In This paper a decoupled control of a doublyfed induction machine used in generation mode (DFIG) is presented. It provides decoupled regulation of the primary side active and reactive power and it is suitable for both electric energy generation and drive applications. The mathematical model of the machine written in an appropriate d-q reference frame is established to investigate simulations. In order to control the power flowing between the stator of the DFIG and the network, a decoupled control of active and reactive power is synthesized using PI controllers. Their respective performances are in terms of stator currents references tracking.Mots clefs -DFIG, active and reactive power, decoupled control, robustness.

Abstract:In this paper, an improved direct power control with space vector modulation for a 3-phase 3-level neutral point clamped converter supplied by unbalanced and/or distorted grid voltage is proposed. The main objective of the control scheme is to obtain balanced and sinusoidal input current with unity power factor under nonideal voltage supply.To achieve the control objectives, compensated active and reactive powers are calculated and added to the referencing one. A theoretical analysis of active and reactive power under a nonideal source is clearly demonstrated. In order to calculate the compensated powers, the extraction of positive, negative, and harmonic sequences of voltage and current is needed and a multiple-complex coefficient filter-based method is used for rapid and accurate extraction. The proposed controller also ensures voltage balance in DC-link capacitors using redundant vectors in the space vector modulation block without the need for additional components. Simulation results verified the effectiveness of the modified control strategy.

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This paper presents different techniques on fault diagnosis in static converters used to supply and control induction heating systems. These techniques allow the detection and the location of the failed semiconductor switches. After an overview of the device with its main features in healthy state, we have afterwards focused on the fault detection and diagnosis in three electronic power converters which constitute the power generator of the induction furnace. For uncontrolled three-phase rectifier, three external methods based on the analysis of lines currents are used: Average currents method, Current space vector trajectory, called Current Park’s vector approach and Spectrum analysis. For the buck converter (chopper), analytic redundancy approach, based on the residues calculation, is used. For the series resonant inverter, a simple and efficient method based on the average voltages analysis, allows the detection and the location of the power switch in fault. The obtained simulation results, in Matlab/Simulink, are presented and discussed. They reveal that the proposed diagnostic techniques are of great interest.

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