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Simulation Based Approach for Determining the Battery Control Strategy of a PV and Battery Pilot System
Abstract
Implementing sophisticated battery control algorithms by overriding the inverter’s built-in battery controls may introduce technical bottlenecks and additional costs. Such an approach is therefore rarely justified for small scale, behind-the-meter storage. This paper focuses on determining the parameters of an inverter-enabled rule-based control strategy so that the battery is governed similarly to when an optimization-based strategy is used. A five-step procedure has been proposed for the determination of the operational parameters. High resolution measurements of the electricity consumption and PV generation of a pilot case are used to simulate system’s operation. Results of the simulations for days with high and low solar insolation are presented.
... For this purpose, Erigeneia targets to deliver an integrated energy management system (EMS) that combines the PV generation and BESS both for community and residential energy storage. Erigeneia goes a step beyond the current EMS, proposing innovative solutions for increasing the PV penetration, while providing grid-supportive strategies, such as power smoothing, frequency support and voltage regulation for both interconnected and islanded grids" [16]. ...
... The advanced forecasting tool will help the DSO to manage the resources more effectively. The detailed methodology and results can be found in [16]. ...
Grid impact indicators hold valuable information
about a prosumer when interpreted carefully. This makes them
quite useful for benchmarking different demand side management
schemes and studying active buildings. In this paper,
the effects that battery storage has on five such indicators
have been addressed in detail. Their values were calculated by
analyzing 20 households with photovoltaics (PVs) for a period
of one year. Measurement data of the households electricity
consumption and PV generation were obtained from a publicly
available database. To improve the scope of the analyses, three
battery control strategies have been used to simulate the battery’s
operation. The findings show that four of the five analyzed
indicators follow certain patters when plotted as a function of the
prosumer’s generation-to-consumption ratio. Similar patterns are
also observed in the absolute changes in the value of all indicators
when storage is integrated.
The recent development of new and innovative home battery systems has been seen by many as a catalyst for a solar energy revolution, and has created high expectations in the sector. Many observers have predicted an uptake of combined PV/battery units which could ultimately disconnect from the grid and lead to autonomous homes or micro-grids. However, most of the comments in social media, blogs or press articles lack proper cost evaluation and realistic simulations. We aim to bridge this gap by simulating self-consumption in various EU countries, for various household profiles, with or without battery. Results indicate that (1) self-consumption is a non-linear, almost asymptotic function of PV and battery sizes. Achieving 100% self-consumption (i.e. allowing for full off-grid operation) is not realistic for the studied countries without excessively oversizing the PV system and/or the battery; (2) although falling fast, the cost of domestic Li-Ion storage is most likely still too high for a large-scale market uptake in Europe; (3) home battery profitability and future uptake depend mainly on the indirect subsidies for self-consumption provided by the structure of retail prices; (4) the self-sufficiency rate varies widely between households. For a given household, the volume of self-consumption cannot be predicted in a deterministic way. Along with these results, this study also provides a database of synthetic household profiles, a simulation tool for the prediction of self-consumption and a method for the optimal sizing of such systems.
The increase of renewable energy penetration in the distribution grid creates a problem concerning the power quality. One of the most critical scenarios occurs in times of excessive power generation combined with low load consumption, which may lead to an overvoltage due to reverse power flows. Grid expansion is often used as a solution to reduce the voltage rise. However as this new cables or transformers are only used a few hours per year, energy storage might be used as a voltage support among other alternatives. This research is embedded in the project SmartPower-Flow 1 , which deals with the optimization of grid expansion versus energy storage at low voltage levels , where the grid expansion results due to increasing renewable power flows. Since both community and residential batteries have their own control and are connected to the same grid, the interaction between these battery systems has to be studied. This study focuses on residential batteries. Current control strategies for residential photovoltaic (PV) storage systems do not efficiently use the battery as a grid voltage support. Therefore, an investigation on the more intelligent control strategy has been conducted. The objective of the study is to determine the best control strategy for residential PV storage systems in Germany based on technical and economic perspectives. The strategy should be able to control the voltage at the point of common coupling (PCC) while still exhibiting a high self-consumption rate (SCR). Finally a qualitative evaluation of the strategies in respect of the SCR, the self-supply ratio (SSR), the curtailment losses rate (CLR) and the ability to limit the peak voltage at the point of common coupling (PVR) is presented.
This paper investigates the potential of using battery energy storage systems in the public low-voltage distribution grid, to defer upgrades needed to increase the penetration of photovoltaics (PV). A multiobjective optimization method is proposed to visualize the trade-offs between three objective functions: voltage regulation, peak power reduction, and annual cost. The method is applied to a near-future scenario, based on a real residential feeder. The results provide insight into the dimensioning and the required specifications of the battery and the inverter. It is found that an inverter without batteries already achieves part of the objectives. Therefore, the added value of batteries to an inverter is discussed. Furthermore, a comparison between lithium-ion and lead-acid battery technologies is presented.
The MATLAB toolbox YALMIP is introduced. It is described how YALMIP can be used to model and solve optimization problems typically occurring in systems and control theory. In this paper, free MATLAB toolbox YALMIP, developed initially to model SDPs and solve these by interfacing eternal solvers. The toolbox makes development of optimization problems in general, and control oriented SDP problems in particular, extremely simple. In fact, learning 3 YALMIP commands is enough for most users to model and solve the optimization problems
Battery energy storage effectively stabilizes the electric grid and aids renewable integration by balancing supply and demand in real time. The importance of such storage is especially crucial in densely populated urban areas, where traditional storage techniques such as pumped hydroelectric energy storage and compressed-air energy storage are often not feasible.
The increasing penetration of renewable energy systems and the electrification of heat and transport sectors in the UK have created business opportunities for flexible technologies, such as battery energy storage (BES). However, BES investments are still not well understood due to a wide range and debatable technology costs that may undermine its business case. In this context, a BES economic analysis will be established to assess the economic viability of current storage business models, particularly associated with multiple service portfolios. Our model quantifies the net present values (NPVs) and payback periods of BES investments considering various business models and state-of-the-art BES technologies. We determine the commercial viability associated with different BES technologies and business models. The developed model compares different technology costs, business models (i.e. energy storage services) and BES lifetimes to perform a comprehensive economic analysis on the business case for investing in BES. Several case studies under current GB market arrangements demonstrate that BES investment associated with multi-service business model offers the best financial benefits to storage investors and achieve payback periods within 10 years’ lifetime.
There has been growing interest in using energy storage to capture solar energy for later use in the home to reduce reliance on the traditional utility. However, few studies have critically assessed the trade-offs associated with storing solar energy rather than sending it to the utility grid, as is typically done today. Here we show that a typical battery system could reduce peak power demand by 8–32% and reduce peak power injections by 5–42%, depending on how it operates. However, storage inefficiencies increase annual energy consumption by 324–591 kWh per household on average. Furthermore, storage operation indirectly increases emissions by 153–303 kg CO2, 0.03–0.20 kg SO2 and 0.04–0.26 kg NOx per Texas household annually. Thus, home energy storage would not automatically reduce emissions or energy consumption unless it directly enables renewable energy.
Falling battery costs and increasing grid power costs have generated new market opportunities. Due to high costs, energy storage systems (ESS) typically require multiple use cases to justify their costs. ESS has shown promise for future economic and technical solutions due to potential benefits from energy storage arbitrage. Historically, ESSs with a directly connected photovoltaic (PV) system could not be placed in a Net Energy Metering (NEM) tariff, due to challenge of determining whether energy comes from a renewable PV source or fossil fuelled energy from a battery. Recent California Public Utility Commission (CPUC) rules have allowed PV paired energy storage systems to interconnect with NEM under very specific conditions. Early reports indicate that some energy arbitrage is possible in Time of Use (TOU) rates. This paper presents a limited economic analysis on the potential of energy arbitrage utilizing a Residential Energy Storage System (RESS) in typical Southern California Homes.
The interest in self-consumption of PV electricity from grid-connected residential systems is increasing among PV system owners and in the scientific community. Self-consumption can be defined as the share of the total PV production directly consumed by the PV system owner. With decreased subsidies for PV electricity in several countries, increased self-consumption could raise the profit of PV systems and lower the stress on the electricity distribution grid. This review paper summarizes existing research on PV self-consumption and options to improve it. Two options for increased self-consumption are included, namely energy storage and load management, also called demand side management (DSM). Most of the papers examine PV-battery systems, sometimes combined with DSM. The results show that it is possible to increase the relative self-consumption by 13–24% points with a battery storage capacity of 0.5–1 kW h per installed kW PV power and between 2% and 15% points with DSM, both compared to the original rate of self-consumption. The total number of papers is however rather limited and further research and more comparative studies are needed to give a comprehensive view of the technologies and their potential. Behavioral responses to PV self-consumption and the impact on the distribution grid also need to be further studied.
Battery systems coupled to photovoltaic (PV) modules for example fulfill one major function: they locally decouple PV generation and consumption of electrical power leading to two major effects. First, they reduce the grid load, especially at peak times and therewith reduce the necessity of a network expansion. And second, they increase the self-consumption in households and therewith help to reduce energy expenses. For the management of PV batteries charge control strategies need to be developed to reach the goals of both the distribution system operators and the local power producer. In this work optimal control strategies regarding various optimization goals are developed on the basis of the predicted household loads and PV generation profiles using the method of dynamic programming. The resulting charge curves are compared and essential differences discussed. Finally, a multi-objective optimization shows that charge control strategies can be derived that take all optimization goals into account.
The use of MATLAB toolbox YALMIP to model and solve optimization problems occuring in systems in control theory was discussed. The toolbox makes development of control oriented SDP problems. Rapid prototyping of an algorithm based on SDP can be done using standard MATLAB commands. YALMIP automatically detects the kind of a problem the user has defined, and selects a suitable solver based on this analysis.