Research On Bi-directional DC-DC Converter Applied To The Elevator Energy-saving System

As a high energy consumption special equipment,elevator energy consumption accounts for 17%-25% of building energy consumption in China,which has enormous energy_saving space.In order to overcome the energy waste and the harmonic pollution problem of the inverter scheme in the traditional elevator energy-consuming braking scheme,this paper proposes a super capacitor energy saving technology of elevator: using super capacitor to store and reuse the regenerative energy of elevator to achieve the purpose of energy saving.The core of this technology is bi-directional DC-DC converter,and the key problems in the application of energy saving elevator are researched.Firstly,this paper analyzes the current power supply scheme of most elevators,determines the function index of bi-directional DC-DC converter based on compatibility,and chooses bi-directional full-bridge topology as the topological scheme of this paper.On this basis,the topology improvement is completed and a double closed loop control scheme based on digital voltage outer loop and analog peak current inner loop is designed.Secondly,this paper makes the design of the system modeling and control strategy.According to the double closed-loop control scheme and the characteristics of the elevator structure,this paper analyzes the system from the current inner loop and the voltage outer loop respectively.Discrete-Pulse modeling method is used to obtain the discrete small signal model of the inner loop of the current.The influence of homogeneous harmonic oscillation and active clamp circuit on the stability of the system is analyzed.The equivalent power level model of the voltage outer loop is obtained by using the state space averaging method,and the control strategy of conventional PI controller and variable parameter PI controller is designed respectively.On this basis,the time domain simulation of MATLAB/Simulink is carried out,and the correctness of the above theory is verified.Finally,in order to validate the feasibility of the scheme,this paper constructs the system experiment platform,and designs the corresponding test plan.The experimental platform includes hardware and software:the hardware part consists of the main topology circuit and the control circuit,and the software is composed of the FPGA program and the DSP program.The test scheme includes the current loop experiment and the voltage Loop experiment,verifying the system dynamic and steady state characteristics respectively.The experimental results show that the design can fulfill the expected function index and satisfy the requirements of the working conditions of elevator system.