Page 333 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

320 Renewable Energy Devices and Systems with Simulations in MATLAB and ANSYS ®
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ABSTRACT
Energy storage devices and systems are now playing a major role in electrical systems from small
electronics to automotive applications and to the utility power grid. This chapter reviews energy
storage devices, management, control, interface, and demonstrations for electrical power systems.
Various types of energy storage systems (ESSs) are discussed with a main focus on batteries and
ultracapacitors. Different types of batteries and their electrical models are explained. Three major
types of ultracapacitors are also discussed. The main concepts of battery management systems,
including functions, controls, and hardware, are introduced. Various power electronics–based inter-
face systems for battery and ultracapacitor charging and discharging are presented. Finally, applica-
tions of ESSs for the utility power grid, including renewable firming, power shifting, and ancillary
services, are discussed.

13.1 INTRODUCTION

There is a shift in the decades-old paradigm of energy generation, distribution, and consumption.
Several technical and nontechnical factors are driving this change including concerns on impacts of
fossil-based fuels, advancement of alternative energy technologies, increasing penetrations of dis-
tributed generations (DG), and demand for higher energy efficiency and reliability [1]. Energy stor-
age systems (ESSs) are acting as enabler to support this paradigm shift. They have been employed
in a wide range of electrical systems from consumer electronics to automotive industry and to
utility-level transmissions and generations. The higher energy density and smaller size of newer
ESS technologies have significantly improved mobile and portable consumer electronic devices. In
the automotive industry, advanced ESSs have enabled efficient hybrid electric vehicles (HEVs) and
electric vehicles (EV). Advancements in energy storage and power electronics technologies have
also transformed industrial energy conversion systems such as uninterruptible power supplies (UPS)
and systems with pulse loads/sources.
In electrical power systems, the emerging paradigm includes new elements such as deregulations,
distributed generations (DG), energy storage, DC systems, and power electronics–based systems at
different power scales. With increasing concerns over energy reliability and security, energy cost,
and environmental concerns over fossil-based sources, alternative energy systems have also expe-
rienced a large growth in recent years. The majority of growth has been happening in renewable
energy systems, especially in solar photovoltaic (PV) and wind energy. When the penetration of
these sources increases in the grid, they are required to participate in the grid support functions. The
intermittent nature of these sources needs support from ESSs to make them dispatchable and more
predictable in the grid operation.
Support for renewable energy systems can be realized at several time lengths from short term
(less than 5 s) to long term (several hours). Short-term support is needed during solar PV clouding,
wind power gusting, and power ramp rate limitation. The appropriate energy storage for this applica-
tion does not need to have high energy capability but must have a large power capability. Long-term
support can include power shifting and spinning reserve function. The daytime solar PV power can
be moved to early evening peak demand hours and energy storage can supplement when forecasted
renewable energy does not occur. For these applications, the ESS must have appropriate energy and
power capabilities.
Electrical utility systems can also take advantages of ESSs at distribution, transmission, and genera-
tion levels. ESSs can help to stabilize the electric power system by providing voltage and frequency
support, load leveling and peak power shaving, spinning reserve, and other ancillary services. They also
count as extra energy capacity for the generation and transmission systems in order to defer the upgrade
cost. Time shifting of the energy delivery is another major benefit of integrating ESSs into grid.
For various applications, different types of ESSs with respective strengths and weaknesses have
been developed. Electrical energy can be converted to several other types of energy and can then be