Regenerative braking strategy for motor hoist by ultracapacitor

Rising concern in environmental issues on global scale has made energy saving in powered equipment a very important subject. In order to improve the energy efficiency and driving range of a motor hoist, a regenerative braking system is designed and discussed. The system takes a unique ultracapacitor-only approach to energy storage system. The bi-directional bride DC/DC converter which regulates current flow to and from the ultracapacitor operates in two modes: boost and buck, depending on the direction of the flow. In order to provide constant input and output current at the ultracapacitor, this system uses a double proportional-integral (PI) control strategy in regulating the duty cycle of PWM to the DC/DC converter. The permanent magnet synchronous motor (PWSM) drive system is also studied. The space vector pulse width modulation (SVPWM) technique, along with a two-closed-loop vector control model, is adopted after detailed analysis of PMSM characteristics. The overall model and control strategy for this regenerative braking system is ultimately built and simulated under the MATLAB and Simulink environment. A test platform is built to obtain experimental results. Analysis of the results reveals that more than half of the gravitational potential energy can be recovered by this system. Simulation and experimentation results testify the validity of the double PI control strategy for interface circuit of ultracapacitor and SVPWM strategy for PMSM.