A current source inverter with advanced circuit and control method

In this paper, a thyristor-based current source inverter (CSI) is proposed, employing single voltage source inverter (VSI) with small power rating as an external circuit. Three tasks are performed by the VSI: 1) turning-off of thyristors; 2) transfer of reactive load energy; 3) clamping peak voltages across the load and thyristors. The proposed CSI system with the small VSI can realize the commutation process of the inductive loads without large AC capacitors and complicated auxiliary circuits accompanying complex controls. Furthermore, the proposed CSI ensures simple and easy control of the commutation process due to the simple switching operation of the VSI. The VSI operates only during commutation periods of the load currents and stops working over the non-commutation periods. Thus, the VSI with small power rating can be used for the proposed CSI system. The feasibility of the proposed CSI system is verified by simulation and experimental results