Abstract:
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.

Description:
RELATED APPLICATION 
     This application claims priority to provisional U.S. Application Ser. No. 60/950,939, filed Jul. 20, 2007. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under contract W9113M-07-C-0133 awarded by the U.S. Army Space and Missile Defense Command. The government has certain rights in the invention. 
    
    
     FIELD 
     This invention relates generally to vehicle power systems and, more particularly, modular vehicle power systems producing AC power from a vehicle&#39;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&#39;s existing power system. Utilizing the vehicle&#39;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 (&lt;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&#39;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&#39;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. 
    
    
     
       DRAWINGS 
         FIG. 1  is an illustration of the environment and capability of the System; 
         FIG. 2  is a system block diagram; 
         FIG. 3  illustrates a heat sink assembly; 
         FIG. 4  illustrates the module series configuration and output filter; 
         FIG. 5  is an illustration of a power module; 
         FIG. 6  is an illustration of power module component locations; 
         FIG. 7  is an illustration of phase power modules with phase A removed; 
         FIG. 8  is an illustration of seal configuration; 
         FIG. 9  is a power board functional diagram; 
         FIG. 10  is an illustration of a calibration display; 
         FIG. 11  is an illustration of a diagnostics display; 
         FIG. 12  is an illustration of a fault condition display; and 
         FIG. 13  is an illustration of a gauges and monitoring display. 
     
    
    
     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. 
     System  10  is 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 extrusions  12  for heat dissipation. System  10  is compact and multiple mounting solutions are possible. System  10  has 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. 
     System  10  gathers its power source from an already established configuration available on a vehicle  14  (see  FIG. 1 ) utilizing, for example, a 28 Volt-DC/400 Ampere alternator. System  10  may contain a power inverter, a speed controller and user&#39;s interface box  18  ( FIG. 2 ). System  10  contains control circuitry  20 , pre-charge &amp; protection circuitry  22 , phase power modules  24  ( 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 interface  18  provides the operator with indicators that display System&#39;s  10  status. 
     System  10  is modular allowing for easier installation and maintenance activities. Each phase power module  24  is interchangeable and functions as one phase of the three phase power system. Each power module  24  can 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 modules  24  is damaged. After removing damaged module  24 , system  10  can function in a one or two phase configuration. 
     System  10  is environmentally sealed from immersion or other harsh conditions utilizing custom rubber seals  26  ( FIG. 3) and 66  ( FIG. 8 ) around all mechanical joints in the chassis. Seals  26  provide protection for the internal components of the system  10 . The unique configuration of seals  26  and  66  make system  10  more rugged. 
     Extrusion  28 , used as a heat-sink for the power board, is designed and machined to include cup  30  installed with seal  26  to house power transformer  32  for each power conversion assembly  34  ( FIG. 9 ). Cup  30  is cooled (and the extrusion heated) and inserted along with environmental seal  26  allowing for a thermal bond (along with an environmental seal). This bond allows for maximum thermal connectivity between fins  12  of extrusion  28  and cup  30 . This bond combined with seal  26  and surrounding potting material provides thermal relief for power transformer  32  and environmental protection for the circuitry. 
     A plurality of power assemblies  34  may be used in each power module  24 . Housing  36  for power assemblies  34  includes mounts to allocate the minimum amount of space necessary to install the circuit boards, output filter  38  and fuse board  40 . Power module  24  is assembled with power assemblies  34  wired 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 filter  38  and fuse  40  boards. 
     System  10  obtains its input power from an alternator or battery source capable of providing 28VDC, e.g. from vehicle  14 . Full output power from System  10  may require the input DC power source to be rated at 400 A or higher. At the input, system  10  is protected by a circuit breaker  42  rated at the overload capacity of the input source. Additionally, each power assembly  34  is protected by a smaller fuse  40  designed to prevent catastrophic damage to the components. After applying input voltage, system  10  provides its output through a series of DC-DC converters  44  and DC-AC inverters  46  arranged for maximum efficiency. The output of inverters  46  is filtered utilizing a distributed output filter  48 . The output voltage, frequency and phase rotation of system  10  are controlled by a signal processor  20  (and software) by manipulating the switching scheme of DC-AC inverters  46 . Signal processor  20  also monitors output current and output voltage to assure safe operation of System  10 . If conditions are not within acceptable parameters, system  10  will shutdown, protecting the components of the system, the load, host vehicle, and operating personnel. 
     System  10  utilizes an individual power board arrangement, where multiple power conversion assemblies  34  are run in series generating the required AC output. Each power assembly  34  generates a portion of the output. 
     System  10  may provide three phase power in a tiered modular package. Each phase power module  24  provides one phase of the three-phase output and is fully interchangeable. If one or more of the power module(s)  24  fail, it can be removed from system  10  and the remaining module(s)  24  will be capable of providing full rated output for an individual phase of system  10 . Each phase module  24  is comprised of three identical power assemblies  34  (with an input clipping circuit  58  and a distributed output filter  48 ). 
     System  10  may 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&#39;s by increasing the switching speed with the voltage; lowering the current requirements and increasing overall efficiency. 
     Each power assembly  34  includes power conversion technology utilizing full H-bridge MOSFET designs. The output of each power assembly  34  is configured in series in order to provide the rated power of system  10  (three power assemblies  34  in series). This configuration provides improved load sharing; increasing efficiency and heat dissipation. 
     System  10  uses a distributed output filter  48  to generate the three phase power. Each power assembly  34  includes a small inductive filter  48 . The output configuration of these boards runs in series adding inductance. At the end of the chain of power assemblies  34 , the full rated signal is filtered through a larger inductor  54  and capacitor  56  to complete the output of the phase. This distributed output filter provides better heat dissipation due to load sharing and improves efficiencies. 
     System  10  uses voltage clipper  58 , protecting system  10  from dangerous transient voltages at the input source. These transients could cause damage to the electronics within system  10 , thus raising the failure rate. Clipper  58  is located in each phase power module  24  and improves the reliability of power module  24  and system  10 . 
     Referring now to System  10  in more detail,  FIG. 2  (System Block Diagram) illustrates the overall system view of System  10 . 
     Communications 
     System  10  publishes parameter information over communications bus  60 . This information is used for an indicator accessory to interface  18  providing the user with system status and fault condition tracking. 
     Control 
     System  10  uses system components to monitor the output voltages and currents to provide necessary automatic protections for the user and system  10 . Control  20  also controls the switching frequency of the DC-AC inverter  46  in order to provide the proper output voltage, frequency and phase rotation. 
     Pre-Charge 
     Pre-charge protection  22  is designed within System hardware allowing the input voltage to the DC-DC converter  44  to ramp slowly during pre-charge conditions. This provides protection to the components of System  10  by slowly applying the input voltage to System  10 . 
     Phase Power Modules 
     Phase power modules  24  of System  10  house DC-DC converters  44 , DC-AC inverters  46 , gate drivers, input clipping circuitry  58  and output filters  48 . Three power assemblies  34  are configured in series to supply the AC output. 
     Safeties (Fuses/Main Power Relay) 
     Circuit breaker  42  and main power relay  62  of System  10  is used for protection purposes for over current faults and is also used for emergency shut-off. 
     General Description 
     Each power assembly  34  is constructed using a machined aluminum extrusion  28  for the greatest surface area for conduction cooling. After this operation is complete, cup  30  is machined to hold power transformer  32  and potting material. Cup  30  and heat-sink  12  are designed for an interference fit to maximize the thermal bond. This maximizes the heat transfer of power transformer  32  (and potting material) into the finned extrusion  28 . Seal  26  is added between cup  30  and heat-sink  28  as part of the system&#39;s environmental sealing scheme. The assembly process is illustrated in  FIG. 3 . After this process, power assemblies  34  are installed onto the heat-sinks completing the operation. 
     Power assemblies  34  are connected in series and utilize a distributed output filter, illustrated in  FIG. 4 . Each power assembly  34  provides a portion of the AC output. The series configuration of power assemblies  34  provides better load sharing and allows system  10  to operate at the high power levels required by the applications. L 1  in this configuration is the internal inductance of each circuit board, and the L 2 /C 1  combination provides the final output filtering  38 . 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. 4  also illustrates input voltage clipper  58  provided by power assembly  34 . The D 1 /R 1  combination 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 assemblies  34  are installed onto completed heat-sinks  28 , as illustrated in  FIG. 5 . Power assemblies  34  are then configured in series, with the input fuse/transient protection board  40  and output filter  38  connected (see  FIG. 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 modules  24  has been engineered to simplify and offer additional safety precautions for both assembly and maintenance of the system. Phase power modules  24  are 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 modules  24 . Each of the three phase modules  24  are 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 module  1 ) remove mounting screws  2 ) remove the phase power module  24  and  3 ) replace the phase power module  24  assembly with another module  24  (see  FIG. 7 ). 
     Standard maintenance cycles for System  10  is reduced based on the modular construction of power modules  24 . This modular configuration also provides extended life cycles of the product. Degraded modes of operation are also possible. If a phase power module  24  is damaged, system  10  can operate in a single or two phase configuration with the remaining power modules  24 . After removing the damaged power module  24 , each of the remaining power modules  24  will be operable at one-third of the full rated load. At the base of phase power modules  24 , the connections are protected by custom seals  66  creating an environmental seal protecting vital system components. Each mechanical joint in the base chassis  68  and phase power module  24  also has a custom seal  66  for the required protection. The seal configuration is illustrated in  FIG. 8 . 
     The electrical design of power assemblies  34  utilize standard MOSFET H-bridge technology for power conversion in DC-DC converter  44  (illustrated in  FIG. 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 transformer  32  required in the design. This also provides less switching losses at the MOSFET&#39;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 converter  44  passes through center-tapped transformer  32  rectifying 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 converter  46  to convert this DC signal into the AC output. The AC gate drive signal is controlled by controller  20  and passes through opto-isolation circuitry before driving the final stage of the inverter. Controller  20  sets the frequency and amplitude of the signal by modulating the switching signal of the MOSFET&#39;s. There is a localized output inductor  48  to reduce the size of the main filter inductor. The series configuration of each power assembly  34  and distributed portion of output filter  48  are illustrated in  FIG. 4  to complete the output of System  10 . The distributed output filter  48  allows better heat dissipation and efficiencies by sharing the inductance between three power assemblies  34 . 
     System  10  provides a modular environmentally sealed approach, protecting the internal components and allowing rugged operation in all environments. System  10  also provides reduced maintenance costs due to the solid state design and provides functionality in the event of a failure of a power module  24 . Each power module  24  is interchangeable and can operate as any phase during operation, dependent on system location. System also provides a distributed output filter  48  allowing for improved efficiencies and heat dissipation. The switching frequency of DC to DC converter  44  is variable dependent on input voltage; providing improved efficiencies and a smaller transformer and switching devices. The series configuration of power assemblies  34  provides 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. 
     System  10  provides rugged three phase AC power for deployment in operations. System  10  is designed to be a light-weight solution when compared to similarly-rated diesel powered tactical quiet generator sets. System  10  is capable of providing three phase power up to 10 kilowatts and single phase power up to 3.3 kilowatts per phase. System  10  may be powered using a 28VDC electrical system of a vehicle. System  10  has 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). System  10  communicates important diagnostic information to other accessories. 
     System  10  has a modular design, saving time in maintenance and allowing partial functionality in the event of a failure or damage. 
     The mechanical alignment of power assemblies  34 , within power modules  24 , of System  10  provides 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 seals  66  of System  10  protects the system  10  in 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 &amp; 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, System  10  provides 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.