Smart Microgrid Systems

Advanced Technologies

KTM Udayanga Hemapala, MK Perera

• Publisher: CRC Press
• Year: 2022
• Print ISBN: 9781032106298
• eBook ISBN: 9781000624908
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

This book highlights microgrids as integrating platforms for distributed generation units, energy storages and local loads, with an emphasis on system performance via innovative approaches. It explains the smart power system concept, transmission, distribution, and utilization, and then looks at distributed generation technologies and hybrid power systems. Smart approaches, an analysis of microgrid design architecture and its implementation, the mitigation of cyber threats, and system optimization are also included. Case studies related to microgrid modeling and simulation are placed at the end of each chapter.

FEATURES

• Focuses on applications of expert systems for microgrid control
• Explores microgrid applications for power networks and applications of expert technologies
• Reviews design and development technologies related to renewable energy for a weak power network
• Discusses cyber security for microgrids
• Includes case studies related to actual developments and research

This book is aimed at researchers and graduate students in power engineering and electronics.

1Overview of Smart Power Systems

DOI: 10.1201/9781003216292-1

1.1The Conventional Power Grid

1.1.1 Overview of a Conventional Power Grid

A conventional power grid consists of four main sections, as shown in Figure 1.1, namely generation, transmission, distribution, and utilization. Conventional power systems are based on large, centralized power generating stations. In most of these power stations, the electricity is generated by burning a fossil fuel and producing steam, which is then used to drive a steam turbine that in turn drives an electrical generator. In addition, conventional generation relies on nuclear power plants or major hydro plants where the capacity of the plant is in the MW range. The generated energy is delivered to the end user through complex transmission and distribution systems. Here, step-up transformers are used to increase the voltage to transmit the electricity to consumer centers, then the voltage is reduced for distribution using step-down transformers. Finally, the electricity comes to the consumer at a specified voltage and with the specified frequency at minimum cost. This process appears seamless to the end user. For example, when you flip a switch the electrical equipment is turned on. However, the existing power network is often described as the most complex machine ever built. It is a real-time energy delivery system. The main goal of the power system is to cater for loads with electricity at the specified voltage and frequency at minimum cost consistent with operating constraints, safety, and so on.

Figure 1.1General structure of a conventional power grid

The main characteristics of a conventional power network can be described as follows:

• High power plant capacity
• Lengthy transmission network
• Uni-directional power flow
• Low load controllability

There are several challenges faced by power system operators in achieving the required performance. The main reason for these challenges is the real-time operation of the electric power system. Real-time means that power is generated, transported, and supplied the moment you turn on some electrical equipment. In addition to that, a power system is subjected to disturbances, such as short circuit faults and lightning strikes, so a properly designed and coordinated power system protection scheme is required. In achieving the main goals of an existing power network, there are engineering tradeoffs between reliability and cost.

1.1.2 Problems Associated with Conventional Power Systems

There are certain problems associated with conventional power systems, as they are based on centralized generating stations. Bulk generation, heavy reliance on fossil fuels and cascading failures can be highlighted as examples.

1.1.2.1 Cascading Failure

Existing power networks are subject to the risk of cascading failures. What is a cascading failure? It is a failure in a system of interconnected parts in which the failure of one part triggers the failures of successive parts. This may result in power interruptions. For example, in an industry, if there is a grid power interruption there is no, or reduced, production, resulting in a loss of revenue. Several examples of cascading failures can be given as follows.

1.1.2.1.1 Fukushima Nuclear Power Plant Accident

This is good example of a cascading failure, where the sequence of events in Figure 1.2 happened in the plant after a tsunami hit the area.

Figure 1.2Sequence of events in Fukushima nuclear power plant accident

1.1.2.1.2 Blackout in Sri Lanka (2020)

After the blackout in 2020, which commenced at around 12.30pm on 17 August and lasted for between 7 and 8 hours, the Minister of Power of Sri Lanka appointed a committee (comprising two administrative officers, an additional secretary in the Ministry of Power who served as the chairman, a retired professor of mechanical engineering, an engineer who was the chairman of a corporation, two senior lecturers in electrical engineering, one senior official from the Ceylon Electricity Board (CEB), and one senior official from the Ministry of Power who was responsible for renewable energy development) to investigate the matter and submit a report within a week. As described in the committee report, one of the important grid substations tripped, so the system frequency increased beyond the current setting for the rate of frequency, tripping the relay of the main coal power plant, Lak Vijaya Power Station (LVPS). As a result, the generator-transformer circuit breakers of all three units of the LVPS made the power plant unavailable to the grid, resulting in a cascading failure.

1.1.2.2 Environmental Issues

Heavy reliance on fossil fuels causes emissions of carbon dioxide, which result in life-threatening conditions as they enhance the greenhouse effect. It is estimated that the annual CO₂ emissions from the world’s energy-related industries total 20 billion tonnes. Greenhouse gas molecules trap heat waves that reflect from the Earth’s surface and reradiate them towards the Earth. This disturbs the natural removal of heat from the Earth’s atmosphere and results in an overall temperature rise. To find solutions for the greenhouse effect, the world is now more concerned about reducing fossil fuel and promoting renewable generation.

1.2 Future Grid

The problems stated above associated with conventional power systems are the main drivers for changing the existing energy infrastructure. Therefore, the existing conventional grid needs to be updated, and the future grid will be more complex than today’s. The future grid will have the following characteristics:

• Decentralized power system with more distributed generation: The distributed nature of a smart grid ensures the integration of decentralized power generation such as solar panels, wind turbines, and biomass generators. The future power system needs to integrate green technologies, as this has now become a compulsory requirement due to global warming and other environmental issues.
• Consumers become producers (Prosumers): A prosumer is an individual who both consumes and produces at the same time.
• Multi-directional power flow: Once consumers become producers, the power flow will be in both directions. The system operators should then have the capability to control the variable distributed generation based on renewable energy. Otherwise, the system may be unstable.
• Flexible loads from participating in demand response programs.
• Adaptive and islanding capabilities.
• Self-healing capabilities: Self-healing refers to the ability to identify power grid problems in real time and safely respond by self-correcting.

When a grid is modernized with one or more of the characteristics listed above, it is converted to a modern grid and referred to as a “smart grid”.

1.2.1 What Is a Smart Grid?

A smart grid is an electrical system integrated with communications and information technology for enhanced grid operations, customer services, and environmental benefits.

For example, a new digital meter on your breaker panel will be a smart device and the initial stage of the realization of a smart grid. Adding a wireless network that reads that meter remotely or a data management system that processes the information will add more benefits. Adding some solar panels on the roof will then be beneficial in terms of distributed generation. The customer may then need some sort of a load controller for their heating, ventilation, and air conditioning system. All of these come as part of a smart grid.

1.2.2 Smart Grid Characteristics

The characteristics of a smart grid are presented in Figure 1.3.

Figure 1.3Smart grid characteristics

The distributed nature of a smart grid ensures the integration of decentralized power generation such as solar panels, wind turbines, and biomass generators. Also, smart grids combine intelligence and control, for the optimum utilization of power production and energy storage resources. The predictive nature of a smart grid refers to the measurement and analysis of anomalies that affect power quality, to prevent emergencies from occurring. In addition, the inh...

Table of contents

• Cover
• Half-Title Page
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Acknowledgements
• Authors
• Introduction
• 1 Overview of Smart Power Systems
• 2 Distributed Generation Technology
• 3 Overview of Microgrids
• 4 Novel Approaches to Microgrid Functions
• 5 Cyber Security for Smart Microgrids
• 6 Expert Systems for Microgrids
• 7 Conclusion
• Index