The impact that power plants employing renewable energy sources have on power systems is no longer negligible due to the ever-increasing portion of the power share that these generation systems represent. Therefore, the static and dynamic effects of these power plants on the grid must be analyzed in at least the same degree of detail as conventional generating units. For this purpose, it is necessary to develop models that are accurate and able to capture the dynamics of interest for the analysis, but also taking into account that they should be manageable and have a good computational performance. In the case of power plants based on photovoltaic (PV) or wind energy, formed by many power converters, an equivalent plant model that reduces the number of devices offers a good tradeoff between accuracy and complexity. Motivated by the analysis of an actual 100 MW PV power plant formed by 100 converters, each of them governed by a synchronous power controller, this paper presents a general method to derive a dynamic equivalent model of a group of converters that use this type of controller. The method is applied to this power plant in order to obtain several equivalent models with different degrees of detail that are compared through simulation. The results prove the accuracy of the equivalent aggregated models under different conditions and allow measuring the reduction in computation time that they achieve.