Luiz A. de S. Ribeiro

Implementation of a High-Efficiency, High-Lifetime, and Low-Cost Converter for an Autonomous Photovoltaic Water Pumping System

This paper proposes a new converter for photovoltaic (PV) water pumping or treatment systems without the use of chemical storage elements, such as batteries. The converter is designed to drive a three-phase induction motor directly from PV energy. The use of a three-phase induction motor presents a better solution to the commercial dc motor water pumping system. The development is oriented to achieve a more efficient, reliable, maintenance-free, and cheaper solution than the standard ones that use dc motors or low-voltage synchronous motors. The developed system is based on a current-fed multiresonant converter also known as resonant two-inductor boost converter (TIBC) and a full-bridge three-phase voltage source inverter (VSI). The classic topology of the TIBC has features like high voltage gain and low input current ripple. In this paper, it is further improved with the use of a nonisolated recovery snubber along with a hysteresis controller and the use of a constant duty cycle control to improve its efficiency. Experimental results show a peak efficiency of 91% at a rated power of 210 W for the dc/dc converter plus the three-phase VSI and a peak efficiency of 93.64% just for the dc/dc converter. The system is expected to have a high lifetime due to the inexistence of electrolytic capacitors, and the total cost of the converter is below 0.43 U

Power Control in AC Isolated Microgrids With Renewable Energy Sources and Energy Storage Systems

/Wp. As a result, the system is a promising solution to be used in isolated locations and to deliver water to poor communities.

Effect of State Feedback Coupling and System Delays on the Transient Performance of Stand-Alone VSI With LC Output Filter

This paper presents a new strategy to control the generated power from energy sources existing in autonomous and isolated microgrids. In this particular study, the power system consists of a power electronic converter supplied by a battery bank, which is used to form the ac grid (grid former converter), an energy source based on a wind turbine with its respective power electronic converter (grid supplier converter), and the power consumers (loads). The main objective of this proposed strategy is to control the state of charge of the battery bank limiting the voltage on its terminals by controlling the power generated by the energy sources. This is done without using dump loads or any physical communication among the power electronic converters or the individual energy source controllers. The electrical frequency of the microgrid is used to inform the power sources and their respective converters about the amount of power that they need to generate in order to maintain the battery-bank charging voltage below or equal its maximum allowable limit. Experimental results are presented to show the feasibility of the proposed control strategy.

Power control in AC autonomous and isolated microgrids with renewable energy sources and energy storage systems

The influence of state feedback coupling in the dynamics performance of power converters for stand-alone microgrids is investigated. Computation and pulsewidth-modulated (PWM) delays are the main factors that limit the achievable bandwidth of current regulators in digital implementations. In particular, the performance of state feedback decoupling is degraded because of these delays. Two decoupling techniques to improve the transient response of the system are investigated, named nonideal and ideal capacitor voltage decoupling, respectively. In particular, the latter solution consists in leading the capacitor voltage on the state feedback decoupling path in order to compensate for system delays. Practical implementation issues are discussed with reference to both the decoupling techniques. A design methodology for the voltage loop that considers the closed-loop transfer functions developed for the inner loop is also provided. A proportional resonant voltage controller is designed according to Nyquist criterion taking into account application requirements. For this purpose, a mathematical expression based on root locus analysis is proposed to find the minimum value of the fundamental resonant gain. Experimental tests performed in accordance to UPS standards verify the theoretical analysis.

Small renewable hybrid systems for stand alone applications

This paper presents a new strategy to control the generated power that comes from the energy sources existing in autonomous and isolated Microgrids. In this particular study, the power system consists of a power electronic converter supplied by a battery bank, which is used to form the AC grid (grid former converter), an energy source based on a wind turbine with its respective power electronic converter (grid supplier converter), and the power consumers (loads). The main objective of this proposed strategy is to control the state of charge of the battery bank limiting the voltage on its terminals by controlling the power generated by the energy sources. This is done without using dump loads or any physical communication among the power electronic converters or the individual energy source controllers. The electrical frequency of the microgrid is used to inform to the power sources and their respective converters the amount of power they need to generate in order to maintain the battery-bank state of charge below or equal its maximum allowable limit. It is proposed a modified droop control to implement this task.

Automatic dynamic range adjustment of a controlled-temperature thermoresistive-based anemometer

To provide renewable energy to stand alone applications the generation system should be composed of different types of energy sources to make better use of the natural resources in these applications. A common practice is to combine wind and solar PV energies in the so called hybrid renewable systems. Due to the long distance, and difficult access the overall system used in these applications must be reliable. And the reliability of the system, specially the inverter used to regulate the AC voltage, is one of the main problems associated to these systems, and is responsible for the lack of confidence in renewable systems at several locations in Brazil. This paper shows the initial results of using renewable hybrid systems specially designed for isolated areas, focusing attention on reliability, efficiency and expansion flexibility. It presents the system description, mode of operation, inverter design, and experimental results measured in a pilot plant located in Lençóis Island, a small isolated community in the northeast region of Brazil.

Efficiency Study of Vertical Distance Variations in Wireless Power Transfer for E-Mobility

The thermoresistive-based hot-wire anemometer operating at a controlled temperature is a classical architecture that is vastly found in the literature. Nevertheless, this architecture presents a problem due to dynamic range variation with respect to the fluid temperature. In this work an alternative architecture of a controlled temperature anemometer with automatic adjustment of the dynamic range is proposed. Simulations of the proposed system using the parameters from a commercial sensor are presented and compared with the results from a classical configuration.

Implementation of a high efficiency and low cost converter for a photovoltaic water pumping system

A wireless power transfer (WPT) system is a safe, convenient, and smart charging solution for electric vehicle (EV) users. However, a drawback of the WPT systems is the reduced efficiency in comparison to the conventional wired charging due to lower coupling. Increasing the volume of EVs in the market and improving the system efficiency even by a few percent, besides being environmentally suitable, will benefit both consumers and distributors. According to the previous studies, efficiency improvement by decreasing the vertical distance (VD) between transmitter (TX) and receiver (RX) coils has been one of the aims of the companies and universities. However, in low VD, system performance becomes highly sensitive, due to the magnetic coupling strength. The focus of this paper is to analyze the effects of decreasing the vertical distances to WPT resonance tank efficiencies. Finally, some of the most significant parameters that affect the system efficiency at low VD, such as the quality factor and the third harmonic interference, are analyzed and a mitigating approach is proposed.

Exploração de energia maremotriz para geração de eletricidade: aspectos básicos e principais tendências

This paper proposes a new converter for photovoltaic water pumping and treatment systems without the use of storage elements. The converter is designed to drive a three-phase induction motor directly from PV solar energy. The use of this motor has the objective of presenting a better solution to the standard DC motor water pumping system. The development is oriented to achieve a commercially viable solution and a market friendly product. The converter topology is based on a Resonant Two Inductor Boost converter and a Three-phase Voltage Source inverter achieving 90% efficiency at a rated power of 210W. The total cost of the proposed converter is below US

Discrete-Time Domain Modeling of Voltage Source Inverters in Standalone Applications: Enhancement of Regulators Performance by Means of Smith Predictor

91.00 and the system is expected to have high lifetime, due to the inexistence of electrolytic capacitors.