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Conventional model predictive control (MPC) of power converter has been widely applied to power inverters achieving high performance, fast dynamic response, and accurate transient control of power converter. However, the MPC strategy is highly reliant on the accuracy of the inverter model used for the controlled system. Consequently, a parameter or model mismatch between the plant and the controller leads to a sub-optimal performance of MPC. In this paper, a new strategy called model-free predictive control (MF-PC) is proposed to improve such problems. The presented approach is based on a recursive least squares algorithm to identify the parameters of an auto-regressive with exogenous input (ARX) model. The proposed method provides an accurate prediction of the controlled variables without requiring detailed knowledge of the physical system. This new approach and is realized by employing a novel state space identification algorithm into the predictive control structure. The performance of the proposed model-free predictive control method is compared with conventional MPC. The simulation and experimental results show that the proposed method is totally robust against parameters and model changes compared with the conventional model based solutions.

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AC-DC hybrid microgrid (HMG) is introduced as the future distribution network to utilize both benefits of alternative and direct currents. Generally, HMG is consisted of ac and dc loads, renewable energy-based distributed generators (DGs), controllable DGs and energy storage systems, and a utility interactive inverter (UII), which provides a bi-directional connection between ac and dc subsystems. In this paper, a inductor, transformer, capacitor, and inductor (LTC-L) topology for the UII has been proposed for managing the power quality of ac subsystem of the HMG. The control strategy of the UII is flexibly changed based on the operating-mode of the HMG. Using the proposed control strategy of the UII in grid-connected mode, not only the voltage quality of the ac-subsystem will be improved, but also the quality of the grid current will be enhanced, considerably. In standalone mode, UII acts as an uninterruptable power supply to minimize the shedding of ac or dc loads. A voltage-current cascaded control structure is used for employing the proposed control strategies. Moreover, two control approaches are investigated on the proposed LTC-L topology of UII, sinusoidal voltage reference (supplying load with pure sinusoidal voltage) and nonsinusoidal voltage reference (supplying load with nonsinusoidal voltage for mitigating grid current harmonics). Effectiveness of the proposed topology and the control strategies are evaluated through a numerical study and discussing the results.Index Terms-Current control, distributed energy resources, microgrid, three phase utility interactive inverter (UII), voltage control.

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