An extension of Newton–Raphson power flow problem

This paper explores an idea to extend Newton–Raphson power flow problem to handle power system transmission line flow limits, by means of generation redispatch and phase shifters. We extend and reformulate the power flow so that it includes a variety of flow limits (thermal, small-signal stability, voltage difference), generation redispatch, and phase shifters. The novelty of the approach is three step procedure (in case any limit violations exist in the system): run ordinary power flow (and identify flow limits violated), solve a set of linear equations using extended power flow Jacobian by adding a new column and a new raw that characterize particular limit, and resolve ordinary power flow with initial solution obtained after the correction made by solution of linear equations. The use of ordinary power flow Jacobian and minimal extensions to it in the case of limits identified makes this approach an attractive alternative for practical use. A simple numerical example and the examples using an approximate model of real-life European Interconnected Power System are included in the paper to illustrate the concept

Dynamic Equivalents of Active Distribution Networks: A short Review

The complexity of modern power systems, despite impressive progress in computational architectures, still necessitate simplified representation of their parts for local dynamic studies. The high penetration of Distributed Generation (DG) at the transmission and distribution network levels, the new load types and increased use of power electronics are among key factors contributing to the systems’ complexity. Particularly, representation of active distribution networks (ADN) in dynamic studies became an important research and practical implementation question. This report shortly reviews previous and existing approaches for dynamic equivalencing of ADNs and offers some recommendations for future research on this important issue. The report is organized as follows. First, the problem of dynamic equivalencing is shortly presented together with approaches to compute them. This is followed by a quick review of past notable works on this problem. Next, the approaches for dynamic equivalencing of ADNs, proposed so far in literature (available to the author), are reviewed. The reports ends with some recommendations for future research

A Component-Based Power System Model-Driven Architecture

This letter describes an approach of applying the model-driven development in power systems. A component-based model-driven architecture,that gives full flexibility of the automation in source code generation,is introduced. A design pattern to code generation is described

New developments in the application of automatic learning to power system control

peer reviewedIn this paper we present the basic principles of supervised learning and reinforcement learning as two complementary frameworks to design control laws or decision policies within the context of power system control. We also review recent developments in the realm of automatic learning methods and discuss their applicability to power system decision and control problems. Simulation results illustrating the potentials of the recently introduced fitted Q iteration learning algorithm in controlling a TCSC device aimed to damp electro-mechanical oscillations in a synthetic 4-machine system, are included in the paper

Trajectory-Based Supplementary Damping Control for Power System Electromechanical Oscillations

This paper considers a trajectory-based approach to determine control signals superimposed to those of existing controllers so as to enhance the damping of electromechanical oscillations. This approach is framed as a discrete-time, multi-step optimization problem which can be solved by model-based and/or by learning-based methods. This paper proposes to apply a model-free tree-based batch mode Reinforcement Learning (RL) algorithm to perform such a supplementary damping control based only on information collected from observed trajectories of the power system. This RL-based supplementary damping control scheme is first implemented on a single generator and then several possibilities are investigated for extending it to multiple generators. Simulations are carried out on a 16-generators medium size power system model, where also possible benefits of combining this RL-based control with Model Predictive Control (MPC) are assessed

A reinforcement learning based discrete supplementary control for power system transient stability enhancement

peer reviewedThis paper proposes an application of a Reinforcement Learning (RL) method to the control of a dynamic brake aimed to enhance power system transient stability. The control law of the resistive brake is in the form of switching strategies. In particular, the paper focuses on the application of a model based RL method, known as prioritized sweeping, a method proven to be suitable in applications in which computation is considered to be cheap. The curse of dimensionality problem is resolved by the system state dimensionality reduction based on the One Machine Infinite Bus (OMIB) transformation. Results obtained by using a synthetic four-machine power system are given to illustrate the performances of the proposed methodology

Increasing the Effectiveness of Interface MW Limits for Maintaining Voltage Security

peer reviewedInterface MW limits are commonly used as surrogates for voltage constraints in DC power flow models. This work proposes a simple improvement to accepted practice so that the interface MW limits better represent actual voltage vulnerability. Weights are assigned to the individual lines in the interface so that the weighted interface MW flows have the same sensitivity to real power injections as the underlying voltage constraints. Calculation of the weights requires the solution of a small dimensional linear regression equation and is of slight computational burden. The weighted interface MW limit is demonstrated to be an accurate proxy for low voltage limits to inter-area transfers using the Nordic test system

Minimal Reduction of Unscheduled Flows for Security Restoration: Application to Phase Shifter Control

More and more transmission system operators, noticeably in Europe, equip their systems with phase shifting transformers to counteract transit flows that take place in a large meshed interconnection. This paper proposes algorithms for the coordinated control of several phase shifters by one operator with the objective of reducing the unscheduled flow through its system. Minimum reduction of unscheduled flow and minimum deviation with respect to present operating point are sought in order to minimize the trouble caused, while ensuring secure operation. Attention is paid to combining pre and post-contingency controls. The resulting algorithms, simple and compatible with real-time applications, are illustrated on a realistic test system

Real-time Corrective Control of Active Distribution Networks

GREDO

Global capacity announcement of electrical distribution systems: A pragmatic approach

We propose a pragmatic procedure to facilitate the connection process of Distributed Generation (DG) with reference to the European regulatory framework where Distribution System Operators (DSOs) are, except in specific cases, not allowed to own their generation. The procedure is termed Global Capacity ANnouncement (GCAN) and is intended to compute the estimates of maximum generation connection amount at appropriate substations in a distribution system, to help generation connection decisions. The pragmatism of the proposed procedure stems from its reliance on the tools that are routinely used in distribution systems planning and operation, and their use such that the possibilities of network sterilization are avoided. The tools involved include: long-term load forecasting, long-term planning of network extension/reinforcement, network reconfiguration, and power flow. Network sterilizing substations are identified through repeated power flow computations. The proposed procedure is supported by results using an artificially created 5-bus test system, the IEEE 33-bus test system, and a part of real-life distribution system of ORES (a Belgian DSO serving a large portion of the Walloon region in Belgium).GREDO