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Introduction
Publications
Publications (96)
Non-intrusive load monitoring is one of the key tools in demand-side management (DSM). Recent advancements in the computational power of processors have accentuated the role of machine learning algorithms e.g., clustering, as a key function in the NILM solutions applied on power grids. In event-based NILM methods, the algorithm detects the transien...
Timely detection and classification of power system events are essential for situation awareness and reliable electricity grid operation. It is also a crucial step with regard to synchrophasor network data management and archiving. In this paper, an event detection and classification method based on the singular value decomposition (SVD) of synchro...
Modern electric power systems are becoming more complex due to the proliferation of distributed energy resources (DERs) and power electronic converters. The increased penetration of power electronic-based DERs gives rise to new instability issues, particularly subsynchronous oscillations (SSO) caused by control system interactions, the induction ge...
Event detection is critical in a non-intrusive load monitoring (NILM) solution. NILM is essential for the imple-mentation of some demand-side management (DSM) techniques. This paper proposes an event detection algorithm based on reinforcement learning for NILM purposes (RLNILM). The proposed method employs a number of simpler traditional event dete...
This paper presents a new observer-based state- feedback servomechanism controller for improving the resilience of a distributed generation unit that is connected to an unbalanced grid through an LCL-based voltage source converter (VSC). Whenever the host grid is unbalanced, double-frequency ripples are imposed on the dc-link capacitor voltage and...
This article presents a controller in stationary frame for enhanced performance of voltage source converters (VSCs) under weak and unbalanced grid conditions. The controller incorporates a nested multiloop structure consisting of an inner phase-locked loop-integrated current controller as well as an outer dc-link voltage control loop based on integ...
This article presents a new control structure for bidirectional power electronic converters. Commonly, a proportional-integrating (PI) controller is used in the dc capacitor voltage loop, to generate the set point for the current controller, which tightly regulates this voltage to a given value. This article shows that such an approach causes stabi...
This article proposes a new control strategy in stationary frame to improve the operational robustness of voltage source converters (VSCs) under weak grid conditions. First, dynamics of the phase-locked loop (PLL) are incorporated into the model of a grid-connected VSC in stationary reference frame. It is rigorously shown that the three-phase PLL i...
The interactions between wind parks and the series-compensated transmission lines can bring about sub- or super-synchronous resonance (SSR) incidents which jeopardize the safe operation of the entire network. In practice, such incidents may emerge under various conditions as different types of wind turbines with various parameters can be deployed a...
This article presents a new current controller in the synchronous reference frame and its associated design for enhancing the performance of three-phase grid-connected inverters, especially against weak-grid conditions. The existing controllers do not perform strongly during high-impedance grid conditions and lead to oscillations and instability is...
This article presents approaches for efficient modeling and systematic design of enhanced phase-locked loop (ePLL) structures. While different ePLL structures have found a wide acceptance for various applications, their modeling and design aspects have not been fully and systematically reported in the existing literature. This article fills this ga...
This article investigates a decoupled vector current control strategy for grid-tied single-phase nine-level Packed E-Cell (PEC) inverters for vehicle-to-grid (V2G) technologies. The control design is based on a loop shaping approach, where performance specifications such as desired closed-loop bandwidth, closed-loop stability, robustness to pure ti...
Faults are extreme events that can adversely affect the voltages in islanded microgrids. This paper provides a new data-driven methodology for timely prediction of the post-fault voltage stability in hybrid AC/DC microgrids. The proposed method performs a binary classification with delay constraints by processing sequences of the short-time mean sq...
This article proposes a supervised learning approach for centralized localization of faults in microgrids with radial configuration that can operate in grid-connected or islanded mode. The key concept is to identify faults by learning and analyzing the features of voltage and current disturbances detected by a microgrid central protection unit. Two...
The proliferation of phasor measurement units (PMUs) presents new challenges in archiving and processing large amounts of synchrophasor data which necessitates advanced data compression methods. This paper proposes a singular value decomposition (SVD)-based method for compression of synchrophasor data, including magnitude, phase-angle, and complex...
This paper proposes a mechanism for time-frequency analysis of post-fault transient response in hybrid AC/DC microgrids. The proposed mechanism is based on the continuous wavelet transform of the electromagnetic transient (EMT) simulation data in grid-connected and islanded modes of operation. The proposed mechanism is used to evaluate the impact o...
This paper presents a vector current controller (in the synchronous reference, or the dq, frame) with negative-sequence current injection capability for three-phase grid-connected converters. This capability is desired for the operation of the converter during unbalanced conditions and also for a certain type of islanding detection. The proposed co...
This paper presents a detailed and rigorous comparison between two vector current control (VCC) approaches for voltage source converters (VSC). A PLL-less VCC (also called the direct power control) has recently been proposed in several major publications with the assumption that it will improve the performance of conventional PLL-based VCC during w...
Phasor data concentrators (PDCs) are essential functions in synchrophasor networks that collect and aggregate phasor measurement unit (PMU) data from across the electric grid. PDC buffers synchrophasor datasets during the “wait time” period, then communicates them to target applications or higher-level PDCs in hierarchy. The time-varying and inhere...
Networked protection systems use information, communication and computation technologies to collect and process sensor data from spatially distributed sensors, and launch protective and control actions by sending commands to local devices. Such protection systems are also capable of supporting specialized tasks including asset control and backup pr...
In this paper, the resilience of a coordinated control system for a set of PV-based distributed energy resources (DERs) against false data injection (FDI) attacks is evaluated. The evaluation is performed using a functional mock-up interface (FMI)-compatible cosimulation platform which enables the interaction of multi-domain simulators (EMTP, MATLA...
This paper presents a new vector current controller for the grid-connected three-phase voltage-source converter (VSC). The VSC is increasingly used in many applications such as distributed generation, motor drives, and high-voltage dc (HVDC) systems. From control system perspective, this presents a two-input two-output coupled problem when transfor...
Wireless communications can facilitate transfer of synchrophasor data between spatially separated phasor measurement units (PMUs) and phasor data concentrators (PDCs). However, such communication systems may impose random access delay and failure on PMU channels that lead to missing synchrophasor data frames at the output of the PDC. This paper pre...
Rigorous evaluation of a synchrophasor network in terms of communication network quality, cyber security, and Phasor Data Concentrator (PDC) performance is presented. To this aim, a co-simulation platform is designed based on the Multi-Agent Environment for Complex System CO-simulation (MECSYCO) platform. The proposed platform is characterized by p...
This paper proposes a real-time algorithm for processing and quality improvement of synchrophasor data (SD). The proposed algorithm first recovers the missing SD reported by phasor measurement units (PMUs), and performs low-rank approximation on data streams. Then, the enhanced data stream can be redirected toward various power system applications....
This paper proposes a robust controller to improve power system stability and mitigate subsynchronous interaction (SSI) between doubly-fed induction generator (DFIG)-based wind farms and series compensated transmission lines. A robust stability analysis is first carried out to show the impact of uncertainties on the SSI phenomenon. The uncertaintie...
This study presents a new method for voltage unbalance compensation in islanded microgrids using distributed resources (i.e. distributed generations, storage systems) and responsive loads. The proposed method adopts the Newton trust-region approach to perform the load flow calculation. The sensitivity coefficients obtained from the load flow soluti...
Distributed energy resources (DERs) often rely on renewable sources whose random power fluctuations bring about voltage disturbances in distribution networks. Under such circumstances, voltage regulation through centralized control of DERs requires reliable detection and coordination mechanisms. This paper proposes a new data-driven approach for vo...
This paper proposes a new and robust control strategy for distributed energy resource (DER) units operating in parallel with a three-phase ac grid that could have unbalance voltages. It is well known that the grid imbalance imposes double-frequency ripples on the dc side capacitor and low-order harmonics on the ac side of a voltage source converter...
The use of supplementary controllers for mitigating subsynchronous control interaction (SSCI) in DFIG-based wind parks is quite promising due to their low investment costs. These SSCI damping controllers are typically designed and tested using an aggregated wind turbine (WT) model that represents the entire wind park (WP). However, no research has...
When voltage source converters (VSCs) are subjected to disturbances or faults, they may not be able to perform the desired control objective, which presents a significant challenge to system operations. One well-known situation is when the converter is subjected to an unbalanced ac voltage with a negative-sequence fundamental voltage injection. Und...
The output power of distributed energy resources (DERs) may experience irregular fluctuations due to variations of renewable sources, which need to be monitored in order to reliably control the grid. This paper proposes a novel approach for centralized detection of such irregularities based on the time-series analysis of the data reported by phasor...
Modern distribution grids are shifting toward resilient and sustainable energy networks through the use of unprecedented number of distributed generation (DG) units and renewable energy sources. However, unlike conventional grids, they are also highly integrative in the sense that, centralized control applications must support critical protective a...
Synchrophasor networks are subject to communication delays and packet dropout which can compromise data integrity and thus jeopardize control and monitoring of smart microgrids. This paper proposes an advanced phasor data concentrators (APDC) capable of counteracting the communication impairments and improving the quality of monitoring of distribut...
The connection of a DG unit to a weak power system is challenging due to stability issues resulted from dynamic interactions between the DG unit and the grid. LCL-based DG unit is a particularly challenging case due to the presence of a high resonant peak in its frequency response. This paper proposes a robust control strategy to overcome the stabi...
This paper performs an extensive review on control schemes and architectures applied to DC microgrids. It covers multi-layer hierarchical control schemes, coordinated control strategies, plug-and-play operations, stability and active damping aspects as well as nonlinear control algorithms. Islanding detection, protection and microgrid clusters cont...
The connection of a DG unit to a weak power system is challenging due to stability issues resulted from dynamic interactions between the DG unit and the grid. LCL-based DG unit is a particularly challenging case due to the presence of a high resonant peak in its frequency response. This paper proposes a robust control strategy to overcome the stabi...
This paper presents a linear-quadratic regulator (LQR) for damping of subsynchronous interaction (SSI) in doubly-fed induction generator (DFIG)-based wind farms. The proposed LQR controller employs a full-state observer to estimate all state variables. The output of the LQR is added to control signals of inner current control loops of DFIG converte...
The distribution static compensator (DSTATCOM) is used for various purposes such as load balancing, harmonic rejection, and power factor correction (PFC) in power distribution networks. In unbalanced and polluted power systems, the classic definition of power factor cannot be used for PFC due to the existence of harmonics and negative sequence comp...
Hierarchical control/protection applications in smart microgrids require knowledge of real-time status of distributed generation (DG) systems. Lack or failure of communications with the microgrid central controller (MGCC) can significantly undermine performance of such applications since the MGCC cannot determine the number of operational energy so...
This paper proposes a new control strategy for damping of power oscillations in a multi-source dc microgrid. A parallel combination of a fuel cell (FC), a photovoltaic (PV) system and a supercapacitor (SC) are used as a hybrid power conversion system (HPCS). The SC compensates for the slow transient response of the FC stack. The HPCS controller com...
An optimal controller for damping of sub synchronous resonance (SSR) due to a series compensated line connected to a DFIG-based wind farm is presented in this paper. The design procedure includes system modeling, analysis of sub synchronous phenomena, linearization of system about an operating point and controller design. The proposed controller is...
Microgrids are prone to network-wide disturbances such as voltage and frequency deviations. Detection of disturbances by a microgrid central controller (MGCC) is therefore necessary for improving the network operation. Motivated by this application, this paper presents a new structure for the centralized detection of disturbances with noisy synchro...
This paper focuses on the problem of voltage control of islanded inverter-interfaced microgrids consisting of several distributed generation (DG) units with radial structure. The main objectives are to (i) design a decentralized/distributed voltage controller with minimum information exchange between DG units and their local controllers (ii) design...
Distributed generation (DG) units are often interfaced to the main grid using power electronic converters including voltage-source converters (VSCs). A VSC offers dc/ac power conversion, high controllability, and fast dynamic response. Because of nonlinearities, uncertainties, and system parameters’ changes involved in the nature of a grid-connecte...
This paper presents a control strategy for an islanded medium voltage microgrid to coordinate hybrid power source (HPS) units and to control interfaced multilevel inverters under unbalanced and nonlinear load conditions. The proposed HPS systems are connected to the loads through a cascaded H-bridge (CHB) multilevel inverter. The CHB multilevel inv...
In this paper, a Linear Parameter Varying (LPV) controller is proposed for the control of an islanded Distributed Generation (DG) system. The DG unit supplies a balanced three-phase passive load through a voltage-sourced converter (VSC). The dynamic model of the islanded DG system is represented by a set of nonlinear equations. Since the objective...
This paper presents a new robust control strategy for an islanded microgrid in the presence of load unmodeled dynamics. The microgrid consists of parallel connection of several electronically interfaced distributed generation units and a local load. The load is parametrically uncertain and topologically unknown and, thus, is the source of unmodeled...
This study presents new sufficient conditions for Hurwitz and Schur stability of interval matrices. Tight bounds for the spectrum of interval matrices are estimated using computationally simple optimisation problems. The conservativeness is reduced further by application of ordinary similarity transformation. A necessary and sufficient vertex based...
This letter presents new sufficient conditions for robust Hurwitz stability of interval matrices. The proposed conditions are based on two approaches: (i) finding a common Lyapunov matrix for the interval family and (ii) converting the robust stability problem into a robust non-singularity problem using Kronecker operations. The main contribution o...
This paper presents a high performance real-time simulator for power electronic systems applications and primarily intended for controller hardware-in-the-loop (CHIL) testing. The novelty of the proposed simulator resides in the massively parallel hardware architecture that efficiently exploits fine-grained parallelism without imposing severe commu...
This paper presents the stability analysis for a single-phase phase-locked loop (PLL) for power systems applications. The dynamical equations of a previously presented single-phase PLL are systematically derived and linearized for design and stability analysis purposes. Based on the linearized model of the PLL, parameters of the loop filter and the...
This paper presents a robust control scheme for an islanded microgrid in the presence of structured uncertainties. The microgrid consists of parallel connection of two Distributed Generation (DG) units and a passive load. The DG units are connected to the passive load by using the power electronics converters. The microgrid model is structurally un...
Pre-compensators are used in multivariable control systems to reduce (or eliminate) open loop system interactions. Classical methods for the design of pre-compensator are traditionally based on static designs. Static pre-compensators are preferred for their simplicity, but are highly unsystematic in the amounts of achievable diagonal dominance. In...
This paper presents stability analysis of a distributed generation (DG) controller, in an islanded mode, based on the Mapping Theorem and the Zero Exclusion Condition, and validates the results based on a laboratory scale experimental setup. The DG unit is interfaced to the host system through a voltage-sourced converter (VSC). The control strategy...
A robust decentralized control strategy for the islanded operation of a microgrid system is proposed in this paper. The microgrid consists of parallel connection of two electronically-coupled distributed generation (DG) units. The DG units are connected to a point of common coupling (PCC) where a passive load is also connected. In the islanded micr...
This paper analytically determines the nondetection zone (NDZ) of an active islanding detection method, and proposes a solution to obviate the NDZ. The method actively injects a negative-sequence current through the interface voltage-sourced converter (VSC) of a distributed generation (DG) unit, as a disturbance signal for islanding detection. The...
This paper presents a control strategy for the autonomous (islanded) operation of a distributed generation (DG) unit. The DG unit supplies a balanced load through a voltage-sourced converter (VSC). To maintain the autonomous operation in the islanded mode, the DG unit should provide its dedicated load with a sinnsoidal voltage with a constant magni...
This paper proposes a control strategy for the autonomous (islanded) operation of a four-wire, electronically-coupled distributed generation (DG) unit which can feed a highly unbalanced load, e.g., due to the presence of single-phase loads. In the grid-connected mode, the power-electronic interface of the DG unit enables the exchange of real and re...
This paper presents a control scheme for microgrids with passive loads. The existing control techniques for distributed generation systems are designed to operate either in the grid-connected or in the islanded mode. In the grid-connected mode of operation, a current-controlled scheme based on d-q variables is used for the regulation of real and re...
A decentralized servomechanism controller for islanded (autonomous) operation of radial connection of two distributed generation (DG) units is proposed in this paper. Each DG unit utilizes a voltage-sourced converter (VSC) for interface to its dedicated load. The DG units and the loads are to operate in the islanded mode of operation. Each DG unit...
A linear time-invariant (LTI) robust servomechanism controller for islanded (autonomous) operation of a distributed generation (DG) unit and its local load is proposed. The DG unit utilizes a voltage-sourced converter (VSC) as the interface medium. The controller design is obtained by introducing a new optimal controller design procedure, in conjun...
This paper presents stability analysis of a distributed generation (DG) controller, in an islanded mode, based on the Mapping Theorem and the Zero Exclusion Condition, and validates the results based on a laboratory scale experimental setup. The DG unit is interfaced to the host system through a voltage-sourced converter (VSC). The control strategy...
AC electric arc furnaces (EAFs) highly reduce power quality of the network by generating disturbances such as flicker and harmonics. These disturbances are due to the nonlinear electromagnetic and thermal field behaviors of the AC arcs. Analysis of these nonlinear behaviors is required for improving power quality in the network. This paper presents...
This paper presents a decentralized control strategy for the autonomous (islanded) operation of parallel connection of two distributed generation (DG) units. The DG units are electronically interfaced to the host grid at the same point of common coupling (FCC), where the local load is also supplied. In the grid-connected mode, the voltage-sourced c...
A novel filter for use in three-phase power systems is introduced. When the input to the filter is a balanced three-phase set of signals, the filter suppresses noise and distortions and extracts a smooth three-phase fundamental component. When the input signal to the filter is unbalanced, it extracts the fundamental positive-sequence component of t...
This paper presents a new control strategy for islanded (autonomous) operation of an electronically coupled distributed generation (DG) unit and its local load. The DG unit utilizes a voltage-sourced converter (VSC) as the coupling medium. In a grid-connected mode, based on the conventional dq-current control strategy, the VSC controls real- and re...
This paper presents an active islanding detection method for a distributed resource (DR) unit which is coupled to a utility grid through a three-phase voltage-sourced converter (VSC). The method is based on injecting a negative-sequence current through the VSC controller and detecting and quantifying the corresponding negative-sequence voltage at t...
This paper develops a dynamic model and designs a control system for autonomous operation of a stand-alone distributed resource (DR). A stand-alone DR includes a distributed resource and a local load which are interfaced electronically. The DR is represented by a DC voltage source in series with a three-phase voltage-sourced inverter and an R filte...
A novel system for decomposing a set of three-phase signals into its constituting symmetrical components is proposed. The system also estimates the frequency, the magnitudes and phase-angles of the sequence components. The system is useful for online estimation of instantaneous symmetrical components and their attributes in the presence of frequenc...
This paper deals with the definition of power factor and reactive current component in a three-phase system. For a single-phase system, power factor and reactive current component are defined based on the phase-angle displacement between the measured voltage and current waveforms. This definition can be directly extended to balanced three-phase sys...
A method for analysis of signals containing harmonics and inter-harmonics is presented and discussed. This method is primarily developed for analysis of power system signals which contain harmonic and inter-harmonic components. However, usefulness of the proposed technique goes beyond the area of power systems and it can be employed for other appli...
This paper presents a novel system for estimating the symmetrical components of a three-phase set of signals in the time-domain. Symmetrical components are significant in the area of power systems and they are used for analysis, design, control and compensation purposes. Viewed in the context of signal processing, the symmetrical components are all...
A novel filter for use in three-phase power systems is introduced. When the input to the filter is a three-phase balanced set of signals, the filter suppresses noise and distortions and extracts a smooth version of the fundamental components. When the input signal to the filter is unbalanced, it extracts the positive-sequence components of the inpu...
This paper introduces a new phase-locked loop (PLL) system. The proposed system provides the dominant frequency component of the input signal and estimates its frequency. The mechanism of the proposed PLL is based on estimating in-phase and quadrature-phase amplitudes of the desired signal and, hence, has application advantages for communication sy...
A new method for estimation of power frequency and its rate of change is presented. Unlike conventional methods which are based on the concept of linearization, the proposed scheme accommodates the inherent nonlinearity of the frequency estimation problem. This makes the method capable of providing a fast and accurate estimate of the frequency when...
This paper provides an adaptive filter for synchronous detection and extraction of harmonics. The filter can be used as integral part of the control system of a power electronic apparatus (e.g., STATCOM, APF, and UPFC) to generate the desired control signals. Stability and convergence analyses of the adaptive filter are presented based on the dynam...
This paper introduces a new adaptive filter for harmonic extraction in Active Power Filters (APF). The performance of this adaptive filtering algorithm is explained on a shunt active power filter connected in parallel with a typical uncontrolled bridge rectifier feeding a variable load. Finally, simulation results obtained confirm the feasibility a...
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