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Real Time Transient Stability Systems
The recovery of a power system subjected to a severe large disturbance is of interest to system planners and operators. Typically the system must be designed and operated in such a way that a specified number of credible contingencies do not result in failure of quality and continuity of power supply to the loads. This calls for accurate calculation of the system dynamic behavior, which includes the dynamic characteristics of the rotating machines, generator controls, static var compensators, loads, protective systems and other controls. Traditional energy management systems use static analytical tools for system static security assessment. These include checking the limit violations from the output of state estimators, Contingency Ranking and Contingency Evaluation. The contingency ranking algorithms are typically based on approximate load flow methods and rank contingencies in the order of maximum to minimum severity. These contingencies are then evaluated in more detail by contingency evaluation algorithms which are typically full AC load flow solution methods. However, these AC load flow based contingency evaluation, fails to capture the dynamic behavior involved during the contingency events, during which time system security could be lost.
Kalkitech solution for dynamic system stability is based on our power system analysis software – PowerApps. The PowerApps Transient Stability Module can be integrated into existing SCADA / EMS system and uses the base case real time state estimation output to perform the contingency evaluation listed by the operators and flag alarms whenever a contingency event results in unacceptable operating conditions.
Support Documents
Transient stability analysis can be used for dynamic analysis over time periods from few seconds to few minutes. Transient Stability Analysis simulation module in PowerApps is used for simulating electromechanical transients in three phase electric power systems. It features an extensive library of equipment and controller models, the capability to include user-defined controls, a very flexible user-interface and powerful graphics. Transient Stability Analysis module utilizes the simultaneous implicit trapezoidal integration solution technique for network, machine and controller equations. The program supports the capability to test the step response of controllers and User Defined Modeling for system equipment and controllers.
Existing EMS facilities in the energy control center of the utility, has state estimation and static security assessment tools, which run according to user defined time schedules. The transient stability analysis module takes the input from the state-estimation module of the EMS and also has its own time schedule, based on the number of contingencies evaluated and duration of time domain simulation for each contingency list. Typically a scheduler is developed to coordinate between the State Estimation outputs and the Dynamic Contingency Evaluation by Transient Stability Algorithm. The operators can configure the scheduler to execute the transient stability algorithm after every specified time interval, which is mentioned in minutes. When the scheduler starts, it obtains the most recent state estimation output, along with network data and data needed for transient stability analysis and contingency event lists. The design is such that, user can examine any number of disturbance scenarios on the base case provided by the state estimation. Each disturbance scenario or contingency scenario may contain one or more disturbance or contingency events.
The operators can specify a set of dynamic state variables to be monitored during dynamic simulation using transient stability simulations. These variables will be continuously displayed during the simulation as and when the monitored state variables are computed and updated by the transient stability algorithm. These may include, generator frequencies, relative rotor angles, bus voltages, line flows, generation outputs, or any other state variables that are computed by the transient stability analysis. Apart from these continuously monitored variables that are displayed for all the chosen contingency lists, operator can examine any other variables of interest that are stored in the report file, by means of suitable graphics and draw conclusions. Thus the facilities provided displays the continuously monitored variables as well as allows for checking the behavior of any other variables of interest from stored simulation output database.
Existing EMS facilities in the energy control center of the utility, has state estimation and static security assessment tools, which run according to user defined time schedules. The transient stability analysis module takes the input from the state-estimation module of the EMS and also has its own time schedule, based on the number of contingencies evaluated and duration of time domain simulation for each contingency list. Typically a scheduler is developed to coordinate between the State Estimation outputs and the Dynamic Contingency Evaluation by Transient Stability Algorithm. The operators can configure the scheduler to execute the transient stability algorithm after every specified time interval, which is mentioned in minutes. When the scheduler starts, it obtains the most recent state estimation output, along with network data and data needed for transient stability analysis and contingency event lists. The design is such that, user can examine any number of disturbance scenarios on the base case provided by the state estimation. Each disturbance scenario or contingency scenario may contain one or more disturbance or contingency events.
The operators can specify a set of dynamic state variables to be monitored during dynamic simulation using transient stability simulations. These variables will be continuously displayed during the simulation as and when the monitored state variables are computed and updated by the transient stability algorithm. These may include, generator frequencies, relative rotor angles, bus voltages, line flows, generation outputs, or any other state variables that are computed by the transient stability analysis. Apart from these continuously monitored variables that are displayed for all the chosen contingency lists, operator can examine any other variables of interest that are stored in the report file, by means of suitable graphics and draw conclusions. Thus the facilities provided displays the continuously monitored variables as well as allows for checking the behavior of any other variables of interest from stored simulation output database.
Typical System Architecture for real-time transient stability studies:
Key Features of the online transient stability system includes:
- Transient Stability models of excitation systems, turbine governors, static-var compensators, power system stabilizers and HVDC controllers
- Facility to monitor the variables of interest during simulation by way of suitable time domain graphics displays
- Storing of all variables of interest and their time domain response for each contingency scenarios and events in a database for later post processing, review
- Modeling of over current relays, under voltage relays, over voltage relays, under frequency relays, over frequency relays, distance relays and their automatic tripping action within the transient stability module
- Asymmetrical bus faults such as single line to ground fault, line to line fault, double line to ground fault, apart from standard three phase faults
- Fault specifications in the middle of line at any distance from the terminal of the line, covering all specified asymmetrical faults
- Single pole open / close and Two Pole open / close or single conductor open / close, two conductor open / close series fault simulations
- Load shedding schemes based on specified frequency
- Load Change specifications during dynamic simulation
- Loss of generation
- Modification of power reference set point as a dynamic event for the generators to alter their Mw output
- FACTS controllers – SVC, TCSC, Phase Shifters, HVDC links and their controls
- Choice of generator models. From, simple classical generators with constant voltage behind transient reactance to modeling detailed synchronous machines with variable voltages behind sub-transient reactances
- Standard IEEE excitation system models and turbine and governor models (standard IEEE models for power system equipments).
Kalkitech PowerApps
PowerApps is an integrated Power Systems Analysis Software and Simulation package that includes the Graphic User Interface, Data Base Manager and Electrical Equipment Parameter Estimation for creating the network one-line diagram and associated database. PowerApps offers both graphical and tabular data entry modes, user-preferred single-line diagram drawing options and advanced facilities for reporting, plotting and customizing the simulation reports. The design of PowerApps recognizes the fact that there is no memory restriction in present day computers. Consequently, PowerApps has no built in dimensioned variables and the needed memory for analysis of any system is allocated dynamically during execution time.
PowerApps calculation engine is the backend of PowerApps that does calculations needed for various power system / electrical system analysis / design and studies. Given below is a summary of the calculation modules available with PowerApps engine
PowerApps is an integrated Power Systems Analysis Software and Simulation package that includes the Graphic User Interface, Data Base Manager and Electrical Equipment Parameter Estimation for creating the network one-line diagram and associated database. PowerApps offers both graphical and tabular data entry modes, user-preferred single-line diagram drawing options and advanced facilities for reporting, plotting and customizing the simulation reports. The design of PowerApps recognizes the fact that there is no memory restriction in present day computers. Consequently, PowerApps has no built in dimensioned variables and the needed memory for analysis of any system is allocated dynamically during execution time.
PowerApps calculation engine is the backend of PowerApps that does calculations needed for various power system / electrical system analysis / design and studies. Given below is a summary of the calculation modules available with PowerApps engine
- Single / three phase load flow analysis
- Short circuit calculations / Conventional / IEC 60909 / ANSI
- Transient Stability Analysis (Large Signal Performance)
- Dynamic Stability Analysis (Small Signal Performance)
- Static Voltage Stability Analysis
- Relay Coordination (Overcurrent phase / earth / instantaneous / distance)
- Motor Starting Studies / Motor Acceleration Studies
- Optimal Power Flow / Economic dispatch / Reactive power optimization
- Harmonic analysis / Filter Design / Impedance Scan
- Short Term Load Forecast
- Long Term Energy and Demand Forecast
- Power System Stabilizer Applications
- Contingency Ranking and Evaluation
- Network Topology Processor
- Observability analysis
- Static State Estimation
- Ground mat design
