Fuzzy Logic Control of Modern Aircraft Electrical Power System during Transient and Steady-State Operating Conditions Reyad Abdel-Fadil, Ahmad Eid Electrical Engineering Department Aswan University Aswan, Egypt ahmadeid@ieee.org Mazen Abdel-Salam Electrical Engineering Department Assiut University Assiut, Egypt Mazen2000as@yahoo.com Abstract— In this paper, a modern civil Aircraft Electrical Power System (AEPS) is modeled, analyzed and controlled using Fuzzy Logic Control (FLC) technique. The FLC control provides a certain behavior for the AEPS during load switching to meet the military standards of the aircraft. FLC control technique used for Generator Control Unit (GCU), AC-DC Controlled rectifier, AC-AC inverter and DC-DC Converter. With this control, the voltage at the main buses (variable frequency bus – 270VDC bus – 28VDC bus-constant frequency bus) lies within standard limits at transient and steady state conditions. At the other hand, the generator frequency lies within standard limits for all the frequency operating range of 400-800Hz. The AEPS is tested using a simulation model in PSIM and the obtained results verify that the FLC is an efficient control technique for the variable frequency aircraft systems. Keywords— fuzzy logic control; modern aircraft; military standards; variable frequency; MEA I. INTRODUCTION The conventional aircraft utilizes a combination of hydraulic, electrical, pneumatic and mechanical power transfer systems. Increasing use of electrical 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 electrical driven primary flight control actuator systems [1]. The concept of More Electrical Aircraft (MEA) implies increasing use of electrical power to drive aircraft subsystems that in the conventional aircraft, have been driven by a combination of mechanical, hydraulic and pneumatic systems. The objective of the MEA is to completely or partially replace the non-electrical power in the aircraft with electricity. This idea was first applied to meet the military for less overall weight of the aircraft, lower maintenance costs, higher reliability and better performance with increasing capacity and rating of the civil aircrafts [2]. The MEA concept is seen as the direction of aircraft power system technology in the future. The aircraft power system will employ multi-voltage level hybrid DC and AC systems. Thus, MEA electrical distribution systems are mainly in the form of multi-converter power systems. The electrical modern aircraft consists of four types of voltages; 400/200VAC(variable frequency), 28VDC and 270VDC [3]. The MEA is anticipated to achieve numerous advantages [4] such as optimizing the aircraft performance and decreasing the operation and maintenance costs. Moreover, MEA reduces the emissions of air pollutant gases from aircrafts, which can contribute in significantly solving some of the problems of climate change. However, the MEA puts some challenges on the aircraft electrical system, both in the amount of the required power, the processing and management of this power. In this paper, modeling, performance and control of an MEA electrical power distribution system is investigated. The MEA aircraft consists of multiple DC and AC buses at variable frequencies to accommodate with variable load types inside the aircraft. Fuzzy-logic-based control of all converters inside the aircraft system is applied. Fuzzy logic control (FLC) provides outstanding advantages over the conventional controllers (PID) such as easiness to develop, cover a wider range of operating conditions, and more readily customizable in natural language terms. The obtained results verify that the FLC is superior compared to conventional control for the modern aircraft electrical power system. Voltages at different buses as well as frequencies meet the aircraft standards [5] during both transient and steady state operating conditions. II. MODERN AIRCRAFT ELECTRICAL POWER SYSTEM The MEA electrical generation and conversion efficiencies are significantly higher than earlier non-MEA aircrafts. The improvement in efficiency is primarily due to the use of a variable frequency (VF) generator and advances in power electronics that allow much higher power conversion efficiencies. For instance, comparing the B787 to the B777, the efficiency measured at the AC output of the generator is 53% compared to 34% and at the ±270 VDC bus the efficiency is 51% compared to 25% [6], respectively. These low values of the efficiencies are due to the low efficiency of the mechanical engine. The Boeing 787 has an engine-mounted generator that produces a variable frequency 230 VAC output voltage. About 30% of the generated power is used directly (variable- frequency loads). The rest of the generated power is divided between the ±270 VDC bus loads using an autotransformer rectifier unit (ATRU) with an efficiency of 97%, the loads 2014 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES) 978-1-4799-6373-7/14/$31.00 ©2014 IEEE