How Many Types Of UPS Power Supply, including offline Ups or Low Frequency Online UPS?


What is an Uninterruptible Power Supply?


The purpose of a UPS is to provide emergency power (usually by a lead/acid battery) to a load when it senses that the input power source has failed. They are different from emergency power systems or standby generators because they provide near-instantaneous protection from power interruption by using a battery (which can be a supercapacitor or flywheel).


When the mains input is normal, the UPS will stabilize the mains and supply it to the load for use. At this time, the UPS is an AC mains voltage stabilizer, and it also charges the battery inside the machine. When the mains is interrupted (power failure) UPS will immediately supply 220V AC power to the load through the method of inverter conversion, so that the load can maintain normal operation and protect the software and hardware of the load from damage.


The battery itself usually has a short runtime (about 5-20 minutes), but it should be enough to either save all that precious data/progress that you have made, gracefully shut everything down, or fix the problem that caused the outage.


A UPS can be used to protect hardware like data centers, computers, and other electrical equipment where an unexpected surge/sag can cause serious problems like data loss, business disruption, and even injuries or fatalities.


Types of Uninterruptible Power Supplies


There are three types of uninterruptible power supplies: Offline/Standby ,Online/Double Conversion , Line-Interactive. Let’s look how their difference.


1. Offline/Standby Uninterruptible Power Supply

Offline uninterruptible power supply, also known as backup uninterruptible power supply. Usually the mains supply power directly to the load through the bypass, and the inverter inside the machine is in a stopped working state. At this time, the UPS power supply is essentially equivalent to a mains voltage stabilizer with poor performance. In addition to the improvement of the amplitude fluctuation, there is basically no improvement in the adverse effects of voltage instability, waveform distortion and interference from the power grid. Only in the event of a power outage, the battery energy is converted into alternating current by the inverter to provide power to the load.


Features of offline uninterruptible power supply:

a. When the mains power is normal, the offline UPS directly outputs to the load without any processing of the mains power, so the ability to suppress mains noise and surge is poor;

b. There is a transition time

c. Poor protection performance

d. Simple structure, small size, light weight, easy control and low cost.


2. Online/Double Conversion Uninterruptible Power Supply

When the mains power supply is normal, it first rectifies the mains AC power supply into a DC power supply, then performs pulse width modulation and filtering, and then converts the DC power into a sine wave AC power supply through the inverter to supply power to the load. Once the mains power is interrupted, the DC power provided by the battery is immediately switched to provide sine wave AC power to the load through the inverter. Therefore, for the online UPS power supply, under normal circumstances, regardless of whether there is mains power, it is powered by the inverter of the UPS power supply to the load, which avoids all the problems caused by the voltage fluctuation and interference of the mains power grid. impact to come. Obviously, the power supply quality of the online UPS power supply is obviously better than that of the backup UPS power supply. Because it can achieve stable frequency and stable power supply to the load, and when the mains power supply is converted to the battery power supply, the conversion time is zero. It truly provides users with a pure sine wave power supply with stable voltage and frequency, so as to provide power protection that meets the needs of the network system.


Features of online UPS:

a. The output power is processed by UPS, and the output power is of high quality;

b. No conversion time;

c. The structure is complex and the cost is high;

d. The protection performance is the best, and the ability to suppress mains noise and surge is strong.


3. Line-Interactive Uninterruptible Power Supply

Online interactive UPS power supply, also known as 3-port UPS power supply, uses a power frequency transformer. From the perspective of energy transfer, the transformer has three ports for energy flow. Port 1 is connected to the mains input; port 2 is connected to the battery through a bidirectional converter; port 3 is output. When mains power is supplied, the alternating current flows into the transformer through port 1, select the appropriate transformer tap to connect under the control of the voltage regulator circuit, and at the same time, under the action of the bidirectional converter of port 2, the output on port 3 is jointly adjusted by the energy conversion of the battery. In order to achieve a better voltage regulation effect; when the mains power fails, the battery supplies power to the transformer through port 2 through the bidirectional converter to maintain the AC output on port 3. In the online interactive UPS power supply, in the process of transformer tap switching, the bidirectional converter works as an inverter. The battery is powered, so the output voltage can be uninterrupted, and there is no switching time during the switching process from the mains power supply to the battery power supply. The circuit implementation of the online interactive UPS power supply is simple, and there is no separate charger, which brings about the reduction of production cost and the improvement of reliability. There is no AC/DC, DC/AC conversion for this type of products when the mains power supply works, which improves the efficiency of the whole machine. Online interactive UPS combines many advantages of backup UPS and online UPS, and is a very good transformation form. However, because it uses a power frequency transformer, it also has the problems of bulkiness and bulk.


Features of Online Interactive UPS:

a. With bidirectional converter design, UPS battery recharge time is short;

b. There is a conversion time;

c. The control structure is complex and the cost is high;

d. The protection performance is between the online and offline UPS, and the ability to suppress mains noise and surge is poor.