A solar thermal power plant presents an environmentally friendly process for producing power. However, due to diurnal and seasonal variations in the availability of solar radiation, as well as uncertainty caused by factors such as cloud cover, efficient operation of a solar thermal power plant is a challenging task. Availability of a dynamic model which represents the process behavior in face of these inevitable variations is a prerequisite for efficiently operating the plant. In this work, we develop a dynamic model for a hybrid solar thermal power plant operating in India. The plant uses two different technologies for solar power collection, namely, a Parabolic Trough Collector (PTC) for heating oil and a Linear Fresnel Reflector (LFR) for generating direct steam. Superheated steam, generated using heat exchangers, drives the turbine generator block to generate electricity. The dynamic model is based on first-principles models of various components in the plant, such as PTC, LFR, heat exchangers, and storage tanks, and captures the integrated nature of plant. The model also incorporates heat losses to quantify night time cooling. A preliminary validation of the developed plant model is also presented using routine field data. The model is then used to simulate the dynamic operation of the plant for two case studies: (i) a two day simulation with field solar insolation profiles corresponding to summer days and (ii) a single day case study with cloud cover. The performances of the PTC and LFR fields as well as the overall plant were quantified and compared using various metrics. The case studies involved cold and warm startup scenarios and highlighted the impact of these initial conditions on the plant performance. The proposed dynamic model can be used for designing optimal operation and advanced control strategies.