Control loop interaction in parallel connected high frequency grid converters

Recent progress in power electronic converters has increased the number of distributed energy sources to the grid. These converters act as a source of harmonics which connected with other loads affect the stability of power grid. Parallel operation of converters is common in power grid depends on the power sharing needs and current rating of power semiconductor devices. Though, these connections improves power handling capability of grid, the dynamic interaction between converters can affect stability of system. This paper addresses the stability issues in parallel connected, high frequency voltage controlled converters with an output LC filter. Studies on interactions between control loops verifies that, harmonic instability introduced by parallel converters can't be stabilized by traditional PI controllers in real power control loop. A new damping algorithm is introduced to suppress these harmonic oscillations caused by the interaction of controllers in grid connected converters.