Long-term monitoring of photovoltaic plants

Peer Reviewe

Long-Term Monitoring of Photovoltaic Plants

This paper deals with a data-acquisition system that has been specifically developed for a long-term monitoring of ten different photovoltaic plants. The main goals of the system consist in estimating the drift of the plant components, mainly photovoltaic modules and power inverters, and comparing the performance of the ten plants, which are based on different technologies and architectures. Owing to these goals, the traceabilityassurance of the obtained measurements is mandatory, hence the data-acquisition system has been designed to be easily calibrated and, if necessary, adjusted to compensate for measuring-chain drifts. In addition, the measurement uncertainty, which has to be suitable to distinguish the behaviour of the different PV plants, has to be stated for each of the estimated parameters. A brief description of the data-acquisition system is provided and its measurement capabilities are highlighted in terms of measured quantities and expected uncertainty. Results that refer to a period of thirty months are also reported

Long-Term Monitoring of Photovoltaic Plants

This paper deals with a data-acquisition system that has been specifically developed for a long-term monitoring of ten different photovoltaic plants. The main goals of the system consist in estimating the drift of the plant components, mainly photovoltaic modules and power inverters, and comparing the performance of the ten plants, which are based on different technologies and architectures. Owing to these goals, the traceabilityassurance of the obtained measurements is mandatory, hence the data-acquisition system has been designed to be easily calibrated and, if necessary, adjusted to compensate for measuring-chain drifts. In addition, the measurement uncertainty, which has to be suitable to distinguish the behaviour of the different PV plants, has to be stated for each of the estimated parameters. A brief description of the data-acquisition system is provided and its measurement capabilities are highlighted in terms of measured quantities and expected uncertainty. Results that refer to a period of thirty months are also reported

A power and energy procedure in operating photovoltaic systems to quantify the losses according to the causes

Recently, after high feed-in tariffs in Italy, retroactive cuts in the energy payments have generated economic concern about several grid-connected photovoltaic (PV) systems with poor performance. In this paper the proposed procedure suggests some rules for determining the sources of losses and thus minimizing poor performance in the energy production. The on-site field inspection, the identification of the irradiance sensors, as close as possible the PV system, and the assessment of energy production are three preliminary steps which do not require experimental tests. The fourth step is to test the arrays of PV modules on-site. The fifth step is to test only the PV strings or single modules belonging to arrays with poor performance (e.g., I-V mismatch). The sixth step is to use the thermo-graphic camera and the electroluminescence at the PV-module level. The seventh step is to monitor the DC racks of each inverter or the individual inverter, if equipped with only one Maximum Power Point Tracker (MPPT). Experimental results on real PV systems show the effectiveness of this procedure

Characterization of a system for measurements on soft ferrites

This paper deals with the characterization of a system for measurements on soft ferrites through a volt-amperometric method. The accurate control of the driving input field is discussed as a critical aspect for the definition of the correct operating conditions on the magnetic sample. A custom-built transimpedance amplifier is characterized in terms of total harmonic distortion and signal-to-noise and distortion ratio of the primary current and shown as a valid configuration for the required purposes. As a main contribution, the uncertainty analyses of the major loop measurement and of the magnetic accommodation measurement of minor asymmetric loops are provided

Effect of A/D conversion static errors on magnetic accommodation measurements

In this paper we analyze how static errors of Analog-to-Digital converters (ADCs) can influence the measurement of magnetic phenomena such as accommodation in soft hysteretic materials. The discussion is carried out through a series of simulation of ADC response curves and applied to simulated signals and data measured on a toroidal soft ferrite core. The final purpose of this work is to analyze the impact of INL on the measurement of the accommodation phenomenon of minor loops in soft magnetic materials

Simultaneous Measurement of Dielectric Properties and Levels of Liquids Using a TDR Method

Several monitoring methods, in the recent years, involved microwave/radio frequency (RF) reflectometry techniques, particularly in remote sensing, environmental and industrial application fields. The main advantages using reflectometry are due to its relevant performance characteristics, in terms of high flexibility, high sensitivity and large application conditions. Furthermore, the time domain reflectometry (TDR) presents some attractive advantages, related to the possible determination of the spatial location and nature of various objects, in real-time and with a non-destructive approach. This makes the TDR technique an appealing candidate for a variety of environmental and industrial applications. Although TDR instruments are commonly used today, particularly for the above mentioned purposes, the state of the art is rather lacking in liquid monitoring applications. In this paper we demonstrate that a suitable combination of TDR detecting functionalities, in terms of spatial localization, dielectric properties estimation and coaxial probe performance characteristics, leads to an enhanced quantitative and qualitative monitoring method. Really, in one shot, the analysis of TDR data allows the measurement of liquid levels, the determination of multiple interfaces in layered media, as well as the evaluation of dielectric properties, such as dielectric permittivity or electrical conductivity. Moreover, some applications to real cases are proposed, referred to petrol–chemical mixtures or water-based liquids, thus validating the approach on a wide range of materials