Power Quality Improvement Using Shunt Active FilterWith Fuzzy Logics

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1 Power Quality Improvement Using Shunt Active FilterWith Fuzzy Logics Kamalesh sharma, Sunil kumar goyal, Nagendra kumar swarnkar Abstract Power quality is a very important issue. Non-linear loads and semi-conductor devices connected to AC electric mains generate unwanted signals (harmonics) in the dynamics of current which are responsible for additional power losses in heat loss and the risk of equipment damage or malfunctioning. In the simulink model of shunt active filter fuzzy logic controller and hysteresis current controller for reducing the harmonic distortion. Powergui tool of mat lab provides the function of FFT analysis which is very important to calculate total harmonic distortion in source current. By taking various firing angles the total harmonic distortion is calculated by FFT analysis. Index Terms Shunt Active Filter, Fuzzy Logics, FFT analysis, Harmonic Distortion I. POWER QUALITY IN POWER SYSTEMS Power quality is a phrase that means different things to different consumers. Power quality is defined in Institute of Electrical and Electronic Engineers (IEEE) Standard IEEE1100 as This is the method of power supply and grounding sensitive electronic equipment and other nonlinear equipment in amanner such that is suitable for the equipment. As appropriate as this description might seem,the limitation of power quality to sensitive electronic equipment and nonlinear equipment might be subjectto disagreement. Electrical equipment susceptible to power quality or more suitableto lack of power quality would fall within a seemingly boundless domain.all electrical devices are prone to failure or malfunction when exposed to one ormore than one power quality problems. Examples of poor power quality A. VOLTAGE SAG Voltage sag (also called a dip ) is a slight decrease in the r.m.s value of line voltage of 10 to 90 percent of the nominal line-voltage. The duration of a sag is 0.5 cycle to 1 minute [ ]. cycles to 1 minute. Sources of voltage swells are line faults and incorrect tap settings in tap changers in substations. C. Transient It is a brief, unidirectional variation in voltage and current, or both on a power line. The Most Common The most common causes of impulsive transients are lightning strikes on power line, switch on or off of inductive loads, or switching in the power distribution system. Interruption: Interruption is the reduction in line-voltage or line-current to less than 10% of the nominal, not exceeding 60 seconds in length. Voltage Imbalance: A voltage imbalance is defined as variation in the amplitudes of 3-phase voltages, relative to another. Flicker: Voltage fluctuations variations in the rms line-voltage are relatively small (less than 5 percent). II. POWER QUALITY INDICES UNDER HARMONIC DISTORTION There are some power quality indices those are comprehensibly described: Total Harmonic Distortion: Total harmonic distortion (THD) is very important index. Which is widely used to describe power quality agenda in transmission and distribution networks. It considers the contribution of every individual harmonic component on the signal. THD is given for voltage and current signals, respectively, as given below: (3.1) B. Voltage swell A voltage swell is the converse to the sag. A swell is a brief increase in the r.m.s of line-voltage of 110 to 180 percent of the nominal line-voltage for duration of 0.5 Manuscript received January 18, 2015 Kamalesh sharma, M.tech Scholar Apex Institute of Engineering College Jaipur Sunil kumar goyal, Assistant Professor,Manipal University, Jaipur Nagendra kumar swarnkar, 3Associate Professor at Apex Institute of Engineering College, Jaipur 9 Telephone Influence Factor (TIF): This index is found in IEEE-5197 as a measure of audio circuit interference produced in electric power systems by harmonics. It will thus use the total harmonic distortion concept influenced by appropriate weighting factors, ωh, that establish the sensitivity of the human ear to noise from different frequencies:

2 Power Quality Improvement Using Shunt Active FilterWith Fuzzy Logics PWM converters (CSI orvsi). The different active power filter methods are shown in Fig 5 (3.4) Displacement, Distortion and Total Power Factor With an increasing harmonic distortion environment, the conventional definition of power factor is that the cosine of the angle between fundamental frequency voltage and current has progressed to consider rms values the signal s, which make up the contribution of electrical components of various frequencies. Thus, displacement power factor (DPF) continues to characterize the power frequency factor (a) (b) Active power filter topologies implemented with PWMVSI.(a) Shunt active power filter.(b) Series active power filter. III. SOURCES OF HARMONICS The ac power system harmonic problems are mainly occur due to the substantial increase of non-linear loads due to technological upgrades, such as the use of power electronics circuits, devices and semiconductor, in ac/dc transmission links, or loads in the control of power systems using power electronic or microprocessor controllers. sources of harmonics are divided into given loads: (a) Domestic loads. (b) Industrial loads. (c) Control devices. B. FUZZY LOGIC Fuzzy logic control is determined from fuzzy set theory in 1965; where transition is between membership and non-membership function. Therefore, limitation or boundaries of fuzzy sets can be undefined and ambiguous; FLC s are an excellent choice when precise mathematical formula calculations are not possible. Fig. 6.1.given below shows block diagram of the fuzzy logic control scheme. Block diagram of fuzzy logic controller SIMULINK MODEL FOR THE NON-LINEAR LOAD SYSTEM WITH SHUNT ACTIVE FILTER Fig Source Harmonics IV. SOLUTION OF HARMONIC DISTORTION In general, used the filters for the harmonic distortion likes, harmonic filter as a passive and active filters. A. ACTIVE FILTERS Active power filters have being developed since beginning of power system, when one of the first prototypes based on instantaneous power theory was reported. The technology of active power filter has been developed during the past two or three decades reaching full growth for harmonics compensation, reactive power and voltage balance in ac power system. All active power filters are developed with 10 Modelling for non-linear load with shunt active filter shows the modeling for shunt active filter with non-linear load,fuzzy logic based for the power quality improvement from harmonic distortion. Whenever circuit breaker is closed the filter is connected with the system of non linear load.

3 V. RESULTS A. WITHOUT SHUNT ACTIVE FILTER THD in source current for firing angle 30 Waveforms of voltages and currents without shunt active filter Harmonic Distortion in Source Current Waveform of source current for firing angle 45 Waveform of source current for firing angle 15 THD in source current for firing angle 45 B. WITH SHUNT ACTIVE FILTER THD in source current for firing angle 15 Waveforms of source voltages and currents with shunt active filter Waveform of source current for firing angle 30 11

4 Power Quality Improvement Using Shunt Active FilterWith Fuzzy Logics Harmonic Distortion in Source Current THD in source current for firing angle 45 Waveform of source current for firing angle 15 THD in source current for firing angle 15 Values for total harmonic distortion can be summarised for different firing angles as follows: TABLE 8.1 THD% FOR THE DIFFERENT FIRING ANGLES Sr. Firing THD% THD% No. angle in (Before (After degree filtering) filtering) CONCLUSION This paper has described and illustrated that when the shunt active filter is connected with the system of non-linear load, current and voltage can be prevented effectively from harmonic distortion. Therefore simulink model of the shunt active filter is very useful for getting the newer controlled strategy or advanced techniques for the filtering of non-linear load. In addition to this powergui FFT analysis provides effective percentage values of total harmonic distortion for different firing angles provided with the system of non linear load which provides prediction of harmonic distortion in current according to the specifications of the system. Waveform of source current for firing angle 45 FUTURE SCOPE In place of shunt active filter simulink model can be designed by using series active filter to eliminate voltage harmonics and to balance and regulate the terminal voltage of load or line. Hybrid configuration can also be used for the compensation of high power systems. Fuzzy logic controller has been used with hysteresis current controller and PLL synchronisation in simulink model, which can be replaced by neural network controller. In the simulink model of shunt active filter REFERENCES [1] JoãoAfonso, MaurícioAredes, Edson Watanabe &Júlio Martins, University of Minho - Industrial Electronics Dept., Shunt Active Filter for Power Quality Improvement, International Conference UIE 2000 Electricity for a Sustainable Urban Development Lisboa, Portugal, pp , 1-4 November [2] Bhim Singh, Kamal Al-Haddad &Ambrish Chandra, A New Control Approach to 3-phase Active Filter for Harmonics and Reactive Power Compensation -IEEE Trans. on Power Systems, Vol. 46, No. 5, pp , Oct

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