Algorithms optimize battery storage Why power electronics for battery storage must do more

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In the ALene Project, research institutions, industry partners, and grid operators work hand in hand to make battery storage fit for the future. The project ranges from the VISMA+ inverter of TU Clausthal to the grid quality measurement by morEnergy. Details in the interview with Dr.-Ing. Christoph Wenge from the Fraunhofer Institute IFF.

The ALene project "Intelligent Algorithms and Power Electronics for a Grid Quality and Energy-efficient Operation of Battery Storage Systems" aims to optimize battery storage systems through improved approaches. The background of the project involves various complex challenges for energy supply, including the decentralization of the supply network due to renewable energies and battery storage. Additionally, there is an increasing load from electrical consumers, producers, and storage systems. To ensure the quality and safety of the grid, measurement and control technology is necessary to stabilize the grid infrastructure.

The collaborative project ALene is a cooperation between industry, grid operators, and research institutions with the aim of developing algorithms and power electronic systems for the optimized, grid-supportive, and multifunctional operation of battery storage systems and testing them in practice. Within the framework of the project, battery storage systems will be equipped with extended system service functions and systemically integrated. To achieve this, specific algorithms will be developed and integrated into system management in combination with advanced power electronic components and intelligent communication technology.

In conversation with Dr.-Ing. Christoph Wenge from the Fraunhofer Institute for Factory Operation and Automation IFF, further details of the project are discussed.

Dr.-Ing. Wenge, what exactly does the collaboration in the ALene joint project look like?

The collaboration in the ALene joint project is based on close cooperation between research institutions, universities, industry partners, and a grid operator, with each organization taking on specific tasks.

Fraunhofer IFF coordinates the project, develops operational algorithms and simulation models, and takes on the overall system integration. TESVOLT contributes its expertise in battery storage, examining and optimizing the operation of battery storage systems and their integration. Power Innovation and TESVOT also focus on the DC/DC converter and battery-friendly control and operational functionality.

Power Innovation and TU Clausthal are jointly working on the DC/AC system, the further development of the converter concept VISMA+, which allows phase-selective feeding and improved grid quality. Magdeburg-Stendal University provides development and evaluation environments for testing and control solutions. The company morEnergy supplies measurement technology for grid quality monitoring and resonance detection, while Harz Energie provides real operational data and conducts field tests.

In an iterative process involving the development, validation, and implementation of new technologies, the partners work closely together to realize a multifunctional, grid-serving battery storage system that contributes to the stabilization and efficiency enhancement of distribution networks.

What specific requirements are placed on power electronics for battery storage to enable grid-serving and multifunctional use?

The grid-supportive and multifunctional use of battery storage systems imposes specific requirements on power electronics that go beyond traditional applications. Central aspects include high efficiency, flexibility, and the ability to provide extended system services. The power electronics must be capable of realizing phase-selective feeding, meaning that voltages and currents can be regulated individually per phase to balance asymmetric grid loads and improve grid quality. This also includes the compensation of voltage fluctuations, reactive power due to distortion, and harmonics.

Another important factor is the ability to dynamically respond to grid requirements, such as by providing instantaneous reserve (synthetic inertia), voltage support, and reactive power control. This requires fast and precise control of the inverters, which must operate reliably even in complex operating modes. Additionally, it is crucial that the power electronics optimize the operation of the battery storage by minimizing current and voltage ripple to extend the lifespan of the battery cells and reduce maintenance efforts. This also includes avoiding high current peaks and optimizing the regulation behavior.

Furthermore, the power electronics must be robust against grid disturbances and ensure high availability, especially in critical operating scenarios such as grid fluctuations or a black start. Innovative concepts like the VISMA+ inverter (Virtual Synchronous Machine) play a central role here, as they enable improved grid symmetry and stability through their specific circuit topology and control. To ensure optimal integration, the interfaces of the power electronics to other system components, such as measurement technology, control systems, and communication infrastructures, must be standardized and flexibly designed.

Additionally, the power electronics must be scalable to enable use across different grid levels and application scenarios, from low-voltage networks to microgrids at the medium-voltage level and island networks. Seamless communication with higher-level control systems and the ability to provide real-time data for grid and system monitoring are essential to ensure adaptive operation management and long-term system optimization.

What communication protocols are necessary to ensure intelligent networking between storage, grid, and consumers?

For intelligent networking between battery storage, the grid, and consumers, communication protocols are necessary to efficiently support both overarching control and local interaction between system components. MQTTs is excellently suited for overarching communication, especially with grid control systems and energy management platforms. As a lightweight protocol, MQTTs enables efficient message transmission even with limited bandwidth. With its Quality of Service (QoS) mechanisms, topics for message categorization, and its ability to scale in IoT environments, MQTTs offers a flexible and secure solution for real-time data transmission. Encryption and authentication mechanisms (TLS/SSL) ensure communication security and pave the way for NIS2-compliant integration into the energy supply.

For local communication between individual components such as the battery management system (BMS), power electronics, and measurement technology, the CAN bus is used. This robust protocol is characterized by its high reliability and low latency, making it ideal for control and regulation tasks in real-time. With its ability to prioritize messages and support deterministic transmissions, the CAN bus provides the precision needed for dynamic and grid-supportive operation management.

Between systems, such as between battery storage and local control units or energy distribution nodes, the industry-proven Modbus TCP/IP is used. This widely used protocol combines simple implementation with reliable data transmission. Modbus TCP/IP is particularly suitable for the integration of heterogeneous systems and allows seamless communication over Ethernet through its clarity and standardization. It supports the transmission of measurements, control commands, and status information between subsystems, ensuring compatibility among different manufacturers.

The combination of MQTTs for overarching communication, CAN bus for local interaction, and Modbus TCP/IP for system integration creates a scalable, secure, and efficient communication infrastructure. This setup allows for flexible adaptation to different requirements and ensures reliable coordination of all involved components in modern energy systems.

How can intelligent algorithms reduce the overall costs for operating battery storage systems?

In the ALene project, intelligent algorithms enable optimized use of battery storage systems that are both battery-friendly and multifunctional. These algorithms extend the lifespan of the battery systems by minimizing current and voltage ripple, which reduces mechanical and thermal stresses. This preserves the battery cells and reduces maintenance costs while simultaneously increasing the system's efficiency.

Furthermore, the algorithms enable the multifunctional operation of the storage systems. They can provide a variety of grid services, including voltage support, reactive power control, frequency stabilization, and the provision of instantaneous reserve (synthetic inertia). Particularly noteworthy is the phase-selective feeding, which balances grid asymmetries and improves voltage quality in distribution networks. This allows local grid phenomena such as voltage band violations or resonances to be compensated, enhancing grid stability.

In addition, the algorithms integrate functions for grid monitoring and diagnostics by evaluating high-resolution data from the AC/DC measurement technology. This allows grid issues such as harmonics or resonances to be accurately identified, and storage systems can be specifically targeted for stabilization. The systems are also capable of responding flexibly to grid requirements, for example, through redispatch measures to relieve congestion points.

The algorithms ensure secure and efficient communication between the components and the overarching grid control systems. They integrate battery storage not only as an energy storage solution but also as an active grid resource that contributes to the overall efficiency and resilience of the energy system, thus making an important contribution to the energy transition.

Are there plans to scale the solutions for use in larger networks or on a national level?

In the ALene project, clear plans are in place to scale the developed solutions for use in larger networks and at the national level. A central focus is the modularity and flexibility of the developed technologies, particularly the intelligent algorithms, power electronics, and communication infrastructure. The system's architecture is designed to be applicable not only in local distribution networks but also in medium-voltage and supraregional grid structures. This includes both the technical scalability and the transferability of operational strategies to different grid levels.

The algorithms to be developed are designed to handle various grid requirements, from control in low-voltage networks to the coordination of large energy storage networks. This is supported by the implementation of open interfaces and standardized protocols like MQTTs and Modbus TCP/IP, which allow seamless integration into existing grid control systems. The solutions can be operated both centrally, such as through overarching grid control systems, and decentrally, for instance, in microgrids or island networks.

An important aspect of scaling is demonstrating the technologies in real-world grid environments and field tests. Insights from these tests contribute to the development of application guidelines and best practices, facilitating the transition from pilot projects to large-scale implementation. In the long term, transferability to national grid structures is ensured by complying with regulatory requirements and collaborating with grid operators like Harz Energie.

Additionally, scaling is promoted by focusing on economic and technological efficiency. The lifespan of the battery systems is maximized through intelligent algorithms, which reduces operating costs and increases attractiveness for larger networks. Thus, the ALene project lays the foundation for the nationwide introduction of multifunctional, grid-supportive battery storage systems, contributing to the stabilization and optimization of the entire energy system. (heh)

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