فایل ورد کامل سیستم های برق فرکانس ثابت هواپیما با کاهش هارمونیک

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تعداد صفحات این فایل: ۲۵ صفحه

هر دو سیستم برق هواپیما معمولی و پیشرفته با توجه به بارهای AC و DC غیر فعال معادل تحت شرایط عملیاتی گذرا و ماندگار برای تمام انواع بارها شبیه سازی و تجزیه و تحلیل شده است. فیلترهای AC منفعل برای کاهش هارمونیک و به حداقل رساندن ولتاژ گذرا در هر دو سیستم برق هواپیماهای پیشرفته و معمولی ارائه شده است. THD برای جریان و ولتاژ برای هر دو هواپیما های معمولی و پیشرفته EPS محاسبه شده و می توان آن را یافت که محتویات هارمونیکی برای سیستم برق هواپیما پیشرفته بسیار پایین تراست.
سیستم های الکتریکی هواپیما پیشرفته بیشتر قابل اعتماد، کارآمد و سیستم ذخیره کننده انرژی می باشند. در سیستم برق هواپیمای معمولی، یک فیلتر هارمونیک مورد نیاز است، در حالی که برای سیستم الکتریکی هواپیماهای پیشرفته، دو فیلتر (در ژنراتور و باس بار AC) مورد نیاز است. برای هر دو سیستم هواپیما زمان صرف شده برای رسیدن به حالت پایدار است تقریبا یکسان برای هر دو هواپیما های معمولی و پیشرفته EPS می باشدو آن را در محدوده استانداردهای هواپیما می یاشد. فیلترها برای جلوگیری ازایجاد زرونانس در هر دو سیستم برق هواپیما معمولی و پیشرفته طراحی شده اند.

عنوان انگلیسی:Constant Frequency Aircraft Electric Power Systems with Harmonic Reduction~~en~~

INTRODUCTION Any conventional aircraft utilizes a combination of hydraulic, electric, pneumatic and mechanical power transfer systems. Increasing use of electric power is seen as the direction of technological opportunity for advanced aircraft power systems based on rapidly evolving technology advancements in power electronics, fault-tolerant electrical power distribution systems and electric-driven primary flight control actuator systems [1]. It is found in [2] that the advanced aircraft electrical power systems are more energyefficient as well as more reliable than their conventional counterparts, as losses in electrical cabling are lower than those in hydraulic or pneumatic piping. The electric systems in advanced aircraft can be designed to provide the right function at the right time. The central hydraulic lines are kept energized during the entire flight. However, the landing gear and secondary flight control require power for only a short time. Electrical systems can be switched on and off as needed, thus conserving power. The coupling between converters performance and filter values complicates the analysis and design problem, which is further compounded by the use of high frequency power supply system. In this paper the conventional and advanced aircraft electric power systems are analyzed and simulated under transient and steady state conditions. A motor-generator set is controlled to provide the aircraft power source which has a constant frequency and voltage magnitude during all loading cases. The harmonic contents are calculated and harmonic mitigation passive filters are designed to meet the respective standards for the voltage and current waveforms on the AC side of the main aircraft power supply. The DC bus voltage is obtained and regulated from a controlled 12-pulse converter to meet the standards concerning the magnitude of the DC voltage and its ripple contents. II. CONVENTIONAL AIRCRAFT SYSTEM Conventional aircraft electric power system (EPS) often consists of two or more engine driven generators to supply the AC loads throughout the aircraft. While the engine driven generators are singly connected to the distribution buses in some civil configurations (i.e. each generator is responsible for a specific numbers of buses), all American and European air forces use the parallel connection configuration. All aircraft needs AC and DC power altogether. This DC power comes from rectification of the AC power using the transformer rectifier units (TRUs). These units are normally 12 pulse configuration [3]. Due to its cyclic operation of these units, it is considered as the harmonic source in the aircraft EPS. These units can increase the voltage distortion and the harmonic contents into the AC side of the aircraft EPS. Increasing harmonics may lead to malfunction of most of the sensitive instruments and circuits inside the aircraft. A typical civil transport aircraft electrical power system is shown in Fig. 1. This is a simplified representation of the Boeing 767 aircraft EPS without including the external power system [4, 5]. The primary AC system comprises identical left and right channels. Each channel has an Integrated Drive Generator (IDG) driven from its respective engine. Each AC generator is rated at 200V-AC, 400Hz, 90kVA and is controlled by its own generator control unit. Bus tie breakers are used to tie both buses together in the event that either generating source is lost. The bus tie breakers can also operate in conjunction with the external power contactor or the auxiliary power breaker to supply both main AC buses. The 90kVA auxiliary power unit can feed the groundhandling and ground-servicing buses. It can also be used as a primary power source on flight on certain aircraft in the event that either left or right generator is lost. Each of the main AC buses feeds utility loads, galley loads, and power conversion equipments. Some loads in aircraft needs DC power generated by using TRUs. In case of either main AC bus or TRU failure, a DC bus tie contactor closes to tie the left and right DC buses together. The main AC buses feed the aircraft galleys which is a major electrical load. That load needs 28V-DC in addition to 115V-AC and may reach a total load of 32 kVA [6, 7]. Both AC buses feed 26V-AC buses via autotransformer to feed certain loads. Other specific feed from the left main bus is a switched feed to the AC-standby (AC-STBY) bus. The battery can feed the essential electrical loads and the main AC buses through inverter (INV) in case of all generators failure. The utility or services loads are distributed throughout the aircraft and may be broadly subdivided into the following: motors and actuation, lighting services, heating services, subsystem controllers and avionics systems. Motors (AC and DC) in an aircraft are used for linear and rotary actuation, control valve operation, engine starting, and cooling fans. Lighting systems in aircraft can be divided into external lighting (navigation, strobe, landing, taxi, inspection, logo lights) and internal lighting (cockpit/flight-deck, passenger information, emergency, bay and evacuation lighting). Lighting may be powered by 28V-DC or 26V-AC provided by auto-transformer from the main AC buses, Fig. 1. The use of electrical power for heating purposes on aircraft can be extensive.

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