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Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Reference Manual Governing Fundamentals and Power Management This manual replaces manuals 01740 and 25195. Manual 26260 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Woodward Governor Company reserves the right to update any portion of this publication at any time. Information provided by Woodward Governor Company is believed to be correct and reliable. However, no responsibility is assumed by Woodward Governor Company unless otherwise expressly undertaken. © Woodward 2004 All Rights Reserved Manual 26260 Governing Fundamentals and Power Management Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Contents CHAPTER 1. INTRODUCTION TO GOVERNING ................................................ 1 Introduction.............................................................................................................1 Other References ...................................................................................................1 What is a Governor?...............................................................................................1 Governor Components ...........................................................................................3 Development of the Modern Governor System......................................................4 CHAPTER 2. HYDRO-MECHANICAL GOVERNORS ........................................... 5 Basic Hydro-mechanical Governor Components...................................................5 The Speeder Spring ...............................................................................................5 Thrust Bearing ........................................................................................................6 Flyweights...............................................................................................................6 Pilot Valve Plunger and Bushing ............................................................................8 Oil Pumps ...............................................................................................................9 Direction of Rotation .............................................................................................10 The Servo (Power) Piston ....................................................................................11 CHAPTER 3. DROOP .................................................................................. 13 Introduction...........................................................................................................13 Why Is Droop Necessary?....................................................................................13 Speed Droop Operation .......................................................................................14 Uses Of Droop......................................................................................................15 Isolated Systems ..................................................................................................18 CHAPTER 4. LINKAGE................................................................................ 22 General .................................................................................................................22 Governor Travel....................................................................................................23 Linear Linkage Arrangements ..............................................................................24 Non-Linear Usage ................................................................................................25 CHAPTER 5. MAGNETIC PICKUPS ............................................................... 26 Introduction...........................................................................................................26 CHAPTER 6. LOAD SENSING, LOAD SHARING, BASE LOADING ................... 30 Load Sensing........................................................................................................30 Load Gain Adjust Potentiometer ..........................................................................30 Balanced Load Bridge ..........................................................................................31 Power Output Sensor ...........................................................................................34 Isochronous Base Load........................................................................................34 CHAPTER 7. SYNCHRONIZATION ................................................................ 39 What Is Synchronization?.....................................................................................39 Why Is Synchronization Important?......................................................................42 How Is Synchronization Accomplished? ..............................................................42 Prediction of the Worst Case Phase Angle Difference (φ) at the Instant of Breaker Closure....................................................................................................44 Woodward i Governing and Power Management Manual 26260 Simpo PDF MergeFundamentals and Split Unregistered Version - http://www.simpopdf.com Contents CHAPTER 8. MANAGING POWER FOR THE DESIRED RESULT .......................46 Peaking or Peak Load Control .............................................................................46 Cogeneration ........................................................................................................51 Single Engine AGLC–Base Load Control.............................................................51 Isolated Bus Isochronous Load Sharing System .................................................57 Multiple Engine AGLC–Base Load Control ..........................................................60 Automatic Paralleling System (2301A) to a Utility Using a Process-Import/Export Control ..................................................................................................................63 Automatic Paralleling System (2301A) to a Utility Using an Automatic Power Transfer And Load (APTL) Control.......................................................................66 Illustrations and Tables Figure 1-1. The Driver is the Governor...................................................................2 Figure 1-2. Speed Balance.....................................................................................2 Figure 2-1. Speeder Spring ....................................................................................5 Figure 2-2. Speeder Spring Deflection ...................................................................6 Figure 2-3. Hydraulic Governor Ballhead ...............................................................6 Figure 2-4. Flyweight Action ...................................................................................7 Figure 2-5. Flyweights to Minimize Friction ............................................................7 Figure 2-6. Pilot Valve Operation Shown “On Speed” ...........................................8 Figure 2-7. Oil Pumps.............................................................................................9 Figure 2-8. Accumulator and Governor Relief Valve............................................10 Figure 2-9. Pump Rotation ...................................................................................10 Figure 2-10. Spring Loaded Servo Piston ............................................................11 Figure 2-11. Differential Power Piston..................................................................12 Figure 3-1. Response Curves of Governor without Droop or Compensation ......13 Figure 3-2. Droop Feedback ................................................................................14 Figure 3-3. Compensated Governor Schematic...................................................15 Figure 3-4. Comparison of 3% Droop Speed Settings for 50% and 100% Load .16 Figure 3-5. 3% and 5% Droop Curves .................................................................16 Figure 3-6. Droop Mode .......................................................................................17 Figure 3-7. Swing Machine...................................................................................18 Figure 3-8. Droop Units ........................................................................................19 Figure 3-9. Base Load with 5% Droop .................................................................20 Figure 3-10. Schematic of Droop Governor .........................................................21 Figure 4-1. Linear Fuel Control ............................................................................22 Figure 4-2. Non-Linear Fuel Control.....................................................................23 Figure 4-3. Correct Use of Governor Travel.........................................................23 Figure 4-4. Nonlinear Carburetor Linkage............................................................25 Figure 5-1. Magnetic Pickup.................................................................................26 Figure 5-2. Low Reluctance Gear Position ..........................................................27 Figure 5-3. High Reluctance Gear Position..........................................................27 Figure 5-4. Magnetic Pickup and Gear Dimensions.............................................28 Figure 5-5. Generated Waveforms.......................................................................29 Figure 6-1. Generator Load Sensor .....................................................................30 Figure 6-2. Balanced Load Bridge........................................................................31 Figure 6-3. Basic Load Sensing Block Diagram...................................................32 ii Woodward Manual 26260 Governing Fundamentals and Power Management Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Illustrations and Tables Figure 6-4. Load Sharing Diagram .......................................................................36 Figure 6-5. Load Sharing Block Diagram .............................................................37 Figure 6-6. Multiple Load Sharing Block Diagram................................................38 Figure 7-1. Number of Phases Must Match Number Of Phases..........................39 Figure 7-2. Phase Rotation Must be the Same Rotation Of Phases....................40 Figure 7-3. Voltage Difference (Generator to Generator) ....................................40 Figure 7-4. Voltage Difference (Generator to Bus) ..............................................40 Figure 7-5. Frequency Difference.........................................................................41 Figure 7-6. Phase Difference ...............................................................................41 Figure 7-7. Checking Phase Match ......................................................................43 Figure 7-8. Checking Phase Rotation and Match ................................................43 Figure 7-9. Phase Angle Relationship..................................................................45 Figure 8-1. "Peaking" or Peak Load Control ........................................................47 Figure 8-2. Base Loading .....................................................................................48 Figure 8-3. Peak Shaving.....................................................................................48 Figure 8-4. Import Power......................................................................................49 Figure 8-5. Import Power (Constant Level) ..........................................................49 Figure 8-6. Export Power .....................................................................................49 Figure 8-7. Export Power (Constant Level)..........................................................50 Figure 8-8. Import/Export Control.........................................................................50 Figure 8-9. Zero Import/Export .............................................................................50 Figure 8-10. Synchronizing to Utility or Plant Bus................................................53 Figure 8-11. Synchronizing Gen Set to Plant Bus or to Utility .............................54 Figure 8-12. Single Engine AGLC Base Load......................................................55 Figure 8-13. Connections for Single Engine AGLC Base Load System ..............56 Figure 8-14. Using AGLC for Soft Load, Soft Unload, and Base Load to an Isolated Bus for Isochronous Load Sharing ....................................58 Figure 8-15. Connections Used with AGLC for Soft Loading, Unloading, and Base Loading with Isochronous Load Sharing Against an Isolated Bus...................................................................................................59 Figure 8-16. Using the AGLC to Base Load Multiple Engines to a Utility ............61 Figure 8-17. Connecting an AGLC to Base Load Multiple Engines to a Utility ....62 Figure 8-18. Using Process-Import/Export Control to Automatically Parallel ......64 Figure 8-19. Connecting Process-Import/Export Control to Paralleling System ..65 Figure 8-20. Using APTL in Automatic Paralleling System..................................67 Figure 8-21. Connecting APTL in Automatic Paralleling System.........................68 Woodward iii Governing and Power Management Manual 26260 Simpo PDF MergeFundamentals and Split Unregistered Version - http://www.simpopdf.com iv Woodward Manual 26260 Governing Fundamentals and Power Management Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Chapter 1. Introduction to Governing Introduction This manual combines former Woodward manuals 25195 (Governing Fundamentals) and 01740 (Power Management). Chapters 1–5 cover basic governing, and chapters 6–9 cover the principles of power management. Other References Other useful references you might find useful can be found on our website (www.woodward.com): Pub. No. 25075A 25070D 25014C 25179C 50516 82715H 82510M 25071J 83402 83408 50511A 50500D 01302 51214 Title Commercial Preservation Packaging for Storage of Mechanical-Hydraulic Controls Electronic Control Installation Guide Gas Engine Governing Glossary of Control Names Governor Linkage for Butterfly Throttle Valves Guide for Handling and Protection: Electronic Controls, PCBs, Modules Magnetic Pickups and Proximity Switches for Electronic Controls Oils for Hydraulic Controls PID Control PLCs for Turbine Control Systems Prediction of Phase Angle at Breaker Closure Simplified Unloading Scheme for Electric Governors Speed Droop & Power Generation Work versus Torque In addition, all product specifications, brochures, catalogs, and application notes (as well as many technical manuals) can be found on the website. What is a Governor? All power sources must be controlled in order to convert the power to useful work. The essential device which controls the speed or power output of an engine, turbine, or other source of power is called a governor. For simplicity, we’ll call the source of power a prime mover. A governor senses the speed (or load) of a prime mover and controls the fuel (or steam) to the prime mover to maintain its speed (or load) at a desired level. In some cases the governor controls other factors that determine the speed or load of the prime mover. In all cases, a governor ends up controlling the energy source to a prime mover to control its power so it can be used for a specific purpose. Woodward 1 Governing and Power Management Manual 26260 Simpo PDF MergeFundamentals and Split Unregistered Version - http://www.simpopdf.com Example—If you’ve ever driven a car, you’ve functioned as a governor when you control the car’s speed under varying driving conditions. Figure 1-1. The Driver is the Governor The driver (governor) adjusts the fuel to maintain a desired speed. If the speed limit is 100 (this is the desired speed), you check the speedometer (the car’s actual speed). If actual speed and desired speed are the same, you hold the throttle steady. If not equal, you increase or decrease throttle position to make the desired speed and the actual speed the same (see Figure 1-2). As the car starts uphill, the load increases and actual speed decreases. The driver notes that actual speed is less than desired speed and moves the throttle to increase speed back to the desired speed at the increased load. As the car goes downhill, the load decreases and actual speed increases. The driver notes that actual speed is greater than desired speed and decrease the throttle to return to the desired speed with the decreased load. Figure 1-2. Speed Balance 2 Woodward Manual 26260 Governing Fundamentals and Power Management Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com If your car has a cruise control, the cruise control is a simple governor. Governor Components All governors have five fundamental components: • A way to set the desired speed. (The driver sets the desired speed mentally.) • A way to sense actual speed. (The driver refers to the speedometer). • A way to compare the actual speed to the desired speed. (The driver compares the two items mentally.) • A way for the governor to change the fuel to the prime mover (moving the rack or fuel valve). (The driver moves the throttle.) • A way to stabilize the engine after a fuel change has been made. In the example, when the car went up a hill, the driver saw the actual speed decrease and moved the throttle to increase the fuel. You will need to increase the fuel an amount to cause the speed to increase. This will give the engine enough power to make the car return to the desired speed with a bigger load. As you see that the actual speed is about to reach the desired speed, you reduce the extra fuel to the exact amount needed to match (balance) the desired speed with the actual speed. The governor does the same thing, using feedback. This feedback closes the loop in the control system which controls the amount of fuel change, based on the rate the desired speed is being reached. This prevents large overshoots or undershoots of speed which is known as hunting, and stabilizes the engine. The opposite is true when the car goes down the hill or load is reduced. 1. Speed Setting Setting the “desired speed” of a governor is necessary to efficiently control prime movers. Modern governors have advanced systems of speed setting which can compensate for a variety of conditions when determining the desired speed. Hydro-mechanical governors use what is known as a speeder spring. The more force applied to this spring, the higher the desired speed setting is. Electronic controls use an electronic force (voltage and current) to set speed. The more the force is increased, the more the output to the fuel increases. Speed setting and the effect on sharing loads between engines will be discussed in other chapters. 2. Woodward Sensing Speed The governor must receive a force that is proportional to the speed of a prime mover. In hydro-mechanical governors, it is done by the centrifugal force of flyweights being rotated from a drive system that is connected to the prime mover, and is directly related to the speed of the prime mover. In electronic controls, this force comes from sensing of the frequency of a magnetic pickup, alternator, or generator which is directly related to the speed of the prime mover. The frequency is then changed to an electronic force that the control can use. In both cases, the faster the engine runs, the stronger the speed sensing force becomes. 3 Governing and Power Management Manual 26260 Simpo PDF MergeFundamentals and Split Unregistered Version - http://www.simpopdf.com 3. Comparing the “Actual Speed” to the “Desired Speed” The force of the “desired speed setting” and the force of the “actual speed” are compared or “summed” together. “Desired speed setting” is a force in one direction and “actual speed” is a force in the opposite direction. When these opposing forces are the same value, their sum will be zero and at that point the governor is controlling actual speed at the point of the desired speed setting. If the “desired speed setting” force is stronger than the “actual speed” force, the governor will increase fuel. If the “actual speed” force is stronger than the “desired speed setting” force, the governor will decrease fuel. As fuel is increased or decreased, these forces will change until they balance or “sum to zero.” In hydro-mechanical governors, these forces are summed at the “thrust bearing”. In electronic controls, these forces are summed at what is known as a “summing point.” Note that other forces can be applied along with these forces to allow the governor to be stabilized and perform other functions (some of these are covered in later chapters). Remember that all forces applied to the “thrust bearing” or “summing point” must algebraically sum up to zero for the governor to control fuel at a steady state. 4. Ways for the Governor to Change Fuel to the Prime Mover The hydro-mechanical governor or actuator normally has a rotational or linear output shaft that is connected to the prime mover‘s fuel system. When the governor needs to make a fuel correction to maintain speed (or load), the output shaft moves in the proper direction to correct the final fuel setting. For electronic controls, an electrical signal is sent to an actuator which converts this electrical signal to a mechanical force to move the fuel setting in the same way the hydro-mechanical governors do. Different types of governors and actuators have different amounts of work output to meet the control needs of various prime movers. 5. Ways to Stabilize the Prime Mover Stabilization is accomplished through a variety of ways, but all of them use a “feedback” system to apply a force to the “thrust bearing” or “summing point.” This “feedback” is normally in the form of either droop or compensation, or in a combination of both. Droop or compensation is usually related to the amount the output shaft is told to move (Chapter 3 describes the essential principle of droop feedback). Note that in many prime mover systems (such as power generation), the speed of the prime mover is fixed. While the governor still controls the prime mover’s speed setting mechanism, the end result of changes in the prime mover’s speed setting under fixed-speed conditions is that an increase or decrease in the speed setting causes the prime mover to take on a larger or smaller load. Development of the Modern Governor System The first modern governors were applied to controlling the speed and load of water wheels (which were used to power many of the early factories during the “Industrial Revolution”. Early governors also controlled steam turbines. The development of gasoline and diesel internal combustion engines required faster and more complex governors. Electrical power generation created a much greater need for more precise governor control of speed and load. Hydro-mechanical governors became ever more complex to meet growing needs for precise control. Since the 1970s, electronic controls have significantly improved and expanded the capabilities of governing systems, controlling not only speed and load, but also electrical loads, exhaust emissions, and many other parameters. 4 Woodward