Research And Development Of The DC/AC Converter On The Energy Absorption Of Regenerative Braking In Metro

With the increase of the subway lines, how to use renewable braking energy, to achieve energy conservation, and to improve the environment has become a common concern of rail transit.Because of the short distance between subway stations and frequently braking of metro vehicles, the system produced considerable regeneration energy. The common solution is equipped with vehicle resistance or ground resistance, resulting in energy waste and the temperature rise of the tunnel, which brings the additional losses because of the ventilation.The regenerative energy feedback converter is capable of returning the regenerative braking energy to the traction AC grid for the use of other equipment, which is a major way of using renewable energy. Combined with scientific research projects, this paper developed the large capacity feed converter used in subway.Firstly, the mathematic model of the feed converter is established, and the steady-state analysis of the PWM converter is carried out under the synchronous rotating coordinate system. Aiming at the subway power supply environment, a set of high-power regenerative braking energy feedback inverter device is designed, which consists of two identical PWM converter and a two-winding transformer secondary side. And the design and selection of main circuit are developed including the power components, AC inductors and the support capacitor of DC side.Secondly, the design scheme of the feedback control system is given, The double-closed-loop control and space vector modulation scheme based on synchronous rotation coordinate system is completed, The control loop and parameters of the voltage outer ring and the inner current loop are designed, By the FPGA + ARM dual control chip composed of the main control board,All the core control algorithms are implemented in the FPGA, and the data communication function is implemented in ARM.. Then the control method is simulated and analyzed under MATLAB. The current and voltage state and its current harmonic characteristics of the converter are investigated operated under the unit factor inverter active current condition, sending inductive reactive current condition and sending capacity condition. And the controllable voltage source is used to simulate the change of the catenary voltage caused by the traction and braking of the train, and then simulate the energy feedback waiting for the energy feedback working state.Finally, the feedback test of regenerative braking energy feedback converter of 2MW subway was carried out. Two measured converters work in the rectifier and inverter conditions respectively, and carrying out a complete power assessment to verify the feasibility of the design. At last, the device was applied to the subway traction power supply site.Feedback test in station and reciprocal feed test between the adjacent stations verify the performance of its hanging network.