Voltage Stability Of Distribution Network Research Articles

Reactive power operability of distributed energy resources for voltage stability of distribution networks

The penetration level of distributed energy resources (DERs) is increasing and has significant impact on the voltage stability of distribution networks. Based on the various types of DERs with distinct reactive power characteristics (RPC), their different contributions to the system voltage stability require classification. Firstly, the features of DERs are reviewed and classified based on their RPC, to investigate different distributed generation technologies for reactive power support in distribution networks. Then, the concept of a relative available transmission capacity index (RATCI), which is based on power transfer margin of the power-voltage curve considering the non-negligible distribution network resistance, is proposed to quantify and evaluate the voltage stability by integrating DERs with the defined reactive power types. Case studies have been conducted for an IEEE 33-bus distribution network to calculate the system RATCI for the mixed integration of DERs. Results show that the multi-type and multi-locational integration of DERs can improve the voltage stability of a distribution network.

Impact of Photovoltaic Penetration on Static Voltage Stability of Distribution Networks: A Probabilistic Approach

Impact of Photovoltaic Penetration on Static Voltage Stability of Distribution Networks: A Probabilistic Approach

Study on the Evaluation Index System and Evaluation Method of Voltage Stability of Distribution Network with High DG Penetration

With the development of new energy technologies, distributed generation (DG) plays a growing role in power distribution networks. Although it solves the power supply problem in some areas, it also poses a challenge to the traditional power grid. To help with this problem, we establish a static voltage stability analysis model for high penetration DG, taking into account its large capacity, and the high fluctuations of its output. Based on the theoretical analysis and the mathematical derivation, we propose an improved voltage stability evaluation index (IVSE) accounting for DG. Finally, using the typical circuit of the IEEE 33 & 69 node system, we simulate high penetration DG access in different locations and capacities. In the simulations, the traditional power flow equation is modified by a continuous parametric equation accounting for DG. Based on consideration of the system transmission power limit, voltage stability margin and system loss, the value of IVSE is demonstrated, in comparison with the traditional index. Thus, we verify that the IVSE index is easy to understand, simple to calculate, and highly versatile.

Hierarchical and Distributed Monitoring of Voltage Stability in Distribution Networks

We consider the problem of quantifying and assessing the steady-state voltage stability in radial distribution networks. Our approach to the voltage stability problem is based on a local, approximate, and yet highly accurate characterization of the determinant of the Jacobian of the power flow equations parameterized according to the branch-flow model. The proposed determinant approximation allows us to construct a voltage stability index that can be computed in a fully distributed or in a hierarchical fashion, resulting in a scalable approach to the assessment of steady-state voltage stability. Finally, we provide upper bounds for the approximation error and we numerically validate the quality and the robustness of the proposed approximation with the IEEE 123-bus test feeder.

Assessment of the impact of demand-side management on distribution network voltage stability

The prospect of electricity market liberalisation, increasing renewable power penetration, and network investment deferral has made demand-side management (DSM) a key feature of future smart grid. This study investigates the effect of DSM actions on voltage stability of distribution network. The analysis performed considers the effect that the load reduction, change in load recovery times, and shifting of different type of load from 1 h to the other can have on overall voltage stability of the network. A generic 295 bus distribution network is used to demonstrate this effect.

A coordinated consistency voltage stability control method of active distribution grid

The presence of distributed generators (DGs) with high penetration poses new challenges in the management and operation of electrical grids. Due to the local character of DGs, they could in principle be used in emergency situations to prevent a voltage instability event of the grid. In this paper, a certain method is proposed to coordinate the operation of virtual power plant (VPP) and conventional voltage regulation device to improve the static voltage stability of distribution network with the multi-agent framework. The concept and the general framework of this coordinated control system is introduced, and the voltage instable nodes are determined based on the voltage instability indicator. The voltage coordinated control model of the distribution system is established according to the multi-agent consistency control theory and the coordinated controllers for agents are designed by solving a problem with bilinear matrix inequality constraints. The suggested method is implemented on an IEEE 33 nodes test system and the simulation results show its efficiency and validity.

Research on maximum allowable capacity of distributed generation in distributed network under global energy internet considering static voltage stability

Due to the characteristics of distribution energy such as randomness, volatility and dispersion, the future distribution network will become an intelligent bidirectional power flow distribution system. In addition, the high penetration of distributed generation (DG) will affect the power quality and voltage stability of distribution network. Focused on the impact of distributed energy insert on static voltage stability of distribution network, the maximum allowable capacity of distribution generation for distribution network considering static voltage stability has been been analysed. Firstly, the structure of the future distribution network is analysed, and the calculation model of power flow is established. Then, based on the continuation power flow method, the penetration of distributed energy when the distribution network is in the critical state of the static voltage stability is evaluated. Moreover, the result is used as one indicator of the maximum allowable capacity of DG in distributed network. Finally, the proposed method is illustrated with a typical system. The simulation results show that, with the reasonable configuration of the distribution network, the allowable capacity of DG in distribution network can be improved and energy resources can be optimally dispatched and shared over a wide area.

Impact of large scale photovoltaic generation on voltage stability in distribution networks

Impact of large scale photovoltaic generation on voltage stability in distribution networks

STABILITY ENHANCEMENT BASED ON DISTRIBUTED GENERATION UNITS IN AL-NAJAF AL-ASHRAF ELECTRICAL NETWORK

The operation and structure of distribution system are changing with the integration of Distributed Generation (DG) units, where these units may have effect on power losses, stability, voltage profile, power quality and other quantities. Therefore the optimum location, size and number of DG units are necessary to avoid the negative impacts on electric power system. In this work, the Particle Swarm Optimization (PSO) technique is used to find the optimal number and locations of DG in order to minimize the active power losses. The thermal limit of transmission lines and transformers was studied to detect the lines or transformers which exceed the limit in order to process it. The voltage stability of distribution network has been investigated, using L index method.Â

Effect of distributed generations on reconfiguration and voltage stability of distribution networks considering average hourly load data

Distributed generation (DG) sources are becoming more popular nowadays and they are inevitable in modern large interconnected power systems to meet enormous demands of electrical energy. Such sources could be photovoltaic cells, wind generation, biomass, combined heat power, fuel cells etc. The location and size of distributed generations (DGs) have more impact on energy losses, voltage stability and other benefits also. A method has been proposed in this paper for the placement of DGs in a distribution network. The best nodes once identified, power injection by DGs is optimised using genetic algorithm and particle swarm optimisation methods to reduce power losses, maintain node voltages and branch currents within specified limits. The methods are also compared for getting the best penetration level of DGs at different load levels. It is observed that reconfiguration with DGs at their locations have great impact on power loss reduction and voltage stability improvement. The effect of power injection by DGs and reconfiguration with DGs to the voltage stability of distribution network is examined using a voltage stability index. The proposed technique is demonstrated through an example of 69 node distribution network.

Effect of distributed generations on reconfiguration and voltage stability of distribution networks considering average hourly load data

Effect of distributed generations on reconfiguration and voltage stability of distribution networks considering average hourly load data

Optimal selection of distributed generating units and its placement for voltage stability enhancement and energy loss minimization

Abstract The integration of distributed generation (DG) in distribution network may significantly affect its performance. Transmission networks are no longer accountable solely for voltage security issues in distribution networks with penetration of DGs. The reactive power support from the DG sources greatly varies with the type of DG units and may potentially distress the larger portion of the network from the voltage stability aspects. This paper presents the analysis for the selection of the best type of DG unit among different categories and its optimal location that can enhance the voltage stability of distribution network with simultaneous improvement in voltage profile. Voltage sensitivity index and bus participation factors derived from continuation power flow and Modal Analysis, respectively, are used together for voltage stability assessment and placement of DGs. Changes in mode shapes and participation factors with the placement of DGs are comprehensively analyzed for 33 and 136 nodes radial distribution network.

Research of the Voltage Stability of Distribution Network Connected Induction Machines

There are a lot of wind power plants based on double feed induction machine technology which are connected to electrical network. These usually don’t consider reactive power (even reactive power consumption), so they generally affect the entire network voltage stability and can cause instability in themselves and become no longer balanced by the torque. This paper presents a method to study the relationship between the active power and voltage at the point of common coupling (PCC) connected wind power plant to identify the voltage stability limit. It is a fundament to define a permitted operation region in complying with the voltage stability limit at the PCC connected wind power.DOI: http://dx.doi.org/10.5755/j01.eee.21.1.9804

Steady‐state and transient voltage stability analysis of a weak distribution system with a remote doubly fed induction generator‐based wind farm

AbstractIn modern, stressed distribution system, voltage stability is a major concern from planning and operation perspectives. Remote wind farm connected to a weak distribution system through a long line could adversely affect the voltage stability of the respective distribution network. This paper investigates the transient and steady‐state voltage issues of a distribution network with a distant doubly fed induction generator (DFIG)‐based wind farm. Results show that a distant DFIG‐based wind farm could improve the voltage stability of a distribution network with a large motor load in steady‐state operating condition as well as following disturbances, like three‐phase faults, sudden load tripping, and motor starting.

The importance of spatial distribution when analysing the impact of electric vehicles on voltage stability in distribution networks

The recent emergence of distributed generation, smart meters, and electric vehicles means that much attention is now being given to network modelling and analysis at the distribution, rather than transmission, level. Many optimisation studies, both regarding technical and economic questions, aim to satisfy the constraints posed by grid infrastructure. We explore in detail one of these network constraints, minimum required voltage, at the distribution level and demonstrate that the physical locations of individual loads in the network play a significant role in determining whether voltages throughout the network remain within required limits or not. Our simulations use real distribution network data and are run on models of two real neighbourhoods. We show that the addition of a single load at a weak point of the network can have the same impact as considerably greater numbers of loads at stronger locations of the network. This has important implications for applications such as electric vehicle charging, and suggests that spatial distribution of loads should be taken into account when analysing network stability.

The Research for the Voltage of Distribution Network Including Distributed Generation

There is a challenge to the voltage stability of distribution network when DG is added to the distribution network. By means of theoretical derivation, three conclusions had been got. The amplitudes of node voltage would rise including DG. The more capacity of DG, the higher node voltages. The same capacity of DG met different nodes would have different effects on the node voltages. The farther away from the equilibrium node, the higher voltages. Through a case, the correctness of theoretical analysis had been proved.

Analytical method of the impact of distributed generation on static voltage stability of distribution network and its development

It can’t be ignored that the impact of distribution network to the static voltage stability of the distributed generation. In this paper, we first introduce the stability indices of the traditional grid on static voltage and the analytical method, in the mean time, we put forward the corresponding advantages and disadvantages and applicable scope. Then, we present a summary of the current research on the impact of distribution network to the static voltage stability of the distributed generation at home and abroad from the two aspects of the static voltage stability indices and analytical methods. In the end, the paper points out a new way to improve the distribution network static voltage stability that with the consistency theory to achieve coordinated control of distributed generation, microgrid, as well as virtual power plants, which will be more advantage. This article has a reference value for the analysis of the impact of distributed generation on static voltage stability of the distribution network, as well as researches the measures to improve the static stability. DOI: http://dx.doi.org/10.11591/telkomnika.v11i9.2255

Distributed Generation Allocation to Improve Steady state Voltage Stability of Distribution Networks using Imperialist Competitive Algorithm

Distributed Generation Allocation to Improve Steady state Voltage Stability of Distribution Networks using Imperialist Competitive Algorithm

Research on Intelligent Reactive Power Optimization Method for Distribution Network with DFIG Wind Farm

In order to ensure the voltage stability of distribution network with doubly fed induction generator, it is more significant to determine the reactive power distribution of the grid reasonably except installation of on load tap changing transformer and shunt capacitor bank. However, the reactive power control capability of doubly fed induction generator is not fully implemented in the reactive power optimization of distribution network. In this paper, on the premise of utilizing wind energy maximally, the wind farm with doubly fed induction generator is considered as a continuous reactive power source to participate in the reactive power optimization. Then the constructed reactive power optimization problem is converted to a nonlinear mixed integer optimization problem which is solved by intelligent genetic algorithm. Finally, the IEEE 16 node system is chosen as an example for simulation, the computation results verify the effectiveness of the proposed algorithm.

Reactive power management of distribution networks with wind generation for improving voltage stability

This paper proposes static and dynamic VAR planning based on the reactive power margin for enhancing dynamic voltage stability of distribution networks with distributed wind generation. Firstly, the impact of high wind penetration on the static voltage stability of the system is analysed and then the effect of composite loads on system dynamics is presented through an accurate time-domain analysis. A new index, reactive power loadability (Q-loadability), is used to measure the vulnerability of the network to voltage collapse. Compensating devices are located using Q-loadability to increase the system voltage stability limit. Finally, a cost-effective combination of shunt capacitor bank and distribution static compensator (D-STATCOM) is determined through static and dynamic analyses to ensure voltage stability of the system after a sudden disturbance for different wind penetration levels. This study takes into account the induction motor dynamic characteristics which influence the transient voltage recovery phenomenon. The results show that the proposed approach can reduce the required sizes of compensating devices which, in turn, reduces costs. It also reduces power losses and improves the voltage regulation of the system.