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**ACTIVE POWER FILTER FOR POWER COMPENSATION**

Presented By: ARUN KUMAR N.K 1OX11EPE01

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ABSTRACT In this Presentation, a new Active Power Filter (APF) control scheme has proposed to improve the performance of the APF. This presentation presents a new technique with instantaneous power theory (P-Q theory) in order to control of APF under non- ideal mains voltage conditions. Performance of the proposed scheme has been found feasible and excellent to that of the instantaneous reactive power algorithms under various non-ideal mains test scenarios. MATLAB/SIMULINK power system toolbox is used to simulate the proposed system. The proposed method’s performance is compared with conventional instantaneous power (P-Q) theory. The simulation results are presented and discussed showing the effectiveness of the control algorithm.

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**CONTENTS INTRODUCTION POWER QUALTITY IN POWER DISTRIBUTION SYSTEMS**

SOLUTIONS TO POWER QUALITY PROBLEMS BASIC PRINCIPLE OF ACTIVE POWER FILTERS TYPES OF THE ACTIVE POWER FILTERS INSTANTANEOUS POWER THEORY THE PROPOSED METHOD SHUNT ACITVE POWER FILTER 3-PHASE 4-WIRE SHUNT ACIVE POWER FILTER WITH RENEWABLE ENERGY INTERFACE SIMULATION RESULTS CONCLUSION REFERENCE

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INTRODUCTION In a modern power system, increasing of loads and non-linear equipment's have been demanding the compensation of the disturbances caused for them. These nonlinear loads may cause poor power factor and high degree of harmonics. Active Power Filter (APF) can solve problems of harmonic and reactive power simultaneously. APF have the ability to adjust the amplitude of the synthesized ac voltage of the inverters by means of pulse width modulation or by control of the dc-link voltage, thus drawing either leading or lagging reactive power from the supply. Shunt APF’s allow the compensation of current harmonics and unbalance, together with power factor correction

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**POWER QUALITY IN POWER DISTRIBUTION SYSTEM**

Power Quality can be defined as the physical physical characteristics of the electrical supply provided under normal operating conditions that do not disturb the customers process. Power Quality problem exists due to change in voltage, current or frequency deviation results in a failure or in a bad operation of the equipment. Power Quality problems are due to Natural Phenomena Switching Phenomena Connection of high power non linear loads Voltage Sags

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**SOLUTIONS TO THE POWER QUALTIY**

There are two approaches to the mitigation of power quality problems. Load Conditioning Line Conditioning A flexible and versatile solution to voltage quality problems is offered by Active Power Filters. Shunt active power filters operate as a controllable current source series active power filters operates as a controllable voltage source Active Filter Connection Load on AC Supply AC Supply On Load Shunt Current Harmonic Filtering. Reactive current compensation. Current unbalance. Voltage Flicker Series Voltage Unbalance Voltage Sag/Swell. Voltage Unbalance. Voltage Distortion. Voltage Interruption. Voltage Flicker and notching.

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**PRINCIPLE OF ACTIVE POWER FILTER**

Fig. Block Diagram of APF 3phase uncontrolled diode bridge rectifier with resistive loading Using the switching mode power converter to perform the harmonic current elimination. The power converter is controlled to generate a compensation current, which is equal but opposite the harmonic and reactive currents generated from the nonlinear load. A voltage source inverter having IGBT switches and an energy storage capacitor on DC bus is implemented as a shunt APF.

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**TYPES OF ACITVE POWER FILTERS**

Shunt Active Power Filters: It compensate current harmonics by injecting equal- but-opposite harmonic compensating current. It operates as a current source injecting the harmonic components generated by the load but phase shifted by 180deg. Fig. Compensation characteristics of a shunt active power filter

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**2. Series Active Power Filters:**

Fig. Series active power filter topology It compensate current system distortion caused by non-linear loads. The high impedance imposed by the series APF is created by generating a voltage of the same frequency that the current harmonic component that needs to be eliminated. Voltage unbalance is corrected by compensating the fundamental frequency negative and zero sequence voltage components of the system.

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**Hybrid Active Power Filters:**

Fig. Hybrid Active power filter By controlling the amplitude of the voltage fundamental component across the coupling transformer, the PF of the power distribution system can be adjusted. The control of the load power factor imposed a higher voltage across the filter capacitor. This type of configuration is very convenient for compensation of high power medium voltage non linear loads

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**INSTANTANEOUS POWER THEORY**

In three-phase circuits, instantaneous currents and voltages are converted to instantaneous space vectors. Three-phase currents and voltages are calculated as following equations In three-phase conventional instantaneous power is calculated as follows: P=eα.iα +eβ.iβ In fact, active power (p) is equal to following equation: P=ea.ia +eb.ib +ec.ic α and β are orthogonal coordinates.

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Continued… Instantaneous real and imaginer powers are calculated as equation The above equation can be written as From above instantaneous compensating current as α and β Co ordinates are given below

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PROPOSED METHOD It must be used when the voltages are distorted or unbalanced and sinusoidal currents are desired. In proposed method, instantaneous voltages are firs tconverted to α-β coordinates and then to stationary d-q coordinates. The produced d-q components of voltages are filtered and reverse converted α-β coordinates. These filtered α-β components of voltages are used in conventional instantaneous power theory.

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**SCHEMATIC DIAGRAM OF SHUNT APF**

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**3-Phase 4-Wire Shunt Active Power Filter with Renewable Energy Interface**

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**BLOCK DIAGRAM OF SHUNT APF WITH RENEWABLE ENERGY INTERFACE**

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SIMULATION RESULTS

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CONCLUSION A new APF control scheme has been proposed to improve the performance of APF under non-ideal mains voltage scenarios. Experimental results in a scaled-down laboratory prototype will be done and reported in future paper. APF, based on the proposed theory, give satisfactory operation even when the system phase voltages are unsymmetrical and distorted, because no distortion appears in the line currents. The APF is found effective to meet IEEE 519 standard recommendations on harmonics levels in all of the non-ideal voltage conditions. The switching frequency and also switching losses are reduced %23 in proposed method

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REFERENCE Engin Özdemir, Member, IEEE, Murat Kale, Şule Özdemir., “Active Power Filter for Power Compensation Under Non-Ideal Mains Voltages” Luis A. Morán, Juan W. Dixon.,- “Using active power filters to improve power quality” Akagi,H., Kanazawa,Y., and Nabae,A., “Instantaneous reactive power compensators comprising switching devices without energy storage components. IEEE Transactions on Industrial Applications, Vol.20, pp , 1984. Singh, B., Haddad K., Chandra, A., “A New Control Approach to Three- Phase Active Filter for Harmonics and Reactive Power Compensation, IEEE Trans. on Power Systems, Vol.13, No.1, pp , 1998.

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