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Papers by Masoud Farhadi

IEEE Transactions on Vehicular Technology, 2023

AC power cycling tests allow the most realistic reliability assessment by applying close to real ... more AC power cycling tests allow the most realistic reliability assessment by applying close to real stress to the device or module under test to meet functional safety standards, which is highly critical for traction applications. This paper presents a comprehensive guideline and shares critical know-how to develop a 120 KVA AC power cycling test setup for high-power Silicon Carbide (SiC) modules. As of today, traction applications can not generate an early warning signal for drivers to replace critical components on time. For this purpose, the suitable precursors for all dominant failure mechanisms are discussed, and the corresponding condition monitoring tools are proposed to monitor the device aging on power converters. These condition monitoring tools are integrated into the built-in desaturation protection circuit of the electric vehicle (EV) gate driver for low-cost, practical implementation. The on-resistance of all twelve switches is monitored online as a temperature-sensitive electrical parameter (TSEP) to measure the junction temperature of the devices. To avoid heavy processing load in the microcontroller, the out-of-order equivalent time sampling technique is developed for data sampling, which leads to a measurement error of less than 1.5%. In addition, the design considerations regarding common mode noise and aging effect on DESAT protection are investigated, and experimental findings are presented.

International Journal of Circuit Theory and Applications, 2020

In order to increase the low voltage of renewable energy systems to a relatively high bus voltage... more In order to increase the low voltage of renewable energy systems to a relatively high bus voltage for the downstream dc-ac grid-connected inverter, a new dc-dc switched-capacitor converter with the potential of output voltage regulation is proposed. The operational principles, with regard to the specific switching conditions, are provided the relationships for the parameter design and efficiency calculation. The topology makes it possible to integrate the high voltage gain and excellent output regulation that open a huge area of applications and create the possibility of maximum power point tracking (MPPT) which is an important advantage of proposed structure. Moreover, the most important advantages of the proposed structure are continuous input current, variety of the dc voltage source values and the cost of the converter in comparison with the conventional structures. A comparison with other similar structures is given to show the merits of the proposed topology. Finally, the experimental results are presented to clarify the theory and feasibility of the proposed converter.

International Journal of Electronics, 2018

Experience shows that semiconductor switches in power electronics systems are the most vulnerable... more Experience shows that semiconductor switches in power electronics systems are the most vulnerable components. One of the most common ways to solve this reliability challenge is component-level redundant design. There are four possible configurations for the redundant design in component-level. This paper presents a comparative reliability analysis between different component-level redundant designs for solid state fault current limiter (SSFCL). The aim of the proposed analysis is to determine the more reliable component-level redundant configuration. The mean time to failure (MTTF) is used as the reliability parameter. Considering both fault types (open circuit and short circuit), the MTTFs of different configurations are calculated. It is demonstrated that more reliable configuration depends on the junction temperature of the semiconductor switches in the steady state. That junction temperature is a function of i) ambient temperature, ii) power loss of the semiconductor switch and iii) thermal resistance of heat sink. Also, results' sensitivity to each parameter is investigated. The results show that in different conditions, various configurations have higher reliability. The experimental results are presented to clarify the theory and feasibility of the proposed approaches. At last, levelized costs of different configurations are analyzed for a fair comparison. Nomenclature λO.C Open circuit rate of unidirectional switch (failures per million calendar hours or FIT, 1 FIT=10 −9 failure/hour).

2020 IEEE Kansas Power and Energy Conference (KPEC 2020), 2020

Transformerless Photovoltaic (PV) grid-connected systems benefit from improved cost, size, weight... more Transformerless Photovoltaic (PV) grid-connected systems benefit from improved cost, size, weight, and efficiency compared to the isolated alternatives. A drawback of the trasnsformerless PV inverters is the leakage current that flows through the parasitic capacitance formed between the PV cells and panel metal frame connected to the earth. The leakage current increases the current harmonics injected into the utility grid, the radiated and conducted electromagnetic interference (EMI), and losses. In this paper, a two-stage three-phase Filter-Clamped (FC) transformerless PV system is employed that reduces the leakage current and output current THD compared to the conventional three-phase inverters. Unlike other transformerless PV inverters, the FC inverter does not require any additional component. The FC transformerless PV inverter is analyzed mathematically and its excellence is compared to the conventional three-phase inverter through simulation results.

IEEE Transactions on Power Electronics , 2018

In this paper, a new fault tolerant DC-AC converter-fed induction motor drive is proposed to main... more In this paper, a new fault tolerant DC-AC converter-fed induction motor drive is proposed to maintain motor as close as possible to its desired normal operation under open- and short-circuit switch failures. The operational principles for fault detection and isolation schemes, are provided. Two control strategies including predictive control and voltage mode-controlled PWM with integral-double-lead controller for two stage of the converter are presented in conjunction with the elaborated discussion. The control strategy determines appropriate switching states for continuous operation of the drive after a fault. The proposed topology makes it possible to integrate the minimal redundant hardware and full tolerance capability which is an important advantage of the proposed topology. Moreover, the most important advantages of the proposed topology are a fast response in a fault condition and low cost of the converter in comparison with the evaluated topologies. A Joule-integral-based method for selecting an appropriate rating of applied fuses has been presented to provide a reliable fault-isolation operation. Also, a comparison with currently available fault-tolerant DC-AC converters is given to show the merits of the proposed topology. Finally, the experimental results are presented to verify the validity of the theoretical analysis and industrial feasibility of the proposed converter.

Engineering Failure Analysis, 2016

Up to now, many modulation techniques have been proposed for neutral point clamped (NPC) inverter... more Up to now, many modulation techniques have been proposed for neutral point clamped (NPC) inverters. In this paper, for the first time, a general methodology is applied to calculate and compare the failure analysis and reliability of NPC inverter with most commonly used control strategies. Also, the mean time to failure (MTTF) of NPC inverter is derived for different control strategies. It is demonstrated that the key feature of control strategies in determining the reliability of inverter is their loss distribution among the switches. The failure rate of components that is relevant to this study and junction temperature calculation is developed, then conduction losses and switching losses of switches for different control strategies are calculated. Finally, the most reliable control strategy is identified. Experimental results obtained have promptly justified the theoretical analysis and outlined procedure.

IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, 2019

This paper proposes a new DC-AC converter with a less number of semiconductor switches and theref... more This paper proposes a new DC-AC converter with a less number of semiconductor switches and therefore gate drive and control circuit components. A salient feature of this inverter is its pure sinusoidal line-to-line voltages with no need for output filter. Also, the proposed inverter improves the voltage utilization factor of the input dc supply compared to four-switch three-phase inverter (first best topology in the literature from the number of switches point of view) and standard six-switch inverter with sine PWM. The proposed inverter is capable of operating with a wide range of output voltages from zero to the full value of the dc input voltage by appropriately altering instantaneous duty-cycle. For the first time to our knowledge, in this paper, a three-phase universal inverter with only three power-switch has been proposed. For the purpose of providing a good compromise between fast transient response and stability, a model predictive controller is proposed. All the design expressions have been derived. A comparison with other DC-AC converters is given to show the merits of the proposed converter. Finally, satisfactory circuit operation is confirmed by experimental results from a laboratory prototype. Index Terms-DC-AC power converters, three phase, pure sinusoidal output voltage, model predictive control (MPC).

Conference Presentations by Masoud Farhadi

2016 1st International Conference on New Research Achievements in Electrical and Computer Engineering

Power Quality (PQ) is one of the major concerns in the power grids. Where various devices such as... more Power Quality (PQ) is one of the major concerns in the power grids. Where various devices such as Dynamic Voltage Restorer (DVR) and Uninterruptible Power Supply (UPS) have been designed and used to control PQ, although these devices have satisfactory performance and they have some problems such as installation restriction and high cost. This paper proposes a multilevel converter-based Unified Power Quality Conditioner (UPQC) to solve the power quality disturbances. Impact of proposed UPQC on the power quality parameters is discussed in the IEEE 14-bus system. In order to verify the results, PSCAD/EMTDC software is used to simulate the system.

The 4th International Reliability Engineering Conference

With the short circuit level increase in power grids, there is a need to increase rating of switc... more With the short circuit level increase in power grids, there is a need to increase rating of switch type fault current limiters (STFCLs), therefore, modularization of STFCLs is inevitable. This paper presents a comparative reliability analysis between the modular and non-modular STFCL topologies. It is demonstrated that modular design causes a considerable reduction in reliability. The aim of the presented study is to increase the reliability of modular fault current limiters using thermal management. The failure rate of STFCL module and junction temperature calculation is developed. The mean time to failure (MTTF) is used as the reliability metric. MTTFs of two topologies are calculated and compared. It is demonstrated that reliability of STFCL depends on the junction temperature of the semiconductor switches in the steady state, that it can be controlled by the thermal resistance of the heat sink. Ranges of the junction temperature and thermal resistance in which the modular configuration is more reliable are formulated. Then numerical studies are presented to verify the efficacy of the proposed approach.