Energy and Power Engineering, 2013, 5, 698-702
doi:10.4236/epe.2013.54B135 Published Online July 2013 (http://www.scirp.org/journal/epe)
Hybrid Power System Power Flow Analysis
Petr Bilik, Jakub Manas, Jan Zidek, Jiri Koziorek
Faculty of Electrical Engineering and Computer Science, VSB-Technical University of Ostrava, Czech Republic
Received March, 2013
ABSTRACT
Hybrid power supply system consists of a number of ind ependent and different sources of electrical energy with differ-
ent operating times during different seasons and with energy storage system. Deployment of a hybrid power system is
expected in places outside the normal distribution network. For the further research and improvements it is necessary to
know in detail the power flow from various sources to the load or to storage battery depending on different seasons. The
paper presents data analysis results computed by application developed for detailed analysis of power flows within hy-
brid power system. Developed application analyses the data from the monitoring system. Data has been acquired and
recorded within last year. This data is visualized as power flows in the individual hybrid power system circuits. To-
gether with electrical po wer the effectiveness and performance parameters of rectif ier and DC/AC converter are evalu-
ated. The paper describes achieved results and needs for further improvements of such solution.
Keywords: Hybrid Power Systems; Data Analysis; Application Software
1. Introduction
A hybrid power system consisting of two photovoltaic
and two wind power stations came to existence last year
at VŠB-TU Ostrava. As its behavior has to be monitored,
the need for measurement and visualization at the hybrid
system arose. The article describing the monitoring sys-
tem was presented at Conference EPE 2011 and its brief
summary is found in Part 2. Now, the hybrid system has
been in operation for more than year and a lot of valu able
data have been collected since then. Therefore, the ap-
plication for evaluation of the measured data, which this
article wants to cover, has been created.
2. The Hybrid Power System by VŠB-TU
Ostrava
The hybrid power system consists of two photovoltaic
and two wind power stations that together charge the
accumulator battery. The battery is also used for the feed
of two lamps of the public lighting. The block diagram of
the system is in Figure 1. The hybrid system uses two
photovoltaic panels of whose performance is 130 W
(FV1) and 200 W (FV 2). The transmission of the energy
from the FV panels to the batteries is controlled by the
regulator (REG). The wind power station VT1 uses for
the conversion of wind energy to electrical energy a 200
W generator with a built-in regulator of charging, so the
regulator can be connected directly to the batteries.
At VT2 is, on the other hand, used a 200 W synchro-
nous 3f generator, whose performance is transferred to
the battery via the rectifier and the regulator (the block
with the diode, see Figure 1). The appliances in the sys-
tem are represented by two lamps of the public lighting
(VO1 and VO2). VO1 is an LED lamp with the input of
40 W and VO2 is a sodium-vapour lamp with the input
of 50 W. Both lamps are operated with the voltage of 230
Vac, which is supplied there by the DC/AC converter.
The battery consists of NiCd accumulators and its result-
ing capacity is 340 Ah at the nominal voltage of 12 Vdc.
[1]
3. The Monitoring System of the Hybrid
Power System
The monitoring system is built on the HW platform NI
CompactRIO. The voltage and currents in all branches of
the circuit are measured, except for the appliances (the
input of VO1 and VO2 is measured together). The
Figure 1. The block diagram of the hybrid power system.
[1]

L. D. NIEM ET AL. 699
individual measuring points are shown in Figure 2. The
monitoring system does not take any electrical energy
from the batteries of the hybrid power system; its feed ing
is dealt with separately and provides uninterrupted op-
eration (UPS). [1]
All the measuring HW is located in the existing out-
door distribution box where there is the whole electrical
equipment of the hybrid power system. This box pro-
vides protection against weather conditions, but it is not
thermally insulated. This places increased demands on
the operating temperature of e a ch component. [1]
All the components are placed on a metal structure lo-
cated in the box. The dimensions of the free internal
space of the box must be taken into consideration when
choosing the components and the layout design. [1]
The measured data are stored in text files (daily re-
cords).
The current measured data are visualized on the web-
site by means of a web server (Figure 3), which is oper-
ated on a remote PC. The data are also backed up on the
PC and can be downloaded by authorized users with the
help of the FTP access.
Figure 2. The block diagram of the measured system and the measuring points. [1]
Figure 3. Visualization of the measured data with the help of the w eb interface .

L. D. NIEM ET AL.
700
4. Application for Evaluation of the Measured
Data
The developed application for evaluation of the measured
data (application) enables graphical display (Figure 4) of
the measured and computed data (performance streams,
component efficiency). The users can specify the accu-
rate time period (the minimum resolution is 1 day) or
they can choose from the menu “The last 3 days”, “The
last week”, …, “The last year” (Figure 5).
The application enables to display up to 4 parameters
in the graph at the same time, when each parameter has
its own vertical axis with its scaling. The application then
processes these data statistically so that the data are di-
vided into certain time parts so that the total number of
samples to the graph was approximately a thousand for
each course of the parameter. The algorithm of searching
for the minimum and maximum value of the parameter
and their display together with their time in the correct
order is the reduction of the data. [3]
Examples of the Measured Data in the Graphic
Form
For the illustration purposes, the results are shown in the
graphic form. It is necessary to point out that the applica-
tion serves for evaluation of the current state of the hy-
brid system and for its optimization, so it is necessary to
take the displayed results with a pinch of salt.
Figure 4. GUI of the application created for the display of the data evaluated in the graph.
Figure 5. GUI of the application created for the evaluated data selection.

L. D. NIEM ET AL. 701
So as something was not d isplayed in the optimum scale
in the graphs, the courses for only one day are shown here.
Figure 6 shows charging of the battery from photo-
voltaic panels. Parameter “P3” is the performance sup-
plied to the regulator, “P3_REG” is the performance
supplied from the regulator, “EF_ REG_FVtoBAT” is the
efficiency of the regulator (from the photovoltaic panels
to the battery). The efficiencies are computed for per-
formances exceeding 10 W (a user-selectable value), so
the efficiency graph is not continuous.
Figures 7 and Figure 8 show the discharging of the
battery into the lights (VO1 an d VO2). In Figure 7, there
is parameter “P3_REG”, i.e. the performance supplied
from the battery to the regulator. Parameter “P4” is the
performance flowing from the regulator to the DC/AC
converter and “EF_REG_BATtoCONV” is the efficiency
of the regulator (from the battery to the converter). Fig-
ure 8 shows parameter “P5”, i.e. the performance con-
sumed in the lights, “EF_ CONV” is the efficiency of the
converter and “U1” is the voltage at the battery. In the
time of approximately 6/7/ 2011 2:15, the regulator eva-
luated that the voltage at the battery is low and stopped
its discharging.
5. Conclusions
The goal of this article was to describe the application for
evaluation of the measured data from the hybrid power
system consisting of two photovoltaic and two wind
power stations.
Figure 6. An example of the application output (charging of the battery from photovoltaic panels).
Figure 7. An example of the application output (discharging of the battery into the lights).

L. D. NIEM ET AL.
702
Figure 8. An example of the application output (discharging of the battery into the lights).
The application allows comfortable and efficient off-
line analysis of internal phenomena in the hybrid power
system at VSB-Technical University of Ostrava. The first
version of application was developed in 2011 and it is
still improved according to final user needs. The actual
version of the monitoring system from 2013 provides
basic monitoring of EMC quantities also and thus it is
used for educational purposes. New features were mostly
allowed by using latest version of graphical development
environment LabVIEW by National Instruments which
made big improvement in cRIO controller and cRIO
FPGA programming efficiency. Issues like harmonic
components on AC parts of circuit and even DC parts of
circuit can be visualized to students. To visualize EMC
phenomena in understandable way is very important for
educational purposes [2].
When the application NI DIAdem for the analysis of
the measured data is used, the creation of measurement
protocols is much comfortable and faster. These signifi-
cant time savings enable the users to concentrate their
time and energy on substantial issues during the research
of the hybrid system. The application uses the concept of
virtual instrumentation, so it is flexible and expandable
according to the future requirements without the need of
higher time sources.
6. Acknowledgements
This work was supported in part by The Ministry of
Education, Youth and Sports of Czech Republic under
the project KONTAKT II registration number LH12183
and in part by VSB-Technical University Ostrava,
FEECS under the project SGS registration number
SP2013/203.
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the Hybrid Power System,” In 12th International Scien-
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[2] P. Drabek and V. Kus, “The Education of EMC at the
UWB,” In Electrical Power Quality and Utilization EP-
QU 2011, pp. 1-6, Lisboa, Portugal, 2011.
[3] M. Tutsch, P. Vojcinak, J. Koziorek and M.
Skrepek, “Using Automated Evaluation of Effi-
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