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Improvement of photovoltaic pumping systems based on standard frequency converters by means of programmable logic controllers
Abstract
Photovoltaic pumping systems (PVPS) based on standard frequency converters (SFCs) are currently experiencing a growing interest in pumping programmes implemented in remote areas because of their high performance in terms of component reliability, low cost, high power range and good availability of components virtually anywhere in the world. However, in practical applications there have appeared a number of problems related to the adaptation of the SFCs to the requirements of the photovoltaic pumping systems (PVPS). Another disadvantage of dedicated PVPS is the difficulty in implementing maximum power point tracking (MPPT). This paper shows that these problems can be solved through the addition of a basic industrial programmable logic controller (PLC) to the system. This PLC does not increase the cost and complexity of the system, but improves the adaptation of the SFC to the photovoltaic pumping system, and increases the overall performance of the system.
... The use of standard industrial-use Frequency Converter (FC), also called Variable-speed Driver, as a PCS in PVPS applications has been the subject of many studies as an alternative to drive conventional centrifugal motor-pump without the need of electrical energy storage (Alonso Abella et al., 2003;Brito and Zilles, 2006;Dos Santos et al., 2020;Fernández-Ramos, 2010;Maranhão et al., 2015;Maranhão et al., 2016). This system is also known as directly coupled PV pumping systems (Chandel et al., 2017), which implies an appropriately sized water reservoir to meet the water demand when solar radiation is insufficient. ...
... This configuration is a viable alternative to the equipment designed specifically for photovoltaic pumping (Alonso Abella et al., 2003;Brito and Zilles, 2006;Chandel et al., 2017;Fernández-Ramos, 2010;Valer et al., 2016). Such configuration adopts equipment present in a wellconsolidated market, with a high degree of reliability and a wide range of manufacturers and power ratings, which is the case for both industrial FC and motor-pump sets. ...
Every centrifugal pump has an optimum efficiency duty point, known as Best Efficient Point (BEP), which is usually specified by the manufacturer. In conventional pumping systems, the centrifugal pump must operate at the rated speed and as close as possible to the BEP for optimal performance. This design approach, based on the BEP concept, is suitable only when the centrifugal pump is supplied by sources that can maintain the pump’s operation at the rated frequency (50 Hz or 60 Hz) and voltage (220 V or 380 V). In photovoltaic pumping systems, the conventional centrifugal pump works at different speeds according to the availability of solar irradiance. Therefore, the BEP concept does not offer the best performance in terms of efficiency. This paper presents a method to determine the operating point that provides maximum efficiency for a given photovoltaic pumping system composed of a conventional centrifugal pump driven by a power control system. This point, referred to as Solar Best Efficiency Point (SBEP), is calculated considering the entire operating range of the pump for a given irradiance and photovoltaic cell temperature profile. According to the results, the SBEP operation, compared to the BEP operation, can increase the daily efficiency of the photovoltaic pumping system by up to 6.7%, depending on the centrifugal pump used. Furthermore, the theoretical approach developed in this paper shows that the selection of the motor-pump set cannot be based solely on the pump’s characteristics, as the motor quality significantly influences system performance.
... Compared to induction motors, PMSM motors have a better power-to-weight ratio and a better dynamic response. This improved performance is a powerful argument to consider the use of this kind of motors in the PVPS, since it would allow to increase the robustness of the system in the face of sudden drop of irradiance (cloud pass), one of the main problems to be solved in this systems [18]. This paper deals with the optimization of the operat PMSM motor directly powered by a PV generator without any energy accumulation element, by means of an appropirate tuning of the control parameters. ...
... The control that has to be carried out must be reverse, that is, if the generator voltage is higher than the setpoint voltage (negative error), the output must be increased so that the power applied to the motor is also increased, causing a reduction in the generator voltage and in the error. On the other hand, if the generator voltage is lower than the setpoint (positive error), the power applied to the by direct current motors [13] directly connected to PV generator or through DC converters [14], the most common system nowadays is the asynchronous induction motor driven by a ing a proportionalderivative (PID) control algorithm, whose control generator voltage and whose output depends essentially on the proper D control parameters, process known of electric vehicles (EVs) has contributed to a great improvement in electric motors features, mainly the permanent magnet synchronous motor brushless DC motors motors, PMSM motors o and a better dynamic This improved performance is a powerful argument to consider the use of this kind of motors in the PVPS, since allow to increase the robustness of the system in the face of sudden drop of irradiance (cloud pass), one of the main problems to be solved in this systems [18]. This paper deals with the optimization of the operation of a PV generator without any energy accumulation element, by means of an appropirate tuning of the control parameters. ...
... The SFC implements a proportional-integral-derivative (PID) control whose control variable is the voltage of the photovoltaic (PV) array and the output variable is the frequency applied to the motor-pump. The type of control is inverse: an increase in voltage causes a decrease in frequency and vice versa (Alonso Abella et al., 2003, Fernández-Ramos et al., 2010. A basic diagram of the system is shown in Fig. 1. ...
... The performance of these systems under conditions of constant irradiance is acceptable but their response to fast changes in irradiance is very slow. This phenomenon is known as "cloud-pass" because it usually occurs when the shadow produced by a cloud reaches the PV array, producing a sudden decrease in the available PV power (Fernández-Ramos et al., 2010). ...
In this work, a systematic study of different tuning rules of proportional-integral (PI) control parameters applied to Photovoltaic Irrigation Systems (PVIS) based on Standard Frequency Converters (SFCs) has been carried out. A laboratory system has been implemented to obtain the PI control parameters by means of the most widely accepted tuning rules in control systems. Based on the step-input response modeling, we have been applied the tuning rules of Ziegler-Nichols (ZNs), Chien-Hrones-Reswick (CHR), Cohen-Coon (C-C), Lambda and AMIGOs. Based on frequency response modeling we have been applied the tuning rules of Ziegler-Nichols (ZNf) and AMIGOf. The PI controller parameters obtained from these tuning rules have been evaluated by performing two types of tests: start-up and sudden drop of the available PV power. The experimental results show that the parameter sets obtained by the ZNs, CHR and AMIGOf rules are the only ones that pass all the start-up tests and that the tests of sudden drop of the available PV power are only passed by the configuration obtained by the AMIGOf rules. Therefore, it has experimentally verified that the AMIGO tuning rules based on the frequency response modeling are the only ones that provide adequate values for the PI control parameters for PV irrigation systems.
... Technical and economic aspects related to photovoltaic pumping systems containing variable-speed drives (PVPS-VSDs) were compared with conventional photovoltaic pumping system (PVPS-C) and Diesel Pump System (DGPS). It is important to highlight although there are other works about PVPS-VSDs [10][11][12][13][14], they are focused in other technical aspects as experimental characteristics and possible configurations. For the technical comparison, the experience acquired by the Laboratório de Sistemas Fotovoltaicos of the Energy and Environment Institute of São Paulo University (LSF-IEE-USP) is used. ...
... The configuration consists in a nationally manufactured VSD installed in an electric box coupled with some electric protections devices, switches and a voltage reducer circuit used in PID feedback. In spite of there are other configurations that include VSD with Programmable Logic Controller and additional external circuits [12][13][14], this configuration was chosen because the VSD is nationally manufactured so it is easy to be replaced and repaired. Prior to their installation, all systems were tested on a test bench for a range of different total heads using a DC source and solar irradiation [22]. ...
Thanks to recent technological advances and the falling price of photovoltaic modules, photovoltaic pumping systems (PVPSs) are more competitive for use in irrigation, especially in remote areas where other power sources are unreliable or unavailable. Nevertheless, several issues remain regarding the purchase, maintenance and replacement of PVPS components. One alternative for traditional PVPS configurations is the use of a variable-speed drive (VSD). The performance of this type of configuration was tested both at a pumping test facility and in the field at a variety of sites. The application of a variable-speed drive can enable the use of locally-manufactured pumps which are not necessarily designed specifically for photovoltaic applications, thus facilitating their replacement and maintenance. Furthermore, VSDs also enable the operation of pumps in power ranges higher than most commercial photovoltaic pumps. VSDs can thus potentially further improve the economic competitiveness of a PVPS, as shown by Life Cycle Cost analysis comparing a conventional (PVPS-C) and a variable-speed drive pumping system (PVPS-VSD). This paper examines these as well as other technical and economic aspects of the application of variable-speed drives for irrigation in Brazil.
... However, an induction motor is technically a competitive choice. Similarly, Fernández-Ramos et al. [81] improved the performance of SPWPSs by using a standard frequency converter and PLCs. It has been proved that the addition of a standard PLC to a SPWPS based on standard frequency converters will avoid the stopping of the system during sudden decreases of the solar radiation. ...
... Benlarbi et al. [80] Fuzzy optimization Fuzzy optimization maximize the global efficiency by increase the drive speed and the water discharge rate Fernández-Ramos et al. [81] Standard frequency converter and PLC ...
... This practically limits the introduction of PVIS on the market. Some examples of the application of these manual tuning methods are found in [24][25][26]. ...
This paper proposes a new automatic tuning method for the proportional-integral (PI) controllers of photovoltaic irrigation systems (PVIS) without the need for any other power source or batteries. It enables the optimisation of the values of the PI parameters (Kp and Ki) automatically, eliminating the requirement for skilled personnel during the installation phase of PVIS. This method is based on the system’s voltage response when a disturbance signal is introduced through the feedforward input of the PI controller. To automatically assess the response properties, two indicators are proposed: the total harmonic distortion (THD), used to evaluate the sine response, and the total square distortion (TSD), used to evaluate the square response. The results indicate that the tuning changes for different irradiance and temperature conditions due to the non-linearity of the system, obtaining the most conservative values at maximum irradiance and temperature. The robustness of the results of the new automatic tuning method to abrupt photovoltaic (PV) power fluctuations due to clouds passing over the PV generator has been experimentally tested and the results show that the obtained tuning values make the PVIS stable, even when PV power drops of 66% occur abruptly.
... The rising energy costs of modernized agriculture in the last few years have increased the need to expand the power of PV pumping systems for large-scale irrigation. The innovations developed in the framework of a European project [32], solving problems associated with PV power intermittences without the need for batteries [33], allowed the implementation of stand-alone high-power photovoltaic irrigation systems (PVIS) [34] that are not only economically feasible but also environmentally sustainable [35]. An alternative solution was the integration of batteries [36], but it was found to not be economically feasible for high power applications. ...
High-power diesel-based or grid-connected irrigation systems are being replaced by battery-free, high-power stand-alone Photovoltaic Irrigation Systems (PVIS) that reduce energy costs by up to 80% and for which no experimental performance data are available. The operation of PVIS is affected by various factors, some unrelated to the quality of the PV system itself, that generate losses that affect their performance: losses that vary with the crop and its irrigation period, losses intrinsic to the PVIS design, and losses that happen as a consequence of the behavior of the end-user. To better understand the impact of each type of loss, the traditional performance ratio was factorized. This paper provides the PV community with experimental data on the performance of a battery-free 160 kWp PV-powered constant-pressure center-pivot irrigation system. The system was analyzed over three years of real operation, during which the performance ratio ranged from 49.0 to 53.2%.
... The choice of a PLC in autonomous systems relies on the device's functional ability to operate independently, based on (its own) programming structure, such as the well-known MPPT algorithm, referred to in the literature [12,13]. With this in mind, authors would be looking for new control and operational components for PLC interaction [14]. ...
The research of the operation of low-power photovoltaic generation plants used for self-contained electric power supply in Siberian climaticconditions is performed in this paper. It provides an analysis of the operation of individual units of an automated control system, and givesrecommendations for the selection of hardware components. The article describes the operational principles, developed based on functionalmodules of the programmable logic controller, ensuring maximum possible use of solar energy in this continuous power supply system. The resultsof plant operation have been obtained, in the form of a power counter log, as well as data on the volume of solar energy produced in both overcastand in sunny weather, throughout the observation period. The article provides visual illustration of generated energy, which could be used to assessthe efficiency and economic viability of the low-power photovoltaic plant. Authors would like to point out that examples of the proposedmethodology for the construction of self-contained power supply systems can be found in existing industrial facilities, on which further scientificresearch can be based.
... The key to optimal PVIS performance is an adequate tuning of the control algorithm, a process that presents great challenges due to the non-linear and non-time-invariant nature of the system [9][10][11]. ...
One of the greatest challenges in stand-alone photovoltaic irrigation systems (PVIS) without batteries is the tuning of PID controllers and the evaluation of their performance once the system is tuned. Tuning method must be applied in clear days (constant irradiance) while performance must be evaluated in the most unfavourable circumstances, which occur when the passage of a cloud causes a sudden drop in available power. In short, tuning and testing must be done under different weather conditions. To solve this problem, a tuning method that is complemented by a method to simulate voltage fluctuations due to cloud passage has been developed. This allows tuning and evaluation of the system’s performance in the same session. Furthermore, the new PI tuning method achieves a better adjustment of the parameters and solves the instability problems that arise when applying traditional closed-loop tuning methods. Both methods use the feedforward input that most variable frequency drivers have. A signal generator is used to carry out the simulation of the clouds. This input is also used to introduce a triangular signal used for the tuning of the PI controller. The results show that the performance of the system, characterized by the voltage of the PV generator, with simulated clouds is similar to the response with real clouds. With regard to the tuning, the new method achieves better performance than previous methods. These methods can be applied on clear days, under conditions of constant irradiance, which greatly simplifies its implementation and greatly reduces the time required for commissioning the system.
... The limitation of power in the current state of the art products is due to two main technical barriers identified by the European Innovation Partnerships on Water (EIP-Water) [29]. On the one hand, the quick intermittence of PV power due to the passing of clouds (up to 80% of PV power variation in one minute [30]) can translate into control instabilities, leading to a sudden motor shutdown, encompassing the water hammer and AC overvoltage that seriously threatens the integrity of both the hydraulic and electric components [31]. On the other hand, PV production and water needs must match as far as possible in time [32,33] to maximize economic returns [34]. ...
The current state of the art of photovoltaic (PV) irrigation systems is limited to PV peak powers below 40 kWp, which does not cover the irrigation needs of farmers, co-operatives, irrigator communities, and agro-industries. This limitation of power is due to two main technical barriers: The quick intermittence of PV power due to the passing of clouds, and the maladjustment between PV production and water needs. This paper presents new solutions that have been developed to overcome these barriers and their application to the design and performance of a 140 kWp hybrid PV-diesel system for the drip irrigation of 195 ha of olive trees in Alter do Chão, Portugal. The performance of the solutions was analysed during two years of real operation. As the performance of the PV system is not only affected by intrinsic-to-design characteristics, but also by circumstances external to the system, new performance indices were developed. As an example, the percentage of use of PV electricity, PVSH, was 78% and 82% in 2017 and 2018, respectively, and the performance ratio of the PV part, PRPV, was 0.79 and 0.80. The economic feasibility was also analysed based on experimental data, resulting in savings in the levelized cost of electricity of 61%.
... Other authors report that hybridization with pre-existing diesel sources can be also an interesting option (IRENA, 2016;Bakelli et al., 2016;Carroquino et al., 2015;Ammar et al., 2015). The door to increase the power of PV irrigation systems was opened with the use of standard frequency converters (Abella et al., 2003;Brito and Zilles, 2006;Fernández-Ramos et al., 2010;Valler et al., 2016) and the possibility of avoiding the problems associated to PV power intermittences (EIP Water, 2012). These problems have been solved and demonstrated by a recent European H2020 project called MASLOWATEN (Maslowaten Project, 2018) developing control algorithms to avoid instabilities in the frequency converter of the PV irrigation systems when clouds are passing over the generator . ...
Over the last decades, traditional olive production has been converted to intensive and super-intensive cultivation
systems, characterized by high plant density and irrigation. Although this conversion improves product quality
and quantity, it requires a larger amount of energy input. The new contributions in this paper are, first, an
analysis of the energy and environmental performance of two commercial-scale high peak-power hybrid photovoltaic
irrigation systems (HPVIS) installed at intensive and super-intensive Mediterranean olive orchards; second,
an analysis of PV hybrid solutions, comparing PV hybridization with the electric power grid and with diesel
generators; and finally, a comparison of the environmental benefits of HPVIS with conventional power sources.
Energy and environmental performances were assessed through energy and carbon payback times (EPBT and
CPBT). The results show EPBT of 1.98 and 4.58 years and CPBT of 1.86 and 9.16 years for HPVIS in Morocco and
Portugal, respectively. Moreover, the HPVIS were able to achieve low emission rates, corresponding to 48 and
103 g CO2e per kWh generated.
The EPBT and CPBT obtained in this studywere directly linkedwith the irrigation schedules of the olive orchards;
therefore, weather conditions and irrigation management may modify the energy and environmental performances
of HPVIS.
The consumption of grid electricity and diesel fuel, before and after the implementation of HPVIS, was also analyzed.
The results obtained show fossil energy savings of 67% for the Moroccan farm and 41% for the Portuguese
... A large number of LCA studies have been carried out on solar energy production technologies [15][16][17][18][19][20] and, specifically, on stand-alone PV plants [21][22][23][24][25][26]. PV systems have been also integrated in several agricultural contexts and, in particular, to supply energy for water pumping for irrigation purposes [27][28][29][30]. In fact, irrigation is usually associated with high fossil energy requirements and thus environmental emissions [31][32][33][34]. ...
A life cycle assessment (LCA) methodology was used to evaluate the cumulative energy demand and the related environmental impact of three large-power stand-alone photovoltaic (PV) irrigation systems ranging from 40 kWp to 360 kWp. The novelty of this analysis is the large power of these systems as the literature up to now is restricted to modeled PV pumping systems scenarios or small power plants, where the size can be a critical factor for energy and environmental issues. The analysis shows that the yearly embodied energy per unit of PV power ranged from 1306 MJ/kWp to 1199 MJ/kWp depending of the PV generator size. Similarly, the related yearly carbon dioxide impacts ranged from 72.6 to 79.8 kg CO2e/kWp. The production of PV modules accounted for the main portion (about 80%) of the primary energy embodied into the PV irrigation system (PVIS). The outcomes of the study also show an inverse trend of the energy and carbon payback times respect to the PV power size: In fact, energy payback time increased from 1.94, to 5.25 years and carbon payback time ranged from 4.62 to 9.38 years. Also the energy return on investment depends on the PV generator dimension, ranging from 12.9 to 4.8. The environmental impact of the stand-alone PV systems was also expressed in reference to the potential amount of electricity generated during the whole PV life. As expected, the largest PVIS performs the best result, obtaining an emission rate of 45.9 g CO2e per kWh, while the smallest one achieves 124.1 g CO2e per kWh. Finally, the energy and environmental indicators obtained in this study are strongly related to the irrigation needs, which in turn are influenced by other factors as the type of cultivated crops, the weather conditions and the water availability.
... The choice of a PLC in autonomous systems relies on the device's functional ability to operate independently, based on (its own) programming structure, such as the well-known MPPT algorithm, referred to in the literature [12,13].With this in mind, authors would be looking for new control and operational components for PLC interaction [14] II. ...
... The choice of a PLC in autonomous systems relies on the device's functional ability to operate independently, based on (its own) programming structure, such as the well-known MPPT algorithm, referred to in the literature [12,13]. With this in mind, authors would be looking for new control and operational components for PLC interaction [14]. ...
The research of the operation of low-power photovoltaic generation plants used for self-contained electric power supply in Siberian climatic conditions is performed in this paper. It provides an analysis of the operation of individual units of an automated control system, and gives recommendations for the selection of hardware components. The article describes the operational principles, developed based on functional modules of the programmable logic controller, ensuring maximum possible use of solar energy in this continuous power supply system. The results of plant operation have been obtained, in the form of a power counter log, as well as data on the volume of solar energy produced in both overcast and in sunny weather, throughout the observation period. The article provides visual illustration of generated energy, which could be used to assess the efficiency and economic viability of the low-power photovoltaic plant. Authors would like to point out that examples of the proposed methodology for the construction of self-contained power supply systems can be found in existing industrial facilities, on which further scientific research can be based.
... Ramos et al. (2010) [28] developed an improvement of photovoltaic pumping systems [PVPS] based on standard frequency converters [SFCs] by using a PLC. PVPS based on SFCs are currently experiencing a growing interest in pumping programs implemented in remote areas because of their high performance in terms of component reliability, low cost, high power range and good availability of components virtually anywhere in the world. ...
As the need of automation increases significantly, a control system needs to be easily programmable, flexible, reliable, robust and cost effective. In this paper a review on the application of programmable logic controller (PLC) in our current market is discussed. Investigations on the applications of PLCs in energy research, engineering studies, industrial control applications and monitoring of plants are reviewed in this paper. PLCs do have its own limitations, but findings indicate that PLCs have more advantages than limitations. This paper concludes that PLCs can be used for any applications whether it is of simple or complicated control system.
... A PLC is an industrial type of controller and it has the ability to withstand very harsh environmental conditions such as temperature and humidity (Fernandez, Fernandez & Poza-Saura 2010). Power supply for the PLC was mainly a solar powered battery system. ...
It is the desire of every motorist to drive an exquisite vehicle, so it is very crucial for players in the automotive industry to keep on improving the quality of vehicles. While the interior components of a vehicle are the most critical components to the overall durability and comfort of a vehicle, it is important to guarantee the quality of these components. Vehicle interior components are usually made of plastic, leather, fabric and painted components which can all be prone to quick ageing. Fading, cracking and distortion are rife in vehicle interior components, and these effects are caused by natural factors such as radiation, moisture and extreme temperature. This phenomenon is known as “weathering”. Tireless work has been done over the decades to carry out weathering tests on automotive components in order to address critical areas during the design process of the components. This paper explores one method of carrying out weathering tests on automotive dashboards in which a metallic testing box is used to simulate the conditions inside a vehicle. The main concern is that the temperature inside the test box can go above the necessary testing range which causes test samples to be destroyed before sufficient data is collected. A temperature control system was developed and installed to monitor the temperature inside the box. Weathering tests are being carried out in extremely harsh environments; therefore both the weathering test box and the temperature control system have to be robust. A solar-powered programmable logic controller (PLC), which has the ability to withstand harsh conditions, was used to monitor and control the system.
... This controller acts as the "brain" of the system, allowing the VSD to deliver power to the load (pump) according to the power available from the photovoltaic (PV) array, i.e., the higher the power available from the source, the greater the volume of water pumped by the system. This application is well established in the scientific community with several published studies [1][2][3][4][5][6][7]. The most important point regarding VSD programming is the PID controller's exact tuning, commonly accomplished by a trial-and-error method, because the system transfer function is unknown [4]. ...
In the present paper, a fuzzy controller applied to a Variable-Speed Drive (VSD) for use in Photovoltaic Pumping Systems (PVPS) is proposed. The fuzzy logic system (FLS) used is embedded in a microcontroller and corresponds to a proportional-derivative controller. A Light-Dependent Resistor (LDR) is used to measure, approximately, the irradiance incident on the PV array. Experimental tests are executed using an Arduino board. The experimental results show that the fuzzy controller is capable of operating the system continuously throughout the day and controlling the direct current (DC) voltage level in the VSD with a good performance.
... But these works were very complicated and time consuming. In addition, MATLAB coding based simulator were used by most of the authors for illustrating -and -curves [11,12]. The problem with these simulators is that they cannot be used for different modules simultaneously. ...
This paper represents a novel modeling technique of PV module with a fuzzy logic based MPPT algorithm and boost converter in Simulink environment. The prime contributions of this work are simplification of PV modeling technique and implementation of fuzzy based MPPT system to track maximum power efficiently. The main highlighted points of this paper are to demonstrate the precise control of the duty cycle with respect to various atmospheric conditions, illustration of PV characteristic curves, and operation analysis of the converter. The proposed system has been applied for three different PV modules SOLKAR 36 W, BP MSX 60 W, and KC85T 87 W. Finally the resultant data has been compared with the theoretical prediction and company specified value to ensure the validity of the system.
... The voltage source inverter is used to supply the induction motor driving a centrifugal pump [7]. ...
Solar energy is of increasing interest in pumping system applications particularly in isolated area. Enhancement of pumping system efficiency depends on optimization of solar energy generation and system consumption. This paper presents an optimally designed and realized solar pumping system which can be used for irrigation, under variation of climate conditions in remote areas, far away from electric grid. The solar pumping system is built at the laboratory level and the tests show correct operation of the proposed system. Streszczenie. Energia słoneczna cieszy się większym zainteresowaniem jako źródło energii dla systemów pompowania wody, szczególnie w odizolowanych regionach. Zwiększenie wydajności pompowania systemu zależy od optymalizacji pozyskiwania energii słonecznej i zużycie energii przez system. W artykule przedstawiono optymalnie zaprojektowany i zrealizowany słoneczny system pompowania, który może być zastosowany do nawadniania, z uwzględnieniem zmienności warunków klimatycznych w odległych obszarach, z dala od sieci elektrycznej. Układ słoneczny pompowania jest zbudowany w laboratorium a testy wykazują prawidłowe działanie proponowanego systemu. (System pompowania zasilanego energią fotowoltaiczną zrealizowany za pomocą mikrokontrolera Intel 80C196KC).
Stand-alone large-power PV irrigation systems without batteries is a recent innovation. This means that their design has not yet reached maturity and there are no experimental data about their performance available. This paper is a contribution, on the one hand, to the systematic tuning of the control of this type of systems and, on the other hand, to the knowledge of their experimental performance data.
A systematic Proportional, Integral and Derivative (PID) control tuning method for frequency converters is proposed, based on the application of the Approximate M-constrained Integral Gain Optimisation (AMIGO) design rules to the frequency response tuning method, and applied to two PV irrigation systems, located respectively in Villena and Aldeanueva de Ebro, Spain, that had a “conservative” tuning by means of an experimental trial and error method.
To check the goodness of this systematic tuning, the experimental performance of both systems has been evaluated from 2017 to 2021. New indices have been proposed to assess both the robustness of the system to PV power fluctuations (the “Number of abrupt stops” and the “Passing-cloud resistance ratio”) and the performance (by factoring the traditional Performance Ratio (PR) to determine the influence of different factors external to the system). Results show that the percentage of abrupt stops improves from 40% and 39.8% in each PV irrigation system prior to systematic tuning to 7.3% and 1.3% after tuning; the passing cloud ratio increases from 65% and 79% to 97.9% and 99.8% and the PR from 61.4% and 60% to 65.7% and 64.7%.
In the present era of technology drift, the Internet of Things (IoT) is a promising technology that shows the considerable transition from enterprises to businesses. In this context, renewable energy has played critical roles in developing the agricultural sector with its functionality to generate power over distant areas and different terrain. There has been a transformation in the way we consume electricity and the way it is operated by the utilities. The smart monitoring features are an efficient way to utilize energy and minimize losses. These losses might be the transmission and distribution losses or losses by the inefficient household wiring or appliances. These losses can be minimized if they are monitored well with relevant data and analytics. This book chapter presents an application of the Internet of Energy (IoE) technology in the renewable sector. The study was carried applying Maximum Power Point Tracking (MPPT) functions and corresponding Remote Monitoring System (RMS) functions. The undertaken site for Solar Water Pump (SWP) installation for irrigation is Bihar Sharif (Nalanda, Bihar). The proposed IoE based technology served maximum power output with high efficiency during operating hours. Here, the farmers may do automatic start/shut, remote start/shut from SMS/web with a health check, and self-diagnostic mechanisms for easy maintenance. Thus, the SWP system emerged as a cost-effective and environment-friendly irrigation solution for remote farmers throughout the year. The solar potential assessment of the site and circuital development were done using PVsyst 7.0 and KiCad software tools, respectively. The successful working of the developed product has been observed at the site.
In this paper, a fuzzy logic based Mandani-type controller is applied to an industrial frequency converter to couple a photovoltaic generator to a conventional centrifugal pump for water pumping applications. The system operates in closed loop and the DC bus voltage regulation of the frequency converter is done indirectly by varying the speed of the pump according to the power provided by the photovoltaic generator. In order to decrease the number of series-connected modules, the working voltage of the photovoltaic generator (maximum power point voltage) must be as close as possible to the minimum voltage limit required by the frequency converter’s input. The proposed algorithm was embedded in a general-purpose microcontroller. Controller performance was evaluated through tests on an experimental bench that allows simulating different water heads. Experimental results shows that the speed of the proposed fuzzy controller allows the operation close to the lower DC voltage limit imposed by the frequency converter, making possible the use of photovoltaic generators with a reduced number of PV modules in series (in this work, 30% fewer modules). The fuzzy controller regulates the photovoltaic generator voltage throughout the day, avoiding frequency converter limitation due to undervoltage errors, even with sudden changes in irradiance.
The coupling of Photovoltaic (PV) and Heat Pump (HP) systems is an attractive alternative for reducing the energy consumption associated to cooling applications, as well as increasing the renewable share in the electric systems. This work presents the results of the technical validation of a stand-alone PV-HP system operating without batteries, for two different control algorithms implemented for the compressor of the HP unit: the Maximum Power Point Tracking control (MPPT) and the inverter control. Both algorithms include a routine for mitigating the solar power fluctuations due to passing clouds, which was able to resist 75% of the clouds registered during the carrying out of the tests. The values of the main Key Performance Indicators (KPIs) traditionally used for the characterization of PV and HP systems –Performance Ratio (PR), Energy Efficiency Ratio (EER) and Seasonal Performance factor (SPF)– were calculated, as well as some new KPIs proposed for PV-HP systems. These new KPIs are proposed to distinguish the loss of performance due to any bad quality of the PV-HP and to external factors such as user behavior or the cooling period. The results show a PR of between 0.17 and 0.5, an EER of between 2.51 and 3.06 and a SPF of between 2.51 and 3.01. The low PR value is explained by the utilization ratios of the system (UREF ranged from 0.27 to 0.77) due to the characteristics of this application, rather than any bad quality in the PV-HP system.
Solar water pumping is an attractive option for irrigation and drinking water supplies in view of increasing diesel costs and grid electricity scarcity. Currently direct coupled DC and AC solar run water pumps are extensively used worldwide. The main objective of this study is to review the performance studies of direct coupled photovoltaic water pump systems (PVWPS) along with a case study of an old functional solar water pump after prolonged outdoor exposure in a western Indian Himalayan location. The updated review critically examines PVWPS performance studies, optimum sizing and the use of electronic controls to improve the efficiency. The intelligent control methods for maximum power point tracking (MPPT) of PV systems are found to improve the PVWPS efficiency under outdoor temperature and irradiance conditions. The techno-economic analysis of PV and diesel pumping shows that PV-based water pumping is more cost-effective than diesel-powered pumping. The study shows that PVWPS are cost effective with little maintenance for water pumping requirements. The case study on the performance evaluation of an old direct coupled DC solar pump shows that only two modules of its mono-crystalline PV generator have degraded substantially after 28 years of field operation affecting its performance. The PV degradation rate is found to be 1.4% per year which is comparable to the reported degradation rate of 1.45% for mono crystalline in India. The system is still found to be capable of generating enough power to pump water at average rate of 829 l/h. The experimental performance results are found to be in close agreement with the simulated results. The performance of PVWPS is found to improve when installed at an optimum tilt angle for the location. These are first time reported results of significance to assess the state of PV pumping technology after a prolonged outdoor exposure for further research.
In this paper, a fuzzy controller applied to variable-speed drive for the use in direct-coupled photovoltaic (PV) pumping systems is proposed. The fuzzy logic system used is of the Mandani type, embedded in a microcontroller, and corresponds to a proportional-derivative controller. A low-power PV module is used to detected variations in the irradiance incident on the PV array. Experimental tests are performed using a motopump testing workbench, which is able to simulate water wells with different manometric heights. The results show that the fuzzy controller is capable of operating the system continuously throughout the day, with an average efficiency of 23%.
Control strategy for standalone solar pumping system based on induction motor and without DC/DC converter has been widely studied and discussed in the literature. This topology is of great concern due its economic issues, especially when a standard frequency converter (SFCs) with scalar control is used instead of a dedicated PV inverter. This paper proposes an external control module to generate SFCs frequency reference in order to ensure both maximum power point tracking (MPPT) and optimize IM power. It is a low cost solution since it requires no additional power equipment. Modeling and design of each system parts are performed to determine the analytic expression of frequency reference. The effectiveness of the proposed approach is illustrated by simulations carried out under PSIM Software, and validated through experimental investigations on a 1.5kW laboratory set-up.
The effective control of high-vibration intensity frequency and its overtime and over-limited is a bottleneck technology of chaotic vibration machine to finish specific operation. A PLC advance control system based on intelligent frequency is developed. Prediction of the possible vibration intensity extreme points and its distribution are processed data mining and prediction by sensor signal amplification, analog-digital conversion, and online monitor. Moreover, advanced control of the overtime and over-limited vibration intensity is achieved by constraint conditions correction and real-time feedback. The advanced control results can be verified by comparing grinding effect of conventional vibration mill with that of advanced control vibration mill. Further, the deaggregation and refinement of super-hard and superfine grinding can be achieved.
A new approach for tracking the maximum power point of photovoltaic arrays is presented. The maximum power point tracker output voltage and current are used for control purposes, rather than for its input voltage and current. It is shown that using the output parameters simplifies the maximum power point tracker controller. Moreover, using this approach, only one out of the two output parameters needs to be sensed. This observation is general and applies regardless of the power stage or the realisation control algorithm. Contrary to what might have previously been assumed, it is theoretically shown that the MPPT control that uses a single output control parameter applies to nearly all practical load types, regardless of the load nature.
Los sistemas de bombeo fotovoltaico empiezan a tener detras de sí una historia de la que es posible extraer conclusiones exitosas que sirven de utilidad para su evolución en el futuro. Una de ellas es que son una solución idónea, si no la más idónea, para suministrar agua en entornos rurales aislados. Ello es debido entre otras cosas a su bajo mantenimiento y adecuación a las necesidades de agua de los distintos núcleos poblacionales. Otra es la constatación de la aceptación que han recibido por parte de las comunidades que ya estan disfrutando de ellas desde hace algún tiempo, que en muchos casos se cifra en años. Pero también, y en el capítulo negativo, está el historial de problemas que han presentado si se consider este tipo de sistemas de una manera global como un conjunto de equipos interconectados que, funcionando correctamente entre si, no ha sido estudiado teniendo en cuenta la comunidad en la que se ubica y, sobre todo, no ha considerado detenidamente aspectos como la distribución del agua desde el depósito hasta los puntos de suministro de los usuarios (fuentes comunales, viviendas individuales, abrevaderos o cultivos). Generalmente se ha puesto una frontera ficticia entre el depósito de almacenamiento y la distribución del agua a los usuarios que ha sido muy perjudicial. Pero no solo ha sido esta cuestión la causa principal de los problemas antes mencionados. Han colaborado también nuevos sistemas y dispositivos no correctamente probados, o inadecuados para ciertos entornos; y, en general, procedimientos de control de calidad aplicados solo a algunas partes de los sistemas. El cuadro pintado con lo dicho en los párrafos anteriores ha motivado la propuesta de una estrategia en el establecimiento de procedimientos de control de calidad en sistemas de bombeo fotovoltaico. Ésta es la aportación de esta tesis doctoral. La estrategia propuesta consta de varias etapas: – Propuesta de unas especificaciones técnicas abarcando equipos, distribución de agua, dimensionado, y subrayando la necesidad de ensayar cuidadosamente toda aquella novedad técnica con la fiabilidad como objetivo global. Detalles importantes a tener en cuenta son la estandarización de sistemas desde un punto de vista de suministro de cierto volúmen de agua en términos diarios. – Realización de unos ensayos previos a las instalaciones en laboratorios pertinentes. El diseño y alcance de los ensayos está iluminado por la idea de la sencillez en equipos e instalaciones. – Identificación de responsables locales de los sistemas y su mantenimiento. – Instalación de sistemas y revisión temprana de los mismos. – Revisión de los sistemas una vez instalados, y lo mismo, después de un período de tiempo de funcionamiento. – Establecimiento de una estructura de mantenimiento local para garantizar una larga vida de los sistemas. Esta estrategia ha sido implementada en la práctica en un extenso programa de bombeo fotovoltaico ejecutado en Marruecos, Argelia y Túnez. Ha consistido en la. instalación de hasta 52 kW en sistemas de bombeo, que han suministrado agua potable en condiciones a más de 40.000 personas. Asimismo se han recogido las enseñanzas aportadas por la experiencia que han sido incluídas en todas y cada una de las etapas presentadas. Abstract Photovoltaic pumping systems start to have a long path behind them, so it's possible to extract useful conclussions that can be taken as lessons regarding its future development. One of them is that they are an ideal solution, (if not the best) to supply water in rural isolated environments. This due to, among other things, their low maintenance needs and to the fact that they fit very well to the water needs of rural communities. Another one is the good accetance from them, from some time now, accounted, in a number of cases, in years. But also, and in the negative side, we have the problems and incidents background that they present if the system is considered, from a global point of view, like something that consists of a series of equipment interconnected, doesn't have been analysed in relation to the environment where it is installed. Specially if, as it's hapens fairly common, the distribution of water from the tank to the point of used by users (taps, public springs, etc), hasn't been taken into account. Usually, a fictitcious border is placed between the tank and supply water means that has been almost always harmful. But, what stated above has not been the only reason for the problems shown by this systems. New devices and technologies, not correctly tested have collaborated to this situation, and in general, quality procedures applied only to some parts of the systems. The scene depicted has motivated the proposal of a strategy in the establishment of quality control procedures in photovoltaic pumping systems. This is the proposal containend in this thesis. This strategy consists of next stages: - Proposal of a technical specifications covering equipment, water supply, sizing, and underlining the need to test carefully every new technology or device with reliability as the final objective. - Performing of a set of tests previous to the installation in proper laboratories. Design and reach of this tests are enlighted by the idea of simplicity in equipment and installatins. - Identification of actors in charge of the systems and their maintenance in the final location. - Systems installation and their early revision. - Systems revision once installed, and the same after certain working period long enough to watch for problems due to aging. - Stablishing of a local maintenance structure to guarantee a long and reliable systems life. This strategy has been implemented in practice in a wide PV pumping program executed in Morocco, Algeria and Tunisia. It has consisted of the installation of up to 52 kW in PV pumping systems, that have, from then on, supplied safe water to more than 40.000 people. Also, the lessons learned have been included in every stage in this work.
The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in PV power generation.
From the daily water demand, total head and the daily average irradiation, is possible to determine the size of the PV generator for pumping systems. However, once the equipment is acquired, some tests are recommended, specially to verify its performance. One of the most relevant parameters to qualify a pumping system is the daily water delivered (m3/day) as a function of daily irradiation (Wh/m2). Facilities that fit different boundaries conditions, as for example constant total head (m) are not easily available, and just few laboratories have this capability. In this way, a simple instrumentation with the capability to determine the daily performance of PV pumping systems is presented. The proposed test tools use a hydraulic circuit with two motopumps, one connected to the PV system and the other to the electric grid. The total head is maintained constant by the variable-speed drive connected to the grid. Copyright © 2006 John Wiley & Sons, Ltd.
This work presents a systematized procedure for the parameter characterization of a variable-speed drive (VSD) for use in applications to photovoltaic pumping systems (PVPS). The study focuses on the process of the PID controller's tuning of the VSD, in order to optimize the configuration. In this work, three methods of tuning are analyzed and the results show that the methods based on the system's response in open-loop are the most suitable, as well as the use of only the integral proportional control actions (PI). Copyright © 2005 John Wiley & Sons, Ltd.
Standard frequency converters (FCs) are evaluated in this work as a universal solution for photovoltaic (PV) water pumping systems. FCs can be connected directly to a PV generator to power centrifugal submersible pumps driven by three-phase asynchronous induction motors. In comparison with dedicated products, the use of standard FCs and centrifugal motopumps encompasses several advantages: power range, broad range of products and technological independence. This paper describes the main rules to implement standard FCs in PV pumping systems, and presents a model to estimate its performance from standard pumps manufacturers' data. The experimental validation of the model is also presented. Copyright © 2003 John Wiley & Sons, Ltd.
Although PV pumping is a mature technology, current PV pumping programmes show reliability deficiencies. This paper proposes procurement specifications and testing procedures in order to assure the technical quality of this kind of system. Testing facilities following the motto ‘keep it as simple as possible’, in order to make their application easier in conventional laboratories in developing countries, have been developed. The lessons learned in the application of this quality control mechanism to a PV pumping programme of 29 systems in Morocco are discussed in order to show the key parameters that should be taken into consideration in future initiatives. Copyright © 2006 John Wiley & Sons, Ltd.
Maximum power point trackers (MPPTs) play an important role in photovoltaic (PV) power systems because they maximize the power output from a PV system for a given set of conditions, and therefore maximize the array efficiency. Thus, an MPPT can minimize the overall system cost. MPPTs find and maintain operation at the maximum power point, using an MPPT algorithm. Many such algorithms have been proposed. However, one particular algorithm, the perturb-and-observe (P&O) method, claimed by many in the literature to be inferior to others, continues to be by far the most widely used method in commercial PV MPPTs. Part of the reason for this is that the published comparisons between methods do not include an experimental comparison between multiple algorithms with all algorithms optimized and a standardized MPPT hardware. This paper provides such a comparison. MPPT algorithm performance is quantified through the MPPT efficiency. In this work, results are obtained for three optimized algorithms, using a microprocessor-controlled MPPT operating from a PV array and also a PV array simulator. It is found that the P&O method, when properly optimized, can have MPPT efficiencies well in excess of 97%, and is highly competitive against other MPPT algorithms. Copyright © 2002 John Wiley & Sons, Ltd.
This paper presents the experience of a PV pumping project being carried-out in the South of Morocco since 1997. At present, the project has reached 18 villages, affecting 15 000 people. Total involved photovoltaic power is 46 kWp, and the total volume of pumped water since the installation of the systems approaches 0.7 × 106 m3. About half the PV systems are based on dedicated inverters, while the rest are based on standard frequency drivers. Both perform very similarly in terms of both efficiency and reliability. Wells have been selected to provide good water taste, and pumped water is distributed to all the individual houses. Average daily water consumption in summer varies from 13 to 50 litres per person depending on ease of water access and ‚urban proximity’. The maintenance infrastructure is based on an agreement between the European supplier company and a local NGO, which is in charge of all the local organizations. Copyright © 2005 John Wiley & Sons, Ltd.
This paper describes the practical design of a portable capacitive load based on insulated gate bipolar transistors (IGBTs), which is used to measure the I–V characteristics of PV arrays with short-circuit currents up to 80 A and open circuit voltages up to 800 V. Such measurement allows on-site characterization of PV arrays under real operating conditions and also provides information for the detection of potential array anomalies, such as broken cells or defective connections. The presented I–V load is easy to reproduce and low-cost, characteristics that are within the reach of small-scale organizations involved in PV electrification projects.
Photovoltaic water pumps (PVP) are an attractive tool for a rural drinking water supply. An international field testing programme verified the technical maturity of PVP and their reliable field operation. Within well defined site selection criteria, the PVP are competitive with or the least-cost option for replacing small diesel-driven pumps. Introduced to the users through an appropriate community participation concept, the PVP achieved a high level of acceptance by the users, as evidenced by their willingness to pay for the consumed water.
In most of the maximum power point tracking (MPPT) methods described currently in the literature, the optimal operation point of the photovoltaic (PV) systems is estimated by linear approximations. However these approximations can lead to less than optimal operating conditions and hence reduce considerably the performances of the PV system. This paper proposes a new approach to determine the maximum power point (MPP) based on measurements of the open-circuit voltage of the PV modules, and a nonlinear expression for the optimal operating voltage is developed based on this open-circuit voltage. The approach is thus a combination of the nonlinear and perturbation and observation (P&O) methods. The experimental results show that the approach improves clearly the tracking efficiency of the maximum power available at the output of the PV modules. The new method reduces the oscillations around the MPP, and increases the average efficiency of the MPPT obtained. The new MPPT method will deliver more power to any generic load or energy storage media.
In the algorithms found in the literature for finding the optimum point of operation MPPT ( maximum power point tracking), of photovoltaic (PV) modules, the initial reference value is fixed arbitrarily and without constraints. This reduces the performance of research into the optimal operation point of PV systems. In order to improve this performance, a MPPT method based on a nonlinear approach is proposed for estimation of the initial value of the reference. The combination of this approach with the perturbation and observation (P and O) method has enabled progress to be made in the search for the optimal operation point of the PV system.
Power processing systems will be a key factor of future photovoltaic (PV) applications. They will play a central role in transferring, to the load and/or to the grid, the electric power produced by the high-efficiency PV cells of the next generation. In order to come up the expectations related to the use of solar energy for producing electrical energy, such systems must ensure high efficiency, modularity, and, particularly, high reliability. The goal of this paper is to provide an overview of the open problems related to PV power processing systems and to focus the attention of researchers and industries on present and future challenges in this field.
The optimization of a photovoltaic pumping system based on an induction motor driven pump that is powered by a solar array is presented in this paper. The motor-pump subsystem is analyzed from the point of view of optimizing the power requirement of the induction motor, which has led to an optimum u-f relationship useful in controlling the motor. The complete pumping system is implemented using a dc-dc converter, a three-phase inverter, and an induction motor-pump set. The dc-dc converter is used as a power conditioner and its duty cycle is controlled so as to match the load to the array. A microprocessor-based controller is used to carry out the load-matching.
Regional Solar Programme. Lessons and Perspectives. Fondation Energies pour Solar-powered electricity: a survey of photovoltaic power in developing countries. Intermediate Technology Publications and UNESCO. Muñ oz, Capacitive load based on IGBTs for on-site characterization of PV arrays
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F OUT progress after a sudden fall in irradiance for two sets of K P1 and T i1
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Contribució n al diseñ o de procedimientos de control de calidad para sistemas de bombeo fotovoltaico On the control of photovoltaic maximum power point tracker via output parameters
- F Poza
Poza, F., 2008. Contribució n al diseñ o de procedimientos de control de calidad para sistemas de bombeo fotovoltaico, Ph.D. Thesis, Escuela Té Superior de Ingenieros de Telecomunicació n – Universidad Polité de Madrid, Spain. Shmilovitz, D., 2005. On the control of photovoltaic maximum power point tracker via output parameters. IEE Proceedings-Electric Power Applications 152, 239–248.
Regional Solar Programme. Lessons and Perspectives. Fondation Energies pour le Monde
- A Liebard
Liebard, A., 1999. Regional Solar Programme. Lessons and Perspectives.
Fondation Energies pour le Monde, Paris.
Solar-powered electricity: a survey of photovoltaic power in developing countries
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survey of photovoltaic power in developing countries. Intermediate
Technology Publications and UNESCO.