Abstract:
A direct current bus management system can include a power management and distribution unit, having a source management section, a bus management section coupled to the source management section, a load management section coupled to the bus management section, a DC bus coupled to the power management and distribution unit, a plurality of DC sources coupled to the source management section and a plurality of loads coupled to the load management section, wherein the bus management section is configured to reconfigure excess DC power on the DC bus from the DC inputs from the plurality of DC sources based on a plurality of priorities, a plurality of feedback signals and a plurality of system parameters.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to electric power generation and distribution, and more particularly to a direct current (DC) bus management controller and method for controlling a DC bus. 
         [0002]    Electrical power systems in hybrid vehicles, such as military hybrid vehicles, can include high voltage direct current (DC) power generation and distribution in systems having multiple loads and power sources. Some of the loads are regenerative loads, such as electrically driven actuators. Regenerative power from these loads may be returned to the distribution (system) bus. Conventional methods utilize shunt regulators to direct the regenerative power into power dissipation resistors. These methods require additional thermal management to reject generated heat losses, and typically do not allow for the capture and re-use of regenerative energy. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    Exemplary embodiments include a direct current bus management system, including a power management and distribution unit, having a source management section, a bus management section coupled to the source management section, a load management section coupled to the bus management section, a DC bus coupled to the power management and distribution unit, a plurality of DC sources coupled to the source management section and a plurality of loads coupled to the load management section, wherein the bus management section is configured to reconfigure excess DC power on the DC bus from the DC inputs from the plurality of DC sources based on a plurality of priorities, a plurality of feedback signals and a plurality of system parameters. 
         [0004]    Additional exemplary embodiments can include a power management and distribution apparatus, including a source management section, a bus management section coupled to the source management section, a load management section coupled to the bus management section, and a DC bus coupled to the source management section, the bus management section, and the load management section, wherein the bus management section is configured to reconfigure excess DC power on the DC bus based on a plurality of priorities, a plurality of feedback signals and a plurality of system parameters. 
         [0005]    Further exemplary embodiments include DC bus management method in a DC bus, the method including comparing a DC bus voltage against a plurality of voltage references, in response to an excess of the DC voltage compared to a first voltage reference of the plurality of voltage references, sending a first control signal instructing a first redirection of DC power in the DC bus, in response to an excess of the DC voltage compared to a second voltage reference of the plurality of voltage references, sending a second control signal instructing a second redirection of DC power in the DC bus and in response to an excess of the DC voltage compared to a third voltage reference of the plurality of voltage references, sending a third control signal instructing a third redirection of DC power in the DC bus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0007]      FIG. 1  illustrates a system diagram of a DC bus management system; 
           [0008]      FIG. 2  illustrates a system diagram of the DC bus management system of  FIG. 1  in further detail; 
           [0009]      FIG. 3  illustrates the DC bus management controller of  FIG. 2 ; and 
           [0010]      FIG. 4  is a flow chart that illustrates a DC management method in accordance with an embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    Embodiments include systems and methods for enabling DC bus system reconfiguration to redirect DC power in a high voltage DC system. The systems and methods described herein harvest regenerative energy by redirecting DC power to the energy storage device or converting the DC power to mechanical energy if the DC power cannot be stored, and thus maintain good power quality on the DC bus without the addition of large DC filters, during load transients. 
         [0012]      FIG. 1  illustrates a system diagram of a DC bus management system  100 . The system  100  includes a power management and distribution (PMAD) unit  105 , which includes a source management section  110  coupled to a bus management section  115 , which is coupled to a load management section  120 .  FIG. 1  thus illustrates the interrelation between functions of each of the source management section  110 , bus management section  115 , and the load management section  120 . The system  100  further includes multiple high voltage DC sources  125  (i.e., source  1 ,  2  . . . N) coupled to the source management section  110 , and multiple loads  130  coupled to the load management section  120 . The system  100  further includes a regenerative load  135  from which regenerative energy can be recovered as further described herein. An energy storage unit  140  and a power dissipater  145  can further be coupled to the bus management section  115 . In one embodiment, the energy storage unit  140  stores redirected DC energy, and the power dissipater  145  dissipates any unrecovered energy. The power dissipater  145  can be a power resistor. The power dissipater  145  can also include a temperature sensor to monitor the temperature. 
         [0013]    The source management section  110 , the bus management section  115  and the load management section  120  include various functions as described herein. In one embodiment, the source management section  110  provides source protective functions including but not limited to: over/under voltage; over-temperature; excessive voltage ripple; and differential protection. In one embodiment, the bus management section  115  provides autonomous reconfiguration and redirection of DC power based on priorities, feedback signals and system parameters for increased efficiency and performance of the system  100 . In one embodiment, the load management section  120  provides load protective functions including but not limited to: over-current; thermal memory; over/under voltage; over-temperature; excessive current ripple; and arc fault detection. The load management section  120  further provides: load stabilization by actively damping load voltage oscillations; current limiting; soft start of capacitive loads; and nuisance trip avoidance. 
         [0014]    As described above, the bus management section  115  provides autonomous reconfiguration and redirection of DC power for increased efficiency and performance of the system  100 . In one embodiment, the bus management section  115  executes a DC bus management process for providing the autonomous reconfiguration and redirection based on priorities, feedback signals and system parameters. The DC bus management process is described further herein and the following description discusses several of the supporting functions. 
         [0015]      FIG. 2  illustrates a system diagram of the DC bus management system  100  of  FIG. 1  in further detail. As described above, the system  100  includes the source management section  110 , the bus management section  115  and the load management section  120 . In one embodiment, one or all of the source management section  110 , the bus management section  115  and the load management section  120  include at least one solid state power controller (SSPC), which are implemented in power distribution systems to replace traditional electromechanical circuit breakers. The functions of the SSPC can include power distribution and protection of power to different loads to name a few. In comparison to electromechanical devices, an SSPC provides fast response time, and eliminates arcing during turn-off transients and bouncing during turn-on transients. SSPCs typically do not suffer severe degradation during repeated fault isolation as compared with electromechanical devices. SSPCs facilitate advanced protection and diagnostics, and provide more efficient power distribution architectures and packaging techniques, due to the smaller size and weight than compared to conventional electromechanical switches. As such, the SSPCs allow the source management section  110 , the bus management section  115  and the load management section  120  to perform the protective functions described herein. The SSPCs can be classified as unidirectional and bidirectional. Both type of SSPCs conduct current in both directions. A unidirectional SSPC can interrupt current only in one direction from source to load and this are implemented in load management. Bidirectional SSPC can interrupt current in both directions that enables source and bus management. 
         [0016]    Referring still to  FIG. 2 , the source management section  110  includes a bidirectional SSPC  111  coupled to a DC bus  200 . The SSPC  111  is further coupled to one or more DC sources  125 , one of which is illustrated in  FIG. 2 . It can be appreciated that the source management section  110  can include an additional SSPC for each additional source. As an illustrative example, the DC source  125  includes a prime mover (e.g., an internal combustion engine)  126 , a permanent magnet generator  127  that generates an AC voltage and an active rectifier  128  that converts the AC voltage to a DC voltage, and is coupled to the SSPC  111 . The bus management section  115  is also coupled to the DC bus  200 . In one embodiment, the bus management section  115  includes a first bidirectional SSPC  116  coupled to the DC bus  200 . The first SSPC  116  is also coupled to the energy storage unit  140 . As illustrated, the energy storage unit  140  further includes a battery  141  coupled to a DC-DC converter  142 , which converts DC to different levels of DC. The bus management section  115  includes a second SSPC  117  that is coupled to the DC bus  200 . The second SSPC  117  is also coupled to the power dissipater  145 . In one embodiment, the bus management section  115  further includes a DC bus management controller  118 . In one embodiment, the DC bus management controller  118  is coupled to the first and second SSPC  116 ,  117 , to the DC sources  125  and to a fan load  150 , which includes a motor drive  151  and fan  152 . In one embodiment, the DC bus management controller  118  redirects the unused DC power to the fan load  150  for cooling purposes if the DC bus management controller  118  cannot redirect the DC power to one of the other reusable sources (e.g., the energy storage unit  140 ). As such, the system  100  can redirect DC power to the fan load  150  to cool the system  100 . As further described herein, the DC bus management controller  118  sends and receives signals to instruct the system  100  how to redirect the DC power. As such, the DC bus management controller  118  coordinates bus connection and time duration to energy storage, energy dissipation (i.e., to the cooling fan), power dissipation to resistive loads, and DC sources. 
         [0017]    The load management section  120  is also coupled to the DC bus  200 . The load management section  120  includes a first SSPC  121  coupled to the DC bus  200  and to the fan load  150 . The load management section  120  further includes a second SSPC  122  coupled to the DC bus  200  and to the regenerative load  135 . The load management section  120  includes a third SSPC  123  coupled to the DC bus  200  and to the non-regenerative load  130 . The first, second and third SSPCs  121 ,  122 ,  123  provide the protective functions to the fan load  150 , the regenerative load  135  and the non-regenerative load  130  as described herein. 
         [0018]      FIG. 3  illustrates the DC bus management controller  118  of  FIG. 2 . As described herein, the DC bus management controller  118  receives various feedback signals  305 , parameters  310  and priorities  315  to determine how to redirect DC power. In one embodiment, the feedback signals  305  include but are not limited to: DC bus voltage; battery voltage; cooling fan speed; and temperature of a power dissipating resistor. The DC bus management controller  118  can monitor the battery charge to determine if the energy storage unit  140  is available to receive energy for storage. The DC bus management controller  118  can monitor the fan  152  speed to see if it is available to speed up in the event of extra DC power. The DC bus management controller  118  can monitor the temperature of the power dissipater  145  to see if it has a temperature suitable to receive extra DC power. 
         [0019]    In one embodiment, the parameters  310  include but are not limited to: DC bus voltage; maximum battery charge rate; maximum fan speed; maximum power dissipation resistor temperature; and maximum generator negative torque. The maximum battery charge rate determines how fast the battery  141  can charge in the event DC energy is directed to the battery  141 . The maximum fan speed determines the speed limit if DC power is diverted to it. The maximum power dissipation resistor temperature determines the upper limit of how high the temperature of the power dissipater  145  can be if DC power is redirected to it. The maximum generator negative torque determines how much reverse torque can be applied in one of the DC loads  125 . 
         [0020]    In one embodiment, the priorities  315  include, but are not limited to: DC bus power quality; energy storage; load increase (e.g., fan load  150 ); power dissipation resistor; and generator torque reversal. As such, priorities can be set to determine how extra DC power is redirected. 
         [0021]    The DC bus management controller  118  can also generate various control signals in response to the received feedback signals  305 , parameters  310  and priorities  315 . In one embodiment, the DC bus management controller  118  can generate: an energy storage signal  320 ; a power dissipation signal  325 ; an active rectifier signal  330 ; and a cooling fan signal  335 . In one embodiment, the energy storage signal  320  controls the first SSPC  116  in the bus management section  115  to enable energy storage in the energy storage unit  140 . In one embodiment, the signal  325  controls the second SSPC  117  in the bus management section  115  to enable power dissipation in the power dissipater  145 . In one embodiment, the third signal  330  is a negative current reference limit (i.e., Iq_neg_limit) that controls negative torque of the permanent magnet generator  127 . In one embodiment, the fourth signal  335  (i.e., spd_ref) sets the speed of the cooling fan (e.g., the fan  152 ). 
         [0022]    The function and form of the signals  320 ,  325 ,  330 ,  335  are further discussed with respect to  FIG. 4 , which illustrates a flow chart of a method  400  of a DC management method (process)  400  in accordance with an embodiment. The method  400  also demonstrates how the DC bus management controller  118  receives several feedback signals  305  and compares them with various parameters  310 . At block  405 , the DC bus management controller  118  checks the DC bus voltage against a first DC reference. If the DC bus voltage is not greater than the first DC reference at block  405 , then the method  400  ends. If the DC bus voltage is greater than the first DC reference at block  405 , then the DC bus management controller  118  determines if the battery  141  is charged at block  410 . If the battery  141  is not charged, then the DC bus management controller  118  determines if a battery charge rate is above a predetermined reference at block  415 . If at block  415 , the battery charge rate is not above the predetermined reference, then at block  425 , the DC bus management controller  118  turns on the first SSPC  116 , which sends the energy storage signal  320  to power on the energy storage unit  140 . If the DC bus management controller  118  determines either that the battery  141  is charged at block  410  or that the battery charge rate is above the predetermined reference at block  415 , then at block  420 , the DC bus management controller  118  turns off the first SSPC  116 , which sends the energy storage signal  320  to power off the energy storage unit  140   
         [0023]    Referring still to  FIG. 4 , processing progresses from both blocks  420  and  425  to block  430  where the DC bus management controller  118  checks the DC bus voltage against a second DC reference. If the DC bus voltage is not greater than the second DC reference then the DC bus management controller  118  sets the speed reference signal  335  to a nominal speed at block  440 , which directly controls the motor drive  151  and thus the fan  152 , and the method  400  ends. If the DC bus voltage is greater than the second DC reference as determined at block  430 , then the DC bus management controller  118  determines if the fan speed is equal to a maximum fan speed parameter at block  435 . If the fan speed is not equal to a maximum fan speed parameter, then at block  445  the DC bus management controller  118  sets the speed reference signal  335  to maximum, and then at block  450 , the DC bus management controller  118  checks the DC bus voltage against a third DC reference at block  450 . If the DC bus voltage is not greater than the third DC reference at block  450 , then the DC bus management controller  118  sets the active rectifier signal  330  to nominal at block  475 , which maintains any negative torque to the permanent magnet generator  127 . In addition, the DC bus management controller  118  turns off the second SSPC  117  at block  465 , which sends the power dissipation signal  325  to power off the power dissipater  145 , and the method  400  ends. If the DC bus voltage is greater than the third DC reference at block  450 , or if the fan speed is not equal to a maximum fan speed parameter at block  435 , then the DC bus management controller  118  determines if the power dissipater  145  temperature is greater than a predetermined reference at block  455 . If the power dissipater  145  temperature is not greater than a predetermined reference at block  455 , then at block  460  the DC bus management controller  118  turns on the second SSPC  117  at block  460 , which sends the power dissipation signal  325  to power on the power dissipater  145 , and the method  400  ends. If the power dissipater  145  temperature is determined to be greater than a predetermined reference at block  455 , then the DC bus management controller  118  turns off the second SSPC  117  at block  465 , which sends the power dissipation signal  325  to power off the power dissipater  145 . In addition, the DC bus management controller  118  sets the active rectifier signal  330  to maximum at block  470 , which increases negative torque to the permanent magnet generator  127  to enable reversal of power flow and reduce dc bus overvoltage condition, and the method  400  ends. 
         [0024]      FIG. 4  illustrates an example of priorities set in the DC bus management controller  118 . In addition, the three reference voltages are increasingly larger. As such, if the first reference is exceeded, then the DC bus management controller  118  redirects the extra DC energy to charge the battery. If the second reference is exceeded, the DC bus management controller  118  attempts to increase cooling to the system  100 . If the fan  152  is already at its maximum speed, and/or of the third reference voltage is exceeded, then the DC bus management controller  118  attempts to decrease the input DC load and if necessary dissipates the extra DC energy. It can be appreciated that the order in which these priorities are set can change in other embodiments. 
         [0025]    The DC bus management controller  118  can be any suitable microcontroller or microprocessor for executing the instructions (e.g., on/off commands) described herein. As such, the suitable microcontroller or microprocessor can be any custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors, a semiconductor based microprocessor (in the form of a microchip or chip set), a microprocessor, or generally any device for executing software instructions. 
         [0026]    Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
         [0027]    The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
         [0028]    Technical effects include the capturing of regenerative energy and improvement of power quality on DC buses. 
         [0029]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.