Stability Analysis of Hydraulic-PV Hybrid Micro-grid Based on Small-signal Dynamic Model

The stability of traditional PV micro-grid based on parallel inverters with power droop controllers are well established. However, paralleling PV inverter which have droop controllers with local hydraulic turbine are widely used in some remote rural area. The non-minimum phase system of hydraulic turbine and the distinction of inertance between hydraulic turbine and inverter have great influence to system stability, so the stability of Hydraulic-PV hybrid micro-grid should be investigated. This paper establishes the small-signal model of hybrid micro-grid systematically and analysis the stability of hybrid power system which contains voltage source inverters, hydraulic turbine with non-elastic water column and governor. A sensitivity analysis based on eigenvalues and root locus is also presented which helps identifying the origin of each of the modes and identifies possible feedback signals for design of controllers to improve the system stability. These theoretical findings are eventually verified through simulation and experimental on laboratory prototypes.