Demand Side Management Unit of an Algerian Isolated Village Power Network

DEMAND SIDE MANAGEMENT UNIT OF AN ALGERIAN ISOLATED VILLAGE POWER NETWORK

Mohamed KESRAOUI Laboratoire Electrification des Entreprises Industrielles, Faculté des Hydrocarbures et de la Chimie Université M’hamed Bougara, Avenue de l’independance, 35000 Boumérdès, ALGERIE E-mail: [email protected], Tel. 00 213 669 53 34 86

Abstract An Electrical Energy Measure and Control Unit is used by a Load Control and Management Unit of a decentralized electrical energy supply system of an isolated Algerian village for the consumer’s power flow control, management and protection against most failures. It provides each consumer with useful information concerning his actual power, energy consumption and tariffs. These data are also transmitted with possible failures information to the LCM Unit using power lines communication. Orders to connect or disconnect any one or all the loads of a consumer are also received and executed by this unit. Protection against short circuit, overload and ground faults is also provided. It is in essence a demand side management unit (DSM). In this paper, the detailed design and implementation of the unit are described. An experimental set up was implemented and a software program written and loaded. Measurements and tests have been performed. Satisfying results have been obtained.

Keywords: Energy Measurement, Demand Side Management, Load Control and Management, Decentralized Energy Supply. Load sharing control, Distribution of electrical energy, Power conditioning, Protection, Software for measurements

ELEKTRISCHE ENERGIE-MANAGEMENT-STEUEREINHEIT EINES ALGERISCHEN DEZENTRALISIERTEN ELEKTRISCHEN VERSORGUNGSSYSTEM

Kurzfassung Eine Elektrische Energie-Management-Steuereinheit wird durch eine Last Management und Steuereinheit eines dezentralisierten elektrischen Energie- Versorgungssystems von einem Algerischen entfernten Dorf für Kontrolle des Kraft-Flusses, Management des Verbrauchs und Schutzes gegen die meisten Fehlschläge verwendet. Es versorgt (stellt bereit) jeden Verbraucher mit nützlicher Information bezüglich seiner effektiven Leistung, Energieverbrauchs und Tarife. Diese Gegebenheiten (Daten) werden auch mit möglicher Fehlschlag-Information der LCM Einheit übersandt, die Starkstromleitungen gebraucht (benutzt). Ordnungen, in Verbindung zu treten oder irgend jemanden oder alle Lasten eines Verbrauchers zu trennen, werden auch erhalten und durch diese Einheit durchgeführt. Schutz gegen kurze Kreislinie, Überlastung und Boden-Fehler wird auch versorgt(bereitgestellt). Es ist in Essenz eine Nachfrage-Seite-Management-Einheit. Diese beitrag enthalt die erklarung und implementierung von dieser Einheit.

Schlüsselwörter Last Steuer- und Management, Dezentralisierte elektrische Energie- Versorgungssystem, Nachfrage-Seite-Management 1. INTRODUCTION

In conventional distribution systems, the utility has usually no automatic remote control over the consumer’s power line input, that is, all consumers’ side operations of connect/disconnect, meters reading and power outage/restoration monitoring are achieved manually by a technician. In developing countries isolated villages where a decentralized electrical energy supply system using renewable energies should be installed, the population has in general no knowledge of electricity basics and safety rules.

Therefore a centralized control of all power flow, management and protection tasks is recommended. The DSM Unit presented in this paper is a fundamental solution to achieve that. In such an isolated village power network as shown in Fig.1, the central LCM Unit where the whole network information/orders processing take place is linked to many Measure and Control units at each consumer’s side.

The LCM Unit is in fact a computer linked to a data base, for consumers historical data storing, analysis and management and has the following tasks to do: Real time data acquisition, load switching according to certain criteria (power availability, consumer priority order, etc.), communication with measure and control units and with the production control unit, load management that is: store consumers historic and event data in database, smooth out daily power peaks and valleys (peak clipping, valley filling and load shifting), billing and further analysis, accurate dispatching of maintenance staff. The DSM Unit which is the object of this paper will be described in the following section.

2. DEMAND SIDE MANAGEMENT UNIT DESCRIPTION

The unit is represented in Fig. 2[1, 2, 3]. The consumer input line current is sensed through a current transformer and fed to a low cost energy meter IC. A microcontroller receives the measured data, outputs the corresponding kWh value to the display circuit together with the applicable tariff. It also stores these data in the PIC EEPROM to prevent possible power shutdown, executes orders received from the LCM Unit to switch ‘ON or OFF’ any one of the three consumer’s loads as follows: S1, a guaranteed low power switch, at the outlet indication ‘Load1’: to be connected to small basic loads (lights, TV& Sat Receiver, Radio). S2, a non critical high power switch, at the outlet indication ‘Load2’: to be connected to high power loads that support energy cut off times in the range of 1 hour (e.g. Refrigerator). Finally S3, an occasional use high power switch, at the outlet indication ‘Load3’: to be connected to Loads with higher energy cut off times ability (e.g. oven, PC, air conditioner, fan, coffee machines etc.).

The unit can also communicate (sends all these data and receives orders) via a PLC Modem (transceiver) node circuit with the LCM Unit. Manual access to the 3 switches is provided to the consumer for managing his electricity bill. For the protection of equipments and persons, the standard commercial circuit breaker is replaced by flexible software called ‘Failures’ protection Routine for earth ground faults and overloads. Short circuit protection is assured by simple 5A fuses at each outlet.

Any overload is detected by the unit in approximately 2 minutes, which is less than the standard commercial circuit breaker time protection of 200 seconds [4]. The 6.5% ground

2 fault warning of the energy meter is not sufficient for person’s protection because for example, for a 2A load current, the ground fault current to be detected must be more than 125mA. An algorithm is used to obtain the standard limit (30mA) of the commercial GFIG. The ground fault detection starts through the receipt of a ‘1’ at pin 4 of the PIC. The PIC will pole or wait for an interrupt at this pin. When this happens, the corresponding consumer’s loads outlets is switched OFF. For load powers greater than 100 W, the measure and control unit starts a ‘CHECK’ routine that lasts 3 seconds and is executed many times per day: the first time at the first detection of loads power higher than 100 W and the other times each 3 hours. It works as follows:

- First disconnects S2 and S3, check for Fault signal: If ‘Yes’ disconnect S1, If ‘No’ then - Disconnect S1 and S3, check for Fault signal: If ‘Yes’ disconnect S2, If ‘No’ then - Disconnect S1 and S2, check for Fault signal: If ‘Yes’ disconnect S3, If ‘No’ then: Stop.

The consumer will not feel this fault check routine, since it lasts only 3 seconds. Although the risk of a ground fault failure happening within 3 hours exists, the check routine frequency can then be increased to improve the protection. For energy management, the load power limit can be for example fixed to 250W for basic loads (S1), and a total household power limit of 400W. Each time the consumer exceeds one of these limits the corresponding loads are disconnected by the LCM Unit. Those limits are taken according to an Algerian village typical average consumption [5].

3. IMPLEMENTATION AND MEASUREMENTS

An experimental set up of the electrical energy measurement and control unit was implemented and a software program was written in assembler language. Compilation and loading have been done through a PICSTART Plus, hardware kit and development software of Microchip company. A PIC Millennium board has been used for the display and RS232 communication in addition to the PIC16F84. The ADE7751 energy meter has an output CF connected to the microcontroller input (Pin 2), which counts the number of pulses in a given time (in our example 2 minutes, due to the adopted calibration) using the PIC timer. The power is then computed by dividing this number by 60. The energy at each instant is simply the collected number of pulses. Software adjustments are needed to get exact information on the display. The FAULT output is also connected to the PIC input (Pin 4). The switch is a SNUBBER less, especially recommended for use on inductive loads, 16 A TRIAC (BTB16 600CW). The TRIAC is controlled by an OPTO-isolator TRIAC driver (MOC3041).

The current channel V1 (pins 2, 3 and 4) is connected to the voltage outputs of the ASM-050 current sensor which operates as the sealed secondary of a current transformer (CT) while the conductor carrying the current to be measured functions as a one turn primary. The power consumption of the supply is around 9.1 VA. This is within the limit of the IEC60136 standard, which limits the maximum power consumption of a meter to 10 VA. For galvanic isolation between the mains coupled meter and the oscilloscope, a transformer is used. The complete test setups and results showing the consumed energy and the actual power for a 2kW electric heater are shown in Fig. 3 and Fig. 4 respectively. The current sensor output voltage for the electric heater in Fig. 5 is around 16 mV and the corresponding input current will be (taking into account the transformer ±10% error) nearly 9A which is equivalent to the current of our 2kW heater. The heater response to an OFF-ON command from the computer is shown in Fig. 6.

3 4. CONCLUSION

Through the demand side and management unit, consumer’s loads control and management is achieved. Consequently energy will be used only where and when it is needed, this has a positive economical impact by reducing waste and thus saving money. The use of this unit has also positive ecological impact. Since it gives the possibility to introduce an adequate tariff organization that encourages the efficient use of the electrical energy gained for example from renewable energies and penalizes the use of that gained from fossil energy. The carbon dioxide emitting would therefore be reduced. Finally it also brings a solution for the problem of electricity basics and safety rules ignorance that generally exists in a developing country like Algeria by allowing the centralizing of the control, the management and the protection tasks.

5. ACKNOWLEDGMENT

The author would like to express his thanks to the Austrian Exchange Service (Österreichischer Austauschdienst, ÖAD) which has sponsored my doctoral studies in Austria and to the department of electrical engineering, University of Leoben, where the complete unit has been implemented.

6. REFERENCES

[1] Kesraoui M., Weiss H. (2006) ‘Laststeuerung in kleinräumigem und schwachem Netz mit Einspeisung erneuerbarer Energie’, EnInnov06, Graz, Austria. (Title translation: Load Control and Management in a Decentralized Electrical Energy Supply System)

[2] Weiss H., Kesraoui M. (2004), ‘Renewable energy in the decentralized energy supply’, APEIE Conference Novosibirsk, Russia.

[3] Weiss H., Kesraoui M. (2004) ” Einsatz erneuerbarer Energien in der dezentralen Energieversorgung in Entwicklungslaendern “ ENOV2004. Graz, Austria.

[4] Academie d’Aix-Marseille, France, Web page: http://stielec.ac-aix-marseille.fr/cours

[5] Algerian ministry of energy and mining: Web page: http://www.mem-algeria.org

[6] M. Dobriceanu, A. Bitoleanu, M. Popescu, G. Vladut, ‘Data Acquisition Equipment for Energy Measuring in Electrical Stations’, EDPE 2005, E05- 65, Dubrovnik, Croatia, Sept 2005.

[7]H.G. Schwabe, H. Weiss,’Implementation of an Advanced Power Electronics Signals Measurement System at 18 MVA Converter’, EPE 2005,946. Dresden Germany, Sept 2005.

[8] N. Tezak, ‘DSP Based Control of Multi system Power Converter for Passengers Coaches’, EDPE 2005, E05-82, Dubrovnik, Croatia, Sept 2005.

[9] Centre de developpement des energies renouvelables (Algerie) : http: // www.cder.dz

Fig. 1.An isolated village power network Fig. 2 Demand Side Management Unit

Energy Meter Card Current Transformer

Switch Circuit

Fig. 3 Test setup with the 2kW heater Fig. 4 Energy and Power values display

Fig. 5 Current Sensor output to the ADE7751 Fig. 6 Heater current for an OFF-ON Command