Anna Magdalena Kosek

An overview of demand side management control schemes for buildings in smart grids

The increasing share of distributed energy resources and renewable energy in power systems results in a highly variable and less controllable energy production. Therefore, in order to ensure stability and to reduce the infrastructure and operation cost of the power grid, flexible and controllable demand is needed. The research area of demand side management is still very much in flux and several options are being presented which can all be used to manage loads in order to achieve a flexible and more responsive demand. These different control schemes are developed with different organization of the power sector in mind and thus can differ significantly in their architecture, their integration into the various markets, their integration into distribution network operation and several other aspects. This paper proposes a classification of load control policies for demand side management in smart buildings, based on external behavior: direct, indirect, transactional and autonomous control; internal operation: decision support system scope, control strategy, failure handling and architecture. This classification assists in providing an overview of the control schemes as well as different ways of representing a building.

Scheduling of domestic water heater power demand for maximizing PV self-consumption using model predictive control

This paper presents a model predictive control (MPC) strategy for maximizing photo-voltaic (PV) self-consumption in a household context exploiting the flexible demand of an electric water heater. The predictive controller uses a water heater model and forecast of the hot water consumption in order to predict the future temperature of the water and it manages its state (on and off) according to the forecasted PV production, which are computed starting from forecast of the solar irradiance. Simulations for the proof of concept and for validating the proposed control strategy are proposed. Results of the control approach are compared with a traditional thermostatic controller using historical measurements of a 10 kW PV installation. Economic results based on the Italian self consumption tariffs are also reported. The model of the water heater complex is a mixed grey and white box and its parameters have been estimated using a real water heater device.

Evaluation of smart grid control strategies in co-simulation — integration of IPSYS and mosaik

This paper presents two different aspects considering a co-simulation of smart grid scenarios. First considers representing the control strategy in a separate discrete event simulation developed in a multi-agent platform. This study investigates the design and implementation of such a simulator. Special attention is given to timing issues presenting time variant and time invariant models. The second aspect presented in this paper is the co-simulation composition, investigating how to integrate a control simulation with other simulators in a co-simulation ecosystem. In this study the attention is given to the co-simulation scheduling, proposing two integration approaches: overall control and separate domain. Results from a proof-of-concept implementation are included.

Fault tolerant aggregation for power system services

Exploiting the flexibility in distributed energy resources (DER) is seen as an important contribution to allow high penetrations of renewable generation in electrical power systems. However, the present control infrastructure in power systems is not well suited for the integration of a very large number of small units. A common approach is to aggregate a portfolio of such units together and expose them to the power system as a single large virtual unit. In order to realize the vision of a Smart Grid, concepts for flexible, resilient and reliable aggregation infrastructures are required. This paper presents such a concept while focusing on the aspect of resilience and fault tolerance. The proposed concept makes use of a multi-level election algorithm to transparently manage the addition, removal, failure and reorganization of units. It has been implemented and tested as a proof-of-concept on the distributed smart grid test bed SYSLAB at the Technical University of Denmark.

Domestic refrigerators temperature prediction strategy for the evaluation of the expected power consumption

This paper discusses and presents a simple temperature prediction strategy for the domestic refrigerator. The main idea is to predict the duration it takes to the cold chamber temperature to reach the thresholds according to the state of the compressor and to the last temperature measurements. The experiments are conducted at SYSLAB facility at DTU Risø Campus having a set of refrigerators working at different set point temperatures, with different ambient temperatures and under different thermal load conditions. The prediction strategy is tested using a set of different refrigerators in order to validate the performances. The challenges to calculate the time with less error pronouncement in temperature, regulating power supply and its duration are also discussed.

Contextual anomaly detection for cyber-physical security in Smart Grids based on an artificial neural network model

This paper presents a contextual anomaly detection method and its use in the discovery of malicious voltage control actions in the low voltage distribution grid. The model-based anomaly detection uses an artificial neural network model to identify a distributed energy resources behaviour under control. An intrusion detection system observes distributed energy resources behaviour, control actions and the power system impact, and is tested together with an ongoing voltage control attack in a co-simulation set-up. The simulation results obtained with a real photovoltaic rooftop power plant data show that the contextual anomaly detection performs on average 55% better in the control detection and over 56% better in the malicious control detection over the point anomaly detection.

Distribution Line Parameter Estimation Under Consideration of Measurement Tolerances

State estimation and control approaches in electric distribution grids rely on precise electric models that may be inaccurate. This work presents a novel method of estimating distribution line parameters using only root mean square voltage and power measurements under consideration of measurement tolerances, noise, and asynchronous timestamps. A measurement tolerance compensation model and an alternative representation of the power flow equations without voltage phase angles are introduced. The line parameters are obtained using numeric methods. The simulation demonstrates in case of the series conductance that the absolute compensated error is -1.05% and -1.07% for both representations, as opposed to the expected uncompensated error of -79.68%. Identification of a laboratory distribution line using real measurement data grid yields a deviation of 6.75% and 4.00%, respectively, from a calculation based on the manufacturers cable specifications and estimated line length. The transformed power flow equations deliver similar results despite the reduced problem complexity.

Activate distributed energy resources' services: Hierarchical voltage controller as an application

The flexibilities from controllable distributed energy resources (DERs) offer the opportunities to mitigate some of the operation problems in the power distribution grid. The provision of system services requires the aggregation and coordination of their flexibilities, in order to obtain the flexible capacity of large scale. In this paper, a hierarchical controller is presented to activate the aggregation, and tries to obtain a global optimum of the grid operation. A distribution grid with large penetration of highly varying generation or load is under the risk that the voltage quality delivered to the end users is very poor. Hence, a coordinated voltage control function is investigated given such control hierarchy utilizing the flexibilities from the DER units to obtain an optimal voltage profile along the distribution feeder. The results are two folded: the controller enables the efficient aggregation and dispatch, and it simplifies the optimization complexity; the involvement of DER flexibilities in voltage services can significantly improve the voltage quality and reduce the grid power loss without additional regulating devices.

Energy shift estimation of demand response activation on refrigerators — A field test study

This paper presents a method to estimate the amount of energy that can be shifted during demand response (DR) activation on domestic refrigerator. Though there are many methods for DR activation like load reduction, load shifting and onsite generation, the method under study is load shifting. Electric heating and cooling equipment like refrigerators, water heaters and space heaters and coolers are preferred for such DR activation because of their energy storing capacity. Accurate estimation of available regulating power and energy shift is important to understand the value of DR activation at any time. In this paper a novel method to estimate the available energy shift from domestic refrigerators with only two measurements, namely fridge cool chamber temperature and compressor power consumption is proposed, discussed and evaluated.

Assessment of distribution grid voltage control strategies in view of deployment

Increasing integration of distributed energy resources (DER) and available monitoring devices in the power distribution grid make system services provided by DERs possible and an integral part of distribution grid operation. Numerous publications have proposed various control solutions by utilizing different capabilities of DERs and regulating devices to assist grid operation. However, very few of them have discussed the opportunities and barriers of deploying the control strategies in practice. This paper reviews some typical control solutions on providing voltage control services. Furthermore, it provides some qualitative discussions on the challenges in view of deployment. Several qualifying metrics are listed to specify the challenges from different perspectives. A metrics comparison diagram is proposed to asses deployment of a control strategy. Five case studies are presented to identify the corresponding advantages and challenges of deployment.