A PV inverter is connected in series with the solar array to form an EPU. The series operator is used to calculate the UGF for an EPU using as­sociative and commutative properties. For the type of the MSS containing elements connected in series, its capacity level for the state kE is the mini­mization of the corresponding capacities of its components. The structure function for an EPU takes the form:

Подпись: (14)Ф. КіР^ = min(wI, kI, wa, ka)

The capacity distribution of the EPU E can be obtained based on the UGF representing capacity distribution of the array and the PV inverter by using the series composition operator

NE f 2n 2

UE{Z) = £ PE, kE ■ Zww = пЦ £ Pa, ka ■ Zw°**, £ PlMl ■ Zw’*

kE=l ka=l k]=l

2n 2

= £ £ (Pa’k*’ p,’ki’zmin (Wa’ka, w,’k0

ka=l fe1 = l (15)

where Ne is the number of states of the EPU and equals to 2(N+1).