[IEEE 2019 International Ural Conference on Electrical Power Engineering (UralCon) - Chelyabinsk, Russia (2019 10 1-2019 10 3)] 2019 International Ural Conference on Electrical Power Engineering (Ural

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2019 International Ural Conference on Electrical Power Engineering (UralCon) 
 
978-1-7281-1743-0/19/$31.00 ©2019 IEEE 
Power Quality in Microgrids with Distributed 
Generation 
 
Andrey V. Shalukho 
Electric Power Engineering Institute 
Nizhny Novgorod State Technical University 
n.a. R. E. Alekseev 
Nizhny Novgorod, Russia 
shaluho@nntu.ru 
Ivan A. Lipuzhin 
Electric Power Engineering Institute 
Nizhny Novgorod State Technical University 
n.a. R. E. Alekseev 
Nizhny Novgorod, Russia 
lipuzhin@nntu.ru 
Alexander A. Voroshilov 
Electric Power Engineering Institute 
Nizhny Novgorod State Technical University 
n.a. R. E. Alekseev 
Nizhny Novgorod, Russia 
alejandro.voroshilov@yandex.ru 
 
 
Abstract—The actual direction of increasing the efficiency of 
distributed generation and renewable energy resources is the 
aggregation of low-power sources in a microgrid or virtual 
power plant. There are many features in these systems: a large 
number of semiconductor equipment, stochastic nature of the 
RES generation and bi-directional power flows. Therefore, an 
important task is to ensure the required power quality 
indicators. The article is devoted to experimental studies of the 
influence of distributed generation sources on the power quality 
at consumer buses. A physical model of a microgrid was 
assembled containing solar and wind power plants simulators 
with the help of a laboratory bench. The power quality 
indicators, such as voltage fluctuations, frequency deviation, 
non-sinusoidality were studied for three operation modes. 
Causes of power quality violations have been identified. 
Solutions to reduce the negative impact of distributed generation 
on the power quality in the microgrid are proposed. 
Keywords—distributed generation, renewable energy 
resources, microgrids, bi-directional power flow, power quality 
I. INTRODUCTION 
Nowadays, the development of distributed generation 
(DG) and renewable energy sources (RES) is an important 
direction in energy security ensuring for the remote consumers 
[1, 2]. A new approach to improving the efficiency of 
renewable energy usage is to aggregate distributed objects 
with their own RES in multi-scale smart systems (minigrid, 
microgrid, nanogrid or virtual power plants) that have the 
ability to exchange electricity between objects. 
Technical devices (energy convertors and switching 
devices, information and communication equipment) allowing 
to ensure information interaction and energy transfer from 
objects with their own power plant to the centralized electrical 
network (CEN), are already available on the electricity market. 
However, the implemented projects on the aggregation of low-
power RES into a single system are rare [3–5], while they are 
absent in Russia. 
The development of DG aggregation technologies requires 
solving a number of technical problems. Many companies, 
organizations and scientific teams are engaged in research in 
this area [6–8]. The most studied areas are: ensuring stable 
operation [9, 10], selecting effective structures [11, 12], 
ensuring information and energy exchange between elements 
[13–15], ensuring the correct operation of relay protection and 
automation [16, 17]. 
Distinctive features of systems with DG are: use of 
semiconductor equipment (inverters, charge controllers), bi-
directional energy flows between the objects and stochastic 
nature of the RES generation. These factors negatively affect 
the power quality at consumer buses [18, 19]. Therefore, an 
important task is to provide required power quality for 
microgrid consumers [20, 21]. 
Researches of the power quality in systems with DG are 
not sufficiently covered in scientific papers. Mathematical and 
computer modeling is used in most studies on this subject [22]. 
These approaches do not allow to fully take into account the 
technical features of the equipment (operation algorithms) and 
to obtain objective data. Therefore, it is necessary to 
supplement the theoretical studies of power quality in systems 
with DG with the results of physical modeling. 
The laboratory bench of a virtual power plant with 
renewable energy sources [23] was developed at NNSTU. It is 
designed to study the operation modes of systems with DG. 
The purpose of this paper is an experimental research of the 
power quality in a system with DG, and the development of 
recommendations for improving the power quality. 
II. MATERIALS AND METHODS 
A model of a microgrid with DG was assembled at the 
laboratory bench for conducting experimental research. The 
following units are included in this model (Fig. 1): 
uninterruptible power source (UPS), regulating transformers 
(AT), active (R) and motor loads (Z), solar and wind power 
plant simulators with storage battery (GB) connected to the 
microgrid using single-phase converters (UZ). Energy sources 
and consumers are aggregated into the microgrid. The 
microgrid is connected to an external network (centralized 
electrical network (CEN)) with the help of UPS and 
transformers. 
The work has been carried out with the financial support of the Ministry 
of Science and Higher Education of the Russian Federation (state task 
№13.2078.2017/4.6 on May 31, 2017). 
54
2019 International Ural Conference on Electrical Power Engineering (UralCon) 
0.4 kV
RW2
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RB
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Q3 Q4
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=
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UZ2
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=UZ4
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Wind Plant
SP
CEN
- installation site of power quality analyzers
1
2
 
Fig. 1. Simplified single-line diagram of the simulated microgrid with DG 
sources. 
The main parameters of the stand are presented in table I. 
TABLE I. LABORATORY BENCH PARAMETERS 
Parameter Value 
Input voltage, V 220 
Active load, W 1900 
Reactive load, VA 550 
Wind generator simulator power W 2000 
Power simulator solar power, W 2000 
These equipment and construction of the microgrid allow 
the study of three operation modes: 
1. microgrid consumers receive power only from the CEN; 
2. microgrid consumers receive power from DG and CEN; 
3. microgrid consumers receive power only from DG and 
surplus electricity is provided to the CEN. 
Oscillograms of current and voltage were obtained with the 
help of the power quality analyzers HT PQA824, and the 
measurements of power quality were made: voltage 
fluctuations, frequency deviation, non-sinusoidality. Values of 
the power quality indicators were recorded at the connection 
points of DG sources to the microgrid (point 1, Fig. 1) and at 
consumers buses (point 2). Control of power quality indicators 
was carried out in accordance with the requirements [24]. 
A research program was developed for each of the modes: 
• turn on the UPS: microgrid receives power from CEN; 
• turn on the DG sources: first solar plant, then after 
reaching the nominal mode, wind plant; 
• turn on and stepwise regulation of the load of the 
consumer without own generation sources; 
• stepwise regulation of the voltage at the connection 
point of the microgrid to the CEN by transformers; 
• turn off the DG sources and UPS. 
III. EXPERIMENTAL RESULTS 
Researches of the three modes of microgrid operation have 
been conducted. The values of voltage fluctuations, frequency 
deviations and voltage harmonic composition are investigated. 
Microgrid operation modes are described by the following 
equations: 
 B CON SB CEN DGP P P P P+ ± = + (1) 
 B CON RPC CEN DGQ Q Q Q Q+ ± = + (2) 
where P, Q – active and reactive power; indexes: B – 
ballast load, C – consumers load, SB – storage battery, CEN – 
centralized electrical network, DG – distributed generation, 
RPC – reactive power compensation. 
It has been established that in modes 2 and 3 a brief 
imbalance of power is possible. This leads to short-term 
increases in current in modes 2 and 3 - up to 70% of the 
parameters of the normalmode; and increases in voltage - up 
to 11.5% of the nominal value (Fig. 2). These factors must be 
considered when choosing the relay protection and automation 
settings. The power of DG sources is small compared to CEN, 
so the problem of excess power from the sequential connection 
of DG sources does not lead to system failures. To avoid large 
deviations of current and voltage levels, it is necessary to 
exclude the possibility of simultaneously switching on DG 
sources. 
Frequency deviation is also possible when DG sources 
supplies the microgrid in modes 2 and 3. Frequency deviations 
above the normal permissible value (0.2 Hz) were not 
recorded in the investigated microgrid (Fig. 3). 
Since the connection of RES is carried out with the help of 
power converting devices, the analysis of the spectrum of the 
highest harmonic components in the investigated microgrid is 
relevant. 
The measurement of harmonic components was carried out 
at the connection point of consumer without own generation 
sources to the microgrid (point 2, Fig. 1). 
55
2019 International Ural Conference on Electrical Power Engineering (UralCon) 
 
a) 
 
b) 
Fig. 2. Oscillograms of current and voltage at the connection point of 
consumer to the microgrid at the start of power output from the DG: a - 
with one DG; b - with two DG. 
 
Fig. 3. Graph of frequency changes in the microgrid with DG. 
The research of harmonic components showed that the 
number of higher harmonics, including multiples of three, 
sharply increases when RES is connected to the microgrid 
using single-phase converters in modes 2 and 3 (Fig. 4, a). 
The negative consequences arising from the presence of 
higher harmonic components are overheating of transformers 
and rotating machines, neutral overload, increased voltages 
between neutral and earth, failure of capacitor banks, tripping 
of circuit breakers and fuses, improper operation of electronic 
equipment and generators, energy loss and network bandwidth 
loss. These problems lead to additional costs, such as higher 
energy consumption, costs due to faster aging of equipment, 
equipment downtime, increased maintenance and repair costs, 
as well as losses due to lower product quality and productivity 
[25]. 
 
a) 
 
b) 
Fig. 4. Spectrum of higher harmonic voltage components on bus of 
consumer: a - without own generation; b - with own generation. 
Possible approaches to reducing the non-sinusoidal 
relationship are the use of filter-compensating devices (FCD) 
and circuit design - connecting converter equipment according 
to the phase multiplication scheme [26]. 
Connection of converters by the phase multiplication 
scheme cannot be an effective solution, since this approach 
56
2019 International Ural Conference on Electrical Power Engineering (UralCon) 
eliminates the possibility of flexible changes in the network 
composition, which is an essential requirement for developing 
networks with DG. 
Similar to the phase multiplication scheme, inefficient in 
networks with distributed generation is the use of passive 
FCD. When using passive FCD, its circuit is tuned to a 
specific frequency. The resonant frequencies of the filter are 
very close to the frequencies of the existing harmonics. When 
designing a passive FCD, careful analysis of the load and 
power quality is of great importance, and the magnitude of the 
network impedance is also very important. Another 
disadvantage of passive resonant filters is that there is always 
the danger of overload due to an increase in load with an 
increased harmonic content and the appearance of other 
sources of distortion. 
The most effective approach to reducing higher harmonics 
is the use of active FCD. The advantage of active filters is that 
they can filter harmonics in systems with varying parameters. 
When using active FCD, neutral conductor currents can be 
reduced (3rd harmonic and harmonics that are multiples of 
three). There is also no mandatory need for careful harmonic 
analysis before designing a filter. A new trend in the use of 
modular filters makes it easy to upgrade without performing 
assembly. In addition to eliminating harmonics, active filters 
can also be used for load balancing, power factor correction. 
The main drawback of active filters is the cost. 
The diagram of voltage harmonic composition on bus of 
consumer with own DG source (Fig. 4, b) shows that the 
values of the harmonic components are within acceptable 
limits. This is due to the fact that the inverters have inside their 
own filter device. 
IV. DISCUSSION 
Based on the conducted research, it can be concluded that 
the connection of DG sources by the single-phase converters 
does not allow adjusting of the power quality in the microgrid. 
Single-phase connection of DG sources leads to a distortion of 
the shape of the sinusoid voltage. 
A scheme for connecting objects with DG to the microgrid 
using three-phase converters (Fig. 5) can be proposed to solve 
this problem. 
This approach supposes a multi-level structure of 
connecting DG sources, which makes it possible to ensure 
high power quality within the microgrid. 
The use of a three-phase system allows one to eliminate 
the negative impact of higher harmonic components without 
installing individual FCD. Permissible levels of harmonics are 
provided with the correct distribution by the phases of the 
objects with DG sources and consumers due to the built-in 
filters of the three-phase inverters. 
This approach involves the division of the microgrid into 
smaller areas. Power supply of a separate section is carried out 
through a three-phase inverter. Consumers with their own 
generation and consumers without their own generation are 
connected to different phases. This solution allows you to 
localize the excess of higher harmonic components on phases 
with consumers connected using their own inverters with the 
FCD function. As a result, the permissible level of harmonics is 
ensured for all consumers within the microgrid. 
A
B
C
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=
= ~
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~
= = ~
UZcont.1 RES1
UZcont.2
RES2
RL1
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GBRES.1
...
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System 1
GBRES.2
RL2
RL3
RL5
~
= = ~
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RES3UZRES.3 GBRES.3
RL4
~
=
~
=
~
=
= ~
UZRESn
UZcont.n RESn
RLn
GBRES.n
System n
 
Fig. 5. Connection of DG sources to the 0.4 kV microgrid by three-phase 
converters. 
Also, the proposed scheme will provide an isolated mode 
of the entire microgrid. When the micro grid is disconnected 
from the CEN, part of the electricity from DG sources can be 
transferred to other consumers in the microgrid. 
However, this approach involves the use of additional 
equipment (three-phase inverter), which leads to a significant 
increase in the system cost. 
V. CONCLUSION 
The article discusses issues of the power quality in 
microgrid with DG. 
The microgrid model with DG (the wind turbine and the 
solar photovoltaic station) was assembled with the help of a 
laboratory bench. Experimental researches of the influence of 
the microgrid operation modes on the power quality have been 
carried out. 
57
2019 International Ural Conference on Electrical Power Engineering (UralCon) 
It has been established that the turn-on of DG sources leads 
to a short-term increase in current and voltage levels in the 
microgrid. This should be taken into account when choosing 
the relay protection and automation systems. The operation of 
DG in the microgrid negatively affects the voltage harmonic 
composition. 
Technical and circuit solutions to ensure the required 
power quality in microgrid with DG were considered. 
REFERENCES 
[1] The energy strategy of Russia for the period until 2030. [Online]. 
Available: http://www.minenergo.gov.ru/aboutminen/energostrategy/ 
[2] A. B. Loskutov, “Solving problems in trasition of electrical industry to 
digital technologies,” Smart Electrical Engineering, no. 1, pp. 9–27, 
2018. 
[3] B. Zhao, X. Zhang, P. Li, and K. Wang, “Optimal sizing, operatingstrategy and operational experience of a bench-alone microgrid on 
Dongfushan Island,” Applied Energy, vol. 113, pp. 1656–1666, 2014. 
[4] M. Braun, Virtual Power Plants in real applications: Pilot 
demonstrations in Spain and England as part of the European project 
FENIX, 2019. 
[5] Wildpolsderied – The Energy Village. [Online]. Available: 
https://www.wildpoldsried.de/ 
[6] O. A. Surzhikova, “Problems and key directions in developing power 
supply in remote and sparsely populated settlements,” Siberian Journal 
of Science, no. 3(4), pp. 103–108, 2012. 
[7] V. P. Kuprianovsky, F. Y. Fokin, S. A. Bulancha, and Y. V. 
Kuprianovsky, “Microgrids – energy, economy, ecology and IT-
services in Smart Cities,” INJOIT, vol. 4, no. 4, pp. 10–19, 2016. 
[8] V. V. Kharchenko, V. B. Adomavichus, and V. A. Gusarov, “RES-
based microgrid as an instrument of distributed energy concept,” 
ISJAEE, no. 2(119), pp. 80–85, 2013. 
[9] P. Ilyshin, “The analysis of dispersed generation influence on power 
system automatics settings and function algorithms,” E3S Web of 
Conf., vol. 58, 2018. 
[10] E. N. Sosnina, A. V. Shalukho, I. A. Lipuzhin, and A. Y. Kechkin, 
“Stability investigation of the virtual power plants electrical systems,” 
IJAER, vol. 10, no. 24, pp. 44363–44368, 2015. 
[11] V. P. Zhukov, D. A. Osipov, D. A. Ulanov, and G. V. Ledukhovsky, 
“Optimal control of the structure and operating conditions of integrated 
power systems,” Vestnik of Ivanovo State Power Engineering 
University. no. 2, pp. 33–37, 2016. 
[12] E. N. Sosnina, A. V. Shalukho, I. A. Lipuzhin, and A. Yu. Kechkin, 
“Optimization of virtual power plant topology with distributed 
generation sources,” Proc. 2018 Int. Conf. and Utility Exhibition on 
Green Energy for Sustainable Development, pp. 1–7, 2018. 
[13] D. Kennedi, “Virtual Power Station - Smart Control of Distributed 
Generation,” Power and Industry of Russia, no. 08(244), pp. 14–15, 
2014. 
[14] E. N. Sosnina, A. I. Chivenkov, A. V. Shalukho, and N. V. Shumskii, 
“Power flow control in a virtual power plant network,” IJRER, vol. 
8(1), рр. 328–335, 2018. 
[15] J. A. Barbosa, R. P. S. Leao, C. F. P. Lima, and M. C. O. Rego, 
“Decentralized energy management system to virtual power plants,” 
RE&PQJ, vol. 1(8), pp. 1079–1085, 2010. 
[16] К. А. Skurihina, А. Yu. Arestova, and D. V. Armeev, “Research of 
microgrid dynamic properties as a part of the power system,” Siberian 
Journal of Science, no. 1(15), pp. 93–102, 2015. 
[17] P. V. Ilyshin, “Peculiarities of the implementation of fission automation 
in generating installations for distributed generation projects,” Proc. Int. 
Conf. and Exhibition Relay Protection and Automation for Electric 
Power Systems, pp. 1–8, 2017. 
[18] D. S. Aleksandrov and E. F. Shcherbakov, Reliability and Quality of 
Power Supply for Enterprises. Ul'yanovsk: UlGTU, 2010. 
[19] L. I. Kovernikova, V. V. Sudnova, and R. G. Shamonov, Electric 
Energy Quality: Current State, Problems and Suggestions for Solving 
Them. Novosibirsk: Nauka, 2017. 
[20] I. S. Kozhuhovskiy, “On the problems of development of small-
distributed energy in Russia,” Proc. ENES 2014, unpublished. 
[21] A. Khokhlov, Y. Melnikov, F. Veselov, D. Kholkin, and K. Datsko, 
Distributed Energy in Russia: Development Potential. Moscow: Energy 
Center of the Moscow School of Management SKOLKOVO, 2018. 
[22] K. V. Suslov, N. N. Solonina, A. S. Smirnov, and Z. V. Solonina, 
“Application of distributed power quality monitoring in MicroGrid,” 
Proc. of Irkutsk State Technical University, vol. 6(89), pp. 185–189, 
2014. 
[23] E. N. Sosnina, A. V. Shalukho, I. A. Lipuzhin, and A. Yu. Kechkin, 
“Laboratory stand of the electrotechnological complex of a virtual 
power plant with renewable energy sources,” RU Patent 185802, 2018. 
[24] GOST 32144-2013. Electric energy. Electromagnetic compatibility of 
technical equipment. Power quality limits in the public power supply 
systems. Мoscow: Standartinform, 2014. 
[25] I. V. Zhezhelenko, Higher Harmonics in Industrial Power Supply 
Systems. Мoscow: Ehnergoatomizdat, 2004. 
[26] K. Shidlovsky and A. Zharkin, Higher Harmonics in Low Voltage 
Networks. Kiev: Naukova Dumka, 2005. 
 
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