Abstract Modern world is under tremendous pressure for [613900]

Abstract — Modern world is under tremendous pressure for
alternative sources of energy and the trends are towards
sustainable energy. Present power systems are facing heavy economic losses for poor power qualities. Efficiency of sustainable energy depends on the power quality of the supply.
Presently, Power Quality issues are major problems for utilities,
customers and end users. The cost of poor PQ is high and gradually rising. The paper gives insights on global economical losses due to poor PQ. The business risk posed by PQ problems is
a real one with even low tech industries exposed to serious
financial losses. It has been observed that the consequences of poor PQ would have large financial impacts on a country’s economy, and more initiatives are required from the concerned
parties and regulating bodies to take corrective measures for
maintaining better power quality. Especially for successful sustainable energy programme, Power Quality Monitoring can help identify the cause of power system disturbances and the
problem conditions on a system before they cause interruptions
or disturbances. In an environment of sustainable energy and modern grid, intelligent PQ monitoring is essentially required to solve different PQ related problems. Authors proposed an intelligent power quality monitoring system using virtual
instrumentation and appropriate data acquisition system to
detect different PQ disturbances. The system is user friendly due to its graphical user interface. The tests were done in the Energy Laboratory of NIT, Silchar (India) and Research Lab, Electrical
Engineering Department, AMU, Aligarh (India). The available
energy in both the labs was solar energy. The qualities monitored include voltage fluctuations, sag, swell, interruptions, harmonics etc. The huge amount of acquired data has been analyzed using
quadratic discriminant analysis technique to determine the
condition of the waveforms. The system shows fast response with accuracy in monitoring desired power qualities.

Index Terms —Power quality, quadratic discriminant,
sustainable energy, virtual instrumentation.
I. INTRODUCTION
RESENT day world is heavily dependent on the
availability of constant and reliable electrical power
supply. The quality of the power supply has gained much importance due to the increased sensitivity of equipments and
devices used by customers. Also power quality of power

Shahedul Haque Laskar is with the National Institute of Technology, NIT,
Silchar, India (phone: +919435178423; e-mail: [anonimizat]).
Sanaullah Khan is professor and the former chair of the Department of
Statistics, Aligarh Muslim University, Aligarh, India (phone:
+919456033796; e-mail: [anonimizat]).
Mohibullah is with the Electrical Engineering Department, Aligarh Muslim
University, India (phone: +919719462637; email:[anonimizat]).
systems affects all connecte d electrical and electronic
equipments and is a measure of deviations in voltage, current, frequency, temperature, force, and torque of particular supply
systems and their components. To fulfill the demand of
required supply, the world is under tremendous pressure for
alternative sources of energy and has been inclined towards
sustainable energy for future source of energy [1],[2]. The energy sources like solar energy, wind energy,
hydroelectric power, tidal power, geothermal power and wave
power are all important types of renewable energy. However if
these energy sources are coupled with the energy efficacy it is
termed as sustainable energy sources. Sustainable Energy is the provision of energy such that it meets the needs of the
future without compromising the ability of future generations
to meet their own needs. It is required to have more efficient means of converting and utilizing these energy. This will
depend on the quality of power supplied and the impact of end
user equipments on that power. But power electronic
equipments are mostly used in sustainable and renewable
energies in different stages for acquisition and conversion or inversion into useable form. Due to increasing sensitivity of
the equipments and devices used by the customers, power
qualities of sustainable energy are affected .
In general, power quality disturbances include those from
short to long-duration variations and flicker, and degrade
product quality, increase downtime, and reduce customer
satisfaction. [3]
Poor PQ results in high costs and that is gradually rising.
The poorer the PQ, the more would be the initiatives required from concerned parties and regulating bodies to adopt
corrective measures to ensure better PQ. As a consequence,
the economy of a country is largely affected with even low tech industries suffering serious financial losses. Especially for successful sustainable energy programme, Power Quality Monitoring can help identify the cause of power system disturbances and the underlying problem conditions on a
system before they cause interruptions and disturbances.
Due
to this many power utilities perform power quality monitoring as an essential service for their main customers. Essential capabilities of a power quality monitoring system are reduced cost and remote data transmission capability [4]. In literature, several methods have been proposed. A real time power
quality monitoring instrument for detection and classification
of disturbances in a single phase power system was presented in [4]. A low cost embedded solution for measuring power quality parameters based on RISC microprocessor was presented by L. Tomesc, R. Duma, M. Abrudean and P. Dobra Power Quality Monitoring in Sustainable
Energy Systems
Shahedul Haque Laskar, Senior Member, IEEE , Sanaullah Khan, and Mohibullah, Member, IEEE
P

[5]. But the method needs to reduce negative effects of errors
in measurements, implementation trade-offs, and to maximize the executions speed.
A web-based supply voltage monitoring system based on a
compact microprocessor module provides a low-cost and flexible solution for monitoring the power quality of electricity supply [6]. The hardware used consists of a module and few electronic equipments. Another power quality monitoring system capable of capturing and retrieving
electrical quantities related to harmonics and distortion levels
had been described by C J Farhat [7]. Some other methods are proposed based on FFT, wavelet, ANN, Kalman Filter, Petri-net, Adaline, Espirit etc. But each method has some pros and cons [8] [9]. No single method is capable to monitor efficiently all the PQ parameters.
In an environment of sustainable energy, modern grid and
insertion of renewable energy into modern or future grid, an intelligent PQ monitoring is essentially required to solve
different PQ related problems. [8],[10]. Authors proposed an
intelligent power quality monitoring system using virtual
instrumentation, high performance data acquisition system and
higher order statistics to detect and analyze different PQ disturbances. The system is user friendly due to its graphical
user interface. The tests were done in the Energy Laboratory
of NIT, Silchar (India) and Research Lab, Electrical Engineering Department, AMU, Aligarh (India) using solar
energy as the source in both the cases. The parameters
monitored include voltage fluctuations, sag, swell,
interruptions, harmonics etc. The huge amount of acquired
data has been analyzed using quadratic discriminant analysis technique to determine the condition of the waveforms. The
system shows fast response with high accuracy in monitoring
desired power qualities.
II. IMPACTS
ON GLOBAL ECONOMY
The cost of energy or a KWHr not supplied because of an
outage is much higher than the cost of a KWHr that is
supplied when needed. The global bill for poor power quality is more than 500 billion euros per year which is 50% of the turnover of the global electricity sector. For many business uses, the cost of poor PQ is higher than the electricity bill and the cost is rising.[8]
The global average energy consumption is steeply rising.
The projections of Indian average energy consumption has been shown in Fig.1. Due to high average increase of energy demand, India needs to have sustainable energy productions to meet the huge energy requirements. The Government of India is
trying to accelerate solar power generation with the aim of
generating at least 10% of electricity through solar energy by 2012. Poor PQ has serious impact on Indian economy. A joint study by the manufacturers association of information technology(MAIT) and emersion network
power(India) has thrown up the finding that network power
downtime costs Indian economy more than Rs.43000 crores annually(2008) and this has been steeply rising. Similarly, economic cost of outages of Bangladesh amounted to 1.72% (US $778millions) of the Country GDP in 2001.

Fig. 1. Indian average energy consumption projections

Industrial losses due to poor PQ had been estimated as $150-
$200 billion dolla rs for European Union (2001) [8],[12].
Therefore, an efficient and intelligent monitoring is essential to avoid staggering economic losses due to poor power quality and to meet the challenges.
III.
SOLAR ENERGY IN INDIA AND PQ MONITORING
Solar Energy is one of the cleanest and greenest
technologies. Solar electric panels produce DC. Necessary
conversion is done for AC applications. A solar electric
system may be completely independent of the grid or designed
to primarily feed power into the grid [11]. The solar radiation in India is very much satisfactory and most parts are suitable
for generating power from Solar Energy. In such case it is
essential for India to install efficient power quality
monitoring systems to maintain quality and undertake exact
mitigations in time. The support extended by Government of India by way of
providing attractive incentives under Jawaharlal Nehru
National Solar Mission (JNNSM) is generating significant interest in Solar Energy. India has Geographical advantage
with excellent solar radiation across the Country. In fact
Rajasthan has been recently termed as amongst the best in the
world for Solar Energy
[8], [9].
As an alternative source of energy efforts are made to have larger production units from solar, wind mills sources etc. But
many systems (utility/customer) are affected due to absence of
an effective PQM programme. Integration of sustainable
energy with the grid and use of power electronics, power
quality problems have increased in manifold. Monitoring within an industrial, residential or domestic unit can reveal the
origin of problems and give the necessary information for their
solution. Efficient power quality monitoring will provide the information needed to validat e compliance, improve system
stability, and minimize unplanned downtime.

It is therefore an important issue for the successful and efficient operation of existing as well as future energy
systems. In such conditions, monitoring of power quality is the real challenge. An intelligent power quality monitoring system
is an essential requirement of the future energy system. The

PQM should be capable to detect most (and almost all) of the
power quality events and disturbances. Intelligent PQM is the
need for smart grid due to principal functionality
characteristics of Smart Grids.
III. DEVELOPMENT OF THE SYSTEM
The aim of this work is to develop a method that is suitable
for efficient monitoring of power qualities in sustainable
energy system like solar energy etc. The emphasis is therefore on low computational power required to perform the necessary calculations. Stress is also laid on the possibility to detect as many categories of PQ disturbances as possible.
The present work leads to the development of an intelligent
power quality monitoring system by designing virtual
instruments using LabVIEW software and NI’s DAQ system and sensors [13]. Along with LabVIEW, Higher order statistics (HOS) and quadratic discriminant analysis techniques are employed to classify and analyze the huge amount of acquired data to determine the condition of the
waveforms[14]. The system shows fast response with
accuracy in monitoring and analysis of the desired power qualities. Initially, the distortions have been simulated in the labs and measured with the help of the developed virtual instruments
(VIs) using graphical programming in LabVIEW. Different
types of disturbances measurements are done with front panel created on PC monitor. The huge amount of acquired data has been analyzed using quadratic discriminant analysis technique to determine the quality of the supply. The quadratic discriminant function is estimated treating a sample from the
data as a training data. The data can be exported in different
formats in a text file or directly in common software products like Excel etc. The test results of the simulated and the prototype system show the desired performance of the system and thus validate the proposed technique. The beauty of the system is that it can be used for monitoring of power qualities
in both existing power system and sustainable energy systems
with provisions for switching-over .
4.1 Front Panel and block diagram of the system

Its development is based on software using graphical
programming to work along with appropriate hardware to
form a compact single station for power quality monitoring without the use of different devices from different vendors.
This work addresses especially on the measurement of the
signals to detect any disturbances or distortions in the power
supply quality and giving priority to the needs of the domestic
consumers and small-scale industries.
LabVIEW software has been used to design different virtual
instruments (VIs). The simulations VIs are used to generate
voltage waveforms. The interfacing devices are used to
connect the software and hardware through serial communication with some additional / necessary hardware [15]. LabVIEW (Laboratory Virtual Instrument Engineering Workbench) is a graphical development environment which
can be used to conduct scalable tests, measurements, and
control applications, in addition to the ability to interface real-
world signals and analyze data for meaningful information. [13], [15]. In this application, we generate a graphical user interface through which the user can monitor and adjust
different parameters to customize the monitoring tasks. On the other hand, a National Instruments Data Acquisition card is
chosen to interface the analog AC signal as a second step after
using step-down transformer along with voltage divider circuit for signal conditioning. For voltage measurements, magnetic voltage transformers are used (upto 5 KHz). However current probes and Hall Effect voltage transducers are employed to acquire voltage and current signals for accurate sensing.
The following diagram (Fig.2) shows the main elements of
the PQM system.

Fig. 2. Block diagram of power quality monitoring system

4.2. Developed Power Quality Monitor

It consists of a standard Personal Computer (Windows XP
or Vista), data acquisition system/card (National Instruments
PXI-1042 Series /NI 4472), and a Custom made hardware
module. The card can read 8 analogue signals in differential
mode, with a 24 bit Resolution and a 102.4 kS/s sampling
rate, as well as 8 I/O digital lines[13],[14].
Using graphical Programming language (NI LabVIEW) a
number of virtual instruments (VI) are implemented
depending on experimental study and testing. The simulation
VIs are used to generate voltage waveforms in form of sinusoidal output in time domain, rms voltage and the frequency response curves to monitor the operating frequency. The interfacing devices are used to connect the software and
hardware through serial communication.
4.3 System hardware

The PXI-1042 Series (Fig.3) combines a high-performance
8-slot PXI backplane with a high-output power supply and a structural design that has been optimized for maximum usability in a wide range of applications. The chassis’s
modular design ensures a high level of maintainability,
resulting in a very low mean time to repair (MTTR). The PXI-1042 Series fully comply with the PXI Specification, offering advanced timing and synchronization features [12], [13], [15].
The data acquisition system includes a high-performance,
high-accuracy analog input device for the PCI, PXI, or CompactPCI bus. It is specifically designed for demanding dynamic signal acquisition applications. The NI 4472 features eight analog input channels.
Sustainable
energy
Supply Transducers DAQ
Processor
with
LabVIEW
software
Data Storage PC monitor & Display of
power qualities

Fig.3. Front view of data acquisition system (NI PXI 1042)

These channels are simultaneously sampled at a maximum
rate of 102.4 kS/s (Kilo-samples per second) with 24-bit
resolution and multiple triggering modes, including external
digital triggering. Each input channel has an independent software-switchable 4mA current source for Integrated Circuit
Piezoelectric (ICP®)-type accelerometers and microphone
preamplifiers

4.4 Basic Software Design
4.4.1 Different VIs:
Initially, a signal generator VI has been designed for
simulating a voltage signal using LabVIEW. The input to
which is the sampling frequency, number of samples, number
of channels, sampling mode, maximum and minimum range
of the input voltage. The output is observed on the front panel
graphical display. Then different VIs are designed and tested.
The different VIs used are DAQmx virtual channel VI,
DAQmx timing VI, DAQmx start task VI, DAQmx READ
VI, DAQmax stop task VI, DAQmax clear task VI, along
with other VIs for THD, frequency, alarm, etc. DAQmx is the
latest NI-DAQ driver with new VIs, functions, and
development tools controlling measurement devices. Detailed
descriptions are available in national instrument’s user
manuals [13], [14], [15]. Other VI’s used in the programmes include Harmonic
distortion analyzer VI, Basic DC- RMS value VI, frequency
estimating VI. During designing of VIs the standards of power qualities are followed [16], [17], [18].

The block diagram is the VI's source code, constructed in
LabVIEW's graphical programming language, G. The block
diagram is the actual executable program. The components of
a block diagram are lower-level VIs, built-in functions, constants, and program execution control structures. Wires are
connected properly in the block diagram to the appropriate
objects and flow of data between them is checked.
Front panel objects have corresponding terminals on the
block diagram so that data can pass from the user to the program and back to the user. The fig.4 shows the block
diagram of the PQMS (Power Quality Monitoring System).

Fig.4. Front panel of the developed power quality
monitoring system

Signal conditioning is performed on analogue signals
(voltage or current) to convert them into a form suitable for
interfacing with other elements in the system hardware. For
this system, the authors used current and voltage transducers
to acquire voltage and current signals.
Signal conditioning circuit is required to overcome any
problem including deviation of the transformer or transducer
output voltage from the specified limit, when interfacing the
main supply to the rest of the system [11], [12], [14].

V. MONITORING AND ANALYSIS
5.1 Monitoring observations of power qualities:
Using LabVIEW internal programmes, different noise or
disturbances were generated to view different events of power quality on simulated signals by the developed Power Quality
Monitoring System. Then the simulation blocks were replaced
by Data Acquisition palettes.
A large number of readings were recorded during
observations of monitoring performed by the developed system. Fig. 5 show some typical distortions or disturbances
captured during monitoring of simulated disturbances in the
laboratory.

Fig.5. PQ disturbances monitored by the developed method

The waveforms captured show different power quality
events or disturbances, including voltage sag, swell, interruptions, transients, harmonics etc.
Capturing and monitoring of power spectrum are done by
developing virtual instrument with the Front panel shown in Fig.4, which has been found to give efficient responses for constant voltage with changing load and also for a constant load with variable input voltages(for single or three phase system).
The Virtual Instrument will function as Sub-VI of PQMS,
for monitoring of power spectrum, including instantaneous power, apparent power, active power, reactive power, instantaneous distortion power. The table I shows the summary report of power quality monitoring of 200 KVA UPS Input at NITS Systems.

Table I

Power Quality Summary of UPS Input at NITS Systems:

Location: 200 KVA UPS Input at NITS Systems
System used Developed PQMS
Date Started Time
Started Date Ended Time
Ended
12/31/2011 4:41:00
PM 12/31/2011 4:51:00
PM

Parameter Ph 1 Ph2 Ph3 Sum
Frequency 49.84
Line Voltage V 410.5 407.8 408.3
V Thd % 2.5 2.6 2.5
Line Current A 81.3 75.1 75.7
I Thd % 11.5 12.6 10.7
Input Watts 12499.7 11030.56 12096.4 35626.7
Watt hours in
10 mins 2117.04 1866.28 2036.44 6019.76
PF 0.651 0.621 0.679
DPF 0.656 0.628 0.684
Predominant %current Harmonics
Order Ph1 Ph2 Ph3
5th 7.4 8.4 6.6
7th 2 1.7 1.8
9th 1.3 1.5 0.6
11th 2.7 3.6 2.5
13th 7.2 7.7 6.6

The table II shows the summary report of power quality
monitoring of 200 KVA UPS output at NITS Systems.
The tables I and II show extract of actual recordings, which
would be helpful for assessment of power quality of the
systems. UPS input has about 15% input current harmonics distortion as it has 12 pulse rectifier at the input. Similarly it has been observed that the blower motors which have thyristor rectifiers at input are affected due to a lot of input current
harmonic distortion. This completely satisfies the result
observed from the panel of the system and thus shows its high (nearly100%) accuracy in monitoring of harmonics (THD) and supply voltage and current. Observations of the system are compared with a Yokoga wa Power Quality Analyzer
(Model W1806-F-HE/EX6/G5) and found coincidence of
most of the readings (few deviations between 0.5 to 1.0 % of
true value), and thus shows the accuracy and reliability of the developed system.

Table II

Power Quality Summary of UPS Input at NITS Systems:

Location: 200 KVA UPS Output at NITS Systems
System used Developed PQMS
Date Started Time
Started Date Ended Time
Ended
12/31/2011 5:05:00
PM 12/31/2011 5:15:00
PM

Parameter Ph 1 Ph2 Ph3 Sum
Frequency 49.88
Line Voltage V 400 399.3 400.7
V Thd % 0.8 0.9 1
Line Current A 66.5 44.7 41
I Thd % 43.2 59.6 62.5
Output Watts 13874.8 8532.46 7895.23 30302.5
Watt hours in
10 mins 2295.42 1405.69 1309.56 5010.7
PF 0.902 0.829 0.833
DPF 0.982 0.967 0.987
Predominant %current Harmonics
Order Ph1 Ph2 Ph3
2nd 1.3 4.1 4.7
3rd 38.3 51.9 53.4
4th 1.7 5.5 4.2
5th 15 18 19.7
7th 8 10 14.4
9th 8.4 16.1 16.9
11th 4.2 7.6 8.3
13th 1.7 3.5 3.4

Power quality monitoring pie diagram of a plant supplied
by solar energy at Silchar has been shown in fig.6. The observations of solar irradiation monitored for the period July-
August, 2011 and for a week are shown in fig.7. The system
monitors solar energy at the source as well as at the customers end. The detailed analysis of case studies of power quality monitoring in sustainable energy system will appear in authors other papers.

Fig. 6. Power quality monitoring pie diagram of a plant
supplied by solar energy at Silchar.

Depending on the requirements of monitoring, different or
respective sub-VIs can be added with the main VI and thus we can monitor all the feasible and required qualities with a single Virtual Instrument(VI).

Acquired data can be exported in different formats in a text
file, HTML or directly in common software products or evaluation software provided by National Instruments. It has
been found during investigations and analysis that the sources
of disturbances can be determined by simultaneous measurement or monitoring of voltage and current. Custom power devices like STATCOM/DVR/ UPQC help to restore or maintain PQ within limiting values. The characterization and extraction of features are
enhanced with the combination of Higher-Order Statistics
(HOS) and quadratic discriminant along with the software [15]. This has improved the function of data processing, image reconstruction, harmonic retrieval, time delay estimation, adaptive filtering, array processing and blind equalization.
The developed PQM system is simple due to user friendly
graphical interfaces and uses a reduced cost platform in
comparison to other sophisticated methods involving costly equipments and accessories.

Fig.7. Solar irradiance monitored by the developed system

VI. CONCLUSIONS

Global economy has been affected due to poor PQ of the supply systems. Power qualities of sustainable energy are also
affected due to increasing sensitivity of the equipments and devices used by the customers, and need proper monitoring and analysis for mitigation purposes. Majority of the existing methods of PQ monitoring methods have significant
drawbacks in their response like slow or inability to monitor
all the disturbances.
The authors have presented a new power quality monitoring
system using virtual instrumentation based on LabVIEW software and National Instrument’s Data acquisition system.

The characterization and extraction of features are enhanced
with the combination of Higher-Order Statistics (HOS) and
quadratic discriminant along with the software. The
performances of the system has been tested on single phase and three phase systems run by existing power supply, and specially in monitoring of power qualities in sustainable energy systems. The system is suitable for utilities and end
users for its efficiency of monitoring power qualities at the
source as well as at users end.
The system can be upgraded to any advanced or newer
version of LabVIEW and the hardware can be replaced by any compatible data acquisition system or card.

VII. FUTURE EXTENSION

PQ is still an open issue since a useful, automated, on-line,
robust and intelligent monitoring system is still missing.. No single existing method is sufficient to monitor all the PQ
parameters with fastness and accuracy. This work can be
extended for predicting future power quality of sustainable energy system, especially solar energy and automatic application of mitigations against poor PQ.

A
CKNOWLEDGMENT

The authors thank authorities of NIT, Silchar, and AMU,
Aligarh for providing necessary facilities to perform different
monitoring works using institute and university laboratories.
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