نشریه فناوری های نوین مهندسی برق در سیستم انرژی سبز
سال سوم شماره 2 (پیاپی 10، تابستان 1403)

In this paper, a new isolated bidirectional converter is presented so that by using a new snubber without any additional switch, soft switching is provided for both main switches and the energy of the snubber circuit is transferred to the output. The number of proposed converter elements is low and its control is very simple because only one switc5h operates on each side and the other switch does not take command signal. One of its features is not using separate inductors in the snubber circuit and using the third coil for the snubber circuit. The performance of the proposed converter has been fully analyzed and simulated in PSPICE software, the results of which confirm the theoretical analysis of the converter. On the other hand, an 80W prototype has been made from it, and its practical results have been presented.

Nowadays, increasing the cost of electrical energy, especially at the peak load duration, besides the environmental caused by fossil fuels, have made the peak shaving problem by clean and renewable energies, one of the important as well as essential subjects in electric power industry. Hence, in this paper, combination of the photovoltaic power plant and the battery storage system is used to solve the peak shaving problem. In doing so, a new formulation is proposed for determining the optimal capacity of the photovoltaic power plant as well as battery storage. In the considered constraints in the mentioned formulation, technical issues and economic problems are combined together in an appropriate manner. Moreover, solving the optimization problem is performed regarding the consumption load profile as well as the hourly cost of the electrical energy of under-consideration costumer, and also the expected value of the inflation and the electrical energy cost in the future years. After that, the obtained solution is evaluated in terms of the economic feasibility and its interaction with the upstream electric power distribution network. Another considerable point in this paper is the use of the real data in an actual network for simulations. The simulation results, confirm the convenient performance as well as good efficiency of the proposed method.

Step-Up DC-DC Converters are widely used in electric vehicles, because the use of batteries and fuel cells increases the voltage level to drive the electric motor. One of the problems of step-up converters is the increase in volume and weight due to step-up transformers. So far, various methods, such as switched capacitor, coupled inductor and multiplier circuits, have been used to eliminate the transformer and reduce the volume and weight of the circuit. To further reduce the volume and weight of the circuit, it is necessary to increase the switching frequency, which is possible only by using the soft switching method. Using an auxiliary switch to create soft switching conditions is common in most methods, because not using an auxiliary switch imposes voltage and current stress on the circuit. In this article, a step-up converter with an auxiliary circuit of zero voltage transition (ZVT) is presented, which provides switching conditions at zero voltage to turn on the switch and switching at zero voltage to turn off the switch. The voltage stress of the converter is very low, and all the diodes are switched off at zero current, so they do not have reverse recovery problems. Also, in addition to absorbing the energy of the leakage inductor, the clamp capacitor helps to increase the gain of the converter. The provided converter is simulated in P-Spice software. To check the performance of the converter, a laboratory model with a power of 150 watts has been designed and tested.

In this paper, a new two-input converter with zero voltage switching for green energy hybrid systems is presented. In the proposed converter, a new auxiliary circuit is used to create zero voltage switching with the least number of auxiliary elements. The auxiliary circuit not only provides zero voltageswitching conditions, but also absorbs the energy of the leakage inductance and prevents voltage spikesacross the main switches. On the other hand, the use of coupled-inductors also increases the gain of the converter and greatly reduces the voltage stress on the switches. The proposed converter has been designed with a 120 watts power and simulated in PSICE software, and also a prototype has been made to prove the theoretical analysis of the circuit.

In this paper, an optimization model based on stochastic quadratic mixed integer programming to provide an integrated energy management of electricity and heat in electrical and thermal microgrids, taking into account the uncertainty of renewable energy sources, location of electricity generation sources and combined heat and power (CHP) along with energy and thermal storage systems and demand side management are provided in island operation and connected to the grid. A multi-objective function including minimization of energy loss, voltage deviation, cost of resource utilization, as well as reduction of renewable energy sources and reduction of installation cost is considered. The IEEE 69 bus distribution network was selected for analysis and coding was done in MATLAB software and CVX optimization package. The proposed model is also solved by the most powerful existing solver called Gurobi. The obtained results show the performance and accuracy of the proposed model.

The motivation to reduce environmental pollution has caused the rapid growth of renewable energy sources (RES) in power systems. However, several technical challenges are common in the high penetration of RES and wind farms (WF). The most important challenge is to achieve frequency stability in new systems. Because WF provide less storage, power compared to synchronous generators. In addition, due to the connection of wind farms to the AC grid through electronic power converters, new power systems have little inertia and WF cannot participate in frequency regulation with other conventional production sources in normal operation. Recently, with the increasing expansion of wind farms in power systems, their participation in supporting and stabilizing the frequency in the event of disturbances in the production or consumption of power systems has been highly considered. Therefore, in this research, firstly, it investigates the way of simulating the inertia of synchronous generators in wind turbines in order to increase the inertia of power and frequency control systems. Then, a review of various strategies and the latest developments in the field of solving the challenges of the presence of wind farms in the direction of temporary frequency support in power systems has been done. Finally, the studies conducted in inertial control techniques and system frequency for variable speed wind turbines have been investigated, categorized and compared.