Enhancing PV-inverters for the new medium voltage grid codes - lessons learned from testing central PV-inverters >100kW

With the fast increasing amount of photovoltaic power generation, the impact of PV power plants on the power quality and the stability of the electricity networks increases. In order to ensure stable and reliable grid operation, network operators release new grid codes. In Germany the new BDEW medium-voltage grid codes were released in 2008. PV power plants that feed into the medium-voltage grid are now faced with the requirement to behave similarly to classical power plants. They have to provide active and reactive power supply and must prove low-voltage-ride-through capability. At Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) we have brought a new Megawatt Laboratory into operation in order to test PV inverters, of powers over 100 kW, according to the new grid codes. This paper presents the lessons learned form our testing activities.