A New Composite Control Strategy for Large-Signal Stabilization of Constant Power Loads in Islanded AC Microgrids

Large operating range in an islanded AC microgrid feeding constant power loads (CPLs) will cause both the severe amplitude wave and harmonic distortion of the bus voltage. This paper proposes a new composite control strategy to realize the large-signal stabilization for an islanded AC microgrid feeding CPLs. Firstly, a three-phase inverter system feeding CPLs is constructed in a dq rotating coordinate form. Secondly, the nonlinear disturbance observer technique is introduced to accurately and simultaneously estimate the current of the CPLs and coupling interactions, serving as feed-forward compensations for the AC bus voltage controller. Then a composite strategy can be designed by executing a feedback domination procedure. For the issue of voltage regulation under the large variation of CPLs and control targets, the proposed control strategy exhibits three merits: large-signal stability, fast performance recovery ability and concise control form. The tuning process of the control parameters are illustrated in the simulation. The effectiveness and priority of the proposed strategy are demonstrated by abundant of hardware-in-loop (HIL) and experimental results.