Now we have V_{dc_mpp} for solar modules, but it varies with the change in environmental conditions. Therefore, an approximate is required for the voltage range for whole day operation is required. For figure below the values taken are from 30-50 V.



Now using the above mentioned data we will find the important parameters of the flyback transformer [1].

• Find the amplitude of the output current 
• I_A= (2*P_o)/V_{grid_peak}                                                          (1)
• = 2*220/311 =1.286 A    
• Find the turn ratio "N" by using the following formula
• N= (η * V_{dc_mpp} )/V_{grid_rms}                                               (2)
• = (0.9* 40)/220 = 0.1636 
• This value is approx equal to 6. So transformer turn ratio will be 1:6. This vale can alternatively be calculated based on the current ratio of primary and secondary currents as given in page 3433 of reference given below. 
• Now measure the peak primary using following formula
• I_{p_max} = I_A* (V_{grid_peak}/V_{dc_min} + 1/N)                          (3)
• = 1.286 * (311/30 +1/1/6) = 21.04 A
• Using I_{p_max} , we can find the value of primary inductance as follows, here the value of  δ_max  taken as 0.5 
• Lp= (V_{dc_min} * δ_max ) / I_{p_max} * f_s                                  (4)
• = 30 *0.5/(21.04*200k) = 3.564 µH
• Based on the value of L_p we can find secondary inductance by using equation (5)
• L_s=L_p/(n²)                                                                              (5)
• =   3.564 /(1/36) = 128.3 µ H
• During the experimentation the values of L_p and L_s needs adjustment that is in between 3-4% of the values calculated above.
• For simulation in PSIM we need to calculate the magnetizing inductance "L_m" of the transformer. It should be kept in mind that the L_m is very important in transformer design. If value of L_m is low then high peak current will flow in primary winding, Which means high current stress on primary side switch. If the value of L_m is very high then system may operate in continuous conduction mode which leads to a distorted output voltage. The expression for L_m is given below [2]
• L_m= V_{dc_mpp} 2 *  δ_{max ²} / (4 P_pv * f_s) 
• =2.25 µ H