Flexible alternating current transmission systems
As the new generation is trying to move away from non-renewable energy sources, and in that case, the role of FACTS devices is increasing in large proportions in the stability of Grid Stations. Transmission System Operators (TSOs) enforce strict grid policies so that there remains good support from all the renewable devices distributed in different locations. However, the need for controllable devices such as SVCs and STSTCOMs is still there.
Power distribution generation units (DGs) and flexible AC transmission systems (FACTS) are changing how the power industry functions. They are enabling more localized and reliable systems than ever before.
This study presents different techniques for optimizing a system comprising DG and FACTS devices for optimal siting of the DG units and FACTS devices.
AC Transmission systems FACTS
FACTS are power electronic devices that have combined power electronic components with a power system component. The advantages of FACTS devices are to improve the system performance or to provide solutions to the power problems at the Grid stations.
Worldwide, people are working hard to introduce unique applications to FACTS devices.
Application of FACTS Devices in Power Systems:
Controlling the reactive power and dealing with reactive power demands have become quite simple and easy by using these devices. The benefits of FACTS are to improve the installations that are in existing form, offering other crucial advantages as discussed below:
- Increases power transfer capability
- Regulate Voltage Profile
- Active and reactive power flow control
- Improves transient and dynamic stability
- Enhance power quality
- Develops voltage regulation
Series and Shunt Compensations of Transmission lines:
Two compensation techniques are used for the FACTS devices based on the connection type with the power network.
- Series compensation
- Shunt compensation
The line having the series impedance causes the voltage drop, so the series compensation helps reduce the series impedance by increasing the transmittable power.
In this type of compensation, there is a parallel connection between FACTS devices and the transmission line. The line is injected with the current for voltage regulation at the connection point.
Flexible AC transmission systems Controller Classification:
The type of connection with the power system FACTS types is discussed below.
The voltage is introduced with the line voltage in series in the series controller. Reactive power can be supplied or consumed using this type of controller. This reactive power is needed when the transmission line load is increased.
The devices can be:
- Reactor (Impedance devices)
- Harmonic frequency
To meet the desired requirement, it can be a combination of these.
To introduce the current at the connection point in the system, these controllers are connected in the shunt with the line. They can be:
- Variable Impedance
- Variable source
- Combination of variable impedance and source.
Combined Series-Series Controller:
These combined controllers are unified controllers in which each line is employed with a different series controller for reactive series power compensation and to send the real power among the lines.
Type of these controllers is:
IPFC is used to balance the power flow that is real and reactive in the lines, so they should help maximum power transmission.
Combined Series-Shunt Controller:
These combined controllers are a combination of different series controllers and shunt controllers. These are also unified flow controllers with series and shunt elements.
The current is injected with the controller’s series part, and voltage is introduced with the controller’s shunt part in the line.
- TCPST (Thyristor Controlled Phase Shifting Transformer)
- UPFC (Unified Power Flow Controller)
- TCPAR (Thyristor Controlled Phase Angle Regulator)
MATLAB Code for FACTS Devices:
The discussion is about how to find the optimal location for FACTS through Matlab Programming. FACTS Devices are generally used for to compensate voltages and reactive power as well. In the case the of IEEE 14 bus system, voltage magnitude can be adjusted using suitable FACTS if there is over-voltage.
Distribution System Parameters
IEEE 14 Bus System Data is considered for the power system network evaluation.
Considered Optimization for Voltage Stability
- Genetic Algorithm (GA) 2. Artificial Bee Colony
Interested to implement through, particle swarm optimization algorithm matlab code, already an article present in this blog.
Cases considered for Reactive Power Control
A load flow is a simulation that analyzes the power distribution network to identify the amount of energy in the grid at a given time. Electricity (or electrical power) is a measure of how much work, or “load,” will be put on a system when a given amount of current flows through that system.
1. Without optimization (DG & FACTS)
lfybus % form the bus admittance matrix lfnewton % Load flow solution by Newton-Raphson method busout % Prints the power flow solution on the screen lineflow % computes and displays the line flow and losses ploss=real(SLT); qloss=imag(SLT); lc=evalin('base','lc'); ampct=max(max(abs(lc))); maxVm=max(abs(Vm)) minVm=min(abs(Vm)) ploss qloss assignin('base', 'ampct', ampct); assignin('base', 'ploss', ploss)
2. Distributed Generation (DG)
3. DG & FACTS
Power flow solution by Newton-Raphson method is considered.
% Power flow solution by Newton-Raphson method % Copyright (c) 1998-2010 by H. Saadat % Revision 1 (Aug. 99) To include two or more parallel lines ns=0; ng=0; Vm=0; delta=0; yload=0; deltad=0; nbus = length(busdata(:,1)); kb=;Vm=; delta=; Pd=; Qd=; Pg=; Qg=; Qmin=; Qmax=; % Added (6-8-00) Pk=; P=; Qk=; Q=; S=; V=; % Added (6-8-00) for k=1:nbus n=busdata(k,1); kb(n)=busdata(k,2); Vm(n)=busdata(k,3); delta(n)=busdata(k, 4); Pd(n)=busdata(k,5); Qd(n)=busdata(k,6); Pg(n)=busdata(k,7); Qg(n) = busdata(k,8); Qmin(n)=busdata(k, 9); Qmax(n)=busdata(k, 10); Qsh(n)=busdata(k, 11); if Vm(n) <= 0 Vm(n) = 1.0; V(n) = 1 + j*0; else delta(n) = pi/180*delta(n); V(n) = Vm(n)*(cos(delta(n)) + j*sin(delta(n))); P(n)=(Pg(n)-Pd(n))/basemva; Q(n)=(Qg(n)-Qd(n)+ Qsh(n))/basemva; S(n) = P(n) + j*Q(n); end end
The program is designed through MATLAB Script, and this study’s objective is mentioned below.
1. Location and size of FACTS and Distributed Generation (DG)
2. Power Loss Real and Reactive
3. Voltage Deviation
Advantages of FACTS Devices:
This article discussed how the FACTS technology enhances power system performance. The benefits it provides us and the new research going on to minimize the cost of the power electronic components. How many applications are there, and what are the benefits it provides. Different types of controllers, such as series controllers, shunt controllers, and two types of combined controllers, are discussed.
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