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In this paper, coupling between active and reactive powers in conventional direct power control (DPC) strategies is analyzed and a new direct DPC method for doubly fed induction machine without rotor position sensors is presented. Coupling analysis is done on an improved DPC strategy with rotor flux controllers in the stator reference frame. The presented control strategy is done by controlling the rotor flux in the grid flux reference frame. The rotor flux command is calculated using a predicted stator flux, the stator current command, and the stator resistance. Moreover, the rotor position is estimated by comparing measured and estimated values of the rotor current. Furthermore, to reduce the method's sensitivity to the parameter inaccuracies, the mutual inductance of the machine is updated during the machine operation by the error between the magnitudes of the measured and estimated values of the rotor current. Index Terms-Component, direct decoupled power control (DDPC), direct power control (DPC), doubly fed induction generator (DFIG), doubly fed induction machine (DFIM), model reference adaptive system (MRAS), sensorless.NOMENCLATURE Ψ s , Ψ r Stator and rotor flux linkage, vectors. V s , V r Stator and rotor voltage vectors. I s , I r Stator and rotor current vectors. ω 1 , ω r , ω slip Synchronous, mechanical, and slip speeds. R s , R r Stator and rotor resistance. L ls , L lr Stator and rotor leakage inductance. L m Machine mutual inductance.

Flyback inverter is known as a low cost solution for photovoltaic (PV) ac module application. This study presents a two-switch flyback inverter followed by a low frequency unfolding bridge for fractional horse power water pumping systems. This topology mitigates the problem of high-voltage transients at switch turn off which commonly exists in single switch flyback inverters. Moreover, the proposed control strategy achieves an integration of a novel sensorless maximum power point tracking (MPPT) algorithm as well as a constant v/f control for the efficient utilisation of both the PV panel and the motor. The proposed control algorithm minimises the cost and simplifies the control strategy. The validity and capability of the proposed method are verified by both simulation and practical results of a DSP-based two-switch flyback solar micro inverter for a fractional horsepower water pumping system.

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