Photovoltaic Storage System Research Articles

A Method of Dynamic Extended Reactive Power Optimization in Distribution Network Containing Photovoltaic-Storage System

The grid-integration of Photovoltaic-Storage System brings some undefined factors to the network. In order to make full use of the adjusting ability of Photovoltaic-Storage System (PSS), this paper puts forward a reactive power optimization model, which are used to construct the objective function based on power loss and the device adjusting cost, including energy storage adjusting cost. By using Cataclysmic Genetic Algorithm to solve this optimization problem, and comparing with other optimization method, the result proved that: the method of dynamic extended reactive power optimization this article puts forward, can enhance the effect of reactive power optimization, including reducing power loss and device adjusting cost, meanwhile, it gives consideration to the safety of voltage.

Design criteria for the optimal sizing of integrated photovoltaic-storage systems

The paper aims at presenting a methodology to choose the proper sizing of an integrated Photovoltaic unit and a storage architecture starting from the knowledge of the load and solar irradiance time profiles. To do this, first a simple logic to manage the charging/discharging of the storage is proposed, then the function representing the overall cost during the whole life of the system is derived. The computation of the cost function for different photovoltaic and storage sizes allows finding the best sizing of the system. Finally, a thorough economic analysis is conducted to provide criteria to check whether the investment is economically advantageous. This is done considering the impact of the economic variables which are more influential on the investment key assessment parameters. The proposed methodology has been validated in different realistic test cases against the results provided by an energy management system, showing an excellent agreement between the approaches. Moreover, the economic analysis has been applied to four realistic situations in order to tailor the microgrid components ratings on the specific test case.

Impacts of a forecast-based operation strategy for grid-connected PV storage systems on profitability and the energy system

Integrating photovoltaic (PV) produced electricity into the electric power system is proving to be a growing challenge due to its fluctuating nature. The combination of more rigid regulation for feed-in of PV production and steadily rising electricity prices means that battery systems are becoming more attractive to private households as a way of upping their self-consumption. At the same time, batteries make the household’s electricity purchasing strategy more complex. For these reasons, control concepts are required for PV + battery systems that ensure grid-friendly operation as well as considering the household’s primary objectives. This paper presents a forecast-based modelling approach for the operation of a battery in combination with a grid-connected PV system. PV production and electricity demand are forecasted on an hourly time-resolution using artificial neural networks (ANN). The battery charging and discharging is optimized to maximize self-consumption, and additionally a variable feed-in tariff is considered to incentivize a grid-friendly operation. The developed model was applied for a household with 3300 kWh electricity consumption equipped with a 5 kWp PV system and a 5 kWh battery. For this case, we show that the model enables a grid-friendly operation of the battery as well as an intensified usage. However, the inevitable forecasting errors lead to overall lower economic benefits for the consumer in comparison with a simple strategy that only maximizes self-consumption. Considering the inaccuracy of forecasting, we conclude that if a grid-friendly integration of PV + battery systems is to be promoted in the future, households should be provided with better forecasting data or offered other incentives to compensate their lost benefits.

On the influence of jurisdiction on the profitability of residential photovoltaic-storage systems: A multi-national case study

Policy makers in many jurisdictions have implemented incentive schemes such as ‘feed-in tariffs’ (FIT) and upfront purchase subsidies to encourage consumers to self-generate parts of their power requirements by solar energy. We quantitatively study the impact of jurisdiction-specific solar radiation profile, the typical residential loads, the cost of system components, the price of grid electricity, and incentive programs on photovoltaic (PV) and storage system profitability in Germany, Ontario, and Austin, Texas. In each jurisdiction, for a range of PV and storage system sizes, we compute the optimal use of the system, and hence the best possible profitability of that system in that jurisdiction over a 20 year life span. This methodology allows us to quantitatively estimate the influence of a jurisdiction on the (best possible) profitability of PV-storage systems. We find that the choice of jurisdiction has significant impact on the profitability of PV-storage systems. We also find that policy makers can use the price of grid electricity as well as upfront subsidies to influence profitability, and therefore adoption.

The active control strategy on the output power for photovoltaic-storage systems based on extended PQ-QV-PV Node

In order to solve the problem of voltage exceeding specified limits and improve the penetration of photovoltaic in distribution network, we can make full use of the active power regulation ability of energy storage(ES) and the reactive power regulation ability of grid-connected photovoltaic inverter to provide support of active power and reactive power for distribution network. A strategy of actively controlling the output power for photovoltaic-storage system based on extended PQ-QV-PV node by analyzing the voltage regulating mechanism of point of commom coupling(PCC) of photovoltaic with energy storage(PVES) by controlling photovoltaic inverter and energy storage. The strategy set a small wave range of voltage to every photovoltaic by making the type of PCC convert among PQ, PV and QV. The simulation results indicate that the active control method can provide a better solution to the problem of voltage exceeding specified limits when photovoltaic is connectted to electric distribution network.

Sizing of Battery Converters for Residential PV Storage Systems

With the increasing number of domestic PV (photovoltaic) installations connected to battery energy storage systems for self-supply purposes in Germany, new research topics such as the sizing of the required system components have emerged. In this paper, the impact of the rated battery converter power on the utilization of PV-attached battery systems in residential buildings is discussed. First, the ratio between the battery converter rating and the storage capacity is analyzed for a variety of residential battery systems available on the market. Thereafter, simulations with a temporal resolution of 1 s are performed in order to identify how the rated battery converter power affects the energy throughput of the battery system taking account of the characteristic conversion efficiency curves. The results show that battery converter sizes in the range of 4 to 5 kW are optimal in terms of maximum discharged energy for the most system configurations under study. However, battery converters rated between 30 to 50% of the optimal power rating are sufficient to provide more than 95% of the maximum dischargeable energy from the battery system. Based on these findings, it can be concluded that small-sized battery converters rated at 1.5 to 2 kW are sufficient for residential self consumption applications.

Feasibility study of an islanded microgrid in rural area consisting of PV, wind, biomass and battery energy storage system

Renewable energy systems are proving to be promising and environment friendly sources of electricity generation, particularly, in countries with inadequate fossil fuel resources. In recent years, wind, solar photovoltaic (PV) and biomass based systems have been drawing more attention to provide electricity to isolated or energy deficient regions. This paper presents a hybrid PV-wind generation system along with biomass and storage to fulfill the electrical load demand of a small area. For optimal sizing of components, a recently introduced swarm based artificial bee colony (ABC) algorithm is applied. To verify the strength of the proposed technique, the results are compared with the results obtained from the standard software tool, hybrid optimization model for electric renewable (HOMER) and particle swarm optimization (PSO) algorithm. It has been verified from the results that the ABC algorithm has good convergence property and ability to provide good quality results. Further, for critical case such as the failure of any source, the behavior of the proposed system has been observed. It is evident from the results that the proposed scheme is able to manage a smooth power flow with the same optimal configuration.

Techno-economic comparison of a schedule-based and a forecast-based control strategy for residential photovoltaic storage systems in Germany

In Germany, the huge integration of small photovoltaic (PV) systems into the distribution grid during the past years leads to power quality issues due to the intermittent generation and reverse power flow in periods of low demand. To decrease this impact, different solutions are being investigated. The scope of this paper is to compare different strategies to control the charge power for residential PV storage systems for different load curves and to decide which might be the economically most profitable strategy. For this purpose, three different PV storage system control strategies were analyzed using MATLAB®to perform 1-year simulations on a minute step base. Measured input data from a PV system in the south of Germany were combined with four measured (extreme) load profiles and a standard load profile to conduct a sensitivity analysis. Performance indicators, such as self-consumption ratio (SCR), self-supply ratio (SSR), and share of losses ratio (SLR), were used to compare the different control strategies. Furthermore, an economic analysis of these results was performed to obtain the profitability of every control strategy and to determine the most profitable strategy, considering the household owner’s benefits.

An energy management model to study energy and peak power savings from PV and storage in demand responsive buildings

Demand Response (DR) applications along with strategically deployed solar photovoltaic (PV) and ice storage systems at the building level can help reduce building peak demand and energy consumption. Research shows that no work has been carried out to study the impact of integrated control of PV and ice storage on improving building operation and energy savings in demand responsive buildings. This can enable building operators to take advantage of different electricity prices and enable utilities to spread the demand over whole day. This research presents a model to study coordinated control of building end-use loads including cooling, lighting and plug loads, together with PV and ice storage integrated with packaged air conditioning (AC) units. This is used to study their impacts on peak demand and energy consumption in a simulated medium-sized office building located in Virginia/Maryland, U.S. area. Research findings provide an improved understanding of the contribution of DR, solar PV and ice storage systems towards reducing building peak electricity demand and energy consumption while being sensitive to occupant thermal and lighting needs.

A novel approach for optimal combinations of wind, PV, and energy storage system in diesel-free isolated communities

A new approach for optimal combinations of Hybrid Renewable Energy Systems (HRESs) is proposed, for diesel-free remote communities and related decision-making problems. The objective of the design is to satisfy the load with total cost’s minimization considering related constraints, where all analytical equations are given. The proposed system is a DC configuration for renewable energy integration in which Wind Turbines (WTs) are connected to the DC bus and the battery system removes the fluctuations in the DC bus. The WT is assumed to be well controlled to obtain the power curve and provide proper electricity to the grid. It is found that WT and Photovoltaic (PV) systems should be considered simultaneously on diesel-free generation islands to achieve a reliable and optimized configuration. A novel strategy is introduced for determining the range of batteries, which can be determined using the renewable energy potential to satisfy the load. It is also demonstrated that WTs are an essential power component in real HRES installations. It is illustrated that the range of WT operation must be first taken into account in real installations. Increasing WT fraction from an initial value, for instance 8%, to a desired value of about 33%, can lead to significant reductions in total cost as well as in the number of PV systems and batteries, even if the WT cost is significantly higher than that of PVs. A WT fraction higher than approximately 50% should not be considered. Finally, discussions are extended to consider the optimum WT fraction in a HRES.

An Underfrequency Load Shedding Scheme for Hybrid and Multiarea Power Systems

The purpose of underfrequency load shedding (UFLS) is to maintain the frequency of an interconnected or island power system within permissible limits in case of severe power deficits. Thus, the proper performance of UFLS scheme is of great importance. In hybrid power systems, disconnecting and connecting the power generation sources and loads result in variations in the system parameters. Moreover, the output power of some distributed energy resources, such as photovoltaic (PV) or wind turbine generator (WTG), might change during the load shedding process. These factors may affect the performance of the load shedding scheme and decrease the reliability of power system. Hence, in this paper, a UFLS scheme is proposed that has two advantages: 1) it is independent of power system parameters; and 2) it considers power generation variations during the load shedding process. To verify the effectiveness of the proposed load shedding method, simulation studies are carried out on a hybrid power system including PV, WTG, fuel cell, diesel generator, and battery energy storage system. Finally, the performance of the proposed method on a multiarea power system is evaluated.

Control and Optimization of Grid-Tied Photovoltaic Storage Systems Using Model Predictive Control

In this paper, we develop optimization and control methods for a grid-tied photovoltaic (PV) storage system. The storage component consists of two separate units, a large slower moving unit for energy shifting and arbitrage and a small rapid charging unit for smoothing. We use a Model Predictive Control (MPC) framework to allow the units to automatically and dynamically adapt to changes in PV output while responding to external system operator requests or price signals. At each time step, the system is modeled using convex objectives and constraints and solved to obtain a control schedule for the storage units across the MPC horizon. For each subsequent time step, the first step of the schedule is executed before repeating the optimization process to account for changes in the operating environment and predictions due to availability of additional information. We present simulation results that demonstrate the ability of this optimization framework to respond dynamically in real time to external price signals and provide increased system benefits including smoother power output while respecting and maintaining the functional requirements of the storage units and power converters.

A comparison of some methods of stochastic modelling of solar energy photovoltaic storage systems

A comparison of some methods of stochastic modelling of solar energy photovoltaic storage systems