Power quality is essential for smooth functioning of industrial process. As industries expand, utilities become more interconnected and usage of electrically equipment increases, power quality is jeopardized. The quality of power in the power system is severely affected by the presence of harmonics. This harmonics adversely effects the power system performance. Some of the effects are over heating of metal parts, noise in motors, low efficiency in motors etc. The effects produced by the harmonics are reduced by adopting some corrective measures. VFD users have many choices when it comes to harmonic filtering. Of course they may do nothing, or they may choose to employ one of the many techniques of filtering available. Each filtering technique offers specific benefits and has a different cost associated with it. Some may have the potential to interfere with the power system while others will not. For best overall results when using reactors or harmonic filters, be sure to install them as close as possible to the non-linear loads which they are filtering. When you minimize harmonics directly at their source you will be cleaning up the internal facility mains wiring. This will also reduce the burden on upstream electrical equipment such as circuit breakers, fuses, disconnect switches, conductors and transformers. The proper application of harmonic filtering techniques can extend equipment life and will often improve equipment reliability and facility productivity.
Since last 25 years there has been an increase in the use of solid state electronic technology. This new, highly efficient, electronic technology provides product quality with increased productivity. Today, we are able to produce products at costs less than in the years passed, with the introduction of automation by using the solid state electronic technology .This new technology requires clear electric power.
The conventional speed control systems are being replaced by modern power electronic systems, bringing a verity of advantages to the users. Classic examples are DC $ AC drives, UPS, soft stators, etc. Since the thrusters converter technology is rapidly gaining in the modern industrial plants, the power supply systems are contaminated as the ideal sinusoidal current and voltage waveforms are getting distorted. This is in turn is affecting the performance of the equipment in the electrical network.
WHAT IS POWER QUALITY?
Adequate to superior power quality is essential for the smooth functioning of critical industrial processes. As industries expand, utilities become more interconnected and usage of electronically controlled equipment increases, power quality is jeopardized. Most large industrial and commercial sites are served by overhead lines with feeders that are subject to unpredictable and sporadic events, e.g. lightning and contact with tree limbs. Most distribution circuits have resoling devices that clear temporary faults through a timed series of trip and close operations.
This minimizes the possibility of long-term outages but leads to a number of minor power disturbances. These typically occur several times a month. Many electric utilities have increased the voltage at which they distribute power. This allows a single circuit to serve more customers or deliver higher loads, and reduces energy losses in the system. But it often means the overhead distribution circuit is longer, with more exposure to disturbances. And disturbances travel farther because of lower system impedances associated with higher voltage circuits. Sophisticated new systems are providing vastly increased efficiency and control in critical processes. But with their high sensitivity even to brief variations in electric power quality, today's computer-driven devices fail when power is disturbed for even a few milliseconds.
This Project comprises of 5 separate cases of Power Quality, Reactive Power and Modulated Power Filter Compensators. These cases have been modulated with and without compensation devices and have been simulated using both Matlab/Simulink and PSCAD software.
The 5 cases are as follows:
1. Power Quality Enhancement Using Modulated Power Filter
2. Power Quality Enhancement and Voltage regulation Using Modulated Power Filter
3. Power Quality Enhancement Using STATCOM
4. Power Quality Enhancement addressing the Tingle Voltage Issue
5. Power Quality Enhancement and Voltage regulation Using STATCOM
Detail information about the cases and digital simulation are shown under section 8.1.1 and under the Appendices A to E.
The research course project EE6723 addresses the current issues of Electric Power Supply Pollution, Power Quality (PQ) and Harmonic Distortion Problems. The term “Power Quality” is in general a broad concept and is associated with electrical distribution and utilization systems that experience any voltage, current or frequency deviation from normal operation. For ideal electrical systems, the supplied power should have perfect current and voltage sinusoidal waveforms, being safe and reliable. But the reality is that the electric utilities controls the voltage levels and quality but are unable to control the current, since the load profile dictates the shape of the current waveform. Thus, the utility should maintain the bus voltage quality at all times. This simple consideration makes power quality (PQ) equal to voltage quality as shown in Figure 1.1
Defining precisely the Power Quality is a tremendous task; one of the common definitions is:
Definition 1: “Power quality is a summarizing concept, including different criteria to Judge the technical quality of an electric power delivery”. Another definition is developed and adopted by Ontario Hydro:
Definition 2: “Power Quality is the degree to which both the utilization and delivery of electric power affects the performance of electric equipment”.
In general there is no unique definition of power quality. The power quality problem can be viewed from two different angles related to each side of the utility meter, namely the Utility and the Consumer. An alternative definition of PQ is adopted:
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