<html><head><base href="x-msg://1919/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>The power quality should not be adversely affected. </div><div><br></div><div>While I'm sure different manufacturers may limit power in different ways, in theory all the inverter is doing is moving the array off its MPP. Here's a description from AE:</div><div><br></div><div><div><font class="Apple-style-span" color="#192b7a">If the power available from the array exceeds the nameplate rating of the inverter, the inverter will limit </font></div><div><font class="Apple-style-span" color="#192b7a">the power and current coming from the array to the inverter’s maximum nameplate power and </font></div><div><font class="Apple-style-span" color="#192b7a">current rating. The inverter does this by reducing the DC input current, which causes the DC </font></div><div><font class="Apple-style-span" color="#192b7a">operating voltage to rise above the maximum power point of the array, thereby ‘clipping’ the </font></div><div><font class="Apple-style-span" color="#192b7a">array output. This effectively limits the output of the array without stressing the inverter.</font></div></div><div><br></div><div><a href="http://solarenergy.advanced-energy.com/upload/File/Application Notes/DCLoadingOfPVPinverters.55-600100-75-A.pdf">http://solarenergy.advanced-energy.com/upload/File/Application%20Notes/DCLoadingOfPVPinverters.55-600100-75-A.pdf</a></div><div><br></div><div>On Mar 22, 2013, at 9:52 AM, William Dorsett wrote:</div><div><br class="Apple-interchange-newline"><blockquote type="cite"><div lang="EN-US" link="blue" vlink="purple"><div class="WordSection1" style="page: WordSection1; "><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">OK, if the upper limit if the curve is “flat topped” do we get increased problems with harmonic noise at the knee as you would in modified “square” wave?<o:p></o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Bill Dorsett<o:p></o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Manhattan, KS<o:p></o:p></span></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "><o:p> </o:p></span></div><div><div style="border-right-style: none; border-bottom-style: none; border-left-style: none; border-width: initial; border-color: initial; border-top-style: solid; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding-top: 3pt; padding-right: 0in; padding-bottom: 0in; padding-left: 0in; "><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "><span class="Apple-converted-space"> </span><a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" style="color: blue; text-decoration: underline; ">re-wrenches-bounces@lists.re-wrenches.org</a><span class="Apple-converted-space"> </span>[mailto:re-wrenches-bounces@lists.re-wrenches.org]<span class="Apple-converted-space"> </span><b>On Behalf Of<span class="Apple-converted-space"> </span></b>David Brearley<br><b>Sent:</b><span class="Apple-converted-space"> </span>Friday, March 22, 2013 8:43 AM<br><b>To:</b><span class="Apple-converted-space"> </span>RE-wrenches<br><b>Subject:</b><span class="Apple-converted-space"> </span>Re: [RE-wrenches] P1 micro performance<o:p></o:p></span></div></div></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Thanks for the clarification. <o:p></o:p></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">FWIW: Flat topping is exactly what occurs. Inverter limiting clips the inverter output power curve (not the voltage or current wave forms). The chart below has one data point for every hour of the year. The clipped/flat-top area is the result of the 225 kW inverter limiting the power output of a 385 kW array: <o:p></o:p></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span><image001.jpg></span><o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div><div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">On Mar 22, 2013, at 1:07 AM, boB wrote:<o:p></o:p></div></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br><br><o:p></o:p></div><div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">On 3/21/2013 9:59 PM, Exeltech wrote:<o:p></o:p></div></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt; "><table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top" style="padding-top: 0in; padding-right: 0in; padding-bottom: 0in; padding-left: 0in; "><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Wrenches,<br><br>I'm probably a lone voice on this .. and not intending to get overly picky.<o:p></o:p></div></td></tr></tbody></table></blockquote><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br><br>No, two lonely voices, Dan.<br><br>I associate clipping with audio waveforms which stops<br>the negative or positive voltage peaks flat. Also called<br>flat-topping.<br><br>Limiting is like turning down the volume. The waveform<br>stays the same and does not distort as it would if it<br>were being flat topped (and flat bottomed)<br><br>Thanks !<br>boB<br><br><br><br><br><br><o:p></o:p></div><table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top" style="padding-top: 0in; padding-right: 0in; padding-bottom: 0in; padding-left: 0in; "><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br>Could we call power limiting what it is .. "limiting", and not "clipping"?<br><br>Clipping implies distortion, which isn't the case here. Limiting is just that.<br>The inverter output is limited to some maximum value -- not "clipped".<br><br>The output power curve flattens when integrated over time, but this still isn't<br>distortion in the waveform. It's simply a point in the output where the derivative<br>is zero. Not increasing, not decreasing. Just .. zero. No additional increase<br>in the output for an increase in available energy at the input. Think "governor"<br>on an engine....<br><br>Thanks.<br><br><br>Dan Lepinski, Sr. Engineer<br>Exeltech / Exeltech Solar Products<br><br><br>--- On<span class="Apple-converted-space"> </span><b>Thu, 3/21/13, David Brearley<span class="Apple-converted-space"> </span><i><a href="mailto:david.brearley@solarprofessional.com" style="color: blue; text-decoration: underline; "><david.brearley@solarprofessional.com></a></i></b><span class="Apple-converted-space"> </span>wrote:<br><br><o:p></o:p></div><p class="MsoNormal" style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 12pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br>From: David Brearley<span class="Apple-converted-space"> </span><a href="mailto:david.brearley@solarprofessional.com" style="color: blue; text-decoration: underline; "><david.brearley@solarprofessional.com></a><br>Subject: Re: [RE-wrenches] P1 micro performance<br>To: "RE-wrenches"<span class="Apple-converted-space"> </span><a href="mailto:re-wrenches@lists.re-wrenches.org" style="color: blue; text-decoration: underline; "><re-wrenches@lists.re-wrenches.org></a><br>Date: Thursday, March 21, 2013, 11:37 PM<o:p></o:p></p><div id="yiv2118386813"><div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Thanks for sharing the screen capture, Marco.<o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Interesting issues to think about here. This is actually prime clipping season in many places (not sure about Hawaii) due to the cool weather. While there are more sun-hours in the summer, the cell temperatures are often high enough that you won't tend to see rated power out of the modules. <o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">While I'm not running performance models for work, the people who do are routinely increasing dc-to-ac ratios, often as high as 1.4-to-1. Having said that, most inverters aren't installed on a roof. (Not yet anyway.) <o:p></o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">I'd probably lean to a more conservative sizing ratio for micros. While I can imagine some scenarios where I'd be comfortable with a 215 W micro on a 265 W module—like a flat roof install in Vermont, which reportedly doesn't see 1,000 W/m^2 very often—I wouldn't try that here in Texas.<o:p></o:p></div></div></div></div></td></tr></tbody></table><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br><br><o:p></o:p></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><p class="MsoNormal" style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 12pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">_______________________________________________<br>List sponsored by Home Power magazine<br><br>List Address:<span class="Apple-converted-space"> </span><a href="mailto:RE-wrenches@lists.re-wrenches.org" style="color: blue; text-decoration: underline; ">RE-wrenches@lists.re-wrenches.org</a><br><br>Change email address & settings:<br><a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" style="color: blue; text-decoration: underline; ">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br><br>List-Archive:<span class="Apple-converted-space"> </span><a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org" style="color: blue; text-decoration: underline; ">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br><br>List rules & etiquette:<br><a href="http://www.re-wrenches.org/etiquette.htm" style="color: blue; text-decoration: underline; ">www.re-wrenches.org/etiquette.htm</a><br><br>Check out participant bios:<br><a href="http://www.members.re-wrenches.org" style="color: blue; text-decoration: underline; ">www.members.re-wrenches.org</a><o:p></o:p></p></div><div style="margin-top: 0in; margin-right: 0in; margin-left: 0in; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div></div></div></div>_______________________________________________<br>List sponsored by Home Power magazine<br><br>List Address:<span class="Apple-converted-space"> </span><a href="mailto:RE-wrenches@lists.re-wrenches.org" style="color: blue; text-decoration: underline; ">RE-wrenches@lists.re-wrenches.org</a><br><br>Change email address & settings:<br><a href="http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org" style="color: blue; text-decoration: underline; ">http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org</a><br><br>List-Archive:<span class="Apple-converted-space"> </span><a href="http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org" style="color: blue; text-decoration: underline; ">http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org</a><br><br>List rules & etiquette:<br><a href="http://www.re-wrenches.org/etiquette.htm" style="color: blue; text-decoration: underline; ">www.re-wrenches.org/etiquette.htm</a><br><br>Check out participant bios:<br><a href="http://www.members.re-wrenches.org" style="color: blue; text-decoration: underline; ">www.members.re-wrenches.org</a><br><br></div></blockquote></div><br></body></html>