Dynamic security constrained optimal power flow/VAr planning

Traditionally security constrained optimal power flow and VAr planning methods consider static security observing voltage profile and flow constraints under normal and post contingency conditions. Ideally, these formulations should be extended to consider dynamic security. This paper reports on a BC Hydro/CEPEL joint effort establishing a dynamic security constrained OPF/VAr planning tool which considers simultaneously static constraints as well as voltage stability constraints. This paper covers the details of formulation and implementation of the tool together with the test results on a large scale North American utility system and a reduced Brazilian system     

Load modeling for power flow and transient stability computerstudies

A novel method is presented for preparing load models for power flow and stability studies. The LOADSYN load model synthesis software package transforms data on load class mix, composition, and characteristics into the form required for commonly used flow and transient stability simulation programs. Typical default data have been developed for load composition and characteristics. The load-modeling techniques used in this software and results of initial testing are described. Significant improvements in simulation accuracy are demonstrated     

A future application environment for BC Hydro's EMS

The paper reports on the results of a tailored collaboration project sponsored by BC Hydro and EPRI to review the state-of-the-art in EMS architectures addressing the necessary attributes of a modern EMS with respect to scalability, database and user interface openness, flexibility and conformance to industry standards, as well as to provide a migration path for the existing BC Hydro's EMS. This review was intended to assist BC Hydro in identifying functionality and standard requirements of future EMS procurements and a migration path for a future BC Hydro application program environment. The proposed migration path was prototyped to verify its prudence and applicability in providing an open architecture environment for EMS applications. The BC Hydro On-Line Voltage Stability Analysis (OLVSA) application developed by BC Hydro and Powertech Labs was chosen and integrated into the prototype     

Power system equipment aging

This article discussed the issues around power system equipment aging, including concepts of equipment lifetime, approaches to estimating the mean life and age, Weibull and normal-distribution-based models to assess the end-of-life failure probability. The relationship between aging and maintenance activities, limitations of maintenance in extending equipment life, and determination of timing of retirement were also discussed. A few examples showing actual data of transformers, cables, and reactors at BCTC have been presented. Maintenance activities can extend the life of equipment but could be very costly for equipment at their end-of-life stage. A compromise between maintenance and replacement must be carefully considered. RCM and probabilistic analysis approaches are available for utilities to guide maintenance activities and manage aged assets in a more efficient and economic manner.     

Load Models for Large-Scale Stability Studies from End-User Consumption

This paper summarizes improvements in the application of load models in power system stability studies by utilizing end-user energy consumption data to identify the composition of loads. The project included derivation and compilation of customer load characteristics for the Ontario Hydro System and subsequent interfacing with a transient stability program. Results from these models were compared with recordings of a recent Ontario Hydro system disturbance.     

Dynamic security contingency screening and ranking using neuralnetworks

This paper summarizes BC Hydro's experience in applying neural networks to dynamic security contingency screening and ranking. The idea is to use the information on the prevailing operating condition and directly provide contingency screening and ranking using a trained neural network. To train the two neural networks for the large scale systems of BC Hydro and Hydro Quebec, in total 1691 detailed transient stability simulation were conducted, 1158 for BC Hydro system and 533 for the Hydro Quebec system. The simulation program was equipped with the energy margin calculation module (second kick) to measure the energy margin in each run. The first set of results showed poor performance for the neural networks in assessing the dynamic security. However a number of corrective measures improved the results significantly. These corrective measures included: 1) the effectiveness of output; 2) the number of outputs; 3) the type of features (static versus dynamic); 4) the number of features; 5) system partitioning; and 6) the ratio of training samples to features. The final results obtained using the large scale systems of BC Hydro and Hydro Quebec demonstrates a good potential for neural network in dynamic security assessment contingency screening and ranking.     

Large scale voltage stability constrained optimal VAr planning andvoltage stability applications using existing OPF/optimal VAr planningtools

Traditionally in optimal VAr planning, the feasible operation has been translated as observing voltage profile criteria ensuring that the system voltage profile is acceptable for system normal and post contingency conditions. This feasibility definition is not sufficient when considering the VAr planning practice of the utilities concerned with voltage stability problems. Presently, these utilities use two reinforcement criteria for VAr additions. While for VAr design in the regions the voltage profile criteria is considered, for bulk transmission system VAr resources are designed to guard against voltage instability. This paper reports on the findings of a recently completed EPRI project evaluating the existing optimal VAr planning/OPF tools for voltage stability constrained VAr planning and voltage stability applications. Two of the selected tools were adapted to address these applications on four large scale utility systems (up to 6000 buses). The results were also verified using EPRI's voltage stability program (VSTAB). The results obtained indicate that OPF/VAr planning tools can be used to address voltage stability constrained VAr planning and voltage stability applications in an accurate way. Additional advantages offered by these tools are easier procedures, less computation and avoidance of engineering judgment in identifying the amount of VAr requirement at the candidate sites     

Opening Up for Interoperability

An overview of the open architecture for the control center modernization and consolidation project at British Columbia Transmission Corporation (BCTC) is discussed. The design is based on the technology strategy of creating a long-term, cost-effective, sound, and sustainable solution. The integration solution provided allows modular introduction of new applications and upgrading of individual applications without impacting the rest of the system. The approach consists of a pragmatic, real-world decision-making framework that addresses multiple conflicting requirements and constraints. The architecture creates an open and flexible framework for evolving the consolidated control centers into a scalable infrastructure for evolution and implementation of a long-term roadmap.     

General nonlinear modal representation of large scale power systems

In this paper an approach is devised to represent, and study the behavior of, nonlinear dynamic systems using general nonlinear modal representation. This approach is shown to compare favorably to the normal form of vector field technique, the other methodology used for this purpose, in that it is valid under resonance conditions and it does not require nonlinear transformation. By representing the system more accurately and in terms of its modes and their interactions, it would be better suited to be used for understanding and analyzing complex behavior of stressed power system and also in designing various controls for the system. This method can represent a nonlinear system with any order of nonlinearity and provides the solution to the system nonlinear differential equation employing Laplace transformation. The accuracy and robustness of the method has been validated using three systems, two of which model realistic utility power systems under stressed conditions.