The frequency stability challenge
In recent years, electricity production from distributed renewable energy generators in Germany increased significantly due to the German Renewable Energy Sources Act. Photovoltaic power plants have shown the highest growths rates in 2009 and 2010. About two thirds of photovoltaic power plants in Continental Europe are connected to low voltage networks. Related grid codes allow for distributed generation only to operate within frequency ranges that are in many cases extremely close to nominal frequency. At an abnormal system condition the frequency of a region may increase above those thresholds and distributed generators would disconnect within immediately. The paper investigates the related potential frequency stability problem and analyses mitigation measures.
Please also see the corresponding study made by Ecofys and IFK on behalf of the FNN/VDE that recommends the retrofitting of solar power systems to solve the so-called 50.2-hertz problem.