Response Of Power System Research Articles

Control Strategy of BESS for Providing Both Virtual Inertia and Primary Frequency Response in the Korean Power System

As the battery energy storage system (BESS) has been considered to be a solution to the diminished performance of frequency response in the Korean power system, in which renewable energy resources (RESs) are expected to increase rapidly, this paper proposes a control strategy for providing both the virtual inertia and primary frequency response considering the MW-scale BESS installed by the Korea Electricity Power Corporation (KEPCO). The benefit of such a fast and flexible BESS can be maximized by the proposed control strategy for making it provide both the inertia and primary frequency response, which would be deficit with the increased RES. In the proposed control strategy, the state of charge (SOC) is maintained in the specific range in which the life cycle is maximized, the interference of SOC recovery by frequency control is minimized, the responding capacity for providing the virtual inertia response is maximized during the transient period, and the performance requirements for frequency response are satisfied. The effectiveness of the proposed strategy is verified by both Korean power system model-based simulation and on-site operations.

Risk Assessment of Rare Events in Probabilistic Power Flow via Hybrid Multi-Surrogate Method

The risks associated with rare events threatening the security of power system operation are of paramount importance to power system planners and operators. To analyze the risks caused by high-impact, low-frequency rare events, an immensely large number of samples are typically required for the Monte-Carlo (MC) method on the high-fidelity power system model to achieve a sufficient accuracy, thereby rendering this approach computationally prohibitive. To handle this problem efficiently, it is desirable to construct a surrogate model for the power system response. However, the straightforward MC sampling of the low-fidelity surrogate can lead to biased results in the low-probability tail regions that are vital to risk assessment. Moreover, a single surrogate is unable to handle the topology uncertainties caused by random branch outages. To overcome these issues, we propose a hybrid multi-surrogate (HMS) method based on the polynomial chaos expansion (PCE) with low-probability tail events reevaluated by the high-fidelity model through a probabilistic analysis. This method improves the computational efficiency of the MC method for rare-event risk assessment by leveraging multi-fidelity models while retaining the desired accuracy. Simulations conducted in three test systems verify the excellent performances of the HMS method.

On the Impact of the Dead-Band of Power System Stabilizers and Frequency Regulation on Power System Stability

This letter studies the impact of the dead-band in the input signal of power system stabilizers (PSSs) on the transient response of power systems. The letter provides a taxonomy of the dynamic behavior of the system in various scenarios: no PSS, PSS without dead-band, and PSS with dead-band. For the latter, the dead-band stability margin and the interaction of the PSS with the system loading level as well as primary and secondary frequency regulators are discussed. The oscillatory behavior of the system is rigorously studied through the monodromy matrix and limit cycles are characterized by means of Floquet multipliers. The IEEE 14-bus system serves to illustrate the aforementioned scenarios.

FOSSMC for AGC of Multi-Area Power System in Open Market Environment

This paper presents a Fractional Order based Second Order Sliding Mode Controller (FOSSMC) for Load Frequency Control (LFC) of Deregulated Multi Area Power System (DMAPS). In this paper a new control strategy have been proposed to improve dynamic response of multi area power system under one possible contract scenario by considering bilateral contracts. This proposed new FOSSMC strategy capable of dealing with frequency deviations for sudden change of load on DISCOs. The advantage of FOSSMC in terms of exhibiting dynamic response compared to group of factional order controllers such as Fractional Order PI(FOPI), Fractional Order Fuzzy Controller(FOFLC) and Fractional Order Sliding Mode Controller(FOSMC) and conventional PI controller.

The Case for Global Positioning System Arcing and High Satellite Arc Rates

The Global Positioning System (GPS) satellites arc into the space environment. Evidence for this consists of undispersed impulsive radio frequency signals are shown in the dual-frequency RF receivers, that are on-board all GPS satellites, with high rates that track the charging electron environment, detection of appropriate amplitude short-timescale pulses from GPS satellites at 327 and 430 MHz with the Arecibo 305-m Gordon radiotelescope that do not appear in off-source scans, and arcing on laboratory GPS-like solar arrays at voltages similar to those inferred from GPS arc thresholds. In addition, GPS satellites (up to the Block IIRM) have power degradation (in excess of that expected from radiation) of about 1.5% per year. This degradation is primarily in the short-circuit current, consistent with contamination on the solar array cover glasses, which was detected by a thermal monitor on one GPS satellite solar array, and to be consistent with the power degradation observed on a highly arced GPS-like laboratory solar array if extrapolated to GPS undispersed event rates. The GPS arc rates required for solar array contamination and consistent with the onboard observed event rates are very high, in fact, higher than the rates measured previously on SCATHA, CTS, and other satellites. It is conjectured that the effects of these arcs on satellite power systems have been routinely prevented by highly filtering the power system and antenna response, that most satellites have had no way to detect arcing, and that most power losses up to the present time have been ascribed to radiation damage. Results of new optical and radio-frequency radio frequency observations of satellite arcing are discussed, as well as laboratory measurements confirming the high arc rates and their consequences.

Salp swarm algorithm-based optimal load frequency control of hybrid renewable power systems with communication delay and excitation cross-coupling effect

This paper proposes a new application of the salp swarm algorithm (SSA) to fine-tune the gains of proportional-integral-derivative (PID) controllers of load frequency control (LFC) of a multi-area hybrid renewable nonlinear power system. To analyze the system nonlinearity, a dead-band is implemented in the governor model, a generation rate constraint is employed with the turbine model, and a communication delay time of phase measuring unit devices is carried out in the secondary automatic LFC loop. An exact model is established to take into consideration the effect of cross-coupling between the excitation control system and LFC loop. A single and multi-objective functions are performed to test the validity of the proposed controllers. To obtain a more realistic study, real wind speed data are involved in the wind farm model and real sun irradiations for a photovoltaic system that captured from a field test are incorporated to check the validity of the SSA-PID controllers under power system nonlinearities and renewable energy sources variability and uncertainties. The effectiveness of SSA-PID controller is compared with other optimization methods based-PID controller under several operating conditions. With the proposed controller, the LFC dynamic responses of multi-area hybrid nonlinear power systems shall be further enhanced.

Power system responses to geomagnetic disturbances recognized using phasor measurement recordings

Geomagnetically induced currents (GICs) flowing through transformers result in a DC bias, which poses a threat to safe and stable power grid operation. To evaluate the influence of geomagnetic storms on power systems, it is necessary to study actual power system responses. In this paper, the power system response is represented separately using current and reactive power measurements acquired using phasor measurement units (PMUs). On the basis of the data obtained from a wide-area measurement system, the power system responses to geomagnetic disturbances at Yangquan Substation, Shanxi, China were obtained. By employing the plane wave method, the data acquired during two mild magnetic storms at the Shisanling Geomagnetic Observatory were used to calculate the electric field and GIC at Yangquan Substation. The response variables and calculated GIC results agreed well, and the response variables were thus applied to assess the GIC level in the power system. The results show that the fluctuations in the PMU measurements were caused by GICs in the power system, laying the foundation for a significantly more detailed geomagnetic storm risk monitor.

Impacts of Responsive Loads and Energy Storage System on Frequency Response of a Multi-Machine Power System

In recent decades, the power grid’s configuration is shifting towards a smart grid where responsive loads and energy storage systems (ESS) are finding an increased role in the power system operation. In the presented work, a mathematical formulation for frequency response analysis of a multi-machine power system is developed, considering the individual and combined roles of ESS and responsive loads. The validity of the developed model is demonstrated with the help of multiple case studies, which consider the various configurations of the power system. Moreover, different combinations of capacities of generation units, ESS and responsive loads are also simulated. With the help of mathematical model and simulation results, it is demonstrated that ESS and responsive loads may improve the economy and performance of the power system even during the failure of a certain portion of generation capacity. Though the case studies consider non-reheat turbines only, the mathematical model and conclusions are equally valid for other types of turbines as well.

Designing centralised and distributed system integrity protection schemes for enhanced electric grid resiliency

System integrity protection schemes (SIPSs) are installed at substations to preserve power system stability by preventing bottlenecks in transmission and distribution networks and improving the overall reliability. SIPSs are also referred to as remedial action schemes, emergency control systems, special protection systems, and wide-area control schemes. Typical SIPSs have centralised computing architectures with applications to ensure reliable power system responses during transmission outages, remediate regional transmission bottlenecks caused by delays in the construction of new lines, prevent severe instability and blackouts due to faults and inadvertent disconnections, prevent line damage resulting from thermal limits, avoid voltage collapse, and protect against other critical events in the power system. This study proposes a distributed computing architecture for SIPSs, including algorithms that use DC and AC optimal power flow. The authors classify SIPS applications based on control types and propose novel algorithms for next-generation SIPSs using synchrophasors and real-time technology. The authors also propose testing requirements and architectures for validating SIPSs prior to field installation. Lastly, the authors share results obtained using the proposed SIPS for a transmission overload condition caused by excessive wind generation.

Improving Angle Stability by Switching Shunt Reactors in Mixed Overhead Cable Lines. An Italian 400 kV Case Study

Stringent environmental constraints make the construction of new transmission overhead lines more and more difficult. Alternatively, today it is possible to use cable lines for high (HV) and extra-high (EHV) voltage systems. The configuration of the so-called mixed lines can create some problems in the operation of the electrical system, both during steady-state and transient conditions. In particular, the system stability is one of the main concerns when analyzing the dynamic response of power systems. In this paper, the study of angular stability of a system containing a mixed line is presented: a specific control logic applied to the shunt reactors of the mixed line is proposed as improvement of the overall system stability. The proposed switching logic is first discussed from a theoretical point of view and validated with two different testing systems. Then, the existing overhead-cable lines connecting Sicily to the rest of continental Europe 400 kV power system are taken as case study for the application of the proposed switching strategy. Several simulations are performed in the power system analysis software NEPLAN360: the results show the fundamental role of the timing of the control actions applied on the shunt reactors in helping the system to keep the stability. The proposed control proves to be an effective support to the system subjected to critical contingencies, contributing decisively to avoid the angular separation between areas and therefore to preserve the stability of the system.

Distributed Nash equilibrium computation in aggregative games: An event-triggered algorithm

This paper is concerned with the problem of distributed Nash equilibrium computation in aggregative games. Note that the traditional computation algorithms are designed based on time-scheduled communication strategy, which may lead to high communication consumption of the whole network. To reduce the consumption, this paper proposes a novel distributed algorithm with an event-triggered mechanism, where the communication between any two agents is only carried out when an edge-based event condition is triggered. In the convergence analysis of the proposed algorithm, an important event-related error variable is firstly defined. Then, based on a zero-sum property of this event-related error, two key relations on the agents’ estimates in the proposed algorithm are provided. Further, by using these relations, it is proven that the agents’ estimates can achieve a Nash equilibrium under a proper event-triggering condition. Finally, examples on the demand response of power systems are presented to verify the theoretical findings.

Research on the Responses of the Hybrid Power System based on Energy Profiles

Abstract The article contains the chosen results of research on the use of energy profiles controlling the operation of a group of devices powered by a hybrid power source. The concept of using alternative energy sources allows to reduce the total weight of the power system and model its behavior during work. Modern fuel cells are characterized with a very high energy density to mass ratio [Wh/kg], and the additional cooperation of supercapacitors and lithium-ion batteries supporting their operation ensures continuous operation and the required dynamics response while maintaining a low mass of the power supply system. The author presented the general configuration of the layout model, as well as the results of tests of individual elements included in the physical implementation of the hybrid power system.

Assesment of Power Quality Disturbances For Grid Integration of PV Power Plants

Power Quality problems, which have become an important consumer issue in recent years, are defined as changes in voltage, current, or frequency in the power system. Among the factors affecting energy quality in grid-connected PV systems are island mode operation, current and voltage harmonics, transients, flicker, interruption, DC offset, notches, frequency changes, voltage sag / swell, voltage imbalances in the system and power factor. Because of the power quality problems, several transmission and distribution losses can occur due to both the consumers and the generators. Also, the integration of PV power plants to the main grid will cause several power quality problems, and a reliable operation of the grid with PV power plants is a significant issue for distributed generation. Thus, the first step in preparing a reliable algorithm for detecting power quality events occurring in the current grid is to model a power system in which power quality impairments can be analyzed. In this work, the power quality disturbances that occur in the low-voltage grid that is fed through both the main grid and the grid-connected PV system are modeled and investigated. Developed electric power distribution model includes simulation of voltage sags caused by three phase fault, transformer energization and asynchronous motor switching, voltage swells caused by three phase fault, transients due to large capacitor bank switching, harmonics and notches caused by the load connected via the power converter. Examination of the power quality disturbances with simulation clearly revealed the resulting waveforms, the response of the electrical power system to the fault conditions. Another advantage of the realized study is that the developed model can be used to measure the performance of the PV connected distributed generation system in fault detection and classification studies.

Estimation of the resonance between forcing and weakly stable oscillations in power systems

Using a simple test example, this paper demonstrates that a weakly damped eigen-oscillation of an electric power system can lead to a loss of stability in the presence of its resonance with forcing oscillation. Such resonant interactions can risk the power system security, as confirmed by recent events in the Western American and Nordic power systems. Conventional eigenvalue analysis cannot detect the observed instability due to its non-linear nature. We show that the critical condition for the appearance of this type of instability can be the value of the perturbation energy accumulated in the system over time. To quantify the risk of stability loss, we examine the model of forcing oscillations and the resonance response of power system in a linear approximation and compare it with the simulation results for the two-area Kundur test system.

Research on ordered charge and discharge of cluster electric vehicle based on index selection

The basic characteristics of electric vehicles are important basis for studying the behavior of electric vehicles. According to the basic characteristics of electric vehicles, this paper establishes an electric vehicle convergence model and its control strategy with demand-side response. Taking into account the demand for electric vehicles, electric vehicle aggregators and power companies, reducing the cost of control, while reducing the impact on electric vehicles. Based on the real-time state of charge, the conditions of electric vehicle in the network and other factors to build the assessment model of the scheduling potential, and then put forward the demand response indicators of electric vehicles, and give the corresponding aggregation strategy. considering the multiple constraints , such as the cost constraints of electric vehicles participating in grid regulation, the charging requirements of electric vehicle owners, and the battery consumption of electric vehicles, a control strategy model is proposed for electric vehicles participating in demand response of power systems. The simulation test shows that the aggregation strategy can not only meet the travel needs of electric vehicle owners, but also reduce the impact on the electric vehicle caused by frequent switching of charge and discharge status. In addition, it can also reduce the cost of grid regulation.

Analysis of necessary primary reserve of a high wind penetration power system

The increasing wind power penetration poses a great challenge to the operation stability of the traditional power system. The current mainstream wind turbines are variable speed wind turbines. Some of the traditional power supplies are replaced by large-scale wind power integration. The inertia of a variable speed wind turbine is decoupled by power electronic converters from the power network and therefore does not intrinsically contribute to power system inertia. The principle of the power system frequency regulation is introduced. The primary frequency response of the high wind penetration power system is analysed based on a typical power system frequency response model and the primary frequency characteristic of the wind turbine. Necessary primary reserves provided by wind farms are studied based on the real data of a specific power system.

MAPE - An Alternative Fitness Metric for Prony Analysis of Power System Signals

Abstract Phasor Measurement Units have facilitated tracking of oscillations in power system response signals. This has provided an impetus for identifying unstable component modes directly from oscillatory signals. Prony analysis, the earliest method proposed for this purpose, throws up some trivial modes. These not only distract the analyzer but also prolong processing time thereby delaying corrective action. Hence the fitness metric chosen should serve to minimize the number of trivial modes. The conventional fitness metric is Signal-to-Noise Ratio (SNR), which is actually Signal-to- Estimation error Ratio (SER). This paper proposes that Mean Absolute Percentage Error (MAPE) can also serve well as a fitness metric. It is shown through case studies carried out on well-known four-machine power system that there are a few cases where MAPE performs better than SER while in some instances SER works better. This inference is verified even in the presence of measurement noise. Hence a novel fitness metric is proposed combining MAPE with SER. Case studies on simulated signals obtained from New England-power system prove that this novel metric can achieve considerable reduction in processing time. Besides, an exponential binary search has been suggested for determining the optimal model order in minimum number of iterations.

Risk-based method to secure power systems against cyber-physical faults with cascading impacts: a system protection scheme application

The utilization levels of the transmission network can be enhanced by the use of automated protection schemes that rapidly respond to disturbances. However, such corrective systems may suffer from malfunctions that have the potential to exacerbate the impact of the disturbance. This paper addresses the challenge of jointly optimizing the dispatch of generators and protection settings in this context. This requires a holistic assessment of the cyber (protection logic) and physical (network) systems, considering the failures in each part and their interplay. Special protection schemes are used as a prototypical example of such a system. An iterative optimization method is proposed that relies on power system response simulations in order to perform detailed impact assessments and compare candidate solutions. The candidate solutions are generated on the basis of a security-constrained dispatch that also secures the system against a set of cyber failure modes. A case study is developed for a generation rejection scheme on the IEEE reliability test system (RTS): candidate solutions are produced based on a mixed integer linear programming optimisation model, and loss-of-load costs are computed using a basic cascading outage algorithm. It is shown that the partial security approach is able to identify solutions that provide a good balance of operational costs and loss-of-load risks, both in a fixed dispatch and variable dispatch context.

Impacts of Inter-annual Wind and Solar Variations on the European Power System

SummaryWeather-dependent renewable energy resources are playing a key role in decarbonizing electricity. There is a growing body of analysis on the impacts of wind and solar variability on power system operation. Existing studies tend to use a single or typical year of generation data, which overlooks the substantial year-to-year fluctuation in weather, or to only consider variation in the meteorological inputs, which overlooks the complex response of an interconnected power system. Here, we address these gaps by combining detailed continent-wide modeling of Europe's future power system with 30 years of historical weather data. The most representative single years are 1989 and 2012, but using multiple years reveals a 5-fold increase in Europe's inter-annual variability of CO2 emissions and total generation costs from 2015 to 2030. We also find that several metrics generalize to linear functions of variable renewable penetration: CO2 emissions, curtailment of renewables, wholesale prices, and total system costs.

Load frequency control of multi-area interconnected thermal power system: artificial intelligence-based approach

In the current work, an ant colony optimisation (ACO) optimisation technique for load frequency control was proposed for tuning the performance of the proportional-integral-derivative (PID) controller gain values. This led to oscillations suppression in the power system response. A system consisted of three equal thermal generating units equipped with (PID) controller was investigated. The PID controller gain values are obtained by using three different cost functions such as the integral square error (ISE), integral time absolute error (ITAE) and integral absolute error (IAE). Time domain specifications of the settling time and overshoot were considered in the system response analysis.