On-line Parameter Estimation of the Polarization Curve of a Fuel Cell with Guaranteed Convergence Properties: Theoretical and Experimental Results

In this paper, we address the problem of online parameter estimation of a Proton Exchange Membrane Fuel Cell (PEMFC) polarization curve, that is the static relation between the voltage and the current of the PEMFC. The task of designing this estimator -- even off-line -- is complicated by the fact that the uncertain parameters enter the curve in a highly nonlinear fashion, namely in the form of nonseparable nonlinearities. We consider several scenarios for the model of the polarization curve, starting from the standard full model and including several popular simplifications to this complicated mathematical function. In all cases, we derive separable regression equations -- either linearly or nonlinearly parameterized -- which are instrumental for the implementation of the parameter estimators. We concentrate our attention on on-line estimation schemes for which, under suitable excitation conditions, global parameter convergence is ensured. Due to these global convergence properties, the estimators are robust to unavoidable additive noise and structural uncertainty. Moreover, their on-line nature endows the schemes with the ability to track (slow) parameter variations, that occur during the operation of the PEMFC. These two features -- unavailable in time-consuming off-line data-fitting procedures -- make the proposed estimators helpful for on-line time-saving characterization of a given PEMFC, and the implementation of fault-detection procedures and model-based adaptive control strategies. Simulation and experimental results that validate the theoretical claims are presented.Comment: 16 pages, 18 figures, requires IEEEtran.cls 2015/08/26 version V1.8

A 5LCHB Inverter for PV transformerless applications with reduced leakage ground current

Transformerless inverters for photovoltaic systems are widely used as it features low cost, volume, and weight. Thus, in recent years, its study has been of great interest to the research community. In this paper a transformerless cascade multilevel inverter for photovoltaic applications with leakage ground current compensation capability is presented. The proposed solution involves a second-order LC output filter with a particular connection, which is referred to as the DC-link-tied LC output filter. This solution is aimed to deal with the leakage-ground current issue, regardless of the considered PWM strategy. The mathematical model of the system involving such a particular LC output passive filter configuration is presented, out of which, both the differential-mode and the common-mode models are obtained. These models are used to explain the leakage-ground current improvement of the proposed DC-link-tied LC output filter. This hardware solution is evaluated under different modulation schemes to contrast the converter output response and the leakage-ground current performance. Finally, simulation and experimental results are performed using a 1 kW academic prototype to assess the performance of the proposed DC-link-tied LC output filter used in a transformerless inverter application.Peer ReviewedObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesPostprint (published version

CONTROL DE UN MOTOR BRUSHLESS PARA APLICACIÓN A VEHÍCULOS ELÉCTRICOS

Tesis de Maestrí

A PI + Sliding-Mode Controller Based on the Discontinuous Conduction Mode for an Unidirectional Buck–Boost Converter with Electric Vehicle Applications

This paper solves the buck–boost converter operation problem in the discontinuous conduction mode and the feeding a DC bus of a combined battery/solar-powered electric vehicle grid. Since the sun’s radiation has a very important effect on the performance of photovoltaic solar modules due to its continuous variation, the main task of the system under study is the regulation of the output voltage from an MPPT system located at the output of the panels in order to obtain a DC bus voltage that is fixed to 24 V. This is ensured via a double-loop scheme, where the current inner loop relies on sliding-mode control; meanwhile, the outer voltage loop considers a proportional–integral action. Additionally, the current loop implements an adaptive hysteresis logic in order to operate at a fixed frequency. The closed-loop system’s performance is checked via numerical results with respect to step changes in the load, input voltage, and output voltage reference variations

Passivity-Based Control for Output Voltage Regulation in a Fuel Cell/Boost Converter System

In this paper, a passivity-based control (PBC) scheme for output voltage regulation in a fuel-cell/boost converter system is designed and validated through real-time numerical results. The proposed control scheme is designed as a current-mode control (CMC) scheme with an outer loop (voltage) for voltage regulation and an inner loop (current) for current reference tracking. The inner loop’s design considers the Euler–Lagrange (E-L) formulation to implement a standard PBC and the outer loop is implemented through a standard PI controller. Furthermore, an adaptive law based on immersion and invariance (I&I) theory is designed to enhance the closed-loop system behavior through asymptotic approximation of uncertain parameters such as load and inductor parasitic resistance. The closed-loop system is tested under two scenarios using real-time simulations, where precision and robustness are shown with respect to variations in the fuel cell voltage, load, and output voltage reference

Development of an Equivalent Electronic Circuit Model for PEMFC Voltage Based on Different Input Electrical Currents

The technological development and exploration of the proton exchange membrane fuel cell have relied on several mathematical models. However, despite the wide variety of models, the equivalent electronic circuit model is the most suitable for describing electrical behavior, designing electronic interfaces, and analyzing control and reliability strategies. In addition to the fact that this type of model is scarce to model the fuel cell voltage, an equivalent electronic circuit model that depends only on the input current has not been reported (in general, the reported mathematical models take into account additional variables such as humidity, temperature, pressure, etc.). For this reason, this work focuses on developing an equivalent electronic circuit model for the fuel cell voltage that depends only on the input current. Besides, the configuration of the proposed circuit (one voltage source, two capacitors, and three resistors) is simpler than the circuits proposed in previous works. To validate the model and its parameters, current tests from $1.2~kW$ Nexa® fuel cell power module were used. The comparison between the experimental data and the developed model confirms the efficiency of the equivalent electronic circuit model to reproduce the fuel cell voltage as a function of the current

Hybrid PWM Techniques for a DCM-232 Three-Phase Transformerless Inverter with Reduced Leakage Ground Current

Pulse Width Modulation (PWM) strategies are crucial for controlling DC–AC power converters. In particular, transformerless inverters require specific PWM techniques to improve efficiency and to deal with leakage ground current issues. In this paper, three hybrid PWM methods are proposed for a DCM-232 three-phase topology. These methods are based on the concepts of carrier-based PWM and space vector modulation. Calculations of time intervals for active and null vectors are performed in a conventional way, and the resulting waveforms are compared with a carrier signal. The digital signals obtained are processed using Boolean functions, generating ten signals to control the DCM-232 three-phase inverter. The performance of the three proposed PWM methods is evaluated considering the reduction in leakage ground current and efficiency. The proposed modulation techniques have relevant performances complying with international standards, which make them suitable for transformerless three-phase photovoltaic (PV) inverter markets. To validate the proposed hybrid PWM strategies, numerical simulations and experimental tests were performed