Asymmetric Current Control of Grid Connected 3-Phase Cascaded H-Bridge Multilevel Inverter

A flexible current control scheme is proposed based on three phase symmetrical component extraction for the control of cascaded H-Bridge multilevel inverter in grid connected battery storage application. To drive and compensate the unbalanced currents in grid tie operation, the proposed method provides more flexibility as compared to the classic vector oriented current control scheme by means of injecting or extracting unequal magnitudes of currents in each phase. Unbalanced line currents are decomposed into their symmetrical sequence components. Filter based extracted positive, negative and zero sequence components are controlled separately by means of PI controllers in rotating dqreference frame. The control method simulation results in MATLAB and Simulink are validated with hardware measurements.