Fundamentals of Smart Grid Systems

By Muhammad Kamran

Fundamentals of Smart Grid Systems offers an expansive introduction to the operationalization, integration, and management of smart grids—the distributed, renewable, responsive, and highly efficient power grid on the verge of radically transforming our energy system. The book reviews the design of smart grid systems, their associated technologies, and operations, helping users develop a modern foundational understanding of smart grid systems and many of their advanced implementations, where sophisticated technologies are employed. The work serves as a guidebook and primer for early career researchers, with a rich integration of current science, modern applications, and future implementations.

• Presents critical enabling technologies of smart grid systems alongside relevant aspects of their design, modeling, control, and operations, accompanied by numerical examples
• Discusses how to approach the integration and management of renewable energy sources in smart grid environments
• Features didactic pedagogical elements, including end-of-chapter problems, supplemental slideshows, and figurative elements to clarify and explain complex concepts
• Focuses on modern applications and current implementations in industry, such as power electronics for smart grids, AI and machine learning-driven modeling, advanced control strategies, and electric vehicles

• Language: English
• Publisher: Academic Press
• Release date: Dec 1, 2022
• ISBN: 9780323995610

Muhammad Kamran

Dr Muhammad Kamran is a PhD candidate at Gdansk University and former lecturer in the department of Electrical Engineering and Technology, Riphah International University, Pakistan. He has published 20 articles in international journals and published the book Renewable Energy Conversion Systems in 2021. He is interested in smart grid power systems, grid integration and conversion of renewable energy, power electronics and solar photovoltaic systems.

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Chapter 1: Introduction to smart grids

Abstract

Innovations in renewable energy sources, varying energy demand patterns, and energy-saving policies have rendered obsolete the concept of the conventional power grid. A new concept of an intelligent power grid consisting of flexible functionality and reliable information and communication technologies (ICT) has replaced the conventional power grid and is termed a smart grid. Conventional power grids contain all the components at the power generation station to ensure power transmission, power distribution, and power consumption. Power-generating units are the bulk ones like coal, oil, and gas-based steam power plants, gas power plants, hydropower plants, nuclear power plants, and combined heat and power plants. Bulk power stations may also include wind power plants and solar photovoltaic systems. The smart grid infrastructure consists of thousands of smart sensors, smart meters, advanced metering infrastructure (AMI), distributed generation sources, communication technologies, demand-side management, energy management systems, energy storage systems, and electric vehicles. All these technologies and instruments communicate with each other intelligently to make the grid smart.

Keywords

Smart grid; Communication technologies; Electric vehicles; Smart meters; Energy forecasting

1.1: Introduction

Innovations in renewable energy sources, varying energy demand patterns, and energy-saving policies have rendered obsolete the concept of the conventional power grid. A new concept of an intelligent power grid consisting of flexible functionality and reliable information and communication technologies (ICT) has replaced the conventional power grid and is termed a smart grid. Conventional power grids contain all the components at the power generation station to ensure power transmission, power distribution, and power consumption. Power-generating units are the bulk ones like coal, oil, and gas-based steam power plants, gas power plants, hydropower plants, nuclear power plants, and combined heat and power plants. Bulk power stations may also include wind power plants and solar photovoltaic (PV) systems. The smart grid infrastructure consists of thousands of smart sensors, smart meters, advanced metering infrastructure (AMI), distributed generation sources, communication technologies, demand-side management, energy management systems, energy storage systems, and electric vehicles. All these technologies and instruments communicate with each other intelligently to make the grid smart.

All renewable energy-based production can be connected to the smart grid. Since renewable energy sources are intermittent, if one source is not available the other source will balance the load. Since the smart grid is connected to the Internet for communication purposes, the privacy and security of customers are challenges in the advancement of the smart grid. Hackers may attack the network and identify whether a customer is at home by their energy consumption pattern, and use this information to burgle a house. Hackers may also steal the credit information of a customer.

1.2: Conventional grid

The conventional grid refers to the electricity grid, which consists of power generation facilities, transmission lines, substations distribution lines, and the consumer load. Currently, we plug into a switch and power on electrical appliances. One thing worth mentioning here about the conventional power grid is that it contains unidirectional grids in which electricity flows from the power generation facility to the substation and the end user. The existing conventional power grid was established in the 1890s, and over time advancements were accepted and adopted in delivering the power from generation to the end user.

1.3: Problems with conventional grid

The installation of the conventional grid started in 1870s and the equipment used in conventional grids involves old technology that requires continuous maintenance to ensure uninterrupted flow of electricity from generation to the consumer. With advancements in power grid equipment and the introduction of distributed generation, smart metering, energy storage systems, and the smart grid concept, the challanges in the adoption of the smart grid have been increased. Following are the challanges in the development of the smart grid.

•Conventional power plants, especially fossil fuel-based power plants, were built near localities without keeping in mind the community of remote areas that generate the concept of off-grid energy systems. The energy needs of the growing population and the newly constructed localities are not connected to the conventional power grid, and are out of the main progressive stream of their country.

•Conventional grids are unable to incorporate energy demands during peak hours, which creates the problem of load shedding.

•In conventional grids, if consumers are producing their own electricity through renewable energy sources such as wind turbines, solar PV systems, or biogas power plants, they are not able to sell their surplus energy to the grid.

•The power flow and communication in the conventional grid are unidirectional, i.e., from power generation to the consumer. This system is incapable of estimating the situation of power shortage on the generation side and the requirement of power on the consumer side.

•The power grid is at the risk of collapse because of the load imbalance. When the load demand exceeds the power generation, the system collapses and a complete shutdown may occur.

•Electricity meters in the conventional power grid system are obsolete, providing information only in terms of total energy consumed. They do not record the exact time of the energy consumed, which would indicate whether it was consumed during peak or off-peak hours.

1.4: What is a smart grid?

A smart grid is the electric power grid, which establishes a communication network between the power supplier and the power consumer with the help of smart sensors, smart meters, electric vehicles, and power-generating utilities. The smart grid introduces an energy management system that helps in balancing the energy demand and supply to produce and consume electricity efficiently at a lower cost. A comparison between the conventional power grid and the smart grid is shown in Table 1.1. The Energy independence and security Act (EISA 2007) has indicated the following features of a smart grid.

•The efficiency, security, and reliability of the smart grid are increased by the advancement of control technology and communication technology.

•The resources and operation of the smart grid are optimized and secured.

•Renewable energy resources and the distributed generation are integrated.

•Demand-side management is developed in the smart grid.

•The consumer can control the energy consumption pattern and can communicate with the grid in real time.

•Energy storage systems are developed and ancillary services are obtained through hybrid and plug-in hybrid electric vehicles.

•Smart appliances, devices, smart meters, and smart sensors used by the consumer can be integrated into the system.

Table 1.1

1.5: Overview of the smart grid

This section details the infrastructure of the smart grid which includes the architecture of the smart grid, distributed generation, electric vehicles, energy storage systems, smart and fast measuring, sensing instruments, integrated communication between all elements of the smart grid, etc. Fig. 1.1 provides an overview of the smart grid.

Fig. 1.1

Fig. 1.1 Overview of the smart grid.

1.5.1: Smart grid architecture

The difference between the conventional power grid and the smart grid is their architecture. The architecture of the smart grid consists of different layers like the application layer, communication layer, and the power system layer. The infrastructure of the smart grid is shown in Fig. 1.2.

Fig. 1.2

Fig. 1.2 Comprehensive infrastructure and architecture of the smart grid consisting of generation, transmission, distribution, and consumption.

1.5.1.1: Application layer

The application layer enables customer applications, smart meter applications, and power grid applications. In customer applications, it enables home automation, real-time pricing, and demand management. In smart meter applications, it enables auto meter reading, and communication between the consumer and the power company about billing and energy demand in real-time.

1.5.1.2: Communication layer

The architecture of the communication layer is the major difference between the conventional and the smart grid. All the communication between the consumer, smart meter, and the power utility is done through the communication layer. The signals from all the sensors used in the smart grid and in response the signals from the controller to take action are transmitted in the communication layer. A communication network based on geography is divided into the following categories, and a comparison between them is given in Table 1.2.

•Home area network (HAN): also known as the customer area network, this enables smart home devices and appliances, and connects them to the smart meter. The range of the HAN is short and the communication reliability with a low data rate is high. Implementation costs and the energy consumption of HAN are lower than the other types of the area networks.

•Building area network (BAN): this is a local area network (LAN) similar to the HAN and covers a whole building. If a floor of a building is considered a LAN, then the combination of the LANs of all the floors is considered the BAN.

•Industry area network (IAN): this is a more complex network covering a whole factory or an industry.

•Neighborhood area network (NAN): this is responsible for connecting a HAN, BAN, and IAN to a WAN. A NAN allows users to connect to the Internet quickly at a very low cost. Since the range of the NAN is high, its data rate is also high. In the smart grid, a NAN connects thousands of smart meters to the database.

•Wide area network (WAN): this is a large area network that enables communication over a large geographic area. In the smart grid, a WAN is used by a NAN to send and receive data from thousands of microgrids, smart meters, and other components of the smart grid. Since a large volume of information is carried by a WAN, a high data rate is required for communication, and optical fiber is commonly used for WAN communication.

Table 1.2

1.5.1.3: Power system layer

The power system layer works like the conventional power grid, and handles the generation, transmission, and distribution of power in the smart grid.

1.5.2: Grid monitoring

The reliability and the power quality of the smart grid are ensured by continuous monitoring of the system. If the voltage, current, frequency, and/or power of the grid are beyond the permissible limits, the performance of smart devices and sensors is degraded. Smart sensors, advanced metering infrastructure, and the SCADA system are used to implement smart grid monitoring.

1.5.3: Electric vehicles

Another technology that is part of the smart grid is the electrification of a vehicle, termed the electric vehicle (EV). Different configurations are adopted in EVs. Battery electric vehicles (BEVs) use only battery storage that is externally charged from the grid; no other source of energy like an internal combustion engine is integrated. Hybrid electric vehicles (HEVs) include parallel hybrid electric vehicles, series hybrid electric vehicles, and series-parallel hybrid energy systems. HEVs use two sources of energy: an internal combustion engine and a battery pack. If the state of charge (SOC) of the battery is high, the electric motor uses the battery for transmission. If the SOC of the battery is low, the engine works and provides the transmission. Plug-in hybrid electric vehicles (PHEVs) are the same HEVs with an additional feature of external charging from the grid. Fuel cell EVs use a compressed hydrogen fuel tank and a fuel cell stack. These EVs also provide various ancillary services to the grid. In cases where a grid is not available in a remote area, an EV can be a source of backup power.

1.5.4: Distributed generation

Distributed generation (DG) is defined as the generation of electricity using conventional or the renewable energy sources to feed the load connected to the distribution network. If the distribution network is connected to the transmission network, it may sell and purchase electricity for the grid. Depending upon the location of the DG, the range is defined as a few kilowatts to 400 MW. However, renewable energy sources are abundant but intermittent. The availability of the energy sources and the efficiency of the related energy-harnessing technology decide the efficiency of the DG. The various energy technologies that are considered part of DG are conventional technologies, renewable energy technologies, and mixture of both conventional and renewable energy technologies.

DG technologies are categorized as follows based on the energy source:

(1)DG sources based on conventional fossil fuel-based power plants (microturbine, reciprocating engine, Stirling engine, combined cycle gas turbine, combustion gas turbine, etc.);

(2)DG sources based on renewable energy sources like solar PV systems, wind, biogas, geothermal, micro-hydro, and fuel cell; and.

(3)mixed DG energy sources where conventional and renewable energy sources in combination form a microgrid.

DG technologies like solar PV arrays, wind turbines, solar thermal, micro-hydro, diesel engines, fuel cells, and storage systems are modular and available in smaller units that can be installed in the system and removed from the system in a very short time. Other DG technologies are reciprocating engines, combined cycle gas turbines, microturbines, combustion gas turbines, and Stirling engines.

1.5.5: Smart metering

In conventional meters, recording done manually by a meter reader could be erroneously recorded, and the intervention of the consumer also makes the system unreliable. Fig. 1.3 shows the infrastructure of a conventional meter in which all the communication and the power flow are unidirectional from power generation to the end user, and all is done manually. Smart metering is the key concept in implementing the smart grid concept. The smart meter's various functions include net metering. This is the billing mechanism in which the consumer can dispatch their generated electricity from the renewable energy sources to the grid when they are generating energy that is surplus to their requirements. They can later import electricity from the grid when their production is lower than the energy they need. At the end of the month, a net bill is sent by the company to the consumer. Depending on the net metering policy of the country or province, the consumer receives a retail price per unit of electricity sold to the grid, which encourages people to invest in renewable energy power generation.

Fig. 1.3

Fig. 1.3 Infrastructure of conventional meter showing unidirectional communication and power flow.

A smart meter, in addition to recording the energy imported from the grid and exported to the grid, records the power factor, current, and voltage level. For clarity in billing, smart meters specify for consumers the energy consumed in peak hours and off-peak hours. The infrastructure of smart metering is shown in Fig. 1.4, in which the communication between the database and the power consumption is bidirectional through information and communication technology (ICT) and the smart meter. The advanced metering infrastructure (AMI) provides the following advanced functions in the smart meter:

•statistics on power usage;

•prepayments and postpayments;

•electricity theft prevention;

•different events like power off;

•peak hours and off-peak hours;

•meter cover opening; and

Fig. 1.4

Fig. 1.4 Infrastructure of smart meter showing bidirectional communication and power flow.

The smart meter also monitors the overvoltage, undervoltage, voltage and current imbalance, power factor, voltage, and current.

1.5.6: Energy management

People's lifestyles are reflected in their per capita energy consumption. With an increase in energy demand, the production of energy should also be increased to balance demand and supply. The unpredictable load and intermittent renewable energy sources require either a larger network or an energy management system (EMS) for the smooth operation of the system. The basic components of an EMS are a communication system, renewable energy sources, smart meter, power utility, hybrid electric vehicles, and load. All these components are connected with a bidirectional power flow and two-way communication, as shown in Fig. 1.5. An EMS is the main feature of a smart grid because it:

•is a digitalized automatic system free from human intervention, which reduces errors in load and resource prediction;

•helps in balancing the energy production and consumption, which optimizes the system and reduces the cost of energy; and

•helps in implementing the demand response.

Fig. 1.5

Fig. 1.5 Energy management system in a smart grid.

An EMS is applied to the following three main actors of the smart grid.

•Electricity producers use the EMS to optimize the power production, keeping in view the energy demand. For example, if energy demands fluctuate at a specific time, the power producer may shut down some of the generators that generate expensive units of electricity. Similarly, on a cloudy day, the power producer may shift the load to other renewable energy sources like wind, biomass, biogas, etc.

•System operators use the EMS to regulate the power flow in the transmission and distribution system, reducing the line losses and increasing the penetration of the renewable energy-based electricity.

•Power consumers use the EMS to minimize power consumption during peak hours by scheduling the load.

1.5.7: Energy forecasting

In addition to the smart meter and the network of sensors, forecasting is another key feature of the smart grid. In a smart grid, three types of forecasting are performed: energy demand forecasting, energy production forecasting, and price forecasting. The consumption of energy is estimated by considering the energy demand by residential, commercial, and industrial energy consumers. Energy production forecasting is performed considering the availability of renewable energy sources like wind speed, solar irradiance, biomass, and geothermal energy. Price forecasting depends on the time of energy production and the source of energy from which electricity is being generated. Which technology for a single energy source is being used to harness the energy also impacts the price of the end product, i.e., electricity. Concerning the time horizon, the following types of forecasting are performed:

•very short-term forecasting (VSTF);

•short-term forecasting (STF);

•medium-term forecasting (MTF); and

•long-term forecasting (LTF).

The following methods are used for the above-stated time horizon types of forecasting:

•statistical

•machine learning

•deep learning

•probabilistic

•probabilistic deep learning

•hybrid

•preprocessing.

1.5.8: Demand response

The ability provided by the smart grid to consumers to alter their pattern of energy consumption by decreasing or shifting their electricity usage in response to peak hours for the sake of incentives is termed demand response (DR). Advanced metering infrastructure (AMI) and communication between the power-producing company and the end user let them decide when to produce and when to consume electricity, respectively. DR programs are used to balance the demand and supply of electricity. Customers are engaged in DR by being offered different incentives like time of use pricing, variable peak pricing, critical peak pricing, critical peak rebates, and real-time pricing. DR can also be part of the home energy management system (HEMS), where a consumer can switch off appliances that require heavy loads during peak hours, such as air conditioners and air and water heaters, and switch them on only during off-peak hours.

1.5.9: Energy storage system

Another key component of the smart grid is the energy storage system (ESS). In a conventional grid, the integration of the ESS is not feasible, but the smart grid and distributed energy sources make it possible to incorporate the ESS. With advancements and innovations in renewable energy sources and their harnessing techniques, distributed generation has become a novel concept, and the ESS is an essential component of the hybrid energy system and the smart grid. It helps to bridge the gap between energy production and energy demand. Because of the intermittent and unpredictable nature of renewable energy sources like solar and wind, grid ancillary services are not easy to obtain. The ESS is the best solution to incorporate these services. Ancillary services include grid stabilization, renewable energy integration, power quality, frequency regulation, load following, peak shaving, spinning reserve, time-shifting, and transient stability. Energy is stored in three different forms: electromagnetic, mechanical, and chemical. Technologies that are used to store energy in an electromagnetic form are capacitors, supercapacitors, and superconductors. Mechanical technologies to store the energy are pumped hydro energy storage systems, compressed air energy storage systems, and flywheel energy storage systems. Chemical energy is stored in the form of conventional batteries, flow batteries, and regenerative fuel cells.

1.6: Smart grid communication

1.6.1: Wireless communication

1.6.1.1: Cellular communication

Cellular communication is the most feasible option for the placement of communication infrastructure, since this system already exists in the telecommunication framework. Cellular technology is a reliable, high-quality, and high data rate network. Technology is still in development stages. Different technologies for cellular communication are the global system for mobile communication (GSM), general packet for radio service (GPRS), enhanced data rate for GSM evaluation (EDGE), the universal mobile telecommunication system (UMTS), high-speed packet access (HSPA), and long-term evolution-advanced (LTE-A) [1,2]. These cellular technologies are being used for electric vehicle communication, wide area networks (WANs), advanced metering infrastructure (AMI), and house area networks (HANs). The land area is divided into small areas called cells; multiple frequencies are assigned to a cell, and that cell contains the corresponding radio base station, as shown in Fig. 1.6. These frequencies can be reused in other cells, but not in adjacent cells, to avoid signal interference. Smart devices in the cells are connected to the base station, which is connected to the rest of the network through the mobile switching center (MSC) [3,4]. The power utility is also connected to the network. The application of cellular communication in the smart grid is shown in Fig. 1.6.

Fig. 1.6

Fig. 1.6 Cellular communication in a smart grid.

1.6.1.2: WiMAX

Worldwide interoperability for microwave access (WiMAX) is a wireless communication technology based on the set of IEEE 802.16 standards. WiMAX is similar to LTE and competes with it. It works within a range of 50 km with a 70 Mbps data rate. WiMAX works in two frequency bands. The frequency band of the line of sight communication is 11–66 GHz and for nonline of sight communication, it is 2–11 GHz [5]. WiMAX can also work as a network by scaling it to the local and regional levels. The IEEE 802.16 standard defines the physical and MAC layers. Multiple input multiple output (MIMO) and orthogonal frequency division multiple access (OFDMA) antennas are provided by the physical layer, which increases the nonline of sight capabilities. Secure and reliable communication is ensured by the media access control (MAC) layer by enabling data encryption standards (DES) and advanced encryption standards (AES). Because of the signal loss or attenuation, coverage of WiMAX becomes limited, which is its only drawback