Smart Grid and Enabling Technologies. Frede Blaabjerg

supply and grid support. Therefore, the storage provides a way to settle the peaks and valleys of supply and end disruptive electricity supply. Storage technologies needs more advances to accomplishing higher power and energy capacities to enabling large‐scale deployment. ES systems are combined with advanced power electronics as the interface with the electrical grid. The technical benefits of ES are various forms of grid support [22]. Distributed storage systems may have enormous potential to provide various services to the grid such as supporting the grid's voltage and frequency, providing spinning reserves, enhancing national grid security, and improving grid resiliency. Distributed ES systems are installed at a number of locations on and off the grid. Such systems have two main elements for charging and bi‐directional energy flow as shown in Figure 1.9. Most of the existing large‐ and utility‐scale storage resources are hydro and pumped storage. ES can also provide many financial benefits [24].

      Effective storage relies on storing and discharging electricity at the required time, and in a way that relies on clear and automatic pricing signals transmitted to smart storage systems. Such storage can give a solution to some challenges, for example, the power congestion at the distribution level, hence avoid/defer potential upgrades in grid infrastructure. However, there are many storage related challenges that must be taken into consideration such as [25]:

       Policies enhancement on net metering, DR, grid reliability standards, generation‐based incentives vs hybrid solutions, and the need to consider energy efficiency policies at equipment level vs efficiency at the systemic level.

       Distortion of price signals due to subsidies or lack of real‐time pricing signals for consumers.

       Need to consider life‐cycle vs capital costs for the selection of government‐funded projects.Figure 1.9 The distributed energy storage system.

       Awareness of available technologies and opportunities in various sectors.

       Cost of technology role for the localization and system integration.

       Need for innovative business models.

       Need for financing mechanisms.

      1.5.3 Demand Response

      The concept of DR has emerged as a solution to demand‐side control in the microgrid [26]. Using smart meters and the bidirectional way of communication in the SG opens the door to the technology to participate in the electricity market improvement [27]. The DR programs can be defined as the most successful solution to solve the peak‐load burden on the grid and engage customers in the wholesale market operations. A greater number of active consumers can change the profile of the load by minimizing or maximizing the demand as per the generation instructions. This ensures that the load will follow the generation, rather than the generation following the load as in the current energy paradigm. However, these types of programs attract a number of customers' schemes, but designing it remains a major challenge. Most DR programs and the challenges faced when implementing these programs will be presented in detail in Chapter 11.

      1.5.4 Integrated Communications

      Communication infrastructure is essential for the effective functioning of SGs. The implementation of communication technologies guarantees the decrease of energy consumption, ensures best implementation of the SG, and provides coordination among all SGs' components from generation to the end‐users. Examples of existing communication network technologies used for SG are fiber optics, WLAN, cellular communication, WiMAX, and power pine communication (PLC). Detailed discussion of the integrated communication in the SG and a comparison of communication infrastructure between the legacy grid and the SG communication standards and research challenges and future trends are presented in Chapter 8.

      1.5.4.1 Communication Networks

The communication system connects various components of SG architecture for real‐time control, monitoring, and data utilization. Integrated communication is the connector for all SG technologies. The communication infrastructure of the SG is predicated upon three types of networks: Home Area Network (HAN), Neighborhood Area Network (NAN), and Wide Area Network (WAN). Figure 1.10 shows the diagram of the SG communication infrastructure [28]. HAN is installed and operated in a small area (tens of meters) and has a lower transmission data rate of hundreds of bits per second. HAN consists of a broadband internet connection used to communicate and share the data between devices over a network connection and smart meters. HAN offers more efficient home energy management [28]. NAN is installed and operated in an area over hundreds of meters. A number of HANs can be connected to one NAN to transmit the data of other NAN networks and to local data centers for storage and further analytics. The NAN has a 2 Kbps transmission data rate. Different technologies can be used to implement the NAN network such as PLC, Wi‐Fi, and Cellular [29].

      WAN is installed and operated in an area of tens of kilometers and it contains several NANs and LDCs. The communication between SG components such as renewable energy generation, transmission, distribution, and the operator control center are predicated upon a WAN network [30]. SG communication infrastructures share the same main challenge, which is how to be merged effectively. A number of technologies can be employed to the SG to achieve an effective merge between communication infrastructure. These technologies are ZigBee, WLAN, Cellular networks, and Power Line Communication (PLC).

      ZigBee is utilized in applications requiring a small data rate, prolonged battery life, low price, and safe networking. Applications also include wireless light switches, traffic control systems, meters for in‐home‐displays, and extra consumer and industrial devices that require a short‐range of wireless data transmission at relatively low rates. The benefits of ZigBee application in the SG are low cost, decreased size, and relatively decreased bandwidth. The drawbacks of the ZigBee are the small battery which suggests a short lifetime, small memory, limited data rate, and low processing capability [31].

Figure 1.10 Schematic diagram communication infrastructure for the SG.

WLAN is a wireless local area network (WLAN) that links two or more devices through the use of spread‐spectrum or Orthogonal Frequency Division Multiplexing (OFDM) [32] and generally delivering a connection through an access point to the internet. This provides customers with the chance to roam around in a local coverage area and at the same time maintain connection with the network. The benefits of WLAN are low price, huge installations worldwide, and plug and play (PnP) devices. The main drawback of WLAN is possible interferences with other devices that communicate on similar frequencies.

      Cellular networks are vastly employed in the majority of countries and possess a well‐recognized infrastructure. Cellular networks could be utilized for communication among a number of components and devices in the SG. There are a number of current technologies for cellular communication including GSM, GPRS, 3G, 4G, 5G, and WiMAX [33]. The benefits of the cellular networks are presently available infrastructure across a vast area of implementation, elevated rates of data transmission, existing security systems implemented in cellular communication. The main drawback is that cellular networks are shared with other customers and are not fully devoted to SG communications.

      1.5.4.2 Power Line Communication (PLC)

      PLC permits data exchange among devices