STABILIZATION CONTROL FOR ZVRT ENHANCING

IN HYBRID BASED PMSG WIND GENERATOR AND

SOLAR SYSTEM USING SEPIC CONVERTER

A PROJECT REPORT

Submitted by
A.JAGATHEESWARAN -953221105011
R.KEVIN -953221105017
K.SUBBIAH -953221105304
Of
BACHELOR OF ENGINEERING
In
ELECTRICAL AND ELECTRONICS ENGINEERING

UNIVERSITY VOC COLLEGE OF ENGINEERING,

THOOTHUKUDI

ANNA UNIVERSITY: CHENNAI 600 025

MAY 2025

i
 ANNA UNIVERSITY: CHENNAI 600 025
BONAFIDE CERTIFICATE

Certified that this project report is the bona fide work of “Stabilization
Control for ZVRT Enhancing in Hybrid Based PMSG Wind Generator and
Solar System Using SEPIC Converter”

A.JAGATHEESWARAN -953221105011
R.KEVIN -953221105017
K.SUBBIAH -953221105304
Who carried out the project work under my Supervision

SIGNATURE SIGNATURE
Dr. P.ANITHA M.E., Ph.D., Mr.T.THENTHIRUPPATHI.M.E.,
HEAD OF THE DEPARTMENT PROJECT GUIDE
Department of Electrical and Department of Electrical and
Electronics Engineering, Electronics Engineering,
University VOC College of Engineering, University VOC College of Engineering,
Thoothukudi, Tamil Nadu – 628008 Thoothukudi, Tamil Nadu –628008

Submitted for the VIVA-VOCE Examination held on ………………….

INTERNAL EXAMINER EXTERNAL EXAMINER

ii
 ACKNOWLEDGEMENT

First and foremost, we express our deep sense of appreciation to Dr. C.

PETER DEVADAS, M.E., Ph.D., Dean and Head of the Department of
Electronics and Communication Engineering, University VOC College of
Engineering, Thoothukudi, for his valuable support and guidance throughout the
academic year.

We also wish to express our sincere gratitude to Dr.P.ANITHA,

M.E.,Ph.D., Assistant Professor and Head of the Department of Electrical and
Electronics Engineering, University VOC College of Engineering, Thoothukudi,
for her consistent encouragement, academic guidance, and for providing all the
necessary resources and support throughout the duration of our project.

We are extremely grateful to our respected project guide,

Mr.T.THENTHIRUPPATHI, M.E., Faculty of Department of Electrical and
Electronics Engineering, for his constant supervision, insightful suggestions, and
for sharing his technical expertise at every critical stage of the project. His
mentorship played a crucial role in shaping our ideas and helping us overcome
technical challenges.

We are also deeply grateful to the other faculty members of the Department
of Electrical and Electronics Engineering for their motivation, technical advice,
and encouragement to the project.

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 Abstract

This project proposes a hybrid renewable energy system integrating a

PMSG-based wind generator and a solar PV array, connected through a SEPIC

converter for effective voltage regulation. A Supercapacitor Energy Storage

System (SC-ESS) is employed to support voltage stability during grid faults,

enhancing the system’s Zero Voltage Ride Through (ZVRT) capability. To

optimize dynamic performance, a Grey Wolf Optimizer (GWO)-based control

strategy is implemented to fine-tune converter parameters in real-time. The

system is modelled in MATLAB/Simulink and tested under variable inputs and

fault conditions. Simulation results confirm improved fault ride-through, stable

DC-link voltage, and uninterrupted power flow, proving the system’s suitability

for smart grid integration and resilient renewable energy applications .

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 TABLE OF CONTENTS

CHAPTER TITLE PAGE

NO NO
ABSTRACT iv
LIST OF FIGURES viii
LIST OF ABBREVIATION ix
1 INTRODUCTION 1-8
1.1 OVERVIEW OF RENEWABLE ENERGY 1
SYSTEMS
1.2 NEED FOR HYBRID WIND-SOLAR 3
INTEGRATION
1.3 IMPORTANCE OF ZVRT IN GRID SYSTEMS 4

1.4 MOTIVATION AND OBJECTIVE OF THE 6

PROJECT
1.5 SCOPE OF THE PROJECT 8

2 LITERATURE SURVEY 9-11

3 EXSISTING SYSTEM 12-18
3.1 OVERVIEW OF CONVENTIONAL ZVRT 12
TECHNIQUES
3.2 TRADITIONAL WIND-SOLAR 13
INTEGRATION CHALLENGES

v
CHAPTER TITTLE PAGE
NO NO

3.3 LIMITATIONS OF BIDIRECTIONAL BUCK- 14

BOOST CONVERTER
3.4 DRAWBACKS OF FIXED-GAIN 16
CONTROLLERS
3.5 ABSENCE OF FAST-ACTING STORAGE 17
SYSTEMS

3.6 CONCLUSION 18

4 PROPOSED SYSTEM 19-28

4.1 SYSTEM ARCHITECTURE AND 19
COMPONENTS
4.2 WIND ENERGY CONVERSION SUBSYSTEM 20
4.3 SOLAR PHOTOVOLTAIC SUBSYSTEM 21
4.4 SEPIC CONVERTER FOR POWER 21
CONDITIONING
4.5 SUPERCAPACITOR ENERGY STORAGE 23
SYSTEM
4.6 GWO-BASED CONTROL STRATEGY 24
4.7 INTEGRATION AND POWER FLOW 24
MANAGEMENT

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CHAPTER TITTLE PAGE
NO NO
4.8 ADVANTAGES OF THE PROPOSED SYSTEM 25
4.9 SUMMARY 28
5 DESIGN AND SIMULATION 29-35
5.1 SIMULATION ENVIRONMENT SETUP 29
5.2 WIND ENERGY SYSTEM MODELLING 30
5.3 SOLAR PV ARRAY MODELLING 30
5.4 SEPIC CONVERTER DESIGN AND CONTROL 31
5.5 SUPERCAPACITOR STORAGE SYSTEM 32
DESIGN
5.6 GREY WOLF OPTIMIZER (GWO) 33
IMPLEMENTATION
5.7 FAULT INJECTION AND SCENARIO 34
TESTING
5.8 KEY PERFORMANCE METRICS 35
5.9 SUMMARY 35
6 RESULTS AND DISCUSSION 36-43
6.1 OUTPUT OF PMSG-BASED WIND TURBINE 36
6.2 OUTPUT OF SOLAR PV SYSTEM 36
6.3 OUTPUT AFTER GRID-SIDE CONVERTER (GSC) 39
6.4 FILTERED GRID OUTPUT AFTER GSC 41
7 CONCLUSION 44
REFERENCES 45-46

vii
 LIST OF FIGURES

FIGURE TITTLE PAGE

NO NO

3.1 Block diagram of PMSG based WG in existing 14

system
3.2 Schematic diagram of BBBC controller. 15
4.1 Block diagram of Proposed System 20
4.2 Hybrid Solar and Wind power system 22
4.3 Rotor side convertor 23
4.4 Gride side control system 25
5.1 solar power system 31
5..2 subsystem of controls 33
6.1 DC link voltage 37
6.2 Machine side converter current 38
6.3 Machine side converter voltage 38
6.4 Grid side converter current 40
6.5 Grid side converter voltage 40
6.6 Grid current 42
6.7 Grid Voltage 42

viii
 LIST OF ABBREVIATIONS
Abbreviation Full Form

ZVRT Zero Voltage Ride Through

PMSG Permanent Magnet Synchronous Generator
PV Photovoltaic
SC-ESS Supercapacitor Energy Storage System
SEPIC Single-Ended Primary Inductor Converter
GWO Grey Wolf Optimizer
MPPT Maximum Power Point Tracking
RL Load Resistive-Inductive Load
DC Direct Current
AC Alternating Current
THD Total Harmonic Distortion
PI Controller Proportional–Integral Controller
ANN Artificial Neural Network
IoT Internet of Things
RTDS Real-Time Digital Simulator
MATLAB Matrix Laboratory
Simulink Simulation and Link
PWM Pulse Width Modulation
FFT Fast Fourier Transform
DFIG Doubly Fed Induction Generator
SVM Support Vector Machine

ix
 CHAPTER 1

INTRODUCTION

1.1 Overview of Renewable Energy System

Renewable energy systems harness energy from naturally replenishing

sources such as sunlight, wind, water, and biomass. These systems play a crucial
role in reducing dependence on fossil fuels, mitigating climate change, and
enhancing energy security. Unlike conventional energy sources, renewables are
abundant, sustainable, and environmentally friendly.

Types of Renewable Energy Systems:

1. Solar Energy Systems: These systems convert sunlight into electricity

using photovoltaic (PV) cells. Solar PV systems are scalable, from small
rooftop installations to large solar farms, and can operate independently or
in grid-connected mode.
2. Wind Energy Systems: Wind turbines convert kinetic energy from wind
into electrical energy. Permanent Magnet Synchronous Generators
(PMSGs) are commonly used due to their high efficiency and reliability in
variable wind conditions.
3. Hydro power Systems: These generate electricity by using the flow of
water to spin turbines. Hydropower is one of the oldest and most reliable
renewable technologies, often used for large-scale power generation.
4. Biomass Energy Systems: Biomass systems generate power by burning
organic materials like agricultural waste, wood, and municipal solid waste.
These systems contribute to waste management and energy generation
simultaneously.

1
 5. Geothermal Energy Systems: These extract heat from the Earth’s core to
produce electricity and provide heating. Geothermal plants offer a stable
energy output irrespective of weather conditions.

Hybrid Renewable Energy Systems:

To overcome the limitations of standalone renewable sources (such as solar

unavailability at night or wind variability), hybrid systems are developed by
integrating multiple energy sources. A common combination is solar PV and
wind turbines, which complement each other based on time of day and weather
conditions.

Key Components of Renewable Energy Systems:

• Energy Sources: Solar panels, wind turbines, etc.

• Power Converters: DC-DC converters (like SEPIC) and inverters for
voltage regulation and grid integration.
• Energy Storage Systems: Batteries or supercapacitors to store excess
energy and provide support during voltage sags or faults.
• Control Algorithms: Techniques like Maximum Power Point Tracking
(MPPT) and optimization methods (e.g., Grey Wolf Optimizer) to enhance
system efficiency and reliability.

Advantages of Renewable Energy Systems:

• Environmentally friendly and carbon-free

• Sustainable and inexhaustible
• Reduces electricity bills and operating costs
• Enhances grid stability when coupled with smart control techniques
• Provides rural electrification and energy access

2
 Renewable energy systems are vital to a sustainable energy future. Their
integration with advanced storage and control technologies makes them more
reliable and efficient, especially in modern smart grid applications.

1.2 Need for Hybrid Wind-Solar Integration

The integration of wind and solar energy systems into a single hybrid
configuration has gained significant attention in recent years due to the limitations
of standalone renewable energy sources. While both wind and solar power are
sustainable and environmentally friendly, their intermittent and unpredictable
nature poses challenges to ensuring a stable and reliable power supply.

Limitations of Individual Systems:

• Solar PV System Limitations: Solar panels depend on sunlight, which is

available only during daytime and is affected by weather conditions such
as clouds or rain. Energy production is zero at night and inconsistent during
cloudy periods.
• Wind Energy System Limitations: Wind energy systems rely on wind
availability, which is highly variable throughout the day and across
different seasons. There are times when wind speeds are too low to
generate usable power.

Advantages of Hybrid Integration:

To overcome the above limitations, a hybrid wind-solar energy system

combines both sources, providing a more balanced and continuous energy supply.
The key advantages of this approach include:

3
 1. Complementary Nature: Solar and wind resources often complement
each other. For example, solar radiation is typically stronger during
summer, while wind speeds may be higher during winter or at night.
2. Improved Power Reliability: By integrating both sources, the hybrid
system ensures a more reliable and steady power output, especially in off-
grid and rural applications.
3. Reduced Storage Requirements: Hybrid systems reduce the need for
large-scale energy storage solutions (like batteries), as one source can
support the load when the other is unavailable.
4. Enhanced Grid Support: When connected to the grid, hybrid systems
contribute to better load balancing and can support Zero Voltage Ride
Through (ZVRT) capabilities more effectively with proper control
strategies.
5. Better Utilization of Infrastructure: The shared use of power electronics
(like SEPIC converters and inverters), controllers, and SC-ESS results in
cost efficiency and better system management.
6. Economic and Environmental Benefits: Reduced fuel costs, lower
emissions, and optimized land use make hybrid systems attractive for
sustainable development goals.

1.3 Importance of ZVRT (Zero Voltage Ride Through) in Grid Systems

Zero Voltage Ride Through (ZVRT), also known as Low Voltage Ride
Through (LVRT), is a critical requirement in modern power systems for both
conventional and renewable energy generators. It refers to the ability of a power-
generating unit to remain connected to the grid and continue operating during a
temporary voltage drop (fault) rather than disconnecting immediately.

As renewable energy penetration increases, particularly through wind and

solar systems, the grid becomes more sensitive to disturbances. If a large number

4
of generators disconnect during voltage sags, it can lead to widespread instability,
cascading failures, or even complete blackouts. ZVRT capability ensures that
power sources "ride through" the disturbance and support grid recovery.

Key Reasons ZVRT is Important in Grid-Connected Systems:

1. Grid Stability and Reliability

• ZVRT ensures that generating units do not trip offline during short-term
faults (e.g., lightning strikes, line-to-ground faults).
• This prevents sudden drops in power supply, which could otherwise
destabilize the grid.

2. Compliance with Grid Codes

• Most utility operators and grid regulators (like IEEE, CEA in India, and
ENTSO-E in Europe) mandate that generators, including wind and solar
units, must have ZVRT capability.
• Failing to comply may result in disconnection from the grid or penalties.

3. Support for Fault Recovery

• Systems with ZVRT can inject reactive power during faults, aiding in the
quick recovery of grid voltage.
• This behaviour supports fault clearance and faster restoration of normal
operation.

4. Prevention of Cascading Failures

• If multiple renewable units disconnect during a fault, it could overload

remaining units and cause a chain reaction of failures.
• ZVRT-capable systems prevent this by staying online and easing the load
redistribution.
5
5. Enhancing the Role of Renewables

• For renewables to be trusted as major contributors to the energy mix, they

must offer similar or better performance than conventional generators
during faults.
• ZVRT helps elevate the reliability of wind and solar systems to grid
standards.

Application in This Project:

In this project, ZVRT enhancement is achieved by:

• Using a Permanent Magnet Synchronous Generator (PMSG) for wind

energy, which is naturally more fault-tolerant.
• Incorporating a SEPIC converter and supercapacitor energy storage (SC-
ESS) for voltage stabilization.
• Employing the Grey Wolf Optimizer (GWO) to dynamically adjust control
parameters for faster and more effective ride-through behaviour.

This improves the ability of the hybrid wind-solar system to withstand and
recover from grid faults, ensuring continuous power delivery and system
resilience.

1.4 Motivation and Objective of the Project

Motivation

The increasing dependence on renewable energy has introduced new

challenges to the stability and reliability of modern power systems. Among these,
the intermittent nature of wind and solar sources poses a significant risk during
grid disturbances such as voltage dips or faults. During such events, renewable
generators often disconnect from the grid, worsening the situation.

6
 This issue is particularly concerning as grid codes across the world now
mandate that power-generating units must remain operational during transient
faults — a feature known as Zero Voltage Ride Through (ZVRT). Many existing
systems lack sufficient voltage support mechanisms during such events,
especially when power conversion and control strategies are not optimized.

Moreover, most current systems use conventional converters and basic

energy storage techniques that may not respond quickly or efficiently under
dynamic conditions. This project is motivated by the need for a smarter, faster,
and more stable hybrid renewable system that can remain grid-connected and
support voltage restoration during disturbances.

Objective

The main objective of this project is to design and simulate a hybrid wind-
solar energy system that improves ZVRT performance using modern converter
and control strategies. The key goals include:

1. Integration of PMSG-Based Wind Generator and Solar PV System:

Combine wind and solar energy sources to ensure continuous power
generation.
2. Utilization of SEPIC Converter: Implement a Single-Ended Primary
Inductor Converter (SEPIC) for effective voltage regulation and power
transfer between sources and load.
3. Incorporation of Supercapacitor Energy Storage System (SC-ESS):
Use fast-response supercapacitors to stabilize voltage during sudden faults.
4. Optimization Using Grey Wolf Optimizer (GWO): Employ a nature-
inspired optimization algorithm to tune control parameters for better
system performance during disturbances.

7
 5. Simulation and Analysis: Use MATLAB/Simulink to model the system
and analyse its behaviour under both normal and fault conditions.

1.5 Scope of the Project

This project aims to design and analyse a hybrid renewable energy system
that can maintain continuous operation during grid faults, with a specific focus
on improving Zero Voltage Ride Through (ZVRT) capability. The system
combines a wind turbine driven by a Permanent Magnet Synchronous Generator
(PMSG) and a solar photovoltaic (PV) array, both integrated through a SEPIC
(Single-Ended Primary Inductor Converter). This converter plays a key role in
stabilizing the DC-link voltage during power fluctuations.

To further enhance voltage support during transient events, a

Supercapacitor Energy Storage System (SC-ESS) is included. This fast-response
energy storage helps manage voltage dips effectively. To improve the system’s
dynamic response, the Grey Wolf Optimizer (GWO)—an evolutionary algorithm
inspired by the hunting behaviour of wolves—is used to tune the control strategy
for better performance under different grid fault scenarios.

The scope of this work covers:

• Modelling a hybrid wind-solar setup in MATLAB/Simulink.

• Designing a SEPIC converter for stable voltage regulation.
• Integrating a supercapacitor for energy buffering during faults.
• Implementing and testing GWO for control parameter optimization.
• Evaluating system performance under normal and faulted grid conditions.

8
 CHAPTER 2

LITERATURE SURVEY

Design and Simulation of DC to DC Boost and SEPIC Converters using

MPPT for Photovoltaic System using MATLAB/SIMULINK:

This paper presents the design and simulation of Boost and SEPIC
converters integrated with MPPT techniques for photovoltaic systems. The
SEPIC converter, in particular, is highlighted for its ability to provide both step-
up and step-down voltage regulation with a non-inverting output, making it ideal
for PV systems experiencing fluctuating irradiance. The study uses
MATLAB/Simulink for performance analysis and compares the voltage stability
and dynamic response of both converters. This work supports the selection of the
SEPIC converter in the proposed hybrid system by demonstrating its superior
adaptability and efficiency in solar energy applications.

Dynamic Modelling and Control of PMSG based Stand-alone Wind Energy

Conversion System:
This paper focuses on the modelling and control of a standalone Wind
Energy Conversion System (WECS) using a Permanent Magnet Synchronous
Generator (PMSG). It provides detailed mathematical modelling and control
strategies for voltage and frequency regulation under variable wind conditions.
The authors emphasize the efficiency and reliability of PMSGs in standalone
mode, which do not require external excitation or gearboxes. This work is
relevant to the current project as it forms the basis for modelling and simulating
the PMSG in the hybrid system, ensuring stable operation even during wind speed
variations.

9
Enhancing Zero Voltage Ride Through of PMSG-Based Wind Generator
With Interchange of Converter Control and Optimized Supercapacitor
Energy Storage System
This study introduces a novel control method to improve the Zero Voltage
Ride Through (ZVRT) capability of PMSG-based wind generators. It proposes
an interchangeable control between converters and integrates a supercapacitor-
based energy storage system to maintain DC-link voltage during voltage dips.
The optimized control strategy enhances grid code compliance and voltage
stability during grid faults. This paper serves as the base for the current project
and is directly extended by incorporating solar integration and a SEPIC converter
for hybrid energy stabilization.

Performance Improvement of a Grid Connected Direct Drive Wind Turbine

Using Supercapacitor Energy Storage:
This paper explores the use of supercapacitor energy storage systems (SC-
ESS) for enhancing the performance of grid-connected direct-drive wind
turbines, particularly during transient faults. By injecting or absorbing power
during grid disturbances, the SC-ESS helps in mitigating voltage sags and
improving the fault ride-through capability. The authors validate the system
through simulation results, showing significant improvements in power quality.
This supports the use of SC-ESS in the proposed system to stabilize the DC-link
and improve ZVRT performance.

Comprehensive Review on Low Voltage Ride Through Capability of Wind

Turbine Generators
This review paper summarizes various LVRT techniques for different
types of wind turbine generators, including DFIG, SCIG, and PMSG. It evaluates
control strategies, grid code requirements, and the role of energy storage in

10
enhancing ride-through performance. The paper identifies the PMSG as having
strong potential for ZVRT with appropriate converter and control configurations.
The insights from this review help validate the design choices in the present
project, particularly the focus on PMSG with enhanced control strategies and
energy storage.

Enhanced Low-Voltage Ride-Through Coordinated Control for PMSG

Wind Turbines and Energy Storage Systems Considering Pitch and Inertia
Response
This paper proposes a coordinated LVRT control strategy combining pitch
control, inertia emulation, and energy storage systems for PMSG wind turbines.
It demonstrates how these combined responses improve the voltage profile and
system resilience during faults. The method is validated through simulations,
showing its effectiveness in reducing voltage dips and oscillations. The proposed
project extends this idea by implementing a SEPIC converter and optimized
control for a hybrid energy system to achieve similar ZVRT enhancement .

Design and Control of a SEPIC Converter for Solar PV Applications With

Fast Dynamic Response

This paper introduces a SEPIC converter design tailored for solar PV

applications, emphasizing its fast dynamic response and voltage regulation under
rapid changes in solar irradiance. The authors develop a control strategy to
quickly stabilize output voltage and maintain MPPT operation. This work is
essential in demonstrating the effectiveness of the SEPIC converter in solar PV
systems, which is directly applied in the current hybrid project to maintain voltage
stability and enhance system responsiveness.

11
 CHAPTER 3

Existing System

3.1 Overview of Conventional ZVRT Techniques

Conventional Zero Voltage Ride Through (ZVRT) strategies in renewable

energy systems are designed to ensure that generators remain connected to the
grid during short-term voltage sags or faults. These methods typically employ
basic fault-handling techniques that allow the system to momentarily withstand
disturbances without disconnecting.

Some of the commonly used approaches include:

• Crowbar Circuits: These are hardware-based protection circuits used

mainly in doubly-fed induction generators (DFIGs). They short-circuit the
rotor windings temporarily during a voltage dip to protect the converter.
However, they may cause power injection to cease temporarily, reducing
support to the grid.
• Reactive Power Injection: Inverters are sometimes programmed to inject
reactive power during faults to support grid voltage restoration. While this
helps maintain voltage levels, it is usually limited by the inverter's capacity
and may not be effective in deep sags.
• Pre-programmed Inverter Logic: Some systems use built-in ride-
through control logic where the inverter remains connected for a specific
time after voltage drops. If voltage does not recover within the ride-through
window, the system disconnects for safety.

Despite their utility, these conventional ZVRT techniques suffer from

limited adaptability. They are often designed for predefined conditions and do not

12
respond well to highly dynamic scenarios such as fluctuating generation, sudden
load changes, or unbalanced faults. Moreover, they generally lack real-time
intelligence, making them inadequate for modern smart grid applications that
demand robust, adaptive, and fast-response fault management.

3.2 Traditional Wind-Solar Integration Challenges

Integrating wind and solar power sources into a single hybrid system offers
increased energy availability and improved reliability. However, traditional
wind-solar hybrid configurations often face several challenges, particularly in
terms of system coordination, stability, and fault resilience.

One of the main challenges arises from the inconsistent and unpredictable
nature of both wind and solar resources. Wind speeds and solar irradiance levels
fluctuate independently and irregularly, which leads to non-uniform power
generation. In conventional systems, wind and solar subsystems typically operate
in isolation, with separate power conditioning units and minimal synchronization.
This lack of integration often results in inefficient energy transfer, increased
system losses, and unstable DC-link voltage levels.

Another limitation is the difficulty in voltage regulation across the

combined system. When both sources feed into a common load or grid
connection, mismatches in their voltage levels and output characteristics can
cause power imbalances. Traditional systems using simple boost or buck
converters often cannot handle such variable input conditions effectively.

Moreover, during grid disturbances or sudden load changes, conventional

systems are unable to coordinate reactive power support or maintain voltage
stability. This is mainly due to the use of fixed control strategies that lack
adaptability. Without real-time response and intelligent coordination, these

13
systems are prone to voltage collapse or complete shutdown during critical
operating conditions.

Overall, the absence of centralized control, intelligent decision-making,

and advanced power management in traditional wind-solar systems significantly
reduces their ability to perform reliably under dynamic grid conditions.

Fig.No.3.1: Block diagram of PMSG based WG in existing system

3.3 Limitations of Bidirectional Buck-Boost Converter (BBBC)

The Bidirectional Buck-Boost Converter (BBBC) is commonly used in

traditional hybrid renewable systems for managing energy flow between sources,
storage devices, and loads. It offers the flexibility to operate in both buck (step-
down) and boost (step-up) modes, which is essential when interfacing variable
renewable inputs like wind and solar. Despite its functional advantages, the
BBBC has several technical and performance limitations when applied to fast-
changing and fault-prone grid environments.

One major drawback is its slow dynamic response during rapid voltage or
load changes. Under transient conditions, the BBBC often exhibits sluggish
adjustment in duty cycle, which delays voltage regulation and makes the system
prone to instability. This is particularly critical during grid faults or sudden dips

14
in renewable generation, where immediate voltage compensation is essential to
prevent system disconnection.

Another issue lies in its discontinuous input current mode, which

introduces high ripple into the source side (especially solar PV). This not only
reduces the efficiency of energy conversion but also imposes thermal stress on
the converter components, ultimately affecting their lifespan

Fig.No.3.2: Schematic diagram of BBBC controller.

The switching losses and control complexity increase significantly when

the converter operates at high frequencies required for real-time power regulation.
Moreover, during bidirectional operation, ensuring smooth mode transition
between charging and discharging states is challenging without advanced control
logic, which is typically absent in conventional systems.

BBBCs also lack inherent fault-handling capability. In the absence of

predictive or adaptive control algorithms, these converters cannot respond
effectively to faults, resulting in voltage dips and potential system failure.

Due to these drawbacks, BBBCs are less suited for systems where high-
speed control, fault ride-through capability, and voltage stability are critical—
necessitating the exploration of better alternatives like the SEPIC converter.

15
3.4 Drawbacks of Fixed-Gain Controllers

Fixed-gain controllers, such as conventional PI (Proportional–Integral) or

PID (Proportional–Integral–Derivative) systems, are widely used in traditional
power converter control. While they are simple and effective under constant
operating conditions, they become inadequate when the system operates in a
dynamic or fault-prone environment — which is common in renewable energy
systems.

One of the core limitations is that these controllers are not adaptive. The
gain values are manually tuned based on a specific set of operating conditions.
However, in a real-world hybrid system, factors such as solar irradiance, wind
speed, grid voltage, and load demand change frequently. Under such conditions,
a controller with fixed gains cannot respond optimally, leading to delayed or
insufficient corrective action.

Additionally, during grid faults or disturbances like voltage dips, fixed-

gain controllers often fail to stabilize the DC-link voltage quickly, causing
oscillations or temporary power interruptions. This makes it difficult to meet
strict grid code requirements such as Zero Voltage Ride Through (ZVRT), where
the system is expected to remain online and support the grid during faults.

These controllers also suffer from limited tuning flexibility. Manual tuning
is time-consuming and typically does not yield the best performance across all
operating conditions. Moreover, they lack the intelligence to adjust their behavior
based on real-time measurements or predictive patterns.

To improve control performance, modern renewable systems are adopting

adaptive and AI-based controllers, which can adjust their parameters on the fly.
This ensures faster response, better fault handling, and enhanced stability under
changing operating conditions.

16
3.5 Absence of Fast-Acting Storage Systems

In conventional hybrid renewable energy systems, energy storage is

typically provided through batteries, such as lead-acid or lithium-ion cells. While
these storage solutions are useful for energy balancing and long-term power
backup, they are not ideal for handling sudden voltage fluctuations or short-
duration disturbances, particularly during fault conditions.

One of the major limitations of batteries is their slow response time. When
a sudden voltage dip occurs—such as during a grid fault or a transient power
demand—the time it takes for the battery system to detect the drop, initiate
discharge, and supply compensating power is often too long to prevent temporary
instability. This lag can lead to DC-link voltage collapse, inverter malfunction, or
even unintentional disconnection from the grid.

Additionally, frequent charge-discharge cycles during short transients

accelerate battery degradation, reducing their lifespan and increasing
maintenance costs. Batteries are also not well-suited for applications that demand
high power bursts over short intervals, which are common in Zero Voltage Ride
Through (ZVRT) events.

Moreover, traditional systems lack any high-speed buffer storage, such as

supercapacitors, which are specifically designed to deliver rapid bursts of power.
Supercapacitors can charge and discharge within milliseconds, making them ideal
for mitigating short-term fluctuations and enhancing voltage ride-through
performance.

17
 The absence of fast-acting energy storage in conventional systems means
they often struggle to stabilize voltage during faults, reducing their effectiveness
in modern smart grids that require responsive and reliable power systems.

3.6 Conclusion

This chapter has highlighted the key limitations present in conventional

renewable energy systems, particularly in the context of hybrid wind-solar
integration and their response to grid disturbances. Traditional ZVRT techniques,
though widely used, are often based on static protection schemes and lack the
intelligence or adaptability needed to respond to rapidly changing grid conditions.

We have seen that conventional systems often operate with isolated control
of wind and solar resources, which leads to poor coordination and unstable power
delivery. Furthermore, the use of Bidirectional Buck-Boost Converters (BBBCs)
introduces issues such as switching losses, delayed response during faults, and
ripple-induced inefficiencies.

The dependence on fixed-gain PI controllers further restricts the system’s

ability to adapt to dynamic conditions, resulting in slower voltage recovery and
reduced system resilience. Additionally, the absence of fast-response energy
storage systems like supercapacitors makes traditional designs ineffective at
supporting the grid during transient faults or short-term voltage drops.

Overall, the existing system architecture lacks the real-time control, fault
resilience, and high-speed voltage support required for compliance with modern
grid standards such as ZVRT. These limitations emphasize the need for a more
advanced system that incorporates intelligent control strategies, efficient power
conversion, and responsive storage solutions features addressed in the proposed
system discussed in the following chapter.

18
 CHAPTER 4

PROPOSED SYSTEM

4.1 System Architecture and Components

The proposed system integrates multiple renewable energy sources to

ensure continuous and reliable power generation even during grid disturbances.
The architecture combines a Permanent Magnet Synchronous Generator
(PMSG)-based wind turbine and a solar photovoltaic (PV) array as primary
energy sources. Both sources feed into a SEPIC (Single-Ended Primary Inductor
Converter), which regulates and stabilizes the voltage at the DC-link.

To further enhance voltage stability, a Supercapacitor Energy Storage

System (SC-ESS) is connected to the DC-link, allowing rapid energy injection or
absorption during transient events such as voltage sags or short circuits. The DC
power from the hybrid system is then converted to AC using a grid-tied inverter.

The overall operation is governed by an advanced control system

optimized by the Grey Wolf Optimizer (GWO) algorithm. The synergy among
these components ensures optimal power flow, voltage regulation, and fault
tolerance, making the system suitable for integration with modern power grids
that demand high stability and reliability.

19
 Fig.No.4.1: Block diagram of Proposed System

4.2 Wind Energy Conversion Subsystem

Wind energy conversion in this system uses a Permanent Magnet

Synchronous Generator (PMSG) coupled directly to a wind turbine. PMSGs are
preferred for wind applications because they do not require an external excitation
source, which reduces energy losses and increases system efficiency. Their
compact design and high power density allow for lightweight and maintenance-
friendly setups.

The turbine blades capture kinetic energy from wind and convert it into
mechanical rotational energy. This mechanical energy drives the PMSG, which
produces a variable-frequency AC output. To integrate this with the rest of the
system, the AC output is rectified to DC. Control techniques are applied to

20
regulate the rotor speed and generator torque to maximize power extraction while
preventing mechanical stress.

The PMSG’s ability to operate efficiently over a range of wind speeds

makes it ideal for hybrid systems, where power output needs to be smooth and
reliable despite natural variations.

4.3 Solar Photovoltaic Subsystem

The solar photovoltaic (PV) subsystem converts sunlight directly into

electrical energy using semiconductor-based solar cells. The electrical output
varies depending on factors such as solar irradiance and ambient temperature.
Since solar power is intermittent and changes throughout the day, maximizing
energy extraction is crucial.

To achieve this, a Maximum Power Point Tracking (MPPT) algorithm is

employed. MPPT continuously adjusts the operating voltage of the PV array to
ensure it delivers maximum power under changing environmental conditions.
The DC output from the PV array is then supplied to the SEPIC converter, which
stabilizes the voltage for further processing.

The PV system complements the wind generator by providing energy

during daylight hours, thus improving overall system reliability and reducing
dependence on a single energy source.

4.4 SEPIC Converter for Power Conditioning

The SEPIC (Single-Ended Primary Inductor Converter) serves as a

versatile DC-DC power converter capable of stepping the input voltage up or
21
down. This flexibility is particularly beneficial in hybrid renewable systems,
where input voltages from wind and solar sources fluctuate widely due to varying
environmental conditions.

One of the main advantages of the SEPIC converter is its continuous input
current characteristic, which reduces current ripple and improves the lifespan of
the connected renewable sources. By controlling the duty cycle of the converter's
switching element, the SEPIC regulates the DC-link voltage to a desired constant
level.

During transient events such as grid faults, the SEPIC’s rapid response helps
maintain voltage stability by balancing power flow between the renewable
sources, the energy storage system, and the grid. Its bidirectional power flow
capability allows it to handle both charging and discharging of the supercapacitor,
thus enhancing system resilience.

Fig.No.4.2: Hybrid Solar and Wind power system

22
4.5 Supercapacitor Energy Storage System

The Supercapacitor Energy Storage System (SC-ESS) plays a critical role

in mitigating voltage fluctuations and providing instantaneous power support
during disturbances. Supercapacitors, unlike batteries, have exceptionally high
power density and can charge and discharge rapidly over millions of cycles
without significant degradation.

In the proposed system, the SC-ESS is connected at the DC-link. During a

voltage sag or fault, the supercapacitor discharges energy to maintain the voltage
level, preventing the system from disconnecting and allowing continuous power
delivery. Once the grid recovers, the supercapacitor quickly recharges, ready for
the next transient event.

Fig.No.4.3: Rotor side convertor

This fast-response energy storage is essential for enhancing the Zero

Voltage Ride Through (ZVRT) capability, as it compensates for the sudden
imbalance between generation and load during faults, ensuring the system’s
stable operation.

23
4.6 GWO-Based Control Strategy

Efficient and adaptive control is vital for managing the complex

interactions between multiple energy sources, converters, and storage devices in
a hybrid system. The Grey Wolf Optimizer (GWO) algorithm is utilized to
dynamically optimize the control parameters, ensuring the system can adapt to
varying operating conditions.

GWO is inspired by the social hierarchy and cooperative hunting behavior

of grey wolves. It effectively balances exploration (searching new solutions) and
exploitation (refining known good solutions) to find optimal parameters for
controlling the SEPIC converter and energy flow.

By continuously tuning controller gains, the GWO improves the system’s

response to voltage dips and faults, minimizing overshoot and settling time. This
intelligent optimization ensures the hybrid system can maintain stable voltage,
smooth power delivery, and comply with grid requirements during disturbances.

4.7 Integration and Power Flow Management

The integration of wind, solar, energy storage, and control systems requires
careful management of power flow to maximize efficiency and reliability. The
proposed system intelligently coordinates power contributions from the wind
turbine and solar PV based on availability and demand.

The SEPIC converter regulates the DC-link voltage by adjusting its

switching actions in response to input variations and load changes.
Simultaneously, the supercapacitor either absorbs excess energy or supplies
deficit power, smoothing out voltage fluctuations.

24
 The GWO-based controller monitors the system’s operating parameters
and dynamically adjusts converter controls to optimize performance, especially
during fault conditions. This ensures that power flows smoothly from generation
sources through storage to the grid, maintaining continuous and stable electricity
supply

4.8 Advantages of the Proposed System

The hybrid renewable energy system combining a PMSG-based wind

turbine, solar PV array, SEPIC converter, supercapacitor energy storage, and
GWO-optimized control offers several notable advantages:

Fig.No.4.4: Gride side control system

25
Improved Reliability and Availability

By integrating two complementary renewable sources—wind and solar—

the system reduces the risk of power interruption due to resource variability.
When solar power output declines at night or during cloudy weather, wind energy
can compensate, and vice versa. This complementary relationship ensures a more
consistent energy supply and reduces reliance on any single energy source, thus
enhancing the overall system reliability.

Enhanced Fault Ride-Through Capability

The inclusion of a Supercapacitor Energy Storage System (SC-ESS) and a

fast-responding SEPIC converter allows the system to maintain voltage levels
during grid disturbances such as voltage sags or short circuits. The supercapacitor
acts as a rapid energy buffer, discharging instantaneously to support the DC-link
voltage and prevent disconnection from the grid. This feature, combined with
optimized control strategies, significantly improves the Zero Voltage Ride
Through (ZVRT) capability, which is critical for grid code compliance and
system stability.

Adaptive and Intelligent Control

Utilizing the Grey Wolf Optimizer (GWO) for control parameter tuning
enables the system to dynamically adjust to changing operating conditions.
Unlike fixed-gain controllers, the GWO-based controller continuously optimizes
system response, minimizing voltage overshoot, settling time, and steady-state
error during transient events. This intelligent control improves the system's

26
performance in maintaining stable voltage and smooth power delivery, even
under varying load and generation conditions

Efficient Power Conversion and Voltage Regulation

The SEPIC converter topology provides a significant advantage by

offering both step-up and step-down voltage conversion while maintaining
continuous input current. This reduces the electrical stress on renewable sources
and minimizes current ripple, which can otherwise lead to efficiency losses and
component degradation. By ensuring stable DC-link voltage despite fluctuating
inputs, the SEPIC converter enhances the overall energy conversion efficiency
and extends component life.

Rapid Response and Longevity of Energy Storage

Supercapacitors have extremely fast charge-discharge cycles compared to

batteries, enabling immediate reaction to voltage fluctuations during transient
grid events. Their high power density and long lifecycle mean they can endure
millions of cycles without significant degradation, reducing maintenance and
replacement costs. This rapid response capability is essential for stabilizing the
system during faults and maintaining continuous power flow.

Scalability and Modular Design

The modular nature of this hybrid system allows it to be easily scaled up

or down depending on energy demand or available resources. Additional wind
turbines, solar arrays, or supercapacitors can be integrated without redesigning
the entire system. This flexibility supports future expansion and adaptability to
different grid environments or power levels.

27
Grid Code Compliance and Enhanced Stability

With increasing renewable penetration, grid codes globally require power

systems to exhibit fault ride-through capabilities to prevent cascading failures.
The proposed system’s design meets these regulatory requirements by combining
robust hardware components with intelligent control. This compliance ensures
that the system can be reliably integrated into smart grids, contributing to overall
grid stability and resilience.

Environmental and Economic Benefits

By maximizing the use of renewable energy sources and improving fault

tolerance, the system reduces dependency on fossil fuel-based backup power,
thereby lowering greenhouse gas emissions. The increased efficiency and
longevity of components result in lower operational costs over time. Moreover,
the hybrid design ensures a more predictable energy output, reducing the need for
expensive energy storage or backup generation.

4.9 Conclusion

This chapter detailed the proposed hybrid renewable energy system aimed
at enhancing Zero Voltage Ride Through performance and grid stability. By
integrating a PMSG-based wind turbine, a solar PV array, a SEPIC converter, a
supercapacitor energy storage system, and an intelligent GWO-optimized control
scheme, the system achieves a robust, efficient, and fault-tolerant configuration.
The following chapters will describe the modelling, simulation, and performance
evaluation of this system under various operational scenarios.

28
 CHAPTER 5

DESIGN AND SIMULATION

The goal of this chapter is to develop a comprehensive simulation model

for the proposed hybrid renewable energy system, consisting of a PMSG-based
wind turbine, a solar photovoltaic (PV) system, a SEPIC converter, a
supercapacitor energy storage system, and a Grey Wolf Optimizer (GWO)-based
intelligent controller. Using MATLAB/Simulink, the system is designed and
tested under various operating conditions, including normal, faulted, and post-
fault states. The simulations assess the system’s behaviour with a focus on
maintaining DC-link voltage stability and satisfying Zero Voltage Ride Through
(ZVRT) requirements.

5.1 Simulation Environment Setup

The simulation is built using MATLAB/Simulink due to its versatility in

modelling electrical systems, control loops, and dynamic responses. Component
models are designed to reflect realistic electrical parameters and behaviour.

• Time Step: Fixed-step solver is used with a step size of 1 µs for high-
resolution switching control.
• Simulation Duration: 3 seconds total, with a fault event triggered at 1.5
seconds and cleared at 1.7 seconds.
• Voltage Setpoint: DC-link voltage maintained at 400 V
• GWO Optimization Frequency: Re-tuning every 0.1 seconds based on
system error
• System Load: Resistive-inductive (RL) load connected to grid

All systems are integrated into a master Simulink model, allowing synchronized
and controlled data flow between blocks.

29
5.2 Wind Energy System Modelling

The wind turbine is simulated using a variable wind speed profile to capture
real-world fluctuations. The turbine model includes aerodynamic modelling,
which calculates mechanical torque based on wind speed, blade radius, and air
density.

• Generator Model: The PMSG is modelled using the dq-axis equations in

a rotating reference frame, enabling precise control of current and torque.
• Rectifier: A three-phase diode bridge is used to convert AC output from
the generator to DC before feeding into the DC-link.
• Control Logic: A speed controller regulates turbine operation to ensure
optimal energy extraction under different wind conditions.

Wind speed is varied between 8 m/s to 14 m/s throughout the simulation to

test system adaptability.

5.3 Solar PV Array Modelling

The PV array is modelled as a series-parallel configuration of PV modules,

with a current-voltage (I-V) characteristic curve generated using standard single-
diode equations.

• Input Parameters:
o Irradiance: 600–1000 W/m² (step changes during simulation)
o Temperature: Maintained at 25°C
• MPPT Algorithm: A Perturb and Observe (P&O) method is used to track
the maximum power point under changing conditions.
• Output Behaviour: Voltage varies with load and irradiance; current varies
proportionally with sunlight.

30
This setup ensures that the solar subsystem works efficiently and complements
the wind subsystem under varied conditions.

Fig.No.5.1: solar power system

5.4 SEPIC Converter Design and Control

The SEPIC converter is chosen for its capability to handle both rising and
falling input voltages without inverting the polarity.

• Component Ratings:
o Inductors: Designed to limit current ripple to less than 10%
o Capacitors: Sized to maintain output voltage with minimal ripple
o MOSFET: Switched using PWM signals at 20 kHz
• Control Strategy:
o Output voltage is sensed and compared with the reference
o The error is fed to a GWO-optimized PI controller
o PWM duty cycle is adjusted in real-time to regulate voltage

This converter plays a key role in maintaining a stable voltage across the
DC-link, especially during rapid fluctuations from wind or solar sources.

31
5.5 Supercapacitor Storage System Design

The supercapacitor is modelled as a voltage-controlled storage device with

internal resistance (ESR) and capacitance. It operates in bidirectional mode—
absorbing or supplying energy depending on the system condition.

• Key Features:
o Fast charge/discharge with minimal delay
o Acts as a temporary buffer during transient faults
o Provides high power for short durations
• Control Logic:
o If DC-link voltage drops below threshold, capacitor discharges
o If voltage rises above threshold, capacitor charges
o State-of-charge is monitored to avoid overcharging

The SC-ESS effectively stabilizes the voltage during voltage sags and
reduces strain on renewable sources during rapid load changes.

32
 Fig.No.5.2 subsystem of controls

5.6 Grey Wolf Optimizer (GWO) Implementation

The GWO algorithm is implemented in MATLAB and integrated with the

Simulink model through a control interface block.

• Objective Function: Minimization of voltage deviation and controller

response time
• Variables Optimized: Proportional (Kp) and integral (Ki) gains of the PI
controller

33
 • Working Principle:
o Alpha (best solution), Beta, and Delta (next best) wolves guide the
search
o The search space is updated based on the simulated 'hunting'
behaviour
o The controller parameters are adjusted iteratively to achieve optimal
system performance

GWO ensures real-time adaptability, allowing the system to maintain

stable operation even when system conditions change rapidly.

5.7 Fault Injection and Scenario Testing

A grid fault is introduced at 1.5 seconds by reducing grid voltage to near zero
for 0.2 seconds to simulate a worst-case ZVRT scenario.

• Before Fault:
o System operates under balanced generation and demand
o DC-link voltage remains close to reference (400 V)
• During Fault:
o Grid voltage drops; inverter ceases normal operation
o Supercapacitor discharges to maintain DC-link voltage
o GWO updates control actions to minimize voltage error
• After Fault:

o Grid voltage restores at 1.7 seconds

o System rebalances; supercapacitor recharges

o GWO re-tunes controller to stabilize quickly

34
 This test validates the ability of the system to stay connected and operate
within safe voltage margins during and after faults.

5.8 Key Performance Metrics

The simulation is analysed using the following indicators:

Metric Observed Result

DC-Link Voltage Deviation < 5% during fault
Recovery Time < 0.3 seconds post-fault
Power Continuity No interruption during disturbance
Voltage Ripple (DC-Link) < 2% under full-load conditions
GWO Convergence Time < 5 iterations for each tuning cycle
Energy Contribution (SC-ESS) 10–12% of total power during transient phase

The data confirms that the system maintains operational continuity and
voltage stability even in harsh fault conditions.

5.9 Summary

This chapter presented the detailed modelling and simulation of each

component in the proposed hybrid renewable system. MATLAB/Simulink
provided a dynamic and accurate environment for testing the interaction between
energy sources, converters, storage, and control systems. The coordinated
operation of the SEPIC converter, supercapacitor, and GWO-based controller
enables the system to maintain steady-state voltage and demonstrate ZVRT
compliance. These results validate the viability of the proposed model as a
resilient and intelligent solution for future renewable integration.

35
 CHAPTER 6

RESULTS AND DISCUSSION

The proposed hybrid renewable energy system was modelled and

simulated in MATLAB/Simulink to evaluate its performance under varying
conditions and fault scenarios. This chapter presents the key simulation results of
the individual and integrated components, including the PMSG-based wind
turbine, solar PV system, output after the grid-side converter (GSC), and the final
combined system response.

6.1 Output of PMSG-Based Wind Turbine

The wind turbine model was implemented using a variable-speed

Permanent Magnet Synchronous Generator (PMSG). The output voltage of the
wind generator varied with wind speed and was processed through the machine-
side converter (MSC). The MPPT algorithm was used to extract maximum power
from the wind. During steady wind conditions, the PMSG delivered a stable
three-phase AC output with consistent frequency and amplitude. Under varying
wind speed, the MPPT effectively tracked the optimal operating point, ensuring
maximum power extraction. The active power output ranged between 1.2 kW and
2.5 kW depending on wind input, and the DC-link voltage after conversion was
regulated around 400 V.

6.2 Output of Solar PV System

The solar PV system was modelled under standard test conditions (1000
W/m² irradiance, 25°C) and integrated with a SEPIC converter for voltage
stabilization. The PV array produced a DC output voltage in the range of 100–
150 V, which was then boosted and regulated by the SEPIC converter to match
the DC-link voltage. Even under varying irradiance conditions, the SEPIC

36
converter effectively maintained the output voltage at around 400 V. The ANN-
based MPPT ensured accurate and fast tracking of the maximum power point,
delivering stable power between 0.8 kW and 1.6 kW depending on solar input.

Fig.No.6.1 DC link voltage

37
 Fig.No.2 Machine side converter current

Fig.No.6.3 Machine side converter voltage

38
6.3 Output After Grid-Side Converter (GSC)

The combined DC power from the wind and solar systems was fed into the
grid-side converter. The GSC performed DC-AC conversion and synchronized
the output with grid parameters using voltage-oriented control (VOC). The three-
phase output current and voltage were sinusoidal and in phase with grid reference.
Total Harmonic Distortion (THD) was maintained below 5%, satisfying IEEE
519 standards. The GSC also controlled reactive power injection and maintained
the DC-link voltage stability under dynamic load and fault conditions.

During fault events, especially under simulated three-phase voltage sags,

the GSC output power dropped to zero, triggering the proposed control strategy.
The Grey Wolf Optimizer (GWO) dynamically adjusted the converter gains, and
the Supercapacitor Energy Storage System (SC-ESS) injected stored energy to
maintain DC-link voltage within limits. Post-fault, the GSC resumed normal
operation with minimal delay and voltage overshoot.

39
 Fig.No.6.4 Grid side converter current

Fig.No.6.5 Grid side converter voltage

40
6.4 Filtered Grid Output After GSC

After DC-AC conversion by the Grid Side Converter (GSC), the output
voltage and current were passed through an RC filter to eliminate high-frequency
switching harmonics before injecting into the grid. The filter played a crucial role
in ensuring smooth sinusoidal waveforms with minimal distortion.

The RC filter effectively attenuated high-frequency noise and provided

clean three-phase voltage suitable for grid connection. Post-filter, the voltage
remained synchronized with the grid reference in both phase and frequency. The
Total Harmonic Distortion (THD) in the voltage and current remained below 5%,
ensuring compliance with IEEE 519 standards.

During fault conditions, including complete voltage sag (ZVRT), the

filtered output quickly stabilized after the support from the SC-ESS and control
action of the Grey Wolf Optimizer (GWO). Once the fault cleared, the GSC
resumed normal operation, and the filtered output seamlessly reconnected to the
grid with minimal transient behaviour. The RC filter ensured the output
waveform met grid quality requirements throughout

41
Fig.No.6.6 Grid current

Fig.No.6.7 Grid voltage

42
Summery

The simulation results validate the effectiveness of the proposed hybrid

system. The coordinated operation of the wind and solar subsystems, efficient
energy conversion using SEPIC and back-to-back converters, and intelligent
GWO-based control ensured stable and reliable operation. The system
successfully met the objectives of ZVRT enhancement, voltage stability, and
improved power quality under various operating conditions.

43
 CHAPTER 7

CONCLUSION

This project developed a hybrid renewable energy system combining a

PMSG-based wind generator and a solar PV array, integrated through a SEPIC
converter and supported by a supercapacitor energy storage system. The primary
objective was to enhance Zero Voltage Ride Through (ZVRT) capability and
maintain stable operation during grid faults.

Simulation results demonstrated that the SEPIC converter effectively

stabilized the DC-link voltage, while the supercapacitor provided quick power
support during voltage sags. The use of the Grey Wolf Optimizer (GWO) enabled
real-time tuning of control parameters, improving the system’s dynamic response
during disturbances. The filtered output from the grid-side converter remained
stable and synchronized with grid conditions.

The proposed system proved to be reliable and responsive under various

scenarios, successfully meeting ZVRT requirements and offering a practical
solution for smart grid integration of renewable energy.

44
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