This report describes an algorithm, implemented in Matlab/Simulink, designed to reduce the variability of photovoltaic (PV) power output by using a battery. The purpose of the battery is to add power to the PV output (or subtract) to smooth out the high frequency components of the PV power that that occur during periods with transient cloud shadows on the PV array. The control system is challenged with the task of reducing short-term PV output variability while avoiding overworking the battery both in terms of capacity and ramp capability. The algorithm proposed by Sandia is purposely very simple to facilitate implementation in a real-time controller. The control structure has two additional inputs to which the battery can respond. For example, the battery could respond to PV variability, load variability or area control error (ACE) or a combination of the three. 4 ACKNOWLEDGMENTSThis work was funded by the US Department of Energy Solar Energy Technologies Program.5

Article 690.11 in the 2011 National Electrical Code ® (NEC ® ) requires new photovoltaic (PV) systems on or penetrating a building to include a listed arc fault protection device. Currently there is little experimental or empirical research into the behavior of the arcing frequencies through PV components despite the potential for modules and other PV components to filter or attenuate arcing signatures that could render the arc detector ineffective. To model AC arcing signal propagation along PV strings, the well-studied DC diode models were found to inadequately capture the behavior of high frequency arcing signals. Instead dynamic equivalent circuit models of PV modules were required to describe the impedance for alternating currents in modules. The nonlinearities present in PV cells resulting from irradiance, temperature, frequency, and bias voltage variations make modeling these systems challenging. Linearized dynamic equivalent circuits were created for multiple PV module manufacturers and module technologies. The equivalent resistances and capacitances for the modules were determined using impedance spectroscopy with no bias voltage and no irradiance. The equivalent circuit model was employed to evaluate modules having irradiance conditions that could not be measured directly with the instrumentation. Although there was a wide range of circuit component values, the complex impedance model does not predict filtering of arc fault frequencies in PV strings for any irradiance level. Experimental results with no irradiance agree with the model and show nearly no attenuation for 1 Hz to 100 kHz input frequencies. 4 ACKNOWLEDGMENTSThis work was funded by the US Department of Energy Solar Energy Technologies Program.5

With the release of the revised version of the Swiss standard SIA 181:2006 "Protection Against Noise in Buildings", a measurement technique was introduced for simulating user-generated noise in bathtubs, shower cubicles, wash basins etc. employing a pendulous hammer. Despite the undoubted advantages of the measurement method, over the past few years questions have increasingly been raised regarding various issues involved in its use. The characteristics of the pendulous hammer are insufficiently well specified in the standard and a procedure specifying a periodic check of the instrument is lacking. The measurement method itself is described in inadequate detail, so that (for example) depending on the choice of the excitation, potentially very diff erent results may be obtained. In addition, no information is given regarding the measurement uncertainty. The standard gives level corrections for diff erent excitation scenarios. This allows a comparison of the diff erence between the level of the original noise and that generated by the pendulous hammer. The validity of these level corrections is now, to a certain extent, being challenged. In addition, it has been suggested that – depending on the constructional details - the airborne noise emitted by acoustic radiation from the component under investigation is excessive, thereby potentially falsifying the measured values. These issues have been investigated by Empa and, based on a comprehensive set of laboratory and field measurements, clarified. Measurement protocols are given for various components, and the measurement uncertainty has been evaluated. The eff ect of airborne noise has been shown to be acceptable for tests conducted in accordance with the SIA 181 standard. Sufficient measurement data is now available to allow the level corrections to be determined. Finally, specifications for the pendulous hammer itself have been formulated.