Vvvf Technology And Speed Control Using On Hydraulic Elevator

Hydraulic elevator is being widely used for its specific advantages comparing with traction elevator, such as lower noise level, smaller space in the building. By now most of the hydraulic control system is controlled by proportional valve. But we find that this type of hydraulic elevator consumed large energy, and the dithering and shocking of elevator occurred frequently when elevator starting and leveling. Base on a new type of hydraulic elevator development, the theme of this dissertation is researching the speed control of elevator starting and leveling and the method of Variable Voltage Variable Frequency (VVVF) driven.The performance of starting and leveling is the key factor when we estimate elevator dynamic characteristic. We analyze the factor which determine the internal leakage value of pump, and then introduce the method of compensation. With compensation of the leakage and balance of the pressure, an optimized starting speed control process has been obtained. The traditional hydraulic elevator has a creeping before they stopped. This new type of elevator has an encoder fixed in the governor, which can feedback the speed and the position of car to the system. So we designed the software which calculate the deceleration point automatically. By this way, this new type of hydraulic elevator can directly stop at floor level without creeping. The validity of new method is proven by performing an experiment of elevator.The application of VVVF driven is another important content in this dissertation. The motor speed of hydraulic pump is controlled with VVVF technique, so that the overflow of oil and the energy wasting can be reduced. The structure of software is introduced. We analyze the relationship among torque, oil temperature and flow speed. A temperature and flow speed-feedfoward is used in speed control loop. The Transvector Control principle is explained detailedly. The structure of current control loop base on this principle and the function of different part for the loop are introduced. At last, a method to identify the motor parameters is provided.