A Monitoring and Control System for HID Lamps

Transcription

1 A Monitoring and Control System for HID Lamps Abstract This paper will present the study and implementation of a control and supervision system for electronic ballast of high intensity discharge (HID) lamps used in public illumination. This system makes possible to supervise the state and to control all functions of an electronic ballast remotely, allowing: dimming, report fails in the system, power consumption measurement, control of power flow, time schedule, electronic ballast protection against damages, inrush current protection for the PFP and minimize the acoustic resonant phenomenon in the HID lamps. A communication network was implemented using modems connected in the power line (Power Line Carrier PLC), allowing the communication between electronic ballasts. A protocol for this communication was proposed and implemented. I. INTRODUCTION Brazil faced a serious energy crisis in 2001, manly, by the lack of investments to allow the energy matrix diversification and to extend the energy distribution systems. Also contributed to aggravate the energy problem, the economic growth in this period, that increases the demand for energy. Many corrective actions were taken to mitigate this serious problem. The government was forced to implement an energy rationing, which consisted in overtaxing or even cutting energy supply from consumers which exceeds the prefixed energy quotes. One solution founded by city halls during the rationing, was the reduction of the energy demand spent in public illumination. Implanted in many cities, the action consisted in turn on only half of the total lamps, in random form. But this solution should not be implemented in all zones of a town, for security guard and illumination quality reasons. The objective of this work is to describe the implementation of a control and supervision system for electronic ballast of high intensity discharge (HID) lamps. These lamps are widely used in public illumination. This system makes possible to supervise the state and to control all functions of an electronic ballast remotely, allowing: dimming, report fails in the system, power consumption measurement, control of power flow, timing, electronic ballast protection against damages, inrush current protection for the PFP and minimize the acoustic resonant phenomenon. This system allows reducing the energy consumption spent in public illumination, by an individual control of dimming and timing schedule for all lamps. The system also makes possible to minimize the costs with logistic in the control of the public illumination system. For this implementation, a communication between master ballast and slave ballasts is necessary, allowing to program and to control all lamps. This communication was implemented using PLC modems that minimize the system implementation costs. II. THE HID LAMPS The HID (High Intensity Discharge) lamps [1] has an architecture as "a lamp inside another lamp", for which the arc pipe is suspended inside of an external bulb. The HID lamps radiate energy on a great part of the visible spectrum [2]. These

2 lamps provide a good color reproduction (it has IRC 23 color reproduction index) and are widely used in public illumination. They are available up to 130 lm/w of luminous efficiency and temperature color of 2100 K, approximately. The HID lamps as other electric discharge lamps, need ballast to operate correctly. The Ballast is an auxiliary equipment linked between the power line and the discharge lamp. The Ballast has two main functions: guarantees the ignition of the lamp through the application of a high voltage pulse between the lamp electrodes and limits the current that will circulate through it. The lamp would be quickly destroyed without current limitation, due the negative resistance characteristic of the lamp. The ballast can be of two types: electromagnetic or electronic. III. THE ILLUMINATION SYSTEM The illumination system is represented in Fig. 1. This system has master ballast and diverse remote slave ballasts connected through a communication network. The communication between these units is made using a modem connected directly in the power line. Figure 1. Block diagram of the system. Modems PLC are used for short distance communication, then was necessary to add a connection between master ballasts using radio transceiver. This new network allows connecting all master ballasts between them and to a central of control. The master and the slaves ballasts contains an Analog Device AduC812 microcontroller, that has as main features: 8051 compatible core, 8k bytes on-chip Flash/EE Program Memory, 640 bytes on-chip Flash/EE Data Memory, 8 multiplexed channel 12-bit ADCs, 2 channel 12-bit voltage output DACs, watchdog timer, 32 programmable I/O lines and a serial I/O UART. The Fig. 2 presents the development board based on the AduC812, elaborated for this project.

3 Figure 2. Development board from AduC812. Diverse circuits of support were connected to the microcontroller: a photocell - to verify the environment luminosity, a zero crossing circuit detector - that will be used for inrush current protection, a soft start circuit - for the Power Factor Pre- Regulator (PFP), a modem PLC for communication between the central ballast and the slave ballasts, a real time clock (RTC) for current measure and to schedule all functions of the ballast, used to determine the energy consumption and, a optical isolate circuit, for make the control of a half-bridge inverter used in the ballast. The Fig 3 shown the master ballast block diagram of the considered system. Figure 3- Master ballast block diagram. A RTC (Real Time Clock) was add in the project to allow to drive lamps in preprogrammed hours and to make possible electrical rates. The RTC DS1307 (Maxxim) was chosen in this implementation. This choice was made verifying the characteristics of the existing components and its costs. Moreover, this RTC has a 56 bytes NVRAM, automatic power-fail detecting and switch circuit, consumption less then 500nAhr using a battery backup, that allows the retention of the stored data for more then 10 years in the total absence of power, using only one lithium battery with 48mAhr. The NVRAM (Non Volatile Random Access Memory) in this CI is used to keep on the information of power consumption eliminating an external EEPROM memory. In this system was added a photocell in order to determine the environment luminosity conditions. The photocell produces an analogical signal that is measured by an internal A/D converter of the AduC812 that will convert into a digital luminosity

4 measure. In according with NBR5123 Brazilian standards [6] the lamps turn on when the luminosity level is between 3 and 20 LUX and turn off when the environment light level was 1.2 to 4 times the turn on level, until 80 LUX maximum luminosity level. In this project, the lamp turn on when the environment luminosity is under 15 LUX and turn off when the environment luminosity is above 60 LUX, being, this way, according with NBR5123 Brazilian standards. A power line zero detector was implemented because it was necessary to develop a soft start to electronic ballast PFP. This mechanism slowly charge the output PFP capacitor, avoiding a peak current that takes a diodes supersizing and a possible burning of these. The electronic ballast consists of a tuned LCC filter that is drived by a half bridge inverter. The inverter drive control signal is generated by a digital PLL (Phase Locked Loop) implemented in an Altera EPM7064 FPGA that allows the variation of frequency and duty cycle. Changing the programmed signal sent to the FPGA, we could obtain the lamp dimming, reducing the power consumption. To avoid acoustic resonance is an important topic discussed between research community. With this system is possible to study different control strategies for minimizing of this phenomenon. The proposed electronic ballast has new functions in relation with the commercial ones. They can communicate with a remote master, without the need of an additional cabling, using the PLC modem. The implemented modem is based on Philips TDA 5051 IC, and allows the management system to program and to collect information of the ballast. In this implementation, the master is a local master, which is responsible for the communication with all the electronic ballasts of a certain region, allowing to evaluate the defects in the ballasts, to have the access to the power consumption, verify the state of the lamp and to make the dimmer and send the collected data through a RF connection for a general master where these data can be stored for posterior processing. The general master can program the local master in order to allow modifying the illumination in one determined region without affect the behavior on the other areas. We can then resume the characteristics of this ballast as: x Possibility of electrical rates; x Dimming; x Fail lamp and ballast check; x To check the lamp state (turned on or turned off); x Communication between ballast; x Remote control; IV. THE COMMUNICATION PROTOCOL The communication interface was though to allow individual or collective lamp driving command, dimming, time programming the lamps to turn on or off and, also, reduced dimming intensity at rush time. For this porpoise, it was implemented a PPP (Point to Point Protocol) protocol based on SLIP (Serial Line IP) protocol. The communication frame implemented is presented in Fig. 4.

5 Figure 4 Communication frame implemented. This frame is composed by 5 fields. The first one controls the frame size, the second one is the destination of the data, the third one tells which function should be executed, the fourth one brings the command operands and the fifth one is responsible for checking the data integrity. Looking for validating the communication protocol, a testing program was developed for frame exchange between the master and the slave units. This program was developed in DELPHI 5 and its presentation screen is shown in Fig. 5. Figure 5: Program for communication protocol testing. A PC is used as master unit and is connected to the network to communicate with the slave units. The developed program sends commands like: turn on the lamp, turn off the lamp, verify the energy consumption, and others commands that are sent at the user s choice. When a program is executed, for example, dimming, a frame is sent to the slave unit, connected by the power line. After this frame is sent to the slave unit, the master unit waits for a slave response in the same shape that will indicate if the command was accepted or if happened some error. If the master does not receive the response frame, this error would be signalized as a timeout error. The others are shown in the screen as frame error, or malfunctioning circuit error. With the usage of this simulator, we can depurate and test all the communication protocol system.

6 V. CONCLUSIONS The study of a monitoring and control system for HID lamp ballasts using FPGA and microcontroller circuit, with a network communication based on standard protocol like SLIP protocol was considered and implemented in this work. The implementation of the system for controlling and monitoring will obtain an expressive reduction in the energy consumption in public illumination. The reduction in the energy consumption can be obtained with the control of the individualized luminous flow, the drive of lamps in predetermined schedules or in determined luminosity conditions and the programmed interruption of the lamps in some established criterion. The development and the future implementation of this prototype in industrial scale could permit to substitute the conventional ballast, the igniter, the capacitor and the photocell for the drive of this lamps, bringing innumerable advantages as remote control, checkup the circuit state, measure the power consumption, high power factor, dimming and individualize drive control of the lamps become possible. VI. REFERENCES [1] Chr. Meyer, Discharge Lamps, Philips Techinical Library [2] J.R. Coaton, Lamps and Lighting, fourth edition, Arnold [3] NBR5123 Relé Fotoelétrico e Tomada para Iluminação Especificação e Método de Ensaio, ABNT, Abr [4] Bum Suk Kang and Hee Jun Kim, High Power Factor Electronic Ballast for high pressure sodium lamp, IEEE Technical Conference, TENCON, Cheju, Korea, Sep., 1999.