Open Access
A tool for the performance evaluation and failure detection of Amareleja PV plant (Acciona) from SCADA
(2015) Muñoz Escribano, Mikel; Parra Laita, Íñigo de la; García Solano, Miguel; Marcos Álvarez, Javier; Pérez, Miguel; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
This paper describes a tool developed for the performance evaluation and failure detection in a 45.6 MWp PV plant installed by the company Acciona in Amareleja (Portugal). The paper describes the PV plant configuration and its SCADA (Supervisory Control And Data Acquisition), the measured variables and the main functionalities of the software. Some of these functionalities are the automatic and accurate PSTC (Power under standard test conditions1) calculation for each generator and for the whole PV Plant, the reference production that would be delivered by the PV plant assuming a 100% availability, the hierarchy of SCADA alarms, the detection of long-term trends and degradation in PV generators, possible hidden problems in the different equipment and systems composing the PV plant, etc. This tool entered into operation in 2011 and is working properly since then.
Open Access
On the calculation of the STC power of PV generators by using typical monitoring system data
(2017) Muñoz Escribano, Mikel; Parra Laita, Íñigo de la; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
The properly in-field characterization of the power at Standard Test Conditions, PSTC, of PV generators is becoming increasingly important in order to evaluate their performance and its evolution in time. Within the state of art, the PSTC characterization procedures of PV arrays are mainly based on I-V curve measurements or PDC measurements performed by precision wattmeters. Those characterizations are usually carried out during discrete measurement campaigns, which does not allow a continuous tracking of the PSTC evolution. In this paper a new PSTC characterization procedure is proposed which is based on the DC power measurements performed by the own PV inverters connected to the PV arrays. This procedure enables an automatic and continuous calculation of the PSTC, which allows to observe its evolution and to detect possible anomalous trends, premature degradations, etc. The procedure has been validated in several PV generators of the large-scale Amareleja PV Plant (45.6 MWp). As showed in this paper, by using several day data and applying the adequate filters, a high accuracy in the PSTC calculation can be achieved, a similar accuracy to that obtained by using precision wattmeter measurements.
Open Access
PV power forecasting using a parametric model
(2015) Muñoz Escribano, Mikel; Parra Laita, Íñigo de la; García Solano, Miguel; Marcos Álvarez, Javier; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
Nowadays, accurate AC power output forecast of PV plants can play a significant role for both the system operators and PV plant owners. The first group has to program the dispatch of the electric system and the second one needs to plan their energy commercialization schedule up front. Therefore, after analyzing the existing commercial services of PV production forecast, it has been identified the potential to improve the models used to calculate the AC power output from irradiance and ambient temperature forecasts. Then, in this paper, a parametric model is proposed in order to improve the forecast performance. This model provides the AC power at the output of the PV plan using as input variables predicted ambient temperature and predicted global horizontal irradiance, both obtained from open sources. It has been evaluated and validated using historical production data of a fixed generator (2,24kWp) and a large PV power plant (45MWp) and historical forecast data from the open source Meteogalicia In addition, a toolbox to implement this parametric methodology has been built upon the Matlab environment. The toolbox has been developed to provide the PV plant production one day in advance.
Open Access
Compensation of forecast error in large PV plants with battery storage: associated strategies
(2017) Marcos Álvarez, Javier; Parra Laita, Íñigo de la; Muñoz Escribano, Mikel; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
As penetration rates of utility-scale photovoltaics (PV) increases, large PV plants will participate in the daily wholesale electricity market in the same way that wind farms. Then, PV plant owner can receive some kind of economic penalty depending on the forecast deviation. This opens the way to use a battery energy storage system (BESS) to compensate the prediction errors. Taking advance of the several 1-hour intra-diary market sessions, the PV plant owner can correct the prediction for the next hours. Hence, a 1-hour BESS SOC control can be implemented to avoid large energy requirements. Here we present two novel strategies which allow a large PV-BESS plant to fulfil the programme referred.
Open Access
A comparative study of degradation and performance of thin film photovoltaic generators versus a multi-crystalline generator
(2013) Parra Laita, Íñigo de la; García Solano, Miguel; Marcos Álvarez, Javier; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica
Thin film solar cells (TFSC) are supposed to have higher energy yield rates than crystalline silicon (Si-x) mainly possible by some enhancements like lower temperature coefficient and higher absorption of diffuse light. Although several papers deal with this topic, there are uncertainties and there is no conclusive outcome to their performance compared to Si-x. The aim of this paper is to contribute to the state of the art on this topic providing experimental data of degradation and performance of several commercially available TFSC generators (CdTe, CIGS, a-Si, a Si/µSi) and a conventional Si x. The energy yield of the TFSC generators during two years is compared to the Si-x one which is supposed to be the standard.
Open Access
Ramp-rate control in large PV plants: battery vs. short-term forecast
(IEEE, 2018) Marcos Álvarez, Javier; Parra Laita, Íñigo de la; Cirés Buey, Eulalia; Wang, Guang Chao; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
The changeability in the power produced by utility-scale PV plants caused by shadows due to passing clouds can compromise grid stability. Traditionally, some kind of energy storage systems (ESS) is proposed as the solution to reduce power variations below the limits imposed by new grid codes regulations. However, recent short-term forecast sources open the door to control the variability without batteries, using only inverter limitation. This option entails some energy curtailment losses that has not been yet addressed. This paper quantifies these losses for the first time using a meaningful database of 5 s one year data for a 38.5 MW PV plant in a perfect forecast scenery. Finally, we compare the economic cost of installing a lithium-ion battery vs. the inverter limitation solution. The results obtained indicate that battery-less strategies must not be neglected for ramp-rate control, since they can be more cost-effective using perfect forecast for any ramp value.
Open Access
On the on-site measurement of the degradation rate of crystalline silicon PV modules at plant level
(IEEE, 2018) Pascual Miqueleiz, Julio María; Berrueta Irigoyen, Alberto; Marcos Álvarez, Javier; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
This paper proposes a method for measuring the degradation rate of crystalline silicon PV modules at plant level in two different ways as a form of verification. As actual levels of degradation rate have been observed to be as low as 0.2%/a, the uncertainties make it difficult to measure this value accurately at plant level. However, despite the low value, it is still important to know the actual degradation rate due to its impact on energy yield. In this paper, two ways of measuring the degradation rate at plant level are proposed. These two methods, with different uncertainty sources, are proposed to be used jointly in order to have a better approach to the real value. Finally, an example of measurement in a 1.78 MW PV plant is presented.
Open Access
The potential of forecasting in reducing the LCOE in PV plants under ramp-rate restrictions
(Elsevier, 2019) Cirés Buey, Eulalia; Marcos Álvarez, Javier; Parra Laita, Íñigo de la; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
An increasing number of grid codes are requiring the limitation of the PV output power fluctuation over a given time scale. Batteries represent the most obvious solution to smooth power fluctuations, with the corresponding negative impact on the PV energy cost. However, short-term forecasting is currently being proposed as a tool to reduce battery capacity requirements or even completely remove it. Although these solutions decrease or avoid the battery cost, it also entails some energy curtailment losses which obviously raise the final cost of PV energy. This energy losses, currently unknown, are independent of the forecasting accuracy and represent the minimal additional cost in the hypothetical case of a perfect prediction. Thus, this paper compares Levelized Cost of Energy (LCOE) of three ramp-rate control strategies in order to determine which would give the lowest cost: battery-based, ideal short-term forecasting, or a combination of both. Results show that curtailment losses would be small enough to make battery-less strategy an appropriate choice, so it is worthwhile improving short-term forecasting in view of the potential LCOE savings. Database is taken from high resolution measurements recorded for over a year at 8 PV plants ranging from 1 to 46 MWp.
Open Access
Control strategies to smooth short-term power fluctuations in large photovoltaic plants using battery storage systems
(MDPI, 2014) Marcos Álvarez, Javier; Parra Laita, Íñigo de la; García Solano, Miguel; Marroyo Palomo, Luis; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa
The variations in irradiance produced by changes in cloud cover can cause rapid fluctuations in the power generated by large photovoltaic (PV) plants. As the PV power share in the grid increases, such fluctuations may adversely affect power quality and reliability. Thus, energy storage systems (ESS) are necessary in order to smooth power fluctuations below the maximum allowable. This article first proposes a new control strategy (step-control), to improve the results in relation to two state-of-the-art strategies, ramp-rate control and moving average. It also presents a method to quantify the storage capacity requirements according to the three different smoothing strategies and for different PV plant sizes. Finally, simulations shows that, although the moving-average (MA) strategy requires the smallest capacity, it presents more losses (2–3 times more) and produces a much higher number of cycles over the ESS (around 10 times more), making it unsuitable with storage technologies as lithium-ion. The step-control shown as a better option in scenery with exigent ramp restrictions (around 2%/min) and distributed generation against the ramp-rate control in all ESS key aspects: 20% less of capacity, up to 30% less of losses and a 40% less of ageing. All the simulations were based on real PV production data, taken every 5 s in the course of one year (2012) from a number of systems with power outputs ranging from 550 kW to 40 MW.