International Journal of IT, Engineering and Applied Sciences Research (IJIEASR)
Volume 4, No. 6, June 2015
ISSN: 2319-4413
54
Kavita Sao , Department of Electrical Engineering, CSVTU University, Bhilai
Veenita Swarnkar , Department of Electrical Engineering, CSVTU University, Bhilai
Dr. Satya Prakash Dubey , Department of Electrical Engineering, CSVTU University, Bhilai
The present paper describes Fuzzy logic and PI controller Shunt Hybrid Active Power Filter (SHAPF) designed for harmonic compensation and reactive power under variable conditions. Therefore the power quality can be increase efficiently by using this Shunt hybrid active power filter. The main purpose of this work is
Fuzzy logic and PI controller based regulator, the shunt active power filter to compensate harmonics and reactive power by nonlinear load to enhance power quality is implemented for three wire system.The various simulation results are presented under steady state conditions and performance of Fuzzy and PI controllers is compared.
Simulation results obtained show that the performance of fuzzy controller is found to be better than PI controller.
Shunt Active power filters (SAPFs); DC link voltage,
Fuzzy logic ,PI controller,VSI.
Thus, a power quality issue exists if any of the voltage, current or frequency various from sinusoidal nature occurs. Power quality issues are generally in commercial , industrial and utility networks as the power electronics appliance is normally used in these fields. These appliances produce harmonics and reactive power. It is very important to mitigate the dominant harmonics and therefore Total Harmonic Distortion
(THD) below 5% as specified in IEEE 519 harmonic standard [1].
To lessen the effect of harmonic distortion is removed by Active filter. To overcome this issue shunt Active
Power Filter (SAPF) is brought into effect. Active power filter is a flexible and dynamic solution for the mitigation of harmonic current due to their compact size, no requirement of tuning and static operation. Active power filter acts as harmonic current source to provide emphatic result to mitigate for harmonic currents as well as reactive power. It has the capacity to inject harmonic current into the AC system with the same amplitude but in opposite phase of the load [2]. As the SAPF is complex with cost effective parameter control, the shunt active power filter has been preferable in the subject of harmonic solution. Shunt active power filter gives the efficacious active filter, which implies the advantages of eliminates the harmonics and reactive power shown in figure1.
Figure 1. Shunt Active Filter Configuration
Accuracy of this shunt active power filter is depending upon the estimate of harmonic current and production of reference current. Paper present a three phase Fuzzy logic and PI controlled shunt hybrid active power filter is proposed [3], [4], [5]. To create the shunt active power filter model more dynamic and robust in nature in this paper a Fuzzy logic and PI controller have been used to make an easy estimate of reference currents. Low pass is used to generate fundamental from non-ideal voltage source. The extract fundamental currents are then subtracted from source current to calculate the reference signal i.e. harmonic current. The planned controller has self-learning with high accuracy and simple architecture and it can be successfully applied for harmonic filtering under different power system operating conditions. This paper presents, The Shunt power filter using Fuzzy logic and PI controller to control the harmonics under dissimilar non-sinusoidal and unbalanced source/load conditions for its presentation. i-Explore International Research Journal Consortium www.irjcjournals.org

International Journal of IT, Engineering and Applied Sciences Research (IJIEASR)
Volume 4, No. 6, June 2015
ISSN: 2319-4413
55
Three phase shunt active power filter is used as prototype shown in figure 2. Shunt active Power filter is used produce mitigation current in opposite phase.
Power circuit for SAPF is planned as An IGBT based three-phase voltage source inverter with DC storage capacitor for better mitigation of non-sinusoidal unbalanced /balanced loads. Active power filter has two various control schemes; one is Fuzzy logic controller that accounts for reference current production and a second PI controller for DC voltage regulation.Fuzzy logic and PI controller comprises three adaptive linear neurons to extract the fundamental components of the three phase voltages from non-sinusoidal supply [6]. The capacitors are planning to limit the DC voltage ripple to a particular value, typically 1 to 2 %. In this case the capacitor should be planned for the worst case. Since the shunt active filter will operate in several modes (balanced or unbalanced load), then the injection of mitigation current is complete in order to nullify or compensate the harmonic currents. Injection of this mitigation current gives enhanced power quality. The performance of the shunt active power filters is dependent to a great extent upon the method used for the estimate of reference current. etc. They have also decreased efficiency by drawing reactive current component of the distribution network [8]. In order to overcome these issues, active power filter (APFs) has been developed. The voltage-source- inverter (VSI)-based shunt active power filter has been used in present and known as a viable solution the control scheme, in which the necessary mitigating currents are determined by sensing line currents only, which is easy to implement. The system uses a conventional proportional plus integral (PI) controller for the generation of a reference current.

Basic Compensation Principal
APF A current regulated voltage source inverter with required passive equipments is used as an APF as shown in fig 1. It is controlled to supply /drawa compensated current from/to the utility, such that it eliminate harmonic and reactive Current of the non-linear load. Therefore, the resulting total current drawn from the AC mains is sinusoidal. Ideally, the APF requirements to produce just sufficient reactive and harmonic current to compensate the non-linear loads in the line.
Figure 2. Proposed topology of shunt active power filter
A.
SHUNT ACTIVE POWER FILTER
In a present electrical distribution system, there has been a rapid increase of distorted loads, such as power supplies, domestic appliances, rectifier gear, and adjustable speed drives (ASD), etc. As the number of these loads rises, harmonic currents generate by these loads may become very significant. These harmonics could lead to a variety of different power system issues ,including the distorted voltage waveforms, gear overheating, malfunction in system protection, incorrect power flow metering, excessive neutral currents, light flicker
Fig.3 Shunt Active Power Filter with Non – Linear
B.
Load
REFERENCE COMPENSATION
CURRENT ESTIMATION
The following equations explain the procedure used for reference compensation current calculations.Let us consider i s
(t) is the instantaneous source current,
i l
(t ) is the instantaneous load current, and i c
(t) is the instantaneous compensating current rom Fig.3 according to Kirchhoff’s current law [18], the instantaneous currents can be written 𝑖 𝑠
𝑡 = 𝑖 𝑙
𝑡 − 𝑖 𝑐
𝑡
Let the instantaneous source voltage be 𝑣 𝑠
(𝑡) = 𝑣 𝑚 𝑠𝑖𝑛  𝑡
If a nonlinear load is applied, the load current will be
Divided into two parts, 1st is the fundamental component and 2nd is the harmonic component and can be i-Explore International Research Journal Consortium www.irjcjournals.org

International Journal of IT, Engineering and Applied Sciences Research (IJIEASR)
Volume 4, No. 6, June 2015
ISSN: 2319-4413
56 represented as
∞
= 𝐼
1
𝑆𝑖𝑛(𝑛𝜔𝑡 + 𝑖
𝐿
𝑡 = 𝐼 𝑛
𝑆𝑖𝑛(𝑛𝜔𝑡 +
 𝑛
) + 𝑛=1 𝑛=2
𝐼
2
𝑆𝑖𝑛(𝑛𝜔𝑡 +
 𝑛
)
 𝑛
)
The instantaneous load power can be given in terms of source voltage and load current as
= 𝑉 𝑚 𝑠𝑖𝑛 
1
𝐼
1
+ 𝑠𝑖𝑛
𝑉 𝑚
2 𝑝 𝜔𝑡 ∗ 𝑐𝑜𝑠 𝑠𝑖𝑛𝜔𝑡 ∗
𝐿
= 𝑃 𝑓

𝑡 = 𝑣
∞ 𝑛 𝑛=2
+ 𝑉 𝑚
𝐼 𝑛
𝑡 + 𝑃 𝑠
𝐼 𝑟
𝑡 ∗ 𝑖 𝑙
1
(𝑡) 𝑠𝑖𝑛𝜔𝑡 ∗ 𝑐𝑜𝑠𝜔𝑡 ∗ 𝑠𝑖𝑛⁡(𝑛𝜔𝑡 +
𝑡 + 𝑃 ℎ
 𝑛
(𝑡)
) (1)
From Equation (1), real (fundamental) power is drawn by the load
𝑃 𝑓
𝑡 = 𝑉 𝑚
𝐼
1 𝑠𝑖𝑛 2 𝜔𝑡 ∗ 𝑐𝑜𝑠  𝑛
= 𝑉 𝑠
𝑡 + 𝐼 𝑠
(𝑡)
(2)
From Equation (2), the fundamental source current supplied
𝐼 𝑠
𝑡 =
𝑃 𝑓
𝑉 𝑠
Where
𝐼 𝑠𝑚
(𝑡)
(𝑡)
= 𝐼
= 𝐼
1
1 𝑐𝑜𝑠 𝑐𝑜𝑠 
1
 𝑛 𝑠𝑖𝑛  𝑡 = 𝐼 𝑚 𝑠𝑖𝑛𝜔𝑡
Also, present are some switching losses in the PWM converter.Therefore, the utility must supply a small overhead for the capacitor leaking and converter switching losses in addition to the real power of the load. Hence, total peak current supplied by the supply
𝐼 𝑠𝑝
= 𝐼 𝑠𝑚
+ 𝐼 𝑠1
(3)
If the active filter provides the total reactive and harmonic power, then i s
(t) will be in phase with the utility voltage and will be sinusoidal. The active filter must provide the following compensation current: 𝑖 𝑐
𝑡 = 𝑖
𝐿
𝑡 − 𝑖 𝑠
(𝑡)
Hence, for the accurate and instantaneous compensation of reactive and harmonic power, it is necessary to calculate i s
(t), which the fundamental component of load current is. This will be considered as the reference current.The main meaning of the control scheme is shown in figure 3 to maintain the sourecs current waveform Sinusoidal, identification of harmonic content, regulation of DC voltage and controlling system of SAPF is necessary which provides mitigating current to the power system as well as supply harmonic currents to the three phase variable load at the same instant. For the proper response of APF the extraction of the fundamental component of current of variable input, reference , current generation, DC voltage regulation and injection of compensation currents is essential tasks
[10]. These tasks could achieve only with the reference source current (I*sm), result in three phase reference supply currents (I*sa, I*sb, I*sc). The reference supply currents and sensed supply currents (Isa, Isb, Isc) are the inputs for the pulse generator, which generates the firing pulses for the gating signals to the IGBT’s of the active power filter[11], [12]. Hysteresis current control is a method of controlling a voltage source inverter so that the output current is generated which follows a reference current waveform.
C.
FUZZY LOGIC CONTROLLER
The fuzzy control scheme as shown in Fig. 4 consists offuzzification, defuzzification, and decision making unit[20]. The change in error, input are error and the output is given to drive circuit to get the signal. The inputs get fuzzified within fuzzification block and sends to decision making block to get the output by seeing the data sets and rule base. The output is given to defuzzification block to get the corresponding crisp values. They will be send to drive circuit to decide the signal.
Fig. 4 Fuzzy Control System
Fig. 5& 6shows the fuzzy inference system consists ofmembership functions and the method of decision making i.e. Mamdani. Here the membership functions are
(i) error (e) (ii) change in error (ce) and (iii) output of
FLC (o). The error is the difference between Vdc and
V dc , ref V . Change in Error is the derivative of DC V
.These two are the input membership functions and the output of the FLC is the output membership function. Fig.
6 shows Membership functions of Error, Change in Error and Output [7]. It shows the minimum and maximum values of membership functions and the ranges of membership functions. now only three membership functions are used small, medium and big for the ease of framing fuzzy inference system in all the membership functions. These consist of data of the system how it behaves. These require sflip flops or storing devices.
Fig.5 Fuzzy Inference System i-Explore International Research Journal Consortium www.irjcjournals.org

International Journal of IT, Engineering and Applied Sciences Research (IJIEASR)
Volume 4, No. 6, June 2015
ISSN: 2319-4413
57
Fig. 6. Degree of Membership Functions of Error,
Change in Error and Output
D.
Proportional Integral Controller
The PI controller algorithm involve two part parameters; the Proportional and the Integral. The Proportional value determine the reaction to the current error; the Integral determine the reaction based on the sum of recent errors.
A comparison of the average and the reference values of the DC bus voltage for the shunt AF results in a voltage error, which is fed to a proportional integral (PI) controller and the output of the PI controller is multiplied by the mains voltage waveform Vsa, Vsb, Vsc in order to obtain the supply reference currents isa*, isb*, isc*. A PI controller used to control the DC-bus voltage is shown in
Figure 6 whose transfer function can be represent as
𝐻 𝑆 = 𝐾 𝑝
+
𝐾
𝑆 𝑖
Where, kp is the proportional constant that determines the dynamic response of the DC-bus voltage control,and ki is he integration constant that determines it’s settling time
.
2
0
-2
6
4
-200
0
8
-4
-6
-8
0
100
50
0
-50
-100
-150
Figure 7. PI controller for DC-bus voltage control
It can be noted that if kp and ki are large, the DC-bus voltage regulation is dominant, and the steadystate DCbus voltage error is low. On the hand, if kp and ki are small, the real power unbalance gives little effect to the transient performance. Therefore, the proper selection of kp and ki is essentially important to satisfy above mentioned two control performances. The computed three-phase supply reference currents are compared with the sensed supply currents and are given to a hysteresis current controller to generate the switching signals to the switches of the shunt AF which makes the supply currents follow its reference values [13].
The system parameters: Load resistance R
L
= 100WR,
Load inductance L
L
=37mH, Supply Phase voltage = 240
V, Supply line parameters Rs =1W, Ls = 3mH, Inverter
DC bus capacitor =2000μF, Reference Voltage = 480V,
Hysteresis band limit =0.5A and Switching frequency
=10kHz, PI controller parameters are Ki =30, Kp = 0.5.
The Active Power Filter with proposed Fuzzy logic and Pi controller was modeled and simulated in MATLAB. The proposed controller simulated with balanced nonlinear loads with sinusoidal/distorted, balanced conditions of source voltages.
200
150
0.2
0.2
0.4
0.4
0.6
0.6
0.8
0.8
1
Time(Sec)
1
Time(Sec)
1.2
1.2
1.4
1.4
1.6
1.6
1.8
1.8
x 10
2
5 x 10
2
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International Journal of IT, Engineering and Applied Sciences Research (IJIEASR)
Volume 4, No. 6, June 2015
ISSN: 2319-4413
58
200
100
0
0
0
-10
-20
-30
-40
0
40
30
20
10
500
400
300
40
30
20
10
0
-10
-20
0 0.2
0.2
0.2
0.4
0.4
0.4
0.6
0.6
0.6
0.8
1
Time(Sec)
1.2
0.8
1
Time(Sec)
1.2
0.8
1
Time(Sec)
1.2
1.4
1.4
1.4
1.6
1.6
1.6
1.8
2 x 10
5
1.8
x 10 5
2
1.8
x 10
2
5
40
30
20
10
0
-10
-20
-30
-40
0
450
400
350
300
250
200
150
100
50
0
0
5
-10
-15
0
-5
15
10
-20
-25
0 0.2
0.2
0.2
0.4
0.4
0.4
0.6
0.6
0.6
0.8
0.8
1
Time(Sec)
1
Time(Sec)
1.2
1.2
0.8
1
Time(Sec)
1.2
1.4
1.4
1.4
1.6
1.6
1.6
1.8
1.8
x 10
5
2 x 10
5
2
1.8
x 10 5
2
4
2
0
-2
8
6
-4
-6
-8
0
100
50
0
-50
-100
-150
-200
0
200
150
Fig. 8. Waveforms of PI Controller Shunt Active
Power Filter (THD of source current = 5.07%)
0.2
0.4
0.6
0.8
1
Time(Sec)
1.2
1.4
1.6
1.8
0.2
0.4
0.6
0.8
1
Time(Sec)
1.2
1.4
1.6
1.8
x 10
5
2
Fig. 9. Waveforms of Shunt Active Power Filter with
FLC (THD in source current = 4.70%)
The In this paper proposed both Fuzzy Logic and PI controller was verified through simulation studies with
MATLAB. Proposed controller pro supply accurately.
The shunt APF with fuzzy logic controller is capable of
Reactive Power Compensation and Harmonic
Reduction.The PI controller can also give Simulation results obtained show that the performance of fuzzy controller is found to be better than PI controller.. This operation is not feasible practically, as it is difficult to x 10
5
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59 change PI parameters with every load changes. The fuzzy logic controller is therefore more suitable for much cause.
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International Journal of IT, Engineering and Applied Sciences Research (IJIEASR)
Volume 4, No. 6, June 2015
ISSN: 2319-4413
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