MohammadReza Zolghadri | Sharif University of Technology (original) (raw)

Papers by MohammadReza Zolghadri

2022 IEEE International Conference on Environment and Electrical Engineering and 2022 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe)

2019 IEEE International Conference on Industrial Technology (ICIT)

In a transformerless grid-connected photovoltaic system, many issues arise from the leakage curre... more In a transformerless grid-connected photovoltaic system, many issues arise from the leakage current flow into the ground, as EMI problems. The leakage current is originated from the common-mode voltage fluctuations. In this paper, the common-mode voltage harmonics in a three-phase quasi-Z-source inverter are analyzed using Fourier transform and a closed-loop formulation is presented for the harmonics value. The shoot-through mode in a quasi-Z-source inverter causes extra fluctuations in the common-mode voltage comparing to a classic inverter. The proposed harmonic analysis method provides a systematic way to figure out how shoot-through mode and also other parameters affect the common-mode voltage. As an achievement of this method, it is possible to determine the work point of the system with the minimum leakage current. The experimental results from a reduced-voltage quasi-Z-source inverter prototype are presented to confirm the theatrical analysis.

2022 13th Power Electronics, Drive Systems, and Technologies Conference (PEDSTC)

2021 12th Power Electronics, Drive Systems, and Technologies Conference (PEDSTC), 2021

A new high step-up boost converter with an active clamp circuit to eliminate voltage spike caused... more A new high step-up boost converter with an active clamp circuit to eliminate voltage spike caused by leakage inductor is introduced in this paper. The introduced power converter has a high voltage gain for variable input voltage from 48V to 80V. Since both main and auxiliary switches turn on with zero voltage switching (ZVS) and all the diodes turn off under zero current switching (ZCS) condition, switching losses and EMI noises are strongly degraded. Therefore, the converter’s efficiency is improved significantly. Simulation results show a 96.4% peak efficiency and 95.4% average efficiency. The proposed topology is suitable for low-input-voltage and low-output power applications such as solar panels or fuel cells applications.

2019 10th International Power Electronics, Drive Systems and Technologies Conference (PEDSTC), 2019

In this paper, a new post-fault vector control of an induction motor, fed by a faulty Cascaded H-... more In this paper, a new post-fault vector control of an induction motor, fed by a faulty Cascaded H-Bridge (CHB) inverter, is presented. Among fault tolerant control methods, waveform based methods are suitable for closed-loop control and provide higher output voltage. In order to control the speed of the motor, a rotor field oriented control (RFOC) is used. During the fault, the FOC is modified to decrease the fault impact on the motor as low as possible. The proposed method is validated by means of simulation results for different loads and faults. The results show an improvement in both the final operating point and the transient response of the motor.

2018 Australasian Universities Power Engineering Conference (AUPEC), 2018

This paper demonstrates a new DC to DC gain cell —boost type—which satisfies the need for high vo... more This paper demonstrates a new DC to DC gain cell —boost type—which satisfies the need for high voltage gain and efficiency as well as low complexity for renewable energy applications. This topology enjoys both pulse width modulation (PWM) and frequency variant method (FVM) in order to achieve desirable characteristic for applying in solar and wind plants. In this regard, this cell provides high efficiency, which resulted from using zero current transition (ZCT) to reduce switching losses, and high voltage gain as well as a low input current ripple. State planes are used to analyze the behavior of the cell. The main characteristics of this cell are illustrated using simulation results and are compared with other well-known structures. The comparison results show the proposed converter provides more gain at low duty cycle than most usual ones.

2017 IEEE International Conference on Environment and Electrical Engineering and 2017 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), 2017

Conventional back-to-back converters with input power factor correction are still the best soluti... more Conventional back-to-back converters with input power factor correction are still the best solution for motor drive applications which are usually subjected to considerable load changes during their operation. Since converter components, especially input-side inductances are designed for nominal power rating, the rated input power factor and input current distortion aren't achievable in light loads. In this paper a control method is proposed to improve the input current distortion and input power factor in light loads. This is achieved by increasing the switching frequency according to the reduction in load. Since conduction and switching losses decrease in light loads, the overall losses by rising in switching frequency remain almost constant where the current is reducing. In this work, the total losses are considered proportional with the current. The effectiveness of the method is verified by simulations in which the input current distortion and power factor are improved usin...

The full-text may be used and/or reproduced, and given to third parties in any format or medium, ... more The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.

2017 IEEE Vehicle Power and Propulsion Conference (VPPC), 2017

A three-phase dual active bridge (DAB) topology has been widely applied in high power DC-DC conve... more A three-phase dual active bridge (DAB) topology has been widely applied in high power DC-DC conversion due to its advantages such as bidirectional power transfer, inherent soft switching capability and small filter size. In order to reach the high power density, the volume of the converter must be decreased. The basic idea to reduce the component size is to increase the switching frequency which causes the higher switching loss and reduces the efficiency of the converter. In this paper, the power losses of the three-phase DAB dc/dc converter are formulated and the variation of the efficiency as a function of switching frequency is investigated. In this analysis, the switching loss of the bridges for ZVS and hard switching operation is calculated with consideration the non-linearity of the drain- source capacitors of the switches. The theoretical results are verified using simulation and in a 50 kW experimental setup.

IECON 2021 – 47th Annual Conference of the IEEE Industrial Electronics Society, 2021

This paper introduces a straightforward technique for parameters estimation of the RC equivalent ... more This paper introduces a straightforward technique for parameters estimation of the RC equivalent circuit model of a battery cell with the main aim of its implementation in real-time digital simulator frameworks. The RC model parameters are precisely estimated by the analysis of the battery cell voltage curve during relaxation time using the pulse current test. In this regard, Least-squares fitting is used to mitigate the error of the battery cell voltage response, which leads to a precise estimation of the RC model parameters as a function of the state-of-charge. Exponential and Gaussian functions are utilized to define the resistances and the capacitances in the RC model respectively based upon previously estimated parameters. The performance of the proposed modeling approach is initially compared with a reference electrochemical battery cell model in MapleSim software, and then, this RC model is adapted for its implementation in a real-time digital simulator system. The achieved results demonstrate not only the accuracy of the modeling approach at different operating conditions but also its performance in real-time digital simulation applications.

2017 8th Power Electronics, Drive Systems & Technologies Conference (PEDSTC), 2017

Dual active bridge isolated bidirectional DC converter (DAB-IBDC) has a poor efficiency at light ... more Dual active bridge isolated bidirectional DC converter (DAB-IBDC) has a poor efficiency at light loads and non-unity voltage conversion ratio. In this paper the current stress of the converter is analyzed and the effect of maximum phase shift ratio and leakage inductance on the current stress of the converter is investigated. In order to increase the efficiency of the converter and reduce the current stress, the current stress optimization has been done and the design procedure is presented. Simulation results are used to validate the results of the theoretical analysis.

2018 Australasian Universities Power Engineering Conference (AUPEC), 2018

Dual Active Bridge Isolated Bi-directional DC-DC Converter (DAB-IBDC) is suitable for a variety o... more Dual Active Bridge Isolated Bi-directional DC-DC Converter (DAB-IBDC) is suitable for a variety of important applications. In this paper, a new method is proposed to identify and localize transistor open-circuit fault (TOCF) for a three-phase DAB-IBDC. The operation of three-phase DAB-IBDC during TOCF is analyzed. Consequences and features of this failure have been investigated. Subsequently, a fault diagnosis scheme is proposed for this type of failure with the capability of locating the defected transistor using the polarity of transformer currents DC component. The main advantages of this scheme are minimum additional sensors and insensitivity to converter operational conditions. The transformer and its magnetic inductance is also considered in this method. Finally, simulation results are presented to evaluate the validity of analyses and performance of fault diagnosis method.

2020 11th Power Electronics, Drive Systems, and Technologies Conference (PEDSTC), 2020

Nowadays, Programmable Electronic AC Load (PEAL) is widely used to test various devices such as s... more Nowadays, Programmable Electronic AC Load (PEAL) is widely used to test various devices such as solar inverters, UPSs, filters, generators, and generally test all AC power and measuring devices. In this paper, Model Predictive Current Control (MPCC) is used for control of a programmable AC load. In each period, switching state that minimizes the cost function is selected and applied to the converter. Cost function is the square of the current components error. The effect of the horizon of prediction on the quality of the load current is investigated. To decrease the calculations burden, a limited search pool is used. Simulation results confirm that using two steps prediction horizon with limited search pool can generate currents with acceptable THD.

2021 12th Power Electronics, Drive Systems, and Technologies Conference (PEDSTC), 2021

In this study, a new LLC resonant converter for high-voltage high-power applications is introduce... more In this study, a new LLC resonant converter for high-voltage high-power applications is introduced. The introduced power converter is a two-phase interleaved full-bridge based that uses a transformer with secondary and tertiary windings to obtain higher output voltage. Zero voltage switching (ZVS) at MOSFETs turn on and zero current switching (ZCS) for all the output diodes at turn off are achieved for a wide range of input voltage (100 V–200 V) and output power (200 W–1500 W) variations. Simulation results show a 95% peak efficiency.

2017 IEEE International Conference on Environment and Electrical Engineering and 2017 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), 2017

IEEE Transactions on Industrial Electronics, 2021

Cascaded split-source inverter (CSSI) is a new single-stage modular multilevel topology. Each cel... more Cascaded split-source inverter (CSSI) is a new single-stage modular multilevel topology. Each cell of this converter converts dc to ac power in the buck or boost operation mode without any additional power switch. This article develops a design method based on a detailed model for CSSI. This model shows that energy storage elements experience double-fundamental frequency ripples besides high-frequency ones. It accurately calculates voltage gains and capacitor voltage and inductor current ripples. On the other hand, common carrier-based multilevel modulations have been modified in terms of both reference and carrier signals to control the inverter under symmetric and asymmetric conditions. With proposed simple modulations, the cell inductor is charged with the constant duty cycle. Also, the reverse recovery of diodes occurs in the minimum level of input current once per switching cycle and output power is distributed equally between cells. These characteristics reduce power losses, the input inductance of each cell, and the complexity of the system model. By phase-shifted pulsewidth modulation (PWM), the output voltage harmonics of three-cell CSSI are centralized around multiples of the triple switching frequency. In this method, high-frequency ripples on the network impedance are one-third of those in level-shifted PWM. Also, CSSI has been compared with cascaded multilevel inverters with voltage boosting ability and other SSI-based multilevel topologies. Validity of operation principles, mathematical relations, and modulation schemes are verified through simulation and experimental results.

IEEE Transactions on Power Electronics, 2018

The leakage current originated from the fluctuations of the common-mode voltage (CMV) is an issue... more The leakage current originated from the fluctuations of the common-mode voltage (CMV) is an issue in a transformerless grid-connected photovoltaic (PV) system. In this paper, a modified space vector modulation based on the Fourier transform analysis is proposed to reduce the leakage current in a three-phase quasi-Z-source inverter (qZSI). The CMV harmonic content in a qZSI contains low and high-frequency harmonics which cause safety and EMI problems respectively. By implementing the proposed modulation in a three-phase qZSI, the low-frequency harmonics of the CMV are mainly reduced. The distribution of the high-frequency harmonics is also modified in a way they can be simply filtered. Passive filtering in a qZSI using other modulation techniques is less effective than using this method. Applying the proposed modulation in the presence of a high-frequency inductive-capacitive filter results in the strong suppression of both high and low-frequency harmonics (more than 90% in the investigated case). A reduced-voltage prototype is designed to evaluate the modulation method. The experimental results from this prototype verify the accuracy of the proposed technique.

IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society, 2015

Fault tolerant ability is one of the most important tasks in high power converters. In this paper... more Fault tolerant ability is one of the most important tasks in high power converters. In this paper, a comparison between conventional fault tolerant methods is done for four applicable methods. For this purpose, their performance is investigated in specific case study and simulation results are used to illustrate their advantages and disadvantages. The most important features taken into account are maximum available voltage, harmonic distortion of output voltage and input current, and magnitude of common mode voltage. Finally, a decision algorithm based on the results is suggested to select suitable method to control inverter under specific faulty condition.

2015 IEEE 15th International Conference on Environment and Electrical Engineering (EEEIC), 2015

In this paper, a novel reduced switch cascaded transformer multilevel inverter is proposed. In th... more In this paper, a novel reduced switch cascaded transformer multilevel inverter is proposed. In this structure, a new structure is replaced with conventional H-bridge inverter. It consists of four high frequency switches, two line frequency switches, and two transformers which can be assembled in one core with a specific winding connection. This topology can produce 5 or 7 voltage levels depending on transformers turns ratio. The simplicity and modularity are its advantages compared to the existing structures. Beside these advantages, due to its similarity with H-Bridge converter, it is possible to use a modified technique based on conventional phase shift pulse width modulation to generate switching pulses. Finally, the proposed inverter is simulated in Simulink. The results show the effectiveness of the proposed structure with the aforementioned advantages.

The 6th Power Electronics, Drive Systems & Technologies Conference (PEDSTC2015), 2015