J. M. Lenz

New methodology to determinate photovoltaic parameters of solar panels

This paper presents a discussion about a methodology to obtain the main parameters of solar panels and power converters in photovoltaic systems. This study is essential to obtain the maximum power transfer from the PV source to the mains grid or a load. It is also presented a formal mathematical model based on the experimental data acquisition of the key parameters of a photovoltaic cell which are: shunt and series resistances, photo generated current, the ideality factor and the diode reverse saturation current.

DC electronic load based on an interleaved chopper converter to determine photovoltaic panel and fuel cell biasing curves

This paper presents the description of a DC electronic load based on an interleaved chopper converter to determine the biasing and dynamics characteristics of either fuel cells (FCs) and photovoltaic panels (PVs). Variable loads are used for experimental data acquisition of I-V power supply characteristics in a way that several operating points can be easily obtained. Laboratory load current tests using ordinary power resistors are not an easy solution due to their size, cost and overall weight. To resolve that it is proposed in this paper that the current through electronically varying loads can give better resolution to the I-V characteristics of FC and PV sources. The interleaved operation of the chopper converter ensures an input high frequency current ripple, reducing so the input LC filters size and converter volume. The converter transfer function is analyzed and controllers are designed to obtain a fast dynamic response and insure good stability in steady state operation. It is presented the converter operating principles, operating states and design. The simulated and results are compared to each other in order to prove the electronic load effectiveness in acquiring the I-V biasing curves of fuel cells and photovoltaic panels.

MPPT for Magnus wind turbines based on cylinders rotation speed

This paper proposes a method to reach the maximum power point of a Magnus wind turbine. Firstly, a special discussion is made about this turbine and its behavior showing that this turbine is a special case of the horizontal axis wind generator, using rotating cylinders instead of fixed blades. Secondly, it is presented an explanation of how some maximum power point trackers (MPPT) can be used with wind energy conversion system and, specially, the divided step hill climbing search method (HCS). The MPPT method proposed for the Magnus turbine is based on the control of cylinder rotation speed to change the tip speed ratio. Finally, simulation results are presented with the proposed MPPT method applied to a Magnus wind turbine.

Electronically adjustable load for testing three phase AC systems

Some equipment such as AC voltage sources, power generators, inverters, and others converters have to be exhaustively tested before being used. To implement these tests it is necessary, in many cases, to use variable AC loads, such as passive (inductive, capacitive and resistive) and active loads (battery chargers and photovoltaic panels). This paper presents an analysis and design of an AC electronic load to emulate either purely active and reactive three-phase loads or other impedance combinations. This electronic variable load allows the user set precisely the amount of power required for practical experiments and bench tests. Furthermore, this work presents the modeling of a voltage source converter (VSC) and a buck converter, used to purpose of emulating a variable and adjustable load. Also it is discussed the compensators design to control the converter and is presented simulation results with the electronically adjustable load to active and reactive power consumption.

DC-link electrolyte capacitor lifetime analysis for a PV boost converter

A lifetime analysis was performed on the DC-link capacitor of a photovoltaic power-processing system composed of a boost converter in the first stage. It was investigated how the switching frequency and ripple current design choice affect the capacitor lifetime. Through an electro-thermal modeling, the capacitor operating condition was obtained for various levels of power processing, based on a real photovoltaic mission profile built for ten years period of weather data. The lifetime of three different designs of electrolyte capacitor bank was analyzed and discussed. Analyzed results showed that the increase of the converters current ripple diminishes much the of capacitors lifetime. A discussion is presented about the tradeoff between choosing capacitors with low equivalent series resistance and increasing the number of capacitors on the DC-link.