O. Ruhle

Faster than real time: Dynamic security assessment for foresighted control actions

In this paper, implementation of power system dynamic security assessment (DSA) into real time simulation environment is described. For this purpose, a powerful simulation system has been used and a flexible security assessment framework developed. The DSA system constructed is user oriented and enables simple evaluation of power system security. The assessment is made in respect to some user defined security constraints considering normal or contingency provoked system operation. For reporting of the results different visualization formats are available. The DSA system is fully automatic and can process any number of study cases without user interaction. It targets high flexibility in power system research and maximum performance at minimum hardware requirements.

MaWind - tool for the aggregation of wind farm models

The existing software for the simulation of power system operation was mainly developed and optimized for the analysis of conventional systems that are characterized by a low number of large, central synchronous generators. New forms of power generation, like wind turbines, that are characterized by a high number of small units can not be analyzed effectively with this software. In this paper a new software tool, MaWind, for the aggregation of wind farm models for dynamic system analysis is described. The MaWind tool uses a new mathematical approach to represent wind generation in system analysis. The background of this method, the method itself and some representative results of the calculation with MaWind are presented in the paper. MaWind allows for significant reduction of the model complexity while retaining a good approximation of dynamic farm behavior at the same time.

Vision 2020: Blackout prevention by combined protection and network security assessment

The paper presents the application of software tools to simulate system dynamic behaviour together with the possibility to select critical contingencies of an electrical energy system. The protection system with relay functions, characteristics, settings and communication schemes will be considered. Possible visualization methods are presented which can support the operators to select critical system states - either of the primary or the protection system. Insecure operating conditions can be monitored in the time domain using the full system representation in real time or by calculating the eigenvalues of the system to monitor weakly damped system states and stability margins. Warnings about unselective protected areas can popup for fast information or they can be shown with the corresponding relays in single-line diagrams as a basis for a new protection coordination study. The locations of short circuits with corresponding trip times and unselective trips or no trips can be monitored in two- or three-dimensional diagrams. The optimized settings can be directly transmitted to relays, which are able to receive the adaptive settings.

Generic modeling of a line commutated HVDC system for power system stability studies

This paper will reveal a novel comprehensive approach for generic modeling and control design of line commutated HVDC systems. The model will be developed based on the essential HVDC equations and transfer functions. Due to comparing the generic model with an EMT (Electro-Magnetic Transient) HVDC model the consistence of the dynamic behavior will be shown. Furthermore modeling of additional HVDC system facilities like transformer tap-changers and AC filters will be annotated. Control design schemes for line commutated HVDC systems will be derived and the interactions of the controllers applied to the developed model will be investigated.

Vision 2020 dynamic security assessment in real time environment

In this paper, implementation of power system dynamic security assessment (DSA) into real time simulation environment is described. For this purpose, a powerful simulation system has been used and a flexible security assessment framework developed. The DSA system constructed is user oriented and enables simple evaluation of power system security. The assessment is made in respect to some user defined security constraints considering normal or contingency provoked system operation. For reporting of the results different visualization formats are available. The DSA system is fully automatic and can process any number of study cases without user interaction. It targets high flexibility in power system research and maximum performance at minimum hardware requirements.

DSA-Visualisation Monitoring and Ranking of System Dynamic Behaviour

The paper presents the application of a software tool to simulate system dynamic behavior together with the possibility to select critical contingencies of an electrical energy system. These cases are visualized and a ranking decision is introduced to support the operators to select critical system states. Insecure operating conditions can be monitored in the time domain using the full system representation in real time or by calculating the eigenvalues of the system to monitored weakly damped system states and stability margins.

Dynamic Security Assessment to protect systems after severe fault situations

In the last 10 years the number of severe fault situations and black-outs world wide is increasing. The classical static security assessment is used to monitor the system situation after contingencies, but is not able to take into account the complex dynamic behaviour of an electrical system together with the control of generators and grid equipment like switched capacitors or FACTS together with the protection reaction in unforeseeable situations after severe system faults. The paper describes a modern dynamic security assessment (DSA) system which allows handling predefined dynamic contingencies in real-time and intelligent proceeding and evaluation. The base of the system is the system simulation tool PSStrade NETOMAC, which can simulate the dynamic behaviour of large electrical systems including control and protection. A contingency builder allows the user to define the interesting contingency scenarios like outage of grid elements, generators or combination of outages or system faults like short circuits, etc. The events can be calculated in real time which means, that about 200 contingency cases can be handled in about 10 minutes, depending on the system size. The DSA-system analyses the events using an intelligent and flexible criteria editor which gives the opportunity to select criteria for critical system time behaviour. These criteria allow to observe how critical a system reacts checking under voltages, frequency, angle differences in the grid, overcurrents, machine angle, etc. The information about severe cases is available in a protocol for easy recalculation of critical cases in details with more parameters checked and monitored. The results can be used to monitor the overall situation of a system periodically. The automatic monitoring of critical events is under construction.

Generic modeling of a self-commutated multilevel VSC HVDC system for power system stability studies

This paper provides a generic stability model of a self-commutated multilevel VSC (Voltage Source Converter) HVDC (High Voltage Direct Current) and its appropriate control. At first the approach of modeling depicts the independence of the AC and DC quantities and therefore two separate models - one for the AC and one for the DC side - can be figured out. The AC side model is developed in the dq frame out of the according differential equations. For the DC side no further transformation is required. Regarding the fact of balanced energy terms the two models can be merged. The consolidation of both models reveals a comprehensive large signal model of a multilevel based HVDC system which can be used for detailed analyses in power system stability studies. Due to the comparison of the generic stability model with an EMT (Electro-Magnetic Transient) HVDC model the consistence of the dynamic behavior is shown.

Dynamic protection and security assessment for highly loaded power systems

The paper presents the application of software tools to simulate system dynamic behavior together with the possibility to select critical contingencies of an electrical energy system. The protection system, which is connected to the primary system via vts, cts and trip contacts, is running in parallel during system simulations, with all necessary relay functions, characteristics, settings and communication schemes. Possible visualization methods are presented which can support the operators to select critical system states — either of the primary or the protection system. Insecure operating conditions can be monitored in the time domain using the full system representation in real time or by calculating the eigenvalues of the system to monitor weakly damped system states and stability margins. Warnings about unselective protected areas can popup for fast information or they can be shown with the corresponding relays in single-line diagrams as a basis for new necessary protection coordination study. The locations of short circuits with corresponding trip times and unselective trips or no trips can be monitored in two- or three-dimensional diagrams. The optimized settings can be directly transmitted to relays, which are able to receive the adaptive settings.

Real-time stability assessment in the control centers of the ISO of Bosnia and Herzegovina and a National Dispatching System in North Africa

This paper describes the implementation of real-time stability assessment in the power system control centers of the Independent System Operator in Bosnia and Herzegovina (NOS-BiH) and, respectively, a National Dispatching System in North Africa. These solutions are conceptually different in terms of stability assessment scope and techniques -- but are very similar in terms of implementation approach. At the NIS-BiH, it provides for rapidly quantifying the risk of blackout, tracking the distance to instability in real-time, and presenting the results in meaningful and user-friendly formats. The technique is based on a fast steady-state stability algorithm that computes the maximum system loadability for the current state and for postulated contingencies. The stability application is seamlessly integrated with the SINAUT Spectrum SCADA/EMS and runs automatically after each successful execution of the State Estimator and/or Dispatchers Power Flow. The North Africa solution is based on dynamic security analysis aimed at evaluating the transient system stability conditions in advance of performing scheduled system outages, e.g., major switching actions such as switching transmission lines or large capacitors. Practical experience results are presented and illustrated.