This paper proposes a new control algorithm that improves the dynamic performance in distributed maximum power point tracking systems. Systems with these architectures allow to increase the photovoltaic power harvested in case of partial shading and irradiance mismatch. The classical approach adopts distributed DC/DC power electronics and control without any centralized action, which makes difficult to know whether the system is working on its optimal operating point or not. The new control algorithm presented in this paper exploits the benefits of the vectorial multi-variable perturb & observe logic and acts on the control sequence under varying irradiance conditions, reducing voltage stresses at the DC/DC converters output terminals. In addition, the matching with the DC-bus voltage control is discussed, providing a centralized control to the overall system, a fact barely addressed in literature. Simulation results and experimental measurements validate the proposed approach showing improved dynamic performance and system stability.

The extraction of winding resistance from impedance measurements needs a compensation of undesirable effects e.g. core loss and distributed winding capacitance. This paper rigorously shows that the core loss (or core-loss resistance) measured with the two-winding method always includes the effect of the winding mutual resistance. At high frequencies, this effect becomes more prominent and can cause an overestimation of the measured core-loss resistance. As a result, the compensated winding resistances can be significantly underestimated. To mitigate this effect, this paper proposes to measure the core-loss resistance on an auxiliary 1:1 transformer with single-turn windings. Consequently, it is scaled to obtain the actual core loss. The proposed analysis and method is applicable to multiwinding systems. For validation, this paper considers a gapped transformer with litz-wire winding for high-frequency operations. The experimental results are validated against the results from its 3D finite element (FE) model. The litz-wire winding is considered in the FE model by means of a homogenization approach. With the method proposed in this paper, the experimentally extracted winding resistances become more accurate and are in good agreement with the FE results.

This paper focuses on a minimal current sensing strategy and fault detection of Switched Reluctance Machines (SRMs). In order to reduce the number of required current sensors in multiphase motor drives, the optimal selection and location of current sensors is presented in consideration of the precise actual phase current measurement, open- and short-circuit fault detection. The proposed scheme requires two current sensors to replace the phase current sensors placed in each phase without any additional devices for multiphase SRMs to achieve a more compact and low-cost drive. Different current regulation methods are employed for single phase conducting region and commutation region. To obtain the phase currents from the proposed approach, different settings of the pulse-width modulation (PWM) signals for adjacent phases during the commutation region are implemented. The simulation and experiments on a four-phase 8/6 pole SRM are carried out to verify the effectiveness of this approach in the healthy and faulty cases.

This paper deals with on-line software fault detection and isolation method for a drive composed of a fourleg inverter and a three-phase permanent magnet synchronous machine. The considered faults are single-phase open-circuit and current sensor outage. The method is based on the monitoring of the abc currents with phase-locked loops and the `CUSUM' algorithm for the decision system. The impact of the considered faults is examined: first, in case there is no modification of the control and then in case a control reconfiguration is performed taking into account the fault diagnosis. Closed-loop operation is performed before, during and after the fault. Experimental results show that the latter case allows maintaining the drive in safe operation.

Condition monitoring and fault diagnosis are essential to improve the reliability and availability of wind turbines (WTs). In such systems, power switches and sensors are some of the components most susceptible to faults. In this context, this article proposes a new diagnostic method for WTs based on doubly-fed induction generators with the ability to handle insulated gate bipolar transistor (IGBT) faults, rotor and stator current sensor outages, and stator voltage sensor outages. The proposed method is based on an augmented state and disturbance observer combined with a statistical chi-square $(\chi ^{2})$ test, adaptive thresholds, and normalized diagnostic variables to ensure reliable diagnosis regardless of the operating conditions. The robustness and effectiveness of the proposed approach have been verified experimentally on a 15-kW test bench under the various faults considered.

This paper proposes new analytical expressions of indicators for inter-turn and phase-to-phase short-circuit fault diagnosis in permanent-magnet synchronous machines. The proposed indicators are deduced from symmetrical components of phase currents in the αβ reference frame. They are able to reflect the fault severity and location, are independent from the electrical pulsation and the rotor initial angle, and are robust regarding the loss of some measurements. Hence, they can be used for fault isolation and identification. Experimental tests have been carried out and show promising results. Furthermore, the presented algorithm does not use fast Fourier transforms and, therefore, avoids delays in fault isolation inherent to this technique.