Online coherency identification and stability condition for large interconnected power systems using an unsupervised data mining technique

Identification of coherent generators and the determination of the stability system condition in large interconnected power system is one of the key steps to carry out different control system strategies to avoid a partial or complete blackout of a power system. However, the oscillatory trends, the larger amount data available and the non-linear dynamic behaviour of the frequency measurements often mislead the appropriate knowledge of the actual coherent groups, making wide-area coherency monitoring a challenging task. This paper presents a novel online unsupervised data mining technique to identify coherent groups, to detect the power system disturbance event and determine status stability condition of the system. The innovative part of the proposed approach resides on combining traditional plain algorithms such as singular value decomposition (SVD) and K -means for clustering together with new concept based on clustering slopes. The proposed combination provides an added value to other applications relying on similar algorithms available in the literature. To validate the effectiveness of the proposed method, two case studies are presented, where data is extracted from the large and comprehensive initial dynamic model of ENTSO-E and the results compared to other alternative methods available in the literature

Centralized wide area damping controller for power system oscillation problems

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper, three different centralized control designs that vary on complexity are presented to damp inter-area oscillations in large power systems. All the controls are based on phasor measurements. The first two proposed architectures use simple proportional gains that consider availability of measurements from different areas of the system and fulfill different optimization functions. The third controller is based on a more sophisticated Linear Quadratic Gaussian approach which requires access to the state space model of the system under investigation. The novelty of the proposed scheme resides in designing a single control to command the most influence group of machines in the system. To illustrate the effectiveness of the proposed algorithms, simulations results in the IEEE New England model are presented

Detection of frequency deviations for monitoring of power systems

​© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this work an algorithm for identification of power system frequency deviation is presented. The proposed approach can be used to monitor frequency measurements from syncrophasor measurement units (PMU) and to store data only for important events and save storage in the local server. The detection algorithm use a sliding window that rise a flag if the measured frequency deviates from a predefined set point. If the alarm flag is constant over several sliding windows, an event is captured and locally stored for further analysis. To demonstrate the effectiveness of the proposed approach, real PMU measurements from the Swiss power system are used as input

Implementation of quasi-static time series simulations for analysis of the impact of electric vehicles on the grid

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper, symmetrical electric vehicle charging impacts in existing low-voltage distribution grid are investigated throughout proposed methodology and their results analysed. Symmetrical loading- and voltage-related impacts are assessed for the extensive grid. A synthetic EV mix pattern was used with the purpose to demonstrate a universal observation of charging impacts. These patterns were allocated quasi-randomly to the points of common coupling within the grid based on predefined scenarios - 8, 10, 12 and 20 percent. Subsequently, quasi-static time series simulations for a duration of one year in 10-minute time steps were executed. Consequently, this paper yields results, which offer practical insight in the maximum share of electric vehicle charging in low-voltage distribution grids and provide guidance for future decision-making of distribution grid operators

Power-to-Gas Concept for Integration of Increased Photovoltaic Generation into the Distribution

AbstractAccording to the Energy Strategy 2050 set forth by the Swiss federal government, Photovoltaic (PV) energy shall make up one fifth of the nation's total energy production in 2050. Such a drastic expansion rate of PV and the resulting excess energy thereof can lead to so-called reverse power flow in the low voltage (LV) grid as demonstrated in previous studies. Power-to-Gas (PtG) represents a suitable storage solution to resolve the situation by absorbing the excess PV energy. This paper presents a qualitative and quantitative feasibility analysis of the PtG technology in the future Swiss LV grid. For this purpose, PtG is integrated in simulation into the grid for absorbing the excess PV energy while producing hydrogen. This hydrogen is assumed to be sold in the mobility sector. Three different operational scenarios are established with respect to the input energy source to the PtG plant, including the excess PV energy, curtailed PV excess energy and PV excess energy plus the energy from the grid. Summing up the results, it can be concluded that the PtG plant is still far from economically viable even though significant improvement can be accomplished to the hydrogen production costs by adopting the active PV curtailment and by purchasing additional energy from the grid. The future study to be undertaken by the authors, with respect to economical viability of the PtG, will include other sources of value, including production of methane as main product, production of oxygen and heat as by-products, and provision of services such as biogas upgrading, frequency regulation and voltage

Integration and management of PV-battery systems in the grid

The paper describes recent developments and implementation of a method and a prototype solving the problem of optimal integration of PV-battery energy storage systems into the power grid. The first practical results achieved in cooperation with ABB Switzerland Ltd. using a real-time prototype of the developed advanced battery controller and the largest Li-Ion battery installed in Switzerland at the electric power utility of the canton of Zurich (EKZ) are presented

Techno-economic evaluation of voltage dependent active and reactive power control to reduce voltage violations in distribution grids

High penetration of PV plants or numerous electric vehicle (EV) charging station stations connected to the low voltage distribution grids (LVDG) may cause a voltage rise or voltage decrease respectively. There are several measures of maintaining the voltage stability such as grid reinforcement, battery energy storage, line voltage regulator, etc., although they vary in effectiveness and economic viability. This paper focuses on using decentralised voltagedependent active and reactive power (PQ(V)) control of PV inverters to stabilise the voltage in the grid. Using two grid models in Southern Germany and Switzerland the best PQ(V) control strategy is evaluated using load flow calculations. The weakest node in the first grid exhibits a maximum voltage of 1.072 pu on a sunny day. Due to the implementation of the PQ(V) control the maximum voltage is reduced to 1.024 pu at the same node. Costs considered for PQ(V) control are the PV yield loss and the additional reactive power compensation, which amount to roughly CHF 2’600.- per year. The future installation of EV charging stations may positively interact with PV feed-in. The voltage decrease can further be limited using PQ(V) control. Further grids and means for voltage stabilisation will be analysed in the future

Open source module for the investigation of the impact of electric vehicles in a low voltage grid

This paper provides an open-source Python-based module overview focused on simulating the integration of electric vehicles in a low voltage grid. This module aims to investigate the possible effects that the integration of electric vehicles could have on the operability of the power network. The electric grid conditions are estimated by analysing line loading, voltage values at the final customer, and transformers’ loading. The following tool enables modelling electric grids composed of basic grid elements such as lines, two-winding transformers, predefined load profiles and generated electric vehicle load profiles based on a statistical approach. The module performs time-series simulations through a secondary software, OpenDSS, with result exporting functionality for further analysis, and a graphical user interface

Electric vehicles load profile generator based on the probability density functions

This paper provides a prototype of an Electric Vehicles Load Profile Generator based on the probability density function of several parameters such as arrival time, total connection time, energy demand, and the information about the vehicle's battery size of charge and the power level of the charger. This tool of simulation, realised with Python, allows the generation of random EV load profiles and, in the next step, simulates the integration of these patterns in a defined grid through open-source and commercial software's. The Quasi-dynamic simulation approach is used since load profiles are time depending. The electric vehicles load profile generator is tested by simulating scenarios of different load profiles at points of common coupling with proposed simplification to allows maximising the precision of the results and at the same time to minimise the needed simulation time

Investigation of harmonic issues in distribution grids due to high share of electric vehicles

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.With the advent of power electronics, the application of solid-state electronics for the control and conversion of electric power is substantially increasing at the expenses of simple rotating machines and linear loads. This leads to power quality problems due to the sinewave distortion of current and voltage caused by such power-electronics-based equipment. Consequently, the investigation and understanding of harmonic emissions caused by those devices become of major importance in order to assure a continuous and reliable operation of the electrical distribution grid. The following paper aims to investigate the harmonic issues in distribution grids, due to power electronic devices with particular focus on electric vehicle chargers