Question

Design a solar PV generating installation to meet the following specifications: Peak rating 7.5kW Inverter AC voltage 230 V, single-phase Module (panel) specifications are: Peak rating 400 W Voltage at maximum rating: 50 V Current at maximum rating: 8 A. Determine the number of parallel strings, the number of modules per string, a suitable DC voltage and amplitude modulation index Ma value in the range 0.75 Ma <0.97

Answer 1

I am designing a single phase square wave inverter using these solar panels. The amplitude modulation index M_A for an inverter is given by

M_A V_S = V_P ...(1)

where V_S is the DC voltage obtained from the system and V_P is the peak voltage of the AC system. SInce our system is 230V AC, the peak voltage is 230*1.414= 325.22. Say if I am keeping M_A at 0.8 value the DC voltage comes out to be:

M_A = 325.22/0.8 = 406.525

So let's finalise our system to 400 V DC. Hence the new M_A will be (V_P /V_S) 325.22/400 = 0.813. Now one module gives 50 V at maximum power. So in order to get 400 V, we need 400/50 = 8 such panels in series.

Now the total power derived from the system is 7.5 kW peak. We know

P = V. I

7500 = 400 * I

==> I = 18.75 .

Lets round it off to 19.

So now we know that,

1) Total no of modules = 19*8 = 152

2) No of modules in series = 19

3) Total no of strings in parallel = 8