Ebrahim Shayesteh

Static Equivalent of Distribution Grids With High Penetration of PV Systems

High penetrations of photovoltaic (PV) systems within load pockets in distribution grids have changed pure consumers to prosumers. This can cause technical challenges in distribution and transmission grids, such as overvoltage and reverse power flow. Embedding voltage support schemes into PVs, such as standard

Multi-Station Equivalents for Short-Term Hydropower Scheduling

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Impact of health indicators on maintenance management and operation of power systems

characteristic proposed by the German grid codes, may cause more changes in the steady-state behavior of distribution grids and, in turn, the transmission side. Accordingly, it is important to properly model active distribution grids to analyze the system impacts of these changes to plan and operate future smart power grids. However, due to the high dimension of distribution grids, considering a detailed distribution grid to study the transmission side or a fraction of the distribution grid is either cumbersome or impractical. Therefore, it is required to develop a reasonable equivalent that can fairly capture the dominant behavior of the distribution grids. The aim of this paper is to use gray-box modeling concepts to develop a static equivalent of distribution grids comprising a large number of PV systems embedded with voltage support schemes. In the proposed model, the PV systems are aggregated as a separate entity, and not as a negative load, which is traditionally done. The results demonstrate the superior quality of the proposed model compared with the model with PV systems as the negative load.

Reliability-centered asset management using component reliability importance

Hydropower scheduling in day-ahead electricity markets is complex due to uncertainty in the electricity price. Internal cascade dependency of hydro power plants can also increase this complexity. One way to overcome this complexity is to replace the original hydropower system by an equivalent system, which provides simulation results sufficiently close to the ones of the original system. This paper presents a method to obtain multi-station equivalent models using a bilevel optimization problem, where the objective is to minimize the difference in outcomes between the original and the equivalent models. This bilevel problem is then transformed into a single-level optimization problem that can be solved using standard optimization techniques. Finally, the errors between the simulation results of the original and equivalent hydropower models are computed and analyzed for a Swedish system to show the accuracy of different multi-station equivalents.

Reliability Evaluation of Distribution Structures Considering the Presence of False Trips

This article proposes a maintenance management and risk reduction approach. The approach introduces two reliability-based indexes called condition indicator and risk indicator. Condition indicator is a unit-less parameter that comes directly from monitored condition of a component and converts the categorical condition into a numerical value. Risk indicator in megawatt represents the risk imposed by the health of a component onto the system. To demonstrate application of the indicators, they are implemented through an hourly network constraint unit commitment problem and applied in a test system where the analysis of impact of condition of the generators to the operation is the new contribution. The results demonstrate how addition of such indicators will impact the operation of the grid and maintenance scheduling. The results show the benefit for the system operator as the overall failure risk in the system is taken into account, and the benefit for the asset owner as the direct impact of the maintenance to be carried out can be investigated. Two of the main outcomes of the maintenance management and risk reduction approach are as follows: asset owners can analyze their maintenance strategies and evaluate their impacts in the maintenance scheduling, and system operators can operate the grid with higher security and lower risk of failure.

Analysing correlated events in power system using fault statistics

Asset management is an important topic in all fields especially in power system which has very high investment costs and very expensive elements. Reliability Centered Asset Management (RCAM) is an effective technique to perform the power system asset management with quantitative methods such that, on the one hand, the total cost is minimized and, on the other hand, the reliability of the system is maximized. Nevertheless, the need for an appropriate optimization-based algorithm for RCAM implementation in power system is still sensed. This paper proposes an algorithm to fulfil such needs including the following steps. First, the component reliability importance index is calculated for all components of the system. Then, a set of all potential maintenance strategies of each component are defined and together with the component reliability importance indices are used as inputs in the third step. In the third step, an optimization problem is proposed to select the optimum maintenance strategy for each component in the system. The proposed three-step algorithm is tested on a Swedish distribution system. The results highlight the advantages of the proposed method for well-organizing the maintenance strategies for all components of the system.

Multi-Objective Coordinated Droop-Based Voltage Regulation in Distribution Grids with PV Systems

This paper presents a method for modeling the different modes of failures in a substation and feeder architecture along with updating the possible false tripping scenarios in it. A traditional approach to collectively assess the failure modes using reliability block diagram is reviewed, and the method is updated to count in the unaccounted false tripping scenarios. A generalizable radial feeder branching structure is adopted and the effect of total feeder length and number of feeders from each busbar is examined and modeled with the help of the updated reliability block diagram. The modeled trends are also studied from real-world substation architectures. Thus, the analysis attains an improved estimation of the complex hidden failure probabilities combining theoretical and practical models.

Two partitioning methods for multi‐area studies in large power systems

Power system automation requires logical presumptions made on practical grids to correctly comprehend and manage complex and correlated faults occurring in real world systems. Traditional grid fault analysis methods lack in-depth understanding of these complex events and demand development of approaches that make use of available data to address this problem. Here, the traditional classification approach and challenges relating control equipment in power system are reviewed and a method observing the affected customers during faults along with grid design is discussed based on Swedish case study data. Various contrasting observations are made on the data recorded over two time periods to understand the trend developing over years. Moreover, it will be shown that the classification method also has potential in identifying weak spots in the grid when it comes to the reliability of control equipment.