Research On Key Technologys Of Bidirectional DC-DC Converter In Energy Saving Elevator System

The elevator is playing a more and more important role in our lives, and itsenergy consumption is becoming a severe problem. In this paper, an energy savingtechnique based on the super capacitor is presented: the energy is saved in the waythat the super capacitor stores energy when the elevator machine feeds back andreleases it when the machine is in need. In this system, the bidirectional DC-DCconverter is the core to energy saving system.The DC-DC converter is analyzed using small signal modeling, and theopen-loop transfer function of the system is given, based on which the AVR and theACR are designed. The simulation analysis is then given and the experimental test isalso made.When the traction machine is accelerated or decelerated, the bidirectionalDC-DC converter, which is used in the energy saving elevator, may suffer greatdisturbance. Therefore, the DC-DC converter is analyzed using large signalmodeling, and a new nonlinear control strategy is presented; parameters of the maincircuit and the control circuit of the converter are also optimized according to thelarge signal model and the feeding control methods.In the energy saving elevator, stability problems must exist in the cascadedsystem when the bidirectional DC-DC converter is connected with to the inverter. Sothe input and output impedance of each module are studied and the DC-DCconverter parameters are modified to guarantee that|Z_o|<<|Z_in|is true whether theconverter works in voltage current mode.A12kw prototype based on the bidirectional Buck-Boost topology structure isset up and the system hardware and software design is given. It is then applied in theenergy saving elevator system, and charging and discharging experiments are madeon the super capacitor, which verifies that the DC-DC converter can meet energysaving elevator system requirements.