Showing 11 results for Babaei
S. Babaeinejad Sarookolaee, A. Akbari- Foroud,
Volume 9, Issue 2 (June 2013)
Abstract
This study focuses on one of the most effective type of capacity markets named Capacity Subscription (CS) market which is predicted to be widely used in the upcoming smart grids. Despite variant researches done about the mechanism and structure of capacity markets, their performances have been rarely tested in the presence of network constraints. Considering this deficiency, we tried to propose a new method to determine capacity prices in the network considering the transmission line flow limitations named Local capacity Prices (LP). This method is quite new and has not been tried before in any other similar researches. The philosophy of the proposed method is to determine capacity prices considering each consumer share of total peak demand. The first advantage of LP is that the consumers who benefit from the transmission facilities and are the responsible for transmission congestions, pay higher capacity prices than those whom their needed electricity is prepared locally. The second advantage of LP is that consumers connected to the same bus do not have to pay same capacity price due to their different shares of total peak demand. For more clarification, two other different methods named Branches Flow limit as a Global Limit (BFGL) and Locational Capacity Prices (LCP) are proposed and compared to the LP method in order to show LP method efficiency. The numerical results obtained from case studies show that the LP method follows more justice market procedure which results in more efficient capacity prices in comparison to BFGL and LCP methods.
N. Tabrizi, E. Babaei, M. Mehdinejad,
Volume 12, Issue 1 (March 2016)
Abstract
Reactive power plays an important role in supporting real power transmission, maintaining system voltages within proper limits and overall system reliability. In this paper, the production cost of reactive power, cost of the system transmission loss, investment cost of capacitor banks and absolute value of total voltage deviation (TVD) are included into the objective function of the power flow problem. Then, by using particle swarm optimization algorithm (PSO), the problem is solved. The proposed PSO algorithm is implemented on standard IEEE 14-bus and IEEE 57-bus test systems and with using fuzzy satisfying method the optimal solutions are determined. The fuzzy goals are quantified by defining their corresponding membership functions and the decision maker is then asked to specify the desirable membership values. The obtained results show that solving this problem by using the proposed method gives much better results than all the other algorithms.
E. Babaei, M. R. Farzinnia,
Volume 12, Issue 1 (March 2016)
Abstract
In this paper, a new topology for Interline Dynamic Voltage Restorer (IDVR) is proposed. This topology contains two direct three-phase converters which have been connected together by a common fictitious dc-link. According to the kind of the disturbances, both of the converters can be employed as a rectifier or inverter. The converters receive the required compensation energy from the gird through the direct link which is provided by the dual-proposed switches. Due to the lack of the huge storage elements, the practical prototype of the proposed topology is more economical in comparison with the traditional structure. Moreover, compensating for long time duration is possible due to the unlimited eternal energy which is provided from the grids. The low volume, cost and weight are the additional features of the proposed topology in comparison with traditional types. This topology is capable to compensate both of the balanced and unbalanced disturbances. Furthermore, restoring the deep sags and power outages will be possible with the support from the other grid. Unlike the conventional topologies, the capability of compensation is independent from the power flow and the power factor of each grid. The performance of the proposed IDVR topology is validated by computer simulation with PSCAD/EMTDC software.
E. Babaei, Z. Saadatizadeh, S. Laali,
Volume 12, Issue 2 (June 2016)
Abstract
In this paper, a new bidirectional buck-boost dc-dc converter with capability of soft switching and zero input current ripple is proposed. The coupled inductor is used in the proposed converter to eliminate the input current ripple. In the proposed converter, zero voltage switching (ZVS) and zero current switching (ZCS) can be obtained for the main and auxiliary switches, respectively. In addition, the proposed topology is analyzed in all operating modes and all equations of voltage and current for components are obtained. Moreover, the required conditions for soft switching operation and also achieving zero input current ripple are calculated. Finally, the acuracy performance of the proposed converter is reconfirmed through simulation results in EMTDC/PSCAD software program.
S. Laali, E. Babaei, Z. Saadatizadeh,
Volume 12, Issue 3 (September 2016)
Abstract
In this paper, several optimum structures of a cascaded multilevel inverter is proposed. This optimization is based on generation a constant number of output voltage levels by using minimum number of power switches or dc voltage sources or minimum amount of blocked voltage by power switches. In addition, the optimum structure for a constant number of dc voltage sources by using minimum number of power switches is obtained. In these optimizations, all of the presented algorithms to generate a desired sinosuidal waveform of the cascaded multilevel inverter are considered. Then, the proposed optimum topologies are compared with several conventional cascaded multilevel invereters that have been presented in literature. These comparisons are from the number of required power switches, dc voltag sources, variabilty the magnitude of dc voltage source and the value of blocked voltage by switches points of view. The conduction and switching losses of the proposed topologies are calculated. In addition, a 49-level cascaded inverter based on the proposed optimum topologies is designed. Moreover, the designed topologies are compared to each other from the amount of blocked voltage by swithes, the maximum magnitude of output voltage levels and the number of required power electronic devices such as power switches, driver circuits and diodes points of view. Finally, the ability of the optimium topology in generation all voltage levels (even and odd) by using minimum number of power switches is reconfirmed thruogh PSCAD/EMTDC simulation and experimental results on a 49-level inverter.
J. Fallah Ardashir, M. Sabahi, S. H. Hosseini, E. Babaei, G. B. Gharehpetian,
Volume 13, Issue 2 (June 2017)
Abstract
This paper proposes a new single phase transformerless Photovoltaic (PV) inverter for grid connected systems. It consists of six power switches, two diodes, one capacitor and filter at the output stage. The neutral of the grid is directly connected to the negative terminal of the source. This results in constant common mode voltage and zero leakage current. Model Predictive Controller (MPC) technique is used to modulate the converter to reduce the output current ripple and filter requirements. The main advantages of this inverter are compact size, low cost, flexible grounding configuration. Due to brevity, the operating principle and analysis of the proposed circuit are presented in brief. Simulation and experimental results of 200W prototype are shown at the end to validate the proposed topology and concept. The results obtained clearly verifies the performance of the proposed inverter and its practical application for grid connected PV systems.
E. Babaei, T. Ahmadzadeh,
Volume 13, Issue 4 (December 2017)
Abstract
First of all, in this paper, the topology and operation of the three-phase three-level Z-source inverter based on neutral-point-clamped (Z-NPC) are studied. Moreover, different combinations of permissible switching states and control signals are explained for this inverter. In this paper, the topology of the three-phase three-level Z-NPC inverter is extended for an n-level state. Also, a combination of allowed switching states with relevant mathematical equations is presented for the proposed n-level Z-NPC inverter. In comparison with multilevel voltage-source inverters (only voltage-boost capability), the proposed multilevel Z-NPC inverter is a single-stage converter and it has a buck-boost capability of voltage. On the other hand, the control of two-stage converters compared to single-stage converters can be more difficult because of existing more active and passive components. In this paper, two new PWM control methods are also proposed for various multilevel Z-NPC inverters. One advantage of the proposed PWM control methods in comparison with conventional PWM control methods is maintaining the charge balance of the dc-link capacitors in neutral point. The correct performance of the proposed multilevel Z-NPC topology and PWM control methods are verified by the obtained results of analysis and simulations performed in the PSCAD software.
E. Babaei, H. Feyzi, R. Gholizadeh-Roshanagh,
Volume 13, Issue 4 (December 2017)
Abstract
In this paper, a generalized buck-boost Z-H converter based on switched inductors is proposed. This structure consists of a set of series connected switched-inductor cells. The voltage conversion ratio of the proposed structure is adjusted by changing the number of cells and the duty cycle. Like the conventional Z-H converter, the shoot-through switching state and the diode before LC network are eliminated. The proposed converter can provide high voltage gain in low duty cycles. Considering different values for duty cycle, the proposed structure works in two operating zones. In the first operating zone, it works as a buck-boost converter and in the second operating zone, it works as a boost converter. In this paper, a complete analysis of the proposed converter is presented. In order to confirm the accuracy of mathematic calculations, the simulations results by using PSCAD/EMTDC software are given.
E. Babaei, M. Shadnam Zarbil, E. Shokati Asl,
Volume 15, Issue 1 (March 2019)
Abstract
In this paper, a new topology for cascaded multilevel inverter based on quasi-Z-source converter is proposed. In the proposed topology the magnitude of output DC voltage is not limited to the sum of magnitude of DC voltage sources. Moreover, the reliability of the circuit due to capability of short circuit by Z-source network is increased. The quasi-Z- source converter in different modes is analyzed and the voltage gain is obtained. Also, the values of quasi-Z-source network components are designed. In the proposed topology, the number of DC voltage sources, the number of switches, installation area and cost in comparison with conventional multilevel inverters are significantly reduced. Three algorithms to determine the magnitude of DC voltage sources are proposed. Then the optimal structures for the minimum number of switches and DC voltage sources to generate the maximum voltage levels are presented. Moreover, the control method for the proposed topology is described. To verify the performance of the proposed topology, simulation and experimental results of proposed topology are presented.
F. Masoudinia, E. Babaei, M. Sabahi, H. Alipour,
Volume 16, Issue 1 (March 2020)
Abstract
In this paper, a new structure for cascade multilevel inverter is presented which consists of a series connection of several sub-multilevel units. Each sub-multilevel unit comprises of eight unidirectional switches, two bidirectional switches, and six DC voltage sources. For the proposed cascade topology, two algorithms are presented to produce all possible levels at the output voltage waveform. The required analysis of the voltage rating on the switches is provided. In order to verify the performance of the proposed inverter, the experimental results for a 15-level inverter are provided. The experimented 15-level inverter is compared with the other presented inverters in literature in terms of the number of DC voltage sources, switches, drivers, and blocked voltage by switches. The results of comparisons indicate that the experimented 15-level inverter requires lower power electronic elements. Moreover, the blocked voltage on the switches of the proposed topology is less than other topologies.
T. Ahmadzadeh, E. Babaei, M. Sabahi, T. Abedinzadeh,
Volume 16, Issue 4 (December 2020)
Abstract
The main purposes of a transformerless grid-connected photovoltaic (PV) system consist of the reduction of leakage current, extraction of maximum power point (MPP), tracking of MPP (MPPT), controlling the active and reactive powers, and having the unity power factor. To achieve the above-mentioned aims, the following actions have been performed in this paper. First of all, a brief analysis of the transformerless PV system has been done by using the conventional full-bridge (FB) topologies with two bipolar and unipolar PWM techniques. Then, an effective solution has been also introduced to significantly reduce the leakage current in the conventional H5 FB topology. Moreover, a proper control method has been proposed by using the combination of the fractional open-circuit voltage (FOCV) and the model predictive control (MPC) strategies to extract the MPP from PV panels, control the injection of the reactive power to the gird and have the unity power factor. At last, the simulation results performed in PSCAD software will be used to prove the correct performance of the proposed control method in the improved H5 FB topology.
