Historical Background of the Origin of the Speeddroop, Additional Control Signals and Analogic Retrofit of a Governor of a Francis Turbine, Using Operational Amplifier IC741

Abstract

It is well known that governors of turbines, moving synchronous machines are responsible to maintain the rotation of the rotor of the generator constant and then the electric frequency constant, independently of the changes of electric loads connected to the power electric net. This paper treats about the origin and necessity of the permanent and transitory speedoops in the control mash of a governor. First, we develop the historical background origin of a governor. The basic controls actions are studied, and the analogic circuits related, using operational amplifiers. Then, as an easier way, the author uses an analogic generic PID governor to explain how the permanent speedroop is needed to set the power delivered by a hydraulic turbine (Francis) and then the transitory speedroop. Additional control signal as Power Joint Control and Automatic Generation Control-AGC are introduced. As a suggestion, a simple analogic Power Joint Control circuit example, using operational amplifier 741 is given, but not tested in a workbench. The using of the Automatic Control Generation-AGC, a supplementary control, is introduced because of the necessity to correct the frequency deviations. It is also given a simple circuit example of AGC, not tested in a workbench. This paper ends with an analogic retrofit of a governor of Francis turbine of decade of 1960 of 180 MW using analogic electronic. The author employs IC 741 operational amplifier. Prior simulations of the Laplace’s model of the governor were made using Matlab-Simulink. Because of the little acquisition time of the available oscilloscope, the author made a transformation in the original Laplace model that reduced the step response time by a factor of 20 but the methodology and know-how to make an analogic retrofit was conquered. The governor was built and tested in a workbench. The hydraulic circuit was simulated with 741 amp ops. The electronic simulation corresponded to the mathematics simulations showing the success of the analogic retrofit. The physical space needed by the equipment was reduced from the size of a refrigerator to a size of a shoe box. Although an analogic retrofit is considered obsolete today, the analogic retrofit has robustness, and it is cheaper.