Fridrik Rafn Isleifsson

Simulation model developed for a small-scale PV system in distribution networks

This paper presents a PV panel simulation model using the single-diode four-parameter model based on data sheet values. The model was implemented first in MATLAB/Simulink, and the results have been compared with the data sheet values and characteristics of the PV panels in standard test conditions. Moreover to point out the strong dependency on ambient conditions and its influence on array operation and to validate simulation results with measured data a complex model has also been developed. A PV inverter model, using the same equations and parameters as in MATLAB/Simulink has also been developed and implemented in PowerFactory to study load flow, steady-state voltage stability and dynamic behavior of a distributed power system.

Evaluating frequency quality of Nordic system using PMU data

This paper focuses on analysing frequency quality of Nordic power system using measurements from phasor measurement units (PMU). The PMU data of one year long period is used which has very high time resolution (20 ms per sample) and is able to provide detailed information in evaluating frequency quality and its correlation with time. The results show that the frequency quality of the Nordic power system is not satisfactory according to the suggested requirements. The electricity market operation is found to be one of the major reasons behind. Based on the results, discussion of frequency control for future power system is made where several new technologies of interests are suggested to be investigated.

Development of tools for simulation systems in a distribution network and validated by measurements

The increasing amount of DER components into distribution networks involves the development of accurate simulation models that take into account an increasing number of factors that influence the output power from the DG systems. This paper presents two simulation models: a PV panel model using the single-diode four-parameter model based on data sheet values and a VRB system model based on the efficiency of different components and the power losses. The models were implemented first in MATLAB/Simulink and the results have been compared with the data sheet values and with the characteristics of the units. Moreover to point out the strong dependency on ambient conditions and its influence on array operation and to validate simulation results with measured data a complex model has also been developed. A PV inverter model and a VRB inverter model, using the same equations and parameters as in MATLAB/Simulink, has also been developed and implemented in Power Factory to study load flow, steady-state voltage stability and dynamic behavior of a distribution power system.

Online AMR Domestic Load Profile Characteristic Change Monitor to Support Ancillary Demand Services

With conventional generation capacity being constrained on environmental grounds and renewable alternatives carrying capacity uncertainties, increasingly accurate forecasts of demand are likely to be required in future power systems: highly distributed renewable generation penetrating low voltage networks must be matched to small dynamic loads, while spinning reserves of conventional generation that are required to maintain security of supply, must be reduced to more efficient margins. Domestic loads, likely to form significant proportions of the loads on islanded power systems such as those in remote rural communities, are currently modeled with homogenous and coarse load profiles developed from aggregated data. An objective of AMR deployment is to clarify the nature and variability of the residential LV customer. In this paper, an algorithm for tracking the consistency of the behavior of small loads is presented. This would allow them to be assessed for their availability to provide demand services to the grid. In the method presented, significant changes in behavior are detected using Bayesian changepoint analysis which tracks a multivariate Gaussian representation of a residential load profile on a day to day basis. A hypothetical single phase feeder, representative of an islanded rural power system, is used to illustrate the detected heterogeneity of load behavior consistency.

Day-ahead scheduling of a photovoltaic plant by the energy management of a storage system

The paper discusses and describes a system for energy management of a 10 kW PV plant coupled with a 15 kW-190 kWh storage system. The overall idea is, by knowing the meteorological forecast for the next 24h, to dispatch the PV system and to be able to grant the scheduled hourly energy profile by a proper management of the storage. Due to forecast inaccuracies, the energy manager controls the storage in order to ensure that the plan for hourly energy production is respected, minimizing the storage itself usage. The experimental study is carried out in SYSLAB, a distributed power system test facility at DTU Riso Campus and part of PowerLabDK. Both the PV and the storage are connected to the local network and are fully controllable through the SCADA system. The control management and the models are implemented in Matlab-Simulink, which can be interfaced with SYSLAB.

Use of local dynamic electricity prices for indirect control of DER power units

The regulation capability that may be provided by the individual small-scale distributed energy resources (DER power units) may be insignificant. However, the aggregated response from a large number of DER power units can be significant and thereby provide valuable system services to the power system. A challenge is to find a cheap, simple and robust way to requests the proper power regulation by the DER power units. The use of broadcasted, dynamic power prices and volunteer responses is one option. The paper presents a proposal for and an illustration of advanced generation of local, dynamic electricity prices for indirect control of active power. The local, dynamic electricity prices are realised as dynamic adjustments of the quasi-stationary global power price. The aims of the dynamic price adjustments are to prevent overloading of the grid, to reduce the grid power losses and to regulate the grid voltage. The algorithms generating the local prices are dynamically adjusted according to the actual realised responses to the dynamic prices. Results are presented from an adapted version of the control principle implemented and tested in DTUs experimental research power system, SYSLAB, including wind power, solar power, flexible load and electrical storage. The local power price generation is based on the actual Nord Pool DK2 Spot prices on hourly basis as the quasi-stationary global electricity price, and the local SYSLABs power exchange with the national grid as basis for the dynamic price adjustment. (4 pages)

Experimental testing for stability analysis of distributed energy resources components with storage devices and loads

The distributed energy resources (DER) contains several technologies, such as diesel engines, small wind turbines, photovoltaic inverters, etc. The control of DER components with storage devices and (controllable) loads, such as batteries, capacitors, dump loads, are central to the concept of the Micro Grids (MGs). A MG can operate interconnected to the main distribution grid or in islanded mode. This paper presents experimental tests for static and dynamic stability analysis carried out in a dedicated laboratory for research in distributed control and micro-grid with a high share of renewable energy production. Moreover to point out, on a laboratory scale, the coupling between DR and storage and to effectively compensate wind fluctuations a number of tests have been done. In order to find out the parameters of various types of DER components for dynamic simulation models a number of tests are required under different operation modes and loads. The testing reporting here includes three modes of operation: stand alone, parallel/hybrid and grid connection.