فهرست مطالب mehran sabahi

Switched Boost Inverter (SBI) operates in buck-boost mode with an extensive spectrum of output voltage obtainable from a specific source voltage. Also, this structure provides superior protection against Electromagnetic Wave Interference (EMI) juxtaposed with the traditional impedance source inverter. The number of energy storage elements in this structure has been reduced, which increases the efficiency of the converter in low-power applications, reducing cost, size, and weight. In this paper, this inverter is analyzed and investigated in different operating modes and steady-state. Also, three different pulse width modulation (PWM) control techniques are presented for this inverter. Simulation results are presented in PSCAD-EMTDC software to validate the calculated relationships and confirm their performance in three different switching methods.

In recent years, the development of electric vehicles has accelerated. In this manuscript, a new control method is proposed to maintain the stability of the front and rear wheel independent drive type electric vehicle (FRID EV) on the roads with a low friction coefficient. This control method specifies an optimized bound proportionally to the state of the road’s surface for the torque values produced by the front and rear electric motors to prevent the vehicle from slipping. In addition, a fuzzy logic-based braking system is proposed to improve the vehicle performance during decelerating. The vehicle is described by the model with three degrees of freedom that provides good accuracy. The tires are modeled based on the magic formula. To evaluate the effectiveness of the proposed method, simulations have been carried out in MATLAB/SIMULINK software environment. The results show that the proposed control method can well maintain the stability of the electric vehicle on dry and slippery roads, during moving straight, accelerating or decelerating, as well as turning. As a result, the vehicle is prevented from slipping and locking the wheels.

To overcome the low output voltage of Renewable Energy Sources (RESs) such as photovoltaic arrays (PVAs) and fuel cells, a new multi-input DC/DC converter is presented in this paper. This converter is based on a combination of modified quadratic buck-boost converters, Switched Inductors (SIs), and Voltage Multiplier Modules (VMMs). The high voltage gain can be achieved by adjusting the duty cycle and turn ratio of the coupled inductor of VMM. This structure inherits all the advantages of the SEPIC converter and using a bidirectional input port (in which an Energy Storage System (ESS) can be connected) and several unidirectional input ports. The load power can be flexibly divided among various power sources. Due to the buck-boost characteristics of the presented converter, it is suitable to charge-discharge the ESS. A Coupled Inductor (CI) is used to couple energy from input to the output equipped with the VMM. Moreover, the use of SI reduces the rise time and ripple of the input current. The stability of the proposed converter against momentary changes of VPV and Ro is the main advantage of this converter. Moreover, considering a secondary ESS as Vi instead of PV allows the converter to be active 24 hours a day. In this converter, the use of two ESSs guarantees the supply of the required output power. In addition, two bidirectional input ports prepare the ESSs charging and discharging capabilities. To verify the analysis and feasibilities of the proposed converter, simulation results are presented.

In this paper, a light emitting diode (LED) driver with multiple outputs, suitable to use with DC grid supply, is proposed. The proposed LED driver provides the ability to individually control the brightness of each output channel. In order to control the output power of each channel, a burst control mode is employed resulting in reduction of conduction losses. Moreover, the half bridge switches are turned on and off at zero voltage (ZV) with a fixed switching frequency; therefore, the switching losses is reduced and efficiency is further increased. Design and implementation have been simplified by choosing the same structure of the resonant series for outputs. A two-channel DC/DC converter is simulated and tested to verify the theoretical analyses.The presented converter operates above resonant frequency to decrease total harmonic distortion and reduce the size and weight of the components. Therefore, it is suitable for high power application of multi-channel drivers.

This work proposes a new multilevel inverter consisting of basic and submultilevel units. The basic unit is made-up of four isolated dc voltage sources, two bidirectional switches and ten unidirectional switches. To increase the number of the output voltage levels, a cascaded architecture based on series connection of sub-multilevel is proposed. The proposed inverter utilizes two algorithms to determine the values of dc voltage sources. Number of IGBTs, dc voltage sources, gate driver circuits, variety of dc voltage sources and peak standing voltage on the switches are calculated and their optimization to produce maximum number of levels in output voltage is investigated. To examine advantages of the proposed inverter, the topology is compared with other topologies. The results show superiority of proposed topology over most conventional topologies, in number of circuit components. Finally, to confirm the performance of the proposed multilevel inverter, experimental results of a 25-level inverter prototype are provided.

DGs and capacitor banks are installed to optimize the performance of many distribution networks. Typically, the problem of optimizing the overall performance of the distribution network is examined with multi-objective purposes. Network optimization purposes are usually varied and sometimes contradictory. Therefore, the problem search space is very large due to the variety of purposes. This paper presents a modified Pareto local search function for optimal placement of DGs and capacitor banks. To limit the search space and find Pareto points, a new combination method including Pareto chart and a weight function has been used. The optimal operation of the distribution network is performed by three single objective functions related to the voltage stability index, voltage profile of buses and power loss. In this method, a modified per-unit system is presented to align single objective functions and their weighting coefficients. The network is studied with three different loads. So that, the network is examined in the final stage by increasing the load and reaching bus voltage stability margins. The particle swarm optimization method is applied to solving placement problems. In addition, locating and sizing DG and capacitor banks, tap setting of on load tap changer transformer is adjusted by the proposed method. To show the effectiveness of the purposed method, simulations are applied to 69 bus radial system. The results indicated the favorable advantage of the proposed method to improve the overall performance of the distribution network.

In power converters, the total harmonic distortion (THD) can be decreased by using two strategies which are filtering and controlling methods. The filtering strategy is indeed costly because of using hardware devices (such as capacitor and inductor). A suitable strategy to control the modern power converters without using the hardware devices is the pulse width modulation (PWM) technique. In this paper, three new PWM control methods based on mathematical equations for various Z-source inverters (ZSIs) are proposed. Controlling the duty cycles of switches is the basic idea of these methods to control the output voltage. The proposed control methods are analyzed under the circumstances of constant input and balanced output voltage (CIBOV) and ripple input and balanced output voltage (RIBOV). The advantages of proposed methods are control of voltage, current and harmonic distortion. Other advantages of these methods are lower value for THD and elimination of low-order harmonics. The correctness operation of the proposed PWM techniques is proved by using the simulation results.

An Electric Vehicle Battery Charger (EVBC) faces serious challenges as continuous charging voltage ripple, charging speed, input voltage level variations, and its ability to adapt to the Battery State of Charge (BSOC). A proper controller has an important role to prepare all the mentioned above. A nonlinear one such as sliding mode controller (SMC) is eminently suitable for solving these issues. Therefore, an improved SMC, to take control of a DC/DC boost converter as an EVBC, is presented in this work. This proposed controller has a more robust structure in the input voltage significant variations than the other SMCs. Therefore, this provides the capability to apply various kinds of power supplies as input voltages in EVBC stations. The EVBC power and battery voltage/capacity are assumed 14 kW and 400V/60Ah, respectively in this converter. The simulation results in Matlab Simulink verify the controller’s high performance compared with the other SMCs.

A novel current source multilevel inverter is introduced in this paper which is an appropriate alternative to be employed for low/medium power applications. the proposed converter is formed basic modules which paralleling these modules increse output current levels and improve quality of injected current to load or grid. in order to validate advantages of proposed converter versus the several multilevel current source inverters, a full comparison is provided. the simulation results shows the good performance of the proposed converter in off grid and grid-connected applications. Also experimental results for single-phase load confirm the practicablity of the proposed converter.

This paper presents a single-phase transformer-less flying capacitor inverter (FCI) for applications in grid-tied PV systems. In this structure, the neutral point of the grid is connected directly to the negative terminal of PV, so the common mode (CM) leakage current eliminate without using any control strategy. The main merits of this inverter are flexible grounding configuration and high safety. A fractional-order proportional resonant (FPR) controller is employed for the proposed FCI to improve its performance during transient and steady state operation. The low output current ripple of the proposed FPR controller against parameter uncertainties is compared with conventional proportional resonant (PR) controller. The capability of controllers is investigated for parametric changes. The grid connected inverter can achieve the maximum power point tracking (MPPT) of the solar panels and inject a sinusoidal current into the grid with FPR controller. Finally, performance of the proposed controller scheme as well as the grid-tied FCI topology are verified through simulation results.

Many control schemes have been proposed for induction motor and permanent magnet synchronous motor control, which are almost highly complex and non-linear. Also, a simple and efficient method for unified control of the electric moto are rarely investigated. In this paper, a novel control method based on rotor flux orientation is proposed. The novelties of proposed method are elimination of q-axis current loop (one controller is omitted) and utilization of a new dynamic current rate limiter. Also, unlike the conventional methods, the proposed control method could be applied on both induction motor and permanent magnet synchronous motor with only minor modifications. In addition to mentioned advantages, the torque ripple and current harmonic is reduced, too. Theoretical survey and simulation results clearly show the capability of proposed method for high and low speed applications in steady and transient states.

As regards the number of electric vehicles and their batteries energies vary in charging or discharging modes, the vehicle to grid technology can act as a variable load in charging mode or as a variable energy source in discharging mode. In this paper, a new approach is proposed. In the proposed approach, the control of the connection node voltage and the coordination of the charging and discharging of the EVs batteries are considered as the variable objective functions. The constraints are determined by several parameters such as the state of charge, connection node voltage, and charging-discharging time. Based on the proposed approach, the decision variables, which are the active and reactive powers exchanged between the EVs aggregator and the grid, are determined to achieve the defined objective functions. Reduction of grid losses in the peak load hours is the other advantage of the proposed approach. The simulations for a typical distribution system with V2G capabilities, based on the proposed approach, are carried out and tested for the different scenarios in charging and discharging modes. Finally, to lend credence to the proposed method, its results are compared with the results of the conventional method.

Parallel, standby and series configurations are different types of power switch configuration that can be considered in semiconductor switches to improve the reliability of power electronic converters and theirs lifetime, especially in specific application such as high power industrial applications, satellites, power electronic interface for renewable energies and etc. In this paper, the reliability models of series traditional configuration and the new type are developed based on the Markov process. The mean time to failure (MTTF) of series and new configuration are derived. The reliability and MTTF of triple and new configuration are compared together. In some cases, some redundancy configurations have the same MTTF in a boundary condition. The analytical result illustrated that the new configuration is a suitable alternative instead of the standby configuration. The result showed the series and parallel configuration are suitable for high voltage and high current applications .

Nowadays multilevel converters have progressed in high power and renewable energy applications¡ because of their ability to generate multiple voltage levels. But the balancing of capacitor voltage¡ the existing of multiple DC sources and particularly protection issues in renewable energy application are the main problems of these multilevel converters. The proposed inverter in this paper¡ by modifying the structure of existing five-level multicell inverter with the new control method for this inverter¡ in addition to having the ability to maintain the capacitor voltage in the specified value¡ it also obviates the protection problems of them. Also the modified inverter has the ability of safety¡ connectivity of solar cells and obtaining maximum power. Finally¡ the operation of the proposed inverter and control method and mathematical analyzing is verified by simulation results with PSCAD/EMTDC software.

In practical applications of inverters, unbalanced conditions may be occurred. For instance, semiconductor switches of a converter may not be exactly the same or switching circuit may be unbalanced. This unbalance leads to additional harmonics in the output of converter. The additional harmonics usually are not considered in the design of circuit, so cause many problems. For precise investigation of these harmonics, a new model of inverter based on switching functions is presented. With this model, analytical equations of harmonics in unbalanced switching are calculated. These analytical equations can be used for designing process such as investigation of optimal cases or elimination of undesired harmonics. The accuracy of the analytical calculations is verified by simulation results. As well, an experimental prototype is constructed to verify analytical results.

In this paper, a new structure for quasi-Z-source inverters based on the combination of switched inductors and transformers is proposed. In the proposed inverter, the high voltage gain is achieved by increasing the ratio of the transformer and the number of switched inductor cells. For proposed structure, the principles operation and calculations of voltage gains and average value of the voltage across the capacitors are provided. Power losses of the proposed structure are calculated and the efficiency comparison between the proposed and other structures is given. To determine the advantages and disadvantages of the proposed inverter, the comprehensive comparison between the proposed and conventional topologies is given. To prove the correctness operation of the proposed inverter, the simulation results in PSCAD/EMTDC are used.

The Cúk converter, which has voltage buck and boost ability, offers high flexibility as an interface device for solar panels. In addition, current ripple can be more reduced because of two input and output inductors at both sides. This paper presents a new application of current-variable inductors in a Cúk converter that reduces the size and capacity of storage elements. Because of two inductors in structure, implementation of these variable inductors is important; therefore, the proposed design leads to cost and size savings, increases the performance interval of tracker to gain solar energy at lower sunlight levels, and simplifies control strategy. To validate the effectiveness of this structure, the analytical analysis, simulation results using PSCAD/EMTDC software and experimental results are presented.

Use of an electric differential (ED) in electric vehicle has many advantages. Despite its long reported success and possible advantages in terms of flexibility and direct torque control of the wheels during cornering and risky manoeuvres, the ED has several problems that have limited its applicability, for instance, an increment of control loops and an increase of computational effort. In this paper, an electric differential for an electric vehicle with four independent driven motors is proposed. The proposed ED is easy-to-implement and hasn’t the problems of previous EDs. This ED has been developed for four wheels steering vehicles. The synchronization action is achieved by using an Improved Fictitious Master technique, and the Ackerman principle is used to compute an adaptive desired wheel speed. The proposed ED is simulated and the operation of system is studied. The simulation results show that ED ensures both reliability and good path tracking.

In this article, a multi-objective function for placement of Distributed Generation (DG) and capacitors with the tap setting of Under Load Tap Changer (ULTC) Transformer is introduced. Most of the recent articles have paid less attention to DG, capacitor placement and ULTC effects in the distribution network simultaneously. In simulations, a comparison between different modes was carried out with, and without tap setting of ULTC. Simultaneous DG, capacitor placement, and ULTC transformer tap setting improve the voltage profile of load buses globally. In addition, they can also reduce loss and increase Available Transfer Capability (ATC). The IEEE 41-bus radial distribution network is used to illustrate the effectiveness and feasibility of the proposed approach.