Present-day small hydropower plants (SHPs) have a large development potential because of the increasing interest in renewable resources and distributed energy generation; however, the variable hydrological conditions that are found in run-of-the-river projects require operations over a wide range of water flow and head variations. Special control methods and system topologies are needed to maintain the high efficiency of energy conversion systems.This paper presents a complete SHP solution based on an innovative generation unit (hydro-set): a propeller turbine is integrated with a permanent magnet synchronous generator working at a variable speed in a grid-connected system that utilises an ac/dc/ac converter. The main elements of this energy conversion system are described. A dedicated control strategy is proposed and verified. All of the results presented here originate from an actual 150-kW SHP that contains two innovative hydro-sets working in parallel on the same river.

This article focuses on modeling of an Axial Flux Permanent Magnet Generator (AFPMG). The authors analyzed selected variants of disk generators, including coreless stator constructions and with iron core ones, also taking into account the Permanent Magnet (PM) arrangement in order to show the way to obtain the optimal machine characteristics based on analytical equations. In addition to the full model, which takes into account the higher harmonics of the magnetic field distribution, the paper presents a simplified mathematical model developed for generator operation cases such as standalone, connected to a 3-phase power grid and loaded with a diode rectifier. The analytical and finite-element method (FEM) calculations were performed as well as laboratory tests to confirm the correctness of presented model assumptions.

Obtaining energy from renewable resources is a worldwide trend in the age of increasing energy demand. Hydropower has some potential in this field, especially for low-power locations. However, construction of such facilities requires high expenses, which is why some attempts at lowering the costs have been made, i.e., by proposing alternative solutions to the classic ones. This paper proposes a selection of options for small hydropower plants (SHP) that lower the investment costs while keeping up profitable operations. The proposed solutions concern simplifying the turbine’s and generator’s integration by installing them in dedicated prefabricated concrete modules. A rare but simple and cheap semi-Kaplan type of turbine with a non-classical spiral inflow is proposed. The turbine operates a permanent magnet (PM)-excited generator, converting the energy at a variable rotational speed. Thanks to this approach, it is possible to simplify the regulation system and eliminate expensive mechanical transmission. However, on the power grid side, a power electronic converter (PEC) must be coupled with the generator. The advantage of this solution compared to the classical ones is that the reliability of power electronics is much higher than that of mechanical systems. This paper presents modeling research on semi-Kaplan turbines’ series development, and a dedicated PM generator is presented as an example of a complete hydro unit with 50 kW power.

This paper presents a model of 3-phase axial flux coreless generator with permanent magnets located on the rotor. Such design solutions are often carried out amateurishly and used in small domestic wind power plants. The premise priority of creating a mathematical model of the generator, presented in this article, was simplicity and reference to the classic solutions of electric machines. The interaction of higher harmonics of flux density distribution on the Electromotive Force (EMF) shape is considered. The analytical relationships of mathematical model are verified on the base of the laboratory tests.

Small hydropower plants (SHPs) can significantly exploit the unutilised hydropower potential in Europe. In particular, this applies to run-of-the-river power plants with low heads. Variable speed technology, high-efficiency, and low-speed synchronous generators with permanent magnets (PMSGs) can significantly improve the efficiency of such SHPs. Unfortunately, the cost of design and implementation of PMSGs for a specific SHP remains significantly high compared to a classic induction generator. This study proposes to reduce the cost of PMSG production by applying a new idea of modular construction of the generator. The proposed solution assumes the possibility of using a universal segment to implement generators of different power (through parallel connection) and rotational speed (by reconfiguring the stator winding). The generator parameters are determined on the basis of an analysis of Poland's hydropower potential and matched to the hydro set with a discharge of 1 to 10 m3/s and heads of 1.5 to 3.5 m. A full-size prototype of a 120 kW three-segment generator is developed. Prototype tests for various configurations of segment windings confirmed that the idea of a modular generator is possible for industrial implementation. However, further optimization work related to improving the efficiency, symmetry, and repeatability of segments is recommended.