Abstract:
A method and apparatus for distributing control of multiple engines amongst the engines in a power generation system that has a central controller, comprises the steps of: receiving aboard each engine from the central controller a control signal representative of a desired fuel flow; metering fuel at a fuel metering point aboard each engine; sensing at least one parameter aboard each engine proximate the fuel metering point that is representative of fuel flow; adjusting the fuel metering aboard each engine to cause the sensed parameter to correlate to the desired fuel flow; and transmitting a monitoring signal from each engine to the central controller that is representative of the adjusted fuel metering.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to engine control systems, and more particularly to control of power systems that comprise multiple engines. 
       BACKGROUND OF THE INVENTION 
       [0002]    Many power systems have applications that require multiple engines. For instance, electrical power systems may have multiple gas turbines, each with their own electrical generator load that contributes power to an electrical power grid. It is important to monitor and control the output of the engines so that the power that their respective generators contribute to the grid is such that their total cumulative power stays within a desired cumulative power level range at all times. 
         [0003]    Control systems for controlling the power of the engines in the system generally rely on the function of a central controller for monitoring and controlling the operation of all the engines in the system. Because monitoring and control of each engine requires multiple transducers per engine, both the central controller and the communications link between the central controller and the engines may become complex and require high data rates. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention generally comprises a method and apparatus for distributing control of multiple engines amongst the engines in a power generation system that has a central controller, comprising the steps of: receiving aboard each engine from the central controller a control signal representative of a desired fuel flow; metering fuel at a fuel metering point aboard each engine; sensing at least one parameter aboard each engine proximate the fuel metering point that is representative of fuel flow; adjusting the fuel metering aboard each engine to cause the sensed parameter to correlate to the desired fuel flow; and transmitting a monitoring signal from each engine to the central controller that is representative of the adjusted fuel metering. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a schematic diagram of a distributed engine control system according to a possible embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0006]      FIG. 1  is a schematic diagram of distributed engine control system  2  according to a possible embodiment of the invention. The control system comprises multiple engines  4  in communication with a central controller  6  by way of a wired or wireless communications link  8 . For purposes of illustration only,  FIG. 1  shows three of the engines  4 , and engines  4  of the gas turbine type. The control system  2  may alternatively have as little as two engines  4  or more than three engines  4 , and the engines  4  may be of another type, such as of the reciprocating internal combustion type. Each engine  4  drives a load  10  by way of an engine drive shaft  12 . The load  10  may be mechanical or electrical. By way of example only,  FIG. 1  shows each load  10  as an electrical generator, with each electrical generator load  10  coupled to a common electrical grid  14 . 
         [0007]    Each engine  14  has a fuel control valve  16  for metering fuel at a fuel metering point along a fuel line  18 . The valve  16  has at least a valve actuator  20  and a valve position sensor  22  that senses the position of the valve  16 . A fuel valve controller  24  drives the actuator  20  with an actuator drive signal by way of an actuator control line  26 . The valve position sensor  22  generates a valve position signal representative of valve position and transmits it to the valve controller  24  by way of a valve position signal line  28 . 
         [0008]    In one mode of operation, the central controller  6  may transmit a control signal representative of a desired fuel flow to each engine  4  by way of its fuel line  18 , such as a desired fuel valve position signal or a desired fuel flow signal. If the control signal comprises a desired valve position signal, the valve controller  24  compares the valve position signal that it receives on the valve position signal line  28  and generates a respective actuator drive signal on the actuator control line  26  to adjust the position of the valve  16  so that the valve position signal on the valve position line  28  correlates to the control signal from the central controller  6  that represents desired valve position. If the control signal comprises a desired flow signal, the valve controller  24  may correlate the control signal with a desired position of the valve  16  and generate a respective actuator drive signal on the actuator control line  26  to adjust the position of the valve  16  so that the valve position signal on the valve position line  28  correlates to the desired valve position. The valve controller  24  may transmit a monitoring signal to the central controller  6  by way of the communications link  8  that is representative of the adjusted fuel metering, such as the valve position signal on the valve position line  28 . 
         [0009]    The valve controller  24  may correlate the position of the valve  16  as represented by the valve position signal on the valve position line  28  with the effective flow area of the fuel at the fuel metering point along the fuel line  18 . Furthermore, the valve controller  24  may correlate the position of the valve  16  as represented by the valve position signal on the valve position line  28  with actual fuel flow through the fuel line  18  and generate the monitoring signal as representing this actual fuel flow. 
         [0010]    The valve controller  24  may receive additional signals from additional sensors that represent other fuel flow parameters. For instance, an upstream fuel pressure sensor  30  that senses fuel pressure upstream of the fuel metering point may generate an upstream fuel pressure signal representative of the sensed pressure on an upstream fuel pressure signal line  32 . A fuel temperature sensor  34  that senses fuel temperature upstream of the fuel metering point may generate an upstream fuel temperature signal representative of the sensed temperature on an upstream fuel temperature signal line  36 . A downstream fuel pressure sensor  38  that senses fuel pressure downstream of the fuel metering point may generate a downstream fuel pressure signal representative of the sensed pressure on a downstream fuel pressure signal line  40 . 
         [0011]    The valve controller  24  may correlate the effective flow area of the valve  18  as represented by the valve position signal on the valve position line  28 , the upstream fuel pressure signal on the upstream fuel pressure signal line  32 , the upstream fuel temperature signal on the upstream fuel temperature signal line  36  and the downstream fuel pressure signal on the downstream fuel pressure signal line  40  with actual fuel mass flow. In this case, the control signal from the central controller  6  may represent desired fuel mass flow, and the valve controller  24  may compare the actual fuel mass flow to the desired fuel mass flow and generate the actuator drive signal on the actuator control line  26  to adjust the position of the valve  16  so that the actual fuel mass flow matches the desired fuel mass flow. 
         [0012]    Each engine  4  has a compressor  42  and a turbine  44  that couples to its drive shaft  12 . A compressor inlet temperature sensor  46  may sense compressor inlet temperature and generate a compressor inlet temperature signal representative of the sensed temperature on a compressor inlet temperature signal line  48 . A turbine inlet temperature sensor  50  may sense turbine inlet temperature and generate a turbine inlet temperature signal representative of the sensed temperature on a turbine inlet temperature signal line  52 . An engine speed sensor  54  may sense engine speed and generate an engine speed signal representative of the measured speed on an engine speed signal line  56 . 
         [0013]    The valve controller  24  may analyse engine parameters as represented by the compressor inlet temperature signal on the compressor inlet temperature signal line  48 , the turbine inlet temperature signal on the turbine inlet temperature signal line  52  and the engine speed signal on the engine speed signal line  56  and compare them with desired engine operating characteristics. The valve controller  24  may compare the actual engine operating characteristics to the desired engine operating characteristics and generate the actuator drive signal on the actuator control line  26  to adjust the position of the valve  16  so that the actual engine operating characteristics correlate with the desired engine operating characteristics. The desired engine operating characteristics may comprise setpoints, such as an engine speed setpoint and a turbine input temperature setpoint, and engine operating schedules, such as engine start, acceleration and deceleration schedules, speed-based fuel schedules and an engine temperature schedule. 
         [0014]    The central controller  6  may correlate the monitoring signal that it receives the valve controller  24  aboard each engine  4  with a level of a power system parameter, such as the level of power that the electrical generator load  10  of each engine  4  delivers to the common electrical grid  16 , then compare the correlated power system level with a desired power system level and finally adjust its control signal that it transmits to the valve controller  24  aboard each engine  4  in response to any difference between the correlated power system level and the desired power system level. The desired power level may be a cumulative power level for all of the engines  4 , in which case the central controller  6  correlates each monitor signal from the valve controller  24  of each engine  4  to a corresponding level of the power system parameter, combines the correlated engine power system levels to produce a cumulative correlated power system level and adjusts its control signal that it transmits to the valve controller  24  aboard each engine  4  in response to any difference between the cumulative correlated power system level and the desired power system level. 
         [0015]    Since the central controller  6  and the communication link  8  only has to handle the monitoring signal from the valve controller  24  aboard each engine  4  and the controller  6  needs only transmit a control signal to the valve controller  24  aboard each engine  4  that represents a single desired fuel system parameter, the complexity and data rate of both are greatly reduced with the distributed control system  2 . The described embodiments of the invention are only some illustrative implementations of the invention wherein changes and substitutions of the various parts and arrangement thereof are within the scope of the invention as set forth in the attached claims.