Quoc Tuan Tran

Simulation-based validation of smart grids - status quo and future research trends

Smart grid systems are characterized by high complexity due to interactions between a traditional passive network and active power electronic components, coupled using communication links. Additionally, automation and information technology plays an important role in order to operate and optimize such cyber-physical energy systems with a high(er) penetration of fluctuating renewable generation and controllable loads. As a result of these developments the validation on the system level becomes much more important during the whole engineering and deployment process, today. In earlier development stages and for larger system configurations laboratory-based testing is not always an option. Due to recent developments, simulation-based approaches are now an appropriate tool to support the development, implementation, and roll-out of smart grid solutions. This paper discusses the current state of simulation-based approaches and outlines the necessary future research and development directions in the domain of power and energy systems.

Minimal aging operating strategies for battery energy storage systems in photovoltaic applications

High capital investment cost for batteries constitute a major obstacle to the widespread deployment of battery energy storage systems (BESSs) as a tool to support the integration of renewable energy sources into the electricity grid. BESSs are already operated in commercial MW-scaled photovoltaic (PV) installations to facilitate power production levelling and participation in auxiliary services, such as frequency and voltage control. The optimization of dispatch schedules has been employed in the past to aid the sizing of BESS and drive down capital expenditures by limiting the installed battery capacity to the minimum required for the application. In this work, an optimized operation strategy is used to reduce replacement costs for the batteries by adapting the state-of-charge and power solicitation to achieve minimized aging. To this end, a simplified model for both calendar and cycle aging of Li-ion batteries is integrated into a mixed-integer linear programming algorithm. Results from a simulation using typical specifications for a BESS operated in a PV power plant in French overseas regions are presented and discussed.

Multi-agent system for day-ahead energy management of microgrid.

The decentralization of control and management in electrical grid is an important evolution to integrate distributed generation into the power grids ensuring power reliability, quality and safety. Microgrids and Multi-Agent Systems are considered the key to apply this evolution. This paper presents a Multi-Agent System architecture (developed in JADE) for Microgrid operation. Furthermore, a rule-based algorithm for day-ahead energy management of Microgrid considering dynamic market prices is presented.

Normalized least mean squares observer for battery parameter estimation

Energy storage systems in Smart Grid applications can provide key services to transform the current power system through large-scale integration of renewable energy sources. They can assist in stabilizing the intermittent energy production, improve power quality and mitigate system peak loads. With the integration of energy storage systems into the grid, accurate and adaptive modeling becomes a necessity, in order to gain robust real-time control, in terms of network stability and energy supply forecasting. In this context, we propose an adaptive observer technique to identify the values of battery model parameters for the design of robust, low-maintenance battery management systems and integration alongside models of energy sources and electric loads into a real-time Smart Grid management system. The adaptive parameter estimation is based on a normalized recursive least mean squares algorithm and state-space mapping with a low computational burden which can accurately track parameter variations due to changing operating conditions and battery aging. Experimental data from commercial Li-Ion battery cells are used to validate the observer design and test results are reported.

Impact of European market frameworks on integration of photovoltaics in virtual power plants

The sustained development of renewable electric power sources demands new solutions for the integration of small-scale, distributed and volatile generation with limited predictability into the European energy markets and power grid. The aggregation of multiple distributed energy resources with adjustable loads and energy storage systems on a conceptual level as virtual power plants and on a geographical level in micro-grids has received widespread attention as a means to increasing the predictability and reliability of renewable sources and facilitating their participation in energy markets and auxiliary services such as frequency control reserve. In this work, the various rules and regulations for energy and reserve power markets in France, Italy and Germany are reviewed and studied for their impact on the market participation of a small-scale virtual power plant featuring photovoltaic sources and battery storage systems by using a mixed-integer linear programming model for dispatch optimization. Results show that existing minimal amount constraints have a particularly limiting effect on the integration of distributed sources into reserve markets and that reducing reserve contract duration can enhance the ability of VPPs to participate in reserve provision.

Gradient descent observer for on-line battery parameter and state coestimation

Transformation of energy supply towards fully renewable generation presupposes readily available distributed energy storage systems to compensate the variability of renewable sources. Battery energy storage systems (BESS) connected to the grid via power electronics are well suited to be deployed in large numbers in Smart Grid applications to provide system services like load balancing, grid stabilizing and power quality management. Control and optimization of BESS operation rely on the availability of accurate and adaptive models. In particular, dispatch optimization in energy management systems demands regularly updated, simple and reliable battery models. As time-consuming parameterization testing imposes additional costs and operating constraints on BESS, adaptive battery parameter and state coestimation provides an inexpensive on-line solution. A novel observer technique based on gradient descent optimization, that provides estimates of unknown and variable battery parameters and of the internal battery state, is proposed in this work. The coestimation is validated using experimental data from commercial Li-Ion batteries and the test results are reported.

CIM and OPC UA for interoperability of micro-grid platforms

In this paper, we are interested in the problem of interoperability of micro-grid platforms, particularly in information and communication layers. The implementation of Common Information Model (CIM) semantic over OPC Unified Architecture (OPC UA) protocol, particularly the mapping of CIM semantic to OPC UA address space, is also considered, to ensure that the exchanged data is mutually and correctly understood by all the partners of the network We provide some insights about requirements to deliver OPC-based application via WAN connection. This combination brings CIM semantic to the OPC UA communication and allows the provision of OPC-based applications via WAN connection. This contribution enables a seamless and meaningful communication among partners of the collaboration network and provides a strong support for interoperability of micro-grid platforms.

Novel hybrid cloud based SCADA approach for interoperability of micro-grid platforms

In the context of smart grid development, this paper considers the problem of interoperability of micro-grid platforms, particularly among research institutions. Various levels of interoperability are introduced with the respective requirements. The primary aim of the paper is to propose a suitable private hybrid cloud based SCADA architecture satisfying various necessities in the framework of interoperability of micro-grid platforms while maintaining security restrictions. Due to the limited time restriction of critical SCADA functions in the electrical grid, only selected non-critical SCADA functions are accessible to partners from the private cloud. The critical SCADA tasks functionality remains under control of local server, thus, a hybrid cloud architecture. The communication model is based on Platform as a Service (PaaS) delivery model of cloud computing.