Abstract:
The entire right, title and interest in and to this application and all subject matter disclosed and/or claimed therein, including any and all divisions, continuations, reissues, etc., thereof are, effective as of the date of execution of this application, assigned, transferred, sold and set over by the applicant(s) named herein to Deere &amp; Company, a Delaware corporation having offices at Moline, Ill. 61265, U.S.A., together with all rights to file, and to claim priorities in connection with, corresponding patent applications in any and all foreign countries in the name of Deere &amp; Company or otherwise.

Description:
[0001]    This document (including all drawings) claims priority based on U.S. provisional application Ser. No. 60/781,167, filed Mar. 10, 2006, under 35 U.S.C. 119(e). 
     
    
       [0002]    This invention was made with U.S. government support under Cooperative Agreement No. DE-FC26-05NT42422 awarded by the Department of Energy (DOE). The U.S. government has certain rights in this invention. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates to a method and system for managing an electrical output of a turbogenerator. 
       BACKGROUND OF THE INVENTION 
       [0004]    A turbogenerator may comprise a turbine in communication with exhaust gas or steam associated with an internal combustion engine. The turbine is mechanically coupled to a primary generator or alternator that generates electrical energy that may be used by one or more components of the vehicle. The internal combustion engine may mechanically drive a secondary alternator or generator that generates electrical power. Accordingly, there is need to manage an output of both the primary generator and the secondary generator to use efficiently the generated power. 
       SUMMARY OF THE INVENTION 
       [0005]    The system and method manages an electrical output of a turbogenerator in accordance with multiple modes. In a first mode, a direct current (DC) bus receives power from a turbogenerator output via a rectifier where turbogenerator revolutions per unit time (e.g., revolutions per minute (RPM)) or an electrical output level of a turbogenerator output meet or exceed a minimum threshold. In a second mode, if the turbogenerator revolutions per unit time or electrical output level of a turbogenerator output are less than the minimum threshold, the electric drive motor or a generator mechanically powered by the engine provides electrical energy to the direct current bus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a block diagram of one embodiment of a system for managing an electrical output of a turbogenerator. 
           [0007]      FIG. 2  shows illustrative schematic representations for corresponding blocks of  FIG. 1 . 
           [0008]      FIG. 3  is a flow chart of one embodiment of a method for managing an electrical output of a turbogenerator. 
           [0009]      FIG. 4  is a flow chart of another embodiment of a method for managing an electrical output of a turbogenerator. 
           [0010]      FIG. 5  is a block diagram of another embodiment of a system for managing an electrical output of a turbogenerator. 
           [0011]      FIG. 6  is a block diagram of yet another embodiment of a system for managing an electrical output of a turbogenerator. 
           [0012]      FIG. 7  is a flow chart of another embodiment of a method for managing an electrical output of a turbogenerator. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    In  FIG. 1  and  FIG. 2 , a turbogenerator electrical output  11  of a turbogenerator  10  is coupled to a rectifier input  13  of a rectifier  12 . A rectifier output  15  of the rectifier  12  is connected to a filter input  17  of a filter  16 . The filter  16  filters the direct current signal for the direct current (DC) bus  14 . A filter output  19  of the filter  16  is coupled to an inverter  26 . The inverter  26  communicates a control signal (e.g., variable frequency or variable pulse width modulated signal) to a motor/generator  28 . The motor/generator  28  comprises: (a) a motor or electric drive in a propulsion mode and (b) a generator or alternator during a power generation mode. In the propulsion mode, the motor is capable of rotating a motor output shaft, whereas in the power generation mode the generator converts mechanical rotational energy into electrical energy. It is understood by those of skill in the art that the terms “motor”, “generator”, or “alternator” could be used generally interchangeably with “motor/generator,” without any loss of functionality, limitation of mode, or meaning with the caveat that “alternator” may appropriately refers to alternating current (AC) configurations. 
         [0014]    A converter  30  (e.g., DC-DC converter or Buck converter) is coupled across the direct current bus  14 , the filter output  19 , or both to provide a direct current (DC) output port  31 . The filter output  19  may feed electrical energy to an input of the converter  30 . The converter  30  provides direct current (DC) at the output port  31  at a desired output level (e.g., higher or lower than the level of the DC bus  14 ). For example, the converter  30  regulates a second voltage level (or desired output level) associated with an output port  31  to differ from a first voltage level associated with the direct current bus  14 . 
         [0015]    A first sensor  18  (e.g., tachometer) is associated with a turbogenerator. The first sensor  18  measures the rotation per unit time, angular displacement per unit time, rotational velocity, rotational speed, or rotational acceleration of a shaft, rotor, turbine, turbine blade or other rotational member of a turbogenerator  10 . In one configuration, the first sensor  18  may monitor a number of voltage pulses per unit time associated with the rectifier  12  or the back electromotive force (EMF) produced in the windings of the primary generator  42  to infer or estimate the rotational speed of the shaft, rotor, turbine, or turbine blades. 
         [0016]    A second sensor  48  may comprise any sensor that detects braking or deceleration of the vehicle. For example, the second sensor  48  may comprise one or more accelerometers associated with the vehicle, a contact switch or an optical switch associated with the brake pedal of the vehicle, a piezo-electric device associated with the brake actuator or braking pads, a electro-hydraulic flow sensor, or another suitable sensor. The first sensor  18  and the second sensor  48  are coupled to a mode controller  22  to provide input data or input signals thereto. 
         [0017]    The mode controller  22  controls the motor/generator  28 . For example, the mode controller  22  may select a propulsion state or an energy generation state of the motor/generator  28  based on the input data or input signals from the sensors ( 18 ,  48 ). The mode controller  22  may comprise a comparator, a logic circuit, a logic unit, programmable digital signal processors, a microcontroller, or other data processor or a software module that determines whether the turbogenerator revolutions per unit time, or first sensor data or a signal representative thereof, exceed a minimum threshold or reference range. If the turbogenerator revolutions per unit time exceed the minimum threshold or range, the mode controller  22  may generate one or more control signals to control the states of switches in the switching circuit  24 . 
         [0018]    In an alternate embodiment, the mode controller  22  controls one or more states of a secondary generator  20 . For example, the mode controller  22  may activate (or engage) an electromagnetic clutch to impart rotational energy directly or indirectly from a shaft (e.g., crankshaft) of the internal combustion engine  50  to the secondary generator  20  in the second mode, whereas the mode controller  22  may deactivate (or disengage) an electromagnetic clutch to remove rotational energy from the secondary generator  20  in the first mode. 
         [0019]    In one embodiment, the turbogenerator  10  comprises a turbine (e.g., an exhaust-driven turbine) in communication with exhaust gas or steam associated with an internal combustion engine  50 . The turbine is mechanically coupled to a primary generator  42  (e.g., alternator) that generates electrical energy that may be used by one or more components of the vehicle. Although the internal combustion engine  50  may be run at target or target range of revolutions per unit time (e.g., 1,800 to 2,200 revolutions per minute) of a shaft (e.g., crankshaft) for efficient operation, the internal combustion engine  50  may be run at virtually any revolutions per unit time within its operational range. A fuel delivery system (e.g., fuel injection system or carburetion system) may be associated with a controller (e.g., regulator) for metering or otherwise regulating the flow of fuel to maintain the target or target range of revolutions per unit time, for example. 
         [0020]    The internal combustion engine  50  is capable of driving the secondary generator  20  (e.g., alternator) to generate electrical power. The secondary generator  20  may be associated with a clutch (e.g., an electromagnetic clutch), but is not necessarily associated with a clutch, for coupling and decoupling to mechanical or rotational energy provided by the engine  50 . 
         [0021]    The electrical output of the secondary generator  20  may be rectified within the secondary generator  20  or via a secondary rectifier coupled to an electrical output of the secondary generator  20 . The rectified electrical output of the secondary generator  20  is coupled to the direct current bus  14 . For example, the electrical output of the secondary generator  20  and the filter  16  are coupled in parallel to the DC bus  14 . The rectifier  12  provides isolation to prevent the electrical current generated by the secondary generator  20  from flowing into the primary generator  42  (e.g., the windings of the primary generator  42 ). 
         [0022]    In one embodiment, as best illustrated in  FIG. 2 , the rectifier  12  comprises pairs of diodes. Each pair comprises a first diode  27  coupled in series to a second diode  29 . An anode of the first diode  27  is coupled to one rail of the unrectified DC bus  25 , whereas a cathode of the second diode  29  is coupled to another rail of the unrectified DC bus  25 . 
         [0023]    In one embodiment, the filter  16  may comprise the combination of a capacitor  31  placed in parallel across the rectified DC bus  25 , and an inductor  33  in series with one rail of the unrectified DC bus  25 . The capacitor  31  may comprise an electrolytic capacitor or a similar capacitor to smooth voltage ripples (or electrical transients) that might otherwise appear on the DC bus  14 . In one configuration, the frequency response of rectifier  12 , the filter  16  or both is selected to reduce or attenuate unwanted harmonics in the generated electrical energy of the primary generator  42  by a minimum amount at the DC bus  14 . 
         [0024]    The inverter  26  may comprise one or more semiconductors arranged in a switch mode configuration. Here, the semiconductors are shown as NPN transistors (e.g., power switching transistors) for illustrative purposes. Although the schematic representation of the inverter  26  omits biasing networks and control circuitry for the NPN transistors and other components, such biasing networks and control circuitry for switch mode inverters are generally well known. 
         [0025]    In general, the mode controller  22  may provide one or more of the following: (1) biasing networks and control circuitry (e.g., logic circuits) to operate the inverter  26  one or more distinct modes, (2) control data or control signal to operate the inverter in one or more distinct modes, (3) biasing networks and control circuitry (e.g., logic circuits) to operate the secondary generator  20  or an electromagnetic clutch associated therewith in one or more distinct states, and (4) control data or control signals to operate the secondary generator  20  or electromagnetic clutch associated therewith in one or more distinct states. In a first mode, the mode controller  22  controls the inverter  26  to support the acceptance of generated electrical energy from the primary generator  42 , the secondary generator  20 , or both. Further, the mode controller  22  controls the inverter  26  to support the flow of the generated electrical energy from the primary generator  42  to the DC bus  14  or the motor/generator  28 . In the second mode, mode controller  22  supports the generation of electrical energy by the motor/generator  28  and its flow from the motor/generator  28  to the DC bus  14 . 
         [0026]    In the first mode, the inverter  26  may chop or process the DC signal on the DC bus  14  to output an alternating current (AC) output signal suitable for energizing the drive motor  28 . In one example, the inverter  26  provides a variable frequency drive signal with one or more phases for the motor  28 . In another example of the first mode, the inverter  26  supports the pulse-width modulation of the inputted DC signal at the inverter input  21  to produce a variable or controllable AC output signal for driving the motor/generator  28 . 
         [0027]    In the second mode, the mode controller  22  or inverter  26  may control the switches (e.g., NPN transistors) to regulate the voltage and current of electrical energy output by the motor/generator  28  and to provide rectification of any alternating current output to a direct current output. 
         [0028]    In one example, the converter  30  (e.g., DC-DC converter) may comprise a Buck converter  30 . In one embodiment, the converter  30  accepts a DC input voltage from the DC bus  14  and provides a different DC output voltage at the output port  31 . For example, the output port  31  of the converter  30  provides a higher or lower voltage DC output. The output port  31  may be used to power auxiliary components, electronics, electric fans, electric motors, electric fuel pumps, electric pumps, or other electrical or electronic devices or vehicular accessories besides the drive motor  28 . Further, the converter  30  may provide noise isolation or regulation of the DC voltage output at the output port  31 . 
         [0029]    Although the configuration of  FIG. 2  illustrates the converter  30  as a step-down Buck converter  30  in which the DC voltage level from the DC bus  14  is generally decreased, any configuration of converter  30  may be used and falls within the scope of the invention. For example, interchanging the diode  31  and inductor  33  in the circuit of  FIG. 2  results in a step-up Buck converter  30  or boosting Buck converters that may be used for DC-DC converter  30  in which the DC voltage level from the DC bus  14  is generally increased at the output port  31  and higher than that of the DC bus  14 . Other types of DC converters for DC-DC converter  30  include inverting, push-pull, half-bridge and full bridge, among other possibilities. Some DC converters may support bi-directional current flow with voltage regulated output for output port  31 , such that an energy storage device (e.g., battery of a desired voltage level or range) could be coupled across the output port  31  to provide reserve electrical energy for the motor/generator  28 . 
         [0030]    The system of  FIG. 1  and  FIG. 2  may operate any of several distinct power generation modes, which may be applied alternately are cumulatively. Under a first mode, a turbine  40  of the turbogenerator  10  provides electrical power from the turbine&#39;s conversion of exhaust gas into mechanical energy. The primary generator  42  converts the mechanical energy into electrical energy, which the switching circuit  24  may make available to the drive motor  28 , the converter  30 , or both. The first mode is active when the turbogenerator revolutions per unit time (e.g., RPM) is above or equal to a minimum threshold. 
         [0031]    In an alternate embodiment, the first mode may include the secondary generator  20  providing electrical energy to the DC bus  14  in parallel with the turbogenerator output the primary generator  42 . For example, the mode controller  22  may control (e.g., activate or deactivate) an electromagnetic clutch associated with the secondary generator  20  to selectively apply or withdraw rotational energy to the secondary generator  20  from the internal combustion engine  50  in accordance with load requirements or demand on the DC bus  14 . 
         [0032]    Under a second mode, the internal combustion engine  50  mechanically drives a secondary generator  20  to convert mechanical energy into electrical energy. The second mode is generally active when the turbogenerator revolutions per unit time (e.g., RPM) are below the minimum threshold. 
         [0033]    In a third mode or regenerative braking mode, the motor/generator  28  acts as a tertiary generator for the vehicle. In the third mode, the motor/generator  28  or tertiary generator may be coupled to the inverter  26  to facilitate rectification of an alternating current signal provided by the motor  28  or tertiary generator, regulation of the generated electrical current, and voltage, or both rectification and regulation. The third mode is active when the vehicle is braking or when the vehicle is decelerating in accordance with an operator&#39;s input or otherwise. 
         [0034]    The system for managing electrical output of a turbogenerator may support the simultaneous operation of multiple modes, among the first mode, the second mode and the third mode. To support operation in multiple modes, the rectifier  12  and inverter  26  facilitate parallel interconnections of two or more outputs associated with the primary generator  42 , the secondary generator  20 , and the tertiary generator (i.e., the motor  28 ). In an alternate embodiment, one or more diode networks may be used at the DC bus  14  for coupling and isolating the output signals of the generators ( 42 ,  20 , and  28 ) in parallel. Each diode network may comprise at least one diode, or multiple diodes in parallel, for a corresponding terminal of the DC voltage bus at a corresponding generator output. For example, a first diode network is placed in series with a DC terminal output (e.g., positive terminal) of the primary generator  42 , a second network is placed in series with the DC terminal output (e.g., a positive terminal) of the secondary generator  20 , and the third diode network is coupled in series with the DC terminal output (e.g., positive terminal) of the tertiary generator, and the appropriate terminals (e.g., cathode terminals where the above DC terminal is positive and anode where the DC terminal polarity is negative) of the diode networks are coupled together at a common connection node that feeds the common DC terminal (e.g., positive terminal) of the DC bus  14 . The diode networks facilitate simultaneous application of or power generation in at least two of the first mode, the second mode, and the third mode. Further, such diode networks may support redundancy or a controlled failure mode, where the rectifier  12  is disabled or fails. 
         [0035]      FIG. 3  is a method for managing electrical output of a turbogenerator  10  in accordance with multiple modes. The system of  FIG. 1  and  FIG. 2  may be applied to carry out the method of  FIG. 3 . The method of  FIG. 3  begins in step S 100 . 
         [0036]    In step S 100 , a first sensor  18  detects revolutions per unit time (e.g., revolutions per minute (RPM)) for a turbogenerator  10 . The first sensor  18  may comprise a tachometer or another sensor for measuring turbogenerator revolutions per unit time of a shaft, rotor, turbine, or other rotation member associated with the turbogenerator  10 . For example, the shaft, rotor, or other rotational member of the primary generator  42  may be associated with a magnet (or electromagnet) for rotation therewith. Alternately, a shaft, rotor, turbine blades or other rotational member of the turbine  40  may be associated with a magnet for rotation therewith. A stationary sensing coil coupled to a detection circuit may measure or count current fluctuations (or voltage fluctuations) per unit time imparted into coil to estimate the revolutions per unit time of the shaft, rotor, turbine blades, or other rotational member. 
         [0037]    In step S 102 , the mode controller  22  determines if turbogenerator revolutions per unit time meet or exceed a minimum threshold. The user may establish the minimum threshold that is proportional to or based on the electrical energy (e.g., current level, voltage level, or both) generated by the turbogenerator  10  at or above the minimum threshold, for example. The electrical energy generated by the turbogenerator  10  below the threshold may be insufficient to produce a reliable direct current (DC) waveform at the DC bus  14  that is capable of driving the motor  28  via the inverter  26 . If the turbogenerator revolutions per unit time meet or exceed the minimum threshold, the method continues with step S 104 . However, if the turbogenerator revolutions per unit time do not exceed the minimum threshold, the method continues with step S 108 . 
         [0038]    In step S 104 , the turbogenerator  10  supplies or outputs electrical energy to at least one of a rectifier  12  and a direct current (DC) bus  14  in a first mode. For example, the rectifier  12  rectifies the outputted electrical energy from the turbogenerator output prior  11  to applying it to the direct current bus  14  in the first mode. The mode controller  22  controls the inverter  26  to accept output electrical energy from a turbogenerator output  11  (e.g., primary generator output) in a first mode. 
         [0039]    In one illustrative example, step S 104  may be carried out as follows. The turbine  40  imparts mechanical rotation of the primary generator  42  to produce alternating current (AC) electrical energy, which is rectified by the rectifier  12 . The rectifier output  15  and the filter input  17  are associated with the unfiltered or unrectified DC bus. The filter  16  filters the rectified signal for the filter output  19 . The filter output  19  may provide the generated electrical energy to the DC bus  14 . 
         [0040]    In step S 106 , following step S 104 , or simultaneously therewith, the mode controller  22  controls the inverter  26  to accept to output electrical energy from the primary generator  42  for the electric drive motor  28  in the first mode. In turn, the converter  30  provides a DC output voltage at the DC output port  31 . 
         [0041]    In step S 108 , the secondary generator  20  supplies or outputs a generator output to the direct current bus  14  in a second mode. Further, the mode controller  22  controls the inverter  26  to accept output electrical power from a generator output of the secondary generator  20  to the direct current bus  14  in the second mode. Step S 108  may be carried out in accordance with several techniques that may be applied cumulatively or separately. 
         [0042]    The method of  FIG. 4  is similar to the method of  FIG. 3 , except steps S 107  and S 109  are added. Like reference numbers in  FIG. 3  and  FIG. 4  indicate like steps or procedures. Step S 107  may be executed after step S 106 , for example. 
         [0043]    In step S 107 , a mode controller  22  or second sensor  48  determines whether a vehicle is braking or whether an operator is applying the brakes of the braking system. The braking system may comprise a hydraulic braking system, an electrical braking system, a mechanical braking system, a friction braking system, a magnetic or electromagnetic braking system, or the like. If the vehicle is braking or if an operator is applying the brakes, the method continues with step S 109 . However, if the vehicle is not braking, the method continues with step S 104 . 
         [0044]    In step S 109 , the electric drive motor/generator  28  (which is also referred to as the tertiary generator when operating in a power generation mode) outputs electrical energy to the direct current bus  14  (e.g., via the inverter  26 ), while operating in a power generation mode or regenerative braking mode. The drive motor/generator  28  may complement or supersede the braking function of the other braking system of the vehicle, during step S 109 . In accordance with one example of carrying out step S 109 , the mode controller  22  may control the inverter  26  to act as a supplemental rectifier and a regulator of electrical output generated by the motor/generator  28 . 
         [0045]    Accordingly, in step S 109  the drive motor  28  is used in a power generation mode as a tertiary power generator by opposing the motion or momentum of the vehicle, either alone or in combination with the braking system of the vehicle. In step S 109 , the mode controller  22  may determine that the drive motor/generator  28  is generally not used as a tertiary power generator if the vehicle is not moving or if the operator needs to increase the speed or acceleration of the vehicle, or if the internal combustion engine does not indirectly or directly drive at least one wheel of the vehicle, for example. 
         [0046]    In step S 106 , the turbogenerator  10  or primary generator  42  provides the outputted electrical energy to at least one of a DC output port and the electric drive motor in the first mode. Step S 106  is described in greater detail in conjunction with  FIG. 3 . 
         [0047]    The system of  FIG. 5  is similar to the system of  FIG. 1 , except the system of  FIG. 5  deletes the second sensor  48 . Like reference numbers in  FIG. 1 ,  FIG. 2 , and  FIG. 5  indicate like elements. 
         [0048]    The system of  FIG. 6  is similar to the system of  FIG. 1 , except the system of  FIG. 6  replaces first sensor  18  with first sensor  118  and deletes the second sensor  48 . Like reference numbers in  FIG. 1 ,  FIG. 2 , and  FIG. 4  indicate like elements. 
         [0049]    The first sensor  118  comprises an electrical level sensor. For example, the electrical level sensor may comprise a voltage meter, a current meter, a comparator, a resistive bridge, or another circuit for measuring changes in current or voltage or signal quality generated by the primary generator  42  of the turbogenerator  10 . Rather than measuring the turbogenerator revolutions per unit time, the first sensor  118  measures changes in current, voltage or signal quality to facilitate determination of the proper mode by the mode controller  22 . For example, if the electrical output current level or voltage level (e.g., current level or voltage level) of the primary generator  42  falls above or equals a minimum threshold, the mode controller  22  may instruct the switching circuit  124  to operate in a first mode. However, if the current level or voltage level is less than a minimum threshold, the mode controller  22  may instruct the switching circuit  124  to operate in a second mode. 
         [0050]    The method of  FIG. 7  is similar to the method of  FIG. 3 , except  FIG. 7  replaces step S 100  and S 102 , with steps S 200  and S 202 , respectively. Like reference numbers in  FIG. 7  and  FIG. 3  indicate like steps or procedures. 
         [0051]    In step S 200 , a first sensor  118  detects an electrical output level (e.g., current level, voltage level) outputted by the turbogenerator  10  or the primary generator  42  during an evaluation time window. As previously indicated, the speed sensor  118  may comprise a volt meter, a voltage level detector, a comparator, a current meter, a current detector, or another sensor for measuring an electrical output of the primary generator  42 . 
         [0052]    In step S 202 , the mode controller  22  determines if the detected electrical level exceeds a minimum threshold. The user may establish the minimum threshold with reference to the electrical energy (e.g., current level, voltage level, or both) generated by the turbogenerator  10  under various load conditions, for example. The electrical energy generated by the turbogenerator  10  below the threshold may be insufficient to produce a reliable direct current (DC) waveform at the DC bus  14  that is capable of driving the motor  28  via the inverter  26 . If the detected electrical level exceeds a minimum threshold, the method continues with step S 104 . However, if the detected electrical level does not exceed the minimum threshold, the method continues with step S 108 . Steps S 104  and S 108  were previously described in conjunction with  FIG. 3 , and apply equally to  FIG. 7 . 
         [0053]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.