INTERNATIONAL POWER SYSTEM CONFRENCE | Year:2003 | دوره:18 |Papers Count:10

SINCE THE ADVENT OF ELECTRICITY RESTRUCTURING IN EARLY 1980’S, A VARIETY OF RESTRUCTURING MODELS HAVE BEEN ADOPTED IN DIFFERENT COUNTRIES. THE UNBUNDLING OF GENERATION FROM TRANSMISSION AND DISTRIBUTION AS SEPARATE BUSINESSES IS PREVALENT AMONG DIFFERENT MODELS. THE TRANSMISSION SECTOR IS GENERALLY REGARDED AS A NATURAL MONOPOLY, AND REMAINS REGULATED IN ORDER TO PERMIT A COMPETITIVE ENVIRONMENT FOR GENERATION AND SUPPLY SERVICES. NON-DISCRIMINATORY ACCESS AND PRICING OF TRANSMISSION IS GENERALLY MANDATED IN ORDER TO FACILITATE COMPETITION IN WHOLESALE GENERATION AND SUPPLY. IN MOST MARKET DESIGNS THE TRANSMISSION SECTOR AND ITS PRODUCTS AND SERVICES ARE FURTHER UNBUNDLED ACCOMMODATING DIFFERENT WHOLESALE MARKET PLAYERS, PRODUCTS, AND SERVICES, AS WELL AS THE PROVISION OR TRADING OF PRODUCTS AND SERVICES AS SEPARATE COMMODITIES. THE USUAL WHOLESALE MARKET PLAYERS ARE THE TRANSMISSION OWNERS (TO), INDEPENDENT SYSTEM OPERATORS (ISO), POWER EXCHANGES (PX) AND TRANSMISSION USERS OR THEIR AGENTS (SOMETIMES CALLED SCHEDULING COORDINATORS; SC). THE USUAL UNBUNDLING OF TRANSMISSION SERVICES INCLUDES SEPARATION OF BASIC NETWORK TRANSPORT SERVICES (“WIRES” SERVICE) FROM TRANSMISSION SUPPORT SERVICES (“ANCILLARY SERVICES”). THE PRIMARY MARKET COMMODITIES AND SERVICES ARE ENERGY, ANCILLARY SERVICES, AND TRANSMISSION SERVICES (INCLUDING CONGESTION MANAGEMENT AND TRANSMISSION RIGHTS). EXPERIENCE WITH DEREGULATED ELECTRICITY MARKETS THUS FAR HAS SHOWN THAT THE ASSUMPTION THAT MARKETS WILL NATURALLY PRODUCE COMPETITIVE RESULTS IS NOT JUSTIFIED. THE EXISTING ISOS AND POWER EXCHANGES ALL HAVE DEVELOPED OR ARE DEVELOPING SYSTEMS AND PROCEDURES TO ACCOMPLISH THE MONITORING TASK IN THEIR MARKETS. MARKET MONITORING IS CONCERNED PRIMARILY WITH ENSURING EFFICIENT MARKET PERFORMANCE BY IDENTIFYING AND MITIGATING MARKET INEFFICIENCIES, THE POTENTIAL FOR MARKET ABUSES AND MARKET POWER PROBLEMS. IN THIS PAPER, WE PRESENT AN OVERVIEW OF THE EVOLVING STRUCTURAL MODELS OF THE DEREGULATED ELECTRICITY MARKETS, ALONG WITH A SUMMARY OF THE USUAL PRODUCTS AND SERVICES, AND MARKET DESIGNS ADOPTED. WE ALSO DEFINE MARKET POWER AND IDENTIFY FACTORS THAT ALLOW THE EXERCISE OF MARKET POWER IN ELECTRICITY MARKETS, PROPOSE MARKET EFFICIENCY OBJECTIVES THAT SHOULD BE USED TO DESIGN MARKET RULES THAT DISCOURAGE GAMING, AND PROVIDE AN OVERVIEW OF THE KEY ELEMENTS NECESSARY FOR EFFECTIVE DESIGN AND IMPLEMENTATION OF MARKET MONITORING SYSTEMS. EMPHASIS IS PLACED ON THE WHOLESALE ELECTRICITY MARKETS AS THE FIRST STEP IN ELECTRICITY RESTRUCTURING. RETAIL OPEN ACCESS IS NOT TREATED HERE IN ANY DETAIL.

ROTOR BAR CURRENT MEASUREMENT IS A VALUABLE STEP IN VERIFYING THE THEORY OF ELECTRICAL MACHINES DESIGN AND CONTROL. HOWEVER, BECAUSE THE ROTOR IS MOVING, THE APPROACH IS DIFFICULT TO IMPLEMENT. THIS PAPER PRESENTS THE DESIGN AND EVALUTION OF AN APPROACH TO REAL-TIME ROTOR BAR CURRENT MEASUREMENT USING THE ROGOWSKI COIL AS A CURRENT TRANSDUCER. ROGOWSKI COILS HAVE BECOME AN INCREASINGLY POPULAR METHOD OF MEASURING CURRENT WITHIN POWER ELECTRONICS EQUIPMENT DUE TO THEIR ADVANTAGES OF LOW INSERTION LOSS AND REDUCED SIZE COMPARED TO AN EQUIVALENT CURRENT TRANSFORMER. THE DESIGN OF THE ASSOCIATED INTEGRATING AMPLIFIER IS DISCUSSED IN DETAIL, INCLUDING THE ADVANTAGE, TRADEOFFS AND LIMITATION OF THE APPROACH. BLUETOOTH WIRELESS TECHNOLOGY IS EMPLOYED TO TRANSMIT DATA BETWEEN THE MOVING ROTOR AND THE COMPUTER WHICH LOGS THE DATA. EXPERIMENTAL RESULTS FROM A SYSTEM FOR MEASURING THE ROTOR BAR CURRENT IN A BRUSHLESS DOUBLY FED MACHINE (BDFM) ARE PRESENTED.

NUCLEAR POWER REACTORS ARE, IN NATURE NONLINEAR AND TIME VARYING. THESE CHARACTERISTICS MUST BE CONSIDERED, IF LARGE POWER VARIATIONS OCCUR IN THEIR WORKING REGIME. IN THIS PAPER A ROBUST OPTIMAL GAIN SCHEDULING CONTROLLER FOR REGULATING THE POWER OF A NUCLEAR REACTOR HAS BEEN DESIGNED AND SIMULATED. THE PROPOSED CONTROLLER IS CAPABLE OF REGULATING POWER LEVELS IN A WIDE POWER RANGE (10% TO 100% POWER LEVELS). THE CONTROLLER ACHIEVES A FAST AND GOOD TRANSIENT RESPONSE. THE SIMULATION RESULTS SHOW THAT THE PROPOSED CONTROLLER OUTPERFORMS THE FIXED OPTIMAL CONTROL RECENTLY CITED IN THE LITERATURE FOR NUCLEAR POWER PLANTS.

SWITCHED RELUCTANCE (SR) MOTOR HAS REMARKABLE CHARACTERISTICS THAT MAKE IT ATTRACTIVE FOR HIGH-SPEED APPLICATIONS. AS THE MOTOR’S SPEED INCREASES THE SHAPE OF THE CURRENT WAVEFORM CHANGES IN SUCH WAY THAT LIMITS THE PRODUCTION OF MOTORING TORQUE. AT HIGH SPEEDS, IT IS POSSIBLE FOR THE PHASE CURRENT NEVER REACHES THE DESIRED VALUE DUE TO THE SELF E.M.F. OF THE MOTOR, THEREFORE, THE TORQUE FALLS OFF. IN ORDER TO REMEDY THIS PROBLEM, THE PHASE TURN ON ANGLE IS ADVANCED IN SUCH WAY THAT THE PHASE COMMUTATION BEGINS SOONER. ADVANCING THE COMMUTATION ANGLE OFFERS THE ADVANTAGES OF GETTING THE CURRENT INTO THE PHASE WINDING WHILE THE INDUCTANCE OF THE PHASE IS LOW, AND ALSO OF HAVING A LITTLE MORE TIME TO GET THE CURRENT OUT OF THE PHASE WINDING BEFORE THE ROTOR REACHES THE NEGATIVE TORQUE REGION. SINCE THE SR MOTOR IS A VARIABLE SPEED MOTOR THEN, THE AMOUNT OF ADVANCING FOR THE TURN ON ANGLE SHOULD BE ACCOMPLISHED AUTOMATICALLY ACCORDING TO THE SPEED OF THE MOTOR, MEANING, AS THE MOTOR’ PEED INCREASES SO SHOULD THE TURN ON ANGLE AND VICE VERSA. IN THIS RESPECT, THIS PAPER INTRODUCES A MECHANICAL GOVERNOR MOUNTED ON THE SHAFT OF A SR MOTOR TO ACHIEVE THIS TASK. THE OPENING OF THE GOVERNOR’S ARMS CAUSES 0-14 DEGREES AUTOMATIC ADJUSTMENT IN THE TURN ON ANGLE FROM STAND STILL TO A PRE-SET SPEED. A LINEAR ANALYSIS OF THE CURRENT WAVEFORM FOR THE MOTOR UNDER DIFFERENT ADVANCEMENTS OF THE TURN ON ANGLE HAS BEEN PERFORMED AND THE PLOTS ARE SHOWN. FINALLY, THE EXPERIMENTAL RESULTS OF EMPLOYING THE GOVERNOR ON A 6X4 SR MOTOR ARE PRESENTED.

IN THIS PAPER DESIGN, COMPUTATIONAL ASPECTS AND EXPERIMENTAL RESULTS OF A MICROPROCESSOR BASED DIGITAL TRANSFORMER DIFFERENTIAL RELAY IS DESCRIBED. HALF CYCLE FOURIER ALGORITHM IS USED TO ESTIMATE CURRENT PHASORS. PERFORMANCE OF THE PROPOSED RELAY IS TESTED FOR DIFFERENT FAULTS INCLUDING INTERNAL AND EXTERNAL FAULTS. THE ABILITY OF THE RELAY TO RESTRAINT FOR INRUSH CURRENT IS DISCUSSED AND DEMONSTRATED. TEST RESULTS OF THE PROPOSED ALGORITHM HIGHLIGHT THE ABILITIES OF THE ALGORITHM. TEST RESULTS FOR EXTERNAL FAULT, INTERNAL FAULT AND INRUSH CURRENT ARE PRESENTED IN THE PAPER.

THIS PAPER PRESENTS A PRACTICAL AND EFFICIENT METHOD FOR LONG-TERM GENERATING MAINTENANCE SCHEDULING WITH VARIOUS CONSTRAINTS FOR THE DEREGULATED POWER SYSTEM. USING THE BENDERS DECOMPOSITION, AN APPROACH HAS BEEN DEVELOPED FOR THE LONG-TERM MAINTENANCE SCHEDULING OF GENERATING UNITS. THIS APPROACH IS EFFICIENT BECAUSE A SOLUTION IS OBTAINED USUALLY WITHIN A FEW ITERATIONS. THE RESULTING LONG-TERM GENERATION MAINTENANCE SCHEDULING PROVIDES THE TIME INTERVALS, FOR A ONE YEAR PLANNING HORIZON, WHEN GENERATING UNITS IN A GENCO IS TAKEN OFF-LINE FOR PLANNED PREVENTIVE MAINTENANCE. THE ALGORITHM MINIMIZES THE TOTAL OPERATING COST FOR A GENCO. SINCE IN A COMPETITIVE DEREGULATED ENVIRONMENT, BOTH GENCO AND ISO (INDEPENDENT SYSTEM OPERATOR) ARE OPERATED INDEPENDENTLY OF EACH OTHER, WE APPLY BENDERS DECOMPOSITION TO INCLUDE THE ISO’S CONSTRAINTS IN THE LONG-TERM GENERATING MAINTENANCE-SCHEDULING PROBLEM TO MEET THE ENERGY DEMANDS, RELIABILITY AND OTHER SYSTEM REQUIREMENTS.

HARMONIC POLLUTION HAS BECOME A SERIOUS PROBLEM IN RECENT YEARS. HARMONICS ARE INTRODUCED INTO POWER SYSTEMS DUE TO NON-LINEAR LOADS OR SYSTEM COMPONENTS PRESENTING NON-LINEAR BEHAVIOR. AN ACTIVE POWER FILTER IS ONE METHOD USED TO MINIMIZE THE EFFECTS OF THE HARMONIC. HOWEVER, ACTIVE HARMONIC FILTER USUALLY REQUIRES SOME COMPLICATED ALGORITHM FOR IMPLEMENTATION. THIS PAPER PRESENTS A NEW APPROACH TO DESIGN AND DEVELOP AN ACTIVE HARMONIC FILTER WHICH HAS LESS COMPLEXITY COMPARED TO OTHER CONVENTIONAL ACTIVE HARMONIC FILTERS. IT CAN BE IMPLEMENTED BY INJECTING THE INVERSION FORM OF THE HARMONIC INTO THE MAIN LINE, WHICH RESULTS A LOWER VALUE OF HARMONIC CONTENT. IN OTHER WORDS, THE HARMONIC COMPONENT NEEDED BY THE NON- LINEAR LOAD IS PROVIDED BY THE ACTIVE FILTER RATHER THAN THE AC SOURCE.

INSULATION COORDINATION OF SUBSTATION EQUIPMENT, CABLES AND POWER LINES IS USUALLY VERIFIED BY TYPE AND ROUTINE TESTS IN FACTORY. TO GUARANTEE THE INSULATION COORDINATION IN SERVICE IT IS NECESSARY TO DEMONSTRATE THAT INSULATION OF THE EQUIPMENT IS WITHOUT TRANSPORTATION FAULTS AND CORRECTLY ASSEMBLED. THIS IS USUALLY DONE BY HV TESTS ON SITE. THE PAPER INFORMS ABOUT THE GENERAL PRINCIPLES FOR HV ON-SITE TESTING AS THEY ARE PREPARED BY THE IEC WORKING 42.13 FOR A NEW PART 3 OF THE IEC STANDARD 60060. AS EXAMPLES REQUIREMENTS AND TEST EQUIPMENT FOR ONSITE TESTING OF GAS-INSULATED SUBSTATIONS (GIS) AND HV XLPE CABLES ARE DESCRIBED. FINALLY THE RELATIONS BETWEEN ON-SITE TESTING BEFORE COMMISSIONING ON THE ONE HAND AND AFTER REPAIR OR FOR DIAGNOSTIC PURPOSES ARE CONSIDERED.

THE REQUIREMENT OF ANY POWER GENERATING UTILITY IS TO ACHIEVE RELIABLE AND TROUBLE FREE POWER GENERATION IN THEIR FACILITIES. SYSTEMS FOR ON-LINE QUALITY AND RELIABILITY ASSESSMENT OF HIGH VOLTAGE POWER EQUIPMENT HAVE BECOME VERY POPULAR IN RECENT YEARS. BY HAVING ACCESS TO POWER EQUIPMENT WHILE IN NORMAL OPERATION, PLANT ENGINEERS HAVE BEEN ABLE TO AVOID CATASTROPHIC IN SERVICE FAILURES, COSTLY FORCED OUTAGES OF POWER GENERATORS AND ASSOCIATED EQUIPMENT, AS WELL AS PROLONG SIGNIFICANTLY THE LIFE OF THE EQUIPMENT. BY EARLY DETECTION OF DEVELOPING PROBLEMS ON POWER SYSTEMS, MAINTENANCE CAN BE SCHEDULED PROMPTLY AND ONLY WHEN NECESSARY. PLANNING OF WORK AND RESOURCES CAN BE DONE WELL IN ADVANCE, WHICH WILL TREMENDOUSLY REDUCE THE COST OF SUCH INTERVENTION. ALSO BY PERFORM ING TEST BEFORE AND AFTER REPAIR IT IS EASY TO CONTROL THE EFFECTIVENESS OF REPAIR. ON-LINE MONITORING SYSTEMS WHICH ARE NON-DESTRUCTIVE, RELIABLE, QUICK AND EASY TO USE, HAVE IN FACT BECOME A KIND OF STANDARD IN MANY POWER UTILITIES WORLDWIDE. A MAJOR PROBLEM IN HV POWER EQUIPMENT IS ELECTRICAL INSULATION. ONE ONLINE TEST FOR THE INTEGRITY OF POWER EQUIPMENT IS THE PD (PARTIAL DISCHARGE) TEST FOR ELECTRICAL INSULATION. THE PD TEST BESIDES TESTING POWER GENERATORS AND MOTORS IS ALSO APPLICABLE FOR FACTORY SCREENING OF STATOR BARS, TESTING HV POWER CABLES AND POWER TRANSFORMERS.

TEMPERATURE IS THE MOST IMPORTANT FACTOR IN LOAD FORECASTING OF POWER SYSTEM ANALYSIS. PARTICULARLY IN SHORT-TERM LOAD FORECASTING, IT PLAYS AN IMPORTANT ROLE IN INCREASE/DECREASE OF ENERGY CONSUMPTION. FOR INSTANCE, ACCORDING TO THE JAPANESE POWER INDUSTRY ANNOUNCEMENT IN 2001, INCREASE OF 1 DEGREE CELSIUS WILL CAUSE ABOUT 5GW INCREASE IN ELECTRIC POWER CONSUMPTION AT THE SUMMER PEAK. THIS AMOUNT IS AS SAME AS CONSUMPTION POWER USED BY 1.6 MILLION GENERAL HOUSEHOLDS OR AMOUNT OF GENERATED POWER BY 5 LARGE-SCALE UTILITY POWER PLANTS. ON THE OTHER SIDE, 1 DEGREE CELSIUS OF TEMPERATURE CHANGE HAD CAUSED ABOUT 1.85GW INCREASE IN POWER CONSUMPTION IN THE WINTER OF YEAR 2000. BASICALLY, THE SHORT-TERM TEMPERATURE (HOURLY UP TO 1 WEEK AHEAD) IS RESEARCHED AND PREDICTED BY ENVIRONMENT AGENCIES OF EVERY COUNTRY. THEREFORE, IT IS EASY TO OBTAIN THE FORECASTED TEMPERATURE DATA FROM THOSE AGENCIES, NEWSPAPERS, TV NEWS AND SO ON. HOWEVER, IT IS DIFFICULT TO OBTAIN THE HOURLY TEMPERATURE BEYOND 1 WEEK. ALTHOUGH JAPAN METEOROLOGICAL AGENCY (JMA), WHICH USES THE NUMERICAL WEATHER PREDICTIONS (NWP), ANNOUNCES THE FORECASTING DATA UP TO 1 OR 2 MONTHS AHEAD, BUT THEY ARE EXPRESSED ONLY AS “HIGH” OR “LOW” WHICH IS COMPARED WITH NORMAL YEARS. THIS MEANS, WE CAN ONLY KNOW THAT THE TEMPERATURE MAY GOES UP OR COMES DOWN EVERY DAY. IN ADDITION, SUPER-COMPUTER PROCESSES IT WITH LOTS OF COMPLEX METEOROLOGICAL FORMULATIONS. THE APPLIED DATA THE ONES WHICH HAVE OBSERVED BY WEATHER SATELLITE ALL OVER THE WORLD. HOWEVER, IF THE TEMPERATURE COULD BE PREDICTED FOR A LONGER PERIOD, IT BECOMES EVEN A USEFUL FACTOR FOR PROJECTING A BETTER RESOLUTION FOR THE LONG-TERM LOAD FORECASTING, PREDICTION OF FUEL AMOUNT NECESSARY FOR NEXT COUPLE MONTHS OF POWER PLANTS AND SOFORTH. IN THIS PAPER, SOME INTELLIGENT METHODOLOGIES SUCH AS ARTIFICIAL NEURAL NETWORK AND A COMBINED NEURO-GENETIC ALGORITHM HAVE BEEN USED TO PREDICT THE TEMPERATURE UP TO ONE MONTH AHEAD.