Vibration-adaptive energy management technology for self-sufficient wireless ECP braking systems on heavy-haul trains

Abstract

To address insufficient power supply for wireless electronically controlled pneumatic (ECP) braking systems on railway freight wagons, a self-sufficient system can be developed by using rotary electromagnetic vibration energy harvesters (VEHs) to harness the secondary suspension vibrations. However, stochastic vibrations result in irregular and time-varying operational states of the system, posing challenges in efficient energy extraction, conversion and storage. In this paper, we propose a highly integrated and efficient energy management technology to simultaneously achieve vibration-adaptive maximum power point tracking (MPPT) and energy management functions. The vibration-adaptive MPPT is formulated through an analysis on the circuit DC side, estimating the optimal power generation state of the system based on the generator velocity. The energy management circuit (EMC) is implemented with a one-stage design based on a four-switch buck/boost (FSBB) topology embedded with a function-integrated control algorithm, simplifying the conventional two-stage structures and reducing unnecessary energy loss. In system integration tests, the EMC successfully achieves instantaneous MPPT under time-varying vibrations, achieving an average power of 1.83 to 14.03 W, along with an energy conversion efficiency of 83.3 to 89.2 %, at wagon speeds of 50 to 70 km/h. Additionally, a coupling model of the freight wagon and self-sufficient wireless ECP braking system is established to conduct an energy budget analysis, revealing that the system generates excess energy during high-speed operations. Thus, a system reliability enhancement strategy (SRES) based on the EMC is proposed to regulate the system damping, reducing the system energy input and mechanical loads, and achieving an RMS force reduction by up to 36 %. This study offers a versatile and reliable energy management approach for electromagnetic vibration energy harvesting, as well as a control interface for electromagnetic VEHs to adapt their mechanical properties to diverse application scenarios.