B. Bletterie

The voltage rise caused by photovoltaic (PV) power feed‐in is one of the main network constraints limiting the PV penetration in distribution networks. In this paper, a local voltage control approach for PV inverters based on reactive power management is proposed and investigated into detail. Through a parametric study, various inverter settings are considered and compared for a real medium voltage network with a high PV penetration level and for which a demonstration is planned within the project MetaPV. The purpose of this work is to investigate the suitability of such control concepts to compensate the voltage rise caused by the PV power feed‐in and to provide some guidance on the adjustment of the settings of such control mechanisms. For the assessment of the performance of the control concept with different settings, extensive load flow simulations have been performed for a voltage‐dependent reactive power control (Q(V) characteristics) on the basis of 15‐minute profiles. As a result, voltage time‐series over a period of 1 year are obtained for each case and analysed into details. Apart from the voltage profiles, other features such as network losses and reactive energy import have been quantified because they are also of noticeable importance for network operators. The simulation results show that suitable settings are necessary to maintain the voltage within the prescribed limits. A comparison between the considered cases shows that reactive power control Q(V) with a power factor down to 0.9 is necessary to achieve satisfying results. The use of a dead‐band is recommended for the voltage‐dependent reactive power control in order to limit the losses and reactive energy import. Copyright © 2011 John Wiley & Sons, Ltd.

The availability of accurate performance figures for photovoltaic (PV) inverters is of prime importance when it comes to the selection of products, the design of installations or the estimation of the annual yield. This paper proposes an improvement of the current practise by introducing a new quantity to quantify the performance of inverters: the maximal achievable European efficiency. This quantity can be based on the distribution of the annual yield as a function of maximum power point (MPP) power and voltage or on the existing weighting factors of the European efficiency. In a first step, the concept of the required MPP voltage window is introduced on the basis of a detailed analysis of the operating conditions for a typical location in Central Europe. It quantifies the voltage window in which the inverter shall operate and in which the average efficiency shall be calculated. In a second step, a method to process the efficiency measurements as they are now commonly performed is described. By combining the detailed characterisation of the inverter efficiency and the distribution of the annual irradiation as function of the operating conditions, an average and a maximal efficiency over the whole inverter specified MPP voltage range are obtained. They provide a very valuable information about the overall performance of the inverter and about its sensitivity to the plant configuration. As a good compromise between simplicity and accuracy, the proposed concept of achievable European efficiency should be preferred to the current practises. Copyright © 2010 John Wiley & Sons, Ltd.