A hybrid control method for a bidirectional converter used in micro-grid systems

The stability control and power quality improvement of micro-grid systems using a bidirectional converter is studied. In consideration of the fact that the traditional converters like dynamic voltage regulator (DVR), static var generator (SVG), active power filter (APF) cannot be directly applied to micro grids due to the reasons of their dynamic response, power level and economy, a compound control method based on the nonlinear control theory is proposed. The method uses feedback linearization to control the inner current loop to turn the complex nonlinear system into a linear system, and fully decouples active and reactive current to improve the tracking precision and dynamic response of the inner current roop, and also improve fast response capability of the voltage outer loop; at the same time, it uses the sliding mode to control the voltage outer loop to solve the problem of time-varying parameters and to improve the robustness and anti-interference of the outer loop voltage. The experiments show that this composite control method has the abilities of fast dynamic response, higher precision, smaller harmonic of the AC side current, and the DC side voltage has the fast dynamic response.