icaaet-502.pdf

Proceedings of International Conference on Advances in Applied Engineering and Technology – 2015, May 14-16, 2015.

Organized by Syed Ammal Engineering College, Ramanathapuram, Tamilnadu, India.

CASCADED H-BRIDGE MULTILEVEL INVERTER BASED

DISTRIBUTION STATCOM FOR COMPENSATION OF

REACTIVE POWER AND HARMONICS

1P.K.Mani,

2Dr.K.Siddappa Naidu,

1Associate Professor, Department of Electrical and Electronics Engineering, VEL TECH MULTITECH, Chennai-600062. 2Professor, School of Electrical and Electronics Engineering, VEL TECH UNIVERSITY, Avadi, Chennai-600062.

Abstract— The STATCOM used in distribution systems is

called DSTACOM (Distribution-STACOM) and its

configuration is the same, but with small modifications.

It can exchange both active and reactive power with the

distribution system by varying the amplitude and phase angle of

the converter voltage with respect to the line terminal voltage.

A multilevel inverter can reduce the device voltage and the

output harmonics by increasing the number of output voltage

levels. There are several types of multilevel inverters: cascaded

H-bridge (CHB), neutral point clamped, flying capacitor. In

particular, among these topologies, CHB inverters are being

widely used because of their modularity and simplicity. Various

modulation methods can be applied to CRB inverters. CHB

inverters can also increase the number of output voltage levels

easily by increasing the number of H -bridges. This paper

presents a DSTATCOM with a proportional integral controller

based CHB multilevel inverter for the harmonics and

reactive power mitigation of the nonlinear loads. This type of

arrangements have been widely used for PQ applications due to

increase in the number of voltage levels, low switching losses,

low electromagnetic compatibility for hybrid filters and higher

order harmonic elimination.

Keywords— Power Quality, DSTATCOM, CHB, THD,

Nonlinear loads.

1. INTRODUCTION

Power quality is a comprehensive term that squeezes

all features related with amplitude, phase and frequency of the

voltage and current waveforms existing in a power circuit [1].

Poor power quality may result either from transient conditions

accumulate in the power circuit or from the installation of non-

linear loads.

The power quality becomes considerably inferior at

the points where the loads are associated to the distribution

grid. A single client may cause considerable reductions in

power quality for many other consumers [2]. Understanding

power quality issues is a good starting point for solving any

power quality difficulty and understanding the power quality

terms and definitions is crucial to getting familiar with the

power quality substance [3].

During last decade, substantial research has been

carried out in innovating different new configurations for

harmonic mitigation in ac-dc converter with R-L load. There

have been a number of developments in control techniques

used in power system. A comprehensive review of active filter

(AF) configurations, control strategies, selection of

components, other related economic and technical

considerations and their selection for specific applications are

found [4].

K. V. Kumar presented the performance comparison of

Shunt Active Power Filter (SAPF) and Hybrid Active

Power Filter (HAPF) with three different nonlinear loads.

Two different PI controllers based on average load active

power and synchronous reference frame theory are

employed in this simulation study. MATLAB/ SIMULINK

is used for the simulation of SAPF and HAPF.

Comparison of three shunt active power filter

algorithms also studied [5].

Combined system of shunt passive and series active

filter for a four-wire three-phase system has been designed and

simulated with MATLAB/SIMULINK. The system combined

mitigates the source current harmonics and compensates also

unbalance voltages reducing the problems of using only a

shunt passive filter.Therefore, a new control method based in

the power vector theory has been proposed [6]

An assessment and comparison of hybrid active

filters, including their topologies, ratings, and control

algorithms. Simulations are presented, along with a

comprehensive topology and performance comparison. In

addition, a modified "p-q" theory is introduced for control

strategies, which is more feasible for extracting harmonic

components for distorted load voltages [7].

E. R. Ribeiro has been presented a series active filter

using a simple control technique. The series active filter is

applied as a controlled voltage source contrary to its

common usage as variable impedance. It reduces the terminal

harmonic voltages, supplying linear or even nonlinear

loads with a good quality voltage waveform. The operation

principle, control strategy, and theoretical analysis of the active

filter are presented [8].



A control scheme based on synchronous d-q-0

transformation for a hybrid series voltage compensator and the

effectiveness of the new control scheme in compensating for

voltage sags, distortion and voltage flickers is demonstrated

using simulation results. Its dual role as a harmonic

isolator is also described. A comparison between the

proposed schemes against an existing control scheme is

presented via simulation. [9].

Hideaki Fujita presents a combined system of a passive filter

and a small- rated active filter, both connected in series with

each other. The passive filter removes load produced

harmonics just as a conventional one does. On the other hand,

the active filter plays a role in improving the filtering

characteristics of the passive filter [10].

2. HARMONICS

Harmonics are sinusoidal voltages or currents having

frequencies that are whole multiples of the frequency at which

the supply system is designed to operate (e.g. 50Hz or 60 Hz).

A 250 Hz sine-wave signal, superposed onto the fundamental

50 Hz mains frequency, will be designated as the 5th

harmonic

or as the harmonic of 5th order (5 x 50 Hz). With this circuitry

the DC Bus will only charge when the AC sine wave voltage is

greater than the DC capacitor voltage, this results current draw

only at the peaks of the sine waves instead of the whole sine

wave.

A Rectifier circuit found in Three Phase applications. Again

the DC Capacitor will only charge when the Phase to Phase

voltage is greater than the bus DC voltage.

Fig .1: Harmonic voltage at PCC

3. Total Harmonic distortion (THD)

IEEE 519 sets limits on total harmonic distortion (THD) for

the utility side of the meter

Utility is responsible for the voltage distortion at the

point of common coupling (PCC) between the utility and the

end user.

Total harmonic distortion is a way to evaluate the

voltage distortion effects of injecting harmonic currents into

the utility’s system.

(RMS of the harmonic content / RMS value of the

fundamental) * 100

Total harmonic distortion (THD) is a term used to describe the

net deviation of a nonlinear waveform from ideal sine

waveform characteristics.

4. HARMONIC WAVES

Fig .2: Harmonic waves

5. ADVANTAGES OF CASCADED H-BRIDGE

INVERTER

•The advantages of Cascade H-Bridge inverter are low

harmonic distortion, reduced number of switches and

suppression of switching losses.

• Eliminate capacitor banks.

• It’s compact size.

• More reliable.

6. PROPOSED SYSTEM

Fig .3: Block diagram of proposed system



7. COMPONENTS USED

• PIC16F874A/877A (CONTROL CIRCUIT)

• IC HCF4050BE (DRIVER CIRCUIT)

• IC MCT2E (OPTO ISOLATOR)

• 2N2905A (TRANSISTOR)

• TRANSFORMER (230/9V & 230/12V)

• RESISTOR (100K&1K)

• IRF84027K MOSFET (INVERTING UNIT)

• RECTIFIER UNIT

8. DRIVER CIRCUIT

Fig .4: Driver circuit

9. POWER SUPPLY UNIT

Fig .5: Power supply unit

10. HARDWARE SET UP

Fig .6: Hardware setup

11. MATLAB SIMULATION RESULTS

Fig .7: Simulation of CHB inverter



Fig .8: Output voltage of CHB inverter

Fig .9: Capacitor voltages

Fig .10: DSTATCOM with CHB inverter

Fig .11: Load Voltage

Fig .11: Load voltage

Fig .12: Output current



Fig .13: DSTATCOM / R phase pulse generation

Fig .14: R phase reference and carrier signals

Fig .15: GATE pulses for R phase

12. CONCLUSION

A DSTATCOM with five levels Cascaded H-Bridge inverter is

investigated.

Mathematical model for single H-Bridge inverter is developed

which can be extended to multilevel H-Bridge.

The source voltage , load voltage , source current,

load current, power factor simulation results under nonlinear

loads are presented.

Total Harmonics Distortion reduced to 48.5%.

REFERENCES

[1] Han, Senior Member, IEEE, B. Bae, H. Kim and S.

Baek, “Combined Operation of Unified Power-Quality

Conditioner with Distributed Generation”, IEEE Transactions

on power delivery, vol. 21, no. 1, January 2006.

[2] Mauricio Aredes, Klemens Heumann, Edson H.

Watanabe, “An Universal Active Power Line Conditioner”,

IEEE Transactions on Power Delivery, Vol. 13, No. 2, April

1998.

[3] Javier A. Munoz, Jose R. Espinoza, Luis A. Moran and

Carlos R.Baier, “Design of a Modular UPQC Configuration

Integrating a Components Economical Analysis”, IEEE

Transactions on power delivery, vol. 24, no. 4, October 2009.

[4] B. Singh, and K. Al-Haddad, “A review of active filters

for power quality improvement,”IEEE Transactions on

Industrial Electronics, vol. 46, no. 5, pp. 960-971, Oct. 1999.

[5] Charles. S, and G. Bhuvaneswari, “Comparison of three

phase shunt active power filter algorithms,” International

Journal of Computer and Electrical Engineering, vol. 2, no. 1,

pp. 175- 180, Feb. 2010.

[6] S. P. Litran, P. Salmeron, J. R. Vazquez, and J. L. Flores,

“Compensation of voltage unbalance and current harmonics

with a series active power filter,” Renewable Energy & Power

Quality Journal, no. 3, Mar. 2005.

[7] L. Chen, and A. V. Jouanne, “A comparison and

assessment of hybrid filter topologies and control algorithms,”

IEEE/PESC Ann. Meeting Conf, vol. 2, pp. 565-570.

[8] E. R. Ribeiro, and I. Barbi, “Harmonic voltage reduction

using a series active filter under different load

conditions,” IEEE Transactions on Power Electronics,

vol. 21, no. 5, pp. 1394-1402, Sep. 2006.

[9] KannanKarthik, and J.E.Quaicoe, “Voltage

compensation and harmonic suppression using series active

and shunt passive filters,” Electrical and Computer

Engineering, Canadian conference, vol. 1, 2000, p. 582-586.



[10] H. Fujita, and H. Akagi, “A practical approach

to harmonics compensation in power systems series

connection of passive and active filters,” IEEE Transactions

on Industry Applications, vol. 27, no. 6, pp. 1020-1025, Nov.

1991.

About the authors

P.K.Mani has completed his B.E.

Electrical and Electronics Engineering

and M.E. Power Systems Engineering at

Anna University, Chennai. At present he

is working as Associate Professor in

Electrical and Electronics Engineering

Dept, Vel Tech Multitech Dr.Rangarajan

Dr.SakunthalaEngineering college, Chennai-600062.Currently

he is doing Ph.D in Veltech Dr.RR&Dr.SRTechnical

University in the field of power quality. Mobile. No: +91

9445260989. Email: [email protected].

Dr.K.Siddappa Naidu finished his

B.E.Electrical Engineering from Sri

Venkateswara University, Tirupati in

1973 and got post-graduation from IISC,

Bangalore in 1976 and Ph.D. from the

same institute in 1994. He has worked in

various capacities in NGEF

Transformers Research & Development from 1979 to 2000.He

worked as HOD EEE,Vice Principal and Principal in different

Engineering colleges from 2000 to 2012.Presently working as

Dean, School of Electrical Engineering in Vel Tech Dr.RR

Dr.SR Technical University, Avadi, Chennai-600062.He has

published many papers in international and national journals.

His research interests are partial discharge measurements in

HV Insulation & Apparatus, online monitoring of HV power

apparatus, Sub synchronous, Renewable energy systems and

power quality.

mailto:[email protected]

icaaet-502.pdf

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