A practical implementation of wireless sensor network based smart home system for smart grid integration

A Practical Implementation of Wireless Sensor Network based Smart Home System for Smart Grid Integration Minh-Triet Nguyen, Lap-Luat Nguyen, Tuan-Duc Nguyen International University of V

A Practical Implementation of Wireless Sensor Network based Smart Home System for Smart Grid

Integration

Minh-Triet Nguyen, Lap-Luat Nguyen, Tuan-Duc Nguyen International University of Vietnam National University, Vietnam

Email: ntduc@hcmiu.edu.vn

Abstract—This paper presents a hardware design of smart

grid home gateway that integrates smart home network to be

compatible for smart grid integration In this network, a Smart

Grid Home Gateway can control the electrical appliances based

on the programming schedule or data received from control

center Moreover, some low cost wireless transceivers for Smart

Grid are investigated and a simple wireless network topology

based on star routing protocol for Smart Grid Home Network

is also proposed Final, demonstration results display an actual

SGHG prototype to verify the system

Index Terms—Smart grid, electricity meter, wireless

commu-nication, WSN, home network, saving energy consumption

I INTRODUCTION

Electricity becomes the most important thing in modern

life Today, a chain effect with serious consequences can be

occurred in case of the interruption such as a power failure

affecting the banking system management, communications,

transportation and security Because the sustainable growth

must be ensured in the future, people need a new kind of

power grid This technology is not only built from the current

architecture platform that can handle the signal bit of modern

digital devices, but also capable of automatic control,

moni-toring and managing the complexity of the electrical system

as well as the growing demand for electricity One of the main

developments and important technologies in the power system

is the Smart Grid [1] The Smart Grid can be known as an

integration of the modern systems as information technology

and communication networks into the traditional grid This

combination allows providers and consumers to communicate

two-way via better controlling and management of electrical

energy in the transmission, distribution and consumption In

addition, the Smart Grid also unlocks enormous potential of

the current power grid such as: push of the renewable energy

source, improve the safety and stability of the power supply

with the participation of consumers [2]

Given that the relative studies in [3], [4] and [5], the smart

grid system consists of two main layers known as smart grid

system layers and network layers Figure 1 shows components

which are contained by two main layers This research focuses

on the design of a smart grid system in the home area network

(HAN) Especially, a hardware prototype (smart grid home

gateway) for the central control circuit of the household is

introduced

A smart grid home gateway (SGHG) has to response

func-tions as optimal power distribution and limitation overload

on the grid system, increase energy production efficiency and

Fig 1 Smart grid architecture

reduce wasteful consumption of energy for fake load More-over, it also helps effective utilization of renewable energy sources, decreases cost of energy consumption and contributes environmental protection [6] [7] To reach these requirements, the SGHG is designed with the following capabilities: 1) Communication and monitoring

a) Noting continuity energy consumption in real time b) Collecting data of electricity prices or the state of the grid from the center control

c) Management of the operational of the electrical equipment in the home

2) Intelligent Control a) Self-adjusting power usage mode according to in-formation received

b) Change the power usage based on time (program-ming schedule)

Basically, there are two types of data infrastructure that is essential for the data transmission in a smart grid system The first pathway is between the sensors and the electrical appliances with the SGHG, the second one is from the SGHG to control center According to the development of the innovative wireless technologies, recent research studies [8] [9] present the wireless sensor networks (WSNs) technology

as a key solution for monitoring and securing the electrical transmission and distribution The advantages of the WSN in the Smart Grid: low-cost infrastructure, rapid deployment and flexible connection to difficult areas, aggregate intelligence via parallel processing [10] [11] These are reasons why the WSN has emerged as a safe and effective concept [12]

The paper describes an efficient hardware design of smart

grid home network for integrating the electrical appliances

to the smart grid system, in particular the smart grid home

network The paper also presents the pratical test for SGHG

and SHGN to verify their ability in real life

The rest of this paper is organized as follows In Section

II, we describe in more details about components of the smart

grid system in household Section III - IV then looks at the

prototype hardware design and wireless module selection and

some basic information of software designs respectively The

practical implementation is described in Section V In section

VI, the performance is evaluated Finally, section VII has the

conclusion

II SMART GRID NETWORK ELEMENTS

The smart grid home network (SGHN) gives users the

ability of monitoring in real time Every 60 minutes, number

of power consumption will be reported on the SGHG by the

electricity meter SGHG also controls the electrical equipment

in the home wireless network and wireless control button

Be-sides that, the SGHN provides the option of using alternative

energy sources By this way, a system of renewable energy

generators like solar energy and a windmill generator will

be equipped and used as replaced energy in the household

Moreover, the SGHG collects data about the status of the

power grid as the update of electricity price via a service portal

energy through WSN or GPRS connection

Fig 2 Smart grid home area

A model of SGHN is presented in figure 2 In order to

meet the above features, the SGHN builds on three parts

named as: (1) the electricity meter, (2) the SGHG and (3)

the wireless home network Each of them contains some

information or characteristics, which integrate different units

or active functions between them They can be further defined

as follows:

1) Electricity meter: It is next generation of an energy

meter, a replacement for existing meters Data from

electricity meter to house display, which gives users the

real-time feedback on the power consumption and how

much it cost The electricity meter works by

communi-cating with control center in a variety of different ways,

including using wireless technology to send data

2) SGHG: Smart grid home gateway is technically capable

of delivering the functionality of monitoring and con-trolling energy consumption in household Furthermore,

it can also receive information remotely, such as from the control center to update price information or status

of current grid In the field of WSN, this design is used to send control signals to connected end-devices node i Receiving data from smart energy meter ii Analyzing requested data and sending command due to the programming scenarios iii Storing the data in case want recheck iv Communicate with users via LCD or

PC using FT232 port

3) Wireless home network: Derived from the system re-quirements, a star topology network is chosen In this topology, every node communicates directly with the gateway or the data collector Due to a simple com-munication of networking, this topology simplifies the network wherever it is realizable Although the quality connection between controlling-device nodes with the gateway is weak with large distance, this topology is still the best choice for network in household where the coverage area is around 30 to 50 meters The most important advantage of the star topology, which decides

it as key topology of this study, is independent ability

of network In case of errors, when one node is cut off, there is no effect on other nodes and whole network still operates normally Fig 3 represents the network topology for the SGHN for a normal apartment

Fig 3 Home network topology

III HARDWAREDESIGN

A Electricity meter

Electricity meter structure is designed based on the same platform of meter node structure in the world In this study, accuracy in measurement and low cost material are considered

as the important factors for the electricity meter platform Figure 4 shows the block diagram of the platform It com-poses of power supply module which includes AC and DC

Fig 4 Hardware structure of electricity meter

power supply modules; Counter energy meter and Calibration

module

Fig 5 Electricity meter platform

Figure 5 presents the prototype of the energy metering

circuit, which is based on the Microchip MCP3905 energy

metering IC MCP3905 is a DSP-based instantaneous power

integrator that supplies a pulse output which is proportional

to the amount of energy consumed It uses an internal

14-bit ADC to sample the voltage and current The MCP3905A

design is specified with an energy measurement error of 0.1%

typical across 1:500 dynamic ranges for high accuracy energy

meter designs

B Smart Grid Home Gateway

The prototype hardware block diagram of the SGHG is

displayed in Fig 6 The main processor is based on 8-bit

AVR Microcontroller Atmega1284A Its functionality analyzes

Fig 6 Hardware structure of SGHG

the complicated events, operates the firmware, and processes the control algorithms In addition, this circuit integrates both function modules and wireless communication module Func-tion modules have to ensure not only the accuracy operaFunc-tion

in real time but also the backup storage of system That is the reason why it composes Real-time clock, SD card and Keyboard A Texas Instruments Sub-GHz RF CC1110 is used

as the major transceiver of Wireless communication group Next part will show the explanation of this choice In case

of error in Wireless network, module GPRS/3G is designed

as backup option The power group is a combination between

a 12V-1.5A SMPS and a power regulator With objective as easy installation and operation, human interface group, which consists of RS-232/FT232 and LCD module, is also developed

An interesting issue in design is the size of the circuit Figure

7 shows the design of smart grid home gateway platform

Fig 7 Smart grid home gateway platform

C Wireless module selection

The most advantage of modern wireless transceiver is optimal wireless communication among sensor nodes Some useful common features of transceivers can be listed as: error detection and correction, received signal strength indicator (RSSI), advanced encryption standard (AES) for security issue, automatic acknowledgment (ACK), etc

Table I gives the comparison between some popular wireless transceivers in the market such as: MRF24J40MC and XBee, Bluetooth and CC1110 As can be seen clearly, CC1110 from Texas Instrument is not the best transceivers in the outdoor condition However, in scope of this study, CC1110 satisfies some key requirements namely: Standard of Frequency Band, Sensitivity at Max Data Rate, Indoor Transmission Range, Battery Life and Price It needs to notice that frequency band

of CC1110 is based on the standard frequency for smart grid in the world Hence, system using this module can combine with the other systems as unification Furthermore, the Sleep Mode Current of CC1110 supports the longer battery time-life than the others Finally, low cost is a strong point of this module Following these reasons, in our work, CC1110 is confirmed as the best transceiver to design wireless platforms for SGHN

TABLE I

C OMPARISION AMONG POPULA WIRELESS TRANSCEIVERSR

Features

ZigBee/

IEEE 802.15 4

Bluetooth/

IEEE 802.15.1

Sub-Ghz Standard TI

Frequency

333/433/

868Mhz Max Data

Rate

250 Kbps

250 Kbps

800 Kbps

500 Kbps Sensitivity

at Max

Data Rate

-108 dBm

-92 dBm

-82 dBm

-110 dBm Transmission

Topology Star, Mesh Star, Mesh Point to point,Star Star

Battery Life

(days)

100 1,000+

100

Max No.

Security AES

(128bit)

AES (128bit)

SAFER (64/128bit) SoC(8bit) Price/

IV SOFTWAREDESIGN

Algorithms control of the SGHG are programed in

8-bit MCU ATMEGA1284A by CodeVision AVR compiler A

basic scenario about automation control of the SGHG will be

displayed in figure 8 Fig 8 shows the sequence of operation

steps that will be taken by SGHG On receiving messages

about equipment status, the SGHG checks permission from

the user After checking, it will analyze these messages by

the schedules operation time and advertised energy level of

devices Finally, the SGHG decides these devices will operate

or not As an example, in case of rush hour, all of devices in

level 1 and 2 (high power consumption) will be advised to turn

off For all cases, as soon as the SGHG command instruction

is decided, it will be sent to control devices node for next

operating step

Moreover, some module functions such as: LCD interface,

UART communication, SD Card and Real-Time integration

are also embedded by this complier

V PRACTICAL IMPLEMENTATION

Figure 9 shows a prototype system has been implemented

in a typical experiment, an electricity meter, a SGHG and 6

controls located in different places of the house to set up the

system The electricity meters deployed in power measurement

input data to record the energy consumption of the entire house

and through SGHG to monitor and manage the status of

elec-tricity devices This gateway connects to other devices via the

wireless home network and Sub-GHz distribution center via

3G communication Beside the ability to collect and process

the information from the distribution center, SGHG also has

responsibility to maintain the operation of electrical equipment

according to the pre-programmed scenarios to reduce to the

lowest level of power consumption To prove the feasibility of

the study, a test script was conducted as described below

Table II shows some common devices using household

electricity for the power levels and different time use There

Fig 8 Flowchart of energy saving algorithm

Fig 9 Implementation of energy monitoring smart grid home system

TABLE II PARAMETERS OF ELECTRICAL DEVICES IN EXPERIMENT

Name of Devices

Level of Energy Quantity

Time (h)

Power Consumption (W) Compact

Incandescent

Electrical

Fluorescent

are three levels of equipment, which specify based on energy consumption capacity of device In this experiment, six con-trolling nodes are connected to twelve devices

According to profile of Vietnam Electricity (EVN) , Fig.10 presents a distribution of time and price energy using in normal

Fig 10 Distribution of price and hour energy using in VietNam

day There are three kinds of time namely: low, normal and

rush hour The price of energy consumption also change with

the kind of time

The purpose of this demonstration was conducted

dis-tributed power consumption over time in the logical way Thus,

the system will reduce the overload on the network during

rush hours and the energy wasted on false load in low hours

Moreover, it also helps users reduce energy cost

VI PERFORMANCE EVALUATION

A Energy consumption saving algorithm testing

Fig 11 shows the result for energy consumption from the

demonstration system of electricity appliances in the table II

during a normal day The blue columns present system which

has applied energy saving algorithm while the red columns are

inverse system it’s important to note that, the peak of blue

column is much lower than the red column and the difference

between blue column is not as large as the red column Based

on this result, we can proves that the system with energy

saving algorithm is better than the other one

Fig 11 The result of energy consumption in demonstration

Table III presents that it is possible to reduce to 84% level

of energy when the SGHG with energy saving algorithm

is applied than a situation without it The usage time of

energy also reduced because of distributing the time for the

Incandescent lamp and Fluorescnet lamp, which consume

much energy From the result of table III, that we could analyze 16% of energy and 18% of price were saved

TABLE III

COMPARE OF ENERGY CONSUMPTION

Type ConsumptionTotal Energy Total Price

Saving Rate Energy Price Home energy

consumption without energy saving algorithm applied

5645 Wh 17,389

(VND) 100% 100% Home energy

consumption with energy saving algorithm applied

4757 Wh 14,385(VND) 84% 82%

B Delay performance

We carry out the delay performance evaluation of the system

by measuring the time latency Time latency is defined as the taken time for a packet sent from SGHG to a determined controlling node and then sent back to the SGHG The packet delay is calculated by the time latency divided by two One hundred of packets have been sent and received for calculation the average delay of the system When the distance is more than 15m or two walls the delay raises very fast because weak signal strength that make the packet error rate increase, more packets have been resent that lead to the quick increase of delay time The result is presented in table IV

TABLE IV

PERFORMANCE OF WIRELESS NETWORK IN SMART GRID HOME AREA

Node Distance(m) Latency(ms) Stability(%)

VII CONCLUSION

In this paper, an efficient hardware design of SGHG has been developed for integrating the electrical appliances to the smart grid system The SGHG can be operated with the SGHN based on programmed scenarios We have also developed a practical system to verify functions of the SGHG which is attached to the electricity devices From the experiment results,

we have shown that the energy consumption can be controlled due to the load change and time usage Then we compared the performances between with and without the this system Energy can be saved effectively, with the smart grid system Moreover, the low cost and low power wireless hardware based

on Texas Instrument CC1110 SoC is selected for SGHN to create a simple but efficient star routing wireless network Through a practical test, the reliability of data transmission

of this module for SGHN is proved

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