Over-Voltage Protection for Pico-Hydro Generation Using PV Microinverters

Innovative, low-cost, environmentally friendly and renewable resource-based solutions are emerging to meet growing global energy demand. Hydroelectric technology is quite old and mature. Despite its importance, it is associated with large plants, with environmental impact. On contrary, small-scale systems, called pico-hydro systems (up to 5 kW) are not yet explored. Anyway, the exploration of pico-hydro systems has been increasing consistently, from the first off-grid applications in remote places to distributed generation, with the injection of the generated energy in the main grid or microgrids. Very recently, there have been advances in grid connection of these small-scale systems, using off-the-shelf components. Indeed, pico-hydro systems can be connected to the grid using off-the-shelf components, namely photovoltaic inverters. Thus, grid-connected pico-hydro systems have gained an enormous potential in distributed production. However, in situations of over-power, or whenever the generator is under no load, there is a need for effective over-voltage protection, unlike photovoltaic systems. The goal of this paper is to propose an over-voltage protection circuit, designed to ensure the integration of low-power pico-hydro systems connected to the grid using conventional photovoltaic microinverters. Extensive tests were performed on an experimental platform using three microinverters easily found on the market and a low power generator (300 W) developed for small wind turbines. The experimental results, demonstrated the performance of the proposed over-voltage protection circuit in four different situations, presented in this work, thus avoiding irreversible damages of generators and microinverters, in the context of the above described grid connection approach.