Impact of GPS spoofing on HVDC modulation

This paper investigates a variety of scenarios in which control signals utilized in high-voltage DC (HVDC) modulation are subjected to oscillatory error due to GPS spoofing of phasor measurement unit (PMU) time synchronization. The result of this spoofing is the presence of forced oscillations in a system through HVDC modulation due to cyclic erroneous measurements. These scenarios are tested in the Kundur two-area system with a supplementary HVDC line which utilizes various supplementary controllers for modulation. The simulation results are examined for system transient behavior as well as for the observable small-signal effects of the GPS spoofed control signals across the system. It is found that the harmonics of the spoofed control signal frequencies can interact with the inter-area modes of the system, resulting in resonant oscillations and the severity of the oscillations is dependent upon the magnitude of the time-error and the damping levels of the system modes

An Assessment of PIER Electric Grid Research 2003-2014 White Paper

This white paper describes the circumstances in California around the turn of the 21st century that led the California Energy Commission (CEC) to direct additional Public Interest Energy Research funds to address critical electric grid issues, especially those arising from integrating high penetrations of variable renewable generation with the electric grid. It contains an assessment of the beneficial science and technology advances of the resultant portfolio of electric grid research projects administered under the direction of the CEC by a competitively selected contractor, the University of California’s California Institute for Energy and the Environment, from 2003-2014

MANGO ? Modal Analysis for Grid Operation: A Method for Damping Improvement through Operating Point Adjustment

Small signal stability problems are one of the major threats to grid stability and reliability in the U.S. power grid. An undamped mode can cause large-amplitude oscillations and may result in system breakups and large-scale blackouts. There have been several incidents of system-wide oscillations. Of those incidents, the most notable is the August 10, 1996 western system breakup, a result of undamped system-wide oscillations. Significant efforts have been devoted to monitoring system oscillatory behaviors from measurements in the past 20 years. The deployment of phasor measurement units (PMU) provides high-precision, time-synchronized data needed for detecting oscillation modes. Measurement-based modal analysis, also known as ModeMeter, uses real-time phasor measurements to identify system oscillation modes and their damping. Low damping indicates potential system stability issues. Modal analysis has been demonstrated with phasor measurements to have the capability of estimating system modes from both oscillation signals and ambient data. With more and more phasor measurements available and ModeMeter techniques maturing, there is yet a need for methods to bring modal analysis from monitoring to actions. The methods should be able to associate low damping with grid operating conditions, so operators or automated operation schemes can respond when low damping is observed. The work presented in this report aims to develop such a method and establish a Modal Analysis for Grid Operation (MANGO) procedure to aid grid operation decision making to increase inter-area modal damping. The procedure can provide operation suggestions (such as increasing generation or decreasing load) for mitigating inter-area oscillations

Oscillation Analysis and its Mitigation Using Inverter-Based Resources in Large-Scale Power Grids

In today\u27s interconnected power grids, forced oscillations and poorly damped low-frequency oscillations are major concerns that can damage equipment, limit power transfer capability, and deteriorate power system stability. The first part of the dissertation focuses on the impact of a wide-area power oscillation damping (POD) controller via voltage source converter-based high voltage direct current (VSC-HVDC) in enhancing the power system stability and improving the damping of low-frequency oscillation. The POD controller\u27s performance was investigated under a three-phase temporary line fault. The Great Britain (G.B.) power grid model validated the POD controller performance via active power modulation of VSC-HVDC through TSAT-RTDS hybrid simulation. The developed POD controller is also implemented on a general-purpose hardware platform CompactRIO and tested on a hardware-in-the-loop (HIL) test setup with actual PMU devices and a communication network impairment simulator. A variety of real-world operating conditions is considered in the HIL tests, including measurement error/noise, occasional/consecutive data package losses, constant/random time delays, and multiple backups PMUs. The second part of the dissertation proposes a two‐dimensional scanning forced oscillation grid vulnerability analysis method to identify areas/zones and oscillation frequency in the system critical to forced oscillation. These critical areas/zones can be considered effective actuator locations to deploy forced oscillation damping controllers. Additionally, a POD controller through inverter-based resources (IBRs) is proposed to reduce the forced oscillation impact on the entire grid. The proposed method is tested when the external perturbation is active power and compared with the reactive power perturbation result. The proposed method is validated through a case study on the 2000-bus synthetic Texas power system model. The simulation results demonstrate that the critical areas/zones of forced oscillation are related to the areas that highly participate in the natural oscillation. Furthermore, forced oscillation through active power disturbance can have a more severe impact than reactive power disturbance, especially at resonance. The proposed forced oscillation controller can mitigate the impact of the forced oscillation on the entire system when the actuator is close to the forced oscillation source. In addition, active power modulation of IBR can provide better damping performance than reactive power modulation

Measurement-Based Monitoring and Control in Power Systems with High Renewable Penetrations

Power systems are experiencing rapid changes in their generation mixes because of the increasing integration of inverter-based resources (IBRs) and the retirement of traditional generations. This opens opportunities for a cleaner energy outlook but also poses challenges to the safe operation of the power networks. Enhanced monitoring and control based on the increasingly available measurements are essential in assisting stable operation and effective planning for these evolving systems. First, awareness of the evolving dynamic characteristics is quintessential for secure operation and corrective planning. A quantified monitoring study that keeps track of the inertial response and primary frequency response is conducted on the Eastern Interconnection (EI) for the past decade with field data. Whereas the inertia declined by at least 10%, the primary frequency response experienced an unexpected increase. The findings unveiled in the trending analysis also led to an improved event MW size estimation method, as well as discussions about regional dynamics. Experiencing a faster and deeper renewable integration, the Continental Europe Synchronous Area (CESA) system has been threatened by more frequent occurrences of inter-area oscillations during light-load high-renewable periods. A measurement-based oscillation damping control scheme is proposed for CESA with reduced reliance on system models. The design, implementation, and hardware-in-the-loop (HIL) testing of the controller are discussed in detail. Despite the challenges, the increasing presence of IBRs also brings opportunities for fast and efficient controls. Together with synchronized measurement, IBRs have the potential to flexibly complement traditional frequency and voltage control schemes for improved frequency and voltage recovery. The design, implementation, and HIL testing of the measurement-based frequency and voltage control for the New York State Grid are presented. In addition to the transmission level development, IBRs deployed in distribution networks can also be valuable assets in emergency islanding situations if controlled properly. A power management module is proposed to take advantage of measurements and automatically control the electric boundaries of islanded microgrids for maximized power utilization and improved frequency regulation. The module is designed to be adaptive to arbitrary non-meshed topologies with multiple source locations for increased flexibility, expedited deployment, and reduced cost

Novel Control of PV Solar Farms as STATCOM (PV-STATCOM) for Frequency Control and Power Oscillation Damping

Frequency stability and low-frequency power oscillations are two major concerns in modern power systems. PV-STATCOM is a patented concept which enables PV inverters to provide STATCOM functions, during day and night, as well as real power modulation during daytime. This thesis aims to utilize PV-STATCOM capability effectively for enhancing frequency stability and power oscillations damping. A novel, simultaneous real power-based Fast Frequency Response (FFR) and reactive power-based Power Oscillation Damping (POD) control is proposed for PV-STATCOMs. This control not only significantly reduces system under- and over-frequency deviations, but also uses the unutilized capacity of PV inverters to enhance damping of critical modes. A novel night and day Reactive power-based Frequency Control (RFC) is proposed for PV-STATCOMs, that deploys the unutilized reactive power capacity of PV-STATCOM for frequency stability improvement. RFC modulates the system voltage, via PV-STATCOM voltage control loop, to control the power of voltage-sensitive loads and reduce the generation-demand imbalance. Sensitivity studies show that the load type and its composition, and location of RFC-equipped PV-STATCOM play a significant role in the efficacy of proposed controls. RFC not only provides a 24/7 complementary frequency support service but potentially obviates the impact of system inertia loss due to replacement of conventional synchronous generators by inverter-based generators. A new combined RFC and POD controller is also proposed for PV-STATCOM utilizing unused reactive power capacity of PV inverters. The studies show that depending on PV-STATCOM location, the proposed combined RFC+POD controller can effectively enhance system frequency stability and power oscillations damping. This thesis also proposes a fast power-frequency droop for PV generators and an enhanced synthetic inertial response for wind generators. These two controls operate in a harmonized manner to provide improved frequency support while reducing the stresses on wind generators. The proposed PV-STATCOM grid support functionalities can potentially open up new revenue streams for solar farms. The mechanisms of such financial compensations are expected to develop in near future with the unprecedented growth of solar farms globally. MATLAB based simulation studies are performed on two-area-four-machine and 12-bus study systems using modified WECC generic dynamic models for PV plants, wind plants and loads

Power system security enhancement through direct non-disruptive load control

The transition to a competitive market structure raises significant concerns regarding reliability of the power grid. A need to build tools for security assessment that produce operating limit boundaries for both static and dynamic contingencies is recognized. Besides, an increase in overall uncertainty in operating conditions makes corrective actions at times ineffective leaving the system vulnerable to instability. The tools that are in place for stability enhancement are mostly corrective and suffer from lack of robustness to operating condition changes. They often pose serious coordination challenges. With deregulation, there have also been ownership and responsibility issues associated with stability controls. However, the changing utility business model and the developments in enabling technologies such as two-way communication, metering, and control open up several new possibilities for power system security enhancement. This research proposes preventive modulation of selected loads through direct control for power system security enhancement. Two main contributions of this research are the following: development of an analysis framework and two conceptually different analysis approaches for load modulation to enhance oscillatory stability, and the development and study of algorithms for real-time modulation of thermostatic loads.;The underlying analysis framework is based on the Structured Singular Value (SSV or mu) theory. Based on the above framework, two fundamentally different approaches towards analysis of the amount of load modulation for desired stability performance have been developed. Both the approaches have been tested on two different test systems: CIGRE Nordic test system and an equivalent of the Western Electric Coordinating Council test system.;This research also develops algorithms for real-time modulation of thermostatic loads that use the results of the analysis. In line with some recent load management programs executed by utilities, two different algorithms based on dynamic programming are proposed for air-conditioner loads, while a decision-tree based algorithm is proposed for water-heater loads. An optimization framework has been developed employing the above algorithms. Monte Carlo simulations have been performed using this framework with the objective of studying the impact of different parameters and constraints on the effectiveness as well as the effect of control.;The conclusions drawn from this research strongly advocate direct load control for stability enhancement from the perspectives of robustness and coordination, as well as economic viability and the developments towards availability of the institutional framework for load participation in providing system reliability services