The management and utilization of power can be significantly impacted by the quality of the power supply in electrical power systems. Electrical power systems operate as nonlinear loads, causing a waveform to deform and contain harmonics of both the current and voltage. These loads' generated current and voltage harmonics may result in problems like an increase in power losses, conductor deterioration, and adverse effects on distribution systems and other electrical components. Thus, it is essential to examine the overall effect on these harmonics.
Total harmonic distortion(THD) is the sum of all the harmonics that are present in a given system. You can evaluate the level of distortion in the system using THD. For the benefit of users, below is a description of the notion of distortion with total frequency in distribution networks.
Total Harmonic Distortion (THD): What is it?
Understanding THD is a very challenging phenomenon. However, it becomes simpler when broken down into the simplest harmonics and distortion definitions. Other switching devices, like solar PV inverters, could alter the voltage of the system and lead to abnormal conditions in delicate loads.
Despite the current economic difficulties, electricity suppliers and end users continue to expand their facilities and increase their load counts. Over the next few years, other facilities with meager or no capacity will be grid-connected. More loads will come onto the grid as a result of the fierce competition in many industries. The added load could result in additional power quality problems. The first problem to arise will be with the quality of the power. One of the problems with power quality is harmonics in the power distribution network.
The growing use of PV solar panels is related to this. The front-end of power conservation networks may be affected by the addition of a power inverter if harmonic voltages are a concern. Surges and voltage fluctuations function similarly to harmonic distortion. These problems might be caused by numerous end users.
A power system with AC supply and load
Both linear and non-linear electrical loads can affect the power quality that the device receives. Because linear loads draw sinusoidal currents, they do not introduce distortion
The idea of a sine wave with no harmonics
Contrarily, nonlinear loads draw a current that is not sinusoidal. Due to the distortion in the voltage caused by the current's different waveform when flowing in the sine wave's direction. The sinusoid's behaviour as shown can change as a result of the distortion. Harmonics is the term for this.
Harmonics are frequency components that match the waveform's fundamental frequency. For instance, the third, second, and fourth harmonic elements are equal to 120Hz, 180Hz, 300Hz, and 240Hz, respectively, when the 6Hz fundamental waveform is used. Since there are no harmonics in a perfect sinusoidal wave, the wave is not distorted.
Harmonics in the power factor correction process
A little bit of mystery surrounds the existence of power factor corrections in the voltage and current harmonics. The real power as a function of voltage and that of the power source that is represented by make up the two components of the total installation current.
The sum of Ipower and Reactive Power is Total2.
You can figure out the power factor by
Regulations for New South Wales Service and Installation (March 1999) For instance, it mandates that users maintain a power factor that ranges from 0.9 in lagging to 1. Other power sectors are governed by tariffs that require end-users to maintain power factors as close to equality as possible, thereby reducing the reactive current. Shunt capacitor installation can be used to achieve this. The equation above is changed as follows when harmonics are present, which causes the frequency component of the current to increase:
Itotal2 = Ipower2 + Ireactive2 + Iharmonic2
Ireactivegets is close to zero in a variety of situations, such as the installation of a computer, but Inharmonic can be extremely high, meaning that the power factor will be lower than the unity value. When a user installs power factor-correcting capacitors, the power factor will increase as a result of the current passing through the capacitor, increasing the installation's total current and degrading or worsening the power factor.
How is Total Harmonic Distortion calculated?
The susceptibility of the equipment and emission are the two aspects of harmonics that the end users must take into account.
The degree to which equipment could be harmed or destroyed by harmonic distortion is referred to as susceptibility. It is based on the voltage that the apparatus can handle. Equipment emission, which depends on the device and the amount of harmonic current drawn, determines how quickly the supply is delivered.
THD is defined as the total harmonic distortion (THD) as the sum of all harmonics from either the current or voltage waveform divided by the fundamental component of the voltage and current sinewave.
The amount of image distortion is expressed as a percentage of THD.
The RMS value of the two voltages is calculated, for instance, if a harmonic voltage of 20 volts and a sinewave voltage of 240 volts are combined.
V2 = V12 + VH 2
V2 = 2402 + 202 = 24O.8 volts
A percentage is then used to represent THD. The THD will then be displayed as a percentage and is based on:
The behavior of PV inverters can be evaluated through field measurements of their power quality under actual operating conditions.
How are harmonics analyzed?
- Obtain information from the source system. The data is in the form of short-circuit current, and it can be used to calculate the equipment's resistance.
- Analyze the installation's main harmonic sources.
- It is possible to simulate the installation of the electric power network based on the harmonic order of each. As the frequency rises, inductive reaction grows while capacitive reactance shrinks and resistivity stays constant.
- Analyze and evaluate the voltage present at the point where harmonic current and harmonic impedance join.
How can harmonics be reduced in an electronic system?
If you intend to install significant harmonics and distorting loads that comply with Australian standards, AS 2279.2 should be taken into account. Consult a professional or local expert if you don't have any prior experience analyzing total harmonic distortion. It is possible to take these options into account if there are too many harmonics after the calculation.
- Ask the local supplier for a description of the smaller harmonic current.
- the placement of extra equipment that draws a range of harmonic currents. This can stop your power supply system from spreading.
- A harmonic filter, made up of resistors, capacitors, and inductors, can be used.
- A suitable detuning inductor should be connected to it to prevent the capacitor from absorbing large harmonic currents if the distortion is brought on by an expansion of power factor capacitors or power factor capacitors.
- If the project is large, the local power provider may make changes to the system to reduce system resistance.
- The construction of commercial facilities can make use of the aforementioned elements and analysis.