Photovoltaic reliability, using micro inverter

<div style="text-align: justify;">In my previous article I presented the principle for avoiding production losses  when photovoltaic systems are located in such cases where there is shadow of  trees, dust, chimneys, antenna, other buildings … We speak of photovoltaic shading.<br /> Then I presented a good solution to avoid these which is distributed MPP Tracking: one micro inverter per photovoltaic module to track individual Maximum Power Point. I also detailed 2 design approaches with pro’s & con’s arguments.<br /> In this article, I will give some concerns and questions about photovoltaic reliability.</div><div style="text-align: justify;"><br /> </div><div style="text-align: center;"><img alt="http://engineering.electrical-equipment.org/wp-content/uploads/2010/02/photovoltaic-shading1.jpg" src="http://engineering.electrical-equipment.org/wp-content/uploads/2010/02/photovoltaic-shading1.jpg" /></div><div style="text-align: justify;"><br /> <div style="background-color: orange; color: red; text-align: center;">photovoltaic shading</div><br /> It’s a main point and certainly the success key factor of this disruptive innovation.<br /> A manufacturer writes “no failure point”: that‘s great! But when a micro converter is embedded on the photovoltaic module and fixed on a roof, it’s not acceptable to have failure. This is not thinking to have a field engineer or installer which climb on the roof, uninstall a photovoltaic module and break water tightness (in case of BIPV)  for a US50$ micro-converter part only !<br /> <br /> The design must integrate the unfavourable constraints for the component choice (very low temperature the winter (- 20°C), very high temperature the summer (+70°C)). To be serious, a manufacturer should describe which working profile conditions are using for the design…<br /> <br /> This is the most critical point and a lot of manufacturers are not talkative on this topic.<br /> <br /> One indicates: “specific components are chosen for reliability design (HALT). Also those tests have run for the equivalent of over 50 years”. It’s great, but it’s not serious: the life time indicate nothing about photovoltaic reliability!<br /> (for example : I can keep a car during 20 years (20 Years life time) and every week the car mechanic repair it (7 days MTBF))<br /> <br /> What is the Photovoltaic reliability of distributed system? What is the true MTBF or the true “lambda” ?<br /> <br /> How many chances have a customer to have a failure on his roof? How will customer ROI be impacted if we have to repair it during the life-time. That is the true and one question I have to request myself before suggests it on his roof! <br /> To summarize<br /> <br /> In my point of view this distributed technology applied to photovoltaic sytem is a very interesting new approach of solar energy harvest with a lot of benefices under specific condition. But today this technology is developed by very small companies witch take not enough in count the photovoltaic reliability aspect. It’s a shame because this innovation could be nip in the bud.<br /> <br /> Yves Jeanjean</div>

Photovoltaic reliability, using micro inverter

In my previous article I presented the principle for avoiding production losses  when photovoltaic systems are located in such cases where t...

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PRACTICAL AND IDEAL TRANSFORMER

<div style="background-color: yellow; color: red; text-align: center;"><span style="font-size: large;">Ideal Transformer On Load.</span></div><div style="background-color: white; color: red; text-align: justify;"><span style="font-size: large;"> </span></div><div style="text-align: justify;">As the transformer is loaded, current I2 flows in the secondary. When this current I2 flows through N2 it produces a flux <span style="color: black;">φ</span>2 . The polarity of <span style="color: black;">φ</span>2 is such that it opposes the main flux <span style="color: black;">φ</span>M. The instantaneous effect of this opposition is that <span style="color: black;">φ</span>M is reduced and instantaneously the induced voltage E1 in the primary is less than V1. <br /> <br /> Because of this voltage difference, the primary current I1 increases, and as it passes through the primary turns N1, it produces an magneto motive force (mmf) to counter the instantaneous reduction in <span style="color: black;">φ</span>M . The effect of this increased primary mmf is to bring the flux in the core back to the original value of <span style="color: black;">φ</span>M.<br /> <br /> Therefore when the supply voltage V1 is constant, despite changes in load current, the flux in a transformer remains at a constant value causing a voltage E1  to be induced in the primary windings and a voltage E2 to be induced in the secondary windings. This relationship neglects the magnetizing current demanded by the imperfections of the core.</div><div style="text-align: justify;"></div><div style="text-align: justify;"></div><br /> <div style="background-color: yellow; color: red; text-align: center;"><span style="font-size: large;">PRACTICAL OR NON IDEAL TRANSFORMER</span></div><br /> Transformation of energy is not perfect. Not all the flux produced by the primary winding links with the secondary, for example transformer has a leakage reactance. Establishing a flux involves the drawing of a magnetizing current. Pulsation’s of the flux  in the core produce a core loss due to HYSTERESIS and EDDY CURRENTS.<br /> <br /> The continuing loss of energy to the core produces heat which must be removed from the transformer.<br /> <br /> <div style="text-align: justify;"><br /> </div>

PRACTICAL AND IDEAL TRANSFORMER

Ideal Transformer On Load.   As the transformer is loaded, current I2 flows in the secondary. When this current I2 flows through N2 it produ...

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