Power Quality Improvement in Inter connected solar

System using STATCOM

Suseela K, Soundarya M,
Department of Electronics and Communication Engineering, Electrical and Electronics Engineering
Surya Engineering college, Mettukadai, Erode,Tamilnadu
susi170291@gmail.com,s ou ndar ya kkls @gma il. com

Abstract— Natural energy sources, often regarded as EXISTING SYSTEM

alternatives to conventional energy, pose new challenges
when incorporated into the electrical grid. Specifically, the In today's electric power grids, power quality is a critical concern
incorporation of solar energy systems into the grid can frequently resulting in costly consequences such as sensitive equipment
significantly impact power quality. Key issues include active tripping and production downtime. The demand for enhanced voltage
power fluctuations, voltage variations, flicker harmonics, and stability and consistent power quality has grown substantially. One
transient switching behaviors. This project investigates the proven solution is the dynamic voltage restorer, a custom power device
power quality problems arising from grid-connected solar designed to restore voltage levels at the load end when supply-side
power systems and a control scheme. A STATCOM-based disturbances occur. This paper introduces a novel DVR design using a
compensator is designed and simulated using Simulink in the double flying capacitor multicellular DFCM converter for medium-
power system blackout. The study highlights both the voltage applications. Although this topology uses a greater number of
degradation in power quality due to solar integration and the switching devices compared to traditional inverters, it offers improved
improvements achievable through STATCOM control and voltage regulation.
implementation. Power quality issues at the point of common
coupling (PCC) often caused by non-linear loads are
addressed using a STATCOM interfaced with the grid. A PROPOSED SYSTEM
specialized control strategy is adopted to extend STATCOM
functionality to also act as a shunt active filter, further
Among various renewable sources, solar energy is considered the
enhancing power quality.
most cost-effective for producing electricity on a per-kilowatt-hour
basis. While it is a highly beneficial and eco-friendly energy source, its
Keywords: renewable energy source, power quality integration with the electrical grid can introduce power quality issues
improvement, STATCOM grid, integration interfacing unit such as voltage sags, swells, harmonics, and others. Moreover, solar
power systems are also vulnerable to occasional grid faults. To mitigate
these issues, this research explores the integration of a STATCOM with
INTRODUCTION a solar energy system. The STATCOM compensates for voltage sags
and other disturbances. Allowing solar energy to continue stable
Distributed generators DGs such as solar photovoltaic systems operation under fault conditions, this setup eliminates the need for line-
offer notable advantages to distribution networks, including frequency step-up isolation transformers and can achieve improved
cleaner energy and reduced transmission losses. However, they power quality through optimized control.
also introduce several operational challenges. These include
steady-state and temporary overvoltage (TOV), voltage The primary function of the STATCOM in the proposed system is
imbalance harmonic distortion, and the increased cycling of to dynamically regulate voltage at the point of common coupling
conventional voltage regulators like on-load tap changers (PCC) by injecting or absorbing reactive power, thereby ensuring
(OLTS) and capacitor banks. These traditional voltage control system stability and enhancing power quality.
devices are inherently slow, often responding within seconds to
minutes. Furthermore, they operate based on unidirectional
power flow and may not perform reliably in systems with Voltage Sags and Swells: During grid disturbances or sudden load
bidirectional power flow, which is a common feature in solar- changes, the STATCOM injects or absorbs reactive power to stabilize
powered distributed generation. To address these challenges, the voltage levels, preventing sags (under-voltage) or swells (over-
flexible AC transmission devices (FACTS), such as the static var voltage) at the PCC.
compensator (SVC) and STATCOM, are employed. Among
these, STATCOM offers a significantly faster dynamic response, Harmonics Compensation: By employing advanced control
typically within 1 to 3 cycles, making it well-suited for voltage strategies (e.g., synchronous reference frame control, hysteresis
regulation in modern power systems. control, or PQ theory), the STATCOM can filter out harmonics caused
by nonlinear loads and solar inverter switching operations.
 MERITS

DEFINITION OF POWER QUALITY  Eliminates the need for line-frequency isolation

transformers .
 Improves total harmonic distortion by employing a PID
controller.
 Reduces switching losses, enhancing system efficiency

NEED OF BETTER POWER QUALITY

Power quality is becoming an important concern because of many

reasons. Some major reasons are

The fluctuation of voltage, current, or frequency from its optimal value

that may prompt maloperation of the equipment can be considered an
issue in the power quality. The term "electromagnetic compatibility" is
also used in place of power.

To increase the efficiency of power systems, many new devices, such

as shunt capacitors and adjustable-speed motor drives, are gaining
popularity. These devices increase the harmonic level of the power
system, which increases the concern.

*Power electronic devices and loads that make use of control based on
microprocessors and microcontrollers are more affected by power
quality issues.

Fig1.1 Proposed Block Diagram COMMON DISTURBANCES IN POWER SYSTEM

Short Duration Voltage Variation

The duration of short- duration voltage variation is very short, i.e., less
A consistent amplitude and one constant frequency sinusoidal
than 1 min. The main reasons for this are large load energization, fault
signal are considered an ideal current or voltage signal. The
conditions, etc. Short -duration voltage variation includes voltage sag,
quality of voltage taken from the utility or that delivered to the
voltage swell , and interruption.
consumer is referred to as voltage or current quality. The
fluctuation of voltage, current, or frequency from its optimal
value that may prompt maloperation of the equipment can be Voltage Swell
considered an issue in the power quality. The term
"electromagnetic compatibility" is also used in place of power It’s the increase in the line voltage (rms) to 1.1-1.8% of the nominal
quality; they are strongly related but not exactly the same. As line voltage for a small period of half a cycle to 1 min. The main cause
indicated by the IEEE Principles, power quality can be for this is swells can be switching off of a large load.
characterized as the method of grounding and supplying
sensitive equipment with power to achieve a reasonable and Voltage Sag
agreeable performance of the equipment. Overall power quality
represents a blend of the quality of the current and voltage. It’s a decrease in the line voltage (rms) to 10 to 90 % of the standard
Voltage quality at the point of connection is governed by the line voltage for a period of half a cycle to a minute. It is also referred to
network operator, whereas the quality of current at the as “dip.” The main cause for this voltage sag is the starting of large
connection point is governed by the client's load. Taking into induction motors.
account the prerequisites, power quality can have various
different meanings and significances. In the view of the
manufacturer, the term power quality can be characterized as PROBLEMSREGARDIN POWERQUALITY
the way in which there ought to be no voltage variety and no
noise generation in the system of grounding. In the context of Voltage Sag (Or Dip)
utility design, it can be considered as voltage availability. The
distribution system is worst affected because of the power
quality problems. Power quality becomes poor at the points
where loads are connected with the distribution system. So
here we’ll try to upgrade the quality of power of the
distribution system.
 Fig 1.2 Voltage Sag human error Bad coordination or failure of protection devices.
90% of the nominal rms Voltage at the power frequency, for
durations of 0. 5 cycle to 1 minute. Voltage Spike

Causes:

Faults in consumer’s installation Faulton the

transmission or distribution network Most of the times faults
occur on parallel feeders. Connection of heavy loads and
start-up of large motors.
Consequences: Tripping of contactors and electromechanical
relays Malfunction of information technology equipment, Fig 1.5 Voltage Spike
namely microprocessor-based control systems(PCs, PLCs,
ASDs, etc)
that may lead to a process stoppage. Disconnection and loss of Description: Very fast variation of the voltage value for durations
efficiency in electric rotating machine from a several microseconds to few milliseconds. These variations
may reach thousands of volts, even in low voltage
Very Short Interruptions
Description:Totalinterruptionofelectricalsupplyfordurationfro Voltage Swell
mfew milliseconds to one or two seconds.
Description: Momentary increase of the voltage, at the power
frequency, outside the normal tolerances, with duration of more
than one cycle and typically less than a few seconds.

Fig 1.3 Very Short Interruptions

Causes: Fig 1.6 Voltage Swell

Causes:
The main fault causes are insulation failure, lightning and
insulator flashover. Mainly due to the opening and
Start/stop of heavy loads, badly dimensioned power sources.
automatic reclose of protection devices to decommission a
Badly regulated transformers (mainly during off-peak hours).
faulty section of the network.

Consequences: Loss of information and malfunction of data Consequences:

processing equipment. Tripping of protection devices. Flickering of lighting and screens.Data loss. Stoppage or damage of
Stoppage of sensitive equipment such as, ASDs, PCs, PLCs, sensitive equipment, if the voltage values aretoo high.
if they’re not prepared to deal with this situation.
Long Interruptions Harmonic Distortion
Description: Voltage or current waveforms assume non-sinusoidal
shape. The waveform corresponds to the sum of different sine-waves
with different magnitude and phase, having frequencies that are
multiples of power-system frequency.

Fig 1.4 Long Interruptions

Description: Total interruption of electrical supply for duration

greater than 1 to 2 seconds.

Causes:

Equipment failure in the power system network. Storms and

objects (trees, cars, etc) striking lines or poles. Fire and
Fig 1.7 Harmonic Distortion
 The STATCOM working, it transforms DC side voltage into the output
Classic sources: electric machines working above the knee of voltage of AC side with the electrical network frequency, which is
the magnetization curve (magnetic saturation), arc furnaces, equivalent to a voltage type inverter, It is equivalent to an amplitude
welding machines, rectifiers, and DC brush motors. and phase controlled AC voltage source here [7]. The actual phase
equivalent circuit and phase diagram as shown in Figure 2, taking into
Modern sources: account loss of the circuit; it can be considered the loss as resistance
which connect reactor. The grid voltage and the output AC voltage of
all non-linear loads, such as power electronics equipment STATCOM is VS and VSTA, the voltage of reactance is VL, the
including ASDs, switched mode power supplies, data reactor equivalent impedance is R, inductive reactance is X, electric
processing equipment, high efficiency lighting. current is I. The phase difference of the voltage VS and current I is not
Voltage Fluctuation 90°, it is smaller than 90° with a δ angles, grid provides power to
supplement the circuit loss, when VSTA> VS, current leads the
Consequences: Most consequences are common to under voltage, STATCOM is equivalent to a continuous adjustable capacitor,
voltages. The most perceptible consequence is the flickering It is a capacitive mode of operation, absorb reactive power; when the
of lighting and screens, giving the impression of unsteadiness VSTA<VS, current lags the voltage, STATCOM is equivalent to a
of visual perception. continuously adjustable inductance, It is perceptual mode and power.
The STATCOM (or SSC) is a shunt-connected reactive-power
compensation device that is capable of generating and/ or absorbing
Noise reactive power and in which the output can be varied to control the
specific parameters of an electric power system. It is in general a solid-
state switching converter capable of generating or absorbing
independently controllable real and reactive power at its output
terminals when it is fed from an energy source or energy-storage device
at its input terminals. Specifically, the STATCOM considered is a
voltage- source converter that, from a given input of dc voltage,
produces a set of 3- phase ac-output voltages, each in phase with and
coupled to the corresponding ac system voltage through a relatively
small reactance (which is provided by either an interface reactor or the
leakage inductance of a coupling transformer).
The dc voltage is provided by an energy-storage capacitor and a
STATCOM can improve power-system performance in such areas as
the following:
1. The dynamic voltage control in transmission and distribution
Fig 1.7 Noise systems;

2. The power-oscillation damping in power-transmission systems;

3. The transient stability;

4. The voltage flicker control; and

STATIC SYNCHRONOUS COMPENSATOR
(STATCOM):
STATCOM is a three-phase and shunt connected power
TYPICAL STATCOM APPLICATIONS
electronics based device. It is connected near the load at the
distribution systems. The reference source current used to * Utilities with weak grid knots or fluctuating reactive loads,
decide the switching of the STATCOM has two parts. One is
*Unbalanced loads,
real fundamental frequency component of the load current,
which is being extracted using Adeline and another component,
which corresponds to the losses in the STATCOM, are *Arc furnaces,
estimated using
The commutated bridge circuit through the reactor or directly *Wind farms,
parallel to the grid, a properly adjusted bridge circuit in AC
side output voltage amplitude and phase, or directly control the *Wood chippers,
AC current, can make the circuit to absorb or emit to meet the
requirements of the reactive current, achieve the purpose of
dynamic reactive power compensation. According to the *Welding operations,
structure of STATCOM, it can be divided two types: voltage
bridge type circuit and the current bridge type circuit. In fact, *Car crushers & shredders,
due to the reasons of operational efficiency, practical uses is
mostly voltage bridge type circuit, so STATCOM specifically *Industrial mills,
refers to Using self commutation voltage bridge circuit as a
dynamic reactive power compensation device. Device main
*Mining shovels & hoists,
circuit structure as Power switch devices uses the switch
device IGBT which have the capacity of self-switching off.
 *Harbor cranes. Because a single solar panel can only produce a limited amount of
power, many installations contain several panels. This is known as a
MAIN ADVANTAGES OF STATCOM photovoltaic array. A photovoltaic installation typically includes an
array of solar panels, an inverter, batteries and interconnection wiring.
* Continuous and dynamic voltage control, Solar panels use light energy (photons) from the sun to generate
electricity through the photovoltaic effect. The structural (load
* High dynamic and very fast response time, carrying) member of a module can either be the top layer (superstreet)
or the back layer (substrate). The majority of modules use wafer-
based crystalline silicon cells or a thin-film cell based on cadmium
* Enables grid code compliance,
telluride or silicon. Crystalline silicon, which is commonly used in the
wafer form in photovoltaic (PV) modules, is derived from silicon, a
* Maximum reactive current over extended voltage range, commonly used semi-conductor. A solar cell or photovoltaic cell is a
wide area electronic device that converts solar energy into electricity
* High efficiency, by the photovoltaic effect. Photovoltaic is the field of technology and
research related to the application of solar cells as solar energy.
* Single phase control for unbalanced loads Sometimes the term solar cell is reserved for devices intended
specifically to capture energy from sunlight, while the term
* Power Factor To Unity photovoltaic cell is used when the source is unspecified. Assemblies
of cells are used to make solar modules, or photovoltaic arrays.
In order to use the cells in practical applications, they must be:
PHOTOVOLTAIC MODULE: Connected electrically to one another and to the rest of the system
protected from mechanical damage during manufacture, transport,
installation and use (in particular against hail impact, wind and snow
loads). This is especially important for wafer-based silicon cells which
are brittle.

Protected from moisture, which corrodes metal contacts and

interconnects, (and for thin-film cells the transparent conductive oxide
layer) thus decreasing performance and lifetime.
Most modules are usually rigid, but there are some flexible modules
available, based on thin-film cells.

Fig 1.9 Solar Panel

Electrical connections are made in series to achieve a desired output

voltage and/or in parallel to provide a desired amount of current
source capability.
Diodes are included to avoid overheating of cells in case of partial
Fig 2.0 inverter

Fig 1.8 Photovoltaic module

Solar Panel
A solar panel (photovoltaic module or photovoltaic panel) is a
packaged interconnected assembly of solar cells, also known as
photovoltaic cells. The solar panel is used as a component in a
larger photovoltaic system to offer electricity for commercial
and residential applications.
shading. Since cell heating reduces the operating efficiency it
is desirable to minimize the heating. Very few modules
incorporate any design features to decrease temperature,
however installers try to provide good ventilation behind the
module(1).
New designs of module include concentrator modules in which
the light is concentrated by an array of lenses or mirrors onto
an array of small cells. This allows the use of cells with a very
high-cost per unit area (such as gallium arsenide) in a cost-
competitive way.
Fig 2.1 Convrting DC to AC
Depending on construction, the photovoltaic can cover a range
of frequencies of light and can produce electricity from them,
but sometimes cannot cover the entire solar spectrum Converting DC to AC
(specifically, ultraviolet, infrared and low or diffused light).
Hence much of incident sunlight energy is wasted when used
for solar panels, although they can give far higher efficiencies
if illuminated with monochromatic light. Another design An inverter converts the DC electricity from sources such as batteries,
concept is to split the light into different wavelength ranges solar panels, or fuel cells to AC electricity. The electricity can be at any
and direct the beams onto different cells tuned to the required voltage; in particular it can operate AC equipment designed
appropriate wavelength ranges.[2] This is projected to raise for mains operation, or rectified to produce DC at any desired voltage
efficiency by 50%. Also, the use of infrared photovoltaic cells
can increase the efficiencies, producing power at night.

APPLICATION OF SOLAR CELL:

*Cells are used for powering small devices such as electronic

calculators. .
Fig 2.2 Grid Tie Inverter
*Photovoltaic arrays generate a form of renewable electricity,
particularly useful in situations where electrical power from the
grid is unavailable such as in remote area power systems
Grid tie inverters can feed energy back into the distribution network
*Earth-orbiting satellites and space probes, remote because they produce alternating current with the same wave shape and
radiotelephones and water pumping applications. frequency as supplied by the distribution system. They can also switch
off automatically in the event of a blackout.

INVERTER
RESULT AND DESCUSION
An inverter is an electrical device that converts direct current
(DC) to alternating current (AC); the converted AC can be at MATLAB is a high-performance language for technical
any required voltage and frequency with the use of appropriate computing. It integrates computation, visualization, and
transformers, switching, and control circuits. programming in an easy-to-use environment where problems
Static inverters have no moving parts and are used in a wide and solutions are expressed in familiar mathematical notation.
range of applications, from small switching power supplies in
computers, to large electric utility high-voltage direct current
applications that transport bulk power. Inverters are commonly
used to supply AC power from DC sources such a solar panels
or batteries.

The electrical inverter is a high-power electronic oscillator. It

is so named because early mechanical AC to DC converters
was made to work in reverse, and thus was "inverted”, to
convert DC to AC.
Fig 2.3 BlackBox
Associated with a system is the so-called state vector which
loosely speaking contains the required information at time that
together with knowledge of the input for time greater than, CONCLUSION
uniquely determines the output for. A general continuous The project presents the STATCOM-based control scheme for power
dynamical system can be modeled by using the following set of quality improvement in grid connected solar generating system and
ordinary differential and algebraic equations. with nonlinear load. The power quality issues and its consequences on
the consumer and electric utility are presented. The operation of the
Simulink Library Browser control system developed for the STATCOM-BESS in
MATLAB/SIMULINK for maintaining the power quality is simulated.
Simulink can be launched by typing>> Simulink in the It has a capability to cancel out the harmonic parts of the load current.
Simulink icon in the Command window of the default Mat lab It maintains the source voltage and current in-phase and support the
desktop reactive power demand for the solar power and load at PCC in the grid
system, thus it gives an opportunity to enhance the utilization factor of
a transmission line. The integrated wind generation and STATCOM
with BESS have shown the outstanding performance. Thus the
proposed scheme in the grid connected system fulfills the power
quality.

References:
[1] A. Sannino, “Global power systems for sustainable development”,
in IEEE General Meeting, Denver, CO, Vol. 3, Jun. 2004, pp. 3-5.

[2] Roger C. Dugan, Mark F. McGranaghan, Surya Santoso, H.

Wayne Beaty, “Electrical Power System Quality”, McGraw-Hill, pp.
203-210.

[3] Narain g. Hingorani, Laszlo gyugyi,“Understanding FACTS, IEEE

The library’s functionalities are divided into eight groups (click Press, pp.5-9.
on any of the category icons for both the UNIX or Windows
versions). For example the categories Sources and Sinks [4] E. Muljadi, C. P. Butterfield, J. Chacon and H.
contain various kinds of inputs and ways to handle or display
the output respectively. Also, it contains the group Continuous Romanowitz,“Power Quality Aspects in a Wind Power Plant”, Power
that will be used later deals with dynamical systems Engineering Society General Meeting, 2006, pp. 6-10.

[5] Adriano Abrantes, “Overview of Power Quality Aspects in Wind

Generation”, IEEE 2010, pp. 11-14.

[6] Jan T. Bialasiewicz,“Renewable Energy Systems with

Photovoltaic Power Generators: Operation and Modelling”, IEEE
Transactions on Industrial Electronics, Vol. 55, No. 7, July 2008, pp.
5-8.

[7] Wind Turbine Generating System Part 21, International standard-

IEC 61400 21, 2001, pp. 4-7.

[8] “Indian Wind Grid Code Draft report on Jul. 2009, pp. 15-18.

[9] Moataz Ammar, “Flicker Emission of Distributed Wind Power:

A Review of Impacts, Modelling, Grid Codes and Mitigation
Techniques”, IEEE 2012, pp.7.