SWES_Unit-V.ppt
- 1. 1 VISION AND MISSION OF THE DEPARTMENT Vision We envision the Department as one of the best in the region with a stimulating Environment to make an impact on, and lead in the field through its Education and Research. Mission The mission of the Department is to provide an excellent and comprehensive education in the field of Electrical and Electronics Engineering which in turn mould students for a wide range of careers and to exhibit a high level of Professionalism, ethical behavior and social responsibility.
- 2. 2 PROGRAMME OUTCOMES(POs): A graduate of Electrical and Electronics Engineering will have ability to: 1. Engineering knowledge 2. Problem analysis 3. Design/development of solutions 4. Conduct investigations of complex problems 5. Modern tool usage 6. The engineer and society 7. Environment and sustainability 8. Ethics 9. Individual and team work 10. Project management and finance 11. Communication 12. Life-long learning PROGRAMMME SPECIFIC OUTCOMES 1. Able to analyze, design, and implement electrical & electronics systems and deal with the rapid pace of industrial innovations and developments. 2. Skillful to use application and control techniques to conventional and nonconventional energy systems.
- 3. 3 Course: Solar and Wind Energy Systems Course Code: 20A26DT Course outcomes: At the end of the course the student will be able to Blooms Level 1. Discuss energy scenario and the consequent growth of the power generation from renewable energy sources. L2 2. Describe basic physics of wind and solar power generation. L2 3. Analyze power electronic interfaces for wind and solar generation. L4 4. Analyze grid integration of solar and wind energy systems. L4 Prescribed Text Books 1. G.D. Rai. Non-Conventional Energy Sources. Khanna Publishers, Delhi, 2007. 2. Khan B.H., Non-Conventional Energy Resources, Tata McGraw Hill, New Delhi,2006 Reference Books: 1. Twidell&Wier, Renewable Energy Resources , CRC Press( Taylor & Francis) 2. T. Ackermann, Wind Power in Power Systems, John Wiley and Sons Ltd., 2005. 3. S. P. Sukhatme, Solar Energy: Principles of Thermal Collection and Storage, McGraw Hill, 1984
- 4. 4 ••••••••••••••••••••••••••••••••••••••••• Solar and Wind Energy Systems ANNAMACHARYA INSTITUTE OF TECHNOLOGY AND SCIENCES :: RAJAMPET (AUTONOMOUS) Unit 5 Network Integration Issues Syllabus: Overview of grid code technical requirements. Fault ride-through for wind farms - real and reactive power regulation, voltage and frequency operating limits, solar PV and wind farm behavior during grid disturbances. Power quality issues. Power system interconnection experiences in the world. Hybrid and isolated operations of solar PV and wind systems.
- 5. Overview of grid code technical requirements A grid code is a technical specification which defines the parameters of a facility connected to a public electric grid to ensure the safety, security, proper functioning of the electric system and economics. The facility can be an Power Generating Plant, a consumer, or another network. The grid code is specified by an authority who are responsible for the system integrity and network operation. The grid code indicates the network operators (distribution or transmission system operators), representatives of, the regulating body etc. The contents of a grid code is not fixed, it may vary depending on the transmission company's requirements. Typically, a grid code will specify the required behavior of a connected generator during system disturbances such as voltage regulation, power factor corrections and reactive power supply, response to a system fault (e.g. short- circuit), response to frequency changes on the grid, and requirement to "ride through" short interruptions of the connection.
- 6. There is not a common grid code in all countries and each electric grid has its own grid code. Indian Electricity grid code: The are issued by the Central Electricity Regulatory Commission 1. Role of various Organizations and their Linkages: It defines the functions of the various organizations involved in the field of grid operation and management and their organizational linkages so as to facilitate development and smooth operation of Regional Grids and National Grid at large so far as it relates to the IEGC. 2. Planning Code for Inter-state Transmission: It defines various aspects of Planning relating to Inter-State transmission systems. 3. Connection Code: It covers some of the technical standards for connection to the grid of wind and solar generating facilities, so far not covered under the CEA (Technical Standards for connectivity to the Grid).
- 7. 4. Operating code: Operating philosophy. System Security Aspects Demand Estimation for Operational Purposes Demand Management Periodic Reports Outage Planning
- 8. Solar and Wind Energy - Integration
- 9. Advantages of Solar and Wind Energy - Integration 1. The Oil and gas are the carbon fuels are responsible for harmful greenhouse gas emissions that affect air, water and soil quality, and contribute to environmental degradation and climate change. As carbon-free and renewable energy sources, wind and solar can help reduce the world's dependence on oil and gas. 2. wind and solar energy can give homeowners and businesses the ability to generate and store electricity onsite, giving them backup power when their needs cannot be filled by the traditional utilities grid. 3. Solar panel installations are easy to do and can create energy bill savings. 4. Both solar energy and wind energy are on the path to becoming the world's most affordable sources of energy. "Land-based utility-scale wind is one of the lowest-priced energy sources 5. The price of harnessing the solar power is reduced each year due to technology.
- 10. 5. The reliability of the system is enhanced. 6. The size of battery storage can be reduced slightly Dis-advantages (or) Practical issues/challenges of Solar and Wind Energy - Integration 1. It can lead to high initial cost and equipment failure. 2. Power quality problems: such as frequency disorder, voltage/current harmonics, low power factor, voltage variation etc. 3. Renewable energy sources depend on weather, climate and geographical location, therefore this type of energy generation is not appropriate for the region. 4. Lack of information and awareness about the benefits and need of renewable energy. 5. Integration more complex because the uncertainty in energy production due to renewable energy. For example, solar powered electricity is generated only when sunshine is available and turns off at night; wind energy also depends on the availability of wind, so if the wind speed is very low, the turbine will not turn, and this result in zero power flow to the grid or too much wind can damage the generator.
- 11. 6. Low capacity factor: Renewable energy plants run only when sun or wind cooperates. According to the Energy Information Administration, the average capacity for utility- scale solar PV was around 28%; for wind 34%. 7. Power Variability: This is the biggest issue/challenge. The power generated by the plants that run on fuel is oscillating (i.e ramped up and down). But renewable energy plants produce power only when the wind is blowing or the sun is shining. Grid operators don't control the Renewable Energy sources. Unit 5 Network Integration Issues Overview of grid code technical requirements. Fault ride-through for wind farms - real and reactive power regulation, voltage and frequency operating limits, solar PV and wind farm behavior during grid disturbances. Power quality issues. Power system interconnection experiences in the world. Hybrid and isolated operations of solar PV and wind systems.
- 12. It is the capability of electric generators to stay connected in short periods of under/ lower electric network voltage (voltage sag). It is also called under-voltage ride through (UVRT), or low voltage ride through (LVRT). It is needed at distribution level (wind parks, PV systems, distributed cogeneration, etc.) to prevent a short circuit at HV or EHV level which is caused due to loss of generation. Fault ride-through(FRT) for wind farms Many generator designs use electric current flowing through windings to produce the magnetic field on which the motor or generator operates. This is in contrast to designs that use permanent magnets to generate this field instead. Such devices may have a minimum working voltage, below which the device does not work correctly, or does so at greatly reduced efficiency. Some will disconnect themselves from the circuit when these conditions apply.
- 13. This effect is more pronounced in doubly-fed induction generators (DFIG), which have two sets of powered magnetic windings, than in squirrel-cage induction generators which have only one. When the Synchronous generators are used for generation, it becomes become unstable, if the voltage of the stator winding goes below a certain threshold. Similar requirements are now becoming common on large solar power installations that likewise might cause instability in the event of a widespread disconnection of generating units The application/ device may, during and after the dip, be required to * Disconnect and stay disconnected until manually ordered to reconnect. * Disconnect temporarily from the grid, but reconnect and continue operation after the dip * Stay operational and not disconnect from the grid. * Stay connected and support the grid with reactive power.
- 14. Power quality issues in Grid (interconnected system)/WECS The power quality studies are of importance to WECS/Grid (interconnected systems) when it feeding the power to distribution circuit with source impedance and customer. The term power quality refers to the variation in supply voltage, current and frequency. For example, when the load on the grid/WECS is more, the turbine get retard at generation plant. This results in reduction in voltage and more severely reduction in the supply frequency. 1. Issue of voltage variation If a large proportion of the grid load is supplied by wind turbines, the wind speed changes can cause voltage variation, flicker effects in normal operation. This issue can expected in particular in the case of generator connected to the grid at fixed speed. In case of large wind turbines, better output smoothing can achieve in the short time range using variable speed operation. The speed regulation range is an important factor while smoothing the output power variations with the large speed variations.
- 15. 2. Issue of voltage dip/sag A voltage dip/sag is a sudden drop in the voltage magnitude in in range of 0.1 to 0.9pu of nominal voltage for short period of time i.e <1min. It may be caused by various faults in the grid, transmission and distribution networks, faults in the connected equipment or high inrush, over loads, short circuits etc. This problem is considered in the power quality and wind turbine generating system operation and computed according to the rule given in IEC 61400-3-7 standard. The start up of wind turbine causes a sudden reduction of voltage. The relative % voltage change due to switching operation of wind turbine is calculated as Sw - Rated apparent power of wind turbine , SK* short circuit apparent power of grid. The voltage dips of 3% in most of the cases are acceptable. When evaluating flicker and power variation within 95% of maximum variation band corresponding to a standard deviation are evaluated.
- 16. 3. Harmonics The harmonics distortion caused by non-linear load such as electric arc furnaces, variable speed drives, large concentrations of arc discharge lamps, saturation of magnetization of transformer and a distorted line current. The effect of harmonics in the power system can lead to degradation of power quality at the consumer’s terminal, increase of power losses, and malfunction in communication system. The harmonics voltage and current should be limited to acceptable level at the point of wind turbine connection in the system. Generally, passive LC resonant filters have been used to solve power quality problems. However, these filters have the demerits of fixed compensation, large size, and the resonance itself. The wave shape of the grid voltage is not sinusoidal with the harmonics. There are always harmonics voltages in the grid such as integer harmonic of 5th and 7th order which affect the grid voltage.
- 17. Today’s variable speed turbines are equipped with self commutated PWM inverter system. This type of inverter system has advantage that both the active and reactive power can be controlled, but it also produced a harmonic current. Therefore filters are necessary to reduce the harmonics. Traditional wind turbines are equipped with induction generators. Induction generator is preferred because they are inexpensive, rugged and requires little maintenance. Unfortunately induction generators require reactive power from the grid to operate. When wind turbine is equipped with an induction generator and fixed capacitor are used for reactive compensation then the risk of self excitation may occur during off grid operation. 4. Reactive power The effective control of reactive power can improve the power quality and stabilize the grid. Although reactive power is unable to provide actual working benefit, it is often used to adjust voltage, so it is a useful tool for maintaining desired voltage level.
- 18. 5. Flickers Flicker is the one of the important power quality aspects in wind turbine generating system. Flicker has widely been considered as a serious drawback and may limit for the maximum amount of wind power generation that can be connected to the grid. Flicker is induced by voltage fluctuations, which are caused by load flow changes in the grid. There are many factors that affect flicker emission of grid connected wind turbines during continuous operation, such as wind characteristics and grid conditions. Variable-speed wind turbines have shown better performance related to flicker emission in comparison with fixed-speed wind turbines. Several solutions have been proposed to mitigate the flicker caused by grid-connected wind turbines. The mostly adopted technique is the reactive power compensation. It can be realized by the grid-side converter of variable-speed wind turbines or the Static synchronous compensator connected at the point of common coupling (PCC). The flicker level depends on the amplitude, shape and repetition frequency of the fluctuated voltage waveform. Evaluating the flicker level is based on the flicker meter described in IEC61000-4-15.
- 19. Voltage variations exist in the power grid is due to the mismatch in the reactive power between demand and available powers. Frequency variation in the power system exists due to the mismatch between the supply of power and demand for the power. Voltage and frequency operating limits (of grid): In spite of all these variations, there is a certain limit for the operation limits (allowable variations) for voltage and frequency parameters dictated by the Grid Code. The variations in voltage and frequency below its operating limits will make the power grid as unhealthy and restoration steps will be taken to make the power grid healthy. In India, according to Electricity Grid Code, the operation variation in the frequency and voltage allowed is given as As per Indian Electricity Grid Code (IEGC) rules the permissible variation of voltage at the consumer end is upto ±6%. In case of low or medium voltage i.e. upto 33 kV, the permissible variation of voltage is ±6% to ±9%. In case of high voltage supply i.e. more than 33 kV, the permissible variation of voltage is more than ±9%.
- 20. As per the Indian Electricity Grid Code (IEGC) Rules 1956, the permissible range for grid frequency is ± 3 % of nominal i.e. 48.5 Hz to 51.5 Hz. When the supply of electricity exactly matches the load demand, grid frequency is held at a stable level. Grid operators, seek to continuously balance electricity supply with load to maintain the proper frequency. Practically, Frequency of the system will vary as load and generation change.