Power System Frequency Fluctuations Research Articles

Decentralized control strategy of thermostatically controlled loads considering the energy efficiency ratio and measurement error correction

The elimination of traditional thermal generators and the increase of renewable energy source access reduced the inertia of the power system, and thermostatically controlled loads have the potential to provide ancillary services to the power system. This paper introduces a decentralized control strategy for thermostatically controlled loads (TCLs), which focuses on assisting large-scale TCLs in providing frequency support to power systems while considering energy efficiency ratio and measurement error correction. Initially, the nonlinear relationship between heat flow and TCLs’ power is modeled using a polynomial relationship, and the coefficients are determined through a data-driven method to enhance accuracy in TCLs modeling and assess their regulation potential precisely. Subsequently, a decentralized control strategy tailored for power system frequency regulation is developed. To account for measurement errors in TCLs controllers, a measurement error back-correction method is proposed. Simulation examples demonstrate the effectiveness of the proposed control strategy in achieving accurate modeling and control of TCLs and reducing power system frequency fluctuations.

GWO- and SSA-Tuned PID Control for Frequency Regulation in Multi-Area PowerNetwork Integrated with Plug-in Electric Vehicle

ABSTRACT The Plug-in Electric Vehicles (PEVs) can be influential in containing power system frequency fluctuations. This study, therefore, investigates the efficacy of frequency regulation for PEV-integrated multi-area power network using Grey Wolf Optimizer (GWO) and Salp Swarm Algorithm (SSA) optimized Proportional-Integral-Derivative (PID) control. Instant investigation not only brings out the relative competence of GWO and SSA but also examines the impact of PEV in improving the system performance. The varying operating conditions are realized by subjecting the system to step and random load variations in either or both of the areas. With the proposed control scheme and involvement of PEV, system frequency and tie-line power excursions settle quicker with their peak swings also getting restricted to a lower value, while the oscillations are arrested as well to a great extent. Further, it’s the SSA that shows its superiority over GWO as per the simulation results executed in MATLAB.

Factors affecting forensic electric network frequency matching – A comprehensive study

The power system frequency fluctuations could be captured by digital recordings and extracted to compare with a reference database for forensic timestamp verification. It is known as the Electric Network Frequency (ENF) criterion, enabled by the properties of random fluctuations and intra-grid consistency. In essence, this is a task of matching a short random sequence within a long reference, whose accuracy is mainly concerned with whether this match could be uniquely correct. In this paper, we comprehensively analyze the factors affecting the reliability of ENF matching, including the length of test recording, length of reference, temporal resolution, and Signal-to-Noise Ratio (SNR). For synthetic analysis, we incorporate the first-order AutoRegressive (AR) ENF model and propose an efficient Time-Frequency Domain noisy ENF synthesis method. Then, the reliability analysis schemes for both synthetic and real-world data are respectively proposed. Through a comprehensive study, we quantitatively reveal that while the SNR is an important external factor to determine whether timestamp verification is viable, the length of test recording is the most important inherent factor, followed by the length of reference. However, the temporal resolution has little impact on performance. Finally, a practical workflow of the ENF-based audio timestamp verification system is proposed, incorporating the discovered results.

Frequency control in power system using Fuel Cell cogeneration system in Kyushu area

This paper applies a method for reducing frequency fluctuations in power system by using Fuel Cell cogeneration system (FC cogeneration). Frequency fluctuation in power system is used as a feedback signal to a controller of FC cogeneration. In addition, the potential of power system for controlling frequency is estimated from the supply and demand record, and the timing, when power system requires the control from FC cogeneration, is determined. Thus, the effectiveness of the method is analyzed, considering the conditions in Kyushu area. The impact of the proposed method is high since the available capacity for the frequency control in power system is small in the evening. Even if 13.7% of the capacity for regulating frequency which is the pumped storage power generation on 22nd May 2019 is reduced, the FC cogeneration can regulate the frequency in power system.

Efficient Model for Accurate Assessment of Frequency Support by Large Populations of Plug-in Electric Vehicles

In recent years, plug-in electric vehicles (PEVs) have gained immense popularity and are on a trajectory of constant growth. As a result, power systems are confronted with new issues and challenges, threatening their safety and reliability. PEVs are currently treated as simple loads due to their low penetration. However, as their numbers are growing, PEVs could potentially be exploited as distributed energy storage devices providing ancillary services to the network. Batteries used in PEVs are developed to deliver instantaneously active power, making them an excellent solution for system frequency support. This paper proposes a detailed dynamic model that is able to simulate frequency support capability from a large number of PEVs, using an innovative aggregate battery model that takes into account the most significant constraints at PEV and aggregate battery levels. The cost optimization algorithm, which is the most time-consuming process of the problem, is executed only at the aggregate battery level, thereby reducing the computational requirements of the model without compromising the obtained accuracy. The proposed method is applied to the power system of Crete exploiting detailed statistical data of EV mobility. It is proven that PEVs can effectively support power system frequency fluctuations without any significant deviation from their optimal operation.

Fuel Cell Co-generation and PCS Control for Suppressing Frequency and Voltage Fluctuation due to PV Power

The purpose of this study is to control active power of fuel cell co-generation system and reactive power of power conditioning system to suppress frequency fluctuation in power system and voltage fluctuation in distribution system caused by variation of photovoltaic power. The governor-free control for fuel cell co-generation system is applied to reduce frequency fluctuation in power system. A method which controls power fluctuation in distribution system for power conditioning system is applied to reduce voltage fluctuation. The authors reveal the effectiveness of the method by a simulation model. The results suggest that fuel cell co-generation system and power conditioning system work to reduce each targeted fluctuation.

Energy Storage Auxiliary Frequency Modulation Control Strategy Considering ACE and SOC of Energy Storage

As more and more unconventional energy sources are being applied in the field of power generation, the frequency fluctuation of power system becomes more and more serious. The frequency modulation of thermal power unit has disadvantages such as long response time and slow climbing speed. Battery energy storage has gradually become a research hotspot in power system frequency modulation due to its quick response and flexible regulation. This article first introduced the control method based on the signal of ACE (Area Control Error), which is the basic way of secondary frequency modulation and analyzed the features of the basic control mode. Then it zoned the signal of ACE and SOC of the battery energy storage system. On this basis, different frequency modulation methods were proposed according to the requirements of frequency modulation and the characteristics of the output of different regions. In addition, the fuzzy controller is used to smooth the output of the energy storage system under the normal adjustment of the regional control deviation and the normal charging and discharging state of SOC. Finally, a two-region interconnection simulation system was established based on the MATLAB simulation platform, and the simulation results verified the effectiveness of the proposed control strategy.

Simulation analyses of stabilization control of power system frequency fluctuations resulting from wind farm output by gas turbine thermal power plant

AbstractThis paper presents a basic study about the control ability of LNG thermal power plant driven by Motor‐assisting Gas Turbine (MGT) for frequency stabilization of power grid system. An analytical model of the regulation system with assisting motor and gas turbine is developed, and its performance for frequency stabilization under fluctuating power due to renewable energy sources is investigated by numerical simulation analyses.

Simulation Analyses of Stabilization Control of Power System Frequency Fluctuations Resulting from Wind Farm Output by Gas Turbine Thermal Power Plant

Simulation Analyses of Stabilization Control of Power System Frequency Fluctuations Resulting from Wind Farm Output by Gas Turbine Thermal Power Plant

Frequency Control of Power System with Renewable Power Sources by HVDC Interconnection Line and Battery Considering Energy Balancing

Recently, introduction of renewable energy sources like wind power generation and photovoltaic power generation has been increasing from the viewpoint of environmental problems. However, renewable energy power supplies have unstable output due to the influence of weather conditions such as wind speed variations, which may cause fluctuations of voltage and frequency in the power system. This paper proposes fuzzy PD based virtual inertia control system to decrease frequency fluctuations in power system caused by fluctuating output of renewable energy sources. The proposed new method is based on the coordinated control of HVDC interconnection line and battery, and energy balancing control is also incorporated in it. Finally, it is concluded that the proposed system is very effective for suppressing the frequency fluctuations of the power system due to the large-scale wind power generation and solar power generation and also for keeping the energy balancing in the HVDC transmission line.

A Virtual Filter Approach for Wind Energy Conversion Systems for Mitigating Power System Frequency Fluctuations

The increasing penetration of wind power may deteriorate power system frequency performance. This paper proposes a novel virtual filter (VF) approach for a grid-connected wind energy conversion system to mitigate power system frequency fluctuations. The principle is to modify the traditional wind power controller to emulate a physical energy storage system to smooth the wind power output. The VF proposed in this paper is tuned as a band-stop filter to selectively reject the power system frequency-sensitive components in wind power output. Therefore, the power system frequency fluctuations can be correspondingly reduced with only a small amount loss of wind energy. The advantages of the proposed VF are: 1) no need for a physical deployment of energy storage system, 2) no need for power system frequency signal and communication channel, and 3) ability to selectively filter the power system frequency sensitive components. Simulation results verified the outstanding performance of the proposed VF in system frequency fluctuation mitigation, while with less wind energy loss comparing with existing method.

可変速揚水発電機の不感帯型周波数制御による電力系統周波数変動の安定化

This paper proposes a new control system for Adjustable-Speed Pumped-Storage Generator (ASG) to decrease frequency fluctuations of power system with a large amount of wind farm introduced. When a large amount of wind power generation is connected to the power system, it can decrease power quality, e. g., frequency variations. There are some methods to suppress the frequency fluctuation in the power system, among which ASG can be an effective countermeasure. However, there has not been sufficient report on the frequency control by using ASG. This paper proposes a new output control system with dead band for ASG to smooth frequency fluctuations of the power system arisen from fluctuating output of the wind farm.

可変速風力発電機のオンライン出力帯域制御による電力系統周波数変動抑制

可変速風力発電機のオンライン出力帯域制御による電力系統周波数変動抑制

An Effective Control Scheme of a Back-to-Back Converter with Shunt-Connected HTS SMES for Frequency Regulation of an Islanded Microgrid

High temperature superconducting magnetic energy storage (HTS SMES) is known as an effective solution to significantly decrease the voltage and power fluctuations of grid connected wind power generation system (WPGS). This paper implements an effective control scheme of a back-to- back converter with shunt-connected HTS SMES for the frequency regulation of an islanded microgrid. The back-to-back converter is used to connect the WPGS to the grid. A large-scale HTS SMES is linked to the DC side of the back-to-back converter through a two-quadrant DC/DC chopper. An adaptive control strategy is implemented for the back-to-back converter and the two-quadrant DC/DC chopper to improve the efficiency of the whole system. The performance of the proposed control system was evaluated in a test power system using PSCAD/EMTDC. The simulation results clearly show that the back-to-back converter with shunt-connected HTS SMES operates effectively with the proposed control strategy for stabilizing the power system frequency fluctuations.

Microcontroller Based Under/Over Frequency Relay for Power System Protection

This paper investigates the frequency fluctuation in power system and protect the power system from its harmful effects. Therefore we design a Microcontroller Based Under/Over Frequency Relay. In this paper we use microcontroller AT89S52 for protecting the power system from the problem of frequency fluctuation. When frequency goes below or above from desired value then electromagnetic relay trip and isolate our power system from its harmful effect. Electromechanical protective relays operate by either magnetic attraction, or magnetic induction. Frequency Variation also decrease the life of the equipment and directly affect the overall production of the plant.

Time-Domain Simulation of Power System Frequency Fluctuations Caused by Intermittent Wind Power

Wind power is uncertain. When the proportion of wind power capacity is large, the impact of the randomness of the output power on the grid frequency is more significant. Aiming at system stability influence after integrating a high capacity of wind turbines, this paper introduces the dynamic simulation model for electric power system with wind power, and makes an equivalent transformation processing for the wind turbine and generator. By using improved Euler method, this paper analyzes the impact of system frequency through time-domain simulation when disturbance occurs at wind farm side. Simulation results show that when wind speed changes, the established model and algorithm can effectively simulate the dynamic response of the frequency, and also these results can provide a reference for the frequency stability when wind turbines integrate into power system.

Operating Characteristic Analysis of HTS SMES for Frequency Stabilization of Dispersed Power Generation System

This paper analyses operating characteristic of high temperature superconducting magnetic energy storage (HTS SMES) for frequency stabilization of dispersed power generation system. The wind power generation system (WPGS) fluctuates due to wind speed variation and affects the frequency and voltage fluctuations of the utility. SMES is probably a key technology to overcome these fluctuations. To stabilize power system frequency, a large-scale HTS SMES is connected to the terminal of the WPGS. The authors analysed the load side frequencies using two different configurations of SMES, one consisting of a single magnet and the other of a dual magnet. From the simulation results, it can be concluded that the SMES is a useful device for stabilizing the power system frequency fluctuations, and a dual magnet type SMES is more effective for frequency stabilizing but exhibits more AC loss due to the increased operating current than a single magnet type.

小規模系統に分散配置された可制御負荷による系統周波数制御法

From depletion of energy resources and consideration to natural environment, dispersed power system such as wind power generator is scheduled for introduction. Additionally, all electrification apartment house or residence and electric vehicles are increase in recent years. However, due to the fluctuating power from renewable energy sources and loads, frequency fluctuation of power system become problematic. This paper presents a methodology for grid frequency control by distributed controllable loads. This system consists of diesel generator, wind farm, and loads. By applying power consumption controller with H∞ control theory, grid frequency fluctuation is maintained around rated value. In order to verify the effectiveness of the proposed system, MATLAB/Simulink is used in simulations.