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

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

Integration of thermoelectric generators (TEG) in solar PVT panels

Photovoltaic-thermal hybrid panels (PVT) simultaneously generate electricity and heat with a greater overall efficiency than photovoltaic (PV) and thermal (ST) panels independently. Hybrid PVT-TEG intends to go a step further by integrating thermoelectric modules (TEG) that, based on the Seebeck effect, produce electricity from a temperature difference, thus allowing an additional production of electricity and thus an increase of energy efficiency. In this paper, the design and construction of an experimental installation, consisting of two solar collectors PVT, one of them with 19 TEG modules integrated is presented. This prototype will allow to observe the increase in the electrical production that can be obtained by introducing TEG in PVT modules and the differences in the behaviour (yields and W/Q ratio) between modules with and without TEG

Energy arbitrage in PV-PHS systems

In this paper, we use MHOGA software for the evaluation of adding pumped hydro storage (PHS) for energy arbitrage in utility-scale PV generating systems. PHS is used for electricity price arbitrage, pumping water from the lower reservoir to the upper reservoir with the PV generation during hours of low electricity price and generating electricity by means of the stored water with the turbine during hours of high price (during these hours the PV generator also injects its production to the grid). The control strategy creates setpoints for the use of the pump and the turbine, trying to obtain the maximum benefits from the electricity sold to the grid, maximizing the net present value (NPV). An example of application is shown, obtaining conclusions about the economical viability of the PV-PHS system compared to the PV-only system: in the case studied in this work, it is not worth to add PHS to the PV system

Energy and environmental benefits of an integrated solar photovoltaic and thermal hybrid, seasonal storage and heat pump system for social housing

A facility based on a photovoltaic and thermal hybrid solar field with a seasonal storage tank coupled to a water-to-water heat pump is presented in this paper as an adequate energy supply system for a building of social homes in Zaragoza (Spain), currently under construction. Two types of complementary software have been used for the complete design, sizing, and simulation of the system. DesignBuilder was used to determine the hourly demands from the construction drawings, and TRNSYS was then implemented to dynamically simulate the whole energy system. System performance has been tested in terms of 3E aspects (energy, environmental and economic) with a few well-known key performance indicators. Results obtained by the combined use of the demand simulation software and quantification with different indicators (KPI) show that the proposed solution is suitable for this building: the calculated coverage of the domestic hot water demand is about 80%, the payback period is 8.5 years, and the installation could avoid 44, 200 kgCO2/year of global warming potential. To sum up, this paper shows how this novel, high-efficiency heating system is a good solution for social housing, owing to its low energy costs and a possible subsidization of a fraction of the high initial investment. © 2022 The Author

Electricity price arbitrage in utility-scale PV-plus-battery systems

In this paper, we use MHOGA software for the optimization of an AC-coupled utility-scale PV-plus-battery system. Batteries are used for price arbitrage, being charged with the photovoltaic (PV) generation during hours of low electricity price and discharged during hours of high price. The correct estimation of the battery lifetime has great importance in the calculation of the net present value, to do this advanced models for estimating the Li-ion battery lifetime (considering cycle and calendar ageing) are used. With present components costs, considering the Spanish SPOT price of 2021 with an expected increase of 1% annual, the AC coupled utility-scale PV-plusbattery isn’t economically viable comparing to the PV-only system. If electricity hourly price was multiplied by two, in certain cases adding battery to the PV system would be profitable

Utility-scale renewable hydrogen generation by wind turbines

In this paper, we use MHOGA software for the evaluation of a hydrogen generation system powered by wind turbines. We study the state of the art of the electrolyzers, obtaining the most important characteristics and costs of PEM electrolyzers. The optimization of a Wind-H2 system is performed, obtaining the best combination of components (wind turbines and electrolyzer) and control strategy for the hydrogen production. We will compare to the Wind-only system (wind farm which injects all the electricity produced to the gird). Two cases have been evaluated regarding the electricity price: Spanish SPOT price of 2019 and of 2021, with an expected increase of 1% annual. The Wind-H2 system can be competitive to the Wind-only system if the hydrogen sale price is 4.8 €/kg for the case of 2019 SPOT prices and 6.7 €/kg for the case of 2021 SPOT prices, considering 1% annual increase in the SPOT prices and 2% for the hydrogen price

Analysis of the Hybridization of PV Plants with a BESS for Annual Constant Power Operation

The electrical generation of photovoltaic systems is variable and non-dispatchable. Energy storage systems can provide the system with energy management capabilities. In particular, with a hybrid system that combines a photovoltaic system and an energy storage system, it is possible to deliver firm power to the grid, if it is correctly dimensioned and operated. The objective of this work is to study the most appropriate relationship between the capacity of the battery energy storage system (BESS) and the peak power of the photovoltaic generator that enables the delivery of constant power throughout the year. Analysis parameters are presented that help to decide the most convenient energy injection constant value (PV-CPG set point) and the size of the storage system. As a case study, the most suitable battery capacity for a 1 MWp photovoltaic system with a battery located in Zaragoza (Spain), and the most convenient annual setpoint values for its operation are analyzed