Interfacing Techniques for Electromagnetic Transient (EMT) and Transient Stability (TS) Simulation

Transcription

1 Interfacing Techniques for Electromagnetic Transient (EMT) and Transient Stability (TS) Simulation Venkata Dinavahi University of Alberta Edmonton, Alberta, Canada. July 2016

2 Outline 1 Introduction 2 Definitions 3 Properties and Limitations 4 Hybrid TS-EMT simulator 5 Integrated simulation 6 Summary

3 Task Force paper Interfacing techniques for transient stability and electromagnetic transient programs IEEE Trans. on Power Delivery, vol. 24, no. 4, pp , Oct

4 Transient stability (TS) The ability of an interconnected power system to maintain its machines in synchronism when the system is perturbed by a large disturbance. Electromagnetic transient (EMT) The response of power system elements to a perturbation caused by external electromagnetic fields such as lightning or to a change in the physical configuration of the network such as switching and loading.

5 Competing modeling needs of TS & EMT simulators Transient stability (TS) simulation Large systems described by nonlinear DAEs. Phasor modeling of power system components. Positive sequence, single-phase analysis. Large integration step-size. A restriction for detailed representation of nonlinear elements and dynamically fast events. Electromagnetic transient (EMT) simulation Detailed modeling of relatively small systems described by nonlinear ODEs. Instantaneous modeling, unsymmetrical, three-phase analysis. Small integration step-size. A restriction for large system sizes.

6 Need for a hybrid simulator Both TS and EMT simulators have merits and drawbacks. A hybrid simulator with EMT-type accuracy and TS-type speed is useful for comprehensive simulation of power systems. The original system is split into two parts: detailed system (EMT) and external system (TS). Detailed System 1 Detailed System 2 Interface Bus 1 Interface Bus 2 External System Detailed System n Interface Bus n

7 Features of a hybrid TS-EMT simulator 1 Detailed system: domain of EMT simulation, corresponds to one or more portions of power system requiring detailed modeling. 2 External system: domain of TS simulation, remainder of the power system. 3 Interface buses: points at which the detailed and external systems interact and exchange data. 4 Interaction protocol: predefined sequential actions which coordinate data exchange. Serial protocol: at each time instant only one simulator runs while the other is idle. Parallel protocol: both simulators run simultaneously.

8 TS-EMT Interaction protocols Conventional protocol TS time-step TS Simulator EMT Simulator EMT time-step Data Exchange Since EMT and TS simulators use different time steps (µs vs. ms), a protocol is required to exchange data and to update equivalent circuits. The time-step of TS simulator is an integer multiple of that of the EMT simulator, and data exchange occurs at common points. The interaction protocol determines which simulator must run and what the sequence of data exchange is.

9 TS-EMT Interaction protocols (contd.) Serial 1 5 t0 t1 t2 t3 TS Parallel 4 t0 t1 t2 TS EMT t0 1 t1 t2 t3 3 EMT t0 t1 t2 2 4 TS 1 5 t 0 t 1 t 2 t 3 Predictor 2 4 TS t 0 t 1 t 2 t3 EMT t0 t1 t2 t3 1 3 EMT t 0 t 1 t 2 t 3

10 Issues involved in the design of a hybrid TS-EMT simulator Equivalent models of external and detailed systems. Identifying domains of study and locations of interface buses. Exchanging data between TS & EMT simulators. Organizing interaction protocol between the simulators. EMT Simulator Waveform-to-Phasor Phasor-to-Waveform TS Simulator

11 Integrated TS-EMT simulation Integrative modeling of EMT and TS as an alternative interfacing method. The models of interest are represented on the basis of frequency-adaptive scheme to cover the application spectrum of EMT and TS. This scheme introduces the shift frequency as an extra simulation parameter in addition to the time-step. Frequency shifting enables the tracking of the instantaneous signal or the envelope. Similar to EMT-type programs, companion models for basic network elements can be constructed.

12 Summary Interfacing is advantageous to leverage benefits of two or more simulation programs. While concepts are well known, challenges remain in implementation of interfacing. New topics of interfacing require investigation. The work of the Task Force is ongoing. You are invited to join. Thank you!