3.4.4. Converter

The converter keeps the flow of electric power between the alternating current (AC) link and direct current (DC) link devices. It converts the electrical power from DC to AC. In the inverter mode, it changes the electricity from DC to AC and from AC to DC while operating as a rectifier. The costs of the economic variables of the power converter are given in Table 9. The technical data of the selected converter are given in Table 12 [50]. The converter capacity level is obtained using:

$$\mathbf{C} = (\mathbf{3} \times L\_i) + L\_r \tag{6}$$

Here, *Li* and *Lr* refer to the inductive and resistive loads.


**Table 12.** The technical data of the selected converter.

*3.5. Evaluation Criteria*

3.5.1. The Net Present Cost (*NPC)*

The *NPC* comprises the initial cost, cost of replacement of individual devices, operation cost, maintenance cost, etc. It is an economic variable used to assess the optimum system of different combinations of system configurations. The following equation is used to analyze the *NPC* (for convenience, denoted as *CNPC*) [68]:

$$\mathcal{C}\_{NPC} = \frac{TAC}{CRF(i, N)}\tag{7}$$

Here, the total annualized cost (USD/year) is denoted by *TAC*, *N* represents the number of years, and *i* refers to the yearly real discount rate in percent. The capital recovery factor (*CRF*) is calculated using Equation (8) below:

$$CRF(i, N) = \frac{i(1+i)^N}{\left(1+i\right)^N - 1} \tag{8}$$

The yearly real discount rate with regard to the anticipated inflation rate (ƒ) and nominal discount rate (*i* ) is obtained from Equation (9) below:

$$d = \frac{i'-f}{1+f} \tag{9}$$
