<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">Dear Mike,<div><br></div><div>As co-author of upcoming book "The Handbook of Solar Water Pumping", we have expanded its definition to include micro and national grid-tied systems in which pumping is synchronized with power availability from PV. I had known about frequency-based load control for microgrids (from an SMA-based microgrid I toured in Israel). I had no idea it was a happening system on public grids until I read your response here. I love how it requires no communication lines or digital signals. It's a "natural" and logical concept from the old days of spinning generators under varying load.</div><div><br></div><div>I see your PG&E reference, but is there also a reference text you can recommend that I can use in the book as a universal explanation of how this works? It can be SMA documentation, or other ref. You can reply here if it's useful to the list, and/or contact me off-line.</div><div><br></div><div>Thanks! – Windy<br><div><br><blockquote type="cite"><div>On Dec 1, 2022, at 5:47 PM, re-wrenches-request@lists.re-wrenches.org wrote:</div><br class="Apple-interchange-newline"><div><meta charset="UTF-8"><div style="caret-color: rgb(0, 0, 0); font-family: ArialMT; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin: 0px;"><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif; color: rgb(127, 127, 127);"><b>From:<span class="Apple-converted-space"> </span></b></span><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif;">Harry Mahon <<a href="mailto:Michael.Mahon@sma-america.com" style="color: blue; text-decoration: underline;">Michael.Mahon@sma-america.com</a>><br></span></div><div style="caret-color: rgb(0, 0, 0); font-family: ArialMT; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin: 0px;"><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif; color: rgb(127, 127, 127);"><b>Subject:<span class="Apple-converted-space"> </span></b></span><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif;"><b>Re: [RE-wrenches] AC Coupling Standard?</b><br></span></div><div style="caret-color: rgb(0, 0, 0); font-family: ArialMT; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin: 0px;"><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif; color: rgb(127, 127, 127);"><b>Date:<span class="Apple-converted-space"> </span></b></span><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif;">December 1, 2022 at 5:47:18 PM MST<br></span></div><div style="caret-color: rgb(0, 0, 0); font-family: ArialMT; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; margin: 0px;"><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif; color: rgb(127, 127, 127);"><b>To:<span class="Apple-converted-space"> </span></b></span><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif;">RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" style="color: blue; text-decoration: underline;">re-wrenches@lists.re-wrenches.org</a>><br></span></div><br style="caret-color: rgb(0, 0, 0); font-family: ArialMT; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><br style="caret-color: rgb(0, 0, 0); font-family: ArialMT; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: ArialMT; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;"><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;"><span style="font-size: 12pt;">Definitely it is possible for newer grid-interactive inverters. However, for grid-tied operation, the utility that runs the grid sets the rules (and sets the setpoints as it were), and it can be confusing....<o:p></o:p></span></div><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;">Looking at PG&E’s Rule 21 tarriff (submitted Aug 12, 2022, effective Nov 4, 2022) Freq-Watt reuirements are:<o:p></o:p></div><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;">“When system frequency exceeds 60.036 Hz, the active power output produced by the Smart Inverter shall be reduced by 50% of real power nameplate rating per hertz (5% of real power nameplate rating reduction per 0.1 hertz)”<o:p></o:p></div><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;">Bottom of Sheet 207 of :<span class="Apple-converted-space"> </span><a href="https://www.pge.com/tariffs/assets/pdf/tariffbook/ELEC_RULES_21.pdf" style="color: blue; text-decoration: underline;">https://www.pge.com/tariffs/assets/pdf/tariffbook/ELEC_RULES_21.pdf</a><o:p></o:p></div><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;">So a 5kW inverter needs to ramp at 2.5kW/Hz. But if it is only producing 2.5kW, it has to be at 0W at 61.036Hz.....<o:p></o:p></div><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p> </o:p></div><div style="margin: 0in; font-size: 11pt; font-family: Calibri, sans-serif;">Mike</div></div></div></blockquote></div><br></div></body></html>