UNIT - V
Q1.Requirements of hybrid/combined use of different renewable and distributed sources:
The hybrid or combined use of different renewable and distributed energy sources typically requires careful
consideration of factors such as energy availability, compatibility of technologies, grid integration, and control
systems. It's important to assess the potential of each source to complement one another, ensuring a stable and
reliable energy supply. Additionally, proper planning and optimization are crucial for maximizing efficiency and
minimizing costs in such systems.When integrating different renewable and distributed energy sources in a hybrid
system, here are some key requirements and considerations:
1. Resource Assessment: Assess the availability and variability of each renewable energy source (such as solar,
wind, hydro, biomass) at the specific location. This helps determine the potential energy generation and the best
mix of sources to achieve a consistent power output.
2. Technological Compatibility: Ensure that the selected energy sources and technologies are compatible with
each other in terms of voltage levels, frequency, and control systems. This may involve using inverters, converters,
or energy storage systems to manage the variability and intermittency of certain sources.
3. Energy Storage: Incorporate energy storage solutions (batteries, pumped hydro, compressed air, etc.) to store
excess energy during peak generation periods and release it during low-generation periods. This helps maintain a
steady power supply and balance demand fluctuations.
4. Control and Management Systems: Implement advanced control algorithms and management systems to
optimize the operation of the hybrid system. This involves monitoring energy generation, storage levels, and
demand to make real-time decisions for efficient energy dispatch.
5. Grid Integration: Ensure seamless integration with the existing electrical grid by adhering to grid codes,
regulations, and safety standards. Proper synchronization with the grid is essential to avoid instability and grid
disturbances.
6. Backup and Redundancy: Plan for backup power sources or backup systems to ensure reliability during
unexpected downtimes or maintenance activities. This could involve having a backup generator or utilizing the grid
as a backup source.
7. Cost Analysis: Perform a thorough economic analysis to assess the feasibility and cost-effectiveness of the
hybrid system. Consider factors such as initial investment, operating and maintenance costs, potential revenue
from energy sales, and incentives.
8. Environmental Impact: Evaluate the environmental benefits of the hybrid system, including reductions in
greenhouse gas emissions, local pollution, and reliance on non-renewable energy sources.
9. Local Regulations and Permits: Obtain the necessary permits and adhere to local regulations and zoning
requirements for renewable energy installations and hybrid systems.
10. Scalability and Future Expansion: Design the system with scalability in mind, allowing for future expansions or
the addition of new renewable sources as technology advances or energy demand increases.
By addressing these requirements and considerations, a hybrid system can effectively harness the strengths of
different renewable and distributed energy sources to provide a reliable, sustainable, and cost-effective energy
solution.
Q2.Need of energy storage, Control of frequency and voltage of distributed generation in
Stand-alone and Grid-connected mode:
In both stand-alone and grid-connected modes, controlling the frequency and voltage of distributed generation
involves monitoring and adjusting power output. In stand-alone mode, you need to ensure stability by regulating
frequency and voltage within acceptable limits. In grid-connected mode, the control interacts with the grid to
maintain synchronization and proper power flow. Advanced control algorithms and communication systems are
often used for effective management.Here are more details on controlling the frequency and voltage of distributed
generation in both stand-alone and grid-connected modes:
1. Stand-Alone Mode:
- Frequency Control: In stand-alone systems like microgrids or isolated power systems, frequency stability is
crucial. Frequency is primarily controlled by adjusting the generation output. If frequency rises, generation can be
reduced, and if it drops, generation can be increased. This can be achieved using droop control or various other
control strategies.
- Voltage Control: Voltage regulation is essential to maintain the quality of power supply. Voltage is typically
controlled using voltage regulators or tap changers on transformers. When voltage rises above a set limit,
generation can be curtailed, and when it falls, additional generation can be brought online.
2. Grid-Connected Mode:
- Frequency Control: In grid-connected systems, frequency is usually maintained by the utility company.
Distributed generators (DGs) adjust their output in response to frequency deviations to help stabilize the grid. If
frequency goes up, DGs can reduce output, and if it goes down, they can increase output.
- Voltage Control: Voltage regulation in grid-connected mode is more complex due to interactions with the grid.
DGs need to manage reactive power to control voltage levels. They can provide or absorb reactive power based on
grid conditions using devices like static VAR compensators (SVCs) or power factor correction units.
3. Advanced Control Strategies:
- Droop Control: This method adjusts the power output of generators based on frequency or voltage deviations
from a reference value. It maintains power sharing between different generators while maintaining stability.
- Voltage-Frequency Control: This strategy combines both frequency and voltage control, ensuring proper
operation under varying load conditions.
- Smart Inverters: Distributed generators, especially solar PV systems, can incorporate smart inverters that
actively regulate voltage and frequency according to grid requirements.
- Energy Management Systems (EMS): These systems monitor and control multiple distributed generators,
optimizing their operation based on load demand and grid conditions.
4. Communication and Monitoring:
- Real-time communication between distributed generators and a central control system is essential for effective
control. This allows quick response to grid events and dynamic adjustments.
- Monitoring systems collect data on frequency, voltage, load demand, and other parameters, enabling operators
to make informed decisions for control.
These control strategies and technologies work together to ensure that distributed generation systems can
contribute positively to grid stability and power quality, whether operating in stand-alone or grid-connected
modes.
Q3.Use of energy storage and power electronics interfaces for the connection to grid and
loads :
Energy storage and power electronic interface are used for connecting to grid and load in a variety of ways,
including:
Frequency regulation: Energy storage systems can be used to regulate the frequency of the power grid by
absorbing or injecting power when needed. This is important to maintain the stability of the grid and prevent
blackouts.
Peak shaving: Energy storage systems can be used to store energy during periods of low demand and then
discharge it during periods of high demand. This helps to reduce the peak load on the grid, which can save money
and improve reliability.
Load shifting: Energy storage systems can be used to shift loads from peak to off-peak hours. This can help to
reduce the cost of electricity for consumers and businesses.
Backup power: Energy storage systems can provide backup power during outages or emergencies. This is essential
for critical infrastructure such as hospitals and data centers.
Renewable energy integration: Energy storage systems can help to integrate renewable energy sources such as
solar and wind power into the grid. This is because renewable energy sources are intermittent, and energy storage
can be used to store energy when it is produced and then discharge it when it is needed.
The power electronic interface is the device that connects the energy storage system to the grid. It converts the DC
power from the energy storage system to the AC power that is used by the grid. The power electronic interface
also controls the flow of power between the energy storage system and the grid.
The use of energy storage and power electronic interface is becoming increasingly important as the power grid
becomes more complex and reliant on renewable energy sources. These technologies can help to improve the
reliability, efficiency, and sustainability of the power grid.
Q4.Design and optimization of size of renewable sources and storages:
The design and optimization of the size of renewable sources and storages is a complex task that takes into
account a variety of factors, including:
•
•
•
•
The amount of renewable energy that is available in the region
The load profile of the area
The cost of renewable energy sources and storage technologies
The reliability and availability of renewable energy sources
•
The environmental impact of renewable energy sources and storage technologies
The goal of the design and optimization process is to find a solution that minimizes the cost of meeting the energy
demand while also meeting the reliability and environmental requirements.There are a number of different
optimization techniques that can be used to design and optimize the size of renewable sources and storages. Some
of the most common techniques include:
Linear programming: This technique is used to find the optimal solution to a problem with a set of linear
constraints.
Mixed-integer linear programming:This technique is used to find the optimal solution to a problem with a
combination of linear and integer constraints.
Genetic algorithms:This technique is a heuristic optimization technique that uses a process of natural selection to
find the optimal solution.
Particle swarm optimization: This technique is another heuristic optimization technique that uses a swarm of
particles to find the optimal solution.
The choice of optimization technique depends on the specific problem being solved. For example, linear
programming is often a good choice for problems with a small number of variables and constraints, while mixedinteger linear programming is often a good choice for problems with a large number of variables and constraints.
Once the optimal solution has been found, the next step is to implement the solution. This may involve installing
renewable energy sources and storage technologies, as well as making changes to the grid. The implementation
process should take into account the cost of the equipment, the availability of skilled labor, and the environmental
impact of the project.
The design and optimization of the size of renewable sources and storages is a complex task, but it is an important
one. By carefully considering all of the factors involved, it is possible to design a system that meets the energy
needs of a region while also being cost-effective and environmentally friendly.
Here are some additional considerations that may be important in the design and optimization of renewable
sources and storages:
•
•
•
•
The location of the renewable energy sources and storages.
The impact of the renewable energy sources and storages on the local environment.
The regulatory environment for renewable energy sources and storages.
The availability of financing for renewable energy projects.
The design and optimization of renewable sources and storages is a rapidly evolving field. As new technologies
emerge and the cost of renewable energy continues to fall, it is likely that the optimal design of renewable energy
systems will continue to change.
THE END