Improvement of Power Quality by Using Hybrid Fuzzy ... - IEEE Xplore

Improvement of Power Quality by Using Hybrid Fuzzy Controlled based IPQC at Various Load Conditions G. Satyanarayana1, K.N.V. Prasad2, G. Ranjith Kumar3, K. Lakshmi Ganesh4 1

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PG Scholar, IEEE Member, 2,34Assistant Professor Department of Electrical & Electronics Engineering 1 Sri Vasavi Engineering College, Tadepalligudem, India 2 MIC College of Technology, Vijayawada, 3CJITS, Warangal, 4Narayana Engineering College, Nellore. 1,2,3,4

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[email protected], [email protected],[email protected], [email protected].

Abstract- Dis-similar traditionalistic passive type harmonic power filters, modern active type harmonic power filters have the favorable multiple functions: harmonic filtering, damping, reactive-power control for power factor correction and voltage regulation, load balancing, voltage-flicker reduction etc., This paper presents a hybrid fuzzy logic controlled based improved power quality conditioner used to counterbalance for harmonic distortion in three-phase system. The IPQC employs a very simplest methodology for the calculation of the reference compensation current based on FFT Analysis. The presented improved power quality conditioner is able to operate in different load conditions (balanced, unbalanced, variable). Classical filters may not have adequate performance in fast varying conditions. But auto tuned active power filter gives outperform results for harmonic minimization, reactive power compensation and power factor improvement. The proposed auto tuned shunt active filter maintains the THD well within IEEE-519 standards. The proposed methodology is extensively tested for wide range of different Loads with Improved dynamic behavior of IPQC using hybrid fuzzy logic controller. Keywords - Active power filter, Hybrid fuzzy controller, IPQC (Improved Power Quality Conditioner), Power Quality Improvement.

I. INTRODUCTION Power quality is a growing concern for a wide range of customers. Most of the essential international standards define power quality as the super natural characteristics of the utility electrical supply provided under normal operating conditions, which does not disrupt or disturb the customer’s processes. However, it is most valuable to notice that the quality of power supply implies basically voltage quality and supply reliability, uninterrupted flow of energy at such as un-notched sinusoidal voltage at the fundamental magnitude level and frequency. Usually the term power quality refers to maintaining a

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sinusoidal waveform of bus voltages at rated voltage and frequency [1]. The waveform of electric power at generation stage is purely sinusoidal and free from any distortion. Many of the Power conversion and consumption equipment are also designed to function under pure sinusoidal voltage waveforms. However, there are many devices that misshape or distort the waveform. Harmonic interference problems render by bulge solid state converters become progressively serious as they are widely used in industrial applications and transmission/distribution systems. Nonlinear loads drawing misshape sinusoidal Currents from three-phase sinusoidal voltages from power generating stations. High-power diode or thyristor rectifiers, cyclo-converters, and arc furnaces are typically characterized as harmonic-producing loads, because electric power utilities the individual nonlinear loads installed by high-power consumers on power distribution systems in many cases. Each of these loads produces a high amount of harmonic current. The utilities can determine the point of common coupling (PCC) of highrated consumers who place their own harmonic-producing loads on power distribution systems. One of the eliciting proposals to compensate the power quality problems. Modern active harmonic power filters are outstanding in filtering performance, smaller in physical size, and more adaptable in application, compared to handed-down passive harmonic filters using capacitors, inductors, and/or resistors. However, the active filters are slightly humble in cost and operating loss, compared to the passive filters, even at present. Active power filters conscious for power conditioning are also referred to as “active power line conditioners,” “active power quality conditioners,” “improved power quality conditioners (IPQCs),” etc.

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Fig.1. Block Diagram of a power system network with APF OFF

for minimizing the harmonics and power quality improvement is not a new issue rather various authors have discussed some innovative methodologies using these tools [5]. The most important observation from the work reported by various researchers for power quality improvement is the Design of active power filter under ‘fixed load’ conditions or for loads with slow and small variation [6]. As loads in real life are mostly variable, there is necessitate to modeled an active power filter, which is capable of maintaining the THD within the certain norms [7], under variable load conditions. This paper, therefore, presents an auto tuned active power filter using Mamdani fuzzy-controller structure to control the harmonics under variable balanced and unbalanced load conditions. But as far as we know, a comprehensive approach has not been available for modeling and analysis of hybrid fuzzy logic controlled based APF using MATLAB/Simulink. In this paper, a comprehensive simulation model with hybrid fuzzy logic controller is presented. MATLAB/fuzzy logic toolbox is used to design FLC, which is integrated into simulations with Simulink. II. SHUNT ACTIVE POWER FILTER PROPOSED SYSTEM

Fig.2. Block Diagram of a power system network with APF ON

A three-phase power system has been selected to study the performance of the APF system. Comparison of Fig. 1 and 2 shows the compensation principle of a shunt active power filter. APF injects a current magnitude is equal but in phase opposition to generated harmonic current. There are so many techniques have been applied to obtaining a generation of reference signal for the active filter. One method is the generation of a voltage proportional to the source current harmonics. (1) From the analysis point of view, the ideal condition would be that the proportionality constant, k, between the active power filter output voltage and source current harmonics, had a high value. However, at the limit this would be an infinite value and would mean that the control objective was impossible to achieve. The chosen k value is usually small so as to avoid high power active filters and instabilities in the system. However, the choice of the appropriate k value is an unsolved question since it is related to the passive filter and the source impedance values. Besides, this strategy is not suitable for use in systems with variable loads because the passive filter reactive power is constant, and therefore, the set compensation equipment and load has a variable power factor. Latterly, fuzzy logic controller has implemented a outstanding deal of interest in so many applications and has been introduced in the power electronics technology as well as power system network applications [3]-[4]. The favour of fuzzy logic controllers over the traditional PI controller are they do not need an accurate mathematical model; they can work with inaccurate inputs and handle nonlinearity, it may be more robust than the traditional PI controller. Use of intelligence controllers

In an ultra modern electrical distribution system, there has been a rapid increase of nonlinear loads, such as power electronic apparatus like power supplies, rectifier equipment, domestic appliances, and adjustable speed drives (ASD), etc. As the number of these loads may increases, harmful harmonics currents generated by these loads may become very considerable. These harmful harmonics can cause to a variety of different power quality problems including the distorted voltage waveforms, malfunction in system protection, equipment overheating, excessive neutral currents, inaccurate power flow metering, light flicker etc. It may goes to efficiency reduction by drawing reactive current component from the distribution network [8]. In order to overcome these problems, active power filters (APFs, named as IPQC) have been developed. The voltage-source inverter (VSI)-based shunt active power filter is a new technology has been implemented in recent years and recognized as a viable solution, in which the required compensation currents are resolved by sensing line currents only, which is simple and easy to design. The scheme uses a traditional proportional plus integral (PI) controller for generating reference current signal. IPQC is supported under the basis of shunt active power filter, the compensation procedure is based on the instantaneous real- reactive power theory; it provides good and better compensation characteristics in steady state condition as well as transient state conditions [11]. The instantaneous real- reactive power theory generating reference current signals required to compensate the distorted line current harmonics and also reactive power. It also tries to maintain the dc-bus voltage across the capacitor at constant value. The main and important characteristic of this real- reactive power theory is the simple

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and easy of the calculations, which involves algebraic calculations etc. [12].

the oscillative portion of the instantaneous active current of the load then source current will be pure sinusoidal.

Figure 5: α-β-0 coordinates transformation

The instantaneous power theory or p-q theory was introduced by Akagi in 1983. This terminology uses algebra transformation also know as Clarke transformation for three phase current and voltage. The three phase voltage and current are transformed into α-β using eq. (3) and eq. (4), where iabc are three phase line current and vabc are three phase line voltage [2].

Fig.3. Block diagram representation of shunt active power filter

The previous analysis has made an extraordinary importance to IPQC. The shunt active power filter control scheme must calculate for the credit of current reference signals from each individual phase of the voltage source inverter using instantaneous real- reactive power conditioner, this block diagram as shown in Fig.4. But as far as we know, a comprehensive approach has not been available for modeling and analysis of hybrid fuzzy logic controlled based IPQC using MATLAB/Simulink platform.

= 2/3

1

1/2

0

3/2

1/√2 1 =

2/3

1/√2 1/2

0 1/√2

3/2 1/√2

1/2 3/2

(3)

1/√2 1/2 3/2

(4)

1/√2

Concern to p-q theory, the active power and reactive power for three phase power system network might be given as shown in eq. (5) and eq. (6). (5) — (6) For system doesn’t have any neutral connection, the zero sequence are not existed and the mathematical equation will be presented in matrix form as shown in eq. (7). (7)

Fig.4. Reference current generator using instantaneous real- reactive power theory

III.

CONCEPT OF INSTANTANEOUS POWER THEORY

The proposed instantaneous real-reactive power theory is designed based up on conventional or formal p-q theory or instantaneous power theory concept and uses simple arithmetic and algebraic manipulations. And also manipulate in both transient and steady-state as well as for generic voltage and current power systems. Mostly the active power filter generates

Basically active and reactive power can be distinguished into two parts which are AC part and DC part as shown in eq. (8) and eq. (9). In this way we get the DC part of the active and reactive power, the signals necessitate to be filtered by using low pass filter. This low-pass filter will vanish the high frequency component and generates the fundamental part. (8) (9) Then harmonized to p-q theory the active power is expressed by DC part of α-β reference current, which is rearranged as shown in eq. (10). =

(10)

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Therefore three phase actual reference currentt for active power filter might be given as shown in eq. (11)

2/3

1 1/2 1/2

IV.

0 3/2

(11)

3/2

HYBRID BASED FUZZY LOGIC C CONTROLLER

The ceremonious various control strateggies needs exact mathematical models for describing the dynam mic behavior of the system. These formal methods are generatinng the overshoot during the transient period then error is veery high for the variable loads and disturbances [6]. A hybrid ffuzzy controller is a special fuzzy system that can be used as a controlled mplementation of parameter in a regular closed loop system. Im hybrid fuzzy controller is also same as fuzzzy controller; it provides a conventional methodology ffor representing, implementing and manipulating a human heuuristic knowledge about how to design a controller to control the entire system [7]. Various techniques of hybrid fuzzy logic coontroller (HFLC) have been used in many applications [8-11]. The HFLC technique is a very accurate one and modeel-free technique, inherently vigorous to load side disturbances with the ease of implemented the system. However the usage of normal fuzzy controllers is limited because of many more ddisadvantages. So, in order to provoke the drawbacks of fuzzy logiic controller. Hybrid Fuzzy logic controller (HFLC) is proposed for the well developed and sophisticated simulation model of IPFC. Simulation model of IPFC is considered as preecise performance during transient condition and steady state conndition with the PI and FLC and effectiveness of HFLC is examinned by the results of various load simulations [12]. The HFLC has the advantages of formal PI controller along with fuzzy control action. The influenced term in the HFLC is the proportionnal gain which is responsible to degrade overshoot and oscillatiions. Membership functions of the HFLC inputs, e and e, and tthe output, u are defined on the ordinary normalized domain [-1, 1] as shown in fig. 6. A. Fuzzy Logic Membership Functions: No need requirement of fuzzy logic exxact mathematical model. Instead, they are implemented basedd up on general knowledge of the plant. Fuzzy controllers are designed to accommodate the varying operating pointts. Fuzzy Logic Controller is implemented to manipulate the cchange in voltage of the conditioner using Mamdani style fuzzy inference system [13]. There are two input variables; error (e) annd change of error (de) are used in fuzzy logic system and singlle output variable (u) is steady state signal of the converter then, error free response is directly given to the system.

Fig.6. Membership functions for Inpu ut, Change in input, Output.

nctions for input (error (e)), Fig.11. Shows the membership fun Change in input (change of error (de)), ( Output variable (u). B. Fuzzy Logic Rules n is to manipulate the output The existent of this dissertation voltage of the converter. The chang ge in error and error of the output voltage will be the inputs of fuzzy f logic controller. These 2 inputs are designed to divided d into seven groups; NL: Negative Large, NM: Negative Meedium, NS: Negative Small, ZO: Zero Area, PS: Positive small,, PM: Positive Medium and PL: Positive Large and its parameteer [14]. These fuzzy control rules for error and change of error can c be referred that is shown as below fig.7.

Fig.7. Rules for fuzzy lo ogic controller

V. MATLAB/SIMULINK MODEL LLING AND SIMULATION RESULT TS The compensated electrical network was developed in MATLAB/Simulink, and the strateegy was applied to a three phase system with balanced, un-balaanced & variable loads. Here the simulation part is carried out by b three cases 1. Non-linear load without Filter 2. Non-linear lo oad with dc link controlled based shunt active power filter. 3. Non-linear N load with hybrid fuzzy controlled based shunt active power p filter at different load conditions.

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Fig.11 FFT Analysis of Phase-A Source current without Active power filter Fig.8. Simulink block diagram representation of shunt active hybrid type power filter (IPQC)

Case 1: Non-linear load without Filter:

Fig.11 represents the FFT analysis of Phase –A Source current without shunt active power filter. The THD of source current is 28.29%. Case 2: Non-linear load with dc link controlled based shunt active power filter:

Fig.9. Source Voltage, Source Current, Load Current – without filter

Fig.9 represents the three phase source voltages, three phase source currents and load currents respectively without Active power filter. Here evaluates the without shunt active power filter load current and source currents are same.

Fig.12. Source Voltage, Source Current, Load Current – with dc link controller

Fig.12 represents the three phase source voltages, three phase source currents and load currents respectively with dc link controlled based shunt active power filter. Here evaluates the with shunt active power filter load current are distorted and source currents are harmonic free response.

Fig.10. Power Factor – without filter

Fig.10 represents the power factor of the system without shunt active power filter.

Fig.13. Power Factor – with dc link controller

Fig.13. represents the power factor of the system with dc link controller based shunt active power filter.

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Fig.16 represents the power factor of the system with hybrid fuzzy controlled based shunt active power filter.

Fig.14 FFT Analysis of Phase-A Source current without Active power filter

Fig.14 represents the FFT analysis of Phase –A Source current without active power filter. The THD of source current is 3.04%. Case 3: Non-linear load with hybrid fuzzy controlled based shunt active power filter at different load conditions. A. Fixed Balanced Load:

Fig.17. FFT Analysis of Phase-A Source current with hybrid fuzzy controlled based shunt active power filter

Fig.17 represents the FFT analysis of Phase –A Source current with hybrid fuzzy based shunt active power filter. The THD of source current is 1.03%. B. Fixed Un-Balanced Load:

Fig.15. Source Voltage, Source Current, Load Current – with hybrid fuzzy controller (Balanced Load)

Fig.15. represents the three phase source voltages, three phase source currents and load currents respectively with hybrid fuzzy based shunt active power filter with fixed balanced load.

Fig.18. Source Voltage, Source Current, Load Current – with hybrid fuzzy controller (Fixed Un-Balanced Load)

Fig.18. represents the three phase source voltages, three phase source currents and load currents respectively with hybrid fuzzy based shunt active power filter with fixed unbalanced load.

Fig.16. Power Factor – hybrid fuzzy controller

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Fig.17 represents the FFT analysis of Phase –A Source current with hybrid fuzzy based shunt active power filter. The THD of source current is 0.19%. VI.


Fig.19 represents the FFT analysis of Phase –A Source current with hybrid fuzzy based shunt active power filter. The THD of source current is 1.14%. C. Variable Load:

Fig.20. Source Voltage, Source Current, Load Current – with hybrid fuzzy controller (Variable Load)

Fig.20. represents the three phase source voltages, three phase source currents and load currents respectively with hybrid fuzzy based shunt active power filter with variable load.


CONCLUSION

Before the active filter was started, a large amount of harmonic current still remained in source current. This means that the “pure” passive filter provides unsatisfactory performance in terms of harmonic filtering. After the active filter was started source current, became almost sinusoidal, showing that the active filter improves the filtering performance of the passive filter. The comparative results of both the cases proves that the performance of shunt active power filter with hybrid-fuzzy controller is superior to that with conventional P-I controller. Thus, by using hybrid-fuzzy controller the transient response of power system network has been improved greatly and the dynamic response of the same has been made faster. REFERENCES [1] E. H. Watanabe, R. M. Stephan, M. Aredes, “New Concepts of Instantaneous Active and Reactive Powers in Electrical Systems with Generic Loads”- IEEE Trans. Power Delivery, Vol.8, No.2, pp.697-703, 1993. [2] Joao Afonso, Carlos Couto, Julio Martins “Active Filters with Control Based on the p-q Theory”- IEEE Industrial Elects Society Nletter-2000. [3] Leszek S. Czarnecki “Instantaneous Reactive Power p-q Theory and Power Properties of Three-Phase Systems”- IEEE Trans on Power, VOL. 21, NO. 1, pp 362-367, 2006. [4] E. H. Watanabe, H. Akagi, M. Aredes “Instantaneous p-q Power Theory for Compensating Non sinusoidal Systems”- International School on Non sinusoidal Currents and Compensation Lagow, Poland-2008. [5]. Y. S. Kim, J. S. Kim, and S. H. Ko, “Three-phase three-wire series active power filter, which compensates for harmonics and reactive power,” IEE Proc. Electric. Power Applications, vol. 151, no. 3, pp. 276–282, May 2004. [6] Karuppanan P and Kamala Kanta Mahapatra “Shunt Active Power Line Conditioners for Compensating Harmonics and Reactive Power”Proceedings of the International Conference on Environment and Electrical Engineering (EEEIC), pp.277 – 280, May 2010. [7]. Karuppanan P and Kamala kanta Mahapatra “PID with PLL Synchronization controlled Shunt APLC under Non-sinusoidal and Unbalanced conditions” National Power Electronics Conference (NPEC) Proceedings, IITRoorkee, June-2010. [8] S.K. Jain, P. Agrawal and H.O. Gupta “Fuzzy logic controlled shunt active power filter for power quality improvement”-IEE proc.electr.power.appl, Vol 149, No.5, pp.317-328, Sept-2002 [9] S. Saad, L. Zellouma “Fuzzy logic controller for three-level shunt active filter compensating harmonics and reactive power” Electric Power Systems Research, pp.1337–1341 May-2009 [10] V. S. C. Raviraj and P. C. Sen “Comparative Study of Proportional– Integral, Sliding Mode, and Fuzzy Logic Controllers for Power Converters” IEEE Tran Industry Vol 33, No. 2, pp.518-524, Appl-1997. [11] Marcelo Godoy Simoes, Bimal K. Bose, and Ronald J. Spiegel “Design and Performance Evaluation of a Fuzzy-Logic-Based Variable-Speed Wind Generation System” IEEE Trans on Industry Applications, Vol.33, No.4, pp.460-465, Aug-1997 [12] G.K. Singh, A.K. Singh, R. Mitra “A simple fuzzy logic based robust active power filter for harmonics minimization under random load variation” science direct-Electric Power Systems Research 77 pp.1101– 1111, 2007. [13]. B. K. Bose, Expert Systems, Fuzzy Logic and Neural Network Application in Power Electronics and Motion Control. Piscataway, NJ: IEEE Press, 1999, ch. 11.

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[14] Dell ‘Aquila, A. Lecci, and V. G. Monopoli, “Fuzzy controlled active filter driven by an innovative current reference for cost reduction,” in proc. IEEE Int. symp. Ind. Electron. vol. 3, May 26-29, 2002, pp. 948-952. [15] N. Chellammal, K.N.V Prasad, Dr. S. S Dash , Y. S Anil Kumar, A. Murali Krishna, “Performance Analysis of three Phase Cascaded H-Bridge Multi Level Inverter for Under Voltage and Over Voltage Conditions” in in IET Conf., ISBN: 978-9-38043-000-3, pp: 254 – 258, July 2011. [16] K.N.V. Prasad, G. Ranjith kumar, Y.S.Anil kumar, G. Satya narayana, “Realization of Cascaded H-Bridge5-Level Multilevel Inverter as Dynamic Voltage Restorer” in IEEE Conf., ISBN: 978-1-4673-2907-1, pp:1-6, Jan 2013.

Biographies G. Satyanarayana was born in Andhrapradesh, India in 1988. He received his B.Tech and M.Tech degrees in Electrical & Electronics Engineering from JNTU Hyderabad and JNTU Kakinada University, Andhrapradesh, India in 2009 and 2012 respectively. His area of interests is Power Quality Improvement, FACTS Controllers, Intelligence Controllers, and Multilevel Inverters. K.N.V. Prasad was born in Andhrapradesh, India in 1986. He received his B.Tech and M.Tech degrees in Electrical & Electronics Engineering from JNTU Hyderabad and S.R.M University, Chennai, India in 2008 and 2011 respectively. He is currently working as Assistant professor in MIC College of Technology, Vijayawada, Andhrapradesh, India. He has published ten technical research papers in various international conferences. His area of interests includes Power Quality, Multilevel Inverters, Special machines and Fuzzy Logic Controllers, Custom Power Devices. G. Ranjithkumar was born in Andhrapradesh, India in 1986. He received his B.Tech and M.Tech degrees in Electrical & Electronics Engineering from JNTU Hyderabad and S.R.M University, Chennai, India in 2008 and 2011 respectively. He is currently working as Assistant professor in Christu Jyoti Institute of Technology & Science, Warangal, Andhrapradesh, India. He has published six technical research papers in various international conferences. His area of interests includes Multilevel Inverters, Electrical Drives, Special machines, Renewable Energy Sources and Soft Computing Techniques. Mr. K. Lakshmi Ganesh obtained his Bachelor of Engineering in Electrical and Electronics Engineering from Anurag Engineering College, Kodad, Andhrapradesh. He Completed his Master of Technology in Power Electronics in Sri Vasavi Engineering College, Andhrapradesh, India. His area of interest includes Multilevel Inverters and Electrical Machines. He is currently working as Assistant Professor of Electrical and Electronics Engineering Department at Narayana Engineering College and Nellore, Andhrapradesh, India.

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