# PVsyst's forum

Welcome on PVsyst's forum.
 It is currently Wed Sep 23, 2020 2:44 pm

 All times are UTC+02:00

 Post new topic  Reply to topic Page 1 of 1 [ 1 post ]
 Print view Previous topic | Next topic
Author Message
 Post subject: Inverter Efficiency CurvePostPosted: Mon Jan 05, 2015 5:11 pm

Joined: Tue Nov 11, 2014 9:31 am
Posts: 10
Dear Mermoud,

I am trying to understand the modelling of the inverter effciency in PVsyst. I have some problems to undestand the way PVsyst uses in order to build the efficency curve starting from the max and Euro efficiency.
In the Help "Grid inverters, Efficiency curve" you write:
------------------------------------------------------
Interpretation of the efficiency curve:
- Up to the power threshold (often named "Starting operating at ..." in datasheets), the input power corresponds to internal consumption for the internal needs of the device, and doesn't produce power.
- From this threshold, the device is supposed to produce an AC power proportionally to (Pin - PThresh).
- This production is penalized by an ohmic loss of the internal components (transformer and transistors), which increases quadratically with power (like R · I²). When translated into efficiency, this gives a maximum efficiency usually around 50-60% of the nominal power.

PVsyst model for automatic construction of the efficiency profile
In most of the specifications, the manufacturers or databases give the so-called European Efficiency (or CEC efficiency in the US) which is intended to provide an average efficiency over yearly operating conditions.
From these two values specified by the user - Maximum efficiency and European efficiency - PVsyst constructs a default profile, with the following hypothesis:
- The AC production is proportional to the DC available energy, minus the Pthresh "internal consumption",
- The efficiency is penalized by a resistive loss of the output circuitry (transistors and transformer), in a quadratic way as function of the power (R * I²),
- This transfer curve has to match the specified maximum power value, at a DC power arbitrarily fixed at a value of 60% of Pnom,
- The Pthresh "effective" value (=> slope of the curve) is adjusted in order to match the Euro (or CEC) average efficiency.
The contribution of the Resistive loss is fixed according to a normalized resistance factor, proportionally to the difference between the given Max- and Euro- efficiency. The normalized resistance factor commands the losses at high powers (above the 60% point), with respect to the losses due to Pin_threshold. We choose a usual value of 3.0 (arbitrary units) as default.
--------------------------------------------------

Could you please explain in an easier way this modelling method and why, if the threshold is 8000W (imposed by the manufacturer), do you calculate a Pthresh "effective" value? How do you calculate this "effective" value?

Top
 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Post new topic  Reply to topic Page 1 of 1 [ 1 post ]

 All times are UTC+02:00

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

Search for:
 Jump to:  Select a forum ------------------ PVsyst SA Announcements (read only)    Latest news - Bifacial Modelling and 3D Drawing    PVsyst's forum rules FAQ (read only)    Installation and use of PVsyst    Meteo data    PV Components    Shadings and tracking    Simulations : parameters    Simulations : results    Standalone and pumping systems Your questions about PVsyst    Howto    Problems / Bugs    Meteo data    PV Components    Shadings and tracking    Simulations    Suggestions    Tutorials : Feedback and requests Links    PVsyst website    YouTube Channel