Combined Primary Frequency and Virtual Inertia Response Control Scheme of Variable-Speed Dish-Stirling System

The potential of variable-speed dish-Stirling (VSDS) solar-thermal generating plant in providing grid frequency support is investigated. In the proposed VSDS frequency support control scheme, the reference speed of the Stirling engine is regulated to track a deloaded power curve which is governed by the solar insolation level. The gain of a supplementary speed-frequency droop controller is then set to meet the primary frequency control requirement. Further uniqueness of the VSDS control scheme pertains to the provision of virtual inertia response by regulating the kinetic energy in the rotating mass of the engine-generator and the thermal energy in the heat absorber/receivers. Small-signal analysis shows that the frequency support scheme is inherently stable, and it will provide higher degree of damping as the penetration level of the VSDS system and/or the solar insolation level increase. The efficacy of the proposed scheme is validated by computer simulation

An average-value model of kinematic Stirling engine for the study of variable-speed operations of dish-stirling solar-thermal generating system

A simplified model of the Stirling engine is developed for the study of grid-connected variable-speed operations of dish-Stirling (DS) solar-thermal power plant. The model relates the average values of the engine state variables and also takes into account engine losses, the variations of heater temperature and total mass of the working gas in the engine cylinder. The improved model is compared with the existing models and the new model is shown to be more suitable for grid-related studies and control system design. © 2014 IEEE