Dynamic Overvoltage Conditions Experienced at a PV Solar Power Plant

We present the results from an investigation of the cause of dynamic overvoltage conditions experienced at a solar power plant, that resulted from energizing the PV solar plant 34.5 kV collection system feeders using a back-up diesel generator. The diesel generator unit was installed at the solar plant for emergency back-up power to the project, in case of 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 was performed using EMTP software program, to investigate the cause of these dynamic overvoltage conditions at the solar power plant. A detailed transient model of the solar plant and the diesel generator were developed using EMTP. The EMTP simulations were useful in replicating the overvoltage event measurement recordings from the site, and the simulation results from the study, 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. The study evaluated various solution alternatives and mitigation strategies to reduce these dynamic overvoltages to acceptable conditions.