Modular current source AC-Drive: A simple control scheme

Recent developments in current source topologies involve the staking of standard topologies to handle large currents as in medium voltage AC-drives. These solutions deal with (a) balancing currents among the topologies, (b) operating the group at unitary displacement power factor, and (c) accomplishing AC input current quality requirements. This paper presents a simple control strategy to achieve the objectives (a) and (b) in a stacked current source topology. In addition, the objective (c) is achieved by integrating the DC link current controllers with a modified master PLL algorithm, thus unity displacement power factor is reached before, during and after transient requirements. On the other hand, the input current quality is improved by using an optimized multilevel modulation technique. Complete mathematical formulations as well as experimental results validate the proposed approach.