Single-phase current source converter with new modulation approach and power decoupling

Abstract

In this work it is presented a Current Source Converter (CSC) topology that helps to mitigate double line frequency power ripple (low frequency) effect. Low frequency power ripple presented in single-phase systems propagates through DC-bus converter. This low frequency ripple reduction allows to increase the power converter density by reducing the volume of the DC inductor, without lack of stiffness at the DC-bus. The low frequency mitigation is achieved by using a different single-phase CSC topology that uses three series-connected switches per leg. Thus, it allows independent control for two merged CSCs which share the same DC-bus and the middle switches of the leg. This solution is adequate to connect photovoltaic panels to the electrical grid, among others applications. Evaluation of such a solution by assuming grid modeling is useful and may require powerful simulation tools such as real-time simulator. In order to comply with power processing restrictions, a low frequency model is derived. Performance of both models (high and low frequency) are compared to ensure usability of the low frequency model. Control strategies and modulation are presented. Simulation results are provided to validate the theoretical approach, and real-time simulation results, as well.