THIS PAPER ADDRESSES THE CURRENT STATUS AND FUTURE RESEARCH AND DEVELOPMENT PERSPECTIVES ASSOCIATED WITH TECHNOLOGIES TO HARNESS OFFSHORE RENEWABLE ENERGY, INCLUDING OFFSHORE WIND, WAVES, TIDES, OCEAN CURRENTS, AND THERMAL AND SALINITY GRADIENT, IN SOUTH AMERICA (SA). IT FOCUSES ON FIVE COUNTRIES: ARGENTINA, BRAZIL, CHILE, COLOMBIA AND URUGUAY. AT FIRST, A COMPREHENSIVE SURVEY PRESENTS THE NUMBER OF SCIENTIFIC PAPERS CLASSIFIED BASED ON THE RESOURCE TO SHOW THE TENDENCY AND IMPORTANCE OF SUCH SUBJECTS IN THE ACADEMIC COMMUNITY. EACH COUNTRY?S ELECTRICITY MATRIX AND GRID CONNECTION ARE SHOWN TO UNDERSTAND THE REGION?S RENEWABLE SOURCE PARTICIPATION SITUATION. THE POTENTIAL OF OFFSHORE RENEWABLE RESOURCES IS ADDRESSED BY CONSIDERING THE PUBLISHED TECHNICAL PAPERS IN SCIENTIFIC JOURNALS. THE MAIN CONFLICTS AND SYNERGIES ASSOCIATED WITH OCEAN SPACE UTILIZATION ARE PRESENTED BY CONSIDERING THE EXCLUSIVE ECONOMIC ZONE OF EACH COUNTRY. THE STATUS OF THE REGULATORY FRAMEWORKS TO PROMOTE AND DEVELOPMENT OF OFFSHORE RENEWABLE ENERGIES IS PRESENTED. TWO SECTIONS ARE DEDICATED TO PRESENTING THE ACTIVE, DECOMMISSIONED AND PLANNED PROJECTS, RESEARCH GROUPS AND LABORATORY INFRASTRUCTURES TO DEVELOP THE TECHNOLOGIES. THE LAST SECTION DISCUSSES THE FUTURE PERSPECTIVES ON THE DEVELOPMENT OF THIS SECTOR IN SA. IT IS OBSERVED THAT SA, WITH MORE THAN 25,000 KM OF COASTLINE, HAS A GREAT POTENTIAL FOR OFFSHORE RENEWABLE ENERGY; HOWEVER, SO FAR, THESE RESOURCES HAVE NOT BEEN EXPLORED COMMERCIALLY. LARGER INVESTMENT IN THE SECTOR, ESTABLISHING AN ADEQUATE LEGAL FRAMEWORK AND DEPLOYING FULL-SCALE DEMONSTRATION PROJECTS AT SEA ARE NECESSARY FOR THE COMMERCIALIZATION OF SUCH TECHNOLOGIES IN SA.

RENEWABLE ENERGIES HAVE BROUGHT A SOLUTION FOR PERMANENT AND INEXHAUSTIBLE ENERGY MANAGEMENT. THE APPLICATIONS ARE NUMEROUS AND EVERY DAY MORE ACCESSIBLE FOR SMALLER COMPANIES THAT NEED TO REDUCED THEIR ENERGY EXPENSES. THIS PAPER STUDIES AND ANALYSES THE ECONOMIC IMPACT OF SOLAR ENERGY INSTALLATION ON A SMALL FARM CLOSE TO QUILLÓN, CHILE, A LITTLE TOWN WHOSE ECONOMY IS MAINLY BASED ON FRUITS AND VEGETABLES PRODUCTION. THE PROPOSED METHODOLOGY DIVIDES THE ANALYSIS INTO THREE CASES, WHICH DETERMINE THE SELECTION OF THE NUMBER OF PANELS ACCORDING TO (1) SUPPLYING OF THE TOTAL DEMAND IN THE MONTH WITH THE HIGHEST SOLAR IRRADIATION, (2) SUPPLYING OF THE TOTAL DEMAND IN THE MONTH WITH THE LOWEST SOLAR IRRADIATION, AND (3) SUPPLYING THE TOTAL DEMAND WITHOUT HAVING ENERGY EXCESSES INJECTED INTO THE GRID, BUT ONLY PRODUCE FOR SELF-SUPPLYING. ALL THE CASES ARE STUDIED AND THEREFORE THE DECISION MAY FOLLOW THE ECONOMIC ASPECT OF INVESTMENT IN THE SHORT, MIDDLE, AND LONG TERM. THUS, THESE ALTERNATIVES ARE VISIBLE FOR PRODUCERS TO TAKE THE OPTION THAT BEST FITS THEM.

THE AUTOMOTIVE INDUSTRY CONTINUOUSLY ENHANCES VEHICLE DESIGN TO MEET THE GROWING DEMAND FOR MORE EFFICIENT VEHICLES. COMPUTATIONAL DESIGN AND NUMERICAL SIMULATION ARE ESSENTIAL TOOLS FOR DEVELOPING CONCEPT CARS WITH LOWER CARBON EMISSIONS AND REDUCED COSTS. UNDERGROUND ROADS ARE PROPOSED AS AN ATTRACTIVE ALTERNATIVE FOR REDUCING SURFACE CONGESTION, IMPROVING TRAFFIC FLOW, REDUCING TRAVEL TIMES AND MINIMIZING NOISE POLLUTION IN URBAN AREAS, CREATING A QUIETER AND MORE LIVABLE ENVIRONMENT FOR RESIDENTS. IN THIS CONTEXT, A CONCEPT CAR BODY DESIGN FOR UNDERGROUND TUNNELS WAS PROPOSED, INSPIRED BY THE MAKO SHARK SHAPE DUE TO ITS EXCEPTIONAL OPERATIONAL KINETIC QUALITIES. THE PROPOSED BIOMIMETIC-BASED METHOD USING COMPUTATIONAL FLUID DYNAMICS FOR ENGINEERING DESIGN INCLUDES AN ITERATIVE PROCESS AND CAR BODY OPTIMIZATION IN TERMS OF LIFT AND DRAG PERFORMANCE. A MESH SENSITIVITY AND CONVERGENCE ANALYSIS WAS PERFORMED IN ORDER TO ENSURE THE RELIABILITY OF NUMERICAL RESULTS. THE UNIQUE SURFACE SHAPE OF THE SHARK ENABLED REMARKABLE AERODYNAMIC PERFORMANCE FOR THE CONCEPT CAR, ACHIEVING A DRAG COEFFICIENT VALUE OF 0.28. THE ADDITION OF AN AERODYNAMIC DIFFUSER IMPROVED DOWNFORCE BY REDUCING 58% OF THE LIFT COEFFICIENT TO A FINAL VALUE OF 0.02. BENCHMARK VALIDATION WAS CARRIED OUT USING REPORTED RESULTS FROM SOURCES AVAILABLE IN THE LITERATURE. THE PROPOSED BIOMIMETIC DESIGN PROCESS BASED ON COMPUTATIONAL FLUID MODELING REDUCES THE TIME AND RESOURCES REQUIRED TO CREATE NEW CONCEPT CAR MODELS. THIS APPROACH HELPS TO ACHIEVE EFFICIENT AUTOMOTIVE SOLUTIONS WITH LOW AERODYNAMIC DRAG FOR A LOW-CARBON FUTURE.

THE OBJECTIVE OF THIS WORK IS TO STUDY HOW TO MINIMISE WAVE REFLECTION IN THE WAVE CHANNEL OF THE UNIVERSIDAD DEL BIOBIO WAVE LAB BY MEANS OF DIFFERENT POROUS MEDIA. THE EXPERIMENTAL STUDY WAS MADE DEFINING SIX INITIAL WAVE STATES, IN WHICH ALL EXPERIMENTS WERE CARRIED OUT. FOUR SITUATIONS WERE COMPARED: FIRST, WITHOUT ANY WAVE ABSORBER; SECOND WITH A SPONGE WAVE ABSORBER ALREADY PRESENT IN THE CHANNEL; THIRD WITH A POROUS PLATE ABSORBER IN SERIES; AND FINALLY WITH A TRIANGULAR MESH ABSORBER WITH SPONGES. WAVE TRAIN-FREE SURFACE ELEVATION DATA WERE COLLECTED USING THREE CAREFULLY SPACED ULTRASOUND SENSORS AND USED TO CALCULATE THE REFLECTION COEFFICIENT ASSOCIATED WITH EACH WAVE STRUCTURE AND PARAMETER. THE RESULTS REVEALED THAT THE FIRST SCENARIO SHOWED THE HIGHEST REFLECTION COEFFICIENT, WHILE THE SECOND SCENARIO SHOWED THE SECOND HIGHEST REFLECTION COEFFICIENT. ON THE OTHER HAND, THE THIRD SITUATION PRESENTED THE LOWEST REFLECTION COEFFICIENT, AND IN THE LAST SITUATION, A SLIGHTLY HIGHER COEFFICIENT THAN THE THIRD CASE WAS OBTAINED. THESE RESULTS HIGHLIGHT THE EFFICIENCY OF THE TWO PROPOSED ABSORBER STRUCTURES AND THEIR PERFORMANCE IN REFLECTION REDUCTION. IN CONCLUSION, THE POROUS PLATE ABSORBER SHOWED HIGHER MITIGATION OF THE REFLECTION, FOLLOWED BY THE TRIANGULAR MESH ABSORBER AND SPONGES. THIS STUDY COULD CONTRIBUTE TO FUTURE RESEARCH CONDUCTED IN THE WAVE-GENERATING CHANNEL, PROVIDING VALUABLE INSIGHT FOR PRACTICAL APPLICATIONS IN THE FIELD OF COASTAL RESEARCH AND ENGINEERING.

IN THIS PAPER, WE EMPLOY AN EXPERIMENTALLY DESIGNED MODEL PREDICTIVE CONTROL (MPC) FRAMEWORK COUPLED WITH A KALMAN FILTER TO REGULATE A POINT ABSORBER WAVE ENERGY CONVERTER (WEC). THIS METHODOLOGY ENTAILS THE UTILIZATION OF A MATHEMATICAL MODEL REPRESENTING THE POINT ABSORBER, ENABLING THE CONTROLLER TO ANTICIPATE THE ENERGY CONVERTER'S FUTURE BEHAVIOR. EXECUTING THE MPC NECESSITATES REAL-TIME DATA FROM SENSORS, WHICH CAN BE SUBJECT TO WHITE NOISE. THROUGH THE APPLICATION OF THE KALMAN FILTER, THESE INHERENT ERRORS ARE EFFECTIVELY MITIGATED, ENABLING ACCURATE ESTIMATION OF ADJUSTED STATE VARIABLES. THIS, IN TURN, LEADS TO THE GENERATION OF CONTROL SIGNALS AND SYSTEM OUTPUTS THAT CORRESPOND TO POSITION AND VELOCITY. THE OUTCOMES OF THE STUDY HIGHLIGHT THAT THIS CONTROL STRATEGY EXERTS A POSITIVE INFLUENCE ON POWER EXTRACTION, AS IT ENSURES ALIGNMENT BETWEEN VELOCITY AND EXCITATION FORCE, ULTIMATELY ENHANCING THE EFFICIENCY OF THE PROCESS.

WAVE ENERGY HAS THE POTENTIAL TO PROVIDE A SUSTAINABLE SOLUTION FOR GLOBAL ENERGY DEMANDS, PARTICULARLY IN COASTAL REGIONS. THIS STUDY EXPLORES THE USE OF REINFORCEMENT LEARNING (RL), SPECIFICALLY THE Q-LEARNING ALGORITHM, TO OPTIMISE THE ENERGY EXTRACTION CAPABILITIES OF A WAVE ENERGY CONVERTER (WEC) USING A SINGLE-BODY POINT ABSORBER WITH RESISTIVE CONTROL. EXPERIMENTAL VALIDATION DEMONSTRATED THAT Q-LEARNING EFFECTIVELY OPTIMISES THE POWER TAKE-OFF (PTO) DAMPING COEFFICIENT, LEADING TO AN ENERGY OUTPUT THAT CLOSELY ALIGNS WITH THEORETICAL PREDICTIONS. THE STABILITY OBSERVED AFTER APPROXIMATELY 40 EPISODES HIGHLIGHTS THE CAPABILITY OF Q-LEARNING FOR REAL-TIME OPTIMISATION, EVEN UNDER IRREGULAR WAVE CONDITIONS. THE RESULTS ALSO SHOWED AN IMPROVEMENT IN EFFICIENCY OF 12% FOR THE THEORETICAL CASE AND 11.3% FOR THE EXPERIMENTAL CASE FROM THE INITIAL TO THE OPTIMISED STATE, UNDERSCORING THE EFFECTIVENESS OF THE RL STRATEGY. THE SIMPLICITY OF THE RESISTIVE CONTROL STRATEGY MAKES IT A VIABLE SOLUTION FOR PRACTICAL ENGINEERING APPLICATIONS, REDUCING THE COMPLEXITY AND COST OF DEPLOYMENT. THIS STUDY PROVIDES A SIGNIFICANT STEP TOWARDS BRIDGING THE GAP BETWEEN THE THEORETICAL MODELLING AND EXPERIMENTAL IMPLEMENTATION OF RL-BASED WEC SYSTEMS, CONTRIBUTING TO THE ADVANCEMENT OF SUSTAINABLE OCEAN ENERGY TECHNOLOGIES.

EFFECTIVE CONTROL STRATEGIES ARE ESSENTIAL FOR OPTIMIZING WAVE ENERGY PRODUCTION. WHILE THEORETICAL STUDIES HAVE EXPLORED VARIOUS CONTROL APPROACHES, EXPERIMENTAL VALIDATION OF THESE METHODS REMAINS LIMITED. THIS STUDY PROPOSES A DAMPING ADJUSTMENT METHOD AS A MEANS TO ENABLE THE EXPERIMENTAL APPLICATION OF RESISTIVE CONTROL IN WAVE ENERGY SYSTEMS. THE SYSTEM?S DAMPING IS ADJUSTED THROUGH A VARIABLE ELECTRICAL RESISTANCE COUPLED TO THE GENERATOR. A MATHEMATICAL MODEL IS DEVELOPED TO CAPTURE THE INTERACTION BETWEEN THE WAVE ENERGY CONVERTER, GENERATOR, AND VARIABLE RESISTANCE. EXPERIMENTAL VALIDATION DEMONSTRATES A GOOD FIT BETWEEN THE EXPERIMENTAL RESULTS AND THE MATHEMATICAL MODEL. FOUR DIFFERENT DC MACHINES ACTING AS GENERATORS ARE TESTED TO EVALUATE THE INFLUENCE OF THE MODEL?S PARAMETERS ON CONTROL CAPABILITY. RESULTS INDICATE THAT DC MACHINES WITH LESS INTERNAL RESISTANCE ALLOW A WIDER RANGE OF DAMPING AND POWER ADJUSTMENT BY USING EXTERNAL RESISTANCE. THE PROPOSED METHOD SHOWS PROMISING RESULTS, EMPHASIZING THE SIGNIFICANCE OF THE DC MACHINE PARAMETERS IN ACHIEVING EFFECTIVE CONTROL OVER SYSTEM VARIABLES. THESE FINDINGS CONTRIBUTE TO THE DEVELOPMENT OF EFFICIENT AND RELIABLE CONTROL STRATEGIES FOR ENHANCING WAVE ENERGY PRODUCTION AT SMALL SCALES.

ABSTRACT?IN THE PRESENT WORK, A PARAMETRIC STUDY OF THE INFLUENCE OF EXTERNAL VENTILATION IN THE BEHAVIOR OF THE THERMAL CHARACTERISTICS OF A REAL GREENHOUSE IS DEVELOPED BY USING A NUMERICAL MODEL IMPLEMENTED IN THE COMPUTATIONAL FLUID DYNAMICS SOFTWARE ANSYS FLUENT 2019R3. SUCH MODEL ALLOWS TO CORRECTLY DESIGN AN AUTOMATIC CONTROL OF THERMAL PROPERTIES IN GREENHOUSES. TWO DIFFERENT MODELS ARE PRESENTED, THE FIRST ONE USES NATURAL VENTILATION AND THE SECOND MODEL USES FORCED VENTILATION BY USING 22 FANS OF 40 CM OF RADIUS EACH. ONLY THE FIRST MODEL INCLUDES THE EXTERNAL FLUID DOMAIN. THE CULTIVATED CROP IS LETTUCE AND ITS INFLUENCE IN THE MODEL IS INCLUDED AS A POROUS MEDIA AND A WATER VAPOUR SOURCE. SOLAR RADIATION IS ADDED USING THE SURFACE TO SURFACE MODEL (S2S) AND IN ORDER TO INCLUDE THE AIR HUMIDITY, THE LOCAL MASS FRACTION IS PREDICTED THROUGH THE SOLUTION OF A CONVECTION-DIFFUSION EQUATION FOR EACH SPECIES. RESULTS FROM THE FIRST MODEL SHOWS THAT THE TEMPERATURE DISTRIBUTION IS UNEVEN INSIDE THE GREENHOUSE AND MOST IMPORTANT THAT THE THERMAL CHARACTERISTICS ARE NOT THE RECOMMENDED FOR THE LETTUCE CROP. THE SECOND MODEL SHOWS THAT AFTER REACHING THERMAL EQUILIBRIUM THE AVERAGE TEMPERATURE IS REDUCED A 175 % AND THE RELATIVE HUMIDITY INCREASE 13.5 % BY VARYING THE FAN INLET VELOCITY FROM 1 TO 10 M/S, WHILE A CHANGE IN THE INLET TEMPERATURE FROM 2 C TO 20 C AND CONSTANT VELOCITY CHANGES THE AVERAGE TEMPERATURE IN 82% AND THE RELATIVE HUMIDITY IN 4.7%. FINALLY A VARIATION FROM 10 TO 100 % OF THE RELATIVE HUMIDITY AT THE INLET DOES NOT AFFECT THE AVERAGE TEMPERATURE BUT INCREASE THE RELATIVE HUMIDITY 24% INSIDE THE GREENHOUSE.

THE USE OF NUMERICAL MODELS IN THE AGRICULTURAL INDUSTRY IS BECOMING MORE COMMON TO SOLVE DIFFERENT ISSUES, FOR EXAMPLE DESIGN OPTIMIZATION OR MODEL BASED CONTROL DESIGN. NEVERTHELESS, SUCH NUMERICAL MODELS ARE COMPUTATIONALLY EXPENSIVE AND IMPRACTICAL FOR CONTROL DESIGN. THIS WORK SHOWS A METHODOLOGY FOR OBTAINING A REDUCED ORDER MODEL THAT PREDICTS THE THERMAL BEHAVIOR OF A GREENHOUSE, IN ORDER TO DESIGN CONTROL SYSTEMS TO REGULATE THE BEHAVIOR OF THE INTERNAL MICROCLIMATE OF GREENHOUSES. THIS MODEL IS OBTAINED THROUGH SYSTEM IDENTIFICATION APPLIED TO THE DATA OBTAINED FROM A NUMERICAL GREENHOUSE (NG), MODELLED USING COMPUTATIONAL FLUID DYNAMICS (CFD) THROUGH ANSYS FLUENT 2019R3 SOFTWARE. THE CFD MODEL IS EXPERIMENTALLY VALIDATED BY COMPARING THE TEMPERATURE DISTRIBUTION INSIDE THE GREENHOUSE WHEN TURNING ON AND OFF A SET OF FANS, OBTAINING A 1.28% ROOT MEAN SQUARE ERROR. SUBSEQUENTLY, NUMERICAL SIMULATIONS OF TURNING ON AND OFF OF FANS ARE CARRIED OUT TO OBTAIN TEMPERATURE DATA AND TO OBTAIN A MODEL THAT RELATES THE ON TIME WITH THE AVERAGE TEMPERATURE INSIDE THE GREENHOUSE. DIFFERENT STRUCTURES WERE USED IN THE IDENT TOOL OF MATLAB, WHERE THE BEST FIT WAS FOUND FOR A SIMPLE LINEAR FUNCTION WITH DELAY WITH 61% OF RELATION TO THE SIMULATED DATA FROM THE NG AND 62% WHEN COMPARED WITH EXPERIMENTAL DATA.

WAVE ENERGY HAS ENORMOUS POTENTIAL AND MANY GOOD QUALITIES, SUCH AS ITS PREDICTABILITY, ENERGY DENSITY AND LOW VARIABILITY. NEVERTHELESS, THIS TYPE OF ENERGY STILL NEEDS TO BE COMPETITIVE AGAINST OTHER TYPES OF RENEWABLE ENERGY, LIKE WIND OR SOLAR ONES. THIS IS MAINLY DUE TO ITS HIGH COST. ONE SOLUTION TO REDUCE THE COST OF WAVE ENERGY IS THE USE OF CONTROL STRATEGIES. IN THIS WORK, A SIMPLE POINT ABSORBER BASED ON THE DIMENSIONS OF AN ONGOING PROJECT, NAMED LAFKENEWEN, IS MODELED WITH LINEAR POTENTIAL THEORY AND THE SOFTWARE ANSYS-AQWA. THREE DIFFERENT CONTROL STRATEGIES, REACTIVE CONTROL, LATCHING CONTROL AND RESISTIVE CONTROL, ARE COMPARED FOR A REGULAR WAVE THAT REPRESENTS THE MEAN SEA STATE OF THE PROJECT SITE LOCATION. RESULTS SHOW THAT THE REACTIVE CONTROL CAN ACHIEVE UP TO 18 KW BUT FOR UNREALISTIC CONDITIONS. LATCHING CONTROL ALLOWS CONVERTING UP TO 4 KW SHOWING BETTER PERFORMANCE THAN THE RESISTIVE CONTROL, WHICH ONLY ALLOWS UP TO 0.8 KW AVERAGE.

IN ORDER TO DESIGN AND EVALUATE THE BEHAVIOUR OF A NUMERICALLY OPTIMISED WAVE ENERGY CONVERTER (WEC), A RECOMMENDED PROCEDURE IS TO INITIALLY STUDY SMALL SCALE MODELS IN CONTROLLED LABORATORY CONDITIONS AND THEN PROGRESS FURTHER UP UNTIL THE FULL-SCALE IS REACHED. AT ANY POINT, AN IMPORTANT STEP IS THE CORRECT SELECTION OF THE WAVE THEORY TO MODEL THE DYNAMICAL BEHAVIOUR OF THE WEC. MOST AUTHORS RECOMMEND THE SELECTION OF A WAVE THEORY BASED ON DIMENSIONAL PARAMETERS, WHICH USUALLY DOES NOT CONSIDER THE MODEL SCALE. IN THIS WORK, THE SCALE EFFECTS FOR A POINT ABSORBER ARE STUDIED BASED ON NUMERICAL SIMULATIONS FOR THREE DIFFERENT REGULAR WAVES CONDITIONS. FURTHERMORE, THREE DIFFERENT WAVE THEORIES ARE USED TO SIMULATE TWO SCALES 1:1 AND 1:50. THE WEC-WAVE INTERACTION IS MODELLED BY USING A NUMERICAL WAVE TANK IMPLEMENTED IN ANSYS-FLUENT WITH A FLOATING OBJECT REPRESENTING THE WEC. RESULTS SHOW THAT THE NORMALISED DIFFERENCE BETWEEN 1:1 AND 1:50 MODELS, KEEPING THE SAME WAVE THEORY FLUCTUATE BETWEEN 30% AND 58% OF THE WEC HEAVE MOTION AND THAT A WRONG SELECTION OF THE WAVE THEORY CAN LEAD TO DIFFERENCES UP TO 138% FOR THE SAME VARIABLE. IT IS ALSO FOUND THAT THE LIMITS FOR THE USE OF WAVE THEORIES DEPENDS ON THE PARTICULAR MODEL AND THAT THE RANGE OF APPLICABILITY OF DIFFERENT THEORIES CAN BE EXTENDED.

DISTORTED VOLTAGE SUPPLIED AS UNBALANCED AND/OR NON-CONSTANT FREQUENCY CAN BE FOUND IN WEAK GRIDS, SUCH AS MICROGRIDS, OR SYSTEMS WORKING IN ISLANDING MODE. THESE KINDS OF SYSTEMS ARE MORE SENSITIVE UNDER LOAD CHANGES. PARTICULARLY, AN UNBALANCED VOLTAGE SUPPLY MAY BE PRODUCED FOR LARGE, SINGLE-PHASE LOADS. ON THE OTHER HAND, THE CONNECTION/DISCONNECTION OF HIGH CURRENT LOADS MAY LEAD TO IMPORTANT FREQUENCY VARIATION, ESPECIALLY IN WEAK GRIDS WHERE THE SHORT CIRCUIT CURRENT CAPACITY IS REDUCED. THESE CONDITIONS MAKE THE CONTROL OF THE POWER CONVERTER A MORE DIFFICULT TASK, BECAUSE OF THE VARIATIONS IN THE FREQUENCY AND UNBALANCING. TO ADDRESS THESE ISSUES, THIS PAPER PROPOSES A RESONANT CONTROL ALGORITHM TO DEAL WITH VARIATIONS IN THE VOLTAGE AMPLITUDE AS WELL AS GRID FREQUENCY WHEN A DISTORTED POWER SUPPLY IS CONSIDERED. THE FREQUENCY VARIATION IS AN IMPORTANT DRAWBACK FOR RESONANT CONTROL BECAUSE THE RESONANCE MUST BE TUNED AT THE GRID FREQUENCY. THIS ISSUE IS OVERCOME BY USING A VARIABLE SAMPLING FREQUENCY IN ORDER TO AVOID RE-TUNING THE CONTROLLER PARAMETERS. ON THE OTHER HAND, UNDER UNBALANCED CONDITIONS, THE PROPOSED METHOD RELAXES THE PHASE WITH LOWER VOLTAGE AMPLITUDE BY TAKING MORE POWER FROM THE OTHER PHASES IN ORDER TO HELP THE STABILITY OF THE GRID SUPPLY. TO CORROBORATE THE MATHEMATICAL ANALYSIS AND THE PROPOSED CONTROL, A STABILITY STUDY IS PERFORMED, INCLUDING EXPERIMENTAL AND SIMULATED RESULTS.

REINFORCEMENT LEARNING (RL) TECHNIQUES ARE APPLIED IN DIFFERENT AREAS TO OPTIMIZE PARAMETERS, ONE APPLICATION IS THE USE OF RL IN THE ENERGY MAXIMIZATION OBTAINED FROM WAVE ENERGY CONVERTERS (WEC). THE MAIN ADVANTAGE OF RL IS THAT IT CAN OPTIMIZE THE GENERATION EVEN WHEN THERE ARE CHANGES IN THE WAVE AND IN THE WEC CHARACTERISTICS. Q-LEARNING AND SARSA RL-BASED APPROACHES ARE PRESENTED IN THIS WORK, IN ORDER TO OPTIMIZE A REACTIVE AND A RESISTIVE CONTROL APPLIED TO A LABORATORY-SCALE POINT ABSORBER WEC. THE PROPOSED APPROACHES ARE EVALUATED ON THREE REGULAR WAVE CONDITIONS USING A MODEL BASED ON A ONE-DEGREE OF FREEDOM SYSTEM, WHERE THE POWER TAKE OFF FORCES INCLUDE THE VARIABLE DAMPING AND STIFFNESS THAT ARE REGULATED BY THE CONTROL AND OPTIMIZED BY THE RL. RESULTS SHOWN A CORRECT BEHAVIOR OF THE RL ALGORITHMS OPTIMIZING BOTH CONTROL TECHNIQUES. NEVERTHELESS, REACTIVE CONTROL ACHIEVE UP TO 239% HIGHER ENERGY THAN THE RESISTIVE CONTROL FOR THE SAME CONDITIONS. IN RELATION WITH THE COMPARISON BETWEEN THE TWO RL ALGORITHMS, Q-LEARING PRESENT A FASTER CONVERGENCE THAN SARSA, BUT THE RESULTS FROM BOTH ALGORITHMS ARE PRACTICALLY THE SAME.