Research And Development Of Hydraulic Turbine Governor Based On S7-200 PLC

Microprocessor-based governor is an important device in the hydraulic turbine control system. Recent years, the PLC technology has been widely applied in the field. In the first part of the paper, the principal and characteristics of the hydraulic turbine governor are discussed, then the history, current status and trends of hydraulic turbine governor are described. Then analyzes and discuss some technology of hydraulic turbine governor, including the system structure, regulating laws, control strategy and the technology of hydraulic turbine governor. SIMENS S7-200 PLC CPU226 is used to realize the basic function of turbine governor; the hardware and software of this system are analyzed in detail.By the virtual of the S7-200 PLC, the frequency measurement unit is designed. There is difference frequency measurement requirement for every part of PID regulating, difference between dynamic quality and static quality in response time and accuracy. According to these, it use the interrupt functions and high-speed counter of the SIMENS S7-200 PLC CPU226 basic unit and some peripheral circuit to measure frequency; In software designed, the procedure frame of hydraulic-turbine governor and disperse process of parallel PID are analyzed, An improved PID algorithm is adopted to realize a PID regulation mode with variable structure and parameters; The mechanical liquid-pressure system of the hydraulic-turbine governor is with electric-hydraulic converter unit of step motor . According to the drive character of five phase of response step motor, a variable frequency regulated voltage driver unit is designed in order to realize interface between PLC and driver of step motor. The interface utilizes the high-speed pulse function of PLC basicunit to realize the control frequency of pulse, PWM regulate voltage and to make use of drivers of step motor control step motor.The hydraulic-turbine governor sufficiency use interior function of S7-200 and a few peripheral circuits to realize primary function of microprocessor-based governor, the governor has the advantage of reliable, simple and small size. For simple program, extend easily and high performance but low cost, it will be widely used medium or small hydropower plants governor. It will enhance the automation level of hydropower plants governor.