TỐI ƯU HÓA VẬN HÀNH HỆ THỐNG ĐIỆN

Course Outline Concept and definition Introduction to optimization Economic dispatch Unit commitment Optimal power flow Hydrothermal coordination Smart grid optimization Project presentationCourse Outline Concept and definition Introduction to optimization Economic dispatch Unit commitment Optimal power flow Hydrothermal coordination Smart grid optimization Project presentation

2/16/2014 TỐI ƯU HÓA VẬN HÀNH HỆ THỐNG ĐIỆN Chapter 1: CONCEPT AND DEFINITION by Dr.Vo Ngoc Dieu Department of Power Systems HCMC University of Technology Email: vndieu@gmail.com Introduction • • • • • • • In 1831, Michael Faraday’s many years of efforts rewarded when he discovered electromagnetic induction Later, he invented the first generator Today, electric energy technologies have a central role in social and economic development at all scales Energy is closely linked to environmental pollution and degradation, to economic development and quality of life Today, we are mostly dependent on nonrenewable fossil fuels that have been and will continue to be a major cause of pollution and climate change Finding sustainable alternatives is becoming increasingly urgent Operation and control of power system is an extremely complex task 2/16/2014 Definitions • • • • Electric Capacity is a term that defines the rated continuous loadcarrying ability, expressed in megawatts (MW) or megavolt-amperes (MVA) of generation, transmission, or other electrical equipment Electric Energy is the term that defines the generation or use of electric power by a device over a period of time It is expressed in kilowatt-hours (kWh), megawatt-hours (MWh), or gigawatt-hours (GWh) In context of electric circuits, the term ‘load’ refers to any device in which power is being dissipated (i.e consumed) In larger context of the power system, loads are usually modeled in an aggregated way rather than an individual appliance Load may refer to an entire household, a city block or all the customers within a certain region Type of loads • Resistive loads (25%): Heating and lighting equipments e.g.Toaster, iron, electric blankets, Incandescent lamps • Motors (70%): Compressors (air conditioner, refrigerator) Pumps (well, pool), Fans Household appliances (washer, mixer, vacuum cleaner) Large commercial 3-phase motors (grocery store chiller) Power tools (hand drill, lawn mower) Electric street cars Basically ‘anything’ that moves! • Electronic devices (5%): Power supplies for computers etc Transformers (adapter, battery charger) 2/16/2014 Type of loads • From system’s point of view, there are broad category of loads: Domestic, Commercial, Industrial, Agriculture and others Domestic: lights, fans, domestic appliances like heaters, refrigerators, air conditioners, mixers, ovens, small motors etc Demand factor = 0.7 to 1.0; Diversity factor = 1.2 to 1.3; Load factor = 0.1 to 0.15 Commercial: Lightings for shops, advertising hoardings, fans, AC etc Demand factor = 0.9 to 1.0; Diversity factor = 1.1 to 1.2; Load factor = 0.25 to 0.3 Industrial: Small scale industries: 0-20kW Medium scale industries: 20-100kW Large scale industries: above 100kW Type of loads ……Cont’d Industrial loads need power over a longer period which remains fairly uniform throughout the day For heavy industries: Demand factor = 0.85 to 0.9; Load factor = 0.7 to 0.8 Agriculture: Supplying water for irrigation using pumps driven by motors Demand factor = 0.9 to 1; Diversity factor = 1.0 to 1.5; Load factor = 0.15 to 0.25 Other Loads: Bulk supplies, street lights, traction, government loads which have their own peculiar characteristics “Load” is an externally given quantity, a variable beyond control, in a completely unselfconscious manner 2/16/2014 Calculations Demand Factor = Diversity Factor = Load Factor = Actual Maximum Demand Total Connected Load Sum of individual maximum demands Actual Peak of the system Average Load over a given time period Peak Load during the same time period Electric Power System Operation • Operational objectives of a power system have been to provide a continuous quality service with minimum cost to the user These objectives are: First Objective: Supplying the energy user with quality service, i.e., at acceptable voltage and frequency Second Objective: Meeting the first objective with acceptable impact upon the environment Third Objective: Meeting the first and second objectives continuously, i.e., with adequate security and reliability Fourth Objective: Meeting the first, second, and third objectives with optimum economy, i.e., minimum cost to the energy user • The term “continuous service” can be translated to mean “secure and reliable service” 2/16/2014 Operation Control • The primary functions of operations control are satisfying the instantaneous load on a second-to-second and minute-to-minute basis Some of these functions are: Load Frequency Control On-Line Load Flow Economic Dispatch Calculation (EDC) Operating Reserve Calculation (ORC) Operation Control……Cont’d • • Load Frequency Control (LFC) This function is also referred to as governor response As the load demand of the power system increases, the speed of generators will decrease and this will reduce the system frequency Similarly, as system load demand decreases, the speed of the system generators would increase and this will increase the system frequency The power system frequency control must be maintained for the power system grid to remain stable Online Load Flow (OLF): This function generally utilizes the output of network topology, i.e the real time network model, and the bus injections from state estimation for purpose of security monitoring, security analysis and penalty factor calculations This function performs “if then condition” to determine the possible system states (voltages) in face of system outages such as loss of a line due to weather condition or sudden loss of a generator 10 2/16/2014 Operation Control……Cont’d • • Economic Dispatch Calculation: Economic dispatch calculation of a power system determines the loading of each generator on a minute-by-minute basis so as to minimize the operating costs Operating Reserve Calculation: The objective of operating reserve calculation is to calculate the actual reserve carried by each unit and to check whether or not there is a sufficient reserve in a system The operating reserve consists of spinning reserve (synchronized), nonspinning reserve (non-synchronized), and interruptible load 11 Operation Philosophy - Important Terms • Stability: - Continuance of intact operation following a disturbance It depends on the operating condition and the nature of the physical disturbance • Security: - Degree of risk in power system ability to survive imminent disturbances (contingencies) without interruption of customer service It relates to robustness of the system to imminent disturbances and, hence, depends on the system operating condition as well as the contingent probability of disturbances • Reliability: - Probability of power system satisfactory operation over the long run It denotes the ability to supply adequate electric service on a nearly continuous basis, with few interruptions over an extended time period 12 2/16/2014 Operation Philosophy - Threats of Power Systems Security • • Frequency instability - is inability of a power system to maintain steady frequency within the operating limits - it is in its nature rather a tracking than truly a stability control problem Voltage instability - the inability of a power system to maintain steady acceptable voltages at all buses - system enters a state of voltage instability when a disturbance, increase in load demand, or change in system conditions causes a progressive and uncontrollable drop in voltage 13 Operation Philosophy - Threats of Power Systems Security • • • Transient angular instability - inability of the power system to maintain synchronism when subjected to a severe transient disturbance Small-signal angular instability - inability of the power system to maintain synchronism under small disturbances - modes: • local • Inter-area Cascading spreading of components overloads and outages 14 2/16/2014 Operation Philosophy - Operation States - Normal – no equipment overloaded The system can withstand any contingency without violating any of constraints - Alert – no equipment overloaded yet The system is weakened - a contingency may cause an overloading of equipment, resulting in emergency state - Emergency – Some equipment overloaded If no control action executed, system progresses into In Extremis - In Extremis – Cascading spreading of system components outages resulting in partial or system-wide blackout - Restoration – Energizing of the system or its parts and reconnection and resynchronization of system parts 15 Operation Philosophy - Operation States - 16 2/16/2014 Operation Philosophy - Security • • Security: - “degree of risk in power system ability to survive imminent disturbances (contingencies) without interruption of customer service It relates to robustness of the system to imminent disturbances and, hence, depends on the system operating condition as well as the contingent probability of disturbances.” - Normal state is secure - All other states are insecure The transition/border between Normal and Alert state is expressed by N – criterion: - Outage of a single component can not lead to violation of operation limits of any other component 17 Operation Philosophy - Preventive Control • Preventive Control: - to keep the system in Normal state - to bring the system back into Normal state - Hierarchical automatic control: • Frequency control • Voltage control - Centralized manual control: • Decision support tools • Operator judgment 18 2/16/2014 Operation Philosophy - Preventive Control • Preventive control measures: - Generation redispatch (change of active power production of generators) - Change of reference points of controllable devices (e.g FACTS, phase-shifting transformers) - Start-up of generation units - Change of voltage reference points of generators and voltage control devices (e.g Static Var Compensator) - Switching of shunt elements (e.g reactors, capacitors) - Change of substation configuration (e.g busbars splitting) 19 Operation Philosophy - Emergency Control • Emergency control: - to stop the further system degradation and failure propagation - to bring the system back into Alert state - Protection based systems • Under frequency load shedding (UFLS) schemes • Under voltage load shedding (UVLS) schemes • System Protection Schemes (SPS) - Damping control 20 10 2/16/2014 17 18 2/16/2014 19 20 10 2/16/2014 21 22 11 2/16/2014 23 24 12 2/16/2014 25 26 13 2/16/2014 27 28 14 2/16/2014 29 30 15 2/16/2014 31 32 16 2/16/2014 33 34 17 2/16/2014 35 36 18 2/16/2014 37 38 19 2/16/2014 39 40 20 2/16/2014 41 42 21 2/16/2014 43 44 22 2/16/2014 45 46 23 ... several tie-lines) - NTC is theoretical value (parallel flows etc.) 31 16 2/16/2014 TỐI ƯU HÓA VẬN HÀNH HỆ THỐNG ĐIỆN Chapter 2: INTRODUCTION TO OPTIMIZATION Dr Vo Ngoc Dieu Department of Power