Dynamic Overvoltage Conditions Experienced at a Solar Power Plant

This paper presents a case study occurring at a 208 MW solar photovoltaic (PV) power plant. The site suffered damages from dynamic overvoltage conditions during the energization of the 34.5 kV collection system from a diesel generator. The diesel generator unit was installed for emergency back-up power to the project, in case of a 230 kV power outage from the connecting transmission utility system. The back-up power source was provided to allow the operation of the solar power tracking system during emergency conditions. A subsequent study of the failures was done using a detailed ElectroMagnetic Transient (EMT) software transient model of the solar plant and the diesel generator. The simulation results concluded that the diesel generator did not have sufficient capability to pick up capacitive loads and therefore, the unit was unable to control the overvoltage conditions which led to the overvoltage event that caused equipment damage to the PV inverters and their auxiliary systems. Several mitigation strategies and issues related to the back-up diesel generator operation were investigated.