The Application of Artificial Intelligence to Electricity Power System

Copyright © IFAC Skill Based Automated Production. Vienna. Austria 1989

THE APPLICATION OF ARTIFICIAL INTELLIGENCE TO ELECTRICITY POWER SYSTEM S. Yamakawa*, S. Aida*, K. Hagino*, N. Honda* and T . Shimizu** *University of Electro-Communications. 1 -5-1 Chofugaoka, Chofu-shi, Tokyo 182, Japan **Technological University of Nagaoka, 1603-1 Kamitomioka-machi Nagamine, Nagaoka-shi, Niigata, Japan

A technology for electricity power diversification has been Abstract developing in the individual equipments by using power conversion technology, however, is falling behind in th is process of diversification in the energy supply. The diversification in electricity power lust be also investigated from the supplier's viewpoints. The theme we will take up is the basic problem seen in every from of supply - the importance of its diversification, especially that of A.C. frequency. It is the aim of our study to make it clear how a new system for an electricity power supply should be, which enables to cope with various demands of consumers appropriately. We will survey the actual circumstances of type of power supply and util ization in general load and special load. Further we wi 11 investigate appl ications of frequency conversion technologi es in various fields. Then, we wi II design a model of a system of varied power supply and uti I ization. The structure of the new system wil I be a hierachical type and the introduction of artificial intelligence will be discussed for higher level In this system, we wi II be able to plan the power supplying cont ro 11 er. schedule and to operate optimal Iy from the total system's viewpoints based on the knowledge base about past experiences, for example, of emergencies or the fluctuation of energy consumption in every situation. Keywords Artificial intell igence; El ect ric power system; Power converters; Power suppl ies.

cOlllputer, and "AI" is Artificial Intelligence. These are necessary technology for moresystematizing. From above co nsideration, the technological innovation in a field betwee n "energy and information" ma y appear by diversifi cation of energy-uti I ization. As the fi rst step, hence, we will ex amine pos si bility of utilization of various e lectri c ity pow e r from both technological and institutional view point, and comprehend actual circumstances in user-side as much as possible. And, we design a model of a system of varied power supply and uti lization to es tabl ish an innovational system technology of "3C&AI" and evaluate the model. It is the aim to make a sys t em of supply and utilization of electricity power in the information network .

I. INTRODUCTION

It is a purpose of this study in relation with various electricity power to actualize effi c ient and effective utili zation of ener gy . When we consider energy, we may consider in the 3-domains "matter, energy, information", that construct lIIodern c ivilization . We ob tain a lot of matter by making energy act on various natural resources, and succeeded in constructing modern civ ili zatio n. DeveloPlllent of information technology, which is based on computer, is as astonishing as technological innovation of matter, for ex ample, superconducti vi ty and amorphou s. This field is noticed as "3C&AI" te cnology, wh ere "3C" are Communication technology, Control technology and Command te c hnology bas ed on

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THE ACTUAL CIRCUMSTANCE VARIOUS ELECTRICITY

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Yamakawa et al.

UTILIZATION

2.3

or 2.1

The actual circulstances of the technology for uti I ization of various electricity

The function and efficiency of semiconductor-devices is concerned in the development of power devices. But from the latter half of 1970 to 1980's, new devices appeared, and are developing, for example, Gate-Turn-Off thyrister (GTO thyrister) and Static-Induction type device (SI device). The power conversion and control technology made rapid progress, because of introducing control theory and digital control method owing to inexpensive licroprocessor with enough process i ng speed and ab i I i ty. Combining with control technology, it becale possible to control not only power frequency but also power waveform. That influences uti I ization of electricity power and is propelling force for high-efficiencization, miniaturization, energy saving and progress of reliability in each equipment. AC motors with inverter drive can realize higher responce, larger capacity and higher speed adjustable motor than DC motors, and are used much more for domestic equipments than general industry. Non-interruption power unit which always supply constant frequency and voltage is one of necessary power electronic equipment in the advanced informationized society. Besides, activefilter etc. are made practicable as power control units which generate free waveform and compensate reactive power and higher harmonics. Like this, power conversion technology is becoming of daily necessity, and seems to become wide-spread with solving each technical problem. It seems that constructing techology of the total system including these power conversion technology make rapid progress with computer technology, transmition communication technology and higher control technology. 2.2

The actual circumstances of technology for utilization of various electricity from users' view-point

The actual circumstances were investigated in inquiring to a maker. As a result. voltage and frequency are transformed variously in almost equipments. A lot of equipments use low voltage, which becomes various.

The actual circumstances and the future of supply

On the present distribution system, 100V a 200V are suppl ied for deund of low vol tage and 6 kV is supplied for deland of high voltage in Japan. Their frequency is 50Hz or 60Hz. I t is prepared to use 100V and 200V together for home use, and to use 200V and 400V together for slall factories. As the above lentioned, allost equiplents transform voltage and frequency in themselves. Rapid progress of frequency transforling technology in recent years made more possible to supply various frequency power, it is not only useful for energy saving but can make good effect for improvement of productivity expect. It seems that problems of higher harlonics wil I grow in future from pervasion of semiconductor appl ied equipments. At present, countermeasures at the source (special user, equipments side) are mainly taken, but the degree of suppression has limits frol performance of equipments. Based on suppression in the source, therefore, it is also necessary to take the countermeasures in co-operation with power supplyers, makers and demanders. Rei iabi I ity and high qual i tyzation of power supply are a indispensable and important problem for high-informationizing society which develops with computer .

m.

THE GAP AND PROBLEMS BETWEEN USERS AND SUPPLVERS

3.1

Recognition of problems

utilization of various electricity has been already real ized in many field in user's side. The system in which power is transformed individ ually in each equipment is efficient for domestic equipment, however, it is not always eff icient and effective uti I ization style in factory and tall-building in which mass power is necessary. Therefore, we should classify forms of power uti I ization in every block and every production process. and establ ish the best utilization systems for each equipment. 3.2

The problems which should be solved in System

When we regard the electric power system as the total system which includes supplyers, equiplllents and users. following problems ap-

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Application of Artificial Intelligence

converter and charging batteries.

pear. I) It is unefficient each equip.ent has a converter respectively. In general, a converter has bad power factor, and tend to generate higher harmonics. So,it's a disadvantage in point of a countermeasure against higher harmonic that each equiplent has a converter respectively.

Because in present equiplents there are many equiplents which use directly or transform to other frequency after transforming to D.e. However, the voltage ranges wide, it isn't realistic to prepare many kinds of voltage, so we will limit to several kinds.

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2) If frequency is higher, miniaturization of a lotor and a tramsforler is lore possible in principle. And the luminous efficacy of fluorescent lalP gets improvement. There are factories and complexes with a lot of load (ex:high speed motor) which have advantage in higher frequency power. But the present power supply is made to unify in 50Hz and 60Hz. It is difficult in single frequency to frexible interface between supplyer, equipments and user, for convenience, efficency and comfort.

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Advantages of this model

By adopting this model, the following advantages are expected. IV. THE MODEL TO SUPPLY DIVERSE AND HIGH QUALITY ELECTRICUTY POWER 4.1

I) A barrier between 50Hz and 60Hz will be able to overcome.

An outl ine of model

Then, we propose the system of varied electricity power supply and uti I ization in Fig.1 and Fig.2 based on above consideration. The concept of this system is shown in the following; I) Centralization and abridgement conversion function, which each has, make progress in low-cost, saving and energy-saving in the system (High-efficient ization).

of power equipment spacetotal

2) Non-interruption function which can comply selectively with reliability required in each equiPllent (High-reliabil itization). 3) The measures to cope with higher harmonic, which is increasing as development of equipment with power conversion function, are taken off at the source concentrically (H igh-qua I i tyzat ion). In this case, following points are taken into consideration. • The present 50Hz A.C is supplied directly to usual equipments . • This system supplies D.C though batteries after transforming to D.C by a

2) Because a converter in each equipment can be omitted with direct supply of D.C; a) it wi II enable equiplents to liniaturize and to descrease in weight, b) high efficient converter wi I I be able to be adopted by central ization, so it wil I enable A.C-D.C transform loss to decrease. c) setting an active-filter in input stage from 50Hz syste. wil I make high-harmonic suppressed collectively, resulting in decrease the influence to main system, d) it is useful for co-operation with D.C output co-generation system and the connection with emergency power. 3) High rei iabi I ity and high-efficiency of power supp I y will become poss i b I e with noninterruption power system. 4) Miniaturization and high-efficiency of transformers and high speed motors wi 11 be expected with 400Hz supply. 5) Because of central conversion into D.C with converter after receiving and of then supplying of A.C with inverter, a) it becomes easy to synthesize the control systell as the total system including supplyer, equipment and user,

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b) higher amenity wil I be attained through diffusion of equiplents with inverter, c) high qual ity flexible control and userfriendly systel structure becole possible by cOlbining with host cOIPuter and inforlation communication systel. 4.3

Evaluation of the new systel

We applied the system to an OA-building, in which more high-qual ity and reI iabil ity for power supply are required, and then we evaluated the systel. (i) Establ ishing a model An established lodel is an office with 50012. Capacity of illumination, air-conditioner and OA-equiplents is referred to the actual faci I ities in Tama Branch of Tokyo Electric Power Company. Main prerequisite 0 the evaluation • The cost of the centralized conversion equiplent is calculated on the assumption that it is lass-producted such as CVCF which are on the market. • It is assumed that conversion device in the side of equipments which correspond to supplied voltage by the new systel are developed. • Their cost is calculated on the assuIPtion that they are mass-producted in the same degree as present.

(2)

The resulut is shown in Table . i. It shows that this system is better than present one.

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4.4 Each problem that has to be examined This system makes use of batteries for supplying D.C, mass-capacity high-efficiency battery, for instance Natrium/sulfer battery, is necessary. For D.C supply, a) At the present,because there are few equipment correpond to D.C supply, almost of them are articles on special o rd er .

i49

b) Because of various voltage of D.C, D.C-D.C converters will be necessary as lany as the number of the kind of voltage. c) Makeup and cutoff of circuits are lore difficult than A.C. For translitting high frequncy power, there are some problems, e.g systel stabi lity fal Is because of large charging current,voltage drop is large for the reactance,Power loss grow up. It is necessary to examine about the place and object of appl ication of 400Hz supply. One of the problems for power transforl technology is to real ize high-frequency swi tchi ng. 4.5

Possibil ity of expanding this model

Because this system once transform power into D.C, it seems to be possi bl e to appl y itself to distributed power system as a fuel battery power system etc. in the future. Because of essentially discrete action of this system,that based on ON-OFF control action, it is appropriate to using digital control and information processing system. This means that it becomes easy to combine host computer system with several sensors and cOI.unication I ine, so it wi II give flexible means to control the form of energy service according to the load or the state of users. It seems that the intell igent bui Iding is introduced more and 110re in the future, in this case, high qual ity and high reI iabi I ity of energy service are foundamental. COlbining with host system, this system wi II be extended as the basic model for the power supply system to the bui Iding with new concept that integrates organically basic service; "energy service", "information processing and communication" and "Ianagelent of bui Iding". This systel has possibil ity that it wil I progress to lore flexible and intel I igent power supply system with fuzzy control and A.I. And in consequence, the amenity in environments wil I be increaced.

V. CONCLUSION; The task in the future We have surveyed actual circumstances of power supply and utilization. And we have proposed a model of a new system of varied electricity power supply and uti I ization, and evaluated it. Then, the result showed that this lodel is better than present one.

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The diversification in the energy supply wil I be developed lore and more. so it is important to consider how supplying style is better for user and to make the system with latching between supplyer and user. As the tasks to study. we wi II think of various goals; not only stabil ity but also efficiency. amenity. convenience etc .• and consider concrete means to realize in electricity power util ization of user. The concrete tasks in the future are the fo II ow i ng; a) Introduction of new control technique to the new lIode I ; AI technology may be introduced into space'environment control. for example airconditioning and illuminating. to improve such efficiency and amenity by the new system. As a means to rea I i ze so system. it seells that i ntroduct ion of fuzzy control is effective. For the introduction of fuzzy control. the following problems arise; constructing control system. extraction of control rules. determination of the me.bership function. verification of dyna.ic be' havior. Concretely. we are studying the control of illumination with fuzzy control. b) Optimization for kinds of electricity; In relation to the kinds of electricity supplyed fro. the central ized conversion equipment, we have to find the optimulI electricity as a whole of system. We have to measure efficiency in each kind of electricity at several points between 0-100% oprational level. c) Analysis and evaluation with a experimenta I model; Measurements of higher-harmonics. measurements of electromagnetic induction at 400Hz. etc. d) Safety of a system; Safety has to be ensured against pul ling out a plug or error conection in D.C.

ACKNOWLEDGEMENT This study is the co-operative project with Tokyo Electric Power COIPany. The authors thank thel for their co-operation to write this paper.

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REFERENCE S. Yuakawa. S. Aida. K. Hagino et al.. "On the appl ication of Artificial IntelI igence for Power Supply and Uti I ization Syste .... PCIM'SS PROCEEDINGS 1 (POWER CONVERSION). pp. 333-342.