249 research outputs found
On the linear profile of indices for the prediction of saddle-node and limit-induced bifurcation points in power systems
No full textThis brief analyzes the linear profiles presented by certain classes of bifurcation indices with respect to the variation of the loading parameter in power systems. The bifurcation indices discussed here are used in practice to predict proximity to saddle-node and some types of limit-induced bifurcations, given their special profiles. Thus, the linearity of these indices is studied with the help of a simple generic test system. Local analyses and observations are also presented and discussed for realistic power-system models
Loss reduction and loadability enhancement with DG: A dual-index analytical approach
No full textThe high penetration of distributed generation (DG) is a new challenge for traditional distribution systems. Power injections from DG units change network power flows, thereby influencing system losses and voltage stability. This paper presents a new multiobjective index (IMO)-based analytical approach to determine the optimal size and power factor of DG unit for reducing power losses and enhancing loadability. This index is defined as a combination of active and reactive power loss indices by optimally assigning a weight to each index such that the IMO can reach a minimum level. At this level, the optimal location and weights are identified. The proposed methodology has been tested on three typical distribution systems with different characteristics and validated using an exhaustive load flow (ELF) solution. The results show that DG operation with optimal power factor and appropriate weights for active and reactive power losses can significantly reduce power losses and enhance loadability
A simple approach for distributed generation integration considering benefits for DNO
No full textThis paper proposes a simple analytical strategy for distributed generation (DG) integration considering the benefit for distribution network operator (DNO) under the unbundled environment where DG units are owned by DG developers. This benefit arises from network reinforcement deferral and loss reduction due to optimal DG size and operating power factor. The optimal size and power factor are strategically calculated for each location to achieve the highest benefit using the analytical approach. A computational procedure is also developed to accommodate a predefined number of DG units using the proposed approach. The results obtained on a 69-bus test distribution system demonstrate the effectiveness of the proposed methodology and computational procedure. It is observed that the optimal power factor operation can achieve the maximum benefit for DNO, while achieving the optimum voltage profiles and maximizing DG penetration
A dual-index based analytical approach for DG planning considering power losses
No full textThis paper presents a new multiobjective index-based analytical methodology to calculate the optimal size and power factor of distributed generation (DG) unit at various locations. This multiobjective index (IMO) is related to real and reactive power losses. A computational procedure is also developed to specify the best location where the IMO value is the lowest. The results obtained on a 38-bus test system demonstrate the effectiveness of the proposed methodology and computational procedure as validated by an exhaustive load flow solution (ELF). The optimal power factor and indices weights can minimize the IMO value while maximizing DG penetration and achieving the best voltage profile
An optimal operating strategy of DG unit for power loss reduction in distribution systems
No full textThis paper presents a strategy for optimal operation of distributed generation (DG) unit for minimizing distribution system power losses. An analytical approach is used to determine the optimal size and power factor of DG unit when it is placed at various locations. A computational procedure is also developed to identify the best placement at which the total system loss is the lowest. The proposed approach has been tested on a 33-bus distribution system. Importance of operating DG unit at appropriate power factor (PF) for minimizing power losses is first highlighted using an exhaustive load flow solution. The developed method is then used to calculate the optimal power factor. The results demonstrate the validity of the proposed approach in terms of optimal power factor, loss reduction and computational time. It is also shown that the optimal power factor operation can minimize power losses while achieving the optimum voltage profile enhancement and maximizing DG penetration
Assessing the impact of loss reduction on distributed generation investment decisions
No full textThis paper proposes a methodology for evaluating the impact of loss reduction on DG investment decisions. In this methodology, new analytical expressions are first proposed to quickly capture the optimal power factor of each DG unit to maximize loss reduction. The decision for the optimal location, size and number of DG units is then obtained through a benefit-cost analysis over a given planning horizon. Here, the total benefit includes energy sales and additional benefits, namely loss reduction, network upgrade deferral and emission reduction. The total cost is a sum of capital, operation and maintenance costs. The methodology has been applied to a 69-bus test distribution system. The results show that the additional benefits including loss reduction are imperative. Inclusion of these in the analysis would result in faster DG investment recovery
Load leveling and loss reduction by ES in a primary distribution system with PV Units
No full textEnergy Storage (ES) has become an important element in Active Distribution Networks (ADNs) due to progressive integration of renewable energy such as photovoltaic (PV). ES enables high penetration of intermittent PV while bringing several additional benefits to the network. Such benefits include loss reduction, voltage profile improvement and reverse power flow avoidance. This paper presents an analysis of energy loss reduction in a radial distribution network with PV units through load levelling using ES. Simulations are conducted using the GridLAB-D software tool. Analyses show that ES allocated close to the load achieves an energy loss reduction higher than that near the substation. Optimal ES capacity obtained through load leveling produces a maximum energy loss reduction. This capacity is adequate to bring the system load factor close to unity. It is also shown that distributed ES allocation can yield almost twice loss reductions higher than centralized ES placement
Short-term Voltage Stability of Distribution Grids with Medium-scale PV Plants due to Asymmetrical Faults
No full text© 2019 IEEE. With the increasing penetration of photo-voltaic (PV) units into electrical grids, particularly in distribution networks (DNs), the concern of short-term voltage instability (STVI) are growing in the presence of induction motor (IM) loads. On the event of unsymmetrical faults, STVI issues could be more complicated as the next-generation PV systems would require negative sequence power injection into the grid in conjunction with positive one. Therefore, this paper comprehensively investigates the impact of negative sequence power on the short-term voltage stability (STVS) of DNs. The method of characterizing an unbalanced fault and supplementary controls for PV systems are developed. Different case studies are conducted on a balanced IEEE 4 bus and an unbalanced IEEE 13 bus system by injecting different level of negative sequence power considering with and without peak current limitation of the PV converters. It is observed that STVS is likely to be weakened in case of large negative sequence power penetration, while injecting high positive sequence power can cause excessive voltage swell resulting inverter disconnections. Therefore, both positive and negative sequence powers need to be injected optimally to ensure the system's security following a fault
A new grid-support strategy with PV units to enhance short-term voltage stability
No full textModern grid codes demand the integration of voltage support capability with photo-voltaic (PV) generators to ensure a secure and reliable grid operation. On the other hand, short-term voltage instability (STVI) of distribution networks (DNs) is one of the key issues to be addressed due to the rising proportion of induction motor (IM) loads. However, the literature lacks an extensive analysis of short-term voltage stability (STVS) following an unsymmetrical fault in a DN, as well as an effective voltage-support strategy for PV units to improve the STVS while mitigating the excessive voltage swell. Therefore, at first, this paper thoroughly investigates the STVS of a DN subjected to an unbalanced fault. It is perceived that voltage support through conventional methods can increase the risk of STVI and excessive voltage swell. Secondly, a new voltage-support strategy is proposed based on the negative sequence voltage at the point of common coupling (PCC) to improve the STVS and to limit the voltage swell within requirement. The key features of the proposed method are (1) fast and accurate estimation of a network's impedance at PCC is not required, and (2) can be re-designed considering the network behaviors. The proposed method is validated on two IEEE benchmark test systems, and the provided results designate the effectiveness in improving the STVS and alleviating over voltage issues in a DN
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