Sawsan Henein

Smart robust voltage control for distribution networks using interval arithmetic and state machine concepts

Due to the connection of a great number of distributed generation (DG) plants, a critical voltage regulation problem in medium voltage distribution networks arises. After a synthetic survey of different strategies reported in literature to solve this problem, a voltage control concept for smart distribution networks with high penetration of distributed generation is presented. It makes use of all the possible means of intervention usually available in a distribution network and asks for an additional communication infrastructure due to its centralized structure. The proposed concept is a compromise between nearly global optimal operation and ease of implementation. Control actions are hierarchically organized by means of a state machine which constitutes the core of the decision logic of the controller. The voltage controller decisions regarding reactive and active power control of the controllable distributed plants are based on a linearised model of the distribution network. The model is valid in a broad range of operation. Uncertainties are accounted by interval arithmetic methods. Efficient operation is guaranteed by constrained optimization. The control concept has been extensively validated by simulation runs with load and generation profiles from real life operation in a distribution network located in Vorarlberg, Austria. Results are very promising so that the real implementation as a prototype will be carried out in two distribution networks in two different regions of Austria in the near future.

Development and validation of a coordinated voltage controller using real-time simulation

This paper describes the process of developing and validating controller concepts using real-time simulation capabilities. The process from the proof-of-concept to the prototype and finally to the realization and the advantage of testing in a real-time simulation environment is demonstrated in a test case. The test case is based on an example in the safety critical domain of electric power systems - the coordinated voltage controller of the DG-DemoNet project. The possibilities and advantages of controller-hardware-in-the-loop (C-HIL) concepts compared to offline simulation are discussed.

Simulation of multi-domain energy systems based on the functional mock-up interface specification

Novel concepts for energy systems increasingly focus on solutions that go beyond the scope of traditional engineering domains. Unfortunately, there is still a lack of appropriate modeling and simulation tools for applications in energy-related multi-domain systems. However, well-established methods from other scientific and industrial areas provide promising approaches to overcome the associated challenges. This paper explores the applicability of the Functional Mock-up Interface (FMI) specification within this context. To this end, a versatile simulation environment prototype is presented, which is dedicated to investigate and utilize the full range of possibilities offered by the FMI specification. The presented examples demonstrate the potential of including well-established tools and models from multiple domains with minimal effort into a modern FMI-based simulation framework.

Agent-Based Impact Analysis of Electric Vehicles on a Rural Medium Voltage Distribution Network Using Traffic Survey Data

Based on trips of more than 10,000 cars, the impact of charging electric vehicles on a rural medium voltage network is analysed and presented. Traffic is simulated by micro-simulation where each of the electric vehicles is represented by an agent. The total demand for charging battery electric vehicles and plug-in hybrid vehicles for one day in summer and winter is determined. Two different charging scenarios (end-of-travel-day and opportunity charging) as well as temperature influence are compared. Results show that due to concurrency the impact on the voltage is significant in terms of increasing penetration levels, especially with the end-of-travel-day charging scenario.

Dynamic Co-simulation of agent-based controlled charging electric vehicles and their impacts on low-voltage networks

During the last decades the electric vehicles (EVs) technologies are developing rapidly which may lead to a significant penetration level in the mobility market in the near future. As a consequence of these high penetration levels, power grids, especially on the low voltage level, might face a number of technical problems. These can be transformer and cables overloads, feeder congestions and especially voltage limits violations. Renewables may introduce a solution for part of these problems but not all of them. In order to minimize peak loads caused by charging EVs, intelligent control algorithms for EV charging are needed. This paper focuses on a dynamic co-simulation environment which enables the realistic evaluation of the impact of charging EVs on electrical networks. This co-simulation environment also simulates the behavior of the EVs and estimates the required charging power. In order to test the co-simulation environment a study case is analyzed for a rural residential network with a high penetration of photovoltaic systems.

Increasing the Utilization Ratio of Photovoltaic Energy by Network Hybridization

The traditional architecture of electric power networks is limiting the usage of massive decentralized photovoltaic energy to the immediate neighborhood of the production units. When generation largely exceeds local consumption, solar energy production needs to be curtailed in order to avoid equipment overloading and power quality problems. The necessary investment in grid infrastructure to overcome this limitation represents a serious adoption barrier for renewable energy. In this work we explore a solution path based on the concept of hybrid energy grids investigated by the European OrPHEuS project, where different energy carrier networks benefit from mutual energy transfer. Applying the hybridization principle, we consider the approach to feed surplus energy into the domestic hot water systems of residential houses and thus reduce energy (e.g. fossil fuel) consumption of the primary heating system. We examine various strategies for controlling this energy exchange process, ranging from purely local decision schemata to fully centralized control algorithms. In an extensive experimental study, based on accurate simulations of the electricity grid and the thermodynamics of domestic hot water systems, we confirm the feasibility of our approach and determine the best choices of devices and control strategies. In our simulations we were able to reduce the yearly usage of heating fuel by 65% utilizing surplus energy from local solar panels.

Gap analysis of future energy grids

Based on existing low and medium voltage grids from distribution system operators and future scenarios of PV and EV penetration, critical load scenarios which lead to violations of relevant KPIs are to be developed in the scope of PlanGridEV. In the course of the gap analysis the expected limits of DER hosting capacities were identified. The method for developing and simulating the different scenarios is following a state-of-the-art approach. Results for each power grid and scenario are addressing specific KPIs. The main goal of this analysis was to assess the current EV and PV hosting capacity of existing low voltage and medium voltage grids and identify the factors which limit this hosting capacity. It is shown that European DSOs share similar structures. Depending on voltage level and topology type, specific KPIs were violated by increasing numbers of RES or EVs. Indications for synergies between PV and EVs could be identified due to an increased hosting capacity in the extra PV scenario.