Stability Analysis of Permanent Magnet Generator System With Load Current Compensating Method

This paper proposes a load current compensation method (LCCM) of the PWM-controlled permanent magnet generator (PMG) system to address the stability issue caused by constant power load (CPL) for aircraft electrical power system (EPS). Firstly, the input impedance of the CPL, that is, speed-controlled permanent magnet motor drive system, and the output impedance of PMG system are deduced with small-signal analysis. Based on the Middlebrook impedance criterion, the stability issue caused by the CPL is analyzed, including the influence of voltage loop bandwidth and ratio of resistive load. Then, three different modes of LCCM are analyzed and compared in terms of damping factor, sensitivity to voltage loop bandwidth, system stability and dynamic performance of DC-link voltage. In order to further illustrate the advantages of LCCM, the comparison of intermediate-loop-based LCCM and DC-link voltage compensating method (DCVCM) are also presented in terms of stability and dynamic performance of DC-link voltage. Finally, experimental results with a permanent magnet motor drive system considered as CPL are provided to validate the analysis and demonstrate the effectiveness of the LCCM.

I. Introduction

The development of more electric aircraft(MEA) has brought great changes to the aircraft electrical power system(EPS) and load system. As for EPS, the high voltage direct current (HVDC) system presents several advantages such as high efficiency, reduced weight, and the absence of reactive power compensation devices [1]–[5]. Combined with permanent magnet generator (PMG)-based PWM-controlled rectifier, HVDC EPS will be the most promising configuration for the future MEA applications [6].