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In this paper, a two-dimensional time-stepping finite-element model of a large hydrogenerator considering field interturn short circuits (ITSCs) default is developed and presented. The study quantified the impact of the degree of rotor ITSC on the radial magnetic flux density, radial force density, unbalanced magnetic pull, and electromagnetic torque of a 74-MVA industrial large hydrogenerator with 76 poles. The proposed numerical model was validated by comparing computed and experimentally measured magnetic flux density of a chosen healthy machine; good agreement between measured and computed results is obtained. Moreover, a detection method using two search coils installed on stator teeth is used. This method allows by inspection of the peak value the quantification of the degree of ITSC. The average value of the magnetic flux density of the defective pole decreases linearly (more than 5%) with the increase of the number of ITSCs; as well, the unbalanced magnetic pull increases with a polynomial of degree 2 with the increase of the degree of ITSC.

The aim of this paper is to introduce power quality added function to the standard Vienna rectifier in order to compensate reactive power and to cancel current-type harmonics drawn by nonlinear loads connected to the same point of common coupling. A theoretical investigation that demonstrates the ability of such topology to compensate harmonics and limited reactive power is first presented. Then, the design and implementation of a linear quadratic regulator with integral action is presented. The converter is controlled as a whole i.e., a multiple-input-multiple-output system, and uses an augmented model that was developed in the d- q frame. Experimental results obtained with a digital-signal-processor-based DS1103 controller and the converter operating at a 20-kHz switching frequency proved the effectiveness of the theoretical study and the high performance of the proposed control strategy in compensating load harmonics and limited reactive power.

This paper presents the design and implementation of a linear quadratic regulator (LQR) with integral action (LQRI) for a three-phase three-wire shunt active filter (SAF). The integral action is added so as to cancel the steady-state errors for reference tracking or disturbance rejection, knowing that the standard LQR provides only proportional gains. The controller is designed to achieve DC bus voltage regulation and harmonics and reactive power compensation. The converter model is set in the d-q rotating reference frame. The latter is augmented with the integral of the q component of the SAF currents and DC bus voltage to achieve integral action. The controller's performance depends on the weighting matrix, which is chosen to ensure satisfactory response. The converter is controlled as a whole, i.e., a multi-input-multioutput system and a fixed pulsewidth modulation at 10 kHz is used to generate the gating signals of the power devices. The system is tested for harmonics, reactive power, and load unbalance compensation for balanced/unbalanced loads. The experimental results obtained with a digital signal processor-based implementation of the controller on the DS1104 of dSPACE show good performance in terms of DC bus voltage regulation (small overshoot and very fast time response) and a low total harmonic distortion of AC line currents.