Guidelines for the technical assessment of harmonic, flicker and unbalance emission limits for PV-distributed generation

Photovoltaic-distributed generation (PV-DG) is increasingly being embedded in distribution networks, and this is the source of a wide range of PQ problems. Consequently, the distribution network operator needs a coherent set of technical requirements for individual PV-DG units as well as for system EMC management in order to ensure PQ. Currently, the EMC poses the following challenges for PV-DG units connected to the distribution network: (a) PV-DG individual equipment should limit its emissions according to particular product-family standards with specific tests under a given set of conditions; (b) PV-DG units should be incorporated as a ‘user’, and its emissions managed according to existing allocation practices. This paper gives an overview of the current state of knowledge within the context of IEC regulations, particularly in regards to harmonics, flicker, and voltage unbalance. It thus focuses on the assessment of emission levels for (large) PV-DG units connected to LV and MV networks, as reflected in IEC publications. Such evaluation procedures are all based on a common philosophy. When no standard values are available, optimal values for certain variables (e.g. planning levels, transfer coefficients, and others), are proposed. A brief description is also provided of methods for measuring disturbing emissions and the PQ indices that characterize such emissions. Finally, recommendations are given regarding existing product family standards with a view to creating a set of PV-DG equipment standards.

► PQ technical requirements for PV-DG units and for system EMC management are needed.
► The state of IEC regulations for harmonics, flicker and unbalance is analysed.
► The assessment of emissions for PV-DG units connected to LV/MV networks is presented.
► PV-DG equipment standards are obtained from existing product family standards.