Micro-hydro power has a large potential in the renewable energy context. Variable speed technique is preferable to improve the hydraulic power profitability and optimise the hydraulic transient process. First, a review of hydraulic modelling approaches is addressed. In particular, an improved hydraulic modelling approach based on the `Hill charts' measurements is presented. Furthermore, representative power topologies employed to variable speed micro-hydro power generation systems are reviewed. A direct drive permanent magnet synchronous generator topology is implemented in this paper. Experiments are provided to verify effectiveness of the hydraulic model built and its control algorithms. Conclusions are indicated in the end.