DC Contactors for Energy Storage Systems

Introduction to Energy storage systems

The DC contactors are used widely in Energy Storage Systems (ESS), along with the other applications such as: electric vehicles, car charging, etc. After reading this article, you will have a better understanding regarding the basics of Energy Storage Systems and the connection of the ESS with the contactors using a battery.  
The capturing of the energy produced at one time, in order to use it at later time, is known as energy storage. The device or the mean of the storage is usually a battery or accumulator. There are different forms of energies, heat energy, kinetic energy, electrical potential and chemical energy. Some of the energy forms are difficult to store, they need to be converted into economical and convenient storable types.  
Energy storage system is a type of system which is used as a storage for the power supply and electrical energy. It performs the following functions: voltage regulation, valley filling, peak cutting transition and frequency modulation. It generates a smooth output for the wind and solar power generation. There are many advantages of using an energy storage system such as: it reduces the unpredictable nature and the irregularity of the energy stored. It also supports your electricity expense. In the case of any grid failure it can be used for isolated operations and it will ensure you an uninterrupted power supply.
One of the significant parts of the power system is the Energy Storage System (ESS), which formed the foundation of making a new microgrid for energy. As soon as the link of the energy storage is established, the demand side management is realized. The load over the system is suppressed and this makes the overall power equipment more reliable and also reduces the cost of the electricity. The whole process indicates the applications of renewable energy.  It also proves to take part in frequency modulation, regulation of voltage, compensates for the fluctuating load and to enhance the stability of power system.

Energy Storage System Operating

ESS operating steps are categorized as: Charging Period and Discharging period. The charging period is applicable at the time when the network electrical energy is available (off-peak time) at a lower cost. The discharging period is the time when ESS stored energy is utilized (peak-time). During this period the network energy is expensive.

Brief Introduction to Energy Storage System (ESS) Terminologies

The large-scale application of the Energy Storage System is the Battery Energy Storage System (BESS). There are three major terms used for energy storage systems: Power Conversion System (PCS), Battery Management System (BMS) and Energy Management System (EMS).    
PCS consists of AC/DC converter. It receives the instruction from the background controller via communication. The variables involved in the commands depend upon the power instruction size and symbol control converter transmits on the discharging and charging of the battery. The medium of communication between the PCS and BMS is the Controller Area Network (CAN), in order to obtain status information of the battery pack to ensure the safe charging, discharging and protective operation of the battery.
Battery Management System (BMS) is for the maintenance and management of each battery to protect it from getting overcharged or over discharged, check battery status and enhance battery life. BMS consists of display module, electrical equipment, control module, battery pack, module for battery information to collect battery pack, and wireless communication.
The grid dispatching automation system is generally known as Energy Management System (EMS). There are multiple functions of EMS, it collects the monitoring information of distribution cabinet, PCS inverter, battery pack and many other data regarding energy storage container. It integrates the data for display, perform commands to dispatch grid and adjusts cloud server. It also optimizes energy storage charging and discharging behavior in the enclosure and maximize battery life. You should select the device-side energy storage approach and the generation-side depending on the various energy storage box implementation scenarios.

Main Performance Requirements of DC Contactors for Energy Storage System

There are two main type of renewable energy storage systems called wind power plants and photovoltaic (PV).  The requirement of efficient current networks in the production industry is increasing day by day. Therefore, safe switching techniques for high DC load is the major requirement for the electro-mechanical machineries. For this purpose, contactors are used and they should be smart enough to reliably extinguish and handle high voltages and currents. You can find the best DC contactors for your Energy Storage Systems at HOSTON. We provide the best photovoltaic and wind energy generation system contactors.
The basic feature of Energy Storage System is to have a voltage range between 500-1000Vdc, the port for charging and discharging is the same and has to perform work for hours. The characteristics of the main contactor in the ESS is to have 1000Vdc, it has no polarity, the temperature rise of coil and main contact is low. The function of fuses, contactors and breakers is to prevent the short circuit, undervoltage, overvoltage, over temperature, overcurrent and any other unusual damage to the system.

Applications of DC contactors in Solar PV Cells

Solar is the type of renewable energy source that converts the sunlight into electrical energy using Photovoltaic (PV) cells. The main devices used in the PV system are PV cells, an inverter to convert the DC to AC voltage, Combiners, Trackers to adjust the angles of the PV cells, switching devices to protect from short circuits and lastly the distribution transformers for the transformation of low voltage to high voltage.

Why is DC contactor needed in PV cells?

As the electricity produced by the PV cells is in DC, therefore, PV systems comprises of some major applications regarding DC switching techniques and contactors. The contactors are generally beneficial when there is a requirement of at least once per day switching or remote control. In the PV cell the DC contactors are used for disconnecting the inverter from strings of PV when the output is low. In order to optimize the system efficiency, the contactors change the configuration of the strings.

Failure Modes of DC contactors

When you buy a contactor for your Energy Storage System (ESS), it is important to consider important failure factors related to the DC contactors to prevent them from damage and to save your cost.
There are two types of failure modes in DC contactors, burning of studs and contact welding. The burning of studs can be caused due to the bad connection between external environment and DC contactors. This problem can be solved by flexible installation and assembling using the proper torque requirements. The cause for contact welding could be the improper arc extinguishing or the leakage of contact air. This could be prevented by choosing the contactors with epoxy filling and glue sealing. You can find all these related DC contactors at HOTSON. Following are the contactors available at our website.

HOTSON product line for DC switching for Energy Storage Systems

All the DC contactors are Epoxy filled with the current rated from 30A – 1000A. The contact polarity for all the contactors is non-polar, which is the main requirement of Energy Storage System. Following DC contactors are available at HOTSON EVQ30, EVQ100, EVQ150, EVQ200, EVQ250, EVQ300, EVQ350, EVQ400, EVQ500, EVQ600 and EVQ1000. EVQ200 and EVQ250 are the double coiled contactors, all the other DC contactors are single coiled contactors.