Grid-connected Systems Powered by Solar Energy Implemented with

Fuzzy based Voltage Source Converters

RAJA SATHISH KUMAR1, Y. V. BALARAMA KRISHNA RAO2,*,

VENKATA KOTESWARA RAO N.3

1Department of Electrical and Electronics Engineering,

Keshav Memorial Institute of Technology,

Hyderabad

INDIA

2Department of Electrical and Electronics Engineering,

Guru Nanak Institutions Technical Campus, Ibrahimpatnam,

Telangana-501506,

INDIA

3Department of Electrical and Electronics Engineering,

Stann's College of Engineering and Technology,

Chirala, Andhra Pradesh- 523187,

INDIA

*Corresponding Author

Abstract: - Solar energy systems connected to the electrical grid are known as grid-tied solar power systems or

solar power-connected grid systems. Grid-tied solar inverters are only capable of producing active electricity

since they are made to produce power at a unity power factor. The grid alone can meet the load's requirement

for reactive power. Reactive power drawn from the grid relative to active power has increased significantly

with the sharp rise in the deployment of distributed energy resources based on renewable energy. This has an

impact on the grid's power quality. The amount of reactive power that the grid must supply will decrease if the

grid-tied solar inverter is designed to be intelligent enough to provide reactive power in addition to active

power. This work's primary goal is to generate the necessary pulses for a three-phase inverter, which will aid in

producing reactive power and ultimately help achieve the work's primary objective. Fuzzy logic is a complex

approach that takes advantage of the flexibility and adaptability of fuzzy systems to manage Voltage Source

Converters (VSCs) for three-phase inverter operation. The primary circuit is simulated in the

MATLAB/Simulink environment, giving the desired results.

Key-Words: - Voltage Source Converters (VSCs), Fuzzy logic systems, Reactive power, Solar energy, Grid

connected systems, Power factor.

Received: March 8, 2023. Revised: December 15, 2023. Accepted: December 27, 2023. Published: March 12, 2024.

1 Introduction

Traditionally, grid-tied solar inverters have been

built to run at unity power factor, which implies that

they can only generate active power. Electrical loads

tend to use more inductive reactive power since they

are primarily inductive loads. This reactive power

requirement is now met solely by the grid. The

grid's performance is impacted by the growing

number of Distributed Energy Resources (DERs)

that only supply active power, resulting in a low site

power factor from the utility's perspective. In the

past, FACTS devices were used to inject and absorb

reactive power to mitigate power quality difficulties.

Depending on the need, several FACTS device

kinds, including series, shunt, series-series, and

series-shunt, are employed. However, these devices

have several errors, including enormous size, high

cost, large installation space, etc. These factors

make it necessary to control the reactive power flow

within the power system network since this could

also have an impact on voltage regulation. Control

schemes to provide reactive power alongside active

WSEAS TRANSACTIONS on POWER SYSTEMS

DOI: 10.37394/232016.2024.19.8

Raja Sathish Kumar,

Y. V. Balarama Krishna Rao, Venkata Koteswara Rao N.

E-ISSN: 2224-350X

Volume 19, 2024

power for grid-tied solar inverters are explored. The

use of VAR compensators by more grid-tied

inverters will aid in grid voltage management and

lessen the requirement for pricey capacitor banks.

There are two primary ways to utilize the reactive

power capability of smart inverters: either by

oversizing the inverter or by reducing active power,

[1], [2]. There is an additional expense associated

with oversizing the inverter that must be considered.

Active power curtailment refers to the decrease of

active power and can be achieved in a variety of

ways. For example, the maximum power point can

be fixed at, say, 70% of the rated power or the PCC

voltage can be used as the reference voltage.

Owners of PV systems make less money using this

strategy because the installed solar PV panels

produce less energy, [3], [4], [5].

Overuse of traditional fossil fuels has destroyed

the environment and produced power in recent

decades. Resources based on renewable energy (RE)

are implemented as an unconventional and

alternative power source to address this problem.

Feed-in tariffs, the cost of PV panels, and supportive

government regulations have all incentivized

residential and commercial customers to make use

of this technology and support the production of

sustainable electricity. On the other hand,

combining renewable energy sources (RE) with

conventional energy sources improved the

distribution network's dependability, particularly

under bad circumstances, and also reduced the

different limitations of RE resources. Because PV

power is stochastic, RE-based grid-interfaced

systems use storage devices (compressed air,

batteries, and ultra-capacitors) to smooth out the

power flow. The battery, which is connected to the

DC link using a bidirectional converter (BDC)

circuit, is used to regulate the flow of electricity, [6].

When integrating renewable energy sources (RE)

with the AC grid, the voltage source converter

(VSC) provides better power quality and control

over the flow of both active and reactive electricity.

Grid code requires RE sources with distribution

networks to have autonomous power control (active

and reactive), which serves as additional grid

assistance, [7], [8]. Consequently, to link with the

AC grid directly, a grid-integrated uninterruptible

dual-mode power converter is needed. The power

quality of grid current and voltage is distorted by the

presence of nonlinear loads at the AC side, such as

computers, welding machines, lights, special

machines, etc., [9]. To address this problem, a grid-

interfaced converter is used to implement

changeable digital filter-based control, providing

harmonic current to the nonlinear loads. According

to IEEE standard 519, [10], the power quality at the

grid side thereby continues to be harmonic Several

control algorithms are used to enhance the power

quality of the hybrid solar PV-BES coupled with the

grid-interfaced system (HPVBGS), [11]. The

estimate of fundamental frequency components

from the distorted input signal has made adaptive

filtering renowned. These digital filters are very

efficient and offer very versatile parameter

realizations, [12], [13]. To obtain the desired filter

structure in variable digital filters, delay elements

are substituted by all-pass filter structures of the

appropriate order. The adaptive algorithms' least

mean square (LMS) and least mean fourth (LMF)

emphasize adaptively altering the weight, [14].

When the grid is not optimal, an adaptive lattice

filter is used in the active power filter to compensate

for harmonics. Such FIR-based digital filters have

also been put through testing by some authors in

frequency adaptive synchronization units for grid

systems. Other methods have also been proposed for

harmonic compensation: fixed frequency PLL

(FFPLL), dual SOGI (DSOGI-PLL), synchronous

reference frame (SRF-PLL), and second-order

generalized integrator (SOGI-PLL), [15]. It removes

the requirement for a low-pass filter (LPF) by

identifying the essential component of the non-

sinusoidal waveform. Nevertheless, to handle highly

polluted environments, these structures still require

an extra filtering step. In this research, a control

scheme based on variable digital filtering (VDF) is

proposed and applied to mitigate load current

harmonics in HPVBGS. Forming the control

independent of load behavior validates the filter's

effective operation in the presence of a highly

nonlinear load. In this work, switching pulses for

VSC are controlled via dual-mode operated digital

filter-based control, [16], [17]. In HPVBGS,

harmonics are mitigated via the VSC. The single-

phase input signal is transformed into distortion-free

sinusoidal vectors (in-phase and quadrature-phase)

in the α-β frame by the single-phase quadrature

signal generator (QSG), which is also necessary for

the D-Q transformation needed to generate a

reference current, [18], [19].

2 About Fuzzy Logic Controller

(FLC)

The rule-based fuzzifier interface and fuzzifier are

two crucial FLC phases. In addition to the VSC,

another controller included in the suggested control

architecture is the FLC. Three blocks are crucial in

producing output signals that are then utilized to

WSEAS TRANSACTIONS on POWER SYSTEMS

DOI: 10.37394/232016.2024.19.8

Raja Sathish Kumar,

Y. V. Balarama Krishna Rao, Venkata Koteswara Rao N.

E-ISSN: 2224-350X

Volume 19, 2024

generate controlling signals for the converter

switches. Here, the fuzzification block receives the

change in error and error value, and this block

output is provided as the fuzzy inference's input

[20]. Figure 1 shows the fuzzy inference block, will

produce output following the comparison with the

rule base, which is then used as input for

defuzzification. Eventually, the necessary output

will be produced. This procedure will then carry on

for the duration of the circuit's operation.

INTERFACE ENGINEFUZZYFIER DEFUZ

ZIFIER

COMPUTATED

ERROR

DC-DC CONVERTER

RULE BASE

REFERENCE

VOLTAE

Fig. 1: Block diagram representation of FLC

3 Proposed Model Representation

Solar Power

Generation

DC-DC Boost

Converter

Three Phase

Inverter

Three Phase

Measurement

Three

Phase

Transfor

mer

Power

System

Network

Voltage

Source

Converter

Control

Fig. 2: Block diagram representation with the

proposed technique

Figure 2 represents the proposed model with a

voltage source converter with the fuzzy logic

controller. The complete block diagram includes PV

generating systems which are used to produce the

power to the load in DC form with some voltage

level. The DC-DC converter at the PV side is used

here to step up and regulate the output voltage of the

PV system. Further, the three-phase inverter is used

here to convert the DC voltage of the rectifier into a

three-phase AC supply. The three outputs of the

converter are given to the power system to feed the

loads through three-phase transformers with step

voltage which will help to reduce the line losses and

will improve the overall system efficacy. The main

aim of this model is to develop the controlled pulse

signals to the switches of the three inverters with

proper control technique and this will be achieved

with the use of a fuzzy logic controller which will

lead to producing less ripple content out response

and improve the overall system performance.

Additionally, the projected system will able to

provide the reactive power by the non-conventional

energy source which will give the extra benefit to

the system and reduce the burden on the main grid.

4 Results and Discussions

In this section results related proposed technique

were projected with power, voltage, and current

waveform representations. The main circuit was

implemented in MATLAB/Simulink environment

and simulated, obtaining the necessary results.

Fig. 3: Active power curve representation of the

generated by the non-conventional energy source

Figure 3 shows the active power production

generated by the PV array based on the available

irradiance and temperature. In this work, the

irradiance value considers the max value as 1000

w/m2 and the minimum value as 250 w/m2. Parallel

the temperature value is also considered the

dynamical value with a minimum of 25 degrees and

max value is 50 degrees. Both irradiance and

temperature waveforms are represented in Figure 10

and are provided to the PV cell as input to obtain

necessary power generation.

Fig. 4: Reactive power curve representation of the

generated by the non-conventional energy source

The reactive power production using

nonconventional energy sources is represented in

Figure 4. This reactive power production will reduce

the overall extra burden on the grid system which

helps to improve the overall system efficiency.

WSEAS TRANSACTIONS on POWER SYSTEMS

DOI: 10.37394/232016.2024.19.8

Raja Sathish Kumar,

Y. V. Balarama Krishna Rao, Venkata Koteswara Rao N.

E-ISSN: 2224-350X

Volume 19, 2024

Fig. 5: DC-DC Converter output parameters

representation connect at PV Array side

Figure 5 shows the current and voltage value

representation of the converter which is connected

to the PV array side. Here the current value of the

converter follows the irradiance curve.

Fig. 6: Representation of the output parameters at

the grid side

Grid side current and voltage values

representation is shown in Figure 6. Here the grid

side voltage looks high and the current value is less

since using step up transformer output voltage of the

three-phase inverter is increased and the current

value is reduced.

Fig. 7: Representation of the three-phase inverter

output parameters

The three-phase inverter output voltage and

current values are represented in Figure 7. Here the

current values seem more than the grid current value

where whereas voltage value is more at the grid side

compared to the phase output voltage value.

Fig. 8: Modulation index and actual, reference

voltage values representation

The modulation index value and actual and

reference voltage values of the converter are shown

in Figure 8.

Fig. 9: PV Array output parameters representation

Figure 9 demonstrates the output parameters of

the PV array which includes voltage, current, and

power curves, here the current value Cleary flowed

the irradiance value which is input to the solar plant.

Fig. 10: Input Parameters representation of the solar

system

Input parameters to the PV system with

irradiance and temperature are represented in Figure

10.

5 Conclusion

RES and utility integration is one of the most

important steps towards a smart grid. Solar power

generation is one of the renewable energy sources

that the government supports. The increasing

availability of solar light and the rapid advancement

of power electronics technology have led to the

growing popularity of photovoltaic systems. The

WSEAS TRANSACTIONS on POWER SYSTEMS

DOI: 10.37394/232016.2024.19.8

Raja Sathish Kumar,

Y. V. Balarama Krishna Rao, Venkata Koteswara Rao N.

E-ISSN: 2224-350X

Volume 19, 2024

advantage of PV systems is that, depending on their

operational and technical specifications, they can

function in both standalone and grid-integrated

modes. Grid-connected photovoltaic systems have

shown themselves to be a workable alternative for

heavily stressed grids. As a result, the researcher's

ongoing efforts have allowed the modest standalone

PV system to become a grid-tied PV system. A grid-

tied photovoltaic system's primary benefits are its

ease of use, comparatively cheap maintenance and

operation expenses, and lower electricity bills. By

grid-tied PV system specifications also presents a

significant obstacle. To create the necessary active

and reactive powers for the linked loads in the entire

system, the synchronization between the inverter

and the grid is studied. Key ideas in grid

synchronization are outlined.

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DOI: 10.37394/232016.2024.19.8

Raja Sathish Kumar,

Y. V. Balarama Krishna Rao, Venkata Koteswara Rao N.

E-ISSN: 2224-350X

Volume 19, 2024

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

The authors equally contributed to the present

research, at all stages from the formulation of the

problem to the final findings and solution.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

No funding was received for conducting this study.

Conflict of Interest

The authors have no conflicts of interest to declare.

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(Attribution 4.0 International, CC BY 4.0)

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WSEAS TRANSACTIONS on POWER SYSTEMS

DOI: 10.37394/232016.2024.19.8

Raja Sathish Kumar,

Y. V. Balarama Krishna Rao, Venkata Koteswara Rao N.

E-ISSN: 2224-350X

Volume 19, 2024