**3.1.2 Physical modeling**

58 Electrical Generation and Distribution Systems and Power Quality Disturbances

A dynamical system can be classified in terms of known structures and parameters of the system, shown in Fig.5, and classified as a "White Box" if all structures and parameters are known, a "Grey Box" , if some structures and parameters known and a "Black Box" if none

Structure Parameter

Black box

Grey box

White box

Parameter

Structure ure

Structure Parameter

Par

Fig. 5. Dynamical system classifications by structures and parameters

Steps in system identification can be described as the following process, shown in Fig. 6.

Goal of Modeling

Model structure selection

Model Estimation

Model Validation

Application

The primary goal of modeling is to predict behaviors of inverters for PV systems or to simulate their outputs and related values. The other important goal is to acquire

Experimental

Data collection and processing

Physical Modeling

Structure Parameter

Known Missing

**3.1 Principle of system identification** 

Structure Paramter

Fig. 6. System identification processes Each step can be described as follows

**3.1.1 Goal of modeling** 

are known [55]**.** 

Photovoltaic inverters, particularly commercial products, compose of two parts, i.e. a power circuit and a control circuit. Power electronic components convert, transfer and control power from input to output. The control system, switching topologies of power electronics are done by complex digital controls.
