System and method for vehicle based uninterruptable power supply

A system and method for controlling a vehicle-based source of uninterruptable power is disclosed. The vehicle-based UPS includes an energy storage system located on-board a vehicle and configured to generate DC power transferable to an external load, and an DC-AC inverter connected to the on-board energy storage system to receive the DC power therefrom and invert the DC power to an AC power useable by the external load. The vehicle-based UPS also includes a charging device located on-board the vehicle and connected to the on-board energy storage system to provide recharging power thereto and a control system. The control system is configured to determine one of a state-of-charge (SOC) and a voltage of the energy storage system and selectively operate the charging device to provide the recharging power to the energy storage system to maintain the SOC or voltage of the energy storage system within a pre-determined range.

BACKGROUND OF THE INVENTION

The invention relates generally to an uninterruptable power supply (UPS) and, more particularly, to a vehicle-based UPS and system for controlling operation of the vehicle-based UPS.

Emergency sources of power are known as important devices in various applications and industries for providing a safeguard against power outages. It is recognized that the need for dependable and long-lasting sources of emergency power may increase in the near future as utility grid failures become more prevalent. That is, due to the number and severity of storms (lightning, wind, fallen trees, ice, etc), the overload of the country's aging utility's transmission and distribution components, and the potential threat of terrorism, the likelihood of utility grid failures is increasing.

Various types of devices are known for providing such emergency power. Devices such as a gasoline, diesel, propane, or other fueled version of an auxiliary or emergency generator are typically interfaced via a transfer switch to a subset of electrical circuits in a home to provide emergency power. An additional source of emergency power is an Uninterruptible Power Supply (UPS). An UPS is preferred in some instance to generators, as a UPS maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available, as compared to an auxiliary power supply or a standby generator, which do not provide instant protection from a momentary power interruption as is desired for certain types of equipment. For example, a UPS is typically used to protect computers, telecommunication equipment, medical equipment, or other electrical equipment where an unexpected power disruption could cause serious business disruption or data loss, or pose other significant consequences.

It is recognized, however, that UPS systems have their limitations. A key issue with conventional UPS systems is whether the limited amount of energy that is stored in the UPS's battery is sufficient to operate the a device for an extended period of time. For example, individuals that require the use of portable AC powered medical equipment and health monitors need a backup source of power that can last for the duration of the night (depending on the specific medical equipment required) or in a worst case, for the duration of a utility grid failure. Devices such as constant pressure airway passages (CPAP), oxygen concentrators, portable respirators, and heart monitors, need to be ensured of a proper supply of power in order to ensure patient well-being. As the average age of the population increases, there is also an increasing need for such critical care devices and systems, and thereby an associated need for systems that can provide adequate, extended length powering of those devices during utility grid outages.

Therefore, it would be desirable to design a UPS system that provides extended power for external loads in the event of a utility grid failure. It is further desired that such a UPS system provide a steady power source and be maintained at a desirable state of charge (SOC)

BRIEF DESCRIPTION OF THE INVENTION

The invention is a directed method and apparatus for controlling a vehicle-based source of uninterruptable power. An on-board energy storage system, charging device and control system are provided to form a vehicle-based uninterruptable power supply (UPS). The control system selectively operates the charging device to maintain a state-of-charge (SOC) and/or voltage of the energy storage system within a pre-determined range and allow for the vehicle to provide a source of uninterruptable power.

In accordance with one aspect of the invention, a vehicle-based uninterruptable power supply (UPS) system includes an energy storage system located on-board a vehicle and configured to generate DC power transferable to an external load and an DC-AC inverter connected to the on-board energy storage system to receive the DC power therefrom and invert the DC power to an AC power useable by the external load. The vehicle-based UPS also includes a charging device located on-board the vehicle and connected to the on-board energy storage system to provide a recharging power thereto and a control system. The control system is configured to determine one of a state-of-charge (SOC) and a voltage of the energy storage system and selectively operate the charging device to provide the recharging power to the energy storage system to maintain the one of the SOC and the voltage of the energy storage system within a pre-determined range.

In accordance with another aspect of the invention, a method for supplying uninterruptable power includes the steps of detecting connection of an external load to an on-board energy storage system of a vehicle and providing power from the on-board energy storage system to the external load upon connection thereto. The method also includes the steps of detecting one of a voltage and a state of charge (SOC) of the on-board energy storage system and, if the one of the voltage and the SOC of the on-board energy storage system is below a pre-determined threshold, then activating a charging unit connected to the on-board energy storage system to supply a recharging power thereto and maintain the one of the SOC and the voltage of the on-board energy storage system within a pre-determined range.

In accordance with yet another aspect of the invention, a control system for controlling the supply of uninterruptable power from a vehicular on-board energy storage system to an external load is programmed to detect connection of an external load to an on-board energy storage system of a vehicle and measure one of a voltage and a state of charge (SOC) of the on-board energy storage system upon connection of the external load. The control system is further programmed to activate a charging device connected to the on-board energy storage system to supply a recharging power thereto if the one of the voltage and the SOC of the on-board energy storage system is outside a pre-determined range and deactivate the charging device if the one of the voltage and the SOC of the on-board energy storage system is within the pre-determined range.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the invention are directed to systems and methods for supplying uninterruptable power to an external load from a vehicle-based power source. A propulsion system for use in a vehicle, such as a Battery Electric Vehicle (BEV), a Hybrid-Electric Vehicle (HEV), or a Plug-in Hybrid Electric Vehicle (PHEV), includes therein an on-board energy storage system with an on-board device or unit for charging the on-board energy storage system, such as an auxiliary power unit (APU) in the case of a HEV or PHEV. A control system is included in the vehicle propulsion system to control operation of the on-board energy storage system and the on-board charging device, so as to provide uninterruptable power to the external load and to maintain a voltage and/or state-of-charge (SOC) of the on-board energy storage system within an acceptable range.

Referring toFIG. 1, a block schematic diagram of a vehicle-based uninterruptable power supply (UPS)10is shown as incorporated into a vehicle propulsion system. The vehicle-based UPS10includes therein an on-board energy storage system12, an on-board device or mechanism14for charging the on-board energy storage system12, a DC-AC inverter16, and a control system18included on a vehicle20. The on-board energy storage system12includes one or more energy storage units13(e.g., 12 V starting-lighting-ignition (SLI) battery, traction battery, and/or hybrid traction battery arrangements), as will be described in detail below with respect to various embodiments of the invention, and is configured to provide electric power for driving one or more electric motors22coupled in driving relationship to wheels (not shown) of the vehicle20and/or provide electric power to auxiliary devices (e.g., lights, windshield wipers) on the vehicle, as well as provide a supply of uninterruptable DC power to an external load24. The on-board charging device14(i.e., charging unit) is connected to the on-board energy storage system12to supplement power for driving the electric motor(s)22and/or to supply a recharging power to one or more of the energy storage units13in the on-board energy storage system12. According to embodiments of the invention, when the vehicle is a HEV or PHEV, the charging device14can be in the form of an auxiliary power unit (APU), such as an internal combustion engine, a hydrogen fuel cell arrangement, or other similar power generating system. Alternatively, charging device14can be in the form of a DC-DC converter when the vehicle is a BEV. The DC-AC inverter16of the propulsion system for vehicle-based UPS10is connected to the on-board energy storage system12to receive the DC power therefrom and invert the DC power to an AC power useable by the external load24. Thus, for example, DC-AC inverter16can be configured to receive a 12 V DC power from on-board energy storage system12and convert that power to a 120 V AC power (or 230 V AC power for other applications or countries) for use by the external load24. In another example, the DC-AC inverter16can be configured to receive a greater than 12 V DC power from on-board energy storage system12and convert that power to a 120 V AC power for use by the external load24

A control system18is included in vehicle-based UPS10and connected to each of the on-board energy storage system12and the on-board charging device14. In operation, control system18is configured to operate on-board energy storage system12and on-board charging device14to provide controlled power to drive electric motor(s)22coupled in driving relationship to wheels of the vehicle20as part of the vehicle propulsion system (not shown). Additionally, control system18functions to determine a state-of-charge (SOC) and/or a voltage of the on-board energy storage system12and to maintain the SOC/voltage of the on-board energy storage system12within a pre-determined range to provide uninterruptable power to the DC-AC inverter16and the external load24. To maintain the SOC/voltage of the on-board energy storage system12, control system18selectively operates on-board charging device14to provide for a recharging power to the on-board energy storage system12. That is, if the SOC/voltage of the on-board energy storage system12is determined to be within an acceptable range, then control system18allows vehicle-based UPS10to continue to supply power to the external load24from the on-board energy storage system12without activating the on-board charging device14. If, however, the SOC/voltage of the on-board energy storage system12is determined to be outside of an acceptable range, then control system18activates charging device14to provide recharging power to one or more of the energy storage units13in the on-board energy storage system12to increase the SOC/voltage thereof.

As shown inFIG. 1, control system18includes therein inputs33from a sensor system26and from a mode switch28. According to embodiments of the invention, mode switch28can be in the form of a key ignition switch or of a separate switch included in vehicle, such as a dash mounted switch. If mode switch28is a separate dash mounted switch, it can be configured to be alternated only between an Off mode and an Emergency Power mode. If mode switch28is a key ignition switch, the switch can be configured to be set to a plurality of modes to allow for different modes of operation of the vehicle, such as an Off mode, a Vehicle Accessory mode, a Vehicle Start/Run mode, and an Emergency Power mode. When the mode switch28is set to the Emergency Power mode, the vehicle-based UPS10is activated to provide power to external load24connected to the vehicle-based UPS by way of a plug-in receptacle30. That is, control system18can selectively activate on-board charging device14to recharge at least one of the energy storage unit(s)13of the on-board energy storage system12to provide external load24with uninterruptable power. According to an embodiment of the invention, when the Emergency Power mode is selected, control system18further acts to deactivate motor(s)22and a traction inverter32in vehicle20to prevent torque generation at wheels (not shown) of the vehicle20.

As further shown inFIG. 1, inputs33from sensor system26provide information to control system18on a plurality of vehicle-related parameters that control operation of the UPS10. Sensor system26includes a SOC/voltage sensor34that measures a SOC/voltage of the on-board energy storage system12at various times during operation thereof. Based on a sensed SOC/voltage of the on-board energy storage system12, control system18controls operation of the on-board charging device14to provide recharging power to the on-board energy storage system. That is, if the SOC/voltage of the on-board energy storage system12is outside of a pre-determined range or below a certain threshold, as measured by SOC/voltage sensor34, control system18activates the charging device14to generate and transmit additional power to the on-board energy storage system12. Once the SOC/voltage of the on-board energy storage system12is back within an acceptable range, as measured by the SOC/voltage sensor34, the control system18then deactivates the charging device14and continues monitoring the SOC/voltage of the on-board energy storage system12. This cycle of measuring the SOC/voltage and activating/deactivating the charging device14will continue until the mode switch28is switched out of the “Emergency Power” mode.

Also included in sensor system26is a transmission gear status sensor36configured to provide information to the control system18regarding the gear (i.e., PRNDL) in which vehicle20is presently engaged. A parking brake engagement status sensor38can also be included in sensor system26to provide information to the control system18as to whether the vehicle parking brake is engaged. According to one embodiment of the invention, as another source of information to control system18, a fuel level sensor40measures a level of fuel remaining for the charging device14(e.g., APU), such as a level of gasoline or diesel fuel remaining for an internal combustion engine. If the information provided by sensor system26indicates that vehicle20is in a “Park” gear, and/or that the parking brake is engaged, and that the fuel level is at an acceptable amount, control system18allows for activation of the charging device14as needed to maintain the SOC/voltage of the on-board energy storage system12within its acceptable range so as to provide a vehicle-based UPS10for providing power to the external load24.

As another source of information to control system18, a carbon monoxide (CO) sensor42is included in sensor system26that provides data regarding the level of CO in the vicinity of the vehicle20and whether that level is above a certain threshold limit. In the event that the CO sensor42detects a CO level exceeding a pre-determined threshold, or in the event that fuel level sensor40detects a low fuel level, control system18is configured to generate a command to shut down (i.e., deactivate) operation of charging device14(e.g., combustion engine). According to one embodiment of the invention, control system18can also generate an alarm based on the sensed CO level or low fuel level to alert an operator of such an occurrence. The sensor system26thus provides a series of information parameters to control system18to restrict operation of the charging device14when the vehicle-based UPS10is operating in Emergency Power mode.

Referring now toFIG. 2, a technique implemented by control system18to control operation of the vehicle-based UPS10is shown. The technique44initiates at STEP45and proceeds with a determination of whether the vehicle-based UPS is in an Emergency Power mode of operation at STEP46. That is, a determination is made as to whether a mode switch configured to switch operational modes of the vehicle-based UPS and/or operational modes of the vehicle itself is set to an Emergency Power setting/mode. If the vehicle-based UPS is not in an Emergency Power mode48, the technique44starts over. If the vehicle-based UPS is in an Emergency Power mode of operation50, the technique44continues at STEP52, where the status of the on-board energy storage system is monitored. That is, at STEP52, a state-of-charge (SOC) and/or voltage of the specific on-board energy storage system that supplies electrical power to the DC-AC inverter is measured to determine a level of the SOC/voltage thereof.

A determination is made at STEP54as to whether the SOC/voltage of the on-board energy storage system is above a pre-determined threshold or within a pre-determined range. If the SOC/voltage of the on-board energy storage system is within the pre-determined range56, the SOC/voltage of the on-board energy storage system is considered to be at an acceptable level for providing power to an external load, and no recharging of the on-board energy storage system is performed. Thus, the on-board charging device, which can comprise a DC-DC converter in an electric vehicle and/or an APU in a HEV or PHEV, is either directed to remain in a deactivated state, or caused to enter a deactivated state, at STEP57. If, however, the SOC/voltage of the on-board energy storage system is outside the pre-determined range58, it is determined that recharging of the on-board energy storage system by way of the charging device is desired (i.e., recharging of one or more of the energy storage units in the energy storage system). Prior to recharging of the on-board energy storage system, a plurality of vehicle-related parameters are sensed at STEP60. According to embodiments of the invention, these vehicle-related parameters can include, but are not limited to, a transmission gear status, a parking brake engagement status, a fuel level, and a carbon monoxide (CO) level. A determination is made at STEP62if the vehicle-related parameters are at an acceptable status/level. For example, a determination is made if the transmission gear and parking brake are at an acceptable setting (i.e., transmission gear in “Park” and parking brake engaged), and the fuel and CO are at acceptable levels. If the vehicle-related parameters are not at an acceptable status/level64, then activation of the charging device for recharging the on-board energy storage system is prevented at STEP66. If the vehicle-related parameters are at an acceptable status/level68, then the charging device (i.e., DC-DC converter or APU) is activated at STEP70, and power generated by the charging device is transferred to one or more of the energy storage units in the on-board energy storage system to provide recharging power thereto. Upon activation of the charging device to recharge the on-board energy storage system, the technique44returns to STEP52for continued monitoring of the SOC/voltage of the on-board energy storage system. Once the recharging power supplied to the on-board energy storage system by the charging device is sufficient to bring the SOC/voltage back within the pre-determined acceptable range (as determined at STEP54), the charging device is then deactivated at STEP57. The technique44thus provides for controlled operation of the vehicle-based UPS based on the determining of a SOC/voltage of the on-board energy storage system and based on the selective operation of the charging device to supply the recharging power to the on-board energy storage system to maintain the SOC/voltage of the on-board energy storage system within a pre-determined range.

Referring now toFIG. 3, a vehicle-based UPS72is shown as incorporated into a BEV AC propulsion system, according to one embodiment of the invention. The vehicle-based UPS72includes an on-board energy storage system74included on the vehicle20in the form of a 12 V Starting Lighting and Ignition (SLI) battery76and high voltage traction battery78(e.g., 300 V nominal). The high voltage traction battery78supplies power to an electric motor80to drive the motor, and is coupled thereto by way of a DC link81and a traction inverter82, which transfers AC power to the motor80based on an external torque command. Provided the mode switch28is in position for normal driving, and in response to a torque command based on an operator command, high voltage traction battery78provides power to drive the electric motor80.

Also included in the vehicle-based UPS72is an on-board charging device73(i.e., charging unit) that is coupled to the on-board energy storage system74to provide a recharging power thereto. As shown inFIG. 3, the charging device73includes an isolated DC-DC converter86connected between the SLI battery76and the high voltage traction battery78. When activated, DC-DC converter86allows for a transfer of recharging power from high voltage traction battery78to the SLI battery76and conditions the power to provide a proper charge to the SLI battery. That is, DC-DC converter86receives a DC power from high voltage traction battery78and conditions the power for transfer to the SLI battery76to provide charge thereto. Thus, upon activation of DC-DC converter86, high voltage traction battery78can provide power to SLI battery76to recharge the SLI battery as it is drained due to its providing power to an external load88connected to the vehicle-based UPS72. To transfer and condition power from the SLI battery76to the external load88, a DC-AC inverter92and power receptacle94are included in vehicle-based UPS72. The DC-AC inverter92receives a DC power from the SLI battery76and inverts the DC power to an AC power useable by the external load88. Power receptacle94then allows for connection of the external load88to the vehicle-based UPS72.

When the vehicle20is not running, and power is being supplied to the external load88from the vehicle-based UPS72, the SOC/voltage of the high voltage SLI battery76will begin to decline and will eventually fall below a pre-determined acceptable amount (i.e., fall outside an acceptable range), To determine when a transfer of power from the high voltage traction battery78to SLI battery76is desired (as provided by DC-DC converter86), a control system90in vehicle-based UPS72is configured to sense a SOC/voltage of the SLI battery76. If the SOC/voltage of the SLI battery76is outside an acceptable range, control system90activates the DC-DC converter86to transfer energy from the high voltage traction battery78to recharge the SLI battery76and maintain proper SOC/voltage on the SLI battery76to continue to supply power to either internal or external loads. More specifically, when control system90is switched to an “Emergency Power” mode and when a sensed SOC/voltage of the SLI battery76is outside an acceptable range, control system90is configured to activate DC-DC converter86to transfer energy from the high voltage traction battery78to the SLI battery76to supply a recharging power thereto. Control system90continues to measure the SOC/voltage of the SLI battery76as power is being transferred thereto by the DC-DC converter86and high voltage traction battery78. Thus, when the SOC/voltage of the SLI battery76is raised back into the acceptable range, control system90acts to deactivate DC-DC converter86, to terminate transfer of power from the high voltage traction battery78. In such a manner, control system90thus ensures that the SLI battery76is not operated outside its normal range of SOC/voltage due to the supply of power to the external load88. Battery life of SLI battery76will thus not be degraded based on operation of the external load88.

Beneficially, in a propulsion system for a BEV, the capacity and energy storage rating of the high voltage traction battery78is significantly higher than the high voltage traction battery in a HEV. For example, today's HEVs may have a high voltage traction battery with total energy rating of 1-2 kWh, while a high voltage traction battery in a propulsion system for an EV may have total energy rating in excess of 15 kWh. Thus, the vehicle-based UPS72in a BEV is expected to remain operational (i.e., SOC/voltage of the on-board energy storage system remains within an acceptable range) for a duration of time that is sufficient for the UPS72to operate critical medical equipment or other external devices/loads.

Also shown inFIG. 3, in phantom, is an auxiliary power unit (APU)97that, according to another embodiment of the invention, is included in the propulsion system for the vehicle-based UPS72when the propulsion system is based on a Hybrid Electric Vehicle (HEV) AC propulsion system. The APU97forms part of the charging device73(along with DC-DC converter) to supply additional recharging power to the on-board energy storage system12. The APU97includes therein an internal combustion engine84, along with an alternator83and diode-rectifier device85connected to the engine84to condition the recharging power provided by combustion engine and convert the recharging power to a DC power. Provided the mode switch28is in position for normal driving and in response to a torque command, based on an operator command, combustion engine84provides supplemental DC power to high voltage traction battery78to drive the electric motor80.

As set forth above, when the vehicle20is not running, and power is being supplied to the external load88from the vehicle-based UPS72, the SOC/voltage of the on-board energy storage system74begins to decline. In addition to SLI battery76being drained, high voltage traction battery78will also begin to decline and will eventually fall below a pre-determined acceptable amount (i.e., fall outside an acceptable range), based on its selective supplying of power to SLI battery76. When such a drop in the SOC/voltage of the high voltage traction battery78occurs, control system90in vehicle is further configured to selectively activate the APU97(i.e., activate the internal combustion engine84) to recharge the high voltage traction battery78(and the SLI battery76). More specifically, when control system90is switched to an “Emergency Power” mode and when a sensed SOC/voltage of the high voltage traction battery78is outside an acceptable range, control system90is configured to activate internal combustion engine84to supply a recharging power thereto. Control system90continues to measure the SOC/voltage of the high voltage traction battery78as power is being transferred thereto by internal combustion engine84. Thus, when the SOC/voltage of the high voltage traction battery78is raised back into the acceptable range, control system90acts to deactivate internal combustion engine84. Thus, by selectively activating the DC-DC converter86and the APU97, control system90ensures that the respective batteries (SLI battery76and high voltage traction battery78) are not operated outside their normal range of SOC/voltage due to the supply of power to the external load88. Battery life of SLI battery76and high voltage traction battery78will thus not be degraded based on operation of the external load88.

Additional embodiments of vehicle-based UPS are shown inFIGS. 4 and 5and incorporate on-board energy storage systems on a vehicle20as described in detail in U.S. Pat. No. 7,049,792 to King. As shown inFIG. 4, a vehicle-based UPS95is based on a Battery Electric Vehicle (BEV) AC propulsion system, where an on-board energy storage system96includes a high energy density battery99, which, according to the embodiment, is an electrically rechargeable battery. High energy density battery99can be formed as, for example, a sodium-metal-halide battery having an energy density of 120 W-hr/kg, or possibly a lithium-ion battery with energy density of 110 W-hr/kg. High energy density battery99is coupled to a DC link98that connects to a traction inverter100and a motor102. A boost converter circuit104is positioned on the DC link98between high energy density battery99and motor102to boost the voltage available from the electrically rechargeable high energy density battery99. A dynamic retarder106is coupled across the DC link98on the inverter100end of the link and is operated to limit the DC voltage developed on DC link98when the motor102is operated in a regenerative mode returning electric power to the link through the inverter100when the on-board energy storage units are not able to accept the level of regenerative power being developed by the motor102to the link through the inverter100.

Also included in the on-board energy storage system96is a SLI battery101. Connected between the high energy density battery99and the SLI battery101is a charging device103in the form of an isolated, bi-directional DC-DC converter. When activated, the bi-directional DC-DC converter103allows for a transfer of recharging power from SLI battery101to the high energy density battery99. When the vehicle20is not running, and power is being supplied to the external load88from the vehicle-based UPS95, the SOC/voltage of the high energy density battery99will begin to decline and will eventually fall below a pre-determined acceptable amount (i.e., fall outside an acceptable range). To determine when a transfer of power from the SLI battery101to high energy density battery99is desired (as provided by DC-DC converter103), control system120in vehicle-based UPS95is configured to sense a SOC/voltage of the high energy density battery99. If the SOC/voltage of the high energy density battery99is outside an acceptable range, control system120activates the bi-directional DC-DC converter103to transfer energy from the SLI battery101to recharge the high energy density battery99and maintain proper SOC/voltage therein.

According to another embodiment of the invention, and as shown inFIG. 5, a vehicle-based UPS107includes an on-board energy storage system108in the form of a hybrid battery configuration and is based on a BEV propulsion system. The hybrid battery configuration108includes a high energy density battery110, such as a sodium-metal-halide battery having an energy density of 120 W-hr/kg, or possibly a lithium-ion battery with energy density of 110 W-hr/kg, and a high power density battery112, such as a nickel cadmium battery having a power density in excess of 350 W/kg, or a lithium-ion battery having a power density in excess of 1,000 W/kg, across the DC link98on the inverter100side of the boost converter104. The hybrid battery configuration108provides high power response for acceleration or heavy pulsed load conditions using the high power density battery112, while at the same time providing for extended range of operation of the vehicle using the high energy density battery110. In this embodiment, when the motor102is used to effect electrical retarding of the vehicle20, the regenerative energy produced by the motor102can be transferred to both the high power density battery112and the high energy battery through the bi-directional boost converter104to effectively recharge the on-board batteries and extend the operating range of the vehicle20. Preferably, the terminal voltage of the high energy density battery110is less than the terminal voltage of the high power density battery112so that without the boost converter104, there would be no power flow from the battery110to the battery112. This allows the boost converter104to be controlled in a manner to regulate the amount of energy drawn from or supplied to the high energy density battery110. Energy will be drawn from high energy density battery110either when power demand by the motor102is greater than can be supplied by high power density battery112or when the energy is needed to recharge high power density battery112from high energy density battery110, or a combination of power from each battery110,112depending on the specific control algorithm.

In the BEV configuration shown inFIG. 5, when the vehicle20is not running and power is being supplied to the external load88from the vehicle-based UPS107, the bi-directional boost converter104also acts as a charging device to allow for a transfer of recharging power from high power density battery112to the high energy density battery110. That is, as power is being supplied to the external load88from the vehicle-based UPS107and the SOC/voltage of the high energy density battery110begins to decline and approach a pre-determined SOC/voltage threshold, the bi-directional boost converter104can be activated to allow for a transfer of recharging power from high power density battery112to the high energy density battery110. To determine when a transfer of power from the high power density battery112to the high energy density battery110is desired, control system120in vehicle-based UPS107is configured to sense a SOC/voltage of the high energy density battery110. If the SOC/voltage of the high energy density battery110is outside an acceptable range, control system120activates the bi-directional boost converter104to transfer energy from the high power density battery112to recharge the high energy density battery110and maintain proper SOC/voltage therein.

According to additional embodiments of the invention, each of the vehicle-based UPSs95,107ofFIGS. 4 and 5may be based on/incorporated into an HEV AC propulsion system, and thus may contain an additional charging device113in the form of an APU, as shown in phantom inFIGS. 4 and 5. The APU113includes a combustion engine114that is connected to the on-board energy storage system96,108(i.e., high energy density battery99,110) to provide a recharging power thereto. An alternator116and diode-rectifier device118are included to condition the recharging power provided by combustion engine114and convert the recharging power to a DC power. The recharging power provided by combustion engine114is transmitted to high energy density battery99,110to increase a SOC/voltage therein. The control system120in vehicle20is configured to selectively activate internal combustion engine114to recharge the high energy density battery99,110. More specifically, when control system120is switched to an “Emergency Power” mode and when a sensed SOC/voltage of the high energy density battery99,110is determined to be outside an acceptable range, control system120is configured to activate internal combustion engine114to supply a recharging power thereto. Control system120continues to measure the SOC/voltage of the high energy density battery99,110as power is being transferred thereto by internal combustion engine114. Thus, when the SOC/voltage of the high energy density battery99,110is raised back into the acceptable range, control system120acts to deactivate internal combustion engine114, and stored energy from the high energy density battery99,110is again used to power the external load88. While APU113is described above as providing recharging power to high energy density battery99,110, it is also understood that recharging power is also provided to SLI battery101(FIG. 4) and high power density battery112in the on-board energy storage systems96,108. Control system120thus functions to maintain SOC/voltage of the on-board energy storage system96,108within its normal range during the supply of power to the external load88.

The embodiments of the vehicle-based UPS95,107shown inFIGS. 4 and 5are capable of storing increased amounts of energy in on-board energy storage system96,108. Thus, the vehicle-based UPS95,107is designed to have an increased power rating and to be used to power more demanding (i.e., higher powered) external loads. Thus, vehicle-based UPS95,107includes therein a ground fault current interrupter (GFCI) circuit121to terminate power output from the vehicle-based UPS when appropriate.

Referring now toFIG. 6, a vehicle-based UPS122is shown as incorporated into a Plug-In Hybrid Vehicle (PHEV) propulsion system according to another embodiment of the invention. An on-board energy storage system124of vehicle-based UPS122includes multiple on-board energy storage units, which include a high-specific energy battery126(e.g., a sodium metal halide battery having an energy density of 120 W-hr/kg, or a lithium-ion battery having an energy density of 110 W-hr/kg) and a high-specific power battery128(e.g., a nickel cadmium battery having a power density of 350 W/kg or greater, or a lithium-ion power battery having a power density of 1,000 W/kg or higher). Additionally, on-board energy storage system124includes one or more ultracapacitor energy storage devices130. The ultracapacitor storage device(s)130provides increased power storage in on-board energy storage system124, thus allowing for vehicle-based UPS122to provide higher pulsed power to an external load132and operate for longer periods of time without engaging a charging device134in the vehicle-based UPS122for providing recharging power.

As shown inFIG. 6, the charging device134of a propulsion system for vehicle-based UPS122includes a plurality of auxiliary power units (APUs) for generating energy. That is, as one mechanism for providing recharging power to on-board energy storage system124, charging device134includes one or more fuel cells135forming a fuel cell assembly136. In an exemplary embodiment, the fuel cell assembly136is formed of a plurality of hydrogen fuel cells135that generate power. Beneficially, operation of the hydrogen fuel cell assembly136produces heat and water vapor and does not produce carbon monoxide emissions, as do the gasoline and diesel fueled APU's in other embodiments of the invention. The power generated by the fuel cell assembly136is conditioned by diode-rectifier device138before being transferred to high-specific energy battery126and/or ultracapacitor storage device(s)130to provide recharging power thereto. As another mechanism for providing recharging power to on-board energy storage system124, charging device134includes a plug-in140that allows for connection of the vehicle-based UPS122to a utility grid. When vehicle20is not in operation (and the utility grid is operable), the plug-in140can be connected to a utility grid to receive AC power therefrom. The AC power from the utility grid is passed through an AC-DC charger interface142(i.e., a voltage and current controlled rectifier) to condition the power for transfer to the on-board energy storage system124. The power received through plug-in140from the utility grid is supplied to recharge on-board energy storage system124.

To provide power to a traction inverter144and motor146and propel the vehicle20in a normal (i.e., “Run”) mode of operation, power from fuel cell assembly136may be transmitted to one or more boost converters148and power from high specific energy battery126and ultracapacitor storage device(s)130is transmitted to a plurality of bi-directional buck/boost converters150coupled thereto. The boost converter148and the plurality of bi-directional buck/boost converters150are coupled to a DC link152, and, in operation, the boost converter148boosts the voltage from the fuel cell assembly136and supplies the boosted voltage to DC link152. When necessary, the plurality of bi-directional buck/boost converters150boosts the voltage from the high-specific energy battery126and ultracapacitor storage device(s)130and supplies the boosted voltage to DC link152. The level to which the fuel cell voltages are boosted, as well as the level to which the energy storage device voltage is boosted depends on the manner in which the plurality of bi-directional buck/boost converters150and the boost converter148are controlled. In combination with the boosted voltages from the fuel cell assembly136, the high-specific energy battery126, and the ultracapacitor storage device(s)130, voltage from the high-specific power battery128is used as needed to provide controlled power to traction inverter144and motor146coupled in driving relationship to wheels of the vehicle20or mechanical load for selected applications as part of the propulsion system.

A control system154is also included in vehicle-based UPS122and is configured to monitor and control operation of the on-board energy storage system124and charging device134. When vehicle-based UPS122is set to an Emergency Power mode, as determined by a mode switch28setting, control system acts to flip a power switch156in vehicle-based UPS122. Power switch156is switched from a setting allowing power transfer from a utility grid to on-board energy storage system124(through plug-in140) to a setting (i.e., Emergency Power mode) in which vehicle-based UPS122provides power to an external load132.

In addition to switching of the vehicle-based UPS122to Emergency Power mode, control system154also functions to selectively activate fuel cell assembly136to recharge the on-board energy storage system124. Control system154measures a SOC/voltage of the on-board energy storage system124(i.e., high-specific energy battery126, high-specific power battery128, and ultracapacitor energy storage device(s)130) via a SOC/voltage sensor34(FIG. 1) and determines whether the SOC/voltage is outside an acceptable pre-determined range. If the measured SOC/voltage is determined to be outside an acceptable pre-determined range, control system154generates a command to activate fuel cell assembly136to supply a recharging power to the on-board energy storage system124. Control system154continues to measure the SOC/voltage of the on-board energy storage system124as power is being transferred thereto by fuel cell assembly136. Thus, when the SOC/voltage of the on-board energy storage system124is raised back into the acceptable range, control system154acts to shut-down/deactivate fuel cell assembly136. Control system154thus functions to maintain SOC/voltage of the on-board energy storage system124within its normal range during the supply of power to the external load132.

While various embodiments of on-board energy storage system and charging devices are shown and described inFIGS. 3-6, it is envisioned that other forms and configurations of on-board energy storage system and charging devices can also be included in the vehicle-based UPS. For example, an on-board energy storage system as set forth in U.S. Pat. No. 5,373,195 to King (i.e., high voltage traction battery and boost converter combination) could also be implemented in the vehicle-based UPS according to another embodiment of the invention. According to embodiments of the invention, the control system, and the technique implemented thereby as shown and described with respect toFIG. 2, is configured to monitor and control operation of the various embodiments of on-board energy storage system and charging device (e.g., DC-DC converters and APUs) to provide a source of uninterruptable power to external loads.

A technical contribution for the disclosed method and apparatus is that is provides for a controller implemented technique for controlling operation of a propulsion system for a vehicle-based UPS. The control system controls operation of an on-board energy storage system and on-board charging device(s), so as to provide uninterruptable power to an external load and maintain a voltage and/or state-of-charge (SOC) of the on-board energy storage system within an acceptable range.

Therefore, according to one embodiment of the invention, a vehicle-based uninterruptable power supply (UPS) system includes an energy storage system located on-board a vehicle and configured to generate DC power transferable to an external load and an DC-AC inverter connected to the on-board energy storage system to receive the DC power therefrom and invert the DC power to an AC power useable by the external load. The vehicle-based UPS also includes a charging device located on-board the vehicle and connected to the on-board energy storage system to provide a recharging power thereto and a control system. The control system is configured to determine one of a state-of-charge (SOC) and a voltage of the energy storage system and selectively operate the charging device to provide the recharging power to the energy storage system to maintain the one of the SOC and the voltage of the energy storage system within a pre-determined range.

According to another embodiment of the invention, a method for supplying uninterruptable power includes the steps of detecting connection of an external load to an on-board energy storage system of a vehicle and providing power from the on-board energy storage system to the external load upon connection thereto. The method also includes the steps of detecting one of a voltage and a state of charge (SOC) of the on-board energy storage system and, if the one of the voltage and the SOC of the on-board energy storage system is below a pre-determined threshold, then activating a charging unit connected to the on-board energy storage system to supply a recharging power thereto and maintain the one of the SOC and the voltage of the on-board energy storage system within a pre-determined range.

According to yet another embodiment of the invention, a control system for controlling the supply of uninterruptable power from a vehicular on-board energy storage system to an external load is programmed to detect connection of an external load to an on-board energy storage system of a vehicle and measure one of a voltage and a state of charge (SOC) of the on-board energy storage system upon connection of the external load. The control system is further programmed to activate a charging device connected to the on-board energy storage system to supply a recharging power thereto if the one of the voltage and the SOC of the on-board energy storage system is outside a pre-determined range and deactivate the charging device if the one of the voltage and the SOC of the on-board energy storage system is within the pre-determined range.