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UWE Bristol Engineering showcase 2015

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Ahmed Baraka<br />

BEng (Hons) Electronic <strong>Engineering</strong><br />

Project Supervisor<br />

Dr Hassan Nouri<br />

STATCOM ​Inverter Switching Techniques: Investigation Using<br />

MATLAB/Simulink<br />

1. Overview<br />

Static synchronous compensator (STATCOM) allows full utilization of existing power generation and transmission facilities. DC/AC inverter is a key component of<br />

the STATCOM device. The inverter takes a DC voltage from a battery, a solar panel or any DC storage devices as input, and converts it into an AC voltage output.<br />

This conversion is globally useful especially in places where the electrical infrastructure is not well-developed, since it provides a reliable mechanism to power<br />

up AC appliances like electronic medical instruments in case of system failure or brownouts. This research focuses on investigating various Pulse Width<br />

Modulation (PWM) switching schemes used for STATCOM inverter.<br />

2. Single phase DC/AC inverter<br />

MATLAB/Simulink has been used to design the building block for Sinusoidal PWM (SPWM). Signals, generated by SPWM drive the DC/AC inverter. As a<br />

results, the inverter produces an output current, which is only distorted by 0.54%. This means that most of the energy stored in batteries, or solar panels<br />

will be transformed into a desirable form with minimum losses, thus, increasing the efficiency of the inverter.<br />

Project summary<br />

The main aim of this project is to investigate and<br />

compare different Pulse Width Modulation (PWM)<br />

switching techniques for the purpose of identifying<br />

the total harmonics distortion (THD) of the output<br />

current waveform. The technique with the least THD<br />

is to be used to study the performance of STATCOM.<br />

Project Objectives<br />

• To investigate various available switching<br />

techniques used for STATCOM inverters.<br />

• To simulate available switching schemes on a<br />

multilevel, single phase and three phase inverter<br />

using MATLAB/Simulink.<br />

• To demonstrate the phase shifting properties of<br />

the generated waveform by studying the<br />

performance of STATCOM.<br />

3. STATCOM Performance<br />

Ideally, the voltage level at the customer end needs to be maintained at a certain level, regardless of any changes to the nature of the load. However, the load<br />

bus bar faces variations in voltage level, when new loads are connected to the grid. The two main loads are: inductive loads, which cause the voltage at the<br />

customer end to drop down, and capacitive loads, which cause the voltage at the customer end to go up. This problem is overcome by connecting the<br />

STATCOM device to the system to act as a guard, which keeps the voltage maintained regardless of the nature of the load.<br />

3.1 Inductive loads<br />

3.2 Capacitive loads<br />

Project Conclusion<br />

• Upon simulation and investigation, sinusoidal<br />

PWM has proven to be a very practical and<br />

reliable switching technique.<br />

• On a small scale, sinusoidal PWM can be used to<br />

drive inverters to transform the continuous<br />

current produced by the photovoltaic cells into<br />

alternating current, ready to be directly absorbed<br />

into the electricity distribution grid.<br />

• On a large scale, the sinusoidal PWM inverter can<br />

be used to design a closed loop control system<br />

that compensates the flow of reactive power in<br />

existing systems, thus, stabilising the voltage<br />

level.

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