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International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
162
Simulation of Adaptive Hybrid Shunt Active
Power Filter Under Non-Linear Load to Improve
Power Quality
Ritesh Chaurasiya* and Girraj Prasad Rathor
Department of Electrical and Electronics Engineering,
Technocrats Institute of Technology & Science, Bhopal, Madhya Pradesh, India.
Date of publication (dd/mm/yyyy): 25/09/2021
Abstract – Decrease in the cost of power electronic devices and improvement in the efficiency of both power
converters and energy storage components have increased the applicability of new technological solutions such as
Custom Power (CP) and Flexible AC Transmission Systems (FACTS) Devices. Active Power Filter (APF) is one of the
CP devices and can mitigate harmonics, reactive power and unbalanced load currents originating from load side. In
this study, a comprehensive review of APF studies, the advantages and disadvantages of each presented techniques
are presented. The study also helps the researchers to select the optimum control strategies and power circuit
configuration for APF applications.
Keywords – Hysteresis Band Controller, SAPF, HSAPF, Power System, PWM, Harmonics.
I. INTRODUCTION
In a modern electrical power system, a large quantity of power electronics equipment has been introduced.
These wide range of units of power conversion, power electronic equipment and nonlinear loads such as
adjustable speed drives, household appliances, saturation in transformer etc, cause increase in harmonics at the
ac mains [1]. Due to new development in technology and electronics equipment as per future requirement
numbers of non-linear loads are increasing exponentially, due to this production of non-characteristic and
characteristics harmonics occur in a modern power system [2].
During last two decades the development of thyristors has brought the supple in the control but on the second
side it has brought harmonics to the system also. These loads draw non-sinusoidal current from ac mains and
degrade the system performance [1, 3, 4]. By using tuned filters, we can eliminate the characteristics harmonics
but the non-characteristics harmonics elimination is the major problem. Non-Characteristics harmonics are
different from the characterizes harmonics and these are not governed by any of the order or equation [4]. For
the firing of voltage source inverter (VSI) used in the Active power filter system used a various number of
control algorithm. It uses APF system largely for improving reliability and performance by using control
algorithm [5, 6]. Shunt active power filter needs an accurate control algorithm for robust performance under
source and load unbalances and it is widely used in modern electric power distribution system.
Power electronics-based devices are a major key component of today’s modern power processing, at the
transmission as well as the distribution level because of the numerous advantages offered by them. These
devices, equipment, nonlinear load including saturated transformers, arc furnaces and semiconductor switches
and so on, draw non-sinusoidal currents from the utility [7, 8, 9]. The presence of harmonics and reactive power
in the grid is harmful, because it will cause additional power losses and malfunctions of the grid components
[8]. Conventionally, passive filters consisting of tuned L-C components have been widely used to suppress
harmonics because of their low initial cost and high efficiency. However, passive filters have many
International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
163
disadvantages, such as large size, mistuning, instability and resonance with load and utility impedances [10].
Active Power Filters have become an alternative solution for controlling current harmonics in supply networks
at the low to medium voltage distribution level or for reactive power and/or voltage control at high voltage
distribution level [11, 12].
Due to the wide spread of power electronics equipment in modern electrical power systems, the increase of
the harmonics disturbance in the ac mains currents has become a more important due to the adverse effects on
all equipment [13]. Modern electrical systems, due to wide spread of power conversion units and power
electronics equipment, causes an increasing harmonics disturbance in the ac mains currents [14]. The causes and
adverse effects of harmonics were discussed earlier; this phenomenon is also termed as harmonic pollution [15].
There are two types of harmonics:
Characteristic Harmonic -
These are always available in the system even the system is purely balanced and ideal; these harmonics are
governed by certain mathematical equations. When the order of harmonics increases then its magnitude
decreases [16]. Usually, even harmonics are ignored because of their dying nature due to symmetry. The order
of odd harmonics is given by, where n is any natural number p is number of pulses.
Non-Characteristic Harmonic -
Harmonic of the nature other than characteristic harmonics are termed as non-characteristic harmonic. It
happened due to unbalance and distortion in AC voltages and unequal transformer leakage impedances. These
are also called residual harmonics. By using the passive tuned filter, the order of characteristic harmonics can be
eliminated, whereas for elimination of latter type we need different filtering scheme [15, 16].
II. PASSIVE FILTERS
Passive filter is a device used as harmonic improvement in the power distribution system. These are power
filters which consist of combination of passive elements like resistances (R), Inductances (L) and Capacitances
(C). We can tune the circuit to bypass a harmonic frequency by proper selection of values of R, L, and C. The
passive filters which are usually used in the power system are single tuned filter, double tuned filters and high
pass filters. These types of filters offer zero impedance to specific frequency and thus those are passed to ground
[12, 15, 16].
11
1( )hZ h L
h C
(1)
1
Lh
C (2)
III. ACTIVE POWER FILTER
Active Power filters have wide range application in modern electrical distribution system for eliminating the
harmonics associated with it. The Shunt active power filter (SAPF) is one of power filters which have needs an
accurate control algorithm that provides robust performance and it better dynamic performance. The control
methods are responsible for generating the reference currents which used to trigger the Voltage Source Inverters
(VSI). Harmonic injection in power system due to various nonlinear loads such as uninterrupted power suppliers
International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
164
(UPS), adjustable speed drives (ASD), furnaces and single-phase computer power supply etc. has resulted
serious power quality problems and hence we need of Active Power filter [10, 12, 16].
APF system can be divided into two sections as given in Figure 1: The control unit and the power circuit. The
control unit consists of reference signal generation, gate signal generation, capacitor voltage balance control and
voltage/current measurement [8, 10]. Power circuit of APF is generally comprised of energy storage unit,
DC/AC converter, harmonic filter and system protection.
Power
Supply
APF SYSTEM
Control Unit: Reference signal generation, gate
signal generation, capacitor voltage balance
control and voltage measurement
Power Circuit: Energy storage unit, DC/AC
converter, harmonic filter and system protection
CURRENT QUALITY
IMPROVEMENT
Active Power Filter
Load
Fig. 1. Basic representation of APF [8].
Control Strategies and Algorithms
In any active power filter system, control algorithms have major role for deciding the performance of
harmonic compensation. The gate pulses provided are provided using the control algorithms to the voltage
source inverter used in filtering system. It makes a closed loop control on the harmonic current present in the
line and compares with ac sinusoidal source to get an error [6, 8, 12]. This error is passed through some
controllers and control algorithms to generate pulses for VSI. The reliability and performance of any active
power filtering largely depend on control algorithms used in the system, there are many numbers of control
algorithms proposed in the last decade some of which work good under balanced and unbalanced conditions
also. Input to the control block is source current, load current and the DC link voltage [10].
IV. INSTANTANEOUS REACTIVE POWER THEORY
This theory was developed by Akagi. The use of this theory is for converting a three phase three wire system
to two phase system. The original theory was named p-q formulation [1].
1 11
2 2 2
3 3 30
2 2
rL
yL
bL
vv
vv
v
(3)
1 11
2 2 2
3 3 30
2 2
rL
yL
bL
ii
ii
i
(4)
This control algorithm gives a basic way to find the reference currents for the Shunt APF system. The theory
is based on the park transformation [6]; it transfers the three - phase axis mains voltage and currents to αβ axis
[6, 10]. The transformation can be written in the equations (3) and (4).
International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
165
v v ip
iq v v
(5)
The Instantaneous reactive power algorithm, also known as p-q theory, defines the active, reactive powers,
where P and Q can be decomposed as combination of mean and alternating part as in equations (6) and (7).
p p p (6)
q q q (7)
~*
*
r
r
v vip
v vi q
(8)
*
*
*
*
*
1 0
1 3
2 2
1 3
2 2
rL
r
yL
r
bL
ii
ii
i
(9)
It is considered taking into account the magnitude of per phase voltage because the compensating current.
Then synchronous detection concept is using the equal current spreading method of current to determine the
three-phase compensating current to be given by the active filter.
V. PROPOSED HYBRID SHUNT ACTIVE POWER FILTER (HSAPF)
HSAPF topology is designed by using a low-rated SAPF and a low-cost shunt passive LC filter. The proposed
HSAPF has the merits of both active and passive filters, and eliminates the disadvantages of pure active and
passive filters. Schematic diagram of HSAPF is shown in Fig. 2.
Fig. 2. Block diagram of proposed Hybrid Shunt Active Power Filter (HSAPF) [3].
The shunt-connected LC passive filter is comprised of single-tuned 5th and 7th harmonic filters and double-
tuned 11th and 13th harmonic filters. The filtering characteristic is not satisfactory when passive filter is
International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
166
connected alone. Thus, APF is inserted into the existing passive filter configuration to improve the overall
performance. SAPF operates as a current controlled voltage source and injects the compensation currents into
the system. If only active filter is used, then the power rating required for PWM.
VI. SIMULATION
In figure 4 the HSAPF is implemented in parallel to the nonlinear load, load is either rectifier or the other
nonlinear arrangement. Here the grid voltage is taken as 100V, 50 Hz.
Fig. 3. Simulation model of Hybrid Shunt Active Power Filter.
With the defined parameters through the bus to the nonlinear load, the HSAPF is connected in parallel with
load and compensate the harmonics odd harmonics generating in the line. Furthermore, the actual response of
the whole system is finding out by the simulation.
VII. RESULTS AND DISCUSSION
In figure 4 the source side voltage is shown, which is three phase voltage and balanced, provided to the
nonlinear three phase load.
Fig. 4. Source side voltage (SAPF).
In figure 5 the grid or source current is shown, here we can see that for initially certain time of interval (from
0 to .65 sec.) it is not proper due to nonlinear load with HSAPF arrangement.
Fig. 5. Source side voltage (HSAPF).
International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
167
The figure 6 showing the load side voltage for the SAPF, while the load is nonlinear, the quality of signal can
also be seen in the waveform.
Fig. 6. Load side voltage (SAPF).
The figure 7 showing the load side voltage for the HSAPF, while the load is nonlinear and this better than the
SAPF arrangement.
Fig. 7. Load side voltage (HSAPF).
The source side current is with the harmonics i.e., disturbances exist in the load current shown in figure 8.
Fig. 8. Source side current (SAPF).
The source side current is also with the harmonics i.e., disturbances exist in the load current shown in figure
9, the quality of this current is in HSAPF. Which is better than the SAPF.
Fig. 9. Source side current (HSAPF).
The load side current output is shown in figure 10, the compensation current which is adjusting according to
the compensation requirement for power quality improvement, the waveform showing the quick response of
SAPF. But here the profile of current is not so good.
Fig. 10. Load side current (SAPF).
International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
168
The load side current output is shown in figure 11 the compensation current which is adjusting according to
the compensation requirement for power quality improvement, the waveform showing the quick response of
HSAPF.
Fig. 11. Load side current (HSAPF).
The THD value is measured by FFT analysis of the respective outputs.
(a) (b)
Fig. 12. Load Side Voltage FFT Analysis (a) in SAPF (b) in HSAPF.
The source voltage quality disturbs due to nonlinear load, for that purpose only the APF is used. Load voltage
FFT analysis is done for the measurement of THD to evaluate the performance of the SAPF and HSAPF. Here it
is very clear that the THD value is same for the both the cases i.e., irrespective to the load. From the FFT
analysis it is clear that the THD in case of SAPF is .99% while it is 0% in HSAPF.
(a) (b)
Fig. 13. Source side Voltage FFT Analysis (a) in SAPF (b) in HSAPF.
International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
169
By using HSAPF the quality is improving by .02% that is showing in the FFT window in the figure 13 in the
results. In figure 14 is showing the response of the system for SAPF and HSAPF, the THD analysis is showing
the relative performance of the system. The THD value is irrespective to the load and the THD in case of SAPF
is 27.60% while in case of HSAPF it is 0.48%.
(a) (b)
Fig. 14. Load Current FFT Analysis (a) in SAPF (b) in HSAPF.
In figure 15 it is showing the response of the system for SAPF and HSAPF, the THD analysis is showing the
relative performance of the system. The THD value is differ by 6.83%. This is clear to say that HSAPF is
working more accurately.
(a) (b)
Fig. 15. Source Current FFT Analysis (a) with PI Control (b) without PI Control.
The performance analysis of the SAPF is tabulated as the THD value is calculated, from the table is clear that
PI controlled SAPF is working efficiently.
Table I. THD of Source Current, Source Voltage, Load Current and Load voltage of the filter used.
Sr. No. Technique Used
% THD
Source Current Source Voltage Load Current Load voltage
1 SAPF 6.84 1.01 27.60 .99
2 HSAPF 0.01 0.99 0.48 0.00
International Journal of Electronics Communication and Computer Engineering
Volume 12, Issue 5, ISSN (Online): 2249–071X
Copyright © 2021 IJECCE, All right reserved
170
VIII. CONCLUSION AND FUTURE SCOPE
The paper presents comparative analysis of instantaneous reactive power and dc link voltage PI control
algorithms for shunt APF in order to eliminate harmonic frequency present in the AC source current. It is
possible to obtain the acceptable THD values for source currents by using the proposed method. The model has
been simulated to demonstrate the feasibility and effectiveness of the study using MATLAB SIMULINK.
Different existing evolutionary or soft techniques are more effective and are using widely in various applications
so, it may possible that the performance of the SAPF can be improved significantly.
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AUTHOR’S PROFILE
First Author
Ritesh Chaurasiya, Department of Electrical and Electronics Engineering, Technocrats Institute of Technology & Science, Bhopal,
Madhya Pradesh, India.
Second Author
Girraj Prasad Rathor, Department of Electrical and Electronics Engineering, Technocrats Institute of Technology & Science, Bhopal,
Madhya Pradesh, India.