Modular vehicle power system

A modular vehicle power system for a vehicle, the modular vehicle power system obtaining DC power the vehicle and producing AC power and method therefore. A plurality of power modules, each of the plurality of power modules receiving the DC power from the vehicle and producing the AC power, wherein each of the plurality of power modules are independent and interchangeable.

FIELD

This invention relates generally to vehicle power systems and, more particularly, modular vehicle power systems producing AC power from a vehicle's DC power and methods thereof.

BACKGROUND

Compact, and potentially mobile, AC electrical power for a variety of electronic equipment is needed. Military applications include tactical wheeled vehicles which may need AC electrical power for associated tactical equipment such as radar sets, command and control shelters and other portable equipment.

Other areas where mobile power may be desired include, but are not limited to, storm/disaster relief efforts, e.g., hurricanes, first responders, health care, facility emergency power, water purification centers, communications centers, retail shops and gas/refueling centers.

A common means to establish the capability of providing a sufficient supply of AC electrical power is to tow a trailer-mounted AC electrical power generator that is powered by diesel or other fuel. A trailer-towed solution, however, tends to be bulky and limits the maneuverability of the towing vehicle. Further, the separate trailer-towed generation system usually requires its own specialized operation and maintenance skill set.

SUMMARY

Thus, there is a significant need for a compact, mobile, AC power generation system which may be mounted in or on the tactical vehicle and which is powered by the vehicle's existing power system. Utilizing the vehicle's engine may reduce the skill set that may be required because there may be no additional power plant to maintain/operate and may also remove the necessity of having separate fueling systems which may reduce (re)fueling schedules.

Such so-called On Board Vehicle Power (“OBVP”) systems may be essential for mobile applications, where AC power requirements is required but trailer towed or conventional generator-based solutions are not practical. These applications are most relevant to, but not limited to, military applications. In on board vehicle power, the vehicle itself becomes the electric power generator providing AC power from the DC power from the electrical system of the vehicle itself. The System may be used for mobile power generation or in stationary mode applications. Increased mobility of power generation equipment is needed because trailer-towed generator solutions are not suitable for all locations where AC power may be needed. Applications where an OBVP-styled solution would be better able to meet AC power requirements than a conventional generator-based solution would be: 1) Applications that require significant AC power “on-the-move” 2) Applications that require AC power, but also require a limited footprint (e.g. no room for a generator) 3) Applications that require AC power but it is not possible to transport a generator (e.g. a helicopter drop of a single vehicle for transportation and AC power needs like battery chargers, portable equipment chargers, and intermittent operation of stationary AC powered equipment like tools, environmental control equipment, and portable tools) 4) Any small generator (<10 KW) application could also be served by an OBVP-styled solution. Provisions for extreme environmental conditions were designed into the System. These environmental provisions allow OBVP-equipped vehicles to have the same water-fording and environmental limits as vehicles that do not have OBVP. This capability expands the capabilities of an OBVP-equipped vehicle without unnecessarily limiting normal vehicle uses and applications. Also, these environmental considerations make the system more suitable for installations on tactical wheeled vehicles.

Embodiments of the invention provide a highly mobile and rugged power-inverter system designed to withstand harsh environments, while providing on-demand power for deployment in battle theaters. Embodiments of the light weight power system (as compared to diesel powered tactical quiet generator sets) may offer three compact mounting schemes located on the High Mobility Multipurpose Wheeled Vehicle (HMMWV), therefore eliminating the trailer towed diesel power generator solution. The System may be designed to meet stringent military requirements from the ground up. The System may be capable of providing peak three phase power outputs up to 10 KW and/or single phase outputs up to 3.3 KW. The System may be operational for both single phase (@ 120VAC) and three phase outputs (@ 208VAC); using the vehicle's 28VDC input source. The System may be able to produce voltage outputs at 50 Hz (for international applications), 60 Hz (for domestic applications) and 400 Hz (for aircraft and radar applications). The System may offer calibration parameters in order to customize the inverter for the specific requirements. The System may also have a communications protocol interface capable of transferring data to an independent throttle control system, whose purpose is to monitor the electrical load across the output and vary the vehicle's engine RPM to maintain optimum vehicle efficiency. The System may include accessories that provide functional feedback of the system as it relates to calibration, diagnostics and fault condition tracking.

In an embodiment, the present invention provides a modular vehicle power system for a vehicle, the modular vehicle power system obtaining DC power the vehicle and producing AC power. A plurality of power modules, each of the plurality of power modules receiving the DC power from the vehicle and producing the AC power, wherein each of the plurality of power modules are independent and interchangeable.

In an embodiment, the vehicle power system comprises at least three of each of the plurality of power modules, each one of the at least three of the plurality of power modules being associated with one of at least three phases of the AC power.

In an embodiment, the DC power has an input voltage and wherein each of the plurality of power modules utilize a variable switching frequency based upon the input voltage.

In an embodiment, the variable switching frequency increases as the input voltage increases.

In an embodiment, the variable switching frequency maintains an approximately constant voltage/frequency relationship.

In an embodiment, each of the plurality of power modules comprises a first power converter receiving the DC power from the vehicle, the first power converter utilizing a full MOSFET H-bridge producing a first AC power output; a center-tapped power transformer receiving and rectifying the first AC power output to create a filtered DC voltage; and a second power converter receiving the filtered DC signal, the second power converter utilizing a full MOSFET H-bridge to convert the filtered DC signal into a second AC power output.

In an embodiment, each of the plurality of power modules further comprises a local inductor output filter coupled to the second AC power output providing a first filtered AC output.

In an embodiment, each of the plurality of power modules further comprises an input power clipping circuit operatively coupled to the DC power.

In an embodiment, each of the plurality of power modules comprises a plurality of power boards.

In an embodiment, each of the plurality of power boards of each of the plurality of power modules are coupled in series.

In an embodiment, each of the plurality of power boards has a first power converter receiving the DC power from the vehicle, the first power converter utilizing a full MOSFET H-bridge producing a first AC power output; a center-tapped power transformer receiving and rectifying the first AC power output to create a filtered DC voltage; and a second power converter receiving the filtered DC signal, the second power converter utilizing a full MOSFET H-bridge to convert the filtered DC signal into a second AC power output.

In an embodiment, the system has a general output filter coupled to the second AC power output of each of the plurality of power boards producing a combined AC output representing a power output for one of each of the at least three single phases of the AC power.

In an embodiment, the second power converter operates at near 100% duty cycle.

In an embodiment, the system has a system chassis and wherein each of the plurality of power modules are individually, removably electrically, mechanically and thermally coupled to the system chassis.

In an embodiment, each of the plurality of power modules are substantially environmentally sealed from liquid immersion.

In an embodiment, wherein an individual seal between the system chassis and each of the plurality of power modules.

In an embodiment, each of the plurality of power modules further has a heatsink, a power transformer and a machined transformer cup, the machined transformer cup and the individual seal coupling the power transformer to the heatsink providing thermal conductivity between the power transformer and the heatsink.

In an embodiment, the vehicle has a motor coupled with a throttle control and wherein the modular vehicle power system further comprises a speed controller operatively coupled with the throttle control of the vehicle and with each of the plurality of power modules to increase a speed of the motor of the vehicle in response an increased applied load from the modular vehicle power system.

In an embodiment, the present invention provides a method of providing AC power from a vehicle producing DC power. A plurality of independent and interchangeable power modules, each of the plurality of power modules receiving the DC power from the vehicle and producing the AC power, are provided. The plurality of independent and interchangeable power modules are operated to provide multiple phase AC power. Each of the plurality independent and interchangeable power modules may operate for any one phase of the multiple phase AC power.

In an embodiment, at least three of each of the plurality of power modules are provided, each one of the at least three of the plurality of power modules being associated with one of at least three phases of the AC power.

In an embodiment, a variable switching frequency based upon the input voltage is utilized.

In an embodiment, the variable switching frequency increases/decreases as the input voltage increases/decreases.

In an embodiment, the variable switching frequency maintains an approximately constant voltage/frequency relationship.

In an embodiment, a plurality of power boards for each of the plurality of power modules is provided.

In an embodiment, each of the plurality of power boards of each of the plurality of power modules are coupled in series.

In an embodiment, each of the plurality of power modules are removably electrically, mechanically and thermally coupled to a system chassis.

In an embodiment, each of the plurality of power modules are substantially sealed from liquid immersion.

In an embodiment, an individual seal between the system chassis and each of the plurality of power modules.

In an embodiment, a power transformer is thermally coupled to a heatsink.

In an embodiment, a throttle of the vehicle is increased responsive to an increased load for the AC power.

DESCRIPTION

The contents of provisional U.S. Application Ser. No. 60/950,939, filed Jul. 20, 2007, is hereby incorporated by reference in its entirety.

System10is a fully enclosed chassis utilizing conduction cooled techniques for heat dissipation requirements. System is a waterproof system designed to withstand harsh environments, as well as rugged terrain. The exterior shell contains finned extrusions12for heat dissipation. System10is compact and multiple mounting solutions are possible. System10has an overall size of approximately 29.75 inches by 21 inches by 15.25 inches and can provide AC power in excess of 10 kilowatts peak.

System10gathers its power source from an already established configuration available on a vehicle14(seeFIG. 1) utilizing, for example, a 28 Volt-DC/400 Ampere alternator. System10may contain a power inverter, a speed controller and user's interface box18(FIG. 2). System10contains control circuitry20, pre-charge & protection circuitry22, phase power modules24(3) with voltage and current feedback capabilities. The speed controller monitors the vehicle and power systems to provide a response to the throttle in the event additional RPM is required for the applied load. System interface18provides the operator with indicators that display System's10status.

System10is modular allowing for easier installation and maintenance activities. Each phase power module24is interchangeable and functions as one phase of the three phase power system. Each power module24can be removed and replaced quickly. This lowers maintenance costs, limits down-time, and increases reliability. The modular approach also allows limited system functionality if one of the modules24is damaged. After removing damaged module24, system10can function in a one or two phase configuration.

System10is environmentally sealed from immersion or other harsh conditions utilizing custom rubber seals26(FIG. 3) and 66(FIG. 8) around all mechanical joints in the chassis. Seals26provide protection for the internal components of the system10. The unique configuration of seals26and66make system10more rugged.

Extrusion28, used as a heat-sink for the power board, is designed and machined to include cup30installed with seal26to house power transformer32for each power conversion assembly34(FIG. 9). Cup30is cooled (and the extrusion heated) and inserted along with environmental seal26allowing for a thermal bond (along with an environmental seal). This bond allows for maximum thermal connectivity between fins12of extrusion28and cup30. This bond combined with seal26and surrounding potting material provides thermal relief for power transformer32and environmental protection for the circuitry.

A plurality of power assemblies34may be used in each power module24. Housing36for power assemblies34includes mounts to allocate the minimum amount of space necessary to install the circuit boards, output filter38and fuse board40. Power module24is assembled with power assemblies34wired in series and adjacent to each other in order to minimize the amount of wire needed for connections and to allow the space for mounting necessary filter38and fuse40boards.

System10obtains its input power from an alternator or battery source capable of providing 28VDC, e.g. from vehicle14. Full output power from System10may require the input DC power source to be rated at 400 A or higher. At the input, system10is protected by a circuit breaker42rated at the overload capacity of the input source. Additionally, each power assembly34is protected by a smaller fuse40designed to prevent catastrophic damage to the components. After applying input voltage, system10provides its output through a series of DC-DC converters44and DC-AC inverters46arranged for maximum efficiency. The output of inverters46is filtered utilizing a distributed output filter48. The output voltage, frequency and phase rotation of system10are controlled by a signal processor20(and software) by manipulating the switching scheme of DC-AC inverters46. Signal processor20also monitors output current and output voltage to assure safe operation of System10. If conditions are not within acceptable parameters, system10will shutdown, protecting the components of the system, the load, host vehicle, and operating personnel.

System10utilizes an individual power board arrangement, where multiple power conversion assemblies34are run in series generating the required AC output. Each power assembly34generates a portion of the output.

System10may provide three phase power in a tiered modular package. Each phase power module24provides one phase of the three-phase output and is fully interchangeable. If one or more of the power module(s)24fail, it can be removed from system10and the remaining module(s)24will be capable of providing full rated output for an individual phase of system10. Each phase module24is comprised of three identical power assemblies34(with an input clipping circuit58and a distributed output filter48).

System10may utilize a variable switching frequency, based on input voltage, to the power conversion electronics to maintain a constant voltage/frequency relationship reducing the size of the transformer required in the design. This also provides less switching losses at the MOSFET's by increasing the switching speed with the voltage; lowering the current requirements and increasing overall efficiency.

Each power assembly34includes power conversion technology utilizing full H-bridge MOSFET designs. The output of each power assembly34is configured in series in order to provide the rated power of system10(three power assemblies34in series). This configuration provides improved load sharing; increasing efficiency and heat dissipation.

System10uses a distributed output filter48to generate the three phase power. Each power assembly34includes a small inductive filter48. The output configuration of these boards runs in series adding inductance. At the end of the chain of power assemblies34, the full rated signal is filtered through a larger inductor54and capacitor56to complete the output of the phase. This distributed output filter provides better heat dissipation due to load sharing and improves efficiencies.

System10uses voltage clipper58, protecting system10from dangerous transient voltages at the input source. These transients could cause damage to the electronics within system10, thus raising the failure rate. Clipper58is located in each phase power module24and improves the reliability of power module24and system10.

Referring now to System10in more detail,FIG. 2(System Block Diagram) illustrates the overall system view of System10.

Communications

System10publishes parameter information over communications bus60. This information is used for an indicator accessory to interface18providing the user with system status and fault condition tracking.

Control

System10uses system components to monitor the output voltages and currents to provide necessary automatic protections for the user and system10. Control20also controls the switching frequency of the DC-AC inverter46in order to provide the proper output voltage, frequency and phase rotation.

Pre-charge protection22is designed within System hardware allowing the input voltage to the DC-DC converter44to ramp slowly during pre-charge conditions. This provides protection to the components of System10by slowly applying the input voltage to System10.

Phase Power Modules

Phase power modules24of System10house DC-DC converters44, DC-AC inverters46, gate drivers, input clipping circuitry58and output filters48. Three power assemblies34are configured in series to supply the AC output.

Circuit breaker42and main power relay62of System10is used for protection purposes for over current faults and is also used for emergency shut-off.

General Description

Each power assembly34is constructed using a machined aluminum extrusion28for the greatest surface area for conduction cooling. After this operation is complete, cup30is machined to hold power transformer32and potting material. Cup30and heat-sink12are designed for an interference fit to maximize the thermal bond. This maximizes the heat transfer of power transformer32(and potting material) into the finned extrusion28. Seal26is added between cup30and heat-sink28as part of the system's environmental sealing scheme. The assembly process is illustrated inFIG. 3. After this process, power assemblies34are installed onto the heat-sinks completing the operation.

Power assemblies34are connected in series and utilize a distributed output filter, illustrated inFIG. 4. Each power assembly34provides a portion of the AC output. The series configuration of power assemblies34provides better load sharing and allows system10to operate at the high power levels required by the applications. L1in this configuration is the internal inductance of each circuit board, and the L2/C1combination provides the final output filtering38. These are tuned together in order to provide the proper heat dissipation, improving the efficiency of each phase and transferring some of the heat away from the power boards.FIG. 4also illustrates input voltage clipper58provided by power assembly34. The D1/R1combination provides protection to the system by ensuring the transient voltages are snubbed before causing damage to the internal components. This part of System may be uniquely designed to operate in a +28VDC automotive environment (provided by the input source).

Power assemblies34are installed onto completed heat-sinks28, as illustrated inFIG. 5. Power assemblies34are then configured in series, with the input fuse/transient protection board40and output filter38connected (seeFIG. 6). The mounting methods for the fuse board and output filter prepare the system for rugged environments, while maintaining the crucial electrical characteristics for operation.

The configuration for the three individual phase power modules24has been engineered to simplify and offer additional safety precautions for both assembly and maintenance of the system. Phase power modules24are constructed to provide rugged, environmentally sealed enclosures for the power electronics. This concept was taken one step further in developing a means of interconnects eliminating the need for wiring requirements when replacing any of the three power phase modules24. Each of the three phase modules24are interchangeable, they can be placed in any of the A, B, or C phase slots and can be swapped as needed. To remove a phase power module1) remove mounting screws2) remove the phase power module24and3) replace the phase power module24assembly with another module24(seeFIG. 7).

Standard maintenance cycles for System10is reduced based on the modular construction of power modules24. This modular configuration also provides extended life cycles of the product. Degraded modes of operation are also possible. If a phase power module24is damaged, system10can operate in a single or two phase configuration with the remaining power modules24. After removing the damaged power module24, each of the remaining power modules24will be operable at one-third of the full rated load. At the base of phase power modules24, the connections are protected by custom seals66creating an environmental seal protecting vital system components. Each mechanical joint in the base chassis68and phase power module24also has a custom seal66for the required protection. The seal configuration is illustrated inFIG. 8.

The electrical design of power assemblies34utilize standard MOSFET H-bridge technology for power conversion in DC-DC converter44(illustrated inFIG. 9). This technology utilizes a variable switching frequency at the DC gate driver signal based on input voltage. This maintains a constant voltage/frequency relationship reducing the size of transformer32required in the design. This also provides less switching losses at the MOSFET's by increasing the switching frequency only when the voltage is higher and the current requirements are lower (increasing overall efficiency). Variable switching frequency for the power converters provides better efficiency and a reduced part counts and also provides for a smaller transformer. The DC gate driver monitors the MOSFET voltage drop during an ‘ON’ state; reducing component count and losses and compensating for a defective low voltage gate drive output. The output of DC-DC converter44passes through center-tapped transformer32rectifying the high frequency AC output is rectified to create a filtered DC voltage with increased potential. This DC voltage passes through another H-bridge DC-AC converter46to convert this DC signal into the AC output. The AC gate drive signal is controlled by controller20and passes through opto-isolation circuitry before driving the final stage of the inverter. Controller20sets the frequency and amplitude of the signal by modulating the switching signal of the MOSFET's. There is a localized output inductor48to reduce the size of the main filter inductor. The series configuration of each power assembly34and distributed portion of output filter48are illustrated inFIG. 4to complete the output of System10. The distributed output filter48allows better heat dissipation and efficiencies by sharing the inductance between three power assemblies34.

System10provides a modular environmentally sealed approach, protecting the internal components and allowing rugged operation in all environments. System10also provides reduced maintenance costs due to the solid state design and provides functionality in the event of a failure of a power module24. Each power module24is interchangeable and can operate as any phase during operation, dependent on system location. System also provides a distributed output filter48allowing for improved efficiencies and heat dissipation. The switching frequency of DC to DC converter44is variable dependent on input voltage; providing improved efficiencies and a smaller transformer and switching devices. The series configuration of power assemblies34provides improved load sharing and thermal performance. The orientation and location of the components present an advantage in mechanical assembly and provide a space saving solution.

System10provides rugged three phase AC power for deployment in operations. System10is designed to be a light-weight solution when compared to similarly-rated diesel powered tactical quiet generator sets. System10is capable of providing three phase power up to 10 kilowatts and single phase power up to 3.3 kilowatts per phase. System10may be powered using a 28VDC electrical system of a vehicle. System10has a variable frequency at the output, selectable between 50 Hz (for international applications), 60 Hz (for domestic applications) and 400 Hz (for aircraft and radar applications). System10communicates important diagnostic information to other accessories.

System10has a modular design, saving time in maintenance and allowing partial functionality in the event of a failure or damage.

The mechanical alignment of power assemblies34, within power modules24, of System10provides space savings and ease of assembly. This alignment is also electrically unique, proving AC power utilizing three power boards in a series configuration.

The configuration of the environmental seals66of System10protects the system10in harsh environments.

Detailed monitoring of the system is important in managing its performance and calibrating operational parameters in order to achieve optimum performance based on the anticipated load demands of the target retrofit vehicle. Set-up and support functions are managed through a specialized software package utilizing a USB interface available for communication protocol-exchange in support of critical calibration & monitoring of the VPS10K system. This interface supports calibration (FIG. 10), diagnostics (FIG. 11), fault condition tracking (FIG. 12) and gauges and other monitoring (FIG. 13).

Overall, System10provides a unique solution to mobile three phase power.

An embodiment provides a modular mechanical design to allow for easier maintenance and installation.

An embodiment provides a seal configuration protecting the invention from harsh environments.

An embodiment provides a thermal configuration for the power transformer within the heat-sink allowing for better heat transfer in this application.

An embodiment provides a layout of the power boards, fuse board and output filter, maximizing space for the critical design criteria of this invention.

An embodiment provides an electrical design of the power boards, which functionally work in series to provide the AC output.

An embodiment provides a tiered modular package; providing functionality in the case of a failure, and fully interchangeable components.

An embodiment provides a distributed output filter that adds the filtering in series with the power boards and then completes the filtering at the output. This allows for better efficiency and heat dissipation.

An embodiment provides a voltage clipping technology, which provides protection to the system in a +28VDC automotive environment.

An embodiment provides a variable switching frequency for the power converters provides better efficiency and a reduced part sizes for the transformer and switching devices.

An embodiment provides a center tapped transformer for the rectification of the high frequency AC to DC section reduces the losses, as well as the component count.

An embodiment makes the output DC to AC inverter do all the voltage regulation operating the input DC to DC converter at near 100% duty cycle thereby reducing losses and eliminating components.

Thus, embodiments of the on-board vehicle power system and method are disclosed. One skilled in the art will appreciate that the present invention can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation, and the present invention is limited only by the claims that follow.