Single phase Shunt Active Filter for Harmonic Filtering

(1)

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459,ISO 9001:2008 Certified Journal, Volume 4, Issue 4, April 2014)

123

Single phase Shunt Active Filter for Harmonic Filtering

Preeti Yadav

1

, Swati Maurya

2

, Yashaswini Singh

3

, Divya Garg

4

M.Tech (PED), Galgotias University, Gautam Buddh Nagar, Yamuna Expressway, Greater Noida, U.P 203201

Abstract— Active ﬁlters are designed to improve the power quality in distribution networks. The use of shunt active power filters (SAPF) is to eliminate the harmonic currents and to compensate reactive power for linear/nonlinear loads. “Hysteresis band” control topology is used to produce trigger signals required by inverter for producing “reference current.”

Keywords—PQ, THD, VSI , Hysteresis control , Shunt Active Power Filter.

I. INTRODUCTION

Power system harmonics are a menace to electric power systems with hazardous consequences. The line current harmonics increase the losses, instability, and also voltage distortion which decrease the system output. Both passive and active filters have been used near harmonic producing loads or at the point of common coupling to block the

current harmonics. Voltage and current harmonics has

become a serious problem in transmission and distribution systems in recent years. To solve the current harmonic related problems, passive filters connected in several circuit configurations present a low cost solution. However, passive filter implementations to filter out the current harmonics have the following disadvantages:

• Possibility of resonances with the source impedance • Supply impedance dependent system performance • Fixed compensation [1]

To eliminate the disadvantages of passive filters, active filters are used. Current harmonics, reactive power

compensation and voltage regulation are the main

functions of active filters, which improve the power

quality. Hysteresis band current control (HBCC) technique

is used for the generation of firing pulses to the inverter.

II. POWER QUALITY

Power quality (PQ) is the set of limits of electrical properties that allows electrical systems to function in their intended manner without significant loss of performance or life. Presence of non linear loads degrades quality of power due to the introduction of harmonics.

Non-Linear load connected to Power System

III. HARMONICS AND ITS EFFECTS

A harmonic of a wave is a component of frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. There are two types of harmonics in electrical power systems, namely current harmonics and voltage harmonics, which are distortions to current and voltage wave’s respectively. Harmonics results into higher power losses in distribution system. One of the most important problem is the interference problems in communication systems .It may also results into operation failures of electronic equipments.

IV. SHUNT ACTIVE FILTER

(2)

International Journal of Emerging Technology and Advanced Engineering

124

SHUNT ACTIVE FILTER

V. HYSTERESIS CONTROL

Hysteresis can be used to filter signals so that the output reacts slowly by taking recent history into account. Variable switching frequency makes it difficult to choose filter components. For higher order harmonics it will require excessively high switching frequency.

BLOCK DIAGRAM

VI. VOLTAGE FEED FORWARD TECHNIQUE

With voltage feed forward technique, low total harmonic distortion ( THD) of the converter current is obtained with an excellent transient performance which reduces converter’s output voltage overshoot during step-up-line voltage transients.

Vinv = Vac + RIref + Lf (dIref /dt)

Iref is the current commanded by the control system,

R is the equivalent loss resistance (includes winding, switch power loss etc.) ,

Lf is the filter inductance

Vac is the source voltage

For this accurate value of R and Lf should be known.

The value of R is operating point dependent (through switch power losses) and cannot be known accurately. If these values are precisely known then current control would have been 'free of dynamics' i.e., the bandwidth of current control loop would have been infinite. But there are inaccuracies in the estimation of the parameters and inaccuracies in the measurement of Vac.

VII. HARMONIC CURRENT CALCULATOR

With the help of harmonic current calculator sensed load current is multiplied with unit amplitude sine and cosine waves. The Products are integrated over one half cycle. The sampled outputs at end of half cycle will be the amplitude of active and reactive component respectively. After sampling, the integrators are reset to start the next cycle of integration. Unit sine and cosine templates are multiplied by these amplitudes to re-create the active and reactive fundamental components .Their sum is subtracted from the total load current. The result gives instantaneous harmonic content in the load current to be sent to the output. The maximum delay in the calculation is one half-cycle time. This method of calculation is insensitive to the presence of harmonics in supply voltage.

VIII. SIMULATION

(3)

International Journal of Emerging Technology and Advanced Engineering

125

B. Simulation of Harmonic current Calculator

C. Simulation of Voltage Source Inverter (VSI) using

Voltage Feed Forward Technique

IX. SIMUALTION RESULTS

I. RCLOAD

A.Load Current

B.Source Current

C.Inverter Current

D.Capacitor Voltage

E.Voltage of inverter employing voltage feed forward

(4)

International Journal of Emerging Technology and Advanced Engineering

126

II. RL LOAD

A. Load Current

B. Source Current

C. Inverter Current

D. Capacitor Voltage

E. Voltage of inverter employing voltage feed forward

technique

X. CONCLUSION

Nonlinear loads generate harmonic. Pulse width modulated DC source powered ―voltage Shunt Active Filter (SAF)‖ removed harmonics and improved power parameters very effectively. Simulation result indicates that SAF produced required reference current for harmonic and

reactive power compensation. Hysteresis-based control

(5)

International Journal of Emerging Technology and Advanced Engineering

127 REFERENCES

[1] O. Ucak, I. Kocabas, A. Terciyanli , ―DESIGN and

IMPLEMENTATION of a SHUNT ACTIVE POWER FILTER with REDUCED DC LINK VOLTAGE‖- Support Programme for Research Projects of Public Institutions of TUBITAK (Program Code: 1007) with the project entitled ―Guc Kalitesi Milli Projesi‖ (Project Code: 105G129)

[2] Sangu Ravindra, Dr. V .C. Veera Reddy, Dr. S. Sivanagaraju

,―design of shunt active power filter to eliminate the harmonic current and to compensate the reactive power under distorted and imbalanced source voltages in steady state‖- International journal of Engineering Trends and Technology- Volume2Issue3- 2011.

[3] Rejil C, AnzariM and Arun Kumar ― Design and Simulation of

Three Phase Shunt Active Power Filter Using SRF Theory‖- Advance in Electronic and Electric Engineering .ISSN 2231-1297, Volume 3, Number 6 (2013), pp. 651-660 © Research India Publications.

[4] Chandra, A , Singh, B ., Singh, B.N., Al-Haddad, K., ―An improved

control algorithm of shunt active filter for voltage regulation, harmonic elimination, power factor correction and balancing of nonlinear loads‖. IEEE Transactions on Power Electronics, vol. 15, nº 3, (May/Jun. 2000), pp. 495-507, ISSN 0885-8993.

[5] Zeng, J., Yu, C., Qi, Q., Yan, Z., Ni, Y., Zhang, B.L., Chen, S. & Wu, F.F., ―A novel hysteresis current control for active power filter with constant frequency‖. Electric Power Systems Research, vol. 68, (2004), pp. 75-82, ISSN 0378-7796.

[6] B Singh, and K Al-Haddad, ―A Review of Power Filters for Power

Quality Improvement‖, IEEE Transactions on Industrial Electronics,Vol. 46, no. 5, pp. 960-71, Oct. 1999.

[7] M V Atadie, and J A Pomilo, ―Single – Phase Shunt Active Filter: A