Super Twisting Sliding Mode Control Strategy for Input Series Output Parallel Converters

In this paper, a super twisting sliding mode control method (ST-SMC) is proposed for an isolated input series output parallel current source converter (ISOP-CSC). The main idea behind the input series output parallel connection is to share the input voltage and output current among the converter cells. Since the input current of each cell has to be identical, the control strategy should be able to provide an accurate phase angle to each cell at the same time. The decentralized control method requires a current sensor for each cell. Therefore, the controller performance can be affected by faults, measurement errors and noises in the slave cell's current sensor. To overcome this issue, the proposed ST-SMC method generates the phase shift between the primary side switching signals of the master cell. After that, the generated phase shift value is transferred to the slave modules. Thus, the same phase angle value is used for each cell and the current sensor is only needed for the master cell. Furthermore, the proposed method doesn't need any voltage sensor. The effectiveness of the proposed control method is investigated by experimental studies that are performed on an ISOP-CSC prototype. The results reveal that the proposed method successfully regulates the input current to reference value under both steady-state and dynamic transition conditions.