A coordinated control hybrid MPPT algorithm for a grid-tied PV system considering a VDCIQ control structure

In this paper, a new coordinated maximum power point tracking (MPPT) algorithm has been developed for a grid-tied PV system, whose inverter follows a VDCIQ control scheme. The control objectives of this system are shared between 2 converters: a DC boost converter which performs MPPT of the PV plant, and an inverter which is responsible for DC voltage setpoint control, specific reactive current injection under request and reduced harmonic content of AC grid currents. The proposed algorithm operates upon a proper switching amongst conventional MPPT algorithms, namely perturb and observe (P&O) and incremental conductance (IC) algorithms, to take advantage of the best characteristics of each MPPT method with a different step size and considering the influence of the inverter control constants. Two coordination schemes are proposed for this algorithm to prioritise the improvement of different performance aspects over others. The impact of the proposed algorithm according to the 2 coordination schemes is evaluated and compared with the impact of conventional MPPT algorithms according to the trackability of power, the impact on DC voltage and on the AC grid side. The results are analysed by simulations conducted in MATLAB-Simulink

Analysis of photovoltaic plants with battery energy storage systems (PV-BESS) for monthly constant power operation

Photovoltaic generation is one of the key technologies in the production of electricity from renewable sources. However, the intermittent nature of solar radiation poses a challenge to effectively integrate this renewable resource into the electrical power system. The price reduction of battery storage systems in the coming years presents an opportunity for their practical combination with utility-scale photovoltaic plants. The integration of properly sized photovoltaic and battery energy storage systems (PV-BESS) for the delivery of constant power not only guarantees high energy availability, but also enables a possible increase in the number of PV installations and the PV penetration. A massive data analysis with long-term simulations is carried out and indicators of energy unavailability of the combined system are identified to assess the reliability of power production. The proposed indicators allow to determine the appropriate sizing of the battery energy storage system for a utility-scale photovoltaic plant in a planning stage, as well as suggest the recommended operating points made for each month through a set of graphs and indicators. The presence of an inflection zone has been observed, beyond which any increase in storage does not generate significant reductions in the unavailability of energy. This critical zone is considered the sweet spot for the size of the storage, beyond which it is not sensible to increase its size. Identifying the critical point is crucial to determining the optimal storage size. The system is capable of providing reliable supply of constant power in monthly periods while ensuring capacity credit levels above 95%, which increases the penetration of this renewable resource. Despite the fact that the study focuses exclusively on the analysis from an energy perspective, it is important to consider the constraints associated to real storage systems and limit their oversizing

Firm capacity of PV+STG systems

The security of supply becomes a key variable of the electrical system. Due to the discontinuity of solar irradiance, PV generators are essentially not dispatchable and they operate only when there is solar resource but cannot ensure their availability when the energy is needed, so PV systems are considered having a null capacity credit. Energy storage is considered a key for the power sector and its sustainability and different options need to be exploited. The objective of this paper is analyse the optimum size of the required battery, its relations with the peak power of the generation system and the optimum operation setpoint of a PV+STG system for providing firm capacity. © 2022, European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ). All rights reserved

Sizing of on-grid photovoltaic systems for water pumping in irrigation communities

This paper describes a technical-economical analysis to achieve the most appropriate sizing of grid-connected photovoltaic systems for water pumping in irrigation communities. The profitability of different tracking systems are analysed based on the price of the electrical energy consumed from the network. The case study of a real pumping system of an irrigation community located in Zaragoza (Spain) is presented, which supplies a geographical area of 2000 Ha, with six 630kW pumps and eight 110kW units

Recent Developments of Photovoltaics Integrated with Battery Storage Systems and Related Feed-In Tariff Policies: A Review

The paper presents a review of the recent developments of photovoltaics integrated with battery storage systems (PV-BESs) and related to feed-in tariff policies. The integrated photovoltaic battery systems are separately discussed in the regulatory context of Germany, Italy, Spain, United Kingdom, Australia, and Greece; the attention of this paper is focused on those integrated systems subject to incentivisation policies such as feed-in tariff. Most of the contributions reported in this paper consider already existing incentive schemes; the remaining part of the contributions proposes interesting and novel feed-in tariff schemes. All the contributions provide an important resource for carrying out further research on a new era of incentive policies in order to promote storage technologies and integrated photovoltaic battery systems in smart grids and smart cities. Recent incentive policies adopted in Germany, Italy, Spain, and Australia are also discussed

Analysis and optimization of a heat pump system coupled to an installation of PVT panels and a seasonal storage tank on an educational building

A water-water solar-assisted heat pump (SAHP) is projected on an under construction academic building at the University of Zaragoza (Spain). It integrates a heat pump heating system with photovoltaic/thermal collectors and seasonal storage. Because of its innovative design, considerably higher performances than a conventional type air-source heat pump are expected. This paper shows the simulation of the system performed in TRNSYS, a graphically based software used to simulate the behavior of transient systems. In addition, starting from the current design of the energy system, different sensibility analysis are simulated in order to study alternative configurations of the heating system. The solar coverage of the current installation design is about 60% and the expected savings yield to a payback period of 15, 4 years. Three alternative configurations are proposed in this work, reaching up to around 98% of solar coverage. The study results show the technical and economic feasibility of the heating installation based on a solar assisted heat pump with implementation of seasonal storage in an educational building located in a middle latitude

Solar-assisted heat pump coupled to solar hybrid panels

A water-water solar-assisted heat pump (SAHP) is going to be installed on an academic building at the University of Zaragoza (Spain). It integrates a heat pump heating system with photovoltaics/thermal collectors and seasonal storage. Considerably higher performances than a conventional type air-source heat pump are expected to be reached. This paper shows the simulation of the system performed in trnsys, a graphically based software used to simulate the behaviour of transient systems. The obtained energy and monetary savings are analysed

Analysis of a domestic trigeneration scheme with hybrid renewable energy sources and desalting techniques

In this paper, experimental tests of a hybrid trigeneration pilot unit based on renewable energy sources are presented and analyzed. The plant provides electricity by coupling four photovoltaic/thermal collectors and a micro-wind turbine, fresh water by means of hybrid desalination (membrane distillation, and reverse osmosis), and sanitary hot water coming from the photovoltaic/thermal collectors and an evacuated tubes collector. Plant design was previously modeled to cover the power, freshwater and sanitary hot water for a typical family home (four residents) isolated from the power and water networks. The hybrid pilot unit has been tested from May 2017 to March 2018 in Zaragoza (Spain). Results from those tests show that daytime assessment of power, freshwater and sanitary hot water produced allowed a good coverage of scheduled energy and water demands. Flexible operation due to the combined production of power and heat was also observed. State of charge of the batteries and the temperature of the sanitary hot water tank are the key control variables, which allow to give priority to power, freshwater or sanitary hot water production according to the ordered demands or economic incentives. Environmental assessment of the pilot unit along its life cycle also has shown very low impacts with respect to the conventional supply of energy and water

A renewable energy community of DC nanogrids for providing balancing services

The massive expansion of Distributed Energy Resources and schedulable loads have forced a variation of generation, transmission, and final usage of electricity towards the paradigm of Smart Communities microgrids and of Renewable Energy Communities. In the paper, the use of multiple DC microgrids for residential applications, i.e., the nanogrids, in order to compose and create a renewable energy community, is hypothesized. The DC Bus Signaling distributed control strategy for the power management of each individual nanogrid is applied to satisfy the power flow requests sent from an aggregator. It is important to underline that this is an adaptive control strategy, i.e., it is used when the nanogrid provides a service to the aggregator and when not. In addition, the value of the DC bus voltage of each nanogrid is communicated to the aggregator. In this way, the aggregator is aware of the regulation capacity that each nanogrid can provide and which flexible resources are used to provide this capacity. The effectiveness of the proposed control strategy is demonstrated via numerical experiments. The energy community considered in the paper consists of five nanogrids, interfaced to a common ML-LV substation. The nanogrids, equipped with a photovoltaic plant and a set of lithium-ion batteries, participate in the balancing service depending on its local generation and storage capacity. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

An Advanced Multicarrier Residential Energy Hub System Based on Mixed Integer Linear Programming

This work proposes a multicarrier energy hub system with the objective of minimizing the economy cost and the CO2 emissions of a residential building without sacrificing the household comfort and increasing the exploitation of renewable energy in daily life. The energy hub combines the electrical grid and natural gas network, a gas boiler, a heat pump, a photovoltaic plant, and a photovoltaic/thermal (PV/T) system. In addition, to increase the overall performance of the system, a battery-based energy storage system is integrated. To evaluate the optimal capacity of each energy hub component, an optimization scheduling process and the optimization problem have been solved with the YALMIP platform in the MATLAB environment. The result showed that this advanced system not only can decrease the economic cost and CO2 emissions but also reduce the impact to electrical grid