Development Of A6kVA Three-Phase Aeronautical Static Inverter

Aeronautical static inverter (ASI) is one kind of the secondary power supplies onaircraft, and it converts the electrical energy from the main power supply to a115V,400Hz AC voltage to feed the electronic equipment on the aircraft. Three-phase combined ASIhas strong ability to power unbalanced three-phase load and can realize modularization, andit is a good approach for achieving high efficiency, high power density and high reliability.This thesis is dedicated to the development of a6kVA three-phase ASI.The output LC filter of the inverter exhibits a resonant peak, which leads tomagnification of the harmonics near the resonance frequency and even instability of theinverter. Inserting a resistor in parallel or series with the filter inductor or filter capacitor iseffective to damp the resonance oscillation. With respect to side effect on the conversiongain, a resistor in series with the inductor and a resistor in parallel with the capacitor aremore competitive than the other two passive damping solutions. However, the additionalloss of the damping resistor will decrease the efficiency of the inverter. To overcome thisdisadvantage, active damping solution is preferred. Through some equivalenttransformation of the block diagram, it is proved that the active damping by feedbackingthe inductor-current has the same damping ability as the resistor in series with the inductor,and the active damping by feedbacking the capacitor-current has the same damping abilityas the resistor in parallel with the capacitor. Compared with the active damping byfeedbacking the inductor-current, the active damping by feedbacking the capacitor currenthas a lower steady-state error.Calculation delay and zero-order hold are the unique characteristics of digitalcontrolled system, this thesis explains the causes, and builds the discrete-time model of theinverter. Based on the requirements of steady-state error and stability, the satisfactoryregion of the controller parameters is derived, and then the parameters of the PI regulatorand the feedback coefficient of the capacitor current are chosen. Considering the fluctuationof the input voltage, and the variety of the inductance or capacitance, the adaptation of theselected parameters is verified. It is proved that the close-loop system is robust.A6kVA prototype is built and tested in the laboratory. The design of hardware andsoftware is presented in this thesis in detail. The experimental results are well in accordance with the target.