Commissioning and Operational Control of Photovoltaic Power Plants through Online Simulation

Abstract

Photovoltaic system simulation tools are mostly used for the planning and yield prediction of power plants.During the commissioning procedure and especially during the operation of a photovoltaic power plant simple algorithms are used to convert the measured power under varying irradiance conditions to standard test conditions. Faults are only detected, if there is a significant deviation between the photovoltaic system power or daily production and the estimated production based on measured irradiance levels. In large PV power plants this can result in high economic losses, which could be reduced if the monitoring mechanisms were supported by precise modelling of the photovoltaic generator.In this work, an integrated monitoring and simulation method was developed and tested for very precise online simulation of photovoltaic power plants. The method is based on detailed one or two diode current-voltage curve modelling of the photovoltaic generator. Depending on the technology, between six (crystalline) and ten (thin films) modelling parameters for the IV curve are required. The parameters are either derived from the data sheet information of the PV modules or more precisely from measured IV curves of the modules at difference irradiance levels.Using simulated IV curves, an MPP tracking algorithm and voltage dependent inverter models, a simulation accuracy of 2% is reached, so that any problems with the PV generator can reliably be detected. Using internet based communication technology for the data exchange, the online simulation can be carried out directly on the site of the photovoltaic power plant or from any remote location. Remote simulation offers the advantage to the PV plant operator, that it can also be done as a simulation service and that the software environment does not need to be purchased.To demonstrate the method, online simulation of several grid connected PV generators up to the MW power range is carried out during the commissioning and operation of photovoltaic plants. A powerful visualisation within the same software environment includes both the monitored and the simulated online data sets, so that a very efficient fault detection scheme is available. The method is excellently suited to provide automatic and real time fault detection and significantly improve the commissioning procedure for photovoltaic plants of all sizes.