Stability Study of DC Electric Power System with Paralleled Generators for More-Electric Aircraft 2014-01-2114
Many More-Electric Aircraft (MEA) Electric Power System (EPS) architecture paradigms are being studied in order to provide the on-board electrical loads with high-quality supply and to ensure safe operation. EPS with dc distribution appears to be more promising due to higher efficiency, higher reliability, easier integration and lower overall weight. Another advantage of dc systems is the ease of sources paralleling, together with the optimization of load power sharing, this can lead to further EPS weight reduction. The DC bus can be fed by multiple sources such as generators, batteries and other energy storage devices.
Many loads in MEA EPS are tightly controlled by power electronic converters and often behave as constant power loads (CPL). These are known as main contributors to the degradation of EPS stability margins. Therefore, stability study is one of the key topics in the assessment of potential EPS architecture candidates.
This study deals with stability study of an example EPS consisting of two permanent-magnet starter-generators feeding a mixed load. The generators are controlled in flux-weakening mode and they feed the main dc bus with currents according to the droop characteristics. The mathematical model of such EPS is developed and used for detailed stability study. The system eigenvalues contours are investigated with the variation of the key system parameters including bandwidth of main control loops, length of the cables, load power level and others. The achieved analytical results are verified by the time-domain simulations.