Design and integration of the battery energy storage system in more electric aircraft

• Main Author: Tariq, Mohd
• Other Authors: Ali Iftekhar Maswood
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2019
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Electric power
• Online Access: https://hdl.handle.net/10356/106430; http://hdl.handle.net/10220/47960
• Institution: Nanyang Technological University

In this thesis a detailed study on the battery technologies used in aircrafts in the last five decades is done. A general background of the battery system is studied and the performance of the batteries based on energy densities and low temperature capabilities is evaluated for the deployment in the more electric aircraft (MEA). Evolution of MEA with its power system architecture and load profile is analysed to understand the requirements of the battery system. The electrical load profile of the MEA “Aircraft X” is designed and modeled. Different types of electrical loads such as primary/conventional loads, the environmental control system (ECS) load, anti-icing (wing ice protection) loads, various electrical actuators (aileron, spoilers, rudder) loads and signal communication (RADAR etc.) loads are designed and modeled. Furthermore, starting profile of engine starter generator (ESG), transient stability profile of military standard (MIL-STD-704F) and emergency load profile of the MEA “Aircraft X” are also studied and analysed. Thus, all these electrical loads are combined and an algorithm is successfully obtained to separate the constant and transient loads. An effective battery system is designed for supplying the transient loads by considering the weight saving and cost analysis factors between Li-ion and Ni-Cd batteries. Based on the analysis, Li-ion battery with Lithium ferrous phosphate (LFP) chemistry is designed and proposed for the MEA “Aircraft X”. The designed LFP based battery system is also modeled using the modified shepherd equation wherein the voltage polarization term is added to have a lower complexity and more proximity with the battery model block in MATLAB®. After the design and modeling of the proposed Li-ion battery system, the battery charger (phase shifted high power bidirectional dc-dc “PSHPBD” converter) is designed and modeled. The design of the components of PSHPBD converter is done keeping in view the requirement of maximum power transfer in the MEA environment. Zero voltage switching (ZVS) operation in wide range is also considered for design of the PSHPBD converter for MEA operating parameters. The PSHPBD converter is modeled using the Fourier series based harmonic analysis wherein an optimal harmonic number (h=7) is chosen by considering the proximity and complexity between the modeled converter and switch model. The battery energy storage system “BESS” (consisting of the battery system and the PSHPBD converter) is successfully integrated with the power distribution 270V dc bus architecture of the MEA and tested under different dynamic conditions using three different control techniques. Firstly, a direct estimation based technique is proposed for determining the phase shift of the PSHPBD converter (used as a charger for the batteries). Secondly, a current mode control for the single phase shift control technique for the PSHPBD converter is proposed. The proposed control technique has an inherent capability of current limit. Thirdly, a peak current controller is proposed which provides a limit on the peak current and provides a fast transient response. The advantages of using the proposed peak current control in avoiding the saturation of the transformer core is also reported in the work. In integration, finally the study and analysis of zero current switching (ZCS) inverter for integration of BESS to ESG set in MEA “Aircraft X” is discussed. Furthermore, a control method which can improve the life of the BESS in MEA is discussed in which three different modes of control based on the load estimation are given. Depending upon the load on the BESS, the corresponding control structure is implemented/activated leading to reduction in RMS current flow in the charger circuit and average current flow in the battery system thereby reducing the losses and temperature rise in the BESS, which eventually leads to an increase in the life of the BESS. Finally, a multi-functional battery charger (MFBC) is proposed for integration of BESS to the power distribution network in MEA. A novel control method is devised for suitable transfer and sharing of power between different buses. Based on the placement and applicability of the MFBC, many new dc power distribution architectures for MEA are proposed wherein energy storage system can be integrated into aircraft network leading towards fault tolerant operation and weight optimization in the MEA.