Gérard Champenois

An Improved Maximum Power Point Tracking for Photovoltaic Grid-Connected Inverter Based on Voltage-Oriented Control

In this paper, an improved maximum power point (MPP) tracking (MPPT) with better performance based on voltage-oriented control (VOC) is proposed to solve a fast-changing irradiation problem. In VOC, a cascaded control structure with an outer dc link voltage control loop and an inner current control loop is used. The currents are controlled in a synchronous orthogonal d,q frame using a decoupled feedback control. The reference current of proportional-integral (PI) d-axis controller is extracted from the dc-side voltage regulator by applying the energy-balancing control. Furthermore, in order to achieve a unity power factor, the q-axis reference is set to zero. The MPPT controller is applied to the reference of the outer loop control dc voltage photovoltaic (PV). Without PV array power measurement, the proposed MPPT identifies the correct direction of the MPP by processing the d-axis current reflecting the power grid side and the signal error of the PI outer loop designed to only represent the change in power due to the changing atmospheric conditions. The robust tracking capability under rapidly increasing and decreasing irradiance is verified experimentally with a PV array emulator. Simulations and experimental results demonstrate that the proposed method provides effective, fast, and perfect tracking.

Diagnosis by parameter estimation of stator and rotor faults occurring in induction machines

In this paper, the authors give a new model of squirrel-cage induction motors under stator and rotor faults. First, they study an original model that takes into account the effects of interturn faults resulting in the shorting of one or more circuits of stator-phase winding. They introduce, thus, additional parameters to explain the fault in the three stator phases. Then, they propose a new faulty model dedicated to broken rotor bars detection. The corresponding diagnosis procedure based on parameter estimation of the stator and rotor faulty model is proposed. The estimation technique is performed by taking into account prior information available on the safe system operating in nominal conditions. A special three-phase induction machine has been designed and constructed in order to simulate true faulty experiments. Experimental test results show good agreement and demonstrate the possibility of detection and localization of previous failures.

An Effective Neural Approach for the Automatic Location of Stator Interturn Faults in Induction Motor

This paper presents a neural approach to detect and locate automatically an interturn short-circuit fault in the stator windings of the induction machine. The fault detection and location are achieved by a feedforward multilayer-perceptron neural network (NN) trained by back propagation. The location process is based on monitoring the three-phase shifts between the line current and the phase voltage of the machine. The required data for training and testing the NN are experimentally generated from a three-phase induction motor with different interturn short-circuit faults. Simulation, as well as experimental, results are presented in this paper to demonstrate the effectiveness of the used method.

Original article: Life cycle cost, embodied energy and loss of power supply probability for the optimal design of hybrid power systems

Stand-alone hybrid renewable energy systems are more reliable than one-energy source systems. However, their design is crucial. For this reason, a new methodology with the aim to design an autonomous hybrid PV-wind-battery system is proposed here. Based on a triple multi-objective optimization (MOP), this methodology combines life cycle cost (LCC), embodied energy (EE) and loss of power supply probability (LPSP). For a location, meteorological and load data have been collected and assessed. Then, components of the system and optimization objectives have been modelled. Finally, an optimal configuration has been carried out using a dynamic model and applying a controlled elitist genetic algorithm for multi-objective optimization. This methodology has been applied successfully for the sizing of a PV-wind-battery system to supply at least 95% of yearly total electric demand of a residential house. Results indicate that such a method, through its multitude Pareto front solutions, will help designers to take into consideration both economic and environmental aspects.

Nondissipative String Current Diverter for Solving the Cascaded DC–DC Converter Connection Problem in Photovoltaic Power Generation System

Frequently considered one of the promising solutions for grid connection of the photovoltaic (PV) power generation system, module-integrated converters have been the focus of numerous papers. Most of the proposed approaches thus far have relied on the use of series string of the dc-dc converter to create a high-voltage string connected to the dc-ac inverter. The boost converter is better in this application. However, under inhomogeneous irradiation, the power generated by each PV module and the output dc voltage of each boost become unbalanced so that the output currents of each boost are balanced and equal to the string current. In this case, the boost converter cannot always deliver all the power from a mixture of shaded panels and those delivering full power. In this paper, a nondissipative string current diverter is proposed to overcome this problem. One important feature of the proposed circuit herein is the ability to effectively decouple each converter from the rest of the string, making it insensitive to change in the string current. Hence, it is possible to obtain the maximum power from the PV module with the maximum power point tracking algorithm implemented on each dc-dc converter and to do so at the optimum efficiency. The simulation and experimental results verify that the proposed topology exhibits notable performances despite inhomogeneous irradiation. On the other hand, the string current diverter circuit is very easy to control and does not operate without inhomogeneous irradiation, so the topology efficiency is improved for any type of irradiation.

New Expressions of Symmetrical Components of the Induction Motor Under Stator Faults

This paper proposes new expressions of symmetrical components (SCs) of the stator currents of the induction motor (IM) in steady state and under different stator faults, useful to ensure an efficient fault diagnosis. In this paper, the considered stator faults are interturns short circuit, phase-to-phase, and single-phase-to-ground faults. An analytical study of the behavior of these expressions shows that, under balanced supply voltage, the phase angle and the magnitude of the negative- and zero-sequence currents can be considered as reliable indicators of stator faults of the IM. The behavior of the developed expressions of the SCs is also verified experimentally on a 1.1-kW IM under different fault conditions, different frequencies, and different load conditions. The good agreement between the analytical and experimental values leads to consider the negative- and zero-sequence currents as powerful and effective indicators of stator faults.

PI Controlled Three-phase Shunt Active Power Filter for Power Quality Improvement

Abstract The simulation and experimental study of proportional integrator (PI) controlled DC bus voltage of three phase shunt active power filter (APF) to improve power quality by compensating harmonics and reactive power required by nonlinear load is proposed. The compensation process is based on sensing mains currents only, an approach different from conventional methods, which usually require harmonics or reactive volt-ampere values of the load. The non-sinusoidal mains voltage problem is resolved by using phase locked loop (PLL) system. Pulse width modulation (PWM) signal generation is based on hysteresis control comparators to obtain the switching signals.ű Various simulation and experimental results are presented under steady state and transient conditions.

Synchronous Generator Output Voltage Real-Time Feedback Control via

A new approach on synchronous generator (SG) output voltage control is presented. The originality of such a strategy is based on the excitation structure that integrates a permanent-magnet generator combined with a modern control method: the H infin. The main motivation of this paper is the debatable results obtained with the classical excitation structure controlled by a traditional PID controller. The SG model as well as the control strategy will be presented. The implementation in real time domain and a comparison with the classical structure will allow us to prove the efficiency of the proposed structure compared to the classical one as regards the reference tracking and signal quality.

H_\infty

This paper analyses the synchronous machine modeling by taken into account the machine parameters usually used in industry and those used in researcher’s domains. Two models are presented. The first one is developed in the (d, q) natural reference frames and the other one is referred to the (d, q) stator reference frame. To do this, two methods are proposed to compute the reduction factor of the field winding without any input from design information. It is shown that the reduction factors of the (d, q) damper windings do not influence on the terminal behavior of the machine. This means that it is possible to know the terminal behavior of the machine without knowing the real inductances and resistances of the damper windings. The accuracy of these models is validated by experimental tests.

Strategy

Abstract Generally, battery lifespan depends on the number of cycles and depth of discharge (DOD). Nevertheless, in a renewable hybrid power system, charge and discharge cycles are random and not regular. Therefore, it is important to develop an aging model suitable to this case. Thus, in this paper, a pertinent way for aging lead–acid batteries connected to a stand-alone multi-source renewable system has been developed. It is based on the Rain Flow method for counting cycles and considers instantaneous DOD and average temperature. In fact, for each functioning year, a classification of the number of cycles according to the DOD is done. Then, based on these data, the battery degradation rate is estimated so that it is possible to draw conclusions about battery lifespan. The method has been successfully applied to a multi-source power system simulated dynamically under Matlab/Simulink. This last takes into account with good accuracy several inputs and elements such as sun irradiation, wind speed, load profile, photovoltaic generator, wind turbine, and diesel generator. Results show the influence of the DOD and the batteries nominal capacity on their lifespan. A mean of eight years’ life is detected. Finally, a reasonable over-sizing may favor battery longevity.