Patent Publication Number: US-2022216815-A1

Title: Fast por trim correction

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to generator control, and more particularly to fault detection for generator control. 
     2. Description of Related Art 
     Sensors can be used on generator feeders to generate feedback for controlling the generator. It is possible to lose control of a generator if the sensor is defective or becomes defective, even if the generator, feeder, and loads are fully functional. One way of handling this event is to shut down the generator until the defect in the sensor can be corrected. 
     The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for faster fault detection and correction. This disclosure provides a solution for this need. 
     SUMMARY 
     A system comprises a generator control unit (GCU) configured to control a generator. The system includes a first sensor connected to provide feedback to the GCU for generator control. The first sensor is configured to sense at least one of voltage and/or current in a feeder connecting between the generator and a load. The system also includes a second sensor connected to provide feedback to the GCU for generator control. The second sensor is configured to sense at least one of voltage and/or current in the feeder connecting between the generator and the load. The first and second sensors are configured to connect to the feeder apart from one another with feeder impedance therebetween. 
     The first sensor can be configured to sense at least one of voltage and/or current in each one of three phases of the feeder, and the second sensor can be configured to sense at least one of voltage and/or current in each one of three phases of the feeder. 
     The system can further include the generator operatively connected to be controlled by the GCU, and the can be feeder connected to supply power from the generator to a load. The first sensor can be electrically closer to the generator than to a load end of the feeder than the second sensor relative to feeder impedance. 
     The system can also include logic in the GCU, which can be configured to cause the GCU to use feedback from the first and second sensors to control the generator. The logic can be configured to detect faults in each of the first and second sensors and continue operation of the generator in the event of only one of the sensors faulting. The logic can be configured to cause the GCU to detect a discrepancy between the first and second sensors, decide whether the first sensor is at fault or whether the second sensor is at fault when detecting the discrepancy, and control the generator based on feedback from whichever of the first or second sensors are not at fault. 
     Detecting a discrepancy can include comparing summed magnitudes or magnitudes squared of voltage and/or current sensed for each of three phases of the feeder for each of the first and second sensor versus a respective threshold [V_OSF_TH and −V_OSF_TH] for each of VPOR_OSF (voltage open sense failure at the point of regulation for the second sensor) and VGEN_OSF (voltage open sense failure at the point of the first sensor). VPOR_OSF can be logic for comparing the V_OSF_Th threshold to the summed magnitudes or magnitudes squared of voltage and/or current sensed for each of three phases of the feeder for each of the first and second sensor. VGEN_OSF can be logic for comparing the −V_OSF_Th threshold to the summed magnitudes or magnitudes squared of voltage and/or current sensed for each of three phases of the feeder for each of the first and second sensor. 
     Each of the VPOR_OSF and VGEN_OSF can connect through a latch to a respective switch for switching off faulty feedback from the respective one of the first and second sensors to the GCU. Detecting the discrepancy can also include transforming three phases from each of the first and second sensors to Alpha-Beta coordinates, then taking the magnitude of the Alpha-Beta for each. 
     The system can include filtering when deciding. The system can filter based on whether the difference of magnitudes (or magnitudes squares) exceeds a threshold a certain number of consecutive times. Additionally, or alternatively, the system can filter by difference of magnitudes (or magnitudes squares) is a processed through an infinite impulse response (IIR) filter. Additionally, or alternatively, the system can filter by difference of magnitudes (or magnitudes squares) is a processed through a finite impulse response (FIR) filter. 
     A method comprises using feedback from first and second sensors spaced apart along a feeder to control a generator powering a load through the feeder. The method also includes detecting a fault in one of the first and second sensors and continuing operation of the generator. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is a schematic plan view of an embodiment of a generator control system constructed in accordance with the present disclosure, showing feedback control circuit; 
         FIG. 2  is a schematic logic diagram showing the generator control unit of  FIG. 1 ; 
         FIG. 3  is a schematic logic diagram showing a method of calculating magnitudes squared; 
         FIG. 4  is a schematic logic diagram showing a method of calculating magnitudes; 
         FIG. 5  is a schematic logic diagram showing another method of calculating a magnitudes or magnitudes squared; 
         FIG. 6  is a schematic box diagram showing a method in accordance with at least one aspect of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of a system in accordance with the disclosure is shown in  FIG. 1  and is designated generally by reference character  100 . Other embodiments of systems in accordance with the disclosure, or aspects thereof, are provided in  FIGS. 2-5 , as will be described. The systems and methods described herein can be used to quickly determine a fault and accommodate using minimal resources. 
     A system  100  comprises a generator control unit (GCU)  102  that can be configured to control a generator  104 . The generator  104  can be operatively connected to the GCU  102  to be controlled by the GCU  102 , and the feeder  108  can be connected to the generator  104  to supply power from the generator  104  to a load  110 . The system  100  can include a first sensor  106  connected to a feeder  108  to provide feedback to the GCU  102  for generator control. The first sensor  106  can be configured to sense at least one of voltage and/or current in the feeder  108 , the feeder  108  connecting between the generator  104  and the load  110 . The system  100  can also include a second sensor  112  connected to the feeder  108  to provide feedback to the GCU  102  for generator control. The second sensor  112  can also be configured to sense at least one of voltage and/or current in the feeder  108 . The first and second sensors  106 , 112  can be configured to connect to the feeder  108  separated by a feeder impedance  114 . 
     As shown in  FIG. 1 , the first sensor and second sensors  106 ,  112  each can be configured to sense at least one of voltage and/or current in each one of three phases, a,b,c, of respective portions of the feeder  108 . For example, the first sensor  106  can be electrically closer to the generator  104  than to the load  110  end of the feeder  108  than the second sensor  112  relative to the feeder impedance  114 . 
     Referring now to  FIG. 2 , the system  100  can also include logic in the GCU  102 . The logic can include machine readable instructions, digital circuitry, analog circuitry, any combination of thereof, and/or any other suitable form of logic. The logic can be configured to cause the GCU  102  to use feedback from the first and second sensors  106 , 112  to control the generator  104 . For example, the logic can be configured to detect faults in each of the first and second sensors  106 , 112 , and even if a fault is detected, the logic can continue operation of the generator  104 . In embodiments, the logic can be configured to cause the GCU  102  to detect a discrepancy between the first and second sensors  106 , 112  and decide whether the first sensor  106  is at fault or whether the second sensor  112  is at fault. After detection and determination of which sensor has faulted, the logic can then control the generator  104  based on feedback from whichever of the first or second sensors  106 , 112  are not at fault. This process will be described in more detail below. 
     In  FIG. 2 , feedback from the first sensor  106  is represented by V_GEN_abc_Sense, and feedback from the second sensor  112  is represented by V_POR_abc_Sense. The logic can then calculate the sum voltage/current magnitude or the voltage/current magnitude square for each of V_POR_abc_Sense and V_GEN_abc_Sense using either of the methods shown in  FIGS. 3-4 . For example,  FIG. 3  shows a method for calculating a magnitude squared, while  FIG. 4  shows a method for calculating a magnitude.  FIG. 5  shows an alternative method for calculating either a magnitude and/or a magnitude squared. While  FIG. 5  shows a square root step, it should be appreciated that this step is optional if a magnitude is desired over a magnitude squared. 
     In order to quickly detect a discrepancy, the logic can then compare the summed magnitudes or magnitudes squared  120 , 122  of voltage and/or current sensed for each of three phases a,b,c of the feeder  108  for each of the first and second sensor  106 , 112  versus a respective threshold [e.g. V_OSF_TH and −V_OSF_TH] for each of VPOR_OSF (voltage open sense failure at the point of regulation for the second sensor) and VGEN_OSF (voltage open sense failure at the point of the first sensor), e.g. using a comparator  124 . 
     VPOR_OSF can represent logic for comparing the V_OSF_Th threshold to the summed magnitudes or magnitudes squared  120 , 122  of voltage and/or current sensed for each of three phases a,b,c of the feeder  108  for each of the first and second sensor  106 , 112 . VGEN_OSF can represent logic for comparing the −V_OSF_Th threshold to the summed magnitudes or magnitudes squared  120 , 112  of voltage and/or current sensed for each of three phases a,b,c of the feeder  108  for each of the first and second sensor  106 , 112 . 
     After comparing the sensed voltage and/or current with the threshold as described above, each of the VPOR_OSF and VGEN_OSF can connect through a respective latch  116  to a respective switch  118 . The latch  116  latch can be disposed within each branch of the logic diagram as shown, so that the latch  116  can suppress a faulted sense. Once a sense has passed through latch  116 , the latch  116  must be reset to resume normal two sense operation. If a fault is detected in either branch, the switches  118  can then switch off faulty feedback from the respective one of the first and second sensors  106 , 112  to the GCU  102 . Optionally, when detecting a discrepancy, the logic can include transforming three phases from each of the first and second sensors  106 , 112  to Alpha-Beta coordinates, and then taking the magnitude of the Alpha-Beta for each, for example as shown in  FIG. 5 . 
     The system  100  can include filtering when deciding which of the first and/or second sensors  106 , 112  is experiencing fault. The system can filter based on whether the difference of magnitudes  120  (or magnitudes squared  122 ) exceeds a threshold a certain number of consecutive times. Additionally, or alternatively, the filter can be a difference of magnitudes  120  (or magnitudes squared  122 ) is processed through an infinite impulse response (IIR) filter, for example a low pass filter. Additionally, or alternatively, the filter can be difference of magnitudes (or magnitudes squared  122 ) is processed through a finite impulse response (FIR) filter, for example a moving average filter. 
     In  FIG. 6 , a method  200  can comprise, at box  202 , using feedback from first and second sensors  106 , 112  spaced apart along a feeder  108  to control a generator  104  powering a load  110  through the feeder  108 . The method  200  can also include, at box  204 , detecting a fault in one of the first and second sensors  106 ,  112  and continuing operation of the generator  104 . In embodiments, the method  200  can include filtering when detecting a fault in one of the sensors  106 , 112  and deciding which sensor  106 , 112  is at fault, as shown at box  206 . 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for faster detection of faults within a feeder. Redundancy of sensors allows for optimization of logic to very quickly sense fault and correct with minimal resources. While the apparatus and methods of the subject disclosure have been shown and described, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.