Free-piston linear generators (FPLGs) have attractive application prospects for hybrid electric vehicles (HEVs) owing to their high-efficiency, low-emissions and multi-fuel flexibility. In order to achieve long-term stable operation, the hybrid system design and full-cycle operation strategy are essential factors that should be considered. A 25 kW FPLG consisting of an internal combustion engine (ICE), a linear electric machine (LEM) and a gas spring (GS) is designed. To improve the power density and generating efficiency, the LEM is assembled with two modular flat-type double-sided PM LEM units, which sandwich a common moving-magnet plate supported by a middle keel beam and bilateral slide guide rails to enhance the stiffness of the moving plate. For the convenience of operation processes analysis, the coupling hybrid system is modeled mathematically and a full cycle simulation model is established. Top-level systemic control strategies including the starting, stable operating, fault recovering and stopping strategies are analyzed and discussed. The analysis results validate that the system can run stably and robustly with the proposed full cycle operation strategy. The effective electric output power can reach 26.36 kW with an overall system efficiency of 36.32%.

This paper proposes a decoupling design approach for a free-piston linear generator (FPLG) constituted of three key components, including a combustion chamber, a linear generator and a gas spring serving as rebounding device. The approach is based on the distribution of the system power and efficiency, which provides a theoretical design method from the viewpoint of the overall power and efficiency demands. The energy flow and conversion processes of the FPLG are analyzed, and the power and efficiency demands of the thermal-mechanical and mechanical-electrical energy conversion are confirmed. The energy and efficiency distributions of the expansion and compression strokes within a single stable operation cycle are analyzed and determined. Detailed design methodologies of crucial geometric dimensions and operational parameters of each key component are described. The feasibility of the proposed decoupling design approach is validated through several design examples with different output power.

Power system visualization is a technology combining power science with multi-disciplinary science, which integrates with computer graphics, and geography, ergonomics and other disciplines. Power system visualization provides a vivid way for the engineer to study energy management system in a variety of means. This paper presented a framework of visualization platform in power system, around the supporting platform technology and hierarchical display technology of visualization. By comparison, we make decision on graphics development kit. Two-dimension and three-dimension visualization techniques are demonstrated in this paper. These visualization techniques enrich power system visualization. Hierarchical tree view and multi-theme window display technology are presented for more information. By using this framework of visualization, dispatcher can find problem in time and take appropriate measures. The visualization platform has been applied in the China's smart power grid construction and brings significant social and economic benefits. The visualization platform hugely enhanced dispatch level of power system, and is helpful to transfer traditional dispatching into intelligent dispatching.