One of the most important problems related to DC-DC converters is the phenomena of power switch failures. Therefore, applying soft-switching technique to these kinds of converters without adding extra active switch would improve their reliability. In this study, a new high reliable topology with the facility of the soft-switching operation for three-phase interleaved boost converter is proposed. The proposed structure is implemented by adding three inductors to the conventional structure. Automatically, the used power switches in the suggested topology, are turned on under zero voltage condition. In addition, the diodes are turned off under zero current condition. Using this method, the switching losses of semiconductors are reduced. Moreover, there is no additional active switch in the proposed topology. These two advantages cause the reliability of proposed topology to be significantly improved. The comparison results with other similar topologies are presented. Based on comparison results, it is shown that the reliability of the proposed topology is much better than others. Simulation and experimental results are compared with verifying the desired operation of the proposed structure.

This paper presents a novel design of step-up DC-DC converters whose merits are: (i) The continuity of the input current has been kept; (ii) The polarity of the output voltage has been kept positive which provides the same ground of the input source and load; (iii) The low voltage gain of the quadratic converters has been solved that it can increase the input voltage to 10 times more by the low value of the duty cycle; (iv) Apart from the high value of the voltage gain, the semiconductors' voltage and current stresses were lower than the output voltage and input current of the converter which are the highest value of the voltage and current respectively and semiconductor based components do not suffer from high value of the current/voltage stresses; (v) Additionally, the voltage/current stresses are low, and the efficiency is good according to its 90 percent value. The analysis of the non-ideal voltage gain has been done and its better function has been deduced by comparing it with the recently proposed non-isolated topologies. Additionally, the non-isolated voltage gain has been studied for different output power levels. The efficiency has been extracted and discussed for varying duty cycles and output power based on ignoring some losses. Experimental results and simulation outcomes from the PLECS software have been compared along with theoretical relationships. The prototype of the topology has been tested at 100 W output power, 100 V output voltage, and 10 V input voltage.INDEX TERMS DC-DC converters, high step-up converters, high voltage gain, voltage doubler structure.

In this paper, a new high efficiency soft-switching non-isolated three-port converter (TPC) is proposed. In the conventional TPC, three switches are required to process power in different directions between inputs and output. Providing soft-switching condition for all switches using a low number of auxiliary components is a challenging task. In this paper, the conventional TPC topology is modified by changing its structure and adding a simple auxiliary circuit such that all switches operate under soft-switching condition in all operating modes. To reduce the volume of the converter, the magnetic components are integrated using a coupled inductor in the auxiliary soft-switching cell. In this paper, various converter operating modes are presented, and design considerations are discussed. Finally, a prototype 200 W, 100 V converter is implemented in the laboratory, and the theoretical analysis is validated by the experimental results.INDEX TERMS Distributed energy systems, dc-dc converters, soft-switching, hybrid power system, multi-input converter.

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Frequency stability is an important issue for the operation of islanded microgrids. Since the upstream grid does not support the islanded microgrids, the power control and frequency regulation encounter serious problems. By increasing the penetration of the renewable energy sources in microgrids, optimizing the parameters of the load frequency controller plays a great role in frequency stability, which is currently being investigated by researchers. The status of loads and generation sources are received by the control center of a microgrid via a communication system and the control center can regulate the output power of renewable energy sources and/or power storage devices. An inherent delay in the communication system or other parts like sensors sampling rates may lead microgrids to have unstable operation states. Reducing the delay in the communication system, as one of the main delay origins, can play an important role in improving fluctuation mitigation, which on the other hand increases the cost of communication system operation. In addition, application of ultra-capacitor banks, as a virtual inertial tool, can be considered as an effective solution to damp frequency oscillations. However, when the ultra-capacitor size is increased, the virtual inertia also increases, which in turn increases the costs. Therefore, it is essential to use a suitable optimization algorithm to determine the optimum parameters. In this paper, the communication system delay and ultra-capacitor size along with the parameters of the secondary controller are obtained by using a Non-dominated Sorting Genetic Algorithm II (NSGA-II) algorithm as well as by considering the costs. To cover frequency oscillations and the cost of microgrid operation, two fitness functions are defined. The frequency oscillations of the case study are investigated considering the stochastic behavior of the load and the output of the renewable energy sources.

In the BLDC motor-drive system, the leakage current from a motor to a ground network and existence of high-frequency components of the DC link current are the most important factors that cause conducting interference. The leakage currents of the motors, flow through common ground, will interfere with other equipment because of the high density of electrical and electronic systems in the spacecraft and aircrafts. Moreover, generally there are common DC buses in the mentioned systems, which aggravate the problem. Function of the electric motor causes appearance of the high-frequency components in the DC link current, which can interfere with other subsystems. In this paper, the analysis of electromagnetic noise and presentation of the proposed method based on the frequency spectrum of the DC link current and the leakage current from the motor to the ground network are done. The proposed method presents a new process based on the filtering method to overcome EMI. To cover the requirement analysis, the Maxwell software is used.