Hierarchical current tracking in multiswitching systems

The present paper deals with an innovative approach to control compound multiswitching converter systems. The proposed modulation strategy directly controls the external current. A simple tracking algorithm working at very high frequency manages the switching of the system as a whole. Once the switching action is decided by a master routine, the choose of which leg has to be effectively switched is demanded to a separate slave routine. An acceleration algorithm and a maximum leg currents protection are also adopted. Under the proposed approach the system bandwidth is related to the global switching frequency equal to the valve frequency multiplied by the number of valves. As long as the external current is directly measured and processed by the master control, cumulative errors from acquisitions and processing of single leg currents are avoided. Consequently both system dynamics and accuracy over external current are greatly improved. Details of the proposed control and simulation results are reported.