Dear All,
I am hereby attaching the datasheet of SMA Inverter. I am particularly interested in Sunny Central 800 CP XT. See page 3 in the attached document "SMA Datasheet.pdf"
I have highlighted certain parameters therein.
Now my questions are this:
1. For minimum MPP voltage they must have done Output rated voltage * 1.4142 = 360*1.4142 = 509V. Do you know why it is taken as 530V i.e. nearly 20 V higher. Is there any thumb-rule to do so? Can't they take 510V instead?
2. Here they have given the MPPT range as 641 to 850 V. Do you know how to select this range?
3. The max. DC short circuit current is taken as 2500A. Do you know how did they arrive at this value? any equation or something?
Thanks and Regards,
Aalok
Hi Aalok,
All your queries in this posting are best answered by the designers themselves. So would you wish to consider asking Sunny Central about all this ?
Besides, there could be some proprietary issues about an open discussion on some of them, since you are placed with another commercial venture.
Just a suggestion ! Please don't take it otherwise.
-Sanjay
Hello Aalok,
Actually there are many algorithms that exist to calculate the MPPT including : Hill climbing P&O,fractional Voc, fractional Isc , slide control, etc.. These different techniques depends on several factors which can form the MPPT voltage window for the system including the Nominal Operating Cell Temperature (NOCT). The aim of this MPPT to adjust the voltage at the PV array terminals such that it will maximize its output power. For more information I have attached a useful material.
Related to the MPPT volatge range , it depends on the temperature as shown that the temp. range from 25 (winter ) to 50 (summer) which has an impact on the output .
The short circuit current (Isc) is always above the maximum current in normal operating conditions. Practically, it occured during grid failures as for example voltage dips. I have attached a report from SMA that describe more about the short circuit current.
I wish you find this useful and good luck in your study.
-Hassan
This kind of inverter could be a 3ph Bridge so DC voltage must be higher than Vgrid peak. The maximun grid voltage is 414 so the minimun dc voltage that ensures that your converter works well is 414*sqrt(2)=585.. any way you need higher voltage ensure a good pwm behaviour. 585/0.9=650V. (more or less )
The maximun input current could be the breakers current...
The range of MPPT can be easily obtained by knowing the short circuit current rating of your application. Like if the short circuit rating is 12A you can just ask for a MPPT of 12-15A with rated voltage of your solar array.
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