Abstract:
Methods and systems for an engine generator set that includes an electrical generator configured to provide electrical energy to a first load rated at a first voltage and a first frequency, and to provide electrical energy to a second load rated at a second voltage and a second, a prime mover coupled to the generator through a shaft, and configured to rotate the shaft at a first rotational speed at the first frequency and to rotate the shaft at a second rotational at the second frequency, and an engine generator set control system that includes a generator control system configured to control an output of the electrical generator, an engine control system configured to control a rotational speed of the shaft, and an output selector configured to modify the output of the engine generator set from the first voltage and the first frequency to at least one of the second voltage and the second frequency.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to electrical generator control systems and more particularly, to selectable frequency, voltage, protection and output ratings for electrical generators.  
         [0002]     Engine generator sets are commonly utilized as prime or backup power sources for electrically driven equipment in applications and locations having different power supply requirements. For example, many locales require a 50 Hertz (Hz) electrical output, while others require a 60 Hz output, to match the operating frequency of the local grid. Engine generator set applications may have different power requirements. Voltage and frequency requirements of equipment powered by the engine generator set may vary. For example, in the United States 480V and 60 Hz is a common requirement for electrical equipment, whereas European applications are more likely to need 400V and 50 Hz power. Engine generator sets that are able to provide a certain power level at one voltage and frequency may not be able to supply the same power at another voltage and frequency.  
         [0003]     Known engine generator sets are configured to accommodate operation in areas that include electrical systems having 50 Hz or 60 Hz. If an engine generator set is moved from one area to another having a different operating frequency, modifications to settings of generator protection devices, to electrically-powered auxiliary equipment, and to mechanical components are typically required.  
         [0004]     Typically, engine generator set auxiliary equipment is powered from the output of the engine generator set. Accordingly, electrical equipment such as pump motors operate at the frequency that the engine generator set is designed to operate. Furthermore, mechanical components coupled to electric motors are sized to accommodate the output power levels of the electric motors to which the mechanical component is coupled.  
         [0005]     Voltage regulators are typically designed to operate with a variety of different engine generator sets with a wide range of capabilities. Thus, a particular engine generator set, may not be capable of operating at all voltage choices available on the voltage regulator. The engine generator set also may not be able to meet the same power rating at one voltage as it can at a different voltage. In addition to setting the engine and voltage ratings for a particular application, relays and other protective devices contained in the engine generator set control system will need to be reset or replaced when the operation of the engine generator set is to be changed from one frequency to another. Protective relaying, such as over and under voltage relays and over and under frequency relays, disconnects a load, shuts down the engine, prevents excitation of the generator or protects the engine generator set in some other manner if a condition that could cause damage to the engine generator set is detected. For example, if the voltage exceeds the acceptable rating and the engine generator set has an overvoltage relay, the relay may trip a circuit breaker and disconnect the load, thus preventing damage to both the generator and the load. Relays must be set correctly to operate. For example, the voltage level at which the overvoltage relay will trip a circuit breaker is typically set manually.  
         [0006]     To change the operation of an engine generator set from one operating frequency to a different frequency, a user may need a variety of skills. The user may need to change the engine rating, to change the voltage and frequency on the voltage regulator manually, to set protective relays, and to replace motors, pumps, heaters and other auxiliary equipment, and to ensure all settings and ratings are compatible with each other and the engine generator set. Technicians with these skills may be difficult to find in the remote areas where engine generator sets often run. The amount of labor and the cost of parts required may reduce the feasibility of a particular application, and the more steps the technician has to take to setup a engine generator set, the more chances there are for error.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0007]     In one embodiment, an engine generator set that includes an electrical generator configured to provide electrical energy to a first load rated at a first voltage and a first frequency, and to provide electrical energy to a second load rated at a second voltage and a second, a prime mover coupled to the generator through a shaft, and configured to rotate the shaft at a first rotational speed at the first frequency and to rotate the shaft at a second rotational at the second frequency, and an engine generator set control system that includes a generator control system configured to control an output of the electrical generator, an engine control system configured to control a rotational speed of the shaft, and an output selector configured to modify the output of the engine generator set from the first voltage and the first frequency to at least one of the second voltage and the second frequency.  
         [0008]     In another embodiment, a method of operating an engine generator set includes selecting an operating voltage and frequency from a plurality of predetermined operating voltages of the engine generator set from a first voltage and a first frequency to a second voltage and a second frequency, selecting the selected operating voltage and frequency for an electrical distribution panel electrically coupled to an output of the engine generator set such that electrical loads and electrical protection equipment coupled to the electrical distribution panel are configured to operate using the selected voltage and frequency, and selecting the selected operating voltage and frequency for a generator switchgear electrically coupled to an output of the engine generator set such that generator protection equipment coupled to the generator output are configured to operate using the selected voltage and frequency.  
         [0009]     In yet another embodiment, an engine generator set output conversion system includes an output selector configured to modify the output of an engine generator set from a first output voltage and a first frequency to a second output voltage and a second frequency wherein the first output voltage is different than the second output voltage and the first frequency is different than the second output frequency, and a relay communicatively coupled to the output selector, the relay configured to select a first transformer tap corresponding to the first output voltage and select a second transformer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic block diagram of an exemplary embodiment of an engine generator set;  
         [0011]      FIG. 2  is a schematic block diagram of an exemplary embodiment of circuit breaker panel shown in  FIG. 1 ; and  
         [0012]      FIG. 3  is a flow diagram of an exemplary method of operating the engine generator set Shown in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.  
         [0014]      FIG. 1  is a schematic block diagram of an exemplary embodiment of an engine generator set  10 . Engine generator set  10  is coupled to a load  12  through a circuit breaker panel  14 . In the exemplary embodiment, the engine generator set  10  includes an internal combustion engine  16 , a generator  18  and a engine generator set control system  20 . Circuit breaker panel  14  electrically couples the engine generator set  10  to load  12 .  
         [0015]     In the exemplary embodiment, engine  16  is a gas turbine engine including at least one compressor  22 , a combustor  24 , a high pressure turbine  26 , a low pressure turbine  28 , an inlet  30 , and an exhaust nozzle  32  connected serially. In one embodiment, engine  10  is a TM2500 engine commercially available from General Electric Company, Cincinnati, Ohio. Compressor  22  and turbine  26  are coupled by a first shaft  34 , and turbine  28  and generator  18  are coupled by a second shaft  36 .  
         [0016]     In operation, air flows into engine inlet  30  through compressor  22  and is compressed. The compressed air is then delivered to combustor  24  where it is mixed with fuel and ignited. Airflow from combustor  24  drives rotating turbines  26  and  28  and exits gas turbine engine  16  through exhaust nozzle  32 .  
         [0017]     In the exemplary embodiment, generator  18  is an AC generator mechanically coupled to shaft  36  such that the engine rpm determines the frequency of the AC power produced by generator  18 . Generator  18  is coupled to circuit breaker panel  14  through leads  38  that transmit the AC power produced by generator  18  at a predetermined voltage and frequency to load  12  through the circuit breaker panel  14 . In an alternative embodiment, leads  26  are coupled to load  12  through bus bars and disconnect switches (not shown).  
         [0018]     In the exemplary embodiment, engine generator set control system  20  includes an engine generator set control panel  40 , an ECM  42 , an automatic voltage regulator  44 , an overvoltage relay  46 , an undervoltage relay  48 , an overfrequency relay  50 , and an underfrequency relay  52 . In an alternative embodiment, control system  20  is contained in one or more control modules. In another alternative embodiment, control system  20  may not include relays  46 ,  48 ,  50 , and  52 , or the relays  46 ,  48 ,  50 , and  52  may be part of voltage regulator  44 , control panel  40  or another portion of control system  20 . In the exemplary embodiment, control system  20  is physically located with engine  16  and generator  18 . In an alternative embodiment, control system  20  or parts of control system  20  may be remotely located.  
         [0019]     Generator control panel  40  includes an interface  54  to facilitate entering data into control system  20  and controlling engine  16 . Interface  54  includes a display area  56  and a keypad  58 . An output selector  60  is used to select an operating frequency of engine generator set  10 . In the exemplary embodiment, output selector  60  is a key lock switch. In various embodiments, output selector  60  may be embodied as a password protected field on display  56 , a submenu of display  56 , or a separate keypad that requires a combination of entries to change the status of output selector  60 .  
         [0020]      FIG. 2  is a schematic block diagram of an exemplary embodiment of circuit breaker panel  14  (shown in  FIG. 1 ). In the exemplary embodiment, circuit breaker panel  14  includes a circuit breaker  200  that is configured to receive electrical power and selectively transmit the received electrical power to a line distribution, for example, a substation (not shown). Circuit breaker  200  is housed within a cubicle  202  of circuit breaker panel  14 . A trip unit  204  is configured to receive electrical signals indicative of electrical parameters passing through line  38  from sensors  208 . In the exemplary embodiment, sensors  208  include a potential transformer (PT) and a current transformer (CT). Trip unit  204  generates a trip signal using the electrical signals from sensors  208  to trip circuit breaker  200  when the electrical parameters exceed a threshold or other predetermined characteristic.  
         [0021]     A transformer  210  housed in a cubicle  212  steps the voltage on line  38  down to a level suitable for use in supplying electrical power to auxiliary equipment associated with engine generator set  10 . Transformer  210  is selectively tapped to provide a plurality of output voltages, such as 400 VAC and 480 VAC. Transformer  210  is coupled to a bus system to transmit electrical power to auxiliary loads coupled to respective circuit breakers in a cubicle  214 . In the exemplary embodiment, a first circuit breaker  216  supplies a pump motor  218 , a second circuit breaker  220  supplies a heater  221 , a third circuit breaker  222  supplies an oil mist eliminator  224 , and a fourth circuit breaker  226  supplies a fan motor  228 . In various embodiments, other auxiliary equipment is supplied electrical power from cubicle  214 .  
         [0022]     In the exemplary embodiment, each of trip unit  206 , transformer  210 , and breakers  216 ,  220 ,  222 , and  226  are communicatively coupled to output selector  60  through a network  230 . During operation, output selector  60  is set to a predetermined frequency of operation for engine generator set  10 . Accordingly, such setting is communicated to trip unit  206 , transformer  210 , and breakers  216 ,  220 ,  222  and  226 . Additional equipment such as engine generator set control panel  40 , ECM  42 , automatic voltage regulator  44 , overvoltage relay  46 , undervoltage relay  48 , overfrequency relay  50 , and underfrequency relay  52  may also be communicatively coupled to network  230 .  
         [0023]      FIG. 3  is a flow diagram of an exemplary method  300  of operating engine generator set  10 . Method  300  includes converting  302  switchgear associated with engine generator set  10  from an operational configuration for using the first voltage to the second voltage. Such conversion includes aligning taps on the secondary windings of potential transformers from a first tap to a second tap. A set on electrical contacts in a secondary circuit of the transformer are associated with output selector  60  such that the contacts align the secondary of the potential transformer to provide a first sensing voltage in a first position and a second sensing voltage when selected to a second position. In the exemplary embodiment, the potential transformer is tapped to provide an 115 VAC sensing voltage when electrical generator  16  output is 11,500 VAC and a 120 VAC sensing voltage when electrical generator  16  output is 11,400 VAC.  
         [0024]     Output selector  60  also controls conversion  304  of a motor control center (MCC) that supplies power to the auxiliary equipment that supports the operation of engine generator set  10 . For example, a lighting distribution panel primary winding is switched  306  from providing 400V to 480V and motor overload settings are modified  308  for 60 Hz operation from, for example, 50 Hz operation.  
         [0025]     In the exemplary embodiment, other auxiliary equipment and control devices are configured to operate at the frequency and voltage selected by output selector  60 . A fuel control &amp; sequencer system is switched  310  to operate at the selected frequency and voltage. A MW range WX device control system settings are modified  312  and other protective device settings are also modified  314  to operate at the frequency and voltage selected by output selector  60 . Such protective devices include an integrated generator protection system (IGPS), Digital Multi-Function Meter (DMMF), a Digital Synchronizing Module (DSM), and an automatic voltage regulator (AVR) device. At least some auxiliary equipment used to support the operation of system  10  includes a multi-power supply capability such that a selection of one configuration out of a plurality of available configurations permits operation of the auxiliary equipment at different selectable voltages and frequencies. Auxiliary equipment is also supplied from a constant output power supply coupled to system  10  output, for example, all lighting, computer feeder, wall sockets, emergency lighting and control house battery vent fans and generator lube oil mist eliminator operates  316  at 230V and all AC motors and igniter circuits operate from special reserved 130 VAC circuits from the lighting distribution panel. Additionally, other auxiliary equipment is oversized  318  to accommodate multiple power supplies such as heaters for ventilation, equipment conditioning, and fluid systems heaters are oversized at 60 Hz to acconunodate lower output power when operating at 50 Hz, and auxiliary pump/motor sets are oversized at 60 Hz to meet the flow requirements at 50 Hz and enclosure blower heaters for winterization are dual rated for 50/60 Hz, 400/480V at 3 kW. Output selector  60  modifies the configuration of engine generator set  10  for operation at the first voltage and frequency, and modifies the configuration of the protection system and distribution system operating voltage, and support systems to the configuration for operation at the second voltage and frequency in less than about twenty milliseconds from operator initiation.  
         [0026]     The above-described embodiments of an engine generator set facilitate providing power to a plurality of electrical systems with minimal reconfiguration of the engine generator and auxiliary equipment. Exemplary embodiments of engine generator set methods and apparatus are described above in detail. The engine generator set components illustrated are not limited to the specific embodiments described herein, but rather, components of each engine generator set may be utilized independently and separately from other components described herein. For example, the engine generator set components described above may also be used in combination with different engine generator set. A technical effect of the various embodiments of the systems and methods described herein facilitating generating electrical power for a variety of electrical systems where the likelihood of operator error in reconfiguring the set is substantially reduced.  
         [0027]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.