Conference Agenda

This paper presents techniques to interface a Transient Stability Analysis (TSA) based model to an ElectroMagnetic Transient (EMT) based model running on a Real Time Digital Simulator. Practical challenges of implementing such an interface are discussed. The proposed TSA model can be simulated using a substantially larger time-step compared to the EMT model. The interface between the EMT model and the TSA model is implemented using a transmission line modeled using Dynamic Phasors (DP). Time-step delay is the primary cause of numerical instability in co-simulations. In this work, a traveling wave model of a transmission line is used to decouple the EMT and TSA networks. The interface requires that the propagation delay of the interfaced transmission lines be greater than the EMT time-step even though the TSA is simulated using a much larger time-step than the EMT model. The proposed technique is validated using the IEEE 39 bus system and a power system with 500 buses.

The main purpose of this research is to speed-up real-time simulations of electromagnetic transients (EMTs) using sparse linear solver techniques. This paper presents the integration of a direct sparse linear solver (KLU) into a real-time software for EMT simulation. This solver is combined with parallelization of network solution. Fill-in reduction techniques are investigated as well as partial refactorization to speed-up computations. The pivoting technique during refactorization is asserted in terms of simulation stability as compared to existing sparse solver based on code generation without pivoting. Performance and validation are studied on practical power system cases with real-time Hardware-In-the-Loop (HIL) simulation. Substantial performance gains, up to 50%, are obtained using fill-in reduction and partial refactorization. Pivoting is necessary to maintain numerical stability.

This paper proposes a one-stage and oscillation free numerical integration method using the compact scheme for electromagnetic transient simulations. Since the compact scheme becomes L-stable at a moment when a circuit suddenly changes to a stiff system, the method is capable of suppressing the spurious numerical oscillations. Moreover, the compact scheme, which is a one-stage method, does not produce spurious spikes due to nonlinear elements. The compact scheme is compared with the trapezoidal method, the two-stage diagonally implicit Runge-Kutta (2S-DIRK) and the trapezoidal method with the second order backward difference formula (TR-BDF2). It follows from the comparison that the compact scheme does not produce the spurious numerical oscillations and spikes.

Hydro-Québec built two static var compensators at the 735-kV La Verendrye substation in 1985. Each has a capacity of +330/-110 Mvar to help regulate system voltage and power system dynamic. They exceeded their useful life, and their operation was becoming challenging due to the aging control technology. Spare part availability and cost were also becoming an issue. A refurbishment project was thus undertaken. Due to design constraints, a hybrid SVC was selected: traditional thyristor-switched capacitors are used, but thyristor-controlled inductors are replaced by full-bridge modular multilevel converters. Throughout the ongoing project, hardware-in-the-loop real-time simulation was used for dynamic performance testing, factory acceptance tests and pre-commissioning studies. Two modeling approaches were used to represent the hybrid SVC: conventional electromagnetic transient simulation and small time-step approach. As this paper demonstrates, both approaches are valid in this case and produce matching results if simulation contrivances are not neglected.

At Hydro-Québec, power system studies are mainly done with offline electromagnetic transient simulation tools and real-time simulation is typically reserved for hardware-in-the-loop studies related to HVDC and compensation system commissioning. However, there is a growing internal need to pursue large-scale power studies incorporating physical systems to explore wide-area monitoring, protection, and control strategies: large power systems must then be ported from offline software to the real-time environment. The current paper presents lessons learned over the years about the offline to real-time porting process. As Hydro-Québec is involved in simulation tool development, software-related issues and challenges are presented and discussed. Details are then provided regarding the porting process of a large-scale power system required for wide-area control explorations. Prior to waveform comparison and performance assessment, modeling details and required modifications on the original simulation schematic are presented. In closing, electromagnetic transient modeling best practices and tricks to facilitate porting offline simulations to real-time are reported here to help users increase the efficiency and performance of their offline simulations and prepare them for real-time operation.

This paper aims to present a guideline formodeling and normative instructions for short-circuit (SC)and transient recovery voltage (TRV) analysis of mediumvoltage circuit-breakers installed in a real industrial system.The Alternative Transient Program (ATP) through its graphicalinterface ATPDraw was used in the work. The criteria usedfor modeling the analyzed industrial system are presented indetail. For a better understanding of the technical informationrequired for the modeling employed in TRV and SC studies,a set of detailed and typical data used is presented in orderto contribute to the reproduction of this case study in otherexpanding industrial power systems. The instructions for SCand TRV evaluation of circuit-breakers are based on the limitsdescribed by IEC standards and other references. The resultsare presented by discussing the effects of industrial expansionon the evaluated medium-voltage circuit breakers.