Chapter - 4 Design and Development of Smart Harmonic Analyzer 4.1 Introduction: There is steady evolution in the field of generation, distribution, and use of electricity since many years. New methods and innovations in the field of generation and use of electricity triggered the industrial revolution, and then onwards there is consistent contribution of scientists and engineers, to continue this evolution further. In the beginning, electrical machines and devices were crude. They were consuming large amounts of electricity and were performing quite well. The machines were designed mainly with the concern of cost and the performance considerations were secondary. They were susceptible to various power quality anomalies existed at the time, but the effects were not readily noticeable. It was partly due to the robustness of the machines and partly due to the lack of effective ways to measure power quality parameters. However, around last 30-40 years or so, the industrial growth and development demands for products which will be economically competitive. It meant that electrical machines were becoming smaller and more efficient and were designed without performance margins. At the same time, other factors were started coming into picture. Increased demands for electricity created extensive 106
generation of power and distribution grids. Industries demanded for large generation of power. It was also reflected in the residential sector. Ultimately it resulted into limit on the stretching of electricity generation. Today, electrical utilities are no longer operated independently. They are part of a large network of utilities tied together in a complex grid. The combination of these factors has created the complexity in electrical systems which ultimately demands for power quality. Power quality is a simple term, yet it describes a multitude of issues that are found in any electrical power system. The concept of good and bad power depends on the end user. If a piece of equipment functions satisfactorily, the user feels that the power is good. If the equipment does not function as per the requirements or fails prematurely, there is a feeling that the power quality is bad. In between these limits, several grades or layers of power quality may exist, depending on the perspective of the power user. Understanding power quality issues is a good starting point for solving any power quality problem. Ideally the utility should supply a perfectly sinusoidal voltage Signal at every consumer location. However, due to number of reasons, utilities often find it hard to preserve such desirable conditions. The deviation of the voltage and Current waveforms from sinusoidal waveform is described as waveform distortion, often expressed as harmonic distortion. Harmonic distortion is not new and it constitutes at present as one of the main concerns for engineers in the several stages of energy utilization especially distribution system. Today s increased use of nonlinear loads inject voltage and current harmonics in electrical distribution networks and creates new problems of power 107
quality in the power System. Conventional power systems are designed to operate on sinusoidal power supply. Electric utilities strive to supply consumers with reliable & pure sinusoidal electric power that does not represent a damaging threat to their equipment. From 2003, in the restructured power system, many power supplying companies came into existence. The generation, transmission and distribution companies are now separate entities. In this competitive market, prices of the power are associated to power quality. Hence it is very important to monitor and ensure power quality. The harmonic analyzer is developed with extensive study of available harmonic analyzers in the market and improving on them along with the development of customized software. The meter is developed keeping in mind the qualities like versatility with respect to accuracy, cost, applicability, ease of modifications through coding, Remote monitoring, Report generation and Data logging. The developed harmonic analyzer and analogous technology used will prove to be a foundation in discovering the anomalies in harmonics and power measurement. 4.2 Design Features: The Harmonic analyzer is developed with extensive study of available harmonic analyzers in the market and improving on them along with the development of customized software. The meter is developed keeping in mind the qualities like versatility with respect to accuracy, cost, applicability, ease of modifications through Coding, Remote monitoring, Report generation and Data logging. The developed harmonic analyzer and analogous technology used will prove to be a 108
foundation in discovering the anomalies in harmonics and power measurement. The Smart Harmonic analyzer is developed using ADE 7880 with inbuilt DSP processor for measurement of harmonic parameters along with the PIC microcontroller & GSM MODEM. Graphical User Interface is developed to assess the harmonics and generating their reports for Data Logging. A smart communication is developed between harmonic meter and mobile phone using GSM communication. The connected meter at the consumer end can be remotely monitored via short message service (SMS) on the mobile phone. 4.2.1 Block Diagram: Fig. 4.1 shows the block diagram of the developed smart harmonic analyzer. Ring type Current Transformers (CT) with ratio of 5 / 1mA are used as current sensors. Fig. 4.1 Block diagram of Smart Harmonic Analyzer 109
The current signals and three phase four wire voltage signals are given as an input to IC 7880. This is multifunctional energy metering integrated circuit (IC) with harmonic consideration. The various system parameters and harmonics are measured by ADE 7880. PIC micro-controller is coded to read these parameters and display it on LCD display. These parameters are also given to Personal Computer (PC) through serial communication. The data is assessed on PC and reports are generated. The generated report contains all system parameters like voltage, currents of all the three phases, Active power, true power factor and depletion power factor, harmonics in the form of Total Harmonic Distortion (THD) of voltage and current as well as individual harmonic distortion. The meter is also communicating all the displayed parameters to the GSM MODEM. When STATUS query is received from the configured mobile number, developed smart meter will communicate all the parameters on the mobile phone via Short Message Service (SMS). 4.2.2 Hardware Circuit: Hardware development include circuit design of ADE section, Micro-controller section, power supply circuit and GSM circuit. Its PCB design layout component mounting and testing. All these steps are described in Fig. 4.2. 110
Circuit Design for ADE 7880 section, Micro-controller section, Power supply circuit PCB Layout design. Development of PCB Component selection & Component mounting Trouble Shooting Fig.: 4.2 Flowchart of hardware circuit development. 4.2.3 Software system Software coding is done in embedded C language. This coding is done for A. Micro-controller to perform following functions 1. To read the parameters measured by ADE 7880 2. Conversion of coded register values to real world values. 3. Displaying these parameters to LCD. 4. Sending these parameters at every cycle to Personal computer. 111
5. Sending these parameters to GSM MODEM as and when trigger is received. B. GSM Coding performs following tasks 1. When GSM is connected display the message on LCD screen. 2. When configuration query is received then configure the mobile number with GSM MODEM. 3. Send the message "Configured Successfully" to configured mobile. 4. If "STATUS" request is received then send all received parameters to mobile in the form of "Short Message Service". 5. Continuously keep checking for "STATUS" request. C. PC report generation using C#.net coding A code is developed for creating pages which will display the following 1. All three phase parameters i.e. voltage, current, Fundamental KW, Harmonic KW, Fundamental KWhr, Harmonic KWhr, DPF, TPF, V THD and I THD. 2. Plotting the Bar-chart of Harmonic magnitude in DB w.r.t. order of harmonic for the selected phase. 3. Energy meter Report generation for all the monitored values in the form of pdf file or in excel sheet format for user selected Start and Stop request. 4. Harmonic report generation for individual voltage and current harmonics of each phase. Storing these reports date wise and time wise. 112
4.2.4 System Flowchart Fig. 4.3 Main system flow-chart The main flowchart shown in Fig. 4.3 indicates various steps taken during the operation of the system. The operational features of the system include 1. Initialization of micro-controller ports, LCD, UART, SPI etc. 2. Initialization of ADE IC and its setting. 113
3. Initialization of global variables. 4. Checking of data from ADE and receiving it after suitable duration as indicated in ADE flowchart. 5. Operation of GSM, development of PC communication code and display of parameters through LCD. 4.3 Component Details: 4.3.1: Ring type Current Transformers: The main function of current transformer is to reduce the current to measurement level. RING TYPE CT which has an opening in the center to accommodate a primary conductor ( busbar or cable ) through it. Ring type CT are normally preferred over other types of CT, because they are simple in construction, mechanically stronger and cheaper. In a ring type / bar primary type CT the working ampere-turns are determined by the primary current and therefore necessarily,the accuracy that can be offered with this CT becomes progressively inferior as the rated primary current decreases. If higher accuracy and burdens are required for CT of low primary current then wound types CT's are used.three ring type CTs are used of rating 5 Amp/ 1 m Amp. 114
Fig.: 4.4 Ring type current transformer (5 / 1 mamp) 4.3.2 ADE 7880: ADE 7880 is 40 pin IC. It is a high accuracy, 3-phase electrical energy measurement IC with serial interfaces and three flexible pulse outputs. The ADE 7880 device incorporates analog-to-digital converters (ADCs), a digital integrator, reference circuitry, and all of the signal processing required to perform the total (fundamental and harmonic) active, and apparent energy measurements, rms calculations, as well as fundamental-only active and reactive energy measurements. In addition, the ADE 7880 computes the rms of harmonics on the phase and neutral currents and on the phase voltages, together with the active, reactive and apparent powers, and the power factor and harmonic distortion on each harmonic for all phases. Total harmonic distortion (THD) is computed for all currents and voltages. A fixed function digital signal processor (DSP) executes this signal processing. The DSP 115
program is stored in the internal ROM memory. The ADE 7880 is suitable for measuring active, reactive, and apparent energy in various 3-phase configurations, such as delta or star services with, both, three and four wire networks. The ADE 7880 computes the total active power on each phase. Total active power includes calculations of fundamental and harmonic components of the voltages and currents. In addition, the ADE 7880 computes the fundamental active power and the power determined by the fundamental components of the voltages and currents. 4.3.2.2 PinConfiguration Fig. 4.5 Pin configuration of ADE 7880 It has total 40 pins and Quad in package. The connections of the important pins is tabulated below. This IC is manufactured by the Analog Devices. It 116
measures all system parameters along with harmonic considerations. It has inbuilt DSP processor to measure all the parameters. Table: 4.1 Pin functions of ADE 7880 PIN NO. FUNCTION 2,3 Mode selection (mode 0 Normal power mode) 4 Chip RESET 5 3.3V 7,8,9,12,13,14,15,16 Three line currents phase and neutral 17 Voltage reference of 1.2 volts 19,22,23 Three phase voltages 27,28 CLK IN and CLK OUT 37,38 DATA IN and DATA OUT to PIC MC 39 Slave select 4.3.2.3 Schematic diagram Fig. 4.6 shown, is the connection diagram of harmonic measurement section. The main IC used is the ADE 7880 from Analog Devices which is three phase energy measuring IC with Harmonic considerations. Three Ring type Current Transformers (CT) are used of rating 5 A /1 ma to sense the current in each phase namely R, Y and B. Four voltage terminals are connected through voltage protection circuit i.e. VR, VY, VB and VN.An external crystal is connected to generate a CLK frequency of 16.38MHz. ADE IC is operated in PM0 mode which is normal power mode. In this mode all the 117
registers hold their default value. Fig. 4.7 shows the PCB board developed for ADE 7880 IC. Fig. 4.7 PCB board of ADE 7880 118
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4.3.2.4 Operational Flow chart of ADE 7880 Fig. 4.8 shows the operational flowchart of ADE 7880. In overall operation of the meter, when micro-controllers fetch data from ADE 7880 IC then all data fetching operations are performed as shown in the flow-chart. Different flags are used to check the status of various register. when the data in register is ready to get fetch by the micro-controller then corresponding flag is set to '1' otherwise it will be '0'. One by one different flags are checked and all parameters like voltage, current, power, power factor, total harmonic distortion etc. for all the three phases are read from ADE 7880. When all the parameters are ready, it waits in the main flow-chart for the request from either PC section or from GSM section. 120
Fig. 4.8 Operational Flow chart of ADE 7880 121
4.3.3 PIC micro-controller: PIC18F4520 is40 Pin Enhanced Flash Microcontrollers with inbuilt 10-Bit A/D convertor which has the following main features- C compiler optimized architecture Optional extended instruction set 100,000 erase/write cycle Enhanced Flash program memory typical 1,000,000 erase/write cycle Data EEPROM memory typical Flash/Data EEPROM Retention: 100 years typical Self-programmable under software control Priority levels for interrupts Extended Watchdog Timer (WDT): Programmable period from 4 ms to 131s In-Circuit Debug (ICD) 4.3.3.1 PIN Diagram: Fig.4.10 Pin diagram of PIC 18F4520 122
Table: 4.2 Pin functions of PIC 18F4520 Pin name Pin no. Pin name Pin name Pin no. Description Description Pin no. Description MCLR 1 Master Clear (Reset) input. This pin is an active-low OSC1 13 Oscillator crystal input or external clock source input OSC2 14 Oscillator crystal output. Connects to crystal or resonator in Crystal Oscillator mode RB0-RB7 port. 33-40 PORTB is a bidirectional I/O VSS 12 Ground reference for logic and I/O pins. VDD 11, 32 Positive supply for logic and I/O pins. TX 25 asynchronous transmit RX 26 asynchronous receive 4.3.3.2 Schematic diagram of Micro-controller Fig. 4.9 shows the connection diagram of Micro-controller section. PIC18F4520 is 40 pin IC.A clock frequency of 16MHZ is created by an external crystal oscillator connected to pin no. 13 & 14.The signals are invoked from ADE 7880 in controller and are displayed on the LCD display. The complete task is executed through microcontroller coding. This coding is done in embedded C language and then burn into an IC. The signals are transmitted and received serially through pin no. 25 & 26. 123
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Fig.4.11 shows the developed PCB for the micro-controller section. In this circuit micro-controller is connected to various input output devices like LCD display, ADE 7880, GSM MODEM and personal computer through its peripheral components. Fig. 4.11 PCB board of PIC 18F4520 4.3.4 LCD Display 2 X 16 LCD display is used to provide rolling display of various quantities like kw, kva, kvar, kwh and voltage or current THD. Fig. 4.13 shows the pictorial view of LCD display which is located in the meter at the consumers location to view all the parameters at any instant. 125
Fig. 4.13 LCD Display Table: 4.3 Pin functions of LCD display 4.3.5 Power Supply section : Power supply circuit for ADE section is 3.3V DC, for Micro-controller section, it is +5 volts DC and -12 V AC. IC 7805 is +5 volts fixed voltage regulator and IC 317 is adjustable voltage regulator used to 126
generate required biasing voltage of 3.3 V for ADE and 5V for microcontroller section. The other components are bridge Rectifier and filter circuits. Special Disk type Capacitors are used to reduce the noise. Fig. 4.14 shows the two different power source circuits and Fig. 4.12 depicts the schematic diagram of power supply section. Fig. 4.14 Power supply circuit 127
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4.3.6 RS232 to USB convertor The USB-RS232-PCB is a USB to RS232 level serial UART converter PCB incorporating USB to Serial UART interface IC device which handles all the USB signaling and protocols. The PCB provides a fast, simple way to connect devices with a RS232 level serial interface to USB. Each USB-RS232-PCB contains a small internal electronic circuit board, utilizing the FT232R plus a USB type-a connector. The integrated electronics also include an RS232 level shifter plus Tx and Rx LEDs which give a visual indication of UART traffic. Fig. 4.15 RS232 to USB port convertor 4.3.7 GSM MODEM GSM/GPRS RS232 Modem is built with SIMCOM Make SIM900 Quad-band GSM/GPRS engine, works on frequencies 850 MHz, 900 MHz, 1800 MHz and 1900 MHz. It is very compact in size and easy to use as plug in GSM Modem. The Modem is designed with RS232 Level converter circuitry, which allows to 129
directly interface PC Serial port.the baud rate can be configurable from 9600-115200 through AT command. Initially Modem is in Autobaud mode. This GSM/GPRS RS232 Modem is having internal TCP/IP stack to enable to connect with internet via GPRS. It is suitable for SMS as well as DATA transfer application. The modem needed only 3 wires (Tx,Rx,GND) except Power supply to interface with microcontroller/host PC.Using this modem, it is possible to send & Read SMS, connect to internet via GPRS through simple AT commands. Fig. 4.16 GSM/GPRS RS232 Modem 130
4.3.7.1 Operational flowchart of GSM When micro-controller attains the GSM MODEM's request then following steps are performed. 1. Micro-controller checks the received data format of the short message service (SMS). If it is in required format then it follows further steps otherwise it treats it as garbage data and ends up with the further procedure. 2. It data received is in correct format then it configures the assigned mobile number and sends the reply as " configured successfully ". 3. It waits for status query. When status query is received, it sends all parameters from micro-controller to configured mobile number in the form of short message service. 4. continuously it keeps on checking for further queries. Fig. 4.17 shows the operational flow-chart of GSM MODEM. 131
Fig. : 4.17 Operational flow-chart of GSM 132
4.3.8 PC communication The measured system parameters and harmonics are taken in personal computer for data logging. The reports are generated to save the history of load point in tabular format. The coding is done to develop Graphical User Interface and to save the reports created in different formats. Fig. 4.18 shows the operational flow-chart of PC communication. When the query is received from PC side the micro-controller serves it by sending the data received from ADE 7880 section to the personal computer serially through RS 232 serial interface. Different reports are generated in computer to serve the function of data logger. 133
Fig.: 4.18 Flow-chart of PC communication 134
4.3.8.1 Reports generated Following Fig. 4.19,4.20, 4.21, 4.22 represents the sample of software report generation developed on PC. Harmonics are represented in terms of bar chart as shown in Fig.4.19 Energy meter parameters can be displayed in the form of tabular format as shown in Fig. 4.20. Continuous monitoring of consumed power and energy in tabular format can be done as shown in Fig.4.21. Harmonic report generation in the form of RMS value of individual harmonic component is shown in Fig. 4.22. Fig. 4.19 PC report generation 135
Fig.: 4.20 Power Analyzer report generation Fig. 4.21 Bar chart representation of individual harmonics 136
Fig. 4.22 Harmonic report generation 4.4 Functional Description The present work deals with more realistic measurement of energy of a complex current- voltage source which contains harmonics. The unaccountability of harmonics power consumed put the utility to loss. There is a need to develop a new harmonic measuring meter, which considers the harmonic power along with the rated frequency power. The new smart harmonic-meter developed is versatile, sophisticated and accurate in measuring energy consumption. It is developed with a communication feature with the mobile phone. Hence the utility can remotely monitor the quantities on its configured mobile phone in the form of SMS as and when required. As compared to 137
standard equipments available in the market, the meter developed is much cheaper and easy to use with added facility of remote monitoring. It mainly deals with the development of hardware using ADE 7880 along with the PIC microcontroller, GSM MODEM and GUI development. Graphical User Interface is developed to assess the harmonics and generating their reports for Data Logging. A smart communication is developed between developed harmonic meter and mobile phone using GSM communication. The connected meter at the consumer end can be remotely monitored via SMS on the mobile phone. It also describes the software details of the developed system as well as the observed results of interfacing between mobile phone and GSM modem. The three phase four wire voltages through protection circuit i.e. V R, V Y, V B, V N and three phase currents through current transformer i.e. I R, IY and IB are inputs to the IC ADE 7880. It measures all the system parameters and harmonics. All these values are stored in the registers inside it. PIC microcontroller is used to read these values from registers and are converted to real world values through coding. These monitored parameters are then continuously displayed on the LCD display. when PC communication link is complete then these parameters are also send to computer for data logging. When GSM request is activated then these parameters are send to GSM MODEM for remote communication on mobile phone. The cycle repeats after every 1sec. 138