نشریه تحقیقات نوین در سیستم های قدرت هوشمند
سال دوازدهم شماره 2 (پیاپی 34، تابستان 1402)

Today, global attention has been drawn to energy production through renewable sources, especially solar energy. Partial shading conditions have created challenging issues for maximum power point tracking, including trapping at local maximum power points, slow tracking time, and fluctuations in power output during tracking time. Therefore, in order to overcome the problems related to shading conditions and deal with local peaks, researchers have presented various hybrid techniques based on fuzzy controllers and meta-heuristic algorithms. Among all meta-heuristic algorithms, particle swarm optimization and gray wolf algorithm are the most common optimization methods due to their easy implementation, simplicity and low computational load. But the drawbacks of these algorithms are the low convergence speed and the difficulty in adjusting their parameters, and they may be caught under the rapid changes of solar radiation and shading conditions in local peaks. To deal with these problems, a new hybrid structure based on type two fuzzy controller and squirrel search algorithm has been used in this research. The type two fuzzy controller is used instead of the normal fuzzy controller and it is optimized and adjusted by the squirrel search algorithm which is used instead of the gray wolf algorithm. In this structure, by applying four radiation patterns, the effectiveness of the proposed controller has been investigated. The simulation results in MATLAB software show that the efficiency of the proposed method is about 99% on average, And using the proposed method, compared to not using it, reduces the settling time by about 36%, increases the maximum power tracking speed, and reduction of power fluctuations is possible.

Existing power grids are inefficient, due to the lack of energy management and the lack of storage, so power plants have to produce more to maintain power quality. But by using network savers, the need to build more power plants is reduced and network stability is improved and many of these inefficiencies will be remedied. By launching this market, consumers are encouraged to optimally manage their consumption, sell power to the grid during peak hours, increase network stability, and compensate grid shortages through the nearest storage network operator due to proximity to the storage. Consumers cause the least transmission line losses. In this paper, using the proposed multi-objective fuzzy multi-objective optimization problem for modeling of energy storage systems (ESS) planning in active distribution networks (ADS) considers the impact of ESS optimization strategy. Finally, the modified IEEE standard 33-bus distribution system will be used to evaluate the feasibility and performance of the proposed model by examining the two hybrid algorithms.

In this paper, a zero-voltage switching step-down converter is presented, which uses the technique of coupled inductor and series capacitor to reduce the voltage gain. Therefore, the voltage stress on the switches is reduced. The auxiliary circuit has the minimum number of elements, on the other hand, the auxiliary switch is also switched under ZV, and the reverse recovery problem of the freewheeling diode is also solved. The energy of the leakage inductor is discharged to the capacitor C and is properly transferred to the output. As a result, the capacitor C not only absorbs the energy of the leakage inductance, but also causes a further decrease in the voltage gain. Since the switches are operated complementary, it is easy to implement the control circuit. The simulation results show an increase in efficiency by 4% compared to the hard switching counterpart. Also, to confirm the correctness of the theoretical analyzes of the proposed high step-down converter, a 50 W practical prototype has been made.

Cascaded multilevel inverters are very attractive for advanced systems such as energy conversion, flexible transmission systems, drives, etc. One of the most important features of multilevel inverters is the production of high-quality waves, modularity, operation without a transformer, the ability to change voltage and current, and operation at high voltages. However, multilevel inverters have disadvantages, usually due to the presence of a large number of components, especially power semiconductor switches. In recent years, the proposal of new multilevel inverters with fewer components has been one of the most important topics discussed in power system academic forums. The main purpose of this paper is to summarize and compare the recent cascaded multilevel structures with fewer components based on their advantages, disadvantages, and structure. In one category, cascaded multilevel inverters are divided into symmetric and asymmetric categories that both groups will be investigated in this study. To confirm the optimal performance of multilevel inverters, the simulation results have been evaluated in MATLAB/SIMULINK software.

Due to the widespread use of electric motors in various industries, checking the conditions and diagnosing its possible faults in the early stages is one of the most important goals of intelligent industrial monitoring equipment in modern factories. Bearings are one of the mechanical parts that often fail during operation. The mechanical faults of the electric motor show themselves as vibration in the motor, which can be used to diagnose the fault, especially in the early stages. In addition, noise in industrial environments usually has less impact on vibration because vibration is extracted directly from the motor body or its base. According to this explanation, in this research, a bearing fault detection method is proposed using wavelet transform of the vibration signal in induction motors, which can detect the defect with very high accuracy. The proposed method was implemented on two different databases using Matlab 2021. The obtained results, compared with the latest articles in this field, confirmed the effectiveness of proposed method based on criteria such as accuracy and correctness. In the meantime, the advantages of proposed method, such as high speed, low calculations and its robustness to noise, were also shown.

Power system design and controls are done with stability and reliability. Frequency is one of the important variables to stabilize the speed of engine loads. Considering the vital role of gas turbines in producing electricity without harmful effects on the environment, in this paper, utilizing the Rowen model for the frequency power system, the load-frequency control with the secondary control loop has been examined. For this reason, the design is done by the transfer function and state space. To begin with, the conventional PID controller is designed utilizing CHR and CC calculations in order to increase the system speed, eliminate disturbance and reduce the sum of overshoot. At that point, LQR linear optimal controller is utilized. Finally, due to the uncertainty and disturbance, H2/H∞ robust controller has been considered with the three conditions of nominal performance, robust stability, and reduction of disturbance.  The simulation results obtained with/without the presence of disturbance have been checked and compared in MATLAB software. The results of the simulations show the success of the proposed H2/H∞ robust control strategy in terms of convergence rate and fluctuation range among all the control strategies examined.