Slide 1

Dr C.V.RAMAN INSTITUTE OF SCIENCE AND TECHNOLOGYPresented byAnshul PaulB.E(EEE) 8th sem Harmonic detection due to non-linear Load using matlab A seminar onintroductionAny significant deviation in the waveform magnitude or frequency is a potential power quality problem.

Due to non-linear loads the voltage and current waveforms will no longer be sinusoidal.

The term harmonics are defined as sinusoidal voltages or currents having frequencies that are integer multiples of the fundamental frequency.

Active power filters are mainly used to reduce harmonics in power system.contentsPower quality

FACTORS AFFECTING POWER QUALITY

ELECTRICAL LOADS

Harmonics

SOURCES OF HARMONICS

EFFECTS OF HARMONICS

TOTAL HARMONIC DISTORTION

About matlab

Matlab model Power qualityPower quality is actually the quality of the voltage which is delivered by the utility to the customer.

It is the set of electrical boundaries that allows a piece of equipment to function in its intended manner without significant loss of performance.

The power quality is determined by the performance and productivity of the end user equipment.

Power-quality problem is defined as an occurrence in a non-standard voltage, current, or frequency deviation that results in a failure of end-use equipments.

FACTORS AFFECTING POWER QUALITY Steady-State Voltage and Frequency Magnitude

Voltage Sags

Grounding

Harmonics

Transients

Voltage Fluctuations and Flicker

ELECTRICAL LOADSLinear loads Non-linear loads Resistance is constant

Current is proportional to voltage Resistance is not-constant

Current is not proportional to voltage VVIIharmonicsHarmonics are defined as sinusoidal voltages or currents having frequencies that are integer multiples of the fundamental frequency. Voltage function, v(t) =V sin(t) ... (1) Current function, i(t) = I sin(t ) (2)

The non sinusoidal voltage & current waveform can be expressed as follows:

V (t)= V0 + V1Sin(t) + V2 Sin(2t) + V3 Sin(3t) + V4 Sin(4t)+ +Vn Sin(nt). ...(3) I(t) = I0 + I1Sin(t) + I2 Sin(2t) + I3 Sin(3t) + I4 Sin(4t)..+In Sin(nt). .(4)

I1

I2

I3Third Harmonic (3f)Second Harmonic (2f)Fundamental (f)SOURCES OF HARMONICS Distributed non-linear components of small rating.

Large static power converters and transmission system power electronic devices.

randomly varying nonlinear loads.Nonlinear loads can be broadly divided into two categories;

Voltage based converter type loads.Current based converter type loads. EFFECTS OF HARMONICS Voltage distortion

Increased value of RMS currents

Overheating of power transformers

De-rating of distribution equipment

Overloading of phase and neutral conductors

Parallel resonances between the utility system

Decreases efficiency of motorTOTAL HARMONIC DISTORTION Total harmonic distortion is the ratio between the RMS value of the harmonics and the RMS value of the fundamental.

Where V1 is the fundamental component of voltage V2,V3,V4,.Vn are the harmonic componentsAbout matlab It is a high-level language for numerical computation. It provides vast library of mathematical functions. It provides built-in graphics for visualizing data.It provides tools for building applications Uses of MATLAB:-

Signal Processing and Communications Image and Video Processing Control Systems Test and Measurement

Matlab model Three phase rectifier with resistive load

Source voltage waveform

Source current waveform

Load voltage and current waveform

THD for source current

Conclusion These non linear loads are the main source of harmonic current distortion of the supply mains.

Most industries uses large number of non-linear loads.

Fast Fourier transform can be used to determine total harmonic distortion.

If frequencies of harmonic components are known, filtration can be easily provided.

Further compensation can be provided using active, passive and hybrid filters.

queries;