Voltage control with the help of C&I energy storage systems
Voltage control in electrical grids is becoming increasingly important with the increasing decentralization of energy supply and the growing share of renewable energies. Commercial & Industrial (C&I) energy storage systems have established themselves as an effective solution for supporting grid stability and, in particular, voltage control. This article examines how such storage systems can contribute to voltage control and which technical and economic aspects must be considered.
Fundamentals of Voltage Control
Voltage control refers to maintaining the grid voltage within defined limits. In most European countries, a nominal voltage of 230V/400V with a tolerance of ±10% is prescribed. These limits must not be exceeded to ensure the functionality of connected devices and grid stability. With the increase in decentralized feed-ins, particularly from photovoltaic and wind power systems, voltage control presents grid operators with new challenges.
Traditionally, voltage control is achieved by central power plants, voltage regulators, and compensation systems. However, increasingly decentralized generation structures are leading to new voltage problems: High feed-ins from renewable energies can lead to local voltage increases, while high consumption without local generation can lead to voltage drops. These fluctuations must be compensated to ensure grid stability.
How C&I storage systems work for voltage control
C&I energy storage systems can both absorb and release energy due to their bidirectional operation, making them ideal for voltage control. The basic mechanisms by which storage systems influence voltage are based on the relationship between active and reactive power on the one hand, and the grid voltage on the other.
When the grid voltage is increased, the storage system can absorb active power (charging mode), which leads to a voltage reduction. Conversely, at low voltages, active power can be fed into the grid (discharging mode), which increases the voltage. However, the provision of reactive power is particularly effective: Inductive reactive power lowers the voltage, while capacitive reactive power raises it. Modern C&I storage systems can implement these control mechanisms in milliseconds.
The power electronics installed in C&I storage systems, especially the inverters, are capable of providing reactive power regardless of the storage system's state of charge. This means that a storage system can continue to contribute to voltage maintenance even when fully discharged or fully charged. This property makes C&I storage particularly valuable for grid stabilization.
Voltage control using C&I energy storage systems
Voltage control in electrical grids is becoming increasingly important with the increasing decentralization of energy supply and the growing share of renewable energies. Commercial & Industrial (C&I) energy storage systems have established themselves as an effective solution for supporting grid stability and, in particular, voltage control. This article examines how such storage systems can contribute to voltage control and which technical and economic aspects must be considered.
Fundamentals of Voltage Control
Voltage control refers to maintaining the grid voltage within defined limits. In most European countries, a nominal voltage of 230V/400V with a tolerance of ±10% is prescribed. These limits must not be exceeded to ensure the functionality of connected devices and grid stability. With the increase in decentralized feed-ins, particularly from photovoltaic and wind power systems, voltage control presents grid operators with new challenges.
Traditionally, voltage control is achieved by central power plants, voltage regulators, and compensation systems. However, increasingly decentralized generation structures are leading to new voltage problems: High feed-ins from renewable energies can lead to local voltage increases, while high consumption without local generation can lead to voltage drops. These fluctuations must be compensated to ensure grid stability.
How C&I storage systems work for voltage control
C&I energy storage systems can both absorb and release energy due to their bidirectional operation, making them ideal for voltage control. The basic mechanisms by which storage systems influence voltage are based on the relationship between active and reactive power on the one hand, and the grid voltage on the other.
When the grid voltage is increased, the storage system can absorb active power (charging mode), which leads to a voltage reduction. Conversely, at low voltages, active power can be fed into the grid (discharging mode), which increases the voltage. However, the provision of reactive power is particularly effective: Inductive reactive power lowers the voltage, while capacitive reactive power raises it. Modern C&I storage systems can implement these control mechanisms in milliseconds.
The power electronics installed in C&I storage systems, especially the inverters, are capable of providing reactive power regardless of the storage system's state of charge. This means that a storage system can continue to contribute to voltage maintenance even when fully discharged or fully charged. This property makes C&I storage particularly valuable for grid stabilization.
Technical Requirements for Storage Systems for Voltage Stabilization
For effective use in voltage stabilization, C&I storage systems must meet specific technical requirements. They require sufficiently dimensioned power electronics that can respond quickly to voltage changes. The inverter should be oversized to be able to provide sufficient reactive power in addition to active power. The so-called apparent power operating range, often represented as a PQ diagram, defines the simultaneous provision of active and reactive power.
Modern C&I storage systems have fast communication interfaces that enable responses within milliseconds. They are equipped with precise voltage measuring devices and contain complex control algorithms that monitor local grid parameters and adjust the system response accordingly. The control software can react autonomously to local voltage changes as well as respond to external control signals from the grid operator.
Another important aspect is the reliability of the system. Since voltage maintenance is a critical grid service, C&I storage systems must have high availability. This is ensured through redundant components, careful design, and regular maintenance. The systems should function reliably even under extreme grid conditions and have fault ride-through capabilities to bridge short-term grid disruptions.
Implementation Strategies for Voltage Control
Various strategies have been established for the implementation of C&I storage systems for voltage control. With local voltage control, the system reacts autonomously to measured voltage values at the connection point. This strategy is particularly suitable for areas with known voltage problems and does not require external communication.
In more complex scenarios, coordinated control approaches are used. Here, multiple storage systems communicate with each other or are controlled by a higher-level entity to optimize voltage control in a larger grid section. This strategy maximizes effectiveness and prevents conflicting control interventions by different systems.
Predictive control approaches are also increasingly being pursued. By incorporating feed-in and load forecasts, potential voltage problems can be anticipated and counteracted early. This improves the efficiency of voltage control while preserving battery life by avoiding unnecessary control interventions.
The integration of voltage control into a holistic energy management system is particularly effective. In addition to voltage control, other goals such as self-consumption optimization, peak load management, or market participation are also pursued. Intelligent algorithms can optimally balance these sometimes competing goals to maximize both economic benefits and contribute to grid stability.
Economic Aspects of Voltage Control with Storage Systems
The economics of voltage control through C&I storage systems are complex. For grid operators, the use of storage systems for voltage control offers an alternative to conventional grid expansion. Especially in regions with high feed-in of renewable energy, a storage system can be more cost-effective than reinforcing lines or building new substations. The flexibility and rapid implementation of storage systems represents a further economic advantage.
For operators of C&I storage systems, the provision of voltage control can represent an additional source of income. In some markets, remuneration mechanisms for grid services, including voltage control, already exist. These can be structured either as direct payments, as a reduction in network charges or as preferential network access. A further possibility is the combination of different use cases (stacking of benefits), which improves the overall economic viability of the storage system.
Various cost factors must be considered when calculating the economic viability: the investment costs for the storage system, additional costs for the specific voltage support design (such as oversized inverters), maintenance and operating costs, and potential opportunity costs if the storage is used for voltage support and not available for other profitable applications.
The payback period for a storage system used primarily for voltage support depends heavily on local market conditions and regulatory frameworks. In markets with established compensation mechanisms for network services, it can be 5-8 years, which is attractive compared to other infrastructure investments.
Technical Requirements for Storage Systems for Voltage Stabilization
For effective use in voltage stabilization, C&I storage systems must meet specific technical requirements. They require sufficiently dimensioned power electronics that can respond quickly to voltage changes. The inverter should be oversized to be able to provide sufficient reactive power in addition to active power. The so-called apparent power operating range, often represented as a PQ diagram, defines the simultaneous provision of active and reactive power.
Modern C&I storage systems have fast communication interfaces that enable responses within milliseconds. They are equipped with precise voltage measuring devices and contain complex control algorithms that monitor local grid parameters and adjust the system response accordingly. The control software can react autonomously to local voltage changes as well as respond to external control signals from the grid operator.
Another important aspect is the reliability of the system. Since voltage maintenance is a critical grid service, C&I storage systems must have high availability. This is ensured through redundant components, careful design, and regular maintenance. The systems should function reliably even under extreme grid conditions and have fault ride-through capabilities to bridge short-term grid disruptions.
Implementation Strategies for Voltage Control
Various strategies have been established for implementing C&I storage systems for voltage control. With local voltage control, the system reacts autonomously to measured voltage values at the connection point. This strategy is particularly suitable for areas with known voltage problems and does not require external communication.
In more complex scenarios, coordinated control approaches are used. Here, multiple storage systems communicate with each other or are controlled by a higher-level entity to optimize voltage control in a larger grid section. This strategy maximizes effectiveness and prevents conflicting control interventions by different systems.
Predictive control approaches are also increasingly being pursued. By incorporating feed-in and load forecasts, potential voltage problems can be anticipated and counteracted early. This improves the efficiency of voltage control while preserving battery life by avoiding unnecessary control interventions.
The integration of voltage control into a holistic energy management system is particularly effective. In addition to voltage control, other goals such as self-consumption optimization, peak load management, or market participation are also pursued. Intelligent algorithms can optimally balance these sometimes competing goals to maximize both economic benefits and contribute to grid stability.
Economic Aspects of Voltage Control with Storage Systems
The economic consideration of voltage control through C&I storage systems is complex. For grid operators, the use of storage systems for voltage control offers an alternative to conventional grid expansion. Especially in regions with high feed-in of renewable energy, a storage system can be more cost-effective than reinforcing lines or building new substations. The flexibility and rapid implementation of storage systems represents a further economic advantage.
For operators of C&I storage systems, the provision of voltage control can represent an additional source of income. In some markets, remuneration mechanisms for grid services, including voltage control, already exist. These can be structured either as direct payments, as a reduction in network charges or as preferential network access. A further possibility is the combination of different use cases (stacking of benefits), which improves the overall economic viability of the storage system.
Various cost factors must be considered when calculating the economic viability: the investment costs for the storage system, additional costs for the specific voltage support design (such as oversized inverters), maintenance and operating costs, and potential opportunity costs if the storage is used for voltage support and not available for other profitable applications.
The payback period for a storage system used primarily for voltage support depends heavily on local market conditions and regulatory frameworks. In markets with established compensation mechanisms for network services, it can be 5-8 years, which is attractive compared to other infrastructure investments.
Practical Examples of Voltage Stabilization with C&I Storage Systems
A vivid example of the successful use of C&I storage systems for voltage stabilization can be found in a rural distribution grid with high PV penetration. Here, a 500 kWh / 250 kW storage system was installed at the end of a medium-voltage line that regularly suffered from voltage surges caused by PV feed-in. The system was equipped with an inverter that was 30% oversized to provide sufficient reactive power.
Operating data shows that the system was able to reduce voltage fluctuations by an average of 60%. During the midday hours, the system absorbs excess PV energy, thereby lowering the grid voltage. In addition, it continuously provides inductive reactive power to further stabilize the voltage. In the evening hours, when consumption increases and the voltage tends to drop, the system releases energy and provides capacitive reactive power.
Through these measures, the grid operator was able to avoid costly grid expansion while simultaneously enabling the integration of additional renewable energies. For the storage operator, a payback period of seven years resulted from the combination of compensation for grid services, reduced grid fees, and additional income from arbitrage transactions on the electricity exchange.
Future Developments and Potential
The future development of voltage control with C&I storage systems will be largely determined by technological advances and the further development of the regulatory framework. From a technological perspective, more powerful inverters can be expected that can respond even more precisely and quickly to voltage changes. Advanced battery chemistries will enable longer service lives and higher cycle stability, further improving the economic viability of the systems.
On the regulatory side, further development of remuneration mechanisms for grid services is to be expected. Many markets are working on transparent and market-based approaches that enable performance-based remuneration for flexibility options such as storage systems. The increasing digitalization of power grids also enables more precise recording and remuneration of the grid services actually provided.
One promising approach is the integration of C&I storage systems into virtual power plants or flexibility platforms. Here, several decentralized systems can be bundled and controlled in a coordinated manner to offer grid services on a larger scale. This also opens up access to grid service markets for smaller storage systems and improves the overall efficiency of voltage control.
In the long term, an increasing integration of various flexibility options can be expected. In addition to battery storage, other technologies such as controllable loads, electric vehicles, and Power-to-X systems will also contribute to voltage control. C&I storage systems will play a central role in this thanks to their rapid responsiveness and flexible deployment.
Conclusion
C&I energy storage systems have established themselves as a valuable tool for voltage control in modern power grids. Thanks to their ability to provide both active and reactive power, they can respond flexibly and quickly to voltage changes, thus contributing to grid stability. Technological developments and increasing experience in operating such systems are continuously improving their effectiveness and cost-effectiveness.
For grid operators, C&I storage systems offer a cost-effective alternative to conventional grid expansion, especially in regions with high renewable energy penetration. For storage operators, the provision of voltage control opens up additional revenue streams and improves the overall economic efficiency of their systems.
With the ongoing transformation of the energy system toward decentralized and renewable structures, the importance of voltage control will continue to increase. C&I storage systems will play a key role in this, making a significant contribution to the successful integration of renewable energies and maintaining grid stability.
Practical examples of voltage control with C&I storage systems
A vivid example of the successful use of C&I storage systems for voltage control can be found in a rural distribution grid with high PV penetration. Here, a 500 kWh / 250 kW storage system was installed at the end of a medium-voltage line that regularly suffered from voltage surges caused by PV feed-in. The system was equipped with an inverter that was 30% oversized to provide sufficient reactive power.
The operating data shows that the system was able to reduce voltage fluctuations by an average of 60%. During the midday hours, the system absorbs excess PV energy, thereby reducing the grid voltage. It also continuously provides inductive reactive power to further stabilize the voltage. In the evenings, when consumption increases and the voltage tends to drop, the system releases energy and provides capacitive reactive power.
Through these measures, the grid operator was able to avoid costly grid expansion while simultaneously enabling the integration of additional renewable energies. For the storage operator, a payback period of seven years resulted from the combination of compensation for grid services, reduced grid fees, and additional income from arbitrage transactions on the electricity exchange.
Future Developments and Potential
The future development of voltage control with C&I storage systems will be largely determined by technological advances and the further development of the regulatory framework. From a technological perspective, more powerful inverters can be expected that can respond even more precisely and quickly to voltage changes. Advanced battery chemistries will enable longer service lives and higher cycle stability, further improving the economic viability of the systems.
On the regulatory side, further development of remuneration mechanisms for grid services is to be expected. Many markets are working on transparent and market-based approaches that enable performance-based remuneration for flexibility options such as storage systems. The increasing digitalization of power grids also enables more precise recording and remuneration of the grid services actually provided.
One promising approach is the integration of C&I storage systems into virtual power plants or flexibility platforms. Here, several decentralized systems can be bundled and controlled in a coordinated manner to offer grid services on a larger scale. This also opens up access to grid service markets for smaller storage systems and improves the overall efficiency of voltage control.
In the long term, an increasing integration of various flexibility options can be expected. In addition to battery storage, other technologies such as controllable loads, electric vehicles, and Power-to-X systems will also contribute to voltage control. C&I storage systems will play a central role in this thanks to their rapid responsiveness and flexible deployment.
Conclusion
C&I energy storage systems have established themselves as a valuable tool for voltage control in modern power grids. Thanks to their ability to provide both active and reactive power, they can respond flexibly and quickly to voltage changes, thus contributing to grid stability. Technological developments and increasing experience in operating such systems are continuously improving their effectiveness and cost-effectiveness.
For grid operators, C&I storage systems offer a cost-effective alternative to conventional grid expansion, especially in regions with high renewable energy penetration. For storage operators, the provision of voltage control opens up additional revenue streams and improves the overall economic efficiency of their systems.
With the ongoing transformation of the energy system toward decentralized and renewable structures, the importance of voltage control will continue to increase. C&I storage systems will play a key role in this, making a significant contribution to the successful integration of renewable energies and maintaining grid stability.