L.R. Linares’s research while affiliated with University of British Columbia and other places

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Publications (12)


Fig. 1. Sample network for MATE explanation. 
Fig. 4. Interconnection of a fast and slow subsystem. 
Fig. 5. Timeline of the simulation at a general time interval when latency is exploited.
Fig. 6. Thevenin equivalent representation of slow and fast subnetworks at linking nodes.
Fig. 7. Thevenin equivalent voltage source linear interpolation for 1T = 41t. 

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Multirate Simulations With Simultaneous-Solution Using Direct Integration Methods in a Partitioned Network Environment
  • Article
  • Full-text available

January 2007

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435 Reads

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44 Citations

IEEE Transactions on Circuits and Systems I Regular Papers

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Jr. Zanetta L. C

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Luis R. Linares

Multirate simulation of electric networks exhibiting a wide variety of time constants decreases the simulation runtimes by exploiting the property of circuit latency. The fundamental idea is to use different integration steps for different network subsystems, according to the requirements of accuracy of each subsystem. Programs that exploit circuit latency are usually based on relaxation methods that require iterations among the different subsystems of the original networks. These methods lack the numerical robustness of direct implicit integration methods used in circuit simulators and are not adequate for real-time simulation due to their non-uniform solution times. This paper proposes circuit latency exploitation without iterations making use of the concept of interlinked Multi-Area Thevenin Equivalents (MATE). Results are presented showing the efficiency and accuracy of the method

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Multilevel MATE for Efficient Simultaneous Solution of Control Systems and Nonlinearities in the OVNI Simulator

September 2006

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85 Reads

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47 Citations

Power Systems, IEEE Transactions on

This paper presents the solution approach for simulation of control systems and nonlinearities used in UBC's Object Virtual Network Integrator (OVNI) power system simulator. OVNI is aimed at simulation of full-size power system networks in real time using integrated software/hardware solutions. The software solution is based on the Multiarea Thevenin Equivalent (MATE) network partitioning framework. Multilevel MATE expands the concept of MATE to a subsystem level, allowing for the efficient inclusion of controllers' equations and nonlinearities


Electromagnetic transients simulation with different time steps–The latency approach

January 2003

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67 Reads

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12 Citations

This paper presents techniques for an efficient and accurate latency exploitation of electric network solutions based on time-domain transients simulation program, such as the "Electromagnetic Transients Program" (EMTP). Latency or multirate simulation is related to the capability of numeri-cally solving the differential equations governing the behav-iour of electric networks with multiple integration steps. With this approach, the limitations of a single and fixed-size inte-gration step as required by EMTP-type programs can be overcome, resulting in a decreased number of numerical op-erations for a given total simulation time. Using the MATE solution framework of "Multi-Area Thévenin Equivalents", latency exploitation is achieved using non-iterative solutions. A test case is derived and results are presented and compared with those obtained from conventional EMTP simulations.


A resynchronization algorithm for topological changes in real time fast transients simulation

January 2002

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50 Reads

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15 Citations

To guarantee the synchronization between the digital simulation and the associated equipment that inter-faces it with the real world, as well as to reduce the com-putational burden necessary during every integration step, real time digital simulation of electric power networks rely on the use of constant-size integration steps. The network state is determined only at certain equidistant points along the time axis, the deadline-rendezvous points. These series of rendezvous points mark the synchronism between the simu-lator and the real world. Changes of the network topology occur, however, asynchronously with respect to that stream of samples. In simulators of the EMTP type, accounting for those topological changes is currently postponed until two deadline-rendezvous points later. This delay introduces un-acceptable errors in the simulation, particularly in cases with an intense switching as in the case of simulation of power electronics devices. In this paper, a new method with re-duced computational overhead and no prediction, for the in-clusion of those topological changes as soon as possible, is introduced. Keywords -EMTP simulation of power electronic de-vices, switching asynchronous events in fixed time steps simulators, numerical oscillations in circuit solutions, real time simulations, the OVNI simulator.


Efficient and accurate representation of asynchronous network structure changing phenomena in digital real time simulators

June 2000

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83 Reads

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44 Citations

Power Systems, IEEE Transactions on

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Luis Linares

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[...]

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Xavier Lombard

Due to synchronization requirements related to the interfacing with external systems, digital real time simulators of electromagnetic transients for equipment testing employ a constant integration time step width for solving the network equations. Therefore, the network solution is only calculated at discrete and equidistantly spaced time instants while in reality the time domain is continuous. Changes in network structure that occur between the discrete solution points are generally not simulated exactly. This can lead to switching control mistakes and numerical problems. In this paper the novel clock synchronized structure changing concept, which allows the accurate and efficient simulation of structural changes at arbitrary time instants, is presented


Efficient HVDC converter model for real time transients simulation

March 1999

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48 Reads

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21 Citations

Power Systems, IEEE Transactions on

An efficient model has been developed to simulate high voltage direct current (HVDC) power converters in real-time transient simulators. Real time performance of 45 μs per solution step has been achieved for a 12-pulse monopolar converter and 81 μs for the bipolar converter using a single processor Pentium Pro 200 MHz desktop computer. The HVDC power converter model is solved simultaneously with the power network. Simultaneous solution makes the model capable of sustained long-time simulation for real time testing of system performance and control functions


OVNI: an object approach to real-time power system simulators

September 1998

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50 Reads

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64 Citations

This paper presents the solution approach and implementation strategy followed in the development of the OVNI (“Object Virtual Network Integrator”) power system simulator. OVNI's aim is to represent full-size power system networks for real-time and online simulation. To cope with the dimensions of the problem, partitioning techniques are required, both in the system solution and in the hardware implementation. OVNI implements the MATE concept (“multi-area tearing equivalent”) for network partitioning. In addition to the considerable solution speedups that can be achieved, the MATE concept is particularly suited for software implementation using object-oriented techniques and for hardware implementation using parallel processing schemes


Current transformers and coupling-capacitor voltage transformers in real-time simulations

February 1997

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69 Reads

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48 Citations

IEEE Transactions on Power Delivery

This paper describes two models: a saturable current transformer model (CT) and a wide-band coupling capacitor voltage transformer suitable for real-time transients simulation. By using very efficient network reduction and network synthesis techniques, the operations count for these models is kept to a minimum. The accuracy of the models has been tested in connection with our real-time transients simulator RTNS and compared to conventional EMTP models



Real-time EMTP-based transients simulation

September 1994

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53 Reads

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116 Citations

Power Systems, IEEE Transactions on

A computer program has been written for the simulation of power system transients in real time. The program is based on EMTP models and solution techniques optimized for maximum performance in superscalar computer architectures. Timings ranging from 38 to 107 μs have been obtained for systems from 18 to 30 nodes using an IBM RISC System/6000 Model 560 workstation. These timings are considered adequate for real-time testing of protective relaying equipment. The program is compatible with existing EMTP data cases


Citations (10)


... See Fig.1.1. These efforts are part of the OVNI project [18], [13], [19], [20], [21] Figure 1.1: Relation among research projects at UBC power system group real-time power system simulator. By breaking the power network solution into subparts while maintaining simultaneous solution of all the parts, the Real-Time Power Systems group at UBC has developed a PC-Cluster simulator made up of an extensible number of off-the-shelf inexpensive PC boards that is capable of simulating in real-time fast system phenomena for systems of practically any size just by extending the number of PC boards interconnected. ...

Reference:

Step-by-Step Eigenvalue Analysis With EMTP discrete-time Solutions
Network Decoupling by Latency Exploitation and Distributed Hardware Architecture
  • Citing Article

... Thus corrective measures to account for the errors due to ITS events are needed. These corrective measures utilize time stamping techniques and interpolations/extrapolations to (i) register the exact switching time instance, (ii) determine the system variables at the switching time instant, and (iii) resynchronize the simulator output with the simulation time grid [19][20][21][22][23][24]. It should be noted that the corrective measures have limitations. ...

A resynchronization algorithm for topological changes in real time fast transients simulation
  • Citing Article
  • January 2002

... This part of the network is integrated using an integration step greater than the one used for the network part modeled in detail. Multirate models previously proposed12 are based on only one low-frequency channel. Clearly its computing requirements are reduced as long as the decimation factor is increased. ...

Electromagnetic transients simulation with different time steps–The latency approach
  • Citing Article
  • January 2003

... Of these works, the parallelization of EMTP stands out through the automatic detection of submatrices decoupled by transmission lines [4], [5]; methodology that has already been implemented in recent versions of EMTP-RV and PSCAD/EMTDC but that is limited to the number of cores available in the CPU. Also, since 2000, methods have been presented based on the division of EPS into subsystems or areas that can be solved independently and in parallel [6]. These methods gave rise to the MATE (Multi-Area Thevenin Equivalents) solution framework that adds to the strategy of division into subsystems the concept of Thevenin equivalents, which allows reconciling the solution of the subsystems through a reduced system for the links between subsystems [7], [8]. ...

OVNI: an object approach to real-time power system simulators
  • Citing Conference Paper
  • September 1998

... This method is particularly suitable for power systems containing IGCT because the high-speed switching characteristics of the IGCT require the simulation algorithm to accurately capture rapid dynamics. References [73,74] propose a multi-rate electromagnetic transient simulation based on latency technology, optimizing the solution process of slow dynamic systems and fully utilizing the results of fast dynamic systems (such as IGCT operations), thereby improving the accuracy and efficiency of the simulation. Reference [75] utilizes fully implicit integration and interpolation methods and achieves parallelization of the simulation algorithm through transmission line partitioning, proposing a parallel multi-rate electromagnetic transient simulation algorithm suitable for power systems containing IGCT. ...

Multirate Simulations With Simultaneous-Solution Using Direct Integration Methods in a Partitioned Network Environment

IEEE Transactions on Circuits and Systems I Regular Papers

... Data on iron losses in the saturation region at high flux densities are not available in the catalog, so they are obtained using linear interpolation. The Piecewise Linear Saturation Model [24,92,93] is commonly employed to calculate steel losses and account for the saturation phenomenon. This model only requires values for the saturation curve, which are specified for each steel grade. ...

Current transformers and coupling-capacitor voltage transformers in real-time simulations
  • Citing Article
  • February 1997

IEEE Transactions on Power Delivery

... In contrast, the delay-free decoupling method has better numerical stability. Diakoptics [18] was the earliest delay-free network partition idea, which was further developed by relevant scholars into a series of interface models such as bordered blocked diagonal matrix method [19,20], compensation model [21,22], and multi-area Thevenin equivalent model [23,24]. These methods used the associated branch to divide independent subsystems, and they could also be called the branch cutting method. ...

Multilevel MATE for Efficient Simultaneous Solution of Control Systems and Nonlinearities in the OVNI Simulator
  • Citing Article
  • September 2006

Power Systems, IEEE Transactions on

... On the other hand, switching operation events do not occur exactly at the constant-step intervals, and delays in the switching operation cause the emergence of unreal "spikes" [21] in the waveform and, thus, harmonics, which requires an accurate simulation of the switching operation through the variable time-step algorithm or interpolation method [22,23]. This requires multiple interpolations [22,24] or flexible integration for readjustment in the simulation of transients [25] to achieve resynchronization during real-time simulations. The interpolation method is a good choice because it does not change the admittance matrix of the network. ...

Efficient and accurate representation of asynchronous network structure changing phenomena in digital real time simulators

Power Systems, IEEE Transactions on

... Also, since MATE uses the MNA branch equations, switches can be modeled to prevent topological changes to the system which avoids re-triangularization of subsystems [41]. For applications such as HVDC converter, significant speedups have been reported [3]. ...

Efficient HVDC converter model for real time transients simulation
  • Citing Article
  • March 1999

Power Systems, IEEE Transactions on

... To allow for the growing size of analyzed systems, while maintaining a high resolution in the time domain required by switching devices, many simulations employ techniques of parallel computing [4][5][6][7][8][9], such as parallelization of calculations of different components [10,11]. Modern power electronics devices are increasingly penetrating power systems, while requiring even smaller time-steps and, thus, slowing down simulations [12]. ...

Real-time EMTP-based transients simulation
  • Citing Article
  • September 1994

Power Systems, IEEE Transactions on