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Grid-connected power converters are controlled by the current loop, the voltage being delivered by the grid. The proposed state feedback current control has three components: the state feedback, the forcing component to achieve the desired state x1 and the compensating feed forward of the perturbation. Moreover, the control of the power converter, through the external DC-link voltage loop, and internal current loop, assures zero steady state error, and power quality performances. In order to prove the quality of the proposed control, a regenerative load has been used, and the corresponding simulation results are provided.

This paper presents futures from experimental investigation of an autonomous small power wind system. The envisaged wind system is based on a PMSG (Permanent Magnet Synchronous Generator) directly connected to the wind turbine shaft, while the DC output load is supplied by a rectifier and a chopper. The DC load is considered as a resistive load with wide values range. Experimental investigations are provided in partial load regime. The power optimization is performed through a power loop in two ways: by controlling the electrical power or by controlling the electromechanical power. For the above two situations it is shown how the optimization power loop reference and power loop feedbacks can be set, in order to obtain maximum electrical power, for each wind speed value corresponding to the partial load regime. It was also highlighted that for a wide range of DC load values the mechanical and electrical powers are not constant as it should be corresponding to the mathematical model of the optimal conversion. This is due to mechanic-electrical subsystem processes. The electrical power variation range with the load should be provided by the manufacturer in the low-power wind system data sheet.

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