Synchronous machine is a two-excitation machine and is widely used in energy conversion systems such as wind energy conversion system and hydropower plants. Providing and regulating the direct current of the excitation coil of the synchronous machine is the main task of the excitation system. The excitation system in the synchronous machine must have a high voltage limit. For high reliability, each generator has its own exciter. The excitation system by controlling the excitation voltage can control the voltage and reactive transmission power and strengthen the stability of the system and cause the proper operation of a power system. In the dynamic analysis of the power system, to check the stability of the synchronous generator, it is enough to consider the excitation system and its primary drive controls can be ignored. In this article, the aim is to study and simulate the behavior of a no-load synchronous generator equipped with a static excitation system. Changes in the output voltage of the excitation system due to changes in the parameters of the excitation gain reduction (TGR) and the excitation system stabilizer (ESS) have been investigated. The simulation results show the effect of TGR and ESS on damping the oscillatory response and reducing the settling time of the response. تفاصيل المقالة

The complexity of communication and the size of different areas of power systems are increasing, and the development of the power system requires the optimal allocation of electric power produced by a large number of system generators. Electric energy production in power systems is one of the most important issues in modern systems, along with minimizing the total production cost of the generator units in the power system. Economic load distribution is a common optimization problem in power systems. In this article, the economic distribution of the load between the production units has been done by limiting the minimum and maximum power range between the generator units. To carry out the economic distribution of the load, the repetition method of the Lagrange coefficient is used. To show the study data, the simulation results for a power system with two production units and taking into account losses and a power system with three production units and without losses are presented. Distinct fuel functions are considered for the units in the study. تفاصيل المقالة

چکیده: تولید انرژی الکتریکی پاک از اساسی‌ترین نیازهای پیش روی بشر امروز است. از این رو استفاده از نیروگاه‌هایی تولید برق که سوخت‌های تجدیدپذیر و سازگار با محیط زیست (انرژی‌های نو) به‌عنوان سوخت پایه آن‌هاست، بشدت مورد اقبال قرار گرفته است. حال آنکه سطح ولتاژ خروجی نیروگاه‌های محلی تولید انرژی الکتریکی بر پایه انرژی‌های نو، به عنوان ولتاژ ورودی طبقات بعدی (اینورترها و ...)، پایین است. از این‌رو محققان سعی کرده‌اند با استفاده از مبدل‌های افزایندهDC/DC این عیب را برطرف سازند. ساختارهای مربوط به این مبدل‌ها بر اساس انتظارات طراح مانند ضریب بهره ولتاژ، توان خروجی، بازده، مشخصات ولتاژ ورودی و ... متفاوت است. مبدل‌های افزاینده به کمک کلیدزنی و ذخیره انرژی در سلف خود، وظیفه افزایش ولتاژ DC را بر عهده دارند. اما همین ساختار ساده را می‌‌توان به کمک ترفندهای جدید همچون، استفاده از تزویج مغناطیسی، افزودن مدارات افزاینده غیر فعال به ساختار مبدل‌، ایجاد ساختارهای کامل‌تر با بهره بردن از چندین کلید اکتیو و حتی ترکیب چند ساختار با هم به نقطه مطلوبی از نظر بهره ولتاژ رساند. از سوی دیگر با روش‌های کلیدزنی نرم ( رزونانس و اسنابر و ...) راندمان مبدل‌های افزاینده در محدوده قابل قبولی قرار می‌گیرند. در این مقاله، انواعی از نیروگاه‌های بر پایه انرژی‌های نو و سپس مبدل‌های افزاینده که از اساسی‌ترین ارکان یک نیروگاه بر پایه انرژی‌های نو هستند، از نظر ساختارهای افزاینده و روش‌های کاربردی جهت بهینه‌سازی این مبدل‌ها به خصوص از نظر کاهش تلفات و افزایش راندمان دسته‌بندی شده است. تفاصيل المقالة

اگرچه مبدل‌های رزونانسی LLC دارای سابقه نسبتاً زیادی می‌باشند، اما اخیراً این مبدل‌ها مخصوصاً با به کارگیری توپولوژی نیم‌پل از محبوبیت ویژه برخوردار شده‌اند. در بسیاری از کاربردها مانند ATX PCها و تلویزیون‌های صفحه تخت که نیازمند راندمان و توانایی انتقال چگالی توان بالایی هستند، استفاده از مبدل رزونانسی LLC نیم‌پل با توجه به معایب بسیار کمی که دارد، بهترین راه‌حل می‌باشد. یکی از مشکلات طراحی این مبدل، پیچیدگی روابط حاکم بر مدار و غیرخطی بودن معادلات است. در این مقاله از روش FHA به منظور تحلیل مدار استفاده شده است، که با در نظر گرفتن تنها هارمونیک اصلی از بسط فوریه ولتاژ و جریان، روشی مناسب برای به دست آوردن بهره ولتاژ مبدل ارائه می‌کند. سپس با استفاده از نرم افزار PSpice طراحی انجام شده شبیه‌سازی، و در انتها نتایج عملی مبدل ساخته شده برای توان 75 وات با راندمان حدود 93% آورده شده است. همچنین نتایج شبیه‌سازی تأیید کننده نتایج عملی می‌باشد تفاصيل المقالة

Stepping motors are normally operated without feedback and may suffer from loss of synchroni-zation. The permanent magnet stepper motor (PMSM) is generally two-phase. In this paper, the nonlinear dynamic equations governing the performance of the permanent magnet stepper motor are linearized at an operating point for small signal stability studies. Small signal stability is the system ability to maintain synchronism when a small disturbance occurs. It is based on the state space averaging approach. A detailed description of the method, results, and conclusions are also presented. Finally, simulation results for three motors have been reported and compared تفاصيل المقالة

Power system is a nonlinear and temporal variable system. Different parts of the system change at different times and times with changing loads or loss of generators and disturbances. Power system stability and attenuation of low frequency fluctuations are very important. To increase the damping power and stability of the dynamic system, power system stabilizers are used to reduce fluctuations by generating additional control signals for the generator excitation system. In this paper, to improve the stability of the power system dynamic, a power system stabilizer based on synergistic control theory with an excitation system stabilizer according to a simplified nonlinear power system is used. The power system stabilizer has been studied in a single machine system connected to an infinite bus. The results show that the use of power system stabilizer and excita-tion system stabilizer for all nonlinear dynamic systems performs better than synergistic PSS, conventional PSS, and a system without stabilizer. تفاصيل المقالة

In this paper, a novel application that uses the broadband noise from a ship-of-opportunity to estimate the scattering from underwater objects is reported. The propagation is based on the normal-mode model. The source localization (location of propeller) is initially realized using incoherent broadband matched-field processing. Then, by utilizing an estimator that relies on Normal-Modes, the target echo below the sea surface is calculated to evaluate the location of the target. The proposed idea is illustrated using simulation and then verified using the acoustic data from a 2019 underwater communication trial in Grand Passage, Nova Scotia in Canada. Experimental results show that the proposed technique can be a reliable signaling method and environmentally friendly that can be applied to the fields of underwater communication and ocean monitoring for a shallow water environment. تفاصيل المقالة

Sensitive loads cannot tolerate voltage sags and swells in power distribution networks and lots of problems are engendered for them. Therefore, dif f e rent instruments are pla nn ed to compensate volt a ge swells and sags. Between them dynamic voltage restorer (DVR) has found special import a n c e, because it operates better than others for this purpose and restores voltage to its initial value conveniently. A DVR is a power-electronic controller that can protect sensitive loads from disturbances in the supply system. The DVR is installed in series to the network. In this paper 9 level cascaded inverters with cas ca d ed transfor m e r s are used in DVR internal circuit, but the difference in magnetic flux in cascading transformers has adverse effects on the plan. Therefore, a new switching pattern is used تفاصيل المقالة

Fluorescent lamps are used as one of the most important sources of light in residential and commercial applications. A method to increase the power factor in electronic ballasts is proposed in this paper. For the power factor correction circuit, the amplification-based switching method is used, which increases the power factor and provides the DC voltage for starting the half-bridge inverter circuit. Finally, the laboratory sample of the circuit is made at a voltage of 110 V with a power factor of 0.996. This circuit has an efficiency of 94.7% and a total harmonic distortion less than 5%. In addition, the pressure on the lamp at the moment of commissioning is reduced, which increases the life of the lamp. تفاصيل المقالة

From a steady state point of view, FACTS devices operate by increasing or decreasing voltage, supplying or absorbing reactive power, and controlling the impedance of a series of transmission lines or phase angles. There are two types of power fluctuation damping controllers in power systems: power system stabilization (PSS) and FACTS POD controllers. The planning and operation condition of electrical power systems are changing due to a variety of causes. Flexible ac transmission system (FACTS) controller helps in raising dynamic stability limit and provide better power flow control. Static synchronous series compensator (SSSC) is one of the important members of series FACTS controller, which consists of a solid-state voltage source inverter coupled with a transformer that is connected in series with a transmission line. In this paper is presented the effect of SSSC for damping power system oscillation. The complete digital simulation is performed in the Matlab Simulink environment. . تفاصيل المقالة

The purpose using capacitors in distribution networks is to reduce the total losses of the network. Capacitors help regulate the power factor and voltage in the electrical distribution system, and can be controlled remotely, in and out of the system. Capacitor placement depends on the objective function, which is usually single objective or multi objective. In this paper, the amount of capacitor at minimum load is determined using a genetic algorithm. The calculation is done at peak load to determine the sensitivity of power losses. By using this method, the increase of the voltage caused by the lead phase of the system is prevented in the minimum load. A multi-purpose objective function to simultaneously reduce losses and improve the voltage profile of the optimal capacitor size in each section is detected by a genetic algorithm. To show the efficiency of the method, the capacitor placement results are compared using DIGSIENT software. تفاصيل المقالة

The most crucial approach for power and control system implementation is optimal power flow because it yields the lowest operating costs and maintains the safety margins for the control variables. An essential component of the flexible AC transmission system (FACTS) is the unified power flow controller (UPFC). It is designed to provide multiple types of energy system compensation and can be utilized for controlling the reactive and active electrical power in transmission lines and bus voltages independently and at the same time. Considerable studies have been published in the UPFC engineering applications area using various techniques. Due to its versatile capabilities, UPFC is recognized as one of the most promising FACTS devices for modern power systems. UPFC is used to improve reactive power mismatch control and system stability. A brief review of UPFC applications for increasing power system flexibility and controllability has been conducted and summarized. This paper also discusses the utilization of artificial intelligence in the placement of UPFC in power systems. تفاصيل المقالة