P. Sanchis

Energy-Sampled Data Modeling of a Cascade H-Bridge Multilevel Converter for Grid-connected PV Systems

This paper presents an energy-sampled data model of a cascade H-bridge multilevel converter for single-phase multi-string grid-connected photovoltaic systems. Based on this model a control scheme for the power converter is obtained. The achievement of the DC-AC conversion with an efficient PV energy extraction, low harmonic distortion and output unity power factor is validated with simulation results

Analysis of neutral-point voltage balancing problem in three-level neutral-point-clamped inverters with SVPWM modulation

In this paper, the evolution and the control options of the neutral point potential in NPC inverters with SVPWM modulation are analysed. In this analysis, the different components that can be found in the phase current are taken into account: fundamental, DC current and harmonics. Firstly, the current injected in the neutral point by the nonredundant medium vectors is evaluated for each phase current component. The only components that inject DC current in neutral point are demonstrated to be the even and nonmultiple of 3 current harmonics. This DC current tends to unbalance the neutral point potential. Finally, the compensation of this DC current by means of both the small redundant vectors and the fundamental component of the phase current is analysed. This study allows the maximum amplitude of the phase current harmonics to be determined without losing the neutral point potential control with the SVPWM modulation.

Battery management fuzzy control for a grid- tied microgrid with renewable generation

A fuzzy logic controller design for the battery management of a grid-tied real domestic microgrid including 6 kWp of PV and 6kW wind power renewable generators is presented. The fuzzy controller parameters design is undertaken on the basis of the minimization of a set of quality indices such as the battery dynamic range and the power variation range exchanged with the grid. The features of the proposed approach are highlighted with yearly real data by numerical simulations of the power profile injected into the grid and the battery state of charge.

Optimal Fuzzy Logic EMS design for residential grid-connected microgrid with hybrid renewable generation and storage

This paper presents the design of an optimal Energy Management System (EMS) based on a Fuzzy Logic Controller (FLC) for a residential grid-connected microgrid with hybrid renewable generation (wind, photovoltaic) and storage system. The aim of the fuzzy EMS design is to minimize the grid fluctuations and to preserve the storage system lifetime. The proposed EMS uses a FLC to anticipate the appropriate value of the grid power regarding the microgrid energetic rate-of-change and the battery State-of-Charge (SOC). The performance of the proposed EMS is verified through numerical simulations using real data provided by Public University of Navarres (UPNa) microgrid. The simulation results have demonstrated the proper behavior of the proposed fuzzy EMS, since a low-frequency grid power profile with minimum fluctuations is achieved.

Operation and control of a high performance inverter consisting of a buck-boost and a zero switching losses H-bridge for photovoltaic systems

This paper analyses the control of a especial inverter topology consisting of a buck-boost and a H-bridge in which the first one generates a rectified output voltage and the second one inverts one of each two half cycles. As a consequence, the H-bridge commutates at twice the line frequency and, what is more important, at zero voltage. Switching losses are therefore zero, and global losses of the inverter topology are very small achieving thus a high performance. In addition, the AC output voltage can be lower or greater than the DC input voltage. Both properties make this topology very interesting for photovoltaic systems. The main drawback of the structure is that the buck-boost has to be controlled in a variable operating point condition. This paper proposes two new control loops for the inductor current and the output voltage that include different compensations and feed-forward loops. This control strategy makes possible a fast and accurate control of the inverter output voltage. In addition, it achieves a high immunity to external perturbations such as input voltage and output load disturbances. Simulation tests show the robust performance in these situations as well as in case of transient short circuits and nonlinear loads connection.

EMI filter inductor size for transformerless PV systems based on the full bridge structure

This paper analyses the influence of the modulation technique on the size of the grid EMI filter inductor in a full bridge converter for photovoltaic systems. Additionally, the use of an alternative modulation technique is proposed which exhibits the best compromise concerning efficiency, current quality and EMI filter size.

Energy management strategy for a grid-tied residential microgrid based on Fuzzy Logic and power forecasting

This paper extends a previous design of an energy management strategy based on Fuzzy Logic Control (FLC) for a residential grid-tied microgrid including a Hybrid Renewable Energy System (HRES) and an Energy Storage System (ESS). The main goal of the proposed design is to improve the grid power profile while satisfying the constraints established by the ESS. The strategy extension includes generation and demand forecasting in order to predict the future behavior of the microgrid. According to the forecast error and the battery State-of-Charge (SOC) the proposed strategy increases/decreases the grid power with the purpose of smoothing the power exchanged with the grid. The performance of the proposed strategy is verified through comparative numerical simulations using real data measured at the microgrid of the Public University of Navarre (UPNa).

Fostering Industry-Academia synergies in the curricular development of engineering education

One of the main elements in Curricular Development within the European Higher Education Area (EHEA) is to promote ties between Industry and Academia, both in terms of curricular content as well as in terms of methodological approach. In this work, synergy between Industry and Academia is analyzed in the joint development of Final Degree Projects and Master Thesis in several engineering disciplines. The overall results show clear benefits in this interaction to students, industry members and faculty members in terms of educative process as well as to enhance potential collaboration opportunities.

The role of university-industry liaisons in achieving comprehensive curricula in engineering

The proposed methodology and multiple forms of feedback can serve as a consistent tool in order to achieve a comprehensive learning experience, which develops beyond University and aids with lifelong learning itineraries for industry and with enhanced research relations for academia. The development of Final Degree Projects as well Masters Thesis has proved to be a valuable tool for students, faculty and industrial members. For students, it is a good opportunity to gain insight into real world working environments and project demands. For academia, it provides information on how to update existing teaching curricula in engineering degrees, and opens the door to new joint ventures in Terms of research with industry. For industry members, it is a natural mechanism to have access to state of the art research and a good pool of future workers in their institutions. Overall, the experience is very well perceived by all actors and the feedback obtained up to this date will provide valuable information in preparing imminent Final Degree projects for the EHEA adapted four-year programs, as well as for the new Master Degrees under development.

Fuzzy energy management strategy based on microgrid energy rate-of-change applied to an electro-thermal residential microgrid

This work presents the design of a fuzzy energy management strategy to smooth the grid power profile of grid-connected electro-thermal microgrid. The electro-thermal microgrid under study includes electric and thermal renewable generation, electric and thermal energy storage, and electric and thermal loads. In this new scenario, the main goal of the energy management strategy is to use the excess of power coming from the microgrid to cover part of the power needed by the thermal generation system to keep the water temperature in the thermal storage system in a suitable range to supply Domestic Hot Water (DHW) required in the house. The performance of the proposed strategy is verified through simulations using real data measured at the microgrid of the Public University of Navarre (UPNa). The simulation results have demonstrated the proper behavior of the proposed strategy minimizing the grid power fluctuations and the amount of energy supplied by the mains.