Voltage stability assessment is a major issue in monitoring the power system stability. Different voltage stability indices (VSIs) have been proposed in the literature for voltage stability assessment. These indices can be used for distributed generation (DG) placement and sizing, detecting the weak lines and buses and triggering the countermeasures against voltage instability. This paper reviews the VSIs from different aspects such as concepts, assumptions, critical values and equations. The review results provide a comprehensive background to find out the future works in this field and select the best VSI for different applications like DG placement and sizing and voltage stability assessment.

A comprehensive review of the voltage stability indices

Internet of Things (IoT) technologies have been broadly applied in smart grid for monitoring physical or environmental conditions. Especially, state estimation is an important IoT-based application in smart grid, which is used in system monitoring to get the best estimate of the power grid state through an analysis of the meter measurements and power system topologies. However, false data injection attack (FDIA) is a severe threat to state estimation, which is known for the difficulty of detection. In this paper, we propose an efficient detection scheme against FDIA. First, two parameters that reflect the physical property of smart grid are investigated. One parameter is the control signal from the controller to the static Var compensator (CSSVC). A large CSSVC indicates there exists the intense voltage fluctuation. The other parameter is the quantitative node voltage stability index (NVSI). A larger NVSI indicates a higher vulnerability level. Second, according to the values of the CSSVC and NVSI, an optimized clustering algorithm is proposed to distribute the potential vulnerable nodes into several classes. Finally, based on these classes, a detection method is proposed for the real-time detection of the FDIA. The simulation results show that the proposed scheme can detect the FDIA effectively.

Achieving Efficient Detection Against False Data Injection Attacks in Smart Grid

This paper examines the feasibility of coordinating variable-speed wind farms with other power system devices, such as flexible ac transmission systems and synchronous generators, to damp low-frequency oscillations. For this purpose, an observer-based state-feedback approach is used to build a power oscillation damping (POD) controller, implemented through coordinated actions of multiple control devices, and able to manage several measurement channels. The wide-area POD controller also presents a time-delay compensation stage to mitigate adverse effects of latency involved in wide-area communication systems. Several practical issues are discussed and analyzed, such as measurement and control selection, model-order reduction, transmission time-delay compensation, impact of the POD control on wind farms, and robustness aspects. The control performance is evaluated and compared with other control schemes using eigenvalue analyses and nonlinear time-domain simulations over a wide range of operating conditions, for example, severe system faults, N - 1 outage contingencies, load/generation shedding, and line tripping.

Power Oscillation Damping Improvement by Adding Multiple Wind Farms to Wide-Area Coordinating Controls

Inter-area low frequency electromagnetic oscillation (LFEO) in inter-connected power systems is one of the major barriers to improve the dynamic performance of power systems, since they could either limit the amount of power transfer on the tie-lines or endanger the dynamic stability of the power systems. With the high penetration of wind and photovoltaic (PV) power plants in power systems, LFEO is becoming a problem worth more attention in renewable energy age and must be better solved in order to accept more wind and PV power in power systems. Wide-area damping control (WADC) has gained popularity in suppression of inter-area LFEO recently. Many control strategies have been developed on WADC design. This paper aims to provide a general review on practical issues, typical WADC off-line and adaptive design methods and engineering cases regarding WADC implementations. These practical issues include design flow, mode analysis, choice of actuator and feedback signal, system identification and the effect of time delay. In terms of designing WADC controllers, both offline and adaptive methods have been reviewed and compared. Finally, WADC engineering cases all around the world are summarized.

A review on wide-area damping control to restrain inter-area low frequency oscillation for large-scale power systems with increasing renewable generation

Identification of vulnerable node clusters against false data injection attack in an AMI based Smart Grid

Voltage stability improvement is a challenging issue in planning and security assessment of power systems. As modern systems are being operated under heavily stressed conditions with reduced stability margins, incorporation of voltage stability criteria in the operation of power systems began receiving great attention. This study presents a novel voltage stability constrained optimal power flow (VSC-OPF) approach based on static line voltage stability indices to simultaneously improve voltage stability and minimise power system losses under stressed and contingency conditions. The proposed methodology uses a voltage collapse proximity indicator (VCPI) to provide important information about the proximity of the system to voltage instability. The VCPI index is incorporated into the optimal power flow (OPF) formulation in two ways; first it can be added as a new voltage stability constraint in the OPF constraints, or used as a voltage stability objective function. The proposed approach has been evaluated on the standard IEEE 30-bus and 57-bus test systems under different cases and compared with two well proved VSC-OPF approaches based on the bus voltage indicator L - index and the minimum singular value. The simulation results are promising and demonstrate the effectiveness of the proposed VSC-OPF based on the line voltage stability index.

Preventive control approach for voltage stability improvement using voltage stability constrained optimal power flow based on static line voltage stability indices

Wide-area measurements have been proposed to coordinate generator excitations and Static Var Compensator (SVC) auxiliary controls. The wide-area coordinating controller (WACC) utilizes remote signals to compensate the interactions between SVC and generator variables, therefore it provides an additional damping of both local and inter-area oscillations. However time delays introduced by remote measurement and control signals may affect the performance of the controller. This paper focuses on the impact of time delay on power oscillation damping and the application of Smith prediction approach to preserve power system performance with large time delays. Anderson and Farmer four-generator nine-bus power system is used to illustrate delay effect on mode damping and the advantage of delay compensation. Simulation results show that generator speeds and SVC bus voltage oscillations are still well damped for various time delays with the Smith predictor approach.

Wide-area coordinating control of SVCs and synchronous generators with signal transmission delay compensation

This paper presents a new control design method based on wide-area measurements to coordinate generator excitations and static var compensator (SVC) auxiliary controls A new state space model comprising a multimachine power system and a SVC is first derived This model clearly shows the interactions between SVC and generator variables Next, generator excitations and the SVC auxiliary input are synthesized to decouple the subsystems These control signals utilize remote measurements and compensate the interactions between the SVC and generators The proposed control strategy provides an additional damping of inter-area oscillations Therefore, it also enhances the global stability of the power system The effectiveness of the new control strategy is tested using the Anderson and Farmer four-generator nine-bus power system Simulation results demonstrate that generator speeds, SVC and generator terminal voltages oscillations are well damped when the coordinating controller is used

Wide-area measurements based coordination of SVCs and synchronous generators

SimPowerSystems (SPS) is a software package for the modeling and simulation of electric power systems in the Simulink environment. The SPS library contains models of various components used in power systems such as three-phase machines, transformers, loads, lines, etc. However, there is no library devoted to excitation systems. Therefore, it was proposed to develop a library for these systems. This paper presents a newly developed MATLAB/Simulink library for excitation system models recommended by IEEE. Application example is included to verify the performance and the accuracy of the developed models. Furthermore, a comparison with results from PSS/E is performed.

Development of a new library of IEEE excitation systems and its validation with PSS/E

Power system optimization while improving system security and performance has become a major challenge in power systems planning and operation. As modern systems are being operated under heavily stressed conditions with reduced stability margins, incorporation of voltage stability criteria in the operation of power systems has become necessary. This paper presents a novel voltage stability constrained optimal power flow approach based on the line voltage stability indices. The objective of the new VSC-OPF is to add the voltage collapse proximity indicator (VCPI) into the OPF constraints to simultaneously minimize power losses and improve voltage stability. The proposed approach has been evaluated and compared with conventional OPF on the IEEE 30-bus test system under different cases. The simulation results are promising and demonstrate the effectiveness of the proposed VSC-OPF using the line voltage stability index.

Tarik Zabaiou

Papers

Preventive control approach for voltage stability improvement using voltage stability constrained optimal power flow based on static line voltage stability indices

Wide-area coordinating control of SVCs and synchronous generators with signal transmission delay compensation

Wide-area measurements based coordination of SVCs and synchronous generators

Development of a new library of IEEE excitation systems and its validation with PSS/E

VSC-OPF based on line voltage indices for power system losses minimization and voltage stability improvement