Iraj Rahimi Pordanjani

Voltage Stability Monitoring Based on the Concept of Coupled Single-Port Circuit

Summary form only given: This paper reveals that the impedance match (or the Thevenin circuit) based voltage stability monitoring techniques have problems to predict voltage stability limits when applied to multi-load power systems. Power system loads are nonlinear and dynamic. They cannot be simply represented as Thevenin circuit parameters for impedance match analysis. To overcome these difficulties, a new concept called “coupled single-port circuit” is proposed in this paper. The concept decouples a meshed network into individual single generator versus single bus network and, as a result, a modified version of the impedance match theorem can be used. This leads to a real-time voltage stability monitoring scheme without the need to estimate Thevenin parameters. The scheme can estimate voltage stability margin and identify weak areas in a system based on the SCADA and PMU data. Case studies conducted on several test systems have verified the validity of the proposed method.

An Event-Driven Demand Response Scheme for Power System Security Enhancement

Demand response has become a key feature of the future smart grid. In addition to having advanced communication and computing infrastructures, a successful demand response program must respond to the needs of a power system. In other words, the efficiency and security of a power system dictate the locations, amounts and speeds of the load reductions of a demand response program. In this paper, we propose an event-driven emergency demand response scheme to prevent a power system from experiencing voltage collapse. A technique to design such a scheme is presented. This technique is able to provide key setting parameters such as the amount of demand reductions at various locations to arm the demand response infrastructure. The validity of the proposed technique has been verified by using several test power systems.

A Network Decoupling Transform for Phasor Data Based Voltage Stability Analysis and Monitoring

It is well known that a power network can be represented as a multinode, multibranch Thevenin circuit connecting loads to generators. This paper shows that eigen-decomposition can be performed on the Thevenin impedance matrix, creating a set of decoupled single-node, single-branch equivalent circuits. The decoupled circuits can reveal important characteristics of a power system. By applying the transform to calculated or measured voltage phasor data, a technique for tracking the modes of voltage collapse and for identifying areas vulnerable to voltage collapse has been developed. Case studies conducted on multiple power systems have confirmed the effectiveness of the proposed method. In addition to voltage stability applications, the proposed transform presents a new approach for processing and interpreting multilocation phasor data.

Identification of Critical Components for Voltage Stability Assessment Using Channel Components Transform

Channel Components Transform (CCT) is a recently developed technique to decouple interconnected power networks. This paper aims to further explore the CCT and extend its applications. Methods and algorithms are proposed to extend its application in identifying the critical generators and branches of a network from the voltage stability perspective. The proposed methods are verified by case studies conducted on multiple test systems. This paper also demonstrates the capability of the CCT to work properly when a limited number of phasor measurement units are available. For this purpose, a strategy is proposed to determine the number and location of PMU installations that are sufficient to track the modes of voltage collapse and associated critical components. The proposed allocation strategy is examined through case studies of an actual power system.

A Novel Genetic Programming Approach for Frequency-Dependent Modeling

Frequency-dependent modeling of devices and systems is a common practice in several fields, such as power systems, microwave systems, and electronics systems. The modeling process usually involves converting the tabulated frequency-response data into a compact equivalent circuit model. The main drawback of the currently existing methods such as vector fitting is that the obtained model is often nonpassive, leading to unstable simulations. In order to overcome this problem, this paper proposes a genetic programming (GP) approach to generate equivalent circuits with guaranteed passivity. The proposed method starts with a nonoptimal initial equivalent circuit. Both the elements and the topology of this circuit are then evolved by the proposed GP-based method, and an accurate equivalent circuit is obtained. Key ideas and detailed algorithms are presented in this paper. Finally, the performance of the proposed method is verified by using different case studies.

A New Optimal Meter Placement Method for Obtaining a Transmission System Indices

This paper introduces an improved optimal monitoring program which identifies optimal locations of meters. First, analytical expressions for the calculation of voltage sag magnitude due to the faults at every point of a transmission system are derived. Balanced and unbalanced faults are considered. Then an integer programming-based modeling is proposed for choosing the optimal locations of power quality meters. A genetic algorithm is used to solve the optimization problem. Optimization problem modeling and estimation of sag performance in non-monitored buses are made with high precision. The flexibility of the method has been increased by considering the fault positions on the lines as well as buses. The computer algorithm is applied to a real transmission network and the results show the method is successful.

A network decoupling transform for phasor data based voltage stability analysis and monitoring

Summary form only given. It is well known that a power network can be represented as a multinode, multibranch Thevenin circuit connecting loads to generators. This paper shows that eigen-decomposition can be performed on the Thevenin impedance matrix, creating a set of decoupled single-node, single-branch equivalent circuits. The decoupled circuits can reveal important characteristics of a power system. By applying the transform to calculated or measured voltage phasor data, a technique for tracking the modes of voltage collapse and for identifying areas vulnerable to voltage collapse has been developed. Case studies conducted on multiple power systems have confirmed the effectiveness of the proposed method. In addition to voltage stability applications, the proposed transform presents a new approach for processing and interpreting multilocation phasor data.

A transformation technique for decoupling power networks

This paper shows that a multi-generator, multi-load and multi-branch network is mathematically equivalent to a system that has one generator supplying one load through one transmission line that has multiple “phases”. Based on this observation, a transformation is proposed to analyze complex power systems. The Transform results in a set of decoupled one-source one-load networks, very similar to the creation of sequence networks with the symmetrical components transform. By analyzing the characteristics of each decoupled network, one can extract important information, such as voltage instability modes, of a complex power network. The proposed transform has the potential to establish the theoretical foundation for processing and interpreting multi-location phasor data collected by wide-area monitoring systems.

Identification of critical components for voltage stability assessment using channel components transform

Channel Components Transform (CCT) is a recently developed technique to decouple interconnected power networks. This paper aims to further explore the CCT and extend its applications. Methods and algorithms are proposed to extend its application in identifying the critical generators and branches of a network from the voltage stability perspective. The proposed methods are verified by case studies conducted on multiple test systems. This paper also demonstrates the capability of the CCT to work properly when a limited number of phasor measurement units are available. For this purpose, a strategy is proposed to determine the number and location of PMU installations that are sufficient to track the modes of voltage collapse and associated critical components. The proposed allocation strategy is examined through case studies of an actual power system.

Voltage stability monitoring based on the concept of coupled single-port circuit

This paper reveals that the impedance match (or the Thevenin circuit) based voltage stability monitoring techniques have problems to predict voltage stability limits when applied to multi-load power systems. Power system loads are nonlinear and dynamic. They cannot be simply represented as Thevenin circuit parameters for impedance match analysis. To overcome these difficulties, a new concept called “coupled single-port circuit” is proposed in this paper. The concept decouples a meshed network into individual single generator versus single bus network and, as a result, a modified version of the impedance match theorem can be used. This leads to a real-time voltage stability monitoring scheme without the need to estimate Thevenin parameters. The scheme can estimate voltage stability margin and identify weak areas in a system based on the SCADA and PMU data. Case studies conducted on several test systems have verified the validity of the proposed method.