1- Introduction

2- Wind Energy System

3- WECS Topologies and Generators

4- Power Converters

5- Conclusions and Recommendations

Reference

Abstract

Sources of renewable energy such as wind energy are indigenous and can help in decreasing the reliance on non-renewable energy sources. After introducing the history of wind energy production in Egypt and worldwide besides its techno-economic importance, this paper presents a comparative review on the wind energy conversion systems (WECS). The horizontal and vertical types of wind turbines with their mathematical dynamic models are discussed. Different types of electrical generators used in WECS in addition to their advantages and disadvantages are illustrated. The various AC-AC converters topologies for WECS are explained with a detailed discussion for their features.

Introduction

Worldwide energy demand is rapidly expanding due to the continuous economic progress and the power electronic technologies development. Conversely, traditional petroleum derivatives, for example, coal, oil and flammable gas, which have been the key energy source since the industrial revolution, are confronting rapid consumption. Therefore, the mission to create inexhaustible and clean sources of energy from wind, solar and hydrogen energy becomes more convenient. Among these numerous sustainable assets, wind energy encourages business prospects in substantial power in favor of its safe and naturally sustainable behavior, zero emission, competitive and inexhaustible nature [1, 2]. In 2018, wind energy provides around 5% of the total energy consumption of the world [3]. It is anticipated that energy from wind will be about (20 % and 35%) of the total world’s energy in (2030 and 2050) respectively [4]. The worldwide wind energy production has reached 690.8 GW in 2018 from around 19057 wind farms and Europe had the first place with 259 GW and 13290 wind farms [6]. Figure 1(a) depicts the global wind power production in the last two decades in 2018[5]. Production of wind power for the top five countries across the world in 2018 is illustrated in Figure 1(b). China has the highest wind production in the world with 123.805 GW [5]. The USA provides the highest wind power in Americas and the second in the world with 98.94 GW [7]. Germany is the highest in Europe and the third in the world with 52.828 GW. Africa has the lower wind energy production in the world continents with 5.7 GW with 87 wind farms as depicted in Figure 1(c) [5]. Wind power in South Africa is the highest in Africa with 2295 MW [5]. Egypt has the third place and produces around 810 MW of wind energy and the potential of this production is expected to reach (1500 MW and 2500 MW) in (2030 and 2050) respectively [5]. The electrical power generation from wind energy in Egypt started in 1997 by 6 MW and increased gradually as shown in Figure 1(d) to reach 810 MW in 2018 [5]. In onshore, the blowing wind from the sea to land is usually less than perfect. In addition to, the tendency of waves increases and short period swell is created [8]. Therefore, there is an increased interest for offshore wind, as the breeze is regularly more grounded and more uniform in surface of ocean than aground and the expected generated power from the planned offshore is 143.36 GW [9]. European nations are the pioneers in offshore wind. For around 20 years, Denmark has been using it to supply power. Offshore wind in the USA and similar nations can possibly turn into a noteworthy energy hotspot for household applications as waterfront wind sources are plenty [10].

Nowadays, the development of power electronics has reached a level that encourages designers to consider the feasibility of DC-distribution power systems in various forms and application fields [1,2]. Some companies offer proven solutions for High Voltage DC (HVDC) transmission systems [3–5]. However, at present few Medium Voltage DC (MVDC) power systems exist and most of them are in a prototyping or experimental stage [6], therefore in this market sector no or very few ready-to-use solutions can be found yet. Nevertheless, both public research centers and R & D units of leading private companies are working in this direction [7–14]. A leading sector for the study and experimentation of MVDC power systems is the marine sector [15], where important investments have been and are being made to develop this technology [16]. At present the Integrated Power System (IPS) [17,18] of largest commercial vessels is characterized by a Medium Voltage AC (MVAC) distribution. A promising solution to improve IPS performance relies on moving from MVAC to MVDC power systems [19,20]. Compared to its MVAC counterpart, MVDC distribution has several advantages [21–24] such as: • no need for phase angle synchronization of power sources, which simplifies connection and disconnection procedures for power generation and storage devices of different type and size; • reducing the size and ratings of on-board switchgear and cables and elimination of bulky low frequency transformers; • improved management of fault currents, system reconfiguration and power flow in transient and emergency conditions; • enhanced efficiency thanks to the elimination of reactive current and to the possibility of variable speed prime mover operation; • removal of frequency constraints from the design and operation of generator sets [25], leading to size and weight reduction for generators and reducing the running cost gap between gas turbines and diesel engines. This can make it more affordable to use gas turbines, which are known to produce much less polluting emissions than diesel engines [26]. Nevertheless, MVDC power systems pose several technical challenges [22–24,27], such as system protection [28] and network stability [29,30], and further development of industrial equipment for MVDC applications is needed in order for the transition to MVDC shipboard power systems to become a significant reality [31]. Actually, the convenience to use a MVDC distribution depends on the availability of three key components: reliable and efficient power sources, high power DC/DC converters with acceptable cost and efficiency to be employed as Solid State Transformers (SST) [32] (namely power converter systems serving the same purpose as power transformer in AC grids, i.e. to adapt voltage levels and ensure galvanic isolation) and protection systems against short circuits, which are much more critical than in AC systems mainly because it is not possible to take advantage of zero crossings for current interruption [33].

nverter-interfaced distributed generator (DG) is the basic building block of the rising microgrid paradigm [1]. Various types of DG such as photovoltaic, wind turbine and fuel cell are interfaced to the microgrid through power electronic converters/ inverters [2]. The inverter-interfaced DGs are flexible and have fast response speed. Such advantages make DGs easier to operate and control than conventional synchronous generators (SGs) [3]. However, controlling microgrids consisted of such DGs are challenging due to the negligible inertia, intermittent generations, together with severe load changes. If the challenges are not handled properly, the advantages and potentials of the inverter-interfaced microgrid cannot be fully unlocked. Since microgrid is one of the key components for the future smart grid, its performance somehow determines whether the successful deployment of smart grid can be achieved. Thus, operation and control of microgrids have been a hot research area over the last decade. There are significant differences between traditional large-scale power systems and inverter-interfaced microgrids [4]. Traditional control solutions, which have been proven to be effective for large-scale power systems, cannot be introduced to microgrids without modifications [4]. The first and the easiest type of solutions is to increase the “virtual” inertia of the inverter-interfaced microgrids so that microgrids can behave similarly to the traditional power systems [5]. However, these solutions cannot fully unleash the potential of microgrids in terms of flexibility and response speed. The second category of solutions is to model such microgrids as fully decoupled subsystems with impacts of neighboring subsystems formulated as measurable disturbances. At primary control level, droop and inner cascaded loops of proportional-integral (PI) controls are deployed to track the control references regulated by the upper secondary control level. Since microgrids are modeled similar to that of unmanned vehicle systems that have no physical connections among subsystems, many existing solutions in cooperative control [6-7], optimal control [8-9] and game theory [10-11] can be introduced. In the past years, there are many successful developments along this route. These works definitely promote researches on microgrid controls and help bridge the gaps among related societies, especially controls, power systems, and power electronics [5-11]. However, there are still many open problems that deserve further investigation.

این مقاله یک استراتژی کنترلی مطلوب را برای ارسال نیروی سیستم دیزلی-باتری- گرید گره خورده با فتوولتائیک (PV)، به نیرو یا برق هیترهای گرمایشی پمپ ابی (HPWH) را توسعه داده است. این سیستم شامل مدول های PV، گرید ، باتری، HPWH، ژنراتور دیزلی (DG) و دیگر لوازم خانگی یا معمول است. PV می تواند بطور همزمان نیروی بیش از حد تغزیه ای را به گرید بدهد و بار را ارائه دهد. باتری به عنوان منبع ذخیره سازی ارزان و بصرفه انرژی اوج گرید بسته به تعرفه زمان مصرف برق (TOU) مورد استفاده قرار می گیرد درحالیکه DG منبع نیروی پشتیبان است. تابع هدف مدل، به حداقل رساندن هزینه انرژی و سوخت است درحالیکه مبادله انرژی PV را به حداکثر برساند. TOU یک پارامتر کنترلی مهم در مدل است. جریان نیرو از هر منبع، متغیرهای کنترلی هستند. کنترل مطلوب، پتانسیل زیادی را برای تحقق ساخت انرژی خالص صفر عملی و همچنین تقاضا به سمت مدیریت را نشان می دهد زیرا مدل با محدودیت های فنی و عملیاتی روبرو است. مطالعه موردی براساس نصب 3x16kW HPWH در هتل Pretoria در افریقای جنوبی انجام شده است. شبیه سازی در طول سالها روی داده های فصلی انتخابی با استفاده از تقاضای واقعی اندازه گیری HPWH اجرا شده است. مسئله کنترل مطلوب، با استفاده از برنامه غیرخطی عددصحیح مختلط حل شده است و نتایج، نشان دادند که چگونه TOU، صرفه جویی که در این مقاله ارائه شده است را تحت تاثیر قرار می دهد.