Introduction to energy Router: Architecture and functions for energy Internet

This article is about North Carolina State University A very important paper ：

The translation is as follows ：

Abstract : The next generation power system is called smart grid , A large number of renewable energy resources will be included , Fundamentally change the paradigm of energy management . In order to effectively manage the energy supply and demand in the power grid , The energy router is needed to dynamically adjust the energy distribution in the power grid , Energy Internet . This paper discusses the functional expectation of energy router design , The architecture and communication performance of the energy router are preliminarily studied . This paper records our progress in the design and implementation of energy routers , This is the key equipment to realize intelligent energy management in smart grid .

1. introduction

In recent years , The global attention to energy shortage and environmental problems is growing , Urge countries around the world to actively study the next generation power system characterized by renewable energy resources and intelligent energy management —— Smart grid . The energy development of smart grid will change significantly , From the heavy dependence on fossil fuels to solar energy 、 wind 、 Water power 、 The tides 、 geothermal 、 Waste is equally distributed 、 Diversified renewable energy resources . Smart grid is not only the use of renewable energy , At the same time, it is also a comprehensive upgrade of the traditional power system in energy management [2]. In traditional power system , Energy flows one way from the power plant to users , With centralized power generation 、 Characteristics of one-way transmission . by comparison , Smart grid supports distributed and flexible energy management paradigm . In this revolutionary energy management system , Energy is generated by maximizing the use of renewable resources , In a distributed way , A large number of grid users are energy producers , It is also an energy consumer [3],[4].

The dual role of grid users is similar to that of Internet users : Every Internet user is a contributor and beneficiary of information exchange on the network , Every grid user can buy and sell the energy of the grid . Due to the similarity between energy flow and information flow , Smart grid [5] It is named energy Internet . In the Internet , Packet router plays a vital role in information transmission . Again , In Smart Grid , We need energy routers that manage power transmission and distribution . Energy router will become a key component of smart grid . Smart grid is a new research field , At present, it is still in the original research stage , At present, there is no report on the research results of energy router design . In this paper , We try to provide a high-level overview of the functional expectations and research challenges of energy routers . seeing the name of a thing one thinks of its function , Energy router is a technology that integrates power transmission and information exchange . It undertakes two major tasks , namely Dynamic adjustment of energy flow and real-time communication between power plants , These two tasks also interact . therefore , We will discuss the functional requirements of energy routers in energy control and communication between devices , And how they are integrated into intelligent energy management entities . In addition to functional requirements , This paper also introduces the framework design of energy router and the preliminary experimental results of communication support for energy router . The work of this paper shows our current vision and achievable results , Therefore, we also discussed the next research direction . The rest of this article is organized as follows . In the second part , We outline the main features of smart grid , And map them to the functional expectations of the energy router . In the third section , We start with Power Electronics 、 The design requirements of the energy router are discussed in detail from three aspects of communication and control intelligence . The fourth section introduces the framework design of our energy router , The fifth section introduces its communication support , The sixth section discusses our future research work , Finally, the seventh section summarizes this paper .

2. Smart grid and energy router : Full functions are expected

In order to understand the key dependence of smart grid on energy router , We first outline the expected functions of smart grid , Then it discusses how the energy router supports these functions . Smart grid as a comprehensive upgrade of the existing power system , Contains a lot of new features , Among them, the most important new features include renewable energy and intelligent energy management to optimize energy utilization . To be specific , The functions of smart grid can be divided into 7 Fields [6]、[7]: Generate electricity in batches 、 Electricity transmission 、 distribution 、 function 、 market 、 Customer 、 Service provider . Energy router is a technical component in the operation of smart grid . Next, we discuss the application of energy router in various fields .

2.1. The use of energy routers in smart grids

1) Mass power generation :

Energy mainly comes from distributed energy . These energy sources are usually connected to the local power load . When local supply exceeds local demand , The remaining energy flows into the grid through the energy router . When the local energy is insufficient , The power grid provides insufficient energy through the energy router .

2) Transport domain :

The transmission domain is responsible for transmitting energy from the generator to the consumer . In the case of energy resource distribution , The transmission domain needs to dynamically schedule energy from the remaining energy , After meeting local needs . Therefore, energy router is needed to realize dynamic energy flow .

3) Distribution domain :

Energy distribution through the energy router . When user needs change over time , Energy routers are also responsible for tracking demand changes , To dynamically adapt to energy distribution .

4) Operational domain :

In order to optimize the operation , Grid status information must be collected , For example, the current energy generation capacity of distributed energy 、 Current energy demand of different customers . The status information is obtained from the energy router used in power transmission and distribution

5) Market domain :

The goal of the market domain is to achieve a balance between supply and demand , Therefore, energy supply and demand information must be collected from all parts of the power grid , In order to make the market domain work normally . Information collection relies on energy routers deployed on the grid .

6) Customer areas :

Customers buy energy from the grid through energy routers . When customers also generate energy from renewable resources , The energy router will adjust the energy demand and supply for its connected customers . If the total energy produced by users exceeds their own needs , The excess energy will be sold back to the grid through the energy router .

7) Service provider area :

Service providers can have their own energy production facilities , Energy can also be purchased from distributed renewable energy resources , And sell to customers . They need to know the current energy supply and demand information , To optimize services . Access to information depends on energy routers .

2.2. Energy router function

User level and grid level discussions show , Energy router is the basic equipment of smart grid construction . Because they are widely used in grids , They undertake a wide range of functions . Similar to internet router , Energy routers also have different location related tasks , Generally, it can be divided into user level functions and grid level functions .

1) User level functionality :

When the energy router is located at the edge of the grid , Connect directly with customers . Users mainly include distributed renewable energy 、 There are three types of distributed energy storage devices and loads . These users have built a microgrid , Take the energy router as the central coordinator . Every user in the same microgrid has a dialogue with the energy router for all energy services . Next we will discuss all the user level functions required by the energy router .

User attachments

Smart grid has an easy-to-use plug and play energy interface . When users connect to the smart grid through the energy router , The energy router is responsible for finding new user attachments , And configure it , For correct operation .

The service request

When an additional user wants to start a service , Users will send to the energy router “ The service request ” news . then , The energy router will “ Service acceptance ” Message reply to user , And control the solid-state transformer to provide energy services .

Status update

When the user state changes , Send a status update message to the energy router . The energy router updates its current user status .

Termination of services

When the user terminates the service , It sends... To the energy router “ Termination of services ” news , Then disconnect from the energy router . The energy router notifies the solid-state transformer to stop outputting power to the user . The detachment of users . When the user disconnects from the grid , The energy router detected a disconnection , And update its user interface accordingly . Detection is made possible by periodically detecting the presence of users and listening to user responses . If the energy router does not receive a reply from the user within a certain period of time , The user is considered disconnected .

2) Grid level functions :

Energy routers are not only connected to energy customers , It also communicates with other energy routers in the grid , Realize intelligent energy management .
The energy router manages its microgrid in two ways . They are grid connection mode and island mode . In grid connection mode , The energy router connects its microgrid to the smart grid , Energy enters and exits the microgrid through the energy router . The energy router acts as an energy flow regulator , Respond to the energy supply and demand of microgrid . In island mode , The energy router disconnects the microgrid from the power grid to protect the microgrid .
Distributed renewable energy and distributed energy storage equipment in microgrid must be able to adapt to local load . In order to maximize the running time , The energy router minimizes the power consumption of low priority tasks .

Several typical operation scenarios will be discussed below ( It combines user level requirements and grid level requirements ).
In a sunny day , When the photovoltaic system is ready to convert solar energy into electric energy , Send energy generation request to energy router . The energy router checks the local power demand , Including current load demand and energy capacity of distributed energy storage equipment , Then confirm with photovoltaic system , Start solar energy conversion . When the sun sets , Photovoltaic system stops generating electricity , Load demand increases . The photovoltaic system sends a service termination message to the energy router , And disconnect from the power grid . The energy router informs the distributed energy storage device to start energy supply . Early in the night , Wind turbines may be ready to generate electricity . It sends the service request to the energy router . Energy router and wind turbine confirmation , Start the power conversion and inject it into the microgrid . If the electricity generated by the wind turbine exceeds the local demand , The remaining electricity will be sold back to the grid . otherwise , The energy router requests insufficient energy from the grid . Late at night , The burden is lighter . The energy router starts charging the plug-in electric vehicle used the next morning , Charge the distributed energy storage equipment used in the next temporary power shortage . In the daytime when the electricity price of residential users is the lowest , The energy router of residential users arranges most of the energy consumption in their microgrid . contrary , For industrial users , The electricity price during the day is the highest , Their energy router may schedule non urgent tasks to the evening . therefore , The energy router dynamically determines the power consumption according to the cost .

3. Design requirements of energy router

The energy router bears the important power control function , Implement correctly in smart grid 、 Efficient energy management . It is power electronics 、 Technology integration of communication and Automation . therefore , Its design requirements include the following three aspects .

3.1 Requirements for power electronic equipment

Energy routers need power electronic devices to realize the automatic distribution and management of energy . It can be seen from the above application scenarios , The energy router collects power demand and supply information from the grid in real time , And dynamically adjust the power distribution and supply information according to the demand and demand . In the energy router , Power electronic device is the interface between intelligent management module and solid-state transformer . Power electronic equipment must be able to quickly 、 Run reliably , To ensure that the commands sent by the intelligent management module can be executed correctly .

3.2 Communication needs

The operation of the energy router depends on the grid status information it collects . for example , When the energy router detects “ Local load increases ” when , Start the photovoltaic system to generate electricity , When it is detected that the power supply device is not working properly , Turn off the power supply . The communication between energy routers must meet three conditions .

1) Transmission delay :

Communication delay defines the maximum time for a particular message to reach its destination through the communication network . Messages communicated between energy routers may have different network delay requirements [8],[9], This depends on the type of event that triggered the message . Most time critical messages in the smart grid need to be as small as 3 Millisecond transmission delay . therefore , The energy router must have fast enough processing and communication capabilities , To ensure low latency information exchange .

2) Communication reliability :

Communication between energy routers must be reliable [10]-[12]. The design of the energy router must minimize the failure probability . Besides , The energy router must have the ability of communication fault detection , In order to quickly retransmit the lost message . If the energy router encounters equipment failure , The remaining energy routers should be able to continue communication through the bypass .

3) Information security :

The information exchanged between the energy routers includes grid operation instructions . Forged or fake messages will endanger grid operations . therefore , The energy router must ensure the security of communication . A properly designed security mechanism is needed to prevent unauthorized users from reading and changing the information communicated between energy routers . If a malicious user injects a fake message , The energy router should be able to detect forgery and discard these messages .

3.3 Distributed grid intelligence

In addition to power electronics and communications , The energy router must also have a distributed grid intelligent module , In order to make a wise judgment on the energy management in the power grid . The grid intelligent module uses the information collected by the communication module , Determine the control changes to be carried out in the grid through the cooperation of energy routers . Each energy router is responsible for a microgrid , Combine the distributed power grid status information collected by different energy routers , Realize smart grid operation decision .

4. Energy router architecture design

In this section , We propose an energy router architecture , It combines power electronics 、 Communication and distributed grid intelligent module . In the power transmission and distribution system , Due to different equipment locations , The variation range of voltage and current is large . In our proposed energy router design , We used a 20 KVA solid-state transformer as an example . The energy router architecture proposed in this paper has been slightly modified , It can be applied to other solid-state transformers with different load capacities . We are in the picture 1 Our energy router architecture is described in .

4.1 Power electronics module

The core function of the power electronic module is to convert the high-voltage electric energy on the transmission line into different levels of low-voltage suitable for electrical appliances . therefore , The module consists of a series of sub transformers connected in sequence , Perform voltage conversion , Such as 7.2kV Convert AC to 10 kV Alternating current (ac) ,10 kV Convert AC to 400 V Alternating current (ac) ,400 V Convert AC to 120 V Alternating current (ac) , Obtain the power supply of the sub transformer from the output of the sub transformer . The sub transformer acts as the interface of different electrical appliances , Connected to various electrical interfaces . These interfaces provide plug and play power services for many appliances , And connect to the smart grid .

4.2 Communication module

The communication module of the energy router consists of two components , A component is used for internal communication within the energy router , Another component is used for internal communication between different energy routers . In the figure 1 In the architecture shown , Internal communication components are also known as power communication interfaces . This component is responsible for managing the communication between the solid-state transformer controller and each electrical port . Internal communication components can be designed as a dedicated communication board built with embedded systems .
It provides communication facilities , Information exchange infrastructure connected to smart grid . Network access technology includes ZigBee、 Ethernet and WLAN . The communication board can be connected with SST Independent board with separate control board , It can also be SST Control board integrated components . If it is a separate board , Serial link can be used for connection between two boards 、USB Or other possible technologies . chart 1 Take serial connection as an example .

4.3 Power grid intelligent module

The power grid intelligent module is integrated in SST In the control panel . It collects the status information of the energy router from the communication module , And optimize the management of energy production and distribution within the microgrid, between point-to-point microgrids . The operation decision of the intelligent module communicates with the power quality management component , The power quality management component is responsible for changing the configuration of solid-state transformers accordingly . Typical changes include port activation 、 Equipment accessories and grid connection .

5. Realization and experiment of communication module

We have implemented a communication module prototype for our proposed energy router architecture . This module is built as an independent embedded system , Send and receive through universal asynchronism (UART) The serial link is connected to the solid-state transformer controller ( This article calls it SST controller ) On . The communication modules of different energy routers exchange information through the communication network . The schematic diagram of the communication module and its connection with other energy router components is shown in Figure 2 Shown .

5.1 Realization

We use Technologic Systems The company's TS7250 Embedded system ( This paper is named ARM plate ) To build communication modules .ARM A single board is a general-purpose single board computer , have 200mhz ARM CPU and 64mb Memory , Run on modified Linux On the kernel , Provide WiFi、 Ethernet 、USB And serial port and other communication interfaces .SST The controller is implemented as a separate board , Sample the state value from the solid-state transformer and change the configuration . In order to allow ARM Plate and SST Communication between controller boards , It has been established ARM-SST Serial communication protocol ( Here's an explanation ), On two boards UART Work on the interface .ARM The board serves as the external communication interface of the peer-to-peer energy router . A variety of network technologies can be used in different energy routers to connect ARM plate , Like Ethereum 、 WLAN and ZigBee. We have implemented all three types of connections . However , Network connection alone is not enough to support information exchange function . In order to ensure the reliability of communication , Network layer protocol and transport layer protocol are required . Distributed network protocol is used in our prototype (DNP3).

1) ARM-SST Communication protocol :

We define ARM Board and SST Message format exchanged between controller boards , Designed ARM-SST Communication protocol . Pictured 3 Shown , The message format contains multiple fields .“start” Field indicates the beginning of the message ,“payload
type” Field indicates whether the message contains set points or all points . from ARM To SST Controller “ Payload ” from 6 Each 2 The set value of bytes consists of , And from SST Controller to ARM Of “ Payload ” Received by 6 Set values and 12 Simulation points . The last byte represents the packet checksum . When ARM When the board receives the control command from the network , These orders will pass UART The serial link is forwarded to SST controller .SST The set value received by the controller is responsible for controlling the interface power supply device , Such as relays and circuit breakers . As a response to the set value ,SST The controller sends the same control point and attaches the current state field of the storage structure ( Simulation point ) To admit ARM. The structure of storage is based on I/O The input value of the port is updated regularly . When a new setpoint is received from the network ,ARM The board keeps moving SST The controller sends the setpoint , Until we get confirmation .

2) Distributed network protocol :

DNP3 It's a kind of openness 、 robust 、 Efficient network protocol , It is specially designed for reliable operation in the harsh environment of power utility automation system . It can be used to monitor many physical processes and information status of remote locations through communication networks , Such as power consumption 、 voltage 、 Current and temperature .DNP3 Protocol support TCP/IP Stack communication . We use DNP3 As a network protocol between communication modules of different energy routers .

5.2 experiment

We have tested our prototype communication module , To measure packet delay . Packet delay is an important performance index in power system communication , Because the time critical commands in the power system must be transmitted and delivered in time . especially , We tested packet latency in three scenarios . In each scene , It's not the same length (16~ 4096 byte ) The data package passed through DNP3 Protocol transfer ,DNP3 The protocol runs TCP/IP On the protocol stack .

Via Ethernet TS7250-TS7250. Two TS7250 The embedded system passes 100 Mbps Ethernet connection switch . Every TS7250 To configure a 200mhz Of ARM-9 CPU and 64mb Memory , install Linux operating system . The measured packet delay is 0.8 ~ 1.6 Between milliseconds . adopt 802.11 b TS7250-TS7250. Two TS7250 Embedded system in its USB The port is connected WiFi Encrypted dog , And connect to the shared 802.11b Access points for communication . The measured delay is 3.2 To 17 Change between milliseconds .TS7250-ZigBee gateway .TS7250 The embedded system is connected through serial port Xbee-Pro Communication board , adopt 802.15.4 ZigBee Gateway for data exchange . The measured delay is 12 To 86 Change between milliseconds . In smart grid communication , Most of the time critical messages need to be as small as 3 Millisecond delay limit . However , It can be observed from the experimental results , In all tested Wireless Networks , The actual communication delay exceeds the bound . Be careful , When the network experiences heavy background traffic load or uses a more complex multi hop network , Delay performance will become worse . therefore , How to improve the packet transmission speed between communication modules of different energy routers is still a challenging research problem .

6. Future work

The work done in this paper is our outlook for the construction of energy routers , It is also our preliminary achievement in communication . There is still a lot of work to be done to realize the energy router . According to the three functional modules we determined , Our next work can be divided into the following three directions . We are currently trying to make SST Control panel , And connect it to the solid-state transformer .SST The controller board consists of a DSP Chip and a FPGA Chip composition , It can be read automatically by programming SST State information , And change if necessary SST To configure . The communication delay of the communication module needs to be improved . Our current experimental results show that , The packet delay of wireless network is significantly greater than that of Ethernet . However , Wireless network will be an important communication equipment in power system . therefore , How to shorten the packet delay in wireless networks needs further research . The reliability and security of communication will also be studied . At present, we have not studied grid intelligence . It plays an important role in realizing efficient energy management of power grid . Building this module requires a deep understanding of the energy distribution in the power grid , Advanced automatic real-time decision-making software is needed to dynamically adjust the operation of energy routers .

7. Conclusion

In the future smart grid , Energy router will be the foundation and indispensable equipment to support intelligent energy management . In this paper , We discussed different scenarios , For the use of energy routers in the power grid , Functional expectation of energy router design . On the basis of functional analysis , A design architecture of energy router is proposed , The architecture consists of Power Electronics 、 Communication and power grid intelligence are composed of three modules . It realizes some functions of the communication module , The delay performance of the communication module is tested . Experimental results show that , To make the energy router have good communication performance in wireless network , Further research is needed . Last , We discuss the next step of the design and implementation of the energy router . This paper summarizes our progress in the construction of energy routers , We hope that the work in this paper can promote our understanding of the function and implementation of energy router .

8. peferences