A novel bounded cooperative multi-rate current-sharing control for parallel charging system with directed communication

In order to address the output current imbalanced problem of a parallel charging system with directed communication for energy storage type light rail vehicles, a cooperative current-sharing scheme is proposed in this paper. This parallel charging system is a non-identical nonlinear multi-agent systems with bounded input constraints by considering each charger as an agent. Each charger transmits the current state information to its neighbors via communication network, which can be modeled by a directed graph. Input-output feedback linearization is introduced to convert the current-sharing control of non-identical nonlinear parallel charging system into a first-order multi-rate integrator current consensus-tracking problem. To satisfy the boundedness of control input, a general saturation function is put forward to design the bounded cooperative current-sharing control law based on the nearest neighborhood rule. A novel Lyapunov candidate function depending on the communication topology is proposed to rigorously prove the cooperative current-sharing stability of closed-loop system, which is under the fixed directed topology provided that the digraph only has a directed spanning tree. Several charging schemes are compared and analyzed. The output current of parallel chargers can be balanced by adopting the proposed approach, which is verified by simulating a parallel charging test system.