This paper studies the differences in a synthetic inertia controller of using two different feedback measurements: (i) an estimate of the rate of change of frequency from local voltage measurements, and (ii) a remote machine acceleration from a generator nearby to the actuator. The device that provides the synthetic inertia action is a converter interfaced generator (CIG). The paper carries out analysis in the frequency domain, using Bode plots, to show that synthetic inertia control using frequency estimates is more prone to instabilities than for the case where a machine speed is used. The paper then proposes a controller (or a filter) to mitigate these effects. In addition, the paper shows the effects that a delay of the machine speed signal of the nearby generator has on the synthetic inertia control of the system and how a controller is also needed in this case. Finally, the paper shows the difference in performance of a synthetic inertia controller when using these different measurement signals with simulations in time domain a electromagnetic transient program platform.
This paper presents a preliminary investigation on controlling the existing high voltage dc (HVDC) links connecting the North American western interconnection (WI) to the other interconnections, to provide damping to inter-area oscillations. The control scheme is meant to damp inter-area modes of oscillation in the WI by using wide area synchrophasor feedback. A custom model is developed in General Electric's PSLF software for the wide area damping control scheme, and simulations are analyzed on a validated full 22,000 bus WI model. Results indicate that implementing the proposed control technique to the existing HVDC links in the WI can significantly improve the damping of the inter-area modes of the system.
A significant amount of converter-based generation, such as wind and photovoltaic, is being integrated into thebulk electric power grid to fulfill the future electric demand. Such converter-based distributed energy resources (DERs) will be providing multiple grid support functions (GSFs) to supportvoltage and frequency control of the power system. In thispaper, we present the development of a MA /Simulink-based simulation model to study power system dynamics whenDERs are equipped with GSFs. The simulation model of aninverter with GSFs is validated through comparisons against thecharacteristic curves for each function of the IEEE 1547-2018standard. The normalized root-mean-square-error (NRMSE) wascalculated to be less than 2%. The developed model is then used ina sample power systems dynamics study under various operatingconditions. Results show the exnected resnonse of inverfers withGSFs, properly supporting the grid voltage and frequency andmaintaining the value within an acceptable range.
This paper presents a new method for detecting power quality disturbances, such as faults. The method is based on the dynamic mode decomposition (DMD)-a data-driven method to estimate linear dynamics whose eigenvalues and eigenvectors approximate those of the Koopman operator. The proposed method uses the real part of the main eigenvalue estimated by the DMD as the key indicator that a power quality event has occurred. The paper shows how the proposed method can be used to detect events using current and voltage signals to distinguish different faults. Because the proposed method is window-based, the effect that the window size has on the performance of the approach is analyzed. In addition, a study on the effect that noise has on the proposed approach is presented.
As a result of the increase in penetration of inverter-based generation such as wind and solar, the dynamics of the grid are being modified. These modifications may threaten the stability of the power system since the dynamics of these devices are completely different from those of rotating generators. Protection schemes need to evolve with the changes in the grid to successfully deliver their objectives of maintaining safe and reliable grid operations. This paper explores the theory of traveling waves and how they can be used to enable fast protection mechanisms. It surveys a list of signal processing methods to extract information on power system signals following a disturbance. The paper also presents a literature review of traveling wave-based protection methods at the transmission and distribution levels of the grid and for AC and DC configurations. The paper then discusses simulations tools to help design and implement protection schemes. A discussion of the anticipated evolution of protection mechanisms with the challenges facing the grid is also presented.
As renewable energy sources are becoming more dominant in electric grids, particularly in micro grids, new approaches for designing, operating, and controlling these systems are required. The integration of renewable energy devices such as photovoltaics and wind turbines require system design considerations to mitigate potential power quality issues caused by highly variable generation. Power system simulations play an important role in understanding stability and performance of electrical power systems. This paper discusses the modeling of the Global Laboratory for Energy Asset Management and Manufacturing (GLEAMM) micro grid integrated with the Sandia National Laboratories Scaled Wind Farm Technology (SWiFT) test site, providing a dynamic simulation model for power flow and transient stability analysis. A description of the system as well as the dynamic models is presented.
Power system operations are fundamentally changed by the growing installation of wind generation systems. The undispatchable nature of wind turbine generators (WTGs) causes the operating conditions of power systems to be more volatile. At the same time, the converter-based interface of WTGs are capable, and are increasingly expected to, provide voltage and frequency regulation capabilities. Monitoring of power systems becomes critical under these anticipated conditions and high resolution data, such as synchrophasors, are crucial for this task. This paper presents an approximate low-order model of WTGs that can be readily estimated from available synchrophasor measurements. The identification of the parameters of the model can be used to approximate the control performance of WTGs and their contributions to frequency and voltage regulation.
The state of California is leading the nation with respect to solar energy and storage. The California Energy Commission has mandated that starting in 2020 all new homes must be solar powered. In 2010 the California state legislature adopted an energy storage mandate AB 2514. This required California's three largest utilities to contract for an additiona11.3 GW of energy storage by 2020, coming online by 2024. Therefore, there is keen interest in the potential advantages of deploying solar combined with energy storage. This paper formulates the optimization problem to identify the maximum potential revenue from pairing storage with solar and participating in the California Independent System Operator (CAISO) day ahead market for energy. Using the optimization formulation, five years of historical market data (2014-2018) for 2, 172 price nodes were analyzed to identify trends and opportunities for the deployment of solar plus storage.
This paper presents model formulations for generators that have the ability to use multiple fuels and to switch between them if necessary. These models are used to generate different scenarios of fuel switching penetration from a test power system. With these scenarios, for a severe disruption in the fuel supply to multiple generators, the paper analyzes the effect that fuel switching has on the resilience of the power system. Load not served is used as the proxy metric to evaluate power system resilience. The paper shows that the presence of generators with fuel switching capabilities considerably reduces the amount and duration of the load shed by the system facing the fuel disruption.
Transient stability is highly correlated to the inertia connected to the synchronous grid. Most of the modern control schemes for maintaining transient stability involve generator tripping schemes. However, these type of schemes may become difficult to implement because of the inertia reduction associated with the increase in inverter-based and distributed generation. This paper presents the effect of using machine acceleration feedback in a real-power injection control scheme to improve transient stability without generator tripping. This scheme is based on the equal area criterion and tested on a one machine infinite bus and a two machine system. Its applicability in a multimachine power system is demonstrated on a reduced-order western North American power system. Simulation results indicate that the proposed control strategy provides a simple and effective method for improving transient stability.
Fast-frequency control strategies have been proposed in the literature to maintain inertial response of electric generation and help with the frequency regulation of the system. However, it is challenging to deploy such strategies when the inertia constant of the system is unknown and time-varying. In this paper, we present a data-driven system identification approach for an energy storage system (ESS) operator to identify the inertial response of the system (and consequently the inertia constant). The method is first tested and validated with a simulated genset model using small changes in the system load as the excitation signal and measuring the corresponding change in frequency. The validated method is then used to experimentally identify the inertia constant of a genset. The inertia constant of the simulated genset model was estimated with an error of less than 5% which provides a reasonable estimate for the ESS operator to properly tune the parameters of a fast-frequency controller.