Integration of Wind Energy Resources with Conventional Grids
As we are progressing in time, the non-renewable energy resources are running out and soon they won’t be enough to meet our needs. As necessity is the mother of invention, this need keeps pushing us to develop alternative energy resources which will eventually replace all the conventional energy sources one day. This development in the Power Generation sector gives new challenges to Power Engineers each day, and they strive to meet these challenges with the help of the latest technologies. In this blog, we will be discussing one of the most significant renewable energy resources today, which is being used across the globe. This blog will put some light on the technical challenges associated with the generation and integration of Wind Energy systems into conventional grids, and how these challenges are conquered through Power Engineering solutions.
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Wind Energy
As this self-explanatory term suggests, wind energy means to use wind intelligently in order to generate energy through it. For this purpose, we use wind turbines, which fetch wind kinetic energy and convert it into a rotary motion that is further converted into Electrical Energy through a generator. So, the primary components of a wind turbine are Turbine blades, rotor, gearbox, generator, and sometimes also DC/AC converters. Turbines are categorized as vertical and horizontal axis wind turbines, which can further be categorized into Fixed and Variable speed wind turbines.
Types of Wind Turbines
Horizontal Axis Wind Turbines
Horizontal Axis wind turbines are the most widely used wind turbines around the globe. As they have relatively higher power generation efficiency in regions with consistent wind conditions, and most wind power plants are situated in areas where we can have higher yields of power with as much as possible consistent winds throughout the year. Horizontal Axis wind turbines have their rotational axis parallel to the wind stream and ground, and they are usually set up high above the ground on tubular structures.
Vertical Axis Wind Turbines
Vertical Axis wind turbines have their fins placed vertically, and the rotational axis of vertical axis wind turbines is perpendicular to the ground. This property provides them the versatility of utilizing the wind from 360 degrees unlike horizontal axis wind turbines and makes them more appropriate for areas with relatively inconsistent wind conditions. Therefore, these are highly applicable in residential areas while on the contrary, horizontal axis wind turbines require more consistent wind conditions which is why they are mostly used in wind power plants.
Fixed Speed Wind Turbines
Fixed speed wind turbines have their speed determined by the gear ratio and generator design according to the Grid Frequency while it is irrespective of the wind speed. These generators are made to work with the highest efficiency at a specific speed, and there is a significant decrease in efficiency when the speed of the wind varies from the specified value. Some of these generators can work efficiently around two different values of wind speed as they are built with two sets of windings. One set, with a higher number of poles, is utilized when the speed is low while the other with a lower number of poles is used when the wind speed is comparatively higher. These generators with two sets of windings provide higher overall efficiency than the former ones. Fixed speed wind turbines have lower costs and higher reliability than variable speed wind turbines.
Variable Speed Wind Turbines
Variable speed wind turbines are becoming increasingly common with the passage of time. Their speed varies with the changes in wind speed, and they always tend to achieve maximum efficiency with respect to the speed of the wind. This increases the complexity of the Wind turbine, and the generators are not directly coupled to the grid while they are connected through the Power Inverters. When power is generated through a variable speed turbine, its frequency varies, and therefore we need to insert power inverters between the generator and grids. Some of these Power inverters generate odd harmonics and consume reactive power. To eliminate harmonics from the system, harmonic filters are used while for reactive power compensation different methods can be used, including the addition of capacitor banks in the system. These factors increase the complexity and cost of the system. Therefore, Variable speed turbines are considered technologically advanced and involve high initial costs. But they provide a significant increase in the efficiency of the system which eventually leads to higher power yields, and relatively puts less mechanical stress on the Turbine itself.
The below-mentioned figure shows, the power generated with respect to different Turbine speeds, the line ‘T’ represents fixed speed wind turbine while the curve ‘S’ represents Variable speed wind turbine. It can be observed that there is a significant variation in power generation by both the turbines, but the curve ‘S’ follows the maximum point of each speed curve, which means that the maximum possible output would be generated through the variable speed wind turbine at different wind speeds, while the constant speed wind turbine would only be generating maximum power at 9 m/s, while during all other wind speeds its output will be lesser than the maximum possible output power.
Factors Affecting the Stability of a Wind Integrated Power Grid
For a successful operation of a power generation system and the utilities, it is compulsory to maintain the power quality of the system. Power quality must be maintained while attaining a complete balance between the power being generated, and the power being utilized by the consumer. Among all the considerations regarding the power quality, voltage variations and keeping a smooth sinusoidal wave are major concern that needs to be focused on throughout the power generation process. Now, we are going to see the factors that are to be looked upon in order to attain these outcomes.
- Voltage Instability and Flickering
- Causes of Harmonics and their Effect on Power Quality
- Reactive Power
- Line impedance and Associated Grid Strength
- Maintaining Generation Frequency
Click here to read detailed explanation of each factor affecting the stability of a wind integrated power grid.
How do Power System Studies Increase System Stability, and ensure Power Quality?
Power System Design software enables us to Model these grids, and generation resources. A perfectly modeled system would help us simulate and analyze all kinds of scenarios that can take place during the operation of these Generation resources. Through these simulations, we can thoroughly study the response of our system, to all kinds of faults and Source/Load variations. Transient stability analysis would enable us to look for the response of each component at any given instant. We can study these responses and propose solutions to counter these effects. Moreover, such proposed remedies, like adding capacitor banks for the sake of voltage stability or increasing the generator’s torque to counter the overloading. These remedies can be further added to the system by modifying our model, and again we can analyze the results and how far are we able to counter such scenarios.
Engineers at AllumiaX perform Power System Engineering Studies in compliance with NEC, IEC and IEEE Standards. Get in touch with us here and avail our services.
