Newton-Raphson Based Load Flow Analysis Of AC/DC Distributed Systems With Distributed Generation

ABSTRACT

TABLE OF CONTENTS

Cover page/Title page

Certification page

Executive summary

CHAPTER ONE

• Introduction
  • Background of the Study
  • Problem Statement
  • Aims and Objective
  • Scope of the Study
  • Significance of the study

CHAPTER TWO

• Literature Review
  • Ac Distribution
  • c. Distribution
  • Distributed Generation
  • Environmental Impacts Of Distributed Generation
  • Review Of Related Studies

CHAPTER THREE

• Method
  • Loadflowanalysis
  • Newton-raphsonmethod
  • Discussion
  • Conclusion

CHAPTER ONE

1.0                                          INTRODUCTION

1.1                             BACKGROUND OF THE STUDY

World is trying to take urgent actions to reduce greenhouse emissions produced by the electricity sector since fossil fuels are mainly used to generate electricity. In order to have a more sustainable and environmentally friendly energy system, the electricity generation procedure is changing from fossil fuel dominant structure towards a more renewable and distributed one. Therefore, many countries are trying to adapt renewable energy resources to their electric power system while they are also working hard to meet their increasing electricity demand. Until today, power systems were mostly one directional in a way that generated electricity was being transferred by transmission systems to distribution systems where consumers are connected. As of today, however, electricity can be generated and consumed within the distribution system resulting in a bidirectional power flow. Additionally, EV charging stations may behave as generators to supply surplus energy to the utility grid and battery systems may behave like loads when they are getting charged. Therefore, overall complexity of the system increases and the electrical power system evolves into a smart and AC/DC hybrid structure. The fact that present distribution systems need to adapt increasing utilization of DC generators and loads implies that the traditional AC oriented power flow analysis also needs to change to meet new requirements for a hybrid power system. Many researches are presented on AC/DC load flow with focus on high voltage DC 2 (HVDC) transmission systems in the literature but these methods are not convenient for hybrid distribution systems since those methods are weak for systems where DC bus penetration is high and that increases complexity of the algorithm. Additionally, it is most probable that future smart AC/DC distribution systems will have several intersecting AC and DC nodes, branches, different AC or DC generators and loads coupled together, therefore decoupled methods which separate main AC/DC grid into several subgrids may not be suitable to be applied for coupled AC/DC distribution systems (ahmed et al ., 2018). Moreover, it is stated in (Baradar et al., 2013) that compared to the unified method, the sequential method is more complex, may have convergence problems in some cases and takes more time to converge to a solution because whole AC solution must be recalculated each time for a parameter update on the DC side. It is also indicated for the sequential method that algorithm reliability decreases and becomes more complex as the iterative loop number increases (Baradar et al., 2011). The advantage of Newton-Raphson iterative method is that it converges faster than other approaches owing to its quadratic feature. Therefore, this seminar have focused on an integrated methodology for load flow analysis of AC/DC distribution systems that are combinations of AC and DC microgrids. The proposed approach contributes such that a Newton-Raphson based iterative method for overall system level power transfers between AC and DC sub-networks is presented by utilizing AC/DC voltage source converters and several possible connection types in a hybrid distribution system with DC/DC converters are considered. Proposed load flow method takes into account all converter losses and is able to obtain power flow through converters connected at different buses. This method helps to reduce algorithm complexity and has the advantage of faster convergence speed with high accuracy compared to other approaches by combining AC and DC line flows.

1.2     STATEMENT OF THE PROBLEM

Increasing concerns about climate change and global pollution rates emphasized the importance of renewable energy resources. Rising pressure to utilize green energy alternatives requires some changes and rearrangements on the available alternative current (AC) oriented electric power system. Moreover, electric charging stations, renewable and distributed electricity sources like battery storage systems, solar power plants use direct current (DC) and additional power conversion is needed for their integration into the current distribution network. This study shall explain the concept of developing a hybrid AC/DC smart grid using load flow analysis approaches applied on hybrid AC/DC transmission systems.

1.3    AIM AND OBJECTIVES OF THE STUDY

The main aim of this work is to study the newton-raphson based load flow analysis of ac/dc distributed systems with distributed generation. The objectives of the study are:

1. To explain the concept of developing a hybrid AC/DC smart grid using load flow analysis approaches applied on hybrid AC/DC transmission systems.
2. To carry out a load flow calculation in AC/DC distribution systems.

• To proposed Newton -Raphsonmethod using Matlab in other to investigate the impacts of on Distributed generation.

1. To generate different kind of mathematical models of different kinds of DGs.

1.4 SCOPE OF THE STUDY

The scope of the seminar is to develop an integrated load flow approach for AC/DC distribution networks, which include a variety of power electronic devices as well as distributed energy sources. In the method presented, AC and DC power flow equations shall be combined and solved using Newton-Raphson algorithm with a modified Jacobian matrix. Commonly used DC/DC converters and voltage source converters present in the grid shall be represented with their respective models. This load flow calculation method shall be implemented on MATLAB and simulations are performed for different distribution test systems, which utilize a variety of converter models and load profiles.

1.5     SIGNIFICANCE OF THE STUDY

This study will serve as a source of knowing steps to reduce greenhouse emissions produced by the electricity sector since fossil fuels are mainly used to generate electricity in order to have a more sustainable and environmentally friendly energy system.

This study will serve as a means of having a wider knowledge about Hybrid AC/DC distribution systems, power flow equations and Newton-Raphson iteration.