Adedayo A. Yusuff

Optimal location identification of FACTS devices through genetic algorithm and the network structural characteristics techniques

In this paper, the use of techniques based on the Artificial Intelligent (AI) and the network topological structure of the power system network, for optimal location of the reactive power compensator is investigated. To determine the suitable location for the power electronics based UPFC and TCSC FACTS devices, with the proposed Network Structural Characteristics Participation factor (NSCPF), the critical mode and the associated eigenvectors of the system are found. Comparative analysis with an optimization technique of genetic algorithm (GA) to determine the optimal location, size and rating of each UPFC and TCSC FACTS devices is also carried out. All the techniques presented are tested on the IEEE 14 bus power system. The results of simulation obtained show that, the proposed NSCPF is more superior in the identification of suitable nodes for the placement of FACTS devices compared to the traditional approach of GA, as it saves time and require no iteration processes before the best location is identified.

Identification of suitable nodes for the placement of reactive power compensators

The occurrence of Voltage collapse has been considered a frequent phenomenon in the recent time and has been a growing concern to the power system utility. Thus, the importance of identifying nodes where reactive power compensator can be placed for voltage stability enhancement. This paper proposed a technique based on the network topological structure of the power system. The suggested technique is found by computing the critical mode and the associated eigenvectors of the system. The node, which has the highest contributions to the critical mode identified is computed and considered as the weakest node. Comparative analysis of the suggested approach with the power flow based technique of modal analysis is also done. The results obtained show that suitable node for the placement of reactive power compensators is better identified using the suggested approach as it saves time and does not depend on performing a time consuming power flow solution before the weakest node is identified.

Inherent structural characteristics based approach for solving generation-load allocation problems

The topological properties of power networks emanate from the interconnections of the components within the networks. These structural properties can easily be captured by the network bus impedance or admittance matrix as formulated in the fundamental circuit theory law (Ohms law) for efficient allocation of electric energy among the consumers. In this paper, the solution to load allocation problems within power networks is considered using the inherent structural characteristics of power systems. A generalized coefficient matrix called Generation-Load Allocation (GLA) matrix which is a function of the network structural interconnections is formulated. This matrix is employed to determine the percentage allocation of power contribution by each generator to serve the various given loads on the network. The mathematical formulations based on the Ohms laws are presented. The simulations were carried out in Matlab 2010a environment. This study uses a practical power network of Nigerian 28-bus system for illustration and results are discussed.

Mitigation of cascade blackout in Power Systems by using Widest Path and Power Flow Redistribution Algorithms

Large cascade blackouts are generally catastrophic both economically and socially, when they occur. In this work, a transmission constrained, 5-bus power grid was simulated using PowerWorld and the impact of lines outages on the violation of loading capacities of network links was studied. We use the Widest Path Algorithm(WPA) and Power Flow Redistribution Algorithm(PFRA) to redistribute power flow in the network, using lines residual capacity and thermal capacity as criteria for redistribution. In cases, where (WPA) and (PFRA) could not reduce line loading, such path gives indication of where transmission should be reinforced. In this work, we propose a new and innovative techniques for mitigation of cascade blackout and well as network reinforcement.

Static voltage stability enhancement using FACTS controller

The modern day power system is faced with challenges of voltage instability and has become a great concern to the power system industries. In this work, we proposed a technique of the Network structural Characteristics Participation Factor (NSCPF) to identify the most critical node where reactive power compensator can be placed for voltage stability enhancement. The approach is based on the use of eigenvalue decomposition technique on the submatrix of the partitioned bus admittance matrix. Conventional power flow based approach of voltage stability index (L-Index) and the modal analysis methods are used as benchmarks to the proposed approach to determine its effectiveness. The STATCOM FACTS controller is in turn installed at the critical bus as identified by both techniques. Simulation results obtained show that, the suggested approach saves time and is more advantageous in identifying the suitable bus for the placement of STATCOM.

Estimation of Wind Speed Statistical Distribution at Vredendal, South Africa

In this work various statistical methods for estimating the distribution of wind speed at given site are studied and compared. It has always been accepted that Weibull fits the wind speed data better as it has performed well at many sites. This notion is subject to an investigation by comparing Weibull with Rayleigh, Lognormal and Gamma for wind speed. The results of goodness of fit tests using root mean square (RMSE) and coefficient of determination (R) showed that Gamma distribution fits the data better than Weibull, Rayleigh and Lognormal.

Inherent structural characteristics approach for solving loss allocation problems

The solution to the well-known loss allocation problems in interconnected power networks has usually been through power-flow analysis. This power-flow based approach is computationally intensive and the results may not converge for large practical power systems. This paper, therefore, explores an alternative approach to solving this problem using the Inherent Structural Characteristics Theory (ISCT) [6]. The total transmission loss within power network based on both the ISCT and power-flow-based approach is determined, and then used to allocate losses to loads in the network. The results obtained from the two approaches are compared. The ISCT approach, apart from being faster, allocates the total loss within the network to loads in a fairer, equitable and transparent manner. Matlab 2013a is employed as a simulation tool. The sparsity inherent in power networks is explored to reduce the computational intensity and computer memory required. This new approach is tested on a standard IEEE 14-bus system and a practical system of the Nigerian 40-bus network. The results obtained from the simulations show the ISCT approach to be superior.

Detection of weak bus through Fast Voltage Stability index and inherent structural characteristics of power system

Modern power system is large, complex and characterized by continuous increase in electrical load demand. As a result, the system is stressed to operate closer to stability limit and this may result in voltage collapse. Therefore, it becomes imperative to implement techniques for detecting collapse in bus bar or lines before its occurrence in the power system. This paper presents the concept of inherent structural characteristics of power networks and the power flow based technique of the Fast Voltage Stability index (FVSI). To detect the weakest line with respect to a bus using the conventional based approach of the Fast Voltage Stability Index (FVSI), a repetitive power flow solution is performed while varying the reactive power load at a particular load bus. The line or bus that has its FVSI closest or equal to 1 is identified as the weakest line or bus. The concept of inherent structural characteristics of the power network is formulated based on the fundamental circuit theory laws which employs the use of eigenvalue decomposition method in predicting the bus liable to instability. The two approaches are then compared. The result obtained shows that, weak bus is better detected through the concept of inherent structural characteristics of power network as it saves time and does not involve performing the time consuming traditional load flow before the weak bus is known.

Prediction of voltage collapse through voltage collapse proximity index and inherent structural characteristics of power system

The frequent incident of voltage collapse in the modern power system due to incessant increase in load demand has posed a great challenge to power system utilities. This paper demonstrates the concept of inherent structural characteristics and the traditional approach of voltage collapse proximity index (VCPI) in predicting the collapse point in the power system network. The conventional technique for collapse point detection through the use of the voltage collapse proximity index is achieved by running a repetitive load flow solution while increasing the reactive power load of a particular load bus. On the other hand, the approach due to inherent structural characteristics of power system is formulated based on the fundamental circuit theory laws and it employs the use of eigenvalue decomposition method in predicting the bus liable to instability. The results of the simulations show that voltage collapse point is easier and quicker to predict with the technique based on the inherent structural characteristics without necessarily going through the rigor of a time consuming and repetitive load flow based voltage collapse point proximity index (VCPI).

Identification of critical buses and weak transmission lines using inherent structural characteristics theory

Power system components are susceptible to failures that could result in island formation which is highly undesirable and should be avoided. For a safe and reliable power system operation, all insecure operating states such as critical nodes and sets of candidate transmission links that could cause cascading outages within the networks must be quickly detected and identified in advance. This paper, therefore, investigates the relevance of Inherent Structural Characteristics Theory (ISCT) approach in this respect An insightful solution of the approach based on the atomic theory analogy is proposed. A Coupling Strength Index (CSI), which is capable of detecting the critical buses and weak transmission links within the power network is proposed. The effectiveness of the approach is tested using a 10-bus power system of equivalent Southern Indian network. Matlab 2013b environment is employed for the simulations. The results show viability of the approach for enhancing the operation of stressed power networks.