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7.2 Detailed Functional Architecture of Smart Grid

7.2.1 Functional Architecture of Smart Metering and Load Control

Note that although there are no explicit data flows and interactions from Management Functions to either End-User Functions or Power Grid Functions, there exist many relevant interactions with Management Functions. Similarly, Security Functions also interact with all other function blocks. Although there should be lines connecting the Security Functions with others, for ease of reading, those are not shown in the figure.

7.2.1.1 End-User Functions

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  DR Function: This function group covers all operations in the Customer domain for the major smart grid application that the customers interact with Service Provider domain and Smart metering.
  
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     DR Client Function: This function interacts with the DR (Demand Response) Application Function in the Application Functions for subscription to the service and dynamic pricing information. For industrial customers, this function also enables the management of industrial energy consumption per their needs.
     
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     Home Energy Management (EMS) Function: This function monitors the energy consumption of appliances and the dynamic pricing information, and interacts with homeowner in order to control appliances, and generation and storage devices in the customer premises. This function provides notification of power outage to utility companies, and responds to mitigation and recovery signals during a scheduled or unscheduled energy outage.
     
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     Metering Information Retrieval: This function retrieves meter reading information either directly from meters, or indirectly through the Smart Metering Application in the Applications Functions. Metering information may also be obtained from sub-meters in the customer premises.
     
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  Home /Business/ Industrial Network Functions: This function set provides communications function in the home/building/industrial through a Home Area Network (HAN), Building Area Network (BAN), and Industrial Area Network (IAN), respectively. The HAN/BAN/IAN interconnects all appliances and equipments, EMS, PEV charging stations, generation and storage facilities, and meters. Major sub-functions include:
  
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     Configuration: It manages the membership of the HAN/BAN/IAN, as equipment joins and leaves the network. It interacts with the Security Functions to authenticate the members, to authorize the operations they could perform, and the information they could send and receive, and to maintain encryption key information.
     
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     Bridging: As the HAN/BAN/IAN may consist of multiple transmission mediums and PHY/MAC communications protocols, this bridging function, either at the Link or Network layer, allows the EMS to communicate with all members in the HAN.
     
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     Energy Service Interface (ESI) Functions: For home ESI, it refers to the interface between the HAN and the Network Functions. It is more than the simple “gateway” logical device in a communications network. It is an “Energy Service Interface” that gates information in/out of HAN like a firewall and performs other functions. For industrial, it provides bi-directional logical interface that supports the communication of information between industrial energy automation and other entities in smart grid.
     
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  PEV Charging Function: This interacts with the Energy Control Functions and Customer Bill Function in the Application Functions to manage the charging rate and billing information.
  
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  Generation & Storage Management Function: This function manages the facilities for local energy source. It interacts with EMS for switching of power for consumption at customer premises or distribution to Power Grid. It also interacts with Energy Control Functions for feeding of power to the grid.
  

7.2.1.2 Application Functions in Smart Metering and Load Control

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  Smart Meter Headend Function: This function pairs with the Meter Reading function to provide the necessary smart metering functions for initiation of meter readings, and then performs further processing of collected data. It may interact with the data aggregation function in the Metering Network Function. It interacts with the Information Storage Function on meter reading database as well as with the Security Functions associated with security and privacy areas.
  
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  DR Application Function: This function pairs with the DR Client in the End-User Functions to effect the Demand Response operations in managing the demand of energy. It interacts with Energy Monitor and Control function and other market functions (not shown in Figure 4) to determine the price of energy dynamically. It interacts with DR Client Function for customer registration/de-registration of clients, and interacts with Customer Subscription/Billing Function.
  
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  Information Handling / Storage Function: The function addresses the syntax, semantics, and storage aspect of all information related to the smart metering and load control application.
  
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  Business Data Transport Function: This function handles the networking function for supporting business related activities. It interacts with all external counter-parts of this application.
  
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  Energy Pricing Function: This function determines the energy price based on energy market operation, power utility’s policy, customer’s demand, and others.
  

7.2.1.3 Smart Metering Functions

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  Meter Reading Function: This function concerns operations of physical smart metering devices; it provides meter readings at the command of Smart Metering application. The data passes through the Metering Network Function and Core Network/Transport Function as well as the Business Network function. The Meters may provide meter readings to End-User Functions through the Energy Service Interface (ESI) that may be a part of meter, or interacts with the Network Function. An alternate path is for the Energy Management Station (EMS) to inquire the meter database in the applications functional group.
  
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  Meter Control and Maintenance Function: This function, interacting with the Smart Meter Headend Function in the application functional group, provides the management and maintenance of meters and metering infrastructure, such as service initiation or termination, testing, fault detection and recovery, firmware update, and others. It also interacts with the Security Functions group for authentication, authorization, accounting, and auditing functions.
  
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  Fault monitoring and protection: This function enables real-time two way communication between customers and utilities (e.g., service providers) for monitoring and control to improve stability of the grid. It provides the exchange of tailored metering data, event or alarm information. The features include voltage and energy use monitoring, identification of faulty meters, verification of restoration after outage, outage detection, isolation and restoration, and others.
  

7.2.1.4 Energy Control Functions

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  Load Monitor and Control Function: This provides the capability to monitor and control the system load. It interacts with the Demand Response Function in the End-User Functions to achieve necessary load reductions. It also interacts with the Load Monitor and Control Function in the Power Grid Functions group to control the distribution of power in response to changing load of PEV charging.
  

7.2.1.5 Network Functions

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  Metering Data Transport Function: This function provides the connectivity for meters in a small geographical area, and data aggregation for meter readings in the area, and connectivity for End-User Functions group in homes or buildings through Gateway function. The network that supports this function is denoted as Neighbourhood Area Network (NAN).
  
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  Core Data Transport Function: This function is described in Section 7.1.
  

7.2.1.6 Management Functions

7.2.1.7 Security Functions

7.2.2 Functional Architecture of Energy Distribution and Management

A way to accomplish this goal is the deployment of ubiquitous networked sensors and measurement devices, and the software system to understand and ultimately optimize the management of grid components, grid behaviour and performance, and to anticipate, prevent, or respond to the problems before disruptions can arise.

The functional models of these two areas are shown in Figures 5 and 6 below. In particular, Figure 5 shows the functional model for power grid monitoring and control, and Figure 6 shows the functional model for energy usage and distribution management. These two figures follow the model shown in Figure 3 in Section 7.1 with eight major function groups – Application, Network, Power Grid, End-User, Energy Control, Smart Metering, Management, and Security Functions. Within each function group, a number of functions are detailed. The lines between function boxes indicate data flows and interactions between them. Note that several functions appear in both figures, some provide common functions to both applications, and some provide unique functions to each application. The Security and Management Functions are referred to Section 7.1.

Figure 5 Functional Model of Power Grid Monitoring and Control

Figure 6: Functional Model of Energy Usage and Distribution Management

This function group covers the functions for users of electricity, including home, commercial, and industrial users. Major functions of this group were already discussed in the Demand Response and Energy Control application in Section 7.2.1. Two functions applicable to power grid monitoring and control are repeated here: (i) the local generation and storage function or Distributed Energy Resources (DER) and (ii) the networking function.

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  DER (Local Generation & Storage) Function: The generation and storage facilities composing the DER at the customer site may participate in the grid monitoring and control application by providing status information to the grid and allowing the grid operator to control the feeding of power to the grid. The status and control information are transferred from/to the corresponding DER Control Function in the Energy Control Functions group through the premises network and core network functions. Note that the local generation and storage facilities on DER could be autonomous or locally controlled as well as centrally controlled by a grid operator.
  
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  DR Client Function: This function interacts with the DR Application Function in Application Functions group to control the usage of energy using dynamic pricing. During the period of peak demand the utilities raise the price through DR Application Function to reduce demand and at the same time DER Function is used to increase power supply.
  

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  Home/Business/Industrial Network Function: This function is described in Section 7.2.1.1 for Home Network Function.
  

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  The HAN transports data between all appliances and equipment (e.g., EMS, PEV charging stations, DER, and others). ESI/LAN provides the secured and effective communication functions that enable the interactions between relevant HAN devices and utility network.
  
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  The Business/Industrial Networks transport data between devices in commercial and industrial premises. This function interconnects meters, DER, PEV charging stations, BEMS (Building Energy Management System), and others. BEMS monitors and controls all conventional BAS (Building Automation System) of electric power and HVAC (heating, ventilating, and air conditioning) as well as FMS (facility management system). Business Network Function guaranties secured and effective data transport functions that enable the interactions between relevant systems and BEMS, and the interactions between BEMS and utility network.
  

7.2.2.2 Power Grid Functions

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  DER Function: The distributed generation and storage devices associated with DER Function may be embedded in the transmission/distribution systems or in distributed micro-grids. Therefore those DER need to interact with DER Control Function in Energy Control Functions group so that their status are available, and their outputs are fed into the grid as needed. This function also allows industrial customer to integrate their production and storage into the grid.
  
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  Protection and Control Function: This function, either at the command of the Operation Control Function in the Application Functions group or initiated automatically based on local sensing or measurement data, executes necessary protection, recovery, and control operations in a Power Grid station – generation, transmission, or distribution station. Within a station, it interacts with Operation Control Function through Substation LAN/SCADA Network Function.
  

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  Sensing and Measurement Function: This function is provided by sensors and measurement devices located at the power distribution system. New generation of devices, such as Intelligent Electronic Devices (IED) and Phasor Measurement Unit (PMU), could provide more accurate, real-time information Operation Control Function and Energy Control Functions to manage the operations of the power grid.
  
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  Time Synchronization Function: This function maintains and synchronizes high resolution clocks in substations and the power grids. Measurement data (e.g., PMU data) needs to include accurate time stamps before forwarding to the Energy Control Functions group.
  
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  Data Aggregation Function: The measurement data may be aggregated before forwarding to the Energy Control Functions group, which will be de-aggregated for further processing.
  
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  Substation LAN/SCADA Real-time Data Transport Function: This function enables the communications between devices within the Power Grid station, and between these devices and external Functions group through the SCADA Real-time Transport Function and Core Network Transport Function. This function provides the secured and real time delivery and management of data and information to SCADA control centre. Minimum message forwarding delay and delay variation are major requirements in this function.
  

7.2.2.3 Application Functions

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  Operation Control Function: This function is responsible for monitoring the day-to-day operation of the grid. It ensures the reliability, frequency and voltage stability, transient angular stability and small signal angular stability in the power system. This function provides the functionality to monitor the status of processes under control, modify control settings, and manually override automatic control operations in the event of emergency. This function also interacts with the rest of the Application Functions, in particularly with the Energy Usage Management Function to ensure supply meets demand. This function includes simulation and forecasting.
  
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  Asset Management Function: In addition to the normal business operations, this function could be established and used for the correlation of measurement reports, for display, and used by the operators in performing the Operation Control Function, and maintaining and upgrading systems.
  
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  Energy Usage Management Function: This function, in conjunction with Operation Control function and other functions, controls the demand response of electricity. On the supply side, it interacts with the Capacity Planning Function to estimate the short and long term demands, and with the Wholesale Marketing Function to secure supply. On the demand side, it interacts with DR Application Function using dynamic pricing and other means (e.g., capacity) to control the energy usage.
  
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  Wholesale Marketing Function: The open market provides means for efficient distribution between the suppliers and energy distributors. It affects the other functions such as bringing DER online, changing the DR pricing, and others.
  
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  Capacity Planning Function: Capacity planning from the Operations perspective is mainly a short term planning in projecting the available supply so that the Energy Usage Management Function and Wholesale Marketing Function can take appropriate actions.
  
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  Demand Forecast Function: This function projects the short term demand based on usage trend and other information such as weather forecast information.
  
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  DR Application Function: This function manages the Demand Response application discussed in Section 7.1; it receives the energy supply and demand information from Operation Control Function and interacts with Wholesale Marketing Function to dynamically determine the price of energy. It is responsible for managing the demand of energy and supports the utilities to balance the demand and response with the efficient energy delivery and usage.
  
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  Smart Meter Headend Function: This is part of DR application (as described in Section 7.2.1) that obtains the energy usage information for the Energy Usage Management Function.
  

This functional group enables the intelligent, reliable, and effective utilization of energy consumption and distribution and provides the self-repairing and self-optimizing management of power grid.

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  DER Control Function: DER pairs with the DER Function in the Power Grid Functions group to monitor the status of distributed energy resources and control the flow of electricity into the grid.
  
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  Load Monitor and Control Function: This function provides the capability to monitor and control the load power transmission and distribution. It either initiates load balancing operation in the power grid, or interacts with the DER Control Function to bring the power sources online or offline. It also interacts with the Energy Usage Management Function for system wide supply and demand management. Note that DER could be autonomous or locally controlled as well as controlled by DER Control Function.
  
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  Fault Location/Isolation/Recovery Function: This function enables the fault detection and recovery of grid infrastructure. It interacts with the Sensing and Measurement Function and the DER Control Function to improve the reliability of energy distribution by identifying the faults quickly, providing quick response to isolate the faults, and taking effective system outage recovery actions such as informing the status of power grid, reacting to the information from others, and predicting and preventing the impact of control function to other grids.
  
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  Wide-Area Situational Awareness (WASA) Function: This function represents the monitoring of the power grid across wide geographic areas. The WASA Function in the group interfaces with the WASA function of other utility’s Smart Gird, exchanges grid status with each other, reacts to status information from others, and project the impact of local control action to other power grids.
  
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  Time Synchronization Function: Just like the Time Synchronization Function in stations of the power grid, the home office for the energy control needs to maintain and synchronize clocks, so that events in the grid could be correlated for other functions to be interpreted as status data and take actions accurately.
  
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  Data Aggregation/De-Aggregation Function: This function interacts with the Sensing and Management Function to de-aggregate data from grid-monitoring devices (e.g., PMU and others) and aggregate control information to be sent downstream.
  

The Smart Metering Functions group consists of the following function:

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  Meter Reading Function: Similar to Smart Metering and Load Control discussed in Section 7.2.1, Meter Reading Function in energy distribution is concerned with the operations of smart metering. The meter reading data are transmitted through the Core Network Transport Function. It interacts with DR Application Function and Energy Usage Management Function. The meters may provide meter readings to End-User Functions through the Energy Service Interface (ESI), which may be a part of meter or, interact with the Network Functions. It also provides the End-User energy consumption information to help Energy Usage Management Function to realize energy consumption management in real time.
  

This function group enables the communication between all function groups. A unique characteristic of this group is that it carries the time sensitive and low delay tolerance real-time information. To accomplish this, the traditional dictated SCADA network can continue to be used. If the shared transport network, such as IP-network, is adopted, a strong Quality of Service (QoS) control is required.

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  SCADA Real-time Transport Function: This function supports the real-time communication between the Power Grid Functions group and the Energy Control Functions/the Operation Control Function groups.
  
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  QoS Management Function: The QoS Management Function is described in Section 7.1.
  
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  Core Data Transport Function: This function is described in Section 7.1.
  

The Management Functions are described in Section 7.1.

The Security Functions are described in Section 7.1.