Power System Frequency Regulation Research Articles

Load frequency regulation of multi-area power systems with communication delay via cascaded improved ADRC

Load frequency regulation (LFR) is regarded as a significant method for the stable operation of modern power grids. However, the LFR is facing many challenges such as communication delays in the area control error, and external disturbances caused by renewable energy integrating into power grids. This paper presents a cascaded improved active disturbance rejection control (ADRC) to handle these control challenges, where the inner and outer controllers are the improved ADRC and regular ADRC, respectively. The advantages of the improved ADRC to reject external disturbances and system uncurtains are discussed by simulations. Then a practical parameter tuning method is provided to guide the selection of controller parameters. Finally, comparative simulations are implemented to illustrate the abilities of the proposed control scheme in different cases. The proposed control structure can handle the communication delay well and have a strong ability to reject the disturbances of uncertain consumed power and wind power. The simulation results imply that the cascaded improved ADRC may have broad application prospects for the LFR.

A dynamics-constrained method for distributed frequency regulation in low-inertia power systems

An increasing number of power electronics-interfaced renewable energy sources are integrated into the power grids. Such power systems suffer from poor frequency dynamic behaviors due to the decreasing rotational inertia and governor damping, thus are vulnerable to disturbances. A widely investigated approach to improve the frequency dynamics of the system is to imitate the synchronous generator responses by power converter control. In this paper, a dynamics-constrained frequency control method is proposed to bridge the gap between frequency dynamics optimization and secondary frequency control in low-inertia power systems. An intraday optimization model is formulated for the optimal tuning of the converter control parameters with guaranteed frequency security, and a distributed model predictive controller is developed for recovering the frequency economically. Case studies demonstrate the practicability of the proposed dynamic constrained frequency regulation approach and further comparison illustrates the computational efficiency and scalability of the proposed distributed algorithm.

An optimal frequency regulation in interconnected power system through differential evolution and firefly algorithm

Automatic generation control is extensively used to regulate power plants in a modern area of the power system network. In this paper, automatic generation and frequency control in interconnected power system is presented. A multisource such as thermal, hydro, and gas-based power plant is considered in this study, which is carried out by incorporating nonlinearity like generation rate constants, HVDC link, and the conventional PID controller design. Further, an optimal setting of the PID controller is performed by employing evolutionary, and metaheuristic algorithm-based approaches such as differential evolution and firefly algorithm, respectively. With these algorithms, the proposed model has been tested with their performance evaluation and comparison characteristics are discoursed. The robustness of the proposed controllers is assessed based on comparative analyses to regulate the interconnected power network’s frequency profile under different loading conditions. The stability analysis is performed using the Eigen and Nyquist plots to assess the proposed controllers’ efficacy. Besides, the frequency control study is summarized with comparative assessment through various performance indices such as settling time, peak overshoot and undershoots under different operating conditions. Finally, the proposed control scheme, in the interconnected power system, is validated through a real-time digital simulation platform, i.e., OPAL-RT 5142. The comparison of simulation and real-time results demonstrates the effectiveness of the FA-optimized PID controller in comparison with that of the DE-optimized PID controller.

Secondary Frequency Regulation Control Strategy with Electric Vehicles Considering User Travel Uncertainty

The premise of electric vehicles (EVs) participating in the frequency regulation (FR) of power systems is to satisfy the charging demands of users. In view of problems such as the uncertainty of EV users’ departure time and the increase in power supply pressure due to disordered charging in the frequency regulation process of EV clusters, a secondary frequency regulation control strategy with EVs considering user travel uncertainty is proposed. Firstly, EV charging history was analyzed, a reliability parameter was introduced to describe the user travel uncertainty, and an individual EV controllable domain model based on reliability correction was constructed. Then, EV clusters were grouped according to charging urgency and state of charge (SOC), and the controllable capacity of EV clusters was determined. Finally, EV frequency regulation capability parameters and charging urgency parameters were defined to determine the EV frequency regulation priority list, combined with the EV state grouping and priority list, and the EV cluster frequency control strategy was proposed. The simulation results show that the proposed strategy can satisfy the charging demands of users under uncertain travel conditions, reduce the power supply pressure of the power system caused by EVs entering the forced charging state, and effectively suppress frequency deviation.

A comprehensive review of wind power based power system frequency regulation

A comprehensive review of wind power based power system frequency regulation

Non-integer disturbance observer-aided resilient frequency controller applied to hybrid power system

This work made the earliest effort to investigate the performance of a non-integer disturbance observer (NiDob)-aided non-integer sliding mode controller (NiSMC)/second-order SMC (SOSMC) for frequency regulation of an islanded hybrid power system with matched/mismatched uncertainties. The unavoidable presence of unknown system disturbances, uncertainties, and practical limitations of control inputs are considered while developing the proposed resilient nonlinear controllers. Firstly, a NiDob is designed to estimate unknown bounded aggregated plant uncertainties. Subsequently, an improved NiSMC/SOSMC is developed by conveniently augmenting disturbance estimation. Quasi-oppositional marine predators' algorithm (QOMPA) is applied to obtain the near-optimum gains of the proposed frequency controllers minimizing an integral error-based objective function. The finite-time convergence of NiDob and closed-loop asymptotic stability of the studied power system has been established using the Mittag-Leffler/Lyapunov argument. The usefulness and practicability of the applied frequency have been demonstrated by performing a comparative study with SMC, NiSMC (without NiDob), NiDob-aided NiSMC, and other results reported in the literature. The numerical simulations showcase the efficacy of the applied control methodology regarding minimal chattering, faster disturbance rejection, and improved transient performance. The proficiency of the developed control methodology is validated on an IEEE-39/IEEE-68 bus testbed. Finally, the ability of the suggested resilient control algorithm in the detection and mitigation of deception-type cyber-attacks has been tested and affirmed in cyber-physical environments.

Resilient virtual synchronous generator approach using DC-link capacitor energy for frequency support of interconnected renewable power systems

Modern interconnected power systems with many renewable energy sources (RESs) are more susceptible to disturbances than conventional power systems because they lack the inertia constant. Therefore, this study presents an advanced frequency control strategy for interconnected power systems considering high RESs penetration relying on the virtual inertia control (VIC) strategy-based high voltage direct current (HVDC) link, thus improving the dynamic frequency performance of future power systems. The HVDC link has been used as a DC capacitor which stores the electrostatic energy. This stored energy can supply the earliest active power support in automatic generation control system operation. Moreover, this paper develops the conventional VIC strategy based on the HVDC link by considering the dynamic behavior of a virtual rotor that mimics the inertia and damping properties of actual synchronous machines, thus stabilizing future renewable power systems. Also, this paper proposes a novel frequency control scheme based on the inertia emulation-based HVDC link and a virtual synchronous generator, which mimics the virtual rotor and virtual frequency control loops, to improve further the frequency regulation of low-inertia modern interconnected power systems. The parameters of the virtual synchronous generator scheme are optimally adjusted utilizing particle swarm optimization. The utility and superiority of the proposed VIC strategies based on the HVDC link are confirmed by contrasting them with the conventional VIC strategy relying on the HVDC link in the studied interconnected power system against various load/renewables interruptions, uncertainties, and physical restrictions. MATLAB/Simulink® software was used to simulate the results of the investigated system.

Cloud-Edge Hosted Digital Twins for Coordinated Control of Distributed Energy Resources

This paper presents a novel approach for realizing coordinated control of Distributed Energy Resources (DERs) based on cloud-hosted and edge-hosted digital twins (DTs) of DERs. DERs are playing an increasingly important role in supporting the frequency regulation of power systems with massive integration of renewable resources. However, due to the significant differences in DERs’ capability and characteristics, individual and un-coordinated responses from DERs could lead to a less effective overall response with undesirable traits, e.g. slow response, severe overshoots, etc. Therefore, the coordination of DERs is critical to ensure the desirable aggregated overall response. A major shortcoming of conventional centralized or distributed approaches is their significant reliance on real-time communications. This paper addresses the challenges by the application of DTs that can be hosted in the cloud for the centralized control approach and the edge for the distributed approach to minimize the need for real-time communications, while being able to achieve the overall coordination among DERs. The proposed DT-based coordinated control is validated using a realistic real-time simulation test setup, and the results demonstrate that the DT-based coordinated control can significantly improve the aggregated DERs’ response, thus offering effective support to the grid during contingency events.

Strategy of 5G Base Station Energy Storage Participating in the Power System Frequency Regulation

Strategy of 5G Base Station Energy Storage Participating in the Power System Frequency Regulation

Decentralized event-triggered sliding mode scheme for frequency regulation of multi-area power systems under deception attacks

This paper investigates the frequency regulation problem of networked multi-area power systems subject to random deception attacks. Due to the increasing integration of wireless communication devices in power systems, the frequency stability highly relies on the efficiency and security of information transmission. To alleviate the communication burden, a decentralized dynamic event-triggered (ET) scheme is proposed, in which each area transmits the measurement via its own ET rule. Moreover, the coefficients of dynamic variables are designed based on the state variations and the attack probability for different areas. Then, a decentralized ET sliding mode controller is proposed to restore the frequency. Both the mean square exponentially ultimate boundedness of the power systems and reachability of the specified sliding surface are analyzed, and the corresponding conditions are given. Compared with the widely adopted centralized schemes, the proposed decentralized ET control scheme is easier to implement and can ensure more reasonable transmission considering attack probability for different areas; meanwhile, the deception attacks on different areas are considered to occur independently. Finally, simulation results of a three-area power system are provided.

Analysis of energy storage demand for peak shaving and frequency regulation of power systems with high penetration of renewable energy

Energy storage (ES) can mitigate the pressure of peak shaving and frequency regulation in power systems with high penetration of renewable energy (RE) caused by uncertainty and inflexibility. However, the demand for ES capacity to enhance the peak shaving and frequency regulation capability of power systems with high penetration of RE has not been clarified at present. In this context, this study provides an approach to analyzing the ES demand capacity for peak shaving and frequency regulation. Firstly, to portray the uncertainty of the net load, a scenario set generation method is proposed based on the quantile regression analysis and Gaussian mixture model clustering. Then, a multi-scenario and multi-time scale optimal operation model is established to handle the uncertainty of net load, and the power correction model for ES operations is established to accommodate the balance of ES charging/discharging and optimization of system operation cost. Finally, based on the solution results of the above models, the method for determining the system's demand for ES capacity is proposed, and the relationship between the penetration of RE, ES power and capacity, and the confidence level of meeting demand is obtained. Numerical studies show that with a confidence level of 90% for satisfying demand, the 49.5% RE penetration system (the maximum load is 9896.42 MW) needs ES power and capacity of 1358 MW and 4122 MWh for peaking and ES power and capacity of 478 MW and 47 MWh for frequency regulation. Further, as the penetration of RE increases, the proportion of ES demand power to the system's power supply capacity and duration demand of ES also increase.

Direct Search Algorithm for Load Frequency Control of a Time-Delayed Electric Vehicle Aggregator

This article addresses the topic of frequency regulation of a single-area power system connected to an electric vehicle (EV) aggregator over a non-ideal communication network. It is considered that the command control action is received by the EV aggregator with constant delay and the power system includes uncertain parameters. Due to the presence of uncertainties and the delay term, the frequency regulation problem is non-convex and hard to solve. The present approaches in the literature convert the non-convex control design problem into a convex problem with a set of Linear Matrix Inequalities (LMIs), which is conservative and in many cases results infeasibility. In this paper, an innovative iterative algorithm, called direct search, is employed for the time-delayed system to design the unknown parameters of a pre-assumed controller. The controller choice is not limited and various controllers’ structures can be assumed. Without loss of generality, a proportional-integral (PI) controller is designed. The novel direct search algorithm can determine a feasible solution whenever at least one solution lays in the design space. Hence, by selecting a wide design space, we can anticipate that the PI controller guarantees closed-loop stability. Numerical simulations are carried out to demonstrate the performance of the developed controller compared to the state-of-the-art approach.

Role of Distributed Inverter-Based-Resources in Bulk Grid Primary Frequency Response Through HELICS Based SMTD Co-Simulation

In the recent years, there has been an increase in distributed inverter-based resources (D-IBRs) in the system that is impacting the grid performance. Dynamic transmission and distribution (T&D) co-simulation is an effective method to evaluate the impact of D-IBRs on the system response, however, implementation is a challenge. This article innovatively achieves accurate T&D model coordination with inclusion of dynamic models of power electronic controls. It also demonstrates that D-IBRs operating with grid-forming (GFM) controls with frequency support capability can aid in primary frequency regulation in a low-inertia power system. The article discusses the fundamentals of dynamic T&D co-simulation to analyze the primary frequency response on the IEEE 39-Bus transmission system coupled to IEEE 123-Bus distribution system with D-IBRs with GFM controls. To demonstrate scalability, a large system (286383 T&D buses) is co-simulated: IEEE 39-bus transmission system with all load buses coupled to a total of 2328 parallel IEEE 123-Bus distribution feeders containing a mix of D-IBRs is considered. The article also discusses the use of parallel computation used for distribution system solutions enabled in the scalable multi-timescale T&D co-simulation framework along with computation time comparisons between the large and small system simulations with GFM inverter dynamics.

Review on Soft Computing-Based Controllers for Frequency Regulation of Diverse Traditional, Hybrid, and Future Power Systems

In recent decades the power system has become a complex network, to design a load frequency control (LFC) requires solving a complex equation. Optimisation techniques are essentially required to optimise the parameters of different controllers used for LFC issues in the power system. In a unified power system, the LFC is examined from all angles using different optimisation strategies to optimise the conventional PI, PID, cascaded, and fuzzy controllers as well as recently designed controllers. This manuscript specifically reviews the use of soft computing techniques in the frequency regulation of the power system with single/multiple areas that include conventional, renewable, and combinations of both, with FACTS devices and certain energy storage devices such as superconductor magnetic energy storage (SMES) and battery sources. Furthermore, deregulated power systems and microgrids are also considered for the study. To regulate LFC under various disturbances such as generation rate constraints (GRC) and dead band control, a few additional control approaches are utilised. Models of the power system are discussed and analysed. In addition, the merits and drawbacks of the studied techniques/structures that address design and implementation issues—as well as control issues that relate to the LFC problems—have been discussed.

Multi-resolution based PID controller for frequency regulation of a hybrid power system with multiple interconnected systems

Automatic generation control (AGC) in modern power systems (PS) is difficult because the output power of many power resources is intermittent, and the load and system parameters vary widely. In this paper, a novel control scheme known as the wavelet based multiresolution proportional integral derivative (MRPID) controller for multiple interconnected hybrid power sources is presented. The discrete wavelet transform (DWT) is used in the proposed wavelet based MRPID controller to split the error between the actual and target responses into different frequency components at several stages. To ensure optimum system performance, the gains of the MRPID controller are fine-tuned using the Fox Optimizer Algorithm (FOA), a new powerful metaheuristic technique. The proposed MRPID controller is evaluated in a three-area hybrid system where each area contains a combination of conventional generation (gas, thermal reheat and hydro) and renewable generation sources (solar, and wind). The proposed controller also accounts for system non-linearities, including boiler dynamics, time delay, dead band, generation rate limitation, system uncertainties, and load changes. In the hybrid system studied, the proposed MRPID is compared with FOA-tuned PID and PI controllers. The proposed MRPID controller tuned with FOA algorithm effectively reducing the peak overshoot of 89.03%, 76.89 and 56.96% and undershoot of 69.52%,66.90 and 94.29% for ∆Ptie12, ∆Ptie23 and ∆Ptie13 respectively as compared to FOA based PI controller.

Multi‐objective salp swarm algorithm‐based fractional order fuzzy precompensated PDPI controller for frequency regulation of hybrid power system

AbstractSignificant number of renewable sources when integrated with distributed generations and energy storage components form a sustainable power system called hybrid power system (HPS). But the stochastic nature of the sources and continuous variation of load cause serious issues in the power systems like frequency instability. Our work proposes a novel approach for load frequency control (LFC) of the proposed system. For the work, both frequency deviation and control signal are used to give the input signal to energy storage components. A new fuzzy‐based controller called fractional order fuzzy precompensated PDPI (FO‐FPPDPI) controller for LFC of the mentioned HPS is suggested in this paper. The controller is optimized by a nature inspired multi‐objective salp swarm algorithm (MSSA). The comparison of the proposed approach with the classical PID controller and Fuzzy PID (FPID) controller is carried out by taking several system operating conditions. Robustness of the FO‐FPPDPI controller is also validated for system parameter variations and the superiority of the proposed control strategy over PID and FPID controllers is validated for all the situations. Finally, the control strategy is realized in OPAL‐RT to measure its fidelity with the simulation results.

Cases of CFPID regulator for frequency regulation of power systems

In consistently expanding region and construction of present-day Power System having trouble request vulnerabilities, the utilization of learned and lively recurrence power technique is fundamental for good working of Power-station. To enhanced regulator boundaries, a SCiWOA has been utilized. Frequency soundness and control are perhaps the main issues in interconnected force matrices plan and operation. Several control circles are working to keep up with the framework recurrence at its set points. The majority of supply request adjusting is accomplished by controlling the yield of dispatchable creating units. Next viable utilization of Power-framework recurrence control is performed by planning a CFPID regulator for a brilliant matrix framework having limitless sources like sun situated, wind & photo-voltaic. All in all, to evaluate the framework performance, the time-domain simulations of different cases are considered.

Performance analysis of proportional integral derivative controller for frequency regulation of an interconnected power system integrated with renewable energy sources

This paper focuses on conducting a performance analysis of classical proportional integral derivative (PID) controller for frequency regulation in multi-area interconnected power system. The power system considered in the analysis includes wind and solar power sources integrated with thermal and hydal system. In area 1 along with thermal unit, WPG is appended and in second control area, a hydal unit is appended with SPG. The simulation of the present work is performed using MATLAB/Simulink. The dynamic responses obtained using the simulation using PID controller and without any controller have been compared. It is clearly demonstrated from the results that implementation of a PID controller effectively reduces the fluctuations in the system and hence, aids in order to maintain constant frequency.

Decentralized Optimized Integral Sliding Mode-Based Load Frequency Control for Interconnected Multi-Area Power Systems

In this paper, a decentralized load frequency control (LFC) is proposed for the frequency regulation of multi-area power systems applying optimized integral sliding mode control (OISMC) scheme. A modified particle swarm optimization (MPSO) algorithm is utilised to optimize the control variables of the proposed controller for improving the performance of frequency response. A comprehensive model of a multi-area power system is developed where each area is considered to power from conventional sources, renewable energy resources (RERs), and electrical vehicle (EV) aggregators. Different types of interconnectors have been considered to tie different power regions. This system is subjected to random generation and loading conditions, as well as model uncertainties, which cause its frequency and area control error (ACE) to deviate from their nominal values. A decentralised OISMC is implemented for the proposed model to keep the frequency variation within the nominal range. Further, a validation study investigates the performance of the proposed control technique in MATLAB simulation environment to mimic the real power system operation. This study includes different test scenarios considering the dynamic events such as variations in load demand, amount of generated power, participation factor of EV reserve, system parameters, disturbances, and time delay. The simulated results support better frequency regulation with the suggested OISMC compared to other alternative control approaches.

Leader Harris Hawks algorithm based optimal controller for automatic generation control in PV-hydro-wind integrated power network

• A novel attempt has been put together to design a Model Predictive Control based on the leader Harris Hawks Optimization approach for a PV integrated LFC system. Further, a combined AVR-LFC loop has been designed for a PV, wind and hydro integrated hybrid power system. • The validation of the controller's better performance has been obtained through a thorough comparative analysis where the transient response attributes from the proposed controller have been compared with the exiting controllers available in the literature. Also, the convergence mobility of the proposed LHHO optimizer has been compared with HHO, WOA, and PSO algorithms. • To further strengthen the frequency stability of the network, the authors have proposed and implemented the virtual inertia and capacitive energy storage devices in association with the LHHO-MPC controller. • The robust nature of the proposed controller algorithm has been assessed under different test case scenarios where the step load perturbation (SLP) values have been varied randomly, and the stochastic load model has been considered. Also, various nonlinearities and reduced inertia cases have been presented to show the efficiency of the proposed LHHO-MPC controller working in coordination with CES and VI units. The work in this manuscript aims at designing a novel control strategy based on the Model Predictive Controller aided with Leader Harris Hawks Optimization (MPC-LHHO) algorithm for the regulation of frequency and voltage in renewable penetrated power systems. Herein, two cases have been considered where the first case discusses the frequency stabilization in a thermal power system linked with the solar photovoltaic (PV) plant. Subsequently, the second case features the simultaneous voltage and frequency regulation in a hybrid interconnected power system including thermal, wind, diesel, photovoltaic, and hydro generation units. Additionally, for both cases, the proposed MPC-LHHO algorithm has been evaluated in coordination with the capacitive energy storage and virtual inertia units. Furthermore, the stability analysis of the controlled PV-thermal system has been conducted using eigenvalues and pole-zero plots. In both cases, the effectiveness of the proposed algorithm has been tested after considering diverse scenarios including random loading, nonlinearities, time delays, reduced inertia and stochastic variations in load. For all these cases the presented algorithm has given a stable response and has ensured proper regulation of voltage and frequency in the renewable integrated power system network.