Predictive Set Point Modulation Control for Supercapacitor Storage Systems of Catenary-Free Trams

Supercapacitors have been considered as a promising choice for public transportation electrification, e.g., catenary-free trams, as the only power source. Due to the frequent stops and drastic load changes of trams, the DC bus of supercapacitor storage systems exhibits significant voltage fluctuations, which degrades the reliable operation of trams. In this article, we propose a predictive set point modulation control method for supercapacitors storage systems, where the reference voltage is regulated in real time based on the prediction of DC bus voltage, which can effectively suppress the voltage fluctuations. We first model the supercapacitor storage systems based on the averaging method. Then, a cascade control framework is designed to regulate the DC bus voltage. A predictive set point modulation control method is designed to suppress the voltage fluctuations without changing the closed-loop system structure. We built a laboratory hardware platform to illustrate the performance of the proposed method. Both simulation and experiment results verify that the proposed method can effectively suppress the voltage fluctuations of the DC bus when compared with classical methods.