Interconnected Power System Model Research Articles

A Low-Frequency Oscillation Suppression Method for Regional Interconnected Power Systems with High-Permeability Wind Power.

With the integration of large-scale wind power into the power grid, the impact on system stability, especially the issue of low-frequency oscillations caused by small disturbances, is becoming increasingly prominent. Therefore, this paper proposes a damping quantitative analysis method for regional interconnected power systems incorporating large-scale wind power. Using the cross-entropy particle swarm optimization (CE-PSO) algorithm, the control parameters of wind turbines are optimized to suppress low-frequency oscillations in interconnected systems. The method begins with the state equation of the interconnected power system in two regions; it deduces the characteristic polynomial of the interconnected system, including wind farms, and takes into account the influence of wind power integration on the electrical connectivity of the system. Subsequently, the influence of wind turbine control parameters on the system is quantified, and a quantitative analysis model of the impact of wind power integration on system damping characteristics is constructed. Based on this, an optimization model for wind turbine control parameters is established, and the CE-PSO algorithm is utilized to achieve suppression of low-frequency oscillations in interconnected power grids with wind power integration. Finally, the accuracy and effectiveness of the proposed method are verified through a typical electromagnetic transient simulation model of the two-region interconnected power system.

Droop Frequency Limit Control and Its Parameter Optimization in VSC-HVDC Interconnected Power Grids

With the gradual emergence of trends such as the asynchronous interconnection of power grids and the increasing penetration of renewable energy, the issues of ultra-low-frequency oscillations and low-frequency stability in power grids have become more prominent, posing serious challenges to the safety and stability of systems. The voltage-source converter-based HVDC (VSC-HVDC) interconnection is an effective solution to the frequency stability problems faced by regional power grids. VSC-HVDC can participate in system frequency stability control through a frequency limit controller (FLC). This paper first analyses the basic principles of how VSC-HVDC participates in system frequency stability control. Then, in response to the frequency stability control requirements of the sending and receiving power systems, a droop FLC strategy is designed. Furthermore, a multi-objective optimization method for the parameters of the droop FLC is proposed. Finally, a large-scale electromagnetic transient simulation model of the VSC-HVDC interconnected power system is constructed to verify the effectiveness of the proposed droop FLC method.

Proximity Index Value Based Systematized Approximation of Higher-Order Interconnected Power System Model

Proximity Index Value Based Systematized Approximation of Higher-Order Interconnected Power System Model

Security load frequency control model of interconnected power system based on deception attack.

The interconnected power system connects the power grids of different regions through transmission lines, achieving power interconnection and resource sharing. However, data is transmitted through open power networks and is more susceptible to network attacks. To improve the stability of interconnected power systems under deception attacks, three scenarios of system security load frequency control were studied. Based on the construction of a dynamic model of load frequency control, an event-triggered strategy was used to reduce the communication frequency between nodes, resulting in a reduction in the amount of network transmission data. A sliding mode controller was constructed to solve the problem of event-triggered sliding mode security load frequency control. Elastic event-triggered sliding mode load frequency control for interconnected power systems under mixed attacks. The simulation results showed that using the load frequency control model triggered by events, the load frequency deviation of the interconnected power system can be stabilized at around 12 seconds, effectively saving the cost of network resources. Under the regulation of the load frequency control model based on sliding mode control, the interconnected power system stabilized in 10 seconds, reducing the load of network transmission. The elastic event-triggered sliding mode load frequency control model can ensure stable transmission of power data under various attacks and has good anti-interference performance. The results of this study have played an important role in achieving the stability of power resource supply. Compared with previous studies on individual power systems, this study solves the attack problem of interconnected power systems and considers the frequency control problem of system security loads under mixed attacks, enabling the system to recover stability faster.

Fractional-Order Load Frequency Control of an Interconnected Power System with a Hydrogen Energy-Storage Unit

Modern power systems are confronted with widespread concern on the frequency stability issue due to the widespread integration of randomly fluctuating renewable resources. To address the above concern, this work introduces a load-frequency-control (LFC) scheme based on a parameter tuning strategy for fractional-order proportional–integral–derivative (FOPID) controller. Firstly, a two-area interconnected power system (IPS) model, including thermal, hydro, solar, wind, and gas power generator and a hydrogen-based energy-storage unit, is established. Then, a FOPID controller is designed for this IPS model, and an improved gradient-based optimizer (IGBO) is developed to adaptively regulate the parameters of the FOPID controllers. Finally, the effectiveness of the offered LFC scheme is tested through load disturbance and renewable energy fluctuations test scenarios and provides a comparison and robustness analysis among different schemes. The test results validated that the offered LFC scheme can effectively suppress the frequency fluctuations of the IPS and has excellent robustness.

Influence mechanism and virtual power system stabiliser method of virtual synchronous generator for low‐frequency oscillation of power system

AbstractThe virtual synchronous generator (SG) (VSG) can not only enhance the inertia of the grid, but also introduce the oscillation characteristics of SG, which is easy to interact with the power angle of SG in the grid, and even produce low‐frequency oscillation (LFO). The authors first construct a two‐machine interconnected power system model containing VSG and traditional SG. The model is linearised to construct the state space equations to obtain the Phillips–Heffron model with VSG. The LFO path of action between VSG and SG is analysed. To reduce the negative damping torque provided by VSG to SG through this path, a virtual power system stabiliser (VPSS) is proposed and the controller parameters are adjusted according to the phase compensation method. Finally, the effectiveness of VPSS is verified by modal analysis and simulation comparison.

Design of Observer-Based Discrete-Type PID Control for Reconstructed Jump Model of Interconnected Power System Under Hybrid Attacks

In this article, observed-based discrete proportion-integration-differentiation (PID) control for multi-area interconnected power systems is addressed under hybrid attacks. Firstly, a reconstructed jump model for interconnected power systems is proposed by taking the circumstance of data packet loss into consideration, which caused by the stochastic transmission delay of sampled data. Then, different from the traditional continuous-type PID control, an observer-based discrete-type PID control strategy is designed for discrete-time power system. Besides, due to the sampled data may be tampered or shield in open communication networks, the hybrid attacks, i.e., deception attacks and denial-of-service attacks, with random manners are considered. Furthermore, an input-to-state stable criterion is derived by constructing appropriate Lyapunov-Krasovskii functionals. Finally, the discrete-type PID controllers and observer are achieved, and the validity of proposed approach are also demonstrated in the illustrative examples section.

Decentralized observer‐based integral sliding mode control design of large‐scale interconnected systems and its application to doubly fed induction generator‐based wind farm model

SummaryThis paper presents the design of a decentralized observer‐based control scheme for large‐scale interconnected systems based on the integral sliding mode control (ISMC) approach. To do this, a novel decentralized observer is designed via the ISMC approach that helps to estimate the unmeasured states. Then, by constructing a suitable Lyapunov function, sufficient conditions are derived in terms of matrix inequality, which guarantees the asymptotic stability of the interconnected system and the ultimate boundedness of estimation errors under external disturbances. An interconnected power system (IPS) integrated with a doubly fed induction generator (DFIG)‐based wind farm model is provided as a direct application. Theoretical conditions are validated through numerical simulations, in this regard, a well‐structured model of IPS with a DFIG‐based wind farm is introduced. From the simulation results, it is proven that the proposed decentralized observer‐based ISMC can provide a better estimation of the internal states in two area IPS with DFIG‐based wind farm.

An approach for the aggregation of power system controllers with different topologies

This paper proposes an approach to aggregate non-structured power system controllers preserving the dynamical characteristics of the original devices. The method is based on linear operations that use the frequency response of the elements, resulting in an accurate input–output description of the equivalent controller when compared to the original ones. The developed method was applied to a model of the future interconnected Paraguayan-Argentinean power system to produce a dynamic equivalent used in a real-time simulator to test the special protection scheme needed for the safe operation of the this future system. Transient and small-signal stability studies presented matching simulation results in the time domain with significantly reduced computational burden and processing time.

Robust self tuned AGC controller for wind energy penetrated power system

This paper presents the self-tuned Automatic Generation Control for an interconnected power system with dominant wind energy penetration. The uncertain behavior of wind power plant has random fluctuations on the frequency of the power system and optimum performance cannot be achieved by the fixed structure controller. Thus, the self-tuned controller can handle the load disturbances of varying nature efficiently, by generating control signal based on least square method and minimum variance strategy. A two-area interconnected power system model consists of thermal, hydro and doubly fed induction generator-based wind power plants with dominant participation factor and random power output is considered for the simulation study. The self-tuned AGC efficiently regulates the variation in area control error caused by load disturbance and wind fluctuation, by adjusting its parameter automatically based on least square algorithm. Moreover, controller parameters also adjust its parameters qualitatively based on equipment parameter under various operating condition.

Novel chaos game optimization tuned-fractional-order PID fractional-order PI controller for load\u2013frequency control of interconnected power systems

In this work, chaos game optimization (CGO), a robust optimization approach, is employed for efficient design of a novel cascade controller for four test systems with interconnected power systems (IPSs) to tackle load–frequency control (LFC) difficulties. The CGO method is based on chaos theory principles, in which the structure of fractals is seen via the chaotic game principle and the fractals’ self-similarity characteristics are considered. CGO is applied in LFC studies as a novel application, which reveals further research gaps to be filled. For practical implementation, it is also highly desirable to keep the controller structure simple. Accordingly, in this paper, a CGO-based controller of fractional-order (FO) proportional–integral–derivative–FO proportional–integral (FOPID–FOPI) controller is proposed, and the integral time multiplied absolute error performance function is used. Initially, the proposed CGO-based FOPID–FOPI controller is tested with and without the nonlinearity of the governor dead band for a two-area two-source model of a non-reheat unit. This is a common test system in the literature. A two-area multi-unit system with reheater–hydro–gas in both areas is implemented. To further generalize the advantages of the proposed scheme, a model of a three-area hydrothermal IPS including generation rate constraint nonlinearity is employed. For each test system, comparisons with relevant existing studies are performed. These demonstrate the superiority of the proposed scheme in reducing settling time, and frequency and tie-line power deviations.

Frequency Regulation Model of Bulk Power Systems With Energy Storage

This paper presents a Frequency Regulation (FR) model of a large interconnected power system including Energy Storage Systems (ESSs) such as Battery Energy Storage Systems (BESSs) and Flywheel Energy Storage Systems (FESSs), considering all relevant stages in the frequency control process. Communication delays are considered in the transmission of the signals in the FR control loop and ESSs, and their State of Charge (SoC) management model is considered. The system, ESSs and SoC components are modelled in detail from a FR perspective. The model is validated using real system and ESSs data, based on a practical transient stability model of the North American Eastern Interconnection (NAEI), and the results show that the proposed model accurately represents the FR process of a large interconnected power network including ESS, and can be used for long-term FR studies. The impact of communication delays and SoC management of ESS facilities in the Area Control Error (ACE) is also studied and discussed, as well as the computational efficiency of the proposed FR model.

Research on wind farm participating in AGC based on wind power variogram characteristics.

The increasing integration of large-scale wind power aggravates the difficulty of maintaining system frequency deviations in a certain range. The frequency regulation pressure of conventional generators increases, which requires wind farms to participate in system frequency regulation. In this paper, a multi-area interconnected power system frequency response model with wind power is established. Based on the frequency response model, the state space model of regional interconnected power system is presented. Then, the wind power variogram characteristics are introduced for estimating wind power variations in different time-scales. By predicting the wind power variations in AGC time-scale, a strategy of wind farm participating in AGC system is proposed and performed based on model predictive control (MPC). The control strategy makes the conventional units and wind farms to participate in AGC system coordinately. Simulation results are provided which verifies the feasibility and validity of the proposed strategy.

Decentralized Detection and Mitigation of Multiple False Data Injection Attacks in Multiarea Power Systems

This article presents an observer-based decentralized detection and mitigation (ODDM) scheme for the interconnected power system subject to multiarea multichannel false data injection attacks (FDIAs). In the ODDM scheme, the FDIAs on the measurement channel and control channel of power system are modeled as unknown input and unknown output, respectively, which are described by extended states of the system. A state and attack observer (SAO) is developed using local measurements for each control area of power system, so as to simultaneously estimate the system states and attack signals in the presence of model uncertainties. During the occurrence of malicious attacks, the attack estimations provided by observer can automatically detect the FDIA on each control area. Besides, the load frequency control system is reconfigured by attack compensation based on the attack estimations of observer, thus achieving the mitigation of multiarea multichannel FDIAs. Case studies are undertaken on a three-area interconnected power system model under the conditions of single attack, multiple attack, and parameter variations to validate the performance of the proposed ODDM scheme.

A load frequency control strategy based on disturbance reconstruction for multi-area interconnected power system with hybrid energy storage system

In order to handle the problem of frequency fluctuations caused by load disturbances in multi-area interconnected power systems, a sliding mode control strategy for hybrid energy storage system has been designed by combining interval observer and disturbance reconstruction technology. The hybrid energy storage system composed of a battery and a super capacitor has been used to improve the performance of load frequency control systems. Using the load frequency control model of the multi-area interconnected power system, the interval observers are designed for each area to get the information about interval bounds of the system state in each area online. Then, the load disturbance in each area is reconstructed online using the estimation information of system state, and a sliding mode controller based on interval disturbance reconstruction is designed for power consumption and storage of the hybrid energy storage system, so as to stabilize the power grid frequency. Simulation results have shown that the proposed control strategy can effectively suppress the frequency and tie-line power fluctuations caused by load disturbances, and ensure the reliability and stability of the power system.

Computationally Efficient Optimal Control for Unstable Power System Models

In this article, the focus is mainly on gaining the optimal control for the unstable power system models and stabilizing them through the Riccati-based feedback stabilization process with sparsity-preserving techniques. We are to find the solution of the Continuous-time Algebraic Riccati Equations (CAREs) governed from the unstable power system models derived from the Brazilian Inter-Connected Power System (BIPS) models, which are large-scale sparse index-1 descriptor systems. We propose the projection-based Rational Krylov Subspace Method (RKSM) for the iterative computation of the solution of the CAREs. The novelties of RKSM are sparsity-preserving computations and the implementation of time-convenient adaptive shift parameters. We modify the Low-Rank Cholesky-Factor integrated Alternating Direction Implicit (LRCF-ADI) technique-based nested iterative Kleinman–Newton (KN) method to a sparse form and adjust this to solve the desired CAREs. We compare the results achieved by the Kleinman–Newton method with that of using the RKSM. The applicability and adaptability of the proposed techniques are justified numerically with MATLAB simulations. Transient behaviors of the target models are investigated for comparative analysis through the tabular and graphical approaches.

Controller parameters tuning of water cycle algorithm and its application to load frequency control of multi-area power systems using TD-TI cascade control

In this study, a nature-inspired optimization tool called the water cycle algorithm (WCA) and its practical application to efficiently design a cascade controller for two area interconnected power system model is put forward to address the issues in load frequency control (LFC). The cascade control (CC) structure is one of the most effective controllers for improving the performance of a control scheme in power applications, particularly when disturbances occur. In this paper, a well-systematized combination of the WCA and a well-designed cascade tilt-derivative tilt-integral (TD-TI) cascade controller is introduced, and an error performance function, for example, the integral time absolute error, is taken. The proposed WCA-based effective TD-TI, TID, and PID strategy are executed as one broadly two area multi-source model with/without HVDC link under many scenarios to verify the effectiveness of the proposed system under a high-load perturbation and some critical parameters associated with the interconnected power system. Simulation results reveal that the proposed technique provides superior performance to that of newly published schemes such as many objective/PID, TLBO/PID, IPA/TID and IGWO/Fuzzy-PID controllers. The dynamic investigation is also completed with consideration of the random load pattern, which sufficiently reveals the superior performance of the WCA/TD-TI scheme.

Expansion Planning Method of Offshore Multiplatform Power System With Wind Power Considering Cable Size Selection

With the expansion of the scale of subsea oil and gas resource exploitation, the offshore multiplatform interconnected power systems have become the main form of offshore platform group energy supply. The offshore multiplatform interconnected power system with wind power can effectively reduce the system fuel consumption and carbon emission, which has become an important direction for the development of future offshore multiplatform interconnected power systems. In this paper, the scenario method is adopted to portray the wind power output. System evaluation indicators considering the economy, reliability and environmental benefits of the system are proposed. Considering the nonnegligible impact of the cable size selection problem on the system economic cost, this paper introduces cable size selection variables in the expansion planning model of the offshore multiplatform interconnected power system with wind power to achieve accurate optimization of the system planning scheme but also greatly increases the difficulty of solving the model. A model linearization method is applied to linearize the nonlinear part of the model, so that the optimized model is a mixed-integer linear programming model under the determined system topology, and thus can be solved using commercial planning software. In addition, an improved genetic algorithm is proposed to optimize the system topology, which improves the efficiency of the model solution. The cases of different scale verify the validity of the model and the solution algorithm and show the impact of the maximum penetration rate of wind power on the total system cost.

Actuator fault-tolerant load frequency control for interconnected power systems with hybrid energy storage system

Aiming at the problem of hybrid energy storage faults in large interconnected power systems, an integrated fault-tolerant control scheme is proposed to deal with actuator faults and external disturbances. Firstly, the hybrid energy storage system is introduced based on the traditional interconnected power system, and a new topological structure is given. Secondly, the state-space model of each area in the given topological structure is established considering the external disturbance and actuator fault of the power system. Then the sliding mode observer is designed and the fault-tolerant control of interconnected power systems is realized according to the estimated value and sliding mode technology. Finally, the simulation results on the model of four-area interconnected power system show that the proposed observer can realize fault estimation in a short time, and the fault-tolerant control effect is satisfied with nearly 30% reduction of regional control error compared with the traditional method.

Frequency stability of interconnected power systems using atom search optimization algorithm

This paper explores the dynamic controller design issue for load frequency control (LFC) of a practical interconnected power system model. In view of this, the three-degree-of-freedom proportional-integral-derivative (3DOF-PID) controller architecture and LFC performance analysis for the proposed atom search optimization (ASO) is presented. The consistency of the form and acceptability of the well-known PID controller’s responses ultimately enforces to use in this work. The proposed ASO algorithm efficiently combines search space discovery and exploitation that yield promising solutions at the termination condition. The test system investigated is a four-area model with each region consisting of identical thermal unit. The system is also connected in one area with an interline power flow controller. The simulation results presented showed the superiority of ASO based 3DOF-PID controller in terms of settling time, peak variance, and magnitude of oscillation.