DC-link capacitor second carrier band switching harmonic current reduction in two-level back-to-back converters

This paper proposes an active switching harmonic current reduction method within the DC-link capacitor of two-level, three-phase, back-to-back converters. The method is based on the derived analytical solution for switching harmonic currents in the DC-link. It is shown that by controlling the PWM carrier waveform’s phase angles, the harmonics in the 2nd carrier band of the rectifier and the inverter can be synchronized such that cancellation occurs in the DC-link capacitor. This synchronization is provided by harmonic phase feedback control. The feasibility of the proposed approach has been verified experimentally and results are presented in the pape

Stability assessment of a high speed permanent magnet machine based aircraft electrical power system

Starting an aircraft engine with an electrical machine has been one of the major trends for future aircraft. This paper studies the stability of a permanent-magnet machine (PMM) based aircraft starter/generator (S/G) system. Using control-to-output transfer functions, the stability analysis of this S/G system is thoroughly studied. The impact of the key parameters including the control parameters is analysed. Simulation and experimental results support the analytical result

Active DC-link capacitor harmonic current reduction in two-level back-to-back converter

The paper proposes a method of active switching harmonics current reduction in the DC-link capacitor of a two-level, three-phase, back-to-back converter. Based on the derived analytical solution for switching harmonic currents in the DC-link, it is shown that by specific control over the PWM carriers’ phase angles, the targeted harmonics of the rectifier and the inverter can be synchronized in phase such that their cancellation occurs in the DC-link capacitor. This synchronization is provided by harmonic phase feedback control. The three step procedure to implement the method is detailed in the paper. The effectiveness of the proposed approach is verified experimentally

Modeling and impedance analysis of a single DC bus-based multiple-source multiple-load electrical power system

The impedance based stability assessment method has been widely used to assess the stability of interconnected systems in different application areas. This paper deals with the source/load impedance analysis of the droop-controlled multiple sources multiple loads system which is a promising candidate in the future more-electric aircraft (MEA). This paper develops a mathematical model of the PMSG-based variable frequency generation system, derives the output impedance of the source subsystem including converter dynamics and shows the effect of parameters variation on source impedance and load impedance. A dynamic droop controller is proposed to provide the active damping to the system. In addition, the impedance analysis is extended to a generalized single bus-based multiple sources multiple loads system in which power losses are also investigated. The aforementioned analytical result is confirmed by experimental results

Stability Analysis and Control Design for Hybrid AC-DC More-Electric Aircraft Power Systems

This thesis studies the stability of a more-electric aircraft (MEA) power system with hybrid converters and loads, and proposes a control design method using state feedback. The MEA is aimed to replace the conventional nonelectric power in aircraft with electric power in order to reduce the size and weight of the aircraft power system. This thesis considers a model of the MEA power system consisting of the following components: converters with uncontrolled diodes and controlled rectifiers, ideal constant power loads (CPL), and non-ideal CPL driven by electromechanical actuators. The system has narrow stability range under the conventional two-loop PI control. To improve control performance, a full-state feedback control method is developed that can significantly increase the stability margin of the MEA power system

Current-Fed Isolated DC/DC Converter for Future Aerospace Microgrids

High-performance power conversion equipment is currently gaining an increasing interest for aircraft applications. In particular, isolated bidirectional dc/dc converters are often proposed for modern aircraft distribution systems. A current-fed isolated dc/dc converter, named active-clamp active-bridge topology, is identified as the most promising for the proposed application, interfacing a 270-V dc network with a 28-V dc network. A comparison between the selected topology and the well-known dual-active-bridge topology has been carried out and an experimental prototype has been manufactured for the selected conversion architecture. Simulation and experimental results are provided in order to validate the tradeoff and the design of the proposed converter