Performance Evaluation And Analysis Of 1Kva Solar Powered Inverter Considering Harmonic Emissions And Injection

ABSTRACT

Solar photovoltaics (PV) systems whether rooftop are ground-mounted have gained attraction globally in recent years due to (a) reduced PV module prices, (b) maturing inverter technology, and (c) incentives through feed-in tariff (FiT) or net metering. The large penetration of grid-connected PVs coupled with nonlinear loads and bidirectional power flows impacts grid voltage levels and total harmonic distortion (THD) at the low-voltage (LV) distribution feeder. In this study, LV power quality issues with significant nonlinear loads were evaluated at the point of common coupling (PCC). Various cases of PV penetration (0 to 100%) were evaluated for practical feeder data in a weak grid environment and tested at the radial modified IEEE-34 bus system to evaluate total harmonic distortion in the current (THDi) and voltage (THDv) at PCC along with the seasonal variations.

TABLE OF CONTENTS

Cover page

Title page

Approval page

Dedication

Acknowledgement

Abstract

Chapter one

1.0      Introduction

• Background of the project
• Problem statement
• Aim and objective of the study
• Scope of the study
• Significance of the project

CHAPTER TWO

LITERATURE REVIEW

• Introduction
• Solar Power
• Power Quality Issues Related to PVIS
• Main Systems of Solar Power Generation

CHAPTER THREE

METHODOLOGY

• System Block Diagram
• Modeling of the PV inverter for harmonic analysis
• Current harmonic caused by DC-link voltage ripple

CHAPTER FOUR

• Simulation And Experimental Results

CHAPTER FIVE       

• Conclusion

References

CHAPTER ONE

1.0                                                      INTRODUCTION

1.1                                        BACKGROUND OF THE STUDY

Solar is a proven and significant renewable energy source, offering a more economical way to generate electricity and curb carbon emissions to meet energy and climate goals. If energy companies replaced their most expensive coal plants with new solar power projects or onshore wind farms, totalling 500 GW globally, they could save billions of naira every year and reduce total global carbon emissions by 5%, according to the International Renewable Energy Agency.

However, as solar power becomes more prominent, it is important to remember that it is a dynamic system and not immune to challenges. When a photovoltaic (PV) system is connected to the grid, new power quality issues can occur due to the intermittency and instability of solar energy.

In an electric power system, a harmonic of a voltage or current waveform is a sinusoidal wave whose frequency is an integer multiple of the fundamental frequency, which needs consideration when using solar energy. The ideal power source for all power systems is smooth sinusoidal waves. However, when waveforms deviate from a sinewave shape, they become harmonics. Inverters that convert the DC current to AC current can also create harmonics.

Photovoltaic (PV) systems that is connected to the grid have become a viable option in low-voltage (LV) networks due to the introduction of lucrative policy frameworks such as metering and significant cost reduction in PV system installation [Baig et al, 2020: Kim et al, 2009: Camilo et al, 2018]. Consequently, a large amount of solar PV is expected to be connected to utility grids in coming years. A considerable amount of solar PV is already connected to weak grids; this large penetration of solar PV at the LV distribution grid has a significant effect on harmonic pollution levels in the network. Power quality issues related to the low power factor of nonlinear loads and high harmonic current emissions from solar PV inverters at the LV network greatly affect the network performance. The power electronic inverters that do not produce pure sinewaves introduce harmonics into the system when connected to the low-voltage grid. From the perspective of power quality, it is desirable that a pure sinusoidal waveform of current is obtained at the output of the grid-connected PV inverter. However, due to the presence of power electronic inverters, harmonics may arise at the output of the inverter and travel through the impedance of the distribution system, resulting in distortion of the sinusoidal voltage waveform of the utility grid. Maximum power point tracking (MPPT), anti-islanding, grid fault conditions, and energy measurement are important characteristics of PV inverter [Kim et al, 2009]. Usually, residential PV systems have small to medium sizes (1 to 15 kW_p) compared to the high short-circuit levels of the distribution grid. Therefore, distortion in system voltage is almost negligible when a single PV system is connected to the grid. However, when multiple connections are made at the same feeder or distribution grid, it may affect the system voltage at the point of common coupling (PCC).

For sustainable operation of the power system, harmonic analysis facilitates the integration of grid-connected solar PV into the system. To gauge the harmonic impacts triggered by grid-connected solar PV systems, several studies have been performed over the past few years [Camilo et al, 2018].

Harmonics are also introduced by the presence of nonlinear loads and switching devices connected to the grid. Residential nonlinear loads generally comprise devices such as transformers, compact fluorescent lamps (CFL), light-emitting diodes (LED), fluorescent tubes, air conditioners, inverters, mobile chargers, switch-mode power supplies (SMPS), TV, computers, and laptop chargers. SMPS are commonly present in laptops, computers, TV, and battery chargers for mobile phones. Globally, nonlinear loads in residential settings make up 38–42% of the utility loads, while lighting loads vary from 40 to 70%. Nonlinear loads, when supplied with sinusoidal voltage sources, produce harmonics in the supply waveform and consequently affect the operation of other linear devices connected to the distribution grid.

1.2        Problem Statement

Photovoltaic systems (PV-systems) connected to the grid with DC/AC-converters are subject to harmonic current emission which depends on the type of technology used, on the control strategy of the DC/AC-inverter, on the existence of high- or low-frequency coupling transformer and on the harmonic voltages prevailing in the AC-power system. A dominant role on the harmonic current emission is also given by the performance of the AC/DC-inverter under partial loading (generating) conditions [1]. According to research, Harmonics are also introduced by the presence of nonlinear loads used in the residents. Nonlinear loads, when supplied with sinusoidal voltage sources, produce harmonics in the supply waveform and consequently affect the operation of other linear devices connected to the distribution grid.

1.3        Aim and Objectives Of The Study

The main aim of this work is to analyze the performance of 1kva solar powered inverter considering harmonic emissions. The objectives are as below:

1. To understand the effect the effect of harmonics on the operation of a solar inverter.
2. To study the causes of harmonics in inverter system

• To understand the effect of nonlinear load in power system

1.4        Scope of the Study

The scope of this work focused on investigating the different levels of THD produced at PCC in the LV network under varying penetrations of solar PV along with the existence of balanced household nonlinear loads. Various regulatory requirements and standards exist for grid-connected PV systems in terms of voltage and current distortions due to the presence of harmonics at PCC.

1.4        Significance of The Study

This study will be of great benefit to the producers of solar inverter in that it will be help them to consider the effect of harmonics during their production. To the student involved, this study will help them to understand the meaning harmonics and its impact in power device – inverter.