Netzkontor GmbH

Explaining Control Power

Control power, also known as control energy, is an essential system service for stabilizing the grid frequency in the power grid. Since power grids cannot store energy, the power fed into the grid must always equal the power drawn from it. Control power balances out short-term fluctuations between generation and consumption to keep the grid frequency constant at 50 hertz. 

Types of Control Power

Control power is divided into three main categories:

• Primary control power (PRL): Is automatically activated within seconds to correct immediate frequency deviations.
• Secondary control power (SCP): Is used after PCP and stabilizes the frequency within minutes.
• Tertiary control power (minute reserve): Activated manually or automatically to compensate for longer-lasting imbalances.

Positive and Negative Control Power

Regulating power can be either positive or negative:

• Positive control power: Increases generation or reduces consumption when the grid frequency falls below 50 hertz.
• Negative control power: Reduces power generation or increases consumption when the grid frequency rises above 50 hertz.

Provision and Market Mechanisms

Transmission system operators (TSOs) procure control power through tenders on the control power market. Prequalified suppliers, including power plant operators, battery storage facilities, and flexible consumers, are eligible to participate. Compensation is based on capacity and energy prices, depending on the provision and actual use of the control power. 

Significance for the Energy Transition

As the share of renewable energy in the electricity mix increases, the importance of balancing power grows. Fluctuating feed-in from wind and solar plants requires flexible balancing mechanisms to ensure grid stability.