Search

In this paper, the resilient control issue of virtual power plants (VPPs) under hybrid cyber attacks, specifically focusing on denial-of-service (DoS) and false data injection (FDI) attacks is first addressed. To solve this problem, a novel distributed resilient clustering secondary control technique is developed to ensure the normal operation of the VPP under cyber attacks. Specifically, an FDI attack estimation technique is first introduced to precisely estimate unknown FDI attacks affecting the bulk power supply. Based on the estimator, distributed resilient secondary controllers are designed to effectively combat the effects of FDI attacks and help achieve the frequency and voltage restoration as well as the proportional allocation of power requirement and state-of-charge (SoC) balancing of energy storage systems (ESSs). Under the proposed FDI attack estimation-based cooperative resilient secondary controller, the stability of the closed-loop systems subjected to hybrid FDI and DoS attacks is rigorously analyzed using Lyapunov theory. Finally, several simulation examples are introduced to verify the effectiveness of the proposed method.

Existing grid-forming inverter control schemes for distributed energy resources (DERs) primarily rely on active power (P)-frequency (f) and reactive power (Q)-voltage (V) droop mechanisms that are tailored for highly inductive transmission grids. However, in weak distribution grids where P and Q are highly coupled due to their resistive network characteristics, these control schemes cannot provide independent and accurate f and V regulation. This will further deteriorate the dynamic and stability performance, potentially resulting in inverter and load tripping during disturbances. To address this challenge, this paper proposes an innovative decoupling grid-forming control scheme, which is designed based on a systematic perspective that considers the inherent coupling characteristic of the entire distribution grid. The small-signal stability of the proposed controller is analyzed by varying controller parameters and the grid strength. The effectiveness of this controller is comprehensively verified using both MATLAB and OPAL-RT platforms by comparing it with existing grid-forming control strategies. The results show that the proposed controller can effectively decouple P and Q regulation in weak distribution grids. It enables DERs to provide independent, accurate, and autonomous f and V regulation, thus improving grid stability and dynamics. The proposed control strategy is cost-effective, communication-free, and can be easily commercialized due to its straightforward and robust circuit design.

With the increasing integration of renewable energy into power grids, ensuring the stability and reliability of power grids has become crucial. The intermittency of renewable energy poses a challenge for the frequency and voltage control of power grids. As an adjustable flexible load, electric vehicles (EVs) have emerged as an important solution for grid frequency and voltage control. A joint control and optimization strategy for electric vehicle aggregators (EVAs) to participate in grid frequency and voltage regulation based on a cloud-edge collaborative hierarchical scheduling architecture is proposed, and a multi-timescale EV charging pile cluster (EVC) scheduling model is established with the goal of maximizing the EVA profit. The strategy and model are grounded in the ancillary service market process. The EVA forecasts and optimizes to declare the active and reactive power capacities of the EVC to the market before the day and hour and controls the EVC to respond quickly and accurately to the frequency and voltage regulation instructions in the real-time stage. The methods of rolling optimization, model predictive control, evaluation of the feasible energy region and real-time capacity correction are adopted to coordinate the active and reactive power of EVC. The feasibility and effectiveness of the strategy are verified by an example, which provides an important reference for EVAs participating in power grid interactions.

Abstract This paper proposes a disturbance‐observer‐based control (DOBC) scheme for frequency and voltage regulation in modern power systems with high renewable energy sources (RES) penetration. The proposed approach acts as a feed‐forward control that improves the dynamic performance of the conventional proportional‐integral‐derivative controller. The proposed voltage and frequency control has been validated through hardware‐in‐loop implementation on OPAL‐RT, and testing on laboratory‐scale experimental test setup. The robustness of the proposed control scheme has been validated through simulations under worst‐case and stochastic uncertainties to mitigate real‐time variability in RES output and load. Real‐time simulation results depict superior performance of the proposed control strategy in comparison to several well‐established techniques under practical operating conditions, in the presence of communication delay and white noise. To validate the proposed control on laboratory‐scale experimental setup, the digital twin of the physical plant transfer function has been designed. Results reveal that the proposed DOBC control scheme drastically improves the system performance without rendering much computational burden under practical operation scenarios.

This article presents the combined frequency and voltage regulation of two area interconnected power systems. In addition to conventional generations, renewable energy sources such as wind plants, solar PV plants, and geothermal power plants are considered. The COOT algorithm optimized PID + D2 controller is presented for the first time and its performance found superior to commonly employed PI and PID controllers. The individual and combined effects of the boiler dynamics (BD) non-linearity and superconducting magnetic energy storage (SMES) systems are presented. Studies confirmed that the BD non-linearity jeopardizes, and the presence of SMES suppresses the system dynamics oscillations. The COOT based PID + D2 controller performs well even for the higher magnitudes of perturbations over the PID controller. Sensitivity analysis confirms the toughness of PID + D2 controller parameter values for widely varied time constants of the geothermal plant. The COOT algorithm optimized PID + D2 controller outperforms the PID controller in arbitrary load pattern perturbation. The COOT algorithm shows better convergence and figure of demerit characteristics compared with particle swarm optimization and firefly algorithms. The obtained simulation results are also tested successfully through OPAL-RT OP4500 RT-LAB-RCP/HIL system for their real-time validation.

The paper proposes a control scheme to improve the dynamic response of power systems through the automatic regulators of converter-based Distributed Energy Resources (DERs). In this scheme, both active and reactive power control of DERs are varied to regulate both frequency and voltage, as opposed to current practice where frequency and voltage controllers are decoupled. To assess the proposed control against the current state-of-art, the paper also defines a metric that captures the combined effect of frequency/voltage response at any given bus of the network. Results indicate that the proposed control strategy leads to a significant improvement in the stability and performance of the overall power system. These results are based on a comprehensive case study carried out by employing a modified version of the IEEE 39-bus benchmark system, where a portion of the synchronous machines is substituted by converter-interfaced DERs. The impact on the proposed control of load models, the $R/X$ ratio of network lines, as well as the level of DER penetration to the grid, are properly evaluated and conclusions are duly drawn. [ABSTRACT FROM AUTHOR]

This paper deals with the development of a control technique for the control of voltage source converters (VSCs) as an interface between renewable energy sources (RESs) and power grids. The lack of inertia in converter-based generators and their unconventional dynamic behavior increase the negative impacts on the power grid, unlike the operation of the conventional synchronous generators (SGs). In this sense, the proposed control technique emulates the behavior of SGs in the control loop of the interfaced converter acting as a grid-forming power generator. Thus, supportive functionalities for enhancing electric grid stability (e.g., frequency oscillation damping) will be provided by interfaced converter as a virtual synchronous generator (VSG). The main targets of the proposed control technique include virtual inertia emulation, frequency oscillation damping, primary and secondary frequency regulation, and voltage regulation. The main contribution of this work over the existing methods is that the optimal values for swing equation parameters are employed to ensure well-designed damping feature of the VSG-based converter which adapts grid-connected and islanded operating modes, enabling a smooth resynchronizing to the grid as its plug-and-play capability requirement. The control structure is evaluated through simulation in MATLAB/Simulink.

Due to the inherent limitations of the Traditional Droop Controller (TDC), an enhanced droop controller, known as Robust Droop Controller (RDC) has been proposed in previous works. However, this controller cannot compensate for the error in measured frequency, which can potentially contribute to the errors in proper reactive power-sharing as well as degrade frequency regulation. This paper introduces an Arctan-Based Robust Droop Controller (ABRDC) that modifies the RDC for Linverter to address this issue. The controller, rather than utilizing a linear function, utilizes an arctan-based function for power/frequency droop control. Various simulations were performed in Matlab/Simulink to test the performance of the proposed ABRDC. The results showed that it successfully reduces the frequency error, resulting in improved frequency regulation as well as adequate reactive load power-sharing. The comparative study showed that the ABRDC scheme is more effective than the RDC scheme. [ABSTRACT FROM AUTHOR]

Conventional grid-code specifications for dynamic ancillary services provision such as fast frequency and voltage regulation are typically defined by means of piece-wise linear step-response capability curves in the time domain. However, although the specification of such time-domain curves is straightforward, their practical implementation in a converter-based generation system is not immediate, and no customary methods have been developed yet. In this paper, we thus propose a systematic approach for the practical implementation of piece-wise linear time-domain curves to provide dynamic ancillary services by converter-based generation systems, while ensuring grid-code and device-level requirements to be reliably satisfied. Namely, we translate the piece-wise linear time-domain curves for active and reactive power provision in response to a frequency and voltage step change into a desired rational parametric transfer function in the frequency domain, which defines a dynamic response behavior to be realized by the converter. The obtained transfer function can be easily implemented e.g. via a proportional-integral (PI)-based matching control in the power loop of standard converter control architectures. We demonstrate the performance of our method in numerical grid-code compliance tests, and reveal its superiority over classical droop and virtual inertia schemes which may not satisfy the grid codes due to their structural limitations. • Implementing piece-wise linear grid-code curves in converters lacks standard methods. • Our approach implements piece-wise linear grid-code curves for converter systems. • We convert time-domain grid-code curves to frequency-domain transfer functions. • The transfer functions can be implemented in standard converter control setups. [ABSTRACT FROM AUTHOR]

This study introduces a three-phase virtual synchronous motor (VSM) control and its possible application for providing fast-charging service from off-board chargers of electric vehicles (EVs). The main circuit of the off-board charger consists of a three-phase voltage source PWM rectifier (VSR) and a resonant LLC zero-voltage-switching converter. In the proposed control approach, VSM-controlled pre-stage VSR emulates the external characteristics of a synchronous motor (SM), simultaneously, droop control based on charging mode in the VSM can satisfy the demand of the EVs constant-current fast-charging; The post-stage DC–DC converter is responsible for stabilizing the DC bus voltage. The feature of this control strategy is that VSM and fast charging control are implemented by the pre-stage converter, which has better coordination. In the MATLAB, the equivalent synchronous grid of the distribution network supplies to the power battery through the off-board charger, and the effectiveness of the presented control is demonstrated by typical working conditions. [ABSTRACT FROM AUTHOR]

Renewable energy, distributed generation, and micro-grid technology have been widely concerned for a long time. The traditional grid-connected inverter control strategy does not take into account the problem of inertia which is short and fast to cause the frequency change. The virtual synchronous generator control strategy is adopted to simulate the synchronous generator characteristics, which enhanced the inertia and damp of the system. For the micro-grid of wind power grid-connected, the storage battery is arranged on the AC side of the permanent magnet direct-drive wind turbine, and the model of the virtual synchronous generator is established. Thus the grid-connected performance of large-scale wind farm is improved. Here, the effect of moment of inertia in the virtual synchronous generator and the grid-connected regulation of virtual synchronous generator are verified by using PSCAD/EMTDC. The simulation results show that the grid-connected inverter controlled by the virtual synchronous generator is approximately equivalent to the synchronous generator in external characteristic. The grid-connected inverter based virtual synchronous generator control has a beneficial to adjust frequency and voltage, and can enhance the standby inertia of new energy and grid power generation. [ABSTRACT FROM AUTHOR]

This study introduces a three-phase virtual synchronous motor (VSM) control and its possible application for providing fast-charging service from off-board chargers of electric vehicles (EVs). The main circuit of the off-board charger consists of a three-phase voltage source PWM rectifier (VSR) and a resonant LLC zero-voltage-switching converter. In the proposed control approach, VSM-controlled pre-stage VSR emulates the external characteristics of a synchronous motor (SM), simultaneously, droop control based on charging mode in the VSM can satisfy the demand of the EVs constant-current fast-charging; The post-stage DC–DC converter is responsible for stabilizing the DC bus voltage. The feature of this control strategy is that VSM and fast charging control are implemented by the pre-stage converter, which has better coordination. In the MATLAB, the equivalent synchronous grid of the distribution network supplies to the power battery through the off-board charger, and the effectiveness of the presented control is demonstrated by typical working conditions.

This paper presents a multi-stage fuel consumption minimization method in an autonomous voltage source converter (VSC)-based microgrids considering microgrid small signal stability (SSS) margin, frequency and voltage regulation, and the minimum and maximum allowable range of active and reactive output power of VSCs. In VSC-based microgrid, the parameters of each VSC power sharing controller have significant influence on microgrid SSS margin, frequency and voltage regulation, and the ratio of active and reactive power shared between VSCs. Considering all of these effects in fuel consumption minimization method with straightforward technique leads to having a complicated constrained optimization problem, which cannot be solved in a short time. The computation time of solving this optimization problem is very important in practical applications. In order to eliminate this problem, a multi-stage method is developed in this paper. This method can optimize the fuel consumption and consider the output active and reactive power limit, SSS margin, and frequency and voltage regulation in different stages without significant interactions on each other. Hence, the computation time is strongly reduced. The simulation results in a microgrid, which has a wind turbine, two gas turbines, and a micro-turbine with heat load, demonstrate the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]