This paper develops a resilient distributed control mechanism that ensures voltage regulation and... more This paper develops a resilient distributed control mechanism that ensures voltage regulation and proportional current sharing in DC microgrids while under unknown cyber-attacks. The attackers are assumed to inject false data to the actuators of microgrid control systems. The proposed resilient control algorithm steers the DC microgrid as close as possible to the desired equilibrium regardless of the potential unknown attacks and guarantees average voltage regulation and proportional current sharing in DC microgrids. The proposed resilient control design does not require any knowledge on the nature or the locations of cyber-attacks. By virtue of a graph theoretical approach and a Lyapunov-based framework, it is shown that the proposed resilient control strategy guarantees the stability of DC microgrids. The efficiency and resilience of the proposed distributed control approach is demonstrated via simulation scenarios on a DC microgrid consisting of eight distributed generation units while under attack.
The purpose of this paper is to explore the applicability of linear time-invariant (LTI) dynamica... more The purpose of this paper is to explore the applicability of linear time-invariant (LTI) dynamical systems with polytopic uncertainty for modeling and control of islanded DC microgrids under plug-and-play (PnP) functionality of distributed generations (DGs). We develop a robust decentralized voltage control framework to ensure robust stability and reliable operation for islanded DC microgrids. The problem of voltage control of islanded DC microrgids with PnP operation of DGs is formulated as a convex optimization problem with structural constraints on some decision variables. The proposed control scheme offers several advantages including decentralized voltage control with no communication link, transient stability/performance, plug-and-play capability, scalability of design, applicability to microgrids with general topology, and robustness to microgrid uncertainties. The effectiveness of the proposed control approach is evaluated through simulation studies carried out in MATLAB/SimPowerSystems Toolbox.
The extensive use of electric vehicles (EVs) can reduce concerns about climate change and fossil ... more The extensive use of electric vehicles (EVs) can reduce concerns about climate change and fossil fuel shortages. One of the main obstacles to accepting EVs is the limitation of charging stations, which consists of high-charge batteries and high-energy charging infrastructure. A new transformer-less topology for boost dc-dc converters with higher power density and lower switch stress is proposed in this paper, which may be a suitable candidate for high-power fast-charging battery chargers of EVs. Throughout this paper, two operating modes of the proposed converter, continuous current mode (CCM) and discontinuous current mode (DCM), are analyzed in detail. Additionally, critical inductances and design considerations for the proposed converter are calculated. Finally, real-time verifications based on hardware-in-loop (HiL) simulation are carried out to assess the correctness of the proposed theoretical concepts.
IEEE Transactions on Control Systems Technology, 2016
This paper proposes a decentralized control strategy for the voltage regulation of islanded inver... more This paper proposes a decentralized control strategy for the voltage regulation of islanded inverter-interfaced microgrids. We show that an inverter-interfaced microgrid under plugand-play (PnP) functionality of distributed generations (DGs) can be cast as a linear time-invariant (LTI) system subject to polytopic-type uncertainty. Then, by virtue of this novel description and use of the results from theory of robust control, the microgrid control system guarantees stability and a desired performance even in the case of PnP operation of DGs. The robust controller is a solution of a convex optimization problem. The main properties of the proposed controller are that 1) it is fully decentralized and local controllers of DGs use only local measurements, 2) the controller guarantees the stability of the overall system, 3) the controller allows plug-and-play functionality of DGs in microgrids, 4) the controller is robust against microgrid topology change. Various case studies, based on timedomain simulations in MATLAB/SimPowerSystems Toolbox, are carried out to evaluate the performance of the proposed control strategy in terms of voltage tracking, microgrid topology change, plug-and-play capability features, and load changes.
This paper focuses on the problem of voltage control of islanded inverterinterfaced microgrids co... more This paper focuses on the problem of voltage control of islanded inverterinterfaced microgrids consisting of several distributed generation (DG) units with parallel 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 a fixed-/low-order dynamic output feedback controller which ensures stability as well as desired performance of the microgrid system in spite of load parameter uncertainties. To this end, the problem is formulated as an optimization problem which is the minimization of the cardinality of a pattern matrix subject to an H ∞ performance constraint. Since the problem is intrinsically non-convex, a convex design procedure for the controller synthesis is proposed in this paper. The effectiveness of the proposed controller is evaluated through simulation studies and Hardware-In-the-Loop (HIL) verifications. The simulation and experimental results demonstrate that the effectiveness of the proposed control strategy.
52nd IEEE Conference on Decision and Control, 2013
In this paper, a new approach to fixed-order H∞ and H2 output feedback control of MIMO discrete-t... more In this paper, a new approach to fixed-order H∞ and H2 output feedback control of MIMO discrete-time systems with polytopic uncertainty is proposed. The main idea of this approach is based on the definition of SPR-pair matrices and the use of some instrumental matrices which operates as a tool to overcome the original non-convexity of fixed-order controller design. Then, stability condition as well as H∞ and H2 performance constraints are presented by a set of linear matrix inequalities with linearly parameter dependent Lyapunov matrices. Iterative algorithm for update on the instrumental matrices monotonically converges to a suboptimal solution. Simulation results show the effectiveness of the proposed approach.
Determination of the order of a model is the key first step towards modeling any dynamic systems,... more Determination of the order of a model is the key first step towards modeling any dynamic systems, particularly two-dimensional processes. In this paper, a new method for two-dimensional (2-D) Gaussian ARMA model order determination is proposed. In the proposed method, the AR and MA orders are first independently determined, then the procedure for model order determination of the 2-D ARMA model is outlined. The model is assumed to be causal, stable, linear, and spatial shift-invariant with p(1) x p(2) quarter-plane (QP) support. Numerical simulations are presented to show the effectiveness of the proposed new approach.
In this paper, a new method for fixed-order controller design of systems with polytopic uncertain... more In this paper, a new method for fixed-order controller design of systems with polytopic uncertainty in their state space representation is proposed. The approach uses the strictly positive realness (SPRness) of some transfer functions, as a tool to decouple the controller parameters and the Lyapunov matrices and represent the stability conditions and the performance criteria by a set of linear matrix inequalities. The quality of this convex approximation depends on the choice of a central state matrix. It is shown that this central matrix can be computed from a set of initial fixed-order controllers computed for each vertex of the polytope. The stability of the closed-loop polytopic system is guaranteed by a linear parameter dependent Lyapunov matrix. The results are extended to fixed-order H ∞ controller design for SISO systems.
This paper develops a resilient distributed control mechanism that ensures voltage regulation and... more This paper develops a resilient distributed control mechanism that ensures voltage regulation and proportional current sharing in DC microgrids while under unknown cyber-attacks. The attackers are assumed to inject false data to the actuators of microgrid control systems. The proposed resilient control algorithm steers the DC microgrid as close as possible to the desired equilibrium regardless of the potential unknown attacks and guarantees average voltage regulation and proportional current sharing in DC microgrids. The proposed resilient control design does not require any knowledge on the nature or the locations of cyber-attacks. By virtue of a graph theoretical approach and a Lyapunov-based framework, it is shown that the proposed resilient control strategy guarantees the stability of DC microgrids. The efficiency and resilience of the proposed distributed control approach is demonstrated via simulation scenarios on a DC microgrid consisting of eight distributed generation units while under attack.
The purpose of this paper is to explore the applicability of linear time-invariant (LTI) dynamica... more The purpose of this paper is to explore the applicability of linear time-invariant (LTI) dynamical systems with polytopic uncertainty for modeling and control of islanded DC microgrids under plug-and-play (PnP) functionality of distributed generations (DGs). We develop a robust decentralized voltage control framework to ensure robust stability and reliable operation for islanded DC microgrids. The problem of voltage control of islanded DC microrgids with PnP operation of DGs is formulated as a convex optimization problem with structural constraints on some decision variables. The proposed control scheme offers several advantages including decentralized voltage control with no communication link, transient stability/performance, plug-and-play capability, scalability of design, applicability to microgrids with general topology, and robustness to microgrid uncertainties. The effectiveness of the proposed control approach is evaluated through simulation studies carried out in MATLAB/SimPowerSystems Toolbox.
The extensive use of electric vehicles (EVs) can reduce concerns about climate change and fossil ... more The extensive use of electric vehicles (EVs) can reduce concerns about climate change and fossil fuel shortages. One of the main obstacles to accepting EVs is the limitation of charging stations, which consists of high-charge batteries and high-energy charging infrastructure. A new transformer-less topology for boost dc-dc converters with higher power density and lower switch stress is proposed in this paper, which may be a suitable candidate for high-power fast-charging battery chargers of EVs. Throughout this paper, two operating modes of the proposed converter, continuous current mode (CCM) and discontinuous current mode (DCM), are analyzed in detail. Additionally, critical inductances and design considerations for the proposed converter are calculated. Finally, real-time verifications based on hardware-in-loop (HiL) simulation are carried out to assess the correctness of the proposed theoretical concepts.
IEEE Transactions on Control Systems Technology, 2016
This paper proposes a decentralized control strategy for the voltage regulation of islanded inver... more This paper proposes a decentralized control strategy for the voltage regulation of islanded inverter-interfaced microgrids. We show that an inverter-interfaced microgrid under plugand-play (PnP) functionality of distributed generations (DGs) can be cast as a linear time-invariant (LTI) system subject to polytopic-type uncertainty. Then, by virtue of this novel description and use of the results from theory of robust control, the microgrid control system guarantees stability and a desired performance even in the case of PnP operation of DGs. The robust controller is a solution of a convex optimization problem. The main properties of the proposed controller are that 1) it is fully decentralized and local controllers of DGs use only local measurements, 2) the controller guarantees the stability of the overall system, 3) the controller allows plug-and-play functionality of DGs in microgrids, 4) the controller is robust against microgrid topology change. Various case studies, based on timedomain simulations in MATLAB/SimPowerSystems Toolbox, are carried out to evaluate the performance of the proposed control strategy in terms of voltage tracking, microgrid topology change, plug-and-play capability features, and load changes.
This paper focuses on the problem of voltage control of islanded inverterinterfaced microgrids co... more This paper focuses on the problem of voltage control of islanded inverterinterfaced microgrids consisting of several distributed generation (DG) units with parallel 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 a fixed-/low-order dynamic output feedback controller which ensures stability as well as desired performance of the microgrid system in spite of load parameter uncertainties. To this end, the problem is formulated as an optimization problem which is the minimization of the cardinality of a pattern matrix subject to an H ∞ performance constraint. Since the problem is intrinsically non-convex, a convex design procedure for the controller synthesis is proposed in this paper. The effectiveness of the proposed controller is evaluated through simulation studies and Hardware-In-the-Loop (HIL) verifications. The simulation and experimental results demonstrate that the effectiveness of the proposed control strategy.
52nd IEEE Conference on Decision and Control, 2013
In this paper, a new approach to fixed-order H∞ and H2 output feedback control of MIMO discrete-t... more In this paper, a new approach to fixed-order H∞ and H2 output feedback control of MIMO discrete-time systems with polytopic uncertainty is proposed. The main idea of this approach is based on the definition of SPR-pair matrices and the use of some instrumental matrices which operates as a tool to overcome the original non-convexity of fixed-order controller design. Then, stability condition as well as H∞ and H2 performance constraints are presented by a set of linear matrix inequalities with linearly parameter dependent Lyapunov matrices. Iterative algorithm for update on the instrumental matrices monotonically converges to a suboptimal solution. Simulation results show the effectiveness of the proposed approach.
Determination of the order of a model is the key first step towards modeling any dynamic systems,... more Determination of the order of a model is the key first step towards modeling any dynamic systems, particularly two-dimensional processes. In this paper, a new method for two-dimensional (2-D) Gaussian ARMA model order determination is proposed. In the proposed method, the AR and MA orders are first independently determined, then the procedure for model order determination of the 2-D ARMA model is outlined. The model is assumed to be causal, stable, linear, and spatial shift-invariant with p(1) x p(2) quarter-plane (QP) support. Numerical simulations are presented to show the effectiveness of the proposed new approach.
In this paper, a new method for fixed-order controller design of systems with polytopic uncertain... more In this paper, a new method for fixed-order controller design of systems with polytopic uncertainty in their state space representation is proposed. The approach uses the strictly positive realness (SPRness) of some transfer functions, as a tool to decouple the controller parameters and the Lyapunov matrices and represent the stability conditions and the performance criteria by a set of linear matrix inequalities. The quality of this convex approximation depends on the choice of a central state matrix. It is shown that this central matrix can be computed from a set of initial fixed-order controllers computed for each vertex of the polytope. The stability of the closed-loop polytopic system is guaranteed by a linear parameter dependent Lyapunov matrix. The results are extended to fixed-order H ∞ controller design for SISO systems.
Uploads
Papers by Mahdieh Sadabadi