J.PRAKASH

 The term power quality means different things to different people.  Power quality is the interaction of electronic equipment within the electrical environment. This consists of generators, Transformers, breakers, wiring and grounding.  A good quality power supply would be one that is always available, always within voltage and frequency tolerances and has a pure noise- free sinusoidal wave shape.

 Power quality is an increasingly important issue for all electrical consumer.  Problems with powering and grounding can cause data and processing errors that affect production and service quality.  Each time production is interrupted electrical consumer, your loses the margin on the product that is not manufactured and sold

 Blackouts  Harmonic distortion  Transients  Under or over voltage  Dips (or sags) and surges

 Lights flickering? It could be the result of voltage fluctuations in your facility's electrical system.  Overloaded power circuits are typically the cause behind under-voltage conditions.

 Harmonic

 Harmonic current are generated to small extent and at low distortion level by. 1- Generation equipment. 2- transmission equipment. 3- Distribution equipment. 4- Industrial load. 5- Domestic load.

 Power filters.  Line reactors.  Dynamic voltage restorer.

 Filter is a device that removes something from whatever passes through it.  To eliminate line-current harmonics.  To reduce electrical interference.  Any combination of Passive (R, L and C) and/or active (transistors or operational amplifiers) elements designed to select or rejects a band of frequencies.

 Mainly shunt type and usually connected in parallel with power system or electric load  Provide low impendence (Z F ) path to ground for all harmonic currents at one or more tuned harmonic frequencies.

 Excellent performance despite variation of the system frequency.  Self-adaptation to changes in the network impedance.  Reduced size, allowing implementation using container techniques.  In addition to reducing installation time, this makes it possible to test the complete equipment as a system at the factory before shipment.

 Use op amps with resistor and capacitors in their feed loops.  Active filters can have high input impedance,low out put impedance.  Easier to design than passive filters.  Using Op amp can achieve very good accuracy.

 Inductor:- Block high frequency signal, conducts low frequency signal  Capacitor:- Conducts high frequency signal, block low frequency signal  Resistor:- No frequency selective properties, but are used to determine time constants of the circuit

 Simple and common  Filter impedance Z f =R-j[ ω L-1/ ω C]  Acts as low impedance at the tuned frequency  effectively shunts most harmonic at frequencies below or above the tuned value  Resonance Frequency f r =1/[2 π  (LC)]  Used to filter specific dominant frequency

The input harmonic current distortion can be reduced by simple addition of input line reactance. The inductive reactance of an input line reactor allows 50 Hz or 60 Hz currents to pass easily but presents considerably higher impedance to all other harmonic frequencies.. Harmonic currents are thus attenuated by the reactance offered by the line reactor.

 The DVR is composed by the following main parts:  voltage source converter (VSC)  Voltage injection transformer  Passive filter  Energy storage

 Signal processing techniques are applied for real time measurement of power quality parameters such as frequency, voltage, harmonics, flicker and disturbances.

(1) Digital filtering technique (2) Kalman filter technique (3) Fast Fourier Transform and statistical method

 Power Quality becoming a concern.  Awareness is growing among industries.  Utility monitors voltage, costumer dictate current.  Many nonlinear loads exist, increasing.