Papers by Mahdieh Sadabadi
IEEE Transactions on Power Electronics
European Journal of Control
Designs
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.
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.
IEEE Control Systems Letters
IEEE Systems Journal
In this article, an improved robust control strategy for voltage stabilization and desired perfor... more In this article, an improved robust control strategy for voltage stabilization and desired performance satisfaction of islanded inverter-interfaced microgrids consisting of several distributed generations (DGs) with general topology is presented. The main advantages of the proposed control manner are as follows: 1) its structure is fully decentralized, 2) the design process is scalable, 3) it does not impose any limitations on the microgrid parameters and line dynamics, 4) it provides stability and the desired performance of nominal microgrid system, 5) it maintains robust stability as well as robust performance of the closed-loop system against microgrid topology changes, plug-and-play (PnP) operation of DG units, and load unmodeled dynamics, and 6) each local controller is obtained from a unique convex optimization problem which results in optimal performance of the system and also robustness to several sequential changes. To achieve these objectives, first, each DG subsystem is modeled as a linear time-invariant (LTI) system affected by disturbances caused by the local load current and the load voltages of its neighboring DGs. Next, the PnP functionality of DGs and the microgrid topology changes are modeled as a new polytopic-type uncertainty. Thereafter, the design problem is transformed into a dynamic output feedback controller for an LTI system subject to polytopic-type uncertainty with H ∞ performance criteria. Finally, a convex linear-matrix-inequality-based optimization problem with a noniterative direct synthesis process is proposed to solve the controller design problem. The performance of the presented controller is appraised via several simulation studies accomplished in MATLAB/SimPowerSystems Toolbox.
International Journal of Electrical Power & Energy Systems
SummaryAcross a range of motor and cognitive tasks, cortical activity can be accurately described... more SummaryAcross a range of motor and cognitive tasks, cortical activity can be accurately described by low-dimensional dynamics unfolding from specific initial conditions on every trial. These “preparatory states” largely determine the subsequent evolution of both neural activity and behaviour, and their importance raises questions regarding how they are — or ought to be — set. Here, we formulate motor preparation as optimal prospective control of future movements. The solution is a form of internal control of cortical circuit dynamics, which can be implemented as a thalamo-cortical loop gated by the basal ganglia. Critically, optimal control predicts selective quenching of variability in components of preparatory population activity that have future motor consequences, but not in others. This is consistent with recent perturbation experiments performed in mice, and with our novel analysis of monkey motor cortex activity during reaching. Together, these results suggest optimal anticip...
IEEE Transactions on Power Systems
Constant power loads (CPLs) impose instability issues in DC microgrids due to their negative impe... more Constant power loads (CPLs) impose instability issues in DC microgrids due to their negative impedance characteristics. This paper studies the problem of voltage control design of DC microgrids with CPLs. It is assumed that the power of CPLs is uncertain and belongs to a given interval leading to an infinite number of equilibrium points of the system. We develop a polytope model for DC microgrids with uncertain CPLs. Using this model, a robust two-degree-of-freedom (2DOF) feedback-feedforward voltage control framework is then proposed. The voltage controller is obtained by a solution of a set of linear matrix inequalities. The voltage control design strategy for each distributed generation (DG) unit is scalable and independent of the other DGs. The effectiveness of the proposed control approach is evaluated through simulation studies in MATLAB/SimPowerSystems Toolbox.
European Journal of Control
IEEE Transactions on Smart Grid
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.
IEEE Transactions on Industrial Electronics
The connection of a DG unit to a weak power system is challenging due to stability issues resulte... more 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 stability issues of an LCL-based DG unit connected to a weak grid. The main advantage of the proposed control strategy is that it guarantees stability and satisfactory transient performance against the variations of grid impedance. Moreover, it is able to decouple the d-and q channels of the control system which enables independent regulation of the real and reactive output power of the DG unit. Real-time simulations and experimental tests illustrate the effectiveness of the proposed controller in terms of improved transient performance, robust stability, and satisfactory controller set-point tracking.
Annual Reviews in Control, 2016
This paper reviews the vast literature on static output feedback design for linear time-invariant... more This paper reviews the vast literature on static output feedback design for linear time-invariant systems including classical results and recent developments. In particular, we focus on static output feedback synthesis with performance specifications, structured static output feedback, and robustness. The paper provides a comprehensive review on existing design approaches including iterative linear matrix inequalities heuristics, linear matrix inequalities with rank constraints, methods with decoupled Lyapunov matrices, and non-Lyapunov-based approaches. We describe the main difficulties of dealing with static output feedback design and summarize the main features, advantages, and limitations of existing design methods.
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.
2013 European Control Conference, 2013
2007 IEEE International Conference on Control Applications, 2007
ABSTRACT
2007 IEEE Lausanne Power Tech, 2007
The new approach for identification of synchronous generator using Hammerstein model and with pie... more The new approach for identification of synchronous generator using Hammerstein model and with piecewise linear map is investigated in this paper. In this method, synchronous generator model consists of a linear-dynamic block and a nonlinear-static block. The identification method simultaneously approximates these blocks without requiring prior assumptions on the form of the static non-linearity. In this study, the field voltage is considered as the input and the active output power and the terminal voltage are considered as the outputs of the synchronous generator. Experimental results show good accuracy of the identified model.
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Papers by Mahdieh Sadabadi