Robert Entriken

Reserve determination for system with large wind generation

This paper presents an application of the stochastic optimal power flow method to determine the energy and reserve schedules for a system with large amount of wind generation. Unlike contingency analysis, the requirements for operating reserves based on the stochastic optimal power flow are not predefined. Instead, the reserve requirement is generated to meet both the system reliability and economic efficiency under system uncertainties. Wind generation is modeled as an uncertain power injection in the stochastic optimal power flow problem. The case study on the WSCC-179 bus system with a large uncertain wind resource in the Tehachapi area shows the impact of intermittent generation on the reserve requirement, and so identifies and addresses emerging system issues regarding the installation of large-scale wind generation. A comparison of the reserve procurement for different levels of wind generation shows the necessity of adequate reserve for system with large wind generation.

Agent-Based Simulation of an Automatic Mitigation Procedure

This paper describes experiments using computer-based agents to simulate the impact of the California ISOs proposed Automatic Mitigation Procedure on market behavior. The agents play the role of market participants by formulating bids to maximize their profits. They exercise their skills under a number of scenarios with and without AMP being present and for various levels of demand and transfer capability over a simple, two-node market. The results of these experiments indicate that AMP is effective in reducing market clearing prices under situations when they would otherwise reach the price cap. In congested networks, congestion rents can be fleeting when suppliers are able to equalize prices across zones through strategic bidding. The analysis of significant issues such as the long-term effect of the AMP on investment incentives or its potential to help coordinate out-of-market activities lies beyond the capabilities of this type of simulation.

Dynamic interactions among multiple FACTS controllers — A survey

Increasing number of Flexible AC Transmission System (FACTS) devices have been be installed to reinforce the existing grid and build the envisioned “Smartness” into the grid through controls and optimization. However, it has been noticed that adverse interactions among multiple FACTS controllers may occur when they are not properly coordinated with each other and other slowly acting system equipment. These interactions can amplify oscillations and even destabilize the system by influencing the damping properties of individual FACTS controllers or increasing voltage deviations. This paper presents an extensive survey on the existing cases, system studies and assessment techniques to help system planners understand the underlying mechanism of diverse interactions among multiple FACTS controllers and develop coordinated control schemes for preventing or mitigating any harmful interactions. Control interactions are categorized and discussed in terms of their root causes and resulting frequency ranges. Unfriendly interactions involving shunt FACTS devices are detailed in which Korean Electric Power Corporation (KEPCO) is particularly interested.

Risk Limiting Dispatch

Risk Limiting Dispatch (RLD) is a new framework that integrates complex inputs and allows decision makers to balance tradeoffs and quantify benefits from increased flexibility and improved forecasting. This paper describes a process of forward-contracting for production capacity while considering the full range of operational uncertainties in generation, demand, forecasts, prices, and the risks of unmet demand or excess generation in real time. RLD accounts for reducing uncertainty, increasing costs, and the opportunity for corrective action at future decision points as one approaches that moment. The stochastic formulation of RLD integrates multiple uncertainties into a unified framework and accepts all kinds of probability distributions. This dynamic optimization approach is comprehensive and considers the flexibility of recourse actions taken at later decision stages, when updated information and improved forecasts become available. For instance, Smart Grid sensor data can be used to update the conditional probability distributions in the formulation. A reliability constraint is accommodated directly in terms of the power balance between supply and demand in real time. Alternative quantitative measures of the risk of power imbalance can be incorporated. For example, optimization can be conducted under the requirement that the risk of power imbalance in real time should be less than 0.1% (or any number).

Language Constructs for Modeling Stochastic Linear Programs

This paper introduces two tokens of syntax for algebraic modeling languages that are sufficient to model a wide variety of stochastic optimization problems. The tokens are used to declare random parameters and to define a precedence relationship between different random events. It is necessary to make a number of assumptions in order to use this syntax, and it is through these assumptions, which cover the areas of model structure, time, replication, and stages, that we can attain a deeper understanding of this class of problem.

Stochastic optimal power flow in systems with wind power

This paper outlines recent work on development of an optimal power flow (OPF) model for use in systems with large amounts of uncertainty, specifically from wind generation. By incorporating the stochastic nature of wind into the OPF, and thus producing a Stochastic OPF (STOPF), the results seen are more robust to wind power output forecast inaccuracies, as well as uncertainties about load, generator and transmission outages. The STOPF problem solves for re-dispatch schedules after contingencies and other uncertain events represented in the model. Hence, it can be formulated to determine the system reserve requirements, validate the sufficiency of reserve procurement, and obtain fast redispatch strategies in real time system operations. Enhancements to an existing STOPF model are described; applications of the model to areas related to high wind power operations are then shown.

Sample Effects of extreme weather on power systems and components, part I: Sample effects on distribution systems

Extreme weather can impact the power system and its components in a number of ways. This paper covers some of these impacts on the electric power system, specifically distribution transformers and underground cables.

Preliminary evaluation of an energy and reserve co-optimization market design for the ISO New England

This paper documents the two parallel activities, the development of a market simulation model of forward and realtime reserve trading, and the results and analysis of numerous experiments on those markets. The experiments serve to incrementally construct our understanding of these markets and to validate the performance of the simulation software. The overall character of the results is typical of economic systems with many interacting commodities utilizing scarce transport. In this case, the forward and real-time reserve products are traded along with energy, transmission, and interfaces. Interfaces act to hold transmission system capacity in reserve, by restricting the total flow over multiple lines to be less than their combined transfer capability. The complications of these interactions can be understood from the constructive process followed throughout the report. We consider the single simultaneous settlement of energy and reserve over uncongested and congested networks and also two settlements of reserve. Competitive and strategic bidding strategies play a critical role in benchmarking and in understanding the potential for the exercise of market power. Experiments with a simplified version of the ISO-NE power system match the past market performance well and help identify potential issues in data collection and market performance.

Linear analysis for determining and visualizing critical thermal boundaries of power systems

System operators need to constantly assess the security of a power system and take actions in order to maintain safe operation. To do this, they need to quantify the proximity of the security constraints, determine the most critical ones, and then execute a set of actions designed to restore safety margins. A particularly important set of security constraints is thermal overload limits of transformers and transmission lines. However, current thermal security assessment practices typically rely on guessing critical power transfers, require repetitive computer simulations, and are limited to two-dimensional nomograms that are constructed off-line. We present techniques for making this process more efficient and effective that use a linear system model and are based on the analysis of a polyhedron in the space of generator and load powers. These techniques have been tested on three real power networks, one of which has 45k buses.

Elementary Analysis of Energy Options for Resource Adequacy

We examine a few elementary cases of forward contracting and a process by which capacity contracts with energy strike prices can lead to incentives for enhanced competition. To motivate and to better enhance the readers understanding of the experiments in the body of this report, we provide an elementary analysis of markets for electricity capacity and energy. It is structured as a sequence of problems and potential solutions for a cast of characters: a regulator, a single buyer, and either a monopoly supply or a duopoly of identical suppliers in a market. This paper lays out sufficient conditions for a competitive equilibrium in the face of inelastic demand using use of two types of contracts, with a monopoly supplier and a symmetric duopoly