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This paper describes an integrated operational simulation tool that combines various stochastic unit commitment and economic dispatch models together that consider stochastic loads and variable generation at multiple operational timescales. The tool includes four distinct configurable sub-models within: day-ahead security-constrained unit commitment (SCUC), real-time SCUC, real-time security-constrained economic dispatch (SCED), and automatic generation control (AGC). The unit commitment and dispatch sub-models within can be configured to meet multiple load and variable generation (VG) scenarios with configurable first stage and second-stage decisions determined where first-stage decisions are passed on and second-stage decisions are later determined by other sub-models in a continuous manner. The progressive hedging algorithm (PHA) is applied to solve the stochastic models to maintain the computational tractability of the proposed models. Comparative case studies, considering various configurations of stochastic and deterministic sub-models are conducted in low wind and high wind penetration scenarios to highlight the advantages of the stochastic programming during different decision-making processes. The effectiveness of the proposed method is evaluated with sensitivity tests using both economic and short-term reliability metrics to provide a broader view of its impact at different timescales and decision-making processes.

The electric power industry landscape is continually evolving. As emerging technologies such as wind and solar generating systems become more cost effective, traditional power system operating strategies will need to be re-evaluated. The presence of wind and solar generation (commonly referred to as variable generation or VG) can increase variability and uncertainty in the net-load profile. One mechanism to mitigate this issue is to schedule and dispatch additional operating reserves. These operating reserves aim to ensure that there is enough capacity online in the system to account for the increased variability and uncertainty occurring at finer temporal resolutions. A new operating reserve strategy, referred to as flexibility reserve, has been introduced in some regions. A similar implementation is explored in this study, and its implications on power system operations are analysed. Results show that flexibility reserve products can improve economic metrics, particularly in significantly reducing the number of scarcity pricing events, with minimal impacts on reliability metrics and production costs. The production costs increased due to increased VG curtailment - i.e. including the flexible ramping product in the commitment of excess thermal capacity that needed to remain online at the expense of VG output.

The electric power system has continuously evolved in order to accommodate new technologies and operating strategies. As the penetration of integrated variable generation in the system increases, it is beneficial to develop strategies that can help mitigate their effect on the grid. Historically, power system operators have held excess capacity during the commitment and dispatch process to allow the system to handle unforeseen load ramping events. As variable generation resources increase, sufficient flexibility scheduled in the system is required to ensure that system performance is not deteriorated in the presence of additional variability and uncertainty. This paper presents a systematic comparison of various flexibility reserve strategies. Several of them are implemented and applied in a common test system, in order to evaluate their effect on the economic and reliable operations. Furthermore, a three stage reserve modifier algorithm is proposed and evaluated for its ability to improve system performance.

The Pan-Canadian Wind Integration Study (PCWIS) is the largest of its kind in Canada and was performed to better understand the operational implications of high penetration of wind energy in the power system. A rigorous calculation of the wind capacity value was performed to estimate the potential contribution of the resource to firm capacity. Once this capacity was calculated, the study team assessed the economic and environmental effect of retiring enough coal capacity so that total system's reserves would remain unchanged. The results are presented in this paper, along with a bookend sensitivity, where all of Canada's coal power is retired.

The integration of large amounts of variable renewable generation can increase the demand on flexible resources in the power system. Conventional hydropower can be an important asset for managing variability and uncertainty in the power system, but multi-purpose reservoirs are often limited by non-power constraints. Previous large-scale variable generation integration studies have simulated the operation of the electric system under different penetration levels but often with simplified representations of hydropower to avoid complex non-power constraints. This paper illustrates the value of bridging the gap between power system models and detailed hydropower models with a demonstration case. The United States Western Interconnection is modeled with PLEXOS, and ten large reservoirs on the Columbia River are modeled with RiverWare. The results show the effect of detailed hydropower modeling on the power system and its benefits to the power system, such as the decrease in overall production cost and the reduction of variable generation curtailment.

Electric power systems are currently experiencing a paradigm shift from a traditionally static system to a system that is becoming increasingly more dynamic and variable. Emerging technologies are forcing power system operators to adapt to their performance characteristics. These technologies, such as distributed generation and energy storage systems, have changed the traditional idea of a distribution system with power flowing in one direction into a distribution system with bidirectional flows. Variable generation, in the form of wind and solar generation, also increases the variability and uncertainty in the system. As such, power system operators are revisiting the ways in which they treat this evolving power system, namely by modifying their operating reserve methodologies. This paper intends to show an in-depth analysis on different operating reserve methodologies and investigate their impacts on power system reliability and economic efficiency.

Solar generation is experiencing an exponential growth in power systems worldwide and, along with wind power, is posing new challenges to power system operations. Those challenges are characterized by an increase of system variability and uncertainty across many time scales: from days, down to hours, minutes, and seconds. Much of the research in the area has focused on the effect of solar forecasting across hours or days. This paper presents a methodology to capture the effect of short-term forecasting strategies and analyzes the economic and reliability implications of utilizing a simple, yet effective forecasting method for solar PV in intra-day operations.

Power system operators schedule additional capacity above or below the amount required to meet the expected demand at any time interval to ensure reliable operation. This excess capacity is known as operating reserve. This reserve helps protect against the inherent variability and uncertainty found in the system. As more variable generation resources are connected to the system, the amount of variability and uncertainty is expected to increase. To hedge against this, new operating strategies are being explored. These strategies include developing additional ancillary services and modifying scheduling strategies. This paper presents the results of simulating an additional operating reserve product, referred to as "flexibility reserve," on the IEEE 118-bus test system, and it presents the operational implications on costs, reliability, and pricing that this additional operating reserve may produce.

Operating reserve requirements are a key component of modern power systems, and they contribute to maintaining reliable operations with minimum economic impact. No universal method exists for determining reserve requirements, thus there is a need for a thorough study and performance comparison of the different existing methodologies. Increasing penetrations of variable generation (VG) on electric power systems are posed to increase system uncertainty and variability, thus the need for additional reserve also increases. This paper presents background information on operating reserve and its relationship to VG. A consistent comparison of three methodologies to calculate regulating and flexibility reserve in systems with VG is performed.

Hydro power is one of the most flexible sources of electricity production. Power systems with considerable amounts of flexible hydro power potentially offer easier integration of variable generation, e.g., wind and solar. However, there exist operational constraints to ensure mid-/long-term security of supply while keeping river flows and reservoirs levels within permitted limits. In order to properly assess the effective available hydro power flexibility and its value for storage, a detailed assessment of hydro power is essential. Due to the inherent uncertainty of the weather-dependent hydrological cycle, regulation constraints on the hydro system, and uncertainty of internal load as well as variable generation (wind and solar), this assessment is complex. Hence, it requires proper modeling of all the underlying interactions between hydro power and the power system, with a large share of other variable renewables. A summary of existing experience of wind integration in hydro-dominated power systems clearly points to strict simulation methodologies. Recommendations include requirements for techno-economic models to correctly assess strategies for hydro power and pumped storage dispatch. These models are based not only on seasonal water inflow variations but also on variable generation, and all these are in time horizons from very short term up to multiple years, depending on the studied system. Another important recommendation is to include a geographically detailed description of hydro power systems, rivers' flows, and reservoirs as well as grid topology and congestion.

Variable generation is on track to become a significant contributor to electric power systems worldwide. Thus, it is important to analyze the effect that renewables will have on the reliability of systems. In this paper we present a new tool being implemented at the National Renewable Energy Laboratory, which allows the inclusion of variable generation in the power system resource adequacy. The tool is used to quantify a first estimate of the potential contribution of transmission to reliability in highly interconnected systems and an example is provided using the Western Interconnection footprint.