Droop compensation using current feedback

A system includes a boost converter configured to amplify input voltage received from one or more power sources into output voltage. The system also includes a current sensor configured to sense a current of the input voltage for example, by induction. The system further includes a controller configured to adjust an amplification of the boost converter in response to the current sensed by the current sensor. When utilized in each of a plurality of power source modules coupled to a common load, the power source modules adjust the amplifications of their boost converters towards equalization of their output voltages and their currents in response to sensed currents of the input voltages changing through demand of the common load. Associated systems and methods are also disclosed.

FIELD

The present invention is generally related to power sources, and more particularly to controllers associated therewith.

BACKGROUND

It is often advantageous to couple different power sources together to supply a greater quantity of power than achievable by any individual source. For example, electrochemical cells are often coupled together to form electrochemical cell systems (i.e., batteries). In some electrochemical cell systems, it may be advantageous to control each electrochemical cell therein, or subsets of the electrochemical cells therein, so as to increase overall system efficiency in supplying power to a load. For example, where one or more electrochemical cells (e.g., grouped into modules) in the electrochemical cell system fail or experience a performance drop relative to the other electrochemical cells or modules, it may be desirable to attempt to equalize currents between different cells, while sharing power between the modules. In particular, generally equal module lifespan across the system may be based more on the current draw associated with each module than on the total energy or power supplied by the module. Such a configuration may facilitate a uniform replacement schedule for modules in the system by generally equalizing the lifespans of each of the modules of the system.

Conventionally, to share currents across electrochemical cells, slave cells or modules are tied to a master cell or module, so that the master cell or module establishes the current draw for the system. Where the master cell or module fails or experiences other performance degradation, however, the entire system's performance may correspondingly degrade. Among other disadvantages, this conventional method fails to maintain the independence of modules.

Accordingly, the disclosure of the present application endeavors to accomplish these and other results.

SUMMARY

According to an embodiment, a system includes a boost converter configured to amplify input voltage received from one or more power sources into output voltage. The system also includes a current sensor configured to sense a current of the input voltage. Current can be measured by a magnetic method (i.e. induction) or purely resistive method (i.e. precise resistor) or a combination of these methods. The system further includes a controller configured to adjust an amplification of the boost converter in response to the current sensed by the current sensor.

According to another embodiment, a system includes a plurality of power source modules. Each power source module includes a boost converter configured to amplify input voltage received from one or more power sources into output voltage. Each power source module also includes a current sensor configured to sense a current of the input voltage for example, by induction. Each power source module further includes a controller configured to adjust an amplification of the boost converter in response to the current sensed by the current sensor. The plurality of power source modules are coupled to a common load through the output voltage. The plurality of power source modules adjust the amplifications of their boost converters towards equalization of their output voltages and their currents in response to sensed currents of the input voltages changing through demand of the common load.

According to another embodiment, a method of equalizing current across a plurality of power sources coupled to a common load includes, for each of the power sources, amplifying, using a boost converter, input voltage received from one or more power sources into output voltage. For each of the power sources, the method also includes sensing, using a current sensor, a current of the input voltage by induction. For each of the power sources, the method further includes adjusting an amount of said amplifying in response to the current sensed by the current sensor. By adjusting the amount of said amplifying, the plurality of power sources approach a stable equilibrium of output voltages and currents.

Other aspects of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

DETAILED DESCRIPTION

FIG. 1illustrates a schematic view of an electrochemical cell system100. In the illustrated embodiment, the electrochemical cell system100includes a plurality of cell modules110(individually cell modules110a,110b, and110N-N being an integer of 3 or more), each including a plurality of electrochemical cells therein. It may be appreciated that the electrochemical cell system100may include any appropriate number of cell modules110therein (e.g., two or more). In various embodiments, the cell modules110may include a different number of electrochemical cells120therein. In the illustrated embodiment, each module110includes eight electrochemical cells120(specifically, electrochemical cells120a(i-viii) in cell module110a, electrochemical cells120b(i-viii) in cell module110b, and electrochemical cells120N(i-viii) in cell module110N).

In an embodiment the electrochemical cells120of each cell module110may be subdivided into two interface groups, each having an associated cell interface unit130. As shown, cell interface unit130a(a) may group cells120a(i)-(iv), while cell interface unit130a(b) may group cells120a(v)-(viii). Similarly, cell interface unit130b(a) may group cells120b(i)-(iv), while cell interface unit130b(b) may group cells120b(v)-(viii). Furthermore, cell interface unit130N(a) may group cells120N(i)-(iv), while cell interface unit130N(b) may group cells120N(v)-(viii). In an embodiment, the cell interface units130may link the cells120associated therewith in series. Additionally, the cell interface units130may themselves be linked in series. As such, the voltage of each of the cells120in a given cell module110may add up. In the illustrated embodiment, with eight electrochemical cells120in each cell module110, if each electrochemical cell110supplies 1 VDC volt, then the eight cells120in series may supply 8 VDC. It may be appreciated that different cell modules110may supply different voltages (e.g., one cell module supplies 8 VDC, while another supplies 6 VDC).

While the electrochemical cells120may vary across embodiments, in some embodiments one or more of the cells120, and/or other features of the electrochemical cell system100, may include elements or arrangements from one or more of U.S. patent application Ser. No. 12/385,217 (issued as U.S. Pat. No. 8,168,337), Ser. No. 12/385,489 (issued as U.S. Pat. No. 8,309,259), Ser. No. 12/549,617 (issued as U.S. Pat. No. 8,491,763), Ser. Nos. 12/631,484, 12/776,962, 12/885,268, 13/028,496, 13/083,929, 13/167,930, 13/185,658, 13/230,549, 13/299,167, 13/362,775, 13/531,962, 13/532,374 13/566,948, and 13/668,180, each of which are incorporated herein in their entireties by reference. That is, the cells (and the system made up of those cells) may be a rechargeable power source (also referred to as secondary cells), which may be charged by an external power source (e.g., solar cells, wind turbines, geothermally generated electricity, hydrodynamically generated electricity, engine/brake generated electricity, the main power grid, etc.) and discharged as needed/desired (e.g., as back-up power, to discharge stored power, in lieu of a fossil fuel engine, etc.).

In some embodiments the cell interface units130may be configured to monitor the status of each cell120associated therewith, and may provide switching or other functionality configured to isolate or otherwise bypass faulty cells120, such as is described in U.S. patent application Ser. No. 13/299,167, incorporated by reference above. As another example, in embodiments where one or more of the electrochemical cells120are metal-air cells, the cells120may be utilized at least in part to power a cathode blowers140(individually cathode blowers140a,140b, and140N as illustrated) associated with the cell modules110, which may be configured to direct a flow of air or other oxidant to oxidant electrodes associated with each of the cells120, as described in U.S. patent application Ser. No. 13/531,962, entitled “Immersible Gaseous Oxidant Cathode for Electrochemical Cell System,” incorporated by reference in its entirety above.

For each module110, a cluster control unit150(individually cluster control units150a,150b, and150N in the illustrated embodiment) links the cell interface units130, and provides programmatic control thereof via a serial communications interface (SCI) associated with each. The cluster control units150may be linked to each other through a Controller Area Network (CAN) Bus160. Programmatic or other control of the cell modules110may be provided from a main control unit170, which may also be linked to the CAN Bus160. Embodiments of such programmatic control are described in greater detail below. In some embodiments, such as that illustrated, an AC Fail circuit180may also be implemented in the electrochemical cell system100, and may be coupled to the main control unit170and each of the cluster control units150. The AC Fail circuit180may be configured to direct the cluster control units150of the cell modules110to supply power to an AC Bus190on an as-needed basis. For example, if AC power on the grid fails, the AC Fail circuit180may be configured to draw power from the electrochemical cells120. It may be appreciated that in some embodiments the AC Bus190may generally receive DC power from the cell modules110, however may be associated with an inverter configured to convert the DC power to AC power. In other embodiments, each cell module110may include one or more inverters, configured to supply AC voltage across the AC Bus190. In some embodiments, the AC Bus190may be coupled to the main control unit170(e.g., through any appropriate sensor or sensing system), as illustrated by the dashed line therebetween inFIG. 1. In an embodiment, the main control unit170may control an inverter associated with the AC bus190. In some embodiments, the functions of the AC Fail circuit180may be combined with the CAN Bus160, or any other appropriate another control link.

It may be desirable to perform droop compensation in the electrochemical cell system100, so as to facilitate equalization of currents, which may correspondingly equalize a lifecycle of the cell modules110and the electrochemical cells120therein. By equalization of currents, it may be understood that the droop compensation may facilitate generally or essentially equalizing the currents (e.g., driving the currents towards equalization, into a state generally regarded in the art as being equalized). In an embodiment, droop compensation may be performed utilizing a control circuit associated with a controller in each cluster control unit150. As such, in some embodiments droop compensation may be performed on a cell module by cell module basis. In other embodiments, droop compensation may be performed among subsets of the cell modules110, such as by being implemented at the level of the cell interface units130. In still other embodiments, droop compensation may be performed on a cell by cell basis, being implemented associated with each individual electrochemical cells120. Other implementations are also possible.

FIG. 2illustrates a control block diagram for a control circuit200illustrating an example of how droop compensation may be implemented (e.g., on the electrochemical cell system100) according to an embodiment. In the illustrated embodiment, the control circuit200shows that the control scheme operates on a conversion from a boost input voltage210to a boost output voltage220, via a boost circuit225(i.e., a converter), described in greater detail below. In the example illustrated, the boost input voltage210is shown as being 8 VDC nominal. It may be appreciated that such an input voltage may result from the summation in series of each of the eight electrochemical cells120associated with each electrochemical cell module110, outputting 1 VDC each. Additionally, as shown, in an embodiment the boost output voltage220may be stepped up (i.e., amplified) to 52 VDC nominal by the boost circuit225. In the example illustrated, the 52 VDC→42 VDC range may be based on telecom requirements, wherein all loads are active at 52 VDC, noncritical loads (NCL) drop out at 48 VDC, and only critical loads (CL) are kept active around 42-45 VDC. While having a CL voltage range instead of a fixed value is uncommon, the range may be based on any customer desired range. It may be appreciated that one could adjust scaling factors to accommodate the ranges. As described in greater detail below, the amplification of the boost circuit225may be variable, so as to provide the desired droop compensation. In an embodiment, the boost output voltage220may be output to the AC Bus190of the electrochemical cell system100.

In an embodiment, to perform the droop compensation using the control circuit200, a fixed reference voltage230is received at a first summation junction240. In the illustrated embodiment, the fixed reference voltage230is 5 VDC. It may be appreciated that the 5 VDC may be an exemplary scaling point, and could be anywhere from 1 VDC to 10 VDC in some embodiments, depending on nominal board operating voltage. The fixed reference voltage230may be provided by any appropriate source, including, for example, ultimately from one or more of the electrochemical cells120, or from a separate power source. At the first summation junction240, the fixed reference voltage230may have a first voltage modifier250subtracted therefrom. As described in greater detail below, the first voltage modifier250may be computed from a sensed current (I) associated with the boost input voltage210. A software voltage adjustment260may also be applied at the first summation junction240, also being subtracted from the fixed voltage reference230. In some embodiments, the software voltage adjustment260may be computed or otherwise derived from properties of the cell, or may be received as a user input. In an embodiment, the software voltage adjustment260may range from 0V to 0.962V, as described in greater detail below. It may be appreciated that the value 0.962 may be calculated as a scaling factor based on the 5 VDC reference. When the scaling factor is at zero, boost output voltage is 52 VDC. When the scaling factor is at 0.962, however, the boost output voltage is 42 VDC. The adjustment alteration may be based on user control of what loads are active (i.e. critical loads, non-critical loads). The value may be any number and is only dependent the boost output voltage range desired. The summation of the fixed reference voltage230, minus the software voltage adjustment260and the first voltage modifier250, may be output as a voltage reference270.

The voltage reference270may be input into a second summation junction280. At the second summation junction280, a second voltage modifier290may be subtracted from the voltage reference270. As shown in the illustrated embodiment, the second voltage modifier290may be computed based on the boost output voltage220, which may form a PI loop (i.e., a proportional-integral loop, wherein the control circuit200comprises a PI controller). In particular, in an embodiment, the boost output voltage220may be fed into a step down op-amp300, which in the exemplary embodiment ofFIG. 2, has a gain of 0.096. This is so in the illustrated embodiment because the boost output voltage220is nominally 52 VDC, while the fixed reference voltage230is 5 VDC (52 VDC*0.096≈5 VDC).

If there were no load associated with the boost output voltage220, then there would be no current associated with the boost input voltage210. As such, the first voltage modifier250associated with the lack of a sensed current would be zero, and (absent any software voltage adjustment260) the voltage reference270would be the same as the fixed reference voltage230. With the gain of the step down op-amp300being associated with the fixed reference voltage230, in such a situation the voltage reference270would be equal to the second voltage modifier290, resulting in an error output310, i.e., e(t), of zero. It may be appreciated that where the boost output voltage220drops, the second voltage modifier290also drops, creating a non-zero error output310. As described in greater detail below, the error output310may be utilized to modify the amplification of the boost circuit225from the boost input voltage210to the boost output voltage220, to compensate for the change.

When a load is applied to the boost output voltage220, the first voltage modifier250, associated with a current associated with the boost input voltage210, may adjust the voltage reference270. Specifically, with the addition of a load, the current associated with the boost input voltage210may increase from zero to a positive value. As shown inFIG. 2, to detect the current of the boost input voltage210, the boost circuit225may include therein a current sensor320. In an embodiment, a wire carrying the boost input voltage210may be run through the current sensor320, which may pick up an associated magnetic field associated therewith, and output an inductor current measurement325that is proportional to the magnetic field. The current may be measured by the current sensor320as amperes (A). Such an ampere inductor current measurement325may be converted into a voltage reading by a current to voltage converter330(as the controls implemented in the control circuit200may generally operate in voltages). The inductor current measurement325, as converted to a voltage, may then be fed back through the control circuit200to establish the first voltage modifier250, described above. It may therefore be appreciated that because the first voltage modifier250is utilized in establishing the voltage reference270, the inductor current measurement325is also utilized to establish the error output310. In some embodiments, the current sensor320may sense current by other means besides induction. For example, a current sense resistor may be employed with known precision resistance.

As shown, the error output310is utilized to establish a current reference335(i.e., “I-ref”) for the control circuit200. It may be appreciated that in some embodiments the system implementing the control circuit200(e.g., the system100) may have a current limit of 40 ADC. Such a current limit may correspond to a 2.5 VDC limit in the control circuit200. It may be appreciated that the 40 ADC limit may be by user requirement, and may be a protection limit so, for example, if customer load sources more than 40 A out of module, this will limit input current from modules. If bus is shorted, 40 A limit will clamp, thus only allowing 40 A for protection purposes. The example selection of a 2.5V limit in the illustrated embodiment is user selected, and in some embodiments could range from approximately 1V to 10V. If bus is overloaded (e.g., a shorted out bus), the output voltage is forced to zero, and the error output will saturate. The saturated error output may command I-ref to go high (however capped by the limit). As an example, with a current swing or a customer demand of 40 A, the boost output voltage will go below 52 VDC, but it is desirable to stay above 48 VDC so as not to drop out critical loads CL. Accordingly, when input current is 40 A, the 480 mV value may be scaled from the 5 VDC exemplary selection, similar to the software adjustments. In the illustrated embodiment, the error output310associated with the voltage reference270passes through a voltage limiter340, which limits the error output310to 2.5V, corresponding to 40 ADC. The error output310, as limited by the voltage limiter340, may be considered the current reference335. Similarly, because a 40 A limit may exist for the measurement of the current sensor320, the current to voltage converter330may also correspond to a limit of 2.5V, which amounts to 62.5 mV/A. A step down op-amp350having a gain or 0.192 may reduce the influence of the inductor current on the control circuit200to 12 mV/A (480 mV=40 ADC). In some embodiments, the reduced voltage associated with the inductor current may then be fed into a timing delay360. In the illustrated embodiment, the timing delay360may be for 100 ms. Other time delays are also possible in other embodiments. It may be appreciated that the timing delay360may be configured to slow down the operation of the control loop, which may dampen out the loop of the control circuit200, to prevent high oscillation before achieving stability, as described in greater detail below. It may be appreciated that some embodiments might not include a timing delay360, but might include other mechanisms to prevent undesirable oscillation of the loop of the control circuit200.

The reduced voltage associated with the inductor current, which in the illustrated embodiment results from the step down op-amp350, and may be time delayed by the timing delay360, may thus be fed back into the first summation junction240as the first voltage modifier250, which determines the voltage reference270. Having utilized the inductor current to establish the error output310associated with the voltage reference250, the inductor current may then be utilized to establish an error output370associated with the current reference335. Specifically, the current reference335, established based on the voltage reference270and the reduced boost output voltage220(as the second voltage modifier290) may be adjusted at a third summation junction380. In an embodiment the inductor current measurement325, converted to a voltage by the current to voltage converter330, may be subtracted directly from the current reference325. In other embodiments, such as that illustrated, a fourth summation junction390may allow the inductor current measurement325, as converted to a voltage, to be modified by a software current adjustment400. In some embodiments, the software current adjustment400may be computed or otherwise derived from properties of the cell, or may be received as a user input. In an embodiment, the software current adjustment400may be measured as a voltage, and may be between 0 and 2.5V, corresponding to being between 0 and 40 ADC, as described above. Regardless, by subtracting the inductor current measurement325(e.g., as converted to voltage by the current to voltage converter330, and potentially as modified by the software current adjustment400) from the current reference335, the error output370associated with the current reference335may be computed. The error output370may then be received by the boost circuit225, and may determine an error input for a pulse width modulator410thereof. The pulse width modulator410may be configured to dictate how much current is drawn by the boost circuit225, and may be tied into the boost circuit225in such a manner so as to modify the boost amplification from the boost input voltage210to the boost output voltage220, as described below.

Because the boost output voltage220is fed back through the control circuit200in a manner that in part determines the error output310associated with the reference voltage270, and because that boost output voltage220, in conjunction with the load demands, varies the current supplied in the boost input voltage210(sensed by the current sensor320as inductor current325), which is fed back to determine at least in part the voltage reference270and the current reference335, it may be understood that the boost circuit225as a whole will modulate the boost in response to current demands associated with the load coupled to the boost output voltage220. With multiple boost circuits225coupled to a common load, where each is controlled by control schemes such as that found in the control circuit200, the boost circuits225are independent from one another in their operation, however may respond to one another through the demands of the load on the associated boost output voltages220. The operation of this responsiveness is discussed below.

It may be appreciated that the cell or cells associated with whichever one of the boost circuits225is outputting a greatest boost output voltage220would initially attempt to supply all of the power to the load. The effect of that boost circuit225attempting to supply all of the power to the load would be an associated increase in the inductor current, as discussed above. The increase in inductor current then causes the control circuit200to droop the boost output voltage220for that boost circuit225. Once the boost output voltage220from the boost circuit225falls below that of a second boost circuit225(having what was previously the second highest boost output voltage220) the second boost circuit225would then itself attempt to supply all of the power to the load. This would cause the second boost circuit225to droop its boost output voltage220. The process would then repeat, creating a cycle where the boost circuits225and associated cells attempt to supply all of the power to the load, and the output voltages “droop” in response, which causes other boost circuits225and associated cells to continue the cycle. It may be appreciated that the amount by which the boost circuit225droops the boost output voltage220depends on the error output370established based on the current reference335. For example, where the current reference335saturates at the 40 A limit, the boost circuit225may droop the boost output voltage220close to zero to compensate.

Through the cycle, the different boost circuits225and associated cells may oscillate as to which is attempting to fully power the load. Eventually, all boost circuits225would trend towards a stable equilibrium, where each of the boost circuits225have the same boost output voltage220and similarly, have the same current reference335. Even though the current reference335will be driven towards equalization across all controllers, the output current from the boost circuits225(e.g., associated with the boost output voltages220, and coupled in parallel to the load) may be different for each converter. Accordingly, the current associated with the boost input voltage210(e.g., as measured by the current sensor320as the input inductor current325) would also be driven towards equalization by the boost circuit225. It may be appreciated that the equalization of currents, and the common boost output voltage220across different cells or cell modules, is independent of the boost input voltage210obtained from the cell or cell modules.

Such independent ability of each cell or module to attempt to equalize current may be beneficial to enhance performance and lifespan of the cells of the system. To apply this understanding in the context of the system100inFIG. 1, if the control schemes of the control circuit200are implemented in each of the cluster control units150, a load associated with the AC Bus190may cause the cluster control units150to react to one another, varying the amplification of the boost circuits225associated with each to attempt to equalize current demands across the cell modules110. Thus, if the cell module110ainitially has the highest boost output voltage220being output to the AC Bus190, the electrochemical cells120a(i-viii) would attempt to supply all of the power to the load, and the current sensor320would identify the increased current associated therewith. The sensed current would be fed back through the control circuit200of the cell module110a, causing the boost circuit225of the cluster control unit150ato droop the amplification to supply a smaller boost output voltage220. If cell module110bsubsequently has the greatest boost output voltage220, then the electrochemical cells120b(i-viii) would attempt to supply all of the power to the load via the AC Bus190, causing a corresponding increase in the current sensed in the cluster control unit150b. The current would be fed back through the control circuit200of the cluster control unit150b, causing the boost circuit225to similarly droop the amplification. This may occur through the boost circuits225associated with each of the cluster control units130of the cell modules110, until each of the boost circuits225achieve a stabilization point, with generally equal current being drawn by the cell modules110.

It may be appreciated that the boost circuit225may vary across embodiments, and may be of any appropriate configuration. Boost circuits225typically include two or more semiconductor switches. For example, in the illustrated embodiment the boost circuit225includes a Field Effect Transistor (FET)420, and a diode430. The FET420opens and closes according to a duty cycle440(i.e., “D”) provided by the pulse width modulator410. Boost circuits225may further include one or more energy storage elements. In the illustrated embodiment, the boost circuit225includes an input inductor450, and a pair of capacitors460. In operation, the switching of the FET420, in conjunction with the stored energy in the input inductor450and the capacitors460, results in the boost output voltage220being greater than the boost input voltage210, with the amount of amplification, in the present embodiment, being variable depending on the duty cycle440from the pulse width modulator410.

It may be appreciated that the control circuit200may be implemented in a variety of systems, including but not limited to system100ofFIG. 1. Further, the source of the boost input voltage210may vary across embodiments. While in the illustrated embodiment eight cells (e.g.,120N(i-viii)) are electrically coupled together in series to provide an 8 VDC source for the boost input voltage210, in other embodiments, the control circuits200may be implemented on individual electrochemical cells120(e.g., such that the boost input voltage210is 1 VDC). It may further be appreciated that the cell modules110and/or the electrochemical cells120therein may vary across embodiments.

As noted above, in some embodiments, the electrochemical cells120may include features from those listed applications incorporated by reference herein. For example, in some embodiments the electrochemical cells120may include a plurality of permeable electrode bodies. In some embodiments the plurality of permeable electrode bodies may be configured to be electrically connected to one another through charging of the electrochemical cell120. In some embodiments the permeable electrode bodies may be selectively coupled to either an anode or a cathode in the electrochemical cell120during charging of the electrochemical cell120, so as to form a plurality of electrochemical cells within each electrochemical cell120(e.g., by alternatively associating different permeable electrode bodies with the anode and the cathode, so that fuel grows on some of the permeable electrode bodies towards others of the permeable electrode bodies).

Likewise, during discharge of the cells120, in some embodiments, the external load associated with the AC Bus190may only be coupled to the terminal permeable electrode body, distal from an oxidant reduction electrode of each electrochemical cell120, so that fuel consumption may occur in series from between each of the permeable electrode bodies. In other embodiments, the external load may be coupled to some of the electrode bodies in parallel, as described in detail in U.S. patent application Ser. No. 12/385,489, incorporated above by reference. In some embodiments, a switching system such as that described in U.S. patent application Ser. No. 13/299,167, incorporated above by reference, may facilitate selective electrical connections between the permeable electrode bodies. In some embodiments, the cells may be configured for charge/discharge mode switching, as is described in U.S. patent application Ser. No. 12/885,268, incorporated by reference above.

In some embodiments including a switching system, switches associated therewith may be controlled by a controller, which may be of any suitable construction and configuration. In the system100ofFIG. 1, such controllers may be associated with each cell120, each cell interface unit130, each cluster control unit150, or with the main control unit170. In some embodiments, the controllers may have a hierarchal association with one another, such that a more superior controller (e.g., in the main control unit170) may transmit commands to lower controllers (e.g., in the cluster control units150). In some embodiments, one or more of the controllers may include features conforming generally to those disclosed in U.S. application Ser. Nos. 13/083,929, 13/230,549 and 13/299,167, incorporated by reference above. In various embodiments, the control of the switches of a switching system may be determined based on a user selection, a sensor reading, or by any other input. In some embodiments, the controller(s) may also function to manage connectivity between the load and the AC Bus190, or may selectively supply power (e.g., over the AC Bus190) to the electrochemical cells120for recharging thereof. As noted above, in some embodiments, the controller may include appropriate logic or circuitry for actuating bypass switches associated with each electrochemical cell120coupled in the cell interface units130or otherwise in the cell modules110, in response to detecting a voltage reaching a predetermined threshold (such as drop below a predetermined threshold).

The foregoing illustrated embodiments have been provided solely for illustrating the structural and functional principles of the present invention and are not intended to be limiting. For example, the present invention may be practiced using a variety of fuels, oxidizers, electrolytes, and/or overall structural configurations or materials. Thus, the present invention is intended to encompass all modifications, substitutions, alterations, and equivalents within the spirit and scope of the following appended claims.