ABSTRACT:
Shunt
active power filter (SAPF) belongs to the class of custom power devices (CPDs)
and offers compensation to harmonics originated owing to customer side
nonlinear loads, reactive power and unbalance in the distribution power
networks functioning in current control mode (CCM). The performance of a SAPF
as a harmonic compensator entirely relies on the control technique i.e. the
precise detection of the harmonic current components of load that are necessary
to be compensated. In the present work, a 3-phase SAPF, inspired by a Lyapunov
function based control approach, has been designed for compensation of harmonics
resulted in the feeder current owing to the customer side nonlinearity. A
control law is determined in the proposed strategy which makes the derivative
of the Lyapunov function consistently a negative one for an entire set of
stable states. The DC-link capacitor voltage is regulated at constant reference
through the proportional-integral (PI) controller. In this method rating of the
shunt active power filter is considerably reduced than the other two broadly
employed conventional methods. Furthermore, the harmonic compensation efficacy
of the proposed Lyapunov function based SAPF is compared with the one based on other
two conventional approaches under four different system scenarios namely a
simple nonlinear load with and without utility side voltage distortion, a
modified IEEE 13 bus test distribution system loaded with a 3-phase chopper fed
direct current (DC) motor drive at a single bus and last especially for
increasing the harmonic-constrained penetration level of renewable energy.
Results obtained through simulation performed in MATLAB/Simulink shows that
total harmonic distortion (THD) of source current and dynamic, as well as steady-state
performance with Lyapunov function based controller, is significantly improved
than the other two conventional methods. Also, the robust compensation
performance of the SAPF empowers it to deal with the high penetration of
renewable energy.
KEYWORDS:
1. SAPF
2. Lyapunov
function
3. Harmonic
compensation
4. Hysteresis controller
5. Renewable
energy
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Figure 1. Configuration Of Sapf.
EXPECTED SIMULATION
RESULTS:
Figure 2. Waveforms Of Lyapunov
Function Based Control Technique (A-B) Before And (C-E) After Compensation.
Figure 3. Fft Analysis A) Before Compensation, B) After Compensation.
Figure 4. Dynamic Performance Of Sapf Using P-Q Theory With An Unbalanced Or Distorted Source Voltage.
Figure 4. (Continued.) Dynamic Performance Of Sapf Using P-Q Theory With An Unbalanced Or Distorted Source Voltage.
Figure 5. Dynamic Performance Of Sapf Using Srf Theory With An Unbalanced Or Distorted Source Voltage.
Figure 5. (Continued.) Dynamic Performance Of Sapf Using Srf Theory With An Unbalanced Or Distorted Source Voltage.
CONCLUSION:
A
control algorithm, based on the Lyapunov function, is proposed for SAPF to
mitigate harmonics and reactive power compensation of nonlinear loads. The
performance of SAPF has been found satisfactory under all four cases of the study.
The control algorithm is established on the Lyapunov function for achieving
global stability in the system. The simulation results validate the control
approach for SAPF. A hysteresis controller has been used to generate a
switching signal for the voltage source inverter. Based on simulation results
following conclusions have been drawn.
1)
All the control algorithm's (p-q theory, SRF theory, Lyapunov function based
control theory) performance found satisfactory i.e. THD is less than 5%
according to IEEE 519 standards.
2)
Under the fully fundamental plus balanced source voltage and purely nonlinear
loading condition Lyapunov function-based control algorithm gives the best
performance over the other two control algorithms which are commonly used.
3)
The THD of the source current under the Lyapunov function based control
algorithm is 1.61% in phase a, 2.33% in phase b, 1.99% in phase c when applied
on a two-bus system under purely nonlinear load. In the case of a modified
13-bus system, the same with Lyapunov function based control algorithm is 1.59%
in phase a, 1.61% in phase b, 1.52% in phase c.
4)
In case of distortion and unbalance present in the utility's voltage, the
detection of the reference current is accurately performed by the Lyapunov
function-based control algorithm and superiorly in contract to the other two
control algorithms.
5)
It is also inferred that the dynamic response of the system with the Lyapunov
function-based control algorithm to be better than the other two control algorithms.
6)
Last but not the least, the harmonic and reactive power compensation offered by
Lyapunov function-based SAPF is better also in the case of renewable energy's penetration.
The proposed theory-based SAPF has the potential of enhancing the penetration
level of HC-HC of the modern and polluted DPS up to more extent.
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