Patent Publication Number: US-9413184-B2

Title: Pre-charging and voltage supply system for a DC-AC inverter

Description:
BACKGROUND 
     The inventor herein has recognized a need for an improved pre-charging and voltage supply system and a method for pre-charging and supplying voltages to an DC-AC inverter, which eliminates a pre-charging contactor and a pre-charging resistor. 
     SUMMARY 
     A pre-charging and voltage supply system for a DC-AC inverter in accordance with an exemplary embodiment is provided. The pre-charging and voltage supply system includes a first battery having a first anode and a first cathode. The first battery is adapted to generate a first voltage level between the first anode and the first cathode. The pre-charging and voltage supply system further includes a contactor electrically coupled in series with and between the first anode and an electrical node. The pre-charging and voltage supply system further includes a first voltage sensor electrically coupled between and to the electrical node and the first cathode. The first voltage sensor is adapted to generate a first voltage signal indicative of a voltage level between the electrical node and the first cathode. The pre-charging and voltage supply system further includes a DC-DC voltage converter electrically coupled between and to the electrical node and the first cathode. The pre-charging and voltage supply system further includes a second battery having a second anode and a second cathode. The second anode is electrically coupled to the DC-DC voltage converter. The second battery is adapted to generate a second voltage level between the second anode and the second cathode. The second voltage level is less than the first voltage level. The pre-charging and voltage supply system further includes a microprocessor operably coupled to the first voltage sensor and the DC-DC voltage converter. The microprocessor is programmed to generate a first control signal to induce the DC-DC voltage converter to increase a voltage level between the electrical node and the first cathode, utilizing a voltage from the second battery. The microprocessor is further programmed to generate a second control signal to induce the contactor to transition a contact from an open operational position to a closed operational position such that the first voltage level from the first battery is applied to the DC-AC inverter, if the voltage level between the electrical node and the first cathode is greater than a threshold voltage level. 
     A method for pre-charging and supplying voltages to an DC-AC inverter in accordance with another exemplary embodiment is provided. The method includes providing a pre-charging and voltage supply system having a first battery, a contactor, a first voltage sensor, a DC-DC voltage converter, a second battery, and a microprocessor. The first battery has a first anode and a first cathode. The contactor is electrically coupled in series with and between the first anode and an electrical node. The first voltage sensor is electrically coupled between and to the electrical node and the first cathode. The DC-DC voltage converter is electrically coupled between and to the electrical node and the first cathode. The second battery has a second anode and a second cathode. The second anode is electrically coupled to the DC-DC voltage converter. The DC-AC inverter is electrically coupled between and to the electrical node and the first cathode. The microprocessor is operably coupled to the first voltage sensor and the DC-DC voltage converter. The method includes generating a first voltage level between the first anode and the first cathode of the first battery. The method further includes generating a second voltage level between the second anode and the second cathode of the second battery. The second voltage level is less than the first voltage level. The method further includes generating a first control signal from the microprocessor to induce the DC-DC voltage converter to increase a voltage level between the electrical node and the first cathode, utilizing the second voltage level. The method further includes generating a first voltage signal indicative of the voltage level between the electrical node and the first cathode, utilizing the first voltage sensor, which is received by the microprocessor. The method further includes generating a second control signal to induce the contactor to transition a contact from an open operational position to a closed operational position utilizing the microprocessor such that the first voltage level from the first battery is applied to the DC-AC inverter, if the voltage level between the electrical node and the first cathode is greater than the threshold voltage level. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of an electric vehicle having a pre-charging and voltage supply system in accordance with an exemplary embodiment, an AC-DC inverter, and a vehicle motor system; and 
         FIGS. 2-3  are flowcharts of a method for pre-charging and supplying voltages to a DC-AC inverter in accordance with another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an electric vehicle  10  having a pre-charging and voltage supply system  30  in accordance with an exemplary embodiment, a DC-AC inverter  40 , a vehicle motor system  50 , and a vehicle controller  52  is illustrated. An advantage of the pre-charging and voltage supply system  30  is that the system  30  utilizes a DC-DC voltage converter  120  and a second battery  130  to pre-charge capacitors in the DC-AC inverter  40 , instead of using an additional pre-charging contactor and an additional pre-charging resistor. 
     The pre-charging and voltage supply system  30  is provided to pre-charge at least one capacitor in the DC-AC inverter  40  to limit an amount of electrical inrush current from the first battery  60  into the DC-AC inverter  40  when the contactor  80  has a closed operational position. After the pre-charging operation, the system  30  provides an operational voltage level from the first battery  60  to the DC-AC inverter  40 , and sends a control signal to the DC-AC inverter  40  to induce the DC-AC inverter  40  to output AC voltages corresponding to a desired torque amount. 
     The pre-charging and voltage supply system  30  includes the first battery  60 , a voltage sensor  70 , the contactor  80 , a contactor driver  90 , an electrical node  100 , a voltage sensor  110 , the DC-DC voltage converter  120 , and a second battery  130 . 
     The first battery  60  has an anode  140  and a cathode  142 . The first battery  60  is adapted to generate a first voltage level between the anode  140  and the cathode  142 . In an exemplary embodiment, the first battery  60  comprises a lithium-ion battery pack having a plurality of battery cells electrically coupled together therein. Of course, in an alternative embodiment the first battery  60  could comprise another type of battery such as a nickel-cadmium battery a nickel-metal-hydride battery, or a lead acid battery for example. Further, in an exemplary embodiment, the first battery  60  outputs substantially 48 volts DC (VDC). Of course, in an alternative embodiment, the first battery  60  could output another voltage level. For example, the first battery  60  could output a voltage in a range of 300-400 VDC, or in a range greater than 400 VDC. 
     The voltage sensor  70  is the electrically coupled in parallel with the first battery  60 , and further electrically coupled to the anode  140  and the cathode  142  of the first battery  60 . The voltage sensor  70  is adapted to generate a voltage signal (V P ) indicative of a voltage level output by the first battery  60 . The microprocessor  135  receives the voltage signal (V P ) from the voltage sensor  70  and determines the voltage level output by the first battery  60  based on the voltage signal (V P ). 
     The contactor  80  is electrically coupled in series with and between the first anode  60  and the electrical node  100 . The contactor  80  includes a contactor coil  82  and a contact  83 . When the microprocessor  135  generates a control signal that is received by the contactor driver  90 , the contactor driver  90  energizes the contactor coil  82  which moves the contact  83  to a closed operational position. Alternately, when the microprocessor  135  stops generating the control signal, the contactor driver  90  de-energizes the contactor coil  82  which moves the contact  83  to an open operational position. 
     The voltage sensor  110  is electrically coupled between and to the electrical node  100  and the cathode  142 . The voltage sensor  110  is adapted to generate a voltage signal (V L ) indicative of a voltage level between the electrical node  100  and the cathode  142 . The microprocessor  135  receives the voltage signal (V L ) from the voltage sensor  110  and determines the voltage level voltage level between the electrical node  100  and the cathode  142  based on the voltage signal (V L ). 
     The DC-DC voltage converter  120  is electrically coupled between and to the electrical node  100  and the cathode  142 . The DC-DC voltage converter  120  is further electrically coupled to the anode  240  of the battery  130 . The DC-DC voltage converter  120  is provided to output a voltage level between the electrical node  100  and the cathode  142  that is greater than a voltage level output by the battery  130 , utilizing the voltage level output by the battery  130 , to pre-charge at least one capacitor in the DC-AC inverter  40 . During operation, the microprocessor  135  generates a control signal is received by the DC-DC voltage converter  120 , and in response the DC-DC voltage converter  120  outputs a predetermined voltage level between the electrical node  100  and the cathode  142  based on the control signal. 
     The second battery  130  has an anode  240  and a cathode  242 . The anode  240  is electrically coupled to the DC-DC voltage converter  120 . In an exemplary embodiment, the cathode  242  is electrically coupled to the cathode  142  such that the cathode  242  and the cathode  142  have a common electrical ground. In an alternative embodiment, the cathode  242  is not electrically coupled to the cathode  142  such that the cathode  242  and the cathode  142  do not have a common electrical ground. The second battery  130  is adapted to generate a voltage level between the anode  240  and the cathode  242  which is less than a voltage level output by the battery  60 . In an exemplary embodiment, the second battery  130  is a lead acid battery. Of course, in an alternative embodiment the second battery  130  could comprise another type of battery such as a nickel-cadmium battery, a nickel-metal-hydride battery, or a lithium-ion battery for example. Further, in an exemplary embodiment, the second battery  130  outputs substantially 12 VDC. Of course, in an alternative embodiment, the second battery  130  could output another voltage level. 
     The DC-AC inverter  40  is electrically coupled between and to the electrical node  100  and the cathode  142 . Further, the DC-AC inverter  40  is electrically coupled to the vehicle motor system  50  via the electrical lines  270 ,  272 ,  274 . Still further, the DC-AC inverter  40  operably communicates with the microprocessor  135 . During a pre-charging operation, when the contact  83  has an open operational position, the DC-AC inverter  40  is adapted to receive a voltage level from the DC-DC voltage converter  120  which pre-charges at least one capacitor in the DC-AC inverter  40  in order to reduce an electrical inrush current into the DC-AC inverter  40  when the contact  83  transitions to a closed operational position. Thereafter, when the contact  83  has the closed operational position, the DC-AC inverter  40  receives a voltage level from the first battery  60 . Further, the microprocessor  135  generates a control signal to induce the DC-AC inverter to output AC voltages on the electrical lines  270 ,  272 ,  274  to induce the vehicle motor system  50  to output a desired torque amount. 
     The microprocessor  135  is operably coupled to the voltage sensor  70 , the voltage sensor  110 , the DC-DC voltage converter  120 , and the DC-AC inverter  40 . The microprocessor  135  operably communicates with a memory device  136  and stores data and operational instructions in the memory device  136 . The microprocessor  135  is programmed to perform operational steps which will be described in greater detail below. 
     Referring to  FIGS. 1-3 , a flowchart of a method for pre-charging and supplying voltages to a DC-AC inverter in accordance with another exemplary embodiment will now be described. 
     At step  400 , a user provides the pre-charging and voltage supply system  30  having the first battery  60 , the contactor  80 , the voltage sensor  110 , the DC-DC voltage converter  120 , the second battery  130 , the voltage sensor  70 , and the microprocessor  135 . The first battery  60  has an anode  140  and a cathode  142 . The contactor  80  is electrically coupled in series with and between the anode  140  and an electrical node  100 . The voltage sensor  110  is electrically coupled between and to the electrical node  100  and the cathode  142 . The DC-DC voltage converter  120  is electrically coupled between and to the electrical node  100  and the cathode  142 . The second battery  130  has an anode  240  and a cathode  242 . The anode  240  is electrically coupled to the DC-DC voltage converter  120 . The cathode  242  is electrically coupled to the cathode  142 . The voltage sensor  70  is electrically coupled in parallel to the first battery  60 . The microprocessor  135  is operably coupled to the voltage sensors  70 ,  110  and the DC-DC voltage converter  120 . After step  400 , the method advances to step  402 . 
     At step  402 , the user provides the DC-AC inverter  40  electrically coupled between and to the electrical node  100  and the cathode  142 . The microprocessor  135  is further operably coupled to the DC-AC inverter  40 . After step  402 , the method advances to step  404 . 
     At step  404 , the first battery  60  generates a first voltage level between the anode  140  and the cathode  142 . After step  404 , the method advances to step  406 . 
     At step  406 , the voltage sensor  70  generates a voltage signal indicative of the first voltage level that is received by the microprocessor  135 . After step  406 , the method advances to step  408 . 
     At step  408 , the microprocessor  135  determines a threshold voltage level for determining when to close the contactor utilizing the following equation: threshold voltage level=amplitude of first voltage signal*0.9. After step  408 , the method advances to step  410 . 
     At step  410 , the second battery  130  generates a second voltage level between the anode  240  and the cathode  242  that is received by the DC-DC voltage converter  120 . The second voltage level is less than the first voltage level. After step  410 , the method advances to step  420 . 
     At step  420 , the microprocessor  135  generates a first control signal to induce the DC-DC voltage converter  120  to increase a voltage level between the electrical node  100  and the cathode  142 , utilizing the second voltage level from the second battery  130  to charge capacitors in the DC-AC inverter  40  and to charge capacitors in the DC-DC converter  120 . After step  420 , the method advances to step  422 . 
     At step  422 , the voltage sensor  110  generates a first voltage signal indicative of a voltage level between the electrical node  100  and the cathode  142  that is received by the microprocessor  135 . After step  422 , the method advances to step  424 . 
     At step  424 , the microprocessor  135  makes a determination as to whether the voltage level between the electrical node  100  and the cathode  142  is greater than the threshold voltage level. The value of step  424  equals “yes”, the method advances to step  426 . Otherwise, the method returns to step  424 . 
     At step  426 , the microprocessor  135  generates a second control signal to induce the contactor  80  to transition the contact  83  from an open operational position to a closed operational position such that the first voltage level is applied to the DC-AC inverter  40 . After step  426 , the method advances to step  428 . 
     At step  428 , the microprocessor  135  receives a message indicating a desired torque amount from a vehicle controller  52 . After step  428 , the method advances to step  430 . 
     At step  430 , the microprocessor  135  sends a third control signal to the DC-AC inverter  40  indicating the desired torque amount. After step  430 , the method advances to step  432 . 
     At step  432 , the DC-AC inverter  40  outputs AC voltages to the vehicle motor system  50  based on the third control signal such that the vehicle motor system  50  produces the desired torque amount. 
     The above-described method can be at least partially embodied in the form of one or more memory devices or computer readable media having computer-executable instructions for practicing the methods. The memory devices can comprise one or more of the following: hard drives, RAM memory, flash memory, and other computer-readable media known to those skilled in the art; wherein, when the computer-executable instructions are loaded into and executed by one or more computers or microprocessors, the one or more computers or microprocessors become an apparatus programmed to practice the associated steps of the method. 
     The pre-charging and voltage supply system and the method described herein provide a substantial advantage over other systems and methods. In particular, the pre-charging and voltage supply system and method provide a technical effect of utilizing a DC-DC voltage converter and a battery (e.g., 12 VDC battery) to pre-charge capacitors in the DC-AC inverter to reduce an amount of electrical inrush current into the DC-AC inverter when a main contactor has a closed operational position. 
     While the claimed 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 claimed 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 claimed invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the claimed invention is not to be seen as limited by the foregoing description.