Sliding Mode Load Frequency Control Research Articles

Optimized sliding mode control for improved frequency response in an Islanded microgrid system

ABSTRACT This paper presents an enhanced Sliding Mode Control (SMC) approach in an Islanded Microgrid (IMG) system for regulating its frequency. The system encounters unpredictable disturbances arising from internal and external factors such as fluctuations in generation and demand, parameter variations, time delay, and many more. These factors challenge the frequency control during load fluctuations. To overcome these challenges, an Integral Sliding Mode-Load Frequency Control (ISM-LFC) as a robust control strategy employing integral sliding surface is proposed to regulate the system frequency. Particle Swarm Optimization (PSO) technique is used for optimal performance of ISM-LFC by meticulously determining the control variable parameters. A Simulink model of the IMG system in MATLAB is developed for conducting a comprehensive simulation analysis under diverse operational scenarios. The result outcomes affirm the effectiveness of the proposed controller using Integral sliding surface and modified saturation function-based control law for improved frequency response. Furthermore, comparative analysis with other alternative control strategies validates the improved performance of optimised ISM-LFC for frequency stabilisation.

Security concern and fuzzy output sliding mode load frequency control of power systems

This research investigates the concern of security in multi-area load frequency control (LFC) power systems using fuzzy logic output sliding mode control approach. A motion-trends-based deception attack model is proposed to represent malicious threats from communication networks. The motion-trends-based deception attack model enhances the destructive effect of deception attacks by monitoring changes in system state. In terms of the security concerns, a fuzzy-based output sliding mode control (OSMC) is applied to protect the power system from potential cyber-attacks. We provide sufficient conditions for the power systems stability under motion-trends-based deception attack. An initial controller gain that will bring the power system to stability is calculated by linear matrix inequalities (LMIs). The obtained controller gain provides a design method for fuzzy logic member functions. Fuzzy logic is then used to adjust the resulting controller gain to improve power system performance. The simulation results validate the usefulness of the proposed strategy, and indicate the viability of fuzzy logic in fine-tuning controllers.

Switching-Like Event-Triggered Sliding Mode Load Frequency Control for Networked Power Systems Under Energy-Limited DoS Attacks

Switching-Like Event-Triggered Sliding Mode Load Frequency Control for Networked Power Systems Under Energy-Limited DoS Attacks

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 Sliding Mode Load Frequency Control and Stability Analysis for Interconnected Power Systems With Time-Varying Delay

The universal use of open communication networks in interconnected power systems has changed the constant delay in the formerly dedicated channels into time-varying delay. The delay will deteriorate the dynamic performance of the load frequency control and lead to system frequency instability. This paper presents a fractional-order sliding mode controller for interconnected power systems with time-varying delay and performs stability analysis based on the Lyapunov direct method. Firstly, fractional-order integral sliding mode control is used to improve the stability of interconnected power systems containing time-varying delay. This expands the delay margin by taking advantage of the scalability of the fractional-order to the sliding mode surface. Then, the Riemann-Liouville fractional-order Lyapunov functional is introduced to stability analysis. This reduced the conservatism of the stability analysis by adjusting the upper limit of the functional integral. Lastly, combining Lyapunov's theory and integral inequality to obtain the stability conditions of the time-varying delay power system described by linear matrix inequality, and bring the stability margin of the system. The simulation results show that the designed controller can guarantee that the maximum delay time of the system is less than a predefined upper limit. The proposed control strategy obtains a larger stability margin than the other four scenarios. Additional simulation study was also conducted to verify its robustness to load variations and wind fluctuations.

Load frequency control in power systems by a robust backstepping sliding mode controller design

This paper presents a novel sliding-mode load frequency control (LFC) strategy for two-area thermal interconnected power system. Backstepping technique is utilized to design the controller. The sliding control method can be motivated heuristically by reasoning that one would expect better tracking performance exposed to parametric uncertainties and load disturbances. The controlled system’s asymptotic stability and the robustness of the controlled system are proved mathematically utilizing the Lyapunov theorem. Moreover, it is shown numerically that the proposed controller can diminish the intensity of the frequency oscillations caused by the load disturbance. The advantages of the proposed control approach are shown by comparing the results of proposed controller based on backstepping sliding mode control (BSMC) and other control approaches designed with the second order smc (SOSMC), observer-based BSMC (OBSMC) and port-Hamiltonian system and cascade system based proportional integral derivative (PHPID) controllers.

Event-Triggered Sliding Mode Load Frequency Control of Multiarea Power Systems Under Periodic Denial-of-Service Attacks

A sliding mode load frequency control (SMLFC) problem is committed for interconnected power systems under periodic denial-of-service (DoS) attacks. A suitable sliding surface is designed to deduce the state space equation in the multiarea power systems. An event-triggered device is used to determine whether the sampling state should be transmitted, and a new event-triggered condition is provided to match periodic DoS attacks. By utilizing the multiple Lyapunov–Krasovskii function approach, the globally exponential stability is proved based on matrix inequalities and the exponential stability criterion is subsequently obtained in terms of linear matrix inequalities. A suitable control law is established to ensure the reachability of power system. The feasibility and superiority of the proposed SMLFC are illustrated by numerical examples.

Memory-Based Adaptive Sliding Mode Load Frequency Control in Interconnected Power Systems With Energy Storage

Memory-Based Adaptive Sliding Mode Load Frequency Control in Interconnected Power Systems With Energy Storage

Resilient and event‐triggered sliding mode load frequency control for multi‐area power systems under hybrid cyber attacks

The attacks on power systems have been happening all the time, and gradually changing from a single attack to hybrid multiple cyber attacks. Such hybrid attacks may cause more catastrophic damages to the security and safety of multi-area power systems. Here, the security control problem is analyzed for multi-area power systems under hybrid cyber attacks. Two Lyapunov–Krasovskii functionals are constructed, and by utilizing the second-order canonical Bessel–Legendre inequality, sufficient conditions are derived for stability criteria under resilient event-triggered mechanism. A bound with H ∞ $H_{\infty }$ security performance is obtained under hybrid cyber attacks. A proper controller is synthesized to ensure that the trajectory of the multi-area power systems can be driven onto the prescribed sliding surface. Finally, numerical examples and simulated results demonstrate the effectiveness and correctness of the proposed scheme.

Decentralized Disturbance Observer-Based Sliding Mode Load Frequency Control in Multiarea Interconnected Power Systems

The load frequency control (LFC) problem in interconnected multiarea power systems is facing more challenges due to increasing uncertainties caused by the penetration of intermittent renewable energy resources, random changes in load patterns, uncertainties in system parameters and unmodeled system dynamics, leading to a compromised reliability of power systems and increasing the risk of power outages. In responding to this problem, this paper proposes a decentralized disturbance observer-based sliding mode LFC scheme for multiarea interlinked power systems with external disturbances. First, a reduced power system order is constructed by lumping disturbances from tie-line power deviations, load variations and the output power from renewable energy resources. The disturbance observer is then designed to estimate the lumped disturbance, which is further utilized to construct a novel integral-based sliding surface. The necessary and sufficient conditions to determine the tuning parameters of the sliding surface are then formulated in terms of linear matrix inequalities (LMIs), thus guaranteeing that the resultant sliding mode dynamics meet the <i>H</i>_&#x221E; performance requirements. The sliding mode controller is then synthesized to drive the system trajectories onto the predesigned sliding surface in finite time in the presence of a lumped disturbance. From a practical perspective, the merit of the proposed control method minimizes the impact of the lumped disturbance on the system frequency, which has not been considered to date in sliding mode LFC design. Numerical simulations are illustrated to validate the effectiveness of the proposed LFC strategy and verify its advantages over other approaches.

Observer-Based Sliding Mode Load Frequency Control of Power Systems under Deception Attack

This study investigates the observer-based sliding mode load frequency control for multiarea interconnected power systems under deception attack. By introducing the observer and combining it with the system state equation, the expression of the system error is obtained. A sliding mode surface is proposed to make sure the state of the systems to be stable. Then, the state equation of the system under sliding mode control is derived. The asymptotic stability of the whole system is proved by using the linear matrix inequality (LMI) technique and Lyapunov stability theory. Furthermore, a sliding mode control law is proposed to ensure that the attacked power system can reach a stable position. Numerical simulation results are presented to support the correctness of the results.

Event-triggered sliding mode load frequency control for multi-area interconnected power systems under deception attacks

Event-triggered sliding mode load frequency control for multi-area interconnected power systems under deception attacks

Fuzzy logic-based integral sliding mode control of multi-area power systems integrated with wind farms

The objective of the study is to design the fuzzy-based integral sliding mode control, which resolves the stability issues of multi-area interconnected power systems (MAIPS) integrated with wind farm (WF) involving the delays. The contribution can be categorized into two sections. Firstly, the dynamical characteristics of the power system are acquired various factors such as output from the wind generator, the existence of time-delays. The derived model becomes nonlinear due to WF integration and complications occur during the stability analysis. In such a situation, the Takagi–Sugeno (T-S) fuzzy approach is employed to approximate the nonlinear model into linear sub-models. However, the nonlinearities of WF can be linearized at a certain operating point which does not ensure the accuracy of the model. Secondly, to ensure stable performance, the suitable controller scheme becomes necessary and different types of control algorithms are available in the literature for the conventional power system model. This study focuses on designing the controller that copes with the T-S fuzzy model. We design a fuzzy-based integral sliding mode load frequency control (FISMLFC) controller and theoretically validate their performance by utilizing the Lyapunov stability theory and linear matrix inequalities (LMIs). Further, two-area MAIPS is simulated under the experimental values and their results are provided.

Nonlinear disturbance observer based adaptive super twisting sliding mode load frequency control for nonlinear interconnected power network

AbstractThis article revisits the study of load frequency control (LFC) problem in an interconnected nonlinear power network under mismatched disturbance. Unlike previous works, a more realistic interconnected power network with nonlinear coupling between control areas and also including nonlinearities like generation rate constraint (GRC) and governor dead band (GDB) is under study. An adaptive super twisting sliding mode controller (ST‐SMC) is designed based on system states and estimated disturbance. The nonlinear disturbance observer (NDO) estimates the mismatch between the electrical and mechanical power and then the estimated value is employed in the controller design to compensate the disturbance. The proposed control scheme ensures faster frequency and tie‐line power stabilization compared with techniques existing in the literature. The robustness of the proposed design is validated under random varying step load disturbance and with two area four machine Kundur's test system. The closed loop system stability is theoretically proved using the Lyapunov function. Simulation results confirm the effectiveness of the proposed design in a two‐area interconnected power network.

Adaptive Super Twisting Sliding Mode Load Frequency Control for an Interconnected Power Network with Nonlinear Coupling Between Control Areas

The article revisits the design of sliding mode control (SMC) for load frequency problems in power systems. Unlike works reported earlier, an adaptive super twisting SMC (ST-SMC) is designed for two area interconnected power network under load disturbance. The two control areas are nonlinearly coupled to each other making the control objective more challenging. The proposed design ensures asymptotic convergence of frequency and tie line power deviations under any load disturbance. In practice, the bounds of unknown disturbances in a power network are often not known. Therefore, dynamically adapted gains are considered in the design of the ST-SMC that ensures better control efficiency without controller gains being overestimated. The proposed controller is compared with conventional SMC designed for interconnected power systems. The merit of the proposed design is observed in control input which is significantly less affected by chattering without any loss in the control accuracy. The proposed design is also validated with typical nonlinearities in power systems like generation rate constraints (GRC) and governor dead band (GDB). The effectiveness of the proposed design is shown by simulation.

Prediction-based super twisting sliding mode load frequency control for multi-area interconnected power systems with state and input time delays using disturbance observer

A shift in paradigm from dedicated to open communication channels in power systems has made them prone to constant and time-varying delays. This paper tackles a novel load frequency control (LFC) problem in the presence of constant and time-varying delays in state and control input under load disturbances. The presence of time delays can deteriorate the performance of the controller or even destabilise the system. The above problem is addressed through a prediction-based super twisting sliding mode control (ST-SMC) using a state and disturbance observer. The proposed design achieves finite-time convergence of frequency and tie-line power deviation. The said design is validated under ramp and random step disturbance, with nonlinearities like generation rate constraints and governor deadband, with an integration of renewable energy and also with IEEE 39 bus power system. The closed-loop stability is proven thanks to candidate Lyapunov function and verified by simulations.

Robust H∞ load frequency control of multi-area power system with time delay: a sliding mode control approach

This paper is devoted to investigate the robust H U+221E sliding mode load frequency control U+0028 SMLFC U+0029 of multi-area power system with time delay. By taking into account stochastic disturbances induced by the integration of renewable energies, a new sliding surface function is constructed to guarantee the fast response and robust performance, then the sliding mode control law is designed to guarantee the reach ability of the sliding surface in a finite-time interval. The sufficient robust frequency stabilization result for multi-area power system with time delay is presented in terms of linear matrix inequalities U+0028 LMIs U+0029. Finally, a two-area power system is provided to illustrate the usefulness and effectiveness of the obtained results.

The Coordinated Control of Wind-Diesel Hybrid Micro-Grid Based on Sliding Mode Method and Load Estimation

In order to reduce the frequency deviation resulting from renewable energy fluctuation and load variance, the coordination control strategy for isolated wind-diesel hybrid micro-grid is proposed by taking advantage of smart neural network observer and sliding mode method. For diesel generator system side, the sliding mode load frequency control including load variance is designed to regulate the output power. For the wind turbine generator system side, the sliding mode pitch angle control considering load variance is constructed to smooth the wind turbine generator output power fluctuation. Furthermore, the different coordinated strategies are proposed to realize the plug and play for the hybrid micro-grid, it is easy to see that the control accuracy can be improved by the designed neural network adaptive observer and considering the load variation. The effectiveness of the proposed control strategy is validated through real time digital simulator platform under different operation condition.

Sliding mode load frequency control for multi‐area time‐delay power system with wind power integration

The interconnected time-delay power system has become an important issue for the open communication network. Meanwhile, due to the output power fluctuation of integrated wind energy, load frequency control (LFC) for power system with variable sources and loads has become more complicated. The novel decentralised sliding mode (SM) LFC strategy is proposed for multi-area time-delay power system with significant wind power penetration. The appropriate switching surface gain is selected to assure the stability of power system with mismatched uncertainties. The SM controller is constructed to satisfy the hitting condition. At last, the SM controller is proved by using the real-time digital simulator device under different case of time delay, wind penetration, load disturbance and operating point. The test results show that the proposed SM LFC can reduce frequency deviation and tie-line power fluctuation effectively.

Observer based robust integral sliding mode load frequency control for wind power systems

This paper investigates the load frequency control (LFC) for wind power systems with modeling uncertainties and variant loads. Since the system state is difficult to be accurately measured due to perturbation of nonlinear load, an observer is designed for reconstructing a substitution system state. Afterwards, an integral sliding surface is designed and a sliding mode LFC (SMLFC) strategy is proposed for reducing frequency deviations of the overall power system. Remarkably, it has been pointed out that a larger convergence rate of the observer error system has positive influences on the SMLFC performances, while the larger observer gain deteriorates the dynamic behavior. For seeking an acceptable balance so as to determine the optimal controller parameters, a collaborative design algorithm is proposed. The proposed method not only guarantees the asymptotical stability of overall power systems but also capable of improving the system robustness. Numerical examples are provided to demonstrate the effectiveness of the proposed methods.