Bidirectional partial power converter interface for energy storage systems to provide peak shaving in grid-tied PV plants

The ever growing participation of modern renewable resources in electric markets has shaken the paradigm of generation-demand constant match. Most modern renewables add intermittent behaviour and high variability to electric markets, forcing other renewables and themselves to perform power curtailment and/or having extra generating units connected to the network to compensate power, voltage and frequency variations. In order to handle this scenario, Energy Storage Systems (ESSs) have risen as enabling technologies capable to provide backup energy to compensate power, voltage and frequency fluctuations and, at the same time, offer additional benefits as ancillary services, peak shaving, load shifting, base load generation, etc. This paper presents a novel bidirectional Partial Power Converter (PPC), as an interface between a Battery ESS (BESS) and a grid-tied Photovoltaic (PV) plant. To obtain a better understanding of the converter, its mathematical model is presented and its operation modes are explained. The main purpose of this configuration is to provide peak shaving capability to a grid-tied PV plant, while providing a high efficiency BESS. Simulation results show the operation of the full system (grid-tied PV plant and BESS), performing peak shaving under a step-down and up in solar irradiation

Energy storage for complementary services in grid-tied PV systems

The continuous increase in penetration of renewable-based power plants together with the intermittent and variable nature of those natural resources have made grid stability issues a major concern, imposing limitations to higher penetration rates. Energy Storage Systems (ESS) have arise as an enabling technology capable of providing PV/ESS configurations with additional capabilities, as such as ancillary or complementary services. This work presents a complete analysis of three difierent complementary services (Maximum Power Ramp Rate limitations, Power Clipping and Peak Shaving). Additionally two different PV/ESS configurations are analysed. For that purpose, three different power converter interfaces between PV and ESS were tested. The results obtained from those tests, showing the performance of the aforementioned complementary services, are presented in this thesis. Moreover, the experimental validation of a PV/ESS, which consists of a full bridge based partial power converter as power interface between PV system and ESS, is also presented in this document. This document also includes two different ESS sizing strategies, each for an specific complementary service. These sizing strategies rely on a prediction of a year of PV power generation obtained from annual measurements of irradiance and temperature. In both cases, the resulting power prediction is contrasted against a desired power profile

Energy storage for complementary services in grid-tied PV systems

The continuous increase in penetration of renewable-based power plants together with the intermittent and variable nature of those natural resources have made grid stability issues a major concern, imposing limitations to higher penetration rates. Energy Storage Systems (ESS) have arise as an enabling technology capable of providing PV/ESS configurations with additional capabilities, as such as ancillary or complementary services. This work presents a complete analysis of three difierent complementary services (Maximum Power Ramp Rate limitations, Power Clipping and Peak Shaving). Additionally two different PV/ESS configurations are analysed. For that purpose, three different power converter interfaces between PV and ESS were tested. The results obtained from those tests, showing the performance of the aforementioned complementary services, are presented in this thesis. Moreover, the experimental validation of a PV/ESS, which consists of a full bridge based partial power converter as power interface between PV system and ESS, is also presented in this document. This document also includes two different ESS sizing strategies, each for an specific complementary service. These sizing strategies rely on a prediction of a year of PV power generation obtained from annual measurements of irradiance and temperature. In both cases, the resulting power prediction is contrasted against a desired power profile

Development of Multiport Single Stage Bidirectional Converter for Photovoltaic and Energy Storage Integration

The energy market is on the verge of a paradigm shift as the emergence of renewable energy sources over traditional fossil fuel based energy supply has started to become cost competitive and viable. Unfortunately, most of the attractive renewable sources come with inherent challenges such as: intermittency and unreliability. This is problematic for today\u27s stable, day ahead market based power system. Fortunately, it is well established that energy storage devices can compensate for renewable sources shortcomings. This makes the integration of energy storage with the renewable energy sources, one of the biggest challenges of modern distributed generation solution. This work discusses, the current state of the art of power conversion systems that integrate photovoltaic and battery energy storage systems. It is established that the control of bidirectional power flow to the energy storage device can be improved by optimizing its modulation and control. Traditional multistage conversion systems offers the required power delivery options, but suffers from a rigid power management system, reduced efficiency and increased cost. To solve this problem, a novel three port converter was developed which allows bidirectional power flow between the battery and the load, and unidirectional power flow from the photovoltaic port. The individual two-port portions of the three port converter were optimized in terms of modulation scheme. This leads to optimization of the proposed converter, for all possible power flow modes. In the second stage of the project, the three port converter was improved both in terms of cost and efficiency by proposing an improved topology. The improved three port converter has reduced functionality but is a perfect fit for the targeted microinverter application. The overall control system was designed to achieve improved reference tracking for power management and output AC voltage control. The bidirectional converter and both the proposed three port converters were analyzed theoretically. Finally, experimental prototypes were built to verify their performance

Grid-Connected Energy Storage Systems: State-of-the-Art and Emerging Technologies

High penetration of renewable energy resources in the power system results in various new challenges for power system operators. One of the promising solutions to sustain the quality and reliability of the power system is the integration of energy storage systems (ESSs). This article investigates the current and emerging trends and technologies for grid-connected ESSs. Different technologies of ESSs categorized as mechanical, electrical, electrochemical, chemical, and thermal are briefly explained. Especially, a detailed review of battery ESSs (BESSs) is provided as they are attracting much attention owing, in part, to the ongoing electrification of transportation. Then, the services that grid-connected ESSs provide to the grid are discussed. Grid connection of the BESSs requires power electronic converters. Therefore, a survey of popular power converter topologies, including transformer-based, transformerless with distributed or common dc-link, and hybrid systems, along with some discussions for implementing advanced grid support functionalities in the BESS control, is presented. Furthermore, the requirements of new standards and grid codes for grid-connected BESSs are reviewed for several countries around the globe. Finally, emerging technologies, including flexible power control of photovoltaic systems, hydrogen, and second-life batteries from electric vehicles, are discussed in this article.This work was supported in part by the Office of Naval Research Global under Grant N62909-19-1-2081, in part by the National Research Foundation of Singapore Investigatorship under Award NRFI2017-08, and in part by the I2001E0069 Industrial Alignment Funding. (Corresponding author: Josep Pou.

A Case Study on Application of Fuzzy Logic based Controller for Peak Load Shaving in a Typical Household\u27s Per Day Electricity Consumption

The cost of electricity for consumers depends on the cost of generation, transmission, and distribution of power. The electrical load consumed by consumers per day is not constant throughout the day. The utilities must be capable of meeting the load demand, which means they must have enough electricity generation potential and necessary infrastructure. This cost is significant. However, the revenue they generate will only be for the actual use of electricity by the consumers. In general, the electrical power generation is done in stages, always generating a base load. As demand changes throughout the day, additional stages of power generation are brought online to meet the changes in demand. This approach of management is known as supply-side management. Theoretically, if it is possible to manage the load such that there is lower peak demand and the difference between peak load and base load were minimized, the generation capability and grid infrastructure required to provide reliable power would be reduced resulting in lower costs for utility companies and ultimately consumers. This management strategy is referred to as demand-side management or demand response. In this research, a small-scale smart grid is modeled in Simulink to mimic the electrical grid. A Smart controller based on fuzzy logic is developed to control charging and discharging of an electric vehicle battery to provide extra power during peak times and to act as load (storing energy) during off-peak time to provide a more manageable and balanced load as seen by the grid. A comparative study is presented of electricity consumption throughout the day with or without the smart controller. The results show the significant reduction in peak demand, much smoother load curve for the grid, and a decrease in per kilowatt cost of electricity for the given day when newer pricing structures are applied

Microgrid Modeling and Grid Interconnection Studies

The demand for renewable energies and their integration to the grid has become more pressing than ever before due to the various reasons including increasing population energy demand, depleting fossil fuels, increasing atmospheric population, etc. Thus the vision of a sustainable future requires easy and reliable integration of renewable distributed generators to the grid. This master’s thesis studies the dynamics of distributed generators when they are connected with the main grid. Simulink MATLAB is used for the design and simulations of this system. Three distributed generators are used in this system: Photo-voltaic converter, Fuel cell and diesel generator. The control and design of the power electronics converters is done to function properly in both grid-connected and islanding mode. The turbine governors in diesel generators control the proper functioning of diesel generator in both modes. The converters in both battery and PV make sure that they work properly in both grid-connected and islanding mode. The control of battery converter is designed in a way to function for load-shaving during unplanned load changes in the microgrid. This fully functioning microgrid is then connected with the main grid using Kundur’s two-area system and simulated for various faults and load changes. A collection of data at the point of common coupling which is the point of connection of microgrid and main grid is gathered for various cases in the grid-connected mode. The cases for faults in the external grid are simulated and then WEKA software is used to develop decision trees. The development of the decision trees can help in predicting the decision of islanding of microgrid. By increasing this database for more scenarios; the response of the generators in grid and distributed generators in microgrid can be studied with decision trees giving more accurate results

Advanced Signal Processing Techniques Applied to Power Systems Control and Analysis

The work published in this book is related to the application of advanced signal processing in smart grids, including power quality, data management, stability and economic management in presence of renewable energy sources, energy storage systems, and electric vehicles. The distinct architecture of smart grids has prompted investigations into the use of advanced algorithms combined with signal processing methods to provide optimal results. The presented applications are focused on data management with cloud computing, power quality assessment, photovoltaic power plant control, and electrical vehicle charge stations, all supported by modern AI-based optimization methods