Research On Application Of Frequency Conversion And Speed Adjustment Based On PLC For Hydropower Station Crane

With the development of giant hydropower station in china, hydroelectric projects' construction and operation need the oversize crane equipments to have high performance control. The hydropower station's cranes are used in Power Station's set or Installation. If there is failure in the process of installation, It will be a great impact on the project, causing significant damage to equipment and economic losses, so the high reliability of crane is very important. In addition, the crane must be operated smoothly, parked positioning accuracy and has a wide speed range, in order to meet the demands of all conditions. Because there are few staff in the hydropower stations, it demands crane on the high level of automation and self-diagnosis function.Three-phase AC asynchronous motor was selected for the drive system of Hydropower station crane. The method of Adjustable-speed including adjustable voltage speed control or adjustable series with resistance speed control, is characterized by large energy loss, mechanical shock, the high skill requirements for operators, low work efficiency. Control methods in which use Relay-contactor control loop, have high failure rate, and can't monitor various parameters. In a word, the electrical control system of traditional crane can't meet cranes' high reliability, flexible and intelligent demands.With the development of microelectronic technology, power electronics and microprocessor technology, transistors converter and programmable logical controller (PLC) came into existing. Inverter not only overcomes many shortcomings of AC Drive, but also it uses vector control method that can compare with DC motor speed performance. Frequency Conversion Adjustable-speed has excellent startup, speed regulation, braking performance, high efficiency, high power factor and energy-saving effect. It was recognized as the most promising speed regulation method. Frequency Conversion Adjustable-speed shows its superiority especially in crane domain. With the high reliability, the use of flexible and low maintenance working, PLC is widely used in industrial areas.For Hydropower giant cranes' control requirements and characteristics, this paper researches on the existing hydropower stations crane control characteristics, compares the existing technical programs, determines a suitable Frequency Conversion Adjustable-speed structure and control; designs the crane's control system processes, protracts control flow charts and determines the number of PLC units. And this paper focuses on crane's network structure, connection methods, human-machine interface and procedures design. For some special function of Hydropower cranes, this paper puts forward some control ideas which solve some key technologies, such as: automatically correcting deviation, and designs associated with software and hardware.After longer actual operation, this control system fully meets the performance requirements, and has high level of automation, perfect function and high reliability characteristics.