Journal of Applied Dynamic Systems and Control
Volume:1 Issue: 1, Summer and Autumn 2018

In this paper, a simple method based on Field-Oriented Control (FOC) algorithm is proposed for Fault-Tolerant Control (FTC) of star-connected 3-phase Induction Motor (IM) drives for the Electric Vehicle (EV) applications. The proposed method is able to control 3-phase IM drive under both normal and stator winding open-phase fault conditions. The proposed FTC system is derived from a conventional FOC and requires only minor changes in parameters of the machine. The simulation results show that performance of the proposed control system is satisfactory in the case of 3-phase IM drive under open-phase fault.

In industrial systems, performance of a spacecraft is always affected by the presence of uncertainties and disturbances. In this paper, we study the application of a combination of Fault-Tolerant Control (FTC) designs based on fractional calculus and Terminal Sliding Mode Control (FOTSMC) for a spacecraft in the presence of external disturbances. The proposed controller shows better control performance compared to existing terminal sliding mode control (TSMC).Moreover, in our design, the control law does not need a fault detection and isolation mechanism. The sliding mode control protects controller against disturbances and uncertainties while the fractional calculus provides robust performance. The performance of the proposed fractional-order controller, as compared with other controllers, is provided via numerical simulations. The results clearly demonstrate better performance of the fractional order terminal sliding mode control for an actuator fault in comparison with the terminal sliding mode control. The analytical stability analysis of the closed-loop control system is also provided by the Lyapunov direct method for fractional-order system.

This paper presents a new modeling technique for fuel cell based switching converters. Often a step-up converter is used in the fuel cell applications due to its relative low voltage. Here a boost converter is used to convert the fuel cell voltage to the desired load level. The aim of this paper is to study through analysis and simulation, the voltage mode control and dynamic modeling of series interconnected topology of a fuel cell based system. Euler-Lagrange (EL) equation is used here as a modeling technique which relies on the energy balance equilibrium because fuel cell based systems can be considered as an energy processing structure. The fuel cell must be protected against the current harmonics or sudden transients so that it provides the regulated voltage for output load. We use a LC filter between fuel cell and converter to prevent the current harmonics from reaching the fuel cell since this may lead to oxygen starvation phenomena around the electrodes surface or other faults. The proposed modelling procedure is applicable for any other converter based on fuel cells. Finally, simulation is done by PSIM and MATLAB softwares to validate the proposed modeling technique. We run both the frequency and time domain analysis to show that the proposed modeling technique coincides exactly with the simulation results.

Fuel Cells do not respond to higher frequency contents of load changes due to their inherent large time constants; thus, if any disturbance occurs in the system loading, it would cause negative effects on power quality of the system. This is especially of high importance in microgrids which contain critical loads with low inertia requirements. Sudden changes in load points could cause significant frequency and voltage variations. Hence, proper measures such as energy storage systems should be taken into microgrids for improving their stability. In this paper, a new method based on Ultra-Capacitor (UC) with bidirectional converter has been proposed to solve this drawback of fuel cells. The UC is used to modify the system's frequency response with a fast and efficient controller. The proposed method is simulated for a sample test system in MATLAB/SIMULINK environment and results are presented to illustrate its performance. Based on the results, the system can manage its frequency and voltage variations effectively by the proposed configuration.

An energy system that produces work, heat and so forth, contains unintended remaining flows of matter or energy called residues. In the conventional thermo economic cost accounting methods, as it is already known, the problem of the residues cost has not been considered thoroughly. The residues cost allocation is a complex problem practically, because it is intertwined with the nature of such flows and the way they are formed. There are several options for the residues cost allocation among which two more important options are: (1) distribution of the residues cost proportionally to the exergy and (2) distribution of the residues cost proportionally to the entropy generation or negentropy. In this paper, for the residues cost distribution ratio, two alternative options are proposed. The proposed options are applied to a combined cycle and results are compared with two different possible options. The results suggest that the proposed options are more proper and reasonable than the alternative options.

In this paper, a hybrid system based on wind turbines, solar arrays and fuel cells is designed optimally in the view of economical and technical aspects. The objective of the hybrid system optimization is to minimize the system net peresent cost(NPC) while considering the reliability as a constraint. The economical designing aspect is defined as equivalent loss factor (ELF) of reliability. The NPC consist of capital, operation and maintenance, replacement and, especially, loss of load costs. The data of load, solar radiation and definitive wind speed are from the North West of Iran. It is assumed that between the system components, i.e., wind turbine, photovoltaic array and inverter, there is a forced outage probability. The cuckoo optimization (COA) and firefly algorithms(FA) are applied to optimize the hybrid system components and the results are compared with the last studies. The results show that the COA method is superior to the FA and the last studies, with respect to the economical and technical aspects and convergence speed. They also show that complete consideration of the components availability and the availability of inverter increases the generation costs of the system, but improves the system reliability indices, too.

A power system stabilizer (PSS) is an ancillary device used for improving stability of otherwise poorly stable power system. It helps to restore the system back to the operating point after disturbances like load changes or faulty situations are withdrawn or smoother transition from one to another operating point. Originally, power system stabilizers are installed to add damping to local oscillatory modes, which were destabilized by high gain, fast acting exciters. Its property is to provide damping torque to reduce the electromechanical oscillations introduced in the system under disturbances. In this paper, first, we analyze different types of small signal stabilities of a power system using linearized model and then, design a stabilizer for Single Machine Infinite Bus (SMIB) system. A comparison between the effect of Linear Optimal Control plus PSS (LOC-PSS) and Conventional PSS(CPSS) in terms of either power system responses or its eigen-values due to different load condition is reported. Simulation results show the LOC- PSS is robust for such nonlinear dynamic system and achieves better performance than the CPSS in damping oscillations. The effectiveness of the PSS for different load disturbances is illustrated with simulation carried out in MATLAB software.

Induction Motors (IM) are one of the main and voltage sensitive loads within industrial centers whose start-up and loading characteristics affect the nearby loads adversely. The performance of induction motors is influenced by their supply voltage; thus, such faults as short circuits can lead to their instability. Distributed Generation Units (DGUs), recently applied by electric utilities and consumers with a remarkable growth, can provide the desired  ctive power based on a proper control algorithm and configuration of such voltage source converters as parallel, series and hybrid in one hand, and compensate for various power quality and voltage regulation problems, on the other; hence so called Flexible Distributed Generation (FDG). In this paper, a new interface is introduced for onnecting DGUs to the distribution network. The proposed interface is not only able to provide some portion of active power to loads, but also maintains the nominal voltage for a wide range of operational conditions. Hence, it can replace such compensation devices as Distribution Static Compensators (D-STATCOM) or On-Load Tap Changer transformers (OLTC), which have already being used for voltage regulation of distribution networks. Within the interface, a fuzzy controller is used for the voltage control loop. Computer simulation in MATLAB Simulink proves the performance enhancement of the interface.