Full state feedback control of steam temperature in a once-through direct steam generation receiver powered by a paraboloidal dish

DSG plants in a once-through configuration convert water into superheated steam suitable for a steam turbine, with a single pass of the fluid through the receiver. The control problem is to manipulate the feed-water mass flow to maintain a desired steam condition (e.g. temperature) under variable solar radiation. This paper presents a full state linear feedback controller for the steam temperature for a once-through direct steam generation system, featuring a 500 m² paraboloidal dish concentrator and a mono-tube cavity receiver at the Australian National University. The controller manipulates the feed-water mass flow at the receiver inlet to maintain a predetermined specific enthalpy at the receiver outlet, compensating for variations in direct normal irradiation (DNI) and other ambient conditions. The linear controller features three separate regulation mechanisms: a feedforward law to anticipate changes in DNI; a full state feedback loop that uses a state observer for the receiver and an additional output feedback integrator loop for robustness. Experimental results show that the linear controller can successfully control the temperature of the SG4 receiver, provided that it is adequately tuned.