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This lecture will discuss the integration of renewable energy into the grid. This integration imposes several challenges, which can be categorized into three different challenges:

• Automation challenges
• Operational challenges
• Planning challenges

Automation challenges

The challenges covered by this category are challenges that need to be addressed by automation. This means that an immediate response is needed. Therefore, the solutions to these challenges have to be technical and do not account for human intervention. Examples of this type of challenge are listed below:

• Lower system inertia
• Frequency containment and restauration
• Two-way power flow
• Protection blinding
• Power system islanding
• Fault current contribution
• Black start
• Grid forming
• Power smoothing
• Voltage support

By integrating renewable energy sources into the grid, fossil fuel-based generators are replaced. Although they are unsustainable, these generators are very stable and reliable, which guarantees a stable and reliable grid. An essential part of these generators is the synchronous generator, which can be seen as a rotating mass containing kinetic and thermal energy. The synchronous generators were used to provide reliability services. The main challenge for renewable energy is to find other ways to provide these reliability services.

Another aspect of automation challenges is that the topology of the electric grid will change. Historically, the generation was centralized, and the power flow was always unidirectional. When renewables are integrated, the generation will be decentralized, and the power flow will be bidirectional.

Operational challenges

These challenges are solved in a time frame of minutes, hours, or days. They require actions from the grid operator and the power plant to be solved. Examples of operational challenges are:

• Grid congestion
• Commitment of controllable units
• Balancing of variable renewable power Ramping in response to intermittency of renewables

The most central challenge of operational challenges is power balancing. This means that the supply has to always match demand. Since electricity cannot be stored easily in large quantities, balancing is essential for the functionality of a power grid.

Another aspect of power balancing with renewable energy is dealing with uncertainty and variability. These aspects can be overcome with better forecasting algorithms and flexible controllable assets. A grid has a high flexibility if the grid can maintain the balance in the presence of rapidly changing and uncertain renewables. Originally, flexibility was found on the generation side. However, it is currently found in the demand response and storage.

Planning challenges

The third category covers challenges that are related to security of the supply and ensuring that there is always enough controllable generation in the grid to deal with the other challenges. The time frame of these challenges is typically much longer than the other types of challenges, such as planning the capacity and location of a generator. Examples of planning challenges are:

• Security of supply
• Sufficient generation reserve capacity
• Sufficient transmission and distribution grid capacity

Conclusion

This lecture introduced the different challenges that arise with the integration of renewable energy generators in the grid. These challenges can be divided into three different categories. First, the automation challenges were discussed, which are related to actions that need to happen automatically. Then the operational challenges were covered, which are challenges, which need to be adressed by human actions. Finally, the planning challenges were adressed, which are related to long-term human decisions.