**3.2 Unified Power Flow Controller (UPFC)**

An equivalent circuit of the UPFC as shown in Fig. 17 can be derived based on the operation principle of the UPFC (Achat et al., 2004) , (Mahdad et al., 2005).

Fig. 17. Equivalent circuit based on solid state voltages sources

The UPFC equivalent circuit described in Fig. 17 is represented by the following voltage sources:

$$E\_{v\mathbb{R}} = V\_{v\mathbb{R}} \left( \cos \left( \mathcal{S}\_{v\mathbb{R}} \right) + j \sin \left( \mathcal{S}\_{v\mathbb{R}} \right) \right) \tag{10}$$

$$E\_{c\mathbb{R}} = V\_{c\mathbb{R}} \left( \cos(\mathcal{S}\_{c\mathbb{R}}) + j \sin(\mathcal{S}\_{c\mathbb{R}}) \right) \tag{11}$$

Where *VvR* and *VcR* are the controllable magnitude,

Understanding Power Quality Based FACTS

*M\_Newton* 

*M\_Mdl\_FACTS* 

*M\_Rvoltage* 

*M\_FACTS* 

*M\_Bus* 

*Matlab Functions* 

*M\_Data M\_Branch* 

*M\_branch* 

*M\_Rstability* 

*M\_SVC* 

*M\_TCSC* 

*M\_UPFC* 

*M\_STATCOM* 

**M\_Plot** 

Fig. 19. Flowchart of the proposed basic SimFACTS

• Power flow calculation based Newton-Raphson algorithm • Understanding power quality based FACTS devices • Voltage Stability based continuation power flow (CPF)

Genetic Algorithm (GA), and Particle Swarm Optimization (PSO).

FACTS Location

CPF

Critical buses

Using Interactive Educational GUI Matlab Package 219

numerical tabular forms. Fig. 19 illustrates the components of the proposed strategy based FACTS technology. The SimFACTS tool includes the following application programs:

• Economic dispatch based conventional methods and global optimization methods like

Data base

Ybus

Modified Jacobian

3 4 1 2 ⎥ ⎦

*Convergence* 

**Yes** 

• Power Flow Solution • Indices of power Quality • Voltage deviation • Power loss • Power transit limits

<sup>⎤</sup> <sup>⎢</sup>

*J J J J*

⎣ ⎡ mod

**No** 

NR

FACTS Models

Shunt Series Hybrid

min max *V VV vR vR vR* ≤ ≤ , and phase angle,

0 2 *vR* ≤ ≤ δ π of the voltage source representing the shunt converter. The magnitude *VcR* and phase angle *cR* δ of the voltage source representing the series converter are controlled between limits:ij min max *V VV cR cR cR* ≤ ≤ , and 0 2 *cR* ≤ ≤ δ π.

#### **3.3 Thyristor Controlled Reactor (TCSC)**

The TCSC power flow model presented in this section is based on the simple concept of a variable series reactance, the value of which is adjusted automatically to constrain the power flow across the branch to a desired value.

Fig. 18. Principle of thyristor controlled series capacitor (TCSC)

The amount of reactance is determined efficiently using Newton's method. The changing reactance shown in Fig. 18 represents the equivalent reactance of all the series connected modules making up the TCSC, when operating in either the inductive and capacitive region. The equivalent reactance of line *Xij* is defined as:

$$X\_{ij} = X\_{\text{line}} + X\_{T \text{CC}} \tag{12}$$

Where, *Xline* is the transmission line reactance, and *XTCSC* is the TCSC reactance. The level of the applied compensation of the practical TCSC usually between 20% inductive and 80% capacitive.

#### **4. Understanding power quality based FACTS controllers using FACTS Simulator (SimFACTS Power Flow package)**

The advantages of the proposed graphical user interface tool lie in the quick and the dynamic interpretation of the results and the interactive visual communication between users and computer solution processes. The physical and technical phenomena and data of the power flow, and the impact of different FACTS devices installed in a practical network can be easily understood if the results are displayed in the graphic windows rather than

δ

The TCSC power flow model presented in this section is based on the simple concept of a variable series reactance, the value of which is adjusted automatically to constrain the power

*C* 

*Vf Vt*

*XTCSC*

of the voltage source representing the shunt converter. The magnitude *VcR* and

 π.

*reg*

*L* 

*t* 

The amount of reactance is determined efficiently using Newton's method. The changing reactance shown in Fig. 18 represents the equivalent reactance of all the series connected modules making up the TCSC, when operating in either the inductive and capacitive region.

Where, *Xline* is the transmission line reactance, and *XTCSC* is the TCSC reactance. The level of the applied compensation of the practical TCSC usually between 20% inductive and 80%

The advantages of the proposed graphical user interface tool lie in the quick and the dynamic interpretation of the results and the interactive visual communication between users and computer solution processes. The physical and technical phenomena and data of the power flow, and the impact of different FACTS devices installed in a practical network can be easily understood if the results are displayed in the graphic windows rather than

**4. Understanding power quality based FACTS controllers using FACTS** 

*ft P f t* 

*XX X ij* = + *line TCSC* (12)

It

*Capacitive Operative* 

of the voltage source representing the series converter are controlled

min max *V VV vR vR vR* ≤ ≤ , and phase angle,

between limits:ij min max *V VV cR cR cR* ≤ ≤ , and 0 2 *cR* ≤ ≤

*reg ft <sup>P</sup> <sup>f</sup>*

The equivalent reactance of line *Xij* is defined as:

**Simulator (SimFACTS Power Flow package)** 

*If*

*Inductive Operative* 

Fig. 18. Principle of thyristor controlled series capacitor (TCSC)

**3.3 Thyristor Controlled Reactor (TCSC)** 

flow across the branch to a desired value.

δ

0 2 *vR* ≤ ≤ δ

capacitive.

 π

phase angle *cR*

numerical tabular forms. Fig. 19 illustrates the components of the proposed strategy based FACTS technology. The SimFACTS tool includes the following application programs:


Fig. 19. Flowchart of the proposed basic SimFACTS

Understanding Power Quality Based FACTS

three methods:

in this option.

of the different FACTS Controllers.

• Simple Genetic Algorithm (SGA) • Particle swarm Optimization (PSO)

continuation power flow analysis.

• Basic economic dispatch based Lagrange method

controllers to control the reactive power at a specified location.

• **Results**: This is an option provided for the user to view all results.

Fig. 21. Structure of the developed simulator incorporating FACTS devices

at different power system situation.

The Newton-Raphson algorithm modified based on the FACTS models and used to calculate all the necessary electrical values involved on the power flow study. The simple software proposed is capable of doing simulations for several models of FACTS controllers

Using Interactive Educational GUI Matlab Package 221

• **Optimal Power Flow**: In this version (ver.1.0): the user can calculate the OPF using

• **Reactive Power Control**: In this version (ver.1): the user can choose the FACTS

• **Voltage Stability Analysis based Continuation Power Flow:** this section alows user to test the impact of FACTS devices in voltage stability and system loadability using

• **Help**: The objectives, scope and functions of each of the components are briefly given

data entry. The submenu 'FACTS Controller' designed to enter in details the data base

Fig. 20. The package for FACTS modelling and analysis (SimFACTS) with three languages: **Arabic**, **English** and **French**

In the literature many educational Graphical tools for power system study and analysis developed for the purpose of the power system education and training ().

This section reveals how the software package developed works by showing the effects of the introduction of different FACTS devices like the SVC, STATCOM, TCSC, SSSC and the UPFC Controllers. Fig. 20 shows the global functionality of the package graphical user interface based Matlab as a tool to demonstrate the impact of FACTS devices on power system operation and control.
