapacitors, supercapacitors, lithium-ion capacitors, etc.).

[0021] The power conditioning module 102 includes a power converter 116 and a switchboard 118 that connects the converter 116 to each of the circuit protection devices 104. A transformer 120 electrically couples the converter 116 and the power conditioning module 102 to a power grid and / or another suitable power source 122. The SSCBs 106 can be, for example, the large-scale distributed energy resources 124 of the BESS 108 shown in Figure 1 The method 100 further includes one or more solid state switches 146 (see Figure 4 ) for turning on and off selected ones of the SSCBs 106 to increase or decrease (as desired at a particular time during a particular application) the current exchanged with the associated battery rack(s) 112. The circuit protection system and method 100 facilitates bi-directional energy flow (i.e., the BESS 108 operates in both a charging scenario and a discharging scenario in conjunction with the power converter 116). Thus, the circuit protection system and method 100 described throughout this document can operate to improve the balancing of charging and discharging current from the battery rack(s) 112 in particular response to unbalanced current or thermal conditions. This can result in improved health and increased useful life of the BESS 108. The system and method 100 can be a cost-effective solution to circuit protection by providing integrated control and protection functions with the SSCBs 106. In contrast, conventional mechanical disconnects cannot switch DC current as frequently, thus having a relatively long operating time and a relatively short useful life. The system and method 100 can also include adjusting one or more trip characteristics (see Figure 9A and 9B ) of the SSCBs 106 to improve system reliability and availability.

[0022] The system and method 100 of the present invention can use the SSCB(s) 106 to provide a combination of both current control and short circuit protection for distributed energy resources such as the BESS 108. In example prior art systems, relatively low capacity BESSs (e.g., less than 100 kWh), such as those utilized in electric vehicle and / or residential photovoltaic applications (e.g., solar panels), are directly controlled by the power converter 116. In this example configuration, the current exchanged with the BESS 108 is properly regulated by the power converter. However, in high capacity BESS(s) (e.g., greater than 100 kWh to less than 100 MWh) such as those utilized in grid scale storage, railroad, and marine applications, multiple battery strings / racks 112 in a parallel configuration are generally preferred. Multiple battery racks 112 are connected to a large power converter 116, as shown in Figure 1 and 2 but the power converter 116 can not be able to control the current exchanged with the individual battery racks 112 in the presence of current imbalances.

[0023] According to the system and method 100 of the present invention, the current of the parallel connected distributed energy resources is balanced by controlling the SSCB(s) 106. Referring again to Figure 1 , each of the battery strings / racks 112 includes an output connection 130. The SSCB(s) 106 are each attached to an associated one of the output connections 130. In Figure 1 , the battery pack(s) 110 include one or more battery racks 112 operably connected to a local bus 132 disposed within a pack container or housing. The battery pack(s) 110 can be operably connected to the power converter 116 directly or through a switchboard 118. In an example embodiment, the power converter 116 can have a capacity of 500 kW.

[0024] Referring now to Figure 2 , an embodiment of the system and method 100 is shown in which the battery racks 112 are directly connected to the power conditioning module 102. As Figure 1In an embodiment, each of the battery racks 112 has one of the SSCBs 106 installed with it. Additionally or alternatively, one or more of the SSCBs 106 can be installed in the switchboard 118 of the power conditioning module 102. In this embodiment, the SSCBs 106 can control both the battery rack current and interrupt overcurrent and / or thermal overload in the system 100 if current control is desired. The SSCBs 106 also provide improved protection for the batteries, cables, busbars, switches, converters, etc. that make up the system 100 because the SSCBs 106 enable fast fault interruption relative to conventional circuit breakers. The system and method 100 provide for more reliable operation of the BESS 108 by selectively reducing the current of individual battery racks experiencing stress. This feature further helps to balance temperature and state of charge (SOC) across the number of battery racks 112. Still further, the introduction of the SSCBs 106 is less expensive than either a DC / DC converter for each of the battery racks 112 or oversizing the number of battery racks 112.

[0025] Referring now to Figure 3 , a configuration of the SSCBs 106 within an example one of the battery banks 110 is illustrated. In this example, the SSCBs are associated with each of the battery racks 112. However, at the bank level, the SSCBs can also be used as the circuit protection devices 104 Figure 1 Still referring to Figure 3 , the battery bank 110 can include one or more rack battery management systems (BMSs) 136 and a bank BMS 138. Each of the rack BMSs 136 is in communication with the bank BMS 138, and the bank BMS 138 is in communication with a local controller 140 and / or a system-level controller 142 (e.g., supervisory control and data acquisition (SCADA)). In an example embodiment, the system-level controller 142 can be a networked controller supervising multiple local controllers and battery banks. The control functions of the SSCBs 106 can be integrated into the bank BMS 138, or can include a separate local controller 140 to communicate with the bank BMS 138, a controller of the power converter (not shown), and / or the system-level controller 142. The rack BMSs 136 monitor battery status and update the local controller 142 regarding the status. The local controller 140 receives information from the bank BMS 138 in order to implement current balancing control across the battery racks 112. The local controller 140 can also send the status of the SSCBs 106 and / or other suitable control and protection parameters to a system operator and / or the system-level controller 142. Additionally, the local controller 140 can receive system commands from the system-level controller 142 that direct the operation of the SSCBs 106. From the system-level controller 142, the local controller 140 can receive a command to trip the SSCBs 106 in response to a fault condition, such as an overcurrent condition, a thermal overload condition, or a command to trip the SSCBs 106 from the system-level controller 142. Figure 3In the depicted example embodiment, the local controller 140 collects status information about the battery rack 112 through the group BMS 138 and sends on / off digital control signals 144 to the selected SSCB(s) 106. The on / off digital control signals 144 can be pulse width modulated (PWM) signals or other suitable control protocols can be implemented. By controlling the on and off periods of one or more solid state switches 146 (see Figure 4 ) of the SSCB(s) 106, the system 100 affects current distribution between and among the one or more battery racks 112.

[0026] An example embodiment of the SSCB(s) 106 is illustrated in Figure 4 . The SSCB 106 includes a solid state switch 146 for current interruption and on / off control, a mechanical switch 148 for current isolation, a snubber 150 (e.g., resistor and capacitor), and a metal oxide varistor (MOV) circuit 152 for voltage clamping protection of the main solid state switch 146. The SSCB 106 can also include a sensing circuit 154, a detection / control circuit 156, and a gate driver circuit 158. A coil driver circuit 160 can be operably coupled with the mechanical switch 148 and configured to open and close the mechanical switch 148. During an example of on / off current control operation of the SSCB 106, the mechanical switch 148 can remain closed and the main solid state switch 146 can be turned on and off according to the on / off digital control signals 144 received by the SSCB 106 from the local group controller 140 (see Figure 3 ). By providing current interruption with the solid state switch 146, arcing can be prevented or the frequency and / or severity of arcing events can be reduced. In addition, current interruption implemented by the solid state switch 146 can provide a relatively fast response speed and / or longer useful life of circuit protection components. When the solid state switch 146 is distributing nominal battery current, the snubber 150 (again, e.g., resistor and / or capacitor) absorbs transient energy. During exemplary operation, the MOV circuit 152 is activated only when current exceeds a high threshold level and is interrupted due to a fault. Thus, even though the MOV circuit 152 is limited to relatively few operations, the entire SSCB 106 does not have to endure the same limited number of operations because the MOV circuit 152 should not be activated often compared to the cumulative number of repeated operations of the SSCB(s) 106 and / or the system 100.

[0027] The SSCB(s) 106 also provide overcurrent protection when a fault (e.g., short circuit, thermal overload, etc.) is present in the system 100. For example, if a short circuit fault occurs at the connection to the local bus 132 in the battery pack(s) 110, the SSCB(s) 106 can sense the current indicative of the fault (e.g., through the sensing circuit 154), and the detection / control circuit 156 identifies the current as a short circuit fault. In response to the fault detection, the SSCB(s) 106 turn off the solid state switches 146 and the gate driver circuits 158 associated therewith. Residual energy in the SSCB(s) 106 is absorbed by the MOV circuit 152 and snubber 150, and any residual current is decayed to zero. After a brief delay, the mechanical switch 14 opens when the current is zero, and operates to provide galvanic isolation.

[0028] The fault interruption process according to the system and / or method 100 can be relatively fast, e.g., 10 to 100 microseconds. Due to this interruption speed, the fault current is limited to a low level and degradation of the battery 114 due to the occurrence of a fault condition is avoided. The high speed overcurrent protection (i.e., fault interruption) also reduces the design requirements for the local bus 132 and other DC components (e.g., within the power conditioning module 102), as lower DC short circuit withstand capability can be recommended for these components. In addition, the exemplary trip curve of the SSCB(s) 106 can have improved consistency compared to conventional fuses. Still further, the trip curve of the SSCB(s) 106 does not shift over time due to environmental temperature variations and / or due to aging, which can be the case for conventional fuses.

[0029] Manufacturing processes for manufacturing batteries cause varying battery parameters due to quality control and / or cost limitations. Battery parameter variability can also result from degradation during operation due to different environmental conditions (e.g., temperature, location, etc.), mismatched cable and / or contact resistance, and different degradation rates. Thus, because the number of battery racks 112 are connected in parallel, current and / or thermal imbalances are likely to exist within the large scale BESS(s) 108 contemplated by the present disclosure.

[0030] In Figure 5The operation of an example embodiment is illustrated by a current waveform diagram. This example can include charging or discharging while the power converter 116 is operating according to the constant current control mode 162. First through eighth rack currents Ii through I8are shown. Rack currents I2through I8are similar to each other; however, the first rack current Ii experiences a relatively large current stress. Therefore, to balance the rack currents Ii through I8, the first rack current Ii should be reduced. This reduction can be implemented by operating the solid state switches 146 within the SSCB 106 connected to the first battery rack 112 through which the first rack current Ii passes. The SSCB 106 turns off its solid state switches 146 to interrupt the current for a period of time Ti (see Figure 5 ), and turns the solid state switches 146 back on for the remainder of the control cycle period T. In an example embodiment, the control cycle period T can be in the range of a few seconds, which is close to the rate of change of the system power profile, to minimize negative effects on the target battery rack 112. The constant current control mode 162 is activated for a sequence of control cycle periods T (e.g., one or more seconds) until any or most of the current imbalance issues are mitigated. During the constant current control mode 162 of the SSCB(s) 106, the average current for rack 1 can be expressed as:

[0031] I avg1 = I avg -I avg x Ti / T (1),

[0032] where

[0033] I avg = I dc / (M x N) (2),

[0034] where N is the number of racks 112 in each of the battery packs 110, and where M is the number of battery packs 110. I dc is the total current regulated by the DC port of the power converter 116. This total current is typically requested by the SCADA 142 to provide certain charging or discharging power according to the power demand on the BESS 108. The power converter 116 regulates the total current I dc of the BESS 108, but does not affect the current distribution among the battery racks 112. However, with respect to equation (1), the modification of the off period Ti and the control cycle T allows the SSCB(s) 106 to effectively reduce the first battery rack current Ii, thereby reducing the rack current Ii to the average rack current I avg below. The adjustment of the rack currents can also address imbalanced thermal conditions by reducing the current to a rack 112 experiencing thermal overload or by increasing the current to a rack 112 experiencing thermal conditions that are less than desired for optimal charging conditions.

[0035] In the constant current control mode 162, a decrease in the first bank current II (or another subset of the battery bank 112) can slightly increase the current delivered to the remaining subset of the battery bank 112. For example, the SSCB 106 for controlling the battery bank currents I2to I8may remain closed and conductive. The remaining battery bank 112 bank currents I2to I8may be expressed as:

[0036] I avg2-8 = I avg + I avg x T1 / [T x (M x N - 1)] (3).

[0037] Since the sub-expression (M x N - 1) generally produces a large denominator value, the increase in current in the unmodified bank 112 is negligible. Thus, the system and / or method 100 implements an effective decrease in the bank 112 current.

[0038] Reference is now made to Figure 6 , another example operation of the system and / or method 100 is illustrated by a current waveform diagram. In Figure 6 , the power converter 116 is operating in a constant voltage charge control mode 164 to further increase the state of charge of the battery bank 112. Constant voltage charging can be desirable to follow constant current charging in order to increase the state of charge. In this example, the decrease in bank current II is proportional to the ratio of T1to T, and the unmanipulated subset of the bank 112 maintains its bank currents I2to I8unaffected.

[0039] Figure 7 is a current waveform diagram illustrating one embodiment of the system / method 100, where the SSCB 106 operates to increase the current through a subset of the battery bank 112 while the power converter 116 is in the constant current control mode 162. In Figure 7In the example embodiment, the first rack current Ii and the second rack current I2 are targeted for increase, while the other rack currents I3 through I8 remain unaffected. The battery racks 112a through 112h are divided into groups. The present example embodiment has four groups (or subsets), and each group includes two battery racks 112. This control cycle includes one or more sub-control cycles 168 each having a cycle period T. In the exemplary embodiment, the number of sub-control cycles 168 is one less than the number of groups into which the battery racks 112 are divided. Thus, the present example includes three sub-control cycles 168. The SSCB(s) 106 associated with the rack currents Ii, I2 are continuously on during the sub-control cycles 168. In the first sub-control cycle 168a, the rack currents I3, I4 are interrupted for a period Ti by their corresponding SSCB 106. During the same sub-control cycle 168a, the other rack currents Ii, I2, I5 through I8 are increased. In the second sub-control cycle 168b, the rack currents I5, I6 are interrupted for a period Ti by the associated SSCB(s) 106, thereby increasing the other rack currents, including Ii, I2. Then, in the third sub-control cycle 168c, the rack currents I7, I8 are interrupted for a period Ti, thereby increasing the other rack currents, including Ii, I2.

[0040] Thus, for each full control cycle, the rack currents Ii, I2 are increased three times for a period of 3T. Thus, the rack currents Ii, I2 are significantly increased in their average current magnitude. Likewise, the rack currents I3 through I8 each experience a current decrease for one period and an increase for two periods, thereby compensating for the single decrease period. Thus, the overall average of the rack currents Ii through I8 is maintained and the average of I3 through I8 is slightly decreased compared to normal / optimal operation. However, the average current magnitude of the rack currents Ii, I2 is increased, as expressed by the following equation:

[0041] I avg1-2 = I avg + I avg x Ti / [T x (Y - 1)] (4).

[0042] The relatively small decrease in the rack currents I3 through I8 can be expressed as:

[0043] I 3-8 = I avg - I avg x Ti / [T x (Y - 1) 2 ] (5).

[0044] The impact on current control of the target battery rack 112a, 112b is three times the modification experienced by the remaining battery racks 112c-112h. T1, T, the number of target battery racks, and / or the ratio of target battery racks to total battery racks can be customized individually or in numerous combinations such that rack current can be effectively controlled. Still further, the fast response time of the SSCB(s) 106 limits peak fault current thereby mitigating internal damage to the batteries 114. This feature also benefits the BESS(es) 108 by reducing the expected short circuit withstand capability of cables, busbars, switches, converters, etc. as mentioned above.

[0045] In example embodiments, the SSCB(s) 106 can include adjustable trip curves. It is common for the BESS(es) 108 to experience configuration changes, e.g., addition of batteries, removal of batteries, inclusion of batteries with different battery parameters, etc. Conventionally, these configuration changes would require reselection and replacement of protection devices, e.g., fuses, with fixed trip curves. However, because the SSCB(s) 106 facilitate adjustable and customizable trip curves, their replacement can be delayed and / or forgone. The time current curve (TCC) of the SSCB(s) 106 can be reconfigured according to updated parameters of the batteries 114 and the overall BESS 108.

[0046] Conventional fuses have fixed TCCs or melting curves, which present difficulties with achieving full coordination and / or selectivity with fuses at all fault currents. The SSCB(s) 106 can provide ultrafast, i.e., <1 millisecond, protection to prevent high fault currents and / or uncontrolled thermal events from damaging the batteries 114. As described above, the SSCB(s) 106 can provide adjustable trip curves to facilitate circuit protection consistency, reliability, and / or protection coordination during various and numerous fault conditions.

[0047] Reference is now made to Figure 8 FIG. 1 illustrates an example of a BESS 108 to illustrate the relative locations of a first fault Fl and a second fault F2. The first fault Fl is located at the utility source side of the BESS 108 and the second fault F2 is located at the battery side of the BESS 108. Figure 8 P1 in FIG. 1 can be a fuse, a mechanical breaker, or one or more of the SSCB(s) 106. When a fuse or mechanical breaker is disposed downstream of a faster responding SSCB, a mis-trip or compromise of full protection coordination can occur because the SSCB(s) 106 reach the trip threshold before the downstream fuse begins to arc or the mechanical breaker begins to open.

[0048] Figure 9A and 9BThe adjustable trip characteristics of the SSCB(s) 106 enable selectivity and / or customization. In an example embodiment, Figure 8 P1 represents a fuse and in Figure 9A the protection response for the fuses at the first fault Fl and the second fault F2 is shown. The TCC of the SSCB(s) 106 at SI and S2 is lower than the TCC of P1 because the nominal current of SI and S2 is lower compared to P1. At the second fault F2, the SSCB 106 associated with SI trips first due to the high fault current. At the first fault Fl, the fuse represented by P1 trips first due to the high fault current. If both SSCBs 106 represented by SI and S2 reach their trip threshold before the fuse P1 starts arcing, they can also trip. In some conditions, for example, if the TCC of the SSCB(s) 106 at SI and S2 is low enough, SI and S2 can even trip before the fuse at P1 trips. As mentioned above, if a fuse with a fixed TCC is implemented at the battery 114 (not shown), selectivity can be sacrificed. In contrast, when SSCBs 106 are implemented, the TCC of SI and S2 can be shifted upwards at Fl to facilitate the desired protection coordination and establish a sufficient time difference between the trip of the downstream fuse P1 and the trip of the upstream SSCB 106. In addition to adjusting the TCC, reclosing control of the SSCB(s) 106 can also be included to assist in protection coordination. Thus, once the fault condition is cleared by P1, the SSCB(s) 106 can be reclosed. The reclosing can be performed before the isolators (mechanical switches 148) in one or more of the activated SSCB(s) 106.

[0049] In another example embodiment, Figure 8 P1 represents a relatively fast mechanical circuit breaker. In this embodiment, instantaneous overcurrent protection can be implemented for short circuit protection. The time domain trip response at the first fault Fl and the second fault F2 is shown in Figure 9B The threshold current of the SSCB(s) 106 at SI and S2 is lower than the current through P1, the mechanical circuit breaker represented by P1, because the nominal current of the SSCBs at SI and S2 is lower compared to the mechanical circuit breaker represented by P1. At the first fault Fl, the threshold current of the SSCB(s) 106 is increased to ensure sufficient protection coordination and a sufficient time difference, i.e., delay, between the trip of the downstream mechanical circuit breaker P1 and the trip of the upstream SSCB(s) 106 at SI and S2.

[0050] In practical applications, the fault current flows through the SSCB 106 of S1 in opposite directions during the first fault Fl and the second fault F2. Once the SSCB 106 of S1 senses that the fault current direction is opposite to the reference direction with one or more analog circuit components, the adjustment of the TCC or threshold of the SSCB 106 at S1 can be achieved. In response to the sensing of S1, the system level controller 142 can then issue commands to S2,... Sn to change their TCC and overcurrent threshold. With the SSCB(s) 106 disposed near each of the battery 114, the protection coordination enables the circuit protection device closest to the fault location to open before the other downstream circuit protection devices. Thus, the impact of the overload condition is minimized and the reliability and availability, i.e., uptime, of the BESS 108 is improved.

[0051] The embodiments detailed above can be combined, in whole or in part, with any of the alternative embodiments described.

[0052] Industry applicability

[0053] The above invention can represent an improvement in the art by providing current control and / or balancing and short circuit protection for large scale direct parallel distributed DC energy resources, including but not limited to battery energy storage systems, fuel cell systems, super capacitor systems, hybrid energy storage systems, and / or photovoltaic power stations. Balancing and control of battery rack currents, temperatures, state of charge, and / or other battery parameters are critical to predicting and / or extending the useful life of the batteries in large scale BESS(s). Current imbalances can result from battery cell manufacturing and / or can be related to some other factors encountered during actual BESS operation, such as varying positions of battery cells, varying ambient temperatures, and varying rates of aging among numerous battery cells. Still further, observed current imbalances increase when the rates of degradation of target battery racks are different. The current imbalances experienced by individual racks can further accelerate the aging of the batteries and increase the likelihood of safety issues. In turn, more and more variations lead to more current imbalances, thereby further accelerating the degradation of the batteries and more rapidly increasing the current imbalances. Thus, the presently disclosed system and method are an improvement in the art because the current controllability is increased for individual battery racks within a large scale BESS and / or other battery systems. The protection and control described in the present invention can be extended to distributed AC energy resources.

[0054] While a few embodiments have been shown and described, numerous modifications and other embodiments will occur to those skilled in the art without materially departing from the spirit of the invention, and the scope of protection is only limited in the scope of the claims.

[0055] Headings and subheadings, if any, are used for convenience only and do not limit the application. The word "exemplary" is used herein to mean serving as an example, instance or illustration. Any aspect or embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or embodiments. The terms comprising, having, include, containing, etc. are to be construed as open-ended terms (meaning affecting the claim can include more than the recited elements to achieve the effect that would be fulfilled by the elemental) unless otherwise stated. The term "consisting of" is to be construed as a closed term meaning when the claim recites consisting of, it means the recited elements are all that can be present and no additional elements can be present. The term "consisting essentially of is to be construed as a closed term meaning when the claim recites consisting essentially of, it means the recited elements are all that can be present and any additional elements are present in a minor amount that do not contribute to the effect that would be fulfilled by the elemental. The terms first, second, and the like can be used to describe different elements, however, the elements should not be limited by these terms. The terms "first", "second", and the like are generally used to distinguish one element from another and are not necessarily used to describe a sequential or chronological order. For example, a first element and a second element can be used to describe different elements that are grouped together or two elements that are adjacent to each other.

[0056] The phrases, unless otherwise specified, "in one aspect," "in an aspect," "in some aspects," "in one or more aspects," "some aspects," "one or more aspects," "an implementation," "one implementation," and the like generally mean that a certain feature, structure, or characteristic described in connection with that aspect is included in at least one implementation of the present technology. The appearances of the phrases, unless otherwise specified, "in one aspect," "in an aspect," "in some aspects," "in one or more aspects," "some aspects," "one or more aspects," "an implementation," "one implementation," and the like, in various places in the specification are not necessarily all referring to the same aspect. The phrases "in one aspect," "in an aspect," "in some aspects," "in one or more aspects," "some aspects," "one or more aspects,” “an implementation,” “one implementation,” and the like, are generally used for ease of

[0057] The disclosed systems and methods are well adapted to attain the ends and advantages mentioned as well as those inherent therein. The particular implementations disclosed above are illustrative only of the intended application and are not limiting of the disclosure. For example, although the present disclosure describes a number of implementations, other implementations can be used instead or in addition. Changes in form and detail can be made without departing from the spirit of the disclosure. Further, although the disclosure has been described herein in the context of particular implementations, the implementations described herein can also be implemented in a wide variety of other contexts. Accordingly, the disclosure is not intended to be limited to the contexts of the particular implementations described herein, but rather can be used in any context. The systems and methods illustratively disclosed herein can suitably be practiced in the absence of any element or elements not specifically disclosed herein.

[0058] It should be understood that the described instructions, operations, and systems can generally be integrated together in a single software / hardware product or packaged into multiple software / hardware products.

[0059] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the application (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of "a" or "an" element or "the" element to convey the understanding that there is only one of the named species. The use of the term "at least one" followed by a list of elements should be interpreted as meaning one or more elements from the list. The use of the term "one" followed by a list of elements should be interpreted as meaning exactly one of the named elements, unless otherwise indicated herein or clearly contradicted by context. The use of the terms "first," "second," "third," and / or "fourth," and / or the like in the context of describing the application (especially in the context of the following claims) are not always used in their typical order, nor used consecutively, to describe distinct structures, entities, and / or elements. Rather, these terms can be used solely as labels to more readily identify certain unique or critical elements in certain embodiments of the present application. The use of any and all examples or exemplary language (e.g., "such as") provided herein is intended merely to better illuminate the application and does not pose a limitation on the scope of the application otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the application.

Claims

1. An energy storage system, comprising: a power source; a plurality of energy storage components; a solid state circuit breaker disposed between the power source and the plurality of energy storage components such that electrical power is exchanged between the power source and the plurality of energy storage components through the solid state circuit breaker; and a controller configured to operate the solid state circuit breaker to (i) control current exchanged with the plurality of energy storage components and (ii) protect the plurality of energy storage components from the power source during a fault condition, wherein the controller is configured to operate the solid state circuit breaker to manipulate current exchanged with a first subset of the plurality of energy storage components in response to an imbalance of at least one of (i) a state of charge of the plurality of energy storage components and (ii) a temperature of the plurality of energy storage components.

2. The energy storage system of claim 1, further comprising a plurality of solid state circuit breakers, wherein the controller is configured to individually operate each of the plurality of solid state circuit breakers to selectively reduce current to the first subset of the plurality of energy storage components.

3. The energy storage system of claim 2, wherein reducing current to the first subset of the plurality of energy storage components causes an increase in current to a second subset of the plurality of energy storage components.

4. The energy storage system of claim 3, wherein the controller is configured to select the first subset and the second subset of the plurality of energy storage components in response to the imbalance.

5. The energy storage system of claim 4, wherein the controller is configured to interchange the first subset and the second subset of the plurality of energy storage components.

6. The energy storage system of claim 2, wherein the plurality of solid state circuit breakers each comprise a solid state switch operable to control current flow through that solid state circuit breaker.

7. The energy storage system of claim 2, wherein the plurality of solid state circuit breakers each have an adjustable time current curve.

8. The energy storage system of claim 7, further comprising at least one of a fuse and a mechanical circuit breaker disposed between the power source and the plurality of solid state circuit breakers, wherein the controller is configured to adjust the adjustable time current curve of each solid state circuit breaker to produce circuit protection in combination with the at least one of the fuse and the mechanical circuit breaker.

9. The energy storage system of any one of claims 1-8, wherein the plurality of energy storage components each comprise one or more batteries in a parallel configuration.

10. The energy storage system of claim 9, wherein the controller is configured to operate the solid state circuit breaker in response to at least one of (i) a state of charge of the one or more batteries and (ii) a temperature of the one or more batteries.

11. A method of protecting an energy storage system, the method comprising: directing power through a solid state circuit breaker to exchange the power between a power source and a plurality of energy storage components; and operating the solid state circuit breaker to (i) control current exchanged with the plurality of energy storage components and (ii) protect the plurality of energy storage components from the power source during a fault condition, wherein the solid state circuit breaker is operated to manipulate current exchanged with a first subset of the plurality of energy storage components in response to an imbalance of at least one of (i) a state of charge of the plurality of energy storage components and (ii) a temperature of the plurality of energy storage components.

12. The method of claim 11, further comprising controlling the solid state circuit breaker to protect the plurality of energy storage components from a fault condition comprising one of an overcurrent, a short circuit, and a thermal overload.

13. The method of claim 12, further comprising controlling the solid state circuit breaker to protect the plurality of energy storage components from an imbalance condition comprising at least one of an imbalanced current and an imbalanced temperature.

14. The method of claim 13, further comprising: dividing a plurality of solid state circuit breakers into a plurality of subsets; and controlling different subsets of the plurality of subsets differently in response to at least one of the fault condition and the imbalance condition.

15. A circuit protection system, comprising: a power source electrically coupled with a load; a first circuit breaker having an adjustable time-current curve; one of a second circuit breaker or a fuse, the second circuit breaker or the fuse having a fixed time-current curve; and a controller coupled to the first circuit breaker and configured to adjust the adjustable time-current curve in response to a protection parameter; wherein a first overload threshold of the first circuit breaker is determined by the adjustable time-current curve, and wherein a second overload threshold of the second circuit breaker or the fuse is determined by the fixed time-current curve.

16. The circuit protection system of claim 15, wherein the second overload threshold is greater than the first overload threshold.

17. The circuit protection system of any one of claims 15-16, wherein the first circuit breaker is a solid state circuit breaker and is reset by the controller in response to an abatement of an overload condition.

18. The circuit protection system of claim 17, wherein the controller adjusts the adjustable time-current curve of the first circuit breaker in response to a replacement of the second circuit breaker or the fuse.

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