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© 2018 IJRAR January 2019, Volume 6, Issue 1 www.ijrar.org (E-ISSN 2348-1269, P- ISSN 2349-5138)
IJRAR19J1023 International Journal of Research and Analytical Reviews (IJRAR) www.ijrar.org 157
Performance Improvement of Renewable Energy
Sources Inverter for Interface with Smart Grid
1Manoj D. Patil, 2K. Vadirajacharya 1Assistant Professor, 2 Professor
1Department of Electrical Engineering, 2Department of Electrical Engineering 1ADCET, Ashta, Sangli, Maharashtra, India. 2DBATU, Lonere, Raigad, Maharashtra, India
Abstract: The aim of this project is to analysis and improve the performance of the power quality problems (voltage sag,
swell and harmonics) to grid connection with the help of inverter used in distributed generation. Renewable energy resources
demand is continuously increasing nowadays, it connected in distribution systems utilizing power electronic converters. This
paper presents the concept of grid tied solar inverter as hardware and software in MATLAB/SIMULINK to improve the
performances of PQ. It is also interfacing with RES (Renewable Energy Resources) with the electric grid. The grid interface
inverter can improve the performance of following functions they are (1) power converter to inject power generated from
renewable energy sources to the grid, (2) Shunt Active power filter to compensate current unbalance, load current harmonics, load
reactive power demand. The controller controls the real power and reactive power supplied by the distributed generation at the
PCC. In the gird side currents always maintained as balanced and the unity power factor. This work is carried out using software
MATLAB/SIMULINK.
Index Terms - Active Power Filter (APF), Distributed Generation (DG), Power Quality (PQ), Renewable Energy Sources
(RES), Point of Common Coupling (PCC).
I. INTRODUCTION
In recent years there has been an increasing interest in moving away from large centralized power generation towards distribution
energy resources. But increasing air pollution, global warming concerns, diminishing fossil fuels and their increasing cost have
made it necessary to look towards renewable sources as a future energy solution. There are many advantages for use as a
distributed energy resource, mainly as a peaking power source. Renewable energy source utilized because of its environment
friendliness, sufficient availability, and it produces the good efficiency [1][2].
Inverter
Load
Control
Technique
Renewable
Energy Soures
Grid
Fig. 1: Basic block diagram of solar grid tie Inverter
Renewable energy source (RES) synthesis distribution level is termed as distributed generation (DG). The utility is concerned due
to the high penetration level of intermittent RES in distribution systems. By using proposed technology it improve the voltage
stability, voltage regulation and power-quality (PQ) problems. With the power electronics and digital control technology, the
distribution energy systems can now be easily controlled to improve the circuit operation with improving the power quality
performances at the place of the Point of Common Coupling (PCC). The non-linear load current harmonics may result in voltage
harmonics and can create a power quality problem in the power system network. Active Power Filter (APF) is mainly used to
compensate the load current harmonics and load unbalance at distribution level [3][4].
The grid-interfacing inverter can excellently be utilized to produced functions as transfer of active power harvested from the
renewable energy resources (wind, solar, etc.), load reactive power demand, current harmonics compensation at the point of
common coupling , current unbalance and neutral current compensation in case of 3-phase 4-wire system as shown in fig.2.
© 2018 IJRAR January 2019, Volume 6, Issue 1 www.ijrar.org (E-ISSN 2348-1269, P- ISSN 2349-5138)
IJRAR19J1023 International Journal of Research and Analytical Reviews (IJRAR) www.ijrar.org 158
Grid
Set of
3-
phase
and 1-
phase
loads
DSP
Control
External Hysteresis
Board
Renewable
Energy
Sources
P1 P4 P3 P6 P5 P2 P7 P8
Ia*
Ib*
In*
Ic*
S1 S3 S5 S7
S4 S6 S2 S8
Lsh
ILa
ILb
ILc
ILn
I in
vb
I invc
I in
vn
I inva
Ia Ib Ic InVa Vb Vc
Δ-ΥDistribution
Transformer
AB
C
N
VDC
Fig. 2: Schematic Diagram of a Proposed Circuit with Renewable Energy System
II. OVERVIEW OF A PHOTOVOLTAIC (PV) MODULE
To understand the PV module characteristics it is necessary to study about the PV cell at first. A PV cell is the basic structural
unit of the PV module that generates current carriers when sunlight falls on it. The power generated by these PV cell is very
small. To increase the output power the PV cells are connected in series or parallel to form PV module.
Rsh
Rs
Fig. 3: Equivalent Circuit of PV Cell
The main characteristics equation of the PV module is given by
𝐼 = 𝐼𝑝𝑣 − 𝐼𝑜 [𝑒𝑥𝑝(𝑞(𝑣+𝐼𝑅𝑠))
∝𝐾𝑇− 1] − 𝑉+𝐼𝑅𝑠
𝑅𝑠ℎ …(1)
Solar PV Module in MatLab Simulation
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Fig.4: MatLab Solar PV model
Solar PV & IV Characteristics
Prepared the MatLab simulation model Fig.4 according to Eq. (1) & we got following results
Fig. 5(a): Solar Cell PV Characteristics
Fig. 5(b): IV Characteristics
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III. SYSTEM DESCRIPTION
The RES may be a DC source or an AC source with rectifier coupled to dc-link. Usually, the fuel cell and photovoltaic energy
sources generate power at variable low dc voltage, while the variable speed wind turbines generate power at variable ac voltage.
Thus, the power generated from these renewable sources needs power conditioning (i.e., dc/dc or ac/dc) before connecting dc-
link.
1. DC-Link Voltage and Power Control Operation
2. Control of Grid Interfacing Inverter
3a. DC-Link Voltage and Power Control Operation
Due to the intermittent nature of RES, the generated power is of variable nature. The dc-link plays an important role in
transferring this variable power from the renewable energy source to the grid. RES are represented as current sources connected
to the dc-link of a grid-interfacing inverter. The current injected by RES into dc-link at voltage level can be given
𝐼𝑑𝑐1 =𝑃𝑅𝐸𝑆
𝑉𝑑𝑐 …(2)
Renewable
Energy
Sources
Power Grid
DC-Link
PRES PG
Pinv = PG + Ploss
Idc2Idc1
Vdc
Fig. 6: DC-Link Equivalent Diagram
3b. Control of Grid Interfacing Inverter
The control diagram of grid- interfacing inverter for a 3-phase 4-wire system as shown fig.2 the fourth leg of inverter is used to
compensate the neutral current of the load. The approach is to regulate the power at PCC. It is shown in this paper that the grid
interfacing inverter can effectively be utilized to perform following important functions: 1) to transfer of active power harvested
from the renewable resources (wind, solar, etc.); 2) load reactive power demand support; 3) current harmonics compensation at
PCC; and 4) current unbalance and neutral current The duty ratio of inverter switches are varied in a power cycle such that the
combination of load and inverter injected power appears as the balanced resistive load to the grid. The regulation of dc-link
voltage carries the information regarding the exchange of active power in between renewable source and grid. Thus the output of
dc-link voltage regulator results in an active current[5].
Components Used in the System
The components used in the systems are PLL, PIC controller, MOSFET switches and filter circuit.
Phase-Locked-Loop (PLL)
For dominant totally different operations in many communication systems, computers and lots of electronic applications, part
fastened loop are often used as an effect system. It's used for generating associate in nursing signal that has a part associated with
signaling part. PLL circuit in FM transmitter may be a control system feedback system. This part latched loop keeps the generated
signal and reference signal in a much fastened relationship. The most unusefulness of victimization associate FM transmitter is
counteracted by victimization this part latched loop scheme. If we tend to use a straightforward semiconductor unit based mostly
generator circuit, then we are able to observe the drift in frequency. This drift in frequency is caused because of completely
different instabilities like load-induced in power rails, inherent generator, thermally evoked, mechanical phenomenon forces, and
so on. This drift in frequency causes downside at the receiving finish and therefore, the receiving person needs to retune the radio
or FM transmitter radio like car-radio or hand-held radio.
PIC Controller
By using PIC controller triggering pulses are generated to the inverter side. It uses Single-supply 5V In-Circuit Serial
Programming circuit. It has wide operating voltage range (2.0V to 5.5V). It consumes Low-power. It has five input/output pins.
Triggering pulses are given to the MOSFET switch.
PI controller
The actual dc link voltage is sensed and passed through a first order low pass filter (LPF) to eliminate the presence of switching
ripples on the dc link voltage and in the generated reference current signals. The difference of the filtered dc link voltage and
reference dc link voltage (Vdc*) is given to a discrete PI regulator to maintain a constant dc link voltage under varying generation
and load conditions. The dc link voltage error Vdcerr(n) at nth sampling instant is given as
𝑉𝑑𝑐𝑒𝑟𝑟(𝑛) = 𝑉𝑑𝑐(𝑛)∗ − 𝑉𝑑𝑐(𝑛) …(3)
The output of discrete PI regulator at nth sampling instant is expressed as
𝐼𝑚(𝑛) = 𝐼𝑚(𝑛−1) + (𝑉𝑑𝑐𝑒𝑟𝑟(𝑛) − 𝑉𝑑𝑐𝑒𝑟𝑟(𝑛−1)) + 𝐾𝐼𝑉𝑑𝑐𝑉𝑑𝑐𝑒𝑟𝑟(𝑛) …(4)
Filter
A filter may be a device or method that removes from an indication some unwanted element or feature. Filtering may be a
category of signal process, the shaping feature of filters being the whole or partial suppression of some side of the signal.
© 2018 IJRAR January 2019, Volume 6, Issue 1 www.ijrar.org (E-ISSN 2348-1269, P- ISSN 2349-5138)
IJRAR19J1023 International Journal of Research and Analytical Reviews (IJRAR) www.ijrar.org 161
IV. FINAL SIMULATION MODEL WITH SOLAR GRID TIE INVERTER FOR PQ IMPROVEMENT
Fig. 7: Simulation Circuit Diagram
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V. SIMULATION RESULTS
It has observed that the THD value for PI is 64.16% for 60cycles
Grid Active and Reactive Power Results with Both Controllers
It observed that the reference signal generated by inverter to compensate the reactive power is same as grid signal with 180deg
phase shift.
Fig. 8: Load Current THD with PI Controller
Fig. 9: Grid Active & Reactive Power
Inverter Active and Reactive Power Results
Fig. 10: Inverter Active and Reactive Power
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IJRAR19J1023 International Journal of Research and Analytical Reviews (IJRAR) www.ijrar.org 163
VI. HARDWARE RESULTS
As shown in Fig. 1 Basic block diagram of grid tie inverter. Single phase Prototype Hardware is prepared & shown that voltage
amplitude & waveform at grid side & inverter side are mating so inverters are synchronized with grid. Waveforms are shown in
fig.11 and Fig.12 with hardware photographs.
Fig. 11: Hardware Board with Output Verification
Fig. 12: Grid and Inverter Output Waveform.
VII. CONCLUSION
In this project improved the performance of the power quality problems (voltage sag, swell and harmonics) and to grid connection
with the help of inverter used in distributed generation. This paper presented a PI logic controller in order to improve the
performances of PQ. It is also interfaced with RES (Renewable Energy Resources) with the electric grid with 1ph prototype
hardware. The grid interfacing inverter has improved the performance of power converter to inject power generated from
Renewable energy sources to the grid, shunt Active power filter to compensate current unbalance, load current harmonics, load
reactive power demand. The controller controls the real power and reactive power supplied by the distributed generation at the
PCC. In the gird side currents always maintained as balanced and the unity power factor.
REFERENCES
[1] Mukhtiar Singh, Vinod Khadkikar, Ambrish Candra, “Grid interconnection of renewable Energy sources at the distribution
level with power-quality improvement features,” IEEE Trans. Power Delivery, vol. 26, no. 1, pp. 307-315, Jan. 2011
[2] Manoj D. Patil, K. Vadirajacharya, “ALO optimized Neural Network Controlled Three Phase Five Level Cascaded H-Bridge
Inverter for Integrating PV Panel with Smart Grid” in Institute of Advanced Scientific Research Publications; Journal of
Advanced Research in Dynamical and Control Systems (JARDCS), Volume-10, Special Issue-09, pp.2127-2139.
[3] Manoj D. Patil, Mithun Aush, K. Vadirajacharya, “Grid Tied Solar Inverter at Distribution Level with Power Quality
Improvement” in Research India Publications; International Journal of Applied Engineering Research, Print ISSN: 0973-
4562, Online ISSN: 1087-1090, April 2015, Special Issues, Volume-10, Number-9, pp.8741-8745.
[4] Manoj D. Patil, K. Vadirajacharya, “Grid Tied Solar using 3-Phase Cascaded H-Bridge Multilevel Inverter at Distribution
level with Power Quality Improvement” in International Journal of Advance Foundation and Research in Science and
Engineering, ISSN 2349-4794, Volume-2, Special Issue, Vivruti-2016, 2016, pp.178-191.
[5] Manoj D. Patil, Rohit G. Ramteke, “L-C Filter Design Implementation and Comparative Study with Various PWM
Techniques for DCMLI” in IEEE Xplore Digital Library & International Conference on Energy Systems and Applications
(ICESA-2015) organised by Dr. D. Y. Patil Institute of Engineering and Technology Pune in association with IEEE pune
section, held from 30th October to 1st November 2015, pp.347-352.