What is energy storage system and what are the types of energy storage device

What is energy storage systems

Energy storage systems can also be called as restoring technologies, they are used to provide the ride-through capability to the electric loads in case of poor electric power quality. The use of electrical loads is high because of its need, because of the modernization use of electrical loads is high and these have made the power quality reliability and stability a critical issue. Nowadays the use of electronic loads is very high and it has made power quality a critical issue. The power generation transmission and distribution system must be able to supply uninterrupted power supply by maintaining the power quality. There are several constraints like generation capacity and the slower response of alternators to system disturbances, affect the stability and the overall performance of the system. So the need for energy storage capability to maintain the power quality of the grid is high.

What is the need for energy storage technologies

Energy storage devices and equipment are mostly used for three purposes, they are energy stabilization, ride-through capability, and dispatchability. The ride through capability is the ability of the energy storage device to provide the proper amount of energy to the load. Energy stabilization will be helpful to the load to provide a proper stable output, with the help of the energy storage device. Dispatchability is needed for certain energy sources like photovoltaic or wind energy systems in which power production requires energy sources like wind and sunlight, so these energy sources sometimes may not provide the required energy and that’s why a backup is required.

What are the types of energy storage device


A flywheel is an electromechanical device that couples a rotating electric machine with a rotating mass to store energy. The motor or generator draws power provided by the grid to keep the rotor of the flywheel spinning. In the case of a power disturbance, the kinetic energy which is stored in the rotor is transformed to DC electric energy by the generator, and the energy is delivered at constant frequency and voltage through an inverter and a control system.


Supercapacitors are DC energy sources, it is also known as ultra-capacitors providing energy output at the grid frequency. These capacitors will provide power during voltage sags. In the super-capacitors, the capacitance is very large because the distance between the plate is very small and because of the area of the conductor surface.

Dynamic voltage restorer

DVR is a voltage source which is connected to load in series, the output voltage of the DVR is kept constant at the load terminals by the help of step-up transformer and stored energy to inject active and reactive power in the output supply through a voltage converter.

Transient voltage surge suppressor

These are used as an interface between the power source and the sensitive loads so that it could clamp the transient voltage before it reaches the load. these devices mostly have a non-linear resistance component which limits the excessive line voltage and conducts any excess impulse energy to the ground.

Constant voltage transformer

CVT can be considered as a solution for power quality, they are used to mitigate the effects of voltage sags and transients. In order to maintain a constant voltage, they use two principles that are normally avoided: resonance and core saturation. When the resonance occurs, the current will increase to a point that causes the saturation of the magnetic core of the transformer. If the magnetic core is saturated, then the magnetic flux will remain constant and the transformer will provide constant output. If the CVT is not used properly then it will create many power quality problems.

Noise filters

Noise filters can remove the unwanted frequency current or voltage signals before reaching the sensitive equipment. It can be accomplished by the combination of capacitors and inductance which would create a low impedance path to the fundamental frequency and high impedance to the higher frequency, which is a low pass filter.

Isolation transformers

These transformers are used to isolate sensitive loads from transients and noise which is deriving from the mains. In certain cases the isolation transformers keep the harmonic currents generated by the loads from getting upstream the transformer. The peculiarity of the isolation transformer is that it is a grounded shield made of magnetic foil located between the primary and the secondary. So any noise or transient that comes from the source is transmitted through the capacitance between the primary and the shield and on to the ground and does not reach the load.

Static VAR compensators

These devices use a combination of capacitors and reactors to regulate the voltage quickly. Solid-state switches control the insertion of capacitors and reactors at the right magnitude to prevent the voltage from fluctuating. SVR’s major application is to regulate the voltage level in high voltage and removes the flicker caused by large loads.

Harmonic filters

Harmonic filters are used to remove the undesirable harmonics, they are divided into two types active and passive filters. The passive filter provides a low impedance path to the frequencies of the harmonics to be attenuated using passive components. Active filters analyze the current consumed by the load and create a current that cancels the harmonic current generated by the loads.