The Need for System-Level Validation and Testing of Cyber-Physical Systems

By Thomas Strasser

Future power systems have to integrate a higher amount of distributed, renewable energy resources in order to cope with a growing electricity demand, while at the same time trying to reduce the emission of greenhouse gases. In addition, power system operators are nowadays confronted with further challenges, due to the highly dynamic and stochastic behaviour of renewables, and the need to integrate controllable loads. Furthermore, due to ongoing changes to policy and regulatory frameworks, technology developments and the liberalization of energy markets, the resulting design and operation of the future electric energy system has to be updated.

Background and Motivation

Sophisticated component and systems design approaches, intelligent information and communication architectures, and distributed automation concepts provide ways to cope with the above-mentioned challenges and to turn the existing power system into an intelligent system-of-systems, that is, a “Cyber-Physical Energy System (CPES)” (more commonly known as the “Smart Grid”'). Due to the considerably higher complexity of such a CPES, comprising of the power system, automation, protection, Information and Communication Technology (ICT), and system services, it is expected that the design and validation of smart grid configurations will play a major role in future technology and system developments.

However, an integrated approach for the design and evaluation of smart grid configurations incorporating these diverse constituent parts remains evasive. Validation approaches available today focus mainly on component-oriented methods. In order to guarantee a sustainable, affordable and secure supply of electricity through the transition to a future smart grid with considerably higher complexity and innovation, new design, validation and testing methods appropriate for cyber-physical systems are required.

Proper system-level validation and testing methods have not been developed until recently, while a suitably integrated Research Infrastructure (RI) for CPES is neither fully available nor easily accessible which fulfils the following main requirements:

• A cyber-physical, multi-domain approach for analyzing and validating CPES at the system level is missing; existing methods are mainly focusing on the component level – system integration topics including analysis and evaluation are not yet addressed in a holistic manner.
• A holistic validation framework (incl. analysis and evaluation/benchmark criteria) and the corresponding RI with proper methods and tools needs to be developed.
• Harmonized and standardized evaluation procedures need to be developed.
• Highly-specialized professionals, engineers and researchers that understand smart grid systems in a cyber-physical manner need to be trained on a broad scale.

Proposed Approach and Solution

In order to overcome the lack in power system validation and testing as outlined above, eighteen research institutions from eleven European countries are joining their forces and cooperating within the European-funded RI project called “European Research Infrastructure supporting Smart Grid Systems Technology Development, Validation and Roll Out (ERIGrid)”. The project aims to address the challenges raised above by developing a holistic, cyber-physical systems-oriented approach for testing smart grid systems. This integrated European smart grid RI targets the following points:

• Creation of a single point of reference promoting research, technology development, and innovation on all aspects of smart grid systems validation
• Development of a coordinated and integrated approach using the partners’ expertise and infrastructures more effectively, adding value to research projects, and promoting European leadership in smart grid systems
• Facilitating a wider sharing of knowledge, tools, and techniques across fields and between academia and industry across Europe
• Accelerating pre-normative research and promoting the rapid transfer of research results into industrial-related standards to support future smart grids development, validation and roll out

In order to realize the above mentioned project goals the following main research and development activities have been identified for the ERIGrid project:

• Development of a formalized, holistic validation procedure for testing smart grid systems and corresponding configurations
• Improvement of simulation and lab-based testing methods supporting the validation activities
• The provision of a corresponding and integrated pan-European RI based on the partner’s laboratories

The holistic testing methodology and corresponding tools should facilitate conducting tests and experiments representative of integrated smart grid systems by testing and experimentation across distributed RIs, which might not necessarily be functionally interconnected.

Additionally, training and education concepts are also developed to support the overall research activities. An interesting point in the ERIGrid approach is to provide free access to the integrated RI (i.e., partner’s smart grid laboratories) and the corresponding methods and tools for external user groups from industry and academia.

Conclusions

The expected large-scale roll-out of smart grid products and solutions during the next few years requires a multi-disciplinary understanding of several domains. The validation and testing of such complex solutions gets more important as in the past and there is a clear shift from component-level to system-level testing. An integrated, cyber-physical systems based, multi-domain approach for a holistic testing of smart grid solutions is currently still missing which is addressed by the ERIGrid approach. Four main research priorities have been identified in this project to tackle the shortcomings in today’s validation and testing of power systems and corresponding components. The research focus is put onto the development of a holistic validation procedure and the improvement of simulation-based methods, hardware-in-the-loop approaches, and lab-based testing, which can be combined in a flexible manner. The integration and online connection of the partners’ labs is also a very helpful service for the validation of complex smart grid systems.