Power-flow study

About: Power-flow study is a research topic. Over the lifetime, 8091 publications have been published within this topic receiving 155053 citations. The topic is also known as: load-flow study.

Contingency-Constrained Unit Commitment in Meshed Isolated Power Systems

Abstract: This paper presents a mixed-integer linear optimization problem for unit commitment and economic dispatch of power generators in a meshed isolated power system. The optimization problem is referred to as the optimal reserve planning problem (ORPP). The ORPP guarantees that the system frequency is kept above a predefined limit in the event of a contingency. The minimum frequency constraints are formulated using novel sufficient conditions that take into account the system inertia and the dynamics of the power generators. The proposed sufficient conditions are attractive from both a computational and a modelling point of view. We compare the ORPP to a unit commitment problem that only considers the stationary behavior of the frequency. Simulations based on a Faroe Islands case study show that, without being overly conservative, potential blackouts and power outages can be avoided using the ORPP. In the particular case study, the cost increase associated with the additional security provided by the ORPP is less than 3%.

Network Capacity Assessment of Combined Heat and Power-Based Distributed Generation in Urban Energy Infrastructures

Abstract: The growing penetration of distributed generation (DG) and use of combined heat and power (CHP) techniques have made electrical distribution systems and water distribution systems increasingly interdependent. This paper proposes an integrated dispatch model that offers a generalized means for determining the potential accommodated DG capacity along with appropriate DG sitting for given urban electricity and water system configurations. The AC optimal power flow (ACOPF)-based system model was developed for each phase of a modified electrical distribution test feeder. A corresponding water distribution system was then designed with its mathematical model developed. A mathematical model of the CHP-based DG system was also developed to couple the electricity and water systems. Results indicate the optimal DG capacity and its optimal sitting based on urban electricity and water infrastructures. The present water network cannot support the complete recovery of the exhaust heat. The mutual impacts on operational performances of CHP-based DG units and urban energy infrastructures were also investigated.

A comparison of voltage stability indices

Abstract: The stressful condition of power system and high transmission losses leads to voltage security and reliability problems of system operation. If the voltage stability is not assessed and the problems occurred are not mitigated properly, cascading events may occur and this may lead to voltage collapse or blackout events. Therefore, there is a need to assess the voltage stability in order to detect the voltage collapse point and mitigate it when it occurs. This paper aims to compare four existing voltage stability index performance towards reactive and real power load changes. The performances are analyzed theoretically, and using simulation on IEEE 30-bus test system. Total power loss is also observed for each case. The comparison shows that all indices are prone to either reactive or real load power changes only. None of the indices are sensitive towards both power loads changes. Meanwhile, the total power loss is mostly contributed by reactive power losses.

Reactive power optimization based on genetic algorithm

Abstract: This paper presents an improved genetic algorithm (GA) for optimizing power system reactive power. Based on a basic GA, an integer/float mixed coding GA is proposed in this paper. The objective function of the proposed method is to minimize the system active power loss. The control variables are generator bus voltages, transformer tap positions and switchable shunt capacitor banks. The refined GA overcomes the drawbacks of conventional reactive power optimization methods. The proposed method has been applied to the practical ward-Hale 6 bus system and IEEE 30-bus system. The test results show that this method is a very feasible and practical method.

Optimal power flow analysis of a Switzerland׳s transmission system for long-term capacity planning

Abstract: Optimal power flow modelling of large and complex power transmission networks is an essential tool for investors and policy makers for the development of energy technologies, security, trade, and policy-making. However, an analysis of a country׳s power system can be impeded by scarcity of operational information. This paper presents an integrated approach of geographically indexed production, demand and grid modelling for large-area power systems. This approach is validated through the accurate identification of transmission lines in Switzerland that have been earmarked for improvement. Furthermore, methods are developed to account for variance in the loading of transmission lines, and physical models are used to accurately model wind-generated electricity. A scenario for the development of wind power in Switzerland is analyzed and it is shown that in prospective regions of wind power development Switzerland׳s grid is capable in its current state of providing congestion-free dispatch.