Advanced Measurement and Monitoring for Distribution Grids

  Copyright: RWTH Aachen Measurement infrastructure for future distribution grids

This research project aims at developing advanced measure- ment and monitoring methods for future distribution grids. Advanced control and operation systems for distribution grids can be facilitated by the use of emerging measurement technologies such as Smart Metering and Phasor Measure- ment Units (PMUs) providing more accurate and extensive measurement information to enable real-time monitoring, state estimation and system analysis.

The fundamental changes undergoing in distribution grids, including the deployment of volatile and distributed gene- ration, the arising of prosumer behavior and new demand side services, are accompanied by increasing system com- plexity, dynamics and uncertainty. Situation awareness is of essential importance to enable reliable and efficient control and operation applications. However, an appropriate mea- surement and monitoring system is still in demand.

To assist distribution system operators in making decisions to upgrade the measurement infrastructure for the upco- ming changes, a holistic, optimal meter placement procedu- re has been developed. This combines traditional and emer- ging measurements, especially provided from smart meters and phasor measurement units, yielding a comprehensive measurement infrastructure. The meter placement problem is addressed by a stochastic optimization method, with the goal of limiting the overall uncertainty of state estimation, while minimizing the investment costs. Different load and generation conditions, different grid topologies, robustness in case of measurement device failure and degradation, as well as measurements with non-Gaussian probabilistic na- ture are taken into account in the optimal placement.

Dynamic phasor measurement methods based on the so- called Taylor-Fourier Transform, using weighted least square and Kalman filter, have been developed to achieve accurate synchrophasor and frequency measurements suitable for application in distribution grids. In addition, a prototype de- vice has been built to demonstrate the level of compliance of the methods with the IEEE synchrophasor standards. This device can be used for monitoring applications in future distribution grids, such as state estimation and harmonic measurements.

Regarding distribution system state estimation (DSSE), we have developed a state estimator with three-phase forma- lization, considering coupling effects and shunt admittan- ces, to track unbalance features in distribution grids. An analysis of factors that affect the quality of the DSSE has been performed, taking into account several measurement types, different availability and accuracy of measurements. The results of the sensitivity analysis show in particular that the branch measurements improve sensibly the accuracy of the estimation with regards to pure injection measure- ments. Furthermore, the availability of an accurate common time reference, such as in case of PMUs significantly affects the solution. Finally, we are implementing new models of load profiles based on statistical information about modern Home Energy Systems, including operation of electric heating systems and domestic PV and actual usage of home appliances. Such load profiles are used as source of pseudo- measurements. We are investigating and characterizing the deviation of these new load profiles in order to verify the reliability of “classical” pseudo-measurements and their im- pact on the accuracy of the state estimate.

This work is carried out in cooperation with Prof. Carlo Mus- cas and his research group, at the University of Cagliari, Italy.