Abstract:
A turbo compounding system may include a turbo generator having a switched reluctance machine having at least one pole-matched rotor and stator pair, a single phase inverter coupled to the turbo generator and further coupled to a direct current link, an inverter coupled to the direct current link, a motor generator coupled to the inverter.

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to the field of power supply systems, and more particularly to a system for paralleling power supplies. 
     BACKGROUND 
     Electrical energy in the form of Alternating Current (AC) is a commonly available power source found in buildings, including homes. AC power is typically supplied by a central utility via power lines or from a physical plant that is part of a facility. However, many common devices, including electronic circuits and DC motors, utilize electrical energy in the form of Direct Current (DC), which is electrical current that flows in only one direction. Thus, it is often desirable to convert AC power to DC power. 
     Power supply systems convert AC power to DC power suitable for powering electrical components, also known as a load. It is often desirable to combine multiple redundant power supplies in parallel to supply a given load requirement. When power supplies are combined in parallel, the output of each power supply may be combined to produce a shared output, or common output load. When multiple power supplies are combined in parallel, reliability and efficiency for the power supply system may be improved. Redundant parallel-connected power supplies may increase reliability for the overall power supply system whereby a failure of a power supply will cause other power supplies to supply enough current for support of a maximum load. 
     SUMMARY 
     Accordingly, the present disclosure is directed to a system for paralleling power supplies. In one embodiment, a system for paralleling power supplies may be connected to multiple power supplies to parallel the power supplies with approximately equal current sharing amongst the multiple power supplies. A system for paralleling power supplies may include a parallel controlling logic and may be coupled to a load output terminal of each power supply and a remote sense terminal of each power supply to share current amongst the multiple power supplies. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the present disclosure. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate subject matter of the disclosure. Together, the descriptions and the drawings serve to explain the principles of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The numerous advantages of the disclosure may be better understood by those skilled in the art by reference to the accompanying figures in which: 
         FIG. 1  is a diagram illustrating a conventional paralleled power supply system known to the art; 
         FIG. 2  is a diagram illustrating a paralleling system for paralleling power supplies; 
         FIG. 3  is a circuit diagram illustrating a paralleling system for paralleling power supplies; and 
         FIG. 4  is a flow diagram representing a method for supplying power for a data storage system. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings. 
     Referring generally to  FIGS. 2 through 3 , a paralleling system for paralleling power supplies connected to multiple power supplies to parallel the power supplies with approximately equal current sharing amongst the multiple power supplies. Paralleled power supplies may refer to independent power supplies which are combined to form a shared output, also known as a common output load. Paralleled power supplies may combine multiple power supplies in a power supply system to supply power for a given load requirement. A power supply system with paralleled power supplies may provide enhanced reliability through redundancy whereby a failure of a single power supply may be overcome through operation of another power supply. Additionally, a power supply system with paralleled power supplies for a given load may produce additional benefits including form factor considerations and heat removal. 
     For example, it is contemplated that paralleling system for paralleling power supplies may be employed in information handling systems, such as a computing system of a data storage system and/or storage rack, shelf and the like. Data storage systems require a reliable power system to ensure valid read and write access to data on a continuous basis. A factor of efficient operation of data storage systems is heat removal. Components such as modules containing processor units or power supplies may also require more cooling capacity. Data storage systems and information handling systems require proper airflow over waste heat generating components, such as power supplies. Through employment of multiple power supplies in combination with the paralleling system of the present invention, the form factor of the power supplies may be reduced and heat generated from the power supplies may be reduced. Consequently, a data storage system employing a power supply system of the present invention may increase reliability of the data storage system with more efficient heat removal. 
     While power supply systems may be paralleled, load current may not be equally shared amongst multiple power supplies. A drawback associated with unequal current load sharing is the stress placed on individual power supplies. For example, a first power supply of a paralleled power supply system may be operating at a higher current load and a higher temperature than a second power supply of the paralleled power supply system. A power supply that operates at a higher temperature reduces reliability of the power supply and negatively affects the reliability of the overall power supply system. 
       FIG. 1  illustrates a conventional paralleled power supply system  100 . A conventional paralleled power supply system  100  may include a first power supply  110  and a second power supply  120 . A first power supply  110  may include a load output terminal  130 , a remote sense terminal  135  and a share bus output terminal  140 . A second power supply  120  may include a load output terminal  150 , a remote sense terminal  155  and a share bus output terminal  160 . Conventional paralleled power supply system  100  may supply load  170  with power with approximately equal current sharing amongst the first power supply  110  and the second power supply  120  by employment of the share bus  180  coupled to share bus output terminal  140  of power supply  110  and share bus output terminal  160  of power supply  120 . Remote sense terminals  135 ,  155  may be connected to load  170 . Remote sense terminals  135 ,  155  may be coupled to a feedback amplifier associated with each power supply  110 ,  120 . Remote sense terminals  135 ,  155  compensate for output lead losses and provide a remote point for regulation. By coupling remote sense terminals  135 ,  155  with load  170 , power supplies  110 ,  120  may adjust their output parameters, such as a supply voltage, at their own output terminals to compensate for resistance of load leads, relays, connectors and the like to provide a desired output voltage at the terminals of load  170 . 
     Power supplies  110 ,  120  may produce and transfer current information delivered by each power supply  110 ,  120  across the share bus  180 . Current information may be provided through a voltage input or digital word. A power supply providing higher current may control the share bus  180  whereby the other power supply increases power delivery to match the power supply supplying the higher current. Share bus  180  may transfer current sharing information amongst power supply  110  and power supply  120  of the conventional paralleled powers supply system  100 . By controlling operation of each power supply through information transmitted across the share bus  180 , approximately equal current sharing amongst power supply  110  and power supply  120  may be achieved. A drawback associated with the paralleled power supply system  100  is the high cost associated with the power supplies  110 ,  120  which include share bus output terminals  140 , 160 . Power supplies  110 ,  120  with share bus output terminals  140 ,  160  cost significantly more than power supplies without share bus output terminals. 
       FIG. 2  illustrates a paralleling system  200 . Paralleling system  200  may be employed with multiple power supplies to parallel the multiple power supplies with approximately equal current sharing amongst the multiple power supplies. Paralleling system  200  may be operable with multiple power supplies which do not require share bus output terminals while ensuring approximately equal current sharing amongst the power supplies. 
     Paralleling system  200  may be operable with a first power supply  210  and a second power supply  220 . Power supply  210  may include a load output terminal  230  and remote sense terminal  240 . Power supply  220  may include a load output terminal  250  and remote sense terminal  260 . Paralleling system  200  may be coupled to each load output terminal  230 ,  250  and each remote sense terminal  240 ,  260  of each power supply  210 ,  220 . Paralleling system  200  may parallel power supplies  210 ,  220  with approximately equal current sharing amongst the power supplies  210 ,  220  to supply a load  270  with a shared output. Paralleling system  200  may operate with the remote sense terminals  240 ,  260  to provide appropriate feedback to the remote sense terminals  240 ,  260  whereby the power supplies  210 ,  220  may adjust their output parameters to ensure approximately equal current sharing amongst power supplies  210 ,  220 . Paralleling system  200  may receive output from power supply  210  and power supply  220  and may supply a pair of OR diodes to isolate one of the power supplies  210 ,  220  from the common output to the load  270  if one power supply should fail. Failure of a power supply may include an output of a power supply being shorted to ground. It should be understood by those with ordinary skill in the art that ground terminals (not shown) would be included for operation with the load output terminals and remote sense terminals with power supplies paralleled by paralleling system  200 . 
       FIG. 3  is a circuit diagram illustrating a paralleling circuit  300  for paralleling power supplies. Paralleling circuit  300  may be one embodiment of paralleling system  200 . Paralleling circuit  300  may parallel power supply  302  and power supply  304 . Power supply  302  may include a voltage input reference  306  coupled to an error amplifier  308 . Error amplifier  308  may be coupled to a controlled power output  310  which supplies power, after filtering, to the load output  312 . Power supply  302  may include a remote sense terminal  314  which is operatively connected to the error amplifier  308  to allow an adjustment of the output of power supply  302  depending upon the voltage of the remote sense terminal  314 . 
     Power supply  304  may include a voltage input reference  316  coupled to an error amplifier  318 . Error amplifier  318  may be coupled to a controlled power output  320  which supplies power, after filtering, to the load output  322 . Power supply  304  may include a remote sense terminal  324 . Power supply  304  may include a remote sense terminal  324  which is operatively connected to the error amplifier  318  to allow an adjustment of the output of power supply  304  depending upon the voltage of the remote sense terminal  324 . While power supplies  302 ,  304  may be paralleled by paralleling circuit  300 , it is contemplated that any type of power supply may be employed. It is further contemplated that paralleling circuit  300  may be operable with any type of power supply configuration, including DC/DC power supplies and AC/DC power supplies which include remote sense terminals. 
     Paralleling circuit  300  may be coupled to load output  312  of power supply  302  and load output  322  of power supply  304 . Additionally, paralleling circuit  300  may be coupled to remote sense terminal  314  of power supply  302  and remote sense terminal  324  of power supply  304 . It should be understood that any type of junction may be employed as terminals including connectors and pins. 
     Paralleling circuit  300  may be coupled with the remote sense terminals  314 ,  324  for implementation of current sharing logic of the paralleling circuit  300  to parallel power supplies  302 ,  304  between the minimum and maximum specified load. Parallel controlling logic of paralleling circuit  300  may include current sensors  326 ,  328 , operational amplifiers  330 ,  332 ,  334 ,  336  and a paralleling bus  342 . Current sensor  326  may be coupled to the load output  312  of power supply  312 . Current sensor  328  may be coupled to load output  322  of power supply  304 . Current sensors  326 ,  328  may be any type of current sensing devices and may provide current reading information, for example, in the form of a current sense voltage, for the paralleling circuit  300 . Operational amplifier  330  may be coupled to current sensor  326  and may compare an output current sense voltage of current sensor  326  for power supply  302  in comparison with a voltage across the paralleling bus  342 . Operational amplifier  334  may be coupled to current sensor  328  and may compare the output current sense voltage of current sensor  328  for power supply  304  with the voltage across paralleling bus  342 . 
     Operational amplifiers  332 ,  336  may each compare the voltage across paralleling bus  342  with output current sensed voltage by current sensor  326  for power supply  302  and current sensor  328  for power supply  304  to provide any necessary gain to remote sense terminals  314 ,  324  respectively. Thus, if the voltage of remote sense terminal  314  divided by two resistors to the inverting input terminal of error amplifier  308  is less than the voltage of voltage input reference  306 , power supply  302  may increase its output to ensure approximately equal current sharing amongst power supplies  302 ,  304 . In another example, if the voltage of remote sense terminal  324  divided by two resistors to the inverting input terminal of error amplifier  318  is greater than the voltage of voltage input reference  316 , power supply  304  may decrease its output to ensure approximately equal current sharing amongst power supplies  302 ,  304 . It is contemplated that each power supply  302 ,  304 , may simultaneously increase/decrease or decrease/increase output to ensure approximately equal current sharing amongst power supplies  302 ,  304 . While operational amplifiers are described, it is contemplated that other types of amplifiers may be employed without departing from the scope and intent of the present invention. 
     Paralleling circuit  300  may include an OR diode circuit, such as OR diodes  338 ,  340 , which may deliver current to the load  344 . Paralleling circuit  300  may also include a feedback conductor  346  for power supply  302  and feedback conductor  348  for power supply  304 . OR diodes may provide isolation for power supplies  302 ,  304  and may prevent reverse current flow within power supplies  302 ,  304 . OR diodes may be a conventional diode and may be a Schottky diode. In another embodiment, OR diodes may be implemented with a field effect transistor and a driver. For example, OR diode  338 ,  340  may be implemented as a body diode of a transistor, such as a MOSFET, whereby the transistor is turned on, shunting the body diode with a very low voltage drop when the current is moving through the body diode. 
     Body diodes of a MOSFET may act as output “OR” diodes as the body diodes may be shunted by the MOSFET when the MOSFETS is switched on. Current may be allowed to pass with minimal power dissipation while providing isolation for power supplies  302 ,  304 . When current flows from the anode to cathode of a body diode of MOSFET, a driver may detect the current flow and provide a gate voltage to the MOSFET. This may cause MOSFET to turn on, allowing current to flow through from power supply  302 ,  304  to load  344  with minimal power dissipation. In an embodiment of the invention, MOSFET may be a very low “on resistance” type of transistor. Thus, power dissipation may be an amount of the drain to source current squared (lds 2 ) times the drain to source resistance of the MOSFET when on (RDSon). 
     Reverse current flow into power supply  302 ,  304  may be prevented. MOSFET may be back biased which may be detected by the driver which turns the gate voltage for MOSFET  310  off. Thus, the flow of reverse current into power supply will be prevented. An advantageous aspect of the OR diode is the rate at which the MOSFET is shut off after detection of reverse current flow, typically a few microseconds. 
     It should be understood that driver may include any device, circuitry and the like to provide a high or low output depending upon the value of two inputs. While driver may be implemented as a comparator, such as an operational amplifier, it should be understood by those with ordinary skill in the art that other types and configurations may be utilized in order to provide the functionality of a driver. Additionally, comparator may be equipped with independent voltage supplies, resistor-capacitor filtering, and the like to provide more precise voltage monitoring by driver. Additionally, it should be understood that other types of transistors may be employed in lieu of a MOSFET to achieve similar functionality. For example, a bipolar junction transistor may be employed to operate similarly to a diode while providing low power dissipation. Additionally, it is also contemplated that the functional equivalent of a MOSFET may be implemented by those with ordinary skill in the art the by use of two MOSFETS, one transistor functioning as a switching mechanism and another transistor functioning as the body diode without departing from the scope and spirit of the present invention. 
     It is contemplated that current sharing may be achieved when, in the instance of a two power supply system, each power supply is providing about one half of the total load current. It is further contemplated that paralleling circuit  300  may be employed with power supply systems comprising three or more power supplies with each power supply providing an approximately equal load current. It should be understood by those with ordinary skill in the art that an approximately equal load current may be defined as each load current supplied by each power supply may be within a five percent (5%) difference of each other. For example, a first power supply may supply 52% of the load current and a second power supply may supply 48% of the load current. Since the load current supplied by the first power supply may be within 5% (e.g. a 4% difference) of the load current supplied by the second power supply, then it is contemplated that each power supply provides an approximately equal load current. However, a first power supply may supply 54% of the load current and a second power supply may supply 46% of the load current, (an 8% difference). In such a scenario, it is contemplated that each power supply is not providing approximately equal load current. 
     Referring to  FIG. 4 , a flow diagram representing a method  400  for supplying power for a data storage system. It is contemplated that paralleling system  200  may execute method  400  for supplying power for a data storage system. Method  400  may begin by receiving a first output from a first power supply and a second output from a second power supply  410 . Next, method  400  may include detecting a current amount supplied by each of the first power supply and the second power supply  420 . Method  400  may include supplying a common output to the data storage system from the first output and the second output  430 . Next, method  400  may including providing a first voltage reference to a first remote sense terminal of the first power supply based upon the current amount supplied by the first power supply  440  and providing a second voltage reference to a second remote sense terminal of the second power supply based upon the current amount supplied by the second power supply  450 . It is contemplated that the first power supply and the second power supply adjust their output based upon the first voltage reference and the second voltage reference to produce the common output with current being approximately equally shared between the first power supply and the second power supply. Method  400  may include detecting a failure of first power supply  460  and providing an adjusted second voltage reference to increase output of a second power supply  470  to supply the data storage system with an appropriate current output. For example, paralleling circuit  300  may detect the lack of current output from a first power supply and accordingly the voltage reference supplied to the remote sense terminal of the second power supply may be adjusted. The adjustment of the voltage reference supplied to the second power supply may cause the second power supply to increase its output to supply an appropriate current output for the data storage system. 
     It is believed that the paralleling system of the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes.