Generation of electricity from renewable sources has become a necessity, particularly due to environmental concerns. In order for renewable sources to provide reliable power, their sporadic availability under certain conditions and the lack of control over the resource must be addressed. Different renewable energy sources and storage technologies bring various properties to the table, and power systems must be adapted and constructed to accommodate these. Power electronics and micro-grids play key roles in enabling the use of renewable energy in the evolving smarter grids. This book, written by well-known researchers with broad expertise and successful publication records, provides a systematic overview of modern power systems with integrated renewable energy. Chapters provide concise coverage of renewable energy generation, of storage technologies including chemical, electrostatic and thermal storage systems, and of energy integration, power conditioning systems, economic dispatch and scheduling, EV integration, as well as communications and cyber-security in power systems. This work is a highly valuable resource for researchers in industry and academia involved with renewable energy technology and power systems, for advanced students of related subjects, and for utilities engineers and professionals.
Inspec keywords: power generation scheduling; power system security; wind power; electric vehicles; power distribution economics; thermal energy storage; power generation economics; security of data; mechanical energy storage; power generation control; distributed power generation; renewable energy sources; load flow; solar power; fuel cells; tidal power stations
Other keywords: power systems Cybersecurity; modelling and control; generation scheduling; electrochemical energy storage systems; fuel cells; distributed energy resources Integration; microgrids; economic dispatch; ocean energy; mechanical energy storage systems; hybrid thermal and wind plants; tidal energy; power conditioning systems; thermal energy storage; electrical energy storage; wind energy; renewable energy; biomass energy; load flow analysis; solar energy; power grids; chemical energy storage systems; electric vehicles; power-to-gas
Subjects: Power system control; Solar energy; Fuel cells; Storage in mechanical energy; Distributed power generation; General electrical engineering topics; Tidal and flow energy; General control topics; Power system management, operation and economics; Wind power plants; General; Solar power stations and photovoltaic power systems; Transportation; Tidal power stations and plants; Wind energy; Storage in thermal energy; Data security; Control of electric power systems; Fuel cells; Power system protection
A power grid is dedicated to serve both large and small consumers with electrical energy. In developing the power grid, the focus of power system planners and operators is primarily aimed at providing electrical energy to the customers as economically as possible and with a high degree of reliability and supply quality. The term 'grid' denotes the entire electric system infrastructure, which is also commonly known as 'electric power system'. Thus, the two terms 'grid' and 'power system' are often used interchangeably. A brief description of conventional power systems, recent developments and future perspectives based on new enabling technologies, advanced controllers and communication facilities is presented in this chapter.
One of the most mature technologies for renewable resources is the wind energy. The wind is a motion of air masses caused by the different thermal conditions of these masses. The energy produced by this motion can be converted into another form of energy, such as electric energy. This approach, known as wind power generation, has grown rapidly during the past few decades in many countries around the world. Major catalysts for this rapid growth have arisen in the recent past: continuous technological advances in power electronics, controls and physical attributes (e.g. tower heights and blades) as well as cost reduction and significant advancements in understanding the access of wind power generation to the grid. Consequently, more attention is paid to high penetration of wind power sources in power systems as these sources are not only a means to reduce CO2 gas emissions but also an economic alternative. This chapter is focused on the description of wind system components and their functions being combined to convert the wind power to electrical output power. The basic relations necessary to design the wind turbine (WT) and evaluate its performance are introduced. The recommended controllers are also explained as the wind speed varies with time and yields a fluctuating character to the system. Different terms may be used when talking about the wind system such as wind generator, wind turbine generator, wind-driven generator and wind energy conversion system. In this chapter and in most literature, the term `wind turbine' is used. It is to be noted that the power is the energy per unit time.
Solar is the Latin word of the sun and solar energy is radiant light and heat from the sun that is a powerful source of energy. Many applications may use solar energy such as heating, cooling, ventilation, illumination, transport, cooking, water heating, water treatment, fuel production, electricity production, energy storage systems (ESSs) and buildings. It is found, statistically, that the amount of solar energy from the sun falling on the earth in one hour is more than that used by everyone in the world in one year. So, it is an important source of renewable energy, and solar technologies are broadly characterized as either active solar or passive solar depending on how they capture and distribute solar energy or convert it into solar power. Large-scale solar thermal systems, concentrating solar power (CSP) technology, can be used for electricity production. To study and analyse a utility grid supported by such active solar energy, it entails understanding how the solar energy is converted into electricity especially when using PV or CSP technologies.Parabolic troughs, linear Fresnel systems and power towers can be coupled to steam cycles of 10-200 MW of electric capacity, with thermal cycle efficiencies of 30%-40%. The values for parabolic troughs, by far the most mature technology, have been demonstrated in the field.
Ocean space has a huge amount of energy. Useful electric energy, generally known as 'ocean energy', can be derived from the ocean. It is an alternative renewable energy source (RES), like solar and wind energy. The important feature of ocean energy resources is that they have the highest density among the other sources of renewable energy.
Useful electric energy can be derived from the ocean waves and is known as 'ocean wave energy'. Physics of waves and their different forms as well as estimation of energy and its conversion into electrical energy.wave and thermal energy Useful electric energy can be derived from the ocean waves and is known as 'ocean wave energy'. Physics of waves and their different forms as well as estimation of energy and its conversion into electrical energy are explained in the forthcoming sections. 5.1 Wave energy concept Wave energy is the energy contained in the waves that are caused by winds blowing across the surface of the sea. Friction transfers some of the wind energy to the water thus forming waves.Wave energy is not tidal energy even though both fall under the category of ocean energy. While the tidal energy consists of long period oscillations, sea waves of short period are generated by the action of the wind.The devices used to capture wave energy and convert it into electrical energy are known as 'wave energy converters' (WECs).
The process of photosynthesis enables green plants to capture the electromagnetic radiation from the sun and transform it into chemical energy, with the biomass energy obtained by reversing this photosynthesis process. The stored energy within the living matter is released when the chemical compounds within the organic materials are broken down due to decomposition. The organic residue left over from this process is called 'biomass'. When biomass is burnt, the chemical energy in biomass is released as heat. Biomass can be burnt directly or converted to liquid biofuels or biogas that can be burnt as fuels. Therefore, biomass energy can be produced from a total natural process and source, and consequently it is regarded as a green and climate-friendly form of energy, making biomass energy a renewable energy resource unlike fossil fuels.
DERs are small, modular, energy generation and storage technologies that provide electric energy installed on site and of a size meeting local need. Furthermore, DER systems may be either connected to the local electric grid or isolated from the grid in stand-alone applications. DER technologies include renewable energy sources (e.g. wind turbines and solar photovoltaics), micro turbines, reciprocating engines, combustion turbines, cogeneration and electrical energy storage (EES) systems. Utilities can use DER technologies to delay, reduce or even eliminate the need to obtain additional central power generation, transmission and distribution equipment and infrastructure. Meanwhile, DER systems can provide voltage support and enhance local reliability. Therefore, the perspective of the electrical power grid in future can be seen as an integration of conventional generation and DERs and consequently the power flow can be bi-directional as shown in Figure 7.2.
Among the energy storage system (EES) types based on the form of energy stored (Chapter 7, Section 7.7), mechanical energy storage (MES) systems are one of these technologies. They include pumped hydroelectric storage (PRES), compressed air energy storage (CAES) and flywheels (FWs). PRES technology is suitable for energy management applications that move the power over longer time scales and require continuous discharge ratings of several hours and more. CAES is adequate for short- and long -duration energy management applications, whereas FWs can be used for power quality applications that require rapid response (less than a second), transient stability and frequency regulation. Principles and operation of each technology are described in the forthcoming sections.
A fuel cell (FC) is a static device having energy conversion function. Chemical energy of a fuel is supplied as an input to the FC, which converts it directly into electrical energy. Energy conversion results from a chemical reaction of positively charged hydrogen ions with oxygen or another oxidizing agent. FCs using hydrogen (H2 ) may be called 'hydrogen FCs'. They are different from batteries in that a continuous source of fuel and oxygen (or air) are required to sustain the chemical reaction, whereas the chemicals in batteries react with each other to generate an electromotive force (EMF). FCs can produce electricity continuously if the proper inputs are supplied. They can be used, as an alternative energy source with low emission of pollutant gases, for primary and backup power for commercial, industrial and residential buildings as well as in remote or inaccessible areas.
Electrochemical energy storage (EcES) systems are technologically mature for practical use. The electricity is stored as chemical energy, which can be delivered in the form of electrical energy using electrochemical reactions. They include all types of battery energy storage (BES): (i) conventional secondary (rechargeable) BES such as lead -acid (PbA), nickel cadmium (NiCd), nickel metal hydrate (NiMI-1), lithium ion (Li -ion), metal air (Me -air), sodium sulphur (NaS) and sodium nickel chloride (NaNiC1) batteries and (ii) flow batteries (FBs) such as vanadium redox (VR) and hybrid FBs.
This chapter presents the working principles and applications of electrostatic, magnetic and thermal energy storage systems. Electrostatic energy storage systems use supercapacitors to store energy in the form of electrostatic field. Magnetic energy storage uses magnetic coils that can store energy in the form of electromagnetic field. Large flowing currents in the coils are necessary to store a significant amount of energy and consequently the losses, which are proportional to the current squared, will also be high. Thus, the focus on superconducting coils is important as the resistance of the coils becomes zero in the superconductivity state. Thermal energy storage (TES) is a technology that stocks thermal energy by heating or cooling a storage medium so that the stored energy can be used later for heating and cooling applications and power generation.
These days, the trend towards developing electric vehicles technologies, aiming to enlarge the scale of electric vehicles use, is growing rapidly. The catalyst that makes the engineers and researchers motivated to work on this trend is the great concern about the environment, particularly noise and exhaust emissions, in addition to the continuous progress in batteries and fuel cells manufacturing and technology. It is, therefore, essential to understand the principles behind the design of electric vehicles as well as the relevant technological and environmental issues.
Power conditioning systems (PCSs) are power electronics devices/circuits that act as electrical interface between the utility power grid or demand and renewable sources or energy storage systems. A PCS is a dedicated device for power processing to output a voltage or current in a form adequate for the end user. The processing is based on one or a combination of some of the following functions: AC-DC conversion; DC-DC conversion; DC-AC conversion; AC-AC conversion; elimination of voltage ripples by filters; and monitoring and control.
To solve problems such as high energy costs or low electric power reliability at consumer's facilities, distributed energy resources (DERs) could be the solution that energy managers are looking for. DERs can deliver the same electricity services provided by centralized resources, including large-scale generators, and transmission and distribution network assets. Many DERs can be deployed at different scales and exhibit economical and technical benefits. For instance, solar PVs can be deployed at the kilowatt scale on residential rooftops, at the scale of several hundred kilowatts to 10 MW on commercial rooftops or ground-mounted arrays, or tens to hundreds of megawatts rating in the utility-scale solar farms. DER technology is developing at a fast rate, and it can provide electrical energy where required. In addition, DER systems can be either connected to the local electric grid or isolated from the grid in stand-alone applications.
Economic dispatch (ED) of power system could be defmed as the process of allocating specific generating units and the generation levels to the committed units in the mix with the primary objective of minimizing fuel cost or emissions or both while sustaining system constraints. This means that the total load demand plus system losses are satisfied at the minimum cost while satisfying different technical constraints of the network and power sources.
Electricity demand can exhibit large variations from weekdays to weekends, one day to another, peak to off-peak hours as well as from one season to another. As explained in Chapter 15, optimal loading of each generating unit in a power system encountering conventional thermal units integrated with renewable wind sources can be determined using economic dispatch (ED) techniques. All available generating units can be turned on to meet the demand, but it is usually not economical to continuously run all the units available all the time. Hence, it is desirable to look for an efficient economic short-term generation scheduling that plays an important role in the economic operation of a power system. The principal objective of the short-term generation scheduling is to efficiently determine the commitment of generating units as well as the economic loading of each committed unit so that the forecasted load demand and spinning reserve can be met over a short period ranging from 1 day to 1 week. The resultant schedule should minimize the system production cost during a specified period while simultaneously satisfying system and operational unit constraints.
The techniques of load flow analysis are of utmost importance to analyse, plan and design the power system. Power flow analysis defines the power system parameters at normal and abnormal operating conditions through the calculation of current or power flow in the lines of the interconnected transmission network, voltages at all nodes of the power system and the power delivered from generating sources.
Internal combustion engine vehicles using fossil fuels are at present the dominant energy sources for transportation sector. In the future, some problems may occur because of the fossil fuel availability and the continuous increase in fuel price. In addition, burning the fossil fuels produces greenhouse gases (GHGs) that highly affect the global climate change. Electrification of transportation sector seems to be one of the feasible solutions to these problems. Electric vehicles (EVs) such as plug-in hybrid electric vehicles (PHEVs) and plug-in electric vehicles (PEVs) will transfer energy demand from fossil fuels to electricity for transportation sector. Thus, reducing the pollution and alleviating issues that may compromise security can be achieved.
The global warming and other environmental hazards of conventional sources of electrical energy push the energy sector continuously towards distributed energy resources (DERs), especially renewable sources [1]. The fluctuating power produced by renewable sources such as wind and solar photovoltaic (PV) systems may bring challenges in generation/load power balance. With increasing penetration of renewable energy, the function of such distributed generation (DG) is changing from an auxiliary role to a primary role in the energy sector. DERs, renewable or non-renewable, and energy storage systems (ESSs) are integrated into what is known as a microgrid (MG). An MG deals mainly with the issues associated with the integration of such intermittent renewable energy sources (RES s) and ESSs. It gives many advantages not only for power balance but also for environmental challenges, economic benefits and grid reliability requirements [2]. Moreover, MG handles many technical issues in decentralized form [3,4]. There are intensive interests to develop and study the future horizon of MG concept throughout the world [4]. Generally, MG is a small -size, discrete electricity framework consisting of a collection of DG units and loads. It may operate in grid -connected or islanded mode and provide seamless transition between the two modes. MG may also include conventional generators such as diesel -based synchronous generators to mitigate the effects of the intermittency nature of RESs. Furthermore, many RESs act as inverter -based sources as inverters are used to interface them with the host grid or AC loads.
As explained in Chapter 1, great attention is continuously paid by power engineers and researchers in making the power grid a smarter grid (SG). The power grid is getting more complicated in configuration as it includes not only the conventional elements, such as generation, transmission and distribution systems with unidirectional power flow, but now also the distributed generation (DG) units and energy storage systems. DG units can be directly connected to the transmission and/ or distribution system or integrated together constituting microgrid(s), which can be connected to the distribution system at different locations. This developing configuration makes the power fl ow bi-directional rather than uni-directional. To achieve the desired technical, environmental and economic benefits, e.g. reliability and flexibility enhancement, emission reduction and power quality improvement, the power grid must be augmented with assets and systems that will enable it to operate in an optimal manner keeping customer satisfaction. Smart metering, communication and cybersecurity systems are of utmost importance to be incorporated into the power grid with a goal of modernizing the legacy electricity network and achieving smart characteristics. Cybersecurity is discussed in Chapter 21, whereas a brief introduction to smart metering and communication systems is given in this chapter.
Power system is a massive and complex system. Being highly dependent on ICT, with communications and networking systems, exposes the grid to potential vulnerabilities to physical attack or cyberattack . Thus, with the need to mitigate the risk of compromising reliability and security of power system operation, and surmounting the probable severe consequences from customer information leakage to cascade failures that may lead to complete blackout and eradication of the infrastructure, cybersecurity is becoming an issue of utmost importance in the design of the information network.
It is essential to obtain the probability density function (pdf) of the actual power output of wind or solar photovoltaic energy systems, especially for planning and analysing a power system incorporating such renewable sources of energy. Probability density function is a statistical expression that defines a probability distribution for a continuous random variable as opposed to a discrete random variable.
The modified IEEE 24-bus system without hydro generation is taken as a test system. Its transmission network consists of 24-bus bars connected by 38 lines and transformers and the generation system includes 26 thermal units at locations as shown in the single-line-diagram.