نشریه مهندسی برق و مهندسی کامپیوتر ایران
سال هفدهم شماره 2 (پیاپی 51، تابستان 1398)

In electric vehicle’s nonlinear dynamic equations, some parameters has uncertainty such as the coefficient of rolling resistance, drag coefficient, armature resistance and field winding resistance. Design of a controller that is robust in the presence of these parametric uncertainties and also in presence of external disturbances, and on the other hand simultaneously satisfies the optimality criteria, is a challenging issue. In practical applications, in addition to the above problem, the computational load of the control input should also be considered and provide a rational interaction between the controller's desirable performance and the calculations volume. In the present paper, a robust optimal stable fuzzy controller based on the parallel distributed compensation is designed, using Takagi-Sugeno fuzzy model of electric vehicle. The stabilizer feedback gains of fuzzy model, the upper bound of the uncertainties, the upper bound of the disturbances effect, and the upper bound of the cost function are obtained completely offline, through the solving of a minimization problem based on the linear matrix inequality. Therefore, the calculation volume of the control input is extremely low. This allows the practical implementation of the proposed controller. The favorable performance of the proposed controller is demonstrated in five-step simulations.

Microgrid technology makes possible coordination and effective use of different energy resources for supplying loads. In order to have synchronous operation between inverter resources during the occurrence of islanding condition, the use of droop controller structure would be beneficial. In this paper, the conventional droop controller is modified to divide proportional power between resources and cause accurate voltage setting in output resources. By providing a model for connected inverter to the nonlinear load, a harmonic droop controller has been designed. By droop controller related to each harmonic, the harmonic voltages are calculated and add to the reference voltage. Therefore the quality of the output voltage is improved. Then the inverter voltage control loop would be modified with resistance impedance in the presence of non-linear loads, so that, in combination with harmonic droop controller, THD of output voltage considerably reduced. Simulation results show the ability of suggested method in reduction of harmonic voltages in inverters parallel operation.

This paper presents optimal design of a six-phase permanent magnet synchronous generator (PMSG) for use in direct drive wind turbines. High Dimensions and manufacturing cost and low efficiency are the disadvantages of generators connected to wind turbines without gearbox because of their low nominal speed. Therefore, the main purpose of this paper is to optimize the design of the PMSG based on the reduction of losses and the construction cost of the generator. For this purpose, the relations governing the design of the radial flux PMSG have been introduced and then a design algorithm has been extracted. Subsequently, by defining a multi-objective optimization problem and using the particle swarm optimization (PSO) algorithm, the optimum design variables are determined in a suitable range and the minimum losses and construction cost of the generator are obtained. The optimal design has been verified by using finite element analysis.

Renewable energy sources cannot provide load power continuously which is an important challenge in applying these sources. Therefore, usually several renewable sources; such as, solar cells and fuel cells are applied simultaneously. A converter can be applied for each source which results in high implementation cost. Therefore, multi input converters are used to reduce cost and volume of the system. In this paper, a new soft switching multi input converter is proposed. In this converter by applying one additional switch, soft switching is achieved for all main switches. The proposed converter is analyzed and design considerations are discussed.

The cascaded H-bridge converter is one of the useful multilevel converters for high power applications. The unbalancing of cells DC bus voltages is a major issue in this topology especially when the capacitors are charged from the grid, which mainly is caused by the different losses of cells. In this paper a new method is proposed for balancing the cells DC bus voltages without need to measure the cells current. This method is named as “adaptive carrier phase shift”, which is based on the phase shift pulse width modulation. The balancing between the cells DC bus voltages is achieved by measuring the voltages and changing the carrier phase shift. This method is analyzed mathematically and is used to balance a 7-level cascaded H-bridge STATCOM. The feasibility and appropriate function of balancing method is investigated by the simulation studies in the MATLAB/Simulink software.

Reliability centered maintenance is a tool for managing the maintenance of deteriorating assets. The basis of this method is the identification of failure mode of equipment, deterioration process, and maintenance scheduling to reduce the risk of failure and maintenance costs. One of the maintenance methods used in reliability-based maintenance is inspection-based maintenance. In inspection-based maintenance, a decision about the type of maintenance is made after an inspection and determination of the deterioration status of equipment. In this paper, a model for annual maintenance scheduling of network equipment is provided. The scheduling problem is formulated as a probabilistic model with binary variables as inspection times and the optimal maintenance strategy is determined. This model is implemented on a transformer and sensitivity analysis is performed to analyze the effect of inspection and outage cost.

In this paper, we present a new scheme named advanced spatial modulation for multiple input multiple output (MIMO) systems. Advanced spatial modulation achieves more spectral efficiency than ordinary spatial modulation with using power divider and set the phase of active transmit antennas. Using Power divider enable us to have more than one active antenna in a time slot with only one RF-chain in transmitter. Additionally, we can allocate more spatial bits with map information bits into the phase of the transmit antenna. Then, the performance of the proposed system is simulated and is compared with ordinary spatial modulation and some MIMO techniques such as orthogonal space time block code and V-BLAST.

In this paper, a 1:8 Ku-band(15-18 GHz) power divider/combiner based on Ridge Gap Waveguide(RGW) technology is designed and simulated which can be extended to arbitrary 1:N power divider/combiners. In the proposed structure a piece of metal and T-junctions with multisection impedance matching are used. Return loss of the simulated power divider is better than -10 dB at 15-18 GHz frequency band. Also the insertion loss from input to each output is almost -9dB which was expected. Also difference between phases of the insertion loss from input port to each output port is less than 0.9 degree..